Preparation method of ultra-high temperature suspension stabilizer, product thereof and application in oil well cement

Abstract

The present invention relates to the technical field of oil exploration, and particularly to a preparation method of a super-high temperature suspension stabilizer, a product thereof, and an application thereof in oil well cement. The preparation method comprises the following steps: dissolving 2-acrylamide-2-methylpropanesulfonic acid monomer, a temperature-sensitive monomer, and N-vinylpyrrolidone monomer in water to obtain a monomer solution; adding an initiator to the monomer solution and heating to 30-60 °C to obtain a mixed solution; adding a reducing agent to the mixed solution for reaction to obtain a polymer solution; and performing freeze-drying on the polymer solution to obtain the super-high temperature suspension stabilizer. Adding the suspension stabilizer obtained by the preparation method into an oil well cement slurry system can maintain the suspension stability of the cement slurry in a super-high temperature environment and will not cause the initial consistency of the cement slurry to be too high. The raw materials of the present invention are convenient to obtain, the preparation method is simple, and it meets the application requirements, can effectively improve the suspension stability of the super-high temperature cement slurry system, and ensure the safety of the cementing operation.

Description

Technical Field

[0001] The present invention relates to the technical field of oil exploration, and particularly to a preparation method and product of an ultra-high temperature suspension stabilizer and its application in oil well cement. Background Art

[0002] Cementing operation is an important link in oil and gas field development, and its quality is directly related to the production efficiency and safety of oil and gas wells. During the cementing process, the stability of the cement slurry is one of the key factors to ensure the cementing quality. With the continuous deepening of oil and gas exploration and development, deep and ultra-deep oil and gas resources have become important exploration targets. However, the high-temperature and high-pressure environment poses extremely high requirements on the performance of the cement slurry for cementing. At ultra-high temperatures, water is in a supercritical state, its viscosity drops sharply, and the resistance to particle settlement in the system decreases; the high-temperature dilution effect of polymer additives is serious, and their supporting force and viscous force are greatly reduced; the intensified thermal movement of solid-phase particles and the aggregation between particles accelerate the particle settlement speed. All these factors will lead to the instability of the cement slurry system. Severe particle settlement will cause an increase in the solid-phase content at the bottom of the slurry column, an increase in consistency, an increase in density, a shortening of the thickening time, and the deterioration of the comprehensive performance of the cement slurry; while more free liquid is generated in the upper layer, and a water ring or water band is formed at the top of the cement slurry to provide a channel for oil, gas, and water channeling, seriously affecting the interlayer sealing quality.

[0003] In engineering, suspension stabilizers are often added to alleviate the suspension instability and water separation of the cement slurry. Natural mineral ultra-high temperature suspension stabilizers mainly include some specially treated mineral materials, such as silica fume, metakaolin, etc. These mineral materials can form a stable suspension system at high temperatures and have good high-temperature resistance. At the same time, they can also form good compatibility with other additives to improve the overall performance of the cement slurry. However, in an ultra-high temperature environment, the thermal movement of inorganic suspension material particles intensifies, the viscosity of the water body decreases, resulting in a reduction in its viscous force and the collapse of the supporting framework, and its hydration and dispersion ability in a high-salt formation environment is severely inhibited, thus reducing its efficiency in an ultra-high temperature environment. Organic polymer materials are another type of commonly used suspension stabilizers, which can be dispersed in water to form an intertwined network structure. Their strong hydrophilic groups form hydrogen bonds with water molecules to adsorb water molecules, reducing the degree of freedom of water molecules, thereby increasing the liquid-phase viscosity, increasing the viscosity between cement particles, increasing the static shear force of the cement slurry, and improving the suspension stability of the slurry. Natural polymer materials are greatly affected by temperature. Higher temperatures will cause different degrees of degradation of natural organic polymer materials and affect the suspension stability of the slurry. Synthetic polymer suspension stabilizers can be prepared according to product technical requirements through molecular structure design, selection of suitable functional monomers, and special processing techniques. These polymers can form a stable suspension system at high temperatures and have good temperature and salt resistance performance.

