Geologia Petrolera de Venezuela

Chapter 1

Petroleum Geology of Venezuela

General geology

The history of oil exploration

in Venezuela

Petroleum basins

1

P E T R O L E U M G E O L O G Y O F V E N E Z U E L A

1

Gulf of Venezuela

La Paz

Alturitas

El RosarioRío de Oro

Los Manueles

Las Cruces

Tarra

Urdaneta

Boscán

Lama

Mérida

San Cristóbal

La Alquitrana

La VictoriaGuafita

Barinas

Silván

SincoSilvestre

MERIDA

TACHIRA

COLOMBIA

BARINAS

APURE

Motatán

TRUJILLO

LamarLagocentro

CeutaTomoraro

LaConcepción

W.Mara Mara Sibucara

Maracaibo MediaHombre Pintado

Las Palmas

Tiguale

El Mamón

Barquisimeto

San Felipe

CARABOBO

GUARICO

COJEDES

PORTUGUESA

ARAGUAMIRANDA

Valencia

Los Teques

Yucal - Placer

Roblecito ValleJobal

SabanIpire

Bella Vista

Punzón

Las Mercedes

Palacio

MACHETE

BelénRuiz

DakoaGuavinita

Tucupido

Copa Macoya

San Carlos

CaracasD.F.

Guanare

San Juande los Morros

San Fernandode Apure

Maracay

FALCON

LARA

CoroLa Vela

La Velaoffshore

Cumarebo

Mene de Maurda

Cabimas

Ambrosio

Tía JuanaLagunillas

Bachaquero

Mene Grande

ZULIA

BOLIVAR

– 1,300,000 m

– 1,200,000 m

– 1,100,000 m

– 1,000,000 m

– 900,000 m

– 800,000 m

– 700,000 m

– 600,000 m 100,000 m 200,000 m 300,000 m 400,000 m 500,000 m 600,000 m 700,000 m 800,000 m 900,000

100,000 m 200,000 m 300,000 m 400,000 m 500,000 m 600,000 m 700,000 m 800,000 m 900,000

LakeMaracaibo

YARACUY

Caribbean Sea

Tu y

Riv eruata

River

Guárico River

Apure River

Meta River

Arauca RiverArauca Ri ver

Ca tat umbo

River

Gu asare

Riv

er

Tocu yo

River

fig 1.36

fig 1.40

Fig 1.43

Fig

1.48

Fig

1

.48

Fig 1.45

Fig

1.48

LegendOil field State Boundaries

Cross Section

State Capitol

River

Gas field

Condensate field

Oil + Condensate field

00 20 40 60 80 miles

20 40 60 80 100 120 km

Trujillo

A pure

River

Figure 1.0

Location map of oil fields in Venezuela.

1 2

BO

GUARICO

ARAGUAMIRANDA

ANZOATEGUI

MONAGAS

SUCRE

N. ESPARTA

Los Teques

Yucal - Placer

Roblecito ValleJobal

SabanIpire

BarsoBella Vista

Punzón

Las Mercedes

Palacio

MACHETEPAO

ORINOCO BELTHAMACA

CascaEl Roble

San Roque

San Joaquín

Santa AnaEl Toco

Guere

Budare ElotesTrico

Oficina

Chimire

Boca Nipa

Naroo

Guara

Dación

Leona

Lobo

OscuroteOritupano

Adas

Melones

Acema - CasmaAcemaMata

Oveja

Kaki

Mapiri

Cantaura

Maulpa Carisito

Aguasay

Onado

Casma

La Florida

Santa Rosa

ZUATA

BelénRuiz

DakoaGuavinita

Tucupido

BarcelonaQuiamare

Cumaná

La Ceiba

Greater Anacoarea

Greater Oficinaarea

Tacat

Pirital

JusepínMaturin

Temblador

Jobo

MorichalPilón

UracoaBombal

Tucupita

OrocualQuiriquire

El FurrialCarito

Greater Tembladorarea

ReclamationZone

Santa Bárbara

Manresa

Río CaribeLa Asunción

CocheCubagua

MejillonesPatao

Posa

Dragón

Loran

Tajali

Trinidad

Pedernales

Copa Macoya

CaracasD.F.

San Juande los Morros

San Fernandode Apure

Maracay

BOLIVAR

AMACURO

BOLIVAR

1,300,000 m –

1,200,000 m –

1,100,000 m –

1,000,000 m –

900,000 m –

00 m 700,000 m 800,000 m 900,000 m

00 m 700,000 m 800,000 m 900,000 m 1,000,000 m 1,100,000 m 1,200,000 m 1,300,000 m 1,400,000 m

DELTA

Bitor AreaCerroNegro

Caribbean Sea

Gulf of Paria

CiudadBolívar

Tobago

Tu y

Riv er

Margarita Island

Greater Anaco area Greater Oficina area

G ua nipa Rive r

Tigre Riv e r

San Juan

River

Unare River

Orin oco River

Caro

ni

Ri ver

Aro

Rive

r

ZuataRive

r

Ca ur a Ri

ver

Guárico River

Apure River

Fig

1.48

Fig

1

.48

Fig 1.45

Fig 1.50 Fig 1.50

Fig 1.55

Fig

1.48

IntroductionThe purpose of this chapter on the

Petroleum Geology and Basins of Venezuela

is to give the reader a general overview of

the geology of the country. Our knowledge

has been greatly enhanced by the oil

industry and mining activities that have been

ongoing for almost a century. Without

entering into a detailed analysis of the

numerous and unsolved problems with the

geology, we have integrated the information

presented in many papers and books written

on Venezuelan geology. We have tried to

attribute the original contributions of all

authors, and have also presented summa-

tions based upon our own experience. We

have avoided specialized and detailed points

of view concerning stratigraphy, sedi-

mentology and geotectonic evolution,

instead choosing to simplify the geology

because of our diverse readership and

limited writing space. For non-specialized

readers, we include a Glossary at the end of

the chapter, and also a time chart with the

main geological ages indicated and a

geopolitical map with all Venezuelan cities

and places cited in the text (Fig. 1.0). Also,

we include a section called the “History of

Oil Exploration in Venezuela” for those who

may be interested in the history and growth

of Venezuela’s most important industry. At

the end of the chapter, a list of references

consulted for the compilation of figures and

text is provided. We also include references

to other papers and books that should be

useful to those who wish to study the

geology of Venezuelan petroleum basins in

more detail.

Physiographic provincesThere are five main physiographic

provinces in Venezuela (Fig. 1.1):

1. Mountain ranges

a.Venezuelan Andes system

b.Caribbean mountain system (Perijá

Range, San Luis and Baragua Ranges, La

Costa Mountain Range)

2. Foothill regions

3. Coastal plains

4. Mainland plains

5. Guayana Province.

Rocks of a wide age range (Precambrian

through Neogene) are found in the

mountain ranges of La Costa and the Andes.

Their formation history is closely associated

with the evolution of the northern margin of

the South American plate from the Eocene to

the present. The foothill regions (9430 km2)

are covered by Neogene molassic sediments

whose main physiographic features are

terraces formed during glaciation/deglacia-

tion processes.


31

The Venezuelan physio-

graphic provinces are:

1) The mountain belts:

Venezuelan Andes and the

Caribbean Mountain System

(Perijá, San Luis; Baragua

and La Costa Range); 2) the

foothills; 3) the coastal plains;

4) the plains between the

Orinoco River and the moun-

tain belts; 5) and the

Guayana Province or Massif

(after NB-18-ll map; MMH,

1976).

Maracaibo

S. Cristóbal

Mérida Barinas

GuanareTrujillo

LakeMaracaibo

Coro

BarquisimetoValencia

Los TequesCaracas Barcelona

Cumaná

Porlamar

Ciudad Bolívar

Carúpano

Tucupita

Puerto Ayacucho

Caribbean Sea

BrazilColombia

Brazil

Colo

mbi

a

Trinidad

Gu

yan

a

Rio Orinoco

AtlanticOcean

0

50

100

150

200 km

SanFernando

San Luis Range

Baragua Range

Venezuelan Andes Perij

á Ra

nge La Costa Range C. de La Costa

Guayana

Massif

ArubaBonaire

La Tortuga Tobago

Grenada

Rio Meta

Rec

lam

atio

n Z

on

e

ArayaParia

Rio Arauca

Rio Apure

Rio PortuguesaRio G

uarico

Rio TigreR. Guanipa

Cariaco

72˚ 68˚ 64˚ 60˚

72˚ 68˚ 64˚ 60˚

11˚

7˚

3˚

11˚

7˚

3˚

0-100 m Plains andCoastal Plains

FoothillRegions

MountainBelts

100- 250 mSeaLevel

250

to >

500

0 m

Guajira Peninsula

Gulf of

Venezuela

ParaguanáPeninsula

Interior Range(Central Branch)

Interior Range(Eastern Branch)

N

Maturín

Figure 1.1

1

G E N E R A L G E O L O G Y P R E C A M B R I A N

4

The coastal plains (117,220 km2) are

concentrated in four broad regions: 1) north

of Falcón State (Fig.1.0), 2) Barcelona

coastline (Anzoátegui State), 3) Orinoco

River delta (Delta Amacuro State), and 4)

north of Sucre State. The mainland plains

(260,000 km2), with an extensive drainage

network, encompass the land between the

northern mountain ranges and the Guayana

Province; they are the result of the

sedimentary filling of the Eastern and

Barinas-Apure Basins.

In the south is the Guayana Province

(also called “Guayana Massif,” “Guayana

Shield,” or “Guayana Cratón” in the

geological literature) with 425,000 km2 of

Precambrian-age terranes, with some

Pleistocene plains built by the Orinoco River

and some of its tributaries.

Precambrian terranes The Venezuelan Precambrian terranes

outcrop in the main mountain ranges of the

country and in the Guayana Province.

Because of the tectonic history of the north-

ern South American plate, both allochtho-

nous and autochthonous Precambrian rocks

are found. Figure 1.2 shows the distribution

of these terranes; those located north of the

Orinoco River were overridden by Paleozoic-

age crustal fragments that were accreted, or

added, to the South American plate.

The autochthonous terranes are located

in the Guayana Province, and also form part

of the basement of the Paleozoic to Cenozoic

sedimentary basins south of the Apure Fault.

There are four provinces of Precambrian

rocks in the Guayana Province: Imataca,

Pastora, Cuchivero and Roraima (Fig. 1.2).

It has not been possible to discriminate

different provinces (with respect to age) in

the basement of the oil basins to the north of

Guayana Province; this is because there are

few wells that have reached the basement in

these basins and the available descriptive

information is scarce.

The accretion of allochthonous terranes

on the South America plate began during the

Early Paleozoic (Caledonian Orogeny: 570 to

385 Ma); part of these rocks outcrop near

Mérida and San Cristóbal in western

Venezuela. Later, during the Hercinian

Orogeny (385 to 245 Ma), occurred the

suturation, or welding of the allochthonous

blocks. These included Precambrian rocks,

among which only the granitic rocks of the

Sierra Nevada in the Santa Marta Massif

(Colombia) have been dated (Fig. 1.2). The

last collision began during the Cretaceous;

this allochthon includes rocks of

Precambrian age near the city of Caracas

(Federal District) and south of Valencia

(Carabobo State).

N

Cenozoic Orogenic Belt

Late Paleozoic Orogenic Belt

Early Paleozoic Orogenic Belt

Paleozoic and Cenozoic Basinsof the Precambrian Basement

Eastern Basin of the Precambrian Basement,Imataca Province Possible Extension

Imataca Province

Overthrusting

Pastora Province

Cuchivero Province

Roraima Province

Boundaries of theCordilleran Systems

Caracas

SantaMarta

East

ern

Ran

ge

Wes

tern

Ran

ge

UpperPaleozoicOrogenic

Belt Lower Paleozoic

OrogenicBelt

Cenozoic OrogenicBelt

Paci

fic O

cean

Caribbean Sea62˚78˚

8˚

4˚

Caribbean FrontalThrust

Brazil

CuchiveroProvince

Valencia

BogotáPaleozoic and CenozoicBasins as a Precambrian

Basement

Colombia

SanCristóbal

Mérida

Apure Fault

Venezuela

CiudadBolívar

PastoraProvince

ImatacaProvince

Pana

ma I

sthm

us

Trinidad

300 km0

Guayana ShieldCuchiveroProvince

RoraimaProvince

Altamira

Fault

Rec

lam

atio

nZo

ne

Espino

Graben

Figure 1.2

Northern South America´s

distribution of allochthonous

terranes in which

Precambrian rocks are

present. These terranes

were sequentially sutured to

the South American

continent during the

Ordovician-Silurian and later

during Late Mesozoic

through Recent.

Paleozoic terranesThe rocks of Paleozoic age in Venezuela

are found in several regions, geologically

grouped as allochthonous or autochthonous

terranes of South America. The auto-

chthonous terranes are found in the

subsurface of the Barinas-Apure and Eastern

Basins (Fig. 1.21), south of the Apure Fault

(Fig. 1.3). These rocks are typical “red beds”

from Gondwana (South America and Africa

before its rupture) and Laurentia (North

America and Greenland before its rupture);

they are preserved only in the deep

structural depressions of these Venezuelan

basins. The allochthonous terranes are

distinguished by the age in which they were

tectonically accreted to the north of the

South American plate; there are those

accreted during the Early Paleozoic, others

during the Late Paleozoic and the latest

during the Mesozoic.

Distribution

Figure 1.3 shows the distribution of

allochthonous terranes that were welded to

the Lower Paleozoic autochthons during

Ordovician–Silurian time. Those rocks

accreted during the Lower Paleozoic are

now considered part of the basement from

the point of view of later Caribbean tectonic

history. They include that part of the

orogenic belt north of the Apure Fault, the

actual Andes and Maracaibo Basin.

In the Andes, rocks of the Lower

Paleozoic allochthonous terranes include

granitic and shelf/slope sedimentary rocks

(Ordovician–Silurian). Ordovician metase-

dimentary rocks are found in the subsurface

basement of the Maracaibo Basin and in the

Andes. Devonian-age allochthonous terranes,

welded to South America during the Late

Paleozoic, outcrop in the Perijá Mountains.

Part of the accretionary history of the

Upper Paleozoic onto the Lower Paleozoic

includes granitic rocks, formed as a result of

subduction below the northern border of

South America. These include rocks of the El

Baúl region (Permian age) and those found

in the subsurface of Eastern, Barinas-Apure

and Maracaibo Basins (Carboniferous age).

The accreted belt included sedimentary

sequences of Carboniferous and Permian

ages; these rocks now outcrop in the Perijá

and Andes Mountains.

The last of these allochthonous terranes

is the Caribbean Mountain System that

extends from Guajira Peninsula (Western

North Venezuela) to Paria Peninsula (Eastern

North Venezuela), including the subsurface

basement of the Gulf of Venezuela and the

La Costa Mountain Range. In this terrane

Paleozoic rocks of Devonian to Permian

ages are found.


51

Guayana Shield


Upper Paleozoic Orogenic Belt

Lower Paleozoic Basin

Lower Paleozoic Orogenic Belt

Guayana Shield

Caracas

ReclamationZone

Brazil

Venezuela

Colombia

Espino

Graben

Altamira

Fault

Bogotá

El Baúl

SantaMarta

Caparo

East

ern

Ran

ge

Wes

tern

Ran

ge

UpperPaleozoicOrogenic

Belt Early Paleozoic Orogenic Belt

LowerPaleozoic

Basin


Caribbean Sea

62˚

62˚

78˚

78˚

8˚ 8˚

4˚ 4˚

CaribbeanFrontal Thrust

Apure Fault

N

PanamáIsthmus

0 100 200 300 km

Overthrusting

Boundaries of theCordilleran Systems

Pac

ific

Oce

an

Northern South America´s

distribution of allochthonous

terranes in which Paleozoic

rocks are present. These

terranes were sequentially

sutured during the

Ordovician and Silurian, then

during the Carboniferous and

finally during Late Mesozoic

through Recent.

Figure 1.3

1 6

Mesozoic terranes

Triassic-Jurassic

The Triassic is not present in Venezuela

or, at least, no evidence of its presence has

been found and documented. The oldest

part of the Jurassic system (208 to 181 Ma) is

represented by Volcánicas de la Ge (Perijá)

and Volcánicas de Guacamayas (El Baúl),

which predated the red bed sedimentation

of the La Quinta Formation and the whole

expansion process related to the Gulf of

Mexico or Proto-Caribe opening. They are

the lateral equivalents of the Volcánicas de

El Totumo (Perijá) (Fig. 1.4),

In Venezuela, the Pangean continent

(the supercontinent comprising America,

Europe and Africa) rifting produced several

main structural features that later influenced

the evolution of the Venezuelan sedimentary

basins. Inside continental Venezuela, the

Proto-Caribe opening induced the

development of northeast-oriented exten-

sion valleys or grabens (Fig. 1.5). Among

these valleys are the Apure-Mantecal,

Espino, Andes-Perijá and Maracaibo grabens.

It has been postulated that the Jurassic rocks

in the deepest parts of the Interior Mountain

Range of Eastern Venezuela were involved

in this deformation, as deduced by the trend

of the main grabens, such as Apure-Mantecal

and Espino. However, this theory has not yet

been proven.

All these grabens were filled during

the Jurassic by red bed (continental)

sediments, diverse volcanics, and occasional

shallow-marine clastics and limestones.

Their preserved sequences outcrop in many

places: the Guajira and Paraguaná Peninsulas

(Cojoro and Cocinas Groups; Pueblo Nuevo

Formation), and the widespread La Quinta

Formation of Western Venezuela. They also

occur in the subsurface of Eastern Venezuela

Basin (Ipire Formation).

G E N E R A L G E O L O G Y P A L E O Z O I C A N D M E S O Z O I C

Age Perijá and Guajira Andes Guárico and Cojedes La Costa Range

Jurassic

Triassic

Conglomerates

Seco Cojoro/COCINASLa Quinta

El TotumoMacoita

La GéTinacoa Volcanics

La Quinta Ipire

Pueblo NuevoLas Brisas (Zenda)

Macuro

? ?

Guacamayas?

