Free and sorbed low-to-medium molecular weight thermovaporized hydrocarbons (<C₂₀) are the main organic compounds released at the temperature range corresponding to the Rock-Eval^® Shale Play^TMSh0 parameter (100°C–200°C), whereas medium and high molecular weight thermovaporized compounds (< C₃₀) are the predominant components that are thermal released in the temperature range corresponding to the Shale Play Sh1 parameter (200°C–350°C). Now, an analytical methodology is proposed here to predict the quantity of free versus sorbed hydrocarbons still present in any liquid-rich sedimentary rock. The method compares shale play parameters (Sh0 and Sh1) obtained from both whole-rock samples and their corresponding organic matter (OM) concentrates isolated by standard nonoxidizing acid treatments and drying procedures. The hydrocarbon content obtained from whole rock (HC_Total,rock) is mainly considered as the total amount of free liquid hydrocarbons (HC_Free) and sorbed liquid hydrocarbons (HC_Sorbed,OM) still contained in the investigated rock sample.

The hydrocarbon content obtained from OM concentrates, however, only reflects the sorbed liquid hydrocarbons.

In these equations, TOC_rock is the total organic carbon of the rock sample; TOC_OM corresponds to the TOC content of the OM concentrate sample; Mass_rock is the initial mass of the rock sample; Mass_OM is the initial mass of the OM concentrate sample; FIDsignal_rock^Sh0+Sh1 is the flame ionization detection (FID) signal that corresponds to the global surface area under each thermal peak (Sh0 and Sh1) generated by the Rock-Eval FID; FIDsignal_OM^Sh0+Sh1 corresponds to the global surface area under each thermal peak (Sh0 and Sh1) measured by the Rock-Eval FID between 100°C and 350°C after the themovaporization of the OM concentrate sample. Free liquid hydrocarbons are finally calculated as the difference between these last two values (HC_Free &equals; HC_Total,rock − HC_Sorbed,OM). This paper illustrates the application of this methodology on rock samples derived from the Vaca Muerta Formation (Argentina). Along the selected vertical profile, the lower rock interval contains approximately 60% of sorbed liquid hydrocarbons, whereas the upper sample contains more than 90% free liquid hydrocarbons. The parameters FreeHC^Sh0 and FreeHC^Sh0+Sh1 could be used to identify potential producible free liquid hydrocarbons intervals in early exploration campaigns.