Methods for searching for oil and gas. Exploration work for oil and gas is carried out sequentially from the regional stage to the prospecting stage and then to the exploration stage. Each stage is divided into two stages, at which a large complex of works is carried out, carried out by joint ventures

The purpose of prospecting and exploration work is to identify, evaluate reserves and prepare for the development of industrial oil and gas deposits. During prospecting and exploration work the following are used: Geological methods. Geologists travel to the area under study and carry out field work: they study the rock layers exposed on the surface, their composition and angles of inclination. Upon returning home, the materials are processed. The result is a geological map and geological sections of the area. Geological map is a projection of rock outcrops onto the day surface. An anticline on a geological map looks like an oval spot, in the center of which there are more ancient breeds, and on the periphery – younger ones. Geophysical methods: seismic prospecting, electrical prospecting and magnetic prospecting. Seismic exploration is based on the use of propagation patterns in earth's crust artificially created elastic waves. Electrical exploration based on the different electrical conductivity of rocks. Magnetic prospecting based on different magnetic permeability of rocks. TO Hydrogeochemical methods include gas, fluorescent bit-monologue, radioactive shooting and hydrochemical method. Drilling and well testing used for the purpose of delineating deposits, as well as determining the depth and thickness of oil and gas bearing formations. Core analysis allows you to determine its oil and gas content.

8. The role of drilling operations at various stages of development of oil and gas resources.

Drilling is one of the most advanced methods today for constructing a channel connecting the productive formation with the surface. Through drilling, a well is constructed, a drilling rig and technological equipment are carried out for special work (delivery special tool, geophysical equipment, formation testing, etc.), completion is carried out: intermediate, production strings and tubing, perforators and pumps are lowered. In addition, wells are repaired using drilling. But well exploration can also be done through drilling.

9. Stages of prospecting and exploration work

Exploration work is carried out in two stages: prospecting and exploration. The prospecting stage includes three stages: 1) regional geological and geophysical work; 2) preparing areas for deep exploratory drilling; 3) search for deposits. At the first stage, possible oil and gas bearing zones are identified, their reserves are assessed and areas for exploration work are established. At the second stage, a more detailed study is carried out (seismic exploration). At the third stage, exploratory wells are drilled to discover deposits. The first wells are drilled to maximum depth. As a result, a preliminary assessment of reserves is made and recommendations are made for their further exploration. The exploration stage is carried out in one stage. The main goal of this stage is to prepare fields for development. Deposits and reservoir properties of productive horizons must be delineated. Upon completion of exploration work, industrial reserves are calculated and recommendations are made for putting fields into development. Currently, space surveys are widely used as part of the search phase.

