Plant composite corrosion inhibitor for oil field and preparation method thereof

Abstract

This invention relates to a plant-based composite corrosion inhibitor for oilfield use and its preparation method, belonging to the field of oilfield chemical agent preparation technology. The plant-based composite corrosion inhibitor comprises a first plant component, a second plant component, a corrosion inhibitor synergist, and an organic solvent. The first plant component is zeaxanthin and its derivatives obtained from marigolds through supercritical CO2 extraction; the second plant component is prepared from loofah leaves, guava leaves, and Eclipta prostrata in a mass ratio of 5:8:9; the corrosion inhibitor synergist is a mixture of potassium iodide, 8-hydroxyquinoline, and sodium dodecylbenzenesulfonate in a mass ratio of 3:4:2; the organic solvent is 82% ethanol. The composite corrosion inhibitor of this invention can form a dense protective film on carbon steel surfaces, exhibiting excellent corrosion inhibition effects, and its main components are plant extracts, reducing the presence of harmful chemical components in the corrosion inhibitor.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical agent preparation technology, specifically relating to an oilfield plant-based composite corrosion inhibitor and its preparation method. Background Technology

[0002] In oil and gas field development, severe metal corrosion is a common problem. Using corrosion inhibitors is the most common and economical method for metal corrosion prevention. They are easy to use and can achieve good corrosion inhibition effects with only low concentrations. Commonly used corrosion inhibitors can be divided into inorganic and organic corrosion inhibitors based on their chemical structure. Inorganic corrosion inhibitors mostly contain highly electronegative atoms such as phosphorus, sulfur, nitrogen, and oxygen, such as arsenates, phosphates, and chromates. Organic corrosion inhibitors mostly contain unsaturated bonds or large conjugated systems of organic heterocyclic compounds, such as amides, Schiff bases, and pyridines. Although the above-mentioned corrosion inhibitors have good corrosion inhibition efficiency, their synthesis routes are complex, their prices are high, they are not biodegradable, and they are usually toxic. Large-scale use can easily cause red tides and algal blooms, leading to eutrophication of water bodies and damage to the soil environment. Therefore, it is necessary to find corrosion inhibitors with high corrosion inhibition efficiency and environmental friendliness.

[0003] Studies have shown that organic compounds in plants containing unsaturated structures, π bonds, and heteroatoms such as C, N, S, and O readily adsorb onto metal surfaces, forming a protective film that acts as a potential corrosion inhibitor. To date, numerous examples of plant extracts used as corrosion inhibitors have been documented, including orange peel, grapefruit peel, aloe vera, bitter tea, ginkgo fruit, and olive leaves, all exhibiting good corrosion inhibition effects. Because plants are non-toxic, non-polluting, biodegradable, and their preparation and use pose minimal harm to humans and the environment, they are a driving force for the development of corrosion inhibitors and related technologies. However, current plant-based corrosion inhibitors also suffer from the following problems: they are unstable during use, easily decompose and deteriorate, require large quantities, and their corrosion inhibition efficiency drops sharply when environmental conditions change, making them difficult to apply in engineering practice. Summary of the Invention

[0004] This invention relates to a plant-based composite corrosion inhibitor for oilfield use and its preparation method, which solves the problems of existing plant extract corrosion inhibitors being unstable, easily decomposed and deteriorated, requiring large amounts, and subject to harsh application conditions, making them difficult to apply in engineering practice, and improves the various corrosion inhibition properties of plant-based corrosion inhibitors.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A plant-based composite corrosion inhibitor for oilfield use is prepared from the following raw materials in parts by weight: 15-25 parts of a first plant component, 9-18 parts of a second plant component, 6-9 parts of a corrosion inhibitor synergist, and 30-50 parts of an organic solvent.

[0007] The raw material for the first plant component is marigold, and the raw materials for the second plant component are loofah leaves, guava leaves, and Eclipta prostrata.

[0008] Further, the preparation steps of the first plant component are as follows: fresh marigolds are washed, disinfected with anhydrous ethanol, dried at 40°C, and then ground into powder. The obtained marigold powder is placed in the extraction vessel of a supercritical fluid extractor. Supercritical CO2 is used as the solvent and flows upward at a constant flow rate of 0.012 kg / min for 6 hours. Anhydrous ethanol is used as a co-solvent and is sent to a preheated container located in front of the extraction vessel by a high-performance liquid chromatography pump. The extraction pressure of the extraction vessel is 36.7 MPa and the extraction temperature is 40.5°C. At the end of each cycle, the outflow is depressurized in a heated back pressure valve, and the extract is collected in a cooled two-chamber collection container. Zeaxanthin and its derivatives are dissolved in ethanol. After removing the solvent by evaporation, the first plant component is obtained.

