Gemini surfactants, their preparation methods and applications

Abstract

This invention relates to the field of oilfield chemical technology, and discloses a gemini surfactant, its preparation method, and its application. The gemini surfactant comprises the structure shown in Formula I, where R is a C1-C8 alkyl group or a C6-C8 aryl group; Y... ‑ SO3 ‑ M + The ions are alkali metal ions or alkaline earth metal ions; m = 1-30; n = 1-15. The gemini surfactant of this invention can be used as a viscosity reducer for heavy oil, exhibiting strong viscosity-reducing ability. Through the effective increase of the strength of the oil-water interface film via polyoxyethylene and polyoxypropylene segments, it has a good emulsifying effect, which is beneficial for the migration of oil-water emulsions in rock pores, expanding the swept area, significantly reducing residual oil saturation, and resulting in good oil displacement effect.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to gemini surfactants, their preparation methods, and applications. Background Technology

[0002] Following the initial exploitation of heavy oil reservoirs, water injection is widely used in their development. Although waterflooding achieves higher recovery rates than primary oil recovery, severe water channeling due to formation heterogeneity and significant differences in oil-water mobility ratios leads to small swept-through volumes and low recovery rates. A large amount of residual oil remains trapped underground after waterflooding, with recovery rates for ordinary heavy oil reservoirs reaching only 1-10%. Therefore, finding effective methods to reduce heavy oil viscosity, increase swept-through range, and improve recovery rates during waterflooding development is of great significance.

[0003] Methods to suppress water fingering during waterflooding development include injecting plugging agents to block large water flow channels, or adding chemical agents such as polymers, alkalis, and surfactants to the water to increase the water sweep efficiency. While adding polymers can increase water viscosity, reduce the mobility ratio of heavy oil to water, and improve the waterflood sweep efficiency, polymers are long-chain organic compounds. On the one hand, their long molecular chains break when flowing in porous formation media; on the other hand, polymers easily adhere to rock surfaces, resulting in a still low sweep efficiency in formations far from the injection well. Although alkalis can react with acidic components in crude oil to emulsify heavy oil into an oil-water emulsion, generally increasing recovery to around 10%, excessive alkali can cause alkali sensitivity, leading to severe formation scaling and damaging the reservoir's pore structure. Surfactant flooding is considered an effective method to improve heavy oil recovery after waterflooding and has been widely studied and applied. Surfactants can alter the wettability of rocks, detach oil films adhering to the rock face, reduce the interfacial tension between oil and water, and emulsify heavy oil into an oil-water emulsion to reduce viscosity, thus significantly improving oil displacement efficiency. After injection into the formation, the emulsification, emulsion migration, and long-term stability of the emulsion flooding system directly affect its application performance. However, when using existing surfactants, due to the repulsive effect between surfactant ions, their distribution at the oil / water interface is relatively loose, resulting in poor interfacial film stability. Furthermore, the flow capacity of the oil-water emulsion in porous media and the relationship between droplet size and the size of the porous media are also crucial. The droplet size of the oil-water emulsion formed by surfactants and heavy oil is typically greater than 20 μm, while the reservoir pore throat size is typically less than 10 μm. When the emulsion droplets pass through the pore throat, the Jamin effect occurs, creating additional resistance and leading to excessive injection pressure. When the droplet size of the oil-water emulsion is smaller than or much smaller than the throat diameter, there is almost no additional resistance, reducing the difficulty of heavy oil recovery.

[0004] Therefore, there is an urgent need to develop a multifunctional surfactant that can effectively improve the recovery rate of heavy oil fields. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor interfacial film stability and excessive injection pressure in existing surfactants, and to provide a gemini surfactant, its preparation method, and its application. The gemini surfactant of this invention is an ultra-short carbon chain extended gemini surfactant, which has good water solubility, high interfacial activity, controllable interfacial strength, and is highly efficient and inexpensive. It also exhibits long-term stability and can be used as a viscosity reducer for heavy oil to effectively improve the recovery rate of heavy oil.

[0006] To achieve the above objectives, a first aspect of the present invention provides a gemini surfactant comprising the structure shown in Formula I.

