Compound acid fracturing method for carbonate reservoir

Abstract

The invention provides a compound acid fracturing method for a carbonate reservoir. The method comprises steps as follows: (1) a pad fluid stage: a surface cross-linked acid is injected into a stratum with the displacement ranging from 1.0 m<3> / min to 3.0 m<3> / min; (2) a main sand adding stage: fracturing fluid gel and sand are mixed and injected into the stratum with the displacement ranging from 4.0 m<3> / min to 5.5 m<3> / min; (3) a closed acidizing stage: a closed acid is injected with the displacement ranging from 4.0 m<3> / min to 5.5 m<3> / min, a sand-carrying fluid formed by mixing the fracturing fluid gel with the sand is fed into the stratum in a displacement manner, and when a formed artificial fracture is longer than 130 m, the closed acid is continuously injected with the displacement reduced to range from 1.0 m<3> / min to 1.5 m<3> / min; (4) a displacement stage: a displacement fluid is injected with the displacement ranging from 1.0 m<3> / min to 1.5 m<3> / min. The total volume of the injected fluids is in a range of 680-750 m<3>, and ratios of the volumes of the injected fluids to the volume of total fluids injected into the stratum are as follows: in procedure (1), the surface cross-linked acid accounts for 40%-45%; in procedure (2), the sum of the fracturing fluid gel and the sand accounts for 45%-50%; in procedure (3), the closed acid accounts for 4%-5%; in procedure (4), the displacement fluid accounts for 6%-10%. With the adoption of the method, the flow conductivity of the fracture and the productivity of an oil well are greatly increased.

Description

technical field [0001] The invention relates to the field of oil reservoir exploitation, in particular to a composite acid fracturing method for carbonate rock reservoirs. Background technique [0002] In the early stage of composite acid fracturing technology, the high-viscosity fracturing fluid jelly was injected into the well with a displacement that greatly exceeded the absorption capacity of the formation by using the ground high-pressure pump group, and a fracture was generated in the formation near the bottom of the well, and a certain amount of proppant was added to form the fracture. Obtain the conductivity; in the later stage, the acid solution is injected to etch the wall of the fracture, and the micro-fractures in the formation are connected to increase the conductivity of the fracture. However, after the fracturing fluid gel enters the formation, it will form a dense filter cake around the fracture due to fluid loss. The acid liquid injected later cannot fully c...

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Problems solved by technology

[0003] Aiming at the problem that the existing compound acid fracturing stimulation effect is poor and cannot effectively increase the oil and gas production of carbonate rock reservoirs, the present invention combines ground cross-linked acid fracturing and hydraulic fracturing to provide a carbonate rock reservoir multilayer high-efficiency composite acid fracturing method

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