Figure 1.4

1

23

3

3

4

Caribbean SeaParaguaná

Colombia

Perij

á

12˚ 12˚

8˚ 8˚

63˚

63˚

73˚

73˚

Andes

Coro

Caracas

Maturín

Maracaibo

EspinoGraben

Apure-MantecalGraben

Trinidad

Urica Fault

SantanderMassif

Guajira

0 100 200 300 km

El Pilar Fault

N

Figure 1.5

Correlation chart of the most

important Triassic-Jurassic

units in Venezuela.

Distribution of Jurassic rocks: 1) in Perijá Range; 2) as part of the economic

basement of Maracaibo Basin; 3) in the Andes; 4) in Barinas-Apure and Eastern

Venezuela Basins (Apure-Mantecal and Espino Graben). It is believed that they are

involved in deep thrusting within Eastern Venezuela´s Interior Range (after Bartok,

1993; Passalacqua et. al., 1995; and Lugo and Mann, 1995).

Cretaceous

Early Cretaceous. The major sedi-

mentary facies distribution and stratigraphy

of Early Cretaceous rocks (146 to 95 Ma) are

shown in Figs. 1.6 and 1.7.

In Western Venezuela, the sedimentation

was initially controlled by the Jurassic graben-

fault systems. This is evidenced by the

variable thicknesses of Rio Negro Formation

clastics, which range from more than 2 km

near the south of Machiques Trough, to only

a few meters thick in some places of the

North-Andean flank. Later the subsidence

stabilised and there was an extensive

transgression of an open sea over the Western

Venezuelan shelf causing the carbonate

sedimentation of the Cogollo Group. The

lateral clastic equivalent of these carbonates

in the Cratón or Guayana Province margins is

the Aguardiente Formation. In Central Vene-

zuela, there are some remains of an older


71

Barranquín

TEMBLADORCanoa

Peñas Altas

Río Negro

0 200 km

El Cantil

Mac

hiqu

esT

hro

ug

hU

riban

teTh

roug

h

Exposed Igneous and MetamorphicBasement (Guayana Shield).

Continental-Fluvial EnvironmentSandy Clastics

Coastal and Transitional EnvironmentSandy-Shale Clastics

Shelf EnvironmentCarbonates

Hemipelagic/PelagicLimestones and Shales

Sediment SupplyDirection

Chimana

Aguardiente

COGOLLO

SUCRE

GuayanaShield

(?) N

Figure 1.6

Age

Albian

Aptian

Barremian

Neocomian?

Río Negro

Tibú

MachiquesPiché Apón

Lisure

Maraca COGOLLO

Perijá and Lake Maracaibo

Andes and Barinas-Apure

La Grita (Capacho)

Aguardiente

GuáimarosTibú Apón

Río Negro"Basal Clastics"

(Exotic Blocks)

?

?

Macaira Limestone?

?

Northern Guárico EasternInterior Range

Querecual(*)

( , "Valle Grande")Cutacual

Chimana

"Guácharo"

El Cantil"El Mapurite"

García

Taguarumo

Picuda

Barranquín

Morro Blanco

Venados"Río Solo"

"Punceres"

S

U

C

R

E

Sand / Sandstone Reservoir

Sand / Seal Pairs

Seal

Source Rock

The Querecual Formation extends to the Late Cretaceous

Carbonate Reservoir

(*)

?

?

Correlation chart of the most important Early Cretaceous units of Venezuela. Informal units are within quotation marks.

See Yoris, 1985, 1988, 1992, on Sucre Group.

Figure 1.7

Distribution of dominant sedimentary facies during the Neocomian-Albian (Early

Cretaceous) north of the Guayana Shield. Representative stratigraphical units of this

facies association are indicated.

1 8

(also Early Cretaceous) carbonate shelf,

which is discontinuous along the

deformation (mountain) front to the north of

Guárico State (Macaira Limestone).

In Eastern Venezuela, the sedimentary

history resembles that of a passive “Atlantic”

type margin. These rocks belong to the Sucre

Group, which at the base are sandy clastics

and some shelf limestones of the Barranquín

Formation (whose thickness is more uniform

than its Western Venezuela equivalent). Later,

extensive and well defined carbonate-clastic

shelf sedimentation was developed (El Cantil

and Chimana Formations). The main

difference with the Early Cretaceous of

Western Venezuela is that in the Interior

Range of Eastern Venezuela, the lower

contact with older sequences is unknown

and the thicknesses of the Early Cretaceous

units are greater. For example, the

Barranquín Formation is more than 1 km

thick everywhere, with massive, carbonate

shelf sedimentation in its middle part (Morro

Blanco Member of Barremian age–114 to 118

Ma) in the northernmost outcrops.

The thickness of both El Cantil and Chimana

Formations is several times the thickness of

their lateral equivalent in Western Venezuela,

the Cogollo Group.

Late Cretaceous. The distribution of

paleoenvironments and stratigraphic units

during the Late Cretaceous is shown in Figs.

1.8 and 1.9. Figure 1.10 condenses the

correlation chart for these units for all of

Venezuela.

A diachronic and extensive marine

invasion began at the end of the Albian,

moving from east to west and invading the

south of Venezuela, which had been

emerged and undergoing erosion since Late

Jurassic and possibly Paleozoic times. This

marine invasion coincides with the

worldwide transgressive pulse of the Late

Cretaceous, recorded in America and Europe

through the sedimentation of organic-rich

limestones, shales and cherts; these rocks are

recognized in Venezuela as the Querecual-

San Antonio (Guayuta Group), Mucaria,

Navay and La Luna Formations. The

maximum transgression and lack of oxygen

is believed to have occurred between the

Turonian and the Campanian (72 to 91 Ma).

The La Luna, Navay and Querecual

Formations are the source rocks for the oil

basins of Venezuela, and were deposited

during the late Albian to the Turonian (95 to

88 Ma). The La Luna Formation ranges

between 50 and 300 m thick in Western

Venezuela, while the Navay Formation is

close to 600 m thick in the South-Andean

Flank and thickens to the northeast.

In Western Venezuela, the lateral facies

variations of these source rocks consist of

pelagic and phosphatic limestones, dark

shales and shelly limestones that grade to

sandy clastics and glauconitic facies in the

southeastern flank of the Andes in Tachira

State. In North-Central Venezuela, these

facies occur in the Mucaria Formation and

Guayuta Group .

G E N E R A L G E O L O G Y M E S O Z O I C

Dominant sedimentary facies

distribution during the

Cenomanian-Campanian

(Late Cretaceous) at the

northern edge of the

Guayana Shield North. Typical

units of these sets of facies

are indicated.

Continental-Fluvial Sandy Clastics

Coastal and Transitional Sandyand Shaly Clastics

Bathyal (Pelagic) and Shelf ShalyLimestone, Chert and Siliceous Mudstone

Bathyal and Abyssal Hemipelagic/Pelagic Shales and Limestones

Igneous-Metamorphic Basement(Guayana Craton) Shelf Carbonates

?

Socuy Mucaria La Luna

Capacho Navay

Escandalosa TEMBLADOR

0 200 km

N

Maracaibo

CaracasMaturín

Barcelona

Gua

yacá

n

Guayana Shield

Infante GUAYUTA

Figure 1.8

The Guayuta Group is thickest in North-

Eastern Venezuela, being more than 1 km thick

in its type area (Anzoátegui State). In the

Eastern Basin, this unit changes laterally to the

south, losing its source rock character by giving

way to sedimentation from shallower

environments, from shelf to coastline and even

continental, which are defined in the

subsurface as the Canoa and Tigre Formations

(Temblador Group).

The Late Cretaceous in Venezuela ends in

the Maastrichtian, with units that are regressive

relative to the deeper environments of the

source rock.

In Perijá and the Maracaibo Basin,

the La Luna Formation grades vertically to

glauconitic limestones (Socuy Member), and

dark shales with thin sandstones defined as

the Colon and Mito Juan Formations. In

the North-Andean Flank, the glauconitic-

phosphatic Tres Esquinas Member is present,

which is the possible diachronic equivalent of

the Socuy Member, underlying the dark shales

of the Colón Formation.

In the South-Andean Flank, the upper

contact with the source rock is gradational to

erosive with the basal sandstones of Burgüita

Formation.


91

Sandy Clastics Clay-Silt Clasts

Shallow MarineCarbonates

Positive Areas

Sedimentary SupplyDirection

Postulated Depocenter Axis

Thrust Front

?

?

?

?

? ?

?

Deform

ation

Front A

dvance

Mito Juan

CujisalSan Juan

Marine Sediments (Undifferentiated)

Colón

Río de Oro

N

Igneous-MetamorphicBasement

GuayanaShield

Burgüita

Positive areas that includePaleozoic and Mesozoic rocks

Figure 1.9

Age

Maastrichtian

Campanian

Santonian

Coniacian

Turonian

Cenomanian

Perijá and Lake Maracaibo Flank

North-AndeanFlank

South-Andean North ofGuárico

Southern FlankEastern Basin

EasternInterior Range

Mito Juan Mito Juan

Colón Colón

Socuy

La Luna

(Regional hiatusat the base?)

Tres Esquinas

Guayacán

Capacho

Seboruco

Burgüita

Quevedo

Nav

ay

La Morita

Guayacán / Caliza "O"

Escandalosa

Guárico

?

?

?

"Exotic Blocks "

Tigre

TEMBLADORGROUP

Canoa Querecual

San Antonio

San JuanVidoño

Reservoir (Carbonate)

Reservoir (Sandy)

Sand / Seal Pairs

Seal

Source Rock

Infante

(Mucaria, San Antonio, Querecual,

" )"Río Chávez"

"Querecual of the North

GUAYUTA

G

U

A

Y

U

T

A

La Luna

?

Figure 1.10

Sedimentary facies distribution during the Maastrichtian (Late Cretaceous) at the

northern edge of the Guayana Shield. Typical units of these sets of facies are

indicated. Notice that the axis of the Western Venezuela depocenter is subparallel

to the deformation front, as a consequence of the plate collision between Nazca

and South American plates.

Correlation chart of the most important Late Cretaceous units of Venezuela. Guárico and Vidoño Formations

continue through the Paleocene; Canoa and Querecual Formations start by the end of Late Albian.

1 10

In North-Central Venezuela, the lateral

equivalents of the Mucaria Formation grade

vertically to the hemipelagic and turbidite

sequences of the lower Guarico Formation.

To the east, the bathyal sandstones of the San

Juan Formation overlie the black cherts and

sandstones of the San Antonio Formation.

Then, in turn, the San Juan Formation grades

vertically to the dark shales of the Vidoño

Formation (late Maastrichtian–60 to 65 Ma).

Cenozoic terrains

Paleogene

Paleocene-Eocene of Western Venezuela.

During late Cretaceous (Fig. 1.9) to early

Paleocene, Western Venezuela was affected

by the collision between the Nazca Plate

(Pacific Ocean) and Western Colombia. There

is evidence that the sedimentation of the

Orocué Group (and probably Guasare and

Marcelina Formations) was controlled by the

deformation fronts of this collision (Fig. 1.11).

These fronts generated successively younger

depocenters to the east of the actual Perijá

Mountain range.

Figure 1.11 summarizes the sedi-

mentation and gradual evolution of the

deformation front as the Caribbean plate

passed north of the South American plate

during the Paleocene-Eocene. For simplicity,

several formations are summarized by one

name only (e.g., “Misoa” refers to the

sedimentation of lateral equivalents and/or

closely related units, such as the Misoa, Caús

and Paují Formations). Each “event” carries

the most distinctive formation or group name.

To the northeast of the South American

plate, the oblique collision of the Lesser

Antilles arc generated a series of sheets, or

nappes, trending towards the south and

southeast. These control the turbidite

sedimentation of formations such as Trujillo

and Morán.

G E N E R A L G E O L O G Y C E N O Z O I C

V

V

V

V

V

Misoa

Orocué/Mirador

Orocue/Mirador

Guárico

Trujillo

Misoa

Gobernador

Humocaro

La Victoria

Pagüey

Shallow Clastics

Caribbean Plate

Maracaibo-Sta. Marta

BlockCentral American Arc

Andean Block

ShallowClastics

ShallowClasticsW

este

rnR

ange

of

Col

ombi

aC

ollis

ion

N

SM-B

B

Maracaibo

Gobernador

MatatereMorán

Foredeep

La Victoria

Mar

ine

Clast

ics

Early Paleocene *

Early Eocene*

Middle Paleocene *

Farallón Plate

Trujillo

Guasare/Marcelina

South AmericanBlock

(*) Deformation Front Position

EL Baúl Lineament

Roblecito

Guárico

Barcelona

Carbonates

Lesser Antilles Arc

Guayana Shield

0 50 km

= Barco-Los Cuervos-Mirador-Carbonera Fms. Event (Paleocene-Eocene)

= Garrapata-Guárico Fms. Event (Paleocene)

= Trujillo Fm. Event (Paleocene-Eocene)

= Misoa-Caús-Paují Fms. Event (Eocene)

= Direction of sediment supply

= Gobernador-Masparrito Fms. Event (Eocene)

= Humocaro-Quebrada Arriba Fms. Event (Eocene)

= La Victoria-Santa Rita-Jarillal Fms. Event (Eocene)

= Exposed areas

= Thrust front

Humocaro Peñas Blancas

Truj

illo

Pauj

í

Figure 1.11

ESE migration of the

Caribbean deformation front

and associated episutural

sedimentation during

Paleocene-Eocene times.

The Andean-South American

boundary was located at

the present position of the

Santa Marta-Bucaramanga

(SM-B) and Bocono

(B) fault systems.

On the other hand, during the

Paleocene, to the north and west of

Maracaibo Basin, the Guasare Formation

was deposited in shallower environments

further away from the deformation fronts,

and afterwards the Marcelina Formation in

coastal-marsh environments.

During the Eocene, a complex sedi-

mentary setting existed in the Maracaibo

Basin. Distinct deltaic/estuarine, coastal/fluvial

and marine systems developed, depending on

their geographic position with respect to the

different deformation fronts, such as in Perijá

or later on in Lara to the east. Formations such

as Barco-Los Cuervos and Mirador-Carbonera

(deposited between the Paleocene and Middle

Eocene–65-40 Ma) represent two similar

sedimentary pulses of fluvial-deltaic origin in

the western part of Maracaibo Basin. In the

central part of the basin, the Guasare, Trujillo,

Misoa, Caús and Paují Formations were more

marine lateral equivalents of the Barco-Los

Cuervos and Mirador-Carbonera, with a

relative, gradual deepening of environments

to the northeast. In the Barbacoas region, east

of Trujillo State, the average depth of the

Eocene sea was shallow enough to deposit

the transitional and coastal-marine sediments

of Gobernador-Masparrito and Humocaro-

Quebrada Arriba Formations. Meanwhile, in

Falcón State just north of the south-verging

deformation fronts, the La Victoria-Santa Rita

and Jarillal Formations were deposited. This

sedimentation was associated with exten-

sional basin subsidence related to along-strike

faulting (i.e., a “pull- apart” basin) (Fig. 1.12).

Paleocene - Eocene of North -Central

Venezuela. Part of the accretion due to the

Lesser Antilles is probably represented by the

sediments of the Guárico Formation, plus the

limestone and other older units in the

olistostromes. During the Paleogene and

Neogene, this fold and thrust belt migrated to

the south and east of the nothern margin of


111

?

Pull-Apart Basin

200 Km

Foredeep Sediments Thrust Front

Positive Areas

Shallow Clastic Sediments

Volc

anic

Arc

CaribbeanPlate Late Eocene

?South American Plate

Frontal Thrust

N

Advance of Allochthonous Terranes

Oca Fault System

MaximumSubsidence Area

Figure 1.12

XX

V

V

?

Paleocene-Eocene

Caribbean PlateExtinct Volcanic Arc

LesserAntilles

Positive Area

AtlanticOcean

Pampatar-Punta Carnero

Vidoño-Caratas

??

?

?

?

??

Peñas Blancas

Maturín

0 50 Km

Slop

e

Barcelona

South American Plate

Roblecito

Clastic Shelf

N

Oceanic Sedimentation (Undifferentiated)

Caribbean DeformationLimit

Act

ive

Volc

anic

Arc

Foredeep Tinajitas

Shallow Sandy Clastics

Turbidites

Limestones

Lime-Clay Clastics Predominate over the Sandy Clastics (Slope Environment)

Direction of Sediment Supply

Positive Areas

Thrust Front

Caratas

Figure 1.13

Generation of pull-apart basins at the boundary between the Caribbean and South

American plates; the maximum subsidence areas were located north of Falcón State

at this time (Late Eocene) (after Macellari, 1995).

Regional geologic framework for the sedimentation at the northern flank of the

Eastern Basin during the Paleocene-Eocene.

1 12

the South American plate. Those rocks

originally sedimented in the trough just in

front of the belt (the foredeep) were later

uplifted, eroded and re-sedimented into

the trough.

While the Caribbean plate moved to the

east between the South American and North

American plates, the influence of the fold

and thrust belts also moved, but to the

south, producing the new foredeep of the

Roblecito Formation, with a probable age

between the Late Eocene and Oligocene (?)

(39-23 Ma). South of the new foredeep, the

lithosphere bent due to the new load,

causing the influx of the clastics that

produced the La Pascua Formation.

Paleocene-Eocene of Eastern Venezuela.

During the Paleocene and Early Eocene, the

sedimentation was not influenced by the

Caribbean deformation fronts. The Vidoño

(hemipelagic marls, siltstones and clays) and

Caratas (sandstones) Formations accumu-

lated on a passive continental margin slope.

It is possible that the influence of the

oblique collision of the Caribbean plate on

Eastern Venezuela began in the Middle

Eocene—the first evidence may be in the

sandy-glauconitic and foraminiferal-rich

carbonates deposited on the foredeep

margins located north of Venezuela (Peñas

Blancas and Punta Carnero Formations and

Tinajitas Member of Caratas Formation). On

Margarita Island, the sandy and carbonate-

rich turbidites of the Pampatar (sandy rich)

and Punta Carnero (carbonate rich)

Formations represent a separate sedimen-

tation from the Guárico and Roblecito, both

in time and space, and are probably related

to accretion near Barbados.

Figure 1.13 summarizes conceptually

the relationship between stratigraphic units

and deformation fronts. Figure 1.14 sum-

marizes the Paleocene-Eocene stratigraphic

nomenclature, emphasizing the potential

character of each unit as a seal or reservoir.


?

?

?

San Juan

Vidoño

Caratas

Tinajitas

?

