Experimental study on the flow characteristics of supercritical CO2 in reservoir sandstones from the Ordos Basin, China

Abstract

Understanding the flow characteristics of supercritical CO₂ in dry sandstones or those with low water content provides crucial information on the flow behavior in near-wellbore zone. We conducted supercritical CO₂ core flooding experiments using sandstone cores extracted from potential CO₂ reservoirs in the Ordos Basin, China. During the experiments, we reduced the water content of saturated cores by flushing with dry CO₂ and subsequently vacuumizing them at a temperature of 35°C to simulate sandstones with low water content. The experimental results demonstrate that the CO₂ permeability was initially high during the low differential pressure stage and remained constant as the differential pressure increased. In the carbonic acid solution injection experiment, we observed an increase in the flow rate of the solution with the continuous interaction in the cores from the Shanxi and Shihezi groups, while the Yanchang group exhibited the opposite effect. This increase in permeability can be attributed to mineral dissolution and the loss of fine particles. Conversely, the blockage of fine particles or the precipitation of dissolved minerals may lead to a decrease in permeability. After the CO₂–water–rock interaction, the CO₂ permeability decreased compared to before the interaction, indicating that adsorbed water, the precipitation of dissolved mineral, or pore throat blockage by fine particles could induce this permeability decrease. The impact of adsorbed water on the decrease in CO₂ permeability is significant. Additionally, the CO₂–water–rock interaction caused corrosion on the anorthite surface. Furthermore, calcite dispersed in connected pores displayed a more pronounced dissolution compared to cemented calcite. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.