Preparation method of chemical applied to oil field

Abstract

The invention belongs to the technical field of oil field chemical material preparation, discloses a preparation method of a chemical applied to an oil field, and aims to overcome the defects that an existing oil field corrosion inhibitor is single in function and cannot synchronously cope with the problems of corrosion, microorganism breeding and scaling. The method comprises five steps of raw material pretreatment, corrosion inhibition main agent synthesis, functional component compounding, nanoparticle doping and post-treatment. The method comprises the following steps: preparing seven raw materials including 25-40 parts by weight of an imidazoline derivative and the like, and ultrasonically dispersing nano silicon dioxide in ethanol to obtain a nano dispersion liquid; synthesizing a corrosion inhibition main agent from the imidazoline derivative and thiourea at 50-60 DEG C; adding dodecyl dimethyl benzyl ammonium chloride and polymaleic anhydride, and compounding at 70-80 DEG C; and finally, adding deionized water, stirring and filtering to obtain a finished product. The product has the functions of efficient corrosion inhibition, bacteriostasis and scale prevention, the metal surface film-forming performance is improved through nanometer doping, and the product is suitable for complex oilfield corrosion environments such as injection-production integration.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical material preparation technology, specifically, it relates to a method for preparing chemicals for oilfield applications. Background Technology

[0002] With the continuous development of most oilfields in my country, many have entered the mid-to-late stages of production. To increase well production and improve ultimate recovery, most oilfields employ water injection technology. However, while increasing well production, water injection also causes severe corrosion problems, especially in wells using an integrated injection-production (transportation) alternating production model. Under the same wellbore conditions, the media, flow rate, temperature, dissolved oxygen, hydrogen sulfide, carbon dioxide, and microorganisms in this model differ significantly. The corrosive environments during injection and production (transportation) are vastly different, causing severe corrosion to the surface gathering and transportation system and downhole tubing, affecting normal oilfield production and posing significant safety hazards. Therefore, to mitigate the damage to oil production equipment and pipelines, certain anti-corrosion technologies must be adopted. Adding intelligent corrosion inhibitors is an effective measure that is both widely applicable and cost-effective.

[0003] Currently, corrosion in oilfields is often accompanied by microbial growth and scaling. The metabolic activities of microorganisms such as sulfate-reducing bacteria (SRB) produce hydrogen sulfide, leading to a 30%-50% increase in corrosion rate. Meanwhile, Ca²⁺ and Mg²⁺ ions in water easily form carbonate scale, which covers the metal surface, preventing corrosion inhibitors from effectively contacting the corrosion interface and reducing the efficiency of corrosion inhibition by more than 60%. Existing intelligent corrosion inhibitors only possess a single corrosion inhibition function and cannot simultaneously address both microbial corrosion and scaling issues, resulting in an imperfect corrosion control system that requires improvement. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a chemical for oilfield applications, comprising the following steps:

[0006] Step S1: Raw material pretreatment: Prepare the following raw materials by weight: 25-40 parts imidazoline derivative, 15-25 parts dodecyl dimethyl benzyl ammonium chloride, 10-20 parts polymaleic anhydride, 5-10 parts thiourea, 3-8 parts nano silica, 10-15 parts ethanol, and 20-30 parts deionized water; add nano silica to ethanol and ultrasonically disperse for 30-45 min to obtain a nano dispersion;

[0007] Step S2: Synthesis of corrosion inhibitor: Add imidazoline derivative to reaction vessel, heat to 50-60℃, stir at 200-300 r / min, add thiourea, stir and react for 1-1.5 h to obtain corrosion inhibitor;

[0008] Step S3: Functional component compounding: Add dodecyl dimethyl benzyl ammonium chloride and polymaleic anhydride to the corrosion inhibitor in sequence, heat to 70-80℃, stir at 350-450 r / min, react for 2-2.5 h, until the viscosity of the system stabilizes at 80-100 mPa·s;

[0009] Step S4: Nanoparticle doping: Add the nanoparticle dispersion dropwise to the reaction system, keep warm and stir for 1.5-2 hours after the addition is complete, and then cool down to 40-50℃;

[0010] Step S5: Post-treatment: Add deionized water and stir for 30-40 minutes, then filter to obtain the chemical.

