Gases the natural fuels

General information and geology. Industr. layers g. p. g. are encountered in the form of the self-contained accumulations, not connected with some with other mineral; in the form of the gas-petroleum layers, in which gaseous hydrocarbons are in full or in part dissolved in the oil or find in the free state and fill the increased part of the deposit (gas caps) or the upper parts of the being communicated horizons of gas-petroleum formation; in the form of the gas-condensate layers, in which the gas is enriched liquid, preim. by the low-boiling hydrocarbons.

G. p. g. consist of methane, ethane, propane and butane, sometimes contain the admixtures of the low-boiling-point liquid hydrocarbons - pentane, of the hexane, etc; in them be present also the carbon dioxide, nitrogen, hydrogen sulfide and inert gases. Many layers g. p. g., which lie at the depth not more than 1,5 km, consist almost of one methane with the small admixtures of its homologues (ethane, propane, butane), of nitrogen, argon, sometimes carbon dioxide and hydrogen sulfide; the content of the homologues of methane usually grows with the depth. In the gas-condensate layers the content of the homologues of methane is considerably higher than methane. The same it is characteristic for gasOV of petroleum following. In separate ra -zovyx layers is observed the increased carbon-dioxide content, hydrogen sulfide and nitrogen. Are encountered g. p. g. in the deposits of all geological systems beginning from the end of the Proterozoic (Fig. 1), also, at different depths, but most frequently to 3 km. Are formed by g. p. g. in essence as a result of katagenetich. the transformations of the organic substance of the sedimentary rocks (see Gthe basics of the earth's crust). Deposits g. p. g. are formed in the natural traps on the migration lengths of gas.

Fig. 1. Confinement of gases of natural fuels to different geological systems (along horizontal - letter designations of geological systems, on the vertical line- volume of gas in billion. m³).

Migration occurs as a result of static or the dynamic load of the species, which squeeze out gas, and also with the free gas diffusion of the high-pressure areas in the zones of smaller pressure. Is distinguished extra-reservoir regional migration through great thicknesses of the species of different permeability by the capillaries, the times, the breakings and the cracks and the intra-reservoir local migration of those of inside well permeated is stratified, that collect gas.

Gas deposits on the special features of their structure are divided into two groups: stratified and massive (Fig. 2). In the stratified deposits the accumulations of gas are timed to the specific layer- collectors. Massive deposits are not subordinated in their localization to the specific layers. Are most common among the stratified the crest deposits, preserved powerful clay or halide casing. The sandy, sandy- silt -vye and silt species, frequently interstratified by clays, serve as underground natural reservoirs for 85% of total number of gas and gas-condensate deposits; in remaining 15% of cases the carbonate rocks are the collectors of gas. A series of the deposits, subordinated to the united of geologich. to structure, composes separate layers. The structures of layers are different for the plicated and platform conditions. In the plicated regions two groups of structures, connected with the anticlines and the monoclines, are separated. In the platform regions 4 groups of the structures are planned: dome-shaped and brachyanticlinal raisings, erosional and rip massifs, monoclines, synclinal saggings. All gas and gas-petroleum layers are timed to one or other gas and petroleum bearing sedimentary (sedimentary- rock) pond or another, which is the autonomous regions of large and it lasts, sinkings in the contemporary structure of the earth's crust. 4 groups are distinguished among them: timed to the intraplatform saggings (for example, Michigan and Illinoysskiy bass. Sev. America, Volga-Ural obl. USSR); timed to the caved in boundary parts of the platforms (for example, Zap.- Siberian in THE USSR); controlled by the cavities of the revived mountains (ponds of rocky mountains into THE USA, the ponds of Fergana and Tadzhik cavities in THE USSR); connected with the foothill and internal cavities of the young Alps of mountain construction (California bass, in THE USA, Sakhalin bass, in THE USSR). Increasingly more it is opened gas deposits in the zone of shelf and in the shallow ponds (for example, in northern m. large gas fields - West -Sol, It kh'yuit, Leman- bank).

Fig. 2. Types of the deposits of gas. Stratified: I- crest not violatedded; II tectonic screened; III - lithologically limited. Massive: Iv- crest; V- displaced; 1 - sandstones; 2- aleurolites; Eglin; 4 limestones and dolomites; 5- anhydrite; 6- gas.

