Modified fly ash ceramsite proppant and preparation method thereof, and combined proppant and preparation method and application thereof

Abstract

The invention discloses a modified fly ash ceramsite proppant and a preparation method thereof, and a combined proppant and a preparation method and application thereof, and relates to the technical field of shale oil and gas fracturing. The modified fly ash ceramsite proppant comprises the following components which are mixed and granulated: fly ash, bauxite, barite powder, a recycled molecular sieve, a recycled mesoporous material, optional calcite powder and optional bentonite. The environment-friendly propping agent disclosed by the invention solves the problems of high production cost and application cost of the fracturing propping agent taking aluminum-containing minerals as main raw materials, and takes the harmless treatment of recyclable resources and industrial wastes in the whole industrial chain of the petrochemical industry into consideration, and the industrial wastes of the downstream of the oil refining and chemical industry are applied to the upstream petroleum fracturing propping agent.

Description

Technical Field

[0001] This invention relates to the field of shale oil and gas fracturing technology, and more specifically, to a modified fly ash ceramsite proppant and its preparation method, and a combined proppant and its preparation method and application. Background Technology

[0002] Currently, quartz sand and ceramsite are the main technical materials for proppant in fracturing horizontal wells. Traditional quartz sand and ceramsite are widely available and have relatively low density, but their large quantities result in excessively high fracturing costs per well, limiting their application in multi-stage horizontal wells and deep / ultra-deep horizontal wells in shale oil and gas. Coated proppant offers improved sphericity, reduces apparent and bulk density, increases resistance to fracturing, and can also reduce fracturing fluid usage; however, due to its high unit price, it is often not used extensively in fracturing operations to control costs.

[0003] Fly ash is the fine ash collected from the flue gas after coal combustion, and it is a major solid waste discharged from coal-fired power plants. The main oxide components of fly ash from my country's thermal power plants are SiO2, Al2O3, FeO, Fe2O3, CaO, and TiO2. With the development of the power industry, the amount of fly ash emitted by coal-fired power plants has increased year by year, becoming one of the largest industrial waste emissions in my country. Large amounts of untreated fly ash will generate dust and pollute the atmosphere; however, fly ash can be utilized as a resource, such as as an admixture in concrete and as an admixture in fracturing proppant.

[0004] Molecular sieves are synthetically produced hydrated aluminosilicates with molecule-sieving properties, also known as zeolites. Their general chemical formula is (M'2M)O·Al2O3·xSiO2·yH2O, where M' and M are monovalent and divalent cations, respectively, such as K+. + Na + and Ca 2+ Ba 2+ Molecular sieves, etc., possess numerous uniformly sized and orderly arranged pores. Different pore sizes allow for the separation of molecules of varying sizes and shapes, exhibiting strong adsorption capacity, high selectivity, good strength, and high temperature resistance. They are widely used in the petrochemical industry and are excellent adsorbents for coal gas dehydration and waste gas purification. Currently, with the increasing demand for capacity reduction in large-scale petrochemical enterprises, a large number of molecular sieve adsorbents are being phased out and recycled.

[0005] Mesoporous materials refer to a class of porous materials with pore sizes ranging from 2 to 50 nm. Mesoporous materials possess extremely high specific surface areas, regular and ordered pore structures, narrow pore size distributions, and continuously adjustable pore sizes, enabling them to play a crucial role in the adsorption and separation of large molecules, especially in catalytic reactions, where many microporous zeolite molecular sieves struggle. Furthermore, the ordered pores of these materials can act as "miniature reactors," assembling uniform and stable "guest" materials at the nanoscale to form "host-guest materials." Due to the host-guest effect and the potential small size and quantum size effects of the guest materials, they hold promise for widespread applications in electrode materials, optoelectronic devices, microelectronics, chemical sensors, and nonlinear optical materials. Therefore, mesoporous materials have broad applications in biology, optoelectronics, and petrochemicals. Currently, with the increasing demand for capacity reduction in large-scale petrochemical enterprises, a large amount of catalytic mesoporous materials are being phased out and recycled.

[0006] In recent years, proppant substitutes based on ceramsite and proppant, with industrial waste as a supplementary material, have seen rapid development. These industrial wastes often possess high strength, good roundness and sphericity, regular and orderly pore structure, and suitable particle size. They are also chemically stable. The low cost and environmental friendliness of industrial waste greatly meet the application specifications and requirements of fracturing proppants.

[0007] Chinese patent CN103805160A relates to a method for preparing a high-content fly ash ceramsite proppant. This method mainly overcomes the shortcomings of existing technologies, achieving a fly ash content of 30%–75%. Specifically, it includes the following steps: 1) Mixing 20–65 wt% bauxite, 30–75 wt% fly ash, 0–5 wt% calcite powder, 0–10 wt% talc powder, 1–5 wt% titanium dioxide, 0–20 wt% soft refractory clay, and 1–5 wt% barite powder evenly to obtain raw materials; 2) Placing the raw materials in a ball mill and ball milling them until the particle size is less than 48 μm to obtain a mixed powder; 3) Placing the mixed powder in a closed-loop mixing mill for granulation, while simultaneously adding a 10% sodium silicate aqueous solution in multiple batches. The total mass of the added sodium silicate aqueous solution is 9-27% of the mixed powder, resulting in ceramsite green bodies; 3) The mixed powder is placed in a closed mixing machine for granulation, and a 10% sodium silicate aqueous solution is added in multiple batches during granulation, with the total mass of the added sodium silicate aqueous solution being 9-27% of the mixed powder, resulting in ceramsite green bodies; 5) The raw material pellets are placed in a heating furnace, first heated to 600-700℃ at a rate of 3-5℃ / min, then heated to 1350-1500℃ at a rate of 10-15℃ / min, held at this temperature for 40-120min, and then cooled with the furnace to obtain the high-content fly ash ceramsite proppant. This invention significantly reduces the amount of bauxite in the raw materials without affecting the performance of the ceramsite proppant, thereby greatly reducing costs and resource consumption.

