Method for testing the degree of hydrolysis and anionicity of partially hydrolyzed polyacrylamides containing amps

Abstract

The present application relates to the technical field of oil and gas field development chemical flooding enhanced oil recovery, and particularly relates to a method for testing hydrolysis degree and anionic degree of partially hydrolyzed polyacrylamide containing AMPS. The method comprises the following steps: weighing the dry powder of partially hydrolyzed polyacrylamide containing AMPS, testing the solid content of the dry powder, multiplying the solid content of the dry powder by the mass of the dry powder to obtain the effective content of the dry powder; using an organic element analyzer to test the content of sulfur element in the dried dry powder, using the content of sulfur element to obtain the content of AMPSNa and the amount of substance of AMPS; using the potentiometric titration method to test and calculate the amount of substance of hydrolyzed carboxylate and the amount of substance of unhydrolyzed amide; and calculating the hydrolysis degree and the anionic degree of the partially hydrolyzed polyacrylamide containing AMPS. The present application can measure the hydrolysis degree and the anionic degree of the partially hydrolyzed polyacrylamide containing AMPS, and is of great significance for quality control of temperature-resistant and salt-resistant polymers and research and development of new polymers in high-temperature and high-salt reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of chemical flooding to enhance oil and gas field recovery, and in particular to a method for testing the hydrolysis degree and anion degree of partially hydrolyzed polyacrylamide containing AMPS. Background Art

[0002] In oil and gas field development, polymer flooding has demonstrated excellent results in enhancing oil recovery. The chemical agents used in polymer flooding are partially hydrolyzed polyacrylamide polymers. The degree of hydrolysis is a key parameter determining the rheological behavior, stability, and solubility of partially hydrolyzed polyacrylamide. The anions produced by hydrolysis exert strong electrostatic repulsion in aqueous solutions, causing the coils to expand and producing a significant thickening effect. However, this repulsive effect of the anionic groups is significantly dependent on the salinity of the water, particularly the presence of divalent ions. The association of divalent ions with carboxylic acid groups reduces the water solubility of the polymer, and even causes precipitation at high degrees of hydrolysis. Therefore, accurately determining the degree of hydrolysis of polymers is crucial for controlling the performance of polymer flooding agents, understanding the relationship between their structure and performance, and effectively predicting their performance.

[0003] Currently, there are established methods for testing the degree of hydrolysis and anionicity of partially hydrolyzed polyacrylamide used in oil recovery. The degree of hydrolysis of polyacrylamide is primarily determined using the standard acid-base titration method specified in the national standard GB 12005.6-89, with a composite indicator used to determine the titration endpoint. The content of charged group segments in partially hydrolyzed polyacrylamide is known as its ionicity. When the anionic group is a carboxyl group, often derived from an amide group via hydrolysis, its content is also known as the degree of hydrolysis. The molecular structure of partially hydrolyzed polyacrylamide is shown below. This polymer contains two molecular groups: an amide group and a carboxylic acid group, the hydrolyzed charged group of the amide group.

[0004]

[0005] With the expansion of chemical flooding and technological advancements, polymer flooding is increasingly being used in high-temperature, high-calcium and high-magnesium reservoirs. To ensure the polymer's flooding effectiveness, AMPS monomers are added to improve the polymer's calcium and magnesium tolerance. The addition of AMPS changes the polymer's structure. Furthermore, the AMPS monomer contains a charged sulfonic acid group, resulting in inconsistencies in the ionicity and degree of hydrolysis of this type of polymer. The molecular structure of partially hydrolyzed polyacrylamide containing AMPS is shown below. This polymer contains three molecular groups: an amide group, a carboxylic acid group, the hydrolyzed charged group of the amide group, and a sulfonic acid group.

