Search

Gases from bottom sediments of the Laptev–Siberian Sea zone contain methane (up to 8.3047 cm3/kg) and its homologues (up to pentane including) totaling 0.0259 cm3/kg. The established values of the carbon isotope composition of methane (δ13С), the molecular weight of the hydrocarbon fraction, the weight concentrations of С1–С5 hydrocarbons and their ratios, the "wetness" and "transformation" coefficients of the hydrocarbons fraction indicate the presence of various syngenetic and epigenetic gases in different source rocks: bottom sediments, peatlands, coal, gas, and gas hydrate? deposits, solid bitumen, igneous rocks, and inferred oil and gas reservoirs. It has been established that the vertical and lateral distribution of hydrocarbon gases in sediments depends on the influence of a complex of geological factors: fold and fault tectonics, magmatism and seismic activity in the region, coal, oil and gas potential and bitumen content, organic saturation and lithological composition, hydrogeological, geocryological, and other conditions for accumulation of gases or their degassing. [ABSTRACT FROM AUTHOR]

The data of gas-geochemical studies of bottom sediments of the Laptev—Siberian Sea transition zone are presented. The established isotope–geochemical parameters indicate the domination of epigenetic hydrocarbon gases of various gas sources in the sediments. Methane concentrations up to 8.3047 cm3/kg and the sum of homologues up to 0.0260 cm3/kg indicate the formation of hydrocarbon anomalies exceeding the anomaly criteria for Arctic shelf sediments by a factor of 166 and 26. The main geological factors for the formation and distribution of anomalies in the bottom sediments of the Laptev–Siberian Sea transition zone are the high gas content of the underlying sediments and gas sources, the fold and fault tectonics, the geostructural position, the seismic activity, and the depth of occurrence of hydrocarbon gas sources. [ABSTRACT FROM AUTHOR]

The paper is devoted to comparative analysis of detailed gas-geochemical studies carried out in the Alekseev Bay (Peter the Great Gulf, Japan Sea) in 1989 and 2022. The distribution of methane and carbon dioxide in water is given in details. CTD measurements were made to determine water temperature and salinity. The main regularities in the distribution of gas geochemical fields in the Alekseev Bay (Peter the Great Gulf) are shown basing on the available geological information, taking into account the materials of the predecessors. The results obtained are in demand both in theoretical studies of the gas geochemical fields distribution on the Earth's surface in connection with the seismotectonic and geological features of the region, and in the practice of developing methods and technologies for measuring the balance flows of the main greenhouse gases, emission and absorption. The results are also relevant for the implementation of research programs within the "climate agenda." [ABSTRACT FROM AUTHOR]

Based on the lithological and gas-geochemical studies and a comprehensive interpretation of the available materials, the main factors of the formation and distribution of grain size distribution, water-physical properties, organic saturation, as well as concentrations and geochemical parameters of hydrocarbon (HC) gases in seafloor sediments of geostructures in the western part of the East Siberian Sea are summarized and analyzed. It has been established that the sediments in the northern and central parts of the studied region are represented by aleurite–pelites; in the southern part, by aleurite–pelite–psammites with the following parameters: Corg—0.6–2.0%, natural moisture content (hereafter, wetness)—18–43%, density—1.5–2.0 g/cm3, open porosity—17–33%, concentrations of methane and its homologs—0.001–5.934 and 0.00003–0.0312 cm3/kg, respectively, molecular mass of the HC fraction—16.05–22.6 g/mol, coefficients of "wetness", "dryness", and transformation—0.2–51, 1–1999, and 0.2–50.8%, respectively, and δ13С‒СН4 varying from –82.7 to –38.4‰. Based on the values of gas-geochemical parameters, eleven types of gas sources were identified in bottom sediments. The results showed that the formation of HC anomalies in sediments is governed mainly by their reservoir properties, Corg content, sampling depths, integrated influence of geological factors, such as gas saturation of the underlying sediments, type of gas sources, fault and fold tectonics, position of geostructures, thickness of Quaternary sediments, content of coal and gas, and age of the folded basement. Anomalies of HC gases are associated to a lesser extent with the lithological composition and density parameters of sediments. [ABSTRACT FROM AUTHOR]

