Barite powder not prone to moisture absorption and good in dispersity and preparation method of barite powder

Abstract

The invention relates to the technical field of drilling fluid in petroleum and natural gas development, and provides barite powder difficult to absorb moisture and good in dispersity and a preparation method of the barite powder. The barite powder is compounded by coating fine-particle-size barite powder with first coarse-particle-size barite powder, second fine-particle-size barite powder and third starch nanocrystals; complementary advantages of barite with different particle sizes are brought into full play, the storage stability of the mixed barite is improved, the adverse effect on the viscosity of the drilling fluid is reduced, and the dispersity and the suspension property are good. By coating the starch nanocrystals, the environmental humidity sensitivity of the fine-particle-size barite powder coated by the third starch nanocrystals is reduced, so that the possibility of moisture absorption and agglomeration in the storage process of the fine-particle-size barite powder is reduced, and the mixed barite powder with good long-term storage stability can be obtained. The starch nanocrystal particles are fine and good in coating performance, barite particles can form smoother spheres, friction force among the particles is reduced, resistance among the particles during flowing is reduced, and the fluidity of the drilling fluid is improved.

Description

Technical Field

[0001] This application relates to the technical field of drilling fluids in oil and gas development, and specifically relates to a barite powder with good moisture absorption resistance and good dispersibility and a preparation method thereof. Background Art

[0002] In oil and gas exploration and development drilling, drilling fluids can be used to cool the drill bit, lubricate the rotating drill string to prevent it from adhering to the wellbore wall, prevent blowouts by acting as a hydrostatic head on the wellbore leading to formation fluids, and remove drill cuttings from the wellbore, etc. Usually, weighting agents are added to the drilling fluid to increase the density of the drilling fluid, achieve stable wellbore walls, balance formation pressures, and prevent blowout accidents, etc. The weighting agent is generally selected from ground solid materials with a high specific gravity. It has the characteristics of being not easily worn, being easily crushed, being insoluble in water, and is prepared by processes such as crushing, grinding, and flotation.

[0003] Currently, the commonly used weighting agents mainly include barite powder, limestone powder, iron ore powder, ilmenite powder, and galena powder. Among them, limestone powder has a relatively low density and can only be used to prepare low-density drilling fluids; iron ore powder and ilmenite powder have a relatively high density and can be used to prepare high-density drilling fluids, but they have a relatively high hardness and cause relatively serious wear to drill tools, drill bits, and pumps; galena powder has the highest density, up to 7.4 - 7.7 g / cm 3 , and can be used to prepare ultra-high density drilling fluids to control abnormal high pressures in the formation. However, this weighting agent has a high cost and a small supply, and is only used in special cases where the formation pore pressure is extremely high. Compared with other types of weighting agents, barite has the characteristics of high density and low cost, and is the most widely used weighting agent.

[0004] Barite powder is a natural ore mainly composed of BaSO 4 , orthorhombic system, and the density of chemically pure barium sulfate is 4.5 g / cm 3 , and it is almost insoluble in water and has stable chemical properties. Due to the differences in the types and quantities of associated minerals in natural barite ores, as well as the differences in beneficiation processes and levels, the density of commercial barite in China is generally between 4.0 - 4.6 g / cm 3. There are mainly two categories of barite purification methods, namely physical purification and chemical purification. The main physical purification methods of barite are: hand selection, gravity separation, and magnetic separation. The main chemical purification methods are: flotation purification, calcination purification, leaching purification, etc. With the increasing depletion of high-quality and single-type barite ores, most barite ores in China have low grades and are closely associated with other metal and non-metal ores. Therefore, flotation plays an important role in barite beneficiation. In addition, after barite powder is used as a weighting agent for drilling fluids, improper treatment can cause environmental pollution. Recycling barite from used drilling fluids through flotation methods has become an effective means to reduce costs and recycle resources. However, for barite powder obtained by flotation methods, due to the adsorption of flotation reagents (such as oleic acid, saponified oleic acid, etc.) on the surface of barite, the mineral has a strong hydrophobic effect, increasing the shear force of the barite slurry and resulting in the viscosity of barite powder exceeding the national standard requirements. Existing technologies often use methods such as soaking, cleaning, and calcination to remove the adsorbed flotation reagents, but this will undoubtedly greatly increase the cost, and treatments such as calcination will also affect its particle size stability.

[0005] Barite used as drilling mud generally needs to reach a fineness of more than 325 mesh. If the particle size of barite is too large, precipitation is likely to occur, and the dispersibility of barite in the drilling fluid is poor. Using barite with a small particle size, even fine barite powder or ultra-fine barite powder (below 10 microns, below 6 μm), has the effect of reducing sedimentation, good particle dispersibility. However, due to the small particle size, agglomeration is likely to occur. The particles have a large surface area and will inappropriately increase the viscosity of the drilling fluid, affecting the rheology of the drilling fluid. Usually, the use of barite with too small a particle size needs to be strictly limited. In addition, in existing technologies, micro-powder barite is coated with a special polymer during grinding. After the polymer coating, the agglomeration phenomenon caused by the increase in the surface energy of micro-powder barite can be greatly inhibited, making the increase in viscosity within an acceptable range, so that barite with a small particle size can be used more. However, the coated polymer has strong water absorption during storage, is prone to moisture absorption and agglomeration, and the particle agglomeration phenomenon is serious during storage. Due to the limitations of drilling site conditions, it is difficult to ensure that the raw materials are not affected by moisture, etc., which also limits the use of fine barite powder and ultra-fine barite powder with small particles to improve the dispersibility of barite, and further leads to the difficulty of effectively and low-costly making full use of barite resources (the particle sizes of various ore sources vary greatly due to different processing technologies, and further processing will increase unnecessary costs).

[0006] In summary, the particle size distribution, preparation process, and storage conditions of barite particles affect the efficient and low-cost utilization of barite as a weighting agent in drilling fluids, and have a significant impact on the viscosity and rheology of drilling fluids. How to obtain low-cost barite powder that can be stored for a long time without moisture absorption and has good dispersibility in drilling fluids is an important development direction for the effective and low-cost utilization of barite resources. Summary of the Invention

[0007] Overcoming the deficiencies of the prior art, the present application provides a barite powder that is not easily hygroscopic and has good dispersibility, and a preparation method thereof. The barite powder obtained by the flotation method and adsorbed with flotation reagents can be directly utilized. The compound utilization of barite powders with different particle sizes is not easily deposited, has good dispersibility, has little adverse effect on the viscosity and rheology of drilling fluids, is not easily hygroscopic and agglomerated during storage, and realizes the effective, low-cost and full utilization of barite resources.

[0008] The embodiments of the present application are implemented as follows:

[0009] In a first aspect, the present application provides an example of a barite powder that is not easily hygroscopic and has good dispersibility. The barite powder includes, based on the total mass: the content of the first coarse particle size barite powder is 5-10 wt%, the content of the second fine particle size barite powder is 20-40 wt%, and the content of the third starch nanocrystal-coated fine particle size barite powder is 55-70 wt%;

[0010] The particle size of the first coarse particle size barite powder: the particle size of the second fine particle size barite powder is 1.43:1-5.3:1, and the particle size of the first coarse particle size barite powder is 46-59 μm; the particle size of the second fine particle size barite powder is 11-32 μm; based on the total mass of the third starch nanocrystal-coated fine particle size barite powder, the third starch nanocrystal-coated fine particle size barite powder includes: 97.5-98 wt% of fine particle size barite powder; 0.6-1.1 wt% of silane coupling agent; 0.8-1.5 wt% of starch nanocrystals; the particle size of the fine particle size barite powder is 2-9 μm.

[0011] Optionally, the particle size of the first coarse particle size barite powder: the particle size of the second fine particle size barite powder is 2.6:1-3.6:1; the particle size of the first coarse particle size barite powder is 46-54 μm; the particle size of the second fine particle size barite powder is 13-18 μm.

