Plant-based nano petroleum viscosity reducer and preparation method thereof

Abstract

The invention relates to the technical field of oil exploitation, in particular to a plant-based nano oil viscosity reducer and a preparation method thereof. The environment-friendly water-based cleaning agent is prepared from the following raw materials in parts by weight: 5 to 10 parts of vegetable oil-based surfactant, 3 to 6 parts of composite biological enzyme, 2 to 5 parts of emulsifier, 1 to 3 parts of penetrant, 40 to 60 parts of bentonite-based composite material, 25 to 35 parts of nano silicate, 0.3 to 0.8 part of stabilizer, 0.1 to 0.6 part of wetting agent and 120 to 150 parts of water. The plant-based nano petroleum viscosity reducer disclosed by the invention is composed of the plant-based raw materials, the matched inorganic materials and the macromolecular organic materials, so that an efficient pressure-bearing zone can be formed in a gap on a rock stratum, the stability of the rock stratum is enhanced, a well wall is stabilized in a crude oil exploitation process, and the viscosity of the crude oil is reduced; and meanwhile, heavy oil on the surfaces of rock minerals can be rapidly stripped, the complexing force of polycyclic aromatic hydrocarbon and the rock minerals is reduced, the oil-water interfacial tension is effectively reduced, petroleum is fully emulsified, the viscosity is reduced, and the flowability of the petroleum is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum extraction, in particular to a plant-based nano petroleum viscosity reducer and a preparation method thereof. Background Art

[0002] As we all know, heavy oil has high viscosity and density, which makes it difficult to drive in the reservoir environment and has too much flow resistance during transportation. Therefore, the exploitation of heavy oil faces a series of problems such as high cost and difficulty in exploitation. In terms of chemical composition, heavy oil is mainly a mixture of various hydrocarbons and non-hydrocarbons. The relative content of various components is different, and their physical properties are also different. Among them, the content of asphaltene and colloid in heavy oil is particularly high, and their structure is complex and the molecular weight is large. Microstructural studies on the interaction of asphaltene and colloid show that their molecules contain a large number of hydroxyl, carboxyl or amino groups, forming strong hydrogen bond interactions between colloid molecules, between asphaltene molecules, and between colloid and asphaltene molecules. At the same time, the aromatic condensed ring planes of asphaltene molecules overlap and stack together, and are fixed by hydrogen bonds between polar groups to form asphaltene particles. The colloid molecules overlap and stack on the surface of asphaltene particles with aromatic condensed ring planes, and are fixed by hydrogen bonds to form a coating layer of asphaltene particles. These particles are then connected to each other through multiple hydrogen bonds to form supramolecular aggregates, which ultimately create the high viscosity characteristics of heavy oil.

[0003] Therefore, in order to reduce the viscosity of heavy oil, its aggregate structure must be broken. For example, Chinese patent CN113755147A discloses a petroleum viscosity reducer and its preparation process, which specifically includes (A) preparing raw materials by weight, weighing diethanolamine, dichloroethane, epichlorohydrin, polyacrylate, alkylphenol polyoxyethylene ether, polyethylene glycol, octadecanoyl chloride, phosphorus pentoxide, sodium hydroxide, and deionized water; (B) adding diethanolamine and dichloroethane to a mixing container A in a petroleum viscosity reducer preparation device, controlling the temperature in the mixing container to 60-100°C, and continuously introducing nitrogen protection into the mixing container, and obtaining a mixture A after stirring; (C) then adding epichlorohydrin, polypropylene, and propylene glycol to the mixture; (D) adding diethanolamine and dichloroethane to the mixture; (E) adding epichlorohydrin, polypropylene, and propylene glycol to the mixture; (F) adding epichlorohydrin, polypropylene, and propylene glycol to the mixture; (F) adding epichlorohydrin, polypropylene, and propylene glycol to the mixture; (F) adding epichlorohydrin, polypropylene, and propylene glycol to the mixture; (G ... Acid esters, alkylphenol polyoxyethylene ether and deionized water are stirred and mixed in a mixing container B in a petroleum viscosity reducer preparation device to obtain a mixture B; (D) the mixture B is then dripped into the mixture A in the mixing container A, with 1-2 drops being dripped per second until the mixture B is completely dripped into the mixture A; although the petroleum viscosity reducer can reduce the viscosity of crude oil to a certain extent and improve the recovery rate of crude oil, as the crude oil separates from the rock layer where it is adsorbed, the rock layer loses the filling of crude oil, the structure of the rock layer will change, microcracks are likely to appear, resulting in instability of the well wall structure, which is likely to cause well wall collapse accidents. Summary of the invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a plant-based nano-petroleum viscosity reducer and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions: A plant-based nano-petroleum viscosity reducer, wherein the raw materials include, by weight, 5-10 parts of a plant oil-based surfactant, 3-6 parts of a composite biological enzyme, 2-5 parts of an emulsifier, 1-3 parts of a penetrant, 40-60 parts of a bentonite-based composite material, 25-35 parts of a nano-silicate, 0.3-0.8 parts of a stabilizer, 0.1-0.6 parts of a wetting agent, and 120-150 parts of water; The vegetable oil-based surfactant is at least one of a castor oil-based surfactant, a palm oil-based surfactant, and a soybean oil-based surfactant; The composite biological enzyme is composed of esterase, protease, laccase and peroxidase in a mass ratio of 1: (1.2-1.8): (1.0-1.3): (2.0-2.5); The emulsifier is a biological emulsifier, selected from any one of xanthan gum and rhamnolipid; The penetrant is a mixture of alkyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether in a mass ratio of 1: (1.0-1.3); The wetting agent is polyethylene glycol; The stabilizer is at least one of disodium EDTA and sodium citrate.

