Blocking composition for killing wells and method for producing same

Abstract

The group of inventions relates to the field of oil and gas production, and more particularly to technology for killing wells at oil and gas fields. The technical result of the group of inventions is that of simplifying the process of repairing wells, as well as improving the efficiency with which wells are killed at various fields across a wide range of reservoir temperatures (from 40 to 105°С) and for different periods of time (depending on the type of well repair). The technical result is achieved in that a composition for killing wells, which is provided in the form of a self-destructing polymer with a three-dimensional structure and is produced by mixing a monomer, a crosslinker and an initiator in water and by subsequent drying, is characterized by a water swelling index (α) of not less than 4 on the first day at a temperature of 40°C or more.

Description

[0001] BLOCKING COMPOSITION FOR SHUTTING DOWN WELLS AND A METHOD FOR ITS MANUFACTURING

[0002] The group of inventions relates to the oil and gas production field, namely to the technology of killing wells at fields, including those complicated by abnormally low reservoir pressures, as well as other development sites, and can be used in well repair.

[0003] In the last decade, there has been a tendency to develop various compositions / formulations for the oil and gas industry, including pre-crosslinked gel particles obtained from a monomer and a crosslinker by means of an initiator. For example, a composition is known that is used in the implementation of methods for increasing oil recovery, in particular in the implementation of secondary and tertiary oil production methods (Patent of the Russian Federation No. 2630543, published on 11.09.2017), comprising: expandable polymer microparticles comprising acrylamide-based polymers cross-linked using unstable cross-linking agents and stable cross-linking agents; wherein said acrylamide-based polymers have the ability to undergo a transamidation reaction; wherein said microparticles are mixed with a liquid and an unreacted tertiary cross-linking agent that comprises polyethyleneimine PEI ("PE1"); and the tertiary cross-linking agent has the ability to further covalently cross-link said microparticles via a transamidation reaction at a temperature of from 65.56 to 87.78 °C after the unstable cross-linking agent is destroyed to form a stable gel.

[0004] A composition is known, also used in the implementation of methods for enhancing oil recovery, in particular in the implementation of secondary and tertiary oil production methods (B. Bai, J. Zhou, Y. Liu. Thermo-Dissoluble Polymer for In-Depth Mobility Control. 2013. https: / / doi.org / 10.2523 / IPTC-16991-MS), obtained using a monomer represented by acrylamide and acrylic acid, a crosslinker represented by polyethylene glycol and [NbF-methylenebisacrylamide, and an initiator represented by [NHK,]'-tetramethylethylenediamine and potassium persulfate.

[0005] It should be emphasized that the above-described variants of compositions / compositions are characterized by a limited scope of application and are used for a specific purpose, in particular, when implementing methods for increasing oil recovery. In addition, there are known cementing compositions that include pre-crosslinked gel particles, which are most widely used in the construction of oil and gas wells in the technological process of their cementing. For example, a high-temperature-resistant cementing composition is known (Chinese Patent Application No. 109280542 (A), published on January 29, 2019), comprising 2 to 5 wt.% polysaccharide, 0.01 to 0.025 wt.% initiator, 20 to 25% low-molecular monomer, 1.2 to 1.5 wt.% crosslinking agent A, 1.3 to 1.7 crosslinking agent B, 0.04 to 0.1 wt.% hardener, 0.03 to 0.3 wt.% pH maintainer, and the rest is water.

[0006] The described cement composition is characterized by a limited scope of application, and is used in drilling and completing wells in the temperature range from 100 to 150 °C. In turn, the use of the above composition in the implementation of the well killing process is ineffective and labor-intensive, since the subsequent launch of the well will be complicated, and in some cases impossible, at least due to the difficulty of removing the cement composition from the well after the killing operations.

[0007] It should be emphasized that the use of well blocking and killing compounds allows for a certain period of time to create back pressure on the formation to stop the production of formation fluid for the purpose of wellbore repair. Moreover, the analysis of the mining and geological conditions of well operation at large oil and gas condensate fields in the Russian Federation has shown that traditional killing compounds / fluids used in the initial period of field development are of little use and ineffective at a late stage of operation, especially at abnormally low formation pressures (ALRP). Since high infiltration of these compounds / fluids under conditions of high repression contributes to the formation of a significant zone of their penetration into the formation, which sharply worsens the filtration characteristics of the formation and creates a number of difficult-to-solve problems during well development after repair.In addition, in some cases, well killing with traditional well killing compounds / fluids is not possible, since they are absorbed in the highly drained interval of the perforation zone, followed by gas production from less drained intervals and gas breakthrough at the wellhead, which necessitates repeated well killing operations.

[0008] In this regard, for well killing in fields complicated by abnormally low formation pressures, compositions are being developed, the use of which, firstly, ensures stable temporary isolation of productive formations, and secondly, minimizes any negative impact on the bottomhole formation zone for subsequent well commissioning after technological killing operations. For example, a blocking fluid for well killing with abnormally low formation pressure is known (Patent of the Russian Federation No. 2373252, published on 20.11.2009), containing an acyclic acid expressed by the formula SpNgp т Og, where T is 2 or 4 or 6, a carbon-chain polymer, caustic soda, a hydrophobic mineral filler and gas condensate, with the following ratio of components, vol.%: the specified acyclic acid from 18.0 to 24.0 carbon-chain polymer from 2.0 to 3.0 caustic soda from 13.1 to 15.0 hydrophobic mineral filler from 30.0 to 50.0 gas condensate - the rest.

