Viscosity reducer, preparation method thereof, viscosity reduction composition and application

Abstract

According to the viscosity reducer and the preparation method thereof, the viscosity reduction composition and the application thereof, by adopting an amide group, multi-imino groups and amino groups and based on the idea of hydrogen bond dominated non-covalent interaction reconstruction, the micromolecular viscosity reducer with multiple hydrogen bond sites is adopted, and the viscosity reducer has an excellent viscosity reduction effect on heavy oil with high asphaltene content; the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy oil viscosity reduction, and particularly to a viscosity reducer, a preparation method thereof, a viscosity reduction composition and an application. Background Art

[0002] At present, the development of unconventional oil resources has gradually become a research hotspot in the energy field. Among them, heavy oil, as a representative of unconventional oil resources, is rich in reserves, accounting for more than 70% of the world's total oil reserves. However, due to its high density, high viscosity and poor fluidity, the exploitation, transportation and processing of heavy oil face many technical challenges. These problems not only affect the economic utilization of heavy oil resources, but also exacerbate the environmental pressure in exploration, storage, transportation and oil sludge treatment.

[0003] Therefore, how to efficiently reduce the viscosity of heavy oil and improve its fluidity has become an important research direction in the petroleum industry.

[0004] At present, the technologies for reducing the viscosity of heavy oil mainly include thermal recovery, dilution viscosity reduction and chemical viscosity reduction. Thermal recovery technology reduces the viscosity of heavy oil by heating it. Although the effect is significant, it has high energy consumption, large equipment investment, and may bring problems of increased carbon emissions. Dilution viscosity reduction reduces the viscosity of heavy oil by adding light hydrocarbons or diluents, but the consumption of diluents is large, the cost is high, and it may cause technical problems in subsequent processing. In this context, chemical viscosity reducers have gradually become the focus of research. Chemical viscosity reducers effectively improve the fluidity of heavy oil by adjusting the intermolecular interactions of asphaltenes or resins. Among them, oil-soluble viscosity reducers have attracted much attention because of no post-treatment problems. However, their viscosity reduction effect is often limited by the complexity of the preparation process and the difficult-to-control reaction conditions. At the same time, their high production cost and potential environmental pollution problems also limit their large-scale application.

[0005] Chinese Patent CN110950997A discloses a polymer heavy oil emulsifying viscosity reducer, which includes the following components: acrylamide, sulfobetaine monomer and itaconic acid double long-chain ester monomer, and can effectively emulsify heavy oil. There are anions, cations, etc. in the structure of the polymer heavy oil emulsifying viscosity reducer, which further improves the water solubility of the whole polymer. The presence of anions and cations makes the polymer have good temperature resistance. Applying the polymer heavy oil emulsifying viscosity reducer to the viscosity reduction of heavy oil, and configuring it into an active aqueous solution of 0.1-1 wt%, with the continuous increase of salinity, it can still have a good emulsifying viscosity reduction effect on heavy oil. Low salinity has little effect, and the viscosity reduction rate remains 91% at a salinity of 150,000, meeting the anti-salt requirement. However, after using the emulsifying viscosity reducer for heavy oil exploitation, the efficient dehydration of the emulsion and the subsequent water treatment process are still problems to be solved.

[0006] Chinese Patent CN118599511A discloses a preparation method and application of a silica nanocomposite heavy oil viscosity reducer. First, SiO2 nanoparticles are synthesized, and a temperature-sensitive poly(methacryloyl sulfobetaine) polymer is grafted onto their surface, successfully preparing a temperature-sensitive SiO2-PSBMA nano-viscosity reducer. This viscosity reducer exhibits excellent viscosity reduction effect at high temperatures, can effectively reduce the viscosity of heavy oil, improve its fluidity, and thus significantly enhance the recovery efficiency and transportation convenience of heavy oil. Experimental results show that the viscosity reduction rate of this viscosity reducer for GD2 heavy oil is as high as 96.41%. However, the economic cost required for nanoparticles as viscosity reducers is relatively high, and it is difficult to recycle and reuse them. Removing nanoparticles from heavy oil in subsequent processes is a complex task and difficult to completely remove, which will reduce the quality of heavy oil.

[0007] Chinese Patent CN117304465A discloses a hyperbranched oil-soluble polyester heavy oil viscosity reducer and its preparation method. This viscosity reducer is obtained by the esterification reaction of trimethylolpropane, glycerol and succinic anhydride to form a hyperbranched polyester, and then the resulting hyperbranched polyester is subjected to a transesterification reaction with methyl erucate and methyl cinnamate. The docos-13-ene group and 3-phenyl-2-propenyl group in the molecule of this viscosity reducer can produce hydrophobic-lipophilic interactions with the aromatic polycycles of heavy oil molecules, and its hyperbranched structure in molecular form enables it to effectively disperse heavy oil aggregates, macroscopically showing a good viscosity reduction effect on heavy oil, and the viscosity reduction rate of heavy oil is above 60%. This oil-soluble viscosity reducer does not have the problem of post-treatment, but its viscosity reduction effect is not good, the synthesis steps are cumbersome, and the cost is relatively high.

[0008] Therefore, developing highly efficient, low-cost and environmentally friendly viscosity reducers is one of the key directions for future heavy oil treatment technologies. Summary of the Invention

[0009] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a viscosity reducer, its preparation method, viscosity reduction composition and application. By using a compound containing amide group, long-chain hydrocarbon group, imino group and amino group as the viscosity reducer, it can form hydrogen bonds with the polar groups of asphaltenes in heavy oil, destroy its hydrogen bond network, simultaneously inhibit the aggregation of asphaltenes, and promote the dispersion of asphaltenes, which can significantly reduce the viscosity of heavy oil.

[0010] To achieve this purpose, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides a viscosity reducer, and the structural formula of the viscosity reducer is shown in formula (1):

[0012]

[0013] Among them, R1 is a hydrocarbon group with a carbon atom number greater than or equal to 10, and the value range of n is 3-10.

