The Problem On Fully-Coupled Rock Deformation & Fluid Flow And Its Engineering Application

Coupling of fluid flow and rock or soil matrix deformation has recently become more and more of interest in the field of petroleum, civil, environmental, geological and mining engineering. Based on brief review of the theoretical development in the mechanics of porous media, this dissertation is oriented towards the development of a framework for hydro-mechanics models. Simultaneously a finite element model has been presented, by which the numerical simulation for well failure is performed.Firstly, reviewing and summarizing some basic concepts of rock seepage, relations are developed to define parameters changes resulting from hydro-mechanics coupling, which account for the coupling characteristic between fluid flow and rock deformation. Especially changes in porosity and permeability are addressed more; the test of mud shale properties by water encroachment are taken. the changing law of shale mechanics parameters was established; effect stress laws build a bridge between seepage field and stress field, in chapter 2 different formulae are given.Secondly, based on effect stress laws and Darcy laws, A general set of assumptions and idealizations of the physical nature of the porous medium are outlined and the governing equations are obtained by applying the conservation laws of mass and momentum to each phase and the solid-fluid mixture, including the fluid-solid models of single-phase and two-phase fluid flow in continuum medium and a naturally fractured formation. Since the finite element method has its own advantages in designing grid system and treating complicated boundary, a generalized Galerkin procedure is devised to establish the coupled finite elementequation set with u - p form.Finally, from a point of solid-fluid coupling, its application to the problem of well failure is presented in this section. the numerical simulation for one well and wellgroup shows the significant insight into casing damage mechanism that spatial gradient in pore pressure induced by production and injection in a low permeability reservoir or bad quality formations may perturb the local stresses and cause unsymmetrical stress and pore pressure redistributions in the vicinity of the borehole, then subsurface deformations are sufficient enough to result in well failure. Through experiments and geomechanical simulation, corresponding measures should be taken that is to keep local equilibrium between injection and production and prevent increasing spatial and temporal gradients in pore pressure.