the barnett shale as a model for unconventional shale gas...

Humble Geochemical Services

The Barnett Shale as a Model for Unconventional

Shale Gas Exploration©

Dan JarvieHumble Geochemical Services

Division of Humble Instruments & Services, Inc.

Copyright 2003 Humble Instruments & Services, Inc. All rights reserved.


Humble, Texas(Houston is our largest suburb)


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 / ProductionFinding bypassed pay and predicting pre-test, pre-completion oil quality


Fractured Shale Petroleum Systems

• An organic rich, black shale is the source of hydrocarbons:

1. from bacterial decomposition of organic matter2. from primary thermogenic decomposition of OM3. from secondary thermogenic cracking of oil

• May be the reservoir or other horizons may be primary or secondary reservoirs

• Have generation induced microfractures and perhaps tectonic fractures

• Undergo episodic generation, expulsion, and venting with maturation


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

Oil and gas


USGS Data on Gas Bearing Shales

nana1.6 - 1.91-2.5*LewisShale

San Juan

20**(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 ** author’s estimate


Gas Production from Fractured Shales

BarnettShale

est. 2002based on97 BCF

in first halfof 2002

Ref: Hill, 2000; Bowker, 2002


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

Ref: Modified from Armentrout, 2001


Distribution of Organic Matter in Rock Sample (low maturity)

DispersedOrganicMatter:

the “source”of

oil + assoc. gas

Rock Sample

TOC

Live Carbon

Organic Matter (Kerogen)Oil

Gas

Total Organic Carbon (T.O.C.)

Dead Carbon

Dead Carbon

Oil Prone Gas ProneS2 (and Tmax)S1 S4

Ref: Jarvie, 1991


Compositional Yields from PrimaryCracking of Barnett Shale

CORRECTED MACT10 PY/GC YIELDS*

22%

55%

13% 10%

C1C2-C4C5-C14C15+


Total Organic Carbon (TOC)

OMOilGas

Maturation of Organic Maturity


O.M.OilGas

DeadCarbon

DeadCarbon

Dead Carbon

Dead Carbon

DeadCarbon

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


OMOil Dead CarbonGas


Episodic expulsion also changes the mix


OMOilGas


Dead CarbonOilGas

OilGas

Expulsion

Generation fracture

Dead Carbon

Dead Carbon

Dead Carbon

OM

TOC

OMOil

Residual oil, OM, and DC in rock

Dead Carbon


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

TOC

OMOil Dead Carbon

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

Initially: Wet Gas

Dry Gasat highmaturities


FT. WORTHBASIN

LLANOUPLIFT

MUENSTER ARCH

BENDARCH

RED RIVER ARCH

OU

ACHI

TA S

TRUC

TRUA

L BE

LT

TEXAS

StudyArea

Ft. Worth Basin

Location andprincipal

geologicalfeatures

delimiting thebasin


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


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.


In 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

Stratigraphic Column


Barnett Shale:Petroleum Potential and Maturity Trend

0200400600800

100012001400

380 430 480 530 580

THERMAL MATURITY (Tmax in oC)

BO

/ A

F (b

ased

on

S2)

Kerogen transformationtrend line

Lampasasoutcrops !

Gas Window

If high TOCthese are also gas windowdespite low (unreliable)

Tmax values


General Observations

• High TOC marine shales are more efficient expellers of hydrocarbons– 1% poor 3% fair 10% excellent

• High TOC and clay content aid retention of hydrocarbons by adsorption

• Episodic expellers, a.k.a. pressure cookers: Generate HCs, form vapor lock – critical pressure exceeded, vent, and reseal; repeated depending on burial history


Generation of Oil and Gas

Organic Matter Oil

Wet-DryGas

Dead Carbon

Dry GasBiodegradation

SecondaryCrackingSource of Gas

in Barnett Shale

• Gas from OMCracking

• Gas fromOil Cracking


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

CACULATED TRANSFORMATION RATESfor BARNET OM CRACKING and

OIL CRACKING to GAS

PrimaryKerogenCracking

SecondaryOil-to-GasCracking


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 - Ave. Values

• 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


Transformation Ratio

A measure of the extent of kerogen conversion

• to determine this with reasonable accuracy, the original potential of the soruce rock must be determined