[0014] The viscosity reducer provided by the present invention is especially a heavy oil viscosity reducer. The principle of its excellent viscosity reduction effect on heavy oil is as follows:

[0015] (1) The amide group, imino group and amino group in the viscosity reducer can form hydrogen bonds with the polar groups in asphaltene / resin molecules, destroying the original hydrogen bond network between asphaltene molecules and between asphaltene and resin molecules, promoting the dispersion of asphaltene and resin molecules, and this dispersion effect effectively reduces the viscosity of heavy oil.

[0016] (2) The viscosity reducer contains one amide group and multiple imino groups and amino groups at the same time. Compared with the compound containing only one amide group, the multiple imino groups and amino groups of the viscosity reducer of the present invention can provide multiple hydrogen bond sites, and have better hydrogen bond substitution ability and cooperative depolymerization effect on the original hydrogen bond network of asphaltene, so as to better reduce the viscosity of heavy oil containing asphaltene.

[0017] (3) The viscosity reducer contains a long-chain hydrocarbon group R1, and these long chains can adsorb on the periphery of asphaltene, thereby generating a steric hindrance effect, inhibiting the aggregation of asphaltene, and further reducing the viscosity of heavy oil containing asphaltene.

[0018] (4) The viscosity reducer controls the number of n within a reasonable range, which can not only avoid the situation of too high self-viscosity but also provide multiple hydrogen bond sites.

[0019] The viscosity reducer with small molecules and multiple hydrogen bond sites provided by the present invention, compared with emulsifying viscosity reducers and nanoparticle-type viscosity reducers, does not have the problem of post-treatment, and can be directly injected into the reservoir system or used in cooperation with other viscosity reduction technologies (such as dilution with light oil for viscosity reduction); compared with complex heavy oil systems, oil-soluble viscosity reducers have the problem of poor viscosity reduction effect, while the viscosity reducer provided by the present invention has a better viscosity reduction effect, and the preparation process of oil-soluble viscosity reducers is complex and the cost is high.

[0020] Specifically, R1 is a hydrocarbon group with the number of carbon atoms greater than or equal to 10, and its number of carbon atoms is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30, etc.

[0021] The value range of n is 3, 4, 5, 6, 7, 8, 9 or 10.

[0022] Preferably, the R1 is an olefin-containing group, the number of carbon atoms of the R1 is 10-20, and preferably 15-18.

[0023] Preferably, the value range of n is 3-5.

[0024] Preferably, the structural formula of the viscosity reducer is as shown in Formula (2):

[0025]

[0026] Preferably, C 17 H 33 - has a structural formula of CH3(CH2)7CH=CH(CH2)7-.

[0027] Through research, the present invention finds that the viscosity reducer with the structure of Formula (2) above has excellent viscosity reduction effect on heavy oil containing asphaltene. Among them, it not only provides long-chain alkyl groups, but also contains double bonds, and has better compatibility with heavy oil on the basis of excellent steric hindrance.

[0028] In a second aspect, the present invention provides a preparation method of the viscosity reducer described in the first aspect, and the preparation method includes:

[0029] An organic acid and ethylenediamine are subjected to amidation reaction to prepare the viscosity reducer.

[0030] The organic acid has a carbon atom number greater than or equal to 11, and can be, for example, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or 31, etc.

[0031] The ethylenediamine has 4 to 11 nitrogen atoms, and can be, for example, 4, 5, 6, 7, 8, 9, 10 or 11, etc.

[0032] By subjecting an organic acid with a long-chain hydrocarbon group and ethylenediamine to amidation reaction, the present invention can obtain a compound with the structure shown in Formula (1), and this compound has excellent viscosity reduction effect.

[0033] Preferably, the organic acid has a carbon atom number of 11 to 21, and is preferably 16 to 19.

[0034] Preferably, the ethylenediamine has 4 to 6 nitrogen atoms.

[0035] Preferably, the organic acid is oleic acid, and / or the ethylenediamine is tetraethylenepentamine.

[0036] The present invention preferably uses the above two reaction raw materials for amidation reaction, and can obtain a viscosity reducer with the structure of Formula (2), which has excellent viscosity reduction effect.

[0037] When using the above raw materials, the reaction that occurs is as shown in the following equation:

[0038]

[0039] Preferably, the molar ratio of the organic acid to the vinylamine in the amidation reaction is 1:(1-2). For example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0040] Preferably, the temperature of the amidation reaction is 140-180 °C. For example, it can be 140 °C, 145 °C, 149 °C, 154 °C, 158 °C, 163 °C, 167 °C, 172 °C, 176 °C or 180 °C, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0041] Preferably, a protective gas is introduced into the amidation reaction.

[0042] Preferably, the protective gas includes any one or a combination of at least two of nitrogen, helium or carbon dioxide.

[0043] Preferably, the time of the amidation reaction is 2-6 h. For example, it can be 2 h, 2.5 h, 2.9 h, 3.4 h, 3.8 h, 4.3 h, 4.7 h, 5.2 h, 5.6 h or 6 h, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0044] Preferably, the stirring speed of the amidation reaction is 50 r / min - 100 r / min. For example, it can be 50 r / min, 55 r / min, 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, 85 r / min, 90 r / min, 95 r / min or 100 r / min, etc.

[0045] Preferably, after the amidation reaction in the preparation method, a separation step is further included.

[0046] Preferably, the separation step includes: mixing and extracting the reaction product after the amidation reaction with an organic solvent, and performing liquid-liquid phase separation to obtain an organic phase; the organic phase is successively washed and the solvent is removed to obtain the viscosity reducer.

[0047] Preferably, the organic solvent used in the separation step includes any one or a combination of at least two of ethyl acetate, dichloromethane, toluene or ether. Among them, typical but non-limiting combinations are the combination of ethyl acetate and dichloromethane, the combination of toluene and dichloromethane, the combination of ethyl acetate and toluene, the combination of ether and dichloromethane, and the combination of ethyl acetate and ether.

