An oil-resistant and anti-freezing corrosion-resistant foaming agent for gas wells and a preparation method and application thereof

Abstract

The application belongs to the technical field of natural gas exploitation, and particularly relates to an oil-resistant and freeze-resistant corrosion-inhibiting foaming agent for gas wells and a preparation method and application thereof. The oil-resistant and freeze-resistant corrosion-inhibiting foaming agent for gas wells comprises, in mass parts, 40-70 parts of sodium alpha-olefin sulfonate, 10-20 parts of cocamide propyl amine oxide, 1-10 parts of modified nanoparticles, 20-40 parts of betaine amphoteric ionic surfactant, 5-15 parts of corrosion inhibitor, 1-15 parts of polyvinyl pyrrolidone, and the balance of water. After aging at a low temperature of-30 DEG C, the foaming agent has a liquid carrying rate of up to 83.8% in a range of 10%-50% condensate content, a high resistance to salinity of up to 2*10<5> mg / L, and an inhibition rate of up to 75% in a composite sample liquid of 20 wt% condensate, 20 wt% methanol and saturated CO2. The foaming agent can meet the requirements of extreme composite working conditions such as high salinity, condensate pollution and acid gas corrosion in the middle and late stages of gas well development, and can realize the dual functions of drainage gas recovery and downhole protection.

Description

Technical Field

[0001] This invention relates to the field of natural gas extraction technology, and more specifically, to an oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells, its preparation method, and its application. Background Technology

[0002] In natural gas well production, foam drainage gas production is a primary method for addressing the problem of fluid accumulation at the bottom of the well. Its core principle is to use a foaming agent to transform the accumulated fluid into stable foam, which is then carried out of the wellbore by gas flow to maintain normal gas well production. The foaming agent, as the core additive in foam drainage gas production, directly determines the drainage efficiency.

[0003] As natural gas well development enters the middle and late stages, the extraction conditions in some gas fields become increasingly harsh—the decrease in formation pressure causes a large amount of light hydrocarbons to precipitate out, forming condensate oil and mixing into the bottom fluid; these condensate oil droplets easily invade the liquid film structure of foam, causing a sharp decrease in the stability of foam generated by conventional foaming agents, which seriously affects the liquid carrying efficiency.

[0004] Meanwhile, in some acidic gas reservoirs, if they contain a certain concentration of H2S and CO2, they will interact with formation water to cause severe corrosion to equipment. Although traditionally corrosion inhibitors can be added to meet production needs, when foam drainage is implemented in the middle and later stages of extraction, the corrosion inhibitors will interact with the foaming agents, leading to deterioration of foam stability, and the addition of corrosion inhibitors must be stopped.

[0005] Common foaming agents used in drainage and gas extraction, such as betaine and sodium dodecyl sulfate, are mostly single-function. They are insufficient to meet the demands of such harsh environments. To address this, the industry has attempted to use compounding techniques—selecting compatible foaming agents and corrosion inhibitors to reduce corrosion while simultaneously draining water. However, achieving compatibility between the components remains a challenge.

[0006] In some frigid regions, this problem is even more complex. To prevent the bottom fluid from freezing, antifreeze agents such as methanol need to be added. However, methanol will reduce the foaming ability and foam stability of some foaming agents. Therefore, developing an integrated foaming agent that combines high foaming efficiency, strong resistance to oil interference, suitability for low-temperature conditions, and corrosion inhibition is of great significance for improving the efficiency of gas field development and reducing equipment maintenance costs in complex environments. Summary of the Invention

[0007] One object of the present invention is to solve at least the above-mentioned problems and / or defects. In order to address the shortcomings of conventional foaming agents, which are mainly single-function and difficult to meet the needs of use in harsh environments, the present invention provides an oil-resistant, antifreeze, and corrosion-inhibiting foaming agent, its preparation method, and its application.

[0008] The objective of this invention is achieved as follows: In a first aspect, this invention provides an oil-resistant, antifreeze, and corrosion-inhibiting foaming agent, comprising, by weight, 40-70 parts of sodium α-olefin sulfonate, 10-20 parts of cocamidopropylamine oxide, 1-10 parts of modified nanoparticles, 20-40 parts of betaine-based zwitterionic surfactant, 5-15 parts of corrosion inhibitor, 1-15 parts of polyvinylpyrrolidone, and the balance being water.

[0009] The essence of foam drainage gas production in gas wells is to transform the liquid accumulated at the bottom of the well into stable foam using a foaming agent, and then discharge the foam from the wellbore using the carrying capacity of the natural gas flow. Therefore, the foaming capacity and foam stability of the foaming agent are the core performance indicators. In this invention, betaine-based zwitterionic surfactants and sodium α-olefin sulfonate within the aforementioned range are used as the main foaming components, and cocamidopropylamine oxide is used as a foaming aid.

[0010] Among them, sodium α-olefin sulfonate has excellent foaming properties. It can maintain stable surface activity under acidic conditions and is resistant to acids, alkalis and hard water. Compared with other foaming agents, betaine zwitterionic surfactant has outstanding advantages in temperature resistance and salt resistance. The combination of the two produces a synergistic effect, which can greatly enhance the foaming performance of the foaming agent and ensure that the foaming agent can still stably generate foam in complex environments.

