evaluation of hydrocarbon generation and storage in the

1Humble Geochemical Services Division Special BEG / PTTC Presentation

Evaluation of Hydrocarbon Generation and Storage in the Barnett Shale,

Ft. Worth Basin, Texas©

Dan JarvieHumble Geochemical Services

Division of Humble Instruments & Services, Inc.

Copyright 2004 Humble Instruments & Services, Inc. All rights reserved.


Co-authors

• Rich Pollastro, USGS• Ron Hill, USGS• Kent Bowker, Encana• Brenda Claxton, Consultant• Jack Burgess, Humble Geochemical


Acknowledgements

• Jones Company – Jeff Jones• Many former MEC personnel• Republic Energy – Dan Stewart• Dallas Production – David Martineau• U.S. Geological Survey

– Dave King, Augusta Warden, Paul Lillis• ExxonMobil• Don Hall, Fluid Inclusion Technologies• Colleagues at Humble


Humble, Texas

Humble, Texas ca. 1905


Talk Outline

1. Background information2. Geochemical parameters3. Barnett Shale Geochemical Characteristics

a) Organic richnessb) Thermal maturityc) Gas contentd) Gas yields

4. Risking prospects based on geochemical data


Shales yield oil and gas in various basins:there exist numerous similarities and significant differences among these systems

Biogenic gas

Oil

Oil

OilOil and Gas

Gas

Gas and some oil

Oil

Oil and gasOil and gas

Oil and some gas

Ref: USGS

Barnett and

Woodford Oil and gas

Humble, Texas


Petroleum Geochemistry

• ExplorationHigh-grading plays/prospects for likelihood of hydrocarbon charge

– Source rocks– Oil typing– Correlations– Inversions

• Production

Assessing reservoirs and well plumbing

– Reservoir continuity– Commingled allocation– EOR assessment– Well plumbing


Exploration / Production:Fractured Shale Gas

• Confirming pay type (oil vs. gas) at a given maturity• Finding bypassed pay and predicting pretest, pre-

completion oil quality• Predicting gas yields (SCF/ton)• Identifying well and basinal sweet spots for gas

production• Predicting calorific value (BTUs) of gas• Predicting GOR values


Petroleum System Definition:Components and Processes

Source RockSource RockMigration RouteMigration RouteReservoir RockReservoir RockSeal RockSeal RockTrapTrap

ComponentsComponents

GenerationGenerationMigrationMigrationAccumulationAccumulationPreservationPreservation

ProcessesProcesses

For high flow rate gas

in fracturedshales,

must have oildestruction !

Top&

Bottom

If any of these components are missing or improperly timed,no commercial accumulation of hydrocarbons will occur.

Ref: Modified from Armentrout, 2001


Petroleum System, Play Definition, and RiskPetroleum System, Play Definition, and Risk

Generation and MigrationGeneration and Migration

Source Source ExtentExtentSeal Seal

ExtentExtent

Critical ReconstructionCritical Reconstruction

PresentPresent PastPast

ComponentsComponents

HC ChargeHC Charge

PreservationPreservation

TimeTime PresentPresent

Timing SheetsTiming Sheets

Play MapsPlay Maps TrapTrap

ThermalMaturityFacies

Ref: Modified from Jeff Brown, Mobil, 1999Ref: Modified from Jeff Brown, Mobil, 1999


Fractured shales yield oil and gas in various basins:there exist numerous similarities and differences among these systems

Biogenic gas

Oil

Oil

OilOil and Gas

Gas

Gas and some oil

Oil

Oil and gasOil and gas

Oil and some gas

Ref: USGS

Barnett and

Woodford Oil and gas


USGS Data on Gas Bearing Shales

nana1.6 - 1.91-2.5*LewisShale

San Juan

26.7 (min.)3.4 - 100.6 - 1.6*

1-12*Ave. 4.5

BarnettShale

Ft. Worth

86 - 1601.9 - 19.20.4 - 1.01-25NewAlbanyShale

Illinois

35 - 7611 - 190.4 - 0.61-20AntrimShale

Michigan

225 -24814.5 - 27.50.4 - 1.3%1-4.5*

Ohio Shale

Appalachian

Shale Gas

in place(Tcf)

EstimatedRecoverable

Shale Gas(Tcf)

Range ofMaturities

(%Ro)

T.O.C.(wt.%)

FormationBasin

* modified from USGS


Shale Petroleum Systems

• An organic rich, black “shale” provides the source biomass and oil and/or gas are derived from:

1. bacterial decomposition of organic matter to dry gas2. primary thermogenic decomposition of OM to oil and gas3. secondary thermogenic cracking of oil to gas

• May be the reservoir or sands may be primary or secondary reservoirs

• Have generation-induced microfractures• Undergo episodic generation, expulsion, and venting with

maturation• May be tectonically fractured (essential for oil, gas?)


