Evaluation method of oilfield produced water scale inhibitor

Abstract

The invention discloses an evaluation method for an anti-scaling agent of oilfield produced water. The evaluation method comprises the following steps: preparing an anti-scaling agent water sample and a blank water sample by utilizing the oilfield produced water or simulated produced water; standing the scale inhibitor water sample and the blank water sample to form scales; calculating the anti-scaling rate of the anti-scaling agent by using the scale quality difference between the anti-scaling agent water sample and the blank water sample; the method solves the problem of serious evaluation distortion caused by high dilution ratio of a water sample with high calcium and magnesium ions when the scale inhibitor is evaluated by conventionally detecting the concentration change of scale-forming cations in produced water added with the scale inhibitor and not added with the scale inhibitor.

Description

Technical Field

[0001] The present invention relates to the field of oilfield surface produced fluid, produced water surface treatment and produced water reinjection, and in particular to a physical evaluation method of an anti-scaling agent for oilfield produced water. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Due to the oversaturation of calcium, magnesium ions and aluminosilicates in the produced water of oil fields, the produced fluid and produced water are scaled at the wellhead, pipeline, valve, before and after the delivery pump, as well as on the oil-water separation treatment and sewage treatment facilities during the production, ground collection and water treatment process. Common scales mainly include inorganic scales such as carbonate scale, silica scale, sulfate scale and iron compounds, and there are also certain organic scales. Adding corresponding anti-scaling agents is one of the economical and effective solutions. The mechanism of anti-scaling is generally believed to be the lattice distortion theory, adding anti-scaling agents during the growth of scale to prevent the crystal nucleus of scale from growing and forming an unstable structure; the complex solubilization theory, adding anti-scaling agents to form stable water-soluble complexes with scale-forming cations to prevent the formation of scale; the dispersion mechanism theory, the anti-scaling agent is enriched in the diffusion boundary layer near the growing crystal nucleus, forming a double electric layer and hindering the aggregation of scale-forming ions or molecular clusters on the metal surface.

[0004] At present, oil fields generally use indoor simulated produced water as the medium, complex titration or inductively coupled plasma (ICP) as the detection means, and measure the difference in the content of free scale-forming ions such as calcium, magnesium, and silicon in blank water samples and water samples with scale inhibitors to evaluate the scale inhibition efficiency of scale inhibitors. This method has the following problems for oil field produced water with high mineral content and high calcium, magnesium, and silicon content, such as poor measurement accuracy and unclear titration endpoint, which affect the evaluation results of scale inhibitors.

[0005] First, the concentration range of scaling ions detected by titration is usually 2-100 mg / L. When the content of scaling ions such as calcium, magnesium and silicon in produced water is much greater than the detection limit of complexometric titration or inductively coupled plasma (icp), titration detection requires a higher dilution multiple. The error caused by dilution is much greater than the error of the detection method itself. Secondly, scaling of produced water with high silicon ion content is mainly silica scale, such as Figure 1-3 The pictures shown, as well as the SEM and spectral analysis, show that the main scaling components of the sewage treatment system in a strong alkaline ternary block of Daqing Oilfield are amorphous silica and silicate. However, the change in calcium / magnesium ion content cannot accurately determine the anti-scaling efficiency of the anti-scaling agent. At the same time, the method of detecting calcium and magnesium ions is only applicable to the evaluation of the effect of chelating anti-scaling agents based on the complex solubilization theory, and is not applicable to the evaluation of the effect of dispersed anti-scaling agents based on the dispersion mechanism theory.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the invention

[0007] In view of this, the present invention provides a method for evaluating scale inhibitors for oilfield produced water with high calcium, magnesium and silicon content, which solves the problem of severe evaluation distortion caused by the high dilution multiple of high calcium and magnesium ion water samples when evaluating scale inhibitors by conventional detection of changes in scale-forming cation concentrations in produced water with and without adding scale inhibitors.

[0008] To achieve the above-mentioned object of the invention, the method for evaluating oilfield produced water antiscalant comprises the following steps:

[0009] Use oilfield produced water or simulated produced water to prepare anti-scaling agent water samples and blank water samples;

[0010] Keeping the antiscalant water sample and the blank water sample still to form scale;

[0011] The anti-scaling rate of the anti-scaling agent is calculated using the scale quality difference between the anti-scaling agent water sample and the blank water sample.

