Temperature-resistant gel temporary plugging agent and preparation method thereof

Abstract

The application discloses a temperature-resistant gel temporary plugging agent and a preparation method thereof, and relates to the technical field of oil field chemicals. The temperature-resistant gel temporary plugging agent is prepared by the following steps: taking acrylamide monomers, unsaturated sulfonate monomers and a first monomer and dissolving, then adding tetraglycine, an initiator and a degradable crosslinking agent and reacting, and after the reaction is completed, crushing, drying and granulating to obtain the temperature-resistant gel temporary plugging agent; the first monomer is prepared by esterification reaction of N,N-dihydroxyethyl glycine and allyl alcohol. The temperature-resistant gel temporary plugging agent prepared by the application has good temperature resistance and can resist a temperature of 120 DEG C, and the temperature-resistant gel temporary plugging agent has high expansion rate, degradability and strength under the temperature condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemistry, in particular to a temperature-resistant gel temporary plugging agent and a preparation method thereof. BACKGROUND

[0002] The gel temporary plugging agent is a new type of temporary plugging agent, which is usually represented by polyacrylamide gel. It is mainly prepared by free radical polymerization and cross-linking of acrylamide monomers. However, the strength and temperature resistance of conventional polyacrylamide gel particles are relatively low. Therefore, in the prior art, corresponding modified monomers are usually added to modify them. For example, sulfonic acid monomers and rigid monomers are used to improve the temperature resistance.

[0003] Polyacrylamide temporary plugging agents are divided into above-ground gel-forming temporary plugging agents and underground gel-forming temporary plugging agents according to their cross-linking time. The underground gel-forming temporary plugging agent refers to injecting acrylamide polymers, cross-linking agents and gel breakers into the formation. Under the action of the cross-linking agent, the acrylamide polymer is cross-linked to form a gel or a gel, thereby completing the temporary plugging. The temporary plugging agent is then degraded and broken by the gel breaker. The above-ground gel-forming temporary plugging agent, also known as pre-crosslinked gel, refers to the reaction of polymers and cross-linking agents on the ground (factory) to prepare gel particles, which are then degraded and broken by an external gel breaker. However, the temporary plugging agents in the prior art have a contradiction between temperature resistance, strength and degradability: if the temporary plugging agent has better temperature resistance and higher strength, it needs to add more modified monomers (such as rigid monomers). However, when the content of the modified monomer is higher, the degradability of the temporary plugging agent is poor. SUMMARY

[0004] In view of the above technical problems, the present application aims to solve the defects of the prior art by providing a temperature-resistant gel temporary plugging agent and a preparation method thereof.

[0005] The present application adopts the following technical solutions:

[0006] A preparation method of a temperature-resistant gel temporary plugging agent, by weight, includes the following steps: 10 parts of acrylamide monomers, 1-3 parts of unsaturated sulfonate monomers and 0.5-3 parts of a first monomer are dissolved, then 0.1-0.5 parts of tetraglycine, an initiator and a degradable cross-linking agent are added and reacted. After the reaction is completed, it is crushed, dried and granulated to obtain the temperature-resistant gel temporary plugging agent; the first monomer is prepared by esterification reaction of N,N-dihydroxyethyl glycine and allyl alcohol.

[0007] In the present application, the unsaturated sulfonate monomer has the same effect as the conventional one, i.e. increasing the temperature resistance of the gel particles. As to the first monomer, it contains abundant functional groups, i.e. carboxylate, amino and hydroxyl groups, and has abundant intramolecular hydrogen bonds, through N, N-di-hydroxyethyl glycine and allyl alcohol. Meanwhile, the added tetraglycine has both amino and carboxylate groups, which can not only reduce the gel reaction time, but also greatly increase the strength and temperature resistance of the gel particles; and since the tetraglycine is in a chain shape and contains multiple hydrophilic groups in the molecule, it can further increase the performance of the gel particles. Meanwhile, similar to the preparation process of the conventional pre-crosslinking gel, the total concentration of the acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium and the first monomer in water is usually 15-25%.

