RU2323244C1 - Method of preparing solid foaming agent for removing liquid from gas or gas condensate wells - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: particular objective of invention is removal of high-mineralization (including formation) water and mixtures thereof with gas condensate from marginal gas and gas condensate wells. In a method of preparing solid foaming agent including mixing nonionic surfactant with urea and molding resulting mixture, urea is preliminarily dissolved in water preheated to 50-90°C at weight ratio (9-10):1, respectively, and mixture is then heated to form true solution. Nonionic surfactant is heated to 40-80°C and mixed with true solution of urea at weight ratio (1.0-1.4):1, respectively. Before molding, to resulting liquid-crystalline component mixture is added a water-soluble polymer at weight ratio 1:(0.01-0.05), respectively, or mixture of water-soluble polymer and dissolution retardant at weight ratio liquid-crystalline component mixture/water-soluble polymer/dissolution retardant 1:(0.01-0.05):(0.4-0.6).

EFFECT: increased strength properties of solid foaming agent and enhanced absolute carrying-out capacity thereof.

4 cl, 3 dwg, 6 ex

Description

The invention relates to the gas industry and can be used to remove highly mineralized, including produced, water and mixtures thereof with gas condensate from low-rate gas and gas condensate wells.

Analysis of the current level of technology showed the following:

- there is a known method of removing liquid from gas wells using a solid foaming agent (see US patent No. 4237977 dated 02.02.1979, class E21B 21/14, published 09.12.1980, Skyline Produkts Ltd, ISM, issue 81, No. 8, 1981). The technical solution provides a method for producing a solid foaming agent. A non-ionic water-soluble surface-active substance (surfactant) is mixed with powdered urea, incubated for 24-48 hours to form a solid urea adduct and pressed to a density above 1200 kg / m ³ . To remove liquid from gas wells, the resulting urea adduct is introduced into the latter, which forms a foam when gas is supplied through water. With this foam, fluid is gradually removed from the well.

According to the technology, the initial components — powdered urea and liquid nonionic surfactant — are mixed in a ratio of 1: 1 to 9: 1 by weight, respectively, which form a coarse heterogeneous system. In this case, a nonionic surfactant — adsorbate, due to physicochemical adsorption on the urea surface — the adsorbent interacts with the formation of a urea adduct (a complex compound of urea and a nonionic surfactant). According to the theoretical ideas of the authors, as a result of the system’s tendency to decrease surface energy at the phase boundary, an adsorption interaction occurs between the initial components due to dispersion (Van der Waals) forces and induced electrostatic attraction. For the formation of a urea adduct, it is necessary to overcome the energy barrier (activation energy), for which pressure is often used, as a result, the urea molecules rearrange, forming a structure consisting of hexagonal prisms adjoining by planes to each other in the form of honeycombs. With this rearrangement, regardless of the type of substance to be attached, the same structure is formed with the same arrangement of urea molecules and the distance between them. Between the planes of the prisms, channels are formed that are filled with nonionic surfactant molecules (direct chains), i.e., the formation of a urea adduct occurs. The shape of the channels resembles a helix, inside them the molecules of a nonionic surfactant join under the action of dispersion (Van der Waals) forces and induced electrostatic attraction. The cross section of the channel is 6 Å in the wide and 5 Å in the narrow part. Nonionic surfactants have straight chain sites (cross section 4.1 Å); therefore, urea adducts are easily formed. The kinetics and completeness of the formation of the urea adduct are directly dependent on the specific (interphase) contact surface of the components of the system. Since the interaction process proceeds only at the phase boundary, the urea molecules inside the adsorbent particles will remain unreacted. As a result, the obtained solid foaming agent is a solid solution of a urea adduct and an excess of urea, while the phases (in different ratios) are fairly evenly distributed throughout the substance in the form of separate dispersed inclusions.

The disadvantage of this method is the following:

- reduced strength properties of the solid foaming agent. Urea, being an anisotropic crystalline substance in excess, gives brittleness to a solid foaming agent. Estimated compressive strength - 1.0 MPa, bending - 0.5 MPa, which can lead to the destruction of the solid foaming agent during transportation or falling into the well;

- low absolute endurance of solid foaming agent.

The results obtained in a laboratory setup can be expressed in terms of relative or absolute values, which in different ways reflect the endurance index of solid blowing agents. Absolute stamina is determined by the formula

,

,

where ν _a is the absolute capacity of the solid foaming agent, kg / m ³ ;

V _vzh - the volume of the produced reservoir fluid, m ³ ;

m is the mass of the sample of a solid foaming agent, kg

The volume of fluid, m ³ , is determined by the formula

V _L = V ₁ -V ₂ ,

where V ₁ is the volume of liquid filled in the laboratory setup, m ³ ;

V ₂ - the volume of fluid remaining in the laboratory setup, m ³ .

