Bi b i d R i Fl Ch i i Wh did h P bili G ?Bi t b ti d R i Fl Ch t i ti Wh did th P bilit G ?Bioturbation and Reservoir Flow Characteristics: Where did the Permeability Go?Bioturbation and Reservoir Flow Characteristics: Where did the Permeability Go?Bioturbation and Reservoir Flow Characteristics: Where did the Permeability Go?Bioturbation and Reservoir Flow Characteristics: Where did the Permeability Go?y1 1 1 1R ld R M D ll1 D id L M t h 1 d K th i L A 1 1 W t Vi i i G l i l d E i S P ORonald R McDowell1 David L Matchen1 and Katharine L Avary1; 1 West Virginia Geological and Economic Survey P ORonald R McDowell1 David L Matchen1 and Katharine L Avary1; 1 - West Virginia Geological and Economic Survey P ORonald R. McDowell , David L. Matchen , and Katharine L. Avary ; West Virginia Geological and Economic Survey, P. O. , , y ; g g y,

B 879 M t WV 26507 0879Box 879 Morgantown WV 26507 0879Box 879 Morgantown WV 26507-0879Box 879, Morgantown, WV 26507-0879Box 879, Morgantown, WV 26507 0879gABSTRACTABSTRACT TOO

PT P

Effects of bioturbation on sediment permeability are not always intuitive

TO

Effects of bioturbation on sediment permeability are not always intuitive. Pp y yBioturbation may alter sorting disturb sedimentary layering "pipe" sediment EFFECTS OFBioturbation may alter sorting, disturb sedimentary layering, "pipe" sediment EFFECTS OFy g y y g p pand fluids between sedimentary units add or remove organic matter and clay or EFFECTS OFand fluids between sedimentary units, add or remove organic matter and clay, or EFFECTS OF y g ychange pore fluid chemistry Permeability may increase only to disappear duringchange pore fluid chemistry. Permeability may increase only to disappear during BIOTURBATIONg p y y y y pp gdiagenesis BIOTURBATION:diagenesis. BIOTURBATION:g

The Devonian Gordon sandstone of West Virginia and Pennsylvania repreThe Devonian Gordon sandstone of West Virginia and Pennsylvania repre-g y psents a strandplain deposit from the westernmost advance of the Acadian clasticsents a strandplain deposit from the westernmost advance of the Acadian clastic p pwedge Core recovered from this unit in the Jacksonburg oil field in West Virwedge. Core recovered from this unit in the Jacksonburg oil field in West Vir- Mixes and homogenizes existingg gginia comprises sandstone shale and conglomerate The sandstones are the Mixes and homogenizes existingginia comprises sandstone, shale, and conglomerate. The sandstones are the Mixes and homogenizes existing g p gmost important and most problematic Some form prolific pay units others are

g gi imost important and most problematic. Some form prolific pay units, others are sedimentary materialsp p p p y

"tight" and unproductive sedimentary materials"tight" and unproductive. sedimentary materialsg pGordon sandstones consist monotonously of very fine to fine grained quartzGordon sandstones consist monotonously of very fine- to fine-grained quartz y y g q

sand with quartz pebble layers Sandstones are differentiated by the presence orsand with quartz pebble layers. Sandstones are differentiated by the presence or q p y y pabsence of distinctive sedimentary structures primarily well preserved traceabsence of distinctive sedimentary structures, primarily well-preserved trace y p y pfossils and ripple scale crossbedding Logs of the bioturbated sandstones showfossils and ripple-scale crossbedding. Logs of the bioturbated sandstones show

A i i fpp g g

high densities; core permeabilities are <20 mD Bioturbation probably enhanced Allows the introduction of 1 cmhigh densities; core permeabilities are <20 mD. Bioturbation probably enhanced Allows the introduction of1 1 cmg p p y

porosity and permeability but left cross stratal "pathways" open to mineralizingAllows the introduction of 1 cmporosity and permeability but left cross-stratal "pathways" open to mineralizing “ ti ” di t i t i ti

p y p y p y p gpore fluids Silica and siderite cements filled all pore space On the other hand “exotic” sediment into existingpore fluids. Silica and siderite cements filled all pore space. On the other hand, exotic sediment into existingp p pthe "featureless" sandstones have low log densities; core permeabilities range

gPhotomicrograph showing burrows in micritic limestone that havethe "featureless" sandstones have low log densities; core permeabilities range sedimentary materials Photomicrograph showing burrows in micritic limestone that have g p g

from 50 to 500 mD Pore space may have been maintained by early entry of sedimentary materials been infilled with fecal pellets fossil debris and quartz silt Samplefrom 50 to 500 mD. Pore space may have been maintained by early entry of sedimentary materialsPhotomicrograph showing sedimentary laminae in calcite cemented been infilled with fecal pellets, fossil debris, and quartz silt. Samplep y y y ypetroleum or because pathways to cementing fluids were absent A remaining

yPhotomicrograph showing sedimentary laminae in calcite-cemented from Middle Ordovician Lehman Formation eastern Nye Co NVpetroleum or because pathways to cementing fluids were absent. A remaining quartz siltstone disturbed by bioturbation A single partially clay from Middle Ordovician Lehman Formation, eastern Nye Co., NV, p p y g gquestion is whether the featureless sandstones were always devoid of sedimen

quartz siltstone disturbed by bioturbation. A single, partially clay- 17 7 m above base of unitquestion is whether the featureless sandstones were always devoid of sedimen- lined burrow is preserved near the top of the slide Sample from 17.7 m above base of unit. q ytary structures or had them removed by thorough bioturbation This work was

lined burrow is preserved near the top of the slide. Sample from tary structures or had them removed by thorough bioturbation. This work was Middle Ordovician Lower Antelope Valley Limestone westerny y gfunded by U S Department of Energy contract DE AC26 98BC15104