[0006]

[0007] Currently, there is no method for testing the hydrolysis degree and anionicity of heat-resistant and salt-resistant partially hydrolyzed polyacrylamide containing AMPS monomers. Summary of the Invention

[0008] The main purpose of the present invention is to provide a method for testing the hydrolysis degree and anionicity of partially hydrolyzed polyacrylamide containing AMPS. The method of the present invention can improve the accuracy of the determination of the hydrolysis degree and anionicity of partially hydrolyzed polyacrylamide containing AMPS.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for testing the hydrolysis degree and anionicity of partially hydrolyzed polyacrylamide containing AMPS, which comprises the following steps:

[0011] Weigh the partially hydrolyzed polyacrylamide powder containing AMPS to be tested, dry it, determine the sulfur content in the powder after drying, and calculate the AMPSNa content and the amount of AMPS substance in the powder;

[0012] An aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested is prepared, and the amount of hydrolyzed carboxylate and unhydrolyzed amide groups is calculated by potentiometric titration.

[0013] The hydrolysis degree and anionicity of the partially hydrolyzed polyacrylamide containing AMPS were calculated based on the amounts of carboxylate, AMPS and amide substances.

[0014] Furthermore, the partially hydrolyzed polyacrylamide powder containing AMPS to be tested is dried at 100-150° C. for 1-5 hours, cooled for 1-2 hours, and then the solid content of the powder is measured.

[0015] Furthermore, the specific steps of calculating the amount of hydrolyzed carboxylate and the amount of unhydrolyzed amide by potentiometric titration include the following:

[0016] Potentiometric titrator calibration;

[0017] Preparation of acid standard solution and concentration determination: Use the prepared acid standard solution to titrate the sodium carbonate solution using the equivalence point titration method, record the volume of acid consumed at the second equivalence point, and calculate the concentration of the acid standard solution;

[0018] Sodium chloride was added to the prepared aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested, and the mixture was stirred evenly; a sodium chloride solution of the same concentration was used as a blank control;

[0019] Select endpoint titration method for titration and record the volume of acid standard solution used for sample and blank titration.

[0020] Furthermore, the concentration of the aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested is prepared to be 500-700 mg / L.

[0021] Furthermore, the endpoint pH value in the endpoint titration method is 3.

[0022] Furthermore, the calculation formula for the hydrolysis degree of partially hydrolyzed polyacrylamide containing AMPS is:

[0023] Degree of hydrolysis = amount of carboxylic acid group substance / (amount of carboxylic acid group substance + amount of AMPS substance + amount of amide group substance);

[0024] The formula for calculating the anionicity is:

[0025] Anionicity = (amount of carboxylic acid group substance + amount of AMPS group substance) / (amount of carboxylic acid group substance + amount of AMPS group substance + amount of amide group substance).

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The method of the present invention measures the solid content of polymer dry powder and the sulfur content in the dried powder to obtain the AMPSNa content and the amount of AMPS. Potentiometric titration is then used to measure and calculate the amount of hydrolyzed carboxylate groups and the amount of unhydrolyzed amide groups, ultimately calculating the degree of hydrolysis and anionicity of the partially hydrolyzed polyacrylamide containing AMPS. The method of the present invention can relatively accurately measure the degree of hydrolysis and anionicity of the partially hydrolyzed polyacrylamide containing AMPS, and is of great significance for the quality control of heat-resistant and salt-resistant polymers for high-temperature and high-salinity oil reservoirs, as well as for the development of new polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 The present invention provides a flow chart of the method for testing the hydrolysis degree and anionicity of the partially hydrolyzed polyacrylamide containing AMPS. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations and / or combinations thereof.

[0032] like Figure 1 As shown, the method for testing the hydrolysis degree and anionicity of the partially hydrolyzed polyacrylamide containing AMPS comprises the following steps:

[0033] Weigh the partially hydrolyzed polyacrylamide powder containing AMPS to be tested, dry it, determine the sulfur content in the powder after drying, and calculate the AMPSNa content and the amount of AMPS substance in the powder;

[0034] An aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested is prepared, and the amount of hydrolyzed carboxylate and unhydrolyzed amide groups is calculated by potentiometric titration.

[0035] The hydrolysis degree and anionicity of the partially hydrolyzed polyacrylamide containing AMPS were calculated based on the amounts of carboxylate, AMPS and amide substances.

