Experimental test method for effective length of acid etching crack

Abstract

The invention provides an experimental test method for the effective length of an acid etching crack. The method comprises the following steps that acid liquor and multiple groups of rock plates are prepared; the acid liquor sequentially passes through the fractures simulated by each group of rock plates for acid liquor displacement, and the acid liquor concentration at the outlet of the fracture simulated by each group of rock plates and the fracture length corresponding to the outlet are measured; the acid liquor concentration of each group is fit with the crack length to obtain a relational expression between the acid liquor concentration and the crack length; and according to the relational expression obtained by fitting, the crack length when the acid liquor concentration is reduced to a preset concentration threshold value is determined to be the effective length of the acid etching crack. Or, the method comprises the following steps of preparing acid liquor and multiple groups of rock plates, enabling the acid liquor to sequentially pass through the cracks simulated by each group of rock plates to carry out acid liquor displacement, and measuring the concentration of the acid liquor at the outlets of the cracks simulated by each group of rock plates until the measured concentration value of the acid liquor is lower than a preset concentration threshold value, and when the acid liquor concentration value is lower than the preset concentration threshold value for the first time, determining the corresponding crack length at the outlet of the rock plate simulation crack to be the effective length of the acid etching crack.

Description

technical field [0001] The invention belongs to the technical field of exploration and development of oil and gas reservoirs, and in particular relates to an experimental test method for the effective length of acid-etched fractures. Background technique [0002] Acid fracturing technology is the most important reservoir stimulation measure for carbonate reservoirs, and the extension length of acid-etched fractures is an important index for evaluating the effect of acid fracturing, and also an important basis for designing and optimizing acid fracturing operations. Acid fracturing is to use acid liquid as the fracturing fluid under the pressure higher than the fracture pressure of the formation to perform fracturing without proppant, relying on the dissolution of the acid liquid to dissolve the wall surface of the fracture into an uneven surface, so that the pump can be stopped and unloaded. The cracked walls will not be completely closed after compression. [0003] The con...

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Problems solved by technology

[0004] Existing simulations of acid-etched cracks are all aimed at obtaining fracture morphology and fracture conductivity. For example, CN108152183A discloses a test method for acid-etched fracture etching morphology and conductivity, but does not mention the length of acid-etched fractures. method of acquisition

[0005] The rock slab used in the existing simulation of acid-etched cracks is a cuboid rock slab with a curved end face, which is small in size and cannot well simulate the formation process of tensional acid-etched cracks in the actual on-site acid fracturing construction process. The simulation experiment not very representative

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