A method for preparing nano-titanium dioxide materials for oil displacement

Abstract

This invention discloses a method for preparing nano-titanium dioxide materials for oil displacement, comprising: adding nano-titanium dioxide to deionized water and stirring to form a uniform suspension slurry; then adjusting the pH to 8.5-9.5 using 10wt% NaOH solution to obtain slurry a; adding a certain amount of ethanol solution of tetraethyl orthosilicate or tetraethyl orthosilicate to slurry a, and simultaneously adding ammonia solution to maintain the pH of the entire slurry system within the range of 9-10, and aging for 30 min to obtain slurry b; then adding a certain amount of sodium aluminate solution and aluminum sulfate solution to slurry b, maintaining the pH of the entire slurry system within the range of 8-10, and aging for 30 min to obtain slurry c; then adding a certain amount of sulfonate to slurry c, and continuously stirring for 3-8 h to sulfonate and modify the coated nano-titanium dioxide to obtain slurry d; finally filtering, washing, and drying slurry d to obtain the final product. The method of this invention has the advantages of simple operation, low cost, and good controllability, and has promotional application value in the field of oil displacement nanomaterial production technology.

Description

Technical Field

[0001] This invention belongs to the field of materials and chemical engineering, and specifically relates to a method for preparing nano-titanium dioxide materials for oil displacement. Background Technology

[0002] Low-permeability reservoirs are generally characterized by poor physical properties and complex pore-throat structures. Studies have shown that submicron pores account for the largest proportion (>75%) in low-permeability reservoirs, forming the primary oil storage space. Matrix permeability is typically below 0.1 mD, porosity generally does not exceed 10%, and pore-throat diameter is less than 1 μm. These unique characteristics of the reservoirs make conventional oil displacement technologies ineffective. Currently, for the development of heterogeneous, low-permeability reservoirs, commonly used gas-driven and chemical-driven methods suffer from the following prominent problems: poor injection capability, as conventional chemical agents have large molecular sizes, making it difficult to penetrate submicron-level pore throats, resulting in a limited reach of the displacing fluid; poor environmental adaptability, as conventional polymers and surfactants are prone to degradation and precipitation under high temperature and high salinity conditions, leading to a significant decrease in performance; reservoir damage, as alkali in ternary composite flooding can cause scaling at the injection and production ends, making it difficult to meet the needs of efficient development of poorly shaped reservoirs; and high economic costs, as large quantities of chemical agents are used and significant adsorption losses increase extraction costs.

[0003] Highly efficient nanomaterials for oil displacement based on submicron throat scale offer a novel approach to solving the aforementioned challenges. Nanomaterials possess unique properties such as small size effect, surface effect, interface effect, and quantum effect. Their particle size can be as small as 20-100 nm, enabling them to easily penetrate the tiny pores of low-permeability reservoirs. The core technological advantages of nanomaterials for oil displacement are reflected in: improved injection performance—nanoparticles can weaken hydrogen bonding between water molecules, reducing the water molecule network structure and making it easier for water to enter smaller throats; reduced interfacial tension—the high specific surface area allows nanoparticles to effectively reduce oil-water interfacial tension even at low concentrations, promoting oil droplet coalescence and flow; altered wettability—nanoparticles can effectively change rock wettability (from oleophilic to hydrophilic), increasing wedge separation pressure and enhancing the ability to strip crude oil from the rock surface; and improved oil washing efficiency—nanoparticles easily form stable emulsions with crude oil within the reservoir, expanding the swept volume and improving oil displacement efficiency. Summary of the Invention

[0004] The purpose of this invention is to address the deficiencies and shortcomings of existing technologies by providing a method for preparing nano-titanium dioxide materials for oil displacement. This method uses nano-titanium dioxide as raw material, performs surface treatment with SiO2 and Al2O3, followed by sulfonation surface modification. The focus is on improving the high-temperature and high-salt resistance of the oil displacement agent and reducing interfacial tension, thereby increasing the oil displacement efficiency of nano-titanium dioxide as an oil displacement agent.

