A method for determining the concentration of a polymer in a solution after static adsorption using a capillary viscometer

Abstract

The application provides a method for determining the concentration of a polymer in a solution after static adsorption by using a capillary viscometer, wherein the diluent obtained by diluting the polymer solution before and after static adsorption satisfies the Huggins equation: η sp / c = [η] + k'[η] 2 c in a certain concentration range, so that by setting two groups of experiments (a reference experiment group and a to-be-tested experiment group), the specific viscosity η sp of the polymer before static adsorption (the reference experiment group) is determined by using the capillary viscometer, the specific viscosity-concentration relationship curve is drawn, a linear regression equation η sp / c = k*c + b is obtained, the linear regression equation coefficient does not change with the concentration before and after static adsorption, and by using the principle, the specific viscosity of the polymer after static adsorption (the to-be-tested experiment group) is further determined, the concentration of the polymer in the to-be-tested experiment group and the static adsorption amount of the quartz sand to the sample are calculated by substituting the linear regression equation, and no chemical reaction occurs in the determination process, the operation is simple, and the influencing factors are few.

Description

Technical Field

[0001] This invention relates to the field of laboratory evaluation experiments on chemical agents used for oil displacement in oil and gas field development in the petroleum industry, specifically to a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer. Background Technology

[0002] As an important measure for stabilizing crude oil production, polymer flooding technology has been widely applied in domestic oilfields. Among the polymers used for oil displacement, partially hydrolyzed polyacrylamide is the most common. Performance evaluation and testing of composite oil displacement systems composed of partially hydrolyzed polyacrylamide, surfactants, and alkalis are of great significance for guiding scheme design and improving field recovery rates.

[0003] Static adsorption testing is an important test indicator in the performance test methods of composite oil displacement systems (SY / T 6424-2014). It examines the changes in the concentration and adsorption amount of polymers, surfactants, and alkalis after static adsorption of the composite system solution by quartz sand. Current methods for determining polymer concentration include turbidity method, starch-cadmium iodide method, liquid chromatography, phenol-sulfuric acid method, and flocculation method.

[0004] The turbidity method is based on the principle that the turbidity value of the chloramide insoluble substance formed by the reaction of polymer with sodium hypochlorite under acidic conditions is proportional to the polymer concentration. However, this method has disadvantages such as the generation of toxic vapors during the chemical reaction and the susceptibility of the measurement results to interference from colored substances.

[0005] The starch-cadmium iodide method is currently the most commonly used method for polymer concentration determination. This method is based on the first step of the Hoffmann rearrangement reaction. Under acidic conditions, the amide groups in the polymer are oxidized with bromine water, and then the excess bromine is reduced with sodium formate. The amide oxidation product, in the presence of linear starch, oxidizes iodide ions to form a blue starch iodide. The concentration of this blue starch iodide at a specific wavelength shows a linear relationship with its absorbance. This method is susceptible to various factors such as pH value, the amount of saturated bromine water added, the bromination reaction time, the colorimetric ions, and the stability of the starch-iodide complex, requiring control of numerous chemical reaction conditions.

[0006] Liquid chromatography (LC) uses a chromatographic column to separate polyacrylamide molecules from low molecular weight components, uses a detector to detect the characteristic peaks of the polymer eluted from the column, and integrates the peak areas to determine the polymer concentration. This method measures the percentage content of the polymer in the solution, rather than its mass concentration, and has the disadvantages of expensive equipment and high daily maintenance costs.

[0007] The phenol-sulfuric acid method is only applicable to polysaccharide polymers, and the flocculation method is only applicable to the qualitative analysis of polymers containing acrylamide. It cannot be used to determine the polymer concentration in the solution after static adsorption.

[0008] A comprehensive analysis of the above five experimental methods for determining the polymer concentration in the solution after static adsorption reveals that they either have drawbacks such as high detection costs, the need to construct chemical reactions, strict control of the reaction degree, and numerous limiting factors. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer. This method involves diluting the polymer solution before and after static adsorption. The resulting diluted solution, within a certain concentration range, exhibits a specific viscosity that satisfies the Huggins equation: η sp / c=[η]+k'[η] 2 c. Furthermore, the equation coefficients do not change with the concentration before and after static adsorption. Based on this principle, a capillary viscometer is used to determine the intrinsic viscosity and curve equation of the polymer before static adsorption (reference experimental group). The specific viscosity of the polymer after static adsorption (experimental group to be tested) is further determined. Substituting these values ​​into the above curve equation, the concentration of the polymer in the experimental group to be tested and the static adsorption amount of quartz sand on the sample are calculated. No chemical reaction occurs during the measurement process, the operation is simple, and there are few influencing factors.

