Chemical liquid for recovering crude oil

Abstract

[Problem] To provide a chemical liquid that is for recovering crude oil, that has excellent salt resistance at high temperature and / or high salt concentration, and that exhibits a high crude oil recovery rate. [Solution] This chemical liquid for recovering crude oil is characterized by containing: a cationic silane compound; an aqueous silica sol having an average particle size of 3-500 nm; and at least one cationic surfactant.

Description

Chemicals for crude oil recovery

[0001] The present invention relates to a crude oil recovery chemical solution that has excellent salt tolerance and a high crude oil recovery rate, and is used in surfactant flooding, one of the enhanced oil recovery ("EOR") flooding methods in which crude oil is recovered by injecting the chemical solution into an oil reservoir in an inland or offshore oil field.

[0002] There are three methods for recovering (extracting) crude oil from oil reservoirs: primary, secondary, and tertiary recovery (or enhanced oil recovery (EOR)). Different recovery methods are applied for each stage over time. Primary recovery methods include artesian oil recovery, which utilizes the natural pressure and gravity of the oil reservoir, and artificial oil recovery, which uses artificial oil recovery techniques such as pumps. The crude oil recovery rate for primary recovery, which combines these methods, is said to be approximately 20%. Secondary recovery methods include water flooding and reservoir pressure maintenance, which inject water or natural gas to restore reservoir pressure and increase oil production after production declines in primary recovery. Even with primary and secondary recovery combined, the crude oil recovery rate is said to be approximately 40%, with the majority of the crude oil remaining in the underground oil reservoir. Therefore, in order to recover more crude oil and to recover additional crude oil from oil reservoirs where crude oil has already been recovered from easy-to-recover areas, a method for enhanced crude oil recovery using tertiary recovery, or EOR, has been proposed.

[0003] EOR flooding methods include thermal flooding, gas flooding, microbial flooding, and chemical flooding. Chemical flooding is a technology that increases crude oil extraction efficiency by injecting a chemical solution appropriate for the purpose into the oil reservoir, reducing the interfacial tension between the oil reservoir and the fluid, and improving the fluidity of the crude oil itself. Depending on the chemical solution used, it can be classified into polymer flooding, surfactant flooding, micelle flooding, etc.

[0004] Surfactant flooding is a method of recovering crude oil by injecting a series of fluids containing a surfactant-based solution into an oil reservoir to reduce the interfacial tension between crude oil and water, thereby mobilizing the trapped crude oil in the reservoir through capillary action. In this method, alkyl allyl sulfonates, for example, are used alone as surfactants, or in combination with co-surfactants and / or adjuvants. Alkyl allyl sulfonates are commonly used because they not only reduce the interfacial tension between oil and water, but also exhibit various phase behaviors when used with various salt concentrations, as described below. At low salt concentrations, alkyl allyl sulfonates tend to remain in the aqueous phase, but at high salt concentrations, they tend to remain in the oil phase. At mid-point salt concentrations, microemulsions are formed, resulting in significant amounts of oil and brine in the microemulsion phase, which is known to result in high crude oil recovery potential. Specific alkylxylene sulfonates have also been proposed as surfactants for EOR with low interfacial tension (see Patent Document 1).

[0005] Micellar flooding is a method of recovering petroleum by creating a microemulsion from water and crude oil and injecting the microemulsion, known as a micellar solution, into an underground reservoir. Many surfactants have been disclosed for producing micellar solutions (see Patent Documents 2 to 4). Various anionic, nonionic, and cationic surfactants have been disclosed as surfactants for use in this flooding method, including petroleum sulfonates, alkyl aryl sulfonates, alkanesulfonates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyhydric alcohol fatty acid esters, and alkyltrimethylammonium salts. Furthermore, a micellar solution for oil recovery containing an internal olefin sulfonate having 10 to 30 carbon atoms and an α-olefin sulfonate having 10 to 30 carbon atoms has been disclosed (see Patent Document 5).

[0006] Furthermore, in a micellar polymer flooding method, which is one of the conventional polymer flooding methods in which both micellar slag (a mixture of petroleum product sulfonate, auxiliary agent, brine, and oil) and polymer are injected, a crude oil recovery agent has been proposed that consists of a water-soluble polymer and a nonionic surfactant made of an amide compound that is a reaction product of a fatty acid and an alkanolamine and an alkylene oxide adduct thereof, in order to obtain a stable and high crude oil recovery rate (see Patent Document 6).

[0007] Meanwhile, a method for improving the recovery rate of crude oil, gas, and water from hydrocarbon reservoirs or oil wells has been disclosed, which involves injecting 1-100 nm nanoparticles (e.g., silicon dioxide) mixed in a wetting agent consisting of water or a hydrocarbon carrier fluid composed of an α-olefin sulfonate salt into a hydrocarbon reservoir or oil well (see Patent Document 7). This document discloses a method for efficiently stripping oil droplets adhering to rock surfaces by injecting nanoparticles mixed in a wetting agent consisting of water or a hydrocarbon carrier fluid into a hydrocarbon reservoir or oil well, thereby increasing the dissociation pressure. Furthermore, a crude oil recovery chemical containing a silane compound, an aqueous silica sol, an anionic surfactant, and a nonionic surfactant has been disclosed as a crude oil recovery chemical with excellent high-temperature and salt resistance for use in surfactant flooding (see Patent Document 8). This document aims to improve crude oil recovery by incorporating fine particles such as aqueous silica sol (colloidal silica) into the crude oil recovery chemical, in anticipation of improving the effectiveness of stripping crude oil from rock surfaces.

[0008] Japanese Patent No. 5026264 U.S. Patent No. 3,506,070 U.S. Patent No. 3,613,786 U.S. Patent No. 3,740,343 JP-B No. 1-35157 JP-B No. 5-86989 U.S. Patent Publication No. 2010 / 0096139 International Publication No. 2019 / 054414

[0009] In order to further enhance the effect of improving crude oil recovery using the above-mentioned nanoparticles, colloidal silica, and other fine particles, it is necessary for the particles to be stable in the chemical solution containing the nanoparticles without agglomeration or denaturation. Because underground hydrocarbon reservoirs to which such chemical solutions are applied are subject to high temperatures, the chemical solution containing the nanoparticles must be heat-resistant. During preparation and use, the chemical solution may come into contact with not only low-salinity but also high-salinity brines, so the chemical solution must be salt-tolerant at the aforementioned high temperatures and high-salinity brines.

[0010]

[0003] Furthermore, in order to improve the crude oil recovery performance of crude oil recovery chemicals, it has been considered essential to include an anionic surfactant that is effective in removing crude oil adhering to rocks such as sandstone or carbonates in underground or subsea oil reservoirs. However, anionic surfactants have poor high-temperature and salt resistance, and when injected into high-temperature, high-salinity oil reservoirs, they decompose in a short period of time, preventing the crude oil recovery effect from being fully demonstrated. Colloidal silica, which is expected to have the above-mentioned crude oil recovery effect, also has poor high-temperature and salt resistance when used alone, and when injected into a high-temperature, high-salinity oil phase, it gels in a short period of time, preventing the crude oil recovery effect from being fully demonstrated. As shown in Patent Document 8, although efforts have been made to improve the high-temperature and salt resistance of crude oil recovery chemicals, there is a demand for chemicals that have salt resistance at higher temperatures or high salt concentrations.

[0011] The present invention aims to provide a crude oil recovery chemical liquid used in EOR flooding, which recovers crude oil by injecting the chemical liquid into an oil reservoir in an inland or offshore oil field, that has excellent salt resistance at higher temperatures and / or high salinity concentrations and a high crude oil recovery rate.

[0012] As a result of intensive research conducted by the present inventors to solve the above problems, they focused on cationic surfactants and found that a chemical solution combining a cationic silane compound, an aqueous silica sol having an average particle size of 3 to 500 nm, and one or more types of cationic surfactants is a chemical solution for crude oil recovery that has superior heat resistance and salt resistance at high temperatures exceeding 100°C and superior salt resistance at high salt concentrations exceeding 10 mass%, compared to chemical solutions that use conventional anionic surfactants, and that has excellent crude oil recovery properties.

[0013] That is, the present invention relates, as a first aspect, to a chemical solution for crude oil recovery, characterized by containing a cationic silane compound, an aqueous silica sol having an average particle size of 3 to 500 nm, and one or more cationic surfactants. As a second aspect, the present invention relates to the chemical solution for crude oil recovery according to the first aspect, in which the aqueous silica sol contains silica particles formed by bonding at least a portion of the cationic silane compound to the surface of at least a portion of the silica particles in the sol. As a third aspect, the present invention relates to the chemical solution for crude oil recovery according to the first or second aspect, in which the cationic silane compound is at least one compound selected from the group consisting of a silane coupling agent having an amino group, an alkoxysilane having an amino group, a silazanes having an amino group, and a siloxane having an amino group. As a fourth aspect, the present invention relates to the chemical solution for crude oil recovery according to any one of the first to third aspects, further containing an amphoteric surfactant. As a fifth aspect, the present invention relates to the chemical solution for crude oil recovery according to any one of the first to fourth aspects, further containing a nonionic surfactant. As a sixth aspect, the present invention relates to the chemical liquid for crude oil recovery according to any one of the first to fifth aspects, wherein the aqueous silica sol is contained in an amount of 0.01% by mass to 50% by mass, calculated as a silica solid content, based on the total mass of the chemical liquid for crude oil recovery. As a seventh aspect, the present invention relates to the chemical liquid for crude oil recovery according to any one of the first to sixth aspects, wherein the silane compound is contained in a mass ratio of 0.001 to 10.0 relative to the silica solid content of the aqueous silica sol. As an eighth aspect, the present invention relates to the chemical liquid for crude oil recovery according to any one of the first to seventh aspects, wherein the cationic surfactant is selected from the group consisting of alkylamine salts, quaternary ammonium salts, and alkylpyridinium salts. As a ninth aspect, the present invention relates to the chemical liquid for crude oil recovery according to any one of the first to eighth aspects, wherein the cationic surfactant is contained in a mass ratio of 0.001 or more and less than 0.4 relative to the silica solid content of the chemical liquid for crude oil recovery. As a tenth aspect, the present invention relates to the chemical solution for crude oil recovery according to any one of the fourth to ninth aspects, in which the amphoteric surfactant is selected from the group consisting of a carboxybetaine salt, a 2-alkylimidazoline derivative type, a glycine type, and an amine oxide type.

