AAPG Mid-Continent Section Meeting September 10, 2007

Conventional Wisdom Conventional Wisdom Applied to Oklahoma Gas Applied to Oklahoma Gas

ShalesShales

Brian J. CardottBrian J. CardottOklahoma Geological Oklahoma Geological

SurveySurvey

OutlineOutlineConventional Wisdom of Gas Conventional Wisdom of Gas ShalesShalesOklahoma Woodford ShaleOklahoma Woodford ShaleOklahoma Woodford GasOklahoma Woodford Gas--Shale Shale PlayPlay

Conventional Wisdom Conventional Wisdom [Non[Non--Negotiable Parameters] Negotiable Parameters]

Necessary for Gas Necessary for Gas ShalesShales(summarized from others (summarized from others

working on the Barnett Shale)working on the Barnett Shale)

Fractures (permeability)Fractures (permeability)Gas Source Rock (Gas Generation, Gas Source Rock (Gas Generation, Storage, and Preservation)Storage, and Preservation)

FracturesFracturesLithologyLithology must be fracturemust be fracture--able able (e.g., silica(e.g., silica--rich shale) rich shale) Fractures must stay inFractures must stay in--zone (e.g., zone (e.g., need fracture barriers; stay away need fracture barriers; stay away from faults)from faults)Natural vs. induced fractures Natural vs. induced fractures (gas(gas--filled; not waterfilled; not water--, oil, oil--, or , or mineralmineral--filled fractures)filled fractures)

Example of Poor Gas ShaleExample of Poor Gas Shale

Weathered Clay-Rich Sylvan Shale (“Thud”)

Example of Good Gas ShaleExample of Good Gas Shale

Fractured, Silica-Rich Woodford Shale (“Ping”)

Gas Generation: OrganicGas Generation: Organic--Rich Rich Black Shale/SiltstoneBlack Shale/Siltstone

Organic Matter TypeOrganic Matter Type: : Type II (oil generative) Type II (oil generative) KerogenKerogenOrganic Matter QuantityOrganic Matter Quantity: minimum : minimum of 2% TOC (depends on thermal of 2% TOC (depends on thermal maturity)maturity)Thermal MaturityThermal Maturity (highest gas rates (highest gas rates in gas window, >1.4% in gas window, >1.4% VRoVRo))

0.0

0.5

1.0

1.5

2.0

2.5

3.0

150 200 250 300 350Hydrous Pyrolysis Temperature for 72 Hours ( C)

Mahogany (Type-I)

New Albany (Type-II)

Ghareb-Israel (Type-IISi)

Ghareb-Jordan (Type-IISj)

Wilcox Lignite (Type-III)

o

Thermogenic Gas fromSource Rocks

Figure 2: Volume of hydrocarbon gas (C1-C5) generated by hydrous pyrolysisfrom thermally immature source rocks bearing different kerogen types (Lewanand Henry, 2001). From Lewan, 2002

Gas Generation by Kerogen TypeAt 350°C for 72 h, Type-I and -II kerogensgenerate 1.8 times as much thermogenic gas as Type-III kerogen

VRo Values Maturity

<0.55% Immature

0.55-1.15% Oil Window (peak

oil at 0.90%VRo)

1.15-1.40% Condensate–Wet-

Gas Window

>1.40% Dry-Gas WindowFrom Jarvie and others, 2005

Guidelines for the Barnett Shale (Based on Rock-Eval Pyrolysis)

From Lewan, 2002

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 0.5 1.0 1 .5 2.0 2.5 3.0 3.5 4.0V itrin ite R eflectance (% R o)

O il-C racking G asT su zu ki e t a l ., 1 9 9 9 )

Sou rce -Rock G as(K n a u ss e t a l . 1 9 9 7 )

O ilG ene ra tion

(Hu n t e t a l ., 1 9 9 1 )

Heating Rate = 5o C/ m.y.Surface Temp. = 15o C

S.R. Age = 80 Mao

F igu re 1 : G ene ra tion o f o il and gas from an 80 -Ma sou rce rock with T ype -IIke rogen and associa ted crude o il. Cu rves a re based on k ine tic pa rame te rsde te rmined by hyd rous and hyd ro the rma l pyro lys is and EASY% R o (Swweeney andBurnham, 1990 ).

