Modified micro-nano spherical trimanganese tetraoxide weighting agent, preparation method thereof and water-based well killing fluid

Abstract

This invention provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, its preparation method, and a water-based kill fluid. The preparation method of the modified micro / nano-sized spherical manganese tetroxide weighting agent of this invention is as follows: activated carbon and manganese salt are contacted, followed by drying, high-temperature calcination, and low-temperature calcination to obtain micro / nano-sized spherical manganese tetroxide; the micro / nano-sized spherical manganese tetroxide is reacted with vinyl sulfonate to obtain a solid initiator; in the presence of an oxidizing agent and a reducing agent, the solid initiator is reacted with alkenylphenol and N-vinylpyrrolidone to obtain the modified micro / nano-sized spherical manganese tetroxide weighting agent. The modified micro / nano-sized spherical manganese tetroxide weighting agent of this invention is prepared by this method. The water-based kill fluid provided by this invention contains this modified micro / nano-sized spherical manganese tetroxide weighting agent. The modified micro / nano-sized spherical manganese tetroxide weighting agent of this invention exhibits excellent dispersion stability, suspension stability, and temperature and salt resistance.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development, specifically to a modified micro-nano spherical manganese tetroxide weighting agent, its preparation method, and a water-based well control fluid. Background Technology

[0002] Currently, with the development of oil and gas well exploration and development, deep and ultra-deep oil and gas resources have become important replacement areas. However, during early development operations, oil and gas wells are prone to anomalies or production stoppages, thus requiring well workover and completion operations to restore production. During well workover operations, kill fluid is needed to provide a certain hydrostatic pressure to prevent well kicks or blowouts. Simultaneously, kill fluid also supports the tubing, prevents wellbore collapse, and ensures the safety of well workover and completion operations. Among these, kill fluid weighting agents can increase the hydrostatic pressure of the kill fluid to meet the requirements of controlling formation fluids during kill fluid operations. Therefore, providing a weighting agent for kill fluids is essential.

[0003] Because high-density kill fluids contain a high proportion of weighting agents, the weighting materials and some drill cuttings are subjected to long-term high shearing and abrasive action from the drill bit under high temperature and pressure, leading to an increase in fine particles in the kill fluid and making its rheological properties extremely difficult to control. Currently, the main methods to improve the rheological properties of kill fluids are dilution with water or viscosity reduction with additives. However, this weakens the structural strength of the kill fluid and its ability to suspend weighting agents such as barite, causes some weighting agents to settle, deteriorates the performance of the kill fluid, and even threatens the safety of well workover operations. In extreme cases, a vicious cycle of "weighting—thickening—viscosity reduction—weighting agent precipitation—density decrease—re-weighting" can occur, inducing complex downhole conditions.

[0004] The density of manganese tetroxide is approximately 4.856 g / cm³. 3 Manganese tetroxide (MnO) can be used to adjust the density of kill fluids. According to Stokes' sedimentation law, the smaller the particle size of a solid, the slower its settling velocity in a solution. When the particle size of solid particles is maintained at the micro-nano level, its suspension stability in the solution is further improved. To improve its dispersibility in kill fluids, most manufacturers mechanically pulverize manganese tetroxide to obtain micron-sized powder. However, compared to spherical particles, irregular solids reduce the lubrication coefficient of the kill fluid to some extent, leading to poorer lubrication performance; at the same time, irregularly shaped solid powders often exhibit poor suspension stability.

[0005] CN112375552A discloses a solids-free, clean, low-damage kill fluid and its preparation method. This solids-free, clean, low-damage kill fluid comprises 1.5-2.5% viscosifier, 0.8-1.2% filtration reducer, 0.05-0.2% inorganic salt crystallization inhibitor, 8-30% weighting agent, 0.5-2% clay stabilizer, and the balance being water. This kill fluid is used for well control during drilling and well workover operations in downhole environments. It exhibits good compatibility with formations, low damage, no pollution, adjustable density, and good fluidity. However, this invention does not involve the development of weighting agent materials; it only involves simple compounding.

[0006] CN107987806B discloses a monovalent salt weighting agent, its preparation method, and its application. This monovalent salt weighting agent comprises the following components in parts by weight: 28-48 parts monovalent organic salt, 4-6 parts industrial salt, 20-33 parts sodium dihydrogen phosphate, 19-32 parts disodium hydrogen phosphate, and 3-5 parts potassium phosphate. Under the synergistic effect of the above-mentioned weight ratio of monovalent organic salt, industrial salt, sodium dihydrogen phosphate, disodium hydrogen phosphate, and potassium phosphate, when used in combination with well-killing fluid, it can achieve a well-killing fluid density of 1.40-1.65 g / cm³. 3 This invention breaks through the upper limit of density in conventional solid-free saturated kill fluids, providing stable pressure to formation fluids and preventing well kicks and blowouts. Furthermore, kill fluids using this weighting agent do not experience precipitation, have low leakage, and do not damage oil reservoirs or clog reservoir pore throats or downhole tools. Moreover, this monovalent salt weighting agent has a simple composition, making it easy to promote and use. However, this invention primarily focuses on the development of solid-free kill fluids. In kill fluids containing solids, inorganic salts can affect the bonding between clay, solid particles, and polymer molecules, thus limiting its applicability.

[0007] CN106335929B discloses a method for preparing manganese tetroxide with micro / nano structures. The method involves adding manganese powder to an alcohol-water mixture, using an ammonium salt as a catalyst, heating to 40-115°C, and stirring for a period of time to obtain white manganese hydroxide. Then, air is bubbled into the manganese hydroxide solution for 2-10 hours, followed by washing, drying, and grinding to obtain the manganese tetroxide product with micro / nano structures. This invention involves reactions carried out at low temperature and normal pressure, resulting in a simple and low-cost preparation process; the prepared manganese tetroxide product has a high specific surface area.

[0008] CN107540022B relates to a method and system for preparing manganese tetroxide. The method involves: introducing micro-nano bubbles into a reaction liquid mixture containing a manganese source to obtain a liquid-gas mixture containing micro-nano bubbles and the reaction liquid mixture; reacting the mixture to obtain manganese tetroxide; wherein the micro-nano bubbles contain an oxidizing gas; and the average valence of manganese in the manganese source is less than 8 / 3. This invention improves the oxidation reaction rate and shortens the oxidation reaction time by introducing micro-nano bubbles containing an oxidizing gas into a reaction system containing a manganese source; it also improves the formation rate of manganese tetroxide, reduces the particle size of manganese tetroxide, improves the integrity of manganese tetroxide crystal development, and reduces crystal defects.

