An oilfield sewage treatment antifouling agent and a preparation method thereof

Abstract

The application discloses a preparation method of an oilfield sewage treatment antifouling agent, and comprises the following steps: dissolving citric acid and an organic phosphonic acid containing nitrogen elements in water to prepare a reaction solution; after heating reaction of the reaction solution, centrifugal filtration is performed, and the filtrate is concentrated and dried to obtain phosphorus-doped nanometer carbon quantum dots, and the preparation is completed. The carbon quantum dots formed by the method are stable in property, simple in composition, and long in antifouling time, and the carbon quantum dots can prevent the formation of metal ion precipitates in water for a long time, so that the antifouling efficiency is realized.

Description

Technical Field

[0001] This invention relates to the field of scale inhibitor technology, specifically to a scale inhibitor for oilfield wastewater treatment and its preparation method. Background Technology

[0002] During oilfield extraction, produced water and injected water contain varying levels of calcium. 2+ Mg 2+ Ba 2+ 、Sr 2+ CO3 2- SO4 2- Scale-forming ions, along with changes in the external environment (temperature, pressure, etc.), lead to scaling in formations, wellbores, and surface pipelines. Common scale types in oilfields include calcium carbonate scale, calcium sulfate scale, strontium sulfate scale, and barium sulfate scale. Corrosion products such as ferrous carbonate, ferrous sulfide, ferrous hydroxide, and ferric oxide, as well as substances with high solubility and high content that easily precipitate under certain conditions (such as sodium chloride), are also frequently included. Scale formation within the wellbore results in severe scaling on the pump rod body of some production wells, severe wear on the injection molding rod centralizer, wear on the piston surface, severe wear and scaling on the inner wall of the tubing, and severe scaling in the tailpipe, seriously affecting the lifespan of oilfield production equipment. Scale formation impacts the stability and normal operation of oilfield production; therefore, preventing scale formation has become one of the most important issues in oilfield development.

[0003] Currently, there are three types of scale prevention technologies used in oilfields: physical methods, process methods, and chemical methods. Physical methods utilize the specific functions of physical instruments and equipment to inhibit scale formation, commonly using ultrasonic waves, magnetic fields, and other similar techniques. Process methods involve altering or controlling certain process conditions to disrupt or reduce the chances of scale formation. Chemical methods involve adding chemical scale inhibitors, utilizing their complexing, solubilizing, dispersing, and lattice distortion effects to prevent scale formation. Due to their effectiveness, wide applicability, and flexibility, chemical methods are widely used in oilfields.

[0004] However, current scale inhibitors suffer from instability and short-lived action. In practical applications, scale inhibitors need to be injected into oil wells daily, significantly increasing labor costs. A search revealed the following relevant existing technologies:

[0005] Patent CN105152367A reports an environmentally friendly corrosion and scale inhibitor for oilfield reinjection water and its preparation method, belonging to the field of petroleum additive technology. This environmentally friendly corrosion and scale inhibitor for oilfield reinjection water is prepared from raw materials including *Dendrobium nobile* extract, methyl dihydroartemisinate, citric acid, tannic acid, sodium mercaptobenzothiazole, gluconate-δ-lactone, potassium guaiacol sulfonate, sulfosuccinate, N-(3-triethoxysilylpropyl)glucosamide, ethyl acetate, ethanol, and water through a series of steps. The preparation process of this scale inhibitor is cumbersome, requires a large number of raw materials, and exhibits poor stability.

[0006] Patent CN109705831A discloses an oilfield scale inhibitor, comprising a first scale inhibitor, a second scale inhibitor, and a third scale inhibitor. The first scale inhibitor comprises: 8-10 parts of sodium ethylenediaminetetramethylenephosphonate, 5-8 parts of aminotrimethylenephosphonic acid, 3-5 parts of hydroxyethylidene diphosphonic acid, 2-phosphonobutane, and 5-8 parts of 1,2,4-tricarboxylic acid. The second scale inhibitor comprises: 15-20 parts of maleic anhydride, 5-10 parts of acrylic acid, 5-8 parts of hydroxypropyl acrylate, and 0.5-1 part of ammonium persulfate. The third scale inhibitor comprises: 10-12 parts of polyepoxysuccinic acid, 8-10 parts of polyaspartic acid, 5-8 parts of modified imidazoline, 0.5-1 part of modified quaternary ammonium salt, and 0.05-0.1 parts of sodium polyacrylate. However, this scale inhibitor has a complicated preparation process, requires a large amount of raw materials, and exhibits poor stability.