[0011] When cocamidopropylamine oxide is used as a foaming aid, it can synergistically reduce the overall surface tension of the system when combined with the main foaming components sodium α-olefin sulfonate and betaine zwitterionic surfactant, making it easier for bubbles to form and helping to enhance the strength of the foam liquid film, thereby enhancing foam stability and improving the system's resistance to oil interference.

[0012] The betaine-type zwitterionic surfactant is selected from at least one of cocamidopropyl hydroxysulfonate betaine, lauramide propyl betaine, and erucamide propyl betaine, or, in order to better adapt to complex environments, it may be a mixture of two or more of these betaines.

[0013] In one embodiment of the present invention, the particle size of the modified nanoparticles is controlled between 10 nm and 800 nm; specifically, the particle size is preferably controlled at 50 nm, and is selected from one or more combinations of nano silica, nano alumina, nano titanium dioxide, nano copper oxide, nano zirconium dioxide, nano calcium carbonate or nano montmorillonite, as the main foam-stabilizing component in the foaming agent.

[0014] The advantage of using modified nanoparticles as the main foam stabilizing component lies in their insensitivity to temperature, stronger stability in complex environments, and good compatibility with betaine zwitterionic surfactants and sodium α-olefin sulfonate anionic surfactants. They can be adsorbed at the gas-liquid interface, enhancing the mechanical strength of the foam liquid film and ensuring the stability of foam generated by the foaming agent under complex environments.

[0015] In one embodiment of the present invention, the modified nanoparticle foam stabilizer is surface-hydrophobically modified nano-silica, which allows the nanoparticles to be better and more firmly anchored at the gas-liquid interface of the foam, thereby enhancing the mechanical strength of the foam liquid film and improving the stability and anti-interference ability of the foam.

[0016] Specifically, the modified nano-silica is nano-silica that has been modified with a silane coupling agent and then grafted with perfluoropolyether segments. After modification with the perfluoropolyether segments, the nano-silica is both hydrophobic and oleophobic, effectively resisting the adhesion and spreading of condensate oil on the surface of the nanoparticles. This allows it to remain stably anchored at the gas-liquid interface even in high-oil environments, continuously enhancing the foam film. Examples of this application demonstrate that, in foaming components primarily composed of the surfactant of this invention, the modified nano-silica exhibits higher foaming and foam-stabilizing performance under the same conditions than nano-silica modified only with a silane coupling agent.

[0017] Polyvinylpyrrolidone (PVP) is used as a dispersant and auxiliary foam stabilizer. On the one hand, it enhances the dispersibility of modified nanoparticles in the system, ensuring their stable existence and migration to the gas-liquid interface, thus fully exerting the foam stabilizing effect. On the other hand, PPVP can also be adsorbed onto the bubble liquid film, thereby delaying liquid film drainage and gas diffusion by enhancing the viscoelasticity of the liquid film, which helps maintain the integrity of the foam structure.

[0018] In one embodiment of the present invention, the corrosion inhibitor is composed of sodium molybdate, alkyl imidazoline quaternary ammonium salt and organophosphonate. The three components do not conflict at their sites of action and have good synergistic corrosion inhibition. They can be stacked to form a more complete protection and improve the corrosion inhibition effect in complex environments.

[0019] Specifically, sodium molybdate, as an inorganic passivating corrosion inhibitor, exhibits good compatibility with amphoteric and anionic surfactants in the system, forming a dense oxide film on the metal surface to inhibit corrosion reactions. Alkyl imidazoline quaternary ammonium salts possess both corrosion inhibition and foaming-aiding functions: their hydrophobic long chains and polar head groups can be directionally adsorbed at the metal interface, effectively blocking corrosive media. As a cationic surfactant, it can enhance the interfacial film strength with the anionic surfactant α-olefin sulfonate in a high-oil-phase environment through electrostatic interactions, thereby improving foam stability and resistance to condensate interference. The phosphonic acid groups in organophosphonates can complex high-valence metal ions such as Ca²⁺ and Mg²⁺ in mineralized water, preventing them from binding with surfactants to form flocculation or precipitation, thus maintaining system stability.

[0020] In a second aspect, the present invention provides a method for preparing modified nanoparticles, specifically comprising the following steps: S11, pretreating the nanoparticles to obtain nanoparticles with activated surface hydroxyl groups; S12, dispersing the nanoparticles obtained in S11 in a dispersion medium to obtain solution A; dissolving an epoxy silicone coupling agent in the dispersion medium to obtain solution B; uniformly adding solution B to solution A to obtain a mixture; heating and stirring the mixture, followed by separation, washing, and drying to obtain a silane coupling agent modified precursor A; S13, dispersing the precursor A obtained in S12 in an organic solvent, adding a terminal amino fluorocarbon chain compound, heating and stirring the mixture, followed by separation, washing, and drying to obtain a modified nanoparticle foam stabilizer.

