Ultra-high temperature and large temperature difference retarding agent for oil well cement and preparation method thereof

Abstract

The application discloses an ultrahigh-temperature large-temperature-difference retarding agent for oil well cement and a preparation method thereof. The ultrahigh-temperature large-temperature-difference retarding agent for oil well cement is obtained through copolymerization reaction of water as a solvent, azobisdimethylaminoformamide hydrochloride as an initiator and monomers of vinyl phosphonic acid, diethyl vinyl phosphonate, divinylbenzene, triphenyl ethenyl phenol polyoxyethylene ether and N-vinyl pyrrolidone. The ultrahigh-temperature large-temperature-difference retarding agent for oil well cement is a polymer made of monomers with rigid groups, the polymer does not decompose under ultrahigh-temperature conditions and still maintains original retarding performance, the thickening time is convenient to adjust, and the retarding agent dosage is not increased, so the strength of the top cement stone is also developed relatively fast, and over-retarding is avoided.

Description

Technical Field

[0001] This application relates to the field of drilling technology, and in particular to an ultra-high temperature large temperature difference retarder for oil well cement and its preparation method. Background Technology

[0002] As exploration and development move towards deeper and ultra-deeper formations, the high bottom-hole temperatures and large temperature gradients will place extremely high demands on cement slurry systems, especially high-temperature retarders. For example, deep wells in the Kuqa foreland of Tarim, Anyue in Sichuan, Qinghai, and the Bohai Bay exceed 6000m in depth, while wells in the Keshen block of Tarim are close to 8000m deep, with expected bottom-hole circulating temperatures exceeding 200-240℃. High-temperature and ultra-high-temperature deep well cementing operations are time-consuming, thus requiring a longer cement slurry thickening time to ensure construction safety. Furthermore, the cement slurry must begin developing strength immediately after thickening to facilitate sealing the bottom layer. Current trends indicate increasingly longer sealing sections, making the rapid strength development of the top cement stone under large temperature differences increasingly crucial. Additionally, the bottom layer being sealed is often a high-permeability reservoir, requiring a lower water loss rate than typical cementing requirements (less than 50 mL). Finally, high-temperature deep and ultra-deep well cementing carries high risks and requires a long preparation time. Therefore, after the cement slurry is prepared, several days are needed before cementing. Thus, even after several days of aging, the cement slurry thickening time must still exceed the safe construction time to ensure safe operation.

[0003] The original retarders in cement slurry systems under high-temperature and ultra-high-temperature conditions mainly suffer from the following problems: Under ultra-high-temperature conditions, the retarder structure decomposes, leading to abnormal retarder function and difficulty in adjusting thickening time; under ultra-high-temperature conditions, the amount of retarder added to the cement slurry is very large, resulting in slow strength development at the top of the large temperature difference or excessively slowed setting; the retarder has a similar structure to the water loss control agent, which damages the water loss performance of the cement slurry; after the cement slurry is mixed with water, because the retarder is an acidic compound, it reacts with the rust in the iron tank used for water mixing, resulting in a significant reduction in the thickening time of the aged cement slurry. The performance of high-temperature and ultra-high-temperature retarders has become a technical bottleneck restricting further improvements in deep well and ultra-deep well technology. Summary of the Invention

[0004] This application provides an ultra-high temperature large temperature difference retarder for oil well cement and its preparation method, which can solve the problems of difficulty in adjusting the thickening time of ultra-high temperature (circulating temperature above 180-200℃); ultra-retarded setting of cement stone at the top of large temperature difference; low water loss of cement slurry required in deep and ultra-deep high-permeability reservoirs; damage to the water loss performance of cement slurry by existing retarder; and severe shortening of thickening time due to the reaction of existing acidic retarder with rust in iron can after cement slurry is mixed with water.

[0005] The following technical solution was adopted in this application:

[0006] This application provides an ultra-high temperature and large temperature difference retarder for oil well cement, which is obtained by copolymerization of water as solvent, azobisisobutyramidine hydrochloride as initiator, and vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether and N-vinylpyrrolidone as monomers.

[0007] Furthermore, the amount of vinylphosphonic acid fed is 7-10 wt% of the total amount of raw materials used in the preparation.