Key Points of Talk• Barnett was buried deeper and exposed to much higher

temperatures in the past• No correlation between depth and thermal exposure across

the basin• Barnett is Type II, low sulfur oil prone kerogen (when

immature)• Gas yields is stored in a “sorbed” state as well as in a “free”

state in interstitial pores• Multiple geochemical parameters can be used to assess gas

versus oil fairways• Gas yields are extremely high, but consistent with organic

richness and original hydrocarbon generation potential• Some gas and oil has been lost from the Barnett system

through episodic expulsion or limited tectonic fracturing, but a very high percentage remains in the Barnett itself


Talk Outline





Distribution of Organic Matter in Rock Sample (low maturity)

DispersedOrganicMatter:

the “source”of

oil + assoc. gas

Rock Sample

TOC

Live Carbon Dead Carbon

Total Organic Carbon (T.O.C.)

Oil Organic Matter (Kerogen) Dead Carbon

Rock-Eval TerminologyGasJarvie, 1991


Distribution of Organic Matter in Rock Sample (low maturity)

Live Carbon Dead Carbon

Total Organic Carbon (T.O.C.)

Dead CarbonOil Organic Matter (Kerogen)

Oil Prone Gas Prone Rock-Eval TerminologyGas

Rock-Eval or SR Analyzer - terminology

S2 (and Tmax)S1 S4

Jarvie, 1991


What is the minimum TOC required of a source rock to generate a

“commercial” reservoir?

1. Depends on the volumetricsa. thickness (there is “good” and “bad” thickness)b. areal extent

2. Depends on ability to expel hydrocarbonsa. organic rich source rocks expel hydrocarbons readilyb. organic lean rocks cannot expel efficiently

3. From a laboratory viewpoint… it depends on what type of sample that is being evaluated: outcrop, cuttings, core

4. Answer:1. About 1.00% if cuttings (but depends on item 1.a above)2. About 2.00% if core (but depends on item 1.a above)3. However, the best source rocks are generally above 2% (at low maturity)


Rock-Eval or SR Analyzer “Pyrogram”

S1

S2

Tmax

Temperature trace (nonisothermalat 25oC/min)

300oC

600oC

Time (mins.)

Yield

S4


Why do we care about TOC and Rock-Eval / SR Analyzer data?

• TOC– indicative of the quantity of

organic matter available for formation of hydrocarbons

– directly proportional to the yield of gas

– allows evaluation of organic matter transformation

• Rock-Eval / SR Analyzer– shows the presence of free

oil– shows the remaining

generation potential for calculation of kerogen transformation

– provides an indication of thermal maturity

– provides the present day kerogen type (oil or gas prone)


Gas Yields Proportional to TOC values

y = 66.59x + 60.154R2 = 0.7642

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12TOTAL ORGANC CARBON (TOC)

GAS

YIE

LD

Ref: Chattanooga Shale


Expulsion Efficiency is Related to TOC(but is dependent upon heating rate)

Temperature

Oil

Yie

ld (m

g O

il/g

TOC

) 10% TOC3% TOC1% TOC

Ref: Burnham and Braun, 1991

about 10oCseparation atlow heating

rates; decreases

with higherheating rates


Relationship of TOC and Porosity to Formation Density

FORMATION DENSITY (g/cm3)

T.O

.C. (

wt.%

)PO

RO

SITY

(%)

2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7

20

15

10

5

030

20

10

0

EMPIRICAL RELATIONSHIPBETWEEN TOC AND DENSITYFOR LOW POROSITY DEVONIAN-MISSISSIPPIAN SHALES

TOC = 0%TOC = 5%TOC = 10%

CALCULATED RELATIONSHIPBETWEEN POROSITY ANDFORMATION DENSITY FOR3 DIFFERENT TOC VALUES


TYPE I: LACUSTRINE OIL PRONE SOURCE ROCKS

LABILE60%

REFRACTORY10%

INERT20%

EOM10%

TYPE II: MARINE OIL PRONE SOURCE ROCKS

LABILE40%

REFRACTORY10%

INERT40%

EOM10%

TYPE III: GAS PRONE SOURCE ROCKS

REFRACTORY25%INERT

60%

LABILE5%

EOM10%

Oil ProneFractions

Gas ProneFractions

Type I

Type II

Type III

Importance of

Quality of Organic Matter –Kerogen

Type:Differences in Organic

Matter Types

by product distribution


Sorption Capacity of Different Kerogen Types

0

10

20

30

40

50

60

70

80

90

100

I II III

KEROGEN TYPE

SOR

PTIO

N C

APA

CIT

Y (m

g H

C/g

TO

C)

Ref: Noble et al., 1997


Maturation of Organic Matter

Total Organic Carbon (TOC) DeadCarbonDead

CarbonGas Oil OM

Total Organic Carbon (TOC) DeadCarbon

DeadCarbonGas Oil O.M.

