A hydrate shell growth model in bubble flow of water-dominated system considering intrinsic kinetics, mass and heat transfer mechanisms

The gas hydrate formed in the wellbore or pipeline may pose severe challenges to pressure control and flow assurance. One key issue to address the hydrate problem is the intercoupling of hydrate shell growth characteristics and multiphase flow behaviors, which has not been studied thoroughly in the bubble flow of a water-dominated system. In this study, we develop a fully coupled hydro-thermo-hydrate model considering the interactions of hydrate intrinsic kinetics, mass and heat transfer, and hydrodynamics mechanisms. In the model, the varying concentration of gas on the outside of a hydrate shell, is introduced to describe the dynamic equilibrium between the gas outward diffusion within the hydrate shell, hydrate formation kinetics at the hydrate/liquid interface, and gas dissolution into liquid. The simulation results agree well with the experimental data. Using the proposed model, we study a special kick development mechanism caused by the phase transition of gas traps during deepwater horizontal drilling. The simulated results show that there exists a hydrate phase stability field in the wellbore during deepwater drilling. As the migration of gas traps, the hydrate growth on the bubble surface, which is closely related to the formation and decomposition of hydrate and the dissolution and desolvation of gas, may result in an abrupt and rapid gas kick. The proposed model adds further insights into quantitatively characterizing the hydrate growth and interphase mass transfer rules in the bubble flow of water-dominated systems.