High-strength self-degrading gel temporary plugging agent and preparation method thereof

Abstract

The application discloses a high-strength self-degradation gel temporary plugging agent and a preparation method thereof, and relates to the technical field of oil and gas field development. The temporary plugging agent is prepared by the following steps: firstly, a multi-arm crosslinking agent is prepared by reacting a di-primary amine compound with unsaturated glycidol; then, acrylamide monomers, acid monomers, rigid monomers and 2-methacryloyloxyethyl phosphorylcholine monomers are reacted under the action of the multi-arm crosslinking agent and an initiator; and finally, the reaction product is crushed, dried and granulated. The high-strength self-degradation gel temporary plugging agent prepared by the application has high strength, can be self-degraded, and has a high permeability recovery rate of a reservoir after degradation, and has a small influence on the reservoir.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field development, and particularly relates to a high-strength self-degradable gel temporary plugging agent and a preparation method thereof. BACKGROUND

[0002] The staged fracturing is a method of horizontal well fracturing construction, which is to carry out fracturing construction on the horizontal well by stages and multiple times to effectively improve the oil layer production in low-permeability reservoirs. When the staged fracturing is carried out, the artificial fractures that have been fractured need to be temporarily plugged to prevent the fracturing fluid from entering the artificial fractures.

[0003] The existing temporary plugging methods usually include mechanical plugging and chemical plugging. The mechanical plugging needs to lower mechanical plugging tools such as bridge plugs and packers into the wellbore, and needs to raise and lower the pipe column multiple times, which leads to high operation cost. After the fracturing construction is completed, the bridge plugs and packers need to be dissolved and ground, which takes a relatively long time and also has the risk of sand sticking to the pipe column. The chemical plugging usually lowers a temporary plugging agent into the fractures to form a plugging zone and thus complete the temporary plugging. The existing temporary plugging agent is usually a degradable polymer, such as polyglycolic acid, polylactic acid, and degradable polyacrylamide. However, although the degradable effect of the polyglycolic acid and polylactic acid temporary plugging agent is good, its cost is extremely high. The degradable polyacrylamide temporary plugging agent is a new temporary plugging agent in recent years, which uses polyethylene glycol diacrylate as a crosslinking agent. The crosslinking agent degrades quickly under high temperature conditions, which leads to the degradation of the temporary plugging agent particles and thus restores the permeability of the fractures.

[0004] The existing degradable polyacrylamide gel particles are difficult to balance their strength and degradability. When polyethylene glycol diacrylate is used as a crosslinking agent, the gel particles can self-degrade, but the strength of the synthesized gel particles is low. At the same time, the temporary plugging agent using polyethylene glycol diacrylate as a crosslinking agent has poor temperature resistance, which degrades quickly in an environment above 80℃, and is difficult to meet the actual use requirements. SUMMARY

[0005] In view of the above technical problems, the present application aims at the defects of the prior art and provides a high-strength self-degradable gel temporary plugging agent and a preparation method thereof.

[0006] The present application adopts the following technical scheme: a preparation method of a high-strength self-degradable gel temporary plugging agent, comprising the following steps:

[0007] The molar ratio of the di-primary amine compound and the unsaturated glycidol is 1:3-4.1, the di-primary amine compound and the unsaturated glycidol are respectively added into a solvent and dissolved, then the di-primary amine compound solution is added dropwise into the unsaturated glycidol solution under the conditions of 20-35 DEG C, a catalyst and a polymerization inhibitor, and the reaction is carried out, after the reaction is completed, low-boiling substances are removed by distillation under reduced pressure, and a multi-arm crosslinking agent is obtained; the unsaturated glycidol is one of glycidyl acrylate and glycidyl methacrylate, and the di-primary amine compound is one of propylene diamine, 1,3-diamino-2-propanol and butylene diamine;

[0008] The acrylamide monomer, the acid monomer, the rigid monomer and the 2-methacryloyloxyethyl phosphorylcholine monomer are polymerized under the action of an initiator and the multi-arm crosslinking agent, and after polymerization, the product is crushed, dried and granulated.