Dead CarbonTotal Organic Carbon (TOC)

OMOil Dead CarbonGas

1. OM is converted to oil and gas; slight increased in dead carbon2. 1 continues, but oil cracks to gas also


Episodic expulsion also changes the mix

Total Organic Carbon (TOC)

OMOilGas

Total Organic Carbon (TOC)

Gas Dead CarbonOil

OilGas

Expulsion

Generation fracture

TOC

OMOil

Residual oil, OM, and DC in rock

Dead Carbon

Dead Carbon

Dead Carbon

Dead Carbon

OM


Identification of oil, wet or

dry gasby

fingerprinting directly from

cuttings or core chips:

TEGCAlso useful

for GORprediction

Oil Prone

Gas Prone

min0 2 4 6 8 10 12 14 16

pA

0

100

200

300

400

500

FID1 A, (C:\PROJECTS\MEC\H00-11~1\TEGC\31220000.D)

C9

C10 C

11

C12

C13

C14

C15

C16

C17

C18

C19

C20

C21

C22

C23

C24

C25

C30

C35

min2 4 6 8 10 12 14 16 18

pA

0

50

100

150

200

250

300

350

400

450

FID1 A, (C:\PROJECTS\MEC\H00-11~2\H00-11~1\31560000.D)

C9

C10

C11

C12

C13 C

14

C15

C16

C17

C18

C19

C20


Crude Oil: Hydrocarbons + Nonhydrocarbons

0

10

20

30

40

50

60

Satura

tes

Aromati

cs

Resins

Asphalt

enes

Source rock

Migrated crudeoil

Destructionof

Non-Hydrocarbons

Importantto allowgas toflow


Residual Oil and Residual OMare cracked to gas (if sufficient depth of burial)

TOC

Dead CarbonOil OM

Gas wetness is controlledby thermal maturity andperhaps physicochemicalinteraction of oil with claysin Barnett

GasInitially: Wet Gas

Dry Gasat highmaturities


How can we assess thermal history of a source rock?

• Maturation parameters are indicative of the maximum paleo-temperature that a source rock has reached– Rock-Eval Tmax (chemical)– Vitrinite reflectance (visual)– Kerogen transformation ratio– Composition of products (may depend on

migration)


Organic Matter Maturation:Change in Color, Vitrinite Reflectivity

%Ro = 0.70 %Ro = 0.90%Ro = 0.55

%Ro = 1.40%Ro = 1.10


Vitrinite Reflectance:reported as a single value, but almost always a

distribution of values – what is the correct value?

0

5

10

15

20

25

30

35

40

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0

% VRo

Freq

uenc

y

Average %Ro = 0.48Std. Dev. = 0.07No. Pts. = 31


InertiniteInertiniteRecycled VitriniteRecycled VitriniteSolid bitumenSolid bitumen

AgeSample typeDepthMixed Kerogen


Vitrinite Reflectance:Microscopist must determine the indigenous

population from TAI and Tmax data

0

5

10

15

20

25

30

35

40

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0

% VRo

Freq

uenc

y



InertiniteInertiniteRecycled VitriniteRecycled VitriniteSolid bitumenSolid bitumen

AgeSample typeDepthMixed Kerogen


Tmax vs. VRo Correlation

Immature Oil Zone Wet Gas Dry Gas Zone

550

500

465450

430

4000.0 0.5 1.0 1.5 2.0

Vitrinite Reflectance (%Ro)

Tmax

(o C)

VRo(eq.) = 0.0180(Tmax)-7.16VRo(eq.) Tmax(oC) Maturity

0.60 431 Early Mature0.90 448 Peak Oil Generation1.00 453 Earliest Condensate-Gas window1.10 4591.20 4641.30 4701.40 476 Dry Gas Window1.70 4922.00 509 Ref: Jarvie et al., 2001


432 0.62%Tmax Equi. Ro (vitrinite reflect)

435 0.67%437 0.71%443 0.81% 455 1.03% 470 1.30%

CONVERSIONTO OIL and

GAS

INCREASINGTHERMALMATURITY

89%36%

TOCp / 0.64 = TOCo

Remainingpotentialdecreases

Tmax increases

TOC HIOriginal TOCs can be

back calculated on high maturity samples:

Oil Window

Gas Window

Jarvie and Lundell, 1991


Interpreted Maturation based on vitrinite reflectance values

• <0.60 Immature• 0.60 - 1.00 Oil window• 1.00 – 1.40 Condensate/Wet Gas Window• >1.40 Dry Gas Window

Producible gas may be found at about 1.0%Ro


Present-day versus Paleo-Temperatures of the Barnett

0 50 100 150 200 250 300

Pale

otem

pera

ture

s(w

here

in g

asw

indo

w)

Pres

ent d

ayB

arne

ttte

mpe

ratu

res

TEMPERATURE (oC)

Present-day Barnetttemperatures

82-100oC

Paleotemperaturesof Barnett in gas zone

82-100oC140-180oC


Fluid Inclusion Analysis


Fluid Inclusion Gas Dryness

MEC T.P. SIMS #2 FLUID INCLUSION GAS DRYNESS7620

7640

7660

7680

7700

7720

7740

7760

77800% 20% 40% 60% 80% 100%

GAS DRYNESS from fluid inclusion data

DEP

TH (f

eet)

SIMS #2 measured thermal maturity = ca. 1.66% VRo


CALIBRATED FLUID INCLUSION GAS DRYNESS to equivalent vitrinite reflectance for Sims #2 well

762076407660768077007720774077607780

0.00 0.50 1.00 1.50 2.00 2.50

EQ VRo from fluid inclusion gas dryness ratio

DEP

TH (f

eet)

Ave. = 1.62%


High-graded FIS Population (>80% dry)

MEC T.P. SIMS #2 FLUID INCLUSION GAS DRYNESS

7620

7640

7660

7680

7700

7720

7740

7760

778070% 80% 90% 100%

GAS DRYNESS from fluid inclusion data

DEP

TH (f

eet)

