The relation of the northwestern shelf deep geological structure of the Black Sea with the phenomenon of gas seeps

Oleksii O Likhosherstov,Olexandr M Shevchenko,Sergii V Goshovskyi,Svitlana G Slonitska

doi:10.15421/112044

Abstract

Geophysical model inputs were the results of a survey on an anomalous magnetic field and a gravitational field of the Black Sea’s north-western shelf. Thegeophysical profiles of the complex effective parameter (CEP) are calculated and graphed. Complex effective parameter characterizes the relationship between the effective densities and the magnetization by their spatial distribution. Effective parameters (magnetization, density, CEP) were calculated within the studyarea with their distribution on the optimum depth. The profiles are meridional and parallel to each other, direction of the profiles from south to north. The distance between the profiles is 50 kilometers. The generalized deep structure of the study area was elucidated using the graphed profiles. The distribution of CEP on vertical sections within the shelf zone of the western Black Sea basin emphasizes the position in the space of tectonic elements. That is gives an idea about the nature and structure of the region’s lithosphere and their relationship with the spatial distribution of deposits and manifestations of hydrocarbons. Structural and geological interpretation of the CEP profile data was performed. According to the spatial consistency of the correlation by structures, the profiles are conditionally divided into two groups, the western and the eastern. Structural differences in profiles are explained by the presence of the Odesa-Sinop fault zone between the groups. According to the results of profiles interpretation and works of previous researchers, paleogeodynamic processes were established. That significantly complicated the geological structure of the Black Sea’s north-western shelf. The interpretation of the CEP field distribution gives additional arguments in favour of the Earth crust evolution on the north-western shelf of the Black Sea in the conditions of a passive continental margin with short periods of reverse motions with obligatory subduction due to the activation of rifting, the nature of which is yet to be studied. According to the results of interpretation, the presence of the Earth’s crust destruction zone was established. With the help of spatial analysis, the spatial regularities of the gas seeping manifestations with the zone of destruction of the Earth’s crust of continental type and sites of rising of the mantle surface are established.

Highlights

The combination of properties of the Black Sea natural gas seepage phenomenon and its magnitude have aroused great interest among experts in Ukraine, Black Sea and Western European countries.Seep gases contain 80-99 percent of methane.The emissions of these gases can be very powerful; they can be considered as a hydrocarbon resource, for the production of which there is no need to drill wells.Previous researchers have collected a large amount of information (Egorov, Artemov&Gulin, 2011; Shnyukov, Kobolev&Pasynkov, 2013), that allows gas emissions to be connected with the geological features of the Black Sea bottom and, as a consequence, connected with deep active faults, which gives grounds to link the nature of the origin of methane with deep faults, as with sources
Today there is no single viewpoint on this feature.Two hypotheses compete for explaining the methane origin in seeps: biological methane origin and the migratory methane origin.The magnitude of gas seeps and the lack of their confinement to the places of probable organic materials’ accumulation cast doubt on the dominance of the methane genesis biological hypothesis
Data and research methods.A long-term geophysical study of the geological structure for the territory of Ukraine and analysis of the data obtained in the course of the performed studies indicate its complex deep structure, which is reflected in geophysical fields.But numerous highly qualified researchers have studied the distribution of geological heterogeneities mainly on the research area

Summary

Introduction

The combination of properties of the Black Sea natural gas seepage phenomenon and its magnitude have aroused great interest among experts in Ukraine, Black Sea and Western European countries.Seep gases contain 80-99 percent of methane.The emissions of these gases can be very powerful; they can be considered as a hydrocarbon resource, for the production of which there is no need to drill wells.Previous researchers have collected a large amount of information (Egorov, Artemov&Gulin, 2011; Shnyukov, Kobolev&Pasynkov, 2013), that allows gas emissions to be connected with the geological features of the Black Sea bottom and, as a consequence, connected with deep active faults, which gives grounds to link the nature of the origin of methane with deep faults, as with sources. За результатами інтерпретації профілів та роботами попередніх дослідників встановлено палеогеодинамічні процеси, що суттєво ускладнили структурно-геологічну будову Північно-західного шельфу Чорного моря.

Results

Conclusion