A viscosity reducer for scCO2 raffinate heavy oil, its preparation method, viscosity reducer composition and application.

Abstract

This invention relates to the field of heavy oil viscosity reduction technology, providing a viscosity reducer for scCO2 raffinate heavy oil, its preparation method, viscosity reducer composition, and application. The viscosity reducer comprises an aromatic ring and a long-chain aliphatic hydrocarbon group; the long-chain aliphatic hydrocarbon group is linked to the aromatic ring through an amide structure; the long-chain aliphatic hydrocarbon group has 15-22 carbon atoms. The viscosity reducer provided by this invention can target the cementing network in scCO2 raffinate heavy oil, significantly reducing the viscosity of scCO2 raffinate heavy oil and achieving efficient viscosity reduction.

Description

Technical Field

[0001] This invention relates to the field of heavy oil viscosity reduction technology, and in particular to a viscosity reducer for scCO2 raffinate heavy oil, its preparation method, viscosity reducer composition, and application. Background Technology

[0002] Supercritical carbon dioxide (scCO2) has low viscosity, high diffusivity, and strong solubility for light and middle fractions, and can be used for heavy oil extraction and enhanced oil recovery.

[0003] However, after scCO2 preferentially carries light and intermediate components away from crude oil, the remaining oil phase is not simply unretrieved residue, but rather constitutes redistributed raffinate heavy oil. Its natural dilution and solubilization media are reduced, and gums and asphaltenes are relatively enriched, resulting in significantly deteriorated fluidity.

[0004] Existing methods for reducing the viscosity of heavy oil mainly include heating, dilution with hydrocarbon solvents, emulsification, polymer / surfactant-assisted treatment, and oil-soluble molecular additives. Heating relies on continuous external energy, dilution requires a large amount of solvent, and emulsification systems usually require the addition of an aqueous phase and involve subsequent demulsification. For scCO2 raffinate heavy oil, the above methods are difficult to directly control the reconstructed oil phase agglomerate network after extraction.

[0005] In summary, to reduce the viscosity of scCO2 raffinate heavy oil, it is necessary to develop new viscosity reduction systems and processes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a viscosity reducer for scCO2 raffinate heavy oil, its preparation method, viscosity reducer composition, and application. By using a compound containing amide groups, long-chain aliphatic groups, and benzene rings as a viscosity reducer, it can serve as a molecular target for the viscosity-inducing effect of scCO2 raffinate heavy oil, and can significantly reduce the viscosity of scCO2 raffinate heavy oil.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a viscosity reducer for scCO2 raffinate heavy oil, the viscosity reducer comprising an aromatic ring and a long-chain aliphatic hydrocarbon group. The long-chain aliphatic hydrocarbon group is linked to the aromatic ring via an amide structure. The long-chain aliphatic hydrocarbon group has 15 to 22 carbon atoms, for example, 15, 16, 17, 18, 19, 20, 21, or 22, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0008] The applicant's research revealed that the significantly higher viscosity of scCO2 raffinate heavy oil is due to the presence of numerous molecular targets that lead to increased viscosity. These molecular targets include: First, enhanced self-association between gum molecules in the residual heavy oil; second, aromatic enrichment and near-neutral electrostatic potential molecular surfaces in gum and asphaltenes; third, a dense network of heavy component aggregation maintained by both dispersion attraction and aromatic accumulation; and fourth, local polar sites such as carbonyl groups, hydroxyl groups, and nitrogen-containing groups in the heavy components.

[0009] The viscosity reducer for scCO2 raffinate heavy oil in this invention has the following special design: (1) The amide group has strong dipolarity. The carbonyl oxygen can act as a hydrogen bond acceptor and form hydrogen bonds or dipolar interactions with hydroxyl, carboxyl and other heteroatom-containing polar sites in gums and asphaltenes, thereby achieving polar anchoring of heavy component aggregates in scCO2 raffinate.

[0010] In the selection of polar groups, amide groups can achieve a good balance between polar adsorption and oil phase compatibility, exhibiting a strong yet moderate dipole effect. Furthermore, the carbonyl oxygen acts as a hydrogen bond acceptor, providing excellent anchoring. In contrast, other polar groups struggle to achieve the same effect. For example, amino groups are strongly basic and may protonate or form salts with acidic components in heavy oils, such as naphthenic acids and phenolic hydroxyl groups, significantly enhancing the polarity of the molecule. Excessive local adsorption may cause the viscosity reducer to remain at the polar sites outside the aggregate, reducing its solubility in the non-polar oil phase and its ability to diffuse into aromatic aggregates. Moreover, amino groups lack a carbonyl group and cannot provide the carbonyl dipole and corresponding electron distribution found in amides. Hydroxyl groups can act as both hydrogen bond donors and acceptors, easily forming strong self-associative hydrogen bonds between viscosity reducer molecules, potentially leading to molecular aggregation, increased melting point, or decreased low-temperature oil solubility. However, the effective region of hydroxyl groups is relatively localized, lacking the significant dipole effect provided by the carbonyl group of amides. Sulfone groups have large dipole moments and excessively high polarity, which can easily increase the crystallization tendency and melting point of compounds, and reduce their compatibility in heavy oil. Strong local dipoles may also cause overly concentrated and rigid adsorption, which is not conducive to molecules entering the aromatic enrichment regions of gums and asphaltenes.

[0011] (2) The aromatic ring directly connected to the amide group can form π-π, CH···π and dispersion with the aromatic core of the gum and asphaltenes, promoting the viscosity reducer to approach the aromatic accumulation area.

[0012] (3) Long-chain aliphatic hydrocarbon groups improve the oil phase compatibility of viscosity reducers through van der Waals interactions with alkyl structures in scCO2 raffinate, and form a flexible space layer on the surface of aggregates to inhibit the re-approach and dense stacking of heavy components.

[0013] In summary, the amide group is mainly responsible for polar anchoring, the aromatic ring is responsible for aromatic structure matching, and the long-chain aliphatic hydrocarbon group is responsible for oil phase solubilization and steric hindrance stabilization.

[0014] Preferably, the aromatic ring comprises a benzene ring.

[0015] Preferably, the number of aromatic rings is 1 to 2.

[0016] Preferably, the long-chain aliphatic hydrocarbon group has 17 carbon atoms.

[0017] Preferably, the long-chain aliphatic hydrocarbon group contains a carbon-carbon double bond.

