Additives for cementing, cement slurries and methods of making the additives

Abstract

The application provides a cementing additive, a cement slurry and a preparation method of the additive, and relates to the technical field of oil and gas resource exploitation.The cementing additive comprises: a surface of the additive is coated with a silicon dioxide coating film, a core of the additive is a mineral material particle, and an inner side of the coating film is fused and mixed with a surface of the mineral material particle to form a glassy substance containing a microcrystalline structure.The cementing additive is mainly used for preparing a cement stone for cementing under high temperature and preventing strength decay.Because the surface of the cementing additive is coated with the silicon dioxide coating film and the inner side of the coating film contains the glassy substance with the microcrystalline structure, the cementing additive has excellent high-temperature stability in a cementing process under the condition of 150-240 DEG C well conditions, can reduce a reaction speed of the mineral material particle and the cement stone, and can improve a late strength of the cement stone.

Description

Technical Field

[0001] This application relates to the field of oil and gas resource extraction technology, and in particular to a cementing additive, cement slurry, and a method for preparing the additive. Background Technology

[0002] In oil and gas resource extraction, over 34% of oil and gas resources are located in complex reservoirs such as deep and ultra-deep formations, where downhole operations are conducted in high-temperature environments (≥150℃), placing higher demands on cementing processes and materials. Cementing is a crucial step in the oil and gas resource extraction process, typically using silicate cement systems as cementing materials. This involves injecting cement slurry into the annular space between the wellbore and casing, which then solidifies to form silicate cement stone, sealing the oil, gas, and water layers within the wellbore. However, at temperatures above 110℃, especially at bottomhole temperatures exceeding 150℃, silicate cement stone is prone to forming dicalcium silicate hydrate (α-C2SH) crystals, leading to a gradual decline in the strength of the silicate cement stone and ultimately cementing failure, resulting in significant economic losses.

[0003] In related technologies, in order to solve the problem of strength degradation of silicate cement stone under high temperature conditions, different types of silicon are usually introduced as additives to prevent strength degradation. This method is more effective below 150℃, but when the temperature is higher than 150℃, especially above 200℃, the strength degradation of silicate cement stone is still quite obvious. Summary of the Invention

[0004] This application provides a cementing additive, cement slurry, and a method for preparing the additive, which are used to improve the later strength of cement stone.

[0005] In a first aspect, this application provides a cementing additive, comprising: a silica coating film on the surface of the additive, mineral material particles as the core of the additive, and a glassy substance containing a microcrystalline structure formed by melting and mixing the inner side of the coating film with the surface of the mineral material particles.

[0006] In one possible implementation, the additive is a regular spherical particle.

[0007] In one possible implementation, the additive has a maximum particle size of 50-200 mesh, a compressive strength of 50-100 MPa, and a density of 1.8-2.6 g / cm³.

[0008] In one possible implementation, the maximum particle size of the mineral material is 60 mesh to 240 mesh.

[0009] Secondly, this application provides a method for preparing a cementing additive, comprising: preparing the cementing additive as described in the first aspect and / or various possible cementing additives described in the first aspect, wherein the preparation method includes:

[0010] The solid materials in the components are finely ground to the set requirements to obtain a uniform mixture.

[0011] The mixed materials are granulated using physical granulation or chemical granulation methods to obtain mineral material particles;

[0012] The precursor particles are obtained by coating the surface of mineral material particles with a silicon-containing liquid material in the composition and then drying them.

[0013] The precursor particles are calcined at high temperature to harden their surface and form a silica coating. The inner side of the coating is melt-mixed with the surface of the mineral material particles to form a glassy substance with a microcrystalline structure, thus obtaining a cementing additive.

[0014] In one possible implementation, the components are: 40-60% silicon dioxide, 20-40% aluminum oxide, 2-10% alkaline earth metal oxides, 2-10% alkali metal oxides, and 0-5% other substances; wherein, of the 40-60% silicon dioxide, 50% silicon dioxide is a silicon-containing liquid material and the other 50% silicon dioxide is a silicon-containing solid mineral material.

[0015] In one possible implementation, the requirement is set that the solid particles in the mixture pass through a 300-mesh sieve, and / or that the maximum particle size of the precursor particles is 50-200 mesh.

[0016] In one possible implementation, high-temperature calcination involves feeding the precursor particles into a dynamic powder calcination furnace and calcining them at 1200°C to 1500°C for 2 to 4 hours.

[0017] In one possible implementation, the physical granulation method includes introducing an appropriate amount of liquid substance, physically compacting it, and then feeding it into a low-shear mill for pulverization to prepare precursor particles, wherein the liquid substance includes water and / or ethanol.

[0018] Thirdly, this application provides a cement slurry for cementing, comprising: as described in the first aspect and / or various possible cementing additives described in the first aspect. Optionally, the density of the cement slurry ranges from 1.20 g / cm³ to 2.60 g / cm³.

