Environment-friendly branched hydroxylamine cross-linking agent as well as preparation method and application thereof

Abstract

The preparation method comprises the following steps: (1) adding aldehyde and water into a reactor, transferring the reactor into an oil bath or a water bath, heating to a first temperature, stirring until a mixed solution becomes clear and transparent, then adding an aqueous solution of alkali into the reactor, and reacting for 2-4 hours at a first temperature; the preparation method comprises the following steps: adding a catalyst into a reactor, adjusting the pH value to be alkaline, adding polyamine into the reactor, reacting to obtain a reaction solution, standing, and grinding the reaction solution after the reaction solution becomes solid to obtain a branched hydroxylamine cross-linking agent intermediate; (2) pouring the branched hydroxylamine cross-linking agent intermediate into a reactor, transferring the reactor into an oil bath or a water bath, adding a proper amount of alcohol into the reactor, heating to a second temperature, dropwise adding acid into the reactor, adjusting the pH value to be acidic, starting an etherification reaction to obtain a reaction solution, adding a small amount of an aqueous solution of alkali into the reactor, adjusting the pH value to be weakly alkaline, and reacting for 2-3 hours; and performing reduced pressure distillation to obtain the environment-friendly branched hydroxylamine cross-linking agent.

Description

Technical Field

[0001] The present invention relates to the field of oilfield chemistry, and particularly relates to an environmentally friendly branched hydroxylamine crosslinking agent, a preparation method thereof, and an application thereof. Background Art

[0002] Most of the onshore oilfields in China have entered the high water cut development stage. The comprehensive water cut of the produced fluid from oil wells is often above 90%, and the water flooding efficiency is very low. At the same time, separating and treating the water in the produced fluid will incur huge economic costs. According to statistics, the annual cost of treating excessive produced water in the world's oil industry is about 4.5×10 10 US dollars. Therefore, in order to increase oil production and reduce water production, the water shutoff and profile control technology has emerged as the times require.

[0003] Currently, the most commonly used water shutoff and profile control technology in oilfields is the chemical water shutoff and profile control technology. By injecting chemical profile control and water shutoff agents into the underground reservoir, a non-flowing gel body is formed in the high-permeability layer or the water flow channel area to prevent water from flowing into the oil well, or to force the water to flow into the area with a high crude oil content, improving the oil displacement efficiency to achieve the effect of increasing oil production and reducing water production.

[0004] Currently, the profile control and water shutoff agents used at home and abroad are mainly polymer gels, which can account for more than 80% of the field applications. The crosslinking agents used in the polymer gel system in domestic oilfields are mainly organic chromium crosslinking agents and phenolic resin crosslinking agents.

[0005] The phenolic resin crosslinking agent is prepared by an artificial synthesis method. Chinese Patent Application CN115403720A discloses a phenolic resin crosslinking agent and a preparation method thereof. The phenolic resin crosslinking agent includes 100 parts by mass of phenol, 215 - 260 parts by mass of formaldehyde solution, 15 - 32 parts by mass of sodium hydroxide solution, 4 - 10 parts by mass of barium hydroxide solution, 16 - 32 parts by mass of mutual solvent, and polyhydroxy phenol. Its main mechanism is that phenol and formaldehyde undergo dehydration condensation under certain conditions to form hydroxymethyl crosslinking sites, which can then react with the amide groups on the polyacrylamide molecule. However, phenol in the raw materials has biological toxicity, and the reaction degree is uncontrollable. The raw materials are likely to remain in the product, posing environmental protection hazards.

[0006] Metal ion crosslinking agents (such as chromium ions, aluminum ions, zirconium ions, etc.) form polynuclear hydroxy-bridged complex ions in water and can form gels with carboxyl groups on polyacrylamide molecules through coordination reactions. Chinese Patent CN1003048B discloses a preparation method of a zirconium gel water shutoff agent, which consists of 0.3%-2.0% polyacrylamide or methylene polyacrylamide and inorganic zirconium compounds. Among them, the inorganic zirconium compounds include zirconium oxychloride, zirconium tetrachloride, zirconium sulfate, and zirconium nitrate. The plugging agent can be used for water shutoff in oil wells and profile control in injection wells, but the gelation time is short, and the double-fluid injection process needs to be adopted, and deep plugging and profile control cannot be achieved. Subsequently, a gel system crosslinked with organic zirconium was gradually formed. However, chromium crosslinking agents also have biological toxicity. Another example is that Chinese Patent CN102936490B discloses a preparation method of an environmentally friendly multi-scale zirconium gel dispersion plugging agent. The method includes treating the formed gel system by mechanical shearing to make the gel form a gel dispersion at the nano, micro, or millimeter level. The mass fraction of non-ionic polyacrylamide in the gelling solution is 0.6%-1%, and the mass fraction of zirconium acetate crosslinking agent is 1%-2%. It gels after standing at 30°C; using a colloid mill as the shearing equipment, adjusting the rotation speed and shearing distance of the colloid mill, adding the gel and water into the colloid mill according to a mass ratio of 1-6:1, and circulating and shearing until evenly dispersed to obtain a multi-scale zirconium gel dispersion solution. The plugging agent consists of an aqueous solution of non-ionic polyacrylamide and industrial-grade zirconium acetate, and the gelation time at 30°C is 102 minutes. Even though acetate can complex zirconium ions to a certain extent and delay the release rate of zirconium ions, the plugging agent still gels too quickly at low temperatures and cannot be directly used as a deep plugging and profile control agent, and chromium crosslinking agents also have biological toxicity.