[0008] In an embodiment of the present application, the acrylamide monomer is one of acrylamide and methacrylamide. This is a common monomer in the art and is the core of the polyacrylamide gel particles.

[0009] In an embodiment of the present application, the unsaturated sulfonate monomer is one of 2-acrylamide-2-methylpropanesulfonic acid or its salt and sodium p-styrenesulfonate. Although both can be used, 2-acrylamide-2-methylpropanesulfonic acid or its salt is usually selected.

[0010] In an embodiment of the present application, the initiator is one of persulfate, water-soluble oxidation-reduction initiator and water-soluble azo initiator, and the amount of the initiator is 0.1-0.5% of the total mass of the acrylamide monomer, the unsaturated sulfonate monomer and the first monomer. The initiator has a close relationship with the reaction time and the reaction temperature, for example, the initiation temperature of the persulfate initiator is usually 60-80℃; the water-soluble oxidation-reduction initiator usually refers to the combination of persulfate and bisulfite, and the initiation temperature thereof is usually 20-50℃; the water-soluble azo initiator, such as azobisdimethylamidinum dihydrochloride, has a common initiation temperature of 40-60℃. As to the specific reaction time, it is usually 1-3h, and can also be determined according to the gel state.

[0011] One embodiment of the present application is that the degradable crosslinking agent is at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol diacrylate, and ethylene glycol dimethacrylate. These are common degradable crosslinking agents in the art, in which polyethylene glycol diacrylate and polyethylene glycol dimethacrylate are polymers with long chain length, and the molecular weight of the polyethylene glycol chain in the molecular chain is usually 200-1000, both of which can be applied to the present application. Such crosslinking agents are characterized by being more easily degradable, but the strength is relatively low. Ethylene glycol diacrylate and ethylene glycol dimethacrylate are short-chain degradable crosslinking agents, which have relatively high strength when used alone, but relatively slow degradation speed, and incomplete degradation in a short time. Similar to the amount of crosslinking agent of the rest of the temporary plugging agent, the amount of degradable crosslinking agent in the present application is 0.1-1.0% of the total mass of acrylamide monomer, unsaturated sulfonate monomer and first monomer.

[0012] Further, the degradable crosslinking agent is a mixture of ethylene glycol dimethacrylate and polyethylene glycol diacrylate with a mass ratio of 1:1-3, and the polyethylene glycol diacrylate is one of PEGDA400, PEGDA600 and PEGDA800. The inventors have found through a large number of tests that the crosslinking agent thus combined has both high strength and fast degradation speed.

[0013] One embodiment of the present application is that the preparation method of the first monomer comprises the following steps: dissolving N,N-dihydroxyethyl glycine and allyl alcohol in DMF (N,N-dimethylformamide), then adding a catalyst, a polymerization inhibitor and a dehydration material, heating to 90-110°C and reacting for 6-12 hours, and after the reaction is completed, separating and purifying the product to obtain the first monomer; the molar ratio of N,N-dihydroxyethyl glycine to allyl alcohol is 1:1.2-1.8, the amount of the catalyst p-toluenesulfonic acid is 5-12% of the molar amount of N,N-dihydroxyethyl glycine, the amount of the polymerization inhibitor hydroquinone is 0.1-0.8% of the mass of allyl alcohol, and the amount of the dehydration material molecular sieve is 3-8% of the mass of DMF.

[0014] Further, the separation and purification step is as follows: taking the product, adding saturated sodium bicarbonate solution dropwise to adjust the pH of the product to 6-8, filtering out the solid phase, and removing low-boiling substances by distillation under reduced pressure to obtain the product. The saturated sodium bicarbonate solution is used to neutralize the acid (N,N-dihydroxyethyl glycine and p-toluenesulfonic acid) in the preparation process of the first monomer. These neutralized products will settle in the solvent to form a solid phase, resulting in turbidity of the solution. In addition, the product itself contains molecular sieve. Therefore, the solid phase is filtered out by filtration (suction filtration). The main low-boiling substances in the liquid phase after filtering out the solid phase are DMF, water (brought by saturated sodium bicarbonate) and allyl alcohol. Therefore, the distillation temperature under reduced pressure can be set to about 80-95°C.

