Silicon-free defoamer for oil and gas fields and preparation method thereof

Abstract

The present application relates to the technical field of oil and gas field chemicals, and particularly relates to a silicon-free defoaming agent for oil and gas fields and a preparation method thereof, which contains, in parts by weight, 10-15 parts of defoaming agent active substance, 40-60 parts of industrial white oil, 1-10 parts of emulsifier, 5-10 parts of thickening agent and 5-10 parts of defoaming aid; wherein the defoaming agent active substance is obtained by treating carbon nanotubes with concentrated nitric acid to obtain functionalized carbon nanotubes, then grafting alkyl glycoside and polyether chain in sequence, and finally capping with isocyanate compounds. The defoaming agent prepared by the present application can avoid the problem of silicon scale, has stable defoaming effect, is resistant to high temperature, strong acid and alkali, is environmentally friendly, and is suitable for drilling, oil extraction and other links of oil and gas fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field chemicals, and particularly relates to a silicon-free defoaming agent for oil and gas fields and a preparation method thereof. BACKGROUND

[0002] In the development process of oil and gas fields, a large amount of foam is easily generated due to fluid agitation, chemical agent reaction and gas-liquid mixing and other factors. The foam hinders the oil and gas separation process, reduces the mining and transportation efficiency, can cause the transportation pipeline to be blocked, increases the operation load of the pump body and other equipment, and even causes pressure fluctuation, brings safety hazards, and has an adverse effect on the normal production of the oil and gas field.

[0003] To solve the problem of foam, the industry generally uses defoaming agents for control. The defoaming agents on the market are mainly divided into two types of silicon-containing and silicon-free types. The silicon-containing defoaming agent has a relatively fast initial defoaming speed and has been widely used in the field of oil and gas fields.

[0004] However, the silicon-containing defoaming agent has obvious disadvantages. The silicon component contained in the silicon-containing defoaming agent is easy to deposit and scale on the inner wall of the equipment and the surface of the pipeline, which not only affects the heat transfer efficiency of the equipment, but also interferes with the subsequent oil and gas dehydration, desalting and other treatment processes. At the same time, the silicon component can penetrate into the formation and block the formation pores, and damage the reservoir permeability, which is not conducive to the sustainable development of the oil and gas field. The existing silicon-free defoaming agents mostly have the problems of low defoaming efficiency and poor foam inhibition durability. In the harsh environment of high temperature, strong acid and alkali commonly seen in oil and gas fields, the silicon-free defoaming agents are easy to decompose or precipitate, have insufficient stability, and are difficult to maintain the defoaming effect for a long time. Some products also have the problem of poor biodegradability, which does not meet the requirements of current oil and gas field environmental protection development, and cannot meet the needs of long-term stable production. SUMMARY

[0005] The present application aims to solve the problems in the prior art that the silicon-containing defoaming agent is easy to deposit and scale, damages the reservoir, and the existing silicon-free defoaming agent has low defoaming efficiency, poor foam inhibition durability, insufficient stability in the high temperature, strong acid and alkali environment, and some products have poor biodegradability, and provides a silicon-free defoaming agent for oil and gas fields and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A silicon-free defoaming agent for oil and gas fields, comprising the following components in parts by weight: 10-15 parts of defoaming agent active substance, 40-60 parts of industrial white oil, 1-10 parts of emulsifier, 5-10 parts of thickening agent, and 5-10 parts of defoaming aid.

[0008] Preferably, the preparation method of the defoaming agent active substance comprises the following steps:

[0009] S1: weigh the carbon nanotubes, add them to a reactor containing deionized water, then ultrasonic treat for 15-30 min at a power of 150-250 W to form a uniform suspension; then add concentrated nitric acid to the suspension, start stirring and heat to 70-80 DEG C, keep refluxing for 3-4 h, then pour the reaction mixture into deionized water to dilute, then centrifugalize at a speed of 7000-8000 rpm for 10-20 min, discard the supernatant and collect the black precipitate at the bottom; wash the black precipitate with deionized water until the pH value approaches neutral, vacuum filter with a 0.6-0.8 um filter membrane, and dry in a vacuum drying oven at 60-65 DEG C for 10-12 h to obtain functionalized carbon nanotubes, which are sealed and stored for use;

[0010] S2: add the functionalized carbon nanotubes to a reactor containing toluene, ultrasonic treat for 20-40 min, then add alkyl glycoside, continue stirring until completely dissolved; then add p-toluenesulfonic acid, start stirring and heat to 100-110 DEG C, keep reacting for 6-8 h, after the reaction is completed, vacuum filter the reaction mixture, collect the solid product, wash with a large amount of anhydrous ethanol to remove unreacted substances, then wash with deionized water until neutral, and finally dry the product in a vacuum drying oven at 60-70 DEG C for 10-12 h to obtain alkyl glycoside grafted functionalized carbon nanotubes;

