Abstract

Brittleness is an important mechanical characteristic of rock and is critical to shale reservoir, which is characterized with low porosity and low permeability. Brittleness evaluation of cap rock plays an important role in the site selection, operation, and maintenance of underground gas storage. However, it is still a difficult problem for conducting a quantitative brittleness evaluation. In this article, the brittleness of X9’s cap rock has been evaluated by the five available effective methods that are based on mineral composition, elastic parameters, stress-strain curve, analytic hierarchy process, and fuzzy analytical hierarchy process, respectively, and the results of them are general, weak, weak, general, and general, respectively. Combined with the five evaluation results, a comprehensive brittleness evaluation based on geometric regular polygon method is proposed. The results show that the brittleness of X9’s cap rock is faint. Because of the comprehensive consideration of the limitations of existing brittleness evaluation methods, the excessive idealization of conventional regular polygon method, and the irrationality of division in evaluation grades, this method is improved based on the conventional regular polygon method and has advantages of comprehensive utility, strong feasibility, reliable result, and wide application range and can be used to evaluate similar targets.

Issue Section:
Technical Papers
Keywords:
cap rock, gas storage, brittleness, comprehensive evaluation, geometric regular polygon

References

1.
Zhao
 
F.
,
Sun
 
Q.
, and
Zhang
 
W.
, “
Quantitative Analysis of the Influence of Temperature and Confining Pressure on Brittleness of Granite: A Review
,”
Acta Geodynamica et Geomaterialia
 
17
, no. 
1
(February
2020
):
39
–
50
, https://doi.org/10.13168/AGG.2020.0003
2.
Wang
 
T.
,
Zhang
 
T.
,
Ranjith
 
P. G.
,
Li
 
Y.
,
Song
 
Z.
,
Wang
 
S.
, and
Zhao
 
W.
, “
A New Approach to the Evaluation of Rock Mass Rupture and Brittleness under Triaxial Stress Condition
,”
Journal of Petroleum Science and Engineering
 
184
(January
2020
): 106482, https://doi.org/10.1016/j.petrol.2019.106482
3.
Wang
 
Q.
,
Zhang
 
B.
,
Guo
 
S.
, and
Han
 
J.
, “
Effect of Anisotropy, Angle, and Critical Tensile Stress and Confining Pressures on Evaluation of Shale Brittleness Index—Part 1: Methodology and Laboratory Study
,”
Interpretation: A Journal of Subsurface Characterization
 
7
, no. 
3
(August
2019
):
T637
–
T646
, https://doi.org/10.1190/int-2018-0143.1
Google Scholar
Crossref
Search ADS
 
4.
Morley
 
A.
,
Strength of Materials
(
London
:
Longman
,
1944
).
5.
Obert
 
L.
 and
Duvall
 
W.
,
Rock Mechanics and the Design of Structures in Rock
(
Hoboken, NJ
:
John Wiley
,
1967
).
6.
Evans
 
B.
,
Fredrich
 
J. T.
, and
Wong
 
T.-F.
, “
The Brittle-Ductile Transition in Rocks: Recent Experimental and Theoretical Progress
,” in
The Brittle-Ductile Transition in Rocks
, ed.
Duba
 
A. G.
,
Durham
 
W. B.
,
Handin
 
J. W.
, and
Wang
 
H. F.
 (
Washington, DC
:
American Geophysical Union
,
1990
),
1
–
20
, https://doi.org/10.1029/GM056p0001
Google Scholar
Crossref
Search ADS
 
7.
Fu
 
Y.
,
Ma
 
F.
,
Zeng
 
L.
,
She
 
C.
, and
Chen
 
Y.
, “
Key Techniques of Experimental Evaluation in the Fracturing Treatment for Shale Gas Reservoirs
,”
Natural Gas Industry
 
31
, no. 
4
(April
2011
):
51
–
54
, https://doi.org/10.3787/j.issn.1000-0976.2011.04.012
8.
Li
 
Q.
,
Chen
 
M.
,
Wang
 
F. P.
,
Jin
 
Y.
, and
Li
 
Z.
, “
Influences of Engineering Factors on Shale Gas Productivity: A Case Study from the Haynesville Shale Gas Reservoir in North America
,”
Natural Gas Industry
 
32
, no. 
4
(April
2012
):
54
–
59
, https://doi.org/10.3787/j.issn.1000-0976.2012.04.013
9.
Jiang
 