[0005] To achieve the above objectives, the present invention provides a method for preparing nano-titanium dioxide materials for oil displacement, the method mainly comprising the following steps:

[0006] Step a: Add nano-titanium dioxide to deionized water and stir to form a uniform suspension slurry. Then, use 10wt% NaOH solution to adjust its pH to 8.5-9.5 to obtain slurry a.

[0007] Step b: Add a certain amount of ethanol solution of tetraethyl orthosilicate or tetraethyl orthosilicate to slurry a, and at the same time add ammonia solution to maintain the pH of the entire slurry system in the range of 9 to 10, and age for 30 minutes to obtain slurry b.

[0008] Step c: Next, add a certain amount of sodium aluminate solution and aluminum sulfate solution to slurry b, maintain the pH of the entire slurry system in the range of 8 to 10, and age for 30 minutes to obtain slurry c;

[0009] Step d: Then, a certain amount of sulfonate is added to slurry c, and the mixture is stirred continuously for 3-8 hours to sulfonate the coated nano-titanium dioxide and obtain slurry d.

[0010] Step e: Finally, the slurry d is filtered, washed, and dried to obtain the final product.

[0011] In a preferred embodiment of the present invention, the production temperatures of slurry a, slurry b, slurry c, and slurry d in step ad are all maintained at 80°C to 95°C.

[0012] In a preferred embodiment of the present invention, the nano-titanium dioxide in step a is one or a mixture of two types: rutile and anatase.

[0013] Furthermore, the mass fraction of nano-titanium dioxide in the slurry a obtained in step a is 15% to 25%.

[0014] Further, in step b, the concentration of the ethanol solution of tetrabutyl or tetraethyl orthosilicate is 100 g / L, the amount added is based on SiO2, and the mass ratio of SiO2 to TiO2 is 0:100 to 10:100.

[0015] Further, in step c, the concentrations of both the sodium aluminate solution and the aluminum sulfate solution are 100 g / L, and the mass ratio based on Al2O3 is 5:5 to 6:4. The total amount of sodium aluminate solution and aluminum sulfate solution added is based on Al2O3, and the mass ratio of Al2O3 to TiO2 is 0:100 to 8:100.

[0016] Furthermore, in step d, the mass ratio of sulfonate added to TiO2 is 0.5:100 to 8:100.

[0017] In step d, the sulfonate is one or a mixture of several of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium hexadecylbenzene sulfonate, sodium petroleum sulfonate, and sodium lignin sulfonate.

[0018] Implementing this invention has the following beneficial effects:

[0019] The preparation method of the nano-titanium dioxide material for oil displacement of the present invention, compared with other methods, improves the high temperature resistance and salt resistance of nano-titanium dioxide by depositing a dense SiO2 film layer on the surface of nano-titanium dioxide through butyl or tetraethyl orthosilicate; by controlling the pH and rate of co-deposition of sodium aluminate solution and aluminum sulfate solution, a boehmite-type Al2O3 film layer is deposited on the surface of nano-titanium dioxide, which improves the dispersibility of nano-titanium dioxide in aqueous solution; and the subsequent sulfonation modification with sulfonate can reduce the interfacial tension of nano-titanium dioxide in aqueous solution and promote the coalescence and flow of oil droplets in oil displacement.

[0020] The method of the present invention has the advantages of simple operation, low cost and good controllability, and has promotion and application value in the field of oil displacement nanomaterial production technology. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The preparation method of this nano-titanium dioxide material for oil displacement includes the following steps:

[0023] Step a: Add nano-titanium dioxide to deionized water and stir to form a uniform suspension slurry. Then, use 10wt% NaOH solution to adjust its pH to 8.5-9.5 to obtain slurry a with a mass fraction of 15%-25% nano-titanium dioxide. The nano-titanium dioxide is one or a mixture of two types: rutile and anatase.

[0024] Step b: Add a certain amount of ethanol solution of butyl or tetraethyl orthosilicate with a concentration of 100 g / L to slurry a (the amount added is based on SiO2, and the mass ratio of SiO2 to TiO2 is 0:100 to 10:100), and at the same time add ammonia solution to maintain the pH of the entire slurry system in the range of 9 to 10. Aging for 30 min yields slurry b.

