Method for detecting concentration of polymer in oilfield produced water

Abstract

The invention relates to the field of oilfield sewage detection, and discloses a method for detecting the concentration of a polymer in oilfield produced water, which comprises the following steps: respectively carrying out demulsification, filtration and extraction treatment on produced water and injection water; respectively adding a phase separating agent polyaluminum ferric sulfate solution into the treated produced water sample and the injection water sample, and carrying out vacuum suction filtration by using a microfiltration membrane after full reaction; after suction filtration is completed, the microfiltration membranes are placed in a vessel to be dried, and the mass of the microfiltration membranes is weighed after cooling; and calculating the concentration of the polymer in the produced water according to the ratio of the mass difference of the weighed microporous filter membrane to the volume of the water sample. The method is suitable for detecting the concentration of the polymer in the oil field wellhead polymer-containing produced liquid, can solve the problems that an original detection method is complex in operation, high in technical requirement and prone to causing environmental pollution, meets the work requirements of clean and environment-friendly development and production, meanwhile reduces the detection cost, improves the detection efficiency and facilitates large-scale application and popularization of an oil field.

Description

Technical Field

[0001] This invention relates to the field of oilfield wastewater testing, and specifically to a method for detecting polymer concentration in oilfield produced water. Background Technology

[0002] With the continuous development of oilfields, chemical flooding has become an important means of stabilizing production in the old oilfields of Shengli Oilfield. Polymer flooding is the main field for chemical flooding experiments, contributing to stable crude oil production and gradually becoming one of the leading technologies for improving oil recovery. The produced fluids from polymer-flooded reservoirs often contain a certain concentration of polymers, and according to field statistics, the polymer concentration in the produced fluids can sometimes reach 200-1000 mg / L. Accurately detecting the polymer concentration in the produced fluids of polymer-flooded reservoirs is of great reference value for understanding the form in which polymers exist in the formation after polymer flooding and for further improving the recovery rate of crude oil in the reservoir.

[0003] The current method for detecting polymer concentration at the Shengli oilfield site is the starch-cadmium iodide method. As described in the patent specification "A polymer-containing sludge depolymerizing agent and its preparation method" (CN104910323B), the specific determination steps of the starch-cadmium iodide method are as follows: (1) Standard curve plotting: Prepare a 1200 mg / L aqueous solution of standard sample polyacrylamide, and take a certain amount of the original solution and dilute it with distilled water to make standard solutions of 12, 24, 48, 60, and 120 mg / L respectively. Take 2 ml of each solution, and then use ultraviolet spectrophotometry to measure absorbance (A). Plot a standard curve with A as the vertical axis and polyacrylamide concentration (C) as the horizontal axis. Use linear regression to obtain the linear relationship between absorbance (A) and polyacrylamide concentration (C). (2) Accurately transfer 2 ml of distilled water (blank) and the water sample to be tested into a 50 ml volumetric flask respectively using a pipette; (3) Add 5 ml of pH 5.0 acetate-sodium acetate buffer solution and mix well; (4) Add 15 ml of distilled water to dilute and mix well; (5) Add 2 ml of saturated bromine water, shake well and let it react for 10 min; (6) Add 10 ml of sodium formate solution with a mass concentration of 1%, shake well and let it react for 5 min; (7) Add 5 ml of starch-cadmium iodide colorimetric reagent, dilute with water to the 50 ml mark, shake well and let it react for 10 min, and then measure the absorbance at 585 nm using a UV spectrophotometer. Calculate the polyacrylamide concentration based on the linear relationship between absorbance (A) and polyacrylamide concentration (C).

