Coupled Model for Analysis of Multilayer Reservoir in Commingled Production

Abstract

Abstract Presently, most of multilayer reservoirs are modeled as a one single zone system by averaging the reservoir properties correspondent to each zone in the reservoir. This procedure is easy for the analysis of the total production and wellhead pressure. Nevertheless, the result of this type of modeling would rarely be accurate because a one-zone system does not take into account that each zone's pressure decline independently. This pressure decline for each zone affects the overall production and would amount to inter-flow and to early depletion of one of the zones. Therefore this study attempts at coupling the wellbore hydraulics and pay-zone fluid behavior to determine the contribution of the various zones to the overall production in multilayer reservoirs. The study employed analytical solutions to the equations that model the fluid flow in porous media and considered that pressure difference between the producing zones at the sandface allows wellbore inter-flow during any stage of the reservoir's life and no pay-zone inter-flow. The result of typical production scenarios are presented by developing a robust simulator allowing the calculation of the prevailing fluid flow and pressure profiles along the wellbore and the various reservoir zones of different rock properties. The simulation approach presented here allows the user to set the optimal production, injection, or shut-in conditions at the surface for reservoir systems containing two zones.