A polymer medicament and oil well anti-sulfate scale microcapsule scale inhibitor and a preparation method thereof

Abstract

The application provides a polymer agent and a microcapsule anti-scaling agent for preventing sulfate scale of an oil well and a preparation method thereof. The microcapsule anti-scaling agent comprises a nucleating agent, a polymer wall material and a polymer agent. The amount of the polymer wall material and the nucleating agent is 1.2-1.5 times and 0.8-1.2 times the mass of a polymer agent preparation raw material, maleic anhydride, fluorine-containing acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, respectively. The microcapsule anti-scaling agent for preventing sulfate scale of an oil well provided by the application has a polymer agent molecular chain with a fluorine-containing group introduced through a polymerization reaction, and a hexafluoropropylene oxide oligomer is used as the capsule wall, so that the fluorine content in the total mass of the anti-scaling agent is greater than 20%. The anti-scaling agent has good temperature resistance and dispersibility in high salinity water at a well bottom temperature of the oil well of 120 DEG C or above, and the release and dissolution speed can be controlled under different temperature conditions.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to a microcapsule scale inhibitor for preventing sulfate scale in oil wells and its preparation method. Background Technology

[0002] Sulfate scale (Ba / SrSO4) can easily form between injected water and formation water in oil wells, or between produced water from different formations, due to incompatibility. Sulfate scale has extremely low solubility and is difficult to dissolve in both acids and alkalis, posing many challenges to normal oil well production.

[0003] The main techniques for preventing and controlling sulfate scale are achieved by adding chemical scale inhibitors. Currently, commonly used sulfate scale inhibitors mainly include polyphosphonate scale inhibitors (such as aminotrimethylenephosphonic acid ATMP, sodium ethylenediaminetetramethylenephosphonate, hydroxyethylidene diphosphonic acid HEDP, diethylenetriaminepentamethylenephosphonic acid DTPMP, etc.), polycarboxylate scale inhibitors (such as polyaspartate, hydrolyzed polymaleic anhydride HPMA, phosphonocarboxylic acid copolymer POCA, etc.), and sulfonic acid copolymer scale inhibitors (such as binary, ternary, and quaternary copolymers of acrylic acid with acrylates, sulfonates, phosphonic acids, and 2-acrylamido-2-methylpropanesulfonic acid AMPS, etc.).

[0004] Microencapsulation technology uses natural or synthetic polymer materials as capsule walls to encapsulate solid or liquid agents into drug reservoir-type microcapsules, allowing the encapsulated drug components to be slowly released at a certain rate. This can improve the stability of the agent; enhance the reactivity of the encapsulated agent; extend the service life of scale inhibitors; reduce the frequency of drug addition; and allow for the continuous and slow release of agents into the wellbore and formation environment as needed.

[0005] However, existing domestic and international sulfate scale inhibitor technologies have the following six limitations: (1) Liquid scale inhibitors diffuse quickly and have low density; (2) Solid block scale inhibitors cannot be replenished through the annulus during normal production; (3) Solid particle scale inhibitors cannot be injected through high-pressure pumps in high-pressure wells, resulting in slow injection; (4) When the wellbore temperature is >60℃, the scale inhibitor and its capsules are released rapidly, resulting in poor scale prevention effect; (5) They cannot be adsorbed in large quantities on the surface of the oil well tubing and are easily carried out by the produced fluid, resulting in a short scale prevention cycle; (6) In high-mineralized produced fluid oil wells, the scale prevention rate is low, and even with high dosage and high concentration, the scale prevention rate is less than 60%. Therefore, it is urgent to design a sulfate scale inhibitor with high density, slow diffusion, high injection efficiency, good salt resistance, long scale prevention cycle, and high scale prevention rate that can be replenished through the annulus. Summary of the Invention

[0006] The purpose of this invention is to provide a polymer agent that has good adsorption and suspension effects on sulfate microcrystals.

