Acid liquor gelling agent and preparation method thereof

Abstract

The invention discloses an acid liquor gelling agent and a preparation method thereof, and belongs to the technical field of chemical assistants for oil fields, the acid liquor gelling agent is obtained by polymerization reaction of a comonomer mixture through an initiator and a molecular regulator, the comonomer mixture comprises acrylamide, methylacryloyloxyethyl trimethyl ammonium chloride, methylacryloyloxyethyl ammonium propanesulfonate, methylacryloyloxyethyl naphthyl ammonium chloride, a cosolvent, a chelating agent and deionized water; the comonomer mixture is prepared from the following components in percentage by mass: 5 to 10 percent of acrylamide, 30 to 50 percent of methylacryloyloxyethyl trimethyl ammonium chloride, 1 to 5 percent of methylacryloyloxyethyl ammonium propanesulfonate, 0.1 to 0.5 percent of methylacryloyloxyethyl naphthyl ammonium chloride, 0.1 to 0.2 percent of cosolvent, 0.01 to 0.05 percent of chelating agent and the balance of deionized water. According to the acid liquor gelatinizing agent, the viscosity of acid liquor can reach 20 mPa.s under the condition of 180 DEG C, and the acid liquor gelatinizing agent has good temperature resistance and can meet the acid fracturing construction requirements of reservoirs at the temperature of 180 DEG C.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical additives for oil fields, and particularly relates to an acid liquid gelling agent and a preparation method thereof. Background Art

[0002] With the rapid development of the national economy, the demand for energy is increasing. Carbonate reservoirs are rich in oil and gas resources, and their oil and gas production accounts for a high proportion, making them the key direction of oil and gas exploration and development. However, carbonate reservoirs are highly heterogeneous and have poor reservoir properties, so it is usually necessary to increase the production of the reservoirs. Acid fracturing is the most commonly used measure for increasing the production of carbonate reservoirs, and the effect of reservoir transformation is closely related to the effective action distance of the acid. Under high temperature conditions, conventional acid systems have severe filtration loss, fast acid-rock reaction speed, and short effective action distance, making it difficult to achieve the effect of deep acidification. Adding a gelling agent to the acid can effectively increase the viscosity of the acid, reduce the acid loss rate, and reduce the hydrogen ion mass transfer rate, thereby slowing down the acid-rock reaction rate, increasing the effective action distance of the acid, and achieving the purpose of deep acidification.

[0003] In the prior art, a Chinese invention patent document with announcement number CN116535566A and publication date August 4, 2023 discloses a high-temperature resistant acid fracturing gelling agent and a preparation method thereof, wherein monomer A is a water-soluble polymerizable monomer with a double bond, monomer B is a sulfonic acid monomer with a double bond, and the cationic hydrophobic functional monomer is a monomer with a hydrophobic chain and a rigid group. The high temperature resistant acid fracturing gelling agent of the present invention has a relative molecular weight of 6 million to 8 million, has good water solubility, acid solubility, viscosity increasing, temperature resistance, and shear resistance, and can be applied to acid fracturing construction in oil production above 160°C; the Chinese invention patent document with announcement number CN106318369B and announcement date March 29, 2019 discloses a cationic gelling acid thickener and a preparation method thereof, the gelling acid thickener is a copolymer of four monomers: acrylamide, a phosphorus-containing cationic monomer, dimethyldiallylammonium chloride, and 2-acrylamido-2-methylpropanesulfonic acid, the cationic gelling acid thickener has the advantages of short swelling time, good temperature resistance, high residual acid flowback efficiency, little damage to the reservoir, etc., and can meet the acid fracturing construction requirements of a reservoir at 140°C.

