METHOD OF INCREASING OIL RECOVERY OF CARBONATE OIL FORMATION WITH RECOVERY OF FORMATION PRESSURE Russian patent published in 2019 - IPC E21B43/22 E21B43/27 E21B47/06 

FIELD: oil industry.

SUBSTANCE: invention relates to the oil-producing industry. In the method for increasing oil recovery of a carbonate oil formation with recovery of formation pressure, a well is selected, which exploits oil-saturated formation with current reservoir pressure of not more than 0.6·P, where P is initial formation pressure, operations are performed in two main successive stages. First stage is aimed at recovery of formation pressure, at which to well is pumped at flow rate of 2–10 m³/h working fluid – water with total mineralization of 0.8–1.2 of total mineralization of formation water, pumping is carried out until wellhead pressure increases to value of not more than 0.2·P, then, at wellhead (0.2–0.4)·P solution of 1–10 % surfactant in working fluid is pumped in the working liquid, total volume of injected surfactant solution is determined at 0.5–5.0 m³ per meter of effective oil-saturated thickness of formation, after which working fluid is again injected until well head pressure increases to 0.4·P, process exposure is carried out for not more than 48 hours, during which the drop of wellhead pressure is analyzed, and when it falls, working fluid is pumped to increase wellhead pressure to 0.4·P. Second stage is aimed at impact on rock skeleton, for this purpose pumping of complex acid composition is performed with addition of surfactant, water, retarders of reaction of acid with rock, clay stabilizers, reagents for creation of self-deflecting acid compositions and/or acid emulsions, composition and concentration of which are determined by laboratory tests depending on filtration properties of the formation, wherein concentration of pure acid in the complex acid composition is set at level of 12–20 %, pumping is carried out at wellhead pressure of not more than 0.45·P, volume V_a pumped complex acid composition is determined at rate of 1–7 m³ per meter of effective oil-saturated formation thickness, complex acid composition is pumped by working liquid with volume (0.2–1.0)·V_a under wellhead pressure of not more than 0.45·P, after which process exposure is carried out for not more than 24 hours, the well is developed by swabbing or using deep-pumping equipment, and the well is put into operation. Operations to increase oil recovery of carbonate oil formation in this well are repeated every 2–4 years.

EFFECT: technical result is increase of oil recovery of carbonate oil formation.

1 cl, 2 ex