Method for preparing material resistant to carbon dioxide corrosion, and corresponding cement slurry system

Abstract

Provided in the present application are a method for preparing a material resistant to carbon dioxide corrosion, and a corresponding cement slurry system. The method comprises: ultrasonically dispersing kaolin having a kaolinite mineral content of greater than 95% in water to obtain a kaolin suspension; sequentially subjecting the kaolin suspension, to which an intercalating agent is added, to treatments of centrifugal dispersion, dehydration, and ultrafine wet grinding to obtain a micro-nano-sized kaolin material; then calcining the micro-nano-sized kaolin material at a high temperature to obtain micro-nano-sized metakaolin; and mixing the micro-nano-sized metakaolin with micro-nano-sized silica powder in a preset ratio to obtain a material resistant to carbon dioxide corrosion. The kaolin used in the technical solution is stable and chemically inert at a high temperature. A micro-nano-sized metakaolin having uniform distribution and high durability is obtained after subjecting kaolin to treatments such as ultrasonic dispersion, centrifugal dispersion and high-temperature calcination, and then mixing the micro-nano-sized metakaolin with silica, such that a material having high resistance to carbon dioxide corrosion can be prepared.

Description

Preparation method of carbon dioxide corrosion resistant material and corresponding cement slurry system

[0001] This application claims priority to Chinese Patent Application No. 202411569522.3, filed on November 5, 2024, entitled "Preparation Method of Anti-Carbon Dioxide Corrosion Material and Corresponding Cement Slurry System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of oil and gas well cementing technology, and in particular to a method for preparing a carbon dioxide corrosion resistant material and a corresponding cement slurry system. Background Technology

[0003] With rapid economic development, the demand for high-performance anti-corrosion materials is constantly increasing across various industries. Anti-carbon dioxide corrosion materials are widely used in petroleum, natural gas, chemical, and marine engineering fields to ensure the safe and reliable operation of concrete in highly corrosive environments. Carbon dioxide corrosion can lead to leaks or cracks in concrete or well cement sheaths, especially in high-risk industries such as oil and gas. Research on anti-carbon dioxide corrosion materials helps reduce safety hazards and protect personnel and the environment.

[0004] Currently, the main anti-carbon dioxide corrosion materials used are organic anti-corrosion additives, including resins and latexes; and external admixtures with anti-corrosion properties, including clay minerals, microsilica, fly ash, and ultrafine slag. However, these materials are not very stable and are prone to forming pores or cracks, resulting in poor anti-corrosion effects.

[0005] Therefore, how to develop a high-performance material resistant to carbon dioxide corrosion has become an urgent technical problem to be solved. Summary of the Invention

[0006] This application provides a method for preparing a carbon dioxide corrosion resistant material and a corresponding cement slurry system to solve the problems in the prior art regarding how to develop a high-performance carbon dioxide corrosion resistant material.

[0007] In a first aspect, embodiments of this application provide a method for preparing a carbon dioxide corrosion resistant material, comprising:

[0008] Kaolin with a kaolinite mineral content greater than 95% was ultrasonically dispersed in water to obtain a kaolin suspension.

[0009] The kaolin suspension with added intercalating agent was subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding in sequence to obtain micro-nano kaolin material;

[0010] The micro-nano-scale kaolin material was calcined at high temperature to obtain micro-nano-scale metakaolin.

[0011] The micro-nano grade metakaolin and micro-nano grade silica powder are mixed in a preset ratio to obtain the carbon dioxide corrosion resistant material.

[0012] In one or more embodiments, the high-temperature calcination of the micro-nano-scale kaolin material to obtain micro-nano-scale metakaolin includes:

[0013] The micro-nano-scale kaolin material is evenly spread in the calcining furnace to a thickness of less than 5 cm.

[0014] The furnace temperature of the calcining furnace is increased from room temperature to between 700°C and 850°C at a heating rate of 5°C / min.

[0015] When the furnace temperature reaches between 700°C and 850°C, it is kept at a constant temperature for 2 to 3 hours to obtain the micro-nano-scale metakaolin.

[0016] In one or more embodiments, before the micro-nano-scale kaolin material is calcined at high temperature to obtain micro-nano-scale metakaolin, the method further includes:

[0017] The micro-nano-scale kaolin material is uniformly pulverized to obtain micro-nano-scale kaolin material with uniform particle size.

[0018] In one or more embodiments, the kaolin suspension with added intercalating agent is sequentially subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding to obtain micro-nano-scale kaolin materials, including:

[0019] After adding an intercalating agent to the kaolin suspension, centrifugation was performed, and excess adhering intercalating agent was washed with ethanol to obtain a composite product.

[0020] The composite product is subjected to dehydration treatment to obtain the dehydrated composite product;

[0021] Sodium hexametaphosphate dispersant was added to the dehydrated composite product, and ultrafine wet grinding was performed to obtain the micro-nano kaolin material.

[0022] Preferably, the particle size of the micro-nano kaolin material is between 1 μm and 10 μm.

[0023] In one or more embodiments, the step of mixing the micro / nano-sized metakaolin and micro / nano-sized silica powder in a preset ratio to obtain the carbon dioxide corrosion resistant material includes:

[0024] The micro-nano-sized metakaolin and the micro-nano-sized silica powder are mechanically mixed according to the preset ratio to obtain a mixture.