[0021] In one embodiment of the present invention, the dispersion medium is tetrahydrofuran; the epoxy silicone coupling agent is 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; the organic solvent is toluene; the terminal amino fluorocarbon chain compound is amino perfluoropolyether (PFPE-NH2); and the epoxy-containing polyether compound is polyethylene glycol glycidyl ether.

[0022] In a third aspect, this invention provides a method for preparing an oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells, comprising the following steps: 40-70 parts of sodium α-olefin sulfonate, 10-20 parts of cocamidopropylamine oxide, and 20-40 parts of betaine-based surfactant are stirred evenly to obtain base liquid A; 5-15 parts of corrosion inhibitor are premixed and dissolved in water at a ratio of molybdate, imidazoline quaternary ammonium salt, and organophosphate in a ratio of 2-4:1-3:1-3 to obtain base liquid B; 1-10 parts of modified nanoparticles and 1-15 parts of polyvinylpyrrolidone are ultrasonically dispersed in water to obtain base liquid C; base liquid B and base liquid C are slowly added to base liquid A at 40°C while stirring, and the remaining water is added to obtain the foaming agent.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) The foaming agent provided by this invention achieves integrated functions of oil resistance, corrosion inhibition, methanol resistance, high-efficiency foaming, and stable liquid carrying capacity through multi-component synergistic design, solving the defects of conventional foaming agents that are single-function and difficult to adapt to harsh environments. Specifically, after aging at -30℃, the foaming agent of this invention can achieve a liquid carrying capacity of up to 83.8% in the range of condensate oil content of 10% to 50%, and a mineralization resistance of up to 2×10 5 mg / L; within the methanol content range of 10% to 50%, the foaming force of the foaming agent can still maintain above 171 mm at 0 minutes, the foam decay rate can be as low as 7.3% at 5 minutes, the liquid carrying capacity is not less than 73.8%, the overall foaming performance is stable, the foam liquid carrying capacity is large, and the corrosion inhibition rate can reach more than 75% in a composite sample of 20wt% condensate oil, 20wt% methanol, and saturated CO2; it can meet the extreme composite conditions of high salinity, condensate oil pollution, and acid gas corrosion in the middle and late stages of gas well development, and realize the dual function of drainage and gas production and downhole protection.

[0025] (2) The foaming agent provided by the present invention has a scientific and reasonable configuration of each component, which realizes multiple functions of efficient foaming, stable foam, tolerance to harsh environment and efficient corrosion inhibition. Specifically, the present invention uses betaine-type zwitterionic surfactant and sodium α-olefin sulfonate as the main foaming components and cocamidopropylamine oxide as the foaming aid. The three work together to ensure the foaming ability of the foaming agent in complex environment. Modified nanoparticles are used as the main foam stabilizing component, and polyvinylpyrrolidone is used as a dispersant and auxiliary foam stabilizer to enhance the dispersibility of modified nanoparticles in the system, ensure their stable existence and migration to the gas-liquid interface, and give full play to the foam stabilizing effect. Modified nanoparticles have good compatibility with foaming components such as sodium α-olefin sulfonate anionic surfactant and betaine-type zwitterionic surfactant, which can enhance foam stability and liquid carrying capacity. Sodium molybdate, alkyl imidazoline quaternary ammonium salt and organophosphonate are compounded as corrosion inhibitors, which have good corrosion inhibition synergy and can be superimposed to form a more complete protection and improve the corrosion inhibition effect in complex environment.

[0026] (3) The foaming agent provided by this invention uses modified nanoparticles as the foam-stabilizing component. After basic hydrophobic modification, the nanoparticles can spontaneously migrate to the gas-liquid interface and anchor, enhancing the mechanical strength of the foam liquid film. Combined with foaming components such as betaine zwitterionic surfactant and sodium α-olefin sulfonate anionic surfactant, it synergistically improves the stability of the foam. Furthermore, after modification with perfluoropolyether segments, the hydrophobicity is enhanced, and it is both hydrophobic and oleophobic. In environments containing high levels of condensate oil, it helps reduce the adsorption of condensate oil on the particle surface. Examples of this invention demonstrate that its foam-stabilizing performance is further improved compared to modification with only silane coupling agents. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in multiple embodiments of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Preparation Example 1

[0030] 1) A modified nanoparticle foam stabilizer, wherein the modified nanoparticles used in the embodiments of the present invention are all prepared by the following method:

[0031] Step 1: Prepare nano-SiO2 (average particle size 50nm, specific surface area 200±30m²). 2 / g) was dispersed in anhydrous ethanol and sonicated at 40kHz for 10-30 min to form a suspension with a mass concentration of 10%; hydrochloric acid was added dropwise to adjust the pH to 3-4, 1wt% PEG-400 was added, and the suspension was sonicated at 40kHz for 0.5-2 h in a 40℃ water bath. After filtration, the suspension was washed three times with ethanol solution, then washed three times with water until neutral, and dried under vacuum at 60℃ to obtain activated nano-SiO2.

