Evaporite rocks as a factor in formation of non-structural traps

The paper considers the improvement in classification of oil and gas traps formed in non-anticlinal conditions. The relevant aim is to expand the areas where hydrocarbon accumulations are searched for and to take into account the new search attributes. Evaporite rocks, widely developed in many oil and gas basins, have properties that contribute to the preservation of hydrocarbon deposits. Depending on the structural features of the salt formations, their impact on the location of oil and gas deposits varies. The deposits associated with the evaporite rocks are analyzed. Types of traps, the main factor in formation of which are evaporites, are defined. Such traps are proposed to be treated as a separate category. Keywords: evaporite rocks; non-structural and combined traps; hydrocarbon accumulations; classifications of traps; tectonic style; sealed reservoirs.

Experimental capabilities of seismic emission tomography for solving the problems of searching and exploration of deep hydrocarbon accumulations

The standard seismic prospecting has been designed to investigate thin layering at shallow depths. At depths more than 4 km the rocks are significantly compacted, change their properties and it is often impossible to trace clear horizons by reflected waves. In the crystalline basement and lower horizons of the sedimentary cover the block structure of rocks is clearly manifested. Taking this into account geological models should be developed and other predictive indicators should be used when searching for hydrocarbon accumulations. For the study of great depths more informative seismic methods are emission and transmission tomography which have been developed in detail in seismology. This article discusses prognostic indicators different from seismic prospecting and presents experimental results confirming the success of emission tomography in their detection using the example of field studies at developed hydrocarbon deposit and other geophysical objects. The range of working depths of research covers the entire crust of the Earth including the crust-mantle transition zone. Keywords: seismic emission; emission tomography; rocks; hydrocarbon deposits.

Features of the composition of gas sorbed in the rocks of the upper part of the sedimentary cover section

The topicality of the article is determined by the insufficient reliability of geochemical oil and gas exploration data for the localization of petroliferous geological objects. Geochemical surveys are carried out to mapping hydrocarbon anomalies caused by vertical migration of fluid from hydrocarbon deposits. Practice shows that not all anomalies in the content of hydrocarbons in the near-surface environment are related to the oil-bearing capacity of a given subsoil area. Therefore, when interpreting the data of geochemical oil and gas prospecting surveys, it is necessary to take into account not only quantitative indicators (namely, content of hydrocarbon gases on the surface), but also the composition of the gas sorbed by the near-surface substrate. The purpose of the article is to determine the composition of the dissipated gases in the rocks of the upper part of the section, to reveal the inter-component relationships, and, on this basis, to determine the genesis of each gas component sorbed by the rocks of the upper part of the section. To solve this problem, statistical processing of data on the component content of gas from core degassing of shallow (up to 30 m) wells drilled in the petroliferous territory of the north of Western Siberia was carried out. The obtained results confirmed the genetic heterogeneity of dissipated hydrocarbons and inorganic gases in the upper part of the sedimentary cover.

The geosolitonic concept of high output hydrocarbon deposits formation

Based on the well-known results of studies of the ether-geosoliton concept of the growing Earth, the article presents the conclusions that made it possible to propose a model of thermonuclear synthesis of chemical elements that form renewable reserves of developed oil and gas fields. It was revealed that local zones of abnormally high production rates of production wells and, accordingly, large cumulative production at developed fields in Western Siberia are due to the restoration of recoverable reserves due to geosoliton degassing. Therefore, when interpreting the results of geological and geophysical studies, it is necessary to pay attention to the identified geosoliton degassing channels, since in the works of R. M. Bembel and others found that they contributed to the formation of a number of hydrocarbon deposits in Western Siberia. When interpreting the results of geological-geophysical and physicochemical studies of the fields being developed, it is recommended to study the data of the ring high-resolution seismic exploration technology in order to identify unique areas of renewable reserves, which can significantly increase the component yield of hydrocarbon deposits.