[0025] The mixture is mixed and ground by an air jet mill to obtain the carbon dioxide corrosion resistant material.

[0026] Secondly, embodiments of this application provide a carbon dioxide corrosion resistant cement, comprising: a carbon dioxide corrosion resistant material, silicate cement, water, and admixtures.

[0027] In one or more embodiments, the additive includes at least one of the following: a water loss reducing agent, a reinforcing material, a dispersant, a weight-reducing agent, an anti-gas channeling agent, a toughening material, a defoamer, or a foam suppressant.

[0028] In one or more embodiments, the amount of silicate cement is on the order of 100;

[0029] In one or more embodiments, the amount of water is on the order of 47 to 53, and the amount of the carbon dioxide corrosion resistant material is on the order of 5 to 15.

[0030] In one or more embodiments, the silicate cement is Grade G oil well cement.

[0031] This application provides a method for preparing a carbon dioxide corrosion resistant material and a corresponding cement slurry system. The method involves ultrasonically dispersing kaolinite with a kaolinite mineral content greater than 95% in water to obtain a kaolinite suspension. The kaolinite suspension, with the addition of an intercalating agent, is then subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding to obtain micro-nano-sized kaolinite material. This micro-nano-sized kaolinite material is then calcined at high temperature to obtain micro-nano-sized metakaolinite. The micro-nano-sized metakaolinite and micro-nano-sized silica powder are mixed in a predetermined ratio to obtain the carbon dioxide corrosion resistant material. This technical solution uses kaolinite with a kaolinite mineral content greater than 95%, which exhibits stability and chemical inertness at high temperatures. Ultrasonic dispersion of the kaolinite reduces material agglomeration and improves the uniformity of the suspension. Centrifugal dispersion, dehydration, grinding, and high-temperature calcination processes yield uniformly distributed and highly durable micro-nano-sized metakaolinite. Mixing this with silica powder produces a material with high carbon dioxide corrosion resistance. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] Figure 1 is a schematic flowchart of the preparation method of the anti-carbon dioxide corrosion material provided in the embodiment of this application;

[0034] Figure 2 is a schematic flowchart of the preparation method of the anti-carbon dioxide corrosion material provided in the embodiment of this application;

[0035] Figure 3 is a schematic flowchart of the preparation method of the anti-carbon dioxide corrosion material provided in the embodiment of this application;

[0036] Figure 4 is a scanning electron microscope image of the carbon dioxide corrosion resistant material provided in the embodiment of this application;

[0037] Figure 5 is a schematic diagram of the structure of the anti-carbon dioxide corrosion cement slurry system provided in the embodiment of this application.

[0038] The accompanying drawings have illustrated specific embodiments of this disclosure, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this disclosure to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] Before introducing the embodiments of this application, the application background of the embodiments of this application will be explained first:

[0041] With rapid economic development, the demand for high-performance anti-corrosion materials is constantly increasing across various industries. Anti-carbon dioxide corrosion materials are widely used in petroleum, natural gas, chemical, and marine engineering fields to ensure the safe and reliable operation of concrete in highly corrosive environments. Carbon dioxide corrosion can lead to leaks or cracks in concrete or well cement sheaths, especially in high-risk industries such as oil and gas. Research on anti-carbon dioxide corrosion materials helps reduce safety hazards.

[0042] Carbon capture, utilization, and storage (CCUS) technology has attracted much attention as a feasible technology that can significantly reduce carbon dioxide emissions. Among them, the integrity of cement sheath corrosion is one of the key technologies that determines whether a carbon dioxide geological storage project can be successfully implemented and ultimately achieve 100-year storage.

[0043] Currently, CCUS well cementing still primarily uses low-density silicate cement systems. However, silicate cement is subject to rapid corrosion in high-concentration carbon dioxide environments, leading to increased permeability and weakened strength, resulting in a loss of its sealing ability. Furthermore, low-density cement stone (i.e., solidified cement) often exhibits higher porosity and permeability after solidification due to its high liquid-to-solid ratio. This characteristic further exacerbates serious consequences such as decreased oil and gas recovery and carbon dioxide burial. Some cementing processes also involve mixing magnesium olivine, manganese olivine, and calcium magnesium olivine, followed by ball milling, drying, pressing, sintering, cooling, pulverizing, and high-temperature calcination to obtain carbon dioxide corrosion-resistant materials. The resulting powder material has a particle size of approximately 325 mesh. Due to this high particle size, it is difficult to disperse uniformly in the cement slurry, forming an uneven mixture that affects the overall corrosion resistance.

[0044] In addition, the carbon dioxide corrosion-resistant materials used in low-density anti-corrosion cement slurries are mainly organic anti-corrosion admixtures, including resins and latexes; and admixtures with anti-corrosion properties, including clay minerals, microsilica, fly ash, and ultrafine slag. However, these materials have the following problems: organic anti-corrosion admixtures such as resins and latexes have durability or stability issues, and their protective effect may decrease after prolonged exposure to corrosive environments; clay minerals are unevenly dispersed and have poor bonding with cement slurry, leading to the formation of pores or cracks within the material, thus reducing its anti-corrosion effect; while the application of admixtures such as microsilica and ultrafine slag is limited and also affects the properties of the cement slurry, making compatibility design difficult and unable to meet the requirements of cementing operations.

[0045] Therefore, how to develop a high-performance carbon dioxide corrosion resistant material and how to prepare cement have become urgent technical problems to be solved.