0.6-1.1% Ro

0.5-2.2% Ro 1.6-3.3% Ro

Type II Kerogen Gas Generation (Hydrous Pyrolysis)

75% gas by 1.1% Ro

93% gas by 1.5% Ro

Woodford Shale Woodford Shale StratigraphyStratigraphyBased on conodonts, Hass and Huddle (1965) determined a Late Devonian (Frasnian) age for most of the formation; uppermost part is Early Mississippian (Kinderhookian)

unconformity

From Conant and Swanson, 1961

Paleogeography and Facies Distribution in the Late Devonian

From Kirkland and others, 1992

Geologic Provinces of Oklahoma

Isopach Map of Woodford Shale

From Comer, 1992

From Comer, 1992

Woodford Shale

Oklahoma Shale-Gas Wells143 Wells, 1939–2006

0

20

40

60

80

100

120

1930 1940 1950 1960 1970 1980 1990 2000 2010

Year

Num

ber o

f Wel

ls

CaneyWoodford

275 Wells, 1939–2007

Application of Advanced Completion Technology

1939-2007Woodford Gas Shales

15,310 ft (IP 234 Mcf; 7BO 42° API; GOR 33,429)

553 ft (IP 122 Mcf)

2003–2007Woodford Gas Shales

185 Wells

4 Caney/Woodford

3 Sycamore/Woodford

95 Horizontal Woodford

Why is the Woodford Shale Gas Play where it is?

Generalized Structure Map of Woodford

Shale, Eastern Oklahoma

Map prepared by R. Vance Hall using Petra

Woodford Shale is the oldest rock in Oklahoma that contained wood (vitrinite) from the progymnospermArchaeopteris(organ genus Callixylon)

Vitrinite Reflectance of Woodford Shale, Eastern Oklahoma

Cardott, in preparation

VRo mean based on minimum of 20 measurements from whole-rock pellets

Map prepared by R. Vance Hall using Petra

MISSISSIPPIAN

& OLDER

OUTCROP

AREA

CHOCTAW FAULT

11

1

1

433

2

22

1

1

1.310.56

0.790.59

0.782.19

0.64

0.64

2

1.73

2.09

1.371.79

1.981.870.57

1.23

1.050.86

0.741

0.72

3.32

2.69

0.52

2.94

0.58

0.5

0.550.57

0.58

0.830.77

1.14

1.230.79

2.53

0.570.56

0.6

1.69

0.82

3.462.4

2.442.48

3.41 3.43.6

3.363.44

4.85

6.36

4.76

.59 0.56

0.54

0.49

0.57

0.5

0.5

0.5

0.56

2.81 3.47

2.252.26

1.88

0.52

0.64

0.62

0.63

1.88

1.892.52

2.51

0.49

0.51

1.15

1.66

1.622.85

0.94

1.61

2.01

1.58

2.31

1.03

Isoreflectance Map of the Woodford Shale in Eastern Oklahoma

Cardott, in preparation

Map prepared by R. Vance Hall using Petra

Woodford Gas-Shale Play isprimarily in eastern Oklahoma(western Arkoma Basin)where the shale is:

(1) in the gas window (pushing the lower limits to the west)

(2) greater than 100 ft thick

(3) relatively shallow (<12,000 ft)

Structure and Vitrinite Reflectance of Woodford Shale, Southern Oklahoma

Cardott, in preparation

0.610.66

0.58

0.63

0.550.60

0.55

0.580.69

0.490.52

2.192.22

2.13

2.45

0.820.56

0.55

0.55

0.53

0.58

0.560.63

0.52

0.49

0.770.70

0.640.50 0.50

0.49

0.58

0.560.54

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Vitrinite Reflectance (%Ro)D

epth

(fee

t)Southern Oklahoma VRo vs Depth

<1MMcf/mo

oiloil

steep decline

Madill

Aylesworth

1939-1996Woodford Gas Shales

21 Wells

1 Sycamore/Woodford

1992 1994 1996 1998 2000 2002 2004 2006 2008 201010

100

1,000

10,000

100,000

GRIFFIN-OLMSTEAD - MADILL

Time

Prod

uctio

n R

ates

Gas Production (mcf)

Oil Production (bbl)Gas Production (mcf)Water Production (bbl)

Cimarex Energy 3 Griffin-Olmstead (Marshall CO, 16-5S-5E; IP 747 Mcfd; 4,052-4,135 ft)

