Composition, preparation and application of retarder for ultra-high temperature cementing

Abstract

The present invention relates to the composition, preparation and application of a retarder for ultra-high temperature cementing and cementing slurry. The synthetic monomers of the high temperature retarder include: 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), N,N-dimethylacrylamide (DMAA), and vinylphosphonic acid (VPA). The high temperature retarder contains a constituent unit A shown in Formula 1, a constituent unit B shown in Formula 2, a constituent unit C shown in Formula 3, and a constituent unit D shown in Formula 4. The ultra-high temperature retarder of the present invention has stable chemical properties and a temperature resistance of up to 250°C. While having high temperature resistance, it does not affect the sedimentation stability of cement slurry at high temperatures, can significantly prolong the thickening time of cement slurry at high temperatures, and the cement stone has higher early strength at low temperatures. It effectively solves the problem of reduced retarding effect caused by severe sedimentation of cement slurry at high temperatures, and can ensure the quality and safety of cementing construction.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well development, and in particular to an ultra-high temperature retarder suitable for oil and gas well cementing. The invention relates to a preparation method and application of an ultra-high temperature retarder suitable for deep well and ultra-deep well cementing. The ultra-high temperature retarder has an excellent retarding effect under ultra-high temperature environments of deep wells and ultra-deep wells, and has a significant right-angle thickening phenomenon. While ensuring sufficient thickening time, the cement slurry can have good settling stability, thereby meeting the requirements of cementing operations. Background Art

[0002] With the continuous exploitation of conventional shallow oil and gas resources in my country, most of these resources are nearing depletion, with limited recoverable reserves and an increasing challenge in increasing and stabilizing production. To increase crude oil production, future oil and gas exploration and development will gradually shift towards deep, ultra-deep wells, and complex formations. A key challenge in cementing deep and ultra-deep wells lies in the high formation temperatures. Cementing faces significant ultra-high temperature challenges, and effectively controlling the appropriate thickening time of the cement slurry is crucial. Furthermore, with the current demands for simplifying wellbore structure, reducing costs, and improving drilling efficiency, deep well cementing faces an increasing number of challenges. One of these is the cement slurry's settling stability. Common ultra-high temperature retarders currently have strong dispersibility, which reduces the initial consistency of the cement slurry after their addition, directly impacting cementing quality. This poses additional challenges to cementing engineering, particularly the design of cement slurries. Since cement slurry systems are designed based on bottom hole temperature, in order to ensure the safe pumping of cement slurry under ultra-high temperature conditions, a large amount of traditional ultra-high temperature retarders are usually added to prolong the thickening time, improve the rheological properties, and extend the pumping time. However, while the retarder adapts to the extremely high temperature and pressure environment, due to decomposition, the sedimentation stability of the cement slurry deteriorates, resulting in excessive dispersion and a significant decrease in consistency, resulting in a reduced retarding effect and severe sedimentation of the cement slurry.

[0003] Therefore, in the study of high-temperature cement slurry systems, the system's high-temperature stability is a critical indicator, not only affecting the safety of the cementing process but also its quality. At low temperatures, due to the cement slurry's strong suspension stability, sedimentation is not a significant issue. However, at high temperatures, the increased molecular motion within the cement slurry system reduces the intermolecular viscosity, deteriorating the system's suspension stability. This accelerates the sedimentation of high-density, low-specific-surface-area cement and admixture particles, leading to instability in the cement slurry system. Traditional high-temperature retarders have strong dispersibility, significantly reducing consistency. Severe sedimentation can lead to a reduction in the retarding effect.

[0004] As one of the three most important admixtures in cement slurry, retarders play a crucial role in controlling the setting time of cement slurry and maintaining its pumpability. They are particularly essential in high-temperature, high-pressure deep wells, where the thickening time of cement slurry is drastically shortened and cement strength decays significantly. Currently, the ultra-high-temperature retarders commonly used in cementing slurries include the following: lignin sulfonates and their derivatives, cellulose and its derivatives, hydroxycarboxylic acids and their salts, and inorganic acids (salts). However, these agents all suffer from shortcomings such as abnormal thickening at high temperatures, unstable quality, and temperature sensitivity. Furthermore, current ultra-high-temperature retarders can easily lead to over-dispersion of cement slurries, and they also have numerous deficiencies in controlling cement slurry sedimentation stability and developing low-temperature strength, hindering the effective guarantee of oil well cementing quality and safety.

