Determination of polymer content in oilfield produced water

Abstract

The embodiment of the present application discloses a method for determining the concentration of polymers in oilfield produced water, which belongs to the field of oil and gas extraction technology. The method includes: adding a zirconium ion compound and an acidic compound to a standard solution to prepare a zirconium ion solution; adding methylthymol blue to the standard solution to prepare a color developer solution; mixing the zirconium ion solution with oilfield produced water to obtain a first reaction solution; mixing the first reaction solution with a color developer solution to obtain a second reaction solution; reading the absorbance value of the second reaction solution under visible light; and determining the concentration of polymers in oilfield produced water based on the absorbance value. In the embodiment of the present application, after determining the absorbance value corresponding to the oilfield produced water through the oilfield produced water, the zirconium ion solution, and the color developer solution, the absorbance value can be brought into the calculation model of the polymer to determine the concentration of the polymer in the oilfield produced water, thereby simplifying the method for determining the concentration of polymers in oilfield produced water.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of oil and gas extraction, and in particular to a method for determining the polymer content in produced water of an oil field. Background Art

[0002] Polymers such as polyacrylamide and its derivatives, cellulose and its derivatives, guar gum and its derivatives have the advantages of good viscosity and suspension, and are widely used in various processes in the oil field exploitation process. For example, polyacrylamide and its derivatives are usually used in oil field oil displacement and profile adjustment processes; cellulose and its derivatives are usually used in oil field fracturing processes; guar gum and its derivatives are usually used in oil field well repair processes. In order to effectively track each process, the polymer content in the produced water of each process is usually measured to determine the effectiveness of each process.

[0003] In the related technology, taking polyacrylamide and its derivatives as an example, gel chromatography, chemiluminescence nitrogen determination method, etc. However, gel chromatography and chemiluminescence nitrogen determination method are often difficult to promote due to the high cost of testing instruments. Therefore, a simpler method for determining polymer content is urgently needed. Summary of the invention

[0004] The embodiment of the present application provides a method for determining the concentration of polymers in oilfield produced water, which can conveniently determine the concentration of polymers in oilfield produced water. The technical solution is as follows:

[0005] A method for determining the polymer concentration in oilfield produced water is provided, the method comprising:

[0006] Adding a zirconium ion compound and an acidic compound to a standard solution to prepare a zirconium ion solution, wherein the pH value of the zirconium ion solution is greater than or equal to 3.5 and less than or equal to 4.5;

[0007] Adding methylthymol blue to the standard solution to prepare a color developing agent solution;

[0008] The zirconium ion solution and the oilfield produced water are mixed and reacted in a first preset ratio, and allowed to stand for a first preset time to obtain a first reaction solution, wherein the content of the polymer in the first reaction solution is 0;

[0009] The first reaction solution and the developer solution are mixed and reacted in a second preset ratio, and left to stand for a second preset time to obtain a second reaction solution, wherein the content of zirconium ions in the second reaction solution is 0;

[0010] Reading the absorbance value of the second reaction solution under visible light by a spectrophotometer;

[0011] The concentration of the polymer in the produced water of the oil field is determined based on the absorbance value and the calculation model of the polymer.

[0012] Optionally, the step of adding a zirconium ion compound and an acidic compound to a standard solution to prepare a zirconium ion solution comprises:

[0013] adding zirconium hydroxide to the standard solution to prepare a zirconium hydroxide solution;

[0014] adding hydrochloric acid to the zirconium hydroxide solution to adjust the pH value of the zirconium hydroxide solution;

[0015] The zirconium hydroxide solution after adjusting the pH value is used as the zirconium ion solution.

[0016] Optionally, hexadecyltrimethylammonium bromide is also added to the developer solution.

[0017] Optionally, the mass ratio of the cetyltrimethylammonium bromide to the methylthymol blue is 10:1.

[0018] Optionally, the standard solution is distilled water or purified water.

[0019] Optionally, the wavelength of the visible light is 630 nanometers.

[0020] Optionally, the concentration of zirconium ions in the zirconium ion solution is 100 mg / L, the concentration of methylthymol blue in the developer solution is 400 mg / L, the first preset ratio is 1:1, and the second preset ratio is 10:1.

[0021] Optionally, determining the concentration of the polymer in the oilfield produced water based on the absorbance value and the calculation model of the polymer includes:

[0022] Determining a corresponding target calculation model based on the type of polymer in the produced water of the oil field;

[0023] Based on the absorbance value and the target calculation model, the concentration of the polymer in the produced water of the oil field is determined.

