Novel Gemini anionic surfactant as well as preparation method and application thereof

Abstract

The invention relates to an oil exploitation auxiliary agent, in particular to a novel Gemini anionic surfactant as well as a preparation method and application thereof, fatty alcohol-polyoxyethylene ether, 3, 5-dichloroaniline, 1, 3-propane diamine and sodium 2-chloroethane-1-sulfonate are used as raw materials, and the Gemini anionic surfactant containing multiple hydrophilic chain segments and hydrophobic chain segments is synthesized by rigid benzene rings. The anionic surfactant is easy to dissolve in water, has higher surface activity, is small in dosage, and saves the cost in actual use. The oil-based mud flushing agent is formed by the oil-based mud flushing agent, the nonionic surfactant, the cosolvent, the chelating agent and the penetrating agent, all the components cooperate with one another to form the flushing agent with excellent flushing efficiency at high temperature and high salt, and the oil-based mud flushing agent is good in compatibility with cement paste and oil-based mud.

Description

Technical Field

[0001] This invention relates to the field of oil well additives technology, specifically to a modified polyoxyethylene ether surfactant, particularly a novel Gemini anionic surfactant, its preparation method, and its applications. Background Technology

[0002] With the exploration and development of oil resources, oil-based drilling mud, due to its excellent lubricity, high-temperature stability, and anti-fouling properties, is widely used in shale gas, deepwater drilling, and high-temperature and high-pressure wells. However, the oil-based mud deposits and mud cakes formed on the wellbore severely affect the interfacial bonding strength between the cement sheath and the wellbore, resulting in the cement sheath not being effectively isolated from the formation, posing significant safety hazards such as interlayer crossflow or annular crossflow.

[0003] To remove oil-based mud deposits and mud cake from the wellbore, improve interfacial wettability, and enhance interfacial bonding strength and cementing quality, oil-based mud flushing agents are used for flushing. Traditional oil-based mud flushing agents use single-chain surfactants (such as Span-80, sodium dodecylbenzene sulfonate, and fatty alcohol polyoxyethylene ether), which have good flushing effects in conventional systems. However, in high-temperature and high-salt environments with higher requirements for flushing agents, they suffer from insufficient surface activity, low wetting reversal efficiency, and poor temperature resistance (easily decomposed at >100℃), making it difficult to meet the cementing quality requirements under complex well conditions.

[0004] In recent years, unlike traditional surfactants with their single hydrophilic and hydrophobic groups, Gemini surfactants possess a "multiple hydrophilic groups-multiple hydrophobic chains-linking group" structure, exhibiting superior interfacial activity. The rigid benzene ring serves as the linking group, covalently connecting the hydrophilic and hydrophobic segments. This unique structure not only weakens the electrostatic repulsion between hydrophilic chains but also enhances the synergistic effect between hydrophobic chains. Therefore, Gemini surfactants exhibit ultra-low critical micelle concentration (CMC) and rapid wetting. This characteristic provides a new approach to solving the challenges of oil-based mud flushing.

[0005] This invention, based on molecular engineering principles, designs and synthesizes a novel high-temperature and salt-resistant Gemini anionic surfactant (code-named ASS-n). By compounding a nonionic surfactant, co-solvent, metal chelating agent, and penetrant, a highly efficient oil-based mud flushing agent is constructed. Furthermore, by focusing on the surface activity mechanism of this novel Gemini anionic surfactant, the formulated oil-based mud flushing agent exhibits excellent flushing efficiency under high-temperature and high-salt conditions and demonstrates good compatibility with cement slurry and oil-based mud. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel Gemini anionic surfactant, its preparation method, and its application. This invention solves the problems of water separation and surface activity failure of fatty alcohol polyoxyethylene ethers under high temperature and high salt conditions, and also solves the problem of poor compatibility between ordinary surfactants and cement slurry and oil-based mud.

[0007] The objective of this invention is achieved through the following technical solution: Firstly, a novel Gemini anionic surfactant is provided, with the following structural formula: The reaction equation for the novel Gemini anionic surfactant, taking maleic acid as an example:

[0008] Secondly, a novel method for preparing a Gemini anionic surfactant is provided, comprising the following steps: S1. First, measure out fatty alcohol polyoxyethylene ether and solvent acetone and place them in a container. Then add sodium hydroxide (NaOH) to adjust the pH to 8-10. Then add 3,5-dichloroaniline and react at 80℃-100℃ for a period of time. The reaction time is usually in the range of 4-6 hours. After the reaction was completed, a small amount of water was added to quench the reaction, and then the product was washed, filtered, and dried to obtain intermediate product I. S2. First, measure out acetone and place it in a container. Then, weigh out intermediate product I and add it to the container. Next, add NaOH to adjust the pH to 7-8. Add 1,3-propanediamine dropwise and react at 40℃ for a period of time. The reaction time should be in the range of 4-8 hours. After the reaction was completed, the product was washed, filtered, and dried to obtain intermediate product II. S3. Measure out the organic diacid, methanol, and deionized water and place them in a container. Add potassium carbonate to adjust the pH to 8-10. Then add intermediate product II and react at 60℃-80℃ for a period of time. The reaction time should be in the range of 10-12 hours. S4. Weigh intermediate product III and measure deionized water into a container. Adjust the pH to 8-10 using a buffer solution composed of NaHCO3 and Na2CO3. Then add sodium 2-chloroethane-1-sulfonate and adjust the reaction temperature to 80-100℃ under reflux for a period of time. The reaction time is usually in the range of 6-8 hours. After the reaction was completed, HCl was added to adjust the pH to 3-5, and then the product was washed, filtered, and dried to obtain the final product, a novel Gemini anionic surfactant, designated ASS-n. The concentration of HCl was easily selected as 0.1 mol / L.

[0009] It should be noted that thin-layer chromatography (TLC) was used to monitor the reaction process in steps S1-S4. The developing solution used for TLC, by volume, is as follows: V in S1... （石油醚） V （乙酸乙酯） =4:1, V is used in S2 （乙醇） V （环己烷） =1:5, V is used in S3 (乙酸乙酯) V （甲醇 The ratio is 7:3, and V is used in S4. （异丙醇） V （水） V （浓氨水） =4:1:1.

[0010] Furthermore, in step S1, the fatty alcohol polyoxyethylene ether measured has the structural formula RO(CH2CH2O). n H; where n is 3, 7 or 9, and R is one of dodecyl, tetradecyl, hexadecyl or octadecyl.

[0011] Furthermore, in step S2, 1,3-propanediamine can be replaced with 1,2-ethylenediamine, 1,4-butanediamine, or 1,5-pentanediamine.

[0012] Furthermore, in step S3, the organic diacid is one of maleic acid, fumaric acid, and itaconic acid.

[0013] Furthermore, in S4, sodium 2-chloroethane-1-sulfonate can be replaced with sodium 3-chloropropane-1-sulfonate, sodium 4-chlorobutane-1-sulfonate, or sodium 5-chloropentane-1-sulfonate.

[0014] Thirdly, an application of a novel Gemini anionic surfactant is provided for the preparation of an oil-based mud flushing agent that can perform efficient flushing under high temperature and high salt conditions. The oil-based mud flushing agent is a mixture of the following substances: by weight, it includes 5-10% of the Gemini anionic surfactant described in any one of claims 1 to 6, 3-5% of the nonionic surfactant, 5-10% of the cosolvent, 0.5-1.5% of the chelating agent, 1-3% of the penetrant, and the remainder is water; The nonionic surfactant is a mixture of polyoxyethylene dehydrated sorbitan monooleate and dehydrated sorbitan fatty acid ester in a weight ratio of 2:1. The preparation steps of the oil-based mud flushing agent are as follows: First, weigh out the water, Gemini surfactant, and nonionic surfactant, and stir at 100-150 r / min for 20 min until completely dissolved to obtain a mixed solution; Add the cosolvent and chelating agent, and stir at 300-500 r / min for 1 hour at 45°C.

[0015] Furthermore, the solvent is one or two of ethylene glycol butyl ether, cyclohexane, n-butanol, isopropanol, petroleum ether, and propylene glycol butyl ether.

[0016] Furthermore, the chelating agent is one of sodium tripolyphosphate, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylidene diphosphonic acid, and aminotrimethylphosphonic acid.

[0017] Furthermore, the penetrant is one of JFC, high-strength penetrant JFC-E, high-temperature penetrant JFC-M, or fast penetrant JFC-2.

[0018] To facilitate understanding, the core points of this plan will be explained.

[0019] First, special groups and chain segments were introduced, resulting in the corresponding structure.

[0020] a. It possesses multiple hydrophilic and hydrophobic segments. The general structural formula of AEO-n raw materials is RO(OCH2CH2)nH, where R is a long-chain alkane, such as decacarbonyl or dodecane, which is a hydrophobic segment. -O(OCH2CH2)nH contains an O atom and is a hydrophilic segment. The benzene ring is a linking group and is also a hydrophobic segment. The propyl group between the two benzene rings is a hydrophobic segment, while segments containing carboxyl and sulfonic acid groups are hydrophilic segments.