[0012] Optionally, based on the total mass of the third starch nanocrystal-coated fine particle size barite powder, the third starch nanocrystal-coated fine particle size barite powder includes: 97.5-98% of fine particle size barite powder; 0.6-1.1% of silane coupling agent; 0.8-1.5% of starch nanocrystals, and 0.4-0.7% of montmorillonite.

[0013] Optionally, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0014] In a second aspect, the present application provides an example of a preparation method of a barite powder that is not easily hygroscopic and has good dispersibility, for preparing the barite powder that is not easily hygroscopic and has good dispersibility as described above. The method includes:

[0015] S1: Preparation of third starch nanocrystal-coated fine-particle-size barite powder: Add fine-particle-size barite powder to a high-speed mixer according to the mass ratio of the fine-particle-size barite powder, spray a silane coupling agent on the surface of the fine-particle-size barite powder, mix and stir at the first temperature for the first set time to obtain the first coated fine-particle-size barite powder. Then, weigh starch nanocrystal powder according to the mass ratio of the starch nanocrystals, add water and stir to obtain a starch nanocrystal-containing solution, and spray it onto the surface of the first coated fine-particle-size barite powder. Mix and stir at the second temperature for the second set time, and after drying and cooling, obtain the third starch nanocrystal-coated fine-particle-size barite powder;

[0016] S2: Stir the first coarse-particle-size barite powder, the second fine-particle-size barite powder, and the third starch nanocrystal-coated fine-particle-size barite powder prepared in step S1 in a second stirrer for the third set time to obtain barite powder with good moisture-proof and dispersibility.

[0017] Optionally, the stirring speed of the high-speed mixer is 1600 - 2100 r / min, the first temperature is 70 - 90 °C, the first set time is 10 - 15 minutes, the second temperature is 91 - 132 °C, the second set time is 20 - 30 minutes, and the third set time is 20 - 30 minutes.

[0018] Optionally, in step S1, for the preparation of the third starch nanocrystal-coated fine-particle-size barite powder: Weigh starch nanocrystal powder according to the mass ratio of the starch nanocrystals, add water and stir to obtain a starch nanocrystal-containing solution, and spray it onto the surface of the first coated fine-particle-size barite powder. At the same time, introduce ozone with a gas flow rate of 0.5 - 2 L / min into the high-speed mixer for 5 - 6 minutes, mix and stir at the second temperature for the second set time, and after drying and cooling, obtain the third starch nanocrystal-coated fine-particle-size barite powder.

[0019] Optionally, in step S1, during the preparation of the third starch nanocrystal-coated fine-particle-size barite powder, after introducing ozone with a gas flow rate of 0.5 - 2 L / min into the high-speed mixer for 5 - 6 minutes, add montmorillonite and mix and stir.

[0020] Optionally, in step S1, weigh starch nanocrystal powder according to the mass ratio of the starch nanocrystals, add water and ammonia water, stir to obtain a starch nanocrystal-containing solution, and control the pH value of the starch nanocrystal-containing solution to 9.5 - 10.

[0021] Optionally, in S2: When stirring the first coarse-particle-size barite powder, the second fine-particle-size barite powder, and the third starch nanocrystal-coated fine-particle-size barite powder prepared in step S1 in a second stirrer for the third set time, spray sodium hexametaphosphate accounting for 0.1 - 0.3% of the total mass of the barite powder with good moisture-proof and dispersibility on the surface of the particle mixture.

[0022] The beneficial effects include:

[0023] A barite powder with good moisture absorption resistance and dispersibility and a preparation method thereof provided by the present invention, through the functions of supporting the skeleton, separating, and reducing viscosity of the first coarse-grained barite powder with a coarse particle size that has little influence on the viscosity of the drilling fluid, the second fine-grained barite powder with a medium particle size matching the particle size of the first coarse-grained barite powder for suspension support, increasing the packing density, reducing the moisture flow path between particles, etc., and the addition of the third starch nanocrystal-coated fine particle size barite powder weighting material with a large proportion of fine particles, which plays a role in reducing the flow friction of the drilling fluid, suspension support, increasing the packing density, reducing the moisture flow path between particles, etc. between the large particle weighting materials. The particle size gradually decreases from a small proportion of coarse particle sizes, and the usage proportion gradually increases. Combining their respective characteristics, giving full play to the complementary advantages of barite with different particle sizes, improving the storage stability of the mixed barite, reducing the adverse impact on the viscosity of the drilling fluid, and having good dispersibility and suspension.

[0024] By using a silane coupling agent as a "bridge" between inorganic and organic substances, close combination between the two is achieved. By coating starch nanocrystals with active hydroxyl groups on the surface, the formed third starch nanocrystal-coated fine particle size barite powder particles with multi-layer stable coating have appropriate hydrophilicity, good dispersibility and suspension in the drilling fluid. The starch nanocrystals have a regular lamellar structure with high crystallinity, which has a certain barrier effect on the permeation of water vapor, oxygen, etc. Thereby reducing the sensitivity of the third starch nanocrystal-coated fine particle size barite powder to environmental humidity, reducing the possibility of moisture absorption, agglomeration and caking during storage, and facilitating the acquisition of mixed barite powder with good long-term storage stability. The starch nanocrystal particles are small and have good coating properties, which is conducive to making the barite particles form smoother spherical shapes, reducing the friction between particles, reducing the resistance between particles during flow, and improving the fluidity of the drilling fluid. Specific embodiments

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0026] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the technical field to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as here.

[0027] Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention means the presence of the stated features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. The phrase "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0028] For the barite powder obtained by the flotation method, the adsorbed flotation reagent has a strong hydrophobic effect, which increases the viscosity of the drilling fluid and the direct utilization efficiency is not high. The large-particle-size barite powder is easy to deposit and has poor dispersibility. The small-particle-size barite powder is easy to agglomerate, resulting in an increase in the viscosity of the drilling fluid. By modifying and coating the small-particle-size barite powder with polymers, it has strong water absorption during storage and is easy to absorb moisture and agglomerate. There are many problems in the use of both large- and small-particle-size barite powders, which makes it difficult to effectively, low-cost and fully utilize barite resources, and has a significant impact on the viscosity and rheology of the drilling fluid. Therefore, the embodiments of the present invention provide a barite powder with good moisture resistance and dispersibility and a preparation method thereof.

[0029] Exemplarily, a barite powder with good moisture resistance and dispersibility is provided. The barite powder includes, based on the total mass: the content of the first coarse-particle-size barite powder is 5-10 wt% (which can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.), the content of the second fine-particle-size barite powder is 20-40 wt% (which can be 20 wt%, 23 wt%, 27 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, etc.), and the content of the third starch nanocrystal-coated fine-particle-size barite powder is 55-70 wt% (which can be 55 wt%, 57 wt%, 59 wt%, 62 wt%, 64 wt%, 67 wt%, 69 wt%, 70 wt%, etc.).

