A cementing flushing fluid and its preparation method

Abstract

This invention provides a cementing flushing fluid and its preparation method, belonging to the field of flushing fluid technology. The method includes the following steps: dissolving benzyl quaternized cyclodextrin and biphenyl dichlorobenzyl in [BMIm]Cl / FeCl3 ionic liquid, stirring at high temperature, filtering, washing, Soxhlet extraction, and vacuum drying to obtain a porous cyclodextrin polymer; dissolving the porous cyclodextrin polymer in water and allowing it to stand, then adding silanized SiO2 nanoparticles, mixing and stirring, filtering, and vacuum drying to obtain a SiO2 / porous cyclodextrin polymer composite material; mixing monoethanolamine, sodium cocoaminopropionate, and water, stirring, adding the SiO2 / porous cyclodextrin polymer composite material, and stirring at high speed to obtain the cementing flushing fluid. The cementing flushing fluid prepared by this invention has good compatibility with drilling fluid and cement slurry, and can be used in cementing operations to flush residual drilling fluid and filter cake from the wellbore and casing walls, and also has certain high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of flushing fluid technology, specifically to a cementing flushing fluid and its preparation method. Background Technology

[0002] In the drilling process of oil exploration, drilling fluid is an essential material to ensure the smooth progress of drilling operations. Drilling fluid has multiple functions, mainly including cooling and lubricating the drill bit, reducing drill bit wear, controlling formation pressure, transmitting hydraulic power, and acquiring downhole data; its most important role is to clean the bottom of the well, carry away rock cuttings, and ensure the continuity and smoothness of drilling operations.

[0003] Compared to water-based drilling fluids, oil-based drilling fluids are better suited for high-temperature, high-pressure, easily collapsed, and complex geological conditions, making them the best system for drilling through unstable formations. They are primarily composed of diesel fuel, organic clay, barite, and additives. However, some problems arise when using oil-based drilling fluids. When the oil-based drilling fluid comes into contact with the wellbore, a filter cake layer forms due to the interaction between the solid particles of the drilling fluid and the wellbore. This filter cake layer forms an oil slurry or film on the wellbore, exhibiting significant incompatibility with the cement sheath. This results in a substantial reduction in the bonding performance between the cement and the wellbore. Studies have shown that the interface between the residual oil film from the oil-based drilling fluid and the cement has almost no bonding strength, leading to poor cementing quality and impacting subsequent oil and gas well production and exploitation.

[0004] To overcome the problems caused by residual contamination from oil-based drilling fluids, flushing fluid is often used to clean the wellbore before cementing operations. The main function of flushing fluid is to remove oil film, oil slurry, and other residual contaminants from the wellbore, so that the subsequent cement can bond well with the wellbore, ensuring the consolidation strength of the cement sheath and thus improving cementing efficiency.

[0005] Existing flushing fluids are mostly emulsified flushing agents, which remove residual oil films on the wellbore by emulsifying the flushing agent with the oil on the wellbore. However, they are only effective at removing filter cake layers (such as organic polymers, clay mineral particles, salt ions, and other contaminants) formed by oil-based drilling fluids on the wellbore. Generally, the filter cake layer has a strong bond with the wellbore, and the emulsifier cannot completely remove these substances, resulting in contaminants remaining on the wellbore. This affects the bonding performance of the cement sheath and leads to a decline in cementing quality. Furthermore, under high temperature and high pressure environments, a single emulsifier may lose its activity, causing the oil film to fail to rupture completely or even redeposit, affecting the subsequent bonding of cement to the wellbore.

[0006] Therefore, there is a need to provide a cementing flushing fluid and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0007] In view of this, the present invention provides a cementing flushing fluid and its preparation method, which has good compatibility with drilling fluid and cement slurry, can be used to flush residual drilling fluid and filter cake layer on the well wall during cementing operations, and has certain high temperature resistance.

[0008] To achieve the above objectives, the present invention provides a method for preparing cementing flushing fluid, comprising the following steps:

[0009] S1. Under an inert gas environment, benzyl quaternized cyclodextrin and biphenyl dichlorobenzyl were dissolved in [BMIm]Cl / FeCl3 ionic liquid, stirred at high temperature, filtered to collect the precipitate, washed, Soxhlet extracted, and vacuum dried to obtain porous cyclodextrin polymer.

[0010] S2. After dissolving the porous cyclodextrin polymer in water and allowing it to stand, add silanized SiO2 nanoparticles, mix and stir, filter to collect the precipitate, and vacuum dry to obtain the SiO2 / porous cyclodextrin polymer composite material.

[0011] S3. After mixing and stirring monoethanolamine, sodium cocoyl aminopropionate and water, add SiO2 / porous cyclodextrin polymer composite material and stir at high speed to prepare cementing flushing fluid.