[0008] Chinese patent CN114433017A belongs to the field of adsorption separation technology, specifically involving a high-strength molecular sieve adsorbent and its preparation method. This method mainly overcomes the fact that the existing technology cannot control the formation process of the mesopores of the molecular sieve, which is not conducive to improving the yield and molding strength of the molecular sieve. A method for preparing a high-strength molecular sieve adsorbent includes the following: (1) placing the molecular sieve raw material, binder, and molding aid in a rotary molding machine, and mixing it with a spray aqueous solution containing a high decomposition temperature pore-forming agent to obtain granular seeds; (2) continuing to mold the granular seeds obtained in step (1) in the molding machine, and adjusting the spray solution to an aqueous solution containing a medium decomposition temperature pore-forming agent to obtain spherical particles with increased diameter; (3) adjusting the spray solution to an aqueous solution containing a low decomposition temperature pore-forming agent, and continuing to mold to obtain spherical particles with increased diameter; (4) drying and calcining the spherical molecular sieve obtained in step (3) to obtain the adsorbent product. This invention introduces pore-forming agents with different decomposition temperatures at different stages of molecular sieve forming, and controls the calcination temperature to allow the pore-forming agents in the inner and outer layers to decompose and form pores at different stages. This not only generates a large number of mesoporous structures, but also reduces the internal breakage of the molecular sieve due to the staged and hierarchical decomposition of the pore-forming agents. The resulting molecular sieve product has a low breakage rate, low wear rate, high strength, good mass transfer effect, and excellent adsorption performance.

[0009] Chinese Patent CN106632760A, in order to overcome the defect of low catalytic activity of supported catalysts made with existing supports in ethylene polymerization, provides a spherical aluminum-containing mesoporous composite material suitable for use as a support, and a method for preparing the spherical aluminum-containing mesoporous composite material. The spherical aluminum-containing mesoporous composite material prepared by the method, the supported catalyst containing the spherical aluminum-containing mesoporous composite material, the method for preparing the supported catalyst, the application of the supported catalyst in ethylene polymerization, and the method for carrying out ethylene polymerization using the supported catalyst, the specific steps are as follows: (1) Provide a three-dimensional... (1) A mesoporous molecular sieve material with a square channel structure or a filter cake of a mesoporous molecular sieve material with a three-dimensional cubic channel structure is used as component a; (2) Silica gel or a filter cake of silica gel is provided as component b; (3) Component a and component b are mixed and ball-milled in a high-alumina ceramic jar, and the solid powder obtained after ball milling is slurried with water, and then the slurry is spray-dried; This invention utilizes a high-strength aluminum-containing macroporous dual-pore mesoporous composite material synthesized by ball milling in a high-alumina ceramic and spray drying, a composite material of polyethylene catalyst is obtained after loading polyethylene catalyst, and it is used in the reaction process of ethylene polymerization to obtain polyethylene products.

[0010] In the petrochemical industry, the environmental friendliness of materials has always been a key focus, especially in oil fracturing technology, where the selection of environmentally friendly proppant is crucial. Oil proppant, as a type of ceramic particle product, is widely used in oilfield downhole support due to its high fracturing strength and stability, aiming to increase oil and gas production. It not only needs sufficient compressive strength and abrasion resistance, but also needs to be easily pumpable downhole and not chemically react with fracturing fluids and reservoir fluids under high-temperature conditions.

[0011] However, despite significant improvements in environmental friendliness and functionality of existing petroleum proppants, some shortcomings remain in practical applications. For example, the main cost of fly ash proppants comes from bauxite, and the high cost of the bauxite supply chain poses a significant environmental challenge due to pollution. Low bauxite content reduces the propping effect of fly ash proppants, and current technologies do not consider how to maintain the propping effect of fly ash proppants with low bauxite content. Furthermore, current technologies do not explore the influence of the microstructure and surface properties of different particles on performance, while these factors are often crucial to the performance of proppants in practical applications. Therefore, to further improve the efficiency and environmental friendliness of petroleum fracturing technology, future research should focus more on developing novel combined proppants and delve deeper into the impact of proppant microstructure and surface properties on their performance. Simultaneously, it is necessary to strengthen the performance evaluation of proppants under high temperature and high pressure conditions to ensure their stability and reliability under complex geological conditions. Summary of the Invention

[0012] To address the problems existing in the prior art, this invention provides a modified fly ash ceramsite proppant and its preparation method, as well as a combined proppant and its preparation method and application. The environmentally friendly proppant of this invention solves the problem of high production and application costs for fracturing proppants made primarily from aluminum-containing minerals. It also considers the reusability of resources across the entire petrochemical industry chain and the harmless treatment of industrial waste, applying downstream industrial waste from oil refining and chemical processes to upstream petroleum fracturing proppant applications.

[0013] One of the objectives of this invention is to provide a modified fly ash ceramsite proppant.

[0014] The modified fly ash ceramsite proppant of the present invention comprises the following components for mixed granulation:

[0015] Fly ash, bauxite, barite powder, recycled molecular sieves, recycled mesoporous materials, optional local calcite powder and optional local bentonite;

[0016] Based on a total weight of 100 wt% for fly ash, bauxite, barite powder, recycled molecular sieves, recycled mesoporous materials, optional local calcite powder, and optional local bentonite:

[0017]

[0018] In a preferred embodiment of the present invention:

[0019] Based on a total weight of 100 wt% for fly ash, bauxite, barite powder, recycled molecular sieves, recycled mesoporous materials, optional local calcite powder, and optional local bentonite:

[0020]

[0021] This invention significantly improves the flowability and reduces the cost of proppant by introducing recycled molecular sieves and recycled mesoporous materials into the proppant.

[0022] (1) Mechanism for enhancing flow guidance capability:

[0023] Increasing particle surface area and porosity: Recycled molecular sieves (such as zeolites) and recycled mesoporous materials (such as MCM-41 and SBA-15) possess highly developed pore structures and large specific surface areas. This allows for the formation of more micropores and mesoporous channels between proppant particles. These pores effectively guide fluid flow, making it easier for oil and gas fluids to pass through the proppant, thereby significantly improving conductivity.