[0032] Step 2: Disperse the activated nano-SiO2 obtained in Step 1 in tetrahydrofuran (THF) and stir at room temperature to prepare a 10% (w / w) solution A; dissolve 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane in tetrahydrofuran (THF) to prepare a 5%–8% (w / w) solution B; add solution B dropwise to solution A at a uniform rate of 0.5–1 ml / min to obtain a mixture; heat the mixture to 40–60 °C and stir the reaction for 4–8 h; after separation, washing, and drying, obtain the silane coupling agent modified precursor A;

[0033] Step 3: Disperse 12g of precursor A obtained in Step 2 in 120mL of toluene; add 15g of amino-based perfluoropolyether (PFPE-NH2) and 1g of triethylamine, heat to 80℃, stir and react for 6-8h, and then separate, wash and dry to obtain the modified nanoparticle foam stabilizer.

[0034] 2) A foaming agent. In the embodiments of the present invention, the foaming agent can be prepared by the following method: 40-70 parts of sodium α-olefin sulfonate, 10-20 parts of cocamidopropylamine oxide, and 20-40 parts of betaine surfactant are stirred evenly to obtain base liquid A; 5-15 parts of corrosion inhibitor are premixed and dissolved in water according to the ratio of molybdate, imidazoline quaternary ammonium salt and organophosphate in (2-4):(1-3):(1-3) to obtain base liquid B; 1-10 parts of modified nanoparticles and 1-15 parts of polyvinylpyrrolidone are ultrasonically dispersed in water to obtain base liquid C; base liquid B and base liquid C are slowly added to base liquid A at 40°C while stirring, and the remaining water is added to obtain the foaming agent.

[0035] Preparation of Control Example 1,

[0036] This comparative example provides a nanoparticle foam stabilizer, prepared by the following method:

[0037] Step 1: Prepare nano-SiO2 (average particle size 50nm, specific surface area 200±30m²). 2 / g) was dispersed in anhydrous ethanol and sonicated at 40kHz for 10-30 min to form a suspension with a mass concentration of 10%; hydrochloric acid was added dropwise to adjust the pH to 3-4, 1wt% PEG-400 was added, and the suspension was sonicated at 40kHz for 0.5-2 h in a 40℃ water bath. After filtration, the suspension was washed three times with ethanol solution, then washed three times with water until neutral, and dried under vacuum at 60℃ to obtain activated nano-SiO2.

[0038] Step 2: Disperse the activated nano-SiO2 obtained in Step 1 in tetrahydrofuran (THF) and stir at room temperature to prepare a 10% (w / w) solution A; dissolve 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane in tetrahydrofuran (THF) to prepare a 5%–8% (w / w) solution B; add solution B dropwise to solution A at a uniform rate of 0.5–1 ml / min to obtain a mixture; heat the mixture to 40–60 °C and stir the reaction for 4–8 h. After separation, washing, and drying, obtain a silane coupling agent modified nanoparticle foam stabilizer.

[0039] Example 1

[0040] This embodiment provides a foaming agent comprising: 22.5g sodium α-olefin sulfonate, 7.5g cocamidopropylamine oxide, 20g cocamidopropyl hydroxysulfonyl betaine, 2g modified nano silica, 5g polyvinylpyrrolidone, 1.5g sodium molybdate, 0.75g alkyl imidazoline quaternary ammonium salt, 0.75g hydroxyethylidene diphosphonic acid, and the balance being water.

[0041] The preparation method of the above foaming agent is as follows: Take 7.5g of cocamidopropylamine oxide, 22.5g of sodium α-olefin sulfonate, and 20g of cocamidopropyl hydroxysulfonate in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 1.5g of sodium molybdate, 0.75g of alkyl imidazoline quaternary ammonium salt, and 0.75g of hydroxyethylidene diphosphonic acid and stir until dissolved to obtain base solution B; take another 20mL of water, add 2g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record it as H1.

[0042] Example 2

[0043] This embodiment provides a foaming agent comprising: 22.5g sodium α-olefin sulfonate, 7.5g cocamidopropylamine oxide, 20g lauramide propyl betaine, 3g modified nano silica, 5g polyvinylpyrrolidone, 2.4g sodium molybdate, 0.8g alkyl imidazoline quaternary ammonium salt, 0.8g hydroxyethylidene diphosphonic acid, with the remainder being water.

[0044] The above foaming agent is prepared as follows: 7.5g of cocamidopropylamine oxide, 22.5g of sodium α-olefin sulfonate, and 20g of lauramide propyl betaine are placed in a beaker and stirred at low speed until homogeneous to obtain base solution A; 10mL of water is measured, and 2.4g of sodium molybdate, 0.8g of alkyl imidazoline quaternary ammonium salt, and 0.8g of hydroxyethylidene diphosphonic acid are added and stirred to dissolve to obtain base solution B; 20mL of water is taken separately, and 3g of modified nano silica and 5g of polyvinylpyrrolidone are added and ultrasonically dispersed to obtain base solution C; Base solution B and base solution C are slowly added to base solution A at 40℃, stirred evenly, and the volume is adjusted to 100mL, which is recorded as H2.

