A surfactant for fracturing oil displacement and a preparation method thereof

Abstract

A betaine surfactant is disclosed, and its structural formula is shown as formula (1). In addition, a preparation method thereof is also disclosed, which comprises the following steps: respectively reacting a compound of formula (3) and a compound of formula (4) with sodium 3-chloro-2-hydroxypropanesulfonate to obtain a compound of formula (5) and a compound of formula (6); reacting the compound of formula (5) and the compound of formula (6) with a compound of formula (7) to obtain a compound of formula (8); and reacting the compound of formula (8) with a halogenated ethane. The surfactant is easier to arrange closely on a gas-liquid interface, has stronger ability to reduce water surface tension, and requires lower surfactant concentration to reduce water surface tension by 20 mN / m.

Description

Technical Field

[0001] This invention belongs to the field of oilfield surfactant technology; it relates to a surfactant for fracturing and oil displacement and its preparation method, specifically to a betaine-type surfactant and its preparation method. Background Technology

[0002] Surfactant flooding, as the most commonly used method for enhancing oil recovery in tertiary oil recovery technology, has the following main mechanisms of action: First, it reduces interfacial tension. By adding surfactants, the surface tension at the oil-water interface is reduced, making oil droplets easier to deform and increasing the flow velocity of crude oil in the formation. Second, it reverses wetting, as surfactants improve the wettability of rock surfaces, thereby reducing the adhesion of oil droplets to the rock surface. Third, it emulsifies, as the addition of surfactants causes crude oil to form an emulsion system, thereby improving the mobility ratio of the oil and water phases and increasing the sweep efficiency. Fourth, it promotes coalescence and carry-over, as the injection of surfactants can promote the aggregation of oil droplets to form oil bands, increasing the oil displacement efficiency. Fifth, it increases charge density, as when anionic surfactants are injected, they adsorb onto oil droplets and rock surfaces, increasing the electrostatic repulsion between them, making oil droplets easier to carry away and improving the oil washing efficiency. Sixth, it alters the rheological properties of crude oil, as the addition of surfactants can weaken the formation of large molecular network structures in crude oil, reduce the shear stress of crude oil, and improve the recovery rate.

[0003] Amphoteric surfactants, due to the presence of two or more hydrophilic groups (cationic, anionic, or nonionic) in their molecular structure, can simultaneously exhibit a variety of excellent surface properties. The main types include betaine-type, amino acid-type, imidazoline-type, amine oxide-type, and lecithin-type. Because of their strong wetting, foaming, detergency, emulsifying, and dispersing abilities, amphoteric surfactants are commonly used in the leather, detergent, and personal care product industries.

[0004] Chinese invention patent application CN103113869A discloses a dual-long-chain alkylhydroxysulfonate betaine surfactant and an oil displacement agent. Under conditions of a total surfactant concentration of 0.01-0.5%, without the addition of alkali, and at 53.2°C, the oil displacement agent prepared using the dual-long-chain alkylhydroxysulfonate betaine surfactant of this invention can reduce the interfacial tension between crude oil and water to 10. -3 On the order of mN / m.

[0005] Chinese invention patent application CN101966437A discloses a sulfobetaine-type amphoteric gemini surfactant. This surfactant is an N,N'-sulfobetaine compound. The specific synthetic route involves first using an aliphatic diamine to undergo a substitution reaction with a long-chain bromoalkane to generate an intermediate product, and then using the intermediate product to undergo a quaternization reaction with 1,3-propanesulfonyl lactone and 1,4-butanesulfonyl lactone to generate the target product. The sulfobetaine-type gemini surfactant has excellent surface properties. Its critical micelle concentration is 2-3 orders of magnitude lower than that of the corresponding single-chain surfactants, and its surface tension at the critical micelle concentration is 26.47 mN / m, which is much lower than that of the corresponding single-chain surfactants.

[0006] However, the surfactants in existing technologies are relatively difficult to arrange tightly at the gas-liquid interface, and their ability to reduce the surface tension of water is still insufficient. The surfactant concentration required to reduce the surface tension of water by 20 mN / m is relatively high.

[0007] Therefore, there is an urgent need to provide a betaine-type surfactant for improving surface properties and its preparation method. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a betaine-type surfactant for improving surface properties and a method for preparing the same.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a betaine-type surfactant, the structural formula of which is shown in formula (1).

