UA60461C2 - Method and gas-producing complex for extraction and processing methane from sea gas-hydrate deposits - Google Patents

Abstract

Gas-producing complex (GPC) for extraction and processing methane and natural gas from sea gas-hydrate deposits (GD) of warm and cold seas includes platform, drill rig, equipped wells immersed to GD field, pump and lift-transportation equipment, heat-power gas-hydrate electric power generating unit, appliance for preparation of carrier that melts gas-hydrates in GD, methane liquefier. GD platform has bottom gas-collection cover that is placed just over GD, it is arranged as sealed from above hemisphere turned with open convex side to sea bottom, through this well pipes are lowered, and in the upper part gas discharge pipe is placed, its upper end is connected to branch pipe of gas liquefier inlet. Wells are arranged as supercharge-extraction system that is hydraulically interconnected by gas-bearing gas-hydrate layer and combined of 3-6 rows of those wells. As appliance for preparation of carrier that melts gas-hydrates in GD the GPC includes freezing or gas-hydrate desalter – separator of sea water, its supercharge branch pipe for concentrate of sea water or for salt-concentrate suspension is connected to inlet of wells and / or smelter of gas-hydrates of heat-power gas-hydrate electric power generating unit. Heat-power gas-hydrate electric power generating unit GPC includes gas-hydrate crystallizer of continuous action arranged as vertical pipeline immersed to cold sea level to depth 300-600 m and gas-hydrate smelter with periodic action arranged as sectional one, each its section is equipped with technological branch pipes for inlet-outlet of reagents and heat exchanger that has branch pipe for inlet of warm water of surface layer of sea, at that one of sections of smelter that produces high pressure gas-methane, at about 50-200 MPa, includes heat exchanger with intake of heat carrier at temperature 30-50 °C and with its branch pipe for high pressure gas injection it is connected to branch pipe of well inlet. Method for extraction and processing of methane and natural gas from sea gas-hydrate deposits of warm and cold seas that is realized by means of GPC, provides increased completeness of extraction of methane from different in depth of bedding gas-hydrate layers at decrease of power consumption.

Description

Description of the invention

The invention relates to the extraction of natural gas (the main component - methane) from underwater gas hydrate 2 deposits (GP) of warm and cold seas in warm and cold seasons and its processing (increasing the pressure for electricity generation and destruction of the gas hydrate layer, as well as liquefaction of this methane for the convenience of its transportation and disposal, as well as higher sales prices).

In the Black Sea, for example, GPs are located at depths of 300-1000m. The depth of the lower limit of the zone of hydrate formation is on average 400-500 m under the seabed. The density of methane resources hidden in bottom sediments with a thickness of 300m is estimated at 1170-1384 million m3/km7. Gas resources in gas hydrates throughout

The Black Sea is estimated at 100-280 trillion cubic meters (Ukraine will have enough of this gas for at least 25 centuries). About 90 marine GPs have already been found around the world (USA, Russia, Norway, Japan, Canada, Mexico, Panama,

Brazil, Australia, India, New Caledonia, etc.), the amount of methane in which is equal to 85905 of all the world's 75 hydrocarbon resources. This is a new yet undeveloped giant source of hydrocarbons. Especially huge GP of cold seas (for example, the amount of gas hydrate methane in the Barents Sea - 1100 trillion m", in

Sea of Okhotsk - 1200 trillion m). To date, underwater gas hydrate deposits have not yet been developed in the world, but underwater gas deposits are being developed, which is not in the gas hydrate solid state, but in the gas state. The methods and devices for the development of these two different fields have many common techniques. There are several proposals for methane extraction from GP: (1). Yu.F. Makogon (VNIIYGAZ, Moscow) Hydrate! natural gases. Nedra Publishing House, Moscow, 1974;

I2). MaKkodop UE (Texas AEM OMPimegeyu). Seoiodisai apa iesppoiiodu azresiv oi daz Nuaigafevs ip (pe Ipaiiap oiepoge. Rgoseedipoz oi (Pe 3-y Ipiegpaiopa! BROeorpuzisv Sopiegepse. Mem Oeipi, 24 Rergoagu, 2000:

IZY. Trebyl F.A., Makogon Y.F., Basniev K.S. More natural gas. Moscow. Nedra", 1976. p. 1. Excavating mining and bottom works - an underwater excavator moves along the bottom of the sea, which removes the top soil layer by layer, which in the form of pulp is raised by an air elevator or pumped out by a pump to the surface of the sea, methane is degassed from gas hydrates during removal pressure, gas is collected on the surface of the sea, compressed and transported.

The disadvantages of this method are obvious - the development of special underwater deep-sea equipment is necessary, its high cost, bad ecology (the soil must be moved to another place), it is impossible to develop deep gas-hydrate layers, high energy costs (because methane must be compressed from 0.1 up to 5-12 MPa). со 2. The pressure in the gas-hydrate layer below the equilibrium pressure of the existence of gas-hydrates (1,2) is extinguished. At the same time, the gas must be sucked to the surface of the sea by compressors.

The disadvantages of this method are well known to gas production specialists - hydrates, melting when the pressure is reduced by 3.5 at the expense of their internal energy, reduce their temperature (according to the principle of Le Chatelier), as well as "from the surrounding soil to about 02С (especially in cold seas), which leads to ice formation in the area of the wellbore and stoppage of flow; very high costs of electricity for the operation of compressors (because the pressure in the gas-hydrate layer must be significantly reduced to determine the effect).

C. By increasing the temperature of the HP by providing, for example, hot water heated by some heat source, or by the heat of a nuclear reactor placed directly in the HP |1,2,31. Disadvantages - in the case of hot water supply - high heat consumption (high heat of fusion of gas hydrates of methane - 3785kJ/kg of methane in the composition of the gas hydrate, in addition, it is necessary to heat not only gas hydrates - they are in the soil "" about 1095 by mass - and the soil itself!); in the case of a nuclear reactor - high capital costs and non-ecological. 4. The introduction of glycols, methanol, alcohols, brines (CassiSi 25) and other reagents-inhibitors of hydrate formation into the gas production plant. This method is used in gas production |1,2,31 b Disadvantages - the high cost of reagents, you need a lot of them, and most importantly, most of them are not environmentally friendly.

If we use Sasi", then for a gas production complex (GDC) with a productivity of 1 billion cubic meters per year, approximately Ttrain/day of this salt is needed. t» This last analog (1,2) is the closest to the proposed invention. This analogue has features in common with the invention, which consist of: o - drilling of the shutters in the GP and their reconstruction (cementation of casing pipes, preparation of the well bottom, "" rebuilding of the filter in the bottom; - preliminary deformation of gas-bearing layers to increase their fracturing and gas permeability, for example, by firing cumulative charges and other actions: - preparation and supply of warm water or other heat carrier to the GP; - melting of gas hydrates with warm water or a hydrate formation inhibitor, as a melting gas hydrate carrier iF) "at the location" of the location of gas hydrates in the GP or by reducing the pressure in the gas hydrate layer , selection

Because of production gas from the gas station, its collection and removal to the surface; - pressing it to 10-20 MPa and liquefying it, and performing all these operations at the expense of electricity produced directly and autonomously in the gas production complex.

Until now, there are still no gas production units (GPC) in the world that extract gas from underwater gas fields, but there are quite a few

GDCs that extract gas from underwater deposits of conventional (that is, not gas hydrate) gas. These latest MPCs have the following features in common with the features of the proposed MPC. on which it is proposed to extract gas from the GP, namely: - have a platform that is firmly or dynamically positioned over the selected point in various ways; in b5 one of these methods, the dynamic maintenance of the semi-submersible platform in the horizontal plane is carried out with the help of thrusters; compensation of movements in casing pipes is done by hinges; vertical movements of the platform during sea waves are compensated by special compensators that ensure constant tensioning of casing pipes regardless of the impact of the platform during sea waves (all this technique is also used in the invention); - have a drilling rig, - have extraction wells immersed in the gas-bearing layer; - have pumping and lifting and transport equipment; - have a thermoelectric power generating unit that does not use the thermobaric difference of sea water to reduce electricity consumption; 70 - have a device for preparing the medium that melts the gas hydrates in the GP; - have a methane liquefier that does not use a column of sea water to reduce electricity consumption.

Tasks to be solved by our proposal: 1. Extraction of methane from underwater hydroelectric power stations of warm and cold seas at any time of the year and at any depth by environmentally friendly measures; 2. Improvement of the kinetics of the gas hydrate melting process in the gas hydrate layer; increasing the completeness of methane extraction from gas hydrate layers of different depths; concomitant extraction of subhydrated gas, as well as oil. 3. Reducing the energy consumption of the gas production complex (GPC) and, in the last resort, getting closer to avoiding the need to burn part of the gas directly on the GPC platform to produce electricity; 4. Increase (this is the main thing) of GDK's profitability.

The fulfillment of the set tasks is achieved by the fact that in the method of extraction and processing of natural gas from marine gas hydrate deposits of the GP of warm and cold seas, which includes drilling wells in these GPs and their reconstruction, preliminary deformation of gas-bearing layers to increase their fracturing and gas permeability, for example, by shooting cumulative charges and other actions, preparation and supply of warm water or other heat carrier to the hydroelectric power station, melting of gas hydrates with warm water or other melting medium "according to the location" of their location in the gas hydrate layer of the underwater hydroelectric power station or by reducing the pressure in the gas hydrate layer, removing production gas from the hydroelectric power station, collecting it and diverting it to the surface of the sea, pressing it to 10-20 MPa and (8) liquefaction, and with the performance of all these operations at the expense of electricity produced directly and autonomously in the gas production complex, gas extraction from the gas station is carried out by a system of hydraulically connected discharge and suction wells that are operated for using 3 options. - a gradual deepening of 20-5 Ω in the GP as its upper layers are produced, d) - a gradual rise of 20-50m as the lower layers of the GP are produced, « - simultaneous production of several layers of the GP along its entire height by the fact that the wells work in in the modes of injection of the melting medium and extraction of gas alternately, while in the mode of injection, /-«2 is fed into the wells

Зз5 melting coolant, as well as, alternatingly, high-pressure gas, and in the extraction mode from the wells, gas from molten gas hydrates, spent concentrate and water from molten gas hydrates, as well as well blowout products, for example, soil particles, are taken from the wells; - as a melting medium, a 10-25956 seawater concentrate or a salt-concentrate suspension, in which there are 3-1595 salt crystals in a saturated solution of seawater of eutectic concentration, which are "concentrated, for example, by freezing or gas-hydrate method, or sub-hydrate gas and subhydrated water - from the underlying layers with geothermal temperatures of 302С and more, with a pressure of 2 MPa and more. exceeds the pressure of the overlying HP, into which this heat carrier is injected by gravity, or liquid or compressed "" carbon dioxide extracted from industrial waste gases or atmospheric air; - gas after melting of gas hydrates in the gas hydrate layer is accumulated directly near the bottom of the sea under the pressure of the hydrostatic column of sea water and fed to the input of the last stage of compression of the liquefaction cycle;

Ge - a part of the produced gas drawn to the surface is compressed to 50-200 MPa and periodically fed into the gas station, warning of the introduction of the melting medium into it with gas blows; o - to drive a heat-power electric generating unit, produce high-pressure gas, as well as liquefy methane, the thermobaric difference of sea water at sea level is used by contacting methane with sea water at depths of 300-600 m, the formation of gas hydrates in this cold, deep level of the sea, b » the pumping of these gas hydrates in the form of a gas hydrate suspension to the surface of the sea and their melting at

EVEN at a temperature of 18-259C by the heat of surface seawater (in the warm season), or (in the cold season) by contact with a 10-2596 concentration of seawater or a salt-concentrate suspension in which there are salt crystals in a saturated solution of salts of eutectic concentration, and the total the concentration of salts in the dry residue reaches up to ZB5Uyu, by which the gas is thermally compressed to a pressure of 8-20MPa before it is fed to the turbine of the thermal power plant or to the methane liquefier. (F) In addition, the fulfillment of the tasks is achieved by the fact that the wells work in injection mode in all 3 operating options during the time period when they are located 3-20 m deeper than the wells that work in gas extraction mode. Moreover, prior to or simultaneously with the development of the HP using a system of wells above and below this HP, overhydrated and underhydrated gas, as well as hydrohydrated oil and gas condensate are taken using, for example, fountain pipes. At the same time, the sealing of casing pipes of wells, which separates gas hydrate layers from the overlying non-hydrate aquifer layers, in the presence of thermodynamic conditions of hydrate formation, is performed using temporary thermoreversible cementation with gas hydrates by introducing cooled methane or natural gas enriched with 65 heavy components - ethane into the sealing cracks. with propane, butanes, and the transfer of the GDC after the production of the gas under it to the second yet-to-be-developed gas production is carried out after raising all the operational pipes and the gas collection cap to the lower edge of the gas production platform. In addition, in the method in the warm season in warm seas at cold sea level at depths of 50-500 m, a refrigerating and at the same time hydrate-forming agent (freons 22, 134a8 and others, Н5, СО» and others) comes into contact with a mixture of sea water and its concentrate with a concentration of 3 -2095 salts, forming gas hydrates, then the gas hydrate suspension is raised to the surface of the sea, the gas hydrates are separated from the product concentrate with a concentration of 10-2595, washed from the concentrate and melted to produce desalinated pure melt drinking water.