Madill Field

Cumulative Gas Production 1,776,752 Mcf

Ave

rage

Mon

thly

Pr

oduc

tion

(Mcf

)

Completed as OIL well in McLish 6,536-6,544 ft on 11/4/55; OIL-WO well in McLish and Bromide 5,664-5,696 ft on 5/18/56; GAS-WO to Woodford on 3/21/92

(Gas production data supplied by Petroleum Information/Dwights LLC dba IHS Energy Group, © 2007, IHS Energy Group)

100

1,000

10,000

100,000

1,000,000

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

2006

Date

Ave

rage

Ann

ual

Pro

duct

ion

(Mcf

)

Verdad Oil & Gas 1 Mary Haynie(Bryan CO, 22-6S-7E; IP 962 Mcfd; 3,710-4,054 ft)

346 MMcf

75 MMcf

AylesworthField

Cumulative Production 2,298,658 Mcf

Completed as GAS well in Misener4,192-4,227 ft on 6/27/58; GAS-WO(plugback) in Woodford on 11/22/74

(Gas production data supplied by Petroleum Information/Dwights LLC dba IHS Energy Group, © 2007, IHS Energy Group)

10

100

1,000

10,000

100,000

1,000,000

10,000,000

Jan-

04

Apr

-04

Jul-0

4

Oct

-04

Jan-

05

Apr

-05

Jul-0

5

Oct

-05

Jan-

06

Apr

-06

Jul-0

6

Oct

-06

Jan-

07

Apr

-07

Jul-0

7

Oct

-07

Date

Ave

rage

Mon

thly

Pro

duct

ion

(Mcf

)

GasOil

Woodford Shale Production (2003-2007 wells)

Cumulative Production 19,333,211 Mcf gas, 21,187 BBLS oil/condensatefrom 134 wells (excludes 10 OWWO)

(Gas production data supplied by PI/Dwights LLC, © 2007, IHS Energy Group)

Woodford Shale Oil/Condensate Production (25 of 152 wells; 2003-2007)

@1.0% Ro

@0.6% Ro40° API oilGOR 22,776

@1.3% Ro

@1.3% Ro55° API condensateGOR 87,555

@0.6% RoGOR 41,210

Oil: 10-48° API Condensate: >49° API Gas well: GOR >15,000 Oil well: GOR <10,000

Gas Storage and ProductionProduction decline

curves suggest initial gas production is as free gas in fractures

Gas Production ultimately depends on fracture connectivity with gas storage sites (free and sorbed gas)

Devon Energy 1-26 Edwards horizontal Woodford well (2005)

100

1,000

10,000

100,000

Jan-

05

Mar

-05

May

-05

Jul-0

5

Sep-

05

Nov

-05

Jan-

06

Mar

-06

May

-06

Jul-0

6

Sep-

06

Nov

-06

Jan-

07

Mar

-07

May

-07

Date

Ave

rage

Mon

thly

Pro

duct

ion

(Mcf

)

59,764 Mcf

Taylor and others (1998)

KEROGEN NETWORK (SOLID BITUMEN; IMPSONITE)

Solid bitumen network may be important for gas storage and migration by diffusion

ORGANIC NETWORK IN WOODFORD (AOM; SOLID HYDROCARBON)

0.94% VRo

Solid hydrocarbon network visible by 0.9% VRo

ORGANIC NETWORK IN WOODFORD (AOM; SOLID HYDROCARBON)

7.28% VRo

Solid hydrocarbon network noticeable at high thermal maturity

1

10

100

1,000

10,000

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000

Depth (feet)

Initi

al P

oten

tial (

Mcf

d)

WoodfordWoodford Horizontal

All 175 wells: depth 570-15,310 ft; IP: 3-8,930 Mcfd

93 horizontal wells: depth 5,450-11,867 TVD; IP 125-8,930 Mcfd

Woodford Shale Gas Wells, 2003-2007

SUMMARY OF WOODFORD GAS SHALE PLAYWoodford Shale contains Type II Kerogen with adequate

TOC

Woodford Shale is silica rich (e.g., fracture-able)

Most Woodford Shale gas play is in eastern Oklahoma at >1.1% Ro

Some Woodford Shale gas potential is in southern Oklahoma at <1.1% Ro

Organic network may be important for gas diffusion in shales

THANK YOU

Typical Calf Creek point of Woodford chert found in Haskell County, Oklahoma (Norman Transcript, March 11, 2007, p. E1)