A low-temperature, high-efficiency demulsifier and its preparation method

Abstract

This invention relates to the field of oilfield chemicals technology, specifically to a low-temperature, high-efficiency demulsifier and its preparation method. The demulsifier comprises a demulsifying active ingredient, prepared by reacting branched polyoxypropylene triamine sequentially with polyethylene glycol monomethyl ether acrylate, benzyl glycidyl ether, and dodecyl glycidyl ether, followed by partial salting with DL-lactic acid. Based on 1000 parts by weight of branched polyoxypropylene triamine, the proportions of each raw material are as follows: 220-276 parts of polyethylene glycol monomethyl ether acrylate, 68-88 parts of benzyl glycidyl ether, 52-72 parts of dodecyl glycidyl ether, and 59-68 parts of DL-lactic acid (85% by weight). This invention solves the problems of low dehydration efficiency and turbid effluent in existing demulsifiers at low temperatures by constructing a single molecular demulsifying active ingredient with a specific gradient structure, making it suitable for low-temperature gathering and transportation of produced fluids from CO2-enhanced oil recovery.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemicals technology, and in particular to a low-temperature, high-efficiency demulsifier and its preparation method. Background Technology

[0002] With the development of tertiary oil recovery technology, CO2 enhanced oil recovery (CEOR) has become one of the core technologies for stabilizing production in major domestic oilfields due to its ability to significantly improve crude oil recovery and its carbon sequestration potential. However, in actual production, CO2 partially dissolves in associated water after being injected into the formation, making the produced fluid weakly acidic. Simultaneously, a large amount of rock and mineral particles detach, and asphaltenes and colloids precipitate, forming a dense oil-water emulsion system stabilized by CO2 bubbles, fine solid particles, and organic colloids. Under low-temperature gathering and transportation conditions, the viscosity of this type of emulsion increases sharply, and the oil-water interface film strength is significantly enhanced. Traditional demulsifiers often face problems such as slow low-temperature diffusion rates and insufficient interfacial replacement capacity, leading to prolonged dehydration cycles, turbid dehydrated water, and blurred oil-water interface stratification, severely affecting the operating efficiency of subsequent processing equipment and the quality of crude oil.

[0003] Existing low-temperature demulsification technologies are mainly developing along two routes: one is to reduce interfacial tension by combining cationic, anionic, and nonionic surfactants and utilizing the synergistic effect of different components; the other is to adjust the ethylene oxide / propylene oxide segment ratio of polyether demulsifiers to optimize their HLB value to adapt to low-temperature environments. For example, CN113621405A uses a multi-component surfactant compound, which can achieve a demulsification water content of <0.2% at 36-43℃, but when the temperature drops to around 10℃, the low-temperature fluidity and interfacial activity of the compound system decrease significantly; the P-51T polyether demulsifier relies on the EO / PO ratio for control, and cannot effectively cope with the special challenges of the weakly acidic environment and solid-liquid-liquid multiphase emulsion stability in CO2 flooded produced fluids. These existing technologies essentially treat hydrophilicity, hydrophobicity, and ionicity as independent adjustment variables, without constructing a molecular structure with synergistic effects for the interfacial characteristics of CO2-driven emulsification systems. This makes it difficult to simultaneously meet the comprehensive performance requirements of rapid dehydration, low effluent turbidity, and a clear oil-water interface at a low temperature of 10°C. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a low-temperature high-efficiency demulsifier and its preparation method, so as to solve the problem that existing low-temperature demulsifiers cannot achieve rapid dehydration, low water content in the dehydrated oil, low turbidity of the dehydrated water and clear oil-water interface in the multiphase stable system of CO2 flooded oil produced fluid at around 10℃.

[0005] To achieve the above objectives, the present invention provides a low-temperature, high-efficiency demulsifier, wherein the low-temperature, high-efficiency demulsifier comprises a demulsifying active ingredient. The demulsifying active ingredient is obtained by reacting branched polyoxypropylene triamine sequentially with polyethylene glycol monomethyl ether acrylate, benzyl glycidyl ether, and dodecyl glycidyl ether, followed by partial salting with DL-lactic acid. Based on 1000 parts by weight of the branched polyoxypropylene triamine, the polyethylene glycol monomethyl ether acrylate comprises 220-276 parts by weight, the benzyl glycidyl ether comprises 68-88 parts by weight, the dodecyl glycidyl ether comprises 52-72 parts by weight, and the DL-lactic acid with a mass fraction of 85% comprises 59-68 parts by weight.

[0006] Preferably, the branched polyoxypropylene triamine is a polyoxypropylene skeleton ternary primary amine with a number average molecular weight of 2000-4000.

[0007] Preferably, the number average molecular weight of the polyethylene glycol monomethyl ether acrylate is 400-550.

