Energy supplementation method by asynchronous injection and production to enhance oil production from oil-water co-layers

In the middle and later development stages of water flooding in oil-water co-layer reservoirs, water channeling intensifies, and the development performance deteriorates significantly. Therefore, there is an urgent need to improve water injection methods to enhance reservoir energy. The microscopic oil-water two-phase flow mechanisms in reservoirs with original bound water saturation and varying movable water saturation were analyzed. Furthermore, water flooding experiments on core samples with movable water saturation, as well as numerical simulations of water flooding development in oil-water co-layer reservoirs were conducted. The research suggests that, compared to reservoirs containing only bound water saturation, oil-water co-layer reservoirs experience a significantly faster increase in water cut during the middle and later stages of development due to the pressure transfer capability caused by the original movable water, and the conventional water injection methods and parameters exhibit obvious limitations. Continuous water injection accelerates the rate of water channeling in production wells, primarily because capillary forces gradually weaken after the injection front reaches the production well, causing water phase permeability to increase progressively. Asynchronous cyclic water injection can achieve ultra-high-intensity water injection, and rapidly replenish reservoir energy, enabling a twofold increase in fluid production and oil production. Therefore, asynchronous injection-production methods can address the issue of poor water flooding performance caused by movable water in oil-water co-layer reservoirs.