[0030] The first coarse-grained barite powder, with the particle size of the first coarse-grained barite powder being 46 - 59 μm (which can be 46 μm, 48 μm, 51 μm, 53 μm, 56 μm, 59 μm, etc.); the first coarse-grained barite powder with a larger particle size is selected. For the barite powder within this particle size range, the apparent viscosity effect and plastic viscosity effect are small. After adding the weighting agent within this particle size range to the drilling fluid system, the viscosity of the drilling fluid system is less affected, enabling the drilling fluid to have better rheology. It can be used as a suspension support skeleton for the weighting agent. At the same time, the barite powder with larger particles is less affected by moisture during storage, is not easy to agglomerate when absorbing moisture, and after being mixed with fine-particle-size particles, it has a certain blocking effect on the absorption of moisture and agglomeration of fine-particle-size particles, which can improve the long-term storage stability of the overall barite powder mixture with different particle sizes, and is also beneficial to the utilization of coarse-grained barite powder resources. The content of the first coarse-grained barite powder is 5 - 10 wt%. Due to the relatively large particle size of the first coarse-grained barite powder, it is easy to settle in the drilling fluid, so its usage ratio should be limited and should not be too high. If it is greater than the above content range, there is a greater risk of settlement of the first coarse-grained barite powder in the drilling fluid; if it is less than the above content range, the blocking effect on the absorption of moisture and agglomeration of fine-particle-size particles is not obvious, and if the usage ratio is too low, the usage ratio of the fine-grained barite is too high, which is not conducive to the drilling fluid having better rheology. Preferably, the particle size of the first coarse-grained barite powder is 46 - 54 μm; it is less affected by moisture during storage, is not easy to agglomerate when absorbing moisture, and at the same time enables the drilling fluid to have better rheology.

[0031] The second fine particle size barite powder, the particle size of the second fine particle size barite powder is 11-32 μm (which can be 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 21 μm, 24 μm, 26 μm, 28 μm, 29 μm, 31 μm, 32 μm); the barite powder within this particle size range has a moderate particle size, is not easily settled in the drilling fluid, has good suspension and dispersion properties. Its particle size is smaller than that of the first coarse particle size barite powder, and it can be filled between the coarse particle size particles, providing a certain supporting effect on the larger particle size particles suspended in the drilling fluid, facilitating the reduction of the settlement of the first coarse particle size barite powder, improving the dispersion performance of the barite powder, and increasing the filling density of the mixed barite powder. Although its particle size becomes smaller and it is more affected by moisture during storage compared with barite powder with a larger particle size, due to the barrier effect of the barite powder with larger particles, the possibility of moisture absorption, agglomeration and caking during its storage can be greatly reduced. And since it is filled between the coarse particle size particles and the coarse particle size barite particles with less impact on the viscosity of the drilling fluid system are adopted, it can also reduce the adverse effects such as excessive increase in the viscosity of the drilling fluid system caused by the second fine particle size barite powder, making the drilling fluid have good rheological properties. In order to make the weighting agent have good dispersion and suspension properties in the drilling fluid system, the content of the second fine particle size barite powder can be 20-40 wt%; if it is greater than this range, there is too much powder filled between the coarse particle size particles, reducing the barrier effect of the barite powder with larger particles and increasing the possibility of moisture absorption, agglomeration and caking during its storage; if it is less than this range, there is too little powder filled between the coarse particle size particles, which is not conducive to reducing the settlement of the first coarse particle size barite powder and is not conducive to the lower filling density of the mixed barite powder. Preferably, the particle size of the second fine particle size barite powder is 13-18 μm. This further increases the filling density of the mixed barite powder, makes it not easily settled in the drilling fluid, and has better suspension and dispersion properties.

[0032] The particle size of the first coarse-grained barite powder: the particle size of the second fine-grained barite powder is 1.43:1 - 5.3:1. It can be seen that the particle sizes of the first coarse-grained barite powder and the second fine-grained barite powder are different, and both have a better selection range. However, when the first coarse-grained barite powder and the second fine-grained barite powder are mixed, if the particle size difference is too large, it will reduce the mixing filling density of the two. The gaps between the powder particles are large, increasing the path for moisture and the like to flow into the interior of the mixed powder during storage, and increasing the possibility of moisture absorption, agglomeration, and caking during storage. A too large particle size difference will also weaken the supporting effect of the fine-grained powder on the coarse-grained powder in the drilling fluid. By limiting the ratio of the particle size of the first coarse-grained barite powder to the particle size of the second fine-grained barite powder, it is beneficial for the first coarse-grained barite powder and the second fine-grained barite powder to be mixed with a better particle size, thus avoiding the above-mentioned adverse effects. Preferably, the particle size of the first coarse-grained barite powder: the particle size of the second fine-grained barite powder is 2.6:1 - 3.6:1. By further optimizing the particle size ratio, it is beneficial to reduce the particle size difference when the first coarse-grained barite powder and the second fine-grained barite powder are mixed, improve the mixing filling density of the two, reduce the gaps between the powder particles, and reduce the possibility of moisture absorption, agglomeration, and caking during storage.

[0033] The third starch nanocrystal-coated fine-sized barite powder is obtained by coating and modifying fine-sized barite powder with a particle size of 2-9 μm (which can be 2 μm, 4 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc.) with starch nanocrystals to obtain the third starch nanocrystal-coated fine-sized barite powder with a particle size similar to that of the fine-sized barite powder. Using barite with a very small particle size has the effect of reducing sedimentation, good particle dispersibility, good suspension in drilling fluid, and good dispersibility. Its particle size is smaller than that of the first coarse-sized barite powder and the second fine-sized barite powder, and it can be further filled between the coarse-sized and medium-sized particles, providing a certain supporting effect on larger-sized particles suspended in the drilling fluid, facilitating the reduction of sedimentation of the first coarse-sized barite powder and the second fine-sized barite powder, improving the dispersion performance of the barite powder, and increasing the packing density of the mixed barite powder. Since it is dispersed between the gaps of the first coarse-sized barite powder and the second fine-sized barite powder and blocked by different particles, while reducing the possibility of agglomeration and caking of the third starch nanocrystal-coated fine-sized barite powder, it also separates different-sized powders such as the first coarse-sized barite powder and the second fine-sized barite powder. After preparing the drilling fluid, the fine particles reduce the frictional resistance between particles during flow, and the packing density increases significantly, the gaps between particles decrease, and the possibility of moisture and the like flowing into the interior of the mixed particles decreases, reducing the possibility of their agglomeration and caking, especially the possibility of moisture absorption and agglomeration caking during storage, which is beneficial to improving the storage stability of the mixed barite powder. Filled between the coarse-sized and medium-sized particles, by using coarse-sized barite particles that have less impact on the viscosity of the drilling fluid system, it can reduce the adverse effects such as excessive increase in viscosity of the drilling fluid system caused by the over-fineness of the third starch nanocrystal-coated fine-sized barite powder, making the drilling fluid have good rheology. At the same time, it expands the available particle size range of barite powder applied as a drilling fluid weighting agent, which is beneficial to the utilization of barite ore powder obtained by flotation and recycled barite ore powder. In order to make the weighting agent have good dispersibility, suspension, and storage resistance in the drilling fluid system, the content of the third starch nanocrystal-coated fine-sized barite powder is 55-70 wt%. If it is greater than this range, there is too much powder filled between the coarse and medium-sized particles, reducing the blocking effect of the larger-sized barite powder. The addition of too fine and excessive particles to the drilling fluid causes too large an agglomeration and viscosity increase effect, affecting the rheology of the drilling fluid and increasing the possibility of moisture absorption and agglomeration caking during its storage, increasing the viscosity of the drilling fluid; if it is less than this range, there is too little powder filled between the coarse and medium-sized particles, which is not conducive to reducing the sedimentation of the first coarse-sized barite powder, not conducive to increasing the packing density of the mixed barite powder, and not conducive to reducing the flow friction resistance of the drilling fluid.

[0034] Through the functions of supporting framework, separating, viscosity reduction, etc. of the first coarse particle size barite powder with coarse particle size that has little influence on the viscosity of drilling fluid, the second fine particle size barite powder with medium particle size matching the particle size of the first coarse particle size barite powder for suspension support, increasing packing density, reducing the moisture circulation path between particles, etc., and the addition of the third starch nanocrystal-coated fine particle size barite powder weighting material with a large proportion of fine particles, which plays the roles of reducing the flow friction of drilling fluid, suspension support, increasing packing density, reducing the moisture circulation path between particles, etc. between the large particle weighting materials, with the particle size gradually decreasing from the small proportion of coarse particle size and the usage proportion gradually increasing, combining their respective characteristics, giving full play to the complementary advantages of barite with different particle sizes, improving the storage stability of the mixed barite, reducing the adverse impact on the viscosity of drilling fluid, and having good dispersibility and suspension.

