Preparation method of temperature-resistant and salt-resistant oil well cement slurry fluid loss agent

Abstract

The invention relates to the technical field of well cementation for oil and gas well development, and discloses a preparation method of a temperature-resistant and salt-resistant oil well cement slurry fluid loss agent. The invention relates to a water-retaining agent, which is prepared by initiating polymerization of 50 to 60 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 to 20 parts of acrylamide, 5 to 8 parts of trans-butenedioic acid, 3 to 15 parts of alkenyl pyromellitic imide modified SiO2, 0.3 to 0.6 part of ammonium persulfate and sodium hydrogen sulfite. Wherein a rigid benzene ring with good thermal stability and a pyromellitic imide structure are introduced into alkenyl pyromellitic imide modified SiO2, so that the dehydration effect of a large number of counter ions on a copolymer can be weakened, the adsorption and hydration of the copolymer on the surfaces of cement particles are facilitated, and excellent temperature resistance and salt tolerance are shown; the prepared fluid loss agent has good performance of controlling water loss and improving rheological property of cement paste, can be widely applied to well cementation of high-temperature ultra-deep wells and high-salt-content strata, and greatly widens the application range of the fluid loss agent in the well cementation field.

Description

Technical Field

[0001] The invention relates to the technical field of well cementing for oil and gas well development, in particular to a method for preparing a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer. Background Art

[0002] In the process of oil and gas drilling and cementing, the control of water loss of cement slurry is a key issue. Due to the complex formation conditions and harsh downhole environment, cement slurry is prone to water loss under the action of pressure difference, and free water will filter out of the cement slurry and enter the formation. This process is usually called water loss of cement slurry. If the water loss of cement slurry is not effectively controlled, it will cause a series of problems such as poor fluidity of cement slurry, shortened thickening time, and even loss of flowability of cement slurry in severe cases, thereby causing serious accidents. In addition, a large amount of cement slurry filtrate enters the oil and gas layer, which will cause damage to the oil and gas layer and is not conducive to the protection of the oil and gas layer. At present, the water loss reducer of oil well cement slurry has the defects of low temperature and salt resistance, easy decomposition at high temperature, causing excessive slow setting of slurry, and reduced control of filtration loss. Therefore, the development of a temperature and salt resistant oil well cement slurry water loss reducer is of great significance to improving the safety and quality of cementing construction.

[0003] In the prior art, there are many types of oil well cement fluid loss reducers used in cement operations, among which cellulose ethers, polyvinyl alcohols, polyacrylamides, and poly 2-acrylamide-2-methylpropane sulfonic acid (AMPS) are commonly used. AMPS has become the main synthetic monomer of fluid loss reducers because of its good salt resistance. However, it is easy to degrade, hydrolyze and desorb functional groups under high temperature and strong alkali, and loses its fluid loss reducing effect, making it difficult to further improve its temperature resistance. In addition, the amide group in the acrylamide / acrylic acid copolymer will hydrolyze to form a carboxyl group at a high temperature, and the thickening time will be "inverted" at a temperature above 70°C, that is, the same formula In this case, the higher the temperature, the longer the thickening time; Patent No. CN101412600B discloses an oil well cement fluid loss reducer. In order to avoid the "inverted" phenomenon of cement slurry, N,N-dimethylacrylamide is introduced to replace acrylamide, but the viscosity increasing ability of N,N-dimethylacrylamide monomer is not as good as that of acrylamide, resulting in poor suspension stability of cement slurry; CN1775896A discloses an oil field cementing dispersed fluid loss reducer and a preparation method thereof. The main body adopts a cross-linked polyvinyl alcohol polymer, which has poor high temperature and salt resistance, and needs to add a dispersant. The preparation process is relatively complicated, which is not conducive to the promotion of the product. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer, which solves the problem that the existing fluid loss reducer has poor high temperature resistance and salt resistance, and has the characteristics of adjustable thickening time and excellent mechanical properties.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer is carried out according to the following steps:

[0007] Step (1), under nitrogen atmosphere, add 100 parts by weight of nano-SiO 2 , ethanol and deionized water, after being evenly dispersed, 5-12 parts of alkenyl benzimide siloxane are added, the pH of the system is adjusted to 3-5 with glacial acetic acid, and the reaction is stirred. After the reaction is completed, the alkenyl benzimide modified SiO is obtained after filtering, washing and drying under reduced pressure. 2 .