Ministry of Education of the Russian Federation Russian State University of Oil and Gas named after. I.M.Gubkina Introduction 3 Chapter 1. Search and exploration of oil and gas fields 4 1.1. Methods for searching and exploration of oil and gas fields 4 Geological methods 4 Geophysical methods 5 Hydrogeochemical methods 6 Drilling and testing wells 6 1.2. Stages of prospecting and exploration 7 1.3. Classification of oil and gas deposits 8 1.4. Problems in searching for and exploring oil and gas, drilling wells 10 Chapter 2. Methodology for accelerated exploration of gas fields 14 2.1. Basic provisions for accelerated exploration and commissioning of gas fields 14 General principles 14 Methods for accelerating exploration applicable to all groups of gas fields 15 Methodology for exploration of gas fields in new areas 16 2.2. Improving the methodology for accelerated exploration of gas fields 17 2.3. Methods for exploration of small complex gas deposits (using the example of the fields of Western Ciscaucasia) 18 List of references used: 21 Introduction Oil and natural gas are one of the main minerals that have been used by man since ancient times. Oil production began to grow at a particularly rapid pace after drilling wells began to be used to extract it from the bowels of the earth. Typically, the date of birth in the country of the oil and gas industry is considered to be the receipt of a gush of oil from a well (Table 1). | | | |Table 1 | |First industrial inflows of oil | |from wells in the main oil-producing countries of the world | | | | | | |Country |Year |Country |Year | |Canada |1857 |Algeria |1880 | |Germany |1859 |Cuba |1880 | |USA |1859 |France |1881 | |Italy |1860 |Mexico |1882 | |Romania |1861 |Indonesia |1885 | |USSR |1864 |India |1888 | |Japan |1872 |Yugoslavia |1890 | |Poland |1874 |Peru |1896 | From the table 1 it follows that the oil industry in different countries The world has existed for only 110 - 140 years, but during this period of time, oil and gas production has increased by more than 40 thousand times. In 1860 world production oil amounted to only 70 thousand tons, in 1970 2280 million tons were extracted, and in 1996 already 3168 million tons. Fast growth production is associated with the conditions of occurrence and extraction of this mineral. Oil and gas are confined to sedimentary rocks and are distributed regionally. Moreover, in each sedimentation basin there is a concentration of their main reserves in a relatively limited number of deposits. All this, taking into account the increasing consumption of oil and gas in industry and the possibility of their rapid and economical extraction from the subsoil, make these minerals the object of priority searches. Chapter 1. Search and exploration of oil and gas fields 1 Methods of search and exploration of oil and gas fields The purpose of prospecting and exploration is to identify, evaluate reserves and prepare for the development of industrial deposits of oil and gas. During prospecting and exploration work, geological, geophysical, hydrogeochemical methods are used, as well as well drilling and research. Geological methods Conducting geological surveys precedes all other types of prospecting work. To do this, geologists travel to the area under study and carry out so-called field work. During them, they study the rock layers exposed on the surface, their composition and angles of inclination. To analyze bedrock covered with modern sediments, pits up to 3 cm deep are dug. And in order to get an idea of deeper-lying rocks, mapping wells up to 600 m deep are drilled. Upon returning home, office work is carried out, i.e. processing of materials collected during the previous stage. The result of desk work is a geological map and geological sections of the area (Fig. 1). Rice. 1. Anticline on a geological map and a geological section through it along line AB. Breeds: 1-youngest; 2-less young; 3 - the most ancient Geological map is a projection of rock outcrops onto the surface. An anticline on a geological map looks like an oval spot, with older rocks in the center and younger rocks on the periphery. However, no matter how carefully the geological survey is carried out, it makes it possible to judge the structure of only the upper part of the rocks. Geophysical methods are used to “probe” the deep interior. Geophysical methods Geophysical methods include seismic prospecting, electrical prospecting and magnetic prospecting. Seismic exploration (Fig. 2) is based on the use of patterns of propagation of artificially created elastic waves in the earth's crust. Waves are created in one of the following ways: 1) by the explosion of special charges in wells up to 30 m deep; 2) vibrators; 3) converters of explosive energy into mechanical energy. Rice. 2. Schematic diagram seismic exploration: 1-source of elastic waves; 2 seismic receivers; 3-seismic station The speed of propagation of seismic waves in rocks of different densities is not the same: the denser the rock, the faster the waves penetrate through it. At the interface between two media with different densities, elastic vibrations are partially reflected, returning to the surface of the earth, and partially refracted, they continue their movement deep into the subsurface to a new interface. Reflected seismic waves are captured by geophones. By then deciphering the resulting graphs of vibrations of the earth's surface, experts determine the depth of the rocks that reflected the waves and their angle of inclination. Electrical prospecting is based on the different electrical conductivities of rocks. Thus, granites, limestones, sandstones saturated with salty mineralized water conduct electricity well, while clays and sandstones saturated with oil have very low electrical conductivity. Gravity exploration is based on the dependence of gravity on the Earth's surface on the density of rocks. Rocks saturated with oil or gas have a lower density than the same rocks containing water. The task of gravity reconnaissance is to identify areas with abnormally low gravity. Magnetic prospecting is based on the different magnetic permeability of rocks. Our planet is a huge magnet around which there is a magnetic field. Depending on the composition of rocks, the presence of oil and gas, this magnetic field is distorted in varying degrees. Magnetometers are often installed on airplanes that fly over the study area at a certain altitude. Aeromagnetic surveying makes it possible to identify anticlines at a depth of up to 7 km, even if their height is no more than 200...300 m. Geological and geophysical methods mainly reveal the structure of sedimentary rocks and possible traps for oil and gas. However, the presence of a trap does not mean the presence of an oil or gas deposit. Hydrogeochemical methods of subsurface exploration help to identify from the total number of discovered structures those that are most promising for oil and gas, without drilling wells. Hydrogeochemical methods Hydrochemical methods include gas, fluorescent-bit-monological, radioactive surveys and hydrochemical methods. Gas surveying involves determining the presence of hydrocarbon gases in rock and groundwater samples taken from a depth of 2 to 50 m. A halo of hydrocarbon gas dispersion is formed around any oil and gas deposit due to their filtration and diffusion through the pores and cracks of the rocks. Using gas analyzers with a sensitivity of 10-5...10-6%, it is recorded increased content hydrocarbon gases in samples taken directly above the deposit. The disadvantage of the method is that the anomaly may be displaced relative to the deposit (due to the inclined occurrence of the overlying strata, for example) or be associated with non-industrial deposits. The use of luminescent-bitumen survey is based on the fact that above oil deposits the content of bitumen in the rock is increased, on the one hand, and on the phenomenon of luminescence of bitumen in ultraviolet light, on the other. Based on the nature of the glow of the selected rock sample, a conclusion is drawn about the presence of oil in the proposed deposit. It is known that anywhere on our planet there is a so-called radiation background, caused by the presence of radioactive transuranium elements in its depths, as well as the influence of cosmic radiation. Experts were able to establish that the background radiation above oil and gas deposits was reduced. Radioactive surveying is carried out to detect the specified anomalies of background radiation. The disadvantage of the method is that radioactive anomalies in the near-surface layers can be caused by a number of other natural causes. Therefore, this method is still used to a limited extent. The hydrochemical method is based on the study chemical composition groundwater and the content of dissolved gases in them, as well as organic substances, in particular, arenes. As you approach the deposit, the concentration of these components in the waters increases, which allows you to conclude that there is oil or gas in the traps. Drilling and testing of wells Drilling of wells is used to delineate deposits, as well as determine the depth and thickness of oil and gas bearing formations. Even during the drilling process, cylindrical core samples of rocks occurring at different depths are taken. Core analysis allows you to determine its oil and gas content. However, core is taken along the entire length of the well only in exceptional cases. Therefore, after completion of drilling, a mandatory procedure is to study the well using geophysical methods. The most common method for studying wells is electrical logging. In this case, after removing the drill pipes, a device is lowered into the well on a cable to determine electrical properties rocks penetrated by the well. The measurement results are presented in the form of electrical logs. By deciphering them, the depths of permeable formations with high electrical resistivity are determined, which indicates the presence of oil in them. The practice of electrical logging has shown that it reliably identifies oil-bearing formations in sandy-clayey rocks, but in carbonate deposits the possibilities of electrical logging are limited. Therefore, other methods of studying wells are also used: measuring temperature along the well section (thermometric method), measuring the speed of sound in rocks (acoustic method), measuring the natural radioactivity of rocks (radiometric method), etc. 2 Stages of prospecting and exploration work Exploration work is carried out in two stages: search and exploration. The exploration stage includes three stages: 1) regional geological and geophysical work: 2) preparation of areas for deep exploratory drilling; 3) search for deposits. At the first stage, possible oil and gas bearing zones are identified using geological and geophysical methods, their reserves are assessed and priority areas for further exploration work are established. At the second stage, a more detailed study of oil and gas zones is carried out using geological and geophysical methods. In this case, preference is given to seismic exploration, which allows one to study the structure of the subsurface to great depths. At the third stage of exploration, exploratory wells are drilled to discover deposits. The first exploration wells to study the entire thickness of sedimentary rocks are usually drilled to the maximum depth. After this, each of the “floors” of the deposits is explored in turn, starting from the top. As a result of these works, a preliminary assessment of the reserves of newly discovered deposits is made and recommendations are given for their further exploration. The exploration phase is carried out in one stage. The main goal of this stage is to prepare fields for development. During the exploration process, deposits and reservoir properties of productive horizons must be delineated. Upon completion of exploration work, industrial reserves are calculated and recommendations are given for putting fields into development. Currently, space surveys are widely used as part of the search phase. Even the first aviators noticed that from a bird's eye view small details of the relief are not visible, but large formations that seemed scattered on the ground turn out to be elements of something unified. Archaeologists were among the first to take advantage of this effect. It turned out that in deserts the ruins of ancient cities affect the shape of the sand ridges above them, and in the middle zone - a different color of vegetation above the ruins. Geologists also adopted aerial photography. In relation to the search for mineral deposits, it began to be called aerial geological survey. New method search has proven itself perfectly (especially in the desert and steppe regions of Central Asia, Western Kazakhstan and Ciscaucasia). However, it turned out that an aerial photograph covering an area of up to 500...700 km2 does not allow identifying particularly large geological objects. Therefore, they began to use images from space for search purposes. The advantage of space photographs is that they depict areas of the earth's surface that are tens and even hundreds of times larger than the areas on the aerial photograph. At the same time, the masking influence of soil and vegetation cover is eliminated, relief details are hidden, and individual fragments of the earth's crust structures are combined into something integral. Aerogeological research involves visual observations, as well as various types of surveys - photographic, television, spectrometric, infrared, radar. With visual observations, astronauts have the opportunity to judge the structure of shelves, as well as select objects for further study from space. With the help of photographic and television filming, you can see very large geological elements of the Earth - megastructures or morphostructures. During spectrometric surveys, the spectrum of natural electromagnetic radiation from natural objects is studied in different frequency ranges. Infrared imaging makes it possible to establish regional and global thermal anomalies of the Earth, and radar imaging makes it possible to study its surface regardless of the presence of cloud cover. Space research no mineral deposits are discovered. With their help, geological structures are found where oil and gas deposits can be located. Subsequently, geological expeditions conduct field research in these places and give a final conclusion about the presence or absence of these minerals. However, despite the fact that the modern prospecting geologist is quite well “armed”, the effectiveness of prospecting for oil and gas remains an urgent problem . This is evidenced by a significant number of “dry” wells (which did not lead to the discovery of industrial hydrocarbon deposits). The first large Damam field in Saudi Arabia was discovered after unsuccessful drilling of 8 exploratory wells laid on the same structure, and the unique Hassi Mesaoud field (Algeria) was discovered after 20 “dry” wells. First large deposits oil in the North Sea was discovered after the world's largest companies drilled 200 wells (either “dry” or only with gas shows). The largest oil field in North America, Prudhoe Bay, measuring 70 by 16 km with recoverable oil reserves of about 2 billion tons, was discovered after drilling 46 exploration wells on the northern slope of Alaska. There are similar examples in domestic practice. Before the discovery of the giant Astrakhon gas condensate field, 16 unproductive exploration wells were drilled. Another 14 “dry” wells had to be drilled before the Elenovskoye gas condensate field, second in reserves in the Astrakhan region, was found. On average, the success rate for searching for oil and gas fields around the world is about 0.3. Thus, only every third drilled object turns out to be a field. But this is only on average. Lower success rates are also common. Geologists deal with nature, in which not all connections between objects and phenomena have been sufficiently studied. In addition, the equipment used in searching for deposits is still far from perfect, and its readings cannot always be interpreted unambiguously. 