RU2706276C1 - Method of hydration inhibiting - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to methods of inhibiting formation of gas hydrates in different hydrocarbon-containing liquids and gases containing water and hydrate-forming agents, and can be used in processes of extraction, processing and transportation of hydrocarbon material to prevent formation of gas hydrates. Method of inhibiting hydration by introducing into an inhibited medium a composition containing a water-soluble polymer, a surfactant, an antifoaming agent, water and a solvent: methanol, ethanol, mono- and oligomeric ethylene glycols, mono- and oligomeric propylene glycols, glycerol, monoalkyl esters C₁-C₄ of mono- and oligomeric ethylene glycols, monoalkyl esters C₁-C₄ of mono- and oligomeric propylene glycols, ethanolamines or mixture thereof, wastes from chemical industries which are by-products of hydration of ethylene oxide and propylene oxide, still residues of production of alkyl ethers of monoethylene glycol, where the surfactant used is a compound selected from a group of compounds having said formulas, with the following ratio of components, wt%: water-soluble polymer 1.0–25.0, surfactant 2.0–20.0, antifoaming agent 0–10.0, water 0–15.0, solvent – balance.

EFFECT: high inhibiting power of the method, preventing formation of hydrates both kinematically and simultaneously by kinetic and thermodynamic mechanisms, wider temperature range of use thereof, possibility to prevent ice formation in the inhibited medium in low-temperature conditions, simplification of pumping and proportioning processes of the composition used in this method.

1 cl, 1 tbl, 6 ex

Description

The invention relates to methods of inhibiting the formation of gas hydrates in various hydrocarbon-containing liquids and gases containing, containing water and hydrate-forming agents and can be used in the processes of production, processing and transportation of hydrocarbon raw materials to prevent the formation of gas hydrates.

Gas hydrates are a special case of inclusion compounds, which are formed during the incorporation of low molecular weight substances into the cavity of the crystal lattice formed by hydrogen-bonded water molecules. The formation of hydrates occurs in the presence of free water and a suitable hydrate former (CH ₄ , C ₂ H ₆ , C ₃ H ₈ , i-C ₄ H ₁₀ , n-C ₄ H ₁₀ , CO ₂ , H ₂ S, N ₂ , etc. n.) under certain thermobaric conditions, depending on the composition of the system. During the extraction and transportation of hydrocarbon feedstocks, complications often arise associated with the formation of gas hydrates in the wellbore, pipelines and equipment. Due to the action of capillary forces, hydrate crystals are subject to agglomeration, which leads to the formation of hydrate plugs, which can completely block the flow of fluids in the wellbore, pipeline section or in technological equipment. The formation of hydrates is an undesirable phenomenon, as it leads to a halt in the technological processes of production, transportation, and processing of hydrocarbon raw materials. In this regard, an urgent scientific and technical task is to develop new, more effective methods for inhibiting gas hydrates.

A known method of inhibiting the formation of hydrates, including the use of individual thermodynamic inhibitors of hydrate formation (TIG), in particular, low molecular weight alcohols (methanol and oligomeric glycols) (RU 2049957, 1998). High working concentrations of TIG in the aqueous phase (up to 70% wt.) Reduce the activity of water in solution, which leads to a decrease in the equilibrium temperature of hydrate formation and ice crystallization in such systems. The advantage of the method is the possibility of its use in low-temperature conditions below 0 ° C, when simultaneous prevention of the formation of ice and hydrates is required. The disadvantages of the method are the increased consumption of inhibitors due to their high working concentrations in the aqueous phase (up to 70% by weight), high toxicity and fire hazard of lower alcohols, high solubility of methanol in compressed gas and, as a result, increased specific consumption due to entrainment with a gas stream .

Known methods of preventing agglomeration of gas hydrates and the formation of hydrate plugs based on the use of anti-agglomerates (US 6444852, 2002; US 7958939, 2001; CA 2983402, 2016). These reagents belong to the so-called low-dose hydrate inhibitors (working concentrations in the aqueous phase of 0.1-2% wt.) And are inherently surfactants that do not affect the thermodynamic conditions of hydrate formation, do not slow down the hydration nucleation, but, when this, contribute to the formation of a hydrated fluid suspension, which can be freely transported in multiphase flow mode without the formation of hydrate plugs. Thus, in essence, anti-agglomerants are inhibitors of gas hydrate deposits. The disadvantages of the method are that, due to low concentrations in the aqueous phase, anti-agglomerates do not lower the freezing point of water and, therefore, cannot be used in low-temperature conditions when simultaneous prevention of the formation of ice and gas hydrates is required. In addition, for the effective operation of anti-agglomerants, the presence of a liquid hydrocarbon phase (oil, condensate) is required for the formation and stabilization of an inverse water-in-oil emulsion. The need for the destruction of the emulsion when using anti-agglomerates significantly complicates the process.