At the same time, the process of hydrate formation of the refrigerating and simultaneously hydrate-forming agent is carried out under the parameters of gas-hydrate eutectic, after which the gas-hydrate-salt-concentrate suspension is divided into 7/o gas-hydrate-concentrate suspension and the salt-concentrate suspension, for example, by precipitation, salt is separated from the concentrate, for example, by filtration of the concentrate and subsequent squeezing silt mass, accumulate and use in the cold season to make a concentrate by mixing salt with sea water.

At the same time, in cold seas, the process of hydrate formation of the refrigerating and simultaneously hydrate-forming agent is carried out at the surface level of the sea, producing a 10-2596th concentrate or salt.

At the same time, a part of methane gas hydrates is melted at an elevated temperature of 30-509C due to the supply of low-potential heat, which is, for example, extracted during the liquefaction of methane, producing high-pressure gas of the order of 50-200MPa. At the same time, when using the thermobaric difference of sea water at the depth of the sea to liquefy methane, the melting of gas hydrates is carried out step by step in the following sequence of processes that carry out the "addition" and "subtraction" of gas flows that have different pressures: first, the gas hydrates are drained from the interhydrate water by draining it and then blowing the hydrate mass with gas, then the gas hydrates are compressed with a lower pressure return gas of 0.6-1MPa, which is taken from the methane liquefaction cycle, then melted by heat exchange with warm surface seawater, then the gas hydrates are re-compressed with a medium pressure return gas of 2-6MPa, which is taken from the cycle of liquefaction of methane, and gas. which is taken from the gas hydrate deposit as a product, then liquid propane is taken from the melting zone, then finally the gas hydrates are melted by a combination of heat exchange with warm surface seawater and the introduction into the melting zone of gas hydrates of seawater concentrate or salt concentrate suspension, which are taken from the cycle i) desalination -separation of sea water; In the method, it is necessary to win the initial seawater concentrate or the initial salt-concentrate suspension, which must be fed for the melting of gas hydrates into the gas-hydrate layer of the GP, as well as in the section of the melter for the production of electricity and the production of high-pressure gas, determined according to the equation сон -внв ек tka y-zo zhk -v her in which

Sn - the required consumption of the initial (initial) seawater concentrate or salt-concentrate suspension of seawater; (Se)

Ov s - the amount of water in the composition of gas hydrates, which must be melted;

Zn - the initial concentration (mass fraction - here and below) of the seawater concentrate or the initial concentration of the salt-concentrate suspension based on the dry salt residue; "

Zk - the final concentration of the seawater concentrate of the salt-concentrate suspension after the melting of gas hydrates; шщ с Зо - the concentration of gas hydrates in the gas hydrate layer of the GP before their melting or the concentration of gas hydrates in the gas hydrate suspension in the sections of the smelter before their melting; "» 51 - the concentration of salts in seawater, which is part of the intercrystalline liquid;

A - specific mass of gas hydrate, kg (gas hydrate)/kg (gas in the composition of gas hydrate).

The proposed method is implemented in a gas production complex (GPC) for extraction and processing of methane and (o) natural gas from marine gas hydrate deposits of the GP of warm and cold seas, which includes a platform, o a drilling rig, wells immersed in the GP formation, pumping and lifting - transport equipment, thermal power gas hydrate power generating unit, a device for preparing a medium that melts gas hydrates in

Fsh» GP, methane liquefier, in that: - the GDK platform has a bottom gas collection cap, which is placed directly above the GP, made in the form of a sealed hemisphere from above, which is turned with its open concave side to the bottom of the sea, through which - wells are lowered, and in the upper part has a gas outlet pipe, the upper end of which is connected to the inlet of the gas liquefier; - the wells are made in the form of an injection-extraction system, hydraulically interconnected by a gas-bearing gas hydrate layer and composed of 3-6 rows of these wells; - as a device for preparing the medium that melts gas hydrates in the GP, the GDC has a freezing or

Ф, gas hydrate desalination-separator of sea water, the injection of which through the sea water concentrate or through the salt concentrate suspension is connected to the entrance of the wells and/or the gas hydrate melter of the thermal power gas hydrate power generating plant; bo - the thermal power gas hydrate power generating plant of the GDK includes a continuously acting gas hydrate crystallizer, made in the form of a vertical pipeline immersed in the cold sea level to a depth of 300-60 Ohm, and a batch gas hydrate melter, made sectional, each section of which has a heat exchanger, which has the entrance of warm sea-level water, and one of the sections of the smelter, which produces high-pressure methane gas of the order of 50-200MPa, has a heat exchanger with an inlet of a heat carrier with a temperature of 65 30-509С7 and its high-pressure gas injection is connected to the well entrance. In addition, in this GDC, the gas collection cap is made of a low thermal conductivity thin sheet material, for example, plastic (Teflon and the like), moves freely in the vertical direction along the casing pipes to rise to the sea surface by means of a sealed peripheral ring pipe pontoon attached to the lower edge of the gas collection cap and having inlets and outlets of water and air under a pressure of 10-20 MPa; in addition, the cap has on its hemisphere vertical conductors in the form of pipes 0.5-2 m long, through which well casing pipes are lowered, and in the upper part of the conductors there are packers that seal the well space between them and the casing pipes, and in the lower part of the conductors are placed packers that seal bypass windows of casing pipes.

In addition, in this GDC, the pipeline-crystallizer of gas hydrates of the thermal power gas hydrate /o power generating plant has on its outer surface filtering sections for discharging sea water, but retaining gas hydrates, and at the open bottom end - an underwater pump-charger of cold deep sea water; the entrances of the sections of the smelter for the gas-hydrate suspension of seawater concentrate or salt-concentrate suspension, as well as for the outlets of compressed gas and the discharge of the concentrate, are made in parallel, and the sections of the smelter have a pump for pumping through them warm surface /5 sea water, and in their lower part filter grates under which there are reservoirs of gas hydrate melt water.

In addition, in this GDC, the freezing or gas-hydrate desalination-separator of seawater has a eutectic stage in its composition, the outlet of which is connected to the seawater concentrate with the inlet of the wells that supply the concentrate to the HP, as well as to the section of the methane gas-hydrates melter of the gas-hydrate thermal power plant 2о , and the salt output, for example, from the screw salt separator, is connected to the accumulator of these salts and further - to the input of the above-mentioned wells and sections of the gas hydrate melter.

At the same time, the sections of the smelter have inlets for methane liquefier gas return flows, as well as methane from a gas hydrate deposit, and an outlet for liquid propane, located in the upper part of the gas hydrate melt water reservoirs. with

The essence of the invention is illustrated in Fig. 1-16.

Fig. 1 - types of hydrate textures of methane in the soil; (8)

Fig. 2 - phase diagram of methane, natural gas and its components in fresh water;

Fig. 3 - lowering the temperature of the hydrate formation of methane and natural gas due to the presence of salts;

Fig. 4 - typical vertical distribution of temperature, salinity, concentration of hydrogen sulfide in the Black Sea;

Fig. 5 - schemes of GP on the bottom of the sea; (se)

Fig. b6 - the driving forces of formation of BP); and melting of AT" hydrates in GP at a depth of 100 Ohm; "

Fig. 7 - a system of wells drilled to the depth of the GP;

Fig. 8 - the same, top view; at

Fig. 9 is a scheme of a methane liquefier, which uses the hydrostatic pressure of sea water to reduce "o electricity consumption;

Fig. 10 - methane liquefaction cycle on the temperature-entropy diagram;

Fig. 11 - diagram of a gas-hydrate desalinator-separator of sea water;

Fig. 12 - cycle of a gas-hydrate desalination-separator, which uses the thermobaric difference of sea "

WATER at the depth of the sea, in the temperature-pressure diagram; - in c Fig. 13 - diagram of a thermal power gas hydrate plant intended for the production of electricity; and Fig. 14 - cycle of a gas-hydrate thermal power plant, which uses the thermobaric difference of sea water "" at the depth of the sea, in the temperature-pressure diagram.

Fig. 15 - scheme of liquefaction of methane, which uses the hydrostatic pressure of sea water and the thermobaric difference of sea water along the depth of the sea to reduce electricity consumption. b In order to facilitate the understanding of the invention for an expert, I consider it necessary to first introduce several concepts of gas hydrates. o According to Fig. 1, the types of hydrate textures of methane, which were isolated during the experiment on the hydration of sands of different granulometric composition, are: 1 - massive, 2 - crusty. C - porphyry, 4 - lenticular, 4 - layered.

Fig. 2 (phase diagram of methane, natural gas and its components in fresh water) shows b" equilibrium hydrate curves for: methane СН /х, ethane СоНв, propane СзНз, natural gas (quantity of methane - ко 71.695), hydrogen sulfide NOС, oxygen OO", nitrogen Mo, carbon dioxide CO. To the right of these equilibrium hydrate curves there are gas-water, to the left - gas-hydrate-water (with an excess of water) or gas-hydrate-gas (with an excess of gas).

An admixture of heavy components to methane (this is the composition of natural gas) - ethane, propane, butanes, as well as HO and CO" shifts the equilibrium hydrate curve to the right, lowering the pressure and increasing the temperature of hydrate formation. When the curve for methane is crossed from right to left, methane gas hydrates are formed with the release of heat (F) of hydrate formation; when crossing the same curve from left to right, they melt with the absorption of heat of fusion t (3785kJ/kg of methane, which was included in the composition of the gas hydrate).

When the gas comes into contact with the salt solution, the equilibrium hydrate curve (for example, for methane) shifts to the left. Figure 3 shows a decrease in the hydrate formation temperature of methane and natural gas due to the presence of salts (for natural gas, Masi brine, for methane, Masi brine, for natural gas, SaSSi brine). For example (Fig. 3), the 2096th Massey solution reduces the temperature of methane hydrate formation by 1029, the 2956th Massey solution (the approximate equivalent of the bottom water of the Black Sea) - by approximately 0.596.

