METHOD OF OIL RESERVOIR DEVELOPMENT BY INJECTION OF WATER WITH CHANGING PROPERTIES Russian patent published in 2019 - IPC E21B43/20 

FIELD: oil and gas industry.

SUBSTANCE: method comprises the cyclical increasing and decreasing of pumping pressure of the operation agent in injection wells, application of highly- and low-mineralized water as the operation agents, the extraction of products from production wells. Initially, a non-homogeneous section of the oil-saturated reservoir is selected with a permeability spread of not less than 30%, provided that there are migratable clay particles in the pores, and the reservoir permeability decreases by at least 3 times when the particales are exposed to low-mineralized water. Low-mineralized water is used from the surface watercourses - rivers, lakes, seas; water is preliminary decontaminated and filtered. The stratal water is used as highly-mineralized water. Initially, the highly-mineralized water is injected into the injection well for 10-100 days. Then a gradual decrease in the mineralization of the injected water begins - from highly-mineralized water to low-mineralized water, wherein the sequence of reduction is carried out by adding the low-mineralized water to highly-mineralized water and substituting at each subsequent stage by 10-20%, 20-40%, 40-60%, 60-80% and 80-100%. The duration of each stage is 5-20 days. Then, in the same sequence and with the same duration of the stages, the low-mineralized water is replaced with highly-mineralized water. Cycles of mineralization increasing-decreasing of injected water are repeated many times. In each subsequent cycle of decreasing the mineralization, the injection pressure is increased, and in each subsequent cycle of increasing the mineralization of injected water, the injection pressure is decreased.

EFFECT: increase in the oil recovery coefficient of oil reservoirs with nonuniform permeability due to application of water injection with change in its mineralization.

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