Nano surfactant for oil washing, preparation and application thereof

Abstract

The present invention provides a nano surfactant for oil washing, preparation and application thereof. The preparation method comprises the following steps: uniformly mixing a water-soluble component, an oil-soluble component and a surfactant to obtain a premix; heating the premix to 140-300°C under an atmospheric environment so that the material is in a molten state and a polycondensation reaction occurs between the materials, and after reacting for 10-180 minutes, nanoparticles having a hydrophilic group and a hydrophobic group are obtained. The prepared nano surfactant can have a high oil washing efficiency (more than 50%) at a relatively low concentration (0.005-0.1wt%), is not easily adsorbed by the formation, has a relatively low dynamic adsorption amount (≤5%), can emit a relatively strong fluorescence after being excited by light, and can be used as a fluorescent tracer to monitor the concentration and extraction of the nano surfactant underground. The preparation process is simple, the raw material cost is low, it is non-toxic, and it is easy to realize large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of tertiary oil recovery, and specifically comprises a nano surfactant for oil washing, and its preparation and application. Background Art

[0002] Surfactants have been used in many oil fields. They have good injectability and can peel off the residual oil film in the low permeability layer from the rock wall. They can achieve the effect of oil washing by changing wettability, reducing interfacial tension, emulsification and other effects. The key to improving the recovery rate of surfactants lies in their oil washing efficiency. However, surfactants have poor versatility for different oil fields. The types and proportions of surfactants that achieve ultra-low interfacial tension in different oils and formation waters are different. At present, the surfactants used for oil recovery are small molecules, which are easily adsorbed by the formation and diluted by the formation water. When they reach the oil layer, the concentration is not enough to make the oil and water reach ultra-low interfacial tension, which will reduce the oil washing efficiency. Therefore, the only way to solve this problem is to increase the injection concentration, which increases the cost, and a large amount of surfactants injected into the formation will cause certain pollution.

[0003] Nanomaterials are a new generation of oil displacement agents with great potential. They have low viscosity and nano-scale dispersion size, which can pass through the narrow pore throats of low permeability layers into the deep reservoirs. They mainly achieve oil displacement by changing the wettability of the rock wall to strip the oil from the rock wall surface. Nanoparticles have a larger specific surface area and higher activity and modification space. Currently, modified nano-SiO2 particles, modified graphene, and various metal oxides have been applied, but there are certain problems that limit their large-scale application. For example, SiO2 has a large density and is easy to agglomerate, which is easy to cause deposition; inorganic particles such as metal oxides are easy to cause formation damage; the preparation process of modified Janus graphene oxide is relatively complex and difficult, with low yield and high cost. In addition, the current modified nanoparticles are prepared first and then amphiphilic modification is performed on them, which is costly, low yield, and difficult to process. In order to achieve the requirement of stable dispersion in water, only an appropriate amount of hydrophobic groups can be introduced into the dilute dispersion, and the introduction of more hydrophobic groups will cause particle agglomeration and flocculation, resulting in a small number of hydrophobic groups on the surface.

[0004] Therefore, it is urgent to develop a one-step method for synthesizing nanosurfactants so that the obtained material has the dual advantages of surfactants and nanomaterials, and at the same time, the material contains more abundant hydrophilic and hydrophobic groups and has a lower dynamic adsorption capacity to reduce the problem of being easily adsorbed by formations during tertiary oil recovery. Summary of the invention

[0005] In view of the above problems existing in the prior art, the first object of the present invention is to provide a method for preparing a nano surfactant for washing oil. The preparation method adopts a solid phase method or a semi-solid phase method, and each raw material is molten under high temperature conditions, and then a polycondensation reaction occurs between the molten materials to form nanoparticles with strong surface (interface) activity and strong fluorescence under certain light wavelength excitation, i.e., nano surfactant. The whole preparation process is simple to operate, the raw material cost is low, it is non-toxic, and it is easy to achieve large-scale production.

[0006] The second object of the present invention is to provide a nano surfactant prepared by the above-mentioned preparation method. The nano surfactant can make the oil-water interfacial tension reach 10 at a relatively low concentration (0.005-0.1wt%). -1 -10 -2 mN / m, has a high oil washing efficiency (more than 50%), is not easily adsorbed by the formation, has a low dynamic adsorption capacity (≤5%), and can emit strong fluorescence after being excited by light. It can be used as a fluorescent tracer to monitor the concentration and production of nano-surfactants underground.

[0007] The third object of the present invention is to provide an application of the nano surfactant as described above in tertiary oil recovery of low permeability reservoirs or high temperature and high salinity reservoirs.

[0008] To achieve the above first object, the technical solution adopted by the present invention includes:

[0009] The present invention discloses a method for preparing a nano surfactant for oil washing, comprising the following steps:

[0010] Evenly mixing the water-soluble component, the oil-soluble component and the surfactant to obtain a premix;

[0011] The premix is ​​heated to 140-300° C. in an atmospheric environment to make the material molten and cause polycondensation reaction between the materials. After the reaction lasts for 10-180 minutes, nanoparticles having hydrophilic groups and hydrophobic groups are obtained.

