Chapter 3 (Petroleum Systems, Origin and Migration)
Transcript of Chapter 3 (Petroleum Systems, Origin and Migration)
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
1/56
Chapter 3
Petroleum Systems
The Origin of Oil & GasSource Rocks, Generation and
Migration
1
Presenter: Leigh Brooks
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
2/56
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
3/56
Major producing Shales in USA
+Eagle Ford Shale
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
4/56
The Petroleum System
Is! The essential elements and processes and allgenetically"related hydrocarbons that occur inpetroleum sho#s and accumulations #hoseprovenance is a single pod of active source rock!
Source Rock
Migration Route
Reservoir Rock
Seal Rock
Trap
Elements
Generation and
Expulsion
Migration
Accumulation
Preservation
Processes
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
5/56
24803
Petroleu# S"ste# &le#entsPetroleu# S"ste# &le#ents
Source $ockSource $ock
Top Seal $ockTop Seal $ock
$eservoir $ock$eservoir $ock
!nticlinal 'rap!nticlinal 'rap
(Organic $ich%(Organic $ich%
(Impermeable)
(Porous/Permeable)
PotentialMigration Route
Petroleum System elements
critical components of a productive system
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
6/56
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
7/56
24803
Petroleu# S"ste# &le#entsPetroleu# S"ste# &le#ents
'20*'20*
350*350*GenerationGeneration
MigrationMigration
Seal $ockSeal $ock
$eservoir$ock$eservoir$ock
OilOil
+ater+ater
as)apas)ap
&ntrap#ent&ntrap#entAccumulation
andpreservation
Source Rock
Petroleum Systemprocesses that act on the elements to result in a hydrocarbon accumulation! eneration
discussed here is for ther#all" #ature sedi#ents! -ote biogenic or bacterial
gas forms at lo# temperatures
.'00deg )
.'/5deg )
and expulsion
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
8/56
Generation " 0urial of source rock to a temperature andpressure regime sufficient to convert organic matter
into hydrocarbon! 1ifferent types of organic matter re2uiredifferent temperatures to produce oil! Sufficient volumes ofhydrocarbon need to be generated #ithin the source rock tocreate high enough pressures to force epulsion of thehydrocarbon from the source rock
Migration 34pulsion of hydrocarbon out of the source
rockand movement up#ards and into a trap, if present
'i#ing " for effective entrapment, trap must form before orduring hydrocarbon migration
!ccu#ulation " A volume of hydrocarbon that migrates intoa trap faster than the trap leaks results in an accumulation
Preser(ation " 5ydrocarbon remains in the reservoir and is
not too adversely affected by biodegradation or #ater"#ashing
Petroleum System processes
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
9/56
Diagenesis
Ro = 0.5
Ro = !.0
Catagenesis
Metagenesis
K4
K3
K2
K1
K
K
Oil Phase"Out
Oil Gas
Oil Gas
Oil Gas
Cond
Gas
Gas
Less *"drogen More *"drogen
#erogen
Onset of OilGeneration
Horsield and Rullkotter! 1994
0urial to
reater
and 5otter1epths
eneration " Thermal maturation history
thermal cracking of kerogen to form hydrocarbons
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
10/56
400 300 200 100
Paleo"oic Meso"oic Cen#
P $KJTPM% P Litholog&
Rock
Unit
%epth
(Km)
Source
Reservoir
Seal
Overburden
1
2
3
Placer Fm
George Sh
Boar Ss
%eer Sh
Elk Fm
Top gas 'indo'
Critical Moment
Thick
Fm
R
Magoon and %o'! 1994
Generation
Time of 34pulsion and 6igration! (Trap must already e4ist for oiland gas to be trapped%
Top oil 'indo'
Timing " 0urial history chart plot of depth andmodelled temperature vs geological time to estimate #hen generation occurred
'i#e #ill "rs
+eore
present
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
11/56
1 2
400 300 200 100
Paleo"oic Meso"oic Ceno"oic
% M P P TR J K P $
Geologic Time(ScaleMill &rs beore present
PetroleumSystem Events
Source Rock
Reservoir Rock
Seal Rock
Overburden
Trap FormationGeneration! Migration!and Accumulation
Preservation
Critical Moment1# estern $orthSlope2# East(central $orthSlope
Petroleum Systems 3vents )hart to #ork
out #hether essential elements are present and the timing good-orth Slope, Alaska
'i#ing is critical
0
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