[0007] Another objective of this invention is to provide a microcapsule scale inhibitor for preventing sulfate scaling in oil wells, overcoming the aforementioned technical problems in the prior art. Specifically, the introduction of amide groups further enhances the solubility of the polymer molecular structure, better preventing gel formation; the incorporation of sulfonic acid groups enhances the dispersibility of the polymer during the scale prevention process, resulting in a more pronounced crystal distortion effect; and the introduction of fluorinated acrylic acid and hexafluoropropylene oxide oligomers improves the temperature resistance of the scale inhibitor.

[0008] Another objective of this invention is to provide a method for preparing a microcapsule anti-sulfate scale agent for oil wells, which is prepared by supercritical carbon dioxide rapid expansion method.

[0009] Therefore, the technical solution provided by the present invention is as follows:

[0010] A polymeric pharmaceutical agent with the following structural formula:

[0011]

[0012] Where m, n, j, and k all represent the degree of aggregation, which are integers ≥ 1.

[0013] It is prepared by free radical polymerization of maleic anhydride (MA), fluorinated acrylic acid (FA), methacrylic acid (MAA), and 2-acrylamido-2-methylpropanesulfonic acid under the action of an initiator. The mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is (6-10):(10-17):(1-5):(2.5-5). Maleic anhydride is dissolved in water before participating in the reaction, and the amount of water added to 0.1-0.25 mol of maleic anhydride is 200-250 ml.

[0014] The fluorinated acrylic acid is CF3CF2COOH, CF3CHFCOOH, CF3CH2COOH, CHF2CF2COOH, CHF2CHFCOOH, CHF2CH2COOH, CH2FCF2COOH, CH2FCHFCOOH, CH2FCH2COOH, CH3CF2COOH, CH3CHFCOOH.

[0015] The initiator is ammonium persulfate or potassium persulfate.

[0016] A microcapsule scale inhibitor for preventing sulfate scale in oil wells includes a nucleating agent, a polymer wall material, and the polymer agent. The amounts of the polymer wall material and the nucleating agent are 1.2-1.5 times and 0.8-1.2 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0017] The microcapsule antiscalant is prepared by encapsulating MA, FA, MAA and AMPS free radical polymerization product MA-FA-MAA-AMPS (polymer agent) with hexafluoropropylene oxide oligomer (polymer wall material) and nucleating agent.

[0018] The nucleating agent is ammonium halide, specifically NH4Cl, NH4Br, or NH4I.

[0019] The hexafluoropropylene oxide oligomer has a relative molecular weight between 300 and 1000 and has the following structural formula:

[0020]

[0021] Where n = 2, 3, 4, 15, and R is -COOH, -COOCH3, -COF, or -CONH2.

[0022] The molecular structure of hexafluoropropylene oxide oligomers contains only three elements: C, F, and O. The presence of CO bonds in the main chain gives the molecule strong flexibility. Furthermore, the abundant presence of F generates strong electrostatic repulsion, causing the CF and -CF3 structural units connected to the CC and COC main chains to extend outwards and distance themselves from each other to form a highly efficient protective layer that surrounds the CC main chain. This endows hexafluoropropylene oxide oligomers with excellent thermal stability and high corrosion resistance.

[0023] A method for preparing a microcapsule scale inhibitor for preventing sulfate scaling in oil wells includes the following steps:

[0024] Step 1) Preparation of polymer reagent: Maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid are added to a container in a mass ratio of (6-10):(10-17):(1-5):(2.5-5), and then an initiator is added. The mixture is prepared by free radical polymerization at a certain temperature.

[0025] Step 2) Preparation of microcapsule antiscalant: Using the prescribed amount of hexafluoropropylene oxide oligomer as the wall material, the polymer agent and the prescribed amount of ammonium chloride nucleating agent are encapsulated and prepared by supercritical carbon dioxide rapid expansion method.

[0026] Step 1) The specific process is as follows:

[0027] Add the prescribed amount of water and maleic anhydride to the reaction vessel, and while stirring, raise the temperature to 60°C. After the maleic anhydride is completely dissolved, add the monomer mixture to the system through a constant pressure dropping funnel. The monomer mixture consists of a uniform mixture of the prescribed amounts of fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. After the addition is complete, add the initiator dropwise. The amount of initiator is 1.5-2.0% of the total mass of maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. The titration time is 1-2 hours. After the addition is complete, maintain the temperature at 60-90°C and continue stirring for 2-6 hours. After concentration and cooling, a white, high-viscosity liquid is obtained, which is the final product.