[0012] In the present disclosure and possible embodiments, free water in the on-site produced fluid is filtered through filter paper and filter membrane to obtain the oilfield produced water.

[0013] In the present disclosure and possible embodiments, a method for preparing a water sample of an antiscalant using oilfield produced water comprises:

[0014] Add 50-60 mL of distilled water to 2.00 g ± 0.01 g of anti-scaling agent, and after the anti-scaling agent is dissolved, transfer it into a 100 mL volumetric flask and make up the volume to obtain an anti-scaling agent solution with a concentration of 20,000 mg / L;

[0015] 1 mL of the antiscalant solution was measured and placed in a test bottle, 199 mL of the oilfield produced water was added, and the solution was shaken 10 times to obtain the antiscalant water sample.

[0016] In the present disclosure and possible embodiments, a method for preparing a blank water sample using oilfield produced water includes:

[0017] 199 mL of the oilfield produced water was measured and put into a test bottle, 1 mL of distilled water was added, and the bottle was shaken 10 times to obtain the blank water sample.

[0018] In the present disclosure and possible embodiments, a method for preparing simulated produced water includes:

[0019] The anion and cation concentrations of the produced water from the oil field are measured by ion chromatography, inductively coupled ion emission spectrometry or atomic absorption spectrometry, and the mineral concentration in the produced water from the oil field is calculated based on the anion and cation balance;

[0020] Calculate the content of scaling cations according to the mineral concentration, calculate the mineral composition according to the content of scaling cations, weigh the alkaline earth metal or alkali metal chloride, add water to dissolve it and then adjust the volume to obtain a scaling cation solution;

[0021] The scaling anion content is calculated according to the mineral concentration, the mineral composition is calculated according to the scaling anion content, the scaling anion sodium salt is weighed, and water is added to dissolve it and then constant volume is obtained to obtain a scaling anion solution.

[0022] In the present disclosure and possible embodiments, a method for preparing a water sample of an antiscalant using simulated produced water comprises:

[0023] Add 50-60 mL of distilled water to 2.00 g ± 0.01 g of anti-scaling agent, and after the anti-scaling agent is dissolved, transfer it into a 100 mL volumetric flask and make up the volume to obtain an anti-scaling agent solution with a concentration of 20,000 mg / L;

[0024] Measure 1 mL of the antiscalant solution into a test bottle, add 99 mL of the scale-forming cation solution, shake well, add 100 mL of the scale-forming anion solution, and shake by hand 10 times to obtain the antiscalant water sample.

[0025] In the present disclosure and possible embodiments, a method for preparing a blank water sample using simulated produced water includes:

[0026] 1 mL of distilled water was measured and placed in a test bottle, and 99 mL of the scaling cation solution and 100 mL of the scaling anion solution were added, and the blank water sample was obtained by hand shaking 10 times.

[0027] In the present disclosure and possible embodiments, the antiscalant water sample and the blank water sample are placed in the same heat preservation state and kept still for the same set time to form the scale.

[0028] In the present disclosure and possible embodiments, the blank water sample and the anti-scaling agent water sample that form the scale are filtered through a filter membrane, and the filter membrane is weighed after drying to a constant weight to obtain the scale mass of the blank water sample and the anti-scaling agent water sample.

[0029] In the present disclosure and possible embodiments, the pore size of the filter membrane is 0.45 μm.

[0030] The present disclosure has the following beneficial effects:

[0031] The anti-scaling agent evaluation method of the present invention adopts the method of measuring the difference in the quality of scale generated by a blank water sample and an anti-scaling agent water sample under a certain temperature environment to evaluate the anti-scaling rate of the anti-scaling agent, and is suitable for evaluating the anti-scaling agent of produced water containing alkaline earth metal carbonate scale such as calcium and magnesium, sulfate scale, amorphous silicon scale or a mixture of several types of scales, and the evaluation result is more comprehensive; quantitative analysis is performed by weighing the mass of the scale, thereby avoiding the error caused by the high dilution multiple required for complexometric titration or inductively coupled plasma (ICP) detection to meet the detection limit of the titration due to the excessively high calcium and magnesium content; compared with the scale-forming ion detection method, the measurement accuracy depends on the mass weighing, thereby avoiding the error caused by the different endpoint judgments of different operators; thereby effectively solving the problem of serious evaluation distortion caused by the high dilution multiple of the high calcium and magnesium ion water sample when evaluating the anti-scaling agent by conventionally detecting the change in the concentration of scale-forming cations in produced water with and without the addition of anti-scaling agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0033] Figure 1 It is the silica scale in the sewage treatment system of a strong alkaline ternary block in Daqing Oilfield in the background technology;

[0034] Figure 2 yes Figure 1 Scanning electron microscope image of silica scale in sewage;

[0035] Figure 3 yes Figure 1 Energy spectrum of silica scale in sewage;

[0036] Figure 4 is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0037] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure.