[0007] Current scale inhibitors suffer from instability and short action time. It is necessary to develop a scale inhibitor that is stable and has a long action time to solve the problem of scale buildup in wellbores causing damage to oil production equipment. Summary of the Invention

[0008] This invention provides a scale inhibitor with stable properties and long-lasting action time. The specific technical solution is as follows:

[0009] A method for preparing an oilfield wastewater treatment scale inhibitor includes the following steps:

[0010] Citric acid and nitrogen-containing organophosphonic acid were dissolved in water to prepare a reaction solution. The reaction solution was heated and then centrifuged and filtered. The filtrate was concentrated and dried to obtain phosphorus-doped carbon nanoparticles, thus completing the preparation.

[0011] Preferably, the organophosphonic acid is at least one of aminotrimethylphosphonic acid, ethylenediaminetetramethylphosphonic acid, and diethylenetriaminepentamethylphosphonic acid.

[0012] Preferably, the mass ratio of citric acid to the nitrogen-containing organophosphonic acid is 1:0.5-1.

[0013] Preferably, the reaction solution is heated to 180-280°C.

[0014] Preferably, the heating reaction time is 3-8 hours.

[0015] Preferably, the method further includes the following steps: adding the prepared phosphorus-doped carbon nanoparticles to hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1,2,4-tricarboxylic acid, adding water, stirring, and heating to react, thereby completing the preparation.

[0016] Preferably, the heating reaction temperature is 50-80℃.

[0017] Preferably, the heating reaction time is 10-15 min.

[0018] The provided preparation method has the following technical effects:

[0019] Citric acid is the carbon source for synthesizing carbon quantum dots. Organophosphonic acids containing nitrogen mainly provide the nitrogen source for the reaction. Phosphonic acid is selected by phosphorus doping on the surface of carbon dots. Under high temperature and high pressure conditions, the two react to generate phosphorus-doped nano carbon quantum dots. The carbon quantum dots formed by this method are stable, have a simple composition, and maintain scale inhibition for a long time. These carbon quantum dots can prevent metal ions in water from forming precipitates for a long time, thus achieving scale inhibition performance.

[0020] Preferably, the organophosphate is at least one of aminotrimethylphosphonic acid, ethylenediaminetetramethylphosphonic acid, and diethylenetriaminepentamethylphosphonic acid, which has a wide range of choices.

[0021] As a preferred option, the mass ratio is limited to 1:0.5-1 to ensure that the carbon dopant surface is doped with as much P as possible. According to elemental scanning analysis, the optimal elemental proportion can reach 20%, which can make the product properties stable.

[0022] Preferably, the reaction solution is heated to 180-280°C. The hydrothermal preparation of carbon quantum dots needs to be carried out at a temperature above 180°C, but if the temperature is too high, other substances may be generated. Therefore, an upper temperature limit of 280°C is set.

[0023] As a preferred method, the yield of carbon points below 3 hours will decrease, while those above 8 hours will not improve the yield and will increase energy consumption.

[0024] Preferably, the carbon quantum dots are combined with hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1,2,4-tricarboxylic acid. The hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1,2,4-tricarboxylic acid will chelate with the carbon quantum dots, and unstable ligands can be formed on the surface of the hydroxyethylidene diphosphonic acid or 2-phosphonobutane to achieve slow release and further enhance the anti-scaling effect. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a method for preparing a scale inhibitor for oilfield wastewater treatment, comprising the following steps:

[0027] Citric acid and nitrogen-containing organophosphonic acid were dissolved in water to prepare a reaction solution. The reaction solution was heated and then centrifuged and filtered. The filtrate was concentrated and dried to obtain phosphorus-doped carbon nanoparticles, thus completing the preparation.

[0028] Citric acid is the carbon source for synthesizing carbon quantum dots. Organophosphonic acids containing nitrogen mainly provide the nitrogen source for the reaction. Phosphonic acid is selected by phosphorus doping on the surface of carbon dots. Under high temperature and high pressure conditions, the two react to generate phosphorus-doped nano carbon quantum dots. The carbon quantum dots formed by this method are stable, have a simple composition, and maintain scale inhibition for a long time. These carbon quantum dots can prevent metal ions in water from forming precipitates for a long time, thus achieving scale inhibition performance.

[0029] The organophosphonic acid is at least one of aminotrimethylphosphonic acid, ethylenediaminetetramethylphosphonic acid, and diethylenetriaminepentamethylphosphonic acid.

[0030] Organophosphoric acid is at least one of aminotrimethylphosphonic acid, ethylenediaminetetramethylphosphonic acid, and diethylenetriaminepentamethylphosphonic acid, which offers a wide range of choices.

