A functional crosslinking agent, its preparation method and application

Abstract

The application discloses a functional crosslinking agent and a preparation method and application thereof, relates to the field of oil field chemistry and applied technology, and the structure of the functional crosslinking agent comprises a quaternary ammonium salt structure, an ester group and a conjugated non-planar central core. The functional crosslinking agent can be self-degraded under certain temperature conditions without additional conditions such as light, acidic conditions or alkaline conditions. The method is simple, reliable and high in yield, and is suitable for large-scale industrial production. A three-dimensional network structure is formed through chemical crosslinking. Under the action of an embedded catalyst, weak bonds in the functional crosslinking agent are broken, the three-dimensional network structure is disintegrated, linear low-molecular-weight water-soluble polymers are generated and dissolved in formation water, a low-viscosity fluid is formed, and the subsequent water injection is not affected, so that temporary plugging and repair of low-temperature oil wells can be realized.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemistry and application technology, and in particular to a functional crosslinking agent, its preparation method, and its application. Background Technology

[0002] In oilfields employing water injection development, a large number of pressurized water injection wells require inspection and workover operations annually as development progresses, resulting in substantial operational demands. Conventional well control measures involve large overflows during tubing string setup and setup, posing significant well control risks and making flowback fluid treatment difficult. Currently, pressurized water injection well operations primarily employ two methods: conventional operations after depressurization and live operation, to ensure the smooth conduct of inspection and workover operations for high-pressure water injection wells. Because wellhead pressures in pressurized water injection wells in oilfields are generally high, with tubing pressures typically exceeding 10 MPa, depressurization involves a very large drainage volume and costly wastewater treatment, while the long blowout cycle also impacts operational efficiency. Live operation, with its complex tubing string setup and setup procedures, long average well dwell time, and high operational costs, further complicates the process.

[0003] Before gelation, polymer gel materials exhibit good rheological properties and are easy to inject; after gelation, they are deformable and have adjustable plugging strength. Therefore, polymer gels offer unique advantages for plugging operations. Due to their high deformability, polymer gel materials are not limited by leakage channels. After injection, they can crosslink and copolymerize easily flowing polymer or monomer solutions to form non-flowing gels or jelly, which can achieve plugging effects in extremely small channels. This material is liquid before injection, and after injection, under formation conditions, it transforms into a solid gel with a three-dimensional network structure due to crosslinking, exhibiting excellent plugging properties. However, currently available similar gel-based plugging agents in China are difficult to apply for temporary plugging operations, facing problems such as difficulty in gel breaking, reservoir contamination, and high risks and difficulties in on-site construction.

[0004] Patent document CN107619371B discloses "o-nitrobenzene diacetal ethyl acrylate and its preparation method and application as a crosslinking agent with dual degradation properties." Using o-nitrobenzenealdehyde, trimethyl orthoformate, and hydroxyethyl acrylate as starting materials, a two-step substitution reaction yields the target product, o-nitrobenzene diacetal ethyl acrylate. This o-nitrobenzene diacetal ethyl acrylate contains an ether group in its structure, has an application temperature of 50℃~90℃, and requires light and acidic conditions for degradation. Summary of the Invention

[0005] The purpose of this invention is to provide a functional crosslinking agent, its preparation method, and its application, which can effectively overcome the problems of existing gel-based plugging agents in oilfields using low-temperature water injection development models, such as difficulty in breaking down the gel, inability to spontaneously degrade, and reservoir contamination. To achieve the above objective, this invention provides the following technical solution:

[0006] The first objective of this invention is to provide a functional crosslinking agent, the general structural formula of which is as follows:

[0007]

[0008] In the formula:

[0009] R1 = H, CH3;

[0010] R2=CH2CH2, CH2CH2CH2, CH(CH3)CH2, CH2CH2CH2CH2;

[0011]

[0012] X = F, Cl, Br, I.

[0013] Furthermore, the general structural formula of the crosslinking agent is as follows:

[0014]

[0015] In the formula:

[0016] R1 = H;

[0017] R2=CH2CH2CH2, CH(CH3)CH2;

[0018]

[0019] X = F, Cl, Br, I.

[0020] A second objective of this invention is to provide a method for preparing a functional crosslinking agent, the method comprising the following steps:

[0021] Step S1: Dissolve alkenyl tertiary amine ester compound A in an organic solvent, stir thoroughly until homogeneous, then add an appropriate amount of polymerization inhibitor and haloalkyl compound B, and stir thoroughly at room temperature until homogeneous before use.

