Pyrolytic data verification in potential assessment and catagenetic transformation of the Proterozoic low-carbon formations of Eastern Siberia

Abstract

The ancient Precambrian formations of Eastern Siberia include oil and gas source rock (SR) interlayers, but in most cases, they can’t be classified as high-carbon ones, because the actual organic carbon content in these strata is low and rarely exceeds 10%. This point effect the approach to the available geochemical data interpretation and the method of quality samples selection. The aim of the work was to determine methods for pyrolytic data verification and the oil and gas Lower Vendian SR quality assess, that based on the results of geochemical researches. It was identified, that before SR catagenetic transformation analyzation by the Tmax parameter and determining the OM type, samples with a low generation potential or with the migrated bitumen presence should be excluded from the consideration. The presence of secondary epigenetic bitumen also indicates the active HC fluids migration within the basin. After data verification, the SR properties were assessed. So lower Vendian SRs have OM with a satisfactory and high generation potential, second type and low maturity in most cases. The oil and gas window zones are located within large depressions and troughs. In addition, the local heating was noted in zones with a large number of faults, where the heating was conducted due to the intrusions introduction and the hydrothermal fluids action.