A type of amphoteric polyether carboxylate viscosity reducer containing polyether segments, its preparation method and application

Abstract

This invention discloses an amphoteric polyether carboxylate viscosity reducer containing polyether segments, its preparation method, and its applications. Belonging to the field of heavy oil extraction technology, the polyether segments in the block polyether carboxylate possess lipophilic properties, allowing them to insert into heavy oil particles and interact with asphalt molecules, disrupting the network structure formed by asphaltene accumulation at the oil-water interface, thereby reducing the viscosity of the heavy oil. Sulfonic acid and carboxylic acid groups, through hydrogen bonding, firmly adsorb water molecules onto the polyether segments, forming a water layer, further increasing the spacing between heavy oil particles, reducing the cohesive force of the heavy oil, and thus further reducing its viscosity. Compared with traditional free radical polymerization, it has a precisely controllable structure and superior viscosity-reducing performance, achieving a viscosity reduction rate of over 97% for heavy oil. In practical applications, it exhibits excellent viscosity-reducing effects and has significant application value for heavy oil extraction and transportation.

Description

Technical Field

[0001] This invention belongs to the field of heavy oil extraction technology, specifically relating to an amphoteric polyether carboxylate viscosity reducer containing polyether segments, its preparation method, and its application. Background Technology

[0002] The high viscosity and low fluidity of heavy oil pose significant challenges to its extraction and utilization. To overcome these difficulties, the global oil industry has been continuously exploring and innovating extraction technologies. Traditional thermal extraction methods, such as steam injection and steam drive, while improving the fluidity of heavy oil to some extent, are energy-intensive and have certain environmental impacts.

[0003] Emulsification viscosity reduction technology, as a relatively environmentally friendly and economical method, has received widespread attention globally in recent years. By adding specific surfactants to heavy oil, a stable emulsion can be formed, thereby significantly reducing viscosity and improving fluidity. Amphoteric surfactants, especially block polyether polycarboxylate salts, have shown excellent effects in heavy oil viscosity reduction due to their unique structure and properties. These surfactants can carry both positive and negative charges simultaneously, enabling them to form stable emulsions in heavy oil and effectively reduce viscosity. With the continuous development of polymer chemistry, various advanced polymerization technologies, such as RAFT polymerization, are increasingly being applied to surfactant synthesis. These technologies provide the possibility of precisely controlling the molecular weight, structure, and properties of polymers, thus promising the synthesis of more efficient heavy oil viscosity reducers. The technical challenges of heavy oil extraction and utilization are not only a national issue but also a common challenge faced by the global petroleum industry.

[0004] To address the issues of high viscosity and poor low-temperature fluidity in heavy oil, it is necessary to develop a highly efficient chemical viscosity reducer to achieve efficient viscosity reduction in heavy oil and solve the technical challenges in heavy oil extraction and utilization. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an amphoteric polyether carboxylate viscosity reducer containing polyether segments, its preparation method and application, so as to solve the technical problems of high viscosity and poor low-temperature fluidity of heavy oil.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses an amphoteric polyether carboxylate viscosity reducer containing polyether segments, wherein the amphoteric polyether carboxylate viscosity reducer containing polyether segments is a ternary block polyether carboxylate; the structural formula is:

[0008]

[0009] Where a = 5 to 20, b = 20 to 80, c = 2 to 8, and n = 5 to 25.

[0010] This invention also discloses a method for preparing the above-mentioned amphoteric polyether carboxylate viscosity reducer containing polyether segments, comprising: dividing an initiator into three parts; mixing the first part of the initiator with a chain transfer agent and an allyl polyoxyethylene ether solution; introducing nitrogen gas; after the first stirring reaction is completed; first adding the second part of the initiator; then adding diallyl dimethyl ammonium chloride solution; after the second stirring reaction is completed; then adding the third part of the initiator; finally slowly adding an acrylic acid solution; after the third stirring reaction is completed; adjusting the pH value to 7-8 to obtain the amphoteric polyether carboxylate viscosity reducer containing polyether segments.

[0011] Preferably, the initiator is one of azobisisobutylamidine hydrochloride, dimethyl azobisisobutyrate, and benzoyl peroxide; and the chain transfer agent is one of dithiocarbamate, xanthate, and trithiocarbonate.

[0012] More preferably, the azobisisobutylamidine hydrochloride is azobisisobutyronitrile; and the trithiocarbonate is S-S'-bis(a,a'-dimethyl-a”-acetic acid)-trithiocarbonate.

[0013] Preferably, the molar ratio of the first initiator to the second initiator to the third initiator is 1:1:(3-5).

[0014] Preferably, the acrylic acid solution is prepared by dissolving 8-10g of acrylic acid in 18-22g of water; the diallyl dimethyl ammonium chloride solution is prepared by dissolving 4-6g of diallyl dimethyl ammonium chloride in 9-14g of water; and the allyl polyoxyethylene ether solution is prepared by dissolving 15-18g of allyl polyoxyethylene ether in 35-42g of water.

