Preparation method of spherical manganous-manganic oxide particles for well drilling or well cementation

Abstract

The invention discloses a preparation method of spherical manganous-manganic oxide particles for well drilling or well cementation, which is characterized in that manganese nitrate and manganese acetate are compounded to realize the coupling of rapid oxidation and mild decomposition, effectively inhibit shell burst and hollow structure and improve the density and integrity of the particles; the introduced polyvinyl alcohol and citric acid can make the fog drop drying process more stable, and the problems of carbon residues and impure phases caused by a traditional surfactant are avoided. Furthermore, a three-stage spray pyrolysis method is adopted, stable evaporation, rapid phase formation and low-temperature curing of the solvent are achieved, and the problems of agglomeration, secondary sintering and insufficient crystal form development in the prior art are solved. The prepared spherical manganous-manganic oxide particles are concentrated in particle size, high in density and good in sphericity degree, can effectively reduce the viscosity of cement paste and reduce the settlement risk, have excellent suspension stability and flowability, are suitable for weighting requirements of high-density oil well cement paste and drilling fluid, and have wide application prospects in oil and gas drilling and well cementation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield drilling and cementing, in particular to a preparation method of spherical manganese tetroxide particles for drilling or cementing. BACKGROUND

[0002] In the oil and gas drilling and cementing engineering, in order to maintain the bottom hole pressure balance, prevent blowout and well wall collapse, it is usually necessary to add high-density weighting agent in the drilling fluid or cementing cement system. Commonly used weighting materials include barite (BaSO4), hematite (Fe2O3), calcium carbonate (CaCO3) and metal powder, etc. Although these traditional weighting agents have wide sources and low cost, they generally have limited density, non-ideal particle morphology, limited acid and alkali resistance and chemical stability, and poor compatibility with cementing cement systems.

[0003] Spherical manganese tetroxide (Mn3O4) is considered as a high-quality functional material to replace traditional barite and hematite due to its high theoretical density (about 4.8 g / cm 3 , strong chemical stability and excellent wear resistance, which can effectively improve the drilling fluid density control accuracy, enhance the density and mechanical properties of cementing cement stone, and has irreplaceable application potential in deep and ultra-deep oil and gas exploration and development.

[0004] However, the current industrialized preparation process of spherical manganese tetroxide still has many technical bottlenecks, especially in the control of key performance indicators D 90 , density and sphericity, which seriously restricts its large-scale application in oil and gas drilling and cementing engineering. The existing preparation processes mainly include high-temperature calcination method, hydrothermal synthesis method and sol-gel method, but these methods have certain defects respectively.

[0005] In terms of particle size, the high-temperature calcination method prepares the product by high-temperature decomposition of manganese salt precursor. Due to the uneven temperature field distribution in the calcination furnace, the particle growth rate difference is large, and the particle size widening phenomenon occurs. The excessively large D 90 value will lead to the decrease of the dispersion stability of the drilling fluid, and the particles are easy to settle and block the wellbore; at the same time, it will increase the consistency of the cementing slurry and reduce its flow performance, affecting the construction efficiency. Although the hydrothermal synthesis method can refine the particle size to a certain extent, the crystal nucleus growth rate in the reaction system is difficult to accurately control, and agglomerates are easily formed, which requires additional addition of dispersants in actual application, and cannot meet the strict requirements of different well conditions on particle size accuracy.

[0006] In terms of density, the national standard SY / T 5504.7-2024 stipulates that the density of micro-manganese oil well cement weighting agent should be 4.60 g / cm 3 above, while the actual density of the spherical manganese tetroxide prepared by the existing process is 4.2 g / cm 3The density of the spherical trimanganese tetroxide is lower than its theoretical density 4.8 g / cm³, and the core reasons are as follows: firstly, internal pores and lattice defects are prone to be generated in the high-temperature cooling or solution crystallization stage in the preparation process; secondly, the overall density is reduced due to the introduction of impurities such as calcium and silicon caused by insufficient purity of raw materials; and thirdly, it is difficult to completely remove the hydroxyl or water molecules adsorbed on the surface, forming a low-density surface layer. The density reduction of the spherical trimanganese tetroxide will result in that it cannot fully play the weighting function, and the addition amount needs to be increased to achieve the target drilling fluid density, thereby increasing the construction cost and slurry compatibility difficulty.