[0019] The cementing additive, cement slurry, and preparation method of the additive provided in this application have a core of mineral material particles. These mineral material particles can react with the hydration products of cement stone, thereby reducing the calcium-silicon ratio of the hydration products and generating dense and stable hydration products. The silica coating in the additive is melt-mixed with the surface of the mineral material particles to form a glassy substance with a microcrystalline structure. This glassy substance with a microcrystalline structure has excellent high-temperature stability during cementing under well conditions of 150~240℃, which can slow down the reaction between the mineral material particles and the hydration products of cement stone, alleviate the strength decay of cement stone at high temperatures, and improve the later strength of cement stone. Attached Figure Description

[0020] The accompanying drawings of the embodiments described herein are incorporated in and form part of this specification, illustrating those consistent with this application and serving, together with the specification, to explain the principles of this application.

[0021] Figure 1 This is a schematic diagram of the microstructure of the cementing additive provided in the embodiments of this application;

[0022] Figure 2 This is a schematic flowchart illustrating the preparation method of cementing additives provided in the embodiments of this application.

[0023] The accompanying drawings illustrate specific embodiments of this application, 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 concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0024] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0025] First, a brief introduction to the relevant background of this application will be given.

[0026] Although my country's total oil and gas resources are relatively abundant, their distribution is relatively scattered. Furthermore, with the deepening of development, complex well conditions such as deep wells, ultra-deep wells, and unconventional wells are becoming more concentrated. Data shows that over 34% of oil and gas resources are located in complex reservoirs such as deep and ultra-deep formations, where the downhole environment is at high temperatures (≥150℃), placing higher demands on oil and gas extraction technologies and related materials.

[0027] Cementing is a crucial step in oil and gas resource extraction. It typically uses silicate cement systems as the cementing material. Cement slurry is injected into the annular space between the wellbore and casing, and the slurry solidifies to form silicate cement stone, sealing oil, gas, and water layers within the wellbore. However, as bottom-hole temperatures rise, silicate cement stone is prone to forming dicalcium silicate hydrate (α-C2SH) crystals at temperatures above 110°C, leading to a gradual decline in cement stone strength. Data from 2-day, 7-day, 14-day, and 28-day curing tests revealed a significant decrease in cement stone strength at 14, 28, and 42 days compared to previous levels, resulting in cementing failure. This strength degradation is particularly pronounced at bottom-hole temperatures exceeding 150°C, leading to severe economic losses.

[0028] In related technologies, to address the challenge of strength degradation under high-temperature conditions at the bottom of wells, different types of silicon are typically introduced as anti-degradation additives. However, at temperatures above 150℃, especially above 200℃, simply introducing silicon almost completely negates the anti-degradation effect on cement stone. Therefore, it is hoped that innovative research and development of process systems and anti-degradation materials can solve the problem of long-term strength degradation of cement stone under high-temperature conditions.

[0029] Related technology 1 uses one or more of ultrafine cement, ultrafine silica powder, quartz sand, and metakaolin as high-temperature reinforcing materials, and one or more of whiskers and fibers as inorganic toughening materials. Cement slurry using high-temperature reinforcing materials and inorganic toughening materials is cured at 120℃, 150℃, and 180℃ for 2 days and 7 days respectively, and strength tests are conducted. It cannot be shown that cement stone using high-temperature reinforcing materials and inorganic toughening materials as additives has high-temperature anti-fading performance for more than 7 days.

[0030] Related technology 2 discloses "a composite ultra-high temperature cement stone mechanical modification material and its preparation method," which uses 400-mesh acid-washed quartz sand as the first high-temperature strength anti-fading material, a mixture of two of wollastonite, kyanite, calcite, and bauxite as the second high-temperature strength anti-fading material, and halloysite nanotubes as the ultra-high temperature toughening material. The materials used are complex and expensive, significantly increasing cementing costs and lacking wide applicability.

[0031] Related technology 3 discloses "a high-temperature strength degradation resistant agent suitable for thermal mining cement," which uses a mixture of quartz sand (200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh), microsilica, expanded perlite, fly ash, diatomaceous earth, early strength activator, and dispersant in a certain proportion as a high-temperature strength degradation resistant agent. Because the cement stone strength measured after 72 hours of curing is significantly higher than that measured after 7 days of curing, the cement stone using the high-temperature strength degradation resistant agent exhibits significant strength degradation at high temperatures.

[0032] To address the aforementioned issues, the inventors developed a cementing additive by rationally proportioning and optimizing the preparation process of various materials, including modified silicon sources, highly active artificial volcanic ash materials, and natural calcium apatite minerals. This cementing additive features high-temperature resistance, low friction, and easy compatibility. It can inhibit the formation of harmful crystalline phases in cement paste at high and ultra-high temperatures, positively promoting the long-term strength development of cement paste. Simultaneously, it exhibits good compatibility with other admixtures in ultra-high temperature cement slurry, improving the rheological properties of the cement slurry and reducing construction friction, without affecting the basic properties of the cement slurry such as thickening time. It plays a crucial role in improving the performance of ultra-high temperature cement slurry, ensuring the cementing quality and long-term sealing integrity of deep and ultra-deep wells, and guaranteeing the safety of cementing operations.

