Changes in Thermal Conductivity of the Rocks of the West Siberian Basin Lithosphere in the Vicinity of the Tumenskaya SG-6 Well

Abstract

Numerical reconstructions of the thermal regime of the lithosphere of the West Siberian basin in the Koltogor-Urengoi graben in the vicinity of the Tyumenskaya SG-6 superdeep well are used to analyze the depth distribution of thermal conductivity of basin rocks. Five depth intervals which differ in the character of changes in thermal conductivity of rocks are distinguished: the permafrost zone, the sedimentary section below this zone, the zone of anomalous rock weakening, the consolidated crust, and the mantle. The algorithms for calculating the thermal conductivity are considered and the main factors affecting its change with depth are determined for each of the five intervals. A sharp decrease in the thermal conductivity of rocks in the bottom part of the sedimentary cover and in the basement top in the vicinity of the SG-6 well is associated with rock weakening due to tectonic fracturing and hydrothermal erosion. The analysis suggests that the stationarity conditions of the process are not observed in optical scanning thermal conductivity measurements and, therefore, this method may overestimate the true thermal conductivity of rocks.