Slow-dissolving type solid corrosion inhibitor dropping pill

Abstract

The invention relates to a slow-dissolving type solid corrosion inhibitor dropping pill, and belongs to the field of solid corrosion inhibitors. The slow-dissolving type solid corrosion inhibitor dropping pill is composed of a dropping pill inner core and a coating, the dropping pill inner core is composed of the following components in parts by mass: 40-45 parts of dialkyl imidazoline quaternary ammonium salt, 54-55 parts of an adhesive and 1-5 parts of a weighting agent, and the material of the coating is an organosilicon polyacrylate copolymer. The diameter of the corrosion inhibitor can reach below 3mm, and the corrosion inhibitor can be used for addition of small cased wells. And a film formed by the corrosion inhibitor disclosed by the invention is relatively good in temperature resistance and stability, can isolate a corrosion medium from the metal pipe in a long-acting manner, can quickly reach the bottom of the well, and is not easy to adhere and hang on the wall.

Description

Technical Field

[0001] This invention relates to a slow-dissolving solid corrosion inhibitor pellet, belonging to the field of solid corrosion inhibitors. Background Technology

[0002] As oilfields enter the mid-to-late stages of production, they face increasingly harsh environments, with most wells having water cuts exceeding 90%. Treating produced water and reinjecting it underground achieves wastewater recycling, improving oil recovery rates while effectively protecting the environment. However, oilfield wastewater is complex, a mixture primarily composed of water, but also including solid impurities, suspended oil particles, dissolved gases, salts, and some organic matter, leading to corrosion and scaling of grounding pipelines. Currently, the most common oil recovery technology is CO2 recovery, which uses carbon dioxide flooding or CO2 huff and puff to enhance oil recovery. This technology is widely used in many oilfields across the country. However, CO2 recovery has a problem: the carbon dioxide injected into the formation corrodes wellbores, sucker rods, pumps, and gathering pipelines when extracted with oil and water, causing significant economic losses, safety hazards, and environmental pollution.

[0003] Currently, adding liquid corrosion inhibitors to the casing during oil production is an effective measure to suppress or mitigate corrosion and has been widely used. The liquid corrosion inhibitor dissolves in the produced fluid. As the produced fluid is produced, the adsorption effect on the metal causes the liquid corrosion inhibitor to form a pre-resistance film on the inner wall of the tubing and below the liquid surface of the casing, thereby isolating the corrosive medium from contact with the metal tubing and achieving the purpose of protecting the oil casing. However, some shortcomings have been exposed during use: corrosion inhibitors added at the endpoints are easily adsorbed by suspended solid impurities in the wastewater or catalytically degraded by impurities in the wastewater, reducing their performance; intermittent injection results in uneven dosing and a short effective protection time (generally within 3 days).

[0004] In recent years, solid corrosion inhibitors have begun to be applied in the field of oil well corrosion prevention. Solid corrosion inhibitors are mainly carried by water replenishment through the oil well casing to the artificial bottom of the well. Under high-temperature conditions downhole, they are slowly released and, as the produced fluid is pumped out, form a pre-resistance film on the inner wall of the tubing, thus achieving a corrosion-preventing effect. Currently, the diameter of solid corrosion inhibitors used in the field is all above 5mm. When added to the oil well casing, the limitations of the four-inch casing wellbore (limited annulus, effective space only 4mm) cause compression and adhesion phenomena during the addition process. Furthermore, current solid corrosion inhibitors are produced using traditional tableting machines. Once the particle size decreases (≤3mm), according to the principle that pressure increases with decreasing specific surface area while pressure remains constant, the pressure on the main bearing of the tableting machine will increase exponentially. The tungsten steel shaft currently used will break when producing small-particle solid corrosion inhibitors, making it impossible to produce solid corrosion inhibitors ≤3mm using the current tableting process.