• multiple formulasS2original – S2present / S2original

HIoriginal –HIpresent / HIoriginal


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

Original HI = 445 Present day HI = 44

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


Producibility and Gas Content

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

• Gas content is directly proportional to TOC and maturity

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


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


Volumetric Calculation Chart

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+09 1.E+10 1.E+11 1.E+12 1.E+13 1.E+14 1.E+15 1.E+16

MASS OF HYDROCARBONS (kg)

OIL

EQ

UIV

ALE

NT,

30o A

PI (b

bl)

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

GA

S EQ

UIV

ALE

NT

(ft3)

OIL EQUI.GAS EQUI.

Schmoker, 1994

Requires:

TOCHI originalHI presentSource thicknessSource areal extentSource density

Schmoker’s chart for conversionof hydrocarbon mass to volumes

of oil or gas equivalent


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 TCF


JON ESF ISH ER

EA ST LA N DCA L LAH A N

BRO W N

CO M A NCH E

ER A TH

BO SQ UE

H IL L

M cL EN NA N

HO OD

SOM ER VILLE

JO HN SO N

TA RR AN TPA R KERPA LO P IN TOST EPH EN SSH AC K EL F OR D

THR OC KM O RTO N YO UN G

JA C K W ISE DEN TO N

M O NTA GUE

HA M IL TON

0 10 20 30Scale in Miles

N

Mills

San Saba Lampasas

Coryell

Ft. Worth Basin2000 PRODUCTION GORs by county

GOR=1000

GOR=3000

GOR=5000+

Source: TRRC

Gas Composition based on Production Results by County (ave.)

no production


JON ESF ISH ER

EA ST LA N DCA L LAH A N

BRO W N

CO M A NCH E

ER A TH

BO SQ UE

H IL L

M cL EN NA N

HO OD

SOM ER VILLE

JO HN SO N

TA RR AN TPA R KERPA LO P IN TOST EPH EN SSH AC K EL F OR D

THR OC KM O RTO N YO UN G

JA C K W ISE DEN TO N

M O NTA GUE

HA M IL TON

0 10 20 30Scale in Miles

N

Mills

San Saba Lampasas

Coryell

Generalized Maturity Mapbased on TRCC production data (YTD 2000)

OilGas w/OilDry Gas


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


Eastland County: Also in gas zone,different burial history


ViolaMarble Falls

Modified from Pallastro, 2002

The presence orabsence of top andbottom seals hasimpact on fracturing


Risking Geochemical Data

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

generated– impacts expulsion efficiency

0.0 to 1.0% : Poor risk for oil or gas> 1.0 % : Good risk for oil or gas

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


Risking Geochemical Data (cont.)

• Ro: 0.2%Ro to 4.0%Ro post mature

• 0.55%Ro = onset of oil generation• 0.90%Ro = peak oil generation• 1.10%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



• TR: 0-100 % conversion of organic matter

– 0.0 to 50.0 % TR – primarily oil– 50.0 to 75.0% TR – mixed oil and gas– 75.0 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 75.0 : mixed oil and gas– 75.0 to 90.0 : primarily gas– > 90.0 : dry gas

Poor Riskfor Gas

Good riskfor gas


Finding High BTU Gas:Ft. Worth Basin

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

GAS CALORIFIC VALUE (BTU)

DR

Y-t

o-W

ET

GA

S R

AT

IO

V. HighMaturity

HighMaturity Mod.

Maturity

BTU contentis controlled bywet gas content

(and nonhydrocarbon gases, if present

BTU contentis inversely proportional

to maturity



• 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


Shale Gas Evaluation Criteria:Geochemical Risk Factors

TOC [10]

Ro [2.2]

GAS [1000000]Tmax [600]

TR [1]

TOC < 1.00%

%Ro < 1.1

< 100,000 ppmheadspace gas

Tmax < 450

TR < 0.70

Minimum valuesfor gas prospects


Shale Gas Evaluation Criteria:Wise County Example

TOC [10]

Ro [2.2]

GAS [1000000]Tmax [600]

TR [1]

High maturity shale:All risk factors favorablefor high BTU gas

Min. valuesfor gas prospects


Shale Gas Evaluation Criteria:Barnett Analog – Gas but Oil Window Maturity

TOC [10]

Ro [2.2]

GAS [1000000]Tmax [600]

TR [1]



Antrim Shale:Biogenic Petroleum System

TOC [10]

Ro [2.2]

GAS [1000000]Tmax [600]

TR [1]

Measured Antrim data



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?