[0012] This invention generates a polymer by reacting modified β-cyclodextrin with biphenyl dichlorobenzyl in a homogeneous [BMIm]Cl / FeCl3 ionic liquid system, which serves as both a solvent and a Lewis acid catalyst. The polymer chains crosslink to form a porous network structure, resulting in a porous cyclodextrin polymer with a large specific surface area, enabling rapid adsorption of contaminants. Furthermore, this invention grafts SiO2 nanoparticles onto the porous cyclodextrin polymer. Due to their high hardness, SiO2 nanoparticles can impact the filter cake layer formed on the well wall in high-speed fluid, disrupting its dense structure. The porous cyclodextrin polymer can adsorb detached oil film and filter cake fragments, synergistically improving flushing efficiency. Additionally, silanized SiO2 nanoparticles reduce polymer shrinkage at high temperatures, improving overall high-temperature resistance, and the pores can still adsorb colloidal particles at high temperatures.

[0013] This invention uses sodium cocoaminopropionate as a surfactant component. Sodium cocoaminopropionate is a sodium salt of an amide, which can be decomposed into amino acids and fatty acids, exhibiting high biodegradability. Sodium cocoaminopropionate contains a hydrophilic end (alanine salt) and a hydrophobic end (fatty acid group), which can reduce oil / water interfacial tension. This invention, in conjunction with the amphiphilic structure of monoethanolamine, utilizes the small molecular size of monoethanolamine to fill the gaps between sodium cocoaminopropionate molecules, achieving a tighter directional arrangement at the oil / water interface, reducing intermolecular repulsion, further reducing interfacial tension while imparting better high-temperature resistance. Furthermore, the filter cake layer formed by drilling fluid typically contains negatively charged clay particles with adsorbed lipophilic organic matter on their surface. The lipophilic end of sodium cocoaminopropionate combines with the oil film on the surface of the clay particles, causing the particle surface to change from lipophilic (oil film coverage) to hydrophilic, i.e., reversing the oil-wet surface of the particles to a water-wet surface, eliminating oil-water interfacial tension, and accelerating the removal efficiency of contaminants by water flow.

[0014] Optionally, the benzyl quaternized cyclodextrin is prepared by mixing and stirring quaternized cyclodextrin and anhydrous N,N-dimethylformamide solution in an ice bath for 10 min, then adding sodium hydride and stirring for 15-30 min, finally slowly adding benzyl bromide, reacting at room temperature for 24 h, quenching the reaction with methanol, diluting with water, extracting with dichloromethane four times, and then rotary evaporating.

[0015] In this invention, β-cyclodextrin is modified with glycidyltrimethylammonium chloride, and its surface is grafted with quaternary ammonium groups, which endows the molecule with strong positive charge. The positive charge can better adsorb negatively charged drilling fluid particles (such as clay and oil film) through electrostatic interaction, so as to clean the residual drilling fluid on the well wall and the filter cake layer formed therein. The benzyl group of benzyl bromide modifies the edge of the cyclodextrin cavity, and the hydrophobic cavity can encapsulate the oily components in the drilling fluid (such as calcium oleate and crude oil residue), thereby achieving oil and dirt removal.

[0016] Optionally, the quaternized cyclodextrin is obtained by dissolving β-cyclodextrin in a 1.0 mol / L NaOH solution, slowly adding a 3% (w / w) aqueous solution of 2,3-epoxypropyltrimethylammonium chloride, stirring at 50-60°C for 16-24 h, adjusting the pH to 7-7.5 with hydrochloric acid, filtering to collect the precipitate, and freeze-drying for 8-12 h.

[0017] Optionally, the [BMIm]Cl / FeCl3 ionic liquid is obtained by vacuum drying 1-butyl-3-methylimidazolium chloride and FeCl3 at 60°C for 24 h; then, under a nitrogen atmosphere, FeCl3 is added to a reaction vessel containing 1-butyl-3-methylimidazolium chloride and stirred for 14 h.

[0018] This invention utilizes the interaction between FeCl3 and the imidazole cation in 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) to form an ion pair. This process releases a certain amount of heat and simultaneously forms a viscous liquid.

[0019] Optionally, the mass ratio of 1-butyl-3-methylimidazolium chloride to FeCl3 in the [BMIm]Cl / FeCl3 ionic liquid is 5:6.

[0020] Optionally, in step S1, the inert gas is nitrogen, the high-temperature stirring temperature is 75~85℃ and the time is 16~20h, the washing agent is water and methanol, the washing number is 2~5 times, the solvent used for Soxhlet extraction is methanol and the time is 18~24h, and the vacuum drying time is 12~16h and the temperature is 60~80℃.

[0021] Optionally, the silanized SiO2 nanoparticles are prepared by dropping 3-aminopropyltriethoxysilane into a 90% (v / v) aqueous solution of ethanol, adjusting the pH to 3.0 with acetic acid, stirring magnetically for 30 min, and then adding dropwise to a 5% (w / w) SiO2 nanoparticle-ethanol dispersion. Under nitrogen protection, the mixture is stirred at 80°C for 10 h, centrifuged for 15 min, the precipitate is collected, washed three times with ethanol and deionized water, and then vacuum dried at 80°C for 10 h.

[0022] In this invention, the 3-aminopropyltriethoxysilane-modified SiO2 nanoparticles in the SiO2 / porous cyclodextrin polymer composite material can react with Ca in water-in-oil drilling fluid. 2+ Mg 2+ Fe 3+ When metal ions form coordination bonds, the cavities in the porous cyclodextrin polymer can encapsulate organometallic complexes (such as calcium oleate) in the oil phase, thus preventing metal ions from reacting with surfactants and reducing surfactant activity.