12/56
Spill PointSpill Point
Seal Rock(Mudstone)Reservoir Rock
(Sandstone)Migration rom*Kitchen+
1$ Early Generation
!$ %ate Generation
Gas displaces all
oil
Gas beginning todisplace oil
%isplaced oil
accumulates
Petroleu# S"ste# A%&namic Entit&
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
13/56
34ample petroleum system7 )ritical moment determined by
0urial history chart plot of depth and modelled temperature vs geologicaltime (millions of years before present% to estimate #hen generation occurred
400 300 200 100
Paleo"oic Meso"oic Cen#
P $KJTPM% P Litholog&
Rock
Unit
%epth
(Km)
Source
Reservoir
Seal
Overburden
1
2
3
Placer Fm
George Sh
Boar Ss
%eer Sh
Elk Fm
Top gas 'indo'
Critical Moment
Thick
Fm
R
Magoon and %o'! 1994
Generation
2506a "Time of 34pulsion and 6igration due to rapid burial!
Top oil 'indo'
0
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
14/56
An e4ample Petroleum System at )ritical interval of time
(6oment% " map or plan vie#
Magoon and %o'!1994
Teapot O'ens
Pod o Active
Source Rock Just
Big Oil
Hard& Luck&
,ero Edge o
Reservoir Rock
Immature Source Rock
Raven
Marginal
!50 Ma million years ago$
A A
%avid
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
15/56
PO% OF ACTIVE SOURCE
ROCK
34ample Petroleum System at )ritical 6oment
)ritical 6oment 8 Time of 34pulsion96igration
Magoon and %o'! 1994
Over'urden
Seal
Reservoir
Source
STRATIGRAPHIC
E-TE$T OF
PETROLEUM SYSTEM
Trap Trap
Essential
elements opetroleum
s&stem
Under'urdenSedim
entary
'asin
"fill
GEOGRAP(ICEXTENT O) PETRO%EUMS*STEM
!50 MaTrap
Petroleum accumulation
Top o oil 'indo'
Bottom o oil 'indo'
Location or burial histor& chart
A A
!50 Ma million years ago$
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
16/56
400 300 200 100 Geologic Time
Scale
Petroleum
S&stem Events
Rock Units
Source Rock
Reservoir Rock
Seal Rock
Trap Formation
Overburden Rock
Gen/Migration/Accum
Preservation
Critical Moment
Paleo"oic Meso"oic Ceno"oic
% M P P TR J K P $
Elemen
ts
Processes
Magoon and %o'!1994
Petroleum System 3vents )hartTiming of 3lements and Processes
Critical Moment
Time of 34pulsion and 6igration! (Trap must already e4ist%
0
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
17/56
GEOGRAP(ICEXTENT O) PETRO%EUMS*STEM
Present"Day
STRATIGRAPHIC
E-TE$T OF
PETROLEUM SYSTEM
Petroleum accumulationTop o oil 'indo'
Bottom o oil 'indo'
Trap TrapTrap
Seal
Reservoir
Source
Under'urden
Over'urden
A A
Magoon and %o'! 1994
Present day e4ample Petroleum system cross section
vie# "things have changed since the critical moment
-ote this pool #as
charged early, before
the latest structuring,
#hich separated this
trap from the source!+ithout #orking out
the timing of
generation and
migration, you might
conclude this structure
could not contain
hydrocarbons due tono viable migration
path#ay from mature
source
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
18/56
Petroleum consists mainly ofhydrocarbons, composed of )and 5 atoms (oil, condensate,
gas%! Other components mayinclude -itrogen, O4ygen,Sulphur and traces of metals
)omprises a large number of
compounds ranging from gasto solid ()' to )50%, #hich canbe divided into % #aingroups: aro#atics,napthenes, +ranchedalkanes and nor#al alkanes
Oils have average 59) of '!5"2!0and thus re2uire largeamounts of 5 for them to becreated
)omposition of Petroleum
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
19/56
Origin of Oil and as Source $ocks
Petroleum is derived from organic #atter -OM) deposited in fine grainedsediments! This O6 consists of proteins, carbohydrates (incl! sugars &cellulose%, lignins (in #ood and bark% and lipids (vegetable oils, fats and#a4es%
T#o main sources of O6" '! auatic organis#s gro/ing in oceans and lakes, mainly algaeand phytoplankton (microscopic plants% and bacteria! :sually v minoranimal remains (;ooplankton, eg foraminifera #hose shell remains formchalk, radiolarians, crustaceans such as krill, etc%
" 2! remains of terrestrial -land) plants carried to the site of deposition
! good source rock reuires a suicient concentration o OM to +epreser(ed
diatomsAlgal bloom off 3ngland
Source
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
20/56
The production of plankton (floating organisms% in the #orld is prodigious!