[0008] Step (2), by weight, 50-60 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10-20 parts of acrylamide, 5-8 parts of trans-butenedioic acid and 3-15 parts of alkenylbenzimide modified SiO 2 Dissolve in deionized water, adjust the pH to 6-7 with sodium hydroxide aqueous solution, introduce nitrogen, heat to 60-80°C, add 0.3-0.6 parts of initiator dropwise, continue the reaction for 2-5 hours, cool naturally to room temperature, and obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

[0009] Preferably, in step (1), the reaction temperature is 50-65° C. and the reaction time is 5-10 h.

[0010] Preferably, in step (2), the initiator is ammonium persulfate and sodium bisulfite in a mass ratio of 1:1.

[0011] Preferably, the mass fraction of the sodium hydroxide aqueous solution in step (2) is 20-30%.

[0012] Preferably, the preparation method of alkenyl benzimide siloxane in step (1) is carried out according to the following steps:

[0013] Step S1, under a nitrogen atmosphere, add pyromellitic dianhydride and glacial acetic acid to a reaction flask, stir evenly, add (E)-3-(4-aminophenyl)acrylic acid, stir to react, after the reaction is completed, cool to room temperature, filter, wash with deionized water, and recrystallize with toluene to obtain alkenyl pyromellitic imide diacid.

[0014] Step S2: under nitrogen atmosphere, add alkenyl benzimide diacid, thionyl chloride and N,N-dimethylformamide into a reaction flask, react at 60-80° C. for 2-5 h, remove excess thionyl chloride under reduced pressure to obtain alkenyl benzimide dichloride.

[0015] Step S3, under a nitrogen atmosphere, add alkenyl benzimide dichloride and tetrahydrofuran to a reaction flask, stir evenly, add N-[3-(trimethoxysilyl)propyl]aniline and triethylamine, stir to react, after the reaction is completed, extract with chloroform and deionized water, concentrate the organic phase, and dry to obtain alkenyl benzimide siloxane.

[0016] Preferably, in step S1, the molar ratio of pyromellitic dianhydride to (E)-3-(4-aminophenyl)acrylic acid is 1:2.1-2.3.

[0017] Preferably, in step S1, the reaction temperature is 105-120° C., and the reaction time is 18-32 h.

[0018] Preferably, in step S2, the molar ratio of alkenyl benzimide diacid to thionyl chloride is 1:3.2-4.5.

[0019] Preferably, in step S3, the molar ratio of alkenylbenzimido dichloride, N-[3-(trimethoxysilyl)propyl]aniline and triethylamine is 1:2.02-2.1:2.5-2.8.

[0020] Preferably, the reaction temperature in step S3 is 40-60°C and the reaction time is 12-24h; the structural formula of the alkenyl benzimide siloxane is

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Good high temperature resistance: Nano-SiO 2 The surface grafted polymer is affected by temperature and the intermolecular movement is intensified. The polymer side chains are gradually extended, which improves the density of the cement cake and reduces the permeability of the cement. The functional groups on the polymer molecules can be firmly adsorbed on the SiO 2 The microporous surface has a certain binding effect on polar water molecules, which hinders the water loss of the cement slurry system. Therefore, the slurry system can withstand the deep well and ultra-deep well cementing operations at a high temperature of 240°C. The introduction of rigid benzene rings and polybenzimide increases the chain gyration radius of the copolymer and has higher thermal stability. The amide group, sulfonic acid group, carboxyl group and nano-SiO 2 The synergistic adsorption effect makes it more firmly adsorbed on cement particles, the high-temperature desorption phenomenon slows down, and the temperature resistance is better.

