A Proppant Flowback Mechanical Model Based on Different Wettability of the Proppant Particle Surface

Abstract

When large amounts of proppant flow back during fracture cleanup, it directly leads to low fracture conductivity and damages the production equipment. Therefore, it is very important to understand the mechanisms of proppant flow back. In this paper, the proppant was regarded as a spheroidal particle and the forces acting a top particle layer was analyzed after fracture closure. Based on the principle of moment equilibrium, a mechanical model which considered different wettability of the proppant particle surface was then established. The model was then evaluated to determine the critical flowback velocity of the fracturing fluid. The results showed that existence of a liquid bridge force rendered the critical flowback velocity of water wet proppant greater than that of neutral or oil wet proppant. When the water wet proppant size was very small, the liquid bridge force had a greater impact on critical flowback velocity than proppant size. Direction of the liquid bridge force and viscosity of the fracturing fluid were also influencing factors on critical flowback velocity. These results provide a basis for understanding and improving proppant flowback and pack stability.KeywordsProppant flowbackWettabilityLiquid bridge forceCritical velocity