[0004] The chemical reagents used in the starch-cadmium iodide method are acetate-sodium acetate buffer solution, saturated bromine water, 1% sodium formate solution, and starch-cadmium iodide reagent. The buffer solution is used to adjust the pH value of the solution to 5.0, at which point the detection value of polymer concentration is relatively stable. However, this method has the following limitations: (1) Since the detection limit of the starch-cadmium iodide method is 4.5-100 mg / L, it is only suitable for produced fluids with low polymer concentration. It is more difficult and less accurate to detect produced fluids with high polymer concentration. (2) Although the starch-cadmium iodide method uses fewer instruments and has a lower cost, bromine water is a highly toxic substance and is very harmful to the experimenters. (3) The starch-cadmium iodide method has high requirements for the operation of the experimenters, and the detection accuracy is also closely related to the operation skills of the experimenters. (4) The starch-cadmium iodide method requires a very high level of standard curve preparation and blank oilfield injection water should be used. However, polymers are currently found in oilfield produced fluids, with concentrations ranging from tens to hundreds of mg / L, making it difficult for simulated water to accurately reflect the oilfield conditions. Summary of the Invention

[0005] To overcome the shortcomings of existing starch-cadmium iodide technology, this invention provides a method for detecting polymer concentration in oilfield produced water. This is a novel method for polymer concentration analysis, and its technical solution is as follows: A method for detecting polymer concentration in oilfield produced water, comprising the following steps: (1) The extracted water is subjected to demulsification, filtration and extraction treatment; (2) Add a phase separation agent to the extracted water sample after step (1), and after the reaction is complete, use a vacuum filter material for vacuum filtration. (3) After the filtration in step (2) is completed, place the filtration material in a container to dry it. After drying, cool it and then weigh the mass of the filtration material. (4) The injected water is subjected to demulsification, filtration and extraction; (5) Add a phase separation agent to the injected water sample after step (4), and after the reaction is complete, perform vacuum filtration using a filtration material; (6) After the filtration in step (5) is completed, place the filtration material in a container to dry it. After drying, cool it and then weigh the mass of the filtration material. (7) Calculate the concentration of polymer in the extracted water based on the ratio of the difference in mass of the filtration material weighed in steps (3) and (6) to the volume of the water sample.

[0006] Furthermore, the filtration material is selected from microporous filter membranes.

[0007] Furthermore, the phase separating agent is a polyaluminum ferric sulfate solution.

[0008] Furthermore, the mass concentration of the polyaluminum ferric sulfate solution is 5% to 6%.

[0009] Furthermore, the ratio of the phase separating agent to the volume of the extracted water sample in step (2) and the ratio of the phase separating agent to the volume of the injected water sample in step (5) are both 1:5 to 1:10.

[0010] Furthermore, the reaction time for both steps (2) and (5) is 3 to 6 minutes.

[0011] Furthermore, the drying temperature in steps (3) and (6) is 80-100℃, and the drying time is 0.5-1h.

[0012] Furthermore, the cooling temperature in steps (3) and (6) is 25-27°C, and the cooling time is 5-10 minutes.

[0013] Furthermore, the produced water in step (1) is produced water from the wellhead of an oil well, the filter material is qualitative filter paper, and the extractant is an organic solvent.

[0014] Furthermore, the organic solvent is petroleum ether or solvent oil.

[0015] Compared with the prior art, the present invention has the following main advantages: 1. This invention addresses the adverse effects of suspended oil, suspended solids, and surfactants in polymer-containing produced fluids on detection results. After filtration and extraction, a phase-separating agent is added to separate polymer molecules from the water sample. The sample is then filtered, dried, and weighed to calculate the concentration of polymer molecules in the produced fluid. Through optimization of the polymer phase separation-precipitation-filtration method, an efficient on-site detection process is formed.

[0016] 2. This invention is applicable to the detection of polymer concentration in polymer-containing produced fluids at oilfield wellheads, and can provide guidance for polymer injection operations. After this method is put into use, it can solve the problems of complex operation, high technical requirements, and environmental pollution associated with the original detection methods, adapting to the needs of clean and environmentally friendly development and production. At the same time, it reduces detection costs, improves detection efficiency, and is conducive to large-scale application in oilfields.