[0048] Preferably, the mass ratio of the organic solvent to the material after reaction is 1:1 to 2, for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.

[0049] Preferably, the temperature of the mixed extraction is 30 to 50 °C, for example, it can be 30 °C, 33 °C, 35 °C, 37 °C, 39 °C, 42 °C, 44 °C, 46 °C, 48 °C or 50 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0050] Preferably, the washing includes: washing impurities in the organic phase with a sodium chloride solution.

[0051] Preferably, the sodium chloride solution is a saturated sodium chloride solution.

[0052] Preferably, the impurities include unreacted ethylenediamine and by-products.

[0053] Preferably, the by-products include any one or at least two combinations of polysubstituted amides, crosslinked polymers or oleic acid oxidation products. Among them, typical but non-limiting combinations are combinations of polysubstituted amides and crosslinked polymers, combinations of oleic acid oxidation products and crosslinked polymers, combinations of polysubstituted amides and oleic acid oxidation products, and combinations of oleic acid oxidation products, polysubstituted amides and crosslinked polymers. Among them, the crosslinked polymer includes a polymer formed by self-polymerization of the amide product.

[0054] Preferably, the temperature of the washing is 30 to 50 °C, for example, it can be 30 °C, 33 °C, 35 °C, 37 °C, 39 °C, 42 °C, 44 °C, 46 °C, 48 °C or 50 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0055] Preferably, the method for removing the solvent includes evaporating to remove the solvent.

[0056] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0057] An organic acid and ethylenediamine are mixed in a molar ratio of 1:(1 to 2), and amidation reaction is carried out at 140 to 180 °C, 50 r / min to 100 r / min and under a protective atmosphere for 2 to 6 h to prepare the viscosity reducer, obtaining the material after reaction; wherein the protective atmosphere includes any one or at least two combinations of nitrogen, helium or carbon dioxide;

[0058] The reaction product after the amidation reaction is mixed and extracted with an organic solvent at 30-50°C. The mass ratio of the organic solvent to the reaction product after the reaction is 1:1-2, and liquid-liquid phase separation is carried out to obtain an organic phase. The impurities in the organic phase are washed with a saturated sodium chloride solution, and the solvent is evaporated to obtain the viscosity reducer.

[0059] The present invention does not have any special restrictions on the washing in the above process, and any device and method known to those skilled in the art that can be used for washing can be adopted, and it can also be adjusted according to the actual process. For example, it can be rinsing, immersion washing, etc.

[0060] Preferably, the evaporation includes vacuum evaporation.

[0061] In a third aspect, the present invention provides a viscosity-reducing composition, which includes an organic solvent and the viscosity reducer described above.

[0062] Preferably, the organic solvent in the viscosity-reducing composition includes any one or at least two combinations of octane, diesel, toluene, mesitylene or xylene. Typical but non-limiting combinations are combinations of octane and diesel, toluene and diesel, octane and toluene, mesitylene and diesel, octane and mesitylene, and combinations of mesitylene, octane and diesel.

[0063] The present invention further preferably uses the viscosity reducer in combination with the above organic solvent, which can simultaneously have a synergistic effect of unlocking the asphalt structure and enhancing dissolution, so as to have a better viscosity-reducing effect.

[0064] Preferably, the mass ratio of the viscosity reducer to the organic solvent in the viscosity-reducing composition is (1-4):(1-10). The mass fraction of the viscosity reducer can be, for example, 1, 1.2, 1.3, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8 or 4, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable. The mass fraction of the organic solvent can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0065] The present invention preferably controls the mass ratio of the viscosity reducer to the organic solvent within the above range, which can better improve the viscosity-reducing effect and has broad application prospects.

[0066] In a fourth aspect, the present invention provides an application of the viscosity reducer described in the first aspect or the viscosity-reducing composition described in the third aspect. The viscosity reducer or the viscosity-reducing composition is used to reduce the viscosity of heavy oil.

[0067] Preferably, the viscosity of the heavy oil itself at 20 °C ranges from 3000 to 60000 mPa·s. For example, it can be 3000 mPa·s, 3330 mPa·s, 3660 mPa·s, 4000 mPa·s, 4330 mPa·s, 4660 mPa·s, 5000 mPa·s, 5330 mPa·s, 5660 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 15000 mPa·s, 20000 mPa·s, 30000 mPa·s, 40000 mPa·s, 45000 mPa·s, 50000 mPa·s, 55000 mPa·s, 60000 mPa·s, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0068] Preferably, the composition of the heavy oil includes saturates, aromatics, resins, and asphaltenes.

[0069] Preferably, the content of asphaltenes in the heavy oil is 20 - 40 wt%. For example, it can be 20 wt%, 23 wt%, 25 wt%, 27 wt%, 29 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, or 40 wt%, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0070] The viscosity reducer of the present invention is particularly suitable for heavy oils with a high asphaltene content. The reason why heavy oils with a high asphaltene content have a high viscosity is mainly that the asphaltenes themselves have a large number of hydrogen bonds, forming a hydrogen bond network structure, which leads to a high viscosity of the heavy oil. Based on the characteristics of the strong polarity and high molecular weight of asphaltenes, the present invention uses a strategy of reconstructing non-covalent interactions and adopts a small molecule viscosity reducer with multiple hydrogen bond sites. Starting from the structural analysis of the key viscosity-causing components in heavy oil, the viscosity-causing mechanism of heavy oil, the molecular design of the viscosity reducer, and the action mechanism of the viscosity reducer are fully combined, providing a new approach for achieving precise viscosity reduction in complex heavy oil systems.

