Field practice demonstrates the applicability and high efficiency of unsteady-state cyclic flooding to enhance oil recovery of complex reservoirs with heterogeneous permeability. This method is achievable and is often considered as one of the flooding options. Another water injection technology is polymer flooding which is also considered an effective strategy for the development of reservoirs with heterogeneous permeability. The authors proposed a new polymer flooding technology combining unsteady-state cyclic flooding and polymer injection. When injecting polymer solution into the reservoir, the water mobility decreases while the reservoir pressure grows up which enhances oil production. In the case of alternating injection of working agents, during the polymer injection phase, the reservoir pressure also increases, and declines during the water injection phase. Therefore, in order to compensate for the pressure decline during the water injection phase and to maintain the oil production profile, it is proposed to increase the volume of injected water in a certain period of time. To implement this approach, a new technology of cyclic polymer injection has been developed. The technology provides for maintaining increased reservoir pressure at all polymer and water injection cycles by applying forced water injection drive. At the same time, the water injection pressure should not exceed the opening pressure for both natural and induced fractures in the reservoir rocks. The ratio of polymer and water injection cycles in the forced drive is to be simulated on a specific flow simulation area planned for applying polymer flooding technology. The model runs show that the introduction of a new technology can provide an additional increase in oil recovery factor of 4.1 - 4.5% compared to conventional polymer flooding while reducing polymer consumption and project costs.
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