[0007] For the sphericity, the national standard SY / T 5504.7-2024 stipulates that the sphericity of the micro-manganese oil well cement weighting agent should reach 0.8 or more, and the ideal spherical particles need to have high roundness (ideal sphericity is 1.0) to reduce fluid friction and improve particle flowability, but the trimanganese tetroxide particles prepared by the high-temperature calcination method are mostly irregular blocks or ellipsoidal, and the sphericity is only 0.6-0.75; although the product prepared by the hydrothermal synthesis method is close to spherical, the surface is prone to form protrusions or depressions, and the sphericity is difficult to break through 0.8; due to the uneven interfacial tension in the gel forming process of the sol-gel method, spindle-shaped or polyhedral particles are easily generated, which cannot meet the requirements of oil and gas engineering on particle flowability. Low sphericity particles will significantly increase the apparent viscosity and yield value of the drilling fluid, aggravate the friction torque in the drilling process, and reduce the density of the cement stone, affecting the sealing performance of the wellbore.

[0008] In summary, the defects of the existing spherical trimanganese tetroxide preparation process in D 90 , density and sphericity have become the main obstacles to its large-scale application in oil and gas drilling and cementing engineering. Therefore, it is of great significance to develop a spherical trimanganese tetroxide preparation method that can simultaneously realize D 90 precise control, high density and high sphericity to promote the progress of deep oil and gas exploration and development technology. SUMMARY

[0009] In order to overcome the above-mentioned defects and deficiencies in the prior art, the present application provides a preparation method of spherical trimanganese tetroxide particles for drilling or cementing.

[0010] The first object of the present application is to provide a spherical trimanganese tetroxide particle.

[0011] The second object of the present application is to provide a preparation method of a spherical trimanganese tetroxide particle.

[0012] The third object of the present application is to provide a spherical trimanganese tetroxide particle prepared by the above-mentioned preparation method.

[0013] The fourth object of the present application is to provide the application of the above-mentioned spherical trimanganese tetroxide particle as a weighting agent for oil and gas drilling or a weighting agent for cementing.

[0014] A fifth object of the present application is to provide a high-density cement slurry.

[0015] The present application claims the following: A spherical trimanganese tetroxide particle, wherein the D 90 particle size is 13.5-17.7 μm, the density is 4.5-4.7 g / cm 3 , and the sphericity is ≥0.85.

[0016] Preferably, the D 90 particle size of the spherical trimanganese tetroxide particle is 17.0-17.7 μm, the density is 4.6-4.7 g / cm 3 , and the sphericity is ≥0.85.

[0017] More preferably, the D 90 particle size of the spherical trimanganese tetroxide particle is 17.61 μm, the density is 4.66 g / cm 3 , and the sphericity is 0.89.