[0004] Although various current suspension stabilizers can meet the requirements of high-temperature cement slurries at 140 - 180°C, they are less applicable to ultra-high-temperature cement slurries above 200°C. Summary of the Invention

[0005] Based on the above, the present invention provides a preparation method of an ultra-high-temperature suspension stabilizer, the product thereof, and its application in oil well cement. The cement slurry added with this suspension stabilizer will not have an overly large consistency at normal temperature (20°C), but can maintain a certain consistency at ultra-high temperature (above 200°C).

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a preparation method of an ultra-high-temperature suspension stabilizer, which includes the following steps:

[0008] Step 1: Dissolve 2-acrylamido-2-methylpropanesulfonic acid monomer, temperature-sensitive monomer, and N-vinylpyrrolidone monomer in water to obtain a monomer solution;

[0009] Step 2: Add an initiator to the monomer solution and heat it to 30 - 60°C to obtain a mixed solution;

[0010] Step 3: Add a reducing agent to the mixed solution for reaction to obtain a polymer solution;

[0011] Step 4: Perform freeze-drying on the polymer solution to obtain the ultra-high-temperature suspension stabilizer.

[0012] Another technical solution of the present invention is an ultra-high-temperature suspension stabilizer prepared according to the above preparation method.

[0013] Another technical solution of the present invention is the application of the above ultra-high-temperature suspension stabilizer in a cementing project.

[0014] Another technical solution of the present invention is a cement slurry, the raw materials of which include the above ultra-high-temperature suspension stabilizer.

[0015] The present invention discloses the following technical effects:

[0016] 1. The preparation method of the present invention has a simple process and inexpensive and easily available raw materials, which is conducive to large-scale production.

[0017] 2. Most of the existing suspension stabilizers are applicable to high-temperature cement slurries at 140 - 180°C. The present invention makes up for the defect that the existing suspension stabilizers cannot be used in ultra-high-temperature cement slurries.

[0018] 3. Although some existing technologies can meet the requirements of the suspension stability of cement slurry at high temperatures, they will increase the consistency of cement slurry at normal temperatures, resulting in difficulties in mixing the slurry. The present invention remedies this technical defect, such that the initial consistency of the cement slurry added with this suspension stabilizer does not exceed 40 Bc, and at the same time, it can maintain the suspension stability at ultra-high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a comparative infrared spectrum diagram of the ultra-high temperature suspension stabilizers prepared in Example 1 and Example 4 of the present invention.

[0021] Figure 2 It is a thermogravimetric curve of the ultra-high temperature suspension stabilizers prepared in Example 1 and Example 4 of the present invention; among them, (a) is Example 1, and (b) is Example 4. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing specific implementation modes and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0025] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0026] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0027] The first aspect of the present invention provides a preparation method of a super-high temperature suspension stabilizer, comprising the following steps:

[0028] Step 1, dissolving 2-acrylamido-2-methylpropanesulfonic acid monomer, temperature-sensitive monomer, and N-vinylpyrrolidone monomer in water to obtain a monomer solution;

[0029] Step 2, adding an initiator to the monomer solution and heating to 30-60 °C to obtain a mixed solution;

[0030] Step 3, adding a reducing agent to the mixed solution for reaction to obtain a polymer solution;

[0031] Step 4, freeze-drying the polymer solution to obtain the super-high temperature suspension stabilizer.

[0032] In a preferred embodiment of the present invention, the pH of the monomer solution is 6-7.

[0033] The present invention regulates the pH of the monomer solution by adding an alkali solution such as NaOH solution.

[0034] In a preferred embodiment of the present invention, the temperature-sensitive monomer is N,N-diethylacrylamide, N,N-dimethylacrylamide, or N-isopropylacrylamide.

[0035] In a preferred embodiment of the present invention, the mass ratio of the 2-acrylamido-2-methylpropanesulfonic acid monomer, the temperature-sensitive monomer, and the N-vinylpyrrolidone monomer is (28-30):(8-10):(1-2).