[0011] S3: at room temperature, add the alkyl glycoside grafted functionalized carbon nanotubes and double metal cyanide complex to a reaction kettle, replace with nitrogen, set the kettle pressure to -0.1 MPa to -0.2 MPa, heat to 150-160 DEG C, vacuumize for 0.5-1 h, pass the monomer under negative pressure to raise the kettle pressure to 0.2-0.3 MPa, react; when the kettle pressure drops sharply and the temperature rises to 175-185 DEG C, then continue passing the monomer at 140-150 DEG C; when the kettle pressure drops to -0.1 MPa to -0.2 MPa again, stop passing the monomer, cool to 120-130 DEG C, vacuumize for 1-2 h, and finally cool to room temperature to discharge, to obtain polyether chain-alkyl glycoside double grafted functionalized carbon nanotubes;

[0012] S4: weigh the polyether chain-alkyl glycoside double grafted functionalized carbon nanotubes, add them to a reactor containing anhydrous N,N-dimethylformamide, ultrasonic treat for 20 min to prepare a dispersion; then under nitrogen protection, stir at 70-80 DEG C for 0.5-1 h, add organotin catalyst to the dispersion, separately dissolve the isocyanate compound in anhydrous N,N-dimethylformamide, transfer to a constant pressure dropping funnel, and add to the reactor under nitrogen protection and continuous stirring, then heat to 85-95 DEG C, keep reacting for 7-8 h, after the reaction is completed, cool to room temperature, pour the reaction mixture into anhydrous methanol to precipitate, centrifugalize to collect the solid product, wash to remove unreacted substances, and then place in a vacuum drying oven at 55-65 DEG C to dry for 12-14 h, to obtain the defoaming agent active substance.

[0013] Preferably, in step S1, the mass ratio of the carbon nanotube to concentrated nitric acid is 1:5-20.

[0014] Preferably, in step S2, the alkyl glycoside is any one of alkyl glycoside 0810, alkyl glycoside 0814, alkyl glycoside 1214, and alkyl glycoside 1618; the mass ratio of the functionalized carbon nanotube, alkyl glycoside, and p-toluenesulfonic acid is 1:0.6-6:0.01-0.09.

[0015] Preferably, in step S3, the monomer is at least one of ethylene oxide and propylene oxide; the mass of the double metal cyanide complex is 0.1-1.5% of the mass of the alkyl glycoside grafted functionalized carbon nanotube.

[0016] Preferably, in step S4, the organotin catalyst is any one of dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin diacetate; the isocyanate compound is any one of 4-fluorophenyl isocyanate, 2-fluorophenyl isocyanate, 3-fluorophenyl isocyanate, 2,4-difluorophenyl isocyanate, 3,4-difluorophenyl isocyanate, 2,5-difluorophenyl isocyanate, 3-(trifluoromethyl)phenyl isocyanate, 2-(trifluoromethyl)phenyl isocyanate, and 4-(trifluoromethyl)phenyl isocyanate; the molar ratio of the polyether chain-alkyl glycoside double-grafted functionalized carbon nanotube, isocyanate compound, and organotin catalyst is 1:1.05-1.2:0.01-0.05.

[0017] Through the above technical solution, the carbon nanotube is acidized by concentrated nitric acid to obtain a functionalized carbon nanotube containing carboxyl groups on the surface; the carboxyl groups in the structure of the functionalized carbon nanotube and the alkyl glycoside containing multiple hydroxyl groups undergo dehydration condensation under the catalysis of p-toluenesulfonic acid, forming stable ester bonds, thereby covalently connecting the alkyl glycoside molecules to the surface of the carbon nanotube to obtain an alkyl glycoside grafted functionalized carbon nanotube; under the high-efficiency catalysis of the double metal cyanide, the hydroxyl groups in the structure of the alkyl glycoside grafted functionalized carbon nanotube serve as active initiation points to initiate the ring-opening polymerization of ethylene oxide or propylene oxide monomers, thereby growing complex-structure hyperbranched or crosslinked polyether chains in situ on the surface of the carbon nanotube to obtain a polyether chain-alkyl glycoside double-grafted functionalized carbon nanotube; under the catalysis of the organotin catalyst, the terminal hydroxyl groups in the structure of the polyether chain-alkyl glycoside double-grafted functionalized carbon nanotube react with the isocyanate groups in the structure of the isocyanate compound to generate carbamate bonds, thereby capping the polyether chains with benzene rings containing fluorine atoms, and finally obtaining a defoamer active substance with a carbon nanotube as a rigid core and sequentially connected on the surface of the carbon nanotube are biobased alkyl glycoside, hyperbranched polyether chain, and fluorine-containing hydrophobic end groups, which are multiple grafting structures.