[0007] In addition, polyethyleneimine is an environmentally friendly crosslinking agent that has been studied more in recent years. Reddy et al. from Halliburton Company in the United States pointed out in a paper that the imino groups on polyethyleneimine molecules can crosslink with polymers through transamination reactions. Chinese Patent Application CN106694907A discloses a preparation method of a polyethyleneimine-based water shutoff and profile control agent. The plugging agent consists of 0.05%-0.5% partially hydrolyzed polyacrylamide, 0.01%-0.5% polyethyleneimine, 0.05%-1.0% gelation retarder, 0.1%-3.0%, 0.01%-0.05% regulator. The gelation time of this plugging agent at 150°C is more than 6 days, and the gel strength is greater than 0.075 MPa. Due to the high cost of polyethyleneimine, this system has not been widely promoted and applied in China at present.

[0008] In summary, the following deficiencies exist in the use of polymer gels: ① Both organic chromium crosslinkers and phenolic resin crosslinkers have varying degrees of biological toxicity. With the increasing demand for green environmental protection in oilfield development, the above products have gradually become unable to meet the environmental protection requirements. ② As waterflooding development continues to deepen, the remaining oil in the near-wellbore area is becoming less and less, and the plugging and profile control idea has changed from traditional "near-wellbore plugging" to "far-wellbore profile control". Therefore, higher requirements are put forward for the migration ability of gels in the formation. Organic chromium gels generally have a short gelation time, and trivalent chromium ions have serious adsorption problems in the formation and cannot migrate to the deep part of the formation. In contrast, phenolic gels gel slowly, but their gelation time is mainly achieved by adjusting the component concentration, and the controllability of gelation is relatively low. Summary of the Invention

[0009] Object of the Invention: Aiming at the deficiencies of the above-mentioned existing technologies, the present invention discloses an environmentally friendly branched hydroxylamine crosslinker and its preparation method and application. The present invention uses polyamine with low biological toxicity as a raw material, forms hydroxymethyl crosslinking sites by reacting with formaldehyde, thereby realizing the environmental protection upgrade of the plugging agent; and then shields the hydroxymethyl through etherification reaction. Under formation conditions, the ether bond gradually breaks and slowly releases hydroxymethyl, thereby prolonging the gelation time and realizing deep plugging and profile control.

[0010] Technical Solution: An environmentally friendly branched hydroxylamine crosslinker, whose structural formula is shown in any one of formulas (1)-(3):

[0011]

[0012] Wherein:

[0013] R is one of methyl, ethyl, and butyl, preferably methyl or butyl.

[0014] A preparation method of the above-mentioned environmentally friendly branched hydroxylamine crosslinker, comprising the following steps:

[0015] (1) Add appropriate amounts of aldehyde and water to a reactor equipped with a condensing device and a stirring device to obtain a mixed solution, transfer the reactor to an oil bath or a water bath, turn on the condensing device and the stirring device, heat to a first temperature, continuously stir until the mixed solution becomes clear and transparent, then add an aqueous solution of a certain amount of alkali to the reactor, adjust its pH value to alkaline, and finally add an appropriate amount of polyamine to the reactor. After reacting for a period of time, obtain a reaction solution, take out the reaction solution, let it stand in the air, and after the reaction solution becomes solid, grind it to obtain a branched hydroxylamine crosslinker intermediate;

[0016] (2) Take an appropriate amount of the branched hydroxylamine crosslinker intermediate obtained in step (1), pour it into a reactor equipped with a condensing device and a stirring device, and move the reactor to an oil bath or a water bath. Start the condensing device and the stirring device; add an appropriate amount of alcohol to the reactor, heat it to a second temperature, then dropwise add an acid to the reactor to adjust its pH value to acidic, and start the etherification reaction. After reacting for a period of time, a reaction solution is obtained. Add a small amount of an aqueous solution of alkali to the reactor to adjust the pH value of the reaction solution to weakly alkaline, and distill off the excess alcohol and water under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinker.

[0017] Further, the aldehyde in step (1) is at least one of formaldehyde or paraformaldehyde, preferably formaldehyde.

[0018] Further, the aqueous solution of alkali in step (1) is at least one of an aqueous solution of sodium hydroxide, an aqueous solution of sodium bicarbonate, and an aqueous solution of sodium carbonate, preferably an aqueous solution of sodium carbonate;

[0019] The mass concentration of the aqueous solution of alkali is 5%-20%.

[0020] Further, the polyamine in step (1) is at least one of 1,3,5-triazine-2,4,6-triamine, pyrazine-2,5-diamine, and 4,6-pyrimidinediamine, preferably 1,3,5-triazine-2,4,6-triamine.

[0021] Further, in step (1), an appropriate amount of polyamine is added to the reactor. After the polyamine is dissolved, the molar ratio of the aldehyde to the polyamine in the reaction system is (8-10):1;

[0022] The mass ratio of the aldehyde to the water in step (1) is 100:(100-1000).

[0023] Further, the first temperature in step (1) is 40-80°C, preferably 70-75°C.

[0024] Further, in step (1), a certain amount of an aqueous solution of alkali is added to the reactor to adjust its pH value to 8-12, preferably 9-11.

[0025] Further, the reaction time of the aldehyde and the polyamine in step (1) is at least 20 minutes, preferably 20-120 minutes.

[0026] Further, the alcohol in step (2) is at least one of methanol, ethanol, and butanol, preferably methanol.

