A capsule-coating material with chelating ability, and a preparation method and application thereof

Abstract

The application discloses a capsule coating material with chelating capacity and a preparation method and application thereof. The capsule coating material is composed of the following raw materials in parts by weight: 25-35 parts of p-aminostyrene, 55-65 parts of butyl acrylate, 5-15 parts of acrylic acid, 0.10-0.15 parts of a pH regulator, 36-50 parts of an amino protecting agent, 0.2-0.4 parts of OP-10, 0.2-0.4 parts of Span 60, 8-12 parts of an initiator, 0.1 part of trimethylsilyl trifluoromethanesulfonate and 80-100 parts of deionized water, and 80 parts of dioxane. The capsule coating material has strong chelating capacity and can chelate various metal ions in water; meanwhile, the capsule coating material has certain acid resistance and can be used for coating solid powders such as ammonium sulfate, enzyme gel breaker and potassium carbonate, can be used as a coating material of an additive in an acidification system and can be used as a coating material of a fracturing additive.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, specifically relating to a chelating capsule material, its preparation method, and its application. Background Technology

[0002] Encapsulation technology enables the slow release of pharmaceutical agents and has been widely applied in industrial fields such as pesticides, coatings, food, biological products, adhesives, cosmetics, catalysts, pharmaceuticals, and self-healing materials, achieving significant economic benefits and attracting widespread attention from various sectors.

[0003] In recent years, capsule technology has rapidly entered the field of oil and gas well development, enabling the slow release of reagents under special conditions. For example, capsule-encapsulated breaker agents used in fracturing avoid direct contact between the breaker and the fracturing fluid, significantly reducing the initial viscosity reduction caused by the breaker and resulting in better sand-suspending properties. The slow release of the breaker by the capsule allows for rapid breaker release in the later stages of fracturing. Another example is the use of capsule-encapsulated gas pressurizing materials during acidizing to accelerate flowback, preventing rapid surface reaction of the gas pressurizing materials.

[0004] Current capsules achieve slow drug release, but this is their only function, making them limited and unable to meet the needs of multifunctional applications under certain conditions. For example, during acidification, the acid reacts with the formation and tubing to produce various metal ions. If these ions are not promptly flushed back into the formation, they can easily form secondary precipitates, clogging micropores and significantly reducing the acidification effect. Therefore, new requirements are placed on the chelating ability of capsules. Providing capsules with chelating capabilities would be of great significance. Summary of the Invention

[0005] In view of the differences in existing technologies, the present invention provides a capsule-encapsulating material with chelating ability, its preparation method and application. The capsule-encapsulating material can slowly release the capsule core and has good chelating ability, and can be used in fracturing fluid or acidizing fluid.

[0006] A chelating capsule encapsulation material is composed of the following raw materials in parts by weight: 25-35 parts of p-aminostyrene, 55-65 parts of butyl acrylate, 5-15 parts of acrylic acid, 0.10-0.15 parts of pH adjuster, 36-50 parts of amino protectant, 0.2-0.4 parts of OP-10, 0.2-0.4 parts of Span 60, 8-12 parts of initiator, 0.1 parts of trimethylsilyl trifluoromethanesulfonate, 80-100 parts of deionized water, and 80 parts of dioxane.

[0007] Preferably, the amino protecting agent is di-tert-butyl dicarbonate, and the pH adjusting agent is sodium hydroxide.

[0008] Preferably, the initiator is a 4-6 wt% aqueous solution of ammonium persulfate.

[0009] The preparation method of the capsule encapsulation material with chelating ability is as follows: (1) Take dioxane and a portion of deionized water, add p-aminostyrene, then add pH adjuster and amino protectant in sequence, react for 1-1.5 h to obtain Boc protected amine liquid; (2) Take a portion of butyl acrylate and mix it with OP-10, Span 60 and the remaining deionized water. Purge with nitrogen for 15-20 min, stir, heat to 70±2℃, add an initiator, and then add a mixture of acrylic acid and the remaining butyl acrylate dropwise while stirring. After the addition is complete, add the Boc protective amine liquid dropwise. After the addition is complete, react for 1-1.5 h, then cool to room temperature, add trimethylsilyl trifluoromethanesulfonate, and react for 2-2.5 h to obtain an acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsion, which is the capsule encapsulation material.

