A Semi-Analytical Method to Predict Well Deliverability in Gas-Condensate Reservoirs

Abstract

Abstract A fine-grid simulation is needed to capture the build up of a condensate bank near wells operating below the dew point pressure. However, full-field simulations with a sufficiently fine grid will often not be feasible or will require very long computational times. A semi-analytical method has been developed that can be used to accurately predict the gas and condensate production rates from such wells and that has some advantages over the pseudo pressure approach. The semi- analytical method includes the effects of capillary number (high velocity) and non-Darcy flow. The new method has been implemented in a compositional reservoir simulator and verified with fine-grid compositional simulation results for both lean and rich gas-condensate fluids. Pressures, saturations, relative permeabilities, viscosities and densities calculated with the semi-analytical method are in excellent agreement with the results of fine-grid compositional simulations. Coarse grid simulations with grid block sizes on the order of 200 ft coupled with the semi-analytical method in grid blocks with wells yielded production rates as accurate as fine grid simulations with grid block sizes on the order of 2 ft. The method was tested for single-layer, multi-layer and multiwell gas-condensate reservoirs and found to give accurate results.