High-temperature-resistant tough cement paste system and application thereof

Abstract

The invention discloses a high-temperature-resistant tough cement paste system and application thereof. The high-temperature-resistant tough cement paste system is prepared from the following components in parts by weight: 90 to 110 parts by weight of oil well cement, 20 to 35 parts by weight of high-temperature-resistant elastic enhancer, 1.2 to 3.0 parts by weight of interface enhanced stabilizer, 15 to 80 parts by weight of high-temperature stabilizer, 0 to 15 parts by weight of oil field additive and 50 to 80 parts by weight of water. After being cured, the cement paste system can keep excellent toughness and sealing integrity under the conditions of high temperature (larger than or equal to 150 DEG C) and complex stress, has the advantages of being good in high temperature resistance, low in elasticity modulus and high in impact toughness, and is used for well cementation operation of deep wells, ultra-deep wells and geothermal wells with the temperature larger than or equal to 150 DEG C; the problems that an existing cement paste system is poor in elastic deformation capacity and impact toughness of traditional set cement in the high-temperature well cementation operation of deep wells, ultra-deep wells and geothermal wells can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well and geothermal well cementing engineering. Specifically, it is a high-temperature-resistant ductile cement slurry system and its application. BACKGROUND

[0002] With the extension of oil and gas exploration and development to deep, deep sea and unconventional fields, cementing operations are facing severe challenges such as high temperature and high pressure (HPHT), salt and gypsum layer creep, and multiple fracturing impacts. The traditional cement stone has inherent brittleness, and its elastic modulus is much higher than that of the formation and casing, which is easy to produce micro annular space, radial cracks and other damages under alternating stress, resulting in interlayer sealing failure and serious threat to the long-term integrity of the wellbore.

[0003] At present, the cement stone toughness is often improved by adding latex, fiber and other materials. However, in a high temperature environment exceeding 150℃, ordinary polymer materials (such as conventional styrene-butadiene latex and ethylene-vinyl acetate copolymer EVA) will degrade and harden, losing the toughening effect. Pure fiber toughening has limited contribution to reducing the elastic modulus of cement stone. Therefore, developing a cement slurry system that can still maintain excellent elastic deformation ability and impact resistance toughness at high temperature is a technical problem to be solved in the field. SUMMARY

[0004] To this end, the technical problem to be solved by the present application is to provide a high-temperature-resistant ductile cement slurry system and its application, which can maintain excellent toughness and sealing integrity under high temperature (≥ 150℃) and complex stress conditions after solidification, has the advantages of good high temperature resistance, low elastic modulus and strong impact resistance, and can solve the problem of poor elastic deformation ability and impact resistance of traditional cement stone in the high temperature cementing operation of deep well, ultra-deep well and geothermal well.

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

[0006] A high-temperature-resistant ductile cement slurry system, which is composed of the following components by weight: 90-110 parts by weight of oil well cement, 20-35 parts by weight of high-temperature-resistant elastic reinforcing agent, 1.2-3.0 parts by weight of interfacial reinforcing stabilizer, 15-80 parts by weight of high-temperature stabilizer, 0-15 parts by weight of oil field additives and 50-80 parts by weight of water.

[0007] The high-temperature-resistant elastic reinforcing agent mainly plays a high-temperature toughening role, if the amount of the high-temperature-resistant elastic reinforcing agent in the high-temperature-resistant and tough cement slurry system is too much, the strength development of the cement stone will be affected, if the amount is too little, the effect of the high-temperature-resistant elastic reinforcing of the cement slurry cannot reach the expected value, which leads to the increase of the brittleness of the cement sheath and the decrease of the toughness, and easily causes the problems such as the failure of the cementing sealing of the cement sheath; the interface reinforcing type stabilizer mainly plays the role of controlling the filtration loss of the cement slurry and improving the cementing strength of the second interface between the cement stone and the casing and the formation, if the amount of the interface reinforcing type stabilizer in the high-temperature-resistant and tough cement slurry system is too much, the cement slurry system will be thickened seriously, which is not conducive to pumping, and if the amount is too little, the cement slurry system will be unstable and easy to settle; the high-temperature stabilizer is mainly used for preventing the strength recession of the cement stone at high temperature and ensuring the long-term stability of the cement slurry system at high temperature, if the amount of the high-temperature stabilizer is insufficient, the thickening time of the cement slurry will be shortened and the strength will be declined, and if the amount of the high-temperature stabilizer is too much, the rheological property of the cement slurry will be affected, the flowability of the cement slurry will be poor, and the construction difficulty and cost will be increased; through the reasonable design of the amount proportion of the oil well cement, the high-temperature-resistant elastic reinforcing agent, the interface reinforcing type stabilizer, the high-temperature stabilizer, the oil field additive and water in the high-temperature-resistant and tough cement slurry system, the present application can make the components play the role in cooperation, significantly improve the pumpability of the high-temperature-resistant and tough cement slurry system, and effectively improve the elastic deformation capacity, the impact toughness and the cementing effect of the high-temperature-resistant and tough cement slurry system in the high-temperature cementing operation.

