The ''S'' sand Reservoir B CO2 pilot was designed to demonstrate the feasibility of a downward CO2 displacement in a steeply dipping, high temperature and high pressure Gulf Coast reservoir. Research results show that CO2 injection is not a miscible process at the S Sand Reservoir B (SRB) conditions but a CO2-crude oil vaporization process. Vaporization means that the CO2 strips and replaces hydrocarbon components from the crude. The stripping is enhanced with repeated contacts with fresh CO2. Results of experiments indicate that CO2 diluted with five to ten percent of plant gas (primarily methane) would result in a miscible-like displacement process. It also appears that based on slim tube experiments alone, undiluted CO2 might be the most efficient material for the SRB field test. Under SRB reservoir conditions, CO2 not diluted with light hydrocarbons is more dense than the reservoir oil. Fortunately, process mechanisms can work to the benefit of displacement stability. Upon mixing SRB oil and CO2, two phases are formed. The CO2 rich vapor phase is less dense than the liquid phase. Based on a zero dimensional analysis and the phase behavior study results, the vertical displacement by CO2 PG or CO2 alone should be gravity stable at the expected flood conditions. A mixture of five percent by volume of plant gas and 95 percent CO2 is the recommended injection system for this field test. This dilution should allow gravity forces to augment the vaporization process.