High temperature resistant suspending stabilizer for oil well cement and its preparation method

Abstract

The present application relates to the technical field of cement, in particular to a kind of high-temperature-resistant suspending stabilizer for oil well cement and its preparation method, it includes the following raw materials: nano-silica stabilizer, self-repairing micro latex, sulfonated acetone-formaldehyde condensate, sorbitol and fly ash.In the present application, nano-silica stabilizer is used as rigid skeleton, by forming high-strength three-dimensional network structure between cement particles, strong static suspension force and thixotropy are provided, which fundamentally prevents particle settlement at high temperature;And self-repairing micro latex, its hydrophobic association link can be reversibly broken under shear, so that the slurry maintains good pumping rheological property;Once shear stops, association point quickly rebuilds, network strength recovers or even enhances, realizes the self-repairing of suspending capacity, effectively deals with fluctuating conditions downhole.

Description

TECHNICAL FIELD

[0001] The present application relates to the cement technology field, specifically, it relates to a kind of high-temperature-resistant suspending stabilizer for oil well cement and its preparation method. BACKGROUND

[0002] In cementing engineering of oil and gas well, the suspending stability of cement slurry is one of the key performances to ensure cementing quality; Especially in deep well, ultra-deep well and shale gas horizontal well, downhole temperature often exceeds 120 DEG C, even up to 200 DEG C above, accompanied by high salt, high pressure complex environment; Currently widely used suspending stabilizer mainly includes: one is natural polymer and its derivative, such as hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), which provides suspending force by hydration thickening; Two is inorganic material, such as micro-silicon, bentonite or nano-silicon dioxide, which forms gel structure by surface charge and steric hindrance.

[0003] However, existing inorganic nano material is resistant to high temperature but easy to aggregate, and its rigid structure can lead to excessive thickening of cement slurry, affect pumping safety, and it is difficult to realize the coordination and balance of performance under the complex working conditions of high temperature, high salt and strong shear, therefore, we propose a kind of high-temperature-resistant suspending stabilizer for oil well cement and its preparation method. SUMMARY

[0004] The present application provides a kind of high-temperature-resistant suspending stabilizer for oil well cement and its preparation method, to solve the problems that existing inorganic nano material is resistant to high temperature but easy to aggregate, and its rigid structure can lead to excessive thickening of cement slurry, affect pumping safety, and it is difficult to realize the coordination and balance of performance under the complex working conditions of high temperature, high salt and strong shear in the above background technology.

[0005] The present application provides a kind of high-temperature-resistant suspending stabilizer for oil well cement, comprising the following raw materials: nano-silicon dioxide stabilizer, self-repairing micro latex, sulfonated acetone-formaldehyde condensate, sorbitol and fly ash;

[0006] The nano-silicon dioxide stabilizer is prepared by surface modification of nano-silicon dioxide with 3-methacryloxypropyl trimethoxysilane, and then copolymerized with 2-acrylamido-2-methylpropane sulfonic acid on the surface of nano-silicon dioxide.

[0007] Preferably, the components of the raw materials are: nano-silicon dioxide stabilizer 30-60 parts by weight, self-repairing micro latex 10-30 parts by weight, sulfonated acetone-formaldehyde condensate 5-15 parts by weight, sorbitol 2-8 parts by weight and fly ash 20-40 parts by weight.

[0008] Preferably, the preparation method of the nano-silicon dioxide stabilizer is as follows:

[0009] The nano-silica is dispersed in deionized water, ultrasonic dispersion is carried out for 20-30 min at a power of 100-200 W, and 0.01 mol / L acetic acid is used to adjust the pH to 4-5, so as to obtain a nano-silica dispersion liquid with a solid content of 5-10%;

[0010] 3-methacryloxypropyltrimethoxysilane is added into the nano-silica dispersion liquid, stirring is carried out at a speed of 300-400 rpm for 30-60 min, and then the temperature is raised to 60-70 ℃ to continue the reaction for 1-2 h; after cooling, filtration is carried out, and washing is carried out with deionized water until neutral, so as to obtain 3-methacryloxypropyltrimethoxysilane-nano-silica;

[0011] The 3-methacryloxypropyltrimethoxysilane-nano-silica is redispersed in deionized water to obtain a dispersion liquid with a solid content of 5-15%; 2-acrylamido-2-methylpropanesulfonic acid is added into the dispersion liquid, and 0.1 mol / L sodium hydroxide is used to adjust the pH to 6-7; nitrogen is introduced, the temperature is raised to 50-70 ℃, and ammonium persulfate accounting for 0.5-2% of the mass of the 2-acrylamido-2-methylpropanesulfonic acid is added, and the reaction is carried out for 2-4 h;

[0012] After the reaction is completed, cooling is carried out, sodium bisulfite with a molar ratio of 1:1 to the ammonium persulfate is added, and then the reaction liquid is washed, 0.1 mol / L sodium hydroxide is used to adjust the pH to 7-8, and then spray drying is carried out, the inlet temperature is 160-180 ℃, and the outlet temperature is 80-90 ℃, so as to obtain the nano-silica stabilizer.

[0013] Preferably, the mass ratio of the nano-silica to the 3-methacryloxypropyltrimethoxysilane is 1:0.06-0.12.

[0014] Preferably, the mass ratio of the nano-silica to the 2-acrylamido-2-methylpropanesulfonic acid is 1:0.3-1.5.

