A two-dimensional modeling approach of the settling of weighting solids in non-Newtonian drilling fluids

Abstract

During the preparation of oil wells, drilling fluids are employed for various purposes, such as lubricating the drill, removal of cuttings, and controlling the well’s hydrostatic pressure. Pressure control is achieved by increasing the density of these fluids with particulate minerals, like barite. In the cementing stage, the fluid is confined in the annular regions between the casing layers and the rock. The confined fluid undergoes temperature variations, leading to pressure increases in the annular region, known as Annular Pressure Build-Up (APB), which can compromise the integrity of the casings. One APB mitigation strategy consists of leaving an unlined region within the annulus, known as open shoe, so the fluid can flow into the formation if there is an excessive pressure increase. However, the solids within the confined fluid may settle and cover this region entirely. In this context, this study aims to enhance the one-dimensional model previously developed to predict the settling dynamics of weighting materials within annular regions. This will enable the consideration of complex geometries in future research, such as annular diameter contractions and deviated wells. A bench scale case was considered and the results were reassured by the one-dimensional model, in turn validated with experimental data.