[0008] Preferably, the demulsifying active ingredient has an amine-terminated lactate ratio of 55%-65%, a number-average molecular weight of 4140-4470 g / mol, and a dispersion index of 1.31-1.42.

[0009] Preferably, the low-temperature high-efficiency demulsifier is a liquid demulsifier containing isopropanol and deionized water as dispersion media.

[0010] Furthermore, the present invention also provides a method for preparing a low-temperature, high-efficiency demulsifier, comprising the following steps: S1. Branched polyoxypropylene triamine is mixed with isopropanol and pretreated under nitrogen protection to obtain a pretreated system; S2. Polyethylene glycol monomethyl ether acrylate is added to the pretreatment system to react and obtain the first reaction system; S3. Add benzyl glycidyl ether to the first reaction system to carry out the reaction, and obtain the second reaction system; S4. Add dodecyl glycidyl ether to the second reaction system to react and obtain the third reaction system; S5. After preparing an aqueous solution of DL-lactic acid with a mass fraction of 85%, add it to the third reaction system to carry out partial salting to obtain a salting system. S6. Add deionized water and isopropanol to the salinization system, stir and filter to obtain a low-temperature high-efficiency demulsifier.

[0011] Preferably, in step S2, the reaction is carried out at 53-57℃ for 4-6 hours; in step S3, the reaction is carried out at 63-67℃ for 2.5-3.5 hours; and in step S4, the reaction is carried out at 72-78℃ for 3-5 hours.

[0012] Preferably, in step S5, the salting process involves maintaining the temperature at 42-48℃ for 1.5-2.5 hours.

[0013] Preferably, in step S6, deionized water and isopropanol are added to the salinization system, stirred at 38-42°C for 0.8-1.2 hours, and filtered through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0014] The beneficial effects of this invention are: (1) The demulsifying active ingredient of the present invention is based on branched polyoxypropylene triamine. By sequentially introducing short polyoxyethylene outer end, rigid aromatic end group, flexible long chain end group and 55%-65% lactate type end group, a gradient molecular structure of hydrophobic inner segment-hydrophilic outer end-rigid-flexible composite end group-moderately ionized end group is constructed. Test data show that in the simulated produced fluid of CO2 flooding at 10℃ in Example 1, the dehydration rate reached 95.6% in 60 min, the water content of the dehydrated oil was only 0.3%, the turbidity of the dehydrated water was 29.4 NTU, and the thickness of the interfacial transition layer was 1.8 mm. Compared with the blank sample, the dehydration rate increased by 93.5 percentage points, the turbidity decreased by 238.6 NTU, and the interfacial thickness was reduced by 17.7 mm. This solves the problem of insufficient interfacial film replacement capacity and incomplete dehydration of traditional demulsifiers at low temperatures.

[0015] (2) This invention achieves a synergistic effect among structural units through the construction of end groups at specific time intervals and partial salting control: the short polyoxyethylene end groups enhance the low-temperature aqueous phase dispersibility, the aromatic end groups enhance the interfacial film insertion capability, the long-chain alkyl end groups promote oil phase anchoring and water droplet aggregation, and moderate lactation balances the interfacial adsorption and desorption kinetics. Comparative Examples 1-7 show that the absence of any structural unit or the change of the introduction order resulted in a decrease of more than 10% in the dehydration rate and an increase of more than 50 NTU in 60 min, proving that this molecular structure breaks through the limitations of single hydrophilic / hydrophobic regulation and achieves comprehensive performance optimization of low-temperature and efficient demulsification of CO2-driven produced fluid. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0017] The raw materials used in the specific implementation are as follows: branched polyoxypropylene triamine is Huntsman JEFFAMINE T-3000, supplied by Huntsman Corporation, with a number average molecular weight of approximately 3000, belonging to the polyoxypropylene skeleton ternary primary amine; polyethylene glycol monomethyl ether acrylate is Merck Sigma-Aldrich product number 454990, with a number average molecular weight of approximately 480; DL-lactic acid is Merck Sigma-Aldrich product number L1250, with a mass fraction of 85% and CAS number 50-21-5.

[0018] Example 1: Step 1: Add 1000g of branched polyoxypropylene triamine and 120g of isopropanol to a reactor equipped with a stirrer, thermometer, nitrogen inlet pipe and condenser. Turn on the stirrer and purge with nitrogen for 30 minutes. Heat the system to 60°C and maintain it at a relative pressure of -80kPa for 2 hours. Then restore the pressure to normal using nitrogen and cool the system to 45°C. Weigh the material in the reactor and add isopropanol until the total mass of the system is 1120g.