• Thermal maturity at some point in the past to reach 150oC+ for conversion of kerogen to oil/gas and oil to gas

– %Ro > 1.1% but less than 2.1% to avoid reservoir destruction and high CO2 yields

– TR > 0.80– Tmax > 450oC– TOC values > 4%

• Uplift prior to expulsion / venting


Evaluation of Gas Potentialwhile drilling – sweet spot identification

• Gas samples from gas flow line – new technique –an indication of “lost” gas (gas desorbed from the reservoir into the mud)

• Canned cuttings samples (desorbed gas) – the amount of gas (SCF/ton) that will be liberated from cuttings

• Cuttings gas analysis (gas liberated upon crushing cuttings – an indication of “frac” yields)

• TOC, Rock-Eval, TEGC, and vitrinite reflectance analyses (is it rich enough, converted enough (TR and Ro) to have generated commercial amounts of hydrocarbons)


Using Gas Composition and Isotopesfor sweet spot and maturity assessments

-70.00

-65.00

-60.00

-55.00

-50.00

-45.00

-40.00

-35.00

-30.00

-25.00

-20.00-45.00 -40.00 -35.00 -30.00 -25.00 -20.00

δ 13C Ethane (ppt)

δ13C

Met

hane

, Pro

pane

(ppt

)

Methane vs. EthanePropane vs. Ethane

70%

50%

30%

20%

60%

40%

10%

Bact

eria

l Met

hane

3.00%

Ro=0.50%

1.20%

1.00%

0.70%

1.50%

2.00%

700

750

800

850

900

950

1000

1050

1100020406080100

GWR and LHR OVERLAY

GWRLHR

WellSweetSpots


CONCLUSIONS

• Barnett Shale has world-class petroleum potential; limiting factors are – thermal maturity– episodic expulsion– seals (leaky through time due to venting)

• Other unconventional resources have similar characteristics, but also some unique twists

• Risks can be reduced by careful evaluation of thermal maturity (kerogen conversion) and timing of events (generation, expulsion)


ReferencesArmentrout, John The Quest for Energy: Rewarding Careers in Petroleum Exploration, AAPG website slide set, February 2000 (http://www.aapg.org/slide_bank/armentrout_john/index.shtml).

Bowker, K.A., 2002, Recent development of the Barnett Shale play, Fort Worth Basin, RMAG Innovative Gas Exploration Concepts, Denver, CO October 1, 2002.

Burnham, A. K. and Robert L. Braun, 1990, Development of a detailed model of petroleum formation, destruction, and expulsion from lacustrine and marine source rocks, Advances in Organic Geochemistry 1989, Org. Geochem., Vol. 16, Nos. 1-3, pp. 27-39.

Claypool, G. E., and E. A. Mancini, 1989, Geochemical Relationships of Petroleum in Mesozoic Reservoirs to Carbonate Source Rocks of Jurassic Smackover Formation, Southwestern Alabama : AAPG Bulletin, v. 73, p. 904-924.

Demaison, G. and B. J. Huizina, 1994, Genetic Classification of Petroleum Systems Using Three Factors: Charge, Migration, and Entrapment, in: The Petroleum System – From Source to Trap, AAPG Memoir 60, L.B. Magoon and W.G. Dow, eds., AAPG, Tulsa, OK, 655 p.

