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GEOPHYSICAL EXPLORATION, exploration of the earth's interior using physical methods. Geophysical exploration is carried out primarily in the search for oil and gas, ore minerals and groundwater. It differs from geological exploration in that all information about search objects is obtained as a result of interpretation of instrumental measurements, and not through direct observations. Geophysical methods are based on the study of the physical properties of rocks. They are used either to identify mineral deposits (for example, magnetic properties are studied to find iron ores), or to map geological structures such as salt domes and anticlines (where oil accumulates), as well as to map the topography of the ocean floor, oceanic and continental structure the earth's crust, determining the genesis and thickness of loose sediments and bedrock, the thickness of ice sheets and ice floating in the oceans, during archaeological research, etc.

Geophysical methods fall into two categories. The first includes methods for measuring natural earth fields - gravitational, magnetic and electric, and the second - artificially created fields.

Geophysical methods give the best results when the physical properties of the studied and mapped rocks differ significantly from the properties of the adjacent rocks. Geophysical research of all types includes the collection of primary material in the field, processing and geological interpretation of the data obtained. Computers are used at all stages.

The origins of geophysical exploration methods are associated with the beginning of the use of magnetic compasses to search for iron ores and electrical measurements to identify sulfide ores. The use of geophysical techniques expanded in the 1920s as gravimetric and seismic surveys proved effective in locating salt domes and associated oil deposits along the Gulf Coast of the United States and Mexico.

Seismic exploration.

In a solid body, when a force is suddenly applied, elastic vibrations or waves, called seismic waves, arise, spherically propagating from the source of excitation. Information about the internal structure of the Earth is obtained from the analysis of the travel times of seismic waves from the vibration source to the recording devices (the travel times of the waves depend on the density of the medium along their path).

Seismic waves are generated either by artificial explosions in shallow wells or by mechanical vibrators. In marine seismic, an air gun is used to generate seismic waves. Echo-sounding emitters of high-power elastic vibrations, electric spark discharges and other means are also used.

The downward generated waves, reaching a geological boundary (i.e. rocks whose composition differs from the overlying ones), are reflected like an echo. Registration of this “echo” by detectors is called the reflected wave method. Waves refracted at the geological boundary also propagate horizontally (along its surface) over long distances, then refract again, follow to the earth's surface and are recorded far from the seismic source.

Seismic waves are recorded by sensitive instruments, seismic receivers, or geophones, which are located on the earth's surface or in wells at a certain distance from the point of wave excitation. Geophones convert mechanical ground vibrations into electrical signals. In marine exploration, pressure detectors called hydrophones are used to record seismic waves. Elastic vibrations are recorded in the form of a trace on paper, magnetic tape or photographic film, and more recently, usually on electronic media. Interpretation of seismograms allows one to measure the travel time of a wave from the source to the reflecting layer and back to the surface with an accuracy of thousandths of a second. The speed of seismic waves depends on the elasticity and density of the medium in which they propagate. In water it is approx. 1500 m/s, in unconsolidated sands and soils containing air in the pore spaces - 600-1500 m/s, in solid limestones - 2700-6400 m/s and in the densest crystalline rocks up to 6600-8500 m/s (in deep layers of the Earth up to 13,000 m/s).

Reflection.

When using the reflected wave method, registration is carried out by a set of geophones uniformly located on the earth's surface in line with the excitation source. Typically 96 geophone groups are used, each of which has from 6 to 24 devices connected together.

Since the distance to the geophone and the speed of propagation of seismic waves in the rocks under study are known, the depth of the reflecting boundary can be calculated from the travel times of the waves. The wave path can be described as two sides of an isosceles triangle (since the angle of incidence is equal to the angle of reflection), and the depth of the reflective layer corresponds to its vertex. The total length of the sides of such a triangle is equal to the product of the wave's travel time and its speed. Reflection surface depths are calculated over a large enough area to trace formation configurations and identify and map salt domes, reefs, faults, and anticlines. Any of these structures could be an oil trap.

Refraction.