[0009] Further, the preparation steps of the second plant component are as follows: Fresh loofah leaves, guava leaves, and Eclipta prostrata are washed, disinfected, dried, and pulverized. They are then mixed in a mass ratio of 5:8:9, and anhydrous ethanol is added at a liquid-to-material ratio of 13 mL / g. The mixture is soaked for 36 hours. The soaked mixture is ultrasonically cleaned at room temperature for 30 minutes, followed by vacuum filtration to remove insoluble matter. The solution is then concentrated to 1 / 3 volume using a rotary evaporator at 80°C to obtain the second plant component.

[0010] Furthermore, the corrosion inhibitor is prepared by mixing potassium iodide, 8-hydroxyquinoline, and sodium dodecylbenzenesulfonate in a mass ratio of 3:4:2.

[0011] Furthermore, the organic solvent is ethanol with a mass concentration of 82%.

[0012] The present invention discloses a method for preparing a plant-based composite corrosion inhibitor for oilfield use, comprising the following steps:

[0013] (1) Raw material preparation: Prepare the first plant component, the second plant component and the corrosion inhibitor for later use;

[0014] (2) Preparation: Add different mass parts of the first plant component, the second plant component and the corrosion inhibitor to an organic solvent and stir to mix evenly to obtain a plant composite corrosion inhibitor.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] (1) The natural green plant extracts selected in this invention contain flavonoids, amino acids, and polysaccharides. Among them, zeaxanthin and arbutin have large adsorption energies. The N and O atoms in the polar groups of the extract form coordinate bonds with the empty d orbitals of the metal atoms and are adsorbed onto the metal surface. By using the extracts of natural green plants as one of the main components of the corrosion inhibitor, the harmful chemical components in the corrosion inhibitor are reduced, providing a new idea and perspective for the development and design of new and efficient corrosion inhibitors in the future.

[0017] (2) This invention employs two different plant extraction methods. In supercritical fluid extraction, the diffusion coefficient of supercritical CO2 is nearly 100 times that of liquid, enabling it to rapidly penetrate the micropores of marigold powder and extract zeaxanthin and its derivatives quickly and efficiently. Ultrasonic extraction allows plants to release more effective substances in a short time, accelerating the release, dissolution, and diffusion of effective substances within cells.

[0018] (3) The raw materials selected for preparing the plant composite corrosion inhibitor of the present invention are all common plants in life. By adjusting the synergy and compatibility between plant extracts and surfactants, the problems of unstable properties, harsh application conditions, and difficulty in application to engineering practice of existing plant extract corrosion inhibitors are solved, making it suitable for large-scale promotion and use in oil fields.

[0019] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from the understanding of those skilled in the art through study and practice of the invention. Attached Figure Description

[0020] Figure 1 The graph shows the polarization curves of L245N steel in corrosion solutions with different concentrations of corrosion inhibitors in Example 3.

[0021] Figure 2 The impedance spectra of L245N steel in corrosion solutions with different concentrations of corrosion inhibitors in Example 3 are shown.

[0022] Figure 3 The corrosion morphology of L245N steel in Example 3 after immersion in corrosion solutions with no corrosion inhibitor (a) and with 4% corrosion inhibitor by volume (b) for 24 hours is shown. Detailed Implementation

[0023] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] Example 1

[0025] A plant-based composite corrosion inhibitor for oil fields is prepared from the following raw materials in parts by weight: 15 parts of a first plant component, 9 parts of a second plant component, 6 parts of a corrosion inhibitor synergist, and 30 parts of an organic solvent. The organic solvent is ethanol with a mass concentration of 82%. The components of the composite corrosion inhibitor have high solubility in the ethanol solution.