In warm seas, there is a difference in seawater temperature along the depth of the sea. Figure 4 shows a typical vertical b5 distribution of seawater temperature T, concentration of salts in seawater 5, density of seawater p, concentration of hydrogen sulfide Zno in the Black Sea. The dashed lines show the equilibrium curves of hydrate formation for methane and natural gas. Overlaying the phase diagram data on the vertical distribution of pressure and temperature in the sea determines the upper and lower limits of the zones of hydrate formation (ZGU). The upper boundary of the ZGU (Fig. 4) is usually located in the seawater layer and is determined by the intersection of the hydrate equilibrium curve and the curve of seawater temperature change along the depth of the sea. The lower limit of the ZGU is located in the bottom sediment and is determined by the intersection of the curve of the geothermal gradient of the sediment and the hydrate equilibrium curve. For conditions

Fig. A4 the upper limit of the EPA for methane is at a sea depth of 1,000 m, and for natural gas - 200 m. The lower limit, respectively, will be at a depth of 1750 and 1820 m. The thickness of the gas hydrate deposit in the sediments for these conditions is 150 and 220 m. 70 Figure 5 shows possible schemes of GP on the seabed. Marked: 0 - bottom soil, 1 - impermeable layer. 2 - gas reservoir, Z - gas hydrate deposit, 4 - oil deposit, 5 - bottom water, Tf - water temperature, Трр - soil temperature, Тр - equilibrium temperature of hydrate formation, Н /, Но - upper and lower depths of existence of gas hydrates, а- b-s-d- changes in water and soil temperature with depth (a-6b - first the water temperature to a depth of 50-100m decreases to 5-72С, then it is constant almost to the bottom of the sea (р-с), then the temperature of 75" (c-a) at first slightly, and then quickly increases (the Earth's thermal gradient). It can be seen that free gas can be above and below the GP, and below the GP there can be oil and water. Gas hydrates can be both in the bottom layer and in deep layers (one or more, separated by gas-impermeable soil layers) of the seabed.

Warm surface seawater can also melt gas hydrates. its consumption during its cooling in the HP from 212C to 99C per kg of methane, which is released from gas hydrates, is about 75 kg (water)/kg (methane) at a depth of 2 o injection b0Om. At sea depths of more than 1,000 m, due to the increase in the equilibrium melting temperature of gas hydrates (Fig. 2, 4), the heat charge of warm surface water is noticeably reduced and its consumption increases significantly. In this case, as well as when working in the cold season, as well as for the conditions of cold seas, it is advisable to shift the hydrate equilibrium curve to the left, feeding the heated 10-2596th seawater concentrate into the HP.

Fig. 6 shows the driving forces for the formation of AT gas hydrates and the melting of AT gas hydrates in the GP at the depth of

NA1000 m. Curve 0595 is the equilibrium curve of hydrate formation for pure water, curve 295 is the same for a 295 solution of salts. In order for the process of hydrate formation to proceed at a technically acceptable speed, the point of hydrate formation A o must be moved to the left by AT. - the driving force of hydrate formation. Point B here is the melting point of hydrates in pure water, and ATo is the driving force for melting hydrates in pure water. If roseol is introduced into the HP, the equilibrium curve of hydrate formation 095 shifts to the left and the temperature at which gas hydrates exist decreases significantly. Let the temperature of GP be determined by the temperature of point C, and the temperature of point B" - the new melting point with the driving force "with the force of AT". Then the temperature difference AT-TO-Tv: characterizes the thermal potential possessed by the GP itself for dispersing its gas hydrates. If the pressure in the extraction wells is reduced, then the position of point B" h will move to the position of point B" with the result: DI" will change to a greater DT" and AT" will change to o greater DAT", i.e. the conditions of the kinetics (speed) of the smelting process will improve gas hydrates in

From the gas hydrate layer. at

The required consumption of the initial concentrate of sea water or the initial salt concentrate suspension, which must be supplied for the melting of gas hydrates to the gas hydrate layer of the hydroelectric power plant, as well as in the section of the smelter for the generation of electricity and the production of high pressure gas), is determined according to the equation: ) With c in which :z» Sn - the required consumption of the initial (initial) seawater concentrate or salt-concentrate seawater suspension; 415 Ov s - the amount of water in the composition of gas hydrates that must be melted; Y b» Zn - the initial concentration (mass fraction - here and below) of the seawater concentrate or the initial concentration of the salt-concentrate suspension based on the dry salt residue; (ав) Zk - the final concentration of the seawater concentrate of the salt-concentrate suspension after the melting of gas hydrates; te 50 Зо is the concentration of gas hydrates in the gas hydrate layer of the GP before their melting or the concentration of gas hydrates

Ge") in gas hydrate suspension in sections of the smelter before their melting; sh 51 - concentration of salts in seawater, which is part of the intercrystalline liquid;

A - specific mass of gas hydrate, kg (gas hydrate)/kg (gas in the composition of gas hydrate). The derivation of this equation, as well as examples of its use, are given in example 1. The amount of the final concentrate ок, which is formed after the melting of gas hydrates, is determined according to the equation оо ktonzovo|uv to) with Figs. 7 and 8 schematically show the location of the system of wells 6, drilled to the depth of the GP (side and top views) and the view of the gas collection cap 7, which has 2 positions - the lower flooded (peripheral bo ring hermetic pontoon 8 is filled with water and the gas collection cap is at the bottom of the sea) and the upper unflooded (pontoon 8 is filled with gas and the gas collection the cap is raised and is on the surface of the sea or slightly lower - in the near-surface layer of the sea under the platform 9. To carry out these operations, the pontoon 8 has an inlet-outlet of high-pressure gas and an inlet-outlet of seawater). From the platform 9, a system of wells 6 is lowered into the ground, which are passed through the gas collection cap through the conductors 10. The wells penetrate the bottom soil 0, b5 Impermeable layer 1 and gas hydrate layer C; part of the wells (in Fig. 7 it is shown that only one well 11 is lowered into rock 2, which contains free gas).

The mining platform 9 is firmly or dynamically positioned over the selected point of the GP in various ways. On

Fig. 7 shows one of these methods. Dynamic maintenance of the semi-submersible platform in the horizontal plane is carried out with the help of thrusters 12 located on the pontoon 13. Compensation of these movements in the casing pipes is done by hinges 14 (shown only on one well). Vertical movements of the platform during sea waves are compensated by special compensators (not shown), which ensure constant tension of casing pipes regardless of the impact of the platform during sea waves.

To reduce the dimensions of the drilling rig, the casing pipes of the well system can exit the platform at an angle along the seabed (fanning out). From the top of the gas collection cap, the gas outlet 70 pipe 15, the output of which on the platform 9 is connected to the input of the methane liquefier.

The system of wells connected hydraulically in their lower part is 5-15 injection wells (on

Fig. 8 shows crosses - arrow feathers) and 5-15 pull-out pipes (shown by dots - arrowheads in Fig. 8) pipes b with a center-to-center distance that is determined by the following specific characteristics of the gas-hydrate layer and deposit, namely: porosity, gas permeability , the degree of pore filling /5 with gas hydrates. If the distance between the entrances of the wells to the seabed is less than 5 m, gas production becomes more expensive, if the distance is more than 30 m, the pressure depression due to the gas hydrate layer increases.

High-pressure gas (up to 200MPa) is injected into the gas-hydrate formation through injection wells for gas fracturing of the formation, and then the coolant: - warm sea surface water (in the warm season, when its temperature is more than 182); - or its 10-2596th concentrate (in the cold season and in the depths of the sea more bOOm); - or salt concentrate suspension (3-1595 solid salt crystals in a saturated seawater concentrate); - or warm (302C and more) subhydrated gas (from layer 2, Fig. 5); - or warm (302C and more) subhydrated water of the lower layers 5 (Fig. 5), which have a reservoir pressure that exceeds the reservoir pressure of the overlying gas hydrate deposit by 2 MPa or more; Ha - or liquid or compressed carbon dioxide extracted from industrial waste gases and atmospheric air.

The upper end of the injection wells in the injection mode is connected by means of a shut-off and regulating valve to a high-pressure pump, which supplies surface warm seawater or its concentrate and salt-concentrate suspension - from a freezing or gas-hydrate desalinator-separator of seawater with the help of a shut-off and regulating valve. . In addition, the upper end of the injection wells is connected to the high-pressure gas outlet from the gas cannon. The lower end of the injection wells (the bottom) is equipped in the same way as the bottoms of ordinary gas or gas condensate wells (Fig. 7, from A): the lower end of the pump-compressor sho pipes 16 is slightly raised above the shoe of the well; the lower part of the casing b has a perforated perforation 17; the shoe and the perforation of the well are immersed in the filter 18 of bottom-hole soil.

In the case when warm subhydrated gas or subhydrated water from the underlying layers is used as a heat carrier, the lower end of the injection wells is moved to this subhydrated layer, which has an increased pressure compared to the formation pressure of the GP (see the left pipe in Fig. 7 ).

Pulling wells are intended for the removal of gas with decomposing gas hydrates (with a decrease in pressure in the gas hydrate layer) and gas melt water, as well as spent coolant water and well blowdown products. The constructions of injection and extraction wells are the same (cancellation is functional: "pump-compressor pipes of injection wells are transformed into fountain pipes in extraction wells when the mode is changed). ts Each well operates both in the injection mode and in the extraction mode alternately depending on the thermodynamic and gas-dynamic conditions during operation. The injection wells go deeper than the extraction wells connected to them by 3-20m. ?b In the cold season, seawater concentrate is spilled from the lower end of the injection wells. It is heavier than seawater and, filling the volume of the gas hydrate deposit under the injection well, melts the gas hydrates. A slow flow of gas rises to the bottom of the extraction wells and gradually less and less saline of water. If the difference in the heights of the wells would be less than 5m (and at the end -0), then the concentrate, without having time to fully perform its melting action, would be blown into the extraction well. The difference in heights would be more than 1 Ohm is irrational, since it increases the way of filtering gas and water through the porous medium, and in addition - the geological structure of the bottom soil usually layered (a dense layer alternates with a less dense layer). In view of this, the danger of injection and extraction well boots getting into the ground, separated by a gas-water impermeable layer, increases. 5B In the case of such a hydrological environment, when the gas hydrate or gas layer must be separated from the overlying water-bearing layers, the casing pipes have cementation 22 around their circumference, made according to (F, with the help of thermoreversible gas hydrates of methane or natural gas, enriched with heavy components km-ethane, propane This method is possible: 1. if the sections of the casing pipes being cemented are under thermodynamic conditions of 60 hydrate formation (that is, the soil parameters in the pressure-temperature diagram must be to the left of the gas-hydrate equilibrium curve by at least 3-59C (Fig. 2 and b) 2. if the cementing zone is far enough away from the zone of active melting of gas hydrates, which is forcibly carried out during injection of the coolant.

In order to maintain approximately the same distance of water and gas filtration through the gas hydrate layer from 65 injection wells to extraction wells, all wells are evenly placed in a plane in 3-6 parallel rows.

The gas collection cap 7 in Fig. 9 has conductor pipes 10 with a diameter that exceeds the outer diameter of the casing pipes 6 of the wells by 80-200 mm. The number of conductors is equal to the number of wells. Fig. 9 shows only 1 conductor 10 as an example. The upper part of the conductor 10 is firmly and hermetically attached to the gas collector

Cap 7. Cover the annular sections between the conductor and the casing pipe with packers 19 and 20. These packers center the position of the casing pipe 6, preventing its collision with the inner surface of the conductor 10.

In addition, the upper packer 1!9 prevents the escape of gas through the conductor, and the lower packer 20 also performs the function of a valve that covers the bypass window 21, through which gas from the GP flows from the inter-tube space of the casing pipe 6 under the gas collection cap 7. Sealing in a standard packer is provided by a hollow rubber 7/0 cylinder sleeve. With its longitudinal compression, the cuff increases in diameter and is tightly pressed to both pipes. The number of conductors on the surface of the gas collection cap is as much as casing pipes can be located on it. If part of the conductors does not need to be used due to the operating conditions, then sealing plugs (not shown) are put on top of these conductors. The gas collection cap 7 is made of poorly heat-conducting thin-sheet material, such as plastic (Teflon). It moves freely in /5 Vertical direction along casing pipes. Why should the gas collection cap be made of poorly heat-conducting material? The temperature of sea water near the bottom of the sea is usually 5-72C, which is approximately 2-39C7 below the equilibrium temperature of methane hydrate formation. In the GP, in the area of the bush of wells, as well as under cap 7, a zone of elevated temperatures is created, which exceed the temperature of hydrate formation by 3-43.

This prevents the reversible transformation of gas into gas hydrate, which contributes to the normal operation of the gas collection cap, and the prevention of clogging of the gas outlet pipe 15 with gas hydrates. To maintain this non-hydrating aura, a poorly heat-conducting material of the gas collection cap is required, or the supply of warm surface seawater or concentrate under it through the casing pipe and through the bypass window 21.