[0027] Further, the acid in step (2) is one of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, preferably dilute sulfuric acid.

[0028] Further, the aqueous solution of alkali in step (2) is at least one of an aqueous solution of sodium hydroxide, an aqueous solution of sodium bicarbonate, and an aqueous solution of sodium carbonate, preferably an aqueous solution of sodium hydroxide;

[0029] The mass concentration of the aqueous solution of alkali is 5%-20%.

[0030] Further, the mass ratio of the branched hydroxylamine crosslinker intermediate to the alcohol in step (2) is (150-500):100.

[0031] Further, the second temperature in step (2) is 40-70°C, preferably 50-60°C.

[0032] Further, the etherification reaction time in step (2) is at least 30 minutes, preferably 30-120 minutes.

[0033] Further, in step (2), an acid is added dropwise to the reactor to adjust its pH value to 2-5, and the etherification reaction is started. After reacting for 30-120 minutes, a reaction solution is obtained. A small amount of an aqueous solution of alkali is added to the reactor to adjust the pH value of the reaction solution to 8-8.5.

[0034] An environment-friendly branched hydroxylamine crosslinker is prepared by the preparation method described in any one of the above.

[0035] Application of the above environment-friendly branched hydroxylamine crosslinker as a crosslinker for deep water shutoff and profile control in the exploitation of medium-high permeability oil reservoirs.

[0036] Beneficial effects: An environment-friendly branched hydroxylamine crosslinker and its preparation method and application disclosed by the present invention have the following beneficial effects:

[0037] 1. Compared with conventional crosslinkers such as water-soluble phenolic resin, the present invention uses polyamine to replace phenol as a reactant, and the synthesized branched hydroxylamine crosslinker molecule does not contain a benzene ring, realizing the environmental protection upgrade of the plugging agent;

[0038] 2. The environment-friendly branched hydroxylamine crosslinker of the present invention shields the hydroxymethyl groups on the molecule through an etherification reaction, so that the crosslinking sites are slowly released under reservoir conditions, and the controllability of the gelation reaction of the gel is improved, and it can be used for deep water shutoff and profile control operations in medium-high permeability oil reservoirs. Brief description of the drawings

[0039] Figure 1 It is a flow chart of a preparation method of an environment-friendly branched hydroxylamine crosslinker disclosed by the present invention. Detailed description of the specific implementation

[0040] The following is a detailed description of the specific implementation of the present invention.

[0041] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention pertains.

[0042] It should be noted that the terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprises" and / or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, and / or combinations thereof.

[0043] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 - 50 is listed for a specific parameter, ranges of 10 - 40 and 20 - 50 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations.

[0044] If there is no special indication, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0045] If there is no special indication, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0047] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application mean open-ended or may also be closed-ended. For example, the terms "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0048] Unless otherwise specified, the reaction is carried out under normal temperature and normal pressure conditions.

[0049] Unless otherwise specified, all parts or percentages are by weight or weight percentage.

[0050] In the present invention, the substances used are all known substances, which can be purchased or synthesized by known methods.

[0051] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and can all be purchased.

[0052] An environment-friendly branched hydroxylamine crosslinking agent, whose structural formula is shown as any one of formulas (1)-(3):

[0053]

[0054] Wherein:

[0055] R is one of methyl, ethyl, and butyl, preferably methyl or butyl.

[0056] A preparation method of the above-mentioned environment-friendly branched hydroxylamine crosslinking agent includes the following steps:

[0057] (1) Add an appropriate amount of aldehyde and water to a reactor equipped with a condensation device and a stirring device to obtain a mixed solution. Transfer the reactor to an oil bath or a water bath, turn on the condensation device and the stirring device, heat to the first temperature, and continuously stir until the mixed solution becomes clear and transparent. Then add a certain amount of aqueous solution of alkali to the reactor, adjust its pH value to alkaline, and finally add an appropriate amount of polyamine to the reactor. After reacting for a period of time, obtain a reaction solution. Take out the reaction solution and let it stand in the air. After the reaction solution becomes solid, grind it to obtain a branched hydroxylamine crosslinking agent intermediate;

[0058] (2) Take an appropriate amount of the branched hydroxylamine crosslinking agent intermediate obtained in step (1), pour it into a reactor equipped with a condensation device and a stirring device, and transfer the reactor to an oil bath or a water bath. Start the condensation device and the stirring device; add an appropriate amount of alcohol to the reactor, heat to the second temperature, and then dropwise add an acid to the reactor to adjust its pH value to acidic, and start the etherification reaction. After reacting for a period of time, obtain a reaction solution. Add a small amount of aqueous solution of alkali to the reactor to adjust the pH value of the reaction solution to weakly alkaline, and distill off the excess alcohol and water under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinking agent.

[0059] Further, the aldehyde in step (1) is at least one of formaldehyde or paraformaldehyde, preferably formaldehyde.

[0060] Further, the aqueous solution of alkali in step (1) is at least one of sodium hydroxide aqueous solution, sodium bicarbonate aqueous solution, and sodium carbonate aqueous solution, preferably sodium carbonate aqueous solution;

[0061] The mass concentration of the aqueous solution of alkali is 5%-20%.

[0062] Further, the polyamine in step (1) is at least one of 1,3,5-triazine-2,4,6-triamine, pyrazine-2,5-diamine, and 4,6-pyrimidine diamine, preferably 1,3,5-triazine-2,4,6-triamine.