[0012] When preparing nano particle type surfactant in the prior art, usually all is to prepare nano particle first, then carry out hydrophobic modification on surface, the hydrophobic group quantity that this mode can introduce is few, because more hydrophobic groups are connected, on the one hand the hydrophilic group quantity on surface is reduced, on the other hand more hydrophobic groups can make nano particle reunion, can not stably disperse in water.Based on this, the inventor has developed the preparation method of one-step method direct synthesis washing oil nano surfactant, each material required for preparing nano surfactant is heated to molten state, polycondensation reaction is generated between the material in molten state, thereby make the nano particle obtained have more abundant hydrophilic and hydrophobic groups.Adding surfactant simultaneously when feeding, can make water-soluble component and oil-soluble component mix more evenly, can stand reaction under no stirring, surfactant also participates in polycondensation reaction, provides hydrophilic group and hydrophobic group for the nano particle produced by reaction simultaneously, can significantly increase the hydrophobic group quantity introduced on surface, make nano particle have stronger interface activity, have good water dispersibility simultaneously. The whole process is simple to operate, and the reaction time is short. It only needs to fully mix the raw materials and heat them to the molten state for reaction. No additional solvent and catalyst are required. The raw material cost is low, non-toxic, and easy to achieve large-scale production. The obtained nano surfactant has the advantages of both surfactants and nano materials. The low-viscosity and small-sized nano surfactants are easier to enter the low-permeability layer through smaller pore throats. At the same time, the nano particles are not easily adsorbed by the formation, and are easier to peel off after adsorption. The dynamic adsorption amount is small, and it can be used alone without alkali and sacrificial agents, which greatly reduces the use cost. It can also make the crude oil and formation water reach ultra-low interfacial tension. The oil-water interface film formed by the nano particles is more stable than the interface film of the small molecule surfactant, and it can have a higher oil washing efficiency at low concentrations. It has good temperature resistance and salt resistance, thereby improving the current difficulty of oil recovery in low-permeability formations and greatly improving the recovery rate. In addition, the complex structure generated by it can emit strong fluorescence after being excited by light, and it can be used as a fluorescent tracer to monitor the concentration and production of the nano surfactant underground.

[0013] Furthermore, in the premix, the water-soluble component accounts for 20-60wt%, the oil-soluble component accounts for 0-10wt%, and the surfactant accounts for 40-80wt%.

[0014] Furthermore, the water-soluble component includes, but is not limited to, one or more of a water-soluble polybasic organic acid, a water-soluble polybasic organic amine and a water-soluble polyol.

[0015] Furthermore, the water-soluble polybasic organic acid includes, but is not limited to, one or more of citric acid, tartaric acid, oxalic acid, malic acid, malic acid and succinic acid.

[0016] Furthermore, the water-soluble polybasic organic amine includes, but is not limited to, one or more of ethylenediamine, urea, thiourea and melamine.

[0017] Furthermore, the water-soluble polyol includes, but is not limited to, one or more of ethylene glycol, propylene glycol, glycerol, polyethylene glycol, polyglycerol, sorbitol and glucose.

[0018] Furthermore, when the water-soluble component is selected from one or more of citric acid, tartaric acid, malic acid, urea, thiourea, glycerol, polyglycerol and glucose, the performance of the obtained nanosurfactant is better.

[0019] Furthermore, the oil-soluble components include, but are not limited to, one or more of fatty acids, fatty acid esters, fatty amines, fatty alcohols, aromatic acids, aromatic amines, and phenols.

[0020] Further, the fatty acid is C 8- C 18 The saturated or unsaturated fatty acid, the fatty acid ester is C8-C 18 Saturated or unsaturated fatty acid methyl ester, the fatty amine is C 8- C 18 The saturated or unsaturated fatty amine, the fatty alcohol is C 8- C 18 Saturated or unsaturated fatty alcohols.

[0021] Furthermore, the aromatic acid includes, but is not limited to, one or more of benzoic acid, cinnamic acid, phthalic acid, isophthalic acid and terephthalic acid.

[0022] Furthermore, the aromatic amine includes, but is not limited to, one or more of aniline, o-phenylenediamine, m-phenylenediamine and p-phenylenediamine.

[0023] Furthermore, the phenols include, but are not limited to, one or more of phenol, catechol, resorcinol and hydroquinone.

[0024] Furthermore, when the oil-soluble component is selected from one or more of octadecanoic acid, octadecyl alcohol, benzoic acid, cinnamic acid and methyl laurate, the performance of the obtained nano surfactant is better.

[0025] Furthermore, the surfactant includes a water-soluble surfactant and / or an oil-soluble surfactant.

[0026] Further, the water-soluble surfactant includes but is not limited to fatty alcohol polyoxyethylene ether (AEO-7, AEO-9, AEO-15, AEO-20), LAE-9, alkylphenol polyoxyethylene ether (OP-10, OP-15, OP-20), surfactant 6501, Tween 20, Tween 40, Tween 60, Tween 80, C8-C18 alkyl carboxylate sodium, C8-C18 alkylbenzene sulfonate sodium, C8-C18 alkyl sulfonate sodium, C8-C18 alkyl sulfate sodium, AES-3, AOS, FMES, surfactant 1227, table One or more of surfactant 1231, surfactant 1631, surfactant 1831, CTAB, C12-C18 alkyl betaine, C12-C18 alkyl dimethyl hydroxysulfonate, C12-C18 alkyl amidopropyl betaine, C12-C18 alkyl amidopropyl hydroxysulfonate, cocamidopropyl betaine, cocamidopropyl hydroxysulfonate, oleamidopropyl betaine, oleamidopropyl hydroxysulfonate, erucamidopropyl betaine, erucamidopropyl hydroxysulfonate, lauroyl lysine, and 2-hydroxypropyl arginine.

[0027] Furthermore, the oil-soluble surfactant includes but is not limited to one or more of AEO-3, AEO-5, Span 20, Span 40, Span 60, Span 80, C8-C18 saturated or unsaturated fatty acid monoglycerides, C8-C18 saturated or unsaturated fatty acid diglycerides and alkyl tertiary amine salts.

[0028] The selection of raw materials also needs to take into account the actual production situation. In a specific embodiment, the raw materials are selected from non-toxic or low-toxic substances, and the prepared nano-surfactant is a non-toxic substance. In addition, considering that a high-temperature heating reaction is carried out under an atmospheric environment, some water-soluble materials and oil-soluble materials may decompose or generate gases with a certain odor during the reaction, such as amines and phenols. The materials can be optimized according to the above materials. The surfactants are mostly selected from non-toxic daily-use surfactants, which are not easy to decompose and generate gases during high-temperature heating. They only need to be selected according to the application.