[0024] Optionally, before determining the concentration of the polymer in the oilfield produced water based on the absorbance value and the calculation model of the polymer, the method further includes:

[0025] Prepare a reference solution and a plurality of sample solutions, wherein the reference solution and the plurality of sample solutions have the same volume, the polymer content of the reference solution is 0, and the polymer concentrations of the plurality of sample solutions are different;

[0026] The reference solution and the plurality of sample solutions are mixed with the zirconium ion solution according to the first preset ratio, and left to stand for the first preset time to obtain a first reference reaction solution and a plurality of first sample reaction solutions, wherein the content of the polymer in the plurality of first sample reaction solutions is 0;

[0027] The first reference reaction solution and the plurality of first sample reaction solutions are mixed with the developer solution according to the second preset ratio, and left to stand for the second preset time to obtain a second reference reaction solution and a plurality of second sample reaction solutions, wherein the content of zirconium ions in the second reference reaction solution and the plurality of second sample reaction solutions is 0;

[0028] Reading the reference absorbance value of the second reference reaction solution under the visible light and the sample absorbance values ​​of the plurality of second sample reaction solutions under the visible light respectively by the spectrophotometer;

[0029] A computational model for the polymer is determined based on the reference absorbance value, the plurality of polymer concentrations, and the plurality of sample absorbance values.

[0030] Optionally, the polymer concentrations of the plurality of sample solutions are in an arithmetic progression or a proportional progression.

[0031] Optionally, the calculation model of the polymer is the following first formula:

[0032] Y=K(AX)+B (1)

[0033] Wherein, in the first formula, Y refers to the concentration of the polymer, K refers to the slope corresponding to the polymer, A refers to the reference absorbance value corresponding to the polymer, X refers to the absorbance value corresponding to the polymer solution; and B refers to the intercept corresponding to the polymer.

[0034] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

[0035] In an embodiment of the present application, based on the reaction of the prepared zirconium ion solution and the oilfield produced water, the content of the polymer in the first reaction solution is made to be 0; based on the reaction of the configured color developer solution and the first reaction solution, the content of the zirconium ion in the second reaction solution is made to be 0; then, the absorbance value corresponding to the second reaction solution is read by a spectrophotometer, and the absorbance value corresponds to the remaining zirconium ions in the first reaction solution. Then, the absorbance value can be brought into the calculation model of the polymer in the oilfield produced water to determine the concentration of the polymer in the oilfield produced water, thereby simplifying the method for determining the concentration of the polymer in the oilfield produced water. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic flow chart of a method for determining polymer concentration in oilfield produced water provided in an embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the implementation methods of the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0039] Before explaining the embodiments of the present application in detail, the application scenarios involved in the embodiments of the present application are first explained.

[0040] In the process of oilfield exploitation, various technological measures are usually taken to improve the oil and gas recovery rate. For example, fracturing process, well washing process, oil recovery and profile control process, etc. Different types of polymers are usually used in the above-mentioned processes. For example, hydroxymethyl cellulose and its derivatives are usually used as polymers in the fracturing process, hydroxypropyl guar gum and its derivatives are usually used as polymers in the well washing process, and polyacrylamide and its derivatives are usually used as polymers in the oil recovery and profile control process. In order to determine the effectiveness of each process, the polymer concentration in the oilfield produced water (well washing fluid, fracturing fluid, oil recovery and profile control fluid) in each process is usually detected. However, in the related art, when detecting the polymer concentration, the test instrument is expensive and difficult to promote. Based on this scenario, the embodiment of the present application provides a method for determining the polymer concentration in oilfield produced water.

[0041] Figure 1 Schematic diagram of a method for determining the polymer concentration in oilfield produced water provided in an embodiment of the present application. Figure 1 As shown, the method includes the following steps.

[0042] In the embodiment of the present application, in order to facilitate the determination of the polymer concentration in the oilfield produced water, a compound that can react chemically with the polymer and can be quantitatively calibrated in the solution can be added to the oilfield produced water, and then the polymer concentration can be determined by indirect measurement of the chemical. For example, the chemical is a compound containing zirconium ions. Next, the detection of the polymer concentration in the oilfield produced water is explained in detail in combination with the compound containing zirconium ions.

[0043] Step 101: Add a zirconium ion compound and an acidic compound to a standard solution to prepare a zirconium ion solution.

[0044] The standard solution is distilled water or purified water, and of course it can be other liquids, as long as the liquid does not contain polymers, which is not limited in the embodiments of the present application. The compound containing zirconium ions is at least one of zirconium hydroxide, zirconyl chloride, zirconium oxychloride octahydrate, etc. The acidic compound is hydrochloric acid, sulfuric acid, etc., as long as the pH value of the zirconium ion reagent solution can be adjusted.

[0045] Optionally, zirconium hydroxide is added to the standard solution to prepare a zirconium hydroxide solution; hydrochloric acid is added to the zirconium hydroxide solution to adjust the pH value of the zirconium hydroxide solution; and the zirconium hydroxide solution after the pH value is adjusted is used as a zirconium ion solution. Of course, the zirconium ion solution can also be obtained by other configurations, which are not limited in the present embodiment of the application.

