Coal gangue ceramic propping agent for oil exploitation and production method thereof

Abstract

The present application mainly relates to the technical field of oil and gas development auxiliary materials, in particular to a coal gangue ceramic proppant suitable for oil exploitation and a production method thereof, which comprises the following raw materials in parts by mass: coal gangue 63-67 parts, shale 8-12 parts, biomass charcoal 20-25 parts, nano material 1-1.2 parts, glass fiber 5-6 parts, fluxing agent 8-10 parts, and binder 2-2.5 parts; the nano material is selected from nano carbon tubes, and the nano carbon tubes are subjected to surface functionalization treatment and introduction of active groups. The present application adopts the optimized combination of various raw materials such as coal gangue and bamboo biomass charcoal, and an innovative process method to prepare a proppant with high strength, good adsorption and flow guiding performance, chemical stability, heat shock resistance and other excellent comprehensive performance, which can effectively meet the strict requirements of modern oil exploitation on proppants, reduce the production cost, and realize the effective utilization of resources.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of oil and gas development auxiliary materials, in particular to a coal gangue ceramic proppant suitable for oil exploitation and a production method thereof. BACKGROUND

[0002] In the field of oil exploitation, hydraulic fracturing technology is one of the key means to improve oil and gas production. This technology injects high-pressure liquid into the underground oil layer to form cracks in the rock, thereby increasing the flow channel of oil and gas. Proppants play a crucial role in this process, as they are injected into the cracks to support them and prevent them from closing after pressure is released, ensuring that oil and gas can continue to flow smoothly to the wellbore.

[0003] Currently, the commonly used proppants in oil exploitation are mainly quartz sand and ceramic proppants. Quartz sand is relatively inexpensive, but its compressive strength is relatively low, generally between 35MPa and 70MPa, and is only suitable for shallow wells and low-pressure reservoirs. As oil exploitation gradually develops towards deep wells, ultra-deep wells, and complex geological conditions, the performance requirements for proppants, such as compressive strength, are becoming increasingly demanding, and quartz sand is difficult to meet these harsh environmental needs.

[0004] Ceramic proppants have higher compressive strength, generally reaching 70MPa to 140MPa, and are suitable for high-pressure environments such as deep wells. However, traditional ceramic proppants have some problems in the preparation process. On the one hand, the raw materials used are mostly conventional mineral raw materials such as bauxite, which have high costs and limited resources. On the other hand, the adsorption performance, flow conductivity, and chemical stability of proppants prepared by traditional preparation processes still need to be improved. For example, the pore structure of conventional ceramic proppants is not ideal, and their adsorption capacity for impurities and crude oil in the reservoir is limited, which to some extent affects the efficiency of oil and gas exploitation. At the same time, in acidic reservoir environments, some ceramic proppants have high acid solubility, leading to a decrease in the stability of the proppants and a reduction in their service life.

[0005] In addition, in the preparation process of proppants, traditional methods are difficult to accurately control the microstructure and performance of the proppants. For example, in the molding process, it is difficult to form uniform and regular particles, which affects the packing effect and flow conductivity of the proppants in the cracks. In the sintering process, it is also difficult to finely control the microstructure, resulting in the mechanical properties and stability of the proppants being unable to be fully optimized.

[0006] In view of the deficiencies in the prior art, the present application provides a granular ceramic proppant suitable for oil exploitation and a production method thereof, which is prepared by optimizing the combination of various raw materials such as coal gangue and bamboo biomass charcoal, finely pretreating and modifying the raw materials, and innovative process methods such as gradient freeze forming and pulse microwave sintering, and has excellent comprehensive performance, effectively solving the problem that the traditional oil exploitation proppant (such as quartz sand with low compressive strength, ceramic proppant with high raw material cost and performance to be improved, including adsorption, flow conductivity, chemical stability, and the like, and the forming and sintering process being difficult to accurately control the microstructure and performance) cannot meet the strict requirements of modern oil exploitation on the strength, performance, cost and resource utilization of the proppant. SUMMARY

[0007] The present application aims to provide a coal gangue ceramic proppant suitable for oil exploitation and a production method thereof, which is prepared by optimizing the combination of various raw materials such as coal gangue and bamboo biomass charcoal, and innovative process methods, and has high strength, good adsorption and flow conductivity performance, chemical stability and comprehensive performance such as thermal shock resistance, can effectively meet the strict requirements of modern oil exploitation on the proppant, while reducing the production cost and realizing the effective utilization of resources.

[0008] The technical scheme adopted by the present application to solve the above technical problems is as follows:

[0009] In a first aspect, the present application provides a coal gangue ceramic proppant suitable for oil exploitation, which comprises the following raw materials in parts by mass:

[0010] Coal gangue 63-67 parts, shale 8-12 parts, biomass charcoal 20-25 parts, nanomaterial 1-1.2 parts, glass fiber 5-6 parts, fluxing agent 8-10 parts, and binder 2-2.5 parts.

[0011] The nanomaterial is selected from nanocarbon tubes, and the nanocarbon tubes are surface-functionalized and introduced with active groups.

[0012] The action mechanism of each component in the above raw material formula is as follows:

[0013] Coal gangue: as a basic raw material, it provides an attachment and reaction matrix for other raw materials. In cooperation with bamboo biomass charcoal, the ceramic phase formed by coal gangue wraps the pore structure of bamboo biomass charcoal, ensuring the strength of the proppant and retaining the adsorption and flow conductivity performance of bamboo biomass charcoal. The functionalized nanocarbon tubes form chemical bonds through active groups, enhancing the mechanical properties of the proppant. The glass fibers interweave with each other to jointly build the skeletal structure of the proppant, improving the compressive strength.

[0014] Shale: It contains a certain amount of clay minerals and other minerals, which can improve the plasticity and forming performance of the body during the body forming process, making it easier to process into the required shape, and reducing the risk of cracking and deformation during drying and sintering. During the sintering process, the components in the shale react with other raw materials, promoting the formation of a glass phase, filling the intergranular gaps, and improving the density and strength of the proppant.