[0029] The choice of temperature determines the size of the formed nanoparticles and the number of surface groups. Different structures have different reaction difficulties and require different reaction temperatures. In a specific embodiment, when the water-soluble component and the oil-soluble component contain a combination of carboxyl and amino structures, the reaction temperature is preferably 140-200°C; when the water-soluble component and the oil-soluble component do not contain a combination of carboxyl and amino structures, the reaction temperature is preferably 200°C-300°C. For surfactants, they can participate in the reaction within a given temperature range. The choice of surfactant plays a decisive role in the type and number of surface groups and the oil washing efficiency, and plays a key auxiliary and connecting role in the formation of nanoparticles.

[0030] In a specific embodiment, the reaction time and reaction temperature should also be reasonably matched. When the reaction temperature is high, the reaction time can be appropriately shortened, and when the reaction temperature is low, the reaction time can be extended to make the material react more fully. For example, when the reaction temperature is 140-160°C, the reaction time is preferably controlled at 100-180min; when the reaction temperature is 160-180°C, the reaction time is preferably controlled at 80-120min; when the reaction temperature is 180-200°C, the reaction time is preferably controlled at 60-90min; when the reaction temperature is 200°C-260°C, the reaction time is preferably controlled at 50-100min; when the reaction temperature is 260°C-300°C, the reaction time is preferably controlled at 10-60min.

[0031] The mixing of the raw materials also has a great influence on the subsequent polycondensation reaction. Since no external stirring operation is performed during the polycondensation reaction, it is necessary to ensure that the premix is ​​pre-mixed uniformly. In a specific embodiment, the method of obtaining the premix varies according to the state of the raw materials: 1) When the raw materials are all solid raw materials, each raw material can be fully ground into a fine powder of 100-200 mesh using an agate mortar to make the materials contact more fully and achieve the purpose of uniform mixing; if the particle size of each raw material is too large, it is not conducive to the subsequent polycondensation reaction; 2) When the raw materials are all liquid raw materials, it is only necessary to add each raw material in proportion and stir it fully; 3) When the raw materials include both solid raw materials and liquid raw materials, the solid raw materials must be ground first and then added to the liquid raw materials, and stirred fully to form a uniform suspension.

[0032] To achieve the above second purpose, the technical solution adopted by the present invention includes:

[0033] The invention discloses a nano surfactant for oil washing, which is prepared by the above-mentioned preparation method.

[0034] Furthermore, the average particle size of the nano surfactant is 1-20 nm.

[0035] The nanoparticle interface film formed by the nanosurfactant has higher stability than that of small molecule surfactants. The introduction of chemical bonds of the surfactant makes the surface of the nanoparticles carry more hydrophilic and lipophilic groups, which has stronger interfacial activity and is easy to form adsorption at the oil-water interface. The rich amphiphilic groups can greatly reduce the oil-water interfacial tension. Under certain conditions, the interfacial tension can reach 10 -1 -10 -2 mN / m, with more groups and stronger interfacial activity than general nano-modified particles, it is very easy to invade the oil film, change the contact angle between crude oil and rock, form wetting reversal, and achieve the purpose of oil washing by reducing interfacial tension and changing to a suitable contact angle, so it is more effective. The chemically bonded surfactants are distributed on the surface and interspersed in the interior, and will not fall off with the dilution of formation water and the increase of formation temperature. They have better stability and will not agglomerate under high salt conditions. In addition, nano-surfactants not only have good dispersibility, but also their nano-scale size makes it easier to enter the deep oil reservoir, and it is not easy to be adsorbed by the porous structure of the rock. After adsorption, they are easily washed down with the subsequent water flow and continue to enter the oil reservoir to wash oil, and they can have a high ability to reduce interfacial tension and oil washing efficiency in a wide concentration range (0.005-0.1wt%).

[0036] To achieve the third objective above, the technical solution adopted by the present invention includes:

[0037] The present invention discloses an application of the nano surfactant described above in tertiary oil recovery of low-permeability oil reservoirs or high-temperature and high-salinity oil reservoirs.

[0038] Currently, the most efficient surfactant for oil recovery is betaine-type surfactant. Although it can make the crude oil / formation water interfacial tension reach ultra-low within a wide concentration range (0.05%-1%), reducing the problem of formation adsorption leading to concentration reduction and the inability to reach ultra-low interfacial tension, it is only insensitive to concentration and does not fundamentally solve the formation adsorption problem (dynamic adsorption amount is 20-30%), and the oil washing efficiency is not high. When the concentration of betaine-type surfactant is 0.05%, the oil washing efficiency is 20-30%, which cannot meet the tertiary oil recovery technical requirements of various oil reservoirs. The nano surfactant of the present invention can greatly reduce the dynamic adsorption effect, so a lower dosage can be used to achieve a better oil washing effect, reducing the waste of nano surfactants, and greatly reducing the use cost and formation pollution.

[0039] Further, the specific steps of the application are:

[0040] The nanosurfactant is dispersed to a mineralization degree of 5×10 3 -2.2×10 5mg / L of oil field is injected into water to prepare an oil washing system, which is used for tertiary oil recovery in low permeability reservoirs or high-temperature and high-salinity reservoirs.

[0041] Furthermore, the concentration of the nano-surfactant for oil washing in the oil washing system is 0.005-0.1 wt %.

[0042] Furthermore, in the application, the dynamic adsorption amount of the nano-surfactant is ≤5%.