[0006] As a further preferred embodiment of the present invention, the bentonite-based composite material is prepared by the following method: 1) preparing a polyvinyl alcohol aqueous solution, and then mixing the zinc acetate and polyvinyl alcohol in a mass ratio of 1: (3-5), fully mixing the zinc acetate and polyvinyl alcohol solutions to obtain a mixed solution, and then immersing the porous graphene oxide in the mixed solution, placing it in an oven for heat treatment, and then transferring it to a muffle furnace for calcination to obtain a composite nanomaterial; 2) The composite nanomaterial is dispersed in deionized water to obtain a nanomaterial dispersion, and then the nano-iron tetroxide particles are added to the dispersion at a solid-liquid ratio of 1: (80-120) g / mL, mechanically stirred for 1-2 hours, and then subjected to ultrasonic treatment for 1-2 hours. After the treatment is completed, the modified bentonite is added thereto at a solid-liquid ratio of 1: (50-70) g / mL, and after shaking on a shaker for 50-80 minutes, the desired bentonite-based composite material is obtained by washing and drying by centrifugation.

[0007] Furthermore, the heat treatment is specifically performed by heating the temperature to 120-145°C at a rate of 5-8°C / min, keeping the temperature for 1-3h, and then heating the temperature to 200-210°C at a rate of 3-6°C / min, and keeping the temperature for 1-2h; The calcination treatment is specifically performed as follows: calcining at 300-310°C for 30-50min, then heating to 410-420°C at a rate of 5-8°C / min, keeping the temperature for 30-50min, then heating to 540-560°C at a rate of 5-8°C / min, and keeping the temperature for 1-3h.

[0008] Furthermore, the porous graphene oxide is prepared by chemical concentrated acid etching, wherein the concentrated acid is fully mixed with a graphene oxide dispersion having a concentration of 0.5-2.5 mg / mL, wherein the volume ratio of the graphene oxide dispersion to the concentrated acid is 1:(3-8); the mixture is ultrasonically reacted at 200-300 W for 1-2 hours, and then allowed to stand at room temperature, and the concentrated acid is removed by centrifugation, and then dried, wherein the concentrated acid is selected from any one or a combination of concentrated sulfuric acid, concentrated nitric acid, and concentrated phosphoric acid.

[0009] Furthermore, the polyvinyl alcohol aqueous solution has a concentration of 1-5wt%; The nano-dispersion liquid has a solid content of 5-10wt%; The mechanical stirring speed is 1000-1500r / min; The ultrasonic effect has a power of 500-800W; The shaking table oscillates at a speed of 500-800 r / min.

[0010] As a further preferred embodiment of the present invention, the modified bentonite is prepared by the following method: 1) Dissolve potassium antimony tartrate in deionized water, stir thoroughly to dissolve, add polyvinyl pyrrolidone, stir thoroughly to form a mixed solution, then add thioacetamide to the mixed solution, mix thoroughly to obtain a reaction solution; 2) Add the pretreated bentonite to the reaction solution, stir for 20-50 minutes, and after ultrasonic oscillation for 30-40 minutes, transfer to a reactor and heat at a constant temperature of 180-200°C for 24-28 hours. After the reaction is completed, cool to room temperature, wash by centrifugation, and dry to obtain modified bentonite.

[0011] Furthermore, the ratio of potassium antimony tartrate, deionized water, polyvinyl pyrrolidone, and thioacetamide is (7.5-11.0) g: (30-70) mL: (0.2-0.3) g: (1.3-2.0) g; The stirring speed is 180-260r / min; The ultrasonic oscillation has a power of 200-300W.

[0012] As a further preferred embodiment of the present invention, the pretreated bentonite is prepared by the following method: 1) Add 1.1-1.8g of bismuth nitrate to 30-60mL of deionized water, stir thoroughly to dissolve, and obtain a bismuth nitrate solution. Then add 0.3-0.5g of sodium tungstate to 45-80mL of deionized water, stir thoroughly to dissolve, and obtain a sodium tungstate solution. 2) Add the sodium tungstate solution to the bismuth nitrate solution, stir thoroughly and transfer to a high-temperature reactor, react at 160-170°C for 16-20 hours, cool naturally to room temperature, centrifuge, wash repeatedly with deionized water and ethanol, and dry to obtain flower-like nanoparticles; 3) After drying and crushing the bentonite and removing sand by multi-stage water washing, bentonite powder is obtained, the flower-shaped nanoparticles are dispersed in deionized water, and the dispersion is obtained after uniform ultrasonic dispersion. Then, according to a certain solid-liquid ratio, the bentonite powder is placed in a vacuum impregnation tank, evacuated to 50-80Pa, maintained for 20-30min, and then the dispersion is injected. The vacuum is continued to be maintained for 20-30min under the action of 200-300W ultrasound, and the pressure is slowly released to normal pressure. After centrifugal washing, it is dried to obtain the pretreated bentonite.

