A salt mixed microproppant consolidation particle and a method of making the same

Abstract

The application discloses a kind of salt mixed micro proppant consolidation particles and preparation method thereof, and the consolidation particles are prepared by any one of the following methods: solid salt and micro proppant mixture granulation method, solid salt and micro proppant wet mixing drying granulation method or high concentration salt water and micro proppant drying granulation method, using water-soluble salt, micro proppant and micro proppant surface modification material.The micro proppant has low cost, avoids dust pollution, is easy to store and add, can be carried to deep fractures, realizes full propping of fractures, and finally improves the transformation effect.

Description

Technical Field

[0001] This invention belongs to the field of reservoir modification technology, specifically relating to a salt-mixed microproppant solidified particle and its preparation method. Background Technology

[0002] With the continuous development of oil and gas fields, since the beginning of the new century, unconventional reservoirs have become an important component of global oil and gas production capacity and the most important future replacement force. They are also a crucial component in ensuring my country's energy security and improving its energy self-sufficiency rate, possessing critical strategic significance. Unconventional reservoirs include tight oil, shale oil, tight gas, coalbed methane, and shale gas reservoirs. Unconventional oil and gas reserves account for more than 70% of the newly proven oil and gas reserves in China, making them a vital part of my country's exploration and development. Unconventional oil and gas reservoirs are often characterized by large-scale continuous distribution, lack of obvious traps, and a lack of stable economic natural production capacity, often requiring reservoir stimulation to generate industrial oil and gas flows.

[0003] For reservoir stimulation technologies targeting unconventional reservoirs, volumetric fracturing is one of the most important techniques. This technology enables large-scale stimulation of unconventional reservoirs, improves reservoir oil and gas flow, and connects deep reservoirs to oil and gas wellbores, ultimately achieving economical and efficient development of unconventional reservoirs. During volumetric fracturing, large-volume, high-displacement fracturing operations, supplemented by temporary plugging and diversion techniques, can create complex fracture networks in the formation. These fracture networks require proppant support; otherwise, as the pressure within the fractures decreases, the fractures close, and the conductivity drops sharply, severely impacting long-term development. These complex fracture networks consist of primary and secondary fractures. While primary fractures can be supported by conventional proppant, secondary fractures have smaller openings, some even less than 50 μm, making it impossible for commonly used 70 / 140 mesh proppant (106~212 μm) to penetrate and effectively fill them. Using 300-500 mesh microproppant (25-48μm) can penetrate into secondary fractures and provide effective support, thereby ensuring good flow channels to the main fractures in the deep reservoir after fracturing.

[0004] However, the specific surface area of ​​proppant increases continuously as the proppant particle size decreases. When using micro proppant, due to its small particle size and significant surface energy effect, if dry powder is directly added to the fracturing fluid during on-site fracturing operations, it will aggregate under the action of surface energy. This is equivalent to the micro proppant clumping together and the equivalent particle size increasing, which increases the proppant settling velocity, shortens the migration distance, and makes it difficult for the proppant to enter the micro fractures. When using dry powder micro proppant on-site, a large amount of dust pollution will be generated, affecting personnel health and the normal operation of on-site equipment.

[0005] Currently, to overcome the above problems, the main methods used are water-based dispersion systems (Chinese patent CN115960600A) or high-temperature molten salt tower granulation methods (Chinese patent CN104474969A). Although these methods can effectively solve the problem of increased particle size due to proppant agglomeration, they also have limitations such as: (1) the need to prepare a water-based dispersion system for microproppant, which involves complex chemicals and production processes and poses potential damage to the reservoir; (2) the effective content of microproppant in the water-based dispersion system is 35%~50%, which is in liquid state and requires the use of special packaging such as ton containers, making on-site transportation and storage cumbersome; (3) the need to use a special liquid addition pump for adding microproppant, which poses risks such as blockage and jamming of the addition pump; and (4) the lack of solid-liquid mixing function in the process flow.

[0006] Chinese patent CN115960600A discloses a micropropeptide water-based dispersion system and its preparation method. Compared with existing addition methods, the micropropeptide water-based dispersion system can effectively avoid the self-aggregation of micropropeptides in fracturing fluid and avoid the dust hazards generated during the use of micropropeptides. However, this method has the following drawbacks: (1) It requires the preparation of a micropropeptide water-based dispersion system, which involves complex chemicals and production processes, and poses a potential threat to the reservoir; (2) The effective content of micropropeptides in the water-based dispersion system is only 35%~50%, and it is in liquid state, requiring the use of special packaging such as ton containers, which makes on-site transportation and storage cumbersome; (3) It requires the use of a special liquid addition pump to add micropropeptides, and there is a risk of blockage and jamming of the addition pump, making it difficult to inject smoothly on-site.