Low absolute tolerance is due to the low content of nonionic surfactants and increased solubility of solid blowing agents. Our laboratory tests showed that the ratio of the initial components of urea: nonionic surfactant from 0.7: 1 to 1: 1 by weight, respectively, is sufficient to cure most nonionic surfactants. Excess urea, which is a rapidly dissolving surfactant, leads to a decrease in absolute tolerance. From the content of nonionic surfactant - the active part of the solid foaming agent, which is from 10 to 50 wt.%, Depends on the volume of liquid (V _WL ), which can be removed (bound) by the unit mass (m) of the solid foaming agent. The reduced content of nonionic surfactant requires the introduction of a larger mass of solid foaming agent into the well to carry the same amount of fluid, which reflects a low absolute capacity. Putting more solid foaming agent is not economically feasible. Upon contact of a solid foaming agent with a liquid, its components interact with water dipoles. Urea, rapidly dissolving, leads to an increase in the interfacial contact surface of the urea adduct with the liquid. As a result, the dissolution rate of the solid foaming agent is significantly increased, which leads to a decrease in the volume of liquid removed per unit mass of the solid foaming agent, since at the initial time a solution is formed with an excess concentration of nonionic surfactant, which will be carried out in the first portions of the resulting foam by an upward flow of gas. Laboratory studies showed that the dissolution rate was 0.05-0.1 m / h, at this dissolution rate, the solid foaming agent may not reach the bubble zone. Subsequently, this leads to the cost overrun of the solid foaming agent and the shortening of the interoperation period, since the lower layers and new portions of the liquid, which can enter the well within 0.3-1.0 hours, will not be covered by the action of a nonionic surfactant. The efficiency of the process is reduced not only due to the overconsumption of the solid foaming agent, but also due to the reduction of the interoperation period (the time elapsed between two consecutive operations of introducing the solid foaming agent), since the process of fluid flow into the well is often continuous, and a high dissolution rate reduces the action time of the solid foaming agent.

In addition, this technology requires a significant investment of time, a large number of technological operations and related equipment: the need to grind granular urea to a powder state, and the finer the urea fraction, the faster and more complete the urea adduct is formed, keeping the initial system in demountable forms within 24- 48 hours, additional adduct pressing operations using a press (e.g. hydraulic) in the presence of a lubricant;

- as a prototype we took a method of obtaining a solid foaming agent specified in the patent of the Russian Federation No. 2100577 dated 10.17.1995, class. ЕВВ 43/00, 37/00, publ. in OB No. 36 dated 12/27/1997, “Solid foaming agent for removing liquid from gas and gas condensate wells”. According to the method, a non-ionic surfactant is mixed: OP-10 or AF-9 brand neonol, or block copolymers and a carbonic acid derivative containing nitrogen, in the form of a mixture of a complex salt of urea with an acid (hereinafter complex salt of urea): urea oxalate or urea nitrate or urea hydrochloride. Next, the resulting mixture is molded.

The choice of the prototype is due to the increased content in the solid foaming agent of nonionic surfactant up to 57 wt.% Or the ratio of wt.h. components, a carbonic acid derivative containing nitrogen: a nonionic surfactant from 1: 0.52 to 1: 2.28, respectively.

The disadvantage of this method is the following:

- low strength properties of the solid foaming agent. This is due to the impossibility of the formation of adducts between complex urea salts and nonionic surfactants.

Figure 1 shows the structural formula of urea nitrate.

Figure 2 presents the structural formula of urea oxalate.

, Cl^-,

), что приводит к смещению (перераспределению) электронных плотностей.Common to complex urea salts is the structure of the inner sphere of the molecule - the salt cation, which consists of a complexing agent - isocyanic acid (HNCO) and ligands - a hydrogen ion (H ⁺ ) and an ammonia molecule (NH ₃ ). In the salt cation, the carbon atom is in a sp-hybridization state and is bonded to one nitrogen atom and an oxygen atom by double bonds, the NCO bond angle is 180 °. The lone electron pair of the nitrogen atom, which is part of the ammonia molecule, forms a covalent polar bond with the carbon atom by the donor-acceptor mechanism, the bond angle of NCN is 90 °. In addition, the molecule contains strongly polarized atoms (N, O, C), ions (H ⁺ ,

, Cl ^- ,

), which leads to a shift (redistribution) of electron densities.

It is considered (see Grandberg II Organic Chemistry: Textbook. For students. Universities studying agronomy. Special. - 5th ed., Stereotype. - M.: Drofa, 2002. - 672 pp. And Kucheryavy V. I., Lebedev VV Synthesis and application of urea. - L .: Chemistry, 1970), that the bond angles between two nitrogen atoms and an oxygen atom are close to 120 °, the bond length C = O (0.126 nm) and CN (0.133 nm), which indicates strong conjugation in the molecule. This ensures the reactivity of urea molecules to form a hexagonal spatial structure with the formation of stable urea adducts.