Known methods for preventing hydrate formation using low-dose agents of another type - kinetic inhibitors of hydrate formation (CIG) (RU 2137740, 1999; RU 2436806, 2011; RU 2504642, 2013). The properties of kinetic inhibitors are possessed by amphiphilic water-soluble polymers and oligomers of a certain structure, capable of slowing down the processes of hydration nucleation and the growth of hydrate crystals due to specific interactions in an aqueous solution. A decrease in the rate of hydrate nucleation leads to the fact that a system containing hydrate-forming components and water can remain metastable for a considerable time with respect to the hydrate phase, i.e. in the system there is an induction period (delay) in the formation of the hydrated phase. The disadvantage of this method is the low concentration of CIG in the aqueous phase (up to 2% wt.), Which does not allow to lower the equilibrium temperature of crystallization of ice and decomposition of gas hydrates, i.e. there is no influence on the thermodynamics of the process. This fact limits the use of CIG in technological processes at low temperatures, when simultaneous prevention of the formation of ice and gas hydrates is required. In this case, the induction period of hydrate formation significantly depends on the driving force of the process (degree of hypothermia or the difference between the equilibrium and actual temperature of hydrate formation). CIGs become ineffective (the induction period approaches zero) at high values of the degree of hypothermia (above 12 ° C). In addition, CIG significantly inhibit the formation of hydrates of cubic structure I (methane, carbon dioxide, hydrogen sulfide) compared with hydrates of cubic structure II (hydrocarbon gas mixtures).

Also known is a method of inhibiting hydrate formation, including the use of a kinetic hydrate inhibitor of Luvicap EG manufactured by BASF (Wu R. et al. Methane-propane mixed gas hydrate film growth on the surface of water and Luvicap EG solutions // Energy & Fuels. - 2013. - T. 27. - No. 5. - C. 2548-2554). This inhibitor is a 40% solution of poly (N-vinylcaprolactam) in monoethylene glycol.

The disadvantages of this method are the inability to use it at a temperature below minus 12.9 ° C (the pour point of the inhibitor used in the method), technological problems associated with the difficulty of pumping and dosing the used inhibitor due to its high dynamic viscosity (16,700 mPa⋅s at 20 ° C ) In addition, this method does not provide a significant induction period for the formation of a hydrated phase at high values of the degree of hypothermia.

Closer to the invention is a method of inhibiting hydrate formation using a composition for preventing hydrate, salt deposits and corrosion (RU 2504571, 2014), including a surfactant, a polymer: a pyrrolidone or caprolactam copolymer, a terpolymer based on N-vinyl-2 pyrrolidone, polyacrylamide , hypane, polypropylene glycol, polyoxypropylene polyol, dimethylaminoethyl methacrylate, Laprol ether, hydroxyethyl cellulose; scale inhibitor: substituted aminopolycarboxylic or phosphonic acid, disodium salt of ethylenediaminetetraacetic acid and sodium salt of aminomethylene phosphonic acid, hexametaphosphate or sodium tripolyphosphate, ammonium chloride or nitrate; alcohol in the form of a mixture of formalin, or urotropine, or urea-formaldehyde concentrate-KFK: C ₁ -C ₄ monohydroxy alcohol, bottoms from the production of butyl alcohols by oxosynthesis, the ether-aldehyde fraction is a by-product of ethyl alcohol rectification; C ₁ -C ₃ dihydric alcohol, low molecular weight polyethylene glycol and polyglycol Glycoil-1; polyhydric alcohol: glycerin or a product containing it - polyglycerol in a volume ratio of 1: 4-1 and mineralized water in the following ratio, wt.%:

Surfactant or surfactant mixture 0.1-3.0 The specified polymer 0.02-3.0 Specified Scale Inhibitor 0.1-3.0 Specified mixture 5.0-30.0 Mineralized water rest

The disadvantages of this method are as follows.

