The Black Sea region is favorable for understanding the role of fluids in structure formation. The large Kerchen-Taman mud-volcano province has long been known onshore on its northeast. The numerous mud volcanoes there occur largely in regions where thick Oligocene-Miocene Maykop clays are present. Geological and geophysical studies in the deep-water depression to the south of the Crimea have disclosed gentle anticlines that do not have roots in the Eocene sediments. Faults are present at their crests, and in places also sag grabens. Sag grabens occur in various other parts of the sea floor. Seismic bright spots indicate considerable gas saturation of the rocks.
Among the indications of strong gas flows are cones of mud volcanoes. Ten such cones have been found in the central part of the Black Sea, as well as several buried cones that are not expressed in the sea-floor relief. Most of the breccia of these cones consists of Maykop rock. Thickness of the Maykop is particularly great in this part of the Black Sea basin. Seven mud volcanoes have been found in the Sorokin downwarp, which is along the north-central margin of the Black Sea. This also coincides with an area of thick Maykop clays. Above the crests of the Andrusov (central Black Sea between West and East Black Sea depressions) and Shatskiy (northeast Black Sea) swells in the Neogene sediments are numerous faults accompanied by seismic dynamic anomalies and sag craters of small amplitude but rather large area up to several kilometers wide. These features are located everywhere above local highs on the top of the Mesozoic. This is due probably to flow of fluid from Mesozoic rocks.
The sedimentary section of the Black Sea is deformed over large areas, and flow of fluids has played an important role in this process, which is defined as fluidodynamic deformation. Such deformation provides channels for vertical migration of hydrocarbons from oil-gas-source rocks. The main oil-source rocks in the Black Sea basin are generally held to be upper Eocene and Maykop clays. It is proposed here that the main oil has been generated not by all the Maykop clays but only a comparatively narrow stratigraphic interval,
The structural unity of the Oligocene-Neogene downwarps including the West Kuban downwarp with its large oil-gas fields is a basis for a high assessment of its deep-water analogs in the Black Sea - the Sorokin and Tuapse downwarps. The main exploration targets on the Shatskiy and Andrusov swells are anticlinal traps in Mesozoic rocks. Upper Jurassic limestone reefs are promising in some areas.
The gas hydrate deposits of the Black Sea are without doubt related genetically to large deposits of free gas.
Taken from Maysner and Tugolesov, 2001; digested in Petroleum
Geology, vol. 36, no. 3, 2002, in preparation, one seismic section,
one structure map, and one cross section.
Copyright 2002 James Clarke. You are encouraged to print out this
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