A surface-modified hollow glass microsphere and its preparation method, and high-temperature, high-strength, low-density cement slurry.

Abstract

This invention provides a surface-modified hollow glass microsphere, its preparation method, and a high-temperature, high-strength, low-density cement slurry. The preparation method includes: alkaline etching of the hollow glass microspheres to prepare a solution; adding a silane coupling agent to the solution, then mixing it with an amide monomer containing a carbon-carbon double bond and a phosphate ester monomer containing a carbon-carbon double bond; adding an initiator to carry out the reaction; adding a polymerization inhibitor; and finally washing and spray drying to obtain the surface-modified hollow glass microspheres. This invention also provides a high-temperature, high-strength, low-density cement slurry prepared based on the above-mentioned surface-modified hollow glass microspheres. The high-temperature, high-strength, low-density cement slurry provided by this invention has adjustable density, high compressive strength, low API water loss, good rheological properties, zero free fluid, and small density difference; it can provide strong technical support for reducing the risk of well leakage during cementing operations and ensuring the exploration and development benefits of difficult-to-access reserves and unconventional oil and gas resources in complex deep wells and ultra-deep wells.

Description

Technical Field

[0001] This invention relates to a surface-modified hollow glass microsphere and its preparation method, as well as a high-temperature, high-strength, low-density cement slurry, belonging to the field of cementing technology. Background Technology

[0002] With the continuous deepening of oil and gas exploration and development, the number of deep and ultra-deep wells with burial depths exceeding 6000m onshore is constantly increasing. During cementing, these wells often face engineering and technical challenges such as high bottom-hole temperatures, low formation pressure-bearing capacity, narrow safety density windows, and susceptibility to leakage. Furthermore, the formations to be cemented may contain micro-faults, vertical joints, and fractures, leading to severe well leakage and making it difficult to ensure wellbore integrity. Therefore, low-density cement slurry systems are typically used to avoid leakage and low cement slurry return during the cementing process, ensuring cementing quality and exploration and development benefits.

[0003] However, the hollow glass microspheres used in traditional low-density cement slurry systems have a weak bond with silicate oil well cement. Under high-temperature conditions, volume changes or differences in the expansion coefficients of hydration reaction products may cause delamination or cracks between the microspheres and the cement matrix. In addition, the system contains few hydration-active substances and many inert admixtures. Furthermore, the differences in chemical composition and microstructure of silicate cement hydration products caused by high temperatures make low-density cement stone prone to low high-temperature compressive strength and significant attenuation, making it difficult to guarantee the formation sealing effect. At the same time, the overall performance of low-density cement slurry systems is also easily constrained by admixtures. For example, some active reinforcing materials and suspending agents are highly hydrophilic and have significant thickening properties, affecting the rheological properties of cement slurry, resulting in high friction during cement injection and an increased risk of well leakage. Some retarders and fluid loss reducers deteriorate in stability after thermal shock, which may lead to unadjustable thickening time and slow strength development, making it difficult to guarantee wellbore integrity.

[0004] In summary, existing conventional hollow glass microsphere low-density cement slurry systems still have certain shortcomings and room for improvement under high-temperature and easily leaky conditions. In particular, in cementing operations of complex deep and ultra-deep wells with narrow safety density windows, low formation bearing capacity, and high requirements for production layer protection, the slurry has limited applicable temperature, a small density reduction range, and poor rheological properties. After the thickening time meets the construction requirements, the compressive strength is low, the development is slow, and there is attenuation. It is difficult to meet the needs of sealing and exploration and development in deep, high-temperature, and complex formations, and there is an urgent need for improvement. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a surface-modified hollow glass microsphere and its preparation method. Through surface etching and grafting modification, the hollow glass microsphere exhibits high bonding strength with oil well cement, thereby reducing the risk of peeling and cracking between the microsphere and the cement matrix.

[0006] Another objective of this invention is to provide a high-temperature, high-strength, low-density cement slurry prepared using the aforementioned hollow glass microspheres.

[0007] To achieve the above objectives, the present invention provides a method for preparing surface-modified hollow glass microspheres, wherein, by mass, the raw material composition of the surface-modified hollow glass microspheres includes: 50-65 parts of hollow glass microspheres, 7-15 parts of silane coupling agent, 15-20 parts of amide monomer containing carbon-carbon double bonds, and 10-19 parts of phosphate ester monomer containing carbon-carbon double bonds.

[0008] The preparation method includes the following steps:

[0009] Hollow glass microspheres were etched with alkali and a solution was prepared.

[0010] Adding a silane coupling agent to the solution yields hollow glass microspheres with a surface grafted with the silane coupling agent.

[0011] Hollow glass microspheres grafted with silane coupling agent on the surface are mixed with amide monomers containing carbon-carbon double bonds (-C=C-) and phosphate ester monomers containing carbon-carbon double bonds. An initiator is added to carry out the reaction, and then a polymerization inhibitor is added. After washing and spray drying, the surface-modified hollow glass microspheres are obtained.

[0012] In the above preparation method, preferably, the compressive strength of the hollow glass microspheres is 12000 psi.

[0013] In the above preparation method, preferably, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570) and / or γ-aminopropyltriethoxysilane (kH550).

[0014] In the above preparation method, preferably, the amide monomer containing carbon-carbon double bonds includes one or more of N,N'-dimethylacrylamide (DMAA), N-hydroxymethylacrylamide (N-MAM), N-hydroxyethylacrylamide (HEMAA), and N,N-diethylacrylamide (DEAM).

[0015] In the above preparation method, preferably, the phosphate ester monomer containing carbon-carbon double bonds includes one or more of dimethyl vinylphosphonate, diethyl vinyl phosphate, and vinyl phosphoric acid.