World of geologich. the fuel capacities gases on the continents, in the zone of shelves and shallow seas, according to the forecast estimation, reach 10¹⁵ m³, which is equivalent to 10¹² t of oil.

THE USSR possesses enormous resources g. p. g. the largest layers are: Urengoyskoye (4 trillion m³) and Transarctic (1,5 trillion m³), timed to the chalky deposits of Zap.- Siberian bass; Vuktyl'skoye (750 billion. m³) and Orenburg (650 billion. m³) in the Volga-Ural reg.; Gazli (445 billion. m³) in Central Asia; Shebelinka (390 billion. m³) in the Ukraine; Stavropol (220 billion. m³) in the North the Caucasus. Among the foreign countries they have available the largest reserves g. p. g. (estimation of general reserves in trillions of m³): USA (8,3), Algeria (4,0), Iran (3,1), The Netherlands (2,3); they are the largest layers abroad (in trillions of m³): in THE USA - Pankhandl-Kh'yugoton (1,96); in the Netherlands - Slokhteren (Groningen) (1,65); in Algeria - Hussey -Rmel6 (ok. 1). N. b. vassoyevich.

Application. G. p. g. - highly economical energ. fuel-, heat of combustion 32,7 Mdzhm³ (7800 kkal/m³) is above, it widely adapts as by fuel- at the power stations, in ferrous and nonferrous metallurgy, cement and glass industry, with the production of construction materials and for the communal general needs.

Hydrocarbons, which form part g. p. g., raw material for the production of methyl alcohol, formaldehyde, acetaldehyde, acetous acid, acetone and other organic connections. By conversion by oxygen or by water vapor from methane - basic component g. p. g. - is obtained the synthesis gas (SO+N₂), widely used for obtaining ammonia, alcohols and other organic products. By pyrolysis and by the dehydrogenation (see hydrogenation) of methane are obtained acetylene, soot and hydrogen, utilized mainly for the synthesis of ammonia. G. p. g. use also for obtaining the olefin hydrocarbons, and first of all of ethylene and propylene, which are in turn raw material for further organic synthesis. From them produce plastic masses, syn. natural rubbers, skills, the fibers and other products.

S. F. gudkov.

Output g. p. g. includes the extraction of gases from the depths, their collection, calculation and preparation for the transport to user (Vol. n. the development of gas fields), and also the operation of bore holes and ground equipment. The special feature of output g. p. g. from the depths in comparison with the extractions of solid minerals lies in the fact that entire complex way of gas from the layer to the user is hermetically sealed.

Outputs g. p. g. from the natures of sources (for example, the "eternal fires" in Daghestan, Azerbaijan, Iran, etc.) they were used by man from the immemorial times. More lately found a use the natural gas, obtained from the wells and the bore holes (for example, in 1st thousand of n. 3. in China, in Prof. Sychuan', with the drilling of well to the salt was opened Tszylyutszin layer, whose gas served for the evaporation of salt from the solutions). Epizodich. the use of a natural gas, obtained from the randomly open deposits, it continued for a period of many centuries. To sulfurs. 19 v. carry the application of a natural gas as tech. fuel (for example, on the base of layer Daghestan fires it was organized glass production). By searches and by the development of gas deposits they were not occupied up to the 20's. 20 v., when the industr. development of the purely gas fields begins: at first lying at small (ok. of hundreds of m), and then to ever larger depths. The development of layers was conducted primitively during this period: the bore-holes were placed on the deposit on a uniform grid with the distance between them on the average into 1 mile (1,6 km). Output g. p. g. from the bore hole composed 10-20% of the potential productivity of bore hole (its absolutely free debit), and sometimes (with favorable geologich. conditions and to the characteristic of layer) working debits were more.

In the 30's because of the development of technology of drilling of well and the passage at the large depths (1500-3000 m and more) was opened the new type of deposit - gas-condensate; the development of these deposits required the creation of new technology.