[0008] The amount of diethyl vinylphosphonate added is 0.2 to 1 wt% of the total amount of raw materials used in the preparation.

[0009] The amount of divinylbenzene fed into the preparation is 4 to 7 wt% of the total amount of raw materials.

[0010] The amount of tristyrene-based phenol polyoxyethylene ether fed is 5-8 wt% of the total amount of raw materials.

[0011] The amount of N-vinylpyrrolidone added is 5 to 10 wt% of the total amount of raw materials used in the preparation.

[0012] Furthermore, the amount of vinylphosphonic acid fed is 8-9 wt% of the total amount of raw materials used in the preparation.

[0013] The amount of diethyl vinylphosphonate added is 0.5 to 0.8 wt% of the total amount of raw materials used in the preparation.

[0014] The amount of divinylbenzene added is 5-6 wt% of the total amount of raw materials used in the preparation.

[0015] The amount of tristyrene-based phenol polyoxyethylene ether fed is 6-7 wt% of the total amount of raw materials.

[0016] The amount of N-vinylpyrrolidone added is 7-8 wt% of the total amount of raw materials used in the preparation.

[0017] Furthermore, the amount of azobisisobutyramidine hydrochloride added is 0.45 to 0.65 wt% of the total amount of raw materials used in the preparation.

[0018] Furthermore, the amount of azobisisobutyramidine hydrochloride added is 0.53 wt% of the total amount of raw materials used in the preparation.

[0019] This application also provides a method for preparing an ultra-high temperature, large temperature difference retarder for oil well cement, comprising the following steps: dissolving vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone in water to obtain a monomer solution. Dissolving azobisisobutyramidine hydrochloride in the monomer solution to obtain a reaction solution, and allowing the monomers in the reaction solution to undergo a copolymerization reaction under the action of an initiator to obtain the ultra-high temperature, large temperature difference retarder for oil well cement.

[0020] Furthermore, vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone are dissolved in water under nitrogen purging.

[0021] Further, before adding azobisisobutyramidine hydrochloride to the monomer solution, sodium hydroxide is added to the monomer solution, stirred, and the pH is adjusted to 7-8 to obtain a mixed solution.

[0022] Further, after obtaining the mixed solution, the temperature of the mixed solution is adjusted to 60-90℃ while continuously stirring. Then, azobisisobutyramidine hydrochloride is added to the monomer solution, so that the azobisisobutyramidine hydrochloride dissolves in the monomer solution to obtain a reaction solution. The monomer in the reaction solution is then subjected to a copolymerization reaction under the action of an initiator. The reaction is carried out for 3-4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement.

[0023] Furthermore, the reaction vessel containing the reaction solution is placed in a constant-temperature oil bath to adjust the temperature of the reaction solution.

[0024] Compared with the prior art, this application has the following beneficial effects:

[0025] (1) The ultra-high temperature large temperature difference retarder for oil well cement in this application is a polymer made of monomers with rigid groups. Under ultra-high temperature conditions, the polymer does not decompose and still maintains its original retarding performance. The thickening time is easy to adjust and the amount of retarder added is not increased. Therefore, the strength of the top cement stone also develops faster, avoiding ultra-retarded setting.

[0026] (2) The ultra-high temperature large temperature difference retarder for oil well cement in this application uses a monomer with a large molecular chain group, which is significantly different from the existing water loss reducing agent in terms of molecule and molecular weight. In addition, hydrophilic adsorption groups are added. After adopting a reasonable combination of monomer and molecular weight distribution, the cement particles adsorb and form a dense filter cake. In this way, the retarder has the function of assisting water loss, and the water loss of cement slurry is reduced from the original 30-50 mL to less than 20 mL.

[0027] (3) In the preparation process of the ultra-high temperature large temperature difference retarder for oil well cement of this application, the monomer with acidic groups is neutralized to pH=7-8, so that the polymer after polymerization is neutral and therefore does not react with the rust in the iron can. The thickening time after aging remains basically unchanged, ensuring the safe and smooth progress of construction. Detailed Implementation

[0028] The technical methods in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] The embodiments of this application provide an ultra-high temperature large temperature difference retarder for oil well cement. It is obtained by free radical polymerization, using water as solvent, azobisisobutyramidine hydrochloride as initiator, and vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrene-based phenol polyoxyethylene ether and N-vinylpyrrolidone as monomers, in a copolymerization reaction at a certain temperature.

