A Front Tracking Model for Thermal Oil Recovery Processes

A versatile, three-dimensional finite element front tracking model is developed for thermal recovery processes The model approximates the flow domain as regions of homogeneous fluid properties separated by a sharp front and places the primary computational effort on tracking the movement of this front. Flow is approximated as a succession of steady-states based on incompressible fluid flow. Laplace's equation, which is the governing partial differential equation· in each region, is solved by a finite element method subject to exterior and frontal boundary conditions that are dictated by continuity of pressures and conservation of mass and energy across the front. At each time step, normal velocities at the front are calculated and the front is moved explicitly according to these velocities. Since the model treats both condensing and non-condensing fronts as moving discontinuities, continuous alignment of the finite element grid with the front is needed. For this a three-dimensional adaptive grid redistribution scheme has been developed. The model has been tested for accuracy with available data in literature and seems to to provide accurate, dispersion-free numerical solutions with relatively small computing power. The usefulness of the model to simulate e~ects of viscous and gravitational forces, and condensation on displacements in various reservoir/well configurations has been demonstrated. Preliminary sweep efficiency correlations and flooding patterns are provided which can be combined with predictive models to evaluate the performance of thermal recovery processes. This model has the potential to inexpensively simulate field-scale thermal recovery processes such as steam injection and in-situ combustion in heterogeneous reservoirs.