Composite viscosity reducer and its preparation method and application

Abstract

The present invention provides a composite viscosity reducer, its preparation method, and application. The preparation method comprises: placing a mixed solution containing aggregated nanomaterials, an organic additive, and a solvent in a ball milling reactor, injecting gas into the mixed solution until the gas injected into the ball milling reactor reaches a supercritical state, and performing ball milling in the supercritical state; then, depressurizing the ball milling reactor to atmospheric pressure, removing the resulting crude product, and purifying the crude product to obtain the composite viscosity reducer. The organic additive comprises a polymer and / or a monomer. When the monomer is included, the monomer undergoes a polymerization reaction during the ball milling process. The present invention can significantly improve the viscosity reduction efficiency of heavy oil.

Description

Technical Field

[0001] The invention relates to a composite viscosity reducer and a preparation method and application thereof, belonging to the field of oil viscosity reduction in the petroleum industry. Background Art

[0002] Heavy oil has the characteristics of high viscosity and large flow resistance. Its extraction and transportation are difficult and demanding. Therefore, reducing the viscosity of heavy oil and improving its fluidity are of great significance for increasing heavy oil recovery and simplifying the extraction process.

[0003] At present, oil-soluble polymers are commonly used as viscosity reducers to reduce the viscosity of heavy oil. The main method is to destroy the wax network in the heavy oil by utilizing the eutectic and adsorption effects of polymer molecules. There is also a method of adding toluene to the heavy oil to reduce the viscosity of the heavy oil, but the current viscosity reduction efficiency needs to be further improved. Summary of the Invention

[0004] The present invention provides a composite viscosity reducer and a preparation method and application thereof, which has the advantages of high viscosity reduction efficiency and can effectively overcome the defects of the prior art.

[0005] One aspect of the present invention provides a method for preparing a composite viscosity reducer, comprising: placing a mixed solution containing aggregated nanomaterials, an organic additive, and a solvent in a ball milling reaction tank, injecting gas into the mixed solution until the gas injected into the ball milling reaction tank is in a supercritical state, and subjecting the mixed solution to ball milling treatment in the supercritical state; then depressurizing the ball milling reaction tank to normal pressure, taking out the obtained crude product, and purifying the crude product to obtain the composite viscosity reducer; wherein the organic additive comprises a polymer and / or a monomer, and when the monomer is included, the monomer undergoes a polymerization reaction during the ball milling treatment.

[0006] Optionally, the aggregated nanomaterial includes at least one of graphite powder, powdered molybdenum disulfide, powdered boron nitride, attapulgite, and montmorillonite; and / or, the polymer includes a comb polymer; and / or, the polymer includes at least one of ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl alcohol terpolymer, and a multipolymer formed by polymerization of at least three monomers of octadecyl methacrylate, styrene, maleic anhydride, acrylamide, and fumaric acid; and / or, the monomer includes at least one of octadecyl methacrylate, styrene, acrylamide, fumaric acid, and maleic anhydride; and / or, the solvent includes at least one of ethanol, toluene, xylene, N,N-dimethylformamide, kerosene, and diesel.

[0007] Optionally, the mass ratio of the aggregated nanomaterial to the polymer is 10:(1-12); and / or, the mass ratio of the aggregated nanomaterial to the monomer is 5:(5-10); and / or, the mass volume ratio of the aggregated nanomaterial to the solvent is 10g:(40-80)mL.

[0008] Optionally, the mixed liquid further contains a surfactant, wherein the surfactant includes hexadecyltrimethylammonium bromide and / or octadecylamine; and / or the mass ratio of the aggregated nanomaterial to the surfactant is 10:(0.5-3).

[0009] Optionally, the gas includes carbon dioxide; and / or, the supercritical state conditions are: the temperature is controlled in the range of 40 to 80° C., and the pressure is controlled in the range of 10 to 20 MPa; and / or, the ball milling treatment time is 2 to 6 hours.

[0010] Optionally, the process of depressurizing the ball mill reaction tank to normal pressure includes a rapid depressurization process, and the rapid depressurization satisfies: from the start of depressurization, the pressure in the ball mill reaction tank reaches no more than half of the pressure in the supercritical state within 5 seconds.

[0011] Optionally, the viscosity reducer is prepared by using a ball milling assisted supercritical fluid stripping device, the device includes a buffer tank and the ball milling reaction tank, the ball milling reaction tank and the buffer tank are connected through an exhaust channel, the exhaust channel is provided with an outlet valve, the ball milling reaction tank is provided with an air inlet valve, the buffer tank is provided with an exhaust valve, the volume of the ball milling reaction tank is V1, the volume of the buffer tank is V2, and V2 ≥ 2V1, the preparation method comprises: placing the mixed solution in the ball milling reaction tank, keeping the outlet valve closed, and injecting the gas into the ball milling reaction tank through the air inlet valve until the gas injected into the ball milling reaction tank is The gas is in a supercritical state, and then the air inlet valve is closed, and ball milling treatment is carried out in the supercritical state; after the ball milling treatment is completed, the exhaust valve of the buffer tank is kept closed, and the outlet valve is opened to connect the ball milling reaction tank and the buffer tank, so that the ball milling reaction tank is depressurized, and from the time of opening the outlet valve, the pressure in the ball milling reaction tank is released to half of the pressure in the supercritical state within 5 seconds to achieve rapid pressure relief; then the exhaust valve of the buffer tank is opened to connect the ball milling reaction tank and the buffer tank with the external atmosphere, so that the ball milling reaction tank is depressurized to normal pressure; then the crude product is taken out, and after the purification treatment, the viscosity reducer is obtained.

[0012] Another aspect of the present invention provides a composite viscosity reducer prepared according to the above preparation method.

[0013] In another aspect of the present invention, a method for reducing the viscosity of heavy oil is provided, comprising: using the above-mentioned composite viscosity reducer to reduce the viscosity of heavy oil raw materials.

[0014] Optionally, the heavy oil feedstock includes paraffin-based heavy oil and / or cycloalkyl heavy oil; and / or the amount of the composite viscosity reducer is controlled such that the mass of the composite viscosity reducer is 50ppm to 1000ppm of the mass of the heavy oil feedstock.

[0015] In the present invention, ball milling is combined with a supercritical fluid intercalation and exfoliation process to exfoliate aggregated nanomaterials into smaller nanoparticles, and components such as polymers in an organic additive and / or polymers synthesized in situ from monomers in the organic additive during the ball milling process are compounded with the smaller nanoparticles to produce a composite viscosity reducer. This composite viscosity reducer can significantly improve the viscosity reduction efficiency of heavy oils. The prepared viscosity reducer has a wide range of uses and exhibits excellent viscosity reduction effects not only on paraffin-based heavy oils but also on cycloalkyl heavy oils that are difficult to reduce in viscosity and for which existing viscosity reducers are essentially ineffective. In addition, in the preparation process of the present invention, the aggregated nanomaterials do not need to be expanded first. Instead, the aggregated nanomaterials that have not been expanded can be directly used as raw materials for ball milling under a supercritical state to produce a viscosity reducer with high viscosity reduction performance. The preparation process is simple and easy to operate, the raw materials are cheap and readily available, and the cost is low. At the same time, the supercritical intercalation medium (i.e., the supercritical fluid) is recyclable and pollution-free. Thus, the composite viscosity reducer has the advantages of simple preparation process, low cost, and environmental protection, which is of great significance for practical industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 SEM images of graphite and ODA-GNs / 1EVA in the examples;

[0017] Figure 2 TEM image of ODA-GNs / 1EVA in the embodiment;

[0018] Figure 3 : The AFM test results of ODA-GNs / 1EVA in the embodiment (the left picture is the sample image, the right picture is the sample height map, the abscissa of the right picture is distance (Distance), and the ordinate is height (Height));

[0019] Figure 4 FTIR graphs of ODA-GNs / 1EVA, EVA, ODA-GNs, and E10-GNs in the examples (the horizontal axis is wavenumbers, and the vertical axis is transmittance);

[0020] Figure 5The TGA curves of ODA-GNs / 1EVA, ODA-GNs / 2EVA, ODA-GNs / 3EVA, and ODA-GNs / 4EVA in the examples are shown (the abscissa is temperature, and the ordinate is the residual mass percentage of the sample (the ratio of the residual mass to the initial mass));

[0021] Figure 6 The DTG curves of ODA-GNs / 1EVA, ODA-GNs / 2EVA, ODA-GNs / 3EVA, and ODA-GNs / 4EVA in the examples (the abscissa is temperature, and the ordinate is the rate of weight loss (DTG));

[0022] Figure 7 The viscosity of ODA-GNs / 1EVA changes with temperature (viscosity-temperature curve) at different addition amounts (the horizontal axis is temperature and the vertical axis is viscosity);

[0023] Figure 8 is the viscosity reduction rate of ODA-GNs / 1EVA at 25℃ when different addition amounts are added;

[0024] Figure 9 The viscosity-temperature curve of the heavy oil system when different materials are used as viscosity reducers;

[0025] Figure 10 is the viscosity reduction rate at 25°C when different materials are used as viscosity reducers;