[0030] The amount of vinylphosphonic acid added is 7-10 wt% of the total amount of raw materials (i.e., the total amount of solvent, initiator, monomer, and pH adjuster). For example, in some embodiments, the amount of vinylphosphonic acid added is 7 wt% of the total amount of raw materials, in some embodiments, the amount of vinylphosphonic acid added is 8 wt% of the total amount of raw materials, and in some embodiments, the amount of vinylphosphonic acid added is 10 wt% of the total amount of raw materials. These details will not be elaborated further.

[0031] The amount of diethyl vinylphosphonate added is 0.2 to 1 wt% of the total amount of raw materials. For example, in some embodiments, the amount of diethyl vinylphosphonate added is 0.2 wt% of the total amount of raw materials; in some embodiments, the amount of diethyl vinylphosphonate added is 0.5 wt% of the total amount of raw materials; and in some embodiments, the amount of diethyl vinylphosphonate added is 1 wt% of the total amount of raw materials. These details will not be elaborated further.

[0032] The amount of divinylbenzene fed is 4 to 7 wt% of the total amount of raw materials. For example, in some embodiments, the amount of divinylbenzene fed is 4 wt% of the total amount of raw materials, in some embodiments, the amount of divinylbenzene fed is 5 wt% of the total amount of raw materials, and in some embodiments, the amount of divinylbenzene fed is 7 wt% of the total amount of raw materials. These details will not be elaborated further.

[0033] The amount of tristyrene-based phenol polyoxyethylene ether fed into the preparation is 5-8 wt% of the total amount of raw materials. For example, in some embodiments, the amount of tristyrene-based phenol polyoxyethylene ether fed into the preparation is 5 wt% of the total amount of raw materials; in some embodiments, the amount of tristyrene-based phenol polyoxyethylene ether fed into the preparation is 7 wt% of the total amount of raw materials; and in some embodiments, the amount of tristyrene-based phenol polyoxyethylene ether fed into the preparation is 8 wt% of the total amount of raw materials. These details will not be elaborated further.

[0034] The amount of N-vinylpyrrolidone added is 5 to 10 wt% of the total amount of raw materials used in the preparation. For example, in some embodiments, the amount of N-vinylpyrrolidone added is 5 wt% of the total amount of raw materials used in the preparation; in some embodiments, the amount of N-vinylpyrrolidone added is 8 wt% of the total amount of raw materials used in the preparation; and in some embodiments, the amount of N-vinylpyrrolidone added is 10 wt% of the total amount of raw materials used in the preparation. These details will not be elaborated further.

[0035] Preferably, the amount of vinylphosphonic acid fed is 8-9 wt% of the total amount of raw materials used in the preparation.

[0036] The amount of diethyl vinylphosphonate added is 0.5 to 0.8 wt% of the total amount of raw materials used in the preparation.

[0037] The amount of divinylbenzene added is 5-6 wt% of the total amount of raw materials used in the preparation.

[0038] The amount of tristyrene-based phenol polyoxyethylene ether fed is 6-7 wt% of the total amount of raw materials.

[0039] The amount of N-vinylpyrrolidone added is 7-8 wt% of the total amount of raw materials used in the preparation.

[0040] In addition, the amount of azobisisobutyramidine hydrochloride added is 0.45 to 0.65 wt% of the total amount of raw materials. For example, in some embodiments, the amount of azobisisobutyramidine hydrochloride added is 0.45 wt% of the total amount of raw materials; in some embodiments, the amount of azobisisobutyramidine hydrochloride added is 0.50 wt% of the total amount of raw materials; and in some embodiments, the amount of azobisisobutyramidine hydrochloride added is 0.65 wt% of the total amount of raw materials. These details will not be elaborated further.

[0041] Preferably, the amount of azobisisobutyramidine hydrochloride fed into the preparation is 0.53 wt% of the total amount of raw materials.

[0042] Furthermore, the specific temperature ranges from 60 to 90°C. For example, in some embodiments it is 60°C, in some embodiments it is 70°C, and in some embodiments it is 90°C.