[0005] CN106008844A discloses a heat-resistant and salt-tolerant retarder for well cementing. The retarder comprises sodium p-vinylbenzenesulfonate, acrylamide, itaconic acid, and dimethyldiallyl ammonium chloride. The mass ratio of sodium p-vinylbenzenesulfonate, acrylamide, itaconic acid, and dimethyldiallyl ammonium chloride is 12.5-15.0:12.5-15.0:12.5-15.0:4.0-5.0. This oil well cement retarder has excellent heat and salt resistance, but does not address the problem of cement slurry sedimentation stability at high temperatures and cannot prevent excessive dispersion of the cement slurry.

[0006] CN105061661B discloses a medium- and high-temperature retarder for oil well cement. The retarder comprises 10-25 wt% 2-acrylamido-2-methylpropanesulfonic acid, 20-35% acrylic acid, 10-35% itaconic acid, 5-10% N,N-dimethylacrylamide, and 15-35% acrylamide. The retarder is insensitive to dosage and exhibits a good linear relationship between dosage and thickening time, meeting the technical requirements of well cementing. However, the retarder's temperature resistance and the resulting strength of the cement paste are still insufficient.

[0007] In response to the problems with current retarders, a variety of synthetic polymers have been disclosed as oil well cement retarders, but they still have certain deficiencies in terms of sedimentation stability and low-temperature strength development. Currently, most of the polymer-based ultra-high temperature retarders studied and applied are still binary or multi-component copolymers of AMPS and other carboxyl-containing monomers, or other types of polymers, such as polymers containing sulfonic acid and carboxylic acid groups, and polymers containing phosphonic acid and carboxylic acid groups. Ultra-high temperature retarders still need improvement in terms of material grafting, modification, and synthetic polymer materials. In-depth research is needed on the properties of modified monomers. Based on the current research on AMPS multi-component copolymers, new temperature-resistant retarders containing multifunctional monomers are being actively developed. Therefore, in order to ensure the stability of cement slurry and the quality of cementing, a new ultra-high temperature retarder for oil well cement has been prepared. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of existing ultra-high temperature retarders, such as insufficient high-temperature resistance and difficulty controlling cement slurry sedimentation stability, by providing an ultra-high temperature retarder suitable for oil and gas well cementing and a preparation method thereof. This ultra-high temperature retarder can prevent sedimentation caused by deteriorating cement slurry stability.

[0009] To achieve the above objectives, the present invention discloses the composition, preparation, and application of an ultrahigh temperature retarder for cementing and an ultrahigh temperature resistant cementing slurry. The technical solutions are as follows:

[0010] The first aspect of the present invention provides an ultra-high temperature retarder, wherein the constituent monomers of the ultra-high temperature retarder include: 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), N,N-dimethylacrylamide (DMAA), and vinylphosphonic acid (VPA).

[0011] The synthetic monomers are composed of 40-60 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 10-25 parts by weight of acrylic acid (AA), 5.0-15 parts by weight of N,N-dimethylacrylamide (DMAA), and 15-30 parts by weight of vinylphosphonic acid (VPA).

[0012] The ultra-high temperature retarder synthesis process is as follows: first, remove oxygen from the reaction vessel, a ground-mouth three-necked flask, then add 40-60 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to 150-230 parts of deionized water, stir and blend in a stirrer, weigh 10-25 parts of acrylic acid (AA), 5.0-15 parts of N,N-dimethylacrylamide (DMAA), and 15-30 parts of vinylphosphonic acid (VPA), and add them to the stirrer and mix and stir to obtain a mixed reaction solution, which is poured into the ground-mouth three-necked flask; use NaOH solution to adjust the pH value of the reaction solution to 4-5, keep stirring, and rotate at 200-400 rpm until there is no precipitation. Finally, prepare the initiator solution, which needs to be added dropwise to the ground-mouth three-necked flask at a drop rate of 5-10 mL / min, maintain the reaction temperature at 50°C-60°C, stir the reaction for 4-6 hours, and allow it to cool naturally to obtain the ultra-high temperature retarder.

[0013] The ultra-high temperature retarder contains a structural unit A shown in Formula 1, a structural unit B shown in Formula 2, a structural unit C shown in Formula 3, and a structural unit D shown in Formula 4;

[0014]

[0015] Among them, R1, R2, R3 and R4 in the constituent unit A, constituent unit B, constituent unit C and constituent unit D are the same or different, and can be H, a substituted or unsubstituted alkyl group of C1-C4, or one of the constituent units A, B, C, D.

