Crosslinking agent for degradable gel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oilfield chemistry, and discloses a cross-linking agent for degradable gel and a preparation method and application thereof.The preparation method comprises the steps that a compound A is dissolved in an organic solvent and stirred to be uniform, and a first solution is obtained; adding a polymerization inhibitor and a compound B into the first solution, and uniformly stirring at room temperature to obtain a second solution; the second solution is sequentially subjected to heating stirring, diethyl ether washing, ethanol recrystallization, suction filtration and drying, and the cross-linking agent for gel is obtained. According to the invention, a non-conjugated aromatic system is added into a cross-linking agent structure, so that the prepared gel can be automatically degraded under a certain temperature condition; ammonium ions and halide ions are added into a cross-linking agent structure, so that the anti-pollution performance of the gel is enhanced, and the problems that existing gel is difficult to degrade and poor in anti-pollution performance are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and in particular relates to a cross-linking agent for degradable gel, a preparation method and application thereof. Background Art

[0002] Before gelation, polymer gel materials have the characteristics of good rheology and easy injection; after gelation, they have the characteristics of deformability and adjustable plugging strength. Therefore, polymer gel has unique advantages in plugging operations. Since the polymer gel material itself has high deformability and will not be restricted by the leakage channel, after injection, it can be cross-linked and copolymerized by the easy-to-flow polymer or monomer solution to form an immobile jelly or gel, which can produce a plugging effect in extremely small channels. This material is liquid before injection. After injection, under formation conditions, it is transformed into a solid gel with a three-dimensional network structure due to cross-linking, and has good plugging properties.

[0003] However, existing gel plugging agents are difficult to use for temporary plugging operations. There are problems such as difficulty in breaking the gel and reservoir pollution. On-site construction is difficult and risky. There is an urgent need for a cross-linking agent for degradable gel that is easily degradable and has strong anti-pollution properties. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a cross-linking agent for a degradable gel with controllable gelation time, which can spontaneously degrade under certain temperature conditions and has a low viscosity of the product after degradation, as well as a preparation method and application thereof, so as to solve the problems that the existing gel plugging agents are difficult to degrade and have poor anti-pollution performance.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A cross-linking agent for degradable gel, the general structural formula of the cross-linking agent for degradable gel is:

[0007]

[0008] Among them, R1 is Any one of; 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] Further, m=n=6-18.

[0010] In a second aspect, the present invention discloses a method for preparing a cross-linking agent for a degradable gel, comprising the following steps:

[0011] Dissolving compound A in an organic solvent and stirring uniformly to obtain a first solution;

[0012] Adding a polymerization inhibitor and compound B to the first solution and stirring the mixture at room temperature to obtain a second solution;

[0013] The second solution is sequentially heated and stirred, washed with ether, recrystallized with ethanol, filtered and dried to obtain a cross-linking agent for gel;

[0014] The structural formula of compound A is:

[0015]

[0016] The structural formula of compound B is:

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

[0018] Further, the organic solvent includes 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°C.

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

[0022] Furthermore, the inhibitor includes polyphenol or phenothiazine, and the polyphenol is hydroquinone or catechol.

[0023] In a third aspect, the present invention discloses an application of a cross-linking agent for degradable gel in a low-temperature degradable gel plugging agent for oil fields. The cross-linking agent for degradable gel is the cross-linking agent for degradable gel mentioned above.

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

[0025] Wherein, the acrylic monomer includes one or more of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid and acrylonitrile;

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

[0027] Technical effects and advantages of the present invention:

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

[0029] 2. The crosslinking agent for the degradable gel of the present invention contains a non-conjugated aromatic system in its structure, and therefore does not require additional conditions, such as light, acidic conditions or alkaline conditions, and can degrade itself under certain temperature conditions.

[0030] 3. The cross-linking agent for low-temperature degradable gel of the present invention has good anti-pollution performance because of the presence of ammonium ions and halide ions in the structure, and the concentration of calcium and magnesium ions has little effect on the performance of the temporary plugging agent.

