Wellbore Flow Analysis of a Gas-Kick Well During Shut-In

Due to the effects of wellbore storage, shut-in period allows additional inflow of gas bubbles into the annulus. Wellbore and casing pressures rise during shut-in of a gas kick as a consequence of gas upward migration and gas compressibility, which will threaten the safety of well control. Therefore, the variation law of surface and wellbore pressures for a gas kick well during shut-in should be investigated. Based on wellbore storage effect, a new model to the wellbore and casing pressure build-up during shut-in for a gas kick well is developed in this paper. Simulation results show that at different gas kick volumes, the rate of bottom-hole pressure rise increases as the permeability decreases. And surface casing pressure stabilizes quickly for low permeable formations. However, at equal initial annular gaseous volume, the rates of rise of the bottom-hole and surface casing pressures for low permeable formations are slower than for high permeability formations.