[0018] The carbon nanotube in the structure of the defoaming agent active substance is chemically stable, and has a large specific surface area and abundant functional groups; the alkyl glycoside in the multi-graft structure is a good and biodegradable surfactant itself, and its introduction endows the final product with good hydrophilic-lipophilic balance and environmental friendly characteristics; the hyperbranched or crosslinked polyether chain structure in the multi-graft structure is a key feature of the high-efficiency defoaming agent, which can significantly reduce the surface tension and enhance the foam suppressing capacity; the fluorine-containing group structure in the multi-graft structure has extremely low surface energy, and its introduction can greatly enhance the hydrophobicity, chemical stability and spreading capacity on the foam liquid film of the defoaming agent active body, so that the defoaming agent still maintains excellent defoaming performance in harsh environments such as high temperature and strong acid and alkali.

[0019] Preferably, the emulsifier is at least one of fatty alcohol polyoxyethylene ether, Span 20, Span 60, and Span 80.

[0020] Preferably, the thickening agent is any one of hydroxyethyl cellulose, polyvinyl alcohol, and sodium carboxymethyl cellulose.

[0021] Preferably, the defoaming auxiliary agent is at least one of tributyl phosphate, isoamyl alcohol, and n-octanol.

[0022] Preferably, a preparation method of a silicon-free defoaming agent for oil and gas fields comprises the following steps:

[0023] Step 1: the components are weighed according to the above weight proportions and prepared for use;

[0024] Step 2: the defoaming agent active substance and the defoaming auxiliary agent are added to the industrial white oil, mixed and stirred at a speed of 300-400 rpm for 20-30 min, then the thickening agent is added, and the stirring is continued and the temperature is raised to 70-100 DEG C, and the temperature is kept for 1-2 h, and then the temperature is lowered to 30-50 DEG C, to obtain a first mixture;

[0025] Step 3: the first mixture is uniformly mixed with the emulsifier, and after the temperature is lowered to room temperature, it is ground and dispersed in a grinder for 1-2 h to obtain a silicon-free defoaming agent for oil and gas fields.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] 1. The present application does not use silicon components, which can avoid the silicon scale that may be produced by traditional silicon-containing defoaming agents, reduce the plugging of formation pores or equipment pipelines by the silicon scale, and does not significantly interfere with subsequent oil and gas separation, sewage treatment and other processes, which helps to maintain the formation permeability and ensure the normal operation of production equipment, and meets the basic needs of long-term stable production of oil and gas fields.

[0028] 2. The defoaming agent active substance prepared by the present application takes carbon nanotubes as the core, and introduces alkyl glycoside, polyether chain and fluorine-containing end group in sequence through grafting. Among them, the alkyl glycoside can improve the compatibility of the defoaming agent in the target system; the polyether chain can reduce the surface tension of the system and assist in prolonging the foam suppression time; the fluorine-containing end group helps the defoaming agent to spread faster on the foam liquid film. These structures cooperate with each other, so that the defoaming agent can complete defoaming relatively quickly, and can maintain a certain foam suppression time, and under the working conditions of high temperature, strong acid and alkali commonly seen in oil and gas fields, it can still maintain normal use performance, and alleviate the problem of effect attenuation of some traditional defoaming agents under such working conditions.

[0029] 3. The alkyl glycoside in the defoaming agent active substance prepared by the present application belongs to a bio-based material and has a certain biodegradability, which is different from some traditional chemical defoaming agents that are difficult to degrade, and has less long-term burden on the environment. At the same time, there is no obvious heavy metal or toxic and harmful solvent residue in the formula, and the influence on soil and water during use and discharge is relatively controllable, which can meet the basic requirements of current green production of oil and gas fields. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the prior known technology. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0031] Embodiment 1: I. Preparation of defoaming agent active substance:

[0032] S1: 6.20 g of carbon nanotubes was weighed and added to a reactor containing 95 mL of deionized water, and then ultrasonic treatment was carried out at 150 W power for 15 min to form a uniform suspension; then 31 g of concentrated nitric acid was added to the suspension, stirring was started and heating was carried out to 70℃, and the reaction was carried out at reflux for 3 h, then the reaction mixture was diluted by pouring into deionized water, and then centrifugal separation was carried out at a speed of 7000 rpm for 10 min, the supernatant was discarded and the black precipitate at the bottom was collected; the black precipitate was washed with deionized water until the pH value was close to neutral, vacuum filtration was carried out with a 0.6 um filter membrane, and the functionalized carbon nanotubes were obtained by drying in a vacuum drying box at 60℃ for 10 h, and were sealed and stored for later use;

[0033] S2: 4.60 g of functionalized carbon nanotubes was added to a reactor containing 92 mL of toluene, ultrasonic treatment was carried out for 20 min, then 2.76 g of alkyl glycoside 0810 was added, and stirring was continued until complete dissolution; then 0.046 g of p-toluenesulfonic acid was added, stirring was started and heating was carried out to 100℃, and the reaction was carried out for 6 h, after the reaction was completed, the reaction mixture was vacuum filtered, the solid product was collected, washed with a large amount of anhydrous ethanol to remove unreacted substances, then washed with deionized water until neutral, and finally the product was placed in a vacuum drying box and dried at 60℃ for 10 h to obtain alkyl glycoside grafted functionalized carbon nanotubes;

