Two-phase oil migration in compacting sedimentary basins modelled by the finite element method

摘要

In this report, the upstream-weighted finite element method with lumped mass matrix is applied to the modeling of oil migration in compacting sedimentary basins. An implicit formulation is made in Lagrangian coordinates of a pressure, saturation and a temperature equation, which accounts for the immiscible two-phase flow of oil and water, the compaction of the sediments, the generation of oil from solid organic material (kerogen), the eventual pore space generated by kerogen breakdown, and the density variations of the fluids which may set up thermal convection. Validation of the model is done by comparison with a one-dimensional (1D) fractional flow based migration model. A 2D case showing oil expulsion from source rocks, and the filling of a trap is presented. The mass balance of the model is easily checked because all oil in the basin originates from breakdown of kerogen. Compared with more sophisticated alternatives, the present method is suggested as a possible first choice for a numerical method for modelling oil migration in compacting sedimentary basins. 41 refs., 11 figs., 8 tabs.