A Model of the Geological Structure and the Oil and Gas Prospects of Neocomian (Berriasian–Lower Aptian) Sediments of the West Siberia Arctic Regions and the Kara Sea Shelf

Abstract

Abstract —The paper presents a model of the geologic structure of Neocomian (Berriasian–lower Aptian) sediments in the Arctic regions of West Siberia and on the shelf of the Kara Sea. The southern part of the Kara Sea is the northern end of the West Siberian sedimentary basin and is identified as the South Kara regional depression of the West Siberian oil and gas province (OGP). Structural and tectonic analysis was performed, and 97 oil- and gas-promising anticlinal objects (structures of ranks III–IV) were identified in the Neocomian megacomplex relief, including 61 on the continent and 36 on the shelf. In the Yamal and Gydan oil and gas areas (OGA), the Neocomian complex of sediments has a structure typical of West Siberia. The megacomplex includes clinoform and shelf complexes. Clinoforms resulted from the ablation of terrigenous material from the eastern and southeastern edges of the plate and are tilted in the northwestern direction; the depocenter within which the eastern and western clinoforms converge is located in the Urals zone, west of the Nurmin megaswell. In the South Kara regional depression, the Berriasian–lower Aptian megacomplex is also represented by clinoform and shelf complexes. On the Kara Sea shelf, Neocomian clinoforms are tilted in the southern, western, and eastern directions; they resulted from the ablation of sediments from the Novaya Zemlya Archipelago and the Siberian Sill. Throughout most of the South Kara regional depression, clinoforms have a typical structure and contain shelf and Achim sandstones that can concentrate significant volumes of hydrocarbons; in the northeast, in the pre-sill zone, clinoform deposits will be represented by poorly sorted “dump” sandstones.