[0023] Optionally, in step S2, the standing time is 24 hours, the mixing and stirring are carried out under ultrasonic treatment for 10-15 minutes, and the vacuum drying time is 12-16 hours at a temperature of 60-80°C.

[0024] Optionally, in step S3, monoethanolamine, sodium cocoyl aminopropionate, and water are mixed and stirred at 300 rpm for 15-20 min, then xanthan gum and carboxymethyl cellulose are added and mixed and stirred at 4000 rpm for 3-5 min, and finally SiO2 / porous cyclodextrin polymer composite material is added and mixed and stirred at 4000 rpm for 1-5 min to obtain cementing flushing fluid.

[0025] In preparing the cementing flushing fluid, the present invention also adds xanthan gum and carboxymethyl cellulose as suspending agents, which can suspend the SiO2 / porous cyclodextrin polymer composite material in the flushing fluid system, while also thickening and suspending solid particles washed off the well wall surface.

[0026] The present invention also provides a cementing flushing fluid, comprising the following raw materials in parts by weight: 1-5 parts monoethanolamine, 11-33 parts sodium cocoylaminopropionate, 200 parts water, and 20-30 parts SiO2 / porous cyclodextrin polymer composite material;

[0027] The SiO2 / porous cyclodextrin polymer composite material comprises the following raw materials in parts by weight: 20 parts of porous cyclodextrin polymer and 10-30 parts of silanized SiO2 nanoparticles.

[0028] According to the weight ratio of this invention, residual contaminants on the well wall and casing wall can achieve a good flushing effect, further improving cementing efficiency.

[0029] The above-described technical solution of the present invention has at least the following beneficial effects:

[0030] 1. This invention involves reacting modified β-cyclodextrin with biphenyl dichlorobenzyl in a [BMIm]Cl / FeCl3 ionic liquid system to generate a porous cyclodextrin polymer, which is then grafted with SiO2 nanoparticles to form a composite material with high specific surface area and hardness. This material can effectively adsorb pollutants, disrupt the filter cake layer on the well wall, improve flushing efficiency, and possesses good high-temperature resistance, ensuring effective adsorption of colloidal particles even at high temperatures.

[0031] 2. This invention utilizes sodium cocoaminopropionate as a surfactant, which works synergistically with monoethanolamine to reduce the oil / water interfacial tension while achieving a tighter directional arrangement of the oil / water interface, thus enhancing high-temperature resistance. The oleophilic end of sodium cocoaminopropionate binds to the oil film on the surface of clay particles, changing the particle surface from oleophilic to hydrophilic, eliminating the oil-water interfacial tension, thereby accelerating water flow scouring and improving contaminant removal efficiency. Attached Figure Description

[0032] Figure 1 The diagram shows the flushing effect and wetting / overturning of the cementing flushing fluid prepared in Example 1 of this invention.

[0033] Figure 2 This is a diagram showing the state of the mixture after flushing with the cementing flushing fluid prepared in Example 1 of the present invention;

[0034] Figure 3 This is a diagram showing the state of the mixture after flushing with the cementing flushing fluid prepared in Comparative Example 1 of this invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0036] Preparation:

[0037] 20g of 1-butyl-3-methylimidazolium chloride ([BMIm]Cl, CAS: 79917-90-1) and 36g of FeCl3 were vacuum dried at 60℃ for 24h. Then, under a nitrogen atmosphere, FeCl3 was added to a reaction vessel containing 1-butyl-3-methylimidazolium chloride and stirred for 14h to obtain [BMIm]Cl / FeCl3 ionic liquid.

[0038] 2.5 mL of 3-aminopropyltriethoxysilane was added dropwise to a 90% (v / v) aqueous ethanol solution. The pH was adjusted to 3.0 using acetic acid. After magnetic stirring for 30 min, the solution was added dropwise to 50 mL of a 5% (w / w) SiO2 nanoparticle-ethanol dispersion. The mixture was stirred at 80 °C for 10 h under nitrogen protection. After centrifugation for 15 min, the precipitate was collected and washed three times with ethanol and deionized water. The precipitate was then vacuum dried at 80 °C for 10 h to obtain silanized SiO2 nanoparticles.

[0039] Example 1

[0040] 91 g of β-cyclodextrin was dissolved in 160 mL of 1.0 mol / L NaOH solution, and 480 mL of 3% (w / w) 2,3-epoxypropyltrimethylammonium chloride aqueous solution was slowly added. The mixture was stirred at 50 °C for 24 h. After adjusting the pH to 7.5 with hydrochloric acid, the precipitate was filtered and freeze-dried for 12 h to obtain quaternized cyclodextrin. In an ice bath, 85 g of quaternized cyclodextrin and 800 mL of anhydrous N,N-dimethylformamide solution were mixed and stirred for 10 min, followed by the addition of 12 g of sodium hydride and stirring for 30 min. Finally, 56 mL of benzyl bromide was slowly added, and the mixture was reacted at room temperature for 24 h. The reaction was quenched with 200 mL of methanol, diluted with 4 L of water, and extracted four times with 1.2 L of dichloromethane. The organic layer was concentrated by rotary evaporation to obtain benzyl quaternized cyclodextrin.

