A functional polymer for oil and gas fields and its preparation method

Abstract

The present invention relates to the technical field of oil and gas field development materials, and particularly relates to a functional polymer for oil and gas fields and a preparation method thereof. The composition components by weight parts include 30-40 parts of an organic framework material, 20-27 parts of 2-acrylamide-2-methylpropanesulfonic acid, 12-15 parts of nano-silica, and 26-36 parts of a quaternary ammonium salt type cationic gemini surfactant. By adopting the above-mentioned functional polymer for oil and gas fields and the preparation method thereof, the prepared polymer can be used in fracturing fluids, and has excellent thickening effect and good temperature resistance, salt resistance and shear resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development materials, and particularly to a functional polymer for oil and gas fields and a preparation method thereof. Background Art

[0002] Polymers play an important role in reservoir stimulation in oil and gas fields, mainly by enhancing the recovery effect by improving the permeability of the reservoir and the fluidity of crude oil. Specific applications include: 1. Reservoir modification: Polymer solutions can be used to modify low-permeability or extra-low-permeability oil layers. By plugging large pores and improving the permeability of small pores, the microscopic structure of the reservoir is adjusted, enabling injected water or displacing agents to penetrate the oil layer more uniformly and increasing the recoverability of crude oil. 2. Enhancement of fracture conductivity: In hydraulic fracturing operations, polymers as additives to proppant carriers help carry proppants into fractures and form a good support structure in the fractures. At the same time, the wettability of the fracture walls is improved, liquid loss is reduced, and the fracture conductivity is enhanced. 3. Prevention of reservoir damage: Specific polymer formulations can be used in drilling, well completion, and stimulation measures to reduce damage to the reservoir, such as reducing the permeability decline caused by filtrate invasion and maintaining the original productivity of the oil layer.

[0003] In hydraulic fracturing operations, traditional synthetic polymer fracturing fluids use acrylamide-based polymers, and the viscosity of the fracturing fluid is increased through chemical crosslinking. The acrylamide-based polymer fracturing fluid system has basically achieved good thermal stability; it has high viscosity and strong proppant-carrying ability; the thickener system has good anti-swelling properties and low filtrate loss.

[0004] For example, Xiaoqin CAO et al. reported a copolymer of acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, which is suitable for fracturing operations in high-temperature and high-salt oil and gas reservoirs after crosslinking with organic zirconium. Jiang Wenxue et al. also copolymerized acrylamide, N-vinylpyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid, and allyl polyethylene glycol, and then crosslinked with N,N'-methylenebisacrylamide and diethylenetriamine to obtain a low-damage recoverable small-molecule linear gel fracturing fluid. The gel-breaking fluid of this fracturing fluid can be recycled. It has been applied to 56 layers in 16 wells in the oil and gas wells of the Ordos Basin, including 4 horizontal wells. The success rate of fracturing reconstruction is 100%, the continuous proppant-carrying success rate is 100%, the construction pressure and friction are reduced by 23.5%, and the recovery and utilization rate of the flowback fluid is ≥95%.

[0005] In the existing literature reports, similar to the salt-tolerant polymers for oil displacement, the salt-tolerant polymers for fracturing fluids still improve the salt tolerance of the polymers by introducing monomers with sulfonic acid groups, zwitterionic groups or hydrophobic groups into polyacrylamide. However, in the actual use process, different from the polymers for oil displacement, the salt-tolerant polymers for fracturing fluids need to be able to hydrate and thicken quickly in high salinity water. However, the introduction of the above monomers will reduce the molecular weight of the synthesized polymer and cannot achieve rapid viscosity increase in high salinity water, affecting the fracturing effect. Summary of the Invention

[0006] The purpose of the present invention is to provide a functional polymer for oil and gas fields and its preparation method. The prepared polymer can be used in fracturing fluids and has excellent thickening effects and good temperature and salt tolerance and shear resistance.

[0007] To achieve the above purpose, the present invention provides a functional polymer for oil and gas fields, which includes the following components by weight: 30-40 parts of organic framework material, 20-27 parts of 2-acrylamido-2-methylpropanesulfonic acid, 12-15 parts of nano-silica, and 26-36 parts of quaternary ammonium salt type cationic gemini surfactant.

[0008] Preferably, the organic framework material is amino-functionalized UiO-66.

[0009] Preferably, the nano-silica is hydrophilic nano-silica, and the particle size of the hydrophilic nano-silica is 8-15 nm.

