Anti-waxing agent for shale oil and preparation method thereof

Abstract

This invention belongs to the field of wax inhibitor preparation technology, specifically relating to a wax inhibitor for shale oil and its preparation method. The wax inhibitor for shale oil is composed of the following raw materials: modified halloysite, octadecylcyclohexane, docosyl oleate, octadecyl acrylate, polyglycerol-2 isostearate, 2,6-di-tert-butyl-p-cresol, and an oil-based solvent. The wax inhibitor for shale oil of this invention uses modified halloysite, octadecylcyclohexane, and docosyl oleate as the main wax inhibitor components. Modified halloysite has both physical barrier and heterogeneous nucleation effects; octadecylcyclohexane strengthens lattice disturbance and inhibits the regular growth of wax crystals through eutectic interference; docosyl oleate is adsorbed on the surface of wax crystals and inhibits crystal nucleus growth and wax crystal aggregation and deposition through steric hindrance. The synergistic effect between the raw materials ensures that the prepared wax inhibitor has a good wax inhibition rate.

Description

Technical Field

[0001] This invention belongs to the field of wax inhibitor preparation technology, specifically relating to a wax inhibitor for shale oil and its preparation method. Background Technology

[0002] During the actual extraction and surface gathering and transportation of shale oil, factors such as temperature decrease, pressure change and component phase change cause dissolved high-carbon paraffin inside the crude oil to easily precipitate, aggregate and deposit. A large amount of wax continuously adheres and accumulates on the inner walls of the wellbore, downhole tubing and surface gathering and transportation pipelines. This not only significantly reduces the cross-sectional area of ​​fluid flow, increases the resistance to crude oil flow and increases lifting energy consumption, but in severe cases, it can also directly cause pipeline blockage, reduced oil well production or even shutdown, which greatly restricts the efficient and stable production development of shale oil.

[0003] Currently, the more mature anti-wax technologies used in field applications mainly include: internal pipe coating anti-wax technology, cold flow anti-wax technology, chemical anti-wax technology, electromagnetic anti-wax technology, and ultrasonic anti-wax technology, among which chemical anti-wax technology is the most commonly used. Chemical anti-wax agents adsorb onto the surface of paraffin microcrystals, forming a spatial network structure. This causes the precipitated paraffin to form loose, dendritic or aggregated dendritic crystal deposits, effectively preventing wax crystals from agglomerating and adhering to the pipe, thus achieving an anti-wax effect. Commonly used chemical anti-wax agents include polycyclic aromatic hydrocarbon anti-wax agents, surfactant-based anti-wax agents, and polymer-based anti-wax agents, with polymer-based anti-wax agents currently being the most prevalent. Polymer-based anti-wax agents are currently mainly composed of ester-containing copolymers such as acrylate polymers, copolymers of esters and maleic anhydride, copolymers of esters and olefins, and ethylene-vinyl acetate copolymers.

[0004] Patent CN121160307A discloses a pour point depressant and wax inhibitor, which uses graphene oxide, acrylic acid, and additives as raw materials and plays a good role in depressing pour points and preventing waxing in heavy oil. However, the system uses water-soluble surfactants and highly corrosive acid catalysts, which not only fail to achieve dispersion of nanomaterials in the oil phase, but also cause serious corrosion to wellbore and gathering and transportation equipment.

[0005] Currently, existing traditional wax inhibitors have the following shortcomings in practical applications: most products have a single function, relying only on a single polymer chain segment to achieve crystal inhibition and pour point reduction, resulting in low wax inhibition efficiency. Therefore, it is necessary to explore a new type of wax inhibitor for shale oil. Summary of the Invention

[0006] The purpose of this invention is to provide a wax inhibitor for shale oil, which can effectively inhibit paraffin crystallization, precipitate fine and dispersed wax crystals, and prevent wax crystals from agglomerating into a network and blocking channels; in addition, this invention also provides its preparation method.

[0007] The shale oil anti-wax agent of the present invention is composed of the following raw materials by mass percentage: 2.8-3.0% modified halloysite, 2.5-2.7% octadecylcyclohexane, 1.5-1.7% docosyl oleate, 1.0-1.2% polyoctadecyl acrylate, 1.8-2.0% polyglycerol-2 isostearate, 0.2-0.3% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent; wherein, the preparation method of modified halloysite comprises the following steps: ① preparation of pretreated halloysite; ② preparation of hydroxylated halloysite; ③ preparation of double-bonded halloysite; ④ graft polymerization reaction of double-bonded halloysite, 4-tert-butylcyclohexyl methacrylate, and acryloylmorpholine under the action of an initiator to prepare modified halloysite.

[0008] The oil-based solvent is obtained by mixing diesel and kerosene at a volume ratio of 1:0.5.