[0015] In another aspect, the present application provides a preparation method of a high-temperature-resistant suspension stabilizer for oil well cement, for preparing the high-temperature-resistant suspension stabilizer for oil well cement as described above, comprising the following steps:

[0016] S1.1. The following raw materials are weighed: 30-60 parts by weight of the nano-silica stabilizer, 10-30 parts by weight of the self-repairing micro-latex, 5-15 parts by weight of the sulfonated acetone-formaldehyde condensate, 2-8 parts by weight of sorbitol, and 20-40 parts by weight of fly ash;

[0017] S1.2. In a high-speed mixer, the fly ash and the nano-silica stabilizer are dry-mixed at a speed of 200-400 rpm for 15-20 min to obtain a master batch base powder;

[0018] In the premixing tank, add self-repairing micro latex and sorbitol, stir at a speed of 200-400 rpm for 10-15 min to form a liquid phase premix;

[0019] S1.3, add the master batch base powder into the high-speed shearing granulator, spray the liquid phase premix onto the base powder through the spraying device at a shearing speed of 1000-1500 rpm and a stirring speed of 100-200 rpm;

[0020] After spraying is completed, keep shearing mixing for 5 min, then adjust the speed to 300-500 rpm, add sulfonated acetone-formaldehyde condensate and continue mixing for 15-20 min to obtain the material;

[0021] S1.4, transfer the material to a double-cone mixer and homogenize at a speed of 20-30 rpm for 30 min; pass the homogenized material through a 80-100 mesh vibrating screen to obtain the high-temperature resistant suspension stabilizer for oil well cement.

[0022] As a preferred, in the S1.2, the preparation method of the self-repairing micro latex is as follows:

[0023] Dissolve N,N-dimethyl acrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate in deionized water at a mass ratio of 1:5, add 3-5% of sodium dodecyl sulfate based on the total mass of monomers, and emulsify at a high speed of 8000-10000 rpm for 15-20 min to form a pre-emulsion;

[0024] Add one-third of the pre-emulsion to a reaction kettle, add 0.4-0.8% of potassium persulfate solution based on the total mass of monomers, adjust the pH to 6.5-7.5 with 0.1 mol / L sodium hydroxide, and fill with nitrogen for 30 min, then heat to 63-67°C and react for 30-45 min; add the remaining two-thirds of the pre-emulsion through a constant pressure dropping funnel within 2-3 h, and synchronously add 0.2-0.4% of potassium persulfate solution based on the total mass of monomers; after the addition is completed, heat to 70-75°C and react for 1-2 h to obtain an emulsion;

[0025] After the reaction is completed, cool to below 40°C, add 0.1-0.3% of Span 80 and 0.05-0.1% of sodium benzoate based on the total mass of the emulsion, and adjust the pH of the emulsion to 7-8 with 0.1 mol / L sodium hydroxide; concentrate by reduced pressure distillation to a solid content of 20-40% to obtain the self-repairing micro latex.

[0026] As a preferred, the mass ratio of N,N-dimethyl acrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate is 1:0.15-0.3:0.02.

[0027] Preferably, the concentration of the potassium persulfate solution is 0.5-1.0 mol / L.

[0028] Preferably, in S1.3, the atomization pressure of the spraying device is 0.3-0.6 MPa, and the liquid flow rate is 200-500 mL / min.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] In the high-temperature resistant suspension stabilizer for oil well cement and the preparation method thereof, the nano-silica stabilizer serves as a rigid skeleton, forms a high-strength three-dimensional network structure between cement particles, provides strong static suspension force and thixotropy, and fundamentally prevents particle settlement at high temperatures; the self-repairing micro-latex reversibly breaks under the action of shearing, so that the slurry maintains good pumping rheological properties; once the shearing stops, the association points are quickly rebuilt, the network strength is restored or even enhanced, the suspension capacity is self-repaired, and the fluctuating working conditions in the well are effectively coped with; the combination of the two overcomes the defects of high-temperature degradation of traditional polymers and poor rheological properties of inorganic materials, and further provides a reliable performance, safe construction solution for cementing operations in ultra-deep wells, high-temperature and high-salt wells through the rigid and flexible mechanism. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] The present application provides a high-temperature resistant suspension stabilizer for oil well cement, comprising the following raw materials: nano-silica stabilizer, self-repairing micro-latex, sulfonated acetone-formaldehyde condensate, sorbitol and fly ash.

[0033] The nano-silica stabilizer is prepared by surface modification of nano-silica with 3-methacryloxypropyl trimethoxysilane, and then copolymerization of the nano-silica surface with 2-acrylamido-2-methylpropane sulfonic acid.

[0034] Nano silica (CAS: 7631-86-9, average particle size 15-20nm, specific surface area 200±25 m² / g), 3-methacryloyloxypropyltrimethoxysilane (CAS: 2530-85-0), 2-acrylamido-2-methylpropanesulfonic acid (CAS: 15214-89-8), methacryloylethyl sulfobetaine (CAS: 3637-26-1), sorbitol (CAS: 50-70-4), N,N-dimethylacrylamide (CAS: 2680-03-7), purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0035] Lauryl acrylate, CAS: 2156-97-0, purchased from Guangzhou Shanghe Chemical Technology Co., Ltd.

[0036] The synthesis steps of sulfonated acetone-formaldehyde condensate are as follows: Sodium bisulfite aqueous solution is added to a reaction vessel and stirred to dissolve while maintaining the temperature below 50℃; then acetone is slowly added dropwise, maintaining the low temperature until the solution becomes clear; next, formaldehyde solution is added, and the mixture is heated to 80-85℃ and refluxed for 3-4 hours, during which the pH needs to be adjusted to 10; after the reaction is completed, the mixture is cooled to room temperature and adjusted to pH=10.3. Finally, the sulfonated acetone-formaldehyde condensate is obtained by dialysis; wherein the molar ratio of formaldehyde to acetone is 2.0, and the molar ratio of sodium bisulfite to acetone is 0.55.