[0013] As an eleventh aspect, the present invention relates to the chemical solution for crude oil recovery according to any one of the fourth to tenth aspects, wherein the amphoteric surfactant is contained in a mass ratio of 0.001 or more and less than 0.4 relative to the silica solids content of the chemical solution for crude oil recovery. As a twelfth aspect, the present invention relates to the chemical solution for crude oil recovery according to any one of the fourth to eleventh aspects, wherein the nonionic surfactant has an HLB value of 3.0 or more and 20.0 or less, and is selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyalkylene alkylamines, alkylglucosides, polyoxyethylene fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkanolamides.

[0013] As a thirteenth aspect, the present invention relates to the crude oil recovery chemical solution according to any one of the fifth to twelfth aspects, wherein the nonionic surfactant is contained in a mass ratio of 0.001 or more and less than 0.4 relative to the silica solids content of the crude oil recovery chemical solution. As a fourteenth aspect, the present invention relates to a method for recovering crude oil from an underground hydrocarbon-containing layer, the method comprising: (a) injecting into a subterranean formation a crude oil recovery chemical solution containing a cationic silane compound, an aqueous silica sol having an average particle size of 3 to 500 nm, and one or more cationic surfactants; and (b) recovering crude oil from a production well together with the chemical solution injected into the subterranean formation. As a fifteenth aspect, the present invention relates to the method according to the fourteenth aspect, wherein the cationic surfactant is contained in the crude oil recovery chemical solution in an amount of 0.001 or more and less than 0.4 relative to the silica solids content of the crude oil recovery chemical solution. As a sixteenth aspect, the present invention relates to the method according to the fourteenth aspect or the fifteenth aspect, in which the chemical liquid for crude oil recovery further contains an amphoteric surfactant. As a seventeenth aspect, the present invention relates to the method according to any one of the fourteenth aspect to the sixteenth aspect, in which the chemical liquid for crude oil recovery further contains a nonionic surfactant.

[0014] The crude oil recovery chemical solution of the present invention has excellent heat resistance and salt tolerance, particularly at high temperatures exceeding 100°C, and salt tolerance at high salt concentrations exceeding 10% by mass. Even when the chemical solution is diluted with low- to high-salinity brine and injected into an oil reservoir in an inland or offshore oil field, it is a stable chemical solution that does not experience problems such as gelation. Here, saltwater refers to water containing cations such as sodium ions, calcium ions, and magnesium ions and anions such as chloride ions, carbonate ions, and sulfate ions. Examples of saltwater include seawater (expected for use in submarine oil reservoirs in offshore oil fields) and formation water (expected for use in underground oil reservoirs in inland oil fields). Furthermore, the crude oil recovery chemical solution of the present invention is expected to recover crude oil at a high recovery rate due to the expected improved crude oil stripping effect from the rock surface, due to the wedge effect of the nanosilica particles contained in the chemical solution in addition to the crude oil stripping effect of the cationic surfactant.

[0015] The crude oil recovery chemicals targeted by the present invention are often recovered several months after being injected into underground or subsea oil reservoirs. Because the chemicals are exposed to saltwater containing low to high concentrations of sodium ions, calcium ions, and chloride ions at high temperatures of up to 100°C for several months, they are required to be stable and effective in crude oil recovery even under unusually harsh environments.

[0016] The crude oil recovery chemical solution of the present invention is characterized by containing a cationic silane compound, an aqueous silica sol having an average particle size of 3 to 500 nm, and one or more cationic surfactants. The crude oil recovery chemical solution of the present invention is expected to exhibit excellent salt tolerance at high temperatures and / or high salinity concentrations in saltwater, such as seawater or formation water, containing sodium chloride and calcium chloride as its main components, and thus provide excellent crude oil recovery. In other words, the crude oil recovery chemical solution of the present invention can be a chemical solution that exhibits excellent salt tolerance at high temperatures and / or high salinity concentrations. Each component is described in detail below.

[0017] <Aqueous silica sol> Aqueous silica sol refers to a colloidal dispersion system in which an aqueous solvent is used as a dispersion medium and colloidal silica particles are used as a dispersoid, and can be produced by a known method using water glass (aqueous sodium silicate solution) as a raw material. The average particle size of the aqueous silica sol refers to the average particle size of the colloidal silica particles, which are the dispersoid.

[0018] In the present invention, the average particle diameter of the aqueous silica sol (colloidal silica particles) refers to the specific surface area diameter measured by the nitrogen adsorption method (BET method) or the particle diameter measured by the Sears method, unless otherwise specified. The specific surface area diameter (average particle diameter (specific surface area diameter) D (nm)) measured by the nitrogen adsorption method (BET method) is the specific surface area S (m ２ From the particle size (nm) of 1.5g of SiO 2 , the particle size is given by the formula D(nm) = 2720 / S. The particle size by the Sears method refers to the average particle size measured based on the literature: G.W. Sears, Anal. Chem. 28(12) 1981, 1956, "A rapid method for measuring colloidal silica particle size." In detail, ２ The equivalent diameter (specific surface area diameter) is calculated by determining the specific surface area of ​​the colloidal silica from the amount of 0.1N-NaOH required to titrate colloidal silica equivalent to 1000 ppm from pH 4 to pH 9. In the present invention, the average particle diameter of the aqueous silica sol (colloidal silica particles) as determined by the nitrogen adsorption method (BET method) or the Sears method can be 3 to 500 nm, 3 to 300 nm, 3 to 150 nm, 3 to 100 nm, or 3 to 30 nm. An average particle diameter of less than 3 nm is undesirable because the chemical solution becomes unstable. On the other hand, an average particle diameter of more than 500 nm is undesirable because it may clog the pores of sandstone or carbonate rock present in the underground oil field layer, thereby reducing oil recovery.

[0019] The silica particles in the silica sol in the chemical solution can be measured for their average particle size (DLS average particle size) using dynamic light scattering to determine whether the silica particles in the aqueous silica sol are in a dispersed or aggregated state. The DLS average particle size represents the average value of secondary particle diameters (dispersed particle diameters), and the DLS average particle diameter in a completely dispersed state is said to be about twice the average particle diameter (specific surface area diameter obtained by measurement using the nitrogen adsorption method (BET method) or the Sears method, and represents the average value of primary particle diameters). The larger the DLS average particle diameter, the more likely it is that the silica particles in the aqueous silica sol are in an aggregated state. For example, as an example of an aqueous silica sol, the aqueous silica sol Snowtex (registered trademark) ST-O manufactured by Nissan Chemical Industries, Ltd. has an average particle diameter (BET method) of 10 to 11 nm and a DLS average particle diameter of 15 to 20 nm. As will be shown in the examples described later, the chemical solution for crude oil recovery containing this aqueous silica sol and its salt tolerance evaluation sample (salt-containing chemical solution) have a DLS average particle size of 25 nm or less, and this result indicates that the silica particles are almost dispersed in the chemical solution.

[0020] If the chemical solution has good salt tolerance at high temperatures or high salt concentrations, the DLS average particle size after the salt tolerance test is almost the same as the DLS average particle size of the chemical solution. For example, if the ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size of the chemical solution is 8.0 or less, it indicates that the same dispersion state as in the chemical solution is maintained even after the salt tolerance test. However, if the chemical solution has poor salt tolerance at high temperatures or high salt concentrations, the DLS particle size after the salt tolerance test becomes very large, indicating an aggregated state. For the crude oil recovery chemical solution of the present invention, after a high-temperature salt tolerance test (for example, at 120 °C and a salt concentration of 3 mass% for 60 hours), if the ratio of the DLS average particle size after the salt tolerance test to the average particle size before the test is 1.5 or less (the rate of change in average particle size is 150% or less), it can be determined that the salt tolerance at high temperatures is very good. Furthermore, when the chemical solution for crude oil recovery of the present invention is subjected to a high-salinity salt tolerance test (for example, at room temperature for 7 days at a salt concentration of 17% by mass), if the ratio of the DLS average particle size after the salt tolerance test to the average particle size before the test is 1.5 or less (the rate of change in the average particle size is 150% or less), it can be determined that the chemical solution has very good salt tolerance under high salinity conditions.

