The Sukhana Sedimentary Basin, Siberian Platform: Source Rock Characterization and Direct Evidence of Oil and Gas Presence
Authors: Kashirtsev V.A. , Parfenova T.M. , Moiseev S.A. , Chernykh A.V. , Novikov D.A. , Burshtein L.M. , Dolzhenko K.V. , Rogov V.I. , Mel’nik D.S. , Zueva I.N. , Chalaya O.N. 
Published: October 2019

—Despite the known large natural bitumen accumulations and oil seeps in several kimberlite pipes along the periphery of the Sukhana sedimentary basin, interpreted as direct evidence of petroleum potential, the basin still remains one of the least studied (by geological and geophysical methods) regions of the Siberian Platform. The platform cover of the basin is composed by Riphean, Vendian, and Cambrian clastic (terrigenous) and carbonate deposits reaching 5.5–6 km in thickness in the central part of the basin. The hydrogeological specifics of the basin is largely governed by its location within the northern geocryological zone (Olenek cryoartesian basin) and is expressed as a continuous distribution of permafrost aggraded into the permafrost zone of unique thickness. Direct indicators of ore and gas presence are the East Anabar, Central Olenek, and Siligir–Markha fields of natural bitumen and oil shows in kimberlite pipes of the Daldyn–Alakit region (Udachnaya pipe). The bituminous-carbonate sediments of the Khatyspyt Formation (Vendian, Ediacaran) and the highly carbonaceous carbonate–siliceous–shaly sediments of the Kuonamka Formation (lower–middle Cambrian) are the Sukhana source rock complexes. The geochemically substantiated genetic relationship between the natural bitumen deposits of the East Anabar field and the organic matter of the Vendian Khatyspyt Formation makes it possible to estimate the area of the spread of the latter far to the west, beyond the axial part of the basin. Gammacerane, inherited from the organic matter of the Khatyspyt Formation and ranking as well-preserved and most characteristic biomarker of these bitumens, provides a compelling evidence of their consanguinity. The bitumen and oil of kimberlite pipes in the south of the basin, in the area of reefs of the Siligir–Markha bar, are similar in all geochemical criteria to oils of the Nepa–Botuobiya anteclise. In particular, in primary geochemical characteristics (12- and 13-monomethylalkanes, unique secosteranes, identical carbon isotope composition, etc.) the oils of the Udachnaya pipe are identical to the Irelyakh oils (oil field in the Mirnyi arch). No accumulations of oil or natural bitumen genetically related to the highly carbonaceous Kuonamka Formation have been found within the basin. At the same time, “intraformational” shows of viscous oil, solid bitumen, and allochthonous bitumen (bitumen extracted with chloroform) were documented directly in the sections of the formation, which makes the sedimentary basin a very attractive target for “shale oil” exploration. As for the regional assessment of the petroleum potential of the entire basin, its axial part (Sukhana depression) complicated by local uplifts is of the greatest interest. Both the Khatyspyt and Kuonamka Formations are widespread there, with the thermal maturity of their organic matter corresponding to the oil window. In addition, the regional reservoirs at the Vendian–Cambrian boundary have good petrophysical properties on both the western and the eastern flanks of the basin.