This invention relates to the extraction of oil shales and tar sands by using a solvent under supercritical conditions at a temperature within 200.degree. C. or its critical temperature in order to effect extraction of kerogen from the sand or shale.
In the case of shales considerable heat needs to be applied to the shale before effective extraction can occur and extraction in this case may be carried out at a temperature within the range of 370.degree. to 450.degree. C.