[0022] Step S2: Under stirring conditions, the mixture from step S1 is heated and reacted, then washed with ether, recrystallized with ethanol, filtered and dried.

[0023] Furthermore, the synthetic route of the functional crosslinking agent is as follows:

[0024]

[0025] In the formula:

[0026] R1 = H, CH3;

[0027] R2=CH2CH2, CH2CH2CH2, CH(CH3)CH2, CH2CH2CH2CH2;

[0028]

[0029] X = F, Cl, Br, I.

[0030] Furthermore, the synthetic route of the functional crosslinking agent is as follows:

[0031]

[0032] In the formula:

[0033] R1 = H;

[0034] R2=CH2CH2CH2, CH(CH3)CH2;

[0035]

[0036] X = F, Cl, Br, I.

[0037] Furthermore, the organic solvent is one or more of methanol or ethanol.

[0038] Furthermore, the molar mass ratio of compound A to compound B is 4 to 2:1.

[0039] Furthermore, the polymerization inhibitor is a polyphenol or a phenothiazine; the polyphenol is hydroquinone or catechol.

[0040] Furthermore, the conditions for the heating reaction include: a reaction temperature of 40–65°C and a reaction time of 12–48 h.

[0041] A third objective of this invention is to provide an application of a functional crosslinking agent, which is used in a low-temperature degradable gel plugging agent.

[0042] The technical effects and advantages of this invention are as follows:

[0043] (1) The functional crosslinking agent designed in this invention comprises a quaternary ammonium salt structure, ester groups, and a conjugated non-planar central core. It can self-degrade under certain temperature conditions without additional conditions such as light, acidic conditions, or alkaline conditions. This is because the quaternary ammonium salt structure can increase the hydrolysis rate of adjacent ester groups, thereby achieving the required self-degradation performance; the introduction of the conjugated non-planar central core can improve the stability of the crosslinking agent at low temperatures while still meeting the requirements for subsequent self-degradation.

[0044] (2) The method of the present invention can prepare functional crosslinking agents with good performance, and the technology is simple, reliable, and has a high yield, making it suitable for large-scale industrial production.

[0045] (3) The application of the functional crosslinking agent of the present invention in low-temperature biodegradable gel plugging agent is to form a three-dimensional network structure through chemical crosslinking. Under the action of the built-in catalyst, the weak bonds in the functional crosslinking agent break, the three-dimensional network structure disintegrates, and the generated linear low molecular weight water-soluble polymer dissolves in the formation water to form a low viscosity fluid. No backflow is required, and it does not affect subsequent water injection. It can realize temporary plugging and maintenance of low-temperature oilfield wells.

[0046] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 The FT-IR spectrum of the functional crosslinking agent 1 prepared in Example 1 of this invention;

[0049] Figure 2 The image shows the 1H NMR spectrum of the functional crosslinking agent 1 prepared in Example 1 of this invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] To address the shortcomings of existing technologies, the present invention provides the following technical solution:

[0052] The first objective of this invention is to provide a functional crosslinking agent, the general structural formula of which is as follows:

[0053]

[0054] In the formula:

[0055] R1 = H, CH3;

[0056] R2=CH2CH2, CH2CH2CH2, CH(CH3)CH2, CH2CH2CH2CH2;

[0057]

[0058] X = F, Cl, Br, I.

[0059] The aforementioned functional crosslinking agent structure includes a quaternary ammonium salt structure, ester groups, and a conjugated non-planar central core. This structure can self-degrade under certain temperature conditions without the need for additional breaker agents. The quaternary ammonium salt structure can increase the hydrolysis rate of adjacent ester groups, thereby achieving the required self-degradation performance; the introduction of the conjugated non-planar central core can improve the stability of the crosslinking agent at low temperatures, while still meeting the requirements for subsequent self-degradation.

[0060] Preferably, the functional crosslinking agent has the following structural formula:

[0061] R1 = H;

[0062] R2=CH2CH2CH2, CH(CH3)CH2;

[0063]

[0064] X = F, Cl, Br, I.

[0065] The aforementioned preferred functional crosslinking agents can form a more reasonable three-dimensional spatial structure during the crosslinking process, finding a balance between self-degradation and stability.

[0066] A second objective of this invention is to provide a method for preparing a functional crosslinking agent, the method comprising the following steps:

[0067] Step S1: Dissolve compound A in an organic solvent, stir thoroughly until homogeneous, then add an appropriate amount of polymerization inhibitor and compound B, and stir thoroughly at room temperature until homogeneous before use.