[0018] A C=C double bond is not an absolute necessity for achieving basic viscosity reduction. The core function of viscosity reducers still comes from the synergistic effect of amides, aromatic rings, and long-chain hydrocarbon groups. Therefore, long-chain aliphatic hydrocarbon groups can, in principle, be saturated or unsaturated structures. However, a cis-C=C double bond is preferred, as it can cause conformational bending of the long chain, reducing the ability of the hydrocarbon chain to arrange itself regularly and crystallize. This is beneficial for improving the low-temperature oil solubility and dispersion stability of viscosity reducers, and also increases the disturbance to the ordered packing of heavy components.

[0019] Preferably, the viscosity reducer has the structural formula shown in formula (1): Equation (1).

[0020] R1 and R2 are each independently phenyl and / or hydrogen, and at least one of R1 and R2 is phenyl, and R3 is a long-chain aliphatic hydrocarbon group.

[0021] Preferably, the viscosity reducer has the structural formula shown in formula (2): Equation (2).

[0022] In a second aspect, the present invention provides a method for preparing the viscosity reducer described in the first aspect, the method comprising: Aromatic amines undergo nucleophilic substitution reactions with acyl chloride organic compounds to generate the viscosity reducer; the acyl chloride organic compounds have 16 to 23 carbon atoms, for example, 16, 17, 18, 19, 20, 21, 22 or 23, but are not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] Preferably, the aromatic amine includes aniline and / or diphenylamine.

[0024] Preferably, the molar ratio of the aromatic amine to the acyl chloride organic compound is (1.1~1):(1~1.2), for example, it can be 1.1:1, 1.09:1, 1.08:1, 1.07:1, 1.06:1, 1.05:1, 1.04:1, 1.02:1, 1.01:1, 1:1, 1.09:1.1, 1.08:1.1, 1.07:1.1, 1.06:1.1, 1.05:1 1.04:1.1, 1.02:1.1, 1.01:1.1, 1:1.1, 1.1:1.2, 1.09:1.2, 1.08:1.2, 1.07:1.2, 1.06:1.2, 1.05:1.2, 1.04:1.2, 1.02:1.2, 1.01:1.2, or 1:1.2, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0025] Preferably, the acyl chloride organic compound includes oleoyl chloride.

[0026] Preferably, the reaction temperature of the nucleophilic substitution reaction is 20~30℃, for example, it can be 20℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] Preferably, the duration of the nucleophilic substitution reaction is 3 to 6 hours, for example, 3 hours, 3.4 hours, 3.7 hours, 4 hours, 4.4 hours, 4.7 hours, 5 hours, 5.4 hours, 5.7 hours, or 6 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the preparation method includes: dissolving an aromatic amine in an organic solvent under a protective atmosphere and cooling it to a first temperature to obtain a first reaction system; adding an acyl chloride organic compound and an acid-binding agent dropwise to the first reaction system, raising the temperature to the temperature for nucleophilic substitution reaction, and carrying out the nucleophilic substitution reaction to obtain a reaction solution.

[0029] Preferably, the organic solvent includes anhydrous dichloromethane.

[0030] Preferably, the first temperature is 0~5℃, for example, it can be 0℃, 0.6℃, 1.2℃, 1.7℃, 2.3℃, 2.8℃, 3.4℃, 3.9℃, 4.5℃ or 5℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the molar ratio of the acid-binding agent to the acyl chloride organic compound is (1.0~1.3):1, for example, it can be 1.0:1, 1.04:1, 1.07:1, 1.1:1, 1.14:1, 1.17:1, 1.2:1, 1.24:1, 1.27:1 or 1.3:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the acid-binding agent comprises triethylamine and / or N,N-diisopropylethylamine.

[0033] Preferably, the preparation method further includes: adding a quenching agent to the reaction solution, and then washing, drying and concentrating the solution in sequence to obtain a viscosity reducer.

[0034] Preferably, the quenching agent comprises water.

[0035] Preferably, the washing process includes washing with dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated sodium chloride solution in sequence.

[0036] Preferably, the drying process includes drying with anhydrous sodium sulfate.

[0037] Preferably, the concentration includes vacuum concentration.

[0038] Thirdly, the present invention provides a viscosity-reducing composition for scCO2 raffinate heavy oil, comprising the viscosity-reducing agent for scCO2 raffinate heavy oil described in the first aspect.

[0039] Preferably, the viscosity-reducing composition comprises a viscosity reducer and a dispersant, wherein the dispersant comprises an aromatic hydrocarbon dispersant and an unsaturated fatty acid dispersant.

[0040] The present invention preferably uses a combination of aromatic hydrocarbon dispersant and unsaturated fatty acid dispersant as dispersant. The aromatic hydrocarbon dispersant can quickly dissolve the aromatic amide type viscosity reducer and reduce the local viscosity through dilution. The unsaturated fatty acid dispersant has good oil phase compatibility and interface regulation ability. The two work together to enable the viscosity reducer to dissolve rapidly, thereby enabling the viscosity reducer to be quickly and uniformly distributed in the high viscosity scCO2 extract residue heavy oil.

[0041] This invention employs unsaturated fatty acid dispersants, such as linoleic acid, whose two cis C=C double bonds cause its long chain to exhibit significant conformational bending, reducing intermolecular regularity and crystallization ability. If linoleic acid is replaced with saturated long-chain fatty acids such as stearic acid or palmitic acid, the saturated straight chains are more likely to stack parallel and crystallize, potentially increasing the freezing point and low-temperature viscosity of the formulation, leading to slower dispersion or precipitation of the active viscosity reducer. Linoleic acid has a melting point of approximately -5°C, while stearic acid has a melting point of approximately 69–72°C. Therefore, at scCO2 raffinate heavy oil treatment temperatures of 30–50°C, linoleic acid typically remains liquid, while stearic acid may still be in a solid or incompletely molten state, which is detrimental to low-temperature mixing and rapid dispersion. Therefore, while saturated long-chain fatty acids may still provide polar anchoring and oil-phase compatibility, they are expected to be weaker than unsaturated fatty acids in terms of low-temperature fluidity, anti-crystallization ability, and conformational perturbation.

[0042] Preferably, the aromatic hydrocarbon dispersant comprises any one or a combination of at least two of toluene, benzene, xylene, or trimethylbenzene, wherein typical but non-limiting combinations are combinations of toluene and benzene, xylene and benzene, toluene and xylene, trimethylbenzene and benzene, and toluene and trimethylbenzene.