[0043] Beneficial effects of the present invention:

[0044] 1. Using water-soluble components, oil-soluble components and surfactants as raw materials, nanoparticles with abundant hydrophilic and hydrophobic groups, namely nanosurfactants, are directly prepared in a one-step method, which has the dual advantages of surfactants and nanoparticles. The surfactants used in the raw materials can make the materials mix more fully, and directly prepare nanoparticles with other substances in the form of chemical bonds, so that the prepared nanoparticles have more hydrophilic groups and long-chain hydrophobic groups on the surface, have strong interfacial activity, have stronger invasiveness to oil films, and still have good water dispersibility when containing many hydrophobic groups.

[0045] 2. A simple one-pot solid phase or semi-solid phase method is used, and the preparation can be done directly by heating. No additional solvents, catalysts, or complex equipment are required. Large-scale preparation can be done under normal pressure. The materials used are low-cost, non-toxic, and harmless. The obtained products are also non-toxic, greatly reducing the difficulty and cost of production, and without ecological pollution. The prepared nano-sized surfactant is not easily adsorbed by the porous structure of the formation rock, and is also easily washed down by subsequent water flow after adsorption. The dynamic adsorption amount of nanoparticles is small, which reduces the adsorption problem of small molecule surfactants in the formation. No external sacrificial agent is required, and the formation adsorption problem is essentially solved.

[0046] 3. The abundant hydrophilic and lipophilic groups on the surface of nanosurfactants have stronger interfacial activity and interfacial stability than small molecule surfactants and modified nanoparticles. At a relatively low concentration (0.005%-0.1%), the oil-water interfacial tension reaches 10 -1 -10 -2 mN / m, and has a more efficient oil washing efficiency (≥50%) than small molecule surfactants, while having the ability of surfactants to reduce interfacial tension and the property of nanoparticles to change wettability.

[0047] 4. Nano surfactants can emit green or yellow light under the excitation of 350-450nm wavelength, which can be used for fluorescence tracing, timely monitoring the concentration of nano surfactants in the produced fluid, and timely replenishment. The surfactants are connected in the nanoparticles and on the surface in the form of complex chemical bonds, so they have strong temperature and salt resistance. 3-2.2×10 5 mg / L water can be dispersed into nano-sized particles with an average particle size range of 1-20 nm. 3 -2.2×10 5 mg / L) and can exist stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0049] Figure 1 This is a transmission electron microscope photograph of the nanosurfactant prepared in Example 1.

[0050] Figure 2 The XPS test spectrum and structural analysis of the nanosurfactant prepared in Example 1;

[0051] in, Figure 2 (1) is the full spectrum; (2) is the N1s fine spectrum and its analysis; (3) is the C1s fine spectrum and its analysis; (4) is the O1s fine spectrum and its analysis.

[0052] Figure 3 This is the infrared spectrum of the nanosurfactant prepared in Example 1.

[0053] Figure 4 This is the fluorescence spectrum of the nano-surfactant aqueous dispersion solution prepared in Example 1 at an excitation wavelength of 410 nm.

[0054] Figure 5 This is a graph showing the interfacial tension variation of the nanosurfactant prepared in Example 1 under simulated formation conditions. DETAILED DESCRIPTION

[0055] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and drawings. It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In the present invention, in order to simulate the actual application effect of nano surfactants in tertiary oil recovery, the embodiments and comparative examples of the present invention adopt the following steps to carry out the oil washing experiment test of nano surfactants:

[0057] (1) Preparation of oil sands saturated with crude oil

[0058] The simulated formation sand was mixed with the crude oil of the target block in a mass ratio of 4:1, placed in an oven and aged at reservoir temperature for 7 days. The mixture was stirred once a day to ensure that the oil sand was evenly mixed. After aging, crude oil-saturated oil sand was obtained. The composition of the simulated formation sand is shown in Table 1.

[0059] Table 1 Simulated formation sand composition

[0060]

[0061] (2) The nanosurfactant is dispersed to a mineralization degree of 5×10 3 -2.2×10 5 The oil sand saturated with crude oil is mixed with the nano surfactant and oil sand in a mass ratio of 5:1 in the formation simulated water with a concentration of 100 mg / L to prepare an oil washing system. After being kept constant at the simulated formation temperature for 48 hours, the washed crude oil and oil displacement agent water are poured out, and the remaining oil sand is dried to calculate the oil washing efficiency. The specific steps are as follows:

[0062] ① Weigh 20g of aged oil sand and put it into a 250ml sterilized bottle, and the weighed mass is m1. Add 100g of dispersed nanosurfactant formation simulation water dispersion to it, mix thoroughly and let it stand at reservoir temperature for 48h. After standing, use clean cotton yarn to dip out the crude oil floating on the liquid surface and adhering to the bottle wall, pour out the nanosurfactant dispersion in the bottle, and dry it at 100℃ to constant weight to get m2.

[0063] ② The quality of the bottles and oil sands used are the same as those in ①. Use petroleum ether with a boiling range of 90℃-120℃ to elute the crude oil from the oil sand after saturation with crude oil until the petroleum ether becomes colorless. Place the eluted sample bottle in a 120℃ oven and dry it to constant weight, and weigh it to obtain m3.

[0064] The oil washing efficiency is calculated according to formula (1):

[0065]

[0066] ——Oil washing efficiency, %;

[0067] m1——the total mass of the sterilized bottle and oil sand before washing the oil, in g;

[0068] m2——the total mass of the sterilized bottle and oil sand after oil washing, in g;

[0069] m3 – the total mass of the formation sand after washing with the sterilized bottle and petroleum ether, in grams.

[0070] In some embodiments of the present invention, crude oil and formation conditions of Changqing Ansai Oilfield, Shengli Oilfield, Daqing Oilfield, and Xinjiang Tahe Oilfield were selected for oil washing experiments.