[0016] The total mass of the synthetic monomers is 25%-45% of the total mass of deionized water.

[0017] The oxygen in the reaction container is removed by filling nitrogen into the reaction container.

[0018] The initiator solution is a combination of an oxidant and a reducing agent, wherein the oxidant is potassium persulfate, ammonium persulfate or hydrogen peroxide, the reducing agent is sodium sulfite, sodium bisulfite or potassium borohydride, and the molar ratio of the oxidant to the reducing agent is 1-3:1-2.

[0019] The amount of the initiator used is 0.5-1.5% of the total mass of the synthesized monomers.

[0020] The second aspect of the present invention provides an ultra-high temperature resistant cementing slurry, wherein the ultra-high temperature resistant cementing slurry includes the ultra-high temperature retarder described above or the ultra-high temperature retarder prepared by the above method. Based on the total weight of the oil well cement in the cementing slurry, the amount of the ultra-high temperature retarder can be 0.5 to 2 weight%.

[0021] In terms of current general technology, the present invention has the following advantages:

[0022] 1. 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) is a commonly used water-soluble anionic monomer. The sulfonic acid group it contains keeps strong resistance to external acid, alkali and salt corrosion. The amide group also makes it have good hydrolysis stability and excellent thermal stability. The two groups work together to ensure the stability of the copolymerization product structure; vinylphosphonic acid (VPA) contains phosphoric acid groups. After the phosphoric acid groups are adsorbed on the surface of cement particles, they prevent the hydration of cement molecules; acrylic acid (AA) as a reactive monomer containing carboxyl groups increases ultra-high temperature retarding The adsorption capacity of the zwitterionic polymer retarder chain on cement particles hinders the hydration reaction of cement particles, prolonging the thickening time of the cement slurry while ensuring a clear right-angle thickening phenomenon. The N,N-dimethylacrylamide (DMAA) monomer has a double bond and an amide group. Driven by the two methyl groups attached to the nitrogen atom, a hyperconjugated system is formed between the nitrogen, carbonyl group, and double bond, resulting in excellent thermal stability. The phosphate groups in the vinylphosphonic acid (VPA) molecular structure can gradually form insoluble calcium phosphates by reacting with calcium ions in the cement slurry. These insolubles adhere to the surface of cement particles, preventing further cement hydration. 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) is used as the main framework of the zwitterionic polymer retarder group. Its excellent thermal stability can promote the stability and integrity of the retarder macromolecular group at ultra-high temperatures. Furthermore, the ultra-high temperature retarder maintains the dispersion and stability of cement particles, improves the slurry fluidity, and reduces the slurry consistency. This is very beneficial for on-site grouting, allowing the cement slurry to fully fill the casing space and avoid cross-well channeling.

[0023] 2. By introducing monomers with special configurations and non-degradable functional groups, such as sulfonic acid groups, carboxylic acid groups, and phosphonic acid groups, the resulting polymer has significantly improved heat resistance and can effectively prolong the thickening time of cement slurry.

[0024] 2. The ultra-high temperature retarder of the present invention has stable chemical properties and is resistant to ultra-high temperatures without affecting the sedimentation stability of cement slurry at high temperatures. It can effectively prolong the thickening time of oil well cement slurry, and the cement stone has high early strength at low temperatures. The retarder is suitable for cement slurry systems of various densities, and the comprehensive performance of the cement slurry is good. It is compatible with a variety of admixtures and has good compatibility.

[0025] 3. The raw materials for synthesizing the ultra-high temperature retarder are all common materials in the market, with a wide range of sources and low prices. The preparation conditions are not demanding and the preparation method is relatively simple. The success rate of synthesizing polymers is high, the conversion rate is high, and it is suitable for large-scale production and application.

[0026] In summary, the ultra-high temperature retarder of the present invention has excellent high temperature resistance, good comprehensive performance, mature and stable technology, wide material sources, good ultra-high temperature retarding effect, and can be widely used in cementing operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 This is a thickening curve diagram of Example 1 of the present invention at 250°C × 135 MPa when the retarder dosage is 1.0%;

[0029] Figure 2 Comparison of the thickening time of the cement slurries of Examples 1-3 and Comparative Examples 1-5 at 250°C x 135 MPa with a retarder dosage of 1.0%.

