A heavy oil dispersing pour point depressant for oil field drilling and a preparation method thereof

Abstract

The present application relates to the technical field of heavy oil dispersant pour point depressant, in particular to a heavy oil dispersant pour point depressant for oilfield drilling and a preparation method thereof.The present application first prepares epoxy group polysiloxane by preparing epoxy group polysiloxane through silicon hydrogen addition reaction of glycidyl methacrylate and single-end hydrogen-containing polysiloxane, and modifies the epoxy group polysiloxane and KH550 modified graphene oxide by epoxy group and amino group reaction to obtain polysiloxane grafted graphene oxide; then prepares silicone modified polyester pour point depressant by reacting octadecyl acrylate, maleic anhydride, 1-octadecene and 3-(triethoxysilyl)methyl propyl methacrylate; and finally, the silicone modified polyester pour point depressant, ethylene-vinyl acetate pour point depressant solution, polysiloxane grafted graphene oxide and kerosene and Span 80 are compounded to obtain the heavy oil dispersant pour point depressant for oilfield drilling.The dispersant pour point depressant prepared by the present application has excellent pour point depressing effect and is suitable for heavy oil with high wax content.

Description

Technical Field

[0001] This invention relates to the field of heavy oil dispersants and pour point depressants, specifically to a heavy oil dispersant and pour point depressant for oilfield drilling and its preparation method. Background Technology

[0002] Petroleum is the world's most important energy source today. With the continuous exploitation of high-quality petroleum resources, the proportion of low-quality crude oil resources in the total crude oil reserves is increasing. Heavy oil, a type of crude oil with viscous and poor flow properties, accounts for approximately 70% of global crude oil reserves. Improving development technologies to achieve economical and efficient development of heavy oil is crucial to the petroleum industry. Due to the complex chemical composition of heavy oil (high content of wax, asphaltene, etc.), and the fact that wax and asphalt are amorphous materials, exhibiting a fluid state at high temperatures but becoming solid at low temperatures, the accumulation of solid wax during the extraction process from the high-temperature layer to the low-temperature surface leads to wax precipitation, further increasing the difficulty of heavy oil extraction.

[0003] Although various technologies have been developed both domestically and internationally to address the wax precipitation problem in heavy oil, such as the hydrodynamic method, steam method, microbial method, organic solvent method, formation heating method, and thermal cracking method, all of these methods have varying degrees of drawbacks. Adding dispersing pour point depressants is considered the most promising solution due to its simple operation and low energy consumption. By adding pour point depressants to heavy oil, the growth state of wax crystals is altered, improving the flow properties of crude oil. Patent CN201810335639.3 provides an acrylate-grafted alcoholysis EVA crude oil pour point depressant and its preparation method, which combines EVA pour point depressant with tetradecyl methacrylate-glycidyl methacrylate copolymer to lower the wax precipitation temperature, thereby reducing the crude oil pour point. Patent CN201810335620.9 provides a method for preparing a reactive high-pour-point crude oil pour point depressant, which lowers the crude oil pour point by grafting monomers containing active groups onto the traditional pour point depressant ethylene-vinyl acetate copolymer. However, my country has a complex topography and the composition of crude oil varies greatly from region to region, resulting in poor applicability of pour point depressants in existing technologies. Therefore, it is very necessary to provide a heavy oil dispersant for oilfield drilling. Summary of the Invention

[0004] The purpose of this invention is to provide a heavy oil dispersant and pour point depressant for oilfield drilling and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a heavy oil dispersing pour point depressant for oilfield drilling is as follows: organosilicon-modified polyester pour point depressant, ethylene-vinyl acetate pour point depressant solution, kerosene, polysiloxane-grafted graphene oxide, and Span 80 are mixed to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0006] Furthermore, the ethylene-vinyl acetate pour point depressant solution is a mixed solution of ethylene-vinyl acetate pour point depressant and toluene, wherein the content of ethylene-vinyl acetate pour point depressant is 5-10 wt.%.

[0007] Furthermore, the content of each component, by weight, is as follows: 35-40 parts of organosilicon-modified polyester pour point depressant, 20-25 parts of ethylene-vinyl acetate pour point depressant solution, 50-60 parts of kerosene, 3-5 parts of polysiloxane-grafted graphene oxide, and 8-11 parts of Span 80.