[0009] However, neither CN106335929B nor CN107540022B investigated whether the manganese tetroxide prepared by them could be used as a weighting agent for well control fluid.

[0010] Therefore, how to prepare micro-nano spherical manganese tetroxide weighting agents and overcome the problems of poor dispersion and suspension of existing water-based well control fluid weighting agents under high temperature conditions is the current research focus and challenge. Summary of the Invention

[0011] To address the aforementioned technical problems, the present invention aims to provide a modified micro / nano-sized spherical manganese tetroxide weighting agent, its preparation method, and a water-based well control fluid. The modified micro / nano-sized spherical manganese tetroxide weighting agent provided by the present invention exhibits excellent dispersion stability, suspension stability, and temperature resistance.

[0012] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a modified micro / nano-sized spherical manganese tetroxide weighting agent, comprising the following steps:

[0013] (1) Activated carbon and manganese salt are first contacted in the first solvent, and then dried, calcined at high temperature and calcined at low temperature to obtain micro-nano spherical manganese tetroxide;

[0014] (2) The micro-nano spherical manganese tetroxide and vinyl sulfonate are subjected to a second contact reaction in a second solvent, and after drying, a solid initiator is obtained;

[0015] (3) In the presence of an oxidizing agent and a reducing agent, the solid initiator is reacted with alkenylphenol and N-vinylpyrrolidone in a third solvent to obtain the modified micro-nano spherical manganese tetroxide weighting agent.

[0016] In the above preparation method, preferably, in step (1), the manganese salt includes one or a combination of manganese sulfate, manganese nitrate and potassium permanganate.

[0017] In the above preparation method, preferably, in step (1), the first solvent includes water, such as deionized water or distilled water.

[0018] In the above preparation method, preferably, in step (1), the amount of manganese salt added is 10-30g relative to 100mL of the first solvent; more preferably, the amount of manganese salt added is 15-25g relative to 100mL of the first solvent.

[0019] In the above preparation method, preferably, in step (1), the amount of activated carbon added is 8-12g relative to 100mL of the first solvent, that is, the amount of activated carbon added is 80-120g / L.

[0020] In the above preparation method, preferably, in step (1), the temperature of the first contact is 25-40°C, and the time is 5-8 hours. More preferably, the first contact is a static contact. After the first contact is completed, the product can be subjected to conventional separation steps (e.g., filtration and / or centrifugation) before subsequent drying.

[0021] In the above preparation method, preferably, in step (1), the drying temperature is 40-60℃ and the time is 24-48h.

[0022] In the above preparation method, preferably, in step (1), the conditions for high-temperature calcination are: temperature 800-1000℃, time 5-8h. The high-temperature calcination can be carried out in a muffle furnace.

[0023] In the above preparation method, step (1) may include washing and other steps after high-temperature calcination, that is, the product after high-temperature calcination can be dispersed in water and then separated (e.g., filtered) and then subjected to subsequent low-temperature calcination.

[0024] In the above preparation method, preferably, in step (1), the conditions for low-temperature calcination (i.e., heating) are: temperature 200-300℃, time 5-8h.

[0025] In the above preparation method, preferably, the particle size of the micro-nano spherical manganese tetroxide obtained in step (1) is 500-1000 nm.

[0026] In the above preparation method, preferably, in step (2), the vinyl sulfonate (i.e., the vinyl-containing sulfonate) includes one or a combination of several of sodium 2-acrylamido-2-methylpropanesulfonate, sodium allyl sulfonate, sodium styrene sulfonate and sodium vinyl sulfonate.

[0027] In the above preparation method, preferably, in step (2), the second solvent includes water, such as deionized water or distilled water.

[0028] In the above preparation method, preferably, in step (2), the amount of vinyl sulfonate added relative to 100 mL of the second solvent is 0.05-0.5 mol, more preferably 0.1-0.3 mol.

[0029] In the above preparation method, preferably, in step (2), the amount of the micro-nano spherical manganese tetroxide added is 5-30g relative to 100mL of the second solvent, more preferably 10-20g.

[0030] In the above preparation method, preferably, in step (2), the conditions for the second contact reaction are: reaction temperature 25-40℃, reaction time 5-8h. More preferably, the second contact reaction is carried out under stirring at a stirring speed of 600-1000 r / min. After the second contact reaction is completed, the reaction product can be subjected to conventional separation (e.g., filtration and / or centrifugation), washing, and other steps, followed by subsequent drying.

[0031] In the above preparation method, preferably, in step (2), the drying is freeze drying, and the freeze drying conditions are: liquid nitrogen freezing for 8-12 min, freeze drying (vacuum drying) at -50℃ and 9 Pa for 24-48 h.

[0032] In the above preparation method, preferably, in step (3), the alkenylphenol includes one or a combination of several of 3-vinylphenol, 4-vinylphenol and p-allylphenol.

[0033] In the above preparation method, preferably, in step (3), the third solvent includes water, such as deionized water or distilled water.

[0034] In the above preparation method, preferably, in step (3), the amount of the solid initiator added is 10-20g relative to 100mL of the third solvent.

[0035] In the above preparation method, preferably, in step (3), the amount of alkenylphenol added relative to 100 mL of the third solvent is 0.05-0.5 mol, more preferably 0.1-0.3 mol.

[0036] In the above preparation method, preferably, in step (3), the molar ratio of the alkenylphenol to the N-vinylpyrrolidone is 1:(0.5-1.5), more preferably 1:(0.7-1.3).

[0037] In the above preparation method, preferably, in step (3), the oxidant includes ammonium persulfate and / or potassium persulfate, etc.

[0038] In the above preparation method, preferably, in step (3), the reducing agent includes sodium bisulfite, etc.

[0039] In the above preparation method, preferably, in step (3), the amount of oxidant added is 0.001-0.005 mol relative to 100 mL of the third solvent.

[0040] In the above preparation method, preferably, in step (3), the molar ratio of the oxidant to the reducing agent is 1:(0.5-1.5), more preferably 1:(0.8-1.3).

