PHYSICAL MODELING FOR DENSITY MEASUREMENT OF NEAR-SURFACE ROCKS, BY WIRELINE LOGGING AND LOGGING WHILE DRILLING

The results of the creation of full-scale physical models of rocks for the calibration of combined tools of radioactive logging, which include density logging, are presented. Four sets of models were built for different logging problems. 1. Models of porous carbonate reservoirs with borehole (diameter 216 mm), equipped with interchangeable simulators of casing columns (146 mm і 168 mm) with cement sheath and tubing. The models are aimed to calibrate wireline logging tools for investigating the section of uncased and cased oil&gas wells. 2. Models of rocks of different density with borehole (160 mm), equipped with interchangeable drill collars (120 mm, 108 mm, 89 mm). The models are designed to calibrate density tools for logging while drilling horizontal oil&gas wells. 3. Universal models of porous carbonate reservoirs, crossed by holes of three diameters (200 mm, 160 mm, 125 mm). The purpose of the models is to calibrate wireline logging tools for investigation of section of uncased and cased oil&gas wells and tools for logging while drilling horizontal oil&gas wells. 4. Models of near-surface rocks of different density, equipped with a steel pipe (diameter of 51 mm) closely fitting to rock. The purpose of the models is to calibrate density tools for investigation of near-surface rocks when solving engineering-geological, seismic microzoning, ecological, etc problems. Physical models were designed and constructed by the employees of the Institute of Geophysics of the National Academy of Sciences of Ukraine together with partner organizations. The regular use of the models is due to the active work carried out by the Institute of Geophysics, together with partners, to create apparatus-methodical complexes of radioactive logging, which include the density logging. Graduation relationships and calibration functions for new density logging tools, obtained on the constructed physical models, as well as examples of density determination in different well conditions when solving research-and-production problems, are given.

GEOLOGICAL INDUSTRIAL ASSESSMENT AND RANKING OF PROMISING OBJECTS OF THE DOMESTIC BASE OF RARE EARTH ELEMENTS

Changes in the priority areas of financing in the field of subsurface use and their widespread reorientation to the search for alternative sources of raw materials which could ensure the development of modern high-tech industries are the promising direction for the country's growth in sustainable development conditions and Green Energy Transition. And at the moment the only resource that can ensure safe progress in the future and plays an important role in today's technological development is rare earth elements (REE). Within the framework of this study information on the current state of awareness about the REE mining prospects in Ukraine was analyzed and generalized; the systematization and updating of available data on quantitative and qualitative REE ore occurrences and deposits characteristics and their geological and industrial parameters was done; the main obstacles / barriers to the active mining development on these objects of potential extraction were identified. The obtained ranking results of domestic deposits and REE manifestations prove the expediency of investing in geological exploration and mining operations conducted in certain areas, which are identified as the most attractive for further industrial development and generally emphasize the prospects of the studied area and justify the need in intensification of selected rare earth objects field development.

SELF ORGANIZING NEURAL MAPS IN THE PROBLEMS OF ECOLOGICAL MONITORING

There is a certain problem in ecological monitoring of the environment state according to the measured values of a certain abiotic factor. Namely, how to build a continuous map of environmental pollution throughout the controlled area, based on the results of measurements carried out at a finite number of points inside the controlled territory. The aim of the work is to study the possibility of using the method of self organizing neural maps (SOM) for the problems of the ecological monitoring of the environment, and specifically for building an accurate continuous map of environmental pollution on the ground. The materials and methods of researches are the results of measurements the ambient equivalent of the continuous X-ray and gamma radiation dose rate on a territory of the historical center of Kharkiv has been used as research materials; processing of the obtained data by SOM's methods using MatLab 8.1 and STATISTICA 10 computer programs has been done. Results: in the process of 1000 self-learning cycles of a neural network of 100 initial active neurons randomly located on the controlled area map, 25 neural clusters have been obtained, the coordinates of the centers of which practically coincided with the 25 control points coordinates. A continuous map of the background radiation on the controlled area has been built. The accuracy of this map was no worse than 0.25 μR/hour. Conclusions: the possibility of using the SOM methods to build a continuous map of the level of environmental pollution on the ground based on the results of measuring the values of a certain abiotic factor in a finite number of points has been proven. It has been proven that this method is more accurate compared to the methods of regression mapping and cluster analysis, from which it is essentially different. The possibilities for a significant improvement in the accuracy of the method lie in increasing the number of initial neurons on the terrain map and the number of iterations during their training.

