A Finite-Element Method for Modeling Fluid-Pressure Induced Discrete-Fracture Propagation using Random Meshes

摘要

A finite-element method is proposed for simulating the propagation of discrete fractures resulting from fluid injection within a heterogeneous media. The method only allows new fracture surfaces to nucleate at the inter-element faces of a random mesh. The potential crack paths within the random mesh are viewed as instances of realizable crack paths within a random field representation of the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional sense. The explicit facet representation of fractures within this approach is advantageous for modeling coupled fluid-flow within the evolving fracture network. Flow within the fractures is modeled using Reynold's lubrication approximation. Within the flow solution the fractures are represented as two-dimensional surfaces with a spatially varying aperture. This fluid-structure coupling has been applied in both the dynamic regime using explicit time stepping and in the quasi-static regime using a dynamic relaxation method. Applications of interest for this coupled multi-physics model include carbon sequestration, engineered geothermal systems, and hydraulic fracturing. For carbon sequestration, this modeling approach is being used to improve our understanding of potential leakage scenarios through the caprock and possible mitigation strategies.