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›› 2018, Vol. 35 ›› Issue (5): 712-719.DOI: 10.7523/j.issn.2095-6134.2018.05.019

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Chemical reactions and effects of slick water fracturing fluid on the pore structures of shale reservoirs in different deposition environments

SUN Zepeng1,2, WANG Yongli1, WU Baoxiang1, ZHUO Shengguang3, WEI Zhifu1, WANG Gen1, XU Liang1,2   

  1. 1. Key Laboratory of Petroleum Resources, Gansu Province;Key Laboratory of Petroleum Resources Research, Chinese Academy of Sciences, Lanzhou 730000, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China;
    3. Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei, China
  • Received:2017-06-22 Revised:2017-10-25 Online:2018-09-15

Abstract: In order to study the effects of slick water fracturing fluid on the pore structures of different deposition environments (marine, continental, and marine-continental transitional) shale reservoirs in the process of shale gas exploration, the deep basin fluid-rock interaction experimental device was used to simulate the interaction between the slick water fracturing fluid and different shales in the condition of formation (100 ℃, 50 MPa). Through comparing the changes in mineral composition, pore volume, and specific surface area of three different deposition environment shales before and 72 h after reaction, the transformation effects of pore structure were analyzed. The results showed that the mineral composition and pore structure of different deposition environment shales changed after reaction with fracturing fluid. After reaction, the carbonate minerals (calcite and dolomite) of marine shale were corroded and many dissolution pores with diameter of 2-8 μm occurred, which caused the reduction in pore volume and specific surface of nanopore. Because of the continental shale and marine-continental shale contain a large amount of mixed-layer illite/smectite mineral which is liable to dispersion and swelling when reacting with slick water fracturing fluid, the pore volume and specific surface area of these shales decreased after reaction. The results of this study provide scientific basis for study of the physical and chemical interactions between slick water fracturing fluid and different deposition environment shale reservoirs and of the transformation of fracturing fluid.

Key words: different deposition environment shale, slick water fracturing fluid, high temperature and pressure simulation, water-rock interaction

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