Preparation method and application of oil well cement fluid loss agent

Abstract

The invention discloses a preparation method and application of an oil well cement fluid loss agent, and the preparation method comprises the following steps: (1) uniformly mixing and stirring a water-containing N-tert-butyl acrylamide crude product and a long carbon chain quaternary ammonium salt with the carbon chain length of 12-22, and standing to obtain a tertiary amine feed liquid; (2) sequentially adding 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and isopropanol into the sodium carbonate solution, uniformly mixing, and adjusting the pH value to be acidic to obtain a monomer mixed solution; (3) adding the tertiary amine material liquid into the monomer mixed liquid, and uniformly mixing to obtain a mixed raw material liquid; and (4) performing constant-temperature water bath on the mixed raw material solution, adding an ammonium persulfate solution into the mixed raw material solution while stirring, stopping stirring after the reaction is finished, drying and crushing to obtain the oil well cement fluid loss agent. The prepared oil well cement fluid loss agent is added into oil well cement slurry, and the fluidity of the oil well cement slurry can be ensured without adding a dispersing agent.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid loss control agents. Specifically, it is a preparation method and application of an oil well cement fluid loss control agent. Background Art

[0002] During the cementing operation, to ensure the basic properties of the pumped cement slurry, various cementing additives are usually added to the cement slurry. Among them, the fluid loss control agent is the most critical and the most used cementing additive. On the one hand, the fluid loss control agent can ensure that the density, thickening time, rheological properties, etc. of the cement slurry do not change, ensuring the safety of the cementing operation; on the other hand, it can prevent the filtrate of the cement slurry from entering the reservoir and causing varying degrees of damage to the reservoir.

[0003] Currently, most of the commonly used polymer fluid loss control agents for oil well cement are synthesized with 2-acrylamido-2-methylpropanesulfonic acid, acrylamide / N,N-dimethylacrylamide as the main monomers. However, when the fluid loss control agent synthesized with acrylamide / N,N-dimethylacrylamide is used in cement slurry, there is generally a phenomenon of cement slurry thickening, and the rheological properties of the cement slurry become worse, which is not conducive to the pumping of the cement slurry. In severe cases, it will cause cementing failure. Usually, a dispersant needs to be added to change the rheological properties of the cement slurry, which not only increases the cementing cost but also affects the performance of the fluid loss control agent itself. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a preparation method and application of an oil well cement fluid loss control agent, so as to prepare an oil well cement fluid loss control agent with good fluid loss control ability and dispersion performance. When this oil well cement fluid loss control agent is added to the oil well cement slurry, the fluidity of the oil well cement slurry can be ensured without adding an external dispersant.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A preparation method of an oil well cement fluid loss control agent, comprising the following steps:

[0007] Step (1): Mix the crude aqueous N-tert-butylacrylamide and a long-chain quaternary ammonium salt with a carbon chain length of 12 to 22 evenly by stirring to obtain a tertiary amine feed liquid. Since N-tert-butylacrylamide is a hydrophobic monomer and cannot participate in aqueous solution polymerization when directly mixed with monomers such as AMPS, in the present invention, a long-chain quaternary ammonium salt with a carbon chain length of 12 to 22 is used to carry out cationic modification on it, increasing its hydrophilicity and enabling it to participate in polymerization with monomers such as AMPS to synthesize a fluid loss reducer. Moreover, compared with other types of cationic surfactants and quaternary ammonium salt surfactants with other carbon chain lengths, the fluid loss reducer synthesized by using N-tert-butylacrylamide modified with a long-chain quaternary ammonium salt with a carbon chain length of 12 to 22 as one of the monomers has a higher molecular toughness of the polymer chain, and at the same time, the synthesized fluid loss reducer polymer also has more excellent temperature resistance and salt tolerance performance.

[0008] Step (2): Sequentially add 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and isopropanol to the sodium carbonate solution, mix evenly, and then adjust the pH to acidic to obtain a monomer mixture.

