Integrated Multiphase Flow Modeling for Downhole Pressure Predictions

Abstract

Abstract This work presents a new integrated multiphase flow model for downhole pressure predictions. The aim of the model is to produce relatively more accurate downhole pressure predictions under wide flowing conditions while maintaining a simple form. As a component of the integrated model, an improved two-fluid model for segregated flow is proposed. Results of the two-fluid segregated model are compared with five state-of-the-art existing models, while results of the integrated model are compared with three. The proposed integrated model incorporates the state-of-the-art onset of liquid loading predictive model. It classifies the flow into two major categories based on the onset of liquid loading, that are modeled by two different approaches respectively. If liquid loading occurs, the model uses a sophisticated drift-flux model which proved to be simple and relatively accurate when dealing with high liquid holdup. On the other hand, if liquid loading does not occur, an improved two-fluid segregated flow model will be used. The proposed two-fluid model was developed by improving the modeling of wetted perimeters and the liquid wall shear stress. The proposed new two-fluid model for segregated flow outperformed five other existing state-of-the-art models in predicting the liquid holdup and pressure gradient of 11 experimental datasets from the literature. The datasets range widely in pipe diameter, inclination angle, gas density, and flowing conditions. The model succeeds in capturing the effects of inclination angle, pressure or gas density, and liquid and gas superficial velocities on liquid holdup and pressure gradient. The new model eliminates the need of changing interfacial friction factor correlations when the flowing condition variates, significantly reducing the uncertainties and complexities associated with closure relationship selection and alteration. Moreover, the new integrated model outperformed the other multiphase flow models in predicting the downhole pressure of 313 field data points. When dealing with wells that have both segregated and intermittent flows, the new model produces outstanding results compared to other existing state-of-the-art models. In addition, it is capable of predicting the location and amount of liquid loading in a well, which will benefit the design and optimization of artificial lift processes.