Ultralow-density high-strength ceramsite proppant prepared from fly ash and preparation method of ceramsite proppant

Abstract

The invention relates to the technical field of ceramsite material preparation, and discloses an ultralow-density high-strength ceramsite proppant prepared from fly ash and a preparation method, and the proppant is composed of fly ash, clay, quartz sand waste, waste electroceramics, waste ceramic chips, a mineralizer, a binder, an organic fiber explosion-proof agent and a foaming agent. The formula proportion is optimized, liquid phase generation, crystal phase formation and structural densification are achieved at the low-temperature stage, the medium-temperature stage and the high-temperature stage through the segmented sintering process, and the strength and the chemical corrosion resistance of the ceramsite are remarkably improved. The prepared proppant has the volume density of 1.37 g / cm < 3 >-1.40 g / cm < 3 >, the apparent density of 2.55 g / cm < 3 >-2.57 g / cm < 3 >, the breakage rates of 8.40% and 6.09% respectively under the pressure of 52 MPa and 69 MPa, and the acid dissolution rate of 5.26%. According to the invention, resource utilization of industrial wastes such as fly ash, waste electroceramics and the like is realized, the requirements of hydraulic fracturing engineering on light weight and high strength under complex stratum conditions are met, and the propping agent is suitable for crack supporting and diversion operation in oil and gas exploitation.

Description

Technical Field

[0001] The invention relates to the technical field of ceramsite material preparation, in particular to an ultra-low density and high-strength ceramsite proppant made from fly ash and a preparation method thereof. Background Art

[0002] Ceramic granule proppants are the core materials used to maintain the conductivity of formation fractures during oil and gas extraction. Their performance directly affects the stability of fractures and the extraction efficiency. At present, the raw materials for the production of ceramsite proppants are mainly natural mineral resources, such as bauxite and clay. Although these raw materials have good sintering properties and mechanical strength, their mining costs are high and they are facing the problem of gradually decreasing resources. On the other hand, although industrial waste such as fly ash, waste electrical porcelain and waste porcelain pieces contain rich silicon and aluminum components, they are difficult to be effectively utilized in the field of ceramsite proppants due to limitations in particle size, chemical activity and distribution, resulting in waste of resources and environmental burden.

[0003] In order to meet the requirements of complex underground formation environments for proppant performance, the density and strength of ceramsite materials need to be finely controlled. The existing methods for reducing the density of ceramsite mostly rely on reducing density or using lightweight raw materials, but these methods usually result in insufficient compressive resistance of ceramsite under high pressure conditions, which is easy to break and cannot effectively support formation cracks. When increasing the strength, the density is easily increased due to excessive density of the material, which reduces the suspension ability and transportation performance of the proppant in the fracturing fluid. This contradiction between density and strength is an important issue in the improvement of ceramsite proppant technology.

[0004] The sintering process of ceramsite is a key link in determining its performance. The generation and distribution of the crystal phase during the sintering process directly affect the strength and pore structure of ceramsite. In the prior art, due to the lack of fine control of the sintering process and the improper matching of temperature and time, the crystal phase inside the ceramsite is underdeveloped or unevenly distributed, resulting in poor performance of the proppant in terms of mechanical properties and pore uniformity. This structural defect not only affects the compressive resistance, but also has an adverse effect on the conductivity, reducing the application effect of ceramsite in oil and gas production.

[0005] Oil and gas production formations often have complex chemical environments, especially acidic conditions, which have a significant impact on the corrosion of proppants. Ceramic granules are prone to chemical reactions or physical degradation in acidic formations, and their strength gradually decreases, affecting their service life. Some modified granules in the prior art have improved their acid resistance to a certain extent, but problems such as insufficient crystal phase design and insufficient application of mineralizers still limit the optimization of granules' chemical corrosion resistance and make it difficult to adapt to long-term use requirements. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides an ultra-low density and high-strength ceramsite proppant made from fly ash and a preparation method thereof, which solves the problems of the prior art ceramsite proppant in terms of density and strength balance, chemical corrosion resistance and resource utilization of industrial waste.