[0005] Chinese invention patent CN104480473B discloses a solid corrosion inhibitor, comprising a coating wax and solid corrosion inhibitor granules. The solid corrosion inhibitor granules include a water-soluble corrosion inhibitor (glucamide corrosion inhibitor or imidazoline corrosion inhibitor), a solid binder (water-soluble starch, low-gluten flour, gum arabic powder, sodium carboxymethyl cellulose, β-cyclodextrin), a synergist (sodium sulfite, acetone oxime, thiourea), and a foaming and disintegrant (a mixture of sodium bicarbonate and solid organic acid). This solid corrosion inhibitor has a diameter between 5-8 mm, solving the technical problems of limited effective protection distance for pipelines and poor protection of long-distance pipelines by liquid corrosion inhibitors. However, the sodium bicarbonate, solid organic acid, and water-soluble starch in this solid corrosion inhibitor will begin to dissolve at low temperatures. This causes the solid corrosion inhibitor to dissolve prematurely during the application process when used in oil wells, resulting in a large amount of it adhering to the casing wall and affecting the corrosion prevention effect of the inhibitor. Furthermore, this type of solid corrosion inhibitor has a diameter of 5-8 mm, making it unsuitable for application in wells with small casing. Summary of the Invention

[0006] The purpose of this invention is to provide a slow-dissolving solid corrosion inhibitor pellet to solve the problems in the prior art that solid corrosion inhibitors are not suitable for use in small casing wells and that they tend to adhere to the casing wall during the application process.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A slow-dissolving solid corrosion inhibitor pellet consists of a pellet core and a coating. The pellet core is composed of the following components in parts by weight: 40-45 parts of dialkyl imidazoline quaternary ammonium salt, 54-55 parts of binder, and 1-5 parts of weighting agent. The coating material is an organosilicon polyacrylate copolymer.

[0009] This invention, a slow-dissolving solid corrosion inhibitor pellet, is a pioneering invention. By preparing the solid corrosion inhibitor into pellets, this invention effectively reduces the diameter of the solid corrosion inhibitor to below 3mm, making it suitable for application in small casing wells. Furthermore, the main corrosion inhibitor in the pellet core of this application is a dialkyl imidazoline quaternary ammonium salt, enhancing the stability of the slow-dissolving solid corrosion inhibitor. The coating agent is an organosilicon polyacrylate copolymer, which combines film-forming properties, strong adhesion, heat resistance, and hydrophobicity, ensuring the temperature resistance and stability of the corrosion inhibitor film. It can effectively isolate the corrosive medium (formation water) from contact with the metal pipe for a long time; and its hydrophobic properties facilitate the rapid arrival of the corrosion inhibitor at the bottom of the well, preventing adhesion and wall fouling.

[0010] Preferably, the binder is polyglycolic acid. This substance has good thermal stability, high crystallinity (generally 40%–80%), and a melting point of around 225°C. Furthermore, the slow-release rate of polyglycolic acid is lower than that of traditional binders (sodium carboxymethyl cellulose). The solid particles do not break down or disperse before reaching the bottom of the well, which facilitates the stability of the corrosion inhibitor before it reaches the bottom of the well and prevents it from clumping together and blocking the dosing channel.

[0011] Preferably, the glass transition temperature of the polyglycolic acid is 33–38°C.

[0012] Preferably, the weighting agent is composed of calcium chloride and zinc sulfate. The mixture of calcium chloride and zinc sulfate effectively increases the weight of the main corrosion inhibitor, making its specific gravity significantly exceed that of the formation water, thus facilitating its settling to the bottom of the well. Furthermore, both inorganic salts have low solubility in water, requiring a relatively long time to completely dissolve, which helps extend the dissolution time of the slow-release solid corrosion inhibitor and improve its release effect. Simultaneously, after dissolving, this type of weighting agent leaves no residue at the bottom of the well, thus not affecting normal oil well production.

[0013] Preferably, the mass ratio of calcium chloride to zinc sulfate is (0.3-1.5):(0.7-3.5).

[0014] Preferably, the particle size of the slow-dissolving solid corrosion inhibitor pellets is ≤3mm. Pellets of this size are more suitable for application to small-cased wells, such as four-inch casing wells, and are less prone to problems of application compression and adhesion.