Based on the qualitative and quantitative (component) composition of the hydrate inhibitor used in the known method, this method is characterized by low inhibitory ability due to the use of polymers in which the properties of kinetic hydrate inhibitors are slightly expressed (polyacrylamide, hypane, polypropylene glycol, polyoxypropylene polyol, ether brand Laprol, hydroxyethyl cellulose), and due to the low content of polymer and surfactant in the inhibitor, which leads to underdose sufficiently low temperature of hydrate formation onset (kinetic inhibitory effect). The low content of components with antifreeze properties (salts and alcohols) in the inhibitor makes it impossible to use the known method at temperatures below about minus 30 ° C due to the possible crystallization of water. Moreover, the presence in the composition used of components having a function different from the function of inhibiting hydrate formation (scale inhibitor) leads to an additional decrease in the inhibitory ability of the method. Limited miscibility of C ₁ -C ₄ alcohols used in the composition of monohydric alcohols with high salinity formation water (more than 100 g / l), used in large quantities (61-94.78%), also reduces the inhibitory ability of the method.

In addition, the known method is environmentally unsafe due to the presence in the composition used of toxic and carcinogenic formaldehyde and urotropine, which is easily hydrolyzed to form formaldehyde. An additional disadvantage of the composition used in the known method is its potential fire and explosion hazard when using instead of produced water concentrated aqueous solutions of ammonium nitrate and alkali metals capable of playing the role of an oxidizing agent, in combination with alcohols, organic surfactants and polymers that can act as fuel.

Thus, this method is characterized by low efficiency.

The technical problem of the invention is to increase the efficiency of the method of inhibiting hydrate formation - increasing its inhibitory ability, expanding the temperature range of its applicability in low temperature conditions.

This technical problem is solved by the described method of inhibiting hydrate formation by introducing into the inhibitory medium a composition containing a water-soluble polymer, a surfactant, antifoam, water and a solvent: methanol, ethanol, mono- and oligomeric ethylene glycols, mono- and oligomeric propylene glycols, glycerol, monoalkyl C ₁ -C ₄ mono- and oligomeric ethylene glycols, monoalkyl ethers C ₁ -C ₄ mono- and oligomeric propylene glycols, ethanolamines or a mixture thereof, chemical wastes representing e are by-products of hydration of ethylene oxide and propylene oxide, bottoms of the production of monoethylene glycol alkyl esters in the following ratio, wt.%:

water soluble polymer 1.0-25.0 surface-active substance 2.0-20.0 antifoam 0-10,0 water 0-15,0 solvent the rest is up to 100,

moreover, as a surfactant using compounds of the General formula selected from the group including General formulas 1-6:

where R is a hydrocarbon radical With ₆ -C ₁₇ ,

R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ ,

x is from 1 to 5; y is from 1 to 5;

where R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ ,

x is from 1 to 15, y is from 1 to 5;

where R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ ,

x is from 1 to 15, y is from 1 to 5;

where R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ ,

x is from 1 to 15;

where R ₁ , R ₂ , R ₃ , R ₄ - hydrocarbon radicals C ₁ -C ₄ ,

x is from 1 to 15, y is from 1 to 5;

where R ₁ , R ₂ , R ₃ , R ₄ - hydrocarbon radicals C ₁ -C ₄ ,

x is from 1 to 15.

The technical result achieved is to reduce the temperature of the onset of hydrate formation of the hydrate inhibitor (composition) used in the method, to lower its pour point and, as a result, to reduce the temperature of ice formation in the inhibited medium while ensuring prevention of hydrate formation both in kinetic and kinetic and thermodynamic mechanisms.

The essence of the described method of inhibiting hydrate formation is as follows.

The described method can be used to inhibit the formation of gas hydrates in a wide range of ambient temperatures, including in low-temperature conditions (less than 0 ° C), at high values of the degree of supercooling. The method can be used to inhibit gas hydrates of cubic structure I (methane, carbon dioxide, hydrogen sulfide), cubic structure II (hydrocarbon gas mixtures, mixtures of hydrocarbons with non-hydrocarbon components). The method can be used both in two-phase gas-water systems (including mineralized), and in multiphase systems with liquid hydrocarbons (oil, gas condensate). Depending on the concentration of the solvent, the composition used in the method has the properties of a kinetic inhibitor (with a low solvent content of less than 50-60% wt.), Or exhibits dual inhibitory properties (kinetic and thermodynamic effect) with a solvent content of more than 50-60% wt. Changing the type and concentration of solvent in the composition of the inhibitor used in the claimed method, provides the necessary values of the viscosity of the inhibitor, the pour point and crystallization of the inhibitor, as well as the temperature of crystallization of ice in the inhibited medium containing water.