[0011] In a preferred embodiment of the present invention, the imidazoline derivative in step S1 is oleic acid imidazoline or dodecylamine imidazoline with a purity ≥98%.

[0012] In a preferred embodiment of the present invention, the average particle size of the nano-silica in step S1 is 10-30 nm, and the specific surface area is ≥200 m² / g.

[0013] In a preferred embodiment of the present invention, the ultrasonic dispersion power in step S1 is 200-300W and the frequency is 40kHz.

[0014] In a preferred embodiment of the present invention, the reactor in step S2 is equipped with an anchor-type stirring paddle and a condensation reflux device.

[0015] In a preferred embodiment of the present invention, a rotational viscometer is used to monitor viscosity in step S3, and the test temperature is consistent with the reaction temperature.

[0016] In a preferred embodiment of the present invention, after the reaction in step S3 is completed, the system is further aged at 70-80°C for 0.5-1 h.

[0017] In a preferred embodiment of the present invention, the dropping rate of the nano-dispersion in step S4 is 1-2 drops / s.

[0018] In a preferred embodiment of the present invention, the filtration in step S5 uses a filter membrane with a pore size of 0.22 μm.

[0019] In a preferred embodiment of the present invention, the chemical described in step S5 has a viscosity of 50-80 mPa·s at 25°C and a pH value of 6.5-7.5.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention utilizes an imidazoline derivative as the core corrosion inhibitor, combined with thiourea to form a synergistic corrosion inhibition system, significantly improving the corrosion inhibition rate. It introduces dodecyl dimethyl benzyl ammonium chloride as an antibacterial agent, effectively inhibiting sulfate-reducing bacteria. Polymaleic anhydride, as a scale inhibitor, effectively chelates Ca²⁺ and Mg²⁺, significantly improving scale inhibition efficiency and solving the problem of insufficient function of single agents. Through nano-silica doping modification, the dispersibility and adsorption properties of nanoparticles are utilized to enhance the film-forming performance of the agent on the metal surface, resulting in a uniform film thickness and strong adhesion.

[0022] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0023] In the attached diagram:

[0024] Figure 1 This is a flowchart of a chemical preparation method for oilfield applications. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention.

[0026] Specific embodiments are as follows. All embodiments are based on the core preparation method of the invention. The stability and adaptability of the method are verified by adjusting the raw material ratio and process parameters. Unless otherwise specified, all raw materials in the embodiments meet the preferred specifications: imidazoline derivative purity ≥98% (oleic acid imidazoline or dodecylamine imidazoline), nano-silica with an average particle size of 10-30nm and a specific surface area ≥200m² / g, ultrasonic dispersion power of 200-300W / frequency of 40kHz, reaction vessel equipped with anchor-type stirring paddle and condenser reflux device, and 0.22μm filter membrane for filtration.

[0027] Example 1:

[0028] A method for preparing a chemical for oilfield applications, comprising the following steps:

[0029] S1: Raw material pretreatment: By weight, take 30 parts of oleic acid imidazoline, 20 parts of dodecyl dimethyl benzyl ammonium chloride, 15 parts of polymaleic anhydride, 8 parts of thiourea, 5 parts of nano silica, 12 parts of ethanol, and 25 parts of deionized water; add nano silica to ethanol and ultrasonically disperse for 35 min to obtain a uniform nano dispersion (without obvious precipitation).

[0030] S2: Synthesis of corrosion inhibitor: Oleic acid imidazoline was added to the reactor, heated to 55°C, and the stirring speed was adjusted to 250 r / min. Thiourea was slowly added and the reaction was continuously stirred for 1.2 h. During the reaction, the raw materials were prevented from volatilizing by a reflux condenser. Finally, a light yellow transparent corrosion inhibitor was obtained.