[0024] Enhancing the directional and selective permeability of fluids: Reclaimed molecular sieves have specific pore sizes and structures that selectively allow oil and gas molecules to pass through while blocking larger impurity molecules, thereby improving the directional permeability of proppant to oil and gas. This selective flow-guiding function is particularly important for improving oil and gas production rates and helps reduce fluid losses during fracturing.

[0025] Enhancing particle stability and preventing fine particle migration: The presence of recycled molecular sieves and recycled mesoporous materials increases the stability of proppant particles and reduces their breakage rate, thereby preventing fine particle migration during fluid flow. This keeps the proppant channels unobstructed and effectively improves long-term flow conductivity.

[0026] (2) Reduce costs:

[0027] Reducing the use of expensive materials: Traditional proppants often require high contents of materials such as bauxite to ensure strength, but these materials are expensive. Recycled molecular sieves and recycled mesoporous materials can partially replace these components, while still providing excellent structural strength and conductivity at lower mass fractions, thereby reducing the need for expensive raw materials and lowering production costs.

[0028] Improve fracturing performance and reduce operating costs: By enhancing the conductivity of proppant, recovering molecular sieves and mesoporous materials can increase the recovery rate of oil and gas, reduce the number and frequency of subsequent fracturing and production enhancement operations, and thus reduce the maintenance and operating costs of oil and gas wells.

[0029] Extending proppant lifespan: The introduction of recycled molecular sieves and recycled mesoporous materials can enhance the proppant's resistance to pressure and chemical corrosion, thereby increasing its stability and durability downhole. This means that proppant can play a longer-lasting role in fracturing, reducing the frequency of proppant replacement or replenishment, and indirectly lowering long-term operating costs.

[0030] In summary, the addition of recycled molecular sieves and recycled mesoporous materials can not only enhance the proppant's conductivity and selective permeability, but also reduce the demand for high-cost materials, improve the efficiency and economy of fracturing operations, and effectively reduce the overall cost of the fracturing system.

[0031] In a preferred embodiment of the present invention:

[0032] The modified fly ash ceramsite proppant has a mesh size of 40-70 and / or a bulk density of 1.4-1.7 g / cm³. 3 And / or, with an apparent density of 2.3–2.9 g / cm³ 3 .

[0033] In a preferred embodiment of the present invention:

[0034] The particle size of the fly ash, bauxite, barite powder, recycled molecular sieve, recycled mesoporous material, calcite powder and bentonite is less than 35 μm, preferably less than 25 μm.

[0035] In a preferred embodiment of the present invention:

[0036] The fly ash is Class II concrete fly ash; and / or

[0037] The aluminum oxide content in the bauxite is 60%–70%; and / or,

[0038] The recovered molecular sieve is a commonly used deactivated adsorbent molecular sieve in the field, such as deactivated polyurethane electronic potting dehydrated molecular sieve activation powder, deactivated K-13 molecular sieve, deactivated zeolite, etc., which can be directly obtained commercially; and / or,

[0039] The recycled mesoporous material is a deactivated mesoporous material after use, such as deactivated mesoporous silica, deactivated MCM-41 mesoporous material, deactivated SBA-15 mesoporous material, etc., which can be directly obtained commercially; and / or,

[0040] The bentonite is at least one of sodium-based bentonite, calcium-based bentonite, and organo-bentonite.

[0041] A second objective of this invention is to provide a method for preparing the modified fly ash ceramsite proppant as described in one objective of this invention.

[0042] The method for preparing the modified fly ash ceramsite proppant of the present invention includes:

[0043] The activated fly ash, premixed calcined bauxite and barite powder, ultrasonically treated recycled molecular sieve and recycled mesoporous material mixed solution, and optionally local calcite powder and bentonite are mixed and granulated to obtain proto-granules; the proto-granules are sealed, fired and cooled to obtain the modified fly ash ceramsite proppant.

[0044] This invention activates the surface of fly ash through activation treatment, enhancing its reactivity with bauxite and ensuring the stability of the fly ash's pore structure. The activation reaction between fly ash and an alkaline solution dissolves inactive components in the fly ash, increasing its surface activity. The main chemical reactions occurring during the activation process are as follows:

[0045] (1) The reaction between silicon dioxide (SiO2) in fly ash and sodium hydroxide (NaOH):

[0046] Silica reacts with sodium hydroxide under alkaline conditions to form hydrated sodium silicate, which is one of the key reactions for the activation of fly ash.

[0047] SiO₂ + 2NaOH → Na₂SiO₃ + H₂O

[0048] (2) The aluminum oxides (such as aluminum oxide, Al2O3) in fly ash react with sodium hydroxide:

[0049] Fly ash also contains a certain amount of aluminum oxides, which react with NaOH to form sodium aluminate hydrate.

[0050] Al₂O₃ + 2NaOH + 3H₂O → 2NaAl(OH)₄

[0051] (3) Iron oxides (such as Fe2O3) in fly ash react with sodium hydroxide:

[0052] Iron oxides in fly ash may partially dissolve in alkaline solutions to form sodium ferrite, but the reaction is to a lesser extent. The reaction equation is as follows:

[0053] Fe₂O₃ + 2NaOH → 2NaFeO₂ + H₂O

[0054] (4) The reaction between calcium carbonate (CaCO3) in fly ash and sodium hydroxide:

[0055] Calcium carbonate reacts with NaOH under alkaline conditions to produce sodium carbonate and calcium hydroxide.

[0056] CaCO3 + 2NaOH → Na2CO3 + Ca(OH)2

[0057] Activation treatment, through reaction with alkaline solutions, transforms the inactive components in fly ash into soluble substances or active compounds, such as sodium silicate (Na₂SiO₃) and hydrated sodium aluminate (NaAl(OH)₄), thereby enhancing the surface activity and reactivity of the fly ash and providing a good foundation for subsequent processing. These reactions form more active sites and pores on the fly ash surface, increasing the specific surface area and thus enhancing its performance in proppant.