[0023] (2) Good salt resistance: A large number of amide, sulfonic acid, carboxyl and other groups in the fluid loss reducer are strongly polar groups. They can tightly bind to cement particles at any position to polarize water molecules and form a hydration layer, preventing water molecules from penetrating into the interior of cement particles. At the same time, the sulfonic acid and carboxylic acid groups on the molecular chain can increase the negative charge density of the filter cake and have low sensitivity to external cations, making it stable in the pores of the filter cake and not easy to enter the formation, thus having a good fluid loss reduction effect; the introduction of rigid benzene rings and benzimide side groups can, to a certain extent, weaken the presence of a large number of counterions (Na + and Ca 2+ )'s dehydration effect on the copolymer is beneficial to its adsorption and hydration on the surface of cement particles, showing excellent salt resistance.

[0024] (3) Adjustable thickening time and excellent mechanical properties: SiO2 modified by alkenylbenzimide 2 It can be used as a "filler" for cement slurry, can form a hybrid material with a hydrophobic associating polymer, and form a three-dimensional grid structure through "bridging" and cross-linking under the action of pressure difference, which can make the originally loose mud cake more compact, increase the ability to resist deformation, and thus improve the mechanical properties of the cement slurry; the present invention does not have the "inverted phenomenon" of increased thickening time due to increased temperature, indicating that the prepared fluid loss reducer does not produce transitional slow setting due to the increase of amide and carboxyl groups at high temperature, inhibits hydrolysis to a certain extent, and the thickening time is adjustable; the fluid loss reducer of the present invention is used to prepare cement slurries with different experimental formulas, and the comprehensive performance of the cement slurry is excellent, and various performance indicators can meet the requirements for use in cementing projects. DETAILED DESCRIPTION

[0025] Below in conjunction with the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Unless otherwise indicated, the raw materials and reagents used in this application are all commercially available products, or can be prepared by known methods.

[0026] Pyromellitic dianhydride, CAS number is 89-32-7.

[0027] (E)-3-(4-Aminophenyl)acrylic acid 17570-30-8.

[0028] N-[3-(Trimethoxysilyl)propyl]aniline, CAS number is 3068-76-6.

[0029] 2-Acrylamido-2-methylpropanesulfonic acid, CAS number is 5165-97-9.

[0030] Trans-butenedioic acid, CAS number is 110-17-8.

[0031] Example 1

[0032] (1) Under nitrogen atmosphere, 95 mmol of pyromellitic anhydride and 380 mL of glacial acetic acid were added to a reaction flask, stirred evenly, and then 209 mmol of (E)-3-(4-aminophenyl)acrylic acid was added. The mixture was reacted at 110° C. for 24 h, cooled to room temperature, filtered, washed with deionized water, and recrystallized from toluene to obtain alkenyl pyromellitic anhydride diacid. The preparation reaction formula is as follows:

[0033]

[0034] (2) Under nitrogen atmosphere, 80 mmol of alkenylbenzamide diacid, 305 mmol of thionyl chloride and 4 mL of N,N-dimethylformamide were added to a reaction flask, and the mixture was reacted at 70° C. for 4 h. Excess thionyl chloride was removed under reduced pressure to obtain alkenylbenzamide diacid chloride.

[0035] (3) Under nitrogen atmosphere, add 75 mmol of alkenylbenzyl imide dichloride and 600 mL of tetrahydrofuran to the reaction flask, stir evenly, add 154.5 mmol of N-[3-(trimethoxysilyl)propyl]aniline and 195 mmol of triethylamine, react at 50° C. for 16 h, extract with chloroform and deionized water, concentrate the organic phase, and dry to obtain alkenylbenzyl imide siloxane. The preparation reaction formula is as follows:

[0036]

[0037] (4) Under nitrogen atmosphere, add 10 g of nano-SiO 2 , 240 mL of ethanol and 12 mL of deionized water, after being evenly dispersed, 0.5 g of alkenyl benzimide siloxane was added, the pH of the system was adjusted to 4 with glacial acetic acid, and the reaction was carried out at 55 ° C for 9 h. After filtering, washing and drying under reduced pressure, alkenyl benzimide modified SiO 2 .

