Crude oil nanometer pour-point-depressing oil-displacing agent and preparation method and application thereof

Abstract

The invention discloses a crude oil nano pour point depressing oil-displacing agent as well as a preparation method and application thereof, and belongs to the field of pour point depressing agents. The crude oil nano pour point depressing and oil displacement agent comprises the following components in percentage by mass: 5-30% of long-chain fatty acid diethanolamide, 0.5-4% of a cationic surfactant, 0.1-0.3% of an oleophylic modified nano material, 5-20% of an alcohol auxiliary agent, 1-10% of urea and the balance of water. Wherein the oleophylic modified nano material is selected from at least one of oleophylic modified nano silicon dioxide, graphene oxide and nano montmorillonite. The crude oil nanometer pour-point-depressing oil-displacing agent is good in stability and wide in application range, the use cost is reduced, and the pour-point-depressing oil-displacing effect can be achieved. The problems that an existing crude oil pour point depressant is complex in preparation process and narrow in application range are solved.

Description

Technical Field

[0001] This application relates to a crude oil nano-pour point depressant and its preparation method and application, belonging to the field of pour point depressants. Background Technology

[0002] High-pour-point oil reservoirs are abundant, but their crude oil has a high pour point and high wax content, making conventional water injection development prone to problems such as wax deposition and cold damage. Therefore, development is quite difficult, and recovery rates are generally 10%-15% lower than those of ordinary reservoirs in similar formations. The key to solving the problem of high-pour-point oil extraction lies in lowering the pour point of the crude oil and improving its low-temperature fluidity.

[0003] Petroleum pour point depressants are chemical agents widely used in oil pipeline transportation and storage. They inhibit the formation and growth of wax crystals and lower the pour point of petroleum through mechanisms such as adsorption, nucleation, eutectic formation, and solubilization. Representative pour point depressants include ethylene-vinyl acetate copolymers and ethylene-methyl acrylate copolymers. To improve the performance of pour point depressants, researchers are constantly developing new pour point depressant materials, such as modified nano-SiO2 and polymers combined with micro / nano materials. However, current research on the function of pour point depressant systems, both domestically and internationally, is limited to gathering and transportation processes and has not been tested in enhanced oil recovery and oil enhancement.

[0004] Currently, pour point depressants can be divided into two main categories: oil-soluble and water-soluble, each with its own advantages and disadvantages. Oil-soluble pour point depressants are suitable for pipelines and field dosing of crude oil with high wax and low water content because they can dissolve directly in crude oil, are easy to add, have high pour point depressing efficiency (achieving a pour point reduction of 10-14℃ and a viscosity reduction of more than 85% at around 400ppm), have good compatibility with other oil-based additives, and are relatively inexpensive. However, they are prone to failure in water-containing oil systems, have limited effectiveness at extreme low temperatures (below -40℃), and may pose an oil pollution risk. Water-soluble pour point depressants exist in water-based emulsion / dispersion forms, suitable for water-containing drilling fluids, water injection boosting, and other operations. They are environmentally friendly, have low viscosity, are easy to pump, and can be used in conjunction with other water-based additives. Their disadvantages are that they require surfactants to maintain stability, their pour point depressing effect is generally lower than that of oil-soluble depressants (pouring point reduction of only 3-6℃), and they are greatly affected by water quality (hardness, salinity, pH) and storage conditions.

[0005] The existing technical solutions are analyzed and explained as follows: Multi-component nano-hybrid formulation (CN120442231A): This formulation combines lauryl methacrylate-maleic anhydride-α-methylstyrene terpolymer, modified ethylene-vinyl acetate copolymer, two inorganic nano-pour point depressants, antioxidants, and lubricants. It achieves a pour point reduction of 10-14℃ and a viscosity reduction of over 85% at concentrations below 400 ppm, while remaining environmentally friendly and stable over the long term. Advantages: Synergistic improvement in pour point depressant efficiency through multiple components; low dosage; combined antioxidant and lubricating functions. Disadvantages: Complex formulation ratios; high requirements for raw material purity and mixing uniformity in the production process; costs increase with the input of nanomaterials.

[0006] Bispirocyclic viscosity reducer and pour point depressant (CN116426259A): The core is a polymer containing bispirocyclic substituents, which can disrupt the three-dimensional network structure of wax crystals, significantly reducing low-temperature viscosity without affecting crude oil quality. Advantages: Novel chemical structure, particularly effective at reducing viscosity in high-wax oils; high temperature resistance and chemical stability. Disadvantages: The synthesis route involves multiple steps of polymerization, esterification, and aminolysis, resulting in relatively high process costs; large-scale production still requires process optimization.