[0016] In the above preparation method, preferably, the initiator is one or a combination of two or more of the following commonly used in free radical polymerization: ammonium persulfate (APS), potassium persulfate (KPS), and azobisisobutyrazoline hydrochloride (VA-044).

[0017] In the above preparation method, preferably, the chain terminator is p-benzoquinone (PBQ) or hydroquinone (HQ).

[0018] According to a specific embodiment of the present invention, preferably, the above preparation method includes the following specific steps:

[0019] (1) Preparation of hollow glass microspheres with alkaline surface etching

[0020] Hollow glass microspheres are dispersed in deionized water (after addition, they can be stirred at a speed of 800-1000 r / min until homogeneous), and NaOH is slowly added, wherein the mass of NaOH is the same as that of hollow microspheres. Stirring is carried out (stirring at a speed of 500-600 r / min for 1-2 hours), and the temperature is raised to 60℃-80℃ (preferably 80℃). Then, the temperature is cooled to room temperature, and the surface is rinsed with deionized water until neutral to obtain hollow glass microspheres with alkaline etching.

[0021] (2) Preparation of hollow glass microspheres with surface-grafted silane coupling agent

[0022] Hollow glass microspheres with alkali-etched surfaces are dispersed in anhydrous ethanol solution (preferably anhydrous ethanol:deionized water = 9:1 by mass) and heated to 60-70℃ (while heating, the mixture can be stirred at 150-200 r / min for 30-40 min). Silane coupling agent is added dropwise and the process is completed within 2-3 hours to obtain a suspension.

[0023] The suspension was centrifuged to obtain hollow glass microspheres with surface-grafted silane coupling agent, which were then washed and set aside for later use.

[0024] (3) Preparation of surface-modified hollow glass microspheres

[0025] Mix an appropriate amount of deionized water, hollow glass microspheres grafted with silane coupling agent, amide monomers containing carbon-carbon double bonds, and phosphate ester monomers containing carbon-carbon double bonds (after mixing, stir evenly at a speed of 120-150 r / min), and adjust the pH value to 7.

[0026] Add deionized water to bring the solid content in the suspension to 10wt%-17wt% (preferably 13wt%);

[0027] Introduce a protective gas, raise the temperature to the reaction temperature of 40-50℃, add the initiator, keep warm and stir, and react for 3-4 hours.

[0028] Turn off the protective gas, add an appropriate amount of polymerization inhibitor (e.g., 0.1% of the total mass of the active monomers), and continue stirring for an appropriate time (e.g., 20-30 min).

[0029] Cooling, washing with water, and spray drying are used to obtain surface-modified hollow glass microspheres.

[0030] In the above preparation method, preferably, the pH adjuster is a sodium hydroxide (NaOH) solution (concentration 30wt%) and a dilute hydrochloric acid solution (concentration 4mol / L).

[0031] In the above preparation method, preferably, the protective gas during the polymerization reaction is high-purity argon (Ar).

[0032] In the above preparation method, preferably, the solvent used is deionized water or anhydrous ethanol.

[0033] The present invention also provides a surface-modified hollow glass microsphere prepared by the method described above. This surface-modified hollow glass microsphere incorporates hydroxyl groups (-OH) through alkaline etching and is grafted with a silane coupling agent, amide groups, and phosphorus-containing molecular chains.

[0034] Through surface etching and grafting modification techniques, the surface-modified hollow glass microspheres provided by this invention have a smaller difference in expansion coefficients with the cement matrix under high-temperature conditions, higher bonding ability with oil well cement, and a lower risk of peeling and cracking between the microspheres and the cement matrix.

[0035] The present invention also provides a high-temperature, high-strength, low-density cement slurry, wherein, by weight, the raw material composition of the high-temperature, high-strength, low-density cement slurry includes:

[0036] 100 parts of Grade G oil well cement, 10-36 parts of the above-mentioned surface-modified hollow glass microspheres, 15-18 parts of high-temperature strength anti-fading material, 3-6 parts of high-temperature crack-resistant material, 0.7-1 part of dispersant, 2-3 parts of suspension stabilizer, 2-3 parts of co-solvent, 3-4 parts of high-temperature water loss reducer, 1-2.5 parts of high-temperature retarder, 0.5-1 part of defoamer, and 60-74 parts of water.

[0037] In the above-mentioned high-temperature, high-strength, low-density cement slurry, preferably, the G-grade oil well cement is a high sulfate-resistant type (HSR) produced by Jiahua Special Cement Co., Ltd.

[0038] In the aforementioned high-temperature, high-strength, low-density cement slurry, preferably, the high-temperature strength anti-fading material is a compound of 325-mesh composite silica powder and 1500-mesh crystalline silica powder in a mass ratio of 3.5-5:1, produced by Hongrun Quartz Silica Powder Co., Ltd. This invention employs a high-temperature strength anti-fading material composed of different types of silica powder. On one hand, it utilizes the small particle size and good workability to improve the particle size distribution of the system, physically filling the capillary channels and microcracks within the cement slurry system to achieve a denser packing. On the other hand, by adjusting the silica-calcium ratio (Si / Ca) of the cement slurry system and optimizing hydration products, it compensates for developmental defects of cement stone under high-temperature conditions, improves the micro and submicroscopic structure of cement stone, and enhances its mechanical properties.