The components used in the composition (hydrate inhibitor) of the described method significantly slow down the formation of hydrated phase nuclei (nucleation), inhibit the growth of gas hydrate crystals and prevent agglomeration of smaller hydrate crystals into larger ones.

The described method can be used to inhibit hydrates in such hydrocarbon-containing raw materials as, for example, oil-based aqueous emulsions, these emulsions containing hydrocarbon gas, gas condensate, raw materials containing hydrate-forming gas, water, as well as other hydrocarbon-containing raw materials containing water and hydrate-forming components, characteristic , in particular, for the processes of production, processing and transportation of hydrocarbons.

Depending on the specified type of inhibitor, determined by the ratio of solvent to the remaining components, the composition used is introduced into the feedstock in an amount of 0.2-70.0% by weight of the water contained in the specified feedstock. In each case, the optimal dosage can be determined by laboratory tests, depending on the composition of the composition (inhibitor), the composition of the fluids of a particular object (gas, produced water, oil, gas condensate), temperature, pressure.

In the inhibitor used in the described method, poly (N-vinyl lactams), in particular poly (N-vinyl pyrrolidone), poly (N-vinyl piperidone), poly (N-vinyl caprolactam), poly (N-vinyl enantholactam) are used as a water-soluble polymer , polyacrylamide and its derivatives, in particular poly (N-isopropylacrylamide), poly (N-acryloylpyrrolidine), poly (N-glyoxyloylpyrrolidine), poly (N-ethylmethacrylamide), poly (N-isopropylmethacrylamide), polyvinylamide and its derivatives, polyallyl and its derivatives, hyperbranched polyetheramides, polyvinyl alcohol and its roizvodnye, oligopeptides and antifreeze proteins, copolymers containing units of these polymers and other high molecular compounds capable of slowing the process of nucleation and crystal growth of gas hydrates. Preferably, poly (N-vinyl pyrrolidone), poly (N-vinyl piperidone), poly (N-vinyl caprolactam), poly (N-isopropyl acrylamide), polyacryloyl pyrrolidine, poly (N-glyoxyloyl pyrrolidine), poly (N-ethylmeth) are used as the water-soluble polymer. poly (N-isopropylmethacrylamide), poly (N-ethylglycine), poly (N-isopropylglycine), poly (N-propylglycine) and their copolymers with units of N-vinyl pyrrolidone, N-vinyl piperidone, N-vinyl caprolactam, vinyl acetate, vinyl alcohol, , propylene oxide.

In the inhibitor used in the described method, compounds with the above general formulas 1-6 are used as a surfactant. Preferably, compounds of the general formula 1 are used as a surfactant, where R is a C ₈ -C ₁₅ hydrocarbon radical, R ₁ , R ₂ is a C ₁ -C ₄ hydrocarbon radical, x is from 2 to 4, and y is from 1 to 3, compounds of general formula 2, where R ₁ , R ₂ , are hydrocarbon radicals C ₁ -C ₄ , x is from 2 to 14, y is equal to 1 to 3, compounds of general formula 3, where R ₁ , R ₂ are hydrocarbon radicals C ₁ -C ₄ , x is from 2 to 13, y is from 1 to 3, compounds of the general formula 4, where R ₁ , R ₂ are hydrocarbon radicals C ₁ -C ₄ , x is from 2 to 13, compounds of the general formula 5 where R _1, R _2, R _3, R ₄ - carbon odorodnye radicals C ₁ -C _4, x is from 2 to 13, y is from 1 to 3; compounds of General formula 6, where R ₁ , R ₂ , R ₃ , R ₄ - hydrocarbon radicals C ₁ -C ₄ , x is equal to from 2 to 13.

Fatty aliphatic alcohols, nonionic surfactants based on fatty aliphatic alcohols, polydimethylsiloxanes, copolymers of ethylene oxide and propylene oxide are used as a defoamer of the hydrate formation inhibitor of the described method.

