A new type of Cambrian section at the base of the pre-mesozoic complex of the West Siberian petroleum megabasin (based on Vostok-1 stratigraphic well data, Northern Tomsk Region)

Abstract

A new type of Cambrian section penetrated by the Vostok 1 stratigraphic test well in the eastern part of the West Siberian Plate (WSP), Tomsk Region, is described in terms of paleontology. It can be considered a key section for this region. According to a complex of geological and geophysical characteristics, the section in the depth range of 2766‐5010 m was divided into the Churbiga, Paidugina, Pudzhelga, Podelga, Kondes, Shedelga, and Pyzhina Formations, and their first description was made. The Cambrian section in the Vostok 1 well is most similar to those of the Kotuy-Igarka area of the northwestern Siberian Platform, where Cambrian deposits formed in the prereef zone of an open sea basin. Down into the section penetrated by this well, there has been identified the highly carbonaceous siliceous-argillaceous-carbonate Paidugina Formation, which is an analog of the Lower-Middle Cambrian Shumnaya and Kuonamka Formations of the Siberian Platform. The Paidugina Formation, which accumulated on the shelf and slope of the open sea facing the Paleoasian ocean, is considered oil-producing and suggests a high petroleum potential of the cis-Yenisei basin. Furthermore, a highly promising generation‐ accumulation petroleum system has been revealed. Some paleontological evidence for Cambrian deposits in the basement rocks of the eastern West Siberian Plate were first obtained from core studies in the