SIMS #2 measured thermal maturity = ca. 1.66% VRo


Equivalent VRo Values from FIS gas dryness ratio

CALIBRATED FLUID INCLUSION GAS DRYNESS to equivalent vitrinite reflectance for Sims #2 well

762076407660768077007720774077607780

0.00 0.50 1.00 1.50 2.00 2.50

EQ VRo from fluid inclusion gas dryness ratio

DEP

TH (f

eet)

Ave. = 1.76%VRo


Sorption:Physical and

Chemical Processes

Physical = weaklybound gas

Chemical = morestrongly bound

Adsorption:

bound to a solid

Absorption:

in solution


Talk Outline





Ouachita Fold Belt


Ft. Worth Basin:Location-Structural Features

W E

N

S

Pollastro et al., 2004


North-South Cross Section



West-East Cross Section



Depositional Cycles



Generalized Oil vs. Gas Map(Note: most wells do not penetrate Barnett)

Producing Wells in Central TexasProducing Wells in Central Texas

From East to West1. Sherman/Marietta Basin2. Fort Worth Basin3. Bend Arch4. Hardeman Basin5. Eastern Shelf6. Midland Basin

222 111333555

666

444



Barnett Shale Rock Characteristics

• Organic-rich, black shales• Thickness up to 1000 ft., average 300 ft.• Variable lithologic features

– calcareous shale predominates– clay rich shale intervals– cherty intervals– dolomitic intervals

• Microfractures present, but limited visible fractures evident at surface– it has been noted that highly fractured zones have the

lowest production flow rates (Bowker, 2002, 2003)


Lithologic Description

Johnston, 2004


Barnett Thin Section and Log Rock Types

1. Black shales2. Calcareous black shale3. Phosphatic black shales4. Limey grainstones5. Dolomitic black shales

1. Clay-rich; separation of neutron-density logs

2. High Gamma Ray – 130-140 API

3. Highest Gamma Ray –150+ API

4. Lower GR 100-1205. Lower GR 100-120;

neutron and density stack or cross over


MEC W. C. Young #2:Barnett Mineralogy Data

0102030405060708090

100

Clay

Quartz

Felds

par

Pagioc

lase

Calcite

Dolomite

Pyrite

Apatite

6890.5 ft.6920 ft.6936 ft.6944 ft.6953.5 ft.6964 ft.6973 ft.


Barnett Shale - Ave. Values

• All Barnett(n=540)– 3.16 TOC– 2.52 S2– 449 Tmax– 23 HI– 21 NOC– 55 BO/AF

• Low maturity Barnett(n=36)– 3.26 TOC– 7.87 S2– 432 Tmax– 165 HI– 33 NOC– 172 BO/AF

(in both cases primarily cuttings analysis)



• Sims Core(n=46)– 4.45 TOC– 0.60 S2– 555 Tmax– 44 HI– 6 NOC– 13 BO/AF

• Lampasas Outcrops(n=3)– 11.82 TOC– 47.26 S2– 426 Tmax– 395 HI– 31 NOC– 1035 BO/AF


432Tmax TOC S2 HI

5.21 19.80 380435 4.53 13.45 297437 4.11 10.27 250443 3.77 5.88 156455 3.41 1.81 53470 3.32 1.36 41

CONVERSIONTO OIL and

GAS

INCREASINGTHERMALMATURITY

89%36%

TOCp / 0.64 = TOCo

Remainingpotentialdecreases

Tmax increases

TOC HIOriginal TOCs can be

back calculated on high maturity samples:

Experimental Conversion of Barnett Shale


Barnett Shale: Petroleum Yields

0

200

400

600

800

1000

1200

1400

Oil (BO/AF)

Min.Ave.Max.


Depth vs. Thermal Maturity


Newark East FieldVolumetric Calculation

• Calculate mass of organic carbon• Assumptions

– 25 x 37 mi areal extent (2.395739e+13 cm2)– 450 ft. thick (U. and L. Barnett) (13,716 cm)– V = 3.2859956e+17 cm3

– density at 2.4 g/cm3

– TOCpresent = 4.50; TOCoriginal = 6.95– Mass (g TOC) = 3.6540271e+16 g TOC


Calculation of Mass of HCs per gram of TOC

• M = HIo – HI p= 380 – 44= 336 mg hydrocarbons / g TOC


Calculate Hydrocarbons Generated (HCG)

• HCG (kg HC) = R x M x 10-6 kg/mgR in mg HC/g TOCM in g TOC10-6 kg/mg is a conversion from mg to kg

HCG = 336 mg HC/g TOC x 3.6540271e+16 g TOCx 10-6 kg/mg

= 1.2277531e+13 kg HC


Volumes Calculated for Newark East Field only using the

assumptions shown above

1E+15 CF gas ~ 1000 TCF gas

50% conversion loss ~ 500 TCF

1% recoverable ~ 5 TCF8% recoverable ~40 TCF15% recoverable ~75 TCF


Has expulsion of Barnett generated hydrocarbons into younger or older

formations occurred?

• Low maturity oils in the western basin are all Barnett (8 horizons fingerprinted including the deeper Ellenburger) and are very high quality for low maturity (ca. 40oAPI).

