Combined multi-fluid and drift-flux approaches for analysis of pipe flows.

We propose an approach for generalization of 1D transient model for multiphase flows. It allows to combine an arbitrary number of phases with interaction defined by multi-fluid and drift-flux models. Commonly a fluid carries a number of components. The model is based on a graph of fluids and components, where on higher level the flow of several fluids is governed by the multi-fluid approach, while on lower level the relative motion of components within each fluid is described by drift-flux relations. The proposed model is applied to flows in oil and gas wells. The model is implemented numerically using a SIMPLE-like iterative scheme with the geometry conservation based algorithm (GCBA). The numerical realization of the algorithm for an arbitrary number of fluids and components is presented. For illustration, particular cases are considered which are relevant to wellbore flows in oil and gas applications. The introduction of drift-flux correlations into the numerical implementation is discussed. The code is validated against experimental flow patterns and stability study of stratified flows. The typical graphs for gas/liquid transport are discussed. The simulation of phase segregation in a vertical pipe demonstrates the flexibility of model. [ABSTRACT FROM AUTHOR]