Petroleum Exploration and Development >

2021 , Vol. 48 >Issue 5: 916 - 927

DOI: https://doi.org/10.11698/PED.2021.05.04

PETROLEUM EXPLORATION

Microscopic pore-fracture configuration and gas-filled mechanism of shale reservoirs in the western Chongqing area, Sichuan Basin, China

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  • 1. School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China;
    2. Reservoir Evaluation Laboratory of Unconventional Key Laboratory of CNPC, Chengdu 610500, China;
    3. Sichuan Collaborative Innovation Center for Shale Gas Resources and Environment, Chengdu 610500, China;
    4. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083, China;
    5. Department of Earth and Environmental Sciences, University of Texas at Arlington, Arlington, TX 76019, USA;
    6. Chongqing Shale Gas Exploration and Development Company Limited, Chongqing 401120, China;
    7. Development Division of PetroChina Southwest Oil and Gas Field Company, Chengdu 610051, China

Received date: 2021-02-06

  Online published: 2021-09-17

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Abstract

Taking the Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation shale reservoirs in western Chongqing area as the study target, the argon ion polishing scanning electron microscope and nuclear magnetic resonance (NMR) experiments of different saturated wetting media were carried out. Based on the image processing technology and the results of gas desorption, the pore-fracture configuration of the shale reservoirs and its influence on gas-filled mechanism were analyzed. (1) The reservoir space includes organic pores, inorganic pores and micro-fractures and there are obvious differences between wells in the development characteristics of micro-fractures; the organic pores adjacent to the micro-fractures are poorly developed, while the inorganic pores are well preserved. (2) According to the type, development degree and contact relationship of organic pore and micro-fracture, the pore-fracture configuration of the shale reservoir is divided into four types. (3) Based on the differences in NMR T2 spectra of shale samples saturated with oil and water, an evaluation parameter of pore-fracture configuration was constructed and calculated. The smaller the parameter, the better the pore-fracture configuration is. (4) The shale reservoir with good pore-fracture configuration has well-developed organic pores, high porosity, high permeability and high gas content, while the shale reservoir with poor pore-fracture configuration has micro-fractures developed, which improves the natural gas conductivity and leads to low porosity and gas content of the reservoir. (5) Based on pore-fracture configuration, from the perspective of organic matter generating hydrocarbon, micro-fracture providing migration channel, three types of micro gas-filled models of shale gas were established.

Key words： shale reservoir; microscopic pore-fracture configuration; quality parameter; gas bearing characteristics; shale gas; Upper Ordovician Wufeng Formation; Lower Silurian Longmaxi Formation; Sichuan Basin

Cite this article

FU Yonghong, JIANG Yuqiang, DONG Dazhong, HU Qinhong, LEI Zhi’an, PENG Hao, GU Yifan, MA Shaoguang, WANG Zimeng, YIN Xingping, WANG Zhanlei . Microscopic pore-fracture configuration and gas-filled mechanism of shale reservoirs in the western Chongqing area, Sichuan Basin, China[J]. Petroleum Exploration and Development, 2021 , 48(5) : 916 -927 . DOI: 10.11698/PED.2021.05.04

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