[0039] In the aforementioned high-temperature, high-strength, low-density cement slurry, preferably, the high-temperature crack-resistant material comprises: 10-25% calcium sulfate whiskers with a diameter of 1-3 mm, 20-30% basalt fibers with a diameter of 2-4 mm, 14-20% alumina whiskers with a diameter of 1-3 mm, and 30-50% ethylene / vinyl acetate redispersible polymer powder; more preferably, the high-temperature crack-resistant material comprises: 10% calcium sulfate whiskers with a diameter of 1-3 mm, 30% basalt fibers with a diameter of 2-4 mm, 20% alumina whiskers with a diameter of 1-3 mm, and 40% ethylene / vinyl acetate redispersible polymer powder. The high-temperature crack-resistant material is obtained by weighing the above materials according to the proportions, stirring them evenly, and packaging them. The whiskers and chopped fibers in the high-temperature crack-resistant material used in this invention can insert into the interior of cement particles and hydration products, or aggregate and overlap on the surface of the voids in these materials to form a skeletal structure, acting as "reinforcing" and toughening agents to inhibit high-temperature deformation of the cement matrix. The ethylene / vinyl acetate adhesive powder has good thermal stability, strong deformation capacity, and certain adhesion, and can fill between cement particles or between cement particles and surface-modified hollow glass microspheres to form a polymer network, reducing cement stone damage caused by external mechanical or thermal shock. Simultaneously, the presence of whiskers can provide setting centers for the formation of early cement hydration products, promoting the nucleation and growth of hydration products, accelerating the cement hydration process and the development of early strength.

[0040] In the above-mentioned high-temperature, high-strength, low-density cement slurry, preferably, the dispersant is a ketone-aldehyde-based oil well cement dispersant.

[0041] In the above-mentioned high-temperature, high-strength, low-density cement slurry, preferably, the high-temperature water loss reducing agent is a polyacrylamide-based liquid water loss reducing agent.

[0042] In the above-mentioned high-temperature, high-strength, low-density cement slurry, preferably, the high-temperature retarder is a liquid retarder of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) copolymer.

[0043] In the above-mentioned high-temperature, high-strength, low-density cement slurry, preferably, the defoamer is one of tributyl phosphate, polyoxypropylene glycerol, and polydimethylsiloxane.

[0044] In the aforementioned high-temperature, high-strength, low-density cement slurry, preferably, the co-solvent is composed of small-molecule alcohols and alkanolamines, specifically in a ratio of 30% ethylene glycol, 30% triethanolamine, and 40% ethylene glycol ethyl ether. The co-solvent is obtained by weighing the above materials according to the ratio, stirring them evenly, and then packaging them. This invention, using a co-solvent composed of small-molecule alcohols and alkanolamines, can assist in the efficient and uniform distribution of polymer backbones on surface-modified hollow glass microspheres and ethylene / vinyl acetate powder and other polymeric substances in the toughening material within the cement matrix, preventing aggregation and avoiding stress concentration during compressive stress failure.

[0045] In the above-mentioned high-temperature, high-strength, low-density cement slurry, preferably, the suspension stabilizer is a weak gel polymer, prepared according to the technical solution disclosed in patent publication number CN114716605A.

[0046] According to a specific embodiment of the present invention, the preparation method of the above-mentioned high-temperature, high-strength, low-density cement slurry may include the following steps:

[0047] Weigh out oil well cement, surface-modified hollow glass microspheres, high-temperature strength anti-fading material, high-temperature crack-resistant material, and dispersant according to the specified proportions and mix them evenly to obtain a dry mixture; mix high-temperature retarder, high-temperature water loss reducer, co-solvent, suspension stabilizer, defoamer, and water evenly to obtain a wet mixture; at a rotation speed of 4000±200r / min, uniformly introduce the dry mixture into the wet mixture, and after the dry mixture is completely wetted, continue stirring for 35s to obtain a high-temperature resistant, high-strength, low-density cement slurry.

[0048] This invention utilizes a silane coupling agent to graft amide groups and phosphorus-containing molecular chains onto the surface of hollow glass microspheres to obtain surface-modified hollow glass microspheres. The former can improve the adsorption and fixation effect with cement particles and reduce the probability of microspheres delaminating from the cement matrix, while the latter can participate in cement hydration at high temperatures and improve the high-temperature mechanical stability of hydration products at the microsphere-cement interface.

[0049] This invention uses surface-modified hollow glass microspheres as a weight-reducing agent, leveraging their hollow and low-density properties to adjust the density of the cement slurry system. Based on the selection of admixtures and additives, a high-temperature resistant, high-strength, low-density cement slurry system suitable for cementing deep oil and gas reservoirs, low-pressure easily leaking zones, and deep depleted oil and gas reservoirs is formed. This cement slurry system has a low density (1.35-1.50 g / cm³). 3 It features high applicable temperature (165℃, BHST), adjustable thickening time, high compressive strength, no attenuation, low API water loss, and good rheological properties, providing strong technical support for cementing operations in complex deep and ultra-deep wells with low formation pressure capacity, narrow safety density window, and high requirements for production layer protection.

[0050] The high-temperature resistant, high-strength, low-density cement grout provided by this invention has an adjustable density (1.35-1.50 g / cm³). 3 The compressive strength at 165℃ for 24 hours is greater than 18 MPa, and the compressive strength for 48 hours is greater than 22 MPa. It exhibits low API water loss, good rheological properties, zero free liquid content, and a density difference of less than 0.04 g / cm³. 3 It can provide strong technical support for reducing the risk of well leakage during cementing operations, ensuring the exploration and development benefits of difficult-to-access reserves in complex deep wells and ultra-deep wells, and unconventional oil and gas resources. Attached Figure Description

[0051] Figure 1 The image shows the thickening curve of the cement slurry in Example 1.

[0052] Figure 2 The thickening curve of the cement slurry in Example 2 is shown.

[0053] Figure 3 The image shows the thickening curve of the cement slurry in Example 3.

[0054] Figure 4 The image shows the thickening curve of the cement slurry in Example 5.

[0055] Figure 5 The thickening curve is for the cement slurry of Comparative Example 1. Detailed Implementation

[0056] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0057] Raw material descriptions for the examples and comparative examples:

[0058] Hollow glass microspheres, commercially available, with a compressive strength of 12000 psi.

[0059] The silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570), which is chemically pure.

