Известия Томского политехнического университета: Инжиниринг георесурсов (Nov 2017)
Deep sources of heat generationand regional forecast on oil-gas prospects in Tomsk region
Abstract
The relevance of the research is caused by the need to reveal the connection of oil and gas deposits in Tomsk region with a deep structure and rheology of the crust and uppermost mantle. The relations determined are used for oil-gas forecast in areas with obscure prospects. The aim of the work is to research the density contrast of the crust and uppermost mantle - manifestation of rheological properties of geological media - in the 3D-space to reveal the connection of the former with the heat flow and displacement of oil-gas deposits in Tomsk Region; to define and delineate in space probable sources of heat and fluids promoting the formation of hydrocarbon deposits into sedimentary layers. The method used in the study: construction of 3D-rheological gravity models of the crust and uppermost mantle up to depth of 50 km and the correlation analysis. The results. The correlative relation of density contrast - indicator of rheological station of geological media - with a heat flow from PreJurassic basement of the sedimentary layer was determined. This assumes heat and fluid sources inlow crust and uppermost mantle lower viscosity zones, and also direct influence of the latter on hydrocarbon formation in sedimentary stratum. In western areas of Tomsk region the space relation of oil-gas districts with zones of lowered viscosity in the PreJurassic sedimentary layer, basement, lower crust, and uppermost mantle is defined. The authors have revealed great difference of rheological state of the crust in western and eastern areas of Tomsk region. In western areas the crust is less viscous, perhaps - the shattered and, as a consequence, more permeable for deep heat-fluid flows. In eastern areas the crust is more viscous (rigid) and it is characterized by a thickening, that define sharp difference of oil-gas efficiency of the sedimentary stratum in the West and East of Tomsk region. In central areas of the researched region lower viscous zone at the depth interval of 35-60 km - the probable source of a heat and fluids - is found. From the East it is overlapped by rigid sheets into the middle and lower crust. Two areas, perspective for searching for new oil and gas deposits, were recommend according to the presence of lowered viscosity zones in the basement and lower crust in the North and South of Tomsk region.