[0031] S3: Functional ingredient compounding: First, add dodecyl dimethyl benzyl ammonium chloride to the corrosion inhibitor (stir for 10 min until dissolved), then add polymaleic anhydride, heat to 75℃, increase the rotation speed to 400 r / min, and react for 2.2 h; use a rotational viscometer (test temperature 75℃) to monitor in real time, and when the viscosity of the system stabilizes at 90 mPa・s, maintain 75℃ for aging for 0.8 h to ensure that the components react fully;

[0032] S4: Nanoparticle doping: Add the nano-dispersion to the reaction system at a rate of 1.5 drops / s (keep stirring during addition to avoid local agglomeration), and continue stirring for 1.8 hours after addition, then slowly cool to 45°C;

[0033] S5: Post-treatment: Add deionized water, stir for 35 min to adjust the system concentration, filter through a 0.22 μm filter membrane to remove trace undispersed particles, and obtain the target chemical. Test results: Viscosity 65 mPa・s at 25℃, pH 7.0, appearance is a pale white homogeneous liquid, without stratification.

[0034] Example 2:

[0035] The difference between this embodiment and the above embodiments is that a method for preparing chemicals for oilfield applications includes the following steps:

[0036] S1: Raw material pretreatment: By weight, take 40 parts of dodecylamine imidazoline, 25 parts of dodecyl dimethyl benzyl ammonium chloride, 20 parts of polymaleic anhydride, 10 parts of thiourea, 8 parts of nano silica, 15 parts of ethanol, and 30 parts of deionized water; add ethanol to nano silica and ultrasonically disperse for 45 min (power 300W, to ensure uniform particle size dispersion) to obtain a high-concentration nano dispersion.

[0037] S2: Synthesis of corrosion inhibitor: Dodecylamine imidazoline was added to the reactor, heated to 60℃, stirred at 300r / min, and thiourea was added. The reaction was carried out for 1.5h. Because dodecylamine imidazoline has slightly higher reactivity, the reaction time was extended to ensure that it fully combines with thiourea, and a dark yellow viscous corrosion inhibitor was obtained.

[0038] S3: Functional ingredient compounding: Dodecyl dimethyl benzyl ammonium chloride and polymaleic anhydride are added sequentially, the temperature is raised to 80℃, and the rotation speed is increased to 450r / min (high rotation speed avoids agglomeration of high concentration components), and the reaction is carried out for 2.5h; after the viscosity is stabilized at 100mPa・s, it is cured at 80℃ for 1h to enhance the compatibility of components.

[0039] S4: Nanoparticle doping: The nano-dispersion is added at 2 drops / s, kept warm and stirred for 2 hours, and then cooled to 50℃ (high-concentration nanoparticles require a longer stirring time to ensure dispersion).

[0040] S5: Post-treatment: Add deionized water and stir for 40 minutes, then filter to obtain the chemical. Test results: viscosity at 25℃ is 80 mPa・s, pH value is 7.5, appearance is a pale yellow viscous liquid, and no stratification occurs after standing for 30 days.

[0041] Example 3:

[0042] The difference between this embodiment and the above embodiments 1 and 2 is that a method for preparing chemicals for oilfield applications includes the following steps:

[0043] S1: By weight, take 25 parts of oleic acid imidazoline, 15 parts of dodecyl dimethyl benzyl ammonium chloride, 10 parts of polymaleic anhydride, 5 parts of thiourea, 3 parts of nano silica, 10 parts of ethanol, and 20 parts of deionized water; add ethanol to nano silica and ultrasonically disperse for 30 min (power 200W) to obtain a dilute nano dispersion.

[0044] S2: Oleic acid imidazoline was added to the reactor, heated to 50°C, rotated at 200 r / min, and thiourea was added to react for 1 hour. Due to the low dosage of raw materials, the reaction time was shortened to avoid over-reaction, and a light yellow dilute corrosion inhibitor was obtained.

[0045] S3: Add dodecyl dimethyl benzyl ammonium chloride and polymaleic anhydride, heat to 70℃, rotate at 350 r / min, and react for 2 h; after the viscosity stabilizes at 80 mPa·s, ripen at 70℃ for 0.5 h;

[0046] S4: The nano-dispersion was added dropwise at 1 drop / s, kept warm and stirred for 1.5 hours, and then cooled to 40°C;

[0047] S5: Add deionized water and stir for 30 minutes, then filter to obtain the chemical. Test results: viscosity at 25℃ 50 mPa・s, pH value 6.5, appearance is colorless and transparent liquid with good fluidity.

