A demulsifier for breaking the oil-water transition zone in oil and gas gathering and transportation and its preparation method.

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a demulsifier for breaking the oil-water transition zone in oil and gas gathering and transportation, and its preparation method. The preparation method is as follows: In a first reactor, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, diethyl allyl malonate, deionized water, nonylphenol polyoxyethylene ether, sodium alkylphenol ether sulfosuccinate, and sodium dihydrogen phosphate are added and stirred. In a second reactor, 3-[(3-acrylamidopropyl)dimethylammonium]propionate, allyl alcohol polyoxyethylene ether, and deionized water are added and heated to dissolve. In the first reactor, an initiator and sodium bisulfite are added, the temperature is raised, and the reaction is maintained. The mixture from the second reactor is poured in, the reaction continues, the temperature is raised, and the reaction is maintained to obtain a viscous liquid. The solution is dried and granulated to obtain the demulsifier. The demulsifier of this invention has a good demulsification effect, resulting in a clear aqueous phase and a clear oil-water interface after demulsification.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a demulsifier for breaking the oil-water transition zone in oil and gas gathering and transportation, and its preparation method. Background Technology

[0002] In the process of oil and gas gathering and transportation, crude oil produced fluids usually exist in the form of oil-water emulsions. As oilfield development continues to deepen, major oilfields have successively entered the tertiary oil recovery stage. The produced crude oil has changed from the water-in-oil emulsion of the primary oil recovery stage to the oil-in-water emulsion, and the stability of the emulsion system has gradually increased.

[0003] In oil and gas gathering and transportation systems, the treatment of the oil-water transition zone is a crucial step. This zone typically contains numerous small, dispersed oil and water droplets, which are encapsulated by a stable interfacial film, making oil-water separation exceptionally difficult. This stable interfacial film is often formed by the combined action of natural emulsifiers in the crude oil, such as asphaltenes, gums, waxes, and other organic matter, as well as chemical displacement agents added during oil extraction.

[0004] As oilfield development deepens, the composition and properties of crude oil become increasingly complex, making the treatment of the oil-water transition zone more challenging. Traditional demulsifiers often exhibit poor adaptability, high demulsification temperatures, and slow dehydration rates when dealing with such complex systems. Particularly under low-temperature conditions, conventional demulsifiers struggle to effectively break down the oil-water interface film, leading to low oil-water separation efficiency and impacting the quality of exported crude oil and the treatment capacity of downstream wastewater treatment plants.

[0005] CN101113028A discloses a demulsifying and purifying agent, characterized by its composition of the following raw materials by weight percentage: 2%–68% wastewater treatment agent, 2%–37% polyferric sulfate, 5%–45% polyaluminum chloride, 6%–57% anhydrous calcium chloride, and 19%–47% ferric chloride. The preparation method is as follows: wastewater treatment agent, polyferric sulfate, and polyaluminum chloride are added to a mixer, followed by anhydrous calcium chloride and 50% water (the total amount of the four raw materials). The mixture is then thoroughly stirred at 60 rpm to ensure complete dissolution of the solid components for 2–3 hours. Ferric chloride is then added and stirring continues at 50–80 rpm for half an hour to one hour. After stopping the mixer for 6–10 hours, the mixture is filtered and packaged into product containers. This invention requires a concentration of 300–500 mg / L for demulsification, resulting in a large dosage, cumbersome operation, and the generation of a large amount of scum. Furthermore, it leaves a significant amount of the agent in the water, causing secondary pollution.