[0015] Another object of the present application is to provide a temperature-resistant gel temporary plugging agent prepared by any of the above methods.

[0016] The present application has the advantage that the temperature-resistant gel temporary plugging agent prepared by the present application has good temperature resistance, can withstand a temperature of 120℃, and has high swelling rate, degradability and strength at this temperature. DETAILED DESCRIPTION

[0017] In order to have a clearer understanding of the technical features, objects and advantages of the present application, the technical solutions of the present application will be described in detail below in conjunction with the embodiments, but it should not be understood as limiting the scope of the present application.

[0018] In the following examples, the methods used are conventional methods in the art unless otherwise specified.

[0019] In the following examples, the drugs used are conventional commercial products unless otherwise specified.

[0020] Example 1, preparation of the first monomer: take N,N-dihydroxyethyl glycine 32.6g (0.2mol) and allyl alcohol 17.4g (0.3mol) and dissolve in 250mL of DMF, then add p-toluenesulfonic acid 2.76g, hydroquinone 0.086g, 3A molecular sieve 10.0g, stir to dissolve, then heat to 100℃ and react for 8h, after the reaction is completed, cool the reaction liquid to room temperature, add saturated sodium bicarbonate solution dropwise to adjust the pH of the reaction liquid to 7, remove the solid phase by suction filtration, remove the low boiling point material by reduced pressure distillation to obtain the first monomer.

[0021] Preparation of temperature-resistant gel temporary plugging agent: take 100g of acrylamide, 20g of 2-acrylamide-2-methylpropanesulfonic acid sodium and 15g of the first monomer, dissolve in water, then add 3g of tetraglycine, 0.5g of potassium persulfate, 0.36g of ethylene glycol dimethacrylate, 0.72g of PEGDA400 under nitrogen atmosphere, adjust the total concentration of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium and the first monomer to 20wt%, heat to 65℃ and continue to react for 2h, after the reaction is completed, crush, dry and granulate the gel to obtain the temperature-resistant gel temporary plugging agent.

[0022] Example 2, Preparation of the first monomer: N,N-dihydroxyethyl glycine 32.6 g (0.2 mol) and allyl alcohol 17.4 g (0.3 mol) were added to 250 mL of DMF and dissolved, then p-toluenesulfonic acid 2.76 g, hydroquinone 0.044 g, 3A molecular sieves 8.0 g were added, after stirring to dissolve, the temperature was raised to 100°C and reacted for 8 h, after the reaction was completed, the reaction liquid was cooled to room temperature, saturated sodium bicarbonate solution was added dropwise to adjust the pH of the reaction liquid to 7, the solid phase was removed by suction filtration, and the low boiling point material was removed by distillation under reduced pressure to obtain the product.

[0023] Preparation of temperature-resistant gel temporary plugging agent: 100 g of acrylamide, 14 g of 2-acrylamide-2-methylpropanesulfonic acid sodium, and 22 g of the first monomer were dissolved in water, then 4 g of tetraglycine, 0.5 g of potassium persulfate, 0.36 g of ethylene glycol dimethacrylate, and 0.72 g of PEGDA600 were added under a nitrogen atmosphere, the total concentration of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, and the first monomer was adjusted to 23 wt% by adding water, the temperature was raised to 60°C and the reaction was continued for 2 h, after the reaction was completed, the gel was broken, dried, and granulated to obtain the product.

[0024] Example 3, Preparation of the first monomer: The same as Example 1.

[0025] Preparation of temperature-resistant gel temporary plugging agent: 100 g of acrylamide, 26 g of 2-acrylamide-2-methylpropanesulfonic acid sodium, and 10 g of the first monomer were dissolved in water, then 2 g of tetraglycine, 0.5 g of potassium persulfate, and 1.08 g of PEGDA400 were added under a nitrogen atmosphere, the total concentration of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, and the first monomer was adjusted to 20 wt% by adding water, the temperature was raised to 65°C and the reaction was continued for 3 h, after the reaction was completed, the gel was broken, dried, and granulated to obtain the product.

[0026] Example 4, Preparation of the first monomer: The same as Example 1.

