Solid corrosion and bacteria inhibition and scale inhibitor for shale gas well and preparation and application thereof

Abstract

The application discloses a solid corrosion and bacteria inhibition and scale inhibitor for shale gas well, which is a solid gel particle with calcium alginate as a skeleton, and contains imidazoline phosphate, corrosion and bacteria inhibition inhibitor and synergist in a mass ratio of (10-15):(10-15):(5-10). The imidazoline phosphate is obtained by esterification of phytic acid and imidazoline, and at least one phosphoric group in the phytic acid is esterified with the amino group of the imidazoline. The corrosion and bacteria inhibition inhibitor is a combination of acetylenic alcohol methyl quaternary ammonium salt and dipentadecyldimethylammonium chloride. The application also discloses a preparation method of the solid corrosion and bacteria inhibition and scale inhibitor. The solid corrosion and bacteria inhibition and scale inhibitor for shale gas well can be added into the gas well annulus, and is settled at a set position to protect the well bore. Once added, the solid corrosion and bacteria inhibition and scale inhibitor can long-term improve the problems of bacterial corrosion on the upper part of the well bore string, corrosion caused by carbon dioxide and hydrogen sulfide acidic gas on the lower part of the well bore string, and fouling and under-deposit corrosion caused by high temperature on the lower part of the well bore string.

Description

Technical Field

[0001] This invention relates to a solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells, as well as its preparation and application. Background Technology

[0002] During shale gas extraction, several factors are involved: first, large amounts of gases such as carbon dioxide and hydrogen sulfide are produced, which can severely corrode the production tubing; second, sulfate-reducing bacteria (SRB) that proliferate in the formation and later cause bacterial corrosion above 1500 meters in the wellbore; and third, as shale gas wells are developed, the fluid produced from the well corrodes the tubing, leading to scaling and blockage. All three of these factors can cause the tubing to perforate, break, or become blocked, resulting in decreased well production efficiency and increased maintenance costs.

[0003] In existing technologies, shale gas wellbore corrosion prevention involves continuously or frequently injecting liquid corrosion inhibitors to maintain the concentration of the agent in the well at a specific value. However, the diffusion range of the liquid corrosion inhibitor in the wellbore is limited, and it cannot form an effective protection for the entire production tubing. This results in high overall construction costs and poor overall performance. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells and its preparation method thereon, which overcomes or at least partially solves the above problems.

[0005] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells provided by this invention are solid particles that can be added through the annulus of the gas well and settle to a set position to protect the oil casing inside the wellbore.

[0006] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells provided by this invention can not only pre-film metals in the gas phase environment of the gas well; it can also significantly reduce the source of bacterial corrosion, changing passive isolation to active sterilization; and it can enhance the corrosion inhibition effect, changing passive scale removal to active scale prevention, forming a comprehensive anti-corrosion technology with a higher corrosion inhibition rate covering the entire wellbore.

[0007] As one aspect of the present invention, a solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is disclosed. The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is a solid gel particle with calcium alginate as its backbone. The solid gel particle contains imidazoline phosphate, a corrosion inhibitor, and a synergist in a mass ratio of (10-15):(10-15):(5-10). The imidazoline phosphate is obtained by esterification of phytic acid and imidazoline, and at least one phosphate group in the phytic acid undergoes esterification with the amino group of the imidazoline. The corrosion inhibitor is a composition of alkynyloxymethyl quaternary ammonium salt and diecryl dimethyl ammonium chloride, wherein the alkynyloxymethyl quaternary ammonium salt is as shown in formula (1).

[0008]

[0009] Where R is a phenyl group.

[0010] In a specific implementation, the synergist is a composition of dodecylphenol polyoxyethylene ether and hexahydrotriazine in a mass ratio of (0-1):(1-1.5).

[0011] In a specific implementation, the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is a solid gel particle with a particle size of 4-6 mm.

