Thermal History of the Lithosphere of the Koltogor-Urengoi Graben, West Siberian Basin, in the Vicinity of the SG-6 Well: Numerical Reconstruction Using GALO Flat Basin Modeling System

Abstract

The GALO basin modeling system is used to numerically reconstruct the thermal regime of the West Siberian basin lithosphere in the Koltogor-Urengoi graben in the vicinity of the Tyumenskaya SG-6 superdeep well. The reconstruction explains the features in the formation of the thermal regime of the basin, which were not considered in the previous reconstructions of the region. These features include anomalously high growth of the maturity level of the organics in the Jurassic and Triassic rocks, high temperature gradients observed in the upper basement and Triassic–Permian sedimentary complex, the anomalously low rock temperatures in the upper layers of the recent sedimentary section of the basin. The temporal changes in the tectonic subsidence of the basin are analyzed to estimate the intensity and duration of thermal activation events and the extension of its lithosphere. The thermal impact of the sill that intruded into the upper basement horizons in the Lower Jurassic explains the high degree of maturation of the organic matter in the Lower Triassic rocks. Taking into account the abrupt climatic fluctuations in the Pliocene–Quaternary together with hydrothermal activity in the bottom part of the sedimentary cover in the Upper Pliocene–Lower Pleistocene, we obtained the depth profiles of temperatures and vitrinite reflectance, which agree well with the measured values.