[0007]

[0008] In Formula I, R is a C1-C8 alkyl group or a C6-C8 aryl group;

[0009] Y - SO3 - M + They are alkali metal ions or alkaline earth metal ions;

[0010] m = 1-30; n = 1-15.

[0011] A second aspect of the present invention provides a method for preparing a gemini surfactant, the method comprising the following steps:

[0012] S1. Under alkaline conditions, ROH is reacted with epichlorohydrin and thionyl chloride, then with phenol and chlorosulfonic acid, and then neutralized to obtain alkyl-terminated phenol polyoxypropylene ether sulfonate; wherein R is a C1-C8 alkyl or a C6-C8 aryl.

[0013] S2. Reaction of thionyl chloride with polyethylene glycol yields di(terminated-chloroethyl) polyoxyethylene ether;

[0014] S3. The alkyl-terminated phenolic polyoxypropylene ether sulfonate obtained in step S1 is reacted with the di(terminated-chloroethyl) polyoxyethylene ether obtained in step S2 to obtain a gemini surfactant.

[0015] A third aspect of the present invention provides a heavy oil viscosity reducer, the heavy oil viscosity reducer comprising the gemini surfactant described in the first aspect or the gemini surfactant prepared by the preparation method described in the second aspect, and water.

[0016] The fourth aspect of the present invention provides the application of the gemini surfactant as described in the first aspect, the gemini surfactant prepared by the preparation method described in the second aspect, or the heavy oil viscosity reducer described in the third aspect in the development of heavy oil reservoirs.

[0017] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0018] (1) The twin surfactant of the present invention uses a short carbon chain as the alkyl chain, which has good water solubility; it also contains polyoxyethylene (EO) and polyoxypropylene (PO) segments; the polyoxyethylene (EO) linking group in the structure forms a sublayer on the aqueous phase side, which is conducive to the formation of an oil-in-water emulsion and can achieve the purpose of reducing viscosity; the introduction of long PO segments occupies the vacancy on the oil phase side by spiral coiling, so that the surfactant molecules are closely arranged at the oil-water interface, achieving ultra-low interfacial tension.

[0019] (2) The gemini surfactant of the present invention can be used as a viscosity reducer for heavy oil. Through the polyoxyethylene and polyoxypropylene segments, it effectively increases the strength of the oil-water interface film, exhibits good emulsification, facilitates the migration of oil-water emulsions in rock pores, expands the swept area, significantly reduces residual oil saturation, and has a good oil displacement effect. The viscosity reduction rate of the gemini surfactant of the present invention as a viscosity reducer for heavy oil is above 90%, demonstrating strong viscosity reduction capability.

[0020] (3) The droplet size of the water-in-oil emulsion formed by the twin surfactant of the present invention and heavy oil is smaller than or much smaller than the throat diameter, resulting in low transport resistance and easy recovery of heavy oil; it can increase the crude oil recovery rate by more than 37% compared with water drive, and the oil displacement effect is better than other heavy oil viscosity reducers. Attached Figure Description

[0021] Figure 1 The graph shows the interfacial tension data between the surfactant solution and crude oil in Examples 1-5 of this invention.

[0022] Figures 2a-2f The figures show the emulsification performance test results for formation water and the surfactants used in Examples 1-5, respectively.

[0023] Figures 3a-3f The images show the microscopic visualization of the oil displacement effect of formation water and the surfactants used in Examples 1-5, respectively.

[0024] Figures 4a-4e These are droplets of oil-in-water emulsions formed during the displacement process of the surfactant solutions in Examples 1-5, respectively. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] A first aspect of the present invention provides a gemini surfactant, said gemini surfactant comprising the structure shown in Formula I.

[0027]

[0028] In Formula I, R is a C1-C8 alkyl group or a C6-C8 aryl group;

[0029] Y - SO3 - M + They are alkali metal ions or alkaline earth metal ions;

[0030] m = 1-30; n = 1-15.

[0031] According to a preferred embodiment of the present invention, m>n.