[0041] In the above preparation method, preferably, in step (3), the conditions for the third contact reaction are: reaction temperature 65-80℃, reaction time 3-6h, and the third contact reaction is carried out under a nitrogen atmosphere. More preferably, the third contact reaction is carried out under stirring at a stirring speed of 600-800 rpm. After the third contact reaction is completed, the reaction product can be subjected to conventional separation (e.g., filtration and / or centrifugation), washing, and other steps. After drying, the modified micro-nano spherical manganese tetroxide weighting agent is obtained.

[0042] In the above preparation method, preferably, in step (3), the drying temperature is 40-60℃ and the time is 24-48h.

[0043] In step (1) of the preparation method of this invention, activated carbon is used as a carrier to contact manganese salt. The manganese salt can be adsorbed and deposited on the surface of the activated carbon, forming micro-nano-sized spherical manganese tetroxide on the activated carbon under high-temperature calcination and agglomerating growth. Furthermore, the activated carbon will be converted into gas under high-temperature calcination, and the activated carbon can be completely removed after low-temperature calcination. Therefore, micro-nano-sized spherical manganese tetroxide with a large specific surface area and excellent adsorption performance is prepared. Using this micro-nano-sized spherical manganese tetroxide as an adsorbent, the reaction in step (2) is carried out, and a large amount of vinyl sulfonate monomer can be adsorbed on its surface. In step (3), vinyl sulfonate monomers, alkenylphenol monomers, and N-vinylpyrrolidone monomers can all undergo polymerization reactions in the presence of both oxidants and reducing agents. Furthermore, the reaction occurs after the C=C double bonds are opened. The resulting polymer coats the surface of micro / nano-sized spherical manganese tetroxide to form a polymer film. The steric hindrance provided by the macromolecular functional groups on the surface effectively prevents the polymers from entangled and adsorbing, thereby improving the suspension stability of the prepared weighting agent. Vinyl sulfonate monomers and alkenylphenol monomers have side chains with significant steric hindrance effects, and the N-vinylpyrrolidone monomer further enhances the branched rigidity of the polymer molecular chains, thus improving the temperature and salt resistance of the prepared weighting agent.

[0044] The second aspect of this invention provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the above-described preparation method.

[0045] According to a specific embodiment of the present invention, preferably, the density of the modified micro / nano-sized spherical manganese tetroxide weighting agent is 4.6-4.8 g / cm³. 3 More preferably, it is 4.75-4.80 g / cm³. 3 .

[0046] According to a specific embodiment of the present invention, preferably, the average particle size of the modified micro-nano spherical manganese tetroxide weighting agent is 500-2000 nm, more preferably 500-900 nm.

[0047] According to a specific embodiment of the present invention, preferably, when the mass concentration of the suspension of the modified micro-nano spherical manganese tetroxide weighting agent is 1% (the solvent in the suspension is water), the absolute value of the Zeta potential of the suspension of the modified micro-nano spherical manganese tetroxide weighting agent is ≥35mV; more preferably, the absolute value of the Zeta potential of the suspension of the modified micro-nano spherical manganese tetroxide weighting agent is ≥38mV.

[0048] The modified micro / nano-sized spherical manganese tetroxide weighting agent provided by this invention consists of micro / nano-sized spherical manganese tetroxide and a polymer layer coated on the micro / nano-sized spherical manganese tetroxide. Using activated carbon as a carrier, this invention prepares micro / nano-sized spherical manganese tetroxide using a soft template method, resulting in excellent sphericity and good suspension stability. This invention uses the prepared micro / nano-sized spherical manganese tetroxide as an excellent adsorbent, reacting on its surface to form a polymer film structure, which improves the suspension stability of the micro / nano-sized spherical manganese tetroxide and inhibits its aggregation. Ultimately, the prepared modified micro / nano-sized spherical manganese tetroxide weighting agent exhibits excellent dispersion stability, suspension stability, and excellent temperature and salt resistance.

[0049] A third aspect of the present invention provides a water-based kill fluid, wherein the water-based kill fluid comprises the above-mentioned modified micro-nano spherical manganese tetroxide weighting agent.

[0050] In the aforementioned water-based kill fluid, preferably, the amount of the modified micro-nano spherical manganese tetroxide weighting agent added to the water-based kill fluid is determined according to the density requirements of the kill fluid, and is calculated according to the formula shown in equation (1):

[0051]

[0052] In the formula:

[0053] W1—Amount of weighting agent added, in grams;

[0054] ρ1—Density of the original kill fluid, g / cm³ 3 ;

[0055] ρ2 — Density of the kill fluid containing weighting agent, g / cm³ 3 ;

[0056] ρ3 — density of the weighting agent, g / cm³ 3 ;

[0057] V1 — Volume of the original kill fluid, mL.

[0058] The original kill fluid is a water-based kill fluid that does not contain weighting agents.

[0059] The water-based kill fluid of the present invention also includes some treatment agents conventionally used in water-based kill fluids. According to a specific embodiment of the present invention, preferably, the water-based kill fluid further includes one or a combination of the following components: high-temperature shale inhibitor, polymer coating agent, high-temperature filtration reducer, lubricant, flow modifier, and high-temperature stabilizer. The high-temperature shale inhibitor, polymer coating agent, high-temperature filtration reducer, lubricant, flow modifier, and high-temperature stabilizer can all be treatment agents conventionally used in water-based kill fluids in the art, and their addition amounts can also be conventional in the art.

[0060] More preferably, based on the total volume of the water-based kill fluid, it comprises the following components: 0.2-1.0 w / v% zwitterionic coating agent FA367, 0.5-3.0 w / v% sulfonated phenolic resin SMP, 0.5-3.0 w / v% sulfonated asphalt DYFT-1, 2.0-3.0 w / v% lubricant 3# white oil, and the modified micro-nano spherical manganese tetroxide weighting agent (the amount of which is calculated by the above formula (1)).

[0061] According to a specific embodiment of the present invention, preferably, the application temperature of the water-based well-killing fluid is 200-220℃.

