Modeling Churn and Annular Flow Regimes in Vertical and Near-Vertical Pipes with Small and Large Diameters

Abstract

This thesis presents an improved model for gas-liquid two-phase flow in churn and annular flow regimes for small- and large-diameter in vertical and near-vertical pipes. This new model assumes that a net liquid film moves upward along the pipe wall and gas phase moves upward, occupying the majority of the central part of the pipes, and forming a gas core, in both flow regimes. The model is validated using field and laboratory experimental data from several different studies from the literature, in terms of pressure along the wellbore or bottomhole pressure for field conditions (for high-pressure flows in long pipes, and using hydrocarbons fluids), and pressure-gradient and liquid holdup for experimental laboratory data, for pipe diameters ranging from 0.0318 to 0.279 m (1.2520 to 11 in). The proposed model presents an overall better performance when compared to several other multiphase flow models widely used in the oil and gas industry. This model is also tested in the application of prediction of liquid loading in gas wells. Liquid loading is generally associated with a reduction of ultimate recovery of gas wells. Liquid loading inception is simulated using nodal analysis technique. This study suggests that liquid loading initiates when the Inflow Performance Relationship (IPR) curve is tangent to the TPR curve. This study also proposes a new concept of a modified Tubing Performance Relationship (TPR) curve in order to predict the time liquid loading initiates and when the gas well will stop flowing after reaching this condition. Field data is used for validation of this approach. The use of conventional models shows a significant mismatch predicting the inception of liquid loading, while the use of the tangent concept reduces this mismatch significantly.