Large amounts produced in areas rich in nutrients eg sites of up#ellingcurrents
3g #ithin the 0lack Sea every year
2!/ thousand million tons of planktonare produced, containing on the average '"3 of fatty acids and 4"
'
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
21/56
Preservation of Organic matter (O6%
$e2uires an o"gen deicient -anoic) en(iron#ent o deposition,#hich commonly occurs =ust belo# the sediment #ater interface
" #here there is little destruction of O6 by aerobic bacteria andscavengers
" anaerobic bacteria #ill not destroy the O6
Areas of poor #ater circulation such as silled or ponded basins arefavourable! (good circulation leads to o4ygenated #ater and sediment"unfavourable%
Stratified #ater columns, eg thermal or saline stratification, result in poorcirculation of #ater #hich leads to stagnant conditions near the sediment
#ater interface
"
Silled basin models for
ano4ia
Scott +A0S '>>4
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
22/56
Ano4ic conditions are favoured by continued optimum rate of mudstonedeposition, shielding the organic matter (O6% from potentially o4ygenated#aters! Too rapid deposition may dilute the O6 in the sediment and tooslo# allo#s more time to degrade the 2uality of the O6
5igh supply of O6 is obviously favourable to preservation of significantamounts of O6 in sediments! This re2uires a continued supply of nutrientssuch as - and P, #hich is delivered to basins in the run off from rivers orby the up#elling of deep nutrient rich #aters
As the remains of organisms decay, o4ygen is consumed, leaving o4ygendepleted #aters suitable for preservation of O6 if there is poor #atercirculation
"
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
23/56
)onversion of Organic matter to kerogen
+ithin a fe# metres from the surface, biopolymers begin to beconverted into kerogen, a chemically stable, insoluble (in organicsolvents and #ater% substance consisting of huge comple4 moleculescomposed of ),5 and O! This process is largely completed atrelatively shallo# burial depths of 300"'000m
A minor soluble component of the O6 is bitumen, #hich consists ofasphaltenes, resenes and hydrocarbons derived from living material!These hydrocarbons (+io#arkers%, although small in volume areimportant because they retain the chemical characteristics of theirplant source and can thus be used to identify the particular source bed
and to correlate oils! Identifying the source of a particular oil mayassist e4ploration
eg )33alkylcyclohe4ane found in most of the oils in the Perth 0asin is found only in the3arly Triassic basal ?ockatea Shale
Source richness )oncentration of O6 is usually measured by Total Organic )arbon
(TO)% as #eight of )9 unit #eight of rock
+orld average TO) of shales .'
ood (rich% source rocks considered to have TO) @2
Very rich source rocks have TO)@5
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
24/56
3volution of kerogen, including cooking
(catagenesis, sometimes spelt katagenesis% to
produce oil and gas
Thermal
generation of
petroleum
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
25/56
Quality of kerogen
?erogen has been divided into 3main types, #hich #ill yield differenttypes and amounts of hydrocarbon #hen thermally mature
6any source rocks contain mi4tures of the 3main types
'"pe -!lginitic) 34cellent oil source, high in 5, derived from algae and
phytoplankton (microscopic plants%! $elatively rare and occurs inlacustrine (lake% environments or closed marine basins! 3nd membercan produce up to
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
26/56
TOC 2#12T#. TOC #38T#.
