Silicon-based nano anti-drag reinforced oil displacement agent and preparation method thereof

Abstract

The invention discloses a silicon-based nano anti-drag reinforced oil displacement agent and a preparation method thereof, and relates to the technical field of additives for oil-gas field development. The preparation method of the oil-displacing agent comprises the following steps: taking an amino silane coupling agent, and modifying nano silicon dioxide to obtain modified nano silicon dioxide; taking the modified nano silicon dioxide, uniformly dispersing the modified nano silicon dioxide in a dispersing agent, then adding F127 and sodium hydrogen sulfate, reacting under the conditions of deoxygenization and 75-80 DEG C, and after the reaction is finished, separating and purifying to obtain the product. The interfacial tension of the silicon-based nano resistance-reducing reinforced oil-displacing agent and crude oil reaches 10 <-1 > mN / m order of magnitude; the wetting property of an oil reservoir is improved synergistically, the adhesion work of crude oil is reduced, Pickering emulsion is formed through induction, the flow resistance is reduced, and the crude oil recovery rate is greatly increased. The method is reliable in principle, raw materials are cheap and easy to obtain, economic benefits are remarkable, and the method has wide industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of additives for oil and gas field development, and specifically to a silicon-based nano drag reduction enhanced oil displacement agent and a preparation method thereof. Background Art

[0002] At present, traditional crude oil production cannot meet the needs of economic development, and heavy oil resources have received increasing attention. However, due to the high viscosity and poor fluidity of heavy oil, it brings great difficulties to exploitation and transportation. Heavy oil viscosity reduction technology is the key measure to improve the recovery rate of heavy oil reservoirs. At present, the methods for heavy oil viscosity reduction are mainly divided into thermal recovery and cold recovery. Among them, thermal recovery mainly includes steam flooding, steam stimulation and in-situ combustion, etc., but its energy consumption is large and the cost is high. Cold recovery mainly includes dilution with light oil for viscosity reduction, dispersion viscosity reduction and emulsification viscosity reduction, etc. Dilution with light oil for viscosity reduction is restricted by the shortage of light oil. Oil-soluble viscosity reducers have high selectivity for crude oil and are expensive. In contrast, emulsification viscosity reduction has simple operation and good viscosity reduction effect, and is a relatively mature technology. Emulsification viscosity reduction usually reduces the interfacial tension between oil and water and forms a low-viscosity O / W emulsion by adding surfactants to the injection water. Under formation conditions, the surfactants replace the active substances (gums, asphaltenes, etc.) on the surface of heavy oil and adsorb on the oil-water interface, thereby reducing the flow resistance and improving the recovery rate of heavy oil reservoirs. However, the large amount of surfactants used and the large adsorption amount in reservoir rocks lead to poor economic effects, and the formed O / W emulsion has poor stability. There is an urgent need for new materials to replace traditional agents for enhancing oil recovery.

[0003] In recent years, nano materials have gradually attracted everyone's attention due to their unique physical and chemical properties and stronger interfacial activity. Due to the characteristics of nanofluids, they have more excellent properties: nano particles have good dispersion and stability in the moving state, and it is not easy for particles to cluster; they have good shear resistance, salt tolerance and thermal stability in the moving state, avoiding the problem of surfactant precipitation in high-temperature and high-salinity formations; secondly, the smaller particle size of nanofluids enables them to enter smaller pore throats and play a role; nano particles can promote the formation of Pickering emulsions and improve the stability of emulsions; nano particles can also change the structure of water molecular clusters. There are hydrogen bonds between water molecules, and water molecules will be associated by hydrogen bonds into large molecular clusters. The movement of nano particles will affect the movement state of water molecules and improve the water injection ability, which can solve the problem of difficult sweep in low-permeability areas and expand the swept volume.

[0004] However, existing nano particles either have problems with insufficient performance or have the disadvantage of high cost. Summary of the Invention

[0005] To solve at least one of the above problems, the present invention proposes a silicon-based nano drag reduction enhanced oil displacement agent and a preparation method thereof, which have lower cost and better effects.

