Nano oil displacement agent for oil field production and preparation method thereof

Abstract

The invention relates to the technical field of oilfield exploitation, and discloses a nano oil-displacing agent for oilfield exploitation and a preparation method thereof. The nano oil-displacing agent is mainly composed of modified nano silicon dioxide and a surfactant, and a polymer macromolecule is modified on the surface of the nano silicon dioxide as the main body of the nano oil-displacing agent. Under the action of the surfactant, the nano silicon dioxide can flow into the fine throat and micro throat, and the polymer macromolecule with a branched structure can produce a strong interaction force with the rock, thereby firmly adhering to the rock surface, reducing the adhesion of crude oil on the rock surface, thereby constructing a smooth crude oil channel, reducing the flow pressure of the liquid, and thereby improving the fluidity of the crude oil. The cross-linking agent structure contains quaternary ammonium cations, which can greatly enhance the electrostatic repulsion between the nano silicon dioxides, avoid aggregation between each other, thereby being able to efficiently maintain the interfacial tension, greatly reducing the oil-water interfacial tension, and thereby effectively improving the recovery rate of the crude oil.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, and in particular to a nano oil-displacing agent for oilfield exploitation and a preparation method thereof. Background Art

[0002] Oil resources occupy an important position in the global energy structure. However, with the deepening of exploitation, low-permeability and ultra-low-permeability reservoirs have gradually become the main targets of exploitation. Such reservoirs have problems such as high water injection pressure, difficulty in injection, insufficient energy replenishment, and low water flooding efficiency. Traditional oil recovery technology is difficult to achieve ideal recovery effects. In this context, nano-oil recovery technology came into being and quickly became a cutting-edge technology in the field of oil extraction.

[0003] The basic principle of nano-displacement technology is to use nano-materials to improve the structure of injected water, so that it can enter the pores of oil layers with lower permeability, strip and drive the remaining oil, and increase the production of oil wells. Nano-displacement agents transform "conventional water" into "small molecule water" and penetrate into the pores of low-permeability reservoirs that ordinary water cannot inject, thereby expanding the volume of water flooding and increasing recoverable reserves.

[0004] Compared with traditional oil displacement technology, nano oil displacement agents have small molecular size and can penetrate into the pores of low-permeability and ultra-low-permeability reservoirs that traditional methods cannot reach, significantly increasing the swept volume. According to research, nano oil displacement agents can further increase the swept volume of low-permeability areas on the basis of conventional water flooding, thereby improving the recovery rate. In addition, nano oil displacement agents can intelligently capture dispersed oil in the reservoir, aggregate it into oil droplets and form oil walls, thereby improving the displacement efficiency of residual oil. This characteristic enables nano oil displacement agents to automatically find and displace residual oil in the reservoir, thereby improving the recovery rate.

[0005] However, the nano oil-displacing agent itself also has certain defects. Since its nanomaterial generally carries a certain charge, the stability of the nanofluid is poor under high temperature and high salt conditions, and the electrostatic repulsion between each other is reduced. Therefore, it is very easy to aggregate, and then produce flocculation and precipitation, etc., which makes it extremely difficult to inject. Based on this, the present invention provides a nano oil-displacing agent for oil field production and a preparation method thereof, which can solve the problems existing in the prior art. Summary of the invention

[0006] In order to solve the problems mentioned in the background technology, the object of the present invention is to provide a nano oil-displacing agent for oil field production and a preparation method thereof.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing a nano oil-displacing agent for oil field production, the nano oil-displacing agent comprising the following raw materials in parts by weight:

[0009] 0.1-0.2 parts of modified nano silicon dioxide;

[0010] 40-50 parts of surfactant;

[0011] 50-60 parts of water;

[0012] The preparation method is as follows:

[0013] The first step is to weigh and prepare the raw materials according to the weight of each raw material;

[0014] The second step is to add the surfactant into the water, stir and mix for 20-30 minutes to form a mixed solution, then add the modified nano-silica into the mixed solution, and ultrasonically treat it at an ultrasonic frequency of 80-100 kHz for 1-2 hours to obtain a nano-oil displacement agent;

[0015] The preparation method of the modified nano silicon dioxide comprises the following steps:

[0016] Step S1, adding an emulsifier to purified water, and mixing uniformly with mechanical stirring to form an emulsion;

[0017] Step S2, ultrasonically dispersing the nano-silica intermediate in toluene to form a uniform dispersion, then adding the emulsion to the dispersion, mechanically stirring for 20-30 minutes, then adding acrylamide and acrylic acid, stirring and emulsifying for 1-2 hours, and then continuing to add the initiator. After the addition is completed, the temperature is increased to 60-70°C, and after keeping warm and stirring for 4-6 hours, the cross-linking agent is added to the polymerization system, and the stirring is continued for 8-12 hours. The heating is stopped, the temperature is lowered and the material is discharged, and the modified nano-silica can be obtained. The whole process is carried out under nitrogen protection.