[0009] The disadvantage of the known technical solution is the low reliability of the blocking fluid when killing wells with an open and extended horizontal section of the wellbore with fractured carbonate reservoirs during ANRP, since the filter cake formed after killing the well does not ensure the formation of a reliable screen due to the hydrostatic effect of the wellbore liquid column, caused by the low anomaly coefficient.

[0010] Also known is a fluid for killing and completing wells with abnormally low formation pressures (RU Patent No. 2379325, published on 20.01.2010), containing a hydrocarbon base, a fatty acid, a mineral filler - calcium carbonate, wherein in a mixture with a fatty acid it contains a cyclic acid and additionally contains caustic soda in the following ratios of components, wt.%: hydrocarbon base from 46 to 68, acid mixture from 14.1 to 18, caustic soda from 8 to 13, the said mineral filler is the rest.

[0011] A significant drawback of the known technical solution is the limited use of the killing fluid, since its use is only possible for high-temperature wells (from 80 to 130 °C). Another drawback is the use of 8 to 13 wt.% caustic soda in the composition of the described fluid, which is an aggressive substance for both humans and the environment (second hazard class according to GOST 12.1.005-76).

[0012] A viscoelastic composition for killing wells is known (Patent of the Russian Federation No. 2575384, published on 20.02.2016), including cellulose ether, alkali metal hydroxide, complexing agent, internal destructor and water, wherein the composition contains a soluble salt of aluminum or copper as a complexing agent, an internal destructor - encapsulated percarbonate or sodium perborate and an additional weighting agent - sodium chloride or potassium chloride, or calcium chloride, or sodium nitrate, or MNC reagent (active ingredient - calcium and magnesium salts), pH regulator acetic acid or oxalic acid, or citric acid and a water-retaining hydrophobizing additive - ethylene glycol and / or glycerin, or higher dioxane alcohols.

[0013] The disadvantage of the known technical solution is the lack of self-destruction of the viscoelastic composition (VUS) for killing wells, since the process of destruction of the VUS occurs only after additional injection of an activating composition containing citric or sulfamic acid, potassium persulfate or ammonium persulfate or urea peroxyhydrate, a non-ionic surfactant - Neonol AF9-12 or Sinoksol brand B or Reversmol brand B, a demulsifier - Dissolvan 4411 or SNPKh-4802 and water, initiating the action of the internal destructor (encapsulated percarbonate or sodium perborate) in the viscoelastic composition.

[0014] A common significant drawback of the well-killing fluids known from the state of the art, in particular, with abnormally low formation pressures, and, in particular, the technical solutions described above, is the limited use of the well-killing fluid, since their use is mainly possible only in a narrow temperature range. Another significant drawback is the lack of self-destruction (self-destruction) of the compositions / fluids for killing, namely, the compositions described above are characterized by periods of action, during which high structural and mechanical properties of the well-killing fluids are preserved after well repair. As a result, it is not possible to qualitatively remove the well-killing fluid in full after well killing and prevent the existing risks of well loss after repair.In addition, it is not possible to destroy known compositions after well repair without containing a destructor in the blocking composition, or without introducing it into the well in a separate batch after the well killing operation.

[0015] In this regard, researchers are increasingly interested in well-killing blocking compounds that have the property of self-destruction (self-destruction). Thus, some researchers are known to have attempted to develop well-killing compounds that have the property of self-destruction (self-destruction) after a certain period of time. For example, a solution of inverted emulsion for well-killing is known (Patent of the Russian Federation No. 2499131, published on 20.11.2013), containing an oily continuous phase, a non-oily dispersed phase, an emulsifying agent, at least one decomposable material and at least one plugging agent. A method for treating a subterranean formation includes: pumping an inverted emulsion wellbore kill solution into a cased, perforated wellbore that intersects the formation, contacting the formation with the wellkill solution, and allowing the degradable material to at least partially decompose.

[0016] However, the known technical solution has a number of significant disadvantages. Firstly, it is a limited area of ​​application, in particular, the applicability of the decomposable material is possible only in the temperature range from 79 to 149 ° C. Secondly, the insufficient efficiency of well killing using the described composition, since unstable crosslinkers are used in the composition, which leads to low efficiency of well killing with insufficient laboratory study of the agent's properties under the target killing conditions.