Middle Ordovician Lower Antelope Valley Limestone, western funded by U. S. Department of Energy contract DE-AC26-98BC15104. White Co NV 139 m above base of sectiony p gy

Allows the migration of poreWhite Co., NV, 139 m above base of section. Allows the migration of poreAllows the migration of pore g pf i ifluids between sedimentaryfluids between sedimentaryfluids between sedimentary l l di t diff tlayers - leading to differentlayers - leading to different y gcements and cementing historiescements and cementing historiescements and cementing histories gffor burrows and host rockfor burrows and host rockfor burrows and host rock

11.22 m 0m 0.15 mm

V i l i h f il (Sk li h ) dil i ibl i hi b f h i li h lVertical ichnofossils (Skolithos sp.) are readily visible in this outcrop because of their light color.Vertical ichnofossils (Skolithos sp.) are readily visible in this outcrop because of their light color.Th k i fi di i d d d i h l i d i idThe rock is a fine- to medium-grained quartz sandstone cemented with calcite and iron oxide.

V ti l i h f il (Sk li h d A i li ) dil i ibl i thi t b th iThe rock is a fine to medium grained quartz sandstone cemented with calcite and iron oxide.Th b filli i f h d i id i l ki Middl Vertical ichnofossils (Skolithos and Arenicolites sp.) are readily visible in this outcrop because their The burrow fillings consist of the same quartz sandstone; iron oxide cement is lacking. Middle ( p ) y p

filli h b l t d i th i Th k i di i d t d t t dThe burrow fillings consist of the same quartz sandstone; iron oxide cement is lacking. Middle C b i L d S d J ’ H l U h i l 24 b b f i fillings have been lost during weathering. The rock is a medium-grained quartz sandstone cemented Cambrian Lodore Sandstone, Jones’ Hole, Utah, approximately 24 m above base of section. g g g g q

ith bi ti f illit i id d i t f l it Th b filli b blCambrian Lodore Sandstone, Jones Hole, Utah, approximately 24 m above base of section.

with a combination of illite, iron oxide, and minor amounts of calcite. The burrow fillings probably , , g p yi t d f t d t th t b bl d i tl l C t t b t thconsisted of quartz sandstone; the cement was probably predominantly clay. Contact between the q ; p y p y y

L G V t F ti d Middl C b i Fl th d S d t Wi d Ri CLower Gros Ventre Formation and Middle Cambrian Flathead Sandstone, Wind River Canyon, , y ,W i i t l 36 b P b i C b i b dWyoming, approximately 36 m above Precambrian-Cambrian boundary.y g, pp y y

V ti l i h f il (Di l i ) dil i ibl i thi t b fVertical ichnofossils (Diplocraterion sp.) are readily visible in this outcrop because of ( p p ) y pth d k l ti f th i i (“ ” h d “ ki ” k ) Th k ithe dark coloration of their spreiten (“u”-shaped, “working” marks). The rock is a

V ti l i h f il (Sk li h ) dil i ibl i thi t b th i t tp ( p , g )

di i d t d t t d ith bi ti f illit i id d Vertical ichnofossils (Skolithos sp.) are readily visible in this outcrop because they are more resistantmedium-grained quartz sandstone cemented with a combination of illite, iron oxide, and ( p ) y p yt th i th l i di t Th k i di i d t d t t d

g q , ,l it B filli i t f t d t t d ith l it I t t to weathering than enclosing sediments. The rock is a medium-grained quartz sandstone cemented calcite. Burrow fillings consist of quartz sandstone cemented with calcite. In contrast, g g g q

ith bi ti f illit i id d i t f l it Th b filli i t fg q ,

th i f th i h f il h k dl i id t d l l with a combination of illite, iron oxide, and minor amounts of calcite. The burrow fillings consist of the spreiten of these ichnofossils have markedly more iron oxide cement and less cal- , , gt d t ith l it t Middl C b i Fl th d S d t Wi d Ri C

p yit Middl C b i Fl th d S d t Wi d Ri C W i i quartz sandstone with calcite cement. Middle Cambrian Flathead Sandstone, Wind River Canyon, cite. Middle Cambrian Flathead Sandstone, Wind River Canyon, Wyoming, approxi- q , y ,

W i i t l 36 b P b i C b i b d, y , y g, pp

t l 36 b P b i C b i b d Wyoming, approximately 36 m above Precambrian-Cambrian boundary.mately 36 m above Precambrian-Cambrian boundary. y g, pp y yy y

JACKSONBURG FIELD CORE FEATURES GORDONJACKSONBURG FIELD PETROGRAPHIC FEATURES GORDONCORE FEATURES GORDONJACKSONBURG FIELD PETROGRAPHIC FEATURES - GORDONCORE FEATURES - GORDONJACKSONBURG FIELD PETROGRAPHIC FEATURES GORDONCORE FEATURES GORDONThe Jacksonburg field, discovered in 1895, is the largest active oilfield in West Virginia. Over 500 A total of 10 Gordon cores were subjected to examination and testing Of these two were from wells located northeast of theThe Jacksonburg field, discovered in 1895, is the largest active oilfield in West Virginia. Over 500wells were drilled in the field before 1901; most were plugged by 1910 The average well spacing A total of 32 thin sections from selected core intervals were prepared and examinedA total of 10 Gordon cores were subjected to examination and testing. Of these, two were from wells located northeast of thewells were drilled in the field before 1901; most were plugged by 1910. The average well spacing A total of 32 thin sections from selected core intervals were prepared and examined.j g

