1

Sweet Spots

in

Shale Gas and Liquids Plays

Harris Cander

BP America

2

Eagle Ford Fluid Fairways

Map published

by EOG

Sweet spot for liquids

Oil > $80 bbl

Gas < $3 mcf

3

Eagle Ford liquids sweet spot Gas-Oil Ratio at High Pressure

Reservoir Pressure

4

“Unconventional” but still obey principles

Q = k * H *DP

m

Q = well flow rate

k = permeability

H = thickness

DP = Reservoir Pressure – wellbore pressure

m = viscosity

• Viscosity is related to Gas-Oil Ratio…

• Gas-Oil Ratio is related to maturity…

• Pressure is related to maturity and burial and uplift history

• P and m change a lot in a typical shale fairway!

Darcy’s Law

5

0.6 0.8 1 1.2 1.4 1.6 1.8

TSI: Vitrinite-ARCO (%Ro)

0.01

0.1

1

10

100

1000

10000

100000

Ins

tan

tan

eo

us

GL

R E

xp

ell

ed

(s

cf/

stb

)

Instantaneous GLR Expelled (scf/stb)

Instantaneous Expelled Fluid Viscosity (cP)

Shale Maturity vs.

Gas-Oil Ratio & Viscosity

Ro Vitrinite Reflectance

6

Liquids Rate (BOPD) vs. Gas-Oil Ratio

100

1,000

10,000

100,000

0 500 1000 1500 2000

Gas-Oil

Ratio scf/bbl

Liquids Rate BOPD (IP30)

Liquid

Vapor

7

Eagle Ford liquids sweet spot Can we predict composition and pressure?

Reservoir Pressure

8

Previous kinetic model Reach “sorption” threshold of kerogen and then “expel petroleum”

Problem:

Source rocks retain more petroleum than previously thought

Expel less than previously thought

9

Updated BP model • Storage in organic and mineral matrix porosity

• Different % Petroleum Saturations

– Organic and Mineral matrix porosity

• Calculate Gas-Oil Ratio of Retained and Cumulative Expelled petroleum

Source

interval

10

Retained vs. Migrated Gas Oil Ratio BP Eagle Ford Shale model

Gas - Oil

Ratio

scf/bbl

vapor

liquid

11

Gas Oil Ratio predicted from Thermal Stress

Ro Vitrinite

GOR scf/bbl

12

PVT GOR vs. Predicted GOR scf/bbl Good prediction of composition and phase

Actual: 14,680

Model: 13,200

Actual: 6,509

Model: 4,500

Actual: 1,916

Model: 2,800

PVT data courtesy of Corelab

Predicted Gas-Oil Ratio

13

Convert GOR into Viscosity (mobility)

Q = k * H *DP

m

High pressure helps mobility of more viscous liquid phase fluids

Viscosity cp

14

Over-pressure in source rocks

• Petroleum generation?

• Rapid burial?

–Compaction disequilibrium

• How is over-pressure

preserved?

15

• Hydrocarbon generation

• Bitumen network

• Increase in pore pressure

• Expulsion to other beds

Petroleum generation & over-pressure Research from BP Amoco

Immature – dispersed organic matter

Mature – bitumen network develops

Pyrolysis of Woodford Shale

Lewan, 1985

16

Eagle Ford Shale South Texas

A

A’

Eagle Ford Structure (m)

020406080100120140160180

Age

0

5000

10000

15000

20000

De

pth

in

fe

et

PMioceneOlig.EocenePal.L.CretaceousE.CretaceousJurassic

1 – 2 km of uplift in west;

Less in east part of fairway

Eagle Ford

Texas

TIME

DE

PT

H

17

NW-SE Dip section

Eagle Ford

Dimmit Webb Maverick

18

Over-pressure (mudweight) during Eocene

With petroleum generation & expulsion Eagle Ford

expulsion

Without petroleum generation & expulsion

…Still have overpressure

19

Over-pressure and Gas Generation Over-pressure is not linked to gas window

Post-Laramide uplift in west caused loss

of over-pressure and decoupling of GOR

and pressure contours

Over-pressure in the Eagle Ford psi above hydrostatic

85 Ma

20

Burial and maturation create over-pressure;

Uplift can destroy it

Time

Depth

0 Ma 100’s Ma

21

Sweet Spot Changes due to Price Changes

GOR

scf/bbl

“Sweet Spot” at

high Oil prices

“Sweet Spot” at

high Gas prices

22

$weet $pots = Mobility

• Fluid viscosity and reservoir pressure

• Petroleum composition and viscosity can be predicted

– New BP model

– Viscosity and GOR are directly linked to maturity…

• Over-pressure

– Petroleum generation and compaction disequilibrium

– Preserved if uplift is limited

– Must understand burial and uplift history!

• Sweet spots can shift as oil and gas prices change

Q = k * H *DP

m

23

Thanks!

Harris Cander BP

24

25

Exhumation and Over-pressure

Fairway Exhumation Over-pressure

Arkoma Woodford > 10,000 ft Mild to none

Fayetteville > 10,000 ft Mild to none

Anadarko Woodford < 6,000 ft High

Haynesville < 7,000 ft High

Eagle Ford < 6,000 ft High

26

Instantaneous vs. Cumulative GOR increases during generation

120 C

150 C

180 C

Cumulative

Trap

Trap

Instantaneous

27

Exhumation: loss of pressure

Arkoma

High exhumation

Over-pressure lost

Anadarko

Minor exhumation

Over-pressure preserved

Isopach of eroded section

28

Drop in Effective Stress in Eagle Ford Preservation of pore throats

Permeability is not just a function of facies or the rock

Permeability is also a function of pore pressure

Depth

(ft)

Effective Stress (psi)

Eagle Ford

29

Difference in over-pressure With and without petroleum generation & expulsion

With petroleum

generation & expulsion

Without petroleum

generation & expulsion

Real well data

Model

Real well data

Model

Eagle Ford Eagle Ford

0.74 psi/ft 0.66 psi/ft

14 10 12 14 10 12

De

pth

Mud Weight Mud Weight

30

Maturity vs. GOR & Viscosity

100 120 140 160 180 200

Temperature (C)

0.01

0.1

1

10

100

1000

10000

100000

Insta

nta

neo

us G

LR

Exp

ell

ed

(sc

f/s

tb)

Instantaneous GLR Expelled (scf/stb)

Instantaneous Expelled Fluid Viscosity (cP)

Temperature C

31

Eagle Ford Gas Flow Rate (mcfd) Low viscosity gas is more mobile

Rate mcfd

1,000

10,000

100,000

100 1000 10000

Liquid

Vapor

GOR

scf/bbl

32

Sweet Spot depends on local prices

Reservoir Pressure

33

BP scheme also models changes in inorganic

and organic porosity

… with or without over-pressure

0.01 0.1 1

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Organic porosity

Depth

(m)

Porosity (fraction)

Inorganic

porosity