[0013] Furthermore, the dispersion has a solid content of 1-3 wt %; The solid-liquid ratio is 1: (100-130) g / mL.

[0014] A method for preparing a plant-based nano-petroleum viscosity reducer comprises the following steps: Under normal pressure and 50-58℃, slowly add penetrant, wetting agent and stabilizer into water in turn, stir until mixed evenly, raise the temperature to 92-97℃, then add bentonite-based composite materials and nano-silicate, sterilize and then naturally cool to 26-30℃, add vegetable oil-based surfactant, compound biological enzyme and emulsifier, and mix evenly.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, firstly, bismuth nitrate and sodium tungstate are used as precursors to obtain flower-shaped nanoparticles through hydrothermal reaction, and then bentonite is dried, crushed and sanded, and then the flower-shaped nanoparticles are injected into the multi-layer structure of bentonite through vacuum impregnation to obtain pretreated bentonite. In the impregnation process, ultrasonic action is applied to increase the depth and firmness of the nanoparticles embedded in the gaps of the bentonite layer structure. By embedding the nanoparticles, on the one hand, the stability of the layer structure can be increased to avoid the collapse of the layer structure. At the same time, the embedded nanoparticles, due to the petal-shaped outer protrusion structure, can effectively increase the specific surface area and surface roughness of the bentonite, which is conducive to the subsequent deposition of antimony sulfide particles on the surface of the bentonite and forming a stable network structure. Secondly, potassium antimony tartrate and thioacetamide are used as The invention uses antimony source and sulfur source as the deposition matrix, and uses pretreated bentonite as the deposition matrix. Antimony sulfide nanoparticles are deposited on the flower-like structure between the pretreated bentonite layers through hydrothermal reaction. As the reaction proceeds, agglomeration occurs between the antimony sulfide particles, and some network structures grow from the surface. As the antimony sulfide particles gradually disappear, the network structure continues to grow, thereby forming a continuous network structure between the bentonite layers, thereby obtaining modified bentonite. The formation of the network structure can play a good role in transmitting and dispersing stress, and enhance the resistance of the modified bentonite to external forces. By introducing it into the petroleum viscosity reducer, it can be well attached to the cracks on the rock layer to form an efficient pressure-bearing belt, play a supporting role in the cracks, and enhance the stability of the rock layer. In the process of crude oil extraction, the well wall is stabilized and complex accidents such as shrinkage and collapse are not likely to occur.

[0016] At the same time, in order to further enhance the stability of the well wall, in the present invention, zinc acetate and polyvinyl alcohol are used, and the zinc cation interacts with the hydroxyl group on the polyvinyl alcohol to enrich the zinc acetate in the gap of the polyvinyl alcohol, and decomposes in the gap formed by the polyvinyl alcohol through step-by-step rapid heating, and the zinc oxide nanowires are obtained by controlling the heating, and porous graphene oxide is added to the reaction solution, so that the formed zinc oxide nanowires are embedded in the holes of the porous graphene oxide, and are entangled and cross-linked, thereby forming a stable composite nanomaterial, and in order to enhance the bonding strength of the two, vacuum impregnation is performed, assisted by mechanical stirring and ultrasonic action, so that the nano-iron tetroxide particles can be better embedded in the hole gaps where the zinc oxide nanowires and the porous graphene oxide are combined, and the bonding stability of the two is enhanced; finally, modified bentonite is added by shaking, and the nanowires in the composite nanomaterial are very easy to be entangled and cross-linked with the network structure in the modified bentonite, so that they are combined and fixed together to obtain a bentonite-based composite. The invention discloses a material, and because the introduced nano-iron tetroxide particles are magnetic, when they remain in the crude oil, they can be removed by simple magnetic adsorption, and no impurities will be formed in the crude oil. The porous graphene oxide is a lamellar structure, which is easier to be embedded in the fine cracks of the rock layer, and is firmly embedded in the deep cracks of the rock layer, and the zinc oxide nanowires act as a traction rope, pulling the modified bentonite to move into the rock cracks, so that the bentonite-based composite material is completely embedded in the cracks, and plays a role in filling and supporting the cracks, thereby enhancing the stability of the well wall. Moreover, in the cracks, a certain degree of cross-linking will occur between the zinc oxide nanowires to form a network structure, so that an inner and outer double-layer network structure is formed in the bentonite-based composite material, while achieving enhanced resistance to external forces, the hydrated and dispersed clay in the well wall can also be retained to avoid the loss of clay in the well wall, thereby further enhancing the stability of the well wall, so that the well wall structure is stable during crude oil extraction, and accidents such as collapse are not easy to occur.