[0026] Figure 11 The viscosity-temperature curve of the heavy oil system when different materials are used as viscosity reducers;

[0027] Figure 12 is the viscosity reduction rate at 25°C when different materials are used as viscosity reducers;

[0028] Figure 13 The viscosity-temperature curve of the heavy oil system when different materials are used as viscosity reducers;

[0029] Figure 14 is the viscosity reduction rate at 25°C when different materials are used as viscosity reducers;

[0030] Figure 15 Polarized microscope images of the heavy oil raw material and the heavy oil system after viscosity reduction;

[0031] Figure 16 The SEM images of the carbonized products of the heavy oil raw material and the heavy oil system after viscosity reduction are shown;

[0032] Figure 17The viscosity-temperature curve (curve of viscosity changing with temperature) of the heavy oil system when different materials are used as viscosity reducers (the horizontal axis is temperature and the vertical axis is viscosity);

[0033] Figure 18 is the viscosity reduction rate at 25°C when different materials are used as viscosity reducers;

[0034] Figure 19 Schematic diagram of the structure of a ball milling-assisted supercritical fluid exfoliation device in one embodiment of the present invention;

[0035] Figure 20 This is a schematic structural diagram of a ball milling reaction tank in a ball milling-assisted supercritical fluid exfoliation device in one embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0037] The preparation method of the composite viscosity reducer of the present invention comprises the following steps: placing a mixed liquid containing aggregated nanomaterials, an organic auxiliary agent and a solvent in a ball milling reaction tank, injecting gas into the mixed liquid until the gas injected into the ball milling reaction tank is in a supercritical state, and subjecting the mixed liquid to ball milling treatment in the supercritical state; then depressurizing the ball milling reaction tank to normal pressure, taking out the obtained crude product, and purifying the crude product to obtain the composite viscosity reducer; wherein the organic auxiliary agent comprises a polymer and / or a monomer, and when the monomer is included, the monomer undergoes a polymerization reaction during the ball milling treatment, thereby polymerizing to form a polymer.

[0038] During the above preparation process, under a supercritical state, a supercritical fluid formed by the gas injected into the ball milling reaction tank enters the interlayers of the aggregated nanomaterials, intercalates and exfoliates the aggregated nanomaterials to form thinner nanoparticles, and at the same time assists the ball milling modification and compounding process, so that the thinner nanoparticles are compounded with components such as polymers in the organic additives and / or polymers formed by polymerization of monomers to prepare a composite viscosity reducer.

[0039] According to the inventors' research and analysis, in the embodiments of the present invention, on the one hand, the synergistic effect of the supercritical fluid small molecule intercalation and the lateral shear force generated by ball milling is utilized to increase the distance between the layers (or between the bundles) in the aggregated nanomaterial. During the pressure release process after the ball milling treatment, the volume of the fluid molecules expands, causing the lamellar structure (or bundle) structure of the aggregated nanomaterial to dissociate, forming smaller nanoparticles (generally two-dimensional lamellar nanomaterials), increasing their surface area and dispersibility. At the same time, during the exfoliation process of the aggregated nanomaterial, components such as polymers also enter the layers (or bundles) of the aggregated nanomaterial through ball milling. Between, prevent the separated layers and layers (or bundles and bundles) from re-aggregating and stacking, that is, prevent the dispersed nanoparticles from re-aggregating and stacking, so as to obtain a viscosity reducer (generally a two-dimensional lamellar nanocomposite material) composed of smaller nanoparticles and polymers and other components; on the other hand, under the above preparation system, the supercritical fluid acts as an anti-solvent to dilute and expand the mixed liquid, change the solubility of the original solvent for the solute, form a large supersaturation in a short time, and cause the solute therein to crystallize and precipitate, forming a fine particle material with high purity and uniform particle size distribution (i.e., viscosity reducer), while also reducing the amount of solvent used, reducing environmental pollution, and simplifying the preparation process.

[0040] The above-mentioned aggregated nanomaterials are generally sheet nanomaterials with multiple layers (or multiple bundles) formed by the aggregation of single layers (or single bundles) and other units. The layers (or bundles) are mainly combined together by van der Waals forces, presenting an aggregated state.

[0041] Specifically, the aggregated nanomaterials may include at least one of graphite powder, powdered molybdenum disulfide (MoS2), powdered boron nitride (BN), attapulgite (ATP), and montmorillonite (MMT). The two-dimensional nanosheet materials such as graphene, molybdenum disulfide, and boron nitride peeled from them have a thinner sheet structure and weaker interlayer sliding caused by interlayer van der Waals forces, which has the effect of reducing frictional resistance and can improve the viscosity reducing performance of the viscosity reducer.

[0042] In some preferred embodiments, the aggregated nanomaterial includes graphite powder, and the graphene formed by exfoliation of the graphite powder is sp 2 Hybridization, which has a conjugated structure with a large π bond, can increase the ability of the viscosity reducer to destroy the π-π stacking of colloids and asphaltene in heavy oil, thereby dispersing the aggregates of components such as colloids and asphaltene, releasing the oil phase and increasing the fluidity of the oil.

[0043] In addition, the above-mentioned polymer may include a comb polymer, in particular, it may include at least one of ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl alcohol terpolymer, and a multipolymer formed by polymerizing at least three monomers of octadecyl methacrylate, styrene, maleic anhydride, acrylamide, and fumaric acid, wherein the multipolymer includes, for example, a terpolymer formed by polymerizing any three of octadecyl methacrylate, styrene, maleic anhydride, acrylamide, and fumaric acid and / or a pentapolymer formed by polymerizing octadecyl methacrylate, styrene, maleic anhydride, acrylamide, and fumaric acid, etc.

[0044] In some preferred embodiments, polymer comprises ethylene-vinyl acetate copolymer (EVA) and / or ethylene-vinyl acetate-vinyl alcohol terpolymer (EVAL, the alcoholysis product of EVA), adopt this polymer to be conducive to further improving the viscous oil viscosity reducing performance of viscosity reducer, infer that reason may be at least, the viscosity reducer adopting this polymer to make has structures such as long carbon chain and polar group, and the bonding strength degree between polymer and the nanoparticles formed by aggregated nano material peeling is more suitable, long carbon chain and polar group can more fully release and unfold in viscous oil, be more conducive to acting on components such as colloid, asphaltenes inside viscous oil, improve viscosity reducing effect. Although the present invention also can adopt other polymers such as acrylamide-styrene copolymer, polyethylene, research display, adopt EVA and / or EVAL, prepared viscosity reducer performance is more excellent.

[0045] In general, the greater the polymer loading in the nanocomposite prepared by the above-mentioned preparation process (i.e., the greater the amount of polymer used in the preparation process), the better its thermal stability (the higher the temperature corresponding to the second stage thermal gravimetric peak in its TGA test results), and it is beneficial for the viscosity reducer to have more effective structures such as long carbon chains and carbon-based groups. However, if the polymer content is too high, the degree of binding between the polymer and the surface of the nanoparticles in the viscosity reducer will be excessively enhanced, forming an over-coated structure, which is not conducive to the synergistic effect of the polymer and the nanoparticles and will also affect the viscosity reduction performance of the viscosity reducer to a certain extent. Taking these factors into consideration, the mass ratio of the aggregated nanomaterial to the polymer (i.e., the ratio of the mass of the aggregated nanomaterial to the mass of the polymer) can generally be controlled to be 10: (1 to 12), such as 10:1, 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, 10:10, 10:11, 10:12, or a range consisting of any two ratios therein.

[0046] In the embodiment of the present invention, when there are multiple types of polymers, the mass of the polymers refers to the sum of the masses of all polymers; when there are multiple types of aggregated nanomaterials, the mass of the aggregated nanomaterials refers to the sum of the masses of all aggregated nanomaterials.

[0047] In addition, the monomer may include at least one of octadecyl methacrylate (Formula 1), styrene (Formula 2), acrylamide (Formula 3), fumaric acid (Formula 4), and maleic anhydride (Formula 5), ​​and in particular may include at least one of octadecyl methacrylate, styrene, and acrylamide. The use of this monomer is beneficial for further improving the viscosity reducing performance of the viscosity reducer for heavy oil. It is speculated that the reason may be at least that during the ball milling process, the monomer is in situ polymerized into a polymer, so that the viscosity reducer has structures such as long carbon chains and polar groups, and the bonding strength between the polymer and the nanoparticles formed by exfoliation of the aggregated nanomaterial is more appropriate. The long carbon chains and polar groups can be more fully released and expanded in the heavy oil, which is more conducive to acting on components such as colloids and asphaltene in the heavy oil, thereby improving the viscosity reducing effect.

