Modelagem mecanicista do início do fenômeno de surging em bombas centrífugas operando com escoamento bifásico líquido-gás

Abstract

In the oil industry, Electric Submersible Pumping (ESPs) stands out as one of the most used techniques in artificial lifting. However, reservoirs contain significant amounts of natural gas, giving rise to the two-phase liquid gas flow in the production lines. Thus, the presence of the gas phase in the flow must be considered whenever ESPs are used. Depending on the operating conditions, ESPs can be subjected to a significant accumulation of gas in the rotor channels, reducing the flow area of the liquid phase and generating a significant drop in performance a phenomenon known as surging. The occurrence of surging significantly affects the production and life of the pump. With this scenario in mind, the present study introduces a mechanistic model developed to predict the starting point of the surging phenomenon in centrifugal pumps operating with liquid-gas flow. The modeling was developed from a balance of forces on a gas bubble in the rotor channel, where the surging phenomenon occurs. The closing relationships, necessary for the mathematical model, were based on theoretical models and with minimal dependence on empirical correlations, which were corrected and validated with experimental data existing in NUEM and the literature. The sensitivity of both the drag coefficient and the relative velocity, which are relevant interphase parameters of the model, as well as the performance of the model for different operating conditions (phase flow rates, rotational speed, and fluid properties) were evaluated. It is expected that the mathematical model can improve the prediction of the stable operation window of BCSs in the presence of liquid-gas flow, outside the starting point of the surging phenomenon. Among other contributions, this can provide better guidance to engineers in their artificial elevation projects and, as a whole, improve the understanding of the surging phenomenon.