[0021] In the present invention, commercially available aqueous silica sols can be used. Aqueous silica sols with silica concentrations of 5 to 50% by mass are generally commercially available and are preferred because they are easily available. While both alkaline and acidic aqueous silica sols can be used, acidic aqueous silica sols are more preferred. Commercially available acidic aqueous silica sols include Snowtex (trade name) ST-OXS, ST-OS, ST-O, ST-O-40, ST-OL, ST-OYL, ST-OZL-35, and MP-4540M (all manufactured by Nissan Chemical Industries, Ltd.). The silica solids concentration in the aqueous silica sol used is preferably 5 to 55% by mass. Here, the silica solids concentration is a value determined by a calcination method. Specifically, it is the value obtained by calcining an aqueous silica sol at 1000°C for 30 minutes or more and dividing the mass of the calcination residue by the mass of the aqueous silica sol. The mass of the calcination residue is referred to as the "silica solids content."

[0022] In the present invention, the aqueous silica sol is preferably contained in an amount of 0.01 to 50.0 mass %, more preferably 10.0 to 25.0 mass %, for example 15.0 to 25.0 mass %, in terms of silica solid content, based on the total mass of the chemical liquid for crude oil recovery.

[0023] In the crude oil recovery chemical solution of the present invention, the silica particles in the aqueous silica sol may have at least a portion of the cationic silane compound described below bonded to at least a portion of their surface. In the present invention, "at least a portion of the cationic silane compound bonded to at least a portion of the surface of the silica particles" means that the cationic silane compound is bonded to at least a portion of the surface of the silica particles, and includes not only an embodiment in which the silane compound is bonded to the surface of the silica particles, but also an embodiment in which the silane compound covers a portion of the surface of the silica particles, and even an embodiment in which the silane compound covers the entire surface of the silica particles. The particle size of the silica particles in the aqueous silica sol having the cationic silane compound bonded to their surface can be easily measured as the particle size by the dynamic light scattering method described above using a commercially available device.

[0024] <Cationic silane compound> The crude oil recovery chemical solution of the present invention is characterized by containing a cationic silane compound. The inclusion of the cationic silane compound significantly improves the salt resistance of the aqueous silica sol at high temperatures and / or high salt concentrations, thereby maintaining the crude oil recovery effect. Preferred examples of the cationic silane compound include silane coupling agents having an amino group as an organic functional group, alkoxysilanes having an amino group, silazanes having an amino group, and siloxanes having an amino group.

[0025] Examples of the silane coupling agent having an amino group include 3-(2-(2-aminoethylamino)ethylamino)propyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrichlorosilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane.

[0026] In the chemical solution for crude oil recovery of the present invention, the cationic silane compound / aqueous silica sol (silica:SiO ２ Preferably, the silane compound is added in a ratio such that the mass ratio is 0.001 to 10.0. More preferably, the mass ratio is 0.05 to 5.0. If the mass ratio of the cationic silane compound to the silica solid content in the aqueous silica sol is less than 0.001, the salt resistance of the chemical solution at high temperatures and / or high salt concentrations may be impaired, which is undesirable. Furthermore, even if the mass ratio is greater than 10.0, i.e., even if a large amount of the silane compound is added, no further improvement in effect can be expected.

[0027] As described above, in the crude oil recovery chemical solution of the present invention, the silica particles in the aqueous silica sol may have at least a portion of the cationic silane compound bonded to a portion of their surface. Examples of silica particles having a cationic silane compound bonded to at least a portion of their surface include silica particles whose surface is coated with the silane compound. By using silica particles having a cationic silane compound bonded to at least a portion of their surface, such as silica particles whose surface is coated with the silane compound, the salt tolerance of the crude oil recovery chemical solution at high temperatures and / or high salinity can be further improved. Therefore, in a preferred embodiment, the crude oil recovery chemical solution of the present invention includes silica particles in which the aqueous silica sol has at least a portion of the cationic silane compound bonded to at least a portion of the surface of the silica particles in the sol.

[0028] Silica particles having at least a portion of the cationic silane compound bonded to at least a portion of the surface (hereinafter also referred to as "silica particles surface-treated with a silane compound" in this specification) can be obtained by adding a silane compound to an aqueous silica sol in such a ratio that the mass ratio of the silane compound to the silica solid content in the aqueous silica sol is 0.001 to 10.0, and then heat-treating the mixture at 50 to 100°C for 1 to 20 hours. At this time, the amount of surface treatment with the cationic silane compound, i.e., the amount of the silane compound bonded to the silica particle surface, is determined to be within 1 nm of the silica particle surface. ２ Preferably, the number of particles per unit area is, for example, about 0.1 to 15 particles per unit area. If the heat treatment temperature is less than 50°C, the rate of partial hydrolysis of the cationic silane compound slows down, resulting in poor surface treatment efficiency, while if it is higher than 100°C, a dried silica gel is formed, which is undesirable. If the heat treatment time is less than 1 hour, the partial hydrolysis reaction of the cationic silane compound is insufficient, and even if it is longer than 20 hours, the partial hydrolysis reaction of the silane compound is almost saturated, so there is no need to extend the heating time any further.

[0029] <Cationic Surfactant> In the crude oil recovery chemical solution of the present invention, one or more cationic surfactants are used. For example, one to three types of cationic surfactants, two to five types of cationic surfactants, one to two types of cationic surfactants, or two types of cationic surfactants can be combined. Furthermore, a chemical solution containing two or more types of cationic surfactants has the desirable effect of stabilizing the surfactants themselves by allowing the surfactants to penetrate each other and form denser micelles (packing effect). This makes the cationic surfactant more stable, and the crude oil recovery effect is maintained.

[0030] Cationic surfactants include alkylamine salts, quaternary ammonium salts, and alkylpyridinium salts.

[0031] Examples of the alkylamine salt include monoalkylamine salts having one alkyl group having 7 to 20 carbon atoms, dialkylamine salts having one alkyl group having 7 to 20 carbon atoms and one alkyl group having 1 to 8 carbon atoms, and trialkylamine salts having one or two alkyl groups having 7 to 20 carbon atoms and the other alkyl group having 1 to 8 carbon atoms.

[0032] Examples of the quaternary ammonium salt include quaternary ammonium chloride, bromide, iodide, trifluoromethanesulfonate, etc. More specifically, examples of the quaternary ammonium salt include alkyltrimethylammonium chloride and dialkyldimethylammonium chloride, each having one or two alkyl groups having 7 to 20 carbon atoms; alkyltrimethylammonium bromide and dialkyldimethylammonium bromide, each having one or two alkyl groups having 7 to 20 carbon atoms; alkyltrimethylammonium iodide and dialkyldimethylammonium iodide, each having one or two alkyl groups having 7 to 20 carbon atoms; alkyltrimethylammonium sulfate, alkyldimethylethylammonium sulfate, and dialkyldiethylammonium sulfate, each having one or two alkyl groups having 7 to 20 carbon atoms; and alkylbenzalkonium chloride (also known as alkyldimethylbenzylammonium chloride) having an alkyl group having 7 to 20 carbon atoms. Examples of alkyltrimethylammonium chlorides having 7 to 20 carbon atoms include octyltrimethylammonium chloride, lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and stearyltrimethylammonium chloride. Examples of alkyltrimethylammonium bromides having 7 to 20 carbon atoms include octyltrimethylammonium bromide, lauryltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and stearyltrimethylammonium bromide. Examples of alkyldimethylethylammonium sulfates having 7 to 20 carbon atoms include octyldimethylethylammonium sulfate (also known as octyldimethylethylammonium sulfate), lauryldimethylethylammonium sulfate (also known as lauryldimethylethylammonium sulfate), and palmityldimethylethylammonium sulfate (also known as palmityldimethylethylammonium sulfate). Examples of alkylbenzalkonium chlorides having an alkyl group having 7 to 20 carbon atoms (also known as alkyldimethylbenzylammonium chloride) include lauryldimethylbenzylammonium chloride.

[0033] Examples of the alkylpyridinium salt include chlorides, bromides, iodides, trifluoromethanesulfonates, etc. More specific examples of pyridinium salts include alkylpyridinium chlorides having an alkyl group of 1 to 8 carbon atoms; alkylpyridinium bromides having an alkyl group of 1 to 8 carbon atoms; and alkylpyridinium iodides having an alkyl group of 1 to 8 carbon atoms. Examples of pyridinium chlorides having an alkyl group of 1 to 8 carbon atoms include methylpyridinium chloride, ethylpyridinium chloride, propylpyridinium chloride, butylpyridinium chloride, and butylmethylpyridinium chloride.

[0034] In the chemical solution for crude oil recovery of the present invention, the cationic surfactant is preferably contained in a mass ratio of 0.001 or more and less than 0.4 relative to the silica solid content in the aqueous silica sol. A mass ratio of less than 0.001 is undesirable because the salt tolerance of the chemical solution at high temperatures and / or high salt concentrations decreases. A mass ratio of 0.4 or more is also undesirable because the salt tolerance of the chemical solution at high temperatures and / or high salt concentrations decreases.

[0035] <Other Surfactants> The crude oil recovery chemical solution of the present invention may contain, in addition to the cationic surfactant, an amphoteric surfactant and / or a nonionic surfactant, as described below. In the present invention, by preparing a chemical solution containing, in addition to the cationic surfactant, either or both of an amphoteric surfactant and a nonionic surfactant, the cationic surfactant and the amphoteric surfactant and / or the nonionic surfactant penetrate each other to form denser micelles, thereby achieving a more desirable effect of stabilizing the surfactants themselves. As a result, the cationic surfactant and the amphoteric surfactant and / or the nonionic surfactant are stabilized, and the crude oil recovery effect is maintained.