[0062] In summary, the modified micro / nano spherical manganese tetroxide weighting agent provided by this invention has the following superior technical effects:

[0063] (1) Compared with traditional weighting agents, the modified micro-nano spherical manganese tetroxide weighting agent of the present invention uses certain hydrophobic monomers to increase the repulsive force between weighting agents, prevent the agglomeration of micro-nano manganese tetroxide, and effectively improve the dispersion effect of weighting agents; in addition, the preparation method of micro-nano spherical manganese tetroxide provided by the present invention increases the specific surface area of ​​manganese tetroxide and improves the suspension stability of manganese tetroxide in solvents.

[0064] (2) Compared with traditional weighting agents, the modified micro-nano spherical manganese tetroxide weighting agent of the present invention contains abundant functional groups brought by anionic monomers and hydrophobic monomers, and has excellent resistance to temperature and salt pollution, dispersion stability and suspension stability.

[0065] (3) Compared with traditional weighting agents, the reaction conditions of the modified micro-nano spherical manganese tetroxide weighting agent of the present invention are easy to control, the reaction process is relatively stable, and it is easy to industrialize. Attached Figure Description

[0066] Figure 1a This is a scanning electron microscope image of conventional manganese tetroxide powder;

[0067] Figure 1b Scanning electron microscope image of the modified micro / nano-sized spherical manganese tetroxide weighting agent prepared in Example 1. Detailed Implementation

[0068] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0069] In the following examples, comparative examples, and test cases:

[0070] The manganese salt, vinyl sulfonate, alkenylphenol, and N-vinylpyrrolidone used were all provided by Sinopharm Shanghai Test Group.

[0071] The activated carbon, potassium persulfate, ammonium persulfate, and sodium bisulfite used were all supplied by Aladdin Reagent Co., Ltd.

[0072] The zwitterionic coating agent FA367 used was provided by Chengdu Dedao Industrial Co., Ltd.

[0073] The sulfonated phenolic resin SMP and sulfonated pitch DYFT-1 used were provided by Jining Baiyi Chemical Co., Ltd.

[0074] The No. 3 white oil used was supplied by Jiangsu Yingze Energy Co., Ltd.

[0075] The iron-chromium lignin sulfonate used was provided by Shandong Runwan Chemical Co., Ltd.

[0076] The manganese tetroxide powder used was provided by Lianyungang Chuangya Environmental Protection Technology Co., Ltd.

[0077] The average particle size was measured using a Malvern Zetasizer 3000 potentiometric particle size analyzer; the average density was measured using a Leigh density bottle; and the zeta potential was measured using a Malvern Zetasizer 3000 potentiometric particle size analyzer.

[0078] Example 1

[0079] This embodiment provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the following method:

[0080] (1) Add 50g of manganese sulfate to 200mL of deionized water and stir until completely dissolved to obtain a manganese sulfate solution; add 20g of activated carbon to the manganese sulfate solution, let stand at 40℃ for 8h, filter, and dry at 40℃ for 24h to obtain activated carbon particles adsorbed with manganese sulfate; place the activated carbon particles adsorbed with manganese sulfate in a muffle furnace and calcine at 1000℃ for 8h, then disperse the product in water, filter, and then calcine at 300℃ for 8h to obtain micro-nano spherical manganese tetroxide with an average particle size of 582.8nm;

[0081] (2) Add 137.54 g (0.6 mol) of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) to 200 mL of deionized water to obtain an AMPS solution; add 20 g of micro-nano spherical manganese tetroxide prepared in step (1) to the AMPS solution, react at 25 °C and 1000 rpm for 8 h, filter, freeze in liquid nitrogen for 8 min, and vacuum dry at -50 °C and 9 Pa for 24 h to obtain a solid initiator;

[0082] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 20g of the solid initiator prepared in step (2), 72g (0.6mol) of 3-vinylphenol and 99.9g (0.9mol) of N-vinylpyrrolidone were dispersed in 200mL of deionized water. The temperature was raised to 80℃, and 2.7g (0.01mol) of potassium persulfate and 1.35g (0.013mol) of sodium bisulfite were added in sequence. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 800rpm for 6h. After the reaction was completed, the mixture was filtered, washed and dried at 40℃ for 24 hours to obtain the modified micro-nano spherical manganese tetroxide weighting agent, named NSMT-1 (NanoSpheres of Manganese Tetroxide-1).

[0083] The average particle size of NSMT-1 was measured to be 532.95 nm, and the average density was 4.79 g / cm³. 3 .

[0084] Example 2

[0085] This embodiment provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the following method:

[0086] (1) Add 50g of manganese nitrate to 200mL of deionized water and stir until completely dissolved to obtain a manganese nitrate solution; add 20g of activated carbon to the manganese nitrate solution, let stand at 40℃ for 8h, filter, and dry at 50℃ for 36h to obtain activated carbon particles adsorbed with manganese nitrate; place the activated carbon particles adsorbed with manganese sulfate in a muffle furnace and calcine at 1000℃ for 8h, then disperse the product in water, filter, and then calcine at 250℃ (i.e., heat) for 6.5h to obtain micro-nano spherical manganese tetroxide with an average particle size of 686.3nm;

[0087] (2) Add 57.64 g (0.4 mol) sodium allyl sulfonate to 200 mL of deionized water to obtain sodium allyl sulfonate solution; add 30 g of micro-nano spherical manganese tetroxide prepared in step (1) to the sodium allyl sulfonate solution, react at 40 °C and 1000 rpm for 8 h, filter, freeze in liquid nitrogen for 12 min, and vacuum dry at -50 °C and 9 Pa for 24 h to obtain solid initiator;

[0088] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 30g of the solid initiator prepared in step (2), 48g (0.4mol) of 4-vinylphenol and 44.4g (0.4mol) of N-vinylpyrrolidone were dispersed in 200mL of deionized water. The temperature was raised to 80℃, and 1.37g (0.006mol) of ammonium persulfate and 0.62g (0.006mol) of sodium bisulfite were added in sequence. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 800rpm for 6h. After the reaction was completed, the mixture was filtered, washed and dried at 50℃ for 36 hours to obtain the modified micro-nano spherical manganese tetroxide weighting agent, named NSMT-2 (Nano Spheres of Manganese Tetroxide-2).

[0089] The average particle size of NSMT-2 was measured to be 754.38 nm, and the average density was 4.76 g / cm³. 3 .