[0006] The technical solution of the present invention is as follows: A preparation method of a silicon-based nano drag reduction and enhanced oil displacement agent, in parts by mass, includes the following steps:

[0007] Take an amino silane coupling agent and modify nano-silica to obtain modified nano-silica;

[0008] Take 2-4 parts of modified nano-silica and disperse it evenly in a dispersant, then add 15-20 parts of F127 and 4 wt% of sodium bisulfate, and react under the conditions of deoxygenation and at 75-80 °C. After the reaction is completed, separate and purify it to obtain the product.

[0009] One embodiment of the present invention is that the amino silane coupling agent is KH550.

[0010] One embodiment of the present invention is that the preparation method of the modified nano-silica includes the following sub-steps: In parts by mass, take 1-3 parts of nano-silica and disperse it evenly in a dispersant; take 3-7 parts of amino silane coupling agent and add it to water for hydrolysis; under the condition of deoxygenation, mix the nano-silica dispersion liquid and the hydrolyzed amino silane coupling agent and heat up to 75-80 °C for reaction for 3-5 h. After the reaction is completed, separate and purify it to obtain the product. In fact, for the preparation method of the modified nano-silica, it is not limited to the steps disclosed in this step, and its specific preparation method can also be adjusted; or some existing commercial products of KH550-modified nano-silica can all be applied to the present invention.

[0011] Preferably, the dispersant is one of ethanol and water.

[0012] One embodiment of the present invention is that the reaction time is 6-8 h.

[0013] One embodiment of the present invention is that the particle size of the nano-silica is 20-30 nm.

[0014] Another object of the present invention is to disclose a silicon-based nano drag reduction and enhanced oil displacement agent, which is prepared by any of the above methods. The oil displacement agent has good effects and low costs.

[0015] Beneficial effects: The silicon-based nano drag reduction and enhanced oil displacement agent of the present invention has an interfacial tension with crude oil reaching the order of magnitude of 10 -1 mN / m; synergistically improve the wettability of the reservoir, reduce the adhesion work of crude oil and induce the formation of Pickering emulsion, reduce the flow resistance, and greatly improve the crude oil recovery rate. The method has a reliable principle, cheap and easily available raw materials, significant economic benefits, and broad industrial application prospects. Description of the Drawings

[0016] Figure 1This is the infrared test result diagram of the product of Example 1.

[0017] Figure 2 This is a graph showing the thermogravimetric analysis test results of the product of Example 1.

[0018] Figure 3 This is a microscopic morphology of the product of Example 1.

[0019] Figure 4 This is a test diagram of interfacial tension reduction of the products of Examples 1 and 2;

[0020] Figure 5 This is a test diagram of the oil recovery performance of the product of Example 1.

[0021] Figure 6 This is a test diagram of the oil recovery performance of the product of Example 2. DETAILED DESCRIPTION

[0022] The specific implementation modes of the present invention will be described clearly and completely below in conjunction with examples and drawings. Obviously, the described examples are only some embodiments of the present invention, rather than all embodiments.

[0023] In the following examples, F127 refers to a polyoxyethylene polyoxypropylene ether block polymer (poloxamer), which is a conventional commercial product.

[0024] Example 1: Preparation of modified nano-silica: Add 1 g of silica with a particle size of 20 nm to a 250 mL three-necked flask, then add 30 g of ethanol solution, stir at room temperature to ensure that the nano-silica is dispersed; weigh 5 g of KH550 and 10 ml of deionized water in a beaker, mix and hydrolyze them thoroughly, then transfer them to a three-necked flask, mix them thoroughly and deoxygenate them with nitrogen for 30 minutes, graft react in an oil bath at 80°C for 3 hours, purify and dry to obtain amino-terminated nano-silica.

[0025] Preparation of silicon-based nano-drag reduction and enhanced oil displacement agent: add 2g of amino-terminated nano-silica into a 250mL three-necked bottle, then add 30g of anhydrous ethanol, and ultrasonically oscillate for 30min to ensure that the nano-silica modified by the silane coupling agent is fully dispersed; add 15g of F127 and 4wt% of sodium bisulfate into the three-necked bottle, seal and stir, deoxygenate with nitrogen for 30min, carry out grafting reaction at 80°C for 6h, purify and dry to obtain the silicon-based nano-drag reduction and enhanced oil displacement agent.

