Geothermal Regime and Deep Temperatures of the Siberian Platform
The geothermal regime of the southern segment of the East Siberian platform, where more than 200 heat-flow measurements have been carried out, is well-understood. The present work deals with the study of deep temperatures of the southern Siberian platform, based on results of geothermal measurements in more than 70 boreholes. In addition, measurements of thermal properties have been made mostly on core samples representing the Vendian terrigenous deposits and Riphean magmatic and metamorphic basement rocks. The basement rocks may be subdivided into two groups, with thermal conductivity coefficients varying in the range of 2 and 3 W/m/K. Higher coefficients indicate the presence of carbonate-halogen admixtures. Studies have also been made of the borehole thermograms and temperatures at the bottom and top of the Moti suite, of lower Cambrian age. These boreholes vary in depth from 1300 to 6000 m, and the borehole temperatures attain values as high as 70оC. In this region average heat flow is 38±4 mW/m2. Higher heat flow values (45±6 mW/m2) are observed in the anticlinal domes and salt-dome crests, while low heat flow seems to be typical of marginal uplifts. This peculiar geothermal condition is also closely related to hydrodynamic features of the area, where underground seepage flow penetrates to depths of 3-5 km while conductive diffusion of heat prevails in the deeper crust. It is argued that such anomalous conditions exert influence on the dynamics of hydrocarbon accumulation, which in turn is also predetermined by geothermal conditions.