Abstract

Fluid-pressure-driven (or hydraulic) fracturing of rocks is used in several applications including stimulation of unconventional reservoirs, permeability enhancement of geothermal systems, and rock mass pre-conditioning in deep mining. In recent years, there has been a fast growing interest in the development and use of advanced numerical methods to better describe hydraulic fracturing processes. In this paper, recent advances in hydraulic fracturing modeling using a three-dimensional hybrid finite-discrete element (FDEM) code are presented. FDEM is an explicit numerical method which combines continuum mechanics principles with discrete element algorithms to simulate multiple interacting deformable fracturable solids. The effectiveness of the approach is illustrated by simulating two cases of fracture nucleation and growth around a pressurized cylindrical cavity in a homogeneous and isotropic medium. Realistic emergent pressure response and fracture patterns are obtained with the simulated fracture networks highlighting a distinctive 3D interaction of individual fractures around the location of injection.

1. INTRODUCTION

Fluid-pressure-driven (or hydraulic) fracturing is used in several engineering applications, including stimulation of low-permeability oil and gas reservoirs, permeability enhancement of hot dry geothermal systems, and rock mass pre-conditioning in deep mines. Although the process of fluid-pressure-driven fracturing in geomaterials is generally well understood, its quantitative description is still a largely open research topic due to physical complexities and geological uncertainties. In particular, the mechanics of hydraulic fracturing involves complex, non-linear, hydro-mechanical processes occurring on different length scales in a three-dimensional space. One of the main research areas in this field is represented by the development of new simulation tools capable of capturing an increasing number of physical processes with a higher level of detail and with minimal assumptions regarding the problem dimensionality. The goal of this paper is to present the latest advances in the 3D simulation of pressure-induced fracturing processes in brittle rocks using a numerical approach based on a hybrid finite-discrete element method (FDEM).

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