Efficient nano silicon dioxide tackifier as well as preparation method and application thereof

Abstract

The invention discloses an efficient nano silicon dioxide tackifier and a preparation method and application thereof, and relates to the field of oilfield chemistry, the preparation method comprises the following steps: taking nano silicon dioxide, ultrasonically dispersing in a first solvent, and then adding a small amount of a second solvent and a certain amount of a silane coupling agent to obtain preliminarily modified nano silicon dioxide; thirdly, stirring and dispersing acrylic acid and ammonium persulfate in a second solvent to obtain polymer modified silicon dioxide; and finally, dispersing the product, glucosamine sulfate, NMI (N-methylimidazole) and TCFH (N, N, N, N-tetramethyl chlorourea hexafluorophosphate) into a third solvent to react, thereby obtaining the product. The viscosity of crude oil and the oil displacement efficiency can be effectively improved under the conditions of high-salt and high-water-content oil reservoirs, the viscosity of the formed emulsion is increased along with the rise of the water content, and the flow resistance can adapt to the change of the water content, so that the swept volume is increased, and the requirement of the high-salt and high-water-content oil reservoirs for improving the recovery efficiency is met.

Description

Technical Field

[0001] The invention belongs to the field of oilfield chemistry, and in particular relates to a high-efficiency nano-silicon dioxide tackifier and a preparation method and application thereof. Background Art

[0002] In recent years, with the exploitation of oil fields, some oil fields have entered the late stage of high water content exploitation, and the oil field production has gradually decreased. Chemical flooding is an effective method to increase crude oil production, which mainly includes surfactant flooding, polymer flooding, alkaline water flooding, etc. Although surfactants can effectively reduce the oil-water interfacial tension, it is difficult to improve the dominant channel and thus increase the swept volume; polymers are not resistant to high salt. Under high salt conditions, the long polymer chains are easy to curl up and lose their function; alkaline water flooding is simple to operate and low in cost, but the environmental problems it brings cannot be ignored. Therefore, in order to solve the problem of difficulty in simultaneously achieving mobility control and reducing oil-water interfacial tension in the process of improving the recovery of high-salinity and high-water content reservoirs, oil-in-water emulsion flooding is currently a more suitable method.

[0003] Oil-in-water emulsification and viscosity enhancement refers to the process of adding emulsifiers to contact crude oil in the formation environment to form a water-in-oil (W / O) emulsion with controllable viscosity, thereby improving the mobility control ability of the displacement process, increasing the displacement fluid swept volume, and starting the low-permeability area to improve the recovery of crude oil. At present, the main emulsifier is a surfactant. Under high water content conditions, it is difficult to achieve the task of improving the recovery rate because a single surfactant cannot form a stable high-viscosity emulsion. According to existing research, nanofluids can use their own characteristics during the formation displacement process to strip off the crude oil attached to the formation rock and form an emulsion under the shear action of the formation. In addition, some nanomaterials can be adsorbed on the rock surface to improve wettability, thereby better improving the recovery of crude oil. At the same time, nanomaterials can also be adsorbed on the oil-water interface formed, increase the thickness of the liquid film, and enhance the stability of the emulsion during migration.

[0004] It can be seen that, in order to address the problem of low recovery rate of high-salinity and high-water-content oil reservoirs, designing efficient viscosity-increasing nanomaterials is the key to improving the displacement efficiency of high-salinity and high-water-content oil reservoirs. Summary of the invention

[0005] The purpose of the present invention is to provide a high-efficiency nano-silicon dioxide thickener for emulsification and thickening in high-salt and high-water-content oil reservoirs. The specific preparation method is as follows: S1. Add nano-silica to the first solvent according to the proportion, and stir with ultrasonic to obtain surface hydroxylated silica; add 3-(trimethoxysilane)propyl-2-methylacrylate silane coupling agent to the nano-silica suspension, heat and stir under the action of the first catalyst, and then filter, wash and dry to obtain nano-silica modified with silane coupling agent; S2, according to the proportion, add the silane coupling agent modified nano-silica obtained in S1 to the second solvent, and 2 Heating and stirring under the action of atmosphere, and then filtering and washing to obtain polymer-modified nano-silica; S3, according to the proportion, add the polymer modified nano-silica obtained in S2 to the third solvent, in the presence of the third catalyst, N 2 Under the action of the agent, it reacts with the modifier at room temperature, is washed and filtered, and a high-efficiency viscosity-enhancing nano-silica is obtained.