[0017] The plant-based nano-petroleum viscosity reducer of the present invention is composed of plant-based raw materials, inorganic materials and high molecular organic materials. The plant oil-based surfactant and composite enzyme in the plant-based raw materials are used in combination with penetrants, wetting agents, emulsifiers and stabilizers to quickly peel off the thick oil on the surface of rock minerals, destroy the polycyclic aromatic structure formed by porphyrin heavy metals in the thick oil, reduce the complexing force between polycyclic aromatic hydrocarbons and rock minerals, and effectively reduce the oil-water interfacial tension, fully emulsify the oil and reduce the viscosity, thereby greatly improving the fluidity of the oil. The bentonite-based composite material in the inorganic material can It forms an efficient pressure-bearing zone by attaching to the cracks in the rock layer, plays a supporting role in the cracks, enhances the stability of the rock layer, and stabilizes the well wall during crude oil extraction, making it less likely to have complex accidents such as shrinkage and collapse. At the same time, the porous graphene oxide in the bentonite-based composite material, used in combination with nano-silicates, can penetrate between the colloid and asphaltene flaky molecules, break up the aggregates formed by the stacking of colloid and asphaltene, destroy the spatial network structure formed by asphaltene and colloid, and release the light components of the petroleum wrapped therein, thereby effectively reducing the viscosity. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only 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 creative work are within the scope of protection of the present invention.

[0019] In an embodiment of the present invention, the vegetable oil-based surfactant is a castor oil-based surfactant; The composite biological enzyme is composed of esterase, protease, laccase and peroxidase in a mass ratio of 1:1.2:1.3:2.5; The emulsifier is a biological emulsifier selected from xanthan gum; The penetrant is a mixture of alkyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1.3; The wetting agent is polyethylene glycol; The stabilizer is disodium EDTA.

[0020] Example 1 A plant-based nano-petroleum viscosity reducer, the raw materials of which include, by weight, 5 parts of a plant oil-based surfactant, 3 parts of a composite biological enzyme, 2 parts of an emulsifier, 1 part of a penetrant, 40 parts of a bentonite-based composite material, 25 parts of a nano-silicate, 0.3 parts of a stabilizer, 0.1 parts of a wetting agent, and 120 parts of water; The preparation method of the plant-based nano petroleum viscosity reducer comprises the following steps: Under normal pressure and 50°C, slowly add the penetrant, wetting agent and stabilizer to the water in turn, stir until mixed evenly, raise the temperature to 92°C, then add the bentonite-based composite material and nano-silicate, sterilize and then naturally cool to 26°C, add the vegetable oil-based surfactant, compound biological enzyme and emulsifier, and mix evenly.

[0021] The method for preparing the bentonite-based composite material comprises the following steps: 1) Add 1.1g of bismuth nitrate to 30mL of deionized water, stir thoroughly to dissolve, and obtain a bismuth nitrate solution. Then add 0.3g of sodium tungstate to 45mL of deionized water, stir thoroughly to dissolve, and obtain a sodium tungstate solution. 2) Add the sodium tungstate solution to the bismuth nitrate solution, stir thoroughly and transfer to a high-temperature reactor, react at 160°C for 16 hours, cool naturally to room temperature, centrifuge, wash repeatedly with deionized water and ethanol, and dry to obtain flower-like nanoparticles; 3) After drying and crushing the bentonite and washing the bentonite with multiple stages to remove sand, a bentonite powder is obtained, and the flower-shaped nanoparticles are dispersed in deionized water, and a dispersion with a solid content of 1 wt% is obtained after uniform ultrasonic dispersion. Then, the bentonite powder is placed in a vacuum impregnation tank at a solid-liquid ratio of 1:100 g / mL, and the vacuum is evacuated to 50 Pa. After maintaining for 20 minutes, the dispersion is injected, and the pressure is continued to be maintained for 20 minutes under the action of 200 W ultrasound, and the pressure is slowly released to normal pressure. After centrifugal washing, it is dried to obtain a pretreated bentonite; 4) Dissolve 7.5 g of potassium antimony tartrate in 30 mL of deionized water, stir thoroughly to dissolve, add 0.2 g of polyvinyl pyrrolidone, stir thoroughly to form a mixed solution, then add 1.3 g of thioacetamide to the mixed solution, mix well, and obtain a reaction solution; 5) Add the pretreated bentonite to the reaction solution, stir at a speed of 180 r / min for 20 min, and after 200 W ultrasonic oscillation for 30 min, transfer to a reactor and heat at a constant temperature of 180 ° C for 24 h. After the reaction is completed, cool to room temperature, centrifuge and wash, and then dry to obtain modified bentonite; 6) Prepare a polyvinyl alcohol aqueous solution with a concentration of 1wt%, and then mix the zinc acetate and polyvinyl alcohol in a mass ratio of 1:3, fully mix the zinc acetate and polyvinyl alcohol solutions to obtain a mixed solution, and then immerse the porous graphene oxide in the mixed solution, place it in an oven, and heat it to 120°C at a rate of 5°C / min, keep it warm for 1h, then heat it to 200°C at a rate of 3°C / min, keep it warm for 1h, then transfer it to a muffle furnace, roast it at 300°C for 30min, then heat it to 410°C at a rate of 5°C / min, keep it warm for 30min, then heat it to 540°C at a rate of 5°C / min, keep it warm for 1h, and then obtain a composite nanomaterial; 7) The composite nanomaterial is dispersed in deionized water to obtain a nanomaterial dispersion with a solid content of 5 wt%, and then the nano-iron tetroxide particles are added to the dispersion at a solid-liquid ratio of 1:80 g / mL, and mechanically stirred at 1000 r / min for 1 hour, and then subjected to 500 W ultrasonic treatment for 1 hour. After the treatment is completed, the modified bentonite is added thereto at a solid-liquid ratio of 1:50 g / mL, and after shaking on a shaker at 500 r / min for 50 minutes, the dispersion is centrifuged, washed, and dried to obtain the desired bentonite-based composite material; Among them, the porous graphene oxide is prepared by a chemical concentrated acid etching method, wherein concentrated sulfuric acid is fully mixed with a graphene oxide dispersion having a concentration of 0.5 mg / mL, wherein the volume ratio of the graphene oxide dispersion to the concentrated acid is 1:3; after the mixture is ultrasonically reacted at 200 W for 1 hour, it is allowed to stand at room temperature, the concentrated sulfuric acid is removed by centrifugal separation, and then it is dried.