[0090] Example 3

[0091] This embodiment provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the following method:

[0092] (1) Add 30g of potassium permanganate to 200mL of deionized water and stir until it is completely dissolved to obtain a potassium permanganate solution; add 20g of activated carbon to the potassium permanganate solution, let it stand at 25℃ for 5h, filter, and dry at 60℃ for 48h to obtain activated carbon particles adsorbed with potassium permanganate; place the activated carbon particles adsorbed with potassium permanganate in a muffle furnace and calcine at 800℃ for 5h, then disperse the product in water, filter, and then calcine at 200℃ for 5h to obtain micro-nano spherical manganese tetroxide with an average particle size of 754.98nm;

[0093] (2) Add 41.2g (0.2mol) sodium styrene sulfonate to 200mL of deionized water to obtain a sodium styrene sulfonate solution; add 40g of micro-nano spherical manganese tetroxide prepared in step (1) to the sodium styrene sulfonate solution, react at 30℃ and 600rpm for 5h, filter, freeze in liquid nitrogen for 8min, and vacuum dry at -50℃ and 9Pa for 48h to obtain a solid initiator;

[0094] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 40g of the solid initiator prepared in step (2), 26.84g (0.2mol) of p-allylphenol and 15.54g (0.14mol) of N-vinylpyrrolidone were dispersed in 200mL of deionized water. The temperature was raised to 65℃, and 2.7g (0.01mol) of potassium persulfate and 1.04g (0.01mol) of sodium bisulfite were added in sequence. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 600rpm for 3h. After the reaction was completed, the mixture was filtered, washed and dried at 60℃ for 48 hours to obtain the modified micro-nano spherical manganese tetroxide weighting agent, named NSMT-3 (Nano Spheres of Manganese Tetroxide-3).

[0095] The average particle size of NSMT-3 was measured to be 879.42 nm, and the average density was 4.75 g / cm³. 3 .

[0096] Example 4

[0097] This embodiment provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the following method:

[0098] (1) Add 20g of manganese nitrate to 200mL of deionized water and stir until completely dissolved to obtain a manganese nitrate solution; add 20g of activated carbon to the manganese nitrate solution, let stand at 37℃ for 5h, filter, and dry at 45℃ for 30h to obtain activated carbon particles adsorbed with manganese nitrate; place the activated carbon particles adsorbed with manganese nitrate in a muffle furnace and calcine at 980℃ for 5h, then disperse the product in water, filter, and then calcine at 300℃ (i.e., heat) for 5.2h to obtain micro-nano spherical manganese tetroxide with an average particle size of 843.86nm;

[0099] (2) Add 13.0 g (0.1 mol) of sodium vinyl sulfonate to 200 mL of deionized water to obtain a sodium vinyl sulfonate solution; add 10 g of the micro-nano spherical manganese tetroxide prepared in step (1) to the sodium vinyl sulfonate solution, react at 28 °C and 1000 rpm for 5.4 h, filter, freeze in liquid nitrogen for 10 min, and vacuum dry at -50 °C and 9 Pa for 24 h to obtain a solid initiator;

[0100] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 24g of the solid initiator prepared in step (2), 12g (0.1mol) of 4-vinylphenol and 16.65g (0.15mol) of N-vinylpyrrolidone were dispersed in 200mL of deionized water. The temperature was raised to 77℃, and 0.54g (0.002mol) of potassium persulfate and 0.104g (0.001mol) of sodium bisulfite were added in sequence. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 750rpm for 4.8h. After the reaction was completed, the mixture was filtered, washed and dried at 45℃ for 30 hours to obtain the modified micro-nano spherical manganese tetroxide weighting agent, named NSMT-4 (Nano Spheres of Manganese Tetroxide-4).

[0101] The average particle size of NSMT-4 was measured to be 1048.28 nm, and the average density was 4.72 g / cm³. 3 .

[0102] Example 5

[0103] This embodiment provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the following method:

[0104] (1) Add 24g of potassium permanganate to 200mL of deionized water and stir until completely dissolved to obtain a potassium permanganate solution; add 20g of activated carbon to the potassium permanganate solution, let stand at 32℃ for 6.4h, filter, and dry at 55℃ for 40 hours to obtain activated carbon particles adsorbed with potassium permanganate; place the activated carbon particles adsorbed with potassium permanganate in a muffle furnace and calcine at 910℃ for 7.5h, then disperse the product in water, filter, and then calcine at 280℃ for 5.8h to obtain micro-nano spherical manganese tetroxide with an average particle size of 796.34nm;

[0105] (2) Add 115.28 g (0.8 mol) sodium allyl sulfonate to 200 mL of deionized water to obtain sodium allyl sulfonate solution; add 20 g of micro-nano spherical manganese tetroxide prepared in step (1) to the sodium allyl sulfonate solution, react at 34 °C and 750 rpm for 6.6 h, filter, freeze in liquid nitrogen for 11 min, and vacuum dry at -50 °C and 9 Pa for 33 h to obtain solid initiator;

[0106] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 33g of the solid initiator prepared in step (2), 79.2g (0.66mol) of 3-vinylphenol and 36.67g (0.33mol) of N-vinylpyrrolidone were dispersed in 200mL of deionized water, heated to 72℃, and 2.16g (0.008mol) of potassium persulfate and 1.25g (0.012mol) of sodium bisulfite were added in sequence. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 680rpm for 3.2h. After the reaction was completed, the mixture was filtered, washed and dried at 55℃ for 40 hours to obtain the modified micro-nano spherical manganese tetroxide weighting agent, named NSMT-5 (Nano Spheres of Manganese Tetroxide-5).

[0107] The average particle size of NSMT-5 was measured to be 1568.73 nm, and the average density was 4.68 g / cm³. 3 .