[0010] The specific details of the invention are as follows:

[0011] This invention provides a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer, the method comprising the following steps:

[0012] S1. Under certain temperature conditions, the polymer sample to be tested is prepared into a solution with a polymer concentration of c0. Two portions of the polymer concentration of c0 solution are taken to carry out static adsorption experiments without adding quartz sand and with adding quartz sand, respectively, to obtain the first solution and the second solution.

[0013] S2. Take multiple volumes of the first solution and dilute them to obtain polymer solutions with at least four concentration values, including 0, to form a reference experimental group; dilute the second solution to obtain the test experimental group.

[0014] S3. Measure the time it takes for the reference experimental group solutions to flow through a capillary viscometer in order of increasing concentration, plot the specific viscosity-concentration relationship curve, and obtain the linear regression equation η. sp / c = k*c + b;

[0015] S4. Measure the time it takes for the test group to flow through the capillary viscometer and calculate the specific viscosity η. sp and the η sp Substituting into the linear regression equation, the concentration of the polymer in the test group and the static adsorption amount of the test group by the quartz sand are calculated.

[0016] Optionally, in step S1, the experiment of adding quartz sand for static adsorption includes: adding 30-40 mesh quartz sand to the solution with polymer concentration of c0 at a solid-liquid mass ratio of 1:3, fixing it in a constant temperature shaker, and oscillating at a constant temperature of 120 times / min for static adsorption for 24 hours, then centrifuging to separate the supernatant to obtain the second solution.

[0017] Optionally, in step S1, the experiments of static adsorption without adding quartz sand and static adsorption with adding quartz sand are carried out simultaneously under the same experimental conditions, and whether or not quartz sand is added is a single variable.

[0018] Optionally, the certain temperature condition refers to a temperature range of 65 to 120°C.

[0019] Optionally, the solution with a polymer concentration of c0 is: a polymer solution, a polymer + surfactant binary composite oil displacement system solution, a polymer + alkali binary composite oil displacement system solution, or a polymer + surfactant + alkali ternary composite oil displacement system solution.

[0020] The polymer is a partially hydrolyzed polyacrylamide polymer for oil displacement.

[0021] The surfactant is an alkylbenzene sulfonate, and the mass fraction of the surfactant is 0-0.3%; the base is Na2CO3, and the mass fraction of the base is 0-0.3%.

[0022] The value of c0 ranges from 1000 to 2500 mg / L.

[0023] Optionally, the polymer has a viscosity-average relative molecular mass in the range of 3 × 10⁻⁶. 6 ~22×10 6 .

[0024] Optionally, the solvent for the polymer concentration of c0 solution and the solvent for dilution are both NaHCO3-type simulated formation water with a mineralization range of 0 to 6000 mg / L; the composition of the NaHCO3-type simulated formation water includes: distilled water, sodium sulfate, sodium chloride, anhydrous calcium chloride, magnesium chloride hexahydrate, and sodium bicarbonate.

[0025] Optionally, the diluent further includes a buffer solution prepared by dissolving 1.335 g of citric acid monohydrate, 26.6 g of disodium hydrogen phosphate and 116.9 g of sodium chloride in 1000 mL of distilled water.

[0026] Optionally, the capillary viscometer is an Ubbelohde viscometer.

[0027] Optionally, the calculated specific viscosity η can be increased by diluting the first solution and the second solution. sp The value ranges from 0.2 to 1.5.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention provides a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer. This method innovatively utilizes a capillary viscometer to determine the polymer concentration in a solution after static adsorption. The determination process does not require the construction of a chemical reaction, the detection equipment is readily available, and the precision and repeatability meet the requirements for determining the polymer concentration and adsorption amount after static adsorption. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 The following is a flowchart illustrating a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer, according to an embodiment of the present invention.

[0032] Figure 2 The specific viscosity-concentration curves obtained by measuring the reference experimental group using a capillary viscometer provided in this embodiment of the invention are shown.