Kerogen t"pes
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
27/56
Source $ock for Petroleum
Dar+ organic"rich thinlaminae , result of -et season runoff Measured alues
/./ /2
TotalOrganicCar'on
!.!4 1!.20
In"PlacePetroleumS1
LOMPOC uarr& Sample
Montere& Formation! CA
(ydrogenIndex
PyrolyticallyGeneratedPetroleumS!
1 Inch
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
28/56
Oil and gas are formed by the thermalcracking of organic compounds buried infine"grained rocks!
3gAlgae 8 5ydrogen rich 8 Oil"prone! Type '
+ood 8 5ydrogen poor 8 as"prone! Type3b
Types of petroleum produced
Accurate prediction of probable
hydrocarbon type and volume, based onpaleogeographic and productivity models,
is critical to e4ploration success#
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
29/56
Thermal maturation Average geothermal gradient #ithin sedimentary basins is appro4imately 25"30
deg )9km! It depends on heat flo# up through the earth and thermal conductivityof the sediments and varies during the basinBs evolution! Some basins may havehigh heat flo# and be 2uite hot ie have high temperatures at relatively shallo#depths
Increased heat flo# and higher geothermal gradients occur during rifting, #henthe crust is thinnest
Temperatures increase #ith depth and for e4ample may reach '35"'50deg ) atabout 4000m
+hen kerogen in sediments is sub=ected to sufficiently high temperatures fromdeep burial, it is progressively cracked into smaller, simpler molecules
petroleum, #ith increasing temperature! This is kno#n as catagenesis If oil prone kerogen (Types I and II% is present, the first products #ill be heavier
oil! As burial continues and the temperature increases, the hydrocarbonmolecules produced become lighter, moving through the peak oil generationphase to gas" condensate and finally to the end stage #here the oil retained inthe rock is converted to methane and the kerogen to carbon!
A single source rock can produce many oils of different gravities andcharacteristics, depending on the richness of the source rock and the basinBs andoilsB histories
The temperature at #hich peak oil generation occurs is variable, depending onthe type of kerogen and the heating rate among other things, but generally
ranges bet#een ''0and '
50deg )
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
30/56
Thermal maturation general relationship bet#een oil and gasgeneration and various parameters such as vitrinite reflectance ($o%, spore colour
(S)I% etc
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
31/56
Organic richness is measured by routine Total Organic )arbon analyses(TO), 8 #eight of )9 unit #eight of rock as %
The degree of thermal maturity of kerogen can be measured by variousmeans and is important in assessing the history of the basin and sourcerocks! This is critical in assessing remaining e4ploration potential
6easurement methods include (itrinite relectance, Spore )olour
Inde4, e4tracted soluble hydrocarbons, $ock 3val Pyrolysis, gaschromatography, gas chromatography"mass spectrometry
The history and maturity of migrating oils can be studied if traces of theoil are trapped in small inclusions #ithin crystalline cements insandstones " 6olecular )omposition of Inclusions
6easurements
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
32/56
34pulsion and migration
+hen hydrocarbons are formed from the thermal degradation of kerogenthere is an increase in volume ie the oil and gas occupies more spacethan the kerogen! +hen sufficient volumes (high saturation% aregenerated #ithin the source rock, the high pressures produced #ithin thesource rock #ill cause microfracturing of the rock to occur and some ofthe hydrocarbon #ill be epelled into surrounding more porous and
permeable (and lo#er pressured% rock!
34pulsion from rich source rocks #ill occur earlier than in poorer sourcerocks because the critical volume of hydrocarbon #ithin the rock isreached sooner
"
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
33/56
34pulsion and migration
Oil and gas e4pelled into more permeable neighbouring rock such assiltstone and sandstone beds in clastic sediments and into fractures then#igrates up#ards through buoyancy effects, as the petroleum is lighterthan #ater! 1riven by pressure gradients resulting from the buoyancy, theoil and gas takes the easiest path!