[0043] Preferably, the unsaturated fatty acid dispersant includes any one or a combination of at least two of oleic acid, linoleic acid, linolenic acid, or arachidonic acid, wherein typical but non-limiting combinations are the combination of oleic acid and linoleic acid, the combination of linolenic acid and linoleic acid, the combination of oleic acid and linolenic acid, or the combination of arachidonic acid and linoleic acid.

[0044] Preferably, the mass ratio of the viscosity reducer to the dispersant is (0.5~4.0):(2~4), for example, it can be 0.5:2, 0.8:2, 1.0:2, 1.2:2, 1.5:2, 1.8:2, 2.0:2, 2.5:2, 3.0:2, 3.5:2, 4.0:2, 0.5:2.5, 0.8:2.5, 1.0:2.5, 1.2:2.5, 1.5:2.5, 1.8:2.5, 2.0:2.5, 2.5:2.5, 3.0:2.5, 3.5:2.5, 4.0:2.5, 0.5:3, 0.8:3, 1.0:3, 1.2:3, 1.5: 3, 1.8:3, 2.0:3, 2.5:3, 3.0:3, 3.5:3, 4.0:3, 0.5:3.5, 0.8:3.5, 1.0:3.5, 1.2:3.5, 1.5:3.5, 1.8:3.5, 2.0:3.5, 2.5:3.5, 3.0:3.5, 3.5:3.5, 4.0:3.5, 0.5:4, 0.8:4, 1.0:4, 1.2:4, 1.5:4, 1.8:4, 2.0:4, 2.5:4, 3.0:4, 3.5:4, or 4.0:4, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0045] The present invention preferably uses a mass ratio of viscosity reducer to dispersant within the above-mentioned range, which has a better viscosity reduction and dispersing effect.

[0046] Preferably, the mass ratio of aromatic hydrocarbon dispersant to unsaturated fatty acid dispersant in the dispersant is (1.5~2.5):(0.5~1.5), for example, it can be 1.5:0.5, 1.8:0.5, 2.0:0.5, 2.2:0.5, 2.5:0.5, 1.5:0.8, 1.8:0.8, 2.0:0.8, 2.2:0.8, 2.5:0.8, 1.5:1.0, 1.8:1.0, 2.0:1.0, 2.2:1.0, 2.5:1.0, 1.5:1.5, 1.8:1.5, 2.0:1.5, 2.2:1.5 or 2.5:1.5, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] Fourthly, the present invention provides an application of the viscosity reducer for scCO2 extractable heavy oil as described in the first aspect, or the viscosity reducer composition for scCO2 extractable heavy oil as described in the third aspect, wherein the viscosity reducer composition is applied to reduce the viscosity of scCO2 extractable heavy oil.

[0048] Preferably, the viscosity of the scCO2 raffinate heavy oil at 30°C is ≥150000 mPa·s, for example, it can be 150000 mPa·s, 170000 mPa·s, 180000 mPa·s, 190000 mPa·s, 200000 mPa·s, 210000 mPa·s, 220000 mPa·s, 230000 mPa·s, 240000 mPa·s, or 250000 mPa·s, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the viscosity of the scCO2 raffinate heavy oil at 50°C is ≥18000 mPa·s, for example, it can be 18000 mPa·s, 19000 mPa·s, 20000 mPa·s, 21000 mPa·s, 22000 mPa·s, 23000 mPa·s, 24000 mPa·s or 25000 mPa·s, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] Preferably, the scCO2 raffinate heavy oil comprises gum and asphaltenes.

[0051] Preferably, the mass percentage of gum in the scCO2 raffinate is 37.0~41.0 wt%, for example, it can be 37.0 wt%, 37.5 wt%, 37.9 wt%, 38.4 wt%, 38.8 wt%, 39.3 wt%, 39.7 wt%, 40.2 wt%, 40.6 wt%, or 41.0 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the mass percentage of asphaltenes in the scCO2 raffinate is 6.0~8.0 wt%, for example, it can be 6.0 wt%, 6.3 wt%, 6.5 wt%, 6.7 wt%, 6.9 wt%, 7.2 wt%, 7.4 wt%, 7.6 wt%, 7.8 wt%, or 8.0 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, the total interaction energy of the gum-gum complex in the scCO2 raffinate is ≤-28 kcal / mol, for example, it can be -28 kcal / mol, -29 kcal / mol, -30 kcal / mol, -31 kcal / mol, -32 kcal / mol, -33 kcal / mol, -34 kcal / mol, -35 kcal / mol, -36 kcal / mol, -37 kcal / mol, -38 kcal / mol or -40 kcal / mol, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0054] Preferably, the H / C ratio of gums in the scCO2 raffinate is 1.40 to 1.55, for example, it can be 1.40, 1.42, 1.44, 1.46, 1.48, 1.50, 1.52, 1.54 or 1.55, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the H / C ratio of asphaltenes in the scCO2 raffinate is 1.35 to 1.50, for example, it can be 1.35, 1.37, 1.39, 1.41, 1.43, 1.45, 1.47, 1.49 or 1.50, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] The above description of the characteristics of scCO2 raffinate heavy oil shows that, unlike traditional heavy oil, scCO2 raffinate heavy oil has more recombinant polymer molecules and significantly increased viscosity. The total interaction energy of the colloidal-colloidal complex is significantly increased, making it difficult for traditional dilution or dissolution to achieve the desired viscosity reduction effect.

[0057] Preferably, the amount of viscosity reducer added during the viscosity reduction process of the scCO2 raffinate heavy oil is 0.5~4.0 wt%, for example, it can be 0.5 wt%, 0.9 wt%, 1.3 wt%, 1.7 wt%, 2.1 wt%, 2.5 wt%, 2.9 wt%, 3.3 wt%, 3.7 wt%, or 4.0 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Studies have shown that when the amount of viscosity reducer added is controlled within a reasonable range, its viscosity-reducing effect is better and the consumption of viscosity reducer can be reduced.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The viscosity reducer provided by the present invention can specifically target the specific compositional rearrangement and agglomeration structure of the heavy oil residue after scCO2 extraction, rather than relying solely on general heating or solvent dilution. It is a small molecule substance, which is simple to prepare and has a low cost. It can also avoid the post-processing steps of emulsifier and nanoparticle viscosity reduction. Compared with oil-soluble viscosity reducers, it has a better viscosity reduction effect and requires a lower dosage.

[0060] (2) The viscosity reduction agent provided by the present invention has a viscosity reduction rate of over 73% and excellent viscosity reduction effect. Attached Figure Description

[0061] Figure 1 These are infrared spectra of asphaltenes and gums in the scCO2 extract residue used in the embodiments and comparative examples of this invention.