[0007] To achieve the above purpose, the present invention is implemented by the following technical scheme: The ultra-low density and high strength ceramsite proppant made of fly ash includes the following raw materials, calculated by mass: Fly ash: 20 to 60 parts; Clay: 20 to 40 parts; Quartz sand waste: 10 to 30 parts; Waste electrical porcelain: 10 to 20 parts; Waste porcelain pieces: 5 to 10 parts; Mineralizer: 1 to 10 parts; Binder: 1 to 5 parts; Organic fiber explosion-proof agent: 0.5 to 5 parts; Foaming agent: 0.5 to 2 parts.

[0008] Preferably, the fly ash is fly ash dried at 105°C to 110°C.

[0009] Preferably, the clay is one or more of kaolin, bentonite or common clay.

[0010] Preferably, the mineralizer is a mixture of one or more of the following: high-purity calcite, lime powder, dolomite, magnesia, talc, forsterite, wherein the proportion of calcite is preferably more than 50% of the total amount of the mineralizer.

[0011] Preferably, the binder is polyvinyl alcohol.

[0012] Preferably, the organic fiber explosion-proof agent is natural plant fiber or artificial synthetic fiber, the natural plant fiber is one or more of paper fiber, straw fiber, hemp fiber or cotton fiber, and the artificial synthetic fiber is polyethylene fiber or polypropylene fiber.

[0013] Preferably, the foaming agent is sodium lauryl sulfate or sodium α-olefin sulfonate.

[0014] The method for preparing an ultra-low density and high-strength ceramsite proppant made from fly ash comprises the following steps: S1. The fly ash, clay, quartz sand waste, waste electric porcelain, waste porcelain pieces, mineralizer, binder, organic fiber explosion-proof agent and foaming agent are weighed and mixed in proportion; S2. The mixed raw materials are ground, sieved and spray granulated to obtain a semi-finished product; S3. After the semi-finished product is dried, it is sintered in the range of 600° C. to 1300° C., and after cooling, it is sieved to obtain a finished ceramsite proppant.

[0015] Preferably, the sintering process includes staged temperature control, with the temperature of the low temperature stage being 600°C to 900°C, the temperature of the medium temperature stage being 900°C to 1100°C, and the temperature of the high temperature stage being 1100°C to 1300°C.

[0016] Preferably, the raw materials further include an organic fiber explosion-proof agent and a foaming agent, the foaming agent is added during the raw material mixing stage and is uniformly stirred and mixed with other components; the organic fiber explosion-proof agent is added to the raw materials before granulation and is uniformly mixed.

[0017] The present invention provides an ultra-low density high-strength ceramsite proppant made from fly ash and a preparation method thereof. Beneficial effects: 1. The present invention adopts a technical solution of reasonable proportion of fly ash, waste electrical porcelain and waste porcelain pieces and clay, and significantly improves the performance and environmental value of ceramsite proppant by optimizing resource allocation. Compared with the production method relying on high-cost natural raw materials in the prior art, this solution effectively solves the problems of low waste utilization rate and high production cost, and at the same time reduces the burden of industrial waste on the environment, achieving a dual improvement in economic and environmental benefits.

[0018] 2. The present invention uses the synergistic effect of the foaming agent and the mineralizer to construct a uniformly distributed microporous structure during the sintering process, achieving a balance between ultra-low density and high strength. Compared with the proppant in the prior art that fails to effectively control the pore distribution, this solution solves the problem that low-density materials are easily broken under high pressure, making the ceramsite proppant show better compressive resistance in the underground high-pressure environment, meeting the needs of complex working conditions such as oil and gas extraction.

[0019] 3. The present invention adopts a staged temperature rise sintering process design, and generates high-strength crystalline structures such as calcium silicate and calcium aluminate through reaction control in low, medium and high temperature stages. Compared with the uneven distribution of crystalline phases caused by unreasonable sintering temperature control in the prior art, this solution significantly improves the density and mechanical properties of the ceramsite, solves the problems of insufficient strength and unstable performance of traditional proppants, and takes into account the preparation cost and energy consumption control.