[0028] Step 2) The specific process is as follows:

[0029] After heating the high-pressure reactor to the target temperature, the polymer reagent prepared in step 1), along with the hexafluoropropylene oxide oligomer wall material and the nucleating agent ammonium halide, are added to the high-pressure reactor according to the formula. Then, CO2 is introduced into the high-pressure reactor, and the reactor is continuously stirred and CO2 is added to maintain the pressure inside the high-pressure reactor at the CO2 critical pressure of 7.3-10 MPa for 1-3 hours. After that, the pressure relief valve is opened to quickly reduce the pressure. The hexafluoropropylene oxide oligomer microparticles in the reactor collide with the polymer reagent suspended on the surface of the ammonium halide in the recovery chamber, and are uniformly coated on the surface of the polymer reagent to obtain a microcapsule antiscalant.

[0030] The beneficial effects of this invention are:

[0031] The microcapsule scale inhibitor for preventing sulfate scaling in oil wells provided by this invention introduces fluorine-containing groups into the polymer molecular chain prepared by polymerization, while the capsule wall uses hexafluoropropylene oxide oligomer, achieving a fluorine content of more than 20% in the total mass of the scale inhibitor. This ensures that the scale inhibitor has good temperature stability at well bottom temperatures above 120°C and good dispersibility in highly salinized water; it also allows for controllable release and dissolution rates under different temperature conditions.

[0032] The polymer in this microcapsule scale inhibitor has a large molecular weight (close to 10,000). After hydrolysis in the wellbore environment, the negatively charged long chains exhibit good adsorption and suspension effects on sulfate microcrystals. Even at low concentrations, it effectively prevents the growth and adhesion of sulfate crystals. Excellent sulfate scale prevention is achieved even at dosages exceeding 20 mg / L. The addition of ammonium halide, a nucleating agent, ensures its density is >1 g / cm³. 3 It can sink completely to the bottom of the well, and the release of ammonium halide at the bottom of the well can play a role in corrosion inhibition and dispersion.

[0033] This invention uses hexafluoropropylene oxide oligomers (di, tri, tetra, and pentadecomers) with different degrees of polymerization as wall materials to prepare microcapsules with different numbers of pores. This results in different main controlling factors for the release of scale inhibitors (temperature, pH, and calcium / barium / strontium ion concentration response). Thus, it is possible to achieve different release rates under different temperature, pH, and calcium / barium / strontium ion concentration conditions. According to the needs of reservoir scale prevention and control, microcapsule scale inhibitors with different numbers of pores can be mixed and used in a certain proportion.

[0034] During the slow release of this microcapsule scale inhibitor into the oil well, the dissolved fluorine compounds can be adsorbed onto the surface of the steel tubing, forming an oleophilic and hydrophobic adsorption film, thus achieving secondary scale inhibition and corrosion protection of the tubing wall.

[0035] Further details will be provided below. Detailed Implementation

[0036] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0037] Exemplary embodiments of the present invention are now described; however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments is not intended to limit the invention.

[0038] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0039] Example 1:

[0040] This embodiment provides a polymeric pharmaceutical agent with the following structural formula:

[0041]

[0042] Where m, n, j, and k all represent the degree of aggregation, which are integers ≥ 1.

[0043] The polymer reagent is prepared by free radical polymerization of maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid under the action of an initiator. The mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is (6-10):(10-17):(1-5):(2.5-5). Maleic anhydride is dissolved in water before participating in the reaction, and the amount of water added to 0.1-0.25 mol of maleic anhydride is 200-250 ml. The initiator is ammonium persulfate or potassium persulfate.

[0044] This embodiment also provides a microcapsule scale inhibitor for preventing sulfate scale in oil wells, comprising a nucleating agent, a polymer wall material, and the polymer agent, wherein the amounts of the polymer wall material and the nucleating agent are 1.2-1.5 times and 0.8-1.2 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0045] The nucleating agent is ammonium chloride, and the polymer wall material is hexafluoropropylene oxide oligomer.