[0038] (5) 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 16 g of acrylamide, 7 g of trans-butenedioic acid and 3 g of alkenylbenzamide modified SiO 2 Dissolve in deionized water, adjust the pH to 7 with a 25% sodium hydroxide aqueous solution, introduce nitrogen, heat to 70°C, drop 0.5g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, continue to react for 3h, cool naturally to room temperature, and obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

[0039] Example 2

[0040] (1) Under a nitrogen atmosphere, 150 mmol of pyromellitic dianhydride and 450 mL of glacial acetic acid were added to a reaction flask, and after stirring, 315 mmol of (E)-3-(4-aminophenyl)acrylic acid was added, and the mixture was reacted at 120° C. for 18 h. The mixture was cooled to room temperature, filtered, washed with deionized water, and recrystallized with toluene to obtain alkenyl pyromellitic imide diacid.

[0041] (2) Under nitrogen atmosphere, 135 mmol of alkenylbenzamide diacid, 432 mmol of thionyl chloride and 7 mL of N,N-dimethylformamide were added to a reaction flask, and the mixture was reacted at 80° C. for 2 h. Excess thionyl chloride was removed under reduced pressure to obtain alkenylbenzamide diacid chloride.

[0042] (3) Under a nitrogen atmosphere, 120 mmol of alkenylbenzimide dichloride and 720 mL of tetrahydrofuran were added to a reaction flask. After stirring, 242.4 mmol of N-[3-(trimethoxysilyl)propyl]aniline and 300 mmol of triethylamine were added. The mixture was reacted at 60° C. for 12 h. The mixture was extracted with chloroform and deionized water. The organic phase was concentrated and dried to obtain alkenylbenzimide siloxane.

[0043] (4) Under nitrogen atmosphere, add 10 g of nano-SiO 2 , 220 mL of ethanol and 10 mL of deionized water, after being evenly dispersed, 0.7 g of alkenyl benzimide siloxane was added, the pH of the system was adjusted to 5 with glacial acetic acid, and the reaction was carried out at 65 ° C for 5 h. After filtering, washing and drying under reduced pressure, alkenyl benzimide-modified SiO 2 .

[0044] (5) 50 g of 2-acrylamido-2-methylpropanesulfonic acid, 20 g of acrylamide, 5 g of trans-butenedioic acid and 6 g of alkenylbenzamide modified SiO 2 Dissolve in deionized water, adjust the pH to 6 with a 30% sodium hydroxide aqueous solution, introduce nitrogen, heat to 80°C, drop 0.3g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, continue to react for 2h, cool naturally to room temperature, and obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

[0045] Example 3

[0046] (1) Under a nitrogen atmosphere, 40 mmol of pyromellitic dianhydride and 200 mL of glacial acetic acid were added to a reaction flask, and after stirring, 92 mmol of (E)-3-(4-aminophenyl)acrylic acid was added, and the mixture was reacted at 105° C. for 32 h. The mixture was cooled to room temperature, filtered, washed with deionized water, and recrystallized from toluene to obtain alkenyl pyromellitic imide diacid.

[0047] (2) Under nitrogen atmosphere, 35 mmol of alkenylbenzamide diacid, 112 mmol of thionyl chloride and 1.75 mL of N,N-dimethylformamide were added to a reaction flask, and the mixture was reacted at 60° C. for 5 h. Excess thionyl chloride was removed under reduced pressure to obtain alkenylbenzamide diacid chloride.

[0048] (3) Under nitrogen atmosphere, 25 mmol of alkenylbenzimide dichloride and 250 mL of tetrahydrofuran were added to a reaction flask, and after stirring, 52.5 mmol of N-[3-(trimethoxysilyl)propyl]aniline and 70 mmol of triethylamine were added, and the mixture was reacted at 40° C. for 24 h. The mixture was extracted with chloroform and deionized water, and the organic phase was concentrated and dried to obtain alkenylbenzimide siloxane.