[0018] A method for preparing a spherical trimanganese tetroxide particle, comprising the following steps: S1. mixing manganese nitrate, manganese acetate, polyvinyl alcohol, citric acid, ethanol and water to obtain a precursor solution; The mass ratio of the manganese nitrate and the manganese acetate is (80-100):(8-12). S2. performing spray pyrolysis on the precursor solution, wherein the spray pyrolysis comprises three stages performed successively in sequence; In the first stage, the temperature of the spray pyrolysis is 120-260℃, and the holding time is 0.2-1.2 s; this stage is a low-temperature dry decomposition stage, which is used for rapidly evaporating solvents (ethanol and water) and decomposing organic substances, forming a preliminary porous particle structure and a semi-cured shell layer, and avoiding particle melting and agglomeration; In the second stage, the temperature of the spray pyrolysis is 700-800℃, and the holding time is 0.5-2.5 s; this stage is a high-temperature oxidation stage, which is used for promoting the crystal type conversion of manganese oxides (700-800℃ is the preferred window for the phase formation and densification of Mn3O4), and forming spherical particles with high purity and density; In the third stage, the temperature of the spray pyrolysis is less than 200℃, and the temperature is continuously reduced to 23-27℃; in this stage, the gas temperature is reduced to <200℃ within a length of tens of centimeters and is continuously reduced to room temperature (23-27℃), and the purpose is to fix the structure and inhibit agglomeration; rapid cooling can reduce solid-phase sintering and agglomeration at high temperatures, and is helpful to maintaining the sphericity and the integrity of the single particles.

[0019] By employing a unique three-stage spray pyrolysis method, stable solvent evaporation, rapid phase formation, and low-temperature curing are achieved, solving the problems of agglomeration, secondary sintering, and insufficient crystal development in existing technologies.

[0020] Preferably, in the first stage, the spray pyrolysis temperature is 200℃ and the holding time is 0.6 s; In the second stage, the spray pyrolysis temperature is 700℃ and the holding time is 1 s; In the third stage, the spray pyrolysis temperature is 150℃, and then cooled to 23-27℃.

[0021] Preferably, in step S1, the mass ratio of manganese nitrate to manganese acetate is (90-100):(10-12).

[0022] Current technologies generally use manganese nitrate or manganese chloride as the manganese source. During pyrolysis, this easily leads to instantaneous densification of the shell, severe hollowing, particle segregation, and surface roughness. Furthermore, single- or two-temperature-zone pyrolysis results in incomplete phase transformation and wide particle size. In spray pyrolysis for the preparation of manganese tetroxide, manganese sulfate and manganese chloride are typically not used as manganese sources, primarily because their byproduct ions pose a significant hazard to cement and steel systems. Manganese sulfate easily introduces sulfate residues during pyrolysis. Once in cement, these residues react with aluminates to generate excess ettringite, leading to subsequent expansion, strength reduction, and structural cracking. It also triggers sulfate corrosion, compromising the long-term stability of the cement. Manganese chloride introduces chloride ions, which can damage the passivation film of steel in alkaline cement, inducing pitting and stress corrosion, particularly severe in high-temperature, high-pressure oil well environments, posing a significant safety risk. In addition, SO4... 2- and Cl - Manganese nitrate is difficult to completely remove during spray pyrolysis and tends to remain on the particle surface, causing excessive impurities in the product. This invention uses a manganese nitrate-manganese acetate compound system to achieve a coupling of rapid oxidation and mild decomposition, effectively inhibiting shell cracking and hollow structure, improving particle density and integrity, while the byproducts are relatively "clean," reducing adverse effects on cement and steel.

[0023] More preferably, in step S1, the mass ratio of manganese nitrate to manganese acetate is 99.4:11.

[0024] Preferably, in step S1, the mass ratio of polyvinyl alcohol to citric acid is (2-4):(90-125).

[0025] More preferably, in step S1, the mass ratio of polyvinyl alcohol to citric acid is 3.7:119.

[0026] By adding polyvinyl alcohol (PVA) and citric acid to the precursor solution, the solution viscosity and droplet surface tension can be controlled, ensuring uniform atomization and good particle dispersion. During spray pyrolysis, the gases generated by the decomposition of PVA and citric acid are slowly released, forming an internal self-inflating effect that promotes the densification of spherical particles and a smooth surface. PVA and sodium citrate, through a dual control mechanism of "flexible shell + complexation homogenization," make the droplet drying process more stable, avoiding the carbon residue and impurity phase problems associated with traditional surfactants.

[0027] Preferably, in step S1, the mass ratio of ethanol to water is (15-20):(70-75).

[0028] More preferably, in step S1, the mass ratio of ethanol to water is 18:72.

