Analysis of cyclic flooding of layered oil reservoirs

Western Siberia is an important oil-producing region of the Russian Federation, with current oil reserves estimated at approximately 4.88 billion tons. In recent years, annual oil production has declined due to a deteriorating resource base and increasing water cut. Water now accounts for about 90% of the total fluid produced from oil wells. In this regard, it is important to develop and evaluate new enhanced oil recovery methods. This article examines cyclic waterflooding as an enhanced oil recovery method for layered oil reservoirs. The author develops a synthetic two-dimensional, two-phase model of a multilayer reservoir with low-permeability barriers between the layers. This work aims to determine how cyclic water injection impacts the distribution of oil saturation in multilayer reservoirs. The author calculates the incremental oil production, ΔQ, for different numbers and arrangements of layers with different permeability. The researcher then compares several development scenarios using numerical simulation. The results show that cyclic waterflooding can provide substantially different incremental oil production depending on the arrangement of highand low-permeability layers. These results can help identify reservoir intervals with the greatest potential for incremental oil production and support the design of cyclic waterflooding programs. The article identifies three reservoir types based on layer arrangement. The first type has low-permeability layers above high-permeability layers. The second type has high-permeability layers above low-permeability layers. The third type consists of interlayered highand low-permeability units. Increasing the degree of layering, denoted as Kr, reduces the efficiency of cyclic waterflooding in the first and second types. For the third type, cyclic waterflooding becomes more effective when the low-permeability layers form a continuous unit. Mixing layers with different permeability tends to decrease the incremental oil production from cyclic waterflooding. The highest efficiency occurs at Kr=2.

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