[0015] Preferably, the mass ratio of the pellet core to the coating is (99.5–99.9):(0.1–0.5). The amount of coating material used is only sufficient to completely cover the pellet core.

[0016] Preferably, the preparation method of the dialkylimidazoline quaternary ammonium salt is as follows: succinic acid and diethylenetriamine are subjected to an amidation reaction to obtain an amidated product; the amidated product is then subjected to a cyclization reaction to obtain a cyclized product; finally, the cyclized product and a quaternizing agent are subjected to a quaternization reaction to obtain the dialkylimidazoline quaternary ammonium salt; the mass ratio of succinic acid to diethylenetriamine is (35-45):(55-65); the amidation reaction temperature is 160-170℃ and the time is 6-10 h; the cyclization reaction temperature is 190-210℃ and the time is 6-10 h; the quaternization reaction temperature is 140-150℃ and the time is 6-8 h; and the quaternizing agent is ethylene oxide. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the amidation reaction process in the synthesis of dialkyl imidazoline quaternary ammonium salts according to the present invention;

[0018] Figure 2This is a schematic diagram of the cyclization reaction product during the synthesis of the dialkyl imidazoline quaternary ammonium salt of the present invention;

[0019] Figure 3 This is a schematic diagram of the quaternization reaction product in the synthesis process of the dialkyl imidazoline quaternary ammonium salt of the present invention;

[0020] Figure 4 This is a product image of the slow-dissolving solid corrosion inhibitor pellets from Example 1 of the present invention;

[0021] Figure 5 This is a standard curve showing the concentration and absorbance of the solid corrosion inhibitor in Experimental Example 1 of the present invention.

[0022] Figure 6 This is a graph showing the relationship between the release amount of the solid corrosion inhibitor in Experiment Example 1 of the present invention and time.

[0023] Figure 7 This is a graph showing the effect of different temperatures on the slow-release amount of solid corrosion inhibitor pellets in Experimental Example 2 of the present invention;

[0024] Figure 8 This is a field pilot test diagram of Experiment Example 4 of the present invention, conducted in an oilfield. Detailed Implementation

[0025] The slow-dissolving solid corrosion inhibitor pellets of this invention, compared to solid corrosion inhibitors obtained by traditional tableting processes, can achieve a diameter of ≤3mm, facilitating their application in corrosion prevention in small casing wells and filling the technological gap where solid corrosion inhibitors cannot achieve long-term slow dissolution in four-inch casing wells. Furthermore, the core of these pellets is composed of dialkyl imidazoline quaternary ammonium salt, binder, and weighting agent, while the coating material is an organosilicon polyacrylate copolymer. During application, as the wellbore temperature rises, the solid particles do not clump together, ensuring slow dissolution in the produced water at the bottom hole. With the transport of the produced fluid, a continuously spreading and stable pre-stressed film is formed on the inner wall of the tubing and the annulus well wall, enhancing the slow-release effect of the corrosion inhibitor at high-temperature conditions at the bottom hole.

[0026] The dialkyl imidazoline quaternary ammonium salts involved in the following examples and comparative examples were synthesized using succinic acid and diethylenetriamine via amidation, cyclization, and quaternization reactions. The amidation reaction process is as follows: Figure 1 As shown, the structures of the products from the cyclization and quaternization reactions are as follows: Figure 2-3 As shown.

[0027] The preparation method of dialkyl imidazoline quaternary ammonium salt adopts the following steps:

[0028] (1) Add 56g of diethylenetriamine, 45g of succinic acid, and 150mL of xylene to a three-necked flask. The three-necked flask is connected to a condenser, a 300℃ mercury thermometer with a rubber stopper, a water separator, and a stirrer. Heat the three-necked flask to 160-170℃ while stirring until the materials in the three-necked flask are completely dissolved. Then, stir and reflux the materials in the three-necked flask at 160-170℃ for 6-10 hours. During the reaction, water is continuously removed through the water separator. During the stirring and reflux reaction, succinic acid and diethylenetriamine undergo an amidation reaction.