[0033] This application provides a high-temperature resistant cementing additive, which can be mainly used in high-temperature well cementing operations in the oil and gas resource development field. The core of the additive is mineral material particles, which can react with the hydration products of cement stone, thereby reducing the calcium-silicon ratio of the hydration products and generating dense and stable hydration products. In addition, the silica coating in the additive melts and mixes with the surface of the mineral material particles to form a glassy substance containing a microcrystalline structure. This glassy substance containing a microcrystalline structure has excellent high-temperature stability during cementing under well conditions of 150~240℃, which can slow down the reaction between the mineral material particles and the hydration products of cement stone, alleviate the strength decay of cement stone at high temperatures, and improve the later strength of cement stone.

[0034] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0035] One embodiment of this application provides a cementing additive. The surface of the additive is coated with a silica coating film, and the core of the additive is a mineral material particle. The inner side of the coating film is melt-mixed with the surface of the mineral material particle to form a glassy substance containing a microcrystalline structure.

[0036] The cementing additive can be considered as a three-layer core-shell structure consisting of a surface layer, an intermediate layer, and a core. The surface layer is a silica coating, the intermediate layer is a glassy substance, and the core is mineral particles. During cementing operations, the mineral particles in the cementing additive react with the hydration products of the cement stone, thereby reducing the calcium-silicon ratio of the cement hydration products and generating dense and stable hydration products, thus improving the overall strength of the cement stone. Simultaneously, the microcrystalline structure within this cementing additive exhibits excellent high-temperature stability, allowing the reaction between the internal mineral materials and cement hydration products to proceed slowly, thereby increasing the strength of the cement stone at high temperatures and mitigating the problem of strength degradation at high temperatures.

[0037] Optionally, the additive performs best under well conditions with temperatures ranging from 150°C to 240°C. This can be understood as a core-shell structured particulate material that prevents strength degradation of cement stone under conditions of 150–240°C.

[0038] According to further research by the inventors, the additive consists of regularly spherical particles.

[0039] Figure 1 This is a schematic diagram of the microstructure of the cementing additive provided in the embodiments of this application. For example... Figure 1 As shown, the microstructure of the cementing additive is a regular sphere with high sphericity and good particle dispersibility, with almost no agglomeration. The special shape of the cementing additive can act as a "ball bearing" lubricant during the preparation of cement slurry, reducing the flow friction of the cement slurry and thus improving its flow properties.

[0040] Optionally, the maximum particle size of the additive is 50 mesh to 200 mesh, the compressive strength is 50 MPa to 100 MPa, and the density is 1.8 g / cm3 to 2.6 g / cm3.

[0041] Specifically, the maximum particle size of the additive can be 50 mesh to 200 mesh, such as 50 mesh, 100 mesh, 150 mesh, 200 mesh or any combination thereof, which facilitates a slow reaction between the mineral materials in the additive and the hydration products of the cement stone, thereby improving the strength of the cement stone at high temperatures and alleviating the problem of strength degradation of the cement stone at high temperatures.

[0042] The compressive strength of the additive can be 50MPa to 100MPa, meaning that the compressive strength can be any specific value among 50MPa, 60MPa, 70MPa, 80MPa, 90MPa and 100MPa or a range of any two of them.

[0043] The density of the additive can be 1.8 g / cm3 to 2.6 g / cm3, which means that the density of the additive can be any specific value among 1.8 g / cm3, 2.0 g / cm3, 2.2 g / cm3, 2.4 g / cm3 and 2.6 g / cm3 or a range of any two of them.

[0044] Furthermore, the maximum particle size of the mineral material is 60 mesh to 240 mesh. This means that the maximum particle size of the mineral material can be any specific value among 60 mesh, 120 mesh, 180 mesh, 200 mesh, and 240 mesh, or a range of any two of them.

[0045] The cementing additive provided in this application has a silica coating on its surface and a mineral particle core. The inner side of the coating is molten and mixed with the surface of the mineral particle to form a glassy substance with a microcrystalline structure. The mineral particle in the additive can react with the hydration products of cement stone, thereby reducing the calcium-silicon ratio of the cement hydration products and generating a dense and stable hydration product. The silica coating in the additive molten and mixed with the surface of the mineral particle to form a glassy substance with a microcrystalline structure exhibits excellent high-temperature stability during cementing under well conditions of 150~240℃. This allows the reaction between the mineral particle and the hydration product of cement stone to proceed slowly, mitigating the strength degradation of cement stone at high temperatures and improving the later-stage strength of cement stone.