[0015] More preferably, the molar ratio of the first initiator: chain transfer agent: allyl polyoxyethylene ether: diallyl dimethyl ammonium chloride: acrylic acid is 1:(4-6):1:1:(3-5).

[0016] Preferably, the nitrogen gas is introduced for 0.5-1.0 h; the diallyl dimethyl ammonium chloride solution is added for 2.0-4.0 h; and the acrylic acid solution is added for 2.0-4.0 h.

[0017] Preferably, the temperature of the first stirring reaction is 75-85℃ and the time is 6.0-8.0h; the temperature of the second stirring reaction is 75-85℃ and the time is 6.0-8.0h; and the temperature of the third stirring reaction is 75-85℃ and the time is 6.0-8.0h.

[0018] Preferably, the pH value is adjusted to 7-8 using a 30% NaOH aqueous solution.

[0019] The present invention also discloses the application of the amphoteric polyether carboxylate viscosity reducer containing polyether segments prepared by the above preparation method in heavy oil extraction and viscosity reduction, with a viscosity reduction rate of 97.04%-99.04%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses an amphoteric polyether carboxylate viscosity reducer containing polyether segments. The polyether segments themselves possess excellent chemical and thermal stability, allowing the amphoteric polyether carboxylate viscosity reducer to maintain stable performance even under extreme environments, thus broadening its applicability in practical applications. The unique structure of the ternary block polyether carboxylate endows it with unique properties. Specifically, the polyether segments in this block polyether carboxylate are oleophilic, allowing them to insert into heavy oil particles and interact with the asphalt molecules therein. This interaction disrupts the network structure formed by asphaltene accumulation at the oil-water interface, thereby reducing the viscosity of the heavy oil. The ternary block polyether carboxylate also contains two hydrophilic groups: sulfonic acid groups and carboxylic acid groups. These two groups, through hydrogen bonding, can firmly adsorb water molecules onto the polyether segments, forming a water layer. The formation of this water layer further increases the spacing between heavy oil particles, reducing the cohesive force of the heavy oil, thereby further reducing its viscosity. In practical applications, it exhibits excellent viscosity-reducing effects and has significant application value for heavy oil extraction and transportation. Amphoteric block polyether carboxylates can be used to obtain a series of products with different block lengths and contents by adjusting the molecular weight and monomer content. These products exhibit a wide range of hydrophilic-lipophilic balance (HLB) values, allowing for diverse applications. Furthermore, they do not dissociate into ions but remain in an etheric state. The oxygen atoms and hydroxyl groups in these bonds have the ability to form hydrogen bonds with water molecules, making them less susceptible to the influence of strong electrolytes. They possess excellent washing, emulsifying, dispersing, foaming, wetting, and solubilizing properties. In emulsifier systems, block polymers ensure that the oil phase containing pesticide active ingredients is uniformly and stably dispersed in the aqueous phase. They provide excellent sustained-release effects for the active ingredients in microcapsules. They are widely applicable in various formulations, including pesticide spray formulations, water-dispersible granules, and powders.

[0022] This invention also discloses a method for preparing the above-mentioned amphoteric polyether carboxylate viscosity reducer containing polyether segments, comprising: dividing an initiator into three parts; mixing the first part of the initiator with a chain transfer agent and an allyl polyoxyethylene ether solution; purging with nitrogen gas; stirring and reacting; adding the second part of the initiator first; then adding a diallyl dimethyl ammonium chloride solution; after stirring and reacting, adding the third part of the initiator; and finally slowly adding an acrylic acid solution; after stirring and reacting, adjusting the pH to 7-8 to obtain the amphoteric polyether carboxylate viscosity reducer containing polyether segments. The RAFT polymerization method allows for precise control of the polymer's molecular structure, such as molecular weight, segment length, and molecular weight distribution. This precise control results in a prepared polyether carboxylate amphoteric surfactant with superior performance, better adapting to different heavy oil viscosity reduction requirements. Because the polyether segments have good compatibility with hydrocarbon molecules in heavy oil, and the carboxylate groups can form hydrogen bonds with water molecules, this amphoteric surfactant can effectively reduce the viscosity of heavy oil. Polyether carboxylate zwitterionic surfactants can significantly improve the interfacial tension between heavy oil and water, making heavy oil easier to wet and emulsify. This helps reduce the flow resistance of heavy oil and improve its extraction and transportation efficiency. For heavy oil, low-temperature fluidity is a major challenge in its extraction and transportation. Due to the introduction of polyether segments, this zwitterionic surfactant can improve the fluidity of heavy oil at low temperatures to some extent, lower its pour point, and thus broaden the extraction and transportation window. The electrostatic repulsion of carboxyl anions contributes to the dispersion of cement particles. Similarly, the relative molecular mass and carboxyl content have a significant impact on the dispersion effect of cement particles. The hydrophobicity of the main chain molecule and the hydrophilicity of the side chains, as well as the presence of the side group -(OCH2CH2)-, also provide a certain degree of steric stabilization; that is, the surface of cement particles is stabilized by a block or graft copolymer to prevent random aggregation, thereby facilitating the dispersion of cement particles. Compared with traditional chemical viscosity reducers, polyether carboxylate zwitterionic surfactants have better biodegradability and environmental compatibility, resulting in less environmental pollution. This preparation method has beneficial effects such as precise and controllable structure, excellent viscosity-reducing performance, good wetting properties, improved low-temperature fluidity, good environmental friendliness, high flexibility, and theoretical support. It provides a new and efficient viscosity reducer for the extraction and transportation of heavy oil, and can be applied in fields such as concrete water-reducing agents and pesticide dispersants.