[0019] Step 2: Mix 260g of polyethylene glycol monomethyl ether acrylate with 80g of isopropanol to form a dropping solution. Under nitrogen protection and stirring conditions, add the dropping solution to the system obtained in Step 1 at 50°C for 2 hours. During the dropping process, control the reaction temperature between 48°C and 52°C. After the dropping is completed, raise the temperature to 55°C and keep it at that temperature for 5 hours.

[0020] Step 3: Heat the system obtained in Step 2 to 65°C, and add 82g of benzyl glycidyl ether dropwise over 1 hour under nitrogen protection. During the dropwise addition, control the reaction temperature between 63°C and 67°C. After the dropwise addition is complete, continue to keep the temperature for 3 hours.

[0021] Step 4: In the system obtained in Step 3, add 65g of dodecyl glycidyl ether dropwise over 2 hours at 75°C. During the dropwise addition, control the reaction temperature between 72°C and 78°C. After the dropwise addition is complete, continue to keep the temperature at 75°C for 4 hours.

[0022] Step 5: Cool the system obtained in Step 4 to 45℃. Under stirring, mix 62g of 85% DL-lactic acid with 70g of deionized water to form a lactic acid aqueous solution, and add it dropwise to the reaction system over 1 hour. During the dropwise addition, control the temperature between 42℃ and 48℃. After the dropwise addition is complete, maintain the temperature at 45℃ for 2 hours. After the maintenance is complete, take a sample and prepare a 1% aqueous dispersion.

[0023] Step 6: Add 160g of deionized water and 80g of isopropanol to the system obtained in Step 5, stir at 40℃ for 1 hour, and filter through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0024] Example 2: Step 1: Add 1000g of branched polyoxypropylene triamine and 120g of isopropanol to a reactor equipped with a stirrer, thermometer, nitrogen inlet pipe and condenser. Turn on the stirrer and purge with nitrogen for 30 minutes. Heat the system to 60°C and maintain it at a relative pressure of -80kPa for 2 hours. Then restore the pressure to normal using nitrogen and cool the system to 45°C. Weigh the material in the reactor and add isopropanol until the total mass of the system is 1120g.

[0025] Step 2: Mix 230g of polyethylene glycol monomethyl ether acrylate with 80g of isopropanol to form a dropping solution. Under nitrogen protection and stirring conditions, add the dropping solution to the system obtained in Step 1 at 50°C for 2 hours. During the dropping process, control the reaction temperature between 48°C and 52°C. After the dropping is completed, raise the temperature to 55°C and keep it at that temperature for 5 hours.

[0026] Step 3: Heat the system obtained in Step 2 to 65°C, and add 70g of benzyl glycidyl ether dropwise over 1 hour under nitrogen protection. During the dropwise addition, control the reaction temperature between 63°C and 67°C. After the dropwise addition is complete, continue to keep the temperature for 3 hours.

[0027] Step 4: In the system obtained in Step 3, add 55g of dodecyl glycidyl ether dropwise over 2 hours at 75°C. During the dropwise addition, control the reaction temperature between 72°C and 78°C. After the dropwise addition is complete, continue to keep the temperature at 75°C for 4 hours.

[0028] Step 5: Cool the system obtained in Step 4 to 45℃. Under stirring, mix 59g of 85% DL-lactic acid with 70g of deionized water to form a lactic acid aqueous solution, and add it dropwise to the reaction system over 1 hour. During the dropwise addition, control the temperature between 42℃ and 48℃. After the dropwise addition is complete, maintain the temperature at 45℃ for 2 hours. After the maintenance is complete, take a sample and prepare a 1% aqueous dispersion.

[0029] Step 6: Add 160g of deionized water and 80g of isopropanol to the system obtained in Step 5, stir at 40℃ for 1 hour, and filter through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0030] Example 3: Step 1: Add 1000g of branched polyoxypropylene triamine and 120g of isopropanol to a reactor equipped with a stirrer, thermometer, nitrogen inlet pipe and condenser. Turn on the stirrer and purge with nitrogen for 30 minutes. Heat the system to 60°C and maintain it at a relative pressure of -80kPa for 2 hours. Then restore the pressure to normal using nitrogen and cool the system to 45°C. Weigh the material in the reactor and add isopropanol until the total mass of the system is 1120g.

[0031] Step 2: Mix 276g of polyethylene glycol monomethyl ether acrylate with 80g of isopropanol to form a dropping solution. Under nitrogen protection and stirring conditions, add the dropping solution to the system obtained in Step 1 at 50°C for 2 hours. During the dropping process, control the reaction temperature between 48°C and 52°C. After the dropping is completed, raise the temperature to 55°C and keep it at that temperature for 5 hours.

[0032] Step 3: Heat the system obtained in Step 2 to 65°C, and add 84g of benzyl glycidyl ether dropwise over 1 hour under nitrogen protection. During the dropwise addition, control the reaction temperature between 63°C and 67°C. After the dropwise addition is complete, continue to keep the temperature for 3 hours.