Jacksonburg field and were not included as part of the field’s core suite One core was excluded from this suite because it lacked awithin the field was 13 acres per well; initial potentials ranged from 0 to 300 BOPD (barrels of oil Jacksonburg field and were not included as part of the field s core suite. One core was excluded from this suite because it lacked a within the field was 13 acres per well; initial potentials ranged from 0 to 300 BOPD (barrels of oilper day) (King 1980) Primary production has been estimated to lie in the range of 1454 (King

g pcomplete set of geophysical logs; another core was excluded because it only penetrated the top of the Gordonper day) (King, 1980). Primary production has been estimated to lie in the range of 1454 (King, complete set of geophysical logs; another core was excluded because it only penetrated the top of the Gordon.

1980) to 1590 (Morrison, 1991) BOPA (barrels of oil per acre) over an area of 4,338 acres. Pri-p g p y g y p p

1980) to 1590 (Morrison, 1991) BOPA (barrels of oil per acre) over an area of 4,338 acres. Primary production resulting from solution gas drive and gravity drainage produced an estimated

%%%%%%%%%%SOMPE ++ positive correlationmary production resulting from solution gas drive and gravity drainage produced an estimated

%”O

T

%C

L

%O

P

%M

I

%SEC

%PR

%PO

%SEC

%PO

%M

O

OR

T

MEA

ERM

psignificant at 99%

13,000,000 barrels of oil by the mid 1920’s. Waterflooding in the field began on a large scale inTH

E

LAY

PAQ

CA

S

CO

N

IMA

OTA

CO

N

OLY

C

ON

O

TIN

AN

G

MEA

significant at 99%confidence level13,000,000 barrels of oil by the mid 1920 s. Waterflooding in the field began on a large scale in

1990; 1 864 782 barrels of oil were produced as a result of waterflooding through February 1999ER

”

YS

QU

E

SND

A

AR

Y

SSIU

ND

A

CR

Y

OC

R

NGGR

A

AB

I

confidence level

CONGLOMERATE PAY AND NON PAY SANDSTONE1990; 1,864,782 barrels of oil were produced as a result of waterflooding through February, 1999. ”SAR

Y

Y PO

UM

AR

Y

YST

RY

S

AIN

ILITMIXED SHALE AND SANDSTONE CONGLOMERATE PAY AND NON-PAY SANDSTONEThe Jacksonburg field is currently owned and operated by East Resources of Wexford, PA.

Y PO

OR

O

M FE

Y Q

TAL

STASIZ

TY + positive correlationMIXED SHALE AND SANDSTONE P t H 9 (095 741) Thompson Heirs 8 (095 1124) F R Ball 18 (095 1125)The Jacksonburg field is currently owned and operated by East Resources of Wexford, PA. O

RO

OSIT

ELD

QU

A

LLIN

ALLI

ZE ( significant at 95%Peter Horner 9 (095-741) Thompson Heirs 8 (095-1124) F. R. Ball 18 (095-1125)

OSI

TYSPA

AR

TZ

NE Q

INE

(mm

gconfidence level

( )

ITY

ARZQU

A

E QU

m) confidence level

ANALYSIS OF AR

T

UA

R

i l iANALYSIS OF

W t l

TZ

RTZ - - negative correlationCORE PLUG:Wetzel significant at 99%CORE PLUG:

PERMEABILITYconfidence level

PERMEABILITYH = 7 2%

MEAN GRAIN SIZE (mm) negative correlationHigh-angle (~30º)He 7.2%k 0 24 D MEAN GRAIN SIZE (mm) - negative correlation

i ifi t t 95%High-angle ( 30 )

b dkh = 0.24 mD

Tyler SORTING significant at 95%fid l l

- -crossbeds hk = 0 03 mDTyler

%MONOCRYSTALLINE QUARTZconfidence level

Sid itkv 0.03 mD

%MONOCRYSTALLINE QUARTZ

Chondrites Siderite%POLYCRYSTALLINE QUARTZ - -++Chondrites

OHIO %SECONDARY QUARTZPENNSYLVANIA

OHIO %SECONDARY QUARTZANALYSIS OFPENNSYLVANIA%POTASSIUM FELDSPAR + - -++Reverse grading

ANALYSIS OFCORE PLUG %POTASSIUM FELDSPARReverse grading CORE PLUG:

Doddridge %PRIMARY POROSITY ++Doddridge%SECONDARY POROSITY + + +++22 5% %SECONDARY POROSITY + - + +++He= 22.5%%MICAS ++ - +

Hekh = 0 05 mD

S Pa Sandstonekh 0.05 mDk 37 0 D %OPAQUESScour Pay Sandstonekv = 37.0 mD

WEST %CLAYS - +v

VIRGINIA%CLAYS +

E l t f t d h i th l ti%”OTHER” - - - - - - - - -Teichichnus Reverse grading ANALYSIS OFEnlargement of study area showing the location eichichnus Reverse grading ANALYSIS OF

CORE PLUG:of the Jacksonburg field CORE PLUG:KILOMETERS

of the Jacksonburg field.