[0029] (2) After the stirring and reflux reaction is completed, the material in the three-necked flask is heated to 190-210°C and stirred at a constant temperature for 6-10 hours. The amidation product undergoes a cyclization reaction.

[0030] (3) After the reaction is completed under constant temperature, the material in the three-necked flask is cooled to 140-150°C. Then, 100 mL of 30% ethylene oxide solution is slowly added dropwise to the three-necked flask. After the addition is completed, stirring is continued until the solution is completely dissolved. The mixture is then refluxed at 140-150°C for 6-8 hours. Finally, the solvent is evaporated to obtain the solid dialkyl imidazoline quaternary ammonium salt product.

[0031] The polyglycolic acid used in the following examples and comparative examples is manufactured by Jining Huakai Resin Co., Ltd., with product model AL575709986608 and a glass transition temperature of 35°C.

[0032] The silicone polyacrylate copolymers used in the following examples and comparative examples are TEGO Protect 5001, provided by Xiangyu International Trading (Shanghai) Co., Ltd.

[0033] The sodium carboxymethyl cellulose involved in the following examples and comparative examples is manufactured by Shandong Zibo Daole New Material Co., Ltd., and the product model is sodium carboxymethyl cellulose HV-CMC.

[0034] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0035] I. Specific embodiments of the slow-dissolving solid corrosion inhibitor pellets of the present invention are as follows:

[0036] Example 1

[0037] This embodiment of the slow-dissolving solid corrosion inhibitor pellets consists of a pellet core and a coating. The pellet core comprises the following components by weight: 40g of dialkyl imidazoline quaternary ammonium salt, 55g of polyglycolic acid, and 5g of a mixture of calcium chloride and zinc sulfate (wherein calcium chloride is 1.5g and zinc sulfate is 3.5g). The coating material is an organosilicon polyacrylate copolymer. The mass ratio of the pellet core to the coating is (99.5~99.9):(0.1~0.5). The product is as follows... Figure 4 As shown.

[0038] The preparation method of this slow-dissolving solid corrosion inhibitor pellets includes the following steps:

[0039] First, 40g of dialkyl imidazoline quaternary ammonium salt and 200g of water were stirred evenly at 100℃ to obtain a liquid corrosion inhibitor. Then, the liquid corrosion inhibitor was added to a reaction vessel, and 55g of polyglycolic acid and 5g of a mixture of calcium chloride and zinc sulfate were gradually added while the temperature was raised to 120℃. The mixture was stirred at a constant temperature for 1 hour to ensure uniform mixing. Then, the mixture was stirred until all the water in the system was evaporated. The pressure was set to 2MPa, and nitrogen gas was introduced at a constant pressure. The resulting mixture was then dripped using a pelletizing machine (aperture: 1-1.5mm), and cooled with mineral oil to obtain droplet-shaped pellets. 0.5g of organosilicon polyacrylate copolymer was added to the pellets for encapsulation, and finally, droplet-shaped slow-dissolving solid corrosion inhibitor pellets with a diameter of 2-3mm were obtained.

[0040] Example 2

[0041] The slow-dissolving solid corrosion inhibitor pellets of this embodiment consist of a pellet core and a coating. The pellet core is composed of the following components by weight: 42g of dialkyl imidazoline quaternary ammonium salt, 55g of polyglycolic acid, and 3g of a mixture of calcium chloride and zinc sulfate (wherein calcium chloride is 0.9g and zinc sulfate is 2.1g). The coating material is an organosilicon polyacrylate copolymer. The mass ratio of the pellet core to the coating is (99.5~99.9):(0.1~0.5).