• Higher maturity oils in Wise County are also Barnett sourced oils with similar properties although color is slightly different.

Thus, expulsion is episodic (different times and maturities)

n.b. This also explains natural ground water contamination in the basin.


Stratigraphic ColumnIn the Western Ft. WorthBasin, oils from the:•Barnett•Caddo•Canyon•Chester•Chappel•Conglomerate•Ellenburger•Flippen•Gardner•Harry Key Ls•Hodge Eagle•Hope•MoranAre all Barnett-sourcedoils (43) based on oilfingerprinting results(Ref: Jarvie et al, 2001)

Stratigraphic Column: Courtesy of Rich Pollastro, USGS


Geochemical Plot of Ft. Worth Basin Oils: Classical isoprenoid/alkane plot

Pris

tane

/ nC

17(L

og S

cale

)

Phytane / nC18(Log Scale)

GAS CHROMATOGRAPHY DATAINFERRED SOURCE ROCK KEROGEN TYPE AND DEPOSITIONAL ENVIRONMENT

Reducing

Oxidizing

GAS PRONE

Type I

II kero

gen

and humic

coals

MIXED OIL/G

AS PRONE

Type I

I-III k

erogen

mixtures

OIL PRONE

Type I

I kero

gen

algal,

mari

ne

strongly

reducin

g

0.01 0.05 0.1 0.5 1.0 5 100.01

0.05

0.1

0.5

1.0

5

10

Humble Geochemical Services


-75.0

-65.0

-55.0

-45.0

-35.0

-25.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

ETHANE, PROPANE, and BUTANES (vol.%)

d13C

ME

TH

AN

E (p

pt)

Oil Associated Gas

Bacterial Gas

Mixed Bacterial-Thermogenic Gas

Post MatureDry Gas Condensate

Associated Gas

Boonesville gasesBarnettgases

Type of Gas from

Boonesville and Barnett Reservoirs

based on gas composition and carbon

isotopes

Ref: Jarvie et al., 2003


PredictedMaturity

ofBoonesville

andBarnett

Shale Gases

-70.0

-65.0

-60.0

-55.0

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0-45.0 -40.0 -35.0 -30.0 -25.0 -20.0

δ 13C Ethane (ppt)

δ13

C M

etha

ne, P

ropa

ne (p

pt)

Methane vs. EthanePropane vs. Ethane

Bact

eria

l Met

hane

Ro=0.50%

1.20%

1.00%

0.70%

1.50%

2.00%

3.00%

70%

50%

30%

20%

60%

40%

10%

Boonesvillegases

Barnettgases

Boonesville gasesare expelled, oil-associated BarnettShale generated gas



Correlation of Gas Compositionto BTU content based on GASIS database

for counties in Ft. Worth Basin

Correlation of dry gas ratio to calorific values (in BTU) of Ft. Worth Basin gases

y = -1892.1x + 2723.9R2 = 0.7893

0

500

1000

1500

2000

2500

3000

0% 20% 40% 60% 80% 100%

%C1 in C1-C4

BTU

CO

NTE

NT

Less mature

More mature

Dry GasCondensate-Wet GasOil (ca . 25-50oAPI

Oil (ca . <25oAPI

Discountsthe presence

of nonhydrocarbon

gasesthat would alter

the BTUpredictioni.e., do not

use if greaterthan 2% CO2 orN2 are present



Inverse correlation of BTU content to vitrinite reflectance

CORRELATION of VITRINITE REFLECTANCE from Kinetic DATA to CALORIFIC CONTENT

0

500

1000

1500

2000

2500

0.2 0.7 1.2 1.7 2.2

VITRINITE REFLECTANCE

CA

LOR

IFIC

CO

NTE

NT

(BTU

)

Discountsthe presence

of nonhydrocarbon

gasesthat would alter

the BTUpredictioni.e., do not

use if greaterthan 2% CO2 orN2 are present



Speculative Prediction of Gas Flow Rates to Vitrinite Reflectance

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0.2 0.7 1.2 1.7 2.2

VITRINITE REFLECTANCE (%Ro)

DA

ILY

RA

TE (M

CF)



Generation of Oil and Gas

Organic Matter Oil

Wet-DryGas

Dead Carbon

Biodegradation

SecondaryCracking

Dry Gas

Source of Gasin Barnett Shale

• Gas from OMCracking

• Gas fromOil Cracking


Barnett Shale at 0.60%Ro

2% 7%

29%

62%

Dry Gas Wet Gas Condensate Black Oil


3% 13%

37%

47%



6%

27%

36%

31%



10%

38%

29%

23%



17%

48%

20%

15%



52%46%

1%

1%


HydrocarbonCompositional

Yields from Primary

Cracking of Barnett Shale:

at variouslevels ofthermal

maturation



CACULATED TRANSFORMATION RATESfor BARNET OM CRACKING and

OIL CRACKING to GAS

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 50 100 150 200 250 300

TEMPERATURE (oC)

CA

L. T

RA

NSF

OR

MA

TIO

N R

ATI

O(T

R)

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

2.20

CA

L. V

ITR

INIT

E R

EFLE

CTA

NC

E (%

Ro)