Casing pipes 6, which are lowered through the conductors 10 of the gas cap, before entering the ground have a hinged connection 14 (only one is shown in Fig. 7), which ensures their indestructibility during horizontal movements of the gas production platform on the surface of the sea.

Let's consider the technology of operation of the system - gas production complex (GDC). After transportation to the place of gas production, platform 9 is positioned above the gas station. The gas collection cap 7 together with the casing pipes 6 inserted into the conductors 10 are sunk to the bottom of the sea by filling the pontoon 8 with water. First, the first pair is being drilled, and after the test and the results of its routine inspections, the rest of the production wells are being drilled.

After testing and checking the first pair of wells, the operation modes of the gas-hydrated layers are established, their capacity and texture, porosity and gas permeability of the rock (cemented by gas hydrates and without them) are specified, the characteristics of the above and below layers are specified once again: porosity and permeability, gas saturation, moisture, water level in aquifers. The temperature and mountain pressure of all layers, the component composition of gas hydrates and salt water are determined. "That's it

According to the results of the work of the first pair of wells, a number of operational solutions are specified. The main ones are the following: 1. How many production wells should be drilled? For example, the GDK can ensure the operation of 20 wells, and in view of the high porosity of the soil, it is possible to do without the operation of 5 wells. " 2. The option of drilling and exploiting gas hydrate and gas layers, namely: with c - gradual deepening of 20-50 m in the gas field as its upper layers are produced (this option - from top to bottom - is expedient when gas hydrates are on the upper horizon there is no gas-impermeable layer in bottom soil deposits and above, in this case the number of working wells decreases, all of them are switched to injection mode, all gas is collected under the gas collection cap, there is no need for 475 cementing of casing pipes). b Disadvantages of the option - a decrease in gas productivity due to the gradual development of the deposit, increased labor intensity due to the need for repeated drilling operations; o - a gradual rise of 20-50 m as the lower layers of the hydroelectric power plant are produced (this option -bottom-up'-c" is appropriate for a complex geological structure of the deposit, when there is an alternation of gas-hydrate and water-bearing layers; in the case of water-pressure operation of the layers; in the selection of subhydrated gas and oil; when watering wells b" as a result of the penetration of contour or subsurface waters into the bottom and the associated decrease in permeability through "Z gas).

Disadvantages of the option - time-consuming due to repeated work on raising wells; - simultaneous production of several layers of gas over its entire height (this option "over the entire height at once" has the highest gas productivity, the least time-consuming work on moving wells, but it is adapted only in the simplest case: the number of layers to be developed - no more than 2 (-x or 3-x). Option especially

F) is appropriate when using warm gas or warm water from high-pressure lower horizons as a heat carrier. Disadvantages of the option - an increased number (2-3 pieces) of production pipes inside the casing pipe, an increased number of packers, the difficulty of regulating the simultaneous operation of wells on all horizons. 60 3. What coolant should be used for the decomposition of gas hydrates? | at what depths should it be used?

In the warm season - surface sea water (more than 182C) - at depths of no more than bOOm, as well as sea water concentrate. In the cold season and at all depths - sea water concentrate. In the cold season, at all depths and for the formation and fixing of cracks in monolithic layers, a salt-concentrate suspension is used, which, under the pressure of hydraulic fracturing, introduces salt crystals into the cracks and temporarily fixes them (after dissolving such 65 salt crystals in pores filled with hydrates, when the hydrates melt high-pressure gas is released, which fixes and increases cracking).

In particularly favorable cases of presence on lower high-pressure horizons - gas or water of elevated temperature (more than 3022). If present - carbon dioxide, which melts methane gas hydrates, turning itself into carbon dioxide gas hydrate. This is one of the important methods of burying carbon dioxide permanently on the seabed in order to reduce the greenhouse effect. Figure 2 shows that if, for example, at a depth of 400m, carbon dioxide is supplied to the gas station, it will form its gas hydrate at temperatures below 102C, melting methane gas hydrate with the heat of its phase transition, which at this depth will melt at temperatures above 42C. The difference in the equilibrium temperatures of hydrate formation at a pressure of 4 MPa for CO 5 and CH is 62С, which is sufficient for a multidirectional phase transition and regeneration of the heat of such a phase transition. When 70 kg of CO" is introduced into the gas hydrate methane deposit and it is stored in the solid gas hydrate phase, 0.33 bkg of CH is melted.

That is, when extracting 1 billion cubic meters of methane, the MPC can hide 0.927 billion cubic meters? carbon dioxide Since the density of carbon dioxide gas hydrates (1200KG/MU) significantly exceeds the density of bottom sea water (103Okg/mU) and there are unchanged thermodynamic conditions for the existence of CO gas hydrates at the bottom of the sea (low temperature and high pressure), carbon dioxide will remain in the form of bottom gas hydrates forever. 4. On what horizon and at what height should cementing of casing pipes be done? Cementing is necessary to prevent water from entering the bottom of the well through the gap created during drilling between the soil and the casing pipe. Water from this productive horizon from layers not exposed by perforation and gas fracturing, as well as "extraneous" water from higher and lower-lying horizons, will flow through this crack.

This gap can be cemented with a gas-hydrate gap plug 22. The difficulty of this solution is that the place of cementing should not be heated above the temperature of hydrate formation and therefore it tends to be moved away from the place of heating and melting of GP.

Then, taking into account the decisions made, wells are drilled and their bottoms are constructed with filters.

Filters are necessary, since bottomhole zones after melting of gas hydrates in them will represent loose, unstable structures, layer destruction and formation of sand plugs on the bottomhole will occur. and.

The casing pipes are cemented, the necessary packers are installed. Then, the bottom-hole zones of the well are shot with cumulative charges, which is a preliminary dissection of the layer to a length of 1-1.5 m.

Then, high-pressure gas (up to 200MPa), which is much higher than the mining pressure of the layer (15-25MPa), is supplied through the pump-compressor pipes 16 in the GP from a gas gun (Fig. 15). New cracks are formed and expand (h7- cracks that were there before, which leads to a significant increase in the permeability of the formation. The formed cracks can also be temporarily fixed by applying a concentrated salt suspension.

Then, through the pump-compressor pipes 16, the heat carrier specified above in point C of the adopted operating decisions is supplied under a pressure that exceeds the layer pressure. at

The speed of injection of the coolant should be such that it is ahead at every moment of time

On the acceptability of the gas hydrate layer. (se)

Gas hydrates are melted after the heat carrier is introduced into the HP. The gas separated during the melting of hydrates is diverted to the GDK platform in three ways: 1. into the gas collection cap 7, if the gas hydrates melt in the subsoil or in the gas hydrate layer, above which there is gas-permeable soil; 2. through the fountain pipes of 16 extraction wells - there are 2 options here: - c - if the gas pressure at the entrance to the fountain pipes is higher than the gas pressure under the gas collection cap - in this case, it is energetically beneficial to send gas of higher pressure to the "" methane liquefier; this option is used also during "blowing the bottom of wells; - if the gas pressure at the entrance to the fountain pipes is lower than the gas pressure under the gas collection cap (in the case when the point

B: in Fig. b is significantly below point B") - in this case, gas of reduced pressure enters the methane liquefier and (22) electricity consumption increases - but due to the decrease in pressure in the gas hydrate layer, the conditions for the kinetics of the process of melting methane gas hydrates improve; 3. due to the casing pipes of the extraction wells, the bypass window 21 and the packer 20 into the space under the gas-collecting cap (a gas bubble supported by water from below). The gas-collecting cap also plays the role of the previous separator 20, in which the gas is pre-cleaned from solid particles removed from the well, of dripping water and hydrocarbon condensate. The latter is diverted upwards through the condensate drain pipe, which is located "and slightly below the gas discharge pipe 15.

However, when the distance between the bottoms of the injection and extraction wells is excessively large and the gas does not enter the extraction well (this case can be in the initial period of coolant supply from the injection well 22, when gas hydrates still completely plug and cement the pores of the rock), then an explosive situation occurs . Gas hydrates melt, releasing high-pressure gas (20-3 ОМПа). In this case, the gas blocks the supply of the heat carrier and must be diverted to the surface in an emergency order through injection wells (if the supply of the heat carrier is temporarily stopped).

If, when extracting gas, it is necessary to blow out the bottom of the well from soil that has collapsed and 60 has largely lost its strength after the melting of gas hydrates, as well as to remove excess water to prevent flooding of wells, then these operations in the proposed method are performed in the same way as in conventional gas and gas-condensate wells.

For example, if the extraction well is far enough away from the injection well (more than

ZOm) and the thermal influence of the latter is significantly reduced, then the conditions for hydrate formation are created in the wellbore. In this case, prevention of hydrate formation in the wellbore is carried out by injecting seawater concentrate through the annulus, while the product gas is discharged through the fountain pipes. The concentrate introduced into the annular space flows down the walls of the well to the shoe of the fountain (pump-compressor) pipes, from where it is captured by the gas flow and carried to the surface, preventing hydrate formation.

After exhausting the gas reserves in the gas station, the gas collection cap and pump-compressor and casing pipes are raised to the bottom of the GDK platform (Fig. 7) (having previously melted thermoreversible gas hydrate cement on the outer surface of the latter). Such melting is carried out by introducing a heat-salt carrier - warm surface seawater or its concentrate - into the cementing place. After these "lifting operations", the GDK is transported to a new point of the GP. 70 The operation of the wells of the GDK, the devices for the introduction of concentrate into the HPP - gas output from the HPP, and the preparation of the extracted methane for transportation to the mainland is ensured by an interconnected heat energy system, which consists of a functionally interconnected freezing (or gas hydrate) desalinator-separator of sea water, which works at the parameters of salt eutectics, thermal power gas hydrate installation, methane liquefier.

The methane liquefier GDK (Fig. 9 - the first version) consists of a 3-stage compressor (the first stage - 24, /5 the second - 25, the third - 26), refrigerators 27, 28 and 29, water separator 30, low-temperature heat exchangers 31, 32 , 33 and 34, expander 36, refrigerating machine 35, adsorbers 39 and capacity 38 - liquefied methane accumulator.

The methane liquefier effectively uses the hydrostatic column of sea water to reduce electrical losses, if methane is supplied for liquefaction from under the gas collection cap located on the seabed, 2o or directly from extraction wells. The output methane, compressed by the hydrostatic column of sea water (for example, to bMPa - at a sea depth of bOOm), enters in the amount X at the suction of the last 3rd stage of the compressor 26, is compressed in it to 12 MPa and cooled in the final refrigerator 29 to 10 96.

Then methane is separated from moisture in the water separator ZO, cooled to minus 17 2C in the heat exchanger 31 due to the cold return and expander flows, separated from carbon dioxide in one of the two periodically operating adsorbers 39 parallel to the urine 25.

Then the methane is cooled in the heat exchanger 32 to minus 40 by the refrigerating machine 35, after which it is divided into two parts. The first part (direct flow - in the amount of M kg) is cooled first in the heat exchanger 33 to minus 10092С, then in the heat exchanger 34 to minus 10692С, after which it is throttled (throttle valve 37) to a pressure of О0.6MPa and a temperature of minus 1342С. Under these parameters, methane enters the region of wet steam in ch 30 (see Fig. 10) and part of it liquefies, liquid methane accumulates and is then removed from the lower part of the capacity 38 (in the amount of X kg), and the steam that remains (in quantity /M-X/kg) is removed from the upper part of the capacity 38 and directed as a return flow through heat exchangers 34, 33 and chI 31 to the suction of the first stage of the compressor 24. Here the return flow is compressed from O0.6 MPa to 2 MPa, cooled to 102 in the intermediate refrigerator 27. o

З The second part of methane after the heat exchanger 32 (in the amount of /1-M/kg) performs a cooling function - it expands in the expander Zb from 12 to 2 MPa, cooling at the same time to minus 134 C, and in the form of an expander flow passes countercurrently to direct flow, cooling it in heat exchangers 33 and 31.