[0012] As another aspect of the present invention, a method for preparing a solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is provided, the method comprising:

[0013] (1) A cycloalkanoic acid and a polyethylene polyamine are mixed in a molar ratio of 1:1.05 to 1.2, and xylene is added, wherein the amount of xylene added is 10 to 15% of the sum of the mass of the cycloalkanoic acid and the polyethylene polyamine; the mixture is reacted at a temperature gradient of 120 to 165°C, 180 to 190°C and 210 to 235°C to obtain imidazoline; the temperature is lowered to 120 to 135°C, and a NaOH solution is added, wherein the molar ratio of NaOH to the cycloalkanoic acid is 0.5 to 0.8:1; the mixture is stirred, and phytic acid is added, wherein the molar ratio of phytic acid to the cycloalkanoic acid is 0.2 to 1:1; the temperature is raised to 150 to 165°C, and at least one phosphate group in the phytic acid undergoes an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate;

[0014] (2) Aniline, formaldehyde and methylpentynol in a molar ratio of 1:(2.0~2.2):(1.8~2.0) are mixed and kept at 90~95℃ for 6~8h; the temperature is lowered to 80~85℃ and benzyl chloride is added dropwise, wherein the molar ratio of benzyl chloride to aniline is 0.9~1.05:1; after the addition is completed, the temperature is raised to 95~100℃ to obtain alkynyloxymethyl quaternary ammonium salt; the alkynyloxymethyl quaternary ammonium salt in a mass ratio of (2.0~2.4):1 is mixed with diecryldimethylammonium chloride to obtain a corrosion inhibitor and bactericide.

[0015] (3) Add sodium alginate to 60-75 parts by weight of water and stir until dissolved; add 10-15 parts by weight of the imidazoline phosphate obtained in step (1), 10-15 parts by weight of the corrosion inhibitor and bactericidal inhibitor obtained in step (2) and 5-10 parts by weight of the synergist, stir until dissolved, and obtain a mixed solution.

[0016] (4) The mixed solution obtained in step (3) is transferred to a dropper and added dropwise to a calcium chloride aqueous solution to obtain solid gel particles with calcium alginate as the skeleton.

[0017] In a specific implementation, in step (2), the dripping time of benzyl chloride is controlled at 1.5 to 2 hours.

[0018] In a specific implementation, in step (3), the sodium alginate is 3 to 5 parts by mass.

[0019] In a specific implementation, in step (3), the synergist is a composition of dodecylphenol polyoxyethylene ether and hexahydrotriazine in a mass ratio of (0-1):(1-1.5).

[0020] In a specific implementation, in step (4), the mass ratio of calcium chloride to water in the calcium chloride aqueous solution is (20-30):(500-550).

[0021] In a specific implementation, in step (4), the particle size of the solid gel particles is 4 to 6 mm.

[0022] As another aspect of the present invention, it relates to the application of the above-mentioned solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells in shale gas extraction.

[0023] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells provided by this invention has at least the following beneficial effects:

[0024] (1) The solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells provided by the present invention is a solid gel particle formed with calcium alginate as the skeleton, which has good biocompatibility, biodegradability, controllable release and good biological activity.

[0025] (2) The imidazoline phosphate ester provided by the present invention has good anti-corrosion and scale inhibition performance. The nitrogen atom in the five-membered ring can form a coordinate bond with the empty d orbital of Fe metal, resulting in strong chemical adsorption and forming an adsorption film, which reduces or inhibits the contact between the corrosive medium and the metal body, thereby slowing down the corrosion. The phosphate ester and phosphate ions in the side chain have strong chelating ability and can form complexes with metal ions such as calcium, iron, magnesium, and zinc.

[0026] (3) The corrosion inhibitor and bactericidal inhibitor provided by the present invention includes alkynyloxymethyl quaternary ammonium salt and diecryl dimethyl ammonium chloride. Alynyloxymethyl quaternary ammonium salt contains both O and N active atomic groups, which are easy to generate chemical and physical adsorption on the metal surface. It also contains large π bonds, and the electron cloud is easy to move. It also contains quaternary ammonium cations and halide anions with synergistic effects. When adsorbed on the metal surface, it can form multi-center adsorption with multiple groups adsorbed on the metal surface at the same time. This can greatly improve the adsorption activity on the metal surface and enhance the adsorption capacity. In addition, alkynyloxymethyl quaternary ammonium salt can also form a protective film on the metal surface through precipitation, hydrogen bonding and polymerization, which has a good anti-corrosion effect. Furthermore, alkynyloxymethyl quaternary ammonium salt itself has a certain bactericidal effect. Its positively charged nitrogen can act on the cell nucleus of bacteria and inhibit bacterial growth. In addition, quaternary ammonium salt itself has a certain stripping effect and can kill bacteria growing under the adhesion. In addition, the addition of diecryl dimethyl ammonium chloride enhances its bactericidal effect and has a good inhibitory effect on sulfate-reducing bacteria (SRB), saprophytic bacteria (TGB) and iron bacteria (FB).