[0036] <Amphoteric Surfactant> In addition to the cationic surfactant, one or more amphoteric surfactants may be used in the crude oil recovery chemical solution of the present invention. Examples of amphoteric surfactants include carboxybetaine salts, 2-alkylimidazoline derivatives, glycine types, and amine oxide types.

[0037] Examples of carboxybetaine salts include alkyl betaines having 8 to 20 carbon atoms, fatty acid amidopropyl betaines, etc. Examples of alkyl betaines having 8 to 20 carbon atoms include alkyl dimethylaminoacetic acid betaines having 8 to 20 carbon atoms, such as lauryl dimethylaminoacetic acid betaine and stearyl dimethylaminoacetic acid betaine. Examples of fatty acid amidopropyl betaines include cocamidopropyl betaine and cocamidopropyl hydroxysultaine.

[0038] Examples of the 2-alkylimidazoline derivative type include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaines having 8 to 20 carbon atoms, such as N-lauroyl-N'-carboxymethyl-N'-hydroxyethylethyleneimidazolinium betaine, N-cocoyl-N'-carboxymethyl-N'-hydroxyethylethyleneimidazolinium betaine, 2-cocoyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, 2-lauryl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, and 2-undecyl-N,N,N-(hydroxyethylcarboxymethyl)-2-imidazolinium betaine.

[0039] Examples of the glycine type include alkyldiethylenetriaminoacetic acid and dialkyldiethylenetriaminoacetic acid having 8 to 20 carbon atoms.

[0040] Examples of the amine oxide type include alkylamine oxides having 8 to 20 carbon atoms, such as coconut oil alkyldimethylamine N-oxide, lauryldimethylamine N-oxide, and oleyldimethylamine N-oxide.

[0041] In the chemical solution for crude oil recovery of the present invention, the amphoteric surfactant is preferably contained in a ratio of 0.001 or more and less than 0.4 relative to the silica solid content, i.e., silica particles, in the aqueous silica sol. A ratio of less than 0.001 is not preferred because the salt tolerance of the chemical solution at high temperatures and / or high salt concentrations decreases. A ratio of 0.4 or more is also not preferred because the salt tolerance of the chemical solution at high temperatures and / or high salt concentrations decreases.

[0042] <Nonionic Surfactant> In addition to the cationic surfactant, one or more nonionic surfactants can also be used in the oil recovery chemical solution of the present invention. For example, one to five types of nonionic surfactants, one to four types of nonionic surfactants, one to three types of nonionic surfactants, a combination of one or two types of nonionic surfactants, or one type of nonionic surfactant can be used.

[0043] In the present invention, the nonionic surfactant is selected from polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyalkylene alkylamines, alkylglucosides, polyoxyethylene fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkanolamides.

[0044] For example, examples of polyoxyethylene alkyl ethers include polyoxyethylene dodecyl ether (polyoxyethylene lauryl ether), polyoxyethylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene behenyl ether, polyoxyethylene-2-ethylhexyl ether, and polyoxyethylene isodecyl ether. Examples of polyoxyalkylene alkyl ethers include polyoxyalkylene lauryl ether and polyoxyalkylene tridecyl ether. Examples of polyoxyethylene alkyl phenyl ethers include polyoxyethylene styrenated phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene distyrenated phenyl ether, and polyoxyethylene tribenzyl phenyl ether. Examples of polyoxyalkylene alkylamines include, but are not limited to, polyoxyethylene hexylamine, polyoxypropylene hexylamine, polyoxyethylene octylamine, polyoxypropylene octylamine, polyoxyethylene decylamine, polyoxypropylene decylamine, polyoxyethylene dodecylamine, polyoxypropylene dodecylamine, polyoxyethylene oleylamine, polyoxypropylene oleylamine, polyoxyethylene laurylamine, polyoxypropylene laurylamine, polyoxyethylene stearylamine, polyoxypropylene stearylamine, polyoxyethylene tallow amine, and polyoxypropylene tallow amine. Examples of alkyl glucosides include decyl glucoside and lauryl glucoside. Examples of polyoxyethylene fatty acid esters include polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyethylene glycol distearate, polyethylene glycol dioleate, and polypropylene glycol dioleate.Sorbitan fatty acid esters include sorbitan monocaprylate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan monosesquioleate, and ethylene oxide adducts thereof. Polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan triisostearate. Fatty acid alkanolamides include coconut oil fatty acid diethanolamide, beef tallow fatty acid diethanolamide, lauric acid diethanolamide, and oleic acid diethanolamide. Further usable are polyoxyalkyl ethers or polyoxyalkyl glycols such as polyoxyethylene polyoxypropylene glycol, polyoxyethylene fatty acid esters, polyoxyethylene hydrogenated castor oil ether, sorbitan fatty acid ester alkyl ethers, alkyl polyglucosides, sorbitan monooleate, sucrose fatty acid esters, etc. Among the nonionic surfactants, polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers are more preferred because they have good salt tolerance at high temperatures and / or high salt concentrations in the drug solution.

[0045] The HLB value of a nonionic surfactant is a numerical value that represents the balance between hydrophobicity and hydrophilicity, with a substance having no hydrophilic groups having an HLB of 0 and a substance having only hydrophilic groups and no hydrophobic groups having an HLB of 20. In the present invention, it is preferable to use a nonionic surfactant with an HLB value of 3.0 or more and 20.0 or less. From the viewpoint of salt tolerance at high temperatures and / or high salt concentrations of the chemical solution, it is more preferable to use a nonionic surfactant with an HLB value of 10.0 or more and 20.0 or less. Furthermore, from the viewpoint of safety for the human body and the environment, it is more preferable to use a nonionic surfactant with an HLB value of 14.0 or more and 20.0 or less, which is not harmful to the aquatic environment for a long period of time and does not pose concerns about so-called environmental hormones. Furthermore, when two or more nonionic surfactants with different HLB values ​​are used, it is preferable to adjust the HLB value of the mixture, calculated from the weight average of the HLB values ​​and the blending ratio, to 10.0 or more and 20.0 or less. If the HLB value is less than 3.0, the nonionic surfactant is highly hydrophobic, and therefore the aqueous silica sol and cationic surfactant do not mix with the nonionic surfactant in the prepared chemical solution, and the solution separates into two layers, which is not preferable.

[0046] In the crude oil recovery chemical solution of the present invention, the nonionic surfactant is preferably contained in a mass ratio of 0.001 or more to less than 0.4 relative to the silica solid content in the aqueous silica sol. By blending at this ratio, crude oil recovery can be improved. Note that whether the chemical solution contains only one type of nonionic surfactant or two to five types of nonionic surfactants, it has excellent salt tolerance at high temperatures and / or high salinity concentrations, and good crude oil recovery performance can be obtained.

[0047] <Other Components> In order to increase the viscosity of the medicinal solution, water-soluble polymers such as hydroxyethyl cellulose and its salts, hydroxypropyl methyl cellulose and its salts, carboxymethyl cellulose and its salts, pectin, guar gum, xandancum, tamarind gum, carrageenan, etc. may be further added.

[0048] The crude oil recovery chemical solution of the present invention is believed to be a chemical solution in which the compatibility between the silica particles in the aqueous silica sol and the surfactant is improved by using an aqueous silica sol and a cationic silane compound in combination, particularly by including silica particles in the aqueous silica sol having at least a portion of the silane compound bonded to at least a portion of the surface thereof.Furthermore, by combining one or more cationic surfactants, the crude oil recovery chemical solution is believed to have excellent salt tolerance at high temperatures and / or high salinity concentrations.

[0049] <Crude Oil Recovery Method> The crude oil recovery chemical solution of the present invention is useful as a crude oil recovery chemical solution for injecting crude oil from an injection well into a subterranean formation and recovering crude oil from a production well in order to recover crude oil from an underground hydrocarbon-bearing formation. The injection well and the production well may be the same. That is, the crude oil recovery chemical solution of the present invention is used in a method for recovering crude oil from an underground hydrocarbon-bearing formation. For example, the crude oil recovery method can be carried out by including (a) the step of injecting the crude oil recovery chemical solution of the present invention into a subterranean formation, and (b) the step of recovering crude oil from a production well together with the chemical solution injected into the subterranean formation. This crude oil recovery method is also within the scope of the present invention. The crude oil recovery method of the present invention can be carried out by adding the cationic surfactant to the crude oil recovery chemical solution in an amount of 0.001 or more but less than 0.4 by mass relative to the silica solid content of the crude oil recovery chemical solution. The crude oil recovery chemical solution of the present invention can be used in either an acidic or alkaline state.

[0050] The present invention will be described in further detail below based on synthesis examples, examples, and comparative examples, but it should be understood that the present invention is not limited to these examples in any way.