[0015] Biomass charcoal: It has a rich pore structure and high specific surface area. Its unique fibrous pores can guide the directional arrangement of internal pores in the proppant, forming channels that facilitate oil and gas transmission, improving the conductivity of the proppant. At the same time, bamboo biomass charcoal has adsorption effect on impurities and crude oil in the reservoir, which can purify oil and gas and improve the quality of mining.

[0016] Nanomaterials: Select nanotubes with active groups introduced by surface functionalization treatment. After functionalization treatment, active groups are introduced on the surface of nanotubes. These active groups can form chemical bonds or strong physical forces with other raw materials, equivalent to forming "anchoring points" or "bridges" inside ceramic particles, connecting different raw materials together, enhancing the overall bonding force, thereby improving the mechanical properties of proppant particles, making them better resist external forces such as pressure during oil extraction.

[0017] Functionalization treatment changes the surface properties of nanotubes, making them have specific charges or groups, increasing the interaction between nanotubes and the surrounding medium and other raw materials, reducing the tendency of nanotubes to agglomerate, allowing nanotubes to be more uniformly dispersed in the raw material system, thereby improving the dispersion stability of the entire proppant particle during preparation, and maintaining a good dispersion state during pumping, not easy to precipitate or aggregate.

[0018] Glass fiber: It has high strength and high modulus characteristics, with a tensile strength of 1000-3000 MPa and an elastic modulus of up to 70-90 GPa. In the proppant, glass fiber acts as a skeleton reinforcement, significantly improving the compressive strength and crush resistance of the proppant. When the proppant is subjected to external forces, the glass fiber can bear most of the load, effectively preventing the generation and propagation of cracks, thereby ensuring the structural integrity of the proppant in the high-pressure environment of oil extraction. During the sintering process, glass fiber can inhibit the abnormal growth of ceramic grains. The size and distribution of ceramic grains have an important influence on the performance of the proppant, and fine and uniform grains can improve the strength and toughness of the proppant. The presence of glass fiber hinders the growth of grains, making the microstructure of ceramics more uniform and fine, and improving the overall performance of the proppant.

[0019] Coal gangue and shale are the main raw materials of proppants, which provide the basic ingredients for forming ceramics. After mixing with glass fibers, a three-dimensional network structure is formed in the green body, which enhances the overall strength of the green body. During the sintering process, the components in the coal gangue and shale diffuse and react with the glass fibers, forming more stable chemical bonds, further improving the mechanical properties and chemical stability of the proppants.

[0020] Flux: reduces the sintering temperature, promotes the formation of liquid phase, makes the liquid phase uniformly distributed in the green body, fills the gap between particles, and improves the density of the proppants.

[0021] Binder: enhances the bonding force between raw materials during the shaping and sintering process of the green body, ensures the stability and effectiveness of the proppant structure.

[0022] In the implementation manner of the first aspect, the flux is a mixed flux, which includes feldspar, borax and fluorite, and the mass ratio of the feldspar, borax and fluorite is 5:2:1.

[0023] And / or, the binder is a mixed binder, which includes at least two of natural high molecular modified binder, synthetic high molecular binder and thermosetting resin binder.

[0024] In the implementation manner of the first aspect, the binder includes the following mass fractions of binders: natural high molecular modified binder 1.3-1.5 parts, synthetic high molecular binder 0.4-0.5 parts and thermosetting resin binder 0.3-0.5 parts.

[0025] And / or, the natural high molecular modified binder is selected from sodium carboxymethyl cellulose and sodium alginate, and the mass ratio of the sodium carboxymethyl cellulose and sodium alginate is 2:1. Sodium carboxymethyl cellulose has good water solubility and adhesion, and can form a uniform adhesive film on the surface of the raw material particles, effectively bonding the particles together. Sodium alginate has certain gel properties and can cross-link with some metal ions, further enhancing the adhesion effect. The combination of the two can enhance the particle forming strength while reducing impurity residues.

[0026] The synthetic high molecular binder is selected from polyvinyl butyral, which has good flexibility and adhesion, and can form a flexible connection between particles. In oil exploitation proppants, it can balance the flexibility and strength of the particles.

[0027] The thermosetting resin binder is selected from phenolic resin. The phenolic resin can form strong binding force with other raw materials at high temperature, which is crucial for maintaining the structural stability of the proppant in high-temperature oil reservoir environment. In oil exploitation, the downhole temperature is high, and ordinary binders may soften and decompose. However, the phenolic resin can be cured at high temperature to form a solid three-dimensional network structure, preventing the deformation and cracking of the particles.

[0028] The above several binders are mixed to meet the performance requirements of ceramic proppants in oil exploitation from multiple aspects. They can ensure the forming strength and flexibility of the proppant at room temperature, and maintain the structural stability in high-temperature oil reservoir environment, so that the proppant can play a good role in the whole oil exploitation process.

[0029] In the implementable manner of the first aspect, the biomass charcoal is selected from bamboo rich in lignin, and is pyrolyzed at a temperature of 550-650℃ for 2-3 hours by limiting oxygen pyrolysis technology, with an oxygen flow rate of 0.8-1.2 L / min to ensure the regularity and stability of the pore structure.

[0030] The bamboo biomass charcoal and functionalized carbon nanotubes are interwoven with each other. The carbon nanotubes enhance the stability of the pore structure of the bamboo biomass charcoal, and the bamboo biomass charcoal provides a dispersed carrier for the carbon nanotubes, and the two together optimize the microstructure of the proppant. In addition, the bamboo biomass charcoal cooperates with the glass fibers to ensure the adsorption performance of the proppant while enhancing the strength of the part containing the pore structure.

[0031] In the implementable manner of the first aspect, the glass fibers are first treated with a surface coupling agent, and a silane coupling agent is selected. The glass fibers are soaked in a silane coupling agent solution with a mass fraction of 3% for 2-3 hours, and then dried.

[0032] Then, plasma treatment is performed, and oxygen plasma is used with a power of 100-150 W and a treatment time of 5-10 minutes to enhance the interfacial bonding force with other raw materials.

[0033] The silane coupling agent introduces active groups on the surface of the glass fibers to enhance the interfacial bonding force with other raw materials. The plasma treatment further activates the surface of the glass fibers, increases the surface roughness and active sites, makes the coupling agent more firmly combined with the glass fibers, enhances the interaction between the glass fibers and the surrounding matrix, and more effectively plays the role of enhancing the mechanical properties and inhibiting the grain growth.