[0033] Figure 3 The linear regression equation obtained by the starch-cadmium iodide method for determining the experimental group of the present invention is shown in the comparative example.

[0034] Figure 4 This invention provides a capillary viscometer for measuring the specific viscosity-concentration curves of a reference experimental group, as shown in another embodiment of the invention.

[0035] Figure 5 This invention provides a capillary viscometer for measuring the specific viscosity-concentration curves of a reference experimental group, as shown in another embodiment of the invention.

[0036] Figure 6 The specific viscosity-concentration curve obtained by measuring the reference experimental group using a capillary viscometer according to another embodiment of the present invention is shown. Detailed Implementation

[0037] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0038] Specific experimental steps or conditions are not specified in the examples; however, they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0039] This invention provides a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer. Figure 1 The following is a flowchart illustrating a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer, as provided in an embodiment of the present invention. Figure 1 The determination method includes the following steps:

[0040] S1. Under certain temperature conditions, the polymer sample to be tested is prepared into a solution with a polymer concentration of c0. Two portions of the polymer concentration of c0 solution are taken to carry out static adsorption experiments without adding quartz sand and with adding quartz sand, respectively, to obtain the first solution and the second solution.

[0041] In specific implementation, the polymer sample to be tested can be prepared into a 5000 mg / L mother liquor with saline solution, matured evenly, and then diluted to a solution with a concentration of c0. The value of c0 should be controlled within the range of 1000–2500 mg / L. This invention conducts an experiment on the static adsorption of the polymer solution with a concentration of c0 by adding quartz sand, ultimately obtaining a second solution. The process is as follows: 30–40 mesh quartz sand is added to the polymer solution with a concentration of c0 at a solid-liquid mass ratio of 1:3. The solution is fixed in a constant-temperature shaker and subjected to static adsorption at a frequency of 120 times / min at a certain temperature for 24 hours. After centrifugation, the supernatant is separated to obtain the second solution. This invention also conducts an experiment on the static adsorption of the polymer solution with a concentration of c0 without adding quartz sand, ultimately obtaining a first solution. Except for omitting the step of adding quartz sand to the polymer solution, all other processing procedures (experimental conditions) are the same as the experiment on obtaining the second solution by adding quartz sand. Whether or not quartz sand is added is a single variable.

[0042] In specific implementation, the polymer is a partially hydrolyzed polyacrylamide polymer for oil displacement, with a viscosity-average relative molecular mass ranging from 3 × 10⁻⁶. 6 ~22×10 6Since the application environment of partially hydrolyzed polyacrylamide polymers for oil displacement is often at high temperatures, the test method should meet the requirements of oil displacement polymers in high-temperature operating environments. Therefore, the method for determining the polymer concentration in the solution after static adsorption of the oil displacement polymer provided by this invention is a step S1 (static adsorption experiment) conducted using quartz sand at 65-120℃.

[0043] In some embodiments, the polymer used for oil displacement is often used in a composite oil displacement system composed of surfactants, alkalis, etc. Therefore, the solution with a polymer concentration of c0 can be: a polymer solution, a polymer + surfactant binary composite oil displacement system solution, a polymer + alkali binary composite oil displacement system solution, or a polymer + surfactant + alkali ternary composite oil displacement system solution. Wherein, the surfactant is an alkylbenzene sulfonate with a mass fraction of 0–0.3%, and the alkali is Na2CO3 with a mass fraction of 0–0.3%. S2. Take multiple different volumes of the first solution and dilute them to obtain polymer solutions with at least four concentration values, including 0, forming a reference experimental group; dilute the second solution to obtain the test experimental group.

[0044] In practice, the first solution is diluted to control the calculated specific viscosity η. sp The value ranges from 0.2 to 1.5. A polymer solution with a concentration of 0 means that the solution contains only solvent and no polymer. Step S2 is illustrated as follows: Volumes of the first solution (V1, V2, V3, V4) are measured sequentially, and 50 mL of buffer solution is added to each. The solutions are shaken well, transferred to a 100 mL volumetric flask, and diluted to volume with saline solution to obtain five polymer solutions with concentrations of 0, c1, c2, c3, and c4, forming the reference experimental group. Volume of the second solution (V) is measured, 50 mL of buffer solution is added, and the solutions are shaken well. The solutions are transferred to a 100 mL volumetric flask and diluted to volume with saline solution to obtain the test experimental group.

