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