[0009] The method for preparing the modified halloysite comprises the following steps: ① Take halloysite ore, crush it and pass it through a 300-mesh sieve. Dry the obtained halloysite powder at 80℃ for 2 hours. Then place the dried halloysite in hydrochloric acid and stir it at 40℃ for 2 hours. After the reaction is complete, centrifuge it and wash it with deionized water until the pH of the filtrate is 7. Finally, vacuum dry it at 80℃ for 12 hours to prepare pretreated halloysite. ② The pretreated halloysite was placed in a mixture of concentrated sulfuric acid and hydrogen peroxide, sonicated for 30 min, and then stirred at 75°C for 2.0 h. After the reaction was completed, it was naturally cooled to room temperature, and then the reaction solution was poured into ice water, followed by centrifugation, washing with deionized water until the pH of the filtrate was 7, and finally vacuum dried at 70°C for 12 h to prepare hydroxylated halloysite. ③ Hydroxylated halloysite was added to anhydrous toluene and sonicated until uniformly suspended. KH-570 silane coupling agent was added, nitrogen gas was purged for 15 min to remove oxygen, and then the mixture was refluxed and stirred at 111℃ for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain double-bonded halloysite. ④ Add double-bonded halloysite to anhydrous toluene and sonicate until uniformly suspended. Add 4-tert-butylcyclohexyl methacrylate and acryloylmorpholine to the suspension and mix well. Then add the initiator azobisisobutyronitrile, purge with nitrogen for 30 min, and stir at 77℃ for 20 h. After the reaction is completed, centrifuge the reaction solution, collect the solid particles, and after post-processing, prepare modified halloysite.

[0010] Wherein: the concentration of hydrochloric acid in step ① is 1.0 mol / L, and the mass-to-volume ratio of dried halloysite to hydrochloric acid is 1:10, with units of g / mL.

[0011] The preparation method of the concentrated sulfuric acid-hydrogen peroxide mixture in step ② is as follows: the mass concentration of concentrated sulfuric acid is 98%, the mass concentration of hydrogen peroxide is 30%, hydrogen peroxide is added dropwise to concentrated sulfuric acid while stirring, and the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3. After the mixture is completely mixed, it is naturally cooled to room temperature to obtain the concentrated sulfuric acid-hydrogen peroxide mixture.

[0012] In step ②, the ultrasonic frequency is 20kHz and the ultrasonic power is 400W.

[0013] In step ②, the mass-to-volume ratio of halloysite to concentrated sulfuric acid-hydrogen peroxide mixture is 1:20, with units of g / mL.

[0014] In step ②, the volume of ice water is 10 times the volume of the reaction liquid.

[0015] In step ②, the filtrate is washed with deionized water until the pH of the filtrate is 7, and the filtrate is tested with BaCl2 to find that no white precipitate is found.

[0016] In step ③, the mass-to-volume ratio of hydroxylated halloysite to anhydrous toluene is 1:20, with units of g / mL.

[0017] Nitrogen gas is purged throughout the reflux and stirring reaction process in step ③.

[0018] In step ③, the ultrasonic treatment time is 30 minutes, the ultrasonic treatment power is 400W, and the ultrasonic treatment frequency is 20kHz.

[0019] In step ③, the mass of KH-570 silane coupling agent accounts for 5% of the mass of hydroxylated halloysite.

[0020] The washing described in step ③ involves washing once with anhydrous toluene and once with anhydrous ethanol as one cycle, and repeating this cycle three times.

[0021] The drying process described in step ③ involves vacuum drying at 60°C for 12 hours.

[0022] Step 4: Nitrogen gas is introduced throughout the constant-temperature stirring reaction process.

[0023] In step ④, the molar ratio of 4-tert-butylcyclohexyl methacrylate to acryloylmorpholine is 7:3.

[0024] In step ④, the mass ratio of 4-tert-butylcyclohexyl methacrylate to acryloylmorpholine and the mass ratio of double-bonded halloysite is 2:1.

[0025] In step ④, the mass-to-volume ratio of double-bonded halloysite to anhydrous toluene is 1:20, in g / mL.

[0026] In step ④, the ultrasonic treatment time is 30 minutes, the ultrasonic treatment power is 400W, and the ultrasonic treatment frequency is 20kHz.

[0027] In step ④, the mass of azobisisobutyronitrile accounts for 1.5% of the total mass of 4-tert-butylcyclohexyl methacrylate and acryloylmorpholine.

[0028] The post-processing described in step ④ involves first Soxhlet extraction with anhydrous toluene for 12 hours, followed by vacuum drying at 60°C for 12 hours to prepare modified halloysite.

