RECOVERY METHOD OF ZONE-HETEROGENETIC OIL RESERVOIRS BY IMPULSE LOW-MINERALIZED WATER FLOODING Russian patent published in 2017 - IPC E21B43/20 E21B43/30 

FIELD: oil and gas industry.

SUBSTANCE: method is carried out by a cyclic increase and decrease in working substance injection pressure in injection wells. Low-mineralized water is used as a working substance. Injection well is placed in the center. Production wells are arranged around this well. Allowed range of oil-saturated reservoir permeability at the source area is not less than 30%. Low-mineralized water is taken from surface watercourses: rivers, lakes and seas. Water is pre-decontaminated and pre-filtered to suspended solids size less than 0.1 of average reservoir pore size with minimum permeability. Water injection to the injection well is started with a gradual increase in consumption from zero to the value at which injection pressure is (0.7-0.8)*P_rock where P_rock is vertical rock pressure of overlying rocks. Consumption is then reduced to the value at which injection pressure is (0.1-0.2)⋅P_rock. Cycles of increasing/decreasing of low-mineralized water consumption are repeated many times. Consumption increasing and decreasing speed is set equal at the range of 2-50 m³/day per one injection well. Bhp value relation in source production wells is set inversely proportional to their reservoir permeability-formation thickness product.

EFFECT: increased oil recovery of zone-heterogeneous oil reservoirs.