[0008] Furthermore, the preparation method of the organosilicon-modified polyester pour point depressant is as follows: octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilane)methacrylate propyl ester are dispersed in xylene, heated to 80-85℃ under nitrogen atmosphere, and reacted with benzoyl peroxide as an initiator for 8-10 hours. After adding anhydrous ethanol to precipitate, the mixture is filtered under reduced pressure and dried under vacuum to obtain the organosilicon-modified polyester pour point depressant.

[0009] Furthermore, the molar ratio of octadecyl acrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)methacrylate is (4.8–5):(1–1.2):(2.8–3.2):(0.5–0.8).

[0010] Furthermore, the preparation method of polysiloxane-grafted graphene oxide includes the following steps:

[0011] S1: Activate graphene oxide at 300-500℃ for 3-5 hours to obtain high-temperature activated graphene oxide; mix high-temperature activated graphene oxide, KH550, and anhydrous toluene, disperse ultrasonically for 10-15 minutes, heat under reflux for 3-5 hours, centrifuge at 8000-10000 rpm, collect the precipitate, wash with anhydrous ethanol, and dry to obtain amino-modified graphene oxide;

[0012] S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 100-105°C using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 8-10 hours to obtain epoxy polysiloxane.

[0013] S3: Amino-modified graphene oxide and epoxy-based polysiloxane are dispersed in anhydrous isopropanol at a mass ratio of 1:(3-5). After reacting at 70-80℃ for 2-3 hours, the mixture is centrifuged and the precipitate is collected and dried to obtain polysiloxane-grafted graphene oxide.

[0014] Furthermore, in S1, the amounts of each component, by weight, are 5-6 parts of high-temperature activated graphene oxide, 10-12 parts of KH550, and 120 parts of anhydrous toluene.

[0015] Further, in S2, glycidyl methacrylate and single-ended hydrogen-containing polysiloxane react in a 1:1 molar ratio of carbon-carbon double bonds to silicon-hydrogen bonds, wherein the single-ended hydrogen-containing polysiloxane has a molecular weight of 1000-1500.

[0016] Furthermore, in S3, the mass ratio of amino-modified graphene oxide to epoxy-based polysiloxane is 1:(3-5).

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention provides a heavy oil dispersant pour point depressant for oilfield drilling, which combines organosilicon-modified polyester pour point depressant, ethylene-vinyl acetate pour point depressant solution, and polysiloxane-grafted graphene oxide to achieve pour point depressant for complex oil products with high wax content and multiple components.

[0018] Graphene oxide, a two-dimensional material with a large specific surface area, can serve as a nucleation center for wax crystals, guiding their crystallization. By grafting long-chain polysiloxanes onto the surface of graphene oxide, steric hindrance is created, inhibiting the growth and aggregation of wax crystals. This results in finer, more uniformly dispersed wax crystals, preventing the formation of a continuous network structure that could lead to oil solidification. Polysiloxane-grafted graphene oxide exhibits better dispersibility in kerosene, preventing aggregation during storage and thus reducing the performance of the pour point depressant. Organosilicon-modified polyester pour point depressant is obtained by polymerizing octadecyl acrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilane)propyl methacrylate. By introducing polar anhydride groups, hydrogen bonds are formed with polar components such as gums and asphaltenes in crude oil. This facilitates the penetration and dispersion of the pour point depressant molecular chain into the lamellar stacked structure between wax crystals, disrupting the regular spatial structure of the wax crystals and enhancing oil fluidity. Furthermore, the side-chain organosilicon not only possesses good flexibility but also effectively prevents the accumulation of wax crystals around the acute anhydride groups. In addition, since organosilicon has a lower surface energy and better lubrication effect, adding organosilicon-modified polyester pour point depressant and polysiloxane-grafted graphene oxide into heavy oil can effectively reduce the viscosity of heavy oil and improve its flow properties. At the same time, organosilicon has good high-temperature stability, which makes it easy to store, transport and use.

