Study on the Behavior and State of Viscous Fractured Leakage Bridging and Plugging Slurry during the Pump-In and Pressurization Process

Abstract

Clarifying the process of bridging and plugging slurry during pumping and squeezing can effectively improve the efficiency and accuracy of fractured leakage treatment while minimizing impacts on safety and the environment. In this paper, computational fluid dynamics (CFD) numerical simulation and experimentation (hydrostatic settling method) are combined to evaluate the dynamic settlement process of different types of plugging slurry through sedimentation changes, sedimentation volume, sedimentation velocity and sedimentation height for factors such as viscosity, particle size, density and concentration of plugging slurry. The formula of particle sedimentation velocity is combined to obtain the following: When the viscosity of plugging slurry is more than 30 mPa·s, the particle diameter is 1.5 mm (particle size is half the fracture width), and the particle density is 2.0–2.6 g/cm3; it shows good dispersion and plugging performance under pumping pressure and while holding and squeezing after lifting the bit. The simulation results show that the particle density should not exceed two times the plugging slurry density, and the particle concentration has little influence on the particle settling volume.