pore structure and gas recovery in barnett shale · pore structure and gas recovery in barnett...

Pore Structure and Gas Recovery in

Barnett Shale

1

(Max) Qinhong Hua, Sheng Peng

a, Zheyi Gao

a, and

Robert P. Ewingb

a Department of Earth and Environmental

Sciences, University of Texas at Arlington,

Arlington, TX 76019

b Department of Agronomy, Iowa State

University, Ames, IA 50011

(maxhu@uta.edu)

2 http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publications/maps/maps.htm

2000

2008

2004

2006

3 Low gas recovery factor 15-30% for Barnett Shale (King, 2012)

4

Vertical wells

Horizontal wells

Harper and Kostelnik (2010)

5

CH4 size: 0.375 nm

6

http://www.transcanada.com/customerexpress/docs/presentations_general/2009

_North_American_Shale_Gas_Overview_NECA.pdf

nanopore

0.375 nm

7 http://www.transcanada.com/customerexpress/docs/presentations_general/

2009_North_American_Shale_Gas_Overview_NECA.pdf

8

LaFollette, R. 2010. Key Considerations for Hydraulic Fracturing

of Gas Shales. Manager, Shale Gas Technology, BJ Services

Company, September 9, 2010. www.pttc.org/aapg/lafollette.pdf

~1 m/yr movement (advection vs. diffusion ?)

Multiple Approaches to Studying Pore Structure

• Imbibition with samples of different shapes

• Edge-accessible porosity

• Liquid and gas diffusion

• Mercury injection porosimetry

• N2 adsorption/desorption isotherms

• Vapor absorption

• Nuclear Magnetic Resonance Cryoporometry

• SEM imaging after Wood’s metal impregnation

• Focused Ion Beam/SEM imaging

• Pore-scale network modeling

9

Oral at Session

T98: 4:55 pm

(Mon.), Rm.

213BC

Imbibition: Low Pore-Connectivity of Shale Samples

-3.0

-2.0

-1.0

0.0

-1.5 -0.5 0.5 1.5 2.5 3.5

Cu

mu

lati

ve i

mb

ibit

ion

(m

m)

in l

og s

cale

Time (min) in log scale

30 sec 2 hr 20 hr 5 min

Barnett Shale

2,166.8 m (7,109 ft)

Rectangular prism (1.33 cm long × 1.76 cm

wide × 1.43 cm tall)

10

3D Elemental Mapping: Edge-Accessible Porosity

ReO4

- (non-sorbing)

Co2+

(sorbing) Rb (intrinsic) 11

2 µm

12 µm

54 µm

224 µm

12

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

0 2 4 6 8 10

Rel

ati

ve

con

cen

tra

tio

n (

C/C

0)

Diffusion distance (mm)

Re exterior data

Re interior line 1

Re interior line 2

Re background (avg +- stnd dev)

fitted De: 1.46E-11 m2/s

Fitted De: 1.46E-13 m2/s

Barnett shale: 7,136 ft (2,175 m)

saturated diffusion time: 24 hr

Fitted tortuosity: 100 (exterior) and 10,000 (interior)

tD

xerfc

C

C

e22

1

0

eD

D0Saturated Diffusion

13 CH

4 sorption isotherm (ongoing at BEG)

14

CH4 sorption onto shale: moisture, particle size effect

Carrizo location – UT Arlington

Barnett drilling location at 2008

University of Texas at Arlington

http://www.star-telegram.com/2010/09/30/2510136/ut-

arlington-pad-site-exemplifies.html

Barnett drilling location

University of Texas at Arlington

From XTO annual report

16

1 mile (1,609 m; 5,280 ft)

24 horizontal wells from a well pad

17

100

1,000

11/1/2008 7/26/2009 4/20/2010 1/12/2011 10/7/2011 7/1/2012

Av

era

ge

da

ily

pro

du

ctio

n (

mcf

)

Production date

1H 2H 3H 4H 5H

6H 7H 8H 9H 10H

11H 12H 13H 14H 16H

18H 19H 20H 21H 22H

23H 24H

Barnett Shale

UTA wells

Carrizo Oil and Gas, Inc

All 22 Producing UTA Horizontal Wells

18

Decline Slope for 11 Wells (50% of All)

100

1,000

10 100 1000

Av

era

ge

da

ily

pro

du

ctio

n (

mcf

)

Production days

5H 6H 7H 8H

9H 14H 16H 19H

20H 21H 24h

Barnett Shale

UTA wells

Carrizo Oil and Gas, Inc

slope of -0.5

0.5 yr 3 yrs

19

Gas Production Rate in a Fractured Shale System

cf: gas desorption rate [m

3/(kg Pa)]

Dmitriy Silin (RPSEA presentation in 2011)

Silin and Kneafsey (2011; SPE 149489)

Summary

• Steep 1st year decline and low gas recovery

observed in shales

• Pore structure information is essential in

understanding hydrocarbon storage and transport

• Nano-pore shales show low pore connectivity,

which reduces gas diffusion from matrix to

stimulated fractured network

• Gas sorption, affected by moisture and sample

size, further contribute to steep decline and low

recovery

• How to link pore structure and gas sorption

mechanism to field-scale gas recovery ? 20