Numerical Investigation of Particle Bridging near Fracture Entrance

Abstract

ABSTRACT: Particle transport and bridging inside fractures is an important subject in wellbore drilling and completion. For example, when drilling naturally fractured formations, depleted formations, and offshore formations where fractures can be easily induced or reactivated, loss circulation material (LCM) containing high loading of solid particles is commonly used to seal the pre-existing or newly created fractures to prevent mud loss. The particles are expected to bridge the fracture at the entrance area to maximize the sealing effectiveness and efficiency. A different example is the well completion with hydraulic fracturing, in which the proppant particles are injected with fracturing fluids to keep the fractures open after the fracturing pressure is released. To maximize the opening area of the fractures thus the well productivity, the placement of the proppant particles is expected to reach the far region of the fractures, so the particle bridging near the fracture entrance should be avoided. On the other hand, should the objective be promoting multiple fractures, particle bridging against a pre-existing or dominant fracture is beneficial to redirect the fracturing fluid into less conductive fractures. The ability to predict the bridging location and time with given solid particle size and concentration, fluid viscosity and operating parameters will help design drilling fluid, LCM, fracturing fluid, and diverting materials. In this work, a simulator is developed for numerically experimenting the particle bridging in the entrance area of a fracture. The fluid flow in the fracture is simulated by pipe network flow model. The equation of particle advection with fluid is solved using the upwind numerical scheme. The particle bridging is evaluated using a blocking criterion proposed in the literature. After all the implemented computational components are tested and verified, extensive parametric studies are then performed to experiment how various parameters, including particle size and concentration, fluid viscosity and injection rate, influence the particle bridging location and time near the entrance area. Accordingly, a few recommendations are provided to assist the design and selection of diverting and LCM agents.