Preparation method and application of comb-type high-temperature-resistant and salt-resistant polycarboxylic friction reducer

Abstract

The present application relates to oil well cement admixture technical field, disclose a kind of comb type high-temperature-resistant salt-resistant polycarboxylic drag reducer preparation method and application.The preparation method with ether macromolecular monomer, unsaturated monomer containing carboxyl, unsaturated monomer containing sulfonic acid group as main raw material, using oxidation-reduction initiation system and chain transfer agent, by solution droping copolymerization mode, the comb polymer with carboxyl and sulfonic acid group in main chain, and with polyether long side chain is synthesized.The present application introduces sulfonic acid group and long polyether side chain in polymer molecule simultaneously, using the salt-resistant ability of sulfonic acid group and the physical shielding effect of side chain to main chain form double salt-resistant mechanism, solve the main use ketone aldehyde drag reducer in high temperature high salt oil well cement slurry at room temperature insufficient drag reduction performance slurry high temperature again excessive dilution slurry unstable and current building polycarboxylic drag reducer not high temperature, not salt technical problem.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil well cement admixture, in particular to a preparation method and application of a comb-type high-temperature-resistant and salt-resistant polycarboxylic acid drag-reducing agent. BACKGROUND

[0002] In the process of oil and gas exploitation, cementing operation is a key procedure to ensure the integrity of well structure and isolate different formation fluids. Oil well cement slurry needs to be injected into the annulus between well wall and casing through long-distance pumping in high-temperature and high-pressure downhole environment. In order to ensure the pumping performance of cement slurry, it is necessary to add a drag-reducing agent (also known as water-reducing agent or dispersant) to reduce its flow viscosity.

[0003] Polycarboxylic acid drag-reducing agent has been widely used in conventional construction field due to its strong designability of molecular structure and high drag-reducing efficiency, and has been gradually tried to be used in oil well cement system. However, the working conditions of oil well are much harsher than the conventional construction environment, and the existing polycarboxylic acid drag-reducing agent directly applied to oil well cement slurry faces severe challenges. The high-temperature environment in the deep downhole will accelerate the movement of polymer molecules and may cause thermal degradation, especially the space steric structure of polyether side chain in polycarboxylic acid molecules will be destroyed, and the adsorption strength of carboxyl groups on the main chain on the surface of cement particles will be weakened, resulting in a sharp decline in the performance of the drag-reducing agent at high temperature.

[0004] In addition, salt-containing formation water or seawater is often used in the preparation of oil well cement slurry, and a large amount of calcium ions will be released during the hydration process of cement, forming a high-salt, especially high-divalent cation, system. In this environment, on the one hand, high ionic strength will produce salting-out effect, compressing the hydration layer of polymer molecules, making them curl or even fail in solution; on the other hand, a large amount of calcium ions will complex with carboxyl functional groups on the polymer main chain, causing the polymer molecular chain to be "bridged" and lose the dispersion ability. At the same time, the production process of some traditional drag-reducing agents may involve formaldehyde and other environmentally unfriendly substances, which does not conform to the current development direction of green chemical industry.

[0005] Therefore, it is a technical problem to be solved in the field to develop a polycarboxylic acid drag-reducing agent that can maintain stable structure and performance in high-temperature and high-salt downhole environment, and the preparation process is more environmentally friendly. SUMMARY

[0006] The summary part of the present application aims to solve the technical problems of polycarboxylic acid drag-reducing agent in the prior art, such as rapid performance decay in high-temperature and high-salt (especially in divalent ion-containing salt solution) environment, and unstable drag-reducing effect, thereby providing a comb-type polycarboxylic acid drag-reducing agent that can maintain stable structure and performance in high-temperature and high-salt oil well cement slurry system, as well as a preparation method and application thereof.