KEROGEN-to-HYDROCARBONS HYDROCARBONS-to-GAS VITRINITE REFLECTANCE

PrimaryKerogenCracking

SecondaryOil-to-GasCracking


HydrocarbonCompositional

Yields from Primary

andSecondary

Cracking of Barnett Shale:

at variouslevels of

organic matter conversion /

thermal maturity

CALCULATED RATES of KEROGEN and OIL CONVERSIONusing a 1oC/my constant heating rate model

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

70 90 110 130 150 170 190

TEMPERATURE (oC)

CA

L. T

RA

NSF

OR

MA

TIO

N o

f KER

OG

EN

0.20

0.70

1.20

1.70

2.20

2.70

CA

L. V

ITR

INIT

E R

EFLE

CTA

NC

E (%

Ro)

Kerogen to Oil-Gas Cal. Oil-to-Gas TR Cal. Sum Cal.%Vr (alt.y-axis)

17%

48%

20%

15%

3% 13%

37%

47%

KEROGENto

HHYDROCARBONS

OILto

GAS

CUMULATIVEHYDROCARBONS

0.75% Vitrinite Reflectance

1.10% Vitrinite Reflectance




• T. P. Sims #2 Newark East Field(n=46)– 4.45 TOC– 0.60 S2– 555 Tmax– 44 HI– 6 NOC– 13 BO/AF

6.95%TOCorig

30.9- or -

676 BO/AF0.9 BBO20 TCF

S2orig

If acrossNewark E.

Field


Newark East FieldT.P. Sims #2: Transformation Ratio

Present-day HI = 44Original HI = 445

TR = (445-44) / 445 x 100 = 89%i.e., the Barnett Shale in the Sims well

has lost 89% of its original hydrocarbon potential

Note: HI = mg HC/g TOC


Maturation Profile Offsetsuggests 5,500 ft. of erosion

Denton, Tarrant & Wise Counties

0

2000

4000

6000

8000

10000

12000

140000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0


Dep

th (f

eet)

Sweet Spot

Barnett uplifted Present Day Depth ~7500’Estimated Maximum Burial ~13,000’

Denton, Tarrant & Wise Counties

0

2000

4000

6000

8000

10000

12000

140000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0


Dep

th (f

eet)

Sweet Spot

Barnett uplifted Present Day Depth ~7500’Estimated Maximum Burial ~13,000’


Why should there be gas in Johnson County?Primary and secondary gas generation

DUALPHASESYSTEMDUE TO GASGENERATIONFOLLOWEDby PRESSUREandTEMPERATUREDROP IN LAST50 ma


Why is there gas in Wise and Johnson Counties?Primary and secondary gas generation

DUALPHASESYSTEMDUE TO GASGENERATIONFOLLOWEDby PRESSUREandTEMPERATUREDROP IN LAST50 ma


Johnson County: Calculated vs. Measured %Ro

Good matchbetween measured

and calculatedRo


Why is there oil in Montague County?Burial History and Hydrocarbon Generation History

Maximumburialtemperaturesyield onlyoil


Why wasn’t the ORYX GRANT #1 HORIZONTAL WELL COMMERCIAL FOR OIL?

0

50

100

150

200

7750 7800 7850 7900 7950 8000 8050

DEPTH (feet)

NO

RM

ALI

ZED

OIL

CO

NTE

NT

Productive Oil or Gas Intervals

Oil stains - shows

Lean - no production potential

Only 1 zone shows oil saturated Barnett


Other wells have commercial oilthat is evident from simple tests

0

1 0 0 0

2 0 0 0

3 0 0 0

4 0 0 0

5 0 0 0

6 0 0 0

7 0 0 0

8 0 0 0

9 0 0 0

1 0 0 0 0

0 20 40 60 80 100 120 140 160 180 200NORMALIZED OIL CONTENT (mg oil/g TOC)

Reservoir ZonesShows(high maturity

source)

Lean Mod.oil

content

Zones yieldingabout 100 BO/day


Producibility and Gas Content

• Worst production comes from highly fractured (naturally) Barnett (Bowker, 2002)

• Gas content is directly proportional to TOC, kerogen type, and maturity

• BTU content of gas is inversely proportional to thermal maturity (Bowker, 2002)


Total Gas Flowfrom a Barnett Well

1. Lost gas – gas that escapes into the well borewhile drilling (from mud gas analysis)

2. Desorbed gas – gas the desorbs from the Barnettafter a period of time (from cannedcuttings gas analysis)

3. Frac gas – gas that is released from the Barnettupon maceration of the shale samples(from macerating cuttings)


Well Bore, Desorbed, and Residual Gas from the Barnett Shale

Gasliberated

frommaceration(“frac-ing”)

Barnettcuttings

Barnett Shale Gas

43%

18%

39%

"lost" gas desorbed gas "frac" gas

WellBoreGas:Driergasthan

desorbedgasDesorbed

gasfrom

cuttings


Total Gas Flowfrom a Barnett Well

1. Lost gas – free gas that escapes into the well borewhile drilling (from mud gas analysis)

2. Desorbed gas – gas the desorbs from the Barnettafter a period of time (from cannedcuttings gas analysis)

3. Frac gas – gas that is released from the Barnettupon completion of a frac job


Methane IsothermsSims #2, Wise County

T.P. SIMS #2 Various Methane Isotherms

0

50

100

150

200

250

300

0 500 1000 1500 2000 2500 3000 3500 4000 4500

PRESSURE (psia)