[0025] Step c: Next, add a certain amount of sodium aluminate solution and aluminum sulfate solution, both with a concentration of 100 g / L, to slurry b (mass ratio of Al2O3 is 5:5 to 6:4, total amount added is based on Al2O3, mass ratio of Al2O3 to TiO2 is 0:100 to 8:100), maintain the pH of the entire slurry system in the range of 8 to 10, and age for 30 minutes to obtain slurry c.

[0026] Step d: Then, a certain amount of sulfonate (the mass ratio of the amount added to TiO2 is 0.5:100 to 8:100) is added to slurry c, and the mixture is stirred continuously for 3 to 8 hours to sulfonate and modify the coated nano-titanium dioxide to obtain slurry d; wherein, the sulfonate is one or a mixture of several of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium hexadecylbenzene sulfonate, sodium petroleum sulfonate, and sodium lignin sulfonate.

[0027] Step e: Finally, the slurry d is filtered, washed, and dried to obtain the final product.

[0028] In the above steps a, the production temperature of slurry a, slurry b, slurry c, and slurry d is maintained at 80℃~95℃.

[0029] In this invention, there are no particular limitations on the filtration and washing of the final product; any conventional choices in the art can be used. For example, deionized water can be used for washing, and the amount of washing water is generally 10 to 20 times the mass of nano-TiO2.

[0030] The technical solution of the present invention will be described below using specific embodiments:

[0031] Example 1:

[0032] Weigh 15 g of nano-titanium dioxide and dissolve it in 100 mL of water. Stir for 10 min to obtain a suspension, then heat to 80℃. Add 10% NaOH solution to adjust the pH to 9.0, and stir for 20 min to obtain a titanium dioxide precursor solution. Add 3 mL of ethanol solution of tetrabutyl orthosilicate (100 g / L SiO2) using a constant flow pump, while simultaneously adding ammonia solution using a constant flow pump to maintain the pH of the suspension in the range of 9–10. Stir for 30 min for aging. Add 4 mL of aluminic acid solution (100 g / L Al2O3) using a constant flow pump, while simultaneously adding 3.5 mL of aluminum sulfate solution (100 g / L Al2O3) using a constant flow pump to maintain the pH of the suspension in the range of 8–9. Stir for 30 min for aging. Add 0.75 g of sodium dodecyl sulfate, and stir for 180 min. After the reaction is complete, allow to cool naturally, filter, and wash with deionized water. Finally, the material was dried at 120 °C for 12 h to obtain nano-titanium dioxide oil displacement material, which was designated as Sample 1.

[0033] Example 2:

[0034] Weigh 20 g of nano-titanium dioxide and dissolve it in 100 mL of water. Stir for 10 min to obtain a suspension, then heat to 95℃. Add 10% NaOH solution to adjust the pH to 9.5, and stir for 20 min to obtain a titanium dioxide precursor solution. Add 15 mL of tetraethyl orthosilicate ethanol solution (100 g / L SiO2) using a constant flow pump, while simultaneously adding ammonia solution using a constant flow pump to maintain the pH of the suspension within the range of 9–10. Stir for 30 min for aging. Add 2 mL of aluminic acid solution (100 g / L Al2O3) using a constant flow pump, while simultaneously adding 1.75 mL of aluminum sulfate solution (100 g / L Al2O3) using a constant flow pump to maintain the pH of the suspension within the range of 9–10. Stir for 30 min for aging. Add 1.5 g of sodium dodecylbenzenesulfonate, and stir the reaction for 180 min. After the reaction is complete, allow to cool naturally, filter, and wash with deionized water. Finally, the material was dried at 120 °C for 12 h to obtain nano-titanium dioxide oil displacement material, which was designated as sample 2.