[0018] As a further embodiment of the present invention, in step S1, the emulsifier is at least one of polysorbate 80 or sorbitan monostearate.

[0019] As a further solution of the present invention, in step S2, the specific preparation method of the nano-silicon dioxide intermediate is as follows:

[0020] Add nano-silicon dioxide into toluene solvent, and evenly disperse it by ultrasonic dispersion at an ultrasonic frequency of 50-60kHz. Then, add isocyanoethyl methacrylate and dibutyltin dilaurate into the formed dispersion, introduce nitrogen for protection, and then start heating and maintain the temperature at 70-80°C. After continuous stirring for 3-6 hours, remove nitrogen, stop heating, cool and discharge the material, separate the solid material, and thus obtain the nano-silicon dioxide intermediate.

[0021] As a further embodiment of the present invention, in step S2, the initiator is azobisisobutyronitrile or benzoyl peroxide.

[0022] In the above technical scheme, an emulsion polymerization method is adopted. Under the action of an initiator, the unsaturated olefin group on the surface of the nano-silica intermediate is used as a polymerization site, so that the unsaturated monomers acrylamide and acrylic acid are polymerized in situ on the surface of the nano-silica. Then, by adding a cross-linking agent, the remaining polymerized monomers form branched polymerization on the surface of the nano-silica, thereby forming a polymer macromolecule with a branched structure on the surface of the nano-silica, i.e., modified nano-silica.

[0023] As a further solution of the present invention, in step S2, the preparation method of the cross-linking agent is as follows:

[0024] Add 4,6-bis(1-adamantyl)-1,3-diglycidyl ether benzene, dimethylaminoethyl acrylate and ethanol aqueous solution into a reaction kettle filled with nitrogen. After the addition, start stirring until a uniform reaction liquid is formed, add glacial acetic acid dropwise, adjust the pH value of the reaction liquid to 6-7, then increase the temperature to 60-65°C, keep stirring for 4-8h, remove nitrogen, remove low-boiling substances by rotary evaporation, cool and discharge, collect the product, and the cross-linking agent can be obtained.

[0025] As a further embodiment of the present invention, the molar ratio of the 4,6-bis(1-adamantyl)-1,3-diglycidyl ether benzene to dimethylaminoethyl acrylate is 1:2.

[0026] As a further embodiment of the present invention, the volume fraction of the ethanol aqueous solution is 60-70%.

[0027] In the above technical scheme, 4,6-bis(1-adamantyl)-1,3-diglycidyl ether benzene and dimethylaminoethyl acrylate are used as reactants, and the principle that active epoxy groups and tertiary amine groups in each other's structures can undergo quaternization reaction is utilized, and by controlling the molar ratio of the reactants, a cross-linking agent containing two equivalents of quaternary ammonium cationic functional groups in the structure can be prepared.

[0028] As a further embodiment of the present invention, the surfactant is at least one of fatty acid alkanolamide and alkyl glycoside.

[0029] A nano oil-displacing agent for oil field production is prepared by adopting the above preparation method.

[0030] Beneficial effects of the present invention:

[0031] The present invention obtains modified nano silicon dioxide by modifying the polymer macromolecule with branched structure on the surface of nano silicon dioxide, and as the main body of nano oil displacement agent, on the one hand, under the action of surfactant, nano silicon dioxide can flow into nanometer-level thin throat and micro throat, and the polymer macromolecule with branched structure can produce stronger interaction force with rock, and then firmly adhere to the rock surface, reduce the adhesion of crude oil on the rock surface, thereby constructing a smooth crude oil channel, reducing the flow pressure of liquid, and then improving the fluidity of crude oil. In addition, because the cross-linking agent structure contains quaternary ammonium cations, this greatly enhances the electrostatic repulsion between nano silicon dioxide, can effectively avoid aggregation between each other, cause the problem of flocculation, thereby can efficiently maintain interfacial tension, greatly reduce the oil-water interfacial tension, and then effectively improve the recovery rate of crude oil.

