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A geographically related database called MAGIC has been developed, using GIS (Geographic Information System) technology, for MArine Gas seeps and seep IndiCators. A complementary bibliographic database (GASREF) stores details of related publications. The databases include data relating to natural seabed gas seeps and features such as pockmarks, cold seep communities, and methane-derived carbonates which are known to be found in association with seeps. The databases are compiled from published reports (so far restricted to those written in English), and users are able to interrogate the system for specified features from user-defined areas.

Concentrations of water-dissolved methane were measured on the eastern shelf and slope of Sakhalin. Seasonal variability of water structure is chiefly responsible for seasonal differences in methane concentrations in the water body. In the shelf zone the maximum flow of methane to the atmosphere occurs in the cold season; in summer, it is much weaker. The cold season is also the time when the methane-saturated shelf waters reach intermediate depths on the continental slope. In summer, the shelf waters stop sliding down the slope; therefore, no methane anomaly is observed at intermediate depths. Methane concentrations at latitudinal profiles vary from year to year, which is possibly due to variations in seismotectonic activity of the region.
Our observations are important for calculation of the flow of methane from the Earth's interior to water and from water to atmosphere in the western Sea of Okhotsk. The available data show that there are natural sources of methane supply to the atmosphere which depend on season and seismotectonic activity of fault zones, generators and conduits of methane flows. The methane flows in the Sea of Okhotsk participate in the global process of its supply and increase in the atmosphere, which is, likely, responsible for changes in climate (warming) and destruction of the ozone layer.

Evaluating the importance of natural marine hydrocarbon seeps to global methane budgets requires correctly predicting the gas fraction lost by the seep bubbles during transit through the water column. In the Santa Barbara Channel, California, three widely differing seeps (depth, flux, oiliness) were visited and observations were made of seep gas partial pressures, P_n, near the surface for alkanes to n = 5 (pentane) as well as major atmospheric gases, and up welling flows. It was found that alkane P_n decreased exponentially with alkane diffusivity. Seabed seep gas was available for one seep, and exhibited the same trend. For alkanes heavier than methane, the ratio of the surface to sea floor mole fraction showed a linear enhancement with increasing alkane number. Methane behaved differently because the water column became saturated.
A numerical model was developed to study the sensitivity to environmental parameters of the bubble transport of seep gas to the surface. It was found that seep gas transport is highly sensitive to both up welling flows, dissolved gas concentrations, bubble surface cleanliness, and bubble size. The model predicted that up welling flows increase bubble survivability and transport to the surface. It also predicted that dissolved methane concentrations responsible for pressure higher than 0.01 atm increase bubble survivability. When applied to simulating alkanes, the studies showed that only a narrow range in bubble size could explain the observed alkane enhancements. Thus model predictions were in agreement with the observation that a wide size range of bubbles was not observed at the sea surface.

Under consideration are empirical aspects of the mode of hydrocarbon gases in the Caspian Sea. This paper reports concentrations of gas hydrocarbons in the sea water and bottom sediments of the Caspian Sea and describes patterns of their distribution in the water and sedimentary bodies of the region under study. The revealed regularities served as a base for development of methodology, equipment, and approaches to interpretation of data on gas geochemistry in searching for oil and gas in water areas. In addition to solving the problems of search for petroleum, the experimental study provided a possibility to use the results obtained during gas surveys to solve engineering, ecological, and other problems of national economy. The use of gas survey in industry has been outlined in detail.

In connection with the recent discovery of gas hydrates in Lake Baikal, numerous published materials, which could contain any information on the gas seepage from the bottom sediments, have been investigated. We revealed that in the 1930s, both direct and indirect data showing significant escapes of gases (presumably methane) in Lake Baikal were obtained. Analysis of these materials indicates that the dates of the ice steamthroughs opening are later and the intensity of gas escapes from the ice steamthroughs is lower at present as compared to the 1950s. The events of abundant death of pelagic fish golomyanka (Comephorus baicalensis Pall.) as well as specific forms of the ice cover caused by the methane escape, which used to happen in the lake, has not been recorded in Baikal since the 1950s. Thus, it seems that the intensity of gas escapes has significantly decreased for the last 50-60 years. This may be due to lowering of the number of catastrophic (M = 9-10) earthquakes in the Baikal region.

