Cyclic Water Injection: A Simulation Study
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Cyclic waterflooding is a recovery method that increases the cumulative oil production in stratified, heterogeneous reservoirs. The process is based on alternated injection rates and alternating waterflood patterns within the reservoir. Improved oil recovery is achieved by improved sweep of low permeable layers and previously poor swept areas. The thesis presents the results obtained from analytical evaluations and numerical simulations of a 2D and 3D synthetic model. The effect of cyclic injection is controlled by multiple parameters. A sensitivity study related to reservoir pressure, cycle period, injection rate, well spacing, reservoir thickness, wettability, permeability distribution, transmissibility, startup time and waterflood pattern was conducted. From the simulation results, cyclic injection shows promising results related to increased oil production and reduced water production. All the simulated cases produced additional oil in the range of 2-20% compared to a conventional waterflood. The best case was found to be the more intensive injection schemes with a relative short base period, and startup time at high water cut. Improved oil recovery is accompanied by significant decrease in water production. Cyclic water injection can improve a waterflood in terms of improved oil recovery and reduced water production at virtually zero additional cost, and is easy to implement.