[0006] Preferably, in S1, the mass ratio of the hydroxylated silica to the first solvent is 1 g:30-40 ml; the first solvent is a mixture of ethanol and water, and the volume ratio of ethanol to water is 9:1; the mass ratio of 3-(trimethoxysilyl)propyl-2-methylacrylate silane coupling agent to the first catalyst is 10-12 ml:1.5 ml-3 ml; The first catalyst is glacial acetic acid.

[0007] Preferably, S1 is specifically: Add nano-silica to an ethanol aqueous solution, place it in an ultrasonic disperser for ultrasonication at 20-30°C for 20-30 minutes, add 3-(trimethoxysilyl)propyl-2-methylacrylate silane coupling agent and stir for 20-30 minutes to fully hydrolyze the coupling agent to generate silanol; mix the two and use a first catalyst to adjust the pH to 5, and stir the mixture at 65-70°C for 20-26 hours; after the reaction, separate the product by filtering, wash it with anhydrous ethanol for multiple times to remove unreacted silane coupling agent and by-products, and dry it to obtain nano-silica modified with silane coupling agent.

[0008] Preferably, in S2, the mass ratio of the silane coupling agent-modified nano-silica, the second solvent and the second catalyst is 1-1.2 g: 40-50 ml: 2-4 ml; The second solvent is a mixed solution of acrylic acid, ethanol and water, and the mass ratio of the acrylic acid, the ethanol and the water is 50-60:85:3; The second catalyst is a mixture of ammonium persulfate and dilute sulfuric acid, and the mass ratio is 3-3.5:10-13.

[0009] Preferably, S2 is specifically: The silane coupling agent-modified nano-silica obtained in S1 was dispersed in the second solvent, ultrasonically dispersed for 15 min, the pH was adjusted to 3 using the second catalyst, and then heated to 40 °C under N 2 The mixture was heated to 75°C under an aqueous atmosphere and reacted for 6 hours. After the reaction, the polymer-modified nano-silica was obtained by suction filtration and multiple washings with ethanol (to remove unreacted acrylic acid monomers and by-products).

[0010] Preferably, in S3, the amount of the third catalyst added is 1.8-2% of the amount of the third solvent added; The third solvent is acetonitrile; The third catalyst is NMI (N-methylimidazole) and TCFH (N,N,N,N-tetramethylchlorouronium hexafluorophosphate), and the mass ratio is 3.5-4 ml: 0.45-0.6 g; The modifier is glucosamine sulfate, and the amount of the modifier added is 8-10% of the amount of the third solvent added.

[0011] Preferably, S3 is specifically: The polymer-modified nano-silica obtained from S2 was dissolved in the third solvent, ultrasonically dispersed for 10 min, and transferred to a three-necked flask, and then the third catalyst was added, and then N was introduced for 25-30 min. 2 , stirring ultrasonically at 25-30°C, reacting with the modifier under the action of the third catalyst for 20-26 hours, collecting the solid by filtration, washing it three times with ethanol ultrasonically, filtering and drying to obtain the nano-silica thickener.

[0012] The technical effects of the present invention are: (1) The W / O type emulsion formed by the high-efficiency nano-silica thickener of the present invention and crude oil can increase the viscosity of crude oil to more than 15 times of the original value in high-salinity and high-water content oil reservoirs, which can effectively improve the oil washing efficiency and achieve displacement balance.

[0013] (2) In an indoor core displacement experiment, the present invention can improve the recovery rate of high-salinity and high-water-content oil reservoirs by more than 15%, and has excellent ability to improve crude oil recovery.

[0014] (3) Based on the low concentration and high efficiency of the viscosity increasing effect of the viscosity increasing agent in the present invention, the requirements for improving the recovery of crude oil with high salt and high water content can be met.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the synthesis of a high-efficiency nano-silicon dioxide tackifier of the present invention; Figure 2 This is the FT-IR spectrum of a high-efficiency nano-silicon dioxide tackifier of the present invention; Figure 3 This is a viscosity-increasing performance diagram of a high-efficiency nano-silicon dioxide viscosity-increasing agent of the present invention at different concentrations and mineralization degrees; Figure 4This is a viscosity-increasing performance diagram of a high-efficiency nano-silicon dioxide viscosity-increasing agent of the present invention at different water-oil volume ratios and mineralization degrees; Figure 5 This is a diagram showing the results of an experiment on improving oil recovery using a high-efficiency nano-silicon dioxide viscosity enhancer according to the present invention. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0018] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0019] Example 1: Figure 1 As shown, a high-efficiency nano-silicon dioxide thickener, the structural formula of its modified group is as follows: .