[0007] Chinese patent CN104474969A discloses a high-temperature molten salt tower granulation method containing potassium nitrate. Its main feature is the use of binary, ternary, and quaternary mixed raw materials containing potassium nitrate to prepare spherical high-temperature molten salt particles. This improves the mixing uniformity of the raw materials, facilitates use, and avoids the agglomeration of powdered materials. The high-temperature molten salt particles formed by this method are spherical or near-spherical in shape. However, this method requires first dissolving the multi-component salts in water, then concentrating the water, spraying the molten material, and shaping it. Micropropeptides cannot dissolve in water, and the process flow lacks solid-liquid mixing capabilities. Therefore, this method cannot meet the requirements for micropropeptide agglomeration.

[0008] Therefore, providing an economical and efficient microproppant particle that is easy to store and transport in the field, easy to add, and can enter microcracks, as well as its preparation process, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] This invention addresses the problems in existing technologies, such as the small particle size of microproppants leading to significant dust pollution, impacting personnel health and hindering the normal operation of on-site equipment; the tendency of tiny particles to agglomerate due to electrostatic adsorption, resulting in increased equivalent particle size of the microproppant, leading to increased settling velocity, shortened transport distance, and difficulty in proppant penetration into microcracks; and the complexity, high cost, stringent packaging requirements, and high transportation costs of water-based dispersion systems. The aim is to provide a salt-mixed microproppant solidified particle and its preparation method.

[0010] This invention is achieved through the following technical solution: A salt-based mixed micropropped agent solidified particles, comprising the following components and their mass percentages: The percentage of water-soluble salts is 28.5%–69.9%. Micropropeptide 30%~70%; 0.1-0.5% of surface-modifying material for micropropeptides; In the above technical solution, the surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide; the micropropeptide is mixed with a water-soluble salt and solidified into granules.

[0011] In the above technical solution, the water-soluble salt is completely dissolved within 1 to 5 minutes of contact with the fracturing fluid.

[0012] In the above technical solution, the water-soluble salt has a solubility of more than 30 g / L, a melting point of less than 800 °C, stable chemical properties, and is not prone to reacting with formation fluids to produce precipitation, and is not prone to absorbing moisture and clumping.

[0013] In the above technical solution, the water-soluble salt is at least one of NaCl, KCl, or CaCl2.

[0014] In the above technical solution, the surface-modifying substance of the microsupport is an oleophilic and hydrophobic surfactant or a coating process modifier; the oleophilic and hydrophobic surfactant is a reduced graphene oxide, polypropylene fiber, or alkyl ethylene polymer; the coating process modifier is composed of a tackifying substance and an adhesive, and the ratio of the microsupport, tackifying substance, and adhesive is determined by comprehensive calculation based on the surface area of ​​the microsupport, the coating thickness, and the reagent ratio; the tackifying substance is polyacrylamide, epoxy resin, furan, polyester, vinyl ester, or polyurethane; the adhesive is a water-based adhesive, an amine curing agent, an anhydride curing agent, or a UV-curable adhesive; the coating thickness formed by the tackifying substance and the adhesive is ≤5μm.

[0015] In the above technical solution, the micro-proppant particles are 100 mesh to 500 mesh; the micro-proppant is ceramsite or quartz sand.

[0016] In the above technical solution, the particle size of the salt-mixed microproppant solidified particles is 10 mesh to 70 mesh.

[0017] In the above technical solution, the salt-mixed micropropping agent solidified particles can be fully dispersed in fracturing fluids such as slickwater fracturing fluid, VES fracturing fluid, and foam fracturing fluid prepared in water at concentrations of 1000 mg / L to 100000 mg / L, and the water-soluble salts can be completely dissolved in various fracturing fluids.

[0018] In the above technical solution, the salt-mixed microproppant solidified particles can be adjusted by modifying the water-soluble salt composition and particle size, combined with the operating flow rate and wellbore volume, so that the salts in the solidified particles can be completely dissolved, the microproppant can be completely released, and the particles can be fully dispersed in the fracturing fluid as soon as they enter the perforation nozzle.

[0019] During on-site fracturing operations, the salt-mixed microproppant solidified particles are added directly to the mixing tank of the sand mixing truck. The water-soluble salts in the solidified particles can completely dissolve within 1 to 5 minutes of contact with the fracturing fluid, dispersing the microproppant in the fracturing fluid. It is uniformly dispersed in the high-shear and high-disturbance environment of the mixing tank and wellbore, and finally enters the microfractures with the fracturing fluid, effectively supporting the microfractures after the fracturing fractures are closed.