At the above values of the angles in the molecules of complex salts of urea, the formation of adducts between them and nonionic surfactants does not occur. Thus, the components form a coarse dispersed heterogeneous mechanical mixture, the strength properties of which are due to the presence of physical adsorption interaction forces. The adsorption of a nonionic surfactant, an adsorbate, on the surface of complex salts of urea and nitrites of alkali and alkaline earth metal adsorbents arises due to dispersion (Van der Waals) forces and an electrostatic effect intensified as a result of hydrogen bonds.

Figure 3 presents the structural formula of neonol brand AF-9.

Consider the distribution of electron densities in a neonol molecule of the AF-9 brand.

The alkyl radical and the hydrophilic part of the nonionic surfactant molecule represented by ethylene oxide groups (-CH ₂ -CH ₂ -O-) are first-order substituents (positive induction effect) and give the total increased electron density to the benzene nucleus. Oxygen atoms, which have a greater electron affinity, pull electron clouds onto themselves, as a result of which a partial positive charge arises on carbon atoms. A decrease in the electron density on a carbon atom causes an increase in the polarity of the bonds of this atom with hydrogen atoms, as a result of which their reactivity increases. In this case, hydrogen atoms become more active in the formation of hydrogen bonds with more electronegative atoms of adsorbent molecules (N, O, Cl), which have an unshared electron pair. The specific (interphase) surface is very poorly developed, the bonding forces of the physical adsorption interaction are small (energy 5-15 kJ / mol), as a result of which they can easily decompose upon heating (surfactant desorption), under the action of the released gas (gas corrosion), when interacting with polar solvents (water dipoles), etc. Laboratory studies showed that the compressive strength was 0.4 MPa, the flexural strength was 0.6 MPa (see table of the prototype test report). The moisture contained in the well (in natural gas) instantly begins to initiate the process of gas formation. This makes it difficult to use a solid foaming agent in deep or inclined wells, because due to insufficient strength during a fall, it can stick to tubing, deform and begin to carbonate. Similarly, the interaction of adsorbents with other nonionic surfactants is considered;

- reduced absolute endurance of the solid foaming agent.

The reduced absolute endurance of the prototype (0.21-0.26 kg / m ³ ) is associated with an increase in the dissolution rate of the solid foaming agent. The dissolution kinetics will be limited by the rate of heterogeneous reactions, as a result of which the gaseous products (N ₂ , CO ₃ ) released will destroy the structure of the solid foaming agent, which will lead to an increase in the interfacial contact surface of the solid foaming agent with the liquid and an increase in the dissolution rate. The high dissolution rate leads to a decrease in the volume of liquid _removed ( _Vlf ) per unit mass (m) of the solid foaming agent, since at the initial time a solution is formed with an excess concentration of nonionic surfactant, which will be carried out in the first portions of the resulting foam by an upward gas flow. Ultimately, this leads to an over expenditure of the solid foaming agent and a shortening of the interoperation period, since new portions of the fluid, which can enter the well within 0.3-1.0 hours, will not be covered by the action of surfactants. The density of the solid foaming agent is 1010-1030 kg / m ³ , which is not much higher than the density of the liquid in the well, and the gas emitted will keep the solid foaming agent in the upper layers (confirmed by laboratory tests). Excessive concentration of nonionic surfactant in the upper layers of the liquid leads to intensive emulsification of gas condensate and the appearance of a stable emulsion due to the formation of a saturated adsorption layer of nonionic surfactant on the globules of gas condensate, which inhibits the foam formation process. The latter can be revived only by introducing an additional amount of a solid foaming agent.

In addition, the components that make up the solid foaming agent are highly hygroscopic. During storage, even in an airtight shell, a solid foaming agent loses its shape and uniform structure (gas corrosion), as a result of which the strength properties are reduced. Certain substances included in the composition require automatic control of their content in the air of the working area (for example, sodium nitrite belongs to hazard class I with a sharply directed mechanism of action). The technology for mass production of solid blowing agents is complex and time consuming.

The technical result that can be obtained by implementing the invention is reduced to the following:

- increase the strength properties of the solid foaming agent due to the formation of a crystalline structure;

- the absolute endurance of the solid foaming agent increases due to the acquisition of the function of a prolonged action on the removed liquid.