[0108] Example 6

[0109] This embodiment provides a modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the following method:

[0110] (1) Add 60g of manganese sulfate to 200mL of deionized water and stir until completely dissolved to obtain a manganese sulfate solution; add 20g of activated carbon to the manganese sulfate solution, let stand at 28℃ for 7.2h, filter, and dry at 58℃ for 28 hours to obtain activated carbon particles adsorbed with manganese sulfate; place the activated carbon particles adsorbed with manganese sulfate in a muffle furnace and calcine at 860℃ for 6.5h, then disperse the product in water, filter, and then calcine at 240℃ (i.e., heat) for 7.4h to obtain micro-nano spherical manganese tetroxide with an average particle size of 965.27nm;

[0111] (2) Add 130.09 g (1.0 mol) of sodium vinyl sulfonate to 200 mL of deionized water to obtain a sodium vinyl sulfonate solution; add 60 g of the micro-nano spherical manganese tetroxide prepared in step (1) to the sodium vinyl sulfonate solution, react at 37 °C and 620 rpm for 7.6 h, filter, freeze in liquid nitrogen for 9 min, and vacuum dry at -50 °C and 9 Pa for 32 h to obtain a solid initiator;

[0112] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 38g of the solid initiator prepared in step (2), 134.18g (1mol) of p-allylphenol and 166.5g (1.5mol) of N-vinylpyrrolidone were dispersed in 200mL of deionized water. The temperature was raised to 68℃, and 2.16g (0.008mol) of potassium persulfate and 1.04g (0.01mol) of sodium bisulfite were added in sequence. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 620rpm for 5.4h. After the reaction was completed, the mixture was filtered, washed and dried at 58℃ for 28 hours to obtain the modified micro-nano spherical manganese tetroxide weighting agent, named NSMT-6 (Nano Spheres of Manganese Tetroxide-6).

[0113] The average particle size of NSMT-6 was measured to be 1957.38 nm, and the average density was 4.61 g / cm³. 3 .

[0114] Comparative Example 1

[0115] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1. The difference is that activated carbon is not used in step (1). Other raw materials, amounts, and preparation processes are the same as in Example 1, resulting in weighting agent D-1. Its average particle size was measured to be 32.84 μm, and its average density was 4.72 g / cm³. 3 .

[0116] Comparative Example 2

[0117] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1. The difference is that in step (1), the high-temperature calcination temperature in the muffle furnace is changed to 600°C. Other raw materials, dosages, and preparation processes are the same as in Example 1. Weighting agent D-2 is obtained, and its average particle size is measured to be 48.57 μm and its average density is 3.48 g / cm³. 3 .

[0118] Comparative Example 3

[0119] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1, except that step (2) is omitted, that is, vinyl sulfonate (i.e., sodium 2-acrylamido-2-methylpropanesulfonate in Example 1) is not used. Other raw materials, amounts, and preparation processes are the same as in Example 1, resulting in weighting agent D-3, with an average particle size of 15.84 μm and an average density of 4.72 g / cm³. 3 .

[0120] Comparative Example 4

[0121] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1, except that in step (2), the amount of sodium 2-acrylamide-2-methylpropanesulfonate added is changed to 1.68 g. Other raw materials, dosages, and preparation processes are the same as in Example 1, resulting in weighting agent D-4, with an average particle size of 18.54 μm and an average density of 4.68 g / cm³. 3 .

[0122] Comparative Example 5

[0123] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), the amount of 3-vinylphenol added is changed to 1.76g. Other raw materials, amounts, and preparation processes are the same as in Example 1, resulting in weighting agent D-5. Its average particle size is measured to be 14.28μm and its average density is 4.48g / cm³. 3 .

[0124] Comparative Example 6

[0125] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1, except that in step (3), the amount of N-vinylpyrrolidone added is changed to 0.95g. Other raw materials, amounts, and preparation processes are the same as in Example 1, resulting in weighting agent D-6, with an average particle size of 25.24μm and an average density of 4.19g / cm³. 3 .

[0126] Comparative Example 7

[0127] This comparative example provides a weighting agent prepared by the following method: In a 500 mL three-necked round-bottom flask equipped with a thermometer, a stirring rod, and a nitrogen inlet tube, 20 g of manganese tetroxide powder with a particle size of 20 μm, 72 g (0.6 mol) of 3-vinylphenol, and 99.9 g (0.9 mol) of N-vinylpyrrolidone were dispersed in 200 mL of deionized water. The temperature was raised to 80 °C, and 2.7 g (0.01 mol) of potassium persulfate and 1.35 g (0.013 mol) of sodium bisulfite were added sequentially. The reaction was carried out under a nitrogen atmosphere and a stirring speed of 800 rpm for 6 h. After the reaction was completed, the mixture was filtered, washed, and dried at 58 °C for 34 h to obtain the weighting agent D-7, which had an average particle size of 66.72 μm and an average density of 4.85 g / cm³. 3 .

[0128] Comparative Example 8

[0129] This comparative example provides a weighting agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), 3-vinylphenol is replaced with 0.6 mol of styrene. Other raw materials, amounts, and preparation processes are the same as in Example 1, resulting in weighting agent D8. Its average particle size was measured to be 26.72 μm and its average density to be 4.89 g / cm³. 3 .

[0130] Test Example 1

[0131] Preparation of bentonite-based slurry: Add 16g of sodium-based bentonite for well control fluid (Shandong Huwei Bentonite Co., Ltd.) to 400mL of tap water, stir at 10000r / min for 30min, and let stand in a sealed container for 24h to obtain 4% prehydrated bentonite-based slurry.

[0132] Add 900g of the weighting agent prepared in Examples 1-6 and Comparative Examples 1-8 and the manganese tetroxide powder weighting agent to the bentonite-based slurry prepared above. Stir at 10000r / min for 20min and then put the slurry into an aging tank. Place the aging tank in a high-temperature roller heating furnace and heat it at 220℃ for 16h. After cooling to room temperature, stir at 10000r / min for 10min and then test the slurry settling performance.

[0133] The slurry was left to stand at 25±1℃. The density difference between the upper and lower liquid phases of the slurry was measured using a hydrometer for well control fluid. When the density difference was ≥0.02g / cm³, the density difference was considered acceptable. 3 The time was recorded as the slurry settling instability time. The test results are shown in Table 1.

[0134] Test Example 2

[0135] Bentonite-based slurry was prepared according to the method in Test Example 1. Then, 12g of sulfonated phenolic resin SMP, 1.2g of NaOH, 4g of zwitterionic polymer coating agent FA367, and 900g of manganese tetroxide powder for kill fluid were added sequentially to the bentonite-based slurry to prepare kill fluid-based slurry Z1. Kill fluid-based slurry Z1 was placed in an aging tank, which was then placed in a high-temperature roller heating furnace and hot-rolled at 220℃ for 16 hours. After cooling to room temperature, the slurry was stirred at 10000r / min for 10 minutes. The slurry properties were tested, and the results are shown in Table 2.