[0032] The twin surfactant of this invention uses short carbon chains as alkyl chains, which have good water solubility; it also contains polyoxyethylene (EO) segments and polyoxypropylene (PO) segments; the polyoxyethylene (EO) linking groups in the structure form a sublayer on the aqueous phase side, which is conducive to the formation of an oil-in-water emulsion and can achieve the purpose of reducing viscosity, with a viscosity reduction rate of much greater than 90%; the introduction of long PO segments occupies the vacancies on the oil phase side through helical coiling, so that the surfactant molecules are closely arranged at the oil-water interface, achieving ultra-low interfacial tension, with a viscosity reduction rate of much greater than 90%.

[0033] According to some embodiments of the present invention, R is a C4-C8 alkyl group or a C6-C8 aryl group.

[0034] According to some embodiments of the present invention, M + for Na + K + Ca 2+ or Mg 2+ .

[0035] According to the present invention, m = 1-30, for example, 1, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, and any value within the range of any two values, preferably m = 10-30.

[0036] According to the present invention, n = 1-15, for example, 1, 2, 5, 8, 10, 12, 15 and any value in the range of any two values, preferably n = 5-15.

[0037] The gemini surfactant of this invention uses an ultra-short carbon chain (C4-C8) as the alkyl chain, and is an ultra-short carbon chain extended gemini surfactant. Compared with long alkyl carbon chain surfactants, the gemini surfactant of this invention has better water solubility.

[0038] According to some embodiments of the present invention, R is ethylhexyl, isobutyl or phenyl.

[0039] According to some embodiments of the present invention, the interfacial tension of the gemini surfactant is less than 9 × 10⁻⁶. -3 mN / m.

[0040] According to some embodiments of the present invention, the viscosity reduction rate of the gemini surfactant is greater than 90%.

[0041] A second aspect of the present invention provides a method for preparing a gemini surfactant, the method comprising the following steps:

[0042] S1. Under alkaline conditions, ROH alkyl alcohol is reacted with epichlorohydrin and sulfoxide, then reacted with phenol and chlorosulfonic acid, followed by neutralization to obtain alkyl-terminated phenol polyoxypropylene ether sulfonate; wherein R is a C1-C8 alkyl or a C6-C8 aryl; preferably a C4-C8 alkyl or a C6-C8 aryl; more preferably ethylhexyl, isobutyl or phenyl;

[0043] S2. Reaction of thionyl chloride with polyethylene glycol yields di(terminated-chloroethyl) polyoxyethylene ether;

[0044] S3. The alkyl-terminated phenolic polyoxypropylene ether sulfonate obtained in step S1 is reacted with the di(terminated-chloroethyl) polyoxyethylene ether obtained in step S2 to obtain a gemini surfactant.

[0045] According to some embodiments of the present invention, step (1) specifically includes the following steps:

[0046] S11. In the presence of an alkaline catalyst, ROH alkyl alcohol is reacted with epichlorohydrin in a first reaction, and then reacted with thionyl chloride in a second reaction to obtain alkyl alcohol polyoxypropylene ether chloride.

[0047] S12. Under alkaline conditions, the alkyl alcohol polyoxypropylene ether chloride obtained in step S11 is reacted with phenol in a third reaction, then with chlorosulfonic acid in a fourth reaction, and then neutralized to obtain alkyl-terminated phenol polyoxypropylene ether sulfonate.

[0048] According to some embodiments of the present invention, the molar ratio of alkyl alcohol polyoxypropylene ether chloride to phenol is 1:1 to 1:1.5.

[0049] According to some embodiments of the present invention, the molar ratio of alkyl-terminated phenolic polyoxypropylene ether sulfonate to di(terminated-chloroethyl) polyoxyethylene ether is 1.8:1-2:1.

[0050] According to some embodiments of the present invention, the alkaline catalyst is a potassium hydroxide catalyst, and the first reaction is carried out at 150-170°C until the system pressure is zero.

[0051] According to some embodiments of the present invention, the second reaction is carried out under ice-water bath conditions.

[0052] According to some embodiments of the present invention, the third reaction is carried out in a mixed solvent of toluene and dimethylformamide under alkaline conditions of potassium carbonate.

[0053] According to some embodiments of the present invention, the fourth reaction is carried out under ice-water bath conditions.

[0054] According to a particularly preferred embodiment of the present invention, a method for preparing a gemini surfactant specifically includes the following steps:

[0055] (1) Add alkyl alcohol and potassium hydroxide catalyst to a high-pressure reactor, heat to 150-170℃, add a measured amount of epichlorohydrin, and stir until the system pressure is zero. Stop the reaction to obtain alkyl alcohol polyoxypropylene ether.

