Hydrocarbon recovery from porous media using supercritical fluid extraction

Conventional techniques of oil recovery can deliver, on average, only one-third of the crude oil present in the reservoirs while two-thirds of the oil will remain in the rock formations. With the shortage of conventional oil in the world, enhanced oil recovery processes are necessary to free more of the trapped oil from rock formations. The main objective of this project is to assess the extraction efficiency of supercritical (SC) CO2 for oil recovery from soil and rocks. Effects of temperature (40-160° C), pressure (80-350 bar), modifier (heptane, toluene), water content (0-20%), CO2 flow rate (1-5 ml/min), grain size (100-600 μm), and type (sand stone and limestone) on the extraction capacity of SC CO2 and on the composition of extracted hydrocarbons were investigated. Results showed that SC CO2 alone (at 350 bar and 160° C) is capable of extracting over 78% of the original oil present in the soil samples. The extraction efficiency of CO2 increased with pressure and either decreased with temperature (at 250 bar) or remained almost the same (at 350 bar). Chemical modification of CO2 by adding organic solvents increased the extraction efficiency. Presence of water at high concentrations (> 10%) drastically reduced the extraction efficiency.