Well-cementing cement stone reinforcing material and use thereof

Abstract

A well-cementing cement stone reinforcing material and the use thereof. The well-cementing cement stone reinforcing material comprises, according to a mass ratio: 30-50 parts of an active spherical α-Al2O3 micropowder, 30-50 parts of spherical fly ash, 5-20 parts of nano metakaolin, 5-10 parts of a hydrophilic rubber powder, and 5-10 parts of hydrophilic carbon fibers. Adding the well-cementing cement stone reinforcing material to a cement slurry of an oil-gas well can promote the generation of a crystal phase having stable high-temperature strength during the hydration process of the cement slurry, thereby improving the high-temperature strength of cement stone; and can solve the problems of a decline in strength and an increase in permeability of the well-cementing cement stone in an ultra-high temperature environment, thereby effectively ensuring the long-term sealing integrity of a wellbore in an ultra-high temperature environment and preventing the annular pressure of an oil-gas well caused by cement ring damage.

Description

A cement sheath reinforcing material and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202411111778.X filed on August 13, 2024, and entitled "A cement sheath reinforcing material and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of well cementing, and in particular relates to a cement sheath reinforcing material and application thereof. BACKGROUND

[0003] Well cementing is a process of injecting cement into the annular space between the casing and the formation and solidifying to form a cement sheath, which aims to utilize the cementing effect and hardness of the cement sheath to achieve effective interlayer isolation, support and protection of the formation, thereby ensuring long-term sealing integrity of the wellbore and prolonging the service life of the oil and gas well. Good long-term integrity of the wellbore is of great significance to normal production and sustained stability of the oil and gas well. With the deepening of oil and gas exploration and development, the number of complex drilling such as deep wells and ultra-deep wells is increasing, and ultra-high temperature deep wells with bottom hole temperature higher than 200℃ are becoming increasingly common.

[0004] The application patent CN110484223B discloses an oil well cement slurry system for preventing strength decay at high temperature and a preparation method thereof. The cement sheath of the system does not decay in strength within 14 days in the range of 110-180℃, but the strength decays significantly at an ultra-high temperature above 200℃.

[0005] The application patent CN110563428B discloses a well cement for ultra-high temperature deep wells, a preparation method and application thereof. The silicon powder and the anti-decay material jointly act to inhibit the strength decay of the cement sheath at ultra-high temperature. The strength decay rate of the cement sheath is less than 15% within 28 days at 200-240℃, but the strength decays significantly after more than 28 days.

[0006] In the prior art, the strength of the cement sheath decays easily at an ultra-high temperature environment, which leads to interlayer isolation failure and seriously affects the long-term integrity of the wellbore of the high-temperature deep well and shortens the service life of the oil well. SUMMARY

[0007] The main purpose of the present application is to provide a cement sheath reinforcing material, which is added to the cement slurry, and can solve the problems of easy strength decay of the cement sheath at an ultra-high temperature environment and increased permeability.

[0008] The present application also provides a well cementing slurry comprising the cement sheath reinforcing material, and therefore, the cement slurry can solve the problems of easy strength decay of the cement sheath at an ultra-high temperature environment and increased permeability.

[0009] The application also provides a cementing method, which uses the cementing slurry to seal an oil and gas well, and can solve the problem of strength recession and permeability increase of the cement stone under an ultrahigh temperature environment.

[0010] In a first aspect, the application provides a cementing stone reinforcing material, which comprises, in terms of mass ratio, 30-50 parts of active spherical α-Al2O3 micro powder, 30-50 parts of spherical fly ash, 5-20 parts of nano metakaolin, 5-10 parts of hydrophilic rubber powder and 5-10 parts of hydrophilic carbon fiber.

[0011] The cementing stone reinforcing material as described above, wherein the active spherical α-Al2O3 micro powder has an average particle size of 4-5 μm and an Al2O3 content of >95%.

[0012] The cementing stone reinforcing material as described above, wherein the spherical fly ash has an average particle size of 4-5 μm and an Al2O3 content of 30-35%.

[0013] The cementing stone reinforcing material as described above, wherein the nano metakaolin has a thickness of <100 nm, a length of 1-2 μm and an Al2O3 content of 41-45%.

[0014] The cementing stone reinforcing material as described above, wherein the hydrophilic rubber powder has a heat distortion temperature of >260℃ and an average particle size of 10-11 μm.

[0015] The cementing stone reinforcing material as described above, wherein the hydrophilic carbon fiber has a heat distortion temperature of >300℃ and an elastic modulus of >100 GPa.

[0016] The cementing stone reinforcing material as described above, wherein the active spherical α-Al2O3 micro powder is prepared by a method comprising the following processes: ball milling aluminum hydroxide, adding a water solution comprising an additive after sieving, and performing spray drying treatment, calcination treatment, cooling and sieving on a precursor solution formed to obtain the active spherical α-Al2O3 micro powder; and the additive comprises at least one of bentonite, isopropyl alcohol, sodium stearate and polycarboxylic acid water reducer.

[0017] The cementing stone reinforcing material as described above, wherein the hydrophilic rubber powder is prepared by a method comprising the following processes: ultrasonic cleaning and drying treatment of rubber powder, mixing with a sulfuric acid solution, performing sulfonation treatment on the mixed solution, and performing rinsing and drying on the rubber powder after sulfonation treatment to obtain the hydrophilic rubber powder; and / or,

[0018] The hydrophilic carbon fiber is prepared by a method comprising the following steps: ultrasonically cleaning and drying the carbon fiber, mixing it with an aminosulfonic acid solution, microwaving the mixture, and rinsing and drying the microwave-heated carbon fiber to obtain the hydrophilic carbon fiber.