[0056] (2) Under ice-water bath conditions, thionyl chloride was added dropwise to the alkyl alcohol polyoxypropylene ether synthesized above, and the reaction was carried out to obtain the alkyl alcohol polyoxypropylene ether chloride.

[0057] (3) The alkyl alcohol polyoxypropylene ether chlorinated compound and phenol synthesized above were added to a mixed solvent of toluene and dimethylformamide and reacted under potassium carbonate alkaline conditions to obtain alkyl-terminated phenol polyoxypropylene ether compound.

[0058] (4) The alkyl-terminated phenol polyoxypropylene ether compound synthesized above was added to dichloroethane solvent, and chlorosulfonic acid was slowly added dropwise under ice-water bath conditions. After the reaction was completed, it was neutralized with sodium hydroxide solution to obtain alkyl-terminated phenol polyoxypropylene ether sulfonate sodium.

[0059] (5) Under ice-water bath conditions, thionyl chloride is added dropwise to polyethylene glycol to obtain di(terminal-chloroethyl) polyoxyethylene ether.

[0060] (6) The alkyl-terminated sodium phenol polyoxypropylene ether sulfonate and di(terminal-chloroethyl) polyoxyethylene ether synthesized above are added to the reactor. Under continuous stirring, aluminum trichloride is added. After the reaction, alkyl-terminated sodium phenol polyoxypropylene ether sulfonate Gemini type compound with polyoxyethylene ether as the linker is obtained.

[0061] A third aspect of the present invention provides a heavy oil viscosity reducer, the heavy oil viscosity reducer comprising the gemini surfactant described in the first aspect or the gemini surfactant prepared by the preparation method described in the second aspect, and water.

[0062] The twin surfactants of this invention can be used as viscosity reducers for heavy oil. Through the polyoxyethylene and polyoxypropylene segments, they effectively increase the strength of the oil-water interface film, have a good emulsification effect, facilitate the migration of oil-water emulsions in rock pores, expand the sweep area, significantly reduce the residual oil saturation, and have a good oil displacement effect.

[0063] The twin surfactants of this invention have a viscosity reduction rate of over 90% as thick oil viscosity reducers, demonstrating strong viscosity reduction capabilities.

[0064] According to some embodiments of the present invention, the mass concentration of the gemini surfactant in the heavy oil viscosity reducer is 0.01-0.5 wt%.

[0065] The twin surfactant of this invention can effectively improve micro-flooding efficiency when used alone at a concentration of only 0.01-0.5 wt%, which is 37% higher than that of waterflooding, and is suitable for crude oil extraction in heavy oil reservoirs.

[0066] According to some embodiments of the present invention, the water is formation water or simulated formation water.

[0067] According to some embodiments of the present invention, the preparation method of the heavy oil viscosity reducer is as follows:

[0068] (1) Pre-treat the solid sample of the Gemini surfactant, for example, by crushing and grinding it;

[0069] (2) Weigh the amount of the formula sample and add it into a clean reagent bottle;

[0070] (3) Add formation water to the above reagent bottle and stir or shake thoroughly to obtain the desired heavy oil viscosity reducer.

[0071] The fourth aspect of the present invention provides the application of the gemini surfactant as described in the first aspect, the gemini surfactant prepared by the preparation method described in the second aspect, or the heavy oil viscosity reducer described in the third aspect in the development of heavy oil reservoirs.

[0072] The droplet size of the water-in-oil emulsion formed by the twin surfactants of the present invention is smaller than or much smaller than the throat diameter, resulting in low transport resistance and easy recovery of heavy oil. It can increase the crude oil recovery rate by more than 37% compared with water flooding, and its oil displacement effect is better than other heavy oil viscosity reducers.

[0073] The twin surfactants of this invention are designed and synthesized for the oil recovery process of heavy oil reservoirs. They have strong emulsifying ability and can form a synergistic emulsion system of small-sized water-in-oil emulsions.