The refracted wave method is used to study the lithology and depth of rocks, as well as the configuration of deposits and geological formations. It is also used in engineering geological surveys, hydrogeology, marine and petroleum geology. Seismic waves are excited near the earth's surface, and detectors that record refracted waves are located on the earth's surface at some distance from the vibration source (sometimes many kilometers away). The first to reach the detector is the refracted wave that followed the shortest path from the source to the receiver. Using the hodograph (graph of the time of arrival of the first wave pulse to geophones located at different distances from the source), the speed of wave propagation is determined, and then the depth of the refractive surface is calculated.

Gravimetric survey

widely used for reconnaissance of poorly studied areas. In these studies, the force of gravity is measured with such high precision that even small changes in it, due to the presence of buried rock masses, make it possible to determine the depth and shape of their occurrence.

Gravimetric instruments are among the most accurate; they can measure variations in the gravitational field with an accuracy of one hundred millionths. The most typical of these instruments, the gravimeter, uses a horizontal balance bar (pendulum) that deviates from its equilibrium position with the slightest change in the force of gravity.

The Earth's gravitational field is determined by the density of its constituent rocks. Gravimetric reconnaissance does not operate with absolute measurements of the gravitational field, but with the difference in the acceleration of gravity from one point to another. During the gravimetric survey, horizontal changes in the gravitational field due to differences in the composition and density of rocks are recorded. With depth, their density changes in the range from 1.5 g/cm 3 (loose sands) to almost 3.5 g/cm 3 (eclogite). The gradient is even ok. 0.1–0.2 g/cm 3 leads to the occurrence of recognizable anomalies (deviations from the standard value of gravity) if the body under study is large enough, shallow and the noise is not too great, i.e. interference from external sources.

Gravimetric surveying is used to identify salt domes, anticlines, buried ridges, faults, shallow bedrock, intrusions, ore bodies, buried volcanic craters, etc. see also GRAVITY.

Magnetic prospecting

is based on measuring small changes in the geomagnetic field associated with the presence of magnetic minerals in surface sediments or in the geological basement - igneous and metamorphic rocks underlying sedimentary strata. Magnetic variations caused by magnetic minerals are used to search for deposits of iron ores and pyrrhotite, as well as associated sulfide ores. Studies of magnetic variations created by basement rocks make it possible to study the structure of the overlying layers of the earth's crust. When searching for oil and gas bearing strata, magnetic prospecting methods determine the depth, area and structure of sedimentary basins.

The magnetic susceptibility of rocks is measured using the magnetic method. The important iron ore mineral magnetite is characterized by the highest magnetic susceptibility (2-6 times higher than that of two other also highly magnetic minerals - ilmenite and pyrrhotite). Since magnetite is quite widespread, changes in the geomagnetic field are usually associated with the presence of this mineral in rocks. Magnetic minerals associated with igneous basement rocks have a much higher magnetic susceptibility than rocks of the sedimentary cover. This determines the contrasts in their magnetization.

In recent years, based on the study of the magnetization of rocks of the ocean floor, much new information has been obtained about the history of the Earth, especially about the formation of ocean basins and the position of continents in the distant geological past. Rocks often retain residual magnetization corresponding to the geomagnetic field at the time of their formation. Thus, remanent magnetization is a kind of “record” of changes in the Earth’s magnetic field throughout its history. Based on magnetic studies, it has been confirmed that as mid-ocean ridges grew, ocean basins expanded. see also OCEAN .

Magnetic surveys are usually carried out from aircraft using magnetometers. The first aeromagnetic instruments used measuring instruments developed during World War II to detect submarines. see also GEOMAGNETISM.

Electrical or electromagnetic reconnaissance

(electrical prospecting) is intended to study the internal structure of the Earth and the geological environment, search for minerals based on the study of various natural and artificial electromagnetic fields. Electrical prospecting is based on the differentiation of rocks by electromagnetic properties. The nature of electromagnetic fields caused by both artificial and natural sources is determined by the geoelectric structure of the study area. Some geological objects, under certain conditions, are capable of creating their own electric fields. Based on the identified electromagnetic anomaly, conclusions can be drawn aimed at solving the assigned problems.