[0045] S3. Measure the time it takes for the reference experimental group solutions to flow through a capillary viscometer in order of increasing concentration, plot the specific viscosity-concentration relationship curve, and obtain the linear regression equation η. sp / c=k*c+b.

[0046] Step S3 is illustrated as follows: The concentrations are measured in ascending order as 0, c1, c2, c3, c4. The times t0, t1, t2, t3, and t4 for the solution from the reference experimental group to flow out of the capillary viscometer at 30°C are used to determine the concentration. n -t0) / t0 yields the incremental viscosity (η) sp ) n , and by (η sp ) n / c nSpecific viscosity was obtained, and a specific viscosity-concentration relationship curve was plotted to obtain the linear regression equation: η sp / c=k*c+b.

[0047] S4. Measure the time it takes for the test group to flow through the capillary viscometer and calculate the specific viscosity η. sp and the η sp Substituting into the linear regression equation, the concentration of the polymer in the test group and the static adsorption amount of the test group by the quartz sand are calculated.

[0048] Step S4 is exemplified as follows: Measure the time t it takes for the experimental group to flow out of the capillary viscometer at 30℃, and use (t-t0) / t0 to obtain the specific viscosity η. sp Substituting into the linear regression equation: η sp / c=k*c+b, calculate the concentration of polymer in the supernatant after static adsorption by quartz sand, and then obtain the static adsorption amount of the polymer sample to be tested. The specific method is: η sp / c=k*c+b can be transformed into a quadratic equation in terms of concentration c: k*c 2 +b*c-η sp =0, according to the quadratic formula, discarding the negative value, we get Concentration of the test solution before dilution Adsorption capacity

[0049] This invention provides a novel method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer. In the prior art, capillary viscometers are commonly used to measure fluid viscosity and the viscosity-average molecular weight of polymers. This invention innovatively uses a capillary viscometer to determine the polymer concentration in a solution after static adsorption, providing a better option for indoor evaluation experiments of chemical agents used in oil and gas field development in the petroleum industry. Furthermore, using a capillary viscometer for measurement results in low detection costs and eliminates the need for constructing chemical reactions, thus effectively avoiding measurement errors caused by inadequate control of the degree of chemical reaction and greatly simplifying the measurement steps and process.

[0050] This invention involves diluting the polymer solution before and after static adsorption. The resulting diluted solution, within a certain concentration range, exhibits a specific viscosity-concentration relationship that satisfies the Huggins equation: η sp / c=[η]+k'[η] 2 Therefore, by setting up two sets of experiments (the reference experimental group and the test experimental group), a capillary viscometer was used to determine the specific viscosity η of the polymer before static adsorption (the reference experimental group). sp Plot the specific viscosity-concentration relationship curve to obtain the linear regression equation η. sp / c=k*c+b, the coefficients of this linear regression equation do not change with the concentration before and after static adsorption. Using this principle, the specific viscosity of the polymer after static adsorption (in the experimental group to be tested) was further measured. Substituting this into the above linear regression equation, the concentration of the polymer in the experimental group to be tested and the static adsorption amount of quartz sand on the sample were calculated. No chemical reaction occurs during the measurement process, the operation is simple, and there are few influencing factors.

[0051] In some embodiments, the solvent for the polymer concentration of c0 solution and the solvent for dilution are both NaHCO3-type simulated formation water with a mineralization range of 0 to 6000 mg / L; the composition of the NaHCO3-type simulated formation water includes: distilled water, sodium sulfate, sodium chloride, anhydrous calcium chloride, magnesium chloride hexahydrate, and sodium bicarbonate.

[0052] In some embodiments, the diluent further includes a buffer solution prepared by dissolving 1.335 g of citric acid monohydrate, 26.6 g of disodium hydrogen phosphate and 116.9 g of sodium chloride in 1000 mL of distilled water.

[0053] In some embodiments, the capillary viscometer may be an Ubbelohde viscometer.

[0054] To enable those skilled in the art to better understand the present invention, the following specific embodiments illustrate a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer.

[0055] Example 1

[0056] (1) Preparation and linear relationship of specific viscosity-concentration curves of the experimental group were investigated.