3 Classification of oil and gas deposits By oil and gas deposit we mean any natural accumulation of them, confined to a natural trap. Deposits are divided into industrial and non-industrial. A deposit is understood as one deposit or a group of deposits that completely or partially coincide in plan and are controlled by the structure or part of it. Of great practical and theoretical importance is the creation of a unified classification of deposits and deposits, which, among other parameters, also includes the size of reserves. - When classifying oil and gas deposits, parameters such as hydrocarbon composition, trap topography, trap type, screen type, operating flow rates and reservoir type are taken into account. Based on their hydrocarbon composition, deposits are divided into 10 classes: oil, gas, gas condensate, emulsion, oil with a gas cap, oil with a gas condensate cap, gas with an oil rim, gas condensate with an oil rim, emulsion with a gas cap, emulsion with a gas condensate cap. The described classes belong to the category of deposits that are homogeneous in composition, within which, at any point in the oil and gas containing formation, the physical and chemical properties of hydrocarbons are approximately the same. In the deposits of the other six classes, hydrocarbons in reservoir conditions are simultaneously in liquid and gaseous states. These classes of deposits have a double name. In this case, the first place is given to the name of the complex of hydrocarbon compounds, the geological reserves of which constitute more than 50% of the total hydrocarbon reserves in the deposit. The shape of the trap's relief is the second parameter that must be taken into account when comprehensively classifying deposits. It practically coincides with the surface of the base of the rocks shielding the deposit. The shape of traps can be anticlinal, monoclinal, synclinal and complex. Based on the type of trap, deposits are divided into five classes: biogenic protrusion, massive, bedded, bedded-arched, massive-bedded. Only those that are confined to monoclines, synclines and slopes of local uplifts can be classified as reservoir deposits. Layered-arched deposits are called deposits confined to positive local uplifts, within which the height of the deposit is greater than the thickness of the zone. Massive-layered deposits include deposits confined to local uplifts, monoclines or synclines, within which the height of the deposit is less than the thickness of the reservoir. The classification of deposits by screen type is given in Table. 2. In this classification, in addition to the type of screen, it is proposed to take into account the position of this screen relative to the hydrocarbon deposit. To do this, four main zones and their combinations are identified in the trap, and where the normal gravitational position of the oil-water or gas-water contacts is disrupted by pinching zones and other factors, a special term is used to define the position of the screen relative to these zones. This classification does not take into account the factors that determine the inclined or convex-concave position of the surface of oil-water or gas-water contacts. Such cases are grouped under the heading “difficult screen position”. | | | | | | | |Table 2 | |Classification of deposits by screen type | |Screen type |Position of deposits by screen type | | |by |by |by |with |by |by |by |difficult| | |simple|fallen|recovery|all |simple|simple|fallen|e | | |irani|yu |aniya |side|irani|irani|yu and | | | |yu | | |n |yu and |yu and |restore| | | | | | | |fall|recovery | | | | | | | |yu |aniya | | | |Lithological |+ |+ |+ |+ |+ |+ |+ |+ | |Litho-stratigraphy|+ |+ |+ |+ |+ |+ |+ |+ | |physical | | | | | | | | | |Tectonic |+ |+ |+ |+ |+ |+ |+ |+ | |(discontinuous violations)| | | | | | | | | |Lithologo-denudation|+ |+ |+ |+ |+ |+ |+ |+ | | | | | | | | | | |Salt rod |- |- |+ |- |- |- |- |+ | |Clay stock |- |- |+ |- |- |- |- |+ | |Shielded |+ |+ |+ |+ |+ |+ |+ |+ | | water deposits | | | | | | | | | |Mixed |+ |+ |+ |+ |+ |+ |+ |+ | Based on the working flow rates, four classes of deposits are distinguished: high-yield, medium-yield, low-yield, non-industrial. In this classification, the limits of the flow rates of oil and gas deposits differ by one order of magnitude. This is due to the fact that gas deposits are usually explored and exploited by a sparser network of wells. According to the type of reservoir, seven classes of deposits are distinguished: fractured, cavernous, porous, fractured-porous, fractured-cavernous, cavernous-porous and fractured-cavernous-pore. For some gas and gas condensate caps, oil deposits, gas and gas condensate reservoirs, the presence of unrecoverable oil in pores, caverns and fractures should be taken into account, which reduces the volume of reservoir voids and should be taken into account when calculating oil and gas reserves. This classification is incomplete, but it takes into account the most important parameters necessary for choosing exploration methods and the optimal technological scheme for exploitation. 4 Problems in searching for and exploring oil and gas, drilling wells Since ancient times, people have used oil and gas where they were naturally found on the surface of the earth. Such exits still occur today. In our country - in the Caucasus, in the Volga region, the Urals, on the island of Sakhalin. Abroad - in North and South America, Indonesia and the Middle East. All oil and gas manifestations are confined to mountainous areas and intermountain depressions. This is explained by the fact that as a result of complex mountain-building processes, oil and gas-bearing strata that previously lay at great depths ended up close to the surface or even on the surface of the earth. In addition, numerous breaks and cracks appear in the rocks, going to great depths. They also bring oil and natural gas to the surface. The most common releases of natural gas range from barely noticeable bubbles to powerful fountains. On wet soil and on the water surface there are small gas outlets are identified by the bubbles appearing on them. During fountain ejections, when water and rock erupt along with gas, mud cones from several to hundreds of meters high remain on the surface. Representatives of such cones on the Absheron Peninsula are the mud “volcanoes” Touragai (height 300 m) and Kanizadag (490 m). Cones of mud, formed by periodic gas emissions, are also found in northern Iran, Mexico, Romania, the USA and other countries. Natural seeps of oil to the surface occur from the bottom of various reservoirs, through cracks in rocks, through oil-saturated cones (similar to mud cones) and in the form of oil-saturated rocks. On the Ukhta River, small drops of oil are observed emerging from the bottom at short intervals. Oil is constantly released from the bottom of the Caspian Sea near Zhiliy Island. In Dagestan, Chechnya, on the Absheron and Taman peninsulas, as well as in many other places globe There are numerous oil sources. Such surface oil shows are typical for mountainous regions with highly rugged topography, where gullies and ravines cut into oil-bearing strata located near the surface of the earth. Sometimes oil seeps out through conical mounds with craters. The body of the cone consists of thickened oxidized oil and rock. Similar cones are found on Nebit-Dag (Turkmenistan), Mexico and other places. On about. Trinidat, the height of oil cones reaches 20 m, and the area of “oil lakes” consists of thickened and oxidized oil. Therefore, even in hot weather, a person not only does not fall through, but does not even leave marks on their surface. Rocks saturated with oxidized and hardened oil are called “kiras.” They are widespread in the Caucasus, Turkmenistan and Azerbaijan. They are found on plains: on the Volga, for example, there are outcrops of limestone saturated with oil. For a long time, natural oil and gas outputs fully satisfied the needs of mankind. However, the development of human economic activity required more and more energy sources. In an effort to increase the amount of oil consumed, people began to dig wells in places where surface oil showed up, and then drill wells. At first they were laid where oil leaked to the surface of the earth. The number of such places is limited. At the end of the last century, a new promising search method was developed. Drilling began in a straight line connecting two wells already producing oil. In new areas, the search for oil and gas deposits was carried out almost blindly, darting from side to side. It is clear that this could not continue for long, because drilling each well costs thousands of dollars. Therefore, the urgent question arose about where to drill wells in order to accurately find oil and gas. This required an explanation of the origin of oil and gas, and gave a powerful impetus to the development of geology - the science of the composition, structure and history of the Earth, as well as methods for searching and exploring oil and gas fields. Exploration work for oil and gas is carried out sequentially from the regional stage to the prospecting stage and then to the exploration stage. Each stage is divided into two stages, at which a large complex of works is carried out, carried out by specialists of various profiles: geologists, drillers, geophysicists, hydrodynamicists, etc. Among geological research and work, a large place is occupied by drilling wells, their testing, core selection and its study, selection samples of oil, gas and water and their study, etc. The purpose of drilling wells during prospecting and exploration for oil and gas is different. At the regional stage, reference and parametric wells are drilled. Key wells are drilled in poorly studied areas to study the geological structure and oil and gas prospects. Based on the data from reference wells, large structural elements and a section of the earth's crust are identified, the geological history and conditions of possible oil and gas formation and oil and gas accumulation are studied. Support wells are laid, as a rule, to the foundation or to a technically possible depth and in favorable structural conditions (on arches and other elevations). In reference wells, core and cuttings are taken from the entire sediment section, a full range of field geophysical surveys of wells (GIS), sampling of promising horizons, etc. are carried out. Parametric wells are drilled in order to study the geological structure, prospects for oil and gas content and determine the parameters of the physical properties of formations for more effective interpretation of geophysical surveys. They are laid on local elevations along profiles for the regional study of large structural elements. The depth of the wells, as for the reference ones, is selected to the foundation or, if it is impossible to reach it (as, for example, in the Caspian region), to what is technically possible. Exploration wells are drilled to discover oil and gas accumulations in an area prepared by geological and geophysical methods. Exploration wells are considered to be all wells drilled in the exploratory area before receiving an industrial influx of oil or gas. Sections of exploratory wells are studied in detail (core sampling, well logging, sampling, fluid sampling, etc.) The depth of exploratory wells corresponds to the depth of the lowest promising horizon and, depending on the geological structure of different regions and taking into account technical drilling conditions, ranges from 1.5- 2 to 4.5-5.5 km or more. Exploration wells are drilled to evaluate reserves of discovered deposits and localities. Based on the data from exploration wells, the configuration of oil and gas deposits is determined, and the parameters of productive formations and deposits are calculated, and the position of the OWC, GOC, and GWC is determined. Based on exploration wells, oil and gas reserves in open deposits are calculated. In exploration wells, a large range of studies is carried out, including core selection and examination, fluid sampling and testing in laboratories, testing of formations during drilling and testing them after drilling, logging, etc. Drilling of wells for oil and gas, carried out at the stages of regional work and prospecting; exploration, as well as development, is the most labor-intensive and expensive process. High costs when drilling oil and gas wells are due to: the complexity of drilling to great depths, the huge volume of drilling equipment and tools, as well as various materials that are required to carry out this process, including mud, cement, chemicals, etc. In addition, costs increase due to environmental protection measures. The main problems arising in modern conditions when drilling wells, searching and exploring for oil and gas, boil down to the following. 1. The need for drilling in many regions to great depths exceeding 4-4.5 km is associated with the search for hydrocarbons in unexplored low parts of the sediment section. In this regard, the use of more complex but reliable well designs is required to ensure the efficiency and safety of work. At the same time, drilling to a depth of more than 4.8 km is associated with significantly higher costs than when drilling to a shallower depth. 