[0046] The hexafluoropropylene oxide oligomer has a relative molecular weight between 300 and 1000 and has the following structural formula:

[0047]

[0048] Where n = 2, 3, 4, 15, and R is -COOH, -COOCH3, -COF, or -CONH2.

[0049] Principle of this invention:

[0050] Hexafluoropropylene oxide oligomer wall materials, with molecular weights between 300 and 1000, contain only C, F, and O elements in their molecular structure, with CO bonds in the main chain, giving the molecules strong flexibility. Furthermore, the abundant presence of F generates strong electrostatic repulsion, causing the CF and -CF3 structural units connected to the CC and COC main chains to extend outwards and distance themselves from each other to form a highly efficient protective layer that surrounds the CC main chain, endowing this fluoropolymer with excellent high thermal stability and high corrosion resistance. The unique structure of fluoropropylene oxide oligomer wall materials and their special attraction to CO2 molecules give them excellent solubility in supercritical carbon dioxide (scCO2) systems. Ammonium chloride released at the bottom of the well can act as a corrosion inhibitor and dispersant.

[0051] Example 2:

[0052] Based on Example 1, this example provides a polymeric agent in which the mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 6:10:1:2.5.

[0053] This embodiment also provides a microcapsule scale inhibitor for preventing sulfate scale in oil wells, comprising a nucleating agent, a polymer wall material, and the aforementioned polymer agent. The amounts of the polymer wall material and the nucleating agent are 1.2 times and 0.8 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0054] The preparation process is as follows:

[0055] Step 1) Preparation of polymeric pharmaceutical agents

[0056] Add 13.47 g (0.137 mol) of maleic anhydride and 200 mL of distilled water to a 500 mL three-necked round-bottom flask equipped with a spherical condenser, thermometer, and constant-pressure dropping funnel. While stirring, raise the temperature to 60 °C. After the maleic anhydride is completely dissolved, add 22.5 g of fluorinated acrylic acid, 2.25 g of methacrylic acid, and 5.61 g of 2-acrylamido-2-methylpropanesulfonic acid to the system through the constant-pressure dropping funnel. After the addition is complete, slowly add 0.66 g of ammonium persulfate initiator to the reaction system over a titration time of 1.5 h. After the addition is complete, maintain the temperature at 60 °C and continue stirring for 3 h. After concentration and cooling, a white, semi-transparent, viscous liquid is obtained, which is the product.

[0057] Step 2) Preparation of microcapsule antiscalant

[0058] After preheating the high-pressure reactor to 32°C, the polymer reagent prepared in step one, along with 52.60 g of hexafluoropropylene oxide oligomer and 35.1 g of ammonium chloride, were added to a 500 mL high-pressure reactor. CO2 was then rapidly introduced into the reactor, and continuous stirring and CO2 replenishment were maintained to keep the pressure at 7.3 MPa for 1 hour. The poorly soluble polymer reagent remained suspended on the surface of the ammonium chloride, while the highly soluble hexafluoropropylene oxide oligomer dissolved. The pressure was then reduced, and the hexafluoropropylene oxide oligomer collided with the polymer reagent in the recovery chamber, uniformly coating the polymer reagent surface to obtain a fluorinated microcapsule antiscalant. This microcapsule antiscalant, designated FGJ-1, consists of spherical particles with a diameter of 120 nm and a density of 1.3 g / cm³. 3 .

[0059] In this embodiment, the amount of initiator is 1.5% of the total mass of the four monomer polymerization raw materials used in the preparation of the polymer agent; the hexafluoropropylene oxide oligomer is a hexafluoropropylene oxide oligomer dimer (i.e., n=2).

[0060] Example 3:

[0061] Based on Example 1, this example provides a polymeric agent in which the mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid is 7:12:2:3.