[0057] a. Preparation of brine: Add 0.43 mg Na2SO4, 543.46 mg NaCl, 14.43 mg CaCl2, 10.15 mg MgCl2·6H2O, and 877.80 mg NaHCO3 sequentially to an appropriate amount of distilled water. Add the next substance only after each substance has completely dissolved. Transfer the solution to a 1000 mL volumetric flask and dilute to volume with distilled water to obtain a NaHCO3-type simulated formation water with a mineralization of 1440.88 mg / L.

[0058] b. Polymer solution preparation: Weigh (500-2.5 / S) g of brine into a beaker, turn on the electric stirrer, set the speed to 400 r / min, and accurately weigh the viscosity-average relative molecular mass 4.56 × 10⁻⁶ g. 62.5 g / S of polymer P1 sample with a solid content of S = 89.33% was slowly and uniformly added to a vortex over 1 minute, and stirring was continued for 2 hours to obtain a polymer mother liquor of 5000 mg / L. 150 mL of the above polyacrylamide mother liquor was taken and diluted with 350 mL of the above saline solution. The solution was stirred on a magnetic stirrer at 300 rpm for 20 minutes to obtain a polymer solution with an initial concentration c0 of 1500 mg / L.

[0059] c. Preparation of the test and reference experimental group solutions for static adsorption experiments: A certain amount of quartz sand with a particle size range of 30-40 mesh was weighed and placed in a 250 mL stoppered conical flask. The above polymer solution was added at a solid-liquid ratio of 1:3. The stopper was tightened, and the mixture was shaken by hand. The flask was placed in a constant temperature shaker at 65°C with a shaking frequency of 120 times / min for 24 hours. The sample was removed, centrifuged, and the supernatant was used as the test experimental group solution. At the same time, the reference experimental group experiment without the addition of quartz sand was carried out under the same experimental conditions. After centrifugation, the supernatant was used as the reference experimental group solution.

[0060] d. Preparation of buffer solution: Accurately weigh 1.335 g of citric acid monohydrate, 26.6 g of disodium hydrogen phosphate and 116.9 g of sodium chloride, dissolve them in an appropriate amount of distilled water, and transfer them to a 1000 mL volumetric flask and make up to volume.

[0061] e. Preparation of the viscosity-concentration curve for the reference experimental group solution: Prepare six 100mL volumetric flasks. Measure 0mL, 12.29mL, 18.32mL, 23.72mL, 30.04mL, and 32.27mL of the reference experimental group solution into each flask. Add 50mL of buffer solution to each flask using a pipette and mix thoroughly. Dilute to 100mL with saline solution and mix well. Add the solution filtered through a G0 glass frit funnel to a dry Ubbelohde viscometer. Place the Ubbelohde viscometer vertically in a 30℃ constant temperature water bath and maintain the temperature for 10 minutes. Measure the flow time of the solution between the two graduations on the viscometer, accurate to 0.01s. All solutions must be measured using the same viscometer and the same stopwatch. Measurements should be performed sequentially from low to high concentration. The results are shown in Table 1. Before each measurement, the viscometer must be rinsed 2–3 times with the test solution. According to the formula… Calculate the specific viscosity increase of each group of solutions. Where: η sp —Specific viscosity; t—Time in seconds (s) for the diluted polymer solution to flow through the capillary viscometer; t0—Time in seconds (s) for the polymer-free solution to flow through the capillary viscometer. η is used to measure the viscosity of each group of solutions. sp / c value, where c is the mass concentration of the polymer in the diluted solution, i.e., the number of grams of polyacrylamide in 1 mL of sample solution. (η) spPlot a graph with / c as the ordinate and c as the abscissa, draw a curve, and perform regression analysis on the measured data to obtain a linear regression equation. Figure 2 The specific viscosity-concentration curves of the reference experimental group in the embodiments of the present invention are shown, as follows: Figure 2 As shown, the linear regression equation for the viscosity-concentration curve of the reference experimental group is y = 445.9x + 9.2043, with a correlation coefficient R. 2 =0.9998, indicating that after the static adsorption solution was diluted, the concentration of the solution was in the range of 0.018 to 0.074 g / dL, and the specific viscosity showed a good linear relationship with the concentration.

[0062] Table 1. Experimental data for investigating linear relationship.