[0068] In step S2, the mixture from step S1 is heated under stirring conditions, then washed with ether, recrystallized with ethanol, filtered and dried to obtain the functional crosslinking agent.

[0069] Furthermore, the synthetic route of the functional crosslinking agent is as follows:

[0070]

[0071] In the formula:

[0072] R1 = H, CH3;

[0073] R2=CH2CH2, CH2CH2CH2, CH(CH3)CH2, CH2CH2CH2CH2;

[0074]

[0075] X = F, Cl, Br, I;

[0076] Preferably, the functional crosslinking agent has the following structural formula:

[0077] R1 = H;

[0078] R2=CH2CH2CH2, CH(CH3)CH2;

[0079]

[0080] X = F, Cl, Br, I.

[0081] Furthermore, the organic solvent is one or more of methanol or ethanol, and its amount is equal to that of compound A.

[0082] Furthermore, the molar mass ratio of compound A to compound B is 4 to 2:1.

[0083] Further, the polymerization inhibitor is a polyphenol or a phenothiazine, and its addition amount accounts for 0.1% to 0.5% of the total mass of the added substances (i.e., compound A, compound B, organic solvent and polymerization inhibitor); the polyphenol is hydroquinone or catechol.

[0084] Furthermore, the conditions for the heating reaction include: a reaction temperature of 40–65°C and a reaction time of 12–48 h.

[0085] Example 1 (Synthesis of Functional Crosslinking Agent 1)

[0086] Step S1: Dissolve compound A1 in methanol solution, stir thoroughly until homogeneous, then add polymerization inhibitor (phenothiazine) and compound B1, stir thoroughly until homogeneous at room temperature and set aside for use.

[0087] The molar ratio of compound A1 to compound B1 is 2:1;

[0088] Step S2: Under stirring conditions, the mixture from step S1 is heated to 40°C and reacted for 12 hours. After washing with ether, recrystallization with ethanol, filtration and drying, functional crosslinking agent 1 is obtained.

[0089] The synthetic route of functional crosslinking agent 1 is as follows:

[0090]

[0091] Figure 1 The FT-IR spectrum of the functional crosslinking agent 1 prepared in Example 1 of this invention is shown below. Figure 1 Middle, 3270cm -1 The characteristic absorption peak of NH is at 3121 cm⁻¹. -1 The peak at 2958 cm⁻¹ represents the =C—H vibrational absorption peak of the carbon-carbon double bond. -1 The peak at 1723 cm⁻¹ represents the stretching vibration of the C-H bond in the double bond. -1 The peak at 1471 cm⁻¹ represents the stretching vibration of the C=O bond in an ester bond. -1 The peaks at 1278 and 1193 cm⁻¹ are vibrational absorption peaks of C=C. -1 The absorption peaks at 975 cm⁻¹ represent the antisymmetric and symmetric vibrational absorption peaks of C–O, respectively. -1 The peak at this point represents the out-of-plane bending vibration of the =C—H double bond. Infrared spectroscopy reveals characteristic absorption peaks for the benzene ring, carbon-carbon double bond, and ester group in crosslinking agent 1, indicating successful synthesis of the target crosslinking agent.

[0092] Figure 2 The functional crosslinking agent 1 prepared in Example 1 of this invention 1 H NMR spectrum, in Figure 2 In the spectrum, positions 6.41, 6.12, and 5.83 represent the chemical shifts of the carbon-carbon double bond, position 4.59 represents the chemical shift of the proton connecting the ester atom, positions 3.52, 3.30, and 4.50 represent the chemical shifts of the proton connecting the nitrogen atom, and position 7.11 represents the chemical shift of the proton on the benzene ring. The spectrum shows that the synthesized crosslinking agent contains both carbon-carbon double bonds and ester groups, which is consistent with the expected structure of the designed crosslinking agent.

[0093] Example 2 (Synthesis of Functional Crosslinking Agent 2)

[0094] Step S1: Dissolve compound A1 in an ethanol solution, stir thoroughly until homogeneous, then add the polymerization inhibitor (hydroquinone) and compound B2, and stir thoroughly at room temperature until homogeneous before use;

[0095] The molar ratio of compound A1 to compound B2 is 3:1;

[0096] Step S2: Under stirring conditions, the mixture from step S1 is heated to 50°C and reacted for 24 hours. After washing with ether, recrystallization with ethanol, filtration and drying, functional crosslinking agent 2 is obtained.

