A Unified Gas/Liquid Drift-Flux Model for All Wellbore Inclinations

Abstract

Summary Implementation of a drift–flux (DF) multiphase–flow model within a fully coupled wellbore/reservoir simulator is nontrivial because it must adhere to a number of strict requirements to ensure numerical robustness and convergence. The existing DF model that meets these requirements is only fully posed from 2° (from the horizontal) to upward vertical. Our work attempts to extend the current DF model such that it is numerically robust, accurate, and applicable to all well inclinations. To gauge accuracy, model parameterization used 5,805 experimental data points from a well–established data set, along with a second data set comprising 13,440 data points extracted from the OLGA–S library (Schlumberger 2017b). Forecast accuracy of the proposed model is compared with that of two state–of–the–art DF models (applicable to all inclinations but unsuited for coupled simulation), and it exhibits equivalent or better performance. More significantly, the model is shown to be numerically smooth, continuous, and stable for cocurrent flow when implemented in a fully implicit and coupled wellbore/reservoir simulator.