Abstract

Hydraulic fracturing has wide engineering applications including exploration of unconventional resources, Enhanced Geothermal System, storage of radioactive waste and mining. It is a multi-physics and multi-scale problem which makes it difficult to be evaluated numerically. It involves the coupling of at least three physical processes – deformation of rock under applied stress, fracture propagation and fluid flow along fracture. Another challenge comes from the presence of discontinuities (natural fracture network) in different scales in rock mass giving the heterogeneity of rock. Fracture growth is highly sensitive to existing discontinuities which either enhance or suppress the growth. However, their influence is not addressed by commercial hydraulic fracturing simulators. In the seminar, a brief background of hydraulic fracturing and some related geomechanics will be given. Lattice Element Method (LEM) will be introduced. LEM is used to model rock deformation and fracture propagation. It has the advantage of simple representation of fracture and ability to cope with complex fracture growth. It is computationally inexpensive so large 3D model can be coped with. The generation of disordered lattice network for heterogeneous rock. Fluid flow along connected fracture cluster is modeled by pipe network model. Fluid flow of individual pipe is governed by cubic law which describes Newtonian flow along thin parallel plate. By including heterogeneity in rock model, simulations show fractures form a cluster and fluid flow is highly tortuous rather than bi-wing fracture commonly assumed.