La Pascua/ Los Jabillos?Roblecito

PeñasBlancas

?

Guárico

Cerro Misión

La Victoria

Santa Rita

?

Colón

Trujillo

Humoca

Mora

nro

Valle

Hondo

(Misoa/Qda. Arriba/Gobernador)

Masparrito

PagüeyMene Grande

Paují

Caús

Carbonera CarboneraPaují

(Mirador/La Sierra) (Misoa/Mirador)

Los Cuervos

Marcelina

Colon/mito Juan

Western Venezuela:Trujillo, Lara and South-Andean

Flank and Barinas-Apure Falcón Eastern Venezuela

(?) Garrapata

?

?

Seal

Eroded Interval

Eroded/Unconformable

Reservoir (Carbonate)

Reservoir (Sandy)

Sand/Seal Pairs

Colón/Mito Juan

Age

Eocene

Paleocene

Maastricht

Western Venezuela: Perijá, LakeMaracaibo, North-Andean Flank

BarcoGuasare Barco

OROCUE

North-CentralVenezuela

Los Cuervos

Jarillal

OROCUE

?

?

Figure 1.14

Correlation chart for the

Paleocene-Eocene of

Venezuela. The Colón

Formation extends into the

Campanian; the Carbonera,

Paují, La Pascua, Roblecito

and Los Jabillos Formations

extend into the Oligocene.

The Guárico Formation may

reach down to the top of the

Maastrichtian wherever the

Garrapata Formation is

absent.

Oligocene of Western and North-Central

Venezuela. Since the Oligocene, the

sedimentary accumulation in Maracaibo

Basin was preserved mainly on its flanks. To

the west are the sandy clastics of the

Carbonera and Ceibote Formations (El

Fausto Group), to the south and east are the

fine clastics of the León Formation (Fig.

1.15), and to the center is the Icotea

Formation (assigned by several authors to

the Oligocene). The Icotea is only found in

structurally controlled depressions, and its

characteristic lithology consists of siltstones

and claystones, with minor proportions of

sandstones.

The Falcón Basin reached its maximum

development and deepening during the

Oligocene. The sedimentation in the Falcón

region resulted from a different tectonic

setting than that of the Maracaibo Basin,

Barinas-Apure and Eastern Basins. Figure

1.16 shows the extensional basins associated

with major strike-slip faulting, especially in

the north of Falcón State. These gradually

evolved to the east, while the Caribbean

plate moved in the same direction.

In the north of central Venezuela, the

trough containing the Roblecito Formation

migrated to the east and southeast, favoring

the advance of La Pascua sandstones to the

south. These were followed and overlaid by

clastics from the foredeep.

Oligocene of Eastern Venezuela. During

the latest Eocene and Oligocene, the

sedimentation in the Interior Mountain

Range is represented by the Los Jabillos

(diverse sandy clastics), Areo (fine marine

and glauconitic clastics) and part of the

Naricual (shallow marine and coastal-fluvial

pelitic and sandy clastics) Formations.


131

Positive Areas

Thrust Front

Depocenter Axis

Extensional Basin


Area Positive

PositiveArea

Positive Area

El BaúlArc

La Pascua

Carbonera

León Guafita

San Luis / Patiecitos

Pecaya/Agua Salada

Churuguara

CasupalCastillo

Positive Area

GuayanaShield

Shallow SandyClastics

Sandy and PeliticClastics of Shallow andDeep Environmen(Turbidites)

Pelitic Clastics ofShallow Marine Environment

Limestones

Direction ofSediment Supply

0 50 km

?

??

??

?

?

?

Colombia

?

Guacharaca

El Paraíso

Roblecito

N

Figure 1.15

Oligocene-Miocene Caribbean Plate

Oca Fault System

South American Plate

UrumacoTrough

La Vela Cove

La Pascua-Roblecito

Frontal Thrust Advance

(Central-North)

Capiricual-Carapita(Eastern)

ExtensionalTrough

Positive AreasShallow ClasticSediments Plate Movement

Vectors

200 km

N

Basin"Foreland"Incipient

Thrust Front

MainDepocenter

Figure 1.16

Sedimentary regional framework in Western Venezuela (Maracaibo, Falcón, Barinas-

Apure Basins and Guárico Sub-Basin) during the Oligocene. The main depocenters

are located in Táchira (León Formation), Falcón (Pecaya and Agua Salada Formations)

and Guárico (Roblecito Formation).

Maximum development of the Falcón State pull-apart and generation of extensive positive

areas in Maracaibo Basin and northern Falcón. Toward the south and east, the foreland

basin evolved, developing "troughs" like those of the La Pascua-Roblecito Formations (Late

Eocene-Oligocene) and Carapita-Capiricual (Early-Middle Miocene) (after Macellari, 1995).

Figure 1.18

1 14

Figure 1.17 summarizes conceptually

the relationship between the stratigraphic

units and deformation fronts. The double

sediment source for the Naricual Formation

and its equivalents (e.g., Quebradón

Formation) is shown—on the north side is a

fold-and-thrust belt source, and on the south

side is a Cratón Interior source. Something

similar occurs with the La Pascua and

Roblecito Formation equivalents, called the

Merecure Formation in the subsurface of the

southern flank of the Maturín Basin.

Following the diachronism principle, it is

assigned a younger age (Miocene), similar to

the surface Merecure Group.

Figure 1.18 summarizes the Oligocene

stratigraphic nomenclature, characterizing the

units as potential seals or reservoirs.

Neogene and Quaternary

In Venezuela, the Neogene is

characterized by important mountain-

building episodes, which are a direct

consequence of the Caribbean and South

American plate interactions. Figures 1.15 and

1.16 show in a general way the beginning of

the Andean uplift, and the structures

generated by the eastern movement of the

Caribbean plate between the North

American and South American plates during

the Late Oligocene to Early Miocene.


Regional geologic framework for the sedimentation at the north flank of the Eastern

Basin of Venezuela during the Oligocene. There is a strong difference between the

Naricual in the subsurface and as defined in its type region: the "Merecure Formation"

name has been used for subsurface equivalents of the Merecure Group formations

(Los Jabillos, Areo and Naricual Formations) that crop out in the Interior Range.

X X X

vv

Extinct Island Arc Limit of the Caribbean Deformation

Caribbean Plate

Slo

pe

Naricual/Quebradón

?

?

?

N

??

La PascuaClastic Shelf/Transitional

Environment/Deltas

Barcelona Los Jabillos

Merecure/"Naricual"

Chaguaramas

Merecure

Direction of SedimentSupply

Positive Areas

Thrust Front

Silt-clay Clastics Predominate overthe Sand Fraction (Slope Environment)

Shallow Sandy Clastics

0 50 km South American PlateOligocene

Roblecito Areo(?) Areo(?)

Activ

e Islan

dA

rc

Figure 1.17

Eroded/Unconformable Contact

Sandy Reservoir

Sand/Seal Pairs

Seal

Eroded Interval

Age

Oligocene

Late Eoc.

Western Venezuela Perijá

Lake Maracaibo, North-Andean Flank

Western Venezuela Falcón Basin

Ceibote

León

Car

bo

ner

a

Paují/Mene Grande

Carbonera

?

PALMAR/PARANGULA

El Paraíso

(Churuguara/Castillo/Pecaya/San Luis/Agua Salada)

Naricual

Quebradón

Roblecito

La Pascua?

Naricual

Areo

?

Los Jabillos

Palmar Palmar/ParángulaG

u

a

fGuardulio

Caratas/Roblecito ?

MERECURE

?

Pagüey(?)

Western Venezuela, Trujillo, Lara, South-Andean Flank

and Barinas-Apure

North-CentralVenezuela Eastern Venezuela

?

Icotea

Arauca

t

a

i

Correlation chart of the most important Late Eocene through Oligocene units of Venezuela. Paují, Mene Grande and Pagüey Formations

extend into Middle Eocene; El Fausto Group and Churuguara, Castillo, Pecaya, San Luis, Agua Salada and Quebradón Formations extend

into the Miocene.

Figure 1.18

1

During this time, extensional (Falcón Basin)

and foreland basins were created. In

Western Venezuela, the Barinas-Apure

foreland basin was influenced by the

formation of the Colombian and Venezuelan

Andes. The Eastern Venezuela basins

resulted from the oblique collision between

the Caribbean plate and the northwestern

margin of the South American plate. In the

Pliocene (Figs. 1.19 and 1.20), the uplifting

of Northern Venezuela produced the

present-day distribution of petroleum basins

(Fig. 1.21) and generated the La Costa and

Venezuelan Andes mountain ranges

(dividing the Maracaibo and Barinas-Apure

Basins). Figure 1.22 summarizes the

Neogene and Pleistocene stratigraphic units,

showing their potentiality as source rocks,

seals or reservoirs.

In Western Venezuela, the Andean uplift

produced significant thicknesses of molasse

sediments (Guayabo Group, and La Villa, La

Puerta and El Milagro Formations—Fig. 1.22).

In places, both the North-Andean and South-

Andean flanks have molasse sediments that

reach more than 5 km thick (15,000 ft). In the

Perijá Mountain range, the El Fausto Group is

the molasse-equivalent unit, and is related to

the mountains of the deformation front on

the west side of Maracaibo Basin.


15

?

?

Continental Environment Conglomeratesand Sandy Clastics

Deltaic-Fluvial Environment, Sandand Pelitic Clastics

Open-Marine and Foredeep Environment,Pelitic Clastics

Sediments Supply

Fluvial and Coastal Environment Sandy Clastics

Shallow Environment Carbonates

Positive Zones

Thrust Front

El Pilar Fault

Oficina-FreitesMerecure

El Baúl Arc

Per

ijá R

ange

Chaguaramas

AndesColom

bia

Caribbean PlateAgua Salada

Capadare

Barb

ados

Pris

m

La Costa Range

Coro

0

50

100

150

200 km

UrumacoCaujaraoSocorro

CapiricualQuiamareQuebradón

Quiamare

Carapita La Pica

Isla

nd A

rc

La RosaLagunillas La Puerta

LakeMaracaibo

GUAYABOMérida

Oca Fault

Quiriquire

Guayana Shield


N

Las Piedras

Parángula- Río Yuca

El Baúl Arc

QuebradónQuiamare

Merecure

Guayana Shield


Guayana Shield

Barb

ados

Pris

m

Isla

nd A

rc

CarapitaLa Pica

CapiricualQuiamare

QuiriquireLas Piedras

El Pilar Fault

MerecureChaguaramas

Oficina-Freites

Andes

MéridaGUAYABO

La RosaLagunillas La Puerta

LakeMaracaibo

Perij

á Ra

nge

La Costa Range

Oca Fault Capadare

UrumacoCaujaraoSocorro

Agua Salada

Colombia

Caribbean Plate

Coro

0

50 150

100 200 km

Parágula-Río Yuca

?

?

Continental Environment Conglomeratesand Sandy Clastics

Deltaic-Fluvial Environment, Sandand pelitic Clastics

Open-Marine and Foredeep Environment,Pelitic Clastics

Fluvial and Coastal Environment Sandy Clastics

Shallow Environment Carbonates

Positive Zones

Regional geologic framework for the sedimentation in all Venezuela (Maracaibo, Falcón, Barinas-Apure and Eastern basins) during the

Miocene-Pliocene. The largest accumulations of continental sediments occur on the flanks of the Andes and La Costa Range. The most

important reservoirs of Venezuela were deposited during this epoch: La Rosa, Lagunillas, Isnotú (Guayabo Group), Carapita, Oficina,

Chaguaramas and Merecure Formations.

Figure 1.19

1 16

The La Rosa and Lagunillas Formations

predate the distal environments of the Perijá

and Andes molasses. The La Rosa Formation,

with its basal sandstones (Santa Bárbara

Member), is of major petroleum importance.

Its characteristic “middle shale” interval has

lateral sandy variations that are important res-

ervoirs in the eastern coast of Lake.

Maracaibo. Its thickness varies from 70 to

1100 m (230 to 3600 ft) because the unit was

deposited over an irregular erosional surface

and is fault-controlled. The La Rosa

Formation is believed to be Early to Middle

Miocene age (20 to 15 Ma).

The Lagunillas Formation overlays

the La Rosa and consists of transitional

shallow, coastal, and continental sediments

that reach more than 1000 m (3280 ft) thick

in the center of Maracaibo Basin.

It is a very important reservoir in the eastern

coast fields, where it has been divided into

five members, all of which have oil

potential. It is equivalent in age (Middle to

Late Miocene—15 to 6 Ma) to the La Puerta

Formation and part of Guayabo and El

Fausto Groups.

In the Barinas-Apure Basin, the

Parangula and Río Yuca Formations

(continental sediments) are the distal

equivalents of the Guayabo Group.

In the Falcón region, open sea

environments can be found, ranging from

deep-marine turbidites (e.g., Pecaya Forma-

tion) to shallow clastics (e.g., Cerro Pelado

Formation) and carbonates (e.g., San Luis

Formation). The final filling of the Falcón

Basin during the Pliocene was with the

conglomeratic-marine clastics of La Vela

Formation and the continental Coro

Conglomerate (Pliocene-Pleistocene).

In North-Central Venezuela, the main

environments of deposition are fluvial and

continental, resulting in the upper Que-

bradon and Quiamare Formations. They

increase in thickness considerably to the east

and south.


Pliocene/Recent

BoconóFault

San SebastiánFault

Andes

South-AmericanPlate

Trujillo

Range

FalcónBasin

200 km

N

Positive Areas Thrust FrontShallow ClasticSediments Plate Movement

Vectors

MaracaiboBasin

Maximum Subsidence Areas

Caribbean Plate

Oca Fault

Curazao Prominence

North of Venezuela Deep

Figure 1.20

72˚ 68˚ 64˚ 60˚

72˚ 68˚ 64˚ 60˚

11˚

7˚

11˚

7˚

Guayana

Massif

Colombia

Barinas-ApureBasin

S. Cristóbal

Barinas

Trujillo

Venezu

elan Andes E.B.L

La Costa RangeMaracaiboBasin

Perij

á Ra

nge

MaracaiboFalcónBasin Caracas

Cumaná La Costa RangeBarcelona

MaturínGuárico

Sub-basin

Eastern Basin

Porlamar

MargaritaBasin

Caribbean Sea

TrinidadAtlantic

Ocean

Orinoco Belt

Coro

Guy

ana

0

50

100

150

200 km

MaturínSub-basin

SanFernando

Orinoco River

N

Ciudad Bolívar

Rec

lam

atio

nZo

ne

Figure 1.21

Venezuelan petroliferous basins on the basis of its Sedimentary Provinces (after

Pérez de Mejía et. al., 1980). E. B. L. = El Baúl Lineament, Eastern and Barinas-

Apure basins limit.

Northern Venezuela regional

filling of the foreland basins

and uplifting due to the

deformation of extensive

areas associated with the

Bocono, San Sebastián and

Oca fault systems.

Extensional basins persist

north of Falcón State (after

Macellari, 1995.)

To the south of the Guárico Mountain

front, in the Guárico and Maturín Sub-Basins

(including the eastern Interior Mountain

Range), transitional deltaic to shallow-

marine environments are represented by the

Merecure and Oficina Formations (Guárico

and western Anzoátegui States). They are

both of great importance as petroleum

reservoirs. These units change gradationally

to the east to deeper-water environments

represented by the Capiricual and Carapita

Formations. The Carapita Formation is a

distinctive turbidite unit and is also of great

petroleum importance.

To the south, in the Oficina fields and

the Orinoco Belt, are found the diachronical

younger equivalents of the Neogene cycle.

The basal unit, usually discordant over the

Temblador Group, is the sandy Merecure

Formation, and overlying it is the deltaic

Oficina Formation. The Miocene equivalents

of these units in the Guárico Sub-

Basin–Orinoco Belt have been named the

Chaguaramas Formation.

To the northeast, the Maturín Sub-Basin

is filled with shallower facies, such as the

Uchirito and Quiamare Formations in its

northern flank. The Quiamare Formation

represents a great variety of environments:

lagoon, fluvial channels and alluvial fans,

reaching several kilometers in thickness in

Eastern Anzoátegui. On the southern flank,

the Freites Formation shales overlie the

Oficina Formation. These shales are

eventually overlain by the deltaic La Pica

Formation and the molassic Morichito, Las

Piedras and Quiriquire Formations (Pliocene

age). The sedimentary cycle ends with the

Mesa Formation of Pleistocene age.


171

AgePleistocene

Pliocene

LateMiocene

MiddleMiocene

EarlyMiocene

Perijá and Lake Maracaibo Andes Barinas-Apure Falcón Guárico

Sub-BasinMaturín

Sub-BasinInteriorRange

El Milagro

LA PUERTA (*)

La Villa,Los Ranchos,

Lagunillas

EL FAUSTO/La Rosa

Terrazas

?

Betijoque

Isnotú

Palmar

GUAYABO

Parángula

Río Yuca

Guanapa

San Gregorio/Coro

LA PUERTA/Codore/La Vela/Urumaco/

Caujarao

AGUA SALADA

SocorroCerro Pelado

Castillo/Agua ClaraPedregoso/San Luis

Guacharaca

Chaguaramas

Mesa

Las Piedras

La Pica

Freites

Oficina

MerecureCarapita

Uchirito/Capiricual

Quiamare

(N) (S)

Car

apit

a

Las Piedras/Quiriquire

Reservoir (Sandy)

Sand/Seal Pairs

Seal

Source RockReservoir (Carbonate)

?

?

(*) Group

Figure 1.22

Correlation chart of the

most important units in the

Venezuelan Neogene. (N)

and (S) indicate northern

and southern flanks of the

Maturín Sub-Basin.

The El Fausto Group,

and the Palmar, Guaharaca,

Chaguaramas and Merecure

Formations extend into

Late Oligocene.

Figure 1.23

1 18

The beginningBefore the 1800s, only brief references

were made to Venezuelan hydrocarbons in

the literature. The first mention of hydro-

carbons was made by Fernandez de Oviedo

in 1535, where he wrote of oil seepages off

the western shore of Cubagua Island. In 1540,

he referred to the presence of bitumen on the

Gulf of Venezuela shores (Martínez, 1976).

Nothing more is found in the literature until

the early 1800s.

1800 to 1900 In 1814, Alexander von Humboldt

reported asphalt deposits along Venezuela’s

northern shoreline (Martínez, 1976).