[0026] The raw material for the first plant component is marigold. The extraction steps for the first plant component are as follows: Fresh marigold is washed, sterilized with anhydrous ethanol, dried at 40°C, and then ground into powder. The obtained marigold powder is placed in the extraction vessel of a supercritical fluid extractor. Supercritical CO2 is used as the solvent and flows upward at a constant flow rate of 0.012 kg / min for 6 hours. Anhydrous ethanol is used as a co-solvent to change the polarity of CO2. It is sent to a preheated container located in front of the extraction vessel by a high-performance liquid chromatography pump. The extraction pressure in the extraction vessel is 36.7 MPa and the extraction temperature is 40.5°C. At the end of each cycle, the outflow is depressurized in a heated back pressure valve, and the extract is collected in a cooled two-chamber collection container. Zeaxanthin and its derivatives are dissolved in ethanol. After removing the solvent by evaporation, the first plant component is obtained.

[0027] The raw materials for the second plant component were loofah leaves, guava leaves, and Eclipta prostrata. The extraction steps for the second plant component included: taking fresh loofah leaves, guava leaves, and Eclipta prostrata, washing, disinfecting, drying, and pulverizing them, mixing them in a mass ratio of 5:8:9, adding anhydrous ethanol at a liquid-to-solid ratio of 13 mL / g, and soaking for 36 hours. The soaked mixture was then ultrasonically cleaned at room temperature for 30 minutes with an ultrasonic power of 125 W, followed by vacuum filtration to remove insoluble matter, and then using a rotary evaporator at 80°C to concentrate the solution to 1 / 3 of its volume to obtain the second plant component.

[0028] The corrosion inhibitor is a mixture of potassium iodide, 8-hydroxyquinoline, and sodium dodecylbenzenesulfonate in a mass ratio of 3:4:2. As a surfactant, it can further improve the corrosion inhibition effect of the corrosion inhibitor.

[0029] The preparation method of the plant-based composite corrosion inhibitor described in this embodiment includes the following steps:

[0030] (1) Raw material preparation: Prepare the first plant component, the second plant component and the corrosion inhibitor for later use;

[0031] (2) Preparation: Add different mass parts of the first plant component, the second plant component and the corrosion inhibitor to an organic solvent and stir to mix evenly to obtain a plant composite corrosion inhibitor.

[0032] Example 2

[0033] This embodiment is basically the same as Embodiment 1, except that the mass fraction of each component raw material in the composite corrosion inhibitor is different.

[0034] A plant-based composite corrosion inhibitor for oilfield use is prepared from the following raw materials in parts by weight: 20 parts of a first plant component, 13 parts of a second plant component, 6 parts of a corrosion inhibitor synergist, and 36 parts of an organic solvent, wherein the organic solvent is ethanol with a mass concentration of 82%.

[0035] Example 3

[0036] This embodiment is basically the same as Embodiment 1, except that the mass fraction of each component raw material in the composite corrosion inhibitor is different.

[0037] A plant-based composite corrosion inhibitor for oil fields is prepared from the following raw materials in parts by weight: 20 parts of a first plant component, 15 parts of a second plant component, 7 parts of a corrosion inhibitor synergist, and 42 parts of an organic solvent, wherein the organic solvent is ethanol with a mass concentration of 82%.

[0038] Example 4

[0039] This embodiment is basically the same as Embodiment 1, except that the mass fraction of each component raw material in the composite corrosion inhibitor is different.

[0040] A plant-based composite corrosion inhibitor for oilfield use is prepared from the following raw materials in parts by weight: 25 parts of a first plant component, 15 parts of a second plant component, 8 parts of a corrosion inhibitor synergist, and 46 parts of an organic solvent, wherein the organic solvent is ethanol with a mass concentration of 82%.

[0041] Performance test of composite corrosion inhibitor 1

[0042] The composite corrosion inhibitors in Examples 1-4 were subjected to performance testing, and the corrosion inhibition efficiency was evaluated using the industry-standard experimental method (weight loss method). The method is summarized as follows:

[0043] The corrosive solution was simulated oilfield produced water saturated with CO2, and its composition is shown in Table 1 below. The corrosion temperature was 45℃, and the pressure was normal. L245N steel sheets, commonly used in oilfields, were used as the corrosion target. L245N steel was cut into 50mm × 10mm × 3mm metal samples. The samples were polished with wet sandpaper until the surface was mirror-smooth, then washed with deionized water, acetone, and anhydrous ethanol, dried, and weighed. The samples were immersed in a corrosive solution containing 4% (v / v) corrosion inhibitor for a three-day weight loss experiment. Under the same conditions, the mass difference before and after corrosion of the samples in Examples 1–4 was calculated, and the efficiency of the corrosion inhibitor was calculated. The results are expressed as a mass percentage, as shown in Table 2 below.