[0058] In a preferred embodiment of the present invention:

[0059] The activation treatment includes: reacting the fly ash with an alkaline solution to activate it, followed by washing and filtration to obtain activated fly ash; preferably, the weight ratio of the fly ash to the solute in the alkaline solution is (3-10):1, more preferably (4-8):1, and / or, the alkaline solution is a sodium hydroxide solution; and / or, the reaction temperature of the activation reaction is 80-90℃, and / or, the reaction time is 1-3 hours, preferably 1.5-2.5 hours; and / or,

[0060] The calcination temperature of the premixed calcination is 600–800°C, and / or the calcination time is 1–3 hours, preferably 1.5–2.5 hours; by premixing and calcining bauxite and barite powder, the stability and binding properties of the bauxite can be improved, providing a solid foundation for subsequent molding; and / or,

[0061] The total concentration of the recovered molecular sieve and recovered mesoporous material in the mixed solution is 10-15 wt%, and / or, the solvent of the mixed solution is ethanol; and / or, the frequency of the ultrasonic treatment is 20 kHz-50 MHz, preferably 20 kHz-40 kHz, and / or, the time is 20-40 minutes, preferably 25-30 minutes; ultrasonic treatment of the recovered molecular sieve and recovered mesoporous material ensures their uniform distribution in the mixture, helps to form uniform flow channels in the microstructure, and improves the permeability selectivity of the proppant; and / or,

[0062] The granulation is performed using spray drying. Preferably, the feed concentration is 10-60%, and / or the feed flow rate is 5-40 mL / min. Excessive flow rate can affect the drying effect and increase the possibility of particle agglomeration. Alternatively, the inlet air temperature is 150-300℃; higher temperatures result in faster drying but may also lead to the decomposition of heat-sensitive substances. And / or, the outlet air temperature is 80-120℃ to ensure sufficient drying of the material without overheating damage. And / or, the spray pressure is 1-10 MPa; higher pressure produces finer droplets, which helps improve drying efficiency. And / or, the atomizing gas flow rate is 0.2-0.5 m³ / min. 3 / min helps to adjust droplet size and drying rate, and / or, the airflow velocity in the drying tower is 0.5-1.5m / s. Too low an airflow velocity will lead to incomplete drying, while too high an airflow velocity may cause the material to stay in the drying chamber for too short a time, and / or, the relative humidity in the drying tower is 20-40%. Too high a humidity will affect the drying rate, while too low a humidity may cause the material to break or degenerate; spray drying is used to prepare granules, spraying the mixture into droplets and drying them rapidly to form preliminary granules. Spray drying can ensure uniform particle size, which is beneficial for the subsequent formation of a more uniform sintering structure; and / or,

[0063] The protoglobules are 10–100 mesh, preferably 30–70 mesh; and / or,

[0064] The sealing firing process is as follows: heating to 650℃~670℃ at a heating rate of 4℃ / min-6℃ / min, then heating to 1000℃~2000℃ at a heating rate of 15℃ / min-20℃ / min, and firing for more than 1 hour, preferably 1 hour to 3 hours; and / or,

[0065] The cooling rate is 12–17 °C / min. Rapid cooling helps suppress crystal phase transformation, but may lead to increased internal stress within the particles. A suitable cooling rate can effectively balance crystal phase stability and physical stress within the particles. And / or, the cooling atmosphere is nitrogen and / or an inert gas, preferably nitrogen and / or argon, to avoid oxidation or other gases affecting the particle surface. And / or, the cooling gas flow rate is 10–50 L / min. Too low a flow rate will affect the cooling rate, while too high a flow rate will increase gas consumption costs and may lead to particle dust loss. And / or, cooling... The pressure is 0.9-1 atm, and the system pressure is usually maintained at or slightly below atmospheric pressure to ensure the stability of gas flow and avoid micro-oxidation reactions. The cooling start temperature is usually set near the peak temperature after calcination, that is, cooling is carried out immediately after the calcination process to avoid crystal phase transformation caused by staying at high temperature. The cooling termination temperature is usually set close to the ambient temperature (about 25-30℃). The lower termination temperature helps to stabilize the particles in the desired crystal phase state. The proppant particles are rapidly cooled to room temperature in an inert atmosphere or nitrogen to effectively avoid crystal phase transformation.

[0066] In a preferred embodiment of the present invention, the method further includes surface modification treatment of the modified fly ash ceramsite proppant; preferably,

[0067] The surface modification treatment includes: coupling the modified fly ash ceramsite proppant with a silane coupling agent solution; more preferably,

[0068] The concentration of the modified fly ash ceramsite proppant in the silane coupling agent solution is 0.5-3 wt%, more preferably 1-2 wt%; and / or,

[0069] The concentration of the silane coupling agent solution is 1-5 vol%, more preferably 2-3 vol%; this concentration is sufficient to form a uniform and stable coupling agent layer on the proppant surface, which helps to enhance surface adhesion and avoids waste of coupling agent; and / or,

[0070] The silane coupling agent is 3-aminopropyltriethoxysilane and / or octyltriethoxysilane; and / or

[0071] The solvent for the silane coupling agent solution is ethanol; and / or,

[0072] The reaction temperature of the coupling reaction is 20-80℃, more preferably 50-70℃, which can effectively accelerate the reaction rate and activate the coupling agent, while avoiding the decomposition of the coupling agent and improving the modification effect. And / or, the reaction time is 30-120min, more preferably 45-60min. Generally, the longer the processing time, the more fully the coupling agent reacts with the surface of the support. This invention can ensure the effective binding of the coupling agent, obtain a stable surface modification effect, and control the processing cost.

[0073] Modifying the surface of the modified fly ash ceramsite support with a silane coupling agent can significantly improve the oleophilic and hydrophobic properties of the particles. Commonly used silane coupling agents are 3-aminopropyltriethoxysilane (APTES) or octyltriethoxysilane (OTES). Taking octyltriethoxysilane (OTES) as an example, its modification reaction is as follows:

[0074] Hydrolysis reaction: In the presence of water, the ethoxy group (-OCH2CH3) in octyltriethoxysilane (OTES) hydrolyzes to generate a silanol group (-Si-OH) and releases ethanol (CH3CH2OH).