[0009] Step (3): Add the tertiary amine feed liquid to the monomer mixture and mix evenly to obtain a mixed raw material liquid.

[0010] Step (4): Carry out a constant temperature water bath on the mixed raw material liquid, add an ammonium persulfate solution to the mixed raw material liquid while stirring, stop stirring after the reaction is completed and transfer it to a storage tank, and dry and crush it to obtain an oil well cement fluid loss reducer.

[0011] In the preparation method of the above-mentioned oil well cement fluid loss reducer, in step (1), the long-chain quaternary ammonium salt is dodecylamide dimethyl hydroxypropyl ammonium chloride; the mass ratio of the crude aqueous N-tert-butylacrylamide to dodecylamide dimethyl hydroxypropyl ammonium chloride is (20 - 30):(0.2 - 0.5); when the mass ratio of the crude aqueous N-tert-butylacrylamide to dodecylamide dimethyl hydroxypropyl ammonium chloride is within the above range, dodecylamide dimethyl hydroxypropyl ammonium chloride can carry out sufficient cationic modification on N-tert-butylacrylamide to enable it to be completely dissolved in water; if the dosage of dodecylamide dimethyl hydroxypropyl ammonium chloride is lower than the above range, some N-tert-butylacrylamide solids in the crude aqueous N-tert-butylacrylamide will not be completely dissolved, and if the dosage of dodecylamide dimethyl hydroxypropyl ammonium chloride exceeds the above range, it will cause more bubbles when the modified N-tert-butylacrylamide participates in the polymerization reaction as a monomer later, affecting the polymerization effect of the monomer; in the crude aqueous N-tert-butylacrylamide, the mass fraction of N-tert-butylacrylamide is 50 - 55wt%, the mass fraction of sulfonate is 3 - 5wt%, the mass fraction of water is 36 - 48wt%, and the balance is impurities.

[0012] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (1), the mass ratio of the crude N-tert-butylacrylamide containing water to dimethyldihydroxypropylammonium chloride of dodecylamide is 100:1; in the crude N-tert-butylacrylamide containing water, the mass fraction of N-tert-butylacrylamide is 55 wt%, the mass fraction of sulfonate is 5 wt%, the mass fraction of water is 36 wt%, and the balance is impurities.

[0013] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (1), the preparation method of the crude N-tert-butylacrylamide containing water is as follows: water is added to the kettle residue obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid, stirred and mixed evenly, and the filter cake obtained by pressure filtration with a filter press is the crude N-tert-butylacrylamide containing water; the mass-volume ratio of the kettle residue obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid to water is 1 g:(2-3) mL.

[0014] The refined kettle residue of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) belongs to hazardous waste in the chemical industry. In the present invention, through the addition of water for separation treatment, the crude N-tert-butylacrylamide containing water is prepared. In addition to containing N-tert-butylacrylamide, the crude N-tert-butylacrylamide containing water also contains some sulfonates, so that it has both fluid loss control and dispersion characteristics. N-tert-butylacrylamide contains a hydrophobic group. After cationic modification with dimethyldihydroxypropylammonium chloride of dodecylamide, a tertiary amine feed liquid is obtained. The tertiary amine feed liquid is used to synthesize a hydrophobically associating water-soluble polymer. The synthesized water-soluble polymer can increase the viscosity of the aqueous solution, and at the same time increase the molecular toughness of the original polymer chain, improving the temperature and salt tolerance of the original polymer. In addition, the sulfonates contained in the crude N-tert-butylacrylamide containing water can be used as a cement dispersant and applied to the process of oil and gas well cementing operations. It can significantly reduce the water-cement ratio, improve the rheological properties of the cement slurry, and achieve turbulence at a lower displacement and pump pressure, thereby improving the success rate and cementing quality of the cementing operation. It was also found in the experiment that compared with directly adding the substance modified with the crude N-tert-butylacrylamide containing water in the present invention as a raw material to synthesize a fluid loss reducer in the oil well cement slurry, using pure N-tert-butylacrylamide modified with dimethyldihydroxypropylammonium chloride of dodecylamide as the reaction raw material of the monomer fluid loss reducer, and synthesizing the fluid loss reducer polymer by the same method as in the present invention, and adding the same proportion of sulfonates as in the crude N-tert-butylacrylamide containing water in the present invention to the oil well cement slurry, the fluidity of the finally prepared oil well cement slurry is still not as good as that of directly adding the fluid loss reducer prepared by the preparation method of the present invention. This may be because the sulfonates contained in the crude N-tert-butylacrylamide containing water interact with the synthesized polymer under the preparation process conditions of the present invention to form a homogeneous and stable fluid loss reducer-dispersant complex, so that after being added to the oil well cement slurry, it can effectively play the role of fluid loss control while improving the fluidity of the oil well cement slurry.