[0029] The method for preparing the shale oil anti-wax agent of the present invention comprises the following steps: (1) Preparation of oil-based solvents; (2) Take 15% of the total mass of the oil-based solvent in step (1), heat it to 75-80°C, add 2,6-di-tert-butyl-p-cresol and stir to dissolve, then cool to 35-40°C to prepare a stabilizer solution; (3) Take 85% of the total mass of the oil-based solvent in step (1) and heat it to 35-40°C. Then add octadecylcyclohexane, docosyl oleate, polyglycerol-2 isostearate, polyoctadecyl acrylate and the stabilizer solution prepared in step (2) in sequence and stir to dissolve to prepare a mixture. (4) Cool the mixture obtained in step (3) to room temperature, add modified halloysite for ultrasonic dispersion, stir for 30-35 min, and finally degas under vacuum to prepare a wax inhibitor for shale oil.

[0030] Specifically, the preparation of the oil-based solvent in step (1) involves mixing diesel and kerosene evenly, with a volume ratio of diesel to kerosene of 1:0.5.

[0031] 15% of the oil-based solvent by mass is used to pre-dissolve the antioxidant 2,6-di-tert-butyl-p-cresol to prepare a stabilizer solution, and the remaining 85% is used to dissolve the organic components to prepare a mixture.

[0032] In step (3), add octadecylcyclohexane and stir for 5 min, then add docosyl oleate and stir for 10 min, add polyglycerol-2 isostearate and stir for 10 min, add octadecyl polyacrylate and stir for 15 min, and finally add the stabilizer solution prepared in step (2) and stir for 5 min.

[0033] In step (4), the ultrasonic dispersion power is 400W, the ultrasonic dispersion frequency is 20kHz, the pulse mode is used, the ultrasonic wave lasts for 5 seconds, the interval is 2 seconds, and the total effective time is 40-45 minutes.

[0034] In step (4), the stirring speed is 150 r / min.

[0035] In step (4), the vacuum degassing pressure is 0.06 MPa and the vacuum degassing time is 30 min.

[0036] Compared with the prior art, the present invention has the following advantages: (1) The shale oil anti-wax agent of the present invention uses an oil-based solvent as the solvent and modified halloysite, octadecylcyclohexane, and docosyl oleate as the main anti-wax components. Modified halloysite has both physical barrier and heterogeneous nucleation functions; octadecylcyclohexane strengthens lattice disturbance and inhibits the regular growth of wax crystals through eutectic interference; docosyl oleate is adsorbed onto the surface of wax crystals and inhibits crystal nucleus growth through steric hindrance, thus inhibiting wax crystal agglomeration and deposition. In addition, octadecyl polyacrylate, polyglycerol-2 isostearate, and 2,6-di-tert-butyl-p-cresol are also added to the raw materials. The synergistic effect between the various raw materials ensures that the prepared anti-wax agent can effectively inhibit paraffin crystallization, precipitate fine and dispersed wax crystals, and avoid wax crystal agglomeration into a network that blocks channels, resulting in a good anti-wax rate.

[0037] (2) The shale oil anti-wax agent of the present invention uses natural nanotube halloysite as an inorganic carrier. The surface is first purified by elution with dilute acid and the inherent hydroxyl groups are retained. Then, strong oxidation activation is carried out by concentrated sulfuric acid-hydrogen peroxide mixture to increase the hydroxyl density on the halloysite surface and enhance the interfacial reaction activity. Subsequently, KH-570 silane coupling agent is used to construct surface polymerizable double bond anchoring sites on the halloysite surface to provide reactive sites for subsequent free radical grafting polymerization. Finally, through surface-initiated grafting polymerization, the hydrophobic wax-inhibiting 4-tert-butylcyclohexyl methacrylate and the polar dispersed wax crystal acryloylmorpholine copolymer chain are grown in situ on the halloysite surface to obtain nano-modified halloysite with good oil solubility and stable structure.

[0038] (3) The wax inhibitor for shale oil described in this invention, wherein the octadecylcyclohexane and docosyl oleate have the following functions: the C in the octadecylcyclohexane molecule 18 Long carbon chains, similar in structure to paraffin hydrocarbons, can insert into the interlayer of the paraffin lattice. The rigid steric hindrance of the cyclohexyl ring disrupts the regular arrangement of paraffin molecules. The ester group in the docosyl oleate molecule is a weakly polar group, which can preferentially adsorb onto defect sites on the surface of the wax crystal, forming a dense coating film that prevents further adsorption of paraffin molecules from crude oil. 18 Unsaturated chains and C 22 The synergistic effect of long alkyl chains not only enhances compatibility with paraffin but also prevents wax crystals from adhering to each other through steric hindrance, keeping the wax crystals in a small, loose state and making them less likely to deposit on the pipe wall.