[0042] The preparation method of this slow-dissolving solid corrosion inhibitor pellets includes the following steps:

[0043] First, 42g of dialkyl imidazoline quaternary ammonium salt and 200g of water were stirred evenly at 100℃ to obtain a liquid corrosion inhibitor. Then, the liquid corrosion inhibitor was added to a reaction vessel, and 55g of polyglycolic acid and 3g of a mixture of calcium chloride and zinc sulfate were gradually added while the temperature was raised to 120℃. The mixture was stirred at a constant temperature for 1 hour to ensure uniform mixing. Then, the mixture was stirred until all the water in the system was evaporated. The pressure was set to 2MPa, and nitrogen gas was introduced at a constant pressure. The resulting mixture was then dripped using a pelletizing machine (aperture: 1-1.5mm), and cooled with mineral oil to obtain droplet-shaped pellets. 0.3g of organosilicon polyacrylate copolymer was added to the pellets for encapsulation, and finally, droplet-shaped slow-dissolving solid corrosion inhibitor pellets with a diameter of 2-3mm were obtained.

[0044] Example 3

[0045] The slow-dissolving solid corrosion inhibitor pellets of this embodiment consist of a pellet core and a coating. The pellet core is composed of the following components by weight: 45g of dialkyl imidazoline quaternary ammonium salt, 54g of polyglycolic acid, and 1g of a mixture of calcium chloride and zinc sulfate (wherein calcium chloride is 0.3g and zinc sulfate is 0.7g). The coating material is an organosilicon polyacrylate copolymer. The mass ratio of the pellet core to the coating is (99.5~99.9):(0.1~0.5).

[0046] The preparation method of this slow-dissolving solid corrosion inhibitor pellets includes the following steps:

[0047] First, 45g of dialkyl imidazoline quaternary ammonium salt and 200g of water were stirred evenly at 100℃ to obtain a liquid corrosion inhibitor. Then, the liquid corrosion inhibitor was added to a reaction vessel, and 45g of polyglycolic acid and 1g of a mixture of calcium chloride and zinc sulfate were gradually added while the temperature was raised to 120℃. The mixture was stirred at a constant temperature for 1 hour to ensure uniform mixing. Then, the mixture was stirred until all the water in the system was evaporated. The pressure was set to 2MPa, and nitrogen gas was introduced at a constant pressure. The resulting mixture was then dripped using a pelletizing machine (aperture: 1-1.5mm), and cooled with mineral oil to obtain droplet-shaped pellets. 0.1g of organosilicon polyacrylate copolymer was added to the pellets for encapsulation, and finally, droplet-shaped slow-dissolving solid corrosion inhibitor pellets with a diameter of 2-3mm were obtained.

[0048] Comparative Example 1

[0049] The only difference between the slow-dissolving solid corrosion inhibitor pellets of this comparative example and those of Example 2 is that the coating material used in the slow-dissolving solid corrosion inhibitor pellets of this comparative example is composed of heptadecafluorodecyltrimethoxysilane and nano zinc oxide, with a mass ratio of heptadecafluorodecyltrimethoxysilane to nano zinc oxide of 1:9.

[0050] Comparative Example 2

[0051] The only difference between the slow-dissolving solid corrosion inhibitor pellets of this comparative example and the slow-dissolving solid corrosion inhibitor pellets of Example 1 is that polyglycolic acid is replaced with sodium carboxymethyl cellulose in the slow-dissolving solid corrosion inhibitor pellets of this comparative example.

[0052] Experimental Example 1 Solubility

[0053] This experiment was conducted to determine the solubility of the slow-dissolving solid corrosion inhibitor pellets from Example 1. To meet practical requirements and conditions, the experimental temperature was 80°C, and the water sample was artificially prepared to simulate the solubility of the solid corrosion inhibitor. The ionic composition of the artificially prepared water is shown in Table 1.

[0054] Table 1 Ionic composition of water samples

[0055]

[0056] In this experiment, six slow-dissolving solid corrosion inhibitor pellets (0.15g / pellet, 3mm in diameter) from Example 1 were placed in 500mL of artificially prepared water and then placed in an 80℃ oven to observe their dissolution rate. Specifically, water samples containing the dissolved solid corrosion inhibitor were periodically taken out, and the absorbance was measured to calculate the actual concentration of the corrosion inhibitor, thereby calculating the actual amount of corrosion inhibitor released. Before the test, a standard curve of the concentration of the solid corrosion inhibitor versus absorbance was first established, such as... Figure 5 As shown in Table 2, the relationship between the release amount of solid corrosion inhibitor and time is shown in Table 2. Figure 6 As shown.

