Numerical simulation and experiment of the annular pressure variation caused by gas kick/injection in wells

• A transient gas–liquid DFM based on Shi slip relation was proposed for simulating gas kick/injection.
• The simulation results agreed well with data of laboratory experiment and full-scale experiment.
• For fully developed flow, annular pressure variation caused by varying gas inflow rate could be delayed.
• In vertical well, the gravity force had a greater influence on pressure variation than friction force.

Transient gas–liquid two-phase flow usually occurs in wells because of gas inflow. The objective of this paper is to investigate the pressure variation in wellbore caused by gas kick/injection. A general and simple drift flux model based on Shi slip relation is presented for dynamic two-phase flow in wells. The model is numerically solved by the finite volume method and AUSMV scheme. Moreover, a laboratory experiment is implemented to simulate the process of gas kick/injection for a high gas volume fraction. The pressures at different depths of the test section of the annular tube are measured, and the change of the flow behavior is observed during the experiment. The laboratory experiment results and the data of a full-scale experiment provided by Lage et al. (2003) indicate that the annular pressures increase at first and subsequently decrease during the process of gas injection in the experiments, and the pressure increases slightly in the real well. Comparisons between the simulation results and the data of the two experiments show fair agreement in terms of the pressure. The simulation results indicate that the gas and liquid mass flow rates and well depth have a strong influence on the variation of the bottom pressure caused by gas kick/injection. The liquid viscosity slightly affects the variation of the bottom pressure.