[0022] Example 2 A plant-based nano-petroleum viscosity reducer, the raw materials of which include 8 parts of plant oil-based surfactant, 5 parts of composite biological enzyme, 3 parts of emulsifier, 2 parts of penetrant, 52 parts of bentonite-based composite material, 30 parts of nano-silicate, 0.5 parts of stabilizer, 0.3 parts of wetting agent and 130 parts of water in parts by weight; The preparation method of the plant-based nano petroleum viscosity reducer comprises the following steps: Under normal pressure and 53°C, slowly add the penetrant, wetting agent and stabilizer to the water in turn, stir until mixed evenly, raise the temperature to 95°C, then add the bentonite-based composite material and nano-silicate, sterilize and then naturally cool to 28°C, add the vegetable oil-based surfactant, compound biological enzyme and emulsifier, and mix evenly.

[0023] The method for preparing the bentonite-based composite material comprises the following steps: 1) Add 1.5g of bismuth nitrate to 50mL of deionized water, stir thoroughly to dissolve, and obtain a bismuth nitrate solution. Then add 0.4g of sodium tungstate to 65mL of deionized water, stir thoroughly to dissolve, and obtain a sodium tungstate solution. 2) Add the sodium tungstate solution to the bismuth nitrate solution, stir thoroughly and transfer to a high-temperature reactor, react at 165°C for 18 hours, cool naturally to room temperature, centrifuge, wash repeatedly with deionized water and ethanol, and dry to obtain flower-like nanoparticles; 3) After drying and crushing the bentonite and washing the bentonite with multiple stages to remove sand, a bentonite powder is obtained, and the flower-shaped nanoparticles are dispersed in deionized water, and a dispersion with a solid content of 2 wt% is obtained after uniform ultrasonic dispersion. Then, the bentonite powder is placed in a vacuum impregnation tank at a solid-liquid ratio of 1:120 g / mL, and the vacuum is evacuated to 70 Pa. After maintaining for 25 minutes, the dispersion is injected, and the pressure is continued to be maintained for 25 minutes under the action of 250 W ultrasound, and the pressure is slowly released to normal pressure. After centrifugal washing, it is dried to obtain a pretreated bentonite; 4) Dissolve 9.6 g of potassium antimony tartrate in 60 mL of deionized water, stir thoroughly to dissolve, add 0.26 g of polyvinyl pyrrolidone, stir thoroughly to form a mixed solution, then add 1.7 g of thioacetamide to the mixed solution, mix well, and obtain a reaction solution; 5) Add the pretreated bentonite to the reaction solution, stir at a speed of 230 r / min for 40 min, and after 250 W ultrasonic oscillation for 35 min, transfer to a reactor and heat at a constant temperature of 190 ° C for 26 h. After the reaction is completed, cool to room temperature, wash by centrifugation, and then dry to obtain modified bentonite; 6) Prepare a polyvinyl alcohol aqueous solution with a concentration of 3wt%, and then mix the zinc acetate and polyvinyl alcohol in a mass ratio of 1:4, fully mix the zinc acetate and polyvinyl alcohol solutions to obtain a mixed solution, and then immerse the porous graphene oxide in the mixed solution, place it in an oven, and heat it to 135°C at a rate of 7°C / min, keep it warm for 2h, then heat it to 205°C at a rate of 5°C / min, keep it warm for 1.5h, then transfer it to a muffle furnace, roast it at 305°C for 40min, then heat it to 415°C at a rate of 7°C / min, keep it warm for 40min, then heat it to 550°C at a rate of 7°C / min, keep it warm for 2h, and obtain a composite nanomaterial; 7) The composite nanomaterial is dispersed in deionized water to obtain a nanomaterial dispersion with a solid content of 7 wt%, and then the nano-iron tetroxide particles are added to the dispersion at a solid-liquid ratio of 1:100 g / mL, and mechanically stirred at 1200 r / min for 1.5 h, and then subjected to 700 W ultrasonic treatment for 1.5 h. After the treatment is completed, the modified bentonite is added thereto at a solid-liquid ratio of 1:60 g / mL, and after shaking on a shaker at 700 r / min for 60 min, the desired bentonite-based composite material is obtained by washing and drying. Among them, the porous graphene oxide is prepared by a chemical concentrated acid etching method, wherein concentrated sulfuric acid is fully mixed with a graphene oxide dispersion having a concentration of 1.5 mg / mL, wherein the volume ratio of the graphene oxide dispersion to the concentrated acid is 1:5; the mixture is ultrasonically reacted at 250 W for 1.5 hours, and then allowed to stand at room temperature, and the concentrated sulfuric acid is removed by centrifugation, and then dried.