[0051] (Measurement Equipment) The following equipment was used to analyze the aqueous silica sol prepared in the Synthesis Examples (pH value, electrical conductivity, DLS average particle size), the chemical solutions produced in the Examples and Comparative Examples (pH value, electrical conductivity, viscosity, DLS average particle size), and the samples prepared using the chemical solutions after salt resistance tests at high temperatures or high salt concentrations. DLS average particle size (dynamic light scattering particle size): A dynamic light scattering particle size measuring device, Zetasizer Nano (manufactured by the Malvern Division of Spectris Co., Ltd.), was used. pH: A pH meter (manufactured by DKK Toa Corporation), was used. Electrical conductivity: An electrical conductivity meter (manufactured by DKK Toa Corporation), was used. Viscosity: A Brookfield viscometer (manufactured by Tokyo Keiki Co., Ltd.), was used. Surface tension: A surface tensiometer DY-500 (manufactured by Kyowa Interface Science Co., Ltd.), was used. Silica solid content: Calculated from the calcination residue obtained by calcining the aqueous silica sol at 1000°C for 30 minutes or more. The silica solid content concentration was determined by dividing the mass of the calcination residue by the mass of the aqueous silica sol. Silane compound bond amount: An organic trace element analyzer CHNS / O analyzer (PerkinElmer Japan Co., Ltd.) or a TN measuring device TN-2100V Total Nitrogen Analyzer (Mitsubishi Chemical Analytech Co., Ltd.) was used.

[0052] Evaluation of Crude Oil Recovery Chemicals (Silane Compound Bonding Amount Evaluation-1) <Washing> 2 g of the aqueous silica sol produced in Synthesis Examples 1 to 3 (described later) and 4 g of pure water were placed in a 15 mL centrifugal filter unit, Amicon Ultra 15 (Merck), and centrifuged for 20 minutes at a centrifugal force of 2,770 G. After centrifugation, the liquid discharged to the bottom of the filter was discarded, and the same mass of pure water as the discarded liquid was added to the aqueous silica sol concentrated on the filter to redisperse it, followed by another centrifugation for 20 minutes at a rotation speed of 3,000 G. This procedure was repeated a total of four times to obtain an aqueous silica sol from which excess silane compound (not bonded to the silica sol) and lactic acid added during sol production had been removed. <Nitrogen Amount Measurement> The nitrogen amount in the washed aqueous silica sol was measured using a TN analyzer, and the amount of silane compound bonded was calculated from the obtained nitrogen amount using the following formula:

[0053] (Silane Compound Bonding Amount Evaluation-2) <Washing> 2 g of the aqueous silica sol produced in Synthesis Example 4 (described later) and 4 g of pure water were placed in a 15 mL centrifugal filter unit, Amicon Ultra 15 (Merck), and centrifuged for 20 minutes at a centrifugal force of 2,770 G. After centrifugation, the liquid discharged to the bottom of the filter was discarded, and the same mass of pure water as the discarded liquid was added to the concentrated aqueous silica sol on the filter to redisperse it, followed by another centrifugation at a rotation speed of 3,000 G for 20 minutes. The above procedure was repeated a total of four times to obtain an aqueous silica sol from which excess silane compound (not bonded to the silica sol) and lactic acid added during sol production had been removed. <Carbon Amount Measurement> The washed aqueous silica sol was heated and dried at 100°C and pulverized in a mortar to obtain a silica sol powder. The carbon amount of the obtained silica sol powder was measured using an organic trace element metal analyzer, and the amount of silane compound bonded was calculated from the obtained carbon amount using the following formula.

[0054] (Salt Tolerance Evaluation-1) 2408 g of pure water was placed in a 3 L polyethylene container, and then 92 g of seawater powder (trade name Marine Art SF-1, manufactured by Tomita Pharmaceutical Co., Ltd.) was added to prepare salt water 1. A stirrer was placed in a 200 mL polystyrene bottle, and each of the chemical solutions prepared in the following examples or comparative examples, pure water, and salt water 1 were added while stirring with a magnetic stirrer to prepare 150 g of a mixed solution so that the salt concentration was 3% by mass and the silica concentration was 0.5% by mass, and the mixture was stirred for 1 hour. This was used as salt water test sample 1 to evaluate the heat resistance and salt resistance of the chemical solution in salt water 1. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample of the obtained salt water test sample 1 (salt tolerance evaluation sample) were evaluated. 80 g of the saltwater test sample 1 was placed in a 120 mL sealable Teflon (registered trademark) container and sealed. The Teflon (registered trademark) container was then placed in a dryer at 120° C. and maintained at 120° C. for a predetermined time, after which the appearance, pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample were evaluated for saltwater test sample 1. The high-temperature salt resistance was evaluated by judging salt resistance (see <Judgment of salt resistance> below) based on the measurement results of the DLS average particle size of the aqueous silica sol (silica particles) in the sample after maintaining it at 120° C. for a predetermined time (60 hours) and by evaluating the appearance.

[0055] (Salt Tolerance Evaluation-2) 826 g of pure water was placed in a 1 L polystyrene container, followed by the addition of 103 g of sodium chloride, 60 g of calcium chloride, 11 g of magnesium chloride, and 0.4 g of sodium sulfate to prepare salt water 2 (salt concentration 17.4%). After placing a stirrer in a 200 mL polystyrene bottle, each of the chemical solutions prepared in the following Examples or Comparative Examples, pure water, and salt water 2 with a salt concentration of 17.4% were added while stirring with a magnetic stirrer to prepare 150 g of a mixed solution with a salt concentration of 17% by mass and a silica concentration of 0.5% by mass, and stirred for 1 hour. This was used as salt water test sample 2 to evaluate the salt tolerance of the chemical solution in salt water 2 (high salt concentration). The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample of the obtained salt water test sample 2 (salt tolerance evaluation sample) were evaluated. The saltwater test sample 2 was left to stand at room temperature for a predetermined time, and the appearance, pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the sample were evaluated. Salt tolerance at a high salt concentration (17% by mass salt concentration) was evaluated after a predetermined time (7 days) at room temperature by determining salt tolerance based on the measurement of the DLS average particle size of the aqueous silica sol (silica particles) in the sample (see <Determination of Salt Tolerance> below) and evaluating the appearance. <Determination of Salt Tolerance> A: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test was 1.5 or less. B: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test was 1.6 to 8.0. C: The ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size before the test was 8.1 or more. Alternatively, the silica sol gelled, resulting in the formation of a white precipitate, making it impossible to measure the DLS particle size. The salt tolerance test results show that A is the most favorable, followed by B and C in that order.

[0056] [Preparation of Chemical Solution for Crude Oil Recovery: Preparation of Aqueous Sol] (Synthesis Example 1) 400 g of aqueous silica sol (Snowtex (registered trademark) ST-O manufactured by Nissan Chemical Industries, Ltd., silica solids concentration = 20.5 mass%, BET average particle size 11.0 nm, DLS average particle size 17.2 nm) and a magnetic stirrer were placed in a 1 L glass eggplant flask, and then 91.0 g of lactic acid (manufactured by Kanto Chemical Co., Ltd., purity 92%) was added to the silica in the aqueous silica sol while stirring with the magnetic stirrer, and the mixture was stirred at room temperature for 30 minutes. Thereafter, 52.1 g of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (KBM-602 manufactured by Shin-Etsu Chemical Co., Ltd.) was added while stirring. Subsequently, a cooling tube through which tap water was flowing was placed on top of the eggplant flask, and the aqueous silica sol was heated to 60 ° C. while refluxing, maintained at 60 ° C. for 4 hours, and then cooled. After cooling to room temperature, the aqueous sol was taken out. 543.1 g of an aqueous sol containing an aqueous silica sol surface-treated with a silane compound (hereinafter referred to as aqueous silica sol produced in Synthesis Example 1) was obtained, which had a mass ratio of the silane compound to the silica solid content in the aqueous silica sol of 0.64, a silica solid content of 17.5 mass%, a pH of 3.6, an electrical conductivity of 903 μS / cm, and a DLS average particle size of 22.2 nm. The amount of the silane compound (N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane) bound was calculated according to Silane Compound Bonding Amount Evaluation-1, and was found to be 1.0 g per 1 nm of silica sol. ２ 1.2 molecules were bonded per molecule.

[0057] Synthesis Example 2 A 1-L glass recovery flask was charged with 400 g of aqueous silica sol (Snowtex (registered trademark) ST-OXS manufactured by Nissan Chemical Industries, Ltd., silica solids concentration = 10.4 mass%, Sears method average particle size 5.1 nm) and a magnetic stirrer. Then, while stirring with the magnetic stirrer, 10.2 g of lactic acid (manufactured by Kanto Chemical Co., Ltd., purity 92%) was added relative to the silica in the aqueous silica sol, and the mixture was stirred at room temperature for 30 minutes. Subsequently, while stirring, 5.9 g of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (KBM-602 manufactured by Shin-Etsu Chemical Co., Ltd.) was added. Subsequently, a cooling tube through which tap water was flowing was placed on top of the recovery flask, and the aqueous silica sol was heated to 60°C while refluxing, maintained at 60°C for 4 hours, and then cooled. After cooling to room temperature, the aqueous sol was removed. The mass ratio of the silane compound to the silica solid content in the aqueous silica sol was 0.14, the silica solid content was 10.4 mass%, the pH was 3.7, the electrical conductivity was 1140 μS / cm, and the DLS average particle size was 26.6 nm. 416.1 g of an aqueous sol containing an aqueous silica sol surface-treated with a silane compound (hereinafter referred to as aqueous silica sol produced in Synthesis Example 2) was obtained. When the amount of the silane compound (N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane) bound was calculated according to the silane compound binding amount evaluation method, it was found that 1 nm of the silica sol was 26.6 nm. ２ 1.0 molecule was bound per unit area.