[0004] However, the well temperature of domestic oil fields is getting higher and higher, reaching 180℃ or even higher. Conventional gelled acid has poor stability under high temperature conditions, the gelling agent is easy to hydrolyze, and the viscosity retention rate is low, which leads to the acceleration of hydrogen ion mass transfer, making it difficult to play an effective role in slowing down and reducing filtration, and unable to meet the acid fracturing requirements of high-temperature reservoirs. Therefore, it is necessary to develop an acid gelling agent with good temperature resistance under high temperature conditions to address the existing problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes an acid gelling agent and a preparation method thereof. The acid gelling agent has good temperature resistance and can withstand a temperature of up to 180°C, which can meet the acid fracturing construction requirements of a 180°C reservoir.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] An acid gelling agent is a polymer containing a sulfonic acid group and a naphthalene ring structure, wherein the monomer of the sulfonic acid group is ammonium methacryloyloxyethyl propanesulfonate, and the structure thereof is:

[0008]

[0009] The monomer of the naphthalene ring structure is methacryloyloxyethylnaphthyl ammonium chloride, and its structure is:

[0010]

[0011] The acid liquid gelling agent is obtained by polymerization reaction of a comonomer mixture through an initiator and a molecular regulator; the comonomer mixture comprises acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl propane sulfonate ammonium, methacryloyloxyethyl naphthyl ammonium chloride, a solvent, a chelating agent and deionized water; the comonomer mixture comprises, by mass percentage, 5%-10% of acrylamide, 30%-50% of methacryloyloxyethyl trimethyl ammonium chloride, 1%-5% of methacryloyloxyethyl propane sulfonate ammonium, 0.1%-0.5% of methacryloyloxyethyl naphthyl ammonium chloride, 0.1%-0.2% of a solvent, 0.01%-0.05% of a chelating agent, and the rest is deionized water; the molecular structure of the acid liquid gelling agent is:

[0012]

[0013] The values ​​of a:b:c:d are 500-1000:1000-2000:50-100:5-20, and a, b, c, d are all integers; the viscosity average molecular weight of the gelling agent is 3 million to 6 million, and there are no impurities in the components.

[0014] A method for preparing an acid liquid gelling agent comprises the following steps:

[0015] S1. Preparation of ammonium methacryloyloxyethylpropanesulfonate: add dimethylaminoethyl methacrylate and 1,3-propane sultone in an equal molar ratio into a reaction kettle, add a mixed solvent of ethanol and acetone (in a ratio of 1:1), stir evenly, add 0.1% p-hydroxyanisole, and react at 50° C. for 12 hours; after the reaction is completed, remove the solvent by distillation under reduced pressure, wash with acetone 3 times, and dry to obtain ammonium methacryloyloxyethylpropanesulfonate.

[0016] S2. Preparation of methacryloyloxyethyl naphthyl ammonium chloride: add equal proportions of dimethylaminoethyl methacrylate and 2-(chloromethyl)naphthalene into a reaction kettle, add ethanol as a solvent, stir evenly, add 0.1% p-hydroxyanisole, and react at 70° C. for 12 hours; after the reaction, remove the solvent by distillation under reduced pressure, wash with acetone 3 times, and dry to obtain methacryloyloxyethyl naphthyl ammonium chloride.

[0017] S3. Preparation of polymers, including preparation of a comonomer mixture and polymerization reaction; the preparation of the comonomer mixture refers to uniformly mixing acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl ammonium propane sulfonate, methacryloyloxyethyl naphthyl ammonium chloride, a cosolvent, a chelating agent and deionized water; the polymerization reaction refers to placing the comonomer mixture in a sealed and insulated container, passing nitrogen to remove oxygen, and adding an initiator and a molecular weight regulator to carry out a polymerization reaction.

[0018] The copolymer monomer mixture is prepared, and the contents of each component are, by mass percentage, 5%-10% of acrylamide, 30%-50% of methacryloyloxyethyl trimethyl ammonium chloride, 1%-5% of methacryloyloxyethyl ammonium propanesulfonate, 0.1%-0.5% of methacryloyloxyethyl naphthyl ammonium chloride, 0.1%-0.2% of cosolvent, 0.01%-0.05% of chelating agent, and the rest is deionized water.

[0019] The cosolvent is one or more of carbamide, ammonium sulfate, polyethylene glycol 10000, and polyethylene glycol 20000; and the chelating agent is tetrasodium ethylenediaminetetraacetic acid.

[0020] The molecular weight regulator is one or more of sodium formate, isopropyl alcohol and sodium hypophosphite.

[0021] The reaction temperature of the polymerization reaction is controlled at 40° C.-60° C., and the polymerization reaction time is controlled at 5 h-8 h.