[0027] (4) The synergist provided by the present invention is a combination of dodecylphenol polyoxyethylene ether OP-10 and hexahydrotriazine, which increases the dispersion performance of imidazoline phosphate and corrosion inhibitor after dissolution and release, thereby achieving better performance.

[0028] (5) The solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells provided by the present invention is added to the annulus of the shale gas well casing and sinks freely to the bottom of the well. It continuously releases corrosion inhibitor, bactericide and scale inhibitor components through contact with the produced fluid. The effective period of a single addition can be up to 100 days. Detailed Implementation

[0029] The polyethylene polyamine described in this embodiment of the invention is Poly-8, manufactured by Tosoh Corporation of Japan, CAS No.: 68131-73-7, with the structure (CH2CH2NH2)n.

[0030] The CAS number of the cycloalkanoic acid described in this embodiment of the invention is 1338-24-5.

[0031] During their work, the inventors discovered that existing corrosion inhibitors cannot simultaneously address the three factors that cause wellbore corrosion. To achieve good corrosion inhibition of wellbore, multiple corrosion inhibitors need to be used in combination, such as using different inhibitors at the upper and lower parts of the wellbore, which is very unfriendly to downhole operations.

[0032] Through further research and development, the inventors have obtained a solid corrosion inhibitor, bactericide, and scale inhibitor. A single addition can provide long-term relief from bacterial corrosion in the upper part of the wellbore string, corrosion caused by carbon dioxide and hydrogen sulfide acidic gases in the lower part of the wellbore string, and scaling and under-deposit corrosion caused by high temperatures in the lower part.

[0033] Example 1

[0034] Preparation of imidazoline phosphate:

[0035] A cycloalkanoic acid and a polyethylene polyamine in a molar ratio of 1:1.2 were added to a reactor equipped with a reflux condenser. Xylene was added, with the mass of xylene being 10% of the sum of the masses of the cycloalkanoic acid and the polyethylene polyamine. The mixture was kept at 150°C for 3 hours, 180°C for 3 hours, and 220°C for 3 hours to obtain imidazoline. The temperature was lowered to 120°C, and a NaOH solution was added, with a molar ratio of NaOH to cycloalkanoic acid of 0.8:1. The mixture was stirred, and phytic acid was added, with a molar ratio of phytic acid to cycloalkanoic acid of 0.5:1. The temperature was raised to 150°C and kept for 6 hours. At least one phosphate group in the phytic acid underwent an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate.

[0036] Preparation of corrosion-inhibiting and bactericidal inhibitors:

[0037] Aniline, formaldehyde, and methylpentynol in a molar ratio of 1:2:2 were added to a reactor and kept at 90°C for 6 hours. The temperature was then lowered to 80°C, and benzyl chloride was added dropwise. The molar ratio of benzyl chloride to aniline was 1:1, and the addition time was controlled at 1.5 hours. After the addition was completed, the temperature was raised to 95°C and kept at 95°C for 6 hours to obtain alkynyloxymethyl quaternary ammonium salt. The alkynyloxymethyl quaternary ammonium salt was mixed with diecryldimethylammonium chloride at a mass ratio of 2:1 to obtain a corrosion inhibitor and bactericide.

[0038] The reaction equation is as follows:

[0039]

[0040] Where R is (Phenyl)

[0041] Preparation of solid corrosion inhibitors, bactericides, and scale inhibitors for shale gas wells:

[0042] (1) Heat 75 parts by mass of deionized water to 50°C, add 3 parts by mass of sodium alginate, and stir until dissolved; add 10 parts by mass of the above imidazoline phosphate, 10 parts by mass of the above corrosion inhibitor and bactericide, and 5 parts by mass of synergist, and stir until dissolved to obtain a mixed solution; wherein, the synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1.5;

[0043] (2) Add 20 parts by weight of anhydrous calcium chloride to 500 parts by weight of deionized water and stir to obtain an aqueous solution of calcium chloride;

[0044] (3) Transfer the mixed solution obtained in step (1) to a dropper (needle tip inner diameter 4 mm) and add it to the calcium chloride aqueous solution obtained in step (2) to obtain solid gel particles with a particle size of 4-6 mm, which is a solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells.

[0045] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells prepared in this embodiment consists of gel particles with calcium alginate as the backbone. These gel particles contain imidazoline phosphate, a corrosion inhibitor, and a synergist in a mass ratio of 10:10:5. The synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1.5.

