Fracturing criterion of rock hydrofracturing considering pore pressure effect

Traditional hydraulic fracturing theory believes that as the initial pore pressure increases, breakdown of rock will decrease. Previous experimental studies have shown may increase with (gradient), which cannot be explained by traditional theory. The current understanding effect and its gradient during is still unclear. In this study, analyzed based on a large number macroscopic microscopic phenomena in previous study. Then, new fracture criterion built considering pressure-gradient effect. This can reflect main influence factors, including particle size, porosity, pumping flow, inner diameter open hole section, length fracture, height (or section), fluid viscosity, pressure, minimum situ stress tensile strength. examined experiment results show proposed well predict rock, prediction trend consistent results. average error less than 1% when adopting present criterion. parameter sensitivity analyzed. Results increases porosity becomes more apparent larger pressure. It shows pumped flow rate. Besides, it decreases increasing size but decreasing gradually slows down. research provide theoretical basis for mechanism structural modification fluids engineering.