Geology, geography and global energy

Scientific and Technical Journal

NEW DATA ON THE TIME OF FORMATION OF OBJECTS COMPOSED BY BREEDS WITH LOW POROSITY AND PERMEABILITY IN A PRODUCTIVE STRATUM OF ASTRAKHAN CARBONATE MASSIF

2017. 3, pp. 140-146

Komarov Aleksey Yu. - Deputy General Director - Chief Geologist, Ltd. “Gazprom dobycha Astrakhan”, 30 Lenin st., Astrakhan, 414000, Russian Federation, akomarov@astrakhan-dobycha.gazprom.ru

Pykhalov Viktor V. - D.Sc. in Geology and Mineralogy, Professor, Astrakhan State Technical University, 16 Tatishchev st., Astrakhan, 414056, Russian Federation, viktor.pihalov@yandex.ru

Within the Astrakhan arch, large zones with reduced reservoir properties of a productive bashkir reservoir are allocated. These zones are located within the arches of intracrustal diapirs, identified from seismic and drilling data in the thicker of the consolidated crust. In such zones heterogeneities are distinguished, outwardly resembling reef structures, but characterized by the absence of reservoir rocks. such bodies are called colmatized objects. The rocks composing these objects were originally characterized by improved reservoir properties (porosity, permeability). This was facilitated by the biohermic nature of the objects, as well as the presence of increased hydrodynamic activity of deep fluids over the arches of growing intracrustal diapirs. During development of intracrustal diapirism due to the presence of a hydrodynamic connection between Bashkirian rocks and the day surface, areas with improved reservoir properties are formed above the arches of intracrustal diapirs. After the appearance of the evaporite screen in the Early Iren time, the hydrodynamic bond is broken, and the pores and cracks in the Bashkir deposits are filled with calcium. Especially intensive processes of calcium filling of reservoir rocks occur within the zones represented by rocks with initially improved reservoir properties. Reinterpretation of the data from the wells and seismic surveys indicates that the roof of the colmatized objects in the seismic wave field is characterized by intensive reflection and is confined to terrigenous-carbonate deposits of the philippian horizon. These data indirectly indicate that the formation time of the colmatized objects is associated with the formation of the lower irena sequence. There is reason to believe that the time for the completion of an intensive process of secondary changes in the breeds of reservoirs over the areas of distribution of arches of intracrustal diapirs is associated with the second half of the Kungur age.

Key words: , , , , , , , , , Astrakhan arch, porosity, permeability, Kungurian age, secondary processe,

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