METHOD FOR HYDRAULIC FRACTURING OF A FORMATION ON A CARBONATE DEPOSIT OF HIGH-VISCOSITY OIL Russian patent published in 2022 - IPC E21B43/22 E21B43/26 C09K8/58 

FIELD: hydraulic fracturing.

SUBSTANCE: method for hydraulic fracturing of a formation in a carbonate deposit of high-viscosity oil is claimed. The method includes lowering a tubing string into a hydraulic fracturing zone of a productive formation. The method also includes sealing the annulus with a packer, hydraulic fracturing of the formation rock in three stages. The method also includes creating fractures in the formation and subsequent development of the well. Preliminarily, geophysical surveys are carried out, porosity, formation thickness, initial formation pressure P_in.f, formation pressure P_f, water cut of the produced product, the presence of an aquifer in the Protvinsky object are determined. The method also includes selecting a well with formation pressure P_f<0.7⋅P_in.f, an aquifer at the Protvinsk site, water cut of the produced product of more than 60% with no formation pressure maintenance system and previously conducted hydraulic fracturing of the productive formation. Also, the method includes calculating the volume of the pore space of the formation, depending on the porosity, the thickness of the formation and the area of ​​impact. At the first stage of hydraulic fracturing, a composition consisting of a gel-like polyacrylamide - PAA and ethanol is pumped at a ratio of PAA and ethanol of 1:3, respectively, in a volume of 18-23 m³ per 1 m of the formation thickness. At the second stage, liquefied propane is injected in the amount calculated based on the injectivity of the productive formation. After two stages, technological holding is carried out for 2-3 hours. At the third stage, a composition consisting of PAA and ethanol is pumped at a ratio of PAA and ethanol of 1:3, respectively, in a volume of 0.7% of the volume of the pore space of the formation. After that, a technological exposure is carried out for 1-2 hours. Further, the development of the well is carried out to a liquid of constant mineralization.

EFFECT: increasing the efficiency of the method for hydraulic fracturing on a carbonate deposit of high-viscosity oil, improving the reservoir properties of the reservoir, increasing the stability of the insulating barrier against the flow of bottom water, increasing the coverage of the impact on the reservoir, increasing the oil recovery of the reservoir, reducing the water cut of the produced product, as well as expanding the technological capabilities of the method.

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