[0037] fly ash ( (Content 40-60%, Al2O3 content 15-40%, Fe2O3 content 5-15%, and CaO content 1-10%) was purchased from Wuhan Jiyesheng Chemical Co., Ltd.

[0038] Example 1: A method for preparing a high-temperature resistant suspension stabilizer for oil well cement, comprising the following steps:

[0039] S1.1 Weigh the following raw materials in parts by weight: 30 parts by weight of nano silica stabilizer, 10 parts by weight of self-healing micro latex, 5 parts by weight of sulfonated acetone-formaldehyde condensate, 2 parts by weight of sorbitol and 20 parts by weight of fly ash.

[0040] S1.2 In a high-speed mixer, add fly ash and nano silica stabilizer, and dry mix at 400 rpm for 20 minutes to obtain masterbatch powder;

[0041] In a premixing tank, add self-healing micro latex and sorbitol, and stir at 400 rpm for 15 min to form a liquid premix.

[0042] S1.3 Add the masterbatch base powder into a high-speed shear granulator. Spray the liquid premix onto the base powder through a spraying device at a shearing speed of 1200 rpm and a stirring speed of 200 rpm. The atomization pressure is 0.4 MPa and the liquid flow rate is 200 mL / min.

[0043] After spraying is completed, the shearing mixing is maintained for 5 min, then the rotation speed is adjusted to 500 rpm, and the sulfonated acetone-formaldehyde condensate is added to continue mixing for 20 min, to obtain the material;

[0044] S1.4, the material is transferred to a double-cone mixer for homogenization at a rotation speed of 30 rpm for 30 min; the homogenized material is passed through a 100-mesh vibrating screen to obtain the high-temperature-resistant suspending stabilizer for oil well cement.

[0045] The preparation method of the self-repairing micro latex is as follows:

[0046] N,N-dimethyl acrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate (mass ratio 1:0.15:0.02) are dissolved in deionized water at a mass ratio of 1:5, and 4% of the total mass of the monomers is sodium dodecyl sulfate, which is emulsified at a high shear speed of 8000 rpm for 20 min to form a pre-emulsion;

[0047] One-third of the pre-emulsion is added to a reaction kettle, and potassium persulfate (solid) is added in an amount of 0.4% of the total mass of the monomers, and is prepared into a 0.5 mol / L aqueous solution for use, and the pH is adjusted to 7.0 with 0.1 mol / L sodium hydroxide, and nitrogen is filled for 30 min, and then the temperature is raised to 65℃, and reacted for 45 min; the remaining two-thirds of the pre-emulsion is added dropwise through a constant-pressure dropping funnel within 3 h, and 0.2% of the total mass of the monomers of 0.5 mol / L potassium persulfate solution is added dropwise synchronously; after the dropwise addition is completed, the temperature is raised to 70℃ and reacted for 2 h to obtain the emulsion;

[0048] After the reaction is completed, the temperature is lowered to below 40℃, and 0.1% of the total mass of the emulsion of Span 80 and 0.05% of sodium benzoate are added, and the pH of the emulsion is adjusted to 7 with 0.1 mol / L sodium hydroxide; concentrated to a solid content of 30% by vacuum distillation to obtain the self-repairing micro latex.

[0049] The preparation method of the nano-silica stabilizer is as follows:

[0050] Nano-silica is dispersed in deionized water, ultrasonically dispersed at a power of 200 W for 30 min, and the pH is adjusted to 5 with 0.01 mol / L acetic acid to obtain a nano-silica dispersion liquid with a solid content of 5%;

[0051] 3-methacryloyl propyl trimethoxysilane (mass ratio 1:0.06) is added to the nano-silica dispersion liquid, stirred at a speed of 400 rpm for 60 min, and then the temperature is raised to 70℃ and reacted for 2 h; after cooling, filter and wash with deionized water until neutral to obtain 3-methacryloyl propyl trimethoxysilane-nano-silica;

[0052] The 3-methacryloxypropyltrimethoxysilane-nanosilica is re-dispersed in deionized water to obtain a dispersion with a solid content of 5%; 2-acrylamido-2-methylpropanesulfonic acid is added to the dispersion (mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to nanosilica is 1:0.3), and 0.1 mol / L sodium hydroxide is used to adjust the pH to 7; nitrogen is introduced, and the temperature is raised to 50-70°C; 0.5% of ammonium persulfate based on the mass of 2-acrylamido-2-methylpropanesulfonic acid is added, and the reaction is carried out for 4 h;

[0053] After the reaction is completed, the temperature is cooled, sodium bisulfite is added in a molar ratio of 1:1 to ammonium persulfate, and then the reaction solution is washed, the pH is adjusted to 7 with 0.1 mol / L sodium hydroxide, and then spray drying is carried out, with an inlet temperature of 160°C and an outlet temperature of 80°C, to obtain a nanosilica stabilizer.

[0054] Example 2: Compared with Example 1, the difference is that the mass ratio of nanosilica to 3-methacryloxypropyltrimethoxysilane is 1:0.09.

[0055] Example 3: Compared with Example 1, the difference is that the mass ratio of nanosilica to 3-methacryloxypropyltrimethoxysilane is 1:0.12.