[0036] If the addition amount of the temperature-sensitive monomer and N-vinylpyrrolidone is too high, it will cause a significant decrease in the molecular weight of the polymer and even lead to polymerization failure, making the prepared product unable to be used as a suspension stabilizer; if the dosage of the 2-acrylamido-2-methylpropanesulfonic acid monomer is too high while the addition amount of the temperature-sensitive monomer and N-vinylpyrrolidone is too low, it will cause the thermal stability of the prepared product to deteriorate and cannot meet the use requirements at 200 °C.

[0037] The amount of water used in the present invention is 5-10 times the total mass of the monomers.

[0038] In a preferred embodiment of the present invention, the initiator is ammonium persulfate, potassium persulfate or azobisisobutyramidine hydrochloride; the reducing agent is tetramethylethylenediamine or sodium bisulfite.

[0039] In the present invention, adding a reducing agent allows the reaction to proceed at a lower temperature.

[0040] In a preferred embodiment of the present invention, the addition amount of the initiator is 0.6 wt% of the total mass of 2-acrylamido-2-methylpropanesulfonic acid monomer, thermosensitive monomer and N-vinylpyrrolidone monomer; the molar ratio of the initiator to the reducing agent is 1:0.8.

[0041] In a preferred embodiment of the present invention, in step 3, the temperature of the reaction is 30 - 60 °C; the reaction time is 2 - 6 h.

[0042] The reaction is carried out under stirring conditions; the stirring rate is 220 rpm ± 20 rpm.

[0043] After the freeze-drying, it further includes a step of grinding into powder. The present invention has no special requirements for the particle size of grinding, and it is ground into powder form.

[0044] The second aspect of the present invention provides a ultra-high temperature suspension stabilizer prepared by the above preparation method.

[0045] The third aspect of the present invention provides an application of the above ultra-high temperature suspension stabilizer in cementing engineering.

[0046] In cementing engineering, the addition amount of the ultra-high temperature suspension stabilizer in cement is 0.2% - 1% of the mass of the cement. The ultra-high temperature suspension stabilizer of the present invention can meet the construction requirements of corresponding working conditions in cementing engineering, ensure cementing safety, and improve cementing quality.

[0047] The fourth aspect of the present invention provides a cement slurry, the raw materials of which include the above ultra-high temperature suspension stabilizer.

[0048] The ultra-high temperature suspension stabilizer accounts for 0.2% - 1% of the mass of the cement in the cement slurry.

[0049] Adding the suspension stabilizer obtained by the preparation method of the present invention into the oil well cement slurry system can maintain the suspension stability of the cement slurry in an ultra-high temperature environment and will not make the initial consistency of the cement slurry too high. The raw materials of the present invention are convenient to obtain, the preparation method is simple, and it meets the application requirements, which can effectively improve the suspension stability of the ultra-high temperature cement slurry system and ensure the safety of cementing operations.

[0050] The technical solutions described in the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0051] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] A preparation method of an ultra-high temperature suspension stabilizer for oil well cement is as follows:

[0054] Step 1: Sequentially dissolve 28 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of N,N-dimethylacrylamide, and 2 g of N-vinylpyrrolidone in 160 g of deionized water, and adjust the pH to 6.5 with NaOH solution, and stir evenly to obtain a monomer solution;

[0055] Step 2: Add ammonium persulfate to the solution under stirring at 220 rpm ± 20 rpm, and heat to raise the system temperature. Among them, the addition amount of ammonium persulfate is 0.6 wt% of the total mass of the monomers, and the system temperature is 30 °C;

[0056] Step 3: Add tetramethylethylenediamine to the solution obtained in Step 2, maintain at 30 °C, and stir at 220 rpm ± 20 rpm for 4 h to obtain a polymer solution. Among them, the addition amount of tetramethylethylenediamine is 0.8 (mole fraction) of the addition amount of ammonium persulfate;

[0057] Step 4: Freeze-dry the solution obtained in Step 3, grind it to obtain a white powder, which is the ultra-high temperature suspension stabilizer for oil well cement.

