Simulação computacional de um fluido de Herschel-Bulkley em escoamento de Taylor-Couette

Abstract

In the oil and gas exploration, the drilling fluid invasion into the substrate is an issue that results in a financial impact of millions of dollars yearly. One of the methods used to prevent the invasion phenomenon is alter the rheological fluid parameters in a way to allow the formation of an unyielded region adjacent to the formation wall waterproofing it. Therefore, this study objective is to perform a numerical simulation of the flow in an wellbore, using the software Ansys Fluent®, simplifying it by a Taylour-Couette flow inside an annulus with the inner cylinder rotating, using the Herschel-Bulkley model for the fluid viscosity. The formation of an yielded region is investigated by means of the rheological parameters of the fluid (yield stress, power-law index and consistency index), inner cylinder rotation speed and Bingham number influences are investigated in the formation of the unyielded region, and information regarding the wall shear stress of the well and the formation, and the skin friction coefficient are also provided. The main results show that the combination of the rheological fluid parameters associated with the drill rotation speed allow the formation of an unyield region adjacent to the wellbore wall. In general, the increase of the fluid parameters (power-law index and consistency index) results in the decrease of the unyield region, increasing the wall shear stress and the skin friction coefficient. On the other hand, the increase of the yield stress and the Bingham number influences the unyielded region in the opposite way, resulting in the increase of its size. Finally the increase of the yield stress results in the undesired effect of increasing both the wall shear stress and the skin friction coefficient.