[0015] The present invention utilizes the residue of AMPS kettle to prepare crude N-tert-butylacrylamide containing water. The method is simple and it can be directly used to prepare a fluid loss reducer for oil well cement without purifying N-tert-butylacrylamide. This not only effectively utilizes the residue, which is a hazardous waste in the chemical industry, but also, compared with using pure N-tert-butylacrylamide, the prepared fluid loss reducer has a more significant improvement effect on the comprehensive performance of the well cement slurry. Compared with the fluid loss reducer synthesized from acrylamide / N,N-dimethylacrylamide in the same proportion, the fluid loss reducer synthesized from the crude N-tert-butylacrylamide containing water prepared by the present invention has significantly better dispersion ability.

[0016] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (2), the mass fraction of sodium carbonate in the sodium carbonate solution is 5-10 wt%; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and isopropanol is (180-200):(4-6):(1-3); in the monomer mixture, the mass fraction of 2-acrylamido-2-methylpropanesulfonic acid is 24-35 wt%; when adjusting the pH, the pH is adjusted to 5-6 with sodium carbonate. AMPS, acrylic acid, and tertiary amine feed liquid are the main polymer monomers for preparing the fluid loss reducer, isopropanol is the regulator for the molecular weight of the fluid loss reducer polymer, sodium carbonate is the pH regulator, and water is the reaction solvent; if the pH of the prepared monomer mixture is lower than 5, the molecular weight of the fluid loss reducer polymer prepared by the reaction is too large, and if the pH of the prepared monomer mixture is higher than 6, the molecular weight of the fluid loss reducer polymer prepared by the reaction is too small, both of which will affect the use performance of the fluid loss reducer; by controlling the ratio between the main polymer monomers, the dosage of the polymer molecular weight regulator, and the pH value of the monomer mixture, the present invention can make the molecular weight of the polymer prepared by the reaction moderate, which is beneficial to improving the fluid loss reduction and dispersion of the fluid loss reducer.

[0017] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (2), the mass fraction of sodium carbonate in the sodium carbonate solution is 6.5-7.5 wt%; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and isopropanol is 90:2:1; in the monomer mixture, the mass fraction of 2-acrylamido-2-methylpropanesulfonic acid is 24-30 wt%; when adjusting the pH, the pH is adjusted to 5 with sodium carbonate.

[0018] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (3), in the mixed raw material liquid, the mass ratio of the tertiary amine feed liquid to 2-acrylamido-2-methylpropanesulfonic acid is 1:(5-8); if the dosage ratio of the tertiary amine feed liquid to AMPS is too large, the molecular weight of the synthesized fluid loss reducer is too small, which will affect the fluid loss reducing performance of the fluid loss reducer; if the dosage ratio of the two is too small, it will cause the molecular weight of the synthesized fluid loss reducer to be too large, which will have an adverse effect on the rheological properties of the cement slurry when it is used in the oil well cement slurry.

[0019] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (4), the constant temperature water bath temperature is 55-60°C, the stirring rate is 300-400 rpm, and the reaction time is 4-5 h; the mass fraction of the ammonium persulfate solution is 4.5-10 wt%; the dosage of ammonium persulfate is 0.3-0.5 wt% of the total mass of the tertiary amine feed liquid, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid; the drying conditions are: 100-105°C, 5-6 h; after pulverization, it passes through a 50-mesh sieve.