[0023] Furthermore, by systematically studying the effects of monomer addition order, ratio, and chain transfer agent dosage on the properties of polyether carboxylates, this invention has determined optimal synthesis process conditions, thereby improving the performance and efficiency of surfactants.

[0024] This invention also discloses the application of the amphoteric polyether carboxylate viscosity reducer containing polyether segments prepared by the above-mentioned method in heavy oil extraction and viscosity reduction. Its viscosity reduction rate is 97.04%-99.04%, significantly reducing the viscosity of heavy oil, making it smoother during extraction and transportation, and improving extraction efficiency and transportation capacity. Due to the reduced viscosity of heavy oil, the problems of blockage and wear in extraction equipment such as oil pumps and pipelines are effectively alleviated, thereby improving equipment operating efficiency and lifespan. At the same time, it reduces the extraction difficulty and cost caused by excessive viscosity, making the development of heavy oil resources more economical and efficient. During heavy oil transportation, low-viscosity heavy oil is easier to transport through pipelines, reducing pumping pressure and energy consumption, and lowering transportation costs. Furthermore, low-viscosity heavy oil is also more convenient and efficient in storage and processing. Compared with traditional viscosity reducers, this type of amphoteric polyether carboxylate viscosity reducer containing polyether segments generally has better biodegradability and environmental compatibility. This helps reduce environmental pollution during extraction and transportation, meeting current requirements for environmental protection and sustainable development. They are applicable to various types and properties of heavy oil, demonstrating good adaptability and versatility. They maintain stable viscosity-reducing properties under both high and low temperature conditions, providing more options for the exploitation and viscosity reduction of heavy oil resources. Attached Figure Description

[0025] Figure 1 The following are the synthesis steps of the ternary block polyether carboxylate disclosed in Example 4 of the present invention; wherein, (a) is the first stage of synthesizing the ternary block polyether carboxylate, (b) is the second stage of synthesizing the ternary block polyether carboxylate, and (c) is the final stage of synthesizing the ternary block polyether carboxylate.

[0026] Figure 2 This refers to the ternary random polyether carboxylate synthesis steps disclosed in Example 6 of the present invention;

[0027] Figure 3 The image shows the FT-IR spectrum of the amphoteric polyether carboxylate viscosity reducer containing polyether segments disclosed in Example 4 of this invention. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] The present invention will now be described in further detail with reference to the accompanying drawings:

[0031] This invention uses crude oil from the North China Oilfield as the research sample to analyze its composition and physicochemical properties. Gas chromatography-mass spectrometry (GC-MS) and infrared spectroscopy (IR spectroscopy) are used to characterize the crude oil and determine its composition and content. Four-component analysis is performed on the crude oil according to industry standards to determine its components. The viscosity-temperature curve of the crude oil is obtained. A series of novel polyether carboxylate surfactants are designed and synthesized. The emulsifying, viscosity-reducing, wetting, and foaming properties of these novel polyether carboxylate surfactants as viscosity reducers are studied, and the optimal structure of the polyether carboxylate surfactant is selected. Using the novel polyether carboxylate surfactant with the optimal structure, reaction condition optimization experiments are conducted, viscosity-reducing and emulsifying properties are measured, and surface / interfacial tension and wetting properties are examined and evaluated to determine the optimal reaction conditions and deduce the viscosity-reducing mechanism.

[0032] This invention discloses an amphoteric polyether carboxylate viscosity reducer containing polyether segments, comprising ternary block polyether carboxylate and ternary random polyether carboxylate;

[0033] The structural formula of ternary block polyether carboxylate is:

[0034]

[0035] Where a = 5–20, b = 20–80, c = 2–8, n = 5–25;

[0036] The structural formula of the ternary random polyether carboxylate is:

[0037]

[0038] Where a = 5 to 20, b = 20 to 80, c = 2 to 8, and n = 5 to 25.

[0039] The present invention discloses a method for preparing a ternary block polyether carboxylate crude oil viscosity reducer, comprising: dividing an initiator into three parts; mixing the first part of the initiator with a chain transfer agent and an allyl polyoxyethylene ether solution; purging with nitrogen for 0.5-1.0 h; reacting at 75-85°C for 6.0-8.0 h; after the first stirring reaction, adding the second part of the initiator; then adding diallyl dimethyl ammonium chloride solution within 2.0-4.0 h; reacting at 75-85°C for 6.0-8.0 h; after the second stirring reaction, adding the third part of the initiator; and finally slowly adding acrylic acid solution within 2.0-4.0 h; reacting at 75-85°C for 6.0-8.0 h; after the third stirring reaction, adjusting the pH value to 7-8 with a 30% (w / w) NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments with a viscosity reduction rate of 97.04%-99.04%.