[0017] The closest technical solution in terms of the set of essential features to the claimed invention is a well killing composition, a method for its preparation and a method for killing a well using the composition (Patent of China No. 105041261, published on 11.11.2015), adopted as a prototype. The composition is a gel based on a monomer, a crosslinker and an initiator, wherein the mass ratio of the monomer and the crosslinking agent is from 5: 1 to 20: 1. Polyacrylamide or acrylamide copolymer is selected as the monomer, chromium acetate, chromium lactate, aluminum citrate, organic zirconium, hexamethylenetetramine, formaldehyde, phenolic resin or polyethyleneimine are selected as the crosslinker.The composition also represents gel particles obtained by copolymerization of acrylamide monomer with auxiliary monomers, wherein the crosslinking monomer is represented by ethylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate or pentaerythritol tetraacrylate, the auxiliary monomer is represented by 2-acrylamide-2-methylpropanesulfonate sodium N-vinylpyrrolidone, sodium styrene sulfonate or maleimide. The method of preparing the composition consists in that the polymer is taken in a weight ratio of 5: 1 to 20: 1 to the crosslinker depending on the temperature and pressure in the well and the mixture is brought to a homogeneous state. In this case, a specific embodiment of the preparation method includes mixing a salt-resistant polymer and a crosslinker - chromium acetate, in a polymer and crosslinker ratio of 8: 1.The method of killing wells using the described composition includes a stage of calculating the required flow rate of well killing fluid depending on the well volume; a stage of determining the density of the well killing fluid; a stage of determining the formula of the polymer gel; a stage of preparing the well killing fluid, represented by a monomer and a crosslinker with a mass ratio of monomer and crosslinker of 5:1 to 20:1; a stage of pumping the well killing fluid into the well.

[0018] A significant drawback of the known technical solution is the low reliability of the composition when killing wells, including at abnormally low reservoir pressures, since the composition is fed into the well immediately after its preparation without any preparatory operations, such as drying, which leads to low efficiency of its action when killing due to its low swelling coefficient, which ultimately leads to the occurrence of gas-oil-water show (GOWS) and the need to carry out repeated well killing operations. Another drawback is the narrow temperature range of application of the described composition (in the examples of implementation, reservoir temperatures from 25 °C to 35 °C are declared), as well as its low efficiency at large pressure drops, due to its low strength.In addition, the mass ratio of monomer and crosslinking agent from 5:1 to 20:1 is not rational, since in a given range the resulting polymer has low strength and brittleness, which ultimately leads to low efficiency of well killing, accompanied by the occurrence of gas-oil-gas mixture.

[0019] The technical problem that the group of inventions is aimed at solving is the need to improve the performance characteristics of well killing compounds, as well as to simplify the well repair process and increase its efficiency.

[0020] The technical result of the group of inventions is the simplification of the well repair process and the increase in the efficiency of well killing at various fields in a wide range of formation temperatures (from 40 to 105°C) and various time intervals (depending on the type of well repair) while ensuring high productivity of the process of removing the blocking composition after well repair and reducing the time it takes to bring the well into operation.

[0021] An additional technical result of the group of inventions consists in the possibility of increasing the accuracy of regulating the well shutdown time, which can be set depending on the type of well repair, and which is ensured by the time of preservation of the structural and mechanical properties of the composition for killing, after which it self-destructs without introducing a destructor, as well as without additional injection of an activating composition into the well.

[0022] The technical result is achieved due to the fact that the composition for killing wells, represented by a self-destructing polymer of a three-dimensional structure, obtained by mixing a monomer, a crosslinker and an initiator in water, and subsequent drying, is characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more.

[0023] The technical result is achieved due to the fact that a method is implemented for preparing a composition for killing wells, represented by a self-destructing polymer of a three-dimensional structure with a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more, in which a monomer, crosslinker and initiator are mixed in water, after which drying is carried out, wherein the quantitative ratio of the crosslinker, initiator and monomer is, by weight %: crosslinker from 0.25 to 3.16; initiator from 0.1 to 0.99; monomer is the rest, and the amount of water to the total mass of the monomer, crosslinker and initiator is selected from the range from 1 to 4.9 to 1.

[0024] The technical result is achieved due to the fact that a well killing composition is used, in which an inert carrier is pumped into the well with a well killing composition, represented by a self-destructing polymer of a three-dimensional structure, obtained by mixing a monomer, a crosslinker and an initiator in water, and subsequent drying, characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more, and then water is pumped in.

[0025] In the context of the present invention, a crosslinker should be understood to mean at least one substance, a monomer compound, which enters into a polymerization reaction and imparts a three-dimensional structure to the resulting self-destructing polymer, i.e. a compound that is capable of forming crosslinks of polymer chains.

[0026] In the context of the present invention, an initiator should be understood to mean at least one substance capable of starting a radical polymerization reaction, i.e. a substance that easily decomposes into free radicals.

[0027] In the context of the present invention, the monomer should be understood as at least one low-molecular compound capable of entering into a radical polymerization reaction to form a high-molecular polymer. The claimed well killing composition is represented by a self-destructing polymer of a three-dimensional structure obtained by mixing a monomer, a crosslinker and an initiator in water, and subsequent drying, characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more.

[0028] The technical result is achieved due to the fact that the well killing composition is characterized by a list of components: monomer, crosslinker and initiator, providing the formation (in the process of mixing the components and subsequent drying) of a self-destructing polymer of a three-dimensional structure, characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more. The technical result is achieved due to the fact that the resulting polymer (well killing composition) is dry, and when swelling in water, after its injection into the well, is characterized by a given swelling coefficient (a), which ensures the necessary swelling pressure, allowing to block (ensure killing) the well.Thus, when the described polymer is pumped into a well in an inert carrier, and water is subsequently added, the polymer swells in the well, which ensures the creation of the pressure necessary for killing (blocking) the well, depending on the swelling coefficient of the composition used.

[0029] Thus, by means of a crosslinker in the declared compositions for killing wells, the connection of polymer chains and imparting a three-dimensional structure to the synthesized material with different sizes of three-dimensional cells and their different ability to decompose are ensured. The initiator ensures the excitation of radical polymerization and crosslinking of the three-dimensional structure of the composition. The monomer ensures the formation of a polymer chain capable of effectively absorbing surrounding water and swelling.

