Gas Migration Patterns in Porous Media When Gas is Injected at Constant Rate From a Point Source:Determination of Critical Gas Saturation (abstract)

摘要

This paper aims to elucidate the pore level physics of gas migration patterns when gas is injected from a point source at constant rate in a porous medium saturated with a wetting liquid and the gas migration is affected by the interplay of buoyancy forces,viscous forces and capillary forces.The critical gas saturation is a term used in 2-and 3-phase relative permeability measurements and the magnitude of critical gas saturation is often a point of disagreement.An experimental procedure developed for injecting an immiscible gas in packed columns of different cross-sectional area will be reported for measuring the gas hold-up at the time the gas bubbles start to exit the top of a vertically standing column.This gives a low bound on the magnitude of critical gas saturation and depends on the height of a system.By varying the permeability of packed-columns and the properties of liquid-gas fluid pairs,the critical gas saturation can be studied as a function of flow rate of gas injection,fluid properties and pore structure.These displacement conditions are typical of very unstable immiscible displacements,typical of solvent injection schemes in thick reservoirs.Flow visualization results obtained by conducting these experiments in sintered glass bead models with dimensions of 5mm thick by 400 mm wide and 600 mm tall illustrate that buoyancy and capillary forces dominate the gas migration patterns.