[0048]

[0049]

[0050] As mentioned above, the greater the loading amount of the polymer in the nanocomposite material obtained by the above-mentioned preparation process (i.e., the greater the amount of polymer used in the preparation process), the better its thermal stability (in its TGA test results, the temperature corresponding to the thermal gravimetric peak of the second stage is higher), and it is beneficial for the viscosity reducer to have more effective structures such as long carbon chains and carbon-based groups. However, if the polymer content is too much, it will excessively enhance the degree of binding between the polymer and the surface of the nanoparticles in the viscosity reducer, forming an over-coated structure, which is not conducive to the synergistic effect of the polymer and the nanoparticles, and will also affect the viscosity reduction performance of the viscosity reducer to a certain extent. Taking these factors into consideration, in some embodiments, the mass ratio of the aggregated nanomaterial to the monomer can generally be controlled to be 5: (5-10), for example, 5:5, 5:6, 5:7, 5:8, 5:9, 5:10 or a range consisting of any two ratios therein.

[0051] In some preferred embodiments, the monomers include a first monomer and a second monomer, the first monomer includes octadecyl methacrylate and styrene, and the second monomer includes at least one of acrylamide, maleic anhydride, and fumaric acid, wherein the mass ratio of octadecyl methacrylate to styrene can be 5:(0.1-5), such as 5:0.1, 5:0.5, 5:1, 5:2, 5:3, 5:4, 5:5, or a range consisting of any two ratios thereof, and the mass ratio of octadecyl methacrylate to the second monomer is 5:(0.1-5), such as 5:0.1, 5:0.5, 5:1, 5:2, 5:3, 5:4, 5:5, or a range consisting of any two ratios thereof. For example, the monomers include octadecyl methacrylate, styrene, and acrylamide, and the mass ratio of octadecyl methacrylate, styrene, and acrylamide is 5:(0.1-5):(0.1-5).

[0052] In the embodiment of the present invention, when there are multiple monomers, the mass of the monomers refers to the sum of the masses of all monomers. For example, if the monomers include octadecyl methacrylate, styrene, and acrylamide, the mass of the monomers is the sum of the masses of octadecyl methacrylate, styrene, and acrylamide.

[0053] In addition, the mixed solution may also contain a surfactant. The introduction of the surfactant facilitates the dispersion of the components and plays a role in surface modification, thereby improving the dispersibility and lipophilicity of the prepared nanocomposite material and facilitating its application.

[0054] Specifically, the above-mentioned surfactant may include a cationic surfactant, preferably including cetyltrimethylammonium bromide (CTAB) and / or octadecylamine (ODA). Studies have shown that compared with the use of other types of surfactants such as anionic surfactants (such as sodium dodecyl sulfonate or sodium dodecyl sulfate, etc.), the use of the above-mentioned cationic surfactant is more conducive to synergistic effect with other ingredients to prepare a viscosity reducer with excellent viscosity reducing performance, thereby significantly improving the viscosity reducing effect on heavy oil.

[0055] In some preferred embodiments, the mass ratio of aggregated nanomaterials to surfactants can be 10:(0.5-3), for example, 10:0.5, 10:1, 10:1.5, 10:2, 10:2.5, 10:3 or a range consisting of any two ratios therein.

[0056] In specific implementation, the polymer can be dissolved in a solvent to obtain a polymer solution, and then the polymer solution, aggregated nanomaterials, and surfactants are mixed to obtain a mixed liquid, and then the mixed liquid is added to a ball mill reaction tank; alternatively, the monomer, surfactant, and solvent can be mixed to obtain a mixed liquid, and then the mixed liquid is placed in a ball mill reaction tank, but is not limited to this.

[0057] In the above preparation process, the solvent used can specifically include an organic solvent, preferably including at least one of ethanol, toluene, xylene, N,N-dimethylformamide (DMF), kerosene, and diesel, which is more conducive to the synergistic coordination between the components, preparing a viscosity reducer with excellent viscosity reducing performance and improving the preparation efficiency.

[0058] In some embodiments, the mass-to-volume ratio of the aggregated nanomaterial to the solvent (i.e., the ratio of the mass of the aggregated nanomaterial to the volume of the solvent) can be 10g:(40-80)mL, for example, 10g:40mL, 10g:50mL, 10g:60mL, 10g:70mL, 10g:80mL or a range consisting of any two ratios therein.

[0059] In some embodiments, the gas used in the above preparation process may include carbon dioxide, and liquid carbon dioxide in a supercritical state (supercritical carbon dioxide) is used as an intercalation medium for exfoliating aggregated nano-nanomaterials. At the same time, combined with ball milling treatment, it can enhance the material exfoliation, modification and composite effects to obtain a high-performance viscosity reducer.

[0060] Generally, the gas can be in a supercritical state by regulating the temperature, pressure and other conditions in the ball milling reaction tank. The above-mentioned supercritical state conditions can be specifically: the temperature is controlled in the range of 40 to 80° C., for example, 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., or a range consisting of any two thereof, and the pressure is controlled in the range of 10 to 20 MPa (i.e., the pressure in the supercritical state (denoted as P0) is 10 to 20 MPa), for example, 10 MPa, 12 MPa, 15 MPa, 18 MPa, 20 MPa, or a range consisting of any two thereof.

[0061] For example, when the organic auxiliary agent is a polymer, the temperature of the supercritical state can be controlled at 40 to 70° C., which is beneficial to further improve the preparation efficiency and the viscosity reducing performance of the prepared viscosity reducer.

[0062] For example, when the organic auxiliary agent includes the monomer, the temperature of the supercritical state can be controlled at 60-80° C., which is beneficial to the polymerization reaction of the monomer and the peeling of the aggregated nanomaterials, while improving the preparation efficiency and the viscosity reducing performance of the obtained viscosity reducer.

[0063] When the organic additive includes a monomer (i.e., the mixed solution contains a monomer), an initiator may also be introduced into the mixed solution to facilitate the polymerization reaction of the monomer. For example, in some embodiments, after the mixed solution is placed in a ball milling reaction tank, an initiator is added thereto, and gas is injected into the mixture until the gas injected into the ball milling reaction tank reaches a supercritical state, and the ball milling process is performed in the supercritical state.

[0064] In a specific implementation, after the mixed liquid is placed in a ball mill reaction tank, it can be stirred at 60°C to 80°C for 30 minutes to 60 minutes to evenly mix the components in the mixed liquid, and then the initiator is added thereto. For example, an injection port can be provided on the ball mill reaction tank, and the initiator can be injected into the ball mill reaction tank using a syringe.

[0065] The initiator may include azobisisobutyronitrile (AIBN), etc. The mass of the initiator may be 0.8% to 1.2% of the mass of the monomer, for example, 0.8%, 0.9%, 1%, 1.1%, 1.2%, or any two thereof. When there are multiple initiators, the mass of the initiator refers to the sum of the masses of all initiators.

[0066] In addition, the ball milling treatment time may be 2 to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or a range consisting of any two thereof.

[0067] The process of depressurizing the ball milling reaction tank to normal pressure can especially include a rapid depressurization process, which satisfies the following requirements: from the start of depressurization, the pressure in the ball milling reaction tank reaches no more than half of the pressure in the supercritical state (i.e. no more than 0.5P0 (i.e. less than or equal to 0.5P0)) within 5s (i.e. no more than 5s (i.e. less than or equal to 5s)), which is beneficial for the rapid expansion of the volume of fluid molecules in the depressurization process after the ball milling treatment, so that the lamellar structure (or bundle structure) of the aggregated nanomaterial dissociates to form thinner two-dimensional lamellar nanomaterials. For example, in the rapid depressurization process, from the start of depressurization, the pressure reaches no more than half of the pressure in the supercritical state within a time of no more than 0.1s, no more than 0.5s, no more than 1s, no more than 2s, no more than 3s, or no more than 4s.

[0068] The present invention does not impose any particular restrictions on the method for achieving rapid pressure relief. For example, the ball milling reactor can be provided with an exhaust channel for communicating the interior of the ball milling reactor with the outside world. Rapid pressure relief can be achieved by adjusting the size of the exhaust channel and other conditions (the larger the diameter of the exhaust channel or the diameter of its exhaust hole, the faster the pressure relief, and vice versa). A valve is generally provided on the exhaust channel, and the ball milling reactor (ball mill) is provided with a pressure gauge for detecting the pressure inside the ball milling reactor. After the ball milling process is completed, the valve can be opened to start pressure relief. Starting from the time the valve is opened, the pressure inside the ball milling reactor reaches no more than half of the pressure in the supercritical state within 5 seconds, and reaches normal pressure (i.e., the gauge pressure of the pressure gauge is 0) within 70 seconds (i.e., within a time not exceeding 70 seconds).