[0074] The present invention will be described in detail below through examples. Unless otherwise specified in the following examples and comparative examples, conditions were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0075] The interfacial tension parameters were measured according to the "SY / T 5370-2018 Method for Determination of Interfacial Tension";

[0076] The interfacial modulus parameters were measured using an interfacial expansion rheometer and dynamic contact angle meter.

[0077] The viscosity reduction rate of the surfactant was measured using a viscometer.

[0078] The oil displacement performance was measured through microscopic visualization oil displacement experiments.

[0079] In the following preparation examples, P represents the polyoxypropylene segment and E represents the polyoxyethylene segment.

[0080] In the following examples and comparative examples, simulated formation water was used, and the specific parameters are shown in Table 1.

[0081] Table 1. Composition of simulated formation water

[0082] Component content <![CDATA[CaCl2]]> NaCl <![CDATA[MgCl2·6H2O]]> <![CDATA[NaHCO3]]> <![CDATA[Na2CO3]]> TDS g / L 1.928 5.02 0.997 0.301 0.051 8.297

[0083] Preparation Example 1

[0084] Gemini surfactant C 16 P 20 The preparation method of (C6H4O)2E5(SO3)2·2Na includes the following steps:

[0085] (1) Add 0.1 mol of 2-ethylhexanol and 0.026 g of potassium hydroxide catalyst to a high-pressure reactor, heat to 150-170°C, add 1 mol of propylene oxide (58.0 g) dropwise, and stir until the system pressure is zero. Stop the reaction to obtain alkyl alcohol polyoxypropylene ether.

[0086] (2) Under ice-water bath conditions, 0.05 mol of thionyl chloride (13.5 g) was added dropwise to the 0.1 mol of 2-ethyl-hexyl alcohol polyoxypropylene ether (71.0 g) synthesized above, and the reaction was carried out to obtain 2-ethyl-hexyl alcohol polyoxypropylene ether chloride.

[0087] (3) The 0.1 mol 2-ethyl-hexyl alcohol polyoxypropylene ether chloride (72.85 g) and 0.1 mol phenol (9.4 g) synthesized above were added to a mixed solvent of toluene and dimethylformamide and reacted under potassium carbonate alkaline conditions to obtain 2-ethyl-hexyl-terminated phenol polyoxypropylene ether compound.

[0088] (4) The 0.1 mol of 2-ethyl-hexyl-terminated phenol polyoxypropylene ether compound (78.6 g) synthesized above was added to dichloroethane solvent, and 0.105 mol of chlorosulfonic acid (12.23 g) was slowly added dropwise under ice-water bath conditions. After the reaction was completed, it was neutralized with sodium hydroxide solution to obtain sodium 2-ethyl-hexyl-terminated phenol polyoxypropylene ether sulfonate.

[0089] (5) Under ice-water bath conditions, 0.1 mol of thionyl chloride (13.5 g) was added dropwise to 0.1 mol of polyethylene glycol (23.8 g) to obtain di(terminal-chloroethyl) polyoxyethylene ether.

[0090] (6) The synthesized 0.1 mol of 2-ethyl-hexyl-terminated sodium phenolate polyoxypropylene ether sulfonate (88.8 g) and 0.05 mol of di(terminated-chloroethyl) polyoxyethylene ether (13.75 g) were added to a reactor. Under continuous stirring, 0.1 mol of aluminum trichloride (13.35 g) was added. After the reaction, a Gemini-type compound of 2-ethyl-hexyl-terminated sodium phenolate polyoxypropylene ether sulfonate with polyoxyethylene ether as the linker was obtained, namely the Gemini surfactant C. 16 P 20 (C6H4O)2E5(SO3)2·2Na, its structural formula is as follows:

[0091]

[0092] Preparation Example 2

[0093] Gemini surfactant C8P was prepared according to the method of Preparation Example 1. 24 The difference is that 2-ethylhexanol is replaced with an equimolar amount of isobutanol, and polyethylene glycol is replaced with an equimolar amount of hexaethylene glycol.

[0094] Gemini surfactant C8P 24 The structural formula of (C6H4O)2E7(SO3)2·2Na is as follows:

[0095]

[0096] Preparation Example 3

[0097] Gemini surfactant (Ph)2P was prepared according to the method of Preparation Example 1.40 (C6H4O)2E 15 The difference is that 2-ethylhexanol is replaced with an equimolar amount of phenol, and polyethylene glycol is replaced with an equimolar amount of tetradecaethylene glycol.