[0046] To address the technical problems existing in the prior art, the inventors of this application propose the following solution: In the prior art, the particle size of anti-corrosion materials is too high, making it difficult to disperse uniformly in cement slurry preparation. This leads to the formation of pores or cracks within the cement slurry, affecting the overall anti-corrosion performance. Kaolin materials with high mineral content typically exhibit stability and chemical inertness at high temperatures. Therefore, by selecting kaolin materials with a mineral content greater than 95%, and then adding intercalating agents and dispersants, followed by further ultrafine processing and mechanical mixing, uniformly dispersed micro- and nano-sized particles can be obtained. Simultaneously, a carbon dioxide corrosion resistant material with better mechanical strength, thermal stability, and chemical corrosion resistance can be obtained, thus solving the aforementioned technical problems. Therefore, the carbon dioxide corrosion resistant cement slurry system prepared using this material exhibits excellent anti-corrosion performance. When used in CCUS wells, this carbon dioxide corrosion resistant cement can effectively ensure the integrity of the cement sheath seal throughout the entire life cycle of the CCUS well.

[0047] Specifically, Figure 1 is a schematic flowchart of the preparation method of the anti-carbon dioxide corrosion material provided in the embodiment of this application. As shown in Figure 1, the method involved in the embodiment of this application will be described in detail:

[0048] Step 11: Disperse kaolinite with a kaolinite mineral content greater than 95% in water using ultrasonication to obtain a kaolinite suspension.

[0049] In this step, the appropriate amount of kaolin is selected according to the requirements of the application scenario. The mineral composition is determined through chemical analysis to ensure that the selected kaolin mineral content is greater than 95%. Ultrasonic dispersion is performed in water, and the suspension is left to stand for a period of time after treatment to ensure the stability of the kaolin suspension.

[0050] Kaolin is an important non-metallic mineral, primarily composed of kaolinite (chemical formula Al₂Si₂O₅(OH)₄), and also contains small amounts of other minerals. It belongs to the clay mineral family. It is typically white or pale yellow in color and possesses good plasticity and malleability. Dried kaolin has high hardness and is heat-resistant (up to 1200℃ or higher). Kaolin suspension is a slurry formed by dispersing kaolin particles in a liquid medium. The kaolin suspension is uniformly dispersed in the liquid, forming a stable suspension system and preventing sedimentation.

[0051] Specifically, kaolinite with a kaolinite mineral content greater than 95% is usually called super kaolinite or oily kaolinite, and it is characterized by high purity, high whiteness, and high adsorption capacity. In addition, kaolinite with a kaolinite mineral content greater than 95% has the following advantages:

[0052] (a) It is more stable at high temperatures and has strong chemical inertness.

[0053] (b) Maintain shape and dimensional stability during drying and sintering.

[0054] (c) Wide range of applications can reduce production costs and improve product quality.

[0055] Step 12: The kaolin suspension with added intercalating agent is subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding in sequence to obtain micro-nano kaolin material.

[0056] In this step, an intercalating agent is added to the kaolin suspension obtained by ultrasonic dispersion, followed by centrifugal dispersion. The solid particles are dispersed in the liquid by centrifugal force. After dehydration, the kaolin is then ground by ultrafine wet milling to obtain ultrafine micro-nano kaolin material.

[0057] Intercalating agents are additives used to improve material properties. They are substances that can insert into layered structures to form a dispersion layer. They are commonly used to enhance the physical and chemical properties of chemical materials. Intercalating agents can insert into the interlayer spaces of layered materials, making them easier to disperse and process. They can also adjust the surface properties of materials and enhance their affinity for water or organic solvents. Chemical materials with intercalating agents typically exhibit better strength, toughness, and heat resistance. Changing the structure and properties of chemical materials improves their application performance. Different application requirements and material characteristics necessitate the selection of appropriate intercalating agents to achieve optimal results.

[0058] Specifically, commonly used intercalating agents include the following types:

[0059] 1. Quaternary ammonium salts: such as dodecyltrimethylammonium chloride, are often used to modify clay minerals such as montmorillonite.

[0060] 2. Organic acids: such as oleic acid and oxalic acid, can be used to improve the dispersibility and stability of layered materials.

[0061] 3. Polymers: such as polyvinyl alcohol, which help improve the processing performance of materials.

[0062] In one possible implementation, the intercalating agent could be methylformamide.

[0063] Among them, micro- and nano-sized kaolin materials have small particle sizes (micrometer or nanometer level), thus possessing a large specific surface area. This allows for better dispersion in liquids, reducing sedimentation and resulting in excellent performance in adsorption and catalysis. Furthermore, micro- and nano-sized kaolin materials can improve the strength and toughness of composite materials.

[0064] Step 13: Calcine the micro-nano-scale kaolin material at high temperature to obtain micro-nano-scale metakaolin.

[0065] In this step, the micro-nano-scale kaolin material is calcined at high temperature, which can remove the crystal water and adsorbed water in the micro-nano-scale kaolin material, and obtain micro-nano-scale metakaolin with high mechanical strength, high stability and high fire resistance.