Dembicki, Harry, 1986, Oil Show Detection by C5+ Hydrocarbon Mud Logging, SPE Formation Evaluation, pp. 331-334. Jarvie, Daniel M.,

Jarvie, Daniel M., Jack D. Burgess, Alex Morelos, Robert K. Olson, Phil A. Mariotti, and Robert Lindsey, 2001, Permian Basin Petroleum Systems Investigations: Inferences from Oil Geochemistry and Source Rocks, AAPG Mid-Continent Section Meeting, Amarillo, Texas, September 30-October 2, 2001, AAPG Bull. Vol. 85, No.9, pp. 1693-1694, oral presentation.

Jarvie, Daniel M., Brenda L. Claxton, Floyd "Bo" Henk,and John T. Breyer, 2001, Oil and Shale Gas from the Barnett Shale, Ft. Worth Basin, Texas, AAPG National Convention, June 3-6, 2001, Denver, CO, poster presentation.

Jarvie, Daniel M., 2001, Williston Basin Petroleum Systems: Inferences from Oil Geochemistry and Geology, The Mountain Geologist, Vol. 38, No. 1, pp. 19-41

Jarvie, Daniel M., Ron Hill, and Frank Mango, 2001, Effect of inorganic constituents on light hydrocarbon composition and compound distributions of crude oils, 20th International Meeting on Organic Geochemistry, Nancy, France, Sept. 10-14, 2001, abstract.

Jarvie, D.M., 1991, Total Organic Carbon (TOC) Analysis, in Treatise of Petroleum Geology, Handbook of Petroleum Geology, Source and Migration Processes and Evaluation Techniques, Ed. R.K. Merrill, AAPG Press, Tulsa, Ok.

Okui, A. and D. Waples, 1993, Relative permeabilities and hydrocarbon expulsion from source rocks, in: Basin Modelling: Advances and Applications, A.G. Dore et al, eds., NPF Special Publication No. 3, Elsevier, London, 675 p.

Schmoker, James., W., 1994, Volumetric Calculation of Hydrocarbons Generated, AAPG Memoir 60 The Petroleum System –From Source to Trap, L.B. Magoon and W.G. Dow, eds., pp. 323-326.


Appendix

• Terms• Other graphics and maturity/TR/temp correlation

table• Barnett Shale: TOC and Rock-Eval values• Solution to Schmoker’s oil and gas volume

calculation• SPI calculations• Identifying sweet spots• Oil and water saturation curves for SS and Sh• Using geochemistry in unconventional gas plays


Terms• TOC = total organic carbon (organic richness)• %Ro = vitrinite reflectance (thermal maturity indicator)• TR = transformation ratio (extent of conversion of kerogen where e.g.,

(HIo-Hip) / HIo• Rock-Eval S1 = free oil content in rock• Rock-Eval S2 = remaining kerogen content in rock• Rock-Eval Tmax = temperature at maximum S2 yield; an indication of

thermal maturity• Primary cracking kinetics = rate at which kerogen decomposes into

hydrocarbons (oil and gas)• Secondary cracking kinetics = rate at which oil decomposes into gas


Back-calculations of TOC

• At high maturity (85%+ Transformation Ratio (TR))

– TOC present day TOC original• 4.50% 7.00%• 2.00% 3.13%• 8.00% 12.50%

• Different TOCs at high maturity, reflect organofacies differences and impact expulsion and gas yields


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


Derivation of HIoriginal

• From a database of samples of the same organofacies of low thermal maturity– average HI value

• From back calculation or estimation of original – estimate the original potential from HIpresent, visual

kerogen, Tmax, and Ro data

{Organofacies is a single, mappable unit of organic matter of the same type without regard to the inorganic matrix}


BAKKEN CONVERSION WITH INCREASING DEPTH OF BURIAL

0

2000

4000

6000

8000

10000

12000

14000380 400 420 440 460 480 500

Rock-Eval Tmax

DEP

TH (f

t.)

