Experimental Investigation of Anisotropic Thermal Deformation of Oil Shale Under High Temperature and Triaxial Stress Ba
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Original Paper
Experimental Investigation of Anisotropic Thermal Deformation of Oil Shale Under High Temperature and Triaxial Stress Based on Mineral and Micro-fracture Characteristics Dong Yang ,1,2,4 Guoying Wang,1,2 Zhiqin Kang,1,2 Jing Zhao,1,2 and Yiqing Lv3 Received 16 December 2019; accepted 19 March 2020
The anisotropic deformation of oil shale at different temperatures should be given particular attention considering that thermal deformation affects borehole stability, oil and gas permeation channel formation and surface subsidence during the pyrolysis of oil shale. The deformation of oil shale parallel and perpendicular to the bedding directions under different triaxial stresses was studied from room temperature to 600 °C. Evolutions in mineral compositions and thermal fracturing were studied by X-ray diffractometry and computer tomography, respectively. The main results are as follows. (1) Under 2.5 and 5 MPa axial stresses, the thermal deformation perpendicular to the bedding direction shows compressive deformation with increasing temperature, and the strain rate increases sharply at 200 °C, 350 °C and 400 °C. When the axial stress is 10 MPa, the deformation rate increases sharply when the temperature increases to 100 °C, and then, the compression deformation increases almost linearly. (2) Under 2.5 and 5 MPa axial stresses, the thermal deformation parallel to the bedding tends to be expansion–compression–expansion–recompression with increasing temperature. When the axial stress increases to 10 MPa, the overall deformation of the material will be compression deformation, and no expansion deformation will occur with the increase in temperature. (3) The deformation characteristics under the coupled action of temperature and stress are less related to mineral changes but more related to fracture evolution characteristics. (4) Thermal stress has a great influence on the thermal deformation of oil shale perpendicular to the bedding directions but little effect on the thermal deformation parallel to the bedding directions. KEY WORDS: Real-time high temperature, Triaxial stress, Thermal deformation, Anisotropy, Oil shale.
1
Key Lab of In-situ Property-Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China. 2 The In-situ Steam Injection Branch of State Center for Research and Development of Oil Shale Exploitation, Taiyuan 030024, China. 3 College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China. 4 To whom correspondence should be addressed; e-mail: [email protected]
INTRODUCTION Oil shale is an organic-rich sedimentary rock, and it has an orderly arrangement of minerals and special sedimentary structure, which result in very obvious anisotropy in many aspects, such as thermal, hydraulic and mechanical characteristics. Organic matter in oil shale (also known as kerogen) is converted from solid to liquid oil and gas when the
Ó 2020 International Association for Mathematical Geosciences
Yang, Wang, Kang, Zhao, and Lv temperature ri
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