[0020] The preparation method is as follows: (1) Add 1g of nano-silica to an ethanol aqueous solution and place it in an ultrasonic disperser for 20 minutes. Take 5g of 3-(trimethoxysilyl)propyl-2-methylacrylate (KH570) and dissolve it in the nano-silica suspension. Add 5ml of deionized water. Stir for 30 minutes to allow KH570 to fully hydrolyze to generate silanol. Adjust the pH to 5 with glacial acetic acid and stir the reaction at 65°C for 24 hours.

[0021] (2) Filter, wash and dry to obtain silane coupling agent modified nano-silica (MS for short).

[0022] (3) Place MS in a beaker and add 30 ml of deionized water. Ultrasonic dispersion for 15 min. Add 5 g of acrylic acid and 0.3 g of ammonium persulfate to the treated MS solution. Adjust the pH to 3 with dilute sulfuric acid and heat under N 2 The mixture was heated to 75°C under a nitrogen atmosphere for 6 h.

[0023] (4) Filtration, washing and drying are performed to obtain polymer-modified nano-silica (PS for short).

[0024] (5) PS was transferred to a three-necked flask, and 25 mL of acetonitrile was used as solvent. 1.2 g of glucosamine sulfate, 1.2 g of NMI (N-methylimidazole) as an organic base, and 1.5 g of TCFH (tetramethylchlorouronium hexafluorophosphate) as a coupling agent were added in sequence. The reaction was stirred at 25 °C for 24 h.

[0025] (6) Filter, wash and dry to obtain nano-silica thickener (PSD for short).

[0026] Experimental Testing (1) FT-IR test FT-IR was used to analyze the nano-silicon dioxide and the MS, PS, and PSD prepared in Example 1. The results are as follows: Figure 2 shown.

[0027] Depend on Figure 2 It can be seen that in the spectrum of ordinary nano-silicon dioxide, 471.44cm -1 It corresponds to the bending vibration absorption peak of Si-O, and the 802.79cm -1 、953.27cm -1 、1104.62cm -1 It corresponds to the stretching vibration of Si-O bonds in different environments; MS has characteristic peaks similar to those of nano-silicon dioxide, and also has a peak of 1720.50cm -1 The characteristic peak of PS may correspond to the stretching vibration of C=C or C=O. Combined with the experimental reagents, it can be seen that it should be the carbon-carbon double bond in the silane coupling agent. The peak corresponding to PS is 3231.62 cm more than that of MS. -1 and 1720.50cm -1 The peak area of ​​​​the PSD is larger. These two characteristic peaks may be related to the stretching vibration of -OH and C=O, which may be caused by the carboxyl group of polyacrylic acid. -1 、1034.84cm -1 It may be caused by the stretching vibration of S=O and SO, while 3292.27cm -1 This may be due to the stretching vibration of -CO-NH, 1542.04cm -1 This may be caused by the bending vibration of the methylene carbon skeleton in glucosamine sulfate, and 1730.37cm -1 、3231.62cm -1 The characteristic peak did not completely disappear, proving that the carboxyl group in the modified group did not react completely. In summary, the nano-silica viscosity enhancer was successfully synthesized.

[0028] (2) Thickening performance test under different thickening agent concentrations and mineralization conditions Different concentrations (50, 100, 150, 200, 250 ppm) of nano-silica thickener were prepared using simulated formation water with different mineralization (0 g / L, 50 g / L, 220 g / L NaCl), and 100 ppm of dispersant alkylphenol polyoxyethylene ether (OP-10) was added to obtain a high-efficiency nano-thickener. At 65 ° C and a water-oil volume ratio of 3:7, it was placed in a water bath with a magnetic stirrer and stirred for 1.5 hours. After the end, the emulsion viscosity was tested using a Brookifield DV-Ⅲ viscometer. The experimental results are as follows: Figure 3The calculation method of the emulsion viscosity increase rate is shown in Formula 1. (The viscosity of crude oil at 65°C is 9.71 mPa·s) (1); Where, η is the crude oil viscosity reduction rate, %, μ oil is the viscosity of crude oil, mPa·s, μ e is the emulsion viscosity, mPa·s.