[0035] The third starch nanocrystal-coated fine-sized barite powder has relatively small particles and has a greater possibility of agglomeration. The particles have a large surface area, which may inappropriately increase the viscosity of the drilling fluid and affect the rheology of the drilling fluid. During its storage, there is a high possibility of moisture absorption, agglomeration, and caking, which is not conducive to obtaining a mixed barite powder with good long-term storage stability. To further reduce the possibility of agglomeration, increase storage stability, and make it not easily absorb moisture, agglomerate, and cake. Based on the total mass of the third starch nanocrystal-coated fine-sized barite powder, the third starch nanocrystal-coated fine-sized barite powder includes: fine-sized barite powder is 97.5-98% (which can be selected as 97.5%, 97.6%, 97.7%, 97.8%, 98%, etc.); silane coupling agent is 0.6-1.1% (which can be selected as 0.6%, 0.7%, 0.9%, 1.0%, 1.1%, etc.); starch nanocrystals are 0.8-1.5% (which can be selected as 0.8%, 0.9%, 1.1%, 1.3%, 1.5%, etc.). Silane coupling agents usually contain silane groups, which act as a "bridge" between inorganic and organic substances to achieve a tight combination between the two. Silane coupling agents can react with the surface of barite or the hydroxyl groups on its surface to form chemical bonds, thereby organically coating barite. This can improve hydrophobicity and provide a certain barrier to moisture. However, often the hydrophobicity is too high, resulting in poor hydrophilicity and poor dispersibility in water-based drilling fluids. And most silane coupling agents are soluble in water or, although they have poor solubility in water, still have a certain tendency to hydrolyze when encountering water. Therefore, when only silane coupling agents are used to organically coat barite, during long-term storage, it is still greatly affected by moisture and other factors, resulting in fine particles being easily affected by moisture, agglomerating, and caking, and the storage stability is not high. By coating starch nanocrystals with active hydroxyl groups on the surface, starch nanocrystals, as an organic nanoparticle, have characteristics such as a dense structure and certain water-blocking properties. During long-term storage, it can reduce the influence of fine particles by moisture, reduce the adverse effects such as fine particles being easily affected by moisture, agglomerating, and caking, and low storage stability. The active hydroxyl groups on the surface of starch nanocrystals react with silane coupling agents, etc., which can promote the stable coating of the formed silane coupling agent on the starch nanocrystals coated on barite, thereby forming a modified multi-layer stable-coated third starch nanocrystal-coated fine-sized barite powder particle. Starch nanocrystals have relatively high hydrophilicity, and the active hydroxyl groups on the surface of starch nanocrystals react with silane coupling agents, etc., which to a certain extent reduces the strong hydrophilicity of starch nanocrystals. Thus, the formed multi-layer stable-coated third starch nanocrystal-coated fine-sized barite powder particle has appropriate hydrophilicity, good dispersibility, and good suspension in the drilling fluid.

[0036] Natural starch is a polymer composed of amylose and amylopectin. This polymer consists of two parts, namely, an ordered crystalline region and a disordered amorphous region (non-crystalline region). The main component of the amorphous region is amylose with a semi-crystalline structure, while the crystalline region is mainly formed by amylopectin. After the starch granules are gently hydrolyzed by acid, the loosely structured amorphous region is consumed by hydrolysis, and the crystalline region can be retained, thus obtaining nano-scale particles with a higher degree of crystallinity. The average particle size of starch nanocrystals can be 25 - 750 nm, namely starch nanocrystals. Due to the characteristics of wide source, low cost, low production energy consumption, biodegradability, safety and non-toxicity of starch nanocrystals, as a modification aid in barite powder, it is an ideal nano-scale and low-cost modifier that will not significantly increase the cost of the weighting agent. The regular flake structure with a high degree of crystallinity of starch nanocrystals has a certain barrier effect on the permeation of water vapor, oxygen, etc., thereby reducing the sensitivity of the third starch nanocrystal-coated fine particle size barite powder to environmental humidity, and reducing the possibility of moisture absorption, agglomeration and caking during storage, which is conducive to obtaining a mixed barite powder with good long-term storage stability.

[0037] Starch nanocrystal particles are small and have good coating properties, which is conducive to making barite particles form smoother spheres, reducing the friction between particles, and reducing the resistance between particles during flow, thereby improving the fluidity of the drilling fluid. After the outer layer is coated with starch nanocrystals, a network structure is formed by the contact between the starch nanocrystals suspended in the drilling fluid. When the drilling fluid is at rest or at a low shear rate, the network structure can improve the suspension and dispersibility of the particles, and has a better suspension effect on the first coarse particle size barite powder and the second fine particle size barite powder, improving the dispersion and suspension of the mixed barite powder. At a high shear rate, the network structure formed by the contact between the starch nanocrystals suspended in the drilling fluid is easily disassembled, which is beneficial to the drilling fluid to maintain a high rheological property. Therefore, after the outer layer is coated with starch nanocrystals, the adverse effect of the too small particle size of the third starch nanocrystal-coated fine particle size barite powder particles with multi-layer stable coating on the viscosity of the drilling fluid system is greatly reduced. 0.6 - 1.1% of silane coupling agent can improve the stability of the multi-layer coated particles, making the coated particles have moderate hydrophilicity and not easy to agglomerate; less than this range, the stability of the multi-layer coated particles is insufficient, easy to delaminate, affecting the modification effect, and greater than this range, the modified particles have too high hydrophobicity and are easy to agglomerate in the water-based drilling fluid; 0.8 - 1.5% of starch nanocrystals, the third starch nanocrystal-coated fine particle size barite powder particles with multi-layer stable coating have appropriate hydrophilicity, good dispersibility and suspension in the drilling fluid, and good long-term storage stability, making the drilling fluid have good rheological properties. Less than this range, the long-term storage stability becomes worse, and greater than this range, the hydrophilicity of the coated particles increases, generating too many uncoated starch nanocrystals, increasing the cost and causing waste of resources.

[0038] The first coarse particle size barite powder is preferably the powder particles obtained by physical purification methods (hand selection, gravity separation, magnetic separation). There are no flotation agents such as oleic acid and saponified oleic acid adsorbed on the surface of barite, thus avoiding the strong hydrophobic effect of its minerals, which may lead to an increase in the viscosity of barite powder and an increase in the shear force of barite pulp.

[0039] The second fine particle size barite powder and the ultra-fine particle size barite powder can be the barite powders obtained by physical or chemical purification methods. Preferably: the barite powder obtained by the flotation method. More preferably, the ultra-fine particle size barite powder has flotation agents such as oleic acid and saponified oleic acid adsorbed on its surface, and the flotation agents do not need to be removed. The non-removal of flotation agents can reduce costs and avoid the influence of treatments such as calcination for removing flotation agents on its particle size stability. At the same time, the adsorption of flotation agents such as oleic acid and saponified oleic acid on the surface of barite can react with silane coupling agents, etc., accelerating the adhesion of silane coupling agents to barite powder, and then improving the coating stability of starch nanocrystal coating.

[0040] Regarding the above barite powder with good moisture resistance and dispersibility, a preparation method of barite powder with good moisture resistance and dispersibility is provided. The method includes:

[0041] S1: Preparation of the third starch nanocrystal-coated ultra-fine particle size barite powder: Add ultra-fine particle size barite powder to a high-speed mixer according to the mass ratio of ultra-fine particle size barite powder, spray a silane coupling agent on the surface of the ultra-fine particle size barite powder, mix and stir at the first temperature for the first set time to obtain the first-coated ultra-fine particle size barite powder. Then, weigh starch nanocrystal powder according to the mass ratio of starch nanocrystals, add water and stir to obtain a starch nanocrystal-containing solution, spray it on the surface of the first-coated ultra-fine particle size barite powder, mix and stir at the second temperature for the second set time, and obtain the third starch nanocrystal-coated ultra-fine particle size barite powder after drying and cooling.