[0043] The embodiments of this application also provide a method for preparing the above-mentioned ultra-high temperature large temperature difference retarder for oil well cement, characterized by comprising the following steps:

[0044] Step 1: Dissolve vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone in water to obtain a monomer solution.

[0045] In the above steps, vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone are dissolved in water under nitrogen atmosphere.

[0046] Step 2: Dissolve azobisisobutyramidine hydrochloride in the monomer solution to obtain a reaction solution, and allow the monomer in the reaction solution to undergo a copolymerization reaction under the action of an initiator to obtain an ultra-high temperature large temperature difference retarder for oil well cement.

[0047] In the above steps, before adding azobisisobutyramidine hydrochloride to the monomer solution, sodium hydroxide is added to the monomer solution, stirred, and the pH is adjusted to 7-8 to obtain a mixed solution.

[0048] Further, after obtaining the mixed solution, the temperature of the mixed solution is adjusted to 60-90℃ while continuously stirring. Then, azobisisobutyramidine hydrochloride is added to the monomer solution, so that the azobisisobutyramidine hydrochloride dissolves in the monomer solution to obtain a reaction solution. The monomer in the reaction solution is then subjected to a copolymerization reaction under the action of an initiator. The reaction is carried out for 3-4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement.

[0049] The reaction vessel containing the reaction solution is placed in a constant-temperature oil bath to regulate the temperature of the reaction solution.

[0050] The technical solution of this application has the following beneficial effects:

[0051] (1) The polymer of the oil well cement ultra-high temperature large temperature difference retarder of this application contains a large amount of rigid steric hindrance monomers. The molecular structure does not decompose under ultra-high temperature conditions. Therefore, under ultra-high temperature conditions, the thickening time of the cement slurry system with the added retarder of this application can be adjusted within 3 to 12 hours. There will be no super-retarded setting, and the thickening time is basically consistent. Therefore, the top strength of cement stone under 100℃ large temperature difference conditions is rapid within 24 hours.

[0052] (2) The ultra-high temperature large temperature difference retarder for oil well cement in this application has added the adsorbent monomer N-vinylpyrrolidone, but the overall molecular structure and molecular weight distribution are different from the water loss reducer. Therefore, it can form a dense filter cake by adsorbing on cement particles, so that the water loss of the cement slurry system is less than 20 mL.

[0053] (3) The ultra-high temperature and large temperature difference retarder for oil well cement in this application has a pH of 7 to 8. It does not react with rust in the iron can. Therefore, after the cement slurry is mixed with water and aged in the iron can for 7 days, the thickening time does not change.

[0054] In this application, the synthesized retarder can adjust the thickening time of the cement slurry system (3-12 hours) within a bottom-hole circulation temperature range of 120℃ to 260℃, meeting the safety requirements of cementing operations. Furthermore, the cement slurry rapidly develops strength after thickening. When added to the cement slurry system, the synthesized retarder ensures that the top cement stone strength begins to develop within 24 hours within a large temperature difference range of 0-100℃. The synthesized retarder also helps reduce the water loss of the cement slurry, lowering it to below 20 mL, which is beneficial for meeting the cementing requirements of permeable formations. The synthesized retarder is neutral (pH=7) and does not react significantly with rust in the iron container after the cement slurry is mixed with water. The thickening time remains essentially unchanged within 7 days of aging, ensuring safe and smooth construction.

[0055] The technical solution of this application will be described in detail below with reference to specific embodiments:

[0056] Example 1

[0057] Measure 66.93 mL of water and add it to a four-necked flask. Under nitrogen purging, add 8.0 g of vinylphosphonic acid, 0.5 g of diethyl vinylphosphonate, 5.0 g of divinylbenzene, 6.0 g of tristyrene-phenylphenol polyoxyethylene ether, and 7.0 g of N-vinylpyrrolidone. Stir at room temperature until completely dissolved. Add 6.04 g of sodium hydroxide to neutralize the solution to pH 7-8. Continue stirring and raise the oil bath temperature to 80°C. When the solution temperature in the four-necked flask reaches 60°C, add 0.53 g of azobisisobutyramidine hydrochloride solution to the above mixture and stir evenly. React for 4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement, product code: Retarder A.