[0039] (4) The shale oil anti-wax agent of the present invention also contains octadecyl polyacrylate, polyglycerol-2 isostearate, and 2,6-di-tert-butyl-p-cresol in its raw materials. Among them: octadecyl polyacrylate lowers the pour point of shale oil, improves low-temperature fluidity, and synergistically enhances the anti-wax compatibility; polyglycerol-2 isostearate disperses and stabilizes modified halloysite, maintains system homogeneity, and avoids agglomeration and pipe blockage; 2,6-di-tert-butyl-p-cresol has antioxidant and anti-aging properties, and extends the storage period and downhole stability of the anti-wax agent.

[0040] (5) The shale oil anti-wax agent of the present invention uses oil-based solvent as a carrier of functional components and downhole transport medium to ensure the fluidity and compatibility of the system. After diesel and kerosene are mixed at a ratio of 1:0.5, it has the advantages of strong dissolving ability of diesel and low viscosity and low pour point of kerosene. It can completely dissolve all oil-based functional additives, provide a uniform dispersion environment for each component, and has good miscibility with shale oil. After injection, it can quickly merge with crude oil, carry the anti-wax components to diffuse to the wellbore and near-well zone, and cover the wax crystal growth area.

[0041] (6) The shale oil anti-wax agent of the present invention, modified halloysite, works synergistically through a triple mechanism of carrier morphology and bifunctional segments: ① It achieves physical filling and steric hindrance effect through nanotube morphology, hindering the formation of the three-dimensional network skeleton of wax crystals; ② The 4-tert-butylcyclohexyl methacrylate segment has a structural similarity with paraffin molecules, and can undergo affinity adsorption on the surface of wax crystals, interfering with the orderly arrangement of paraffin molecules through steric hindrance effect, inhibiting their preferential growth along specific crystal faces; ③ Acryloylmorpholine copolymer segments are solvated and extended in the oil phase, forming a spatial barrier, enhancing colloidal stability and preventing the bridging and aggregation of wax crystal particles and deposition on the pipe wall through steric hindrance effect. Thus, it effectively solves the problem of easy precipitation of paraffin and blockage of tubing and seepage channels in shale oil extraction.

[0042] (7) The method for preparing the shale oil anti-wax agent of the present invention is simple in preparation process, the parameters are easy to control, and the performance of the prepared anti-wax agent is stable. Detailed Implementation

[0043] The methods for preparing halloysite used in Examples 1-3 and Comparative Examples 1-3 are as follows: The method for preparing the modified halloysite comprises the following steps: ① Take halloysite ore, crush it and pass it through a 300-mesh sieve. Dry the obtained halloysite powder at 80℃ for 2 hours. Then place the dried halloysite in hydrochloric acid and stir it at 40℃ for 2 hours. After the reaction is complete, centrifuge it and wash it with deionized water until the pH of the filtrate is 7. Finally, vacuum dry it at 80℃ for 12 hours to prepare pretreated halloysite. ② The pretreated halloysite was placed in a mixture of concentrated sulfuric acid and hydrogen peroxide, sonicated for 30 min, and then stirred at 75°C for 2.0 h. After the reaction was completed, it was naturally cooled to room temperature, and then the reaction solution was poured into ice water, followed by centrifugation, washing with deionized water until the pH of the filtrate was 7, and finally vacuum dried at 70°C for 12 h to prepare hydroxylated halloysite. ③ Hydroxylated halloysite was added to anhydrous toluene and sonicated until uniformly suspended. KH-570 silane coupling agent was added, nitrogen gas was purged for 15 min to remove oxygen, and then the mixture was refluxed and stirred at 111℃ for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain double-bonded halloysite. ④ Add double-bonded halloysite to anhydrous toluene and sonicate until uniformly suspended. Add 4-tert-butylcyclohexyl methacrylate and acryloylmorpholine to the suspension and mix well. Then add the initiator azobisisobutyronitrile, purge with nitrogen for 30 min, and stir at 77℃ for 20 h. After the reaction is completed, centrifuge the reaction solution, collect the solid particles, and after post-processing, prepare modified halloysite.

[0044] Wherein: the concentration of hydrochloric acid in step ① is 1.0 mol / L, and the mass-to-volume ratio of dried halloysite to hydrochloric acid is 1:10, with units of g / mL.

[0045] The preparation method of the concentrated sulfuric acid-hydrogen peroxide mixture in step ② is as follows: the mass concentration of concentrated sulfuric acid is 98%, the mass concentration of hydrogen peroxide is 30%, hydrogen peroxide is added dropwise to concentrated sulfuric acid while stirring, and the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3. After the mixture is completely mixed, it is naturally cooled to room temperature to obtain the concentrated sulfuric acid-hydrogen peroxide mixture.

[0046] In step ②, the ultrasonic frequency is 20kHz and the ultrasonic power is 400W.

[0047] In step ②, the mass-to-volume ratio of halloysite to concentrated sulfuric acid-hydrogen peroxide mixture is 1:20, with units of g / mL.

[0048] In step ②, the volume of ice water is 10 times the volume of the reaction liquid.