[0049] (4) Under nitrogen atmosphere, add 10 g of nano-SiO 2 , 260 mL of ethanol and 15 mL of deionized water, after being evenly dispersed, 0.9 g of alkenyl benzimide siloxane was added, the pH of the system was adjusted to 3 with glacial acetic acid, and the reaction was carried out at 50 ° C for 10 h. After filtering, washing and drying under reduced pressure, alkenyl benzimide-modified SiO 2 .

[0050] (5) 60 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of acrylamide, 8 g of trans-butenedioic acid and 9 g of alkenylbenzamide modified SiO 2 Dissolve in deionized water, adjust the pH to 6 with a 20% sodium hydroxide aqueous solution, introduce nitrogen, heat to 60°C, drop 0.6g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, continue to react for 5h, cool naturally to room temperature, and obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

[0051] Example 4

[0052] (1) Under a nitrogen atmosphere, 65 mmol of pyromellitic dianhydride and 235 mL of glacial acetic acid were added to a reaction flask, and after stirring, 141.8 mmol of (E)-3-(4-aminophenyl)acrylic acid was added, and the mixture was reacted at 115° C. for 30 h. The mixture was cooled to room temperature, filtered, washed with deionized water, and recrystallized with toluene to obtain alkenyl pyromellitic imide diacid.

[0053] (2) Under nitrogen atmosphere, 55 mmol of alkenylbenzamide diacid, 231 mmol of thionyl chloride and 2.75 mL of N,N-dimethylformamide were added to a reaction flask, and the mixture was reacted at 75° C. for 3 h. Excess thionyl chloride was removed under reduced pressure to obtain alkenylbenzamide diacid chloride.

[0054] (3) Under a nitrogen atmosphere, 50 mmol of alkenylbenzimide dichloride and 440 mL of tetrahydrofuran were added to a reaction flask. After stirring, 104 mmol of N-[3-(trimethoxysilyl)propyl]aniline and 135 mmol of triethylamine were added. The mixture was reacted at 55° C. for 15 h. The mixture was extracted with chloroform and deionized water. The organic phase was concentrated and dried to obtain alkenylbenzimide siloxane.

[0055] (4) Under nitrogen atmosphere, add 10 g of nano-SiO 2 , 245 mL of ethanol and 13 mL of deionized water, after being evenly dispersed, 1.05 g of alkenyl benzimide siloxane was added, the pH of the system was adjusted to 4 with glacial acetic acid, and the reaction was carried out at 55 ° C for 9 h. After filtering, washing and drying under reduced pressure, alkenyl benzimide modified SiO 2 .

[0056] (5) 52 g of 2-acrylamido-2-methylpropanesulfonic acid, 18 g of acrylamide, 6.5 g of trans-butenedioic acid and 12 g of alkenylbenzimide modified SiO 2 Dissolve in deionized water, adjust the pH to 7 with 28% sodium hydroxide aqueous solution, introduce nitrogen, heat to 75°C, drop 0.5g of ammonium persulfate and sodium bisulfite with a mass ratio of 1:1, continue to react for 5h, cool naturally to room temperature, and obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

[0057] Example 5

[0058] (1) Under a nitrogen atmosphere, 30 mmol of pyromellitic dianhydride and 105 mL of glacial acetic acid were added to a reaction flask, and after stirring, 67.2 mmol of (E)-3-(4-aminophenyl)acrylic acid was added, and the mixture was reacted at 115° C. for 25 h. The mixture was cooled to room temperature, filtered, washed with deionized water, and recrystallized with toluene to obtain alkenyl pyromellitic imide diacid.

[0059] (2) Under nitrogen atmosphere, 25 mmol of alkenylbenzamide diacid, 105 mmol of thionyl chloride and 1.25 mL of N,N-dimethylformamide were added to a reaction flask, and the mixture was reacted at 65° C. for 3 h. Excess thionyl chloride was removed under reduced pressure to obtain alkenylbenzamide diacid chloride.

