Changes

Thus, to obtain the total oil yield from a rock sample by Rock-Eval thermal extraction, it is necessary to analyze a whole rock (unextracted) and an extracted rock sample where

Thus, to obtain the total oil yield from a rock sample by Rock-Eval thermal extraction, it is necessary to analyze a whole rock (unextracted) and an extracted rock sample where

:Equation 1

:<math>\text{Total oil} = (S1_{\text{whole rock}} - S1_{\text{extracted rock}}) + (S2_{\text{whole rock}} - S2_{\text{extracted rock}})</math>

This combines any free oil that elutes in the Rock-Eval S1 peak with heavier or pore space trapped oil that elutes from Rock-Eval in the pyrolysis (S2) peak. Certainly, not all of the total oil or extractable organic matter (EOM) is movable oil, but the free oil, as measured by S1, is the more movable oil fraction in the reservoir rock. This oil or bitumen retained in the rock until pyrolysis demonstrates the difficulty of recovering a high percentage of OIP out of an organic-rich tight shale.

This combines any free oil that elutes in the Rock-Eval S1 peak with heavier or pore space trapped oil that elutes from Rock-Eval in the pyrolysis (S2) peak. Certainly, not all of the total oil or extractable organic matter (EOM) is movable oil, but the free oil, as measured by S1, is the more movable oil fraction in the reservoir rock. This oil or bitumen retained in the rock until pyrolysis demonstrates the difficulty of recovering a high percentage of OIP out of an organic-rich tight shale.