[0058] Step 5: Suspension stability performance test: Test the thickening curve of the cement slurry at 200 °C, 100 MPa, and 90 min. After the thickening experiment reaches the target temperature and pressure for 30 min, turn off the motor, cure for 30 min at the experimental temperature and pressure, turn on the motor again, and record the recoil value of the consistency at the moment of starting. After the consistency is stable for a period of time, stop the thickening experiment, lower the temperature to within 90 °C and remove it, stir it and pour it into a 250 mL graduated cylinder, place it in a 90 °C oven, cure for 2 h and then take it out, and measure the density difference between the upper and lower parts of the cement slurry. The cement slurry formula is: 500 g of G-class oil well cement + 35% 200-mesh quartz sand + 1% dispersant DRS-1S + 5% retarder GH-9 + 5% fluid loss reducer DRF-3L + 0.6% ultra-high temperature suspension stabilizer + 49.4% water (the percentages in the cement slurry formula all represent the mass percentages based on G-class oil well cement; the same below).

[0059] The structure of the ultra-high temperature suspension stabilizer prepared in Example 1 is as Figure 1As shown in the figure; (a) in the figure represents Example 1, and (b) represents Example 4. From Figure 1 It can be seen that the product is the target product, and different thermosensitive monomers can all participate in copolymerization and there is no monomer residue in the reaction.

[0060] Example 2

[0061] A preparation method of a ultra-high temperature suspension stabilizer for oil well cement is as follows:

[0062] Step 1, sequentially dissolve 28 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of N,N-diethylacrylamide, and 2 g of N-vinylpyrrolidone in 160 g of deionized water according to mass, and adjust the pH to 6.8 with NaOH solution, and stir evenly to obtain a monomer solution;

[0063] Step 2, add ammonium persulfate to the solution under stirring and heat to raise the temperature of the system. Among them, the addition amount of ammonium persulfate is 0.6 wt% of the total mass of the monomers, and the system temperature is 60 °C;

[0064] Step 3, stir the solution obtained in Step 2 at 60 °C for 0.5 h, wait for the temperature to stabilize and then raise the temperature to 80 °C, and stir at 220 rpm ± 20 rpm for 4 h to obtain a polymer solution.

[0065] Step 4, freeze-dry the solution obtained in Step 3, grind it to obtain a white powder, which is the ultra-high temperature suspension stabilizer for oil well cement.

[0066] Step 5, suspension stability performance test: Test the thickening curve of the cement slurry at 200 °C, 100 MPa, and 90 min. After the thickening experiment reaches the target temperature and pressure for 30 min, turn off the motor, cure for 30 min at the experimental temperature and pressure, turn on the motor again, and record the recoil value of the consistency at the moment of starting. After the consistency is stable after a period of time, stop the thickening experiment, lower the temperature to within 90 °C and remove it, stir and pour it into a 250 mL graduated cylinder, place it in an oven at 90 °C, cure for 2 h and then take it out, and measure the density difference between the upper and lower parts of the cement slurry. The cement slurry formula is: 500 g of G-class oil well cement + 35% 200-mesh quartz sand + 1% dispersant DRS-1S + 5% retarder GH-9 + 5% fluid loss reducer DRF-3L + 0.6% ultra-high temperature suspension stabilizer + 49.4% water.

[0067] Example 3

[0068] A preparation method of a ultra-high temperature suspension stabilizer for oil well cement is as follows:

[0069] Step 1: Dissolve 30 g of 2-acrylamido-2-methylpropanesulfonic acid, 9 g of N,N-dimethylacrylamide, and 1 g of N-vinylpyrrolidone monomer in 160 g of deionized water in sequence by mass. Then adjust the pH to 6.6 with NaOH solution and stir evenly to obtain a monomer solution;

[0070] Step 2: Add ammonium persulfate to the solution under stirring and heat to raise the system temperature. Among them, the addition amount of ammonium persulfate is 0.6 wt% of the total mass of the monomers, and the system temperature is 30 °C;

[0071] Step 3: Add tetramethylethylenediamine to the solution obtained in Step 2, maintain at 30 °C, and stir at 220 rpm ± 20 rpm for 6 h to obtain a polymer solution. Among them, the addition amount of tetramethylethylenediamine is 0.8 (mole fraction) of the addition amount of ammonium persulfate.

[0072] Step 4: The same as Step 4 of Example 1.