[0034] In the implementable manner of the first aspect, the ceramic proppant is a particulate material, and the single-particle compressive strength thereof is 170-200 MPa.

[0035] And / or, the particle size of the granular ceramic proppant is mainly concentrated in the range of 0.4-0.8mm, and the standard deviation of its particle size distribution is less than 0.1, ensuring the uniformity of particle size;

[0036] And / or, the sphericity coefficient of the granular ceramic proppant is greater than 0.85.

[0037] In the implementation mode of the first aspect, the ceramic proppant has a breakage rate of less than or equal to 3% under a closed pressure of 69MPa.

[0038] And / or, the acid solubility of the ceramic proppant is reduced to less than or equal to 1.2%.

[0039] The present application improves the mechanical properties (compressive strength, breakage rate), physical properties (porosity, permeability, sphericity), chemical properties (chemical stability, corrosion resistance) and adsorption properties of the proppant through the synergistic effect of the raw materials, and better adapts to the complex environment of oil exploitation.

[0040] In addition, a large amount of waste such as coal gangue and bamboo biomass charcoal is used, which realizes effective utilization of resources, reduces production cost, reduces pollution of waste to the environment, and meets the requirements of sustainable development.

[0041] In the second aspect, the present application provides a production method of coal gangue ceramic proppant suitable for oil exploitation, for preparing the above-mentioned coal gangue ceramic proppant, which comprises the following steps:

[0042] S1: mixing of ingredients: first, add coal gangue, shale, feldspar, borax and fluorite into a ball mill, add water for wet ball milling for 5-7 hours to obtain mixed slurry with particle size less than 2.5um, then add modified glass fiber, functionalized carbon nanotube, biomass charcoal and binder, and continue to stir and mix for 2-4 hours to ensure uniform dispersion of each component;

[0043] S2: spray granulation: spray the uniformly mixed slurry through a pressure type nozzle, control the inlet air temperature at 180-200 DEG C, and control the outlet air temperature at 80-100 DEG C, so that the slurry is quickly dried into spherical particles in the hot air flow, and the particle size is controlled at 0.4-0.8mm;

[0044] S3: freeze forming: the particles obtained by spray granulation are subjected to secondary treatment, first pre-cooling at a temperature of-4 DEG C to-5 DEG C for 0.5-1 hour, then rapidly cooling to a temperature of-20 DEG C to-25 DEG C for 1.5 hours; the spray granulation and gradient freeze forming process make the particles tend to be regular spherical in the forming process, reduce the fluid flow resistance, and improve the oil and gas flow conductivity.

[0045] S4: Vacuum drying: the frozen particles are preliminarily dried in a vacuum environment to remove most of the water;

[0046] S5: Pulse microwave sintering: the dried particles are placed in a microwave sintering furnace, and the sintering temperature is 1200-1250 DEG C, and the holding time is 2-2.5 hours, wherein the microwave power is alternately changed between 1000-1400 W, and the duration of each pulse is 4-5 minutes, and the interval time is 2-3 minutes, so that the particles are heated more uniformly, and the microstructure is more dense;

[0047] S6: Screening and grading: the sintered particles are screened and graded by a vibrating screen to remove particles with unqualified particle size and irregular shape, so as to ensure uniform product quality.

[0048] In the implementation manner of the second aspect, the nanometer carbon tube is subjected to surface functionalization treatment by using a mixed acid oxidation method combined with ultrasonic assistance, and the treatment method comprises the following steps:

[0049] (1) Mixed acid preparation: concentrated sulfuric acid and concentrated nitric acid are mixed in a volume ratio of 3:1 to prepare a mixed acid solution;

[0050] (2) Reflux treatment: the nanometer carbon tube is added to the prepared mixed acid solution, and reflux reaction is carried out at a temperature of 50-60 DEG C for 2-3 hours;

[0051] (3) Ultrasonic assistance: ultrasonic treatment is carried out at the same time of the reflux reaction, and the ultrasonic power is controlled at 200-300 W.

[0052] The reflux reaction enables the mixed acid to fully contact and chemically react with the nanometer carbon tube, and introduces active groups such as carboxyl and hydroxyl. The ultrasonic assistance produces a cavitation effect, so that the mixed acid fully contacts with the nanometer carbon tube, accelerates the reaction, breaks the agglomeration of the nanometer carbon tube, and makes the functionalization treatment more uniform, thereby enhancing the bonding force with other raw materials.

[0053] The mixed acid oxidation method generally introduces active groups such as hydroxyl (-OH) and carboxyl (-COOH) on the surface of the nanometer carbon tube. These active groups can chemically react with components such as metal oxides in coal gangue and shale, for example, form chemical bonds or complexes with metal ions, and tightly combine the nanometer carbon tube with these inorganic raw materials, thereby enhancing the connection between the inorganic phases in the internal of the proppant particles and improving the overall strength and stability.

[0054] The surface of the glass fiber has certain active sites after treatment, and the active groups on the surface of the nanometer carbon tube can chemically react or physically adsorb with the active sites on the surface of the glass fiber, so that the nanometer carbon tube and the glass fiber are connected with each other, and the synergistic effect between the glass fiber and other raw materials is further enhanced, thereby improving the comprehensive performance of the proppant.

[0055] In the second aspect, the coal gangue is pretreated, and the pretreatment comprises the following steps:

[0056] (1) After the coal gangue is crushed to a particle size of less than 2 mm, magnetic separation is first performed to remove magnetic impurities therein, wherein the magnetic field strength of the magnetic separation is controlled to be 1000-1500 Gauss, the magnetic impurities are removed, and the structure and performance of the proppant are prevented from being affected;

[0057] (2) Then, acid pickling is performed, a hydrochloric acid solution with a mass fraction of 5%-10% is used, and soaking is performed at a temperature of 40-50 DEG C for 2-3 hours to remove soluble metal impurities;

[0058] (3) After the acid pickling, the coal gangue is repeatedly washed with deionized water until neutral, and then calcination is performed at a temperature of 800-900 DEG C for 2-3 hours to obtain the pretreated coal gangue raw material, further remove organic impurities, improve the chemical stability, and make the composition more stable, thereby laying a foundation for preparing high-quality proppants.

