This paper describes a general unstructured grid, EOS-based, fully-implicit thermal simulator for complex reservoir processes. Under the unstructured grid framework, the simulator uses Newton's method to solve component material balance equations, energy balance equation and volume balance equation for component moles, energy and pressure, where chemical reactions and/or external heat sources/sinks are treated in source terms. Because of the similarity among component material balance equations and the energy balance equation, energy is treated as a "component" to achieve a uniform formulation with common code for all simulations (black oil, compositional and thermal).
The thermal simulator was validated using analytical models as well as other thermal simulators. Application of the thermal simulator includes studies of grid-orientation problems and to design and optimise Cold Lake heavy oil development.