A Coupling Model of Gas–Water Two-Phase Productivity for Multilateral Horizontal Wells in a Multilayer Gas Reservoir

A series of complex horizontal wells have been implemented in challenging gas reservoirs. Multilateral horizontal well technology can be used in multilayer gas reservoirs, facilitating the expansion of the gas drainage area and enhancing productivity. Accurate productivity calculations for multilateral wells in multilayer reservoirs are essential for effective reservoir development. However, there have been few studies in this area. This paper introduces a coupling model for calculating the gas–water two-phase productivity of multilateral wells in multilayer reservoirs, based on the principles of conformal transformation and superposition of potential functions. The accuracy of the model is validated by obtaining the distribution of flow along the horizontal wellbore through numerical simulation cases. The results from the field case and sensitivity analysis indicate that the pressure difference increases nonlinearly from the toe to the heel, and the productivity of multilateral wells decreases as the gas–water ratio increases. The method proposed in this paper is applicable for calculating the productivity of multilateral wells in multilayer reservoirs.