[0046] The pH value of the configured zirconium ion solution is greater than or equal to 3.5 and less than or equal to 4.5. Of course, the pH value of the zirconium ion solution may also be other values, as long as the zirconium ions in the zirconium ion solution can react with the polymer and the zirconium ions remaining in the solution after the reaction can be calibrated, and this embodiment of the application does not limit this.

[0047] Among them, when preparing the zirconium ion solution, in order to ensure that the zirconium ions in the zirconium ion solution fully react with the polymer in the oilfield produced water, and that zirconium ions remain in the solution after the reaction for easy calibration, for example, the concentration of zirconium ions in the zirconium ion solution is 100 mg / L. Of course, in other embodiments, the concentration of zirconium ions in the zirconium ion solution can also be other values, as long as the above conditions are met, and the embodiments of the present application are not limited to this.

[0048] Step 102: Add methylthymol blue to the standard solution to prepare a color developing solution.

[0049] When configuring the developer solution, in order to ensure that methylthymol blue can effectively calibrate the zirconium ions in the solution after the reaction, for example, the concentration of methylthymol blue in the developer solution is 400 mg / L. Of course, the concentration of methylthymol blue can also be other values ​​as long as the above conditions are met, and the embodiment of the present application is not limited to this.

[0050] Optionally, hexadecyltrimethylammonium bromide may be added when preparing the developer solution.

[0051] Wherein, hexadecyltrimethylammonium bromide is used as a surfactant to improve the activity of methylthymol blue. When hexadecyltrimethylammonium bromide is added, for example, the mass ratio of hexadecyltrimethylammonium bromide to methylthymol blue is 10:1.

[0052] Of course, the mass ratio of cetyltrimethylammonium bromide to methylthymol blue can also be other ratios, which is not limited in the present embodiment. In addition, after adding cetyltrimethylammonium bromide and methylthymol blue to the standard solution, it can be fully stirred to ensure the uniformity of the developer solution.

[0053] Step 103: Mix the zirconium ion solution and the oilfield produced water according to a first preset ratio for reaction, and let it stand for a first preset time to obtain a first reaction solution.

[0054] When the zirconium ion solution is mixed with the oilfield produced water, the zirconium ions in the zirconium ion solution react with the polymers in the oilfield produced water to fully react to form a zirconium cross-linked polymer gel, and the content of the polymer in the first reaction solution obtained after the reaction is 0, and a certain amount of zirconium ions remain. During the reaction of the zirconium ion solution and the oilfield produced water, they can be fully stirred to ensure the adequacy of the reaction.

[0055] Optionally, in combination with the concentration of zirconium ions in the above zirconium ion solution, the zirconium ion solution and the oilfield produced water can be mixed and reacted at a ratio of 1:1. That is, the first preset ratio is 1:1. Of course, the zirconium ion solution and the oilfield produced water can also be mixed and reacted at a ratio of 1.1:1, 1.2:1 or 1.5:1, etc., as long as the content of the polymer in the first reaction solution after the reaction can be guaranteed to be 0, and this embodiment of the present application does not limit this.

[0056] Step 104: Mix the first reaction solution and the developer solution in a second preset ratio for reaction, and let the mixture stand for a second preset time to obtain a second reaction solution.

[0057] When the first reaction solution is mixed with the developer solution, the remaining zirconium ions in the first reaction solution react with the developer in the developer solution to undergo a fading reaction, and the content of zirconium ions in the second reaction solution obtained after the reaction is 0. During the reaction of the first reaction solution and the developer solution, they can be fully stirred to ensure the adequacy of the reaction.

[0058] Optionally, in combination with the concentration of zirconium ions in the above-mentioned zirconium ion solution, the concentration of the developer in the developer solution, and the mixing ratio of the zirconium ion solution and the oilfield produced water, the first reaction solution and the developer solution can be mixed and reacted at a ratio of 10:1. That is, the second preset ratio is 10:1. Of course, the first reaction solution and the developer solution can also be mixed and reacted at a ratio of 7:1, 8:1 or 9:1, as long as the content of zirconium ions in the second reaction solution after the reaction can be guaranteed to be 0, and this embodiment of the present application does not limit this.

[0059] Step 105: Read the absorbance value of the second reaction solution under visible light using a spectrophotometer.

[0060] After the second reaction solution is obtained through the above step 104, distilled water or purified water can be used as a reference solution, and then the cuvettes respectively containing the reference solution and the second reaction solution are placed in the sample chamber of the spectrophotometer, and the absorbance value of the second reaction solution in the visible light range is read on the spectrophotometer with the reference solution as the reference. The absorbance value corresponds to the concentration of zirconium ions remaining in the first reaction solution.

