Research on Flow Patterns of Two-Phase Fracturing Fluid in Hydraulic Fracture Considering the Fluid Leak-off.

In in situ-generated proppant fracturing technology without proppant injection, the distribution of the flow pattern of two-phase fracturing fluid in the fracture determines the concentration of proppant particles formed by phase change in different positions. Therefore, the study of a two-phase fracturing fluid flow pattern is of great significance to reveal the formation mechanisms of different flow patterns and guide the on-site implementation of the technology. This paper establishes a mathematical model for the two-phase fracturing fluids in fractures based on their physical properties and presents numerical experiments on the flow pattern of two-phase fracturing fluids under different conditions of injection displacement, interfacial tension, and phase change liquid (PCL) ratio. The results show that at lower injection displacements, such as 3 or 4 m/min, it is easier to form striped shape distributions, and at higher injection displacements, such as 5 or 6 m/min, it is easier to form droplet shape distributions. When the interfacial tension is low (15 mN/m), PCL shrinks less and is distributed in strips; when the interfacial tension is high (25, 35, and 45 mN/m), PCL shrinks more and mainly forms droplet-shaped distributions. PCL tends to form discrete droplet shape distributions at PCL volume fractions of 10, and 20%. At 30% volume fraction, PCL is distributed in strips, and at 40% volume fraction, PCL forms strips of a larger size. These findings reveal the changing pattern of two-phase fracturing fluid flow and enrich the theoretical system of in situ-generated proppant fracturing technology, which can provide theoretical support for the on-site implementation of this technology.