[0041] Under nitrogen atmosphere, 40g of benzyl quaternary ammonium cyclodextrin and 33g of biphenyl dichlorobenzyl were dissolved in 260g of [BMIm]Cl / FeCl3 ionic liquid. After mixing and stirring at 85℃ for 16h, the precipitate was collected by filtration. The precipitate was washed five times with water and methanol, and then Soxhlet extraction with methanol was performed for 24h. The precipitate was then vacuum dried at 80℃ for 12h to obtain a porous cyclodextrin polymer. 20g of the porous cyclodextrin polymer was dissolved in 2L of water and allowed to stand for 24h. 30g of silanized SiO2 nanoparticles were added and the mixture was stirred under ultrasonic treatment for 15min. The precipitate was collected by filtration and vacuum dried at 80℃ for 12h to obtain a SiO2 / porous cyclodextrin polymer composite material.

[0042] 5g monoethanolamine, 33g sodium cocoyl aminopropionate, and 200mL water were mixed and stirred at 300rpm for 20min. Then, 5g xanthan gum and 16g carboxymethyl cellulose were added and mixed and stirred at 4000rpm for 5min. Finally, 30g SiO2 / porous cyclodextrin polymer composite material was added and mixed and stirred at 4000rpm for 5min to obtain the cementing flushing fluid.

[0043] Example 2

[0044] 91 g of β-cyclodextrin was dissolved in 160 mL of 1.0 mol / L NaOH solution, and 480 mL of 3% (w / w) 2,3-epoxypropyltrimethylammonium chloride aqueous solution was slowly added. The mixture was stirred at 50 °C for 16 h, and the pH was adjusted to 7 with hydrochloric acid. The precipitate was filtered and freeze-dried for 8 h to obtain quaternized cyclodextrin. In an ice bath, 85 g of quaternized cyclodextrin and 700 mL of anhydrous N,N-dimethylformamide solution were mixed and stirred for 10 min, followed by the addition of 12 g of sodium hydride and stirring for 15 min. Finally, 56 mL of benzyl bromide was slowly added, and the mixture was reacted at room temperature for 24 h. The reaction was quenched with 200 mL of methanol, diluted with 4 L of water, and extracted four times with 1.2 L of dichloromethane. The organic layer was concentrated by rotary evaporation to obtain benzyl quaternized cyclodextrin.

[0045] Under nitrogen atmosphere, 40g of benzyl quaternary ammonium cyclodextrin and 33g of biphenyl dichlorobenzyl were dissolved in 260g of [BMIm]Cl / FeCl3 ionic liquid. After mixing and stirring at 75℃ for 16h, the precipitate was collected by filtration. The precipitate was washed twice with water and methanol, and then Soxhlet extraction with methanol was performed for 18h. The precipitate was then vacuum dried at 60℃ for 12h to obtain a porous cyclodextrin polymer. 20g of the porous cyclodextrin polymer was dissolved in 2L of water and allowed to stand for 24h. 10g of silanized SiO2 nanoparticles were added and the mixture was stirred under ultrasonic treatment for 10min. The precipitate was collected by filtration and vacuum dried at 60℃ for 12h to obtain a SiO2 / porous cyclodextrin polymer composite material.

[0046] 1g monoethanolamine, 11g sodium cocoyl aminopropionate, and 200mL water were mixed and stirred at 300rpm for 15min. Then, 2g xanthan gum and 10g carboxymethyl cellulose were added and mixed and stirred at 4000rpm for 3min. Finally, 20g SiO2 / porous cyclodextrin polymer composite material was added and mixed and stirred at 4000rpm for 1min to obtain the cementing flushing fluid.

[0047] Example 3

[0048] 91 g of β-cyclodextrin was dissolved in 160 mL of 1.0 mol / L NaOH solution, and 480 mL of 3% (w / w) 2,3-epoxypropyltrimethylammonium chloride aqueous solution was slowly added. The mixture was stirred at 60 °C for 24 h, and the pH was adjusted to 7.5 with hydrochloric acid. The precipitate was filtered and freeze-dried for 12 h to obtain quaternized cyclodextrin. In an ice bath, 85 g of quaternized cyclodextrin and 800 mL of anhydrous N,N-dimethylformamide solution were mixed and stirred for 10 min, followed by the addition of 12 g of sodium hydride and stirring for 20 min. Finally, 56 mL of benzyl bromide was slowly added, and the mixture was reacted at room temperature for 24 h. The reaction was quenched with 200 mL of methanol, diluted with 4 L of water, and extracted four times with 1.2 L of dichloromethane. The organic layer was concentrated by rotary evaporation to obtain benzyl quaternized cyclodextrin.

[0049] Under nitrogen atmosphere, 40g of benzyl quaternary ammonium cyclodextrin and 33g of biphenyl dichlorobenzyl were dissolved in 260g of [BMIm]Cl / FeCl3 ionic liquid. After mixing and stirring at 80℃ for 18h, the precipitate was collected by filtration. The precipitate was washed four times with water and methanol, and then Soxhlet extraction with methanol was performed for 20h. The precipitate was then vacuum dried at 80℃ for 16h to obtain a porous cyclodextrin polymer. 20g of the porous cyclodextrin polymer was dissolved in 2L of water and allowed to stand for 24h. 20g of silanized SiO2 nanoparticles were added and the mixture was stirred under ultrasonic treatment for 15min. The precipitate was collected by filtration and vacuum dried at 80℃ for 16h to obtain a SiO2 / porous cyclodextrin polymer composite material.