Bivariate correlation matrix illustrating significant statistical correlations between petrophysical and petrographic = 13 1% Bivariate correlation matrix illustrating significant statistical correlations between petrophysical and petrographicHe= 13.1%features observed in thin section Of particular relevance to this discussion is the strong (>99 %) negative cor-Spiriferid? kh = 3.10 mD features observed in thin section. Of particular relevance to this discussion is the strong (>99 %), negative cor-Spiriferid? kh 3.10 mD

k = 0 08 mDLocation of Jacksonburg field in northwestern West Virginia relation between sorting and mean grain size – finer-grained sediment is potentially more susceptible to bioturba-kv = 0.08 mDLocation of Jacksonburg field in northwestern West Virginia. relation between sorting and mean grain size finer-grained sediment is potentially more susceptible to bioturba-tion simply because less energy is required to move it But by definition very well-sorted fine-grained sedimentMicrofault tion simply because less energy is required to move it. But, by definition, very well-sorted, fine-grained sedimentUnidentified

Microfault

lacks “contrasting” grain sizes that make for easy recognition of bioturbation Unless heavy mineral clay orBivalve lacks contrasting grain sizes that make for easy recognition of bioturbation. Unless heavy mineral, clay, or Bivalve

organic laminae are present it may be practically impossible to tell if this material has been bioturbatedCrinoid Conglomerates actually contain a bimodal distribution of grain sizes: organic laminae are present, it may be practically impossible to tell if this material has been bioturbated.CrinoidPieces

gfine-grained sand and gravel. Texture varies between matrix andPieces g gclast support. Scour surfaces are common and many of the con-clast support. Scour surfaces are common and many of the conglomerate beds appear to be lags Other sedimentary structuresglomerate beds appear to be lags. Other sedimentary structuresinclude low angle bi- and uni-directional cross beds high angle (up to

GORDON RESERVOIRinclude low angle bi- and uni-directional cross beds, high angle (up to45o) crossbeds reverse grading limited ripple beds shale rip up Non-payGORDON RESERVOIR Gordon Lithofacies Mean Primary Secondary Mean Sorting Cements (in order45 ) crossbeds, reverse grading, limited ripple beds, shale rip-upl t d i f il Th f f il i l di

Non pay SandstoneGORDON RESERVOIR (see Matchen Gordon Lithofacies Mean Primary Secondary Mean Sorting Cements (in orderShales are dark-gray, laminated and interbedded with sandstones clasts, and marine fossils. The presence of fossils, including

th h l d i di t th t th l tSandstoneGORDON RESERVOIR (see Matchen Permeability Porosity Porosity Grainsize of abundance)

g y,and siltstones. Bioturbation is abundant: Chondrites and Teichichnus orthocone cephalopods indicates that the conglomerates were

and others 2001 this meeting)y y y )and siltstones. Bioturbation is abundant: Chondrites and Teichichnus

sp are present Siderite clasts and siderite beds 1-2 cm thick are deposited in a marine environment.and others, 2001 - this meeting) Conglomeratic ss 4.042 mD 4.68% 0.63% 1.170 mm Poorly sorted Silica & claysp. are present. Siderite clasts and siderite beds 1 2 cm thick arecommon The sandier portions of the shale beds display ripple Sandstones are fine- to very fine-grained and very well-sorted.g) g y y

L i t d 3 889 D 4 98% 1 53% 0 132 W ll t d Cl & id itcommon. The sandier portions of the shale beds display ripplecrossbeds and cross sections of thin brachiopod and bivalve fossils

Sandstones are fine to very fine grained and very well sorted.Bedding is difficult to distinguish but horizontal laminations and low-

Th i k i hi h J k b fi ld h U D i G d d iLaminated ss 3.889 mD 4.98% 1.53% 0.132 mm Well-sorted Clay & sideritecrossbeds and cross-sections of thin brachiopod and bivalve fossils. Bedding is difficult to distinguish, but horizontal laminations and low

angle crossbedding have been identified Crossbedding is bi-The reservoir rock within the Jacksonburg field , the Upper Devonian Gordon sandstone, is "Featureless" ss (PAY) 43 326 mD 15 98% 2 25% 0 128 mm Well sorted Clayangle crossbedding have been identified. Crossbedding is bi-directional and possibly herringbone Microfaulting occurs in theg , pp ,

considered to be a strandplain deposit representing the greatest westward advance of the AcadianFeatureless ss (PAY) 43.326 mD 15.98% 2.25% 0.128 mm Well-sorted Claydirectional and possibly herringbone. Microfaulting occurs in the

d t f th B ll 18 ll Si l t bbl lconsidered to be a strandplain deposit representing the greatest westward advance of the Acadian l i d Th G d l 50 f i hi k b hi k l d 20 Visibly Bioturbated ss 0 000 mD 0 40% 0 32% 0 340 mm Mod well-sorted Calcite clay & sideritesandstones of the Ball 18 well. Single quartz pebble layers are