YIEL

D (S

CF

/ ton

)

TOTAL GASADSORBED GAS

170-250SCF/ton

60-125SCF/ton

Ref: GRI Report 5086-213-1390, 1991


T.P. Sims #2 Barnett Gas Yields

Gas Yields from Corrected* Adsorption Isothermsat 3800 psi

T.P. Sims #2, Wise County, Texas

Total "Sorbed" "Free" "Sorbed" "Free"Depth Gas Gas Gas * Gas Gas ** TOC(feet) (scf/ton) (scf/ton) (scf/ton) (% of total) (% of total) (wt.%)7640 190 70 120 37% 63% 4.337670 215 124 91 58% 42% 3.927675 213 81 132 38% 62% 4.797682 231 99 132 43% 57% 5.407694 170 106 65 62% 38% 5.667711 125 61 64 49% 51% 3.307721 234 88 147 38% 62% 4.267733 249 117 132 47% 53% 6.857743 70 28 43 39% 61% 0.717755 205 108 97 52% 48% 5.31

Average: 191 88 102 46% 54% 4.45

* GRI publication values recalculated by elimination of bad data points and curve fitting.** by difference


Gas Yields from Methane Isotherm Data on T.P. Sims #2 Well

T.P. SIMS #2 GAS YIELDSfrom methane isotherm data

y = 14.464x + 23.678R2 = 0.6676

y = 27.538x + 67.886R2 = 0.6798

0.0

50.0

100.0

150.0

200.0

250.0

300.0

0 1 2 3 4 5 6 7 8

TOTAL ORGANIC CARBON (TOC in wt.%)

GA

S C

ON

TEN

T (S

CF

/ ton

)

TOTAL GASADSORBED GAS

T.P. SIMS #2 Average Gas Contentscalculated at 3800 psia from methane isotherm data

0.0

50.0

100.0

150.0

200.0

250.0

ADSORBED FREE TOTAL

GA

S C

ON

TEN

T (S

CF

/ ton

)

Ref: GRI Report 5086-213-1390, 1991


T.P. SIMS #2:Relationship of Adsorption

Isotherms and Gas Yields to TOC

T.P. SIMS #2 GAS CONTENT

y = 0.0195xR2 = 0.947

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00

Total Organic Carbon (TOC in wt.%)

Slop

e of

0-5

00 p

si M

etha

ne

Ads

orpt

ion

Isot

herm

(SC

F/to

n/ps

i)

T.P. SIMS #2 GAS CONTENT at 1200 psia

y = 18.759x + 41.962R2 = 0.7367

0

20

40

60

80

100

120

140

160

180

0.00 2.00 4.00 6.00 8.00

Total Organic Carbon (TOC in wt.%)

Gas

Yie

ld (S

CF/

ton)

Ref: GRI Report 5086-213-1390, 1991


Prediction of Gas Yields:using canned cuttings (not SWC)

COMPARISON OF USBM LOST GAS ANALYSIS TO PREDICTIONS FROM SPECIAL HEADSPACE GAS ANALYSIS

8100

8200

8300

8400

8500

8600

8700

8800

8900

90000 50 100 150 200 250 300 350 400 450 500

SCF/ton

Dept

h (fe

et)

USBM LOST GAS CALCULATED FROM CUTTINGS GAS



Advantages of Using Canned Cuttings for Gas Yields Assessment

• Inexpensive– uses well cuttings, not SWC– analytical cost per sample about $50

• Fast results (2-5 days ARS)• Cuttings available for other analyses

– TOC, Rock-Eval, Ro• Mappable across field, by prospects• Indicative of possible flow rates


Talk Outline





Using Geochemistryin Unconventional Plays

• Construct maps• Organic facies (maceral) maps • Maturity and TR maps• Composition (GOR) maps• BTU maps

• Needs to construct maps• Geological/geophysical information• Geochemical data (TOC, RE, Ro, Compo.)


Using Geochemistryin Unconventional Plays

• Construct well and basin models– Burial history curves– Timing of generation and expulsion

• Evaluate amounts expelled (reduces amount of oil to crack to gas)

• Timing of uplift impacts expulsion• Optimize models using geochemical data

such as TOC, Ro, TR


Risking Geochemical Data

• TOC – Quantity of Organic Matter– proportional to the amount of oil and gas

generated– impacts expulsion efficiency– impacts adsorptive capacity

0.0 to 2.0% : Poor risk for oil or gas> 2.0 % : Good risk for oil or gas

Remember in the gas window,TOC may be reduced 30-50%


Risking Geochemical Data:Maturity Assessment

• Ro: 0.2%Ro to 4.0%Ro post mature

• 0.60%Ro = onset of oil generation• 0.90%Ro = peak oil generation• 1.00%Ro = wet gas generation window• 1.40%Ro = dry gas generation window• 2.10%Ro = dry gas only zone• > 2.10 %Ro = reservoir destruction,

CO2 risk

Poor Riskfor Gas

Good riskfor gas


Risking Geochemical Data (cont.)