[0049] In step ②, the filtrate is washed with deionized water until the pH of the filtrate is 7, and the filtrate is tested with BaCl2 to find that no white precipitate is found.

[0050] In step ③, the mass-to-volume ratio of hydroxylated halloysite to anhydrous toluene is 1:20, with units of g / mL.

[0051] Nitrogen gas is purged throughout the reflux and stirring reaction process in step ③.

[0052] In step ③, the ultrasonic treatment time is 30 minutes, the ultrasonic treatment power is 400W, and the ultrasonic treatment frequency is 20kHz.

[0053] In step ③, the mass of KH-570 silane coupling agent accounts for 5% of the mass of hydroxylated halloysite.

[0054] The washing described in step ③ involves washing once with anhydrous toluene and once with anhydrous ethanol as one cycle, and repeating this cycle three times.

[0055] The drying process described in step ③ involves vacuum drying at 60°C for 12 hours.

[0056] Step 4: Nitrogen gas is introduced throughout the constant-temperature stirring reaction process.

[0057] In step ④, the molar ratio of 4-tert-butylcyclohexyl methacrylate to acryloylmorpholine is 7:3.

[0058] In step ④, the mass ratio of 4-tert-butylcyclohexyl methacrylate to acryloylmorpholine and the mass ratio of double-bonded halloysite is 2:1.

[0059] In step ④, the mass-to-volume ratio of double-bonded halloysite to anhydrous toluene is 1:20, in g / mL.

[0060] In step ④, the ultrasonic treatment time is 30 minutes, the ultrasonic treatment power is 400W, and the ultrasonic treatment frequency is 20kHz.

[0061] In step ④, the mass of azobisisobutyronitrile accounts for 1.5% of the total mass of 4-tert-butylcyclohexyl methacrylate and acryloylmorpholine.

[0062] The post-processing described in step ④ involves first Soxhlet extraction with anhydrous toluene for 12 hours, followed by vacuum drying at 60°C for 12 hours to prepare modified halloysite.

[0063] Example 1

[0064] The shale oil anti-wax agent described in Example 1 is composed of the following raw materials by mass percentage: 2.9% modified halloysite, 2.6% octadecylcyclohexane, 1.6% docosyl oleate, 1.1% polyoctadecyl acrylate, 1.9% polyglycerol-2 isostearate, 0.25% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent.

[0065] The oil-based solvent is obtained by mixing diesel and kerosene at a volume ratio of 1:0.5.

[0066] The preparation method of the shale oil anti-wax agent described in Example 1 consists of the following steps: (1) Preparation of oil-based solvents; (2) Take 15% of the total mass of the oil-based solvent in step (1), heat it to 77°C, add 2,6-di-tert-butyl-p-cresol and stir to dissolve, then cool to 37°C to prepare the stabilizer solution; (3) Take 85% of the total mass of the oil-based solvent in step (1) and heat it to 37°C. Then add octadecylcyclohexane, docosyl oleate, polyglycerol-2 isostearate, polyoctadecyl acrylate and the stabilizer solution prepared in step (2) in sequence and stir to dissolve to prepare a mixture. (4) Cool the mixture obtained in step (3) to room temperature, add modified halloysite for ultrasonic dispersion, stir for 33 min, and finally degas under vacuum to prepare a wax inhibitor for shale oil.

[0067] Specifically, the preparation of the oil-based solvent in step (1) involves mixing diesel and kerosene evenly, with a volume ratio of diesel to kerosene of 1:0.5.

[0068] In step (3), add octadecylcyclohexane and stir for 5 min, then add docosyl oleate and stir for 10 min, add polyglycerol-2 isostearate and stir for 10 min, add octadecyl polyacrylate and stir for 15 min, and finally add the stabilizer solution prepared in step (2) and stir for 5 min.

[0069] In step (4), the ultrasonic dispersion power is 400W, the ultrasonic dispersion frequency is 20kHz, the pulse mode is used, the ultrasonic wave lasts for 5 seconds, the interval is 2 seconds, and the total effective time is 42 minutes.

[0070] In step (4), the stirring speed is 150 r / min.

[0071] In step (4), the vacuum degassing pressure is 0.06 MPa and the vacuum degassing time is 30 min.

[0072] Example 2

[0073] The shale oil anti-wax agent described in Example 2 is composed of the following raw materials by mass percentage: 2.8% modified halloysite, 2.7% octadecylcyclohexane, 1.5% docosyl oleate, 1.2% polyoctadecyl acrylate, 1.8% polyglycerol-2 isostearate, 0.2% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent.

[0074] The oil-based solvent is obtained by mixing diesel and kerosene at a volume ratio of 1:0.5.