[0029] Ethanol has low surface tension and viscosity, making it easier to atomize into uniform microdroplets, which is beneficial for forming oxide particles with consistent size and high sphericity. Secondly, ethanol has a low boiling point and rapid evaporation, allowing droplets to dry quickly before entering the high-temperature zone, reducing the formation of hollow, collapsed, or shell-broken particles and facilitating the production of dense, spherical manganese tetroxide particles. Thirdly, ethanol acts as a weak reducing agent and fuel during pyrolysis, helping to stabilize the Mn3O4 phase, inhibiting excessive oxidation to Mn2O3, and simultaneously increasing the local temperature for a more complete reaction. Fourthly, the main byproducts of ethanol combustion are CO2 and H2O, without introducing Cl-. - SO4 2- It removes harmful impurities, making it safer for subsequent cement and steel systems.

[0030] Preferably, in step S2, during the spray pyrolysis, the atomization pressure is 0.2–0.5 MPa and the liquid inlet rate is 10–30 mL / min.

[0031] More preferably, in step S2, during the spray pyrolysis, the atomization pressure is 0.3 MPa and the liquid inlet rate is 20 mL / min.

[0032] Preferably, in step S2, the cooling rate is 90–110 °C / s.

[0033] More preferably, in step S2, the cooling rate is 100°C / s.

[0034] Preferably, in step S2, the atmosphere of the spray pyrolysis is air, which is used to regulate the oxidation of manganese tetroxide.

[0035] The above-described preparation method yields spherical manganese tetroxide particles.

[0036] The above-mentioned spherical manganese tetroxide particles are used as weighting agents for oil and gas drilling or cementing.

[0037] A high-density cement slurry containing the aforementioned spherical manganese tetroxide particles.

[0038] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing spherical manganese tetroxide particles for drilling or cementing. The prepared spherical manganese tetroxide particles have a concentrated particle size, high density, good sphericity, and uniform morphology, which can effectively reduce the viscosity of cement slurry and reduce the risk of settling. They also exhibit excellent suspension stability and fluidity, making them suitable for the weighting requirements of high-density oil well cement slurry and drilling fluid. Furthermore, the preparation method of this invention has advantages such as high process yield, less exhaust gas, lower environmental impact, and less wear on drilling tools and casing, showing broad application prospects in oil and gas drilling and cementing. Attached Figure Description

[0039] Figure 1 The morphology of the spherical manganese tetroxide particles prepared in Example 2 is shown. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0041] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0042] Example 1: A method for preparing spherical manganese tetroxide particles This embodiment provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis, including the following steps: S1. Mix 72 parts by weight of water, 18 parts by weight of ethanol, 0.03 parts by weight of polyvinyl alcohol, 0.97 parts by weight of citric acid, 8.1 parts by weight of manganese nitrate and 0.9 parts by weight of manganese acetate evenly to obtain a precursor solution; S2. The precursor solution was subjected to spray pyrolysis under the following conditions: atomization pressure 0.3 MPa, injection rate 20 mL / min; pyrolysis was carried out sequentially in three stages: the first stage at 200℃ for 0.6 s; the second stage at 700℃ for 1 s; and the third stage at 150℃, cooled to room temperature at a rate of 100℃ / s; the pyrolysis atmosphere was air. After spray pyrolysis, spherical manganese tetroxide particles were obtained.

[0043] Example 2: A method for preparing spherical manganese tetroxide particles This embodiment provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis, including the following steps: S1. Mix 72 parts by weight of water, 18 parts by weight of ethanol, 0.037 parts by weight of polyvinyl alcohol, 1.19 parts by weight of citric acid, 9.94 parts by weight of manganese nitrate and 1.1 parts by weight of manganese acetate evenly to obtain a precursor solution; S2. The precursor solution was subjected to spray pyrolysis under the following conditions: atomization pressure 0.3 MPa, injection rate 20 mL / min; pyrolysis was carried out sequentially in three stages: the first stage at 200℃ for 0.6 s; the second stage at 700℃ for 1 s; and the third stage at 150℃, cooled to room temperature at a rate of 100℃ / s; the pyrolysis atmosphere was air. After spray pyrolysis, spherical manganese tetroxide particles were obtained.