[0020] 4. The present invention significantly improves the chemical stability of ceramsite proppants in acidic formation environments by introducing mineralizers to promote crystal phase formation and combining acid resistance optimization design. Compared with proppants with poor acid resistance in the prior art, this solution solves the problem that the material is prone to failure in a corrosive environment, prolongs the service life of ceramsite proppants, and ensures that it has more reliable application performance under complex formation conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic flow chart of the steps of the preparation method of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example: The embodiment of the present invention provides an ultra-low density and high strength ceramsite proppant made from fly ash. The main raw materials of the ceramsite proppant and their mass proportions are as follows (by mass fraction): Fly ash: 20 to 60 parts: Fly ash is the main light component, and its chemical composition (SiO 2 、Al 2 O 3 ) is the skeleton material of ceramsite, and improves the granulation and sintering performance through the characteristics of fine particle size and high sphericity. The selected fly ash needs to be dried at 105℃~110℃ to remove moisture and ensure the stability of the composition.

[0024] Clay: 20-40 parts: Clay is mainly kaolin, bentonite or ordinary clay, which is used to adjust the density of ceramsite and promote sintering to form a skeleton crystal phase. The particle size of the clay is controlled below 80 mesh to ensure uniform mixing.

[0025] Quartz sand waste: 10 to 30 parts: Quartz sand waste provides skeleton support and generates silicate crystal phase by reacting with other components to enhance structural strength. Waste with a particle size range of 50 μm to 200 μm is selected to match the granulation effect.

[0026] Waste electrical porcelain: 10-20 parts, waste porcelain pieces: 5-10 parts: These waste materials are low-melting-point active materials in the sintering process of ceramsite, providing bonding and forming a stable crystal structure. Waste electrical porcelain and waste porcelain pieces need to be crushed and ground, and the particle size is controlled below 100 mesh.

[0027] Mineralizer: 1 to 10 parts: The mineralizer is a mixture of one or more of high-purity calcite, dolomite, lime powder, magnesia, talc, etc. The mineralizer optimizes the performance of ceramsite by reducing the sintering temperature and adjusting the pore structure, wherein calcite is preferably more than 50% of the total amount of the mineralizer.

[0028] Binder (polyvinyl alcohol): 1 to 5 parts: Polyvinyl alcohol improves the formability of raw material particles in the granulation stage through a binding effect, ensuring particle uniformity and subsequent sintering strength.

[0029] Organic fiber explosion-proof agent: 0.5 to 5 parts: Select natural plant fibers or artificial synthetic fibers (such as paper fibers, polypropylene fibers) with a diameter of 15μm to 35μm and a length of 13mm. Its function is to form an exhaust channel during the sintering process to prevent the particles from exploding.

[0030] Foaming agent (sodium dodecyl sulfate or sodium α-olefin sulfonate): 0.5 to 2 parts: The foaming agent decomposes at high temperature to form a pore structure inside the ceramsite, significantly reducing the density of the ceramsite and improving the pore distribution.

[0031] Please see attached Figure 1 The preparation method of ultra-low density and high strength ceramsite proppant made from fly ash, the specific preparation steps are as follows: Weigh each component according to the above ratio.

[0032] The quartz sand waste, waste electrical porcelain and waste porcelain pieces are crushed to less than 100 mesh respectively and mixed evenly.

[0033] Add fly ash, clay, quartz sand waste, waste electric porcelain, waste porcelain pieces, mineralizer, binder, explosion-proof agent and foaming agent into the mixing equipment and stir and mix. The stirring time is 15 minutes to 30 minutes to ensure that each component is evenly distributed.

[0034] During the mixing process, 5% to 15% water is gradually added to adjust the material humidity to suitable granulation conditions.

[0035] Use spray granulation equipment or drum granulation equipment to control the particle size distribution within the range of 20 mesh to 70 mesh. After granulation, the particles must be uniform in shape and without obvious cracks.

[0036] The granulated particles were placed in a drying device and dried at 120° C. for 5 hours to reduce the moisture content to less than 1%.