[0010] Preferably, the quaternary ammonium salt type cationic gemini surfactant is a hydroxyl quaternary ammonium salt type gemini surfactant, and its chemical general formula is: ,

[0011] where m = 12-16.

[0012] The preparation method of the above functional polymer for oil and gas fields includes the following steps:

[0013] S1. Prepare a quaternary ammonium salt type cationic gemini surfactant

[0014] S1.1. Dissolve epichlorohydrin in an organic solvent to obtain an epichlorohydrin solution;

[0015] S1.2. Dissolve dimethyl long-chain alkyl tertiary amine and a catalyst in an organic solvent. After there is no more smoke, dropwise add the epichlorohydrin solution and react to obtain a quaternary ammonium salt intermediate;

[0016] S1.3. Under alkaline conditions, dropwise add dimethyl long-chain alkyl tertiary amine to the quaternary ammonium salt intermediate and react to synthesize a quaternary ammonium salt type cationic gemini surfactant;

[0017] The chemical reaction equation is as follows:

[0018] ,

[0019] where m = 12 - 16.

[0020] S2. Add the organic framework material, 2 - acrylamido - 2 - methylpropanesulfonic acid, nano - silica, and quaternary ammonium salt - type cationic gemini surfactant into a stirrer and stir for 2 - 4 h to obtain the functional polymer for oil and gas fields.

[0021] Preferably, the organic solvent in S1 is n - propanol or ethanol.

[0022] Preferably, in S1.2, the molar ratio of dimethyl long - chain alkyl tertiary amine to epichlorohydrin is 1:1, and the reaction is a reflux reaction at 30°C.

[0023] Preferably, the catalyst in S1.2 is concentrated hydrochloric acid.

[0024] Preferably, in S1.3, the molar ratio of the quaternary ammonium salt intermediate to dimethyl long - chain alkyl tertiary amine is 1:2, and the reaction is carried out at 40°C for 5 h.

[0025] Preferably, after the reaction in S1.3, the temperature is raised to 50°C for rotary evaporation to obtain the crude product. The crude product is recrystallized with acetone to obtain white crystals, and the quaternary ammonium salt - type cationic gemini surfactant is obtained after suction filtration and drying.

[0026] Advantages of the present invention:

[0027] (1) In the present invention, by mixing and stirring the organic framework material, 2 - acrylamido - 2 - methylpropanesulfonic acid, nano - silica, and quaternary ammonium salt - type cationic gemini surfactant, a functional polymer for oil and gas fields is obtained. The organic framework material is amino - functionalized UiO - 66 containing amino groups, and the quaternary ammonium salt - type cationic gemini surfactant is a hydroxyl - quaternary ammonium salt - type gemini surfactant containing hydroxyl groups. During the mixing and stirring process, nano - silica will be adsorbed into the organic framework material through electrostatic interaction and hydrogen bonding. The amino groups in the organic framework material react with the hydroxyl groups of the quaternary ammonium salt - type cationic gemini surfactant to form a cross - linked structure. The existence of the cross - linked network structure improves the rigidity of the polymer, increases the steric hindrance and hydrolysis resistance, enables the polymer to increase viscosity to reach an effective viscosity, and has good temperature and salt resistance and shear resistance.

[0028] (2) In the polymer for oil and gas fields of the present invention, the framework structure of the organic framework material not only further enhances the rigidity of the polymer but also enables the polymer to have good adsorption, thus facilitating the removal of impurities in wastewater during the fracturing process and improving the fracturing effect of the fracturing fluid.

[0029] (3) In the polymer for oil and gas fields of the present invention, sulfonic acid groups, quaternary ammonium salts, hydroxyl groups, and amino groups can all improve the salt resistance. The hydrogen bonds formed among them can effectively reduce the degree of freedom of the polymer, increase the hydrodynamic volume of the polymer, form a dynamic network structure, and improve the temperature and salt resistance of the polymer.

[0030] The technical solution of the present invention will be further described in detail below through examples. Specific embodiments

[0031] The present invention will be further described below in conjunction with examples. All chemicals and reagents used in the examples are commercially available unless otherwise specified. The present invention will be further described below in conjunction with examples. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention pertains. The above-mentioned features mentioned in the present invention or the features mentioned in the specific examples can be combined arbitrarily. These specific examples are only used to illustrate the present invention and not to limit the scope of the present invention.