[0007] Polymer-silicone oil composite pour point depressant (CN120230294A): This product uses a polymer with a specific structure as its backbone, supplemented with long-chain fatty alcohols, silicone oil, and other additives. It significantly reduces the pour point and has a wide range of applications. Advantages: The formulation balances low pour point and lubricity, making it suitable for various crude oil types. Disadvantages: The cost of high-molecular-weight additives such as silicone oil is relatively high, and other low-temperature additives are still required at extremely low temperatures (below -40℃).

[0008] Low-dose, high-efficiency water-soluble pour point depressant (CN111217961A): Achieves a pour point reduction of over 10°C at 100 ppm, and due to the small amount of water introduced, it has no negative impact on the properties of crude oil or refined oil products; it also possesses additional functions such as room-temperature fluidity, corrosion inhibition, and scale inhibition. Advantages: Extremely low dosage, easy to transport at room temperature, and also provides corrosion and scale inhibition, reducing injection costs. Disadvantages: Sensitive to the water content in crude oil, requiring an aqueous phase stability assessment before injection; phase separation may occur in the aqueous phase at extremely low temperatures, necessitating the addition of antifreeze.

[0009] Existing pour point depressant technologies are more geared towards oil and gas gathering and transportation processes, and have not been tested and applied in enhanced oil recovery and oil enhancement. Furthermore, the production process of some pour point depressants is cumbersome, the synthesis process is complex, and the applicability is narrow, all of which increase the cost of use. Summary of the Invention

[0010] The purpose of this invention is to provide a high-efficiency nano-crude oil pour point depressant that is easy to manufacture and has wide applicability. It can effectively reduce the pour point of crude oil and has high interfacial activity. It can be directly applied to oilfield exploitation to improve the recovery rate.

[0011] Hydrophobically modified silica adsorbs wax molecules from crude oil through surface active sites (such as hydroxyl and alkyl chains), inducing heterogeneous nucleation of wax crystals and promoting the formation of finer, more uniform crystal particles, thus reducing the formation of large-sized wax crystal network structures. The morphology of wax crystals changes from irregular flocculent to regular plate-like or spherical, significantly reducing the bonding strength between wax crystals and weakening the gel network structure. The hydrophobic groups (such as long-chain alkyl groups) on the modified silica surface have enhanced affinity for wax molecules, isolating wax molecule aggregation through adsorption and delaying wax crystal growth and deposition. The high specific surface area of ​​nanoparticles provides numerous adsorption sites, dispersing in crude oil and forming steric hindrance, preventing wax crystal flocculation.

[0012] To improve the recovery rate of high-pour-point oil reservoirs, a nano-pour-depressant oil displacement agent was developed. By adding nanomaterials such as hydrophobically modified silica, modified nano-graphene oxide, and modified nano-montmorillonite, and compounding them with a surfactant system, it effectively lowers the pour point of high-pour-point oil, improves crude oil fluidity, and has high oil-water interface activity. This multi-purpose agent provides a new agent option for the exploitation of high-pour-point oil.

[0013] According to the first aspect of this application, a crude oil nano-pour point depressant and oil displacement agent is provided. This crude oil nano-pour point depressant and oil displacement agent has good stability, a wide range of applications, reduces usage costs, and can achieve the effect of pour point depressing and oil displacement. It solves the problems of complex preparation processes and narrow application range of existing crude oil pour point depressants.

[0014] A crude oil nano-pour point depressant and oil displacement agent, wherein the crude oil nano-pour point depressant and oil displacement agent comprises: 5-30% long-chain fatty acid diethanolamide, 0.5-4% cationic surfactant, 0.1-0.3% lipophilic modified nanomaterials, 5-20% alcohol additives, 1-10% urea, the remainder being water, measured by mass. The lipophilic modified nanomaterial is selected from at least one of lipophilic modified nano-silica, graphene oxide, and nano-montmorillonite.

[0015] Optionally, the crude oil nanoparticle pour point depressant comprises: 8-15% long-chain fatty acid diethanolamide, 1-3% cationic surfactant, 0.1-0.2% lipophilic modified nanomaterials, 12-18% alcohol additives, 3-8% urea, and the remainder is water, measured by mass.