[0063] Further, in step (1), when an appropriate amount of polyamine is added to the reactor, after the polyamine is dissolved, the molar ratio of the aldehyde to the polyamine in the reaction system is (8-10):1;

[0064] In step (1), the mass ratio of the aldehyde to the water is 100:(100-1000).

[0065] Further, the first temperature in step (1) is 40-80°C, preferably 70-75°C.

[0066] Further, in step (1), when a certain amount of aqueous solution of alkali is added to the reactor, adjust its pH value to 8-12, preferably 9-11.

[0067] Further, the reaction time of the aldehyde and the polyamine in step (1) is at least 20 minutes, preferably 20 - 120 minutes.

[0068] Further, the alcohol in step (2) is at least one of methanol, ethanol, and butanol, preferably methanol.

[0069] Further, the acid in step (2) is one of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, preferably dilute sulfuric acid.

[0070] Further, the aqueous solution of the base in step (2) is at least one of an aqueous sodium hydroxide solution, an aqueous sodium bicarbonate solution, and an aqueous sodium carbonate solution, preferably an aqueous sodium hydroxide solution;

[0071] The mass concentration of the aqueous solution of the base is 5% - 20%.

[0072] Further, the mass ratio of the branched hydroxylamine crosslinker intermediate to the alcohol in step (2) is (150 - 500) : 100.

[0073] Further, the second temperature in step (2) is 40 - 70°C, preferably 50 - 60°C.

[0074] Further, the etherification reaction time in step (2) is at least 30 minutes, preferably 30 - 120 minutes.

[0075] Further, in step (2), acid is added dropwise to the reactor to adjust its pH value to 2 - 5, and the etherification reaction is started. After reacting for 30 - 120 minutes, a reaction solution is obtained. A small amount of the aqueous solution of the base is added to the reactor to adjust the pH value of the reaction solution to 8 - 8.5.

[0076] An environmentally friendly branched hydroxylamine crosslinker is prepared by the preparation method described in any one of the above.

[0077] The application of the above - mentioned environmentally friendly branched hydroxylamine crosslinker as a crosslinker for deep - water plugging and profile control in the exploitation of medium - high permeability oil reservoirs.

[0078] In one embodiment, an environmentally friendly branched hydroxylamine crosslinker has a structural formula as shown in formula (1):

[0079] Wherein:

[0080] R is methyl. In another embodiment, R is ethyl. In another embodiment, R is butyl.

[0081] A preparation method of the above - mentioned environmentally friendly branched hydroxylamine crosslinker includes the following steps:

[0082] (1) Add an appropriate amount of aldehyde and water to a reactor equipped with a condensation device and a stirring device to obtain a mixed solution. Transfer the reactor to an oil bath, turn on the condensation device and the stirring device, heat to the first temperature, and continuously stir until the mixed solution becomes clear and transparent. Then, add an aqueous solution of a certain amount of base to the reactor, adjust its pH value to alkaline, and finally add an appropriate amount of polyamine to the reactor. After reacting for a period of time, obtain a reaction solution. Take out the reaction solution and let it stand in the air. After the reaction solution becomes solid, grind it to obtain a branched hydroxylamine crosslinker intermediate;

[0083] (2) Take an appropriate amount of the branched hydroxylamine crosslinker intermediate obtained in step (1), pour it into a reactor equipped with a condensation device and a stirring device, and transfer the reactor to an oil bath. Start the condensation device and the stirring device; add an appropriate amount of alcohol to the reactor, heat to the second temperature, and then dropwise add an acid to the reactor to adjust its pH value to acidic, and start the etherification reaction. After reacting for a period of time, obtain a reaction solution. Add a small amount of aqueous solution of base to the reactor to adjust the pH value of the reaction solution to weakly alkaline, and distill off the excess alcohol and water under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinker.

[0084] Further, the aldehyde in step (1) is formaldehyde.

[0085] Further, the aqueous solution of base in step (1) is an aqueous solution of sodium hydroxide with a mass concentration of 5%.

[0086] Further, the polyamine in step (1) is 4,6-pyrimidine diamine.

[0087] Further, in step (1), an appropriate amount of polyamine is added to the reactor. After the polyamine is dissolved, the molar ratio of the aldehyde to the polyamine in the reaction system is 8:1;

[0088] In step (1), the mass ratio of the aldehyde to the water is 100:100.

[0089] Further, the first temperature in step (1) is 40 °C. In another embodiment, the first temperature in step (1) is 70 °C.

[0090] Further, in step (1), an aqueous solution of a certain amount of base is added to the reactor to adjust its pH value to 8. In another embodiment, it is preferred to add an aqueous solution of a certain amount of base to the reactor in step (1) to adjust its pH value to 9.

[0091] Further, the reaction time of the aldehyde and the polyamine in step (1) is 20 minutes.

[0092] Further, the alcohol in step (2) is methanol.

[0093] Further, the acid described in step (2) is dilute hydrochloric acid.

[0094] Further, the aqueous solution of the base described in step (2) is an aqueous sodium hydroxide solution with a mass concentration of 5%.

[0095] Further, the mass ratio of the branched hydroxylamine crosslinker intermediate to the alcohol described in step (2) is 150:100.

[0096] Further, the second temperature described in step (2) is 40 °C. In another embodiment, the second temperature described in step (2) is 50 °C.

[0097] Further, the etherification reaction time in step (2) is 30 minutes.

[0098] Further, in step (2), acid is added dropwise to the reactor, its pH value is adjusted to 2, the etherification reaction is started, after reacting for 30 minutes, a reaction solution is obtained, a small amount of aqueous solution of base is added to the reactor, and the pH value of the reaction solution is adjusted to 8.