STRATIFICATION OF CRETACEOUS DEPOSITS OF THE SECTION ¹ 29 – ZAKHIDNOÎKTYABRSKA (KARKINITSKO-NORTH CRIMEAN TROUGH) BY PALYNOLOGICAL DATA

The Karkinitsko-North Crimean trough is a promising region of Ukraine for the search for hydrocarbons, and one of the main oil and gas complexes is the Cretaceous.Therefore, a detailed biostratigraphic subdivision of the Cretaceous sediments is important and necessary, which are the basis for further prospecting work and for the correlation of North Crimean trough with the similar age deposits of the adjacent regions. The Neocomian strata are especially problematic for subdivision and correlation. According to the results of the study of microphytofossils, the stratification of Cretaceous deposits of the Karkinitsko-North Crimean trough was carried out on the example of the supporting well ¹ 29 – Zakhidnoîktyabrska. There are four spore-pollen complexes: Barremian, Aptian, Albian and Cenomanian. For the first time, the Cretaceous deposits were dissected according to the systematic composition of dinocysts, as well as the paleontological characteristics of sediments by other groups of microfossils – spores and pollen of higher plants, remnants of green algae, acritarchsand miñroforaminifers.

ELECTRO-OSMOTIC FRACTIONATION OF HYDROGEN ISOTOPES IN ELECTROLYTIC SOLUTIONS USING COMPOSITE PROTON-PERMEABLE MEMBRANES

Based on the analysis of the features of electroosmotic processes that are implemented in proton-conducting membranes, the possibility of fractioning hydrogen isotopes in electrolytes formed using tritiated water (HTO) is estimated. The interaction of the solution with the membranes in their channels leads to polarization and partial dissociation of the electrolyte molecules. In water molecules, when protium is replaced by a heavy isotope of hydrogen, the energy of breaking of hydrogen bonds increases and the process of their dissociation proceeds predominantly according to the scheme: HTO ↔ H+ + TO—. A part of the released protons can join water molecules to form the H3O+ ion. H3O+ and TO— ions are more mobile than other singly charged ions. The main characteristic that determines the suitability of electroosmotic membranes to the fractionation of hydrogen isotopes is proton conductivity. The released protons have anomalously high mobility due to their small size, tunnel and relay movement through hydrogen bonds between adjacent polar groups in the channels of the proton-conducting membranes. To ensure high proton conductivity in the pores and channels of the membranes, modifying substances are fixed, which contain the groups: –ОН- , –NH2, –NH, –SH, –COOH, –SO3H, acid salts and oxides, containing surface proton-conducting groups. To create proton-conducting membranes, it is possible to use surface-modified β-alumina (β-Al2O3(H3O+)) and protonated (H3O+) montmorillonite with ionic conductivity (5х103 – 4х104 Ohm х cm–1). The most effective are surface modifiers with negatively charged sulfonic groups. The imposition of an external electric field leads to the movement of ions in the electrolyte, which leads to a redistribution of the isotope ratio in the near-anode and cathode spaces.

LOCALIZATION FEATURES OF URANIUM MINERALIZATION IN THE TASIAST-TIJIRIT TERRANE, THE REGUIBAT SHIELD

The Reguibat Shield is an area of intensive uranium exploration and about 80 ore occurrences have been discovered in recent decades within its borders. The region of the study is located within the Tasiast-Tijirit terrane, which represents a northwestern part of Archean domain of the Reguibat Shield. The rocks of the terrane are of Mesoarchean age. The main types of rocks are migmatites, gneisses and amphibolites, greenstone associations, granitic intrusions and pegmatites. Samples of pegmatites, granites, ferruginous quartzites and sedimentary rocks that showed an increased radiation level after conducting a ground-based radiometric survey were selected for laboratory studies from the host rocks of the Tasiast-Tijirit terrane. The following types of laboratory analyses were used for the study: 1) spectral analysis by laser-luminescence method to determine the uranium content in samples; 2) atomic emission spectroscopy for the general estimation of concentrations of chemical elements in samples; 3) X-ray fluorescence analysis to determine the chemical composition of samples and its trace elements; 4) electron microprobe analysis to determine the morphology of mineralization and the chemical composition of uranium minerals. Among the Tasiast-Tijirit terrane rocks the increased uranium content was found in the following rock associations: pegmatites and granites; ferruginous quartzites within the banded iron formation; calcretes in sedimentary rocks. According to the results of field and laboratory studies, the main factors of the localization of uranium mineralization in calcretes of the OumDherua area were established. The main geological, physical and chemical conditions essential for the formation of uranium mineralization of the calcrete type within the study region were established. It was found that granites and pegmatites could provide source of uranium for ore mineralization in sedimentary formations, such as surficial and calcrete types. The latter are studied and mined quite intensively in the world including the Reguibat Shield. The study results show the high potential for prospecting and exploration of new uranium occurrences within the Tasiast-Tijirit terrane.