[0017] 3. This invention optimizes the use of polyaluminum ferric sulfate solution as a phase separator suitable for polymer-containing produced water, efficiently extracting polymers from the produced water and improving the efficiency and range of polymer concentration detection. Polyaluminum ferric sulfate solution is a complex polymer with a complex molecular structure, strong separation ability, and superior separation effect compared to traditional aluminum ferric sulfate. It is a clean and environmentally friendly material that causes no pollution to the environment. Detailed Implementation

[0018] First, the preferred method for detecting polymer concentration in the field-collected fluid of this invention is briefly described from an experimental perspective as follows: Polymer standard solutions of 100-600 mg / L and 1%-10% polyaluminum ferric sulfate solutions were prepared for experiments. Different concentrations of polyaluminum ferric sulfate solutions were added to the polymer standard solutions, and after stirring thoroughly for 6 minutes, the mixture was vacuum filtered through a microporous membrane. After filtration, the mixture was dried for 30 minutes (80℃) and cooled for 10 minutes (25℃). Finally, the mixture was weighed using a partial balance to calculate the concentration of the polymer molecules. By adding different concentrations of phase-separating agent, the polymer concentration was measured and compared with the standard solution concentration to calculate the relative error of the experiment.

[0019] Preparation before the experiment: Prepare 100mL of 5% and 100mL of 6% polyaluminum ferric sulfate solution for later use; prepare 500mL of deionized water.

[0020] (1) Filter the collected water sample three times with qualitative filter paper to remove suspended oil and suspended solids; then take 200 mL of the pretreated water sample to be tested and place it in a 500 mL separatory funnel, add 200 mL of petroleum ether extractant, mix and shake for 1 min, release the gas in the funnel, and let it stand for 10 min after each thorough shaking to allow the extractant and water sample to completely separate into layers, and take the lower aqueous phase. Perform three extractions in this way to separate the water sample to be tested for later use.

[0021] (2) Take a certain amount of the extracted water after demulsification, filtration and extraction and put it into a beaker. Add a certain amount of 5% or 6% polyaluminum ferric sulfate solution and react for 3-6 minutes. After the reaction is complete, use an oil-free vacuum pump to filter. When filtering, rinse the residue on the beaker wall and the filter container with deionized water onto the filter membrane to reduce error.

[0022] Before filtration, thoroughly wet the microporous membrane with distilled water, then dry it in an oven for 0.5-1 hour. After cooling to room temperature in a desiccator for 5-10 minutes, weigh the microporous membrane using a 1 / 10000 electronic balance and record the weight as S1. After filtration with an oil-free vacuum pump, place the membrane in a clean petri dish with tweezers and dry it in an oven for 0.5-1 hour (80-100℃). Then, place the petri dish and the membrane together in a desiccator and cool to room temperature for 5-10 minutes. Weigh the microporous membrane using a 1 / 10000 electronic balance and record the weight as S2 (the membrane should be handled with tweezers throughout the process).

[0023] (3) Take a certain amount of water that has been demulsified, filtered and extracted and put it into a beaker. Add a certain amount of 5% or 6% polyaluminum ferric sulfate solution and react for 3-6 minutes. After the reaction is complete, use an oil-free vacuum pump to filter. When filtering, rinse the residue on the beaker wall and the filter container with deionized water onto the filter membrane to reduce error.

[0024] Before filtration, thoroughly wet the microporous membrane with distilled water, then dry it in an oven for 0.5-1 hour. After cooling to room temperature in a desiccator for 5-10 minutes, weigh the microporous membrane using a 1 / 1000 electronic balance and record the weight as S3. After filtration with an oil-free vacuum pump, place the membrane in a clean petri dish with tweezers and dry it in an oven for 0.5-1 hour (80-100℃). Then, place the petri dish and the membrane together in a desiccator and cool to room temperature for 5-10 minutes. Weigh the microporous membrane using a 1 / 1000 electronic balance and record the weight as S4 (the membrane should be handled with tweezers throughout the process).