[0066] High-temperature calcination refers to the process of heating raw materials under high-temperature conditions to alter their physical and chemical properties. High-temperature calcination requires precise control of temperature and time based on the material's characteristics and can be conducted in different atmospheres such as oxygen, nitrogen, or inert gases to achieve varying effects. High-temperature calcination can induce phase transformations in raw materials, causing them to form specific crystalline phases. The calcination process can improve the material's strength, heat resistance, and chemical stability, and alter its particle size and morphology.

[0067] Step 14: Mix micro-nano grade metakaolin and micro-nano grade silica powder in a preset ratio to obtain a carbon dioxide corrosion resistant material.

[0068] In this step, micro- and nano-sized metakaolin and micro- and nano-sized silica powder are mechanically mixed in a V-type mixer in a certain proportion to obtain a uniformly mixed anti-carbon dioxide corrosion material.

[0069] Among them, micro- and nano-sized silica powder typically has a particle size between 1 nanometer and 100 micrometers, and has a large specific surface area and unique physicochemical properties.

[0070] In one possible implementation, the ratio of micro / nano-sized metakaolinite to micro / nano-sized silica powder is 9:1, which can be adjusted appropriately according to the actual application scenario.

[0071] Specifically, micro- and nano-sized metakaolin and micro- and nano-sized silica powder are mixed in a predetermined ratio to obtain a carbon dioxide corrosion resistant material, including:

[0072] Micro- and nano-sized metakaolin and micro- and nano-sized silica powders are mechanically mixed in a preset ratio to obtain a mixture. The mixture is then further mixed and ground using an air jet mill to obtain a carbon dioxide corrosion resistant material.

[0073] In this step, the required metakaolin and silica powders are precisely weighed according to a preset ratio and mechanically mixed. The uniformly mixed micro / nano-sized metakaolin and silica powder mixture is then fed into the air jet mill lance via high-pressure gas. The kinetic energy of the airflow causes the material to rotate at high speed within the chamber. Relevant parameters of the air jet mill are set, including airflow velocity, grinding time, and temperature, to ensure sufficient collision and friction of particles within the mill chamber. The airflow continuously circulates the particles within the mill chamber, improving grinding efficiency. Further mixing and grinding of the material using an air jet mill yields a micro / nano-sized, highly active, carbon dioxide corrosion-resistant material.

[0074] Mechanical mixing can be achieved using equipment such as ball mills, mixers, or planetary mixers.

[0075] In one possible implementation, the airflow velocity of the air jet mill can be from 60 m / s to 100 m / s, the grinding time can be adjusted according to the real-time particle size of the material, and the temperature is generally set between room temperature and 70°C.

[0076] The method for preparing a carbon dioxide corrosion resistant material provided in this application involves ultrasonically dispersing kaolinite with a kaolinite mineral content greater than 95% in water to obtain a kaolinite suspension. The kaolinite suspension, with the addition of an intercalating agent, is then subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding to obtain micro-nano-sized kaolinite material. This micro-nano-sized kaolinite material is then calcined at high temperature to obtain micro-nano-sized metakaolinite. The micro-nano-sized metakaolinite and micro-nano-sized silica powder are mixed in a predetermined ratio to obtain the carbon dioxide corrosion resistant material. This technical solution uses kaolinite with a kaolinite mineral content greater than 95%, which exhibits stability and chemical inertness at high temperatures. Ultrasonic dispersion of the kaolinite reduces material agglomeration and improves the uniformity of the suspension. Centrifugal dispersion, dehydration, grinding, and high-temperature calcination processes yield uniformly distributed and highly durable micro-nano-sized metakaolinite. Mixing this with silica powder produces a material with high carbon dioxide corrosion resistance.

[0077] Based on the above embodiments, Figure 2 is a schematic flowchart of the preparation method of the anti-carbon dioxide corrosion material provided in this application embodiment. As shown in Figure 2, step 13 may include the following steps:

[0078] Step 21: Spread the micro-nano grade kaolin material evenly in the calcining furnace to a thickness of less than 5 cm.

[0079] In this step, a flat plate or scraper is used to evenly spread the micro-nano kaolin material at the bottom of the calcining furnace, controlling the material layer thickness to not exceed 5 cm. This avoids uneven heat distribution caused by excessive material thickness, ensuring the uniform heating of the micro-nano kaolin material in the calcining furnace, thereby improving the quality and efficiency of calcination.

[0080] It is worth noting that, before step 13, the following can also be performed: uniformly crush the micro-nano kaolin material to obtain micro-nano kaolin material with uniform particle size.

[0081] Specifically, a ball mill or other pulverizing equipment is used to uniformly pulverize micro-nano-sized kaolin to reduce the particle size and improve uniformity, thereby obtaining micro-nano-sized kaolin materials with uniform particle size.

[0082] Among these options, the ball mill should be suitable for micro- and nano-scale grinding, such as a planetary ball mill or a vibratory ball mill, which can provide higher energy density and more uniform particle size distribution. Other grinding equipment can be an air jet mill, which uses high-temperature airflow to break down materials and obtain micro- and nano-sized particles; or an ultrasonic mill, which uses shock waves generated by ultrasonic waves to pulverize material particles.

[0083] Step 22: Increase the furnace temperature of the calcining furnace from room temperature to between 700°C and 850°C at a heating rate of 5°C / min.