[0016] Specifically, the crude oil nano-pour point depressant and oil displacement agent is composed of the following components: 10% long-chain fatty acid diethanolamide, 2% cationic surfactant, 0.1% lipophilic modified nanomaterials, 15% alcohol additives, 5% urea, and the remainder is water, measured by mass.

[0017] Optionally, the long-chain fatty acid diethanolamide has the structural formula C0. n H 2n+1 CON(CH2CH2OH)2; Where n is any integer from 5 to 20.

[0018] Optionally, n can be any integer from 8 to 15.

[0019] Specifically, the long-chain fatty acid diethanolamide is coconut oil fatty acid diethanolamine.

[0020] Optionally, the cationic surfactant is at least one selected from octadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, and hexadecylpyridine bromide.

[0021] Optionally, the alcohol auxiliary is at least one selected from ethylene glycol, polyethylene glycol, methanol, ethanol, isopropanol, and glycerol.

[0022] Optionally, the particle size of the oleophilic modified nanomaterial is 20-200 nm.

[0023] Optionally, the particle size of the oleophilic modified nanomaterial is 60-100 nm.

[0024] According to a second aspect of this application, a method for preparing a crude oil nano-pour point depressant and oil displacement agent is provided.

[0025] A method for preparing a crude oil nano-pour point depressant and oil displacement agent includes: S1. Add long-chain fatty acid diethanolamide to water, mix and stir evenly to obtain mixture I; S2. Add cationic surfactant and lipophilic modified nanomaterials to mixture I, mix and stir evenly to obtain mixture II; S3 adds alcohol additives and urea to mixture II, mixes and stirs evenly to obtain a uniform and stable crude oil nano pour point depressant and oil displacement agent.

[0026] As a preferred embodiment, the preparation method of the crude oil nano-pour point depressant and oil displacement agent includes: S1 long-chain fatty acid diethanolamide was added to water and stirred at 500 r / min for 5 minutes at room temperature to obtain mixture I. S2. Add cationic surfactant and lipophilic modified nanomaterials (nanomaterial particle size of 20-150nm) to mixture I, and stir at 500r / min for 10min at room temperature to mix evenly to obtain mixture II. S3 adds alcohol additives and urea to mixture II, and mixes them at a stirring speed of 500 r / min for 10 min at room temperature to obtain a uniform and stable pour point depressant and oil displacement agent.

[0027] According to a third aspect of this application, an application of a crude oil nano-pour point depressant and oil displacement agent is provided.

[0028] The above-mentioned crude oil nano-pour point depressant is used in pour point depressant and oil displacement in high pour point oil reservoirs.

[0029] The beneficial effects that this application can produce include: The crude oil nano-pour point depressant and displacement agent provided in this application, along with its preparation method and application, features a simple preparation method that can be completed in a short time at room temperature, solving the problem of complex preparation processes for existing crude oil pour point depressants. The provided crude oil nano-pour point depressant and displacement agent exhibits good stability, strong time-efficiency, and wide applicability, while also possessing good interfacial activity and a certain pour point depressing effect. It is a multi-purpose agent, reducing oilfield extraction costs and providing new impetus for the extraction of high-pour-point oil. Attached Figure Description

[0030] Figure 1 Photos of the initial synthesis of nano-pour point depressant oil displacement agent #1 and after 30 days under normal temperature and high temperature (70℃) conditions. Detailed Implementation

[0031] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0032] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0033] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0034] Example 1 The preparation steps of the lipophilic modified nano-silica are as follows: An equimolar amount (0.01 mol) of silane coupling agent KH570 and oleic acid were uniformly dispersed in 250 mL of a mixture of ethanol and deionized water (ethanol:water = 7:3). After stirring at 30°C for 1 h, 10 g of nano-silica particles were added to the solution, and the solution was then heated under reflux at 80°C for 6 h. After the reaction, the mixture was centrifuged multiple times, and the product was washed with ethanol and water. The product was then dried in a vacuum drying oven for 12 h to obtain the final product; the average particle size was 80 nm. Step 1: Add 10g of coconut oil fatty acid diethanolamine to 67.9g of deionized water, and stir at 500r / min for 5 minutes at room temperature until the mixture is homogeneous to obtain mixture I; Step 2: Add 2g of hexadecyltrimethylammonium bromide and 0.1g of modified nano-silica to mixture I, and stir at 500r / min for 10min at room temperature until the mixture is homogeneous to obtain mixture II; Step 3: Add 15g of ethylene glycol and 5g of urea to mixture II, and stir at 500r / min for 20 minutes at room temperature until homogeneous, to obtain a uniform and stable pour point depressant and oil displacement agent. This is designated as Nano Pour Point Depressant and Oil Displacement Agent 1#.