Bi t b ti i B hi d bi l d hi dclastic wedge. The Gordon averages nearly 50 feet in thickness, but pay thickness rarely exceeds 20 Visibly Bioturbated ss 0.000 mD 0.40% 0.32% 0.340 mm Mod. well-sorted Calcite, clay, & sideritecommon. Bioturbation is rare. Brachiopod, bivalve and echinodermg g y , p y yfeet; in many places the pay is less than 5 feet thick Grain size is bimodal; the lower part of the fossils are rare.feet; in many places, the pay is less than 5 feet thick. Grain size is bimodal; the lower part of the G d i i d f fi fi i d d i h f id ifi bl di G d h l 7 334 D 4 95% 0 99% 0 541 M d l t d Cl & id itGordon is comprised of fine- to very fine-grained sandstones with few identifiable sedimentary Gordon as a whole 7.334 mD 4.95% 0.99% 0.541 mm Mod. poorly sorted Clay & sideritep y g ystructures and rare single quartz pebble layers The upper part is comprised of fine- to very fine- PETROPHYSICAL FEATURES GORDONstructures and rare, single quartz pebble layers. The upper part is comprised of fine- to very fine-

i d d i b dd d i h l P i hi h fi ld i h fi PETROPHYSICAL FEATURES - GORDONgrained sandstone interbedded with conglomerate. Pay zones within the field occur in the fine- PETROPHYSICAL FEATURES - GORDONg g ygrained sandstones Pay sandstones within the Gordon have been characterized as “featureless” (see Matchen and others 2001grained sandstones. Pay sandstones within the Gordon have been characterized as featureless (see Matchen and others, 2001 -

this meeting) because they are well sorted very fine grained and lack any visible sedimentary structures even inthis meeting) because they are well-sorted, very fine-grained, and lack any visible sedimentary structures even inOf th 796 ll l t d ithi th J k b fi ld 88 h d b th d d it l f thSubsurfaceOutcrop thin section The petrophysical and petrographic characteristics of the pay sandstones within the Gordon standOf the 796 wells located within the Jacksonburg field, 88 had both gamma ray and density logs for theOutcrop thin section. The petrophysical and petrographic characteristics of the pay sandstones within the Gordon standg , g y y gG d i t l L f h f th ll d d t d t ASCII f t bSS

.

P i Big Injun in marked contrast to the Gordon “as a whole ”Gordon interval. Logs for each of these wells were scanned and converted to ASCII format by samp-

MIS Price g ju in marked contrast to the Gordon as a whole. g y p

li th l t 0 25’ i I dditi f th 6 ll i i th fi ld’ itBerea

M

B ling the log at a 0.25’ spacing. In addition, for the 6 wells comprising the field’s core suite, permea-Gantz

BereaBerea g g p g , p g , pbilit t t k b i i t ( fi t th i ht) t 0 25’ i tGantz bility measurements were taken by minipermeameter (see figure to the right) at a 0.25’ spacing to

if

y y p ( g g ) p gll th di t i f h i l l t d bilitFifty-Foot allow the direct comparison of geophysical log parameters and permeability. p g p y g p p y

WHampshire G d OW LHampshire

Formation Gordon LO AL

DEEPER BURIAL - COMPACTIONFormation

AL RI DEEPER BURIAL COMPACTION

AND DISSOLUTION OF FELDSPARSBayard HA UR AND DISSOLUTION OF FELDSPARSBayard

AN SH BU

ElizabethNIA S

Elizabeth

VO

N

Thompson Heirs #8, 95-1124

EV

p ,Core Description, Jacksonburg field

D

p , gDescribed 2/4/99 by Avary, McDowell, Matchen and Hohn CALCITEy y, ,CORE = LOG CALCITE

S b l KYForeknobs Balltown Symbol KeyGY

CLAYForeknobsFormation

Symbol Key

OGGRAIN SIZE CLAY

Formation LO

GRAIN SIZEScour or unconformity

HO

Temco MP 401 Minipermeameter notebookTHSAND G R D it SILICASingle pebble layer Temco MP-401 Minipermeameter, notebook

LITSAND

LT Gamma Ray Density SILICAStylolite computer nitrogen gas cylinder and permea

LSIL

644 VCC M FVF 0 200 2.0 3.0s Siderite Nodules or Clastss

computer, nitrogen gas cylinder, and permea-2770 SIDERITEs s

bility probe (inset) on an outcrop exposure SIDERITE

G li d i hi l f h dClay Drapes bility probe (inset) on an outcrop exposure.

Generalized stratigraphic column for the study area Ripple-scale XbdsGeneralized stratigraphic column for the study area h i d b f i l

Low-Angle s s sshowing outcrop and subsurface terminology. Xbdss

s

ss

s

Cementation history inferred for the Gordonshowing outcrop and subsurface terminology.Clayey Zone in Sandstone

s Cementation history inferred for the Gordon.Bioturbation

y y

G R i bili ( d)Fossils Gamma Ray Density Permeability (md)Fossils y y y ( )s s s Siderite Bed2780

Horizontal Bedding

Bi-Directional Cross Bedding

g

Bi Directional Cross Bedding

Missing core

Fracture

QUESTIONS GORDONQUESTIONS - GORDONQUESTIONS - GORDONS2790 Q

Pay Sandstone2790 y

1 A th “f t l ” d t f th G d bi t b t d t?1. Are the “featureless,” pay sandstones of the Gordon bioturbated or not? , p y1b If th d t bi t b t d h d th till t i it d bilit ? (FJacksonburg field 1b. If the pay sandstones are bioturbated, why do they still retain porosity and permeability? (For s s sJacksonburg field p y , y y p y p y (i th h t i ti f th Vi ibl Bi t b t d d t f th G d i th t bl b )

s s s

s s s comparison, see the characteristics of the Visibly Bioturbated sandstones of the Gordon in the table above.)2800s s s p , y )

