Crosslinking agent for degradable gel, preparation method and application thereof

Abstract

The application belongs to the technical field of oil field chemistry, and discloses a degradable gel crosslinking agent, a preparation method and application thereof, and the preparation method comprises the following steps: dissolving compound A in an organic solvent and stirring uniformly to obtain a first solution; adding a polymerization inhibitor and compound B into the first solution and stirring uniformly at room temperature to obtain a second solution; and sequentially performing heating stirring, ether washing, ethanol recrystallization, suction filtration and drying on the second solution to obtain the gel crosslinking agent. The gel can self-degrade under certain temperature conditions; by adding ammonium ions and halide ions in the structure of the crosslinking agent, the anti-pollution performance of the gel is enhanced, and the problems of poor degradability and poor anti-pollution performance of the existing gel are solved.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, and particularly relates to a crosslinking agent for biodegradable gels, its preparation method, and its application. Background Technology

[0002] 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 in 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.

[0003] However, existing gel-based plugging agents are difficult to apply to temporary plugging operations, and have problems such as difficulty in breaking down the gel and contamination of the reservoir. On-site construction is difficult and risky, and there is an urgent need for a biodegradable crosslinking agent for gels that is easy to degrade and has strong anti-contamination properties. Summary of the Invention

[0004] In order to overcome the defects of the existing technology, the present invention aims to provide a degradable gel crosslinking agent, preparation method and application of which has controllable gelation time, can spontaneously degrade under certain temperature conditions, and produces low viscosity products after degradation, thereby solving the problems of existing gel-type plugging agents being difficult to degrade and having poor anti-pollution performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A crosslinking agent for biodegradable gels, the general structural formula of which is:

[0007]

[0008] Where R1 is , , and Any one of the following; m, n, z are the number of carbon atoms, m=6-18, n=6-18, z=1-18; X is one or more of F, Cl, Br and I.

[0009] Furthermore, m = n = 6 - 18.

[0010] Secondly, this invention discloses a method for preparing a crosslinking agent for biodegradable gels, comprising the following steps:

[0011] Compound A was dissolved in an organic solvent and stirred until homogeneous to obtain the first solution;

[0012] Add the polymerization inhibitor and compound B to the first solution and stir until homogeneous at room temperature to obtain the second solution;

[0013] The second solution was subjected to heating and stirring, washing with ether, recrystallization with ethanol, filtration and drying to obtain a crosslinking agent for gelation.

[0014] The structural formula of compound A is:

[0015]

[0016] The structural formula of compound B is: or or or

[0017] Where m = 6-18, n = 6-18, z = 1-18, and X is one or more of F, Cl, Br, and I.

[0018] Furthermore, the organic solvents include methanol and / or ethanol.

[0019] Furthermore, the molar ratio of compound A to compound B is 4-2:1.

[0020] Furthermore, the heating temperature for heating and stirring is 40-65℃.

[0021] Furthermore, the heating and stirring time is 12-48 hours.

[0022] Furthermore, the polymerization inhibitor includes polyphenols or phenothiazines, wherein the polyphenols are hydroquinone or catechol.

[0023] Thirdly, the present invention discloses the application of a biodegradable gel crosslinking agent in low-temperature biodegradable gel plugging agent for oil fields, wherein the biodegradable gel crosslinking agent is the aforementioned biodegradable gel crosslinking agent.

[0024] Furthermore, the gel plugging agent comprises: 5.0-15 wt% propylene monomer, 1.0-2 wt% crosslinking agent for gelation, 0.01-0.001 wt% initiator, and the balance being water;

[0025] Among them, propylene monomers include one or more of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and acrylonitrile;

[0026] Initiators include ammonium persulfate and / or azobisisobutyramidine hydrochloride.

[0027] The technical effects and advantages of this invention are as follows:

[0028] 1. The gel plugging agent of the present invention is formed by cross-linking reaction of propylene monomer and specific cross-linking agent. Compared with the traditional temperature-resistant gel system formed by cross-linking of propylene monomer and organic cross-linking agent, the gel formed after curing has better high-temperature stability, higher strength and better viscoelastic properties, and has a better sealing effect on leakage channels.

[0029] 2. The crosslinking agent for the biodegradable gel of the present invention does not require additional conditions, such as light, acidic conditions or alkaline conditions, and can degrade on its own under certain temperature conditions.

[0030] 3. The crosslinking agent for low-temperature biodegradable gel of the present invention, due to the presence of ammonium ions and halide ions in its structure, has virtually no effect on the performance of the temporary plugging agent due to the presence of calcium and magnesium ions, and exhibits good anti-fouling performance.

[0031] 4. When the biodegradable gel crosslinking agent of the present invention is applied to the low-temperature biodegradable gel plugging agent, a three-dimensional network structure is formed through chemical crosslinking. Under the action of bottom hole temperature, 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 oilfield wells.

