Depositional Environment in Bobrikovsky Time within the South-east of the Russian Plate

Astarkin, S.V.; Гончаренко, О. П.; Pimenov, Maksim Viktorovich

doi:10.18500/1819-7663-2013-13-1-57-62

Cited by 2 publications

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“…An analysis of the geological sections of the deposits of the Bobrikian horizon suggests that the terrigenous complexes of this age were formed in the coastal-shallow water conditions of the desalinated zone of the marine epicontinental sedimentation basin [17][18][19]. During the period of low sea level of the regressive stage of development of the sea basin, mineral fragments of quartz with a small admixture of orthoclase grains and muscovite flakes accumulated in shallow water.…”

Section: Discussionmentioning

confidence: 99%

Reservoir oil deposits in terrigenous complexes of the Bobrikian horizon of the western slope of the South Tatar arch

Королев

Ескин²,

Korolev³

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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Oil-bearing terrigenous sections of the Bobrikian horizon of the western slope of the South Tatar arch are considered. It has been established that all oil deposits are confined to thin layers of quartz sandstones screened by dense clayed siltstones and argillites. The sandstones were formed in the coastal-shallow conditions of a desalinated epicontinental marine basin during the active removal of clastic material from the coast of the continent. Similar conditions of accumulation caused a large areal distribution of fine-grained sandstones with a consistent thickness along the lateral. During the period of migration of water-oil fluids, calcite cement was leached from sandstones, due to which their porosity increased to 20-25%, the permeability reached 243.0-359.0 mD. Oils in sandstone reservoirs are characterized by an increased content of light and medium fractions of hydrocarbons, the content of heavy hydrocarbons does not exceed 15-20%. Despite the fact that, according to the results of geophysical studies, the rocks are classified as unpromising, weakly oil-bearing, commercial oil flows are obtained from them in a several of oil-bearing structures.

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Section: Discussionmentioning

confidence: 99%

Reservoir oil deposits in terrigenous complexes of the Bobrikian horizon of the western slope of the South Tatar arch

Королев

Ескин²,

Korolev³

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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Features of the transformation of Visean quartz sandstones under the influence of water-oil fluids

et al. 2021

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Research subject. This article analyses specific features of secondary transformations of quartz grains under the influence of water-oil fluids on the example of the Tulsky and Bobrikovsky oil-saturated quartz sandstones of the Demkinskoye oil deposit in the south-east of Tatarstan.Materials and methods. The research was carried out using the methods of optical microscopy, x-ray diffraction and electron paramagnetic resonance (EPR).Results. On the example of the Tulsky and Bobrikovsky oil-saturated Visean quartz sandstones, we analysed the influence of wateroil fluids on rocks and features of the secondary transformations of quartz grains in the Demkinsky oil field in the southeast of Tatarstan Republic. In the oilcharge stage, the spatial redistribution of silica was realized. Quartz grains dissolved in the sole and middle part of the reservoir, precipitating in the form of chalcedony in the top part of the reservoir. The dissolution of quartz grains was promoted by micro defects concentrated on their periphery. The dissolution was triggered by both plastic deformations of minerals at the contacts and an increase in the alkalinity in the pore space up to pH = 9-10. Chalcedony aggregates were formed in the intergranular space of oil-saturated sandstones. Depending on the nucleation point of the siliceous substance and silica concentration in pore fluids, either single spherulitic or agate-type aggregates were formed. According to EPR, the studied chalcedony aggregates have a high content of paramagnetic E'-centres. This was caused by a deficiency of oxygen in the mineral-forming fluid during chalcedony precipitation.Conclusions. Chalcedony precipitation underwent in acidic conditions, which led to silica-type metasomatism in the top part of the reservoir followed by substitution of muscovite grains by morphological fibrous chalcedony. Metasomatism affected the grains of both detrital muscovite and muscovite present as inclusions inside quartz grains. This process indicates the manifestation of surface and bulk diffusion of silica, affecting all clastic components.

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Depositional Environment in Bobrikovsky Time within the South-east of the Russian Plate

Cited by 2 publications

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Reservoir oil deposits in terrigenous complexes of the Bobrikian horizon of the western slope of the South Tatar arch

Reservoir oil deposits in terrigenous complexes of the Bobrikian horizon of the western slope of the South Tatar arch

Features of the transformation of Visean quartz sandstones under the influence of water-oil fluids

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