[0030] The declared well-killing composition is dry, which is achieved by drying the resulting composition (mass) after mixing the components in water, i.e. the residual moisture content in the well-killing composition does not exceed the specified percentage of water. In turn, the dry well-killing composition is characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more.The stated lower limit of the swelling coefficient in water (a) is determined by the achievability of the technical result, in view of the fact that the particle sizes of the water-swelling composition for killing wells and the sizes of the pore channel of the oil reservoir reach a critical ratio for colmatation (blocking) of the reservoir rock at a value of a of at least 4, in this case an increase in the particle sizes of the composition (during swelling) is ensured, at which they become larger than the sizes of the pore channel / crack width, which ultimately leads to an increase in the efficiency of the well killing process at various fields in a wide range of reservoir temperatures (from 40 to 105° C) and various time intervals.If the swelling coefficient in water (a) is less than 4, the technical result is not achieved, since in this case the swelling of the composition (increase in the size of the composition particles) is insufficient for well killing, which makes it impossible to provide sufficient pressure on the formation and to perform its colmatation and blocking. It should also be emphasized that the specified value of the swelling coefficient in water (a) of 4 or more is the most rational for effective well killing and blocking, since in this case it is necessary to supply a smaller amount of blocking composition in an inert carrier when implementing the well killing method than when killing wells with a composition with a swelling coefficient in water (a) of less than 4.

[0031] The swelling coefficient in water (a) of the well killing composition is determined after adding water to it (for example, distilled water, formation water model, etc.) and its subsequent swelling at a temperature of 40°C or more, after which the mass m (g) and volume g (m) are measured. 3 ) of the swollen final product. The swelling coefficient of the composition for suppression is determined by mass and volume methods according to the following formulas: where a т — the swelling coefficient of the composition, determined by the mass method; to is the mass of the sample of the composition for killing, before adding water, g; sh is the mass of the sample of the composition for killing, after adding water, g; where a v — swelling coefficient of the composition, determined by the weight method; vo — volume of the composition for killing, before adding water, m 3 ; v - volume of the killing composition after adding water, m 3 .

[0032] The value of the swelling coefficient a is determined as the arithmetic mean between the values ​​of a т and a v . Determining the swelling coefficient in water (a) on the first day means that measurements are taken at a given temperature after 24 hours have passed since water has been added to the well-killing composition. It is important to note that for the declared compositions at a temperature of 40°C or more, a swelling coefficient in water (a) of at least 4 can be achieved before 24 hours have passed, since the swelling rate of the compositions during their interaction with water may differ depending on the specific composition. After 24 hours, the value of the swelling coefficient in water (a) is the most indicative and characterizes the properties of the well-killing composition.

[0033] In one embodiment of the invention, the crosslinker in the composition may be at least one substance selected from a group of compounds with two reactive multiple chemical bonds formed by residues of acrylic and methacrylic acid derivatives, for example, diethylene glycol diacrylate, N,N'-methylenebisacrylamide, monoethylene glycol diacrylate, polyethyleneglycol-400 diacrylate and other substances of this group known from the prior art. This is due to the fact that the use of substances from a given group makes it possible to obtain a polymer of a three-dimensional structure capable of swelling upon interaction with water, rather than dissolving.

[0034] In one embodiment of the invention, the initiator in the composition may be at least one substance selected from the group of free radical source compounds, for example, ammonium persulfate, potassium persulfate, sodium bisulfite, and other substances of this group known from the prior art.

[0035] In one embodiment of the invention, the monomer in the composition may be at least one substance selected from a group of compounds with one reactive multiple chemical bond located in the residue of acrylic acid and / or in the residue of methacrylic acid and / or in the residue of the vinyl fragment, for example, acrylamide, acrylic acid, methacrylic acid, and other substances of this group known from the prior art. This is due to the fact that the monomers of the given group absorb water to the required extent.

[0036] The above-listed embodiments of the invention and the features disclosed therein further enhance the achievement of the specified technical result.

[0037] In one embodiment of the invention, the composition for killing wells can be represented by particles with a fraction of no more than 1000 μm and, more specifically, a fraction of 400 to 800 μm, which improves the homogeneity of the composition and additionally increases the stability of the swelling and self-destruction process of the composition, which also additionally enhances the achievement of the specified technical result.

[0038] The technical result is achieved by the method of preparing a well killing composition, whereby a specified amount of monomer, crosslinker and initiator is mixed in water, with the amount of water to the total mass of monomer, crosslinker and initiator selected from the range from 1 to 4.9 to 1, after which drying is carried out. As a result, a well killing composition is obtained, represented by a self-destructing polymer of a three-dimensional structure with a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C and more.

[0039] The amount of crosslinker disclosed in the method for preparing the well killing composition is from 0.25 to 3.16 wt.%. The destruction time of the well killing composition and its swelling depend on the structure and amount of crosslinker. It should be noted that exceeding the specified amount of crosslinker (more than 3.16 wt.%) leads to the formation of too many dense three-dimensional mesh structures with a very small pore size. The resulting rigid and dense structure creates steric hindrances to the expansion of the composition and prevents water from entering the three-dimensional polymer network. At the same time, reducing the specified amount of crosslinker (less than 0.25 wt.%) leads to softening of the gel-like mass (polymer of the three-dimensional structure) and a decrease in its stability (a decrease in the destruction time).