Natural gases emanating from the bottom of Baikal occur nearly ubiquitously along the shore, but their maximum concentration is observed at the front of the Selenga delta. In spring, the gas outputs are visible in the form of openings in the Baikal ice. Study was given to 54 openings. The gases are represented mainly by methane (75 vol.% on average), but highly nitrogenous types also occur (80 vol.% on average).
In addition to the explicit discharge of gases in the form of openings, the implicit discharge of gases exists throughout the Ust'-Selenga depression (USD). The chemical types of gases show areal zoning: from nitrogen on the piedmont periphery of the depression to methane in the near-shore band of the modern delta.
Joint analysis of geological, geophysical, and geochemical information proves that the USD sediment is a powerful source of generation of hydrocarbon gases and the similarity of its geologic structure with the South Caspian depression suggests the presence of "mud" volcanoes in Baikal.
A total of Cenozoic depressions of Baikal joint with its sedimentary bed is a potentially gas-bearing basin. Hydrocarbons are generated chiefly at the Baikal bottom, whereas the Selenga delta and other depressions are zones of their transit and accumulation. A regional cap for the natural reservoirs beneath the Baikal bottom may be a gas hydrate layer. Oil fields are hardly possible there, because all the studied gases are extremely dry and the bitumen contents in the USD sediments and grounds are very low. The reported facts and arguments permit the Baikal geology to be considered anew.

Geological, microbiological, and isotopic investigations showed that the bacterial communities form in surface sediments near a hydrothermal source in Frolikha Bay, northern Baikal. The base of these communities is colorless sulfur bacterium Thioploca. The bottom sediments in the region are characterized by intensive processes of sulfate reduction and methane genesis. Organic matter is used mostly for synthesis of methane. Carbon isotope composition in sediments and fauna (to -68.3 ) suggests that the metabolism of the community of bottom sediments of Frolikha Bay is based on biogenic methane utilized by methanotrophic bacteria. The intensity of methane oxidation reaches high values: 1180.4 L CH ₄/kgday.

Based on the concepts of occurrence of submarine gas hydrates as accumulations and on the general regularities of changes in their densities, global assessment of gas amount in gas hydrates of the World ocean is given. It is shown that the shape and the size of gas hydrate accumulations are controlled either by a concentrated flow of gas-containing fluids through the zone of gas hydrate stability and by parameters of their scattering halo or by a dissipated flow of gas-saturated water depending on fluid guides and lithologic peculiarities of the deposits. Geologo-geochemical and geophysical data on 10 best studied accumulations of gas hydrates were analyzed. The average specific (per unit area) content of gas in studied gas hydrate accumulation has been obtained, ca. 6.5108 m³/km². The specific gas content in gas hydrates within all potential gas-hydrate-bearing water areas is ca. 5106 m3/km2. According to data of performed mapping, the total area of these water areas is about 35.7 mln km², i.e., ca. 10% of the area of the World ocean. The total amount of gas, mainly methane, in the world's submarine gas hydrate accumulations is estimated at ca. 21014 m³.

Results of geological investigation of gas hydrate accumulation within the underwater sedimentary Blake Outer Ridge are presented. The study was based on both published and new data that we obtained by processing 164 and 172 ODP leg observations. The geological control over the distribution of gas hydrates is not quite clear despite the detailed seismic surveys and drilling within the study area. The geologic, tectonic, and hydro-geologic conditions in the Blake Outer Ridge area have been analyzed. A radically new technical approach was used: The gas hydrate accumulation was examined as a separate object with its specific characteristics. It has been proved that the investigated gas hydrates formed under the conditions of dissipated percolation of gas-containing fluids, which controlled the shape and the size of the accumulation. Based on geochemical, geophysical, and sedimentological data, the regularities of gas hydrate distribution within the Blake Outer Ridge have been established. The accumulation is controlled by tectonic factors, is of filtration origin, and occurs mainly in coarse-grained sediments.

The magnitude and spatial distribution of potential Black Sea methane hydrate reservoirs has been estimated on the basis of 6