[0031] Preferably, the mass ratio of citric acid to the nitrogen-containing organophosphonic acid is 1:0.5-1.

[0032] The mass ratio is limited to 1:0.5-1 to ensure that the carbon dopant surface is doped with as much P as possible. According to elemental scanning analysis, the optimal elemental percentage can reach 20%, which can make the product properties stable.

[0033] Preferably, the reaction solution is heated to 180-280°C.

[0034] The reaction solution is heated to 180-280℃. The hydrothermal preparation of carbon quantum dots needs to be carried out above 180℃, but if the temperature is too high, other substances may be generated. Therefore, an upper temperature limit of 280℃ is set.

[0035] The reaction time is 3-8 hours. If the reaction time is less than 3 hours, the yield of carbon points will decrease, while if the reaction time is more than 8 hours, it will not improve the yield and will increase energy consumption.

[0036] The process also includes the following steps: adding the prepared phosphorus-doped carbon nanoparticles to hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1,2,4-tricarboxylic acid, adding water, stirring, and heating to react, thus completing the preparation.

[0037] Furthermore, the carbon quantum dots are combined with hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1,2,4-tricarboxylic acid. The hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1,2,4-tricarboxylic acid will chelate with the carbon quantum dots, and unstable ligands can be formed on the surface of the hydroxyethylidene diphosphonic acid or 2-phosphonobutane to achieve slow release and further enhance the anti-scaling effect.

[0038] Several specific embodiments are as follows:

[0039] Example 1

[0040] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0041] Citric acid and aminotrimethylphosphoric acid in a mass ratio of 1:1 were dissolved in deionized water to prepare a reaction solution with a citric acid mass concentration of 10%. The reaction solution was heated to 180℃ and reacted for 8 hours. After centrifugation and filtration, the filtrate was concentrated and dried to obtain phosphorus-doped carbon nanoparticles, which were taken as product A.

[0042] Example 2

[0043] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0044] Citric acid and aminotrimethylphosphoric acid in a mass ratio of 1:0.5 were dissolved in deionized water to prepare a reaction solution with a citric acid mass concentration of 10%. The reaction solution was heated to 280℃ and reacted for 3 hours. After centrifugation and filtration, the filtrate was concentrated and dried to obtain phosphorus-doped carbon nanoparticles, which were taken as product B.

[0045] Example 3

[0046] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0047] Citric acid and aminotrimethylphosphoric acid in a mass ratio of 1:0.8 were dissolved in deionized water to prepare a reaction solution with a citric acid mass concentration of 10%. The reaction solution was heated to 220℃ and reacted for 5 hours. After centrifugation and filtration, the filtrate was concentrated and dried to obtain phosphorus-doped carbon nanoparticles, which were taken as product C.

[0048] Example 4

[0049] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0050] Citric acid and ethylenediaminetetramethylphosphoric acid in a mass ratio of 1:1 were dissolved in deionized water to prepare a reaction solution with a citric acid mass concentration of 10%. The reaction solution was heated to 250℃ and reacted for 6 hours. After centrifugation and filtration, the filtrate was concentrated and dried to obtain phosphorus-doped carbon nanoparticles, which were taken as product D.

[0051] Example 5

[0052] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0053] S11) Dissolve citric acid and aminotrimethylphosphoric acid in deionized water at a mass ratio of 1:0.8 to prepare a reaction solution with a citric acid mass concentration of 10%.

[0054] S12) After heating the reaction solution to 220℃ and reacting for 5 hours, centrifuge and filter the solution. After concentrating and drying the filtrate, phosphorus-doped carbon nanotube quantum dots are obtained.

[0055] S2) Weigh out phosphorus-doped carbon nanoparticles and 2-phosphonobutane in a mass ratio of 1:0.3. Add the weighed phosphorus-doped carbon nanoparticles to 2-phosphonobutane, add water, stir, and heat to 50°C for 15 min to obtain product E.

[0056] Example 6

[0057] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0058] S11) Dissolve citric acid and ethylenediaminetetramethylenephosphoric acid in deionized water at a mass ratio of 1:0.8 to prepare a reaction solution with a citric acid mass concentration of 10%.

[0059] S12) After heating the reaction solution to 220℃ and reacting for 5 hours, centrifuge and filter the solution. After concentrating and drying the filtrate, phosphorus-doped carbon nanotube quantum dots are obtained.

