Numerical simulation of fluid injection-induced fault slip in heterogeneous shale formations

• Published in: Computers and geotechnics Vol. 134; p. 104120
• Main Authors: Zeng, Yijin, Lei, Qinghua, Wang, Zineng, Ding, Shidong, Liu, Kui, Huang, Xin, Huang, Zhaoqin, Wang, Xiaoguang
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.06.2021; Elsevier BV; Elsevier
• Subjects: Applied geology; Computational fluid dynamics; Constitutive relationships; Correlation; Deformation; Earth Sciences; Elasticity; Engineering Sciences; Fault lines; Fault slip; Fields (mathematics); Flow channels; Fluid flow; Fluid injection; Fluids mechanics; Geoengineering; Heterogeneity; Hydraulic fracturing; Hydraulic heterogeneity; Induced seismicity; Injection; Mathematical models; Mechanics; Numerical models; Permeability; Preferential flow; Probability density functions; Probability theory; Reservoirs; Sciences of the Universe; Sedimentary rocks; Seismicity; Shale; Shale reservoir; Shales; Slip; Two dimensional models; Induced seismicity; Fluid injection; Shale reservoir; Fault slip; Hydraulic heterogeneity
• ISSN: 0266-352X; 1873-7633; 1873-7633
• DOI: 10.1016/j.compgeo.2021.104120

We study the impact of reservoir heterogeneity on fault slip in shale reservoirs subject to hydraulic stimulation. We construct a two-dimensional numerical model representing the horizontal cross-section of a faulted heterogeneous shale formation and simulate coupled hydro-mechanical processes in the system during and after high-pressure fluid injection. We conceptualize the natural fault as a geological composite consisting of a fault core and a damage zone that involves a set of subsidiary fractures parallel to the fault strike. We couple the solid deformation and fault displacement with the Darcy flow based on poro-elasticity principles and hydro-mechanical constitutive relations. The heterogeneous nature of the permeability field of the shale reservoir is mimicked as a random field governed by a log-normal probability density function and prescribed correlation lengths. We elucidate the linkage between fault slip and fluid flow field, permitting the capture of the spatio-temporal evolution of preferential flow channels and their consequences on fault slip and induced seismicity. We report a significant role of reservoir heterogeneity in fault reactivation when the hydraulic fracture is away from the fault but at a distance smaller than the correlation length. The results of our research have important implications for many fluid injection-related geoengineering activities.