[0040] The initiator is one of azobisisobutylamidine hydrochloride, dimethyl azobisisobutyrate, and benzoyl peroxide.

[0041] The chain transfer agent is one of dithiocarbamate, xanthate, and trithiocarbonate.

[0042] Preferably, the initiator is azobisisobutyronitrile; the chain transfer agent is S-S'-bis(a,a'-dimethyl-a”-acetic acid)-trithiocarbonate.

[0043] The molar ratio of the first initiator to the second initiator to the third initiator is 1:1:(3-5).

[0044] The acrylic acid solution is prepared by dissolving 8-10g of acrylic acid in 18-22g of water.

[0045] The diallyl dimethyl ammonium chloride solution is prepared by dissolving 4-6 g of diallyl dimethyl ammonium chloride in 9-14 g of water.

[0046] The allyl polyoxyethylene ether solution is prepared by dissolving 15-18g of allyl polyoxyethylene ether in 35-42g of water.

[0047] The first initiator: chain transfer agent: allyl polyoxyethylene ether: diallyl dimethyl ammonium chloride: acrylic acid molar ratio is 1:(4-6):1:1:(3-5).

[0048] The present invention discloses a method for preparing a ternary block polyether carboxylate crude oil viscosity reducer, comprising reacting acrylic acid (AA), diallyl dimethyl ammonium chloride (DADMAC), and allyl polyoxyethylene ether (APEG600) in a molar ratio of AA:DADMAC:APEG600 = (3-5):1:1; specifically including the following steps:

[0049] Step 1: Weigh 0.0060-0.0080g of azobisisobutyronitrile (AIBN) and 0.1800-0.2500g of S-S'-bis(a,a'-dimethyl-a”-acetic acid)-trithiocarbonate (BDATT), weigh 15-18g of APEG600, dissolve them in 35-42g of water, and add all three to a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen gas for half an hour, turn on the cooling water, raise the temperature to 75-85℃, and stir the reaction for 6-8 hours.

[0050] Step 2: Weigh 0.0060-0.0080g of AIBN and add it to a three-necked flask. Weigh 3-5g of DADMAC, dissolve it in 7-12g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of no less than 2 hours, and continue stirring the reaction for 6-8 hours.

[0051] Step 3: Weigh 0.02-0.04g of AIBN and add it to a three-necked flask. Weigh 7-10g of AA, dissolve it in 16-23g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of no less than 2 hours, and continue stirring to react for 6-8 hours.

[0052] Step 4: Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to between 7 and 8 with a 30% NaOH aqueous solution to obtain the ternary block polyether carboxylate crude oil viscosity reducer.

[0053] Furthermore, the order of steps two and three above is reversed.

[0054] The viscosity, surface tension, and contact angle of the obtained crude oil viscosity reducer were tested to screen for the optimal monomer addition sequence.

[0055] Further: In step one, the molar ratio of AIBN to BDATT is 1:4.

[0056] Further: In step one, the molar ratio of AIBN to BDATT is 1:5.

[0057] Further: In step one, the molar ratio of AIBN to BDATT is 1:6.

[0058] The performance was compared again to obtain the optimal solution for structural characterization.

[0059] The present invention discloses a method for preparing a ternary random polyether carboxylate crude oil viscosity reducer, comprising reacting acrylic acid (AA), diallyl dimethyl ammonium chloride (DADMAC), and allyl polyoxyethylene ether (APEG600) in a molar ratio of AA:DADMAC:APEG600 = (3-5):1:1; specifically including the following steps:

[0060] Step 1: Weigh 15-18g of APEG600, dissolve it in 35-42g of water, and add it to a 250mL three-necked flask.

[0061] Step 2: Weigh 0.0300-0.0500g of AIBN and 0.1550-0.2580g of BDATT and add them together with the reactants from Step 1 into a three-necked flask; weigh 8-10g of AA and dissolve it in 18.70-23.40g of water; weigh 4-6g of DADMAC and dissolve it in 10-12g of water.

[0062] Step 3: Transfer the dissolved monomer from Step 2 into a syringe of appropriate size. Place the reactor in a magnetically stirred oil bath, purge nitrogen gas into the flask for 0.5-1 hour, turn on the cooling water, raise the temperature to 75-85℃, turn on the syringe, and add the monomer dropwise over a period of not less than 2 hours. Stir the reaction for 6-8 hours.

[0063] Step 4: Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH value to between 7 and 8 with a 30% NaOH aqueous solution to obtain the ternary random polyether carboxylate crude oil viscosity reducer.