[0084] In this step, ensure the temperature control system and safety devices in the calcining furnace are functioning properly, and that the micro / nano-sized kaolin material has been evenly spread. Set the furnace temperature to room temperature and the heating rate to 5°C / min. Start the calcining furnace and activate the temperature control system, monitoring the furnace temperature in real time to ensure a uniform temperature rise. Use a temperature sensor for accurate measurements and record the data in the temperature control system. When the furnace temperature approaches 700°C, begin adjusting the heating rate to prevent it from becoming too rapid. If necessary, slightly adjust the heating rate during the process of reaching 700°C to 850°C to control the uniformity of the firing process and safely and effectively raise the furnace temperature to between 700°C and 850°C.

[0085] Step 23: When the furnace temperature reaches between 700℃ and 850℃, maintain a constant temperature for calcination for 2 to 3 hours to obtain micro-nano-sized metakaolin.

[0086] In this step, when the furnace temperature reaches the target temperature range (i.e., 700℃ to 850℃), the constant temperature calcination is maintained for 2 to 3 hours to ensure the full calcination of micro- and nano-sized kaolin, thereby obtaining micro- and nano-sized metakaolin with high specific surface area and excellent adsorption properties.

[0087] Generally, a longer calcination time helps stabilize the crystal structure of metakaolin, but excessively long calcination times may lead to particle agglomeration, thus affecting its micro- and nano-scale metakaolin properties. Two hours may be sufficient for higher temperature ranges (850℃), while three hours is suitable for temperatures around 700℃, which helps to ensure complete calcination and uniform material texture.

[0088] The method for preparing a carbon dioxide corrosion resistant material provided in this application involves uniformly spreading micro / nano-sized kaolin material to a thickness of less than 5 cm in a calcining furnace. The furnace temperature is then increased from room temperature to between 700°C and 850°C at a rate of 5°C / min. Afterward, the furnace is calcined at this temperature for 2 to 3 hours to obtain micro / nano-sized metakaolin. This technical solution, through high-temperature calcination of micro / nano-sized kaolin, effectively improves the quality and performance of the kaolin material. The obtained micro / nano-sized metakaolin has a higher specific surface area and better dispersibility, allowing the kaolin material to play a more effective role in the preparation of the carbon dioxide corrosion resistant material.

[0089] Based on the above embodiments, Figure 3 is a schematic flowchart of the preparation method of the anti-carbon dioxide corrosion material provided in this application embodiment. As shown in Figure 3, step 12 may include the following steps:

[0090] Step 31: After adding the intercalating agent to the kaolin suspension, centrifuge the mixture and wash off any excess intercalating agent with ethanol to obtain the composite product.

[0091] An intercalating agent is added to the kaolin suspension in step 11 above, and the mixture is stirred in water at room temperature to promote uniform dispersion of the intercalating agent and intercalation reaction of kaolin. The kaolin suspension containing the intercalating agent is then transferred to a centrifuge for centrifugation and separation. Excess intercalating agent is washed with ethanol to obtain a composite product of kaolin material and intercalating agent.

[0092] Centrifugal separation relies on the centrifugal force generated by a centrifuge to separate different components of materials based on their density differences as they rotate at high speed. Heavier substances move outward and settle at the bottom of the container, while lighter substances remain in the upper liquid layer. Commonly used centrifuges include benchtop centrifuges, industrial centrifuges, ultra-high-speed centrifuges, and centrifugal filters.

[0093] Step 32: Dehydrate the composite product to obtain the dehydrated composite product.

[0094] In this step, the composite product is dehydrated by vacuum filtration and heated under low pressure using a vacuum dryer to remove the solution or water from the composite product, resulting in a high-purity composite product.

[0095] Dehydration can be achieved through various methods, including: thermal drying, which uses a hot air dryer or oven to evaporate moisture; freeze drying, which uses a freeze dryer to freeze the product and then sublimates the moisture in a vacuum environment; spray drying, which uses a spray dryer to atomize liquid materials into droplets and rapidly evaporate moisture in hot air; membrane separation, which uses semi-permeable membranes to separate moisture, such as reverse osmosis and nanofiltration; and centrifugal dehydration, which uses centrifugal force to separate liquid from solid.

[0096] Step 33: Add sodium hexametaphosphate dispersant to the dehydrated composite product and perform ultrafine wet grinding to obtain micro-nano kaolin material.

[0097] In this step, the dried composite product is subjected to ultrafine wet grinding using a nanobead mill. The grinding time and speed are adjusted according to the required particle size and morphology. An appropriate amount of sodium hexametaphosphate dispersant is added during the grinding process to prevent particle agglomeration, and finally micro-nano-scale kaolin material is obtained.

[0098] In this process, an appropriate amount of sodium hexametaphosphate solution is prepared according to the required dispersant concentration. The concentration is generally between 0.5% and 2%, depending on the properties of the composite product and the desired dispersion effect. Ultrafine wet grinding utilizes grinding media (such as balls, rods, etc.) in a liquid medium (usually water or an organic solvent). The particles are subjected to impact and friction in the medium, thus achieving refinement. The grinding equipment can also be a sand mill or an ultrasonic crusher.

[0099] In one possible implementation, the particle size of micro / nano-scale kaolin materials is between 1 μm and 10 μm.

[0100] Specifically, the micro-nano kaolin material (i.e., the composite product) with the intercalating agent is subjected to ultrafine wet grinding. The grinding time is controlled at 8-24 hours until the particle size of the kaolin reaches 1μm to 10μm. The particle size of 1μm to 10μm is considered micro-nano. Under these conditions, the material particles have good dispersibility and stability in cement slurry.

