Solubility and Extraction in Multiple-Contact Miscible Displacements: Comparison of N2 and CO2 Flow Visualization Experiments

Abstract

Summary Results of secondary and tertiary displacements of Maljamar crude oil by N2 and CO2 are compared to examine the effects of solubility and extraction on local displacement efficiency. The flow visualization experiments were performed in pore networks etched in glass plates. In those experiments, the much higher solubility of CO2 in the oil caused only marginal improvement in displacement efficiency over that observed for N2, which was much less soluble. At pressures high enough for CO2 to extract hydrocarbons efficiently, however, displacements were much more efficient. Secondary and tertiary displacements in a more heterogeneous glass model are also compared. In a secondary displacement with high solubility but low extraction, adverse capillary and viscous effects limited the area swept to preferential flow paths. High CO2 solubility did not appear to have significant effects. When water was present in tertiary displacements with efficient extraction and high solubility, combined effects of viscous instability, capillary forces, and heterogeneity sharply reduced sweep efficiency below that observed in secondary displacements in the same model.