[0007] In a first aspect, this application provides a method for preparing a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent, employing the following technical solution:

[0008] A method for preparing a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent includes the following steps:

[0009] Dissolve the ether macromolecular monomer in water to prepare a base solution;

[0010] Dissolve the initiator in water to prepare solution A;

[0011] Solution B is prepared by dissolving an unsaturated monomer containing a carboxyl group, an unsaturated monomer containing a sulfonic acid group, a reducing agent, and a chain transfer agent in water.

[0012] After heating the base liquid to the preset reaction temperature, solution A and solution B are simultaneously added dropwise under stirring. After the addition is complete, the reaction is continued to be carried out at the temperature for 2-4 hours. Then, the mixture is cooled and the pH value is adjusted to 6-7 to obtain the polycarboxylate drag reducer.

[0013] By employing the above-mentioned technical solution, this preparation method initiates polymerization at a relatively low temperature using a redox initiation system (composed of an initiator and a reducing agent). This mild reaction condition facilitates control of polymer chain growth and reduces side reactions. Simultaneously, the molecular weight and distribution of the polymer are controlled by introducing a chain transfer agent. The polymerization reaction copolymerizes ether macromonomers with long polyoxyethylene ether side chains, unsaturated monomers containing carboxyl groups that provide the main adsorption sites, and unsaturated monomers containing sulfonic acid groups that provide strong electrostatic repulsion and resistance to divalent ions onto the same molecular backbone. In the resulting comb-shaped polymer structure, the long polyoxyethylene ether side chains provide steric hindrance, and the sulfonic acid groups provide strong electrostatic repulsion. Their synergistic effect allows the polymer molecules to remain extended in high-temperature, high-salt-concentration aqueous solutions, thereby achieving a sustained drag reduction effect in oil well cement slurry systems.

[0014] Preferably, the raw materials used in the method and their weight parts are as follows:

[0015] 200-300 parts of ether macromolecular monomers;

[0016] 40-50 parts of unsaturated monomers containing carboxyl groups;

[0017] 10-20 parts of unsaturated monomers containing sulfonic acid groups;

[0018] 5-10 parts of initiator;

[0019] 0.2-1.0 parts of reducing agent;

[0020] Chain transfer agent 0.5-1.5 parts.

[0021] By employing the above technical solution, the proportions of the components allow the synthesized polymer to possess suitable side chain lengths, main chain charge densities, and molecular weights. This specific range of combinations ensures effective polymer adsorption on the surface of cement particles, as well as sufficient steric hindrance and electrostatic repulsion between particles, thereby achieving the regulation of the rheological properties of cement paste.

[0022] Preferably, the ether macromonomer is methyl allyl polyoxyethylene ether; the carboxyl-containing unsaturated monomer is a combination of two or three of acrylic acid, itaconic acid, and maleic anhydride; the sulfonic acid-containing unsaturated monomer is one or two of 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate. The initiator is ammonium persulfate, the reducing agent is ascorbic acid, and the chain transfer agent is mercaptoacetic acid.

[0023] By employing the above technical solutions and selecting the specific monomers, initiators, reducing agents, and chain transfer agents, these raw materials possess definite reactivity and functional group characteristics. Methyl allyl polyoxyethylene ether provides stable polyether side chains; acrylic acid, itaconic acid, and maleic anhydride provide carboxyl functional groups with varying reactivity; 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate provide strong sulfonic acid groups insensitive to calcium ions. The redox system composed of ammonium persulfate and ascorbic acid can stably generate free radicals in the aqueous phase. Thioglycolic acid, as a chain transfer agent, has a moderate chain transfer constant, effectively controlling the molecular weight.

[0024] Preferably, in the step of preparing the base liquid, the weight ratio of the ether macromolecular monomer to water is 1:1.

[0025] By adopting the above technical solution, the base liquid prepared at this weight ratio has a moderate viscosity, which ensures the complete dissolution of ether macromolecular monomers and facilitates uniform mixing and heat conduction of materials during subsequent dripping.

[0026] Preferably, the weight ratio of the initiator to the reducing agent is (10-25):1.