The technical result is achieved using known method operations: mixing a nonionic surfactant and a carbonic acid derivative containing nitrogen, and molding the resulting mixture. Moreover, according to the invention: urea is used as a carbonic acid derivative containing nitrogen; it is additionally dissolved in water heated to 50-90 ° C in a ratio (parts by weight) of 9-10: 1, respectively; heating the resulting mixture until a true solution is formed; nonionic surfactant is heated to 40-80 ° C; non-ionic surfactants are mixed with a true urea solution in a ratio (parts by weight) of 1.0-1.4: 1, respectively; before molding, a water-soluble polymer in a ratio (parts by weight) of 1: 0.01-0.05, respectively, or a mixture of a water-soluble polymer and a dissolution retardant in a ratio (parts by weight) of a liquid-crystal mixture of components is added to the resulting liquid crystal mixture of components: water-soluble polymer: a dissolution retardant equal to 1: 0.01-0.05: 0.4-0.6, respectively.

The inventive method meets the condition of novelty.

As urea, carbamide grade B is used according to GOST 2081-92.

As a nonionic surfactant, neonol AF 9-12 is used according to TU 2483-077-05766801-98 Neonols, which is a technical mixture of polyethylene glycol ethers of monoalkyl phenols of the following composition:

C ₉ H ₁₉ C ₆ H ₄ O (C ₂ H ₄ O) _n H,

where C ₉ H ₁₉ is an isononyl alkyl radical attached to phenol mainly in the para position to the hydroxyl group;

n is the average number of moles of ethylene oxide attached to 1 mole of alkyl phenols equal to 9-12,

OP-10 according to GOST 8433-81, which is a product of processing a mixture of mono - and dialkylphenols with oxyethylene,

block copolymers of ethylene and propylene oxides according to TU 38.507-63-09-89 of the general formula:

C _n H _{2n + 1} O (C ₃ H ₆ O) _m (C ₂ H ₄ O) _p N,

where n is the number of carbon atoms in the alkyl radical, equal to 5-15;

m is the number of moles of ethylene oxide equal to 9-45;

p is the number of moles of propylene oxide, equal to 30-180.

The action of these substances in the composition of the solid foaming agent is identical.

As a water-soluble polymer, carboxymethyl cellulose is used in accordance with TU 6-55-40-90, AK-631 polyacrylamide grade A-1510 in accordance with TU 6-02-00209912, polyvinyl alcohol, grade 18/11 in accordance with GOST 10779-78 grade 1. The action of these substances in the composition of the solid foaming agent is identical.

As lignosulfonates, condensed sulphite alcohol bard (KSSB 2) is used in accordance with TU 39-094-75, condensed sulphite alcohol bard (KSSB 5) is used in accordance with TU 17-06-311-94, and sulphite alcohol bard is in accordance with TU 81-04-225-78 . The action of these substances in the composition of the solid foaming agent is identical.

Water is heated to a temperature of 50-90 ° C in order to dissolve the urea in a minimum amount of time (to reduce the loss of urea due to hydrolysis).

Hydrolysis proceeds in 2 stages:

1. CO (NH ₂ ) ₂ ↔NH ₄ OCN (urea water isomerization to ammonium cyanate)

2. NH ₄ OCN + 2H ₂ О↔ (NH ₄ ) ₂ СО ₃

In this case, ammonium cyanate in an aqueous solution dissociates into ions

+NCO^-↔NH₃↑+HNCO (изоциановая кислота)NH ₄ OCN↔

+ NCO ^- ↔NH ₃ ↑ + HNCO (isocyanic acid)

and that NCO ions ^- undergo hydrolysis

+

NCO ^- + 2H ₂ O↔

+

It is believed (see Kucheryavyy V.I., Lebedev V.V. Synthesis and use of urea. - L .: Chemistry, 1970, p.114) that with prolonged heating of the urea-water system, significant losses of urea are possible due to its hydrolysis and irreversible evolution of ammonia. Dissolution kinetics depend on the structure and size of urea solid particles, type of solvent, heating intensity, initial water temperature. Urea dissolution is an endothermic reaction (heat of dissolution in water Q = 57.8 cal / g). At an initial water temperature below 50 ° C, the urea granules are sintered (coarsened) and the time to obtain a true urea solution is significantly increased. An increase in the dissolution time of urea leads to an increase in the losses of the urea due to hydrolysis, which negatively affects the strength properties of the solid foaming agent. At water temperatures above 90 ° C, high evaporation leads to water loss, and boiling is also possible. That is, this operation significantly affects the kinetics of urea dissolution and the final technical result.

