Numerical simulation of mixed-mode hydraulic fracture propagation and interaction with different types of natural fractures in shale gas reservoirs

Abstract

Shale gas reservoirs have an extremely low permeability and porosity; hence, it is necessary to perform hydraulic fracturing to improve production. To design effective stimulation measures, it is necessary to fully understand the propagation of hydraulic fractures and their interactions with natural fractures. In this study, a two-dimensional fully coupled mixed-mode model based on the extended finite-element method (XFEM) is established, which includes rock deformation, fracturing fluid flow and leak-off and mixed-mode fracture propagation. We focused on different factors (Young’s modulus, Poisson’s ratio, in situ stress and fracturing fluid rate) to investigate hydraulic fracture initiation, propagation and interaction with two kinds of natural fractures. The results reveal that all the factors have great influences on the fracture geometry, among which in situ stress has the greatest influence. A smaller frictional coefficient of the natural fracture surface enables the hydraulic fracture to divert into the natural fracture. A smaller interaction angle and lower natural cemented fracture strength allow hydraulic fracture propagation along the cemented natural fracture. In the field, hydraulic fracturing parameters should be adapted to the specific conditions to achieve the desired fracturing effect and better economic exploitation.