In the inhibitor used in the described method, substances such as methanol, ethanol, mono- and oligomeric ethylene glycols (in particular diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol), mono- and oligomeric propylene glycols (in particular, are used as solvent) 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropilenglikol), glycerol monoalkyl ethers (C ₁ -C ₄₎ thereof, ethanolamines (including monoethanolamine, diethanol min, triethanolamine) or mixtures thereof. Preferably, methanol, ethanol, monoethylene glycol, monoethylene glycol alkyl ethers are used as solvent. Most preferably, methanol, monoethylene glycol, buto monoethylene glycol butyl ether is used as a solvent. It is also allowed to use chemical wastes as a solvent, which are by-products of hydration of ethylene oxide and propylene oxide (oligomeric polyethylene glycols and polypropylene glycols), bottoms from the production of monoethylene glycol alkyl esters.

The presence in the inhibitor of a surface-active substance (SAS) of general formulas 1-6 can significantly reduce the content of water-soluble polymer while increasing the inhibitory ability due to the manifestation of the synergistic effect associated with the joint action of the components in the solution, which is an unexpected result. Higher inhibitory ability allows to reduce the dosage of the reagent with the same efficiency of the process of inhibition of gas hydrates or to increase the efficiency of the process of inhibition at the same dosage. The inhibitor used in the proposed method is characterized by a significantly lower viscosity compared with high viscosity inhibitors known from the prior art, for example, Luvicap EG. The use of a solvent in the composition (inhibitor) makes it possible to impart the necessary low-temperature properties to the latter, which makes it possible to use the described method at negative temperatures of the inhibited medium. The introduction of water into the composition is necessary to provide a lower pour point of the inhibitor when glycols and ethanolamines are used as a solvent. The presence of surfactants in the mixture in combination with the polymer component gives the composition the ability not only to prevent the formation of gas hydrates by the kinetic mechanism, but also to prevent agglomeration of the hydrated crystals formed. In addition, when the solvent content is above 50 - 60% wt. the composition can be used as a combined reagent capable of inhibiting the formation of hydrates simultaneously by the kinetic and thermodynamic mechanism, as well as preventing the formation of ice in an inhibited medium under low temperature conditions. The presence of a water-soluble polymer, surfactants and a solvent in the composition in this case can significantly increase the efficiency of the hydrate formation inhibition process and reduce the consumption of a thermodynamic inhibitor.

The composition (hydrate inhibitor) used in the described method is prepared by compounding the components. Solvent and water are metered into a reactor equipped with a stirrer. Stir until a homogeneous solution is formed. After that, a water-soluble polymer and antifoam are added to the resulting mass. Re-mix until smooth. At the final stage, a surfactant is added to the resulting solution and the resulting mixture is homogenized by stirring. The resulting composition (inhibitor) is introduced into the inhibited medium (fluid flow) in various ways, in particular, directly into the raw material, and pumped into the near-well zone or into the pipeline section. The introduction of the inhibitor into the inhibited medium containing water and hydrate-forming components can be carried out using nozzle devices, both in the direction of the fluid flow and against it. Input in countercurrent provides a more rapid and uniform distribution of the inhibitor in the inhibited medium. The described method is preferably carried out at a temperature equal to or higher than the equilibrium temperature of hydration of the medium.

The invention is illustrated by examples, not limiting its use.

Example 1

According to the above technology, a hydrate formation inhibitor of the following composition is prepared,% wt .:

- a water-soluble polymer is a copolymer of N-vinylcaprolactam and N-vinylpyrrolidone 25.0 - surfactant of General formula 2, where R ₁ is the radical CH ₃ , R ₂ is the radical CH ₃ , x is 12, y is 1 20,0 - antifoam - isoamyl alcohol 10.0 - solvent - methanol 45.0

Example 2

According to the above technology, a hydrate formation inhibitor of the following composition is prepared,% wt .:

- water soluble polymer - poly-N-vinylcaprolactam 14.0 - surfactant of General formula 1, where R is a C ₁₁ radical, R ₁ is the radical CH ₃ , R ₂ is the radical C ₂ H ₅ , x is 3, y is 1 12.0 - antifoam - ethoxylated 2,4,7,9-tetramethyl-5-decin-4,7-diol 5,0 - water 10.0 solvent - monoethylene glycol 59.0

