Estabilidade de suspensões pseudoplásticas utilizadas na perfuração de poços de petróleo

Abstract

The indispensability of energy consumption has been stimulating the energy sector to increase its productive capacity. In the Brazilian scenario, oil stands out as an important energy source and in drilling operations drilling fluids are used with the main purposes of cleaning and maintaining hydrostatic pressure of the well. In this context, the targets of this study were evaluate the rheological behavior of drilling fluids, monitor the setting profile of solids from these fluids, propose constitutive equation for pressure on solids and calculate the permeability of porous medium. For this, four drilling fluids differentiated by the oil/water ratio and the addition of calcium carbonate were submitted to rheology and sedimentation laboratory tests to evaluate the solid-fluid interaction. Gamma-ray attenuation, a nondestructive technique, was used to monitor the profile of solids concentration in relation to position and time in batch and gravitational sedimentation, and to obtain constitutive pressure equation in solids. The results allowed to verify the pseudoplasticity and the thixotropy of the fluids and the influence of the calcium carbonate in the sedimentation profile, being a viscosifying component and modifier of the sedimentation rate. The suspension 60/40 oil/ water ratio with carbonate showed the highest values of apparent viscosity and the lowest sedimentation rate and permeability of porous medium, on the other hand, the 80/20 nondensified suspension had the lowest values of apparent viscosity and the highest rates of sedimentation. Thus, it was concluded that the formulation of the drilling fluids should be adequate to the operational and geological conditions of use, and that this study contributed to increase the rheological and stability knowledge of non-newtonian suspensions, consisting of a contribution research on the development and domination of technologies that increase the supply of energy and support the achievement of the country's energy security.