[0019] This invention also found that using high molecular weight hydrogen-containing silicone oil to prepare polysiloxane-grafted graphene leads to a decrease in pour point depressant effect. Analysis suggests this may be due to entanglement between large polysiloxane segments and between polysiloxane and polyester molecular segments, causing mutual interference between pour point depressant components and reducing the pour point depressant effect. After repeated trials, polysiloxane-grafted graphene prepared by controlling the molecular weight of single-end hydrogen-containing polysiloxane to 1000-1500 showed the best effect and could synergistically improve the pour point depressant effect of ethylene-vinyl acetate pour point depressant with organosilicon-modified polyester pour point depressant, thereby increasing the pour point depressant efficiency. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Materials used in this invention and their sources: Graphene oxide is from Changzhou Sixth Element Materials Technology Co., Ltd., model SE2430; single-ended hydrogen-containing polysiloxane is from Anhui Aiyota Silicon Oil Co., Ltd., model IOTA-611; ethylene-vinyl acetate pour point depressant is produced by Guangzhou Binlong Chemical Co., Ltd., wherein the VAc content is 15%.

[0022] Example 1: A method for preparing a heavy oil dispersant and pour point depressant for oilfield drilling, comprising the following steps:

[0023] Step 1:

[0024] S1: Graphene oxide was activated at 300℃ for 3h to obtain high-temperature activated graphene oxide; 5g of high-temperature activated graphene oxide was mixed with 10g of KH550 and 120g of anhydrous toluene, ultrasonically dispersed for 10min, heated under reflux for 3h, centrifuged at 8000rpm, the precipitate was collected and washed with anhydrous ethanol, and dried to obtain amino-modified graphene oxide.

[0025] S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 100°C using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 8 hours to obtain an epoxy-based polysiloxane. The single-ended hydrogen-containing polysiloxane was reacted with glycidyl methacrylate and the single-ended hydrogen-containing polysiloxane at a carbon-carbon double bond and silicon-hydrogen bond molar ratio of 1:1. The single-ended hydrogen-containing polysiloxane had a molecular weight of 1000.

[0026] S3: Amino-modified graphene oxide and epoxy-based polysiloxane were dispersed in anhydrous isopropanol at a mass ratio of 1:3. After reacting at 70°C for 2 hours, the mixture was centrifuged and the precipitate was collected and dried to obtain polysiloxane-grafted graphene oxide.

[0027] Step 2:

[0028] Octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate were dispersed in xylene and heated to 80°C under nitrogen atmosphere. The reaction was initiated by benzoyl peroxide for 8 hours. After precipitation with anhydrous ethanol, the mixture was filtered under reduced pressure and dried under vacuum to obtain an organosilicon-modified polyester pour point depressant. The molar ratio of octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate was 4.8:1:2.8:0.5.

[0029] Step 3: Disperse the ethylene-vinyl acetate pour point depressant in anhydrous toluene to obtain a 5 wt.% ethylene-vinyl acetate pour point depressant solution; mix 35 g of organosilicon-modified polyester pour point depressant, 20 g of ethylene-vinyl acetate pour point depressant solution, 50 g of kerosene, 3 g of polysiloxane-grafted graphene oxide, and 8 g of Span 80 to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0030] Example 2: A method for preparing a heavy oil dispersant and pour point depressant for oilfield drilling, comprising the following steps:

[0031] Step 1:

[0032] S1: Graphene oxide was activated at 400℃ for 4h to obtain high-temperature activated graphene oxide; 5.5g of high-temperature activated graphene oxide was mixed with 11g of KH550 and 120g of anhydrous toluene, ultrasonically dispersed for 13min, heated under reflux for 4h, centrifuged at 9000rpm, the precipitate was collected and washed with anhydrous ethanol, and dried to obtain amino-modified graphene oxide.

[0033] S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 103°C using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 9 hours to obtain an epoxy-based polysiloxane. The single-ended hydrogen-containing polysiloxane and glycidyl methacrylate reacted in a carbon-carbon double bond and silicon-hydrogen bond molar ratio of 1:1. The single-ended hydrogen-containing polysiloxane had a molecular weight of 1200.

[0034] S3: Amino-modified graphene oxide and epoxy-based polysiloxane were dispersed in anhydrous isopropanol at a mass ratio of 1:4. After reacting at 75°C for 2.5 h, the precipitate was collected by centrifugation and dried to obtain polysiloxane-grafted graphene oxide.

[0035] Step 2:

[0036] Octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate were dispersed in xylene and heated to 83°C under nitrogen atmosphere. The reaction was initiated by benzoyl peroxide for 9 hours. After precipitation with anhydrous ethanol, the mixture was filtered under reduced pressure and dried under vacuum to obtain an organosilicon-modified polyester pour point depressant. The molar ratio of octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate was 4.9:1.1:3:0.75.