[0045] Example 3

[0046] This embodiment provides a foaming agent comprising: 22.5g sodium α-olefin sulfonate, 7.5g cocamidopropylamine oxide, 20g erucamide propyl betaine, 4g modified nano silica, 5g polyvinylpyrrolidone, 2g sodium molybdate, 2g alkyl imidazoline quaternary ammonium salt, 1g hydroxyethylidene diphosphonic acid, and the balance being water.

[0047] The above foaming agent is prepared as follows: 7.5g of cocamidopropylamine oxide, 22.5g of sodium α-olefin sulfonate, and 20g of erucamide propyl betaine are placed in a beaker and stirred at low speed until homogeneous to obtain base solution A; 10mL of water is measured, and 2g of sodium molybdate, 2g of alkyl imidazoline quaternary ammonium salt, and 1g of hydroxyethylidene diphosphonic acid are added and stirred to dissolve to obtain base solution B; 20mL of water is taken separately, and 4g of modified nano silica and 5g of polyvinylpyrrolidone are added and ultrasonically dispersed to obtain base solution C; Base solution B and base solution C are slowly added to base solution A at 40℃, stirred evenly, and the volume is adjusted to 100mL, which is recorded as H3.

[0048] Example 4

[0049] This embodiment provides a foaming agent comprising: 28g of sodium α-olefin sulfonate, 8g of cocamidopropylamine oxide, 14g of cocamidopropyl hydroxysulfonyl betaine, 2g of modified nano silica, 5g of polyvinylpyrrolidone, 2.4g of sodium molybdate, 0.8g of alkyl imidazoline quaternary ammonium salt, 0.8g of hydroxyethylidene diphosphonic acid, and the balance being water.

[0050] The above foaming agent is prepared as follows: Take 8g of cocamidopropylamine oxide, 28g of sodium α-olefin sulfonate, and 14g of cocamidopropyl hydroxysulfonate in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 2.4g of sodium molybdate, 0.8g of alkyl imidazoline quaternary ammonium salt, and 0.8g of hydroxyethylidene diphosphonic acid and stir to dissolve to obtain base solution B; take another 20mL of water, add 2g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record as H4.

[0051] Example 5

[0052] This embodiment provides a foaming agent comprising: 28g sodium α-olefin sulfonate, 8g cocamidopropylamine oxide, 14g lauramide propyl betaine, 3g modified nano silica, 5g polyvinylpyrrolidone, 2g sodium molybdate, 2g alkyl imidazoline quaternary ammonium salt, 1g hydroxyethylidene diphosphonic acid, and the balance being water.

[0053] The above foaming agent is prepared as follows: Take 8g of cocamidopropylamine oxide, 28g of sodium α-olefin sulfonate, and 14g of lauramide propyl betaine in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 2g of sodium molybdate, 2g of alkyl imidazoline quaternary ammonium salt, and 1g of hydroxyethylidene diphosphonic acid and stir to dissolve to obtain base solution B; take another 20mL of water, add 3g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record as H5.

[0054] Example 6

[0055] This embodiment provides a foaming agent comprising: 28g sodium α-olefin sulfonate, 8g cocamidopropylamine oxide, 14g erucic acid ammonium betaine, 4g modified nano silica, 5g polyvinylpyrrolidone, 1.5g sodium molybdate, 0.75g alkyl imidazoline quaternary ammonium salt, 0.75g hydroxyethylidene diphosphonic acid, and the balance being water.

[0056] The above foaming agent is prepared as follows: Take 8g of cocamidopropylamine oxide, 28g of sodium α-olefin sulfonate, and 14g of erucamide propyl betaine in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 1.5g of sodium molybdate, 0.75g of alkyl imidazoline quaternary ammonium salt, and 0.75g of hydroxyethylidene diphosphonic acid and stir to dissolve to obtain base solution B; take another 20mL of water, add 4g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record as H6.

[0057] Example 7

[0058] This embodiment provides a foaming agent comprising: 32g of sodium α-olefin sulfonate, 8g of cocamidopropylamine oxide, 10g of cocamidopropyl hydroxysulfonyl betaine, 2g of modified nano silica, 5g of polyvinylpyrrolidone, 2g of sodium molybdate, 2g of alkyl imidazoline quaternary ammonium salt, 1g of hydroxyethylidene diphosphonic acid, and the balance being water.

[0059] The above foaming agent is prepared as follows: Take 8g of cocamidopropylamine oxide, 32g of sodium α-olefin sulfonate, and 10g of cocamidopropyl hydroxysulfonate in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 2g of sodium molybdate, 2g of alkyl imidazoline quaternary ammonium salt, and 1g of hydroxyethylidene diphosphonic acid and stir to dissolve to obtain base solution B; take another 20mL of water, add 2g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record as H7.

[0060] Example 8

[0061] This embodiment provides a foaming agent comprising: 32g sodium α-olefin sulfonate, 8g cocamidopropylamine oxide, 10g lauramide propyl betaine, 3g modified nano silica, 5g polyvinylpyrrolidone, 1.5g sodium molybdate, 0.75g alkyl imidazoline quaternary ammonium salt, 0.75g hydroxyethylidene diphosphonic acid, and the balance being water.

