Development of finite element models for thermal multiphase flow in deformable porous media with anisotropic full permeability tensor

Geomechanics plays an important role in predicting hydrocarbon recovery and solid deformations due to fluid injection and production in unconsolidated formations, such as oil sands reservoirs. Thermal recovery processes, involving steam injection into oil sands reservoir at high temperature and pressure, result in variations in reservoir pressure, saturation and temperature. These variations can in turn lead to stress changes in and around the reservoir. The stress changes can induce significant deformations, thereby leading to permeability alterations. The permeability change due to deformation change is usually assumed to be a function of porosity, volumetric strain, or pore pressure. This type of correlation relates the permeability tensor to a scalar variable, therefore, the changes in permeability must be identical in all directions. However, for the strain-induced anisotropic granular materials such as oil sands, they are not necessarily equal, because the strains in different directions are different.; In this thesis, a novel permeability model, so-called strain-induced permeability model, is used to conduct the coupled numerical simulations. Implementation of this permeability model requires the coupled simulators to handle full permeability tensor, which poses challenge for existing geomecahnics-thermal reservoir simulators, because conventional reservoir simulators are usually developed based on 5-spot (two-dimensional problems) and 7-spot (three-dimensional problems) finite difference schemes in which a diagonal permeability tensor is naturally assumed.; In this thesis, we first derive mathematical models for thermal multiphase flow in deformable porous media. Then a complete set of finite element discretizations to all the governing equations in the coupled system is presented with emphasis on the saturation equation, which is discretized by using the Galerkin least squares finite element scheme.; Based on the mathematical models and the finite element discretizations, five preliminary finite element models are developed, and eventually a coupled geomechanics-thermal reservoir simulator, which incorporates the strain-induced permeability model, is established. In a consistent manner, we numerically solve all the governing equations in the coupled system by using finite element methods. The coupling between geomechanics and thermal fluid flow is treated in this way: we first simultaneously solve the force equilibrium, pressure, and temperature equations using the Galerkin finite element method; then a sequential solution of the saturation equation via the Galerkin least squares stabilized finite element method is carried out in each time step. The performance of the developed finite element models is verified by a number of validation problems.; Finally, several case studies are conducted using the developed finite element models. The numerical calculations clearly show that the Galerkin least squares stabilization technique can improve stability while maintaining consistency and the developed coupled finite element models can represent the events occurring as a result of hot or cold fluid injection into unconsolidated reservoir formation.