The performance of fracturing proppant is very important for reservoir hydraulic fracturing design, roundness and sphericity is an important index to evaluate the performance of proppant. The higher the average roundness-sphericity of the proppant, the stronger the anti-crushing ability, and the better the fracture support effect in the formation, the greater the conductivity and the better the reservoir reconstruction effect. The traditional manual visual method is subjective and inefficient; in this paper, a new method of calculating roundness and sphericity by using image processing technology combined with particle corner mean curvature radius-multiple linear regression is proposed. Compared with the traditional manual visual method, the maximum error of the measurement results is only 5%. The samples used in the study of the effect of proppant roundness and sphericity on fracture conductivity were screened by the new method. In the process of simulating the field fracturing construction scheme, it is found that the low roundness and sphericity caused by proppant breakage in the fracture will lead to the decrease of the gap between the particles to hinder the oil and gas flow and reduce the fracture conductivity. The proppant with high roundness and sphericity can effectively reduce the breakage rate of the proppant squeezed by the formation closure pressure in the fracture. At the same time, At the same time, few scholars have studied the relationship between roundness and sphericity on crushing rate and fracture conductivity. The experimental results provide a basis for field fracturing design proppant optimization, maintaining fracture conductivity and increasing production.

Pre-acid fracturing is an effective technique to improve productivity of tight reservoirs. While acid injection can clean the formation and improve the fracturing performance by reducing the fracture pressure of the reservoir, the chemical reaction of the acid solution with proppant may reduce the compressive strength of the proppant and therefore negatively affect the fracture conductivity. In this study, we experimentally investigated the solubility of the proppant in acid and the effect of acid corrosion on proppant compressive strength and fracture conductivity. The results show that the concentration of the acid solution has the greatest effect on solubility of the proppant, which is followed by the contact reaction time. Though a proppant of larger particle size indicates a lower solubility, the acid corrosion poses a greater damage to its compressive strength and conductivity. The quartz sand proppant exhibits superior stability to ceramic proppant when they are subjected to acid corrosion. The experimental results could serve as reference for selection of proppant and optimization of acid concentration and duration of acid treatment during pre-acid fracturing.