[0031] 4. When the cross-linking agent for degradable gel of the present invention is used in low-temperature degradable gel plugging agent, a three-dimensional network structure is formed by chemical cross-linking. Under the action of bottom hole temperature, weak bonds in the functional cross-linking agent are broken, and the three-dimensional network structure collapses. The generated linear low molecular weight water-soluble polymer dissolves in the formation water to form a low viscosity fluid. No flowback is required and subsequent water injection is not affected. Temporary plugging and maintenance of oil field wells can be achieved.

[0032] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of a method for preparing a cross-linking agent for degradable gel according to the present invention;

[0034] Figure 2 The figure is a relationship diagram between the gelation and degradation performance of the gel plugging agent prepared in Example 3 of the present invention and the concentrations of calcium and magnesium ions. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The present invention provides a cross-linking agent for a degradable gel, and the general structural formula of the cross-linking agent for a degradable gel is:

[0037]

[0038] Among them, R1 is Any one of; 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] Second, as Figure 1 As shown, the present invention discloses a method for preparing a cross-linking agent for a degradable gel, comprising the following steps:

[0041] Dissolving compound A in an organic solvent and stirring uniformly to obtain a first solution;

[0042] Adding a polymerization inhibitor and compound B to the first solution and stirring the mixture at room temperature to obtain a second solution;

[0043] The second solution is sequentially heated and stirred, washed with ether, recrystallized with ethanol, filtered and dried to obtain a cross-linking agent for gel;

[0044] The structural formula of compound A is:

[0045]

[0046] The structural formula of compound B is:

[0047] Wherein, 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 polyphenol or phenothiazine, and the polyphenol is hydroquinone or catechol.

[0053] In a third aspect, the present invention discloses an application of a cross-linking agent for degradable gel in a low-temperature degradable gel plugging agent for oil fields. The cross-linking agent for degradable gel is the cross-linking agent for degradable gel mentioned above.

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

[0055] Wherein, the acrylic monomer includes one or more of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid and acrylonitrile;

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

[0057] In order to better illustrate the present invention, the following examples and comparative examples are provided.

[0058] Example 1

[0059] S1: dissolving compound A in a methanol solution and stirring thoroughly to obtain a first solution;

[0060] S2: adding the polymerization inhibitor phenothiazine and compound B to the first solution, and stirring the mixture at room temperature to obtain a second solution;

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

[0062] S3: The second solution was heated to 40° C. under stirring and reacted for 48 hours. The crosslinker compound for gel was obtained by washing with ether, recrystallizing with ethanol, filtering and drying.

[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 crosslinking agent compound for the prepared gel is:

[0068]

[0069] Example 2

[0070] S1: dissolving compound A in a methanol solution and stirring thoroughly to obtain a first solution;

[0071] S2: adding the polymerization inhibitor phenothiazine and compound B to the first solution, and stirring the mixture at room temperature to obtain a second solution;

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

[0073] S3: The second solution was heated to 40° C. under stirring and reacted for 48 hours. The crosslinker compound for gel was obtained by washing with ether, recrystallizing with ethanol, filtering and drying.

[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 crosslinking agent compound for the prepared gel is:

[0079]

[0080] Example 3

[0081] The low-temperature degradable gel plugging agent was prepared by using the cross-linking agent for degradable gel prepared in Example 1, and the raw material formula was composed of: 15.0wt% acrylamide monomer, 2.0wt% cross-linking agent for degradable gel, 0.01wt% azobisisobutyramidine hydrochloride, and the balance was water.

[0082] The preparation steps include:

[0083] (1) adding water and acrylamide monomer into a reaction container and mixing;

[0084] (2) Adding a cross-linking agent for degradable gel and azobisisobutylamidine hydrochloride to the solution obtained in step (1) to carry out polymerization reaction, and cooling the solution to obtain a low-temperature degradable gel plugging agent.

[0085] Example 4

[0086] The low-temperature degradable gel plugging agent was prepared using the cross-linking agent for degradable gel prepared in Example 2, and the raw material formula was composed of: 5wt% of 2-acrylamide-2-methylpropanesulfonic acid monomer, 1.0wt% of the cross-linking agent for degradable gel, 0.001wt% of azobisisobutyramidine hydrochloride, and the balance was water.