[0071] In the present invention, the total content of nanosurfactants in the liquid after passing through the simulated sand tube is calculated through a dynamic adsorption experiment, and then the dynamic adsorption amount is calculated. The specific experimental steps are as follows:

[0072] Select a glass chromatography column with a length of 406 mm and a diameter of 32 mm, and fill 500 g of simulated formation sand into the chromatography column to about 300 mm. First, wet the sand tube completely with formation simulated water, pour 50 g of nano surfactant formation simulated water dispersion (concentration: 0.1 wt%) from the top of the chromatography column, turn on the chromatography column switch, collect the effluent, wait until the upper liquid surface completely enters below the sand surface, and slowly rinse with formation simulated water. Take samples during the process, use a fluorescence spectrometer to monitor in real time whether the effluent has fluorescence, and the concentration of nano surfactant in the effluent can be monitored in real time according to the standard curve. Pour the sampled liquid into the collection bottle together, wait until the fluorescence value cannot be detected, and then rinse with 50 g of formation simulated water for the last time, test the total concentration c in the collection bottle, and convert it into the washed nano surfactant mass m (where m=Mc) according to the total mass M of the collected liquid. If other small molecule detergents with no fluorescence or very weak fluorescence are detected, high performance liquid chromatography can be used to detect the concentration. The adsorption amount was calculated by formula (2).

[0073]

[0074] Γ——adsorption amount, %;

[0075] m——mass of oil washing agent in the effluent, in g;

[0076] M – total mass of effluent, in g.

[0077] Example 1

[0078] 1g tartaric acid, 1g urea as water-soluble component, 0.5g cinnamic acid as oil-soluble component and 2.5g surfactant 1227 are fully ground and mixed in an agate mortar and ground into a fine powder of 100-200 mesh. The mixture is poured into a crucible and heated to a molten state at 140°C without external stirring. After reacting for 120 minutes, the molten black or brown viscous liquid is cooled at room temperature, taken out and ground into a fine powder to obtain a nano surfactant.

[0079] The conditions of Xinjiang Tahe Oilfield were used as the experimental object, and the obtained nanosurfactant was dispersed into the simulated formation water (mineralization: 2.2×10 5 The dispersed nanosurfactant was mixed with oil sand saturated with Xinjiang Tahe crude oil at a mass ratio of 5:1, kept at a constant temperature for 48 hours at formation temperature (130°C), the washed crude oil and oil displacement agent solution were poured out, and the remaining oil sand was dried and the oil washing efficiency was calculated to be 75%.

[0080] The structure and performance of the nanosurfactant prepared in Example 1 were characterized. In order to prevent the unreacted raw materials from interfering with the test, the prepared nanosurfactant was purified before the structural characterization. The specific purification steps were as follows:

[0081] The obtained nanosurfactant was dispersed in ultrapure water and ultrasonicated for 15 minutes to ensure complete dispersion. The mixture was centrifuged at 15,000 r / min for 10 minutes, the upper liquid was discarded, and the process was repeated five times. The same operation was then repeated five times using dichloromethane. Finally, the same operation was repeated several times using ethanol. The purified nanosurfactant was obtained after drying.

[0082] from Figure 1 It can be seen that the particle size of the nanosurfactant is about 3 nm, evenly distributed, and has good dispersibility; Figure 2 It can be seen that nanosurfactants are central nanoparticles composed of complex structures such as aromatic rings and heterocyclic rings, with alkyl chains, carboxyl groups, amino groups, amide groups, quaternary ammonium salts and other groups connected to the surface; Figure 3 It can be seen that nanosurfactants contain amino, amide, hydroxyl, carboxyl, quaternary ammonium salt, alkyl chain and other groups. Figure 2 and Figure 3 The results show obvious characteristic peaks of surfactants, which proves that surfactants exist in the nanoparticles in the form of chemical bonds; Figure 4 It can be seen that the nanosurfactant can emit strong fluorescence under the excitation of light with a wavelength of 410nm, and its emission peak is at 540nm; Figure 5 It can be seen that under simulated formation conditions and a dispersion concentration of 0.1wt%, the interfacial tension between crude oil and formation water can reach 10 -2 mN / m. The particle size and dynamic adsorption results are shown in Table 2.

[0083] Example 2

[0084] The water-soluble components 1g malic acid, 2g thiourea, 0.3g hexadecyltrimethylammonium bromide, and 1g lauroyl lysine are fully ground and mixed in an agate mortar to form a fine powder of 100-200 mesh, and then slowly poured into 2g octadecyl betaine (35wt% aqueous solution), a surfactant, and fully mixed to form a slurry suspension under stirring. The suspension is poured into a crucible, and heated to a molten state at 200°C without external stirring. After reacting for 80 minutes, the molten black or brown viscous liquid is cooled at room temperature, taken out, and ground into a fine powder to obtain a nano surfactant.

[0085] The Daqing Oilfield was used as the experimental object, and the obtained nanosurfactant was dispersed into the simulated formation water (mineralization: 5×10 3The dispersed nanosurfactant was mixed with oil sand saturated with Daqing crude oil at a mass ratio of 5:1, kept at a constant temperature for 48 hours at formation temperature (65°C), the washed crude oil and oil displacement agent solution were poured out, and the remaining oil sand was dried and the oil washing efficiency was calculated to be 55%.

[0086] The nanosurfactant can emit strong fluorescence under 350nm wavelength excitation, and its emission peak is at 512nm. The particle size and dynamic adsorption results are shown in Table 2.

[0087] Example 3

[0088] 1g of glucose as a water-soluble component, 0.5g of AOS as a surfactant, and 0.7g of lauric acid diglyceride are ground into fine powders of 100-200 mesh, and mixed evenly to obtain a solid mixed fine powder; 1g of methyl laurate as an oil-soluble raw material and 6g of dodecyl dimethyl hydroxysulfobetaine (a 30wt% aqueous solution) as a surfactant are mixed evenly to obtain a mixed liquid; the solid mixed fine powder is slowly poured into the mixed liquid, and fully stirred to form a slurry suspension, and heated to a molten state at 240°C without external stirring, and after reacting for 60 minutes, the molten black or brown viscous liquid is cooled at room temperature, taken out and ground into fine powder to obtain a nano surfactant.