Electrical prospecting has more than 50 methods. This variety of methods is explained by the fact that it uses natural fields of cosmic, atmospheric and electrochemical nature; artificial fields with various methods of their creation and measurement (galvanic, inductive and remote); harmonic fields of a wide frequency range; pulsed fields of different durations; signals of different frequency (from millihertz to hundreds of terahertz) and dynamic ranges are recorded. In addition, electrical prospecting uses the latest advances in electrical engineering and radio electronics. During electrical prospecting, the amplitudes of the electric and magnetic field components, as well as their phases, are measured. Registration is carried out in analogue or digital form. Modern computer technology is widely used in measurements, processing and interpretation of results.

Nuclear geophysical methods

are based on the study of natural radioactivity of rocks or secondary radioactivity arising from neutron or gamma irradiation of rocks. There are gamma, neutron activation, and X-ray radiometric methods. The most widely used method is the gamma method, which measures the intensity of gamma radiation from natural radionuclides contained in rocks. Changes in radioactivity depend on the composition and properties of rocks, which makes it possible to use these methods to study the geological structure of the territory, the processes occurring in the subsurface, and to identify mineral deposits in them.

Edition: Nedra, Moscow, 1971, 344 pp., UDC: 550.8+622.275/.276 (071.1)

Language(s) Russian

The book outlines the geological foundations of prospecting, exploration and development of oil and gas fields to the extent necessary for economic engineers of oil fields and gas fields. It contains information on oil geology, hydrogeology and reservoir physics. Much attention is paid to the description of geophysical methods for studying wells. The geological foundations of the development of oil fields and the systems for developing characteristic types of oil deposits are described in detail. Attention is paid to methods for planning oil production, express methods for calculating oil production in long-term planning.

The book is intended for students of petroleum universities and faculties. It can also be used by engineers and technicians in the oil industry and employees of research institutes

Edition: BSU, Minsk, 2001, 120 pp., UDC: 550.832(075.8)

Language(s) Russian

The textbook covers the main issues of methods of prospecting, exploration, testing and evaluation of deposits of mineral construction raw materials - sand, sand and gravel material, clays, etc. Recommendations are given on the use and integration of geological, geophysical and remote aero- and cosmogeological methods, as well as methodology research of deposits of mineral construction raw materials in various geological conditions. Particular attention is paid to the specifics of searches and exploration of construction raw materials in Quaternary deposits on the territory of Belarus.

Intended for students of geological specialties of BSU. It can be used by geologists of industrial organizations engaged in the search and exploration of mineral deposits

Edition: OSU, Orenburg, 2013, 102 pp., UDC: 550.812.14 (076.5)

Language(s) Russian

The textbook presents tasks and exercises on prospecting, exploration and geological and economic assessment of deposits, a methodology for compiling a course project and a sample course assignment.

The textbook is intended for students of specialty 130101.65 – Applied Geology

Edition: St. Petersburg State Mining Institute, St. Petersburg, 1983, 117 pp., UDC: 550.849.082.75 (075.80), ISBN: 5-230-19525-8

Language(s) Russian

Since the first edition came out in 1960, geoelectrochemical methods have been further developed. The physical and mathematical theories of these methods, new methods of polarization used in KSPC (cyclic, potentiodynamic, etc.) have been developed, the VSPK method has been introduced, new modifications of the PFM method and polarographic logging have been created, and the production of improved equipment has been mastered. The scope of application of the methods is expanding, including their use in Canada, Australia, China, India and other countries.

In this regard, this second edition includes new sections, and the old ones are significantly revised and supplemented.

The textbook for the course “Special chapters of electrical prospecting: geoelectrochemical methods” is intended for students of specialty 08.02 “Geophysical methods of prospecting and exploration” and can be used by students of the Faculty of Education and specialized courses, as well as graduate students

Edition: Nedra, Moscow, 1986, 324 pp., UDC: 550.08 (083)

Language(s) Russian

Basic information about deposits of solid minerals, modern methods of their search and exploration, data on geological documentation, testing and calculation of reserves is provided. In the third edition (2nd ed. - 1974), the content of the sections was updated, a chapter was introduced on the main directions and stages of geological exploration work, and new requirements for the economic assessment of deposits were set out; latest data on testing methods and techniques.