[0021] b. It has a biphenyl ring structure. In step two of the synthesis, propylenediamine is used as a reaction linker to connect the two reaction products I, thus giving it a biphenyl ring structure.

[0022] c. A diacid was introduced. In the third step of synthesis, intermediate II and succinic acid were added to the molecular structure, successfully introducing a diacid and generating intermediate III.

[0023] d. Possesses a bissulfonic acid group. In step four of the synthesis, intermediate III and sodium 2-chloroethane-1-sulfonate were reacted via a substitution reaction, successfully introducing a sulfonic acid group onto the amino functional group of intermediate III.

[0024] II. Differences between the Gemini surfactant in this solution and existing Gemini surfactants.

[0025] a. The Gemini surfactant in this scheme has a novel structure and synthesis method. A Gemini anionic surfactant with multiple hydrophilic and hydrophobic segments was synthesized through a multi-step chemical process, using a rigid benzene ring as a linker. The rigid benzene ring weakens the electrostatic repulsion between hydrophilic chains and enhances the synergistic effect between hydrophobic segments. The structure with multiple hydrophilic and hydrophobic segments gives it superior surface activity.

[0026] b. To meet the actual needs of oil-based mud flushing agents, diacid was introduced to enhance dispersibility and improve compatibility with oil-based mud.

[0027] c. AEO-n (referring to RO(CH2CH2O)) n H) is synthesized and modified into Gemini from raw materials. It has both the excellent cleaning and penetration capabilities of AEO-n and the high temperature and salt resistance capabilities that AEO-n does not have. This makes it still have excellent cleaning capabilities in high temperature and high salt environments, which is beneficial for field use.

[0028] d. The presence of polysulfonic acid groups gives it excellent water solubility, a crucial property in the field of oil well additives.

[0029] In summary, the Gemini surfactant in this solution is based on oil-based mud flushing agents. Combined with field applications, a Gemini surfactant with excellent cleaning ability (high temperature resistance and salt resistance), good compatibility with oil-based mud, and good water solubility was designed and successfully synthesized. It was applied to oil-based mud flushing agents and achieved excellent results.

[0030] The present invention has the following advantages: (1) Gemini’s multiple hydrophilic and hydrophobic segments improve the surface activity and wetting reversal ability of fatty alcohol polyoxyethylene ether. Meanwhile, the linking group in Gemini is a double benzene ring, which gives it excellent resistance to temperature and salt, solving the defects of fatty alcohol polyoxyethylene ether in high temperature and high salt conditions, and surface activity failure. On the other hand, diacid is also introduced into the structure to enhance the dispersibility of surfactants and make them more compatible with cement slurry and oil-based mud. (2) High rinsing efficiency and cost-saving; The Gemini anionic surfactant prepared in this invention has a disulfonic acid group. Compared with traditional monosulfonic acid anionic surfactants, such as sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene ether sulfonate, it has better water solubility and stronger surface activity. It has a good flushing and wetting effect on oil-based mud deposits and mud cakes remaining on the well wall, and the flushing efficiency is high. The Gemini anionic surfactant prepared by this invention and the flushing agent formulated therewith can reduce the amount of flushing agent used to 10-20% while ensuring the flushing efficiency of oil-based mud, thus greatly saving costs. (3) In this invention, the synthesized Gemini anionic surfactant is used in combination with nonionic surfactant and penetrant, and a solvent is used to form a microemulsion, so that the components work together to achieve a more efficient rinsing effect. Attached Figure Description

[0031] Figure 1 The γ-lgC curves for ASS-n and AEO-9 at 25℃ are shown. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0033] (Example 1) This embodiment discloses a method for preparing a Gemini anionic surfactant and a method for preparing an oil-based mud flushing agent.

[0034] Gemini anionic surfactants are prepared through steps S1-S4, and oil-based mud flushing agents are then prepared through steps S5 and S6. Details are as follows: S1. Weigh 50 mL of acetone and 2.40 g of AEO-9 (referring to RO(CH2CH2O)9H) into a 100 mL three-necked flask. Under nitrogen protection, add an aqueous solution containing 0.88 g of sodium hydroxide (NaOH) dropwise in an ice-water bath. After the addition is complete, stir at room temperature for 30 min, then slowly add a DMF solution containing 0.34 g of 3,5-dichloroaniline. React at 80-100 °C for 4-6 h. Monitor the reaction by thin-layer chromatography (TLC). After the reaction is complete, quench the reaction with a small amount of water, then wash with deionized water and saturated brine, filter and dry to obtain intermediate product I.