Geologist Herman Karsten (1851) published

a description of oil seepage sites located

between Betijoque and Escuque, towns in

Trujillo State, southeast of Lake Maracaibo

(Urbani, 1991).

Oil seeps along La Alquitrana Creek in

Táchira State lured local investors into apply-

ing for an exploitation concession under the

name of “Cien Minas de Asfalto.” It was

granted to them in 1878 (Martínez, 1976).

Compañía Minera Petrolia del Táchira

exploited this concession by “open mining”

until 1883, when the first well which

produced oil, Eureka-1, was completed.

Eureka-1 had a production of 1.5 bbl (194

liters) per day (Méndez, 1978). Previously

Salvador-1, the first well drilled in Venezuela,

had been abandoned as dry by this company

after reaching a final depth of 53 m. These

wells were drilled with a percussion rig, the

first oil drilling rig in the country.

1901 to 1920Well locations were chosen by surface

geology and direct hydrocarbon observation

during the first decades of this century.

Bababui-1, a 188-m (617-ft) deep well,

discovered the Guanaco oil field in 1913.

Mene Grande, near Lake Maracaibo’s eastern

shoreline, was the first giant find in

Venezuela (Fig. 1.25). The discovery well

was Zumaque-1, a 135-m (443-ft) well,

drilled after a recommendation by geologist

Ralph Arnold. Arnold and a team of about 50

colleagues systematically explored more than

50 million hectares assigned to General

Asphalt (later Caribbean Petroleum) all over

Venezuela. Of these, 512,000 hectares were

selected for exploitation. Totumo, discovered

in 1913, was the first producer from the

basement, and La Rosa Field, found by the

well Santa Bárbara-1 drilled in 1917, was the

first of a giant later recognized as the Bolívar

Coastal Field (BCF). BCF covers an extensive

land and offshore region on the eastern coast

of Lake Maracaibo. The maximum depth

reached by an exploratory well by 1917 was

1,400 m (4,600 ft).

1921 to 1940From 1920 onward, surface exploration

activity increased (Fig. 1.23). Efforts were

concentrated on Zulia and Falcón States in

western Venezuela, and northern Anzoátegui

and Monagas States in Eastern Venezuela.

T H E H I S T O R Y O F O I L E X P L O R A T I O N I N V E N E Z U E L A

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

100

0

200

300

400

500

600

700

Cre

w -

mo

nth

Wo

rld

War

I

Gre

at D

epre

ssio

n

Wo

rld

War

II

Mas

sive

co

nce

ssio

ns

En

d o

f c

on

cess

ion

s

O.P

.E.P

. Fo

un

dat

ion

Nat

ion

aliz

atio

n

Surface geology

Seismic (2-D + 3-D)

Gravimetry (+magnetometryfrom 1936)

Year

Figure 1.23

Exploratory activity in

Venezuela. Surface methods.

(Source: Martínez, 1976 and

1994; M.E.M., 1985 to 1995;

J. Méndez Z., 1976 and R.

Varela, 1987, in Méndez Z.,

1989; M.M.H.,1962 to 1984).

1

Pioneering gravimetric surveys started in 1924

and contributed to the identification of

regional highs, mainly of igneous-

metamorphic basement close to the surface.

As a result of the surface exploration effort

and subsequent exploratory drilling during

the 1920s, several important discoveries

occurred: La Paz in 1923, and La Concepción

in 1925, in Zulia State; Quiriquire in 1928, in

Monagas State (a giant oilfield in a Pliocene

alluvial fan), and Pedernales (Delta Amacuro)

in 1933, in an anticline produced by mud

diapirism. Other relevant discoveries during

this period were the Bachaquero area (now

within BCF, Zulia) in 1930, and Cumarebo

Field (Falcón State) in 1931.

The year 1933 heralded the beginning of

the use of seismic as a surface tool for

exploration (Fig. 1.23), and results were

quickly seen. Large discoveries occurred in

Eastern Venezuela: in 1936, Temblador, the

first field discovered in southern Monagas; in

1937, the first field of the Greater Oficina

Area was discovered in Anzoátegui State; and

Jusepín Field was found in northern Monagas

in 1938.

Surface geology continued to render

benefits in Monagas: Santa Ana, the first field

of the Greater Anaco Area, was found in

1936; and El Roble and San Joaquín were

found in 1939. Subsurface geology methods,

using regional knowledge, data from core

and ditch samples obtained during drilling,

and electrical well logging as of 1929, gave

very significant results. Some of the

discoveries include Orocual Field (Monagas)

in 1933, and the Eocene Misoa Formation oil

sands of the LL-370 Area (Lagunillas, BCF,

Lake Maracaibo) discovered in 1938. The

maximum exploratory drilling depth reached

by 1940 was 3,400 m (11,150 ft) (Fig. 1.24).

1941 to 1950The exploratory activity during this

decade was affected by World War II and the

post-war world, with large oil needs

prompting an increase in exploratory drilling

(Fig. 1.24). Surface exploration, however,

diminished, since most of the field personnel

went to war. It was not until the end of

WWII that surface activities showed a strong

upward rebound, reaching levels never

before seen in Venezuela (Fig. 1.23). With an

increase in exploratory drilling after the war,

reserves and production doubled during the

decade (Fig. 1.26), and 63 fields were found.

This compares to the 41 fields found from

1880 to 1940. The three most relevant

discoveries were the Las Mercedes Field

(Guárico State) in 1941, commercial oil in

the Cretaceous of La Paz Field (Zulia State)

in 1944, and the giant accumulation of extra-

heavy crude in Boscán (also in Zulia State),

in 1946.


19

Nu

mb

er o

f ex

plo

rato

ry w

ells

per

yea

r

300

200

100

01910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Maxim

um

dep

ths reach

ed

km

1

2

3

4

5

6

7

Wo

rld

War

I

Gre

at D

epre

ssio

n

Wo

rld

War

II

Massiveconcessions

End ofconcessions

Nationalization

Evaluation ofthe Orinoco

Belt

Year

Figure 1.24

Exploration drilling in Venezuela. (Source: Martínez, 1976 and 1994;

M.E.M., 1985 to 1995; Méndez Z., 1976 and Varela, 1987, Méndez Z.,

1989; M.M.H.,1962 to 1984).

1 20

Exploratory drilling added more fields to

the Greater Areas of Oficina, Anaco and Las

Mercedes. The new Hydrocarbons Law of

1943 provided for the duration of all existing

concessions to be extended 40 more years, a

positive move for the oil industry, although

the state’s share in exploitation benefits was

increased by way of taxes. In addition,

abundant new concessions were granted

during 1944 and 1945, which also had a

significant positive effect on exploration.

From 1945 on, exploratory evaluation

intensified and all technology on hand was

applied. Gravimetry and seismic surveys

were carried out in areas offshore of Lake

Maracaibo, and aerial magnetics and other

advanced techniques under development

were tested in Venezuela. These tech-

nologies contributed to a significant increase

in the regional knowledge of the Venezuelan

sedimentary basins. Exploration drilling rigs

reached depths of approximately 5,200 m

(17,000 ft), as can be seen in Fig. 1.24.

1951 to 1960The oil from the Middle East, less

expensive and of good quality, affected the

intensity of Venezuelan exploration, and

surface activity was reduced by more than

half (Fig. 1.23). However, drilling activity

maintained a high level during the decade.

New concessions granted in 1956 and 1957

kept the interest in Venezuelan oil high

throughout the rest of this decade.

Discoveries continued in the Greater Oficina

Area and, to a lesser extent, in Guárico.

During 1957 and 1958, the Lake Maracaibo

region yielded large Tertiary finds in its

central and central-eastern areas, including

Ceuta, Centro, Lama, Lamar and Lago Fields.

The first Venezuelan continental platform

find was Posa-112A, an offshore field in the

Gulf of Paria. The maximum exploratory

drilling depth reached during this period

was 5,348 m (17,541 ft).

1961 to 1976The “no more concessions” policy

adopted by the Venezuelan State greatly

affected the operating strategies of the

concession holders during this pre-

nationalization period. A drastic reduction in

surface exploration activities is shown in Fig.

1.23. By 1968, exploratory drilling reached

the lowest level of activity since 1940.

Exploratory wells were restricted to already

identified areas, with their objectives being

new reservoirs above, below or near known

oil reservoirs. This type of exploration

yielded discoveries such as the deep

Cretaceous in Central Lake and Urdaneta

Fields. Frontier drilling and surface

exploration activities by the concessionaires

ceased completely.


1.500

Millio

ns o

f barrels

Mill

ion

s o

f cu

bic

met

ers

per

yea

r

300

Note: From 1914 to 1954a total of 3.0 billion cubic

meters were incorporated into the reserves through revisions, new

discoveries and extensions.

Men

e G

ran

de

C.C

. Bo

lívar

Los

Bar

roso

s–2

La P

azLa

Co

nce

pci

ón

Qu

iriq

uir

eB

ach

aqu

ero

Ped

ern

ales

La C

ano

a–1

Ofi

cin

aJu

sep

ínLa

s M

erce

des

La P

az a

nd

Mar

a (K

)B

osc

ánLa

Paz

an

d M

ara

(Bas

emen

t)U

rdan

eta

Lam

a, C

entr

oO

rocu

al,

Lam

ar,

Job

o–M

ori

chal

On

ado

Su

r d

el L

ago

Cer

ro N

egro

Pat

aoR

ío C

arib

eLo

ran

, co

cuin

aG

uaf

ita

Inco

rpo

rati

on

of

El F

urr

ial

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

200

100

0

1.000

.500

0

Year

Figure 1.25

Reserves from exploratory

drilling in Venezuela.

(Increments and revisions not

included). (Sources: Martínez,

A.R., 1976, 1987 and 1994;

M.E.M., 1985 to 1995;

M.M.H., 1962 to 1984).

The Corporación Venezolana del

Petróleo (CVP), the Venezuelan State oil

company, was founded in 1960 and started

operations the following year. This company

became the leader in exploration on land

and offshore Venezuela. It acquired 80,000

km of seismic and drilled nearly 200

exploratory wells during this period

(Velarde, 1991). CVP started exploration of

the La Vela area, offshore Falcón State, in

1972, and the evaluation of southern Lake

Maracaibo in 1971 by means of service

contracts. After a bidding process, service

contracts were signed the same year.

A significant discovery during the

period, besides findings in the above-

mentioned La Vela and southern Lake areas,

was Onado Field (1971) in Monagas State.

The exploratory drilling record was 5,813 m

(19,067 ft) in 1976.

CVP and the Ministerio de Minas e

Hidrocarburos started evaluating the Orinoco

Belt by seismic surveys and drilling. By then,

about 60 wells had been drilled by the

concessionaires in the so-called Tar Belt, and

most of them had been abandoned without

testing. The La Canoa 1, a 1,176-m (3857-ft)

deep exploratory well, tested 6 m3 (40 bbl)

per day of 7˚API gravity before being

abandoned (Martínez, 1987). This well,

located in southern Anzoátegui, is

considered to be the discovery well of the

Faja del Orinoco.

1976 (nationalization) to the present

By 1978, state-owned Petróleos de

Venezuela, S.A., a holding in charge of the

nationalized oil industry, assigned the Orinoco

Belt to its existing operating affiliates:

Corpoven, Lagoven, Maraven and Meneven.

They each proceeded to evaluate their

assigned portion. The campaign was finished

five years later (Fig. 1.24) after 669 wells were

drilled, and 15,000 km of Vibroseis seismic

lines and 54,000 km2 of aerial magnetics were

acquired (Martínez, 1987).

Since the nationalization, surface explor-

ation is based almost exclusively on geo-

physics, remote sensing and geochemistry. It

steadily increased until the 1980s (Fig. 1.23),

when it reached its maximum level for the

last 15 years. This activity was directed

toward frontier and traditional areas. 3-D

seismic has been used since the 1980s as an

additional tool for both exploration and

reservoir description.


211

Cu

mu

lati

ve p

rod

uct

ion

an

d r

eser

ves

at y

ear

end

(B

m3 )

5

0

10

BS

TB

70

60

50

40

30

20

10

019201910 1930 1940 1950 1960 1970 1980 1990 2000

Massiveconcessions

O.P.E.P. FoundationEnd of concessions

Production

Reserves

Year

Figure 1.26

Production and reserves in

Venezuela. (Sources:

Martínez, A.R., 1994;

M.E.M., 1985 to 1995;

M.M.H., 1962 to 1984).

1 22

Exploratory objectives have become

deeper and more remote, as the most

significant recent finds show (Fig. 1.25).

These include Patao and other giant gas

fields offshore north of Paria Peninsula (1979

to 1982); Río Caribe condensate accumu-

lation also in the same region (1981); Morro

heavy oil in the Gulf of Paria (1980), and

Loran and Cocuina, gas accumulations east

of Delta Amacuro (1983) (Fig. 1.0). Northern

Monagas and Anzoátegui, both in Eastern

Venezuela, contain the largest discoveries

since 1986 along the El Furrial Trend:

Tertiary and Cretaceous reservoirs that are

more than 4,000 m deep. Western

Venezuela’s Guafita and Victoria findings

near the Colombian border are also quite

significant. An exploratory drilling depth

record of 6,640 m (21,780 ft) was set in 1993.

What now?The future points to more discoveries in

the above frontier areas, as well as

exploration and re-exploration in traditional

areas near existing facilities. New, high-risk

objectives will become the standard of day-

to-day exploration activities; exploration for

bypassed hydrocarbons already has high

priority. Modern drilling technology will

allow deeper and more precise subsurface

evaluation. Improved knowledge of

Venezuelan basins, supported by new

geological and geochemical criteria, and

new seismic acquisition and processing

technologies, will open new frontiers and

substantiate re-exploration. Modern

petrophysical well logging technologies,

some of which are described in other

chapters of this book, already permit

measuring and interpreting a large variety of

rock and fluid properties. Their proper use

will further enable us to accurately assess

the subsurface. Venezuela still has a wealth

of hydrocarbons to be discovered. Figure

1.27 displays graphically the exploratory

success during the last 45 years, showing an

almost 47% success rate with no downward

trend, and Fig. 1.26 shows nearly 1 billion

barrels of oil added during the period. This

is the result of integrating all technologies,

from exploration through enhanced oil

recovery. Venezuelan oil provinces have not

yet disclosed all their secrets; only by using

modern exploration technologies will they

be revealed.


0.50

0.48

0.46

0.44

0.42

0.40

0.38

1950 1960 1970 1980 1990 2000

Nu

mb

er o

f d

isco

veri

esTo

tal n

um

ber

of

exp

lora

tory

wel

ls

YearCumulative exploratory

success since 1950, showing

an almost 47% success rate

with no downward trend

(from M.E.M., 1985 to 1995;

M.M.H., 1962 to 1984).

Figure 1.27

1


23

��

Ag

e

Sou

rce

Roc

k

Res

ervo

ir

Sea

l

Form

atio

n

Thic

knes

s (m

)

Mem

ber

Gra

ph

icLi

tho

log

y

Cre

tace

ou

s

A p

ó n

L i s

u r

e

Maraca

La L

una

M i

s o

a

"C S

and"

"B S

and"

Icotea

La R

osa

L a

g u

n i

l l a

s

Lithological Description

Guasare

Col

ón/

Mito

Jua

n

T e

r t

i a

r y

Socuy

Bac

haqu

ero

300-

900

250

1000

-160

0

120-445

900

100-

300

120

55-1

8050

0-60

0m

RíoNegro

Shales, claystone, weakly consolidatedsandstones, and some interstratified lignites.

50-180

Lagu

na

Lower

Guáim.

Pic

hé

Tib

ú

Sta.Bárbara

Middle

Upper Marine shales with iron-rich concretions;variable amounts of interstratifiedsandstones.

Siltstones, hard shales/mudstones andsandstones.

Intercalation of sandstones, siltstones and some limestone layers in the lower part.

Fossiliferous limestones and calcareoussandstones.Dark and massive microfossiliferous shales, with some thin sandstones and limestone layers.Fetid calcareous limestones and shales,elliptical concretions.

Crystalline limestones with Ostrea Sp., with shale and marl intercalations.

Glauconitic sandstones and sandy limestones, with sandy laminated mud intercalations, and some shelly limestone layers.

Fossiliferous massive limestones, nodular, marly and often calcareous shales.

White coarse-grained sandstones.

��

��

��

��

<180

Figures 1.28 and 1.29

Lake Maracaibo composite stratigraphic column (from Parnaud et al.,

1995, González de Juana et al., 1980, and Roger et al., 1989).

** C t t b Rí N

Bar

co L

os

Cu

ervo

sM

irad

or

Early

-Mid

dle

Eoce

neE

oc.

Pal

eoce

ne

Cre

tace

ou

s

Coarse-grained sandstone toconglomerate.Shaly intervals.

Carbonaceous shales andsiltstones.

Productive interval.Porosity 7.1–20%.Average permeability 149 md.

Carbonaceous sandstones,siltstones and shales.

Ag

e

Sour

ce

Res

er.

Sea

l

Form

.

Th

ick.

(ft)

Lithology


La L

un

aC

OG

OLL

O

250-

650

100-

130

70-1

2010

0 -

300

Hard bluish-gray limestone and few intervals of sandy and calcareous shales.

Calcareous sandstones,glauconitic, sandy andcoquinoid limestones withsome shales.

Thick beds of sandylimestone.

Dense, laminated limestone,dark gray to black,carbonaceous to butiminous,calcareous shales.

Sandy shales; the sand and silt content increase to the top.

Ap

ón

Lisu

reM

arac

a

***

****

****

* *

*

* C b

Mio

cen

eO

ligo

cen

e-M

ioce

ne

EL

FAU

ST

OP

ero

cM

aco

aC

uib

aLo

s R

anch

os

1100

-120

016

0-40

029

5-33

010

6-30

0²6

0033

5-52

015

0-27

815

0-20

050

0-90

013

00-1

500

Sandstones and gray shales with lesser amounts ofsiltstones and conglomerates.

Variegated claystones, red topurple, sandstones andlignites.

Claystones with some siltstones and sandstones.

Claystones and variegatedsiltstones. Thin sandstonesand lignites (scarce).

��

�� Sandstones and conglomerates.<100

*** C ló Mit J

Composite stratigraphic column of the Maracaibo

Basin to North Andes flank (after González de

Juana et al., 1980).