[0037] Step 3: Disperse the ethylene-vinyl acetate pour point depressant in anhydrous toluene to obtain an 8 wt.% ethylene-vinyl acetate pour point depressant solution; mix 38 g of organosilicon-modified polyester pour point depressant, 23 g of ethylene-vinyl acetate pour point depressant solution, 56 g of kerosene, 2.4 g of polysiloxane-grafted graphene oxide, and 9 g of Span 80 to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0038] Example 3: A method for preparing a heavy oil dispersant and pour point depressant for oilfield drilling, comprising the following steps:

[0039] Step 1:

[0040] S1: Graphene oxide was activated at 500℃ for 5h to obtain high-temperature activated graphene oxide; 6g of high-temperature activated graphene oxide was mixed with 12g of KH550 and 120g of anhydrous toluene, ultrasonically dispersed for 15min, heated under reflux for 5h, centrifuged at 10000rpm, the precipitate was collected and washed with anhydrous ethanol, and dried to obtain amino-modified graphene oxide.

[0041] S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 105°C using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 10 hours to obtain an epoxy-based polysiloxane. The single-ended hydrogen-containing polysiloxane and glycidyl methacrylate reacted in a carbon-carbon double bond and silicon-hydrogen bond molar ratio of 1:1. The single-ended hydrogen-containing polysiloxane had a molecular weight of 1500.

[0042] S3: Amino-modified graphene oxide and epoxy-based polysiloxane were dispersed in anhydrous isopropanol at a mass ratio of 1:5. After reacting at 80°C for 3 hours, the precipitate was collected by centrifugation and dried to obtain polysiloxane-grafted graphene oxide.

[0043] Step 2:

[0044] Octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate were dispersed in xylene and heated to 85°C under nitrogen atmosphere. The reaction was carried out for 10 hours with benzoyl peroxide as an initiator. After precipitation with anhydrous ethanol, the mixture was filtered under reduced pressure and dried under vacuum to obtain an organosilicon-modified polyester pour point depressant. The molar ratio of octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate was 5:1.2:3.2:0.8.

[0045] Step 3: Disperse the ethylene-vinyl acetate pour point depressant in anhydrous toluene to obtain a 10 wt.% ethylene-vinyl acetate pour point depressant solution; mix 40 g of organosilicon-modified polyester pour point depressant, 25 g of ethylene-vinyl acetate pour point depressant solution, 60 g of kerosene, 5 g of polysiloxane-grafted graphene oxide, and 11 g of Span 80 to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0046] Comparative Example 1: No modification was made to the graphene oxide, and the other parameters were the same as in Example 1.

[0047] Step 1:

[0048] Octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate were dispersed in xylene and heated to 80°C under nitrogen atmosphere. The reaction was initiated by benzoyl peroxide for 8 hours. After precipitation with anhydrous ethanol, the mixture was filtered under reduced pressure and dried under vacuum to obtain an organosilicon-modified polyester pour point depressant. The molar ratio of octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate was 4.8:1:2.8:0.5.

[0049] Step 2: Disperse the ethylene-vinyl acetate pour point depressant in anhydrous toluene to obtain a 5 wt.% ethylene-vinyl acetate pour point depressant solution; mix 35 g of organosilicon-modified polyester pour point depressant, 20 g of ethylene-vinyl acetate pour point depressant solution, 50 g of kerosene, 1 g of graphene oxide, and 8 g of Span 80 to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0050] Comparative Example 2: A polyester pour point depressant was prepared without the addition of propyl 3-(triethoxysilane)methacrylate, and the remaining parameters were the same as in Example 2.

[0051] Step 1:

[0052] S1: Graphene oxide was activated at 400℃ for 4h to obtain high-temperature activated graphene oxide; 5.5g of high-temperature activated graphene oxide was mixed with 11g of KH550 and 120g of anhydrous toluene, ultrasonically dispersed for 13min, heated under reflux for 4h, centrifuged at 9000rpm, the precipitate was collected and washed with anhydrous ethanol, and dried to obtain amino-modified graphene oxide.

[0053] S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 103°C using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 9 hours to obtain an epoxy-based polysiloxane. The single-ended hydrogen-containing polysiloxane and glycidyl methacrylate reacted in a carbon-carbon double bond and silicon-hydrogen bond molar ratio of 1:1. The single-ended hydrogen-containing polysiloxane had a molecular weight of 1200.