[0020] In the preparation method of the above-mentioned fluid loss reducer for oil well cement, in step (4), the constant temperature water bath temperature is 60°C, the stirring rate is 350-400 rpm, and the reaction time is 5 h; the ammonium persulfate solution is prepared by mixing ammonium persulfate and water according to a mass-volume ratio of 1 g:10 mL; the dosage of ammonium persulfate is 0.45-0.50 wt% of the total mass of the tertiary amine feed liquid, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid; the drying conditions are: 105°C, 5 h.

[0021] An application of a fluid loss reducer for oil well cement, 5-10 parts by weight of the fluid loss reducer for oil well cement prepared by using the above-mentioned preparation method of the fluid loss reducer for oil well cement is added to 800-1000 parts by weight of oil well cement, and 300-400 parts by weight of water is added and mixed and stirred evenly to prepare an oil well cement slurry; preferably, 8 parts by weight of the fluid loss reducer for oil well cement, 800 parts by weight of oil well cement, and 320 parts by weight of water; the oil well cement slurry has good rheology for oil well cementing, and the normal pressure compressive strength after setting for 24 h is greater than 25 MPa.

[0022] The technical solution of the present invention has achieved the following beneficial technical effects:

[0023] 1. The present invention uses 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and a crude product of water-containing N-tert-butylacrylamide modified with a long-chain quaternary ammonium salt having a carbon chain length of 12 to 22 as the main polymer monomers, and uses isopropanol as a polymer molecular weight regulator. By controlling the ratio between the polymer monomers, the amount of the polymer molecular weight regulator, and the pH value of the monomer mixture, the molecular weight of the polymer synthesized by the reaction can be made moderate. The water-soluble polymer synthesized with the crude product of water-containing N-tert-butylacrylamide modified with a long-chain quaternary ammonium salt having a carbon chain length of 12 to 22 as a polymer monomer can increase the molecular toughness of the original polymer chain, thereby improving its temperature and salt resistance performance; using it as a fluid loss reducer can significantly increase the viscosity of the aqueous solution, thereby preparing a fluid loss reducer with good fluid loss reduction and dispersibility.

[0024] 2. The crude product of water-containing N-tert-butylacrylamide self-prepared in the present invention is obtained by using the residue from the refining kettle of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as the raw material and subjecting it to simple water addition treatment followed by pressure filtration. In addition to containing N-tert-butylacrylamide, this crude product of water-containing N-tert-butylacrylamide also contains some sulfonates. The presence of sulfonates enables the fluid loss reducer prepared in the present invention to have both fluid loss control and dispersion characteristics. Therefore, adding the fluid loss reducer prepared by using the preparation raw materials and process conditions of the present invention to the oil well cement slurry can ensure the fluidity of the oil well cement slurry without adding an external dispersant. The preparation method of the oil well cement fluid loss reducer of the present invention effectively utilizes the residue from the refining kettle of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), which belongs to the hazardous waste in the chemical industry. It not only effectively treats chemical waste, but also prepares a fluid loss reducer with good fluid loss reduction and dispersion, reducing the cost of oil well cementing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The thickening curve graph of the oil well cement prepared with the oil well cement fluid loss reducer prepared in Example 1 of the present invention;

[0026] Figure 2 The thickening curve graph of the oil well cement prepared with the oil well cement fluid loss reducer prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Example 1

[0028] The preparation method of the oil well cement fluid loss reducer in this example includes the following steps:

[0029] Step (1): Mix 30 g of the crude product of water-containing N-tert-butylacrylamide and 0.5 g of dodecylamide dimethyl hydroxypropyl ammonium chloride and stir evenly to obtain a tertiary amine liquid.