[0022] The initiator includes an oxidizing agent, a reducing agent and an azo initiator.

[0023] The oxidant is one or more of potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and sodium bromate; the reducing agent is one or more of sodium sulfite, sodium bisulfite, sodium pyrosulfite, ferrous chloride, and ascorbic acid; and the azo initiator is one or more of 2,2'-azobis(2-imidazoline) dihydrochloride, 2,2'-azobisisobutylamidine dihydrochloride, azobisisobutyronitrile, and azobisisoheptylonitrile.

[0024] The amount of the oxidant added is 0.001%-0.003% of the comonomer mixture; the amount of the reducing agent added is 0.001%-0.005% of the comonomer mixture; and the amount of the azo initiator added is 0.01%-0.1% of the comonomer mixture.

[0025] The product obtained by the polymerization reaction is dried at 50° C.-60° C. and crushed to obtain an acid liquid gelling agent.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The gelled acid gelling agent of the present invention, as shown in its chemical structure, has a polymerizable monomer mainly composed of cations, and introduces a zwitterionic polymerizable monomer with a sulfonic acid group. The sulfonic acid group has good temperature resistance and can effectively improve the heat and salt resistance of the gelling agent; the naphthalene ring structure of methacryloyloxyethylnaphthyl ammonium chloride has certain rigidity and hydrophobicity. Under high temperature conditions, the naphthalene ring structure can promote intermolecular association, reduce the molecular thermal motion amplitude, and improve the temperature resistance of the gelling agent. It can be used in the field of acid fracturing construction operations in oil production at 180°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

[0029] Figure 1 This is the rheological test diagram of gelling agent 1;

[0030] Figure 2 This is the rheological test diagram of gelling agent 4. DETAILED DESCRIPTION

[0031] Example 1

[0032] 5% acrylamide, 40% methacryloyloxyethyl trimethyl ammonium chloride, 3% methacryloyloxyethyl propanesulfonate ammonium, 0.2% methacryloyloxyethyl naphthyl ammonium chloride, 0.2% carbonamide and 0.02% tetrasodium ethylenediaminetetraacetate were added to a certain amount of deionized water, stirred evenly, and nitrogen was passed through for 30 minutes to obtain a comonomer mixed solution. 0.001% potassium persulfate, 0.002% sodium bisulfite, 0.01% sodium formate and 0.01% 2,2'-azobisisobutylamidine dihydrochloride were added to the comonomer mixed solution, the polymerization temperature was controlled at 40°C-50°C, and the reaction was carried out for 6 hours. The obtained product was dried at 50°C-60°C and crushed to obtain gelling agent 1.

[0033] Example 2

[0034] 5% acrylamide, 45% methacryloyloxyethyl trimethyl ammonium chloride, 2% methacryloyloxyethyl propanesulfonic acid ammonium, 0.5% methacryloyloxyethyl naphthyl ammonium chloride, 0.2% carbonamide and 0.02% tetrasodium ethylenediaminetetraacetate were added to a certain amount of deionized water, stirred evenly, and nitrogen was passed through for 30 minutes to obtain a comonomer mixed solution. 0.001% ammonium persulfate, 0.002% sodium pyrosulfite, 0.01% sodium hypophosphite and 0.01% 2,2'-azobis(2-imidazoline) dihydrochloride were added to the comonomer mixed solution, the polymerization temperature was controlled at 50°C-55°C, and the reaction was carried out for 5 hours. The obtained product was dried at 50°C-60°C and crushed to obtain gelling agent 2.

[0035] Example 3

[0036] 10% acrylamide, 40% methacryloyloxyethyl trimethyl ammonium chloride, 1% methacryloyloxyethyl propanesulfonic acid ammonium, 0.3% methacryloyloxyethyl naphthyl ammonium chloride, 0.1% ammonium sulfate and 0.01% tetrasodium ethylenediaminetetraacetate were added to a certain amount of deionized water, stirred evenly, and nitrogen was passed through for 30 minutes to obtain a comonomer mixed solution. 0.001% sodium persulfate, 0.002% sodium pyrosulfite, 0.01% isopropyl alcohol, 0.05% azobisisoheptonitrile and 0.05% 2,2'-azobis(2-imidazoline) dihydrochloride were added to the comonomer mixed solution, the polymerization temperature was controlled at 40°C-45°C, and the reaction was carried out for 6 hours. The obtained product was dried at 50°C-60°C and crushed to obtain gelling agent 3.