[0029] Depend on Figure 3 It can be seen that as the concentration of nano thickener increases, the thickening rate also increases. When the thickener concentration is 250ppm, the thickening effect is the best. When the mineralization is 0g / L, 50g / L and 220g / L, the thickening rates are 389.52%, 372.19% and 337.28% respectively. The thickening effect is more than 3 times, showing a good thickening effect in a high-salt environment. This may be because the structural characteristics of the nanomaterial are related to the surface grafted carboxyl polymers, which make the nano thickener and crude oil form a stable three-dimensional network structure, so that it also shows a good thickening effect in a high-salt environment. Compared with the pure water environment, the reason why the thickening rate decreases under high-salt conditions may be that high salt will cause salting out, the concentration of anions and cations in the solution increases, competing with the dispersant for water molecules, weakening the hydration of the dispersant, reducing the solubility and dispersibility of the thickener, and causing the thickening effect to decline.

[0030] (3) Viscosity enhancement test under different water-oil volume ratios and salinity The simulated formation water with different mineralization (0g / L, 50g / L, 220g / L NaCl) was mixed with 250ppm high-efficiency nano-silica thickener and 100ppm OP-10 to prepare nanofluid thickener. The mixture was placed in a water bath with a magnetic stirrer and stirred for 1.5h at 65℃ and different water-oil volume ratios (1:9, 3:7, 4:6, 5:5, 6:4, 7:3). After that, the viscosity of the emulsion was tested with a Brookifield DV-Ⅲ viscometer. The experimental results are shown in the figure. Figure 4 shown.

[0031] Depend on Figure 4 It can be seen that within the experimental range, the viscosity increasing rate of crude oil by high-efficiency nano-silica thickener increases with the increase of water-oil volume ratio, and the crude oil viscosity increasing effect is best when the water content is high (water-oil ratio is 7:3) and the mineralization is 0g / L, 50g / L and 220g / L. The crude oil viscosity increases by more than 15 times, showing good fluidity control ability.

[0032] (4) Enhanced oil recovery test 1000ppm high-efficiency nano-silica and 400ppm OP-10 were used to prepare high-efficiency nano-thickening fluids and the ability of high-efficiency nano-silica thickening fluids to improve oil recovery was measured through core displacement experiments. Cores with a water-tested permeability of 1500mD were selected for core displacement experiments. The specific steps are as follows: First, the cores were vacuumed and saturated with simulated formation water. The cores saturated with water were saturated with crude oil at a rate of 0.1ml / min at 65°C until no water came out of the end of the core holder. The valves at the front and rear ends of the core holder were closed and placed in a 65°C oven for aging for 24h. Then, simulated formation water was injected at a rate of 0.5ml / min, and water injection was stopped after 1PV was injected. Then, 0.6PV nano-silica thickener was injected at a rate of 0.5ml / min, and water was injected at a flow rate of 0.5ml / min until the pressure at the outlet of the core holder stopped changing.

[0033] During the whole process, the injection end pressure, water content, and cumulative recovery factor were recorded every 0.05 PV injection volume, and the water content, recovery factor, and injection end pressure curves were plotted; the recovery factor calculation formula is shown in formula (2).

[0034] (2); Where E is the recovery factor, V c is the cumulative volume of produced oil, ml; V n is the volume of oil in the rock pores, ml.

[0035] The results of the enhanced oil recovery experiment are as follows Figure 5 As shown in the figure, due to the oil-water two-phase flow, the water content of the core is low at this time. With the increase of injection volume, the displacement pressure and recovery rate also increase. The recovery rate after 1 PV of water flooding is 21.40%. Then 0.6 PV of high-efficiency nano-silica thickening fluid was injected. During the injection process, as the injection volume increased, the injection pressure increased again significantly, and W / O emulsion was observed at the outlet of the core holder. After the injection of 0.6 PV nano-thickener, the recovery rate increased slightly. This may be because the nano-thickener and crude oil formed W / O emulsions in some high-water-content areas, which increased the displacement resistance of high-water-content areas and carried out some crude oil. The simulated formation water was continuously injected into the post-water flooding until the pressure stopped changing. It can be seen that the displacement pressure continued to rise during the post-water flooding process, indicating that the nano-thickener was still shearing and emulsifying with the remaining crude oil in the core to form a W / O emulsion, which made the crude oil recovery rate continue to rise. The final recovery rate was 38.21% and the enhanced recovery rate was 16.81%. This shows that high-efficiency nano-silica has excellent ability to enhance crude oil recovery.