[0059] The process method can closely match the characteristics and needs of the raw material formula, fully exert the advantages of each raw material, make the whole preparation process more efficient and stable, ensure the stability and consistency of the proppant product quality, improve the product qualification rate and reliability, and meet the strict standards of oil exploitation on the quality of the proppant. Through the optimized process, the microstructure of the proppant, such as pore size, distribution, and grain size, can be accurately controlled, so that the performance of the proppant can be accurately controlled.

[0060] Compared with the prior art, the present application has the following beneficial effects:

[0061] (1) The traditional proppant such as quartz sand has low compressive strength, and the conventional ceramic proppant is also difficult to meet the needs under complex geological conditions. The single-particle compressive strength of the coal gangue ceramic proppant of the present application reaches 170-200 MPa, which is much higher than that of quartz sand and traditional ceramic proppant. This is due to the sufficient supply and stable performance of the coal gangue, which cooperates with raw materials such as glass fiber and nanometer carbon tube. The glass fiber has high strength and high modulus characteristics, and acts as a skeleton reinforcing body to bear most of the load and effectively prevent crack propagation. The nanometer carbon tube is surface-functionalized, and forms chemical bonding with other raw materials through active groups to enhance the overall structural stability. In combination with the pulse microwave sintering process, the microstructure is accurately controlled to be more compact, and the compressive strength is greatly improved, which can effectively withstand high pressure in deep well, ultra-deep well and complex geological condition reservoir exploitation, prevent crack closure, provide a solid guarantee for oil and gas exploitation, and break through the limitations of the mechanical properties of traditional proppants.

[0062] (2) The traditional proppant pore structure is not ideal, and the adsorption capacity of the reservoir impurities and crude oil is limited, and the flow conductivity is insufficient. The bamboo biomass charcoal is selected in the application, the abundant pore structure and the guided pore directional arrangement in the preparation process are combined, and the pore structure is further optimized by the gradient freeze forming process, so that the proppant porosity is between 35% and 40%. This not only ensures the oil and gas storage and flow space, but also enhances the adsorption capacity of the reservoir impurities and crude oil, and the adsorption capacity is increased by 40% to 60%. At the same time, the reasonable pore structure and particle size distribution (the particle size is mainly concentrated in 0.4-0.8mm, and the particle size distribution standard deviation is less than 0.1), so that the proppant support layer permeability reaches 2000mD-3500mD, the flow conductivity is increased by 25% to 35% than before, the oil and gas recovery efficiency is effectively improved, the oil and gas flows smoothly to the wellbore, and the adsorption and flow conductivity performance is greatly improved.

[0063] (3) In the acidic reservoir environment, the traditional ceramic proppant has high acid solubility, poor stability and insufficient thermal shock resistance, and is difficult to adapt to the temperature fluctuation of the reservoir. The raw materials are pretreated to remove impurities and improve the chemical stability, and then the pulse microwave sintering process is combined to make the microstructure of the proppant dense. The acid solubility is reduced to ≤1.2% through testing, and the stability in the acidic reservoir environment is greatly improved. In addition, the reasonable use of glass fiber, nanometer carbon tube and other raw materials improves the thermal shock resistance of the proppant, and after temperature sudden change for many times, the proppant structure integrity is good, can effectively adapt to the temperature fluctuation of the reservoir, prolongs the service life of the proppant, and solves the problems of the traditional proppant in chemical stability and thermal shock resistance.

[0064] (4) The traditional ceramic proppant mainly uses bauxite and other mineral raw materials with high cost and limited resources. The application creatively uses coal gangue, bamboo biomass charcoal and other raw materials. The coal gangue is an industrial solid waste, which is used for proppant preparation, not only reduces the production cost, but also realizes the resource recycling of waste, in line with the environmental protection concept. At the same time, the bamboo biomass charcoal is widely available, which further optimizes the raw material cost and resource utilization efficiency, and has obvious advantages in reducing cost and resource utilization.

[0065] (5) The traditional preparation process is difficult to accurately control the microstructure and performance of the proppant. The application uses gradient freeze forming, pulse microwave sintering and other innovative processes. The gradient freeze forming makes the particles tend to be regular spherical (sphericity coefficient is greater than 0.85) in the forming process, reduces the fluid flow resistance, improves the oil and gas flow conductivity, and optimizes the pore structure. In the process of pulse microwave sintering, the particles are heated more uniformly, and the microstructure is more dense, so that the particles are heated uniformly, the internal material migration and chemical reaction are promoted, the microstructure is more dense, the mechanical properties and chemical stability of the proppant are greatly improved, the crack closure is effectively prevented, and the acid solubility is reduced to ≤1.2%.

[0066] (6) From raw material pretreatment to final screening grading, the whole process of the present application is strictly controlled to product quality. The coal gangue is pretreated by crushing, magnetic separation, acid washing, calcination and other steps, effectively removing impurities, improving the purity and stability of the raw material; the modification treatment of nanometer carbon tube, glass fiber and other raw materials enhances their compatibility and binding force with other raw materials. The spray granulation precisely controls the particle size in 0.4-0.8mm, and the standard deviation of particle size distribution is less than 0.1, which ensures the uniformity of the product. Finally, through the vibration screen screening grading, the unqualified particles are removed, ensuring that the quality of each batch of proppant is uniform, the performance is stable and reliable, and the strict requirements of oil exploitation are met.

[0067] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 The whole process schematic diagram of the production method of the coal gangue ceramic proppant suitable for oil exploitation according to the embodiments of the present application is shown. DETAILED DESCRIPTION

[0069] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the related drawings, which show several embodiments of the present application. However, the present application can be realized in different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0071] Embodiment 1: The embodiments of the present application provide a production method of coal gangue ceramic proppant suitable for oil exploitation, which comprises the following steps:

[0072] S1: mixing of ingredients:

[0073] (1) Raw material preparation and pretreatment

[0074] Coal gangue pretreatment: The coal gangue is crushed to a particle size of less than 2 mm, and then subjected to magnetic separation, with the magnetic field strength controlled at 1000 Gauss to remove magnetic impurities. Then, acid washing is performed, using a 5% mass fraction hydrochloric acid solution, soaking at 40°C for 3 hours to remove soluble metal impurities. After acid washing, repeated washing with deionized water is performed until neutral, and then calcination at 800°C for 3 hours is performed to further remove organic impurities.