[0019] Secondly, this application provides a cementing slurry, comprising the cementing stone reinforcement material as described above.

[0020] Thirdly, this application provides a cementing method for sealing oil and gas wells using cementing slurry as described above.

[0021] The cement stone reinforcement material provided in this application, when added to the cement slurry of oil and gas wells, can promote the generation of high-temperature strength and stable crystalline phases during the hydration process of the cement slurry, improve the high-temperature strength of the cement stone, solve the problem of strength decay and increased permeability of cement stone under ultra-high temperature environment, effectively ensure the long-term sealing integrity of the wellbore under ultra-high temperature environment, and avoid annular pressure caused by cement sheath damage in oil and gas wells. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments of this application or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 is a scanning electron microscope image of the microstructure of active spherical α-Al2O3 micro powder;

[0024] Figure 2 shows a scanning electron microscope image of the microstructure of ordinary α-Al2O3 micropowder;

[0025] Figure 3 shows the X-ray diffraction analysis of the hydration products of cement stone at different curing times at 220℃ in Example 1.

[0026] Figure 4 shows the X-ray diffraction analysis of the hydration products of cement stone at different curing times at 220℃ in Comparative Example 1.

[0027] Figure 5 shows the pore structure distribution of cement stone in Example 1 and Comparative Example 1 at different curing times at 220℃.

[0028] Figure 6 is a backscatter scanning electron microscope image of cement stone cured at 220℃ for 180 days in Example 1;

[0029] Figure 7 is a backscatter scanning electron microscope image of cement stone in Comparative Example 1 cured at 220℃ for 180 days.

[0030] Figure 8 is a graph showing the thickening curve of cement slurry at 220℃ under high temperature and high pressure in Example 1. DETAILED DESCRIPTION

[0031] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0032] In a first aspect, the present application provides a cement sheath reinforcing material, which comprises, by mass ratio: 30-50 parts of active spherical alpha-Al2O3 micro powder, 30-50 parts of spherical fly ash, 5-20 parts of nano-metakaolin, 5-10 parts of hydrophilic rubber powder, and 5-10 parts of hydrophilic carbon fiber.

[0033] The cement sheath reinforcing material of the present application is obtained by fully mixing and stirring the active spherical alpha-Al2O3 micro powder, the spherical fly ash, the nano-metakaolin, the hydrophilic rubber powder and the hydrophilic carbon fiber according to certain mass parts.

[0034] The cement sheath reinforcing material of the present application adopts three crystal phase stabilizing materials, i.e., the active spherical alpha-Al2O3 micro powder, the spherical fly ash and the nano-metakaolin. According to the activity levels of the three materials and the different participation in the hydration process, the high-temperature reinforcing materials participate in the hydration reaction at different hydration periods, and always form high-temperature stable hydration products. Finally, through the synergistic effect of the three, the long-term strength stability of the cement sheath under the 200-260℃ ultra-high temperature environment is ensured. The two high-temperature resistant toughening materials, i.e., the hydrophilic rubber powder and the hydrophilic carbon fiber, are reasonably compounded to play the synergistic effect of the two, enhance the cement sheath elastic-plastic deformation capacity, prevent the brittle cracking of the cement sheath due to temperature and pressure alternation under the high-temperature and high-pressure environment, and assist the strength stability.

[0035] The cement sheath reinforcing material of the present application adopts the active spherical alpha-Al2O3 micro powder, the spherical fly ash, the nano-metakaolin, the hydrophilic rubber powder and the hydrophilic carbon fiber, which have wide raw material sources, mature preparation technology, can be prepared in large quantities, and are suitable for wide range of field popularization and application. The used materials are specially designed and modified according to the needs, the particle size distribution design is reasonable, and the particle size grading effect with the cement is good. At the same time, through the spherical particle shaping design and the material surface modification, such as hydrophilic modification, the compatibility of the cement sheath reinforcing material and the cement slurry is improved. The addition of the cement sheath reinforcing material has certain improvement effect on the rheological properties, mixing and other construction properties of the cement slurry, can effectively ensure the strength stability of the cement sheath under the 200-260℃ ultra-high temperature environment, ensure the long-term sealing integrity of the ultra-high temperature deep well borehole, and has wide application prospect.

[0036] The cementing slurry reinforcing material provided by the application can promote the generation of stable crystal phase with high temperature strength in the hydration process of the cementing slurry, improve the high temperature strength of the cementing slurry, solve the problems of strength degradation and permeability increase of the cementing slurry under super high temperature environment, effectively ensure the long-term sealing integrity of the wellbore under super high temperature environment, and avoid the annulus pressure caused by the damage of the cement sheath.

[0037] In some embodiments of the application, the average particle size of the active spherical α-Al2O3 micropowder is 4-5 μm, and the Al2O3 content is >95%.

[0038] The average particle size of the active spherical α-Al2O3 micropowder of the application is in a relatively small range, and the Al2O3 content is relatively high. The active spherical α-Al2O3 micropowder is used as one of the main components of the cementing slurry reinforcing material, and its main principle is to utilize the low reactivity of the active spherical α-Al2O3 micropowder to slowly release Al 3+ under super high temperature environment, participate in the later hydration reaction to generate hydrated calcium aluminum silicate minerals, and the active spherical α-Al2O3 micropowder with small average particle size can ensure the formation of uniform, stable and dense hydration phase, reduce the micro defects of the cementing slurry, realize the close packing with the cement base material, improve the mechanical properties of the cementing slurry, and ensure the long-term strength stability of the cementing slurry. At the same time, the spherical surface morphology has a certain "ball bearing" effect, which can effectively improve the construction problems such as poor rheological properties and difficult cementing caused by the addition of a large amount of fine materials, has strong adaptability on site, and is suitable for large-scale popularization and application.