[0033] Step 4: In the system obtained in Step 3, add 63g of dodecyl glycidyl ether dropwise over 2 hours at 75°C. During the dropwise addition, control the reaction temperature between 72°C and 78°C. After the dropwise addition is complete, continue to keep the temperature at 75°C for 4 hours.

[0034] Step 5: Cool the system obtained in Step 4 to 45℃. Under stirring, mix 64g of 85% DL-lactic acid with 70g of deionized water to form a lactic acid aqueous solution, and add it dropwise to the reaction system over 1 hour. During the dropwise addition, control the temperature between 42℃ and 48℃. After the dropwise addition is complete, maintain the temperature at 45℃ for 2 hours. After the maintenance is complete, take a sample and prepare a 1% aqueous dispersion.

[0035] Step 6: Add 160g of deionized water and 80g of isopropanol to the system obtained in Step 5, stir at 40℃ for 1 hour, and filter through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0036] Example 4: Step 1: Add 1000g of branched polyoxypropylene triamine and 120g of isopropanol to a reactor equipped with a stirrer, thermometer, nitrogen inlet pipe and condenser. Turn on the stirrer and purge with nitrogen for 30 minutes. Heat the system to 60°C and maintain it at a relative pressure of -80kPa for 2 hours. Then restore the pressure to normal using nitrogen and cool the system to 45°C. Weigh the material in the reactor and add isopropanol until the total mass of the system is 1120g.

[0037] Step 2: Mix 240g of polyethylene glycol monomethyl ether acrylate with 80g of isopropanol to form a dropping solution. Under nitrogen protection and stirring conditions, add the dropping solution to the system obtained in Step 1 at 50°C for 2 hours. During the dropping process, control the reaction temperature between 48°C and 52°C. After the dropping is completed, raise the temperature to 55°C and keep it at that temperature for 5 hours.

[0038] Step 3: Heat the system obtained in Step 2 to 65°C, and add 76g of benzyl glycidyl ether dropwise over 1 hour under nitrogen protection. During the dropwise addition, control the reaction temperature between 63°C and 67°C. After the dropwise addition is complete, continue to keep the temperature for 3 hours.

[0039] Step 4: In the system obtained in Step 3, add 72g of dodecyl glycidyl ether dropwise over 2 hours at 75°C. During the dropwise addition, control the reaction temperature between 72°C and 78°C. After the dropwise addition is complete, continue to keep the temperature at 75°C for 4 hours.

[0040] Step 5: Cool the system obtained in Step 4 to 45℃. Under stirring, mix 66g of 85% DL-lactic acid with 70g of deionized water to form a lactic acid aqueous solution, and add it dropwise to the reaction system over 1 hour. During the dropwise addition, control the temperature between 42℃ and 48℃. After the dropwise addition is complete, maintain the temperature at 45℃ for 2 hours. After the maintenance is complete, take a sample and prepare a 1% aqueous dispersion.

[0041] Step 6: Add 160g of deionized water and 80g of isopropanol to the system obtained in Step 5, stir at 40℃ for 1 hour, and filter through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0042] Example 5: Step 1: Add 1000g of branched polyoxypropylene triamine and 120g of isopropanol to a reactor equipped with a stirrer, thermometer, nitrogen inlet pipe and condenser. Turn on the stirrer and purge with nitrogen for 30 minutes. Heat the system to 60°C and maintain it at a relative pressure of -80kPa for 2 hours. Then restore the pressure to normal using nitrogen and cool the system to 45°C. Weigh the material in the reactor and add isopropanol until the total mass of the system is 1120g.

[0043] Step 2: Mix 255g of polyethylene glycol monomethyl ether acrylate with 80g of isopropanol to form a dropping solution. Under nitrogen protection and stirring conditions, add the dropping solution to the system obtained in Step 1 at 50°C for 2 hours. During the dropping process, control the reaction temperature between 48°C and 52°C. After the dropping is completed, raise the temperature to 55°C and keep it at that temperature for 5 hours.

[0044] Step 3: Heat the system obtained in Step 2 to 65°C, and add 88g of benzyl glycidyl ether dropwise over 1 hour under nitrogen protection. During the dropwise addition, control the reaction temperature between 63°C and 67°C. After the dropwise addition is complete, continue to keep the temperature for 3 hours.

[0045] Step 4: In the system obtained in Step 3, add 68g of dodecyl glycidyl ether dropwise over 2 hours at 75°C. During the dropwise addition, control the reaction temperature between 72°C and 78°C. After the dropwise addition is complete, continue to keep the temperature at 75°C for 4 hours.