[0054] S3: Amino-modified graphene oxide and epoxy-based polysiloxane were dispersed in anhydrous isopropanol at a mass ratio of 1:4. After reacting at 75°C for 2.5 h, the precipitate was collected by centrifugation and dried to obtain polysiloxane-grafted graphene oxide.

[0055] Step 2:

[0056] Octadecyl methacrylate, maleic anhydride, and 1-octadecene were dispersed in xylene and heated to 83°C under nitrogen atmosphere. The mixture was reacted with benzoyl peroxide as an initiator for 9 hours. After precipitation with anhydrous ethanol, the mixture was filtered under reduced pressure and dried under vacuum to obtain an organosilicon-modified polyester pour point depressant. The molar ratio of octadecyl methacrylate, maleic anhydride, and 1-octadecene was 4.9:1.1:3.

[0057] Step 3: Disperse the ethylene-vinyl acetate pour point depressant in anhydrous toluene to obtain an 8 wt.% ethylene-vinyl acetate pour point depressant solution; mix 38 g of organosilicon-modified polyester pour point depressant, 23 g of ethylene-vinyl acetate pour point depressant solution, 56 g of kerosene, 2.4 g of polysiloxane-grafted graphene oxide, and 9 g of Span 80 to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0058] Comparative Example 3: The molecular weight of the hydrogen-containing silicone oil was increased, while the other parameters were the same as in Example 3.

[0059] Step 1:

[0060] S1: Graphene oxide was activated at 500℃ for 5h to obtain high-temperature activated graphene oxide; 6g of high-temperature activated graphene oxide was mixed with 12g of KH550 and 120g of anhydrous toluene, ultrasonically dispersed for 15min, heated under reflux for 5h, centrifuged at 10000rpm, the precipitate was collected and washed with anhydrous ethanol, and dried to obtain amino-modified graphene oxide.

[0061] S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 105°C using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 10 hours to obtain an epoxy-based polysiloxane. The single-ended hydrogen-containing polysiloxane was reacted with glycidyl methacrylate and the single-ended hydrogen-containing polysiloxane in a carbon-carbon double bond and silicon-hydrogen bond molar ratio of 1:1. The single-ended hydrogen-containing polysiloxane had a molecular weight of 2000.

[0062] S3: Amino-modified graphene oxide and epoxy-based polysiloxane were dispersed in anhydrous isopropanol at a mass ratio of 1:5. After reacting at 80°C for 3 hours, the precipitate was collected by centrifugation and dried to obtain polysiloxane-grafted graphene oxide.

[0063] Step 2:

[0064] Octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate were dispersed in xylene and heated to 85°C under nitrogen atmosphere. The reaction was carried out for 10 hours with benzoyl peroxide as an initiator. After precipitation with anhydrous ethanol, the mixture was filtered under reduced pressure and dried under vacuum to obtain an organosilicon-modified polyester pour point depressant. The molar ratio of octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)propyl methacrylate was 5:1.2:3.2:0.8.

[0065] Step 3: Disperse the ethylene-vinyl acetate pour point depressant in anhydrous toluene to obtain a 10 wt.% ethylene-vinyl acetate pour point depressant solution; mix 40 g of organosilicon-modified polyester pour point depressant, 25 g of ethylene-vinyl acetate pour point depressant solution, 60 g of kerosene, 5 g of polysiloxane-grafted graphene oxide, and 11 g of Span 80 to obtain a heavy oil dispersing pour point depressant for oilfield drilling.

[0066] Experiment: The performance of the heavy oil dispersants and pour point depressants for oilfield drilling prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The test methods are as follows:

[0067] The surface degassed crude oil from the Niuxintuo Oilfield of Liaohe Oilfield was used as the experimental heavy oil, with a viscosity of 1487 mPa·s (50℃), a pour point of 39℃, a resinous asphaltene content of 45.7%, and a wax content of 15.3%. The pour point depressing effect of the heavy oil coagulants in Examples 1-3 and Comparative Examples 1-3 was evaluated. The pour point test was conducted according to the method in GB / T 26985-2018, and the viscosity was measured with a viscometer (50℃). The results are shown in Table 1.

[0068] Table 1.