[0027] By adopting the above technical solution, the weight ratio range controls the generation rate of free radicals in the system, enabling the polymerization reaction to be initiated and carried out smoothly and continuously, avoiding local burst polymerization caused by excessively fast initiation rate or incomplete reaction caused by excessively slow initiation rate.

[0028] Preferably, the preset reaction temperature is 40-60℃; the dropping time for simultaneously adding solution A and solution B is 25-35 minutes; and the reaction is continued at the temperature for 2-4 hours after the dropping is completed.

[0029] By adopting the above technical solution, the combination of the above process parameters provides suitable reaction conditions for the polymerization reaction. The temperature range of 40-60℃ matches the active range of the selected redox initiation system; the dropping time of 25-35 minutes ensures that the monomer can participate uniformly in the growth of the polymerization chain; and the holding time of 2-4 hours ensures a high conversion rate of the monomer, thereby obtaining the target product.

[0030] Secondly, this application provides an application of a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent, employing the following technical solution:

[0031] An application of a comb-type high-temperature and salt-resistant polycarboxylate drag reducer involves using the polycarboxylate drag reducer obtained according to any of the preceding preparation methods in the preparation of oil well cement slurry.

[0032] By employing the above-mentioned technical solution, the prepared comb-shaped polycarboxylate drag reducer is added to oil well cement slurry, where the drag reducer molecules are adsorbed onto the surface of cement particles. The long polyether side chains in its comb-shaped structure form a steric hindrance layer, while the sulfonic acid and carboxyl groups on the main chain impart a negative charge to the particle surface, generating electrostatic repulsion. Under this dual effect, the flocculated structure inside the cement slurry is disintegrated, releasing bound water and thus reducing the apparent viscosity and flow resistance of the cement slurry. This effect reduces the pump pressure required to achieve the same discharge rate during pumping, thereby reducing construction energy consumption and equipment load.

[0033] This invention provides a method for preparing and applying a comb-shaped high-temperature and salt-resistant polycarboxylate drag-reducing agent. It offers the following advantages:

[0034] 1. The comb-type polycarboxylate drag reducer prepared in this invention exhibits excellent high-temperature resistance. The carboxyl groups on its polymer backbone can form a strong chemical adsorption on the surface of cement particles, and this adsorption remains stable under high-temperature conditions. Simultaneously, the long polyether side chains introduced by methyl allyl polyoxyethylene ether possess high thermal stability, maintaining the extended conformation of the molecules even at high temperatures. Through a continuous and effective steric hindrance effect, it prevents cement particles from agglomerating due to intensified thermal motion, thereby ensuring the dispersion performance of the drag reducer under high-temperature conditions.

[0035] 2. The comb-type polycarboxylic acid drag reducer prepared in this invention possesses a dual salt resistance mechanism. First, by copolymerizing and introducing sulfonic acid groups onto the polymer backbone, these groups exhibit strong hydration capabilities and are insensitive to divalent cations, effectively resisting the shrinkage effect of salting out on the polymer molecular chain under high salt concentration environments. Second, the long polyether side chains form a physical shield against the backbone in the molecular structure. This steric hindrance effect prevents high-valent cations such as calcium ions in the slurry from undergoing complexation reactions with the carboxyl groups on the backbone, thereby protecting the functional integrity of the polymer and endowing the drag reducer with excellent salt resistance and divalent ion resistance.

[0036] 3. The preparation method of this invention possesses both technological advantages and environmental friendliness. This method employs a redox initiation system, allowing the polymerization reaction to proceed under mild, low-temperature conditions, avoiding high-temperature side reactions and ensuring efficient synthesis of the target comb structure and consistent product performance. Furthermore, the monomer raw materials and reaction system used in this method are free of harmful substances such as formaldehyde, and the resulting product requires no additional addition of heavy metal ions during use, thus reducing the environmental impact of the entire preparation and application process. Attached Figure Description

[0037] Figure 1 Thickening curve of commercially available building polycarboxylate drag reducer at 85°C;

[0038] Figure 2 This is a thickening curve of PCE-2, the product of Example 2 of the present invention, at 85°C. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to comparative examples and test cases. 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 are within the scope of protection of the present invention.

