Pressure Evolution Mechanism of Marine Shale Reservoirs and Shale Gas Accumulation Model: Evidence from Fluid Inclusions in the Wufeng–Longmaxi Formation in the Basin Margin Structural Transition Zone in Northern Guizhou Province, China

Author:

Li Xingyu12ORCID,Du Wei34,Feng Xia34,Shi Fulun34,Chen Yi34,Wang Yisong34,Jiang Zhenxue12,Luo Qun12

Affiliation:

1. Unconventional Natural Gas Institute, China University of Petroleum, Beijing 102249, China

2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China

3. Key Laboratory of Unconventional Natural Gas Evaluation and Development in Complex Tectonic Areas, Ministry of Natural Resources, Guiyang 550001, China

4. Guizhou Engineering Research Institute of Oil & Gas Exploration and Development, Department of Natural Resources of Guizhou Province, Guiyang 550001, China

Abstract

The Wufeng–Longmaxi Formation in northern Guizhou Province is the dominant shale gas exploration and development strata in China. This study investigates the Shixi and Daozhen synclines, which are located in the basin margin transition zone. This region experienced complex tectonic stages and superimposed transformations, resulting in heterogeneous preservation conditions and shale reservoir pressure evolution in different tectonic units of the Wufeng–Longmaxi Formation. Based on fluid inclusion analysis, the types of fluid inclusion and the fluid filling stages of the Wufeng–Longmaxi shale reservoir were determined by laser Raman analysis and homogenization temperature and salinity tests. It was found that the fluid inclusion density and paleopressure in each filling stage were then restored. The results confirm that: ① Both the Shixi syncline and Daozhen syncline Wufeng–Longmaxi shale reservoirs experienced two fluid filling phases, in the early Yanshanian and late Yanshanian–Himalayan, respectively. In the course of tectonic evolution, the Wufeng–Longmaxi Formation in the Shixi and Daozhen synclines experienced pressure relief to some extent during the two aforementioned key fluid charging periods but remained in overpressurized states overall; ② The Wufeng–Longmaxi Formations of the Shixi and Daozhen synclines are characterized by high-density methane inclusions; ③ Based on the differences in the structural preservation conditions, the pressure evolution mechanisms of the Wufeng–Longmaxi Formation Shales during the important tectonic evolution period in northern Guizhou Province were revealed. Furthermore, differential enrichment and accumulation models of shale gas were established and named “facing thrust structural sealing type (Shixi syncline)” and “reverse fault lateral blocking type (Daozhen syncline)”.

Funder

National Natural Science Foundation of China

Science Foundation for top-notch innovative talents of China University of Petroleum, Beijing

Guizhou Geological Exploration Foundation

Publisher

MDPI AG

Subject

Geology,Geotechnical Engineering and Engineering Geology

Reference71 articles.

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