[0034] S3: At room temperature, 4.50 g of alkyl glycoside-grafted functionalized carbon nanotubes and 0.0045 g of bimetallic cyanide complex were added to a reactor. After nitrogen purging, the reactor pressure was set to -0.1 MPa. The temperature was raised to 150 °C and held. Vacuum was applied for 0.5 h. 4.50 g of ethylene oxide was introduced under negative pressure to raise the reactor pressure to 0.2 MPa for reaction. When the reactor pressure dropped sharply and the temperature rose to 175 °C, ethylene oxide was continued to be introduced at 140 °C. When the reactor pressure dropped to -0.1 MPa again, the ethylene oxide was stopped, the temperature was lowered to 120 °C, vacuum was applied for 1 h, and finally the mixture was cooled to room temperature and discharged to obtain polyether chain-alkyl glycoside double-grafted functionalized carbon nanotubes.

[0035] S4: Weigh 6.20g of polyether-alkyl glycoside double-grafted functionalized carbon nanotubes and add them to 93mL of anhydrous N,N-dimethylformamide in a reactor. Sonicate the mixture for 20min to obtain a dispersion. Then, under nitrogen protection, stir at 70℃ for 0.5h. Add 0.057g of dibutyltin dilaurate to the dispersion. Separately, dissolve 1.52g of 2,4-difluorophenyl isocyanate in 15mL of anhydrous N,N-dimethylformamide and transfer the solution to a constant pressure dropping funnel. Add the solution to the reactor under nitrogen protection and continuous stirring. Then, heat the mixture to 85℃ and maintain the temperature for 7h. After the reaction is complete, cool to room temperature and pour the reaction mixture into anhydrous methanol to precipitate. Centrifuge to collect the solid product. After washing to remove unreacted substances, dry the solid product in a vacuum drying oven at 55℃ for 12h to obtain the defoamer active substance.

[0036] II. Preparation of silicone-free defoamers for oil and gas fields:

[0037] Step 1: Weigh out 10g of defoamer active ingredient, 40g of industrial white oil, 1g of Span 60, 5g of hydroxyethyl cellulose, and 5g of isoamyl alcohol, and set aside.

[0038] Step 2: Add the defoamer active substance and isoamyl alcohol to the industrial white oil, mix and stir at 300 rpm for 20 minutes, then add hydroxyethyl cellulose, continue stirring and heat to 70°C, keep warm for 1 hour, and then cool down to 30°C to obtain the first mixture.

[0039] Step 3: Mix the first mixture with Span 60 until homogeneous, and after cooling to room temperature, transfer it to a grinder for grinding and dispersion for 1 hour to obtain a silicone-free defoamer for oil and gas fields.

[0040] Example 2: I. Preparation of active substances for defoamers:

[0041] S1: 6.2 g of carbon nanotubes were weighed into a reactor containing 100 mL of deionized water, and then ultrasonic treatment was performed for 25 min at a power of 200 W to form a uniform suspension; then 62 g of concentrated nitric acid was added to the suspension, stirring was started and heating was performed to 75°C, and reflux reaction was performed for 3.5 h, then the reaction mixture was poured into deionized water for dilution, followed by centrifugal separation at a speed of 7500 rpm for 15 min, the supernatant was discarded and the black precipitate at the bottom was collected; the black precipitate was washed with deionized water until the pH value was close to neutral, vacuum filtration was performed with a 0.7 um filter membrane, and drying was performed in a vacuum drying box at 62°C for 11 h to obtain functionalized carbon nanotubes, which were sealed and stored for later use;

[0042] S2: 4.60 g of functionalized carbon nanotubes were added to a reactor containing 115 mL of toluene, ultrasonic treatment was performed for 30 min, then 23 g of alkyl glycoside 0810 was added, and stirring was continued until complete dissolution; then 0.322 g of p-toluenesulfonic acid was added, stirring was started and heating was performed to 105°C, and the temperature was maintained for 7 h, after the reaction was completed, the reaction mixture was vacuum filtered, the solid product was collected, washed with a large amount of anhydrous ethanol to remove unreacted substances, then washed with deionized water until neutral, and finally the product was placed in a vacuum drying box and dried at 65°C for 11 h to obtain alkyl glycoside grafted functionalized carbon nanotubes;