[0060] Grade G oil well cement is a high sulfate-resistant (HSR) type, manufactured by Jiahua Special Cement Co., Ltd.

[0061] The high-temperature strength anti-degradation material is made of 325-mesh composite silicon micro powder and 1500-mesh crystalline silicon micro powder in a mass ratio of 5:1, produced by Hongrun Quartz Silicon Micro Powder Co., Ltd.

[0062] The high-temperature crack-resistant material is composed of commercially available inorganic chopped fibers and polymer resin, with the following specific weight percentages: calcium sulfate whiskers (1-3mm) 10%, basalt fibers (2-4mm) 30%, alumina whiskers (1-3mm) 20%, and ethylene / vinyl acetate redispersible polymer powder 40%. The above materials are weighed and stirred evenly according to the specified proportions to obtain the final product. The ethylene / vinyl acetate redispersible polymer powder is DRT-1S, produced and sold by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0063] The dispersant is a commercially available ketone-aldehyde-based oil well cement dispersant.

[0064] The suspension stabilizer is a weak gel polymer, prepared according to the technical solution described in Example 2 of the invention patent No. ZL202110009555.2 (invention title: Weak gelling agent and its preparation method, cement slurry suspension stabilizer and its application).

[0065] The cosolvent is composed of commercially available small molecule alcohols and alkanolamines, with a specific ratio of 30% ethylene glycol, 30% triethanolamine, and 40% ethylene glycol ethyl ether. The above materials are weighed and stirred evenly according to the ratio to obtain the cosolvent.

[0066] High-temperature water loss reducing agent is a commercially available polyacrylamide-based liquid water loss reducing agent.

[0067] High-temperature retarder is a commercially available liquid retarder of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) copolymer.

[0068] The defoamers were commercially available tributyl phosphate, polyoxypropylene glycerol, and polydimethylsiloxane. Specifically, the defoamer in Examples 1-3 was tributyl phosphate, the defoamer in Example 4 was polyoxypropylene glycerol, and the defoamer in Example 5 was polydimethylsiloxane. The defoamer in Comparative Example 1 was tributyl phosphate, and the defoamer in Comparative Example 2 was polydimethylsiloxane.

[0069] Example 1

[0070] This embodiment provides a surface-modified hollow glass microsphere and a high-temperature resistant, high-strength, low-density cement slurry. The specific preparation process is as follows:

[0071] Step 1: Preparation of surface-modified hollow glass microspheres

[0072] (1) Preparation of hollow glass microspheres with alkaline surface etching

[0073] Weigh 58 parts of hollow glass microspheres and pour them into the reactor. Add 250 parts of deionized water and stir at 800 r / min until homogeneous. Add 58 parts of NaOH solution, heat to 80℃ and stir at 500 r / min for 2 hours. Cool to room temperature and rinse with deionized water until neutral. Set aside for later use.

[0074] (2) Preparation of hollow glass microspheres with surface-grafted silane coupling agent

[0075] The alkaline-etched glass microspheres were poured into a reactor, and 200 parts of anhydrous ethanol solution (anhydrous ethanol: deionized water = 9:1) were added. The mixture was stirred at 150 r / min for 30 min while the temperature was raised to 60 °C. 12.5 parts of KH570 were weighed and added dropwise to the reactor over 2 h. The hollow glass microspheres with silane coupling agent on their surface were separated by a high-speed centrifuge and washed with deionized water for later use.

[0076] (3) Preparation of surface-modified hollow glass microspheres

[0077] Hollow glass microspheres grafted with silane coupling agent were poured into a reactor. A certain amount of deionized water, 17 parts of DMAA, and 12.5 parts of VPA were weighed and stirred at 120 r / min until homogeneous. The pH of the suspension was adjusted to 7. Deionized water was added to make the solid content of the suspension reach 13 wt%. Ar was introduced and the temperature was raised to 50℃. APS was added, and the mixture was kept warm and stirred for 3 h. Ar was turned off, PBQ was added, and stirring was continued for 20 min. The mixture was cooled, washed with water, and spray-dried to obtain surface-modified hollow glass microspheres (A).

[0078] The second step is the preparation of a high-temperature resistant, high-strength, low-density cement slurry system.

[0079] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 36 parts hollow glass microspheres (A), 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack-resistant material, 1 part dispersant, 3 parts suspension stabilizer, 3 parts co-solvent, 4 parts high-temperature water loss reducer, 2 parts high-temperature retarder, 1 part defoamer, and 71 parts tap water.

[0080] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.35 × 10⁻⁶. 3 kg / m 3 Thickening curve as shown Figure 1 As shown.

[0081] Example 2

[0082] This embodiment provides a surface-modified hollow glass microsphere and a high-temperature resistant, high-strength, low-density cement slurry. The specific preparation process is as follows:

[0083] Step 1: Preparation of surface-modified hollow glass microspheres

[0084] (1) Preparation of hollow glass microspheres with alkaline surface etching

[0085] Weigh 50 parts of hollow glass microspheres and pour them into the reactor. Add 250 parts of deionized water and stir at 1000 r / min until homogeneous. Add 50 parts of NaOH solution, heat to 80℃ and stir at 600 r / min for 1 h. Cool to room temperature and rinse with deionized water until neutral. Set aside for later use.

[0086] (2) Preparation of hollow glass microspheres with surface-grafted silane coupling agent

[0087] The alkaline-etched glass microspheres were poured into a reactor, and 200 parts of anhydrous ethanol solution (anhydrous ethanol: deionized water = 9:1) were added. The mixture was stirred at 200 r / min for 30 min, while the temperature was raised to 60℃. Seven parts of KH570 were weighed and added dropwise to the reactor over 3 h. The hollow glass microspheres with silane coupling agent on their surface were separated using a high-speed centrifuge and washed with deionized water for later use.