Geochemical data are presented on the Pleistocene sediments from the central part of the outer shelf of the East Siberian Sea, the continental slope and Podvodnikov Basin of the Arctic Ocean. The studied sediments of the outer shelf and continental slope belong to the aleuropelitic type, while those of the shelf edge and the Podvodnikov Basin, to the pelitoaleuritic type. The contents of the psammitic fraction and stone material do not exceed 10 and 1%, respectively. These features predetermine the distribution of the maximum sediment density and median diameters in the sediments of the outer shelf, and the minimum values in the Podvodnikov Basin. The distribution of Corg and Сcarb contents in the studied sediments is characterized by a similar variability. The average wetness content in the bottom sediments in the study area systematically increases in the "shelf–pelagial" direction. The study of the chemical and gas composition of the bottom sediments in the same direction made it possible to distinguish four main groups of geochemical associations in the Pleistocene sediments of the study area. The bottom sediments of the outer shelf are characterized by the maximum concentrations of the first group of chemical elements (Si, Sr, Ba) and methane (up to 0.102 cm3/kg), those of the shelf edge, by the maximum concentrations of the second group (Cd, Hg, U, K, Ca) and the minimum content of methane (up to 0.002 cm3/kg). The sediments of the continental slope have the maximum concentrations of the third group (Cu, Zn, Ti, Be, Nb, Ag, Tl, Pb, Lu, Tm, Tb, Ho, Eu, Yb, Er, Dy), while those of the Podvodnikov Basin, the fourth group (Mn, Fe, Al, Cr, P, Mg, Mo, Ni, Sb, Sn, As, Th, Co, Ga, W, Hf, Rb, V, Cs, Sc, Li, Gd, Sm, Pr, Nd, La, and Ce) and intermediate contents of methane (up to 0.051 cm3/kg). The maximum total concentration of methane homologues (up to С5 including, 0.006 cm3/kg), δ13С-СН4 (up to –36.0‰), δ13С-С2Н6 (up to –17.2‰), molecular mass of the hydrocarbon fraction (up to 27.5 g/mol), coefficient of transformation and "wetness" of the hydrocarbon fraction were found in the Pleistocene sediments of the continental slope and the foot of the Podvodnikov Basin, while the lowest concentrations of these parameters were determined in the outer shelf. The established isotope-gas-geochemical indicators point to the predominance of epigenetic hydrocarbon gases from various gas sources in the studied sediments. The positive and negative correlations between geochemical and isotopic-gas-geochemical indicators have been established. Obtained data were used to estimate the oil and gas prospects of the study area. [ABSTRACT FROM AUTHOR]

This paper reports new data on the composition of hydrocarbon gases in bottom sediments of the Laptev–East Siberian marginal shelf transition zone, the continental slope of the Lomonosov Ridge, and Podvodnikov Basin of the Arctic Ocean. Anomalous concentrations of methane and hydrocarbon gases (up to C5 inclusive) have been established. Gas-geochemical indicators of eight genetic groups of hydrocarbon gases have been determined. The oil-and-gas content of the study area has been predicted based on the data obtained. [ABSTRACT FROM AUTHOR]

New data on the gas and chemical composition of bottom sediments of the marginal-shelf part of the East Siberian Sea, continental slope, and Podvodnikov Basin of the Arctic Ocean are presented. The genetic parameters of seven groups of epigenetic hydrocarbon gases are determined. The distribution areas of the potential oil–gas, gas–oil, and oil deposits have been revealed. Three groups of chemical elements have been specified in bottom sediments. Their maximum concentrations are related to particular geostructures of the area studied. [ABSTRACT FROM AUTHOR]

The results of gas-geochemical studies of the Chaun Depression and the Ayon sedimentary basin of the East Siberian Sea are presented. The natural gas composition in rocks, gas manifestations, and bottom sediments is determined. The indicators of the molecular mass of hydrocarbon fractions and weight concentrations of individual hydrocarbons, in which ratios are of correlation-genetic significance for hydrocarbon gases of the geological formations, are identified. The geochemical classification of hydrocarbon gases from bottom sediments and a schematic map of gas geochemical zoning of the study area are presented. The oil and gas potential of the Chaun Depression and the Ayon sedimentary basin is evaluated. [ABSTRACT FROM AUTHOR]

Anomalous concentrations of dissolved gases, exceeding their background values by an order of magnitude or more, are recorded in the surface and ground waters of the Birofeld Graben of the Middle Amur sedimentary basin. The main geological factors that influence the formation of the gas composition and gas saturation of waters are determined. The gas-geochemical indicators for the dissolved hydrocarbon gases, which make it possible to estimate their genesis and prospects for the oil-and-gas contents of the Birofeld graben, are specified. [ABSTRACT FROM AUTHOR]