[0032] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. DETAILED DESCRIPTION

[0033] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0034] Preparation Example 1

[0035] Preparation of modified nano-silica:

[0036] Step 1: Add 1.5 g of nano-silica to a toluene solvent, and evenly disperse it by ultrasonic dispersion at an ultrasonic frequency of 60 kHz. Then, add 2.5 g of isocyanoethyl methacrylate and 0.1 g of dibutyltin dilaurate to the formed dispersion, introduce nitrogen for protection, and then start heating, maintain the temperature at 75°C, continue stirring for 4 hours, remove nitrogen, stop heating, cool and discharge, separate the solid material, and obtain a nano-silica intermediate;

[0037] Step 2: Add 1 g of sorbitan monostearate to 85 mL of purified water and mix well with mechanical stirring to form an emulsion;

[0038] Step 3: Ultrasonic disperse 0.5 g of nano-silica intermediate in toluene to form a uniform dispersion, then add the emulsion formed in step 2 to the dispersion, mechanically stir for 30 min, then add 1.2 g of acrylamide and 0.6 g of acrylic acid, stir and emulsify for 2 h, and then continue to add 0.1 g of azobisisobutyronitrile. After the addition, raise the temperature to 65 ° C., keep stirring for 6 h, add 0.2 g of cross-linking agent to the polymerization system, continue to keep stirring for 9 h, stop heating, cool and discharge, and the modified nano-silica can be obtained. The whole process is carried out under nitrogen protection.

[0039] The preparation method of the cross-linking agent is as follows:

[0040] To a reactor filled with nitrogen, add 0.1 g of 4,6-bis(1-adamantyl)-1,3-diglycidyl ether benzene, 0.06 g of dimethylaminoethyl acrylate and a 70% ethanol aqueous solution by volume. After the addition, start stirring until a uniform reaction liquid is formed, add glacial acetic acid dropwise, adjust the pH value of the reaction liquid to 7, then raise the temperature to 65°C, keep stirring for 6 hours, remove the nitrogen, remove low-boiling substances by rotary evaporation, cool and discharge, collect the product, and the cross-linking agent can be obtained. Example 1

[0041] A nano oil-displacing agent for oil field production, comprising the following raw materials in parts by weight:

[0042] 0.1 part of modified nano silicon dioxide;

[0043] 40 parts of fatty acid alkanolamides;

[0044] 50 parts water;

[0045] The preparation method is as follows:

[0046] The first step is to weigh and prepare the raw materials according to the weight of each raw material;

[0047] In the second step, fatty acid alkanolamide is added into water, stirred and mixed for 20 minutes to form a mixed solution, and then modified nano-silica is added into the mixed solution, and ultrasonically treated at an ultrasonic frequency of 80 kHz for 2 hours to obtain a nano-oil-displacing agent.

[0048] The preparation method of the modified nano-silicon dioxide is shown in Preparation Example 1, and the same is true for the following. Example 2

[0049] A nano oil-displacing agent for oil field production, comprising the following raw materials in parts by weight:

[0050] 0.15 parts of modified nano silicon dioxide;

[0051] 42 parts of alkyl glycosides;

[0052] 55 parts water;

[0053] The preparation method is as follows:

[0054] The first step is to weigh and prepare the raw materials according to the weight of each raw material;

[0055] In the second step, alkyl glycoside is added into water, and the mixture is stirred for 30 minutes to form a mixed solution. Then, modified nano-silica is added into the mixed solution, and the mixed solution is ultrasonically treated at an ultrasonic frequency of 100 kHz for 1 hour to obtain a nano-oil displacement agent. Example 3

[0056] A nano oil-displacing agent for oil field production, comprising the following raw materials in parts by weight:

[0057] 0.2 parts of modified nano silicon dioxide;

[0058] 50 parts of fatty acid alkanolamides;

[0059] 60 parts of water;

[0060] The preparation method is as follows:

[0061] The first step is to weigh and prepare the raw materials according to the weight of each raw material;

[0062] In the second step, fatty acid alkanolamide is added into water, stirred and mixed for 30 minutes to form a mixed solution, and then modified nano-silica is added into the mixed solution, and ultrasonic treatment is performed at an ultrasonic frequency of 100 kHz for 2 hours to obtain a nano-oil displacement agent.

[0063] Comparative Example 1

[0064] A nano oil-displacing agent for oil field production, comprising the following raw materials in parts by weight:

[0065] 0.15 parts of nano silicon dioxide;

[0066] 42 parts of alkyl glycosides;

[0067] 55 parts water;

[0068] The preparation method is as follows:

[0069] The first step is to weigh and prepare the raw materials according to the weight of each raw material;

[0070] In the second step, alkyl glycoside is added into water, and the mixture is stirred for 30 minutes to form a mixed solution. Then, nano-silica is added into the mixed solution, and the mixed solution is ultrasonically treated at an ultrasonic frequency of 100 kHz for 1 hour to obtain a nano-oil-displacing agent.