2. B recent years More difficult conditions arose for drilling operations and oil and gas exploration. Geological exploration work at the present stage is increasingly moving into regions and areas characterized by complex geographical and geological conditions. First of all, these are hard-to-reach areas, undeveloped and undeveloped, including Western Siberia, the European north, tundra, taiga, permafrost, etc. In addition, drilling and exploration for oil and gas are carried out in difficult geological conditions, including thick layers of rock salt (for example, in the Caspian region), the presence of hydrogen sulfide and other aggressive components in deposits, abnormally high reservoir pressure, etc. These factors create great problems when drilling, searching and exploring for oil and gas. 3. Drilling and searching for hydrocarbons in the waters of the northern and eastern seas washing Russia creates huge problems that are associated with both sophisticated technology drilling, prospecting and exploration of oil and gas, and environmental protection. Entering marine territories is dictated by the need to increase hydrocarbon reserves, especially since there are prospects there. However, this is much more difficult and expensive than drilling, prospecting and exploration, as well as developing oil and gas accumulations on land. When drilling wells at sea compared to land at the same drilling depths, according to foreign data, costs increase by 9-10 times. In addition, when working at sea, costs increase due to greater safety of work, because the most dire consequences and accidents occur at sea, where the scale of pollution of water areas and coasts can be enormous. 4. Drilling to great depths (over 4.5 km) and trouble-free installation of wells is impossible in many regions. This is due to the backwardness of the drilling base, worn-out equipment and lack of effective technologies drilling wells to great depths. Therefore, the challenge is to modernize the drilling base in the coming years and master the technology of ultra-deep drilling (i.e., drilling over 4.5 km - up to 5.6 km or more). 5. Problems arise when drilling horizontal wells and the behavior of geophysical surveys (GIS) in them. As a rule, imperfect drilling equipment leads to failures in the construction of horizontal wells. Errors during drilling are often caused by the lack of accurate information about the current coordinates of the well in relation to geological reference points. Such information is needed especially when approaching a productive formation. 6. An urgent problem is the search for traps and the discovery of non-anticlinal oil and gas accumulations. Many examples from foreign objects indicate that lithological and stratigraphic, as well as lithological-stratigraphic traps can contain huge amounts of oil and gas. In our country, structural traps in which large accumulations of oil and gas are found are more involved. In almost every oil and gas province (OGP), a large number of new regional and local uplifts have been identified, constituting a potential reserve for the discovery of oil and gas deposits. Non-structural traps were of less interest to oil workers, which explains the lack of major discoveries in these conditions, although oil and gas objects with insignificant reserves were identified in many oil and gas fields. But there are reserves for a significant increase in oil and gas reserves, especially in the platform areas of the Ural-Volga region, the Caspian region, Western Siberia, Eastern Siberia, etc. are available. First of all, reserves can be associated with the slopes of large uplifts (arches, megaswells) and the sides of adjacent depressions and troughs, which are widely developed in the mentioned regions. The problem is that we do not yet have reliable methods for searching for non-anticlinal traps. 6. In the field of oil and gas prospecting and exploration, there are problems associated with increasing economic efficiency geological exploration work for oil and gas, the solution of which depends on: improving geophysical research methods in connection with the gradual complication of geological and geographical conditions finding new objects; improvement of search methods various types accumulations of hydrocarbons, including non-anticlinal genesis; increasing the role of scientific forecasting in order to provide the most reliable justification for prospecting work for the future. In addition to the above-mentioned main problems facing oil workers in the field of drilling, prospecting and exploration of oil and gas accumulations, each specific region and area has its own problems. The further increase in proven oil and gas reserves, as well as the economic development of regions and areas and, consequently, the well-being of people depend on the solution to these problems. Chapter 2. Methodology for accelerated exploration of gas fields 2.1. Basic provisions for accelerated exploration and commissioning of gas fields General principles The developed methods for exploration of gas fields can dramatically reduce the cost and speed up the exploration and preparation of these fields for development, which is why they are called rational or accelerated. Accelerated exploration of gas fields should ensure, in a short time, the maximum economic effect from the use of gas from a newly discovered field. This problem is complex and must be solved taking into account economic aspects and the time factor. The exploration stage in the accelerated preparation of gas fields for development is divided into two stages: appraisal exploration and detailed exploration (additional exploration). The stage of appraisal exploration for small and medium-sized fields is completed after receiving gas inflows in two or three wells, for large and unique fields - after drilling a sparse network of wells (one well per 50-100 km2 of deposit area). Subsequent additional exploration of small and medium-sized deposits is carried out using the pilot-industrial operation method. Drilling of exploratory wells should not be carried out. During additional exploration of large and unique fields (deposits), the structure of the internal parts of the deposits is clarified by compacting the grid of exploration wells by drilling OES and observation wells, as well as single exploration wells outside the production drilling zone. The following methods of accelerated exploration of gas fields are used: . sparse network of exploration wells - small and medium-sized deposits are explored with four to five single wells, large single-deposit ones are drilled at the rate of one well per 50 km2 of productive area, unique ones - at the rate of one well per 100 km2 of deposit area; . pilot-industrial operation is used for exploration of mainly small and medium-sized gas deposits, commissioning of pilot-industrial operation is carried out in the presence of two or three wells that have produced gas; the duration of pilot industrial operation has been established for a period of three years, the level of gas extraction during this time should be approximately 10% of the total reserves of the explored deposit; pilot industrial operation is completed by calculating gas reserves using the pressure drop method; to ensure the designed level of gas extraction, if necessary, single IPSs are drilled; . advanced production drilling - highly productive zones of operational drilling of large and unique deposits are further explored by advanced production wells, and the grid of exploration wells is thickened at their expense depending on the nature of the variability of heterogeneity and productivity parameters. When exploring gas fields (deposits) and preparing them for development, the following must be ensured: 1) the presence or absence of an oil rim of industrial significance has been proven (by geological data, trial or pilot industrial operation, gas-dynamic and technical-economic calculations) and, if there is a rim, established conditions of its operation; 2) full testing and research was carried out in several wells in order to obtain the main parameters of the deposit; 3) characteristic structural and geometric features of the deposit structure have been established; 4) the main parameters of reservoirs have been determined, which sufficiently fully characterize the horizons both in section and area; 5) hydrogeological conditions and the possible influence of the water pressure system on the development regime of deposits were clarified; 6) the position of contacts (circuits) of gas and gas-oil deposits is determined; 7) the composition of the gas, the amount of condensate and other related components are determined; 8) all (main in terms of reserves) deposits in the section have been identified. A special place among accelerated methods occupied by the exploration of gas fields using pilot-industrial operation, which makes it possible, with lower costs for exploratory drilling, to obtain the necessary and, in most cases, more reliable data for drawing up a project for the development of these fields while simultaneously extracting gas from them and supplying it to consumers. The latter circumstance is especially important for gas producing areas where existing fields do not provide the necessary gas supply to the consumer. In these cases, the commissioning of gas fields into pilot production is carried out at the early stages of their exploration, and for small deposits or lenses it can be justified even if there is only one exploration well that has produced an industrial flow of gas. Methods for accelerating exploration applicable to all groups of gas fields Exploration of gas deposits should be carried out taking into account the conditions of their formation, which determine the degree of filling of the trap with gas. Under absolute gas-resistant layers, which are sustained strata of salts, as well as anhydrite (at a certain depth), under sustained thick strata of clays with good gas-resistant properties, one should expect the traps to be filled with gas to the top at any height. With less reliable tires, the traps can be filled to the lock at low heights, but at high trap heights you should expect that they will not be completely filled. This is well confirmed by practice in all gas-bearing areas, and this should be taken into account when determining the position of the gas-water contact and establishing the contour of gas deposits. In clean carbonate rocks There cannot be any sustained gas seals. Therefore, industrial gas deposits can only form in them when they are covered with other gas-resistant rocks, which determine the degree of filling of the trap, and hence the altitudinal position of the gas-water reservoir. Gas deposits are in hydrodynamic equilibrium with the surrounding formation water. The study of this equilibrium makes it possible to determine the altitude position of the GWC based on reliable measurements of reservoir water and gas pressure and the displacement of gas or oil deposits during the movement of formation water, which is expressed in the inclination of the GWC or oil-water contact (OWC) towards the lowest water pressure. The use of these opportunities when exploring gas fields can greatly reduce the cost and speed up its implementation. When exploring reservoir gas deposits, very often the first wells do not penetrate the gas-water reservoir, but at the same time there are already wells that have discovered reservoir water beyond the contour of the deposit. Along with using measurements of water pressure in wells drilled at the field or in its immediate vicinity, it is important to study regional hydrogeology, since in the absence of information on water pressure obtained in the area of the explored field, it is possible to determine the direction and nature of the possible displacement of gas and oil deposits. Thus, when several exploration wells discovered gas deposits in the Lower Permian and Carboniferous carbonate deposits of the Orenburg gas condensate field, the altitudinal position of the GWC remained unknown. The water pressure of the considered productive deposits in the area of this field was assessed using regional hydrogeology data, on the basis of which the approximate altitude position of the GWC was calculated at around -1800 m. Exploration of the deposit was focused on opening the calculated contact, and it turned out that in reality it is located at mark -1756 m. Thus, the assessment of the altitudinal position of the GWC using regional hydrogeological data significantly helped to correctly target the exploration of the deposit in question. The development of gas deposits is carried out without contour flooding and with the placement of production wells mainly in the higher parts of the deposits at a considerable distance from the contour. Gas reserves in the peripheral part of the deposit usually constitute a small fraction of its total reserves. This allows exploration of deposits without their detailed delineation, except in cases where the local structure is not clearly identified by geological prospecting and the GWC is inclined, or when there may be an oil rim of industrial importance under the gas deposit. In accordance with the “Classification of Oil and Combustible Gas Reserves,” the introduction of gas deposits into development, including pilot production, is permitted only if they do not contain oil of industrial significance. The search for an oil rim under a gas deposit can greatly complicate the exploration of this deposit. That's why special attention should be given to predicting the presence and nature of such a fringe. Methodology for exploration of gas fields in new areas As already indicated, the main task of exploration of gas fields in new areas is the preparation of gas reserves of C1 categories to justify the construction of new main gas pipelines or gas chemical complexes. The right to conduct design and survey work for the construction of main gas pipelines and field facilities, written in the “Classification of Oil and Combustible Gas Reserves” on the basis of operational calculations of gas reserves, can significantly speed up the commissioning of gas fields in new areas into development. Currently, in a number of areas, gas fields of unique size have been identified that require the construction of main gas pipelines or gas-chemical complexes (Yamburgskoye, Dauletabad-Donmezskoye, Astrakhanskoye, etc.). It is necessary to connect several gas pipelines to one such field or to provide for the alternate commissioning of gas chemical complex capacities. Both gas pipelines and the gas chemical complex are not built simultaneously, but sequentially. To justify the construction of the first line of the gas pipeline (the first stage of the gas chemical complex), it is not at all necessary to explore all the gas reserves of such a field to a known ratio of categories. It is enough to carry out exploration only on a part of the field whose gas reserves are sufficient to justify the construction of this gas pipeline or gas chemical complex of a certain capacity. The adoption of this procedure will allow us to speed up the construction of a gas pipeline or gas chemical complex. At the same time, the accelerated introduction of part of the field into development will facilitate exploration of the field as a whole. After the completion of construction and commissioning of the main gas pipeline in the new area, exploration of new gas fields continues. At the same time, gas resources for the new main gas pipeline may increase. Their identification can occur over a relatively long period of time. What should be the degree of exploration of reserves of gas fields, the gas resources of which can form the basis for the construction of a