Granular urea is gradually poured into heated water with stirring in a ratio by weight 1: 9-10, respectively. With a decrease in the amount of water, the urea concentration in the solution increases, the temperature of obtaining the true urea solution increases, the degree of hydrolysis also, which negatively affects the strength properties of the solid foaming agent. With increasing water content, urea loss increases, as a result of which the strength properties of solid blowing agents decrease. It is believed (see Kucheryavyi V.I., Lebedev V.V. Synthesis and use of urea. - L .: Chemistry, 1970, p. 121) that the constant of isomerization rate (1st stage of hydrolysis) depends on the initial concentration of urea and increases in direct proportion to the water content in the urea solution. In this case, hydrolysis and urea loss associated with this process increase, which negatively affects the strength properties of the solid foaming agent. The amount of water taken more than the claimed ratio may not be associated with additives and makes the solid foaming agent more loose, which also negatively affects the strength properties of the solid foaming agent. The use of the claimed urea-water ratio can significantly reduce the transition temperature of the urea from crystalline to molecular state (melting point at atmospheric pressure 132.7 ° C), avoid its thermal decomposition, as during melting, and use granular urea without preliminary grinding, as indicated in analogue. The choice of solvent - water is due to several reasons: it provides good solubility of urea, has a low viscosity, affordable and cheap (unlike ethanol), non-toxic (unlike methanol and pyridine), it is easily bound by additives (lignosulfonates and water-soluble polymers). The resulting mixture is used to obtain a true urea solution.

The mixture is continued to heat until all urea has dissolved. For a given ratio of urea and water, a saturated solution is obtained at temperatures up to 104 ° C (Kucheryavy V.I., Lebedev V.V. Synthesis and use of urea. - L .: Chemistry, 1970, p. 431). The saturated solution is heated to a temperature of 106-109 ° C, that is, until a true solution is obtained. This is necessary for the implementation of favorable conditions during mixing in order to avoid premature precipitation of solid particles (urea crystals). At temperatures lower than obtaining the true solution, premature precipitation of particles of the solid phase (urea crystals) is possible, which leads to an undesirable decrease in the interaction surface of the components and subsequently a decrease in the absolute endurance of the solid foaming agent. The molecules inside the urea crystals can remain unreacted, which reduces the amount of unreacted nonionic surfactant, they also increase the rate of dissolution of the solid foaming agent. Heating the urea solution above the temperature of obtaining the true solution is not economically feasible and can lead to an increase in urea losses due to hydrolysis, which negatively affects the strength properties of the solid foaming agent. Obtaining a true urea solution allows one to overcome the energy barrier of the formation of a urea adduct associated with the rearrangement of urea molecules in a hexagonal spatial structure (since urea in a true solution is in a molecular state). Energy is stored (accumulated) in the form of the energy of a liquid, which then goes to the heat of the crystallization process. The interaction of the two substances leads to the mutual physicochemical adsorption of the two components with the formation of a complex compound (urea adduct), and the more molecules are involved in this process, the more efficient and complete it is. An increase in the number of “active” urea molecules leads to the maximum possible number of nonionic surfactant molecules that can react, that is, form the maximum amount of urea adduct. Therefore, obtaining a true solution is one of the main conditions for obtaining the maximum technical result.

To ensure sufficient mobility and viscosity necessary for mixing a true solution of urea and a nonionic surfactant, the latter is heated to 40-80 ° C. At a temperature of heating a nonionic surfactant below 40 ° C, a strong supercooling of a true urea solution occurs, which can cause the growth of large crystals, which negatively affects the strength properties of a solid foaming agent. Heating a nonionic surfactant above a temperature of 80 ° C is not economically feasible and does not make any positive changes, in addition, volatile substances that have an unpleasant odor and are harmful to health can evaporate from a nonionic surfactant.

