Optimizing Parameter "Total Organic Carbon Content" for Shale Oil and Gas Resource Assessment: Taking West Canada Sedimentary Basin Devonian Duvernay Shale as an Example

Total organic carbon (TOC) content is regarded as one of the important standards for shale oil and gas "sweet spot" prediction and potential resource evaluation. Taking Devonian Duvernay shale in West Canada sedimentary basin as an example, in this paper uses scanning electron microscope and methane adsorption measurements to discuss the weakness of using measured TOC as parameter for reservoir and gas capacity. Initial TOC was restored, and the measured and initial TOC vs. Langmuir volume was studied to reveal their difference as evaluation parameter. The result suggests that the difference between initial TOC and measured TOC varies significantly with the ratio ranging from 1.69-1.02, which increases with the thermal maturity. Thus, low measured TOC value doesn't represent low initial TOC value. Organic pore growth in Duvernay shale has no correlation with measured TOC, which means that the measured TOC is not the optical parameter to describe shale reservoir. Compared with measured TOC, Langmuir volume exhibits better correlations with initial ones, indicating initial TOC determines gas-adsorption behavior. Thus, in this paper it is evidenced to use initial TOC, rather than measured ones, as shale oil and gas evaluation parameters.