西南石油大学学报(自然科学版) ›› 2019, Vol. 41 ›› Issue (6): 68-74.DOI: 10.11885/j.issn.1674-5086.2019.09.16.07

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Technology of In-situ Toughening of Oil Well Cement in Shale Gas Horizontal Wells

CHENG Xiaowei1,2, ZHANG Gaoyin1,2, MA Zhichao3, LI Bin4, GU Tao4   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    2. School of Materials Science and Engineering, Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    3. First Oil Production Plant, Dagang Oilfield Company, PetroChina, Binhai New Area, Tianjin 300270, China;
    4. Engineering Technology Research Institute, Southwest Oil&Gas Field Company, PetroChina, Guanghan, Sichuan 618300, China
  • Received:2019-09-16 Online:2019-12-10 Published:2019-12-10

Abstract: As a non-homogeneous porous brittle composite material in the development of shale gas horizontal wells, oil well cement is difficult to withstand the heterogeneous load caused by large hydraulic fracturing, resulting in failure of the mechanical integrity of the cement sheath. Researches on oil well cement in-situ toughening technology was carried out. In the study, solid phase sintering and spherical re-quenching techniques were used to obtain microcrystalline brownmillerite (MB) as an in situ toughening material. The research indicates the prepared in-situ toughening material reduced the elastic modulus of the cement based on the improvement of mechanical properties. After 7 days of curing, the compressive strength ccould reach 24 MPa, the tensile strength was increased by 50%, and the elastic modulus was reduced to 5.55 GPa. The toughening mechanism of microcrystalline brownmillerite is: "crack deflection", "crack termination", "consumption fracture energy". The development of this study is great significance to meet the requirements of oil well cement service under shale gas mining conditions, extend the service life of shale gas wells and increase the production capacity of shale gas.

Key words: shale gas horizontal wells, cementing, in-situ toughening materials, mechanical property, shale gas production capacity

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