new main gas pipeline? It is known that main gas pipelines are built mainly on the basis of the gas reserves of single unique gas fields or a group of large gas fields, while the reserves of medium-sized and especially small gas fields play a small role in this case. In accordance with this, when increasing gas reserves for the construction of new main gas pipelines, exploration of unique and large gas fields must comply with the requirements of the "Classification of Oil and Combustible Gas Reserves", while exploration of reserves of medium and especially small gas fields in this case should be limited to bringing them to the category C1. When exploring multi-deposit gas fields, the reserves of which are being explored to support the construction of a new main gas pipeline, attention is focused mainly on the priority preparation for the development of deposits containing the main gas reserves in the field (for example, Cenomanian deposits of multi-deposit fields in the north of Western Siberia). Thus, when exploring gas fields in new areas, accelerated methods are partially used. The absence of a main gas pipeline system determines the primary need for the accelerated preparation of reserves of industrial categories of basic fields. Exploration of small and medium-sized fields in the absence of a local gas consumer is completed at the assessment stage with the preparation of reserves of categories C1 + C2. Acceleration of exploration of basic deposits is achieved by using a sparse network of wells at the evaluation stage and preparing reserves of only industrial category C1. Peripheral areas of the base deposits are further explored by advanced observation and piezometric wells, as well as single exploration wells. Additional exploration of large and unique fields is carried out under the conditions of their stage-by-stage introduction into development. In this regard, the thickening of the grid of exploration wells should be carried out in sections in accordance with the designed direction of the field development of the field. For a control assessment of the reliability of reserves of large and unique gas fields, calculated by the volumetric method using an open grid of wells, the pressure drop method can also be used. This method's prompt assessment of gas reserves in drainage zones of base fields under the conditions of their phased introduction into development increases the efficiency of accelerated exploration. 2.2. Improving the methodology for accelerated exploration of gas fields The high pace of development of the Russian gas industry necessitates the need to reduce exploration time and accelerate preparation for development of gas and gas condensate fields. In this regard, the issues of further improving the methodology for accelerated exploration of gas fields, improving the quality of initial data for design and rapid commissioning, and rational development of deposits are of paramount importance. The main purpose of exploration of gas, gas condensate and gas-oil fields, as well as deposits of other minerals, is to establish their industrial significance and development conditions. It is important to establish the required degree of exploration of deposits, which determines the timing of their exploration. This task must be solved taking into account the specifics of the development of gas and gas-oil fields (deposits), the need and possibility of their accelerated introduction into development and taking into account the optimal technical and economic indicators of the planned exploration and planned development of these fields. Correct consideration of the listed factors will allow exploration of gas and oil and gas fields with the least expenditure of money and time and thereby ensure their accelerated commissioning. Consideration of factors for accelerating exploration should be carried out from the very beginning of the prospecting and exploration process and at all its subsequent stages, including pilot production. Accelerated exploration of large and unique gas fields using a sparse network of wells, followed by their additional exploration during the development process by production drilling, makes it possible in practice and in a short time to obtain all the necessary data for calculating gas reserves and sound development design. The high efficiency at the beginning of the application of the accelerated exploration methodology for large fields was demonstrated by the example of the Medvezhye and Urengoyskoye fields in the north of Western Siberia, where the exploitation of Cenomanian deposits began very soon after their discovery. The country's economy has already received a significant economic effect from the accelerated commissioning of gas fields. Thus, the widespread use of accelerated exploration methods has made it possible to sharply reduce the time required to bring a significant number of gas fields into development and increase the efficiency of their exploration. 2.3. Methodology for exploration of small complex gas deposits (using the example of the fields of Western Ciscaucasia) The number of gas fields with reserves amounting to several billion cubic meters reaches several hundred in Russia as a whole. In order to speed up the commissioning of fields, rational exploration methods using pilot production are widely used in most regions of Russia. One of the main areas where small complex deposits of various types are most fully represented, which, as a rule, were quickly put into pilot production and have now been developed, is Western Ciscaucasia. Using this area as an example, we will consider both the positive and negative aspects of the methodology for conducting prospecting and exploration work and additional exploration of small deposits using the pilot-industrial operation method. In the accelerated preparation of small gas fields for development, it is practiced to divide the exploration stage into two stages: assessment and detailed (additional exploration). At the appraisal stage, the drilling of single exploration wells carries out the operational preparation of reserves in categories C1 + C2 and provides the necessary data for the design of pilot production. At the second stage, after the issue of putting the field into development has been decided, without drilling additional exploration wells, additional exploration is carried out using the pilot-industrial operation method to clarify the operational characteristics, clarify the features of the interaction of individual parts of the deposits and calculate reserves using the pressure drop method. In a number of gas-producing regions with a developed network of gas pipelines (Lower Volga region, Ciscaucasia, etc.), after the drilling of the first exploration wells, the accelerated commissioning of numerous small and medium-sized fields based on reserves of categories C1 and C2 was carried out with their additional exploration using pilot-industrial operation. Results wide application pilot operation confirmed in general high efficiency its use as a method of additional exploration. However, a detailed analysis of the use of pilot industrial exploitation of gas fields for their additional exploration has shown that significant efficiency is achieved mainly only in fields of relatively simple geological structure. At the same time, small and medium-sized complex gas fields, despite their accelerated commissioning through pilot production, continue to be further explored using additional exploration wells, and the possibilities of pilot production as a method of additional exploration are practically not used. The latter leads to significant overexploration and very low efficiency of geological exploration, and the exploitation of complex fields is characterized by low development rates. In the Western Ciscaucasia, considerable experience has been accumulated in the accelerated exploration of small and medium-sized gas fields of complex structure by combining the stages of detailed exploration and pilot industrial operation. Recently, with the help of pilot industrial exploitation, a large number of gas fields have been rapidly brought into development. At the same time, the pilot industrial exploitation of the majority of complex small deposits in the region was carried out mainly without solving the problems of their additional exploration. As a result, after the completion of pilot production, only in rare cases was a sufficient amount of information obtained to more or less confidently resolve the issue of the productive characteristics and reserves of these deposits. The complexity of the productive section, the low quality of the seismic base and the desire of exploration organizations in these conditions to achieve an increase in gas reserves of industrial categories led to the placement of a significant number of delineating exploration wells in small fields even after they were put into development. This approach to additional exploration of small complex gas fields in the Western Ciscaucasia has led to significant overexploration of all of them with low efficiency of exploration work. Since 1966 in Western Ciscaucasia expedited way Almost all newly discovered gas fields were put into development. These small fields were characterized by significant depths of productive horizons (up to 4600 m at the Kuznetsovskoye field), complex seismic geological conditions, pronounced heterogeneity of the productive section, anomalous occurrence of gas and water, elastic-water-pressure production mode, etc. The gas content of such deposits was associated with the Albian-Aptian terrigenous complex of the Lower Cretaceous (most of it), as well as with terrigenous deposits of the Upper (Yubileinoe) and Middle Jurassic (Kuznetsovskoe). Gas deposits are confined to traps of structural (Mitrofanovskoye, Lovlinskoye), lithological (Samurskoye), stratigraphic, hydrodynamic (Sokolovskoye) and combined (Caucasian) types. The gas-bearing area of the considered fields in the region ranges from 2.8 km2 (Dvubraskoye) to 17.3 km2 (Ust-Labinskoye). From one (Ladozhskoe) to five (Yubileinoe) productive horizons have been discovered at the fields. Despite the low quality of area preparation by geophysical methods, a significant part of the small deposits in the region were discovered by the first exploration wells. After receiving a gas fountain, drilling of exploration wells began in the area. The development of almost all the small deposits in the region under consideration took place in three stages: prospecting, exploration-appraisal and exploration-detailing (pilot-industrial operation), and the stage of additional exploration (dataization) at the fields was often unjustifiably delayed almost until the completion of the development of the deposits. After completion of the exploration stage (obtaining an industrial gas influx), work at the evaluation stage of exploration began on the exploration area. Exploration wells were located mainly along a profile system. But at the same time, the distance between them was often greater than the gas deposits themselves. As a result, a significant part of the exploration wells ended up outside the gas-bearing contour. Thus, at the Mitrofanovskoye field, discovered by the first exploratory well, five more wells were drilled to delineate the deposit, of which only one turned out to be productive, and four fell outside the gas-bearing contour. Subsequently, seven more exploration wells were drilled for additional exploration of this field. An analysis of the work methodology for the accelerated development of small, complex gas fields in the Western Ciscaucasia showed that in most cases they were put into pilot production by the first wells that produced production, i.e. with a minimum amount of information about the structure of deposits. For example, the Mitrofanovskoye field was put into pilot production when a total of six exploration wells were drilled there, including two productive ones. 4 Conclusion The importance of the oil and gas industry in the national economy of the country is enormous. Almost all industries, agriculture, transport, medicine and simply the population of the country at the current level of development consume oil, natural gas and petroleum products. At the same time, their consumption within the country increases from year to year. The prospects for the development of the oil and gas complex are associated with the huge potential resources of oil and gas that lie in the depths and have not yet been explored. These include large areas of promising land, both on land and in offshore areas, where there are prerequisites for the discovery of significant accumulations of oil and gas. This applies both to areas where hydrocarbon production has been carried out for a long time, and to those where prospecting work has practically not been carried out. Among the first are the Ural-Volga region, Timan-Pechora, Western Siberia, the Ciscaucasia, the Caspian region, Eastern Siberia, and the Far East (Sakhalin). Significant predicted oil and gas resources are still concentrated in these areas, which need to be explored and increased hydrocarbon reserves in the country in the near future. In these regions, prospects for searching for new oil and gas objects may be associated with: - identifying promising horizons at great depths (more than 4.5 km); - with searches and exploration of oil and gas in carbonate reservoirs; - with the identification of non-structural traps and the search for hydrocarbon deposits on the slopes of arched uplifts and the sides of depressions, etc. In addition, there are prospects for discovering new oil and gas objects in unexplored parts of Russia, where work has not been carried out at all, or was carried out in small volumes and did not give a positive result . These include, for example, the central regions of the European part of Russia. There are depressions in the earth's crust (Moscow and Mezen), filled with a thick layer of ancient sediments. The oil and gas potential of these depressions is associated with sediments of the Vendian (Proterozoic), Lower and Upper Paleozoic. Oil and gas prospects are also associated with unexplored parts of Eastern Siberia and Far East, where possible productive horizons may be in Paleozoic and Mesozoic sediments. These include, for example, the Turguz depression (4 km deep). New discoveries can be made in the Arctic waters of Russia, on the shelf of the Barents and Kara seas, which are a geological continuation of the platform parts of the land of the Russian and West Siberian plates, and the latter are the most productive parts of Russia. List of used literature: 1. Zykin M.Ya., Kozlov V.A., Plotnikov A.A. Methodology for accelerated exploration of gas fields. – M.: Nedra, 1984. 2. Mstislavskaya L.P. Oil and gas production (Questions, problems, solutions): Textbook. – M.: Russian State University of Oil and Gas, 1999. 3. Nesterov I.I., Poteryayeva V.V., Salmanov F.K. Patterns of distribution of large oil and gas fields in the earth's crust. – M.: Nedra, 1975.

