Modelagem do deslocamento de uma fronteira sólida em um meio sólido-líquido

Abstract

Among the drilling techniques used, it is in horizontal drilling that there is a bigger possibility of the formation of a cuttings bed. Under these conditions, the effect of gravity causes the sedimentation of the rock fragments generated during the drilling in the low part of the well. When the drill string are been pulled out of the well, this accumulation of solid particles disturbs the movement of the well bottom equipment that constitutes the BHA (Bottom Hole Assembly), which may cause obstruction of the annular and its consequent sticking. It is the aim of the present work to study the interaction between the cuttings bed with the drilling fluid in the critical region limited by the BHA and the well wall. The problem was approached through the bi-dimensional simulation of the boundaries displacement, which represent an element of the BHA, in a solid-liquid system, where the solid phase represents the cuttings bed and the liquid phase is the drilling fluid. This study intends to investigate the behavior of cuttings bed in this critical region evaluating the influence of operational variables such as boundary velocity, cuttings bed height, viscosity of the liquid phase and cuttings concentration. The simulations are performed in the ANSYS FLUENT® computational fluid dynamics (CFD) software using the Euler-Euler Granular multiphase model. From the obtained results it was possible to identify that the increase of the pull-out velocity and the initial height of the cuttings bed can cause obstruction of the critical region between the wall of the well and the BHA. The model used has difficulty predicting the phenomenon that occurs in the critical region in cases of obstruction resulting in negative normal force values at the vertical boundary.