End the 40's is characterized by intensive development of domestic gas industry and by putting into practice of the scientific methods of developing the gas and gazokondetssatnykh layers. In 1948 hearth of Sov. scientific B. b. lapuk's hands is created the first scientifically substantiated project of the development of gas field (Sultangulovo Kuybyshev reg.). During the subsequent years of promyshl. the layers g. p. g. are developed on the projects, comprised on the basis of the latest achievements of trade geology, hydrodynamics and by other important stage of the mastery of layer appears its reconnaissance. The detailed reconnaissance of gas deposit requires boring the large number of deep bore holes; frequently the quantity of the exploration wells exceeds the necessary number of operational.

The new methods of developing the layers of gas are created and inculcated by Sov. scientists in the postwar period. During the first stage of the mastery of gas deposit it occurs it experimentally -prom. the operation, in the course of which (2-5 years) are refined the characteristics of deposit - the property of layer, the reserves of gas, the productivity of bore holes, the degree of the mobility of stratal water and so forth layer is connected to the nearest gas pipe or serves for the gas supply of local users. Second stage - by prom. the operation, based on the sufficiently complete information about the layer, obtained in the course of experimental- industr. development. In this stage are distinguished three fundamental periods - increasing, constant and falling output. The first period occupies 3-5 years. It is connected with the drilling of well and the equipment of gas trade. In this time it is obtained by 10-20% of the general reserves of gas. The second period continues for ok. 10 years, during which of the deposit it is selected by 55-60% of reserves of gas. A quantity of bore holes at this time grows, since the productivity of each of them individually falls, and general gas bleed on the deposit remains constant. When pressure in the layer is reduced to 5 - 6 Mn/m² (50-60 kgof s/sm²), is put into use the dozhimtsaya gas-compressor station, which increases the pressure of gas, selected from the deposits, to the value, with which usually works main gas pipe. The third period - the falling output - is unconfined in the time. The development of gas deposit occurs in essence of 15-20 years. In this time it is extracted by 80-90% of reserves of gas.

In the prime cost of output g. p. g. 40 - 60% compose initial costs of ekspluatats. of bore holes. So that the bore hole, drilled to the fiery seam, would apply throttle, it suffices it to open; however, high-yield bore holes cannot be completely opened, since with the free outflow of gas can occur the destruction of layer and shaft of borehole, the irrigation of bore hole due to the inflow of stratal water, it will be irrational be expended energy of gas, which is located in the layer under the pressure. Therefore the gas flow is limited, for which the carbine (the local contraction of pipe),installedmost frequently on the head of bore hole usually is used. The daily working debit of bore holes is from tens of m³ to several million. m³.

From the end the 60's in THE USSR are for the first time in the world practice drilled super-power bore holes with a diameter of the operational column of 8-12 inches (200-300 ml).

The productivity of the gas wells depends on the properties of layer, method of its dissection and constructing the face of bore hole. The more permeated the layer, the more powerful it is and the better communicates the layer s vnutr. by the part of the bore hole, the more the producing well. For an increase of the productivity of the gas well in the carbonate rocks (limestones, dolomites) the face is processed by the salt acid, which, reacting with the species, enlarges the channels of the inflow of gas; in the hard species uses the torpedo bombing of the face, as a result of which the critical zone of layer acquires the network of the cracks, which facilitate the motion of gas. The intensification of the inflow of gas is achieved also with the aid of Vol. n. of the hydroblast perforation of casing spring, which improves the degree of soobshchayemosti of layer with the bore hole, and via the hydraulic break of the layer, with which in the layer they are formed by one or several large cracks, filled with the coarse sand, which has low fil'trats. resistance. With the selection of the system of the arrangement of bore holes on the gas field are considered not only the property of layer, but also the topography of locality, the system of the collection of gas, the nature of the exhaustion of deposit, the periods of the putting into commission of compressor station and other bore hole are located over the area of layer evenly along the square or triangular grid or unevenly - with groups. More frequently adapts the group arrangement (Fig. 3), during which the maintenance bore holes is facilitated, the overall automation of the processes of collection, calculation and treating the production is possible. This system usually proves to be most advantageous and according to the economic indices. For example, on the North- Stavropol gas field the group arrangement of bore holes in the center section of the deposit made it possible to reduce (in comparison with the uniform arrangement) more than doubly the number eks -pluataq. of bore holes, which gave savings ok. 10 mln. rub.

Fig. 3. Diagram of the group arrangement of bore holes on the gas trade.