[0101] The specific grinding time can be adjusted according to the particle state and particle size of the material.

[0102] The method for preparing the carbon dioxide corrosion resistant material provided in this application involves adding an intercalating agent to a kaolin suspension, centrifuging the suspension, washing off excess intercalating agent with ethanol to obtain a composite product, then dehydrating the composite product to obtain a dehydrated composite product. Subsequently, sodium hexametaphosphate dispersant is added to the dehydrated composite product, followed by ultrafine wet milling to obtain micro / nano-scale kaolin material. This technical solution, by adding intercalating agents and dispersants to kaolin and performing ultrafine milling, can obtain high-purity micro / nano-scale kaolin material with better thermal stability, compressive strength, and toughness.

[0103] Specifically, Figure 5 is a schematic diagram of the structure of the anti-carbon dioxide corrosion cement slurry system provided in the embodiment of this application. In conjunction with Figure 5, the cement involved in the embodiment of this application will be specifically introduced. This application provides an anti-carbon dioxide corrosion cement slurry system, including: anti-carbon dioxide corrosion material 41, silicate cement 42, water 43, and admixture 44.

[0104] Among them, the carbon dioxide corrosion-resistant material 41 is prepared according to the methods in steps 11 to 14 above, and can effectively inhibit the reaction between carbon dioxide and the components in cement, thus slowing down the carbon dioxide corrosion process. Silicate cement 42 is the main component of the cement slurry system, and the cement slurry system with the addition of the corrosion-resistant material has good mechanical properties and durability.

[0105] Optionally, the silicate cement 42 is on the order of 100, the water 43 is on the order of 47 to 53, and the carbon dioxide corrosion resistant material 41 is on the order of 5 to 15.

[0106] The amount of water 43 is adjusted according to the required workability and hardening speed to ensure that the cement can be effectively hydrated and develop strength.

[0107] Optionally, the admixture 44 includes at least one of the following: a water loss reducing agent, a reinforcing material, a dispersant, a weight-reducing agent, an anti-gas channeling agent, a toughening material, a defoamer, or a foam suppressant.

[0108] The type and dosage of admixtures can be adjusted according to usage requirements. The specific functions of different types of admixtures 44 are as follows:

[0109] Water loss reducer: Used to reduce the loss of moisture from cement mixtures during construction, ensuring the strength and durability of cement paste.

[0110] Reinforcing materials: These enhance the strength and toughness of cement stone and commonly include polymers and fibers.

[0111] Dispersants: help to evenly disperse particles in a mixture, prevent agglomeration, and improve the flowability and workability of the material.

[0112] Lightening agent: Used to reduce the density of cement paste, reduce its weight, and facilitate construction.

[0113] Anti-gas migration agent: Reduces the generation of air bubbles inside cement stone, prevents gas from migrating within the cement stone, and improves structural stability.

[0114] Toughening materials: increase the toughness of cement stone and improve its crack resistance.

[0115] Defoamer: Eliminates air bubbles in the mixture, ensuring the compactness and strength of the material.

[0116] Defoamer: Prevents excessive air bubbles from forming during mixing or construction, maintaining the stability of cement paste.

[0117] In one possible implementation, the water loss reducing agent is an acrylamide-based water loss reducing agent (DRF-1S) produced by CNPC Engineering Institute; the reinforcing material is an ore powder-based reinforcing material (DRB-1S) produced by CNPC Engineering Institute; the dispersant is an aldehyde-ketone condensate dispersant (DRS-1S) produced by CNPC Engineering Institute; the weight-reducing agent is a microsphere-based weight-reducing agent (DRL-1S) produced by CNPC Engineering Institute; the anti-gas channeling agent is a latex polymer-based anti-gas channeling agent (DRT-1S) produced by CNPC Engineering Institute; the toughening material is a polymer-based expansion toughening material (DRE-3S) produced by CNPC Engineering Institute; the defoamer is an organic lipid-based defoamer (DRX-1L) produced by CNPC Engineering Institute; and the foam suppressant is an organic ether-based foam suppressant (DRX-2L) produced by CNPC Engineering Institute.

[0118] Optionally, the silicate cement is Grade G oil well cement.

[0119] Grade G cement possesses high compressive strength and excellent durability, making it suitable for use in complex oil well environments. It has the following characteristics:

[0120] 1) High compressive strength, capable of withstanding high pressure and load in oil wells;

[0121] 2) High temperature resistance ensures the stability of cement underground;

[0122] 3) Corrosion resistance, resisting chemical erosion by downhole fluids and improving long-term service life;

[0123] 4) Good liquidity;

[0124] 5) Highly adaptable, the formula can be adjusted according to different environmental conditions.

[0125] In one possible implementation, the silicate cement is Jiahua G-grade oil well cement.

[0126] The preparation method for the carbon dioxide corrosion resistant material and the corresponding cement slurry system provided in this application can produce the following beneficial effects:

[0127] The micro-nano-scale highly active carbon dioxide corrosion resistant material prepared in this application undergoes a secondary pozzolanic reaction with calcium hydroxide generated during cement hydration. This reaction promotes the further transformation of calcium silicate hydrate (CSH) into the more stable calcium aluminosilicate hydrate (CASH), thereby improving the chemical stability and mechanical strength of the cement paste and reducing the calcium content in the cement matrix, fundamentally inhibiting the corrosion of cement paste by carbon dioxide. Furthermore, due to its ultrafine particle size, the corrosion resistant material prepared in this application can fill the small pores in the cement slurry system, significantly improving the density of the cement paste, reducing porosity, hindering carbon dioxide penetration, and enhancing its corrosion resistance.

