Effects of phase transition on gas kick migration in deepwater horizontal drilling

Abstract

A reliable kick simulator is a valuable tool in improving forward-looking predictions and making correct decisions during well control operations. In this study, a transient coupled model is developed for kick simulation in deepwater horizontal drilling. The model incorporates the mass, momentum, and energy conservation equations within the wellbore, and is coupled with a mass and heat transfer model for gas, liquid, and hydrate phase transitions, a slip relation for gas distribution and rise velocity, and a gas influx model for reservoir coupling. In the model, the transient mass transfer model is used in conjunction with an unsteady temperature model to study the effects of phase transition on gas kick migration.The simulator is validated through comparisons with the measurement results of a kicking well and full-scale kick experiments. The simulated results show consistent trends and are in good quantitative agreement with the collected measurement data.The kick development under various reservoir and construction parameters is analyzed. Gas dissolution and hydrate formation are found to significantly suppress the kick development process, especially at low influx rates or during the early kick stage. For a given pit gain of 3 m3, the error in kick prediction can reach 17.6% if phase transition effects are neglected.