[0035] S2. Weigh 2.69 g of intermediate I and 42 mL of acetone into a 100 mL three-necked flask. Add an aqueous solution containing 0.79 g of NaOH to adjust the pH to 7-8. Add 0.74 g of 1,3-propanediamine in acetone dropwise over 1-2 hours. React at 40 °C for 4-8 hours, monitoring the reaction by TLC. After the reaction is complete, wash with acetone, deionized water, and anhydrous ethanol, filter, and dry to obtain intermediate II.

[0036] S3. Weigh 3.66 g of maleic acid, 35 mL of methanol, and 15 mL of deionized water into a 100 mL three-necked flask. Add 3.03 g of potassium carbonate aqueous solution to adjust the pH to 8-10. Slowly add 3.60 g of intermediate product II in chloroform solution. React at 60-80 °C for 10-12 h. Monitor the reaction process by TLC. After the reaction is complete, wash with deionized water and ethanol, filter, and dry to obtain intermediate product III.

[0037] S4. Weigh 3.63 g of intermediate product III and 70 mL of deionized water into a 100 mL three-necked flask. Adjust the pH to 8-10 using a buffer solution composed of 0.98 g NaHCO3 and 0.38 g Na2CO3. Add a deionized water solution containing 5.72 g of sodium 2-chloroethane-1-sulfonate dropwise at room temperature. After the addition is complete, adjust the reaction temperature to 80-100 °C under reflux and monitor the reaction process by TLC. After the reaction is complete, add 0.1 mol / L HCl to adjust the pH to 3-5, then wash with deionized water, filter, and dry the final product ASS-9.

[0038] S5. Weigh the following components by mass percentage: 5% ASS-9 obtained in step 4, 6% TW80 and 3% SP-80 nonionic surfactants, 5% isopropanol as a cosolvent, 1% ethylenediaminetetraacetic acid as a chelating agent, 2% JFC as a penetrant, and the remainder is water.

[0039] S6. Dissolve the anionic surfactant ASS-9 and the nonionic surfactant in water, then add the cosolvent and chelating agent, and stir at 45°C for 1 hour to fully dissolve and disperse the components, thus obtaining the oil-based mud flushing agent.

[0040] (Example 2) This embodiment discloses a method for preparing a Gemini anionic surfactant and a method for preparing an oil-based mud flushing agent.

[0041] Gemini anionic surfactants are prepared through steps S1-S4, and oil-based mud flushing agents are then prepared through steps S5 and S6. Details are as follows: S1. Weigh 50 mL of acetone and 2.12 g of AEO-7 (referring to RO(CH2CH2O)7H) into a 100 mL three-necked flask. Under nitrogen protection, add an aqueous solution containing 0.83 g of sodium hydroxide (NaOH) dropwise in an ice-water bath. After the addition is complete, stir at room temperature for 30 min, then slowly add a DMF solution containing 0.34 g of 3,5-dichloroaniline. React at 80-100 °C for 4-6 h. Monitor the reaction by thin-layer chromatography (TLC). After the reaction is complete, quench the reaction with a small amount of water, then wash with deionized water and saturated brine, filter and dry to obtain intermediate product I.

[0042] S2. Weigh 2.34 g of intermediate I and 37 mL of acetone into a 100 mL three-necked flask. Add an aqueous solution containing 0.68 g of NaOH to adjust the pH to 7-8. Add 0.74 g of 1,3-propanediamine in acetone dropwise over 1-2 hours. React at 40 °C for 4-8 hours, monitoring the reaction by TLC. After the reaction is complete, wash with acetone, deionized water, and anhydrous ethanol, filter, and dry to obtain intermediate II.

[0043] S3. Weigh 3.66 g of maleic acid, 35 mL of methanol, and 15 mL of deionized water into a 100 mL three-necked flask. Add 3.03 g of potassium carbonate aqueous solution to adjust the pH to 8-10. Slowly add 3.25 g of intermediate product II in chloroform solution. React at 60-80 °C for 10-12 h. Monitor the reaction process by TLC. After the reaction is complete, wash with deionized water and ethanol, filter, and dry to obtain intermediate product III.

[0044] S4. Weigh 3.12 g of intermediate product III and 60 mL of deionized water into a 100 mL three-necked flask. Adjust the pH to 8-10 using a buffer solution composed of 0.88 g NaHCO3 and 0.34 g Na2CO3. Add a deionized water solution containing 5.72 g of sodium 2-chloroethane-1-sulfonate dropwise at room temperature. After the addition is complete, adjust the reaction temperature to 80-100 °C under reflux and monitor the reaction process by TLC. After the reaction is complete, add 0.1 mol / L HCl to adjust the pH to 3-5, then wash with deionized water, filter, and dry the final product ASS-7.

