Study on the conductivity of acid etched fracture under the precise reconstruction of fracture surface

Acid fracturing is a major method of carbonate reservoir exploitation. The non-uniform dissolution of acid liquid on the fracture surface is utilized, which results the grooving corrosion on the fracture surface. The formed acid etching fracture still has a certain fluid conductivity under the effect of closing pressure, which can improve the seepage conditions and increase oil and gas production. The fracture conductivity after acid fracture is an important evaluation index of the acid fracturing effect. Therefore, it is very important to study the fracture conductivity properties. According to the nail-bed model, the fracture surface shape and height of the support are essential factors for calculating the fluid conductivity of acid etched fracture, which can predict the fluid conductivity of acid etched fracture and evaluate the effect of acid etching. The wall topography illustrated with the original height data can’t accurately reconstruct the real acid etched form, and the original methods to obtain the height of support also are different. So an approach to precisely reconstruct the acid etched fracture surface to obtain the support height must be found out. Through the spatial interpolation of irregular triangular mesh method, the precision of the height data of the support body on the fracture surface should be greatly improved, and the height data missing due to technical reasons should be effectively repaired when the initial data are obtained by scanning. A conductivity model of the stress-varying acid-etched fracture was established in this paper, and the heterogeneity of mechanical parameters and mechanical properties of rocks with different acid etched fracture surfaces were mainly considered. Through interpolation of irregular triangular mesh reconstruction, the height data of key parameters were obtained, which accurately could determine the model parameters and finally got the best results. The precise data were applied to the fracture conductivity model. Meanwhile, acid etching fluid directing series experiments were conducted, and the fracture fluid conductivities of different acid etching time were gained. By comparing the data obtained by the fracture conductivity experiments with the model one, it was proved that the model could show the change of fracture conductivity more accurately. Another, the optimal etching time under a certain closing pressure was obtained. The feasibility and adaptability of the irregular grid interpolation methods in the study of fracture conductivity were demonstrated.