[0098] Gemini surfactant (Ph)2P 40 (C6H4O)2E 15 The structural formula of (SO3)2·2Na is as follows:

[0099]

[0100] Preparation Example 4

[0101] Gemini surfactant C8P was prepared according to the method of Preparation Example 1. 30 (C6H4O)2E 10 The difference is that the raw material tetraethylene glycol is replaced with an equimolar amount of nonaethylene glycol.

[0102] Gemini surfactant C8P 30 (C6H4O)2E 10 The structural formula of (SO3)2·2Na is as follows:

[0103]

[0104] Preparation Example 5

[0105] Gemini surfactant C8P was prepared according to the method of Preparation Example 1. 60 (C6H4O)2E 15 The difference is that 2-ethylhexanol is replaced with an equimolar amount of isobutanol, and polyethylene glycol is replaced with an equimolar amount of tetradecaethylene glycol.

[0106] Gemini surfactant C8P 60 (C6H4O)2E 15 The structural formula of (SO3)2·2Na is as follows:

[0107]

[0108] Example 1

[0109] A heavy oil viscosity reducer comprises the following components: 0.1 wt% C 16 P 20 (C6H4O)2E5(SO3)2·2Na and 99.9 wt% formation water.

[0110] Example 2

[0111] A heavy oil viscosity reducer comprises the following components: 0.3 wt% C8P 24 (C6H4O)2E7(SO3)2·2Na and 99.7wt% formation water.

[0112] Example 3

[0113] A heavy oil viscosity reducer comprises the following components: 0.01 wt% of (Ph)2P 40 (C6H4O)2E 15 (SO3)2·2Na and 99.99 wt% formation water.

[0114] Example 4

[0115] A heavy oil viscosity reducer comprises the following components: 0.2 wt% C8P 30 (C6H4O)2E 10 (SO3)2·2Na and 99.8 wt% formation water.

[0116] Example 5

[0117] A heavy oil viscosity reducer comprises the following components: 0.5 wt% C8P 60 (C6H4O)2E 15 (SO3)2·2Na and 99.5 wt% formation water.

[0118] Comparative Example 1

[0119] A heavy oil viscosity reducer comprises the following components: 0.5 wt% dodecylbenzene sulfonate and 99.5 wt% formation water.

[0120] Comparative Example 2

[0121] A heavy oil viscosity reducer comprises the following components: 0.5 wt% petroleum sulfonate and 99.5 wt% formation water.

[0122] Test Example 1

[0123] The interfacial tensions between the surfactants prepared in Examples 1-5, the commercially available dodecylbenzene sulfonate surfactant, and the commercially available petroleum sulfonate surfactant and heavy crude oil were measured. The dynamic interfacial tension data between the above surfactants and heavy crude oil are shown below. Figure 1 As shown in Table 2, the steady-state values ​​of interfacial tension are as follows.

[0124] Interfacial tension determination method: The oil-water interfacial tension was tested according to "SY / T 5370-2018 Interfacial Tension Determination Method". First, solutions of the surfactants prepared in Examples 1-5, commercially available dodecylbenzene sulfonate surfactants, and commercially available petroleum sulfonate surfactants were prepared with formation water to a concentration of 0.3 wt%. The oil-water interfacial tension between heavy crude oil and the above surfactant solutions was determined using the spin-drop method at a temperature of 54°C and a rotation speed of 5000 rpm.

[0125] Test Example 2

[0126] Interfacial expansion rheological experiments were conducted on the heavy oil viscosity reducers of Examples 1-5 and Comparative Examples 1-2, respectively. The interfacial modulus data are shown in Table 2.

[0127] Method for determining interfacial modulus: An expansion rheological experiment was conducted using an interfacial expansion rheology and dynamic contact angle measuring instrument. A suspended droplet was subjected to periodic oscillations, and the instantaneous changes in liquid surface area were captured by a camera. The periodic changes in interfacial tension were measured using droplet shape analysis, and the interfacial modulus value was obtained through theoretical calculation. A higher interfacial modulus value indicates greater interfacial film strength.