[0062] Figure 2 This is the infrared spectrum of the viscosity reducer prepared in Example 1 of the present invention.

[0063] Figure 3 This is the infrared spectrum of the viscosity reducer prepared in Example 2 of the present invention.

[0064] Figure 4 These are the proton NMR spectra of the viscosity reducers prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0065] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0066] Unlike the original heavy oil that has not undergone scCO2 treatment, scCO2 raffinate is a residual oil phase whose composition and aggregate structure have been reconstructed after the selective removal of light and intermediate hydrocarbon components.

[0067] After scCO2 preferentially removes light and intermediate components, the natural dilution and solvation media in the raffinate phase decrease, the contact probability between heavy components increases significantly, and the gums and asphaltenes in the raffinate heavy oil are relatively enriched.

[0068] The applicant's research revealed that the unique changes caused by scCO2 extraction are not only manifested in an increase in the content of heavy components, but also in the reconstruction of a colloidal-dominated aggregate network. The increased viscosity of the raffinate heavy oil is mainly related to the weakening of electrostatic repulsion between colloidal molecules, the enhancement of dispersive attraction, and the formation of a dense aggregate structure. This means that the key to reducing the viscosity of scCO2 raffinate heavy oil is not simply diluting the oil phase, but rather weakening the colloidal-dominated dense aggregate network formed after extraction.

[0069] It is precisely because of the applicant's creative discovery of this technical problem that, in order to solve the above-mentioned pain points, the specific implementation of this invention adopts the following specific solution.

[0070] For ease of experimental comparison, this invention uses a sample of a certain scCO2 raffinate heavy oil as a representative sample, but this does not mean that this invention is only applicable to this scCO2 raffinate heavy oil. Other raffinate heavy oils that require viscosity reduction after supercritical CO2 extraction are also applicable.

[0071] The compositions of the original heavy oil and scCO2 raffinate heavy oil used in the following examples and comparative examples are shown in Table 1.

[0072] Table 1

[0073] The viscosity data of the original heavy oil and scCO2 raffinate heavy oil for the following examples and comparative examples at 30°C and 50°C are shown in Table 2.

[0074] Table 2

[0075] This invention employs a conventional four-component separation method to separate asphaltenes and gums in scCO2 raffinate heavy oil, and performs infrared analysis on the asphaltenes and gums in the scCO2 raffinate heavy oil sample. The infrared results are as follows: Figure 1 As shown in the figure. Elemental analysis of asphaltene and resin was performed, and the normalized composition results are shown in Table 3.

[0076] Table 3

[0077] Example 1 This embodiment provides a viscosity reducer, the structural formula of which is shown in formula (3): Equation (3).

[0078] This embodiment also provides a method for preparing the viscosity reducer, the method comprising the following steps: In a nitrogen protective atmosphere, aniline was dissolved in anhydrous dichloromethane (aniline concentration of 0.10 mol / L) and cooled to a first temperature of 2°C to obtain the first reaction system; According to the molar ratio of acid-binding agent to oleoyl chloride of 1.2:1 and the molar ratio of aniline to oleoyl chloride of 1.1:1, oleoyl chloride and acid-binding agent (triethylamine) were added dropwise to the first reaction system, and the temperature was raised to 25°C, the temperature for nucleophilic substitution reaction, and the nucleophilic substitution reaction was carried out for 4 hours to obtain the reaction solution; Water was added to the reaction solution as a quenching agent, and the solution was washed successively with dilute hydrochloric acid (3.6 wt%), saturated sodium bicarbonate solution and saturated sodium chloride solution. After drying and vacuum concentration, a viscosity reducer was obtained.

[0079] The infrared spectrum of the viscosity reducer obtained in this embodiment is as follows: Figure 2 As shown, the results indicate that the product is at 3290 cm⁻¹ -1 and 1651cm -1 Characteristic peaks appeared nearby, which were deduced to be the stretching vibration absorption peaks of the NH bond and the C=O bond of the amide carbonyl group, indicating that the nucleophilic substitution reaction was successfully completed under the above conditions; the product was observed at 2920 cm⁻¹. -1 and 2850 cm -1 Absorption peaks for asymmetric and symmetric stretching vibrations of long-chain alkyl CH bonds appear nearby, and are located at 1500–1600 cm⁻¹. -1 The presence of aromatic ring skeletal vibration absorption peaks within the range confirms the presence of long-chain aliphatic hydrocarbon groups and benzene ring structures in the product. The above infrared characterization indicates that the structure shown in formula (3) was generated during the synthesis process.

[0080] The NMR spectrum of the viscosity reducer obtained in this embodiment is as follows: Figure 4 As shown, the results indicate that a triplet signal of the terminal —CH3 proton was observed near 0.84 ppm; a strong peak near 1.25 ppm was attributed to the methylene proton in the long-chain alkyl group; a signal near 1.98 ppm was attributed to the allyl methylene proton adjacent to the carbon-carbon double bond; a signal near 2.30 ppm was attributed to the —COCH2— proton adjacent to the amide carbonyl group; a signal near 5.30 ppm was attributed to the —CH=CH— proton; and multiplets in the range of 7.0–7.6 ppm were attributed to benzene ring protons. These characteristic signals are consistent with the structure shown in formula (3). Based on the infrared and NMR results, the target product was successfully synthesized.

[0081] Example 2 This embodiment provides a viscosity reducer, the structural formula of which is shown in formula (4): Equation (4).

[0082] This embodiment also provides a method for preparing the viscosity reducer, the method comprising the following steps: Under a nitrogen protective atmosphere, diphenylamine was dissolved in anhydrous dichloromethane (diphenylamine concentration was 0.394 mol / L) and cooled to a first temperature of 5°C to obtain the first reaction system; According to the molar ratio of acid-binding agent to oleoyl chloride of 1.3:1 and the molar ratio of diphenylamine to oleoyl chloride of 1:1.2, oleoyl chloride and acid-binding agent (triethylamine) were added dropwise to the first reaction system, and the temperature was raised to 20°C, the temperature for nucleophilic substitution reaction, and the nucleophilic substitution reaction was carried out for 6 hours to obtain the reaction solution; Water was added to the reaction solution as a quenching agent, and the solution was washed successively with dilute hydrochloric acid (5 wt%), saturated sodium bicarbonate solution and saturated sodium chloride solution. After drying and vacuum concentration, a viscosity reducer was obtained.