[0035] Example 2 The oleophilic modified graphene oxide was purchased from Changzhou Sixth Element Materials Technology Co., Ltd.; the particle size was 180 nm. Step 1: Add 10g of coconut oil fatty acid diethanolamine to 67.9g of deionized water, and stir at 500r / min for 5 minutes at room temperature until the mixture is homogeneous to obtain mixture I; Step 2: Add 2g of hexadecyltrimethylammonium bromide and 0.1g of lipophilic modified graphene oxide to mixture I, and stir at 500r / min for 10 minutes at room temperature until the mixture is homogeneous to obtain mixture II; Step 3: Add 15g of ethylene glycol and 5g of urea to mixture II, and stir at 500r / min for 20 minutes at room temperature until homogeneous, to obtain a uniform and stable pour point depressant and oil displacement agent. This is designated as Nano Pour Point Depressant and Oil Displacement Agent 2#.

[0036] Example 3 The oleophilic modified nano-montmorillonite was purchased from Zhejiang Fenghong New Material Co., Ltd.; the particle size was 100nm. Step 1: Add 10g of coconut oil fatty acid diethanolamine to 67.9g of deionized water, and stir at 500r / min for 5 minutes at room temperature until the mixture is homogeneous to obtain mixture I; Step 2: Add 2g of cetyltrimethylammonium bromide and 0.1g of lipophilic modified nano-montmorillonite to mixture I, and stir at 500r / min for 10min at room temperature until homogeneous to obtain mixture II; Step 3: Add 15g of ethylene glycol and 5g of urea to mixture II, and stir at 500r / min for 20 minutes at room temperature until homogeneous, to obtain a uniform and stable pour point depressant and oil displacement agent. This is designated as Nano Pour Point Depressant and Oil Displacement Agent 3#.

[0037] Comparative Example 1 The procedure is the same as in Example 1, except that oleophilic modified nano-silica is not used.

[0038] Comparative Example 2 The purchased oil-soluble pour point depressant #1 was purchased from Shandong Deshi Chemical Co., Ltd., with specification DE9817; the purchased oil-soluble pour point depressant #2 was purchased from Sasol Chemical Co., Ltd., with specification T210.

[0039] Using conventional testing methods, we conducted stability tests (at room temperature and 70°C), oil-water interfacial tension tests, wettability tests, and pour point depressant tests.

[0040] Test Example 1: Stability Test The pour point depressants and oil displacement agents of Examples 1-3 were placed under normal temperature / high temperature (70°C) conditions for stability observation. They were also taken out periodically for other performance tests. The results showed that the pour point depressants and oil displacement agents maintained stable performance for 30 days under both normal and high temperature conditions. Figure 1 The image shows the initial synthesis of nano-pour point depressant oil displacement agent #1 and photos taken after 30 days under normal temperature and high temperature (70℃) conditions.

[0041] Test Example 2: Interface Tension Test Preparation of mineralized water: Take 10g of sodium chloride into a 1L beaker, add 1000g of deionized water, and stir evenly to prepare mineralized water with a mineralization of 10000mg / L as formation simulation water. All diluents in the following examples use this mineralized water.

[0042] Preparation of diluent: Take 0.3g of oil displacement agent into a 100ml beaker, add mineralized water to 100g, stir well, and prepare a 0.3% (w / w) diluent.

[0043] The interfacial tension between the oil and water phases of high-pour-point oil and oil displacement agent dilution was tested using a rotating drop interfacial tension tester, with the instrument speed set at 5000 r / min, the instrument heating temperature at 70℃, and the density difference at 0.15.

[0044] The test results are shown in Table 1. It can be seen that the interfacial tension of the described pour point depressant #1 can reach 10. -3 mN / m, the addition of nanomaterials helps to reduce interfacial tension.