[0008] The high-temperature-resistant and tough cement paste system, the high-temperature-resistant and elastic reinforcing agent is a compound of surface modified fluorine rubber and alkali-resistant basalt fiber; the mass fraction of the surface modified fluorine rubber in the high-temperature-resistant and elastic reinforcing agent is 40-70 wt%, which can make the high-temperature-resistant and elastic reinforcing agent have good high-temperature resistance and chemical corrosion resistance; after the surface modified fluorine rubber and the alkali-resistant basalt fiber are added into the high-temperature-resistant and tough cement paste system, the surface modified fluorine rubber and the alkali-resistant basalt fiber can cooperate to significantly improve the elastic deformation capacity and impact toughness of the high-temperature-resistant and tough cement paste system in a high-temperature environment; the surface modified fluorine rubber is fluorine rubber powder with polar functional groups such as hydroxyl and carboxyl introduced by surface modification of a silane coupling agent, the particle size of the surface modified fluorine rubber is less than or equal to 300 μm, controlling the particle size of the fluorine rubber below 300 μm and introducing polar functional groups on the surface of the fluorine rubber can greatly improve the dispersibility of the fluorine rubber particles in the cement paste system and the interfacial adhesion of the fluorine rubber particles and cement hydration products, improve the elastic reinforcing effect of the fluorine rubber particles on the cement paste system, the alkali-resistant basalt fiber is basalt fiber coated with high-temperature-resistant epoxy resin or siloxane coating, the length of the alkali-resistant basalt fiber is 3-12 mm, and the diameter of the alkali-resistant basalt fiber is 10-20 μm; if the length of the alkali-resistant basalt fiber is less than 3 mm, the alkali-resistant basalt fiber will agglomerate when mixed with other components, and then uneven stress distribution will occur in the cement stone; if the length of the alkali-resistant basalt fiber is longer than 12 mm, the alkali-resistant basalt fiber will be easily entangled and knotted, increasing the production difficulty, and the fiber orientation will be inconsistent, so the fiber will be easy to become a crack initiation point when subjected to external force, thereby reducing the impact resistance of the material; by coating the basalt fiber with high-temperature-resistant epoxy resin or siloxane coating and controlling the length and diameter of the alkali-resistant basalt fiber within the above range, the basalt fiber can be ensured to be stable in the strong alkali environment of the cement paste for a long time, so that the toughening effect of the basalt fiber on the cement paste can be fully played.

[0009] The preparation method of the surface modified fluorine rubber includes the following steps:

[0010] Step (A-1), preparing a silane hydrolysis solution: using acetic acid to adjust the pH of an ethanol aqueous solution to be acidic to obtain an acidic ethanol aqueous solution; adding a silane coupling agent into the acidic ethanol aqueous solution while stirring intensively, and continuously stirring until the silane coupling agent is fully hydrolyzed to obtain a clear silane hydrolysis solution;

[0011] Step (A-2), fluorine rubber surface modification: washing the fluorine rubber powder with anhydrous ethanol and drying to obtain dry fluorine rubber; adding the dry fluorine rubber into the silane hydrolysis solution (so that the dry fluorine rubber is immersed in the prepared silane hydrolysis solution), and then slowly stirring in a constant-temperature water bath to fully react, so as to ensure that the grafting reaction is fully carried out; after the reaction is completed, a mixed system is obtained;

[0012] Step (A-3), curing treatment: the solid product obtained by filtering the mixed system is repeatedly washed with anhydrous ethanol to remove the physically adsorbed coupling agent; after washing, vacuum drying treatment is performed to complete curing, and after the vacuum drying treatment is completed, the surface-modified fluorine rubber is obtained, the surface of which is grafted with silane coupling agent, and the surface-modified fluorine rubber can be stored for a long time.

[0013] Due to the low surface energy and strong chemical inertness of the fluorine rubber, the compatibility with the resin matrix is poor, so it is necessary to introduce active groups through surface treatment to improve its wettability and adhesion. The present application can significantly improve the wettability of the fluorine rubber particles in the cement slurry system and improve the interfacial adhesion between the fluorine rubber particles and the cement hydration products by establishing a "molecular bridge" between the fluorine rubber (FKM) surface and the resin matrix with silane coupling agent and introducing polar functional groups such as hydroxyl and carboxyl groups on the surface of the fluorine rubber particles, thereby facilitating the improvement of the elastic reinforcing effect of the fluorine rubber particles on the cement slurry system.

[0014] In the above high-temperature-resistant tough cement slurry system, in step (A-1), the volume fraction of anhydrous ethanol in the ethanol aqueous solution is 85-95%; the pH of the acidic ethanol aqueous solution is 4-5 (in this pH range, the hydrolysis of the silane coupling agent can obtain a clear silane hydrolysate, and it is beneficial to the full conduct of the subsequent surface grafting reaction); the stirring rate during the addition of the silane coupling agent and the hydrolysis of the coupling agent is 250-350 rpm; the addition rate of the silane coupling agent is controlled to be completed in 15-30 min; the continuous stirring time after the addition of the silane coupling agent is 30-60 min; the mass of the added silane coupling agent is 1-3 wt% of the total mass of the ethanol aqueous solution; the silane coupling agent is aminopropyl triethoxysilane;