[0069] project Pour point depressant dosage / ppm Pour point / °C after adding pour point depressant Pour point drop range / ℃ Viscosity / mPa.s Blank group 0 39 / 1487 Example 1 1500 24 15 257 Example 2 1500 22 17 243 Example 3 1500 23 16 268 Comparative Example 1 1500 32 7 764 Comparative Example 2 1500 27 12 1054 Comparative Example 3 1500 29 10 549

[0070] Conclusion: The data in Table 1 show that the heavy oil dispersants and pour point depressants prepared in Examples 1-3 of this invention have better synergy among their components and a significant synergistic effect. They can significantly reduce the pour point and viscosity of crude oil with high wax content, with a pour point reduction of up to 17°C, which is beneficial for heavy oil dispersion. The effect is significantly better than that of Comparative Examples 1-3.

[0071] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 method for preparing a heavy oil dispersant and pour point depressant for oilfield drilling, characterized in that: Organosilicon-modified polyester pour point depressant, ethylene-vinyl acetate pour point depressant solution, kerosene, polysiloxane-grafted graphene oxide, and Span 80 are mixed to obtain a heavy oil dispersing pour point depressant for oilfield drilling. The preparation method of the organosilicon-modified polyester pour point depressant is as follows: Octadecyl methacrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilane)methacrylate propyl ether are dispersed in xylene, heated to 80-85°C under nitrogen atmosphere, and reacted with benzoyl peroxide as an initiator for 8-10 hours. After precipitation with anhydrous ethanol, the mixture is filtered under reduced pressure and dried under vacuum to obtain the organosilicon-modified polyester pour point depressant. The content of each component, by weight, is: 35-40 parts organosilicon-modified polyester pour point depressant, 20-25 parts ethylene-vinyl acetate pour point depressant solution, 50-60 parts kerosene, 3-5 parts polysiloxane-grafted graphene oxide, and 8-11 parts Span 80. The preparation method of the polysiloxane-grafted graphene oxide includes the following steps: S1: Activate graphene oxide at 300~500℃ for 3~5h to obtain high-temperature activated graphene oxide; mix high-temperature activated graphene oxide, KH550 and anhydrous toluene, disperse ultrasonically for 10~15min, heat under reflux for 3~5h, centrifuge at 8000~10000rpm, collect the precipitate and wash with anhydrous ethanol, and dry to obtain amino-modified graphene oxide; S2: Glycidyl methacrylate was dispersed in anhydrous toluene, and a single-ended hydrogen-containing polysiloxane was added at 100-105℃ using isopropanol chloroplatinate solution as a catalyst. The reaction was carried out for 8-10 hours to obtain epoxy polysiloxane. S3: Amino-modified graphene oxide and epoxy-based polysiloxane are dispersed in anhydrous isopropanol at a mass ratio of 1:(3~5). After reacting at 70~80℃ for 2~3h, the precipitate is centrifuged and collected, and dried to obtain polysiloxane-grafted graphene oxide.

2. The preparation method of a heavy oil dispersant and pour point depressant for oilfield drilling according to claim 1, characterized in that: The ethylene-vinyl acetate pour point depressant solution is a mixed solution of ethylene-vinyl acetate pour point depressant and toluene, wherein the content of ethylene-vinyl acetate pour point depressant is 5~10 wt.%.

3. The preparation method of a heavy oil dispersant and pour point depressant for oilfield drilling according to claim 1, characterized in that: The molar ratio of octadecyl acrylate, maleic anhydride, 1-octadecene, and 3-(triethoxysilyl)methacrylate is (4.8~5):(1~1.2):(2.8~3.2):(0.5~0.8).

4. The preparation method of a heavy oil dispersant and pour point depressant for oilfield drilling according to claim 1, characterized in that: In S1, the components are used in the following amounts by weight: 5-6 parts of high-temperature activated graphene oxide, 10-12 parts of KH550, and 120 parts of anhydrous toluene.

5. The preparation method of a heavy oil dispersant and pour point depressant for oilfield drilling according to claim 1, characterized in that... In S2, glycidyl methacrylate and single-ended hydrogen-containing polysiloxane react in a 1:1 molar ratio of carbon-carbon double bonds to silicon-hydrogen bonds, wherein the single-ended hydrogen-containing polysiloxane has a molecular weight of 1000~1500.

6. The method for preparing a heavy oil dispersant and pour point depressant for oilfield drilling according to claim 1, characterized in that: In S3, the mass ratio of amino-modified graphene oxide to epoxy-based polysiloxane is 1:(3~5).

7. The heavy oil dispersant and pour point depressant for oilfield drilling prepared by the preparation method according to any one of claims 1 to 6.