[0006] CN109575984A discloses a crude oil demulsifier for use at room temperature and low temperature. Its components include: 10-50% by mass of a siloxane polyether with a viscosity of 200-300 mPa·s, an HLB value of 7-10, and a closed-cup flash point greater than 60℃; and 50-90% by mass of a mixture of one or more of these as a solvent. The siloxane polyether in the crude oil demulsifier has different structures and molecular weight distributions, exhibiting highly efficient oil-water demulsification. The siloxane possesses low surface tension, low cohesive energy, and low temperature sensitivity, enabling demulsification at a low temperature of 30℃. Furthermore, the amount added is reduced by more than 50% compared to using polyether surfactants alone, resulting in a faster dehydration rate, better demulsification effect, and lower overall cost. However, this demulsifier only achieves a crude oil dehydration rate of 40% after 120 minutes, which cannot meet production needs, and the dehydration effect needs further improvement. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a demulsifier for breaking the oil-water transition zone in oil and gas gathering and transportation, and its preparation method. The demulsifier of this invention exhibits excellent demulsification effect, resulting in a clear aqueous phase and a distinct oil-water interface after demulsification.

[0008] One objective of this invention is to disclose a demulsifier for breaking up the oil-water transition zone in oil and gas gathering and transportation. The molecular formula of the demulsifier is as follows:

[0009]

[0010] In the formula:

[0011] a = 5000 - 50000;

[0012] b = 1000 - 20000;

[0013] c = 2500 - 50000;

[0014] d = 2500 - 50000;

[0015] n is a positive integer between 10 and 20.

[0016] Preferably, the viscosity-average molecular weight of the demulsifier is 10,000,000-20,000,000.

[0017] Another object of the present invention is to provide a method for preparing a demulsifier for breaking the oil-water transition zone in oil and gas gathering and transportation, wherein the specific steps of the preparation method are as follows:

[0018] (1) Purge the first reactor and pipeline with nitrogen for 8-10 min, add (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, allyl malonate diethyl ester, deionized water, nonylphenol polyoxyethylene ether, sodium alkylphenol ether sulfosuccinate, and sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0019] (2) Add 3-[(3-acrylamidopropyl)dimethylammonium]propionate, allyl alcohol polyoxyethylene ether, and deionized water to the second reactor and heat to dissolve;

[0020] (3) Add initiator and sodium bisulfite to the first reactor, heat to 40-50℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it and continue the reaction for 0.5-2h. Heat to 60-70℃ and keep the temperature for 20-30min. Adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0021] (4) The solution is dried and granulated to obtain a demulsifier.

[0022] In this invention, preferably, based on 1 mole of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, the amounts of allyl malonate diethyl ester, 3-[(3-acrylamidopropyl)dimethylammonium]propionate, and allyl alcohol polyoxyethylene ether are 0.2-0.4, 0.5-1, and 0.5-1 moles, respectively.

[0023] In this invention, preferably, in step (1), the mass ratio of deionized water, nonylphenol polyoxyethylene ether, sodium alkylphenol ether sulfosuccinate, sodium dihydrogen phosphate and (3-acryloyloxypropyl)tris(trimethylsiloxy)silane is 3-5:0.2-0.5:0.1-0.2:0.1-0.2:1.

[0024] In this invention, preferably, in step (2), the mass ratio of the deionized water to (3-acryloyloxypropyl)tris(trimethylsiloxy)silane is 6-8:1.

[0025] In this invention, preferably, in step (3), the mass ratio of the initiator, sodium bisulfite and (3-acryloyloxypropyl)tris(trimethylsiloxy)silane is 0.1-0.2:0.05-0.1:1.

[0026] In this invention, preferably, in step (3), the initiator is one of sodium persulfate, potassium persulfate, and ammonium persulfate.

[0027] The synthesis reaction equation for the demulsifier of this invention is as follows:

[0028]

[0029] The demulsifier of this invention is a polymeric demulsifier with polyethylene as the main chain and various long-chain functional groups as side chains. Cationic quaternary ammonium salts neutralize the charge of negatively charged emulsion droplets, reducing electrostatic repulsion between droplets and causing oil droplets to aggregate and release, forming large oil beads, thus achieving demulsification. Silane and siloxane molecules form a hydrophobic film at the oil-water interface, disrupting the original emulsion film and promoting droplet aggregation by reducing interfacial tension. Polyester molecules adsorb at the oil-water interface, disrupting the stability of the interfacial film and achieving flocculation and demulsification. The polyether segment has high flexibility and coils in water, increasing the surface area of ​​the demulsifier molecules adsorbed at the interface, affecting the tight arrangement of demulsifier molecules at the interface, and increasing the ability to reduce the viscosity and elasticity of the oil-water interface. This reduces the strength of the oil-water interfacial film, leading to a shorter oil film life, faster film thinning, and increased dehydration rate of the crude oil emulsion, thus achieving demulsification.

