Gravitational settling of calcium carbonate in different non-Newtonian carboxymethyl cellulose concentrations using the gamma-ray attenuation technique

Abstract In the drilling of oil wells, there are different types of rock formations, which requires fluids with different formulations for each level. These fluids must be pseudoplastic and thixotropic suspensions and they must prevent the sedimentation of particles. In this scenario, this work aimed to evaluate calcium carbonate (CaCO3) sedimentation in fluids with different degrees of pseudoplasticity and thixotropy, to propose constitutive equations for pressure on solids, and to calculate permeability. We characterized fluids with different concentrations of carboxymethyl cellulose and monitored their stability regarding the maintenance of particles in suspension. We used the gamma-ray attenuation technique (TARG). The experiments showed that the non-Newtonian behavior of the fluid influenced particle sedimentation and accommodation, which confirmed the hypothesis that pressure on solids is an exclusive function of particle concentration. We proposed an equation for sediment permeability based on Laruccia (1990) .