[0071] Preferably, the content of resins in the heavy oil is 10 - 25 wt%. For example, it can be 10 wt%, 12 wt%, 14 wt%, 15 wt%, 17 wt%, 19 wt%, 20 wt%, 22 wt%, 24 wt%, or 25 wt%, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0072] Preferably, the content of saturates in the heavy oil is 30 - 40 wt%, for example, 30 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt% or 40 wt%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0073] Preferably, the content of aromatics in the heavy oil is 20 - 30 wt%, for example, 20 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt% or 30 wt%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0074] Preferably, the hydrogen - to - carbon mass ratio of the asphaltene is 0.8 - 1.2:1, for example, 0.8:1, 0.85:1, 0.89:1, 0.94:1, 0.98:1, 1.03:1, 1.07:1, 1.12:1, 1.16:1 or 1.2:1, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0075] Preferably, the addition amount of the viscosity reducer during viscosity reduction is 1 - 4 wt%, for example, 1 wt%, 1.4 wt%, 1.7 wt%, 2 wt%, 2.4 wt%, 2.7 wt%, 3 wt%, 3.4 wt%, 3.7 wt% or 4 wt%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable. Or, the addition amount of the viscosity - reducing composition during viscosity reduction is 2 - 14 wt%, for example, 2 wt%, 34 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt% or 14 wt%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0076] Preferably, the method for using the viscosity reducer for viscosity reduction includes: mixing the viscosity reducer or the viscosity - reducing composition with the heavy oil and stirring to make them evenly mixed.

[0077] Preferably, before mixing the viscosity reducer or the viscosity - reducing composition with the heavy oil, the heavy oil is first heated and pre - stirred to remove the bubbles in the heavy oil.

[0078] Preferably, the rotation speed of the pre - stirring is 50 r / min - 100 r / min, for example, 50 r / min, 55 r / min, 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, 85 r / min, 90 r / min, 95 r / min or 100 r / min, etc.

[0079] Preferably, the heating temperature is 50 to 90 °C. For example, it can be 50 °C, 55 °C, 59 °C, 64 °C, 68 °C, 73 °C, 77 °C, 82 °C, 86 °C or 90 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0080] Preferably, during the process of mixing the viscosity reducer with heavy oil, the stirring speed is 50 r / min to 150 r / min. For example, it can be 50 r / min, 55 r / min, 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, 85 r / min, 90 r / min, 95 r / min, 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min or 150 r / min, etc.

[0081] Preferably, during the process of mixing the viscosity reducer with heavy oil, the stirring time is 10 to 20 min. For example, it can be 10 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0082] Compared with the prior art, the present invention has at least the following beneficial effects:

[0083] (1) The viscosity reducer provided by the present invention is a small molecule substance, which is simple to prepare, has a low cost, and can avoid the post-treatment process of emulsifier and nanoparticle viscosity reduction. Compared with oil-soluble viscosity reducers, it has a better viscosity reduction effect and a low usage amount.

[0084] (2) The viscosity reduction rate of the viscosity reducer provided by the present invention is above 31.95%, preferably above 59%, and the viscosity reduction effect is excellent. Description of the Drawings

[0085] Figure 1 It is the matrix-assisted laser desorption ionization time-of-flight mass spectrometry diagram of asphaltene in heavy oil used in the specific embodiment of the present invention.

[0086] Figure 2 It is the infrared spectrum diagram of asphaltene in heavy oil used in the specific embodiment of the present invention.

[0087] Figure 3 It is the nuclear magnetic resonance hydrogen spectrum diagram of the viscosity reducer prepared in Example 1 of the present invention.

[0088] Figure 4 It is the infrared spectrum diagram of the viscosity reducer prepared in Example 1 of the present invention.

[0089] Figure 5It is a schematic diagram of the fluidity of heavy oil before viscosity reduction at 20°C in Application Example 1 of the present invention.

[0090] Figure 6 It is a schematic diagram of the fluidity of heavy oil after viscosity reduction at 20°C in Application Example 1 of the present invention. Detailed implementation manners

[0091] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the said examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0092] The high viscosity of heavy oil is mainly attributed to its complex chemical composition, especially the relatively high content of asphaltene and resin molecules. Asphaltene is the key component causing the viscosity increase of heavy oil. Its molecular structure contains aromatic rings, long-chain alkanes, and heteroatoms (such as N, O, S, etc.). Due to its largest molecular weight and the most heteroatoms, asphaltene often forms an associative cross-linked structure. This associative cross-linking in the bulk phase will cause a significant increase in the viscosity of heavy oil. Based on a series of characterization analyses, asphaltene mainly covers various functional groups such as sulfoxide, pyridine, pyrrole, thiophene, carbonyl, hydroxyl, ether, and thioether. Due to its high molecular weight, strong polarity, and complex molecular structure, asphaltene molecules interact with each other through hydrogen bonds, van der Waals forces, and π-π stacking, etc., and are prone to aggregate into aggregates, thus significantly increasing the viscosity of heavy oil. Resin molecules can, to a certain extent, enhance the diffusion of asphaltene in the heavy oil matrix and reduce the particle size of asphaltene aggregates. However, the interaction between resin molecules themselves may also lead to aggregation, further increasing the viscosity of heavy oil. This complex molecular interaction mechanism makes the viscosity problem of heavy oil a difficult point. Therefore, for the molecular design of the viscosity reducer in the present invention, it is mainly conceived from disrupting the associative cross-linked structure of asphaltene.

[0093] To solve the above pain points, the following specific solutions are adopted in the detailed implementation manners of the present invention.

[0094] For the convenience of experimental comparison, the crude oil sample in the heavy oil reservoir is used as a representative of heavy oil in the present invention, but it does not mean that the present invention is only applicable to this crude oil sample. Other heavy oils containing asphaltene that need viscosity reduction are also applicable.

[0095] The compositions of the heavy oil samples targeted in the following examples and comparative examples are shown in Table 1.