[0057] Table 2 Relationship between release amount of solid corrosion inhibitor and time

[0058]

[0059] The release of solid corrosion inhibitors occurs in two stages: the first stage involves the dissolution of the surface framework material and the dissolution of the corrosion inhibitor; the second stage involves the diffusion of the corrosion inhibitor from the internal framework outwards. (See Table 2 and...) Figure 6 It can be seen that the release rate of the solid corrosion inhibitor is relatively fast within 72 hours. That is, the dissolution rate of the corrosion inhibitor component in the first stage is relatively fast in the early stage, and it can quickly reach the concentration that effectively protects the metal. After 72 hours, the release rate is relatively slow and basically remains stable, that is, the corrosion inhibitor has reached the stage of slow release.

[0060] Experiment Example 2: Effect of different temperatures on sustained-release amount

[0061] This experiment measured the change in the slow-release amount of the slow-dissolving solid corrosion inhibitor pellets from Example 1 at different temperatures. The results are shown in Table 3. Figure 7As shown. The specific experimental method was carried out in accordance with section 4.5, water solubility test, of SY / T 5273-2014 "Performance Inhibitors for Oilfield Produced Water Treatment". Based on the geothermal gradient of the oilfield, the experimental temperatures were set at 80℃, 90℃, and 100℃.

[0062] Table 3 Relationship between release amount of solid corrosion inhibitor and temperature

[0063] Time (h) 12 24 36 48 72 120 240 360 480 720 Release rate (mg) at 80℃ 15 35 50 57.5 96 119.5 210.5 308.5 394 498 Release rate (mg) at 90℃ 18 40 55 62 98 121 216 317 405 512 Release rate (mg) at 100℃ 23 49 64 71 109 135 230 332 422 569

[0064] From Table 3 and Figure 7 It can be seen that the release amount of corrosion inhibitor gradually increases with the extension of the addition time; between 80 and 100°C, the release amount of corrosion inhibitor also increases with the increase of temperature. However, the change in release amount at different temperatures at the same time is not very large, which reflects the stability of the corrosion inhibitor of the present invention at high temperatures (in the initial stage of corrosion inhibitor release, the difference in release amount between 80 and 100°C is not much, and temperature has little effect on the release rate of corrosion inhibitor).

[0065] Experimental Example 3 Corrosion Inhibition Rate

[0066] This experiment used oilfield produced water and the slow-dissolving solid corrosion inhibitor pellets from Example 1 to determine the static corrosion inhibition rate of pellets with different concentrations at different temperatures. The results are shown in Tables 4-6. The experimental method was carried out in accordance with the provisions of Section 4.7, "Determination of Static Uniform Corrosion Inhibition Rate and Pitting Corrosion Inhibition Rate," of SY / T 5273-2014, "Performance Indicators and Evaluation Methods for Corrosion Inhibitors for Oilfield Produced Water Treatment."

[0067] Table 4 Static corrosion inhibition rate (70℃)

[0068]

[0069] Table 5 Static corrosion inhibition rate (80℃)

[0070]

[0071]

[0072] Table 6 Static corrosion inhibition rate (90℃)

[0073]

[0074] As shown in Table 4-6, under indoor conditions, the blank group without any corrosion inhibitor had the fastest corrosion rate, which was 0.1227 mm / a, exceeding the petrochemical standard of 0.076 mm / a. When the corrosion inhibitor of Example 1 was added and the concentration of the corrosion inhibitor was 100 ppm, the corrosion inhibition rate was greater than 83% and the corrosion rate was less than 0.019 mm / a.

[0075] With increasing corrosion inhibitor concentration, the corrosion inhibition rate increases significantly, reaching a maximum of 97.5%, while the corrosion rate decreases significantly, reaching a minimum of 0.0036 mm / a. Furthermore, at the same concentration, different temperatures have little effect on the corrosion inhibition rate, demonstrating the stability of the corrosion inhibitor of this invention at high temperatures.