[0060] (3) Under a nitrogen atmosphere, 20 mmol of alkenylbenzimide dichloride and 170 mL of tetrahydrofuran were added to a reaction flask. After stirring, 41.6 mmol of N-[3-(trimethoxysilyl)propyl]aniline and 53 mmol of triethylamine were added. The mixture was reacted at 50° C. for 24 h. The mixture was extracted with chloroform and deionized water. The organic phase was concentrated and dried to obtain alkenylbenzimide siloxane.

[0061] (4) Under nitrogen atmosphere, add 10 g of nano-SiO 2 , 235 mL of ethanol and 14 mL of deionized water, after being evenly dispersed, 1.2 g of alkenyl benzimide siloxane was added, the pH of the system was adjusted to 5 with glacial acetic acid, and the reaction was carried out at 65 ° C for 10 h. After filtering, washing and drying under reduced pressure, alkenyl benzimide modified SiO 2 .

[0062] (5) 56 g of 2-acrylamido-2-methylpropanesulfonic acid, 14 g of acrylamide, 6 g of trans-butenedioic acid and 15 g of alkenylbenzamide modified SiO 2 Dissolve in deionized water, adjust the pH to 6 with a 25% sodium hydroxide aqueous solution, introduce nitrogen, heat to 80°C, drop 0.45g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, continue to react for 4h, cool naturally to room temperature, and obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

[0063] Comparative Example 1

[0064] (1) Under nitrogen atmosphere, 80 mmol of trans-butenedioic acid, 305 mmol of thionyl chloride and 4 mL of N,N-dimethylformamide were added to a reaction flask, and the mixture was reacted at 70° C. for 4 h. Excess thionyl chloride was removed under reduced pressure to obtain trans-butenedioyl chloride.

[0065] (2) Under nitrogen atmosphere, 75 mmol of trans-butylene dichloride and 600 mL of tetrahydrofuran were added to the reaction flask. After stirring, 154.5 mmol of N-methyl-3-(trimethoxysilyl)-1-propylamine (structural formula: CAS No. 3069-25-8) and 195 mmol triethylamine, react at 50 ° C for 16 hours, extract with chloroform and deionized water, concentrate the organic phase, and dry it to obtain an alkenyl siloxane monomer (structural formula ).

[0066] (3) Under nitrogen atmosphere, add 10 g of nano-SiO 2 , 240 mL of ethanol and 12 mL of deionized water, after being evenly dispersed, 0.5 g of alkenyl siloxane monomer was added, the pH of the system was adjusted to 4 with glacial acetic acid, and the reaction was carried out at 55 ° C for 9 h. After filtering, washing and drying under reduced pressure, alkenyl-modified SiO 2 .

[0067] (4) 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 16 g of acrylamide, 7 g of trans-butenedioic acid and 3 g of olefin-modified SiO 2Dissolve in deionized water, adjust the pH to 7 with a 25% sodium hydroxide aqueous solution, introduce nitrogen, heat to 70°C, drop 0.5g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, continue to react for 3h, cool naturally to room temperature, and obtain an oil well cement slurry fluid loss reducer.

[0068] Comparative Example 2

[0069] 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 16 g of acrylamide, 7 g of trans-butenedioic acid and 3 g of alkenylbenzamide siloxane (prepared in Example 1) were dissolved in deionized water, the pH was adjusted to 7 with a 25% by mass sodium hydroxide aqueous solution, nitrogen was introduced, the mixture was heated to 70° C., 0.5 g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1 were added dropwise, the reaction was continued for 3 h, and the mixture was naturally cooled to room temperature to obtain an oil well cement slurry fluid loss reducer.

[0070] Comparative Example 3

[0071] 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 16 g of acrylamide, and 7 g of trans-butenedioic acid were dissolved in deionized water, the pH was adjusted to 7 with a 25% by mass sodium hydroxide aqueous solution, nitrogen was introduced, the mixture was heated to 70° C., 0.5 g of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1 were added dropwise, the reaction was continued for 3 h, and the mixture was naturally cooled to room temperature to obtain an oil well cement slurry fluid loss reducer.