[0048] Experimental example:

[0049] Performance testing and verification of beneficial effects

[0050] To quantify and verify the product's advantages in corrosion inhibition, antibacterial activity, scale inhibition, and film formation, a control experiment was designed: the products of Examples 1-3 were used as the test group, commercially available traditional corrosion inhibitors (containing only imidazoline and without antibacterial / scale-preventing functions) were used as control sample C1, and the blank system without any added agents was used as the blank group.

[0051] Basic experimental conditions

[0052] Corrosive medium: Simulating the alternating injection and production environment of an oilfield, the composition includes NaCl 30g / L, CaCl2 2.5g / L, MgCl2 1.5g / L, Na2SO4 0.5g / L, CO2 saturation (partial pressure 0.3MPa), H2S 50mg / L, and sulfate-reducing bacteria (SRB) concentration 10. 6 Cells / mL, pH adjusted to 6.0, temperature controlled at 60℃.

[0053] Test piece: N80 steel test piece commonly used in oil fields, with specifications of 50mm×10mm×3mm, is polished with 1200-grit sandpaper, degreased with acetone, derusted with 10% hydrochloric acid, rinsed with deionized water and dried, and weighed (accuracy 0.0001g) for later use.

[0054] Instruments: Rotary plate corrosion tester, high temperature and high pressure reactor, microbial counter, static scale inhibition tester, scanning electron microscope (SEM), electrochemical workstation (CHI660E).

[0055] Detection methods and indicators

[0056] Corrosion inhibition performance was tested using the weight loss method.

[0057] The test pieces were immersed in a corrosive medium containing 100 mg / L of chemicals and hung at 60℃ and 150 r / min for 72 hours. After removal, they were processed according to the procedure of "rust removal → cleaning → drying → weighing" to calculate the corrosion inhibition rate.

[0058] Corrosion inhibition rate η = (1 - weight loss of test group specimens / weight loss of blank group specimens) × 100%

[0059] (Weight loss = initial weight of the test piece - weight after the test; the blank group is the corrosive medium without added chemicals)

[0060] Antibacterial properties were tested using the erasure dilution method.

[0061] The chemical was added to a culture medium containing SRB at a concentration of 100 mg / L and anaerobically cultured at 37°C for 7 days. The SRB concentration after culture was measured using a microbial counter, and the inhibition rate was calculated.

[0062] Antibacterial rate = (1 - SRB concentration after culture / initial SRB concentration) × 100%, where the initial SRB concentration is 10. 6 The oilfield safety standard is ≤10 cells / mL. 4 cells / mL

[0063] Scale inhibition performance was tested using the static scale inhibition method.

[0064] Add the chemicals at a concentration of 100 mg / L to hard water. Calculate the concentrations as Ca²⁺ 200 mg / L and Mg²⁺ 100 mg / L, expressed as CaCO₃. Let the solution stand at 80℃ for 24 hours. After filtration, determine the residual concentrations of Ca²⁺ + Mg²⁺ in the filtrate using EDTA titration and calculate the scale inhibition rate.

[0065] Scale inhibition rate = (residual concentration of test group / residual concentration of blank group) × 100%; the blank group is hard water without added chemicals, and after standing, Ca²⁺ + Mg²⁺ is greatly reduced due to scaling.

[0066] Film formation performance was assessed using SEM and electrochemical impedance spectroscopy.

[0067] After the test piece was soaked in 100 mg / L of chemical for 2 hours, the morphology of the surface film was observed by SEM (magnification 5000 times). Electrochemical impedance spectroscopy (EIS) in the corrosive medium was measured by an electrochemical workstation, and the protective effect of the film was characterized by charge transfer resistance Rct - the larger the Rct value, the denser the film and the stronger the adhesion.

[0068] Stability was assessed through aging tests.

[0069] The chemicals were aged in a 50℃ oven for 30 days. The changes in corrosion inhibition rate, antibacterial rate, and scale inhibition rate before and after aging were measured. A change rate of ≤5% was considered stable (meeting the requirements for oilfield chemical storage).