[0010] The application of the capsule encapsulation material in the capsule, which is used in the field of oil and gas field technology.

[0011] Preferably, the capsules are prepared using the Wurster fluidized bed method, as detailed below: (a) Add the capsule core to the coating chamber, introduce air and blow it to heat it, control the temperature of the coating chamber, and adjust the air speed to make the capsule core suspend in the coating chamber; (ii) The capsule encapsulation material is atomized by a spraying device and sprayed onto the suspended capsule core, dried into a film, and this step is repeated until the capsule encapsulation material is sprayed. The capsule is then sieved to obtain the capsule.

[0012] Preferably, the mass ratio of the capsule core to the capsule encapsulation material is 5:4; the temperature of the coating chamber is 30-80℃.

[0013] Preferably, the capsule is used in fracturing fluid, and the capsule core is a rupture agent.

[0014] Preferably, the de-gelling agent is ammonium persulfate or an enzyme de-gelling agent.

[0015] Preferably, the capsule is used in an acidification system, and the capsule core is potassium carbonate.

[0016] In this invention, acrylic acid, butyl acrylate, and p-aminostyrene are the main reaction raw materials for the capsule encapsulation material. Sodium hydroxide is used as a pH adjuster for amino protection, di-tert-butyl dicarbonate is used as an amino protectant, and a mixture of dioxane and water is used as the aqueous reaction system for the protection of tert-butyloxycarbonyl (Boc) and amino groups in p-aminostyrene. OP-10 and Span 60 are used as emulsifiers to provide an emulsifying environment for the polymerization reaction, and trimethylsilyltrifluoromethanesulfonate is used as a Boc removal reagent.

[0017] In the synthesis process of the capsule encapsulation material, amino protection is carried out by di-tert-butyl dicarbonate under alkaline conditions and a mixture of dioxane and water, resulting in minimal interference from byproducts and easy removal. Trimethylsilyl trifluoromethanesulfonate is used in the deprotection process, which is mild and neutral, achieving efficient deprotection.

[0018] Advantages of this invention: (1) The capsule encapsulation material is an acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsion, wherein the carboxyl group of acrylic acid and the amino group of p-aminostyrene form a synergistic coordination site, which can simultaneously bind multiple metal ions to form a stable five-membered ring or six-membered ring chelate, so that the capsule encapsulation material has a strong chelating ability and can chelate multiple metal ions in water. (2) In geological environments, the capsule-encapsulated material swells and ruptures, and the copolymer film after swelling and rupture still has a strong chelating ability; (3) The capsule encapsulation material has a certain acid resistance and can encapsulate solid powders such as ammonium sulfate, enzyme de-gelling agent, and potassium carbonate. It can be used as an encapsulation material for additives in acidification systems and as an encapsulation material for fracturing additives. Detailed Implementation

[0019] Example 1 1. A chelating capsule encapsulation material, comprising the following raw materials in parts by weight: 30 parts of p-aminostyrene, 60 parts of butyl acrylate, 10 parts of acrylic acid, 0.10 parts of sodium hydroxide, 43 parts of di-tert-butyl dicarbonate, 0.3 parts of OP-10, 0.3 parts of Span 60, 10 parts of 5wt% ammonium persulfate aqueous solution, 0.1 parts of trimethylsilyl trifluoromethanesulfonate, 90 parts of deionized water, and 80 parts of dioxane; The preparation method of the capsule encapsulation material is as follows: (1) Take a portion of deionized water and dioxane and add p-aminostyrene to it. Then add sodium hydroxide as a pH adjuster and di-tert-butyl dicarbonate as an amino protectant in sequence. React for 1 hour to obtain Boc protected amine liquid. (2) Take one-third of the weight of butyl acrylate and mix it with OP-10, Span 60 and the remaining deionized water. Purge with nitrogen for 15 minutes and stir rapidly to form a uniform emulsion. Heat to 70±2℃ and add an initiator ammonium persulfate aqueous solution. While stirring, add a mixture of acrylic acid and the remaining butyl acrylate dropwise. After the addition is complete, add the Boc protective amine liquid dropwise. React for 1 hour after the addition is complete, then cool to room temperature and add trimethylsilyl trifluoromethanesulfonate. React for 2 hours to obtain an acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsion, which is the capsule encapsulation material.