[0056] Example 4: Compared with Example 1, the difference is that the mass ratio of nanosilica to 2-acrylamido-2-methylpropanesulfonic acid is 1:0.9.

[0057] Example 5: Compared with Example 1, the difference is that the mass ratio of nanosilica to 2-acrylamido-2-methylpropanesulfonic acid is 1:1.5.

[0058] Determination of grafting rate: a small amount of dried nanosilica stabilizer powder (about 5-10 mg) is placed in a platinum crucible in a TGA instrument; under a nitrogen atmosphere, the temperature is raised at a certain rate (such as 10°C / min) from room temperature to 800°C, and the weight change curve with temperature is recorded; the weight loss between 300-600°C mainly corresponds to the decomposition of the surface grafted organic polymer (PAMPS); the grafting rate = (weight loss percentage of the modified sample at 300-600°C - weight loss percentage of the raw material in the same temperature interval) X 100%.

[0059] Determination of dispersion stability: a certain amount (such as 0.5 g) of nanosilica stabilizer is dispersed in 100 mL of deionized water or simulated cement slurry filtrate (containing Ca 2+ 、 The uniform dispersion is obtained after ultrasonic treatment; the dispersion is transferred to a graduated cylinder with a stopper, and is left to stand at a constant temperature (e.g. 25°C and 90°C); the change in the height of the dispersion and the volume of the sediment at the bottom are observed and recorded regularly; the time required for the sediment to reach half the volume (half-settling time) is recorded as a quantitative index.

[0060] Measurement of suspension capacity: the nano-silica stabilizer is added to the oil well cement slurry formulation according to the design, and the cement slurry is prepared by stirring under high temperature and high pressure (e.g. 150°C, 100MPa); the cement slurry is poured into a sedimentation stability tester and placed in a high-temperature curing oven in the vertical direction for a certain period of time (e.g. 2 hours); after the curing is completed, the cylinder is quickly cooled, and the slurry at the top and the bottom is separated; the densities of the slurry at the top and the bottom are measured respectively, and the density difference (Δρ) between the top and the bottom is the sedimentation stability index.

[0061] Table 1 Performance data of nano-silica stabilizers

[0062] grafting ratio dispersion stability suspension ability example 1 18.5% 7 days 0.030 g / cm 3 ]] example 2 22.1% 21 days 0.018 g / cm 3 ]] example 3 20.3% 10 days 0.025 g / cm 3 ]] example 4 38.7% > 30 days 0.010 g / cm 3 ]] example 5 51.4% > 30 days 0.005 g / cm 3 ]]

[0063] Comparing Examples 1, 2 and 3, the grafting rate and various performances first increase and then decrease with the increase of the amount of silane.

[0064] The performance of Example 2 (1:0.09) is better, and the silane coupling agent provides the most suitable active double bond site density, so that the subsequent AMPS polymerization reaction has the highest efficiency, and a dense polymer shell is formed, thereby significantly improving the dispersibility and suspension capacity.

[0065] The performance of Example 3 (1:0.12) decreases instead, because the excessive silane not only cannot provide more effective sites, but also forms multiple layers of coverage on the surface of the nano particles and even homopolymerization occurs, resulting in increased hydrophobicity of the particle surface and easier aggregation, thereby affecting the grafting efficiency and the dispersibility of the final product.

[0066] Comparing Examples 1, 4 and 5, the grafting rate, dispersion stability and suspension capacity are continuously and significantly improved with the increase of the amount of AMPS.

[0067] AMPS is a key monomer that provides steric hindrance and electrostatic repulsion (sulfonic acid group), and increasing its amount directly leads to the formation of a thicker and denser polymer hydration layer on the surface of the nano particles.

[0068] This greatly enhances the repulsion between particles, so the dispersion stability time is greatly extended.

[0069] A thicker polymer layer can form a stronger three-dimensional network structure in the cement slurry, thereby firmly fixing the cement particles, so the suspension capacity is better (Example 5).

[0070] Embodiment 6: A method for preparing a high-temperature-resistant suspension stabilizer for oil well cement, comprising the following steps:

[0071] S1.1, weigh the following raw materials: 60 parts by weight of nano-silica stabilizer, 30 parts by weight of self-repairing micro-latex, 15 parts by weight of sulfonated acetone-formaldehyde condensate, 8 parts by weight of sorbitol, and 40 parts by weight of fly ash;

[0072] S1.2, in a high-speed mixer, add fly ash and nano-silica stabilizer, dry mix at a speed of 400 rpm for 20 min to obtain a master batch base powder;

[0073] In a premixing tank, add self-repairing micro-latex and sorbitol, stir at a speed of 400 rpm for 15 min to form a liquid phase premix;

[0074] S1.3, add the master batch base powder into a high-speed shearing granulator, spray the liquid phase premix onto the base powder through a spraying device at a shearing speed of 1200 rpm and a stirring speed of 200 rpm, the atomizing pressure is 0.4 MPa, and the liquid flow rate is 200 mL / min;

[0075] After spraying is completed, keep shearing mixing for 5 min, then adjust the speed to 500 rpm, add sulfonated acetone-formaldehyde condensate and continue mixing for 20 min to obtain a material;

[0076] S1.4, transfer the material to a double-cone mixer and homogenize at a speed of 30 rpm for 30 min; pass the homogenized material through a 100-mesh vibrating screen to obtain a high-temperature-resistant suspension stabilizer for oil well cement.