[0015] In step (A-2), the drying conditions of the cleaned fluorine rubber are as follows: the drying temperature is 70-90℃, and the drying time is 3-5h; the mass ratio of the dried fluorine rubber to the silane hydrolysate is 1:(12-18); if the ratio of the dried fluorine rubber to the silane hydrolysate is too high, the amount of the silane coupling agent is insufficient, which may lead to insufficient grafting reaction and affect the quality of the final product; if the ratio of the dried fluorine rubber to the silane hydrolysate is too low, the dried fluorine rubber will form non-uniform agglomerates during the grafting reaction, thereby reducing the overall performance of the material; the constant temperature water bath temperature is 50-60℃, the stirring rate is 250-350 rpm, and the reaction time is 2-4h; under the above grafting reaction conditions, the grafting reaction can be fully conducted, and the occurrence of byproduct such as oligomer can be avoided; the fluorine rubber powder is fluorocarbon rubber, the tensile strength is greater than or equal to 10 MPa, the elongation at break is greater than or equal to 150%, and the Mooney viscosity at 121℃ is 30-70; in step (A-3), the vacuum drying temperature is 60-80℃, and the vacuum drying time is 6-8h.

[0016] In the step (A-1), the volume fraction of anhydrous ethanol in the aqueous ethanol solution is 90%; the pH of the acidic aqueous ethanol solution is 4.5; the stirring rate during the addition of the silane coupling agent and the hydrolysis of the coupling agent is 300 rpm; the addition rate of the silane coupling agent is controlled so that the addition of the silane coupling agent is completed in 20 min; the duration of the stirring after the addition of the silane coupling agent is 50 min; and the mass of the added silane coupling agent is 2 wt% of the total mass of the aqueous ethanol solution.

[0017] In the step (A-2), the drying conditions for the cleaned fluororubber are as follows: the drying temperature is 80℃, and the drying time is 4 h; the mass ratio of the dried fluororubber to the silane coupling agent in the silane hydrolysis solution is 1:15; the temperature of the constant-temperature water bath is 55℃, the stirring rate is 300 rpm, and the reaction time is 3 h; the fluororubber powder is FKM 2602 fluorocarbon rubber raw rubber powder produced by Zhonghao Chen Guang Chemical Research Institute, with a tensile strength greater than or equal to 13 MPa, an elongation at break greater than or equal to 160%, a Mooney viscosity at 121℃ of 40-60, and a passing of a 120-mesh sieve; and in the step (A-3), the vacuum drying temperature is 70℃, and the vacuum drying time is 7 h.

[0018] In the above high-temperature-resistant ductile cement slurry system, the method for preparing the alkali-resistant basalt fiber comprises the following steps:

[0019] In the step (B-1), the tetraethyl orthosilicate, methyl triethoxysilane, and the aqueous ethanol solution are mixed to obtain a mixed raw material solution; the pH of the mixed raw material solution is adjusted to be acidic to catalyze the hydrolysis of the tetraethyl orthosilicate and the methyl triethoxysilane, then heating and stirring are performed and a reflux reaction is carried out, after the reflux reaction is completed, a stable and transparent siloxane sol is obtained;

[0020] In the step (B-2), the basalt fiber is subjected to heat treatment, on the one hand to remove the sizing agent coated on the basalt fiber during the production and manufacturing process, and on the other hand to activate the surface of the basalt fiber to improve the interfacial bonding capacity of the basalt fiber with the siloxane sol; the heat-treated basalt fiber is uniformly immersed in the siloxane sol by using the dip-drawing method, and then uniformly drawn out, so that a uniform liquid film is formed on the surface of the basalt fiber, and a sol-coated basalt fiber is obtained;

[0021] In the step (B-3), the sol-coated basalt fiber is subjected to aging treatment at room temperature, so that the sol liquid film on the surface of the basalt fiber is converted into a gel layer through a hydrolysis-condensation reaction, after the aging treatment is completed, a gel-coated basalt fiber is obtained;

[0022] In the step (B-4), the gel-coated basalt fiber is subjected to programmed temperature heat treatment, so that the gel coating on the surface of the basalt fiber is densified and a firm inorganic-organic hybrid (siloxane) protective layer is formed; after the programmed temperature heat treatment is completed, the alkali-resistant basalt fiber is prepared.

[0023] The main weakness of basalt fiber is its poor durability in strong alkaline environment (such as cement-based materials). By coating a dense protective coating on the surface of basalt fiber, the erosion of alkaline substances can be effectively blocked. The present application uses a siloxane hybrid coating method to achieve better bonding of the siloxane coating with the inorganic surface of basalt fiber, thereby imparting better high temperature resistance and chemical stability of basalt fiber in cement paste system.

[0024] In step (B-1), the molar ratio of tetraethyl orthosilicate to methyl triethoxysilane is (2-3):1 (if the molar ratio of tetraethyl orthosilicate to methyl triethoxysilane is too high, the cross-linking is too much, resulting in a final prepared basalt fiber coating with high brittleness, high hardness but poor toughness, and if the amount ratio of the two is too low, the cross-linking is insufficient, resulting in a final prepared basalt fiber coating with poor thermal stability and insufficient alkali resistance), the volume fraction of anhydrous ethanol in the aqueous ethanol solution is 70-80%; the molar concentration of tetraethyl orthosilicate in the mixed raw material solution is 0.5-1.5 mol / L; the pH of the mixed raw material solution is adjusted to 2-3 using 10-20 wt% dilute hydrochloric acid or acetic acid (if the pH is too low, the cross-linking is insufficient and the coating that can effectively block liquid penetration cannot be generated, and if the pH is too high, uneven gelation or precipitation occurs in a short time, reducing the modification effect of the siloxane coating on basalt fiber); the reflux reaction conditions are: temperature 60-70℃, stirring rate 350-400 rpm, time 6-8 h; if the reflux reaction temperature is too low, the viscosity of the siloxane sol increases slowly, and it may continue to thicken or separate during storage; if the reflux reaction temperature is too high, gelation or precipitation occurs in a short time.