[0020] Example 2 A chelating capsule encapsulation material is composed of the following raw materials in parts by weight: 25 parts of p-aminostyrene, 60 parts of butyl acrylate, 15 parts of acrylic acid, 0.10 parts of sodium hydroxide, 36 parts of di-tert-butyl dicarbonate, 0.25 parts of OP-10, 0.35 parts of Span 60, 9 parts of 5 wt% ammonium persulfate aqueous solution, 0.1 parts of trimethylsilyl trifluoromethanesulfonate, 90 parts of deionized water, and 80 parts of dioxane. The preparation method of the capsule encapsulation material is the same as that in Example 1.

[0021] Example 3 A chelating capsule encapsulation material is composed of the following raw materials in parts by weight: 30 parts of p-aminostyrene, 55 parts of butyl acrylate, 15 parts of acrylic acid, 0.12 parts of sodium hydroxide, 43 parts of di-tert-butyl dicarbonate, 0.25 parts of OP-10, 0.30 parts of Span 60, 11 parts of 5 wt% ammonium persulfate aqueous solution, 0.1 parts of trimethylsilyl trifluoromethanesulfonate, 90 parts of deionized water, and 80 parts of dioxane. The preparation method of the capsule encapsulation material is the same as that in Example 1.

[0022] Example 4 1. A chelating capsule encapsulation material, comprising the following raw materials in parts by weight: 35 parts p-aminostyrene, 65 parts butyl acrylate, 5 parts acrylic acid, 0.15 parts sodium hydroxide, 50 parts di-tert-butyl dicarbonate, 0.2 parts OP-10, 0.4 parts Span 60, 8 parts 6wt% ammonium persulfate aqueous solution, 0.1 parts trimethylsilyl trifluoromethanesulfonate, 80 parts deionized water, and 80 parts dioxane; The preparation method of the capsule encapsulation material is as follows: (1) Take a portion of deionized water and dioxane and add p-aminostyrene to it. Then add sodium hydroxide as a pH adjuster and di-tert-butyl dicarbonate as an amino protectant in sequence. React for 1.5 h to obtain Boc protected amine liquid. (2) Take one-third of the weight of butyl acrylate and mix it with OP-10, Span 60 and the remaining deionized water. Purge with nitrogen for 20 min and stir rapidly to form a uniform emulsion. Heat to 70±2℃ and add ammonium persulfate aqueous solution as an initiator. While stirring, add the mixture of acrylic acid and the remaining butyl acrylate dropwise. After the addition is complete, add the Boc protective amine liquid dropwise. React for 1.5 h after the addition is complete, then cool to room temperature and add trimethylsilyl trifluoromethanesulfonate. React for 2.5 h to obtain acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsion, which is the capsule encapsulation material.

[0023] Example 5 A chelating capsule encapsulation material is composed of the following raw materials in parts by weight: 35 parts of p-aminostyrene, 55 parts of butyl acrylate, 10 parts of acrylic acid, 0.15 parts of sodium hydroxide, 50 parts of di-tert-butyl dicarbonate, 0.4 parts of OP-10, 0.2 parts of Span 60, 12 parts of 4 wt% ammonium persulfate aqueous solution, 0.1 parts of trimethylsilyl trifluoromethanesulfonate, 100 parts of deionized water, and 80 parts of dioxane. The preparation method of the capsule encapsulation material is the same as that in Example 1.

[0024] Example 6 A method for preparing a capsule includes the following steps: (a) Add 5.0 parts of potassium carbonate with a particle size of 0.5-2.0 mm as the core to the coating chamber, introduce air and heat it, control the temperature of the coating chamber to 70±2℃, and adjust the air speed to make the core suspend in the coating chamber; (ii) Take 4.0 parts of the capsule encapsulation material described in Example 1, atomize it through a spraying device and spray it onto the suspended capsule core. Maintain the spraying speed at 40g / min, dry it into a film, and repeat this step until the capsule encapsulation material is sprayed. Then, sieve it to obtain the capsule.