[0024] Example 3 A plant-based nano-petroleum viscosity reducer, the raw materials of which include, by weight, 10 parts of a plant oil-based surfactant, 6 parts of a composite biological enzyme, 5 parts of an emulsifier, 3 parts of a penetrant, 60 parts of a bentonite-based composite material, 35 parts of a nano-silicate, 0.8 parts of a stabilizer, 0.6 parts of a wetting agent, and 150 parts of water; The preparation method of the plant-based nano petroleum viscosity reducer comprises the following steps: Under normal pressure and 58°C, slowly add the penetrant, wetting agent and stabilizer to the water in turn, stir until mixed evenly, raise the temperature to 97°C, then add the bentonite-based composite material and nano-silicate, sterilize and then naturally cool to 30°C, add the vegetable oil-based surfactant, compound biological enzyme and emulsifier, and mix evenly.

[0025] The method for preparing the bentonite-based composite material comprises the following steps: 1) Add 1.8g of bismuth nitrate to 60mL of deionized water, stir thoroughly to dissolve, and obtain a bismuth nitrate solution. Then add 0.5g of sodium tungstate to 80mL of deionized water, stir thoroughly to dissolve, and obtain a sodium tungstate solution. 2) Add the sodium tungstate solution to the bismuth nitrate solution, stir thoroughly and transfer to a high-temperature reactor, react at 170°C for 20 hours, cool naturally to room temperature, centrifuge, wash repeatedly with deionized water and ethanol, and dry to obtain flower-like nanoparticles; 3) After drying and crushing the bentonite and washing the bentonite with multiple stages to remove sand, a bentonite powder is obtained, and the flower-shaped nanoparticles are dispersed in deionized water, and a dispersion with a solid content of 3 wt% is obtained after uniform ultrasonic dispersion. Then, the bentonite powder is placed in a vacuum impregnation tank at a solid-liquid ratio of 1:130 g / mL, and the vacuum is evacuated to 80 Pa. After maintaining for 30 minutes, the dispersion is injected, and the pressure is continued to be maintained for 30 minutes under the action of 300 W ultrasound, and the pressure is slowly released to normal pressure. After centrifugal washing, it is dried to obtain a pretreated bentonite; 4) Dissolve 11.0 g of potassium antimony tartrate in 70 mL of deionized water, stir thoroughly to dissolve, add 0.3 g of polyvinyl pyrrolidone, stir thoroughly to form a mixed solution, then add 2.0 g of thioacetamide to the mixed solution, mix well, and obtain a reaction solution; 5) Add the pretreated bentonite to the reaction solution, stir at a speed of 260 r / min for 50 min, and after 300 W ultrasonic oscillation for 40 min, transfer to a reactor and heat at a constant temperature of 200 ° C for 28 h. After the reaction is completed, cool to room temperature, wash by centrifugation, and dry to obtain modified bentonite; 6) Prepare a polyvinyl alcohol aqueous solution with a concentration of 5wt%, and then mix the zinc acetate and polyvinyl alcohol in a mass ratio of 1:5, fully mix the zinc acetate and polyvinyl alcohol solutions to obtain a mixed solution, and then immerse the porous graphene oxide in the mixed solution, place it in an oven, and heat it to 145°C at a rate of 8°C / min, keep it warm for 3h, then heat it to 210°C at a rate of 6°C / min, keep it warm for 2h, then transfer it to a muffle furnace, roast it at 310°C for 50min, then heat it to 420°C at a rate of 8°C / min, keep it warm for 50min, then heat it to 560°C at a rate of 8°C / min, keep it warm for 3h, and then obtain a composite nanomaterial; 7) The composite nanomaterial is dispersed in deionized water to obtain a nanomaterial dispersion with a solid content of 10 wt%, and then the nano-iron tetroxide particles are added to the dispersion at a solid-liquid ratio of 1:120 g / mL, and mechanically stirred at 1500 r / min for 2 hours, and then subjected to 800 W ultrasonic treatment for 2 hours. After the treatment is completed, the modified bentonite is added thereto at a solid-liquid ratio of 1:70 g / mL, and after shaking on a shaker at 800 r / min for 80 minutes, the desired bentonite-based composite material is obtained by washing and drying. Among them, the porous graphene oxide is prepared by a chemical concentrated acid etching method, wherein concentrated sulfuric acid is fully mixed with a graphene oxide dispersion having a concentration of 2.5 mg / mL, wherein the volume ratio of the graphene oxide dispersion to the concentrated acid is 1:8; after the mixture is ultrasonically reacted at 300 W for 2 hours, it is allowed to stand at room temperature, the concentrated sulfuric acid is removed by centrifugal separation, and then it is dried.

[0026] Comparative Example 1: This comparative example is substantially the same as Example 1, except that it does not contain the bentonite-based composite material.

[0027] Comparative Example 2: This comparative example is basically the same as Example 1, except that 1)-2) are omitted in the preparation of the bentonite-based composite material.

[0028] Comparative Example 3: This comparative example is basically the same as Example 1, except that 4)-5) are omitted in the preparation of the bentonite-based composite material.