[0062] The above foaming agent is prepared as follows: Take 8g of cocamidopropylamine oxide, 32g of sodium α-olefin sulfonate, and 10g of lauramide propyl betaine in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 1.5g of sodium molybdate, 0.75g of alkyl imidazoline quaternary ammonium salt, and 0.75g of hydroxyethylidene diphosphonic acid and stir to dissolve to obtain base solution B; take another 20mL of water, add 3g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record as H8.

[0063] Example 9

[0064] This embodiment provides a foaming agent comprising: 32g sodium α-olefin sulfonate, 8g cocamidopropylamine oxide, 10g erucic acid ammonium betaine, 4g modified nano silica, 5g polyvinylpyrrolidone, 2.4g sodium molybdate, 0.8g alkyl imidazoline quaternary ammonium salt, 0.8g hydroxyethylidene diphosphonic acid, with the remainder being water.

[0065] The above foaming agent is prepared as follows: Take 8g of cocamidopropylamine oxide, 32g of sodium α-olefin sulfonate, and 10g of erucamide propyl betaine in a beaker and stir at low speed until homogeneous to obtain base solution A; measure 10mL of water, add 2.4g of sodium molybdate, 0.8g of alkyl imidazoline quaternary ammonium salt, and 0.8g of hydroxyethylidene diphosphonic acid and stir to dissolve to obtain base solution B; take another 20mL of water, add 4g of modified nano silica and 5g of polyvinylpyrrolidone, and disperse by ultrasonication to obtain base solution C; slowly add base solution B and base solution C to base solution A at 40℃, stir evenly and adjust the volume to 100mL, and record as H9.

[0066] Comparison document 1

[0067] This comparative example provides a foaming agent in which modified nano-silica is replaced with unmodified nano-silica, and the other implementation conditions are the same as in Example 5, denoted as L1.

[0068] Comparison document 2

[0069] This comparative example provides a foaming agent in which modified nano-silica is replaced with nanoparticles obtained in the preparation of Control Example 1, and the other implementation conditions are the same as in Example 5, denoted as L2.

[0070] Experimental Example

[0071] To make the beneficial effects of the present invention clearer, the foaming ability, liquid carrying capacity, and foam stabilizing ability of the foaming agents obtained in each embodiment and comparative example in formation water under various environmental conditions will be evaluated below.

[0072] 1) Foaming agent treatment,

[0073] To simulate outdoor scenarios (low-temperature storage, low-temperature well environment, etc.), the foaming agent was placed in a -30℃ low-temperature freezer for 24 hours before the experiment to obtain the foaming agent after low-temperature aging.

[0074] 2) Simulated mineralized water preparation: Simulated mineralized water prepared using sodium chloride and calcium chloride at a concentration ratio of 4:1 includes:

[0075] Basic simulated mineralized water w1

[0076] Preparation method: Weigh 160g NaCl and 40g CaCl2, dissolve them in water, and bring the volume to 1L to obtain simulated mineralized water with a total mineralization of 200g / L;

[0077] Simulation scenario: Used to simulate a typical high-mineralization formation water environment and evaluate the basic performance of foaming agents under basic high-mineralization conditions.

[0078] Simulated mineralized water containing condensate oil w2

[0079] Preparation method: Based on the above-mentioned basic simulated mineralized water, mix in 10%-50wt% condensate oil and stir to form an oil-water mixture system to verify the anti-oil interference ability of the foaming agent.

[0080] Simulated scenario: An environment in which condensate oil mixes with bottom fluid during the mid-to-late stage of gas well development. This is used to verify the anti-oil interference ability of the foaming agent and to evaluate whether the foam stability and fluid carrying efficiency are affected by the oil phase.

[0081] Methanol-containing simulated mineralized water w3

[0082] Preparation method: Based on the above-mentioned basic simulated mineralized water, add 10%~50wt% methanol, stir and mix, and use it to evaluate the methanol resistance of the foaming agent.

[0083] Simulated scenario: In order to prevent gas well freezing and blockage, some operating conditions require the injection of hydration inhibitors into the gas well to ensure normal production; among them, methanol is the most commonly used hydration inhibitor. By verifying the methanol resistance performance of the foaming agent, we can verify whether the foaming agent is suitable for the production requirements of low temperature conditions.

[0084] Composite simulated mineralized water w4

[0085] Preparation method: Based on the above-mentioned basic simulated mineralized water, 20wt% condensate oil and 20wt% methanol were added, and saturated CO2 was introduced as a corrosion medium to evaluate the corrosion inhibition performance of the foaming agent in a multi-factor composite system.

[0086] Simulated scenario: Extremely complex operating conditions in the mid-to-late stage of gas field development, namely, the bottom fluid is simultaneously affected by the mixing of condensate oil, methanol injection, and the dissolution of acidic gases, and assess whether it can simultaneously meet the equipment corrosion prevention requirements.