[0032] Example 1

[0033] The present invention provides a functional polymer for oil and gas fields, which includes the following components by weight: 30 parts of amino-functionalized UiO-66, 20 parts of 2-acrylamido-2-methylpropanesulfonic acid, 12 parts of hydrophilic nano-silica, and 26 parts of hydroxyl quaternary ammonium salt gemini surfactant.

[0034] Example 2

[0035] The present invention provides a functional polymer for oil and gas fields, which includes the following components by weight: 35 parts of amino-functionalized UiO-66, 24 parts of 2-acrylamido-2-methylpropanesulfonic acid, 13 parts of hydrophilic nano-silica, and 30 parts of hydroxyl quaternary ammonium salt gemini surfactant.

[0036] Example 3

[0037] The present invention provides a functional polymer for oil and gas fields, which includes the following components by weight: 40 parts of amino-functionalized UiO-66, 27 parts of 2-acrylamido-2-methylpropanesulfonic acid, 15 parts of hydrophilic nano-silica, and 36 parts of hydroxyl quaternary ammonium salt gemini surfactant.

[0038] Example 4

[0039] The present invention also provides a preparation method of a functional polymer for oil and gas fields, which includes the following steps:

[0040] S1. Prepare a hydroxyl quaternary ammonium salt gemini surfactant

[0041] S1.1. Dissolve 0.05 mol of epichlorohydrin in 30 mL of n-propanol to obtain an epichlorohydrin solution;

[0042] S1.2. Dissolve 0.05 mol of dimethyl long-chain alkyl tertiary amine and 0.05 mol of concentrated hydrochloric acid in 20 mL of n-propanol. After there is no more smoke, add dropwise the epichlorohydrin solution and reflux at 30 °C to obtain a quaternary ammonium salt intermediate;

[0043] S1.3. Under alkaline conditions, add dropwise 0.1 mol of dimethyl long-chain alkyl tertiary amine to the quaternary ammonium salt intermediate, raise the temperature to 40 °C and react for 5 h. When the solution turns tea-yellow, then continue to raise the temperature to 50 °C for rotary evaporation to obtain a crude product. Recrystallize the crude product with acetone to obtain white crystals. After suction filtration and drying, a hydroxyl quaternary ammonium salt type gemini surfactant is obtained.

[0044] S2. Weigh the organic framework material, 2-acrylamido-2-methylpropanesulfonic acid, nano-silica and hydroxyl quaternary ammonium salt type gemini surfactant according to the dosages in Examples 1-3, and then add them to a stirrer and stir for 3 h to obtain the functional polymers for oil and gas fields in Examples 1-3.

[0045] Comparative Example 1

[0046] A polymer for oil and gas fields, comprising the following components by weight: 24 parts of 2-acrylamido-2-methylpropanesulfonic acid, 13 parts of hydrophilic nano-silica and 30 parts of hydroxyl quaternary ammonium salt type gemini surfactant.

[0047] Comparative Example 2

[0048] A polymer for oil and gas fields, comprising the following components by weight: 35 parts of amino-functionalized UiO-66, 24 parts of 2-acrylamido-2-methylpropanesulfonic acid and 13 parts of hydrophilic nano-silica.

[0049] Performance Test

[0050] Disperse the polymers prepared in Examples 1-3 and Comparative Examples 1-2 in water to prepare fracturing fluids for testing.

[0051] (1) Temperature resistance performance test

[0052] Measure the stable viscosities of the above-mentioned fracturing fluids at 80 °C and 130 °C respectively, and the results are shown in Table 1.

[0053] Table 1 Stable viscosities of fracturing fluids at different high temperatures (unit: mPa•s)

[0054]

[0055] As can be seen from Table 1, the fracturing fluids prepared from the polymers of Examples 1-3 of the present invention have good stable viscosities at high temperatures of 80 °C and 130 °C, and are all superior to Comparative Example 1, indicating that the functional polymer for oil and gas fields provided by the present invention has good thickening performance. After heating, the viscosity retention rates of the fracturing fluids prepared from the polymers of Examples 1-3 of the present invention are all above 75%, while the viscosity retention rates of Comparative Examples 1-2 are only about 40%, indicating that the polymer for oil and gas fields provided by the present invention has good high-temperature resistance.

[0056] Salt tolerance performance test

[0057] Using NaCl to simulate the groundwater condition, with the NaCl concentration of 80 g / L, the viscosity of the above-mentioned fracturing fluid was tested at a temperature of 80 °C, and the test results are shown in Table 2.