[0060] S2) Weigh phosphorus-doped carbon nanoparticles and hydroxyethylidene diphosphonic acid in a mass ratio of 1:0.15. Add the weighed phosphorus-doped carbon nanoparticles to isopropanolamine, add water, stir, and heat to 80°C for 10 min to obtain product F.

[0061] Example 7

[0062] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0063] S11) Dissolve citric acid and ethylenediaminetetramethylenephosphoric acid in deionized water at a mass ratio of 1:0.8 to prepare a reaction solution with a citric acid mass concentration of 10%.

[0064] S12) After heating the reaction solution to 220℃ and reacting for 5 hours, centrifuge and filter the solution. After concentrating and drying the filtrate, phosphorus-doped carbon nanotube quantum dots are obtained.

[0065] S2) Weigh phosphorus-doped carbon nanoparticles and hydroxyethylidene diphosphonic acid in a mass ratio of 1:0.2. Add the weighed phosphorus-doped carbon nanoparticles to hydroxyethylidene diphosphonic acid, add water, stir, and heat to 60°C for 12 min to obtain product G.

[0066] Example 8

[0067] A scale inhibitor for oilfield wastewater treatment is prepared by the following method:

[0068] S11) Dissolve citric acid and ethylenediaminetetramethylenephosphoric acid in deionized water at a mass ratio of 1:1 to prepare a reaction solution with a citric acid mass concentration of 10%.

[0069] S12) After heating the reaction solution to 250℃ and reacting for 6 hours, centrifuge and filter the solution. After concentrating and drying the filtrate, phosphorus-doped carbon nanotube quantum dots are obtained.

[0070] S2) Weigh out phosphorus-doped carbon nanoparticles and hydroxyethylidene diphosphonic acid in a mass ratio of 1:0.2. Add the weighed phosphorus-doped carbon nanoparticles to hydroxyethylidene diphosphonic acid, add water, stir, and heat to 60°C for 12 min to obtain product H.

[0071] The water stabilizer prepared above was diluted with water to a solution of 10 mg / L, and then added to the flowing oilfield reinjection water. Dynamic simulation experiments and scale inhibition experiments were conducted, and the test results are as follows:

[0072]

[0073]

[0074] One month after using this scale inhibitor, the oilfield reinjection water pipelines were inspected to observe the scaling condition, which is as follows:

[0075]

[0076] Furthermore, the scale inhibition rate can reach over 90% and maintain this level for a long time, which confirms the stability of the scale inhibitor and avoids the drawback of high cost caused by the need to add more scale inhibitor in existing technologies.

[0077] In other embodiments, the organophosphonic acid was replaced with diethylenetriaminepentamethylenephosphonic acid, or a mixture of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid. The same preparation and experiments were carried out, and the scale inhibition rate could reach more than 90% and the maintenance time was relatively long.

[0078] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Various modifications or equivalent substitutions made by those skilled in the art to the present invention within its spirit and scope of protection also fall within the scope of protection of the present invention.

Claims

1. A method for preparing an antifouling agent for oilfield wastewater treatment, characterized by, The method comprises the following steps: The citric acid and the organic phosphonic acid containing nitrogen element are dissolved in water to prepare a reaction solution; after heating reaction, centrifugal filtration is performed, and the filtrate is concentrated and dried to obtain phosphorus-doped nanometer carbon quantum dots, thereby completing the preparation; The prepared phosphorus-doped nanometer carbon quantum dots are added into hydroxyethylidene diphosphonic acid or 2-phosphonobutane-1, 2, 4-tricarboxylic acid, water is added and stirred, and then heated reaction is performed, thereby completing the preparation; the heating reaction temperature is 50-80℃, and the heating reaction time is 10-15 min.

2. The method for preparing the scale inhibitor for oilfield sewage treatment according to claim 1, characterized in that, The organic phosphonic acid is at least one of aminotrimethylene phosphonic acid, ethylenediamine tetramethylene phosphonic acid and diethylenetriamine pentamethylene phosphonic acid.

3. The method for preparing the scale inhibitor for oilfield wastewater treatment according to claim 1, characterized in that, The mass ratio of the citric acid to the organic phosphonic acid containing nitrogen element is 1:0.5-1.

4. The method of claim 1, wherein the oilfield wastewater treatment antiscalant is prepared by the steps of: The reaction solution is heated to 180-280℃.

5. The method of claim 1, wherein the oilfield wastewater treatment antiscalant is prepared by the steps of: The heating reaction time is 3-8 h.

6. An antifouling agent for oilfield wastewater treatment, characterized by comprising: The antifouling agent is prepared by the preparation method in claims 1-5.

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