Supercritical fluid extraction for the determination of optimum oil recovery conditions

CO₂ under supercritical (SC) conditions is a powerful solvent capable of extracting hydrocarbons from crude oil. The extraction capacity of CO₂ is a function of pressure, temperature and composition of the crude oil. This paper presents the results of a laboratory study investigating the capacity of CO₂ to extract hydrocarbons from an oil-saturated soil under a wide range of pressures and temperatures (80-120 bar for temperatures ranging from 40 to 60 °C and 200-300 bar for temperatures varying from 100 to 140 °C). The soil samples were collected from Sahel oil filed, which is near Bu Hasa oil field (Abu Dhabi, UAE) where the crude oil was obtained from. The extracted oil from the SC CO₂ process and the residual oil remaining in the soil sample were analyzed by gas chromatography to shed more light on the extraction phenomenon. Extraction efficiency of CO₂ increased with pressure and decreased with temperature. Moreover, the amount of extracted heavy fractions increased with pressure for all temperatures. On the other hand, the amount of extracted heavy hydrocarbons decreased with temperature for the low pressure range (80-120 bar) and remained the same for the pressure range of 250-300 bar. The maximum extraction efficiency of CO₂ was 72.4%, which was obtained at the highest pressure (300 bar) and a temperature of 100 °C.