[0083] The infrared spectrum of the viscosity reducer obtained in this embodiment is as follows: Figure 3 As shown, the results indicate that the product is at 1650 cm⁻¹ -1 and 1250cm -1 Characteristic peaks appeared nearby, which were deduced to be the stretching vibration absorption peaks of the C=O bond of the amide carbonyl group and the CN bond of the amide, indicating that the nucleophilic substitution reaction was successfully completed under the above conditions; the product was observed at 2920 cm⁻¹. -1 and 2850 cm -1 Absorption peaks for asymmetric and symmetric stretching vibrations of long-chain alkyl CH bonds appear nearby, in the range of 1500–1600 cm⁻¹. -1 An absorption peak for aromatic ring skeletal vibrations appears within the range, and at 3300 cm⁻¹ -1 No obvious NH stretching vibration absorption peak was observed nearby, consistent with the N,N-disubstituted tertiary amide structure shown in equation (4). The above infrared characterization indicates that the structure shown in equation (4) was generated during the synthesis process.

[0084] The NMR spectrum of the viscosity reducer obtained in this embodiment is as follows: Figure 4 As shown, the results indicate that a triplet signal of the terminal —CH3 proton was observed near 0.84 ppm; a strong peak near 1.25 ppm was attributed to the methylene proton in the long-chain alkyl group; a signal near 1.98 ppm was attributed to the allyl methylene proton adjacent to the carbon-carbon double bond; a signal near 2.30 ppm was attributed to the —COCH2— proton adjacent to the amide carbonyl group; a signal near 5.30 ppm was attributed to the —CH=CH— proton; and multiplets in the range of 7.0–7.4 ppm were attributed to the aromatic hydrogen protons of the two benzene rings. Meanwhile, no obvious N—H proton signal of the amide was observed in the spectrum, consistent with the structure of the N,N-disubstituted tertiary amide shown in formula (4). Based on the infrared and NMR results, the target product was successfully synthesized.

[0085] Example 3 This embodiment provides a viscosity reducer, the structural formula of which is shown in formula (4): Equation (4).

[0086] This embodiment also provides a method for preparing the viscosity reducer, the method comprising the following steps: Under a nitrogen protective atmosphere, diphenylamine was dissolved in anhydrous dichloromethane (aniline concentration of 0.394 mol / L) and cooled to a first temperature of 0°C to obtain the first reaction system; According to the molar ratio of acid-binding agent to oleoyl chloride of 1.0:1 and the molar ratio of diphenylamine to oleoyl chloride of 1:1, oleoyl chloride and acid-binding agent (triethylamine) were added dropwise to the first reaction system, and the temperature was raised to 30°C, the temperature of nucleophilic substitution reaction, and the nucleophilic substitution reaction was carried out for 3 hours to obtain the reaction solution; Water was added to the reaction solution as a quenching agent, and the solution was washed successively with dilute hydrochloric acid (5 wt%), saturated sodium bicarbonate solution and saturated sodium chloride solution. After drying and vacuum concentration, a viscosity reducer was obtained.

[0087] Example 4 This embodiment provides a viscosity reducer, which is octadecylaniline (CAS No.: 637-54-7), specifically as shown in formula (5).

[0088] Equation (5).

[0089] Comparative Example 1 This comparative example provides a viscosity reducer, which is a tetradecanoylaniline (CAS No.: 622-56-0), specifically as shown in formula (6).

[0090] Equation (6).

[0091] Comparative Example 2 This comparative example provides a viscosity reducer, which is N-phenyl-3-cyclopentene-1-carboxamide (CAS No.: 7686-79-5), specifically as shown in formula (7).

[0092] Equation (7).

[0093] Comparative Example 3 This comparative example provides a viscosity reducer, which is a propionyl aniline (CAS No.: 620-71-3), specifically as shown in formula (8).

[0094] Equation (8).

[0095] Comparative Example 4 This comparative example provides a viscosity reducer, which is an octadecylbenzene (CAS No.: 4445-07-2) with the structure shown in formula (9).

[0096] Equation (9).

[0097] Comparative Example 5 This comparative example provides a viscosity reducer, wherein the viscosity reducer adopts C 19 H 39 NO (CAS No.: 20198-92-9), specifically as shown in equation (10).

[0098] Equation (10).

[0099] Comparative Example 6 This comparative example provides a viscosity reducer, wherein the viscosity reducer adopts C 13 H 19 NO (CAS No.: 430463-54-0), specifically as shown in formula (11).

[0100] Equation (11).

[0101] Comparative Example 7 This comparative example provides a viscosity reducer, wherein the viscosity reducer adopts C 11 H 14 OS (CAS No.: 126587-81-3) has the structure shown in equation (12).

[0102] Equation (12).

[0103] In the following application examples, viscosity was measured using a HAAKE Viscotester iQ rheometer with a flat rotor and a 1 mm gap. The viscosity-temperature profile of the heavy oil was obtained at a constant shear rate of 10 s⁻¹. -1 The viscosity of heavy oil at different temperatures was tested, with a measurement time of 180 seconds, and the measurements were performed in parallel three times.

[0104] Unless otherwise specified, all the above-mentioned organic compounds are commercially available products and will not be further specified.

[0105] Application Example 1 This application example provides a viscosity-reducing composition for scCO2 raffinate heavy oil. The viscosity-reducing composition includes a dispersant and the viscosity-reducing agent of Example 1. The dispersant includes an aromatic hydrocarbon dispersant and an unsaturated fatty acid dispersant. The aromatic hydrocarbon dispersant is trimethylbenzene, and the unsaturated fatty acid dispersant is linoleic acid.

[0106] The mass ratio of the viscosity reducer to the dispersant is 2.5:3; the mass ratio of the aromatic hydrocarbon dispersant to the unsaturated fatty acid dispersant in the dispersant is 2:1.

[0107] This application example also provides a method for reducing the viscosity of scCO2 raffinate heavy oil, the method comprising the following steps: The scCO2 raffinate was heated at 70°C and pre-stirred at 300 r / min for 15 min to remove air bubbles. The scCO2 raffinate was then kept at the test temperature for 1 h and immediately placed in a rheometer for measurement; the viscosity value was recorded as η0. 20 g of scCO2 raffinate was taken, and the viscosity-reducing composition from Application Example 1 was added at a viscosity-reducing agent dosage of 2.5 wt%. The mixture was heated at 70°C and stirred at 300 r / min for 15 min to ensure homogeneity. It was then kept at the test temperature for 1 h and immediately placed in a preheated rheometer for measurement; the viscosity value was recorded as η1. The viscosity reduction rate was recorded as... . =(η0-η1) / η0×100%.