[0064] The amphoteric polyether carboxylate viscosity reducer containing polyether segments prepared by the above method was applied to heavy oil extraction and viscosity reduction, and its viscosity reduction rate was 97.04%-99.04%.

[0065] The following examples will help to understand the present invention, but the examples do not limit the invention in any way. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0066] Example 1

[0067] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0068] 1) Weigh 0.0078g of AIBN and 0.2418g of BDATT, weigh 17.151g of APEG600, dissolve them in 40.02g of water, and add all three to a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for half an hour, turn on the cooling water, raise the temperature to 80℃, and stir the reaction for 6 hours.

[0069] 2) Weigh 0.0313g of AIBN and add it to a three-necked flask. Weigh 8.2325g of AA, dissolve it in 19.21g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of not less than 2 hours, and continue stirring to react for 6 hours.

[0070] 3) Weigh 0.0078g of AIBN and add it to a three-necked flask. Weigh 4.6165g of DADMAC, dissolve it in 10.77g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of not less than 2 hours and continue stirring the reaction for 6 hours.

[0071] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0072] Example 2

[0073] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0074] 1) Weigh 0.0078g of AIBN and 0.2418g of BDATT, weigh 17.151g of APEG600, dissolve them in 40.02g of water, and add all three to a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for half an hour, turn on the cooling water, raise the temperature to 80℃, and stir the reaction for 6 hours.

[0075] 2) Weigh 0.0078g of AIBN and add it to a three-necked flask. Weigh 4.6165g of DADMAC, dissolve it in 10.77g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of not less than 2 hours and continue stirring the reaction for 6 hours.

[0076] 3) Weigh 0.0313g of AIBN and add it to a three-necked flask. Weigh 8.2325g of AA, dissolve it in 19.21g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of not less than 2 hours, and continue stirring to react for 6 hours.

[0077] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0078] Example 3

[0079] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0080] 1) Weigh 0.0078g of AIBN and 0.3224g of BDATT (the molar ratio of AIBN to BDATT is 1:4), weigh 17.151g of APEG600, dissolve them in 40.02g of water, and add all three to a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for half an hour, turn on the cooling water, raise the temperature to 80℃, and stir the reaction for 6 hours.

[0081] 2) Weigh 0.0313g of AIBN and add it to a three-necked flask. Weigh 8.2325g of AA, dissolve it in 19.21g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of not less than 2 hours, and continue stirring to react for 6 hours.

[0082] 3) Weigh 0.0078g of AIBN and add it to a three-necked flask. Weigh 4.6165g of DADMAC, dissolve it in 10.77g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of not less than 2 hours and continue stirring the reaction for 6 hours.

[0083] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0084] Example 4

[0085] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0086] 1) Weigh 0.0078g of AIBN and 0.4030g of BDATT (the molar ratio of AIBN to BDATT is 1:5), weigh 17.151g of APEG600, dissolve them in 40.02g of water, and add all three into a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for half an hour, turn on the cooling water, raise the temperature to 80℃, and stir the reaction for 6 hours.

[0087] 2) Weigh 0.0313g of AIBN and add it to a three-necked flask. Weigh 8.2325g of AA, dissolve it in 19.21g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of not less than 2 hours, and continue stirring to react for 6 hours.

[0088] 3) Weigh 0.0078g of AIBN and add it to a three-necked flask. Weigh 4.6165g of DADMAC, dissolve it in 10.77g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of not less than 2 hours and continue stirring the reaction for 6 hours.

[0089] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0090] See Figure 1 The following are the synthesis steps of the ternary block polyether carboxylate disclosed in Example 4 of this invention; wherein, (a) is the first stage of synthesizing the ternary block polyether carboxylate, (b) is the second stage of synthesizing the ternary block polyether carboxylate, and (c) is the final stage of synthesizing the ternary block polyether carboxylate; as can be seen from the figure, attention should be paid to the order of adding substances when synthesizing the ternary block polyether carboxylate. The initiator is divided into three parts, and the initiator of the corresponding stage is added at different stages to synthesize the corresponding intermediate products. The intermediate products are then used in the next stage reaction to obtain the ternary block polyether carboxylate viscosity reducer.

[0091] Figure 2 The figure shows the synthesis steps of ternary random polyether carboxylates disclosed in Example 6 of this invention. As can be seen from the figure, the synthesis of ternary random polyether carboxylates only requires putting all the necessary reactants together and letting them react together. There is no need to pay attention to the order of adding the substances, and the ternary random polyether carboxylates viscosity reducer is obtained.

[0092] Figure 3 The image shows the FT-IR spectrum of the amphoteric polyether carboxylate viscosity reducer containing polyether segments disclosed in Example 4 of this invention; as can be seen from the image, 3318.24 cm⁻¹ -1 The absorption peak at 2878.18 cm⁻¹ is the stretching vibration of the carboxyl hydroxyl group. -1 The peak at 1453.09 cm⁻¹ is the absorption peak of the stretching vibration of the methyl group. -1 The peak at 1106.51 cm⁻¹ is the absorption peak of the bending vibration of the methylene group. -1 The peak at this point is the absorption peak of the stretching vibration of the C=S bond. Based on the above characteristic absorption peaks, we can basically confirm that the target viscosity reducer has been obtained.