[0025] (4) Calculate the polymer weight using the difference: M1=S2-S1 M2=S4-S3 M=M1-M2; The polymer concentration is: C=M / 0.05×1000=20000M (mg / L).

[0026] The present invention will then be described in further detail with reference to specific embodiments. Example 1

[0027] (1) Add 10 mL of 5% polyaluminum ferric sulfate solution to each of the three 50 mL samples of extract after demulsification, filtration and extraction. Stir thoroughly with a glass rod. After 3 min of reaction, the polymer molecules in the extract will be completely separated from the solution and will be precipitated as flocculent or clump-like solids at the bottom of the solution. After adding 10 mL of 5% polyaluminum ferric sulfate solution to 50 mL of injection water, after sufficient reaction, a small amount of flocculent precipitate will be found at the bottom of the container. This is analyzed as the flocculation of micron-sized suspended solids in the water under the action of the separating agent.

[0028] (2) Take two fully moistened and dried microporous filter membranes, weigh and record their mass. Then, after fully moistening them, place them on a vacuum filtration device and filter the reacted extract and the injected water separately. During filtration, rinse the solid matter on the cup wall with deionized water. After filtration, use tweezers to pick up the microporous filter membrane and place it in a petri dish. Dry it in an oven at 80℃ for 0.5h. After drying, place it in a cooler to cool to room temperature (25℃) for 5min. Then weigh the two microporous filter membranes. The ratio of the difference in mass before and after to the sample volume is the concentration of the polymer in the extract. The detection method and the starch-cadmium iodide method used on site were used to detect the same sample. The specific detection results are shown in Table 1.

[0029] Table 1. Comparison of results from different polymer concentration detection methods applied to produced fluids.

[0030] As can be seen from the experimental results in Table 1, the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield were used to test the produced fluid from different wellheads. The results of the two methods were not significantly different, with a maximum relative error of 7.45%, a minimum relative error of 3.45%, and an average relative error of 4.91%. The relative errors of the tests were all less than 10%, which met the technical specifications. Example 2

[0031] (1) Add 10 mL of 5% polyaluminum ferric sulfate solution to each of the three 60 mL samples of collected liquid after demulsification, filtration and extraction. Stir thoroughly with a glass rod. After 4.5 min of reaction, the polymer molecules in the collected liquid will be completely separated from the solution and will be precipitated as flocculent or clump-like solids at the bottom of the solution. After adding 10 mL of 5% polyaluminum ferric sulfate solution to 60 mL of injected water, after sufficient reaction, there will be a small amount of flocculent precipitate at the bottom of the container. This is analyzed as the flocculation of micron-sized suspended solids in the water under the action of the separating agent.

[0032] (2) Take two fully moistened and dried microporous filter membranes, weigh and record their mass. Then, after fully moistening them, place them on a vacuum filtration device and filter the reacted extract and the injected water separately. During filtration, rinse the solid matter on the cup wall with deionized water. After filtration, use tweezers to pick up the microporous filter membrane and place it in a petri dish. Dry it in a 90℃ oven for 45 minutes. After drying, place it in a cooler to cool to room temperature (26℃) for 7.5 minutes. Then weigh the two microporous filter membranes. The difference in mass before and after is the ratio of the sample volume to the polymer concentration in the extract. The same sample was tested using this detection method and the starch-cadmium iodide method used on site. The specific test results are shown in Table 2.