[0020] A method for preparing the aforementioned salt-mixed micropropeptide solidified particles, wherein the preparation method is any one of the following: melt granulation of solid salt and micropropeptide mixture, wet mixing and drying granulation of solid salt and micropropeptide, or drying granulation of high-concentration brine and micropropeptide.

[0021] In the above technical solution, the melt granulation method for the mixture of solid salts and micropropeptides specifically includes the following steps: S1. Crush the water-soluble solid salt and sieve it through a sieve with a mesh size greater than 100 to obtain salt powder; S2. By mixing and stirring, the surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide to obtain the surface-modified micropropeptide. S3. Mix the salt powder obtained in step S1 with the surface-modified micropropeptide obtained in step S2 in proportion to obtain a mixture; S4. Heat the mixture obtained in step S3 to 850℃~1000℃, then spray it at a height of not less than 5m and let it settle by gravity. During the settling process, the particles agglomerate and solidify into particles by the heat dissipation effect of cold air. S5. Screen the solidified particles obtained in step S4, retain the solidified particles within the range of 10 mesh to 70 mesh as solidified particles of salt mixed microproppant, and re-crush and granulate the solidified particles whose particle size does not meet the requirements.

[0022] In the above technical solution, the method of wet mixing and drying granulation of solid salts and micropropeptides specifically includes the following steps: S1. Crush the water-soluble solid salt and sieve it through a sieve with a mesh size greater than 100 to obtain salt powder; S2. By mixing and stirring, the surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide, and 5% to 10% of the mass of water is added to the micropropeptide particles to obtain the surface-modified micropropeptide. S3. Add the surface-modified micropropeller obtained in step S2 into the heating furnace. After turning on the stirring, slowly add 50% of the salt powder obtained in step S1 into the heating furnace so that the surface-modified micropropeller is uniformly coated with salt powder. S4. Heat the mixture obtained in step S3 to 850℃~1000℃ and granulate it uniformly in a roller heating furnace to form small particles; S5. Reduce the temperature of the small particles obtained in step S4 to below 700°C, heat the remaining salt powder to a molten state, spray it onto the surface of the small particles to mix them thoroughly, and continue to granulate them evenly in a roller heating furnace to form large particles. S6. The large particles obtained in step S5 are sieved. The solidified particles with a mesh size of 10 to 70 are retained as solidified particles of salt mixed microproppant. The solidified particles with non-compliant particle sizes are remelted and granulated.

[0023] In the above technical solution, the high-concentration brine and micropropeptide drying and granulation method specifically includes the following steps: S1. Dissolve water-soluble salts in water to form saturated salt water; S2. By mixing and stirring, the surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide to obtain the surface-modified micropropeptide. S3. Mix the surface-modified micropropeptide obtained in step S2 with high-concentration brine in a certain proportion and stir evenly to obtain a mixture; S4. Pour the mixture obtained in step S3 into a roller heating furnace and heat and dry it while rotating, so that the micro-support agent is uniformly mixed in the salt block to obtain solidified particles. S5. Screen the solidified particles and retain the solidified particles within the range of 10 to 70 mesh as solidified particles of salt mixed microproppant. Spray the solidified particles that do not meet the particle size requirements with an appropriate amount of water, dry them again, granulate them, and screen them.

[0024] The beneficial effects of this invention are: This invention provides a salt-mixed microproppant consolidation particle and its preparation method. The on-site microproppant is low in cost, avoids dust pollution, is easy to store and add, can be carried deep into the crack, achieves full support of the crack, and ultimately improves the modification effect.

[0025] The salt-mixed microproppant solidified particles provided by this invention thoroughly mix salt and microproppant, solving a series of problems such as difficulty in on-site addition of microproppant and serious pollution. They offer advantages such as avoiding dust pollution, easy storage and addition, the ability to be carried deep into fractures, achieving full fracture support, and good reservoir stimulation effects. The raw materials for the salt-mixed microproppant solidified particles provided by this invention are simple, readily available, and cost-controllable. The preparation process of the salt-mixed microproppant solidified particles provided by this invention includes various methods such as melt granulation of solid salt and microproppant mixture, wet mixing and drying granulation of solid salt and microproppant, and drying granulation of high-concentration brine and microproppant. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below through specific embodiments.