[0044] Example 3: A method for preparing spherical manganese tetroxide particles This embodiment provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis, including the following steps: S1. Mix 70 parts by weight of water, 15 parts by weight of ethanol, 0.02 parts by weight of polyvinyl alcohol, 0.90 parts by weight of citric acid, 8 parts by weight of manganese nitrate and 0.8 parts by weight of manganese acetate evenly to obtain a precursor solution; S2. The precursor solution was subjected to spray pyrolysis under the following conditions: atomization pressure 0.2 MPa, injection rate 10 mL / min; pyrolysis was carried out sequentially in three stages: the first stage at 120℃ for 0.2 s; the second stage at 700℃ for 0.5 s; and the third stage at 170℃, cooled to room temperature at a rate of 90℃ / s; the pyrolysis atmosphere was air. After spray pyrolysis, spherical manganese tetroxide particles were obtained.

[0045] Example 4: A method for preparing spherical manganese tetroxide particles This embodiment provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis, including the following steps: S1. Mix 75 parts by weight of water, 20 parts by weight of ethanol, 0.04 parts by weight of polyvinyl alcohol, 1.25 parts by weight of citric acid, 10 parts by weight of manganese nitrate and 1.2 parts by weight of manganese acetate evenly to obtain a precursor solution; S2. The precursor solution was subjected to spray pyrolysis under the following conditions: atomization pressure 0.5 MPa, injection rate 30 mL / min; pyrolysis was carried out sequentially in three stages: the first stage at 260℃ for 1.2 s; the second stage at 800℃ for 2.5 s; and the third stage at 140℃, cooled to room temperature at a rate of 110℃ / s; the pyrolysis atmosphere was air. After spray pyrolysis, spherical manganese tetroxide particles were obtained.

[0046] Comparative Example 1 This comparative example provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis, according to Example 1. The difference is that in step S1, the amount of manganese nitrate added is 7.2 parts by weight and the amount of manganese acetate added is 1.8 parts by weight.

[0047] Comparative Example 2 This comparative example provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis, with the difference being that in step S1, the amount of polyvinyl alcohol added is 0.024 parts by weight, the amount of citric acid added is 0.76 parts by weight, the amount of manganese nitrate added is 6.69 parts by weight, and the amount of manganese acetate added is 0.35 parts by weight.

[0048] Comparative Example 3 This comparative example provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis according to Example 2. The difference is that in step S1, the amount of manganese nitrate added is 11.2 parts by weight and the amount of manganese acetate added is 1.98 parts by weight.

[0049] Comparative Example 4 This comparative example provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis according to Example 2, the difference being that in step S2, the temperature of the second stage of pyrolysis is 600°C.

[0050] Comparative Example 5 This comparative example provides a method for preparing spherical manganese tetroxide particles based on spray pyrolysis according to Example 2, the difference being that in step S2, the temperature of the second stage of pyrolysis is 900°C.

[0051] Example 5: Effects of different preparation methods on spherical manganese tetroxide particles D 90 Influence of particle size, density and sphericity I. Experimental Methods The spherical manganese tetroxide particles prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to D... 90 The specific testing steps for particle size, density, and sphericity are as follows: 1. D90 Particle size detection D-values ​​of spherical manganese tetroxide particles were determined using a laser particle size analyzer. 90 First, disperse the powder in water, then gradually inject the sample under cyclic dispersion to ensure the transmittance is within a suitable range; set the sample refractive index and absorbance coefficient, start the measurement, and repeat the test 2-3 times to obtain the average value. The instrument obtains the particle size distribution curve based on light scattering inversion, and then obtains D. 90 Particle size value.