[0040] Examples 1-3:

[0041] Example 1: Synthesis of comb-type high-temperature and salt-resistant polycarboxylate drag reducer PCE-1

[0042] In a four-necked flask equipped with a stirrer, a reflux condenser, and a dropping funnel, add 200g of methyl allyl polyoxyethylene ether (HPEG) and 200g of water, stir to dissolve, and use as the base solution.

[0043] In another beaker, dissolve 5g of ammonium persulfate in 50g of water to make solution A.

[0044] Take another beaker and dissolve 20g of acrylic acid, 20g of itaconic acid, 10g of sodium p-styrenesulfonate, 0.2g of ascorbic acid and 0.5g of mercaptoacetic acid in 100g of water to make solution B.

[0045] After heating the base solution to the set temperature, solutions A and B are simultaneously and uniformly added dropwise over a period of 30 minutes. After the addition is complete, the reaction is maintained at the same temperature for another 2 hours. After the reaction is complete, the solution is cooled to room temperature, and the pH of the product is adjusted to 6-7 using an alkaline solution to obtain the polycarboxylate drag reducer PCE-1.

[0046] Example 2: Synthesis of comb-type high-temperature and salt-resistant polycarboxylate drag reducer PCE-2

[0047] In a four-necked flask equipped with a stirrer, reflux condenser and dropping funnel, add 250g of methyl allyl polyoxyethylene ether (HPEG) and 250g of water, stir to dissolve, and use as the base solution.

[0048] In a separate beaker, dissolve 7.5g of ammonium persulfate in 50g of water to prepare solution A.

[0049] Take another beaker and dissolve 25g acrylic acid, 10g maleic anhydride, 10g itaconic acid, 10g 2-acrylamido-2-methylpropanesulfonic acid, 5g sodium p-styrenesulfonate, 0.6g ascorbic acid and 1.0g mercaptoacetic acid in 100g water to prepare solution B.

[0050] After heating the base solution to the set temperature, solutions A and B are simultaneously and uniformly added dropwise over a period of 30 minutes. After the addition is complete, the reaction is maintained at the same temperature for another 3 hours. After the reaction is complete, the solution is cooled to room temperature, and the pH of the product is adjusted to 6-7 using an alkaline solution to obtain the polycarboxylate drag reducer PCE-2.

[0051] Example 3: Synthesis of comb-type high-temperature and salt-resistant polycarboxylate drag reducer PCE-3

[0052] In a four-necked flask equipped with a stirrer, reflux condenser and dropping funnel, add 300g of methyl allyl polyoxyethylene ether (HPEG) and 300g of water, stir to dissolve, and use as the base solution.

[0053] In a separate beaker, dissolve 10g of ammonium persulfate in 50g of water to prepare solution A.

[0054] Take another beaker and dissolve 30g of acrylic acid, 20g of maleic anhydride, 20g of 2-acrylamido-2-methylpropanesulfonic acid, 1.0g of ascorbic acid and 1.5g of mercaptoacetic acid in 100g of water to prepare solution B.

[0055] After heating the base solution to the set temperature, solutions A and B are simultaneously and uniformly added dropwise over a period of 30 minutes. After the addition is complete, the reaction is maintained at the same temperature for another 4 hours. After the reaction is complete, the solution is cooled to room temperature, and the pH of the product is adjusted to 6-7 using an alkaline solution to obtain the polycarboxylate drag reducer PCE-3.