[0087] 3) Verification of foaming power and foam stabilization ability

[0088] Weigh 3g of foaming agent into a beaker, add simulated mineralized water, and dilute to 500mL to obtain a test sample solution with a foaming agent concentration of 0.6%. The foaming and foam-stabilizing properties of the above foaming solution were determined using the Rosesse foam analysis method. Specific test procedures were performed according to Section 11.4.3 of GB / T13173-2021 "Test Methods for Surfactants and Detergents". The test temperature was 40℃. The foam height of the foaming solution was measured at 0 min (H1) and 5 min (H2), and the foam decay rate was calculated. The foaming and foam-stabilizing abilities of each example and comparative example were evaluated using the foam height and foam decay rate. The foam decay rate η... F =((H1-H2) / H1)×100%.

[0089] 4) Liquid carrying capacity verification

[0090] Weigh 3g of foaming agent into a beaker, add simulated mineralized water, and dilute to 500mL to obtain a sample solution with a foaming agent concentration of 0.6%. Test the liquid-carrying capacity of the foaming agent by generating foam and carrying liquid through aeration. The specific test steps are as specified in Section 6.4 of "SYT7494-2020 Experimental Evaluation Method for Foaming Agents for Oil and Gas Fields". Introduce the sample solution into the foaming tube, generate an airflow of 800mL / min through an air pump, and connect it to the bottom of the foaming tube to make the sample solution foam. Collect the foam carried out by the airflow in a container for 15min. Record the total mass of foam received in the container as m1, the mass of the sample solution added to the foaming tube as m, and the foaming rate K = (m1 / m) × 100%.

[0091] 5) Corrosion Inhibition Performance Verification

[0092] Weigh 3g of foaming agent into a beaker, add simulated mineralized water, and dilute to 500mL to obtain a sample solution with a foaming agent concentration of 0.6% as the dosing test group. The corrosion inhibition performance of the foaming agent was determined using the dipstick method. Specific test procedures were performed according to Section 4.7 of "SY / T5273-2014 Performance Inhibitors and Evaluation Methods for Oilfield Produced Water Treatment". The corrosion inhibition effect was evaluated by observing the mass change of a metal test piece (Q235 steel, approximately 11.5g). Before dosing, the test piece was degreased and dehydrated with petroleum ether and ethanol, and its initial mass was measured. A blank test group without foaming agent was also set up, and the test pieces were kept at a constant temperature for one test cycle. After degreasing, acid leaching, and other treatments, the test pieces were weighed, and the mass loss Δm0 of the blank test group and the mass loss Δm of the dosing group were calculated. 1， Corrosion inhibition rate η c = ((Δm0-Δm1) / Δm0)×100%.

[0093] 6) Test Results

[0094] The test results of foaming power and foam stabilization ability of various embodiments of this application are shown in Tables 1 and 2 below:

[0095] Table 1 Verification of the basic foaming power and foam-stabilizing ability of the foaming agent in this application

[0096]

[0097] As can be seen from Table 1 above, in 200 g / L simulated mineralized water, the foaming ability and foam stabilization ability (foam decay rate) of Examples (H1~H9) are better than those of the comparative examples (L1~L2). This indicates that the foaming agent of this application has better foam generation ability and foam stability in mineralized water environment, is more suitable for highly mineralized environment, and can maintain foam morphology more effectively. In addition, the addition of the modified nanoparticle foam stabilizer obtained in Preparation Example 1 helps to enhance the initial foaming height and foam stabilization performance of the foaming agent. This may be because the modified nanoparticles obtained in Preparation Example 1 are both hydrophobic and oleophobic, which helps to stably adsorb at the gas-liquid interface, synergistically reduce the surface tension of the liquid surface with surfactants, and form a physical barrier to delay foam breakage.

[0098] Table 2 Verification of the foaming power and foam stabilizing ability of the foaming agent of this application under different condensate oil and methanol contents.

[0099]

[0100] 1) As can be seen from Table 2 above, in the sample solution with a condensate oil content of 10wt~30wt%, the foaming performance and foam decay rate of Example (H5) showed relatively small overall changes, indicating that the foaming agent was less affected by the change in condensate oil content and had strong oil resistance. In contrast, the foaming height of Comparative Examples L1 and L2 decreased significantly at a condensate oil content of 20wt%, and the decay rate increased more than that of the Example, indicating that the addition of the modified nano silica obtained in Preparation Example 1 helps to enhance the oil resistance of the foaming agent.

[0101] 2) As can be seen from Table 2 above, in sample solutions with methanol content of 10wt~50wt%, the foaming performance and foam stability of the examples and comparative examples generally show a downward trend with the increase of methanol content, but the overall decrease in the example (H5) is smaller than that in the comparative example; and in sample solutions with methanol content of 10wt~30wt%, the decrease in foaming performance and foam decay rate of the foaming agent in the examples is not obvious, indicating that its influence on methanol content is also relatively limited. The foaming agent in the examples of this application has strong methanol resistance.

[0102] The liquid carrying capacity test results of each embodiment of this application are shown in Table 3 below:

[0103] Table 3. Verification of the liquid carrying capacity of the foaming agent in this application.