Y.
,
Dong
 
D.
,
Qi
 
L.
,
Shen
 
Y.
,
Jiang
 
C.
, and
He
 
F.
, “
Basic Features and Evaluation of Shale Gas Reservoirs
,”
Natural Gas Industry
 
30
, no. 
10
(October
2010
):
7
–
12
, https://doi.org/10.1016/S1876-3804(11)60008-6
10.
Qin
 
X.
,
Wang
 
Z.
,
Yu
 
H.
,
Zheng
 
H.
,
Lei
 
Y.
,
Luo
 
X.
,
Zhang
 
L.
,
Jiang
 
C.
, and
Gao
 
C.
, “
A New Shale Brittleness Evaluation Method Based on Rock Physics and Mineral Compositions
,”
Natural Gas Geoscience
 
27
, no. 
10
(October
2016
):
1924
–
1932
, https://doi.org/10.11764/j.issn.1672-1926.2016.10.1924
11.
Fu
 
X.
,
Yan
 
L.
,
Meng
 
L.
, and
Liu
 
X.
, “
Deformation Mechanism and Vertical Sealing Capacity of Fault in the Mudstone Caprock
,”
Journal of Earth Science
 
30
, no. 
2
(April
2019
):
367
–
375
, https://doi.org/10.1007/s12583-018-0998-7
Google Scholar
Crossref
Search ADS
 
12.
Jia
 
S.
,
Zhang
 
H.
,
Lin
 
J.
,
Wei
 
Q.
,
Liu
 
T.
,
Bi
 
Y.
,
Tang
 
X.
, and
Jiang
 
S.
, “
Quantitative Assessment of the Gas-Sealing Capacity of the Permian Claystone Caprock for the D5 Aquifer Gas Storage in the Litan Sag
,”
Hydrogeology & Engineering Geology
 
43
, no. 
3
(May
2016
):
79
–
86
, https://doi.org/10.16030/j.cnki.issn.1000-3665.2016.03.13
13.
Richiano
 
S.
,
Varela
 
A. N.
,
Gómez-Peral
 
L. E.
,
Cereceda
 
A.
, and
Poiré
 
D. G.
, “
Composition of the Lower Cretaceous Source Rock from the Austral Basin (Río Mayer Formation, Patagonia, Argentina): Regional Implication for Unconventional Reservoirs in the Southern Andes
,”
Marine and Petroleum Geology
 
66
, no. 
4
(September
2015
):
764
–
790
, https://doi.org/10.1016/j.marpetgeo.2015.07.018
14.
He
 
J.
,
Wang
 
H.
,
Tang
 
J.
,
Shangguan
 
Y.
,
Yang
 
X.
,
Gong
 
Y.
,
Zhao
 
R.
, and
Zhou
 
X.
, “
Evaluation of Lacustrine Mudstone Top Sealing Capacity in the Lenghu-5 Area, Qaidam Basin, Tibetan Plateau
,”
Journal of Petroleum Science and Engineering
 
188
(May
2020
): 106973, https://doi.org/10.1016/j.petrol.2020.106973
15.
Rickman
 
R.
,
Mullen
 
M. J.
,
Petre
 
J. E.
,
Grieser
 
W. V.
, and
Kundert
 
D.
, “
A Practical Use of Shale Petrophysics for Stimulation Design Optimization: All Shale Plays Are Not Clones of the Barnett Shale
,” in
SPE Annual Technical Conference and Exhibition
(
Richardson, TX
:
Society of Petroleum Engineers
,
2008
), 115258, https://doi.org/10.2118/115258-MS
Google Scholar
Crossref
Search ADS
 
16.
Liu
 
C.
,
Wang
 
Y.
,
Zhang
 
X.
, and
Du
 
L.
, “
Rock Brittleness Evaluation Method Based on the Complete Stress-Strain Curve
,”
Frattura ed Integrità Strutturale
 
13
, no. 
49
(
2019
):
557
–
567
, https://doi.org/10.3221/IGF-ESIS.49.52
Google Scholar
Crossref
Search ADS
 
