Influence of thermal boundary condition on gas drainage from a semi-sealed narrow channel

摘要

Draining a viscous gas from a semi-sealed narrow conduit is a pore-scale problem of fundamental interest to primary fluid recovery from a petroleum reservoir as well as other applications. Such a drainage flow is entirely driven by the volumetric expansion of the gas and its mass flow rate is determined by the time-rate of decrease of the gas density within the conduit. It was found previously that when thermal effect is completely neglected, the drainage rate differs significantly from that based on the lubrication theory. The present work parametrically explores the influence of thermal boundary condition on the non-isothermal drainage flow from a narrow channel. It is found that as the wall transitions from adiabatic to isothermal condition, the excess density changes from a plane wave solution to a non-plane wave solution; and the drainage rate increases due to thermal damping on the wall, as a strong damping of the acoustic wave accelerates the process towards the final equilibrium. It is shown that when the exit is also cooled and the wall is non-adiabatic, the total recovered fluid mass exceeds the amount based on the isothermal theory determined by the initial and final density difference alone. The isothermal wall condition with the wall maintained at the initial gas temperature produces the most amount of fluid in the shortest time.