[0039] In some embodiments of the application, the average particle size of the spherical fly ash is 4-5 μm, and the Al2O3 content is 30-35%.

[0040] The spherical fly ash of the application can be prepared by the following method: grinding the fly ash from a power plant in a high-energy ball mill for 2 h, sieving, removing carbon, and performing 3 times of separation by a three-stage turbine air separator to finally separate the spherical fly ash with an average particle size of 4-5 μm, and the Al2O3 content of the spherical fly ash is 30-35%, and the SiO2 content is 55-65%.

[0041] The spherical fly ash is used as one of the main components of the cementing slurry reinforcing material, and the main component of the spherical fly ash is active natural aluminosilicate amorphous glass phase. The amorphous phase has high hydration activity at high temperature, can participate in the hydration reaction in the early stage of high temperature cement hydration, ensure the formation of stable calcium aluminosilicate mineral phase with good high temperature resistance in the early stage of hydration, and thus inhibit the early strength degradation of the cementing slurry. The particle size of the spherical fly ash is small, the particle size distribution effect is good, and the spherical fly ash also contains a large number of spherical particles, which can also utilize the ball bearing effect to improve the rheological properties and cementing performance of the cementing slurry.

[0042] In some embodiments of the present application, the nano metakaolin has a thickness < 100 nm, a length of 1-2 μm, and an Al2O3 content of 41-45%.

[0043] The nano metakaolin is used as one of the components of the cement stone reinforcing material in the present application. The main component of the nano metakaolin is natural aluminosilicate, which belongs to a transition phase with poor crystallinity. The thickness of the nano metakaolin is < 100 nm, and the length is 1-2 μm. The nano metakaolin has high activity at high temperatures and can fully play the pozzolanic effect in the early hydration stage. The nano metakaolin participates in the hydration reaction earliest and forms a calcium aluminosilicate mineral phase with good high-temperature stability. Although the overall particle size of the nano metakaolin is in the micron level, the thickness of the nano metakaolin is in the nanometer level, so the nano metakaolin can play the crystal nucleus effect of the nano material and promote the rapid participation of the nano metakaolin and the spherical fly ash in the hydration reaction in the early hydration stage.

[0044] In the present application, the thickness of the nano metakaolin refers to the shortest edge length of the nano metakaolin material, and the length refers to the longest edge length of the nano metakaolin material.

[0045] In some embodiments of the present application, the hydrophilic rubber powder has a thermal deformation temperature > 260°C and an average particle size of 10-11 μm.

[0046] The hydrophilic rubber powder is used as one of the components of the cement stone reinforcing material in the present application. The hydrophilic rubber powder is polyether ether ketone rubber powder and has good compatibility with the cement slurry after hydrophilic treatment. The material has good temperature resistance, and the thermal deformation temperature is > 260°C. The material still has good deformation ability at a temperature of 200-260°C, which can effectively improve the elastic-plastic performance of the cement stone at an ultra-high temperature, prevent the cracking of the cement stone caused by thermal stress at a high temperature, and thus prevent the strength degradation of the cement stone. The average particle size of the hydrophilic rubber powder is 10-11 μm, which is in a suitable range and can avoid affecting the strength of the cement stone due to the excessively large particle size.

[0047] In some embodiments of the present application, the hydrophilic carbon fiber has a thermal deformation temperature > 300°C and an elastic modulus > 100 GPa.

[0048] The hydrophilic carbon fiber is a modified short carbon fiber with a carbon content > 95%, a fiber length of 1-3 mm, and a diameter of 7-12 μm. The hydrophilic carbon fiber is used as one of the components of the cement stone reinforcing material. The hydrophilic carbon fiber has good compatibility with the cement slurry after hydrophilic treatment. The material has good temperature resistance and a high elastic modulus, and the thermal deformation temperature is > 300°C and the elastic modulus is > 100 GPa, which can effectively prevent the cracking of the cement stone caused by the expansion of microcracks in the cement stone and can play a role in toughening and preventing cracking.

[0049] In some embodiments of the present application, the active spherical alpha-Al2O3 micropowder is prepared by a method comprising the following processes: ball milling aluminum hydroxide, adding a water solution containing an additive after sieving, and performing spray drying treatment on the precursor solution formed, calcination treatment, cooling, sieving, to obtain the active spherical alpha-Al2O3 micropowder; the additive comprises at least one of bentonite, isopropyl alcohol, sodium stearate, and polycarboxylic acid water reducer.

[0050] The preparation process of the active spherical alpha-Al2O3 of the present application is as follows: after grinding industrial-grade aluminum hydroxide in a high-energy ball mill for 2-4 h, sieving, and pouring the sieved powder into a water solution containing bentonite, isopropyl alcohol, sodium stearate, polycarboxylic acid water reducer, and other additives, stirring to form a homogeneous precursor solution with a solid content of 60-70%. The prepared precursor solution is prepared into spherical powder by a spray drying device, the spherical powder is calcined in a high-temperature reaction furnace at a temperature of 1300-1400℃ for 5-6 h, rapidly cooled to room temperature, sieved, to obtain the active spherical alpha-Al2O3 powder.

[0051] The preparation method of the active spherical alpha-Al2O3 micropowder of the present application can prepare the active spherical alpha-Al2O3 micropowder described above, which has a certain activity, is spherical, and has an average particle size of 4-5 μm, can effectively improve the long-term strength stability of cement stone, and avoid construction problems such as poor rheological properties of cement paste and difficult ash deposition.