[0075] The preparation method of the shale oil anti-wax agent described in Example 2 consists of the following steps: (1) Preparation of oil-based solvents; (2) Take 15% of the total mass of the oil-based solvent in step (1), heat it to 75°C, add 2,6-di-tert-butyl-p-cresol and stir to dissolve, then cool to 35°C to prepare a stabilizer solution; (3) Take 85% of the total mass of the oil-based solvent in step (1) and heat it to 35°C. Then add octadecylcyclohexane, docosyl oleate, polyglycerol-2 isostearate, polyoctadecyl acrylate and the stabilizer solution prepared in step (2) in sequence and stir to dissolve to prepare a mixture. (4) Cool the mixture obtained in step (3) to room temperature, add modified halloysite for ultrasonic dispersion, stir for 30 min, and finally degas under vacuum to prepare a wax inhibitor for shale oil.

[0076] Specifically, the preparation of the oil-based solvent in step (1) involves mixing diesel and kerosene evenly, with a volume ratio of diesel to kerosene of 1:0.5.

[0077] In step (3), add octadecylcyclohexane and stir for 5 min, then add docosyl oleate and stir for 10 min, add polyglycerol-2 isostearate and stir for 10 min, add octadecyl polyacrylate and stir for 15 min, and finally add the stabilizer solution prepared in step (2) and stir for 5 min.

[0078] In step (4), the ultrasonic dispersion power is 400W, the ultrasonic dispersion frequency is 20kHz, the pulse mode is used, the ultrasonic wave lasts for 5 seconds, the interval is 2 seconds, and the total effective time is 40 minutes.

[0079] In step (4), the stirring speed is 150 r / min.

[0080] In step (4), the vacuum degassing pressure is 0.06 MPa and the vacuum degassing time is 30 min.

[0081] Example 3

[0082] The shale oil anti-wax agent described in Example 3 is composed of the following raw materials by mass percentage: 3.0% modified halloysite, 2.5% octadecylcyclohexane, 1.7% docosyl oleate, 1.0% polyoctadecyl acrylate, 2.0% polyglycerol-2 isostearate, 0.3% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent.

[0083] The oil-based solvent is obtained by mixing diesel and kerosene at a volume ratio of 1:0.5.

[0084] The preparation method of the shale oil anti-wax agent described in Example 3 consists of the following steps: (1) Preparation of oil-based solvents; (2) Take 15% of the total mass of the oil-based solvent in step (1), heat it to 80°C, add 2,6-di-tert-butyl-p-cresol and stir to dissolve, then cool to 40°C to prepare a stabilizer solution; (3) Take 85% of the total mass of the oil-based solvent in step (1) and heat it to 40°C. Then add octadecylcyclohexane, docosyl oleate, polyglycerol-2 isostearate, polyoctadecyl acrylate and the stabilizer solution prepared in step (2) in sequence and stir to dissolve to prepare a mixture. (4) Cool the mixture obtained in step (3) to room temperature, add modified halloysite for ultrasonic dispersion, stir for 35 min, and finally degas under vacuum to prepare a wax inhibitor for shale oil.

[0085] Specifically, the preparation of the oil-based solvent in step (1) involves mixing diesel and kerosene evenly, with a volume ratio of diesel to kerosene of 1:0.5.

[0086] In step (3), add octadecylcyclohexane and stir for 5 min, then add docosyl oleate and stir for 10 min, add polyglycerol-2 isostearate and stir for 10 min, add octadecyl polyacrylate and stir for 15 min, and finally add the stabilizer solution prepared in step (2) and stir for 5 min.

[0087] In step (4), the ultrasonic dispersion power is 400W, the ultrasonic dispersion frequency is 20kHz, the pulse mode is used, the ultrasonic wave lasts for 5 seconds, the interval is 2 seconds, and the total effective time is 45 minutes.

[0088] In step (4), the stirring speed is 150 r / min.

[0089] In step (4), the vacuum degassing pressure is 0.06 MPa and the vacuum degassing time is 30 min.

[0090] Comparative Example 1 The preparation method of the shale oil anti-wax agent described in Comparative Example 1 is the same as that in Example 1, the only difference being the composition of the raw materials. The shale oil anti-wax agent described in Comparative Example 1, by mass percentage, consists of the following raw materials: 2.6% octadecylcyclohexane, 1.6% docosyl oleate, 1.1% polyoctadecyl acrylate, 1.9% polyglycerol-2 isostearate, 0.25% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent.

[0091] Comparative Example 2 The preparation method of the shale oil anti-wax agent described in Comparative Example 2 is the same as that in Example 1, the only difference being the composition of the raw materials. The shale oil anti-wax agent described in Comparative Example 2, by mass percentage, consists of the following raw materials: 2.9% modified halloysite, 1.6% docosyl oleate, 1.1% polyoctadecyl acrylate, 1.9% polyglycerol-2 isostearate, 0.25% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent.