[0040] The amount of initiator disclosed in the method for preparing the well killing composition is from 0.1 to 0.99. When the amount of initiator is reduced (less than 0.1 wt.%), the amount of radicals formed in the reaction system is reduced, while the efficiency of forming a three-dimensional polymer network between the selected monomers does not decrease. It should be noted that an excess amount of initiator (more than 0.99 wt.%) increases the amount of cross-links and, therefore, leads to a decrease in the three-dimensional network (cells) and a decrease in the swelling value of the well killing composition.

[0041] With a decrease in the monomer concentration, the swelling volume of the composition gradually increases, but the total self-destruction time gradually decreases.

[0042] With the specified ratios of components, it is possible to obtain a well-killing composition characterized by the specified swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more. It is important to emphasize that the quantitative composition of the finished well-killing composition (polymer) differs from the quantitative composition used for its preparation, which is understandable to a specialist in this field of technology, and is due to the fact that in the resulting polymer all components are in a form bound by new chemical bonds, and not in their original form. The declared amount of water to the total mass of the monomer, crosslinker and initiator, specified in the range from 1 to 4.9 to 1, ensures the formation of a self-destructing polymer of a three-dimensional structure with sufficient strength.At a ratio of less than 1 to 1, the resulting polymer is quite rigid and brittle, and at a ratio of more than 4.9 to 1, the resulting polymer is quite liquid and loose, which ultimately affects the efficiency of well killing, since in the first case, the polymer can break due to its increased brittleness, and in the second case, the polymer does not meet the requirements for swelling in water (a).

[0043] In the method of preparing the composition for killing wells, a monomer, crosslinker and initiator are added to the water. It is worth noting that this sequence of adding components to the water can be changed.

[0044] The drying stage in the claimed method is aimed at removing water from the resulting composition, which is represented by a self-destructing polymer of a three-dimensional structure with a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more.

[0045] The above-described features are essential and ensure the achievement of the stated technical result, which consists in simplifying the well repair process and increasing the efficiency of well killing at various fields in a wide range of reservoir temperatures (from 40 to 105 °C) and various time intervals (depending on the type of well repair) while ensuring high productivity of the process of removing the blocking composition after well repair and reducing the time it takes to bring the well into operation.

[0046] In one embodiment of the invention, the crosslinker in the method may be at least one substance selected from a group of compounds with two reactive multiple chemical bonds formed by residues of acrylic and methacrylic acid derivatives, for example, diethylene glycol diacrylate, T4, T4'-methylenebisacrylamide, monoethylene glycol diacrylate and other substances of this group known from the prior art. This is due to the fact that the use of substances from a given group makes it possible to obtain a polymer of a three-dimensional structure capable of swelling upon interaction with water, rather than dissolving.

[0047] In one embodiment of the invention, the initiator in the method may be at least one substance selected from a group of free radical sources, such as ammonium persulfate, potassium persulfate, sodium bisulfite, and other substances of this group known from the prior art. In one embodiment of the invention, the monomer in the method may be at least one substance selected from a group of compounds with one reactive multiple chemical bond located in the residue of acrylic acid and / or in the residue of methacrylic acid and / or in the residue of a vinyl fragment, such as acrylamide, acrylic acid, methacrylic acid, and other substances of this group known from the prior art. This is due to the fact that the monomers of a given group absorb water to the required extent.

[0048] The above-listed embodiments of the invention and the features disclosed therein further enhance the achievement of the specified technical result.

[0049] In one embodiment of the method, when adding monomer and crosslinker to water, the resulting solution can be stirred until the monomer and crosslinker are completely dissolved for at least 20 minutes. The stated mixing parameters ensure the homogeneity of the composition, which, in turn, enhances the achievement of the stated technical result.

[0050] In one embodiment of the method, after adding the monomer, crosslinker and initiator, before drying, the resulting composition (gel mass) can be ground using an extruder or other similar devices, due to which the homogeneity of the composition is additionally achieved, which, in turn, enhances the achievement of the declared technical result.

[0051] In one embodiment of the method, the drying of the resulting mass can be carried out at a temperature of 50 to 105 °C, using a drying cabinet or other similar devices, which also further increases the stability of the swelling and self-destruction process of the composition, which, in turn, enhances the achievement of the declared technical result. It should be noted that exceeding the specified temperature can lead to thermal destruction of the components of the composition and its subsequent unsuitability for use.

[0052] In one embodiment of the method, the drying of the resulting mass can be carried out until the residual moisture content is no more than 15%, which also further increases the stability of the swelling process and self-destruction of the composition for killing wells when implementing the method for killing wells, which, in turn, enhances the achievement of the declared technical result.

[0053] In one embodiment of the invention, the obtained mass can be crushed after drying, which also further improves the homogeneity of the composition, which, in turn, enhances the achievement of the claimed technical result. In this case, crushing can be carried out to a fraction of no more than 1000 μm. In a preferred embodiment, ensuring the highest homogeneity of the composition, crushing can be carried out to a fraction of 400 to 800 μm.

