Experimental study of the dynamic mechanism on gas bubbles migration, fragment, coalescence and trapping in a porous media

摘要

Immiscible gas injection recovery is one of the most important methods used for EOR. However, it is very difficult to directly observe the flow of gas bubbles in the reservoir stratum. In our experimental work, we investigated visually the morphological configurations of gas bubbles migration, fragment, coalescence and trapping in different liquid-simulated porous media packs of glass beads. Also, the volume fraction of the trapped gas bubbles in the drainage process were measured. A fast video recording technique was used for the visual observations of the morphological characteristics of the rising gas bubbles in the saturated porous media. The obtained experimental images recorded reveal three types of the rising migration bubbles namely: free migration in the pore throat, attached wall migration on the beads and deformation migration. Additionally, coalescence and fragment have an interdependency for a rising gas bubble. The adsorption and capillary trappings are both two kinds of important trapping mechanisms, which determine the volume fraction of the trapped bubbles. The volume fraction of the trapped bubbles increases with an increment in the gas injection time and rates with the trapped bubbles fluctuating upward and downward due to the more coalescence and fragment after a long gas injection time/period. Lastly, the volume fraction of the trapped bubbles increases with a decrease in the inclination angles and porosities, which influences the areal sweep efficiency for enhanced liquid recovery in a porous media.