[0075] Nano-carbon tube surface functionalization treatment: A mixed acid oxidation method combined with ultrasonic assistance is used. The nano-carbon tubes are added to a mixed solution of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and refluxed at 50°C for 3 hours, with ultrasonic treatment at a power of 200W. After treatment, the nano-carbon tubes are cleaned and dried, so that they have active groups such as carboxyl and hydroxyl groups on their surfaces.

[0076] Glass fiber modification: The glass fibers are first soaked in a 3% mass fraction silane coupling agent solution for 3 hours, and then dried. The dried glass fibers are then placed in a plasma treatment device, and treated with oxygen plasma at a power of 100W for 10 minutes.

[0077] Bamboo biomass charcoal preparation: Bamboo rich in lignin is selected, and subjected to limited oxygen pyrolysis at 550°C and an oxygen flow rate of 0.8L / min for 3 hours to obtain bamboo biomass charcoal.

[0078] Precise weighing of 63 parts of pretreated coal gangue, 12 parts of shale, 20 parts of bamboo biomass charcoal prepared above, 1 part of functionalized nano-carbon tubes, 5 parts of modified glass fibers, 8 parts of flux (long stone, borax, fluorite mixed in a mass ratio of 5:2:1), and 2 parts of binder (1.3 parts of natural polymer modified binder, 0.4 parts of synthetic polymer binder, and 0.3 parts of thermosetting resin binder, wherein the mass ratio of carboxymethyl cellulose sodium and sodium alginate in the natural polymer modified binder is 2:1, the synthetic polymer binder is polyvinyl butyral, and the thermosetting resin binder is phenolic resin) is performed.

[0079] (2) Batch mixing: The pretreated coal gangue, shale, long stone, borax, and fluorite are put into a ball mill, and wet ball milling is performed for 5 hours with water to obtain a mixed slurry with a particle size of less than 2.5μm. Then, the modified glass fibers, functionalized nano-carbon tubes, bamboo biomass charcoal, and binder are added, and continuous stirring and mixing are performed for 2 hours.

[0080] S2: Spray granulation: A pressure type nozzle is used to spray the mixed slurry, with the inlet air temperature set to 180°C and the outlet air temperature set to 80°C, so that the slurry is quickly dried in the hot air stream to form spherical particles with a particle size of 0.4-0.8mm.

[0081] S3: Freeze forming: The spray granulated particles are pre-cooled at -4°C for 1 hour, and then rapidly cooled to -20°C for 1.5 hours.

[0082] S4: Vacuum drying: The frozen particles are placed in a vacuum environment for preliminary drying to remove most of the water.

[0083] S5: Pulse microwave sintering: The dried particles are placed in a microwave sintering furnace, sintered at 1200°C for 2 hours, with microwave power alternating between 1000-1400W, each pulse lasting 4 minutes, and a 2-minute interval.

[0084] S6: Screening and grading: The sintered particles are screened by a vibrating screen to remove unqualified products and ensure uniform quality.

[0085] I. Performance testing of the proppants prepared in Examples 1-5 and Comparative Examples 1-5 is carried out, and the test items and results are shown in the following table:

[0086]

[0087]

[0088] II. Explanation of performance test standards

[0089] Single particle compressive strength: According to SY / T 5108-2014 "Proppant Performance Test Methods for Hydraulic Fracturing and Gravel Packing Operations", the proppant particles are placed between the pressure plates of a pressure testing machine, and a constant loading rate is applied until the particles break, the maximum breaking pressure is recorded, and the average value of multiple particles is taken to obtain the single particle compressive strength.

[0090] Breakage resistance: According to the SY / T 5108-2014 standard, the proppant sample is subjected to pressure for a certain period of time under the specified closure pressure, then the broken proppant is sieved, and the mass of the broken proppant smaller than the specified particle size is weighed and compared with the mass of the original sample to calculate the breakage resistance.

[0091] Particle size distribution standard deviation: A laser particle size analyzer is used to test according to the relevant industry standard for particle size analysis. The proppant sample is dispersed in a suitable medium, and the particle size distribution is measured by laser scattering principle, and then the standard deviation is calculated.

[0092] Sphericity coefficient: According to the method specified in API RP 56 (American Petroleum Institute Recommended Practice 56), the shape of the proppant particles is observed under a microscope and compared with a standard sphericity template, and the average sphericity coefficient is calculated after measuring multiple particles.

[0093] Porosity: tested by gas adsorption method (such as BET method) or mercury intrusion method. According to GB / T 19587-2017 "Gas Adsorption BET Method for Determining Specific Surface Area of Solid Materials", the porosity is calculated by measuring the adsorption amount of gas on the proppant; the mercury intrusion method is to press mercury into the pores of the proppant, and the porosity is calculated according to the amount of mercury intrusion.

[0094] Permeability: tested according to SY / T 6302-2016 "Recommended Practice for Evaluation of Short-term Conductivity of Proppant Pack". Under simulated reservoir conditions, fluid is passed through the proppant pack, and the flow rate and pressure drop of the fluid are measured, and the permeability is calculated according to Darcy's law.

[0095] Adsorption capacity improvement ratio: calculated by comparing the concentration change of a specific adsorbate (such as impurities or crude oil components in a simulated reservoir) before and after the treatment of the proppant. The specific method is to fully contact a certain amount of proppant with a solution containing adsorbate, measure the remaining concentration of adsorbate in the solution after a period of time, compare it with the initial concentration to calculate the adsorption amount, and compare it with the adsorption amount of ordinary proppant prepared without using the method of the present application to obtain the adsorption capacity improvement ratio.

[0096] Acid solubility: according to SY / T 5108-2014 standard, the proppant sample is soaked in an acid solution of a certain concentration and temperature for a certain time, then filtered, washed, dried and weighed, and the acid solubility is obtained by calculating the mass change of the sample before and after acid treatment.