[0061] Optionally, the wavelength of the visible light is 630 nanometers. Of course, in other embodiments, the wavelength of the visible light is other values, for example, the wavelength of the visible light is any value between 400 nanometers and 800 nanometers.

[0062] In the embodiment of the present application, after the absorbance value corresponding to the produced water of the oil field is determined through the above step 105, the calculation model of the polymer can be determined first. Specifically, it can be achieved through the following steps 106 to 110.

[0063] The process of determining the calculation model of the polymer may be performed after step 105, or the calculation model of the polymer may be determined in advance before step 105 is performed, which is not limited in the embodiment of the present application.

[0064] Step 106: Prepare a reference solution and a plurality of sample solutions.

[0065] The volumes of the reference solution and the multiple sample solutions are the same, the polymer content of the reference solution is 0, and the polymer concentrations of the multiple sample solutions are different.

[0066] Optionally, the polymer concentrations of the plurality of sample solutions are in an arithmetic progression or a proportional progression.

[0067] In the embodiment of the present application, when configuring the reference solution and multiple sample solutions, in order to ensure reference, the reference solution and multiple sample solutions are configured with the same basic solution, and in order to ensure that the determined calculation model is more realistic, the basic solution can select blank water produced by the oil field without polymer as the basic solution. Of course, due to the difficulty in obtaining blank water, the standard solution described above can also be used as the basic solution, and the embodiment of the present application does not limit this.

[0068] For example, when the polymer is polyacrylamide and its derivatives, blank water without polyacrylamide produced in the oil field in the oil recovery and profile control process can be used as the basic solution; when the polymer is guar gum and its derivatives, blank water without hydroxypropyl guar gum produced in the oil field in the well washing process can be used as the basic solution; when the polymer is cellulose and its derivatives, blank water without hydroxymethyl cellulose produced in the oil field in the fracturing process can be used as the basic solution.

[0069] In the embodiment of the present application, one base solution can be directly used as a reference solution, and different amounts of polymers of the same type can be added to other base solutions to obtain multiple sample solutions.

[0070] Of course, due to the poor solubility of polymers, when preparing multiple sample solutions, a polymer reference solution may be pre-prepared, and then the polymer reference solution may be diluted to obtain multiple sample solutions, which is not limited in the embodiments of the present application.

[0071] Step 107: mixing the reference solution and the plurality of sample solutions with the zirconium ion solution in a first preset ratio, and standing for a first preset time to obtain a first reference reaction solution and a plurality of first sample reaction solutions.

[0072] The polymer content in the first sample reaction solutions is 0. The specific implementation process of step 107 can refer to the above step 103, and will not be described in detail in the embodiment of the present application.

[0073] Step 108: mixing the first reference reaction solution and the plurality of first sample reaction solutions with the developer solution in a second preset ratio, and standing for a second preset time to obtain a second reference reaction solution and a plurality of second sample reaction solutions.

[0074] The content of zirconium ions in the second reference reaction solution and the plurality of second sample reaction solutions is 0. The specific implementation process of step 107 can refer to the above step 103, and will not be described in detail in the embodiment of the present application.

[0075] Step 109: reading the reference absorbance value of the second reference reaction solution under visible light and the sample absorbance values ​​of the plurality of second sample reaction solutions under visible light respectively by using a spectrophotometer.

[0076] Among them, the specific implementation process of reading the reference absorbance value of the second reference solution in step 109 and reading the absorbance value of the second sample reaction solution can refer to the process of reading the absorbance value of the second reaction solution in the above step 105, and the embodiment of the present application will not be repeated here.

[0077] In combination with the above description, the reference absorbance value corresponds to the zirconium ion concentration in the first reference reaction solution, and the sample absorbance value corresponds to the zirconium ion concentration in the first sample reaction solution.

[0078] Step 110: Determine a computational model of the polymer based on the reference absorbance value, a plurality of polymer concentrations, and a plurality of sample absorbance values.

[0079] Combined with the above description, it can be known that the absorbance difference between the reference absorbance value and the sample absorbance value corresponds to the concentration of zirconium ions reacting with the polymer in the sample solution, that is, the absorbance difference corresponds to the concentration of the polymer in the sample solution. Therefore, the absorbance difference between the reference absorbance value and the absorbance values ​​of multiple samples can be determined first to obtain multiple absorbance differences, which correspond to multiple polymer concentrations one by one. Afterwards, with the absorbance difference as the horizontal coordinate and the polymer concentration as the vertical coordinate, the coordinate points corresponding to each absorbance difference and the corresponding polymer concentration are determined, and then the multiple coordinate points are fitted to obtain a linear equation with the absorbance difference as the independent variable and the polymer concentration as the dependent variable.

[0080] The absorbance difference can be replaced by the reference absorbance value and the absorbance value corresponding to the polymer solution. At this time, since the reference absorbance value is a constant, the independent variable of the linear equation is the absorbance value corresponding to the polymer solution, and the dependent variable is the polymer concentration of the polymer solution.