[0128] Test Example 3

[0129] The emulsification properties of the heavy oil viscosity reducers in Examples 1-5 and Comparative Examples 1-2 were tested using the bottle test method. The stability of the emulsions is as follows: Figures 2a-2f As shown, 2a is the emulsification performance test diagram of formation water, 2b is the emulsification performance test diagram of Example 1, 2c is the emulsification performance test diagram of Example 2, 2d is the emulsification performance test diagram of Example 3, 2e is the emulsification performance test diagram of Example 4, and 2f is the emulsification performance test diagram of Example 5. The test results show that the surfactant of the present invention has strong emulsification ability, slow water separation rate and long phase separation time, and the emulsion formed with crude oil has good stability.

[0130] Emulsification performance test method: First, place the surfactant solution and crude oil in a constant temperature oven at 54℃ in the oil reservoir and age for 30 minutes. Then, take 5 grams of each oil and water at a ratio of 5:5 and add them to a 15mL stoppered test tube and stopper it. Shake it vigorously up and down 100 times by hand to ensure that it is fully emulsified. The desired emulsion can be obtained and kept warm and standing in an oven.

[0131] Test Example 4

[0132] The viscosity of the emulsions formed by the heavy oil viscosity reducers of Examples 1-5 and Comparative Examples 1-2 and crude oil were tested respectively, and the viscosity reduction rate data are shown in Table 2.

[0133] Test method for surfactant viscosity-reducing performance: Take two 50 mL portions of heavy oil (the viscosity of crude oil is 2165 cP at a reservoir temperature of 54℃). One portion is not treated with surfactant solution; the other portion is treated with 0.1 wt% thick oil viscosity reducer. Both portions are placed in a 54℃ oil bath and stirred at 200 r / min for 30 min. The viscosity of each portion of heavy oil is measured. Triple parallel measurements are performed, and the average value is taken. The viscosity reduction rate is calculated as: (crude oil viscosity - viscosity of the emulsion after adding surfactant) / crude oil viscosity.

[0134] Test Example 5

[0135] Microscopic visualization tests were conducted on the oil displacement effects of the heavy oil viscosity reducers in Examples 1-5 and Comparative Examples 1-2 to evaluate the oil displacement performance of the surfactant solutions. The oil displacement efficiency data are shown in Table 2. The oil displacement effect is as follows: Figures 3a-3f As shown, 3a is a microscopic visualization of the oil displacement effect of formation water, 3b is a microscopic visualization of the oil displacement effect of Example 1, 3c is a microscopic visualization of the oil displacement effect of Example 2, 3d is a microscopic visualization of the oil displacement effect of Example 3, 3e is a microscopic visualization of the oil displacement effect of Example 4, and 3f is a microscopic visualization of the oil displacement effect of Example 5.

[0136] Microscopic visualization method for oil displacement experiment: Diluted crude oil of suitable viscosity was injected into a water-wetted model with simulated pore structure characteristics at a constant rate of 20 μL / min until the crude oil filled the entire glass model and no air bubbles were present in the pore throats. In the experiment, an oil displacement agent solution was injected into the chip model at a constant injection rate of 0.1 μL / min, and the process of crude oil displacement in the model was recorded using a microscope in video recording mode. The displacement effect is as follows: Figures 4a-4e As shown, 4a is a droplet of the oil-in-water emulsion formed during the displacement process in Example 1, 4b is a droplet of the oil-in-water emulsion formed during the displacement process in Example 2, 4c is a droplet of the oil-in-water emulsion formed during the displacement process in Example 3, 4d is a droplet of the oil-in-water emulsion formed during the displacement process in Example 4, and 4e is a droplet of the oil-in-water emulsion formed during the displacement process in Example 5.

[0137] Table 2 Test Data

[0138]

[0139] As can be seen from the results in Table 2, the oil-water interfacial tension of the surfactants in Examples 1-5 is all within 10 when used alone at a concentration of only 0.01wt%-0.5wt%. -4 -10 -3 The surfactant of this invention has an excellent ability to reduce interfacial tension, on the order of mN / m.

[0140] The oil displacement agent of the present invention can form an interfacial film with a certain interfacial strength at the crude oil / water interface and has good interfacial film stability.