Comparison of forecast estimates of seabed subsidence of the Yuzhno-Kirinskoye field

The geodynamic consequences of the field development process include the subsidence of the earth’s surface. Monitoring of deformations in offshore fields is difficult and it is necessary to evaluate them by various methods. It is important to investigate how much the calculated amplitude of the seabed subsidence is reduced by taking into account changes in the porosity and compressibility of the pore space with a decrease in reservoir pressure. The analysis of changes in the petrophysical parameters of the reservoirs of the Daginsky horizon during the projected development of the Yuzhno-Kirinskoye hydrocarbon field for depletion and a decrease in formation pressure by 10 MPa showed that the porosity decrease will be 0.038 absolute percent, the compressibility of the pore space will decrease by 0,08 10-3 1/MPa. With the help of the Petrel software, changes in the thickness of the productive layer from 80 to 120 cm were obtained, which can be taken as an estimate of the seabed subsidence in the area of the field. The application of the genetic model of the deformable formation by Kuzmin Yu showed that the maximum amplitude of the seabed subsidence to be 101 cm. Comparison of these estimates of the seabed subsidence indicates their proximity. Taking into account the dynamics of tectonophysical and petrophysical characteristics due to the long-term development of hydrocarbon deposits significantly changes the intensity of the deformation state of the rock mass and the earth’s surface above the field.

Geochemistry of natural gases from sediments of terrigenous and carbonate formations of the Bukhara-Khiva oil and gas region of Uzbekistan

The results of long-term studies of natural gases in the Bukhara-Khiva oil and gas region of Uzbekistan are summarized. The results of studying the composition of gases in hydrocarbon deposits generated by OM of continental (terrigenous deposits of the Cretaceous and Middle Jurassic) and marine (carbonate Jurassic) facies are presented. Regularities of changes in individual constituents of gases (hydrocarbons, hydrogen sulfide, carbon dioxide, nitrogen, etc.) with depth are considered; the influence exerted on the composition of gases by various factors and, above all, those of them, which, in the opinion of most researchers, are the main ones. The revealed patterns are used for predictive assessment of the distribution of various constituents of natural gases in the study area.

Comparative analyses of changes in the ice cover of the Tatar Strait in relation to 1961-1990 and 1991-2020 climate normals

Current warming in the Northern Hemisphere has encompassed not only the surface atmosphere, but also manifested itself in a change in the state of the sea ice cover, as an integral part of the climate system. One of the indicators of the warming was a reduction in ice cover observed in the water area of the Far Eastern seas since the late 1980s. The prospective areas of hydrocarbon deposits discovered in the Tatar Strait, as well as the existing needs for the transportation of hydrocarbons along the shipping routes in the strait, led to the emerging interest in researching the ice regime of the Sea of Japan in the modern climatic era. The proposed paper analyses the changes in ice cover of the Tatar Strait in relation to 1961–1990 and 1991–2020 climate normals. The regularities of the long-term variability of ice cover within non-overlapping 30-year periods were revealed. The analysis of the dynamics of ice cover anomalies, calculated for each normal separately, was carried out. An assessment of the distribution of winter types in the periods under study was carried out. The characteristic features of variations in the intra-seasonal course of ice cover and the dates of the onset of ice phases in different types of winters were identified.

Substantiation of paleohydrodynamic sedimentation modes and identification of missed oil-and-gas saturated areas that are promising for additional exploration of the Lower Cretaceous deposits of the Albian stage of the Achikulak oil field according to geophysical well logging data

In the development of the oil and gas complex, the improvement of methods for studying the patterns of distribution of hydrocarbon deposits is of particular importance. At the same time, scientific research can be carried out in different directions. These include increasing the resolution of various methods of borehole and areal geological and geophysical studies of lithological features and oil-and-gas content, developing new approaches to interpreting well logging results, analyzing the productivity of poorly studied regions and areas of the section, identifying low-amplitude folds and non-anticlinal deposits. The development of hydrocarbon deposits in the Stavropol Territory has been going on for many decades, which has led to reduction of deposits within medium and large anticlinal uplifts. Therefore, the main attention is now paid to the prospect for low-amplitude and small-size uplifts and traps of the non-anticlinal type, which include lithological and stratigraphic ones.