Edition: Higher School, Moscow, 1967, 166 pp., UDC: 553.982

Language(s) Russian

The book discusses the main methods of studying, processing and summarizing factual material obtained in the process of prospecting and exploration for oil and gas in various oil and gas provinces. Considerable attention is paid to the design of prospecting and exploration work and the evaluation of their results at each stage of studying both the field as a whole and individual deposits. This section is illustrated with examples from the practice of search and exploration in our country.

The manual is intended for students of geological exploration and petroleum universities and faculties, as well as for engineering and technical workers involved in the search for oil and gas fields and the exploration of their deposits.

Edition: Nedra, Moscow, 1977, 405 pp., UDC: 550.8(075.8)

Language(s) Russian

The second edition of the book, while maintaining the overall volume, is fundamentally different in structure and content from the first. A special part in which issues of prospecting and exploration of certain types of minerals were considered was completely excluded from the book. At present, the presentation of such selective data is unjustified, since after the publication of the first edition, many detailed monographs on almost all types of mineral raw materials appeared in the Soviet press.

Taking into account modern achievements, the chapters devoted to the search and exploration of mineral deposits have been revised and expanded.

The book is intended for geology students and is of interest to workers in geological exploration and mining enterprises.

Editor(s): Pogrebitsky E.O.

Edition: Nedra, Moscow, 1975, 216 pp., UDC: 550.8(076.5)

Language(s) Russian

The first edition of the problem book was published in 1966. This edition includes the best problems from the first edition, as well as a number of problems compiled over the subsequent period. At the same time, complex tasks have been compiled for individual deposits or areas, including a number of particular tasks, consistently and interconnectedly covering many issues of prospecting, exploration, testing, reserve calculation and geological and economic assessment of deposits. All sections are accompanied by methodological instructions, which provide an example of solving a typical problem . Answers are given to problems that have a numerical solution

The problem book is designed for students of geological exploration universities and faculties.

Lecture No. 17

Objectives, methods of prospecting and exploration of mineral deposits

Plan:

I. Stages of search work.

1. Regional geological study.

2. Geological survey work.

3. Search work.

4. Search and evaluation work.

II. Stages of exploration work.

1. Preliminary reconnaissance.

2. Detailed reconnaissance.

3. operational reconnaissance.

4. Additional exploration.

Keywords: Surveying, prospecting, exploration, regional, stage, scale, geophysical, research, assessment, elements of geological bodies, prospecting prerequisites, prospecting signs, criteria, predicted resources, categories of reserves.

Geological structure of territories (region). The deposits are determined in the process of geological exploration. Geological survey and search are an integral part of these works, which, for the purpose of rational and economical conduct, are carried out in 8 stages.

1) Regional geological study

a) regional geological and geophysical studies on a scale of 1:1000000

b) regional - geophysical, geological surveying, hydrogeological and geotechnical work on a scale of 1:200000.

2) Geological survey work on a scale of 1:50000-1:25000

3) Search work

4) Search and assessment work

5) Preliminary reconnaissance

6) Detailed reconnaissance

7) Operational reconnaissance

8) Additional exploration

9) Operational reconnaissance

The last 4 stages concern exploration work. The main task of geological surveying of any scale is to compile a geological map that graphically displays the elements of geological bodies recorded on the earth's surface or a certain depth section. The latter may coincide with the base or roof of a stratigraphic horizon or the surface of some geological formation.

In the process of geological surveying and analysis of compiled geological maps, factors favorable for ore formation are identified, which are used as prospecting prerequisites. These include climatic, stratigraphic, geophysical, geochemical, geomorphological, magmatic and other indicators. All this indicates the possibility of discovering mineral deposits.

Search signs- these are local factors that directly or indirectly indicate the presence of minerals. Geological mapping at a scale of 1:50000 is accompanied by a general search for minerals, which can be expected based on favorable geological conditions. The general objective of the search is the discovery and geological and economic assessment of mineral deposits.

Search methods are varied and must be used in combination, taking into account landscape and other conditions and types of minerals. The possibilities of their use are determined by the location of the search in relation to the earth's surface. They can be conducted from space, air, wells and the horizons of underground mine workings.