[0033] Table 2 Comparison of results from different polymer concentration detection methods applied to produced fluids

[0034] As can be seen from the experimental results in Table 2, the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield were used to test the produced fluid from different wellheads. The results of the two methods were not significantly different, with a maximum relative error of 6.91%, a minimum relative error of 5.30%, and an average relative error of 6.06%. The relative errors of the tests were all less than 10%, which met the technical specifications. Example 3

[0035] (1) Add 10 mL of 6% polyaluminum ferric sulfate solution to each of the three 70 mL samples of collected fluid after demulsification, filtration and extraction. Stir thoroughly with a glass rod. After 6 min of reaction, the polymer molecules in the collected fluid will be completely separated from the solution and will be precipitated as flocculent or clump-like solids at the bottom of the solution. After adding 10 mL of 6% polyaluminum ferric sulfate solution to 70 mL of injected water, after sufficient reaction, a small amount of flocculent precipitate will be found at the bottom of the container. This is analyzed as the flocculation of micron-sized suspended solids in the water under the action of the separating agent.

[0036] (2) Take two fully moistened and dried microporous filter membranes, weigh and record their mass. Then, after fully moistening them, place them on a vacuum filtration device and filter the reacted extract and the injected water separately. During filtration, rinse the solid matter on the cup wall with deionized water. After filtration, use tweezers to pick up the microporous filter membrane and place it in a petri dish. Dry it in a 100℃ oven for 1 hour. After drying, place it in a cooler and cool it to room temperature (27℃) for 10 minutes. Then weigh the two microporous filter membranes. The ratio of the difference in mass before and after to the sample volume is the concentration of the polymer in the extract. The same sample was tested using this detection method and the starch-cadmium iodide method used on site. The specific test results are shown in Table 3.

[0037] Table 3 Comparison of results from different polymer concentration detection methods in the produced fluid

[0038] As can be seen from the experimental results in Table 3, the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield were used to test the produced fluid from different wellheads. The results of the two methods were not significantly different, with a maximum relative error of 6.18%, a minimum relative error of 3.67%, and an average relative error of 4.75%. The relative errors of the tests were all less than 10%, which met the technical specifications. Example 4

[0039] (1) Add 10 mL of 6% polyaluminum ferric sulfate solution to each of the three 80 mL samples of extract after demulsification, filtration and extraction. Stir thoroughly with a glass rod. After 3 min of reaction, the polymer molecules in the extract will be completely separated from the solution and will be precipitated as flocculent or clump-like solids at the bottom of the solution. After adding 10 mL of 6% polyaluminum ferric sulfate solution to 80 mL of injection water, after sufficient reaction, a small amount of flocculent precipitate will be found at the bottom of the container. This is analyzed as the flocculation of micron-sized suspended solids in the water under the action of the separating agent.

[0040] (2) Take two fully moistened and dried microporous filter membranes, weigh and record their mass. Then, after fully moistening them, place them on a vacuum filtration device and filter the reacted extract and the injected water separately. During filtration, rinse the solid matter on the cup wall with deionized water. After filtration, use tweezers to pick up the microporous filter membrane and place it in a petri dish. Dry it in an oven at 80℃ for 0.5h. After drying, place it in a cooler to cool to room temperature (25℃) for 5min. Then weigh the two microporous filter membranes. The ratio of the difference in mass before and after to the sample volume is the concentration of the polymer in the extract. The detection method and the starch-cadmium iodide method used on site were used to detect the same sample. The specific detection results are shown in Table 4.

[0041] Table 4 Comparison of results from different polymer concentration detection methods in produced fluids

[0042] As can be seen from the experimental results in Table 4, the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield were used to test the produced fluid from different wellheads. The results of the two methods were not significantly different, with a maximum relative error of 8.06%, a minimum relative error of 5.57%, and an average relative error of 6.45%. The relative errors of the tests were all less than 10%, which met the technical specifications. Example 5

[0043] (1) Add 10 mL of 6% polyaluminum ferric sulfate solution to each of the three 90 mL samples of collected fluid after demulsification, filtration and extraction. Stir thoroughly with a glass rod. After 4.5 min of reaction, the polymer molecules in the collected fluid will be completely separated from the solution and will be precipitated as flocculent or clump-like solids at the bottom of the solution. After adding 10 mL of 6% polyaluminum ferric sulfate solution to 90 mL of injected water, after sufficient reaction, there will be a small amount of flocculent precipitate at the bottom of the container. This is analyzed as the flocculation of micron-sized suspended solids in the water under the action of the separating agent.

