Initial insights into releasing bound biomarkers from kerogen matrices using microscale sealed vessel catalytic hydrogenation (MSSV-HY)

Abstract

Microscale Sealed Vessel pyrolysis (MSSV) is a microanalytical technique originally developed for artificially maturing sedimentary organic matter and examining the bulk compositional relationships between kerogen and petroleum. Here, we explore the possibility of modifying the standard MSSV pyrolysis approach to increase biomarker release from macromolecular matrices. This is termed microscale sealed vessel catalytic hydrogenation, or MSSV-HY. Tetralin is employed as hydrogen donor and dispersed sulfide molybdenum as catalyst. Using two kerogen concentrates, one of low maturity (vitrinite reflectance: 0.6 %Ro) and the other over-mature (1.8 %Ro), from the Dalong Mudstone (Permian, Sichuan Basin), the effects of tetralin and catalyst alone and as mixtures, and the tetralin/kerogen ratio on biomarker release have been investigated, and optimum conditions identified. A comparison of results with those of HyPy enabled the utility of the method to be assessed. Biomarkers were generated from the over-mature sample and preserved using MSSV-HY, whereas they were absent in MSSV products. Biomarkers released from the low maturity sample using MSSV were devoid of extended hopanes, and dominated by C27 steranes, whereas the MSSV-HY products were rich in Tm, the extended hopanes, and with C27–C29 regular steranes. MSSV-HY products showed some similarities to HyPy products. The steranes from MSSV-HY were very similar to those from HyPy; although some differences in hopane distributions were discernable (e.g., the abundances of Ts and C30 hopane) due to varied contribution of occluded OM in the HyPy and MSSV-HY analyses. This proof of concept study has shown that off-line MSSV-HY shows great promise as a means for releasing bound biomarkers and reducing secondary cracking because of catalyst associated pressure increase in the MSSV tubes. Its currently planned area of operation is in petroleum systems.