Perspectives on Shale Resource Plays

Both conventional and unconventional petroleum systems assessments involve detailed analysis of the components and processes involved in the generation and storage of petroleum. A key of this assessment is the characterization of organic matter and its thermal maturity. Assessment of kerogen type and thermal maturity requires the use of multiple techniques to fully assess the petrological and geochemical risks associated with exploration and production (E&P) prospects and plays. A combination of visual and chemical techniques provides essential data to elucidate the various risks associated with finding and producing commercial amounts of petroleum. Visual techniques for kerogen characterization provide information that cannot be derived strictly from chemical data. Similarly, chemical data enhances the findings of the organic petrologist. Kerogen type assessment is best provided by visual kerogen analysis and various chemical analyses such as pyrolysis gas chromatography. Detailed analysis such as pyrolysis gas chromatography and laboratory maturation techniques such as microscale sealed vessel analysis provides detailed chemical composition and product type at various levels of thermal maturity. Imaging techniques have advanced the understanding of petroleum storage in source rocks as well as the mineralogical variability. Further input is needed from organic petrologists to understand the full complexity of the organic and inorganic matrix. Thermal maturity is also best addressed by a combination of visual and chemical techniques. The most common technique and industry standard is vitrinite reflectance. However, on marine shale source rocks, vitrinite is typically only present in minor amounts and is morphologically similar to bitumen or at higher thermal maturity, pyrobitumen. A solution to this conundrum is to perform vitrinite reflectance measurements on shales or coaly organic matter up-hole from the shale reservoir of interest. Identification of reasonably organic-rich and more mixed to gas prone organic matter provides indications of up-hole samples more suitable for vitrinite reflectivity analysis. These data can then be projected through the shale of interest if the burial history is understood. Clarification of thermal maturity can be addressed by utilization of chemical techniques especially quantitative aromatic hydrocarbons. It is essential to provide E&P teams interpreted kerogen and thermal maturity data. Otherwise, the complexity of the data can easily confuse experts and management that are not familiar with the idiosyncrasies of such analysis. Not all data can be considered equal due to various limitations such as sample choice for specific analysis.

Keywords: Shale resource plays, Unconventional shale resources development, Organic Geochemistry, Imaging, Interpreted thermal maturity (i%Roe), Sweet spotting.