[0063]

[0064]

[0065] (2) Precision test

[0066] Take 20.00 mL of the test solution from Example 1, transfer it to a volumetric flask, add 50 mL of buffer solution and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. Take six consecutive samples from the above solution. Under the same experimental conditions, measure the time it takes for the solution to flow through the capillary viscometer using the same viscometer, accurate to 0.01 s. The average capillary flow time for the six samples was 146.70 s, with a relative standard deviation (RSD) of 0.61%, indicating high precision. Experimental data are shown in Table 2.

[0067] Table 2 Precision test data

[0068]

[0069] (3) Repeatability test

[0070] Five portions of the test solution from Example 1 were taken, their volumes measured, and placed into volumetric flasks. 50 mL of buffer solution was added, and the flasks were shaken well. The solutions were then diluted to 100 mL with saline solution and shaken well. The solutions were filtered using a G0 glass frit funnel. The Ubbelohde viscometer was placed vertically in a 30°C constant temperature water bath and kept at that temperature for 10 min. The time it took for each solution to flow through the capillary viscometer was measured to an accuracy of 0.01 s. The polymer concentration in the solution after static adsorption was calculated based on t0 and the linear regression equation from Example 1. The average polymer concentration calculated from five measurements was 0.1354 g / dL, with a relative standard deviation (RSD) of 0.043%, indicating good repeatability. The experimental data are shown in Table 3.

[0071] Table 3 Repeatability test data

[0072]

[0073]

[0074] Comparative Example 1: Verification Test of Starch-Cadmium Iodide Method

[0075] The test group solution was prepared according to Example 1. The concentration was determined according to the "6.3 Starch-cadmium iodide method" in the evaluation method of polymers for improving oil recovery in SY / T6576-2016. The test results are shown in Table 4. Figure 3 The linear equation for the comparative starch cadmium iodide method verification experiment provided in the embodiments of the present invention is shown.

[0076] Another sample was prepared using the method described in Example 1, with the concentration determined using a capillary viscometer. The differences between the results obtained by the two methods were then examined. The experimental results are shown in Table 5.

[0077] Table 4. Plotting the standard curve for the starch-cadmium iodide method.

[0078]

[0079] Table 5. Verification test data for starch-cadmium iodide method

[0080]

[0081]

[0082] The experimental results show that the polymer concentration in the solution after static adsorption, determined by the capillary viscometer method of this scheme, is basically consistent with the commonly used starch-cadmium iodide method. Therefore, the capillary viscometer method in this scheme can be used to determine the polymer concentration in the solution after static adsorption.

[0083] Example 2: Determination of polymer concentration in solution after static adsorption

[0084] The viscosity-average relative molecular mass of the polymer sample P2 to be tested is 9.23 × 10⁻⁶. 6 The solid content was 89.91%. The brine used was a simulated formation water with a mineralization of 2689.23 mg / L, prepared by dissolving 34.08 mg Na2SO4, 1310.98 mg NaCl, 29.97 mg CaCl2, 8.12 mg MgCl2·6H2O, and 1310.40 mg NaHCO3 in 1000 mL of distilled water.

[0085] A 5000 mg / L polymer stock solution was prepared according to the polymer preparation method in Example 1. 200 mL of the polyacrylamide stock solution was taken, and 15.00 g of a 10% (w / w) sodium alkylbenzene sulfonate surfactant solution prepared with brine was added. The brine was then added until the solution reached 500 mL. The mixture was stirred on a magnetic stirrer at 300 rpm for 20 min to obtain a binary composite oil displacement system solution of 2000 mg / L polymer + 0.3% surfactant.

[0086] Following the procedure for preparing the test group and reference group solutions in the static adsorption experiment in Example 1, the experiment was carried out at 75°C to obtain the test group solution and the reference group solution.

[0087] Take five volumes of the reference experimental group solution, including 0, add 50 mL of buffer solution to each and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. Measure the time it takes for each solution to flow through a capillary viscometer and plot the specific concentration-viscosity-concentration curve of the reference experimental group solution. The obtained curves are shown below. Figure 4 .

[0088] Measure 20.00 mL of the test group solution, add 50 mL of buffer solution and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. The time it takes for the solution to flow through the capillary viscometer is measured to be 153.06 s. The time for the solvent prepared from the reference test group solution (volume 0) to flow through the capillary viscometer is 94.24 s. The corresponding η can be obtained. sp =0.6242.