The resulting hot liquid components are mixed with a stirrer in the ratio of nonionic surfactant: true urea solution (parts by weight) equal to 1: 1.0-1.4, respectively. With a decrease in the content of nonionic surfactant, the urea content increases, as a result of which the absolute endurance and strength properties of the solid foaming agent decrease. Urea, which is a rapidly dissolving surface-indifferent substance, leads to a decrease in the absolute tolerance. From the content of non-ionic surfactants, the active part of the solid foaming agent, the volume of liquid ( _Vl ), which can be carried out by the unit mass (m) of the solid foaming agent, depends. The decrease in the content of nonionic surfactant requires the introduction of a larger mass of solid foaming agent into the well to carry the same amount of fluid, which subsequently leads to an excessive consumption of solid foaming agent and reflects a low absolute capacity. With an increase in the urea content, the dissolution rate of the solid foaming agent increases, and as a result, a solution with an excess concentration of nonionic surfactant is formed at the initial time, which will be carried out in the first portions of the resulting foam by an upward gas flow. The efficiency of the process is reduced not only due to the overconsumption of the solid foaming agent, but also due to the reduction of the inter-operational period, since the process of fluid flow into the well is often continuous, and a high dissolution rate reduces the duration of the action of the solid foaming agent. An increase in the content of urea, which is an anisotropic crystalline substance, gives the solid foaming agent brittleness (bending strength decreases), which can lead to the destruction of the solid foaming agent during transportation or falling into the well. The increase in the content of nonionic surfactants adversely affects the strength properties of solid blowing agents. The resulting solid foaming agent becomes more ductile (compressive strength decreases), since this amount of urea is not enough to cure a nonionic surfactant. At this stage, urea adduct is formed. The formation of a fine-crystalline structure is achieved due to the fact that the formation of the urea adduct comes from a system with a high specific contact surface between the components using condensation (creating supersaturation). Due to the high specific contact surface of the mixture components, the process of physicochemical adsorption interaction between urea and nonionic surfactant molecules with the formation of a urea adduct proceeds uniformly, quickly and completely. When a true urea solution is injected into a nonionic surfactant, the latter is slightly cooled, which is the driving force of the crystallization process. Since the internal energy of a liquid is higher than that of an ordered solid, the crystallization process is accompanied by the release of heat. The temperature of the mixture rises, which prevents the formation of large crystals of urea adduct. The nucleation of crystals is heterogeneous, since "active" urea molecules, due to mutual physicochemical adsorption with nonionic surfactant molecules, form a large number of urea adduct crystals over the entire volume of the mixture. Each nonionic surfactant molecule can be considered as an active crystallization center, since it has a lower temperature than urea molecules, thereby creating supersaturation around itself. As a result, “active” urea molecules located in close proximity give up part of their internal energy, turning into a crystalline state, form a hexagonal spatial structure around a nonionic surfactant molecule, that is, they form a urea adduct. In addition, technical components may contain impurities, that is, additional centers of crystallization.

As a result, we obtain a liquid-crystal mixture consisting of a large number of small crystals of urea adduct throughout the volume, which positively affects the crystallization of the mixture (a fine-crystalline structure is formed) and the strength properties of the solid foaming agent.

A water-soluble polymer in a weight ratio of 1: 0.01-0.05, respectively, or a mixture of a water-soluble polymer and a dissolution retardant in a weight ratio of is added to the resulting liquid crystal mixture. liquid crystal mixture of components: water-soluble polymer: dissolution retardant, 1: 0.01-0.05: 0.4-0.6, respectively. With a decrease in the content of a water-soluble polymer, the absolute endurance decreases, the strength properties of the solid foaming agent deteriorate, since water may remain unbound. An increase in the content of water-soluble polymer increases the viscosity of the foam, which negatively affects the absolute carrying capacity of the solid foaming agent (the transporting function of the foam is reduced), it is also not economically feasible. With a decrease in the water-soluble polymer and the dissolution retardant, the absolute tolerance decreases as the dissolution rate increases. An increase in the content of a water-soluble polymer and a dissolution inhibitor leads to the fact that the resulting mixture is very difficult to form, the absolute endurance of the solid foaming agent decreases due to an increase in the viscosity of the foam (the transporting function of the foam decreases), which can lead to an increase in hydraulic resistance in the pipeline. In this case, the water-soluble polymer has the most negative effect on the viscosity of the foam, the dissolution retardant does not have a significant effect on the rheological properties of the foams, but with an excess makes molding difficult. A water-soluble polymer and a dissolution retardant increase the strength properties (bind free water to form a single structure) and improve the absolute hardness of the solid foaming agent, as they reduce the dissolution rate of the latter and contribute to the process of emulsification of gas condensate and foam stabilization. A water-soluble polymer and a dissolution retardant also serve as additional crystallization centers, which further contributes to the formation of a fine crystalline structure.

A mixture is fed into the former, which is squeezed into the polyethylene sheath of the required diameter and length. The molded mixture is suspended in a vertical position to avoid deformation, which upon cooling finally crystallizes and hardens. Due to the fact that the moldable mixture has a large number of urea adduct crystals throughout the volume, a single solid fine crystalline structure is formed upon cooling and final crystallization.

High strength properties are of great importance during transportation and in the process of introducing a solid foaming agent into the well. When falling from the upper point of the lubricator to the locking wedge of the buffer valve (distance is about 1.0-1.5 m) and impacts on the walls of the elevator pipes, a solid foaming agent with insufficient bending strength (brittle) may crumble, lose a single structure and not reach the accumulated liquid . In addition, most of the wells in operation are deep and inclined, a solid foaming agent with insufficient compressive strength (plastic) can deform and adhere to the tubing, which can cause high hydraulic resistance in the tubing. Therefore, high strength properties are an important indicator of a solid foaming agent.