[0108] Taking Application Example 1 as an example, the viscosity changes before and after the test were measured under the conditions of 30℃, 40℃, 50℃, 60℃, 70℃ and 80℃. The viscosity data are shown in Table 4.

[0109] Table 4

[0110] As shown in Table 4, the viscosity-reducing composition provided in this application example has an excellent viscosity-reducing effect on scCO2 raffinate heavy oil. The viscosity reduction rate reached over 45% at all temperatures.

[0111] Application Example 2 This application example provides a viscosity-reducing composition for scCO2 raffinate heavy oil. The viscosity-reducing composition includes a dispersant and the viscosity-reducing agent of Example 2. The dispersant includes an aromatic hydrocarbon dispersant and an unsaturated fatty acid dispersant. The aromatic hydrocarbon dispersant is trimethylbenzene, and the unsaturated fatty acid dispersant is linoleic acid.

[0112] The mass ratio of the viscosity reducer to the dispersant is 2:3; the mass ratio of the aromatic hydrocarbon dispersant to the unsaturated fatty acid dispersant in the dispersant is 1.5:1.5.

[0113] This application example also provides a method for reducing the viscosity of scCO2 raffinate heavy oil, the method comprising the following steps: The scCO2 raffinate was heated at 80°C and pre-stirred at 300 r / min for 10 min to remove air bubbles. The scCO2 raffinate was then kept at the test temperature for 1 h and immediately placed in a rheometer for measurement; the viscosity value was recorded as η0. 20 g of scCO2 raffinate was taken, and the viscosity-reducing composition from Application Example 2 was added at a viscosity-reducing agent dosage of 2 wt%. The mixture was heated at 80°C and stirred at 300 r / min for 20 min to ensure homogeneity. It was then kept at the test temperature for 1 h and immediately placed in a preheated rheometer for measurement; the viscosity value was recorded as η1. The viscosity reduction rate was recorded as η1. . =(η0-η1) / η0×100%.

[0114] Application Example 3 This application example provides a viscosity-reducing composition for scCO2 raffinate heavy oil. The viscosity-reducing composition includes a dispersant and the viscosity-reducing agent of Example 3. The dispersant includes an aromatic hydrocarbon dispersant and an unsaturated fatty acid dispersant. The aromatic hydrocarbon dispersant is trimethylbenzene, and the unsaturated fatty acid dispersant is linoleic acid.

[0115] The mass ratio of the viscosity reducer to the dispersant is 4.0:4; the mass ratio of the aromatic hydrocarbon dispersant to the unsaturated fatty acid dispersant in the dispersant is 2.5:1.5.

[0116] This application example also provides a method for reducing the viscosity of scCO2 raffinate heavy oil, the method comprising the following steps: The scCO2 raffinate was heated at 60°C and pre-stirred at 300 r / min for 20 min to remove air bubbles. The scCO2 raffinate was then kept at the test temperature for 1.5 h and immediately placed in a rheometer for measurement; the viscosity value was recorded as η0. 20 g of scCO2 raffinate was taken, and the viscosity-reducing composition from Application Example 3 was added at a viscosity-reducing agent dosage of 4.0 wt%. The mixture was heated at 60°C and stirred at 300 r / min for 15 min to ensure homogeneity. It was then kept at the test temperature for 1 h and immediately placed in a preheated rheometer for measurement; the viscosity value was recorded as η1. The viscosity reduction rate was recorded as... . =(η0-η1) / η0×100%.

[0117] Application Example 4 and Comparative Application Examples 1-7 Application Example 4 and Comparative Examples 1-7 provide a viscosity-reducing composition for scCO2 raffinate heavy oil and a method for reducing the viscosity of scCO2 raffinate heavy oil. Except for the use of the viscosity-reducing agents in Example 4 and Comparative Examples 1-7, the rest are the same as in Application Example 1, and will not be repeated here.

[0118] Application Examples 1-1 to 1-2 Application Examples 1-1 to 1-2 provide a viscosity-reducing composition for scCO2 raffinate heavy oil and a method for reducing viscosity of scCO2 raffinate heavy oil. Except for the addition amounts of viscosity reducer in Example 1 being 0.3wt% and 5.0wt% respectively, the rest are the same as in Application Example 1, and will not be repeated here.

[0119] Application Examples 1-3 Application Examples 1-3 provide a viscosity-reducing composition for scCO2 raffinate heavy oil and a method for reducing viscosity of scCO2 raffinate heavy oil. Except that the amount of dispersant used is all trimethylbenzene, the rest are the same as in Application Example 1, and will not be repeated here.

[0120] Application Examples 1-4 Application Examples 1-4 provide a viscosity-reducing composition for scCO2 raffinate heavy oil and a method for reducing viscosity of scCO2 raffinate heavy oil. Except that the amount of dispersant used is entirely linoleic acid, the rest are the same as in Application Example 1, and will not be repeated here.

[0121] The test results of viscosity changes at 50℃ for the above application examples and comparative examples are shown in Table 5.

[0122] Table 5

[0123] The following points can be observed from Table 5: (1) As can be seen from the combined application examples 1 and 2-3, the viscosity-reducing composition provided by the present invention can significantly reduce the viscosity of scCO2 raffinate heavy oil. At 50°C, its viscosity-reducing effect reaches more than 73%.

[0124] (2) It can be seen from the combined application examples 1, 1-1 and 1-2 that the amount of viscosity reducer added has a relatively preferred range. When the amount of viscosity reducer added reaches a certain amount, further increasing it will not only waste the amount of viscosity reducer, but also will not further improve the viscosity reduction effect.