[0045] S5. Weigh the following components by mass percentage: 5% ASS-7 obtained in step 4, 6% TW80 and 3% SP-80 nonionic surfactants, 5% isopropanol as a cosolvent, 1% ethylenediaminetetraacetic acid as a chelating agent, 2% JFC as a penetrant, and the remainder is water.

[0046] S6. Dissolve the anionic surfactant ASS-7 and the nonionic surfactant in water, then add the cosolvent and chelating agent, and stir at 45°C for 1 hour to fully dissolve and disperse the components, thus obtaining the oil-based mud flushing agent.

[0047] (Example 3) This embodiment discloses a method for preparing a Gemini anionic surfactant and a method for preparing an oil-based mud flushing agent.

[0048] Gemini anionic surfactants are prepared through steps S1-S4, and oil-based mud flushing agents are then prepared through steps S5 and S6. Details are as follows: S1. Weigh 50 mL of acetone and 2.08 g of AEO-3 (referring to RO(CH2CH2O)3H) into a 100 mL three-necked flask. Under nitrogen protection, add an aqueous solution containing 0.80 g of sodium hydroxide (NaOH) dropwise in an ice-water bath. After the addition is complete, stir at room temperature for 30 min, then slowly add a DMF solution containing 0.34 g of 3,5-dichloroaniline. React at 80-100 °C for 4-6 h. Monitor the reaction by thin-layer chromatography (TLC). After the reaction is complete, quench the reaction with a small amount of water, then wash with deionized water and saturated brine, filter and dry to obtain intermediate product I.

[0049] S2. Weigh 2.21 g of intermediate I and 42 mL of acetone into a 100 mL three-necked flask. Add an aqueous solution containing 0.64 g of NaOH to adjust the pH to 7-8. Add 0.74 g of 1,3-propanediamine in acetone dropwise over 1-2 hours. React at 40 °C for 4-8 hours, monitoring the reaction by TLC. After the reaction is complete, wash with acetone, deionized water, and anhydrous ethanol, filter, and dry to obtain intermediate II.

[0050] S3. Weigh 1.83 g of maleic acid, 35 mL of methanol, and 15 mL of deionized water into a 100 mL three-necked flask. Add 3.03 g of potassium carbonate aqueous solution to adjust the pH to 8-10. Slowly add 2.89 g of intermediate product II in chloroform solution. React at 60-80 °C for 10-12 h. Monitor the reaction process by TLC. After the reaction is complete, wash with deionized water and ethanol, filter, and dry to obtain intermediate product III.

[0051] S4. Weigh 2.83 g of intermediate product III and 70 mL of deionized water into a 100 mL three-necked flask. Adjust the pH to 8-10 using a buffer solution composed of 0.78 g NaHCO3 and 0.30 g Na2CO3. Add a deionized water solution containing 5.76 g of sodium 2-chloroethane-1-sulfonate dropwise at room temperature. After the addition is complete, adjust the reaction temperature to 80-100 °C under reflux and monitor the reaction process by TLC. After the reaction is complete, add 0.1 mol / L HCl to adjust the pH to 3-5, then wash with deionized water, filter, and dry the final product ASS-3.

[0052] S5. Weigh the following components by mass percentage: 5% ASS-3 obtained in step 4, 6% TW80 and 3% SP-80 nonionic surfactants, 5% isopropanol as a cosolvent, 1% ethylenediaminetetraacetic acid as a chelating agent, 2% JFC as a penetrant, and the remainder is water.

[0053] S6. Dissolve the anionic surfactant ASS-3 and the nonionic surfactant in water, then add the cosolvent and chelating agent, and stir at 45°C for 1 hour to fully dissolve and disperse the components, thus obtaining the oil-based mud flushing agent.

[0054] (Comparative Example 1) Step 1: Weigh the following ingredients by mass percentage: AEO-9 5%, nonionic surfactants 6% TW80 and 3% SP-80, cosolvent isopropanol 5%, chelating agent ethylenediaminetetraacetic acid 1%, penetrant JFC 2%, and the remainder is water.

[0055] Step 2: Dissolve the anionic surfactant AEO-9 and the nonionic surfactant in water, then add the cosolvent and chelating agent, and stir at 45°C for 1 hour to fully dissolve and disperse the components, thus obtaining the oil-based mud flushing agent.

