Coupled thermo-hydro-mechanical (THM) model for multiphase flow through deformable porous media with double porosity

Abstract

A fully coupled thermo-hydro-deformation (THM) model has been presented in this thesis. The proposed model is based on the concept of effective stress and it consists of a set of governing equations to couple mechanical stress and deformation, multiphase fluid flow and heat transfer in deformable unfractured/fractured porous media. Local thermal non-equilibrium is assumed so that the heat transfer between phases can be captured. Particular attention is given to the mass and energy transfer between the pore and fracture networks.

The governing equations are transformed into finite element formulation and implemented into a numerical program developed in-house which features integrated system design and a user-friendly graphical interface (GUI). Iterative solution strategies are adopted to yield stable numerical results with better accuracy.

The validity of the program is verified using hydro-mechanical and thermoelastic examples available in the published literature. The proposed THM model is used to study consolidation behaviour of saturated and unsaturated soils and fissured clay under isothermal and non-isothermal conditions, oil-water flow in fractured rocks, and transient conduction under different boundary conditions. The model is also applied to investigate enhanced thermal recovery of resources in both unfractured and fractured reservoirs. The outcome provides insight into the effects of fracturing and the incurred benefit in petroleum reservoirs. In addition, parametric study is conducted to identify the importance of some parameters and the impact of data uncertainty.