Figure 1.30

1 24

Maracaibo BasinThe Maracaibo Basin (Fig. 1.21) is the

most important petroliferous basin of Vene-

zuela. The main source rock is the La Luna

Formation (Figs. 1.28 and 1.29) of Late Creta-

ceous age; its facies extend along all of

Western Venezuela and Colombia. There are

some other source rocks of secondary import-

ance in the Cogollo (Machiques Member of the

Apón Formation) and Orocué (Los Cuervos

Formation) Groups. The oil was generated,

migrated and accumulated in several phases,

the Andean uplift being the most important

one. These points will be elaborated later.

The main clastic reservoirs are the Río

Negro and Aguardiente Formations (Creta-

ceous), Orocué Group (Paleocene), Mirador-

Misoa (Eocene), Lagunillas and La Rosa

Formations (Miocene) (see the stratigraphic

columns in Figs. 1.28—Perijá/Lake Maracaibo

—and 1.29—North-Andean Flank). The

outstanding carbonate reservoirs belong to the

Cogollo Group (Early Cretaceous). The most

important regional seals are the Colón (Late

Cretaceous) and Paují (Eocene) Formations.

P E T R O L E U M B A S I N S M A R A C A I B O

E

0

1

2

3

4

5

6

1.8 Km

La VillaLos Ranchos

PerijáRange

Miocene

Paleocene

El Fausto

W

10 km

Post-Miocene

Icotea High Lagunillas

Bachaquero Fault

TrujilloRange

La PuertaLagunillas

La Rosa

Paují

Trujillo

Misoa

Eocene

Jura

ssic

Shaly (Seal)

Sandy / Conglomeratic

Carbonate

Source Rock

Sand/Seal Pairs

Urdañeta

Cretaceous

"B"

"C"

"B"

"C"

Lama

Two

way

tim

e (

sec)

Basement

Misoa

Geological timescale

Petroleumsystem events

Formations

Source rock

Seal

Reservoir

Burial

Trap formationGeneration,migration,

accumulationPreservation

Critical moment

200 150 100 70 60 50 40 30 20 10 0

QCenozoic

MioceneOlig.EocenePaleo.Tertiary

MesozoicTr JL E M L E

KL PP

(Ma)

Note: The sequence ofevents in the petroleumevents system is asfollows: the sedimentaryrecord is indicated in therow named "Formations;"in this case there is sed-iment preservation bet-ween the Early Creta-ceous and the Late Pa-leocene, followed by a 5to 6 Ma hiatus; thenthere are sedimentspreserved between theEarly Eocene and the Eo-cene-Oligocene limit.The source rock is gen-erated at the end of theEarly and part of the LateCretaceous. The seal isdeposited at the end ofthe Late Cretaceous andEocene times. Reservoirrocks are depositedduring the Late Creta-ceous and Eocene. Thesource rock in this

system (La Luna For-mation) is buried duringLate Cretaceous, andpartially unloaded bet-ween the Late Paleoceneand Early Eocene; burialcontinues during the restof the Eocene. Strati-graphic and structuraltraps are formed bet-ween the Late Creta-ceous, Paleocene andLate Eocene. The gener-ation, migration andaccumulation from thesource rock for this sys-tem takes place duringLate Eocene, and thepreservation of the trapstakes place since theOligocene. So the criticalmoment, or the timewhen there is the max-imum probability for oilentrapment and pre-servation, is the Eocene-Oligocene limit.

"Phase 1" petroleum system, Maracaibo Basin (after Talukdar and Marcano, 1994).

East-West Maracaibo

Basin section (after

Parnaud et al., 1995).

Figure 1.30

Figure 1.31

1

Locally, the Machiques Member (Apón

Formation) is a good seal, as well as the

thick interstratified shale intervals of the

reservoirs toward the center of Lake

Maracaibo, such as Misoa, Lagunillas and La

Rosa (Fig. 1.30—Lake Maracaibo EW

section). Other good seals include the shaly

León Formation and some thick intervals of

the molasse (Guayabo and El Fausto Groups;

Andes and Perijá, respectively).

The main oil fields are located on the

Eastern Coast of Lake Maracaibo and the

main production comes from Tertiary

reservoirs; for example, Cabimas, Tía Juana,

Lagunillas, Bachaquero, Mene Grande and

Motatán. On the west coast there are fields

with production from the Cretaceous and

even Tertiary; for example, Urdaneta (Lake

Maracaibo) and several fields of the Perijá

foothills, such as La Concepción, Mara, La

Paz, Boscán and Alturitas. In the central part

of the lake, fields are located along the fault

systems of Lama-Icotea (Fig. 1.30), including

the Lago, Centro, Lama and Lamar Fields.

The oil gravity is quite diverse. In

general, the lighter types occur in the deep

Cretaceous reservoirs, becoming heavier as

depths get shallower. In the upper Tertiary

reservoirs of the lake’s Eastern Coast, some

of the oils have gravities less than 13°API.

Petroleum Systems

Figures 1.31 and 1.32 represent the

northeast Lake Maracaibo petroleum system

generated by the La Luna Formation source

rocks. Oil generation occurs in the northeast

part of the basin, with migration and

accumulation in the southwest during the

Late Eocene. The main traps occur along the

Icotea high, containing Cretaceous and

Eocene reservoirs. The highest probabilities

of accumulation, or critical moment, is

found close to the Oligocene-Eocene

boundary (Fig. 1.31).


25

8

Oca Fault

Lake Maracaibo

Colo

mbi

a

Perij

á Ra

nge

Gulf of Venezuela

Trujillo Range

FalcónBasin

Venezuelan Andes

N

0 km 50

Oil Field, Eocene Reservoir

La Luna System Limit (Phase 1)

Maracaibo Basin Limit

La Luna Source Rock Matured or Over-Matured during the Phase 1 (38 My)

Figure 1.32

Defined petroleum system in the Maracaibo Basin, La Luna Formation source rock,

Phase 1 (38 Ma) (after Talukdar and Marcano, 1994).

Geologic timescale


Formations

Source rock

Seal

Reservoir

Burial

Trap formationGeneration,migration,

accumulationPreservation

Critical moment

200 150 100 70 60 50 40 30 20 10 0

QCenozoic

MioceneOlig.EocenePaleo.

MesozoicTr JL E M L E

KL PP

Tertiary

(Ma)

"Phase 2" petroleum system; Maracaibo Basin (after Talukdar and Marcano, 1994).

Figure 1.33

1 26

Another system results from the

Cretaceous source rock (mainly La Luna

Formation), but in this case it is widespread

across the hydrographic basin of Lake

Maracaibo (Fig. 1.33), reaching over-maturity

conditions in some areas. Generation,

migration and accumulation occurred during

the Andean uplift, filling reservoirs

throughout almost the entire sedimentary

column. The critical moment is considered

to be the present. This system is the most

important for the Tertiary hydrocarbon

accumulation, especially in the structures

of the following areas or fields: Western

region and Eastern Coast of Maracaibo

Lake, Urdaneta and Lama-Icotea (Fig. 1.34).

The third system is related to the

Orocué Group, southwest Lake Maracaibo.

This generation seems to be responsible for

the oil fields to the northeast of Santander

Massif, close to the Colombia-Venezuela

border. Generation, migration and accu-

mulation occurred at the climax of Andean

uplifting (Pliocene), which produced the

complete separation of Maracaibo and

Barinas-Apure oil basins.

P E T R O L E U M B A S I N S M A R A C A I B O

LakeMaracaibo

Gaswindow

Oilwindow

Trujillo Range

Gulf of Venezuela

Col

ombi

aPe

rijá

Rang

e

Santander

Massif

Oil Field

Oil Field/Condensate/Gas

Petroleum SystemLa Luna, Phase 2

Faultkm

0 50

Icot

ea F

ault

N

Matured and Over-MaturedSource Rock Area (Fm. La Luna)during Phase 2 (Present Time)

Defined petroleum system in the Maracaibo Basin, La Luna Formation

source rock, at the present time (after Talukdar and Marcano, 1994).


Gulf of Venezuela FalcónBasin

Venezuelan A

ndes Lake

Maracaibo

Icot

ea F

ault

Orocué Group Limit

Colo

mbi

aPe

rijá

Rang

e

Trujillo Range

Santander

Massif

km

0 50

Condensate or Gas Producing Field

Petroleum System Limit of theOrocué Group

Matured or Over-Matured Orocué Group Limit at the Present Time

Oil Seeps of Continental or Mixed OriginFaults

Marcelina Formation

N

Defined petroleum system at the Maracaibo Basin, Orocué

Group source rock, at the present time (after Talukdar and

Marcano, 1994).

This large structural system reactivated

old structures, and also involved the

igneous-metamorphic basement (Fig. 1.36).

The critical moment is at the present, and

the main reservoir is the Paleogene clastic

sequence (Fig. 1.37).


271

PerijáFault

Macoa AlturitasUrdaneta

Fault

Lama-IcoteaStructure

Lama-IcoteaSystem Fault

North-AndeanFlank

Boconó Fault

Mérida Andes

South-AndeanFlank

Barinas-ApureBasin

20 km

NW SE

Neogene

Paleogene

Late Cretaceous

Early Cretaceous

Jurassic

Igneous-Metamorphic Basement

4 km

Maracaibo BasinPerijáRange

Figure 1.36

Geologicaltime scale


Formations

Preservation

Seal

Reservoir

Burial

Trap formationGeneration, migration,

accumulation

Mesozoic CenozoicTrL E M L E L Paleo. Eocene Olig. Miocene PP

QJ K

200 150 100 70 60 50 3040 20 10 0 (Ma)

Critical moment

Tertiary

Source rock

Figure 1.37

NW-SE structural cross section through the Maracaibo Basin, from the Mérida Andes to the Perijá Range.

"Phase 3" petroleum system; Maracaibo Basin (after Talukdar and Marcano, 1994).

Middle Eocene (Bartoniense) unconformity between the Mirador and Los Cuervos

Formations (Rubio de San Antonio Road, Táchira State). Courtesy of Franklin Yoris.

Mirador Formation

Los Cuervos Formation

Mirador Formation

Los Cuervos Formation

1 28

P E T R O L E U M B A S I N S B A R I N A S - A P U R E B A S I N

Composite stratigraphic column of the South Andean flank, Barinas-Apure

Basin (after González de Juana et al., 1980, and Kiser, 1989).

Tert

iary

Eo

cen

e-O

ligo

cen

e

Ear

ly E

oce

ne

to M

idd

le

Mir

ado

r

?

Leó

n/G

uaf

ita/

Car

bo

ner

a

Mio

cen

e-P

lioce

ne

GU

AYA

BO

/Par

áng

ula

/Río

Yu

ca

Los Cuervos

Sandy clastics.

The Orocúe Group includes Barco Formation (lower) and Los Cuervos Formation (upper), with regional thickness varying from 0 to 838 m in the South-Andean flank. Barco Formation is mainly sandstone while Los Cuervos Formation is finer grained and carbonaceous.

Pal

eoce

ne

OR

OC

UE

Bar

co

Cam

pan

ian

Maa

stri

cht.

Bu

rgü

ita

Cre

tace

ou

sLa

te

Co

nia

cian

-San

ton

ian

Nav

ay

150

- 18

018

0 -

210

Alb

.C

eno

man

ian

-Tu

ron

ian

Esc

and

alo

sa

150

- 42

7

"O"

"P"

"R"

"S"

Pro

du

ctiv

e in

terv

al

La M

orita

Q

ueve

do

Very permeable massive sandstones.

GraphicLithology

LithologicalDescription

Th

ick.

Form

.

Sta

ge

Ser

ies

So

urc

e

Res

erv.

Sea

l

300-

500

350-

420

150-

278

295-

330

160-

400

335-

520

2000

-300

0

*

*

Aguardiente

(m)

Ag

e

Conglomerates, sandstones and claystones in diverse proportions.Generally, these molassic sediments are attributed principally to alluvial fan environments that flanked the Andean Range.

Pelitic and minor sandy sequence. Dissappears toward the Barinas Basin due to erosion prior to the sedimentation of the Parángula Formation.

Sandstones with a slight shaly/silty interval near the top. Time equivalents in the Barinas Basin are: (sandy/calcareous) Gobernador, (shaly) Pagüey and (sandy) El Cobre Formations.

Carbonaceous siltstone and few sandstones.

Sandier sequence as compared with the underlying Navay Formation. Basal sand-stones suggest erosive contact; variable proportions of shale, limestone andsandstone.

Siliceous mudstones, quartzitic sandstones and cherty limestone. Abundant phosphatic beds with fish remains. They constitute the shallow shelf equivalents of the deeper and farther La Luna Formation environments.

Dark shales and siltstones varying laterallyto sandstones, siltstones and limestones. It´s deepest facies is considered a good source rock.

Bioclastic and sandy limestones, often glau-conitic; calcareous ± glauconitic sandstones.

Often calcareous, massive sandstones, with some shale and siltstone intercalations.

Dark gray shales.Sandstones ± calcareous.��

��

��

Bu

rgü

ita

Nav

ayLa

Mo

rita

Qu

eved

oEs

cand

alos

aG

uan

arit

o

Parángula

Form

./Mbr

.

Lith

olog

y

Sou

rce

Res

ervo

ir

Sea

l

Thic

knes

s(m

)

Pag

üey

Pag

üey

/Gu

afit

a/Le

ón

150-

500

150-

427

150-

180

180-

210

350-

420

50-3

0033

0-45

055

0 -

1400


Shales and dark limestones.

Calcareous sandstones and sandy limestones.

<300White coarse-grained sandstones; conglomerates.

Masparrito

Gobernador

Aguardiente

Río Negro

Age

Mid

dle

Eo

cen

e-O

ligo

cen

eC

reta

ceo

us

Mio

-Pl

ioce

ne

Bioclastic and sandy limestones, permea-ble massive sandstones and black shales.

Siliceous mudstone, quartzose sandstones and cherty limestone.

Micaceous, sometimes glauconitic and calcareous sandstone. Lower middle is regionally shalier.

Fine to coarse-grained, pale gray to brown, sandstones sometimes calcareous. Shales and siltstones also included.

Dark gray to bluish orbitoidal limestones.

Sandstone proportion increases in the middle part of the formation; the unit is called "Guaranito Member".

Ferriferous sandstones, carbonaceous, dark gray (often calcareous) fossiliferous siltstones and shales.

Ferriferous sandstones, carbonaceous, dark gray (often calcareous) fossiliferous siltstones and shales.

Coarse-grained conglomerates, fine- grained sandstones, siltstones and variegated claystones.

��

��

?


Composite stratigraphic column for the northern part of

Barinas-Apure Basin (after Parnaud et al., 1995).

Barinas-Apure BasinThe Barinas-Apure Basin (Fig. 1.21) is

located to the SSE of the Andean Mountain

Range. The main source rock is the Navay

Formation (Figs. 1.38 and 1.39), of Late

Cretaceous age and a lateral facies

equivalent of La Luna Formation. Secondary

source rocks have been found in the Orocué

Group (Los Cuervos Formation), but only in

the deepest depocenters, associated with the

great molassic thicknesses caused by the

Andean uplift.

The main clastic reservoirs are the

following formations: Escandalosa and

Burgüita (Cretaceous), Orocué Group

(Paleocene), Mirador-Guafita (Arauca

Member) (Eocene-Oligocene) (Figs. 1.38 and

1.39). The most relevant carbonate reservoirs

are the limestones with secondary porosity

in the Guayacán Member (Limestone),

Escandalosa Formation. Regional-scale seals

are the shale intervals of Burgüita (Late

Cretaceous), Pagüey (Eocene) and Guafita

(Guardulio Member) Formations (Fig. 1.40).


291

0

1

2

3

Two

way

tim

e (s

ec)

3.5 km

km0 100

Guafita

Navay

Aguardiente

Escandalosa

RíoYuca

Parángula

Guardulio

PagüeyGobernador

Paleozoic

NW SE

Source Rock

CarbonateShale (Seal)

Sandy / Conglomeratic

Sand / Seal Pairs

Figure 1.40

Tertiary

?

???

200 150 100 70 60 50 40 30 20 10 0

Cenozoic Geological timescaleQ


Formations

Source rock

Preservation

Seal

Reservoir

Burial

Trap formationGeneration, migration

accumulation

Critical moment

PPMioceneOlig.EocenePaleo.

Mesozoic

Tr J K

L E M L E L

(Ma)

Figure 1.41

NW-SE cross section of the

Barinas-Apure Basin (after

Parnaud et al., 1995).

Events chart for the La Luna-Burgüita (!) petroleum system of the Barinas-Apure

Basin, during the Caribbean terrane’s emplacement over the Mérida High.

Note: Compound names are given to the petroleum

systems, referring to the source rock and the main

reservoir names (for example: La Luna-Burgüita). If

the system is well known by the correlation between

the hydrocarbon in the reservoir and the source rock,

it is annotated with (!). If the system is hypothetical,

with only geochemical evidence about the

hydrocarbon’s origin, it is annotated with (.). Finally,

if the petroleum system is totally speculative, with

only geological or geophysical evidence, it is

annotated with (?).

1 30

The main oil fields are to the south of

Barinas city, the most important being the

San Silvestre, Sinco, La Victoria and Guafita.

La Victoria and Guafita are close to the

Colombia-Venezuela border.

Oil gravities between 22 and 28°API

have been reported in Barinas oil fields. In

Guafita and La Victoria oil fields (Apure),

oil gravities between 30 and 36° API have

been found.

Petroleum systems

Two events account for the generation,

migration and accumulation of hydrocarbons

(Figs. 1.41 and 1.42). The first event is related

to the La Luna-Burgüita system caused by

petroleum generation in Maracaibo Basin

and its migration to the SSE. In this case there

are two seals, both of them of Cretaceous

age. The upper seal is the “basal” shale of

Burgüita Formation, and the lower seal is the

shale of La Morita Member (Navay

Formation). The main reservoirs belong to

Cretaceous formations such as Aguardiente,

Escandalosa (Limestone or Guayacán

Member) and Burgüita (basal sandstones).

The second event is related to the

depocenter of the South-Andean flank, with

a present-time critical moment. The source

rock is still of Cretaceous age and the

reservoir includes Eocene-age formations

such as Gobernador and Pagüey. The

Guardulio Member (Guafita Formation) is

the most important regional seal. In this

second event, it is possible that remigration

of the oil trapped during the Eocene pulse of

La Luna-Burgüita system occurred.