[0036] Preferably, dry powder of the partially hydrolyzed polyacrylamide containing AMPS to be tested is dried at 100-150°C for 1-5 hours, cooled for 1-2 hours, and then the solids content of the powder is determined. The solids content is calculated as the percentage of the sample mass after drying to the sample mass before drying. The effective content of the powder is calculated by multiplying the solids content by the total mass.

[0037] Preferably, the partially hydrolyzed polyacrylamide dry powder containing AMPS is weighed using a 1 / 10000 balance, and the mass of the dry powder is kept consistent each time it is weighed.

[0038] Preferably, the specific steps of calculating the amount of the substance of the hydrolyzed carboxylate group and the amount of the substance of the unhydrolyzed amide group by potentiometric titration include the following:

[0039] Potentiometric titrator calibration;

[0040] Preparation of acid standard solution and concentration determination: Use the prepared acid standard solution to titrate the sodium carbonate solution using the equivalence point titration method, record the volume of acid consumed at the second equivalence point, and calculate the concentration of the acid standard solution;

[0041] Sodium chloride was added to the prepared aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested, and the mixture was stirred evenly; a sodium chloride solution of the same concentration was used as a blank control;

[0042] Select endpoint titration method for titration and record the volume of acid standard solution used for sample and blank titration.

[0043] Preferably, the concentration of the aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested is 500-700 mg / L.

[0044] Preferably, the endpoint pH value in the endpoint titration method is 3.

[0045] Preferably, the degree of hydrolysis of the partially hydrolyzed polyacrylamide containing AMPS is calculated as follows:

[0046] Degree of hydrolysis = amount of carboxylic acid group substance / (amount of carboxylic acid group substance + amount of AMPS substance + amount of amide group substance);

[0047] The formula for calculating the anionicity is:

[0048] Anionicity = (amount of carboxylic acid group substance + amount of AMPS group substance) / (amount of carboxylic acid group substance + amount of AMPS group substance + amount of amide group substance).

[0049] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0050] Glossary:

[0051] The degree of hydrolysis of the partially hydrolyzed polyacrylamide containing AMPS is: the percentage of the number of molecular chains of hydrolyzed carboxylate groups to the total number of molecular chains dissolved in the solution.

[0052] The anionicity of the partially hydrolyzed polyacrylamide containing AMPS is: the percentage of the number of molecular chains containing anionic groups to the total number of molecular chain groups dissolved in the solution.

[0053] Example 1

[0054] The method for testing the degree of hydrolysis and anionicity of partially hydrolyzed polyacrylamide containing AMPS comprises the following steps:

[0055] (1) Weigh 1.0003 g of partially hydrolyzed polyacrylamide powder containing AMPS and place it in an oven at 120°C. After 2 hours, measure the solid content (S) of the polymer.

[0056] The AMPS-containing partially hydrolyzed polyacrylamide dry powder is a partially hydrolyzed polyacrylamide synthesized in a laboratory with a known hydrolysis degree of 22.4% and an AMPS content of 0.00005 mol.

[0057] (2) Weigh the dried polymer powder using a 1 / 100000 balance, place it in an organic element analyzer, and test the sulfur mass fraction W of the polymer.

[0058] (3) Calibration of potentiometric titrator: Prepare standard pH solutions, such as pH = 4.01, 6.86, 9.18, and use the pH calibration function to calibrate the pH system of the instrument.

[0059] (4) Acid standard solution: Measure 9.0 mL of hydrochloric acid and add it to 1000 mL of distilled water. Shake well and pour into the titrant bottle. Weigh 0.16 g of standard anhydrous sodium carbonate, burned to a constant weight at 270°C to 300°C, to the nearest 0.0001 g, and dissolve it in 100 mL of distilled water. Titrate using a potentiometric titrator using the equivalence point titration method. Record the volume of hydrochloric acid consumed at the second equivalence point and calculate the concentration C of the hydrochloric acid standard solution.

[0060] (5) Sample preparation: Weigh 0.0742 g of partially hydrolyzed polyacrylamide containing AMPS (denoted as M) into a 250 mL beaker and dissolve in 100 mL of distilled water for 6 h. Add 3 g of NaCl and stir at 300 rpm for 15 min to ensure uniform dissolution.

