Characteristics and Genetic Mechanism of Pore Throat Structure of Shale Oil Reservoir in Saline Lake—A Case Study of Shale Oil of the Lucaogou Formation in Jimsar Sag, Junggar Basin

Xiaojun Zha, Fuqiang Lai, Xuanbo Gao, Yang Gao, Nan Jiang, Long Luo, Yingyan Li, Jia Wang, Shouchang Peng, Xun Luo and Xianfeng Tan
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Xiaojun Zha: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Fuqiang Lai: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Xuanbo Gao: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Yang Gao: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Kelamayi 834000, China
Nan Jiang: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Long Luo: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Yingyan Li: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Kelamayi 834000, China
Jia Wang: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Shouchang Peng: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Kelamayi 834000, China
Xun Luo: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Xianfeng Tan: College of Petroleum and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China

Energies, 2021, vol. 14, issue 24, 1-25

Abstract: The shale oil reservoir of the Lucaogou Formation in the Jimsar Sag has undergone tectonic movement, regional deposition and complex diagenesis processes. Therefore, various reservoir space types and complex combination patterns of pores have developed, resulting in an intricate pore throat structure. The complex pore throat structure brings great challenges to the classification and evaluation of reservoirs and the efficient development of shale oil. The methods of scanning electron microscopy, high-pressure mercury injection, low-temperature adsorption experiments and thin-slice analysis were used in this study. Mineral, petrology, pore throat structure and evolution process characteristics of the shale oil reservoir were analyzed and discussed qualitatively and quantitatively. Based on these studies, the evolution characteristics and formation mechanisms of different pore throat structures were revealed, and four progressions were made. The reservoir space of the Lucaogou Formation is mainly composed of residual intergranular pores, dissolved pores, intercrystalline pores and fractures. Four types of pore throat structures in the shale oil reservoir of the Lucaogou Formation were quantitatively characterized. Furthermore, the primary pore throat structure was controlled by a sedimentary environment. The pores and throats were reduced and blocked by compaction and cementation, which deteriorates the physical properties of the reservoirs. However, the dissolution of early carbonate, feldspar and tuffaceous minerals and a small amount of carbonate cements by organic acids are the key factors to improve the pore throat structure of the reservoirs. The genetic evolution model of pore throat structures in the shale oil reservoir of the Lucaogou Formation are divided into two types. The large-pore medium-fine throat and medium-pore medium-throat reservoirs are mainly located in the delta front-shallow lake facies and are characterized by the diagenetic assemblage types of weak compaction–weak carbonate cementation–strong dissolution, early medium compaction–medium calcite and dolomite cementation–weak dissolution. The medium-pore fine throats and fine-pore fine throats are mainly developed in shallow lakes and semi-deep lakes. They are characterized by the diagenetic assemblage type of strong compaction–strong calcite cementation–weak dissolution diagenesis. This study provides a comprehensive understanding of the pore throat structure and the genetic mechanism of a complex shale oil reservoir and benefits the exploration and development of shale oil.

Keywords: Jimsar Sag; Lucaogou Formation; shale oil reservoir; pore throat structure; genetic mechanism (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: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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