[0026] Example 2: Preparation of modified nano-silica: Add 1 g of nano-silica with a particle size of 20 nm into a 250 mL three-necked flask, then add 30 g of ethanol solution, stir at room temperature to ensure the dispersion of nano-silica; weigh 7 g of KH550 and mix it with 10 ml of deionized water in a beaker for full hydrolysis, and then transfer it to the three-necked flask. After full mixing, purge with nitrogen to remove oxygen for 30 min, and carry out grafting reaction at 80 °C in an oil bath for 3 h. After purification and drying, amino-terminated nano-silica is obtained.

[0027] Preparation of silica-based nano-drag reduction enhanced oil displacement agent: Add 2 g of amino-terminated nano-silica into a 250 mL three-necked flask, then add 30 g of absolute ethanol, and oscillate ultrasonically for 30 min to ensure the full dispersion of nano-silica modified by silane coupling agent; add 15 g of F127 and 4 wt% of sodium bisulfate into the three-necked flask containing nano-silica modified by silane coupling agent, seal and stir, purge with nitrogen to remove oxygen for 30 min, and carry out grafting reaction at 80 °C in an oil bath for 6 h. After purification and drying, silica-based nano-drag reduction enhanced oil displacement agent is obtained.

[0028] In order to further illustrate the specific performance of the product prepared in the embodiment of the present invention, it is tested below.

[0029] 1. Characterization

[0030] Take the product of Example 1 for infrared test, and the final result is as Figure 1 shown.

[0031] The absorption peak near 3432.5 cm-1 is the characteristic absorption peak of -NH; the absorption peaks near 1103.3 cm-1 and 801 cm-1 are the characteristic absorption peaks of Si-O-Si; the absorption peaks near 1455.4 cm-1, 2967.6 cm-1 and 2873.3 cm-1 are the characteristic absorption peaks of -CH2-. The infrared result shows that the graft modification of nano-silica is successful.

[0032] Take the product of Example 1 and observe its microscopic morphology by scanning electron microscope. The result is as Figure 3 shown. From Figure 3 it can be seen that its overall is nanoscale.

[0033] 2. Thermogravimetric analysis

[0034] Take the product of Example 1 and unmodified nano-silica for thermogravimetric analysis experiment, and the final result is as Figure 2 shown.

[0035] From Figure 2 it can be seen that unmodified nano-SiO 2There is a small amount of mass loss before 200 °C, mainly due to the evaporation of water molecules on its surface and the decomposition of hydroxyl groups. After the temperature is greater than 200 °C, the mass remains basically unchanged. The heat loss of the modified nano-SiO2 mainly occurs at 200 - 600 °C, mainly caused by the high-temperature decomposition of the organic substances grafted on its surface.

[0036] 3. Viscosity Test

[0037] Prepare mineralized water with a salinity of 3×10 4 mg / L (the concentrations of Ca 2+ , Mg 2+ are 2×10 3 mg / L respectively), add the silicon-based nano-drag reduction enhanced oil displacement agent synthesized in Example 1, and prepare a solution with a mass concentration of 0.3%.

[0038] In a 50 mL graduated cylinder, mix the solution and dehydrated crude oil (with a viscosity of 199.2 mPa·s at 75 °C and a shear rate of 7.34 s -1 ) according to the water-oil volume ratios of 5:5, 7:3, 8:2, and 9:1 (the water cut is 50%, 70%, 80%, and 90% in sequence) to prepare a total volume of 30 mL, and seal it; then, under the condition of a 75 °C water bath, stir for 30 min, observe the emulsification situation. After the stirring ends, use a DV-III viscometer to measure the apparent viscosity of the emulsion at 75 °C and a shear rate of 7.34 s -1 as shown in Table 1.