[0054] The achievement of the technical result is ensured by using a well killing composition, in which an inert carrier with a well killing composition is injected into the well, represented by a self-destructing polymer of a three-dimensional structure, obtained by mixing a monomer, a crosslinker and an initiator in water, and subsequent drying, characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more, and then water is injected.

[0055] When an inert carrier with a well-killing composition characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more is pumped into a well, its delivery to the pore channels of the oil formation is ensured. After that, water is pumped, by means of which the inert carrier is removed and contact of the particles of the well-killing composition with water is ensured, as a result of which swelling of the well-killing composition occurs, i.e. an increase in the composition in volume, and colmatation and blocking of the reservoir rock is ensured, i.e. well killing. It should be noted that an inert carrier should be understood as a carrier in which the well-killing composition does not swell, or the swelling is minimal. In one embodiment of the invention, the inert carrier can be selected from a group of hydrocarbon agents, for example, oil, diesel fuel and other hydrocarbon agents known from the prior art.

[0056] In one embodiment of the invention, after pumping an inert carrier with a well-killing composition, a hydrocarbon agent can be additionally pumped, which ensures that the well-killing composition does not interact prematurely with water before it is delivered to the required interval.

[0057] Thus, the group of inventions is characterized by a previously unknown set of essential features from the state of the art. Due to the presence of pre-crosslinked gel particles in the composition - transverse bridges based on monomers, a three-dimensional structure of the polymer is formed, which is able to effectively absorb surrounding water and swell. At the same time, due to the fact that these bridges are represented by ester or amide groups, under temperatures from 40 to 105 °C they are capable of self-destruction at a certain rate depending on the nature of these groups and their number in the composition, thereby leading to the transition of the three-dimensional structure of the polymer to a linear one with the loss of the original properties. In this regard, a specialist will understand what type of monomers can be selected to reduce or increase the stability time of the polymer depending on the temperature and type of water mineralization when killing a specific well.The claimed composition allows for effective well killing at fields, including those characterized by abnormally low reservoir pressures, for a specified time in the temperature range from 40 to 105 °C without additional introduction of a special destructor into the composition for killing, or without introducing a special destructor in a separate batch after killing. As a result, the technical result is achieved, consisting in simplifying the well repair process and increasing the efficiency of well killing at various fields in a wide range of reservoir temperatures (from 40 to 105 °C) and various time intervals (depending on the type of well repair) while ensuring high productivity of the process of removing the blocking composition after well repair and reducing the time for bringing the well to the operating mode.

[0058] The declared composition can be used, for example, for major repairs of wells (repair and insulation work, elimination of leaks in the production casing, elimination of the consequences of accidents, etc.); routine repairs of wells (replacement and / or restoration of parts of well equipment, transfer of wells to another method of operation, repair of flowing wells, etc.) and other types of well repairs.

[0059] A group of inventions can be made from known materials using known means, which indicates its compliance with the patentability criterion of “industrial applicability”.

[0060] The group of inventions possesses a set of essential features previously unknown in the state of the art, which indicates its compliance with the patentability criterion of “novelty”.

[0061] The essential features of the group of inventions are not known from the state of the art, and accordingly the effect of their application is not known. In view of this, the group of inventions meets the patentability criterion of "inventive step".

[0062] The inventions from the group of inventions are interconnected and form a single inventive concept, which indicates that the group of inventions meets the patentability criterion of "unity of invention". Below are specific examples of implementation that illustrate the claimed invention, but do not limit it and which can be changed or supplemented in any way.

[0063] In all the examples described below, the method for preparing the well killing composition was carried out using a process unit containing a reagent mixing tank equipped with raw material loading and unloading windows, a mechanical mixer, and a temperature sensor or thermometer. In addition, a drying cabinet was used.

[0064] Example 1. Water (60 g) was poured into a container for mixing reagents, then a mechanical stirrer was started and 20 g (98.77 wt.%) of monomer (acrylamide) were added to the water in the container with constant stirring. 0.05 g (0.25 wt.%) of crosslinker (methylenebisacrylamide) was added to the resulting solution in the container with constant stirring. The solution was stirred until the monomer and crosslinker were completely dissolved. Then 0.2 g (0.98 wt.%) of initiator (a mixture of ammonium persulfate and sodium bisulfite) were added to the solution with constant stirring. The specified amount of water to the total mass of crosslinker, initiator and monomer was 2.9 to 1. After obtaining the composition (gel mass), it was dried in a drying oven.

[0065] Example 2. The method for preparing the well killing composition is similar to that described in Example 1. 60 g of water were poured into a reagent mixing container, then a mechanical mixer was started and 20 g (95.88 wt.%) of monomer (a mixture of acrylamide and acrylic acid) were added to the water in the container with constant stirring. 0.66 g (3.16 wt.%) of crosslinker (monoethylene glycol diacrylate) were added to the resulting solution in the container with constant stirring. Then 0.2 g (0.96 wt.%) of initiator (ammonium persulfate) were added to the solution. The specified amount of water to the total mass of crosslinker, initiator and monomer is 2.8 to 1.

