Simulação numérica da circulação direta e reversa em broca PDC na perfuração de poços de petróleo

Abstract

The oil reserves are located hundreds of meters, or even kilometers, below the Earth’s surface. Nowadays, this natural resource exploration is made by the rotary drilling process, where a bit is used to build a well and enable the access to the reservoir. In the present study, a numerical simulation of the fluid flow during the drilling was performed. The geometry consists of a PDC (polycrystalline-diamond-compact) bit attached to a drillstring. The simulations were executed by the ANSYS CFX 15.0® software, with the flow being modeled as turbulent (Shear Stress Transport model or SST). For the reason that there aren’t turbulence models for non-Newtonian fluids, the drilling fluid was considered as Newtonian and incompressible. The direct and reverse circulations were compared, analyzing the influence of the fluid’s dynamic viscosity and density, and also the rotation speed and flow rate effects. Relations were studied between these variables and the fluid’s averaged impact force in the bottom of the well, the head loss, the averaged shear stress in the bit and the averaged speed at the exit. The results showed that the flow rate has the biggest influence to the fluid flow and the reverse circulation is more efficient for the majority of the investigated aspects, except the bit region cleaning.