Movable oil extraction from shale with supercritical carbon dioxide

Movable oil extraction experiments from the lower part of third member of Paleogene Shahejie Formation (Es₃^L) in the Zhanhua Sag of Jiyang Depression of Bohai Bay Basin were made to address problems on matrix shale oil exploitation. Various negative pressure and different supercritical carbon dioxide fluid pressures at strata temperature were used after fracturing in a closed system. Only traces of light hydrocarbons (< C₁₅) can flow at strata temperature and negative pressure. The carbon number of the main components of movable oil increases with extraction time with supercritical carbon dioxide under the same strata temperature and fluid pressure, and the contents of movable oil increase with fluid pressure increase. The light and medium weight hydrocarbon components in the free state are extracted effectively and some heavy hydrocarbon components in the bound-state (adsorption and miscible state) are also extracted. It suggests that the technology of supercritical carbon dioxide has a good prospect for improving recovery efficiency of matrix shale oil.