[0042] Dry coating of ultra-fine particle size barite powder by a high-speed mixer is beneficial to form stable and tightly bound coating particles.

[0043] S2: Stir the first coarse particle size barite powder, the second fine particle size barite powder and the third starch nanocrystal-coated ultra-fine particle size barite powder prepared in step S1 in a second stirrer for the third set time to obtain barite powder with good moisture resistance and dispersibility.

[0044] Among them, the stirring speed of the high-speed mixer is 1600 - 2100 r / min (which can be optionally 1600 r / min, 1700 r / min, 1800 r / min, 1900 r / min, 2000 r / min, 2100 r / min, etc.); due to the small particle size of the fine-particle-size barite powder, a high stirring speed is adopted to improve the mixing effect and reduce agglomeration during stirring and coating. If the stirring speed is lower than this, the coating effect will be affected. Especially in the experiment, it is found that when the stirring speed is too low, such as below 1200 r / min, there will be particle agglomeration during the coating process of spraying silane coupling agent, starch nanocrystal solution, etc. on the fine-particle-size barite powder. If it is higher than this speed range, the high speed will affect production economy, and at the same time, there will also be problems such as uneven coating where some materials cannot be coated when coating the particle powder. The first temperature is 70 - 90 °C, which can be optionally 75 - 80 °C; for example, the first temperature can be 70 °C, 73 °C, 75 °C, 77 °C, 80 °C, 84 °C, 85 °C, 88 °C or 90 °C. The first set time is 10 - 15 minutes. For example, the first set time can be 10 minutes, 13 minutes or 15 minutes, etc. When spraying the silane coupling agent on the surface of the fine-particle-size barite powder, controlling the temperature at a lower level is beneficial to the coating and reaction of the silane coupling agent with the fine-particle-size barite powder, and at the same time keeps the silane coupling agent still having a certain reaction activity, which is conducive to the subsequent coating. At this time, the stirring time should not be too long, otherwise it will affect the subsequent coating process. If it is higher than the above temperature range, the reaction activity of the silane coupling agent will decrease, which is not conducive to the subsequent coating. If it is lower than the above temperature range, the coating is not dense and the coating effect is poor due to insufficient reaction between the silane coupling agent and the fine-particle-size barite powder. It can be understood that the silane coupling agent can form a solvent through water, polyethylene glycol, etc. to facilitate spraying.

[0045] The second temperature is 91 - 132 °C, which can be optionally 105 - 119 °C; for example, the second temperature can be 91 °C, 94 °C, 97 °C, 99 °C, 104 °C, 112 °C, 114 °C, 116 °C, 119 °C, 122 °C, 124 °C, 127 °C, 129 °C or 132 °C. The second set time is 20 - 30 minutes. For example, the second set time can be 20 minutes, 27 minutes or 30 minutes, etc. Spraying the starch nanocrystal solution onto the surface of the first-coated fine-particle-size barite powder at a higher temperature is beneficial to the rapid reaction between the starch nanocrystal solution and the silane coupling agent, facilitating the rapid removal of moisture, achieving tight coating and improving the coating effect. If the temperature is too high, it will affect the stability of the starch nanocrystals. If it is lower than the above temperature range, the moisture removal is slow, the coating is not dense, and the coating effect is poor. The third set time is 20 - 30 minutes. For example, the third set time can be 20 minutes, 23 minutes, 25 minutes, 27 minutes or 30 minutes, etc. Stirring for a longer time can make the coated particles tightly coated, more uniform in coating, with sufficient moisture removal, and improve production efficiency.

[0046] The high-speed mixer and the second stirrer achieve mixing and blending in the above process, and the specific stirring form is not limited. For example, it can be a propeller stirrer, a propeller stirrer, a turbine stirrer, a stirring kettle, etc. In S2, barite powder with different particle sizes is mixed without adding additional additives. The main task is to stir evenly. The stirring speed of the second stirrer can be lower than that of the high-speed mixer, and the stirring speed is not limited, and can be 800-1100 r / min.

[0047] In a preferred embodiment, in step S1, the preparation of the third starch nanocrystal-coated fine-particle-size barite powder: Weigh the starch nanocrystal powder according to the mass ratio of the starch nanocrystal, add water and stir to obtain a starch nanocrystal-containing solution, and spray it onto the surface of the first-coated fine-particle-size barite powder. At the same time, ozone with a gas flow rate of 0.5-2 L / min (which can be selected as 0.5 L / min, 0.8 L / min, 1.2 L / min, 1.4 L / min, 1.6 L / min, 1.8 L / min, 2 L / min, etc.) is introduced into the high-speed mixer for 5-6 minutes, and mixed and stirred at the second temperature for the second set time. After drying and cooling, the third starch nanocrystal-coated fine-particle-size barite powder is obtained. When the starch nanocrystal-containing solution is sprayed onto the surface of the first-coated fine-particle-size barite powder, through short-term ozone treatment, the hydroxyl groups on the surface starch nanocrystals are oxidized to carboxyl and carbonyl groups, and the relative hydrophobicity becomes higher, which can reduce the interaction between starch nanocrystal particles during the stirring and coating process, reduce the possibility of aggregation, improve the coating uniformity, improve the dispersibility and suspension of the third starch nanocrystal-coated fine-particle-size barite powder, and is beneficial to improving the rheology of the drilling fluid.

[0048] In a preferred embodiment, the third starch nanocrystal-coated fine-particle-size barite powder includes: fine-particle-size barite powder is 97.5-98%; silane coupling agent is 0.6-1.1%; starch nanocrystal is 0.8-1.5%, and montmorillonite is 0.4-0.7% (which can be selected as 0.4%, 0.5%, 0.6%, 0.7%, etc.).

[0049] Correspondingly, in step S1, in the preparation of the third starch nanocrystal-coated fine-particle-size barite powder, after introducing ozone with a gas flow rate of 0.5-2 L / min into the high-speed mixer for 5-6 minutes, montmorillonite is added for mixing and stirring. It can be understood that the montmorillonite can be mixed in the form of fine powder or sprayed and mixed with a water suspension, etc. No specific limitation is made here.

[0050] Montmorillonite is a kind of clay mineral composed of nanometer-thick negatively charged silicate sheets stacked together by electrostatic interaction between layers. It can undergo chimerization, chemical reactions, etc. with silane coupling agents and starch nanocrystals. Due to its multi-layer structure, it prolongs the diffusion path of moisture into the particle interior, has strong hygroscopicity and expansibility, and has a strong capacity to accommodate moisture on the surface in contact. It can itself be a common component of drilling slurries and has little adverse effect on mixed barite powder. When coating the surface of the first coated fine-particle barite powder by spraying with a starch nanocrystal solution, ozone anti-agglomeration treatment is carried out, and montmorillonite is added to the barite powder particles for coating, and part or all of it is coated on the outer layer of the starch nanocrystal layer or overlaps with the starch nanocrystals, which can make the coated fine-particle barite powder have certain water resistance and moisture accommodation capacity, which is beneficial to improving the moisture tolerance of materials stored for a long time and has better long-term storage stability. Since montmorillonite adsorbs too much water and may form a paste, to avoid large changes in properties, its maximum dosage should be limited within the aforementioned range.