Ground methods are the most reliable, diverse and widespread in the practice of geological exploration. These include large-scale mapping, geochemical, geological-mineralogical, geophysical and mining-drilling methods.

Mining and drilling methods the most reliable of other search methods. They allow a geologist to determine, to a first approximation, the structural conditions for the localization of mineral bodies, their morphology, size and material composition, to trace the variability of these parameters, to assess predicted resources and calculate reserves in category C 2.

Search work are carried out in promising areas within known and potential ore fields, as well as basins of sedimentary minerals. Exploration work is carried out using a complex of the listed methods, based on the landscape and geological features of the location of the deposits, the type of minerals and its industrial and genetic type. As a result of the work, sections are compiled on a scale from 1:25000 to 1:5000, assessing the predicted mineral resources according to the P 2 category, and in well-studied areas - according to the P 2 category. Exploration and assessment work is carried out in areas that have received a positive assessment during general searches or prospecting work and at the request of discoverers. At this stage, the geologist determines the industrial type of the deposit, approximately its contour in plan - with extraction to depth, which makes it possible to calculate reserves of category C 2 and estimate the predicted resources of minerals according to category P 2.

As a result, the manifestation is either rejected, or technical and economic considerations are presented about the prospects of the identified deposit, allowing an informed decision to be made on the feasibility and timing of preliminary exploration

Mineral exploration. The purpose of exploration is to identify industrial mineral deposits, obtain proven reserves of mineral raw materials and other data necessary and sufficient for the rational and subsequent functioning of mining and processing enterprises.

This goal is met by common objectives at each stage of the country’s economic and social development.

Stages of exploration. Exploration work is more labor-intensive and costly than prospecting work. There are 3 stages of exploration: 1) preliminary; 2) detailed 3) operational and 4) additional exploration(after operational reconnaissance). Preliminary exploration is carried out after the prospecting and exploration stage and continues at a higher level to obtain reliable information that can provide a reliable geological, technological and economically sound assessment of the industrial significance of the deposit. At this stage, the geological structure of the deposit, its general dimensions and contours are clarified. Large-scale (up to 1:500) geological maps are compiled.

The main direction is field exploration to the depth of horizons accessible for development (by laying boreholes, geophysical research through underground mine workings, and selecting technological rocks for laboratory testing). The morphology of mineral bodies, their internal structure, conditions of occurrence and quality are determined. In addition, hydrogeological, engineering-geological, mining-geological and other natural conditions affecting the opening and development of the deposit are studied. Such knowledge should provide the possibility of calculating reserves in categories C1 and C2. Based on the results of preliminary exploration, temporary conditions are developed, and a technical and economic report is drawn up on the feasibility of industrial development of the deposit and conducting detailed exploration on it.

Detailed reconnaissance carried out on deposits that have been positively assessed by preliminary exploration and are scheduled for industrial development in the next 5-10 years. It prepares deposits for transfer to industrial use in accordance with the requirements for the classification of deposit reserves and predicted resources of solid minerals. Based on the results of detailed exploration, a feasibility study of permanent conditions is drawn up. According to the approved standards, mineral reserves are calculated and submitted to the State Commission for Reserves under the Ministry of Geology of the Republic of Uzbekistan.

Deposits with approved reserves in the required quantities are submitted for industrial development by the line ministry. Additional exploration of a developed field focuses on less studied areas: deep horizons, bodies or deposits. Operational intelligence begins from the moment of organization of mining and continues throughout the entire period of development of the deposit. In relation to mining operations, it can be advanced or accompanying. Here the contours of mineral bodies, their occurrence conditions, internal structure, qualitative characteristics and quantity of reserves, spatial location of industrial types and varieties, hydrogeological, mining-geological and other factors of deposit development are clarified.

