Modelagem e Simulação Numérica de Escoamentos Simplificados no Fundo de Poço em Perfuração

Abstract

In the present thesis the modeling and simulations of turbulent in downhole flow are presented, using the immersed boundary method to model immersed bodies. In this work, the fluid is injected through the drill pipe and then acclerated by the nozzle. As the fluid discharges from the nozzle, a high speed jet is generated in the downhole region, the fluid then impinges the bottomhole surface and finally flows out the downhole region through the annulus. The nozzle is represented by a sudden contraction. Due to the geometry of the problem, a toroidal vortex takes place. The numerical platform which has a parallel distributed-memory implementation to solve the Navier-Stokes equations. The equations are discretized using the finite volume method. Both advective and diffusive terms are advanced explicitly using and Adams-Bashorth scheme, and the spatial derivatives are discretized using central differencing scheme in a staggered arrangement. The pressure and velocity are coupled using an explicit fractional time-step method. The dynamic subgrid-scale used in large-eddy simulation was implemented. Particles were added in the sidewall near bottomhole surface through the euler-lagrange approach considering one-way coupling. The influence of the flow rates and rotational speeds was evaluated. The characteristic velocity overshoot was found in the contraction plane and immediately downstream. In the rotating cases, the velocity profiles at the contraction plane changes; additionally, for high rotational speeds, the characteristic velocity overshoot does not exhibit neither at the contraction plane nor immediately downstream of it. Due to the geometry of the problem, a toroidal vortex takes place and it grows as the Reynolds number increases and narrow channels are formed on bottomhole surface and near the sidewall; The impact force and the peak pressure on the impacted surface increases with increasing flow rates. As the fluid approaches the bottomhole the streamlines are overlapping and the impact force decreases with increasing rotational speeds.