[0030] The demulsifier of the present invention has a good demulsification effect. For emulsified oil in the oil-water transition zone of gathering and transportation with a concentration of 52000 mg / L, when the concentration is 80 mg / L, the dehydration amount of 100 ml of emulsion reaches 89 ml or more in 90 minutes. The aqueous phase after demulsification is clear, the oil content is less than 100 mg / L, and the oil-water interface is clear. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to specific embodiments and data. It should be understood that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention in any way.

[0032] Example 1

[0033] (1) Purge the first reactor and pipeline with nitrogen for 10 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 10 mmol allyl malonate diethyl ester, 61.35 g deionized water, 4.09 g nonylphenol polyoxyethylene ether, 3.14 g sodium alkylphenol ether sulfosuccinate, and 2.045 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0034] (2) Add 25 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 50 mmol of allyl alcohol polyoxyethylene ether, and 122.7 g of deionized water to the second reactor and heat to dissolve;

[0035] (3) Add 2.045g sodium persulfate and 1.02g sodium bisulfite to the first reactor, heat to 40℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 2 hours, heat to 60℃, keep the temperature for 30 minutes, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0036] (4) The solution is dried and granulated to obtain a demulsifier.

[0037] Example 2

[0038] (1) Purge the first reactor and pipeline with nitrogen for 8 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 10 mmol allyl malonate diethyl ester, 61.35 g deionized water, 4.09 g nonylphenol polyoxyethylene ether, 3.14 g sodium alkylphenol ether sulfosuccinate, and 2.045 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0039] (2) Add 25 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 50 mmol of allyl alcohol polyoxyethylene ether, and 122.7 g of deionized water to the second reactor and heat to dissolve;

[0040] (3) Add 2.045g sodium persulfate and 1.02g sodium bisulfite to the first reactor, heat to 50℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 0.5h, heat to 70℃, keep the temperature for 27min, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0041] (4) The solution is dried and granulated to obtain a demulsifier.

[0042] Example 3

[0043] (1) Purge the first reactor and pipeline with nitrogen for 10 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 20 mmol allyl malonate diethyl ester, 102.3 g deionized water, 10.2 g nonylphenol polyoxyethylene ether, 2.045 g sodium alkylphenol ether sulfosuccinate, and 4.09 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0044] (2) Add 50 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 25 mmol of allyl alcohol polyoxyethylene ether, and 163.6 g of deionized water to the second reactor and heat to dissolve;

[0045] (3) Add 4.09g sodium persulfate and 1.02g sodium bisulfite to the first reactor, heat to 50℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 1 hour, heat to 65℃, keep the temperature for 25 minutes, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0046] (4) The solution is dried and granulated to obtain a demulsifier.

[0047] Example 4

[0048] (1) Purge the first reactor and pipeline with nitrogen for 10 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 10 mmol allyl malonate diethyl ester, 81.3 g deionized water, 8.09 g nonylphenol polyoxyethylene ether, 3.14 g sodium alkylphenol ether sulfosuccinate, and 3.04 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0049] (2) Add 30 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 30 mmol of allyl alcohol polyoxyethylene ether, and 142.7 g of deionized water to the second reactor and heat to dissolve;

[0050] (3) Add 3.04g sodium persulfate and 1.62g sodium bisulfite to the first reactor, heat to 45℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 0.5h, heat to 60℃, keep the temperature for 20min, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0051] (4) The solution is dried and granulated to obtain a demulsifier.