[0050] 2g monoethanolamine, 22g sodium cocoyl aminopropionate, and 200mL water were mixed and stirred at 300rpm for 18min. Then, 4g xanthan gum and 12g carboxymethyl cellulose were added and mixed and stirred at 4000rpm for 4min. Finally, 25g SiO2 / porous cyclodextrin polymer composite material was added and mixed and stirred at 4000rpm for 2min to obtain the cementing flushing fluid.

[0051] Example 4

[0052] 91 g of β-cyclodextrin was dissolved in 160 mL of 1.0 mol / L NaOH solution, and 480 mL of 3% (w / w) 2,3-epoxypropyltrimethylammonium chloride aqueous solution was slowly added. The mixture was stirred at 55 °C for 18 h, and the pH was adjusted to 7.2 with hydrochloric acid. The precipitate was filtered and freeze-dried for 10 h to obtain quaternized cyclodextrin. In an ice bath, 85 g of quaternized cyclodextrin and 750 mL of anhydrous N,N-dimethylformamide solution were mixed and stirred for 10 min, followed by the addition of 12 g of sodium hydride and stirring for another 18 min. Finally, 56 mL of benzyl bromide was slowly added, and the mixture was reacted at room temperature for 24 h. The reaction was quenched with 200 mL of methanol, diluted with 4 L of water, and extracted four times with 1.2 L of dichloromethane. The organic layer was concentrated by rotary evaporation to obtain benzyl quaternized cyclodextrin.

[0053] Under nitrogen atmosphere, 40g of benzyl quaternary ammonium cyclodextrin and 33g of biphenyl dichlorobenzyl were dissolved in 260g of [BMIm]Cl / FeCl3 ionic liquid. After mixing and stirring at 80℃ for 17h, the precipitate was collected by filtration. The precipitate was washed twice with water and methanol, and then Soxhlet extraction with methanol was performed for 22h. The precipitate was then vacuum dried at 65℃ for 14h to obtain a porous cyclodextrin polymer. 20g of the porous cyclodextrin polymer was dissolved in 2L of water and allowed to stand for 24h. 15g of silanized SiO2 nanoparticles were added and the mixture was stirred under ultrasonic treatment for 14min. The precipitate was collected by filtration and vacuum dried at 75℃ for 14h to obtain a SiO2 / porous cyclodextrin polymer composite material.

[0054] 3g monoethanolamine, 33g sodium cocoyl aminopropionate, and 200mL water were mixed and stirred at 300rpm for 16min. Then, 4g xanthan gum and 12g carboxymethyl cellulose were added and mixed and stirred at 4000rpm for 3min. Finally, 22g SiO2 / porous cyclodextrin polymer composite material was added and mixed and stirred at 4000rpm for 4min to obtain the cementing flushing fluid.

[0055] Example 5

[0056] 91 g of β-cyclodextrin was dissolved in 160 mL of 1.0 mol / L NaOH solution, and 480 mL of 3% (w / w) 2,3-epoxypropyltrimethylammonium chloride aqueous solution was slowly added. The mixture was stirred at 65 °C for 20 h, and the pH was adjusted to 7.3 with hydrochloric acid. The precipitate was filtered and freeze-dried for 11 h to obtain quaternized cyclodextrin. In an ice bath, 85 g of quaternized cyclodextrin and 700 mL of anhydrous N,N-dimethylformamide solution were mixed and stirred for 10 min, followed by the addition of 12 g of sodium hydride and stirring for 25 min. Finally, 56 mL of benzyl bromide was slowly added, and the mixture was reacted at room temperature for 24 h. The reaction was quenched with 200 mL of methanol, diluted with 4 L of water, and extracted four times with 1.2 L of dichloromethane. The organic layer was concentrated by rotary evaporation to obtain benzyl quaternized cyclodextrin.

[0057] Under nitrogen atmosphere, 40g of benzyl quaternary ammonium cyclodextrin and 33g of biphenyl dichlorobenzyl were dissolved in 260g of [BMIm]Cl / FeCl3 ionic liquid. After mixing and stirring at 75℃ for 18h, the precipitate was collected by filtration. The precipitate was washed three times with water and methanol, and then Soxhlet extraction with methanol was performed for 22h. The precipitate was then vacuum dried at 75℃ for 13h to obtain a porous cyclodextrin polymer. 20g of the porous cyclodextrin polymer was dissolved in 2L of water and allowed to stand for 24h. 25g of silanized SiO2 nanoparticles were added and the mixture was stirred under ultrasonic treatment for 12min. The precipitate was collected by filtration and vacuum dried at 70℃ for 12h to obtain a SiO2 / porous cyclodextrin polymer composite material.

[0058] 5g monoethanolamine, 11g sodium cocoyl aminopropionate, and 200mL water were mixed and stirred at 300rpm for 17min. Then, 4g xanthan gum and 15g carboxymethyl cellulose were added and mixed and stirred at 4000rpm for 4min. Finally, 26g SiO2 / porous cyclodextrin polymer composite material was added and mixed and stirred at 4000rpm for 2min to obtain the cementing flushing fluid.