[0056] Comparative Examples 1-4:

[0057] Comparative Example 1: Preparation of polycarboxylic acid drag reducer PCE-C1 without sulfonic acid groups

[0058] Compared with Example 2, the difference is that no unsaturated monomers containing sulfonic acid groups are added in the preparation of Solution B (i.e., no 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate are added), and their total amount of 15 parts by weight is replaced with an equal part by weight of acrylic acid. The remaining raw material ratios and preparation processes are the same.

[0059] Comparative Example 2: Preparation of polycarboxylate drag reducer PCE-C2 without chain transfer agent

[0060] Compared with Example 2, the difference is that no chain transfer agent (thioglycolic acid) is added in the preparation of solution B, while the other raw material ratios and preparation processes are the same.

[0061] Comparative Example 3: Preparation of polycarboxylate drag reducer PCE-C3 with main monomer ratios not within the scope of this invention

[0062] Compared with Example 2, the difference is that the amount of ether macromonomer (HPEG) is reduced to 150 parts by weight, which is lower than the range of 200-300 parts defined in this invention. The other raw material ratios and preparation processes are the same.

[0063] Test Example 1-3:

[0064] Test Example 1: Performance Evaluation of the Polycarboxylate Drag Reduction Agent of the Present Invention

[0065] This test case aims to verify the basic properties of the polycarboxylate drag reducer prepared by the method of the present invention in oil well cement slurry, including its dispersion ability in freshwater systems, its performance retention ability under high temperature conditions, and its suitability in brine environments.

[0066] The experimental steps are as follows:

[0067] Cement slurry preparation: According to GB / T19139-2012 "Test Methods for Oil Well Cement", weigh Grade G oil well cement and prepare cement slurry with a water-cement ratio of 0.44. For the freshwater system, use deionized water; for the brine system, use a saturated sodium chloride solution.

[0068] Sample grouping and admixture: A blank control group without any drag-reducing agent was set up. Three other experimental groups were set up, with polycarboxylate drag-reducing agents PCE-1, PCE-2, and PCE-3 prepared in Examples 1, 2, and 3 respectively added to the cement slurry. The dosage of all drag-reducing agents was calculated based on their solid content, which was 0.2% of the cement mass.

[0069] Cement slurry preparation and rheological property testing:

[0070] The test method follows the specifications of GB / T19139-2012. The test is conducted in three stages:

[0071] (a) Initial performance test: The plastic viscosity (PV) and yield point (YP) of the freshly prepared freshwater cement slurry were tested at room temperature.

[0072] (b) High-temperature performance test: The freshly prepared freshwater cement slurry sample was placed in the test cup of the high-temperature and high-pressure rheometer, heated to 85°C according to the set heating program, and after stabilizing at this temperature, its rheological properties were tested directly at 85°C.

[0073] (c) Salt resistance test: Cement slurry was prepared using a saturated sodium chloride solution and its initial rheological properties were tested at room temperature.

[0074] The test results are recorded in Table 1.

[0075] Table 1. Rheological properties of cement paste produced by the embodiments of the present invention under different conditions.

[0076]

[0077] Summary: The test results in Table 1 show that the polymers (PCE-1, PCE-2, PCE-3) prepared by the method of this invention can significantly reduce the plastic viscosity and yield point of cement paste. This effect stems from the molecular structure of the polymers: the carboxyl groups on their main chain adsorb onto the surface of cement particles, while the grafted long polyoxyethylene ether side chains extend in the aqueous phase, hindering the aggregation of cement particles through steric hindrance, thereby keeping the entire suspension system in a dispersed state, macroscopically manifested as improved paste fluidity.

[0078] At a high temperature of 85°C, the rheological parameters of the cement slurry containing the polymer of this invention remained at a low level, while the blank control group could not be measured with stable data due to rapid thickening. This indicates that the polymer has excellent high-temperature stability. The mechanism is that the strongly adsorbent groups on the polymer backbone can be stably fixed to the surface of cement particles at high temperatures. At the same time, the long ether side chains with excellent thermal stability can maintain their extended conformation in the high-temperature environment, continuously providing effective steric hindrance, thereby inhibiting the accelerated flocculation of cement particles caused by high temperature.