After the heat exchanger 31, the return and expander flows are mixed, then this total (in the amount of "/1-X/kg) recirculation flow is compressed by the 2nd compressor 25 blunting from 2 to 6 MPa, cooled in 40 intermediate cooler 28 and enters the suction of З- of compressor stage 26, mixing here with fresh - with the output flow of methane from the gas hydrate deposit of the HPP. "» This scheme has 2 important features, which lead to a decrease in electricity consumption for liquefaction (which is absent in methane liquefiers known in refrigeration technology): 1. In all 3 stages, only the recirculation flow of methane is compressed. Fresh source methane from review 45 of its previous inflation by a hydrostatic column of sea water to bMPa is compressed only in the last (22) stage of the compressor 26. o 2. To cool the gas after the compression stages, cold deep water is used, which lowers the temperature of the gas before compression in the compressor stages to 1090. pi Fig. 10 shows the thermodynamic cycle of methane liquefaction on the temperature-entropy diagram. Cycle

F 20 liquefaction is performed by the following set of processes: 1-12, 2-9, 10-11 - gas compression in compressor stages 24, 25 and 26; ". 12-2, 9-10, 11-3 - gas cooling in refrigerators 27, 28 and 29; - the state of the output methane after the gas collection cap of the GDK and the mixture of this gas with the gas recirculation flow before the compressor stage 26; 99 3-311- direct flow cooling?" in heat exchanger 31;

GF) 3711-31 - cooling of the direct flow of gas in the heat exchanger 32; t 37-5 - cooling of the direct flow of gas by a refrigerating machine in the heat exchanger 33; 5-6 - direct flow cooling in the heat exchanger 34; 60 6-7 - gas throttling in throttle valve 37;

O - state of liquid methane - the obtained product; 37-4 - polytropic expansion of gas in expander 36; 8-13 - heating of the return flow in the heat exchanger 34; 4d-2711113-111 - heating of expander and return flows in heat exchangers 33 and 34-33, respectively; 65 211-2 and 111.1 - heating of the expander and return flows in the heat exchanger 31.

In this scheme, a high-pressure cycle with an expander is used, with the circulation of the expander flow of medium pressure and with the preliminary cooling of the direct flow by an additional refrigerating machine. From the thermodynamic analysis of liquefaction cycles with an expander, it is known that the most optimal pressure of the direct flow after the compressor is 12 MPa.

Thermal calculation of liquefaction was performed with the following initial data: - Temperature of the output gas before the T40-1095 compressor stage; - Temperature of deep cold water is 72C; - The temperature of the surface warm sea water is 212C; - The depth of the sea bOOm, i.e. the water pressure near the bottom of the sea P.o0-6 MPa; 70 - Composition of the source gas - pure methane;

The effective efficiency of the compressor and expander stages is -0.8

The results of the calculation at a sea depth of bOOm, gas compression up to 12 MPa, the share of the expander flow of 0.5 and the gas pressure after the expander of 2 MPa are as follows: - the share of liquefiable gas from the gas that is compressed in the last stage of compression is -0.36; - the share of recirculated gas from the gas that is compressed in the last stage of compression - 0.63; - specific electricity consumption - 924kJ/kg of liquid methane or 0.26kWh/kg.

Note: a similar onshore methane liquefaction cycle (without the use of hydrostatic pumping and without cold deep water) has a specific energy consumption of 0.86 bkWh/kg of liquid methane.

A freezing desalinator-separator of seawater or a gas-hydrate desalinator-separator (GOR), which uses the thermobaric difference of seawater at the depth of the sea (temperatures and pressures), produces a seawater concentrate that melts methane gas hydrates in the GP. Below, the proposals of the invention, which relate to both of these devices, are considered on the example of GOR, as a more complex device and more promising.

The hydrostatic pressure of cold seawater creates favorable conditions for the formation of gas hydrates in the depths of the sea and the implementation of the gas hydrate desalination cycle. After the rise of hydrates to the surface of the sea, the separation and washing of hydrate crystals from brine (i.e. seawater concentrate) and the melting of hydrates, it is possible to obtain fresh water (melt, purified from salts and other impurities, potable) and a concentrate with a salinity up to eutectic. As a refrigerating and at the same time hydrate-forming agent, it is proposed to use freons 22,134a and others, CO" and other refrigerating agents in this invention. For example, for the conditions of the Black Sea, it is suggested to use hydrogen sulfide No5 due to its presence in deep water. h-

Fig. 11 shows a diagram of such a gas hydrate separator separator (HOR). It consists of 2 stages - desalination and concentration (eutectic). what

Desalinating degree (assistant of the USSR Mo355068, Desalinator of the mariner), 10/21/1970| it consists of a pipeline-crystallizer 40 immersed in the cold sea level to a depth of up to 800 m, a separation and washing column of the first stage 41, a gas hydrate melter 42, a condenser 43, and - built into the melter 42, a heat exchanger 44 placed in the warm surface level of the sea, compressor "about 45" and other auxiliary equipment.

The eutectic stage is blocked with the desalination stage and has a common pipeline with it - a crystallizer 40, has a separation and washing column of the second stage 49, a hydrate separator from salts 50 and a salt separator 51.

The output of the eutectic stage on the concentrate is connected by line 52 to the input of the well 6 of the concentrate supply to the GP, and the output on the salt 53 from the screw salt separator 51 is connected to the input of the salt accumulator (not shown). pt) c All devices of the desalination-separator are located on platform 9 (with the exception of the crystallizer pipeline 40 and the heat exchanger 44). ," The concentration interval 10-25956 is determined as follows. The concentration of 1095 reduces the temperature of hydrate formation (Fig. 3) by only 2.5-3.592C, that is, below this limit, the invention is practically inoperable.

It is practically impossible to obtain a concentration of more than 2595, since in a mixture of "sea" salts, in which the Mass is (o) more than 8095, the eutectic concentration of the mixture of salts is exactly 2590.

The GOR works (for example, on the NoZ) as follows. In the lower part of the crystallizer pipeline 40, which is submerged to a depth of 140-200 m, liquid No5 from line 54 is mixed with cold deep water, which enters through the lower open end of the crystallizer pipeline 40, and its concentrate (3-2095 salts), which enters the crystallizer pipeline 40 through line 55. At 162C and 14 MPa in the crystallizer pipeline 40,

F gas hydrates (point A in Fig. 12). The heat released during hydrate formation is removed: - 1. with the original seawater, which is heated in the crystallizer pipeline to 1690; 2. refrigerant (H2.5 is meant here), which boils at 1120; 3. cold sea water washing the outer surface of the crystallizer pipeline. 52 The gas hydrate suspension (10-1295 hydrates and 20-2596 seawater concentrate) is fed by pump 57 into the separation and washing column of the second stage 49, in which the hydrates are pre-washed from the concentrate with brine of moderate concentration (2-795). The 20-2596th co concentrate comes out of the side pockets of the filter grates of the column 49, part of which is sent along line 52 to the gas-hydrate deposit of the GP for melting methane gas hydrates, and the second part along lines 58, 61 and 55 is sent to the pipeline-crystallizer 40 for recirculation. 60 When moving upwards in the column 49, the gas hydrates are partially washed from the surface film of the concentrate and from the upper part of the column 49 are sent by the pump 59 for final washing to the setaraidino washing column of the first stage 41. Here they are washed from the brine of moderate concentration with fresh water. From the upper part of the column 41, the washed gas hydrates are transferred to the melter 42 and melted at 152C and 0.45 MPa (point B in Fig. 12).

The heat of fusion of gas hydrates is introduced by cooling the gaseous agent from 60 2C to 212C, 62 its condensation at a temperature of 2123 in the condenser 43, built into the melter 42, and also as a result of cooling from 199C to 159C fresh water heated in the heat exchanger 44, when it is supplied in contact with hydrates. The hydrates in the melter 42 decompose into a gaseous agent and water. The agent is compressed to 1.8 MPa by the compressor 45, condensed in the condenser 43, then throttled and returned through the line 54 to the pipeline-crystallizer 40. The fresh water from the smelter 42 is divided into three streams: - the first enters the column 41 for washing; - the second - in the heat exchanger 44 for heating in the warm surface level of the sea; - the third - along line 69, through the degasser 46, it is removed from the desalination plant in the form of melted fresh water.

Hydrogen sulfide, dissolved in fresh water, is extracted in the degasser 46 by vacuuming with a vacuum pump 47. 70 Since the concentration of salts in the concentrate pumped into the HP should be, for example, 2095, and the initial concentration of salts in the Black Sea water is about 2905, then the coefficient of extraction of fresh water at the concentration of sea water is 91.895. Since no more than 6-1095 of fresh water enters the composition of gas hydrates during one passage of seawater through the pipeline-crystallizer 40, it is necessary to recirculate the concentrate 5-8 times through the pipeline-crystallizer (along line 55) with a salt concentration of 3-2095 ( the lower and upper limits are determined by 7/5 The possible working interval depending on a number of working parameters of the GOR).

Figure 12 shows the HOR cycle, which uses the thermobaric difference of seawater along the depth of the sea, in the temperature-pressure diagram. On this diagram, SD is the saturation curve of H 25, E-VIT-E is the equilibrium curve of hydrate formation of H 25 in pure water, VIT is the upper invariant point, 4 phases coexist in it - pure water, gaseous and liquid Nz, gas hydrate. For example, for NozZ, the VIT parameters are as follows: T-29.759С, R-2.23MPa). The presence of 20 salts shifts the SD curve to the left until reaching the invariant point of gas-hydrate eutectic TGE, in which 5 phases coexist - roseol of eutectic concentration, gaseous and liquid agent, gas hydrate, salt.

For example, for Noz, TGE parameters are as follows: T-159C, P-1.52mMPa, 5-2595 salts).

The parameters of the processes of formation and melting of H 55 gas hydrates on the P-T diagram are shown by points A and B, respectively. The processes in GOR are as follows: Ha 25 A-1 - the beginning and end of hydrate formation in the crystallizer pipeline, the process proceeds isothermally with a decrease in pressure to equilibrium; o 1-2 - rise of the gas-hydrate suspension to the surface of the sea, the process is isothermal due to its short duration; 2-6 - compression of the suspension by pump 57, the process is isothermal due to its short duration; 6-7 and 7-B - separation and washing of gas hydrates from the brine in crucibles 41 and 49, the process is carried out with a pressure drop h-30 and a decrease in temperature due to the adiabatic melting of part of the hydrates;

B - melting of hydrates in the melting pot 42; at

B-3 - compression of NzZ vapors in compressor 45; chI 3-4" - cooling of the compressed vapors in the melter 42; 4-4 - condensation of the vapors of the agent in the condenser 43; and- 35 4-5 - throttling of the liquid agent and its transportation along the line 54 to the pipeline-crystallizer, the process "occurs in in the area of wet vapor of the agent with a drop in temperature and pressure; 5-5" - boiling of the agent in the crystallizer pipeline; 5"-А - heating of the agent in the crystallizer pipeline.

The driving force of hydrate formation is the temperature difference of BP. between the equilibrium temperature « 40 of hydrate formation in the concentrate (here 2095) and the temperature of the suspension at the same pressure. In our 8s case, AT41-1.59С (Fig. 12). "» Temperature difference during heat transfer of skis by suspension in the crystallizer pipeline and cold " water DC-TS.

The temperature difference during heat transfer when the agent boils is 596.

The driving force of the melting of hydrates is the temperature difference between the temperature of the melting suspension and

Ф the equilibrium temperature of hydrate formation in pure water at the same pressure. In our case, ATO-226. o Temperature difference during heat transfer between the hydrates in the melter and warm water Db-7296. their Temperature difference during heat transfer during condensation agent TA-T8v-69b.