[0059] Example 6

[0060] 91 g of β-cyclodextrin was dissolved in 160 mL of 1.0 mol / L NaOH solution, and 480 mL of 3% (w / w) 2,3-epoxypropyltrimethylammonium chloride aqueous solution was slowly added. The mixture was stirred at 60 °C for 17 h, and the pH was adjusted to 7.5 with hydrochloric acid. The precipitate was filtered and freeze-dried for 10 h to obtain quaternized cyclodextrin. In an ice bath, 85 g of quaternized cyclodextrin and 800 mL of anhydrous N,N-dimethylformamide solution were mixed and stirred for 10 min, followed by the addition of 12 g of sodium hydride and stirring for 25 min. Finally, 56 mL of benzyl bromide was slowly added, and the mixture was reacted at room temperature for 24 h. The reaction was quenched with 200 mL of methanol, diluted with 4 L of water, and extracted four times with 1.2 L of dichloromethane. The organic layer was concentrated by rotary evaporation to obtain benzyl quaternized cyclodextrin.

[0061] Under nitrogen atmosphere, 40g of benzyl quaternary ammonium cyclodextrin and 33g of biphenyl dichlorobenzyl were dissolved in 260g of [BMIm]Cl / FeCl3 ionic liquid. After mixing and stirring at 85℃ for 18h, the precipitate was collected by filtration. The precipitate was washed four times with water and methanol, and then Soxhlet extraction with methanol was performed for 20h. The precipitate was then vacuum dried at 80℃ for 14h to obtain a porous cyclodextrin polymer. 20g of the porous cyclodextrin polymer was dissolved in 2L of water and allowed to stand for 24h. 20g of silanized SiO2 nanoparticles were added and the mixture was stirred under ultrasonic treatment for 12min. The precipitate was collected by filtration and vacuum dried at 70℃ for 14h to obtain a SiO2 / porous cyclodextrin polymer composite material.

[0062] 3g monoethanolamine, 22g sodium cocoyl aminopropionate, and 200mL water were mixed and stirred at 300rpm for 16min. Then, 3g xanthan gum and 12g carboxymethyl cellulose were added and mixed and stirred at 4000rpm for 5min. Finally, 20g SiO2 / porous cyclodextrin polymer composite material was added and mixed and stirred at 4000rpm for 5min to obtain the cementing flushing fluid.

[0063] The present invention also includes comparative examples and related experiments.

[0064] Comparative Example 1

[0065] Compared with Example 1, the only difference is that SiO2 / porous cyclodextrin polymer composite material was not added. The other preparation methods and components are exactly the same, and the final cementing flushing fluid is obtained.

[0066] Comparative Example 2

[0067] Compared with Example 1, the only difference is that silanized SiO2 nanoparticles are directly added to replace the SiO2 / porous cyclodextrin polymer composite material. The other preparation methods and components are exactly the same, and the cementing flushing fluid is finally obtained.

[0068] Comparative Example 3

[0069] Compared with Example 1, the only difference is that a porous cyclodextrin polymer is directly added to replace the SiO2 / porous cyclodextrin polymer composite material. The other preparation methods and components are exactly the same, and the cementing flushing fluid is finally obtained.

[0070] Comparative Example 4

[0071] Compared with Example 1, the only difference is that monoethanolamine was not added, but the other preparation methods and components are exactly the same, and the final cementing flushing fluid is obtained.

[0072] Performance testing

[0073] The performance of the cementing flushing fluids prepared in Examples 1-6 and Comparative Examples 1-4 was tested.

[0074] The flash point of the sample was tested according to the Binski-Martin closed cup method for the determination of flash point in the national standard GB / T261-2021, and the appearance was visually inspected under natural light conditions.

[0075] The cementing flushing fluids prepared in Examples 1-6 and Comparative Examples 1-4 were evaluated for their flushing efficiency using the filter cake method at 50℃ and 80℃, in accordance with the standard Q / HSYF367.1-2017 Evaluation Method for Cementing Pre-fluid. The specific testing procedure was as follows: High-temperature, high-pressure filter paper was placed into the fluid loss meter's fluid loss chamber, and an appropriate amount of drilling fluid was poured in. A filter cake was prepared under the experimental conditions (3.5 MPa, room temperature), with a fluid loss time of 30 minutes. The filter paper with the filter cake was carefully removed, and the drilling fluid on the filter cake was gently washed away with clean water. The mass m1 of the filter paper and filter cake was weighed, and then fixed to the outer cylinder of the rotational viscometer with a rubber band. A photograph was taken and the results recorded. Prepare the rinsing solution according to the formula. Then, stir the prepared rinsing solution in an atmospheric pressure thickener for 20 minutes at the on-site circulating temperature. Pour the solution to the mark on the slurry cup, submerging half of the filter cake. Place the cup on a rotational viscometer and rinse for 7 minutes at 200 rpm. Take photos and record the results. Remove the filter paper and weigh it (m2). Scrape off all the rinsed filter cake from the filter paper and weigh the remaining filter cake and filter paper (m3).