[0037] Heating stage: The dried particles are fed into a rotary kiln and sintered by heating in stages.

[0038] Low temperature stage (600℃~900℃): fly ash, clay and mineralizer initially react to form a liquid phase; the foaming agent decomposes to produce gas, forming a uniform pore structure.

[0039] Medium temperature stage (900℃~1100℃): Active ingredients (such as SiO 2 、Al 2 O 3 , CaO) undergoes a solid phase reaction to generate calcium silicate and calcium aluminate crystal phases, and the strength of the ceramsite is significantly improved.

[0040] High temperature stage (1100℃~1300℃): the crystal structure is stable, the pore distribution is fixed, and the densification of ceramsite is completed.

[0041] Insulation time: Each stage is insulated for 10 minutes to 60 minutes. The specific time is adjusted according to the particle size of the ceramsite and the sintering equipment.

[0042] After sintering, the expanded clay is naturally cooled to room temperature and separated into finished products with specifications of 20-40 mesh, 30-50 mesh, and 40-70 mesh through screening equipment.

[0043] After sintering, the following performance tests are performed on the ceramsite proppant according to the specifications: Specification particle size: Test the particle size distribution of the finished product through standard sieves to ensure that the specifications are 20 mesh to 40 mesh, 30 mesh to 50 mesh, and 40 mesh to 70 mesh.

[0044] Bulk density: Bulk density is tested by pycnometer method; Apparent density: Apparent density is tested by dipping method; Crushing rate: The crushing rate was tested under pressures of 52MPa and 69MPa; Acid solubility: Use acid solution to soak and test the acid solubility.

[0045] In order to specifically illustrate the technical solution of the present invention and its implementation process, several embodiments are provided to demonstrate the preparation method of ceramsite proppant and its performance characteristics. These embodiments fully reflect the innovative design of the present invention in terms of raw material selection, sintering process and performance regulation through different raw material ratios and process parameter optimization. Through the embodiments, those skilled in the art can accurately understand the core technical content of the present invention and reproduce the technical solution of the present invention.

[0046] Example 1 Raw material ratio: Fly ash: 50 parts; Clay: 25 parts; Quartz sand waste: 10 parts; Waste electrical porcelain: 5 parts; Waste porcelain pieces: 5 pieces; Mineralizer (calcite): 3 parts; Binder (polyvinyl alcohol): 1 part; Foaming agent (sodium lauryl sulfate): 0.5 parts; Organic fiber explosion-proof agent (paper fiber): 0.5 parts.

[0047] Weigh the raw materials according to the above proportions, mix the fly ash, clay, quartz sand waste, waste electric porcelain, waste porcelain pieces and mineralizer evenly. Add polyvinyl alcohol as a binder, and gradually add 7% water, stir for 15 minutes to ensure full mixing.

[0048] The granulation was carried out using a drum granulation device, and the particle size was controlled within the range of 30-50 meshes. The moisture content was adjusted to about 10%.

[0049] The granulated particles were placed in a drying oven at 120°C and dried for 3 hours until the moisture content dropped below 1%.

[0050] The pellets are fed into a rotary kiln and heated in stages: 600℃~900℃ for 20 minutes, 900℃~1100℃ for 30 minutes, and 1100℃~1250℃ for 40 minutes. After sintering, they are naturally cooled to room temperature.

[0051] The finished ceramsite proppant with a particle size of 30-50 mesh is obtained by screening.

[0052] Performance Test Results Body density: 1.38g / cm 3 ; Visual density: 2.55g / cm 3 ; Crushing rate: 52MPa: 6.10%; 69MPa: 8.80%; Acid solubility: 5.25%.

[0053] Example 2 Raw material ratio: Fly ash: 40 parts; Clay: 30 parts; Quartz sand waste: 15 parts; Waste electrical porcelain: 5 parts; Mineralizer (mixture of lime powder and dolomite): 6 parts; Binder (polyvinyl alcohol): 2 parts; Foaming agent (sodium α-olefin sulfonate): 1 part; Organic fiber explosion-proof agent (polypropylene fiber): 1 part.