The specified temperature differences during heat transfer are sufficient for the economically acceptable heat transfer surface of the devices. Also, the specific electricity consumption for the operation of the gas-hydrate desalination-separator (GOR) when concentrating 290% seawater to 25956% concentrate is no more than 12kW-g/t (desalinated water). In the freezing plant desalinators-separators - no more than 14 kW-h/t (of desalinated water). 5B According to calculations, in order to melt one kg of methane from gas hydrate, 3.7 kg of 23.1796% concentrate or 2.4 kg of 31.796% salt concentrate suspension should be fed into the gas hydrate layer. Then the specific consumption of electricity

GF) for obtaining methane by concentrating seawater are: for 23.1795 concentrate -

Ф 0.57kW-g/kg (gaseous methane), and for the 31.7905 suspension - 0.51kW-g/kg (gaseous methane).

The operation of GOR in the mode of release of concentrate (10-2595 salts) in the warm sea in the warm season is described above. At 60, the same installation in the warm season when working in the mode of issuing salt (along with the concentrate) accumulates salt for its use in winter (for the preparation of concentrate by mixing salt with seawater). In this case, the separator of hydrates from salts 50 (separator or hydrocyclone) and salt separator 51 (screw squeezer) are included in the GOR. Hydrate formation of the refrigerant (for Black Sea conditions, for example -

Н2г5) are conducted in the crystallizer pipeline at the parameters of gas-hydrate eutectic (for seawater conditions, in which 65 Mass makes about 8095 of all salts - point A in Fig. 12 shifts to the left by 2-3 "C, while the eutectic concentration of salts (mainly Mass )) in gas-hydrate eutectics is about 2590.

After the formation of gas hydrate crystals and salt crystals in the saturated concentrate, the suspension (which is a gas hydrate-salt-concentrate in which the solid phase is about 1095) is raised to the surface of the sea by pump 57 and separated in compartment 50 into a gas hydrate-concentrate suspension (selection of the light dense phase from above) and salt-concentrate suspension (selection of heavy dense phase from below). Separation of the suspension is carried out by sedimentation according to the difference in density, which have the following values: - salt Masi.2N.-o - 1600kg/m3; - NOZ gas hydrate - 1021 kg/m3; - 2596th sea water concentrate - approximately 1200 kg/m3.

The gas hydrate-concentrate suspension from the compartment 50 is directed to the separation and washing column of the second stage 49, in which and after which the processes already described above take place. The salt concentrate suspension from the compartment 50 (solid phase - salts in it 5-890) is directed to the screw salt separator 51, in which the concentrate is first filtered, and then squeezed from the salt in the filter section and then sent for recirculation along lines 56 and 55 into the pipeline -crystallizer 40. The salt squeezed from the concentrate (the final composition of the liquid phase is no more than 3095) immediately or after dehydration is taken to the salt accumulator, from which it is taken in winter for the production of concentrate or salt-concentrate suspension.

In cold seas, in which there is no noticeable temperature difference in the depth of the sea in winter and summer, they are used

HOR, in which the crystallizer is located at the surface level of the sea. The process of hydrate formation of such refrigerants as freons 22, 134a and others is carried out at the surface level of the sea, producing a 10-2595 concentrate, which is then sent to the GP. The thermodynamic benefit of this method is that the temperature of the surrounding environment is reduced to 2-102C. This makes it possible to carry out a refrigerating desalination cycle, usefully using the cold not only to reduce heat inflows and remove the heat of hydrate formation, but also to dump into it the excessive heat of condensation of the refrigerant, which cannot be condensed by the heat of fusion of gas hydrates. with

The GDK on the platform must be completely energy independent. For extraction and liquefaction of methane, the specific electricity costs are 0.025--0.26--0.51-0.795kW-g/kg of liquefied methane, where the first number is the cost of pumping the heat-salt carrier into the gas hydrate layer, the second is the cost of methane liquefaction, the third - costs for the production of seawater concentrate, which is pumped into the GP. According to our calculations, in order to produce this amount of electricity in a traditional way, about 2190 --- extracted methane must be burned in a typical thermal gas turbine installation. "with

In order to reduce the consumption of methane for combustion and increase the energy efficiency of the GDC, an additional solution is advisable - to use cold deep water as a cold heat source of a direct thermal power cycle, and to use the same warm surface water as a hot heat source. at

Scheme of a thermal power gas hydrate plant (TGU) designed for cost-free electricity generation

From the fuel shown in Fig. 13. The TGU consists of a continuously acting crystallizer pipeline 71 submerged "O cold sea level to a depth of 300-6b0Om, a sectional gas hydrate melter 72 of periodic action, which is located either directly at the warm sea level or slightly raised above it, a turbine unit 73, a heat exchanger-crystallizer 74 and pump-hydromotor unit 75. Tandem pipeline-crystallizer 71 and "melter 72" perform the role of a gas-hydrate thermocompressor, which compresses gas not due to mechanical energy, but due to the action of two heat sources - cold and warm. - c The crystallizer pipeline 71 has on its side surface the housings of filter sections 76, which cover the crystallizer pipeline and are hermetically connected to it from above, and have a free outlet of water from below, and the filtering element of which are slits 77 with a width of about 1 mm . at the lower end, a submersible pump 78. a counterweight 79 and the entrance of the pipeline 81, and at the upper end - a pontoon 80. This pontoon creates the unsinkability of the crystallizer pipeline, and the counterweight 79 - the verticality of the structure. b» The sectional gas hydrate melter 72 has identical sections 82, through which heat exchanger tubes 83 pass. o The inter-tube space of the sections is the volume of their loading with gas hydrates, which are retained in the lower part of the sections by filter grates 84. Under these grates, there are accumulators of melt water g» hydrates 85 , the volume of which is equal to the download volume. Above each section there are accumulators of 86 concentrate and 20 sea water or salt concentrate suspension. Inputs of sections 82 of the melter 72 for gas hydrate suspension (line 107) and seawater concentrate or salt concentrate suspension (line 108). as well as the outlets of compressed gas (line 109) and discharge of drainage water and melt water (line 110), recirculation water (line 111) and concentrate (lines 112 and 1127) are made in parallel. One of the sections of the melter has an inlet (not shown ) heat carrier of elevated temperature 30-502C, for example, after the condenser of the refrigerating machine, from which low-potential heat is removed by this heat carrier; in addition, the same section, which plays the role of a gas gun, has an output (not shown) of high-pressure gas of 50-200 MPa, connected to the inlet of pump-compressor pipes 16 (it is this gas that is pumped into the cracks for gas fracturing of the gas hydrate layer). For 1096 hours, the sections work in the mode of filling them with gas hydrate suspension, draining recirculation water and drying gas hydrates, 8095 - in the mode of melting hydrates, 1095 - in the mode of draining melt water of hydrates and 60 of compressed gas discharge. The number of sections is 8-10. Depending on the operating mode, the sections are loaded from above with a gas hydrate suspension (along line 107 ), seawater concentrate or salt concentrate suspension (on line 108). From above, gas of medium pressure 8-20 MPa (in turbine 93) and high pressure 50-200 MPa (in HP) is taken from above. Drainage water and hydrate melt water are discharged from the bottom of the sections through water accumulators 85 into line 110 (into the sea through hydraulic motor 101 - to return part of the mechanical energy) and because the seawater concentrate is discharged into line 112 through hydraulic motor 102 into the GP and into line 1127 through hydraulic motor 1027 in the eutectic stage of the desalinator-separator of sea water. The turbine unit 73 consists of turbine stages 93, 94 and 95, which are mounted on one shaft with an electric generator 96, heat exchangers 98 and 99, as well as a moisture separator 97.

Heat exchanger-crystallizer 74 has pipes 89 with separate pipe spaces 90 (left) and 91 (right). "The seam of the pipe space 90 has an exit from the bottom to the separator 92 of liquid propane from gaseous gas.

The pump-hydromotor unit 75 consists of two pump-hydromotor units. The first one has 4 elements mounted on one shaft - a pump 100 supplying the gas hydrate suspension from the crystallizer pipeline 71 to the gas hydrate melter 72, a hydraulic motor 101, through which drainage water from the melter 72 is discharged into the sea, a 7/0 hydromotor 102, through which it is discharged into the GP seawater concentrate from smelter 72, electric motor 103.

The second unit also has 4 elements mounted on one shaft - pump 104, which pumps warm surface seawater through the pipes of the gas hydrate melter 72, hydraulic motor 105, which discharges the same water into the sea, hydraulic motor 1027, which discharges the seawater concentrate from the melter 72 in the eutectic stage of the desalinator-separator of sea water, and the compensating electric motor 106.

Production of high-pressure gas and electricity is carried out at TSU as follows. Methane with an admixture of liquid propane under pressure, for example, 3.4MPa (at a depth of 340m) is mixed in the lower part of the pipeline-crystallizer 71 with deep cold seawater, which is supplied by an underwater pump 78.

Gas hydrates of methane and propane are formed at 122 (point A; in Fig. 14, the presence of propane shifts the hydrate equilibrium curve to the right, which contributes to the removal of the heat of hydrate formation). The heat of hydrate formation is mainly removed with cold water, which is discharged through the slits 77 of the filter section 76. The temperature differences in this process are here (Fig. 14): on hydrate formation AT.4-22C, with heat transfer di/-520. The residence time of reagents during their rise - water and gas and products - hydrates in the pipeline-crystallizer - 5-7 minutes, which is enough for hydrate formation.

The gas hydrate suspension (the amount of solid phase - hydrates in it is 5-1595) is raised to the surface of the sea and

B is compressed with a pump of 100 to 1 MPa, directing it to section 82 of the melter 72, which work alternately in the mode of filling (H) with their gas-hydrate suspension, melting (P) hydrates and draining (3) concentrate. During operation of any section in the H mode, it is filled with a gas hydrate suspension, while at the same time drainage seawater is filtered from the suspension through the grate 84 into the accumulator 85. After that, the amount of solid phase in the suspension increases to 6095. Then in the same section, the gas hydrates they are dried by blowing them from top to bottom with low-pressure gas from adjacent sections, which are all gas-switched. After that, the amount of the solid phase in the suspension increases to 7095. With all these actions, the drainage seawater o is discharged from the mode H section through the line 110 and the hydraulic motor 101 into the sea. "AND

After the operation of the section in mode H is over, it is transferred to mode P. Warm surface seawater is pumped by pump 104 through pipes 83. Melting of gas hydrates begins. At the first stage of melting o (at first only due to heat supply), the pressure in the section increases from 1 MPa to 3.4 MPa (parameters of point B'na "o

Fig. 14). During this period, water from the initial melt of gas hydrates is discharged from the accumulator of this section through line 110 and hydraulic motor 101 into the sea. Then, the 2596th seawater concentrate or salt-concentrate suspension of seawater is supplied to this section from the desalinator-separator of seawater (Figs. 11 and 12) (that is, salt Ж is a saturated eutectic seawater concentrate, and the total concentration of salts in the dry residue « reaches 3595) and the melting of gas hydrates will already be carried out both due to heat input and due to a 2-second decrease in the temperature of hydrate formation due to an increase in the concentration of salts in the aqueous phase. Mixing and suspension in the section is carried out by recirculation of the water phase with the help of pump 87 along line 113. During this period, the gas hydrate melt is not discharged through line 110, and the 10-2595th seawater concentrate is accumulated in the salt accumulator 85 of the same section. in the second stage of hydrate melting, the pressure in the section increases to 15 MPa (point B" in Fig. 14) and high-pressure gas discharge (15 MPa) into the turbine unit 73 begins.

Ge") After all the gas hydrates have melted, the section is switched to operating mode Z - drain. Along line 112, the seawater concentrate is diverted from the section, with its subsequent supply to the gas hydrate deposit of the HPP. Since - the initial pressure of this concentrate is high and exceeds the pressure in the HP, it is first discharged through the hydraulic motor t" 102 in order to return part of the mechanical work previously spent in the pump 100. The rest of the gas in the section having a lower pressure than is required for supply in turbines, is used in the commutation harness of the smelter. On

Me, lines 1127 and through the hydraulic motor 1027 from section 82, the seawater concentrate is diverted from section 82 with its further supply to the gas hydrate or freezing desalination-separator of seawater (in their eutectic stages, in which the pressure of the seawater separation process is lower than the pressure in the section of the melter 82 ).