[0030] The preparation method of the crude aqueous N-tert-butylacrylamide is as follows: Add 300 mL of water to 100 g of the still residue obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid. After mixing and stirring evenly, the filter cake obtained by pressure filtration through a filter press is the crude aqueous N-tert-butylacrylamide. In the crude aqueous N-tert-butylacrylamide, the mass fraction of N-tert-butylacrylamide is 55 wt%, the mass fraction of sulfonate is 5 wt%, the mass fraction of water is 36 wt%, and the balance is impurities.

[0031] Step (2): Sequentially add 180 g of 2-acrylamido-2-methylpropanesulfonic acid, 4 g of acrylic acid, and 2 g of isopropanol to a sodium carbonate solution (40 g of sodium carbonate and 500 mL of water). After mixing evenly, adjust the pH to 5 with sodium carbonate to obtain a monomer mixture.

[0032] Step (3): Add the tertiary amine feed solution prepared in step (1) to the monomer mixture prepared in step (2) and mix evenly to obtain a mixed feed solution.

[0033] Step (4): Transfer the mixed feed solution to a three-necked flask, place it in a constant temperature water bath at 60 °C, start stirring, and the stirring rate is 350 rpm. When the temperature of the mixed feed solution rises to 60 °C, while stirring, add the prepared ammonium persulfate solution (1 g of ammonium persulfate and 10 g of water) to the mixed feed solution, continue stirring and reacting for 5 h. After the reaction is completed, stop stirring, then naturally cool to room temperature, dry (105 °C, 5 h), crush, and pass through a 50-mesh sieve to obtain the fluid loss reducer for oil well cement.

[0034] Example 2

[0035] The preparation method of the fluid loss reducer for oil well cement in this example includes the following steps:

[0036] Step (1): Mix 25 g of the crude aqueous N-tert-butylacrylamide and 0.3 g of dodecylamide dimethyl hydroxypropyl ammonium chloride evenly by stirring to obtain a tertiary amine feed solution.

[0037] The preparation method of the crude aqueous N-tert-butylacrylamide is as follows: Add 300 mL of water to 100 g of the still residue obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid. After mixing and stirring evenly, the filter cake obtained by pressure filtration through a filter press is the crude aqueous N-tert-butylacrylamide. In the crude aqueous N-tert-butylacrylamide, the mass fraction of N-tert-butylacrylamide is 55 wt%, the content of sulfonate is 5 wt%, the mass fraction of water is 36 wt%, and the balance is impurities.

[0038] Step (2): Sequentially add 180 g of 2-acrylamido-2-methylpropanesulfonic acid, 4 g of acrylic acid, and 2 g of isopropanol to a sodium carbonate solution (30 g of sodium carbonate and 400 g of water). After mixing evenly, adjust the pH to 5 with sodium carbonate to obtain a monomer mixture.

[0039] Step (3): Add the tertiary amine feed solution prepared in step (1) into the monomer mixture solution prepared in step (2) and mix evenly to obtain a mixed raw material solution.

[0040] Step (4): Transfer the mixed raw material solution into a three-necked flask, place it in a constant temperature water bath at 60°C, start stirring, and the stirring rate is 400 rpm; when the temperature of the mixed raw material solution rises to 60°C, add the prepared ammonium persulfate solution (1 g of ammonium persulfate and 10 g of water) to the mixed raw material solution while stirring, continue stirring and reacting for 5 h, stop stirring after the reaction ends, then naturally cool to room temperature, dry (at 105°C, for 5 h), crush, and pass through a 50-mesh sieve to obtain the fluid loss reducer for oil well cement.

[0041] Comparative Example 1

[0042] The preparation method of the fluid loss reducer for oil well cement in this comparative example includes the following steps:

[0043] Step (1): Add 180 g of 2-acrylamido-2-methylpropanesulfonic acid, 4 g of acrylic acid, 15 g of acrylamide, and 2 g of isopropanol to the sodium carbonate solution (40 g of sodium carbonate and 500 g of water) in sequence. After mixing evenly, adjust the pH to 5 with sodium carbonate to obtain a monomer mixture solution.