[0070] Table 1 shows the experimental results and effect analysis.

[0071] Group Corrosion inhibition rate (%) Antibacterial rate (%) Scale inhibition rate (%) Rct (kΩ·cm²) Performance change rate after aging (%) Example 1 92.5 99.2 88.6 1850 ≤3.2 Example 2 95.1 99.5 90.3 2120 ≤2.8 Example 3 89.3 98.8 85.2 1560 ≤3.5 Control sample C1 72.6 12.3 18.5 420 ≤4.0 Blank group 0 0 0 85 -

[0072] The table clearly shows the corrosion inhibition effect: the synergistic system enhances protection; the corrosion inhibition rates of Examples 1-3 all exceed 89%, and Example 2 (high imidazoline + high thiourea) reaches 95.1%, which is 31% higher than the control sample C1 (72.6%). The core reason is the synergistic system of imidazoline-thiourea.

[0073] The cyclic amine structure of imidazoline derivatives adsorbs onto the surface of N80 steel via lone pair electrons, forming a monomolecular adsorption film that blocks direct contact between the corrosive medium and the metal.

[0074] The amino group of thiourea undergoes electronic conjugation with the imidazoline cyclic amine, enhancing the charge density of the adsorption film. At the same time, thiourea forms a stable complex with Fe²⁺ on the metal surface, inhibiting anodic dissolution (the main process of corrosion).

[0075] Example 3 shows that due to the low amount of nano-silica (3 parts), the corrosion inhibition rate is slightly lower (89.3%), which confirms the "filling effect" of nanoparticles - nano-silica can fill the micropores in the adsorption membrane to form a composite membrane of "organic membrane + inorganic nanofiller" and reduce the penetration of corrosive media.

[0076] The control sample C1 contained only imidazoline, without thiourea synergy and nanofilling, resulting in insufficient adsorption membrane density and a significant decrease in corrosion inhibition effect.

[0077] Antibacterial effect: Quaternary ammonium salts block microbial corrosion. The antibacterial rate in Examples 1-3 all exceeded 98.8%, and Example 2 reached 99.5%, which can reduce the SRB concentration to below 10³ cells / mL (far below the oilfield safety standard), while the control sample C1 only had 12.3% (no antibacterial effect). The key lies in the role of dodecyl dimethyl benzyl ammonium chloride (quaternary ammonium salt):

[0078] The cationic groups of quaternary ammonium salts can penetrate the cell membrane of SRB through electrostatic adsorption, destroy the intracellular enzyme system and genetic material, and block its metabolic activities. H2S produced by SRB metabolism accelerates metal corrosion (increasing the corrosion rate by 30%-50%). By inhibiting SRB, quaternary ammonium salts reduce H2S generation from the source and indirectly enhance the corrosion inhibition effect.

[0079] Scale inhibition effect: Polymaleic anhydride chelates and prevents scale buildup. The scale inhibition rates in Examples 1-3 all exceeded 85%, with Example 2 reaching 90.3%, a 388% improvement compared to the control sample C1 (18.5%). The core effect is the chelating and dispersing properties of polymaleic anhydride.

[0080] The carboxyl group in polymaleic anhydride molecules can form stable chelates with Ca²⁺ and Mg²⁺, preventing them from combining with CO₃²⁻ in water to form CaCO₃ and MgCO₃ scale.

[0081] Its polymer chains can be adsorbed onto the surface of scale crystals, changing the growth direction of scale crystals and inhibiting the aggregation of scale crystals into a dense scale layer. Traditional corrosion inhibitors, due to the lack of anti-scaling components, will have scale layers covering the metal surface, preventing the corrosion inhibitor from contacting the corrosion interface and reducing the corrosion inhibition efficiency by more than 60%. However, this invention avoids this problem through the synergistic effect of anti-scaling and corrosion inhibition.

[0082] Film formation effect: Nano-modification enhances film stability: SEM observation shows that: the test pieces of Examples 1-3 form a uniform and continuous film layer (the film thickness of Example 2 is about 2.5 μm), without corrosion pits and scale; due to the low amount of nanomaterials used in Example 3, there are small pores in the film layer in some areas (the film thickness is about 1.2 μm); the film layer of control sample C1 is discontinuous, with multiple corrosion pits and loose scale.

