Identification of the source rock potential and distribution area is the most important stage of the basin analysis and oil, and gas reserves assessment. Based on analysis of the large geochemical and geological data base of the Petroleum geology department of the Lomonosov Moscow State University and integration of different-scale information (pyrolysis results and regional palaeogeographic maps), generation potential, distribution area and maturity of the main source rock intervals of the Barents-Kara Sea shelf are reconstructed. These source rocks wide distribute on the Barents-Kara Sea shelf and are characterized by lateral variability of generation potential and type of organic matter depending on paleogeography. During regional transgressions in Late Devonian, Early Permian, Middle Triassic and Late Jurassic, deposited source rocks with marine organic matter and excellent generation potential. However in the regression periods, during the short-term transgressions, formed Lower Carboniferous, Upper Permian, Induan, Olenekian and Late Triassic source rocks with mixed and terrestrial organic matter and good potential. Upper Devonian shales contain up to 20.6% (average – 3%) of marine organic matter, have an excellent potential and is predicted on the Eastern-Barents megabasin. Upper Devonian source rocks are in the oil window on the steps, platforms and monoclines, while are overmature in the basins. Lower Permian shale-carbonate source rock is enriched with marine organic matter (up to 4%, average – 1.4%) and has a good end excellent potential. Lower Permian source rocks distribute over the entire Barents shelf and also in the North-Kara basin (Akhmatov Fm). These rocks enter the gas window in the Barents Sea shelf, the oil window on the highs and platforms and are immature in the North-Kara basin. Middle Triassic shales contain up to 11.2% of organic matter, there is a significant lateral variability of the features: an excellent generation potential and marine organic matter on the western Barents Sea and poor potential and terrestrial organic matter in the eastern Barents Sea. Middle Triassic source rocks are in the oil window; in the depocenters it generates gas. Upper Jurassic black shales are enriched with marine and mixed organic matter (up to 27,9%, average – 7.3%) and have an excellent potential. On the most Barents-Kara Sea shelf, Upper Jurassic source rock are immature, but are in the oil window in the South-Kara basin and in the deepest parts of the Barents Sea shelf.

No abstract

The idea of this work is to compare the results of geochemical and statistical analyzes in the study of organic matter in extracts of oil and gas source rock. The object of the study were the samples of oil and gas source rocks of the Tutleim and Tyumen Formations, as well as oil samples of the Vikulov Formation and Jurassic and pre-Jurassic deposits in the western part of the West Siberian basin. Among the methods of statistical analysis, the principal component method and the random forest method were used. A heat map of correlations was used as visualization tools. The principal component method helped us to reveal a clear difference between the organic matter of the Tutleim and Tyumen source rocks. The random forest method and the heat map made it possible not only to identify the distinctive geochemical properties for this strata, but also reveals the geological factors of their distinction. Thus, the organic matter of Tyumen source rock turned out to be more mature and it has relatively larger contribution of terrestrial organic matter compared to the Tutleim one. The same set of methods is applied to oil-source rock correlation. The oils of the Vikulov Formation obviously originate from the Tutleim source rock. Oils of Jurassic and pre-Jurassic reservoirs have a predominant contribution of the Tutleim source rock and some similarity (up to 30 %) with the Tyumen one. Oils from the Vikulov Formations are less mature than oils from the Jurassic and pre-Jurassic rocks. This may indicate the continued migration of hydrocarbons to Jurassic and pre-Jurassic deposits and the cessation of migration in the past to the overlying Aptian–Albian Vikulov Formation. Geochemical analysis also revealed the geochemical properties responsible for the maturity of source rocks and the type of organic matter. It confirmed the conclusions made on the basis of the application of methods of statistical analysis.