Characterizing the Precambrian Petroleum Systems of Eastern Siberia: Evidence from Oil Geochemistry and Basin Modeling

Abstract

Abstract Uncertainties regarding the number, location, and areal extent of Precambrian petroleum systems in Eastern Siberia are primarily attributed to a lack of direct source rock data. This study provides an indirect characterization of source rocks contributing to petroliferous areas (PAs) in the southern Lena-Tunguska region through an assessment of available geochemical data from oils and gases contained in reservoirs from the Vendian through lower Cambrian. Geochemical data and basin modeling were used to: (1) establish the number of source rocks contributing to hydrocarbon accumulations; (2) define source rock depositional systems and lithology; (3) estimate source rock thermal maturity; and (4) predict source location and migration patterns. In this study, geochemical interpretations are made on oil and gas data available from the published literature and GeoMark Reservoir Fluid Database and include comparisons of samples from the Nepa-Botuoba, Angara-Yenisey, Katanga Saddle, and Baykit PAs. One-dimensional maturity models of pseudo-wells in the Nepa-Botuoba and Angara-Yenisey PAs are constructed incorporating inferred source rock characteristics to constrain the timing and thermal histories of the petroleum system components. Results from this study confirm that the Eastern Siberian oils are non-biodegraded and were generated within the main oil window from Precambrian sources. Significant geochemical differences among oils from the Nepa-Botuoba, Angara- Yenisey, and Baykit PAs strongly support hydrocarbon generation from three distinct source rocks. Furthermore, biomarker and bulk oil parameters indicate lateral hydrocarbon migration across the Nepa-Botuoba anteclise that originated from a single source. These findings both advance the current understanding of the East Siberian petroleum systems and have direct consequences for prediction of fluid characteristics at the field and reservoir scales.