[0010]

[0011] in,

[0012] Alk independently represents medium- and long-chain fatty acid residues;

[0013] R1 and R2 independently represent hydrogen atoms, halogens, and carbon atoms. 1-4 Alkyl or C 1-4 Alkoxy;

[0014] m and n each independently represent integers from 0 to 4;

[0015] x, y, and z each independently represent integers from 2 to 8.

[0016] In this invention, medium-chain fatty acids refer to fatty acids with 8-12 carbon atoms; long-chain fatty acids refer to fatty acids with 13-20 carbon atoms; and fatty acid residues refer to fatty acid portions with COOH removed.

[0017] According to the betaine-type surfactant of the present invention, the long-chain fatty acid residue is C 8-18 alkyl.

[0018] According to the betaine-type surfactant of the present invention, the long-chain fatty acid residue is C 10-14 alkyl.

[0019] According to the betaine-type surfactant of the present invention, R1 and R2 represent hydrogen atoms.

[0020] According to the betaine-type surfactant of the present invention, x and z each independently represent integers from 2 to 6.

[0021] According to the betaine-type surfactant of the present invention, y represents an integer from 3 to 7.

[0022] The betaine-type surfactant according to the present invention has the structural formula shown in formula (2).

[0023]

[0024] On the other hand, the present invention provides a method for preparing a betaine-type surfactant according to the present invention, comprising:

[0025] i) The compounds of formulas (3) and (4) react with sodium 3-chloro-2-hydroxypropanesulfonate, respectively.

[0026]

[0027] Compounds of formulas (5) and (6) were obtained;

[0028]

[0029] ii) The compounds of formulas (5) and (6) react with the compound of formula (7),

[0030]

[0031] The compound of formula (8) was obtained;

[0032]

[0033] iii) The compound of formula (8) reacts with haloethane to give the compound of formula (1);

[0034] Wherein, Alk, R1-R2, mn, and xz are as defined in claim 1; L is a leaveable group.

[0035] According to the method of the present invention, the molar ratio of the compound of formula (3) to sodium 3-chloro-2-hydroxypropanesulfonate is 1:(0.90-1.1); the molar ratio of the compound of formula (4) to sodium 3-chloro-2-hydroxypropanesulfonate is 1:(0.90-1.1).

[0036] According to the method of the present invention, the molar ratio of the compound of formula (5) to the compound of formula (7) is 1:(1.2-1.8); the molar ratio of the compound of formula (6) to the compound of formula (7) is 1:(1.2-1.8).

[0037] According to the method of the present invention, the molar ratio of the compound of formula (8) to the haloethane is 1:(2-4).

[0038] Compared with the prior art, the betaine-type surfactants of the present invention are more likely to be tightly packed at the gas-liquid interface, and have a stronger ability to reduce the surface tension of water than traditional surfactants. The surfactant concentration required to reduce the surface tension of water by 20 mN / m is lower. Detailed Implementation

[0039] It must be noted that, unless the context clearly specifies otherwise, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” can include one or more referents (i.e., two or more, including two).

[0040] Unless otherwise specified, numerical ranges in this invention are approximate and therefore may include values ​​outside of said range. The numerical range may be expressed in this invention as from “about” a particular value and / or to “about” another particular value. When such a range is expressed, another aspect includes from said one particular value and / or to another particular value. Similarly, when a value is expressed as an approximation using the antecedent “about,” it should be understood that said particular value forms another aspect. It should also be understood that each endpoint in a numerical range is significant in relation to and independent of another endpoint.

[0041] The reference to the weight parts of a specific element or component in the composition or article in the specification and the final claims refers to the weight relationship between that element or component and any other element or component in the composition or article, expressed in parts by weight.

[0042] In this invention, unless specifically indicated otherwise, or implied by the context or customary practice in the art, all solutions referred to herein are aqueous solutions; when the solute in the aqueous solution is a liquid, all fractions and percentages are by volume, and the volume percentage of a component is based on the total volume of the composition or product containing that component; when the solute in the aqueous solution is a solid, all fractions and percentages are by weight, and the weight percentage of a component is based on the total weight of the composition or product containing that component.

[0043] The terms “comprising,” “including,” “having,” and similar expressions used in this invention are not intended to exclude the presence of any optional components, steps, or procedures, whether or not any optional components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all methods claimed by using the term “comprising” may include one or more additional steps, equipment parts or components, and / or substances. In contrast, the term “consisting of” excludes any components, steps, or procedures not specifically described or enumerated. Unless otherwise stated, the term “or” refers to members listed individually and in any combination.

