Advances in Earth Science ›› 2017, Vol. 32 ›› Issue (3): 292-306. doi: 10.11867/j.issn.1001-8166.2017.03.0292

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Process of Diagenetic System in Shale and Its Restrict on Occurrence of SiO 2: A Case Study of the Longmaxi Formation in the Southeast District of Chongqing

Jia Wang 1, 2( ), Xianfeng Tan 1, 2, *( ), Chunlin Zeng 3, Qing Chen 1, 2, Tian Ran 2, Weiwei Xue 4, Xia Li 2, Cen Chen 1, 2   

  1. 1.Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing 401331, China
    2.College of Oil and Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
    3.Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China
    4.School of Earth Science and Engineering, Nanjing University, Nanjing 210023, China
  • Received:2016-12-23 Revised:2017-02-16 Online:2017-03-20 Published:2017-03-20
  • Contact: Xianfeng Tan;
  • About author:

    First author:Wang Jia(1987-), male, Bazhong City, Sichuan Province, Experimenter. Research areas include sedimentology and unconventional oil and gas

  • Supported by:
    Project supported by the Rsearch Project of Innovation Fund of Petro-China“Shale gas reservoir volume fracture horizontal well flow rule research based on fracture deformation mechanism”(No.2015D-5006-0207);Scientific and Technological Research Program of Chongqing Municipal Education Commission“Occurrence and genesis mechanism of brittle minerals in Silurian Longmaxi Formation and its Geological significance in Southeast Chongqing”(No;KJ1601340)

Jia Wang, Xianfeng Tan, Chunlin Zeng, Qing Chen, Tian Ran, Weiwei Xue, Xia Li, Cen Chen. Process of Diagenetic System in Shale and Its Restrict on Occurrence of SiO 2: A Case Study of the Longmaxi Formation in the Southeast District of Chongqing[J]. Advances in Earth Science, 2017, 32(3): 292-306.

The occurrence of SiO2 has important significance for the development of shale gas, and its genetic mechanism is closely associated with the diagenetic system. Based on the data from field outcrops and drilling cores, we systematically studied the main controlling factors of diagenetic system, the diagenetic process model and its influences on the SiO2 occurrence of shale in Longmaxi Formation, by means of X-ray diffraction analysis, cathode luminescence, scanning electron microscope, energy spectrum analysis and other research methods. The results show that the process of diagenetic system of shale in Longmaxi Formation is quite complicated and the diagenetic phenomenon is rich. The diagenetic control factors were greatly influenced by deposition mechanism in the early stage, and restricted by the diagenetic mechanism in the middle and late stage, while they were mainly affected by the tectonic mechanism in the late stage. The diagenesis system had apparent phase characteristics influence by tectonic movement, especially for Himalayan stage. During this period, shale formation were greatly uplifted, which not only promoted the connectivity of shale and the outside system, and made dissolution and micro cracks become more developed, but also changed reservoir physical property, hydrocarbon generation and preservation conditions of hydrocarbon obviously. Generally, the different chemical fluids restricted the origin of siliceous in different evolution stages of diagenetic. The occurrence of SiO2 was mainly composed of continental quartz and opal in the early stage and slowly began to increase typomorphic quartz, while the medium-coarse grained quartz began to develop in the quartz veins after tectonic movements.

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