Ministry of Education of the Russian Federation

Russian State University of Oil and Gas named after. I.M.Gubkina

Introduction... 3

Chapter 1. Search and exploration of oil and gas fields... 4

1.1.Methods of search and exploration of oil and gas fields. 4

Geological methods .. 4

Geophysical methods .. 5

Hydrogeochemical methods .. 6

Drilling and well testing . 6

1.2. Stages of prospecting and exploration work. 7

1.3.Classification of oil and gas deposits. 8

1.4.Problems in searching for and exploring oil and gas, drilling wells... 10

Chapter 2. Methodology for accelerated exploration of gas fields.. 14

2.1. Basic provisions for accelerated exploration and commissioning of gas fields. 14

General principles .. 14

Methods for accelerating exploration applicable to all groups of gas fields . 15

Methodology for exploration of gas fields in new areas . 16

2.2. Improving the methodology for accelerated exploration of gas fields. 17

2.3. Methodology for exploration of small complex gas deposits (using the example of fields in Western Ciscaucasia) 18

List of references used: 21

Oil and natural gas are among the main minerals that have been used by man since ancient times. Oil production began to grow at a particularly rapid pace after drilling wells began to be used to extract it from the bowels of the earth. Typically, the date of birth in the country of the oil and gas industry is considered to be the receipt of a gush of oil from a well (Table 1).

From the table 1 it follows that the oil industry in different countries of the world has existed for only 110–140 years, but during this period of time, oil and gas production has increased by more than 40 thousand times. In 1860, world oil production was only 70 thousand tons, in 1970 2280 million tons were extracted, and in 1996 already 3168 million tons. The rapid growth of production is associated with the conditions of occurrence and extraction of this mineral. Oil and gas are confined to sedimentary rocks and are distributed regionally. Moreover, in each sedimentation basin there is a concentration of their main reserves in a relatively limited number of deposits. All this, taking into account the increasing consumption of oil and gas in industry and the possibility of their rapid and economical extraction from the subsoil, make these minerals the object of priority searches.

Conducting geological surveys precedes all other types of prospecting work. To do this, geologists travel to the area under study and carry out so-called field work. During them, they study the rock layers exposed on the surface, their composition and angles of inclination. To analyze bedrock covered with modern sediments, pits up to 3 cm deep are dug. And in order to get an idea of deeper-lying rocks, mapping wells up to 600 m deep are drilled.

Upon returning home, desk work is performed, i.e. processing of materials collected during the previous stage. The result of desk work is a geological map and geological sections of the area (Fig. 1).

Rice. 1. Anticline on a geological map

and a geological section through it along line AB.

Breeds: 1-youngest; 2-less young;

3-most ancient

A geological map is a projection of rock outcrops onto the surface. An anticline on a geological map looks like an oval spot, with older rocks in the center and younger rocks on the periphery.

However, no matter how carefully the geological survey is carried out, it makes it possible to judge the structure of only the upper part of the rocks. Geophysical methods are used to “probe” the deep interior.

Geophysical methods include seismic prospecting, electrical prospecting and magnetic prospecting.

Seismic exploration (Fig. 2) is based on the use of patterns of propagation of artificially created elastic waves in the earth's crust. Waves are created in one of the following ways:

1) explosion of special charges in wells up to 30 m deep;

2) vibrators;

3) converters of explosive energy into mechanical energy.