[0044] Step (2): Transfer the monomer mixture solution into a three-necked flask, place it in a constant temperature water bath at 60°C, start stirring, and the stirring rate is 350 rpm; when the temperature of the mixed raw material solution rises to 60°C, add the prepared ammonium persulfate solution (1 g of ammonium persulfate and 10 g of water) to the mixed raw material solution while stirring, continue stirring and reacting for 5 h, stop stirring after the reaction ends, then naturally cool to room temperature, dry (at 105°C, for 5 h), crush, and pass through a 50-mesh sieve to obtain the fluid loss reducer for oil well cement.

[0045] Comparative Example 2

[0046] The preparation method of the fluid loss reducer for oil well cement in this comparative example includes the following steps:

[0047] Step (1): Add 180 g of 2-acrylamido-2-methylpropanesulfonic acid, 4 g of acrylic acid, 15 g of N,N-dimethylacrylamide, and 2 g of isopropanol to the sodium carbonate solution (40 g of sodium carbonate and 500 g of water) in sequence. After mixing evenly, adjust the pH to 5 with sodium carbonate to obtain a monomer mixture solution.

[0048] Step (2): Transfer the monomer mixture into a three-necked flask, place it in a constant temperature water bath at 60°C, start stirring, and the stirring rate is 350 rpm. Wait until the temperature of the mixed raw material liquid rises to 60°C, and while stirring, add the prepared ammonium persulfate solution (1 g of ammonium persulfate and 10 g of water) to the mixed raw material liquid. Continue stirring and reacting for 5 h. After the reaction is completed, stop stirring, then naturally cool to room temperature, dry (at 105°C for 5 h), pulverize, and pass through a 50-mesh sieve to obtain the fluid loss reducer for oil well cement.

[0049] Comparative Example 3

[0050] The preparation method of the fluid loss reducer for oil well cement in this comparative example includes the following steps:

[0051] Step (1): Add 180 g of 2-acrylamido-2-methylpropanesulfonic acid, 4 g of acrylic acid, 7.5 g of acrylamide, 7.5 g of N,N-dimethylacrylamide, and 2 g of isopropanol to the sodium carbonate solution (40 g of sodium carbonate and 500 g of water) in sequence. After mixing evenly, adjust the pH to 5 with sodium carbonate to obtain the monomer mixture;

[0052] Step (2): Transfer the monomer mixture into a three-necked flask, place it in a constant temperature water bath at 60°C, start stirring, and the stirring rate is 350 rpm. Wait until the temperature of the mixed raw material liquid rises to 60°C, and while stirring, add the prepared ammonium persulfate solution (1 g of ammonium persulfate and 10 g of water) to the mixed raw material liquid. Continue stirring and reacting for 5 h. After the reaction is completed, stop stirring, then naturally cool to room temperature, dry (at 105°C for 5 h), pulverize, and pass through a 50-mesh sieve to obtain the fluid loss reducer for oil well cement.

[0053] The component ratios of the raw materials used in the preparation of the fluid loss reducer in Example 1, Example 2, and Comparative Examples 1 to 3 are shown in Table 1.

[0054] Table 1

[0055] Raw material Comparative example 1 Comparative example 2 Comparative example 3 Example 1 Example 2 2 - acrylamido - 2 - methylpropanesulfonic acid 180g 180g 180g 180g 180g Acrylic acid 4g 4g 4g 4g 4g Acrylamide 15g 0 7.5g 0 0 N,N - dimethylacrylamide 0 15g 7.5g 0 0 Crude N - tert - butylacrylamide containing water 0 0 0 30g 25g Dodecylamide dimethyl hydroxypropyl ammonium chloride 0 0 0 0.5g 0.3g Isopropanol 2g 2g 2g 2g 2g

[0056] Evaluate and test the application effects of the fluid loss reducers prepared in Example 1, Example 2, and Comparative Examples 1 to 3 in oil well cement slurry. The thickening experiment conditions are: 80°C / 40 MPa / 40 min; the experimental results are shown in Table 2.

