Quantitative analysis of the effect of acidification on in-situ residual fracture openings in laboratory fracturing simulation tests

Abstract

The laboratory fracturing simulation experiment is an important basis for the design and optimization of the on-site hydraulic fracturing process, and the fracture width is a key parameter for evaluating the fracturing effect. However, it is very difficult to directly obtain the in-situ residual fracture opening of the fracturing experiment. The reason is that the specimen is subjected to hydraulic action or other external forces to form a penetrating fracture surface, which displaces the original position of the fracture to be dislocated. This paper focuses on the characterization of the original residual fracture opening after the laboratory fracturing experiment and proposes a visual measurement method for the in-situ fracture width based on 3D digital image scanning technology. Hydraulic and acid fracturing studies confirmed its applicability, and residual fracture holes from the two conventional fracturing experiments were measured at the “mm” level. With the help of the Canny operator, the calculation method of zigzag residual fracture opening is revised, and the measurement accuracy of residual fracture opening is improved by 33.4%. In the meantime, by comparing and analyzing the fracture propagation characteristics of the “severe acid corrosion area” and “slight acid corrosion area” of 10%, 15%, and 20% gelling acid, the relationship between the gradient of the residual fracture opening and the “acidizing effect” and “acid etching efficiency” was obtained. This paper mainly solves the problem that in-situ residual fracture opening cannot be obtained in fracturing experiments and can provide parameter guidance for quantitative evaluation of fracturing effects and estimation of fracturing productivity.