[0096] Table 1

[0097] Component Name Content / wt% Saturates 34.14 Aromatics 24.70 Resins 15.65 Asphaltenes 25.51

[0098] The present invention uses the conventional four-component separation method to separate asphaltene in heavy oil, and conducts matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis and infrared analysis on the molecular elements of asphaltene in this heavy oil sample. The results are respectively as Figure 1 - 2As shown, from Figure 1 - 2 it can be obtained that the molecular weight of the asphaltene monomer structure is 1700 g / mol, and it contains aromatic rings, cycloalkanes, aliphatic chains, and functional groups containing nitrogen, oxygen, and sulfur heteroatoms. And elemental analysis of the asphaltene was carried out, and the elemental normalized composition results are shown in Table 2.

[0099] Table 2

[0100]

[0101] Example 1

[0102] This example provides a viscosity reducer, and the structural formula of the viscosity reducer is as shown in Formula (2):

[0103]

[0104] Among them, C 17 H 33 - The structural formula of - is CH3(CH2)7CH=CH(CH2)7-.

[0105] This example also provides a preparation method of the viscosity reducer, and the preparation method includes the following steps:

[0106] Oleic acid and tetraethylenepentamine are mixed in a molar ratio of 1:1.5, and slowly heated to 150 °C, and amidation reaction is carried out for 5 h at 80 r / min and in a nitrogen atmosphere to prepare the viscosity reducer, and the post-reaction material is obtained;

[0107] Ethyl acetate and the post-reaction material after the amidation reaction are mixed and extracted at 45 °C, the mass ratio of ethyl acetate to the post-reaction material is 1:1.5, and liquid-liquid phase separation is carried out to obtain an organic phase; the impurities in the organic phase are washed with saturated sodium chloride solution, and the solvent is removed by vacuum evaporation under the condition of an absolute pressure of 1.325 kPa to obtain the viscosity reducer.

[0108] The viscosity reducer obtained in this example was subjected to nuclear magnetic analysis and infrared spectrum analysis, respectively as Figure 3 - 4 shown, from Figure 3 it can be seen that a triplet signal of the terminal -CH3 proton is observed at 0.84 ppm. The methylene proton signal of the alkyl chain appears at about 1.25 ppm. The methylene proton signal in the olefin group =CH-CH2- appears at 1.98 ppm, and the signal observed at 5.30 ppm further proves the existence of the double bond. The signal appearing between 2.65 - 3.64 ppm belongs to the methylene protons in tetraethylenepentamine; from Figure 4 it can be seen that the product of the reaction of oleic acid and tetraethylenepentamine is at 1656 cm -1 and 3268 cm -1Characteristic peaks appeared nearby, which were inferred to be the stretching vibration absorption peaks of the C=O double bond and N-H bond in the amide, indicating that the amidation reaction was successfully completed under the above conditions; through literature review, a peak appeared near 1253 cm -1 and the peak near it was the stretching vibration absorption peak of the C-N bond, and a peak near 1656 cm -1 was the deformation vibration of the N-H bond, and obvious characteristic peaks appeared near 2922 cm -1 and 2852 cm -1 , which were the methyl peak and methylene peak respectively. The above infrared characterization structure indicated that tetraethylenepentamine oleate was generated during the synthesis process. According to the spectral results of FTIR and 1 HNMR, it was shown that the target product was successfully synthesized.

[0109] Example 2

[0110] This example provides a viscosity reducer, and the structural formula of the viscosity reducer is shown in Formula (2):

[0111]

[0112] Among them, the structural formula of C 17 H 33 - is CH3(CH2)7CH=CH(CH2)7-.

[0113] This example also provides a preparation method of the viscosity reducer, and the preparation method includes the following steps:

[0114] Oleic acid and tetraethylenepentamine are mixed in a molar ratio of 1:1, and slowly heated to 180 °C, and amidation reaction is carried out for 2 h at 100 r / min and in a helium atmosphere to prepare the viscosity reducer, obtaining the reaction product;

[0115] Dichloromethane and the reaction product after the amidation reaction are mixed and extracted at 50 °C, the mass ratio of dichloromethane to the reaction product is 1:1, and liquid-liquid phase separation is carried out to obtain the organic phase; the organic phase is washed with saturated sodium chloride solution to remove impurities, and the solvent is removed by vacuum evaporation under the condition of an absolute pressure of 1.325 kPa to obtain the viscosity reducer.

[0116] Example 3

[0117] This example provides a viscosity reducer, and the structural formula of the viscosity reducer is shown in Formula (2):

[0118]

[0119] Among them, the structural formula of C 17 H 33 - is CH3(CH2)7CH=CH(CH2)7-.

[0120] This embodiment also provides a method for preparing the viscosity reducer, which comprises the following steps:

[0121] Oleic acid and tetraethylenepentamine are mixed in a molar ratio of 1:2, and the temperature is slowly raised to 140° C., and amidation reaction is carried out at 50 r / min and in a carbon dioxide atmosphere for 6 hours to prepare the viscosity reducer and obtain a reaction material;

[0122] Toluene and the reaction material after the amidation reaction are mixed and extracted at 30° C. The mass ratio of toluene to the reaction material is 1:2, and an organic phase is obtained by liquid-liquid separation. Impurities in the organic phase are washed with a saturated sodium chloride solution, and the solvent is removed by reduced pressure evaporation under an absolute pressure of 1.325 kPa to obtain the viscosity reducer.

[0123] Example 4

[0124] This embodiment provides a viscosity reducer, wherein the preparation method of the viscosity reducer is to replace oleic acid with arachidic acid CH3(CH2) 18 COOH, that is, R1 in the viscosity reducer is replaced by CH3(CH2) 18 -Except for the above, the rest are the same as those in Example 1 and will not be described again.

[0125] Example 5

[0126] This embodiment provides a viscosity reducer. The preparation method of the viscosity reducer is the same as that of Embodiment 1, except that tetraethylenepentamine is replaced by pentaethylenehexamine, that is, n in the final viscosity reducer is 5, and will not be repeated here.

[0127] Example 6

[0128] This embodiment provides a viscosity reducer, which is the same as that of Embodiment 1 except that the temperature of the amidation reaction in the preparation method is 190° C., and will not be described in detail here.