The development of gazokotsdensatnykh layers is accomplished by three osn by methods. The first, widely used in THE USA, lies in the fact that in the layer by means of the reverse rocking in it of gas, from which on the surface are isolated heavy hydrocarbons, is supported sufficiently high pressure (so-called sa1kling- process); therefore the condensate does not fall out in the layer and will be given to the surface in the gaseous state. The extraction of condensate the reverse rocking of emaciated (with the content of heavy hydrocarbons - not more than 10% ) gas into the layer continues, until the large part of the condensate from the deposit is extracted. In this case the reserves of gas are preserved during it lasts, time. The second method lies in the fact that water inject for maintaining the stratified pressure in the fiery seams. This makes it possible to use the extracted gas immediately after the isolation from it of condensate. However, rocking water can lead to the losses of both the gas and the condensate as a result of Vol. n. of jamming gas (incomplete displacement of gas by water). This method adapts rarely. Using the third method gas-condensate layers are developed as purely gas. This method is used when the content of condensate in the gas is small or if the general reserves of gas in the layer are small.

The development of gas field achieves the gas trade, which is the complex, placed in the large territory economy. On the gas trade average to the scale there are tens of bore holes, which are located on the territory, calculated by hundred km². Osn of those -nologic. of the task of gas trade - guarantee of the planned mode of operation of bore holes, the collection of gas on the bore holes, its calculation and preparation for the transport (isolation from the gas of solid and liquid admixtures, condensate of heavy hydrocarbons, the drainage of gas and cleaning from hydrogen sulfide, whose the content there must not exceed 2 g on 100 m³).

The method of the isolation of condensate depends on the temperature, the pressure, the composition of gas and on that, is processed gas of purely gas field or gas-condensate. The natural gas entering from the deposit always contains a some quantity of water; being connected with the hydrocarbons, it forms snow-visible substance - hydrates of the hydrocarbons (see hydrate formation). Hydrates complicate output and transport of gas.

Before transporting g. p. g. to the places of consumption, them they subject to the processing, which has as a goal removal from g. p. g. of mech. admixtures, harmful components (№e), heavy hydrocarbon gases (propane, butane, etc.) and water it is steam. For the removal of mech. admixtures the separators of different construction adapt. The removal of moisture from the gases is accomplished by a low-temperature separation, i.e. by the condensation of water it is steam at low temperatures (to -30 °S), which are developed in the separators as a result of throttling of gas (decrease in pressure of gas 2-4 times), or by the absorption of water it is steam by solid (see adsorption) or liquid (see absorption) substances. By the same methods are separated from the gases heavy hydrocarbon gases with obtaining of damp gasoline washed out from hydrocarbon gases, which then is divided (see rectification) to the stable gasoline washed out from hydrocarbon gases and the commodity light hydrocarbons (tech. propane, tech. butane, propane-butane mixture and other fractions). If necessary from g. p. g. are moved away harmful substances, mainly hydrogen sulfide. For the removal of sulfur from the gases a number of the solid and liquid substances, which connect sulfur, is used. Gas after working on the trade under the pressure 4,5-5,5 Mn/m² (45-55 kgof s/sm²) will be given on the collector for the drainage to the trade gazosbornyy point or to the headwork of main gas pipe. G. p. g. of purely gas fields usually undergo only drainage and cleaning from the solid admixtures.

Passage to the complex design of the development of gas fields, the intensification of the inflow of gas to the bore holes, the automation of installations on the gas trades made it possible to considerably increase the working debits of bore holes, to improve the preparation of gas for the transport and to reduce the prime cost of natural gas.

E. V. levykin.

Lit.: The gas fields OF THE USSR. Reference book, 2 publ., M., 1968; Yeremenko N. A., geology of oil and gas, M., 1968; Smirnov A. S., Shchirkovskiy a. i., output and the transport of gas. M., 1957; Korotaev Yu. p., Polyanskiy a. p., the operation of the gas wells, 2 publ., M., 1961; Shmyglya p. T., the development of gas and gas-condensate layers (theory and practice), of M., 1967; Bases catching M. n., Zhukov a. i., Alekseyev T. S., the preparation of natural gas and condensate for the transport, M., 1968; Development of gas field by the system of the unevenly located bore holes, M., 1968; Whistles s. f., processing the hydrocarbons of natural and casing-head gases, M., 1960.