[0038] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present disclosure, and the drawings are not actually drawn to scale.

[0039] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0040] Figure 4is a flow chart of the method of the present invention; Figure 4 As shown: The method for evaluating scale inhibitors for oilfield produced water of the present invention comprises step S10: preparing scale inhibitor water samples and blank water samples using oilfield produced water or simulated produced water; step S20: keeping the scale inhibitor water samples and the blank water samples still to form scale; step S30: calculating the scale inhibition rate of the scale inhibitor using the scale mass difference between the scale inhibitor water samples and the blank water samples.

[0041] The present invention discloses Figure 4 The evaluation method of the oilfield produced water antiscalant of the present invention is further described in detail. The evaluation method of the specific embodiment follows the following steps:

[0042] 1. Evaluation of antiscalant using oilfield produced water

[0043] According to the conventional means in the art, free water (produced water) in the on-site produced fluid is taken, filtered through double-layer filter paper, and then filtered through a 0.45μm filter membrane to remove emulsified oil droplets and other large particle impurities to obtain experimental oil field produced water; taking the target antiscalant concentration of 100mg / L as an example:

[0044] ① Preparation of antiscaling agent solution

[0045] Weigh 2.00g±0.01g of antiscalant sample into a 100mL beaker, add 50-60mL of distilled water, and after the antiscalant is fully dissolved, transfer to a 100mL volumetric flask to make up the volume, and mix evenly to obtain an antiscalant solution with a concentration of 20000mg / L.

[0046] ②Preparation of blank water sample

[0047] Measure 199 mL of oilfield produced water into a test bottle, add 1 mL of distilled water, cover the bottle cap tightly, and shake it by hand 10 times to obtain a blank water sample.

[0048] ③ Preparation of anti-scaling agent water sample

[0049] Measure 1 mL of 20000 mg / L antiscalant solution into a test bottle; add 199 mL of oilfield produced water, cover the bottle cap tightly, and shake by hand 10 times to obtain an antiscalant water sample.

[0050] ④ Standing to form scale

[0051] The temperature of a water bath or other heat preservation device is adjusted to the temperature for evaluating the antiscaling agent, and the blank water sample and the antiscaling agent water sample are placed together and kept warm for a certain period of time. The heat preservation temperature used in the embodiment of the present disclosure is 40-65°C and the heat preservation time is 8-24h.

[0052] ⑤ Scale weighing

[0053] The blank water sample and the anti-scaling agent water sample were filtered through a 0.45 μm microporous filter membrane to filter out the scale, and the filter membrane was weighed after drying and constant weight to obtain the filter membrane mass increase value, thereby obtaining the scale mass of the blank water sample and the anti-scaling agent water sample respectively.

[0054] 2. Evaluation of antiscalant using simulated produced water

[0055] Take the produced water from the oil field, and use ion chromatography (IC), inductively coupled ion emission spectroscopy (ICP-AES) or atomic absorption spectrometry to measure the anion and cation concentration of the produced water from the oil field. According to the anion and cation balance calculation, the concentration of various minerals in the produced water from the oil field is obtained. With reference to the ion content in the produced water from the oil field, simulated produced water is configured indoors. Take the target antiscalant concentration of 100mg / L as an example:

[0056] ① Preparation of antiscaling agent solution

[0057] Weigh 2.00g±0.01g of antiscalant sample into a 100mL beaker, add 50-60mL of distilled water, and after the antiscalant is fully dissolved, transfer to a 100mL volumetric flask to make up the volume, and mix evenly to obtain an antiscalant solution with a concentration of 20000mg / L.