[0046] Step 5: Cool the system obtained in Step 4 to 45℃. Under stirring, mix 68g of 85% DL-lactic acid with 70g of deionized water to form a lactic acid aqueous solution, and add it dropwise to the reaction system over 1 hour. During the dropwise addition, control the temperature between 42℃ and 48℃. After the dropwise addition is complete, maintain the temperature at 45℃ for 2 hours. After the maintenance is complete, take a sample and prepare a 1% aqueous dispersion.

[0047] Step 6: Add 160g of deionized water and 80g of isopropanol to the system obtained in Step 5, stir at 40℃ for 1 hour, and filter through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0048] Example 6: Step 1: Add 1000g of branched polyoxypropylene triamine and 120g of isopropanol to a reactor equipped with a stirrer, thermometer, nitrogen inlet pipe and condenser. Turn on the stirrer and purge with nitrogen for 30 minutes. Heat the system to 60°C and maintain it at a relative pressure of -80kPa for 2 hours. Then restore the pressure to normal using nitrogen and cool the system to 45°C. Weigh the material in the reactor and add isopropanol until the total mass of the system is 1120g.

[0049] Step 2: Mix 220g of polyethylene glycol monomethyl ether acrylate with 80g of isopropanol to form a dropping solution. Under nitrogen protection and stirring conditions, add the dropping solution to the system obtained in Step 1 at 50°C for 2 hours. During the dropping process, control the reaction temperature between 48°C and 52°C. After the dropping is completed, raise the temperature to 55°C and keep it at that temperature for 5 hours.

[0050] Step 3: Heat the system obtained in Step 2 to 65°C, and add 68g of benzyl glycidyl ether dropwise over 1 hour under nitrogen protection. During the dropwise addition, control the reaction temperature between 63°C and 67°C. After the dropwise addition is complete, continue to keep the temperature for 3 hours.

[0051] Step 4: In the system obtained in Step 3, add 52g of dodecyl glycidyl ether dropwise over 2 hours at 75°C. During the dropwise addition, control the reaction temperature between 72°C and 78°C. After the dropwise addition is complete, continue to keep the temperature at 75°C for 4 hours.

[0052] Step 5: Cool the system obtained in Step 4 to 45℃. Under stirring, mix 60g of 85% DL-lactic acid with 70g of deionized water to form a lactic acid aqueous solution, and add it dropwise to the reaction system over 1 hour. During the dropwise addition, control the temperature between 42℃ and 48℃. After the dropwise addition is complete, keep the solution at 45℃ for 2 hours. After the incubation period, take a sample and prepare a 1% aqueous dispersion.

[0053] Step 6: Add 160g of deionized water and 80g of isopropanol to the system obtained in Step 5, stir at 40℃ for 1 hour, and filter through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

[0054] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that polyethylene glycol monomethyl ether acrylate is not added in step two, the dropping solution in step two is adjusted to 340g isopropanol, and it is added dropwise at 50°C for 2 hours. During the dropwise addition, the reaction temperature is controlled between 48°C and 52°C. After the dropwise addition is completed, the temperature is raised to 55°C and kept at that temperature for 5 hours. The other conditions are the same as in Example 1.

[0055] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that in step three, 82g of benzyl glycidyl ether was replaced with 82g of dodecyl glycidyl ether, and in step four, 65g of dodecyl glycidyl ether was still added; the other conditions were the same as in Example 1.

[0056] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in step four, 65g of dodecyl glycidyl ether is replaced with 65g of benzyl glycidyl ether, while in step three, 82g of benzyl glycidyl ether is still added; the other conditions are the same as in Example 1.

[0057] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that: in step three, 65g of dodecyl glycidyl ether was added dropwise and kept at 65°C for 3 hours; in step four, 82g of benzyl glycidyl ether was added dropwise and kept at 75°C for 4 hours; the remaining conditions were the same as in Example 1.

[0058] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that in step five, the lactic acid aqueous solution formed by 62g of 85% DL-lactic acid and 70g of deionized water was adjusted to a lactic acid aqueous solution formed by 38g of 85% DL-lactic acid and 94g of deionized water; the other conditions were the same as in Example 1.

[0059] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that in step five, the lactic acid aqueous solution formed by 62g of 85% DL-lactic acid and 70g of deionized water was adjusted to a lactic acid aqueous solution formed by 106g of 85% DL-lactic acid and 26g of deionized water; the other conditions are the same as in Example 1.