[0058] Synthesis Example 3 A 1-L glass recovery flask was charged with 400 g of aqueous silica sol (Snowtex (registered trademark) ST-OL manufactured by Nissan Chemical Industries, Ltd., silica solids concentration = 20.5 mass%, BET method average particle size 43 nm) and a magnetic stirrer. Then, while stirring with the magnetic stirrer, 24.8 g of lactic acid (manufactured by Kanto Chemical Co., Ltd., purity 92%) was added relative to the silica in the aqueous silica sol, and the mixture was stirred at room temperature for 30 minutes. Subsequently, while stirring, 14.2 g of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (KBM-602 manufactured by Shin-Etsu Chemical Co., Ltd.) was added. Subsequently, a cooling tube through which tap water was flowing was placed on top of the recovery flask, and the aqueous silica sol was heated to 60°C while refluxing, maintained at 60°C for 4 hours, and then cooled. After cooling to room temperature, the aqueous sol was removed. The mass ratio of the silane compound to the silica solid content in the aqueous silica sol was 0.17, the silica solid content was 19.8 mass%, the pH was 3.7, the electrical conductivity was 870 μS / cm, and the DLS average particle size was 26.6 nm. 439.1 g of an aqueous sol containing an aqueous silica sol surface-treated with a silane compound (hereinafter referred to as the aqueous silica sol produced in Synthesis Example 3) was obtained. When the amount of the silane compound (N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane) bound was calculated according to Silane Compound Bonding Amount Evaluation-1, the amount of the silane compound bound to 1 nm of silica sol was 19.8 mass%. ２ 1.0 molecule was bound per unit area.

[0059] [Preparation of Chemical Solution for Crude Oil Recovery] (Example 1) A stirrer was placed in a 120 mL polystyrene bottle, and 75.3 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 4.3 g of pure water was added, and then 0.4 g of the cationic surfactant hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+%, manufactured by ACROS ORGANICS Co., Ltd.) was added and stirred until completely dissolved, thereby producing the chemical solution of Example 1. At this time, the mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 1 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after keeping it at 120°C for 60 hours, the sample was taken out and evaluated for high-temperature salt resistance according to <Assessment of Salt Tolerance>.

[0060] Example 2 A chemical solution of Example 2 was produced in the same manner as in Example 1, except that the amount of pure water added was 3.3 g and 1.4 g of lauryltrimethylammonium chloride (Cathiogen (registered trademark) TML, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as the cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 2 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and its high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0061] Example 3 A chemical solution of Example 3 was produced in the same manner as in Example 1, except that the amount of pure water added was 3.3 g and 1.3 g of cetyltrimethylammonium chloride (Cathiogen (registered trademark) TMP, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as the cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 3 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and the high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0062] Example 4 A chemical solution of Example 4 was produced in the same manner as in Example 1, except that the amount of pure water added was 3.9 g and 0.8 g of lauryl dimethyl benzyl ammonium chloride (Cathiogen (registered trademark) BC-50, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as the cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH of the chemical solution of Example 4, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and evaluated for High-Temperature Salt Tolerance-1 according to <Assessment of Salt Tolerance>.

[0063] Example 5 A chemical solution of Example 5 was produced in the same manner as in Example 1, except that the amount of pure water added was 3.9 g and 0.8 g of lauryl dimethylethyl ammonium ethyl sulfate (Cathiogen (registered trademark) ES-L, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as the cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 5 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and its high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0064] Example 6 A chemical solution of Example 6 was produced in the same manner as in Example 1, except that the amount of pure water added was 3.9 g and 0.8 g of octyldimethylethylammonium ethyl sulfate (Cathiogen (registered trademark) ES-O, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as the cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 6 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and its high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0065] Example 7 A chemical solution of Example 7 was produced in the same manner as in Example 1, except that the amount of pure water added was 4.1 g and 0.6 g of palmityl dimethylethyl ammonium ethyl sulfate (Cathiogen (registered trademark) ES-P, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as a cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 7 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and its high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0066] Example 8 A stirrer was placed in a 100 mL recovery flask, and 50.5 g of the aqueous silica sol produced in Synthesis Example 1 was added. 2.0 g of pure water was added while stirring with a magnetic stirrer. Next, a cooling tube through which tap water was flowing was placed at the top of the recovery flask, and the aqueous sol was heated to 60°C while refluxing. 0.3 g of the cationic surfactant hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+, manufactured by ACROS ORGANICS Co., Ltd.) was added, and the mixture was stirred until completely dissolved. Next, 0.9 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (registered trademark) EA-157 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), diluted with pure water to an active ingredient content of 70%, was added while stirring at 60°C, and the mixture was then maintained at 60°C for 1 hour to produce the chemical solution of Example 8. At this time, the mass ratio of the cationic surfactant to the silica solids content of the aqueous silica sol was 0.03, and the mass ratio of the nonionic surfactant to the silica solids content of the aqueous silica sol was 0.07. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 8 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after maintaining it at 120°C for 60 hours, the sample was removed and its high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0067] Example 9 A chemical solution of Example 9 was produced in the same manner as in Example 8, except that the amount of pure water added was 1.1 g and 1.1 g of stearyltrimethylammonium chloride (Cathiogen (registered trademark) TMS, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added as the cationic surfactant. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol at this time was 0.03. The pH of the chemical solution of Example 9, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and the high-temperature salt resistance was evaluated according to <Assessment of Salt Tolerance>.

[0068] Example 10 A stirring bar was placed in a 120 mL polystyrene bottle, and 28.2 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 1.4 g of pure water was added, and then 0.08 g of hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+, manufactured by ACROS ORGANICS Co., Ltd.) as a cationic surfactant was added and stirred until completely dissolved. Subsequently, 0.27 g of lauryldimethylaminoacetate betaine (Amogen (registered trademark) S-H, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an amphoteric surfactant was added to produce the medicinal solution of Example 10. At this time, the mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol was 0.016, and the mass ratio of the amphoteric surfactant to the silica solid content of the aqueous silica sol was 0.016. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution were evaluated for Example 10. Salt water test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after being kept at 120°C for 60 hours, the sample was taken out and evaluated for high-temperature salt resistance according to <Assessment of Salt Tolerance>.

[0069] Example 11 A stirring bar was placed in a 120 mL polystyrene bottle, and 28.3 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 0.93 g of pure water was added, and then 0.08 g of hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+, manufactured by ACROS ORGANICS Co., Ltd.) as a cationic surfactant was added and stirred until completely dissolved. Subsequently, 0.27 g of lauryldimethylaminoacetate betaine (Amogen (registered trademark) S-H, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an amphoteric surfactant was added. Thereafter, 0.47 g of a nonionic surfactant, polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen (registered trademark) EA-157 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) diluted with pure water to an active ingredient content of 70%, was added and stirred at room temperature for 1 hour to produce the chemical solution of Example 11. At this time, the mass ratio of the cationic surfactant to the silica solids content of the aqueous silica sol was 0.016, the mass ratio of the amphoteric surfactant to the silica solids content of the aqueous silica sol was 0.016, and the mass ratio of the nonionic surfactant to the silica solids content of the aqueous silica sol was 0.07. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 11 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and evaluated for high-temperature salt resistance according to <Assessment of Salt Tolerance>.

[0070] (Example 12) Using the chemical solution prepared in Example 1, saltwater test sample 2 was prepared according to Salt Tolerance Evaluation-2, and after leaving it to stand at room temperature for 7 days, salt tolerance at high salt concentrations was evaluated according to <Assessment of Salt Tolerance>.

[0071] Example 13 A stirring bar was placed in a 120 mL polystyrene bottle, and 75.3 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 4.5 g of pure water was added, and then 0.2 g of the cationic surfactant hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+, manufactured by ACROS ORGANICS Co., Ltd.) was added and stirred until completely dissolved. Subsequently, 0.7 g of lauryltrimethylammonium chloride (Cathiogen (registered trademark) TML, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added to produce the chemical solution of Example 13. At this time, the mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 13 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after keeping it at 120°C for 60 hours, the sample was taken out and evaluated for high-temperature salt resistance according to <Assessment of Salt Tolerance>.

[0072] Example 14 A stirring bar was placed in a 100 mL recovery flask, and 75.3 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 3.3 g of pure water was added. Subsequently, a cooling tube through which tap water was flowing was installed at the top of the recovery flask, and the aqueous sol was heated to 60°C while refluxing. 0.4 g of the cationic surfactant hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+%, manufactured by ACROS ORGANICS Co., Ltd.) was added and stirred until completely dissolved. Subsequently, 0.9 g of a nonionic surfactant polyoxyalkylene alkylamine with an HLB of 13.6 (Puremeal (registered trademark) CF-60, manufactured by Sanyo Chemical Industries, Ltd.) was added while stirring at 60°C, and the mixture was then maintained at 60°C for 1 hour to produce the chemical solution of Example 14. The mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol was 0.03, and the mass ratio of the nonionic surfactant to the silica solid content of the aqueous silica sol was 0.07. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 14 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and evaluated for high-temperature salt resistance according to <Assessment of Salt Resistance>.

[0073] Example 15 A stirring bar was placed in a 120 mL polystyrene bottle, and 77.2 g of the aqueous silica sol produced in Synthesis Example 2 was added. While stirring with a magnetic stirrer, 2.4 g of pure water was added, and then 0.4 g of the cationic surfactant hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+%, manufactured by ACROS ORGANICS Co., Ltd.) was added and stirred until completely dissolved, thereby producing the chemical solution of Example 15. At this time, the mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol was 0.05. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 15 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after keeping it at 120°C for 60 hours, the sample was taken out and evaluated for high-temperature salt resistance according to <Assessment of Salt Tolerance>.