[0136] Test Example 3

[0137] Bentonite-based slurry was prepared according to the method in Test Example 1. Then, 12g of sulfonated phenolic resin SMP, 1.2g of NaOH, 4g of zwitterionic polymer coating agent FA367, 27g of iron-chromium lignin sulfonate, and 900g of manganese tetroxide powder for kill fluid were added sequentially to the bentonite-based slurry to prepare kill fluid-based slurry Z2. The kill fluid-based slurry Z2 was placed in an aging tank, which was then placed in a high-temperature roller heating furnace and hot-rolled at 220℃ for 16 hours. After cooling to room temperature, the slurry was stirred at 10000r / min for 10 minutes, and the slurry properties were tested. The results are shown in Table 2.

[0138] Test Example 4

[0139] Bentonite-based slurry was prepared according to the method in Test Example 1. Then, 12g of sulfonated phenolic resin SMP, 1.2g of NaOH, 4g of zwitterionic polymer coating agent FA367, and 900g of NSMT-1 were added sequentially to the bentonite-based slurry to prepare kill fluid-based slurry Z3. The kill fluid-based slurry Z3 was placed in an aging tank, which was then placed in a high-temperature roller heating furnace and hot-rolled at 220℃ for 16 hours. After cooling to room temperature, the slurry was stirred at 10000r / min for 10 minutes. The slurry properties were tested, and the results are shown in Table 2.

[0140] Test Example 5

[0141] Add 4g of the weighting agent NSMT-2 and manganese tetroxide powder prepared in Example 2 to 400mL of tap water, stir at 10000rpm for 20min, and test the zeta potential of the suspension using Malvern Zetasizer 3000. The results are shown in Table 3.

[0142] Test Example 6

[0143] The suspension was prepared according to Test Example 4. 4g of iron-chromium lignin sulfonate was added and stirred at 10000rpm for 20min. The zeta potential of the suspension was tested using a Malvern Zetasizer 3000. The results are shown in Table 3.

[0144] Table 1. Effects of different weighting agents on the settling stability of bentonite slurry after hot rolling at 220℃

[0145] Test sample Settlement instability time / h Base paste + 900g NSMT-1 16.8 Base paste + 900g NSMT-2 13.8 Base paste + 900g NSMT-3 14.2 Base paste + 900g NSMT-4 12.6 Base paste + 900g NSMT-5 11.7 Base paste + 900g NSMT-6 11.2 Base slurry + 900g D-1 3.8 Base slurry + 900g D-2 2.6 Base slurry + 900g D-3 2.9 Base slurry + 900g D-4 3.7 Base slurry + 900g D-5 4.5 Base slurry + 900g D-6 5.2 Base slurry + 900g D-7 6.5 Base slurry + 900g D-8 2.2 Base slurry + 900g manganese tetroxide powder 0.2

[0146] As shown in Table 1, after hot rolling at 220℃, the modified micro-nano spherical manganese tetroxide weighting agent NSMT of this invention maintains slurry stability for a longer time than manganese tetroxide powder. Furthermore, after hot rolling at 220℃, NSMT can maintain the stability of the weighted slurry.

[0147] Scanning electron microscopy (SEM) was performed on both manganese tetroxide powder and the modified micro / nano-sized spherical manganese tetroxide weighting agent prepared in Example 1 of this invention. Figure 1a and Figure 1b It can be seen that the modified micro-nano spherical manganese tetroxide weighting agent prepared in Example 1 of the present invention has good sphericity, reaching the micro-nano level, relatively uniform particle size distribution, and no adhesion between particles.

[0148] Table 2. Effects of different weighting agents on the settling stability of the kill fluid formulation after hot rolling at 220℃

[0149] Test sample Settling time / h Z1 1.6 Z2 4.2 Z3 16.5

[0150] As shown in Table 2, the modified micro-nano spherical manganese tetroxide weighting agent NSMT of this invention can effectively maintain the stability of the formulation. After hot rolling at 220℃, iron-chromium lignin sulfonate can effectively maintain the stability of the slurry, but NSMT can still effectively maintain the settling stability of the slurry without the addition of dispersants, and its performance is superior to that of conventional kill fluid weighting formulations with added dispersants.

[0151] Table 3. Zeta potential test results of suspensions with different weighting agents

[0152]

[0153]

[0154] Table 3 shows that the absolute value of the Zeta potential of the 1% NSMT-2 suspension is greater than 40 mV, indicating that the suspension is in a relatively stable state. The average absolute value of the Zeta potential of the 1% manganese tetroxide powder suspension is -3.24 mV, indicating that the manganese tetroxide powder suspension is in an unstable state. The addition of iron-chromium lignin sulfonate increased the absolute value of the Zeta potential of the suspension, indicating that the dispersant can improve the stability of the suspension.

Claims

1. A method for preparing a modified micro / nano-sized spherical manganese tetroxide weighting agent, comprising the following steps: (1) Activated carbon and manganese salt are first contacted in the first solvent, and then dried, calcined at high temperature and calcined at low temperature to obtain micro-nano spherical manganese tetroxide; (2) The micro-nano spherical manganese tetroxide and vinyl sulfonate are subjected to a second contact reaction in a second solvent, and after drying, a solid initiator is obtained; (3) In the presence of an oxidizing agent and a reducing agent, the solid initiator is reacted with alkenylphenol and N-vinylpyrrolidone in a third solvent to obtain the modified micro-nano spherical manganese tetroxide weighting agent. The high-temperature calcination temperature is 800-1000 ℃; The amount of the micro-nano spherical manganese tetroxide added relative to 100 mL of the second solvent is 5-30 g; The amount of vinyl sulfonate added relative to 100 mL of the second solvent is 0.05-0.5 mol; The amount of the solid initiator added relative to 100 mL of the third solvent is 10-20 g; The amount of alkenylphenol added relative to 100 mL of the third solvent is 0.05-0.5 mol; The molar ratio of the alkenylphenol to the N-vinylpyrrolidone is 1:(0.5-1.5).

2. The production method according to claim 1, wherein, In step (1), the manganese salt includes one or a combination of manganese sulfate, manganese nitrate and potassium permanganate.