[0089] The calculated concentration of polymer P2 in the diluted solution was 382.6 mg / L, the static adsorption concentration of polymer P2 in the binary composite oil displacement system solution before dilution was 1913 mg / L, and the static adsorption capacity of quartz sand for polymer P2 in the binary composite oil displacement system was 130.5 mg / g.

[0090] Example 3: Determination of polymer concentration in solution after static adsorption

[0091] The viscosity-average relative molecular mass of the polymer sample P3 to be tested is 16.85 × 10⁻⁶. 6 The solid content is 90.28%. The brine used contains 5.68 mg Na₂SO₄, 665.73 mg NaCl, 29.97 mg CaCl₂, 34.51 mg MgCl₂·6H₂O, and 3382.68 mg NaHCO₃.

[0092] A simulated formation water of type NaHCO3 with a mineralization of 4100.21 mg / L was prepared by dissolving it in 1000 mL of distilled water.

[0093] A polymer stock solution of 5000 mg / L was prepared according to the polymer preparation method in Example 1. 250 mL of the polyacrylamide stock solution was taken, and 15.00 g of a 10% Na₂CO₃ solution prepared with brine was added. The brine was then added until the solution reached 500 mL. The mixture was stirred on a magnetic stirrer at 300 r / min for 20 min to obtain a binary composite oil displacement system solution of 2500 mg / L polymer + 0.3% alkali.

[0094] Following the procedure for preparing the test group and reference group solutions in the static adsorption experiment in Example 1, the experiment was carried out at 95°C to obtain the test group solution and the reference group solution.

[0095] Take five volumes of the reference experimental group solution, including 0, add 50 mL of buffer solution to each and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. Measure the time it takes for each solution to flow through a capillary viscometer and plot the specific concentration-viscosity-concentration curve of the reference experimental group solution. The obtained curves are shown below. Figure 5 .

[0096] Measure 20.00 mL of the test group solution, add 50 mL of buffer solution and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. The time taken to flow through the capillary viscometer was measured to be 147.37 s. The time taken for the solvent prepared from the reference test group solution (0 volume) to flow through the capillary viscometer was 95.08 s. The corresponding η can be obtained. sp =1.18.

[0097] The calculated concentration of polymer P3 in the diluted solution was 454.8 mg / L, the static adsorption concentration of polymer P3 in the binary composite oil displacement system solution before dilution was 2274 mg / L, and the static adsorption capacity of quartz sand for polymer P3 in the binary composite oil displacement system was 271 mg / g.

[0098] Example 4: Determination of polymer concentration in solution after static adsorption

[0099] The viscosity-average relative molecular mass of the polymer sample P4 to be tested is 21.26 × 10⁻⁶. 6 The solid content was 89.52%. The brine used was prepared by dissolving 11.36 mg Na2SO4, 430.56 mg NaCl, 28.86 mg CaCl2, 38.57 mg MgCl2·6H2O, and 5107.20 mg NaHCO3 in 1000 mL of distilled water, resulting in a NaHCO3-type simulated formation water with a mineralization of 5596.03 mg / L.

[0100] A 5000 mg / L polymer stock solution was prepared according to the polymer preparation method in Example 1. 120 mL of the polyacrylamide stock solution was taken, and 10.00 g of a 10% (w / w) sodium alkylbenzene sulfonate surfactant solution prepared with brine and 7.50 g of a 10% (w / w) Na₂CO₃ solution prepared with brine were added. The solution was then further added to a final volume of 500 mL. The mixture was stirred at 300 rpm for 20 min on a magnetic stirrer to obtain a ternary composite oil displacement system solution of 1200 mg / L polymer + 0.2% surfactant solution + 0.15% alkali.

[0101] Following the procedure for preparing the test group and reference group solutions in the static adsorption experiment in Example 1, the experiment was carried out at 120°C to obtain the test group solution and the reference group solution.

[0102] Take five volumes of the reference experimental group solution, including 0, add 50 mL of buffer solution to each and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. Measure the time it takes for each solution to flow through a capillary viscometer and plot the specific concentration-viscosity-concentration curve of the reference experimental group solution. The obtained curves are shown below. Figure 6 .

[0103] Measure 20.00 mL of the test group solution, add 50 mL of buffer solution and shake well. Dilute to 100 mL with saline solution and shake well. Filter using a G0 glass frit funnel. The time it takes for the solution to flow through the capillary viscometer is measured to be 150.24 s. The time for the solvent prepared from the reference test group solution (volume 0) to flow through the capillary viscometer is 96.93 s. The corresponding η can be obtained. sp =0.55.