[0088] (3) Preparation of surface-modified hollow glass microspheres

[0089] Hollow glass microspheres grafted with silane coupling agent were poured into a reactor. A certain amount of deionized water, 20 parts of N-MAM, and 10 parts of DMVP were weighed and stirred at 200 r / min until homogeneous. The pH of the suspension was adjusted to 7. Deionized water was added to make the solid content of the suspension reach 13 wt%. Ar was introduced and the temperature was raised to 45℃. VA-044 was added, and the mixture was kept at this temperature and stirred for 4 h. Ar was turned off, PBQ was added, and stirring was continued for 30 min. The mixture was cooled, washed with acetone and water, and spray-dried to obtain surface-modified hollow glass microspheres (B).

[0090] The second step is the preparation of a high-temperature resistant, high-strength, low-density cement slurry system.

[0091] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 36 parts hollow glass microspheres (B), 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack-resistant material, 1 part dispersant, 3 parts suspension stabilizer, 3 parts co-solvent, 4 parts high-temperature water loss reducer, 2 parts high-temperature retarder, 1 part defoamer, and 71 parts tap water.

[0092] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.35 × 10⁻⁶. 3 kg / m 3 Thickening curve as shown Figure 2 As shown.

[0093] Example 3

[0094] This embodiment provides a surface-modified hollow glass microsphere and a high-temperature resistant, high-strength, low-density cement slurry. The specific preparation process is as follows:

[0095] Step 1: Preparation of surface-modified hollow glass microspheres

[0096] (1) Preparation of hollow glass microspheres with alkaline surface etching

[0097] Weigh 65 parts of hollow glass microspheres and pour them into the reactor. Add 250 parts of deionized water and stir at 800 r / min until homogeneous. Add 65 parts of NaOH solution, heat to 80℃ and stir at 600 r / min for 1 h. Cool to room temperature and rinse with deionized water until neutral. Set aside for later use.

[0098] (2) Preparation of hollow glass microspheres with surface-grafted silane coupling agent

[0099] The alkaline-etched glass microspheres were poured into a reactor, and 200 parts of anhydrous ethanol solution (anhydrous ethanol: deionized water = 9:1) were added. The mixture was stirred at 250 r / min for 40 min while the temperature was raised to 70 °C. 15 parts of KH570 were weighed and added dropwise to the reactor over 3 h. The hollow glass microspheres with silane coupling agent on their surface were separated by a high-speed centrifuge and washed with deionized water for later use.

[0100] (3) Preparation of surface-modified hollow glass microspheres

[0101] Hollow glass microspheres grafted with silane coupling agent were poured into a reactor. A certain amount of deionized water, 15 parts of DEAM, and 19 parts of DEVP were weighed and stirred at 150 r / min until homogeneous. The pH of the suspension was adjusted to 7. Deionized water was added to make the solid content of the suspension reach 13 wt%. Ar was introduced and the temperature was raised to 50 °C. KPS was added, and the mixture was kept warm and stirred for 3 h. Ar was turned off, HQ was added, and stirring was continued for 20 min. The mixture was cooled, washed with acetone and water, and spray-dried to obtain surface-modified hollow glass microspheres (C).

[0102] The second step is the preparation of a high-temperature resistant, high-strength, low-density cement slurry system.

[0103] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 36 parts hollow glass microspheres (C), 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack prevention material, 1 part dispersant, 3 parts suspension stabilizer, 3 parts co-solvent, 4 parts high-temperature water loss reducer, 2 parts high-temperature retarder, 1 part defoamer, and 72 parts tap water.

[0104] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.35 × 10⁻⁶. 3 kg / m 3 Thickening curve as shown Figure 3 As shown.

[0105] Example 4

[0106] This embodiment provides a surface-modified hollow glass microsphere and a high-temperature resistant, high-strength, low-density cement slurry. The specific preparation process is as follows:

[0107] Step 1, Preparation of surface-modified hollow glass microspheres (A), same as in Example 1;

[0108] The second step is the preparation of a high-temperature resistant, high-strength, low-density cement slurry system.

[0109] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 36 parts hollow glass microspheres (A), 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack-resistant material, 1 part dispersant, 2 parts suspension stabilizer, 0 parts co-solvent, 4 parts high-temperature water loss reducer, 2 parts high-temperature retarder, 1 part defoamer, and 74 parts tap water.

[0110] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.35 × 10⁻⁶. 3 kg / m 3 .

[0111] Example 5

[0112] Step 1, Preparation of surface-modified hollow glass microspheres (A), same as in Example 1;

[0113] The second step is the preparation of a high-temperature resistant, high-strength, low-density cement slurry system.

[0114] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 21 parts hollow glass microspheres (A), 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack-resistant material, 0.7 parts dispersant, 2 parts suspension stabilizer, 1 part co-solvent, 3 parts high-temperature water loss reducer, 2 parts high-temperature retarder, 1 part defoamer, and 68 parts tap water.

[0115] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.50 × 10⁻⁶. 3 kg / m 3 .

[0116] Comparative Example 1

[0117] This comparative example provides a cement slurry using commercially available hollow glass microspheres (D).

[0118] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 36 parts hollow glass microspheres, 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack-resistant material, 1 part dispersant, 3 parts suspension stabilizer, 3 parts co-solvent, 4 parts high-temperature water loss reducer, 1 part high-temperature retarder, 1 part defoamer, and 70 parts tap water.

[0119] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.35 × 10⁻⁶. 3 kg / m 3 Thickening curve as shown Figure 4 As shown.