[0039] Table 1 Viscosity of the emulsion formed by the nano-drag reduction enhanced oil displacement agent solution and crude oil

[0040]

[0041] As can be seen from Table 1, the silicon-based nano-drag reduction enhanced oil displacement agent in the examples of the present invention adsorbs at the oil-water interface under shear induction, and forms a Pickering emulsion under the condition of a water cut of 50 - 90%. The Pickering emulsion has a lower viscosity than the crude oil, thereby improving the viscosity of the crude oil and enhancing the oil recovery rate.

[0042] 4. Interfacial Tension Reduction Test

[0043] Use a Krüss SDT rotary drop interfacial tensiometer to measure the interfacial tension (IFT) after dropping crude oil (with a viscosity of 199.2 mPa·s) into the formation aqueous solutions of each example. The interfacial tension between the crude oil and the formation water is 21.6 mPa·s after stabilization. The IFTs of Examples 1 and 2 are as Figure 4 shown, and the interfacial tension reaches the order of 10 -1 mN / m, proving that Examples 1 and 2 have good interfacial tension reduction effects.

[0044] 5. Oil Displacement Test

[0045] Take the silicon-based nano drag reduction enhanced oil displacement agent of Examples 1 and 2, and add water to make it into a 0.3 wt% oil displacement agent dispersion; then use a homogeneous core to test its oil displacement ability at 75 °C. The gas permeability of the homogeneous core is: 400 mD; the diameter is 2.5 cm, and the length is 5 cm; the injection rate during the displacement process is 0.5 mL / min.

[0046] The experimental results are as Figure 5 shown. The oil recovery rate in the pre-waterflood stage of Example 1 is 41.5%; then a silicon-based nano drag reduction enhanced oil displacement agent solution with a total concentration of 0.3% is injected. During the injection process, the injection pressure first decreases and then increases. An O / W type emulsion is observed at the core outlet end, indicating that the silicon-based nano drag reduction enhanced oil displacement agent emulsifies with the crude oil to form a low-viscosity emulsion, improves the mobility ratio during the displacement process, expands the sweep efficiency, and finally increases the oil recovery rate by 23.0%.

[0047] The experimental results are as Figure 6 shown. The oil recovery rate in the pre-waterflood stage of Example 2 is 37.6%; then a silicon-based nano drag reduction enhanced oil displacement agent solution with a total concentration of 0.3% is injected. During the injection process, the injection pressure first decreases and then increases. An O / W type emulsion is observed at the core outlet end, indicating that the silicon-based nano drag reduction enhanced oil displacement agent emulsifies with the crude oil to form a low-viscosity emulsion, improves the mobility ratio during the displacement process, expands the sweep efficiency, and finally increases the oil recovery rate by 24.0%.

[0048] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a silicon-based nano drag-reducing and oil-displacing agent, characterized in that: The method comprises the following steps, in parts by mass: Taking an aminosilane coupling agent and modifying nano-silica to obtain modified nano-silica; Take 2-4 parts of modified nano-silicon dioxide and evenly disperse them in a dispersant, then add 15-20 parts of F127 and 4wt% of sodium bisulfate, react under deoxygenation and 75-80°C conditions, and after the reaction is completed, separate and purify it to obtain the product.

2. The method according to claim 1, characterized in that The aminosilane coupling agent is KH550.

3. The method according to claim 1, characterized in that The preparation method of modified nano-silica comprises the following steps: taking 1 to 3 parts of nano-silica by mass and uniformly dispersing it in a dispersant; taking 3 to 7 parts of aminosilane coupling agent and adding it into water and hydrolyzing it; under deoxygenation conditions, mixing the nano-silica dispersion and the hydrolyzed aminosilane coupling agent and heating them to 75-80°C for reaction for 3 to 5 hours, and after the reaction is completed, separating and purifying it to obtain the modified nano-silica.

4. The method according to claim 1, characterized in that: The reaction time is 6 to 8 hours.

5. The method according to claim 1 or 3, characterized in that: The dispersants are ethanol and water.

6. The method according to claim 1, characterized in that The particle size of the nano silicon dioxide is 20-30 nm.

7. A silicon-based nano drag-reducing and oil-displacing agent, prepared by the method according to any one of claims 1 to 6.

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