[0083] Electrochemical impedance spectroscopy data showed that the Rct values ​​of Examples 1-3 all exceeded 1500 kΩ·cm², and Example 2 reached 2120 kΩ·cm², which is 5 times that of the control sample C1 (420 kΩ·cm²). The high specific surface area of ​​nano-silica allows it to be uniformly dispersed on the metal surface, forming an interpenetrating network structure with organic components, preventing membrane detachment and significantly improving the membrane's anti-permeability performance.

[0084] Stability: Component compatibility ensures long-term effectiveness. The performance change rate after aging in Examples 1-3 was ≤3.5%, meeting storage requirements. This is due to the excellent compatibility of the components.

[0085] The synergistic effect of imidazoline and thiourea is stable and there is no chemical reaction; the quaternary ammonium salt and polymaleic anhydride have complementary charges and do not precipitate; after ultrasonic dispersion of nano-silica with ethanol, there is no aggregation in the system and no stratification after long-term standing.

[0086] Comparative Example: Validation of the Effects of Missing Core Components

[0087] To clarify the necessity of each core component (thiourea, dodecyl dimethyl benzyl ammonium chloride, polymaleic anhydride, and nano silica), a comparative example was designed: the preparation method was completely consistent with Example 1 (baseline group) except for the missing specified components, and the performance testing method was the same as that of Experiment 2.2.

[0088] Comparative Example 1 is the case where thiourea is missing.

[0089] Preparation: Remove thiourea from the raw materials, and keep the remaining proportions and processes the same as in Example 1.

[0090] Test results: corrosion inhibition rate 68.2%, antibacterial rate 99.0%, scale inhibition rate 88.3%, Rct value 1050kΩ・cm².

[0091] Analysis: The corrosion inhibition rate decreased by 26.3% compared to Example 1 (92.5%), and the Rct value decreased by 43.2%—proving that the synergy between thiourea and imidazoline is the key to the high corrosion inhibition rate. Without thiourea, the adsorption film is not dense enough, and the anodic dissolution inhibition effect is weakened.

[0092] Comparative Example 2 under the condition of lacking dodecyl dimethyl benzyl ammonium chloride

[0093] Preparation: Remove dodecyl dimethyl benzyl ammonium chloride from the raw materials, and keep the remaining proportions and processes the same as in Example 1.

[0094] Test results: corrosion inhibition rate 75.6%, antibacterial rate 15.8%, scale inhibition rate 88.5%, Rct value 820kΩ・cm².

[0095] Analysis: The antibacterial rate decreased by 84.1% compared to Example 1 (99.2%), and the corrosion inhibition rate also decreased by 18.3% - because without quaternary ammonium salt to inhibit SRB, SRB multiplied in large quantities and produced H2S, which accelerated metal corrosion. At the same time, the generated ferrous sulfide scale layer destroyed the corrosion inhibition film, resulting in a decrease in corrosion inhibition effect.

[0096] Comparative Example 3 was performed under conditions lacking polymaleic anhydride.

[0097] Preparation: Remove polymaleic anhydride from the raw materials, and keep the remaining proportions and processes the same as in Example 1.

[0098] Test results: corrosion inhibition rate 72.3%, antibacterial rate 99.1%, scale inhibition rate 20.4%, Rct value 780kΩ・cm².

[0099] Analysis: The scale inhibition rate decreased by 77.0% compared to Example 1 (88.6%), and the corrosion inhibition rate decreased by 21.8% - because there was no polymaleic anhydride chelating Ca²⁺ and Mg²⁺, the resulting dense scale layer covered the metal surface, blocking the contact between the corrosion inhibitor and the corrosion interface, resulting in the inability to effectively form a corrosion inhibition film.

[0100] Comparative Example 4 is under the condition of missing nano-silica.

[0101] Preparation: Remove nano-silica from the raw materials, and keep the remaining proportions and processes the same as in Example 1.

[0102] Test results: corrosion inhibition rate 78.5%, antibacterial rate 99.2%, scale inhibition rate 88.4%, Rct value 750kΩ・cm².