[0046] Example 2

[0047] Preparation of imidazoline phosphate:

[0048] A 1:1 molar ratio of naphthenic acid and polyethylene polyamine was added to a reactor equipped with a reflux condenser. Xylene was added, with the mass of xylene being 15% of the sum of the masses of the naphthenic acid and polyethylene polyamine. The mixture was kept at 165°C for 3 hours, 190°C for 3 hours, and 235°C for 3 hours to obtain imidazoline. The temperature was lowered to 135°C, and NaOH solution was added, with a molar ratio of NaOH to naphthenic acid of 0.8:1. The mixture was stirred, and phytic acid was added, with a molar ratio of phytic acid to naphthenic acid of 0.5:1. The temperature was raised to 165°C and kept for 6 hours. At least one phosphate group in the phytic acid underwent an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate.

[0049] Preparation of corrosion-inhibiting and bactericidal inhibitors:

[0050] Aniline, formaldehyde, and methylpentynol in a molar ratio of 1:2:2 were added to a reactor and kept at 95°C for 8 hours. The temperature was then lowered to 85°C, and benzyl chloride was added dropwise. The molar ratio of benzyl chloride to aniline was 1:1, and the addition time was controlled at 2 hours. After the addition was completed, the temperature was raised to 100°C and kept at 6 hours to obtain alkynyloxymethyl quaternary ammonium salt. The alkynyloxymethyl quaternary ammonium salt was mixed with diecryldimethylammonium chloride at a mass ratio of 2:1 to obtain a corrosion inhibitor and bactericide.

[0051] Preparation of solid corrosion inhibitors, bactericides, and scale inhibitors for shale gas wells:

[0052] (1) Heat 60 parts by mass of deionized water to 55°C, add 4 parts by mass of sodium alginate, and stir until dissolved; add 15 parts by mass of the above imidazoline phosphate, 15 parts by mass of the above corrosion inhibitor and bactericide, and 10 parts by mass of synergist, and stir until dissolved to obtain a mixed solution; wherein, the synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1;

[0053] (2) Add 30 parts by weight of anhydrous calcium chloride to 550 parts by weight of deionized water and stir to obtain an aqueous solution of calcium chloride.

[0054] (3) Transfer the mixed solution obtained in step (1) to a dropper (needle tip inner diameter 4 mm) and add it to the calcium chloride aqueous solution obtained in step (2) to obtain solid gel particles with a particle size of 4-6 mm, which is a solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells.

[0055] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells prepared in this embodiment consists of gel particles with calcium alginate as the backbone. These gel particles contain imidazoline phosphate, a corrosion inhibitor, and a synergist in a mass ratio of 15:15:10. The synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1.

[0056] Example 3

[0057] Preparation of imidazoline phosphate:

[0058] A cycloalkanoic acid and a polyethylene polyamine in a molar ratio of 1:1.1 were added to a reactor equipped with a reflux condenser. Xylene was added, with the mass of xylene being 12% of the sum of the masses of the cycloalkanoic acid and the polyethylene polyamine. The mixture was kept at 120°C for 3 hours, 190°C for 3 hours, and 210°C for 3 hours to obtain imidazoline. The temperature was lowered to 125°C, and a NaOH solution was added, with a molar ratio of NaOH to cycloalkanoic acid of 0.5:1. The mixture was stirred, and phytic acid was added, with a molar ratio of phytic acid to cycloalkanoic acid of 0.2:1. The temperature was raised to 155°C and kept for 6 hours. At least one phosphate group in the phytic acid underwent an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate.

[0059] Preparation of corrosion-inhibiting and bactericidal inhibitors:

[0060] Aniline, formaldehyde, and methylpentynol in a molar ratio of 1:2.2:1.8 were added to a reactor and kept at 90°C for 8 hours. The temperature was then lowered to 85°C, and benzyl chloride was added dropwise. The molar ratio of benzyl chloride to aniline was 0.9:1, and the addition time was controlled at 2 hours. After the addition was completed, the temperature was raised to 95°C and kept at 6 hours to obtain alkynyloxymethyl quaternary ammonium salt. The alkynyloxymethyl quaternary ammonium salt was mixed with diecryldimethylammonium chloride at a mass ratio of 2:1 to obtain a corrosion inhibitor and bactericide.

