Numerical modelling of Bingham fluid flow and particle transport in a rough-walled fracture

Abstract

Drilling operations may encounter mud loss which becomes especially aggravated in naturally fractured formations. The dynamics of fluid loss is a complex process, affected by both the rheology and the composition of the fluid as well as by the fracture morphology. A deep understanding of the underlying physics, in particular non-Newtonian fluid flow and particle transport in rough-walled fractures, is required to combat fluid loss by use of e.g. LCM. Previous studies have shown increased aperture channelization and particle transport in the direction perpendicular to the shear displacement with Newtonian fluids. The motivation for and goal of this thesis is to investigate how non-Newtonian fluid flow and particle transport behave in rough-walled fractures subject to shear. One rough-walled fracture with average aperture equal to 0.5 mm and Hurst exponent equal to 0.75 was created by using the recursive subdivision technique. The fracture surfaces were shifted 0.01 m in either coordinate direction. A test matrix of 108 simulations were completed for the two shearing scenarios with flow applied in x- and y-direction. Conclusions drawn from the study include increased fluid channelization for large values of the ratio between yield stress value and applied pressure difference. The fluid's ability to carry particles was greater in the direction perpendicular to the shear displacement. In addition, the distributions of average cross sectional aperture perpendicular to fluid flow was more rough when flow was applied along the direction of shear displacement, leading to yield dominant flow.