Technical means of reconnaissance. These are ditches, trenches, clearings, pits (surface) and adits, crosscut shafts, drifts, cuttings (underground) and boreholes and geophysical exploration methods. The most informative are the mine workings, passed across the strike of ore-bearing structures of bodies and deposits (ditches, pits) and other workings (trenches, drifts, etc.) passed along the strike and dip of ore bodies of deposits, which allows us to trace the variability of their morphology and qualitative composition in these directions. Mines for exploration purposes are rarely used; more often their purpose is combined with the selection of large volume technological samples for factory testing or trial operation. These are the so-called exploration and production mines. Drilling exploration wells are a universal technical means of exploration. Rotary drilling ensures that a core is obtained (an undisturbed column of rock inside the pipe). This type of drilling is called core drilling. What is the main type of exploratory drilling in ore deposits? Core drilling wells can be vertical, inclined and horizontal. The choice of a drilling unit and the design of a drilling rig depends mainly on the projected depth of exploration wells and conditions (300 m rigs, ZiF).

Intelligence system factors influencing their choice. The study of the geological properties of deposits at the exploration stages is carried out using a large volume of boreholes and mine workings.

1. Linear cutting. This is a set of individual interceptions of an ore body by wells and mine workings in one of 3 directions (thickness, strike, dip). The most informative is the direction of strike of the ore body, which coincides with its thickness. Obtaining exploration data in 3 directions allows us to assess the volumetric variability of the geological properties of deposits. Conduct graphic and volumetric modeling by constructing systems of transverse and longitudinal sections, horizontal plans and block diagrams.

2. Drilling systems group is universal, economical and provides complete information on deposits with significant mineral bodies.

3. Group of mountain systems. Here there are systems of ditches, pits, and exploration mines.

4. Group of mining and drilling systems characterized by use in various combinations of mine workings and boreholes.

Factors influencing the choice of exploration systems are divided into geological, mining-technological and geographical-economic: a) The main factor - geological - is the structural and morphological features of the deposit (shapes, sizes, structure); b) mining and technological factors determine the methods of opening and technology for developing a deposit, based on the mining, geological, hydrogeological conditions of the deposit; c) geographical and economic factors have the greatest influence on the choice of exploration systems in working or remote areas with harsh climatic conditions and weak development of productive forces.

Intelligence methods:

The main methods of exploration are:

1. Detailed geological mapping

2. Linear undercutting of mineral bodies by systems of boreholes and mine workings.

3. Geophysical research in mine workings and wells.

4. Geochemical and mineral studies.

Geological mapping is carried out on a topographic basis on a scale from 1:10000 to 1:500, while reference marks are applied to the geological map, exploration wells (using theodolite traverses and geometric leveling) marking horizons, contours of bodies, elements of technological disturbances, etc. are marked.

Linear cutting of bodies mineral exploration is carried out either by exploration systems of boreholes or by systems of mining exploration workings. Valuable for exploration is the geological information obtained in the process of excavation of exploration workings and drilling of wells.

Geophysical research in wells and mine workings are universal in terms of the range of tasks they can solve. They are used to correct geological heterogeneities. “Logging” is widely used, which is based on the influence of local natural and artificially induced physical fields inside wells on a special probe in the sensors of which signals are transmitted via cable to recording and processing ground-based devices. It is determined by spontaneous polarization, apparent resistivity, radioactivity of rocks in the well section (tack logging), vertical magnetic field changes, changes in thermal conditions (thermal logging), etc.

Geological studies are carried out with the aim of linking ore-bearing zones, assessing the ore content of deep horizons, etc. Mineralogical studies are aimed at solving the following problems:

1. Determination of the complete mineral composition of ores and surrounding ore spaces

2. Identification based on the characteristics of the mineral composition, textures and structures of ores of their natural types.

3. Study of mineralogical zoning in addition to geochemical zoning.

Control questions:

1. What are the tasks of geological survey of a field?

2. Why is detailed exploration of the field carried out?

3. What is an ore body, an ore-bearing structure?

4. Transverse and longitudinal sections of deposits?

5. What does geological information provide when designing field developments?

Literatures:

1. Yakusheva A. F. “General Geology”. M. Nedra 1988.

2. Milnuchuk V.I. “General Geology”. M. Nedra 1989.

3. Ershov V.V. “Fundamentals of Geology.” M. Nedra 1986.

4. Ivanova M. F. “General Geology”. M. Nedra 1974.

5. Panyukov P. N. “Fundamentals of Geology.” M. M. Nedra 1978.

The exploration stage for mineral deposits is divided into three stages:

1) preliminary exploration;

2) detailed reconnaissance;

3) operational reconnaissance.