[0125] (3) Combining Application Examples 1, 1-3, and 1-4, it can be seen that in Application Example 1-3, all dispersants used were trimethylbenzene. Although trimethylbenzene can quickly dissolve aromatic amide-type viscosity reducers and reduce local viscosity through dilution, it does not contain polar groups such as carboxyl groups and cannot form sustained hydrogen bonds or dipole stabilizing effects on the polar sites in gums and asphaltenes. Therefore, when only trimethylbenzene is used, the viscosity-reducing effect may depend more on instantaneous solubilization and dilution. When the trimethylbenzene content decreases, volatilizes, or the system undergoes high-temperature aging, the dispersed heavy components may reassociate. Furthermore, the low molecular weight aromatic structure of trimethylbenzene cannot form a long-chain steric hindrance layer, so its ability to inhibit the re-aggregation of heavy components is expected to be weaker than that of the composite system containing linoleic acid, ultimately leading to a decrease in the viscosity-reducing effect. In Application Example 1-4, all dispersants used were linoleic acid, whose viscosity and intermolecular association ability are higher than those of low-viscosity aromatic hydrocarbon solvents. Hydrogen-bonded dimers may also form between carboxylic acid groups. Therefore, when linoleic acid is used alone as the dispersion medium, the initial dissolution rate of the viscosity reducer is slow, and its solvation ability for aromatic amide structures is insufficient, making it difficult to rapidly and uniformly distribute the active molecules in the high-viscosity scCO2 raffinate heavy oil. Furthermore, the polar association of linoleic acid itself may consume some of the polar sites that can interact with heavy components. Using linoleic acid alone may result in problems such as high formulation viscosity, long mixing time, uneven local concentration of active components, and insufficient dispersion rate at low temperatures. Ultimately, the viscosity-reducing effects of Application Examples 1-3 and 1-4 were lower than those of Application Example 1.

[0126] (4) The long-chain aliphatic hydrocarbon group of the viscosity reducer in Application Example 4 does not contain carbon-carbon double bonds, which leads to problems such as increased melting point, low-temperature crystallization, enhanced self-association and decreased space disturbance ability. Compared with Application Example 1, the viscosity reduction effect is reduced.

[0127] (5) In Comparative Example 1, the long-chain aliphatic hydrocarbon group has fewer carbon atoms, making it difficult to achieve the steric hindrance effect and form a large-area dispersive contact with the long alkyl side chains of gums and asphaltenes. Therefore, the viscosity-reducing effect is significantly lower than in Comparative Example 1. In Comparative Example 2, the hydrophobic part is a five-membered cyclic alkenyl group, lacking a carbon atom. 17The compound has a short, flexible long chain. Cyclopentene has a short structure and restricted conformation, preventing it from forming a long-chain steric hindrance layer extending into the oil phase on the aggregate surface. It also struggles to form large-area dispersive contacts with the long alkyl side chains of gums and asphaltenes. The compound has a small molecular weight, resulting in a significantly smaller molecular size and non-polar surface area. Therefore, even if its amide and benzene rings can adsorb onto the aggregates, adsorption is mainly limited to local surfaces, lacking the ability to anchor in the oil phase and inhibit re-aggregation. The viscosity-reducing effect is significantly lower than in Application Example 1. In Comparative Example 3, the acyl side contains only a two-carbon ethyl group, lacking a long-chain aliphatic hydrocarbon group. Propionylaniline has a molecular weight of only 149.19, resulting in a significantly insufficient non-polar surface area and dispersive contact area. Furthermore, it is typically solid at the viscosity-reducing test temperature of 50°C, and its dissolution rate and dispersion uniformity in scCO2 raffinate heavy oil are significantly weaker than the viscosity reducer in Example 1, which contains an oil-containing acyl group. Furthermore, its secondary amides may undergo self-association and crystallization through NH···O=C hydrogen bonds, leading to a further reduction in the effective concentration of the viscosity reducer and ultimately a significant decrease in the viscosity-reducing effect. Comparative Example 4, lacking any amide groups, carbonyl dipoles, hydrogen bond acceptors, and local polar anchoring sites, struggles to directionally adsorb heteroatom-containing polar regions in gums and asphaltenes. Its effect is expected to primarily manifest as non-specific dispersion and limited solvation, failing to simultaneously regulate polar association and aromatic accumulation, resulting in a significantly lower viscosity-reducing effect compared to Application Example 1. Comparative Example 5, lacking aromatic rings, cannot form π–π interactions or large-area aromatic matching with the aromatic cores of gums and asphaltenes, making it difficult to enter densely aggregated aromatic regions. Its viscosity-reducing effect on scCO2 raffinate heavy oil is significantly reduced. In Comparative Example 6, the benzene ring is separated from the amide group by three methylene groups, resulting in spatial separation between the aromatic structure and the amide polar structure. This prevents the formation of the continuous aromatic-amide interaction surface characteristic of N-aryl amides, leading to a decreased viscosity-reducing effect. In Comparative Example 7, sulfone groups were used as polar groups. Their dipole moments are large and their polarity is too high, which easily increases the crystallization tendency and melting point of the compound and reduces its compatibility in heavy oil. Its viscosity-reducing effect on scCO2 raffinate heavy oil is significantly lower than that in Application Example 1.

[0128] Taking Examples 1 and 2 as examples, the effects of viscosity reducers on the Young's modulus and XRD of gums in scCO2 raffinate were studied. The method included: taking equal amounts of scCO2 raffinate, adding the viscosity reducers prepared in Examples 1 and 2 according to a mass ratio of viscosity reducer to scCO2 raffinate of 2.5:100, stirring for 15 min at 70℃ and 300 r / min, and then maintaining the temperature at 50℃ for 1 h to allow the viscosity reducer to fully react with the heavy oil. After the treated heavy oil was cooled to room temperature, it was separated using the SARA four-component separation method: first, n-heptane was added to precipitate and the asphaltene was removed by filtration; then, the obtained deasphalted oil was passed through an adsorption chromatography column to elute the saturated fraction, aromatic fraction, and gums sequentially; the gum eluent was collected, concentrated under reduced pressure, and vacuum dried to constant weight to obtain the gum samples treated with the viscosity reducers in Examples 1 and 2, respectively.

[0129] The Young's modulus and the position of the gum peak (002) in XRD of gum in scCO2 raffinate, gum after treatment in Example 1 and Example 2 were measured respectively, and the results are shown in Table 6.

[0130] Table 6

[0131] Taking Examples 1 and 2 as examples, the effect of viscosity reducer on the XRD of asphaltenes in scCO2 raffinate was studied. The method included: taking equal amounts of scCO2 raffinate, adding the viscosity reducer prepared in Examples 1 and 2 according to the mass ratio of viscosity reducer to scCO2 raffinate of 2.5:100, stirring for 15 min at 70℃ and 300 r / min, and keeping the temperature constant at 50℃ for 1 h to allow the viscosity reducer to fully react with the heavy oil. After the treated heavy oil was cooled to room temperature, n-heptane was added to the scCO2 raffinate heavy oil treated with the viscosity reducer in Examples 1 and 2, respectively. The mass-to-volume ratio of the heavy oil to n-heptane was 1 g: 40 mL. The mixture was heated under reflux for 1 h and then allowed to stand for 12 h to allow the asphaltenes to fully precipitate. The mixture was then filtered, and the precipitate was repeatedly washed with n-heptane until the washing liquid was nearly colorless. The precipitate was collected, dissolved in toluene, concentrated under reduced pressure, and dried under vacuum at 60 °C to constant weight, respectively, to obtain the asphaltenes samples separated after the viscosity reducer treatment in Examples 1 and 2.