[0073] Example 4

[0074] A preparation method of a ultra-high temperature suspension stabilizer for oil well cement is as follows:

[0075] Step 1: Dissolve 30 g of 2-acrylamido-2-methylpropanesulfonic acid, 8 g of N-isopropylacrylamide, and 2 g of N-vinylpyrrolidone monomer in 160 g of deionized water in sequence by mass. Then adjust the pH to 6.6 with NaOH solution and stir evenly to obtain a monomer solution;

[0076] Step 2: Add ammonium persulfate to the solution under stirring and heat to raise the system temperature. Among them, the addition amount of ammonium persulfate is 0.6 wt% of the total mass of the monomers, and the system temperature is 30 °C;

[0077] Step 3: Add tetramethylethylenediamine to the solution obtained in Step 2, maintain at 30 °C, and stir at 220 rpm ± 20 rpm for 4 h to obtain a polymer solution. Among them, the addition amount of tetramethylethylenediamine is 0.8 (mole fraction) of the addition amount of ammonium persulfate;

[0078] Step 4: Freeze-dry the solution obtained in Step 3, grind it to obtain a white powder, which is the ultra-high temperature suspension stabilizer for oil well cement.

[0079] Step 5, Suspension Stability Performance Test: Test the thickening curve of the cement slurry at 200 °C, 100 MPa, and 90 min. After 30 min when the thickening experiment reaches the target temperature and pressure, turn off the motor, cure for 30 min at the experimental temperature and pressure, then turn on the motor again and record the recoil value of the consistency at the moment of starting. After the consistency stabilizes after a period of time, stop the thickening experiment, lower the temperature to within 90 °C and disassemble, stir and pour it into a 250 mL graduated cylinder, place it in a 90 °C oven, take it out after curing for 2 h, and measure the density difference between the upper and lower parts of the cement slurry. The cement slurry formula is: 500 g of G-class oil well cement + 35% of 200-mesh quartz sand + 1% of dispersant DRS-1S + 5% of retarder GH-9 + 5% of fluid loss reducer DRF-3L + 0.6% of ultra-high temperature suspension stabilizer + 49.4% of water.

[0080] Comparative Example 1

[0081] Refer to Example 1, except that when performing the suspension stability performance test, the ultra-high temperature suspension stabilizer is not added (that is, the preparation of the ultra-high temperature suspension stabilizer is omitted, and the addition of the ultra-high temperature suspension stabilizer is omitted during the suspension stability performance test).

[0082] Suspension Stability Performance Test: Test the thickening curve of the cement slurry at 200 °C, 100 MPa, and 90 min. After 30 min when the thickening experiment reaches the target temperature and pressure, turn off the motor, cure for 30 min at the experimental temperature and pressure, then turn on the motor again and record the recoil value of the consistency at the moment of starting. After the consistency stabilizes after a period of time, stop the thickening experiment, lower the temperature to within 90 °C and disassemble, stir and pour it into a 250 mL graduated cylinder, place it in a 90 °C oven, take it out after curing for 2 h, and measure the density difference between the upper and lower parts of the cement slurry. The cement slurry formula is: 500 g of G-class oil well cement + 35% of 200-mesh quartz sand + 1% of dispersant DRS-1S + 5% of retarder GH-9 + 5% of fluid loss reducer DRF-3L + 50% of water.

[0083] Comparative Example 2

[0084] Refer to Example 1, except that when performing the suspension stability performance test, the ultra-high temperature suspension stabilizer is added in different dosages.

[0085] A preparation method of an ultra-high temperature suspension stabilizer for oil well cement is as follows:

[0086] Step 1, sequentially dissolve 28 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of N,N-dimethylacrylamide, and 2 g of N-vinylpyrrolidone in 160 g of deionized water, and adjust the pH to 6.5 with NaOH solution, and stir evenly to obtain a monomer solution;

[0087] Step 2: Add ammonium persulfate to the solution under stirring and heat to increase the system temperature. Herein, the addition amount of ammonium persulfate is 0.6 wt% of the total mass of the monomers, and the temperature is 30°C.

