Title: Thermo-hydro-mechanical-damage coupling mechanism and failure behaviour of caprock in SAGD operations

Authors: Haijing Wang; Chao Zhang; Bo Zhou; Shifeng Xue; Peng Jia; Xiuxing Zhu

Addresses: College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China ' College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China ' College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China ' College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China ' College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China ' College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China

Abstract: A coupled thermo-hydro-mechanical-damage model considering anisotropic stiffness degradation of rock after shear damage is developed for the first time, and the coupling mechanism and failure behaviour of caprock in steam assisted gravity drainage (SAGD) operations are systematically investigated using analytical and numerical approaches. New insights into the failure characteristics of caprock were obtained. The damage of caprock is mostly induced by shear and initiates near the interface directly opposite the well pair in the earliest stage of SAGD production and propagates rapidly to form a main crack. The vertical and zigzag main crack may penetrate the caprock, while the secondary cracks on both sides are mostly inclined and straight that they cannot penetrate the caprock. Failure modes of caprock are observed including penetrating crack, non-penetrating crack and interface damage. This study will be helpful in accurately evaluating the caprock integrity and efficiently breaking interbedded shale or mudstone layers in thermal recovery reservoirs. [Received: June 2, 2023; Accepted: February 13, 2024]

Keywords: thermo-hydro-mechanical-damage; THMD; analytical analysis; numerical simulation; caprock failure; steam assisted gravity drainage; SAGD.

DOI: 10.1504/IJOGCT.2024.140273

International Journal of Oil, Gas and Coal Technology, 2024 Vol.36 No.2, pp.121 - 151

Received: 09 May 2023
Accepted: 13 Feb 2024
Published online: 01 Aug 2024 *

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