The formation of massive sulfide ores with enormous reserves of copper, zinc, gold, and other metals is associated with hydrothermal activity on the ocean floor at depths of 3 to 4 km. Hydrothermal solutions carry a mixture of heavy metal sulfides through the ocean floor, some of which are deposited near the hydrothermal source as various ore structures, while the main mass is dispersed by the bottom currents for tens of kilometers, forming halos of dispersion of ocean hydrotherms. Mapping of such halos is used to search for massive ores. Detailed study of hydrothermal scattering halos is complicated by the fact that it is necessary to investigate at a depth of more than 3 km. Mathematical modeling of hydrothermal halos can be used to obtain additional information, the results of which can be used to interpret the experimental data. The results of numerical calculations of hydrothermal source dispersion halos are in good agreement with the experimental data given in [3, 5].
A complex of geophysical and geoelectrochemical methods for diagnostics of corrosion danger of gas pipelines is offered. On the basis of complex geophysical and geoelectrochemical information it is possible to solve the following problems: high-precision determination of the location and depth of the gas pipeline; detection of places and degree of violations of insulating coating of gas pipelines, accompanying metal corrosion damage; evaluation of attenuation factor of variable component of cathodic protection currents; determination of cathodic protection potential in places of gas pipeline insulation damage; identification of corrosion dangerous areas and evaluation of corrosion hazard of pipelines. The relative contrast of geoelectrochemical anomalies characterizes the duration and intensity of corrosion. The suggested methodology complements the existing methods of gas pipelines condition diagnostics. New method was tested at gas pipelines of Lentransgaz enterprise in 1999-2000. According to the results of complex researches the areas of gas pipelines isolation coating violation were marked with indication of places of corrosion damages of pipelines.
Geoelectrochemical methods: partial extraction of elements method (PEM), diffusive metal extraction method (MEM), method of searching by metal-organic forms of elements (MEF), thermomagnetic geochemical method (TMGM) - have found wide application in search of oil and gas fields onshore. These methods allow to reveal oil and gas traps, including nonstructural ones, in any geological conditions. Low cost and high efficiency of the considered methods allow to recommend them for solving other prospecting tasks. At present, joint efforts of three institutes: St. Petersburg Mining Institute, VIRG - Rudgeofizika and VNIIOkeangeologiya are investigating a new sphere of application of geoelectrochemical methods - offshore oil and gas field prospecting. Developed, theoretically and practically substantiated a new methodology of economic geoelectrochemical prospecting of oil and gas fields on the shelf. This technique is to study the distribution of heavy metals - a microcomponent of oil in the water column. It is proposed to conduct continuous sampling while the ship is moving, which allows to combine geoelectrochemical studies with other geophysical works, such as seismic surveys.
The formation of huge reserves of ore elements is connected with the outputs of high-temperature hydrothermal waters within various volcanically active structures in the World Ocean: Si, Zn, etc. By present time a big factual material on high-temperature hydrothermal activity has been accumulated, but experimental studies are hampered by the fact, that information is collected from depths of 3-4 km. The incompleteness of experimental data can be partially compensated by a theoretical study of the structure of scattering halos of oceanic hydrotherms. A physical and mathematical model of the hydrothermal source scattering halo is considered and numerical simulation of this halo is performed. The model establishes functional dependences between the characteristics of hydrothermal scattering halos, which satisfactorily describe the experimental data. Numerical modeling of hydrothermal scattering halos can be used to fill the gaps in the experimental data and to analyze the results of field studies.
The main method of searching for oil and gas fields on the shelf is seismic survey. Application of inexpensive geochemical methods of hydrocarbon prospecting is aimed at studying bottom sediments and near-bottom waters and leads to detection of a large number of false anomalies related to the activity of methane-producing bacteria. Geoelectrochemical methods based on the study of the distribution in the rocks of mobile and secondary fixed forms of heavy metals, the so-called jet halos of dispersion, are widely used in the search and study of deep-seated ore and oil-and-gas deposits of land. There is an example of successful application of geoelectrochemical methods on the Baltic Sea shelf - employees of VIRG-Rudgeofizika obtained contrasting geoelectrochemical anomalies in the study of bottom samples over the Ladushkinskoe oil field. Therefore, the inclusion of geoelectrochemical methods, which study jet halos of dispersion directly in the water column, into the complex of geophysical methods may become an interesting direction for the search of oil and gas fields on the shelf. The work is devoted to consideration of possibilities of application of geoelectrochemical methods of searches of oil and gas fields of the shelf at sampling (or without sampling - in the liquid phase it is possible to determine concentration of mobile forms of metals in situ) from the middle or upper water column of the shelf. A simplified model of formation of a jet halo over an oil and gas deposit in the water column, developed by Professor O.F. Putikov, is used as the basis. The results of numerical modeling of jet halo on the shelf are considered.