[0030] Figure 3 The compressive strength of the cement pastes of Example 1, Comparative Example 1 and Comparative Example 5 are obtained after curing for 2 days and 7 days at a low temperature of 60°C with a retarder dosage of 1.5%. DETAILED DESCRIPTION

[0031] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0032] The present invention provides an ultrahigh temperature retarder for cementing, wherein the ultrahigh temperature retarder comprises a structural unit A represented by formula 1, a structural unit B represented by formula 2, a structural unit C represented by formula 3, and a structural unit D represented by formula 4;

[0033]

[0034] Among them, R1, R2, R3 and R4 in the constituent unit A, constituent unit B, constituent unit C and constituent unit D are the same or different, and can be H, a substituted or unsubstituted alkyl group of C1-C4, or one of the constituent units A, B, C, D.

[0035] In the present invention, when R1, R2, R3 and R4 are each independently H, the 2-acrylamido-2-methylpropanesulfonic acid (AMPS) provides the structural unit A of formula 1 in the zwitterionic polymer retarder; the N,N-dimethylacrylamide (DMAA) provides the structural unit B of formula 2; the acrylic acid (AA) provides the structural unit C of formula 3; and the vinylphosphonic acid (VPA) provides the structural unit D of formula 4.

[0036] In the present invention, the formula of the cementing slurry is not specifically limited and can be conventionally selected by those skilled in the art. For example, the mass fractions of the components of the cementing slurry system used are specifically as follows:

[0037] Formula 1#: 100 parts of Jiahua G-grade cement + 0.2-2.0 parts of the ultra-high temperature retarder + 2 parts of defoamer + 44 parts of water;

[0038] Formula 2#: 100 parts of Jiahua G-grade cement + 50 parts of silica sand + 0.2-2.0 parts of the temperature-adaptive high-temperature retarder + 2 parts of defoaming agent + 44 parts of water.

[0039] 1. Composition, preparation and application of an ultra-high temperature retarder for cementing

[0040] The specific implementation methods of the present invention are described in detail with reference to the following specific examples and comparative examples to facilitate a comprehensive understanding of the technical achievements of the present invention.

[0041] Example 1

[0042] This embodiment provides an ultra-high temperature retarder for cementing, the formula of which is: by weight, 47.5 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 23 parts of acrylic acid (AA), 13 parts of N,N-dimethylacrylamide (DMAA), and 22 parts of vinylphosphonic acid (VPA);

[0043] The ultra-high temperature retarder synthesis process is as follows: first, remove the oxygen in the ground-mouth three-necked flask of the reaction vessel, then add 47.5 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to 200 parts of deionized water, stir and blend in a stirrer, weigh 23 parts of acrylic acid (AA), 13 parts of N,N-dimethylacrylamide (DMAA), and 22 parts of vinylphosphonic acid (VPA), also add them to the stirrer and mix and stir to obtain a mixed reaction solution, which is poured into the ground-mouth three-necked flask; use NaOH solution to adjust the pH value of the reaction solution to 4-5, preferably, pH 4, keep stirring, and keep the speed at 200-400rpm, preferably, 300rpm, until there is no precipitation. Finally, prepare the initiator solution, which needs to be added dropwise to the ground-mouth three-necked flask at a drop rate of 5-10mL / min, maintain the reaction temperature at 60°C, stir the reaction for 4h, and let it cool naturally to obtain the ultra-high temperature retarder, named H1.

[0044] The initiator is a mixture of ammonium persulfate and sodium bisulfite, the molar ratio of which is 1:1, and the amount of the initiator added is 1.2% of the total weight of the monomers.

[0045] Example 2

[0046] This embodiment provides an ultra-high temperature retarder for cementing, which has a formula of: 53 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 18.7 parts by weight of N,N-dimethylacrylamide (DMAA), 8 parts by weight of acrylic acid (AA), and 30 parts by weight of vinylphosphonic acid (VPA).

[0047] An ultrahigh temperature retarder was prepared in the same manner as in Example 1 to obtain an ultrahigh temperature retarder named H2.

[0048] The ultra-high temperature retarder synthesis process is as follows: First, oxygen is removed from the ground-mouth three-necked flask reaction vessel. Then, 53 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are added to 200 parts of deionized water and stirred in a blender. 18.7 parts of acrylic acid (AA), 8 parts of N,N-dimethylacrylamide (DMAA), and 30 parts of vinylphosphonic acid (VPA) are weighed and added to the blender to mix and stir to obtain a mixed reaction solution. The mixed reaction solution is poured into the ground-mouth three-necked flask. The pH of the reaction solution is adjusted to 4-5, preferably 4, using NaOH solution. Stirring is maintained at 200-400 rpm, preferably 300 rpm, until no precipitation is observed. Finally, an initiator solution is prepared and added dropwise to the ground-mouth three-necked flask at a rate of 5-10 mL / min. The reaction temperature is maintained at 50°C, the reaction is stirred for 5 hours, and the mixture is allowed to cool naturally to obtain the ultra-high temperature retarder, named H2.