[0072] Preparation of cement slurry: It was carried out in accordance with the provisions of the standard GB / T 19139-2012 "Test methods for oil well cement", with a water-cement ratio of 0.56.

[0073] Temperature resistance test: Add the prepared cement slurry into the thickener, set the temperature to 90℃, 150℃ and 240℃ respectively, oxidize the cement slurry at room temperature for 30 minutes, transfer the cured cement slurry to the high temperature and high pressure water loss instrument, and measure the API water loss at 6.9MPa for 30 minutes.

[0074] Table 1 Temperature resistance test

[0075]

[0076] From the test results in the table above, it can be seen that with the increase of temperature, the water loss gradually increases, but the growth rate decreases; at the same temperature, with the modification of SiO 2 With the increase of content, the water loss gradually decreases. In Example 4, the API water loss of cement slurry at 240°C is only 45mL, indicating that the prepared water loss reducer can withstand high temperatures of 240°C. This is because on the one hand, nano-SiO 2The surface grafted polymer is affected by temperature and the intermolecular movement is intensified. The polymer side chains are gradually extended, which improves the density of the cement cake and reduces the permeability of the cement. The functional groups on the polymer molecules can be firmly adsorbed on the SiO 2 The microporous surface has a certain binding effect on polar water molecules, hindering the water loss of the cement slurry system, so the slurry system can withstand the deep well and ultra-deep well cementing operations at a high temperature of 240°C; on the other hand, the introduction of rigid benzene rings and polybenzimide increases the chain gyration radius of the copolymer, which has higher thermal stability. The amide group, sulfonic acid group, carboxyl group and nano-SiO 2 The synergistic adsorption effect makes it more firmly adsorbed on cement particles, the high-temperature desorption phenomenon slows down, and the temperature resistance is better; Comparative Example 1 does not contain rigid benzene rings and benzimide structures, and Comparative Example 2 does not contain nano-SiO 2 In Comparative Example 3, no multifunctional group adsorption was produced, and the product was easily degraded at high temperature, lost its water loss reducing effect, and had poor temperature resistance.

[0077] Salt resistance test: The experimental temperature was 180°C, and salt-containing cement slurries with NaCl mass fractions of 15% and 26.5% were prepared respectively, and the water-cement ratio was 0.50.

[0078] Table 2 Salt resistance performance test

[0079]

[0080] It can be seen from the test results in the above table that the fluid loss reducer of the present application is used in brine of different concentrations, and the API water loss of the cement slurry meets the requirement of less than 50mL for oil layer cementing, and has good salt resistance; this is because on the one hand, a large number of amide groups, sulfonic acid groups, carboxyl groups, etc. in the fluid loss reducer are strongly polar groups, which can be tightly combined with cement particles at any position to polarize water molecules and form a hydration layer to prevent water molecules from penetrating into the interior of cement particles. At the same time, the sulfonic acid group and carboxylic acid group on the molecular chain can increase the negative charge density of the filter cake, and have low sensitivity to external cations, so that it is stable in the pores of the filter cake and is not easy to enter the formation, thereby having a good fluid loss reduction effect; on the other hand, the introduction of rigid benzene rings and benzimide side groups can weaken a large number of counterions (Na + and Ca 2+ )'s dehydration effect on the copolymer is beneficial to its adsorption and hydration on the surface of cement particles, showing excellent salt resistance.

[0081] Mechanical properties and thickening time test: The relevant experiments were carried out in accordance with the petroleum and natural gas industry standard SY / T5504.2-2005 "Evaluation Method for Oil Well Cement Admixtures", and the experimental temperature was 90°C; the compressive strength test conditions were: curing for 24 hours at 110°C and 20.7MPa.

