Estudo da filtração com e sem sedimentação prévia de fluidos de perfuração com comportamento Newtonianos e não-Newtonianos

Abstract

During the process of drilling an oil well, the drilling fluid used may be confined in the annulus for months until the beginning of oil production, forming a settle layer of weighting materials at the bottom of the annular. When exploration starts temperature increases in the well and that cause a volumetric expansion of the confined fluid increasing annular pressure, a phenomenon known as APB, Annular Pressure Build up. If this pressure increasing is too high it might occur the rupture of the coating and tubing collapse. The search for APB mitigation has been a frequent concern in oil production. One way to relieve annular pressure is when the pressure increasing lead to a fracture in the rock formation and/or on the cementin the wells constructed with cement shortfall. In this case, a filtration process stars over the layer of weighting materials, relieving the pressure inside the annulus. Therefore, this work aimed to investigates the properties of the mudcake obtained after a process of filtration preceded or not by seven days sedimentation. The filtrations were performed with Newtonian and non-Newtonian fluids in a HTHP filtration cell for 30 minutes. Parameters such as filtration volume, time of filtration, mudcake thickness, permeability and porosity were obtained. Newtonian fluids were composed by a solution of glycerin and B-1 barite, while non-Newtonian fluids by a solution of xanthan gum or carboxymethylcellulose and PCS-150 barite. Simultaneously, sedimentation tests in a graduate cylinder were performed to evaluate how suspensions of both type of fluids behave at ambient pressure. The results indicated that for Newtonian fluids the volume of filtrate is lower when filtration is preceded by sedimentation, different from non-Newtonian fluids that filtration volume increased with sedimentation