[0049] The initiator is a mixture of ammonium persulfate and sodium bisulfite, the added molar ratio is 2:3, and the added amount of the initiator is 1.0% of the total weight of the monomers.

[0050] Example 3

[0051] This embodiment provides an ultra-high temperature retarder for cementing, which has a formula of: 50 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 12.5 parts of N,N-dimethylacrylamide (DMAA), 10 parts of acrylic acid (AA), and 25 parts of vinylphosphonic acid (VPA).

[0052] The ultra-high temperature retarder synthesis process is as follows: first, remove oxygen from the reaction vessel, a ground three-necked flask, then add 50 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to 200 parts of deionized water, stir and blend in a stirrer, weigh 12.5 parts of acrylic acid (AA), 10 parts of N,N-dimethylacrylamide (DMAA), and 25 parts of vinylphosphonic acid (VPA), also add them to the stirrer and mix and stir to obtain a mixed reaction solution, which is poured into a ground three-necked flask; use NaOH solution to adjust the pH value of the reaction solution to 4-5, preferably, pH 4, keep stirring, and keep the speed at 200-400rpm, preferably, 300rpm, until there is no precipitation. Finally, prepare the initiator solution, which needs to be added dropwise to the ground three-necked flask at a drop rate of 5-10mL / min, maintain the reaction temperature at 55°C, stir the reaction for 4h, and let it cool naturally to obtain the ultra-high temperature retarder, named H3.

[0053] The initiator is a mixture of ammonium persulfate and sodium bisulfite, the molar ratio of which is 2:1, and the amount of the initiator added is 1.5% of the total weight of the monomers.

[0054] Comparative Example 1

[0055] An ultrahigh temperature retarder was prepared according to the same method as in Example 1, except that the weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid, N,N-dimethylacrylamide, and vinylphosphonic acid was 12:5:2.5:1. The ultrahigh temperature retarder prepared was named DH1.

[0056] Comparative Example 2

[0057] An ultrahigh temperature retarder was prepared according to the same method as in Example 1, except that the monomers used were 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, N,N-dimethylaminopropyl acrylamide, and acrylamide, and the mass ratio of the four monomers was 45:9:17:4. The ultrahigh temperature retarder prepared was named DH2.

[0058] Comparative Example 3

[0059] An ultrahigh temperature retarder was prepared using the same method as in Example 1, except that the monomers used were 2-acrylamido-2-methylpropanesulfonic acid and itaconic acid, and the weight ratio of the two monomers was 56.7:13.1. The resulting ultrahigh temperature retarder was named DH3.

[0060] Comparative Example 4

[0061] An ultrahigh temperature retarder was prepared in the same manner as in Example 1, except that the monomers used were 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid, and the weight ratio of the two monomers was 53:12.3. The prepared ultrahigh temperature retarder was named DH4.

[0062] Comparative Example 5

[0063] An ultra-high temperature retarder was prepared according to the same method as in Example 1, except that the monomers used were sodium 2-acrylamido-2-methylpropanesulfonate (AMPS), sodium styrenesulfonate (SSS), and 3-dimethylaminoallylphosphonic acid (DMAAPA), and the mass ratio of the monomers used was 40:30:30. The ultra-high temperature retarder prepared was named DH5.

[0064] Table 1 Sources of experimental drugs

[0065]

[0066] 2. Performance test comparison of ultra-high temperature retarder for cementing

[0067] A cement slurry system was prepared according to the standard GB / T 19139-2003 "Test Methods for Oil Well Cement." Examples 1-3 and Comparative Examples 1-5 were prepared into cement slurries according to the API test standard for cement slurries. The performance of the cement slurry system and admixtures was tested with reference to the standards SY / T 6544-2003 "Performance Requirements for Oil Well Cement Slurries," SY / T 6466-2000 "Evaluation Methods for High-Temperature Resistance of Oil Well Cement," and SY / T 5504.1-2013 "Evaluation Methods for Oil Well Cement Admixtures Part 1: Retarders." The low-temperature compressive strength, thickening time, and other properties of the cement slurry system were tested and compared. Experimental phenomena were observed, experimental patterns were summarized, and experimental conclusions were drawn. The advantages and innovations of the retarder of the present invention were demonstrated from the perspective of parameter testing.