[0025] Example 7 A method for preparing a capsule includes the following steps: (a) Add 5.0 parts of ammonium persulfate with a particle size of 0.5-2.0 mm as the core to the coating chamber, introduce air and heat it by blowing air, control the temperature of the coating chamber to 40±2℃, and adjust the air speed to make the core suspend in the coating chamber; (ii) Take 4.0 parts of the capsule encapsulation material described in Example 2, atomize it through a spraying device and spray it onto the suspended capsule core. Maintain the spraying speed at 30g / min, dry it into a film, and repeat this step until the capsule encapsulation material is sprayed. Then sieve it to obtain the capsule.

[0026] Example 8 A method for preparing a capsule includes the following steps: (i) Add 5.0 parts of enzyme de-gelling agent as the capsule core to the coating chamber, introduce air and heat it, control the temperature of the coating chamber to 35±2℃, adjust the air speed to make the capsule core suspend in the coating chamber; the enzyme de-gelling agent used is SUN-Y600 enzyme de-gelling agent produced by Shandong Dongying Shengshi Petroleum Technology Co., Ltd. (ii) Take 4.0 parts of the capsule encapsulation material described in Example 2, atomize it through a spraying device and spray it onto the suspended capsule core. Maintain the spraying speed at 25g / min, dry it into a film, and repeat this step until the capsule encapsulation material is sprayed. Then sieve it to obtain the capsule.

[0027] Performance testing 1. Chelation capacity test To verify the chelating ability of the capsule encapsulation material, the acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsions prepared in Examples 1-3 were formulated into a 1% aqueous solution. The ability to stabilize iron ions was determined according to the provisions of SY / T 6571, and the scale inhibition rate of calcium carbonate was determined according to the provisions of GB / T 16632-2008. The experimental results are shown in Table 1. To verify the chelating ability of the capsules, the swelling and rupture process of the capsules was simulated by artificial grinding, and a 1wt% aqueous solution was prepared. The ability to stabilize iron ions was determined according to the provisions of SY / T 6571, and the scale inhibition rate of calcium carbonate was determined according to the provisions of GB / T 16632-2008. The experimental results are shown in Table 2. Table 1. Results of Chelation Ability Test of Capsule Encapsulation Materials Table 2. Results of capsule chelation capacity test As shown in Tables 1 and 2, the synthesized capsule encapsulation material, the unground capsules, and the ground capsules all possess certain abilities to stabilize iron ions and inhibit calcium carbonate scale buildup. The chelating ability of the unground capsules is greater than that of the encapsulation material, which may be due to the polymer drying and concentration and further polymerization during capsule preparation. After the capsules are ground, i.e., after simulating capsule swelling and rupture, the ability to stabilize iron ions and inhibit calcium carbonate scale buildup are further enhanced.

[0028] 2. Capsule encapsulation rate detection To test the capsule encapsulation rate, Examples 6 and 7 were selected, and the following experiments were conducted respectively: (a) Take 9g of the capsule described in Example 6 (of which the capsule core contains approximately 5g of potassium carbonate) and dissolve it in 100mL of water. After stirring for 3 minutes, take a water sample and determine the carbonate ion concentration according to the method in national standard GB / T 11925. Convert the concentration to the mass of potassium carbonate using the following formula: , Calculate the capsule encapsulation rate; (ii) Take 9g of the capsules described in Example 7 (approximately 5g of ammonium persulfate core) and dissolve them in 100mL of water. Stir for 1 minute, then take a water sample and determine the ammonium persulfate content according to the method in national standard GB / T 23939-2009. Convert the content to the mass of ammonium persulfate using the following formula: , Calculate the capsule encapsulation rate; The results are shown in Table 3; Table 3 Package Rate Detection Results As shown in Table 3, the capsule encapsulation material provided by the present invention has a high capsule encapsulation rate after being prepared into capsules. The encapsulation rates of Examples 6-7 are all greater than 98%, which can meet the needs of field use.

