Anisotropic Damage to Hard Brittle Shale with Stress and Hydration Coupling

Junchuan Gui, Tianshou Ma, Ping Chen, Heyi Yuan and Zhaoxue Guo
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Junchuan Gui: State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Tianshou Ma: State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Ping Chen: State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Heyi Yuan: Maintenance Center of Northwest Sichuan Gas Field, Southwest Oil and Gas Field Branch, Jiangyou 621709, China
Zhaoxue Guo: State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

Energies, 2018, vol. 11, issue 4, 1-15

Abstract: Acoustic-wave velocities of shale rocks with different coring angles were tested by an acoustic-emission experiment under different confining pressures and soaking time of drilling fluid. Effects of stress and hydration coupling on the acoustic-wave velocities, elastic parameters, and anisotropic damage were analyzed and investigated. The following results were obtained: (1) Acoustic-wave velocities of shale rocks are related to the confining pressure, soaking time, and coring angles. (2) Both Young’s modulus and Poisson’s ratios increase with confining pressure under the same soaking time; under the same confining pressure, the changes of Young’s modulus and Poisson’s ratios with time are not as obvious as the confining pressure, but it shows that the Young’s modulus decreases, while the Poisson’s ratios increase. (3) With increasing confining pressure, the Thomsen coefficient ? showed an increasing trend, whereas the Thomsen coefficient ? exhibited the opposite trend; further, the anisotropy coefficient of P-wave ( ? ) is larger than the anisotropy coefficient of S-wave ( ? ). (4) Damage parameters parallel to bedding are greater than those perpendicular to bedding; when the confining pressure increases, the fracture pores gradually close, and both vertical and horizontal damage parameters are reduced.

Keywords: shale rock; stress dependent; hydration dependent; anisotropy; damage parameters (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
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