[0046] Figure 2 A schematic flowchart of the preparation method of the cementing additive provided in the embodiments of this application. Figure 1 .like Figure 2 As shown, the method includes:

[0047] S201. Grind the solid materials in the components to the set requirements to obtain a uniform mixed material.

[0048] Optionally, the components in the composition can be divided by weight into: 40-60% silicon dioxide, 20-40% aluminum oxide, 2-10% alkaline earth metal oxides, 2-10% alkali metal oxides, and 0-5% other substances; among which, in the 40-60% silicon dioxide, 50% silicon dioxide is a silicon-containing liquid material and 50% silicon dioxide is a silicon-containing solid mineral material.

[0049] Among them, the silicon-containing liquid material can be water glass or silica sol; aluminum oxide can be a high-alumina mineral material; alkaline earth metal oxide can be an alkaline earth metal mineral material containing alkaline earth metal elements such as calcium and magnesium; alkali metal oxide can be an alkali metal mineral material containing alkali metal elements such as sodium and lithium; other substances are impurities introduced when introducing mineral materials.

[0050] A mixture of solid materials, including silicon-containing solid minerals, alumina, alkaline earth metal oxides, alkali metal oxides, and other substances, is initially mixed and then subjected to coarse crushing and fine grinding to obtain a mixed material that meets the specified requirements. The solid materials include silicon-containing solid minerals, alumina, alkaline earth metal oxides, alkali metal oxides, and other substances.

[0051] Optionally, the requirement is that the solid particles in the mixture pass through a 300-mesh sieve. Alternatively, the requirement is that the size of the solid particles in the mixture is less than and / or equal to 48 μm.

[0052] S202. The mixed material is granulated by physical granulation or chemical granulation to obtain mineral material particles.

[0053] Granulation is a process of transforming powdered or fine granular materials into larger particles. In this step, it is ensured that the resulting mineral material particles are not a single solid material, but rather a mixture of different solid materials. The mineral material particles must contain at least the following elements: silicon, aluminum, calcium, magnesium, lithium, sodium, and potassium.

[0054] Preferably, the mixed material can be granulated using a physical granulation method. The physical granulation method involves introducing an appropriate amount of liquid substance, physically compacting it, and then feeding it into a low-shear mill for pulverization to prepare precursor particles. The liquid substance includes water and / or ethanol.

[0055] S203. Using a silicon-containing liquid material in the composition, the surface of the mineral material particles is coated and dried to obtain precursor particles.

[0056] Silicon-containing liquid materials can effectively adhere to the surface of mineral particles, achieving surface coating. The coated mineral particles are then dried, allowing the silicon-containing liquid material to form a solid coating layer on the particle surface, ensuring uniform coating and yielding precursor particles.

[0057] Optionally, the maximum particle size of the precursor particles is 50 mesh to 200 mesh. Alternatively, the maximum particle size of the precursor particles is 75 μm to 300 μm.

[0058] S204. The precursor particles are calcined at high temperature to harden their surface and form a silica coating. The inner side of the coating is melt-mixed with the surface of the mineral material particles to form a glassy substance with a microcrystalline structure, thus obtaining a cementing additive.

[0059] The silica coating hardened on the surface of cementing additives increases compressive strength. Simultaneously, during cementing operations, the glassy substances within the additives slowly dissolve at high temperatures, allowing the core mineral particles to react slowly with the hydration products of the cement stone, generating a dense and stable product that enhances the strength of the cement stone, thus improving the stability and durability of the cementing process.

[0060] Optionally, high-temperature calcination includes feeding the precursor particles into a dynamic powder calcination furnace and calcining them at 1200°C to 1500°C for 2 to 4 hours. The high-temperature calcination temperature of 1200°C to 1500°C means that the temperature can be any specific value from 1200°C, 1300°C, 1400°C, and 1500°C, or a range of any two of these values; the high-temperature calcination time can be any specific value from 2 hours, 3 hours, and 4 hours, or a range of any two of these values. It should be noted that the limitations on the time and temperature of high-temperature calcination are primarily to ensure that the precursor particles can form a structure that meets the requirements. If other combinations of time and temperature can also achieve a structure that meets the requirements, then these combinations also fall within the scope of protection of this application.

[0061] A high-temperature resistant and anti-fading additive for well cementing was prepared by coarsely crushing, grinding, and uniformly mixing mineral materials containing silicon, aluminum, calcium, magnesium, lithium, sodium, and potassium, followed by coating the particles with a silicon-containing liquid material and high-temperature calcination in a dynamic powder calcination furnace. This additive is primarily used in the preparation of high-temperature anti-fading cement stone. Due to its surface coating with silica and internal microcrystalline glassy material, it exhibits excellent high-temperature stability during cementing under well conditions of 150–240℃, significantly reducing the reaction rate between the mineral materials and the cement stone, thereby improving the later-stage strength of the cement stone and mitigating the problem of strength degradation at high temperatures.