1 If th d t t bi t b t d h d th till t i it d bilit ?2800

1c. If the pay sandstones are not bioturbated, why do they still retain porosity and permeability? p y , y y p y p y(F i th h t i ti f th lith l i ithi th G d i th t bl b )(For comparison, see the characteristics of other lithologies within the Gordon in the table above.)( p , g )

2 Wh t l h bi t b ti l d i dif i it d bilit ithi th G d ?P bilit l t d f ll d ll b li 2. What role has bioturbation played in modifying porosity and permeability within the Gordon?“T i l” li h l i d h i l l f f h d ll (Th

Permeability logs were created for all cored wells by sampling p y y g p y p y“Typical” lithologic and geophysical logs for one of the cored wells (Thompson

y g y p gbilit ith th i i t t th 0 25’Typical lithologic and geophysical logs for one of the cored wells (Thompson

H i #8) f h J k b fi ld (S M h d h 2001 hipermeability with the minipermeameter at the same 0.25’

Heirs #8) from the Jacksonburg field. (See Matchen and others, 2001, thisp y pi t l d h di iti i th ll ’ h i l lHeirs #8) from the Jacksonburg field. (See Matchen and others, 2001, this

i )interval used when digitizing the wells’ geophysical logs.

meeting.)g g g p y g

Sh b i l t f d it dR i l t ti h f th A di l ti dmeeting.) Shown above is a plot of gamma ray, density, and permea-Regional stratigraphy of the Acadian clastic wedge p g y, y, p

bilit f F R B ll #18 (095 1125)g g p y g(f B ll d J ll 1988 l t 15 32) bility for F. R. Ball #18 (095-1125).(from Boswell and Jewell, 1988, plate 15, p. 32) y ( )( , , p , p )

ICHNOFOSSIL PERMEABILITY GORDON BIOTURBATION’S EFFECT ON PERMEABILITY GORDONICHNOFOSSIL PERMEABILITY GORDON BIOTURBATION’S EFFECT ON PERMEABILITY GORDONICHNOFOSSIL PERMEABILITY - GORDON BIOTURBATION S EFFECT ON PERMEABILITY - GORDONICHNOFOSSIL PERMEABILITY GORDON BIOTURBATION S EFFECT ON PERMEABILITY GORDONThe visibly bioturbated intervals from four cores were investigated for remaining permeability using the minipermeameter InThe visibly bioturbated intervals from four cores were investigated for remaining permeability using the minipermeameter. Inparticular individual ichnofossils (i e the material infilling those ichnofossils) were examined as were sandstone intervals im SCENARIO 1 NO INTERBEDDED SHALESparticular, individual ichnofossils (i.e., the material infilling those ichnofossils) were examined as were sandstone intervals im- SCENARIO 1 - NO INTERBEDDED SHALESmediately adjacent to visible bioturbation The small inside diameter of the minipermeameter probe tip (0 125” 3 2mm)mediately adjacent to visible bioturbation. The small inside diameter of the minipermeameter probe tip (0.125 - 3.2mm) allowed the acquisition of data from relatively small features; an additional tip with inside diameter (0 0625” 1 6 mm) wasallowed the acquisition of data from relatively small features; an additional tip with inside diameter (0.0625 - 1.6 mm) was

Burrows are filled with sediment from the active sedimentaryalso available but was not used for this study Burrows are filled with sediment from the active sedimentary also available but was not used for this study. layer. Fill may include organic matter and clay.y y g y

57.23 mD E l l i i b i l h b d i b0 mD57.23 mD

3 40 mD Early calcite cementation begins to seal the boundaries between 3.40 mD“Active” Sedimentary Layer

y gsedimentary layers from vertical migration of pore fluids Where

0 mDy y sedimentary layers from vertical migration of pore fluids. Where

i l f il hi i i i i0 mD0 D0 mD vertical trace fossils are present, this cementation may originate in 0 mD0 mD p y g

proximity to burrow fillings thus allowing calcite to penetrateproximity to burrow fillings thus allowing calcite to penetrate d i di l I ddi i h h d i f CONCLUSIONS0 mD0 mD deeper into sedimentary layers. In addition, where the density of CONCLUSIONS0 mD

0 mD0 mD p y y y

trace fossils is greater (i e bioturbation is more intense) the seal0 D

trace fossils is greater (i.e., bioturbation is more intense), the seal i i0 mD is more extensive.

1 The minipermeameter equipped with small diameter probe tips can be used to sample1. The minipermeameter, equipped with small diameter probe tips, can be used to samplebilit f ll l ( illi t ) di t t t h i h f il0 mD permeability of small-scale (millimeters) sedimentary structures such as ichnofossils.

“Active” Sedimentary Layer

6 35 DRecently Buried

y y

2 Th l k f di t t t d t ti i i i th “f t l ”6.35 mD Sediment 2. The lack of sedimentary structures and contrasting grain sizes in the “featureless” pay 0 mD sandstones of the Gordon make it impossible to determine if the sandstones are bioturba-sandstones of the Gordon make it impossible to determine if the sandstones are bioturba

t d H th b f l l it t i t d ith bi t b ti i th0 D Recently Buried ted. However, the absence of early calcite cements associated with bioturbation in other 0 mD

0 DRecently BuriedSediment parts of the Gordon suggests that the “featureless” sandstones have not been bioturbated0 mD

SandstoneSediment parts of the Gordon suggests that the featureless sandstones have not been bioturbated.