17.
Ye
 
Y.
,
Tang
 
S.
, and
Xi
 
Z.
, “
Brittleness Evaluation in Shale Gas Reservoirs and Its Influence on Fracability
,”
Energies
 
13
, no. 
2
(January
2020
): 388, https://doi.org/10.3390/en13020388
18.
Kang
 
Y.
,
Shang
 
C.
,
Zhou
 
H.
,
Huang
 
Y.
,
Zhao
 
Q.
,
Deng
 
Z.
,
Wang
 
H.
, and
Ma
 
Y. Z.
, “
Mineralogical Brittleness Index as a Function of Weighting Brittle Minerals—from Laboratory Tests to Case Study
,”
Journal of Natural Gas Science and Engineering
 
77
(March
2020
): 103278, https://doi.org/10.1016/j.jngse.2020.103278
19.
Diao
 
H.
, “
Rock Mechanical Properties and Brittleness Evaluation of Shale Reservoir
,”
Acta Petrologica Sinica
 
29
, no. 
9
(September
2013
):
3300
–
3306
, https://doi.org/10.1086/671395
20.
Chen
 
Y.
 and
Huang
 
T.
,
Rock Physics
(
Beijing
:
Peking University Press
,
2011
).
21.
Lin
 
J.
,
Jia
 
S.
,
Liu
 
T.
,
Yan
 
A.
, and
Xi
 
Z.
, “
Comprehensive Evaluation of Sealing Ability of Mudstone Cap Rock for X9 Depleted Gas Reservoir in Reconstruction Underground Gas Storage
,”
Chinese Journal of Rock Mechanics and Engineering
 
34
, no. 
S2
(September
2015
):
4099
–
4107
, https://doi.org/10.13722/j.cnki.jrme.2014.1595
22.
Zhang
 
J.
,
Zhang
 
C.
,
Zhang
 
Z.
,
Zhang
 
C.
, and
Nie
 
X.
, “
Brittleness of Tight Gas Reservoirs Based on Stress-Strain Curves
,”
Lithologic Reservoirs
 
29
, no. 
3
(March
2017
):
126
–
131
, https://doi.org/10.3969/j.issn.1673-8926.2017.03.015
23.
Cheng
 
G.
,
Zhao
 
C.
,
Wei
 
T.
, and
Wang
 
J.
, “
Evaluation Method of Brittle Characteristics of Rock Based on Full Stress-Strain Curve and Crack Initiation Stress
,”
Chinese Journal of Rock Mechanics and Engineering
 
37
, no. 
1
(November
2017
):
51
–
59
, https://doi.org/10.13722/j.cnki.jrme.2017.0499
24.
Shu
 
K.
,
Jia
 
S.
,
Gao
 
Y.
,
Geng
 
Y.
,
Ba
 
J.
,
Lei
 
M.
,
Liu
 
T.
, and
Xi
 
Z.
, “
An Improved Method to Evaluate Brittleness of Cap Rock Based on Complete Stress-Strain Curve
,”
Journal of Guangxi University (Natural Science Edition)
 
43
, no. 
1
(February
2018
):
248
–
260
, https://doi.org/10.13624/j.cnki.issn.1001-7445.2018.0248
25.
Shen
 
J.
,
Project Risk Management
(
Beijing
:
China Machine Press
,
2010
).
26.
Zhang
 
L.
,
Li
 
C.
,
Su
 
X.
, and
Liao
 
K.
, “
Determination of Pipeline Risk Factor Weight by Fuzzy Analytical Hierarchy Process
,”
China Petroleum Machinery
 
34
, no. 
6
(June
2006
):
43
–
45
, https://doi.org/10.3969/j.issn.1001-4578.2006.06.013
27.
Jia
 
Z.
,
Song
 
S.
, and
Zhao
 
X.
, “
The Fast Assessment of Mining Subsidence Damage in Yushenfu Mining Area Based on Polygon Area Method
,”
Safety in Coal Mines
 
43
, no. 
7
(July
2012
):
200
–
202
, https://doi.org/10.13347/j.cnki.mkaq.2012.07.049
28.
Chen
 
J.
,
Yue
 
Q.
,
Cao
 
A.
, and
Li
 
Y.
, “
Safety Culture Evaluation in Enterprise Based on Geometric Regular Polygon Evaluation Method
,”
Coal Engineering
 
49
, no. 
4
(April
2017
):
142
–
144
, https://doi.org/10. 11799 /ce201704041
This content is only available via PDF.
All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ASTM International.
You do not currently have access to this content.