[0082] Table 3 Mechanical properties and thickening time test

[0083]

[0084] From the test results in the above table, we can see that the alkenyl benzimide modified SiO 2 It can be used as a "filler" for cement slurry and can form hybrid materials with hydrophobic associating polymers. Under the action of pressure difference, it forms a three-dimensional grid structure through "bridging" and cross-linking, which can make the originally loose mud cake more compact and increase the ability to resist deformation, thereby improving the mechanical properties of cement slurry. 2 With the increase of the content, the thickening time of the cement slurry is prolonged, and there is no "inverted phenomenon" that the thickening time increases due to the increase of temperature, which shows that the prepared fluid loss reducer does not produce transitional slow setting due to the increase of amide groups and carboxyl groups at high temperature, inhibits hydrolysis to a certain extent, and the thickening time is adjustable; the fluid loss reducer of the present invention is used to prepare cement slurries with different experimental formulas, and the comprehensive performance of the cement slurries is excellent, and various performance indicators can meet the requirements for use in cementing projects.

[0085] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer, characterized in that: The preparation method is carried out according to the following steps: Step (1), under a nitrogen atmosphere, add 100 parts by weight of nano-SiO2, ethanol and deionized water to a reaction flask, and after uniform dispersion, add 5-12 parts of alkenyl benzimide siloxane, adjust the pH of the system to 3-5 with glacial acetic acid, stir and react, and after the reaction is completed, filter, wash, and dry under reduced pressure to obtain alkenyl benzimide modified SiO2; Step (2), by weight, dissolving 50-60 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10-20 parts of acrylamide, 5-8 parts of trans-butenedioic acid and 3-15 parts of alkenylbenzimide-modified SiO2 in deionized water, adjusting the pH to 6-7 with an aqueous sodium hydroxide solution, introducing nitrogen, heating to 60-80° C., dropping 0.3-0.6 parts of an initiator, continuing the reaction for 2-5 hours, and naturally cooling to room temperature to obtain a temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer.

2. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 1, characterized in that: In the step (1), the reaction temperature is 50-65° C. and the reaction time is 5-10 h.

3. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 1, characterized in that: In the step (2), the initiator is ammonium persulfate and sodium bisulfite in a mass ratio of 1:

1.

4. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 1, characterized in that: The mass fraction of the sodium hydroxide aqueous solution in step (2) is 20-30%.

5. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 1, characterized in that: The preparation method of alkenyl styrene imide siloxane in step (1) is carried out according to the following steps: Step S1, under a nitrogen atmosphere, add pyromellitic anhydride and glacial acetic acid to a reaction flask, stir evenly, add (E)-3-(4-aminophenyl)acrylic acid, stir to react, and after the reaction is completed, cool to room temperature, filter, wash with deionized water, and recrystallize with toluene to obtain alkenyl pyromellitic imide diacid; Step S2, under a nitrogen atmosphere, add alkenyl benzimide diacid, thionyl chloride and N,N-dimethylformamide to a reaction flask, react at 60-80° C. for 2-5 hours, remove excess thionyl chloride under reduced pressure to obtain alkenyl benzimide dichloride; Step S3, under a nitrogen atmosphere, add alkenyl benzimide dichloride and tetrahydrofuran to a reaction flask, stir evenly, add N-[3-(trimethoxysilyl)propyl]aniline and triethylamine, stir to react, after the reaction is completed, extract with chloroform and deionized water, concentrate the organic phase, and dry to obtain alkenyl benzimide siloxane.

6. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 5, characterized in that: In the step S1, the molar ratio of pyromellitic dianhydride to (E)-3-(4-aminophenyl)acrylic acid is 1:2.1-2.

3.

7. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 5, characterized in that: In step S1, the reaction temperature is 105-120° C. and the reaction time is 18-32 hours.

8. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 5, characterized in that: In the step S2, the molar ratio of alkenylbenzimidic acid to thionyl chloride is 1:3.2-4.

5.

9. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 5, characterized in that: In the step S3, the molar ratio of alkenylbenzimido dichloride, N-[3-(trimethoxysilyl)propyl]aniline and triethylamine is 1:2.02-2.1:2.5-2.

8.

10. The method for preparing the temperature-resistant and salt-resistant oil well cement slurry fluid loss reducer according to claim 5, characterized in that: The reaction temperature in step S3 is 40-60° C. and the reaction time is 12-24 hours; the structural formula of the alkenyl benzimide siloxane is

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