Sandstone

3 In Gordon sandstones without interbedded shales the presence of bioturbationNot-so-recently

3. In Gordon sandstones without interbedded shales, the presence of bioturbation, i ll i th f f ti l d bli i h f il d l l it t ti

0 mD0 D

yBuried Sediment especially in the form of vertical and oblique ichnofossils, and early calcite cementation

0 mD0 mD Buried Sedimentassociated with these trace fossils appear to have formed barriers to interstratal migrationassociated with these trace fossils appear to have formed barriers to interstratal migration f fl id Th l b t dj t di t l b bl d d t dof fluids. These seals between adjacent sedimentary layers probably reduced or prevented

late-stage cementation and helped preserve initial permeability0 mD0 mD

late stage cementation and helped preserve initial permeability.0 mD

4 In Gordon sandstones with interbedded shales the same effect noted in #3 occurred0 mD0 mD

4. In Gordon sandstones with interbedded shales, the same effect noted in #3 occurred. Wh bi t b ti i t th i t t t l l ff ti i i

E l l i i l h b d b diOlder Where bioturbation was more intense, the interstratal seal was effective in preserving

Early calcite cementation seals the boundary between sedimen- Buried Sediment permeability Where bioturbation was less intense an incomplete interstratal seal al-y ytary layers from vertical migration of pore fluids Where vertical Early Calcite

permeability. Where bioturbation was less intense, an incomplete interstratal seal all d di l d ili f di ti ll lt d h l t t dj t it l di ttary layers from vertical migration of pore fluids. Where vertical

f il hi i i i iEarly Calcite lowed dissolved silica from diagenetically altered shales to enter adjacent units leading to

trace fossils are present, this cementation may originate in prox- Cement late-stage silica and clay cements and a reduction in permeabilityp y g pimity to burrow fillings thus allowing calcite to penetrate deeper Shale

Cement late stage silica and clay cements and a reduction in permeability.imity to burrow fillings thus allowing calcite to penetrate deeper i di l NOTE hi l i

0 mDinto sedimentary layers. NOTE: once this seal is present, perme- 5 In the Gordon the combination of bioturbation and early calcite cementation produced0 mD

y y p pability may be preserved in the buried layers

5. In the Gordon, the combination of bioturbation and early calcite cementation produced l th t i d d th i t t t l i ti f fl id b t h d littl ff t i t t t lability may be preserved in the buried layers.

S d tseals that impeded the interstratal migration of fluids but had little effect on intrastratal

Sandstone fluid flow The net effect was to increase vertical compartmentalization of the Gordonfluid flow. The net effect was to increase vertical compartmentalization of the Gordon.

“Active” Sedimentary Layer

P bilit f f F R B ll #19 (095 1126) fP bili f f P H #9 (095 741) fy y

Permeability map for core from F. R. Ball #19 (095-1126) - from a Permeability map for core from Peter Horner #9 (095-741) - from a Recently Burieddepth of 3091 0’ Note the relatively high permeability (> 50 mD)

y p ( )depth of 2885 0’ The only permeability detected is in a bioturbated

Recently BuriedSedimentdepth of 3091.0 . Note the relatively high permeability (> 50 mD)

i h i t l t f il ( b bl Ch d it ) i th l ftdepth of 2885.0 . The only permeability detected is in a bioturbated

d d i h i h f h d f h iSediment

in a horizontal trace fossil (probably Chondrites sp.) in the upper left sandstone pod in the upper right corner of the core and from a hori-REFERENCES CITEDcorner of the core The remainder of the core shows no permeability

p pp gzontal trace fossil (probably Chondrites sp ) All vertical trace fos- REFERENCES CITEDcorner of the core. The remainder of the core shows no permeability.zontal trace fossil (probably Chondrites sp.). All vertical trace fos-il i h l d During diagenesis compacted and altered shales shed dissolved

REFERENCES CITEDsils are tightly cemented. During diagenesis, compacted and altered shales shed dissolved

ili t fl id S d t dj t t i t b dd d h lg y

silica to pore fluids. Sandstones adjacent to interbedded shales and not previously sealed with early cement may be subject to B ll R 1988 St ti hi i f b t f lt i th W tand not previously sealed with early cement, may be subject to l t t ili t ti Additi ll l t l

Boswell, R., 1988, Stratigraphic expression of basement fault zones in northern West late-stage silica cementation. Additionally, clay cement may also Virginia: Geological Society of America Bulletin V 100 p 1988-1998

0 34 mD0 mD formVirginia: Geological Society of America Bulletin, V. 100, p. 1988 1998.

0.34 mD0 mD form.King P 1980 Pilot waterflood justification Stringtown Gordon reservoir Wetzel County

18 56 D94 44 D Not-so-recently King, P., 1980, Pilot waterflood justification, Stringtown Gordon reservoir Wetzel County, W t Vi i i i t l P il C AFE ti d t i t d18.56 mD94.44 mD y

Buried Sediment West Virginia: internal Pennzoil Company AFE supporting document, unpaginated.Buried SedimentE l C l it0 mD Early Calcite

M t h D M D ll R d A K 2001 R i Ch t i ti f thSiO2SiO20 mD

0 mDCement Matchen, D., McDowell, R., and Avary, K., 2001, Reservoir Characterization of the 22

7 59 DCement

Gordon sandstone in Northern West Virginia This Meeting - Wednesday AM Posters7.59 mD Gordon sandstone in Northern West Virginia, This Meeting Wednesday AM Posters.Sandstone