[0066] Example 3. The method for preparing the well killing composition is similar to that described in Example 1. Water (60 g) was poured into a reagent mixing container, then a mechanical mixer was started and 20 g (98.91 wt.%) of monomer (a mixture of acrylamide and methacrylic acid) were added to the water in the container with constant stirring. 0.2 g (0.99 wt.%) of crosslinker (methylenebisacrylamide) were added to the resulting solution in the container with constant stirring. Then 0.02 g (0.1 wt.%) of initiator (potassium persulfate) were added to the solution. The specified amount of water to the total mass of crosslinker, initiator and monomer is 2.9 to 1.

[0067] Example 4. The method for preparing the well killing composition is similar to that described in Example 1. Water (60 g) was poured into a reagent mixing container, then a mechanical mixer was started and 20 g (98.52 wt.%) of monomer (a mixture of acrylamide and acrylic acid) were added to the water in the container with constant stirring. 0.1 g (0.49 wt.%) of crosslinker (methylenebisacrylamide) was added to the resulting solution in the container with constant stirring. Then 0.2 g (0.99 wt.%) of initiator (ammonium persulfate) was added to the solution. The specified amount of water to the total mass of crosslinker, initiator and monomer is 2.9 to 1.

[0068] Example 5. The method for preparing the well killing composition is similar to that described in Example 1. 100 g of water were poured into a container for mixing reagents, then a mechanical mixer was started and 20 g (98.04 wt.%) of monomer (a mixture of acrylamide and acrylic acid) were added to the water in the container with constant stirring. 0.2 g (0.98 wt.%) of crosslinker (N,N'-methylenebisacrylamide) were added to the resulting solution in the container with constant stirring. Then 0.2 g (0.98 wt.%) of initiator (ammonium persulfate) were added to the solution. The specified amount of water to the total mass of crosslinker, initiator and monomer is 4.9 to 1.

[0069] Example 6. The method for preparing the well killing composition is similar to that described in Example 1. 22.5 g of water were poured into a reagent mixing container, then a mechanical mixer was started and 20 g (97.08 wt.%) of monomer (a mixture of acrylamide and acrylic acid) were added to the water in the container with constant stirring. 0.4 g (1.94 wt.%) of crosslinker (monoethylene glycol diacrylate) were added to the resulting solution in the container with constant stirring. Then 0.2 g (0.98 wt.%) of initiator (a mixture of ammonium persulfate and sodium bisulfite) were added to the solution. The specified amount of water to the total mass of crosslinker, initiator and monomer is 1 to 1.

[0070] Table 1 presents the well killing compositions described in examples 1-6. Table 1. Well killing compositions

[0071] The obtained compositions 1-6 were subjected to tests, during which the change in the swelling coefficient (a) of the compositions in water over time and the ability of the compositions to self-destruction at various operating temperatures, in particular at temperatures of 40°C, 60°C, 85°C and 105°C, were investigated.

[0072] The change in the swelling coefficient of the compositions over time was studied as follows. A sample of the final product with a mass of to (g) and a volume of vo (m 3 ) were subjected to swelling in an aqueous medium at a temperature of 40 о C / 60°C / 85 о C / 105°C, after which the mass m (g) and volume g (m) were measured. 3 ) of the swollen final product. The swelling coefficient of the composition was determined by mass and volume methods using the following formulas: where a т — swelling coefficient of the composition determined by the mass method where a v — swelling coefficient of the composition, determined by the gravimetric method

[0073] The value of the swelling coefficient a was determined as the arithmetic mean between the values ​​of a т and a v .

[0074] The swelling coefficient was determined on days 1, 3, 5, 7, 10, 15, 21 and 24. The test results for different temperatures were entered into Table 2.

[0075] Table 2. Results of changes in the swelling coefficient over time

[0076] Based on the results of the tests, during which the change in the swelling coefficient of the compositions was studied over time at different operating temperatures, the ability of the compositions to self-destruction was also assessed. The presence of the process of self-destruction of the compositions was indicated by a decrease in the swelling coefficient, at least in one of the time intervals.

[0077] As can be seen from Table 2, all the compositions presented in the table are characterized by the required value of the swelling coefficient (a) in water (not less than 4) on the first day, while the lowest value of the swelling coefficient in water (a) on the first day at a temperature of 60 ° C is inherent in composition 2. According to Table 2, all the studied compositions are characterized by stability for at least 5 days, with a subsequent process of their self-destruction, which is expressed in a decrease in the degree of swelling on the seventh (composition 3 at 85 ° C) and subsequent days, which indicates high efficiency of the described compositions (their blocking ability) when performing the well killing process in a wide range of reservoir temperatures (from 40 to 105 ° C) and various time intervals (depending on the type of well repair) while ensuring high productivity of the process of removing the blocking composition after well repair and reducing the time of bringing the well to the operating mode.

[0078] In addition, the claimed well-killing composition was used to kill wells in field conditions, for which purpose an inert carrier with the well-killing composition was injected into the well, after which water was injected, then the swelling of the well-sealing composition was expected and the well was repaired, after which the subsequent destruction of the composition was expected in order to depressurize the well.

[0079] The examples provided confirm the production of a composition characterized by the required swelling coefficient, which will provide pressure that allows blocking (killing) the well in a wide range of temperatures. At the same time, a decrease in the swelling coefficient value reflects the process of destruction of the presented compositions, due to which the compositions are easily removed from the well. The study of the blocking composition in field conditions confirmed the achievement of the declared technical result, which consists in simplifying the well repair process and increasing the efficiency of well killing in various fields in a wide range of reservoir temperatures (from 40 to 105 °C) and various time intervals (depending on the type of well repair) while ensuring high productivity of the process of removing the blocking composition after well repair and reducing the time for bringing the well to the operating mode.

