This paper addresses simulation of non-isothermal water-oil displacements in porous media at porescale. The simulation approach was done by coupling Cahn-Hilliard phase field and heat equations using COMSOL Multiphysics (TM). Finite element method with interfacial adaptive mesh refinement was employed to solve the equation system. The approach was first applied to a non-isothermal Poiseuille flow through channel, for verification. The model was further developed to study flow instabilities in displacements through uniform and dual permeability media. Simulations were performed for the uniform medium with different viscosity ratios (M) and capillary numbers (Ca), ranging three orders of magnitude. A stability phase diagram for log-log Ca-M was constructed and showed a good agreement with those obtained by micro-model experiments. Hot water injection in pore scale revealed that active water fingers have a major role in propagating heat to the immobile oil. Fluid displacements in a dual-permeability medium at different Ca and M showed that lowering M exacerbates the water channeling effect in high permeability layer and lowering Ca may result in higher water sweep efficiency due to capillary dominant flow. This work demonstrated the feasibility of polymer gel treatment in dual-permeability medium to increase the resistant of the high permeability layer, hence divert water to the matrix, e.g., un-swept areas. (c) 2014 Elsevier Ltd. All rights reserved.