The gravity dominated CO2 injection has received increased attention in the oil fields as it utilizes gravity force to stably displace the remaining oil after primary and/or secondary recovery. Effect of gravity is also important in some CO2 sequestration in aquifers. To visualize the fluid-solid interaction mechanisms at pore scale and to determine the controlling factors for a stable gravity dominated process, parameters such as fluid and porous media properties should be evaluated. The visualization of displacement process at the pore level could help to identify the critical range of controlling parameters. These visual experimental results could validate the modelling of fluid flow at pore scale. Therefore, an experimental study was conducted using a glass micromodel and visual results have been analysed. The details of experimental setup including micromodel construction, holding rig and the instrumentation have been addressed in this paper.

The experiments were conducted using CO2 injection to displace water at various rates under different gravity conditions. This displacement under pressure slightly above the atmospheric conditions has been characterized as partial miscible displacement. Experimental results determined the relationship of porous media characteristics such as dip angle and porous medium heterogeneities on the process at pore scale. The results were analysed using dimensionless Darcy Rayleigh number and mobility ratio to extend the results at larger scales and different fluids. The experimental results show that Darcy-Rayleigh number is proportional to the displacement efficiency however; at moderate flow rates and the dip angle of 45°, lower recovery was observed compared to horizontal case. Also at dip angle of 45° and with higher viscosity of the defending fluid (lower mobility ratio) a more stable process was observed.

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