[0128] The technical solutions of this application will be clearly and completely described below with reference to the embodiments therein. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0129] To illustrate the anti-carbon dioxide corrosion material and the corresponding cement slurry system provided in the embodiments of this application, specific details are provided in conjunction with Embodiments 1 to 3 and Comparative Examples 1 to 4 of this application:

[0130] Example 1:

[0131] Taking a low-density anti-carbon dioxide corrosion cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 5 parts of anti-carbon dioxide corrosion material, 8 parts of reinforcing material, 1.8 parts of fluid loss reducer, 0.6 parts of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, 4 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 48 parts of water.

[0132] Figure 4 is a scanning electron microscope image of the anti-carbon dioxide corrosion material provided in the embodiment of this application. The specific method for preparing low-density anti-carbon dioxide corrosion cement based on the anti-carbon dioxide corrosion material is as follows:

[0133] Take 100 parts of Jiahua G-grade cement, 5 parts of anti-carbon dioxide corrosion material, 8 parts of reinforcing material, 1.8 parts of water loss reducer, 0.6 parts of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, and 4 parts of toughening material, and mix the dry powder evenly. Weigh 48 parts of water, 0.5 parts of defoamer, and 0.5 parts of antifoaming agent, add them to the water, pour them into a mixer, and rotate the mixer at a low speed (4000±200 rpm). Add the weighed dry powder mixture within 30 seconds, cover the mixer, and continue stirring at a high speed (12000±500 rpm) for 35 seconds to obtain a low-density anti-carbon dioxide corrosion cement slurry with a density of 1.70 g / cm3.

[0134] Example 2:

[0135] Taking a low-density anti-carbon dioxide corrosion cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 10 parts of anti-carbon dioxide corrosion material, 8 parts of reinforcing material, 1.6 parts of fluid loss reducer, 0.8 parts of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, 5 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 51 parts of water.

[0136] The specific method for preparing low-density carbon dioxide corrosion resistant cement based on the carbon dioxide corrosion resistant material is the same as in Example 1.

[0137] Example 3:

[0138] Taking a low-density anti-carbon dioxide corrosion cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 15 parts of anti-carbon dioxide corrosion material, 8 parts of reinforcing material, 1.5 parts of fluid loss reducer, 1 part of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, 5 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 53 parts of water.

[0139] The specific method for preparing low-density carbon dioxide corrosion resistant cement based on the carbon dioxide corrosion resistant material is the same as in Example 1.

[0140] Examples 1 to 3 above are low-density anti-carbon dioxide corrosion cement slurry systems with a density of 1.70 g / cm3 prepared by adding different amounts of the anti-corrosion materials of the present application. Comparative Examples 1 to 4 below are low-density anti-carbon dioxide corrosion cement slurry systems with a density of 1.70 g / cm3 prepared by adding different types of conventional anti-corrosion materials.

[0141] Comparative Example 1 (without added corrosion inhibitors):

[0142] Taking a low-density carbon dioxide corrosion resistant cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 8 parts of reinforcing material, 2 parts of fluid loss reducer, 0.5 parts of dispersant, 6.5 parts of weight-reducing agent, 3 parts of anti-gas channeling agent, 3 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 47 parts of water.

[0143] Comparative Example 2:

[0144] Taking a low-density carbon dioxide corrosion resistant cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 10 parts of traditional carbon dioxide corrosion resistant material (fly ash), 8 parts of reinforcing material, 1.6 parts of water loss reducing agent, 0.8 parts of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, 5 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 52 parts of water.

[0145] Comparative Example 3:

[0146] Taking a low-density anti-carbon dioxide corrosion cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 5 parts of traditional anti-carbon dioxide corrosion material (microsilica), 8 parts of reinforcing material, 1.6 parts of water loss reducing agent, 0.8 parts of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, 5 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 49 parts of water.

[0147] Comparative Example 4:

[0148] Taking a low-density anti-carbon dioxide corrosion cement slurry system with a density of 1.70 g / cm3 as an example, the system consists of 100 parts of Jiahua G-grade oil well cement, 5 parts of traditional anti-carbon dioxide corrosion material (water-soluble resin), 8 parts of reinforcing material, 1.6 parts of water loss reducing agent, 0.8 parts of dispersant, 6.5 parts of weight-reducing agent, 4 parts of anti-gas channeling agent, 5 parts of toughening material, 0.5 parts of defoamer, 0.5 parts of antifoaming agent, and 48 parts of water.

[0149] The cement slurry obtained in Examples 1-3 and Comparative Examples 1-4 were tested for ash-laying time, free liquid, pre-corrosion permeability, and 28-day corrosion permeability. The results are shown in Table 1.

[0150] Table 1 compares the performance of cement prepared using traditional anti-carbon dioxide corrosion materials with that prepared using the anti-carbon dioxide corrosion materials of this embodiment.

[0151] As shown in the test data in Table 1 above, the low-density anti-carbon dioxide corrosion cement slurry containing the anti-carbon dioxide corrosion material prepared in this application embodiment exhibits excellent overall performance. It possesses characteristics such as good slurry setting time and absence of free liquid, ensuring safe operation during cementing operations.