[0043] S3: 4.30 g of alkyl glycoside grafted functionalized carbon nanotubes and 0.043 g of double metal cyanide complex were added to a reaction kettle at room temperature, after nitrogen replacement, the kettle pressure was set to -0.15 MPa, and the temperature was increased to 155°C, vacuum was applied for 0.8 h, 6.45 g of ethylene oxide was introduced under negative pressure to increase the kettle pressure to 0.25 MPa, and the reaction was performed; when the kettle pressure dropped sharply and the temperature increased to 180°C, ethylene oxide was continuously introduced at 145°C; when the kettle pressure decreased to -0.15 MPa again, the introduction of ethylene oxide was stopped, the temperature was decreased to 125°C, and vacuum was applied for 1.5 h, and finally the temperature was cooled to room temperature and the material was discharged, to obtain polyether chain-alkyl glycoside double-grafted functionalized carbon nanotubes;

[0044] S4: 6.20 g of polyether chain-alkyl glycoside double-grafted functionalized carbon nanotubes were weighed into a reactor containing 124 mL of anhydrous N,N-dimethylformamide, and ultrasonic treatment was performed for 20 min to obtain a dispersion; then under nitrogen protection, stirring was performed at 75°C for 0.6 h, 0.176 g of dibutyltin dilaurate was added to the dispersion, 1.66 g of 2,4-difluorophenyl isocyanate was dissolved in 17 mL of anhydrous N,N-dimethylformamide, and then transferred to a constant pressure dropping funnel, and added to the reactor under nitrogen protection and continuous stirring, then the temperature was increased to 90°C, and the temperature was maintained for 7.5 h, after the reaction was completed, the temperature was cooled to room temperature, the reaction mixture was poured into anhydrous methanol for precipitation, the solid product was collected by centrifugation, after washing to remove unreacted substances, the product was placed in a vacuum drying box and dried at 60°C for 13 h to obtain the antifoaming agent active substance.

[0045] II. Preparation of a silicon-free defoamer for oil and gas fields:

[0046] Step 1: Take 14 g of defoamer active substance, 42 g of industrial white oil, 3 g of Span 60, 6 g of hydroxyethyl cellulose, and 7 g of isoamyl alcohol, and set aside;

[0047] Step 2: Add the defoamer active substance and isoamyl alcohol to the industrial white oil and mix at a speed of 350 rpm for 25 minutes. Then add the hydroxyethyl cellulose and continue stirring while heating to 80°C for 1.5 hours. Then cool to 40°C to obtain a first mixture;

[0048] Step 3: Mix the first mixture with Span 60 uniformly, and then grind and disperse in a grinder for 1.5 hours after cooling to room temperature to obtain a silicon-free defoamer for oil and gas fields.

[0049] Example 3: I. Preparation of a defoamer active substance:

[0050] S1: Take 6.2 g of carbon nanotubes and add them to a reactor containing 124 mL of deionized water. Then ultrasonically treat for 30 minutes at a power of 250 W to form a uniform suspension. Then add 124 g of concentrated nitric acid to the suspension, start stirring, and heat to 80°C. Keep the reaction mixture at reflux for 4 hours. Then dilute the reaction mixture by pouring it into deionized water, and then perform centrifugal separation at a speed of 8000 rpm for 20 minutes. Discard the supernatant and collect the black precipitate at the bottom. Wash the black precipitate with deionized water until the pH value approaches neutral, vacuum filter with a 0.8 um filter membrane, and dry in a vacuum drying oven at 65°C for 12 hours to obtain functionalized carbon nanotubes. Seal and store for later use;

[0051] S2: Add 4.60 g of functionalized carbon nanotubes to a reactor containing 138 mL of toluene and ultrasonically treat for 40 minutes. Then add 27.6 g of alkyl glycoside 0810 and continue stirring until completely dissolved. Then add 0.414 g of p-toluenesulfonic acid, start stirring, and heat to 110°C. Keep the reaction mixture at this temperature for 8 hours. After the reaction is complete, vacuum filter the reaction mixture and collect the solid product. Wash the product with a large amount of anhydrous ethanol to remove unreacted substances, and then wash with deionized water until neutral. Finally, dry the product in a vacuum drying oven at 70°C for 12 hours to obtain alkyl glycoside grafted functionalized carbon nanotubes.

[0052] S3: 4.50 g of alkyl polyglycoside grafted functionalized carbon nanotubes and 0.0675 g of double metal cyanide complex were added into a reaction kettle under room temperature, after nitrogen replacement, the kettle pressure was set to -0.2 MPa, and then the temperature was increased to 160 ℃ for heat preservation. After vacuumizing for 1 h, 9 g of ethylene oxide was introduced under negative pressure to increase the kettle pressure to 0.3 MPa for reaction. When the kettle pressure dropped sharply and the temperature increased to 185 ℃, ethylene oxide was continuously introduced at 150 ℃. When the kettle pressure decreased to -0.2 MPa again, the introduction of ethylene oxide was stopped, and the temperature was decreased to 130 ℃. After vacuumizing for 2 h, the temperature was finally cooled to room temperature for discharging. Polyether chain-alkyl polyglycoside double grafting functionalized carbon nanotubes were obtained.