[0068] Test Example 1

[0069] To investigate the effects of varying temperatures and pressures on the retarding effect of ultrahigh-temperature retarders, cement slurries were prepared using Example 1 and Comparative Example 1. Retarder was added at a mass fraction of 0.5-2.0% to the cementing slurries prepared with Formula 1 and Formula 2, respectively. The thickening times were tested at temperatures between 90°C and 250°C. The results are shown in Table 1.

[0070] Table 2 Thickening time of ultra-high temperature retarder for cementing at different temperatures and pressures

[0071]

[0072]

[0073] According to the experimental results in Table 1, we can see that:

[0074] (1) The ultra-high temperature retarder prepared in Example 1 of the present invention has good retarding performance for oil well cement under the conditions of 90-250°C, and has good temperature resistance, which can effectively prolong the thickening time of cement slurry and meet the requirements of cement slurry for cementing at different temperatures.

[0075] (2) When the temperature is the same, the thickening time of cement slurry increases with the increase of retarder addition.

[0076] (3) By introducing phosphate groups, the molecular structure design was optimized, the high temperature resistance of the ultra-high temperature retarder was improved, and the slurry sedimentation stability was better.

[0077] Test Example 2

[0078] Using Examples 1, 2, and 3, and Comparative Examples 1, 2, 3, 4, and 5 as test subjects, 1.0% retarder was added to the cement slurry prepared in Formula 2. The experiments were conducted at a thickening temperature of 120-250°C to measure the thickening time of the cement slurry. The results are shown in Table 3.

[0079] Table 3 Retarding performance test

[0080] Experimental conditions Thickening performance characterization H1 H2 R3 DH1 DH2 DH3 DH4 DH5 60MPa, 120℃ Thickening time (min) 243 251 249 314 310 319 301 311 70MPa, 150℃ Thickening time (min) 333 369 314 269 279 272 243 276 80MPa, 180℃ Thickening time (min) 321 361 305 243 276 258 230 249 90MPa, 200℃ Thickening time (min) 313 354 332 248 263 251 203 204 100MPa, 220℃ Thickening time (min) 302 346 354 188 233 215 176 175 120MPa, 240℃ Thickening time (min) 291 340 328 152 196 184 152 144 135MPa, 250℃ Thickening time (min) 284 326 312 139 174 166 131 124

[0081] As shown in Table 3, the ultra-high temperature retarders H1-H3 prepared in Examples 1-3 of the present invention exhibit excellent retarding properties for oil well cement at temperatures between 120°C and 250°C, while also exhibiting excellent heat resistance. This effectively prolongs the thickening time of the cement slurry, meeting the requirements for cement slurry at various cementing temperatures. Furthermore, the addition of the retarders prepared in these examples exhibits significant right-angle thickening. Once the cement slurry is properly poured between the casings, it quickly loses fluidity and develops early strength, reducing the likelihood of accidents. However, the ultra-high temperature retarders prepared in Comparative Examples DH1 and DH4-5 exhibit poor retarding properties at temperatures between 120°C and 250°C, and even rapidly decline in retarding properties at temperatures above 200°C, rendering them ineffective.

[0082] Test Example 3

[0083] The compressive strength of cement paste was tested to verify the effect of the retarder on improving the early strength of top cement paste under different temperature conditions: Examples 1-3 and Comparative Examples 1-5 were used as test objects. A retarder with a mass fraction of 1.5% was added to the cement slurry prepared in Formula 1#. After thickening at 180°C for 1 hour, 60°C and 90°C were selected as low-temperature temperatures to simulate the top cementing environment. The compressive strength of the cement paste was tested after curing for 1 day, 2 days, 7 days, and 28 days to verify the effect of the ultra-high temperature retarder on improving the early strength of top cement paste under these conditions. The results are shown in Table 4.

[0084] Table 4 Compressive strength test

[0085]

[0086] Retarder must not significantly negatively impact the strength of the cement paste. As shown in Table 4, referring to Examples 1-3 and Comparative Examples 1-5, the ultra-high-temperature retarder has minimal impact on the strength of the cement paste. Cured at top temperatures of 60°C and 90°C for 1, 2, 7, and 28 days, respectively, the cement pastes exhibited high strength, meeting cementing requirements. However, the retarders in Comparative Examples 1-5 significantly impacted strength, posing a potential safety risk to cementing quality in actual field operations.

