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Nuclear geophysical methods
Subject: GEOPHYSICAL METHODS OF RESEARCH
The goal of the course of lectures is to familiarize students with:
It is underlined that best results can only be achieved through a complex of geological and geophysical methods of research. The course contains methodology of conducting magnetometric, gravimetric, electrometric, seismometric, nuclear-geophysical research currently widely used for geological works.
Upon successful completion of the course students should be able to:
Laboratory classes are dedicated to development of skills necessary for solving specific practical tasks requiring knowledge of physical properties of rocks and their dependence on series of geological conditions as well as using corresponding calculations and methods of interpretation of geophysical materials with the help of computer technologies.
Below find the contents of lectures as per corresponding methods of research applied at the time of conducting geophysical works.
Electrical methods of survey and their classification. Description of electrical properties of rocks (necessary electric resistance, dielectric permeability, polarity, electrochemical activity) and their dependence on electrical properties of minerals comprising the rocks, natural solutions filling pores and cavities, pressure, temperature, phenomena taking place at the contact of solid and liquid phases, etc.
General notion of resistance method. Notion of visible resistance. Diagrams of observations (two-, three-, four- electrodes, dipolar, combined, differentiated devices).
Apparatus and equipment used for working with direct and infra low current (compensational, autocompensation methods, electrical stations, etc.). Sources of current – batteries, generators, dry elements, etc. types of grounding and cables used for electrical survey.
Methods of vertical electric and dipolar sounding. Required conditions for application of these methods, methodology of conducting works: selection of shooting criterion, direction of survey works, length of supply line and its growth increments (An, Bn / An-1 Bn-1 ), topographic supply of works. External and internal control over the quality of received materials.
Representation of sounding results (design of diagrams and determining their type), their qualitative (compiling maps of curve types of sounding, similar figures of longitudinal conductivity and absciss of extreme points and vertical electric cross sections) and quantitative (statistical and machine methods) interpretation.
Examples of application of sounding method for solving various geological tasks.
Electrical profiling: selection of the type of device and determining its optimal dimensions, directions of profiles and density of the observation limit. Precision of research.
Practical application of the materials of electrical profiling (compiling diagrams pп, correlation plans, maps of similar resistances and polar diagrams), qualitative and quantitative interpretation of the results of this method.
Application of electroprofiling for solving various geological tasks.
Methods of charged objects, their essence and conditions necessary for application. Scheme of observations, construction of grounding for supply and receiving circle, source of current and construction of measurement equipment. Precision of works. Representation of materials, qualitative and quantitative interpretation of results of observation.
Method of natural electric field (NEF). Reasons of formation of fields of different origin (electrochemical, filtration and diffusive). Methodology of shooting (selection of criteria, scheme of observation, direction for profiles dislocations, equipment, receiving electrodes, etc.) determination of the quality of research. Area of geological application of the method.
Method of caused potentials, its essence and methodology of conduction of works (apparatus and equipment, selection of criteria for shooting, schemes of observation, precision of research, etc.). Representation of results, their qualitative and quantitative interpretation. Examples of application of the method for solving various geological tasks.
Natural impulse electromagnetic field of the Earth, reasons for its formation, ways of measuring and interpretation of received materials.
Nature of the Earth’s magnetism. Elements of the magnetic field of the Earth and their distribution on the surface. Normal and abnormal geomagnetic fields. Change of the elements of the earth’s magnetic fields in the course of time.
Magnetic properties of rocks and their dependence on contents of magnetic minerals in rocks, forms of ore objects, temperature and various geological factors(contents of rocks, level of weathering, cracking, depth of deposition, time of formation, level of metamorphism, etc.).
Selection of method for conduction of magnetic research depending on the type of shooting (general, survey and detailed) – selection of parameters for measuring and equipment, criteria, geodesic support of works, precision of research, etc.
Special types of magnetic survey. (aero-, micromagnetic shooting and underground magnetic survey).
Representation of the results of shooting (compiling diagrams, maps, isodynams, isogons, isoclines). Direct and reversed tasks of magnetic survey. Qualitative and quantitative interpretation of magnetic survey.
Area of application of magnetic survey (study of the Earth’s crust, tectonic zoning, paleomagnetic research, explorations for iron ore and other ore and non-ore mineral deposits, search of structures, geological mapping, micromagnetic shooting).
Gravitational field of the Earth and its constituents. Potential and derivatives of the potential of gravitation. Normal and abnormal gravitational fields and their changes in the course of time. Reductions and abnormalities in gravitation.
Schilnist of rocks and methodology for its determination. Dependence of //// on: mineral contents, porosity, shparuvatost, weathering of rocks, depth of deposits, age, level of metamorphism, etc.
Methodology of conduction of gravimetric research supposing selection of: parameters of measuring, density and form of the observation limit, apparatus, ways of conducting field observations, topographic-geodesic support, precision of measurements. Variometric and gradientometric shooting. Ways of conducting works at the time of surface, marine, air, underground research.
Practical application of the materials of surface gravitational shooting. Representation of the results of shooting (compiling diagrams, plans and isolines), selection of criteria and intervals between isolines.
Fundamentals of the theory of interpretation of gravitational fields. Qualitative and quantitative interpretation using analytic formulas, graphic methods and EOM.
Limits of application of materials of gravimetric measurements at the time of solving engineering-geological and ecological tasks: search and contouring deepened valleys, study of karst of rocks, determining depth and forms of deposition of maternal rocks, mapping tectonic movements.
Seismology and seismic survey. Elements of theory of strain and geometric seismicity. Types of seismic waves and conditions for their formation and spreading in the upper layers of the globe.
Strain properties of rocks and their dependence on geological causes (contents of rocks, porosity, water saturation, density, age, temperature, depth of deposition, etc.).
Notion of seismic channel and portable seismic equipment used for research in relatively not deep areas (100 m): seismic station, seismic receiver, exciter of strain waves, electric supply.
Methodology of conducting seismic research by method of reflected and refracted waves. Conditions for their possible application. Observation systems using methods of seismic profiling and sounding, seismic “X-ray” and carotage. Struggle with obstacles of non-geological nature. Precision of research.
Compiling hodographs of direct, opposing and overlapping waves and approximated hodograph. Systems of observation based on methods of reflected waves. Methods of creating seismic borders. Ways of determining speed of reflected and refracted waves. Determining dynamic module of strain (module of Yunge) and coefficient of Poisson for massif rocks according to the results of field research.
Application of seismic survey for solving geological tasks: study of the Earth’s crust structure, tectonic zoning, search of structures with potential oil and gas deposits, ore and engineering seismic survey.
Using natural and caused radio activity for accomplishing geological tasks. Surface and air gamma-shooting. Apparatus and equipment. Application of radioactive isotopes for explorations for certain mineral deposits. Geological tasks and areas of application of field nuclear geophysical methods.
GEOHYSICAL RESEARCH OF BOREHOLES (CAROTAGE)
Main methods of geophysical research of boreholes and their classification.
Electrical methods of carotage (dielectric and inductive carotage, etc.)
Nuclear research of boreholes (gamma-carotage, gamma-gamma-carotage, neutron methods of carotage). Methods of determining of substance contents of rocks and ores in boreholes.
Areas of application of different methods of carotage.
Methods of study of technical condition of boreholes (cavernometry, inclinometry, perforation, torpedoing).
Qualitative and quantitative interpretation of carotage materials (correlative scheme, combined geological carotage cross-section).
|Course Syllabus||Course Syllabus|
|Syllabus||The syllabus of practical lessons|