[0092] Comparative Example 3 The preparation method of the shale oil anti-wax agent described in Comparative Example 3 is the same as that in Example 1, the only difference being the composition of the raw materials. The shale oil anti-wax agent described in Comparative Example 3, by mass percentage, consists of the following raw materials: 2.9% modified halloysite, 2.6% octadecylcyclohexane, 1.1% polyoctadecyl acrylate, 1.9% polyglycerol-2 isostearate, 0.25% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent.

[0093] According to the provisions of SY / T 6300-2024 "Technical Requirements for Wax Inhibitors and Removals for Oil Production", take two 100g portions of dehydrated shale oil from the target block and keep them at a constant temperature of 25℃ above the wax precipitation point for 60min. Add 0.1g of the wax inhibitor for shale oil prepared in this invention to one portion, and use the other portion as a blank sample. Pour the two oil samples into the test cups of the wax inhibitor tester, control the cooling rate at 1.0℃ / min, stir at 200r / min, and set the final cooling temperature to 3℃ above the shale oil pour point. After reaching the final cooling temperature, stop stirring, pour out the residual oil, wash the inner wall of the test cup with petroleum ether with a boiling range of 60-90℃ and dry it, dry it at 105℃ to constant weight, and weigh the amount of wax. The wax prevention rate was calculated using the following formula: E = (W0 - W1) / W0 × 100%, where W0 is the wax accumulation in the blank sample (in g), and W1 is the wax accumulation in the treated sample (in g). Each sample was measured in triplicate, and the average value was taken as the test result. The results are shown in Table 1 below: Table 1. Performance test results of shale oil wax inhibitors

[0094] As shown in Table 1, the shale oil anti-wax agents prepared in Examples 1-3 are significantly better than those in Comparative Examples 1-3. In Comparative Examples 1-3, the lack of any one of the modified halloysite, octadecylcyclohexane, or docosyl oleate in the raw materials of the anti-wax agents leads to a significant reduction in the anti-wax rate.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A wax inhibitor for shale oil, characterized in that: The modified halloysite, by mass percentage, is composed of the following raw materials: 2.8-3.0% modified halloysite, 2.5-2.7% octadecylcyclohexane, 1.5-1.7% docosyl oleate, 1.0-1.2% polyoctadecyl acrylate, 1.8-2.0% polyglycerol-2 isostearate, 0.2-0.3% 2,6-di-tert-butyl-p-cresol, and the balance being an oil-based solvent. The modified halloysite is prepared by the following steps: ① preparing pretreated halloysite; ② preparing hydroxylated halloysite; ③ preparing double-bonded halloysite; ④ grafting polymerization of double-bonded halloysite, 4-tert-butylcyclohexyl methacrylate, and acryloylmorpholine under the action of an initiator to prepare modified halloysite.

2. The wax inhibitor for shale oil according to claim 1, characterized in that: The oil-based solvent is obtained by mixing diesel and kerosene at a volume ratio of 1:0.

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3. The wax inhibitor for shale oil according to claim 1, characterized in that: The method for preparing the modified halloysite comprises the following steps: ① Take halloysite ore, crush it and pass it through a 300-mesh sieve. Dry the obtained halloysite powder at 80℃ for 2 hours. Then place the dried halloysite in hydrochloric acid and stir it at 40℃ for 2 hours. After the reaction is complete, centrifuge it and wash it with deionized water until the pH of the filtrate is 7. Finally, vacuum dry it at 80℃ for 12 hours to prepare pretreated halloysite. ② The pretreated halloysite was placed in a mixture of concentrated sulfuric acid and hydrogen peroxide, sonicated for 30 min, and then stirred at 75°C for 2.0 h. After the reaction was completed, it was naturally cooled to room temperature, and then the reaction solution was poured into ice water, followed by centrifugation, washing with deionized water until the pH of the filtrate was 7, and finally vacuum dried at 70°C for 12 h to prepare hydroxylated halloysite. ③ Hydroxylated halloysite was added to anhydrous toluene and sonicated until uniformly suspended. KH-570 silane coupling agent was added, nitrogen gas was purged for 15 min to remove oxygen, and then the mixture was refluxed and stirred at 111℃ for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain double-bonded halloysite. ④ Add double-bonded halloysite to anhydrous toluene and sonicate until uniformly suspended. Add 4-tert-butylcyclohexyl methacrylate and acryloylmorpholine to the suspension and mix well. Then add the initiator azobisisobutyronitrile, purge with nitrogen for 30 min, and stir at 77℃ for 20 h. After the reaction is completed, centrifuge the reaction solution, collect the solid particles, and after post-processing, prepare modified halloysite.