[0058] ② Preparation of water sample A (preparation of scaling cation solution)

[0059] Calculate the mineral components according to the measured scaling cation content, weigh the corresponding alkaline earth metal or alkali metal chlorides such as calcium chloride, strontium chloride, magnesium chloride, barium chloride, sodium chloride, potassium chloride, etc., dissolve them in water, and then make up to volume for use.

[0060] ③ Preparation of water sample B (preparation of scaling anion solution)

[0061] Calculate the mineral components according to the determined content of scaling anions, weigh the corresponding sodium silicate, sodium sulfate, sodium carbonate, sodium bicarbonate and other scaling anion sodium salts; add water to dissolve and make up to volume for later use.

[0062] ④Preparation of blank water sample

[0063] Measure 1mL of distilled water into the test bottle; add 99mL of water sample A, then measure 100mL of water sample B and add it slowly and evenly into the test bottle, cover the bottle cap tightly, and shake it by hand 10 times.

[0064] ⑤ Preparation of anti-scaling agent water sample

[0065] Measure 1mL of 20000mg / L antiscalant solution into the test bottle; add 99mL of water sample A, cover and shake well; then measure 100mL of water sample B into the test bottle, cover the bottle tightly, and shake by hand 10 times.

[0066] ⑥ Standing to form scale

[0067] The temperature of the water bath or other heat preservation device is adjusted to the temperature for evaluating the antiscalant, and the blank water sample and the antiscalant water sample are placed together and kept warm.

[0068] ⑦Scale weighing

[0069] After being kept warm for a certain period of time, the blank water sample and the anti-scaling agent water sample were filtered through a 0.45 μm microporous filter membrane, the filter membrane was weighed after drying and constant weight, the increase in the filter membrane mass was measured, and the scale mass of the blank water sample and the anti-scaling agent water sample was obtained respectively.

[0070] 3. The anti-scaling rate is expressed by the following formula:

[0071]

[0072] Where:

[0073] E—anti-scaling rate, %;

[0074] M1—scale mass of anti-scaling agent water sample, mg / L;

[0075] M2—Scale mass of blank water sample, mg / L.

[0076] Example 1

[0077] In this Example 1, the anti-scaling agent evaluation method of the present invention was used to evaluate and screen the anti-scaling agents for produced water of the Dale oil field, and the evaluation was compared with the conventional anti-scaling agent evaluation method for oil fields.

[0078] The ion concentrations of simulated water samples from Amandali Oilfield are shown in Table 1:

[0079] Table 1 Basic ion concentration of water samples from Amandali Oilfield

[0080]

[0081] From the data in Table 1, it can be seen that the calcium ion concentration in the produced water of Amandali Oilfield is 6228 mg / L and the magnesium ion concentration is 1184 mg / L. Due to the high concentrations of calcium and magnesium ions, the evaluation method of conventional scale inhibitors adopts the test of the change of scale-forming cation concentration in the produced water with and without scale inhibitors to evaluate and screen the performance of scale inhibitors. The applicable range of scale-forming ions in the prepared working water samples generally does not exceed 100 mg / L. If the ion concentration exceeds the range, the water sample should be diluted. For example, the determination of the scale prevention rate of calcium carbonate recommended in SY / T 5673 "General Technical Conditions for Scale Inhibitors for Oilfields" is taken as an example. The initial C solution CaCl2·2H2O15.19 g / L, D solution MgCl2·6H2O4.60 g / L, corresponding to a calcium ion concentration of 103 mg / L and a magnesium ion of 22.7 mg / L. After preparing the test solution, the calcium ion concentration is 14.16 mg / L and the magnesium ion is 3.1 mg / L. For the produced water from the Amandali Oilfield, the conventional evaluation method was applied and the water sample was diluted 70 times.

[0082] To match the solution in the SY / T5673 standard, the produced water from the Amandali oilfield was diluted 400 times to prepare the test solution, as shown in Table 2.

[0083] Table 2 Basic ion concentration of Amandali oilfield water sample after dilution 70 times

[0084]

[0085] The evaluation process using the method of the present invention is as follows:

[0086] 1. Preparation method of simulated produced water:

[0087] ① Preparation of water sample A:

[0088] Weigh 77.3g NaCl, 4.551g SrCl2·6H2O, 36.157g anhydrous CaCl2 and 16.651g MgCl2·6H2O into a 50mL beaker; add 50g distilled water to each beaker and stir thoroughly until completely dissolved; add the above solutions into a 1L volumetric flask, make up to volume, and place the solutions in a water bath to keep warm for later use.