Immature MainOil

Zone

WetGasZone

Dry

Gas

Zon

e

BakkenMaturityIncreases

with depth of burial

Price et al., 1984

Tmax showsa logarithmicincrease with

increasing depthof burial


0

100

200

300

400

500

600

700

800

900

1000

330 380 430 480 530 580

Tmax (oC)

HYD

RO

GEN

IND

EX (m

g O

IL/g

TO

C)

Type IOil Prone

Type II (usu. marine)Oil Prone

Type IIIGas Prone

Type IV: Dry Gas Prone

Mixed Type II / IIIOil / Gas Prone

~0.60% Ro

~01.40% Ro

Ave. HI Brown Cty = 396

Ave. HI Eastland Cty = 68

TR(%) = (396-68)/396 x 100

= 83%and

328 mg HC/g TOCgenerated

Extent of OrganicMatter Conversion

Ref: Jarvie and Lundell, 1991


Eastern Ft. Worth Basin:

NoRelationship

between depth of burial and

measured vitrinite

reflectance value

Immature Oil Zone Wet Gas Zone Dry Gas Zone

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0

Ro (%)

-11000

-9900

-8800

-7700

-6600

-5500

-4400

-3300

-2200

-1100

0

Dep

th (f

eet)

Vitrinite Reflectance - Depth Plot

Humble Geochemical Services Division


Importance of

Quality of Organic Matter –Kerogen

Type:Differences in Organic

Matter Types

by product distribution

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


Schematic Cross Section from Brown to Eastland County

Barnett Shale

Mitcham #1 A.E.A. Heirs #1

TOC=4.67%HI = 396Ro = 0.60%Tmax = 434

TOC=3.40%HI = 68Ro = 1.10%Tmax = 454

Bro

wn

Cty

East

land

Cty

Ref: Jarvie and Lundell, 1991


Relative Correlation of Vitrinite Reflectance to Rock-Eval Tmax

0.2

0.4

0.6

0.8

1

1.2

1.4430 435 440 445 450 455 460 465 470

Rock-Eval Tmax (oC)

Vitr

inite

refle

ctan

ce (%

Ro)


General Relationship betweenTransformation Ratio and %Ro

0.2

0.4

0.6

0.8

1

1.2

1.40 0.2 0.4 0.6 0.8 1

TRANSFORMATION RATIO (TR)

VITR

INIT

E R

EFLE

CTA

NC

E (%

Ro)


Measured Oil Cracking in GOM at 3.0oC/my

y = 0.1196e0.0141x

R2 = 0.9997

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

100 120 140 160 180 200 220TEMPERATURE (oC)

VITR

INIT

E R

EFLE

CTA

NC

E (%

Ro)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%Reservoir Temp.Fraction Oil Cracked

SecondaryCrackingof Oil to

Gas

Gulf ofMexico

CaseStudy

Claypooland Mancini,

1989


Relative Flow Rates vs. Thermal Maturityin selected fields

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)

For illustrationpurposes only:

too manyvariables to

be a universalequation


HypothesizedKey

CorrelationsType II

(marine shale)low sulfur

organic matter:

1. Thermal Maturity2. Kerogen Transformation

3. Oil-to-Gas Transformation4. Temperature

2000.992.0na1.00507

1950.951.9na1.00503

1920.901.8na1.00498

1880.871.7na1.00492

1830.811.6na1.00487

1780.721.5na0.99481

1730.581.4na0.98475

1680.451.3na0.97470

1630.281.20.380.96465

1570.201.10.330.81460

1500.051.00.290.67455

1410.000.90.240.52450

1340.000.90.190.37445

1270.000.80.150.23440

1200.000.70.100.08435

Est. Temperature

(oC)

Est. Oil-to-Gas

Cracking

Est. %Ro

Est. PI

Est.TR

Rock-Eval

Tmax (oC)


Calculate Transformation Ratio

TR (mg HC/g TOC) = HIoriginal – HIpresent / HIoriginal

HIpresent = measured Hydrogen Index (HI) from sample at depth (mature) = 150

HIoriginal = measured Hydrogen Index (HI) from immature sample = 380

TR = (380-150) / 380 = 0.61 or 61% conversion



• 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)



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

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


Barnett Shale: Petroleum Yields

0

200

400

600

800

1000

1200

1400

Oil (BO/AF)

Min.Ave.Max.