[0053] S4: 6.20 g of polyether chain-alkyl polyglycoside double grafting functionalized carbon nanotubes were weighed and added into a reactor containing 155 mL of anhydrous N,N-dimethylformamide. After ultrasonic treatment for 20 min, a dispersion was prepared. Then, under nitrogen protection, 0.293 g of dibutyltin dilaurate was added into the dispersion under stirring at 80 ℃ for 1 h. Separately, 1.731 g of 2,4-difluorophenyl isocyanate was dissolved in 17 mL of anhydrous N,N-dimethylformamide, and then transferred into a constant pressure dropping funnel. Under nitrogen protection and continuous stirring, it was added into the reactor. Then, the temperature was increased to 95 ℃, and heat preservation reaction was carried out for 8 h. After the reaction was completed, the temperature was cooled to room temperature. The reaction mixture was poured into anhydrous methanol for precipitation. The solid product was collected by centrifugation. After washing to remove unreacted substances, it was placed in a vacuum drying box for drying at 65 ℃ for 14 h. Thus, the defoamer active substance was obtained.

[0054] II. Preparation of a silicon-free defoamer for oil and gas fields:

[0055] First step: 15 g of defoamer active substance, 60 g of industrial white oil, 10 g of Span 60, 10 g of hydroxyethyl cellulose, and 10 g of isopentyl alcohol were weighed and prepared.

[0056] Second step: The defoamer active substance and isopentyl alcohol were added into the industrial white oil, and mixed and stirred at a speed of 400 rpm for 30 min. Then, the hydroxyethyl cellulose was added, and the stirring was continued while the temperature was increased to 100 ℃ for heat preservation for 2 h. Subsequently, the temperature was decreased to 50 ℃ to obtain a first mixture.

[0057] Third step: The first mixture was uniformly mixed with Span 60. After being cooled to room temperature, it was transferred into a grinding machine for grinding and dispersing for 2 h. Thus, the silicon-free defoamer for oil and gas fields was obtained.

[0058] Comparative Example 1: Based on Example 2, the difference was that step S4 was removed, and the defoamer active substance was replaced by polyether chain-alkyl polyglycoside double grafting functionalized carbon nanotubes to prepare the defoamer. The rest was the same as Example 2.

[0059] Comparative Example 2: On the basis of Example 2, the difference is that the defoaming agent active substance is replaced by polyoxypropylene polyether PPG2000 to prepare a defoaming agent, and the rest is the same as Example 2.

[0060] Comparative Example 3: On the basis of Example 2, the difference is that the defoaming agent active substance is replaced by dimethyl silicone oil to prepare a defoaming agent, and the rest is the same as Example 2.

[0061] Comparative Example 4: On the basis of Example 2, the difference is that the defoaming auxiliary isopentyl alcohol is removed, and the rest is the same as Example 2.

[0062] Comparative Example 5: On the basis of Example 2, the difference is that in step S1, the mass ratio of carbon nanotubes to concentrated nitric acid is 1:3, and the rest is the same as Example 2.

[0063] Comparative Example 6: On the basis of Example 2, the difference is that the defoaming agent active substance is replaced by carbon nanotubes to prepare a defoaming agent, and the rest is the same as Example 2.

[0064] Performance test: The defoaming agents prepared by Example 1-Example 3 and Comparative Example 1-Comparative Example 6 are tested for performance:

[0065] Crude oil foaming experiment: Take 150 mL of crude oil in a 200 mL high-pressure container, and introduce food-grade CO2 with a purity of ≥99.95%. Slowly pressurize to 4.5 MPa and stop aeration, and monitor the pressure for 15 min. When the pressure fluctuation is ≤0.03 MPa, it is considered stable, and the valve is closed. The entire pressurization and stabilization process lasts about 1.2 h. Place at room temperature (25±1℃) for 40 h. During this period, to ensure uniform gas-liquid pressure in the container, invert the high-pressure container once every 5 h, and each time shake for 12 min. The shaking rate is controlled at 1 time / 3 s. When foaming, first let the high-pressure container stand for 5 min to make the gas-liquid interface stable, then invert the container, and slowly adjust the discharge rate to 8 mL / min through a precision flow valve. When the collected crude oil foam volume reaches 100 mL, immediately close the discharge valve, and complete the crude oil foaming.

[0066] Defoaming rate determination: The defoaming rate of a simulated foam system was determined based on the improvement of the "Shengli Oil Administration Bureau Enterprise Standard" Q / SH10202194-2013: 75 mL of the foam was taken in a 100 mL graduated cylinder, and the initial volume was recorded as V1. 0.5 mL of a 1.2% defoaming agent solution was quickly added using a pipette, and a glass rod was immediately used to stir at a frequency of not less than 150 r / min. After stirring for 25 min, the foam volume was recorded as V2. Subsequently, 1.2 mL of a 1.2% defoaming agent solution was added to the system, and it was placed in a 55°C water bath for constant temperature for 35 min, while stirring with a glass rod until the foam completely disappeared. The volume of the oil phase after stirring without foam was read as V3. The defoaming rate (X) was calculated according to the following formula: X = [(V1-V2) / (V0-V3)] x 100%.