[0075] C8H 17 Si(OCH2CH3)3 + 3H2O → C8H 17 Si(OH)3+3CH3CH2OH

[0076] Reaction with hydroxyl groups (-OH) on the surface of fly ash: The generated silanol groups (-Si-OH) will undergo a condensation reaction with the hydroxyl groups on the surface of fly ash particles to form stable silicon-oxygen bonds (Si-O-Si), fixing the octyl chain to the surface of fly ash.

[0077] C8H 17 Si(OH)3 + Si-OH (fly ash surface) → C8H 17 Si-O-Si (fly ash surface) + H2O

[0078] Formation of hydrophobic surfaces: In this way, the surface of fly ash particles is coated with octyl (-C8H) 17 The proppant layer is covered by a hydrophobic layer, which enhances the oleophilic and hydrophobic properties of the particles, making it easier for the proppant to guide oil and gas in the oil and gas fracturing environment and helping to optimize the flow path in oil and gas fracturing.

[0079] A third objective of this invention is to provide a composite proppant.

[0080] The combined proppant of the present invention includes the modified fly ash ceramsite proppant as described in one objective of the present invention, or the modified fly ash ceramsite proppant or mixed proppant prepared by the method described in another objective of the present invention.

[0081] The mixed support is at least one of the following: recycled molecular sieve, recycled mesoporous material, quartz sand, and ceramsite sand.

[0082] In a preferred embodiment of the present invention:

[0083] The weight ratio of the modified fly ash ceramsite proppant to the mixed proppant is (4-6):1, preferably (4-5):1; and / or,

[0084] The particle size of the mixed proppant is 50-210 μm, preferably, for example, 50-70 μm, 105-210 μm, etc.

[0085] The fourth objective of this invention is to provide a method for preparing the combined proppant as described in the third objective of this invention.

[0086] The method for preparing the combined proppant of the present invention includes:

[0087] The combined proppant is prepared by mixing the components.

[0088] The fifth objective of this invention is to provide a combined proppant as described in the third objective of this invention or a combined proppant prepared by the method described in the fourth objective of this invention as a proppant for shale oil and gas fracturing.

[0089] The environmentally friendly proppant provided by this invention features a simple formulation, easy availability in the petrochemical industry, and abundant raw materials. The composition utilizes solid waste fly ash, catalyst waste mesoporous materials, and molecular sieves to fulfill the function of a petroleum fracturing proppant while allowing for landfill disposal of industrial waste, thus avoiding pollution. The main cost of the modified fly ash ceramsite proppant comes from bauxite; reducing the amount of bauxite used effectively lowers the manufacturing cost of the modified fly ash ceramsite proppant and also reduces pollution from the bauxite supply chain. The proppant of this invention can significantly reduce costs by reducing the amount of bauxite without affecting proppant performance, while maintaining a high-strength proppant sand layer. This invention uses deactivated recycled molecular sieves and recycled mesoporous materials, sourced from large-scale oil refining and chemical catalytic refining facilities, which plays a positive role in reducing excess capacity and reusing waste in the petrochemical field. Furthermore, the recycled molecular sieves and recycled mesoporous materials have high strength and high conductivity, further improving the compressive strength, corrosion resistance, and conductivity of the proppant, while better controlling costs. The proppant of this invention exhibits a breakage rate of less than 10% at 52 MPa and an acid solubility of less than 10%. This environmentally friendly proppant has wider applicability, particularly in oil and gas extraction under complex geological conditions. Attached Figure Description

[0090] Figure 1 Figures showing the flow conductivity test results of the proppants prepared in Examples 1-4 and Comparative Examples 1-4. Detailed Implementation

[0091] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0092] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0093] The raw materials used in the preparation examples, embodiments, and comparative examples of this invention are all commercially available products.

[0094] Preparation Example 1

[0095] A modified fly ash ceramsite proppant, comprising the following components for mixed granulation:

[0096] Grade II concrete: 50wt% fly ash, 20wt% bauxite (60% aluminum oxide), 5wt% barite powder, 8wt% recycled molecular sieve (model K-13, Guangdong), 10wt% recycled mesoporous material (MCM-41, Jiangsu), 2wt% calcite powder, and 5wt% bentonite; the particle size of fly ash, bauxite, barite powder, recycled molecular sieve, recycled mesoporous material, calcite powder, and bentonite (NB-100, Inner Mongolia) is less than 35μm.

[0097] Activation treatment: The fly ash of Grade II concrete is activated by reacting with sodium hydroxide solution. The weight ratio of Grade II concrete fly ash to sodium hydroxide solution is 3:1, the reaction temperature is 80℃, and the reaction time is 1 hour. After washing and filtration, the activated fly ash is obtained.

[0098] Premixed calcination: Bauxite and barite powder are mixed and calcined at 600℃ for 1 hour;

[0099] Ultrasonic treatment: The recycled molecular sieve and recycled mesoporous material are mixed with ethanol. The concentration of the recycled molecular sieve and recycled mesoporous material after mixing is 10 wt%. The ultrasonic treatment frequency is 20 kHz and the time is 40 minutes.

[0100] The activated fly ash, premixed calcined bauxite and barite powder, a mixed solution of ultrasonically treated recycled molecular sieve and recycled mesoporous material, calcite powder and bentonite were mixed and spray-dried. The feed concentration was 60%, the feed flow rate was 5 mL / min, the inlet air temperature was 150℃, the outlet air temperature was 80℃, the spray pressure was 1 MPa, and the atomizing gas flow rate was 0.5 m³ / min. 3 The airflow velocity in the drying tower was 1.5 m / s, and the relative humidity inside the drying tower was 20%, producing proto-particles (70 mesh). Sealed firing: the temperature was increased to 650℃ at a heating rate of 4℃ / min, then increased to 2000℃ at a heating rate of 15℃ / min, and fired for 1 hour. Cooling was then performed at a cooling rate of 17℃ / min, using nitrogen as the cooling atmosphere, with a cooling gas flow rate of 10 L / min and a cooling pressure of 1 atm, to obtain modified fly ash ceramsite proppant.