"
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
34/56
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
35/56
*oreland 0asins7 Oil (and gas% in the 3astern Vene;uelan 0asin has
travelled .200
km along simple path#ays to the edge of the basin, #hereover '200billion barrels of biodegraded heavy oil is trapped at shallo#depths in the Orinoco Tar 0elt
Overburden #edge of
sediments shed off
mountains pushed sourcerocks into generation #indo#
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
36/56
TrinidadBs Tar Lake migration to the surface
" #here biodegradation occurs, creating heavy oil9tar
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
37/56
)hemical relations bet#een petroleum hydrocarbons
and other natural hydrocarbons6
Sh l Oil d G
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
38/56
Shale Oil and Gas
Large a#ounts o oil and gas /ill re#ain /ithin ther#all" #atureorganic rich shales -source rocks) even if the shale has been throughthe peak oil generation #indo# and large amounts of oil and gas havebeen e4pelled! 34pulsion efficiency in shales is variable and depends onthe presence of interbedded permeable carrier beds
Porosity of viable shale in shale gas plays may range from 4"5 to@'0, but permeability is very lo#! 6ost of the porosity is in nanoporesformed as the O6 is converted to hydrocarbon
:ntil recently, these shales #ere considered non reservoir (in factseals%, but
If these shales have some natural fracture net#ork and the rightmechanical characteristics (primarily brittleness% to enable them to befractured (fracced% to produce the hydrocarbons contained #ithin, the"#a" +eco#e a (alua+le Shale Resource
Recent de(elop#ents in hori1ontal drilling and racture sti#ulationtechniues and reduced costs allo/ (ast (olu#es o shale toproduce h"drocar+ons econo#icall"
Sh l P t l S t
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
39/56
Shale as Petroleum System
! shale gas s"ste# is a sel$contained source$reser(oir$seal -$trap) s"ste#
In this system, shales that generated the gas also function
as (er" lo/ #atri per#ea+ilit" and lo/ porosit"
reser(oir rocks
The gas in shales occurs both as a free phase #ithin poresand fractures and as gas adsorbed onto organic matter
The adsorbed gas is proportional to the total organic carbon
(TO)% of the shale! *ree gas is proportional to the effective
porosity and gas saturation in the pores
Reservoir
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
40/56
Lo' matrix porosit& is
increased as more pore space
is created throughconversion
o organic matter to
h&drocarbon
Total porosit& generall& 3(10.
%ata rom core and logs
Reservoir
Oil Preservation
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
41/56
+hen oil has been trapped in a reservoir it can be affected by severalprocesses that #ill change the character of the oil
Nor#al #aturation! If the trapped oil is buried further and becomes hotter,the heavier more unstable compounds #ill be cracked to lighter compoundsresulting in the oil becoming lighter (higher API gravity%
2e$asphalting! If do#ndip gas migrates into the oil accumulation, heavierasphaltenes can precipitate (plugging reservoir pores% leaving a lighter oil
ater /ashing! If the oil accumulation is in contact #ith moving a2uifer#ater, the lighter gasoline range hydrocarbons (mostly )5")'0% aredissolved in the #ater and carried a#ay, leaving a heavier oil! A less severebut similar effect can be produced from long distance migration #hich mayresult in oils #ith lo# as Oil $atios (O$%
Biodegradation! This occurs #hen fresh o4ygen charged meteoric #aterscarry aerobic bacteria from the surface to the oil reservoir, #hich must be attemperatures less than about /0deg )! The aerobic bacteria eat the lightermolecules, particularly the normal alkanes, leaving heavier oil (egTrinidad%
The large tar sand accumulations in )anada and
Vene;uela are a result ofbiodegradation and #ater #ashing, at shallo# depths
Oil Preservation
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
42/56
Oils ain4t oils5
0oiling is a simple single #ord
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
43/56
0oiling is a simple, single"#ord
e4planation of ho# crude oil is
separated into its eight basic parts" fractionation
11
1ensity or ravity of oil
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
44/56
1ensity or ravity of oil
One of the most important properties of oil #hich, among other characteristics,
determines its commercial value, is 13-SITY!
Oil density is e4pressed in industry as oil gravity! This is given in a scale
determined by the American Petroleum Institute! Oil gravity is e4pressed indegrees API CDAPIE!