[0056] (Comparative Example 2) Unlike Example 1, step 5 does not use the chelating agent ethylenediaminetetraacetic acid.

[0057] (Comparative Example 3) Unlike Example 1, step 5 does not include the nonionic surfactants TW-80 and SP-80.

[0058] (Comparative Example 4) Unlike Example 1, isopropanol is not used as a co-solvent in step 5.

[0059] (Comparative Example 5) Unlike Example 1, step 5 does not involve the penetrant JFC.

[0060] (Blank example) Unlike Example 1, step 5 does not involve Gemini anionic surfactant or AEO-9.

[0061] (Experimental Example 1) The surface tension changes of the Gemini anionic surfactants ASS-n and AEO-9 prepared in Examples 1-3 at different concentrations were determined. After preparing aqueous solutions of ASS-n or AEO-9 with specific concentration gradients, the surface tension was measured using the platinum ring method according to GB / T 22237-2008, "Determination of Surface Tension of Surfactants". The results are shown in Table 1. Figure 1 As shown.

[0062] Table 1 shows the surface tension of Gemini anionic surfactants ASS-n and AEO-9 at different concentrations at 25℃. Figure 1The surface tensions of ASS-n and AEO-9 at different concentrations, measured by the platinum ring method, are shown. From the curves, initially, the surface tensions of ASS-n and AEO-9 decrease almost linearly with increasing concentration. After reaching a certain concentration, an inflection point appears, which is the critical micelle concentration (CMC). At this point, the surfactant begins to form micelles because the surfactant has already saturated at the gas-liquid interface. If the surfactant concentration continues to increase, the surface tension cannot continue to decrease.

[0063] The surface activity of surfactants can usually be characterized by the critical micelle concentration and the magnitude of surface tension. In Table 1, the CMC of AEO-9 is 1.4 × 10⁻⁶. -4 The concentration of AEO-9 was mol / L, and the γCMC was 33.26 mN / m, indicating that the minimum concentration of AEO-9 was 1.4 × 10⁻⁶. - 4 At a concentration of mol / L, the maximum reduction in surface tension can be achieved, reaching 33.26 mN / m. The modified ASS-n, due to its multiple hydrophilic and hydrophobic segments, exhibits a lower critical micelle concentration and lower surface tension, resulting in stronger surface activity. Among them, ASS-9 at 3.2 × 10⁻⁶ mol / L achieves this maximum reduction. -5 At mol / L, the maximum reduction in surface tension can be achieved, which is 28.31 mN / m.

[0064] (Experimental Example 2) This paper characterizes the wetting reversal ability of surfactants by testing the changes in contact angles of different concentrations of Gemini anionic surfactants on hydrophilic and lipophilic surfaces. The test results are shown in Table 2.

[0065] Table 2 Contact angle test results at different concentrations Table 2 summarizes the contact angle changes of Gemini anionic surfactants ASS-9 and AEO-9 prepared in Example 1 at different concentrations when dropped onto hydrophilic and lipophilic surfaces, respectively. The overall trend shows that with increasing surface area and surfactant concentration, the contact angle of the hydrophilic surface gradually increases, while the contact angle of the lipophilic surface gradually decreases. This is because when the surfactant is dropped onto the lipophilic surface, the hydrophobic segments of the surfactant adsorb onto the surface, while the hydrophilic segments extend into the water, thus causing the lipophilic surface to gradually transform into a hydrophilic surface. Specifically, at the same concentration, the contact angle formed by the Gemini anionic surfactant ASS-9 on the lipophilic surface is smaller, indicating that ASS-9 has better surface wettability. When the concentration reaches 1.2 g / L, the contact angle of the lipophilic surface decreases from 94.3° to 65.4°, changing from lipophilic to hydrophilic, indicating that ASS-9 has a wetting reversal capability.

[0066] (Experimental Example 3) The surfactant was formulated into a rinsing agent, and the rinsing efficiency at different temperatures and salt concentrations was used as a measure of the surfactant's surface activity in a real environment.

[0067] The prepared flushing agent was mixed with water at a mass ratio of 3:7, and then heated and cured at different temperatures in a high-temperature and high-pressure curing autoclave in accordance with the "Test Methods for Cement in Oil Wells GB / T19139-2012".