[0029] Comparative Example 4: This comparative example is substantially the same as Example 1, except that, in the preparation of the bentonite-based composite material, step 6) is omitted.

[0030] Comparative Example 5: This comparative example is substantially the same as Example 1, except that in step 6) of preparing the bentonite-based composite material, graphene oxide is used instead of porous graphene oxide.

[0031] Comparative Example 6: This comparative example is basically the same as Example 1, except that, in the preparation of the bentonite-based composite material, the nano-ferrosoferric oxide in 7) is omitted.

[0032] Test experiment: Experiment 1: Viscosity reduction test of heavy oil The viscosity reducer samples obtained in Examples 1-3 and Comparative Examples 1-6 were added to heavy oil with an initial viscosity of 2500 mPa.s, respectively, and the mass ratio of the viscosity reducer sample to the heavy oil was 2:7. Then, the method specified in Q / SH10201519-2016 "General Technical Conditions for Viscosity Reducers for Heavy Oil" was referred to, wherein the parameter conditions of the viscometer were temperature 50°C, speed 200 rpm, torque 70, the viscosity of the heavy oil after viscosity reduction was tested, and the viscosity reduction rate of the heavy oil was calculated. The results are shown in Table 1.

[0033] Table 1 It can be seen from Table 1 that the oil viscosity reducer in the present invention can effectively reduce the viscosity of heavy oil, greatly improve the fluidity of oil, and improve the production efficiency.

[0034] Experiment 2: Blocking performance test The plugging performance of bentonite-based composite materials in oil viscosity reducers in crude oil production was evaluated by using constant pressure microporous (nanoscale) filter membranes. The microporous filter membrane can be regarded as a cross section of the pore throat of the shale reservoir, simulating the plugging effect of bentonite-based composite materials on the pore throat. It has the advantages of accuracy and convenience, and is suitable for rapid evaluation in the laboratory and on-site. Based on this, the microporous filter membrane was used to replace the filter paper, and the emulsion loss experiment was carried out at 0.1MPa to simulate the plugging of the reservoir pore throat by the bentonite-based composite material.

[0035] The instruments used in the evaluation process include: medium-pressure filtration meter, agitator, sedimentation kettle, roller furnace, and evaluation tank.

[0036] Experimental materials: Example and comparative example samples (solid content 30%), nylon filter membrane (hydrophilic type, membrane diameter 90 mm, pore size 0.4 μm), and special filter paper for drilling fluid (diameter 90 mm).

[0037] Experimental steps: (1) Preparation of dispersion system: Deionized water, bentonite-based composite material, and sodium chloride were used to prepare a dispersion system with a bentonite-based composite material concentration of 20% and a mineralization degree of 5000 mg / L. The system was placed in a sedimentation kettle and aged at 120°C for 12 h. After the aging, the system was allowed to stand at room temperature.

[0038] (2) Nuclear pore membrane plugging experiment: Place the nylon filter membrane at the bottom of the filter loss test tank, clamp it tightly, add 100 mL of the evenly stirred dispersion system into the tank, seal the evaluation tank, and record the time for the dispersion system to be completely filtered out under a pressure of 0.1 MPa.

[0039] The filtration time of the dispersed system is h. The results are shown in Table 2.

[0040] Table 2 It can be seen from Table 2 that when the samples of Examples 1-3 are used, the total filtration time of the dispersed system is greater than 190 min, indicating that the plugging effect is good and the water loss reduction effect is obvious, so that during the crude oil production process, the well wall is stabilized and complex accidents such as shrinkage and collapse are not likely to occur.

[0041] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A plant-based nano-petroleum viscosity reducer, characterized in that: The raw materials include 5-10 parts of vegetable oil-based surfactant, 3-6 parts of composite biological enzyme, 2-5 parts of emulsifier, 1-3 parts of penetrant, 40-60 parts of bentonite-based composite material, 25-35 parts of nano-silicate, 0.3-0.8 parts of stabilizer, 0.1-0.6 parts of wetting agent and 120-150 parts of water according to weight parts; The vegetable oil-based surfactant is at least one of a castor oil-based surfactant, a palm oil-based surfactant, and a soybean oil-based surfactant; The composite biological enzyme is composed of esterase, protease, laccase and peroxidase in a mass ratio of 1: (1.2-1.8): (1.0-1.3): (2.0-2.5); The emulsifier is a biological emulsifier, selected from any one of xanthan gum and rhamnolipid; The penetrant is a mixture of alkyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether in a mass ratio of 1: (1.0-1.3); The wetting agent is polyethylene glycol; The stabilizer is at least one of disodium EDTA and sodium citrate.

2. A plant-based nano-petroleum viscosity reducer according to claim 1, characterized in that: The bentonite-based composite material is prepared by the following method: 1) preparing a polyvinyl alcohol aqueous solution, and then mixing the zinc acetate and polyvinyl alcohol in a mass ratio of 1: (3-5), fully mixing the zinc acetate and polyvinyl alcohol solutions to obtain a mixed solution, and then immersing the porous graphene oxide in the mixed solution, placing it in an oven for heat treatment, and then transferring it to a muffle furnace for calcination to obtain a composite nanomaterial; 2) The composite nanomaterial is dispersed in deionized water to obtain a nanomaterial dispersion, and then the nano-iron tetroxide particles are added to the dispersion at a solid-liquid ratio of 1: (80-120) g / mL, mechanically stirred for 1-2 hours, and then subjected to ultrasonic treatment for 1-2 hours. After the treatment is completed, the modified bentonite is added thereto at a solid-liquid ratio of 1: (50-70) g / mL, and after shaking on a shaker for 50-80 minutes, the desired bentonite-based composite material is obtained by washing and drying by centrifugation.