[0051] Optionally, in step S1, starch nanocrystal powder is weighed according to the mass ratio of starch nanocrystals, water and ammonia water are added, and stirred to obtain a starch nanocrystal solution. The pH value of the starch nanocrystal solution is controlled to be 7.1 - 10. Preferably, the pH value of the starch nanocrystal solution is controlled to be 9.5 - 10. Under alkaline conditions, the agglomeration of starch nanocrystals can be reduced, which is beneficial to the uniform coating of starch nanocrystals on the surface of the first coated fine-particle barite powder, improving long-term storage stability and improving the rheology of drilling fluids.

[0052] Preferably, the silane coupling agent can be selected as γ-aminopropyltriethoxysilane, and the optional model is silane coupling agent kh-550, an amino-functional silane, which is alkaline. It is more conducive to cooperating with the starch nanocrystal solution under alkaline conditions to make the coating layer more tightly combined.

[0053] Optionally, S2: When stirring the first coarse-particle barite powder, the second fine-particle barite powder and the third starch nanocrystal-coated fine-particle barite powder prepared in step S1 in a second stirrer for a third set time, 0.1 - 0.3% of sodium hexametaphosphate based on the total mass of the non-hygroscopic and well-dispersible barite powder is sprayed on the surface of the particle mixture. By spraying a small amount of hydrophilic sodium hexametaphosphate on the mixed powder, the dispersibility and suspension of the overall powder in drilling fluids (such as water-based drilling fluids) can be improved, and it has better rheology of drilling fluids.

[0054] The features and properties of the present application will be further described in detail below in combination with embodiments:

[0055] Example 1

[0056] The third starch nanocrystal-coated fine-particle-size barite powder comprises: 97.6 wt% of fine-particle-size barite powder; 1.0 wt% of silane coupling agent; 1.4 wt% of starch nanocrystals; the particle size of the fine-particle-size barite powder is 5 μm. (Supplementary note: The particle size range is the average particle size of each kind of particle. The particle size of the particles in the powder can fluctuate, and the fluctuation range of the particle size is controlled within 20% of the average particle size value. The following particle sizes are all calculated by the same particle size calculation method). The fine-particle-size barite powder is the barite powder from which the flotation agent has not been removed by the flotation method.

[0057] Preparation of the third starch nanocrystal-coated fine-particle-size barite powder: Add the fine-particle-size barite powder to a high-speed mixer (mixing speed: 1800 r / min) according to the mass ratio of the fine-particle-size barite powder, spray the silane coupling agent onto the surface of the fine-particle-size barite powder, mix and stir at 83 °C for 13 minutes to obtain the first-coated fine-particle-size barite powder. Then, weigh the starch nanocrystal powder according to the mass ratio of the starch nanocrystals, add water and stir to obtain a starch nanocrystal-containing solution, spray it onto the surface of the first-coated fine-particle-size barite powder, mix and stir at 106 °C for 28 minutes, and obtain the third starch nanocrystal-coated fine-particle-size barite powder after drying and cooling.

[0058] The interfacial contact angle is the main criterion for wettability. The larger the interfacial contact angle of the inorganic powder with water, the better the hydrophobicity, while good hydrophilicity is beneficial to rapid dispersion in the water-based drilling fluid and helps to prevent particle agglomeration to a certain extent. The modified third starch nanocrystal-coated fine-particle-size barite powder with a moderate interfacial contact angle (for example, the interfacial contact angle is 97° - 118°) is beneficial to the preparation of the drilling fluid. The interfacial contact angle of the third starch nanocrystal-coated fine-particle-size barite powder obtained in step S1 is measured by the direct tablet pressing measurement method. The test method is (the following tests all use the same test method): Weigh 4.0 g of barite powder and press it into a measurable solid tablet under solid conditions, drop water on the tablet to form a liquid droplet, and use a wetting angle measuring instrument to measure the interfacial contact angle between the modified barite powder and water. After testing, the measured interfacial contact angle is 109°.

[0059] Storage moisture absorption performance test: Take 200 g of barite powder and place it in a test chamber with a temperature maintained at a relative humidity of 70% for different times such as one week, two weeks, and one month to test its weight increase, so as to test the ability of the barite powder to absorb moisture in the air during storage. After testing: The weight increases by 0.3 g in one week, 0.4 g in two weeks, and 0.45 g in one month, and there is no obvious agglomeration and caking of the powder, and it is less affected by humidity during long-term storage.

[0060] Example 2

[0061] A preparation method of barite powder with good moisture absorption resistance and dispersibility. The composition of the prepared barite powder is as follows: the content of the first coarse particle size barite powder is 9 wt%, the content of the second fine particle size barite powder is 28 wt%, and the content of the third starch nanocrystal-coated fine particle size barite powder is 63 wt%. The particle size of the first coarse particle size barite powder is 58 μm; the particle size of the second fine particle size barite powder is 12 μm; the particle size ratio of the first coarse particle size barite powder to the second fine particle size barite powder is 4.8. The third starch nanocrystal-coated fine particle size barite powder can be referred to Example 1. Stir the first coarse particle size barite powder, the second fine particle size barite powder and the third starch nanocrystal-coated fine particle size barite powder prepared in Example 1 in a second stirrer (stirring speed: 850 r / min) for 20 minutes to obtain barite powder with good moisture absorption resistance and dispersibility. For the storage moisture absorption performance test, after testing: the weight increases by 0.4 g in one week, the weight increases by 0.51 g in two weeks, the weight increases by 0.58 g in one month, and there is no obvious agglomeration and caking of the powder, and it is less affected by humidity during long-term storage.

[0062] To reduce the influence of the complex components of the drilling fluid on the test results, the obtained barite powder is added as a weighting agent to the prepared simplified drilling fluid. The components of the simplified drilling fluid include: 4 wt% bentonite, 2% sulfomethylated phenolic resin (SMP), barite weighting agent, and the rest is water, weighted to 2.3 g / cm 3 , Place the weighted drilling fluid in a heating furnace for aging (160 °C, 17 h), let the aged drilling fluid stand and cool to room temperature, observe the sedimentation situation to test the sedimentation stability, then heat the drilling fluid to 40 °C, and test its apparent viscosity and plastic viscosity through a six-speed rotational viscometer to investigate the influence of the weighting agent on the viscosity of the drilling fluid, etc., and then characterize the rheology of the drilling fluid. After testing the drilling fluid directly added with barite powder with good moisture absorption resistance and dispersibility: After letting the aged drilling fluid stand and cool to room temperature, no obvious sedimentation is observed, indicating that the barite powder with good moisture absorption resistance and dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 70, plastic viscosity (PV / mPa·s): 41, both are relatively low, and the rheology of the drilling fluid is better.

[0063] Example 3

[0064] It is basically the same as the barite composition and preparation method in Example 1 and Example 2. The main differences are: the particle size of the first coarse particle size barite powder is 52 μm; the particle size of the second fine particle size barite powder is 17 μm; the particle size ratio of the first coarse particle size barite powder to the second fine particle size barite powder is 3.1. For the storage moisture absorption performance test, after testing: the weight increases by 0.35 g in one week, the weight increases by 0.48 g in two weeks, the weight increases by 0.53 g in one month, and there is no obvious agglomeration and caking of the powder, and it is less affected by humidity during long-term storage.

[0065] The drilling fluid prepared by directly adding barite powder with good moisture absorption resistance and dispersibility was tested: After the aged drilling fluid was allowed to stand and cool to room temperature, no obvious sedimentation was observed, indicating that the barite powder with good moisture absorption resistance and dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 65, plastic viscosity (PV / mPa·s): 39, both are relatively low, and the rheology of the drilling fluid is good. Compared with Example 2, the influence of humidity becomes smaller, and the rheology of the drilling fluid is relatively good.

[0066] Example 4

[0067] It is basically the same as the barite composition and preparation method in Example 1, and the main difference is that: ozone with a gas flow rate of 1 L / min was introduced into the high-speed mixer for 5 minutes. No obvious agglomeration was observed in the powder obtained during the preparation process of Step S1. After testing, the measured interfacial contact angle was 112°.