Rice. 2. Schematic diagram of seismic exploration:

1-source of elastic waves; 2 seismic receivers;

3-seismic station

The speed of propagation of seismic waves in rocks of different densities is not the same: the denser the rock, the faster the waves penetrate through it. At the interface between two media with different densities, elastic vibrations are partially reflected, returning to the surface of the earth, and partially refracted, they continue their movement deep into the subsurface to a new interface. Reflected seismic waves are captured by geophones. By then deciphering the resulting graphs of vibrations of the earth's surface, experts determine the depth of the rocks that reflected the waves and their angle of inclination.

Electrical exploration based on the different electrical conductivity of rocks. Thus, granites, limestones, sandstones saturated with salty mineralized water conduct electricity well, while clays and sandstones saturated with oil have very low electrical conductivity.

Gravity survey based on the dependence of gravity on the Earth's surface on the density of rocks. Rocks saturated with oil or gas have a lower density than the same rocks containing water. The task of gravity reconnaissance is to identify areas with abnormally low gravity.

Magnetic prospecting based on different magnetic permeability of rocks. Our planet is a huge magnet around which there is a magnetic field. Depending on the composition of rocks and the presence of oil and gas, this magnetic field is distorted to varying degrees. Magnetometers are often installed on airplanes that fly over the study area at a certain altitude. Aeromagnetic survey makes it possible to identify anticlines at a depth of up to 7 km, even if their height is no more than 200...300 m.

Geological and geophysical methods mainly reveal the structure of sedimentary rocks and possible traps for oil and gas. However, the presence of a trap does not mean the presence of an oil or gas deposit. Hydrogeochemical methods of subsurface exploration help to identify from the total number of discovered structures those that are most promising for oil and gas, without drilling wells.

Hydrochemical methods include gas, fluorescent bit-monologue, radioactive shooting and hydrochemical methods.

Gas survey consists of determining the presence of hydrocarbon gases in rock and groundwater samples taken from a depth of 2 to 50 m. A halo of hydrocarbon gas dispersion is formed around any oil and gas deposit due to their filtration and diffusion through the pores and cracks of the rocks. Using gas analyzers with a sensitivity of 10 -5 ... 10 -6%, an increased content of hydrocarbon gases is recorded in samples taken directly above the deposit. The disadvantage of the method is that the anomaly may be displaced relative to the deposit (due to the inclined occurrence of the overlying strata, for example) or be associated with non-industrial deposits.

Application luminescent-bituminological survey based on the fact that above oil deposits the bitumen content in the rock is increased, on the one hand, and on the phenomenon of bitumen glowing in ultraviolet light, on the other. Based on the nature of the glow of the selected rock sample, a conclusion is drawn about the presence of oil in the proposed deposit.

It is known that anywhere on our planet there is a so-called radiation background, caused by the presence of radioactive transuranium elements in its depths, as well as the influence of cosmic radiation. Experts were able to establish that the background radiation above oil and gas deposits was reduced. Radioactive survey is carried out to detect the specified anomalies of the background radiation. The disadvantage of the method is that radioactive anomalies in the near-surface layers can be caused by a number of other natural causes. Therefore, this method is still used to a limited extent.

Hydrochemical method is based on the study of the chemical composition of groundwater and the content of dissolved gases in them, as well as organic substances, in particular, arenes. As you approach the deposit, the concentration of these components in the waters increases, which allows you to conclude that there is oil or gas in the traps.

Well drilling is used to delineate deposits, as well as to determine the depth and thickness of oil and gas bearing formations.

Vladimir Khomutko

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Fundamentals of Oil and Gas Geology

Natural oil and natural gas are the most important energy carriers in the modern world. The geography of oil production is very extensive, from Russian Western Siberia to the Persian and Mexican Gulf, and each oil-bearing region has its own characteristics.

Oil exploration is the whole complex work, the purpose of which is to assess the industrial significance of oil and gas fields discovered as a result of geological prospecting, as well as to prepare this field (if its further exploitation is advisable) for development.

The geology of oil and gas is studied by drilling exploratory wells in order to conduct geological studies that make it possible to determine the size of the productive reserves of the discovered field and necessary for further design of field development. The deposit's reserves are calculated either for each individual deposit or for their blocks, and then the results obtained are summarized for the entire deposit. The basics of oil and gas geology imply a whole range of exploration work, since exploration and oil production are inextricably linked, and proper development of oil wells without an exploration stage is impossible.

Exploration of oil and gas fields. Goals and objectives

When carrying out geological exploration work, it is necessary to identify the productivity of the entire deposit as a whole, both in terms of area and depth achievable by modern means.

In the course of such work, the following parameters are determined (textbook “Geology and Geochemistry of Oil and Gas”, Bazhenova O.K.):

structure and types of available traps;
phase states of existing hydrocarbons;
phase boundaries;
external and internal contours of oil and gas content;
field capacity;
its saturation with oil and gas;
lithological properties of productive formations;
their reservoir properties;
physical and chemical characteristics of hydrocarbon raw materials and formation waters;
future well productivity and so on.

In addition, oil and gas exploration makes it possible to evaluate parameters that guarantee the possibility of determining methods for the future development of individual deposits and the entire field, and also justify the oil recovery factor, identify existing patterns that influence changes in the calculated parameters, and their heterogeneity.

To solve these problems, a study is carried out of oil and gas exploration wells, drilled in quantities optimal for specific conditions, allowing the following to be carried out with the proper level of quality:

complex geophysical studies of oil wells;
tests of the studied objects for inflows;
research during testing of operating parameters;
special studies of geophysical, geochemical, hydrodynamic and temperature nature in order to determine regime, reservoir and structural design parameters;
selection of cores in optimal volumes for their subsequent comprehensive laboratory testing;
sampling of gas, oil, formation water and condensate for the same purpose.

The rationale for choosing a specific exploration methodology for studying a field is based on the geography of oil production, analysis of geological research data obtained during prospecting, as well as data obtained as a result of exploration of other fields located in the same territorial area.

Exploration of hydrocarbon deposits should also clarify the model of a specific deposit and adjust the system for its further exploration.

Basic requirements for geological exploration

The exploration process should ensure approximately the same reliability of the data obtained in all areas of the studied deposit. Failure to comply with this principle may lead to repeated exploration of certain areas of the field or lead to geological cases of underexploration.

The geography of the oil and gas region also has a great influence on exploration.

Such uniform reliability is ensured by the use of a uniform network of exploration wells, which is built taking into account the geological structure of each individual deposit in the field.

When designing a system for the location of such exploration wells, their optimal number, the location and order of their drilling, as well as the density of the exploration network are determined. As a rule, an exploration network of wells is used evenly distributed over the entire area of the field, the placement system of which is selected taking into account the shape of the structure and type of deposits, the phase in which hydrocarbon raw materials are located, as well as the depth of productive formations, the location of deposits in space and specific technological conditions ongoing drilling.

If the field under study contains several deposits of oil and/or gas, then exploration is carried out stage by stage.

Each floor includes objects under study, which are separated from each other by a sufficiently large depth. The order of exploration (bottom-up or top-down) is determined after selecting the so-called base deposit, which is made during the drilling of the very first exploration wells. When choosing the exploration order from bottom to top, it is possible to return wells to sample the upper horizons.

If initial reconnaissance reveals that the upper floors are more significant, then work is carried out in a top-down order. The structure of the selected base deposit determines optimal location minimally required quantity wells in the studied field.

The efficiency of placing wells in an area largely depends on how accurately the contour of oil or gas content is determined.

Such a determination must first of all clarify the nature of the surface of such a contour (horizontal, concave or inclined), as well as the depth of the productive formation.

The location of contact zones between oil and formation waters is determined using a set of field geophysics techniques, as well as using studies carried out in perforated wells. To determine the horizontal surface of oil-water contact zones in massive-type deposits, two or three wells are sufficient, and in reservoir-type and lenticular-type deposits significant drilling is required. more wells

Regardless of the geography of the research being carried out, according to the criterion of covering the field area, exploration systems are classified as condensing and creeping.

The thickening system can significantly speed up the exploration process, however, when using it there is a risk that a certain number of wells will fall outside the boundaries of the oil-bearing contour. The use of such an exploration system involves covering the entire expected fishing area with further compaction of the network of exploration wells.

The creeping system consists of gradually studying the area of the studied field using a well network. Using this system eliminates the need for subsequent compaction, but this system requires much more time. On the other hand, the number of uninformative exploration wells is reduced, which, in the end, can lead to significant savings material resources. The creeping system is used, as a rule, for exploration of deposits whose oil-bearing contour is quite complex (including the exploration of non-structural deposits).

Based on such criteria as methods of placing a network of exploration wells, exploration is divided into ring, profile, sector and triangular location systems.

The ring system consists of gradually increasing rings of wells, the center of which is the first oil-bearing industrial well.

