Experimental determination of relative permeabilities and critical gas saturations under solution-gas drive

Relative permeabilities are crucial to predict oil production from underground reservoirs. Multiple previous studies are limited to measuring/estimating relative permeabilities within the region where both phases are mobile. This study presents a novel experimental method to measure the oil relative permeability under presence of the trapped gas for gas-oil systems under depressurization. The experiments were carried out with the carbonaceous reservoir and outcrop samples. The results show a highly variable amount of immobile gas for North Sea chalk (from 8% up to 26% volume) and a significant reduction in oil relative permeability (up to 75%). The relative permeabilities were found to be power-law type functions. A comparison with the previously developed pore-network based model for gas-oil relative permeabilities is presented, allowing for reconstruction of both gas and oil relative permeability curves in the whole saturation range.