[0044] Furthermore, the contents of any patent or non-patent documents referenced in this invention are incorporated herein by full citation, especially regarding definitions disclosed in the relevant field (where there is no inconsistency with any definitions specifically provided herein) and common knowledge.

[0045] In this invention, unless otherwise specified, all parts are parts by weight, temperatures are expressed in °C or at ambient temperature, and pressures are at or near atmospheric pressure. Room temperature means 20-30 °C. Various variations and combinations of reaction conditions exist (e.g., component concentrations, desired solvents, solvent mixtures, temperature, pressure, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method. Only reasonable routine experiments are required to optimize such method conditions.

[0046] Example 1

[0047] In a four-necked round-bottom flask equipped with a stirrer and thermometer, add 160 mL of 75% ethanol solution, then add the compound of formula (9) (60 mmol), sodium 3-chloro-2-hydroxypropanesulfonate (60 mmol), and a small amount of sodium carbonate (2.2 g).

[0048]

[0049] The mixture was heated to reflux and reacted for 12 hours under the same conditions. The reaction endpoint was determined by TLC. After cooling to room temperature, a solid precipitated and was filtered. The solid was washed three times with anhydrous toluene, recrystallized from it with 75% ethanol, and dried to obtain a white powder, which is the compound of formula (10), with a yield of approximately 52%.

[0050]

[0051] In a four-necked round-bottom flask, add 50 mL of 75% ethanol solution (30 mmol) and the compound of formula (10) and a small amount of sodium carbonate (1 g), and stir thoroughly until completely dissolved; then add 1,5-dibromo-n-pentane (22 mmol). React under reflux for 4 h, and proceed directly to the next step after the reaction is complete.

[0052] In a four-necked round-bottom flask, excess bromoethane (45 mmol) was added. The reaction was carried out under reflux for 48 h. The filtrate was cooled to -5 °C using an ice-salt bath, and a solid precipitated. The solid was filtered. The solid was washed three times with petroleum ether and then recrystallized using a mixed solvent of ethanol / acetone (volume ratio 1:6). The solid was dried to obtain a white powder, which is the compound of formula (2).

[0053] The infrared FT-IR spectra of the compounds of formula (2) are shown in Table 1.

[0054] Table 1

[0055]

[0056] Surface performance testing

[0057] The surface properties of the compound of formula (2) in Example 1 were determined using a fully automated surface tensiometer according to the platinum plate method. The results showed that the critical micelle concentration (cmc) of the compound of formula (2) was 1.21 × 10⁻⁶. -5 mol / L; the surface tension value at this concentration is γ cmc The required surfactant concentration C is 20.7 mN / m; the required surfactant concentration C to reduce the surface tension of water by 20 mN / m is 20.7 mN / m. 20 1.03×10 -6 mol / L.

[0058] Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications, substitutions, deletions, corrections or adjustments to the technical solutions of this invention, and these equivalent technical solutions also fall within the scope defined by the claims of this invention.

Claims

1. A betaine-type surfactant, the structural formula of which is shown in formula (2), 2. A method for preparing the betaine-type surfactant according to claim 1, comprising: i) The compounds of formulas (3) and (4) react with sodium 3-chloro-2-hydroxypropanesulfonate, respectively. Compounds of formulas (5) and (6) were obtained; ii) The compounds of formulas (5) and (6) react with the compound of formula (7), The compound of formula (8) was obtained; iii) The compound of formula (8) reacts with haloethane to give the compound of formula (2); Where Alk represents C 12 Alkyl groups, m and n both represent 0, x and z represent 4; y represents 5; L is a leaving group.

3. The method according to claim 2, wherein, The molar ratio of the compound of formula (3) to sodium 3-chloro-2-hydroxypropanesulfonate is 1:(0.90-1.1); the molar ratio of the compound of formula (4) to sodium 3-chloro-2-hydroxypropanesulfonate is 1:(0.90-1.1).

4. The method according to claim 2, wherein, The molar ratio of the compound in formula (5) to the compound in formula (7) is 1:(1.2-1.8); the molar ratio of the compound in formula (6) to the compound in formula (7) is 1:(1.2-1.8).

5. The method according to claim 2, wherein, The molar ratio of the compound in formula (8) to the haloethane is 1:(2-4).

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