A Semianalytical Method To Predict Well Deliverability in Gas-Condensate Reservoirs

Abstract

Summary A fine-grid simulation is needed to capture the buildup of a condensate bank near wells operating below the dewpoint pressure. However, full-field simulations with a sufficiently fine grid will often not be feasible or will require very long computational times. A semianalytical method has been developed that can be used to predict the gas- and condensate-production rates from such wells accurately and that has some advantages over the pseudopressure approach. The semianalytical 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 semianalytical method are in excellent agreement with the results of fine-grid compositional simulations. Coarse-grid simulations with gridblock sizes on the order of 200 ft, coupled with the semianalytical method in gridblocks with wells, yielded production rates as accurate as fine-grid simulations with gridblock sizes on the order of 2 ft. The method was tested for single-layer, multilayer, and multiwell gas-condensate reservoirs and was found to give accurate results.