[0058] Comparative Example 1

[0059] Measure 70.48 mL of water and add it to a four-necked flask. Under nitrogen purging, add 6.0 g of vinylphosphonic acid, 0.5 g of diethyl vinylphosphonate, 5.0 g of divinylbenzene, 6.0 g of tristyrene-phenylphenol polyoxyethylene ether, and 7.0 g of N-vinylpyrrolidone. Stir at room temperature until completely dissolved. Add 4.53 g of sodium hydroxide to neutralize the solution to pH 7-8. Continue stirring and raise the oil bath temperature to 80°C. When the solution temperature in the four-necked flask reaches 60°C, add 0.49 g of azobisisobutyramidine hydrochloride solution to the above mixture and stir evenly. React for 4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement, product code: Retarder B.

[0060] Comparative Example 2

[0061] Measure 59.83 mL of water and add it to a four-necked flask. Under nitrogen purging, add 12.0 g of vinylphosphonic acid, 0.5 g of diethyl vinylphosphonate, 5.0 g of divinylbenzene, 6.0 g of tristyrene-phenylphenol polyoxyethylene ether, and 7.0 g of N-vinylpyrrolidone. Stir at room temperature until completely dissolved. Add 9.06 g of sodium hydroxide to neutralize the solution to pH 7-8. Continue stirring and raise the oil bath temperature to 80°C. When the solution temperature in the four-necked flask reaches 60°C, add 0.61 g of azobisisobutyramidine hydrochloride solution to the above mixture and stir evenly. React for 4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement, product code: Retarder C.

[0062] Comparative Example 3

[0063] Measure 69.99 mL of water and add it to a four-necked flask. Under nitrogen purging, add 8.0 g of vinylphosphonic acid, 0.5 g of diethyl vinylphosphonate, 5.0 g of divinylbenzene, 6.0 g of tristyrene-phenylphenol polyoxyethylene ether, and 4.0 g of N-vinylpyrrolidone. Stir at room temperature until completely dissolved. Add 6.04 g of sodium hydroxide to neutralize the solution to pH 7-8. Continue stirring and raise the oil bath temperature to 80°C. When the solution temperature in the four-necked flask reaches 60°C, add 0.47 g of azobisisobutyramidine hydrochloride solution to the above mixture and stir evenly. React for 4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement, product code: Retarder D.

[0064] Comparative Example 4

[0065] Measure 72.97 mL of water and add it to a four-necked flask. Under nitrogen purging, add 8.0 g of vinylphosphonic acid, 0.5 g of diethyl vinylphosphonate, 5.0 g of divinylbenzene, 6.0 g of tristyrene-phenylphenol polyoxyethylene ether, and 7.0 g of N-vinylpyrrolidone. Stir at room temperature until completely dissolved. Continue stirring and raise the oil bath temperature to 80°C. When the solution temperature in the four-necked flask reaches 60°C, add 0.53 g of azobisisobutyramidine hydrochloride solution to the above mixture and stir evenly. React for 4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement, retarder E.

[0066] Experimental Example 1

[0067] The following cement slurry performance tests were conducted according to GB / T 19139-2012 Oil Well Cement Test Methods.

[0068] Formula 1#: 600g of G-grade oil well cement + 210g of silica fume + 30g of water loss reducer BXF-200L(AF) + 10g of ultra-high temperature and large temperature difference retarder for oil well cement in Example 1 + 320g of water;

[0069] Formula 2#: 600g of G-grade oil well cement + 210g of silica fume + 30g of water loss reducer BXF-200L(AF) + 12g of ultra-high temperature and large temperature difference retarder for oil well cement in Example 1 + 320g of water;

[0070] Formula 3#: 600g of G-grade oil well cement + 210g of silica fume + 30g of water loss reducer BXF-200L(AF) + 15g of ultra-high temperature and large temperature difference retarder for oil well cement in Example 1 + 320g of water;

[0071] Formula 4#: 600g of G-grade oil well cement + 210g of silica fume + 30g of water loss reducer BXF-200L(AF) + 18g of ultra-high temperature and large temperature difference retarder for oil well cement in Example 1 + 320g of water.