[0077] The preparation method of the self-repairing micro-latex is as follows:

[0078] Dissolve N,N-dimethyl acrylamide, methacryloyl ethyl sulfobetaine, and lauryl acrylate (mass ratio 1:0.15:0.02) in deionized water according to a mass ratio of 1:5, and 5% of the total monomer mass of sodium dodecyl sulfate, emulsify at a high speed of 8000 rpm for 20 min to form a pre-emulsion;

[0079] Add one-third of the pre-emulsion to a reaction kettle, add potassium persulfate (solid basis), the amount is 0.8% of the total monomer mass, and prepare a 0.5 mol / L aqueous solution, adjust the pH to 7.0 with 0.1 mol / L sodium hydroxide, and fill with nitrogen for 30 min, then heat to 65℃ and react for 45 min; add the remaining two-thirds of the pre-emulsion through a constant-pressure dropping funnel within 3 h, and synchronously add 0.5 mol / L potassium persulfate solution accounting for 0.4% of the total monomer mass; after the addition is completed, heat to 75℃ and keep for 2 h to obtain an emulsion;

[0080] After the reaction, the temperature was lowered to below 40℃, 0.3% Span 80 and 0.1% sodium benzoate were added based on the total mass of the emulsion, and the pH of the emulsion was adjusted to 7 with 0.1 mol / L sodium hydroxide; concentrated to a solid content of 40% by vacuum distillation to obtain a self-repairing micro latex.

[0081] The preparation method of the nano-silica stabilizer is as follows:

[0082] The nano-silica was dispersed in deionized water, ultrasonically dispersed at a power of 200W for 30min, and the pH was adjusted to 5 with 0.01mol / L acetic acid to obtain a nano-silica dispersion with a solid content of 10%;

[0083] 3-methacryloyloxypropyl trimethoxysilane-nano-silica was obtained by adding 3-methacryloyloxypropyl trimethoxysilane (mass ratio of 1:0.09) to the nano-silica dispersion, stirring at a speed of 400rpm for 60min, and then heating to 70℃ and continuing to react for 2h; after cooling, it was filtered and washed with deionized water until neutral to obtain 3-methacryloyloxypropyl trimethoxysilane-nano-silica;

[0084] The 3-methacryloyloxypropyl trimethoxysilane-nano-silica was redispersed in deionized water to obtain a dispersion with a solid content of 15%; 2-acrylamido-2-methylpropanesulfonic acid was added to the dispersion (mass ratio of 1:0.9 with respect to nano-silica), and the pH was adjusted to 7 with 0.1 mol / L sodium hydroxide; nitrogen was introduced, the temperature was raised to 50-70℃, and 0.5% ammonium persulfate based on the mass of 2-acrylamido-2-methylpropanesulfonic acid was added, and the reaction was carried out for 4h;

[0085] After the reaction was completed, cooling was carried out, sodium bisulfite was added in a molar ratio of 1:1 with respect to ammonium persulfate, and then the reaction solution was washed, the pH was adjusted to 7 with 0.1 mol / L sodium hydroxide, and then spray drying was carried out, with an inlet temperature of 160℃ and an outlet temperature of 80℃, to obtain a nano-silica stabilizer.

[0086] Example 7: The difference between this example and Example 6 is that the mass ratio of N,N-dimethylacrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate is 1:0.22:0.02.

[0087] Example 8: The difference between this example and Example 6 is that the mass ratio of N,N-dimethylacrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate is 1:0.3:0.02.

[0088] Determination of emulsion stability: 5mL of 5% calcium chloride solution was added dropwise to 5mL of emulsion, stirred and then left to stand for 2-4 hours; whether demulsification or flocculation occurred was observed; the micro latex with strong salt calcium resistance should remain uniform without the generation of flocculation.

[0089] Self-healing and rheological property measurement: add micro-latex into cement slurry with a certain amount (e.g. 2% BWOC), stir well; use a rheometer to test at high temperature (e.g. 90℃): recovery test: first apply a low shear rate (1 s -1 ) to measure the initial viscosity; then switch to a high shear rate (500 s -1 ) to simulate pumping shear for 1-2 min; then switch back to the low shear rate (1 s -1 ) to observe the viscosity recovery curve over time.

[0090] Table 2 Performance data of self-healing micro-latex

[0091]

[0092] The centrifugal stability of Examples 6, 7 and 8 is good, but the calcium ion stability is significantly improved with the increase of SBMA proportion.

[0093] The SBMA proportion of Example 6 is low (0.15), and the zwitterionic counterion effect is not enough to completely resist the charge shielding and bridging effect of high concentration Ca 2+ , so there is slight flocculation; the SBMA proportion of Examples 7 and 8 is higher, providing stronger hydration layer and electrostatic repulsion, so as to effectively resist the damage of Ca 2+ and keep the emulsion stable.

[0094] The rheological property is not linearly improved with the increase of SBMA content, but there is an optimal value (Example 7), and both the viscosity recovery rate and the final viscosity are higher.

[0095] The SBMA content in Example 6 is insufficient, and the salt calcium resistance and temperature resistance are slightly weak. The network structure strength itself is weak in high salt and high temperature environment, so the final viscosity after recovery is the lowest.

[0096] The SBMA proportion in Example 7 is just right, which provides excellent salt calcium resistance and forms an ideal network structure with hydrophobic monomer (LA) that is both rigid and flexible; the hydrophobic association points can be efficiently rearranged and combined after shearing, and the strong hydration sheath protects the network from being damaged by high temperature and high salt, so it shows the fastest recovery rate and the strongest final network strength (recovery rate 96%, viscosity 185 mPa·s).