• TR: 0-100 % conversion of organic matter

– 0.0 to 50.0 % TR – primarily oil– 50.0 to 80.0% TR – mixed oil and gas– 80.0 to 90.0% TR – primarily gas– > 90.0% TR – primarily dry gas

Poor Riskfor Gas

Good riskfor gas



• Gas yields: gas wetness ratios (0-100%)• gas flow gas yield• desorbed gas yield• macerated cuttings gas yield

– 0.00 to 50.0 : oil– 50.0 to 80.0 : mixed oil and gas– 80.0 to 90.0 : primarily wet gas– > 90.0 : dry gas

Poor Riskfor Gas

Good riskfor gas



• Seals

– Top seal (Marble Falls)– Middle seal (Forestburg)– Lower seal (Viola)

Poor Riskfor Gas

Good riskfor gas



• Timing of expulsion / Uplift

– No charge build-up– Charge build-up and venting– Charge build-up and no venting

Poor Riskfor Gas

Good riskfor gas



• Thickness of shale(must be considered jointly with TOC)

• Assume 4.5% TOC

– 10 ft.– 50 ft.– 100 ft.– 250 ft– 400 ft– 500+ ft

Poor Riskfor Gas

Good riskfor gas


Risking Polar Plot:Minimum values for various parameters

TOC [10]

Ro [2.2]

GAS [100]Tmax [600]

TR [100]

Suggested minimum valuesfor 5 geochemical parameters


Prospect Evaluation:Poor Gas Prospect – high TOC, but low maturity

TOC [10]

Ro [2.2]

GAS [100]Tmax [600]

TR [100]

Sample has good TOC,but is not a good shalegas prospect due to lowthermal maturity


Antrim Shale:Biogenic Petroleum System

Measured Antrim data

TOC [10]

Ro [2.2]

GAS [100]Tmax [600]

TR [100]

Measured Antrimvalues

Low maturity shale:Different risk factors !If high dry gas contentand low maturity, it islikely biogenic gas


Analytical Programfor Shale Gas Prospects

1. Mud gas samples (ca. every 50 ft.)1. Gas composition2. Carbon isotopes

2. Bottled cuttings samples (ca. every 10-30 ft.)1. Gas composition2. Carbon isotopes

3. TOC on cuttings and core (every 10-30 ft.)4. Rock-Eval or SR Analyzer on cuttings or core (every 10-30 ft.)5. Vitrinite Reflectance on cuttings and core, above and through shale

(good source rocks are vitrinite poor!) (min. 3 prefer profile of well)6. Thermal Alteration Index (TAI) (a maturity assessment)7. Visual kerogen (what type of organic matter is present)8. Light hydrocarbon whole extract gas chromatographic fingerprinting

(on any samples on which vitrinite reflectance is measured)9. Mineralogy including clay speciation10. Gas yields on conventional cores


Know Petroleum System Character

1. Biogenic gas shale petroleum systems2. Mixed biogenic/thermogenic gas shale systems3. Thermogenic gas shale petroleum systems

A. source and reservoir not the samei. timing of expulsion, migration, trap, and seal formationii. dependent upon source rock OM type, maturityiii. could be primary or secondary gas expelled from source

B. source and reservoir the same i. secondary gas generation (maturity/temperature)ii. timing of oil decomposition, episode of expulsion

4. Tight gas sands5. Coal bed methane (primary gas generation)


What does it take for a commercial gas discovery in the Barnett Shale based strictly on geochemical parameters?

• Organic richness• Volumetric extent (primarily controlled by thickness)• Kerogen conversion

– Thermal maturity at some point in the past to reach 140oC+ for conversion of kerogen to oil/gas and oil to gas

• %Ro > 1.0% (but < 2.1% to avoid reservoir destruction and high CO2 yields

• TR > 0.80• Tmax > 455oC

• Possibly uplift prior to expulsion / venting


Evaluation of Gas Potentialwhile drilling – sweet spot identification

• Gas samples from gas flow line – new technique

• Canned cuttings samples (desorbed gas, gas yields)

• Cuttings gas analysis (gas liberated upon crushing)


Key Points of Talk• Barnett was buried deeper and exposed to much higher

temperatures in the past• No correlation between depth and thermal exposure across

the basin• Barnett is Type II, low sulfur oil prone kerogen (when

immature)• Gas yields is stored in a “sorbed” state as well as in a “free”

state in interstitial pores• Multiple geochemical parameters can be used to assess gas

versus oil fairways• Gas yields are extremely high, but consistent with organic

richness and original hydrocarbon generation potential• Some gas and oil has been lost from the Barnett system

through episodic expulsion or limited tectonic fracturing, but a very high percentage remains in the Barnett itself


For more information…

• Contact:

Dan JarvieHumble Geochemical [email protected] BoggsHumble Geochemical [email protected]

Coming soon…publications

mailto:[email protected]?subject=Barnett Shale - Unconventional Gas

mailto:[email protected]?subject=Barnett Shale - Unconventional Gas


Humble Geochemical ServicesDivision Humble Instruments & Services, Inc.

218 Higgins Street Humble, Texas 77338P.O. Box 789 Humble, Texas [email protected]

mailto:[email protected]

evaluation of hydrocarbon generation and storage in the

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