After the high-pressure sections, the gas is separated from the dripping water in the moisture separator 97, then expanded in the 3 stages of the turbine. After adiabatic expansion, the gas cools down a lot (approximately to -352C). The gas before the next stage of the turbine is heated in the heat exchanger-crystallizer 74, as well as in

F) heat exchangers 98 and 99. After the first stage of the turbine 93, the gas flows through line 119 under a pressure of 7.14 MPa into the right pipe space 91, is heated in it to -42C, then through line 120, through the heat exchanger 98, it enters the second stage of the turbine for expansion 94, after which the gas with a pressure of 3.4 MPa (after this process, the gaseous propane contained in the gas mixture is liquefied) along line 118 is directed into the left pipe space 90, is heated in it to - 42C, then through the separator 92 (in which liquid propane is separated from the gas, which is then directed together with the methane gas into the crystallizer pipeline 71 for hydrate formation) along line 117 through the heat exchanger 99 and enters in a small amount (590) for the expansion of the third stage of the turbine 95, after which with a pressure of 1 MPa along the line 121 enters the intertube space of the heat exchanger - crystallizer 74. Here 65 the gas heating mechanism is different. Here, the gas is in contact with recirculating seawater, which is directed here by pump 88 along line 114 from those sections of the gas hydrate melter 72, which are in the H operating mode. When the gas comes into contact with water, gas hydrates are formed (point A", at 1 MPa and 12 C, see Fig. .14), the heat of the phase transition, which is the source of gas heating in the pipe spaces 90 and 91. Thus, the cold gas after the turbines is usefully used in the heat exchanger - crystallizer 74 to obtain approximately 595 gas hydrates and

Removal of their heat of hydrate formation. The gas hydrates formed here are directed along line 116, mixing along the way with hydrates formed in the depths of the sea, to the smelter 72.

In Fig. 14 - the cycle of TGU, which uses the thermobaric difference of sea water along the depth of the sea, in the temperature-pressure diagram. The following equilibrium curves of hydrate formation are shown, which in logarithmic coordinates have the form of straight lines: 1 - methane water; 2 - Massi's methane29o solution (approximate imitation of Black Sea water);

C - methane 2595 mass solution; 4 - throwing 4,896 moles of propane water; 5 - methane 4.895 mole propanun29o Mass solution; 6 - methane 4.895 moles propanun2595 mass solution; 7 - Noz' nvoda; 8 - propane water.

The calculation cycle for the conditions of the Black Sea in the warm season (temperature of cold deep water -7 es, temperature of warm surface water -222С) has the following sequence of processes:

A. - the middle point of formation of gas hydrates of a mixture of methane and liquid propane (4.895 molar) in 290 sea water in the crystallizer pipeline 71 at a depth of 340 m at 122C and 3.4 MPa. Temperature differences in the process: for hydrate formation AT4-22С, during heat transfer Di-596.

A.-K - raising the gas-hydrated suspension to the surface of the sea by pumps 78 and 100 (some cooling of the suspension is due to the melting of part of the hydrates when the hydrostatic pressure is lowered to O0.1 MPa).

K-V. - compression of the suspension by the pump 100 from 0.1 MPa to 1 MPa and feeding it to the melter 72.

B. - the starting point of melting of hydrates in smelter 72 (102, 1MPa). Temperature differences: on melting of hydrates AT»-72C, during heat transfer Li-1296. at

B.-87 - pressure rise of the gas mixture (methane, propane, later - gas) in the smelter during the first stage of melting hydrates due to heat supply from warm surface water.

В'-Во - rise in gas pressure in the smelter during the second stage of melting of hydrates both due to heat supply from warm surface water and due to the supply of 2595th seawater concentrate or its same salt-concentrated suspension. Temperature differences at point Во: on melting of hydrates /АТо-1.52С, at «s heat transfer dl -590.

B" (172С, 15MPa) - point of gas selection for the turbine. h

V»-C - gas expansion in the 1st stage of turbine 93 from 15MPa to 7.14MPa. at

Сб-С - isobaric heating of the gas in the right pipe space of the heat exchanger-crystallizer 74 from -3296 °C to -496.

CH - further heating of gas in heat exchanger 98 from -42C to 1720.

Н-Д - gas expansion in the 2nd stage of turbine 94 from 7.14MPa to 3.4MPa.

Dd-D" - gas heating in the left pipe space of the heat exchanger-crystallizer 74 from -359C to -496, "

D" are the parameters of the liquid propane separation process in the separator 92 and its return to the pipeline-crystallizer 71.

D'-A, - further heating of gas in the heat exchanger 99 from -42C to 1796. ;" A.-E - gas expansion in the 3rd stage of turbine 95 from 3.4MPa to 1MPa.

E-A" - heating of the gas during its contact with seawater and in the process of hydrate formation in the intertube space of the heat exchanger-crystallizer 74. b Temperature differences at point A": for hydrate formation LT-22С, during heat transfer Ai seEREDNYA- 159С.

Ao-Vi - pumping of the gas-hydrate suspension from the heat exchanger-crystallizer 74 to the melter 72 and its heating in this melter. t» The interval of thermocompression of gas to a pressure of 8-20MPa before its supply to the turbine of a thermal power plant or to a methane liquefier is justified as follows. A pressure of 8MPa is the lower pressure limit below which the production of energy does not cover its consumption for the TSU's own needs. A pressure of 20 MPa is the upper limit. It is not advisable to increase the pressure of methane above it during thermocompression, as the temperature difference for the melting of gas hydrates from the upper heat source - the surrounding environment - is greatly reduced (see Fig. 14).

With the parameters shown in Fig. 14, the TGU cycle has the following calculated parameters (in specific values - per 1 kg of methane at point B" - i.e. before the turbine unit): - consumption of cold deep water, which is pumped by pump 78 through the pipeline-crystallizer 71-168.8 kg

F) (water) ukg (methane); ko - win gas hydrate suspension (1595 gas hydrates) after the crystallizer pipeline 71, which is pumped by pump 100 into the melter 72-52.6 kg (suspension) kg (methane); 60 - required consumption (via line 122 from the freezing desalinator-separator of seawater) of the initial salt-concentrate suspension (with the initial total concentration of salts in the concentrate and in the solid phase Zn-Z31,790) - 25.2 kg/kg (methane); - the amount of the final concentrate with a concentration of ZKk-23.1795, which is formed after the melting of gas hydrates - 34.7 kg/kg (methane); 65 - heat load, which is removed in the crystallizer pipeline 71 during hydrate formation -

For 44 kJ/kg (methane);

- the heat load removed in the heat exchanger-crystallizer 74 during hydrate formation - 190.6 kJ/kg (methane); - the heat load of the gas hydrate melter is 72 - 4367 kJ/kg (methane); - electricity production - 299, v8kJ/kg (methane); - production of clean molten desalinated drinking water, which is simultaneously created in the desalinator-separator during the concentration of the concentrate after the smelter from 5 K-23.1790 to Zn-Z1.790 - 9.34 kg (water)/kg (methane).

Gas hydrate deposits of GP usually have low gas permeability, which is evidenced by the preservation of gas reserves directly under the deposit - the so-called subhydrate gas. The low porosity of GP is explained by the formation of gas hydrates in the 7/0 pores of the soil, which cement the loose layer. In view of this, the supply of warm seawater or its concentrate should be prevented by the periodic supply of high-pressure gas (50-200 MPa) to the gas-hydrate layer, the impact of which on the rock from the top down and ejection from the bottom up deforms and destroys the upper deposited layer of the deposit, making it more permeable for subsequent melting of gas hydrates and movement of gas and liquid along it.

The pressure interval of 50-200 MPa is justified as follows. The pressure of 5HOmMPa is the lower limit of pressures that /5 allows further destruction of the gas hydrate layer at shallow depths of 300-500m. It is difficult to obtain a pressure of more than 200MPa in a gas-hydrate thermocompressor, as its productivity is sharply reduced (in the sections of the melter 82, operating periodically, the harmful effect of "dead" space increases greatly).

The methane liquefier (Fig. 15 - second version) simultaneously uses the hydrostatic pressure of seawater and the thermobaric difference of seawater along the depth of the sea to reduce electricity consumption. In such a scheme, electricity is not produced by 2o turbines (part of the work is returned only by hydraulic motors), and the high gas pressure after the melting of gas hydrates is used directly for its liquefaction. Melting of gas hydrates is carried out using the effect of "addition" and "subtraction" of gas flows, which have pressures of different values, which is still unknown in the technique. The scheme of Fig. 15 is a combination of the schemes of installations in Fig. 9 and Fig. 13. Unlike Fig. 9, Fig. 15 does not have stages of compressors 24, 25 and 26, as well as refrigerators 27, 28 and 29. Unlike Fig. 13, Fig. 15 does not have a turbine unit and a heat exchanger - crystallizer 74.

Sections 82 of the melter 72 in Fig. 15 in comparison with the same sections in Fig. 13 additionally have: (8) - gas inlets of return flows of the methane liquefier (input 124 - gas of lower pressure 0.6-1MPa, input 125 - gas of medium pressure 2-6 MPa); - input 126 - methane from a gas hydrate deposit; -- zo - outlet 127 - recirculation methane to the lower end of the pipeline-crystallizer; - output 128 - of recirculating liquid propane, located in the upper part of the accumulators 85 of water re) of gas hydrate melt, to the lower end of the pipeline-crystallizer 71.

The methane liquefier according to the scheme of Fig. 15 works as follows. A gas hydrate suspension is directed from the crystallizer pipeline 71, which works the same as in Fig. 13, into the section 82 of the melter 72. ("in")

Melting of gas hydrates is carried out in the following sequence of processes: first, the gas hydrates are drained from the interhydrate water by draining it and then blowing the hydrate mass with gas, then the gas hydrates are compressed with return gas of a lower pressure of 0.6-1 MPa, which is taken from the methane liquefaction cycle (after heat exchanger 31) , then the gas hydrates are melted by heat exchange with warm surface seawater (circulating through the pipes 83), then the gas hydrates are re-compressed with the medium pressure return gas of 2-6 MPa, which is taken from the methane liquefaction cycle (after the heat exchanger 31), and the gas that is taken from gas hydrate deposit as from product c, then recirculating liquid propane and recirculating methane are taken from the melting zone, which are sent to the lower end of the crystallizer pipeline 71, then the gas hydrates are finally melted in section 82 with a combination of heat exchange from warm surface seawater and supply to the melting zone gas hydrates of sea water concentrate or soleconcent waste suspension, which are selected from the desalination-separation cycle

Sea water (on line 122).

Ф High-pressure 12MPa gas exits from sections 82 of the melter 72 to the methane liquefier via line 131.

Next, the scheme of the methane liquefier in Fig. 15 works in the same way as in Fig. 9. o With the parameters of points A., B1, B" and B0, which are shown in Fig. 14, the methane liquefaction cycle in combination with their devices 71 and 72 has calculated indicators (in specific values - per kg of methane at points B0 - that is, before 5 Methane liquefier) are the same as in the TGU cycle with the exception of: electricity production only by hydraulic motors, (22) which remains after compensating for the operating costs of the pumps paired with them, as well as the refrigerating machine 35 je ha 27 bvkJ/kg (liquefied methane) .

The use of the invention significantly expands the capabilities of the known methods and has the following advantages over them: 1. Supplying the thermal salt carriers proposed in the invention to the gas hydrate layer does not lead to pollution of the former Sea, is an ecologically clean and economically acceptable solution, in addition, in the case of carbon dioxide, it is a solution to reduce the greenhouse effect (F) 2. The combined effect on the gas hydrate layer - salt, thermal, pressure reduction and gas impact allows you to choose

F is the most rational mode of gas production, to increase the rate of gas hydrate melting (improves kinetics) and gas yield of the gas hydrate layer. in 3. The use of the thermobaric difference of sea water and the effect of gas-hydrate thermocompression makes it possible to generate electricity in warm seas in the warm season and thereby facilitate the provision of autonomy

GDK at this time. Accumulation of salt in the summer allows you to have a seawater concentrate for work in the winter as well, with a dual purpose - for feeding into the gas hydrate deposit and for feeding into the thermocompressor melter - for the production of electricity and high-pressure gas. These proposals, as well as the use of hydrostatic column 65 of sea water and the coldness of cold seas, lead to significant energy savings during gas production (by 50-60905, and in some of the most favorable cases - up to 10095).