[0129] Example 7

[0130] This embodiment provides a viscosity reducer, which is the same as that of embodiment 1 except that the temperature of the amidation reaction is 120° C., and will not be described in detail here. A lower temperature will reduce the amidation reaction rate.

[0131] Comparative Example 1

[0132] This comparative example provides a viscosity reducer, which is the same as Example 1 except that n is 1, that is, tetraethylenepentamine is replaced by ethylenediamine, and the rest is not repeated here.

[0133] Comparative Example 2

[0134] This comparative example provides a viscosity reducer. Except that the molecular formula of R1 is CH3(CH2)6-, that is, oleic acid is replaced by caprylic acid, the rest are the same as in Example 1 and will not be elaborated here.

[0135] Application Example 1

[0136] This application example provides a method for reducing the viscosity of heavy oil. The method for reducing the viscosity of heavy oil includes the following steps:

[0137] Pre-stir the heavy oil at 80 °C for 15 min at 80 r / min to remove the bubbles in the heavy oil. Subsequently, keep the heavy oil at the test temperature for 1 h, and immediately put it into a rheometer for measurement. The viscosity value is recorded as g0. Take 20 g of heavy oil, add 3 wt% of the viscosity reducer in Example 1, and stir the mixed material at 80 °C for 15 min at 80 r / min to make it evenly mixed. Subsequently, keep it at the test temperature for 1 h, and immediately put it into a rheometer that has been preheated to the test temperature for measurement. The viscosity values are respectively recorded as g1. The viscosity reduction rate is recorded as

[0138] Taking Application Example 1 as an example, test the viscosity changes before and after under the conditions of 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C. The viscosity data is shown in Table 3.

[0139] Table 3

[0140] Application Example 1 Viscosity before Viscosity Reduction / mPa·s Viscosity after Viscosity Reduction / mPa·s Viscosity Reduction Rate 20℃ 57128.771 26269.235 54.02％ 30℃ 35543.634 8557.6596 75.92％ 40℃ 16772.072 3268.9904 80.51％ 50℃ 5396.1331 1632.3977 69.75％ 60℃ 2270.2234 847.37216 62.67％ 70℃ 1005.4291 514.48431 48.83％

[0141] As can be seen from Table 3, for the heavy oil, the viscosity reducer provided by the present invention can also achieve excellent viscosity reduction effect at low temperatures. Especially when the temperature is between 30 and 50 °C, the viscosity reduction rate can reach more than 69%; moreover, in the temperature range of 20 to 70 °C, the viscosity reduction rate is above 45%, and the viscosity reduction effect is remarkable, with broad application prospects.

[0142] Taking 20 °C as an example, the diagram of the heavy oil before viscosity reduction is as Figure 5 shown, and the diagram of the heavy oil after viscosity reduction is as Figure 6 shown. From Figure 5 - 6 it can be seen that the fluidity of the heavy oil before viscosity reduction has changed significantly, indicating that the viscosity reducer provided by the present invention has excellent viscosity reduction effect.

[0143] Application Example 2

[0144] This application example provides a method for reducing the viscosity of heavy oil. The method for reducing the viscosity of heavy oil includes the following steps:

[0145] Heat the heavy oil at 90 °C and pre-stir it at 100 r / min for 10 min to remove the bubbles in the heavy oil. Then, keep the heavy oil at the test temperature for 1 h, and immediately put it into a rheometer for measurement. The viscosity value is recorded as g0. Take 20 g of heavy oil, add the viscosity reducer in Example 2 at 4 wt%, and stir the mixed material at 150 r / min at 90 °C for 10 min to make it evenly mixed. Then, keep it at the test temperature for 1 h, and immediately put it into a rheometer preheated to the test temperature for measurement. The viscosity values are respectively recorded as g1. The viscosity reduction rate is recorded as

[0146] Application Example 3

[0147] This application example provides a method for reducing the viscosity of heavy oil. The method for reducing the viscosity of heavy oil includes the following steps:

[0148] Heat the heavy oil at 50 °C and pre-stir it at 50 r / min for 20 min to remove the bubbles in the heavy oil. Then, keep the heavy oil at the test temperature for 1 h, and immediately put it into a rheometer for measurement. The viscosity value is recorded as g0. Take 20 g of heavy oil, add the viscosity reducer in Example 3 at 2.2 wt%, and stir the mixed material at 50 r / min at 50 °C for 20 min to make it evenly mixed. Then, keep it at the test temperature for 1 h, and immediately put it into a rheometer preheated to the test temperature for measurement. The viscosity values are respectively recorded as g1. The viscosity reduction rate is recorded as

[0149] Application Examples 4 - 7 and Application Comparative Examples 1 - 2

[0150] Application Examples 4 - 7 and Application Comparative Examples 1 - 2 provide a method for reducing the viscosity of heavy oil. The method for reducing the viscosity of heavy oil is the same as that in Application Example 1 except that the viscosity reducers in Examples 4 - 7 and Comparative Examples 1 - 2 are respectively used, and will not be elaborated here.

[0151] Application Example 8

[0152] This application example provides a method for reducing the viscosity of heavy oil. The method for reducing the viscosity of heavy oil includes the following steps:

[0153] Heat the heavy oil at 85 °C and pre-stir it at 90 r / min for 12 min to remove the bubbles in the heavy oil. Then, keep the heavy oil at the test temperature for 1 h, and immediately put it into a rheometer for measurement. The viscosity value is recorded as g0. Take 20 g of heavy oil, add the viscosity reducer in Example 1 at 2 wt% and toluene at 5 wt%, and stir the mixed material at 100 r / min at 85 °C for 10 min to make it evenly mixed. Then, keep it at the test temperature for 1 h, and immediately put it into a rheometer preheated to the test temperature for measurement. The viscosity values are respectively recorded as g1. The viscosity reduction rate is recorded as

[0154] Application Example 9

[0155] This application example provides a method for reducing the viscosity of heavy oil. The method for reducing the viscosity of heavy oil includes the following steps:

[0156] Heat the heavy oil at 80 °C and pre-stir it at 80 r / min for 14 min to remove the air bubbles in the heavy oil. Subsequently, keep the heavy oil at the test temperature for 1 h, and immediately put it into a rheometer for measurement. The viscosity value is recorded as g0. Take 20 g of heavy oil, add 4 wt% of the viscosity reducer in Example 2 and 3 wt% of octane, and stir the mixed material at 150 r / min for 12 min at 80 °C to make it evenly mixed. Subsequently, keep it at the test temperature for 1 h, and immediately put it into a rheometer that has been preheated to the test temperature for measurement. The viscosity values are respectively recorded as g1. The viscosity reduction rate is recorded as

[0157] Application Example 10

[0158] This application example provides a method for reducing the viscosity of heavy oil. Except that 10 wt% of xylene is additionally added while adding the viscosity reducer, the rest are the same as Application Example 1.

[0159] Application Example 11

[0160] This application example provides a method for reducing the viscosity of heavy oil. Except that 1 wt% of mesitylene is additionally added while adding the viscosity reducer, the rest are the same as Application Example 1.

[0161] Application Example 12

[0162] This application example provides a method for reducing the viscosity of heavy oil. Except that 5 wt% of diesel oil (0#) is additionally added while adding the viscosity reducer, the rest are the same as Application Example 2.

[0163] Application Examples 1-1 to 1-3

[0164] Application Examples 1-1 to 1-3 provide a method for reducing the viscosity of heavy oil. Except that the addition amounts of the viscosity reducer are 1 wt%, 2 wt% and 4 wt% respectively, the rest are the same as Application Example 1, and will not be elaborated here.

[0165] Among them, after viscosity reduction, the viscosities of Application Examples 1-1 to 1-3 at 50 °C are 3672.2496 mPa·s, 2985.2557 mPa·s, and 1633.1317 mPa·s respectively, and the viscosity reduction rates are 31.95%, 44.68% and 69.74% respectively. This shows that better viscosity reduction effects can be achieved under different addition amounts of the viscosity reducer.

[0166] The test results of the viscosity changes of the above application examples and application comparative examples at 50 °C are shown in Table 4.

[0167] Table 4

[0168] Viscosity before Viscosity Reduction / mPa·s Viscosity after Viscosity Reduction / mPa·s Viscosity Reduction Rate Application Example 1 5396.1331 1632.3977 69.75％ Application Example 2 5396.1331 2070.4089 61.63％ Application Example 3 5396.1331 2093.3356 61.21％ Application Example 4 5396.1331 3662.5086 32.13％ Application Example 5 5396.1331 2863.3356 46.94％ Application Example 6 5396.1331 2580.3772 52.18％ Application Example 7 5396.1331 2495.0987 53.76％ Application Example 8 5396.1331 975.0987 81.93％ Application Example 9 5396.1331 1570.6745 70.89％ Application Example 10 5396.1331 246.3267 95.44％ Application Example 11 5396.1331 1402.5622 74.01％ Application Example 12 5396.1331 1341.0441 75.15％ Application Comparative Example 1 5396.1331 3704.5698 31.35％ Application Comparative Example 2 5396.1331 3867.5447 28.33％

[0169] It can be seen from Table 4 as follows:

[0170] (1) From application examples 1 to 3, it can be seen that the viscosity reducer provided by the present invention has an excellent viscosity reduction effect through special molecular structure design. It can achieve good viscosity reduction for heavy oil with a viscosity as high as 5000 mPa·s at 50 °C, and its viscosity reduction rate is above 59%. Moreover, it can be directly injected into the reservoir without subsequent treatment.

[0171] (2) From application examples 1 and 4, it can be seen that after replacing R1 in the final viscosity reducer with CH3(CH2) 18 -, since there is no double bond in arachidic acid, the solubility and compatibility of the final viscosity reducer with heavy oil will be affected to a certain extent. Moreover, the intermolecular force of the formed molecular structure itself is relatively strong, and it is easy to form crystals at low temperatures, which will lead to poor fluidity of the viscosity reducer and even solidification, restricting its application under low-temperature conditions, and thus resulting in a worse viscosity reduction effect than the viscosity reducer used in application example 1.

[0172] Similarly, in the comparison between application example 1 and application comparative example 2, after replacing R1 in the viscosity reducer with CH3(CH2)6-, that is, replacing oleic acid with caprylic acid, since the molecular chain of R1 in the final viscosity reducer is shorter, it is difficult to achieve a better steric hindrance effect, and the hindrance effect on the intermolecular interaction of viscous substances is limited. Therefore, the viscosity reduction ability is relatively poor.

[0173] This shows that by specifically designing the molecular structure of R1 in the present invention, it can simultaneously have a better steric hindrance effect and the compatibility and solubility with heavy oil, thus achieving a better viscosity reduction effect.

[0174] (3) From application examples 1 and 5, it can be seen that in application example 5, pentaethylenehexamine is used, resulting in a longer molecular chain and more amine groups. The final viscosity reducer has a higher viscosity itself and will produce a larger steric hindrance effect, which will hinder the mutual compatibility effect of the viscosity reducer with other oil production substances in the subsequent use process.

[0175] Similarly, by comparing Application Example 1 and Application Comparative Example 1, it can be seen that in Application Comparative Example 1, n was changed to 1. The results showed that tetraethylenepentamine in Application Example 1 contains multiple amino groups, which can provide more active sites to participate in the reaction and form a more complex cross-linked structure. While ethylenediamine in Application Comparative Example 1 has only two amino groups, and the number of active groups is halved. When the viscosity reducer interacts with the viscosity-causing substances, the number of chemical bonds that can be formed is reduced, resulting in the inability to effectively destroy the structure of the viscous substances in the system, and thus reducing the viscosity reduction efficiency.