P E T R O L E U M B A S I N S B A R I N A S - A P U R E B A S I N



Q

PP

MesozoicTr K Tertiary

Formations

Source rock

Preservation

Seal

Reservoir

Burial


accumulation

Critical moment

L M L E S Paleo. Eocene Oligo. Miocene

200 150 100 70 60 50 40 30 20 10 0

CenozoicJ

E

(Ma)

Events chart for the Navay-Gobernador (!) petroleum system, in the Barinas-Apure

Basin north of the Mérida Arc, during the Andean uplift.

La Luna Formation. Picture of an outcrop in the Cuite River (Apure State). Courtesy

of Franklin Yoris.

Figure 1.42

Falcón BasinThe Falcón Basin (see Fig. 1.21) is

located to the east of Maracaibo Basin, and

is separated by the Trujillo Range. The

source rock has been identified as the shales

of the Agua Clara Formation (Fig. 1.43);

however, shales of source rock potential

have also been identified in the deltaic-

marine sediments of Guacharaca and Agua

Salada Formations.

The main clastic reservoirs include the

following formations: Agua Clara (La Vela

Cove and Western Falcón), Socorro

(Cumarebo Oil Field) and La Puerta Group

(Western Falcón) (Fig. 1.43).

The oil fields of Falcón Basin are, from

west to east: Mene Grande de Mauroa,

Media, Hombre Pintado, Las Palmas,

Tiguaje, Mamón, La Vela and Cumarebo.

Petroleum Systems

Figure 1.44 shows the Falcón Basin

petroleum system. Because of the regional

geothermal gradient increase, the main

source rock (Oligocene) generated

hydrocarbons long before the structural

configuration of the entrapment mechanism

was established during the Oligocene-

Miocene transition. The reservoirs are

concentrated in Oligo-Miocene stratigraphic

units, with their structural configuration

being formed between the Late Miocene and

Pliocene. This time lag between the

generation of hydrocarbons and trap

formation led to the loss of large quantities

of hydrocarbons.


311

EocenePaleoceneCretaceous La Quinta

AWSW

La Puerta?

Dabajuro Platform

Urumaco Urumaco

Socorro Socorro

Agua ClaraEocene ?

Cerro PeladoUndifferentiated Basement

Codore

Lines Displacement Lines Displacement

Urumaco Trough

Coro Codore


A'ENE

0 km 40

??

Caujarao

CaujaraoSocorro

DabajuroVenezuela GulfLocationMap Coro

Venezuela

A'

A

La Puerta

Figure 1.43

200 150 100 70 60 50 40 30 20 10 0

Geological timescale Petroleum

system events

Q

PP

Mesozoic Cenozoic

Tr J K Tertiary

Formations

Source rock

Preservation

Seal

Reservoir

Burial

Trap formationGeneration migration

accumulation

Critical moment

L E M L E L Paleo. Eocene Olig. Miocene

(Ma)

Figure 1.44

NE-SW geological/structural

cross section through

the Falcón Basin (after

Macellari, 1995).

Events chart for the Agua Clara petroleum system (!), in the Falcón Basin.

1 32

Eastern BasinThe Eastern Venezuelan Basin (Fig.

1.21) is the second in importance. It is

limited by the La Costa Mountain Range to

the north, by the Orinoco River to the south,

by the Orinoco Delta platform to the east

and by the El Baúl Lineament to the west. It

has been operationally subdivided in two

sub-basins, the Guárico and Maturín.

Guárico Sub-BasinThis subdivision includes Guárico and

part of the oil fields in northern Anzoátegui

state. The sub-basin’s northern flank is

influenced by the deformation front in

which the Guárico Fault system is located

(Fig. 1.45). This deformation front overrides

and overloads Cretaceous and Tertiary rocks,

producing a complex tectonic setting (Fig.

1.46). To the south, the structure is less

complicated—there are structural (exten-

sional) depressions that preserved Jurassic

and Paleozoic rocks (Fig. 1.47) and regional

pinching-out of the Cretaceous-Tertiary

sequences to the south (Fig. 1.48). The main

traps are combination structural-stratigraphic

traps, especially in fields far from the

deformation front.

P E T R O L E U M B A S I N S F A L C O N A N D E A S T E R N B A S I N S

NW-SE cross section on the basis of seismic interpretation and with well control in

the Guarumen mountain front (after Figueroa and Hernandez, 1990). Cretaceous-

Eocene-Oligocene rocks override the autochthonous basal (Early) Oligocene,

indicating a Miocene-Pliocene age for the last deformation.

0 20 40 km

CaribbeanDeformation Belt

Los Roques Island Bonaire Basin

San SebastiánFault

EspinoGraben Orinoco

River

CoastalRange Belt

AltamiraFault

GuáricoFault

La VictoriaFault

Caucagua-El TinacoBelt

Villa de CuraBelt

ThrustingFront Tar

Belt

N

Late-Recent Miocene

Middle Paleocene-Miocene

Cretaceous

Jurassic

Early Paleozoic

Ocean Crust

Precambrian, Paleozoic and MesozoicAccretionary Crust

Precambrian-Paleozoic Continental Crust

Figure 1.45

Allochthonous

Oligocene-Basal

Early Eocene- Middle

0

15000

5000

10000

NW SE

0 1 2km

1100 1080 1060 1040 1020 1000 980 960 940 920

Cretaceous-Eocene

Figure 1.46

Events chart for the Agua

Clara petroleum system (!)

in the Falcón Basin (after

Talukdar and Marcano, 1994).

The main source rock (Guayuta and

Temblador Groups) is currently presumed

to have been overridden by the Guárico

North Deformation Front (Fig. 1.48). Hydro-

carbon generation is related to advance of

the nappe, rapidly bringing the source rock

to the gas window due to tectonic

overloading since at least the Late Eocene.

This may be why the main hydrocarbon in

the fields near the Mountain Front is gas

rather than oil. Nevertheless, generation of

hydrocarbons has been postulated close to

the Late Miocene faults in the Central Guárico

region. The rocks contain marine organic

matter and appear to have migrated only a

short distance. This suggests that the

Temblador Group (Fig. 1.49) is an important

source rock for the oil in the Guárico State

fields. Paraffinic hydrocarbons may have

been generated from source rocks in

reservoir formations such as the Roblecito

and Oficina.

The main oil fields are, from west to

east: Palacio, La Mercedes, Yucal-El Placer,

Tucupido, El Jobal, Socorro and Macoya;

Yucal-El Placer is a gas field. To the south of

Guárico State, the Cretaceous and Tertiary

units gradually pinch-out (Fig. 1.48), creating

stratigraphic traps and asphalt seals in what

has been named the Orinoco Belt (Fig. 1.50).


331

2.0

1.0

0.0

3.0Valle La Pascua N

50 Km2 km0 1MARAVEN

CORPOVEN

Guárico

Anzoátegui

P.F.: 14730'

Basement

Early Cambrian

Jurassic Basalts

Cretaceous Base

(Proj. 2.8 Km to SE)

NESW

NZZ-88XDP = 170m

220240260280300320340360380400

P-C P-6

NZZ-88X

Figure 1.47

0 50 100

km

km

S

Orinoco River

Recent

1000 Carrizal

Chaguaramas

Macapra River

Field

FieldPalacio

Las Mercedes

Temblador

Infante

La Pascua

2000

1000

3000Quartzosesandstone

Basement

0 m

N

Mucaria,Garrapata, Guárico and others

VILLA DE CURA

0 10 20 30 40 50

Chaguaramas N.M

500

1000

2000

m

Cretaceous

Roblecito

AG-D-6 GRICO-6 GXB-1 CAMAZ-1

La Pascua

B

........

..... . .

. ... .- -- -- -

Roblecito

Structural cross sections from a point near the

southern limit of the Guatopo National Park

(Altagracia de Orituco, Guárico State) to the

Orinoco River, approximately 160 km south

of the intersection of the cross section with the

Macapra River, and along the section from wells

G-D-6 to CAMAZ-1, south of Camatagua.

These cross sections show the depth to the

(autochthon) Cretaceous top, below the thrusting

front that includes igneous-metamorphic rocks

(Villa de Cura Group) and Cretaceous-Tertiary

sedimentary rocks such as Mucaria, Garrapata,

Guárico, Roblecito, Peñas Blancas, Naricual,

Quebradón, Quiamare and Chaguaramas Forma-

tions (the last six concentrated in the thrusting

front, in the so-called "Chacual Complex" (after

González de Juana et al., 1980).

Figure 1.48

Seismic line in the NE-SW direction,

through the Jurassic Graben to the

south of the Guárico Sub-Basin (modi-

fied from Daal et al., 1989). This section

shows how the Paleozoic sediments

were preserved (Cambrian as well as

Jurassic with basalt) in the deep parts

of the Espinto Graben. The final well

depth projected over the seismic line

was 14,730 ft (4.490 m).

1 34

The reservoirs are Neogene, and migration

probably occurred not only from north to

south, but from northeast to southeast.

The origin for the naphthenic-paraffinic oil

types is considered to be a Cretaceous

source rock, with tens of kilometers

migration, traveling along the Tertiary basal

discordance (Neogene-Cretaceous and

Neogene-Basement). The Orinoco Belt

extends to the east, delimiting the south

border for the whole Eastern Basin. Its

stratigraphy is shown in the geologic section

of Fig. 1.50.

The most important shale seals are found

in the same units as the reservoirs, e.g.

Roblecito, Chaguaramas and Oficina Forma-

tions. The traps are combinations of structural

(extensional faults) and stratigraphic

(channels) traps.

Petroleum Systems

The Guárico Sub-Basin is complex in its

petroleum system. Four such systems are

recognized: 1) Querecual-Oficina (!) (Fig.

1.51), 2) Temblador-La Pascua (!) (Fig. 1.52),

3) Querecual-Chaguaramas (!) (Fig. 1.53), and

4) Oficina (!) (Fig. 1.54). The source rock of

the Querecual-Oficina system is the

Querecual Formation, which occurs as blocks

and extremely faulted outcrops along the

whole Guárico Mountain Front. After

deposition (Late Cretaceous), it was first

overburdened and then involved in the

Caribbean tectonics during the Eocene and

Oligocene. Reservoir sedimentation (Oficina

and Merecure Formations) occurs during the

Late Oligocene and Miocene, and trap forma-

tion occurs during the structural formation of

the Eastern Basin during the Eocene. The

generation, migration and accumulation of

hydrocarbons have occurred continuously

since the beginning of the Oligocene, from

the deepest part of the thrusting front, to the

southern distal pinch-out of the Eastern Basin.

P E T R O L E U M B A S I N S G U A R I C O S U B - B A S I N

Ofi

cin

aT

i g

r e

T E

M B

L A

D O

R

C a

n o

a

5800'

5836'

5900'

5925'

6117'

6100'

6000'

6421'

6200'

6300'

6400'

Coarse-grained sandstone.

Granular conglomerate.

Lignite, leaves.

Occasional shales.

Dolomitic limestones.

Shales with Lingula.

Dolomitic limestones.Exogyra.

Ferrolithic levels.

Whitish and speckled mudstones interval.

Granite.

Whitish weathered residual rock.

Speckled mudstones and sandstones interval.

Pebble conglomerates.

Pebble conglomerates.

Speckled siltstones.

Whitish siltstones.

Basement

GroupGraphic

Lithology Lithological Description

Form

atio

n

��

So

urc

e R

ock

Res

ervo

ir

Sea

l

?

?

Lithological profile of the Tigre No. 1 well, Guárico State (after

González de Juana et al., 1980).

Figure 1.49

In the Oficina Formation, the Miocene

extensional fault systems are the main

trapping mechanisms for the Guárico and

Maturín (southern flank) Sub-Basins.

Specifically the Querecual-Oficina System

refers only to the area of the Oficina (near the

Guárico-Anzoátegui southern border) in the

Guárico Sub-Basin, located to the south of

Guárico and Anzoátegui states. Its critical

moment is present-time.


351

++

+

++

++

+ ++

+ +

+

Ap

rox.

600

0'

Aproximately 570 km

West East

Machete-Zuata Hamaca-Cerro NegroEastern Province Western Province

Chaguaramas

?Roblecito

La PascuaOficina

Oficina

Freites

Las Piedras

Metamorphic Basement(Precambrian (?) )

K K

PKPK PK

PK

Sandy Reservoir

Sand-Seal Pairs Carbonate Reservoir

Shaly Seals Paleozoic Basement (Sedimentary)

Precambrian Basement (Igneous-Metamorphic)

Carrizal Hato ViejoAltamira

Figure 1.50

Schematic structural configuration of the Orinoco Belt (after Audemard et al., 1985).

200 150 100 70 60 50 40 30 20 10 0



Q

PP

Mesozoic CenozoicTertiary

FormationsSource rock

Seal

Reservoir

Burial


accumulation

Critical moment

Preservation

E Paleo. Eocene Olig. Miocene

(Ma)

Tr J

L E M L

K

L

Figure 1.51

Events chart for the Querecual-Oficina oil system (!), in the Oficina area, Guárico

Sub-Basin (after Talukdar and Marcano, 1994).

El Cantil Formation (Guácharo Member). Areal

view of the “Las Puertas del Guarapiche,”

Monagas State. Courtesy of Franklin Yoris.

1 36

The Temblador-La Pascua System covers

the central area of Guárico State. The main

reservoirs are the Temblador Group proper

and the Roblecito and La Pascua Formations.

The burial of the source rock occurred from

the Eocene, with hydrocarbon generation

since the Oligocene. This produced a big

loss of hydrocarbons, because the structural

traps did not form until the end of Miocene.

The probable critical moment is around the

Miocene-Pliocene limit.

The Querecual-Chaguaramas System is

a consequence of the previously discussed

system. The traps, which are essentially

stratigraphic and asphaltic seals, occur along

the southern border of the Eastern Basin,

creating the Orinoco Belt. The Querecual-

Chaguaramas System is applicable to the

whole of the Orinoco Belt, including the

southern border of the Maturín Sub-Basin,

where the reservoir rocks are the lateral

equivalents of the Chaguaramas Formation

in Guárico Sub-Basin. The critical moment is

believed to be present-time.

In the Oficina System, hydrocarbons are

believed to have been generated from

Miocene source rocks (coals, carbonaceous

siltstones) in the Oficina Formation proper.

The sandstones of the same formation are

the reservoirs, but some of the oil may have

escaped to the underlying Merecure

Formation, with extensional-faulting traps

formed during Late Miocene. The source

rock overburden can be related to the thick

Pliocene (molasse) sequences, associated

with the uplifting of the Interior Mountain

Range and the resulting lithospheric flexure

that generates extensional faulting. The

critical moment is present-time.

P E T R O L E U M B A S I N S G U A R I C O S U B - B A S I N

?

200 150 100 70 60 50 40 30 20 10 0 (Ma)



Q

PP

Mesozoic CenozoicTertiary

Formations

Source rock

Preservation

Seal

Reservoir

Burial


accumulation

Critical moment

E Paleo. Eocene Olig. Miocene

Tr J

L E M L

K

L

Events chart for the Temblador Group-La Pascua (!) petroleum system in central

Guárico (after Talukdar and Marcano, 1994).

Events chart for the Querecual-Chaguaramas (!) petroleum system,

Orinoco River Belt (after Talukdar and Marcano, 1994).

Events chart for the Oficina (!) petroleum system, Oficina area, Guárico Sub-Basin

(after Talukdar and Marcano, 1994).

Figure 1.52

Petroleum system events

?

200 150 100 70 60 50 40 30 20 10 0

Formations

Source rock

Preservation

Seal

Reservoir

Burial


accumulation

Critical moment

Tertiary Q

PPMioceneOlig.EocenePaleo. L E M L E L

TrCenozoic Geological time

scaleMesozoic

(Ma)

J K

Figure 1.53

?

200 150 100 70 60 50 40 30 20 10 0

Q

PPOlig.Paleo. L E M L E L

Tr J KPetroleum

system events

Formations

Source rock

Preservation

Seal

Reservoir

Burial


accumulation

Critical moment

Tertiary

MioceneEocene

Cenozoic Geological timescale

Mesozoic

(Ma)

Figure 1.54

Maturín Sub-BasinThe Maturín Sub-Basin (Fig. 1.55) is the

main Eastern Basin petroliferous unit. The

structural deformation and pinch-out of

stratigraphic units to the south define two

operational domains: north and south of the

Pirital Thrust (Figs. 1.55 and 1.56).

The stratigraphy of the eastern Interior

Range is representative of sedimentation on

the northern flank of the main Maturín Sub-

Basin (Fig. 1.57). A thick and complex

sedimentary sequence ranges from the

Lower Cretaceous to Pleistocene. On the

southern flank, a simpler stratigraphy occurs,

similar to that of the Guárico Sub-Basin in

the subsurface. The Temblador Group (Fig.

1.49) represents the Cretaceous, and the

overlying Tertiary is mainly Oligocene-

Pleistocene, with alternating fluvial-deltaic

and shallow marine environments eventually

overlain by continental sediments (Fig. 1.50).


371

0 20km

10

km

Vertical and horizontal scale

Margarita - Los TestigosPlatform Margarita

Island

ArayaSub-Basin

El PilarFault

Interior Range

Turimiquire

MorichitoBasin

PiritalBlock

Pleistocene

Late Oligocene - Pliocene

Paleocene - Early Oligocene

Cretaceous

Jurassic

Oceanic Crust

Accretionary Crust

Early Paleozoic Continental Crust

DextralTranscurrentComponent

OrinocoRiver

MaturínSub-Basin

CaribbeanPlate South American

Plate

NW SE

Maturín

Figure 1.55

La Quinta Formation

Crystalline BasementShallow Water Sandstones and Limestones

Mesa (Continental)

Undifferentiated Cretaceous Allochthon

Carapita

Upp er Continental

Morichito

ForedeepBasin

Pirital HighBasin

(Piggy-Back)

Las Piedras (Litoral)

Pirital Fault

"Lower Carapita "

La Pica (Marine)

"Middle Carapita "

Litoral

Deep watershales and turbidites

"Upper Carapita " (Litoral)0

2km

Pleistocene

Pliocene

Paleozoic

Late Jurassic

Paleogeneto Late

Cretaceous

Miocene Middle

MioceneLate

S N

Deep watershales and turbidites

TEMBLADOR

Chapapotal

Quiriquire (Continental)Continental

?