[0089] Changqing Ansai Oilfield was used as the experimental object, and the obtained nanosurfactant was dispersed into the simulated formation water (mineralization: 6×10 4 The dispersed nanosurfactant was mixed with the oil sand saturated with Changqing Ansai crude oil at a mass ratio of 5:1, kept at a constant temperature for 48 hours at the formation temperature (60°C), and the washed crude oil and oil displacement agent solution were poured out. The remaining oil sand was dried and the oil washing efficiency was calculated to be 59%.

[0090] The nanosurfactant can emit strong fluorescence under 450nm wavelength excitation, and its emission peak is at 587nm. The particle size and dynamic adsorption results are shown in Table 2.

[0091] Example 4

[0092] Mix 1g glycerol, 1g Tween 80, 1g Span 80, 1g surfactant 6501 and 1g AEO-3 of water-soluble raw materials evenly, pour into a crucible, heat to a molten state at 300°C without external stirring, react for 10 minutes, cool the molten black or brown viscous liquid at room temperature, take it out and grind it into fine powder to obtain a nano surfactant.

[0093] Shengli Oilfield was used as the experimental object, and the obtained nanosurfactant was dispersed into the simulated formation water (mineralization: 4×10 4The dispersed nanosurfactant was mixed with the oil sand saturated with Shengli crude oil at a mass ratio of 5:1, kept at a constant temperature for 48 hours at the formation temperature (90°C), the washed crude oil and oil displacement agent solution were poured out, and the remaining oil sand was dried and the oil washing efficiency was calculated to be 60%.

[0094] The nanosurfactant can emit strong fluorescence under the excitation of 390nm wavelength, and its emission peak is at 525nm. The particle size and dynamic adsorption results are shown in Table 2.

[0095] Example 5

[0096] Grind 2g of citric acid, a water-soluble component, 0.4g of octadecyl alcohol, 1.6g of AES-3, and 2g of sodium dodecyl sulfate, a surfactant, into a fine powder of 100-200 mesh, mix them evenly, pour them into a crucible, heat them to a molten state at 220°C without external stirring, react for 90 minutes, cool the molten black or brown viscous liquid at room temperature, take it out and grind it into fine powder to obtain a nano surfactant.

[0097] Changqing Ansai Oilfield was used as the experimental object, and the obtained nanosurfactant was dispersed into the simulated formation water (mineralization: 6×10 4 The dispersed nanosurfactant was mixed with the oil sand saturated with Changqing Ansai crude oil at a mass ratio of 5:1, kept at a constant temperature for 48 hours at the formation temperature (60°C), and the washed crude oil and oil displacement agent solution were poured out. The remaining oil sand was dried and the oil washing efficiency was calculated to be 62%.

[0098] The nanosurfactant can emit strong fluorescence under 430nm wavelength excitation, and its emission peak is at 565nm. The particle size and dynamic adsorption results are shown in Table 2.

[0099] Example 6

[0100] The conditions of the Bohai Oilfield were used as the test experimental conditions. The nanosurfactant prepared in Example 1 was dispersed into simulated formation water (mineralization degree: 5×10 3 The dispersed nanosurfactant was mixed with the oil sand saturated with Bohai crude oil at a mass ratio of 5:1, and kept at a constant temperature for 48 hours at formation temperature (75°C). The washed crude oil and oil displacement agent solution were poured out, and the remaining oil sand was dried. The oil washing efficiency was calculated to be 51%. The particle size and dynamic adsorption amount are shown in Table 2.

[0101] Example 7

[0102] The experimental process refers to Example 1, the preparation conditions of the nanosurfactant are unchanged, and the conditions of Changqing Ansai Oilfield are used as the experimental conditions. The nanosurfactant prepared in Example 1 is dispersed into simulated formation water (mineralization: 6×10 4 mg / L), the dispersion concentration is 0.1%, the dispersed nano surfactant is mixed with the oil sand saturated with Changqing Ansai crude oil at a mass ratio of 5:1, and the mixture is kept at a constant temperature for 48 hours at the formation temperature (60°C), the washed crude oil and oil displacement agent water are poured out, and the remaining oil sand is dried. The oil washing efficiency is calculated to be 53%. The particle size and dynamic adsorption amount are shown in Table 2.

[0103] Example 8

[0104] The experimental process was based on Example 1. The preparation conditions of the nanosurfactant were unchanged. The conditions of Shengli Oilfield were used as the experimental conditions. The nanosurfactant prepared in Example 1 was dispersed into simulated formation water (mineralization: 4×10 4 mg / L), the dispersion concentration is 0.1%, the dispersed nano surfactant is mixed with the oil sand saturated with Changqing Ansai crude oil at a mass ratio of 5:1, and the mixture is kept at a constant temperature for 48 hours at the formation temperature (90°C), the washed crude oil and oil displacement agent water are poured out, and the remaining oil sand is dried. The oil washing efficiency is calculated to be 52%. The particle size and dynamic adsorption amount are shown in Table 2.

[0105] Table 2 Summary of the performance of the products of Examples 1-8 of the present invention

[0106]

[0107]

[0108] Comparing Examples 1, 6-8, due to the different crude oil compositions and formation conditions in different oil fields, the oil washing efficiency of the same oil washing agent will also be different, but the oil washing mechanism of nano-surfactants is more efficient and more versatile than that of general surfactants. The oil reservoirs under different conditions can reach more than 50%. The components can be fine-tuned according to the composition of the crude oil and the formation conditions to achieve a higher oil washing efficiency.