This division of the exploration stage into stages directly follows from the first principle of exploration - successive approximations.

Preliminary exploration aims to clarify the general dimensions of the deposit and obtain an approximate idea of ​​the shape, size and quality of the main mineral bodies that make up the complex deposit. At this stage, a detailed study of the surface of the field is completed based on the refinement of the large-scale geological map.

If at the prospecting and exploration stage of the prospecting stage geological surveys are often carried out on an eye-based or semi-instrumental basis, then by the start of preliminary exploration it is necessary to have a fairly accurate geological map of a scale of 1: 10,000 - 1: 5000, compiled on an instrumental topographic basis. In accordance with this map, the first exploration work is directed. At the preliminary exploration stage, exploration workings are set according to a certain system and some of them are brought to great depth.

To illuminate the deep horizons of the deposit and fix the lower boundary of mineralization, it is often advisable to immediately drill one or two wells to the depth where the presence of minerals is expected before the gradual drilling of the deposit begins! about minerals, this makes it possible to transfer the reserves of a given deposit or ore body to category C2 or Cx (depending on the type of deposit).

It is advisable to plot exploration workings simultaneously on the existing map of the ore field and on a new topographic base on a scale of 1: 2000-1: 1000 (rarely 1: 5000 or 1: 500).

All these preliminary exploration activities make it possible, with a greater or lesser degree of reliability, to determine the size of the deposit (its general “scale”), the elements of occurrence of ore bodies, and the features of the host rocks; and also approximately determine the quality of the mineral, and sometimes identify the main natural types of ores. Based on preliminary exploration data of the deposit, areas are selected for subsequent detailed exploration. If a very large deposit is being explored, then promising areas for detailed exploration of the first stage make up a small part of the entire deposit. Small deposits usually move entirely to the stage of detailed exploration.

Based on the results of preliminary exploration, reserves are calculated and a technical and economic report (TER) is drawn up, containing a reliable industrial assessment of the deposit.

Detailed exploration is carried out only if the deposit is to be exploited in the coming years. There is no point in investing significantly more funds than preliminary exploration into an object whose industrial development is postponed indefinitely.

At the stage of detailed exploration, the contours of each mineral body are outlined with a high degree of accuracy and its occurrence elements are identified, taking into account all possible changes caused by folds and faults; The research results are plotted on a map compiled at the preliminary exploration stage on a scale from 1: 2000 to 1: 500 (depending on the size and complexity of the deposit).

At the stage of detailed exploration, the deposit is spatially divided into natural types and industrial varieties of minerals based on established industrial conditions (standards). In this regard, in addition to chemical analyzes and mineralogical studies of the mineral, the technological properties of each of its varieties are tested. Issues of water content of the deposit site, physical properties of the surrounding rocks and other mining technical issues, clarified at the preliminary exploration stage only approximately, during detailed exploration should be illuminated on the basis of accurate measurements and special studies.

Naturally, in order to obtain diverse and sufficiently accurate information about the deposit at the stage of detailed exploration, it is necessary to carry out new exploration workings and, thus, tighten the exploration network, especially in the most complex areas in terms of geological structure and in places with the richest accumulations of minerals. However, during this period it is necessary to go through only those workings, the excavation of which cannot be postponed until the stage of operational exploration, since they are necessary for drawing up a project for the exploitation of the field.

Based on detailed exploration, mineral reserves in blocks are already much more accurately calculated according to the varieties identified spatially on exploration plans and sections.

Based on the results of detailed exploration, a technical project for the exploitation of the field is drawn up. Depending on the size of the deposit, after detailed exploration it can be transferred for industrial development either entirely, or in the case of very large objects - in parts. Consequently, the technical project for field development can be general or consist of several parts.

When conducting detailed exploration work, communication with the project organization should be maintained from the very beginning. This makes it possible to take into account the requirements of designers in a timely manner and thereby avoid additional work in the future.

Operational exploration begins from the moment the mineral extraction is organized. It is spatially and temporally slightly ahead of mining operations, accompanying the development of the deposit almost until its completion.

