Hidrodinâmica de fluidos de perfuração em poços de petróleo e reservatório: modelagem e simulação via CFD.

Abstract

Over the decades, oil exploration has become increasingly difficult, since the available reserves are increasingly scarce or are located in regions of complicated access and far from the coast with ever greater depths and because of this, oil well drilling operations have required greater knowledge of what happens at the bottom of the well during drilling for the process to take place with technical and economic feasibility. Aiming at expanding this knowledge, a study was carried out from the perspective of computational fluid dynamics, using the Ansys CFX® software in order to analyze the behavior of variables inside the well during the occurrence of a gas kick. To develop such a study, a representative mathematical modeling of the kick focused in the final part of an oil well and in the part of the reservoir adjacent to the well was defined. The model allowed the evaluation of dynamic behavior, through transient simulations, of variables such as pressure, volumetric fractions of the drilling fluid and gas and surface velocities of the fluids inside the well during drilling. Comparisons were made with drilling fluids with different rheological behaviors and three turbulence models. The influence of the amount of drilling fluid pumped, the amount of gas that invades the well and the porosity of the reservoir rock were also analyzed. Comparing the different types of fluid it was noted that Bingham's fluid was able to penetrate the reservoir rock with greater intensity compared to Ostwald de Waele's fluid. All the turbulence models analyzed showed similar behaviors and, therefore, suitable for the system under analysis. The simulations also showed that by increasing the amount of injected drilling fluid, the amount of gas that enters the well is reduced at the same time that there is an increase in the loss of fluid for formation and, furthermore, that by increasing the amount of gas in the reservoir, either by increasing its entrance speed or by increasing the porosity of the rock leads to an increase in speed and concentration of gas in the annular space. Finally, the influence of the rotation of the drilling column was analyzed, which, in turn, did not present significant deviations in the pressure of the well or in the concentrations with which the fluids move inside the annular space.