Rheological studies and numerical investigation of barite sag potential of drilling fluids with thermochemical fluid additive using computational fluid dynamics (CFD)

The growing advancement in drilling technology had necessitated the development of self-destructive mud cake, which is composed of encapsulated thermochemical fluids (TCF) to facilitate dissolution of filter cake. However, segregation of weighting component, commonly the Barite particles, can lead to various operational problems that should be avoided. In this investigation, the segregation potential of Barite particles ("Barite Sag") in drilling fluids has been investigated. The experimental data from rheological studies have been employed to guide CFD modeling and simulation of multiphase flow of a dense suspension mimicking the conventional oil-based mud (OBM), water-based mud (WBM), and those comprises thermochemical additives viz. OBM_TCF and WBM_TCF. The results revealed that the drillings fluids conform to the shear thinning pseudoplastic behavior within the conditions operated in this study. Notably, the apparent viscosity of the WBM was observed to decrease with increasing temperature between 25 and 50 degrees C but increased afterwards. Evaluation of gravitational settling characteristics revealed that the conventional OBM might have lower sagging potential, at lower temperature, compared with the conventional WBM, due to higher settling velocity of Barite particles in the later. In comparison, at higher temperature, which corresponds to the conditions of the newly formulated muds (i.e., the OBM_TCF and WBM_TCF), it was found that the WBM_TCF exhibit lower potential for Barite sag due to lower settling velocity of the particles compared with that of OBM_TCF. The reason essentially has to do with higher viscosity of the WBM_TCF. The CFD studies have considered both the hydrodynamic forces and shear induced migration of the particles. Analyses of various simulation results including particle flux, particle mass fraction, mixture viscosity, and the pressure drop, consistently revealed that the WBM_TCF might have lower Barite segregation potentials compared with other types of drilling fluids considered in this study.