[0060] Comparative Example 7: The difference between Comparative Example 7 and Example 1 is that steps two, three, four, and five do not employ stepwise dropwise addition and stepwise temperature-controlled reactions. Instead, 260g of polyethylene glycol monomethyl ether acrylate, 82g of benzyl glycidyl ether, 65g of dodecyl glycidyl ether, 62g of DL-lactic acid with a mass fraction of 85%, 80g of isopropanol, and 70g of deionized water are mixed into a single dropwise addition solution and added to the system obtained in step one within 4 hours at 55°C. After the dropwise addition is completed, the system is sequentially kept at 55°C for 5 hours, 65°C for 3 hours, 75°C for 4 hours, and 45°C for 2 hours. The remaining conditions are the same as in Example 1.

[0061] Performance testing: The demulsifiers obtained in Examples 1-6 and Comparative Examples 1-7 were allowed to stand at 25°C for 24 hours, filtered through a 200-mesh stainless steel filter, and the filtrate was used as the test sample. Before testing, each test sample was prepared into a demulsifier working solution with an effective product mass fraction of 1% by mixing isopropanol and deionized water at a mass ratio of 1:1. The simulated carbon dioxide flooded oil produced fluid used in the low-temperature demulsification test was prepared as follows: 700 mL of dehydrated crude oil was taken, the density of which was 0.914 g / cm³ at 20°C.3 The crude oil had a dynamic viscosity of 1200 mPa·s at 10℃, with a wax content of 8.5%, a gum content of 14.5%, an asphaltene content of 6.0%, and an initial water content of 0.30%. 300 mL of simulated produced water was taken, containing sodium chloride (14000 mg / L), calcium chloride (2000 mg / L), magnesium chloride hexahydrate (1000 mg / L), and sodium bicarbonate (1000 mg / L). The simulated produced water was placed in a sealed, pressure-resistant glass container and bubbled under 0.20 MPa carbon dioxide pressure for 30 min to stabilize the aqueous phase pH at 5.6. Subsequently, dehydrated crude oil was mixed with the carbon dioxide-saturated simulated produced water, sheared at 8000 r / min for 8 min at 10℃, and then transferred to a sealed glass bottle for aging at 10℃ for 12 h to obtain a simulated carbon dioxide flooded oil production fluid with a water volume fraction of 30%. All performance tests were performed using the same batch of simulated produced fluid.

[0062] Number-average molecular weight and dispersion coefficient: determined according to GB / T 21863-2008 "Gel permeation chromatography (GPC) using tetrahydrofuran as eluent". Approximately 20 mg of each sample was taken and diluted to 10 mL with tetrahydrofuran to prepare a 2 mg / mL sample solution. After standing at room temperature for 30 min, the solution was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) membrane. The gel permeation chromatograph used tetrahydrofuran as the mobile phase, a flow rate of 1.0 mL / min, a column temperature of 35 °C, and an injection volume of 20 μL. A calibration curve was established using polystyrene standards, and the number-average molecular weight and dispersion coefficient were recorded. Each sample was measured in triplicate, and the arithmetic mean was taken as the test result.

[0063] Amine-terminated lactate ratio: Following the amine value determination method in GB / T 9290-2008 "Analytical Method for Ethoxylated Fatty Amines in Surfactant Industry", a non-aqueous potentiometric titration method was used. 0.5000 g of each of the intermediate sample (before the addition of DL-lactic acid) from step four of the examples or comparative examples, and the final sample obtained in step six, were weighed and added to 50 mL of a 1:1 volume ratio of glacial acetic acid and isopropanol. The mixture was magnetically stirred until completely dispersed, and potentiometric titration was performed using a 0.1000 mol / L perchloric acid-glacial acetic acid standard titration solution, corrected with a blank solvent. The total amine value of the sample before the addition of DL-lactic acid was recorded as A0, and the free amine value of the final sample was recorded as A1. The amine-terminated lactate ratio was calculated using the formula: Amine-terminated lactate ratio = (A0 - A1) / A0 × 100%. Each sample was measured in triplicate.

[0064] Oil-water interfacial tension: Determined using the rotating drop method according to SY / T 5370-2018 "Methods for Determination of Surface and Interfacial Tension". Demulsifier working solution was added to carbon dioxide-saturated simulated produced water to achieve an effective demulsifier product concentration of 80 mg / L, serving as the low-density external phase; dehydrated crude oil was used as the oil phase. The test temperature was controlled at 10℃, and the rotating drop interfacial tension meter was set at 6000 r / min. After the sample was loaded into the test tube, it was kept at a constant temperature for 10 min, followed by droplet image acquisition. The test was conducted continuously for 30 min, and the equilibrium oil-water interfacial tension was recorded when the measured value changed by no more than 0.02 mN / m over 5 consecutive mins. Each sample was measured in triplicate, and the average value was taken as the result.