[0052] Example 5

[0053] (1) Purge the first reactor and pipeline with nitrogen for 10 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 15 mmol allyl malonate diethyl ester, 70.3 g deionized water, 8.09 g nonylphenol polyoxyethylene ether, 2.05 g alkylphenol ether sulfosuccinate sodium salt and 3.2 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0054] (2) Add 38 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 40 mmol of allyl alcohol polyoxyethylene ether, and 150 g of deionized water to the second reactor and heat to dissolve;

[0055] (3) Add 4g of sodium persulfate and 2g of sodium bisulfite to the first reactor, heat to 50°C, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 0.5h, heat to 60°C, keep the temperature for 20min, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0056] (4) The solution is dried and granulated to obtain a demulsifier.

[0057] Example 6

[0058] (1) Purge the first reactor and pipeline with nitrogen for 10 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 10 mmol allyl malonate diethyl ester, 89 g deionized water, 10 g nonylphenol polyoxyethylene ether, 4.09 g sodium alkylphenol ether sulfosuccinate, and 4.09 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0059] (2) Add 29 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 45 mmol of allyl alcohol polyoxyethylene ether, and 152 g of deionized water to the second reactor and heat to dissolve;

[0060] (3) Add 3.5g sodium persulfate and 1.8g sodium bisulfite to the first reactor, heat to 43℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 0.5h, heat to 68℃, keep the temperature for 30min, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0061] (4) The solution is dried and granulated to obtain a demulsifier.

[0062] Example 7

[0063] (1) Purge the first reactor and pipeline with nitrogen for 9 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 18 mmol allyl malonate diethyl ester, 92 g deionized water, 7.8 g nonylphenol polyoxyethylene ether, 2.8 g sodium alkylphenol ether sulfosuccinate, and 2.9 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0064] (2) Add 31 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 36 mmol of allyl alcohol polyoxyethylene ether, and 137.7 g of deionized water to the second reactor and heat to dissolve;

[0065] (3) Add 3.6g sodium persulfate and 1.6g sodium bisulfite to the first reactor, heat to 48℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 1.5h, heat to 63℃, keep the temperature for 30min, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0066] (4) The solution is dried and granulated to obtain a demulsifier.

[0067] Example 8

[0068] (1) Purge the first reactor and pipeline with nitrogen for 8 min, add 50 mmol (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 17 mmol allyl malonate diethyl ester, 91.3 g deionized water, 9.09 g nonylphenol polyoxyethylene ether, 3.84 g sodium alkylphenol ether sulfosuccinate, and 3.04 g sodium dihydrogen phosphate, stir to form an emulsion, and adjust the pH to 7-8 with sodium hydroxide solution;

[0069] (2) Add 45 mmol of 3-[(3-acrylamidopropyl)dimethylammonium]propionate, 35 mmol of allyl alcohol polyoxyethylene ether, and 142.7 g of deionized water to the second reactor and heat to dissolve;

[0070] (3) Add 3.5g sodium persulfate and 1.5g sodium bisulfite to the first reactor, heat to 50℃, keep the temperature for reaction, and when the viscosity begins to rise, quickly pour the mixture from the second reactor into it, continue the reaction for 2 hours, heat to 65℃, keep the temperature for 30 minutes, adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0071] (4) The solution is dried and granulated to obtain a demulsifier.

[0072] Example 9: Performance Evaluation of Demulsifier

[0073] The demulsifying performance of the demulsifier of this invention (Examples 1-8) was tested using crude oil from the oil-water transition zone in a crude oil gathering and transportation tank of an oil production plant in Shengli Oilfield. The oil content of the emulsified oil in the oil-water transition zone was 52,000 mg / L. The evaluation method referred to SY / T 5281-2000 "Test Method for Performance of Crude Oil Demulsifiers". The experimental temperature was 50℃, and the dosage concentration was 40 and 80 mg / L. A comparative experiment was conducted using SP-169 crude oil demulsifier from Haian Petrochemical Plant in Jiangsu Province. The test results are shown in Table 1.