[0032] Other features and advantages of the invention will be set forth in the description which follows, 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, claims and drawings. Attached Figure Description

[0033] Figure 1 This is a flowchart of a method for preparing a crosslinking agent for a biodegradable gel according to the present invention;

[0034] Figure 2 This is a graph showing the relationship between the gelation and degradation properties of the gel plugging agent prepared in Example 3 of the present invention and the concentrations of calcium and magnesium ions. Detailed Implementation

[0035] 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.

[0036] This invention provides a crosslinking agent for biodegradable gels, the general structural formula of which is:

[0037]

[0038] Where R1 is , , and Any one of the following; m, n, z are the number of carbon atoms, m=6-18, n=6-18, z=1-18; X is one or more of F, Cl, Br and I.

[0039] In some embodiments of the present invention, m=n=6-18.

[0040] Secondly, such as Figure 1 As shown, this invention discloses a method for preparing a crosslinking agent for biodegradable gels, comprising the following steps:

[0041] Compound A was dissolved in an organic solvent and stirred until homogeneous to obtain the first solution;

[0042] Add the polymerization inhibitor and compound B to the first solution and stir until homogeneous at room temperature to obtain the second solution;

[0043] The second solution was subjected to heating and stirring, washing with ether, recrystallization with ethanol, filtration and drying to obtain a crosslinking agent for gelation.

[0044] The structural formula of compound A is:

[0045]

[0046] The structural formula of compound B is: or or or

[0047] Where m = 6-18, n = 6-18, z = 1-18, and X is one or more of F, Cl, Br, and I.

[0048] In some embodiments of the present invention, the organic solvent includes methanol and / or ethanol.

[0049] In some embodiments of the present invention, the molar ratio of compound A to compound B is 4-2:1.

[0050] In some embodiments of the present invention, the heating temperature for heating and stirring is 40-65°C.

[0051] In some embodiments of the present invention, the heating and stirring time is 12-48 hours.

[0052] In some embodiments of the present invention, the polymerization inhibitor includes a polyphenol or a phenothiazine, wherein the polyphenol is hydroquinone or catechol.

[0053] Thirdly, the present invention discloses the application of a biodegradable gel crosslinking agent in low-temperature biodegradable gel plugging agent for oil fields, wherein the biodegradable gel crosslinking agent is the aforementioned biodegradable gel crosslinking agent.

[0054] In some embodiments of the present invention, the gel plugging agent comprises: 5.0-15 wt% propylene monomer, 1.0-2 wt% crosslinking agent for gelation, 0.01-0.001 wt% initiator, and the balance being water;

[0055] Among them, propylene monomers include one or more of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and acrylonitrile;

[0056] Initiators include ammonium persulfate and / or azobisisobutyramidine hydrochloride.

[0057] To better illustrate this solution, the following embodiments and comparative examples are also provided.

[0058] Example 1

[0059] S1: Dissolve compound A in methanol solution and stir thoroughly to obtain the first solution;

[0060] S2: Add the polymerization inhibitor phenothiazine and compound B to the first solution, and stir thoroughly at room temperature to obtain the second solution;

[0061] The molar ratio of compound A to compound B is 2:1;

[0062] S3: Under stirring conditions, the second solution was heated to 40°C and reacted for 48 hours. The solution was washed with ether, recrystallized with ethanol, filtered and dried to obtain the crosslinking agent compound for gelation.

[0063] It should be noted that the structural formula of compound A in this embodiment is:

[0064]

[0065] The structural formula of compound B is:

[0066]

[0067] The structural formula of the cross-linking agent compound used to prepare the gel is:

[0068]

[0069] Example 2

[0070] S1: Dissolve compound A in methanol solution and stir thoroughly to obtain the first solution;

[0071] S2: Add the polymerization inhibitor phenothiazine and compound B to the first solution, and stir thoroughly at room temperature to obtain the second solution;

[0072] The molar ratio of compound A to compound B is 3:1;

[0073] S3: Under stirring conditions, the second solution was heated to 40°C and reacted for 48 hours. The solution was washed with ether, recrystallized with ethanol, filtered and dried to obtain the crosslinking agent compound for gelation.

[0074] It should be noted that the structural formula of compound A in this embodiment is:

[0075]

[0076] The structural formula of compound B is:

[0077]

[0078] The structural formula of the cross-linking agent compound used to prepare the gel is:

[0079]

[0080] Example 3

[0081] A low-temperature degradable gel plugging agent was prepared using the degradable gel crosslinking agent obtained in Example 1. The raw material formulation consisted of: 15.0 wt% acrylamide monomer, 2.0 wt% degradable gel crosslinking agent, 0.01 wt% azobisisobutyramidine hydrochloride, and the balance being water.

[0082] The preparation steps include:

[0083] (1) Add water and acrylamide monomer to the reaction vessel and mix well;

[0084] (2) Add a biodegradable gel crosslinking agent and azobisisobutyramidine hydrochloride to the solution obtained in step (1) to carry out a polymerization reaction, and let it stand and cool to obtain a low-temperature biodegradable gel plugging agent.

