Mechanisms by Which an Evaporated Lagoon Sedimentation System Controls Source–Reservoir Preservation in Lei 3 2 Sub-Member Unconventional Oil and Gas

Yongguang Xin (), Wenzheng Li, Hao Zhang, Han Tian, Xiaodong Fu and Zengye Xie
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Yongguang Xin: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Wenzheng Li: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Hao Zhang: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Han Tian: PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China
Xiaodong Fu: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Zengye Xie: PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China

Energies, 2024, vol. 17, issue 4, 1-18

Abstract: The muddy limestone in the Lei 3 2 sub-member of the Middle Triassic Leikoupo Formation in the well Chongtan 1 (CT1) of the Sichuan Basin has yielded promising industrial oil and gas production. This discovery has the potential to become a significant strategic reservoir in the future for oil and gas exploration in the Sichuan Basin. However, the understanding of hydrocarbon accumulation in the muddy limestone of the Lei 3 2 sub-member remains insufficient, which poses limitations on further exploration selection and deployment strategies. This study focuses on the analysis of core samples and laboratory data in the wells CT1 and Jianyang 1 (JY1), aiming to investigate the source rock and reservoir characteristics of the muddy limestone in the Lei 3 2 sub-member, as well as the primary controlling factors influencing the development of the source rock and reservoir. The results show that the Lei 3 2 sub-member in the Central Sichuan Basin is an evaporated lagoon deposition; the tight argillaceous limestone and limy mudstone exhibit the characteristic of source–reservoir integration, belonging to a new type of unconventional oil and gas reservoir. The reservoir space of the argillaceous limestone and limy mudstone in the Lei 3 2 sub-member primarily consists of inorganic and organic micro–nanopores and microfractures. The average porosity and permeability are 2.7% and 0.19 mD, indicating a low-porosity and low-permeability unconventional reservoir. The clay minerals and gypsum content are the important factors influencing reservoir porosity, and the fractures are key factors influencing permeability. This study will elucidate the specific features of hydrocarbon accumulation in the muddy limestone reservoirs of the Lei 3 2 sub-member and provide insights into its exploration potential.

Keywords: Central Sichuan Basin; Lei 3 2 sub-member; lagoon facies; argillaceous limestone and limy mudstone; unconventional oil and gas (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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