[0109] Comparative Example 1

[0110] The experimental process refers to Example 1, except that no water-soluble component was added. When other conditions were unchanged, a nanosurfactant was prepared. 5 The nanosurfactant is almost impossible to disperse in simulated formation water of 100 mg / L, but can be dispersed in a small amount in dichloromethane or toluene. Without using water-soluble raw materials, the obtained nanosurfactant has too weak hydrophilicity and is an oil-dispersible nanosurfactant, which does not meet the application purpose.

[0111] Comparative Example 2

[0112] The experimental process refers to Example 1, except that no surfactant was added. When other conditions were unchanged, a nano surfactant was prepared. 5 mg / L of formation simulated water can be well dispersed, and under the same oil washing experimental test conditions, the oil washing efficiency is 5%. It shows that the group structure of the surfactant is the key factor for the nano surfactant to play the role of oil washing, and in the absence of surfactant, although the oil-soluble component cinnamic acid is easier to participate in the reaction, a certain degree of phase separation will occur during the reaction, so the product particle size is larger. The particle size and dynamic adsorption results are shown in Table 3.

[0113] Comparative Example 3

[0114] The experimental process refers to Example 1, except that no oil-soluble component was added. When other conditions were unchanged, a nanosurfactant was prepared. 5 The nanosurfactant can be well dispersed in the simulated water of the formation of 1000 mg / L, and the oil washing efficiency is 68% under the same oil washing experimental test conditions. The selection of oil-soluble components mainly plays a role in regulating the hydrophilicity and lipophilicity of the nanosurfactant and the compatibility with the crude oil components. The addition amount and composition can be selected according to the composition of the formation crude oil used. The crude oil of Xinjiang Tahe Oilfield contains a large amount of asphaltenes and waxes, and contains a large amount of aromatic ring structures. Therefore, aromatic acid cinnamic acid is selected to increase the matching degree with crude oil. Under the condition of not adding cinnamic acid, the oil washing efficiency is slightly lower than that of Example 1. The particle size and dynamic adsorption amount results are shown in Table 3.

[0115] Comparative Example 4

[0116] Experimental process is with reference to Example 5, the only difference is that no surfactant is added, and when other conditions are unchanged, the obtained product is cooled to room temperature, and is a mixture of yellow paste and black viscous material. Due to the absence of surfactant, the long-chain oil-soluble component octadecyl alcohol is difficult to mix evenly with the water-soluble component, resulting in a large degree of phase separation, so a large amount of oil-soluble components are not in full contact with the water-soluble component, and no effective reaction occurs. When the material compatibility is poor, the surfactant plays a very important role in the uniform mixing of materials.

[0117] Comparative Example 5

[0118] The experimental process is similar to that of Example 1, except that the heating temperature is adjusted to 100°C. When other conditions remain unchanged, the obtained product is an inhomogeneous mixture of a yellow paste and a dark yellow solid. The obtained product cannot be dispersed in water, and no nanoparticles are obtained. When the temperature used does not reach the melting temperature of all materials, most of the materials do not participate in the reaction, so the reaction temperature must be selected to be greater than the melting temperature of the materials used.

[0119] Comparative Example 6

[0120] The experimental process refers to Example 1, except that the heating temperature was adjusted to 260°C. When other conditions remained unchanged, the obtained product was in a black, viscous, and non-flowing state. After cooling to room temperature, it became a black, hard, and brittle solid. It could be used in formation simulated water (mineralization degree: 6×10 4 mg / L) was dispersed into a brown transparent liquid, but it could not be dispersed stably. After the dispersion was left to stand for a period of time, a small amount of black solid agglomerated and precipitated. According to the material structure, the degree of polycondensation reaction would increase after exceeding a certain temperature, resulting in the nanoparticles being too large and difficult to disperse stably. Under the same oil washing experimental test conditions, the oil washing efficiency was only 45%.

[0121] Comparative Example 7

[0122] The experimental process refers to Example 3, except that the heating temperature is adjusted to 160°C. When other conditions remain unchanged, the obtained product is a brown flowing liquid, which becomes a solid with a certain viscosity after cooling to room temperature. The obtained product can be dispersed in water, but it is difficult to observe nanoparticles under an electron microscope. When the temperature used does not reach a certain reaction temperature, the difficult-to-react structure may not be further condensed into nanoparticles, and only a certain degree of condensation reaction occurs. For different reactant structures, the reaction temperature must be greater than a certain temperature to obtain a nanosurfactant. The obtained product is dispersed in formation simulated water (mineralization: 6×10 4 mg / L), under the same oil washing test conditions, its oil washing efficiency is only 20%. The dynamic adsorption results are shown in Table 3.

[0123] Comparative Example 8

[0124] The experimental process is similar to Example 3, except that the heating temperature is adjusted to 400°C. When other conditions remain unchanged, the obtained product is a black non-flowing solid. After cooling to room temperature, it is a black brittle solid. After being crushed and added to the formation simulated water, the dispersibility is significantly deteriorated, and some particles cannot be dispersed into nanometer scale. After standing for a period of time, the solid precipitated at the bottom increases significantly. Too high a temperature will cause the reaction degree of the groups on the surface of the nanoparticles to be too high or decomposed, and the number of groups will be reduced, which will cause the dispersibility of the particles to deteriorate and produce aggregation. The particle size results are shown in Table 3.

[0125] Comparative Example 9

[0126] The oil washing test process is similar to that of Example 4, except that the dispersion concentration prepared in Example 4 is changed to 0.05%, and other conditions remain unchanged, and the oil washing efficiency is 61%. The particle size and dynamic adsorption results are shown in Table 3.

[0127] Comparative Example 10

[0128] The oil washing test process is similar to that of Example 4, except that the dispersion concentration prepared in Example 4 is changed to 0.2%, and other conditions remain unchanged, and the oil washing efficiency is 63%. The particle size and dynamic adsorption results are shown in Table 3.