[0035] Example 3:

[0036] 20 g of nano-titanium dioxide was dissolved in 100 mL of water and stirred for 10 min to obtain a suspension. The solution was then heated to 90 °C. 10% NaOH solution was added to adjust the pH to 9.0, and the mixture was stirred for 20 min to obtain a titanium dioxide precursor solution. 7 mL of aluminic acid solution (calculated as Al2O3, concentration 100 g / L) was added using a constant flow pump, while 6.5 mL of aluminum sulfate solution (calculated as Al2O3, concentration 100 g / L) was added simultaneously using a constant flow pump to maintain the pH of the suspension within the range of 8.5–9.5. The mixture was stirred for 30 min for aging. 1.75 g of sodium hexadecylbenzenesulfonate was added, and the reaction was stirred for 180 min. After the reaction was complete, the mixture was allowed to cool naturally, filtered, and washed with deionized water. Finally, it was dried at 120 °C for 12 h to obtain the nano-titanium dioxide oil displacement material, designated as sample 3.

[0037] Example 4:

[0038] Weigh 25 g of nano-titanium dioxide and dissolve it in 100 mL of water. Stir for 10 min to obtain a suspension, then heat to 95℃. Add 10% NaOH solution to adjust the pH to 9.0, and stir for 20 min to obtain a titanium dioxide precursor solution. Add 3 mL of tetrabutyl orthosilicate solution (100 g / L SiO2) using a constant flow pump, while simultaneously adding ammonia solution using a constant flow pump to maintain the pH of the suspension within the range of 9–10. Stir for 30 min for aging. Add 4 mL of aluminic acid solution (100 g / L Al2O3) using a constant flow pump, while simultaneously adding 3.5 mL of aluminum sulfate solution (100 g / L Al2O3) using a constant flow pump to maintain the pH of the suspension within the range of 9–10. Stir for 30 min for aging. Add 0.75 g of sodium dodecyl sulfonate and 0.5 g of sodium lignin sulfonate, and stir the reaction for 180 min. After the reaction is complete, allow to cool naturally, filter, and wash with deionized water. Finally, the material was dried at 120 °C for 12 h to obtain nano-titanium dioxide oil displacement material, which was designated as sample 4.

[0039] Example 5:

[0040] 25 g of nano-titanium dioxide was dissolved in 100 mL of water and stirred for 10 min to obtain a suspension. The solution was then heated to 85 °C. 10% NaOH solution was added to adjust the pH to 9.0, and the mixture was stirred for 20 min to obtain a titanium dioxide precursor solution. 1 g of sodium dodecyl sulfonate, 1 g of sodium hexadecylbenzene sulfonate, and 1 g of sodium petroleum sulfonate were added, and the mixture was stirred for 400 min. After the reaction was complete, the mixture was allowed to cool naturally, filtered, and washed with deionized water. Finally, it was dried at 120 °C for 12 h to obtain the nano-titanium dioxide oil displacement material, designated as sample 5.

[0041] The effectiveness of the technical solution of this invention is evaluated by detecting the surface tension of the modified nano-titanium dioxide oil displacement material in a surfactant solution:

[0042] First, the surface tension detection method used in this invention will be described in detail:

[0043] A mechanical stirring device was used, and the stirring speed was adjusted and stabilized at 300 r / min. Under continuous stirring, the components were added to the stirring container in a preset order to prepare a composite surfactant solution. The amount and order of addition of each component are as follows: 15 mL APG1214, 22.5 mL OAB-30, 10 mL EAB-40, 1 L AEO-9, 0.5 mL CA-60, 0.5 mL isomeric 1309, 10 mL isopropanol, and 40.5 mL deionized water. After all components were added, the stirring speed was maintained at 300 r / min until the solution in the stirring container became clear and transparent and there were no visible bubbles. Stirring was then stopped to obtain a homogeneous and stable composite surfactant solution. Next, 0.2 g of nano-titanium dioxide powder was weighed and slowly and evenly added to 10 mL of the prepared composite surfactant solution to avoid powder agglomeration. The mixture was then placed in an ultrasonic device, and the power of the ultrasonic device was adjusted to 100 W and kept stable for 1 h of continuous ultrasonic dispersion. During the ultrasonic process, the mixture was ensured to be uniformly stressed. After ultrasonication, a uniformly dispersed nano-titanium dioxide dispersion was obtained. Subsequently, 0.1 mL of the dispersion was accurately transferred from the obtained nano-titanium dioxide dispersion using a pipette and placed in a 100 mL volumetric flask. Deionized water was slowly added to the volumetric flask until the liquid level reached the mark. The flask was then capped and shaken thoroughly to ensure uniform dispersion concentration. The mixture in the volumetric flask was then placed back into the ultrasonic device and kept under ultrasonic conditions for 10 h. To further eliminate concentration inconsistencies, the solution to be tested was obtained. Finally, a calibrated surface tension meter was used to test the surface tension of the solution. During the test, the environmental conditions were kept consistent. After each test, the test dish was cleaned to avoid residual solution affecting subsequent test results. The test was performed in parallel for 3 times, and the surface tension value of each test was recorded. After removing outliers, the average value of the remaining test results was taken as the final surface tension value of the nano-titanium dioxide dispersion.