[0176] This shows that controlling the number of n within a reasonable range in the present invention is more conducive to obtaining a viscosity reducer with better viscosity reduction effect.

[0177] (4) From Application Examples 6 to 7, it can be seen that relatively good viscosity reduction effects can be achieved. However, compared with Application Example 1, the reaction temperature in Application Example 1 is moderate, and the molecular structure of the target product viscosity reducer is more ideal, with a better viscosity reduction effect. In Application Example 6, the temperature of the amidation reaction is relatively high, increasing the probability of side reactions in the reaction system. For example, it may cause thermal decomposition of reactants or products, generating some undesired by-products, which will not only reduce the yield of the target product viscosity reducer but also affect the quality and performance of the viscosity reducer, making the viscosity reduction effect of Application Example 1 better than that of Application Example 6. In Application Example 7, a relatively low temperature for the amidation reaction is used, which is not sufficient to achieve a high conversion rate of the amidation reaction. There will be reactants that are not converted into the target product viscosity reducer, and it will also result in a relatively less ideal molecular structure of the generated viscosity reducer, such as uneven molecular weight distribution and relatively inappropriate degree of branching of the molecular chain, etc. As a result, the viscosity reduction effect of Application Example 1 is ultimately better than that of Application Example 7. This shows that further preferably controlling the temperature of the amidation reaction within a reasonable range in the present invention can further improve the viscosity reduction effect.

[0178] (5) From Application Examples 8 to 12, it can be seen that the present invention preferably combines an organic solvent with a viscosity reducer having a specific structure, and the two act synergistically to further improve the viscosity reduction effect.

[0179] The present invention uses the above-mentioned embodiments to illustrate the detailed features of the present invention. However, 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 improvement to the present invention, equivalent replacement of the technical features selected by the present invention, and addition of auxiliary technical features, as well as the selection of specific methods, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A viscosity reducer, characterized in that, The structural formula of the viscosity reducer is shown in Formula (1): Among them, R1 is a hydrocarbon group with the number of carbon atoms greater than or equal to 10, and the value range of n is 3-10.

2. The viscosity reducer according to claim 1, characterized in that, The R1 is a group containing olefins, and the number of carbon atoms of the R1 is 10-20, preferably 15-18; Preferably, the value range of n is 3-5.

3. The viscosity reducer according to claim 1 or 2, characterized in that, The structural formula of the viscosity reducer is shown in Formula (2):

4. The preparation method of the viscosity reducer according to any one of claims 1 to 3, characterized in that, The preparation method includes: an amidation reaction of an organic acid and ethylenediamine to prepare the viscosity reducer; The number of carbon atoms of the organic acid is greater than or equal to 11, and the number of nitrogen atoms in the ethylenediamine is 4-11.

5. The preparation method according to claim 4, wherein The number of carbon atoms of the organic acid is 11-21, preferably 16-19; Preferably, the number of nitrogen atoms in the ethylenediamine is 4-6; Preferably, the organic acid is oleic acid; and / or the ethylenediamine is tetraethylenepentamine.

6. The preparation method according to claim 4, characterized in that, In the amidation reaction, the molar ratio of the organic acid to the ethylenediamine is 1:(1-2); Preferably, the temperature of the amidation reaction is 140-180°C; Preferably, a protective gas is introduced in the amidation reaction; Preferably, the protective gas includes any one or a combination of at least two of nitrogen, helium or carbon dioxide; Preferably, the time of the amidation reaction is 2-6h; Preferably, the stirring speed of the amidation reaction is 50r / min-100r / min; Preferably, after the amidation reaction, the preparation method further includes a separation step; Preferably, the separation step includes: mixing and extracting the reaction product after the amidation reaction with an organic solvent, and performing liquid-liquid phase separation to obtain an organic phase; the organic phase is successively washed and the solvent is removed to obtain the viscosity reducer; Preferably, the organic solvent used in the separation step includes any one or a combination of at least two of ethyl acetate, dichloromethane, toluene or diethyl ether; Preferably, the mass ratio of the organic solvent to the reaction product after the reaction is 1:1-2; Preferably, the temperature of the mixing extraction is 30-50°C; Preferably, the washing includes: washing the impurities in the organic phase with a sodium chloride solution; Preferably, the impurities include unreacted ethylenediamine and by-products; Preferably, the by-products include any one or a combination of at least two of polysubstituted amides, crosslinked polymers or oleic acid oxidation products; Preferably, the temperature of the washing is 30-50°C; Preferably, the method for removing the solvent includes evaporating the solvent.

7. A viscosity-reducing composition, characterized in that, The viscosity reducing composition includes an organic solvent and the viscosity reducer according to any one of claims 1-3.

8. The viscosity-reducing composition according to claim 7, characterized in that, The organic solvent in the viscosity reducing composition includes any one or a combination of at least two of octane, diesel, toluene, mesitylene or xylene; Preferably, the mass ratio of the viscosity reducer to the organic solvent in the viscosity reducing composition is (1-4):(1-10).

9. Use of the viscosity reducer according to any one of claims 1 to 3, or the viscosity reducing composition according to claim 7 or 8, characterized in that The viscosity reducer, or the viscosity reducing composition is used to reduce the viscosity of heavy oil.

10. The application according to claim 8, characterized in that The viscosity of the heavy oil itself at 20°C ranges from 3000 to 60000 mPa·s; Preferably, the composition of the heavy oil includes saturates, aromatics, resins and asphaltenes; Preferably, the content of asphaltenes in the heavy oil is 20-40 wt%. Preferably, the content of resin in the heavy oil is 10-25 wt%; Preferably, the content of saturates in the heavy oil is 30-40 wt%; Preferably, the content of aromatics in the heavy oil is 20-30 wt%; Preferably, the hydrogen-to-carbon mass ratio of asphaltene is 0.8-1.2:1; Preferably, the addition amount of the viscosity reducer during viscosity reduction is 1-4 wt%, or the addition amount of the viscosity reduction composition during viscosity reduction is 2-14 wt%.

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