Geological trends of occurrence of heavy oil pools in north-eastern part of Timan-Pechora province

The paper is dedicated to studies of common factors of heavy oil pool occurrence in the Timan-Pechora Province. Consumption of oil and petroleum products is increasing, previously explored fields are depleting, and the peak of light oil production is a past history. The authors analyse features of tectonic evolution of large oil and gas accumulation zones in the Timan-Pechora Province, as well as conditions of formation of rock associations bearing heavy oil pools. Main heavy oil reserves of the Timan-Pechora Province are concentrated in the Khoreiversky Depression and Varandey-Adz'vinsky structural and tectonic zone. Varandey-Adz'vinsky structural and tectonic zone is an ancient aulacogen; in present-day plan it is a system of horst-like uplifts. Khoreiversky Depression is a superposed negative structure; in the Basement surface and Lower Palaeozoic deposits, fractured Bol'shezemelsky paleoarch corresponds to this structure. It is found that trends of oil pool occurrence depend on features of geological structure and history of individual structural and tectonic element evolution. Occurrence of heavy oil pools within these structural elements differs in terms of stratigraphic and hypsographic position. Heavy oil pools found in the Varandey-Adz'vinsky structural and tectonic zone belong mainly to the upper stratigraphic horizons (Carboniferous-Permian). The greater part of deep-seated heavy oil is concentrated within the Khoreiversky Depression. Because of low density, oil in the Khoreiversky Depression is lighter. In accordance with common factors of their occurrence, heavy oils are classified into three following groups: low paraffin, paraffin, and high-paraffin. The authors discuss petroleum potential of the shelf part of considered structural elements, and predict phase composition of hydrocarbons