[0027] Example 1 This study focuses on a multi-stage volumetric fracturing well in a horizontal well within a tight sandstone reservoir. The reservoir depth ranges from 2030.1 m to 2045.7 m, with a formation temperature of 64.7℃, a reservoir pressure of 18.1 MPa, and a fracture closure pressure of 36.5 MPa. The reservoir is a naturally fractured tight sandstone gas reservoir with a fracture density of 1.5 fractures / m to 3.0 fractures / m, a porosity of 10.2%, and a permeability of 1.47 mD. The well exhibits poor reservoir properties and requires volumetric fracturing to achieve economical production capacity. To achieve better stimulation and higher production capacity, effective support is needed for the distal fractures formed by volumetric fracturing. Therefore, to ensure smooth field operations and effective support for distal microfractures, 300-mesh powdered ceramic microproppane is used to create consolidated particles. To further improve the suspension performance of the microproppane in the fracturing fluid, a salt-resistant polyacrylamide coating is applied to the surface of the microproppane. Granulation is performed using a melt granulation method involving a mixture of solid salts and microproppane. The specific preparation method is as follows: S1. Pulverize potassium chloride with an effective content of ≥98% and sieve it through a 120-mesh sieve to obtain salt powder; S2. Salt-resistant polyacrylamide is uniformly coated on the surface of microproppant (300-mesh ceramic powder) at a ratio of 0.3% of the mass of the salt-mixed microproppant solidified particles to obtain a surface-modified microproppant. S3. Mix the salt powder prepared in step S1 with the surface-modified micro-support agent prepared in step S2 in a mass ratio of 50:50. S4. Heat the salt powder and micropropeptide mixture formed in step S3 to 1000°C so that the salt powder is in a molten state. Spray the mixture with a 0.5mm nozzle at a height of 30m. Under the action of gravity, the mixture settles. During the settling process, air with a temperature below 30°C is blown in. The heat dissipation effect of the air achieves particle agglomeration and consolidation. S5. Screen the solidified particles and retain the solidified particles within the range of 10 to 30 mesh. Remelt and granulate the solidified particles that do not meet the particle size requirements.

[0028] Example 2 This study focuses on a horizontal multi-stage volumetric fracturing well in a coalbed methane reservoir. The reservoir depth is 1800-1830m, the formation temperature is 70℃, the reservoir pressure is 18.0MPa, and the fracture closure pressure is 34.0MPa. The coal seam exhibits high development of texture and natural fractures, with a permeability of 0.5mD. The reservoir properties are poor, necessitating volumetric fracturing to achieve economical production. Due to the characteristics of the coal seam, complex fractures are easily formed during fracturing. Since coalbed methane is produced through adsorption and desorption, effective support is required at the distal fractures to establish a production path for coalbed methane from the coal seam, microfractures, fractures, and the wellbore. Given the need for strict cost control during fracturing and the low fracture closure pressure, 300-500 mesh fine sand is used during fracturing, thoroughly mixed with high-salinity water, and granulated with microproppant. Granulation is performed using a high-concentration brine and microproppant drying granulation method. The specific preparation method is as follows: S1. Filter high-concentration seawater to remove 500-mesh suspended solids; S2. Using 300-500 mesh silt as a micro-proppant, it is uniformly mixed with high-concentration seawater. The mass ratio of silt to total salt in seawater is 55:45. The mass of total salt in seawater is determined by drying a unit volume of high-concentration seawater. S3. Pour the solid-liquid two-phase mixture into a roller heating furnace and heat and dry it while rotating, so that the micro-support agent is uniformly mixed in the salt block and finally forms solidified particles. S4. Screen the solidified particles, retaining the solidified particles within the range of 10 to 20 mesh. Spray the solidified particles that do not meet the size requirements with 10% water, then dry and granulate again, and screen them.

[0029] This invention thoroughly mixes salt with microproppant, solving the current problems of difficult on-site addition of microproppant, serious pollution, and difficulty in transporting proppant to deep formations. It has the advantages of low dust pollution, simple storage and addition, easy migration in fractures, strong fracture support capacity, and good reservoir stimulation effect. The salt-mixed microproppant solidified particles of this invention use simple, common, environmentally friendly, and cost-controllable raw materials. The preparation method of the salt-mixed microproppant solidified particles of this invention has a simple production process, low energy consumption, and high yield.

[0030] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A salt-mixed microproppane-bonded particle, characterized in that: The components included and their mass percentages are as follows: The percentage of water-soluble salts is 28.5%–69.9%. Micropropeptide 30%~70%; 0.1-0.5% of surface-modifying material for micropropeptides; The surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide; The micropropeptide is mixed with water-soluble salt and solidified into granules.

2. The salt-mixed microproppane-bonded particles according to claim 1, characterized in that: The water-soluble salt dissolves completely within 1 to 5 minutes of contact with the fracturing fluid; the water-soluble salt has a solubility higher than 30 g / L and a melting point lower than 800 °C.