[0069] In some preferred embodiments, the viscosity reducing agent is prepared using a ball milling assisted supercritical fluid stripping device, such as Figure 19As shown, the equipment includes a buffer tank and a ball milling reaction tank, the ball milling reaction tank and the buffer tank are connected through an exhaust channel, the exhaust channel is provided with an outlet valve, the ball milling reaction tank is provided with an air inlet valve, and the buffer tank is provided with an exhaust valve. The volume of the ball milling reaction tank is V1, and the volume of the buffer tank is V2, V2 ≥ 2V1. The preparation method of the above viscosity reducer may include the following steps S1 to S4:

[0070] S1. Place the mixed liquid in a ball mill reaction tank, keep the outlet valve closed, and inject gas into the ball mill reaction tank through the air inlet valve until the gas injected into the ball mill reaction tank is in a supercritical state;

[0071] S2, then close the air inlet valve and perform ball milling under supercritical state;

[0072] S3. After the ball milling treatment is completed, the exhaust valve of the buffer tank is kept closed, and the outlet valve is opened to connect the ball milling reaction tank and the buffer tank, so that the pressure in the ball milling reaction tank is released to half of the pressure at the supercritical state within 5 seconds from the time the outlet valve is opened, thereby achieving rapid pressure relief;

[0073] S4. Then open the exhaust valve of the buffer tank to connect the ball mill reaction tank and the buffer tank to the outside atmosphere, so that the ball mill reaction tank is depressurized to normal pressure, which generally reaches normal pressure within 70 seconds; then take out the crude product, and obtain the viscosity reducer after purification.

[0074] During specific implementation, in step S1, after the mixed liquid is placed in the ball milling reaction tank, the air inlet valve and the outlet valve can be opened first, and the above-mentioned gas for forming a supercritical fluid (such as carbon dioxide) can be filled into the ball milling reaction tank and the buffer tank to discharge the air in the ball milling reaction tank and the buffer tank, and then the outlet valve is closed, and the above-mentioned gas is filled into the ball milling reaction tank until it reaches a supercritical state, and then the air inlet valve is closed to perform ball milling treatment under the supercritical state.

[0075] When the mixed liquid includes the above-mentioned monomers, in step S1, after the mixed liquid is placed in a ball milling reaction tank, the temperature of the mixed liquid can be controlled to 60°C to 80°C, and then an initiator is added thereto, and then the air inlet valve of the ball milling reaction tank is opened to carry out the subsequent process.

[0076] In the above step S3, after the ball milling process is completed, the exhaust valve of the buffer tank is kept closed, and after the outlet valve is opened, the ball mill reaction tank is connected to the buffer tank. After the pressure of the two is stable (for example, after the indication of the pressure gauge used to detect the ball mill reaction tank is stable), the exhaust valve on the buffer tank is opened to release air and pressure until it reaches normal pressure (about 0.1 MPa). Generally, starting from the time when the exhaust valve is opened, the ball mill reaction tank and the buffer tank reach normal pressure within 50s to 70s (that is, the pressure indication of the pressure in the ball mill reaction tank and / or the pressure in the buffer tank is stable).

[0077] Optionally, the air inlet valve can be set at the upper end of the ball mill reaction tank; the exhaust valve can be set at the upper end of the buffer tank, one end of the exhaust channel is connected to the upper end of the ball mill reaction tank and communicated with the ball mill reaction tank, and the other end of the exhaust channel is connected to the upper part of the buffer tank and communicated with the buffer tank. The lower part of the buffer tank can also be provided with a product outlet for taking out the crude product entering the buffer tank.

[0078] Specifically, if Figure 20 As shown, the ball milling-assisted supercritical fluid stripping equipment also includes a base, a bracket connected to the base, a heating jacket, a thermocouple, a pressure gauge and a stirring device arranged on the bracket. The ball milling reaction tank is arranged on the heating jacket. The ball milling reaction tank is used for ball milling treatment. The heating jacket is used to heat the ball milling reaction tank to control the temperature in the ball milling reaction tank. The pressure gauge is used to detect the pressure in the ball milling reaction tank. The thermocouple is used to detect the temperature in the ball milling reaction tank so that the temperature can be more accurately controlled by the heating jacket. The stirring device includes a stirring rod and an electrode for rotating the stirring rod. The stirring rod is used to stir the material and grinding balls in the ball milling reaction tank to implement ball milling treatment. The ball milling reaction tank is provided with a sealing cover for sealing the ball milling reaction tank. The sealing cover is movably mounted on the bracket to facilitate opening or sealing the ball milling reaction tank. The thermocouple, pressure gauge and stirring device are all mounted on the sealing cover. The sealing cover is also provided with an air inlet valve and the above-mentioned exhaust channel. The air inlet valve is used to inject fluids such as carbon dioxide into the ball milling reaction tank. The exhaust channel is used to connect the ball milling reaction tank with the buffer tank after the ball milling treatment is completed to achieve rapid pressure relief.

[0079] Typically, a ball milling reaction tank contains grinding balls for ball milling, such as steel balls and / or zirconium dioxide balls, and may have a diameter of 3 to 8 mm. In a specific implementation, the mixed solution and grinding balls may be added to the ball milling tank, and then gas may be injected into the tank until it reaches a supercritical state before the ball milling process begins. The mass ratio of the steel balls added to the aggregated nanomaterial may generally be 1:80-120, for example 1:100, and the ball milling process may last for 2 to 6 hours. After the ball milling treatment is completed, the heating jacket can be stopped first, and then the outlet valve can be opened to connect the ball milling reaction tank with the product buffer tank to complete the rapid pressure relief. After the pressure display of the equipment stabilizes, the exhaust valve at the upper end of the buffer tank is opened until it reaches normal pressure. Then, the ball milling reaction tank and the crude product entering the buffer tank are taken out (they can be taken out when the temperature reaches room temperature, but are not limited to this), and they are purified, specifically including: washing the crude product with an alcohol solvent and then drying it to obtain a viscosity reducer (powder). The alcohol solvent used includes, for example, ethanol, and the drying temperature can generally be 40-60°C.

[0080] The viscosity reducer provided by the embodiment of the present invention is prepared according to the above-mentioned preparation method, and the viscosity reducer has an extremely thin lamellar structure and a smaller size, so that it has a stronger surface energy and a higher atomic utilization rate. The viscosity reducers such as traditional oil-soluble polymers mainly destroy the wax network in crude oil through the eutectic and adsorption process of molecules, and the viscosity reducer of the present application mainly utilizes the heterogeneous nucleation effect of nanoparticles to make wax crystals more densely crystallized together around the nanoparticles, forming more gaps in the oil phase, greatly destroying the original network structure of the wax crystal aggregates in the viscous oil, thereby making the viscous oil flow better and achieving the purpose of viscosity reduction. In addition, the viscosity reducer of the embodiment of the present invention has a special graphene conjugated structure, which not only has an excellent viscosity reducing effect on paraffin-based viscous oil, but also has a good viscosity reducing effect on cycloalkyl viscous oil containing colloid and asphaltene.

[0081] In some embodiments, the viscosity reducer obtained by the above preparation process is a two-dimensional lamellar nanocomposite material, and its macroscopic appearance is a powder (i.e., nanopowder) composed of nanometer-scale particles, which generally have the following characteristics: (1) its SEM test results show that the particle size is 3 to 5 μm (this size is measured by SEM and is usually the maximum length of the particle), and basically retains the original lamellar morphology of the aggregated nanomaterial, but the original multi-layer aggregation structure of the aggregated nanomaterial is peeled off, and the thickness and number of lamellar layers of the particles formed by the composite with polymer and other components are significantly reduced; (2) its AFM and TEM test results show that the thickness of the particles (or lamellar thickness) is generally between 1.5 and 5 nm, and the number of lamellar layers is basically less than 10 layers, among which the proportion of single-layer particles is greater than 15%, and the proportion of particles with less than 10 layers is more than 99%, and the proportion is the number ratio obtained by transmission electron microscopy (TEM) statistics; (3) its FTIR test results show the characteristic peak of the polymer, combined with SEM, AFM and TEM analysis, indicating that the polymer and other components in the particles exist. The outer layer of smaller nanoparticles formed by the dissociation of aggregated nanomaterials (polymers and other components basically wrap the smaller nanoparticles), the introduction of polymers, surfactants and other components has little effect on the layered morphology and size of the nanoparticles; (4) Its TGA test results show that the nanocomposite material begins to lose weight at about 250-300 ° C; Its DTG analysis results show that the nanocomposite material has two thermal weight loss peaks (that is, it gradually loses weight in two stages after heating). Generally, the thermal weight loss peak of the first stage is between 300-400 ° C, and the thermal weight loss peak of the second stage is between 400-500 ° C. The DTG corresponding to the thermal weight loss peak of the first stage is below 70 μg / min, and the DTG corresponding to the thermal weight loss peak of the second stage is between 100-200 μg / min. This further illustrates that the polymers and other components can generate binding force with the surface of smaller nanoparticles dissociated from aggregated nanomaterials, but the binding force is moderate, so that the long carbon chain and other groups of the nanocomposite material can be fully released and expanded in the heavy oil, fully acting on the internal components of the heavy oil, thereby achieving the purpose of reducing the viscosity of the heavy oil.

