A simulation method for gas-liquid splitting of fluid state in the well during the shutdown and continuous flow stage of intermittent production gas wells

In intermittent production wells, most of which are free of packers, such issues as the gas-liquid production splitting and the changes in liquid levels in annulus space and tubing with shut-in duration occur. The conventional responding measures determine the liquid level changes in the tubing and casing during the shut-in stage by simply assuming the flow direction of the gas and liquid in the tubing and casing at the shoe, which will introduce significant errors. By employing a discrete wellbore model, considering zero-liquid-flow two-phase flow dynamics and pressure equilibrium in the tubing and casing, a gas-liquid splitting model for intermittent gas wells was established. The model allows for the determination of critical parameters, such as pressure distribution, flow pattern changes, fluctuation in liquid column heights and bubble velocities during the zero-liquid-flow liquid column movement. Additionally, a full-scale wellbore experimental setup was constructed to simulate the ascent of bubbles during shut-in periods in intermittent production wells. By using high-speed cameras, the flow pattern distribution in zero-liquid-flow liquid column was captured, and the velocities and pressures of the bubbles in the liquid column were measured. The research results show that bubbles in the zero-liquid-flow liquid column exhibit dispersed and Taylor bubble forms, with Taylor bubbles becoming dominant as gas flow rates increase. The fluid pressures, flow pattern changes and bubble velocities in the established model were verified based on the experimental results, with an accuracy of over 95%. This model can accurately describe the gas-liquid flow pattern and pressure distribution during after flow stage for intermittent gas production wells.