[0044] The average corrosion rate of a sample can be calculated using the weight loss method. The calculation formula is as follows:

[0045]

[0046] In the formula, v is the corrosion rate (mm / y); M is the sample mass before the experiment (g); M1 is the sample mass after the experiment (g); and S is the total area of ​​the sample (cm²). 2 t is the experimental time, in hours; D is the density of the material, in kg / m³. 3 The metal material studied was L245N steel with a density of 7840 kg / m³. 3 .

[0047] Formula for calculating the corrosion inhibition efficiency of corrosion inhibitors:

[0048]

[0049] In the formula, η is the corrosion inhibition efficiency, %; v0, v inh The values ​​represent the corrosion rates before and after the addition of the corrosion inhibitor, in mm / y.

[0050] Table 1. Corrosive Solution Formulation Table

[0051] Chemical reagents NaCl KCl <![CDATA[CaCl2]]> <![CDATA[MgCl2·6H2O]]> <![CDATA[Na2SO4]]> <![CDATA[NaHCO3]]> Concentration (g / L) 16.5577 0.5400 0.4500 1.1178 0.3700 1.6490

[0052] Table 2 Performance test results of composite corrosion inhibitors

[0053] Example Drug concentration % v / v Corrosion inhibition rate % Example 1 4 86.2 Example 2 4 91.5 Example 3 4 95.6 Example 4 4 92.3

[0054] Comparing the experimental results of Examples 1 to 4, it can be seen that the plant-based composite corrosion inhibitor has good corrosion inhibition performance, indicating that the technical solution provided by the present invention is effective.

[0055] Comparing Examples 1 to 4, increasing the proportion of the first and second plant components has a positive impact on the corrosion inhibition effect of the composite corrosion inhibitor, enhancing the corrosion inhibition effect. However, the proportion should not be too high, with the composite corrosion inhibitor composition ratio in Example 3 being the optimal ratio.

[0056] Performance test of composite corrosion inhibitor 2

[0057] The corrosion resistance of the composite corrosion inhibitor prepared in Example 3 was studied using electrochemical methods and corrosion morphology analysis as follows:

[0058] ① Electrochemical Testing: L245N steel was cut into 10mm×10mm×3mm square metal blocks, the surfaces were ground clean, and then encapsulated with epoxy resin. The electrochemical experiment employed a traditional three-electrode system and was conducted on a CS350 (Wuhan KOST Instruments Co., Ltd.) electrochemical workstation. The working electrode was made of L245N steel, the reference electrode was a saturated calomel electrode, and the auxiliary electrode was a platinum electrode. The experiment was carried out in a 45℃ constant temperature water bath.

[0059] The corrosion inhibitor concentration is expressed as the volume ratio between the corrosion inhibitor and the corrosion solution. When testing the polarization curve, the scanning potential range was set to ±200 mV relative to the open circuit potential, and the potentiodynamic scanning rate was set to 0.166 mV / s. The required parameters were then obtained by fitting the data using the Tafel extrapolation method. The corrosion inhibition efficiency (η) was obtained using the following formula:

[0060]

[0061] In the formula, η is the corrosion inhibition efficiency, %; and I corr The corrosion current densities, in μA / cm², are shown before and after the addition of the corrosion inhibitor. 2 .

[0062] ② Surface morphology observation: The L245N steel sample used for morphology observation was 50mm×10mm×3mm in size. After being polished to a bright surface, it was corroded for 24 hours in corrosion solutions with and without corrosion inhibitors, respectively, at a corrosion temperature of 45℃. After drying, its corrosion morphology was observed using a scanning electron microscope.

[0063] Figure 1 The polarization curves of L245N steel obtained from corrosion experiments in corrosion solutions with different concentrations (0%–5%) of corrosion inhibitors are shown. After the addition of the corrosion inhibitor, the corrosion potential shifts positively, with both the cathodic and anodic portions of the curve shifting towards lower current values, indicating that the reactions at both electrodes are effectively suppressed. The corrosion potential E can be obtained from the graph fitting. corr Corrosion current density I corr Anode Tafel slope B a and cathode Tafel slope B c The electrochemical parameters were calculated, and the results are shown in Table 3 below.