[0025] In step (B-2), the method of heat treatment of basalt fiber is: heating at a rate of 5-10℃ / min to 350-400℃, and heat treating at 350-400℃ for 1-2 h, and then naturally cooling to room temperature; the rate of basalt fiber immersion in the siloxane sol is 100-200 mm / min, and the pulling rate is 100-200 mm / min; the standing time after immersion is 30-120 s; by heat treating the basalt fiber under specific conditions and reasonably controlling the rate of basalt fiber immersion in the siloxane sol, the standing time of the basalt fiber in the siloxane sol, and the rate of pulling the basalt fiber out of the siloxane sol, the sol coating on the surface of the basalt fiber can be more uniform and tightly bonded to the basalt fiber, which is beneficial to improving the modification effect of the basalt fiber;

[0026] In step (B-3), the aging treatment method is to place the product at room temperature for 12-24 hours. In step (B-4), the programmed temperature heat treatment method is to heat the product from room temperature to 140-160℃ at a heating rate of 1-3℃ / min, hold it at that temperature for 50-70 minutes, then heat it to 350-400℃ at a heating rate of 1-3℃ / min, hold it at that temperature for 30-60 minutes, and finally cool it to room temperature in the furnace. This programmed temperature heat treatment method densifies the gel coating on the surface of basalt fibers, significantly improving the density of the siloxane coating on the basalt fiber surface and the interfacial bonding performance between the basalt fiber surface and the siloxane coating. This enhances the alkali resistance modification effect of the basalt fibers, allowing the toughening effect of basalt fibers on cement slurry systems to be maximized under various harsh environments.

[0027] In the above-mentioned high-temperature resistant and tough cement slurry system, in step (B-1), the molar ratio of tetraethyl orthosilicate to methyltriethoxysilane is 7:3, the volume fraction of anhydrous ethanol in the ethanol aqueous solution is 75%, the molar concentration of tetraethyl orthosilicate in the mixed raw material solution is 1.0 mol / L, the pH of the mixed raw material solution is adjusted to 2.5 using 15 wt% dilute hydrochloric acid, and the reflux reaction conditions are: temperature 65℃, stirring speed 380 rpm, time 7 h.

[0028] In step (B-2), the basalt fiber heat treatment method is as follows: the temperature is raised to 380℃ at a heating rate of 8℃ / min, and heat-treated at 380℃ for 1.5h, and then naturally cooled to room temperature; the basalt fiber is immersed in the siloxane sol at a rate of 150mm / min, the pulling rate is 150mm / min, and the standing time after immersion is 60s;

[0029] In step (B-3), the aging treatment method is to place the product at room temperature for 18 hours; in step (B-4), the programmed temperature heat treatment method is to raise the temperature from room temperature to 150℃ at a heating rate of 2℃ / min and hold it for 60 minutes; then raise the temperature to 380℃ at a heating rate of 2℃ / min and hold it for 40 minutes.

[0030] The above-mentioned high-temperature resistant and tough cement slurry system has a water-to-solid ratio of 0.3-0.5; the oil well cement is Grade G or Grade H; the interface-reinforcing stabilizer is an amphoteric polymer containing amide and sulfonic acid groups, with a mass ratio of amide to sulfonic acid groups of (1-3):(7-9). Because the amphoteric polymer contains cationic and anionic groups, it interacts with the cement particle surface through electrostatic interactions, hydrogen bonds, and van der Waals forces, effectively adsorbing onto the cement particle surface to form a protective film, preventing excessive aggregation and precipitation of cement particles. The polymer molecular chains intertwine and crosslink to form a three-dimensional network structure, further enhancing the stability of the cement slurry and effectively controlling the filtration loss. The amphoteric polymer forms a stable adsorption layer at the interface, and the flexibility of the molecular chains allows them to form a tighter contact at the interface, thereby improving the interfacial bonding strength. This invention uses an amphoteric polymer containing amide and sulfonic acid groups as an interface-reinforcing stabilizer and rationally controls the ratio of the two groups, effectively controlling the filtration loss of the cement slurry (API filtration loss can be controlled below 50 mL). This significantly improves the bonding strength of the second interface between cement stone and casing / formation; the high-temperature stabilizer is microcrystalline silica material and / or silica powder; the microcrystalline silica material is a mixture of nano-silica and micro-silica powder in a mass ratio of 1:(3-5), and the particle size of nano-silica is 10-30nm, and the particle size of micro-silica powder is 0.1-0.5μm; the silica powder is composed of silica with a particle size of 177-250μm, silica with a particle size of 149-177μm, and silica with a particle size of 74-105μm. The silicates are mixed in a mass ratio of 3:5:2. By controlling the composition, proportion, and particle size of the high-temperature stabilizer within a specific range, the high-temperature stabilizer can fully consume excess free Ca(OH)2 at high temperatures, generating more high-temperature resistant hydrated calcium silicate (CSH) gel, preventing the cement stone strength from declining, and ensuring that the cement slurry system can remain stable for a long time in environments up to 200°C. Oilfield additives include one or a mixture of two or more of the following: drag reducers, retarders, fluid loss reducers, expansion agents, lubricants, or defoamers.