[0104] The calculated concentration of polymer P4 in the diluted solution was 215.66 mg / L, the static adsorption concentration of polymer P4 in the binary composite oil displacement system solution before dilution was 1078 mg / L, and the static adsorption capacity of quartz sand for polymer P4 in the binary composite oil displacement system was 305 mg / g.

[0105] The above provides a detailed description of a method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer. Specific examples have been used to illustrate the principle and implementation of the invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the invention. At the same time, those skilled in the art will recognize that, based on the ideas of the invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A method for determining the polymer concentration in a solution after static adsorption using a capillary viscometer, characterized in that, The method includes the following steps: S1. Under certain temperature conditions, the polymer sample to be tested is prepared to a polymer concentration of... Take two portions of the solution containing the polymer with a concentration of [missing information]. Experiments were conducted on the solutions with and without the addition of quartz sand for static adsorption, respectively, to obtain the first solution and the second solution. S2. Take multiple volumes of the first solution and dilute them to obtain polymer solutions with at least four concentration values, including 0, to form a reference experimental group; dilute the second solution to obtain the test experimental group. S3. Measure the time it takes for the reference experimental group solutions to flow through a capillary viscometer in order of increasing concentration, plot the specific viscosity-concentration relationship curve, and obtain the linear regression equation. ; S4. Measure the time it takes for the test group to flow through the capillary viscometer and calculate the specific viscosity. and the Substituting into the linear regression equation, the concentration of the polymer in the test group and the static adsorption amount of the test group by the quartz sand were calculated. include: Will Convert to concentration The quadratic equation of According to the quadratic formula, discarding negative values, we obtain... Concentration of the test solution before dilution Adsorption capacity .

2. The method according to claim 1, characterized in that, In step S1, the experiment of adding quartz sand for static adsorption includes: adding the polymer at a concentration of... In the solution, 30-40 mesh quartz sand is added at a solid-liquid mass ratio of 1:

3. The solution is fixed in a constant temperature shaker and subjected to static adsorption at a frequency of 120 times / min at a certain temperature for 24 hours. The supernatant is then separated by centrifugation to obtain the second solution.

3. The method according to claim 1 or 2, characterized in that, In step S1, the experiments of static adsorption without adding quartz sand and static adsorption with adding quartz sand are carried out simultaneously under the same experimental conditions, and whether or not quartz sand is added is a single variable.

4. The method according to claim 1 or 2, characterized in that, The specified temperature conditions refer to a temperature range of 65~120℃.

5. The method according to claim 1, characterized in that, The polymer concentration is The solutions are: polymer solutions, polymer + surfactant binary composite oil displacement system solutions, polymer + alkali binary composite oil displacement system solutions, or polymer + surfactant + alkali ternary composite oil displacement system solutions; The polymer is a partially hydrolyzed polyacrylamide polymer for oil displacement. The surfactant is an alkylbenzene sulfonate, and the mass fraction of the surfactant is 0~0.3%; the base is Na2CO3, and the mass fraction of the base is 0~0.3%. The The value range is 1000~2500mg / L.

6. The method according to claim 1 or 5, characterized in that, The viscosity-average relative molecular mass of the polymer is in the range of 3 × 10⁻⁶. 6 ~22×10 6 .

7. The method according to claim 1, characterized in that, The polymer concentration is The solvent for the solution and the solvent for dilution are both NaHCO3-type simulated formation water with a mineralization range of 0~6000 mg / L; the composition of the NaHCO3-type simulated formation water includes: distilled water, sodium sulfate, sodium chloride, anhydrous calcium chloride, magnesium chloride hexahydrate and sodium bicarbonate.

8. The method according to claim 7, characterized in that, The diluent also includes a buffer solution, which is prepared by dissolving 1.335 g of citric acid monohydrate, 26.6 g of disodium hydrogen phosphate and 116.9 g of sodium chloride in 1000 mL of distilled water.

9. The method according to claim 1, characterized in that, The capillary viscometer is an Ubbelohde viscometer.

10. The method according to claim 1, characterized in that, By diluting the first solution and the second solution, the calculated specific viscosity is increased. The value ranges from 0.2 to 1.5.

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