[0152] Experimental results show that increasing the amount of the anti-carbon dioxide corrosion material in this application only has a certain impact on the cement slurry application time, but does not affect the overall performance of the cement paste. Simultaneously, increasing the amount of the anti-carbon dioxide corrosion material can effectively reduce the permeability of uncorroded cement stone and cement stone after 28 days of corrosion, thus improving the anti-corrosion performance of the cement stone. Examples 1-3, with different amounts of anti-carbon dioxide corrosion material added, showed a significant increase in permeability of the cement stone before and after corrosion compared to Comparative Example 1 without the anti-carbon dioxide corrosion material. Compared to Comparative Examples 2-4 with the same amount of anti-carbon dioxide corrosion material added, the reduction in permeability of uncorroded cement stone and cement stone after 28 days of corrosion was significant, indicating that cement prepared using the anti-carbon dioxide corrosion material of this application has excellent anti-carbon dioxide corrosion performance.

[0153] It is worth noting that the micro-nano-scale highly active carbon dioxide corrosion resistant material prepared in this application has the following beneficial effects compared with traditional carbon dioxide corrosion resistant materials:

[0154] (1) The particle size distribution of the carbon dioxide corrosion resistant material is between 1 and 10 μm, which is micro-nano level. The volcanic ash activity of the material is between 120 and 150% after 30 days.

[0155] (2) After adding this material, the cement slurry has good overall performance and can reduce the free liquid content in low-density cement slurry by 50%-100%.

[0156] (3) The permeability of the cement stone that has not been corroded after the addition of this material is between 0.005 and 0.02 mD. After 28 days of corrosion, the permeability of the cement stone is between 0.01 and 0.05 mD, and it still has good anti-corrosion performance.

[0157] (4) The method for preparing the anti-carbon dioxide corrosion material of the present invention has a simple production process, low cost, and large output, and has broad application prospects.

[0158] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a carbon dioxide corrosion resistant material, characterized in that, include: Kaolin with a kaolinite mineral content greater than 95% was ultrasonically dispersed in water to obtain a kaolin suspension. The kaolin suspension with added intercalating agent was subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding in sequence to obtain micro-nano kaolin material; The micro-nano-scale kaolin material was calcined at high temperature to obtain micro-nano-scale metakaolin. The micro-nano-sized metakaolin and micro-nano-sized silica powder are mixed in a preset ratio to obtain the carbon dioxide corrosion resistant material.

2. The method according to claim 1, characterized in that, The process of calcining the micro-nano-sized kaolin material at high temperature to obtain micro-nano-sized metakaolin includes: The micro-nano-scale kaolin material is evenly spread in the calcining furnace to a thickness of less than 5 cm. The furnace temperature of the calcining furnace is increased from room temperature to between 700°C and 850°C at a heating rate of 5°C / min. When the furnace temperature reaches between 700°C and 850°C, it is kept at a constant temperature for 2 to 3 hours to obtain the micro-nano-scale metakaolin.

3. The method according to claim 2, characterized in that, Before the high-temperature calcination of the micro-nano-sized kaolin material to obtain micro-nano-sized metakaolin, the method further includes: The micro-nano-sized kaolin material is uniformly pulverized to obtain micro-nano-sized kaolin material with uniform particle size.

4. The method according to any one of claims 1-3, characterized in that, The kaolin suspension with added intercalating agent is subjected to centrifugal dispersion, dehydration, and ultrafine wet grinding to obtain micro-nano kaolin materials, including: After adding an intercalating agent to the kaolin suspension, centrifugation was performed, and excess adhering intercalating agent was washed with ethanol to obtain a composite product. The composite product is subjected to dehydration treatment to obtain a dehydrated composite product; Sodium hexametaphosphate dispersant was added to the dehydrated composite product, and ultrafine wet grinding was performed to obtain the micro-nano kaolin material.

5. The method according to claim 4, characterized in that, The particle size of the micro-nano kaolin material is between 1 μm and 10 μm.

6. The method according to any one of claims 1-3, characterized in that, The process of mixing the micro-nano-sized metakaolin and micro-nano-sized silica powder in a preset ratio to obtain the carbon dioxide corrosion resistant material includes: The micro-nano-sized metakaolin and the micro-nano-sized silica powder are mechanically mixed according to the preset ratio to obtain a mixture. The mixture is mixed and ground by an air jet mill to obtain the carbon dioxide corrosion resistant material.

7. A carbon dioxide corrosion resistant cement slurry system, characterized in that, include: The carbon dioxide corrosion resistant material, silicate cement, water, and admixtures as described in any one of claims 1-6.

8. The carbon dioxide corrosion resistant cement slurry system according to claim 7, characterized in that, The additives include at least one of the following: water loss reducing agent, reinforcing material, dispersant, weight reducing agent, anti-gas channeling agent, toughening material, defoamer, and antifoaming agent.

9. The carbon dioxide corrosion resistant cement slurry system according to claim 7, characterized in that, The silicate cement has a quantity on the order of 100; Accordingly, the amount of water is on the order of 47 to 53, and the amount of the carbon dioxide corrosion resistant material is on the order of 5 to 15.

10. The carbon dioxide corrosion resistant cement slurry system according to any one of claims 7-9, characterized in that, The silicate cement is Grade G oil well cement.

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