[0062] The method for preparing cementing additives provided in this application involves finely grinding, granulating, and calcining mineral particles at high temperatures to form a cementing additive with a three-layer structure. This cementing additive can react with cement hydration products, thereby reducing the calcium-silicon ratio of the cement hydration products. This achieves the effect of increasing the strength of cement stone at high temperatures and mitigating the strength degradation of cement stone.

[0063] One embodiment of this application provides a cement slurry for cementing, comprising cementing additives as described in any of the above embodiments, wherein the density of the cement slurry ranges from 1.20 g / cm³ to 2.60 g / cm³. This cement slurry can withstand temperatures up to 240°C.

[0064] Using the above-mentioned additives in cement slurry results in a density between 1.20 and 2.60 g / cm³. This means that the density of the cement slurry can be adjusted according to the actual operational needs, ensuring its fluidity and improving its applicability.

[0065] This application has at least the following beneficial effects:

[0066] (1) Except for water glass or silica sol and other silicon-containing liquid materials which are industrial materials, the rest are mineral materials. This increases the added value of mineral materials and has advantages such as environmental protection, safety, wide availability and low cost.

[0067] (2) The precursor particles of different mineral materials are coated with silicon-containing liquid materials, which has the advantages of simple process and low cost.

[0068] (3) The cementing additive material contains 40-60% silica, 20-40% alumina, 2-10% alkaline earth metal oxides, 2-10% alkali metal oxides, and 0-5% other substances. This additive material uses silica and mineral materials fused together as an outer shell, with mineral particles forming the core. This significantly improves the material's stability at high temperatures while greatly reducing the reaction rate between the cementing additive and cement stone, thereby increasing the long-term strength of the cement stone at high temperatures. Furthermore, the structure of the cementing additive enhances the later-stage strength of the cement stone, thus solving the problem of strength degradation of the cement stone at high temperatures.

[0069] To better understand the exemplary embodiments of the additive preparation method described above, further explanation is provided below with specific examples. These examples should not be construed as limiting the scope of this application.

[0070] Table 1. Mass fraction of each component in Examples 1-4

[0071]

[0072] Table 1 shows the mass fraction of each component in the preparation method embodiments of the cementing additives provided in this application. As shown in Table 1, this application provides the component masses of four different cementing additive preparation method embodiments: Formula 1, Formula 2, Formula 3, and Formula 4. The main chemical components of the cementing additives are 40-60% silicon dioxide, 20-40% aluminum oxide, 2-10% alkaline earth metal oxides, 2-10% alkali metal oxides, and 0-5% other substances. The specific preparation process of each cementing additive preparation method embodiment will be described in detail below.

[0073] Example 1: Preparation method of cementing additives

[0074] (1) Weigh the materials according to Formula 1 in Table 1, select solid materials other than water glass in the components and perform coarse crushing and fine grinding to obtain a uniform mixed material that can pass through a 300-mesh standard sieve.

[0075] (2) Next, physical granulation is used for granulation. Weigh out 5% water, which is the same as the total mass of the mixed materials. Add water to the mixed materials and mix evenly. Then compact the mixed materials and dry them at 80°C. Send the dried lumps to a low-shear mill for crushing to obtain mineral material particles that can pass through a 120-mesh standard sieve.

[0076] (3) Then, the mineral material particles are coated with weighed water glass and dried at 120°C to obtain precursor particles.

[0077] (4) Finally, the precursor particles are fed into a powder dynamic calcination furnace and subjected to high dynamic calcination at 1500℃ for 4 hours to harden the surface of the precursor particles and form a silica coating film containing microcrystalline structure. At the same time, the inner side of the silica coating film is fully melted and mixed with the surface of the mineral material particles to form a molten shell of silica and mineral material with a core of mineral material particles, thus obtaining cementing additive 1.

[0078] The cementing additive 1 prepared by the above preparation method can pass through a standard sieve of up to 100 mesh, has a compressive strength of 50 MPa, and a density of 1.8 g / cm3.

[0079] Example 2: Preparation method of cementing additives

[0080] (1) Weigh the materials according to Formula 2 in Table 1, select the solid materials other than silica sol in the components and perform coarse crushing and fine grinding to obtain a uniform mixed material that can pass through a 300-mesh standard sieve.

[0081] (2) Next, granulation is carried out by physical granulation. Weigh anhydrous ethanol equal to 5% of the total mass of the mixed materials. Add water to the mixed materials and mix evenly, then compact the mixture. The compacted mixed materials are then dried at 90°C. The dried lumps are then fed into a low-shear mill for pulverization to obtain mineral material particles that can pass through a 150-mesh standard sieve.

[0082] (3) Then, the mineral material particles are coated with weighed water glass and dried at 110°C to obtain precursor particles.