[0099] An environment-friendly branched hydroxylamine crosslinker is prepared by the preparation method described in any one of the above.

[0100] The application of the above-mentioned environment-friendly branched hydroxylamine crosslinker as a crosslinker for deep water shutoff and profile control in the exploitation of medium-high permeability oil reservoirs.

[0101] In another embodiment, an environment-friendly branched hydroxylamine crosslinker has a structural formula as shown in formula (2):

[0102] Wherein:

[0103] R is methyl. In another embodiment, R is ethyl. In another embodiment, R is butyl.

[0104] A preparation method of the above-mentioned environment-friendly branched hydroxylamine crosslinker includes the following steps:

[0105] (1) Add appropriate amounts of aldehyde and water to a reactor equipped with a condensation device and a stirring device to obtain a mixed solution, transfer the reactor to a water bath, turn on the condensation device and the stirring device, heat to the first temperature, continuously stir until the mixed solution becomes clear and transparent, then add a certain amount of aqueous solution of base to the reactor, adjust its pH value to alkaline, and finally add appropriate amounts of polyamine to the reactor. After reacting for a period of time, a reaction solution is obtained. Take out the reaction solution and let it stand in the air. After the reaction solution becomes solid, grind it to obtain a branched hydroxylamine crosslinker intermediate;

[0106] (2) Take an appropriate amount of the branched hydroxylamine crosslinker intermediate obtained in step (1), pour it into a reactor equipped with a condensation device and a stirring device, move the reactor to a water bath, and start the condensation device and the stirring device; add an appropriate amount of alcohol to the reactor, heat it to a second temperature, then add acid dropwise to the reactor, adjust its pH value to acidic, and start the etherification reaction. After reacting for a period of time, a reaction solution is obtained. Add a small amount of aqueous solution of alkali to the reactor, adjust the pH value of the reaction solution to weakly alkaline, and distill off the excess alcohol and water under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinker.

[0107] Further, the aldehyde in step (1) is paraformaldehyde.

[0108] Further, the aqueous solution of alkali in step (1) is an aqueous solution of sodium bicarbonate with a mass concentration of 20%.

[0109] Further, the polyamine in step (1) is pyrazine-2,5-diamine.

[0110] Further, in step (1), an appropriate amount of polyamine is added to the reactor. After the polyamine is dissolved, the molar ratio of the aldehyde to the polyamine in the reaction system is 10:1;

[0111] In step (1), the mass ratio of the aldehyde to the water is 100:1000.

[0112] Further, the first temperature in step (1) is 80 °C. In another embodiment, the first temperature in step (1) is 75 °C.

[0113] Further, in step (1), a certain amount of aqueous solution of alkali is added to the reactor, and its pH value is adjusted to 12. In another embodiment, in step (1), a certain amount of aqueous solution of alkali is added to the reactor, and its pH value is adjusted to 11.

[0114] Further, the reaction time of the aldehyde and the polyamine in step (1) is 120 minutes.

[0115] Further, the alcohol in step (2) is ethanol.

[0116] Further, the acid in step (2) is dilute sulfuric acid.

[0117] Further, the aqueous solution of alkali in step (2) is an aqueous solution of sodium bicarbonate with a mass concentration of 20%.

[0118] Further, the mass ratio of the branched hydroxylamine crosslinker intermediate to the alcohol in step (2) is 500:100.

[0119] Further, the second temperature in step (2) is 70 °C. In another embodiment, the second temperature in step (2) is 60 °C.

[0120] Further, the etherification reaction time in step (2) is 120 minutes.

[0121] Further, in step (2), an acid is added dropwise to the reactor to adjust its pH value to 5, and the etherification reaction is started. After reacting for 120 minutes, a reaction solution is obtained. A small amount of aqueous alkali solution is added to the reactor to adjust the pH value of the reaction solution to 8.5.

[0122] An environmentally friendly branched hydroxylamine crosslinking agent is prepared by the preparation method described in any one of the above.

[0123] The application of the above-mentioned environmentally friendly branched hydroxylamine crosslinking agent as a crosslinking agent for deep water plugging and profile control in the exploitation of medium-high permeability oil reservoirs.

[0124] In yet another embodiment, an environmentally friendly branched hydroxylamine crosslinking agent has a structural formula as shown in formula (3):

[0125] Wherein:

[0126] R is methyl. In another embodiment, R is ethyl. In another embodiment, R is butyl.

[0127] A preparation method of the above-mentioned environmentally friendly branched hydroxylamine crosslinking agent includes the following steps:

[0128] (1) An appropriate amount of aldehyde and water are added to a reactor equipped with a condensation device and a stirring device to obtain a mixed solution. The reactor is transferred to an oil bath, the condensation device and the stirring device are turned on, and heated to the first temperature. Continuously stir until the mixed solution becomes clear and transparent. Then, a certain amount of aqueous alkali solution is added to the reactor to adjust its pH value to alkaline. Finally, an appropriate amount of polyamine is added to the reactor. After reacting for a period of time, a reaction solution is obtained. The reaction solution is taken out and left to stand in the air. After the reaction solution becomes solid, it is ground to obtain a branched hydroxylamine crosslinking agent intermediate;

[0129] (2) Take an appropriate amount of the branched hydroxylamine crosslinking agent intermediate obtained in step (1), pour it into a reactor equipped with a condensation device and a stirring device, and transfer the reactor to an oil bath. Start the condensation device and the stirring device; add an appropriate amount of alcohol to the reactor, heat to the second temperature, then add an acid dropwise to the reactor to adjust its pH value to acidic, and start the etherification reaction. After reacting for a period of time, a reaction solution is obtained. A small amount of aqueous alkali solution is added to the reactor to adjust the pH value of the reaction solution to weakly alkaline, and excess alcohol and water are removed by vacuum distillation to obtain the environmentally friendly branched hydroxylamine crosslinking agent.