[0031] A high-temperature resistant and tough cement slurry system is characterized in that the high-temperature resistant and tough cement slurry system is used in cementing operations of deep wells, ultra-deep wells, geothermal wells or salt gypsum layer wells with temperatures greater than or equal to 150°C.

[0032] The technical solution of the present invention achieves the following beneficial technical effects:

[0033] In the high-temperature toughness cement slurry system of this invention, surface-modified fluororubber and alkali-resistant basalt fiber, acting as high-temperature elastic reinforcing agents, form a synergistic toughening mechanism of "particle elastic deformation + fiber bridging and crack resistance." Specifically, the surface-modified fluororubber particles maintain elasticity at high temperatures, effectively reducing the elastic modulus of the cement paste (by 30%-50%), while the alkali-resistant basalt fiber provides macroscopic crack resistance. This allows the high-temperature toughness cement slurry system to maintain excellent mechanical properties over a long period at 180℃-200℃. Using microcrystalline silica materials and / or silica powder as high-temperature stabilizers further improves the colloidal stability and interfacial wettability of the cement slurry, effectively enhancing the bonding quality of the two interfaces of the cement sheath and fundamentally preventing the formation of micro-annulus gaps. Furthermore, both surface-modified fluororubber and alkali-resistant basalt fiber are resistant to the high alkalinity of the cement slurry and the corrosion of formation fluids, working synergistically with the high-temperature stabilizers to further ensure the durability of the cement sheath throughout the entire wellbore lifespan. The high-temperature resistant and tough cement slurry system of this invention is flexibly designed and can be adapted to different high-temperature well conditions from 150℃ to 200℃ and above by adjusting the proportion of each component. It has significant advantages, especially in complex formations with salt-gypsum layer creep or multi-stage fracturing. Detailed Implementation

[0034] Example 1

[0035] The water-to-solid ratio of the high-temperature toughness cement slurry system in this embodiment is 0.35, and it consists of the following components: 100 kg of G-grade oil well cement, 15 kg of surface-modified fluororubber, 10 kg of alkali-resistant basalt fiber, 1.5 kg of interface-reinforced stabilizer, 55 kg of high-temperature stabilizer, 1 kg of drag-reducing agent, 1.8 kg of retarder, and 62 kg of water.

[0036] In this embodiment, the G-grade oil well cement is produced by Jiahua Special Cement Co., Ltd.; the interface-reinforced stabilizer is solid G310HS produced by Henan Weihui Chemical Co., Ltd., which is an amphoteric polymer containing amide and sulfonic acid groups, with a molar ratio of approximately 1:4; the high-temperature stabilizer is microcrystalline silica material, which is a mixture of nano-silica and microsilica powder at a mass ratio of 1:4, with the nano-silica having a particle size of 10-30 nm and the microsilica powder having a particle size of 0.1-0.5 μm; the drag-reducing agent is produced by Henan Weihui Chemical Co., Ltd., model USZ; the retarder is produced by Henan Weihui Chemical Co., Ltd., model GH-10. The surface-modified fluororubber passes through a 100-mesh sieve; the alkali-resistant basalt fiber has a length of 6 mm and a diameter of 10-20 μm.

[0037] In this embodiment, the preparation method of surface-modified fluororubber includes the following steps:

[0038] Step (A-1): Preparation of silane hydrolysate: Adjust the pH of 15 kg of 90% ethanol aqueous solution to 4.5 using acetic acid to obtain an acidic ethanol aqueous solution; while stirring at 300 rpm, slowly add 0.3 kg of silane coupling agent aminopropyltriethoxysilane (liquid KH550 produced by Nanjing Nengde New Material Technology Co., Ltd.) to the acidic ethanol aqueous solution, controlling the addition rate of the silane coupling agent to ensure that the silane coupling agent is added completely within 20 min, and then continue stirring for 50 min to allow the silane coupling agent to be fully hydrolyzed, obtaining a clear silane hydrolysate;

[0039] Step (A-2), Surface modification of fluororubber: Fluororubber powder is repeatedly washed with anhydrous ethanol and then dried at 80°C for 4 hours to obtain dried fluororubber; 1 kg of dried fluororubber is added to 15 kg of the above silane hydrolysate, and then placed in a constant temperature water bath at 55°C and stirred at a stirring rate of 300 rpm for 3 hours to allow it to react fully. After the reaction is completed, a mixed system is obtained; In this embodiment, the fluororubber powder used is FKM 2602 type fluorocarbon rubber raw rubber powder produced by Zhonghao Chenguang Chemical Research Institute, with a tensile strength greater than or equal to 13 MPa, an elongation at break greater than or equal to 160%, a Mooney viscosity of 40-60 at 121°C, and passes through a 120-mesh sieve;

[0040] Step (A-3), Curing treatment: The solid product obtained by filtration of the mixed system is washed with anhydrous ethanol. After washing, it is dried in a vacuum environment at 70°C for 7 hours to complete the curing. After vacuum drying, it is passed through a 100-mesh sieve to obtain surface-modified fluororubber.