SANTA ANITA and MERECURE Groups

Figure 1.56

Conceptual NW-SE geological cross section from Margarita-Los Testigos shelf to the Orinoco River. The north flank of the Maturín Sub-

Basin is associated with the thrusting fronts of large cortical blocks, emplaced to the south due to the collision between the Caribbean and

South American plates.

Structural cross section showing the tectono-stratigraphic units in the Maturín Sub-

Basin’s northern flank. The figure also illustrates the complex tectonic and

sedimentary units that constitute the vertical and lateral equivalents of the Carapita

Formation in the subsurface; coeval foredeep environment sediments were

deposited in the south, while north of the Pirital High, a piggy-back basin was

developed, with shallow and continental environments (after Roure et al., 1994). The

Santa Anita Group includes the formations San Juan, Vidoño and Caratas.

1 38

The main source rock in the Interior

Range is the Guayuta Group, especially the

Querecual Formation. Its thickness is double

that of its Western Venezuela lateral

equivalent (La Luna Formation) and it has

similar characteristics as source rock. The

lateral transition of the Cretaceous from the

northern flank of the sub-basin to the

southern Temblador Group is not known in

the subsurface because of the considerable

thickness of the Neogene sequence. Never-

theless, it is believed that the Cretaceous

source rock is still of good quality in the

Greater Oficina Area, which generated part of

the oil present in these fields.

The main source rock for the North

Monagas region was probably Cretaceous

(Guayuta Group), although the possibility of

younger source rocks is not discarded.

Younger source rocks would need organic

matter of continental affinity (e.g., the

Naricual Formation is coaly/carbonaceous).

The most important reservoirs are of

Tertiary age; in North Monagas fields they

consist of Carapita, Naricual, Los Jabillos and

Caratas Formations (Fig. 1.57). Late Creta-

ceous sandstones (San Juan Formation) are

also good reservoirs, and the youngest Mio-

Pliocene reservoirs belong to La Pica and the

molassic Las Piedras-Quiriquire Formations

(Fig. 1.56). Structural traps, such as those in

El Furrial Field (Fig. 1.58) are of prime impor-

tance for hydrocarbon accumulations.

Major regional seals for the Cretaceous-

Tertiary sequence in the northern flank of the

sub-basin are the Vidoño, Areo and Carapita

Formations (Fig. 1.57). The Areo and Carapita

also have lenticular reservoirs, such as the

turbiditic lobes of the Carapita Formation

(Chapapotal Member; see Fig. 1.59).

To the south of the sub-basin, in the

Oficina fields of Anzoátegui and Monagas

states, the main reservoirs are Merecure and

Oficina Formations. Regional shale seals

belong to the same units, and the overlying

Freites Formation is also an important

regional seal.

P E T R O L E U M B A S I N S M A T U R I N S U B - B A S I N

?

?

?

?

?

? ? ?

??

SeriesLithostratigraphic

UnitsLit

holog

y

Los Jabillos

Areo

Naricual

Carapita

Uchirito

Quiamare

MesaLas Piedras,Quiriquire,etc.

Pleistocene Plio-cene

Late

Late

Early

Ear

lyM

idd

.

Mio

cen

e

Ear

lyLa

te

Olig

oce

ne

Late

Ear

lyM

idd

le

Eo

cen

e

Late

Ear

ly

Pal

eoce

ne

?San Juan

San Antonio

?

?

Querecual

Chimana

?

El C

anti

l Guácharo(Upper.)

Guácharo(Low.)

García

Barranquín

?

Cre

tace

ou

sE

arly

Late

5 432

2 = Capas Río Solo 3 = Venados 4 = Morro Blanco 5 = Picuda 6 = Taguarumo 7= Mapurite 8 = Punceres

Transgressive advance

Regressiveprogradation

8

7?


6

1 = Mbr. Tinajitas

Ma

10

20

30

40

50

60

70

80

90

100

110

130

120

Neo

gen

eP

aleo

gen

e

Sandstones and claystones. T = 275 m. Conglomerates, sandstones and often calcareous shale/claystones.T = 3000-4600 m.Calcareous conglomerates.Black calcareous shales, inter-bedded turbiditic sandstones;conglomerates at the top. T = 1000-2000 m.

Sandstones interbedded withcalcareous siltstones and coals.T = 2000 m. Shales, siltstones, and glauco-nitic sandstones. T = 300m

Thick sandstones interbeddedwith dark shales; the TinajitasMember is calcareous and glauconitic.

T = 700-200 m.

Dark shales increasing its sandy contents to the south. T = 700-200 m.

Sandstones and shales.T = 0-650 m.

Siliceous limestones, sand-stones and black cherts. T = 250-500 m.

Pelagic black limestones.T= 650-750 m.Limestones, sandstones and shales, the glauconitic content is high in some places. T= 270-535 m.Bioclastic limestones and argilla-ceous limestones; the sandy contents increase to the top. T = 700-1000 m.Sandstones. T = 157 m.

Shales and limestones. T = 186 m.

Sandstones, limestones andcarbonaceous siltstones. T = 1400-2400 m.

N S

M

M

M

Carbonate reservoir

Seal rock

Sandy reservoir

Sand/seal pairs

General source rockM

V i

d o ñ o

1Caratas

T = Thickness

��

��.. .

. .

. .. .. .. .

. ..

Sou

rce

Res

erv.

Sea

l

?

?

?

8500'

8000'

7500'

7000'

6500'

6000'

5800'5635'

6595'

7190'

8075'

5500'5458'

Las PiedrasLa Pica

LithologicalDescription

ElectricLog

Mem

ber

Ch

ap

ap

ota

l

Form

atio

nC

ar

ap

it

aSandstones with regular shale interbedding (sandy turbidi t ic facies) .

Sandstones with many shaleinterbeddings (sandy turbidi t ic facies) .

Shales with thin sandy beds, probably turbidi t ic .

Mainly shales with some thinsandy beds(probably turbidi t ic) .

Integrated stratigraphic column (time scale) for

the Interior Range (Maturín Sub-Basin northern

flank) (after Yoris, 1992).

Electrical log from Well Q-297, in

Cahipo block of the Quiriquire

Field, State of Monagas. This is

typical of the Chapapotal

Member of the Carapita

Formation (after González de

Juana et al., 1980). The turbidite

regime of the sand-seal pairs of

the Carapita Formation is the

same throughout all the region

(approximately 80 km to the

west of the Quiriquire oil field),

and in the El Furrial Field, 40 km

to the southeast (after Yoris,

1989, 1982).


From west to east the main oil fields in

the north of Monagas state are: Oficina Major

Area, Quiamare, Jusepín, El Furrial, Orocual,

Boquerón, Quiriquire and Pedernales.

In the south the sub-basin also includes

the Orinoco Belt. It has Neogene reservoirs

and Cretaceous source rock, with distal

migration occurring along and across the

Cretaceous-Neogene and Basement-Neogene

discordances.

Oil gravities are quite varied. In El

Furrial and nearby fields medium-type oils

are common; Quiamare-La Ceiba produced

oils with average 41°API; in the Oficina

fields, light, medium and heavy oils are

found; and in the Orinoco Belt the oil is

always heavy. In general, heavy oils are

found at the basin margins with the

youngest and shallowest reservoirs; this is

the case for the Orinoco Belt in the southern

flank and the Quiriquire, Manresa and

Guanoco fields in the northern flank. The

last two fields contain extra-heavy oils.

Petroleum Systems

The main petroleum systems of Maturín

Sub-Basin are: 1) Guayuta-Oficina (!) (Fig.

1.60), and 2) Guayuta-Carapita (!) (Fig. 1.61).

The first one is related to the oil fields of the

southern flank, and includes the Late

Cretaceous Querecual and San Antonio

Formations (Guayuta Group) as the main

source rocks, overloaded (stratigraphically

and tectonically) until the present day. The

main reservoirs include Oligo-Miocene units

such as Merecure, Oficina and Freites

Formations. The principal seals are the

Oficina and Freites Formations, and trap

formation began during the Oligocene defor-

mation and continues to the present.

The generation, migration and accumulation

of hydrocarbons is reaching the critical

moment at the present. Generation began in

the Late Paleocene when the Caribbean

nappes overthrusted the South American

plate, far to the west and northwest of their

actual position.


391

2

3

4

5

1 km

Sec

onds

S NEl Furrial

1400 1500

Carapita

Merecure

Cretaceous

Figure 1.59

200 150 100 70 60 50 40 30 20 10 0

Q

PP

Mesozoic Cenozoic

TR J K Tertiary

Seal

Reservoir

Critical moment

Burial

Generation, migration


(Ma)

Formations

Source rock

Preservation

Trap formation

Geological time scale


accumulation

Structural interpretation from El Furrial Field (after Pernaud et al., 1995). In this section,

the trap is made of a structural high associated with the development of a thrust with

vergence to the south.

Events chart for Guayuta-Oficina (!) petroleum system, Maturín Sub-Basin.

The kitchen is located below the Pirital Block (after Talukdar and Marcano, 1994).

200 150 100 70 60 50 40 30 20 10 0

Geological time scale


Q

PP

Mesozoic Cenozoic

Tr J K Tertiary

Formations

Source rock

Preservation

Seal

Reservoir

Burial

Trap formationGeneration migration

accumulation

Critical moment


(Ma)

Figure 1.61

Events chart for the Guayuta-Carapita (!) petroleum system for the Maturín

Sub-Basin. The kitchen is located both in the autochthonous and in the Furrial

(allochthonous) blocks (after Talukdar and Marcano, 1994).

Figure 1.60

401

This chapter † was written by F.Yoris and M.Ostos (E.I.G.LITOS C.A.)

with the collaboration of the personnel of LITOS C.A. and of L.Zamora.

†The History of Exploration of Venezuela was written by L.Zamora.

P E T R O L E U M B A S I N S M A T U R I N S U B - B A S I N

The second system, the Guayuta-

Carapita (!), is related to the northern flank of

the Maturín Sub-Basin. It is characterized by

heterogeneous reservoirs and seals, with a

younger hydrocarbon generation than the

Guayuta-Oficina system. The generation-

migration and the trap formation are Late

Oligocene to Present, with critical moment at

the present time. Important seals are Vidoño,

Areo and Carapita Formations, with minor

seal capacity in the molassic units such as

Morichito, Las Piedras and Quiriquire

Formations. San Juan, Caratas, Los Jabillos,

Merecure (subsurface “Naricual”), Carapita,

La Pica, Las Piedras and Quiriquire Forma-

tions are important reservoirs.

The kitchen for the Maturín Sub-Basin

source rock is summarized in Fig. 1.62,

showing that the source rock is in a gas

window below the deformation front, and its

maturity zone (oil window) is actually

feeding the sub-basin’s southern flank.

Caribbean Sea

El Pilar Fault

San Francisco Fault

Pirital Thrusting

Deformation Front

Maturín

Orinoco River

Ciudad Bolívar

0 20

km

Inmature

Mature

Very mature

N

Figure 1.62

Hydrocarbons kitchen for the Interior Range and Maturín

Sub-Basin (after Parnaud et al., 1995).

A U T H O R S A N D C O N T R I B U T O R S

The following definitions are either quoted directly or

paraphrased from Bates and Jackson (1987), and are

presented here as a reference for the chapters in this book

that discuss geological concepts. If the reader wants more

information about these terms, the mentioned reference or

specialized books are recommended.

Allochthonous: “Formed or produced elsewhere than in its

present place.” Here, this term is used to designate

portions of Earth’s crust, separated from their original

basement and tectonically transported long distances, and

being finally emplaced as “allochthonous terranes.”

Asthenosphere: see Lithosphere.

Authochthonous: “Formed or produced in the place where

now found.” Here, this term is used for the Earth’s crustal

portions that are rooted on their original basement.

Bathyal: “Pertaining to the ocean environment or depth

zone between 200 and 2000 meters.”

Chert: “Microcrystalline or cryptocrystalline sedimentary

rock consisting dominantly of quartz crystals less than 30

microns in diameter. It may contain amorphous silica or

impurities such as calcite, iron oxide, and the remains of

siliceous and other organisms.”

Clastic sediments: Sediments formed by particles derived

from the erosion/weathering of preexisting rocks or other

sediments, being transported by wind or water. The clastic

fractions are: clay ( < 1/256 mm diameter), silt (1/256 to

1/16 mm), sand (1/16 to 2 mm) and gravel ( > 2 mm).

Rocks dominated by silt and clay fractions are shales and

(siliceous) mudstones, by sand are sandstones, and by

gravel are conglomerates.

Conglomerate: see Clastic sediments.

Diachronism: “The transgression, across time planes or

biozones, by a rock unit whose age differs from place to

place.”

Economic basement: In the oil industry, the oldest rocks

in a given place that do not contain hydrocarbons (ex:

sedimentary Jurassic rocks in the Venezuelan oil basins, or

igneous and metamorphic rocks with no porosity and

permeability).

Gondwana: The Late Paleozoic continent of the Southern

Hemisphere. The term originates from the Gondwana

System of India, which is Carboniferous to Jurassic age

and includes glacially derived and coal sediments.

Graben: Elongated portion of the Earth’s crust, relatively

depressed in comparison with surrounding areas and

bounded by faults on its long sides.

Half-graben: “A depressed block bounded on one side by

a listric fault.” This name is used for some of the relic

portions of Western Venezuela Jurassic grabens in which

the La Quinta Formation outcrops in the Andes.

Hemipelagic sediments: Typical sediments of the

continental margin and abyssal plain. More than 25% of

the fraction coarser than 5 microns must be either

terrigenous, volcanogenic, and/or neritic.

Laurasia: The Northern Hemisphere equivalent of

Gondwana in the Southern Hemisphere, and from which

the Northern Hemisphere continents were derived.

Laurentia: “A name that is widely and confusingly used for

granites and orogenies of Precambrian age in the

Canadian Shield.”

Limestone: A sedimentary rock made up of more than 50%

calcium carbonate (calcite); also a carbonate sedimentary

rock containing more than 95% calcite and less than 5%

dolomite.

Lithosphere: The solid portion of the Earth, including the

crust and part of the upper mantle. Its rigid behavior

contrasts with the underlying asthenosphere, which is

capable of “flow” via convection cells while maintaining

its solid constitution.

Molasse: “An extensive, post-orogenic sedimentary

formation resulting from the wearing down of elevated

mountain ranges,” during or immediately after orogeny. It

is usually very thick.

Nappe: “A sheetlike, allochthonous rock unit, which has

moved on a predominantly horizontal surface.” The

mechanism of transport is usually thrust faulting.

Neritic sediments: Those sediments deposited in a marine

environment between low tide level and the shelf break.

Olistolite: see Olistostrome.

Olistostrome: Stratigraphic intervals made up of chaotic,

lithologically diverse blocks (Olistolites, sometimes up to

several kilometers long), accumulated by sliding and

slumping of unconsolidated sediment.

Orogenesis: “Literally, the process of formation of

mountains.” In modern usage, orogenic mountain chains

are considered the collision boundaries between tectonic

plates.

Pangea: A supercontinent that existed 200 to 300 million

years ago and included most of the existing continental

crust. From this supercontinent the present continents

were derived by fragmentation and displacement via

plate tectonics.


411

421

Pelagic sediments: Marine sediments formed mainly from

open ocean-suspended particles. These particles can be

either nektonic or planktonic. The term pelagic also refers

to the water of the ocean as an environment.

Pull-apart basin: An extensional basin formed between

two strike-slip faults.

Regression: “A retreat or contraction of the sea from land

areas,” with a potential increase in subaerially exposed

areas. A regressive sedimentary sequence is identified

when its sediments’ paleodepth steadily decreases as they

decrease in age.

Sandstone: see Clastic sediments.

Shale: see Clastic sediments.

Siltstone: see Clastic sediments.

Subsidence: “The downward settling of the Earth’s surface

with little or no horizontal motion.” In a sedimentary basin,

an increase in subsidence results in a higher capacity to

receive sediment. If the basin is trough-shaped, the basin

axis reflects the deepest subsidence points.

Tectonic plate: A rigid portion of the Earth’s lithosphere with

seismic activity along its borders. Over geologic time, it has

been postulated that the Earth’s tectonic plates moved over

the asthenosphere via convection cell mechanisms.

Terrain: “A tract or region of the Earth’s surface considered

as a physical feature, an ecological environment, or some

planned activity of man.” Here, the usage is physical

(geological).

Terrane: “A fault-bounded body of rock of regional extent.

A terrane is generally considered to be a discrete

allochthonous fragment of oceanic or continental material

added to a craton at an active margin by accretion.”

Thrust front: Regions of the lithosphere associated with

nappe emplacement; normally they form mountain ranges

near collisional plate limits. Ex: in Venezuela, the Interior

Mountain Range (Serranía del Interior) is considered a

thrust front associated with the nappe emplacement

caused by the collision between the Caribbean and South

American Plates. Thrust fronts are also associated with

“fold and thrust belts”.

Transgression: “The spread or extension of

the sea over land areas.” A transgressive

sedimentary sequence is that in which the

paleodepth of its sediments steadily

increase as they decrease in age.

Trough: An elongated crustal depression,

usually associated with a subduction-type

plate boundary or transformal limit (ex:

Marianas Trough, in the Pacific Ocean).

Troughs (also: foredeeps) can be found

parallel to the trend of “fold and thrust

belts” due to the lithospheric plate flexure

produced by its weight.

Turbidite: Sediment body deposited from

turbidity currents.

Turbidity currents: Density currents

caused by different amounts of matter in

suspension. They commonly occur along

the continental slopes and delta fronts,

where the discharge of sediments can be

very high.

Vergence: The direction of movement of

lithospheric masses involved in thrusting;

also “the direction of overturning or of

inclination of a fold.”