[0052] In some embodiments of the present application, the hydrophilic rubber powder is prepared by a method comprising the following processes: ultrasonic cleaning, drying treatment of rubber powder, mixing with a sulfuric acid solution, sulfonation treatment of the mixed solution, and rinsing and drying of the sulfonated rubber powder, to obtain the hydrophilic rubber powder; and / or,

[0053] The hydrophilic carbon fiber is prepared by a method comprising the following processes: ultrasonic cleaning, drying treatment of carbon fiber, mixing with an aminosulfonic acid solution, microwave heating treatment of the mixed solution, and rinsing and drying of the microwave heating treated carbon fiber.

[0054] The preparation process of the hydrophilic rubber powder of the present application is as follows: the rubber powder is cleaned in a ultrasonic cleaner containing deionized water for 10 min to remove surface impurities and dried, the dried rubber powder is mixed with a sulfuric acid solution with a concentration of 60-80% at a certain ratio, the mixed solution is stirred in a stirrer at a temperature of 30-50℃ at a speed of 100 r / min for 15-30 min for sulfonation treatment, and then the sulfonated rubber powder is rinsed with deionized water and dried, to obtain the hydrophilic rubber powder.

[0055] The hydrophilic carbon fiber is prepared as follows: the carbon fiber is cleaned in an ultrasonic cleaner containing deionized water for 10 min to remove surface impurities and dried, the dried carbon fiber is mixed with a sulfamic acid solution with a concentration of 20-35%, and then the mixture is irradiated and heated in a microwave heater with a heating frequency of 3-5 GHz for 0.5-1 h at a heating temperature of 60-80℃, and finally the microwave treated carbon fiber is washed with deionized water and dried to obtain the hydrophilic carbon fiber.

[0056] The preparation method of the present application can prepare hydrophilic rubber powder and hydrophilic carbon fiber, can improve the compatibility of the well cementing cement stone reinforcing material with the cement slurry, and the addition of the well cementing cement stone reinforcing material has certain improvement effect on the rheological properties and mixing properties of the cement slurry, can effectively ensure the strength stability of the well cementing cement stone under a super-high temperature environment of 200-260℃, ensure the long-term sealing integrity of the wellbore under the super-high temperature environment, and has wide application prospect.

[0057] In a second aspect, the present application provides a well cementing cement slurry comprising the well cementing cement stone reinforcing material as described above.

[0058] The well cementing cement slurry of the present application can solve the problems of easy strength decline and increased permeability of the well cementing cement stone under a super-high temperature environment, because it comprises the well cementing cement stone reinforcing material as described above.

[0059] In a third aspect, the present application provides a well cementing method, which uses the well cementing cement slurry as described above to seal an oil and gas well.

[0060] The well cementing method of the present application can solve the problems of easy strength decline and increased permeability of the well cementing cement stone under a super-high temperature environment, because it uses the well cementing cement slurry as described above to seal an oil and gas well.

[0061] The technical solutions of the present application are further described below in combination with specific examples.

[0062] The information of the materials used in the examples and comparative examples of the present application is as follows:

[0063] 200-mesh silica powder: SiO2 content of 96.5%, Tianjin Yuyang Superfine Mineral Powder Processing Co., Ltd.;

[0064] Oil well cement suspending agent: polysaccharide-based macromolecular compound, BCJ-300S, Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.;

[0065] Oil well cement fluid loss reducer: AMPS / AM / acrylic acid multi-polymer, BXF-200L, Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.;

[0066] Oil well cement retarder: organic phosphate, BCR-260L, Tianjin Zhongyou Boheng Engineering Technology Co., Ltd.;

[0067] Oil well cement drag reducer: polycarboxylic acid, BCD-210L, Tianjin Zhongyou Boheng Engineering Technology Co., Ltd.;

[0068] Oil well cement defoamer: organic ester, G603, Tianjin Zhongyou Boheng Engineering Technology Co., Ltd.

[0069] Example 1

[0070] The preparation method of the cement slurry of the present embodiment comprises the following steps:

[0071] According to the mass ratio, 40 parts of active spherical α-Al2O3 micro powder, 40 parts of spherical fly ash, 10 parts of nano metakaolin, 5 parts of hydrophilic rubber powder, and 5 parts of hydrophilic carbon fiber are mixed to obtain a well cementing cement stone reinforcing material.

[0072] The average particle size of the active spherical α-Al2O3 micro powder is 4.0 μm, and the Al2O3 content is 96%. The active spherical α-Al2O3 micro powder is prepared by the following steps: grinding industrial-grade aluminum hydroxide in a high-energy ball mill for 2 h, then sieving, and then pouring the sieved powder into an aqueous solution containing bentonite, isopropanol, sodium stearate, and polycarboxylic acid water reducer as an additive, and stirring to form a homogeneous precursor solution with a solid content of 40%. The prepared precursor solution is prepared into spherical powder by a spray drying device, and the spherical powder is calcined in a high-temperature reaction furnace at a temperature of 1350℃ for 6 h, and then quickly cooled to room temperature, and then sieved to obtain the active spherical α-Al2O3 powder.

[0073] The average particle size of the spherical fly ash is 4.0 μm, and the Al2O3 content is 30%.

[0074] The thickness of the nano metakaolin is 75 nm, the length is 1.1 μm, and the Al2O3 content is 41%.

[0075] The hydrophilic rubber powder has a thermal deformation temperature of 280℃, and an average particle size of 10.2 μm. The hydrophilic rubber powder is prepared by the following steps: washing the rubber powder in a ultrasonic cleaner containing deionized water for 10 min to remove surface impurities and drying, mixing the dried rubber powder with a 60% sulfuric acid solution, stirring the mixture in a stirrer at a temperature of 40℃ at a speed of 100 r / min for 20 min for sulfonation treatment, then rinsing the sulfonated rubber powder with deionized water and drying to obtain the hydrophilic rubber powder.