3. The preparation method according to claim 1, wherein, In step (1), the first solvent includes water.

4. The production method according to claim 1, wherein In step (1), the amount of manganese salt added is 10-30 g relative to 100 mL of the first solvent.

5. The preparation method according to claim 4, wherein, In step (1), the amount of manganese salt added is 15-25 g relative to 100 mL of the first solvent.

6. The production method according to claim 1, wherein In step (1), the amount of activated carbon added is 8-12 g relative to 100 mL of the first solvent.

7. The production method according to claim 1, wherein In step (1), the temperature of the first contact is 25-40°C and the time is 5-8 h.

8. The production method according to claim 1, wherein In step (1), the first contact is a stationary contact.

9. The production method according to claim 1, wherein In step (1), the drying temperature is 40-60 °C and the time is 24-48 h.

10. The preparation method according to claim 1, wherein, In step (1), the high-temperature calcination time is 5-8 hours.

11. The production method according to claim 1, wherein In step (1), the conditions for low-temperature burning are: temperature 200-300 ℃, time 5-8 h.

12. The preparation method according to claim 1, wherein, In step (2), the vinyl sulfonate includes one or a combination of several of sodium 2-acrylamide-2-methylpropanesulfonate, sodium allyl sulfonate, sodium styrene sulfonate and sodium vinyl sulfonate.

13. The method of producing according to claim 1, wherein, In step (2), the second solvent includes water.

14. The method of producing according to claim 1, wherein, In step (2), the amount of vinyl sulfonate added is 0.1-0.3 mol relative to 100 mL of the second solvent.

15. The method of producing according to claim 1, wherein, In step (2), the amount of the micro-nano spherical manganese tetroxide added is 10-20 g relative to 100 mL of the second solvent.

16. The method of producing according to claim 1, wherein, In step (2), the conditions for the second contact reaction are: reaction temperature 25-40 ℃, reaction time 5-8 h.

17. The method of producing according to claim 1, wherein, In step (2), the second contact reaction is carried out under stirring at a speed of 600-1000 r / min.

18. The method of producing according to claim 1, wherein, In step (2), the drying is freeze drying, and the freeze drying conditions are: freezing with liquid nitrogen for 8-12 min, and freeze drying at -50 ℃ and 9 Pa for 24-48 h.

19. The method of producing according to claim 1, wherein, In step (3), the alkenylphenol includes one or a combination of several of 3-vinylphenol, 4-vinylphenol and p-allylphenol.

20. The preparation method according to claim 1, wherein, In step (3), the third solvent includes water.

21. The method of producing according to claim 1, wherein, In step (3), the amount of alkenylphenol added is 0.1-0.3 mol relative to 100 mL of the third solvent.

22. The preparation method according to claim 1, wherein, In step (3), the molar ratio of the alkenylphenol to the N-vinylpyrrolidone is 1:(0.7-1.3).

23. The method of producing according to claim 1, wherein, In step (3), the oxidant includes ammonium persulfate and / or potassium persulfate.

24. The method of producing according to claim 1, wherein, In step (3), the reducing agent includes sodium bisulfite.

25. The method of producing according to claim 1, wherein, In step (3), the amount of oxidant added is 0.001-0.005 mol relative to 100 mL of the third solvent.

26. The method of producing according to claim 1, wherein, In step (3), the molar ratio of the oxidant to the reducing agent is 1:(0.5-1.5).

27. The preparation method according to claim 26, wherein, In step (3), the molar ratio of the oxidant to the reducing agent is 1:(0.8-1.3).

28. The method of producing according to claim 1, wherein, In step (3), the conditions for the third contact reaction are: reaction temperature 65-80 ℃, reaction time 3-6 h, and the third contact reaction is carried out under a nitrogen atmosphere.

29. The method of producing according to claim 1, wherein, In step (3), the third contact reaction is carried out under stirring at a speed of 600-800 rpm.

30. A modified micro / nano-sized spherical manganese tetroxide weighting agent, which is prepared by the preparation method of the modified micro / nano-sized spherical manganese tetroxide weighting agent according to any one of claims 1-29.

31. The modified micro- to nanoscale spherical manganese tetraoxide ballast of claim 30, wherein, The modified micro / nano-sized spherical manganese tetroxide weighting agent has a density of 4.6-4.8 g / cm³. 3 .

32. The modified micro- to nanoscale spherical manganese tetraoxide ballast of claim 31, wherein, The density of the modified micro-nano spherical trimanganese tetraoxide weighting agent is 4.75-4.80 g / cm 3 .

33. The modified micro- to nanoscale spherical manganese tetraoxide ballast of claim 30, wherein, The modified micro-nano spherical manganese tetroxide weighting agent has an average particle size of 500-2000 nm.

34. The modified micro- to nanoscale spherical manganese tetraoxide ballast of claim 33, wherein, The modified micro-nano spherical manganese tetroxide weighting agent has an average particle size of 500-900 nm.

35. The modified micro- to nanoscale spherical manganese tetraoxide ballast of claim 30, wherein, When the mass concentration of the modified micro-nano spherical manganese tetroxide weighting agent suspension is 1%, the absolute value of the Zeta potential of the modified micro-nano spherical manganese tetroxide weighting agent suspension is ≥35 mV.

36. The modified micro- to nanoscale spherical manganese tetraoxide ballast of claim 35, wherein, When the mass concentration of the modified micro-nano spherical manganese tetroxide weighting agent suspension is 1%, the absolute value of the Zeta potential of the modified micro-nano spherical manganese tetroxide weighting agent suspension is ≥38 mV.

37. A water-based kill fluid, wherein, The water-based well-killing fluid includes any one of the modified micro-nano spherical manganese tetroxide weighting agents according to claims 30-36.

38. The water-based kill fluid of claim 37, wherein, The amount of the modified micro-nano spherical manganese tetroxide weighting agent added to the water-based well control fluid is calculated according to the formula shown in equation (1): （1） In formula (1): W1—Amount of weighting agent added, in grams; p1 - density of the original kill fluid, g / cm 3 ; P2 - density of the weighting agent-containing kill fluid, g / cm 3 ; P3 - density of the weighting agent, g / cm 3 ; V1 — Volume of the original well-killing fluid, mL.

39. The water-based kill fluid of claim 38, wherein, The application temperature of the water-based well-killing fluid is 200-220℃.

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