A Double-Convergence Numerical Algorithm for Gas-Liquid Two-Phase Transient Flow Model

At present, controlled pressure drilling technology has become the main way of modern drilling technology because it can effectively reduce, and even avoid pressure-related complicated drilling accidents, which would greatly reduce drilling costs. As the key technology of controlled pressure drilling, multiphase flow simulator has aroused extensive attention of scholars and oilfield service companies, among which, the gas-liquid two-phase flow simulator is the most basic and common type. Gas-liquid two-phase transient flow model can accurately describe the complex multiphase flowing process in annuli during drilling and a series of models have been developed already. However, the numerical algorithms of them have rarely been mentioned. Aiming at a proposed gas-liquid two-phase transient flow model, which couples with well deliverability model and combines with the steady flow model of whole annulus inclination range, a double-convergence numerical algorithm is developed. Compared with actual field data, satisfactory numerical results show the efficiency of such an algorithm.