Interpretation of electrical logging data from the Hettangian-Aalenian terrigenous reservoirs in the Southeast of Western Siberia

In the southeast of Western Siberia, the most studied are the Upper Jurassic deposits, most of the oil and gas fields being confined to them. However, the probability of discovering new hydrocarbon deposits in the Upper Jurassic horizons is extremely small. Therefore, of great importance is finding new hydrocarbon deposits in less studied deep-lying complexes. The article considers the development of a criterion for determining the saturation type of the terrigenous reservoirs in the Hettangian-Aalenian deposits in the southeast of the West Siberian sedimentary basin. We use the example of the Ust-Tym megadepression, a large depression located in the central part of the Tomsk region. The Lower and Middle Jurassic sections are represented by the Urman and Togur formations, Salat formation (Peshkov formation is its isochronous analogue) and Tyumen formation, and characterized by the alternation of predominantly sandy (potential reservoirs) and argillaceous-carbonaceous (seals) sequences. In the studied interval, tests were carried out in just a few wells, for which reason the identification of deposits and promising objects is complicated. Determining the type of reservoir saturation will significantly improve the assessment of oil and gas potential. As a result of interpreting lateral logging sounding data, the geoelectric parameters of the invasion zone and undisturbed formation were reconstructed for the Lower Jurassic and Aalenian deposits. Based on the well logging data interpretation by means of numerical inversion, we obtained the criterion for the saturation type of the reservoirs (Ju11-17) in the Hettangian-Aalenian complex. The boundary resistivity values for the oil-saturated reservoirs vary from 8 to 20 ohm∙m, while for the water-saturated ones they do not exceed 5 ohm∙m.

About characteristic features of naftides in connection with the process of formation of deposits

Studies have been carried out to assess the qualitative features of fluids, aimed at identifying the regularities in the differentiation of the properties of naphthides during the formation of hydrocarbon deposits outside anticlinal structures. Due to the exhaustion of hydrocarbon reserves associated with anticlinal traps, the main attention is paid to the composition of fluids confined specifically to non-anticlinal structures – to traps of a combined structure. Physicochemical properties, trace element (TE) composition, phase states of naphthides in deposits affected by hypergenetic or catagenetic processes have been analyzed using specific examples; in regions with a possible additional inflow of hydrocarbons (Romashkino group of fields in the Republic of Tatarstan); in the crystalline basement of sedimentary basins. The results of the analysis make it possible to predict the characteristic features of fluids in traps of various types at certain levels of the processes of oil formation, secondary transformation and destruction of accumulations, mainly due to the tectonic regime of the sedimentary basin. With prolonged lateral migration, at great depths with good isolation from surface weathering agents, light oils, depleted in TE, more often of nickel specialization, are found in lithologically and stratigraphically screened traps, and gas condensate accumulations are possible. At shallow depths with poor regional or local seals, heavy, highly viscous hypergene-transformed oils, natural bitumens with high concentrations of industrially significant metals V, Ni, Co, Mo Cd, U were found in traps of pinch-out zones and various types of trap screening. tectonically-screened traps) with a multiphase filling of traps and, at the same time, the influence and inflow of deep ones, i.e. more catagenically transformed fluids, it is possible to detect light oils of the nickel type or gas condensates enriched with elements of “magmatic emanations” – As, Hg, Al, B, rare earth elements. Oils filling combined traps in the crystalline basement within platform oil and gas basins, as a rule, do not differ in their compositional peculiarities in comparison with oils in overlying or adjacent parts of the sedimentary section.