[0061] Preparation of solid corrosion inhibitors, bactericides, and scale inhibitors for shale gas wells:

[0062] (1) Heat 67 parts by mass of deionized water to 50°C, add 5 parts by mass of sodium alginate, and stir until dissolved; add 10 parts by mass of the above imidazoline phosphate, 15 parts by mass of the above corrosion inhibitor and bactericidal inhibitor and 8 parts by mass of synergist, stir until dissolved, and obtain a mixed solution; wherein, the synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1;

[0063] (2) Add 25 parts by weight of anhydrous calcium chloride to 500 parts by weight of deionized water and stir to obtain an aqueous solution of calcium chloride;

[0064] (3) Transfer the mixed solution obtained in step (1) to a dropper (needle tip inner diameter 4 mm) and add it to the calcium chloride aqueous solution obtained in step (2) to obtain solid gel particles with a particle size of 4-6 mm, which is a solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells.

[0065] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells prepared in this embodiment consists of gel particles with calcium alginate as the backbone. These gel particles contain imidazoline phosphate, a corrosion inhibitor, and a synergist in a mass ratio of 10:15:8. The synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1.

[0066] Example 4

[0067] Preparation of imidazoline phosphate:

[0068] A cycloalkanoic acid and a polyethylene polyamine in a molar ratio of 1:1.2 were added to a reactor equipped with a reflux condenser. Xylene was added, with the mass of xylene being 14% of the sum of the masses of the cycloalkanoic acid and the polyethylene polyamine. The mixture was kept at 130°C for 3 hours, 185°C for 3 hours, and 220°C for 3 hours to obtain imidazoline. The temperature was lowered to 130°C, and a NaOH solution was added, with a molar ratio of NaOH to cycloalkanoic acid of 0.5:1. The mixture was stirred, and phytic acid was added, with a molar ratio of phytic acid to cycloalkanoic acid of 0.4:1. The temperature was raised to 155°C and kept for 6 hours. At least one phosphate group in the phytic acid underwent an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate.

[0069] Preparation of corrosion-inhibiting and bactericidal inhibitors:

[0070] Aniline, formaldehyde, and methylpentynol in a molar ratio of 1:2:1.8 were added to a reactor and kept at 90°C for 7 hours. The temperature was then lowered to 85°C, and benzyl chloride was added dropwise. The molar ratio of benzyl chloride to aniline was 1.05:1, and the addition time was controlled at 2 hours. After the addition was completed, the temperature was raised to 100°C and kept at 6 hours to obtain alkynyloxymethyl quaternary ammonium salt. The alkynyloxymethyl quaternary ammonium salt was mixed with diecryldimethylammonium chloride at a mass ratio of 2.4:1 to obtain a corrosion inhibitor and bactericide.

[0071] Preparation of solid corrosion inhibitors, bactericides, and scale inhibitors for shale gas wells:

[0072] (1) Heat 65 parts by mass of deionized water to 50°C, add 4.5 parts by mass of sodium alginate, and stir until dissolved; add 15 parts by mass of the above imidazoline phosphate, 10 parts by mass of the above corrosion inhibitor and bactericide, and 10 parts by mass of synergist, and stir until dissolved to obtain a mixed solution; wherein, the synergist is hexahydrotriazine;

[0073] (2) Add 30 parts by weight of anhydrous calcium chloride to 500 parts by weight of deionized water and stir to obtain an aqueous solution of calcium chloride;

[0074] (3) Transfer the mixed solution obtained in step (1) to a dropper (needle tip inner diameter 4 mm) and add it to the calcium chloride aqueous solution obtained in step (2) to obtain solid gel particles with a particle size of 4-6 mm, which is a solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells.

[0075] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells prepared in this embodiment consists of gel particles with calcium alginate as the backbone. These gel particles contain imidazoline phosphate, a corrosion inhibitor, and a synergist in a mass ratio of 15:10:10. The synergist is hexahydrotriazine.

[0076] Example 5

[0077] Preparation of imidazoline phosphate:

[0078] A cycloalkanoic acid and a polyethylene polyamine in a molar ratio of 1:1.05 were added to a reactor equipped with a reflux condenser. Xylene was added, with the mass of xylene being 12% of the sum of the masses of the cycloalkanoic acid and the polyethylene polyamine. The mixture was kept at 120°C for 3 hours, 190°C for 3 hours, and 210°C for 3 hours to obtain imidazoline. The temperature was lowered to 125°C, and a NaOH solution was added, with a molar ratio of NaOH to cycloalkanoic acid of 0.8:1. The mixture was stirred, and phytic acid was added, with a molar ratio of phytic acid to cycloalkanoic acid of 1:1. The temperature was raised to 155°C and kept for 6 hours. At least one phosphate group in the phytic acid underwent an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate.