Reaching the liquid, solid blowing agents interact with water dipoles and begin to dissolve. Dissolution occurs slowly, therefore, a nonionic surfactant is slowly released, which allows the concentration of the foaming agent to be maintained at the critical micelle concentration for a long time, while obtaining the maximum volume of foam, that is, the volume of liquid _transferred (V _w ) _per unit mass of the solid foaming agent (m). Emulsification of gas condensate is the initial and determining stage of foaming of gas condensate mixtures. Adsorption of a nonionic surfactant on the surface of a gas condensate leads to the formation of a hydrophilic emulsion (dispersed medium — an aqueous solution and two dispersed phases — gas and gas condensate). The activity of a nonionic surfactant in mineralized water does not decrease, since complexes with calcium and magnesium ions are formed. These complexes, adsorbed at the phase boundaries, form a strong adsorption layer of a nonionic surfactant. In addition, water-soluble polymers and lignosulfonates (a dissolution retardant) participate in the formation, which strengthens the adsorption layer of the emulsifier, thereby increasing the absolute capacity of the solid foaming agent.

Before the solid foaming agent is introduced into the well, interval measurements of pressure and temperature are performed by devices, its productivity and the volume of liquid removed by the gas are determined. After analysis of the data obtained, the required amount of solid foaming agent is calculated to completely remove the fluid accumulated in the well.

The amount of solid foaming agent introduced into the well depends on the volume of accumulated liquid, the content of nonionic surfactant in the solid foaming agent and the mass of the latter and is calculated by the formula:

where n is the number of rods of a solid foaming agent needed to remove the liquid, pcs .;

V _W - the volume of accumulated liquid in the column of elevator pipes and the perforation interval, m ³ ;

ν _a is the absolute capacity of the solid foaming agent, m ³ / kg;

a - the content of nonionic surfactants in the solid foaming agent, wt.%;

m is the mass of one solid foaming agent, kg

It follows from the formula that an increase in absolute endurance leads to a decrease in the amount of solid blowing agents necessary to remove fluid from the well. An insufficient amount of solid blowing agents can lead to the fact that part of the fluid in the well remains unexposed. An excessive amount of solid blowing agents slows the well’s output to normal operation, since a viscous foam is formed, which creates a high resistance to gas flow in the tubing.

Based on the analysis of patent documentation and scientific and technical literature, we have not identified the operation or their combination of the distinctive part of the claims of a method for producing a solid foaming agent for removing liquid from wells that perform functions similar to those claimed in the technical result. In this regard, we believe that the proposed technical solution has an inventive step.

For testing, the problematic well of the Yamburg gas condensate field No. 101.3 was selected - vertical. The mineralization of water discharged from the well is 2564.33 mg / l (Ca ²⁺ + Mg ² = 70 mg / l). The volume of liquid removed (V _g ) is 0.78 m ³ , the weight of one solid foaming agent is 0.6-0.7 kg, the content of nonionic surfactant is 47.6-57.8 wt.% (In solid foaming agents using a water-soluble polymer) and 35.4-41.4 wt.% (In solid blowing agents using a water-soluble polymer and a dissolution retardant). According to the formula, the optimal amount of solid foaming agent was calculated and introduced (1 pc using a water-soluble polymer, 2 pc using a water-soluble polymer and a dissolution retardant). To prevent freezing in fountain fittings and tubing used solid foaming agents with a diameter of 50 mm and a length of 400 mm. As a result of introducing solid blowing agents, the accumulated liquid was completely removed, and an increase in gas flow rate of 155 thousand m ³ / day was obtained.

In more detail, the essence of the claimed technology is described by the following examples.

Example 1

Urea in the amount of 117 g (9 parts by weight) is dissolved in 13 g (1 parts by weight) of water heated to 50 ° C. The resulting mixture was continued to warm until a true urea solution (106 ° C) was obtained. Next, neonol in the amount of 182 g (1.4 parts by weight) is heated to 60 ° C and mixed with 130 g (1 parts by weight) of a true urea solution. A liquid crystal mixture is obtained. 312 g (1 parts by weight) of the liquid crystal mixture are mixed with 3.1 g (0.01 parts by weight) of polyacrylamide. The resulting mixture is molded and squeezed into a polyethylene shell 16 cm long and 5 cm in diameter.

Test the resulting solid foaming agent as described in the laboratory test report. The absolute tensile strength of 0.65 m ³ / kg, compressive strength - 1.1 MPa, bending - 2.2 MPa.

Example 2

Urea in the amount of 130 g (10 parts by weight) is dissolved in 13 g (1 parts by weight) of water heated to 60 ° C. Next, the operation is carried out as described in example 1. OP-10 in an amount of 172 g (1.2 parts by weight) is heated to 50 ° C and mixed with 143 g (1 parts by weight) of a true urea solution. A liquid crystal mixture is obtained. 315 g (1 part by weight) of the liquid crystal mixture are mixed with 9.4 g (0.03 parts by weight) of polyvinyl alcohol. Next, carry out the operation as described in example 1.

Absolute tensile strength 0.53 m ³ / kg, compressive strength 1.0 MPa, bending 2.1 MPa.