[0130] Further, the aldehyde in step (1) is formaldehyde.

[0131] Further, the aqueous solution of the base in step (1) is an aqueous solution of sodium carbonate with a mass concentration of 10%. In another embodiment, the aqueous solution of the base in step (1) is a mixture of aqueous solutions of sodium hydroxide, sodium bicarbonate, and sodium carbonate with an equal mass ratio, and the total mass concentration is 12%.

[0132] Further, the polyamine in step (1) is 1,3,5-triazine-2,4,6-triamine.

[0133] Further, an appropriate amount of polyamine is added to the reactor in step (1). After the polyamine is dissolved, the molar ratio of the aldehyde to the polyamine in the reaction system is 9:1;

[0134] The mass ratio of the aldehyde to the water in step (1) is 100:500.

[0135] Further, the first temperature in step (1) is 72 °C.

[0136] Further, a certain amount of the aqueous solution of the base is added to the reactor in step (1), and its pH value is adjusted to 10.

[0137] Further, the reaction time of the aldehyde and the polyamine in step (1) is 60 minutes.

[0138] Further, the alcohol in step (2) is methanol. In another embodiment, the alcohol in step (2) is a mixture of methanol, ethanol, and butanol with an equal mass ratio.

[0139] Further, the acid in step (2) is dilute nitric acid.

[0140] Further, the aqueous solution of the base in step (2) is an aqueous solution of sodium carbonate with a mass concentration of 10%. In another embodiment, the aqueous solution of the base in step (2) is a mixture of aqueous solutions of sodium hydroxide, sodium bicarbonate, and sodium carbonate with an equal mass ratio, and the total mass concentration is 12%.

[0141] Further, the mass ratio of the branched hydroxylamine crosslinker intermediate to the alcohol in step (2) is 200:100.

[0142] Further, the second temperature in step (2) is 55 °C.

[0143] Further, the etherification reaction time in step (2) is 60 minutes.

[0144] Further, in step (2), an acid is added dropwise to the reactor, and its pH value is adjusted to 3 to initiate the etherification reaction. After reacting for 60 minutes, a reaction solution is obtained. A small amount of aqueous alkali solution is added to the reactor to adjust the pH value of the reaction solution to 8.2.

[0145] An environment-friendly branched hydroxylamine crosslinking agent is prepared by the preparation method described in any one of the above.

[0146] The application of the above-mentioned environment-friendly branched hydroxylamine crosslinking agent as a crosslinking agent for deep water plugging and profile control in the exploitation of medium-high permeability oil reservoirs.

[0147] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0148] Example 1

[0149] The environment-friendly branched hydroxylamine crosslinking agent for plugging and profile control and its preparation method comprise the following steps:

[0150] The preparation method of the environment-friendly branched hydroxylamine crosslinking agent comprises the following steps:

[0151] (1) Weigh 120 g of formaldehyde and an appropriate amount of water to prepare a formaldehyde solution with a mass concentration of 37%. Then add the formaldehyde solution and 317 g of water to a 1000 mL four-necked flask; connect the four-necked flask to a condensing and stirring device, heat up to 70 °C, and stir until the system is clear and transparent; add a small amount of aqueous sodium bicarbonate solution to adjust the pH value of the system to 9; add 63 g of 1,3,5-triazine-2,4,6-triamine to the four-necked flask and react for 90 minutes under stirring conditions; after taking out the product, dry and grind it to obtain a branched hydroxylamine crosslinking agent intermediate, where:

[0152] The molar ratio of formaldehyde to 1,3,5-triazine-2,4,6-triamine is 8:1;

[0153] (2) Weigh 91.8 g of the branched hydroxylamine crosslinking agent intermediate and 288 g of methanol and pour them into a 1000 mL four-necked flask; connect the four-necked flask to a condensing and stirring device, heat up to 50 °C; add a small amount of dilute sulfuric acid dropwise to the four-necked flask to adjust the pH value of the system to 3 to initiate the etherification reaction; after reacting for 30 minutes, add a small amount of aqueous sodium hydroxide solution to adjust the pH value of the system to 8; remove the excess water and methanol by vacuum distillation to obtain the environment-friendly branched hydroxylamine crosslinking agent, where:

[0154] The molar ratio of methanol to the branched hydroxylamine crosslinking agent intermediate is 30:1.

[0155] Example 2

[0156] The preparation method of the environment-friendly branched hydroxylamine crosslinking agent comprises the following steps:

[0157] (1) Weigh 135 g of formaldehyde and mix it with an appropriate amount of water to form a formaldehyde solution with a mass concentration of 37%. Then add the formaldehyde solution and 302 g of water to a 1000 mL four-necked flask. Connect the four-necked flask to a condensation and stirring device, heat it to 75 °C, and stir until the system is clear and transparent. Add a small amount of sodium bicarbonate aqueous solution to adjust the pH value of the system to 10. Add 63 g of 1,3,5-triazine-2,4,6-triamine to the four-necked flask and react for 90 minutes under stirring conditions. After taking out the product, dry it and grind it to obtain a branched hydroxylamine crosslinker intermediate, where:

[0158] The molar ratio of formaldehyde to 1,3,5-triazine-2,4,6-triamine is 9:1.