[0068] The rinsing efficiency was tested using the rotational viscosity method. The mass of the rotary rheometer drum was weighed and recorded as m0. Oil-based mud was applied to the drum, weighed, and recorded as m1. Since m1 - m0 < 1.5g, oil-based mud was applied again to the drum until m1 - m0 > 1.5g. The cured rinsing agent was added to the rheology cup, and the drum coated with oil-based mud was placed in the rheology cup containing the rinsing agent. Rinsing was performed at a rotational speed of 200 r / min for 10 minutes. After rinsing, the drum was allowed to stand for 10 minutes, and the combined mass of the drum and the remaining oil-based mud was weighed and recorded as m2. The rinsing efficiency results are shown in Table 3.

[0069] Flushing efficiency is = Table 3. Flushing efficiency test results at 25℃ Table 3 shows that the rinsing agent formulated with the synthetic Gemini anionic surfactant ASS-n has high rinsing efficiency (Examples 1-3). Example 1 investigated the effect of different rinsing agent dosages on rinsing efficiency. The data shows that when the rinsing agent dosage is 5%, the rinsing efficiency is 81.6%, and when the dosage reaches 10%, the rinsing efficiency is 94.7%. Under the same conditions, replacing ASS-n with AEO-9 results in a rinsing efficiency of only 77.7% (Comparative Example 1). This means that in practical applications, the rinsing agent prepared with the Gemini anionic surfactant ASS-n requires a smaller dosage and has lower costs. In Comparative Examples 2-5, the effects of other components in the rinsing agent on rinsing efficiency were investigated. It was found that the absence of nonionic surfactants TW-80 and SP-80, the co-solvent isopropanol, the penetrant JFC, and the chelating agent all had a significant impact on rinsing efficiency.

[0070] Table 4. Test results of flushing efficiency at different temperatures with 10% flushing agent dosage. Table 4 shows the rinsing efficiency test data of the rinsing agent composed of the Gemini anionic surfactant ASS-n synthesized in this invention and the rinsing agent composed of AEO-9 at different temperatures. The experimental data show that the rinsing efficiency of the rinsing agent composed of ASS-n is stable at about 95% at 170℃ and below, while the rinsing efficiency of AEO-9 is similar at 25℃, 50℃ and 90℃, at about 75%. When the temperature is increased to 130℃, the rinsing efficiency decreases significantly. In addition, combined with the rinsing efficiency of blank example 1, the rinsing agent of comparative example 1, AEO-9, has basically no contribution to the rinsing efficiency at 130℃.

[0071] Table 5. Flushing efficiency test data at different salt concentrations. Table 5 shows the statistical data on the rinsing efficiency of rinsing agents composed of ASS-9 (Example 1) or AEO-9 (Comparative Example 1) as a function of salt concentration, with the rinsing agent dosage controlled at 10% at 25°C. The salt concentration ranged from 0% to 32%. The experimental data show that the rinsing efficiency of Example 1 was basically unaffected by the salt concentration. In Comparative Example 1, the rinsing efficiency gradually decreased with increasing salt concentration, dropping to approximately 54% when the salt concentration reached 24% or even higher.

[0072] (Experimental Example 4) The compatibility of the flushing agent with cement slurry and oil-based mud was tested.

[0073] The compatibility of the flushing agent with cement slurry was evaluated by testing the rheology and thickening time of the mixture at different ratios of flushing agent and cement slurry.

[0074] Table 6 Compatibility of Flushing Agent (Example 1) with Cement Slurry The cement slurry formula consists of 560g of oil well grade G cement + 35% silica fume + 6% microsilica + 299g of water + 3.2% water loss reducer + 1.6% retarder. The experimental conditions are 121℃ / 82MPa / 45min, and the cement slurry density is 1.90g / cm3.

[0075] The water loss reducing agent and the retarder are AMPS-type polymers.

[0076] As shown in Table 6, the rheological reading of the cement slurry mixed with the flushing agent gradually decreases as the proportion of flushing agent increases, indicating that the flushing agent does not thicken the cement slurry and has good compatibility with it. Furthermore, the mixing of the flushing agent with the cement slurry does not shorten the thickening time of the cement slurry and does not affect on-site construction.

[0077] Table 7 Compatibility of Flushing Agents with Oil-Based Drilling Mud Experimental conditions: Curing at 93℃ and normal pressure Table 7 shows the rheological data of oil-based mud and flushing agent mixed in different proportions (commonly used proportions on construction sites) after curing at 93℃. It can be seen that neither the oil-based mud nor the flushing agent under different proportions showed thickening or water separation, indicating that the flushing agent and the oil-based mud have good compatibility.