[0054] Weigh fly ash, clay, quartz sand waste, waste electric porcelain and mineralizer. Mix lime powder and dolomite in a ratio of 1:1 and add. Add polyvinyl alcohol solution as a binder, adjust the water content to 10%, and mix for 20 minutes.

[0055] Granulation is carried out by spray granulation equipment, and the particle size is controlled in the range of 40-70 meshes. The moisture content is maintained at about 12%.

[0056] The particles were dried in a 150°C oven for 4 hours.

[0057] Sintering is carried out in a rotary kiln. The low temperature stage (600℃~900℃) is kept warm for 30 minutes, the medium temperature stage (900℃~1100℃) is kept warm for 40 minutes, and the high temperature stage (1100℃~1300℃) is kept warm for 30 minutes. After sintering, it is cooled.

[0058] After screening, the finished ceramsite proppant with a particle size of 40-70 mesh is obtained.

[0059] Performance test results: Body density: 1.37g / cm 3 ; Visual density: 2.55g / cm 3 ; Crushing rate: 52MPa: 4.60%; 69MPa: 6.09%; Acid solubility: 5.25%.

[0060] Example 3 Raw material ratio: Fly ash: 45 parts; Clay: 25 parts; Quartz sand waste: 10 parts; Waste porcelain pieces: 10 pieces; Mineralizer (mixture of calcite and talc): 6 parts; Binder (polyvinyl alcohol): 2 parts; Foaming agent (sodium lauryl sulfate): 1 part; Organic fiber explosion-proof agent (paper fiber): 1 part.

[0061] After weighing fly ash, clay, quartz sand waste, and waste porcelain pieces in proportion, add mineralizer (calcite and talc mixed in a ratio of 2:1). Add polyvinyl alcohol solution with a water content of 8% and mix for 25 minutes to ensure that the raw materials are uniform.

[0062] The granules are made into granules with a particle size range of 20 mesh to 40 mesh by roller granulation equipment. The moisture content is controlled at 11%.

[0063] The particles were treated in a drying oven at 120°C for 3.5 hours, and the moisture content was controlled at about 0.8%.

[0064] The pellets are fed into a rotary kiln and heated in stages. The low temperature stage (600℃~900℃) is kept warm for 25 minutes, the medium temperature stage (900℃~1100℃) is kept warm for 35 minutes, and the high temperature stage (1100℃~1250℃) is kept warm for 50 minutes. After sintering, it is cooled to room temperature.

[0065] The finished ceramsite proppant with a particle size of 20-40 mesh is obtained by screening with a standard sieve.

[0066] Performance test results: Body density: 1.40g / cm 3 ; Visual density: 2.57g / cm 3 ; Crushing rate: 52MPa: 8.40%; Acid solubility: 5.26%.

[0067] Example 4 Raw material ratio: Fly ash: 55 parts; Clay: 20 parts; Quartz sand waste: 10 parts; Waste electrical porcelain: 5 parts; Mineralizer (mixed magnesia and dolomite): 7 parts; Binder (polyvinyl alcohol): 2 parts; Foaming agent (sodium α-olefin sulfonate): 0.8 parts; Organic fiber explosion-proof agent (polypropylene fiber): 0.2 parts.

[0068] Weigh all the raw materials in proportion, mix magnesia and dolomite in a ratio of 1:2 and add them. Add polyvinyl alcohol solution to adjust the water content to 9% and stir evenly for about 15 minutes.

[0069] The spray granulation equipment is used for granulation, and the particle size is controlled within the range of 30 mesh to 50 mesh. The moisture content is adjusted to 10%.

[0070] The drying temperature is 140°C for 3 hours to ensure that the moisture content of the particles does not exceed 1%.

[0071] The particles are fed into a rotary kiln and kept warm for 20 minutes at a low temperature stage (600°C to 850°C), 35 minutes at a medium temperature stage (850°C to 1100°C), and 40 minutes at a high temperature stage (1100°C to 1200°C).

[0072] After cooling, the product is sieved to obtain a finished product with a particle size of 30 to 50 meshes.