[0074] Example 16 A stirring bar was placed in a 120 mL polystyrene bottle, and 76.9 g of the aqueous silica sol produced in Synthesis Example 3 was added. While stirring with a magnetic stirrer, 2.7 g of pure water was added, and then 0.4 g of the cationic surfactant hexadecyltrimethylammonium bromide (Hexadecyltrimethylammonium bromide, 99%+, manufactured by ACROS ORGANICS Co., Ltd.) was added and stirred until completely dissolved, thereby producing the chemical solution of Example 16. At this time, the mass ratio of the cationic surfactant to the silica solid content of the aqueous silica sol was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Example 16 were evaluated. Saltwater test sample 2 was prepared according to Salt Tolerance Evaluation-2, and after standing at room temperature for 7 days, salt tolerance at high salt concentrations was evaluated according to <Assessment of Salt Tolerance>.

[0075] (Example 17) Using the chemical solution prepared in Example 13, saltwater test sample 2 was prepared according to Salt Tolerance Evaluation-2, and after leaving it to stand at room temperature for 7 days, salt tolerance at high salt concentrations was evaluated according to <Assessment of Salt Tolerance>.

[0076] (Example 18) Using the chemical solution prepared in Example 14, saltwater test sample 2 was prepared according to Salt Tolerance Evaluation-2, and after leaving it to stand at room temperature for 7 days, salt tolerance at high salt concentrations was evaluated according to <Assessment of Salt Tolerance>.

[0077] (Example 19) Using the chemical solution prepared in Example 15, saltwater test sample 2 was prepared according to Salt Tolerance Evaluation-2, and after leaving it to stand at room temperature for 7 days, salt tolerance at high salt concentrations was evaluated according to <Assessment of Salt Tolerance>.

[0078] Synthesis Example 4 A 500 mL glass recovery flask was charged with 200 g of aqueous silica sol (Snowtex (registered trademark) ST-O manufactured by Nissan Chemical Industries, Ltd., silica concentration = 20.5 mass%, BET average particle size 11.0 nm, DLS average particle size 17.2 nm) and a magnetic stirrer. While stirring with the magnetic stirrer, 31.8 g of 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO manufactured by Evonik) was added so that the mass ratio of the silane compound to the silica in the aqueous silica sol was 0.16. Subsequently, a cooling tube through which tap water was flowing was placed on top of the recovery flask, and the aqueous sol was heated to 60°C while refluxing, maintained at 60°C for 3 hours, and then cooled. After cooling to room temperature, the aqueous sol was removed. 248.6 g of an aqueous sol containing an aqueous silica sol surface-treated with a silane compound (hereinafter referred to as aqueous silica sol produced in Synthesis Example 4) was obtained, which had a mass ratio of the silane compound to silica in the aqueous sol of 0.16, a silica solids content of 21.0 mass%, a pH of 2.7, an electrical conductivity of 415 μS / cm, and a DLS average particle size of 21.5 nm. When the amount of the silane compound (3-glycidoxypropyltrimethoxysilane) bound was calculated according to Silane Compound Bonding Amount Evaluation-2, it was found that 1 nm of the silica sol was 248.6 g. ２ 1.5 molecules were bonded per unit area.

[0079] Comparative Example 1 A stirring bar was placed in a 120 mL polystyrene bottle, and 101.0 g of the aqueous silica sol produced in Synthesis Example 4 was added while stirring with a magnetic stirrer. 15 g of pure water was added, followed by 0.96 g of anionic surfactant sodium α-olefin sulfonate (Neogen® AO-90, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and stirring until completely dissolved. Subsequently, 0.36 g of anionic surfactant sodium dodecyl sulfate (Shinoline® 90TK-T, manufactured by New Japan Chemical Co., Ltd.) was added and stirring until completely dissolved. Subsequently, 2.07 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether with an HLB of 14.3 (Noigen® EA-157, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) diluted with pure water to an active ingredient concentration of 70% was added, to produce the medicinal solution of Comparative Example 2. The mass ratio of the anionic surfactant to the silica solid content of the aqueous silica sol was 0.03, and the mass ratio of the nonionic surfactant to the silica solid content of the aqueous silica sol was 0.07. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Comparative Example 1 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and evaluated for high-temperature salt resistance according to <Assessment of Salt Resistance>.

[0080] Comparative Example 2 A stirring bar was placed in a 120 mL polystyrene bottle, and 75.3 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 3.2 g of pure water was added, followed by 1.4 g of the amphoteric surfactant lauryl dimethylaminoacetate betaine (Amogen (registered trademark) S-H", active ingredient 30%, Dai-ichi Kogyo Seiyaku Co., Ltd.), and the mixture was stirred until completely dissolved to produce a chemical solution of Comparative Example 2. At this time, the mass ratio of the amphoteric surfactant to the silica solids content of the aqueous silica sol was 0.03. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution of Comparative Example 2 were evaluated. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after holding at 120°C for 60 hours, the sample was removed and evaluated for high-temperature salt resistance according to <Assessment of Salt Tolerance>.

[0081] Comparative Example 3 A stirrer was placed in a 120 mL polystyrene bottle, and 75.3 g of the aqueous silica sol produced in Synthesis Example 1 was added. While stirring with a magnetic stirrer, 2.0 g of pure water was added, followed by 1.4 g of amphoteric surfactant lauryl dimethylaminoacetate betaine (Amogen (registered trademark) S-H", active ingredient 30%, Dai-ichi Kogyo Seiyaku Co., Ltd.) and stirring until completely dissolved. Thereafter, 1.3 g of a nonionic surfactant polyoxyethylene styrenated phenyl ether (Noigen (registered trademark) EA-157, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) with an HLB of 14.3 diluted with pure water to an active ingredient of 70% was added, and the mixture was stirred at room temperature for 1 hour to produce the chemical solution of Comparative Example 3. At this time, the mass ratio of the amphoteric surfactant to the silica solids content of the aqueous silica sol was 0.03, and the mass ratio of the nonionic surfactant to the silica solids content of the aqueous silica sol was 0.07. The pH, electrical conductivity, and DLS average particle size of the aqueous silica sol (silica particles) in the chemical solution were evaluated for Comparative Example 3. Saltwater test sample 1 was prepared according to Salt Tolerance Evaluation-1, and after being kept at 120°C for 60 hours, the sample was removed and evaluated for high-temperature salt resistance according to <Assessment of Salt Resistance>.

[0082] (Comparative Example 4) Using the chemical solution prepared in Comparative Example 1, saltwater test sample 2 was prepared according to Salt Tolerance Evaluation-2, and after leaving it to stand at room temperature for 7 days, salt tolerance at high salt concentrations was evaluated according to <Assessment of Salt Tolerance>.

[0083] Table 1 (Table 1-1, Table 1-2, Table 1-3) shows the physical properties of the chemical solutions and salt resistance evaluation samples (saltwater test samples) for the Examples and Comparative Examples, as well as the results of the salt resistance tests. The types (symbols) of cationic surfactants, amphoteric surfactants, and nonionic surfactants in the tables are as follows:<Cationic surfactants> CTAB: hexadecyltrimethylammonium bromide "Hexadecyltrimethylammonium bromide, 99+%", active ingredient 99% or more, ACROS ORGANICS Co., Ltd. LTAC: lauryltrimethylammonium chloride "Catiogen (registered trademark) TML", active ingredient 30.0%, Dai-ichi Kogyo Seiyaku Co., Ltd. RTMAC1: cetyltrimethylammonium chloride "Catiogen (registered trademark) TMP", active ingredient 30%, Dai-ichi Kogyo Seiyaku Co., Ltd. RTMAC2: stearyltrimethylammonium chloride "Catiogen (registered trademark) TMS", active ingredient 25%, Dai-ichi Kogyo Seiyaku Co., Ltd. RDMBnAC: Lauryl dimethyl benzyl ammonium chloride "Catiogen (registered trademark) BC-50", active ingredient 50%, Dai-ichi Kogyo Seiyaku Co., Ltd. RDMEAS1: Lauryl dimethyl ethyl ammonium ethyl sulfate "Catiogen (registered trademark) ES-L", active ingredient 50%, Dai-ichi Kogyo Seiyaku Co., Ltd. ODMEAS: Octyl dimethyl ethyl ammonium ethyl sulfate "Catiogen (registered trademark) ES-O", active ingredient 50%, Dai-ichi Kogyo Seiyaku Co., Ltd. RDMEAS2: Palmityl dimethyl ethyl ammonium ethyl sulfate "Catiogen (registered trademark) ES-P", active ingredient 70%, Dai-ichi Kogyo Seiyaku Co., Ltd. <Anionic surfactants> AOS: Sodium α-olefin sulfonate "Neogen (registered trademark) AO-90", active ingredient 36.3%, Dai-ichi Kogyo Seiyaku Co., Ltd. SDS: sodium dodecyl sulfate "Shinoline (registered trademark) 90TK-T", active ingredient 96.0%, New Japan Chemical Co., Ltd. <Amphoteric surfactants> RDMAAcB: lauryl dimethylaminoacetic acid betaine "Amogen (registered trademark) S-H", active ingredient 30%, Dai-ichi Kogyo Seiyaku Co., Ltd. <Non-ionic surfactants> EA-157: polyoxyethylene styrenated phenyl ether "Noigen (registered trademark) EA-157", active ingredient 100%, Dai-ichi Kogyo Seiyaku Co., Ltd. PM-CF60: polyoxyalkylene alkylamine "Puremeal (registered trademark) CF-60", active ingredient 100%, Sanyo Chemical Co., Ltd.