[0079] In a brine system composed of saturated sodium chloride solution, the polymer of this invention still exhibits excellent control over the rheological properties of cement slurry. This is because the sulfonic acid groups introduced into the molecular structure, with their strong hydration capacity, help to form a stable hydration layer around the polymer molecules, effectively resisting the dehydration and compression effect of salt ions on the polymer chains. At the same time, the steric hindrance effect generated by the polyether side chains also hinders the contact and complexation between cations and the main chain carboxyl groups, jointly maintaining the dispersion performance of the polymer in a brine environment.

[0080] Test Example 2: Performance Comparison Evaluation

[0081] This test example aims to verify the functionality of specific technical features in the present invention by comparing the performance of the polycarboxylic acid drag reducer prepared in this invention (represented by product PCE-2 in Example 2) with comparative products with different structures and commercially available conventional drag reducers.

[0082] The experimental steps are as follows:

[0083] Test Groups: Set the following test groups:

[0084] This invention group: PCE-2 obtained in Example 2.

[0085] Comparative examples: PCE-C1, PCE-C2, and PCE-C3 prepared by comparative examples 1 to 3.

[0086] Existing technologies include: commercially available naphthalene-based high-efficiency water-reducing agents (sulfonated ketone aldehyde condensate) and commercially available calcium lignosulfonate.

[0087] Blank control group: No drag-reducing agents were added.

[0088] Cement slurry preparation and sample addition: Except for the blank control group, the drag-reducing agents of the other groups were prepared into cement slurry in fresh water system (deionized water) and salt water system (saturated sodium chloride solution) at a solid content of 0.2% of the cement mass.

[0089] Rheological performance comparison test:

[0090] Temperature resistance comparison test: The initial plastic viscosity (PV) and yield point (YP) of the cement slurry prepared in the fresh water system were first tested at room temperature. Then, the cement slurry samples were placed in a high temperature and high pressure rheometer, and their rheological parameters were directly measured at 85°C.

[0091] Salt resistance comparison: The initial plastic viscosity (PV) and yield point (YP) of the cement slurry prepared in the salt water system of each group were tested at room temperature.

[0092] The test results are recorded in Table 2.

[0093] Table 2. Performance Comparison Data of Different Drag-Reducing Agents in Cement Paste

[0094]

[0095] Summary: The data in Table 2 show that the comparison between sample PCE-2 and comparative sample PCE-C1 demonstrates the role of sulfonic acid groups in the molecule. In freshwater systems, their initial properties are similar; however, in saltwater systems, PCE-C1, which lacks sulfonic acid groups, exhibits significantly higher PV and YP values, and a marked decrease in dispersion performance. This confirms that introducing sulfonic acid groups is a key technique for maintaining the polymer's dispersion ability in saltwater environments. The comparison between PCE-2 and other comparative samples (PCE-C2, PCE-C3) demonstrates the necessity of using chain transfer agents and employing specific monomer ratio ranges to obtain polymers with targeted rheological control capabilities.

[0096] The difference in high-temperature stability between PCE-2 and existing samples (sulfonated ketone aldehyde condensate and calcium lignosulfonate) is reflected in the rheological parameters measured directly at 85°C. As shown in Table 2, the PV and YP values ​​of PCE-2 show limited increase at high temperatures, while the corresponding values ​​of sulfonated ketone aldehyde condensate and calcium lignosulfonate show significant increases. This result indicates that the comb-like structure of the present invention, with its main chain adsorption groups and the steric hindrance of the polyether side chains working synergistically, can still maintain effective dispersion of cement particles at high temperatures, and its performance retention is superior to that of drag-reducing agents based on traditional adsorption-electrostatic repulsion mechanisms.