[0072] (1) Thickening properties

[0073] Table 1. Statistics on the thickening time of cement slurry formulations 1# to 4#

[0074]

[0075] As can be seen from Table 1, at temperatures ranging from 120℃ to 260℃, the thickening time of the cement slurry can be adjusted from 3 to 12 hours by changing the dosage of the ultra-high temperature large temperature difference retarder for oil well cement, thus meeting the cementing requirements.

[0076] (2) Strength development time of cement stone at the top under large temperature difference

[0077] Table 2. Statistics on Thickening Time of Formula 4# Cement Slurry

[0078]

[0079] As can be seen from Table 2, cement slurry with added ultra-high temperature and large temperature difference retarder for oil well cement, at temperatures ranging from 120℃ to 260℃, begins to develop strength within 24 hours under a large temperature difference of 100℃, thus meeting the cementing requirements.

[0080] (3) Water loss of cement grout system

[0081] Table 3. Statistics on water loss of cement slurry formulations 1-4.

[0082]

[0083] As can be seen from Table 3, the water loss of cement slurry with ultra-high temperature and large temperature difference retarder for oil well cement is less than 20 mL when the temperature is between 120℃ and 260℃.

[0084] (4) Thickening time of cement slurry system at various temperatures after 7 days of water aging in iron tank.

[0085] Table 4 shows the thickening time of cement slurry formulations 1-4 after 7 days of aging.

[0086]

[0087] As can be seen from the comparison of the thickening time in Table 4 with that in the range of 120℃ to 260℃, after the oil well cement is mixed with water using an ultra-high temperature large temperature difference retarder and aged in an iron tank for 7 days, the thickening time does not change.

[0088] Experimental Example 2

[0089] The following cement slurry systems were tested for performance according to GB / T 19139-2012 Oil Well Cement Test Methods.

[0090] Formula 1*: 600g G-grade oil well cement + 210g silica fume + 30g fluid loss reducer BXF-200L(AF) + 15g retarder A + 320g water;

[0091] Formula 2*: 600g G-grade oil well cement + 210g silica fume + 30g fluid loss reducer BXF-200L(AF) + 15g retarder B + 320g water;

[0092] Formula 3*: 600g G-grade oil well cement + 210g silica fume + 30g fluid loss reducer BXF-200L(AF) + 15g retarder C + 320g water;

[0093] Formula 4*: 600g G-grade oil well cement + 210g silica fume + 30g fluid loss reducer BXF-200L(AF) + 15g retarder D + 320g water;

[0094] Formula 5*: 600g of G-grade oil well cement + 210g of silica fume + 30g of fluid loss reducer BXF-200L(AF) + 15g of retarder E + 320g of water.

[0095] Table 5. Comparison of cement paste performance after adding the retarder products of Example 1 and Comparative Examples 1-4 to cement paste.

[0096]

[0097]

[0098] As can be seen from Table 5, the retarder A product in Example 1 can meet the construction safety requirements in the ultra-high temperature thickening time of cement slurry. The cement stone begins to develop strength within 24 hours at the top, the water loss is <20mL, and the thickening time remains unchanged after 7 days of aging.

[0099] Compared to retarder product A in Example 1, retarder product B in Comparative Example 1 has a too short thickening time in cement slurry, which cannot meet the requirements of well cementing operations. This is because the dosage of the main retarding monomer, vinylphosphonic acid, is too small, resulting in insufficient retarding capacity of the product.

[0100] Compared to retarder product A in Example 1, retarder product C in Comparative Example 2 has an excessively long thickening time in cement slurry, resulting in super-retarded setting. The cement slurry does not thicken within one day, and the top still has not developed strength after four days. This is because the dosage of the main retarding monomer, vinylphosphonic acid, is too high, resulting in an excessively strong retarding ability of the product.

[0101] Compared to retarder product A in Example 1, retarder product D in Comparative Example 3 had a thickening time in cement slurry that met the requirements for cementing operations, but its water loss was relatively large. Retarder product C did not have the function of assisting in reducing water loss. This is because the dosage of the adsorbent monomer N-vinylpyrrolidone was too small, resulting in insufficient adsorption capacity of the product for cement particles, and thus it did not help reduce the water loss of the cement slurry.