[0081] Optionally, the calculation model of the polymer is the following first formula:

[0082] Y=K(AX)+B (1)

[0083] Wherein, in the first formula, Y refers to the concentration of the polymer, K refers to the slope corresponding to the polymer, A refers to the reference absorbance value corresponding to the polymer, X refers to the absorbance value corresponding to the polymer solution; and B refers to the intercept corresponding to the polymer.

[0084] Step 111: Determine the concentration of the polymer in the produced water of the oil field based on the absorbance value and the calculation model of the polymer.

[0085] In combination with the above description, the polymer can be any one of polyacrylamide and its derivatives, guar gum and its derivatives, and cellulose and its derivatives. At this time, in order to determine the concentration of the polymer, the corresponding target calculation model can be determined based on the type of polymer in the oil field produced water; then, the concentration of the polymer in the oil field produced water can be determined based on the absorbance value and the target calculation model.

[0086] In an embodiment of the present application, calculation models of different types of polymers can be determined by pre-configured reference solutions, multiple sample solutions, zirconium ion solutions and color developer solutions. In this way, based on the reaction of the prepared zirconium ion solution and oilfield produced water, the content of polymer in the first reaction solution is made 0; based on the reaction of the configured color developer solution and the first reaction solution, the content of zirconium ions in the second reaction solution is made 0; then, the absorbance value corresponding to the second reaction solution is read by a spectrophotometer, and the absorbance value corresponds to the remaining zirconium ions in the first reaction solution. Then, the absorbance value can be brought into the calculation model corresponding to the polymer in the oilfield produced water to determine the concentration of the polymer in the oilfield produced water, thereby simplifying the method for determining the concentration of the polymer in the oilfield produced water.

[0087] Next, the embodiment of the present application will illustrate three examples to explain the embodiment of the present application.

[0088] Example 1: Detection of the concentration of polyacrylamide and its derivatives in oilfield produced water during oil recovery and profile control process

[0089] Experimental chemicals: zirconium oxychloride octahydrate, analytical grade; hexadecyltrimethylammonium bromide, analytical grade; methylthymol blue, indicator; polyacrylamide, analytical grade.

[0090] The detection method of polyacrylamide and its derivatives in oilfield produced water is as follows:

[0091] (1) A zirconium ion reagent solution having a zirconium ion concentration of 100 mg / L is prepared using distilled water and zirconium oxychloride octahydrate, and the pH of the zirconium ion reagent solution is adjusted to 4 using 10% hydrochloric acid to obtain a zirconium ion solution.

[0092] (2) Prepare a developer solution containing cetyltrimethylammonium bromide and methylthymol blue with distilled water, wherein the concentration of methylthymol blue is 400 mg / L, and the mass ratio of cetyltrimethylammonium bromide to methylthymol blue is 10:1.

[0093] (3) Take 20.0 ml of oilfield produced water, add 20.0 ml of the zirconium ion solution prepared in the above step (1), stir and let stand for 15 minutes to obtain a first reaction solution, the polymer content in the first reaction solution is 0.

[0094] (4) Add 4.0 ml of the developer solution prepared in step (2) above to the first reaction solution, stir evenly and let stand for 10 minutes to obtain a second reaction solution. The content of zirconium ions in the second reaction solution is 0.

[0095] (5) Read the absorbance of the second reaction solution at a wavelength of 630 nanometers on a spectrophotometer and find that the absorbance is 0.40102.

[0096] (6) Prepare a polyacrylamide reference solution with a concentration of 2000 mg / L using polymer-free blank water produced in the oil field. Then, add 0.25 ml, 0.5 ml, 1.0 ml, and 2.0 ml of the polyacrylamide reference solution to four beakers in sequence. Then, add 19.75 ml, 19.5 ml, 19.0 ml, and 18.0 ml of blank water in sequence. Then, stir thoroughly to obtain four sample solutions with polyacrylamide concentrations of 25 mg / L, 50 mg / L, 100 mg / L, and 200 mg / L. Then, add 20 ml of blank water to the fifth beaker as a reference solution.

[0097] (7) Add 20 ml of the zirconium ion solution prepared in the above step (1) to the 4 cups of sample solutions and one cup of reference solution obtained in the above step (3), respectively, stir thoroughly and let stand for 15 minutes to obtain 4 cups of first sample reaction solutions and one cup of first reference reaction solution, wherein the polymer content in the 4 cups of first sample reaction solutions and one cup of first reference reaction solution is 0.

[0098] (8) Add 4.0 ml of the developer solution to each of the four cups of the first sample reaction solution and one cup of the first reference reaction solution in the above step (4), stir thoroughly and let stand for 10 minutes to obtain four cups of the second sample reaction solution and one cup of the second reference reaction solution, wherein the zirconium ion content in the four cups of the second sample reaction solution and one cup of the second reference reaction solution is 0.