[0076] This experiment also determined the dynamic corrosion inhibition rate of the slow-dissolving solid corrosion inhibitor pellets of Example 1 at 80°C, and the results are shown in Table 7.

[0077] This method refers to the test conditions and requirements specified in SY / T 5273-2014 "Performance Inhibitors and Evaluation Methods for Oilfield Produced Water Treatment" 4.8.3 Determination of Dynamic Uniform Corrosion Inhibition Rate and Pitting Corrosion Inhibition Rate. The water sample source is oilfield produced water (the ionic composition of oilfield produced water is shown in Table 8).

[0078] Table 7 Dynamic Corrosion Inhibition Rate

[0079]

[0080] Table 8 Ionic composition of water samples

[0081]

[0082] As can be seen from Table 7, for the dynamic corrosion inhibition rate, the blank corrosion rate without the addition of corrosion inhibitor was 0.1313 mm / a, which exceeded the petrochemical standard of 0.076 mm / a; while after the addition of corrosion inhibitor, the dynamic corrosion inhibition rate exceeded 84%, and the corrosion rate was lower than 0.017 mm / a. Compared with the blank control group, the corrosion rate was significantly reduced.

[0083] Experiment Example 4

[0084] The solid corrosion inhibitors of the examples and comparative examples were compared in terms of solubility and corrosion inhibition rate (the water used for the solubility test was artificially prepared water in Example 1, and the water used for the corrosion inhibition rate test was oilfield produced water in Example 3; the specific ionic composition is shown in Tables 1 and 8, and the experimental methods were carried out in accordance with the requirements of Example 1 and Example 3). The relationship between the release amount and time of the corrosion inhibitors of Examples 1-3 and Comparative Examples 1-2 is shown in Table 9. The test results of static corrosion inhibition rate and dynamic corrosion inhibition rate are shown in Table 10. The concentration of the corrosion inhibitor was 300 ppm during the static corrosion inhibition rate and dynamic corrosion inhibition rate tests.

[0085] The experimental data for the examples and comparative examples are as follows:

[0086] Table 9. Relationship between release amount and time in the Examples and Comparative Examples

[0087] Time (h) 12 24 36 48 72 120 240 360 480 720 Example 1: Release amount (mg) 15 35 50 57.5 96 119.5 210.5 308.5 394 498 Example 2 Release Amount (mg) 16 37 51 59 98 123.5 217.5 316.5 404 511 Example 3 Release amount (mg) 15.7 35.5 50.5 58.5 97 121 213 312.5 400 506 Comparative Example 1 Release Amount (mg) 19 38 55 63 105 137 231 339 451 570 Comparative Example 2 Release Amount (mg) 21 40 57 65 109 140 235.5 345 460 577

[0088] Table 10 Comparison of corrosion inhibition rates between the examples and the comparative examples

[0089] Time (h) Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Static corrosion inhibition rate (70℃) 97.5％ 96.3％ 95.1％ 68.2％ 65.7％ Static corrosion inhibition rate (80℃) 96.9％ 95.3％ 93.2％ 67.3％ 63.4％ Static corrosion inhibition rate (90℃) 94.2％ 93.8％ 90.7％ 65.2％ 60.7％ Dynamic corrosion inhibition rate 95.1％ 94.8％ 91.2％ 66.1％ 61.8％

[0090] Experimental Example 5

[0091] Following successful indoor experiments, this experimental example conducted a pilot field test of the slow-dissolving solid corrosion inhibitor pellets from Example 1 in an oilfield. The pellets were injected via a stationary pipe pump through the casing annulus. Figure 8 As shown.

[0092] The oil wells in this oilfield are suspended 4-inch casing wells. Before the addition of corrosion inhibitors, the maintenance-free period of these wells was 190 days, and the corrosion rate was 0.1178 mm / a. Starting in 2022, the solid corrosion inhibitor pellets of Example 1 were applied. After treatment, the maintenance-free period increased to 463 days, and the corrosion rate decreased to 0.0185 mm / a. Furthermore, the well is currently (667 days after treatment) still in normal production. Therefore, it can be seen that the slow-dissolving solid corrosion inhibitor pellets of this invention have good field application effects and promising prospects for widespread application.