[0087] Test Example 4

[0088] A dosage sensitivity test was conducted according to the standard SY / T5504.1-2013, "Evaluation Methods for Oil Well Cement Admixtures Part 1: Retarders." Using a baseline formulation at a representative temperature, the retarder dosage was increased by 10% to perform a thickening test. The thickening time was then measured. The retarder dosage sensitivity was calculated using the formula. The standard indicator is a dosage sensitivity of ≤25%.

[0089] The thickening time increase rate is calculated using the formula:

[0090]

[0091] Where:

[0092] R D - Sensitivity to retarder dosage, expressed as a percentage;

[0093] t D - Thickening time of cement slurry under the condition of 10% addition, (min);

[0094] t P -Thickening time of the baseline formulation, (min).

[0095] The ultra-high temperature retarder prepared in Example 1 was added at a mass fraction of 0.5-1.1% to the cement slurry prepared with Formula 1# and the cement slurry prepared with Formula 2#, respectively. Experiments were conducted in the temperature range of 90-250°C. The experimental results are shown in Table 5 below.

[0096] Table 5 Dosage sensitivity test

[0097]

[0098] According to the data in Table 5, when the amount of retarder increased, the change rate of thickening time was less than 10%. It can be seen that the ultra-high temperature retarder of the present invention has a small dosage sensitivity coefficient, which can effectively meet the performance requirements of cementing projects and ensure the safety of cementing operations.

[0099] Test Example 5

[0100] A temperature sensitivity test was conducted in accordance with SY / T5504.1-2013, "Evaluation Methods for Oil Well Cement Admixtures Part 1: Retarders." Using a baseline formulation at a representative temperature, the thickening test was conducted by increasing the test temperature by 5°C. The thickening time was read and the temperature sensitivity, under a 5°C increase in test temperature, was calculated using the following formula. The standard indicator is a temperature sensitivity of ≤20%.

[0101]

[0102] In the formula

[0103] R T - Temperature sensitivity of retarder, expressed as a percentage;

[0104] t P -Thickening time of the benchmark formulation, min;

[0105] t T -Thickening time of cement slurry at test temperature T, min.

[0106] 0.5-1.8% by mass of the ultra-high temperature retarder prepared in Example 1 was added to the cementing slurry prepared with Formula 1# and the cementing slurry prepared with Formula 2#, respectively. Thickening experiments were carried out under different temperature and pressure conditions. The experimental results are shown in Table 6 below.

[0107] Table 6 Temperature sensitivity test

[0108]

[0109] According to the data in Table 6, when the temperature increases by 5°C, the temperature sensitivity is less than 20%. This shows that the ultra-high temperature retarder has low temperature sensitivity and can effectively meet the performance requirements of cementing projects and ensure the safety of cementing operations.

[0110] Test Example 6

[0111] 0.5% by mass of the ultra-high temperature retarder described in Example 1 and the ultra-high temperature retarder described in Comparative Example 1 was added to the cementing cement slurry prepared with Formula 1#. The setting time of the cement slurry was tested at 50°C, 70°C, and 90°C. The experimental results are shown in Table 7 below.

[0112] Table 7 Cement slurry setting time test

[0113]

[0114] As can be seen in Table 7, the cement slurry system with the ultrahigh temperature retarder has similar initial setting times at different temperatures, and the difference in setting times does not change much. In contrast, the cement slurry system with the addition of Comparative Example 1 shows significant changes in initial and final setting times with increasing temperature, and its difference in setting times decreases with increasing temperature. Therefore, at low temperatures, the ultrahigh temperature retarder has little effect on the strength development of cement paste.

[0115] Test Example 7

[0116] Using Examples 1-3 and Comparative Examples 1-5 as test objects, an ultra-high temperature retarder with a mass fraction of 1% was added to the cementing cement slurry prepared in Formula 1#. The initial consistency, water separation rate, and upper and lower density difference of the slurry were measured at room temperature and 90°C to verify the improvement effect of the ultra-high temperature retarder on the settlement stability of the cement slurry. The experimental results are shown in Table 8 below.