[0027] Preparation of temperature-resistant gel temporary plugging agent: 100 g of acrylamide, 26 g of 2-acrylamide-2-methylpropanesulfonic acid sodium, and 10 g of the first monomer were dissolved in water, then 2 g of tetraglycine, 0.5 g of potassium persulfate, and 0.6 g of ethylene glycol dimethacrylate were added under a nitrogen atmosphere, the total concentration of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid sodium, and the first monomer was adjusted to 20 wt% by adding water, the temperature was raised to 65°C and the reaction was continued for 3 h, after the reaction was completed, the gel was broken, dried, and granulated to obtain the product.

[0028] Comparative Example 1, compared with Example 1, the difference is that the first monomer is not added, and the rest is the same.

[0029] Comparative Example 2, compared with Example 1, the difference is that tetraglycine is not added, and the rest is the same.

[0030] Comparative Example 3, compared with Example 1, the difference is that tetraglycine is replaced by glycine, and the rest is the same. During the reaction process, the product is gelled in 25 min, and the gelling speed is faster.

[0031] In order to further illustrate the effect of the embodiment of the present application, the following specific method is used for testing.

[0032] 1. Swelling rate test

[0033] Prepare simulated formation water with a salt content of 10000 mg / L (9500 mg / L of sodium chloride and 500 mg / L of calcium chloride), prepare several test tubes, add 0.5 g of the temporary plugging agent and 50 ml of the simulated formation water in the test tubes, and heat to 120℃. The maximum swelling ratio is measured, and the final result is shown in Table 1.

[0034] Table 1. Maximum swelling ratio test result table

[0035]

[0036] As can be seen from Table 1, the temperature-resistant gel temporary plugging agent prepared in the embodiment of the present application has a higher swelling rate under high temperature and high salt conditions. As can be seen from Comparative Examples 1 and 2, the first monomer and tetraglycine have a great effect on the swelling rate of the gel particles.

[0037] 2. Degradation test

[0038] Prepare simulated formation water with a salt content of 10000 mg / L (9500 mg / L of sodium chloride and 500 mg / L of calcium chloride), prepare several test tubes, add 1.0 g of the temporary plugging agent (accurate to 0.1 mg) and 50 ml of the simulated formation water in the test tubes, and heat to 120℃. Observe every 10 h, record the complete degradation time, after degradation, take the product and cool to room temperature, centrifuge at 5000 r / min for 10 min, then take the solid phase, dry and weigh, accurate to 0.1 mg, and calculate the degradation rate: η = (m0-m1) / m0, wherein m0 represents the initial weight of the temporary plugging agent, and m1 represents the weight of the solid phase after degradation.

[0039] Table 2. Degradation test result table

[0040]

[0041] As can be seen from Table 2, the temperature-resistant gel temporary plugging agent prepared in the embodiment of the present application has good degradation performance under high temperature and high salt conditions, and the degradation time is adjustable, which can be adjusted according to the actual situation.

[0042] 3. Breakthrough pressure gradient

[0043] The temporary plugging agents prepared in Examples 1-4 and Comparative Examples 1-3 were added to water to prepare a temporary plugging agent solution with a concentration of 3 wt%. A man-made core with a permeability of about 500 mD was saturated with water at a rate of 1 mL / min using a flow pump at 90°C. After the outlet pressure was stabilized, 0.5 PV of the temporary plugging agent solution was injected, and the temperature was maintained for 5 h. After the temperature maintenance was completed, water was injected into the man-made core at a rate of 1 mL / min using a flow pump, and the highest pressure before the pressure dropped suddenly was recorded. The breakthrough pressure gradient was calculated based on the highest pressure and the length of the core. The temperature was maintained at 90°C for another 10 days (all the temporary plugging agents were completely degraded in 10 days at 90°C according to test results), water was injected into the man-made core at a rate of 1 mL / min using a flow pump until the outlet pressure was stabilized, the permeability of the man-made core was measured, and the permeability recovery rate was calculated. The final results are shown in Table 3.