[0079] Preparation of corrosion-inhibiting and bactericidal inhibitors:

[0080] Aniline, formaldehyde, and methylpentynol in a molar ratio of 1:2.2:1.8 were added to a reactor and kept at 90°C for 7 hours. The temperature was then lowered to 85°C, and benzyl chloride was added dropwise. The molar ratio of benzyl chloride to aniline was 0.9:1, and the addition time was controlled at 2 hours. After the addition was completed, the temperature was raised to 100°C and kept at 6 hours to obtain alkynyloxymethyl quaternary ammonium salt. The alkynyloxymethyl quaternary ammonium salt was mixed with diecryldimethylammonium chloride at a mass ratio of 2.4:1 to obtain a corrosion inhibitor and bactericide.

[0081] Preparation of solid corrosion inhibitors, bactericides, and scale inhibitors for shale gas wells:

[0082] (1) Heat 65 parts by mass of deionized water to 50°C, add 4 parts by mass of sodium alginate, and stir until dissolved; add 10 parts by mass of the above imidazoline phosphate, 15 parts by mass of the above corrosion inhibitor and bactericidal inhibitor and 8 parts by mass of synergist, stir until dissolved, and obtain a mixed solution; wherein, the synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1;

[0083] (2) Add 20 parts by weight of anhydrous calcium chloride to 500 parts by weight of deionized water and stir to obtain an aqueous solution of calcium chloride;

[0084] (3) Transfer the mixed solution obtained in step (1) to a dropper (needle tip inner diameter 4 mm) and add it to the calcium chloride aqueous solution obtained in step (2) to obtain solid gel particles with a particle size of 4-6 mm, which is a solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells.

[0085] The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells prepared in this embodiment is a solid gel particle with calcium alginate as its backbone. The gel particle contains imidazoline phosphate, a corrosion inhibitor, and a synergist in a mass ratio of 10:15:8. The synergist is composed of dodecylphenol polyoxyethylene ether (OP-10) and hexahydrotriazine in a mass ratio of 1:1.

[0086] Experimental Example 1

[0087] The solid corrosion inhibitors, bactericides, and scale inhibitors for shale gas wells prepared in Examples 1-5 were evaluated for their corrosion inhibition, bactericide, and scale prevention properties, respectively.

[0088] The corrosion inhibition performance was evaluated according to standard SY / T 5273-2014 "Performance Indicators and Evaluation Methods of Corrosion Inhibitors for Oilfield Produced Water Treatment". High-pressure dynamic evaluation was adopted (CO2 partial pressure 1 MPa, total pressure 10 MPa, 300 r / min). The water sample used was field water, and the evaluation temperature was 90℃. The dosage of solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells was 100 ppm. The corrosion rate and corrosion inhibition rate results are shown in Table 1.

[0089] The bactericidal performance was evaluated according to the standard SY / T 5757-2010 "General Technical Conditions for Bactericides in Oilfield Injection Water". The evaluation temperature was 50℃, and the dosage of solid corrosion inhibitor, bactericide and scale inhibitor for shale gas wells was 100ppm. The contents of saprophytic bacteria (TGB), sulfate-reducing bacteria (SRB) and iron bacteria (FB) in the water after sterilization were recorded. The results are shown in Table 2.

[0090] The scale inhibition performance was evaluated according to the standard SY / T 5673-2020 "General Technical Conditions for Scale Inhibitors for Oilfield Use", with an evaluation temperature of 70℃ and a dosage of 50ppm for solid corrosion inhibitors and bactericides used in shale gas wells. The results of the scale inhibition rates of calcium carbonate and calcium sulfate are shown in Table 3.

[0091] Table 1

[0092] Example Corrosion rate, mm / a Corrosion inhibition rate, % blank 0.3150 -- Example 1 0.0592 81.21 Example 2 0.0297 90.57 Example 3 0.0372 88.19 Example 4 0.0443 85.94 Example 5 0.0398 87.37

[0093] Table 2

[0094] Example SRB, cells / mL TGB, per mL FB, per mL blank 600 500 250 Example 1 0.6 0.6 0 Example 2 0 0 0 Example 3 0 0.6 0.5 Example 4 0 0 0 Example 5 0 0 0

[0095] Table 3

[0096] Example <![CDATA[CaCO3,%]]> <![CDATA[CaSO4,%]]> Example 1 81 83 Example 2 92 88 Example 3 75 84 Example 4 90 91 Example 5 85 85

[0097] As shown in Table 1, the corrosion inhibition rate of Examples 1-5 is 81.21%-90.57%, which shows that it has a corrosion inhibition effect.