[0097] The too high SBMA content in Example 8 leads to too hydrophilic polymer chains or changes the flexibility of molecular chains, which to some extent weakens the strength of hydrophobic association; although its initial stability is good, the dynamic reversible association network performance is actually decreased.

[0098] Embodiment 9: A method for preparing a high-temperature-resistant suspension stabilizer for oil well cement, comprising the following steps:

[0099] S1.1, weigh the following raw materials: 30 parts by weight of nano-silica stabilizer, 10 parts by weight of self-repairing micro-latex, 10 parts by weight of sulfonated acetone-formaldehyde condensate, 5 parts by weight of sorbitol, and 30 parts by weight of fly ash;

[0100] S1.2, in a high-speed mixer, add fly ash and nano-silica stabilizer, dry mix at a speed of 400 rpm for 20 min to obtain a master batch base powder;

[0101] In a premixing tank, add self-repairing micro-latex and sorbitol, stir at a speed of 400 rpm for 15 min to form a liquid phase premix;

[0102] S1.3, add the master batch base powder into a high-speed shearing granulator, spray the liquid phase premix onto the base powder through a spraying device at a shearing speed of 1200 rpm and a stirring speed of 200 rpm, the atomizing pressure is 0.4 MPa, and the liquid flow rate is 200 mL / min;

[0103] After spraying is completed, keep shearing mixing for 5 min, then adjust the speed to 500 rpm, add sulfonated acetone-formaldehyde condensate and continue mixing for 20 min to obtain a material;

[0104] S1.4, transfer the material to a double-cone mixer and homogenize at a speed of 30 rpm for 30 min; pass the homogenized material through a 100-mesh vibrating screen to obtain a high-temperature-resistant suspension stabilizer for oil well cement.

[0105] The preparation method of the self-repairing micro-latex is as follows:

[0106] Dissolve N,N-dimethyl acrylamide, methacryloyl ethyl sulfobetaine, and lauryl acrylate (mass ratio 1:0.22:0.02) in deionized water according to a mass ratio of 1:5, and 4% of the total monomer mass of sodium dodecyl sulfate, emulsify at a high speed of 8000 rpm for 20 min to form a pre-emulsion;

[0107] Add one-third of the pre-emulsion to a reaction kettle, add potassium persulfate (solid basis), the amount is 0.6% of the total monomer mass, and prepare a 0.5 mol / L aqueous solution, adjust the pH to 7.0 with 0.1 mol / L sodium hydroxide, and fill with nitrogen for 30 min, then heat to 65℃ and react for 45 min; add the remaining two-thirds of the pre-emulsion through a constant-pressure dropping funnel within 3 h, and synchronously add 0.5 mol / L potassium persulfate solution accounting for 0.3% of the total monomer mass; after the addition is completed, heat to 75℃ and react for 2 h to obtain an emulsion;

[0108] After the reaction is completed, the temperature is lowered to below 40℃, 0.2% of Span 80 and 0.05% of sodium benzoate are added based on the total mass of the emulsion, and the pH of the emulsion is adjusted to 7 with 0.1 mol / L sodium hydroxide; concentrated to a solid content of 30% by vacuum distillation to obtain a self-repairing micro latex.

[0109] The preparation method of the nano-silica stabilizer is as follows:

[0110] The nano-silica is dispersed in deionized water, ultrasonically dispersed at a power of 200W for 30min, and the pH is adjusted to 5 with 0.01 mol / L acetic acid to obtain a nano-silica dispersion with a solid content of 7%;

[0111] 3-methacryloyloxypropyltrimethoxysilane-nano-silica is obtained by adding 3-methacryloyloxypropyltrimethoxysilane (mass ratio of 1:0.09) to the nano-silica dispersion, stirring at a speed of 400 rpm for 60 min, and then heating to 70℃ and continuing to react for 2h; after cooling, it is filtered and washed with deionized water until neutral.

[0112] The 3-methacryloyloxypropyltrimethoxysilane-nano-silica is redispersed in deionized water to obtain a dispersion with a solid content of 10%; 2-acrylamido-2-methylpropane sulfonic acid (mass ratio of 1:0.9) is added to the dispersion, and the pH is adjusted to 7 with 0.1 mol / L sodium hydroxide; nitrogen is introduced, the temperature is raised to 70℃, 1.5% of ammonium persulfate based on the mass of 2-acrylamido-2-methylpropane sulfonic acid is added, and the reaction is carried out for 4h.

[0113] After the reaction is completed, the temperature is lowered to below 40℃, 0.2% of Span 80 and 0.05% of sodium benzoate are added based on the total mass of the emulsion, and the pH of the emulsion is adjusted to 7 with 0.1 mol / L sodium hydroxide; concentrated to a solid content of 30% by vacuum distillation to obtain a self-repairing micro latex.

[0114] Example 10: Compared with Example 9, the difference is that the nano-silica stabilizer 45 parts by weight.

[0115] Example 11: Compared with Example 9, the difference is that the nano-silica stabilizer 60 parts by weight.

[0116] Example 12: Compared with Example 9, the difference is that the self-repairing micro latex 20 parts by weight.

[0117] Example 13: Compared with Example 9, the difference is that the self-repairing micro latex 30 parts by weight.