Example 3

According to the above technology, a hydrate formation inhibitor of the following composition is prepared,% wt .:

- water soluble polymer - copolymer N-acryloylpyrrolidine and N-vinylpyrrolidone 1,0 - surfactant of General formula 3, where R ₁ is the radical nC ₄ H ₉ , R ₂ is the radical n-C ₃ H ₇ , x is 7, y is 3 2.0 - water 15.0 - solvent - monoethylene glycol 82.0

Example 4

According to the above technology, a hydrate formation inhibitor of the following composition is prepared,% wt .:

- water soluble polymer - copolymer N-vinylcaprolactam and vinyl alcohol 25.0 - surfactant of General formula 4, where R ₁ is the radical nC ₄ H ₉ , R ₂ is the radical n-C ₄ H ₉ , x is 7 15.0 - antifoam - a copolymer of ethylene oxide and propylene oxide 10.0 - solvent - monoethylene glycol methyl ether 50,0

Example 5

According to the above technology, a hydrate formation inhibitor of the following composition is prepared,% wt .:

- water soluble polymer - poly-N-isopropyl acrylamide 20,0 - surfactant of General formula 5, where R ₁ is the radical CH ₃ , R ₂ is the radical nC ₃ H ₇ , R ₃ is the radical nC ₄ H ₉ , R ₄ is the radical nC ₃ H ₇ , x is 8, y is 2 10.0 - antifoam - ethoxylated 3,5,8,10-tetramethyldodecane-5,8-diol 5,0 - solvent - monoethylene glycol butyl ether 65.0

Example 6

According to the above technology, a hydrate formation inhibitor of the following composition is prepared,% wt .:

- a water-soluble polymer is a copolymer of N-vinylcaprolactam and N-vinylpyrrolidone 2.0 - surfactant of General formula 6, where R ₁ is the radical nC ₄ H ₉ , R ₂ is the radical nC ₄ H ₉ , R ₃ is the radical nC ₄ H ₉ , R ₄ is the radical nC ₄ H ₉ , x is 6 2.0 - antifoam - ethoxylated 2,4,7,9-tetramethyl-5-decin-4,7-diol 1,0 - solvent - ethanol 95.0

The claimed method is illustrated by the example of using a model system consisting of a gas mixture of 95.66% CH ₄ + 4.34% C ₃ H ₈ (mol%) and water as an initial hydrocarbon-containing feedstock.

Samples of hydrate inhibitors are characterized by measuring:

- dynamic viscosity of composition η at a temperature of 20.0 ° C, which is carried out using a Rheotest RV2.1 rotational viscometer at a shear rate of 24.3 s ^-1 ;

- pour point of the composition T _r according to GOST 20287-91 (in the absence of water in the composition) or freezing temperature in accordance with ASTM D 1177 (in the presence of water in the composition);

- the temperature of the onset of hydrate formation T ₁ and the degree of supercooling of the onset of hydrate formation ΔT ₁ characterizing the kinetic inhibitory effect of the sample.

The temperature and degree of supercooling of the onset of hydrate formation is measured by the following procedure.