[0076] The hydrophilic carbon fiber has a thermal deformation temperature of 310 DEG C and an elastic modulus of 210 GPa, and is prepared by the following steps: carbon fibers are cleaned in an ultrasonic cleaner containing deionized water for 10 min to remove surface impurities and dried, the dried carbon fibers are mixed with a 30% amino sulfonic acid solution, and then the mixture is irradiated and heated in a microwave heater with a heating frequency of 4 GHz for 1 h at a heating temperature of 70 DEG C, and finally the microwave treated carbon fibers are washed with deionized water and dried to obtain the hydrophilic carbon fiber.

[0077] The cement slurry formulation is: 100 parts of G-grade oil well cement + 40 parts of 200-mesh silicon powder + 20 parts of cement stone reinforcing material for well cementing + 2 parts of oil well cement suspending agent + 4 parts of oil well cement fluid loss reducer + 4 parts of oil well cement retarder + 3 parts of oil well cement drag reducer + 0.1 part of oil well cement defoaming agent + 50 parts of water.

[0078] The preparation method of the cement slurry is: according to the cement test method specified in GB19139, the powder materials such as cement, silicon powder, cement stone reinforcing material for well cementing, and oil well cement suspending agent, and the liquids such as oil well cement fluid loss reducer, retarder, drag reducer, defoaming agent, and water are mixed uniformly according to the proportions in the formulation. First, pour the liquids into a corrugated mixer, set the mixer speed to 4000 r / min, then slowly pour the powder materials into the mixer and mix with the liquids, after the mixed powder materials are all added to the liquids, set the mixer speed to 12000 r / min, high-speed stirring for 35 s, then stop, add an appropriate amount of defoaming agent, to obtain a uniform and stable cement slurry.

[0079] Example 2

[0080] The preparation method of the cement slurry of Example 2 and Example 1 is basically the same, except that 35 parts of active spherical alpha-Al2O3 micro powder, 45 parts of spherical fly ash, 10 parts of nano-metakaolin, 5 parts of hydrophilic rubber powder, and 5 parts of hydrophilic carbon fiber are weighed according to the mass ratio, and the five are fully mixed to obtain the cement stone reinforcing material for well cementing.

[0081] Example 3

[0082] The preparation method of the cement slurry of Example 3 and Example 1 is basically the same, except that 45 parts of active spherical alpha-Al2O3 micro powder, 35 parts of spherical fly ash, 10 parts of nano-metakaolin, 5 parts of hydrophilic rubber powder, and 5 parts of hydrophilic carbon fiber are weighed according to the mass ratio, and the five are fully mixed to obtain the cement stone reinforcing material for well cementing.

[0083] Example 4

[0084] The preparation method of the cement slurry of Example 4 is basically the same as that of Example 1, except that 35 parts of active spherical α-Al2O3micropowder, 35 parts of spherical fly ash, 20 parts of nano-metakaolin, 5 parts of hydrophilic rubber powder, and 5 parts of hydrophilic carbon fiber are weighed according to the mass ratio, and the five are fully mixed to obtain a well cementing cement stone reinforcing material.

[0085] Example 5

[0086] The preparation method of the cement slurry of Example 5 is basically the same as that of Example 1, except that 35 parts of active spherical α-Al2O3micropowder, 35 parts of spherical fly ash, 10 parts of nano-metakaolin, 10 parts of hydrophilic rubber powder, and 10 parts of hydrophilic carbon fiber are weighed according to the mass ratio, and the five are fully mixed to obtain a well cementing cement stone reinforcing material.

[0087] Example 6

[0088] The preparation method of the cement slurry of Example 6 is basically the same as that of Example 1, except that the average particle size of the active spherical α-Al2O3micropowder is 5.0 μm, and the Al2O3content is 98%.

[0089] Example 7

[0090] The preparation method of the cement slurry of Example 7 is basically the same as that of Example 1, except that the average particle size of the spherical fly ash is 5.0 μm, and the Al2O3content is 35%.

[0091] Example 8

[0092] The preparation method of the cement slurry of Example 8 is basically the same as that of Example 1, except that the thickness of the nano-metakaolin is 90 nm, the length is 2.0 μm, and the Al2O3content is 45%.

[0093] Example 9

[0094] The preparation method of the cement slurry of Example 9 is basically the same as that of Example 1, except that the hydrophilic rubber powder has a heat distortion temperature of 300°C and an average particle size of 11.0 μm.

[0095] Example 10

[0096] The preparation method of the cement slurry of Example 10 is basically the same as that of Example 1, except that the hydrophilic carbon fiber has a heat distortion temperature of 350°C and an elastic modulus of 230 GPa.

[0097] Comparative Example 1

[0098] The cement slurry formulation of Comparative Example 1 is: G-grade oil well cement 100 parts + 200-mesh silica powder 60 parts + oil well cement suspending agent 2 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 4 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0099] Comparative Example 2

[0100] The cement slurry formulation of Comparative Example 2 is: G-grade oil well cement 100 parts + 500-mesh silica powder 60 parts + oil well cement suspending agent 2 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 4 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0101] Comparative Example 3

[0102] The preparation method of the cement slurry of Comparative Example 3 is basically the same as that of Example 1, except that the active spherical α-Al2O3micropowder in Example 1 is replaced by ordinary commercially available α-Al2O3micropowder. The ordinary commercially available α-Al2O3micropowder is high-temperature calcined α-Al2O3, with a calcination temperature of 1700°C, an average particle size of 35 μm, an Al2O3content of 98%, and an irregular shape.