[0045] Test Example 3: Wettability Test Contact angle test: 0.5 mL of the diluent from Test Example 2 was aspirated using a syringe syringe to complete the solution transfer. The instrument was set to manually dispense the droplet. The droplet size was adjusted according to the needle's inner diameter to ensure a volume of approximately (2~5) µL. Through trial drops, the distance between the needle and the core slice was adjusted to ensure the needle did not contact the droplet on the core slice. The droplet dispensing process was video-recorded and saved. The first clear image showing the droplet forming a hemispherical shape 30 seconds after it landed on the core slice was selected, and the horizontal baseline position was adjusted. Under the same conditions, the same sample was measured multiple times, and the average value was recorded.

[0046] Capillary self-absorption height test: At room temperature, pour the test solution into the cuvette up to the top boundary, and add 0.05g of carmine powder for staining. Place the treated capillary (0.3mm inner diameter) vertically in the cuvette. Use a glass slide to keep all test capillary tubes vertical. Read and record the difference between the liquid level in the capillary tube and the height of the cuvette after the capillary tube has been submerged in the liquid for 10 minutes. Take different capillary tubes and measure 3 times, and take the average value.

[0047] The test results are shown in Table 1. The capillary self-absorption height of the pour point depressant #1 can reach 28 mm, and the 5-second rapid wetting contact angle of the core sample on the oil-wet surface measured by the contact angle measuring instrument is 25°.

[0048] Test Example 4: Determining the pour point depressant effect of crude oil. Weigh 10g of high-pour-point crude oil into a beaker, then add 0.1g of pour point depressant to the crude oil. Heat the crude oil with the pour point depressant in a water bath with stirring, slowly raising the temperature to 80℃ and holding it at that temperature for 30 minutes. Place the sample to be tested into a pour point tube, and simultaneously install a thermometer. Place the pour point tube containing the thermometer and the sample into a test tube trough. Obtain the pour point of the crude oil according to the SYT 0541-2009 Crude Oil Pour Point Determination Method, and compare it with the pour point of the blank sample. The difference between the two is the pour point depressant. The test results are shown in Table 1.

[0049] Table 1. Comparison of performance of pour point depressants and oil displacement agents made from different nanomaterials

[0050] The specific test results of nano pour point depressant oil displacement agent 1# are shown in Table 2.

[0051] Table 2

[0052] The pour point depressant 1# and the commercially available pour point depressant in Comparative Example 2 were tested on high pour point oil in a block of Liaohe Oilfield under the same test standards.

[0053] The test results are shown in Table 3.

[0054] Table 3 Comparison of Cough Depression Effects

[0055] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A crude oil nanodep os iting oil-displacing agent, characterized by, The crude oil nano pour point depressant oil displacement agent comprises: 5-30% long-chain fatty acid diethanol amide, 0.5-4% cationic surfactant, 0.1-0.3% oleophilic modified nanomaterial, 5-20% alcohol auxiliary agent, 1-10% urea, and the rest is water, with mass as the measurement basis; The oleophilic modified nanomaterial is at least one of oleophilic modified nanosilica, graphene oxide and nanomontmorillonite.

2. The crude oil nanodep ositing oil-displacing agent according to claim 1, characterized in that, The long chain fatty acid diethanolamide has a structural formula of C n H 2n+1 CON(CH2CH2OH)2; n is any integer in the range of 5-20.

3. The crude oil nanodep ositing oil-displacing agent according to claim 1, characterized in that, The cationic surfactant is at least one of octadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide and cetyl pyridinium bromide.

4. The crude oil nanodep ositing oil-displacing agent of claim 1, wherein, The alcohol auxiliary agent is at least one of ethylene glycol, polyethylene glycol, methanol, ethanol, isopropyl alcohol and glycerol.

5. The crude oil nanodep ositing oil-displacing agent of claim 1, wherein, The particle size of the oleophilic modified nanomaterial is 20-200 nm.

6. The method for preparing the crude oil nano-dewaxing oil displacement agent according to any one of claims 1-5, characterized in that, The method comprises: S1 adding long-chain fatty acid diethanol amide into water, mixing and stirring uniformly to obtain a mixed solution I; S2 adding cationic surfactant and oleophilic modified nanomaterial into the mixed solution I, mixing and stirring uniformly to obtain a mixed solution II; S3 adding alcohol auxiliary agent and urea into the mixed solution II, mixing and stirring uniformly to obtain a uniform and stable crude oil nano pour point depressant oil displacement agent.

7. Application of the crude oil nano pour point depressant oil displacement agent in any one of claims 1-5 in the pour point depression and oil displacement of high pour point oil reservoirs.

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