[0159] (2) Weigh 91.8 g of the branched hydroxylamine crosslinker intermediate and 288 g of methanol and pour them into a 1000 mL four-necked flask. Connect the four-necked flask to a condensation and stirring device and heat it to 50 °C. Drop a small amount of dilute sulfuric acid into the four-necked flask to adjust the pH value of the system to 3 and start the etherification reaction. After reacting for 30 minutes, add a small amount of sodium hydroxide aqueous solution to adjust the pH value of the system to 8. Remove the excess water and methanol by vacuum distillation to obtain an environmentally friendly branched hydroxylamine crosslinker, where:

[0160] The molar ratio of methanol to the intermediate is 30:1.

[0161] Example 3

[0162] A preparation method of an environmentally friendly branched hydroxylamine crosslinker, comprising the following steps:

[0163] (1) Weigh 150 g of formaldehyde and mix it evenly with an appropriate amount of water to form a formaldehyde solution with a mass concentration of 37%. Then add the formaldehyde solution and 287 g of water to a 1000 mL four-necked flask. Connect the four-necked flask to a condensation and stirring device, heat it to 75 °C, and stir until the system is clear and transparent. Add a small amount of sodium bicarbonate aqueous solution to adjust the pH value of the system to 11. Add 63 g of 1,3,5-triazine-2,4,6-triamine to the four-necked flask and react for 120 minutes under stirring conditions. After taking out the product, dry it and grind it to obtain a branched hydroxylamine crosslinker intermediate, where:

[0164] The molar ratio of formaldehyde to 1,3,5-triazine-2,4,6-triamine is 10:1;

[0165] (2) Weigh 91.8 g of the branched hydroxylamine crosslinker intermediate and 336 g of methanol and pour them into a 1000 mL four-necked flask; connect the four-necked flask to a condensing and stirring device and heat it to 60 °C; add a small amount of dilute sulfuric acid dropwise to the four-necked flask, adjust the pH value of the system to 2, and start the etherification reaction; after reacting for 30 minutes, add a small amount of sodium hydroxide aqueous solution to adjust the pH value of the system to 8; distill off the excess water and methanol under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinker, where:

[0166] The molar ratio of methanol to the branched hydroxylamine crosslinker intermediate is 35:1.

[0167] Example 4

[0168] A preparation method of an environmentally friendly branched hydroxylamine crosslinker, comprising the following steps:

[0169] (1) Weigh 120 g of formaldehyde and mix it evenly with an appropriate amount of water to obtain a formaldehyde aqueous solution with a mass concentration of 37%, and then add 317 g of water of this aqueous solution to a 1000 mL four-necked flask; connect the four-necked flask to a condensing and stirring device, heat it to 75 °C, and stir until the system is clear and transparent; add a small amount of sodium bicarbonate aqueous solution to adjust the pH value of the system to 11; add 63 g of 1,3,5-triazine-2,4,6-triamine to the four-necked flask and react for 120 minutes under stirring conditions; take out the product, dry it and grind it to obtain a branched hydroxylamine crosslinker intermediate, where:

[0170] The molar ratio of formaldehyde to 1,3,5-triazine-2,4,6-triamine is 8:1;

[0171] (2) Weigh 91.8 g of the branched hydroxylamine crosslinker intermediate and 336 g of methanol and pour them into a 1000 mL four-necked flask; connect the four-necked flask to a condensing and stirring device and heat it to 60 °C; add a small amount of dilute sulfuric acid dropwise to the four-necked flask, adjust the pH value of the system to 2, and start the etherification reaction; after reacting for 30 minutes, add a small amount of sodium hydroxide aqueous solution to adjust the pH value of the system to 8; distill off the excess water and methanol under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinker, where:

[0172] The molar ratio of methanol to the branched hydroxylamine crosslinker intermediate is 35:1.

[0173] Test Example 1

[0174] Use the environmentally friendly branched hydroxylamine crosslinker prepared in Examples 1-4 to prepare a gel, and measure the gelation time of the gel, the storage modulus after gelation, and the dehydration rate after 60 days of aging.

[0175] (1) Disperse 0.4 g of partially hydrolyzed polyacrylamide (molecular weight 12 million, hydrolysis degree 15%) in 100 g of 1% NaCl brine, and stir at room temperature for 4 hours until the polymer is completely dissolved. Subsequently, add a certain amount of environmentally friendly branched hydroxylamine crosslinking agent and continue to stir for 1 hour to obtain a gel-forming solution.

[0176] (2) Pour 50 g of the gel-forming solution into a stoppered heat-resistant glass tube and age it in an oven at 90 °C. Take out the glass tube at regular intervals and invert it; the fluidity of the gel gradually weakens with the aging time. When the upper edge of the gel cannot touch the bottle cap after inverting the glass tube, it is regarded that the gel has formed, and record the aging time at this time as the gel-forming time.

[0177] (3) After the gel is aged at 90 °C for 5 days, take out the gel and use an Anton Paar MCR 101 shear rheometer to measure the storage modulus of the gel at a strain of 1% and a frequency of 1 Hz.

[0178] (4) After the gel is aged in an oven at 90 °C for 60 days, take out the glass tube, weigh the mass of the water in the glass tube, and measure the dehydration rate of the gel:

[0179] Dehydration rate = mass of water / 50 g × 100%

[0180] The experimental results are shown in Table 1 and Table 2.