[0099] (9) Read the sample absorbance values ​​of 4 cups of the second sample reaction solution at a wavelength of 630 nanometers on a spectrophotometer, and read the reference absorbance value of one cup of the second reference reaction solution at a wavelength of 630 nanometers. The absorbance values ​​obtained are shown in Table 1 below:

[0100] Table 1

[0101] Polymer concentration (mg / L) 0 25 50 100 200 Absorbance value (A) 0.001 0.09182 0.17232 0.32492 0.63182

[0102] (10) With the absorbance difference between the reference absorbance value and the sample absorbance value as the horizontal axis and the polyacrylamide concentration as the vertical axis, a standard curve of polyacrylamide concentration was drawn. The standard equation obtained by linear fitting is as follows:

[0103] Y 1 =-319.8(A 1 -X 1 )+237.09

[0104] Among them, Y 1 refers to the concentration of polyacrylamide, A 1 Refers to the reference absorbance value corresponding to the polyacrylamide solution, X 1 Refers to the absorbance value corresponding to the polyacrylamide solution.

[0105] (11) Substituting the absorbance value read in the above step (5) into the above standard equation, it is obtained that the concentration of polyacrylamide and its derivatives in the oil field produced water is 125.0 mg / L.

[0106] Example 2: Detection of Hydroxypropyl Guar Gum Concentration in Oilfield Produced Water during Fracturing Process

[0107] Experimental chemicals: zirconium hydroxide, analytical grade; hexadecyltrimethylammonium bromide, analytical grade; methylthymol blue (MTB), indicator; hydroxypropyl guar gum, analytical grade.

[0108] The detection method of hydroxypropyl guar gum concentration in oil field produced water is as follows:

[0109] (1) A zirconium ion reagent solution having a zirconium ion concentration of 100 mg / L is prepared using distilled water and zirconium hydroxide, and the pH of the zirconium ion reagent solution is adjusted to 4 using 10% hydrochloric acid to obtain a zirconium ion solution.

[0110] (2) Prepare a developer solution containing cetyltrimethylammonium bromide and methylthymol blue with distilled water, wherein the concentration of methylthymol blue is 400 mg / L, and the mass ratio of cetyltrimethylammonium bromide to methylthymol blue is 10:1.

[0111] (3) Take 20.0 ml of oilfield produced water, add 20.0 ml of the zirconium ion solution prepared in the above step (1), stir and let stand for 15 minutes to obtain a first reaction solution, the polymer content in the first reaction solution is 0.

[0112] (4) Add 4.0 ml of the developer solution prepared in step (2) above to the first reaction solution, stir evenly and let stand for 30 minutes to obtain a second reaction solution. The content of zirconium ions in the second reaction solution is 0.

[0113] (5) Read the absorbance of the second reaction solution at a wavelength of 630 nanometers on a spectrophotometer and find that the absorbance is 0.4777.

[0114] (6) Prepare a 2000 mg / L hydroxypropyl guar gum reference solution using polymer-free blank water produced in the oil field. Then, add 0.25 ml, 0.5 ml, 1.0 ml, and 2.0 ml of the hydroxypropyl guar gum reference solution to four beakers in sequence. Then, add 19.75 ml, 19.5 ml, 19.0 ml, and 18.0 ml of blank water in sequence. Then, stir thoroughly to obtain four sample solutions with hydroxypropyl guar gum concentrations of 25 mg / L, 50 mg / L, 100 mg / L, and 200 mg / L. Then, add 20 ml of blank water to the fifth beaker as a reference solution.

[0115] (7) Add 20 ml of the zirconium ion solution prepared in the above step (1) to the 4 cups of sample solutions and one cup of reference solution obtained in the above step (3), respectively, stir thoroughly and let stand for 15 minutes to obtain 4 cups of first sample reaction solutions and one cup of first reference reaction solution, wherein the polymer content in the 4 cups of first sample reaction solutions and one cup of first reference reaction solution is 0.

[0116] (8) Add 4.0 ml of the developer solution to each of the four cups of the first sample reaction solution and one cup of the first reference reaction solution in the above step (4), stir thoroughly and let stand for 30 minutes to obtain four cups of the second sample reaction solution and one cup of the second reference reaction solution, wherein the zirconium ion content in the four cups of the second sample reaction solution and one cup of the second reference reaction solution is 0.