[0097] III. Performance of Examples and Comparative Examples

[0098] The performance of Examples 1-5 is within the range set by the technical solution. With the optimization of raw material ratio and adjustment of process parameters, the performance of the proppant shows a gradual improvement trend. For example, in Example 5, by increasing the proportion of coal gangue and biomass charcoal and optimizing the sintering process, the single particle compressive strength reaches 200 MPa, the breakage resistance rate is reduced to 2.8%, the porosity reaches 40%, the permeability is as high as 3500 mD, the adsorption capacity improvement ratio is 60%, the acid solubility is as low as 0.8%, and the comprehensive performance is the best.

[0099] Comparative Example 1: using traditional raw materials and simple process, the single particle compressive strength is only 110 MPa, lower than the range of the examples in the technical solution; the breakage resistance rate is as high as 9%; the permeability is only 1300 mD; the adsorption capacity improvement ratio is 18%; the acid solubility reaches 3.5%. Many performance indicators are far inferior to the examples, indicating that the proppant prepared by traditional method is difficult to meet the requirements of modern oil exploitation.

[0100] Comparative Example 2: The nanometer carbon tube is not subjected to functionalization treatment, the single particle compressive strength is 155 MPa, which is lower than the range of the embodiment; the adsorption capacity improvement ratio is 32%, which is also lower than the embodiment, indicating that the functionalization treatment of the nanometer carbon tube is crucial to improving the mechanical properties and adsorption properties of the proppant.

[0101] Comparative Example 3: The glass fiber is not used, the single particle compressive strength is reduced to 140 MPa, and the breakage resistance rate is increased to 6.2%, which reflects the key role of the glass fiber as a reinforcing body in the mechanical properties of the proppant.

[0102] Comparative Example 4: The bamboo biomass charcoal is not used, the porosity is 31%, the permeability is 1700 mD, and the adsorption capacity improvement ratio is 22%, which are all lower than the embodiment, indicating that the bamboo biomass charcoal is indispensable to optimizing the pore structure of the proppant and improving the adsorption and flow conductivity.

[0103] Comparative Example 5: The nanometer carbon tube is not used, the single particle compressive strength is 162 MPa, and the breakage resistance rate is 5.2%, which are lower than the optimal level of the embodiment, indicating that the nanometer carbon tube plays an important role in enhancing the mechanical properties of the proppant.

[0104] Example 2: The present application provides a production method of a coal gangue ceramic proppant suitable for oil exploitation, comprising the following steps:

[0105] (1) Raw material preparation and pretreatment

[0106] Coal gangue pretreatment: After the coal gangue is crushed to a particle size of less than 2 mm, the magnetic field strength is controlled at 1100 Gauss, the acid pickling uses a hydrochloric acid solution with a mass fraction of 6%, and is soaked at 42°C for 2.8 hours, and the calcination temperature is 820°C, and the calcination time is 2.8 hours.

[0107] Nanometer carbon tube surface functionalization treatment: refluxing at 52°C for 2.8 hours, and controlling the ultrasonic power at 220W.

[0108] Glass fiber modification: silane coupling agent soaking for 2.8 hours, plasma treatment power is 110W, and treatment time is 9 minutes.

[0109] Bamboo biomass charcoal preparation: pyrolysis at 570°C for 2.8 hours under the condition of oxygen flow of 0.9L / min.

[0110] The pretreated coal gangue 64 parts, shale 11 parts, bamboo biomass charcoal prepared above 21 parts, functionalized nanometer carbon tube 1.05 parts, modified glass fiber 5.2 parts, fluxing agent 8.5 parts, and binder 2.1 parts (the ratio of each binder component is the same as in Example 1) are weighed.

[0111] (2)Batch mixing: batch mixing stage ball milling for 5.5 hours; spray granulation inlet temperature 185°C; freeze precooling temperature -4.2°C; sintering temperature 1210°C.

[0112] The remaining steps are the same as in Example 1.

[0113] Example 3: The example of the present application provides a production method of coal gangue ceramic proppant suitable for oil exploitation, comprising the following steps:

[0114] (1) Raw material preparation and pretreatment

[0115] Coal gangue pretreatment: magnetic field strength of 1200 Gauss, pickling with 7% hydrochloric acid solution, soaking at 45°C for 2.5 hours, calcination temperature 850°C, calcination for 2.5 hours.

[0116] Nano carbon tube surface functionalization treatment: refluxing at 55°C for 2.5 hours, ultrasonic power 250W.

[0117] Glass fiber modification: silane coupling agent soaking for 2.5 hours, plasma treatment power 125W, treatment time 7.5 minutes.

[0118] Bamboo biomass charcoal preparation: pyrolysis at 600°C, oxygen flow 1L / min for 2.5 hours.

[0119] Take 65 parts of pretreated coal gangue, 10 parts of shale, 22 parts of bamboo biomass charcoal prepared above, 1.1 parts of functionalized nanometer carbon tube, 5.5 parts of modified glass fiber, 9 parts of fluxing agent, 2.25 parts of binder (the ratio of each binder component is the same as in Example 1).

[0120] (2) Batch mixing ball milling for 6 hours; spray granulation inlet temperature 190°C; freeze precooling temperature -4.5°C; sintering temperature 1220°C.

[0121] The remaining steps are the same as in Example 1.

[0122] Example 4: The example of the present application provides a production method of coal gangue ceramic proppant suitable for oil exploitation, comprising the following steps:

[0123] (1) Raw material preparation and pretreatment

[0124] Coal gangue pretreatment: magnetic field strength of 1300 Gauss, pickling with 8% hydrochloric acid solution, soaking at 48°C for 2.2 hours, calcination temperature 880°C, calcination for 2.2 hours.

[0125] Nano carbon tube surface functionalization treatment: refluxing at 58°C for 2.2 hours, ultrasonic power 280W.

[0126] Glass fiber modification: silane coupling agent soaking 2.2 hours, plasma treatment power 140 W, treatment time 6 minutes.

[0127] Bamboo biomass charcoal preparation: pyrolysis at 630℃ for 2.2 hours under the condition of oxygen flow 1.1 L / min.

[0128] Take 66 parts of pretreated coal gangue, 9 parts of shale, 23 parts of bamboo biomass charcoal prepared above, 1.15 parts of functionalized carbon nanotubes, 5.8 parts of modified glass fiber, 9.5 parts of fluxing agent, and 2.3 parts of binder (the proportions of each binder component are the same as in Example 1).