[0097] The synthetic route of functional crosslinking agent 2 is as follows:

[0098]

[0099] Example 3 (Synthesis of Functional Crosslinking Agent 3)

[0100] Step S1: Dissolve compound A1 in an ethanol solution and stir thoroughly until homogeneous; then add the polymerization inhibitor (hydroquinone) and compound B3, and stir thoroughly at room temperature until homogeneous before use.

[0101] The molar ratio of compound A1 to compound B3 is 4:1;

[0102] Step S2: Under stirring conditions, the mixture from step S1 is heated to 65°C and reacted for 48 hours. After washing with ether, recrystallization with ethanol, filtration and drying, the functional crosslinking agent 3 is obtained.

[0103] The synthetic route for functional crosslinking agent 3 is as follows:

[0104]

[0105] Example 4

[0106] The low-temperature degradable gel plugging agents formed by crosslinking using the functional crosslinking agent of the present invention are shown in Table 1. The crosslinking agent used in the control experiment was ethyl o-nitrobenzene diacetal diacrylate, with the following structural formula:

[0107]

[0108] Table 1 Experiments with biodegradable gel plugging agents

[0109]

[0110]

[0111] As shown in Table 1, functional crosslinking agents 1, 2, and 3, used as functional crosslinking agents in combination with propylene monomers and initiators in a biodegradable gel plugging agent formulation, exhibit a suitable temperature range of 50–90°C, an adjustable gelation time of 2–4 hours, a controllable degradation time of 7–10 days, and a post-degradation viscosity ≤10 mPa·s. In contrast, the control system using crosslinking agent 1 is insoluble in water, making it unsuitable for plugging operations in water-injection oilfields. Furthermore, its degradation requires acid or light conditions and may potentially damage the environment. Therefore, the gel plugging agent system constructed using the functional crosslinking agents described in this invention possesses characteristics such as controllable gelation time, spontaneous degradation under certain temperature conditions, and low viscosity of the post-degradation product. Moreover, this gel degrades without the need for additional breaker agents.

[0112] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A functional crosslinking agent, characterized in that, The general structural formula of the crosslinking agent is as follows: ； In the formula: R1 = H or CH3; R2=CH2CH2, CH2CH2CH2, CH(CH3)CH2 or CH2CH2CH2CH2; R3= ； X = F, Cl, Br or I.

2. The functional crosslinking agent according to claim 1, characterized in that, The general structural formula of the crosslinking agent is as follows: ； In the formula: R1=H; R2 = CH2CH2CH2 or CH(CH3)CH2; R3= ； X = F, Cl, Br or I.

3. A method for preparing a functional crosslinking agent as described in claim 1 or 2, characterized in that, The method includes the following steps: Step S1: Dissolve alkenyl tertiary amine ester compound A in an organic solvent, stir thoroughly until homogeneous, then add an appropriate amount of polymerization inhibitor and haloalkyl compound B, and stir thoroughly at room temperature until homogeneous before use. Step S2: Under stirring conditions, the mixture from step S1 is heated and reacted, then washed with ether, recrystallized with ethanol, filtered and dried.

4. The method for preparing a functional crosslinking agent according to claim 3, characterized in that, The synthetic route of the functional crosslinking agent is as follows: ； In the formula: R1 = H or CH3; R2=CH2CH2, CH2CH2CH2, CH(CH3)CH2 or CH2CH2CH2CH2; R3= ； X = F, Cl, Br or I.

5. The method for preparing a functional crosslinking agent according to claim 4, characterized in that, The synthetic route of the functional crosslinking agent is as follows: ； In the formula: R1=H; R2 = CH2CH2CH2 or CH(CH3)CH2; R3= ； X = F, Cl, Br or I.

6. The method for preparing a functional crosslinking agent according to claim 3, characterized in that, The organic solvent is one or more of methanol or ethanol.

7. The method for preparing a functional crosslinking agent according to claim 3, characterized in that, The molar mass ratio of compound A to compound B is 4~2:

1.

8. The method for preparing a functional crosslinking agent according to claim 3, characterized in that, The polymerization inhibitor is a polyphenol or a phenothiazine; the polyphenol is hydroquinone or catechol.

9. The method for preparing a functional crosslinking agent according to claim 3, characterized in that, The conditions for the heating reaction include: a reaction temperature of 40~65 ℃ and a reaction time of 12~48 h.

10. An application of the functional crosslinking agent as described in claim 1 or 2, characterized in that, The functional crosslinking agent is used in low-temperature degradable gel plugging agents.

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