[0009] In the application, a multi-arm crosslinking agent is first prepared, the multi-arm crosslinking agent is prepared by the reaction of the epoxy group in the unsaturated glycidol and the amino group in the di-primary amine compound, and it is known to those skilled in the art that 1 mol of a primary amine group can react with 2 mol of an epoxy group, the reaction can be carried out at normal temperature, the reaction speed is fast, and the reaction yield is extremely high. Meanwhile, the multi-arm crosslinking agent generally refers to a crosslinking agent with three or more active functional groups, and in the application, 1 mol of 1,3-diamino-2-propanol can react with 4 mol of unsaturated glycidol at most. In the reaction process, the temperature cannot be too high, when the temperature is too high, the amino group in the di-primary amine compound can react with the double bond in the unsaturated glycidol to generate side reactions such as Michael addition and amine-ester exchange; meanwhile, the failure of the polymerization inhibitor leads to the self-polymerization of the unsaturated glycidol, resulting in poor crosslinking effect of the final product and affecting the performance of the temporary plugging agent.

[0010] Relatively speaking, the effect of the short-chain di-primary amine compound is relatively better, and in particular, the inventors find that the effect of ethylenediamine is relatively poor, which may be due to the short distance between the two amino groups in ethylenediamine, when the primary amine group is grafted with glycidyl methacrylate to generate a secondary amine, due to steric hindrance, it is difficult to generate a multi-arm crosslinking agent. As for the remaining similar amino acids such as lysine and ornithine, their effects are relatively poor, which may be due to the electron-withdrawing ability of the carboxyl group to the alpha amino group, resulting in the decrease of the nucleophilicity of the amino group; and the existing remaining similar materials such as melamine have a ring structure, the steric hindrance is large, and the effect is relatively poor.

[0011] Compared with the conventional polyethylene glycol diacrylate crosslinking agent, the multi-arm crosslinking agent of the application has high strength on the one hand because it is not a flexible molecular chain and the molecular chain is relatively short, and on the other hand, the crosslinking agent is a multi-arm crosslinking agent, which has high crosslinking density, can not only improve the water absorption ratio of the temporary plugging agent particles, but also further increase the mechanical strength of the temporary plugging agent particles. The self-degradable acrylamide temporary plugging agent of the application has higher strength than the existing conventional temporary plugging agent.

[0012] In the above-mentioned temporary plugging agent, the acrylamide monomer is the main monomer of the temporary plugging agent, the acidic monomer is used for modifying the temporary plugging agent to enhance its performance, the rigid monomer is mainly used for enhancing the strength of the gel particles, and the 2-methacryloyloxyethyl phosphorylcholine monomer can not only increase the water absorption ratio of the temporary plugging agent particles, but also further reduce the influence of inorganic salts on the gel particles.

[0013] For the crushing, drying and granulating operations, they are the conventional operations in the art, and the prepared gel blocks have relatively large sizes, so they are first cut into small blocks, and then the small gel blocks are dried, and the drying temperature can be set to 60 DEG C, 70 DEG C, 80 DEG C, etc., or the drying can be carried out under reduced pressure or by air blowing. After drying, the gel blocks are crushed and granulated by a crusher. The particle size of the gel particles can be set based on the actual reservoir fracture width, such as 50 mesh, 30 mesh, 20 mesh, etc., or the gel particles of multiple different mesh sizes can be compounded.

[0014] In an embodiment of the application, when the multi-arm crosslinking agent is prepared, the catalyst is tetrabutylammonium bromide, the addition amount is 1-1.5% of the total mass of the di-primary amine compound and the unsaturated glycidol, the polymerization inhibitor is p-methoxyphenol, the addition amount is 50-100 ppm, the solvent is DMF, and the reaction time is 15-25 h. The reaction time of the amino group and the epoxy group is fast, and the reaction can be quickly carried out at a low temperature. However, if the reaction is to be completely reacted to generate a tertiary amine, the reaction time needs to be prolonged.