[0076] Calculate the flushing efficiency according to formula (Ⅰ):

[0077] ×100% (Ⅰ)

[0078] In the formula:

[0079] η — Flushing efficiency, %

[0080] m1 — Mass of filter paper and filter cake, in grams (g).

[0081] m2 — Mass of filter cake and filter paper after rinsing with rinsing fluid, in grams (g).

[0082] m3 — The mass of the remaining mud cake and filter paper after scraping off the rinsed filter cake, expressed in grams (g).

[0083] The specific test results of the flash point, appearance, and flushing efficiency of the cementing flushing fluids prepared in Examples 1-6 and Comparative Examples 1-4 at 50℃ and 80℃ are shown in Table 1.

[0084] Table 1

[0085]

[0086] As shown in Table 1, the cementing flushing fluids prepared in Examples 1 to 6 of this invention have good stability, with no solid particle sedimentation. The flash point is >93℃, which is a high flash point liquid, meeting the safety requirements for high-temperature downhole operations. The flushing efficiency is >95% under both 50℃ and 80℃ conditions, indicating good flushing efficiency.

[0087] Analysis of the data in Table 1 shows that, compared to Comparative Example 1, the addition of the SiO2 / porous cyclodextrin polymer composite material in Example 1 significantly improved the flushing efficiency. Comparative Examples 2 and 3, which did not include the SiO2 / porous cyclodextrin polymer composite material but only added a single component from the composite material, experienced a decrease in flushing efficiency. Furthermore, the temperature resistance of the cementing flushing fluids prepared in Comparative Examples 3 and 4 was also affected, with a significant decrease in flushing efficiency at 80℃. This invention also utilized the sandpaper method to jointly evaluate the flushing effect. Specific experimental results of sandpaper flushing using the cementing flushing fluid prepared in Example 1 are shown in [Table 1]. Figure 1 , Figure 1 The left image shows the wall-building state with clean sandpaper and mud; the middle image shows the state of the sandpaper before and after rinsing; and the right image shows the surface wettability state before and after rinsing. Figure 1 It can be seen that after rinsing with the cementing flushing fluid prepared in Example 1, the sandpaper surface is clean and the rinsing interface is wetted by water.

[0088] According to the national standard GB / T 19139-2012 Oil Well Cement Test Method, the rheological compatibility of the cementing flush fluids prepared in Examples 1 to 6 and Comparative Examples 1 to 4 with oil-based drilling fluids at volume ratios of 5:95, 25:75, 50:50, 75:25, 95:5, and the rheological compatibility of the cementing flush fluids with cement slurries at volume ratios of 5:95, 25:75, 50:50, 75:25, 95:5 were determined. The compatibility of different fluids was characterized by the R value. R is the value obtained by subtracting the larger reading of a single fluid (flush fluid, oil-based drilling fluid or cement slurry) at the same rotational speed from the reading of different fluids mixed in proportion at a rotational speed of 300 r / min on a six-speed rotational viscometer. When R ≤ 0, the compatibility is very good; when 0 < R ≤ 40, the incompatibility is mild; when 40 ≤ R < 70, the incompatibility exists; when R ≥ 70, the incompatibility is extremely severe. Test temperature: 80 °C.

[0089] According to the national standard GB / T 19139-2012 Oil Well Cement Test Method, the compatibility of the cementing flush fluids prepared in Examples 1 to 6 and Comparative Examples 1 to 4 with cement slurries was determined, and the ratio of the thickening time T1 (min) of the mixture after the flush fluid and the cement slurry were mixed in a volume ratio of 25:75 to the thickening time T0 (min) of the neat cement slurry. If the ratio A < 1, the compatibility is poor; if the ratio A ≥ 1, the compatibility is good.

[0090] The specific test results of the rheological compatibility of the cementing flush fluids prepared in the above Examples 1 to 6 and Comparative Examples 1 to 4 when mixed with oil-based drilling fluids and cement slurries in different proportions and the compatibility with cement slurries are shown in Table 2.

[0091] Table 2

[0092]

[0093] As can be seen from Table 2, for the cementing flush fluids prepared in Examples 1 to 6 of the present invention when mixed with oil-based drilling fluids and cement slurries in different proportions, the R values at a rotational speed of 300 r / min on a six-speed rotational viscometer are all < 0, and the ratio A of the thickening time of the mixture after the cementing flush fluid and the cement slurry are mixed in a volume ratio of 25:75 is all > 1. This shows that the cementing flush fluids prepared in the present invention have good compatibility with oil-based drilling fluids and cement slurries.

[0094] Combined Figure 2 and Figure 3 it can be seen the state of the mixture after using the cementing flush fluid for flushing. Figure 2 In Figure 2 the cementing flush fluid prepared in Example 1 was used to flush the dirt left by the oil-based drilling fluid. Figure 2 (a) shows the state after flushing. It can be seen that the flush fluid and the drilling fluid are in a compatible state after flushing. From Figure 2 (c) It can be seen that the bottom of the cup is clean and there are no undissolved contaminants; Figure 3 The cementing flushing fluid prepared in a comparative ratio was used to flush out the dirt left by the oil-based drilling fluid. Figure 3 (a) shows the state after flushing. It can be seen that the flushing fluid and drilling fluid are not completely compatible. Figure 3 (b) It can be seen that there is still oil residue at the bottom of the cup. Figure 3 (c) Undissolved lumpy oil sludge cake can be observed at the bottom of the cup; thus, it can be concluded that the cementing flushing fluid prepared by the present invention can be used to flush the residual drilling fluid and filter cake layer on the well wall during cementing operations, and has good flushing efficiency.