[0129] Comparative Example 11

[0130] The oil washing test process is similar to that of Example 4, except that the nano surfactant is replaced with a relatively efficient oil washing surfactant (cetostearyl dimethyl hydroxysulfobetaine) currently available on the market, the dispersion concentration is 0.2%, and other conditions remain unchanged, and the oil washing efficiency is 30%. The dynamic adsorption results are shown in Table 3.

[0131] By comparing Example 4 and Comparative Examples 9-11, it is found that the increase in the concentration of the oil washing agent will increase the oil washing efficiency within a certain range. When the concentration exceeds a certain value, it has almost no effect on the oil washing efficiency. The oil washing efficiency is closely related to the quality of the oil and the conditions of the formation. Some components in crude oil have a strong adsorption effect on sandstone, which is close to permanent adsorption, requiring multiple oil washings or extended oil washing time. However, the oil washing efficiency of nano surfactants is much higher than that of small molecule surfactants, and the dynamic adsorption amount is lower.

[0132] Comparative Example 12

[0133] The water-soluble component 1g tartaric acid, 1g urea, and the oil-soluble component 0.5g cinnamic acid were fully ground and mixed in an agate mortar, ground into a fine powder of 100-200 mesh, poured into a crucible, heated to a molten state at 140°C, reacted for 120 minutes, and the molten black or brown viscous liquid was cooled at room temperature, taken out and ground into a fine powder, dispersed in distilled water to a saturated concentration (1-1.25%), 2.5g surfactant 1227 was dissolved in pure water, and added dropwise to the nanoparticle dispersion under rapid stirring to obtain surfactant-modified nanoparticles. The particle size and dynamic adsorption results are shown in Table 3.

[0134] The conditions of Xinjiang Tahe Oilfield were used as the experimental object, and the modified nanoparticles were dispersed into the simulated formation water (mineralization: 2.2×10 5 mg / L), the dispersion concentration is 0.1wt%. The modified nanoparticle dispersion is mixed with oil sand saturated with Xinjiang Tahe crude oil at a mass ratio of 5:1, and kept at a constant temperature for 48 hours at formation temperature (130°C), and the washed crude oil and oil displacement agent water are poured out. The remaining oil sand is dried and the oil washing efficiency is calculated to be 15%.

[0135] The modified nanoparticles obtained by first synthesizing nanoparticles and then modifying the surface have limited surface modifiable sites, low interfacial activity, and the oil washing efficiency is much lower than that of the nanosurfactant prepared by a one-step method.

[0136] Comparative Example 13

[0137] Experimental process: Referring to Example 2, octadecyl betaine (35 wt% aqueous solution) was replaced with dodecyl betaine (35 wt% aqueous solution), and other conditions remained unchanged. The obtained nanosurfactant was dispersed into the formation simulated water (mineralization: 5×10 3 mg / L), under the same oil washing test conditions, its oil washing efficiency is 58%. The particle size and dynamic adsorption results are shown in Table 3.

[0138] Comparative Example 14

[0139] Experimental process Referring to Example 2, the formula ratio was adjusted to 0.2g malic acid, 0.4g thiourea, 2g hexadecyltrimethylammonium bromide, 1g lauroyl lysine, 4g octadecyl betaine (35wt% aqueous solution), and other conditions remained unchanged. The obtained nanosurfactant was dispersed into the formation simulated water (mineralization degree: 5×10 3 mg / L), under the same oil washing test conditions, its oil washing efficiency is 38%. The particle size and dynamic adsorption results are shown in Table 3.

[0140] From Example 2 and Comparative Examples 13-14, it is known that the ratio of each component in the nanosurfactant will affect its interfacial properties. Too little water-soluble component will lead to insufficient wetting reversal ability, resulting in reduced oil washing efficiency. Surfactant structures of different structures will affect the matching degree of nanosurfactant with crude oil and formation water, resulting in a certain difference in oil washing efficiency, but the oil washing efficiency of products within the formula range can still be greater than 50%.

[0141] Table 3 Performance summary of comparative examples 1-14

[0142]

[0143]

[0144] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a nano surfactant for washing oil, characterized in that: The steps include: Evenly mixing the water-soluble component, the oil-soluble component and the surfactant to obtain a premix; The premix is ​​heated to 140-300° C. in an atmospheric environment to melt the material and cause a polycondensation reaction between the materials. After the reaction lasts for 10-180 minutes, nanoparticles having a hydrophilic group and a hydrophobic group are obtained. The water-soluble component includes one or more of citric acid, tartaric acid, malic acid, urea, thiourea, glycerol, polyglycerol and glucose; The oil-soluble component is selected from one or more of octadecanoic acid, octadecyl alcohol, benzoic acid, cinnamic acid and methyl laurate.

2. The preparation method according to claim 1, characterized in that: In the premix, the water-soluble component accounts for 20-60wt%, the oil-soluble component accounts for 0-10wt%, and the surfactant accounts for 40-80wt%.

3. A nano surfactant for oil washing, characterized in that: The preparation is obtained by the preparation method according to any one of claims 1 to 2.

4. The nano surfactant according to claim 3, characterized in that The average particle size of the nano surfactant is 1-20 nm.

5. Use of the nano surfactant as claimed in claim 3 or 4 in tertiary oil recovery in low permeability reservoirs or high temperature and high salinity reservoirs.

6. The use according to claim 5, characterized in that: The specific steps of the application are: The nanosurfactant is dispersed to a mineralization degree of 5×10 3 -2.2×10 5 mg / L of oil field is injected into water to prepare an oil washing system, which is used for tertiary oil recovery in low permeability reservoirs or high-temperature and high-salinity reservoirs.

7. The use according to claim 6, characterized in that: The concentration of the nano surfactant in the washing oil system is 0.005-0.1wt%.

8. The use according to claim 6, characterized in that: In the application, the dynamic adsorption amount of the nano surfactant is ≤5%.

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