[0044] (2) Take two fully moistened and dried microporous filter membranes, weigh and record their mass. Then, after fully moistening them, place them on a vacuum filtration device and filter the reacted extract and the injected water separately. During filtration, rinse the solid matter on the cup wall with deionized water. After filtration, use tweezers to pick up the microporous filter membrane and place it in a petri dish. Dry it in a 90℃ oven for 45 minutes. After drying, place it in a cooler to cool to room temperature (26℃) for 7.5 minutes. Then weigh the two microporous filter membranes. The ratio of the difference in mass before and after to the sample volume is the concentration of the polymer in the extract. The same sample was tested using this detection method and the starch-cadmium iodide method used on site. The specific test results are shown in Table 5.

[0045] Table 5 Comparison of results from different polymer concentration detection methods in the produced fluid

[0046] As can be seen from the experimental results in Table 5, the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield were used to test the produced fluids from different wellheads. The results of the two methods were not significantly different, with a maximum relative error of 7.48%, a minimum relative error of 5.91%, and an average relative error of 6.68%. The relative errors of the tests were all less than 10%, which met the technical specifications. Example 6

[0047] (1) Add 10 mL of 6% polyaluminum ferric sulfate solution to 100 mL of each of the 3 samples of collected fluid after demulsification, filtration and extraction. Stir thoroughly with a glass rod. After 6 min of reaction, the polymer molecules in the collected fluid will be completely separated from the solution and will be precipitated as flocculent or clump-like solids at the bottom of the solution. After adding 100 mL of 6% polyaluminum ferric sulfate solution to 100 mL of injected water, a small amount of flocculent precipitate will be found at the bottom of the container after the reaction is complete. This is analyzed as the flocculation of micron-sized suspended solids in the water under the action of the separating agent.

[0048] (2) Take two fully moistened and dried microporous filter membranes, weigh and record their mass. Then, after fully moistening them, place them on a vacuum filtration device and filter the reacted extract and the injected water separately. During filtration, rinse the solid matter on the cup wall with deionized water. After filtration, use tweezers to pick up the microporous filter membrane and place it in a petri dish. Dry it in a 100℃ oven for 1 hour. After drying, place it in a cooler and cool it to room temperature (27℃) for 10 minutes. Then weigh the two microporous filter membranes. The difference in mass before and after is the ratio of the sample volume to the polymer concentration in the extract. The same sample was tested using this detection method and the starch-cadmium iodide method used on site. The specific test results are shown in Table 6.

[0049] Table 6. Comparison of results from different polymer concentration detection methods applied to produced fluids.

[0050] As can be seen from the experimental results in Table 6, the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield were used to test the produced fluid from different wellheads. The results of the two methods were not significantly different, with a maximum relative error of 8.45%, a minimum relative error of 4.25%, and an average relative error of 6.89%. The relative errors of the tests were all less than 10%, which met the technical specifications.

[0051] Finally, let me introduce the specific application of the method of this invention in oil fields. Application Example 1

[0052] The produced fluid from eight wells in four blocks of the Shengli Oilfield was tested using the phase separation-precipitation filtration method. The test results were compared with those of the starch-cadmium iodide method used in the field. The experimental results are shown in Table 7.

[0053] Table 7 Comparison of results from different polymer concentration detection methods in produced fluids

[0054] As can be seen from the experimental results in Table 7, the produced fluids from the four blocks were tested using the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield. The results of the two methods were not significantly different, with a maximum relative error of 9.05%, a minimum relative error of 3.26%, and an average relative error of 5.41%. The relative errors of the tests were all less than 10%, which met the technical specifications. Application Example 2

[0055] Produced fluids from eight wells in different blocks of the Shengtuo Oilfield were selected and tested using the phase separation-precipitation filtration method. The results were compared with those obtained using the starch-cadmium iodide method used in the field. The experimental results are shown in Table 8.

