Modelling fluid injection-induced fracture activation, damage growth, seismicity occurrence and connectivity change in naturally fractured rocks

作者：Qinghua Lei, Nima Gholizadeh Doonechaly, Chin‐Fu Tsang · 发表于：International Journal of Rock Mechanics and Mining Sciences · 年份：2021 · DOI：10.1016/j.ijrmms.2020.104598 · 被引用次数：178 · 研究领域：earthquake and tectonic studies、Rock Mechanics and Modeling、Hydraulic Fracturing and Reservoir Analysis

We develop a fully-coupled hydro-mechanical model to simulate fluid injection-induced activation of pre-existing fractures, propagation of new damages, development of seismic activities, and alteration of network connectivity in naturally fractured rocks. The natural fracture system is represented by a discrete fracture network. The stress and strain fields of the fractured porous media are solved in the framework of a finite element model, which mimics the damage evolution in rock matrix based on an elasto-brittle failure criterion and simulates the normal/shear displacement of natural discontinuities based on a non-linear constitutive law. The coupled geomechanics and fluid flow processes in the fractured rock are computed honouring essential coupling mechanisms such as pore pressure-induced shear slip of pre-existing fractures, poro-elastic response of rock matrix, and stress-dependent permeability/storativity of both fractures and rocks. We use the numerical model developed to investigate the hydro-mechanical behaviour of two cases of deeply buried fractured rock in response to high-pressure fluid injection, one case with fracture density just below the percolation threshold and the other above the threshold. We observe a strong control of natural fracture network connectivity on the damage emergence, seismicity occurrence and connectivity change in the rock mass subject to hydraulic stimulation. We also highlight the strong poro-elastic effect that tends to drive heterog...