[0015] In an embodiment of the application, the di-primary amine compound is 1,3-diamino-2-propanol. Compared with the conventional di-primary amine compound, 1,3-diamino-2-propanol has better effect, which may be due to the presence of a hydroxyl group.

[0016] In an embodiment of the application, the mass ratio of the acrylamide monomer, the acidic monomer, the rigid monomer and the 2-methacryloyloxyethyl phosphorylcholine monomer is 10:3-8:0.5-2:0.1-0.3.

[0017] One embodiment of the present application is that the acrylamide monomer is one of acrylamide and methacrylamide, the acidic monomer is at least one of acrylic acid, sodium acrylate, 2-acrylamido-2-methylpropanesulfonic acid sodium, and sodium p-styrenesulfonate; and the rigid monomer is one of N-vinylpyrrolidone and N-vinylimidazole. Among them, for the acidic monomer, the carboxylic monomers such as acrylic acid and sodium acrylate can improve the water absorption ratio of the temporary plugging agent particles, and the sulfonic monomers such as 2-acrylamido-2-methylpropanesulfonic acid sodium and sodium p-styrenesulfonate can also increase the temperature resistance and salt tolerance of the gel particles.

[0018] Further, the acidic monomer is a mixture of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid sodium with a mass ratio of 1:2, and the rigid monomer is N-vinylimidazole. After the combination of such acidic monomer, rigid monomer, and the aforementioned acrylamide monomer and 2-methacryloyloxyethylphosphocholine monomer, the comprehensive performance of the prepared temporary plugging agent particles is optimal.

[0019] One embodiment of the present application is that the initiator is one of persulfate initiator, persulfate / sodium bisulfite initiator, and water-soluble azo initiator, and the amount of the initiator is 0.1-0.8% of the total mass of all monomers; and the amount of the multi-arm crosslinking agent is 0.1-0.5% of the total mass of all monomers.

[0020] One embodiment of the present application is that the polymerization is one of aqueous solution radical polymerization and inverse emulsion polymerization. Both the aqueous solution radical polymerization and the inverse emulsion polymerization referred to herein are conventional methods in the art. The aqueous solution radical polymerization is to add all monomers, initiators, and crosslinking agents into a solvent, and to perform the reaction under the initiation temperature condition, wherein water is used as the solvent. The inverse emulsion polymerization is a polymerization mode in which oil is used as the continuous phase and water phase is used as the dispersed phase. In the present embodiment, all monomers have good water solubility, and the crosslinking agent and the initiator are selected from water-soluble materials, so that the inverse emulsion polymerization can be performed. In the inverse emulsion polymerization, the oil can be selected from white oil and diesel oil. Both the aqueous solution radical polymerization and the inverse emulsion polymerization have their advantages. The reaction condition of the aqueous solution radical polymerization is relatively simple, the cost is low, and the solvent is water, which is environmentally friendly. The reaction speed of the inverse emulsion polymerization is fast, and the performance is relatively good, but the cost is high. The person skilled in the art can select a suitable polymerization method according to the actual situation.

[0021] Another object of the present application is to provide a high-strength self-degradable gel temporary plugging agent prepared by any of the above methods.

[0022] The application has the advantages that the high-strength self-degradable gel temporary plugging agent prepared by the application has high strength, can self-degrade, has high reservoir permeability recovery rate after degradation, and has small influence on the reservoir. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the application, the technical solutions of the application will be described in detail below in combination with examples, but it should not be understood as limiting the implementable scope of the application.

[0024] In the following examples, the methods used are conventional operation methods in the art, unless otherwise specified.

[0025] In the following examples, the medicines used are conventional commercial products, unless otherwise specified.

[0026] In the following examples, the parts used all refer to mass parts, unless otherwise specified.

[0027] In the following examples, the dropwise addition refers to adding one solution into another solution at a speed of not more than 2d / s.