[0044] According to the above method, samples 1-5 obtained in Examples 1-5 were tested, and the test results are shown in Table 1:

[0045] Table 1 Test Results

[0046] Example 1 (Sample 1) 22.29 Example 2 (Sample 2) 21.75 Example 3 (Sample 3) 22.68 Example 4 (Sample 4) 22.70 Example 5 (Sample 5) 22.36

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing nano-titanium dioxide material for oil displacement, characterized in that, Includes the following steps: Step a: Add nano-titanium dioxide to deionized water and stir to form a uniform suspension slurry. Then, use 10wt% NaOH solution to adjust its pH to 8.5-9.5 to obtain slurry a. Step b: Add a certain amount of ethanol solution of tetraethyl orthosilicate or tetraethyl orthosilicate to slurry a, and at the same time add ammonia solution to maintain the pH of the entire slurry system in the range of 9 to 10, and age for 30 minutes to obtain slurry b. Step c: Next, add a certain amount of sodium aluminate solution and aluminum sulfate solution to slurry b, maintain the pH of the entire slurry system in the range of 8 to 10, and age for 30 minutes to obtain slurry c; Step d: Then, a certain amount of sulfonate is added to slurry c, and the mixture is stirred continuously for 3-8 hours to sulfonate the coated nano-titanium dioxide and obtain slurry d. Step e: Finally, the slurry d is filtered, washed, and dried to obtain the final product.

2. The method for preparing nano-titanium dioxide material for oil displacement according to claim 1, characterized in that, The production temperature of slurry a, slurry b, slurry c, and slurry d in step ad is maintained at 80℃~95℃.

3. The method for preparing nano-titanium dioxide material for oil displacement according to claim 1, characterized in that, The nano-titanium dioxide in step a is one or a mixture of two types: rutile and anatase.

4. The method for preparing nano-titanium dioxide material for oil displacement according to claim 3, characterized in that, The mass fraction of nano-titanium dioxide in the slurry a obtained in step a is 15% to 25%.

5. The method for preparing nano-titanium dioxide material for oil displacement according to claim 4, characterized in that, In step b, the concentration of the ethanol solution of tetrabutyl or tetraethyl orthosilicate is 100 g / L, and the amount added is based on SiO2, with a mass ratio of SiO2 to TiO2 of 0:100 to 10:

100.

6. The method for preparing nano-titanium dioxide material for oil displacement according to claim 4, characterized in that, In step c, the concentrations of both the sodium aluminate solution and the aluminum sulfate solution are 100 g / L, and the mass ratio of sodium aluminate solution to aluminum sulfate solution is 5:5 to 6:4 based on Al2O3. The total amount of sodium aluminate solution and aluminum sulfate solution added is based on Al2O3, and the mass ratio of Al2O3 to TiO2 is 0:100 to 8:

100.

7. The method for preparing a nano-titanium dioxide material for oil displacement according to claim 4, characterized in that, The mass ratio of sulfonate to TiO2 in d is 0.5:100 to 8:

100.

8. The method for preparing nano-titanium dioxide material for oil displacement according to claim 7, characterized in that, In step d, the sulfonate is one or a mixture of several of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium hexadecylbenzene sulfonate, sodium petroleum sulfonate, and sodium lignin sulfonate.