Characteristics, Controlling Factors and Reservoir Quality Implications of Inner Fracture Zones in Buried Hills of Archean Covered Metamorphic Rock in Block 13-2, Bozhong Depression

Junjie Lu, Xuanlong Shan (), Jian Yi, Huiyong Li, Peng Xu, Guoli Hao, Ang Li, Shuai Yin (), Shuyue Ren, Chaoyang Liu and Yunqian Shi
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Junjie Lu: College of Earth Science, Jilin University, Changchun 130061, China
Xuanlong Shan: College of Earth Science, Jilin University, Changchun 130061, China
Jian Yi: College of Earth Science, Jilin University, Changchun 130061, China
Huiyong Li: Tianjin Branch of China National Offshore Oil Company Ltd., Tianjin 300459, China
Peng Xu: Tianjin Branch of China National Offshore Oil Company Ltd., Tianjin 300459, China
Guoli Hao: College of Earth Science, Jilin University, Changchun 130061, China
Ang Li: College of Earth Science, Jilin University, Changchun 130061, China
Shuai Yin: School of Earth Science and Engineering, Xi’an Shiyou University, Xi’an 710065, China
Shuyue Ren: College of Earth Science, Jilin University, Changchun 130061, China
Chaoyang Liu: College of Earth Science, Jilin University, Changchun 130061, China
Yunqian Shi: College of Earth Science, Jilin University, Changchun 130061, China

Energies, 2024, vol. 17, issue 6, 1-23

Abstract: Inner fracture zones play a decisive role in the formation of high-quality reservoirs in buried hill reservoirs in covered metamorphic rock. Based on core, sidewall core, thin section, seismic, logging and reservoir physical property data, the fracture development characteristics of the Bozhong 13-2 block buried hill reservoir are described in detail and the controlling factors and the influence on reservoir quality are discussed. The results showed: (1) three groups of tectonic fractures developed in the study area—near-EW-striking, ENE-striking and nearly N–S-striking fractures—were controlled by the early Indosinian thrusting, the late Indosinian to early Yanshanian sinistral strike-slipping and the late Yanshanian late dextral strike-slipping in the Bohai Bay Basin, respectively. The ENE- and nearly-E-W-striking fractures are the most common, and the dip angles of the fractures are mostly between 35° and 75° and thus oblique. (2) The Indosinian-early Yanshanian was the main fracture-forming period, and the dextral strike-slip action in the late Yanshanian was the key to maintaining effective fractures. Imaging logging shows that 97.87% of the fractures are effective fractures. Based on thin section observation, 14.47% of the fractures are unmodified open fractures and 80.37% of the fractures are effective fractures due to reactivation. (3) The late Yanshanian strike-slip fault transformed the deformation adjustment zone formed by the early Indosinian thrust faulting and the core of the fold structure was more conducive to fracture development. The fracture density of a single well located within the deformation adjustment zone and at the core of the fold is between 0.93–1.49 m −1 , the fracture density of a single well located only at the core of the fold is between 0.67–0.75 m −1 and that of a single well located at the wing of the fold is between 0.35–0.59 m −1 . Diabase dike intrusions promoted the development of local fractures. (4) Fractures promote the migration and accumulation of oil and gas, and the fracture density in the oil layer is between 0.81–2.19 m −1 . That in the nonoil layer is between 0.25–1.12 m −1 . In addition, fractures not only provide storage space but also effectively improve the reservoir capacity of the inner fracture zones of buried hill reservoirs by concentrating dissolution.

Keywords: Bohai Bay Basin; Bozhong Depression; Archaeozoic; metamorphic rock; inner curtain zone of buried hills; tectonic fractures (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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