[0104]

[0105] As can be seen from Table 3 above, in the sample solutions with 0~30wt% condensate oil and 0~30wt% methanol content, the liquid carrying capacity of the examples (H2, H5, H7) was significantly higher than that of the comparative examples (L1 and L2). This finding is consistent with the foam stability findings in Table 1. Generally, the liquid carrying capacity of foaming agents is positively correlated with the foam stabilization capacity, indicating that the addition of modified nano-silica helps to enhance the liquid carrying capacity of the foaming agent. As the content of condensate oil and methanol increases, the liquid carrying capacity of the foaming agent shows a decreasing trend, but in the sample solutions with 10wt%~30wt% condensate oil and methanol content, the decrease is small and the overall change is not obvious.

[0106] The liquid carrying capacity test results of each embodiment of this application are shown in Table 4 below:

[0107] Table 4. Verification of the corrosion inhibition performance of the foaming agent in this application.

[0108]

[0109] As shown in Table 4, the foaming agent provided in this application has good corrosion inhibition ability. In a composite sample of 20wt% condensate oil, 20wt% methanol, and saturated CO2, the corrosion inhibition rate can reach more than 75%. This corrosion inhibition effect can meet the requirements of extreme composite conditions such as high salinity, condensate oil pollution, and acid gas corrosion in the middle and late stages of gas well development, and realize the dual function of drainage and gas production and downhole protection.

[0110] In summary, based on the above verification of foaming performance, liquid carrying capacity, and corrosion inhibition performance, the foaming agent provided by this invention is expected to be applied to the drainage and gas production operations in the later stages of complex gas field development, which involves high condensate oil content, requires methanol injection for antifreeze, and is accompanied by CO2 / H2S acidic gas corrosion. By adding the foaming agent prepared in this application to the bottom of the gas well, the problem of complex liquid accumulation in the later stages of gas well development can be specifically solved, the drainage and gas production efficiency can be improved, and the gas well can be quickly restored to normal production, providing key technical support for the long-term, safe, and efficient operation of the gas field.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A foaming agent for gas wells that is oil-resistant, freeze-resistant, and corrosion-inhibiting, characterized in that, By mass, it includes: 40-70 parts of sodium α-olefin sulfonate, 10-20 parts of cocamidopropylamine oxide, 1-10 parts of modified nanoparticle foam stabilizer, 20-40 parts of betaine-based amphoteric surfactant, 5-15 parts of corrosion inhibitor, 1-15 parts of polyvinylpyrrolidone, and the balance being water. The modified nanoparticle foam stabilizer is nano-silica that has been modified with an epoxy silane coupling agent and then grafted with perfluoropolyether segments. The preparation method of the modified nanoparticle foam stabilizer includes the following steps: S11. Pretreatment of nano-silica to obtain nano-silica with surface hydroxyl activated; S12. Disperse the nano-silica obtained in S11 in a dispersion medium to obtain solution A; dissolve 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane in the dispersion medium to obtain solution B; Solution B was added dropwise to solution A at a uniform rate to obtain a mixture; the mixture was heated and stirred to react, and then separated, washed and dried to obtain silane coupling agent modified precursor A; S13. The precursor A obtained in S12 is dispersed in an organic solvent, and amine perfluoropolyether PFPE-NH2 is added. After heating and stirring to react, the mixture is separated, washed and dried to obtain the modified nano silica foam stabilizer.

2. The oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to claim 1, characterized in that, By mass, it comprises: 50-60 parts sodium α-olefin sulfonate, 15-20 parts cocamidopropylamine oxide, 4-8 parts modified nanoparticles, 25-30 parts betaine-based amphoteric surfactant, 8-12 parts corrosion inhibitor, 8-12 parts polyvinylpyrrolidone, and the balance being water.

3. The oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to claim 1, characterized in that, The betaine-based zwitterionic surfactant is selected from at least one of cocamidopropyl hydroxysulfonate betaine, lauramide propyl betaine, erucamide propyl betaine, or a mixture thereof.

4. The oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to claim 1, characterized in that, The particle size of the modified nanoparticle foam stabilizer is controlled between 10 nm and 800 nm.

5. The oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to claim 1, characterized in that, The corrosion inhibitor includes molybdate, imidazoline quaternary ammonium salt and organophosphate, wherein the ratio of molybdate, imidazoline quaternary ammonium salt and organophosphate is 2~4:1~3:1~3.

6. The oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to claim 1, characterized in that, The dispersion medium is tetrahydrofuran.

7. A method for preparing an oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to any one of claims 1 to 6, characterized in that, The process includes the following steps: 40-70 parts of sodium α-olefin sulfonate, 10-20 parts of cocamidopropylamine oxide, and 20-40 parts of betaine surfactant are stirred until homogeneous to obtain base solution A; 5-15 parts of corrosion inhibitor are premixed and dissolved in water at a ratio of molybdate, imidazoline quaternary ammonium salt, and organophosphate in a ratio of 2-4:1-3:1-3 to obtain base solution B; 1-10 parts of modified nanoparticles and 1-15 parts of polyvinylpyrrolidone are ultrasonically dispersed in water to obtain base solution C; Base solution B and base solution C are slowly added to base solution A at 40°C while stirring, and the remaining water is added to obtain a foaming agent.

8. The application of the oil-resistant, antifreeze, and corrosion-inhibiting foaming agent for gas wells according to any one of claims 1 to 6 in gas well drainage and gas production.

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