[0083] (4) Finally, the precursor particles are fed into a powder dynamic calcination furnace and subjected to high dynamic calcination at 1450℃ for 3.2 hours to harden the surface of the precursor particles and form a silica coating film containing microcrystalline structure. At the same time, the inner side of the silica coating film is fully melted and mixed with the surface of the mineral material particles to form a molten shell of silica and mineral material with a core of mineral material particles, thus obtaining cementing additive 2.

[0084] The cementing additive 2 prepared by the above preparation method can pass through a standard sieve of up to 120 mesh, has a compressive strength of 70 MPa, and a density of 2.2 g / cm3.

[0085] Example 3: Preparation method of cementing additives

[0086] (1) Weigh the materials according to Formula 3 in Table 1, select the solid materials other than silica sol in the components and perform coarse crushing and fine grinding to obtain a uniform mixed material that can pass through a 300-mesh standard sieve.

[0087] (2) Next, granulation is carried out by physical granulation. Weigh anhydrous ethanol equal to 3% of the total mass of the mixed materials. Add water to the mixed materials and mix evenly, then compact the mixture. The compacted mixed materials are then dried at 90°C. The dried lumps are then fed into a low-shear mill for pulverization to obtain mineral material particles that can pass through a 200-mesh standard sieve.

[0088] (3) Then, the mineral material particles are coated with weighed water glass and dried at 110°C to obtain precursor particles.

[0089] (4) Finally, the precursor particles are fed into a powder dynamic calcination furnace and subjected to high dynamic calcination at 1400℃ for 2.8h, so that the surface of the precursor particles hardens to form a silica coating film containing microcrystalline structure; at the same time, the inner side of the silica coating film is fully melted and mixed with the surface of the mineral material particles to form a molten shell of silica and mineral material, with the core being mineral material particles, thus obtaining cementing additive 3.

[0090] The cementing additive 3 prepared by the above preparation method can pass through a standard sieve of up to 180 mesh, has a compressive strength of 90 MPa, and a density of 2.4 g / cm3.

[0091] Example 4 of the preparation method of cementing additives

[0092] (1) Weigh the materials according to Formula 4 in Table 1, select the solid materials other than silica sol in the components and perform coarse crushing and fine grinding to obtain a uniform mixed material that can pass through a 300-mesh standard sieve.

[0093] (2) Next, granulation is carried out by physical granulation. Weigh out 3% of the total mass of the mixed materials with distilled water. Add water to the mixed materials and mix evenly. Then compact the mixed materials and dry them at 100°C. The dried lumps are then fed into a low-shear mill for crushing to obtain mineral material particles that can pass through a 240-mesh standard sieve.

[0094] (3) Then, the mineral material particles are coated with weighed water glass and dried at 110°C to obtain precursor particles.

[0095] (4) Finally, the precursor particles are fed into a powder dynamic calcination furnace and subjected to high dynamic calcination at 1300℃ for 2.5h, so that the surface of the precursor particles hardens to form a silica coating film containing microcrystalline structure; at the same time, the inner side of the silica coating film is fully melted and mixed with the surface of the mineral material particles to form a molten shell of silica and mineral material, with the core being mineral material particles, thus obtaining cementing additive 4.

[0096] The cementing additive 4 prepared by the above preparation method can pass through a 200-mesh standard sieve, has a compressive strength of 100 MPa, and a density of 2.6 g / cm3.

[0097] The cementing additives prepared by the various components, upper and lower limits of process parameters, and range values ​​involved in this application can all achieve the technical effects of this application, and will not be listed one by one here.

[0098] To verify the effectiveness of the technical solution of this application, experiments were conducted in accordance with the national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells" to evaluate the thickening performance, fluidity, API water loss, free water content, stability and compressive strength of the cement slurry constructed with the prepared cementing additive.

[0099] The main experimental instruments used included: a 0-60 type corrugated stirrer and an 8240 type high-temperature and high-pressure thickener (from CHANDLER, USA); and an HH-420 type constant temperature digital display water tank (from Changzhou Yineng Experimental Instrument Factory). The oil well cement used was high sulfate-resistant (HSR) grade G oil well cement (from Jiahua Special Cement Co., Ltd.); and the experimental water was distilled water.

[0100] Those skilled in the art should understand that the test data provided in this application are for reference only and do not completely limit or guarantee that the reproduced experimental results will be completely consistent with them. The reproducibility of experimental results may be affected by a variety of factors, including experimental conditions, operating methods, and minor changes in the external environment.

[0101] The experimental parameters for the cement slurry formulations in the comparative and examples conducted in this application, set by weight percentage, are as follows:

[0102] Comparative Example 1:

[0103] 100 parts of Grade G oil well cement, 50 parts of strength stabilizer, 2.5 parts of suspension stabilizer, 2 parts of retarder, 4 parts of fluid loss reducer, 1.2 parts of dispersant, 0.2 parts of defoamer, and 51 parts of water were used. The experimental results are shown in Table 2.

