Controls on the Distribution of Oil, Gas, and Gas-Condensate Pools in the Timan-Pechora Basin

Abstract

The distribution of hydrocarbon pool in the Timan Pechora basin is controlled by various aspects of the geological structure and stratigraphy. Oil pools are confined to tectonically stable areas, and there are often stratigraphically trapped (Omra-Lizha saddle in the Izhma Pechora basin, Khoreyyer depression). Structures in more active tectonic areas (Pechora-Kolva aulacogen and Ukhta-Izhma swell) usually contain complex accumulations of oil, gas, and condensate. The mixed character of these pools proves their multistaged origin involving further gas charge during stages of increased subsidence in the kitchen areas and degassing of oil during later stages of uplift. However, active tectonics led not only to gas-cap development but also, in places, to complete loss of hydrocarbons at the surface. The Varandey Adzhva zone is an example, with its considerable volume of heavy and medium-heavy oils. In the Ural foredeep basins, older oil and gas accumulations at the outer edge and on transverse uplifts were enriched later by gas generated from deeply buried formation the axial part of the orogenic trough and its eastern border. Younger fold structures contain gas and gas-condensate pools charged by gas generated in both orogenic and preorogenic formations and by residual oils re-migrated from preorogenic accumulations that oncemore » existed in the pericratonic region.« less