[0071] Test Case

[0072] a.Interfacial tension test:

[0073] The interfacial tension of the nano oil-displacing agent in the embodiment and the comparative example was tested using a TX-500C interfacial tension measuring instrument. The test temperature was set to 100° C. and the test crude oil was an experimental standard dehydrated crude oil with a wax content of 35%.

[0074] b. Crude oil recovery test:

[0075] An oil displacement experiment was carried out using a core displacement device to simulate reservoir conditions. Multiple artificial heterogeneous cores were taken to measure and record the basic parameters of the cores. The experimental temperature was 80° C. The original oil saturation was recorded, and then water displacement was carried out until the water content reached 95%. After the water displacement was completed, 2 wt% aqueous solutions prepared with the oil displacement agents in the embodiment and the comparative example were respectively injected, and the recovery rate of the cores was recorded.

[0076]

[0077] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nano oil-displacing agent for oil field production, characterized in that: The nano oil-displacing agent comprises the following raw materials in parts by weight: 0.1-0.2 parts of modified nano silicon dioxide; 40-50 parts of surfactant; 50-60 parts of water; The preparation method is as follows: The first step is to weigh and prepare the raw materials according to the weight of each raw material; The second step is to add the surfactant into the water, stir and mix for 20-30 minutes to form a mixed solution, then add the modified nano-silica into the mixed solution, and ultrasonically treat it at an ultrasonic frequency of 80-100 kHz for 1-2 hours to obtain a nano-oil displacement agent; The preparation method of the modified nano silicon dioxide comprises the following steps: Step S1, adding an emulsifier to purified water, and mixing uniformly with mechanical stirring to form an emulsion; Step S2, ultrasonically dispersing the nano-silica intermediate in toluene to form a uniform dispersion, then adding the emulsion to the dispersion, mechanically stirring for 20-30 minutes, then adding acrylamide and acrylic acid, stirring and emulsifying for 1-2 hours, and then continuing to add the initiator. After the addition is completed, the temperature is increased to 60-70° C., and after stirring for 4-6 hours, the cross-linking agent is added to the polymerization system, and the stirring is continued for 8-12 hours. The heating is stopped, the temperature is lowered and the material is discharged, and the modified nano-silica can be obtained. The whole process is carried out under nitrogen protection; The specific preparation method of the nano silicon dioxide intermediate is as follows: Add nano-silicon dioxide to a toluene solvent, and evenly disperse it by ultrasonic dispersion at an ultrasonic frequency of 50-60kHz, then add isocyanoethyl methacrylate and dibutyltin dilaurate to the formed dispersion, introduce nitrogen protection, and then start heating, maintain the temperature at 70-80°C, continue stirring for 3-6 hours, remove nitrogen, stop heating, cool down and discharge, separate the solid material, and obtain a nano-silicon dioxide intermediate; The preparation method of the cross-linking agent is as follows: Add 4,6-bis(1-adamantyl)-1,3-diglycidyl ether benzene, dimethylaminoethyl acrylate and ethanol aqueous solution into a reaction kettle filled with nitrogen. After the addition, start stirring until a uniform reaction liquid is formed, add glacial acetic acid dropwise, adjust the pH value of the reaction liquid to 6-7, then increase the temperature to 60-65°C, keep stirring for 4-8h, remove nitrogen, remove low-boiling substances by rotary evaporation, cool and discharge, collect the product, and the cross-linking agent can be obtained.

2. The method for preparing a nano oil-displacing agent for oil field production according to claim 1, characterized in that: In step S1, the emulsifier is at least one of polysorbate 80 or sorbitan monostearate.

3. The method for preparing a nano oil-displacing agent for oil field production according to claim 1, characterized in that: In step S2, the initiator is azobisisobutyronitrile or benzoyl peroxide.

4. The method for preparing a nano oil-displacing agent for oil field production according to claim 1, characterized in that: The molar ratio of the 4,6-bis(1-adamantyl)-1,3-diglycidyl ether benzene to dimethylaminoethyl acrylate is 1:

2.

5. The method for preparing a nano oil-displacing agent for oil field production according to claim 1, characterized in that: The volume fraction of the ethanol aqueous solution is 60-70%.

6. The method for preparing a nano oil-displacing agent for oil field production according to claim 1, characterized in that: The surfactant is at least one of fatty acid alkanolamide and alkyl glycoside.

7. A nano oil-displacing agent for oil field production, characterized in that: The method is prepared according to any one of claims 1 to 6.

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