[0103] Comparative Example 4

[0104] The preparation method of the cement slurry of Comparative Example 4 is basically the same as that of Example 1, except that the nano-partial kaolin in Example 1 is replaced by ordinary partial kaolin. The ordinary partial kaolin has a length of 10.5 μm, a thickness of 4.5 μm, and an Al2O3content of 42%.

[0105] Comparative Example 5

[0106] The preparation method of the cement slurry of Comparative Example 5 is basically the same as that of Example 1, except that the spherical fly ash in Example 1 is replaced by ordinary fly ash. The ordinary fly ash has an average particle size of 35 μm, an Al2O3content of 29%, and an irregular shape.

[0107] Comparative Example 6

[0108] The preparation method of the cement slurry of Comparative Example 6 is basically the same as that of Example 1, except that the hydrophilic rubber powder in Example 1 is replaced by ordinary rubber powder. The ordinary rubber powder has an average particle size of 11 μm, a heat distortion temperature of 280°C, and is not hydrophilic.

[0109] Comparative Example 7

[0110] The preparation method of the cement slurry of Comparative Example 7 is basically the same as that of Example 1, except that the hydrophilic carbon fiber in Example 1 is replaced by ordinary carbon fiber. The ordinary carbon fiber has a heat distortion temperature of 310°C, an elastic modulus of 210 GPa, and is not hydrophilic.

[0111] Comparative Example 8

[0112] Comparative Example 8 and Example 1 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formula is: G-grade oil well cement 100 parts + 200-mesh silica powder 35 parts + well cement stone strength enhancer 2 parts + oil well cement suspending agent 1 part + oil well cement fluid loss additive 4 parts + oil well cement retarder 1 part + water 46 parts, wherein the strength enhancer includes 5% graphene, 2% polycarboxylic acid dispersant SCS-130L (Texas Continental Shelf Additives Factory) and 93% deionized water by mass percentage, which are prepared by high-speed shearing dispersion.

[0113] Comparative Example 9

[0114] Comparative Example 9 and Example 1 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formula is: G-grade oil well cement 100 parts + first anti-strength decay agent (200-mesh silica powder) 55 parts + first anti-strength decay agent (γ-Al2O3 5 parts + zinc oxide 3 parts + strontium oxide 2 parts) + filler (nanometer silicon dioxide 3 parts + nanometer magnesium oxide 2 parts).

[0115] Test Example: The cement slurries in Examples 1-10 and Comparative Examples 1-9 are poured into 5.08mm*5.08mm*5.08mm curing molds for molding, and the molds containing the cement slurries are placed in a high-temperature and high-pressure curing kettle for curing at 220℃, 21MPa for 3 days, 28 days, 60 days and 180 days, respectively, and the compressive strength and gas permeability of the hardened cement stone are measured, and the results are shown in Table 1.

[0116] Table 1

[0117] Example 11

[0118] Example 11 and Example 1 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formula is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + well cement stone strength enhancer 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 parts + water 50 parts.

[0119] Example 12

[0120] The preparation method of the cement slurry of Example 12 is basically the same as that of Example 2, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + well cement stone reinforcing material 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0121] Example 13

[0122] The preparation method of the cement slurry of Example 13 is basically the same as that of Example 3, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + well cement stone reinforcing material 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0123] Example 14

[0124] The preparation method of the cement slurry of Example 14 is basically the same as that of Example 4, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + well cement stone reinforcing material 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0125] Example 15

[0126] The preparation method of the cement slurry of Example 15 is basically the same as that of Example 5, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + well cement stone reinforcing material 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0127] Example 16

[0128] The preparation method of the cement slurry of Example 16 is basically the same as that of Example 6, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + well cement stone reinforcing material 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0129] Example 17

[0130] The cement slurry of Example 17 was prepared in substantially the same manner as the cement slurry of Example 7, except that the cement slurry formulation was: Class G oil well cement 100 parts + 200 mesh silica flour 40 parts + cement stone strength enhancer 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement friction reducer 3 parts + oil well cement defoamer 0.1 parts + water 50 parts.

[0131] Example 18

[0132] The cement slurry of Example 18 was prepared in substantially the same manner as the cement slurry of Example 8, except that the cement slurry formulation was: Class G oil well cement 100 parts + 200 mesh silica flour 40 parts + cement stone strength enhancer 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement friction reducer 3 parts + oil well cement defoamer 0.1 parts + water 50 parts.

[0133] Example 19

[0134] The cement slurry of Example 19 was prepared in substantially the same manner as the cement slurry of Example 9, except that the cement slurry formulation was: Class G oil well cement 100 parts + 200 mesh silica flour 40 parts + cement stone strength enhancer 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement friction reducer 3 parts + oil well cement defoamer 0.1 parts + water 50 parts.

[0135] Example 20

[0136] The cement slurry of Example 20 was prepared in substantially the same manner as the cement slurry of Example 10, except that the cement slurry formulation was: Class G oil well cement 100 parts + 200 mesh silica flour 40 parts + cement stone strength enhancer 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement friction reducer 3 parts + oil well cement defoamer 0.1 parts + water 50 parts.

[0137] Comparative Example 10

[0138] The cement slurry of Comparative Example 10 had the following formulation: Class G oil well cement 100 parts + 200 mesh silica flour 60 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement friction reducer 3 parts + oil well cement defoamer 0.1 parts + water 50 parts.