[0082] According to the inventors' research, the viscosity reducer of the embodiments of the present invention is used in a small amount, and the added amount can generally be 50ppm to 900ppm by mass of the heavy oil, and can achieve good viscosity reduction efficiency at both high and low temperatures. Specifically, the viscosity of heavy oil generally increases with decreasing temperature. As the temperature decreases, physical changes occur within the heavy oil, such as wax precipitation and colloidal asphalt agglomeration, resulting in a deterioration in the overall fluidity of the heavy oil. The viscosity sudden increase point (inflection point) of the viscosity-temperature curve of the heavy oil is generally the node where the overall fluidity of the heavy oil deteriorates (when the temperature is higher than the temperature corresponding to the viscosity sudden increase point, the increase in the viscosity of the heavy oil as the temperature decreases is generally small. However, after cooling to the temperature corresponding to the viscosity sudden increase point, the viscosity of the heavy oil will increase at a faster rate as the temperature continues to decrease). The viscosity reducer of the present invention can significantly reduce the viscosity of heavy oil even at low temperatures, and can delay the viscosity sudden increase point of the heavy oil by at least about 10°C during the cooling process (i.e., after the viscosity reducer of the present invention is introduced, the temperature corresponding to the viscosity sudden increase point of the heavy oil will be reduced by at least about 10°C). In addition, the viscosity reducer of the present invention has a wide range of uses and can be used for cycloalkyl heavy oil (such as low-sulfur cycloalkyl heavy crude oil, etc.) and paraffin-based heavy oil, and has a significant viscosity reduction effect. The viscosity reduction rate at 25°C can be as high as more than 89%, and the net viscosity reduction rate can be as high as more than 65%.

[0083] The method for reducing the viscosity of heavy oil of the present invention comprises using the above-mentioned viscosity reducer to reduce the viscosity of the heavy oil raw material. In specific implementation, the viscosity reducer can be added to the heavy oil for viscosity reduction by at least one of the following methods: (1) dissolving the viscosity reducer in an oily medium and then adding it to the heavy oil. The oily medium includes, for example, at least one of toluene, xylene, kerosene, and diesel; (2) directly adding the viscosity reducer to the heavy oil, but is not limited thereto. The viscosity reduction treatment process can be carried out at a temperature of 20 to 70° C., but is not limited thereto. The amount of the viscosity reducer can generally be controlled to be 50 ppm to 1000 ppm (i.e., 0.005‰ to 1‰) of the mass of the heavy oil feedstock, for example, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 750 ppm, 800 ppm, 850 ppm, 900 ppm, 950 ppm, 1000 ppm, or a range consisting of any two thereof.

[0084] When the viscosity reducer is dissolved in an oily medium and then added to the heavy oil, the amount of the mixed system formed by dissolving the viscosity reducer in the oily medium can be controlled to meet the following requirements: the volume of the mixed system is 2% to 10% of the volume of the heavy oil raw material, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two thereof.

[0085] During the production of heavy oil, after it is extracted from the surface, it is transported downstream via pipelines. As the pipeline transportation distance increases, the temperature of the heavy oil gradually decreases and its viscosity increases rapidly. By adding the viscosity reducer of the present invention to the heavy oil, the viscosity of the heavy oil can be reduced, thereby suppressing the increase in the viscosity of the heavy oil. Generally, the temperature of the heavy oil is relatively high when it is first extracted from the surface, so the viscosity reducer can be added at this time.

[0086] In some embodiments, the heavy oil feedstock may include paraffin-based heavy oil and / or naphthenic heavy oil.

[0087] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0088] In the following examples, the instrument models used are as follows: scanning electron microscope (SEM): Hitachi SU3500; transmission electron microscope (TEM): FEI Tecnai F20; atomic force microscope (AFM): Multimode8; infrared spectrometer: Thermo Nicolet; thermal analyzer (Netzsch STA409PC); rheometer: Anton Paar MCR 101; polarizing microscope: MoticBA300Pol.

[0089] 1. Example 1

[0090] (1) Preparation of viscosity reducer

[0091] (1-1) Test Example 1

[0092] In this test example 1, the preparation process of the viscosity reducing agent is as follows: Figure 19 and Figure 20 The ball milling-assisted supercritical fluid exfoliation device shown in the figure was prepared as follows:

[0093] 10 g of EVA was dissolved in 300 mL of DMF to obtain a polymer solution; the polymer solution, 50 g of graphite, 5 g of ODA, and a certain amount of 5 mm steel balls were placed in a ball milling reaction tank and sealed;

[0094] The heating jacket was turned on to heat the ball mill reactor to 60°C. At the same time, the air inlet valve on the top of the ball mill reactor was opened to charge carbon dioxide gas into the reactor. When the temperature reached 60°C and the pressure reached 10 MPa (the carbon dioxide charged into the ball mill reactor was in a supercritical state at this time), the air inlet valve was closed. The speed was then set to 400 rpm, and the ball mill reactor was turned on for ball milling for 2 h.

[0095] After the ball milling is completed, the ball milling reaction tank is closed, the heating is stopped, the outlet valve of the exhaust channel is opened, the ball milling reaction tank and the buffer tank are connected for pressure relief, and the pressure in the ball milling reaction tank reaches below 5 MPa within 0.1 s from the time the outlet valve is opened. After the pressure display is stable, the exhaust valve on the buffer tank is opened to connect the ball milling reaction tank and the buffer tank to the outside atmosphere, so that the ball milling reaction tank is pressure-relieved to normal pressure (calculated from the time the exhaust valve is opened, normal pressure (gauge pressure is 0) is basically reached within 60 s). When the temperature and pressure in the ball milling reaction tank and the buffer tank are balanced with the outside (i.e., reaching room temperature and normal pressure), the tank is opened, the materials in the ball milling reaction tank and the buffer tank are taken out, and the crude product obtained by ball milling is separated from the steel balls through a sieve;

[0096] The crude product was washed with ethanol and then dried to obtain a viscosity reducer (graphene powder), which was recorded as ODA-GNs / 1EVA.

[0097] (1-2) Test Examples 2 to 9

[0098] The difference between Experimental Example 2 and Experimental Example 1 is that the amount of EVA is adjusted to 20 g, and the other conditions are the same as those in Experimental Example 1. The prepared viscosity reducer is recorded as ODA-GNs / 2EVA;

[0099] The difference between Experimental Example 3 and Experimental Example 1 is that the amount of EVA is adjusted to 40 g, and the other conditions are the same as those in Experimental Example 1. The prepared viscosity reducer is recorded as ODA-GNs / 4EVA;

[0100] The difference between Test Example 4 and Test Example 1 is that the amount of EVA is adjusted to 60 g, and the other conditions are the same as those of Test Example 1. The prepared viscosity reducer is recorded as ODA-GNs / 6EVA.

[0101] The difference between Experimental Example 5 and Experimental Example 1 is that the amount of EVA is adjusted to 5 g, and the other conditions are the same as those in Experimental Example 1. The prepared viscosity reducer is recorded as ODA-GNs / 0.5EVA;

[0102] The difference between Experimental Example 6 and Experimental Example 1 is that polystyrene is used instead of EVA. The other conditions are the same as those of Experimental Example 1. The prepared viscosity reducer is recorded as ODA-GNS / 1PS.

[0103] The difference between Test Example 7 and Test Example 1 is that acrylamide-styrene copolymer is used instead of EVA. The other conditions are the same as those of Test Example 1. The prepared viscosity reducer is recorded as ODA-GNS / 1PAS.

[0104] The difference between Test Example 8 and Test Example 1 is that sodium dodecyl sulfate is used instead of ODA. The other conditions are the same as those in Test Example 1. The prepared viscosity reducer is recorded as SDS-GNS / 1EVA.

[0105] The difference between Experimental Example 9 and Experimental Example 1 is that oleylamine is used instead of ODA. The other conditions are the same as those of Experimental Example 1. The prepared viscosity reducer is recorded as OA-GNS / 1EVA.

[0106] (1-3) Comparative Examples 1 to 4

[0107] The difference between Comparative Example 1 and Experimental Example 1 is that Comparative Example 1 uses only graphite as raw material, without adding EVA and ODA, and the other conditions are the same as those of Experimental Example 1. The prepared material is recorded as E10-GNs.

[0108] The difference between Comparative Example 2 and Experimental Example 1 is that Comparative Example 2 uses only graphite and ODA as raw materials without adding EVA. The other conditions are the same as those of Experimental Example 1. The prepared material is recorded as ODA-GNs.

[0109] The difference between Comparative Example 3 and Experimental Example 1 is that Comparative Example 2 uses only graphite and EVA as raw materials without adding ODA. The other conditions are the same as those of Experimental Example 1. The prepared material is recorded as E10-GNs / 1EVA.

[0110] The difference between Comparative Example 4 and Experimental Example 1 is that the rapid pressure relief after the ball milling is adjusted to slow pressure relief. The prepared material is recorded as M-ODA-GNs / 1EVA, and the slow pressure relief meets the following requirements: starting from the time when the exhaust hole on the top of the ball milling reactor is opened, the pressure in the ball milling reactor reaches below 5 MPa in about 60 seconds and reaches normal pressure (gauge pressure is 0) in about 120 seconds.

[0111] (2) Viscosity reducer performance test

[0112] (2-1) Characterization of viscosity reducer

[0113] (2-1-1) The characterization test results of the viscosity reducer prepared in Test Example 1 are as follows:

[0114] (1) Figure 1 This is the SEM image obtained by scanning electron microscopy (SEM). Figure 1 (1) (left side) is the SEM image of the graphite used. Figure 1 (2) (right side) is the SEM image of ODA-GNs / 1EVA. Figure 1It can be seen that ODA-GNs / 1EVA basically retains the lamellar morphology of graphite, and its size is basically between 3 and 5 μm, similar to that of graphite, but its thickness is significantly smaller than that of graphite. This indicates that after the preparation process of the above experimental example, the stacked graphite sheets in the graphite are peeled off to form nanoparticles with significantly reduced thickness, thereby preparing the viscosity reducer.