[0064] Table 3 Results of corrosion inhibition experiments

[0065]

[0066] Figure 2 Electrochemical impedance spectroscopy (EIS) spectra of L245N steel obtained from corrosion experiments in solutions containing different concentrations (0%–5%) of corrosion inhibitors are shown. The radius of curvature of the capacitive arc in the high-frequency region first increases and then decreases with increasing inhibitor concentration, indicating that as the inhibitor concentration increases, the protective layer formed by the inhibitor molecules adsorbed on the L245N steel surface becomes more complete, and the charge transfer resistance gradually increases. However, excessive inhibitor addition can adversely affect the adsorption of inhibitor molecules. EIS parameters were fitted using an equivalent circuit diagram, and the fitted parameters are shown in Table 4 below.

[0067] Table 4. Electrochemical impedance spectroscopy fitting results

[0068]

[0069] Figure 3 (a) and Figure 3 (b) The corrosion morphology of L245N steel samples after 24 hours of corrosion in solutions without corrosion inhibitor and with 4% (v / v) corrosion inhibitor, respectively. The scanning electron microscope (SEM) used an accelerating voltage (EHT) of 20 kV, a working distance (WD) of 13.5 mm, a magnification (Mag) of 1000x, and an SE1 detector. The corrosion in the solution without corrosion inhibitor was more severe, resulting in numerous particulate corrosion products adhering to the metal surface. In contrast, the corrosion of L245N steel in the solution with added corrosion inhibitor was less severe, with a smooth metal surface and no obvious large-area corrosion, indicating that the corrosion inhibitor effectively suppressed the corrosion of L245N steel in the corrosion solution.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A plant composite corrosion inhibitor for oil field, characterized by, The plant composite corrosion inhibitor is prepared from the following raw materials in parts by mass: a first plant component 15-25 parts, a second plant component 9-18 parts, an inhibition synergist 6-9 parts, and an organic solvent 30-50 parts; the raw material of the first plant component is marigold, and the preparation steps are specifically as follows: fresh marigold is cleaned, disinfected with anhydrous ethanol, dried at 40°C, and then ground and pulverized; the obtained marigold powder is placed in an extraction kettle of a supercritical extraction instrument, supercritical CO2 is used as a solvent, flows upward at a constant flow rate of 0.012 kg / min for 6 hours, anhydrous ethanol is used as a cosolvent, and is fed into a preheating container before the extraction kettle through a high-performance liquid chromatography pump; the extraction kettle has an extraction pressure of 36.7 MPa and an extraction temperature of 40.5°C; at the end of each cycle, the effluent stream is depressurized in a heated back pressure valve, and the extract is collected in a cooled two-chamber collection container; corn yellow pigment and its derivatives are dissolved in ethanol, and after removal of the solvent by evaporation, the first plant component is obtained; the raw materials of the second plant component are sponge gourd leaves, psidium leaves and eclipta, and the preparation steps are specifically as follows: fresh sponge gourd leaves, psidium leaves and eclipta are cleaned, disinfected, dried, and pulverized; after being mixed at a mass ratio of 5:8:9, anhydrous ethanol is added in a liquid-to-material ratio of 13 mL / g, the mixture is soaked for 36 hours, the soaked mixture is ultrasonically cleaned at room temperature for 30 min using an ultrasonic cleaner, and then the insoluble substances are removed by reduced-pressure suction filtration; the solution is concentrated to 1 / 3 of the volume by rotary evaporation at 80°C using a rotary evaporator, and the second plant component is obtained. ​ 2. The plant composite corrosion inhibitor for oil field as claimed in claim 1 wherein, The inhibition synergist is a mixture of potassium iodide, 8-hydroxyquinoline and sodium dodecylbenzenesulfonate at a mass ratio of 3:4:

2.

3. The plant composite corrosion inhibitor for oil field as claimed in claim 1 wherein, The organic solvent is ethanol with a mass concentration of 82%.

4. The preparation method of the plant composite corrosion inhibitor for oilfields according to any one of claims 1-3, characterized in that, The method comprises the following steps: (1) Raw material preparation: prepare the first plant component, the second plant component and the inhibition synergist for standby use; (2) Preparation: add the first plant component, the second plant component and the inhibition synergist in different mass parts into the organic solvent, stir and mix uniformly to obtain the plant composite corrosion inhibitor.

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