[0052] 2. Density detection Density was determined using a helium hydrometer: the sample was thoroughly dried at approximately 105°C and cooled to room temperature before being weighed and placed in a sealed sample cup. The instrument was repeatedly filled and released with helium, and the volume occupied by the sample was calculated through gas displacement. The density was then obtained by dividing the mass by the volume.

[0053] 3. Sphericity Detection Sphericity was obtained through SEM combined with image analysis: powder was evenly sprinkled on conductive adhesive and gold was sprayed to improve imaging quality. A sufficient number of particle images were randomly taken at an appropriate magnification. Then, ImageJ software was used to outline the particle contours and automatically calculate the sphericity. The closer the value is to 1, the closer it is to a sphere. Finally, the average value of the results for multiple particles was used for evaluation.

[0054] II. Experimental Results D of the spherical manganese tetroxide particles prepared in Examples 1-4 and Comparative Examples 1-5 90 Particle size, density, and sphericity are shown in Table 1. In comparison, the spherical manganese tetroxide particles of Examples 1-4, compared to the comparative examples, showed better particle size distribution at D... 90 The particle size, sphericity, and density are well controlled, and its D 90 The particle size was controlled between 13.54 and 17.61 μm, and the density was controlled between 4.51 and 4.66 g / cm³. 3 sphericity ≥ 0.85.

[0055] Although the spherical manganese tetroxide particles in Comparative Example 1 had the best sphericity, their density was too low, which was not conducive to increasing the specific gravity of the cement slurry. The spherical manganese tetroxide particles in Comparative Example 2 had too fine a particle size and poor morphology, which would lead to a higher viscosity of the slurry. The spherical manganese tetroxide particles in Comparative Example 3 had too large a particle size and insufficient density, which made them prone to settling. The spherical manganese tetroxide particles in Comparative Example 4 had insufficient density, resulting in a poor weighting effect. The spherical manganese tetroxide particles in Comparative Example 5 had poor sphericity, resulting in greater frictional resistance, which would easily wear down the drilling tools and oil casing.

[0056] Considering overall engineering adaptability, rheological control, and economy, the spherical manganese tetroxide particles of Example 2 ( Figure 1Spherical manganese oxide particles are best suited as high-performance weighting materials for oil well cement and drilling fluid systems. These spherical manganese tetroxide particles have a high density (4.66 g / cm³). 3 With its moderate particle size (D90≈17.61 μm) and good sphericity (0.89), it can achieve high weighting efficiency, low viscosity increase, good flowability and suspension stability in the application of weighting agents.

[0057] Table 1 Properties of spherical manganese tetroxide particles

[0058] Example 6: Effect of spherical manganese tetroxide particles prepared by different methods on the properties of high-density cement paste when used as a weighting agent. I. Experimental Methods The spherical manganese tetroxide particles prepared in Examples 1-4 and Comparative Examples 1-5 were used as weighting agents to prepare 2.1 g / cm³ weights of manganese tetroxide particles according to the national standard GB / T19139-2012 "Test Methods for Oil Well Cement". 3 High-density cement slurry is composed of cement, defoamer X60L, retarder H40L, water loss reducer G80L, dispersant F45L, weighting agent, and water. The mass ratio of cement, defoamer X60L, retarder H40L, water loss reducer G80L, dispersant F45L, weighting agent, and water is 100:0.5:1.5:6:2:40:43. Defoamer X60L, retarder H40L, water loss reducer G80L, and dispersant F45L are added to water and stirred at 4200 r / min until homogeneous. Then, the weighting agent and cement are added and stirred at 4200 r / min until homogeneous to obtain the high-density cement slurry.

[0059] The density, rheological properties, and settling stability of high-density cement slurries prepared with different weighting agents were tested according to GB / T19139-2012 "Test Methods for Oil Well Cement". The specific steps are as follows: The prepared high-density cement slurry was cured in a 90℃ atmospheric pressure thickener for 20 min, and its rheological properties were then tested using a six-rotation viscometer (rotation speeds of 3, 6, 100, 200, and 300 r / min).