[0029] 3. Suitability testing of the capsule in fracturing fluid To verify the slow release capability of the capsules in fracturing fluid, using guar gum fracturing fluid as an example, 0.3 wt% hydroxypropyl guar gum was prepared. After sufficient swelling, 0.01 wt% capsules (Example 7 or Example 8) and 0.2 wt% boron crosslinking agent were added under stirring. The mixture was cured at a certain temperature, and the viscosity of the fracturing fluid at different times was tested. The experimental results are shown in Table 4. Table 4. Viscosity of the gel breaking solution at different times (MPa·s) As shown in Table 4, the viscosity of the fracturing fluid system was above 290 MPa·s before 90 min, gel breaking began at 120 min, and the viscosity dropped below 5 MPa·s at 180 min, achieving complete gel breaking. The capsule did not affect the initial viscosity of the fracturing fluid and could achieve slow release.

[0030] 4. Suitability testing of capsules in acidification systems To verify the suitability of the capsules described in Example 6 in acidic solutions, a foaming acid system was used as an example. The foaming acid system is as follows (by weight, 100%): 20% hydrochloric acid + 1% foaming agent (dodecyl dihydroxyethyl ammonium oxide: tetradecyl dihydroxyethyl betaine: dodecyl hydroxypropyl phosphate betaine = 1:1:1) + 1.2% thickener (thickener FS300 from Beijing Xitao Technology Development Co., Ltd.) + 1.8% corrosion inhibitor Schiff base pyridine quaternary ammonium salt + 0.2% fluorocarbon surfactant (sodium perfluorononenoxybenzenesulfonate) + 2.0 % Capsule 1 + 1.0% chelating agent hydroxyethylidene diphosphate, the remainder is water; the gas is CO2; first, hydrochloric acid and water are stirred and mixed evenly, then corrosion inhibitor, fluorocarbon surfactant, capsule, chelating agent are added, the stirring speed is controlled below 800 rpm, then foaming agent is added, and finally thickener is added. After stirring evenly, CO2 gas is introduced until all foam is generated, thus obtaining a strong backflow foam acid system; among which, Schiff base pyridine quaternary ammonium salt is prepared by the method disclosed in "Research on high temperature and high concentration hydrochloric acid Schiff base pyridine quaternary ammonium salt corrosion inhibitor" (Li Junli et al., Surface Technology, 2021, 50 (09): 303-310); According to SY / T 5107, a six-speed rotational viscometer was used at a rotational speed of 100 r / min and a shear rate of 170 s⁻¹. -1 The viscosity of the foam acid system was determined. 200 mL of the strong backflow foam acid system was taken, kept at 90℃ for half an hour, stirred at 5000 rpm for 1 minute, and quickly poured into a 500 mL graduated cylinder. The foam height was recorded; this foam height is the foam volume. Timing was started, and the time until the foam volume decreased to half of the original foam height was the foam half-life. The corrosion rate of the foam acid system at 90℃ was determined using the hanging plate method. A standard marble block was taken, and the dissolution reaction time was measured at 90℃. The dissolution rate and reaction rate were calculated and compared with hydrochloric acid of the same concentration to calculate the relative slow rate. The surface tension and interfacial tension of the residual acid remaining after the foam acid system reacted with the standard marble block were tested according to the specifications in SY / T 5370. Low-permeability cores from the Mawu layer of well Yan 1283 and well Yan 1365-3 in Zhidan, Shaanxi Province, were taken, and the permeability improvement rate of the cores after acid treatment was tested. The ground capsules were mixed with a chelating agent to prepare an aqueous solution of 2.0% capsules + 1.0% chelating agent. The chelating and scale inhibition capabilities of the foam acid system were evaluated based on the chelating and scale inhibition capabilities of this aqueous solution. The stabilizing iron ion capacity of the aqueous solution was determined according to SY / T 6571. The calcium carbonate scale inhibition rate of the aqueous solution was determined according to GB / T 16632-2008. The test results are as follows: The foam acid system with the capsules described in Example 6 exhibited excellent overall performance and did not produce any adverse effects; viscosity was 480 mPa·s, foaming volume was 560 mL, foam half-life was 70 min, iron ion stabilization capacity was 691439 mg / L, calcium carbonate scale inhibition rate was 99.4%, and corrosion rate was 1.72 g / (m³). 2 The dissolution reaction time was 8.5 h, and the reaction rate was 1459 g / (m³). 2 (·h), relative slow rate 94.31%, residual acid surface tension 20.1mN / m, residual acid interfacial tension 0.001mN / m, permeability improvement rate 2158%.

