Micromechanical characteristics and controlling mechanism of deep shale: a case study of well JYA in Pingqiao block, Fuling area

KONG Lingyun; SONG Guangpeng; JIANG Shu; WANG Zihang; LI Jiqing; SHI Xian

doi:10.11781/sysydz202404683

Volume 46 Issue 4

Jul. 2024

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Article Navigation > PETROLEUM GEOLOGY & EXPERIMENT > 2024 > 46(4): 683-697

KONG Lingyun, SONG Guangpeng, JIANG Shu, WANG Zihang, LI Jiqing, SHI Xian. Micromechanical characteristics and controlling mechanism of deep shale: a case study of well JYA in Pingqiao block, Fuling area[J]. PETROLEUM GEOLOGY & EXPERIMENT, 2024, 46(4): 683-697. doi: 10.11781/sysydz202404683

Citation:

KONG Lingyun, SONG Guangpeng, JIANG Shu, WANG Zihang, LI Jiqing, SHI Xian. Micromechanical characteristics and controlling mechanism of deep shale: a case study of well JYA in Pingqiao block, Fuling area[J]. PETROLEUM GEOLOGY & EXPERIMENT, 2024, 46(4): 683-697. doi: 10.11781/sysydz202404683

Citation:

KONG Lingyun, SONG Guangpeng, JIANG Shu, WANG Zihang, LI Jiqing, SHI Xian. Micromechanical characteristics and controlling mechanism of deep shale: a case study of well JYA in Pingqiao block, Fuling area[J]. PETROLEUM GEOLOGY & EXPERIMENT, 2024, 46(4): 683-697. doi: 10.11781/sysydz202404683

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Micromechanical characteristics and controlling mechanism of deep shale: a case study of well JYA in Pingqiao block, Fuling area

doi: 10.11781/sysydz202404683

KONG Lingyun^{1, 2
,},
SONG Guangpeng^{1, 2},
JIANG Shu^{1, 2
,
,},
WANG Zihang^{1, 2},
LI Jiqing³,
SHI Xian⁴

1.
Hubei Provincial Key Laboratory of Oil and Gas Exploration and Development Theory and Technology, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China
2.
Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China
3.
Exploration and Development Research Institute, Jianghan Oilfield Company, SINOPEC, Wuhan, Hubei 430223, China
4.
College of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, China

Received Date: 2023-12-04
Rev Recd Date: 2024-06-06
Publish Date: 2024-07-28

Abstract

Abstract

The deep shale gas in the Fuling area is characterized by complex structures, high crustal stress, significant stress differences, high formation temperatures, high compaction levels, low porosity, low permeability, and complex porosity-permeability variation patterns. One reason for the significant production differences between wells is the insufficient understanding of the geomechanical features and controlling mechanisms of deep shale gas reservoirs, and the inaccurate identification of sweet spots for hydraulic fracturing. This study focuses on the marine shale of the Wufeng-Longmaxi formations in the Fuling area, investigating the micromechanical characteristics and controlling mechanisms of deep shale gas reservoirs through five series of experiments: micro rock mechanics experiments, digital speckle experiments, X-ray diffraction, total organic carbon content measurement, and scanning electron microscopy (SEM). Coupled with digital image processing technology, the changes in stress field and displacement field, and microcrack propagation processes in the Longmaxi shale under loading conditions were meticulously depicted. The deformation and fracture characteristics of the Longmaxi shale were analyzed. Experimental results indicated that the total organic carbon content in the deep shale is approximately 4.2%, with quartz content at 55.4% and clay mineral at 26.9%. The study identified five stages of microdamage evolution in deep shale: compaction, elasticity, uniform crack propagation, crack propagation failure, and brittle failure. Under the influence of brittle minerals such as quartz, and soft components such as organic matter, the microcracks in deep shale exhibit various propagation modes, including transgranular, intergranular, and laminated layer cracks. Additionally, the fracture toughness indices of the deep shale samples were calculated, with Mode Ⅰ index being 8.279 $\mathrm{MPa} \cdot \sqrt{\mathrm{m}}$ and Mode Ⅱ index being 1.243 $\mathrm{MPa} \cdot \sqrt{\mathrm{m}}$. These experimentally obtained fracture toughness indices can be applied to evaluate the brittleness of deep shale, providing guidance for deep shale fracturing modification.
- micromechanical characteristics,
- brittleness characteristics,
- fracturing,
- deep shale,
- Fuling area

All authors disclose no relevant conflict of interests.
The study was designed by JIANG Shu and KONG Lingyun.The experimental operation was completed by SONG Guangpeng and WANG Zihang. LI Jiqing and SHI Xian participated in sample selection. JIANG Shu, KONG Lingyun, SONG Guangpeng, LI Jiqing and SHI Xian participated in the writing and revision of the paper. All authors have read the last version of the paper and consented to its submission.

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References(31)

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Micromechanical characteristics and controlling mechanism of deep shale: a case study of well JYA in Pingqiao block, Fuling area

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