The API gravity scale is based on the 0aume scale! The follo#ing e2uation is usedto go from specific gravity
oAPI 8 C'4'!59 Specific ravity(
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
45/56
ATTRIBUTE AT(ABASCA CO%D%A#E A%BERTACRUDE
Saturates 12"!/ !1 0"0
Aromatics ! 1
Asphaltenes 1 16 0.1"0.!
Resins /5 44 "15
Sulfur3 4
. 4
.5 0.1"!Metals3 ppm
anadium !50 1"5
Nic+el 100 1"5
Reservoir oilviscosity3 cp
5003000 103000"1003000
1
)omparison of conventional crude and heavy oil )anada 15
Gravity 4API "2 10"1! /5
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
46/56
0iogenic as (non thermal%
0iogenic gas is generated at lo# temperatures by decomposition oforganic matter by anaerobic microorganisms!
It consists mainly of methane ()'%, #ith generally minor )O2, -2 and)2(ethane%
0iogenic gas usually can be distinguished from thermogenic gas bychemical and isotopic analyses
6ore than 20 of the #orldFs discovered gas reserves are ofbiogenic origin
The factors that control the level of methane production aftersediment burial are ano4ic environment, sulfate"deficientenvironment, lo# temperature, availability of organic matter, andsufficient pore space!
This generally occurs in areas of rapid deposition and the timing of
these factors is such that most biogenic gas is generated prior toburial depths of ',000m!
'he ther#al #odel does not appl" to this gas, /hich #a" +epresent in +asins /ith no ther#all" #ature source rocks
Case stud"
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
47/56
Case stud""of a relatively simple empirical approach to defining the depth to
and e4tent of potential oil e4pulsion"this approach is reasonable in areas #hich have suffered
continuous subsidence to the present day and #hich are believed
to have had relatively uniform heat flu4 through deposition
+estern Platform, Taranaki 0asin, -e# Gealand
?ey #ell Tane"', #ith detailed geochemical analyses ofpotential coally source rock intervals
-OT
3 6ore rigorous modelling of thermal history of sediments canbe done using the estimated heat flu4 from deeper #ithin thecrust and a model of the thermal conductivity of thesediments
'ane 6
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
48/56
'ane$6
Wainui
Ra+opi
Basement
Potential coally andshaley source intervals
Tane"1
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
49/56
Wainui
Ra+opi
W E N S
Note increasing coallycharacter from Nto S
Wainui and Ra+opi coalscorrelate into depocentre
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
50/56
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
51/56
$akopi *ormation7 $ock"3val! Samples from Tane"'
Oil"prone
Gas"prone
Gas" &oil"prone
GNS Science unpu'l. results$
0
100
!00
/00
400
500
0 10 !0 /0 40 50 60 0 20 0
TOC-t.$
(I&mg(C/gTOC$
Coaly mst.
Shaly coal
Coal
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
52/56
1ecreasingQI, ie oil
generating potential, is dueto oil having been e4pelled
from the coally sediments at
increasing temperature
This defines the maturity
level at #hich e4pulsion
occurs
Increasing maturity
6odelled generation based on geochemical analyses of the O6 in Tane"'!
1iff t O6 ill h diff t ti hi t d d t
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
53/56
Standard -S values for 'ane$6 (Sykes pers comm!%
3005I, /0 TO), 34m thickness (combined coals and shaly coals andmuds%, gogi 0!34 Potential 73 MM++l8k#7 oil and 42660O39km2 gas
'00 '20 '40 '
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
54/56
)onservativetop of oil #indo#
Significant oil e4pelled at
this maturity
3mpiricalmeasurements
used to estimate
top of oil e4pulsion
"consistent #ithestimated
temperature of
.'50
deg )
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
55/56
sea level
Gross thic+ness of mature source roc+
Arange o depths to top o oilexpulsion 'ere used to assess
sensitivit& to estimated gross
volume o mature sediment and
hence to volume o oil expelled
and available to ill traps
3stimated 6ature +ainui9$akopi Thickness from seismic mapping
-
8/9/2019 Chapter 3 (Petroleum Systems, Origin and Migration)
56/56
4500m 0S* 4/00m 0S* 4>00m 0S*