[0115] (2) Figure 2 The TEM images of ODA-GNs / 1EVA obtained by transmission electron microscopy (TEM) analysis ((1) (left image)) and (2) (right image) have different resolutions). It can be seen that ODA-GNs / 1EVA is a thin layer of graphene nanosheets with about 5 single layers stacked, indicating that through the preparation process of the above experimental example, graphene nanosheets with a smaller number of layers were obtained.

[0116] (3) Figure 3 This is the AFM test result of ODA-GNs / 1EVA obtained by atomic force microscopy (AFM). It can be seen that the thickness of its flakes is basically between 1.5nm and 5nm. Combining the test results of SEM, TEM, and AFM, it is measured that the proportion of single-layer graphene nanosheets in the viscosity reducer is greater than 15%, and the proportion of graphene nanosheets with less than 10 layers is more than 99%;

[0117] (4) Figure 4 The FTIR images of ODA-GNs / 1EVA, EVA, ODA-GNs, and E10-GNs obtained by infrared spectrometer analysis show that EVA has obvious characteristic peaks of ethylene vinyl acetate, a small amount of hydroxyl groups appear on the surface of E10-GNs, the surface of ODA-GNs has carbon-hydrogen bonds and carbon-nitrogen bonds, while the surface of graphite does not contain functional groups. Characteristic peaks such as hydroxyl groups, carbon oxygen groups, and carbon-hydrogen bonds appear on the surface of ODA-GNs / 1EVA, indicating that after the preparation process of Experimental Example 1, components such as polymer (EVA) are combined with the outer layer of graphene. Further combined with the test results of SEM, AFM, and TEM, it can be seen that the addition of components such as polymers and surfactants has little effect on the morphology and size of the generated graphene.

[0118] (5) Using a thermal analyzer, ODA-GNs / 1EVA, ODA-GNs / 2EVA, ODA-GNs / 3EVA, and ODA-GNs / 4EVA were subjected to thermogravimetric analysis in an inert atmosphere (the thermogravimetric process was programmed to increase the temperature at a rate of 5°C / min from room temperature (about 30°C) to 600°C, and was carried out under inert gas protection). The results are shown in Figure 5 and Figure 6 ( Figure 5 is the curve of sample weight changing with temperature, Figure 6 is a graph showing the change of weight loss rate with temperature, and the area enclosed by the curve represents the weight loss). Figure 5 It can be seen that the samples basically began to lose weight at around 250-300℃; Figure 6 It can be seen that the DTG curve has two thermal gravimetric loss peaks. The first thermal gravimetric loss peak is between 300 and 400°C, and the second thermal gravimetric loss peak is between 400 and 500°C. The DTG corresponding to the first thermal gravimetric loss peak is below 70 μg / min, and the DTG corresponding to the second thermal gravimetric loss peak is between 100 and 200 μg / min. This shows that when the polymer (EVA) addition level is low, the polymer is able to composite with the graphene surface generated during the graphite exfoliation process. Increasing the polymer addition level increases the polymer loading on the viscosity reducer product and improves the thermal stability of the viscosity reducer product (i.e., the temperature corresponding to the second thermal gravimetric loss peak increases). Relatively speaking, ODA-GNs / 1EVA has a lower polymer content and a lower temperature corresponding to the second thermal gravimetric loss peak. The polymer and other components in it have weaker binding forces with the graphene surface, allowing their long carbon chains and other groups to be more fully released and expanded in the heavy oil, acting on the internal components of the heavy oil, achieving a better effect of reducing the heavy oil viscosity (see the viscosity reduction experiment below).

[0119] (2-1-2) The characterization test results of the viscosity reducers of Test Examples 2 to 5 are similar to those of Test Example 1. Compared with the viscosity reducers of Test Examples 1 to 5, the characterization test results of Test Examples 6 to 9 show that the polymer in the viscosity reducer is tightly adsorbed on the graphene surface and has a strong binding force. Combined with the following viscosity reduction test results, the polymer is tightly adsorbed on the graphene surface, resulting in the effective structure of the viscosity reducer not being completely released in the heavy oil, which affects the viscosity reduction effect of the viscosity reducer to a certain extent. In addition, Comparative Example 4 prepares a viscosity reducer by slow pressure relief, which cannot effectively strip the graphite. The thickness of the obtained product (M-ODA-GNs / 1EVA) is much greater than the thickness of the viscosity reducers of Test Examples 1 to 9, which is basically the same as the thickness of the graphite raw material, and its viscosity reduction performance is poor.

[0120] (2-2) Viscosity reduction test

[0121] During the following experiments, the apparent viscosity reduction rate = (η0-η x ) / η0, η0 is the viscosity of the heavy oil sample without adding viscosity reducer, mPa·s; η x It indicates the viscosity of heavy oil sample after adding viscosity reducer and treating in mPa·s.

[0122] Net viscosity reduction rate = (η1-η i ) / η1, η1 represents the viscosity of crude oil when pure solvent is added, mPa·s; η i It indicates the viscosity of crude oil when a solvent containing a viscosity reducer (such as the mixed system described below) is added, in mPa·s.

[0123] (2-2-1) Viscosity reduction test

[0124] Liaohe heavy oil (low sulfur naphthenic heavy crude oil) was used as the heavy oil raw material, and the experimental process was as follows:

[0125] (1) The heavy oil raw material was placed in a sealed thermostat and heated to 80°C for 10 hours to remove the thermal history (i.e., to eliminate the stress generated by long-term storage at room temperature inside the heavy oil). The heavy oil raw material was then taken out and divided into 20g (about 20mL) small samples and naturally cooled to room temperature (keeping the seal during the cooling process);

[0126] (2) Take 10 mg of ODA-GNs / 1EVA and dissolve it in 5 mL of toluene to obtain a mixed system for later use;

[0127] (3) With reference to the SY / T 0520-2008 standard “Determination of Crude Oil Viscosity by Rotational Viscometer Balance Method” and the SY / T7549-2000 standard “Determination of Crude Oil Viscosity-Temperature Curve by Rotational Viscometer Method”, the viscosity-temperature curve of heavy oil and the viscosity of heavy oil at 25°C were determined:

[0128] A: Take 20g of the heavy oil sample prepared in step (1), add it to the rheometer sample cell, heat it to 70℃, then keep the rheometer shear rate at 10 1 / s and cool it to 25℃ at a heating rate of 2℃ / min, and keep it for 10 minutes. Through this process, measure the viscosity-temperature curve of the heavy oil sample during the cooling process from 70℃ to 25℃, and the viscosity of the heavy oil at 25℃. The results are shown in Figure 2. Figure 7 ;

[0129] B: Take 20g (about 20mL) of the heavy oil sample prepared in step (1), add it to the rheometer sample cell, heat it to 70℃, and then add 1mL (5% of the volume of the heavy oil) of the mixed system prepared in step (2) (the amount of viscosity reducer added is 100ppm (i.e., the mass of the viscosity reducer accounts for 100ppm of the mass of the heavy oil sample)), stir it evenly, control the system temperature to 70℃, and then program the temperature to 25℃ and hold it for 10 minutes. Through this process, the viscosity-temperature curve of the heavy oil sample after adding the viscosity reducer during the cooling process from 70℃ to 25℃, as well as the viscosity of the heavy oil at 25℃ are measured. The results are shown in Figure 2. Figure 7 (See Figure 7 The apparent viscosity reduction rate and net viscosity reduction rate at 25°C are shown in the curve corresponding to 100ppm in the figure); Figure 8 .

[0130] Referring to the above experimental process, only the amount of viscosity reducer added was changed, and the other conditions remained unchanged. The viscosity-temperature curves when the viscosity reducer addition amount was 300ppm, 500ppm, 700ppm, and 900ppm were measured respectively. The results are shown in Figure 7 (See Figure 7The apparent viscosity reduction rate and net viscosity reduction rate at 25°C were measured when the viscosity reducer addition amount was 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm and 900ppm, respectively. The results are shown in Figure 8 .

[0131] Referring to the above experimental process, only the type of viscosity reducer was changed, and the other conditions remained unchanged. The viscosity-temperature curves and the apparent viscosity reduction rate and net viscosity reduction rate at 25°C were measured using toluene, EVA (EVA (Toluene)), and the materials prepared in Test Examples 2 to Test Examples 9 and Comparative Examples 1 to Comparative Examples 4 as viscosity reducers, and the viscosity reducer addition amount was 300ppm. The results are shown in FIG. Figures 9 to 14 .