[0028] Example 1: 9.0 parts of 1,3-diamino-2-propanol and 57.5 parts of glycidyl methacrylate are respectively added into DMF and dissolved, 0.7 parts of tetrabutylammonium bromide is added into the 1,3-diamino-2-propanol solution, and p-methoxyphenol polymerization inhibitor is added into the glycidyl methacrylate solution so that the concentration of p-methoxyphenol is 80 ppm; under the condition of 35℃ and continuous stirring, the 1,3-diamino-2-propanol solution is added dropwise into the glycidyl methacrylate solution, 16h after the dropwise addition is completed, low-boiling substances are removed by distillation under reduced pressure, and a multi-arm crosslinking agent is obtained.

[0029] 10 parts of acrylamide, 1.5 parts of acrylic acid, 3 parts of 2-acrylamido-2-methylpropanesulfonic acid sodium, 1 part of N-vinylimidazole and 0.2 parts of 2-methacryloyloxyethylphosphocholine are added into water and dissolved, the concentration of all monomers is maintained at 25wt%, after nitrogen deoxygenation, 0.30 parts of ammonium persulfate / sodium bisulfite initiator with a mass ratio of 1:1 and 0.36 parts of multi-arm crosslinking agent are subsequently added, and the reaction is carried out at 35℃ for 2h, after the reaction is completed, the gel block is cut, dried, broken and sieved to 50 meshes, and a self-degradable gel temporary plugging agent is obtained.

[0030] Example 2: The difference between this example and example 1 is that 9.0 parts of 1,3-diamino-2-propanol is replaced by 8.8 parts of 1,4-butanediamine, and the rest is the same.

[0031] Example 3: The difference between this example and Example 1 is that the amount of glycidyl methacrylate is adjusted to 44.0 parts, the amount of multi-arm crosslinking agent is adjusted to 0.45 parts, and the rest are the same.

[0032] Example 4: The difference between this example and Example 1 is that the amount of glycidyl methacrylate is adjusted to 50.5 parts, the amount of acrylic acid is adjusted to 2.5 parts, the amount of 2-acrylamido-2-methylpropanesulfonic acid sodium is adjusted to 5 parts, and the rest are the same.

[0033] Example 5: The difference between this example and Example 1 is that no acrylic acid is added, 3 parts of 2-acrylamido-2-methylpropanesulfonic acid sodium is replaced with 4 parts of sodium p-styrenesulfonate, the amount of N-vinylimidazole is adjusted to 0.8 parts, and the amount of 2-methacryloyloxyethyl phosphorylcholine is adjusted to 0.25 parts, and the rest are the same.

[0034] Example 6: The difference between this example and Example 1 is that the amount of N-vinylimidazole is adjusted to 1.5 parts, and the amount of 2-methacryloyloxyethyl phosphorylcholine is adjusted to 0.15 parts, and the rest are the same.

[0035] Comparative Example 1: Compared with Example 1, the difference is that the multi-arm crosslinking agent is replaced with polyethylene glycol dimethacrylate (molecular weight 1000), and the rest are the same.

[0036] Comparative Example 2: Compared with Example 1, the difference is that the multi-arm crosslinking agent is replaced with ethylene glycol dimethacrylate, and the rest are the same.

[0037] Comparative Example 3: Compared with Example 1, the difference is that in the preparation process of the gel particles, 0.39 parts of glycidyl methacrylate and acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid sodium, N-vinylimidazole, and 2-methacryloyloxyethyl phosphorylcholine are added to water and dissolved together, and then 0.06 parts of 1,3-diamino-2-propanol is used as a crosslinking agent, and the initiator is added to the above solution to react, and the rest are the same.

[0038] Comparative Example 4: Compared with Example 1, the difference is that in the preparation process of the multi-arm crosslinking agent, 9.0 parts of 1,3-diamino-2-propanol is replaced with 13.2 parts of ornithine, and the rest are the same.

[0039] Comparative Example 5: Compared with Example 1, the difference is that in the preparation process of the multi-arm crosslinking agent, 9.0 parts of 1,3-diamino-2-propanol is replaced with 6.0 parts of ethylenediamine, and the rest are the same.

[0040] Comparative Example 6, compared with Example 1, the difference lies in that, in the preparation process of the multi-arm crosslinking agent, 9.0 parts of 1,3-diamino-2-propanol is replaced by 12.6 parts of melamine, and the rest is the same.

