Lattice Boltzmann Method simulation of wellbore gas–liquid​ phase transition

Abstract

Whenever the drilling wellbore is at the state of gas–liquid two-phase flow, gas slips and migrates along the drilling fluid. Due to the decreased wellbore temperature and pressure during gas migration, gas volume will gradually increase. When the temperature and pressure reach the critical value of gas–liquid phase, phase change occurs. The volume of natural gas expands suddenly, and a large amount of gas is generated. It easily leads to a well blowout, which is a great challenge to well control. Therefore, analyzing the gas–liquid phase changes in drilling wellbore has important practical significance for realizing well control safety. In this paper, Lattice Boltzmann Method (LBM) is applied to simulate phase transition of wellbore gas–liquid​ two-phase system. Research results show that gas–liquid distribution after phase transition is closely related to the system original density. Compared to the critical density of gas–liquid phase change, when the system original density is lower, continuous gas forms in wellbore. While the system original density is higher, gas phase breaks out into small bubbles and migrates along the wellbore. Phase distribution directly determines gas–liquid two-phase flow pattern in wellbore, which is crucial to wellbore pressure accurate prediction. Some valuable attempts are conducted to investigate gas–liquid two-phase flow in wellbore by using LBM in this research.