[0044] Table 3. Breakthrough pressure gradient test results

[0045]

[0046] As can be seen from Table 3, the temporary plugging agent of the examples has a high permeability recovery rate and has little effect on the permeability of the reservoir after degradation. Meanwhile, as can be seen from Comparative Example 1 and Comparative Example 2, the first monomer and tetraglycine have a great influence on the strength. As can be seen from Comparative Example 3, the strength of the temporary plugging agent is greatly reduced when tetraglycine is replaced by glycine, which may be due to the fact that, compared with tetraglycine, glycine promotes the formation of gel particles more quickly, resulting in a decrease in strength.

[0047] In fact, the test temperature of 90°C was selected because the test time was relatively long, and if the test temperature exceeded 100°C, the risk would be greatly increased. According to the tests of the inventors, the breakthrough pressure gradient of the gel particles prepared in Example 1 at a temperature of 120°C decreased to some extent, but still reached 14.7 MPa / m, which is completely applicable to fracturing and temporary plugging.

[0048] The above merely provides the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical range disclosed in the examples of the present application can be easily thought of by those skilled in the art, which should be encompassed 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 heat-resistant gel temporary plugging agent, characterized in that, The product comprises the following steps, by weight: 10 parts of acrylamide monomer, 1-3 parts of unsaturated sulfonate monomer and 0.5-3 parts of the first monomer are taken and dissolved, then 0.1-0.5 parts of tetrapolyglycine, initiator and degradable crosslinking agent are added and reacted. After the reaction is completed, the product is crushed, dried and granulated to obtain the product. The first monomer is prepared by esterification reaction of N,N-dihydroxyethylglycine and allyl alcohol.

2. The preparation method of the heat-resistant gel temporary plugging agent according to claim 1, characterized in that, The acrylamide monomer is one of acrylamide and methacrylamide.

3. The method for preparing the heat-resistant gel temporary plugging agent according to claim 1, characterized in that, The unsaturated sulfonate monomer is one of 2-acrylamido-2-methylpropanesulfonic acid or its salt, or sodium p-styrenesulfonate.

4. The method for preparing the heat-resistant gel temporary plugging agent according to claim 1, characterized in that, The initiator is one of persulfate, water-soluble redox initiator, or water-soluble azo initiator, and the amount of initiator added is 0.1 to 0.5% of the total mass of acrylamide monomer, unsaturated sulfonate monomer, and the first monomer.

5. The method for preparing the heat-resistant gel temporary plugging agent according to claim 1, characterized in that, The biodegradable crosslinking agent is at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol diacrylate, and ethylene glycol dimethacrylate.

6. The method for preparing the heat-resistant gel temporary plugging agent according to claim 5, characterized in that, The biodegradable crosslinking agent is a mixture of ethylene glycol dimethacrylate and polyethylene glycol diacrylate in a mass ratio of 1:1 to 3, and the polyethylene glycol diacrylate is one of PEGDA400, PEGDA600, and PEGDA800.

7. The method for preparing the heat-resistant gel temporary plugging agent according to claim 1, characterized in that, The preparation method of the first monomer includes the following steps: dissolving N,N-dihydroxyethylglycine and allyl alcohol in DMF, then adding a catalyst, a polymerization inhibitor, and a dehydrating material, heating to 90~110℃ and reacting for 6~12h, and after the reaction is completed, separating and purifying it to obtain the monomer; the molar ratio of N,N-dihydroxyethylglycine and allyl alcohol is 1:1.2~1.8, the catalyst is p-toluenesulfonic acid, and the amount added is 5~12% of the molar amount of N,N-dihydroxyethylglycine, the polymerization inhibitor is hydroquinone, and the amount added is 0.1~0.8% of the mass of allyl alcohol, and the dehydrating material is molecular sieve, and the amount added is 1~5% of the mass of DMF.

8. The method for preparing the heat-resistant gel temporary plugging agent according to claim 7, characterized in that, The separation and purification steps are as follows: Take the product, add saturated sodium bicarbonate solution to adjust the pH of the product to 6-8, filter out the solid phase, and remove low-boiling substances by vacuum distillation to obtain the product.

9. A heat-resistant gel temporary plugging agent, prepared by the method according to any one of claims 1 to 8.

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