FOCAL MECHANISM OF THE LITHUANIAN EARTHQUAKE OF BASED ON WAVEFORM INVERSION

The aim: Determination of focal mechanism of Lithuanian earthquake of 12.06.15 (t0 = 08:18:26.4; 55.52° N, 21.40° E; hs = 0.9 км.; ML = 2.6) by waveform inversion using direct waves and a limited number of stations. Method: Matrix method is used for modelling of seismic wave propagation in the medium modelled as horizontally layered heterogeneous elastic structure. There were obtained the relations of displacement waves on the free surface that were used for seismic tensor determination using only direct P- and S- waves. Determination of seismic tensor and the focal mechanism on the base of developed method for a point source is described. Thus, based on forward modeling, numerical techniques are developed for the inversion of observed waveforms for the components of moment tensor. Results: In the paper, a method is presented for the focal mechanism determination of Lithuanian earthquake of 12.06.15 (ML = 2.6) by waveform inversion using limited number of stations. The focal mechanism is determined using the data from two stations: PABE, SLIТ and from three stations: PABE, MTSE, SLIТ. These seismic stations are the part of BAVSEN (BalticVirtualSeismicNetwork). Scientific novelty: 1. In the paper, a method is presented for moment tensor inversion for the focal mechanism determination of events with a low seismicity. The East Baltic region (EBR) is the region with low seismicity. 2. The focal mechanism is determined using the data from a limited number of stations. Practical significance: The results of focal mechanism determination can be used to study seismicity for regions with a low seismicity using a limited number of stations.

GEOLOGICAL INVESTIGATIONS IN THE UKRAINIAN ANTARCTIC STATION REGION BEFORE 1996

The author submits a chronological account on the history of geological exploration on the Graham Coast and the Wilhelm Archipelago of West Antarctica within the time interval from 1819 to 1996. The state of geological exploration of this area before the creation of the Ukrainian Antarctic Station (UAS) here is determined. A number of conclusions were made regarding: the temporal sequence of individual studies and the geological specifics of the territories covered by them; conditions for carrying out and features of the organization of field works; the reliability of the results of individual geological surveys; the presence of unexplored territories. It was found out that all reconnaissance and geological survey work in the study area was carried out in the 30–50s of the XXth century. Medium-scale geological surveys of individual parts of the Graham Coast and adjacent islands were carried out under unfavorable conditions. This led to the fragmentariness of the created geological maps and their heterogeneous support by field observations. Due to poor ice conditions and local features of the organization of geological routes, numerous bays on the Graham Coast, as well as its hard-to-reach inland territories, have remained completely unexplored. Also, many of the islands of the Wilhelm Archipelago were not covered by geological survey. In particular, there was no way to explore those islands that are remote from the navigable Lemaire Channel, Penola Strait and Grandidier Channel. The Argentine Islands are the only site where a large-scale geological survey has been carried out. But the available large-scale geological map of the Argentine Islands has a number of significant disadvantages. The map contains only petrographic data. There are no elements of bedding of rocks, tectonic deformations, zones of postmagmatic changes, manifestations of ore mineralization. The spatial distribution of the main petrographic representatives does not always correspond to the true one. The relative ages of individual geological bodies are insufficiently substantiated, and sometimes, in general, are determined incorrectly. All of the above-mentioned explains why the level of geological knowledge about the area at the time of the creation of the UAS here remained much worse than in the adjacent territories.

METHODOLOGICAL PRINCIPLES OF GEOPHYSICAL STUDIES OF KARST DANGEROUS TERRITORIES

The article is devoted to the analysis of the methodological principles of applying geophysical research methods in the study of karst-hazardous territories. The tasks that are posed in specialized studies of karst and geophysical methods for their solution are given. Four stages of specialized studies of karst-hazardous territories are identified: reconnaissance-methodological, prospecting, reconnaissance and monitoring. The set of geophysical methods for the development of these stages are determined. It is noted that a rational set of geophysical methods in the study of karst processes is determined for each individual natural environment (individual site). The possibility of performing field research by a separate geophysical method in this area, the presence of differentiation in rocks according to their physical properties which are used by a specific geophysical method and economic efficiency of the application of this geophysical method were taken into account. As an example, some results of geophysical studies carried out in the framework of the Lyubensky field of native sulfur are given.