[0073] Performance test results; Body density: 1.38g / cm 3 ; Visual density: 2.55g / cm 3 ; Crushing rate: 52MPa: 6.10%; 69MPa: 8.80%; Acid solubility: 5.25%.

[0074] In order to further verify the effect of the technical solution of the present invention and highlight its advantages in performance optimization and technical improvement, it is very necessary to compare with the prior art. By designing comparative examples, using formulas or process conditions that do not adopt the key technical points of the present invention, control samples are formed to analyze and illustrate the improvement effects of the present invention in terms of light weight, high strength, chemical corrosion resistance, etc. The setting of comparative examples can more intuitively demonstrate the creativity and practicality of the present invention compared with the prior art.

[0075] Comparative Example 1 (corresponding to Example 1) Difference: The amount of mineralizer is reduced and no foaming agent is used.

[0076] Raw material ratio: Fly ash: 50 parts; Clay: 30 parts; Quartz sand waste: 15 parts; Waste electrical porcelain: 3 parts; Waste porcelain pieces: 2 parts; Mineralizer (calcite): 0.5 parts; Binder (polyvinyl alcohol): 0.5 parts; Organic fiber explosion-proof agent (paper fiber): 0.5 parts.

[0077] Weigh each component, reduce the mineralizer to 0.5 parts, do not add the foaming agent, add the binder to adjust the moisture to 8%, and stir for 15 minutes.

[0078] The drum granulation equipment was used to control the particle size to 30-50 mesh and the moisture content was adjusted to 12%.

[0079] The granules were dried at 120°C for 3 hours until the moisture content dropped to 1%.

[0080] The particles are placed in a rotary kiln and kept warm for 20 minutes at a low temperature stage (600°C to 900°C), 30 minutes at a medium temperature stage (900°C to 1100°C), and 40 minutes at a high temperature stage (1100°C to 1200°C).

[0081] The ceramsite proppant with a particle size of 30 to 50 meshes is obtained by sieving.

[0082] Comparative Example 2 (corresponding to Example 2) Difference: No organic fiber explosion-proof agent is used and the amount of foaming agent is increased.

[0083] Raw material ratio: Fly ash: 45 parts; Clay: 30 parts; Quartz sand waste: 15 parts; Waste electrical porcelain: 5 parts; Mineralizer (mixture of lime powder and dolomite): 3 parts; Binder (polyvinyl alcohol): 2 parts; Foaming agent (sodium α-olefin sulfonate): 3 parts.

[0084] Weigh each component, increase the amount of foaming agent to 3 parts, do not add organic fiber explosion-proof agent, adjust the moisture to 10%, and stir evenly.

[0085] The granules with a particle size of 40-70 mesh were prepared by spray granulation equipment, and the moisture content was maintained at 13%.

[0086] The drying temperature was 150°C and the drying time was 4 hours.

[0087] In the rotary kiln, the low temperature stage (600°C-850°C) is kept warm for 30 minutes, the medium temperature stage (850°C-1100°C) is kept warm for 40 minutes, and the high temperature stage (1100°C-1250°C) is kept warm for 30 minutes.

[0088] The ceramsite proppant with a particle size of 40 to 70 meshes is obtained.

[0089] Comparative Example 3 (corresponding to Example 3) Difference: The mineralizer is replaced with a single component (talc), and the sintering temperature is not segmented.

[0090] Raw material ratio: Fly ash: 40 parts; Clay: 30 parts; Quartz sand waste: 15 parts; Waste porcelain pieces: 10 pieces; Mineralizer (talc): 5 parts; Binder (polyvinyl alcohol): 2 parts; Foaming agent (sodium lauryl sulfate): 2 parts; Organic fiber explosion-proof agent (paper fiber): 1 part.

[0091] The mineralizer was replaced with talcum powder alone, all raw materials were weighed in proportion, the water content was adjusted to 10% after adding polyvinyl alcohol, and stirred evenly for 20 minutes.

[0092] The drum granulating equipment produces granules with a particle size range of 20 mesh to 40 mesh.