[0120] Comparative Example 2

[0121] This comparative example provides a surface-modified hollow glass microsphere and a high-temperature resistant, high-strength, low-density cement slurry. The specific preparation process is as follows:

[0122] Step 1: Preparation of surface-modified hollow glass microspheres

[0123] (1) Preparation of hollow glass microspheres with alkaline surface etching

[0124] Weigh 58 parts of hollow glass microspheres and pour them into the reactor. Add 250 parts of deionized water and stir evenly. Add 58 parts of NaOH solution, heat to 80℃ and stir at 500r / min for 2h. Cool to room temperature and rinse with deionized water until neutral. Set aside for later use.

[0125] (2) Preparation of hollow glass microspheres with surface-grafted silane coupling agent

[0126] The surface-etched glass microspheres were poured into a reactor, and 200 parts of anhydrous ethanol solution (anhydrous ethanol: deionized water = 9:1) were added. The mixture was stirred at 150 r / min for 30 min while the temperature was raised to 60 °C. 12.5 parts of KH570 were weighed and added dropwise to the reactor over 2 h. The hollow glass microspheres with silane coupling agent on their surface were separated by a high-speed centrifuge, washed with deionized water, and spray-dried to obtain surface-modified hollow glass microspheres (E).

[0127] The second step is the preparation of a high-temperature resistant, high-strength, low-density cement slurry system.

[0128] The cement slurry formula is as follows (by weight): 100 parts oil well cement, 36 parts hollow glass microspheres (E), 18 parts high-temperature strength anti-fading material, 4 parts high-temperature crack-resistant material, 1 part dispersant, 3 parts suspension stabilizer, 3 parts co-solvent, 4 parts high-temperature water loss reducer, 2 parts high-temperature retarder, 1 part defoamer, and 71 parts tap water.

[0129] The above raw materials are mixed and stirred evenly to obtain a high-temperature resistant, high-strength, low-density cement slurry with a density of 1.35 × 10⁻⁶. 3 kg / m 3 .

[0130] Experiments were conducted in accordance with the national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells" to evaluate the compressive strength, thickening, water loss, free fluid, density difference, rheological properties of the cement slurry systems in the examples and comparative examples. The relevant results are shown in Table 1.

[0131] The main experimental instruments include: a 30-60 type corrugated stirrer, an 8240 type high-temperature and high-pressure thickener, and a 7357 type high-temperature and high-pressure curing kettle, all products of CHANDLER, USA; a 35SA type rotational viscometer, from Fann, USA; and an HH-420 type constant temperature digital display water tank, from Changzhou Yineng Experimental Instrument Factory.

[0132] Table 1 Properties of Cement Grout System

[0133]

[0134]

[0135] As shown in Table 1, the density of the high-temperature resistant, high-strength, low-density cement slurry system prepared based on surface-modified hollow glass microspheres can range from 1.35 to 1.50 g / cm³. 3 The range is adjusted according to construction needs, and the fluidity is greater than 20cm; at a circulation temperature of 140℃, the initial thickening time in Example 1 is 23Bc, and the thickening time is 221min. Figure 1 Example 2: Initial thickening time 28 Bc, thickening time 208 min ( Figure 2 Example 3: Initial thickening 17 Bc, thickening time 224 min ( Figure 3 Example 5 shows a density of 1.50 g / cm³. 3 The initial thickening time increased to 19 Bc, and the thickening time was 213 min. Figure 4 All examples showed normal thickening curves without any abnormal phenomena such as "bulges" or "steps"; under experimental conditions of 93℃ × 6.9MPa, the water loss Q in Example 1 was [data missing]. 30 The water loss in Example 2 was 44 mL, Q. 30 The water loss in Example 4 was 39 mL, Q. 30 The volume was 46 mL, and no gas perforation occurred during the experiment. At the same time, the rheological properties of each embodiment were good, which is beneficial to reduce friction, reduce pump pressure, and prevent formation leakage.

[0136] Settling stability evaluation showed that, in Example 1, with a suspending agent dosage of 3%, the density difference between the upper and lower layers of the cement slurry after standing for 2 hours was 0.01 g / cm³. 3 After 24 hours of curing, the density difference between the upper and lower parts of the cement stone was measured to be 0.027 g / cm³. 3 In Example 2, the suspending agent dosage was 3%, and after standing for 2 hours, the density difference between the upper and lower parts of the cement slurry was 0.005 g / cm³. 3 After 24 hours of curing, the density difference between the upper and lower parts of the cement stone was measured to be 0.020 g / cm³. 3 In Example 3, the suspending agent dosage was 3%, and after standing for 2 hours, the density difference between the upper and lower parts of the cement slurry was 0.017 g / cm³. 3 After 24 hours of curing, the density difference between the upper and lower parts of the cement stone was measured to be 0.038 g / cm³. 3 The density of Example 5 was 1.50 g / cm³. 3 With a suspending agent dosage of 2%, the density difference between the upper and lower parts of the cement slurry was 0.01 after standing for 2 hours, and the density difference between the upper and lower parts of the cement stone was less than 0.023 g / cm³ after curing for 24 hours. 3The free liquid in each embodiment is 0.

[0137] Based on the premise that all performance characteristics meet the requirements of cementing and well cementing construction, the mechanical properties of the high-temperature resistant, high-strength, low-density cement slurry system of this invention were evaluated. As shown in Table 1, the high-temperature resistant, high-strength, low-density cement slurry system prepared based on surface-modified hollow glass microspheres exhibits an increase in compressive strength under high-temperature conditions with prolonged curing time; under the same curing conditions, the compressive strength further increases with the increase in the density of the cement slurry system.