[0141] The test results show that the five surfactants in the examples all have good viscosity-reducing effects on heavy oil, with little overall difference, and the viscosity reduction rate is above 90%. This indicates that the surfactants of the present invention have strong viscosity-reducing ability. Through microscopic visualization oil displacement experiments, the migration process of the porous-level oil-water emulsion was observed. The test results show that the oil-water emulsion formed by the surfactants of the present invention can expand the swept area, significantly reduce the residual oil saturation, and has a better oil displacement effect, significantly higher than water displacement.

[0142] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A gemini surfactant, characterized in that, The gemini surfactant comprises the structure shown in Formula I. In Formula I, R is a C1-C8 alkyl group or a C6-C8 aryl group; Y - SO3 - M + They are alkali metal ions or alkaline earth metal ions; m = 1 - 30; n = 1 - 15.

2. The gemini surfactant according to claim 1, wherein, R is a C4-C8 alkyl group or a C6-C8 aryl group; And / or, M + for Na + K + Ca 2+ or Mg 2+ ; And / or, m = 10-30; And / or, n = 5-15.

3. The gemini surfactant according to claim 2, wherein, R is ethylhexyl, isobutyl, or phenyl.

4. The gemini surfactant according to any one of claims 1-3, wherein, The interfacial tension of the Gemini surfactant is less than 9 × 10⁻⁶. -3 mN / m; And / or, the viscosity reduction rate of the Gemini surfactant is greater than 90%.

5. A method for preparing a gemini surfactant, characterized in that, The preparation method includes the following steps: S1. Under alkaline conditions, ROH is reacted with epichlorohydrin and thionyl chloride, then with phenol and chlorosulfonic acid, and then neutralized to obtain alkyl-terminated phenol polyoxypropylene ether sulfonate; wherein R is a C1-C8 alkyl or a C6-C8 aryl. S2. Reaction of thionyl chloride with polyethylene glycol yields di(terminated-chloroethyl) polyoxyethylene ether; S3. The alkyl-terminated phenolic polyoxypropylene ether sulfonate obtained in step S1 is reacted with the di(terminated-chloroethyl) polyoxyethylene ether obtained in step S2 to obtain a gemini surfactant.

6. The preparation method according to claim 5, wherein, Step (1) specifically includes the following steps: S11. In the presence of an alkaline catalyst, ROH is reacted with epichlorohydrin in a first reaction, and then reacted with thionyl chloride in a second reaction to obtain alkyl alcohol polyoxypropylene ether chloride. S12. Under alkaline conditions, the alkyl alcohol polyoxypropylene ether chloride obtained in step S11 is reacted with phenol in a third reaction, then with chlorosulfonic acid in a fourth reaction, and then neutralized to obtain alkyl-terminated phenol polyoxypropylene ether sulfonate.

7. The preparation method according to claim 6, wherein, The molar ratio of alkyl alcohol polyoxypropylene ether chloride to phenol is 1:1 to 1:5; And / or, the molar ratio of alkyl-terminated phenolic polyoxypropylene ether sulfonate to di(terminated-chloroethyl) polyoxyethylene ether is 2:1 to 1.8:1; And / or, the alkaline catalyst is a potassium hydroxide catalyst, and the first reaction is carried out at 150-170°C until the system pressure is zero; And / or, the second reaction is carried out under ice-water bath conditions; And / or, the third reaction is carried out under basic potassium carbonate conditions in a mixed solvent of toluene and dimethylformamide; And / or, the fourth reaction is carried out under ice-water bath conditions.

8. A viscosity reducer for heavy oil, characterized in that, The heavy oil viscosity reducer comprises the gemini surfactant as described in any one of claims 1-4 or the gemini surfactant prepared by any one of claims 5-7, and water.

9. The heavy oil viscosity reducer according to claim 8, wherein, The mass concentration of the gemini surfactant in the heavy oil viscosity reducer is 0.01-0.5 wt%. And / or, the water is formation water or simulated formation water.

10. The application of the gemini surfactant as described in any one of claims 1-4, the gemini surfactant prepared by the preparation method described in any one of claims 5-7, or the heavy oil viscosity reducer as described in claim 8 or 9 in the development of heavy oil reservoirs.

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