[0139] Comparative Example 11

[0140] The cement slurry of Comparative Example 11 had the following formulation: Class G oil well cement 100 parts + 500 mesh silica flour 60 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement friction reducer 3 parts + oil well cement defoamer 0.1 parts + water 50 parts.

[0141] Comparative Example 12

[0142] Comparative Example 12 and Comparative Example 3 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + cement stone reinforcing material for well cementing 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0143] Comparative Example 13

[0144] Comparative Example 13 and Comparative Example 4 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + cement stone reinforcing material for well cementing 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0145] Comparative Example 14

[0146] Comparative Example 14 and Comparative Example 5 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + cement stone reinforcing material for well cementing 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0147] Comparative Example 15

[0148] Comparative Example 15 and Comparative Example 6 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + cement stone reinforcing material for well cementing 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0149] Comparative Example 16

[0150] Comparative Example 16 and Comparative Example 7 are substantially the same in the preparation method of the cement slurry, except that the cement slurry formulation is: G-grade oil well cement 100 parts + 200-mesh silica powder 40 parts + cement stone reinforcing material for well cementing 20 parts + oil well cement suspending agent 2.5 parts + oil well cement fluid loss additive 4 parts + oil well cement retarder 5 parts + oil well cement drag reducer 3 parts + oil well cement defoaming agent 0.1 part + water 50 parts.

[0151] Test Example: The cement pastes in Examples 11-20 and Comparative Examples 10-16 were poured into 5.08mm*5.08mm*5.08mm curing molds, and the molds containing the cement pastes were placed into a high-temperature and high-pressure curing kettle, and cured at 260°C and 21MPa for 3 days, 28 days, 60 days and 180 days, and the compressive strength and gas permeability of the hardened cement stone were measured, and the results are shown in Table 2.

[0152] Table 2

[0153] As can be seen from Tables 1-2, in Comparative Examples 1-2 and Comparative Examples 10-11, silicon powder was used as a strength decay prevention material, and the 180-day compressive strength of the cement stone in the 220°C and 260°C ultra-high temperature environment was significantly decayed compared with the 3-day compressive strength, with a decay rate of >60%, and the permeability increased significantly with the increase of the curing time. The experimental results of Examples 1-20 show that after the cement stone reinforcing material of the application is added, the compressive strength of the cement stone increases slowly with the increase of the curing time, and the permeability of the cement stone does not change significantly with the increase of the curing time, and the cement stone always maintains a relatively dense structure. It is shown that after the cement stone reinforcing material is added, high-temperature stable crystal phases are generated in the hydration process of the cement stone, which ensures the stability of the strength of the cement stone. In Comparative Example 3 and Comparative Example 12, ordinary α-Al2O3 micro powder is used to replace spherical active α-Al2O3, and the long-term strength of the cement stone at 60d and 180d shows a decay trend, which shows that the activity of ordinary α-Al2O3 micro powder is low, and it cannot better participate in the hydration reaction to generate high-temperature stable crystal phases in the later period, and cannot effectively inhibit the transformation of harmful crystal phases, resulting in the decay of the long-term strength of the cement stone. In Comparative Example 4 and Comparative Example 13, ordinary metakaolin is used to replace nano metakaolin, and the long-term strength of the cement stone shows a slight decay trend, which shows that the nano metakaolin utilizes its nano crystal nucleus effect to quickly promote other materials to participate in the hydration reaction, so that the high-temperature resistant cement stone shows good high-temperature mechanical properties. In Comparative Example 5 and Comparative Example 14, ordinary fly ash is used to replace spherical fly ash, and the long-term strength of the cement stone shows a slight decay trend, which shows that the spherical ultra-fine fly ash can better participate in the hydration reaction, and at the same time utilize its close packing effect, so that the high-temperature resistant cement stone shows good mechanical properties. In Comparative Example 6 and Comparative Example 15, unhydrophilic treated rubber powder is used to replace hydrophilic treated rubber powder, and in Comparative Example 7 and Comparative Example 16, unhydrophilic treated carbon fiber is used to replace hydrophilic treated carbon fiber, and the long-term strength of the cement stone shows a slight decay trend, which shows that the hydrophilic treated rubber powder and carbon fiber are better dispersed in the cement paste, and better cemented with the cement hydration products, so that the high-temperature resistant cement stone shows good mechanical properties.

[0154] The cement stone formed by the cement paste prepared in Example 1 and Comparative Example 1 was subjected to pore structure analysis, and the results are shown in Table 3.

[0155] Table 3

[0156] As can be seen from Table 3, the total porosity of the cement stone of Example 1 after curing for 180 days is obviously lower than that of the cement stone cured for 3 days, the pore size distribution is more refined, and the cement stone structure is more compact; while the total porosity of the cement stone of Comparative Example 1 after curing for 180 days is greatly increased compared with that of the cement stone cured for 3 days, and the pore size distribution is obviously developed to large pores.

[0157] The mixing time, fluidity, free fluid, water loss, rheological property and other construction properties of the cement slurries prepared from Examples 11-20 and Comparative Examples 10-16 were tested at 220℃ (cycling temperature), and the results are shown in Table 4.

[0158] Table 4

[0159] As can be seen from Table 4, the mixing time of the cement slurries of Examples 11-20 is ≤40s, which is lower than that of the cement slurries of Comparative Examples 10-16. The cement slurries of Examples 11-20 have a flow index n≥0.8 and a consistency coefficient K<0.7, while the cement slurries of Comparative Examples 10-16 have a flow index n<0.8 and a consistency coefficient K>0.8. The cement slurries of Examples 11-20 have a fluidity of 23-25cm, while the cement slurries of Comparative Examples 10-16 have a fluidity of 18-22cm. Compared with the cement slurries of Comparative Examples 10-16, the cement slurries of Examples 11-20 have good rheological properties and better pumping performance in the construction process. At the same time, the cement slurries of Examples 11-20 have lower free fluid and water loss, and the thickening curve is linear and the thickening time meets the requirements of cementing construction time. The overall construction performance of the cement slurries of Examples 11-20 is better than that of the cement slurries of Comparative Examples 10-16.