[0138] The surface-modified hollow glass microspheres (A) used in Example 1 contained 58 parts of hollow glass microspheres, 12.5 parts of silane coupling agent, 17 parts of amide monomers containing -C=C-, and 12.5 parts of phosphate ester monomers containing -C=C-. These were mixed with 100% oil well cement, 36% surface-modified hollow glass microspheres (A), 18% high-temperature strength degradation prevention material, 4% high-temperature crack prevention material, 1% dispersant, 3% suspension stabilizer, 3% co-solvent, 4% high-temperature water loss reducing agent, 2% high-temperature retarder, 1% defoamer, and 71% tap water. The resulting cement slurry had a density of 1.35 g / cm³. 3 The compressive strength after 24 hours of protection at 165℃ was 20.8 MPa and after 48 hours it was 25.3 MPa, an increase of 21.6%.

[0139] The surface-modified hollow glass microspheres (B) used in Example 2 contain 50 parts hollow glass microspheres, 7 parts silane coupling agent, 20 parts amide monomers containing -C=C-, and 10 parts phosphate ester monomers containing -C=C-. These are mixed with 100% oil well cement, 36% surface-modified hollow glass microspheres (B), 18% high-temperature strength degradation prevention material, 4% high-temperature crack prevention material, 1% dispersant, 3% suspension stabilizer, 3% co-solvent, 4% high-temperature water loss reducing agent, 2% high-temperature retarder, 1% defoamer, and 71% tap water. The resulting cement slurry has a density of 1.35 g / cm³. 3 The compressive strength is 22.3 MPa after curing at 165℃ for 24 hours and 26.7 MPa after 48 hours.

[0140] The surface-modified hollow glass microspheres (A) used in Example 4 were the same as those in Example 1. They were mixed with 100% oil well cement, 36% surface-modified hollow glass microspheres (A), 18% high-temperature strength degradation prevention material, 4% high-temperature crack prevention material, 1% dispersant, 2% suspension stabilizer, 0% co-solvent, 4% high-temperature water loss reducing agent, 2% high-temperature retarder, 1% defoamer, and 74% tap water. The resulting cement slurry had a density of 1.35 g / cm³. 3The compressive strength after curing at 165℃ for 24 hours was 18.7 MPa and after 48 hours was 22.5 MPa, maintaining an increasing trend. Compared with Example 1, in Example 4, after the flux in the cement slurry system was reduced to 0, the high-temperature compressive strength after the same curing time was slightly reduced, indicating that it has a certain effect on the uniform dispersion and tight filling of the surface-modified hollow glass microspheres in the cement slurry.

[0141] The surface-modified hollow glass microspheres (A) used in Example 5 were the same as those in Example 1. They were mixed with 100% oil well cement, 21% surface-modified hollow glass microspheres (A), 18% high-temperature strength degradation prevention material, 4% high-temperature crack prevention material, 0.7% dispersant, 2% suspension stabilizer, 1% co-solvent, 3% high-temperature water loss reducer, 2% high-temperature retarder, 1% defoamer, and 68% tap water. The resulting cement slurry had a density of 1.50 g / cm³. 3 The compressive strength is 26.2 MPa after curing at 165℃ for 24 hours and reaches 30.4 MPa after 48 hours.

[0142] In the above embodiments, the surface-modified hollow glass microspheres have a high applicable temperature and a small difference in expansion coefficient with the cement matrix under high-temperature conditions. They exhibit strong bonding ability with silicate oil well cement during the high-temperature curing process of the cement slurry, reducing the risk of delamination and cracking between the microspheres and the cement matrix. When mixed with oil well cement, admixtures, and additives to form a high-temperature resistant, high-strength, low-density cement slurry system, the high-temperature strength-preventing material composed of composite silica powder and crystalline silica powder optimizes the silica-calcium ratio (Si / Ca) of the cement slurry system, adjusts cement hydration products, and prevents the degradation of the cement matrix strength. Furthermore, it improves the particle size distribution and density of the cement slurry system. These two effects combined ensure the high-temperature compressive strength of the cement paste. In high-temperature crack-resistant materials composed of inorganic chopped fibers and polymer resins, the chopped fibers can insert into the interior of cement particles and hydration products, or aggregate and overlap on the porous surfaces of these materials, acting as "reinforcing" and toughening to inhibit high-temperature deformation of the cement matrix. The polymer resin has strong deformation capacity and certain adhesion under high-temperature conditions, allowing it to fill a flexible polymer network between cement particles or between cement particles and surface-modified hollow glass microspheres, reducing cement stone damage caused by external mechanical or thermal impacts. The co-solvent, composed of small-molecule alcohols and alkanolamines, with its small molecular size and strong penetrating power, can assist the extension of polymer molecular chains within the cement matrix, promoting the penetration of active segments into the cement matrix and enhancing the overall effect.

[0143] Commercially available microspheres were used as Comparative Example 1, and hollow glass microspheres that underwent only surface alkaline etching and grafting with silane coupling agent were used as Comparative Example 2. Under the same experimental conditions, the thickening time of Comparative Example 1 was 251 min. Figure 5 Water loss Q 30The density difference of the cement slurry after standing for 2 hours was 0.022 g / cm³, which was 93 mL. 3 Free liquid content 0.36%; compared with Example 1, water loss Q 30 The volume was increased by 49 mL, with little difference in rheological properties. The compressive strength decreased by 44.7% and 37.9% after curing at 165℃ for 24 h and 48 h, respectively. Compared to Example 1, Comparative Example 2 showed a 7.7% longer thickening time and a smaller water loss Q. 30 With an increase of 42 mL, the compressive strength decreased by 40.5% and 25.7% after 24 h and 48 h of curing at 165℃, respectively; simultaneously, free liquid appeared during the settling process of the cement slurry. Experimental results indicate that, under the same density conditions, surface alkali etching and grafting with functional monomers improve the temperature resistance of the microspheres, enhance the physical filling and chemical reaction with the cement matrix, and inhibit the formation of microcracks, thereby improving the compressive strength of the low-density cement slurry system and reducing water loss Q. 30 It also plays a positive role in controlling sedimentation and improving sedimentation stability.