[0062] This embodiment also provides a microcapsule scale inhibitor for preventing sulfate scale in oil wells, comprising a nucleating agent, a polymer wall material, and the aforementioned polymer agent. The amounts of the polymer wall material and the nucleating agent are 1.2 times and 0.8 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0063] The preparation process is as follows:

[0064] Step 1) Preparation of polymeric pharmaceutical agents

[0065] Add 15.75 g (0.161 mol) of maleic anhydride and 250 mL of distilled water to a 500 mL three-necked round-bottom flask equipped with a spherical condenser, thermometer, and constant-pressure dropping funnel. While stirring, raise the temperature to 60 °C. After the maleic anhydride is completely dissolved, add 27.0 g of fluorinated acrylic acid, 4.5 g of methacrylic acid, and 6.75 g of 2-acrylamido-2-methylpropanesulfonic acid to the system through the constant-pressure dropping funnel. After the addition is complete, slowly add 0.86 g of potassium persulfate initiator to the system over a titration time of 2 h. After the addition is complete, maintain the temperature at 60 °C and continue stirring for 4 h. After concentration and cooling, a white, semi-transparent, viscous liquid is obtained, which is the polymer reagent.

[0066] Step 2) Preparation of microcapsule antiscalant

[0067] After preheating the high-pressure reactor to 32°C, the polymer reagent prepared in step one, along with 64.8 g of hexafluoropropylene oxide oligomer and 43.2 g of ammonium chloride, were added to a 500 mL high-pressure reactor. CO2 was then rapidly introduced into the reactor, and stirring and CO2 replenishment were continued to maintain the pressure at 8.5 MPa for 2 hours. The poorly soluble polymer reagent remained suspended on the surface of the ammonium chloride, while the highly soluble hexafluoropropylene oxide oligomer dissolved. The pressure was then reduced, and the hexafluoropropylene oxide oligomer collided with the polymer reagent in the recovery chamber, uniformly coating the polymer reagent surface to obtain a fluorinated microcapsule antiscalant. This microcapsule antiscalant, designated FGJ-2, consists of spherical particles with a diameter of 160 nm and a density of 1.45 g / cm³. 3 .

[0068] In this embodiment, the amount of initiator is 1.6% of the total mass of the four monomer polymerization raw materials used in the preparation of the polymer reagent, and the hexafluoropropylene oxide oligomer is a hexafluoropropylene oxide oligomer trimer (i.e., n=3).

[0069] Example 4:

[0070] Based on Example 1, this example provides a polymeric agent in which the mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 8:15:3:4.

[0071] This embodiment also provides a microcapsule scale inhibitor for preventing sulfate scale in oil wells, comprising a nucleating agent, a polymer wall material, and the aforementioned polymer agent. The amounts of the polymer wall material and the nucleating agent are 1.2 times and 1.0 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0072] The preparation process is as follows:

[0073] Step 1) Preparation of polymeric pharmaceutical agents

[0074] Add 24.0 g (0.245 mol) of maleic anhydride and 250 mL of distilled water to a 500 mL three-necked round-bottom flask equipped with a spherical condenser, thermometer, and constant-pressure dropping funnel. While stirring, raise the temperature to 60 °C. After the maleic anhydride is completely dissolved, add 45.0 g of fluorinated acrylic acid, 9.0 g of methacrylic acid, and 12.0 g of 2-acrylamido-2-methylpropanesulfonic acid to the system through the constant-pressure dropping funnel. After the addition is complete, slowly add 1.44 g of ammonium persulfate initiator to the system over a titration time of 2 h. After the addition is complete, maintain the temperature at 60 °C and continue stirring for 4 h. After concentration and cooling, a white, semi-transparent, viscous liquid is obtained, which is the polymer reagent.

[0075] Step 2) Preparation of microcapsule antiscalant

[0076] After preheating the high-pressure reactor to 32°C, the polymer reagent prepared in step one, along with 108g of hexafluoropropylene oxide oligomer tetramer and 90g of ammonium chloride, were added to a 500mL high-pressure reactor. CO2 was then rapidly introduced into the reactor, and stirring and CO2 replenishment were continued to maintain the pressure at 8.5MPa for 3 hours. The poorly soluble polymer reagent remained suspended on the surface of the ammonium chloride, while the highly soluble hexafluoropropylene oxide oligomer dissolved. Then, by depressurization, the hexafluoropropylene oxide oligomer collided with the polymer reagent in the recovery chamber, uniformly coating the polymer reagent surface to obtain a fluorinated microcapsule antiscalant. This microcapsule antiscalant, designated FGJ-3, consists of spherical particles with a diameter of 220nm and a density of 1.12g / cm³. 3 .