[0067] Acid resistance test: 120 mL of dilute acid aqueous solution (pH = 2.8) was added to a 300 mL beaker, and then 2.5 mL of the defoaming agent solution was added and heated. When flocculation appeared on the liquid surface, the temperature was recorded, which was the precipitation temperature of the defoaming agent. After boiling for 10 min, the liquid surface state was observed after cooling to room temperature.

[0068] Alkali resistance test: 120 mL of sodium hydroxide aqueous solution (pH = 13.2) was added to a 300 mL beaker, and then 2.5 mL of the defoaming agent solution was added and heated. When flocculation appeared on the liquid surface, the temperature was recorded, which was the precipitation temperature of the defoaming agent. After boiling for 10 min, the liquid surface state was observed after cooling to room temperature. The more "+"s, the more serious the precipitation.

[0069] Centrifugal stability test: 0.6 g of the defoaming agent was added to 120 mL of deionized water, and stirred until completely dispersed. The centrifugal stability of the sample was observed after centrifugation at 3500 r / min for 8 min. If there was no stratification or precipitation, it proved that the centrifugal stability was excellent.

[0070] Table 1: Test results of sample properties of examples and comparative examples

[0071]

[0072] Data analysis:

[0073] The defoaming rates of Examples 1-3 all remain at a high level of 89.2%-89.6%, the acid precipitation resistance temperature is 85.8-86.4℃, the alkali precipitation resistance temperature is 84.1-84.7℃, and the stability all shows no delamination and no precipitation, and the overall performance is excellent. This is because the complete defoamer active material preparation process is adopted in the examples, the carbon nanotube is used as the rigid core, and the bio-based alkyl glycoside, the hyperbranched polyether chain and the fluorine-containing hydrophobic end group are sequentially grafted. The large specific surface area and rich functional groups of the carbon nanotube provide a basis for defoaming. The alkyl glycoside gives good hydrophilic-lipophilic balance. The polyether chain significantly reduces the surface tension and enhances the foam suppression capacity. The fluorine-containing group greatly improves the hydrophobicity and chemical stability. The synergistic effect of each component makes the defoamer perform outstandingly in various tests.

[0074] Comparative Example 1 does not perform the fluorine-containing group end capping in step S4, and the defoaming rate is reduced to 78.5%. The acid and alkali precipitation resistance temperatures are reduced to 70.3℃ and 68.5℃, respectively. The precipitation is more obvious, which shows that the fluorine-containing hydrophobic end group is crucial to improving the defoaming efficiency and acid and alkali resistance of the defoamer.

[0075] Comparative Example 2 uses polyoxypropylene polyether PPG2000 as the active material, lacks the rigid support of the carbon nanotube, and lacks the multi-element grafting structure of the alkyl glycoside, the polyether chain and the fluorine-containing end group. The defoaming rate is only 65.2%, the acid and alkali resistance is greatly reduced, and slight delamination occurs, which confirms that the multi-element grafting structure designed in the application is the key to ensuring the defoaming performance.

[0076] Comparative Example 3 uses dimethyl silicone oil as the active material, which has certain defoaming capacity but far less than that of the examples, and a small amount of precipitation occurs, which shows that the multi-element grafting structure of the alkyl glycoside, the polyether chain and the fluorine-containing end group without silicon has advantages in stability and adaptability.

[0077] Comparative Example 4 removes the defoaming auxiliary isopentyl alcohol, and the defoaming rate is reduced to 82.3%. The acid and alkali resistance is slightly reduced, which shows that the defoaming auxiliary can effectively assist in improving the defoaming effect and system stability.

[0078] Comparative Example 5 does not achieve the optimal range of the mass ratio of the carbon nanotube to concentrated nitric acid, the number of carboxyl groups of the functionalized carbon nanotube is insufficient, and the subsequent grafting effect is limited. The defoaming rate is 80.1%, and the acid and alkali resistance is also weakened.

[0079] Comparative Example 6 directly uses the carbon nanotube as the active material without any grafting modification. The defoaming rate is the lowest, the acid and alkali resistance is extremely poor, and obvious delamination and precipitation occur, which fully shows that a single carbon nanotube cannot meet the defoaming demand, and multi-element grafting modification is the core means to improve the defoaming performance, stability and harsh environment resistance of the carbon nanotube.