[0117] (9) Read the sample absorbance values ​​of 4 cups of the second sample reaction solution at a wavelength of 630 nanometers on a spectrophotometer, and read the reference absorbance value of one cup of the second reference reaction solution at a wavelength of 630 nanometers. The absorbance values ​​obtained are shown in Table 2 below:

[0118] Table 2

[0119] Polymer concentration (mg / L) 0 25 50 100 200 Absorbance value (A) 0 0.09169 0.1578 0.3201 0.6191

[0120] (10) With the absorbance difference between the reference absorbance value and the sample absorbance value as the horizontal axis and the hydroxypropyl guar gum concentration as the vertical axis, a standard curve of hydroxypropyl guar gum concentration was drawn. The standard equation obtained by linear fitting is as follows:

[0121] Y 2 =-325.05(A 2 -X 2 )+231.73

[0122] Among them, Y 2 refers to the concentration of hydroxypropyl guar gum, A 2 Refers to the reference absorbance value corresponding to hydroxypropyl guar gum, X 2 It refers to the absorbance value corresponding to the hydroxypropyl guar gum solution.

[0123] (11) Substituting the absorbance value read in the above step (5) into the above standard equation, the concentration of guar gum and its derivatives in the oil field produced water is obtained to be 152.0 mg / L.

[0124] Example 3: Detection of the concentration of hydroxymethylcellulose in oilfield produced water during well washing process

[0125] Experimental chemicals: zirconium oxychloride octahydrate, analytical grade; hexadecyltrimethylammonium bromide, analytical grade; methylthymol blue, indicator; hydroxymethylcellulose, analytical grade.

[0126] The detection method of hydroxymethyl cellulose concentration in oil field produced water is as follows:

[0127] (1) A zirconium ion reagent solution having a zirconium ion concentration of 100 mg / L is prepared using distilled water and zirconium oxychloride octahydrate, and the pH of the zirconium ion reagent solution is adjusted to 4 using 10% hydrochloric acid to obtain a zirconium ion solution.

[0128] (2) Prepare a colorimetric solution containing cetyltrimethylammonium bromide and methylthymol blue with distilled water, with the concentration of methylthymol blue being 400 mg / L.

[0129] Wherein, the mass ratio of hexadecyltrimethylammonium bromide to methylthymol blue is 10:1.

[0130] (3) Take 20.0 ml of oilfield produced water, add 20.0 ml of the zirconium ion solution prepared in the above step (1), stir and let stand for 15 minutes to obtain a first reaction solution, the polymer content in the first reaction solution is 0.

[0131] (4) Add 4.0 ml of the developer solution prepared in step (2) above to the first reaction solution, stir evenly and let stand for 15 minutes to obtain a second reaction solution. The content of zirconium ions in the second reaction solution is 0.

[0132] (5) Read the absorbance of the second reaction solution at a wavelength of 630 nanometers on a spectrophotometer to find that it is 0.35522.

[0133] (6) Prepare a 2000 mg / L hydroxymethyl cellulose reference solution using polymer-free blank water produced in an oil field. Then, add 0.25 ml, 0.5 ml, 1.0 ml, and 2.0 ml of the hydroxymethyl cellulose reference solution to four beakers in sequence. Then, add 19.75 ml, 19.5 ml, 19.0 ml, and 18.0 ml of blank water in sequence. Then, stir thoroughly to obtain four sample solutions with hydroxymethyl cellulose concentrations of 25 mg / L, 50 mg / L, 100 mg / L, and 200 mg / L. Then, add 20 ml of blank water to the fifth beaker as a reference solution.

[0134] (7) Add 20 ml of the zirconium ion solution prepared in the above step (1) to the 4 cups of sample solutions and one cup of reference solution obtained in the above step (3), respectively, stir thoroughly and let stand for 15 minutes to obtain 4 cups of first sample reaction solutions and one cup of first reference reaction solution, wherein the polymer content in the 4 cups of first sample reaction solutions and one cup of first reference reaction solution is 0.

[0135] (8) Add 4.0 ml of the developer solution to each of the four cups of the first sample reaction solution and one cup of the first reference reaction solution in the above step (4), stir thoroughly and let stand for 15 minutes to obtain four cups of the second sample reaction solution and one cup of the second reference reaction solution, wherein the zirconium ion content in the four cups of the second sample reaction solution and one cup of the second reference reaction solution is 0.

[0136] (9) Read the sample absorbance values ​​of 4 cups of the second sample reaction solution at a wavelength of 630 nanometers on a spectrophotometer, and read the reference absorbance value of one cup of the second reference reaction solution at a wavelength of 630 nanometers. The obtained absorbance values ​​are shown in Table 3 below:

[0137] Table 3

[0138] Polymer concentration (mg / L) 0 25 50 100 200 Absorbance value (A) 0.00812 0.10782 0.20032 0.35304 0.66734

[0139] (10) With the absorbance difference between the reference absorbance value and the sample absorbance value as the horizontal axis and the hydroxymethyl cellulose concentration as the vertical axis, a standard curve of hydroxymethyl cellulose concentration was drawn. The standard equation obtained by linear fitting is as follows:

[0140] Y 3 =-307.15(A 3 -X 3 )+201.21

[0141] Among them, Y 3 Refers to the concentration of hydroxymethyl cellulose, A 3 Refers to the reference absorbance value corresponding to hydroxymethyl cellulose, X 3 Refers to the absorbance value corresponding to the hydroxymethyl cellulose solution.