The study is conducted on a laboratory setup Sapphire Rocking Cell RCS6. Using an Ohaus Pioneer PA413C laboratory balance, an aqueous solution of the test samples is prepared. A stainless steel ball with a diameter of 10 mm (stirring element) is placed in each sapphire cell of the RCS6 installation, and 10 ml of an inhibitor solution with a concentration of 1% wt. The ratio of free volume to liquid volume in each cell is 1: 1. The cells are installed in a thermostatic bath of the installation and hermetically closed. The volume of the bath is filled with coolant. The free volume of the cells is purged with hydrate-forming gas in order to remove air. After purging, the cells are filled with hydrate-forming gas to an initial pressure of 60 bar at room temperature 21 ° C. They include mixing the contents of the cells by deviating them from the horizontal position by an angle of ± 45 ° with a frequency of 10 min ^-1 . Stirring remains on throughout the experiment. Periodic deviation of the cells leads to the movement of the ball from one edge of the cell to the other. When moving each time, the ball crosses the gas-liquid interface, which leads to the appearance of shear forces and contributes to the process of nucleation of gas hydrates at the gas-liquid-metal interface. After that, the temperature in the bath is set for 1 hour at such a level that the P, T-conditions in the cells correspond to the two-phase region VL _w (gas-water solution) in the phase diagram near the three-phase equilibrium line VL _w -H (gas-water solution-gas hydrate). After mutual saturation of the gas and liquid phases, the temperature in the bath is lowered at a rate of 1 ° C / h, while visually fixing the contents of sapphire cells and controlling the measurement of temperature and pressure in all cells. The pressure in all cells decreases linearly upon cooling at a rate of 1 ° C until the hydrate formation process begins. Due to the absorption of the hydrate-forming gas, the time dependences deviate from the straight line. The temperature T ₁ and pressure P ₁ in each cell are fixed at which the deviation of these dependences from the lines begins. Based on the previously obtained experimental data on the phase equilibrium conditions of hydrates of a model methane-propane gas mixture, the degree of supercooling ΔТ1 at which hydrate formation begins is calculated. ΔT is the difference between T _eq and T ₁ where T _eq is the equilibrium temperature at a pressure P ₁ for a model gas mixture of 4.34% C ₃ H ₈ + 95.66% CH ₄ . T _{eq is} calculated by polynomial regression equation obtained by processing the experimental results according to the conditions of three-phase equilibrium L _w -VH for a model gas mixture of 4.34% C ₃ H ₈ + 95.66% CH ₄ . At least 12 experiments are carried out for each of the samples, according to the results of which the temperature, pressure, degree of supercooling of the onset of hydrate formation are averaged, and the standard deviation of these values for each of the samples is calculated. The value of ΔT ₁ indicates the effectiveness of inhibitor samples at the stage of nucleation of gas hydrates (kinetic inhibitory effect).

The test results of the samples are shown in table 1.

From the obtained results it follows that the described method has a higher inhibitory ability (the onset of hydrate formation for the composition of the inhibitor used in the inventive method is lower by 7.9-10.8 ° C than for the composition used in the known method), and can also carried out efficiently at lower temperatures of the inhibited and environmental than the known method (below minus 30 ° C), allowing more effectively to prevent the formation of ice in the inhibited medium in a wide range of low-temperature conditions.

Carrying out the described method using a different inhibitory medium, a composition containing other of the above substances, in different concentrations falling within the above range, leads to similar results. Use in the method

containing components in quantities beyond this interval does not lead to the desired results.

Thus, the claimed method is characterized by high inhibitory ability, extended temperature range of applicability, effective prevention of ice formation in the inhibited medium in a wide temperature range, including low temperatures. In addition, the claimed method is more environmentally friendly due to the absence in the composition used of a carcinogenic formaldehyde inhibitor and fireproof (absence in the composition used of the inhibitor of oxygen-containing oxidizing salts).

Claims (22)

A method of inhibiting hydrate formation by introducing into an inhibitory medium a composition containing a water-soluble polymer, a surfactant, antifoam, water and a solvent: methanol, ethanol, mono- and oligomeric ethylene glycols, mono- and oligomeric propylene glycols, glycerin, C ₁ -C ₄ monoalkyl ethers mono- and oligomeric ethylene glycols, monoalkyl ethers of C ₁ -C ₄ mono- and oligomeric propylene glycols, ethanolamines or a mixture thereof, chemical wastes, which are by-products of hydration of ethylene oxide and of pylene oxide, bottoms of the production of monoethylene glycol alkyl esters in the following ratio of components,% wt .: water soluble polymer 1.0-25.0 surface-active substance 2.0-20.0 antifoam 0-10,0 water 0-15,0 solvent the rest is up to 100 moreover, as a surfactant using compounds of the General formula selected from the group including General formulas 1-6:

where R is a hydrocarbon radical With ₆ -C ₁₇ , R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ , x is from 1 to 5; y is from 1 to 5;

where R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ , x is from 1 to 15, y is from 1 to 5;

where R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ , x is from 1 to 15, y is from 1 to 5;

where R ₁ , R ₂ - hydrocarbon radicals C ₁ -C ₄ , x is from 1 to 15;

where R ₁ , R ₂ , R ₃ , R ₄ - hydrocarbon radicals C ₁ -C ₄ , x is from 1 to 15, y is from 1 to 5;

where R ₁ , R ₂ , R ₃ , R ₄ are hydrocarbon radicals C ₁ -C ₄ , x is from 1 to 15.