[0101] Surface modification treatment: The prepared modified fly ash ceramsite proppant was coupled with a 3-aminopropyltriethoxysilane solution. The concentration of the modified fly ash ceramsite proppant in the 3-aminopropyltriethoxysilane solution was 3 wt%, the concentration of the 3-aminopropyltriethoxysilane solution was 5 vol%, and the solvent for the 3-aminopropyltriethoxysilane solution was ethanol. The reaction temperature of the coupling reaction was 80℃, and the reaction time was 120 min. The obtained modified fly ash ceramsite proppant had a particle size of 40-70 mesh and a bulk density of 1.4-1.7 g / cm³. 3 Its apparent density is 2.3–2.9 g / cm³.3 .

[0102] Preparation Example 2

[0103] A modified fly ash ceramsite proppant, comprising the following components for mixed granulation:

[0104] Grade II concrete contains 70 wt% fly ash, 15 wt% bauxite (70% aluminum oxide content), 3 wt% barite powder, 6 wt% recycled molecular sieve (K-13, Guangdong), 3 wt% recycled mesoporous material (MCM-41, Jiangsu), 1 wt% calcite powder, and 2 wt% bentonite (CB-200, Inner Mongolia); the particle size of fly ash, bauxite, barite powder, recycled molecular sieve, recycled mesoporous material, calcite powder, and bentonite is less than 35 μm.

[0105] Activation treatment: The fly ash of Grade II concrete is activated by reacting with sodium hydroxide solution. The weight ratio of Grade II concrete fly ash to sodium hydroxide solution is 10:1, the reaction temperature is 90℃, and the reaction time is 1 hour. After washing and filtration, the activated fly ash is obtained.

[0106] Premixed calcination: Bauxite and barite powder are mixed and calcined at 600℃ for 3 hours;

[0107] Ultrasonic treatment: The recycled molecular sieve and recycled mesoporous material are mixed with ethanol. The concentration of the recycled molecular sieve and recycled mesoporous material after mixing is 10 wt%. The ultrasonic treatment frequency is 50 MHz and the time is 20 minutes.

[0108] The activated fly ash, premixed calcined bauxite and barite powder, a mixed solution of ultrasonically treated recycled molecular sieve and recycled mesoporous material, calcite powder and bentonite were mixed and spray-dried. The feed concentration was 10%, the feed flow rate was 40 mL / min, the inlet air temperature was 300℃, the outlet air temperature was 120℃, the spray pressure was 10 MPa, and the atomizing gas flow rate was 0.2 m³ / min. 3 The airflow velocity in the drying tower was 1.5 m / s, and the relative humidity inside the drying tower was 40%, producing proto-particle pellets (70 mesh). Sealed firing: the temperature was increased to 670℃ at a heating rate of 6℃ / min, then increased to 1000℃ at a heating rate of 20℃ / min, and fired for 1 hour. Cooling was then performed at a cooling rate of 17℃ / min, using nitrogen as the cooling atmosphere, with a cooling gas flow rate of 10 L / min and a cooling pressure of 0.9 atm, to obtain modified fly ash ceramsite proppant.

[0109] Surface modification treatment: The prepared modified fly ash ceramsite proppant was coupled with an octyltriethoxysilane solution. The concentration of the modified fly ash ceramsite proppant in the octyltriethoxysilane solution was 3 wt%, and the concentration of the octyltriethoxysilane solution was 5 vol%. The solvent for the octyltriethoxysilane solution was ethanol. The reaction temperature of the coupling reaction was 80℃, and the reaction time was 120 min. The obtained modified fly ash ceramsite proppant had a mesh size of 40-70 and a bulk density of 1.4-1.7 g / cm³. 3 Its apparent density is 2.3–2.9 g / cm³. 3 .

[0110] Preparation Example 3

[0111] A modified fly ash ceramsite proppant, comprising the following components for mixed granulation:

[0112] Grade II concrete contains 45 wt% fly ash, 30 wt% bauxite (65% aluminum oxide content), 10 wt% barite powder, 5 wt% recycled molecular sieve (K-16, Guangdong), 5 wt% recycled mesoporous material (SBA-15, Jiangsu), 3 wt% calcite powder, and 2 wt% bentonite (OB-300, Inner Mongolia); the particle size of fly ash, bauxite, barite powder, recycled molecular sieve, recycled mesoporous material, calcite powder, and bentonite is less than 35 μm.

[0113] Activation treatment: The fly ash from Grade II concrete is activated by reacting it with sodium hydroxide solution. The weight ratio of the fly ash to the sodium hydroxide solution is 6:1, the reaction temperature is 75℃, and the reaction time is 2 hours. After washing and filtration, the activated fly ash is obtained.

[0114] Premixed calcination: Bauxite and barite powder are mixed and calcined at 650℃ for 3 hours;

[0115] Ultrasonic treatment: The recycled molecular sieve and recycled mesoporous material are mixed with ethanol. The concentration of the recycled molecular sieve and recycled mesoporous material after mixing is 13wt%. The ultrasonic treatment frequency is 35MHz and the time is 20 minutes.

[0116] The activated fly ash, premixed calcined bauxite and barite powder, a mixed solution of ultrasonically treated recycled molecular sieve and recycled mesoporous material, calcite powder and bentonite were mixed and then spray-dried. The feed concentration was 45%, the feed flow rate was 25 mL / min, the inlet air temperature was 200℃, the outlet air temperature was 120℃, the spray pressure was 10 MPa, and the atomizing gas flow rate was 0.5 m³ / min. 3The airflow velocity in the drying tower was 1 m / s, and the relative humidity inside the drying tower was 30%, producing proto-particles (70 mesh). The mixture was then sealed and fired at a heating rate of 6 °C / min to 660 °C, and then at a heating rate of 20 °C / min to 1500 °C for 1 hour. Finally, it was cooled at a cooling rate of 14 °C / min, using nitrogen as the cooling atmosphere, with a cooling gas flow rate of 25 L / min and a cooling pressure of 1 atm, to obtain modified fly ash ceramsite proppant.