[0104] Comparative Example 2:

[0105] 100 parts Grade G oil well cement, 50 parts strength stabilizer, 3 parts suspension stabilizer, 2.5 parts retarder, 4.5 parts fluid loss reducer, 1.2 parts dispersant, 0.2 parts defoamer, and 51 parts water.

[0106] Comparative Example 3:

[0107] 100 parts Grade G oil well cement, 50 parts strength stabilizer, 3 parts suspension stabilizer, 3 parts retarder, 4.5 parts fluid loss reducer, 1.2 parts dispersant, 0.2 parts defoamer, and 51 parts water.

[0108] Example 1:

[0109] 100 parts Grade G oil well cement, 20 parts cementing additive, 50 parts strength stabilizer, 2.5 parts suspension stabilizer, 2 parts retarder, 4 parts fluid loss reducer, 1.2 parts dispersant, 0.2 parts defoamer, and 58 parts water.

[0110] Example 2:

[0111] 100 parts Grade G oil well cement, 25 parts cementing additives, 30 parts strength stabilizer, 35 parts density regulator, 4.5 parts suspension stabilizer, 2.5 parts retarder, 6 parts fluid loss reducer, 1 part dispersant, 0.2 parts defoamer, and 115 parts water.

[0112] Example 3:

[0113] 100 parts Grade G oil well cement, 27 parts cementing additives, 50 parts strength stabilizer, 3 parts suspension stabilizer, 2.7 parts retarder, 3.2 parts fluid loss reducer, 1.2 parts dispersant, 0.2 parts defoamer, and 58 parts water.

[0114] Example 4:

[0115] 100 parts Grade G oil well cement, 30 parts cementing additives, 4.5 parts strength stabilizer, 140 parts density regulator, 5.5 parts suspension stabilizer, 2.9 parts retarder, 4.5 parts fluid loss reducer, 1.5 parts dispersant, 0.2 parts defoamer, and 96 parts water.

[0116] Example 5:

[0117] 100 parts Grade G oil well cement, 35 parts cementing additives, 50 parts strength stabilizer, 4.5 parts suspension stabilizer, 3.2 parts retarder, 5.5 parts fluid loss reducer, 1.5 parts dispersant, 0.2 parts defoamer, and 58 parts water.

[0118] Table 2 shows the experimental test results of the comparative examples and embodiments of this application. As shown in Table 2, the comparative examples and embodiments of this application were tested under different environments. Specifically, the test temperature for comparative example 1 was 150°C, the test temperature for comparative example 2 was 200°C, the test temperature for comparative example 3 was 240°C, the test temperature for embodiment 1 was 150°C, the test temperature for embodiment 2 was 180°C, the test temperature for embodiment 3 was 200°C, the test temperature for embodiment 4 was 220°C, and the test temperature for embodiment 5 was 240°C.

[0119] The flowability of Examples 1, 2, 3, 4 and 5 is greater than 22 cm; the API water loss is less than 50 mL; the free water content is 0; at the same time, the 7-day compressive strength of the conventional density and high / low density systems of all examples is greater than 35 MPa; indicating that the cement slurry for cementing can meet the requirements of cementing construction at least in the temperature range of 150℃ to 240℃.

[0120] As shown in Table 2, the flowability of cement slurry corresponding to Comparative Example 1, Comparative Example 2, and Comparative Example 3 is less than 21, while the flowability of cement slurry corresponding to Example 1, Example 2, Example 3, Example 4, and Example 5 is greater than 22. This indicates that the addition of cementing additives can increase the flowability of cement slurry, confirming that cementing additives can play a "ball bearing" lubricating role, reduce the flow friction resistance of cement slurry, and improve the flow performance of cement slurry, thus exhibiting the effect of reducing friction and resistance.

[0121] Table 2. Experimental test results for comparative examples and embodiments.

[0122]

[0123] The thickening linearity of Comparative Example 2 showed a "bulging" phenomenon, while that of Comparative Example 3 showed a "stepping" phenomenon, indicating that the consistency of the cement slurry corresponding to Comparative Examples 2 and 3 fluctuated abnormally, and their thickening performance was unstable. However, the thickening times of Examples 1, 2, 3, 4, and 5 varied under different experimental temperatures, and the thickening linearity of all examples remained normal. This indicates that the cement slurry with added cementing additives can have its thickening time adjusted, resulting in a cement slurry with relatively stable thickening performance.