[0080] The above features simplify the well repair process and increase its efficiency at various fields in a wide range of formation temperatures (from 40 to 105°C). Analysis of various compositions and their destruction time allows us to confirm the achievement of an additional technical result, namely, the ability to regulate the well killing time depending on the repair time.

[0081] Thus, the described examples indicate the achievement of a technical result consisting in simplifying the well repair process and increasing its efficiency at various fields in a wide range of reservoir temperatures (from 40 to 105 °C) and various time intervals (depending on the type of well repair) while ensuring high productivity of the process of removing the blocking composition after well repair and accelerating the well development process.

Claims

Invention formula 1. A composition for killing wells, represented by a self-destructing polymer of a three-dimensional structure, obtained by mixing a monomer, a crosslinker and an initiator in water, and subsequent drying, characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more.

2. The composition according to claim 1, wherein the crosslinker is at least one substance selected from the group of compounds with two reactive multiple chemical bonds formed by residues of acrylic and methacrylic acid derivatives.

3. The composition according to claim 1, wherein the initiator is at least one substance selected from the group of free radical source compounds.

4. The composition according to claim 1, wherein the monomer is at least one substance selected from the group of compounds with one reactive multiple chemical bond located in the acrylic acid residue and / or in the methacrylic acid residue and / or in the vinyl fragment residue.

5. The composition according to item 2, in which the group of compounds with two reactive multiple chemical bonds formed by residues of acrylic and methacrylic acid derivatives includes at least diethylene glycol diacrylate, N,N'-methylenebisacrylamide, and monoethylene glycol diacrylate.

6. The composition according to paragraph 3, in which the group of compounds of free radical sources includes at least ammonium persulfate, potassium persulfate, and sodium bisulfite.

7. The composition according to item 4, in which the group of compounds with one reactive multiple chemical bond located in the acrylic acid residue and / or in the methacrylic acid residue and / or in the vinyl fragment residue includes at least acrylamide, acrylic acid, and methacrylic acid.

8. The composition according to item 1 is represented by particles with a fraction of no more than 1000 microns.

9. The composition according to I.8 is represented by particles with a fraction from 400 to 800 microns.

10. A method for preparing a composition for killing wells, represented by a self-destructing polymer of a three-dimensional structure with a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more, in which a monomer, crosslinker and initiator are mixed in water, after which drying is carried out, wherein the quantitative ratio of the monomer, crosslinker and initiator is, by weight %: crosslinker from 0.25 to 3.16; initiator from 0.1 to 0.99; monomer is the rest, and the amount of water to the total mass of monomer, crosslinker and initiator is selected from the range from 1 to 4.9 to 1.

11. The method according to claim 10, wherein the crosslinker is at least one substance selected from the group of compounds with two reactive multiple chemical bonds formed by residues of acrylic and methacrylic acid derivatives.

12. The method according to i.10, wherein the initiator is at least one substance selected from the group of free radical source compounds.

13. The method according to i.10, wherein the monomer is at least one substance selected from the group of compounds with one reactive multiple chemical bond located in the acrylic acid residue and / or in the methacrylic acid residue and / or in the vinyl moiety residue.

14. The method according to item 11, wherein the group of compounds with two reactive multiple chemical bonds formed by residues of acrylic and methacrylic acid derivatives includes at least diethylene glycol diacrylate, N-methylenebisacrylamide, and monoethylene glycol diacrylate.

15. The method according to item 12, wherein the group of compounds of free radical sources includes at least ammonium persulfate, potassium persulfate, and sodium bisulfite.

16. The method according to item 13, wherein the group of compounds with one reactive multiple chemical bond located in the acrylic acid residue and / or in the methacrylic acid residue and / or in the vinyl fragment residue includes at least acrylamide, acrylic acid, and methacrylic acid.

17. The method according to I.10, in which the components are mixed for at least 20 minutes.

18. The method according to I.10, in which the resulting composition is ground.

19. The method according to I.10, in which drying is carried out at a temperature from 50 to 105 °C.

20. The method according to I.10, in which drying is carried out until the residual moisture content is no more than 15%.

21. The method according to I.10, in which, after drying the resulting composition, it is crushed.

22. The method according to I.10, in which crushing is carried out to a fraction of no more than 1000 microns.

23. The method according to item 22, wherein crushing is carried out to a fraction of 400 to 800 microns.

24. Use of a well killing composition, in which an inert carrier with a well killing composition, represented by a self-destructing polymer of a three-dimensional structure, obtained by mixing a monomer, crosslinker and initiator in water, and subsequent drying, characterized by a swelling coefficient in water (a) of at least 4 on the first day at a temperature of 40°C or more, is injected into the well, and then water is injected.

25. The use according to claim 24, wherein the inert carrier is selected from the group of hydrocarbon agents.

26. The use according to claim 24, wherein the group of hydrocarbon agents includes at least oil.

27. The use according to claim 24, wherein the group of hydrocarbon agents includes at least diesel fuel.

28. Use according to paragraph 24, wherein after pumping an inert carrier with a composition for killing wells, a hydrocarbon agent is additionally pumped.

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