Comparison of Carbon Dioxide and Methane as Additives at Steamflood Conditions

Abstract

Summary Heavy-oil production from a steamdrive may be improved by adding gases to reduce the steam requirement, to swell the oil, and to reduce oil viscosity. To help compare carbon dioxide (CO2) and methane (CH4), two of the most reasonable choices of gaseous additives, we measured the viscosity and density of a Lloydminster- type heavy oil when saturated with each gas at a single pressure at 25°, 80°, and 150°C. Our measurements were repeated in the presence of a water phase to address the lingering questions about the effect of water on this equilibrium, especially at 150°C. In addition to confirming trends identified by previous authors, the results showed that the benefit of dissolved CH4 diminishes much less rapidly with rising temperature than for CO2. By 150°C the differences in benefit are small, which indicates that CH4 could be a more economical choice than CO2 as a steam additive in many reservoirs. In addition, no effect of equilibrium water was detected.