[0036] Therefore, the present invention adopts the above-mentioned high-efficiency nano-silica thickener and its preparation method and application. Under high-salt and high-water conditions, the emulsion viscosity can reach more than 15 times that of crude oil. The 0.6PV high-efficiency nano-silica thickener can increase the recovery rate by more than 15%, and the recovery rate is significantly improved.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-efficiency nano-silicon dioxide tackifier, characterized in that: The following steps are involved: S1, adding nano-silica to a mixture of a first solvent ethanol and water, stirring with ultrasound to obtain surface hydroxylated silica, then adding 3-(trimethoxysilyl)propyl-2-methylacrylate silane coupling agent, heating and stirring under the action of a first catalyst glacial acetic acid, and then filtering, washing and drying to obtain nano-silica modified with a silane coupling agent; S2, adding the silane coupling agent modified nano-silica obtained in S1 to a mixed solution of a second solvent of acrylic acid, ethanol and water, heating and stirring under the action of a second catalyst of a mixed solution of ammonium persulfate and dilute sulfuric acid and a N2 atmosphere, and then filtering and washing to obtain polymer-modified nano-silica; S3. Add the polymer-modified nano-silica obtained in S2 to the third solvent acetonitrile, react with the modifier glucosamine sulfate in the presence of the third catalyst NMI (N-methylimidazole) and TCFH (N,N,N,N-tetramethylchlorouronium hexafluorophosphate), N2 atmosphere, and 25-30°C, wash and filter to obtain high-efficiency viscosity-enhancing nano-silica.

2. The method for preparing a high-efficiency nano-silicon dioxide tackifier according to claim 1, characterized in that: In S1, the mass ratio of the nano-silica to the first solvent is 1-1.2 g:30-40 ml; the volume ratio of the first solvent ethanol to water is 9:1; the mass ratio of the 3-(trimethoxysilyl)propyl-2-methylacrylate silane coupling agent to the first catalyst is 10-12 ml:1.5 ml-3 ml.

3. The preparation method of the high-efficiency nano-silicon dioxide tackifier according to claim 1, characterized in that: S1 is specifically: The nano-silica is added to an ethanol aqueous solution, placed in an ultrasonic disperser for ultrasonication at 20-30°C for 20-30 minutes, 3-(trimethoxysilyl)propyl-2-methylacrylate silane coupling agent and the first catalyst are added at 65-70°C, and then washed with ethanol, filtered and dried to obtain nano-silica modified with a silane coupling agent.

4. The method for preparing a high-efficiency nano-silicon dioxide tackifier according to claim 1, characterized in that: In S2, the mass ratio of the silane coupling agent-modified nano-silica, the second solvent and the second catalyst is 1-1.2 g: 40-50 ml: 2-4 ml; The mass ratio of the second solvent acrylic acid, ethanol and water is 50-60:85:3; The mass ratio of the second catalyst ammonium persulfate to dilute sulfuric acid is 3-3.5:10-13.

5. The method for preparing a high-efficiency nano-silicon dioxide tackifier according to claim 1, characterized in that: S2 specific: The silane coupling agent-modified nano-silica obtained in S1 is dispersed in the second solvent, ultrasonically dispersed for 15 min, the pH is adjusted using a second catalyst, and heated to 70-75° C. under a N2 atmosphere for reaction for 4-8 h, and filtered and washed to obtain polymer-modified nano-silica.

6. The method for preparing a high-efficiency nano-silicon dioxide tackifier according to claim 1, characterized in that: In S3, the amount of the third catalyst added is 1.8-2% of the amount of the third solvent added; The mass ratio of the third catalyst NMI to TCFH is 3.5-4 ml: 0.45-0.6 g; The amount of the modifier added is 8-10% of the amount of the third solvent added.

7. The method for preparing a high-efficiency nano-silicon dioxide tackifier according to claim 1, characterized in that: S3 is specifically: The polymer modified silica obtained in S2 is added to the third solvent, and then the third catalyst is added, and N2 is introduced for 25 to 30 minutes. Ultrasonic stirring is carried out at 25 to 30°C, and the third catalyst is reacted with the modifier for 20 to 26 hours. The mixture is washed and filtered to obtain high-efficiency viscosity-enhancing nano-silica.

8. A high-efficiency nano-silicon dioxide thickener prepared by the method for preparing a high-efficiency nano-silicon dioxide thickener according to any one of claims 1 to 7, characterized in that: The water, alkylphenol polyoxyethylene ether and the thickening nano silicon dioxide are mixed evenly to obtain a high-efficiency thickening agent.

9. Use of the high-efficiency nano-silicon dioxide viscosity enhancer as claimed in claim 8 in high-salinity and high-water content oil reservoirs.

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