4. An interconnected system of a freezing (or gas hydrate) desalinator-separator of sea water, operating at salt eutectic parameters, a thermal power gas hydrate plant, a methane liquefaction device, devices for inputting into the HP concentrate-outlet from the HP gas - commercially very profitable. It makes it possible to obtain liquefied methane and AT THE SAME TIME desalinated clean melt lightened drinking water. For a GDC operating, for example, in the Black Sea under the conditions of the Crimean shelf (in such a GDC, 45.4 kg of melt water is per kg of liquefied methane) - implementation

MELTING high-quality water to the arid Crimea at the price of all Zkop/l (i.e. 5, bdol/t) gives a profit that is 2 times higher than the profit from the sale of liquefied methane at its highest price (109 dol/1000m3 - for refueling gas cylinder cars - after regasification of methane up to a pressure of 20 MPa).

Claims (8)

The formula of the invention 1. The method of extraction and processing of natural gas from marine gas hydrate deposits (GP) of the warm and 7/5 Cold seas, which includes drilling wells in these GPs and their reconstruction, preliminary deformation of gas-bearing formations to increase their fracturing and gas permeability, for example, by shooting cumulative charges and other actions, preparation and submission of gas hydrates to the hydroelectric power plant "in place" of their location in the gas hydrate layer of the underwater hydroelectric power plant of the melting coolant and removal of the produced gas from the hydroelectric power plant, collecting it after melting the gas hydrates in the gas hydrate layer and bringing it to the surface of the sea, compressing it to 10 -20 MPa and liquefaction, and with the performance of all these operations at the expense of electricity produced directly and autonomously in the gas production complex (GDC), which is distinguished by the fact that gas extraction from the gas production plant is carried out by a system of hydraulically connected injection and extraction wells, which are operated by 3- x options: gradual deepening by 20-50 m in the GP in the course of production of its upper layers, a stepwise rise of 20-50 m in the course of production of lower layers of GP, simultaneous production of several layers of GP throughout its height by ensuring that the wells work in the mode of injection of the melting medium and the mode of gas extraction alternately, and in the injection mode, a melting coolant is fed into the wells, as well as, alternately, high i) pressure gas, and in the extraction mode, gas from molten gas hydrates, spent concentrate and water from molten gas hydrates, as well as well blowout products, such as soil particles, are taken from the wells; "-- z sealing of casing pipes of wells, which separates gas hydrate layers from overlying non-hydrate aquifer layers, in the presence of thermodynamic conditions of hydrate formation, is carried out with the help of temporary thermoreversible cementation with gas hydrates by introducing cooled methane or "g natural gas enriched with heavy components into the sealing gaps - with ethane, propane, butane, and the transfer of the GDK after the production of the GP under it to the second yet-to-be-developed GP is carried out after all operational pipes, as well as the gas collection cap, have been raised to the lower edge of the gas production platform by Zv; "c as a melting medium, a 10-25 9% seawater concentrate or a salt-concentrate suspension, in which a saturated solution of seawater of eutectic concentration contains 3-15,905 salt crystals, which are concentrated, for example, by freezing or gas hydrate method, is fed into the underwater GP; the required consumption of the initial seawater concentrate or the initial salt-concentrate suspension, which must be fed to melt gas hydrates in the gas-hydrate layer of the HPP, as well as in the section of the melter for the generation of electricity and the production of high-pressure gas, is determined according to the equation 9. athlete voVk- B) Ua Yak A-1 where (22) Sn - the required consumption of the initial (output) seawater concentrate or salt-concentrate suspension o seawater; Sv os - the amount of water in the composition of gas hydrates that must be melted; g» Zn - the initial concentration (mass fraction - here and below) of the seawater concentrate or the initial b 20 concentration of the salt-concentrate suspension based on the dry salt residue; Zk is the final concentration of seawater concentrate or salt concentrate suspension after melting of gas hydrates; Zs is the concentration of gas hydrates in the gas hydrate layer of the GP before their melting or the concentration of gas hydrates in the gas hydrate suspension in the sections of the smelter before their melting; 51 is the concentration of salts in seawater that enters to the composition of the intercrystalline liquid; o A is the specific mass of the gas hydrate, kg (gas hydrate)/kg (gas in the composition of the gas hydrate); gas after the melting of the gas hydrates in the gas hydrate layer is accumulated directly near the bottom of the sea under the pressure of the hydrostatic column of sea water and is fed to the entrance to the last the degree of compression of the liquefaction cycle; a part of the produced gas drawn to the surface is compressed to 50-200 MPa and periodically fed into 60 HP, preventing the introduction of a melting medium into it with gas shocks; for driving a thermal power generating plant, producing gas under high pressure, as well as liquefaction methane use the thermobaric difference at sea water at the depth of the sea by contacting methane with seawater at depths of 300-600 m with the formation of gas hydrates in this cold deep level of the sea, pumping these gas hydrates in the form of a gas hydrate suspension to the surface of the sea and melting them at a temperature of 18-25 °C with the heat of the surface sea water or contact with a 10-25 96-th seawater concentrate, or a salt-concentrate suspension in which there are salt crystals in a saturated solution of salts of eutectic concentration, and the total concentration of salts in the dry residue reaches З5 905, thermocompression of the gas is carried out to a pressure of 8-20 MPa before it is fed to the turbine of the thermal power plant or to the methane liquefier. 2. The method according to claim 1, which differs in that when using the thermobaric difference of sea water at the depth of the sea for liquefaction of methane, the melting of gas hydrates is carried out step by step in the following sequence of processes that carry out "addition" and "subtraction" of gas flows that have pressures of different values : first, the gas hydrates are drained from the interhydrate water by draining it, then the hydrate mass is blown with gas, after which the gas hydrates are compressed with return gas of a lower pressure of 0.6-1 MPa, which is taken from the methane liquefaction cycle, melted by heat exchange with warm surface seawater, then the gas hydrates are re-compressed with medium pressure return gas of 2-6 MPa, which is taken from the methane liquefaction cycle, and with the gas taken from the gas hydrate deposit as a product, liquid propane is taken from the melting zone, then at the end the gas hydrates are melted by combining heat exchange with warm surface seawater and submission to zone /5 of the melting of gas hydrates of seawater concentrate a because of the concentrated salt suspension, which is taken from the seawater desalination-separation cycle. C. The method according to claim 1 or 2, which differs in that the wells work in the injection mode in all 3 operating options during the time period when they are located deeper than the wells that work in the gas extraction mode by 3-20 m. 4. The method according to claim 1 or 2, which is distinguished by the fact that, prior to or simultaneously with the development of the hydroelectric power station, superhydrated and subhydrated gas, as well as hydrohydrated oil and gas condensate are taken using a system of wells above and below this hydroelectric power station, using, for example, fountain pipes. 5. The method according to claim 1, which differs in that in the warm season in warm seas at cold sea level at depths of 50-500 m, a refrigerating and at the same time hydrate-forming agent, such as freons 22, 134a and others, H5, с 250 СО" and others, contact with a mixture of sea water and its concentrate with a concentration of 3-20 90 salts, forming gas hydrates, then the gas hydrate suspension is raised to the surface of the sea, the gas hydrates are separated from (o) the product concentrate with a concentration of 10-25 95, washed from the concentrate and melted with production of desalinated clean melt drinking water. b. The method according to claim 5, which differs in that the process of hydrate formation of the refrigerant and simultaneously of the hydrate-forming agent is carried out at the parameters of gas-hydrate eutectic, after which the gas-hydrate-salt-concentrate suspension is divided into a gas-hydrate-concentrate suspension and a salt-concentrate suspension, for example, by precipitation, salt is separated from the concentrate , for example by filtering the concentrate and "subsequent squeezing of the salt mass, are accumulated and used in the cold season for the production of concentrate by mixing salt with sea water. ("in") 7. The method according to claim 5, which differs in that in cold seas the process of hydrate formation of the refrigerant and simultaneously the hydrate-forming agent is carried out at the surface level of the sea, producing 10-25 95% concentrate or salt. 8. The method according to claim 1, which differs in that a part of methane gas hydrates is melted at an elevated temperature of 30-50 °C due to the supply of low-potential heat, which is emitted, for example, in the process of "Methane liquefaction, producing high-pressure gas of the order of 50-200 MPa . -о с 9. Gas extraction complex (GDC) for extraction and processing of methane and natural gas from marine and gas hydrate deposits (GP) of warm and cold seas by the method according to one of claims 1-8, which includes a "" platform, a drilling rig, installed wells immersed in the gas hydrate formation, pumping and lifting and transportation equipment, a thermal power gas hydrate power generating unit, a device for the preparation of the carrier that melts gas hydrates in the gas hydrate, a methane liquefaction device, which differs in that the GDC platform would have a bottom gas collection cap, which is placed directly above the GP, made in the form of a sealed hemisphere from above, which is turned with its open concave side to the bottom of the sea, through which well pipes are lowered, and in the upper part there is a gas outlet pipe, the upper end of which is connected to the inlet nozzle of the gas liquefier, and the gas collection cap is made of a low heat-conducting thin-sheet material, 5p, for example, plastic such as Teflon and the like, with the possibility of vil movement in the vertical (22) direction along the casing pipes to rise to the surface of the sea by means of a sealed peripheral ha-ring pipe pontoon, which is attached to the lower edge of the gas collection cap and has inlets and outlets of water and air under a pressure of 10-20 MPa, in addition to the caps contains on its hemisphere vertical conductors in the form of pipes with a length of 0.5-2 m, through which the casing pipes of wells are lowered, while in the upper part of the Conductors there are packers that seal the space between the wells and casing pipes, and in the lower part of the conductors there are packers, that seal bypass windows of casing pipes; (F) the wells are made in the form of an injection-extraction system, hydraulically interconnected along the gas-bearing gas hydrate layer and composed of 3-6 rows of these wells; the thermal power gas hydrate power generating plant GDK includes a continuously acting gas hydrate crystallizer, made in the form of a vertical pipeline immersed in the cold sea level to a depth of 300-600 m, and a batch gas hydrate melter, made sectional, each section of which is equipped with technological inlet nozzles - outlet of reagents and a heat exchanger with a nozzle for entering warm sea-level water, and one of the sections of the smelter, which produces high-pressure methane gas of the order of 50-200 MPa, contains a heat exchanger with a nozzle for entering a coolant with a temperature of 30-50 2 and 65 a nozzle for injecting high-pressure gas is connected to the nozzle of the well entrance; the pipeline-crystallizer of gas hydrates contains on its outer surface filter sections for discharging sea water and retention of gas hydrates, and at the open bottom end - an underwater pump-charger of cold deep sea water; the inlet nozzles of the melter sections for gas hydrate suspension, seawater concentrate or salt concentrate suspension, as well as the nozzles for the output of compressed gas and ejecting the concentrate are made parallel, in addition, the melter sections contain a pump for pumping warm surface seawater through them, and in its lower part - filter grates, under which are located the water accumulators from the melt of gas hydrates; the sections of the smelter are equipped with gas inlet nozzles for methane liquefaction return flows, as well as methane from the gas hydrate deposit, and a liquid propane outlet nozzle located in the upper part of the water storage tank from the gas hydrate melt; 70 as a device for the preparation of a medium that melts gas hydrates in the gas hydrates in the gas hydrates, the GDC contains a freezing or gas hydrate desalination separator, has a eutectic stage in its composition, the output of which for seawater concentrate is connected to the inlet of the wells that supply the concentrate to the gas hydrates, as well as in sections of the methane gas hydrates melter of the gas hydrate thermal power plant, and the outlet for salt is connected to the accumulator of these salts and further - to the entrance of the above-mentioned wells and sections of the gas hydrates melter. c 7 o "-- (Se) ("in") Zo (Se) - and? 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