[0065] Low-temperature bottle test for dehydration performance: The evaluation method was conducted according to the bottle test approach in SY / T 5280-2018 "General Technical Conditions for Crude Oil Demulsifiers". 100 mL of simulated carbon dioxide flooded oil produced fluid was placed in a stoppered graduated dehydration bottle and equilibrated in a 10℃ constant temperature water bath for 30 min. Demulsifier working solution was added to the dehydration bottle to achieve an effective demulsifier product concentration of 80 mg / L. After tightening the stopper, the bottle was inverted and shaken 200 times with an amplitude of 20 cm each time. After shaking, the bottle was immediately returned to the 10℃ constant temperature water bath to allow settling. The volume of dehydrated water was read at 30 min and 60 min. Using an initial water volume of 30 mL as a baseline, the dehydration rate was calculated using the formula: Dehydration rate = Dehydrated water volume / 30 mL × 100%. Three bottles were tested in parallel for each sample, and a blank sample without demulsifier was also included.

[0066] Water content in the dehydrated oil: determined according to GB / T 8929-2006 "Determination of Water Content in Crude Oil - Distillation Method". After completing the low-temperature flask test for 60 min, the upper oil phases from three parallel flasks of the same sample were combined, avoiding the oil-water interface transition layer. After thorough mixing, 50.0 g of oil sample was weighed, and xylene was added as the distillation solvent. Distillation was carried out using a water receiving device with a condenser until the water volume in the receiver no longer increased within 5 min. The water volume was recorded and converted into the water content of the dehydrated oil.

[0067] Turbidity of the dewatering water: The turbidity was determined according to HJ 1075-2019 "Determination of Turbidity in Water - Turbidity Meter Method". After completing the low-temperature bottle test for 60 minutes, 20 mL of the dewatering water sample was taken from the bottom of the dewatering bottle and transferred to a clean, scratch-free colorimetric bottle, avoiding the introduction of air bubbles and without filtration. The turbidity meter used an 860 nm ± 30 nm light source and a 90° scattering detection method. Before testing, it was calibrated using standard turbidity solutions of 0 NTU, 20 NTU, 100 NTU, and 400 NTU. The sample was equilibrated at 20 ± 2 °C for 10 minutes before measurement. Three consecutive readings were taken, and the average value was used as the turbidity of the dewatering water. The unit of measurement is NTU.

[0068] Oil-water interface transition layer thickness: After completing the low-temperature bottle test for 60 minutes, keep the dehydration bottle in a constant temperature water bath at 10℃ without shaking it. Use a dehydration bottle scale with a resolution of 0.5mm to read the upper and lower boundaries of the milky white or brown transition layer between the oil and water phases, and use the difference between the two as the interface transition layer thickness. If the transition layer boundary is unclear, use the uppermost and lowermost ends of the visible continuous turbidity band as the reading boundaries. Test three bottles in parallel for each sample, and take the average value as the result.

[0069] Table 1 Performance Test Results

[0070] As shown in Table 1, the blank sample could not achieve effective oil-water separation by simply standing in the carbon dioxide-saturated simulated produced fluid at 10℃. The dehydration rate was only 2.1% after 60 minutes, and the water content of the oil after dehydration reached 8.7%. The turbidity of the dehydrated water and the thickness of the interfacial transition layer were 268.0 NTU and 19.5 mm, respectively. This indicates that the simulated produced fluid has high emulsification stability under low temperature, saline and weakly acidic conditions.

[0071] Compared with Example 1, Comparative Example 1 did not introduce the polyethylene glycol monomethyl ether acrylate short polyoxyethylene end group, and its oil-water interfacial tension at 10°C increased to 7.86 mN / m, while its dehydration rate at 60 min decreased to 48.7%. This indicates that relying solely on the branched polyoxypropylene triamine backbone, aromatic end groups, and long-chain end groups is insufficient to simultaneously achieve low-temperature dispersion and interfacial migration. Comparative Example 2 replaced benzyl glycidyl ether with dodecyl glycidyl ether, and Comparative Example 3 replaced dodecyl glycidyl ether with benzyl glycidyl ether. The dehydration rates at 60 min for both were 76.4% and 82.1%, respectively, both lower than the 95.6% of Example 1. This indicates that the aromatic end group and the long-chain alkyl end group are not simply interchangeable; their coexistence is more conducive to reducing interfacial film stability and promoting water droplet coalescence.

[0072] Although the composition of Comparative Example 4 is similar to that of Example 1, the addition of dodecyl glycidyl ether before benzyl glycidyl ether resulted in a dehydration rate of 85.6% at 60 min and a turbidity of 82.6 NTU in the dehydrated water, which was still significantly lower than that of Example 1. This indicates that the order of end-group introduction has a significant impact on the final demulsification performance.