The profile system allows for short term and with the smallest number of wells, explore deposits of almost any type. The use of such a system involves laying a number of profiles that are oriented in the cross of the location of the structure under study (in some cases, at an angle to its long axis). As a rule, the distance between such profiles is approximately twice the distance between wells.

On strata reservoirs of the arched type, cross placement of wells is often used (either on the wings or at the periclinal ends). In fields with a complex structure (for example, such as the Verkhnechonskoye and Kovyktinskoye fields in Western Siberia), modifications of the profile system are used for exploration, such as:

A sector system is essentially a type of ring system. With it, the deposit is divided into sectors, the number of which is determined using analytical techniques, and the exploration wells themselves in these sectors are placed at different absolute elevations.

The triangular well arrangement system makes it possible to uniformly study the field area and effectively expand polygons to determine the size of deposit reserves.

Regardless of the geography of the research, integrated approach to field geophysical and geochemical studies of oil and gas reserves at each specific well allows achieving best effect in the process of studying an oil or gas field.

The choice of a specific complex technique is made depending on:

reservoir properties of rocks;
their lithological composition;
the type of fluids saturating these rocks;
features of filtration in the drilling fluid reservoir;
its composition;
the system by which exploration work is carried out and other factors.

The essence of field geophysical research is to subdivide the section into rocks of different lithological composition, after which lithological and stratigraphic benchmarks are identified, layers are correlated, intervals for core sampling and perforation intervals are selected, and the position of water-oil and gas-oil contact zones is determined.

All this makes it possible to obtain the maximum possible reliable information on reservoir, structural and some operational design parameters. Detailed interpretation of such studies allows us to determine the heterogeneity and quality of the studied reservoirs.

In order to study the reservoir characteristics of the studied deposits, cores are taken from the productive strata, as well as from the underlying and underlying rocks above and below them.

Core sampling intervals are determined taking into account the degree of geological and geophysical knowledge of a particular deposit and the entire deposit as a whole, as well as the thickness, quantity and variability of reservoirs. During core sampling, oil drilling fluids are used, which provide the maximum possible core removal and allow obtaining reliable data regarding the productive saturation of the reservoir formation. If exploration is carried out on stratified, massive or stratified-massive deposits, then core selection is carried out in such a way as to obtain data on parts of productive horizons of different areas and located at different depths.

Based on the results of the core study, the following is determined:

reservoir permeability;
its porosity;
productive saturation;
presence and composition of bound formation water;
displacement coefficient value;
mineral, chemical and granulometric composition of the reservoir;
compressibility;
plastic;
density;
the magnitude of electrical resistance;
ultrasound propagation speed;
swelling;
radioactivity;
carbonate content.

The design parameters of gas and oil reservoirs are determined based on geophysical survey data, core studies and formation testing results (either open hole or cased hole).

Regardless of the type of specific deposit, at least one base well must be drilled at any field, from which a continuous core sample is taken throughout the productive part of the geological section.

In the process of searching and exploring oil and gas fields, exploration work is the most capital-intensive, therefore, the general terms and value of material costs for industrial assessment of oil and gas fields. The volume of capital investments for geological exploration depends on the size of the field, its geological complexity, the depth of productive strata, the economic development of the territory and many other external factors.

The efficiency of the exploration stage is determined by the cost of one ton of raw materials and by the increase in reserves for each meter of each exploration well drilled, as well as by the ratio of the number of production wells producing products to the total number of equipped wells in the entire field. Methods for developing oil wells, methods for developing oil and gas fields and systems for developing oil deposits directly depend on the data obtained at the exploration stage.

Oil is one of the main natural resources of the Russian Federation.

Active search for oil and gas fields

Active search for oil and gas fields continues to be carried out even now. In turn, the richest countries in terms of proven reserves of black gold are the countries of the Near and Middle East, Northern and Latin America, Africa and Southeast Asia.

The task of searching for oil occurrence is to identify, analyze reserves and prepare for industrial development. In the course of such work, hydrogeochemical, geophysical and geological methods are used to search for oil fields, as well as drilling holes and studying them.

Geological techniques are carried out first. During this appointment, geologists come to the study area and carry out the necessary field work there. They examine and study rock deposits that extend onto the surface of the earth, their characteristics and structure, as well as the angle of inclination.

Upon return, the received materials are processed. As a result of these actions, geological maps appear - this is a display of the outcrop of rock on the earth's surface - and sections of the area.

Geophysical techniques and types of search

Geophysical techniques include:

seismic exploration;
gravity survey;
electrical prospecting;
magnetic prospecting.

The first is based on the application of patterns of distribution of artificial elastic waves in the Earth's crust. A component of gravity survey is the dependence of the force of gravity on the earth on the saturation of rock substances. Rocks filled with gas or oil are less dense than rocks that, for example, contain liquid. The objective of this study is to determine a place with a fairly low gravity.

Electrical exploration of oil fields

Electrical exploration of oil fields relies on the different electrical conductivities of minerals. Thus, rocks saturated with this substance have incredibly low electrical conductivity.

The basis of magnetic prospecting is the varied magnetic permeability of rocks.

Hydrogeochemical methods are divided into:

gas;
luminescent-bitumenological;
radioactive survey;
hydrochemical method.

Gas shooting consists of recognizing existence hydrocarbon gas in rock and groundwater samples. Around any oil and gas deposits there is an aura of dispersion of such gases.

Luminescent bitumen survey is based on the fact that a large amount of bitumen is formed in the rock above oil deposits.

The task of radioactive survey is to identify the reduced radiation field that is caused by oil deposits.

The hydrochemical technique is used to study the chemical structure groundwater and the presence of dissolved gas and biological substances in them.

Well drilling is used to create the boundaries of deposits, as well as to identify the extent of occurrence and intensity of oil and gas bearing formations.

The most widely used method for investigating the occurrence of combustible natural resources is electrical logging. It is based on lowering a special device into the opening, which allows you to determine the electrical characteristics of rocks.

Methods for searching oil and gas fields

Oil and gas field prospecting methods are used to identify and analyze reserves. As well as the development of industrial deposits.

There are two phases of prospecting and exploration activities.

The search engine contains three stages:

Local geological and geophysical work. Permissible occurrences of oil and gas are determined, reserves are analyzed, and priority areas for further activities are identified.

Preparing the area for deep drilling. A more thorough study of oil and gas bearing areas is being carried out using geological and geophysical methods.

Search for deposits. Openings are being drilled to install production facilities.

The exploration phase is implemented in one stage. His task is to equip wells for the development process.

Search and exploration of oil and gas fields have made incredible progress in the past few years. At the moment, approximately 1% of the Earth's entire landmass has been explored at a depth of 2-3 kilometers. In addition, the search for offshore deposits is underway.

Industrial oil has been discovered and produced today in 65 countries around the world. The states richest in black gold reserves are: Saudi Arabia, USA, Russian Federation, Iraq, Libya, Iran, Venezuela, Abu Dhabi, Canada.

Also not far behind are Algeria, Nigeria, Qatar, Argentina, Mexico, India and many others. About 10,000 oil and gas fields have been discovered on Earth. Of these, most are located in the Russian Federation: 1,500 oil and 400 gas.

When searching for oil fields, wells are drilled, often in a vertical direction. But modern technologies make it possible to create inclined openings at any angle.

Oil exploration and development

Exploration and development of oil fields is a specific set of actions that allows one to assess the industrial characteristics of oil deposits, prepare and carry out their development.

Technical studies are carried out in each exploration well. Their main trend is to have minimal impact on the environment. Therefore, more needs to be done accurate calculations and drill as few search holes as possible.

Once a deposit is found, it needs to be developed. At this stage, openings are drilled where oil lies, that is, rocks are destroyed.

Fracture can be impact or rotational. During the first method, the rock is crushed with strong blows from a special device, and the debris is removed from the openings by water.

In rotary drilling, crushed particles rise to the surface with the help of a working fluid that circulates in the well.

Oil and gas exploration and its speed depends on the type of rock, the quality of the equipment and the professionalism of the master. In one such production facility, from several tens to a couple of thousand wells are drilled.

In order to coordinate the movement of liquid and gas, the openings are placed in a certain way and used in a special mode. This entire process is called field development.

New methods of searching for oil fields at the exhibition

Exhibition "Oil and Gas" is the largest event in this area in Eastern Europe. This year, as always, the exhibition will take place on the territory of the Expocentre Fairgrounds in Moscow. The most significant companies and well-known manufacturers in the field of technology and science will gather there.

Visitors will be shown the most successful domestic and foreign scientific achievements, latest technologies, business projects, high-quality modern equipment, interesting ideas.

Professionals in the field of “geology and oil and gas exploration” will also be present. They will show their latest developments and successful projects.

Business program "Naftogaz" very diverse. All participants and visitors will have the opportunity to attend conferences, attend lectures and seminars, and take part in discussions and debates.