[0085] Example 4

[0086] A low-temperature degradable gel plugging agent was prepared using the degradable gel crosslinking agent obtained in Example 2. The raw material formulation consisted of: 5 wt% 2-acrylamide-2-methylpropanesulfonic acid monomer, 1.0 wt% degradable gel crosslinking agent, 0.001 wt% azobisisobutyramidine hydrochloride, and the balance being water.

[0087] The preparation steps include:

[0088] (1) Add water and 2-acrylamide-2-methylpropanesulfonic acid monomer to the reaction vessel and mix well;

[0089] (2) Add a biodegradable gel crosslinking agent and azobisisobutyramidine hydrochloride to the solution obtained in step (1) to carry out a polymerization reaction, and let it stand and cool to obtain a low-temperature biodegradable gel plugging agent.

[0090] Comparative Example

[0091] A biodegradable gel plugging agent was prepared by replacing the biodegradable gel in Example 3 with commercially available polyethylene glycol o-phenyl phenyl ether acrylate as a crosslinking agent.

[0092] The low-temperature biodegradable gel plugging agents prepared in Examples 3 and 4 were compared with the biodegradable gel plugging agents prepared in the comparative example. The test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] Table 1 shows that the compound prepared in this scheme, as a crosslinking agent for biodegradable gels, is applicable in a temperature range of 50-70℃, with an adjustable gelation time of 3-4 hours, a controllable degradation time of 6-7 days, and a viscosity ≤10 mPa·s after degradation. In contrast, the comparative plugging agent system is insoluble in water, making it unsuitable for plugging operations in oilfields with water injection development models. Furthermore, its degradation requires acid or light conditions and may damage the environment.

[0096] Furthermore, the antifouling performance of the gel plugging agent prepared in Example 3 was tested. The effects of a total mineralization of 20000 mg / L and calcium and magnesium ion concentrations of 200, 500, 1000, and 2000 mg / L on the gelation and degradation performance of the temporary plugging agent were measured. The results are as follows: Figure 2 As shown, by Figure 2 It can be seen that, due to the presence of ammonium ions and halide ions in the structure, the concentration of calcium and magnesium ions has little effect on the performance of the temporary plugging agent, thus exhibiting good anti-fouling performance.

[0097] In summary, the gel of the present invention does not require additional conditions such as light, acidic or alkaline conditions for application. It can degrade spontaneously under certain temperature conditions, and has the characteristics of controllable gelation time, spontaneous degradation under certain temperature conditions, and low viscosity of the degraded product. By adding ammonium ions and halide ions to the crosslinking agent structure, the influence of calcium and magnesium ion concentrations on the performance of the temporary plugging agent is reduced, thereby improving the anti-fouling performance of the temporary plugging agent.

[0098] 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 crosslinking agent for biodegradable gels, characterized in that, The general structural formula of the crosslinking agent for the biodegradable gel is: Where R1 is , , and Any one of the following; m, n, z are the number of carbon atoms, m=6-18, n=6-18, z=1-18; X is one or more of F, Cl, Br and I.

2. The crosslinking agent for biodegradable gels according to claim 1, characterized in that, m=n=6-18.

3. A method for preparing a crosslinking agent for a biodegradable gel as described in claim 1 or 2, characterized in that, Includes the following steps: Compound A was dissolved in an organic solvent and stirred until homogeneous to obtain the first solution; Add the polymerization inhibitor and compound B to the first solution and stir until homogeneous at room temperature to obtain the second solution; The second solution was subjected to heating and stirring, washing with ether, recrystallization with ethanol, filtration and drying in sequence to obtain a crosslinking agent for gelation. The structural formula of compound A is: The structural formula of compound B is: or or or Where m = 6-18, n = 6-18, z = 1-18, and X is one or more of F, Cl, Br, and I.

4. The method for preparing a crosslinking agent for biodegradable gels according to claim 3, characterized in that, The organic solvents include methanol and / or ethanol.

5. The method for preparing a crosslinking agent for a biodegradable gel according to claim 3, characterized in that, The molar ratio of compound A to compound B is 4-2:

1.

6. The method for preparing a crosslinking agent for a biodegradable gel according to claim 3, characterized in that, The heating temperature for the heating and stirring is 40-65℃.

7. The method for preparing a crosslinking agent for a biodegradable gel according to claim 6, characterized in that, The heating and stirring time is 12-48 hours.

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

9. The application of a biodegradable gel crosslinking agent in low-temperature biodegradable gel plugging agents for oilfields, characterized in that, The crosslinking agent for the biodegradable gel is the crosslinking agent for the biodegradable gel as described in claim 1 or 2.

10. The application of the biodegradable gel crosslinking agent according to claim 9 in a low-temperature biodegradable gel plugging agent for oilfields, characterized in that, The gel plugging agent comprises: 5.0-15 wt% propylene monomer, 1.0-2 wt% crosslinking agent for gelation, 0.01-0.001 wt% initiator, and the balance being water; The propylene monomer includes one or more of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and acrylonitrile; The initiator includes ammonium persulfate and / or azobisisobutyramidine hydrochloride.

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