[0037] Example 4

[0038] 5% acrylamide, 50% methacryloyloxyethyl trimethyl ammonium chloride, 2% methacryloyloxyethyl propanesulfonic acid ammonium, 0.5% methacryloyloxyethyl naphthyl ammonium chloride, 0.1% polyethylene glycol and 0.01% tetrasodium ethylenediaminetetraacetate were added to a certain amount of deionized water, stirred evenly, and nitrogen was passed through for 30 minutes to obtain a comonomer mixed solution. 0.001% sodium persulfate, 0.002% sodium sulfite, 0.01% isopropyl alcohol, 0.05% azobisisobutyronitrile and 0.05% 2,2'-azobisisobutylamidine dihydrochloride were added to the comonomer mixed solution, the polymerization temperature was controlled at 40°C-45°C, and the reaction was carried out for 6 hours. The obtained product was dried at 50°C-60°C and crushed to obtain gelling agent 4.

[0039] To further illustrate the high temperature stability of the gelling agent prepared in the above embodiment, the above gelling agent was subjected to high temperature aging test and rheological property test. The test method is as follows:

[0040] High temperature aging test: At room temperature, add gelling agent to 15% hydrochloric acid and stir for 30 minutes to fully dissolve the gelling agent; put the acid solution into an aging tank and age it at 180°C for 4 hours, then observe whether there are any insoluble substances in the acid solution.

[0041] High temperature rheological test: At room temperature, add 1% gelling agent to 15% hydrochloric acid, stir for 30 minutes to fully dissolve the gelling agent, and use a rheometer at 170s -1 The viscosity of the acid at different temperatures was tested.

[0042] Table 1 Aging test results

[0043] Aging temperature(℃) Aging time (hours) Whether there is insoluble matter Example 1 180 4 none Example 2 180 4 none Example 3 180 4 none Example 4 180 4 none

[0044] As can be seen from Table 1, the gelling agents in Examples 1, 2, 3 and 4 have no obvious insoluble matter after the high temperature aging test, indicating that the degree of hydrolysis of the gelling agent molecules is low under high temperature acidic conditions and has good high temperature stability.

[0045] Attached Figure 1 This is the rheological test diagram of 1% gelling agent 1. It can be seen from the figure that when the temperature reaches 180℃, the viscosity of the acid solution can be maintained at about 15mPa·s, which indicates that the temperature resistance of gelling agent 1 can reach 180℃. Figure 2 This is the rheological test diagram of 1% gelling agent 4. It can be seen from the figure that at 180°C, the viscosity of the acid solution can reach 20mPa·s, which indicates that the temperature resistance of gelling agent 4 can reach 180°C.

Claims

1. An acid gelling agent, characterized in that: It is a polymer containing a sulfonic acid group and a naphthalene ring structure. The monomer of the sulfonic acid group is ammonium methacryloyloxyethyl propanesulfonate, and its structure is: The monomer of the naphthalene ring structure is methacryloyloxyethylnaphthyl ammonium chloride, and its structure is: The acid liquid gelling agent is obtained by polymerization reaction of a comonomer mixture through an initiator and a molecular regulator; the comonomer mixture comprises acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl propane sulfonate ammonium, methacryloyloxyethyl naphthyl ammonium chloride, a solvent, a chelating agent and deionized water; the comonomer mixture comprises, by mass percentage, 5%-10% of acrylamide, 30%-50% of methacryloyloxyethyl trimethyl ammonium chloride, 1%-5% of methacryloyloxyethyl propane sulfonate ammonium, 0.1%-0.5% of methacryloyloxyethyl naphthyl ammonium chloride, 0.1%-0.2% of a solvent, 0.01%-0.05% of a chelating agent, and the rest is deionized water; the molecular structure of the acid liquid gelling agent is: The values ​​of a:b:c:d are 500-1000:1000-2000:50-100:5-20, and a, b, c, d are all integers; the viscosity-average molecular weight of the gelling agent is 3 million to 6 million.

