Generation characteristics of organic matter and distribution of biomarkers in bitumens of the Riphean, Vendian, and Cambrian source rocks of the Siberian Platform

Abstract

The distribution of biomarkers in bitumens of source rocks of different ages in the southern Siberian Platform is studied to elucidate the correlation between oils and their sources. It is shown that the bitumens of Riphean, Vendian, and Lower–Middle Cambrian source rocks are different in some parameters reflecting the type of primary biogenic material, first of all, in the distribution of n-alkanes and acyclic isoprenoids and in the portions of steranes and triterpanes among polycyclic naphthenes. The revealed difference in the composition and distribution of biomarkers in bitumens of source rocks of different ages can be used to identify the sources of hydrocarbons in discovered pools.

Bitumen Resources of the East Siberian Basin

“…Benthic stromatolite-forming bacteria, which appeared in the Early Riphean, together with the Ediacaran fauna and the oldest metazoan invertebrates, may also have contributed to the organic content. Dakhnova et al (2014) also reviewed the geochemical characteristics of Riphean, Vendian and Cambrian potential source rocks of the East Siberian Basin, and these authors agree that, despite their age, these deposits contained source material of sufficient quality and volume to have generated the hydrocarbons observed in Eastern Siberia.…”

“…A detailed analysis of biomarkers within Riphean, Vendian and Lower to Middle Cambrian source rocks within the Aldan-Maya Basin (and other areas of Eastern Siberia) was published by Dakhnova et al (2014). However, they did not use the data to tie allochthonous oils and bitumens to potential source rocks.…”

Geochemistry of Oils and Gases From the Verkhnechonskoye Field, East Siberian Basin: Application of Analytical Results to Reservoir Characterisation

“…The origin of oils in the Nepa-Botuoba Anteclise is poorly understood although it has been investigated for several decades (Petrov, , 1995Filiptsov et al, 1998;Kontorovich et al, 2000;Kashirtsev, 2004;Timoshina, 2005Timoshina, , 2020Neruchev et al, 2006;Melnikov et al, 2008;Bazhenova, 2010;Dakhnova et al, 2010 andKelly et al, 2011;Bazhenova et al, 2014;Boldushevskaya et al, 2021;Fadeeva et al, 2021;Sivkova, 2022). Three models of oil and gas generation, migration and accumulation have been proposed.…”

“…Therefore, Neruchev et al (2006) and Bazhenova (2010) suggested that Vendian source rocks generated most of the oil and gas in the Nepa-Botuoba Anteclise, although few organic-rich intervals of Vendian age have so far actually been identified. The highest TOC values (2.6-4.4%) occur in the Lower Vendian Seralakh Formation in well 2360 in the Ergedeya license area in the Fore-Patoma Trough (Bazhenova et al, 2014;Dakhnova et al, 2014;Fadeeva et al, 2021); TOCs of several percent were recorded in the Vanavara Formation in wells drilled in the Katanga Saddle (Sivkova, 2022). The main problem with the characterization of Vendian source rocks is that thick layers of organic-rich rocks of this age have not been encountered over significant areas in the Siberian Platform.…”

“…9). All the samples have properties that are characteristic of Precambrian oils from the East Siberian Basin (Bazhenova et al, 2014;Dakhnova et al, 2010;Kashirtsev, 2003Kashirtsev, , 2004Kontorovich et al, 2000;Petrov, 1984Petrov, , 1995Timoshina, 2005;Grantham and Wakefield, 1988;Oblasov et al, 2009;Peters et al, 2005;Kelly et al, 2011;Chakhmakhchev et al, 2017;Spaak et al, 2020). For example the oils have low Pr/Ph ratios (0.78-1.00: Table 2), indicating that the precursor source rock organic matter was deposited under reducing conditions (Peters et al, 2005).…”