Natural Fractures and Their Contribution to Natural Gas Migration and Accumulation in Marine Carbonate Reservoirs: Lower Triassic Feixianguan Formation, Northeast Sichuan Basin, China

Cong Guan, Lianbo Zeng (), Yingtao Yao, Hang Zhang, Jiewei Zhang and Dong Liang
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Cong Guan: National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China
Lianbo Zeng: National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China
Yingtao Yao: National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China
Hang Zhang: Northeastern Sichuan Oil and Gas District, PetroChina Southwest Oil and Gas Field Company, Dazhou 635000, China
Jiewei Zhang: Northeastern Sichuan Oil and Gas District, PetroChina Southwest Oil and Gas Field Company, Dazhou 635000, China
Dong Liang: National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China

Sustainability, 2023, vol. 15, issue 23, 1-17

Abstract: The Lower Triassic carbonate succession of the Feixianguan Formation represents a primary focus for gas exploration in the northwestern Sichuan Basin. This study area includes the massive Puguang gas field and other nearby gas fields of considerable size. These carbonate reservoirs display significant heterogeneity, which is primarily influenced by the presence of natural fractures. Extensive documentation of fracture types, characteristics, effectiveness, and their role in enhancing reservoir properties was conducted by examining and analyzing various data sources, including cores, thin sections, image logs, and experimental measurements. Shear fractures primarily characterize the Feixianguan Formation carbonate reservoir, although tensile and diagenetic fractures are also present, albeit in fewer numbers. Tectonic fractures are the dominant type, particularly unfilled ones with dip angles greater than 60° in the NEE–SWW direction. These fractures are mainly filled with calcite. The tectonic fractures were formed in three stages: Late Indosinian-Early Yanshanian, Late Yanshanian-Early Himalayan, and Late Himalayan. These fractures intersect with the in situ stress direction at a small angle in the NE–SW, NEE–SWW, and near E–W directions, contributing to their effectiveness. Compared with the total fracture density, the effective fracture density is the factor in controlling gas production. An increase in the proportion of effective fractures tends to result in a rise in gas productivity. Additionally, the orientation of effective fractures also influences natural gas production. Fractures striking in the E–W and NE–SW directions, which are particularly effective, are associated with high natural gas production.

Keywords: tectonic fractures; fracture characteristics; effectiveness; carbonate reservoir; Sichuan Basin (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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