[0117] Table 8 Sedimentation stability test

[0118]

[0119] As can be seen from Table 8, the cement slurry system with the ultra-high temperature retarder has a higher initial consistency, and the water separation rate and the upper and lower density difference are significantly smaller than those of the cement slurry systems with the ultra-high temperature retarder added to Comparative Examples 1-5. The ultra-high temperature retarder can keep the cement particles dispersed and stable, improve the fluidity of the slurry, and significantly improve the sedimentation stability of the cement slurry.

[0120] In summary, the ultra-high temperature retarder of the present invention can effectively prolong the thickening time of cement slurry at high temperature, ensure the early strength of cement stone at low temperature, and at the same time effectively improve the rheological properties of cement slurry, prevent the settlement stability problem caused by excessive dispersion of cement slurry, thereby improving the comprehensive performance of the cement slurry system, reducing the damage to the cement sheath and casing, preventing the occurrence of accidents such as water channeling and gas channeling, improving the safety of oil well production, meeting the time requirements of cementing projects, and ensuring cementing quality.

Claims

1. An ultra-high temperature retarder, wherein the monomers constituting the ultra-high temperature retarder are: 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), N,N-dimethylacrylamide (DMAA), and vinylphosphonic acid (VPA), wherein the weight ratio of the monomers is: 40-60 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 10-25 parts of acrylic acid (AA), 5.0-15 parts of N,N-dimethylacrylamide (DMAA), and 15-30 parts of vinylphosphonic acid (VPA).

2. A method for preparing the ultra-high temperature retarder according to claim 1, characterized in that: The method comprises the following steps: in the presence of an initiator, mixing 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), N,N-dimethylacrylamide (DMAA), vinylphosphonic acid (VPA) and deionized water, and then performing copolymerization.

3. The method for preparing an ultra-high temperature retarder according to claim 2, wherein the monomer mass ratio is: 40-60 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 10-25 parts of acrylic acid (AA), 5.0-15 parts of N,N-dimethylacrylamide (DMAA), and 15-30 parts of vinylphosphonic acid.

4. The method for preparing an ultrahigh temperature retarder according to claim 2, wherein the total mass of the monomers is 25%-45% of the total mass of deionized water.

5. The method for preparing the ultrahigh temperature retarder according to claim 2, wherein: The pH of the mixed solution after mixing 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), N,N-dimethylacrylamide (DMAA), vinylphosphonic acid (VPA) and the deionized water is 4-5.

6. The method for preparing the ultrahigh temperature retarder according to claim 2, wherein: The initiator adopts a redox initiation system, wherein the oxidant is at least one of ammonium persulfate, potassium persulfate and hydrogen peroxide, the reducing agent is at least one of sodium sulfite, sodium bisulfite and potassium borohydride, and the molar ratio of the oxidant to the reducing agent is (1-3): (1-2).

7. The method for preparing the ultrahigh temperature retarder according to claim 2, wherein: The amount of the initiator used is 0.5-1.5 weight % of the total amount of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), N,N-dimethylacrylamide (DMAA), and vinylphosphonic acid (VPA).

8. The preparation method of the ultra-high temperature retarder according to claim 2, wherein the synthesis process of the ultra-high temperature retarder is as follows: first, 150-230 parts of deionized water are added to a ground three-necked flask, nitrogen is passed through for 15-20 minutes to remove oxygen in the reaction liquid, 40-60 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are added, and stirred and dissolved in a stirrer; then, 10-25 parts of acrylic acid (AA), 5.0-15 parts of N,N-dimethylacrylamide (DMAA), 15-30 parts of ethylene are weighed in sequence; The steps of: adding 1% sodium hydroxide solution to a three-necked flask and stirring the mixture sequentially to obtain a mixed reaction solution; adjusting the pH value of the reaction solution to 4-5 using a 15% NaOH solution, and maintaining stirring at a speed of 200-400 rpm until all monomers are completely dissolved; preparing an initiator solution, and adding the initiator solution dropwise to the ground-joint three-necked flask at a dropping rate of 5-10 mL / min, maintaining a reaction temperature of 50-60° C., stirring the reaction for 4-6 hours, and terminating the reaction; and finally, allowing the reaction solution to cool naturally to obtain an ultra-high temperature retarder.

9. A deep well and ultra-deep well ultra-high temperature resistant cementing slurry, characterized in that: The cementing slurry comprises the ultrahigh temperature retarder as claimed in claim 1, and the amount of the ultrahigh temperature retarder is 0.5 to 2% by weight based on the total weight of the oil well cement in the cementing slurry.

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