[0129] (2) Ball milling for 6.5 hours; spray granulation inlet temperature 195℃; freeze precooling temperature -4.8℃; sintering temperature 1230℃, and the remaining steps are the same as in Example 1.

[0130] Example 5: The present example provides a production method of coal gangue ceramic proppant suitable for oil exploitation, comprising the following steps:

[0131] (1) Raw material preparation and pretreatment

[0132] Coal gangue pretreatment: magnetic field strength 1500 Gauss, acid pickling with 10% hydrochloric acid solution at 50℃ for 2 hours, calcination temperature 900℃, calcination time 2 hours.

[0133] Nano carbon tube surface functionalization treatment: reflux at 60℃ for 2 hours, ultrasonic power 300 W.

[0134] Glass fiber modification: silane coupling agent soaking 2 hours, plasma treatment power 150 W, treatment time 5 minutes.

[0135] Bamboo biomass charcoal preparation: pyrolysis at 650℃ for 2 hours under the condition of oxygen flow 1.2 L / min.

[0136] Take 67 parts of pretreated coal gangue, 8 parts of shale, 25 parts of bamboo biomass charcoal prepared above, 1.2 parts of functionalized carbon nanotubes, 6 parts of modified glass fiber, 10 parts of fluxing agent, and 2.5 parts of binder (the proportions of each binder component are the same as in Example 1).

[0137] (2) Ball milling for 7 hours; spray granulation inlet temperature 200℃; freeze precooling temperature -5℃; sintering temperature 1250℃, and the remaining steps are the same as in Example 1.

[0138] Comparative Example 1: The present comparative example provides a production method of proppant suitable for oil exploitation, comprising the following steps:

[0139] (1) Raw material preparation and pretreatment

[0140] Using traditional ceramic support raw materials, 60 parts bauxite, 15 parts kaolin, 10 parts quartz sand, 5 parts flux (sodium carbonate), and 3 parts binder (ordinary starch) were weighed. The bauxite, kaolin, and quartz sand were simply crushed to a particle size of less than 5 mm, and only preliminary screening was performed to remove obvious impurity particles.

[0141] (2) Ingredient mixing: Add the pre-treated raw materials to a regular mixer and mix for 2 hours.

[0142] (3) Molding process: The traditional molding method is adopted. The mixed raw materials are placed into the mold and shaped under a certain pressure.

[0143] (4) Sintering process: The formed blank is placed in a traditional resistance furnace for sintering. The sintering temperature is set at 1300℃ and the holding time is 3 hours.

[0144] (5) Post-treatment: The sintered proppant is simply sieved to remove obvious large particles and fine powder.

[0145] Comparative Example 2: This invention provides a method for producing a proppant suitable for oil extraction, comprising the following steps:

[0146] (1) Raw material preparation and pretreatment

[0147] Coal gangue pretreatment: Same as the coal gangue pretreatment process in Example 1.

[0148] Glass fiber modification: Same as the glass fiber modification process in Example 1.

[0149] Preparation of bamboo biochar: Same as the preparation process of bamboo biochar in Example 1.

[0150] The raw material composition is the same as in Example 1, but the carbon nanotubes are not surface functionalized.

[0151] (2) The production process is the same as in Example 1.

[0152] Comparative Example 3: This invention provides a method for producing a proppant suitable for oil extraction, comprising the following steps:

[0153] (1) Raw material preparation and pretreatment

[0154] Coal gangue pretreatment: Same as the coal gangue pretreatment process in Example 1.

[0155] Surface functionalization treatment of carbon nanotubes: Same as the surface functionalization treatment process of carbon nanotubes in Example 1.

[0156] Bamboo biochar preparation: Same as the bamboo biochar preparation process in Example 1.

[0157] The raw material composition is the same as Example 1, but no glass fiber is used.

[0158] (2) Production process: The production process is the same as Example 1.

[0159] Comparative Example 4: The present comparative example provides a production method of a proppant suitable for oil exploitation, comprising the following steps:

[0160] (1) Raw material preparation and pretreatment

[0161] Coal gangue pretreatment: the same as the coal gangue pretreatment process in Example 1.

[0162] Nanotube surface functionalization treatment: the same as the nanotube surface functionalization treatment process in Example 1.

[0163] Glass fiber modification: the same as the glass fiber modification process in Example 1.

[0164] The raw material composition is the same as Example 1, but no bamboo biomass charcoal is used.

[0165] (2) Production process: The production process is the same as Example 1.

[0166] Comparative Example 5: The present comparative example provides a production method of a proppant suitable for oil exploitation, comprising the following steps:

[0167] (1) Raw material preparation and pretreatment

[0168] Coal gangue pretreatment: the same as the coal gangue pretreatment process in Example 1.

[0169] Glass fiber modification: the same as the glass fiber modification process in Example 1.

[0170] Bamboo biomass charcoal preparation: the same as the bamboo biomass charcoal preparation process in Example 1.

[0171] The raw material composition is the same as Example 1, but no nanotube is used.

[0172] (2) Production process: The production process is the same as Example 1

[0173] Any numerical values recited herein include all values from the lower to the upper value inclusive of the lower and upper values, and are inclusive of any intervening values as well as any other stated or intervening values. In this respect, the disclosure as has been set forth hereabove is intended to be illustrative, and not restrictive. One skilled in the art could, with access to the present disclosure, utilize one or more embodiments or other adaptations of the present disclosure and still be within the scope of the disclosure. It is therefore intended that the disclosure be considered in all its novel respects to be within the scope of the disclosure.

[0174] Unless otherwise stated, all ranges include endpoints and all numbers are to be read as if qualified by the word "about." The use of "about" with respect to a given value means that the value is approximate, and approaches the stated value within experimental error, which will vary from data point to data point, but will generally be within 1-10%, 1-5%, 1-1%, or 1-0.1% of the given value.

[0175] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and applications other than the examples provided would be apparent upon reading the above description. The scope of the technology should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for the entire scope of such articles and references. The omission of any aspect of the subject matter disclosed herein does not preclude coverage of such aspect, nor does it relinquish any right otherwise had to such aspect under the teaching of the claims. It is contemplated that the subject matter described herein can be practiced with any of the methods, systems, and materials described herein, or equivalents thereof, and that the scope of the claims should not be limited to the particular methods, systems, and materials described herein for descriptive purposes.