[0056] Table 8 Comparison of results from different polymer concentration detection methods in produced fluids

[0057] As can be seen from the experimental results in Table 8, the produced fluids from 8 wells in Shengtuo Oilfield were tested using the phase separation-precipitation filtration method and the starch-cadmium iodide method currently used in the oilfield. The results of the two methods were not significantly different, with a maximum relative error of 9.21%, a minimum relative error of 3.24%, and an average relative error of 6.09%. The relative errors of the tests were all less than 10%, which met the technical specifications. Application Example 3

[0058] Polymer standard solutions with molecular weights of 10 million, 12 million, 13 million, 14 million, and 15 million were prepared using oilfield purified water that does not contain polymers. The solutions were then tested using the phase separation-precipitation filtration method and the starch-cadmium iodide method. The experimental results are shown in Tables 9, 10, 11, 12, and 13.

[0059] Table 9 Comparison of two detection methods for polymer standard solutions with a molecular weight of 10 million

[0060] Table 10 Comparison of two detection methods for polymer standard solutions with a molecular weight of 12 million

[0061] Table 11 Comparison of two detection methods for polymer standard solutions with a molecular weight of 13 million

[0062] Table 12 Comparison of two detection methods for polymer standard solutions with a molecular weight of 14 million

[0063] Table 13 Comparison of two detection methods for polymer standard solutions with a molecular weight of 15 million

[0064] The experimental results in Tables 9 to 13 show that by using the phase separation-precipitation-filtration method and the starch-cadmium iodide method to detect standard polymer solutions with molecular weights of 10 million, 12 million, 13 million, 14 million, and 15 million, respectively, the results show that different polymer molecular weights have good adaptability to the detection methods and a certain degree of stability, achieving good implementation results, and the experimental errors are all below 10%.

Claims

1. A method for detecting polymer concentration in oilfield produced water, characterized in that, Includes the following steps: (1) The extracted water is subjected to demulsification, filtration and extraction treatment; (2) Add a phase separation agent to the extracted water sample after step (1), and after the reaction is complete, use a vacuum filter material for vacuum filtration. (3) After the filtration in step (2) is completed, place the filtration material in a container to dry it. After drying, cool it and then weigh the mass of the filtration material. (4) The injected water is subjected to demulsification, filtration and extraction; (5) Add a phase separation agent to the injected water sample after step (4), and after the reaction is complete, perform vacuum filtration using a filtration material; (6) After the filtration in step (5) is completed, place the filtration material in a container to dry it. After drying, cool it and then weigh the mass of the filtration material. (7) Calculate the concentration of polymer in the extracted water based on the ratio of the difference in mass of the filtration material weighed in steps (3) and (6) to the volume of the water sample.

2. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The filtration material is a microporous filter membrane.

3. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The phase separating agent is a polyaluminum ferric sulfate solution.

4. The method for detecting polymer concentration in oilfield produced water according to claim 3, characterized in that, The mass concentration of the polyaluminum ferric sulfate solution is 5% to 6%.

5. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The ratio of the phase separating agent to the volume of the extracted water sample in step (2) and the ratio of the phase separating agent to the volume of the injected water sample in step (5) are both 1:5 to 1:

10.

6. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The reaction time for both steps (2) and (5) is 3 to 6 minutes.

7. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The drying temperature in steps (3) and (6) is 80-100℃, and the drying time is 0.5-1h.

8. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The cooling temperature for both steps (3) and (6) is 25-27°C, and the cooling time is 5-10 minutes.

9. The method for detecting polymer concentration in oilfield produced water according to claim 1, characterized in that, The produced water in step (1) is the wellhead produced water of the oil well, the filter material is qualitative filter paper, and the extractant is an organic solvent.

10. The method for detecting polymer concentration in oilfield produced water according to claim 9, characterized in that, The organic solvent is petroleum ether or solvent oil.

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