[0041] In order to further illustrate the effect of the embodiment of the present application, the following specific method is used to test it.

[0042] 1, expansion and degradation

[0043] Take a proper amount of the temporary plugging agent prepared in Examples 1-6 and Comparative Examples 1-5 and add it into a vial, then add enough saline (19500 mg / L of sodium chloride, 500 mg / L of calcium chloride), seal the vial, and place it in an oven at 100°C. Record the maximum expansion ratio, then maintain the temperature and record the time of complete degradation, and observe every 10 hours.

[0044] At the same time, after the temporary plugging agent is completely degraded, it is kept for another 10 hours, then the degradation rate is measured by the following method: take the degraded vial, cool it, centrifuge it at 5000 r / min for 10 min, take the solid phase after centrifugation, dry it at 60°C under reduced pressure, weigh the mass of the solid phase, and the final degradation rate calculation formula is: η = (m1-m2) / m1, where η represents the degradation rate, m1 represents the mass of the dry temporary plugging agent before expansion, and m2 represents the mass of the solid phase.

[0045] The final results are shown in Tables 1 and 2.

[0046] Table 1 Expansion and degradation test results

[0047]

[0048] It can be seen from Table 1 that the temporary plugging agent in the embodiment has higher water absorption and swelling performance under high salt conditions. Meanwhile, it has good temperature resistance and can exist stably for a period of time under high temperature conditions. It can be seen from Example 1 and Example 3 that the degradation time of the temporary plugging agent can be adjusted by adjusting the amount of the multi-arm crosslinking agent. It can be seen from Comparative Example 1 that the conventional polyethylene glycol dimethacrylate as the crosslinking agent has poor temperature resistance and is prone to degradation under high temperature conditions. It can be seen from Comparative Example 2 and Comparative Example 4 that the crosslinking agent with a relatively short chain has a relatively low swelling multiple. It can be seen from Comparative Example 3 that when the 1,3-diamino-2-propanol and glycidyl methacrylate are prepared into a multi-arm crosslinking agent in advance, the effect is much better than that of using 1,3-diamino-2-propanol as the crosslinking agent. It can be seen from Comparative Example 5 that when ethylenediamine is used, the effect is poor, which may be due to the short distance between the two amino groups in ethylenediamine. When the primary amine group is grafted with glycidyl methacrylate to form a secondary amine, it is difficult to form a multi-arm crosslinking agent due to steric hindrance. It can be seen from Comparative Example 6 that when melamine is used, the effect is relatively poor.

[0049] 2. Displacement test

[0050] The temporary plugging agents prepared in Examples 1-6 and Comparative Examples 1-5 were taken, water was added to prepare a temporary plugging agent solution with a concentration of 5 wt%, a man-made core with a crack width of 5 mm was taken, quartz sand with a certain particle size was added to the crack to prepare an experimental core with a water permeability of about 3000 mD, the experimental core was added to a core holder and connected to a displacement device, under the condition of 90 DEG C, first, salt water (19500 mg / L of sodium chloride, 500 mg / L of calcium chloride) was injected at a speed of 0.2 mL / min until the displacement pressure was balanced, then, 1 PV of the temporary plugging agent solution was injected, and after 10 h of heat preservation, the salt water was continuously injected at a speed of 0.2 mL / min, the pressure P at the time of pressure drop (pressure drop of more than 10%) in the water flooding process was recorded, and the breakthrough pressure gradient was calculated by the following formula: G = P / L, wherein G represents the breakthrough pressure gradient, MPa / m; and L represents the length of the sand pack tube, m.

[0051] The sand pack tube was continuously heat preserved for 20 d, after the heat preservation was completed, salt water was injected at a speed of 0.2 mL / min until the displacement pressure was balanced, the water permeability k2 was measured, and the permeability recovery rate was calculated: eta = k2 / k1 * 100%, wherein eta represents the permeability recovery rate, k1 represents the water permeability before displacement, and k2 represents the water permeability after gel breaking.