[0093] Example 5

[0094] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0095] 1) Weigh 0.0078g of AIBN and 0.4836g of BDATT (the molar ratio of AIBN to BDATT is 1:6), weigh 17.151g of APEG600, dissolve them in 40.02g of water, and add all three to a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for half an hour, turn on the cooling water, raise the temperature to 80℃, and stir the reaction for 6 hours.

[0096] 2) Weigh 0.0313g of AIBN and add it to a three-necked flask. Weigh 8.2325g of AA, dissolve it in 19.21g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of not less than 2 hours, and continue stirring to react for 6 hours.

[0097] 3) Weigh 0.0078g of AIBN and add it to a three-necked flask. Weigh 4.6165g of DADMAC, dissolve it in 10.77g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of not less than 2 hours and continue stirring the reaction for 6 hours.

[0098] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0099] Example 6

[0100] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0101] 1) Weigh 17.151g of APEG600, dissolve it in 40.02g of water, and add it to a 250mL three-necked flask.

[0102] 2) Weigh 0.0469g of AIBN and 0.2418g of BDATT and add them together with the mixture from step 1) into a three-necked flask; weigh 8.2325g of AA and dissolve it in 19.21g of water; weigh 4.6165g of DADMAC and dissolve it in 10.77g of water.

[0103] 3) Transfer the dissolved monomer from step 2 into a syringe of appropriate size. Place the reactor in a magnetically stirred oil bath, purge nitrogen into the flask for half an hour, turn on the cooling water, raise the temperature to 80°C, turn on the syringe, and add the monomer dropwise over a period of not less than 2 hours. Stir the reaction for 6 hours.

[0104] 4) Transfer the product after the reaction to a beaker, and after it cools to room temperature, adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary random polyether carboxylate crude oil viscosity reducer.

[0105] Example 7

[0106] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0107] 1) Weigh 0.0060g of dimethyl azobisisobutyrate and 0.1800g of dithiocarbamate, weigh 15g of APEG600, dissolve them in 35g of water, and add all three into a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen gas for 0.5 hours, turn on the cooling water, raise the temperature to 75℃, and stir the reaction for 6 hours.

[0108] 2) Weigh 0.0060g of dimethyl azobisisobutyrate and add it to a three-necked flask. Weigh 3g of DADMAC, dissolve it in 7g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of 2 hours and continue stirring the reaction for 6 hours.

[0109] 3) Weigh 0.02g of dimethyl azobisisobutyrate and add it to a three-necked flask. Weigh 8g of AA, dissolve it in 18g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of not less than 2 hours, and continue stirring to react for 6 hours.

[0110] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0111] Example 8

[0112] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0113] 1) Weigh 0.0078g of AIBN and 0.2418g of BDATT, weigh 17.151g of APEG600, dissolve them in 40.02g of water, and add all three to a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for 1 hour, turn on the cooling water, raise the temperature to 80℃, and stir the reaction for 7 hours.

[0114] 2) Weigh 0.0078g of AIBN and add it to a three-necked flask. Weigh 4.6165g of DADMAC, dissolve it in 10.77g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of 3 hours and continue stirring the reaction for 7 hours.

[0115] 3) Weigh 0.0313g of AIBN and add it to a three-necked flask. Weigh 9g of AA, dissolve it in 20g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of 3 hours and continue stirring the reaction for 7 hours.

[0116] 4) Transfer the reacted product into a beaker and let it cool to room temperature. Then adjust the pH to 7.5 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0117] Example 9

[0118] A method for preparing an amphoteric polyether carboxylate viscosity reducer containing polyether segments includes the following steps:

[0119] 1) Weigh 0.0080g of benzoyl peroxide and 0.2500g of xanthate, weigh 18g of APEG600, dissolve them in 42g of water, and add all three into a 250mL three-necked flask. Place the reactor in a magnetically stirred oil bath, purge the flask with nitrogen for 1 hour, turn on the cooling water, raise the temperature to 85℃, and stir the reaction for 8 hours.

[0120] 2) Weigh 0.0080g of benzoyl peroxide and add it to a three-necked flask. Weigh 5g of DADMAC, dissolve it in 12g of water, and transfer it into a syringe of appropriate size. Add the DADMAC dropwise over a period of 4 hours and continue stirring for 8 hours.

[0121] 3) Weigh 0.04g of benzoyl peroxide and add it to a three-necked flask. Weigh 10g of AA, dissolve it in 22g of water, and transfer it into a syringe of appropriate size. Add the AA dropwise over a period of 4 hours and continue stirring the reaction for 8 hours.

[0122] 4) Transfer the product after the reaction to a beaker, and after it cools to room temperature, adjust the pH to 8 with a 30% NaOH aqueous solution to obtain an amphoteric polyether carboxylate viscosity reducer containing polyether segments, namely a ternary block polyether carboxylate crude oil viscosity reducer.