[0068] The moisture absorption performance during storage was tested: After testing, the weight increased by 0.25 g in one week, 0.34 g in two weeks, and 0.38 g in one month, and there was no obvious agglomeration or caking of the powder. During long-term storage, the influence of humidity was small. Compared with Example 1, ozone treatment has a certain ability to improve hydrophobicity, and the influence of humidity becomes smaller.

[0069] Example 5

[0070] It is basically the same as the barite composition and preparation method in Example 4 and Example 2.

[0071] The moisture absorption performance during storage was tested: After testing, the weight increased by 0.27 g in one week, 0.35 g in two weeks, and 0.43 g in one month, and there was no obvious agglomeration or caking of the powder. During long-term storage, the influence of humidity was small.

[0072] The drilling fluid prepared by directly adding barite powder with good moisture absorption resistance and dispersibility was tested: After the aged drilling fluid was allowed to stand and cool to room temperature, no obvious sedimentation was observed, indicating that the barite powder with good moisture absorption resistance and dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 66, plastic viscosity (PV / mPa·s): 37, both are relatively low, and the rheology of the drilling fluid is good. Compared with Example 2, the influence of humidity becomes smaller, and the rheology of the drilling fluid is relatively good.

[0073] Example 6

[0074] It is basically the same as the barite composition and preparation method in Example 4, and the main difference is that: The third starch nanocrystal-coated fine-particle-size barite powder includes: 97.1 wt% of fine-particle-size barite powder; 0.5% of montmorillonite. No obvious agglomeration was observed in the powder obtained during the preparation process of Step S1. After testing, the measured interfacial contact angle was 110°.

[0075] Storage moisture absorption performance test. After testing: the weight increased by 0.20 g in one week, 0.27 g in two weeks, and 0.31 g in one month, and there was no obvious agglomeration and caking of the powder. During long-term storage, it was less affected by humidity. Compared with Example 4, after adding montmorillonite, the influence of humidity became smaller and the storage stability was improved.

[0076] Example 7

[0077] It is basically the same as Example 6 and the barite composition and preparation method of Example 2.

[0078] Storage moisture absorption performance test. After testing: the weight increased by 0.23 g in one week, 0.29 g in two weeks, and 0.34 g in one month, and there was no obvious agglomeration and caking of the powder. During long-term storage, it was less affected by humidity.

[0079] After testing the drilling fluid prepared by directly adding barite powder with good moisture absorption resistance and dispersibility: after the aged drilling fluid was allowed to stand and cool to room temperature, no obvious sedimentation was observed, indicating that the barite powder with good moisture absorption resistance and dispersibility had good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 64, plastic viscosity (PV / mPa·s): 35, both were relatively low, and the rheology of the drilling fluid was better. Compared with Example 2, the influence of humidity became smaller and the rheology of the drilling fluid was relatively better.

[0080] Example 8

[0081] It is basically the same as Example 1 in terms of barite composition and preparation method. The main difference is that: starch nanocrystal powder was weighed according to the mass ratio of starch nanocrystals, added with water and ammonia water, and stirred to obtain a starch nanocrystal-containing solution. The pH value of the starch nanocrystal-containing solution was controlled at 9.5, and silane coupling agent kh-550 was used. After testing, the measured interfacial contact angle was 109°.

[0082] Storage moisture absorption performance test. After testing: the weight increased by 0.28 g in one week, 0.36 g in two weeks, and 0.43 g in one month, and there was no obvious agglomeration and caking of the powder. During long-term storage, it was less affected by humidity. Compared with Example 1, by controlling the alkaline conditions, the prepared powder was less affected by humidity and the storage stability was improved.

[0083] Example 9

[0084] It is basically the same as Example 8 and the barite composition and preparation method of Example 2. Storage moisture absorption performance test. After testing: the weight increased by 0.35 g in one week, 0.46 g in two weeks, and 0.51 g in one month, and there was no obvious agglomeration and caking of the powder. During long-term storage, it was less affected by humidity.

[0085] The drilling fluid prepared by directly adding barite powder with good moisture absorption resistance and good dispersibility: After the aged drilling fluid was allowed to stand and cool to room temperature, no obvious sedimentation was observed, indicating that the barite powder with good moisture absorption resistance and good dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 63, plastic viscosity (PV / mPa·s): 37, both are relatively low, and the rheology of the drilling fluid is good. Compared with Example 2, by controlling the alkaline conditions, the rheology of the drilling fluid is relatively good.

[0086] Example 10

[0087] It is basically the same as the barite composition and preparation method of Example 1 and Example 2. The main difference is that when the first coarse particle size barite powder, the second fine particle size barite powder and the third starch nanocrystal-coated fine particle size barite powder prepared in step S1 are stirred in the second stirrer for the third set time, sodium hexametaphosphate accounting for 0.1% of the total mass of the barite powder with good moisture absorption resistance and good dispersibility is sprayed on the surface of the particle mixture.

[0088] Moisture absorption performance test during storage. After testing: The weight increased by 0.35 g in one week, 0.48 g in two weeks, and 0.53 g in one month, and there was no obvious agglomeration and caking of the powder, and it was less affected by humidity during long-term storage.

[0089] The drilling fluid prepared by directly adding barite powder with good moisture absorption resistance and good dispersibility: After the aged drilling fluid was allowed to stand and cool to room temperature, no obvious sedimentation was observed, indicating that the barite powder with good moisture absorption resistance and good dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 66, plastic viscosity (PV / mPa·s): 40, both are relatively low, and the rheology of the drilling fluid is good. Compared with Example 2, spraying a low content of sodium hexametaphosphate on the barite powder with good moisture absorption resistance and good dispersibility of different particle sizes mixed is helpful for improving the rheology of the drilling fluid.

[0090] Comparative Example 1:

[0091] It is basically the same as the barite composition and preparation method of Example 1. The main difference is that 1.4 wt% of starch nanocrystals was not added, and the corresponding part was replaced by barite. After testing, the measured interfacial contact angle was 123°. Moisture absorption performance test during storage. After testing: The weight increased by 0.5 g in one week, 0.7 g in two weeks, and 0.8 g in one month, and obvious agglomeration and caking of the powder occurred at two weeks.

[0092] Comparing Example 1 and Comparative Example 1, it can be seen that for the barite powder without starch nanocrystal coating, the hydrophobicity increases, the moisture absorption and weight gain are more obvious during long-term storage, and it is more affected by humidity during long-term storage.

[0093] Comparative Example 2:

[0094] It is basically the same as the barite composition and preparation method of Example 1, with the main difference being that 1.0 wt% of silane coupling agent is not added, and the corresponding part is replaced by barite. After testing, the measured interfacial contact angle is 117°. For the storage moisture absorption performance test, after testing: the weight increases by 0.4 g in one week, 0.51 g in two weeks, 0.6 g in one month, and obvious agglomeration and caking occur in the powder after one month.

[0095] Comparing Example 1 and Comparative Example 2, it can be seen that without adding silane coupling agent, it may affect the barite powder coated with starch nanocrystals, increasing the hydrophobicity, having relatively more moisture absorption and weight gain during long-term storage, and being more affected by humidity during long-term storage.

[0096] Comparative Example 3:

[0097] It is basically the same as the barite composition and preparation method of Comparative Example 1 and Example 2. For the storage moisture absorption performance test, after testing: the weight increases by 0.6 g in one week, 0.67 g in two weeks, 0.84 g in one month, and obvious agglomeration and caking occur in the powder after two weeks. Compared with Example 2, the long-term storage stability becomes worse.