[0041] In this embodiment, the preparation method of alkali-resistant basalt fiber includes the following steps:

[0042] Step (B-1): Mix 1.456 kg of tetraethyl orthosilicate (7 mol), 0.534 kg of methyltriethoxysilane (3 mol), and 7 L of 75% ethanol aqueous solution to obtain a mixed raw material solution; adjust the pH of the mixed raw material solution to 2.5 using 15 wt% dilute hydrochloric acid, and then heat to 65°C. Reflux the mixture at this temperature with a stirring rate of 380 rpm for 7 hours. After the reflux reaction is completed, a siloxane sol is obtained.

[0043] Step (B-2): The basalt fiber is heated to 380℃ at a heating rate of 8℃ / min and heat-treated at 380℃ for 1.5h, and then naturally cooled to room temperature; the heat-treated basalt fiber is immersed in siloxane sol at a uniform speed of 150mm / min, and the immersion time is 60s, and then it is pulled out at a uniform speed of 150mm / min to obtain sol-coated basalt fiber;

[0044] Step (B-3): The sol-coated basalt fiber is placed at room temperature for 18 hours for aging treatment. After the aging treatment is completed, gel-coated basalt fiber is obtained.

[0045] Step (B-4): Transfer the gel-coated basalt fiber to a muffle furnace for programmed temperature heat treatment. The programmed temperature heat treatment method is as follows: heat from room temperature to 150℃ at a heating rate of 2℃ / min and hold for 60min; then heat to 380℃ at a heating rate of 2℃ / min and hold for 40min. After the programmed temperature heat treatment is completed, alkali-resistant basalt fiber is obtained.

[0046] The cement slurry was prepared and cured according to API standard procedures. Surface-modified fluororubber particles bonded well with the cement matrix, and alkali-resistant basalt fibers were uniformly distributed within the cement matrix. The high-temperature toughness cement slurry system of this embodiment can be used in wells at 180℃, and its performance test results are shown in Table 1. The test results show that after curing at 180℃ for 7 days, the elastic modulus of the cement stone decreased to 3.5 GPa, the compressive strength was 45 MPa, the tensile strength was 5.2 MPa, and the API filtration loss was 38 mL. In cyclic loading-unloading tests, it exhibited significant plastic deformation capacity, fully meeting the cementing requirements for wells at 180℃.

[0047] Table 1

[0048]

[0049] Example 2

[0050] The water-to-solid ratio of the high-temperature toughness cement slurry system in this embodiment is 0.33, and it consists of the following components: 100 kg of Grade G oil well cement, 20 kg of surface-modified fluororubber, 12 kg of alkali-resistant basalt fiber, 2.0 kg of interface-reinforced stabilizer, 75 kg of high-temperature stabilizer, 1 kg of drag-reducing agent, 2.3 kg of retarder, and 69 kg of water.

[0051] In this embodiment, the G-grade oil well cement is produced by Jiahua Special Cement Co., Ltd.; the interface-reinforced stabilizer is solid G310HS produced by Weihui Chemical Co., Ltd. of Henan Province. This solid G310HS is an amphoteric polymer containing amide and sulfonic acid groups, with a molar ratio of approximately 1:4; the high-temperature stabilizer is composed of 55 kg of microcrystalline silica material and 20 kg of silica powder; the microcrystalline silica material is composed of 11 kg of nano-silica and 44 kg of microsilica powder, and the nano-silica powder... The silica particle size is 10-30 nm, and the micro silica powder particle size is 0.1-0.5 μm. The silica powder is composed of 6 kg of silica with a particle size of 177-250 μm, 10 kg of silica with a particle size of 149-177 μm, and 4 kg of silica with a particle size of 74-105 μm in a mass ratio of 3:5:2. The drag-reducing agent is produced by Weihui Chemical Co., Ltd. of Henan Province, and the model is USZ. The retarder is produced by Weihui Chemical Co., Ltd. of Henan Province, and the model is GH-10. The surface-modified fluororubber passes through a 200-mesh sieve. The alkali-resistant basalt fiber has a length of 9 mm and a diameter of 10-20 μm.

[0052] In this embodiment, the preparation method of surface-modified fluororubber is exactly the same as that of surface-modified fluororubber in Example 1, except that the particle size (300 mesh sieve) of the fluororubber powder used is different. The preparation method of alkali-resistant basalt fiber is also exactly the same as that of alkali-resistant basalt fiber in Example 1, except that the length of the basalt fiber used is different.

[0053] The cement slurry was prepared and cured according to API standard procedures. The high-temperature resistant and tough cement slurry system of this embodiment can be used in wells at 200℃, and its performance test results are shown in Table 2. The test results show that the high-temperature resistant and tough cement slurry system exhibits stable performance and excellent toughness at 200℃, fully meeting the cementing requirements of ultra-deep wells.

[0054] Table 2

[0055]

[0056] Comparative Example

[0057] The only difference between this comparative cement slurry system and Example 1 is that the surface-modified fluororubber in the high-temperature elastic reinforcing agent and the interface-reinforcing stabilizer are not added. Specifically, it is composed of the following components: 100 kg of G-grade oil well cement, 10 kg of alkali-resistant basalt fiber, 55 kg of high-temperature stabilizer, 2.5 kg of fluid loss reducing agent, 1.5 kg of expansion agent, 1 kg of drag reducing agent, 1.8 kg of retarder and 62 kg of water.