Exploration carried out during the exploitation of a mineral deposit is distinguished by the greatest accuracy, since the network of workings used by the explorer is the densest during this period; their number, in addition to previous and new exploration workings, includes many mining development workings: drifts, orts, risers, cuttings. At the stage of operational exploration, the structure of mineral bodies is clarified both in relation to their shapes and in relation to the boundaries separating varieties, as well as minor tectonic disturbances and displacements. Exploration work and underground geological mapping are already carried out at scales from 1: 500 to 1: 100 on a surveying basis, which makes it possible to notice all the necessary and previously unaccounted details of the structure of the field.

All mining issues and issues of mineral processing technology are also subject to clarification for individual, relatively small areas of the deposit, defined by the boundaries of any production area. The stability of the host rocks is no longer considered in general, but for each given block. The influx of groundwater is studied in general, but for a given mine, etc.

Based on operational exploration, the calculation of mineral reserves is carried out most accurately, with detailing for individual small areas (floors, blocks, ledges), which allows for systematic accounting of the minerals extracted and remaining in the depths for each operational area and for various grades. Based on operational exploration data, current production planning for mineral extraction is carried out, preparatory and treatment workings are directed, and a balance of reserves and production is drawn up.

In practice, in some cases the stages of exploration are clearly separated from each other, in others they merge into a continuous chain of the exploration process so that it is difficult to find the boundary between preliminary and detailed exploration (exploitation exploration is usually quite accurately fixed in time at the moment of the start of mineral extraction). But one way or another, these stages exist, and the main practical meaning of 11 x separation is to prevent the transition to detailed exploration, associated with the expenditure of large funds, without conducting preliminary exploration to reject any parts of the deposit or even the entire deposit that turned out to be non-industrial. In a word, detailed exploration is separated from preliminary exploration by drawing up a TED (technical and economic report).

A certain exception is the exploration of very capricious deposits: small nests of optical minerals, precious stones, platinum-bearing chromites, rare-metal pegmatites, etc. For their preliminary exploration, these deposits would require a network of mining exploration workings of almost the same density as is necessary to prepare them for exploitation . Therefore, after the stage of prospecting and exploration, they are immediately subjected to operational exploration, which at the same time is preliminary and detailed. The risk of excessive costs for exploration and exploitation, which is allowed in this case, is usually paid off by the value of the mineral. In some cases, in less capricious fields, detailed and operational exploration also merge into one.

Exploration drilling

Mineral exploration- a set of studies and work carried out with the aim of determining the industrial significance of mineral deposits that have received a positive assessment as a result of prospecting and appraisal work. Deposit exploration is one of the stages of geological exploration work, following the stages of geological surveying and geological prospecting. During geological exploration, the following parameters of mineral deposits are identified:

• geological structure of the mineral deposit;
• spatial location, conditions of occurrence, shape, size and structure of deposits;
• quantity and quality of minerals;
• technological properties of deposits and factors determining the operating conditions of the field.

Stages of mineral deposit exploration

The method of exploration of deposits depends on the appropriate technical means in order to obtain the most complete information on the exploration intersection or the geological volume of the deposit as a whole.

At preliminary reconnaissance Drilling is most often used: percussion-rope (only for placer exploration), core (core and coreless), deep. In some cases (often when exploring deposits of non-ferrous and rare metal ores), deep pits, shallow shafts, and adits are used. Their purpose is to confirm exploratory drilling data, clarify the structure of the most complex sections of the field, and collect technological samples.

Detailed exploration and additional exploration of deposits also involves extensive use of drilling. Some sites also have deep exploration and exploration and production mines. At " operational intelligence" (at a mineral deposit being developed), the main type of work is the excavation of special mine workings (horizontal, vertical and inclined) and drilling of both core (to obtain core) and perforating (coreless) wells. To obtain maximum information about the structure of deposits and the patterns of distribution of minerals with a minimum expenditure of funds, exploration mine workings are located in such a way that they intersect the entire thickness of the promising zone (horizon, structure), and exploration profiles (groups of exploration intersections) are located primarily across the strike of the latter.