[0061] (6) Blank titration: Weigh 100 mL of distilled water into a 250 mL beaker, add 3 g of NaCl, and stir to dissolve evenly. Select the endpoint titration method and titrate with HCl standard solution to an endpoint pH of 3.00. Record the titration volume V1.

[0062] (7) Sample titration: On a calibrated pH titrator, select the endpoint titration method and titrate the sample with HCl standard solution to the endpoint pH = 3.00, and record the titration volume V2.

[0063] (8) Calculation of hydrolysis degree:

[0064] Amount of carboxylic acid group: (V2-V1)*C

[0065] AMPS amount of substance: W*M*S / 32

[0066] Amount of amide substance: [M*S-94*(V2-V1)*C-229*W*M*S / 32] / 71

[0067] Among them, 32 is the molecular weight of sulfur element, 94 is the mass of carboxylic acid group molecular chain, 71 is the mass of amide group molecular chain, and 229 is the mass of sulfonic acid group molecular chain.

[0068] Degree of hydrolysis = amount of carboxylic acid group substance / (amount of carboxylic acid group substance + amount of AMPS substance + amount of amide group substance)

[0069] Anionicity = (amount of carboxylic acid group substance + amount of AMPS substance) / (amount of carboxylic acid group substance + amount of AMPS substance + amount of amide group substance)

[0070] (9) Results:

[0071] The hydrolysis degree and anionicity of the polymer were obtained by using the above measurement results and calculation formula, and compared with the known data. The results are shown in Table 1 below.

[0072] Table 1 Hydrolysis degree and anion degree test results

[0073]

[0074] From the experimental results in Table 1, it can be seen that the hydrolysis degree tested by the existing test method is quite different from the actual hydrolysis degree of the sample, while the experimental results of the test method of the present invention are similar to the actual values ​​of the known samples, and this test method is reasonable.

[0075] The acid-base titration method is the acid-base titration method specified in the national standard GB 12005.6-89.

[0076] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. The method for testing the hydrolysis degree and anionicity of partially hydrolyzed polyacrylamide containing AMPS is characterized by: It includes the following steps: Weigh the partially hydrolyzed polyacrylamide powder containing AMPS to be tested, dry it, determine the sulfur content in the powder after drying, and calculate the AMPSNa content and the amount of AMPS substance in the powder; An aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested is prepared, and the amount of hydrolyzed carboxylate and unhydrolyzed amide groups is calculated by potentiometric titration. The hydrolysis degree and anionicity of the partially hydrolyzed polyacrylamide containing AMPS were calculated based on the amounts of carboxylate, AMPS, and amide groups. Dry the partially hydrolyzed polyacrylamide powder containing AMPS to be tested at 100-150°C for 1-5 hours, cool it for 1-2 hours, and then measure the solid content of the powder; The specific steps for calculating the amount of hydrolyzed carboxylate and unhydrolyzed amide by potentiometric titration include the following: Potentiometric titrator calibration; Preparation of acid standard solution and concentration determination: Use the prepared acid standard solution to titrate the sodium carbonate solution using the equivalence point titration method, record the volume of acid consumed at the second equivalence point, and calculate the concentration of the acid standard solution; Sodium chloride was added to the prepared aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested, and the mixture was stirred evenly; a sodium chloride solution of the same concentration was used as a blank control; Select endpoint titration method for titration and record the volume of acid standard solution used for sample and blank titration; The endpoint pH value in endpoint titration is 3; The calculation formula for the degree of hydrolysis of partially hydrolyzed polyacrylamide containing AMPS is: Degree of hydrolysis = amount of carboxylic acid group substance / (amount of carboxylic acid group substance + amount of AMPS substance + amount of amide group substance); The formula for calculating the anionicity is: Anionicity = (amount of carboxylic acid group substance + amount of AMPS group substance) / (amount of carboxylic acid group substance + amount of AMPS group substance + amount of amide group substance).

2. The method according to claim 1, characterized in that The concentration of the aqueous solution of partially hydrolyzed polyacrylamide containing AMPS to be tested is 500-700 mg / L.

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