[0058] The sources and specifications of G-grade oil well cement, alkali-resistant basalt fiber, high-temperature stabilizer, drag reducer and retarder are exactly the same as in Example 1. The water loss reducing agent is produced by Henan Weihui Chemical Co., Ltd., model G33S; the expansion agent is produced by Henan Weihui Chemical Co., Ltd., model G401.

[0059] The cement paste was prepared and cured according to the API standard procedure. The performance test results of this comparative example are shown in Table 3. The test results show that after curing at 180℃ for 7 days, the elastic modulus of the cement paste is as high as 7.2 GPa, the compressive strength is 38 MPa, but the tensile strength is only 2.8 MPa, exhibiting typical brittleness. Compared with Example 1, under the same stress test, the cement paste has a higher elastic modulus and lower tensile strength, exhibiting obvious brittleness.

[0060] Table 3

[0061]

[0062] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A high-temperature resistant and tough cement slurry system, characterized in that, It is composed of the following components in parts by weight: 90-110 parts by weight of oil well cement, 20-35 parts by weight of high-temperature resistant elastic reinforcing agent, 1.2-3.0 parts by weight of interface-reinforcing stabilizer, 15-80 parts by weight of high-temperature stabilizer, 0-15 parts by weight of oilfield additives, and 50-80 parts by weight of water.

2. The high-temperature resistant and tough cement slurry system according to claim 1, characterized in that, The high-temperature resistant elastic reinforcing agent is a compound composed of surface-modified fluororubber and alkali-resistant basalt fiber. The mass fraction of surface-modified fluororubber in the high-temperature resistant elastic reinforcing agent is 40-70 wt%. The surface-modified fluororubber is a fluororubber powder with polar functional groups, including hydroxyl and carboxyl groups, introduced by surface modification with a silane coupling agent. The particle size of the surface-modified fluororubber is less than or equal to 300 μm. The alkali-resistant basalt fiber is a basalt fiber with a surface coated with high-temperature resistant epoxy resin or siloxane coating. The length of the alkali-resistant basalt fiber is 3-12 mm and the diameter is 10-20 μm.

3. The high-temperature resistant and tough cement slurry system according to claim 2, characterized in that, The preparation method of surface-modified fluororubber includes the following steps: Step (A-1): Preparation of silane hydrolysate: Adjust the pH of the ethanol aqueous solution to acidic using acetic acid to obtain an acidic ethanol aqueous solution; while stirring, add the silane coupling agent to the acidic ethanol aqueous solution and continue stirring until the silane coupling agent is fully hydrolyzed to obtain a clear silane hydrolysate; Step (A-2), Surface modification of fluororubber: Fluororubber powder is washed with anhydrous ethanol and dried to obtain dried fluororubber; the dried fluororubber is added to silane hydrolysate, and then stirred under constant temperature water bath conditions to react fully. After the reaction is completed, a mixed system is obtained. Step (A-3), Curing treatment: The solid product obtained by filtration of the mixed system is washed with anhydrous ethanol. After washing, vacuum drying is performed to complete the curing. After vacuum drying, surface-modified fluororubber is obtained.

4. The high-temperature resistant and tough cement slurry system according to claim 3, characterized in that, In step (A-1), the volume fraction of anhydrous ethanol in the aqueous ethanol solution is 85-95%; the pH of the acidic aqueous ethanol solution is 4-5; the stirring rate during the addition of the silane coupling agent and during the hydrolysis of the coupling agent is 250-350 rpm; the addition rate of the silane coupling agent is controlled so that it is added completely within 15-30 minutes; the stirring time after adding the silane coupling agent is 30-60 minutes; the mass of the added silane coupling agent is 1-3 wt% of the total mass of the aqueous ethanol solution; the silane coupling agent is aminopropyltriethoxysilane. In step (A-2), the drying conditions after cleaning the fluororubber are as follows: drying temperature 70-90℃, drying time 3-5h; mass ratio of dried fluororubber to silane hydrolysate 1:(12-18); constant temperature water bath temperature 50-60℃, stirring speed 250-350rpm, reaction time 2-4h; the fluororubber powder is fluorocarbon rubber with tensile strength greater than or equal to 10MPa, elongation at break greater than or equal to 150%, and Mooney viscosity at 121℃ of 30-70; in step (A-3), the vacuum drying temperature is 60-80℃, and the vacuum drying time is 6-8h.

5. The high-temperature resistant and tough cement slurry system according to claim 4, characterized in that, In step (A-1), the volume fraction of anhydrous ethanol in the aqueous ethanol solution is 90%; the pH of the acidic aqueous ethanol solution is 4.5; the stirring rate during the addition of the silane coupling agent and during the hydrolysis of the coupling agent is 300 rpm; the addition rate of the silane coupling agent is controlled so that it is added completely within 20 minutes; the continuous stirring time after the addition of the silane coupling agent is 50 minutes; and the mass of the added silane coupling agent is 2 wt% of the total mass of the aqueous ethanol solution. In step (A-2), the drying conditions after cleaning the fluororubber are as follows: drying temperature 80℃, drying time 4h; mass ratio of dried fluororubber to silane hydrolysate 1:15; constant temperature water bath temperature 55℃, stirring speed 300rpm, reaction time 3h; the fluororubber powder is FKM 2602 type fluorocarbon rubber raw powder produced by Zhonghao Chenguang Chemical Research Institute, with tensile strength greater than or equal to 13MPa, elongation at break greater than or equal to 160%, Mooney viscosity at 121℃ 40-60, and passing through a 120-mesh sieve; in step (A-3), the vacuum drying temperature is 70℃, and the vacuum drying time is 7h.

