Laboratory for Integrated Research of Environment and Mineral Resources

Sakhalin is of great interest from the point of view of a better understanding of the features of the genesis of natural gas in sedimentary basins and methane flows from geological sources, since the area includes both underwater (oil and gas deposits, gas hydrate accumulations, gas-saturated sediments, sediments, gas flares) and subaerial sources of gas release (active geothermal systems on land, mud volcanoes, mineral springs). As a result of the research and analytical work of the first year, studies were conducted both on land (Daginskaya geothermal system, Lunsky thermal springs) and on the shallow eastern shelf (areas of gas-saturated sediments of the Kirinsky and Lunsky fields) to determine the types of degassing of the lithosphere and the distribution of gases. New gas-geochemical data on the distribution of methane and carbon dioxide were obtained, and the first measurements of dissolved hydrogen sulfide, hydrogen and helium were carried out in the waters of the eastern shallow shelf of O. Sakhalin, as well as thermal springs on the coast. Some of the samples were selected for further isotope analyses of carbon methane (C13) and helium (3He/4He) to establish the genesis of the gases under study. The conducted gas-geochemical studies indicate the presence of intensive sources of degassing in the area of the shallow eastern shelf of Sakhalin. In the bottom layers of water, the content of methane is very high 200-400 nM/l, helium is high 8-18 ppm. The content of dissolved gases in the water increases from east to west, towards the coast, due to an increase in the oil and gas content of rocks from the slope to the shallow shelf. Based on the results of the research, a unique array of complex measurements of hydro-optical and gas-geochemical data on the eastern shelf of Sakhalin Island associated with dissolved methane was obtained. The data are of considerable interest for studying the effect of this gas on the optical properties of the marine environment. Understanding the relationship between dissolved methane content and optical parameters plays an important role in the development of methods for detecting places with high methane content using remote technologies, which have also been applied. A comparison of remote observation data with the results of expedition studies was performed, which showed that the distribution of methane near the surface of the water area and the nearest coast, as well as the distribution of methane in the water column, is determined by the presence of gas migrating from lithospheric sources. The zoning of the Sakhalin shelf was carried out when considering the general geological, geophysical, hydrological and seismic features of the gas hydrate regions of the Tatar Strait (Sea of Japan) and the eastern shelf of Sakhalin Island (Sea of Okhotsk). It was found that shallow (320 m) gas hydrates in the Tatar Strait correspond to similar geophysical, seismic and hydrological conditions as the gas hydrates of the Sea of Okhotsk (1000 m). Three provinces were identified, located in the south-west, south-east and north-east of Sakhalin Island: Tatarskaya, Vostochno-Sakhalinskaya and Deryuginskaya, respectively. These gas hydrate provinces are characterized by the massive presence of gas flares, which are an indicator of gas emissions. Such a hydrological regime, which provides the necessary low temperature of bottom water, comparable to the subarctic water of the Sea of Okhotsk, is a key factor in the formation and existence of the gas hydrate province of the Tatar Strait as an integral part of the Hokkaido-Sakhalin folded region. Microbiological studies were also carried out in the southern part of the Tatar Strait, during which bioindicator genes for bacterial methane synthesis were found. This suggests that a certain proportion of methane in the area is of biological origin.