[0124] The compressive strength test results of the cement stone show that: Comparative Example 1 has a 7-day compressive strength of 35 MPa and a 90-day compressive strength of 25.1 MPa, with a strength degradation of 28.29%; Comparative Example 2 has a 7-day compressive strength of 30 MPa and a 90-day compressive strength of 14.7 MPa, with a strength degradation of 51%; Comparative Example 3 has a 7-day compressive strength of 25 MPa and a 90-day compressive strength of 12.6 MPa, with a strength degradation of 49.6%. The 90-day compressive strength of the comparative examples is less than 35 MPa, and the strength degradation is significant. In contrast, the strength degradation of Examples 1, 2, 3, 4, and 5 is less than 10% at 90 days, and the 90-day strength value of the cement stone for each example is greater than 35 MPa. This indicates that the cement slurry using cementing additives has superior strength and can prevent strength degradation. This confirms that cementing additives can maintain the long-term strength stability of cement, achieving the effect of long-term prevention of cement stone strength degradation.

[0125] Furthermore, the test temperature for Example 1 was 150°C, and the amount of cementing additive added was 20 parts; the test temperature for Example 2 was 180°C, and the amount of cementing additive added was 25 parts; the test temperature for Example 3 was 200°C, and the amount of cementing additive added was 27 parts; the test temperature for Example 4 was 220°C, and the amount of cementing additive added was 30 parts; and the test temperature for Example 5 was 240°C, and the amount of cementing additive added was 35 parts. This demonstrates that as the test temperature of the cement paste gradually increases, increasing the dosage of the cementing additive can still effectively suppress the strength degradation of the cement paste. Simultaneously, increasing the dosage of the cementing additive has almost no impact on the fluidity of the cement slurry, exhibiting excellent characteristics in reducing friction and inhibiting strength degradation.

[0126] Therefore, the cement slurry for cementing constructed based on a cementing additive has a density between 1.20 g / cm³ and 2.60 g / cm³, a compressive strength greater than 35 MPa after 7 days, and a strength degradation of no more than 10% after 90 days of curing with a strength value greater than 35 MPa. The optimal applicable temperature can reach 240℃. It can improve the rheological properties of cement slurry at high temperatures, avoid "bulging" and "stepping" in the thickening curve, and effectively solve the problems of poor fluidity and strength degradation of cement slurry under conditions of 150℃~240℃. The thickening time of the cement slurry has a good linear relationship with temperature and density. It can ensure the safety of cementing construction in deep wells, ultra-deep wells and / or ultra-high temperature deep wells, improve the sealing quality of the cement sheath interface and the integrity of long-term sealing, and is of great significance for improving cementing quality.

[0127] The embodiments described above are merely illustrative of implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0128] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0129] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

[0130] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, they should also be regarded as the content disclosed in this application.

[0131] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A cementing additive, characterized in that, The surface of the additive is coated with a silica coating film, and the core of the additive is a mineral material particle. The inner side of the coating film is melt-mixed with the surface of the mineral material particle to form a glassy substance with a microcrystalline structure.

2. The cementing additive according to claim 1, characterized in that, The additive is in the form of regular spherical particles.

3. The cementing additive according to claim 1 or 2, characterized in that, The additive has a maximum particle size of 50-200 mesh, a compressive strength of 50-100 MPa, and a density of 1.8 g / cm³-2.6 g / cm³.

4. The cementing additive according to claim 1 or 2, characterized in that, The maximum particle size of the mineral material is 60 mesh to 240 mesh.

5. A method for preparing a cementing additive, characterized in that, The method for preparing the cementing additive as described in any one of claims 1 to 4 comprises: The solid materials in the components are finely ground to the set requirements to obtain a uniform mixture. The mixed material is granulated using physical granulation or chemical granulation to obtain mineral material particles; The mineral material particles were coated with a silicon-containing liquid material and then dried to obtain precursor particles. The precursor particles are calcined at high temperature to harden their surface and form a silica coating. The inner side of the coating is melt-mixed with the surface of the mineral material particles to form a glassy substance with a microcrystalline structure, thus obtaining the cementing additive.

6. The preparation method according to claim 5, characterized in that, The content of the components is: 40-60% silicon dioxide, 20-40% aluminum oxide, 2-10% alkaline earth metal oxides, 2-10% alkali metal oxides and 0-5% other substances; Of the 40-60% silica, 50% is a silicon-containing liquid material and the other 50% is a silicon-containing solid mineral material.

7. The preparation method according to claim 5 or 6, characterized in that, The specified requirements are that the solid particles in the mixed material pass through a 300-mesh sieve, and / or the maximum particle size of the precursor particles is 50-200 mesh.

8. The preparation method according to claim 5 or 6, characterized in that, The high-temperature calcination involves feeding the precursor particles into a dynamic powder calcination furnace and calcining them at 1200℃~1500℃ for 2 to 4 hours.

9. The preparation method according to claim 5 or 6, characterized in that, The physical granulation method includes introducing an appropriate amount of liquid substance, physically compacting it, and then feeding it into a low-shear mill for pulverization to prepare precursor particles. The liquid substance includes water and / or ethanol.

10. A cement slurry for cementing wells, characterized in that, The cementing additives include those described in any one of claims 1 to 7, wherein the density of the cement slurry is in the range of 1.20 g / cm3 to 2.60 g / cm3.

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