[0097] In terms of salt resistance, the difference between PCE-2 and PCE-C1 is the most significant, directly reflecting the composition of the technical solution of this invention. PCE-C1, lacking a strong hydration center (sulfonic acid group) in its molecular chain, experiences a sharp decline in dispersion ability due to salt ions compressing its electric double layer and causing molecular chain curling at high salt concentrations. PCE-2, on the other hand, suppresses the negative impact of salt ions on the polymer molecular conformation and dispersion performance through the hydration of sulfonic acid groups in its molecular structure and the steric hindrance effect of the long polyether chain, thus maintaining the rheological parameters of the cement paste at a low level in saturated brine systems.

[0098] Test Example 3:

[0099] This test example aims to compare the performance of the polycarboxylate drag reducer prepared in this invention (represented by PCE-2 product of Example 2) with commercially available building polycarboxylate drag reducers. The amount added to cement at a solid content of 0.20% was tested according to GB / T19139-2012 to verify the function of specific technical features in the technical solution of this invention.

[0100] Table 3

[0101]

[0102] Summarize:

[0103] Table 3 shows that commercially available polycarboxylate drag reducers for construction exhibit good drag reduction effects at room temperature, but fail at high temperatures. (Appendix)Figure 1 This also indicates that commercially available drag-reducing agents reach a consistency of 30 BC at 85℃, exceeding the measurable range of a rotational viscometer. Upon inspection of the slurry cup from the thickener, the consistency was 100 BC, but it did not solidify, remaining in a thick but not solidified state. After stirring, it became a high-viscosity paste-like fluid. (See Table 3 and Appendix...) Figure 2 PCE-2 exhibits slight thickening at high temperatures, which helps maintain sedimentation stability, and its thickening curve is normal. Its rheological properties exceed the requirements of the SY / T5504.3-2018 standard for oil well cement drag reducers, while the dosage requirement is far less than 0.5%, indicating that its drag reduction efficiency is more than 2.5 times that of the standard requirement.

Claims

1. A method for preparing a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent, characterized in that, Includes the following steps: Methyl allyl polyoxyethylene ether, as a macromolecular monomer of the ether class, was dissolved in water to prepare a base solution; Prepare the initiator into solution A; Solution B is prepared by dissolving an unsaturated monomer containing a carboxyl group, an unsaturated monomer containing a sulfonic acid group, a reducing agent, and a chain transfer agent in water. After heating the base liquid to the preset reaction temperature, solution A and solution B are added dropwise simultaneously under stirring. After the addition is complete, the reaction is continued to be kept at the temperature for 2-4 hours. Then, the mixture is cooled and the pH value is adjusted to 6-7 to obtain the polycarboxylic acid drag reducer. The unsaturated monomer containing a carboxyl group is a combination of two or three of acrylic acid, itaconic acid and maleic anhydride. The unsaturated monomer containing a sulfonic acid group is one or both of 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate; The initiator is ammonium persulfate, the reducing agent is ascorbic acid, and the chain transfer agent is mercaptoacetic acid; The preset reaction temperature is 40-60℃; The raw materials and their weight parts used in the preparation method of the polycarboxylic acid drag reducer are as follows: 200-300 parts of ether macromolecular monomers; 40-50 parts of unsaturated monomers containing carboxyl groups; 10-20 parts of unsaturated monomers containing sulfonic acid groups; 5-10 parts of initiator; 0.2-1.0 parts of reducing agent; Chain transfer agent 0.5-1.5 parts; The weight ratio of the initiator to the reducing agent is (10-25):

1.

2. The method for preparing a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent according to claim 1, characterized in that, In the step of preparing the base liquid, the weight ratio of the ether macromolecular monomer to water is 1:

1.

3. The method for preparing a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent according to claim 1, characterized in that, The simultaneous addition of solution A and solution B takes 25-35 minutes.

4. The application of a comb-type high-temperature and salt-resistant polycarboxylate drag-reducing agent, characterized in that, The polycarboxylate drag reducer obtained by the preparation method according to any one of claims 1-3 is applied to the preparation of oil well cement slurry.

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