[0089] ② Preparation of water sample B:

[0090] Weigh 77.3g NaCl, 0.153g anhydrous Na2SO4, and 0.556g anhydrous NaHCO3 respectively into a 50mL beaker; add 50g distilled water to each beaker and stir thoroughly until completely dissolved; add the above solutions to a 1L volumetric flask, make up to volume, and place the solutions in a water bath to keep warm for later use.

[0091] ③ Preparation of antiscalant solution

[0092] The antiscalant to be evaluated is prepared into a 1% concentration and set aside;

[0093] ⑤ Keep the water sample warm and let it stand to form scale

[0094] Take clean and dry different sample bottles and add 0mL, 0.1mL, 0.2mL, 0.3mL, 0.4mL, 0.5mL and 0.6mL of the prepared 1% concentration anti-scalant solution respectively, add 50mL of water sample B to each sample bottle, shake it by hand 10 times, then add 50mL of water sample A again, shake it by hand 10 times to mix the water samples evenly; place the sample bottles in a water bath and let them stand for 16 hours (the on-site treatment water temperature of Amandali Oilfield is 50℃);

[0095] ⑤ Filter with a 0.45μm microporous filter membrane, weigh the filter membrane after drying and constant weight, and measure the increase in the mass of the filter membrane.

[0096] 2. Evaluation results of antiscalant

[0097] The conventional antiscalant evaluation method and the method of the present invention were used to carry out testing using the diluted test solution, and the evaluation results of different antiscalants are shown in Table 3.

[0098] Table 3 Evaluation results of antiscalant for produced water in Amandali Oilfield

[0099]

[0100] Since the conventional anti-scaling agent testing method uses a dilution multiple that is too high, the anti-scaling effect of the anti-scaling agent is seriously distorted as the dilution multiple is restored, making it impossible to objectively evaluate the actual applicability of the agent.

[0101] Example 2

[0102] This Example 2 uses the anti-scaling agent evaluation method of the present invention to evaluate the anti-scaling agent for produced water from oil wells in the northern oil field of Oman National Oil Company, and compares it with a conventional anti-scaling agent evaluation method in oil fields.

[0103] The ion concentrations of simulated water samples from the oil wells of the northern oil field of Oman National Oil Company are shown in Table 4:

[0104] Table 4 Basic ion concentrations of simulated water samples from oil wells in the northern oil field of Oman National Oil Company

[0105]

[0106] From the data in Table 4, it can be seen that the calcium ion concentration in the produced water of the oil wells in the northern oil field of Oman National Oil Company is 4077-10528 mg / L, and the magnesium ion concentration is 228-6308 mg / L. Due to the high concentration of calcium and magnesium ions, the applicable range of scale-forming ions in the working water sample prepared by the evaluation method of conventional anti-scaling agents generally does not exceed 100 mg / L. If the ion concentration exceeds the range, the water sample should be diluted. After preparing the test solution, the calcium ion concentration is 14.16 mg / L and the magnesium ion concentration is 3.1 mg / L. For the produced water of Amandali Oilfield, the calcium ion concentration and magnesium ion concentration need to be diluted 440 times and 381 times respectively using the conventional evaluation method.

[0107] To match the solution in the SY / T5673 standard, the produced water from the oil wells in the northern oil field of the Oman National Oil Company was diluted 70 times to prepare the test solution, as shown in Table 5:

[0108] Table 5 Ion concentration of raw water samples from the northern oilfield of Oman National Oil Company and basic ion concentration after dilution 70 times

[0109]

[0110] 2. Evaluation results of antiscalant

[0111] The conventional antiscalant evaluation method and the method of the present invention were used to carry out testing using the diluted test solution, and the evaluation results of different antiscalants are shown in Table 5.

[0112] Table 5 Evaluation results of scale inhibitors for produced water from the northern oilfield of Oman National Oil Company

[0113]

[0114]

[0115] Since the conventional anti-scaling agent test method has a high dilution multiple, the evaluation result of the dosage of the anti-scaling agent is reduced with the dilution multiple, resulting in amplified test errors, and the actual dosage of the agent cannot be truly evaluated. Comprehensive Application Example 1 and Application Example 2 Conventional anti-scaling agent test and evaluation methods cannot be adapted to the evaluation of anti-scaling agents for oilfield produced water with high calcium and magnesium ions and high mineralization. The use of the method of the present invention to evaluate anti-scaling agents will effectively avoid the problem of unrealistic evaluation results caused by excessively high dilution multiples.