[0142] (11) Substituting the absorbance value read in the above step (5) into the above standard equation, it is obtained that the concentration of cellulose and its derivatives in the oil field produced water is 102.0 mg / L.

[0143] The above description is only an optional embodiment of the embodiments of the present application and is not intended to limit the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A method for determining the polymer concentration in oilfield produced water, characterized in that: The method comprises: Adding a zirconium ion compound and an acidic compound to a standard solution to prepare a zirconium ion solution, wherein the pH value of the zirconium ion solution is greater than or equal to 3.5 and less than or equal to 4.5; Adding methylthymol blue to the standard solution to prepare a color developing agent solution; The zirconium ion solution and the oilfield produced water are mixed and reacted in a first preset ratio, and allowed to stand for a first preset time to obtain a first reaction solution, wherein the content of the polymer in the first reaction solution is 0; The first reaction solution and the developer solution are mixed and reacted in a second preset ratio, and left to stand for a second preset time to obtain a second reaction solution, wherein the content of zirconium ions in the second reaction solution is 0; Reading the absorbance value of the second reaction solution under visible light by a spectrophotometer; The concentration of the polymer in the produced water of the oil field is determined based on the absorbance value and the calculation model of the polymer.

2. The method according to claim 1, characterized in that The step of adding a zirconium ion compound and an acidic compound to a standard solution to prepare a zirconium ion solution comprises: adding zirconium hydroxide to the standard solution to prepare a zirconium hydroxide solution; adding hydrochloric acid to the zirconium hydroxide solution to adjust the pH value of the zirconium hydroxide solution; The zirconium hydroxide solution after adjusting the pH value is used as the zirconium ion solution.

3. The method according to claim 1, characterized in that Hexadecyltrimethylammonium bromide is also added to the developer solution.

4. The method according to claim 3, characterized in that The mass ratio of the cetyltrimethylammonium bromide to the methylthymol blue is 10:

1.

5. The method according to any one of claims 1 to 4, characterized in that: The standard solution is distilled water or purified water.

6. The method according to claim 1, characterized in that The wavelength of the visible light is 630 nanometers.

7. The method according to claim 1, characterized in that The concentration of zirconium ions in the zirconium ion solution is 100 mg / L, the concentration of methylthymol blue in the developer solution is 400 mg / L, the first preset ratio is 1:1, and the second preset ratio is 10:

1.

8. The method according to claim 1, characterized in that The step of determining the concentration of the polymer in the produced water of the oil field based on the absorbance value and the calculation model of the polymer comprises: Determining a corresponding target calculation model based on the type of polymer in the produced water of the oil field; Based on the absorbance value and the target calculation model, the concentration of the polymer in the produced water of the oil field is determined.

9. The method according to claim 1, characterized in that Before determining the concentration of the polymer in the oilfield produced water based on the absorbance value and the calculation model of the polymer, the method further includes: Prepare a reference solution and a plurality of sample solutions, wherein the reference solution and the plurality of sample solutions have the same volume, the polymer content of the reference solution is 0, and the polymer concentrations of the plurality of sample solutions are different; The reference solution and the plurality of sample solutions are mixed with the zirconium ion solution according to the first preset ratio, and left to stand for the first preset time to obtain a first reference reaction solution and a plurality of first sample reaction solutions, wherein the content of the polymer in the plurality of first sample reaction solutions is 0; The first reference reaction solution and the plurality of first sample reaction solutions are mixed with the developer solution according to the second preset ratio, and left to stand for the second preset time to obtain a second reference reaction solution and a plurality of second sample reaction solutions, wherein the content of zirconium ions in the second reference reaction solution and the plurality of second sample reaction solutions is 0; Reading the reference absorbance value of the second reference reaction solution under the visible light and the sample absorbance values ​​of the plurality of second sample reaction solutions under the visible light respectively by the spectrophotometer; A computational model for the polymer is determined based on the reference absorbance value, the plurality of polymer concentrations, and the plurality of sample absorbance values.

10. The method according to claim 9, characterized in that The polymer concentrations of the plurality of sample solutions are in an arithmetic progression or an equal proportion progression.

11. The method according to claim 9, characterized in that The calculation model of the polymer is the following first formula: Y=K(AX)+B (1) Wherein, in the first formula, the Y refers to the concentration of the polymer, the K refers to the slope corresponding to the polymer, the A refers to the reference absorbance value corresponding to the polymer, the X refers to the absorbance value corresponding to the polymer solution; and the B refers to the intercept corresponding to the polymer.

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