Basics of complex geocryological-geophysical analysis for the research of permafrost and gas-hydrogates on the Arctic shelf of Russia

Abstract

The active development of the Russian Arctic in the last 10 years requires relevant data on the bearing capacity of rocks on the Arctic shelf of the Russian Federation. To assess the bearing capacity of soils, knowledge of the distribution and state of permafrost on the Arctic shelf is needed. The article discusses the rationale and possibilities of the proposed integrated geocryological and geophysical analysis. The technique of researches includes realization of sea electroprospecting works, drilling on the shelf, thermometric observations in the drilled wells, bench tests of soils, modeling of electromagnetic and thermal fields on the shelf. It is shown that the most informative geophysical method for studying of permafrost on the shelf is electromagnetic sounding by the TEM method. The most informative geophysical method for studying of permafrost in the transit zone “land-shelf” represents the frequency electromagnetic (FS) sounding. In the article there are examples of standard interpretation of geophysical data and inversion of geophysical data in the mode of the fixed model specific electrical resistivity. With the example of the yamal shelf it is shown that standard interpretation doesn’t allow to receive the unambiguous solution of geocryologic tasks on the shelf. Specific electric results of determination of electric properties of soils in laboratory are necessary in case of inversion of geophysical data in the mode of thickly stratified models and the fixed model. An important component of the offered complex is boring and thermometric research which provide validation of results of geophysical inversion. Measurement of temperatures of soils in the stood wells is especially important in the conditions of the Arctic shelf. Calculations for thermal models complete a complex of researches. The collateral analysis of geoelectric and thermal models allows to estimate depths to a sole of permafrost and also capacities of gaseous-hydrate thicknesses. The use of the developed research complex on the Pechora, Karsky, Laptev and Chukchi seas shelves provided new insights into the distribution, continuity and condition of permafrost and the development of gas hydrates on the shelf of the Russian Arctic seas.