[0123] Example Effect Description

[0124] The selected heavy oil is North China heavy oil, with a viscosity of 4893 mPa·s at a reservoir temperature of 50℃.

[0125] Test temperature: 50℃.

[0126] Emulsion concentration: 10g / L.

[0127] Test methods: The viscosity reduction and wetting properties of the obtained polyether carboxylate were characterized using a viscometer, surface tension meter and contact angle meter, and the structure was characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy.

[0128] Apparent viscosity test of crude oil in North China:

[0129] The viscosity of crude oil from North China was measured using a digital viscometer manufactured by Brookfield Laboratories, USA. Since viscosity is significantly affected by temperature, the crude oil was heated to the test temperature and stabilized for 5–10 minutes before measurement to prevent interference from temperature fluctuations. The viscosity reduction rate was determined according to the China National Offshore Oil Corporation (CNOOC) enterprise standard Q / HS2052—2009, "Implementation Specification for Chemical Viscosity Reduction Process of Heavy Oil". Oil samples were taken from the target wellhead, dehydrated, and degassed. The crude oil viscosity η1 was measured at a specific temperature. A viscosity reducer was prepared into a solution of the target concentration using water samples from the target well. The crude oil and the prepared solution were thoroughly mixed in a specific ratio, and the viscosity η2 of the crude oil emulsion at that temperature was measured. The viscosity reduction rate M was calculated using the following formula.

[0130] M = (η1 - η2) / η1 × 100%

[0131] Surface tension test of crude oil viscosity reducer:

[0132] The surface tension of surfactant solutions of various concentrations was tested using the platinum plate method. The test procedure was as follows: a platinum plate, which had been heated red-hot with an alcohol lamp to remove carbon, was hung on the plate. The liquid to be tested was poured into a watch glass on the worktable. The "up" button was pressed, and the worktable slowly rose, immersing the platinum plate in the liquid. Once equilibrium was reached, the readings were taken and recorded.

[0133] Contact angle test of crude oil viscosity reducer:

[0134] A layer of the oil sample to be tested is evenly coated on a glass slide, heated and melted over an alcohol lamp, and then cooled to solidify. The coating surface is kept flat and parallel to the lens angle of view to obtain relatively reliable results. The sample stage is adjusted to a suitable position and the focus is adjusted for testing. The solution to be tested is slowly dripped onto the surface of the oil sample using a micro-injection needle. When the droplet is in stable contact with the oil surface, the image is frozen and saved. The contact angle is determined using the five-point method, with an adjustment accuracy of 0.05°.

[0135] Table 1. Comparison of emulsion performance of amphoteric polycarboxylate viscosity reducers containing polyether segments prepared in Examples 1-6 with heavy oil.

[0136] Example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Viscosity value (mPa·s) 67 108 55 47 49 145 Viscosity reduction rate (%) 98.67 97.80 98.88 99.04 99.00 97.04 Surface tension (mN / m) 61.26 61.90 60.02 59.18 59.96 63.16 Contact angle (°) 111.89 113.68 108.76 102.71 104.09 117.83

[0137] Table 1 compares the performance of emulsions formed with heavy oil by the amphoteric polycarboxylate viscosity reducers containing polyether segments prepared in Examples 1-6. As can be seen from Table 1, the synthesized amphoteric polycarboxylate viscosity reducers containing polyether segments exhibit significant viscosity-reducing effects, with viscosity reduction rates exceeding 97%. A comparison of data from Examples 1 and 2 shows that the optimal monomer addition order is viscosity reducer number ①, namely APEG600, AA, and DADMAC. A comparison of data from Examples 1, 3, 4, and 5 shows that the optimal amount of chain transfer agent is the viscosity reducer from Example 4 (AIBN:BDATT molar ratio = 1:5), i.e., the chain transfer agent accounts for 0.83% of the total monomer molar amount. A comparison of data from the examples in Table 1 shows that the block copolymers all outperform the random copolymers.

[0138] This invention utilizes RAFT polymerization to synthesize a series of zwitterionic surfactants containing polyether carboxylates from water-soluble monomers acrylic acid (AA), polyoxyethylene ether (PEG), and cationic olefin monomers under the action of the initiator azobisisobutyronitrile (AIBN) and a chain transfer agent. Compared with traditional free radical polymerization, the polycarboxylate dispersants produced by this technology have a precisely controllable structure and superior viscosity-reducing performance. These zwitterionic polyether carboxylates can achieve a viscosity reduction rate of over 97% for heavy oil. This provides a novel and highly efficient viscosity reducer for the extraction and transportation of viscous crude oil. This invention provides a theoretical basis for the application of polycarboxylate polymeric surfactants in the viscosity reduction of heavy oil. This research not only provides a theoretical foundation for applying more polymeric surfactants to the viscosity reduction of heavy oil but also provides a new method for the extraction and viscosity reduction of heavy oil. Block-type polyether polycarboxylate zwitterionic surfactants combine the advantages of both anionic and cationic surfactants and can be used as highly efficient emulsifying viscosity reducers for heavy oil. RAFT (Reversible Addition-Fragmentation Chain Transfer) radical polymerization is becoming a research hotspot in the field of radical polymerization due to its unique advantages such as mild operating conditions and a wide range of monomer options.