[0031] The aforementioned foam acid system was applied in a gas well in northern Shaanxi. The acidizing operation proceeded smoothly, with an acid flowback rate of 95.6%. Production increased significantly after acidizing, with daily gas production increasing by 43.6%. One month later, daily gas production still increased by 35.4%, demonstrating a clear production enhancement effect.

Claims

1. A capsule encapsulation material with chelating ability, characterized in that: It is made from the following raw materials in parts by weight: 25-35 parts of p-aminostyrene, 55-65 parts of butyl acrylate, 5-15 parts of acrylic acid, 0.10-0.15 parts of pH adjuster, 36-50 parts of amino protectant, 0.2-0.4 parts of OP-10, 0.2-0.4 parts of Span 60, 8-12 parts of initiator, 0.1 parts of trimethylsilyl trifluoromethanesulfonate, 80-100 parts of deionized water, and 80 parts of dioxane; The capsule encapsulation material is prepared by the following method: (1) Take dioxane and a portion of deionized water, add p-aminostyrene, then add pH adjuster and amino protectant in sequence, react for 1-1.5 h to obtain Boc protected amine liquid; (2) Take a portion of butyl acrylate and mix it with OP-10, Span 60 and the remaining deionized water. Purge with nitrogen for 15-20 min, stir, heat to 70±2℃, add an initiator, and then add a mixture of acrylic acid and the remaining butyl acrylate dropwise while stirring. After the addition is complete, add the Boc protective amine liquid dropwise. After the addition is complete, react for 1-1.5 h, then cool to room temperature, add trimethylsilyl trifluoromethanesulfonate, and react for 2-2.5 h to obtain an acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsion, which is the capsule encapsulation material.

2. The capsule encapsulation material with chelating ability according to claim 1, characterized in that: The amino protecting agent is di-tert-butyl dicarbonate, and the pH adjusting agent is sodium hydroxide.

3. The capsule encapsulation material with chelating ability according to claim 1, characterized in that: The initiator is a 4-6 wt% aqueous solution of ammonium persulfate.

4. The method for preparing a capsule encapsulation material with chelating ability as described in claim 1, characterized in that: Specifically as follows: (1) Take dioxane and a portion of deionized water, add p-aminostyrene, then add pH adjuster and amino protectant in sequence, react for 1-1.5 h to obtain Boc protected amine liquid; (2) Take a portion of butyl acrylate and mix it with OP-10, Span 60 and the remaining deionized water. Purge with nitrogen for 15-20 min, stir, heat to 70±2℃, add an initiator, and then add a mixture of acrylic acid and the remaining butyl acrylate dropwise while stirring. After the addition is complete, add the Boc protective amine liquid dropwise. After the addition is complete, react for 1-1.5 h, then cool to room temperature, add trimethylsilyl trifluoromethanesulfonate, and react for 2-2.5 h to obtain an acrylic acid-p-aminostyrene-butyl acrylate copolymer emulsion, which is the capsule encapsulation material.

5. The application of the capsule encapsulation material according to claim 1 in a capsule, characterized in that: The capsule is used in the field of oil and gas field technology.

6. The application according to claim 5, characterized in that: The capsules are prepared using the Wurster fluidized bed method, as detailed below: (a) Add the capsule core to the coating chamber, introduce air and blow it to heat it, control the temperature of the coating chamber, and adjust the air speed to make the capsule core suspend in the coating chamber; (ii) The capsule encapsulation material is atomized by a spraying device and sprayed onto the suspended capsule core, dried into a film, and this step is repeated until the capsule encapsulation material is sprayed. The capsule is then sieved to obtain the capsule.

7. The application according to claim 6, characterized in that: The mass ratio of the capsule core to the capsule encapsulation material is 5:4; the temperature of the coating chamber is 30-80℃.

8. The application according to claim 6, characterized in that: The capsule is used in fracturing fluid, and the capsule core is a rupture agent.

9. The application according to claim 8, characterized in that: The de-gluing agent is ammonium persulfate or an enzyme de-gluing agent.

10. The application according to claim 6, characterized in that: The capsule is used in an acidification system, and the capsule core is potassium carbonate.

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