[0103] Analysis: The corrosion inhibition rate decreased by 15.1% compared to Example 1 (92.5%), and the Rct value decreased by 59.5%. SEM showed local detachment of the membrane layer and the presence of pores, proving that the "filling-adsorption" effect of nano-silica is the key to enhancing the density and adhesion of the membrane layer. After its absence, the membrane layer's anti-permeability performance decreased significantly.

[0104] Comparative Example 5: This case involves the absence of a single corrosion inhibitor; it contains only imidazoline.

[0105] Preparation: Use only 30 parts of imidazoline oleate and 70 parts of deionized water, without other ingredients, stir to dissolve and then filter.

[0106] Test results: corrosion inhibition rate 65.8%, antibacterial rate 12.5%, scale inhibition rate 16.3%, Rct value 380kΩ・cm².

[0107] Analysis: All performance indicators are far lower than those of Example 1 and close to those of commercially available control sample C1—proving that a single corrosion inhibitor cannot solve the complex problems of oilfield corrosion, microorganisms, and scaling, and that the multi-component compound design of this invention is irreplaceable.

Claims

1. A method for preparing a chemical for oilfield applications, characterized in that, Includes the following steps: Step S1: Raw material pretreatment: Prepare the following raw materials by weight: 25-40 parts imidazoline derivative, 15-25 parts dodecyl dimethyl benzyl ammonium chloride, 10-20 parts polymaleic anhydride, 5-10 parts thiourea, 3-8 parts nano silica, 10-15 parts ethanol, and 20-30 parts deionized water; add nano silica to ethanol and ultrasonically disperse for 30-45 min to obtain a nano dispersion; Step S2: Synthesis of corrosion inhibitor: Add imidazoline derivative to reaction vessel, heat to 50-60℃, stir at 200-300 r / min, add thiourea, stir and react for 1-1.5 h to obtain corrosion inhibitor; Step S3: Functional component compounding: Add dodecyl dimethyl benzyl ammonium chloride and polymaleic anhydride to the corrosion inhibitor in sequence, heat to 70-80℃, stir at 350-450 r / min, react for 2-2.5 h, until the viscosity of the system stabilizes at 80-100 mPa·s; Step S4: Nanoparticle doping: Add the nanoparticle dispersion dropwise to the reaction system, keep warm and stir for 1.5-2 hours after the addition is complete, and then cool down to 40-50℃; Step S5: Post-treatment: Add deionized water and stir for 30-40 minutes, then filter to obtain the chemical.

2. The method for preparing a chemical for oilfield applications according to claim 1, characterized in that, The imidazoline derivative mentioned in step S1 is oleic acid imidazoline or dodecylamine imidazoline, with a purity ≥98%.

3. The method for preparing a chemical for oilfield applications according to claim 1, characterized in that, The nano-silica described in step S1 has an average particle size of 10-30 nm and a specific surface area ≥200 m² / g.

4. The method for preparing a chemical for oilfield applications according to claim 1, characterized in that, In step S1, the ultrasonic dispersion power is 200-300W and the frequency is 40kHz.

5. A method for preparing a chemical for oilfield applications according to claim 1, characterized in that, The reactor described in step S2 is equipped with an anchor-type stirring paddle and a condenser reflux device.

6. The method for preparing a chemical for oilfield applications according to claim 1, characterized in that, In step S3, a rotational viscometer is used to monitor the viscosity, and the test temperature is the same as the reaction temperature.

7. The method for preparing a chemical for oilfield applications according to claim 1, characterized in that, After the reaction in step S3 is completed, the system is further aged at 70-80℃ for 0.5-1h.

8. A method for preparing a chemical for oilfield applications according to claim 1, characterized in that, In step S4, the dropping rate of the nano-dispersion is 1-2 drops / s.

9. A method for preparing a chemical for oilfield applications according to claim 1, characterized in that, In step S5, a filter membrane with a pore size of 0.22 μm is used for filtration.

10. A method for preparing a chemical for oilfield applications according to claim 1, characterized in that, The chemical described in step S5 has a viscosity of 50-80 mPa·s at 25°C and a pH value of 6.5-7.5.

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