Example 3

Urea in the amount of 135 g (9 parts by weight) is dissolved in 15 g (1 parts by weight) of water heated to 70 ° C. Next, the operation is carried out as described in example 1. Next, the operation is carried out as described in example 1. The block copolymer of ethylene oxide and propylene in an amount of 150 g (1.0 parts by weight) is heated to 70 ° C and mixed with 150 g (1 parts by weight) of a true urea solution. A liquid crystal mixture is obtained. 300 g (1 part by weight) of the liquid crystal mixture are mixed with 15.0 g (0.05 parts by weight) of carboxymethyl cellulose. Next, carry out the operation as described in example 1.

Absolute tensile strength 0.55 m ³ / kg, compressive strength - 1.7 MPa, bending - 3.7 MPa.

Example 4

Urea in the amount of 99 g (9 parts by weight) is dissolved in 11 g (1 parts by weight) of water heated to 80 ° C. Next, the operation is carried out as described in example 1. OP-10 in an amount of 110 g (1.0 parts by weight) is heated to 40 ° C and mixed with 110 g (1 parts by weight) of a true urea solution. A liquid crystal mixture is obtained. 220 g (1 parts by weight) of the liquid crystal mixture are mixed with 2.2 g (0.01 parts by weight) of polyacrylamide and 88.0 g (0.4 parts by weight) of KSSB - 2. Then, operations are carried out as follows: as indicated in example 1.

Absolute tensile strength 0.60 m ³ / kg, compressive strength - 2.0 MPa, bending - 3.4 MPa.

Example 5

Urea in the amount of 90 g (10 parts by weight) is dissolved in 9 g (1 parts by weight) of water heated to 90 ° C. Next, the operation is carried out as described in example 1. The block copolymer of ethylene oxide and propylene in an amount of 119 g (1.2 parts by weight) is heated to 80 ° C and mixed with 99 g (1 part by weight) of a true solution urea. A liquid crystal mixture is obtained. 218 g (1 part by weight) of the liquid crystal mixture are mixed with 6.5 g (0.03 parts by weight) of polyvinyl alcohol and 108.9 g (0.5 parts by weight) of KSSB - 5. Next, the operations are carried out as follows as indicated in example 1.

The absolute tensile strength is 0.57 m ³ / kg, compressive strength - 2.2 MPa, bending - 5.6 MPa.

Example 6

Urea in an amount of 80 g (10 parts by weight) is dissolved in 8 g (1 parts by weight) of water heated to 70 ° C. Next, the operation is carried out as described in example 1. Neonol in an amount of 123 g (1.4 parts by weight) is heated to 60 ° C and mixed with 88 g (1 parts by weight) of a true urea solution. A liquid crystal mixture is obtained. 211 g (1 part by weight) of the liquid crystal mixture are mixed with 10.6 g (0.05 parts by weight) of carboxymethyl cellulose and 126.7 g (0.6 parts by weight) of PRS. Next, carry out the operation as described in example 1.

Absolute tensile strength 0.66 m ³ / kg, compressive strength - 1.8 MPa, bending - 3.6 MPa.

In fact, an excess of the technical parameters of the solid foaming agent obtained by the claimed technology is observed over the indicators of the solid foaming agent obtained by the prototype.

Thus, the claimed technical solution meets the conditions of novelty, inventive step and industrial applicability, i.e. is patentable.

Claims (4)

1. A method of obtaining a solid foaming agent for removing liquid from gas and gas condensate wells, comprising mixing a nonionic surfactant surfactant and a carbonic acid derivative containing nitrogen, and forming the resulting mixture, characterized in that use is made of a carbonic acid derivative containing nitrogen, urea, which is additionally dissolved in water heated to 50-90 ° C, in a ratio (wt.h) equal to 9-10: 1, respectively, followed by heating the mixture to obtain a true solution, a nonionic surfactant is heated to 40-80 ° C and mixed with a true urea solution in a ratio (parts by weight) of 1.0-1.4: 1, respectively; moreover, before molding, a water-soluble polymer in the ratio ( parts by weight) equal to 1: 0.01-0.05, respectively, or a mixture of a water-soluble polymer and a dissolution retardant in the ratio (parts by weight) liquid crystal mixture of components: water-soluble polymer: a dissolution retardant equal to 1: 0.01-0, 05: 0.4-0.6, respectively. 2. The method according to claim 1 _; characterized in that as a nonionic surfactant use reagents selected from the group: neonol, OP-10, block copolymers of ethylene and propylene oxides. 3. The method according to claim 1, characterized in that as a water-soluble polymer using reagents selected from the group: carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol. 4. The method according to claim 1, characterized in that lignosulfonates are used as a dissolution retardant.

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