[0118] Settling stability test: Add the stabilizer at the recommended dosage (e.g. 1.5% BWOC) into G-class oil well cement, and prepare the cement paste according to the standard procedure; pour the cement paste into the settling stability test cylinder of the high temperature and high pressure curing oven, and cure at the target bottom hole temperature (e.g. 150°C or 180°C) and pressure for a certain period of time (usually 2 hours); after the curing, quickly cool down, and carefully separate the paste at the top and bottom of the settling cylinder; measure the density of the paste at the top and bottom, respectively, and the density difference Δρ = |ρbottom - ptop|.

[0119] Rheology and shear thinning test: After the prepared cement paste is cured at room temperature or at high temperature, place it in the constant pressure consistometer or rotary viscometer, and read the values at different rotational speeds (e.g. 3, 6, 100, 200, 300 rpm) from low to high, and calculate the corresponding shear stress and apparent viscosity.

[0120] Dissolution and dispersion test: Under stirring, quickly add 14 g of the sample (simulating the field paste preparation condition, 40 g of cement / 350 mL of water, and the stabilizer dosage is 1.5%) into a measuring cup containing 350 mL of tap water at room temperature, and start timing at the same time, and observe the time when the particles disappear and the solution becomes uniform.

[0121] Table 3 Performance data of high temperature resistant suspending stabilizer for oil well cement

[0122]

[0123] Comparative Examples 9, 10, and 11, with the increase of the amount of nano The settling stability is significantly improved (Δρ decreases from 0.022 to 0.011), but the rheological recovery rate decreases (from 82% to 70%), and the dissolution time is prolonged (from 75 seconds to more than 120 seconds).

[0124] The nano The core that provides the rigid three-dimensional network skeleton, the amount of increase directly enhances the ability to support and suspend the cement particles, so that Δρ becomes smaller.

[0125] Excessive rigid nanoparticles will interfere and destroy the flexible reversible network structure formed by the self-repairing micro-latex through hydrophobic association to a certain extent, so that the efficiency of rebuilding the network after shearing is reduced.

[0126] The nano The stabilizer itself has a slow dissolution and dispersion speed, and is more likely to absorb water and form clumps at high dosage, resulting in a significant extension of the time required for complete dissolution.

[0127] Comparing Examples 9, 12, 13, with the increase of self-healing micro-latex, the rheology recovery rate increased significantly (from 82% to 98%), and the sedimentation stability also improved (the Δρ decreased from 0.022 to 0.016), but the dissolution time increased slightly (from 75 seconds to 105 seconds).

[0128] The increase of the amount of self-healing micro-latex means that the density of reversible physical cross-linking points in the system increases, and the speed and ability of network reconstruction are stronger.

[0129] The stronger and more easily recovered network structure also helps static suspension, so the Δρ decreases.

[0130] The hydrophobic components and polymer chains in the micro-latex need more time to hydrate and stretch, so the increase of the amount will cause the dissolution time to become longer, but the dissolution time of all examples is within the acceptable range (< 120 seconds).

[0131] After the above determination, Example 10 is selected as the optimal example.

[0132] Comparative Example 1: Compared with Example 10, the difference is that no nano-silica stabilizer is added, and silica is directly added.

[0133] Comparative Example 2: Compared with Example 10, the difference is that no self-healing micro-latex is added.

[0134] Comparative Example 3: Compared with Example 10, the difference is that 2-acrylamido-2-methylpropanesulfonic acid is not added in the nano-silica stabilizer.

[0135] Table 4 Performance data of high-temperature resistant suspension stabilizer for oil well cement

[0136]

[0137] Comparative Example 1 uses unmodified nano , the sedimentation stability is very poor (Δρ = 0.038), and the solubility is extremely deteriorated (> 300 seconds).

[0138] Unmodified nano The surface energy is very high, and strong agglomeration forms hard agglomerates that cannot be dispersed. These agglomerates cannot form a uniform three-dimensional network in the cement slurry, but instead settle quickly as heavy particles, leading to suspension failure.

[0139] Comparative Example 2 does not add self-healing micro-latex, and the rheology recovery rate drops to 35%, and the sedimentation stability also decreases significantly (Δρ = 0.028).

[0140] The absence of self-healing micro-latex means the loss of reversible hydrophobic association network; the system relies solely on nano The rigid network support is destroyed irreversibly after high speed shearing, and cannot be recovered, so the viscosity recovery rate is very low; at the same time, the static sedimentation stability is also poor due to the lack of the synergistic suspension effect of the flexible network.

[0141] Comparative Example 3 Nanometer No AMPS grafted, sedimentation stability unqualified (Δρ = 0.031), poor solubility (180 seconds).

[0142] Although the hydrophobic modification is carried out using a silane coupling agent, the AMPS polymer chain is not grafted, and the product cannot effectively prevent the agglomeration of the nanoparticles in a high-salt environment, the strong electrostatic repulsion provided by the sulfonate is also lacking, and the particles are prone to aggregation; this leads to poor dispersibility of the product in water, especially in a salt-containing water slurry filtrate, and the particles are prone to aggregation and precipitation, resulting in suspension failure, and the dissolution speed is also slow.