[0139] This invention addresses the high viscosity and poor low-temperature fluidity of heavy oil from the North China Oilfield. It utilizes the RAFT polymerization method to prepare a series of polyether carboxylate zwitterionic surfactants by combining three monomers: acrylic acid (AA), allyl polyoxyethylene ether (APEG) 600, and diallyl dimethyl ammonium chloride (DADMAC) under the action of azobisisobutyronitrile (AIBN) as the initiator and S-S'-bis(a,a'-dimethyl-a”-acetic acid)-trithiocarbonate (BDATT) as the chain transfer agent, according to different monomer addition sequences and chain transfer agent dosages. The viscosity-reducing and wetting properties of the obtained polyether carboxylates were characterized using a viscometer, surface tension meter, and contact angle meter, combined with infrared spectroscopy. The structure was characterized using spectrometers and proton nuclear magnetic resonance spectrometers. The order of monomer addition, ratio, and amount of chain transfer agent were analyzed and compared with those of traditional random copolymers. The study determined the optimal synthesis process conditions and structure: the optimal monomer addition order for the polyether carboxylate crude oil viscosity reducer was APEG600, AA, and DADMAC. Based on the optimal monomer addition order, the optimal amount of chain transfer agent was 0.83% of the total molar amount of monomers. Compared with the performance of traditional random copolymers, the performance was significantly improved. The optimal polyether carboxylate prepared and applied to heavy oil in the North China Oilfield achieved a viscosity reduction rate of up to 99.04%, exploring a feasible polymerization method for developing novel chemical viscosity reducers.

[0140] In summary, the content of this invention is not limited to the embodiments listed. Any equivalent modifications made by those skilled in the art to the technical solutions of this invention by reading this specification are covered by the claims of this invention.

[0141] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A process for the preparation of an amphoteric polyether carboxylate salt viscosity reducer containing polyether segments, characterized in that, The method comprises the following steps: The initiator is divided into three parts, the first part of initiator is mixed with chain transfer agent and allyl polyoxyethylene ether solution, nitrogen is introduced, after the first stirring reaction, the second part of initiator is added, then diallyl dimethyl ammonium chloride solution is added, after the second stirring reaction, the third part of initiator is added, finally, acrylic acid solution is slowly added, after the third stirring reaction, the pH value is adjusted to 7-8, and the amphoteric polyether carboxylate viscosity reducer containing polyether segment is obtained; The initiator is one of azobisdimethylamino propanesulfonic acid hydrochloride, azobisdimethylformamide and dibenzoyl peroxide; the chain transfer agent is trithiocarbonic acid ester; The molar ratio of the first part of initiator: the second part of initiator: the third part of initiator is 1:1:(3-5); The amphoteric polyether carboxylate viscosity reducer containing polyether segment is a ternary block polyether carboxylate; The acrylic acid solution is prepared by dissolving 8-10 g of acrylic acid in 18-22 g of water; the diallyl dimethyl ammonium chloride solution is prepared by dissolving 4-6 g of diallyl dimethyl ammonium chloride in 9-14 g of water; the allyl polyoxyethylene ether solution is prepared by dissolving 15-18 g of allyl polyoxyethylene ether in 35-42 g of water; The molar ratio of the first part of initiator: chain transfer agent: allyl polyoxyethylene ether: diallyl dimethyl ammonium chloride: acrylic acid is 1:(4-6):1:1:(3-5).

2. The process for the preparation of the amphoteric polyether carboxylate salt viscosity reducer containing polyether segments according to claim 1, characterized in that, The nitrogen is introduced for 0.5-1.0 h; the diallyl dimethyl ammonium chloride solution is added for 2.0-4.0 h; the acrylic acid solution is added for 2.0-4.0 h.

3. The process for the preparation of amphoteric polyether carboxylate salt viscosity reducer containing polyether segment as claimed in claim 1 wherein, The temperature of the first stirring reaction is 75-85℃, and the time is 6.0-8.0 h; the temperature of the second stirring reaction is 75-85℃, and the time is 6.0-8.0 h; the temperature of the third stirring reaction is 75-85℃, and the time is 6.0-8.0 h.

4. The process for preparing the polyether segment-containing amphoteric polyether carboxylate viscoslty reducer according to claim 1, characterized in that, The pH value is adjusted to 7-8 by using 30% NaOH aqueous solution.

5. Use of the amphoteric polyether carboxylate salt viscosity reducer containing polyether segments, prepared by the method according to any one of claims 1 to 4, in the exploitation and viscosity reduction of thick oil, characterized in that, The viscosity reduction rate is 97.04%-99.04%.

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