Development of a transient non-isothermal two-phase flow model for gas kick simulation in HTHP deep well drilling

摘要

The simulation of gas/liquid two-phase flow, considering the heat transfer between the annulus fluid and the surrounding environment, is of significance in predicting temperature and pressure distributions after a gas kick in HTHP deep well drilling. This paper presents the development of a transient non-isothermal two-phase flow model for the dynamic simulation of multiphase flow in the wellbore after a gas kick. The drift-flux model is used to describe gas/liquid two-phase flow, and multiple transient energy conservation equations are used for predicting temperature profiles of fluids in the drillpipe, drillpipe, the fluid in the annulus, casing string, and formation. As for numerical scheme of this strongly coupled model, the advection upstream splitting model (AUSMV) hybrid scheme is adapted for solving flow equations, while the finite difference approach is adapted for simultaneously solving energy conservation equations of the wellbore-formation system. Physical properties of gas and liquid phases are updated at each timestep. Predicted temperature and pressure distributions are validated against the field data. Flow behaviors predicted by the models with and without the heat transfer effect are compared. The effects of some major parameters (reservoir pressure, choke pressure, geothermal gradient, liquid mass flow rate) on temperature, pressure, and gas fraction distributions along the wellbore are investigated.