3. The salt-mixed microproppane-bonded particles according to claim 1, characterized in that: The water-soluble salt is at least one of NaCl, KCl, or CaCl2.

4. The salt-mixed microproppane-bonded particles according to claim 1, characterized in that: The surface-modifying material of the microsupport is an oleophilic and hydrophobic surfactant or a coating process modifier; the oleophilic and hydrophobic surfactant is a reduced graphene oxide, polypropylene fiber, or alkyl ethylene polymer; the coating process modifier is composed of a tackifier and an adhesive; the tackifier is polyacrylamide, epoxy resin, furan, polyester, vinyl ester, or polyurethane; the adhesive is a water-based adhesive, amine curing agent, anhydride curing agent, or UV-curable adhesive; the coating thickness formed by the tackifier and adhesive is ≤5μm.

5. The salt-mixed microproppane-bonded particles according to claim 1, characterized in that: The microproppant particles are 100-500 mesh; the microproppant is ceramsite or quartz sand.

6. The salt-mixed microproppane-bonded particles according to claim 1, characterized in that: The particle size of the salt-mixed microproppant consolidation particles is 10-70 mesh; the salt-mixed microproppant consolidation particles can be fully dispersed in fracturing fluid with a concentration of 1000 mg / L to 100000 mg / L prepared with water, and the water-soluble salts can be completely dissolved in the fracturing fluid; the fracturing fluid is slickwater fracturing fluid, VES fracturing fluid, or foam fracturing fluid.

7. A method for preparing salt-mixed microproppane-bonded particles according to any one of claims 1 to 6, characterized in that: The preparation method is any one of the following: melt granulation of a mixture of solid salts and micropropeptides, wet mixing and drying granulation of solid salts and micropropeptides, or drying granulation of high-concentration brine and micropropeptides.

8. The method for preparing salt-mixed microproppane-bonded particles according to claim 7, characterized in that: The melt granulation method for the mixture of solid salt and micropropeptide specifically includes the following steps: S1. Crush the water-soluble solid salt and sieve it through a sieve with a mesh size greater than 100 to obtain salt powder; S2. The surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide to obtain the surface-modified micropropeptide; S3. Mix the salt powder obtained in step S1 with the surface-modified micropropeptide obtained in step S2 in proportion to obtain a mixture; S4. Heat the mixture obtained in step S3 to 850℃~1000℃, then spray it from a high place and let it settle by gravity to obtain solidified particles. S5. Screen the consolidated particles obtained in step S4, and retain the consolidated particles within the range of 10 mesh to 70 mesh as consolidated particles of salt mixed microproppant.

9. The method for preparing salt-mixed microproppane-bonded particles according to claim 7, characterized in that: The method of wet mixing and drying granulation of solid salts and micropropeptides specifically includes the following steps: S1. Crush the water-soluble solid salt and sieve it through a sieve with a mesh size greater than 100 to obtain salt powder; S2. The surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide, and 5% to 10% of the mass of water is added to the micropropeptide particles to obtain the surface-modified micropropeptide. S3. Add the surface-modified micropropeller obtained in step S2 into the heating furnace. After turning on the stirring, slowly add 50% of the salt powder obtained in step S1 into the heating furnace so that the surface-modified micropropeller is uniformly coated with salt powder. S4. Heat the mixture obtained in step S3 to 850℃~1000℃ and granulate it uniformly in a roller heating furnace to form small particles; S5. Reduce the temperature of the small particles obtained in step S4 to below 700°C, heat the remaining salt powder to a molten state, spray it onto the surface of the small particles to mix them thoroughly, and continue to granulate them evenly in a roller heating furnace to form large particles. S6. The large particles obtained in step S5 are sieved, and the solidified particles within the range of 10 to 70 mesh are retained as solidified particles of salt mixed microproppant.

10. The method for preparing salt-mixed microproppane-bonded particles according to claim 7, characterized in that: The high-concentration brine and micropropeptide drying and granulation method specifically includes the following steps: S1. Dissolve water-soluble salts in clear water to form a high-concentration salt solution; S2. The surface-modifying material of the micropropeptide is uniformly coated on the surface of the micropropeptide to obtain the surface-modified micropropeptide; S3. Mix the surface-modified micropropeptide obtained in step S2 with high-concentration brine in a certain proportion and stir evenly to obtain a mixture; S4. Pour the mixture obtained in step S3 into a roller heating furnace and heat and dry it while rotating, so that the micro-support agent is uniformly mixed in the salt block to obtain solidified particles. S5. Screen the consolidated particles and retain the consolidated particles within the range of 10 to 70 mesh as the consolidated particles of the salt mixed microproppant.