[0077] In this embodiment, the amount of initiator is 1.6% of the total mass of the four monomer polymerization raw materials used in the preparation of the polymer agent, and the hexafluoropropylene oxide oligomer is a hexafluoropropylene oxide oligomer tetramer (i.e., n=4).

[0078] Example 5:

[0079] Based on Example 1, this example provides a polymeric agent in which the mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid is 9:16:5:5.

[0080] This embodiment also provides a microcapsule scale inhibitor for preventing sulfate scale in oil wells, comprising a nucleating agent, a polymer wall material, and the aforementioned polymer agent. The amounts of the polymer wall material and the nucleating agent are 1.2 times and 1.1 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0081] The preparation process is as follows:

[0082] Step 1) Preparation of polymeric pharmaceutical agents

[0083] Add 21.6 g (0.22 mol) of maleic anhydride and 250 mL of distilled water to a 500 mL three-necked round-bottom flask equipped with a spherical condenser, thermometer, and constant-pressure dropping funnel. While stirring, raise the temperature to 60 °C. After the maleic anhydride is completely dissolved, add 38.4 g of fluorinated acrylic acid, 12.0 g of methacrylic acid, and 12.0 g of 2-acrylamido-2-methylpropanesulfonic acid to the system through the constant-pressure dropping funnel. After the addition is complete, slowly add 1.34 g of ammonium persulfate to the system over a titration period of 2 h. After the addition is complete, maintain the temperature at 60 °C and continue stirring for 4 h. After concentration and cooling, a white, semi-transparent, viscous liquid is obtained, which is the polymer reagent.

[0084] Step 2) Preparation of microcapsule antiscalant

[0085] After preheating the high-pressure reactor to 32°C, the polymer reagent prepared in step one, along with 100.8 g of hexafluoropropylene oxide oligomer and 92.4 g of ammonium chloride, were added to a 500 mL high-pressure reactor. CO2 was then rapidly introduced into the reactor, and stirring and CO2 replenishment were continued to maintain the pressure at 10 MPa for 1 hour. The poorly soluble polymer reagent remained suspended on the surface of the ammonium chloride, while the highly soluble hexafluoropropylene oxide oligomer dissolved. Then, by depressurization, the hexafluoropropylene oxide oligomer collided with the polymer reagent in the recovery chamber, uniformly coating the polymer reagent surface to obtain a fluorinated microcapsule antiscalant. This microcapsule antiscalant, designated FGJ-4, consists of spherical particles with a diameter of 300 nm and a density of 1.15 g / cm³. 3 .

[0086] In this embodiment, the amount of initiator is 1.6% of the total mass of the four monomer polymerization raw materials used in the preparation of the polymer reagent, and the hexafluoropropylene oxide oligomer is a hexafluoropropylene oxide oligomer decadecomer (i.e., i=15).

[0087] Example 6:

[0088] Based on Example 1, this example provides a polymeric agent in which the mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid is 7:12:2:3.

[0089] This embodiment also provides a microcapsule scale inhibitor for preventing sulfate scale in oil wells, comprising a nucleating agent, a polymer wall material, and the aforementioned polymer agent. The amounts of the polymer wall material and the nucleating agent are 1.2 times and 1.2 times the mass of the raw materials for preparing the polymer agent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively.

[0090] The preparation process is as follows:

[0091] Step 1) Preparation of polymeric pharmaceutical agents

[0092] Add 15.75 g (0.161 mol) of maleic anhydride and 250 mL of distilled water to a 500 mL three-necked round-bottom flask equipped with a spherical condenser, thermometer, and constant-pressure dropping funnel. While stirring, raise the temperature to 60 °C. After the maleic anhydride is completely dissolved, add 27.0 g of fluorinated acrylic acid, 4.5 g of methacrylic acid, and 6.75 g of 2-acrylamido-2-methylpropanesulfonic acid to the system through the constant-pressure dropping funnel. After the addition is complete, slowly add 0.86 g of ammonium persulfate to the system over a titration period of 2 h. After the addition is complete, maintain the temperature at 60 °C and continue stirring for 4 h. After concentration and cooling, a white, semi-transparent, viscous liquid is obtained, which is the polymer reagent.