[0052] The final test results are shown in Table 2.

[0053] Table 2 Displacement test results

[0054]

[0055] From Table 2, it can be seen that the temporary plugging agent prepared by the embodiment of the present application has a higher breakthrough pressure gradient, which can reach above 23 MPa / m; at the same time, after automatic degradation and gel breaking, the influence on the reservoir permeability is smaller, and the permeability recovery rate can reach above 97%, and the damage to the reservoir is smaller. Referring to Comparative Example 1, it can be seen that when the common degradable crosslinking agent is used, the strength is relatively low; referring to Comparative Examples 2 and 5, it can be seen that when the short-chain ethylene glycol dimethyl acrylate and ethylenediamine are used as the crosslinking agent, although the strength is relatively high, the permeability recovery rate is relatively low; referring to Comparative Example 3, it can be seen that after changing the material adding sequence, the strength of the product decreases rapidly; referring to Comparative Example 4, it can be seen that when the diamino amino acid is used as the raw material of the multi-arm crosslinking agent, the effect is relatively poor. Referring to Comparative Example 6, it can be seen that when the melamine is used as the raw material of the multi-arm crosslinking agent, both the strength and the permeability recovery rate are poor.

[0056] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the embodiments of the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a high-strength self-degrading gel plugging agent, characterized in that, The method comprises the following steps: The molar ratio of the diamino compound and the unsaturated glycidyl are 1:3-4.1, which are respectively added into a solvent and dissolved, then the diamino compound solution is added dropwise into the unsaturated glycidyl solution under the conditions of 20-35℃, a catalyst and a polymerization inhibitor, and the reaction is carried out, after the reaction is completed, low-boiling substances are removed by distillation under reduced pressure to obtain the multi-arm crosslinking agent; the unsaturated glycidyl is one of glycidyl acrylate and glycidyl methacrylate, and the diamino compound is one of propylene diamine, 1,3-diamino-2-propanol and butylene diamine; The acrylamide monomer, the acid monomer, the rigid monomer and the 2-methyl acryloyl oxy ethyl phosphocholine monomer are polymerized under the action of an initiator and the multi-arm crosslinking agent, and after polymerization, the product is crushed, dried and granulated to obtain the product.

2. The method of claim 1, wherein, When the multi-arm crosslinking agent is prepared, the catalyst is tetrabutylammonium bromide, and the addition amount is 1-1.5% of the total mass of the diamino compound and the unsaturated glycidyl; the polymerization inhibitor is p-methoxyphenol, and the addition amount is 50-100 ppm; the solvent is DMF; and the reaction time is 15-25 h.

3. The method of claim 1, wherein, The diamino compound is 1,3-diamino-2-propanol.

4. The method of claim 1, wherein, The mass ratio of the acrylamide monomer, the acid monomer, the rigid monomer and the 2-methyl acryloyl oxy ethyl phosphocholine monomer is 10:3-8:0.5-2:0.1-0.

3.

5. The method of claim 1, wherein, The acrylamide monomer is one of acrylamide and methacrylamide, the acid monomer is at least one of acrylic acid, sodium acrylate, 2-acrylamido-2-methylpropanesulfonic acid sodium and p-styrenesulfonic acid sodium, and the rigid monomer is one of N-vinyl pyrrolidone and N-vinylimidazole.

6. The method of claim 5, wherein, The acid monomer is a mixture of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid sodium with a mass ratio of 1:2, and the rigid monomer is N-vinylimidazole.

7. The method of claim 1, wherein, The initiator is one of persulfate initiators, persulfate / sodium bisulfite initiators and water-soluble azo initiators, the addition amount of the initiator is 0.1-0.8% of the total mass of all the monomers, and the addition amount of the multi-arm crosslinking agent is 0.1-0.5% of the total mass of all the monomers.

8. The method of claim 1, wherein the polymerization is one of aqueous solution radical polymerization and inverse emulsion polymerization.

9. A high-strength self-degradable gel temporary plugging agent prepared by the method of any one of claims 1-8.

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