[0057] The oil well cement slurry formulas of Example 1 and Example 2 are: 800 g of Sichuan Jiahua cement (oil well cement G-grade high resistance Shanjia brand Jiahua cement), 8 g of fluid loss reducer for oil well cement, and 320 g of tap water.

[0058] The formulations of the oil well cement slurries for Comparative Examples 1 to 3 were as follows: 800 g of Sichuan Jiahua cement, 8 g of a fluid loss reducer for oil well cement, 4 g of a dispersant (a ketone-aldehyde condensate type drag reducer for oil well cement, produced by Henan Weihui Chemical Co., Ltd., drag reducer for oil well cement USZ), and 320 g of tap water.

[0059] Table 2

[0060]

[0061]

[0062] As shown in Table 2, by comparing Example 1 with Comparative Examples 1 to 3, it can be seen that compared with the fluid loss reducers synthesized using acrylamide and / or N,N-dimethylacrylamide, the fluid loss reducer prepared from the crude N-tert-butylacrylamide hydrate with a similar proportion has stronger dispersing ability, and its fluid loss and compressive strength performance are close to those of the fluid loss reducers synthesized using acrylamide and / or N,N-dimethylacrylamide. In addition, increasing the dosage of the crude N-tert-butylacrylamide hydrate can improve the dispersing ability of the fluid loss reducer.

[0063] Figure 1 and Figure 2 are the thickening curves of the oil well cement slurries prepared with the fluid loss reducers for oil well cement prepared in Example 1 and Example 2 respectively. It can be seen from the figure that for the fluid loss reducer synthesized from the crude N-tert-butylacrylamide hydrate, its thickening curve is a normal thickening curve, indicating that the crude N-tert-butylacrylamide hydrate obtained by simply treating the raffinate of the AMPS refining kettle in the present invention can be used for the synthesis of the fluid loss reducer for oil well cement, which has good fluid loss reduction performance for the oil well cement slurry, and the prepared fluid loss reducer will not reduce the rheological properties of the oil well cement slurry without adding a dispersant.

[0064] Table 3 shows the test results of the salt resistance and high temperature resistance of the fluid loss reducer for oil well cement prepared in Example 2. In Table 3, the retarder is the AMPS polymer type retarder GH-5 produced by Weihui Chemical Co., Ltd.; Sichuan Jiahua cement is the G-grade high resistance Shanjia brand Jiahua cement for oil well. It can be seen from Table 3 that the fluid loss reducer synthesized using the crude N-tert-butylacrylamide hydrate has good salt resistance and high temperature resistance.

[0065] Table 3

[0066]

[0067]

[0068] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the claims of this patent application.

Claims

1. A preparation method of a fluid loss reducer for oil well cement, characterized in that, It includes the following steps: Step (1): Mix the crude aqueous N-tert-butylacrylamide and a long-chain quaternary ammonium salt with a carbon chain length of 12 to 22 evenly by stirring to obtain a tertiary amine feed liquid; Step (2): Add 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and isopropanol to the sodium carbonate solution in sequence. After mixing evenly, adjust the pH to acidic to obtain a monomer mixture; Step (3): Add the tertiary amine feed liquid to the monomer mixture and mix evenly to obtain a mixed raw material liquid; Step (4): Carry out a constant-temperature water bath on the mixed raw material liquid. While stirring, add an ammonium persulfate solution to the mixed raw material liquid. After the reaction ends, stop stirring, dry and crush to obtain a fluid loss reducer for oil well cement.

2. The preparation method of the fluid loss reducer for oil well cement according to claim 1, characterized in that In step (1), the long-chain quaternary ammonium salt is dodecylamide dimethyl hydroxypropyl ammonium chloride; the mass ratio of the crude aqueous N-tert-butylacrylamide to dodecylamide dimethyl hydroxypropyl ammonium chloride is (20 - 30):(0.2 - 0.5); in the crude aqueous N-tert-butylacrylamide, the mass fraction of N-tert-butylacrylamide is 50 - 55 wt%, the mass fraction of sulfonate is 3 - 5 wt%, the mass fraction of water is 36 - 48 wt%, and the balance is impurities.