[0073] Comparative Example 5 had a lactate ionization rate of only 36.1%, indicating insufficient low-temperature dispersibility and a dehydration rate of 72.8% after 60 minutes. Comparative Example 6 had a lactate ionization rate of 94.3%, which reduced the oil-water interfacial tension to 1.96 mN / m, but the turbidity of the dehydrated water increased to 168.5 NTU. This suggests that excessive ionization may cause the demulsifier to be biased towards the aqueous phase and result in aqueous phase residue or turbidity, thus failing to achieve the best overall demulsification effect.

[0074] After using the one-pot addition method in Comparative Example 7, the dispersion coefficient increased to 1.83, and the dehydration rate was only 81.7% after 60 minutes. This indicates that without step-by-step addition and step-by-step heat preservation, the distribution of end-group structure and the synchronicity of interfacial interaction were both affected. Examples 1-6 all used branched polyoxypropylene triamine as the core, and sequentially introduced short polyoxyethylene end groups, benzyl glycidyl ether end groups, dodecyl glycidyl ether end groups, and some lactate-type end groups. The dehydration rate reached 88.9%-96.8% in 60 minutes, the water content of the dehydrated oil was 0.2%-0.6%, the turbidity of the dehydrated water was 22.7-55.8 NTU, and the thickness of the interfacial transition layer was 1.2-3.4 mm. Among them, Example 3, due to the high amount of short polyoxyethylene end groups and aromatic end groups introduced and the lactate ratio maintained at 60.6%, achieved a dehydration rate of 78.6% in 30 minutes and 96.8% in 60 minutes at 10°C. The water content of the dehydrated oil was only 0.2%, the turbidity of the dehydrated water was 22.7 NTU, and the thickness of the interfacial transition layer was 1.2 mm, showing superior low-temperature rapid demulsification and clear oil-water interface.

[0075] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A low-temperature, high-efficiency demulsifier, characterized in that, The low-temperature high-efficiency demulsifier includes demulsifying active ingredients. The demulsifying active ingredient is obtained by reacting branched polyoxypropylene triamine sequentially with polyethylene glycol monomethyl ether acrylate, benzyl glycidyl ether, and dodecyl glycidyl ether, followed by partial salting with DL-lactic acid. Based on 1000 parts by weight of the branched polyoxypropylene triamine, the polyethylene glycol monomethyl ether acrylate comprises 220-276 parts by weight, the benzyl glycidyl ether comprises 68-88 parts by weight, the dodecyl glycidyl ether comprises 52-72 parts by weight, and the DL-lactic acid with a mass fraction of 85% comprises 59-68 parts by weight.

2. The low-temperature high-efficiency demulsifier according to claim 1, characterized in that, The branched polyoxypropylene triamine is a polyoxypropylene skeleton ternary primary amine with a number average molecular weight of 2000-4000.

3. The low-temperature high-efficiency demulsifier according to claim 1, characterized in that, The number-average molecular weight of the polyethylene glycol monomethyl ether acrylate is 400-550.

4. The low-temperature high-efficiency demulsifier according to claim 1, characterized in that, The demulsifying active ingredient has an amine-terminated lactate ratio of 55%-65%, a number-average molecular weight of 4140-4470 g / mol, and a dispersion index of 1.31-1.

42.

5. The low-temperature high-efficiency demulsifier according to claim 1, characterized in that, The low-temperature high-efficiency demulsifier is a liquid demulsifier containing isopropanol and deionized water as dispersion media.

6. A method for preparing a low-temperature high-efficiency demulsifier according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Branched polyoxypropylene triamine is mixed with isopropanol and pretreated under nitrogen protection to obtain a pretreated system; S2. Polyethylene glycol monomethyl ether acrylate is added to the pretreatment system to react and obtain the first reaction system; S3. Add benzyl glycidyl ether to the first reaction system to carry out the reaction, and obtain the second reaction system; S4. Add dodecyl glycidyl ether to the second reaction system to react and obtain the third reaction system; S5. After preparing an aqueous solution of DL-lactic acid with a mass fraction of 85%, add it to the third reaction system to carry out partial salting to obtain a salting system. S6. Add deionized water and isopropanol to the salinization system, stir and filter to obtain a low-temperature high-efficiency demulsifier.

7. The preparation method according to claim 6, characterized in that, In step S2, the reaction is carried out at 53-57℃ for 4-6 hours; in step S3, the reaction is carried out at 63-67℃ for 2.5-3.5 hours; in step S4, the reaction is carried out at 72-78℃ for 3-5 hours.

8. The preparation method according to claim 6, characterized in that, In step S5, the salting process is carried out at 42-48℃ for 1.5-2.5 hours.

9. The preparation method according to claim 6, characterized in that, In step S6, deionized water and isopropanol are added to the salinization system, stirred at 38-42°C for 0.8-1.2 hours, and filtered through a 200-mesh stainless steel filter to obtain a low-temperature high-efficiency demulsifier.

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