[0117] Surface modification treatment: The prepared modified fly ash ceramsite proppant was coupled with a 3-aminopropyltriethoxysilane solution. The concentration of the modified fly ash ceramsite proppant in the 3-aminopropyltriethoxysilane solution was 3 wt%, the concentration of the 3-aminopropyltriethoxysilane solution was 1 vol%, and the solvent for the 3-aminopropyltriethoxysilane solution was ethanol. The reaction temperature of the coupling reaction was 25℃, and the reaction time was 85 min. The obtained modified fly ash ceramsite proppant had a mesh size of 40-70 and a bulk density of 1.4-1.7 g / cm³. 3 Its apparent density is 2.3–2.9 g / cm³. 3 .

[0118] Example 1

[0119] A composite proppant was prepared by mixing 70-140 mesh quartz sand and the modified fly ash ceramsite proppant prepared in Preparation Example 1 at a weight ratio of 1:4.

[0120] Example 2

[0121] A composite proppant was prepared by mixing 70-140 mesh quartz sand and the modified fly ash ceramsite proppant prepared in Preparation Example 1 at a weight ratio of 1:5.

[0122] Example 3

[0123] A composite proppant was prepared by mixing 70-140 mesh quartz sand and the modified fly ash ceramsite proppant prepared in Preparation Example 1 at a weight ratio of 1:6.

[0124] Example 4

[0125] A combined proppant was prepared by mixing 200-300 mesh recycled molecular sieve and the modified fly ash ceramsite proppant prepared in Preparation Example 1 at a weight ratio of 1:5.

[0126] Comparative Example 1

[0127] 70-140 mesh quartz sand is used as a proppant.

[0128] Comparative Example 2

[0129] 40-70 mesh ceramsite sand is used as a proppant.

[0130] Comparative Example 3

[0131] A proppant is prepared by mixing 70-140 mesh quartz sand and 40-70 mesh ceramsite sand in a 1:1 weight ratio.

[0132] Comparative Example 4

[0133] A proppant is prepared by mixing 70-140 mesh quartz sand and 200-300 mesh recycled molecular sieve at a weight ratio of 5:1.

[0134] The proppant prepared in the above examples and comparative examples were subjected to the following performance tests. The specific test methods refer to SY / T5108-2006. The test results are shown in Table 1 below:

[0135] Table 1

[0136]

[0137] As can be seen from the test results in Table 1, each embodiment demonstrates advantages over the comparative example in several performance aspects:

[0138] The breakage rates at 52 MPa were lower in all examples than in most control examples, especially in Example 4, which had the lowest breakage rate (3.98%), indicating higher resistance to breakage under high pressure. Compared to the breakage rates of the control examples, the examples showed greater advantages in compressive strength, demonstrating their ability to better maintain particle integrity and extend proppant life during fracturing operations.

[0139] All embodiments exhibit a roundness and sphericity of 0.9, higher than Comparative Example 1 (roundness and sphericity both 0.7) and Comparative Example 3 (roundness and sphericity both 0.8), indicating that the embodiments are closer to an ideal sphere in shape. This shape can reduce fluid resistance and improve flowability, making it suitable for fracturing operations that enhance oil and gas flow.

[0140] The proppant prepared in the above embodiments and comparative examples was subjected to a flow conductivity test. The specific test method is described in SY / T5108-2006. The test results are as follows: Figure 1 As shown.

[0141] Figure 1 This is a graph showing the trend of proppant conductivity as a function of closure pressure. The vertical axis represents conductivity (unit: μm). 2The horizontal axis represents the closure pressure (unit: MPa), and the horizontal axis represents the closure pressure. The conductivity of all samples decreased with increasing closure pressure, demonstrating the negative impact of closure pressure on conductivity. This indicates that under higher closure pressures, the proppant structure may compact or the particles may break down, leading to reduced conductivity. The performance indicators of the combined proppants prepared in Examples 1-4 of this invention all meet the requirements for proppant performance in the People's Republic of China Natural Gas Industry Standard SY / T5108-2006.

[0142] The flow-guiding capacity of Examples 1-4 was generally higher than that of Comparative Examples 1-4, especially in the low to medium closing pressure range (10-40 MPa), where the flow-guiding capacity of the Examples was significantly higher than that of the Comparative Examples. This indicates that under the same closing pressure conditions, the Examples have higher flow-guiding performance. Secondly, the flow-guiding capacity of the Comparative Examples decreased more significantly, especially at high closing pressures (above 80 MPa), where the flow-guiding capacity of the Comparative Examples tended to be even lower.

[0143] Of Examples 1-4, Examples 3 and 4 exhibit relatively higher flow-carrying capacity, particularly within the closure pressure range of 20-60 MPa, demonstrating stronger pressure resistance. This indicates that Examples 3 and 4 possess better pressure resistance and flow-carrying performance.

[0144] Performance under extreme closure pressure: Under a high closure pressure of 100 MPa, the conductivity of all samples tended to be lower, but the conductivity of the implementation group still maintained a relative advantage. This indicates that the combined proppant of the embodiments has higher structural stability under high pressure and stronger pressure resistance compared to the comparative examples.

[0145] As can be seen, the embodiments exhibit superior flow-guiding capabilities compared to the comparative examples under various closure pressures, particularly showing a significant improvement in flow-guiding performance under medium and low pressure environments. The combined proppant of the embodiments possesses higher compressive strength and stability, making it suitable for applications with higher closure pressures. In practical applications, embodiments 3 and 4 can be preferred to obtain better flow-guiding effects.