6. The high-temperature resistant and tough cement slurry system according to claim 3, characterized in that, The preparation method of alkali-resistant basalt fiber includes the following steps: Step (B-1): Tetraethyl orthosilicate, methyltriethoxysilane and ethanol aqueous solution are mixed to obtain a mixed raw material solution; the pH of the mixed raw material solution is adjusted to acidic, and then heated and stirred and refluxed. After the reflux reaction is completed, siloxane sol is obtained. Step (B-2): Heat-treat the basalt fiber; immerse the heat-treated basalt fiber in siloxane sol at a uniform speed, and then pull it out at a uniform speed to obtain sol-coated basalt fiber. Step (B-3): The sol-coated basalt fiber is aged at room temperature. After the aging process is completed, gel-coated basalt fiber is obtained. Step (B-4): The gel-coated basalt fiber is subjected to programmed temperature heat treatment. After the programmed temperature heat treatment is completed, alkali-resistant basalt fiber is obtained.

7. The high-temperature resistant and tough cement slurry system according to claim 6, characterized in that, In step (B-1), the molar ratio of tetraethyl orthosilicate to methyltriethoxysilane is (2-3):1, the volume fraction of anhydrous ethanol in the aqueous ethanol solution is 70-80%, the molar concentration of tetraethyl orthosilicate in the mixed raw material solution is 0.5-1.5 mol / L, the pH of the mixed raw material solution is adjusted to 2-3 using 10-20 wt% dilute hydrochloric acid or acetic acid, and the reflux reaction conditions are: temperature 60-70℃, stirring speed 350-400 rpm, time 6-8 h. In step (B-2), the basalt fiber heat treatment method is as follows: the temperature is raised to 350-400℃ at a heating rate of 5-10℃ / min, and heat-treated at 350-400℃ for 1-2 hours, and then naturally cooled to room temperature; the basalt fiber is immersed in the siloxane sol at a rate of 100-200mm / min, and the pulling rate is 100-200mm / min; the standing time after immersion is 30-120s. In step (B-3), the aging treatment method is to place the product at room temperature for 12-24 hours; in step (B-4), the programmed temperature heat treatment method is to raise the temperature from room temperature to 140-160℃ at a heating rate of 1-3℃ / min and hold it for 50-70 minutes; then raise the temperature to 350-400℃ at a heating rate of 1-3℃ / min and hold it for 30-60 minutes, and finally cool it to room temperature with the furnace.

8. The high-temperature resistant and tough cement slurry system according to claim 7, characterized in that, In step (B-1), the molar ratio of tetraethyl orthosilicate to methyltriethoxysilane is 7:3, and the volume fraction of anhydrous ethanol in the aqueous ethanol solution is 75%; the molar concentration of tetraethyl orthosilicate in the mixed raw material solution is 1.0 mol / L; the pH of the mixed raw material solution is adjusted to 2.5 using 15 wt% dilute hydrochloric acid; the reflux reaction conditions are: temperature 65℃, stirring speed 380 rpm, and time 7 h. In step (B-2), the basalt fiber heat treatment method is as follows: the temperature is raised to 380℃ at a heating rate of 8℃ / min, and heat-treated at 380℃ for 1.5h, and then naturally cooled to room temperature; the basalt fiber is immersed in the siloxane sol at a rate of 150mm / min, the pulling rate is 150mm / min, and the standing time after immersion is 60s; In step (B-3), the aging treatment method is to place the product at room temperature for 18 hours; in step (B-4), the programmed temperature heat treatment method is to raise the temperature from room temperature to 150℃ at a heating rate of 2℃ / min and hold it for 60 minutes; then raise the temperature to 380℃ at a heating rate of 2℃ / min and hold it for 40 minutes.

9. The high-temperature resistant and tough cement slurry system according to claim 2, characterized in that, The water-to-solid ratio is 0.3-0.5; the oil well cement is Grade G or Grade H; the interface-reinforced stabilizer is an amphoteric polymer containing amide and sulfonic acid groups, with a mass ratio of amide to sulfonic acid groups of (1-3):(7-9); the high-temperature stabilizer is microcrystalline silica material and / or silica powder; the microcrystalline silica material is a mixture of nano-silica and microsilica powder in a mass ratio of 1:(3-5), and the particle size of the nano-silica is... The particle size of the silica powder is 0.1-0.5μm, with a particle size of 10-30nm. The silica powder is a mixture of silica with a particle size of 177-250μm, silica with a particle size of 149-177μm, and silica with a particle size of 74-105μm in a mass ratio of 3:5:

2. Oilfield additives include one or a mixture of two or more of the following: drag reducers, retarders, fluid loss reducers, expansion agents, lubricants, or defoamers.

10. A high-temperature resistant and tough cement slurry system, characterized in that, The high-temperature resistant and tough cement slurry system as described in any one of claims 1-9 is used in cementing operations for deep wells, ultra-deep wells, and geothermal wells with temperatures greater than or equal to 150°C.

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