[0144] Therefore, the preparation of surface-modified glass microspheres and high-temperature, high-strength, low-density cement slurry based on this technology according to the present invention can achieve a density that can be adjusted (1.35-1.50 g / cm³). 3 This high-performance, low-density cementing fluid exhibits low water loss, good settling and fluidity, and meets the requirements of cementing and injection operations. Simultaneously, it maintains high compressive strength without attenuation even at 165℃. This new invention provides strong technical support for cementing operations in complex deep and ultra-deep wells, as well as unconventional oil and gas wells, where formation bearing capacity is low, safety density windows are narrow, and production layer protection requirements are high.

Claims

1. A method for preparing surface-modified hollow glass microspheres, wherein, The raw material composition of the surface-modified hollow glass microspheres, by weight, includes: 50-65 parts of hollow glass microspheres, 7-15 parts of silane coupling agent, 15-20 parts of amide monomer containing carbon-carbon double bonds, and 10-19 parts of phosphate ester monomer or vinyl phosphate containing carbon-carbon double bonds. The preparation method includes the following steps: Hollow glass microspheres were etched with alkali and a solution was prepared. Adding a silane coupling agent to the solution yields hollow glass microspheres with a surface grafted with the silane coupling agent. Hollow glass microspheres with surface-grafted silane coupling agents are mixed with amide monomers containing carbon-carbon double bonds and phosphate ester monomers containing carbon-carbon double bonds, or hollow glass microspheres with surface-grafted silane coupling agents are mixed with amide monomers containing carbon-carbon double bonds and vinyl phosphate. An initiator is added to initiate the reaction, followed by the addition of a polymerization inhibitor. After washing and spray drying, the surface-modified hollow glass microspheres are obtained.

2. The preparation method according to claim 1, wherein, The hollow glass microspheres have a compressive strength of 12000 psi.

3. The preparation method according to claim 1, wherein, The silane coupling agent is γ-methacryloxypropyltrimethoxysilane and / or γ-aminopropyltriethoxysilane.

4. The preparation method according to claim 1, wherein, The amide monomer containing a carbon-carbon double bond includes one or more of N,N'-dimethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, and N,N-diethylacrylamide.

5. The preparation method according to claim 1, wherein, The phosphate ester monomers containing carbon-carbon double bonds include one or a combination of two of dimethyl vinylphosphonate and diethyl vinyl phosphate.

6. The preparation method according to claim 1, comprising the following specific steps: (1) Preparation of hollow glass microspheres with alkaline etching on the surface Hollow glass microspheres were dispersed in deionized water, and NaOH was slowly added. The same amount of NaOH and hollow glass microspheres were stirred and heated to 60℃-80℃, then cooled to room temperature, and rinsed with deionized water until neutral to obtain hollow glass microspheres with alkaline surface etching. (2) Preparation of hollow glass microspheres with surface-grafted silane coupling agent Hollow glass microspheres with alkali-etched surfaces are dispersed in anhydrous ethanol solution and heated to 60-70℃. A silane coupling agent is added dropwise and the process is completed within 2-3 hours to obtain a suspension. The suspension was centrifuged to obtain hollow glass microspheres with surface-grafted silane coupling agent, which were then washed and set aside for later use. (3) Preparation of surface-modified hollow glass microspheres Mix an appropriate amount of deionized water, hollow glass microspheres grafted with silane coupling agent, amide monomers containing carbon-carbon double bonds, and phosphate ester monomers containing carbon-carbon double bonds, and adjust the pH value to 7; or, mix an appropriate amount of deionized water, hollow glass microspheres grafted with silane coupling agent, amide monomers containing carbon-carbon double bonds, and vinyl phosphate, and adjust the pH value to 7. Add deionized water to bring the solid content in the suspension to 10 wt%-17 wt%. Introduce a protective gas, raise the temperature to the reaction temperature of 40-50℃, add the initiator, keep warm and stir, and react for 3-4 hours. Turn off the protective gas, add an appropriate amount of polymerization inhibitor, and continue stirring for an appropriate time. Cooling, washing with water, and spray drying are used to obtain surface-modified hollow glass microspheres.

7. A surface-modified hollow glass microsphere, which is prepared by the method according to any one of claims 1-6.

8. A high-temperature, high-strength, low-density cement slurry, wherein, The raw material composition of this high-temperature, high-strength, low-density cement paste, by weight, includes: 100 parts of Grade G oil well cement, 10-36 parts of surface-modified hollow glass microspheres as described in claim 7, 15-18 parts of high-temperature strength anti-fading material, 3-6 parts of high-temperature crack-resistant material, 0.7-1 part of dispersant, 2-3 parts of suspension stabilizer, 2-3 parts of co-solvent, 3-4 parts of high-temperature water loss reducing agent, 1-2.5 parts of high-temperature retarder, 0.5-1 part of defoamer, and 60-74 parts of water; The high-temperature strength anti-fading material is composed of 325-mesh composite silicon micro powder and 1500-mesh crystalline silicon micro powder in a mass ratio of 3.5-5:

1. By mass fraction, the composition of the high-temperature crack-resistant material includes: 10-25% calcium sulfate whiskers with a diameter of 1-3 mm, 20-30% basalt fibers with a diameter of 2-4 mm, 14-20% alumina whiskers with a diameter of 1-3 mm, and 30-50% ethylene / vinyl acetate redispersible polymer powder; The high-temperature water loss reducing agent is a polyacrylamide-based liquid water loss reducing agent; The high-temperature retarder is a liquid retarder of 2-acrylamide-2-methylpropanesulfonic acid copolymer.

9. The high-temperature, high-strength, low-density cement grout according to claim 8, wherein, The cosolvent comprises, by mass fraction, 30% ethylene glycol, 30% triethanolamine, and 40% ethylene glycol ethyl ether.

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