G L O S S A R Y

Eonotheme(Eon)

Eratheme(Era)

CenozoicTertiary

Quaternary 1.64

23.3

65

145.8

208

245

290

362.5

408.5

439

510

570

2500

HolocenePleistocene

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Upper (Late)Lower (Early)

Upper (Late)Lower (Early)

Oligocene, Eocene,Paleocene

PiloceneMiocene

Upper (Late)Medium (Middle)

Lower (Early)Upper (Late)

Medium (Middle)Lower (Early)


Lower (Early)


Lower (Early)

Neogene

Paleogene

Mesozoic

Paleozoic

System and Sub-system(Period and Sub-period)

Series(Epoch)

NumericAge(Ma)

Fan

ero

zoic

Pre

cam

bri

an

Prote

rozo

ic

Archaic

Main units of the Chronostratigraphic (Geochronological) Global Standard Scale:

Ages are in millions of years (Ma) corresponding to those of Harland et al (1990)

Salvador (1994 : 86) modified.


431

Albertos, M.A.; Yoris, F.G. and Urbani, F. (1989) Estudio geológico y análisispetrográfico-estadístico de la Formación Guárico y sus equivalentes en lassecciones Altagracia de Orituco-Agua Blanca y Gamelotal-San Francisco deMacaira (estados Guárico y Miranda. VII Congreso Geológico Venezolano.Sociedad Venezolana de Geólogos (Caracas); Memoria 1: 289-314.

Arnstein. R.,E. Cabrera, F. Russomanno, H. Sánchez (1985) RevisiónEstratigráfica de la Cuenca de Venezuela Oriental. En: Espejo, A.; Ríos, J.H. yBellizzia, N.P. de (Edrs.): VI Congreso Geológico Venezolano. SociedadVenezolana de Geólogos (Caracas); Memoria 1: 41-69.

Audemard, F. (1991) Tectonics of western Venezuela. Ph.D. Thesis, RiceUniversity (Houston) :245 p.

Audemard, F. y Lugo, J. (1996) Notes for Petroleum Geology of VenezuelaShort Course. II AAPG/SVG. International Congress & Exhibition, Caracas,1996.

Audemard, F.; Azpiritxaga, Y.; Baumann, P.; Isea, A. y Latreille, M. (1985)Marco geológico del terciario en la Faja Petrolífera del Orinoco de Venezuela.VI Congreso Geológico Venezolano. Sociedad Venezolana de Geólogos(Caracas); Memoria 1: 70-108.

Ave Lallemant, H. and Guth, L.R. (1990) Role of extensional tectonics inexhumation of eclogites and blueschists in an oblique subduction setting:North-Eastern Venezuela. Geology 18: 950-953.

Ave Lallemant, H. (1991) The Caribbean-South American Plate Boundary,Araya Peninsula, Eastern Venezuela. En: Larue, D.K. and Draper, G. (Eds.)12th Caribbean Geol. Conf., Transactions (St. Croix); Miami Geol. Soc.: 461-471.

Barberii, E.E. - Editor Técnico - Quintini Rosales, C.; de la Cruz,M.;Litwinenko, J.; Caro, R. - Coordinadores - (1989) La industria Venezolana deHidrocarburos. Ediciones del CEPET (Caracas) 2 Tomos.

Bartok, P. (1993) Prebreakup geology of the Gulf of Mexico-Caribbean : itsrelation to Triassic and Jurassic rift systems of the region. Tectonics 12 : 441-459.

Bates, R. y Jackson, J. (1980) Glossary of Geology. American GeologicalInstitute (Virginia); 2da.Ed.: 751 p.

Bell, J.S. (1968) Geología del área de Camatagua, Estado Aragua, Venezuela.Bol. Geol. (Caracas) ; 9 (18) : 291-440.

Campos, V., Cabrera, S. de; Lander, R. (1985) Estratigrafía del Noroeste deAnzoátegui. En: Espejo, A.; Ríos, J.H. y Bellizzia, N.P. de (Edrs.): VI CongresoGeológico Venezolano. Sociedad Venezolana de Geólogos (Caracas);Memoria 1: 156-200.

Canache, M.; Pilloud, A.; Truskowski, I.; Crux, J.; Gamarra, S. (1994) RevisiónEstratigráfica de la Sección Cretácica del Río Maraca, Sierra de Perijá,Venezuela. Resumen. V Simposio de Cuencas Subandinas, Memorias;Puerto La Cruz, Venezuela, 1994: 240-241.

Casas, J.; Moreno, J. y Yoris, F.G. (1995) Análisis tectono-sedimentario de laFormación Pampatar (Eoceno Medio), Isla de Margarita (Venezuela). Asoc.Paleont. Arg. (Buenos Aires), Publ. Espec. 3: Paleogeno de América del Sur:27-33.

Castro, M., Mederos, A. (1985) Litoestratigrafía de la Cuenca de Carúpano.En: Espejo, A.; Ríos, J.H. y Bellizzia, N.P. de (Edrs.): VI Congreso GeológicoVenezolano. Sociedad Venezolana de Geólogos (Caracas); Memoria 1: 201-225.

Daal, A. ; González, A. ; Hernández, V. ; Uzcátegui, M. ; Rodríguez, H. ; Pizón,J. Y Choppin, H. (1989) Evolución geológica de la región occidental de lacuenca oriental de Venezuela. VII Congreso Geológico Venezolano. SociedadVenezolana de Geólogos (Caracas); Memoria 2: 389-402.

Chevalier, Y., González, G.; Mata, S.; Santiago, N.; Spano, F. (1995)Estratigrafía Secuencial del Transecto El Pilar - Cerro Negro, Cuenca Orientalde Venezuela. VI Congreso Colombiano del Petróleo, Memorias: 115-125.

Creole Petroleum Corporation (1996) Temas Petroleros. Publicación delDepto. de Relaciones Públicas, Sección Educativa.

CVET -Comisión Venezolana de Estratigrafía y Terminología- (1970) LéxicoEstratigráfico de Venezuela. Bol. Geol. (Caracas) ; Pub. Esp. 4 : 756 p.

Fasola, A., I. Paredes de Ramos (1991) Late Cretaceous PalynologicalAssemblages from El Furrial Area Wells. Revista Técnica Intevep; 2 (1) :3-14,Enero - Junio 1991.

Figueroa, L. y Hernández, H. (1990) Exploración geofísica-geológica del áreade Guarumen. V Congreso Venezolano de Geofísica. Sociedad Venezolana deIngenieros Geofísicos (Caracas) ; Memoria :219-227.

Galea, F. (1985) Bioestratigrafía y Ambiente Sedimentario del Grupo SantaAnita del Cretáceo Superior - Eoceno, Venezuela Nororiental. En: Espejo, A.;Ríos, J.H. y Bellizzia, N.P. de (Edrs.): VI Congreso Geológico Venezolano.Sociedad Venezolana de Geólogos (Caracas); Memoria 1: 703-721.

George, R. y Socas, M. (1994) Historia de maduración termal de rocas madredel Cretácico Superior y Mioceno en la subcuenca de Maturín. V SimposioBolivariano : Exploración Petrolera en las Cuencas Subandinas. SociedadVenezolana de Geólogos (Caracas). Memoria : 405-410.

González de Juana, C.; Iturralde, J.M. y Picard, X. (1980) Geología deVenezuela y de sus Cuencas Petrolíferas. Ediciones Foninves, (Caracas):1031 p.

Harland et al. (1990) A Geologic Time Scale 1989 : Cambridge Univ. Press :163 p.

Janezic, G. ; Toth, D. y Schrayer, G. (1982) Organic Geochemistry. IntegratedGeological Study Eastern Venezuela Basin. Meneven-Gulf (Caracas) ; Parte 2: 194 p.

Kiser, G.D. (1989) Relaciones Estratigráficas de la Cuenca Apure / Llanos conAreas Adyacentes, Venezuela Suroeste y Colombia Oriental. Boletín de laSociedad Venezolana de Geólogos; Monografía 1: 77 p.

Lugo, J., Mann, P. (1995) Jurassic - Eocene Tectonic Evolution of MaracaiboBasin, Venezuela. En : Tankard, A.; Súarez, R.. y Welsink, H.J.: PetroleumBasins of South America : AAPG Mem. 62: 699-725.

Macellari, C.E. (1995) Cenozoic Sedimentation and Tectonics of theSouthwestern Caribbean Pull-Apart Basin, Venezuela and Colombia. En :Tankard, A.; Súarez, R. y Welsink, H.J.: Petroleum Basins of South America :AAPG Mem. 62: 757-780.

Martínez, A.R. (1976) Cronología del Petróleo Venezolano. Colección Cienciay Petróleo 1, Ediciones Foninves, Caracas: 349 p.

Martínez, A. R. (1987) The Orinoco Oil Belt, Venezuela. Journal of PetroleumGeology, 10 (2): 125-134.

Martínez, A. R. (1994) Cronología del Petróleo Venezolano. Ediciones delCEPET, Caracas, 1995; Vol. 2: 462 p.

Méndez, J. O. (1978) La Petrólea del Táchira - Cronología Ilustrada. SVIP,Revista Zumaque, (32): 13-29.

Méndez, J.; Marcano, F.; Valera, R.; González,C.; Kiser, D.; Martínez, A.;Osuna, S.; Russomano, F; Jam,P.; Jiménez, C.; Pérez de Mejía, D.; Gaete,C.P. de; Boesi, T.; White, C. (1989) Exploración. En: Barberii, E.E.(EditorTécnico) La Industria Venezolana de los Hidrocarburos. Ediciones del CEPET,Caracas: 1-157.

Ministerio de Energía y Minas (1985 - 1995) Petróleo y otros DatosEstadísticos (P.O.D.E) Publicación Anual de la Dirección General Sectorial deHidrocarburos - Dirección de Economía de Hidrocarburos, Caracas.

441

B I B L I O G R A P H Y A N D R E F E R E N C E S

Ministerio de Energía y Minas (1962-1984) Petróleo y otros DatosEstadísticos (P.O.D.E.) Publicación anual de la Dirección General - División deEconomía Petrolera, Caracas.

MMH-Ministerio de Minas e Hidrocarburos (1976) Mapa GeológicoEstructural de Venezuela. Ediciones FONINVES (Caracas).

Motiscka, P. (1985) Volcanismo Mesozoico en el subsuelo de la FajaPetrolífera del Orinoco, Estado Guárico, Venezuela. VI Congreso GeológicoVenezolano. Sociedad Venezolana de Geólogos (Caracas); Memoria 3: 1929-1943.

Muñoz, N.G. (1973) Geología sedimentaria del Flysch Eoceno de la Isla deMargarita, Venezuela . Geos (Caracas) 20: 5-64.

Navarro, E.; Ostos, M. y Yoris, F.G. (1988) Revisión y redefinición de unidadeslitoestratigráficas y síntesis de un modelo tectónico para la evolución de laparte norte-central de Venezuela durante el Jurásico Medio-Paleogeno. ActaCientífica Venezolana 39 (5-6): 427-436.

Ortega, J.F., Van Erve, A. y Monroy, Z. de (1987) Formación Guafita : NuevaUnidad Litoestratigráfica del Terciario en el Subsuelo de la Cuenca Barinas -Apure, Venezuela Suroccidental. Boletín de la Sociedad Venezolana deGeólogos 31: 9-35.

Ostos, M. ;Navarro, E. y Urbani, F. (1989) Edad Rb/Sr del Augengneis de Peñade Mora, Cordillera de La Costa. VII Congreso Geológico Venezolano.Sociedad Venezolana de Geólogos (Caracas); Memoria 1: 127-136.

Ostos, M. (1990) Tectonic evolution of the South-Central Caribbean based ongeochemical and structural data. Ph.D. Thesis. Dept. Geol. and Geoph., RiceUniversity (Houston).

Ostos, M. (1992) Tectonic evolution of the South-Central Caribbean based ongeochemical data. Geos (Caracas); (30): 1-294.

Parnaud, F., Gou, Y.; Pascual, J.C.; Capello, M. A.; Truskowski, Y.;Passalacqua, H. y Roure, F. (1995a) Stratigraphic Synthesis of WesternVenezuela. En : Tankard, A.; Suárez, R. y Welsink, H.J.: Petroleum Basins ofSouth America. AAPG Mem. 62: 681-698.

Parnaud, F., Gou, Y.; Pascual, J.C.; Capello, M. A.; Truskowski, Y.;Passalacqua, H. y Roure, F. (1995b) Petroleum Geology of the Central Part ofthe Eastern Venezuela Basin. En : Tankard, A.; Suárez, R. y Welsink, H.J.:Petroleum Basins of South America. AAPG Mem. 62: 741-756.

Passalacqua, H. ; Fernández, F. ; Gou, Y. y Roure, F. (1995) CrustalArchitecture and Strain Partitioning in the Eastern Venezuela Ranges. En :Tankard, A.; Suárez, R. y Welsink, H.J.: Petroleum Basins of South America.AAPG Mem. 62: 667-680.

Pérez de Mejía, D. ;Kiser, G.D. ;Maximowitsch, B. y Young, G. (1980)Geología de Venezuela. En : Felder, B. (Coord.), Brie, A. ;Gartner, J. ; Hepp, V.; Hrabie, M ; Kervella, M. ; Mons., F. ; Mowat, G. ; Neville, N. ; Plomb, J. ;Sadras, W. ; Tejada, A. ; Trassard, J. ; Vidal, J. Y Zinat, D. : Evaluación deFormaciones en Venezuela. Schlumberger Surenco S.A. ;1ra. Ed. : 287 p.

Rivero, F. (1956) Léxico Estratigráfico de Venezuela. Bol. Geol. (Caracas) ;Pub. Esp. 1 : 728 p.

Roger, J.V. (Coord.); Arteaga, N. (Coord. ) Cabrera,J.; Valera, G.; Jam., P.;Castillo, M.; Boesi, T. y Sancevic, Z.A. (1989) Exploración. Sección II :Ingeniería de Yacimientos y Geología de Producción. En: Barberii, E.E.(EditorTécnico) La Industria Venezolana de los Hidrocarburos. Ediciones del CEPET,Caracas, Tomo 1: 2-167 a 2-261.

Roure, F. ; Carnevali, J.O. ; Gou, Y. y Subieta, T. (1994) Geometry and kine-matics of the North Monagas thrust belt (Venezuela). Marine and PetroleumGeology 11 (3) :347-362.

Salvador, A. (1994) International Stratigraphic Guide. I.U.G.S. y GSA (Boulder); 2da Ed. : 214 p.

Smith Jr., F. D. et al. (*) (1962) Cuadro de Correlación de las UnidadesEstratigráficas en Venezuela y Trinidad. En : Aspectos de la Industria Petroleraen Venezuela, SVIP, Congr. Ven. Petr. I, Caracas, 1963. (*) Personal Técnicode las compañías: Shell de Venezuela, Creole Pet. Corp., Mene Grande OilCo., Ministerio de Minas e Hidrocarburos, Mobil Oil Co. de Venezuela,Richmond Exploration Co. y Texas Petroleum Co.

Stainforth, R.M. (1971) La Formación Carapita de Venezuela Oriental, IVCongreso Geológico Venezolano (Caracas); Bol. Geol.; Pub. Esp. 5; (1): 433-463.

Stifano, M.P. (1993) Estratigrafía de la Formación Carapita en su sección tipoy en la sección del pozo ORS-52. Trabajo Especial de Grado. Fac. Ing.; Dpto.Geología (UCV) (2Vol.): 195 p.

Talukdar, S. y Marcano, F. (1994) Petroleum Systems of the Maracaibo Basin,Venezuela. En : Magoon, L. y Dow, W. : ¨The Petroleum System- FromSource to Trap¨. AAPG Memoir 60; 1st. Ed. (Tulsa) : 463-482.

Velarde, H. (1991) Cinco Relatos de Exploración en la Venezuela PetroleraActual. Gerencia Corporativa de Información y Relaciones de PDVSA,Caracas: 231 p.

Vivas, V. y Macsotay, O. (1989) Miembro El Pilar de la Formación Quiamare.Ejemplo de molasa orogénica neogena de Venezuela nororiental. Escuela deGeología Minas y Geofísica, UCV (Caracas) ; Geos 29 : 108-125.

Wright, L.M., Pantin, J.H.; Mohler,W.A.; Spoor,A.; Pantin, B.C. (1962)Exploración. En : Aspectos de la Industria Petrolera en Venezuela, SVIP, ICongreso Venezolano de Petróleo, Caracas, 1963.

Yoris, F.G. (1985) Revisión de la Estratigrafía del Cretáceo Inferior al sur y estede la Serranía del Interior, Venezuela nororiental. En: Espejo, A.; Ríos, J.H. yBellizzia, N.P. de (Edrs.): VI Congreso Geológico Venezolano. SociedadVenezolana de Geólogos (Caracas); Memoria 2: 1343-1393.

Yoris, F.G. (1988) Localidades tipo y secciones de referencia para los miem-bros de la Formación El Cantil en la Serranía del Interior, Venezuela nororien-tal. Boletín de la Sociedad Venezolana de Geólogos (Caracas); 34: 52-70.

Yoris, F.G. (1989) Análisis de los ciclos de sedimentación en la FormaciónCarapita, utilizando los métodos del promedio móvil y series de Fourier. VIICongreso Geológico Venezolano. Sociedad Venezolana de Geólogos(Caracas); Memoria 1: 615-640.

Yoris, F.G., Ostos, M.; Boujana, M.; Pérez, J.; Booth, G.; Packer, S.; Galea, F.y Lander, R. (1996) Detailed Lithostratigraphy and Age Determinations of LaLuna Formation in two sections of S.W. Táchira State (Venezuela). AAPGBull.; 80 (8): 1346.

Yoris, F.G. ; Ostos, M. ; Boujana, M. ; Contreras, O. y Lander, R.(1996) MiradorFormation in SW Táchira State, Venezuela : Potential Reservoir for thePaleogene Sequence. AAPG Bull. 80 (8): 1346.

Yoris, F.G. (1992) Análisis de secuencias clásticas por métodos petrográficosy estadísticos. Tesis Doctoral en Ciencias Geológicas. Fac. Ing.; Dept.Geología (UCV): 1045 p.

Yoris, F.G. (1992) Localidades tipo para los miembros de la FormaciónChimana en la Serranía del Interior, Venezuela nororiental. Geos (Caracas);(30): 295-324.

Young, G. ; Bellizzia, A. ; Renz, H.H. ; Johnson, F. ; Robie, R. y Más Vall, J.(1956) Geología de las cuencas sedimentarias de Venezuela y de sus campospetrolíferos. Bol. Geol. (Caracas) ; Pub. Esp. 2 : 140 p.

Geologia Petrolera de Venezuela

Documents

Transcript of Geologia Petrolera de Venezuela