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


Schmoker’s Volumetric Calculation Chart

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+09 1.E+10 1.E+11 1.E+12 1.E+13 1.E+14 1.E+15 1.E+16

MASS OF HYDROCARBONS (kg)

OIL

EQ

UIV

ALE

NT,

30o A

PI (b

bl)

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

GA

S EQ

UIV

ALE

NT

(ft3)

OIL EQUI.GAS EQUI.

Schmoker, 1994


Source Potential Index (SPI)

• A measure of the potential of a source rock to generate hydrocarbons over a given areal extent

• SPI = h (S1+S2) p / 1000– where h = thickness of source rock– S1+S2 data from Rock-Eval (mg HC/g rock)– p = density, assume 2.5 t/m3

• Must also account for migration and entrapment styles

Ref: Demaison and Huizinga, 1994


SPI – Barnett Shale, Wise County• Assumptions:

– h = 250 ft. or 76.2 m– S1+S2 = 20.00 t/kg rock– p = 2.50 t/m3

• SPI = 76.2 x 20 x 2.5 / 1000= 3.81 t / m2

• Add U. Barnett (150 ft.)= 6.10 t / m2

• Increase S1+S2 (27.79 ave. per unit TOC) based on Lampasas outcrop yields

= 8.34 t / m2

• Maximum S1+S2 at Lampasas = 47.75= 14.38 t / m2


EXAMPLES OF AVERAGE SOURCE POTENTIAL INDICES

(tons HC/m2)

1. Junggar (China): 652. L. Congo (Cabinda): 463. Santa Barbara Channel (U.S.A.): 394. San Joaquin (U.S.A.): 385. Central Sumatra (Indonesia): 346. E. Venezuela fold and thrust belt: 277. Offshore Santa Maria (U.S.A): 21

Ref: Demaison and Huizinga, 1994


EXAMPLES OF SPI (cont.)(tons HC/m2)

8. Middle Magdalena (Colombia): 169. North Sea (U.K.): 1510. Central Arabia (S. Arabia): 1411. Niger Delta (Nigeria): 1412. Gulf of Suez (Egypt): 1413. San Joaquin - Eoc./Oligo. (U.S.A.): 1414. Ft. Worth - Barnett (U.S.A.): 13

Reserves estimated at 10 TCF or ~ 1.67B BOE


Finding High BTU Gas

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

GAS CALORIFIC VALUE (BTU)

DR

Y-t

o-W

ET

GA

S R

AT

IO

V. HighMaturity

HighMaturity Mod.

Maturity

BTU contentis controlled bywet gas content


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


C7-determined Generation Temperatures for Barnett Oils

1.00

1.20

1.40

1.60

1.80

2.00

2.20

80 90 100 110 120 130 140 150

A V ER A GE GEN ER A T ION TEM PER A T U R E ( o C )

SPEARFISH

TYLER

CHARLES - M. CANYON

LODGEPOLE

BAKKEN

NISKU

DUPEROW

DAWSON BAY

WINNIPEGOSIS

INTERLAKE

RED RIVER

WINNIPEG

DEADWOOD

Barnett Oilson trend linewith Bakken oils

IncreasingGOR


GORs can be predicted with some degree of accuracy from both vitrinite reflectance and

oil/condensate light hydrocarbons

Oil

Wet Gas

DryGasR2 = 0.9233

010002000300040005000600070008000

0 0.5 1 1.5 2CAL. VITRINITE REFLECTANCE (%Ro)

CA

L. G

OR


TYPICAL SANDSTONE RESERVOIR ROCK

WATER SATURATION (%)

REL

ATI

VE

PER

MEA

BIL

ITY

Kro

Krw

Kromax

Krwmax

Krx

Swirr Swx Swc

1.0

0.90.80.70.6

0.5

0.4

0.30.20.1

0.00 10 20 30 40 50 60 70 80 90 100


TYPICAL SHALE RESERVOIR ROCKis quite different from a conventional reservoir

WATER SATURATION (%)REL

ATI

VE

PER

MEA

BIL

ITY

Kro

Krw

0 10 20 30 40 50 60 70 80 90 100

1.0

0.90.80.70.6

0.5

0.4

0.30.20.1

0.0

Ref: Okui and Waples, 2000


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

the barnett shale as a model for unconventional shale gas...

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