Abstract: Petroleum Systems of the Pechora Basin, Russia

Steven Schamel, John Smale, Lev Aminov, Valentina Pesetskaya, Albina Paneva

The Pechora basin, a prolific hydrocarbon province in the foreland of the northern Urals, is sufficiently large and geologically complex that no simple model adequately accounts for the distribution of its hydrocarbon resources. The various petroleum systems operative within the basin have been delineated through (a) mapping source rock "richness," vitrinite reflectance, "effectiveness" of principal seals and timing of structural trap formation, (b) geochemical analyses to determine oil-source rock correlations, and (c) thermal maturation modeling. The principal oil fields are hosted within large domes and anticlines formed by inversion of the flanks of the Pechora-Kolva aulacogen, a 100 kilometer wide early Paleozoic graben traversing the center of the basin. Structural inversion beg n as early as the late Visean and ended prior to the Middle Jurassic.

Biomarker analysis of Pechora Basin oils reveals spacial clustering of oil types correlated with three main pre-Visean source rock units: Upper Devonian "Domanik," Middle Devonian-lowermost Frasnian, and Silurian. Visean and younger source rocks tend to be thin, lean or gas-prone. Thermal maturity modeling constrained by vitrinite reflectance measurements indicates that the major oil-prone source rocks entered the oil generation window prior to the Middle Jurassic in virtually all portions of the basin. However, oil generation within Silurian-age source rocks occurred as early as the Late Devonian-Early Carboniferous in the southern Pechora-Kolva aulacogen and Urals foothills. In different parts of the basin, oil was forming and migrating from pre-Visean sources either prior to, durin , or immediately following the time of structural inversion and trap formation. Thus, the spacial distribution of oil types can be related to the interplay of source rock "richness," time of entry into (or out of) the oil generative window, and time of trap formation--all factors that vary systematically across the basin.

The distribution of oils within the Pechora basin can be fully explained by largely in situ migration over relatively short distances. It is not necessary to appeal to large-scale lateral migration from "kitchens" within or beneath the Urals foothills belt.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994