[0098] After testing, the aged drilling fluid was allowed to stand and cool to room temperature, and a small amount of powder sedimentation was observed, indicating that the prepared mixed barite powder has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 87, plastic viscosity (PV / mPa·s): 54. Compared with Example 2, the rheology of the drilling fluid becomes worse, indicating that the barite powder coated with starch nanocrystals has a certain improvement effect on the rheology of the drilling fluid.

[0099] Comparative Example 4:

[0100] It is basically the same as the barite composition and preparation method of Example 1 and Example 2, with the main difference being that the content of the second fine-particle-size barite powder is 37 wt%, and the content of the third starch nanocrystal-coated fine-particle-size barite powder is 63 wt%.

[0101] For the storage moisture absorption performance test, after testing: the weight increases by 0.5 g in one week, 0.64 g in two weeks, 0.78 g in one month, and there is slight agglomeration and caking in the powder after one month.

[0102] After testing the drilling fluid directly added with barite powder that is not easy to absorb moisture and has good dispersibility: the aged drilling fluid was allowed to stand and cool to room temperature, and no obvious sedimentation was observed, indicating that the barite powder that is not easy to absorb moisture and has good dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 78, plastic viscosity (PV / mPa·s): 51, both of which are relatively low, and the rheology of the drilling fluid is better. Compared with Example 2, without adding the first coarse-particle-size barite powder and using a mixture of smaller particles, the dispersibility is better, but it is not conducive to improving the rheology of the drilling fluid and has an adverse effect on the humidity tolerance.

[0103] Comparative Example 5:

[0104] It is basically the same as the barite composition and preparation method of Example 1 and Example 2, without adding particles, and the corresponding step S2 of mixing different particles is omitted. The main difference is that the content of the third starch nanocrystal-coated fine-particle-size barite powder is 100 wt%.

[0105] The prepared barite powder with good moisture absorption resistance and good dispersibility directly added to the drilling fluid was tested: After the aged drilling fluid was allowed to stand and cool to room temperature, no obvious sedimentation was observed, indicating that the barite powder with good moisture absorption resistance and good dispersibility has good dispersibility in the drilling fluid. Apparent viscosity (AV / mPa·s): 85, plastic viscosity (PV / mPa·s): 54, both are relatively high. Compared with Example 2, the first coarse-particle-size barite powder and the second fine-particle-size barite powder are not added, and the third starch nanocrystal-coated fine-particle-size barite powder with a small particle size is used, and the dispersibility is better, but it is not conducive to improving the rheology of the drilling fluid.

[0106] In summary, the barite powder with good moisture absorption resistance and good dispersibility and the preparation method provided by the present invention can directly utilize the barite powder obtained by the flotation method and adsorbed with flotation agents. The compound utilization of barite powders with different particle sizes is not easy to deposit, has good dispersibility, has little adverse effect on the viscosity and rheology of the drilling fluid, is not easy to absorb moisture and agglomerate during storage, and realizes the effective, low-cost and full utilization of barite resources.

[0107] The preferred embodiments of the present invention have been described in detail above, which are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A barite powder that is not easy to absorb moisture and has good dispersibility, characterized in that: The barite powder includes, based on the total mass: a first coarse particle size barite powder content of 5-10wt%, a second fine particle size barite powder content of 20-40wt%, and a third starch nanocrystal coated fine particle size barite powder content of 55-70wt%; The first coarse particle size barite powder particle size: the second fine particle size barite powder particle size is 1.43:1-5.3:1, the first coarse particle size barite powder particle size is 46-59 μm; the second fine particle size barite powder particle size is 11-32 μm; Taking the total mass of the third starch nanocrystal-coated fine-grained barite powder as a benchmark, the third starch nanocrystal-coated fine-grained barite powder includes: fine-grained barite powder 97.5-98wt%; silane coupling agent 0.6-1.1wt%; starch nanocrystal 0.8-1.5wt%; the particle size of the fine-grained barite powder is 2-9μm.

2. The barite powder with good moisture absorption and dispersibility according to claim 1, characterized in that The first coarse particle size of the barite powder: the second fine particle size of the barite powder is 2.6:1-3.6:1; the first coarse particle size of the barite powder is 46-54μm; the second fine particle size of the barite powder is 13-18μm.

3. The barite powder with good moisture absorption and dispersibility according to claim 1 or 2, characterized in that Taking the total mass of the third starch nanocrystal coated fine-grained barite powder as a benchmark, the third starch nanocrystal coated fine-grained barite powder comprises: fine-grained barite powder is 97.5-98%; silane coupling agent is 0.6-1.1%; starch nanocrystal is 0.8-1.5% and montmorillonite is 0.4-0.7%.

4. The barite powder with good moisture absorption and dispersibility according to claim 1, characterized in that The silane coupling agent is γ-aminopropyltriethoxysilane.

5. A method for preparing barite powder with good dispersibility and low moisture absorption, preparing the barite powder with good dispersibility and low moisture absorption as claimed in any one of claims 1 to 4, characterized in that, The method includes: S1: Preparation of the third starch nanocrystal coated fine-grained barite powder: add fine-grained barite powder into a high-speed mixer according to the mass ratio of fine-grained barite powder, spray silane coupling agent on the surface of fine-grained barite powder, mix and stir at a first temperature for a first set time to obtain a first coated fine-grained barite powder, then weigh starch nanocrystal powder according to the mass ratio of starch nanocrystals, add water and stir to obtain a starch nanocrystal solution, spray it on the surface of the first coated fine-grained barite powder, mix and stir at a second temperature for a second set time, and obtain the third starch nanocrystal coated fine-grained barite powder after drying and cooling; S2: stirring the first coarse-grained barite powder, the second fine-grained barite powder, and the third starch nanocrystal-coated fine-grained barite powder prepared in step S1 in a second stirrer for a third set time to obtain barite powder that is not easy to absorb moisture and has good dispersibility.

6. The method for preparing a barite powder having good moisture absorption and good dispersibility according to claim 5, characterized in that: The stirring speed of the high-speed mixer is: 1600-2100r / min, the first temperature is 70-90°C, the first setting time is 10-15 minutes, the second temperature is 91-132°C, the second setting time is 20-30 minutes, and the third setting time is 20-30 minutes.

7. A method for preparing barite powder with good moisture absorption and dispersibility according to claim 5 or 6, characterized in that, In step S1, the third starch nanocrystal coated fine-grained barite powder is prepared: starch nanocrystal powder is weighed according to the mass ratio of starch nanocrystals, water is added and stirred to obtain a starch nanocrystal-containing solution, which is sprayed onto the surface of the first coated fine-grained barite powder. At the same time, ozone with a gas flow rate of 0.5-2L / min is introduced into a high-speed blender for 5-6 minutes, mixed and stirred at a second temperature for a second set time, and the third starch nanocrystal coated fine-grained barite powder is obtained after drying and cooling.

8. A method for preparing barite powder with good moisture absorption and dispersibility according to claim 7, characterized in that, In step S1, in the preparation of the third starch nanocrystal-coated fine-grained barite powder, ozone with a gas flow rate of 0.5-2 L / min is introduced into a high-speed mixer for 5-6 minutes, and then montmorillonite is added for mixing and stirring.

9. The method for preparing a barite powder having good moisture absorption and dispersibility according to claim 5, characterized in that: In step S1, starch nanocrystal powder is weighed and water and ammonia water are added according to the mass ratio of starch nanocrystals, and the mixture is stirred to obtain a starch nanocrystal-containing solution. The pH value of the starch nanocrystal-containing solution is controlled to be 9.5-10.

10. The method for preparing a barite powder having good moisture absorption and good dispersibility according to claim 5, characterized in that: S2: When the first coarse-grained barite powder, the second fine-grained barite powder and the third starch nanocrystal-coated fine-grained barite powder prepared in step S1 are stirred in a second stirrer for a third set time, 0.1-0.3% of the total mass of the barite powder with low moisture absorption and good dispersibility is sprayed on the surface of the particle mixture.