3. The preparation method of the fluid loss reducer for oil well cement according to claim 2, characterized in that, In step (1), the mass ratio of the crude aqueous N-tert-butylacrylamide to dodecylamide dimethyl hydroxypropyl ammonium chloride is 100:1; in the crude aqueous N-tert-butylacrylamide, the mass fraction of N-tert-butylacrylamide is 55 wt%, the mass fraction of sulfonate is 5 wt%, the mass fraction of water is 36 wt%, and the balance is impurities.

4. The preparation method of the fluid loss reducer for oil well cement according to any one of claims 1-3, characterized in that, In step (1), the preparation method of the crude aqueous N-tert-butylacrylamide is: add water to the kettle residue obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid, stir and mix evenly, and the filter cake obtained by pressure filtration with a filter press is the crude aqueous N-tert-butylacrylamide; the mass-volume ratio of the kettle residue obtained from the production of 2-acrylamido-2-methylpropanesulfonic acid to water is 1 g:(2 - 3) mL.

5. The preparation method of the fluid loss reducer for oil well cement according to claim 1, characterized in that, In step (2), the mass fraction of sodium carbonate in the sodium carbonate solution is 5 - 10 wt%; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and isopropanol is (180 - 200):(4 - 6):(1 - 3); in the monomer mixture, the mass fraction of 2-acrylamido-2-methylpropanesulfonic acid is 24 - 35 wt%; when adjusting the pH, use sodium carbonate to adjust the pH to 5 - 6.

6. The preparation method of the fluid loss reducer for oil well cement according to claim 5, characterized in that, In step (2), the mass fraction of sodium carbonate in the sodium carbonate solution is 6.5 - 7.5 wt%; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and isopropanol is 90:2:1; in the monomer mixture, the mass fraction of 2-acrylamido-2-methylpropanesulfonic acid is 24 - 30 wt%; when adjusting the pH, use sodium carbonate to adjust the pH to 5.

7. The preparation method of the fluid loss reducer for oil well cement according to claim 1, characterized in that, In step (3), in the mixed raw material liquid, the mass ratio of the tertiary amine feed liquid to 2-acrylamido-2-methylpropanesulfonic acid is 1:(5 - 8).

8. The preparation method of the fluid loss reducing agent for oil well cement according to claim 1, characterized in that, In step (4), the temperature of the constant temperature water bath is 55 - 60 °C, the stirring rate is 300 - 400 rpm, and the reaction time is 4 - 5 h; the mass fraction of the ammonium persulfate solution is 4.5 - 10 wt%; the dosage of ammonium persulfate is 0.3 - 0.5 wt% of the total mass of the tertiary amine feed liquid, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid; the drying conditions are: 100 - 105 °C, 5 - 6 h; after pulverization, it is sieved through a 50-mesh sieve.

9. The preparation method of the fluid loss reducer for oil well cement according to claim 8, characterized in that, In step (4), the temperature of the constant temperature water bath is 60 °C, the stirring rate is 350 - 400 rpm, and the reaction time is 5 h; the ammonium persulfate solution is prepared by mixing ammonium persulfate and water according to a mass-to-volume ratio of 1 g:10 mL; the dosage of ammonium persulfate is 0.45 - 0.50 wt% of the total mass of the tertiary amine feed liquid, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid; the drying conditions are: 105 °C, 5 h.

10. Application of a fluid loss reducer for oil well cement, characterized in that, 5 - 10 parts by weight of the fluid loss reducer for oil well cement prepared by the preparation method of the fluid loss reducer for oil well cement according to claim 1 is added to 800 - 1000 parts by weight of oil well cement, and 300 - 400 parts by weight of water is added and mixed and stirred evenly to prepare an oil well cement slurry.

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