[0176] The above description is presented to enable any person skilled in the art to practice the present application as claimed. It is not intended to limit the scope of the application as set forth in the claims. Various modifications to the embodiments described in this document will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without the use of the inventive faculty. Thus, the present application is not intended to be limited to the embodiments described herein but is to be accorded the widest scope consistent with the claims.

Claims

1. A coal gangue ceramic proppant suitable for oil extraction, characterized in that, By weight, it includes the following raw materials: The composition includes 63-67 parts coal gangue, 8-12 parts shale, 20-25 parts biochar, 1-1.2 parts nanomaterials, 5-6 parts glass fiber, 8-10 parts flux, and 2-2.5 parts binder. The nanomaterial is selected as carbon nanotubes, and the carbon nanotubes undergo surface functionalization treatment to introduce active groups. The surface functionalization treatment includes the following steps: (1) Preparation of mixed acid: Mix concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 to prepare a mixed acid solution; (2) Reflux treatment: Add carbon nanotubes to the prepared mixed acid solution and reflux for 2 to 3 hours at a temperature of 50℃~60℃; (3) Ultrasonic assistance: Ultrasonic treatment is performed simultaneously with the reflux reaction, and the ultrasonic power is controlled at 200-300W; The biochar is made from bamboo rich in lignin, and is pyrolyzed at 550℃~650℃ for 2~3 hours using oxygen-limited pyrolysis technology, with the oxygen flow rate controlled at 0.8~1.2L / min to ensure a regular and stable pore structure. The glass fiber is first treated with a surface coupling agent, using silane coupling agent. The glass fiber is immersed in a 3% (w / w) silane coupling agent solution for 2-3 hours, then dried, and then subjected to plasma treatment using oxygen plasma at a power of 100-150W for 5-10 minutes to enhance the interfacial bonding with other raw materials.

2. The coal gangue ceramic proppant suitable for oil exploitation according to claim 1, characterized in that, The flux is a mixed flux comprising feldspar, borax and fluorite, and the mass ratio of feldspar, borax and fluorite is 5:2:

1. And / or, the adhesive is a hybrid adhesive, comprising at least two of the following: natural polymer modified adhesives, synthetic polymer adhesives, and thermosetting resin adhesives.

3. The coal gangue ceramic proppant for oil exploitation according to claim 2, characterized in that, The adhesive comprises the following parts by weight: 1.3 to 1.5 parts of natural polymer modified adhesive, 0.4 to 0.5 parts of synthetic polymer adhesive, and 0.3 to 0.5 parts of thermosetting resin adhesive; And / or, the natural polymer modified binder is selected from sodium carboxymethyl cellulose and sodium alginate, and the mass ratio of sodium carboxymethyl cellulose to sodium alginate is 2:1; The synthetic polymer binder is polyvinyl butyral; The thermosetting resin adhesive is selected from phenolic resin.

4. The coal gangue ceramic proppant for oil exploitation according to any one of claims 1-3, characterized in that, The ceramic proppant is a granular material, and its single-particle compressive strength is 170-200 MPa; And / or, the particle size of the particulate ceramic proppant is concentrated in the range of 0.4 to 0.8 mm, and its particle size distribution standard deviation is less than 0.1, ensuring particle size uniformity; And / or, the sphericity coefficient of the particulate ceramic proppant is greater than 0.

85.

5. The coal gangue ceramic proppant for oil exploitation according to claim 4, characterized in that, The ceramic proppant exhibits a breakage rate of ≤3% under a closure pressure of 69 MPa. And / or, the acid solubility of the ceramic support is reduced to ≤1.2%.

6. A method for producing a coal gangue ceramic proppant suitable for oil extraction, characterized in that, The method for preparing the coal gangue ceramic proppant as described in any one of claims 1-5 comprises the following steps: S1: ingredient mixing: first, coal gangue, shale, fluxing agent are added into the ball mill, and water is added for wet ball milling for 5-7 hours to obtain a mixed slurry with a particle size of less than 2.5 μm, then modified glass fiber, functionalized carbon nanotube, biomass charcoal and binder are added, and stirring and mixing are continued for 2-4 hours to ensure uniform dispersion of each component; S2: spray granulation: the uniformly mixed slurry is sprayed and granulated by a pressure nozzle, the inlet air temperature is controlled at 180-200℃, and the outlet air temperature is controlled at 80-100℃, so that the slurry is rapidly dried into spherical particles in the hot air flow, and the particle size is controlled at 0.4-0.8mm; S3: freeze forming: the particles obtained by spray granulation are subjected to secondary treatment, first pre-cooled at a temperature of-4℃ to-5℃ for 0.5-1 hour, then rapidly cooled to a temperature of-20℃ to-25℃ for 1.5 hours; S4: vacuum drying: the frozen particles are preliminarily dried in a vacuum environment to remove most of the water; S5: pulse microwave sintering: the dried particles are placed in a microwave sintering furnace, sintered at a temperature of 1200℃-1250℃ for 2-2.5 hours, wherein the microwave power alternates between 1000-1400W, each pulse lasts for 4-5 minutes, and the interval time is 2-3 minutes, so that the particles are heated more uniformly and the microstructure is more dense; S6: screening and grading: the sintered particles are screened and graded by a vibrating screen to remove particles with unqualified particle size and irregular shape, ensuring uniform product quality.

7. The method of producing coal gangue ceramic proppant for oil production according to claim 6, characterized in that, The coal gangue is pretreated, which includes the following steps: (1) After the coal gangue is crushed to a particle size of less than 2mm, it is first subjected to magnetic separation to remove magnetic impurities, wherein the magnetic field strength of the magnetic separation is controlled at 1000-1500 Gauss; (2) Then, acid washing is performed using a 5%-10% hydrochloric acid solution at a temperature of 40-50℃ for 2-3 hours to remove soluble metal impurities; (3) After acid washing, the coal gangue is repeatedly washed with deionized water until it is neutral, and then calcined at a temperature of 800℃-900℃ for 2-3 hours to obtain the pretreated coal gangue raw material.

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