[0143] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A high temperature resistant suspending stabilizer for oil well cement, characterized by, The raw materials include: 30-60 parts by weight of nano-silica stabilizer, 10-30 parts by weight of self-repairing micro-latex, 5-15 parts by weight of sulfonated acetone-formaldehyde condensate, 2-8 parts by weight of sorbitol and 20-40 parts by weight of fly ash; The nano-silica stabilizer is prepared by surface modification of nano-silica with 3-methacryloxypropyltrimethoxysilane, followed by copolymerization of 2-acrylamido-2-methylpropanesulfonic acid on the surface of nano-silica; The self-repairing micro-latex is prepared by the following method: N,N-dimethylacrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate are dissolved in deionized water at a mass ratio of 1:5, and 3-5% of sodium dodecyl sulfate based on the total mass of monomers is added, and emulsified at a high shear speed of 8000-10000 rpm for 15-20 min to form a pre-emulsion; One third of the pre-emulsion is added to a reaction kettle, 0.4-0.8% of potassium persulfate solution based on the total mass of monomers is added, the pH is adjusted to 6.5-7.5 with 0.1 mol / L sodium hydroxide, nitrogen is filled for 30 min, then the temperature is raised to 63-67℃, and the reaction is carried out for 30-45 min; the remaining two-thirds of the pre-emulsion is added dropwise through a constant-pressure dropping funnel within 2-3 h, and 0.2-0.4% of potassium persulfate solution based on the total mass of monomers is added synchronously; after the dropwise addition is completed, the temperature is raised to 70-75℃ and the reaction is carried out for 1-2 h to obtain the emulsion; After the reaction is completed, the temperature is lowered to below 40℃, 0.1-0.3% of Span 80 and 0.05-0.1% of sodium benzoate based on the total mass of the emulsion are added, and the pH of the emulsion is adjusted to 7-8 with 0.1 mol / L sodium hydroxide; the emulsion is concentrated by vacuum distillation to a solid content of 20-40% to obtain the self-repairing micro-latex.

2. The high temperature resistant suspending stabilizer for oil well cement according to claim 1, characterized by, The preparation method of the nano-silica stabilizer is as follows: Nano-silica is dispersed in deionized water, ultrasonically dispersed at a power of 100-200 W for 20-30 min, and the pH is adjusted to 4-5 with 0.01 mol / L acetic acid to obtain a nano-silica dispersion with a solid content of 5-10%; 3-methacryloxypropyltrimethoxysilane is added to the nano-silica dispersion, stirred at a speed of 300-400 rpm for 30-60 min, and then the temperature is raised to 60-70℃ for 1-2 h of continuous reaction; after cooling, filtration and washing with deionized water until neutral, 3-methacryloxypropyltrimethoxysilane-nano-silica is obtained; 3-methacryloxypropyltrimethoxysilane-nano-silica is redispersed in deionized water to obtain a dispersion with a solid content of 5-15%; 2-acrylamido-2-methylpropanesulfonic acid is added to the dispersion, and the pH is adjusted to 6-7 with 0.1 mol / L sodium hydroxide; nitrogen is introduced, the temperature is raised to 50-70℃, and 0.5-2% of ammonium persulfate based on the mass of 2-acrylamido-2-methylpropanesulfonic acid is added, and the reaction is carried out for 2-4 h; After the reaction is completed, sodium bisulfite is added in a molar ratio of 1:1 with ammonium persulfate, then the reaction solution is washed, the pH is adjusted to 7-8 with 0.1 mol / L sodium hydroxide, and then spray drying is performed at an inlet temperature of 160-180 DEG C and an outlet temperature of 80-90 DEG C to obtain the nano-silica stabilizer.

3. The high temperature resistant suspending stabilizer for oil well cement according to claim 2, characterized by, The mass ratio of the nano-silica to 3-methacryloxypropyltrimethoxysilane is 1:0.06-0.

12.

4. The high temperature resistant suspending stabilizer for oil well cement according to claim 2, characterized by, The mass ratio of the nano-silica to 2-acrylamido-2-methylpropanesulfonic acid is 1:0.3-1.

5.

5. The high temperature resistant suspending stabilizer for oil well cement according to claim 1, characterized by, The mass ratio of the N,N-dimethylacrylamide, methacryloyl ethyl sulfobetaine and lauryl acrylate is 1:0.15-0.3:0.

02.

6. The high temperature resistant suspending stabilizer for oil well cement according to claim 1, characterized by, The concentration of the potassium persulfate solution is 0.5-1.0 mol / L.

7. A method for producing a high temperature resistant suspending stabilizer for oil well cement, for producing the high temperature resistant suspending stabilizer for oil well cement as claimed in any one of claims 1 to 6, characterized by, The preparation method of the high-temperature-resistant suspending stabilizer for oil well cement is as follows: S1.1, the raw materials are weighed by parts by weight; S1.2, in a high-speed mixer, add fly ash and nano-silica stabilizer, dry mix at a speed of 200-400 rpm for 15-20 min to obtain a master batch powder; In a premixing tank, add self-repairing micro latex and sorbitol, stir at a speed of 200-400 rpm for 10-15 min to form a liquid phase premix; S1.3, add the master batch powder to a high-speed shearing granulator, with a shearing speed of 1000-1500 rpm and a stirring speed of 100-200 rpm, spray the liquid phase premix onto the powder through a spraying device; After spraying is completed, keep shearing mixing for 5 min, then adjust the speed to 300-500 rpm, add sulfonated acetone-formaldehyde condensate and continue mixing for 15-20 min to obtain the material; S1.4, transfer the material to a double-cone mixer and homogenize at a speed of 20-30 rpm for 30 min; pass the homogenized material through a 80-100 mesh vibrating screen to obtain the high-temperature-resistant suspending stabilizer for oil well cement.

8. The method for preparing the high-temperature resistant suspension stabilizer for oil well cement according to claim 7, characterized in that, In S1.3, the atomizing pressure of the spraying device is 0.3-0.6 MPa, and the liquid flow rate is 200-500 mL / min.

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