3. A plant-based nano-petroleum viscosity reducer according to claim 2, characterized in that: The heat treatment is specifically performed by heating the temperature to 120-145°C at a rate of 5-8°C / min, keeping the temperature for 1-3h, and then heating the temperature to 200-210°C at a rate of 3-6°C / min, and keeping the temperature for 1-2h. The calcination treatment is specifically performed as follows: calcining at 300-310°C for 30-50min, then heating to 410-420°C at a rate of 5-8°C / min, keeping the temperature for 30-50min, then heating to 540-560°C at a rate of 5-8°C / min, and keeping the temperature for 1-3h.

4. A plant-based nano-petroleum viscosity reducer according to claim 2, characterized in that: The porous graphene oxide is prepared by a chemical concentrated acid etching method, wherein the concentrated acid is fully mixed with a graphene oxide dispersion having a concentration of 0.5-2.5 mg / mL, wherein the volume ratio of the graphene oxide dispersion to the concentrated acid is 1:(3-8); the mixture is subjected to ultrasonic reaction at 200-300 W for 1-2 hours, and then allowed to stand at room temperature, and the concentrated acid is removed by centrifugation, and then dried, wherein the concentrated acid is selected from any one or a combination of concentrated sulfuric acid, concentrated nitric acid, and concentrated phosphoric acid.

5. A plant-based nano-petroleum viscosity reducer according to claim 2, characterized in that: The polyvinyl alcohol aqueous solution has a concentration of 1-5wt%; The nano-dispersion liquid has a solid content of 5-10wt%; The mechanical stirring speed is 1000-1500r / min; The ultrasonic effect has a power of 500-800W; The shaking table oscillates at a speed of 500-800 r / min.

6. A plant-based nano-petroleum viscosity reducer according to claim 2, characterized in that: The modified bentonite is prepared by the following method: 1) Dissolve potassium antimony tartrate in deionized water, stir thoroughly to dissolve, add polyvinyl pyrrolidone, stir thoroughly to form a mixed solution, then add thioacetamide to the mixed solution, mix thoroughly to obtain a reaction solution; 2) Add the pretreated bentonite to the reaction solution, stir for 20-50 minutes, and after ultrasonic oscillation for 30-40 minutes, transfer to a reactor and heat at a constant temperature of 180-200°C for 24-28 hours. After the reaction is completed, cool to room temperature, wash by centrifugation, and dry to obtain modified bentonite.

7. A plant-based nano-petroleum viscosity reducer according to claim 6, characterized in that: The ratio of potassium antimony tartrate, deionized water, polyvinyl pyrrolidone, and thioacetamide is (7.5-11.0) g: (30-70) mL: (0.2-0.3) g: (1.3-2.0) g; The stirring speed is 180-260r / min; The ultrasonic oscillation has a power of 200-300W.

8. The plant-based nano-petroleum viscosity reducer according to claim 6, characterized in that: The pretreated bentonite is prepared as follows: 1) Add 1.1-1.8g of bismuth nitrate to 30-60mL of deionized water, stir thoroughly to dissolve, and obtain a bismuth nitrate solution. Then add 0.3-0.5g of sodium tungstate to 45-80mL of deionized water, stir thoroughly to dissolve, and obtain a sodium tungstate solution. 2) Add the sodium tungstate solution to the bismuth nitrate solution, stir thoroughly and transfer to a high-temperature reactor, react at 160-170°C for 16-20 hours, cool naturally to room temperature, centrifuge, wash repeatedly with deionized water and ethanol, and dry to obtain flower-like nanoparticles; 3) After drying and crushing the bentonite and removing sand by multi-stage water washing, bentonite powder is obtained, the flower-shaped nanoparticles are dispersed in deionized water, and the dispersion is obtained after uniform ultrasonic dispersion. Then, according to a certain solid-liquid ratio, the bentonite powder is placed in a vacuum impregnation tank, evacuated to 50-80Pa, maintained for 20-30min, and then the dispersion is injected. The vacuum is continued to be maintained for 20-30min under the action of 200-300W ultrasound, and the pressure is slowly released to normal pressure. After centrifugal washing, it is dried to obtain the pretreated bentonite.

9. A plant-based nano-petroleum viscosity reducer according to claim 8, characterized in that: The dispersion has a solid content of 1-3wt%; The solid-liquid ratio is 1: (100-130) g / mL.

10. A method for preparing the plant-based nano-petroleum viscosity reducer according to claim 1, characterized in that: The specific steps include: Under normal pressure and 50-58℃, slowly add penetrant, wetting agent and stabilizer into water in turn, stir until mixed evenly, raise the temperature to 92-97℃, then add bentonite-based composite materials and nano-silicate, sterilize and then naturally cool to 26-30℃, add vegetable oil-based surfactant, compound biological enzyme and emulsifier, and mix evenly.

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