[0088] Step 3: Add tetramethylethylenediamine to the solution obtained in Step 2, maintain at 30°C, and stir at 220 rpm ± 20 rpm for 4 h to obtain a polymer solution. Herein, the addition amount of tetramethylethylenediamine is 0.8 (mole fraction) of the addition amount of ammonium persulfate.

[0089] Step 4: Freeze-dry the solution obtained in Step 3, grind it to obtain a white powder, which is the ultra-high temperature suspension stabilizer for oil well cement.

[0090] Step 5: Suspension stability performance test: Test the thickening curve of the cement slurry at 200°C, 100 MPa, and 90 min. After the thickening experiment reaches the target temperature and pressure for 30 min, turn off the motor, cure for 30 min at the experimental temperature and pressure, turn on the motor again, and record the recoil value of the consistency at the moment of starting. After the consistency is stable after a period of time, stop the thickening experiment, lower the temperature to within 90°C and remove, stir and pour it into a 250 mL graduated cylinder, place it in an oven at 90°C, cure for 2 h and then take it out, and measure the density difference between the upper and lower parts of the cement slurry. The cement slurry formula is: 500 g of G-class oil well cement + 35% 200-mesh quartz sand + 1% dispersant DRS-1S + 5% retarder GH-9 + 5% fluid loss reducer DRF-3L + 0.2% ultra-high temperature suspension stabilizer + 49.8% water.

[0091] Comparative Example 3

[0092] Refer to Example 1, except that when performing the suspension stability performance test, the ultra-high temperature suspension stabilizer is added in different amounts.

[0093] A preparation method of an ultra-high temperature suspension stabilizer for oil well cement comprises the following steps:

[0094] Step 1: Dissolve 28 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of N,N-dimethylacrylamide, and 2 g of N-vinylpyrrolidone in 160 g of deionized water in sequence by mass, and adjust the pH to 6.5 with NaOH solution, and stir evenly to obtain a monomer solution.

[0095] Step 2: Add ammonium persulfate to the solution under stirring and heat to increase the system temperature. Herein, the addition amount of ammonium persulfate is 0.6 wt% of the total mass of the monomers, and the temperature is 30°C.

[0096] Step 3: Add tetramethylethylenediamine to the solution obtained in Step 2, maintain at 30°C, and stir at 220 rpm ± 20 rpm for 4 h to obtain a polymer solution. Herein, the addition amount of tetramethylethylenediamine is 0.8 (mole fraction) of the addition amount of ammonium persulfate.

[0097] Step 4: Freeze-dry the solution obtained in Step 3, grind it to obtain a white powder, which is the ultra-high temperature suspension stabilizer for oil well cement.

[0098] Step 5: Suspension stability performance test: Test the thickening curve of the cement slurry at 200 °C, 100 MPa, and 90 min. After the thickening experiment reaches the target temperature and pressure for 30 min, turn off the motor. Cure for 30 min at the experimental temperature and pressure, then turn on the motor again and record the recoil value of the consistency at the moment of starting. After the consistency stabilizes after a period of time, stop the thickening experiment, lower the temperature to within 90 °C and disassemble, stir and pour it into a 250 mL graduated cylinder, place it in an oven at 90 °C, take it out after curing for 2 h, and measure the density difference between the upper and lower layers of the cement slurry. The cement slurry formula is: 500 g of G-class oil well cement + 35% 200-mesh quartz sand + 1% dispersant DRS-1S + 5% retarder GH-9 + 5% fluid loss reducer DRF-3L + 1% ultra-high temperature suspension stabilizer + 49% water.

[0099] Application performance test

[0100] Use an FTIR infrared spectrometer to test the infrared spectrum of the polymer prepared in Example 1. The results are as Figure 2 shown. The infrared test results indicate that all monomers participate in the polymerization and the product is the target product.

[0101] Use a thermal analyzer to conduct a thermogravimetric test on the polymers (ultra-high temperature suspension stabilizers) prepared in Examples 1 and 4. The results are as Figure 2 shown. The thermogravimetric curves show that both ultra-high temperature suspension stabilizers have good high-temperature resistance, and the temperature resistance reaches above 270 °C.

