Tight Carbonate Microstructure and its Controls: A Case Study of Lower Jurassic Da'anzhai Member, Central Sichuan Basin
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This research was supported by the China National Science and Technology Major Project (2016ZX05046-003, 2017ZX05001001-002), Petro-China Innovation Foundation (2018D-5007-0105), Scientific Research Starting Project of SWPU (2017QHZ005). We thank experts for constructive suggestions, we also thank Yang Xuefei of Southwest Petroleum University for her guidance and help in the process of paper’s writing, and Master Sun Yangsha, Gao Qiao, Jiang Huachuan and Xie Shengyang of Southwest Petroleum University for data analysis and part of the drawing.

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    Abstract:

    Cast thin section observation, scanning electron microscopy (SEM), high-pressure mercury injection (HPMI), and nuclear magnetic resonance (NMR) were used to examine the microstructure of tight carbonate reservoirs in the Lower Jurassic Da'anzhai Member, the central Sichuan Basin. The pore space in the Da'anzhai Member is classified into 2 types and 17 subtypes, with nano-scale pore throats of ‘O’, ‘S’, ‘Z’, and ‘I’ shapes. Poorly sorted pore throats vary greatly in diameter; thus, it is difficult for fluid flow to pass through these pore throats. There are three classes of pore throats in carbonate reservoirs, i.e. isolated pores, pores coexisting with fractures, and large pores and fractures. Isolated pores may provide some pore space, but the permeability is low. Pores and fractures coexisting in the reservoir may have a great impact on porosity and permeability; they are the major pore space in the reservoir. Large pores and fractures have a great impact on reservoir properties, but they only account for a limited proportion of total pore space. The microstructure of Da'anzhai reservoirs, which dominates fluid mobility, is dependent on sedimentary environment, diagenesis, and tectonic process. Pore structure is related to sedimentary environment. The occurrence of microfractures, which may improve reservoir properties, is dependent on tectonic process. Diageneses are of utmost importance to pore evolution, cementation and growth of minerals have played an important role in destroying reservoir microstructure.

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LI Bo, WANG Xingzhi, LIU Hongqi, WANG Yongjun, TIAN Jie, HUO Fei, GAO Zhaolong.2020. Tight Carbonate Microstructure and its Controls: A Case Study of Lower Jurassic Da'anzhai Member, Central Sichuan Basin[J]. Acta Geologica Sinica(),94(2):305-321

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History
  • Received:October 31,2018
  • Revised:April 17,2019
  • Online: April 23,2020
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