[0098] Table 2 shows that after sterilization in Example 1, the content of sulfate-reducing bacteria (SRB) in the water was 0.6 CFU / mL, while after sterilization in Examples 2-5, the content of sulfate-reducing bacteria (SRB) in the water was 0. After sterilization in Examples 1-5, the content of saprophytic bacteria (TGB) in the water was 0-0.6 CFU / mL, and the content of iron bacteria (FB) in the water was 0-0.5 CFU / mL. Examples 1-5 showed sterilization effects, with Examples 2-5 exhibiting better sterilization effects.

[0099] As shown in Table 3, the scale inhibition rate of CaCO3 in Example 3 was 75%, while the scale inhibition rates of CaCO3 in Examples 1-2 and 4-5 ranged from 81% to 92%. Examples 1-5 exhibited scale inhibition effects, with Examples 1-2 and 4-5 showing better scale inhibition effects. As shown in Table 1-3, Examples 1-5 all exhibited corrosion inhibition, bactericidal, and scale inhibition effects, with Examples 2, 4, and 5 showing even better corrosion inhibition, bactericidal, and scale inhibition effects.

[0100] Experiment Example 2

[0101] Experiment 2 is a field application of the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells in Example 2: The agent was applied in three shale gas wells (well numbers 1#, 2#, and 3#). All three wells experienced corrosion problems caused by CO2 and trace amounts of H2S produced by sulfate-reducing bacteria. Furthermore, the deep production zones, high temperatures, and susceptibility to scaling led to blockage of production channels and frequent well operations. On November 4, 2023, the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells in Example 2 was applied via air injection through the casing annulus. The corrosion rates before and after application were recorded (see Table 4). The contents of sulfate-reducing bacteria (SRB), saprophytic bacteria (TGB), and iron bacteria (FB) before and after application were recorded (see Table 5). The wellhead calcium ion content before and after application was recorded (see Table 6).

[0102] On November 4, 2023, three shale gas wells (well numbers 1#, 2#, and 3#) were injected with the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells (Example 2) via the casing annulus. The dosage is shown in Table 7. The residual concentration and corrosion rate of the corrosion inhibitor, bactericide, and scale inhibitor in the wellhead produced fluid were recorded on December 1, 2023, January 2, 2024, February 1, 2024, and February 5, 2024, respectively, to determine the shelf life of the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells. The results are shown in Table 7. The criteria for determining the shelf life of the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells were: a residual concentration of the corrosion inhibitor, bactericide, and scale inhibitor in the wellhead produced fluid below 10 ppm and a corrosion rate above 0.076 mm / a, indicating that the agent had been largely released.

[0103] Table 4

[0104] hashtag Corrosion rate before implementation, mm / a Corrosion rate after implementation, mm / a 1# 0.4329 0.0371 2# 0.6654 0.0459 3# 0.3749 0.0324

[0105] Table 5

[0106]

[0107] Table 6

[0108] hashtag <![CDATA[Ca content before implementation, mg / L]]> 2+ Content, mg / L]]> <![CDATA[Ca content after implementation, mg / L]]> 2+ Content, mg / L]]> 1# 120 472 2# 920 4810 3# 204 1212

[0109] Table 7

[0110]

[0111] As shown in Table 4-6:

[0112] The corrosion rate before implementation was 0.3749-0.6654 mm / a, and the corrosion rate after implementation was 0.0324-0.0459 mm / a. The corrosion rate decreased significantly, and the corrosion of the wellbore was effectively suppressed.

[0113] Before implementation, the sulfate-reducing bacteria (SRB) content was 250-600 CFU / mL, and after implementation, it was 0 CFU / mL; before implementation, the saprophytic bacteria (TGB) content was 250-600 CFU / mL, and after implementation, it was 0 CFU / mL; before implementation, the iron bacteria (FB) content was 60-250 CFU / mL, and after implementation, it was 0-0.6 CFU / mL; the bacterial content decreased significantly.

[0114] After implementation #1, the calcium ion content at the wellhead increased from 120 mg / L to 472 mg / L; after implementation #2, the calcium ion content at the wellhead increased from 920 mg / L to 4810 mg / L; and after implementation #3, the calcium ion content at the wellhead increased from 204 mg / L to 1212 mg / L. The significant increase in calcium ion content indicates that scaling inside the wellbore has been effectively suppressed.