[0087] The preparation steps include:

[0088] (1) adding water and 2-acrylamide-2-methylpropanesulfonic acid monomer into a reaction vessel and mixing;

[0089] (2) Adding a cross-linking agent for degradable gel and azobisisobutylamidine hydrochloride to the solution obtained in step (1) to carry out polymerization reaction, and cooling the solution to obtain a low-temperature degradable gel plugging agent.

[0090] Comparative Example

[0091] The degradable gel plugging agent was prepared by replacing the degradable gel cross-linking agent in Example 3 with commercially available polyethylene glycol o-phenylphenyl ether acrylate.

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

[0093] Table 1

[0094]

[0095] As can be seen from Table 1, the compound prepared in this scheme is used as a cross-linking agent for degradable gel in a degradable gel plugging agent. The system is applicable to a temperature range of 50-70°C, a gelling time of 3-4h adjustable, a degradation time of 6-7d controllable, and a viscosity of ≤10mPa·s after degradation. The plugging agent system of the comparative example is firstly insoluble in water and cannot be used for plugging operations in oil fields with water injection development mode. At the same time, its degradation requires acid or light conditions to be degraded, and may also damage the environment.

[0096] Furthermore, the anti-pollution performance of the gel plugging agent prepared in Example 3 was tested, and the effects of the total mineralization of 20000 mg / L and the concentrations of calcium and magnesium ions 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, showing good anti-pollution performance.

[0097] In summary, the present invention adds a non-conjugated aromatic system to the cross-linking agent structure, so that the gel does not require additional conditions, such as light, acidic conditions or alkaline conditions, when used, and can self-degrade under certain temperature conditions, and has the characteristics of controllable gelation time, spontaneous degradation under certain temperature conditions, and low viscosity of the degradation product; by adding ammonium ions and halide ions to the cross-linking agent structure, the influence of the concentration of calcium and magnesium ions on the performance of the temporary plugging agent is reduced, and the anti-pollution performance of the temporary plugging agent is improved.

[0098] Finally, it should be noted that the above 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 aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cross-linking agent for degradable gel, characterized in that: The general structural formula of the cross-linking agent for the degradable gel is: Among them, R1 is Any one of; 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. A cross-linking agent for degradable gel according to claim 1, characterized in that: m=n=6-18.

3. A method for preparing a cross-linking agent for degradable gel, characterized in that: The steps include: Dissolving compound A in an organic solvent and stirring uniformly to obtain a first solution; Adding a polymerization inhibitor and compound B to the first solution and stirring the mixture at room temperature to obtain a second solution; The second solution is sequentially heated and stirred, washed with ether, recrystallized with ethanol, filtered and dried to obtain a cross-linking agent for gel; The structural formula of the compound A is: The structural formula of the compound B is: Wherein, 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 cross-linking agent for degradable gel according to claim 3, characterized in that: The organic solvent includes methanol and / or ethanol.

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

1.

6. The method for preparing a cross-linking agent for degradable gel according to claim 3, characterized in that: The heating temperature of the heating and stirring is 40-65°C.

7. The method for preparing a cross-linking agent for degradable gel according to claim 6, characterized in that: The heating and stirring time is 12-48h.

8. The method for preparing a cross-linking agent for degradable gel according to claim 3, characterized in that: The polymerization inhibitor comprises polyphenol or phenothiazine, and the polyphenol is hydroquinone or catechol.

9. Application of a cross-linking agent for degradable gel in a low-temperature degradable gel plugging agent for oil fields, characterized in that: The cross-linking agent for degradable gel is the cross-linking agent for degradable gel according to claim 1 or 2.

10. The use of a cross-linking agent for degradable gel according to claim 9 in a low-temperature degradable gel plugging agent for oil fields, characterized in that: The gel plugging agent comprises: 5.0-15wt% of propylene monomer, 1.0-2wt% of gel crosslinking agent, 0.01-0.001wt% of initiator, and the balance is water; Wherein, the acrylic monomer includes one or more of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid and acrylonitrile; The initiator includes ammonium persulfate and / or azobisisobutyramidine hydrochloride.

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