[0102] Compared to retarder product A in Example 1, retarder product E in Comparative Example 4, after being mixed with water in cement slurry and aged in an iron container for 7 days, exhibited a drastically shortened thickening time, failing to meet the requirements for cementing operations. This is because sodium hydroxide was not added to neutralize the polymer, and the acidic nature of the retarder reacted with the rust in the iron container, resulting in insufficient effective retarding components and consequently a drastically shortened cement slurry thickening time compared to before aging.

[0103] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made without departing from the spirit and scope of this application. The scope of protection claimed by this application is defined by the appended claims, specification, and their equivalents.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A high-temperature, large-temperature-difference retarder for oil well cement, characterized in that, The preparation method includes the following steps: Vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone were dissolved in water to obtain a monomer solution; Azobisisobutyramidine hydrochloride is dissolved in the monomer solution to obtain a reaction solution, and the monomer in the reaction solution is subjected to a copolymerization reaction under the action of an initiator to obtain an ultra-high temperature large temperature difference retarder for oil well cement. Before adding azobisisobutyramidine hydrochloride to the monomer solution, sodium hydroxide is added to the monomer solution, stirred, and the pH is adjusted to 7-8 to obtain a mixed solution. The amount of vinylphosphonic acid fed is 7-10 wt% of the total amount of raw materials used in the preparation. The amount of diethyl vinylphosphonate added is 0.2 to 1 wt% of the total amount of raw materials used in the preparation. The amount of divinylbenzene fed into the feed is 4-7 wt% of the total amount of raw materials used in the preparation. The amount of the tristyrene-based phenol polyoxyethylene ether fed into the feed is 5-8 wt% of the total amount of raw materials used in the preparation. The amount of N-vinylpyrrolidone added is 5-10 wt% of the total amount of raw materials used in the preparation. The amount of azobisisobutyramidine hydrochloride added is 0.45 to 0.65 wt% of the total amount of raw materials.

2. The ultra-high temperature large temperature difference retarder for oil well cement as described in claim 1, characterized in that, The amount of vinylphosphonic acid fed is 8-9 wt% of the total amount of raw materials used in the preparation. The amount of diethyl vinylphosphonate added is 0.5 to 0.8 wt% of the total amount of raw materials used in the preparation. The amount of divinylbenzene fed into the feed is 5-6 wt% of the total amount of raw materials used in the preparation. The amount of the tristyrene-based phenolic polyoxyethylene ether fed into the feed is 6-7 wt% of the total amount of raw materials used in the preparation. The amount of N-vinylpyrrolidone added is 7-8 wt% of the total amount of raw materials used in the preparation.

3. The ultra-high temperature large temperature difference retarder for oil well cement as described in claim 1, characterized in that, The amount of azobisisobutyramidine hydrochloride added is 0.53 wt% of the total amount of raw materials used in the preparation.

4. A method for preparing the ultra-high temperature large temperature difference retarder for oil well cement according to any one of claims 1-3, characterized in that, Includes the following steps: Vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone were dissolved in water to obtain a monomer solution; Azobisisobutyramidine hydrochloride is dissolved in the monomer solution to obtain a reaction solution, and the monomer in the reaction solution is subjected to a copolymerization reaction under the action of an initiator to obtain an ultra-high temperature large temperature difference retarder for oil well cement. Before adding azobisisobutyramidine hydrochloride to the monomer solution, sodium hydroxide is added to the monomer solution, stirred, and the pH is adjusted to 7-8 to obtain a mixed solution.

5. The preparation method according to claim 4, characterized in that, Vinylphosphonic acid, diethyl vinylphosphonate, divinylbenzene, tristyrylphenol polyoxyethylene ether, and N-vinylpyrrolidone were dissolved in water under nitrogen atmosphere.

6. The preparation method according to claim 4, characterized in that, After obtaining the mixed solution, the temperature of the mixed solution is adjusted to 60-90°C while continuously stirring. Then, azobisisobutyramidine hydrochloride is added to the monomer solution to dissolve the azobisisobutyramidine hydrochloride in the monomer solution, thus obtaining a reaction solution. The monomer in the reaction solution is then subjected to a copolymerization reaction under the action of an initiator for 3-4 hours to obtain an ultra-high temperature large temperature difference retarder for oil well cement.

7. The preparation method according to claim 6, characterized in that, The reaction vessel containing the reaction solution is placed in a constant temperature oil bath to adjust the temperature of the reaction solution.

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