[0093] Step 2) Preparation of microcapsule antiscalant

[0094] After preheating the high-pressure reactor to 32°C, the polymer reagent prepared in step one, along with 32.4 g of hexafluoropropylene oxide oligomer dimer, 32.4 g of hexafluoropropylene oxide oligomer tetramer, and 64.8 g of ammonium chloride, were added to a 500 mL high-pressure reactor. CO2 was then rapidly introduced into the reactor, and stirring and CO2 replenishment were continued to maintain the pressure at 9.0 MPa for 2 hours. The poorly soluble polymer reagent remained suspended on the surface of the ammonium chloride, while the highly soluble hexafluoropropylene oxide oligomer dissolved. Then, by depressurization, capsule-walled microparticles of a specific size precipitated. These microparticles collided with the polymer reagent in the recovery chamber, uniformly coating the polymer reagent surface to obtain a fluorinated microcapsule antiscalant. This microcapsule antiscalant, designated FGJ-5, consists of spherical particles with a diameter of 200 nm and a density of 1.11 g / cm³. 3 .

[0095] In this embodiment, the amount of initiator is 1.6% of the total mass of the four monomer polymerization raw materials used in the preparation of the polymer agent. The hexafluoropropylene oxide oligomer is a mixture of hexafluoropropylene oxide oligomer dimer and tetramer with a mass ratio of 1:1 and a particle size of 60-100 nm.

[0096] The performance of the microcapsule antiscalant prepared in the above embodiments is then tested.

[0097] I. Evaluation of sustained-release performance

[0098] Evaluation method: Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the sustained-release concentration of the active ingredient in the microcapsules using a phosphorus standard working curve.

[0099] Microcapsule antiscalant release rate test procedure:

[0100] Take 10g of microcapsule antiscalant sample and add it to a salt solution with a certain degree of mineralization. Shake at 120℃ and let stand for 24 hours.

[0101] ② Remove the saline solution from the sample from the top and replace it with fresh saline solution, without disturbing the capsule at the bottom.

[0102] ③ After at least 24 hours, test the concentration of the scale inhibitor in the top brine.

[0103] ④ Repeat steps 2 and 3 until the effective ingredient of the microcapsule antiscalant is detected to reach a very low level, and record this lowest agent concentration.

[0104] The effective antiscaling ingredient (ppm) released by the capsule antiscaling agent was detected by ICP.

[0105] The release rates of microencapsulated scale inhibitors FGJ-1, FGJ-2, FGJ-3, FGJ-4, and FGJ-5 were evaluated using the above test methods. The test results are shown in Table 1.

[0106] Table 1 Release of active ingredients in microencapsulated scale inhibitors

[0107]

[0108] The test data above shows that it takes at least 64 days to fully release the drug components inside the capsule. Furthermore, microcapsules prepared using hexafluoropropylene oxide oligomers (di, tri, tetra, and pentameric) with different degrees of polymerization as wall materials exhibit varying release rates of the drug components. Therefore, microcapsule antiscalants of different thicknesses can be mixed in a certain proportion to meet the requirements of controlled release, depending on the needs of reservoir scaling prevention.

[0109] II. Evaluation of the scale prevention rate of microcapsule scale inhibitors

[0110] Evaluation Method: Referring to Q / SY 17126-2019 "Technical Specification for Corrosion and Scale Inhibitors for Oilfield Water Treatment", the barium sulfate scale inhibition rate of microencapsulated scale inhibitors FGJ-1, FGJ-2, FGJ-3, FGJ-4, and FGJ-5 was tested using the following formula. Wherein, Ba... 2 + 加样 The concentration of barium ions in the test solution containing the added chemical scale inhibitor is given in mg / L. 2+ 空白1 The concentration of barium ions in blank solution 1, mg / L; Ba 2+ 空白2 The concentration of barium ions in blank solution 2 is mg / L;

[0111] V 加样 V represents the volume of EDTA standard solution consumed in titrating the barium ion concentration in the solution after adding the scale inhibitor, expressed in mL. 空白1 The volume of EDTA standard solution consumed (mL) to titrate the barium ion concentration in blank solution 1; V 空白2 The volume of EDTA standard solution consumed (mL) to titrate the barium ion concentration in blank solution 2.