Claims

1. A modified fly ash ceramsite proppant, characterized in that... The modified fly ash ceramsite proppant comprises the following components for mixed granulation: Fly ash, bauxite, barite powder, recycled molecular sieves, recycled mesoporous materials, optional local calcite powder and optional local bentonite; Based on a total weight of 100 wt% for fly ash, bauxite, barite powder, recycled molecular sieves, recycled mesoporous materials, optional local calcite powder, and optional local bentonite: Fly ash 45-80 wt%; Bauxite 10~55wt%; 1-10 wt% barite powder; 5-12 wt% of molecular sieves were recovered; 3-15 wt% of recycled mesoporous materials; 0-10 wt% calcite powder; Bentonite 0–10 wt%.

2. The modified fly ash ceramsite proppant according to claim 1, characterized in that: Based on a total weight of 100 wt% for fly ash, bauxite, barite powder, recycled molecular sieves, recycled mesoporous materials, optional local calcite powder, and optional local bentonite: 55-75 wt% fly ash; Bauxite 25~35wt%; 5-10 wt% barite powder; 5-10 wt% of molecular sieves were recovered; 2.5–10 wt% of mesoporous materials were recovered; 5-10 wt% calcite powder; 5-10 wt% bentonite.

3. The modified fly ash ceramsite proppant according to claim 1 or 2, characterized in that: The modified fly ash ceramsite proppant has a mesh size of 40-70 and / or a bulk density of 1.4-1.7 g / cm³. 3 And / or, with an apparent density of 2.3–2.9 g / cm³ 3 .

4. The modified fly ash ceramsite proppant according to claim 1 or 2, characterized in that: The particle size of the fly ash, bauxite, barite powder, recycled molecular sieve, recycled mesoporous material, calcite powder and bentonite is less than 35 μm, preferably less than 25 μm.

5. The modified fly ash ceramsite proppant according to claim 1 or 2, characterized in that: The fly ash is Class II concrete fly ash; and / or The aluminum oxide content in the bauxite is 60%–70%; and / or, The bentonite is at least one of sodium-based bentonite, calcium-based bentonite, and organo-bentonite.

6. A method for preparing a modified fly ash ceramsite proppant as described in any one of claims 1-5, characterized in that... The method includes: The activated fly ash, premixed calcined bauxite and barite powder, ultrasonically treated recycled molecular sieve and recycled mesoporous material mixed solution, and optionally local calcite powder and bentonite are mixed and granulated to obtain proto-granules; the proto-granules are sealed, fired and cooled to obtain the modified fly ash ceramsite proppant.

7. The method according to claim 6, characterized in that: The activation treatment includes: reacting the fly ash with an alkaline solution to activate it, followed by washing and filtration to obtain activated fly ash; preferably, the weight ratio of the fly ash to the solute in the alkaline solution is (3-10):1, more preferably (4-8):1, and / or, the alkaline solution is a sodium hydroxide solution; and / or, the reaction temperature of the activation reaction is 80-90℃, and / or, the reaction time is 1-3 hours, preferably 1.5-2.5 hours; and / or, The calcination temperature of the premixed calcination is 600–800°C, and / or the calcination time is 1–3 hours, preferably 1.5–2.5 hours; and / or, The total concentration of the recovered molecular sieve and recovered mesoporous material in the mixed solution is 10-15 wt%, and / or, the solvent of the mixed solution is ethanol; and / or, the frequency of the ultrasonic treatment is 20 kHz-50 MHz, preferably 20 kHz-40 kHz, and / or, the time is 20-40 minutes, preferably 25-30 minutes; and / or, The granulation is performed by spray drying. Preferably, the feed concentration is 10-60%, and / or the feed flow rate is 5-40 mL / min, and / or the inlet air temperature is 150-300℃, and / or the outlet air temperature is 80-120℃, and / or the spray pressure is 1-10 MPa, and / or the atomizing gas flow rate is 0.2-0.5 m³ / min. 3 / min, and / or, the airflow velocity in the drying tower is 0.5-1.5m / s, and / or, the relative humidity inside the drying tower is 20-40%; and / or, The protoglobules are 10–100 mesh, preferably 30–70 mesh; and / or, The sealing firing process is as follows: heating to 650℃~670℃ at a heating rate of 4℃ / min-6℃ / min, then heating to 1000℃~2000℃ at a heating rate of 15℃ / min-20℃ / min, and firing for more than 1 hour, preferably 1 hour to 3 hours; and / or, The cooling rate is 12-17°C / min, and / or the cooling atmosphere is nitrogen and / or an inert gas, preferably nitrogen and / or argon, and / or the cooling gas flow rate is 10-50 L / min, and / or the cooling pressure is 0.9-1 atm.

8. The method according to claim 6, characterized in that... The method further includes surface modification treatment of the modified fly ash ceramsite proppant; preferably, The surface modification treatment includes: coupling the modified fly ash ceramsite proppant with a silane coupling agent solution; more preferably, The concentration of the modified fly ash ceramsite proppant in the silane coupling agent solution is 0.5-3 wt%, more preferably 1-2 wt%; and / or, The concentration of the silane coupling agent solution is 1-5 vol%, more preferably 2-3 vol%; and / or, The silane coupling agent is 3-aminopropyltriethoxysilane and / or octyltriethoxysilane; and / or The solvent for the silane coupling agent solution is ethanol; and / or, The coupling reaction is carried out at a temperature of 20-80°C, more preferably 50-70°C, and / or for a reaction time of 30-120 min, more preferably 45-60 min.

9. A composite proppant, characterized in that... The combined proppant includes the modified fly ash ceramsite proppant as described in any one of claims 1-5 or the modified fly ash ceramsite proppant or mixed proppant prepared by the method described in any one of claims 6-8; The mixed support is at least one of the following: recycled molecular sieve, recycled mesoporous material, quartz sand, and ceramsite sand.

10. The combined proppant according to claim 9, characterized in that: The weight ratio of the modified fly ash ceramsite proppant to the mixed proppant is (4-6):1, preferably (4-5):1; and / or, The particle size of the mixed proppant is 50-210 μm.

11. A method for preparing the combined proppant as described in claim 9 or 10, characterized in that... The method includes: The combined proppant is prepared by mixing the components.

12. The application of a combined proppant as described in claim 9 or 10, or a combined proppant prepared by the method described in claim 11, as a shale oil and gas fracturing proppant.

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