[0095] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a cementing flushing fluid, characterized in that, Includes the following steps: S1. Under an inert gas environment, benzyl quaternized cyclodextrin and biphenyl dichlorobenzyl were dissolved in [BMIm]Cl / FeCl3 ionic liquid, stirred at high temperature, filtered to collect the precipitate, washed, Soxhlet extracted, and vacuum dried to obtain porous cyclodextrin polymer. S2. After dissolving the porous cyclodextrin polymer in water and allowing it to stand, add silanized SiO2 nanoparticles, mix and stir, filter to collect the precipitate, and vacuum dry to obtain the SiO2 / porous cyclodextrin polymer composite material. S3. After mixing and stirring monoethanolamine, sodium cocoaminopropionate, and water, add SiO2 / porous cyclodextrin polymer composite material and stir at high speed to prepare cementing flushing fluid; wherein the weight parts of the raw materials are: monoethanolamine 1~5 parts, sodium cocoaminopropionate 11~33 parts, water 200 parts, and SiO2 / porous cyclodextrin polymer composite material 20~40 parts.

2. The method for preparing a cementing flushing fluid according to claim 1, characterized in that, The benzyl quaternized cyclodextrin was prepared by mixing and stirring quaternized cyclodextrin and anhydrous N,N-dimethylformamide solution in an ice bath for 10 min, then adding sodium hydride and stirring for 15-30 min, and finally slowly adding benzyl bromide. The reaction was carried out at room temperature for 24 h, the reaction was quenched with methanol, diluted with water, extracted four times with dichloromethane, and then rotary evaporated.

3. A method for preparing a cementing flushing fluid according to claim 2, characterized in that, The quaternized cyclodextrin is obtained by dissolving β-cyclodextrin in a 1.0 mol / L NaOH solution, slowly adding a 3% (w / w) aqueous solution of 2,3-epoxypropyltrimethylammonium chloride, stirring at 50-60°C for 16-24 h, adjusting the pH to 7-7.5 with hydrochloric acid, filtering to collect the precipitate, and freeze-drying for 8-12 h.

4. A method for preparing a cementing flushing fluid according to claim 1, characterized in that, The [BMIm]Cl / FeCl3 ionic liquid was obtained by vacuum drying 1-butyl-3-methylimidazolium chloride and FeCl3 at 60°C for 24 h; then, under a nitrogen atmosphere, FeCl3 was added to a reactor containing 1-butyl-3-methylimidazolium chloride and stirred for 14 h.

5. A method for preparing a cementing flushing fluid according to claim 4, characterized in that, The mass ratio of 1-butyl-3-methylimidazolium chloride to FeCl3 in the [BMIm]Cl / FeCl3 ionic liquid is 5:

6.

6. A method for preparing a cementing flushing fluid according to claim 1, characterized in that, In step S1, the inert gas is nitrogen, the high-temperature stirring temperature is 75~85℃ and the time is 16~20h, the washing agent is water and methanol, the washing number is 2~5 times, the solvent used for Soxhlet extraction is methanol and the time is 18~24h, and the vacuum drying time is 12~16h and the temperature is 60~80℃.

7. A method for preparing a cementing flushing fluid according to claim 1, characterized in that, The silanized SiO2 nanoparticles were prepared by adding 3-aminopropyltriethoxysilane dropwise to a 90% (v / v) aqueous ethanol solution, adjusting the pH to 3.0 with acetic acid, and magnetically stirring for 30 min. The mixture was then added dropwise to a 5% (w / w) SiO2 nanoparticle-ethanol dispersion. Under nitrogen protection, the mixture was stirred at 80°C for 10 h, centrifuged for 15 min, and the precipitate was washed three times sequentially with ethanol and deionized water. The precipitate was then vacuum dried at 80°C for 10 h.

8. A method for preparing a cementing flushing fluid according to claim 1, characterized in that, In step S2, the standing time is 24 hours, the mixing and stirring are carried out under ultrasonic treatment for 10-15 minutes, and the vacuum drying time is 12-16 hours at a temperature of 60-80°C.

9. A method for preparing a cementing flushing fluid according to claim 1, characterized in that, In step S3, monoethanolamine, sodium cocoyl aminopropionate, and water are mixed and stirred at 300 rpm for 15-20 minutes. Then, xanthan gum and carboxymethyl cellulose are added and mixed and stirred at 4000 rpm for 3-5 minutes. Finally, SiO2 / porous cyclodextrin polymer composite material is added and mixed and stirred at 4000 rpm for 1-5 minutes to obtain the cementing flushing fluid.

10. A cementing flushing fluid, characterized in that, The SiO2 / porous cyclodextrin polymer composite material is prepared by the method of preparing a cementing flushing fluid according to any one of claims 1 to 9, and comprises the following raw materials in parts by weight: 20 parts of porous cyclodextrin polymer and 10 to 30 parts of silanized SiO2 nanoparticles.

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