[0102] The performance test results of Examples 1, 2, 4 and Comparative Examples 1, 2, 3 are shown in Table 1. The test contents are the recoil value at the moment of starting and stopping the cement thickening experiment and the density difference test between the upper and lower layers of the cement slurry. The specific content is as follows: Test the thickening curve of the cement slurry at 200 °C, 100 MPa, and 90 min. After the thickening experiment reaches the target temperature and pressure for 30 min, turn off the motor. Cure for 30 min at the experimental temperature and pressure, then turn on the motor again and record the recoil value of the consistency at the moment of starting. After the consistency stabilizes after a period of time, stop the thickening experiment, lower the temperature to within 90 °C and disassemble, stir and pour it into a 250 mL graduated cylinder, place it in an oven at 90 °C, take it out after curing for 2 h, and measure the density difference between the upper and lower layers of the cement slurry. Among them, the initial consistency of the cement slurry shall not exceed 40 Bc. The qualified standard for the start-stop test is that the recoil value is less than 40 Bc, and the qualified standard for the density difference test is that the density difference between the upper and lower layers is less than 0.05 g / cm 3 .

[0103] Table 1 Sedimentation stability test results of ultra-high temperature suspension stabilizer

[0104]

[0105]

[0106] It can be concluded from Table 1 that the shutdown and density difference tests of the ultra-high temperature suspension stabilizers prepared by Examples 1, 2, and 4 of the present invention are all qualified and can meet the requirements; the shutdown and density difference tests of Comparative Example 1 without adding the ultra-high temperature suspension stabilizer are all unqualified; and when the ultra-high temperature suspension stabilizer is added in an amount less than 0.6%, although the density difference test can meet the requirements, the shutdown test is unqualified; except for Comparative Example 1, no free liquid is generated in the upper layer of cement in all density difference tests. The performance test results show that the ultra-high temperature suspension stabilizer prepared by the present invention can meet the sedimentation stability requirements of oil well cement at 200°C, making up for the problem of insufficient temperature resistance of existing suspension stabilizers, and at the same time has good compatibility with various other admixtures such as fluid loss reducers, retarders, etc., which is conducive to construction safety and does not affect the performance of cement.

[0107] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing an ultra-high temperature suspension stabilizer, characterized in that: The following steps are involved: Step 1, dissolving 2-acrylamide-2-methylpropanesulfonic acid monomer, temperature-sensitive monomer, and N-vinyl pyrrolidone monomer in water to obtain a monomer solution; Step 2, adding an initiator to the monomer solution and heating to 30-60° C. to obtain a mixed solution; Step 3, adding a reducing agent to the mixed solution to react and obtain a polymer solution; Step 4, freeze-drying the polymer solution to obtain the ultra-high temperature suspension stabilizer; The temperature-sensitive monomer is N,N-diethylacrylamide, N,N-dimethylacrylamide or N-isopropylacrylamide; The mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid monomer, the temperature-sensitive monomer and the N-vinyl pyrrolidone monomer is (28-30): (8-10): (1-2).

2. The method for preparing the ultrahigh temperature suspension stabilizer according to claim 1, characterized in that: The pH of the monomer solution is 6-7.

3. The method for preparing the ultrahigh temperature suspension stabilizer according to claim 1, characterized in that: The initiator is ammonium persulfate, potassium persulfate or azobisisobutylamidine hydrochloride; the reducing agent is tetramethylethylenediamine or sodium bisulfite.

4. The method for preparing the ultrahigh temperature suspension stabilizer according to claim 1, characterized in that: The added amount of the initiator is 0.6wt% of the total mass of the 2-acrylamide-2-methylpropanesulfonic acid monomer, the temperature-sensitive monomer and the N-vinyl pyrrolidone monomer; the molar ratio of the initiator to the reducing agent is 1:0.

8.

5. The method for preparing the ultrahigh temperature suspension stabilizer according to claim 1, characterized in that: In step 3, the reaction temperature is 30-60° C., and the reaction time is 2-6 h.

6. The ultra-high temperature suspension stabilizer prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the ultra-high temperature suspension stabilizer as claimed in claim 6 in cementing engineering.

8. A cement slurry, characterized in that: The raw materials include the ultra-high temperature suspension stabilizer described in claim 6.

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