2. A method for preparing an acid gelling agent, characterized in that: The following steps are involved: S1. Preparation of ammonium methacryloyloxyethyl propane sulfonate: add dimethylaminoethyl methacrylate and 1,3-propane sultone in an equal molar ratio into a reaction kettle, add a mixed solvent of ethanol and acetone (in a ratio of 1:1), stir evenly, add 0.1% p-hydroxyanisole, and react at 50° C. for 12 hours; after the reaction is completed, remove the solvent by distillation under reduced pressure, wash with acetone 3 times, and dry to obtain ammonium methacryloyloxyethyl propane sulfonate; S2. Preparation of methacryloyloxyethyl naphthyl ammonium chloride: add equal proportions of dimethylaminoethyl methacrylate and 2-(chloromethyl)naphthalene into a reaction kettle, add ethanol as a solvent, stir evenly, add 0.1% p-hydroxyanisole, and react at 70° C. for 12 hours; after the reaction, remove the solvent by distillation under reduced pressure, wash with acetone 3 times, and dry to obtain methacryloyloxyethyl naphthyl ammonium chloride; S3. Preparation of polymers, including preparation of a comonomer mixture and polymerization reaction; the preparation of the comonomer mixture refers to uniformly mixing acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl ammonium propanesulfonate, methacryloyloxyethyl naphthyl ammonium chloride, a cosolvent, a chelating agent and deionized water; the polymerization reaction refers to placing the comonomer mixture in a sealed and insulated container, passing nitrogen to remove oxygen, adding an initiator and a molecular weight regulator to carry out a polymerization reaction, and drying and crushing the product obtained by the polymerization reaction to obtain an acid liquid gelling agent.

3. The method for preparing an acid solution gelling agent according to claim 2, characterized in that: The copolymer monomer mixture is prepared, and the contents of each component are, by mass percentage, 5%-10% of acrylamide, 30%-50% of methacryloyloxyethyl trimethyl ammonium chloride, 1%-5% of methacryloyloxyethyl ammonium propanesulfonate, 0.1%-0.5% of methacryloyloxyethyl naphthyl ammonium chloride, 0.1%-0.2% of cosolvent, 0.01%-0.05% of chelating agent, and the rest is deionized water.

4. The method for preparing an acid solution gelling agent according to claim 2, characterized in that: The cosolvent is one or more of carbamide, ammonium sulfate, polyethylene glycol 10000, and polyethylene glycol 20000; and the chelating agent is tetrasodium ethylenediaminetetraacetic acid.

5. The method for preparing an acid solution gelling agent according to claim 2, characterized in that: The molecular weight regulator is one or more of sodium formate, isopropyl alcohol and sodium hypophosphite.

6. The method for preparing an acid solution gelling agent according to claim 2, characterized in that: In S3, the reaction temperature of the polymerization reaction is controlled at 40° C.-60° C., and the polymerization reaction time is controlled at 5 h-8 h.

7. The method for preparing an acid solution gelling agent according to claim 2, characterized in that: The initiator includes an oxidizing agent, a reducing agent and an azo initiator.

8. The method for preparing an acid solution gelling agent according to claim 7, characterized in that: The oxidant is one or more of potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and sodium bromate; the reducing agent is one or more of sodium sulfite, sodium bisulfite, sodium pyrosulfite, ferrous chloride, and ascorbic acid; and the azo initiator is one or more of 2,2'-azobis(2-imidazoline) dihydrochloride, 2,2'-azobisisobutylamidine dihydrochloride, azobisisobutyronitrile, and azobisisoheptylonitrile.

9. The method for preparing an acid solution gelling agent according to claim 7, characterized in that: The amount of the oxidant added is 0.001%-0.003% of the comonomer mixture; the amount of the reducing agent added is 0.001%-0.005% of the comonomer mixture; and the amount of the azo initiator added is 0.01%-0.1% of the comonomer mixture.

10. The method for preparing an acid solution gelling agent according to claim 2, characterized in that: The temperature at which the product obtained by the polymerization reaction is dried is 50°C-60°C.

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