[0093] Finally, to investigate the influence of the preparation process of the dialkylimidazoline quaternary ammonium salt on the experimental results, the preparation method of the dialkylimidazoline quaternary ammonium salt used in Example 1 was adjusted. Specifically, the mass of succinic acid was adjusted to 35g or 40g, or the mass of diethylenetriamine was adjusted to 55g or 65g. Then, the dialkylimidazoline quaternary ammonium salt prepared after parameter adjustment replaced the dialkylimidazoline quaternary ammonium salt in Example 1, and the test was carried out according to the method of the experimental example. The test results showed that the dialkylimidazoline quaternary ammonium salt prepared after parameter adjustment had similar performance to the slow-dissolving solid corrosion inhibitor pellets prepared by the dialkylimidazoline quaternary ammonium salt in Example 1.

[0094] In addition, the slow-dissolving solid corrosion inhibitor pellets were prepared again according to the preparation method of the slow-dissolving solid corrosion inhibitor pellets in Example 1, except that the polyglycolic acid was replaced with commercially available polyglycolic acid with a glass transition temperature of 33 or 38°C, or the sodium carboxymethyl cellulose was replaced with sodium carboxymethyl cellulose of type LV-CMC. Then, the slow-dissolving solid corrosion inhibitor pellets prepared after adjusting the parameters were tested according to the method of the experimental example. The test results showed that the performance of the slow-dissolving solid corrosion inhibitor pellets prepared after adjusting the parameters was close to that of the slow-dissolving solid corrosion inhibitor pellets prepared in Example 1.

Claims

1. A slow-dissolving solid corrosion inhibitor pellet, characterized in that, It consists of a pellet core and a coating. The pellet core is composed of the following components in parts by weight: 40-45 parts of dialkyl imidazoline quaternary ammonium salt, 54-55 parts of binder, and 1-5 parts of weighting agent. The coating material is an organosilicon polyacrylate copolymer.

2. The slow-dissolving solid corrosion inhibitor pellets according to claim 1, characterized in that, The adhesive is polyglycolic acid.

3. The slow-dissolving solid corrosion inhibitor pellets according to claim 2, characterized in that, The glass transition temperature of the polyglycolic acid is 33–38°C.

4. The slow-dissolving solid corrosion inhibitor pellets according to claim 1, characterized in that, The weighting agent consists of calcium chloride and zinc sulfate.

5. The slow-dissolving solid corrosion inhibitor pellets according to claim 4, characterized in that, The mass ratio of calcium chloride to zinc sulfate is (0.3-1.5):(0.7-3.5).

6. The slow-dissolving solid corrosion inhibitor pellets according to any one of claims 1-5, characterized in that, The particle size of the slow-dissolving solid corrosion inhibitor pellets is ≤3mm.

7. The slow-dissolving solid corrosion inhibitor pellets according to any one of claims 1-5, characterized in that, The mass ratio of the droplet core to the coating is (99.5~99.9):(0.1~0.5).

8. The slow-dissolving solid corrosion inhibitor pellets according to any one of claims 1-5, characterized in that, The preparation method of the dialkylimidazoline quaternary ammonium salt is as follows: succinic acid and diethylenetriamine are subjected to an amidation reaction to obtain an amidation product, the amidation product is then subjected to a cyclization reaction to obtain a cyclization product, and finally the cyclization product and a quaternization reagent are subjected to a quaternization reaction to obtain the dialkylimidazoline quaternary ammonium salt; the mass ratio of succinic acid to diethylenetriamine is (35-45):(55-65), the amidation reaction temperature is 160-170℃ and the time is 6-10h, the cyclization reaction temperature is 190-210℃ and the time is 6-10h, the quaternization reaction temperature is 140-150℃ and the time is 6-8h, and the quaternization reagent is ethylene oxide.

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