Геология

In the established practice of geological exploration for oil and gas conclusions about the facies belonging of the rocks of oil and gas basins and individual exploration areas were made mainly on the basis of the study of core material. Recently for this purpose the results of seismic exploration and well logging have been used. Geophysical methods despite their obvious progress are indirect and intermittent core sampling and incomplete coring make facies analysis difficult.

Geological and geophysical modeling is a modern and classic method of processing and interpretation, which is relevant in the segment of geological exploration of any geophysical method. The article presents the material of two-dimensional modeling based on the results of gravity and seismic exploration in the licensed areas of the Saratov region.

The article presents the methodology of the representative elementary volume definition for 1 m long whole core segments. Scientific articles focused on factors controlling elastic properties are analysed. Terms of additivity and nonadditivity for physical properties of rocks are discussed. The algorithm of core sampling including drilling out of three perpendicular core samples for estimation of elastic anisotropy was used.

A detailed description of the Upper Jurassic formations of the south of the European part of Russia, mainly restricted by the Kimmeridgian and Volgian stages, is given. The characteristic of the reference section is provided for the Vechkusy Formation, and the neostratotype is proposed for the Novikovka Formation. The criteria for drawing the boundaries of local stratigraphic units (formations) and the features of strata distribution are considered in detail.

A method is proposed for calculating the normal compaction curve of rocks for the deep parts of the lithosphere. It is based on the analysis of petrophysical characteristics and interpretation of gravitational anomalies. The main regularities of density changes in the lithosphere of Northern Eurasia are investigated.

A detailed study of the section of the severodvinsky and vyatsky stages of the Upper Permian with layer-by-layer sampling of ichthyofauna in the western part of the Orenburg region (basin of the lower reaches of the Samara River) was carried out. Based on the fish complexes, a paleontological justification of the stratigraphic boundary between the severodvinsky and vyatsky stages was obtained in the region for the first time.

The article presents the methodology of the representative elementary volume definition for two 1 m long whole core segments. Scientific articles focused on practical methods of representative volume calculations using various physical parameter fluctuations have been studied. Porosity values of every whole core fragment evaluated in two ways using the 7.3 cm diameter core samples in the first approach and the 3 cm diameter core samples in the second one have been compared.

The analysis of the distribution of the Kimmeridgian–Volgian ostracods in the section near the village Valy made it possible to establish a sequence of eight communities, the change of which reflects changes in the ecological conditions in the basin. Changes in sea level fluctuations, the main physical and chemical parameters of the ostracod habitat – temperature, salinity of water, oxygen content in it, eutrophy and concentration of organic matter in sediment – are reconstructed. Information on the magnetic susceptibility and its increase after heating was obtained.

Tremabolites sponges known among the Middle-Late Cretaceous beds in Europe are reliably identifiable due to the numerous openings against the background of the skeleton smooth upper surface. The ideas of the level of organization in these sponges and of the species characteristics are far from being univocal. The paper deals with the species diversity of Tremabolites common in the Coniacian – Santonian rocks from the Volga Region. Examples of regeneration and budding in the representatives of the group are presented.

The article presents the analysis of the inner structure of the salt-bearing series within the Caspian Depression. Certain salt-bearing complexes of various ages, compositions and plastic properties are distinguished. Their structural relations and the features of salt-tectogenesis manifestation are evaluated. Up to the present no subsalt uplifts have been confirmed in the Russian sector of the Caspian Depression and no HC fields have been discovered.