In the Neoproterozoic of the Aldan-Maya depression, the rocks of the Malgin (MF), Tsipanda (TF) and Kumakha (KF) Formations are enriched in organic matter (OM) and can be classified as source rocks. High generation potential is typical for the MF and TF (267–511 mg HC/g TOC). The thermal maturity level of OM corresponds to MC12 grade (Tmax is 438–443ºC). Based on the biomarker distribution, the biological precursors of OM in these formations are mostly prokaryotes, including cyanobacteria (hopanes, acyclic biomarkers) and to a lesser extent eukaryotes (the presence of steranes С27-C30) that lived in the Precambrian (the presence of 12- and 13-monomethylalkanes) marine (absence of continental biomarkers, the distributions of acyclic alkanes and steranes) basin with clayey sedimentation (high content of diasteranes). The absence of steranes in some samples (the absence of eukaryotes in the source OM), the MF is likely to have been partly deposited before the emergence of eukaryotes. Most samples have elevated concentrations of low-molecular tricyclanes (2C19-20/C23-26>1), which can be attributed to the specificity of the source biota, although it is not typical for marine OM. A rare homologous series of 2,7-dimethylalkanes that has been recently found by other researchers in some Precambrian strata is present in several samples of the MF and KF and totally absent from all samples of the TF. This may indicate the differences in its biota, depositional environments or its evolution during diagenesis and catagenesis. A distinctive feature of the TF is the high content of ethylcholestanes (C29/C27=2.5).
Two-dimensional modelling of oil-and gas generation history aimed at estimating oil-and gas potential of Paleozoic deposit have been carried out within understudied territory of the north-west of the Siberian platform. The structural imaging data and the results of the geochemical investigations of organic matter such as Rock-Eval pyrolysis, the analysis of the elemental composition of kerogen, the measurements of vitrinite reflectance in coaly inclusions of Upper Paleozoic rocks, the study of biomarker hydrocarbons distribution have been used in the research.This report presents the results of stratigraphic formation thickness analysis with the use of geological survey, drilling, seismic prospecting data; the results of basin modelling and reservoir properties data analysis. The necessity of further detailed study of oil-and gas accumulation zone, adjoining to the Lama-Khantaika trough, has been founded.The results achieved make it possible to carry out reconstruction of oil-and gas generation history, estimate resource base and justify the priority directions of licensing within the undistributed fund of the north-west of the Siberian platform.
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