[0132] The asphaltene peak position (002) in the XRD of the asphaltene in the scCO2 extract residue heavy oil, and the asphaltene after treatment in Example 1 and Example 2 were measured respectively. The results are shown in Table 7.

[0133] Table 7

[0134] Taking Examples 1 and 2 as examples, the total interaction energy of viscosity reducer on asphaltenes and gums in scCO2 raffinate was studied. DFT and MD simulations were performed using software well known to those skilled in the art, and the results are shown in Table 8.

[0135] Table 8

[0136] As can be seen from Tables 6 to 8, the viscosity reducer provided by the present invention can act precisely on the recombinant and aggregated structures in the scCO2 raffinate heavy oil, mainly targeting the enhanced colloidal self-association structure after extraction.

[0137] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A viscosity reducer for scCO2 raffinate heavy oil, characterized by, The viscosity reducer comprises an aromatic ring and a long-chain aliphatic hydrocarbon group; The long-chain aliphatic hydrocarbon group is connected to the aromatic ring through an amide structure; The long-chain aliphatic hydrocarbon group has 15-22 carbon atoms.

2. The viscosity reducing agent according to claim 1, characterized by The aromatic ring comprises a benzene ring; Preferably, the number of the aromatic ring is 1-2.

3. The viscosity reducing agent according to claim 1 or 2, characterized by, The long-chain aliphatic hydrocarbon group has 17 carbon atoms; Preferably, the viscosity reducer has a structural formula as shown in formula (1): Formula (1); wherein R1 and R2 are each independently a phenyl group and / or hydrogen, and at least one of R1 and R2 is a phenyl group, and R3 is a long-chain aliphatic hydrocarbon group; Preferably, the viscosity reducer has a structural formula as shown in formula (2): Formula (2).

4. A method for producing the viscosity reducer as claimed in any one of claims 1 to 3, characterized by, The preparation method comprises: nucleophilic substitution reaction of an aromatic amine and an acyl chloride organic substance to generate the viscosity reducer; The acyl chloride organic substance has 16-23 carbon atoms.

5. The preparation method according to claim 4, characterized in that, The aromatic amine comprises aniline and / or diphenylamine; Preferably, the molar ratio of the aromatic amine to the acyl chloride organic substance is (1.1-1):(1-1.2); Preferably, the acyl chloride organic substance comprises oleoyl chloride.

6. The preparation method according to claim 4, characterized in that, The nucleophilic substitution reaction has a reaction temperature of 20-30℃; Preferably, the nucleophilic substitution reaction has a duration of 3-6h.

7. The preparation method according to claim 4, characterized in that, The preparation method comprises: in a protective atmosphere, dissolving the aromatic amine in an organic solvent and cooling to a first temperature to obtain a first reaction system; adding the acyl chloride organic substance and an acid-binding agent to the first reaction system, and heating to the temperature of the nucleophilic substitution reaction, and performing the nucleophilic substitution reaction to obtain a reaction liquid; Preferably, the organic solvent comprises anhydrous dichloromethane; Preferably, the first temperature is 0-5℃; Preferably, the molar ratio of the acid-binding agent to the acyl chloride organic substance is (1.0-1.3):1; Preferably, the acid-binding agent comprises triethylamine and / or N,N-diisopropylethylamine; Preferably, the preparation method further comprises: adding a quenching agent to the reaction liquid, and sequentially performing washing, drying and concentration to obtain the viscosity reducer; Preferably, the quenching agent comprises water; Preferably, the washing comprises sequentially washing with dilute hydrochloric acid, saturated sodium bicarbonate solution and saturated sodium chloride solution; Preferably, the drying comprises: drying with anhydrous sodium sulfate; Preferably, the concentration comprises concentration under reduced pressure.

8. A viscosity-reducing composition for scCO2 raffinate heavy oil, characterized by comprising The viscosity reducer for the scCO2 raffinate heavy oil according to any one of claims 1-3.

9. The viscosity-reducing composition of claim 8, wherein, The viscosity reducing composition comprises: a viscosity reducer and a dispersant, and the dispersant comprises an aromatic hydrocarbon dispersant and an unsaturated fatty acid dispersant; Preferably, the aromatic hydrocarbon dispersant comprises any one or a combination of at least two of toluene, benzene, xylene or trimethylbenzene; Preferably, the unsaturated fatty acid dispersant comprises any one or a combination of at least two of oleic acid, linoleic acid, linolenic acid or arachidonic acid; Preferably, the mass ratio of the viscosity reducer to the dispersant is (0.5-4.0):(2-4); Preferably, the mass ratio of the aromatic hydrocarbon dispersant to the unsaturated fatty acid dispersant in the dispersant is (1.5-2.5):(0.5-1.5).

10. Use of a viscosity reducer for scCO2 raffinate heavy oil according to any one of claims 1 to 3, or a viscosity reducing composition for scCO2 raffinate heavy oil according to claim 8 or 9, characterized in that, The viscosity reducing composition is applied to viscosity reduction of the scCO2 raffinate heavy oil; Preferably, the viscosity of the scCO2 raffinate heavy oil at 30℃ is ≥150000 mPa·s. Preferably, the viscosity of the scCO2 raffinate heavy oil at 50℃ is ≥18000 mPa·s; Preferably, the scCO2 raffinate heavy oil comprises gum and asphaltene; Preferably, the mass percentage of gum in the scCO2 raffinate heavy oil is 37.0-41.0wt%; Preferably, the mass percentage of asphaltene in the scCO2 raffinate heavy oil is 6.0-8.0wt%; Preferably, the total interaction energy of gum-gum complex in the scCO2 raffinate heavy oil is ≤-28 kcal / mol; Preferably, the H / C ratio of gum in the scCO2 raffinate heavy oil is 1.40-1.55; Preferably, the H / C ratio of asphaltene in the scCO2 raffinate heavy oil is 1.35-1.50; Preferably, the addition amount of viscosity reducer in the viscosity reduction process of the scCO2 raffinate heavy oil is 0.5-4.0wt%.

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