[0093] Treat in a drying oven at 120°C for 3.5 hours.

[0094] During the sintering stage, the temperature is directly heated to 1200°C and kept constant for 1 hour without a staged heating process.

[0095] The ceramsite proppant with a particle size of 20-40 mesh is obtained by sieving.

[0096] Comparative Example 4 (corresponding to Example 4) Difference: The amount of foaming agent is reduced, the moisture is not controlled, and the sintering time is shortened.

[0097] Raw material ratio: Fly ash: 50 parts; Clay: 30 parts; Quartz sand waste: 10 parts; Waste electrical porcelain: 5 parts; Mineralizer (mixed magnesia and dolomite): 3 parts; Binder (polyvinyl alcohol): 1 part; Foaming agent (sodium α-olefin sulfonate): 0.5 parts; Organic fiber explosion-proof agent (polypropylene fiber): 0.5 parts.

[0098] Weigh each component in proportion, reduce the amount of foaming agent to 0.5 parts, do not strictly control the moisture content, and shorten the mixing time to 10 minutes.

[0099] Spray granulation, particle size range is 30 mesh to 50 mesh, and moisture content is not stably adjusted.

[0100] The drying stage treatment time was shortened to 2 hours at a temperature of 120°C.

[0101] During rotary kiln sintering, the low temperature stage (600℃~900℃) is kept warm for 10 minutes, the medium temperature stage (900℃~1100℃) is kept warm for 20 minutes, and the high temperature stage (1100℃~1250℃) is kept warm for 20 minutes, and the total sintering time is shortened.

[0102] The ceramsite proppant with a particle size of 30-50 mesh is obtained by sieving.

[0103] Comparative Example 5 (corresponding to the synthesis of Example 2 and Example 3) Difference: The amount of mineralizer is reduced to 1 part, and the sintering holding time is shortened to the minimum value.

[0104] Raw material ratio: Fly ash: 48 parts; Clay: 28 parts; Quartz sand waste: 12 parts; Waste electrical porcelain: 5 parts; Mineralizer (mixture of calcite and talc): 1 part; Binder (polyvinyl alcohol): 3 parts; Foaming agent (sodium lauryl sulfate): 2 parts; Organic fiber explosion-proof agent (paper fiber): 1 part.

[0105] Reduce the amount of mineralizer to 1 part, keep other proportions unchanged, adjust the moisture to 9%, and shorten the stirring time to 10 minutes.

[0106] The drum granulating equipment is used for granulation, and the particle size is controlled to be 40 mesh to 70 mesh.

[0107] The drying temperature is 120°C and the drying time is shortened to 2 hours.

[0108] The low temperature stage (600℃~900℃) is kept warm for 10 minutes, the medium temperature stage (900℃~1100℃) is kept warm for 15 minutes, and the high temperature stage (1100℃~1200℃) is kept warm for 20 minutes, and the total time is shortened.

[0109] Screening to obtain ceramsite proppant with a particle size of 40 to 70 mesh These comparative examples are fine-tuned based on the parameters in the examples, highlighting the importance of key invention points such as foaming agent dosage, mineralizer ratio, moisture control, and sintering process in performance optimization, laying the foundation for the analysis of subsequent comparative results.

[0110] In order to comprehensively evaluate the performance differences between the examples and the comparative examples, a series of test experiments need to be carried out, including the comparison of comprehensive performances such as compressive resistance, density and acid resistance. The test experiments can not only verify the scientific nature of the technical solution of the present invention, but also explain the specific role of formula optimization and process improvement in improving the performance of ceramsite proppants from a mechanism perspective. Through the comparative analysis of the experimental results, the applicability and technical advantages of the present invention in complex downhole environments can be fully demonstrated.

[0111] Purpose: This experiment aims to comprehensively evaluate the technical effect of the ceramsite proppant of the present invention through tests such as crushing rate, bulk density, apparent density, acid solubility, etc., and verify its improvements over the prior art. The comparative analysis of the embodiments and comparative examples further proves the innovation of the present invention in terms of light weight, high strength and environmental adaptability.