[0132] from Figure 7 It can be seen that the viscosity-temperature curve of the heavy oil feedstock without any viscosity reducer has a viscosity sudden increase point at about 65°C, while the viscosity-temperature curve of the heavy oil system with the viscosity reducer has a viscosity sudden increase point at about 50°C. After the viscosity reducer of Test Example 1 is added, the viscosity of the heavy oil system is significantly reduced. The viscosity of the heavy oil can be significantly reduced under both high and low temperature conditions, and the viscosity sudden increase point is delayed by about 10°C, which effectively improves the fluidity of the heavy oil. Among them, the viscosity reduction effect is particularly excellent when the viscosity reducer addition amount is 100ppm to 700ppm.

[0133] In addition, from Figure 7 It can be seen that compared with toluene and EVA, the viscosity reducer of Test Example 1 exhibits better viscosity reducing effect. The viscosity of the heavy oil system is lower at different temperatures, and the temperature corresponding to the viscosity sudden increase point is lower.

[0134] from Figure 8 It can be seen that the apparent viscosity reduction rate and the net viscosity reduction rate after removing the influence of the solvent achieved by the viscosity reducer of Test Example 1 at 25°C are both high, with the apparent viscosity reduction rate reaching more than 88% and the net viscosity reduction rate reaching more than 59%. In particular, when the viscosity reducer addition amount is 100ppm~800ppm, the apparent viscosity reduction rate is as high as more than 90%, and the net viscosity reduction rate is as high as more than 65%.

[0135] In addition, from Figure 9 and Figure 10 It can be seen that the viscosity reducers of Test Examples 2 to 5 also have good viscosity reducing performance. Figure 11 and Figure 12 It can be seen that the viscosity reducers of Test Examples 6 to 9 also have good viscosity reducing performance, but are inferior to the viscosity reducing performance of the viscosity reducer of Test Example 1. Figure 13 and Figure 14It can be seen that the viscosity reducing performance of the viscosity reducers in Comparative Examples 1 to 4 is inferior to that of the viscosity reducer in Test Example 1. It can be seen that different raw materials and the amounts of each raw material affect the performance of the viscosity reducer. Taking Test Example 6 as an example, the polymer used there is polystyrene, which has low polarity and has a special binding force with sheet materials such as graphene. It is relatively difficult to expand in heavy oil and affect its internal structure. Therefore, although it has a certain heavy oil viscosity reducing effect, it is inferior to that of Test Example 1.

[0136] (2-2-2) Analysis of heavy oil after viscosity reduction

[0137] Taking the heavy oil system after viscosity reduction treatment with ODA-GNs / 1EVA as an example, polarizing microscope analysis and SEM analysis of the carbonized heavy oil system after viscosity reduction were carried out.

[0138] (I) Polarizing microscope analysis

[0139] Polarizing microscope was used to analyze the heavy oil raw material without adding viscosity reducer, and polarizing microscope was used to analyze the heavy oil system after viscosity reduction treatment under the conditions of 300ppm viscosity reducer and 25℃ (the pipeline temperature was simulated during the viscosity reduction treatment. The temperature was high when the heavy oil was first transported. The temperature was 70℃ when the viscosity reducer was added to the heavy oil, and then dropped to 25℃ for polarizing microscope analysis). The polarizing microscope images were obtained (see Figure 15 ), Figure 15 (1) is a polarizing microscope image of heavy oil raw material without adding viscosity reducer. Figure 15 (2) is a polarizing microscope image of a heavy oil + toluene system using toluene as a viscosity reducer. Figure 15 (3) is a polarizing microscope image of the heavy oil + EVA system (heavy oil + EVA) using EVA as a viscosity reducer. Figure 15 (4) is a polarizing microscope image of a heavy oil system (heavy oil + nano viscosity reducer) using ODA-GNs / 1EVA as a viscosity reducer.

[0140] Figure 15 (1) in it shows that at low temperature (25 °C), the wax crystals in the heavy oil feedstock are scattered and cross-linked to form a viscoelastic network, which leads to high viscosity of the heavy oil; Figure 15 (2) in the figure shows that the cross-linking of wax crystals did not improve after adding toluene to the heavy oil; Figure 15 (3) shows that after adding EVA to heavy oil, wax precipitates with polymer carbon chains as crystal nuclei, which can destroy the original cross-linking state of heavy oil to a certain extent, but the improvement effect is very low; Figure 15 (4) shows that after adding the viscosity reducer of Test Example 1, the wax precipitates with the composite nanoparticles as the crystal nucleus and becomes independent and dense wax crystals. At the same time, the long carbon chains and polar groups stretched on the surface prevent the formation of viscoelastic networks in the heavy oil, thereby enhancing the fluidity of the heavy oil system.

[0141] (II) SEM analysis of the carbonized heavy oil system after viscosity reduction

[0142] The heavy oil raw material without viscosity reducer in (I) and the heavy oil system with ODA-GNs / 1EVA as viscosity reducer were calcined at 800°C in argon atmosphere for carbonization, and the carbonized products were analyzed by SEM. Figure 16 , Figure 16 (1) is the SEM image of the carbonized product of heavy oil raw material without adding viscosity reducer. It can be seen that after carbonization, the heavy oil raw material is obviously cross-linked and agglomerated, stacked together. Figure 16 (2) is an SEM image of the carbonized product of the heavy oil system using ODA-GNs / 1EVA as a viscosity reducer. It can be seen that after carbonization, the heavy oil after viscosity reduction does not show stacking aggregation of cross-linked agglomerates, which further illustrates that the viscosity reducer prepared by the preparation method of the present invention can greatly destroy the original network structure of wax crystal aggregates in the heavy oil and has an excellent viscosity reduction effect.

[0143] 2. Example 2

[0144] (1) Preparation of viscosity reducer

[0145] (1-1) Test Example 10

[0146] In this test example 10, the preparation process of the viscosity reducing agent is as follows: Figure 19 and Figure 20 The ball milling-assisted supercritical fluid exfoliation device shown in the figure was prepared as follows:

[0147] 300 mL of toluene, 5 g of graphite, 5 g of octadecyl methacrylate, 0.8 g of styrene, and 0.15 g of acrylamide were mixed to prepare a mixed solution; the mixed solution was added to a ball mill reaction tank, the air inlet valve and the outlet valve were closed, the ball mill reaction tank was sealed, the temperature was raised to 60° C., and stirred for 30 minutes, then an initiator (the mass of the initiator was 1% of the total mass of the monomers) was injected into the ball mill reaction tank with a syringe, and the temperature was maintained at 60° C. The ball mill reaction tank was filled with carbon dioxide gas through the air inlet valve until the pressure reached 10 MPa (at this time, the carbon dioxide filled into the ball mill reaction tank was in a supercritical state), and the air inlet valve was closed; then the rotation speed was set to 400 rpm, and the ball mill reaction tank was opened for ball milling for 5 hours;

[0148] After the ball milling is completed, the ball milling stirring and heating are stopped, the outlet valve of the exhaust channel is opened, and the ball milling reaction tank and the buffer tank are connected for pressure relief. Starting from the time when the outlet valve is opened, the pressure in the ball milling reaction tank reaches below 5 MPa within 0.1 s. After the pressure display is stable, the exhaust valve on the buffer tank is opened to connect the ball milling reaction tank and the buffer tank to the outside atmosphere, so that the ball milling reaction tank is pressure-relieved to normal pressure (starting from opening the exhaust valve, it basically reaches normal pressure (gauge pressure is 0) within 60 s). When the temperature and pressure in the ball milling reaction tank and the buffer tank are balanced with the outside (i.e., reaching room temperature and normal pressure), the tank is opened, the materials in the ball milling reaction tank and the buffer tank are taken out, and the crude product obtained by ball milling is separated from the steel balls through a sieve;

[0149] The crude product was washed with ethanol and then dried to obtain a viscosity reducer (graphene powder), which was recorded as GNs@SSA.

[0150] (1-2) Test Example 10 Test Example 11 to Test Example 12

[0151] The difference between Experimental Example 11 and Experimental Example 10 is that the monomers are: 5 g of octadecyl methacrylate, 1.5 g of styrene, and 2 g of maleic anhydride. The other conditions are the same as those in Experimental Example 1. The prepared viscosity reducer is recorded as GNs@SSM.

[0152] The difference between Experimental Example 12 and Experimental Example 10 is that the monomers are: 5 g of octadecyl methacrylate, 0.9 g of styrene, and 0.3 g of fumaric acid. The other conditions are the same as those in Experimental Example 1. The prepared viscosity reducer is recorded as GNs@SSF.

[0153] (2) Viscosity reducer performance test

[0154] During the following experiments, the apparent viscosity reduction rate = (η0-η x ) / η0, η0 is the viscosity of the heavy oil sample without adding viscosity reducer, mPa·s; η x It indicates the viscosity of heavy oil sample after adding viscosity reducer and treating in mPa·s.

[0155] Net viscosity reduction rate = (η1-η i ) / η1, η1 represents the viscosity of crude oil when pure solvent is added, mPa·s; η i It indicates the viscosity of crude oil when a solvent containing a viscosity reducer (such as the mixed system described below) is added, in mPa·s.