[0074] Table 1. Experimental results of crude oil demulsifier

[0075]

[0076] As can be seen from Table 1:

[0077] (1) When the concentration of the demulsifier of the present invention (Examples 1-8) in the oil-water transition zone of the gathering and transportation of 52000mg / L is 40mg / L, the dehydration amount of 100ml emulsion reaches more than 85ml in 90min. The aqueous phase after demulsification is clear, the oil content is less than 100mg / L, and the oil-water interface is clear. In contrast, the dehydration amount of SP-169 crude oil demulsifier of Jiangsu Haian Petrochemical Plant in 90min is 68ml. The oil-water interface after demulsification is blurred and the oil content is 280mg / L. The demulsification effect is significantly lower than that of the present invention.

[0078] (2) When the concentration of the demulsifier of the present invention (Examples 1-8) in the oil-water transition zone of the gathering and transportation of 52000mg / L is 80mg / L, the dehydration amount of 100ml emulsion reaches 89ml or more in 90min. The aqueous phase after demulsification is clear, the oil content is not higher than 90mg / L, and the oil-water interface is clear. In contrast, the dehydration amount of SP-169 crude oil demulsifier of Jiangsu Haian Petrochemical Plant in 90min is 79ml. The oil-water interface after demulsification is clear, and the oil content is 126mg / L. The demulsification effect is significantly lower than that of the present invention.

[0079] 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 method for preparing a demulsifier for breaking oil-water transition zone in oil and gas gathering and transportation, characterized in that, The specific steps of the preparation method are as follows: (1) The first reactor and pipeline are purged with nitrogen for 8-10 min, (3-acryloyloxypropyl) tris (trimethylsiloxy) silane, allyl malonic acid diethyl ester, deionized water, nonylphenol polyoxyethylene ether, alkylphenol ether sulfosuccinate sodium salt, sodium dihydrogen phosphate are added and stirred to form an emulsion, and the pH is adjusted to 7-8 with sodium hydroxide solution, and the mass ratio of deionized water, nonylphenol polyoxyethylene ether, alkylphenol ether sulfosuccinate sodium salt, sodium dihydrogen phosphate to (3-acryloyloxypropyl) tris (trimethylsiloxy) silane is 3-5:0.2-0.5:0.1-0.2:0.1-0.2:1; (2) 3-[(3-acrylamidopropyl) dimethylammonium] propionate, allyl alcohol polyoxyethylene ether and deionized water are added to the second reactor and heated to dissolve, and the mass ratio of deionized water to (3-acryloyloxypropyl) tris (trimethylsiloxy) silane is 6-8:1; (3) The initiator and sodium bisulfite are added to the first reactor, the initiator is one of sodium persulfate, potassium persulfate and ammonium persulfate, the temperature is raised to 40-50°C, and the reaction is kept for a certain period of time, when the viscosity begins to rise, the mixed solution in the second reactor is quickly poured in, the reaction is continued for 0.5-2 h, the temperature is raised to 60-70°C, and the reaction is kept for 20-30 min, the pH is adjusted to 7-8 with sodium hydroxide solution, and a viscous liquid is obtained, and the mass ratio of initiator, sodium bisulfite to (3-acryloyloxypropyl) tris (trimethylsiloxy) silane is 0.1-0.2:0.05-0.1:1; (4) The solution is dried and granulated to obtain a demulsifier, and the molecular formula of the demulsifier is as follows: In the formula: a=5000-50000； b=1000-20000； c=2500-50000； d=2500-50000； n is a positive integer of 10-20; Based on 1 mole of (3-acryloyloxypropyl) tris (trimethylsiloxy) silane, the amounts of allyl malonic acid diethyl ester, 3-[(3-acrylamidopropyl) dimethylammonium] propionate and allyl alcohol polyoxyethylene ether are 0.2-0.4, 0.5-1 and 0.5-1 mole, respectively.

2. The demulsifier prepared by the preparation method of claim 1.

3. The demulsifier according to claim 2, characterized in that, The viscosity average molecular weight of the demulsifier is 10000000-20000000.

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