[0160] Fig. 1 is a scanning electron microscope image of the micro-morphology of the active spherical α-Al2O3 micro-powder.

[0161] As can be seen from Fig. 1, the active spherical α-Al2O3 micro-powder is spherical.

[0162] Fig. 2 is a scanning electron microscope image of the micro-morphology of the ordinary α-Al2O3 micro-powder.

[0163] As can be seen from Fig. 2, the ordinary α-Al2O3 micro-powder is non-spherical.

[0164] Fig. 3 is an X-ray diffraction analysis diagram of the hydration products of the cement stone of Example 1 at different curing periods at 220℃.

[0165] As can be seen from Fig. 3, the hydration product crystal phase of the cement stone of Example 1 is stable throughout the curing process, and the main crystal phase is the tobermorite crystal phase, and no obvious crystal phase transition occurs.

[0166] Fig. 4 is an X-ray diffraction analysis diagram of the hydration product of the cement stone of Comparative Example 1 at different curing periods at 220°C.

[0167] As can be seen from Fig. 4, the tobermorite crystal phase diffraction peak of the cement stone of Comparative Example 1 gradually disappears with the increase of the curing time, and the tobermorite diffraction peak gradually strengthens, which proves that the crystal phase of the cement stone of Comparative Example 1 has a transition at an ultrahigh temperature, resulting in the degradation of the mechanical properties.

[0168] Fig. 5 is a pore structure distribution diagram of the cement stone of Example 1 and Comparative Example 1 at different curing periods at 220°C.

[0169] As can be seen from Fig. 5, after the cement stone of Example 1 is cured for 180d, compared with the cement stone cured for 3d, the pore size distribution is more refined, and the cement stone structure is more compact; and after the cement stone of Comparative Example 1 is cured for 180d, compared with the cement stone cured for 3d, the pore size distribution obviously develops to the direction of large pores.

[0170] Fig. 6 is a backscattered scanning electron microscope diagram of the cement stone of Example 1 cured at 220°C for 180d.

[0171] As can be seen from Fig. 6, after the cement stone of Example 1 is cured at 220°C for 180d, the microstructure of the cement stone is relatively compact.

[0172] Fig. 7 is a backscattered scanning electron microscope diagram of the cement stone of Comparative Example 1 cured at 220°C for 180d.

[0173] As can be seen from Fig. 7, after the cement stone of Comparative Example 1 is cured at 220°C for 180d, the microstructure is obviously coarsened, and the microdefects and porosity are obviously increased.

[0174] Fig. 8 is a high temperature and high pressure thickening curve diagram of the cement paste of Example 1 at 220°C.

[0175] As can be seen from Fig. 8, the cement paste of Example 1 has good fluidity, which can meet the construction time requirement.

[0176] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A well cement sheath strengthening material, characterized in that, The active spherical alpha-Al2O3 micropowder, the spherical fly ash, the nano metakaolin, the hydrophilic rubber powder and the hydrophilic carbon fiber are included in a mass ratio of 30-50:30-50:5-20:5-10:5-10.

2. The well cemented rock enhancing material of claim 1, wherein, The active spherical alpha-Al2O3 micropowder has an average particle size of 4-5 μm and an Al2O3 content of >95%.

3. The well cemented rock enhancing material according to claim 1 or 2, characterized in that, The spherical fly ash has an average particle size of 4-5 μm and an Al2O3 content of 30-35%.

4. The well cemented rock enhancing material according to any of claims 1-3, characterized in that, The nano metakaolin has a thickness of <100 nm, a length of 1-2 μm and an Al2O3 content of 41-45%.

5. The well cemented rock enhancing material according to any of claims 1-4, characterized in that, The hydrophilic rubber powder has a heat distortion temperature of >260℃ and an average particle size of 10-11 μm.

6. The well cemented rock enhancing material according to any one of claims 1-5, characterized in that, The hydrophilic carbon fiber has a heat distortion temperature of >300℃ and an elastic modulus of >100 GPa.

7. The well cemented rock enhancing material according to any of claims 1-6, characterized in that, The active spherical alpha-Al2O3 micropowder is prepared by a method comprising the following processes: ball milling aluminum hydroxide, sieving, adding a water solution comprising an additive, spray drying the precursor solution, calcining, cooling, sieving, and obtaining the active spherical alpha-Al2O3 micropowder; the additive comprises at least one of bentonite, isopropyl alcohol, sodium stearate and polycarboxylic acid water reducer.

8. The well cemented rock enhancing material according to any of claims 1-7, characterized in that, The hydrophilic rubber powder is prepared by a method comprising the following processes: ultrasonic cleaning and drying rubber powder, mixing with sulfuric acid solution, sulfonating the mixture, rinsing and drying the sulfonated rubber powder, and obtaining the hydrophilic rubber powder; and / or, The hydrophilic carbon fiber is prepared by a method comprising the following processes: ultrasonic cleaning and drying carbon fiber, mixing with sulfamic acid solution, microwave heating the mixture, rinsing and drying the microwave heated carbon fiber, and obtaining the hydrophilic carbon fiber.

9. A cement slurry, characterized in that, The cement stone reinforcing material of any one of claims 1-8.

10. A method of cementing a well, characterized by, Sealing an oil and gas well with the cement slurry of claim 9.

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