17.75 mD Morrison G 1991 Stringtown geologic study: Pennzoil Products Company interoffice17.75 mD Morrison, G., 1991, Stringtown geologic study: Pennzoil Products Company interoffice d 4 l i t d tt h t16 51 mD correspondence, 4 p. plus unpaginated attachment.16.51 mD

OlderSiO Older Buried SedimentSiO

SiO2Buried SedimentSiO2

Permeability map for core from Thompson Heirs #8 (095 1124) from aPermeability map for core from Thompson Heirs #8 (095-1124) - from a depth of 2777.5’. With one exception (see upper right corner), permea-p p ( pp g ), pbility is restricted to fillings in horizontal trace fossilsbility is restricted to fillings in horizontal trace fossils.

bili i hi h d i i l d f fl id i i l b dPermeability within the Gordon is isolated from pore fluids migrating across stratal bounda- Late Silica0 mD

Permeability within the Gordon is isolated from pore fluids migrating across stratal boundai hi i l i ddi i l f f i ( d d Cement0 mD ries. This isolation may prevent additional cements from forming (e. g., Gordon pay sand- Cementries. This isolation may prevent additional cements from forming (e. g., Gordon pay sand

) d l b i i l i i f l i l i lstones) and also acts as a barrier to vertical migration of petroleum. Horizontal or intrastratal Sh lstones) and also acts as a barrier to vertical migration of petroleum. Horizontal or intrastratal i i f fl id i ff d

Shalemigration of fluids is unaffected.migration of fluids is unaffected.

0 mD0 mD 0 mD Sandstone0 mD 0 mD Sandstone

0 mD 6.13 mD SCENARIO 2 INTERBEDDED SHALES0 mD 0 mD SCENARIO 2 - INTERBEDDED SHALESSCENARIO 2 INTERBEDDED SHALES0.48 mD 0 mD 0.60 mD0 mD

B fill d ith di t f th ti di t4.44 mD0 mD Burrows are filled with sediment from the active sedimentary 0 mD layer Fill may include organic matter and clay bili i hi h d b i l d f fl id i i l0 D0 27 mD0 mD layer. Fill may include organic matter and clay. Permeability within the Gordon may be isolated from pore fluids migrating across stratal0 mD0.27 mD

0 mDPermeability within the Gordon may be isolated from pore fluids migrating across stratal b d i h i i i l d i f i h f il (i i i f bi b i ) i bi i0 mD

0 mD boundaries. The initial density of ichnofossils (i.e., intensity of bioturbation) in combination0 mD boundaries. The initial density of ichnofossils (i.e., intensity of bioturbation) in combination i h l l i i h l d i h l f h l l i l6.88 mD with early calcite cementation help determine the completeness of the seal. Relatively

0 mD “Active” Sedimentary Layerwith early calcite cementation help determine the completeness of the seal. Relatively

l l ili d fl id f i i f di i ll l d0 mD1 17 mD

y ycomplete seals prevent silica-saturated fluids from migrating out of diagenetically altered

94.58 mD 0 mD1.17 mD complete seals prevent silica saturated fluids from migrating out of diagenetically altered h l l f l ili d l bili i d (shale layers to form late-stage silica and clay cements - permeability is preserved (e.g.,

Recently Buriedshale layers to form late stage silica and clay cements permeability is preserved (e.g.,

d d ) l i i i l l ll h fl id dj0 mD0 D

Recently BuriedSediment Gordon pay sandstones). Incomplete initial seals allow these fluids to penetrate adjacent

11 97 mD 0 D0 mD Sediment Gordon pay sandstones). Incomplete initial seals allow these fluids to penetrate adjacent

di l l i ll i i bili (11.97 mD 0 mD sedimentary layers - late-stage cementation may remove all remaining permeability (e.g.,sedimentary layers late stage cementation may remove all remaining permeability (e.g., h d d ) i l i l i i f fl id bother Gordon sandstones). Horizontal or intrastratal migration of fluids may or may not be

0 mD 0 mD 0 mDother Gordon sandstones). Horizontal or intrastratal migration of fluids may or may not be ff d d di h i f l i0 mD effected depending on the pervasiveness of late-stage cementation.

0 64 mD Not-so-recently effected depending on the pervasiveness of late stage cementation.

0.64 mD0 D 0 mD

yBuried Sediment

0 mD0 mD 0 mD Buried Sediment

0 mD

0 mD Sh l0 mD Shale

0 mD00 mD SandstoneSandstone

Permeability map for core from Thompson Heirs #8 (095-1124) - from aPermeability map for core from Thompson Heirs #8 (095-1124) - from a d h f 2777 0’ Filli i i l d “ bli ” f il hdepth of 2777.0’. Fillings in vertical and “oblique” trace fossils show p g qno permeability; bioturbated and unbioturbated sandstones show no Permeability map for core from J H Dawson F-14 (095-1532) - from ano permeability; bioturbated and unbioturbated sandstones show no

bili H i l b filli hibi bili iPermeability map for core from J. H. Dawson F-14 (095-1532) - from a d h f 3270 1’ Th l bili d d i hipermeability. Horizontal burrow fillings exhibit permeability ranging depth of 3270.1’. The only permeability detected in this core segmentp y g p y g g

from < 0 5 mD to > 90 mDp y p y g

comes from horizontal burrowsfrom < 0.5 mD to > 90 mD. comes from horizontal burrows.