[0058] Table 2 Viscosity of fracturing fluid in high-salt environment (unit: mPa•s)

[0059]

[0060] As can be seen from Table 2, the fracturing fluids prepared from the polymers of Examples 1-3 of the present invention still have relatively high viscosities in a high-salt environment, and the viscosity retention rates of the fracturing fluids prepared from the polymers of Examples 1-3 of the present invention are all above 70% in a high-salt environment, while the viscosity retention rates of Comparative Examples 1-2 are all less than 40%, indicating that the polymer for oil and gas fields provided by the present invention has good temperature and salt tolerance performance.

[0061] Shear resistance performance test

[0062] After shearing the above-mentioned fracturing fluid at a temperature of 80 °C and a shear rate of 170 S -1 for 60 min, the viscosity was measured, and the results are shown in Table 3.

[0063] Table 3 Viscosity of fracturing fluid at high shear rate (unit: mPa•s)

[0064]

[0065] As can be seen from Table 3, the fracturing fluids prepared from the polymers of Examples 1-3 of the present invention still have relatively high viscosities at a shear rate of 170 S -1 and the viscosity retention rates are all above 60%, while the viscosity retention rates of Comparative Examples 1-2 are only about 30%, indicating that the polymer for oil and gas fields provided by the present invention has good shear resistance performance.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A functional polymer for oil and gas fields, characterized in that: The following components are included by weight: 30-40 parts of organic framework material, 20-27 parts of 2-acrylamide-2-methylpropanesulfonic acid, 12-15 parts of nano-silicon dioxide and 26-36 parts of quaternary ammonium salt type cationic gemini surfactant; The organic framework material is amino UiO-66; The quaternary ammonium salt type cationic gemini surfactant is a hydroxyl quaternary ammonium salt type gemini surfactant, and its general chemical formula is: In the formula, m=12~16.

2. The functional polymer for oil and gas fields according to claim 1, characterized in that: The nano-silica is hydrophilic nano-silica, and the particle size of the hydrophilic nano-silica is 8 to 15 nm.

3. A method for preparing a functional polymer for oil and gas fields as claimed in any one of claims 1 to 2, characterized in that: The following steps are included: S1. Preparation of quaternary ammonium salt type cationic gemini surfactant S1.1, dissolving epichlorohydrin in an organic solvent to obtain an epichlorohydrin solution; S1.2, dissolving a dimethyl long-chain alkyl tertiary amine and a catalyst in an organic solvent, and after the smoke disappears, adding dropwise an epichlorohydrin solution to react to obtain a quaternary ammonium salt intermediate; S1.3, under alkaline conditions, dimethyl long-chain alkyl tertiary amine is added dropwise to the quaternary ammonium salt intermediate to react and synthesize a quaternary ammonium salt type cationic gemini surfactant, which is a hydroxyl quaternary ammonium salt type gemini surfactant; S2. Add the organic framework material amino UiO-66, 2-acrylamide-2-methylpropanesulfonic acid, nano-silica and quaternary ammonium salt type cationic gemini surfactant into a stirrer and stir for 2 to 4 hours to obtain a functional polymer for oil and gas fields.

4. The method for preparing a functional polymer for oil and gas fields according to claim 3, characterized in that: The organic solvent in S1 is n-propanol or ethanol.

5. The method for preparing a functional polymer for oil and gas fields according to claim 3, characterized in that: The molar ratio of dimethyl long-chain alkyl tertiary amine and epichlorohydrin in S1.2 is 1:1, and the reaction is refluxed at 30°C.

6. The method for preparing a functional polymer for oil and gas fields according to claim 3, characterized in that: The catalyst in S1.2 is concentrated hydrochloric acid.

7. The method for preparing a functional polymer for oil and gas fields according to claim 3, characterized in that: The molar ratio of the quaternary ammonium salt intermediate to the dimethyl long-chain alkyl tertiary amine in S1.3 is 1:2, and the reaction is carried out at 40°C for 5 hours.

8. The method for preparing a functional polymer for oil and gas fields according to claim 7, characterized in that: After the reaction in S1.3 is completed, the temperature is raised to 50°C for rotary evaporation to obtain a crude product, the crude product is recrystallized using acetone to obtain white crystals, and the quaternary ammonium salt type cationic gemini surfactant is obtained after filtration and drying.

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