Stability of oil well olefin drilling fluids: solid-liquid sedimentation and rheological characterization

Oil wells drilling processes are a crucial step in petroleum exploration and drilling fluids are an important player in this operation. Both solid-liquid sedimentation stability and appropriate rheological characteristics are significant and desirable aspects for drilling fluid. In this context, this study aimed at analyzing the stability of olefin drilling fluids, differentiated by calcium carbonate additive, related to solid-fluid interaction sedimentation and rheological behavior. Rheology, gravitational, and batch sedimentation experimental tests were performed as both time and function position. A low viscosity viscometer was used for the rheological characterization, and gamma-ray attenuation, a nondestructive technique, was applied to quantify the local volumetric solids concentration in sedimentary regions. The results showed a shear-thinning behavior and thixotropic effects in these fluids and the influence of calcium carbonate in the sedimentation profile. The thickened suspension showed higher values of apparent viscosity and lower sedimentation rates than the non-thickened system. Thus, the formulation of drilling fluids affected the solid-liquid separation process and the rheological behavior of suspensions; and, for that sense, it should be appropriated for drilling exploration.