[0060] The prepared high-density cement slurry was poured into a 250 mL graduated cylinder to full volume. The graduated cylinder was then sealed with a film to prevent moisture evaporation. After standing for 2 hours, the presence of a water layer was observed, and the density of the high-density cement slurry was measured to test its settling stability.

[0061] II. Experimental Results The density, rheological properties, and sedimentation stability of the high-density cement slurries prepared using the spherical manganese tetroxide particles obtained in Examples 1-2 and Comparative Examples 1-5 as weighting agents are shown in Table 2. From the experimental results, the high-density cement slurry prepared in Example 2 exhibits the best overall performance in terms of density, viscosity readings, and sedimentation stability. This high-density cement slurry maintains good fluidity in the medium-to-high shear zone, while also showing a reduced tendency for stratification, indicating that it combines good pumpability and anti-settling performance under high-density conditions, achieving the best overall effect.

[0062] The high-density cement slurry prepared by using the spherical manganese tetroxide particles prepared in Examples 3 and 4 as weighting agents and prepared in the same way was tested for density, rheological properties and sedimentation stability. The results were within the range of density, rheological properties and sedimentation stability of the high-density cement slurry prepared by using the spherical manganese tetroxide particles prepared in Examples 1 and 2 as weighting agents. This shows that the spherical manganese tetroxide particles prepared in Examples 3 and 4 can also have high weighting efficiency, good fluidity and suspension stability.

[0063] Table 2 Performance of High-Density Cement Grout

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A spherical manganese tetroxide particle, characterized in that, The D of the spherical manganese tetroxide particles 90 The particle size is 13.5–17.7 μm, and the density is 4.5–4.7 g / cm³. 3 sphericity ≥ 0.

85.

2. The spherical manganese tetroxide particles according to claim 1, characterized in that, The D of the spherical manganese tetroxide particles 90 The particle size is 17.0–17.7 μm, and the density is 4.6–4.7 g / cm³. 3 sphericity ≥ 0.

85.

3. A method for preparing spherical manganese tetroxide particles, characterized in that, Includes the following steps: S1. Manganese nitrate, manganese acetate, polyvinyl alcohol, citric acid, ethanol and water are mixed to obtain a precursor solution; The mass ratio of manganese nitrate to manganese acetate is (80-100):(8-12). S2. The precursor solution is subjected to spray pyrolysis, wherein the spray pyrolysis comprises three stages performed sequentially. In the first stage, the spray pyrolysis temperature is 120–260℃, and the holding time is 0.2–1.2 s; In the second stage, the spray pyrolysis temperature is 700–800℃, and the holding time is 0.5–2.5 s; In the third stage, the spray pyrolysis temperature is less than 200℃ and then drops to 23-27℃.

4. The preparation method according to claim 3, characterized in that, In step S1, the mass ratio of manganese nitrate to manganese acetate is (90-100):(10-12).

5. The preparation method according to claim 3, characterized in that, In step S1, the mass ratio of polyvinyl alcohol to citric acid is (2-4):(90-125).

6. The preparation method according to claim 3, characterized in that, In step S1, the mass ratio of ethanol to water is (15-20):(70-75).

7. The preparation method according to claim 3, characterized in that, In step S2, the cooling rate is 90-110℃ / s.

8. Spherical manganese tetroxide particles prepared by any one of the preparation methods according to claims 3 to 7.

9. The use of the spherical manganese tetroxide particles according to any one of claims 1 to 2 and / or the spherical manganese tetroxide particles according to claim 8 as a weighting agent for oil and gas drilling or cementing.

10. A high-density cement slurry, characterized in that, It contains spherical manganese tetroxide particles as described in any one of claims 1 to 2 and / or spherical manganese tetroxide particles as described in claim 8.

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