[0112]

[0113] The test results are shown in Table 2:

[0114] Table 2 Scale Inhibition Rate Test Results

[0115]

[0116] Test results show that the barium sulfate scale prevention rate of the microcapsule scale inhibitor provided by this invention is over 84%.

[0117] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A microcapsule scale inhibitor for preventing sulfate scaling in oil wells, characterized in that: The mixture includes a nucleating agent, a polymer wall material, and a polymer reagent, wherein the amounts of the polymer wall material and the nucleating agent are 1.2-1.5 times and 0.8-1.2 times the mass of the raw materials for preparing the polymer reagent, namely maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid, respectively. The polymer reagent is prepared by free radical polymerization of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid under the action of an initiator. The mass ratio of maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is (6-10):(10-17):(1-5):(2.5-5). Maleic anhydride is dissolved in water before participating in the reaction. The amount of water added to 0.1-0.25 mol of maleic anhydride is 200-250 ml. The polymer wall material is a hexafluoropropylene oxide oligomer with a relative molecular weight between 300 and 1000, and its structural formula is: Where n = 2, 3, 4, 15, and R is -COOH, -COOCH3, -COF, or -CONH2.

2. The microcapsule scale inhibitor for preventing sulfate scaling in oil wells according to claim 1, characterized in that: The initiator is ammonium persulfate or potassium persulfate.

3. The microcapsule scale inhibitor for preventing sulfate scaling in oil wells according to claim 1, characterized in that: The nucleating agent is ammonium halide, which is NH4Cl, NH4Br or NH4I.

4. A method for preparing a microcapsule scale inhibitor for preventing sulfate scaling in oil wells according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1) Preparation of polymer reagent: Maleic anhydride, fluorinated acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid are added to a container in a mass ratio of (6-10):(10-17):(1-5):(2.5-5), and then an initiator is added. The mixture is prepared by free radical polymerization at a certain temperature. Step 2) Preparation of microcapsule antiscalant: Using the prescribed amount of hexafluoropropylene oxide oligomer as the wall material, the polymer agent and the prescribed amount of nucleating agent ammonium halide are encapsulated and prepared by supercritical carbon dioxide rapid expansion method.

5. The method for preparing a microcapsule scale inhibitor for preventing sulfate scaling in oil wells according to claim 4, characterized in that, Step 1) The specific process is as follows: Add the prescribed amount of water and maleic anhydride to the reaction vessel, and while stirring, raise the temperature to 60°C. After the maleic anhydride is completely dissolved, add the monomer mixture to the system through a constant pressure dropping funnel. The monomer mixture consists of a uniform mixture of the prescribed amounts of fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. After the addition is complete, add the initiator dropwise. The amount of initiator is 1.5-2.0% of the total mass of maleic anhydride, fluorinated acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. The dropwise addition time is 1-2 hours. After the dropwise addition is complete, maintain the temperature at 60-90°C and continue stirring for 2-6 hours. After concentration and cooling, a white, high-viscosity liquid is obtained, which is the final product.

6. The method for preparing a microcapsule scale inhibitor for preventing sulfate scaling in oil wells according to claim 5, characterized in that, Step 2) The specific process is as follows: After heating the high-pressure reactor to the target temperature, the polymer reagent prepared in step 1), hexafluoropropylene oxide oligomer wall material, and nucleating agent ammonium halide are added to the high-pressure reactor according to the formula. Then, CO2 is introduced into the high-pressure reactor, and the reactor is continuously stirred and CO2 is added to maintain the pressure in the high-pressure reactor at 7.3-10 MPa for 1-3 hours. After that, the pressure relief valve is opened to quickly reduce the pressure. The hexafluoropropylene oxide oligomer in the reactor collides with the polymer reagent suspended on the surface of ammonium halide in the recovery chamber, and uniformly coats the surface of the polymer reagent to obtain a microcapsule antiscalant.

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