[0080] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A non-silicon defoamer for use in oil and gas fields, characterized by, Components comprising the following parts by weight: 10-15 parts of defoaming agent active substance, 40-60 parts of industrial white oil, 1-10 parts of emulsifier, 5-10 parts of thickening agent, 5-10 parts of defoaming auxiliary; The preparation method of the defoaming agent active substance comprises the following steps: S1: weigh the carbon nanotubes, add them into a reactor containing deionized water, then ultrasonic treat for 15-30 min under a power of 150-250 W to form a uniform suspension; then add concentrated nitric acid into the suspension, start stirring and heat to 70-80℃, keep refluxing for 3-4 h, then pour the reaction mixture into deionized water for dilution, then centrifugal separation is carried out at a speed of 7000-8000 rpm for 10-20 min, discard the supernatant and collect the black precipitate at the bottom; wash the black precipitate with deionized water until the pH value is neutral, vacuum filter with a 0.6-0.8 um filter membrane, and dry in a vacuum drying oven at 60-65℃ for 10-12 h to obtain functionalized carbon nanotubes, which are sealed and stored for use; S2: add the functionalized carbon nanotubes into a reactor containing toluene, ultrasonic treat for 20-40 min, then add alkyl glycoside, continue stirring until completely dissolved; then add p-toluenesulfonic acid, start stirring and heat to 100-110℃, keep the temperature for 6-8 h, after the reaction is completed, vacuum filter the reaction mixture, collect the solid product, wash with a large amount of anhydrous ethanol to remove unreacted substances, then wash with deionized water until neutral, finally dry the product in a vacuum drying oven at 60-70℃ for 10-12 h to obtain alkyl glycoside grafted functionalized carbon nanotubes; S3: at room temperature, add the alkyl glycoside grafted functionalized carbon nanotubes and double metal cyanide complex into a reaction kettle, after nitrogen replacement, set the kettle pressure to -0.1 MPa to -0.2 MPa, heat to 150-160℃, vacuum for 0.5-1 h, pass at least one monomer of ethylene oxide and propylene oxide under negative pressure to make the kettle pressure rise to 0.2-0.3 MPa for reaction; when the kettle pressure drops sharply and the temperature rises to 175-185℃, then continue to pass the monomer at 140-150℃; when the kettle pressure drops to -0.1 MPa to -0.2 MPa again, stop passing the monomer, cool to 120-130℃, vacuum for another 1-2 h, and finally cool to room temperature to discharge the product, obtaining polyether chain-alkyl glycoside double grafted functionalized carbon nanotubes; S4: the polyether chain-alkyl glycoside double grafting functionalized carbon nanotubes are weighed, added into a reactor containing anhydrous N,N-dimethylformamide, and ultrasonically treated for 20 min to obtain a dispersion; then under nitrogen protection, stirring at 70-80℃ for 0.5-1h, the organotin catalyst is added into the dispersion, and the isocyanate compound containing a benzene ring structure of fluorine atoms is dissolved in anhydrous N,N-dimethylformamide, transferred to a constant pressure dropping funnel, and added into the reactor under nitrogen protection and continuous stirring; then the temperature is raised to 85-95℃, and the reaction is carried out for 7-8h; after the reaction is completed, the reaction mixture is cooled to room temperature, poured into anhydrous methanol for precipitation, and the solid product is collected by centrifugation; after washing to remove the unreacted substances, the product is placed in a vacuum drying box and dried at 55-65℃ for 12-14h to obtain the antifoaming agent active substance.

2. The non-silicon defoamer for oil and gas fields according to claim 1, characterized in that, In step S1, the mass ratio of the carbon nanotubes to concentrated nitric acid is 1:5-20.

3. The non-silicon defoamer for oil and gas fields according to claim 1, characterized in that, In step S2, the alkyl glycoside is any one of alkyl glycoside 0810, alkyl glycoside 0814, alkyl glycoside 1214, or alkyl glycoside 1618; the mass ratio of the functionalized carbon nanotubes, alkyl glycoside, and p-toluenesulfonic acid is 1:0.6-6:0.01-0.

09.

4. The non-silicon defoamer for oil and gas fields according to claim 1, characterized in that, In step S3, the monomer is at least one of ethylene oxide or propylene oxide; the mass of the double metal cyanide complex is 0.1-1.5% of the mass of the alkyl glycoside grafting functionalized carbon nanotubes.

5. The non-silicon defoamer for oil and gas fields according to claim 1, characterized in that, In step S4, the organotin catalyst is any one of dibutyltin dilaurate, dioctyltin dilaurate, or dibutyltin diacetate; the isocyanate compound is any one of 4-fluorophenyl isocyanate, 2-fluorophenyl isocyanate, 3-fluorophenyl isocyanate, 2,4-difluorophenyl isocyanate, 3,4-difluorophenyl isocyanate, 2,5-difluorophenyl isocyanate, 3-(trifluoromethyl)phenyl isocyanate, 2-(trifluoromethyl)phenyl isocyanate, or 4-(trifluoromethyl)phenyl isocyanate; the molar ratio of the polyether chain-alkyl glycoside double grafting functionalized carbon nanotubes, isocyanate compound, and organotin catalyst is 1:1.05-1.2:0.01-0.05.

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