[0115] As shown in Table 7, the effective period of the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells after a single application is >103 days for No. 1, >103 days for No. 2, and 89 days for No. 3. The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells provided by this invention is added to the annulus of the shale gas well casing, allowing it to settle freely to the bottom of the well. Through contact with the produced fluid, it continuously releases corrosion-inhibiting, bactericidal, and scale-inhibiting components, achieving an effective period of 89–103 days after a single application.

Claims

1. A solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells, characterized in that, The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is a solid gel particle with calcium alginate as its backbone. The solid gel particle contains imidazoline phosphate, corrosion inhibitor, and synergist in a mass ratio of (10-15):(10-15):(5-10). The imidazoline phosphate is obtained by esterification of phytic acid and imidazoline, and at least one phosphate group in the phytic acid is esterified with the amino group of the imidazoline. The corrosion inhibitor is a composition of alkynyloxymethyl quaternary ammonium salt and diecryl dimethyl ammonium chloride. The alkynyloxymethyl quaternary ammonium salt is shown in formula (1). Where R is a phenyl group.

2. The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells according to claim 1, characterized in that, The synergist is a composition of dodecylphenol polyoxyethylene ether and hexahydrotriazine in a mass ratio of (0-1):(1-1.5).

3. The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells according to claim 1, characterized in that, The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is a solid gel particle with a particle size of 4-6 mm.

4. A method for preparing a solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells, characterized in that, The method includes: (1) A cycloalkanoic acid and a polyethylene polyamine are mixed in a molar ratio of 1:1.05 to 1.2, and xylene is added, wherein the amount of xylene added is 10 to 15% of the sum of the mass of the cycloalkanoic acid and the polyethylene polyamine; the mixture is reacted at a temperature gradient of 120 to 165°C, 180 to 190°C and 210 to 235°C to obtain imidazoline; the temperature is lowered to 120 to 135°C, and a NaOH solution is added, wherein the molar ratio of NaOH to the cycloalkanoic acid is 0.5 to 0.8:1; the mixture is stirred, and phytic acid is added, wherein the molar ratio of phytic acid to the cycloalkanoic acid is 0.2 to 1:1; the temperature is raised to 150 to 165°C, and at least one phosphate group in the phytic acid undergoes an esterification reaction with the amino group of the imidazoline to obtain imidazoline phosphate; (2) Aniline, formaldehyde and methylpentynol in a molar ratio of 1:(2.0~2.2):(1.8~2.0) are mixed and kept at 90~95℃ for 6~8h; the temperature is lowered to 80~85℃ and benzyl chloride is added dropwise, wherein the molar ratio of benzyl chloride to aniline is 0.9~1.05:1; after the addition is completed, the temperature is raised to 95~100℃ to react and obtain alkynyloxymethyl quaternary ammonium salt; the alkynyloxymethyl quaternary ammonium salt in a mass ratio of (2.0~2.4):1 is mixed with diecryldimethylammonium chloride to obtain a corrosion inhibitor and bactericide. (3) Add sodium alginate to 60-75 parts by weight of water and stir until dissolved; add 10-15 parts by weight of the imidazoline phosphate obtained in step (1), 10-15 parts by weight of the corrosion inhibitor and bactericidal inhibitor obtained in step (2) and 5-10 parts by weight of the synergist, stir until dissolved, and obtain a mixed solution. (4) The mixed solution obtained in step (3) is transferred to a dropper and added dropwise to a calcium chloride aqueous solution to obtain solid gel particles with calcium alginate as the skeleton.

5. The method according to claim 4, characterized in that, In step (2), the dripping time of benzyl chloride is controlled at 1.5 to 2 hours.

6. The method according to claim 4, characterized in that, In step (3), the sodium alginate is 3 to 5 parts by weight.

7. The method according to claim 4, characterized in that, In step (3), the synergist is a composition of dodecylphenol polyoxyethylene ether and hexahydrotriazine in a mass ratio of (0-1):(1-1.5).

8. The method according to claim 4, characterized in that, In step (4), the mass ratio of calcium chloride to water in the calcium chloride aqueous solution is (20-30):(500-550).

9. The method according to claim 4, characterized in that, In step (4), the particle size of the solid gel particles is 4 to 6 mm.

10. The application of solid corrosion inhibitors, bactericides, and scale inhibitors in shale gas well extraction, characterized in that... The solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells is the solid corrosion inhibitor, bactericide, and scale inhibitor for shale gas wells as described in any of claims 1-3 or the solid corrosion inhibitor, bactericide, and scale inhibitor prepared by any of the methods described in claims 4-9.

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