Investigação numérica da circulação direta e reversa no processo de perfuração de poços de petróleo

Abstract

In this work the comparison of direct and reverse circulation techniques used in oil well drilling is carried out. The understanding of flow dynamics is given by the numerical implementation of a tricone drill bit three-dimensional model subject to a turbulent flow of a Newtonian fluid with and without the presence of solid particles. The fluid-particle coupling is modeled under an one way coupling approach. The study aims to compare the performance of both techniques in cleaning the well and removing the cuttings. Therefore, the influence of parameters such as the rheological properties of the fluid, the particle properties, the drillstring rotation speed and mass flow rate over the flow dynamics of the fluid-particle system is evaluated. The study was conducted with ANSYS CFX 15 and other programs of ANSYS package for pre and post processing. The results indicated that reverse circulation is not suitable for tricone drill bits since the flow pattern makes it difficult to clean the well and remove the cuttings. The variation of operational parameters indicated that, for reverse circulation, higher pressure drops are found for the same flow rate due to the inconsistency of the drill bit geometry with the flow pattern. The pattern found when transporting the solid phase indicates that PDC bits are best suited for reverse circulation, given the difficulty in conduction of the solid phase into the drill is related to the distance from the nozzle to the well bottom, a region of low momentum.