[0078] In summary, the Gemini anionic surfactant synthesized by this invention exhibits excellent surface activity. Its application in the preparation of oil-based mud flushing agents demonstrates high flushing efficiency in harsh environments such as high temperature and high salinity, reducing the amount of flushing agent required and saving costs to some extent. Furthermore, the flushing agent shows good compatibility with cement slurry and oil-based mud, providing a new approach for the preparation of flushing agents for oil-based mud.

[0079] The above embodiments only illustrate preferred implementation methods, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the protection scope of this invention.

Claims

1. A novel Gemini anionic surfactant, characterized in that: Its structural formula is: 。 2. A method for preparing a novel Gemini anionic surfactant, characterized in that: Includes the following steps: S1. First, measure the fatty alcohol polyoxyethylene ether and solvent acetone into a container, then add sodium hydroxide (NaOH) to adjust the pH to 8-10; then add 3,5-dichloroaniline and react at 80℃-100℃ for a period of time. After the reaction was completed, a small amount of water was added to quench the reaction, and then the product was washed, filtered, and dried to obtain intermediate product I. S2. First, measure out acetone and place it in a container. Then, weigh out intermediate product I and add it to the container. Next, add NaOH to adjust the pH to 7-8. Add 1,3-propanediamine dropwise and react at 40°C for a period of time. After the reaction was completed, the product was washed, filtered, and dried to obtain intermediate product II. S3. Measure out organic diacid, methanol and deionized water and place them in a container. Add potassium carbonate to adjust the pH to 8-10. Then add intermediate product II and react at 60℃-80℃ for a period of time. S4. Weigh intermediate product III, measure deionized water and place it in a container, adjust the pH to 8-10 using a buffer solution composed of NaHCO3 and Na2CO3; then add sodium 2-chloroethane-1-sulfonate, adjust the reaction temperature to 80-100℃ and reflux for a period of time. After the reaction was completed, HCl was added to adjust the pH to 3-5, and then the product was washed, filtered, and dried to obtain the final product, a novel Gemini anionic surfactant, which was designated ASS-n.

3. The method for preparing a novel Gemini anionic surfactant according to claim 2, characterized in that: In step S1, the fatty alcohol polyoxyethylene ether measured has the structural formula RO(CH2CH2O). n H; where n is 3, 7 or 9, and R is one of dodecyl, tetradecyl, hexadecyl or octadecyl.

4. A method for preparing a novel Gemini anionic surfactant according to claim 2 or 3, characterized in that: In step S2, 1,3-propanediamine can be replaced with 1,2-ethylenediamine, 1,4-butanediamine, or 1,5-pentanediamine.

5. A method for preparing a novel Gemini anionic surfactant according to claim 2 or 3, characterized in that: In step S3, the organic diacid is one of maleic acid, fumaric acid, and itaconic acid.

6. A method for preparing a novel Gemini anionic surfactant according to claim 2 or 3, characterized in that: In S4, sodium 2-chloroethane-1-sulfonate can be replaced with sodium 3-chloropropane-1-sulfonate, sodium 4-chlorobutane-1-sulfonate, or sodium 5-chloropentane-1-sulfonate.

7. An application of a novel Gemini anionic surfactant, characterized in that: Used to prepare oil-based mud flushing agents that can perform efficient flushing under high temperature and high salinity conditions; The oil-based mud flushing agent is a mixture of the following substances: by weight, it includes 5-10% of the Gemini anionic surfactant described in any one of claims 1 to 6, 3-5% of the nonionic surfactant, 5-10% of the cosolvent, 0.5-1.5% of the chelating agent, 1-3% of the penetrant, and the remainder is water; The nonionic surfactant is a mixture of polyoxyethylene dehydrated sorbitan monooleate and dehydrated sorbitan fatty acid ester in a weight ratio of 2:

1. The preparation steps of the oil-based mud flushing agent are as follows: First, weigh out the water, Gemini surfactant, and nonionic surfactant, and stir until completely dissolved to obtain a mixed solution; Add a solubilizer and a chelating agent, and stir at 45°C for a period of time.

8. The application of the novel Gemini anionic surfactant according to claim 7, characterized in that: The solvent is one or two of ethylene glycol butyl ether, cyclohexane, n-butanol, isopropanol, petroleum ether, and propylene glycol butyl ether.

9. The application of the novel Gemini anionic surfactant according to claim 7, characterized in that: The chelating agent is one of sodium tripolyphosphate, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylidene diphosphonic acid, and aminotrimethylphosphonic acid.

10. The application of the novel Gemini anionic surfactant according to claim 7, characterized in that: The penetrant is one of JFC, JFC-E (a high-strength penetrant), JFC-M (a high-temperature penetrant), or JFC-2 (a fast-penetrating penetrant).

Images