[0181] Table 1 Experimental results when the mass fraction of the crosslinking agent is 0.4%

[0182] Number Gelation time / h Storage modulus / Pa Dehydration rate / % Example 1 116 8.2 2.2％ Example 2 108 7.9 2.6％ Example 3 102 7.8 3.1％ Example 4 118 8.3 2.0％

[0183] Table 2 Experimental results when the mass fraction of the crosslinking agent is 0.6%

[0184] Number Gelation time / h Storage modulus / Pa Dehydration rate / % Example 1 39 13.2 2.8％ Example 2 32 11.8 3.4％ Example 3 32 11.3 3.6％ Example 4 36 12.9 2.2％

[0185] It can be seen from the above table that the hydroxymethyl of the environmentally friendly branched hydroxylamine crosslinking agent of the present invention is slowly released, and the controllability of the gel-forming reaction of the gel is improved, which can be used for deep plugging and profile control operations in medium and high permeability oil reservoirs.

[0186] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. An environmentally friendly branched hydroxylamine crosslinking agent, characterized in that, Its structural formula is shown in any one of formulas (1)-(3): Wherein: R is one of methyl, ethyl, and butyl, preferably methyl or butyl.

2. A preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 1, characterized in that, It includes the following steps: (1) Add appropriate amounts of aldehyde and water to a reactor equipped with a condensation device and a stirring device to obtain a mixed solution, transfer the reactor to an oil bath or a water bath, turn on the condensation device and the stirring device, heat to a first temperature, continuously stir until the mixed solution becomes clear and transparent, then add a certain amount of aqueous solution of alkali to the reactor, adjust its pH value to alkaline, and finally add an appropriate amount of polyamine to the reactor. After reacting for a period of time, obtain a reaction solution. Take out the reaction solution and let it stand in the air. After the reaction solution becomes solid, grind it to obtain a branched hydroxylamine crosslinking agent intermediate; (2) Take an appropriate amount of the branched hydroxylamine crosslinking agent intermediate obtained in step (1), pour it into a reactor equipped with a condensation device and a stirring device, and transfer the reactor to an oil bath or a water bath. Start the condensation device and the stirring device; add an appropriate amount of alcohol to the reactor, heat to a second temperature, then dropwise add an acid to the reactor, adjust its pH value to acidic, and start the etherification reaction. After reacting for a period of time, obtain a reaction solution. Add a small amount of aqueous solution of alkali to the reactor, adjust the pH value of the reaction solution to weakly alkaline, and distill off the excess alcohol and water under reduced pressure to obtain an environmentally friendly branched hydroxylamine crosslinking agent.

3. The preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 2, characterized in that, In step (1), the aldehyde is at least one of formaldehyde or paraformaldehyde, preferably formaldehyde, and / or In step (1), the aqueous solution of alkali is at least one of sodium hydroxide aqueous solution, sodium bicarbonate aqueous solution, and sodium carbonate aqueous solution, preferably sodium carbonate aqueous solution; The mass concentration of the aqueous solution of alkali is 5%-20%.

4. The preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 2, characterized in that, In step (1), the polyamine is at least one of 1,3,5-triazine-2,4,6-triamine, pyrazine-2,5-diamine, and 4,6-pyrimidinediamine, preferably 1,3,5-triazine-2,4,6-triamine, and / or In step (1), when an appropriate amount of polyamine is added to the reactor and the polyamine is dissolved, the molar ratio of the aldehyde to the polyamine in the reaction system is (8-10):1, and / or In step (1), the mass ratio of the aldehyde to the water is 100:(100-1000).

5. The preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 2, characterized in that, In step (1), the first temperature is 40-80°C, preferably 70-75°C, and / or In step (1), add a certain amount of aqueous solution of alkali to the reactor and adjust its pH value to 8-12, preferably 9-11.

6. The preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 2, characterized in that, In step (1), the reaction time of the aldehyde and the polyamine is at least 20 minutes, preferably 20-120 minutes, and / or In step (2), the alcohol is at least one of methanol, ethanol, and butanol, preferably methanol.

7. The preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 2, characterized in that, In step (2), the acid is one of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, preferably dilute sulfuric acid, and / or In step (2), the aqueous solution of alkali is at least one of sodium hydroxide aqueous solution, sodium bicarbonate aqueous solution, and sodium carbonate aqueous solution, preferably sodium hydroxide aqueous solution, and / or The mass concentration of the aqueous solution of alkali is 5%-20%.

8. The preparation method of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 2, characterized in that, The mass ratio of the branched hydroxylamine crosslinking agent intermediate described in step (2) to the alcohol is (150 - 500):100, and / or The second temperature in step (2) is 40 - 70 °C, preferably 50 - 60 °C, and / or The etherification reaction time in step (2) is at least 30 minutes, preferably 30 - 120 minutes, and / or In step (2), an acid is added dropwise to the reactor, and its pH value is adjusted to 2-5. Then the etherification reaction is started. After reacting for 30-120 minutes, a reaction solution is obtained. A small amount of aqueous solution of alkali is added to the reactor, and the pH value of the reaction solution is adjusted to 8-8.5 。 9. An environmentally friendly branched hydroxylamine crosslinking agent prepared by the preparation method according to any one of claims 2-8.

10. Application of the environmentally friendly branched hydroxylamine crosslinking agent according to claim 1 or 9 as a crosslinking agent for deep water shutoff and profile control in the exploitation of medium-high permeability oil reservoirs.

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