[0084] [Crude Oil Recovery Evaluation-1] Using the crude oil recovery chemicals of Example 1, Example 9, and Comparative Example 1, crude oil and Berea sandstone, crude oil recovery evaluation was carried out simulating an underground oil reservoir. The crude oil recovery chemical was adjusted to a 4% by mass salt concentration brine with a silica concentration of 0.5% by mass, and this was used as a crude oil recovery performance evaluation sample. Medium Sour Russian Urals REBCO Crude Oil purchased from ONTA was used as the crude oil. The Berea sandstone sample used was a sample dried at 60°C for 1 day, with a permeability of approximately 100 mD, a pore volume of approximately 5 mL, a length of 2 inches, and a diameter of 1 inch.

[0085] A Berea sandstone sample was immersed in brine with a salt concentration of 4% by mass in a vacuum vessel, and the vessel was depressurized using a vacuum pump to saturate the Berea sandstone sample with brine. The Berea sandstone sample was then removed and the brine saturation was determined by gravimetric analysis. The brine saturation was calculated using the following formula. The specific gravity of the brine was 1.028 g / cm. ３ is. A Berea sandstone sample saturated with brine was set in the core holder of a sweep oil recovery device SRP-350 (manufactured by Vinci). After the temperature of the core holder was raised to 50°C, crude oil was injected into the Berea sandstone sample while applying a lateral pressure of 800 psi to the Berea sandstone sample using a hydraulic pump, and the Berea sandstone sample was then removed from the core holder and transferred to a pressure bottle. The pressure bottle containing the Berea sandstone sample was then filled with crude oil and left to stand at 50°C for 60 days to prepare an aged sample. The oil saturation of the aged sample was determined by gravimetric method. The oil saturation was calculated based on the following formula. The specific gravity of the crude oil was 0.878 g / cm ３ is. The oil-saturated Berea sandstone sample was then reinstalled in the core holder of the SRP-350 sweep oil recovery device. Then, brine with a 4% salt concentration by mass was injected into the Berea sandstone sample at a flow rate of 0.2 mL / min, and the oil recovery rate after saltwater sweeping was calculated from the volume of crude oil that was discharged. Subsequently, the crude oil recovery performance evaluation sample of the Example or Comparative Example prepared as described above was injected into the Berea sandstone sample at a flow rate of 0.2 mL / min, and the oil recovery rate after chemical sweeping was calculated from the volume of crude oil that was discharged. Table 2 shows the oil recovery results for the Example and Comparative Example.

[0086]

[0087]

[0088]

[0089]

[0090] As shown in Table 1 (Table 1-1, Table 1-2, Table 1-3), no layer separation or gelation was observed in any of the chemical solutions of Examples 1 to 11 and 13 to 15, even after heating in salt water at 120°C for a long period of time. Furthermore, with regard to the DLS average particle size of the aqueous silica sol (silica particles) in the samples, the ratio of the DLS average particle size after the salt resistance test to the DLS average particle size of the chemical solution was 1.5 or less, confirming that the silica sol was not altered, was stable, and was a chemical solution with excellent high-temperature salt resistance.

[0091] On the other hand, in Comparative Example 1, in which an anionic silane compound was used instead of a cationic silane compound as the silane compound, and the anionic surfactants AOS and SDS and the nonionic surfactant EA-157 were used instead of a cationic surfactant as the surfactant, Comparative Example 2, in which a cationic silane compound was used as the silane compound but only the amphoteric surfactant RDMMAcB was used, and Comparative Example 3, in which the amphoteric surfactant RDMMAcB and the nonionic surfactant EA-157 were used, a large amount of white gel was produced in the high-temperature salt resistance evaluation, and the high-temperature salt resistance resulted in very poor results.

[0092] Furthermore, as shown in Example 12 (chemical solution prepared in Example 1) in Table 1 (Table 1-2) and Examples 16, 17 (chemical solution prepared in Example 13), 18 (chemical solution prepared in Example 14), and 19 (chemical solution prepared in Example 15) in Table 1-3, the chemical solutions used in these Examples did not show phase separation or gelation even after being kept in saltwater with a salt concentration of 17% by mass for a long period of time. Furthermore, with regard to the DLS average particle size of the aqueous silica sol (silica particles) in the sample, the ratio of the DLS average particle size after the salt tolerance test to the DLS average particle size of the chemical solution was 1.5 or less, confirming from these Examples that the silica sol was stable and did not deteriorate, and that the chemical solutions had excellent salt tolerance at high salt concentrations.

[0093] On the other hand, in Comparative Example 4 (the chemical solution prepared in Comparative Example 1), in which an anionic silane compound was used instead of a cationic silane compound as the silane compound, and anionic surfactants AOS and SDS and nonionic surfactant EA-157 were used instead of a cationic surfactant as the surfactant, a large amount of white gel was produced in the salt tolerance evaluation, and the salt tolerance at high salt concentrations was very poor.

[0094] Furthermore, as shown in Table 2, with regard to the oil recovery rate of the chemicals (oil recovery rate of chemical sweeping), the chemicals of Examples 1 and 9 were found to have an oil-increasing effect after saltwater sweeping. Note that although the chemicals of the Examples showed results for the oil recovery rate of the chemicals (oil recovery rate of chemical sweeping) that were equal to or lower than those of Comparative Example 1, the chemicals of the Examples according to the present invention are chemicals that have improved resistance to high temperatures and high salinity concentrations (see Table 1 (Tables 1-1 to 1-3)), and can be said to be extremely excellent chemicals in that they achieve both salt resistance and improved oil recovery rate.

[0095] From the above results, it has been confirmed that the crude oil recovery chemical liquid of the present invention has excellent high-temperature salt resistance at temperatures exceeding 100°C and / or salt resistance at high salt concentrations exceeding 10 mass%, and is a high-performance crude oil recovery chemical liquid that also has an oil-enhancing effect.

Claims

1. A chemical solution for crude oil recovery, comprising a cationic silane compound, an aqueous silica sol having an average particle size of 3 to 500 nm, and one or more cationic surfactants.

2. The chemical solution for crude oil recovery according to claim 1, wherein the aqueous silica sol contains silica particles in which at least a portion of the cationic silane compound is bonded to the surface of at least a portion of the silica particles in the sol.

3. 2. The chemical solution for crude oil recovery according to claim 1, wherein the cationic silane compound is at least one compound selected from the group consisting of a silane coupling agent having an amino group, an alkoxysilane having an amino group, a silazane having an amino group, and a siloxane having an amino group.

4. The chemical solution for crude oil recovery according to any one of claims 1 to 3, further comprising an amphoteric surfactant.

5. The chemical solution for crude oil recovery according to any one of claims 1 to 3, further comprising a nonionic surfactant.

6. The aqueous silica sol is contained in an amount of 0.01% by mass to 50% by mass, based on the total mass of the crude oil recovery chemical liquid, in terms of silica solid content. The crude oil recovery chemical liquid according to any one of claims 1 to 3.

7. The crude oil recovery chemical solution according to any one of claims 1 to 3, wherein the silane compound is contained in a mass ratio of 0.001 to 10.0 relative to the silica solid content of the aqueous silica sol.

8. The cationic surfactant is selected from the group consisting of alkylamine salts, quaternary ammonium salts, and alkylpyridinium salts. The chemical solution for crude oil recovery according to any one of claims 1 to 3.

9. The crude oil recovery chemical solution according to any one of claims 1 to 3, wherein the cationic surfactant is contained in a mass ratio of 0.001 or more and less than 0.4 relative to the silica solid content of the crude oil recovery chemical solution.

10. The chemical solution for crude oil recovery according to claim 4, wherein the amphoteric surfactant is selected from the group consisting of a carboxybetaine salt, a 2-alkylimidazoline derivative type, a glycine type, and an amine oxide type.

11. 5. The chemical solution for crude oil recovery according to claim 4, wherein the amphoteric surfactant is contained in a mass ratio of 0.001 or more to less than 0.4 with respect to the silica solid content of the chemical solution for crude oil recovery.

12. The nonionic surfactant has an HLB value of 3.0 or more and 20.0 or less, and selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyalkylene alkylamines, alkylglucosides, polyoxyethylene fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkanolamides; The crude oil recovery chemical solution according to claim 5.

13. The chemical solution for crude oil recovery according to claim 5, wherein the nonionic surfactant is contained in a mass ratio of 0.001 or more and less than 0.4 relative to the silica solid content of the chemical solution for crude oil recovery.

14. 1. A method for recovering crude oil from a subterranean hydrocarbon-bearing formation, comprising: (a) injecting a crude oil recovery chemical solution containing a cationic silane compound, an aqueous silica sol having an average particle size of 3 to 500 nm, and one or more cationic surfactants into a subterranean layer; (b) recovering crude oil from the production well together with the chemical solution injected into the subterranean formation; A method comprising:

15. The method according to claim 14, wherein the cationic surfactant is contained in the crude oil recovery chemical liquid in an amount of 0.001 or more and less than 0.4 by mass ratio relative to the silica solid content of the crude oil recovery chemical liquid.

16. The method according to claim 14 or claim 15, wherein the oil recovery chemical solution further contains an amphoteric surfactant.

17. The method according to claim 14 or claim 15, wherein the oil recovery chemical solution further contains a nonionic surfactant.