Numerical Simulation Study on Temporary Plugging and Balanced Fracturing in Unconsolidated Sandstone

Aiming at the problems of non-uniform fracture extension, unknown temporary plugging mechanism and lack of balanced regulation basis in temporary plugging and fracturing of unconsolidated sandstone reservoirs, a fully-coupled numerical model is established to investigate the mechanism of non-planar fracture extension and optimization criteria of temporary plugging parameters. Based on ABAQUS platform, a fully coupled wellbore-formation-fracture model is constructed, integrating tubing unit to simulate wellbore flow, Cohesive unit to characterize fracture extension, and user subroutine to realize dynamic plugging with temporary plugging agent; a multi-case comparative scheme is designed to analyze the effects of different quantities of temporary plugging agent (30%–90%) and timing (20–80 min) on the fracture morphology. The study shows that: completely plugging the dominant fracture will induce new dominant fracture, and the maximum fracture width will be reduced by 20%; partially plugging can significantly improve fracture uniformity, the total fracture length will increase by 106%, and the extreme difference of fracture width will be reduced by 11%; the timing of temporary plugging needs to be in the middle of the fracturing process, and either early or late will lead to the dominance of single/double dominant fracture; the weak cementing characteristics of unconsolidated sandstone will lead to the shear expansion and plastic deformation of the fracture tip, and the high loss of filtration will inhibit the pressure transfer. This paper innovatively establishes a fully coupled model of temporary plugging and fracturing in unconsolidated sandstone, reveals the optimization mechanism of the “partial plugging” strategy, and proposes a quantitative design guideline of 90% plugging rate and 40 min timing, which provides theoretical support for the efficient development of this type of reservoir.