[0156] Liaohe heavy oil (low sulfur naphthenic heavy crude oil) was used as the heavy oil raw material for viscosity reduction experiment. The experimental process is as follows:

[0157] (1) The heavy oil raw material was placed in a sealed thermostat and heated to 80°C for 10 hours to remove the thermal history (i.e., to eliminate the stress generated by long-term storage at room temperature inside the heavy oil). The heavy oil raw material was then taken out and divided into 20 g (about 20 mL) small samples and naturally cooled to room temperature (keeping the seal during the cooling process);

[0158] (2) Take 10 mg of viscosity reducer and dissolve it in 5 mL of toluene to obtain a mixed system for later use;

[0159] (3) With reference to the SY / T 0520-2008 standard “Determination of Crude Oil Viscosity by Rotational Viscometer Balance Method” and the SY / T7549-2000 standard “Determination of Crude Oil Viscosity-Temperature Curve by Rotational Viscometer Method”, the viscosity-temperature curve of heavy oil was determined:

[0160] A: Take 20 g of the heavy oil sample prepared in step (1), add it to the rheometer sample cell, heat it to 70°C, then maintain the rheometer shear rate at 10 1 / s and cool it to 25°C at a heating rate of 2°C / min, and hold it for 10 minutes. Through this process, measure the viscosity-temperature curve of the heavy oil sample during the cooling process from 70°C to 25°C;

[0161] B: Take 20 g (about 20 mL) of the heavy oil sample prepared in step (1), add it to the rheometer sample cell, heat it to 70°C, and then add 1 mL (5% of the volume of the heavy oil) of the mixed system prepared in step (2) (the amount of viscosity reducer added is 100 ppm (i.e., the mass of the viscosity reducer powder accounts for 100 ppm of the mass of the heavy oil sample)) and stir evenly. Control the system temperature to 70°C, then program the temperature to 25°C and hold for 10 minutes. Through this process, the viscosity-temperature curve of the heavy oil sample after adding the viscosity reducer during the cooling process from 70°C to 25°C, as well as the viscosity of the heavy oil at 25°C, are measured, and the apparent viscosity reduction rate and net viscosity reduction rate at 25°C are measured.

[0162] Referring to the above experimental process, only the type of viscosity reducer was changed, and the other conditions remained unchanged. The viscosity-temperature curves of toluene, EVA (ethylene-vinyl acetate copolymer), GNs@SSA, GNs@SSM, and GNs@SSF as viscosity reducers, as well as the apparent viscosity reduction rate and net viscosity reduction rate at 25°C were measured. The results are shown in Table 1. Figure 17 and Figure 18 .

[0163] from Figure 17It can be seen that the viscosity-temperature curve of the heavy oil feedstock without any viscosity reducer has a viscosity sudden increase point at around 65°C, while the viscosity-temperature curve of the heavy oil system with the addition of GNs@SSA, GNs@SSM, and GNs@SSF has a viscosity sudden increase point at around 50°C. After the addition of the viscosity reducers of Test Examples 10 to 12 (i.e., GNs@SSA, GNs@SSM, and GNs@SSF), the viscosity of the heavy oil system is significantly reduced. The viscosity of the heavy oil can be significantly reduced under both high and low temperature conditions, and the viscosity sudden increase point is postponed by about 10°C, effectively improving the fluidity of the heavy oil.

[0164] In addition, from Figure 17 It can be seen that compared with toluene and EVA, the viscosity reducers of Test Examples 10 to 12 exhibit good viscosity reducing effects. The viscosity of the heavy oil system is significantly reduced at different temperatures, and the temperature corresponding to the viscosity sudden increase point is lower.

[0165] from Figure 18 It can be seen that the apparent viscosity reduction rate and the net viscosity reduction rate after removing the influence of the solvent at 25°C achieved by using the viscosity reducers of Test Examples 10 to 12 are significantly improved, among which the apparent viscosity reduction rate reaches more than 89% and the net viscosity reduction rate reaches more than 65%.

[0166] 3. Example 3

[0167] The difference between Example 3 and Experimental Example 10 is that the mixed solution for preparing the viscosity reducer in Example 3 also contains the surfactant ODA, and the mass ratio of graphite to ODA is approximately 10:1.5. The other conditions are the same as the viscosity reducer preparation process of Experimental Example 10.

[0168] Referring to the viscosity reduction test process in Section "II. Viscosity Reducer Performance Test" of Example 2, the viscosity reduction performance of the viscosity reducer prepared in Example 3 was measured (except for the different viscosity reducers used, the remaining conditions were essentially the same as the viscosity reduction test process in Section "II. Viscosity Reducer Performance Test" of Example 2). The test showed that the viscosity reducer prepared in Example 3 exhibited a superior viscosity reduction effect than the viscosity reducer of Test Example 10.

[0169] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite viscosity reducer, characterized in that: include: placing a mixed solution containing aggregated nanomaterials, an organic additive, and a solvent in a ball milling reaction tank, injecting gas into the mixed solution until the gas injected into the ball milling reaction tank reaches a supercritical state, and subjecting the mixed solution to ball milling treatment in the supercritical state; then depressurizing the ball milling reaction tank to normal pressure, taking out the obtained crude product, and purifying the crude product to obtain the composite viscosity reducer; Wherein, the organic auxiliary agent includes a polymer and / or a monomer. When the monomer is included, the monomer undergoes a polymerization reaction during the ball milling process; The mixed solution also contains a surfactant, wherein The surfactant includes cetyltrimethylammonium bromide and / or octadecylamine; The mass ratio of the aggregated nanomaterial to the surfactant is 10:(0.5-3); The aggregated nanomaterial includes at least one of graphite powder, powdered molybdenum disulfide, powdered boron nitride, attapulgite, and montmorillonite; The polymer includes at least one of ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl alcohol terpolymer, and a multipolymer polymerized from at least three monomers selected from octadecyl methacrylate, styrene, maleic anhydride, acrylamide, and fumaric acid; The monomer includes at least one of octadecyl methacrylate, styrene, acrylamide, fumaric acid, and maleic anhydride; The process of depressurizing the ball mill reaction tank to normal pressure includes a rapid depressurization process, and the rapid depressurization satisfies the following conditions: from the start of depressurization, the pressure in the ball mill reaction tank reaches no more than half of the pressure in the supercritical state within 5 seconds.

2. The method for preparing a composite viscosity reducer according to claim 1, wherein The solvent includes at least one of ethanol, toluene, xylene, N,N-dimethylformamide, kerosene, and diesel.

3. The method for preparing a composite viscosity reducer according to claim 1 or 2, wherein: The mass ratio of the aggregated nanomaterial to the polymer is 10:(1-12); and / or, The mass ratio of the aggregated nanomaterial to the monomer is 5:(5-10); and / or, The mass volume ratio of the aggregated nanomaterial to the solvent is 10 g: (40-80) mL.

4. The method for preparing a composite viscosity reducer according to claim 1, wherein: The gas comprises carbon dioxide; and / or, The supercritical state conditions are: temperature controlled within the range of 40-80°C, pressure controlled within the range of 10-20 MPa; and / or, The ball milling treatment time is 2 to 6 hours.

5. The method for preparing a composite viscosity reducer according to claim 1, wherein: The viscosity reducer is prepared using a ball milling-assisted supercritical fluid stripping device, the device comprising a buffer tank and the ball milling reaction tank, the ball milling reaction tank and the buffer tank being connected via an exhaust channel, the exhaust channel being provided with an outlet valve, the ball milling reaction tank being provided with an air inlet valve, and the buffer tank being provided with an exhaust valve, the volume of the ball milling reaction tank being V1, the volume of the buffer tank being V2, and V2 being ≥ 2V1, and the preparation method comprising: The mixed liquid is placed in a ball milling reaction tank, the outlet valve is kept closed, and the gas is injected into the ball milling reaction tank through the air inlet valve until the gas injected into the ball milling reaction tank is in a supercritical state, and then the air inlet valve is closed, and ball milling treatment is carried out under the supercritical state; after the ball milling treatment is completed, the exhaust valve of the buffer tank is kept closed, and the outlet valve is opened to connect the ball milling reaction tank and the buffer tank to relieve the pressure of the ball milling reaction tank, and from the time of opening the outlet valve, the pressure in the ball milling reaction tank is relieved to half of the pressure in the supercritical state within 5 seconds to achieve rapid pressure relief; then the exhaust valve of the buffer tank is opened to connect the ball milling reaction tank and the buffer tank with the external atmosphere to relieve the pressure of the ball milling reaction tank to normal pressure; then the crude product is taken out, and after the purification treatment, the viscosity reducer is obtained.

6. A composite viscosity reducer, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 5.

7. A method for reducing the viscosity of heavy oil, characterized in that: The method comprises using the composite viscosity reducer according to claim 6 to reduce the viscosity of heavy oil raw materials.

8. The method for reducing the viscosity of heavy oil according to claim 7, characterized in that: The heavy oil feedstock includes paraffin-based heavy oil and / or naphthenic heavy oil; and / or, The dosage of the composite viscosity reducer is controlled as follows: the mass of the composite viscosity reducer is 50ppm-1000ppm of the mass of the heavy oil raw material.

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