[0116] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A method for evaluating an oilfield produced water antiscalant, characterized in that: include: Use oilfield produced water or simulated produced water to prepare anti-scaling agent water samples and blank water samples; Keeping the antiscalant water sample and the blank water sample still to form scale; The anti-scaling rate of the anti-scaling agent is calculated using the scale quality difference between the anti-scaling agent water sample and the blank water sample.

2. The method for evaluating oilfield produced water antiscalant according to claim 1, characterized in that: The free water in the on-site produced fluid is filtered through filter paper and filter membrane to obtain the oilfield produced water.

3. The method for evaluating oilfield produced water antiscalant according to claim 2, characterized in that: The method for preparing a water sample of an antiscalant using oilfield produced water comprises: Add 50-60 mL of distilled water to 2.00 g ± 0.01 g of the anti-scaling agent, and after the anti-scaling agent is dissolved, transfer it into a 100 mL volumetric flask and make up the volume to prepare an anti-scaling agent solution with a concentration of 20,000 mg / L; 1 mL of the antiscalant solution was measured and placed in a test bottle, 199 mL of the oilfield produced water was added, and the solution was shaken 10 times to obtain the antiscalant water sample.

4. The method for evaluating oilfield produced water antiscalant according to claim 3, characterized in that: The method of preparing blank water sample using oilfield produced water includes: 199 mL of the oilfield produced water was measured and put into a test bottle, 1 mL of distilled water was added, and the bottle was shaken 10 times to obtain the blank water sample.

5. The method for evaluating oilfield produced water antiscalant according to claim 1, characterized in that: The preparation method of simulated produced water includes: The anion and cation concentrations of the produced water from the oil field are measured by ion chromatography, inductively coupled ion emission spectrometry or atomic absorption spectrometry, and the mineral concentration in the produced water from the oil field is calculated based on the anion and cation balance; Calculate the content of scaling cations according to the mineral concentration, calculate the mineral composition according to the content of scaling cations, weigh the alkaline earth metal or alkali metal chloride, add water to dissolve it and then adjust the volume to obtain a scaling cation solution; The scaling anion content is calculated according to the mineral concentration, the mineral composition is calculated according to the scaling anion content, the scaling anion sodium salt is weighed, and water is added to dissolve it and then constant volume is obtained to obtain a scaling anion solution.

6. The method for evaluating oilfield produced water antiscalant according to claim 5, characterized in that: The method for preparing a water sample of an antiscalant using simulated produced water comprises: Add 50-60 mL of distilled water to 2.00 g ± 0.01 g of the anti-scaling agent, and after the anti-scaling agent is dissolved, transfer it into a 100 mL volumetric flask and make up the volume to prepare an anti-scaling agent solution with a concentration of 20,000 mg / L; Measure 1 mL of the antiscalant solution into a test bottle, add 99 mL of the scale-forming cation solution, shake well, add 100 mL of the scale-forming anion solution, and shake by hand 10 times to obtain the antiscalant water sample.

7. The method for evaluating oilfield produced water antiscalant according to claim 5, characterized in that: The method of preparing blank water samples using simulated produced water includes: Measure 1 mL of distilled water into a test bottle, add 99 mL of the scaling cation solution and 100 mL of the scaling anion solution, and shake by hand 10 times to obtain the blank water sample.

8. The method for evaluating oilfield produced water antiscalant according to any one of claims 1 to 7, characterized in that: The anti-scaling agent water sample and the blank water sample are placed in the same heat preservation state and kept still for the same set time to form the scale.

9. The method for evaluating oilfield produced water antiscalant according to claim 8, characterized in that: The blank water sample and the anti-scaling agent water sample that form the scale are filtered through a filter membrane, and the filter membrane is weighed after drying to a constant weight to obtain the scale mass of the blank water sample and the anti-scaling agent water sample.

10. The method for evaluating oilfield produced water antiscalant according to claim 9, characterized in that: The pore size of the filter membrane is 0.45 μm.

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