4. The wax inhibitor for shale oil according to claim 3, characterized in that: In step ①, the concentration of hydrochloric acid is 1.0 mol / L, and the mass-to-volume ratio of dried halloysite to hydrochloric acid is 1:10, with units of g / mL. The preparation method of the concentrated sulfuric acid-hydrogen peroxide mixture in step ② is as follows: the mass concentration of concentrated sulfuric acid is 98%, the mass concentration of hydrogen peroxide is 30%, hydrogen peroxide is added dropwise to concentrated sulfuric acid while stirring, and the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 7:

3. After the mixture is completely mixed, it is naturally cooled to room temperature to obtain the concentrated sulfuric acid-hydrogen peroxide mixture. In step ②, the ultrasonic frequency is 20kHz and the ultrasonic power is 400W. In step ②, the mass-to-volume ratio of halloysite to concentrated sulfuric acid-hydrogen peroxide mixture is 1:20, in g / mL. In step ②, the volume of ice water is 10 times the volume of the reaction liquid; In step ②, the filtrate is washed with deionized water until the pH of the filtrate is 7, and the filtrate is tested with BaCl2 to find that no white precipitate is found.

5. The wax inhibitor for shale oil according to claim 3, characterized in that: In step ③, the mass-to-volume ratio of hydroxylated halloysite to anhydrous toluene is 1:20, with units of g / mL. Step ③: Nitrogen gas is purged throughout the reflux and stirring reaction process. In step ③, the ultrasonic treatment time is 30 min, the ultrasonic treatment power is 400 W, and the ultrasonic treatment frequency is 20 kHz. In step ③, the mass of KH-570 silane coupling agent accounts for 5% of the mass of hydroxylated halloysite; The washing described in step ③ is to wash once with anhydrous toluene and once with anhydrous ethanol as one cycle, and repeat this cycle 3 times. The drying process described in step ③ involves vacuum drying at 60°C for 12 hours.

6. The wax inhibitor for shale oil according to claim 3, characterized in that: Step 4: Nitrogen gas is purged throughout the constant-temperature stirring reaction. In step ④, the molar ratio of 4-tert-butylcyclohexyl methacrylate to acryloylmorpholine is 7:3; In step ④, the mass ratio of 4-tert-butylcyclohexyl methacrylate to acryloylmorpholine to double-bonded halloysite is 2:1; In step ④, the mass-to-volume ratio of double-bonded halloysite to anhydrous toluene is 1:20, in g / mL. In step ④, the ultrasonic treatment time is 30 minutes, the ultrasonic treatment power is 400W, and the ultrasonic treatment frequency is 20kHz. In step ④, the mass of azobisisobutyronitrile accounts for 1.5% of the combined mass of 4-tert-butylcyclohexyl methacrylate and acryloylmorpholine; The post-processing described in step ④ involves first Soxhlet extraction with anhydrous toluene for 12 hours, followed by vacuum drying at 60°C for 12 hours to prepare modified halloysite.

7. A method for preparing the shale oil anti-wax agent according to claim 1, characterized in that: It consists of the following steps: (1) Preparation of oil-based solvents; (2) Take 15% of the total mass of the oil-based solvent in step (1), heat it to 75-80°C, add 2,6-di-tert-butyl-p-cresol and stir to dissolve, then cool to 35-40°C to prepare a stabilizer solution; (3) Take 85% of the total mass of the oil-based solvent in step (1) and heat it to 35-40°C. Then add octadecylcyclohexane, docosyl oleate, polyglycerol-2 isostearate, polyoctadecyl acrylate and the stabilizer solution prepared in step (2) in sequence and stir to dissolve to prepare a mixture. (4) Cool the mixture obtained in step (3) to room temperature, add modified halloysite for ultrasonic dispersion, stir for 30-35 min, and finally degas under vacuum to prepare a wax inhibitor for shale oil.

8. The method for preparing the shale oil anti-wax agent according to claim 7, characterized in that: The preparation of the oil-based solvent in step (1) specifically involves mixing diesel and kerosene evenly, with a volume ratio of diesel to kerosene of 1:0.

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9. The method for preparing the shale oil anti-wax agent according to claim 7, characterized in that: In step (3), add octadecylcyclohexane and stir for 5 min, then add docosyl oleate and stir for 10 min, add polyglycerol-2 isostearate and stir for 10 min, add octadecyl polyacrylate and stir for 15 min, and finally add the stabilizer solution prepared in step (2) and stir for 5 min.

10. The method for preparing the shale oil anti-wax agent according to claim 7, characterized in that: In step (4), the ultrasonic dispersion power is 400W, the ultrasonic dispersion frequency is 20kHz, the pulse mode is used, the ultrasonic wave lasts for 5 seconds, the interval is 2 seconds, and the total effective time is 40-45 minutes. In step (4), the stirring speed is 150 r / min; In step (4), the vacuum degassing pressure is 0.06 MPa and the vacuum degassing time is 30 min.

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