[0112] Experimental Materials Test samples: Examples 1 to 4: different particle size ranges (20 mesh to 40 mesh, 30 mesh to 50 mesh, 40 mesh to 70 mesh).

[0113] Comparative Examples 1 to 5: Particle size range corresponding to the example.

[0114] Experimental equipment: Fully automatic pressure testing machine (crushing rate test).

[0115] Pycnometer (apparent density test).

[0116] Densitometer (bulk density test).

[0117] Constant temperature water bath and acid dissolution device (acid resistance test).

[0118] Standard sieves (particle size grouping and sieve residue testing).

[0119] Solution: 12:3 HCl:HF (12% by mass HCl and 3% by mass HF, with a 37% HCl concentration).

[0120] Experimental steps and procedures 1. Proppant breakage performance test Experimental methods: The sample was reduced to 100 g of ceramsite sample (the examples and comparative examples were grouped according to the particle size range, respectively) using a sample divider.

[0121] Select the mesh size of the top and bottom sieves that is appropriate for the proppant sample size. Prepare the sieve stack and place it in the sieve shaker.

[0122] Pour the sample obtained after splitting into the top sieve and cover it with the lid.

[0123] Place the sieve assembly in a sieve vibrator and vibrate for 10 minutes.

[0124] Take the group sieve out of the sieve vibrator, and pour out all the samples left in the top sieve and the bottom plate. Only the samples in the bottom sieve are left for the crushing rate test.

[0125] Pour the weighed sample into the crushing chamber. The proppant laying surface in the crushing chamber should be as flat as possible. To ensure that the surface of the proppant sample is flush, the proppant should be poured into the crushing chamber smoothly. If the sieved and weighed sample is poured out of the crushing chamber.

[0126] Insert the piston into the crushing chamber containing the weighed proppant sample without applying any external force except gravity.

[0127] Rotate the piston 180° clockwise once without applying any pressure to ensure that the proppant sample placement surface is flush.

[0128] Carefully lift the crushing chamber and place it directly into the press, directly under the press's uprighting plate. Do not shake or jolt the crushing chamber.

[0129] Pressurize the piston of the crushing chamber at a steady rate for 1 minute. The time to reach the rated pressure should be limited to within 5% of this loading rate time. If it exceeds +2.5% of the predetermined pressure, the test should be stopped and restarted with a new sample.

[0130] The pressure was maintained for 2 min.

[0131] After unloading the pressure, remove the crushing chamber from the press.

[0132] Carefully pour the sample through the same set of sieves used, scraping the sample from the bottom of the crushing chamber to ensure that all the sample is poured out.

[0133] Put the group sieve into the shaker and shake it for 10 minutes.

[0134] Carefully weigh the mass of the crushed material in the tray and record it with an accuracy of 0.1 g.

[0135] Calculate the crushing rate of the crushed sample according to the formula and submit the experimental results according to the crushing rate of the crushed sample.

[0136] Prepare 3 samples for the proppant crushing experiment, conduct 3 experiments under the same crushing stress, and take the average value as the result.

[0137] 2. Proppant bulk density and apparent density test Experimental method: Weigh the mass of the dry empty cylinder in grams.

[0138] The temperature of the test sample is between 18°C and 28°C. Put the proppant sample into a 150 mL beaker.

[0139] Close the outlet of the funnel, center the brass cylinder directly below the outlet of the funnel, and pour the sample from the beaker into the funnel.

[0140] Open the rubber ball valve at the bottom of the funnel to let the proppant flow into the brass cylinder.

[0141] After all the proppant in the funnel has flowed out, smoothly push it with a ruler at the edge of the cylinder to make the proppant level with the surface of the brass cylinder mouth.

[0142] Weigh the mass of the cylinder filled with proppant in grams.

[0143] Calculate the bulk density according to the formula.

[0144] Apparent density: Weigh the mass of the dry empty density bottle in grams and record its mass.

[0145] At ambient temperature, fill the density bottle with the test liquid up to the filling scale line. Ensure that there are no bubbles in the liquid and wipe the liquid on the outer surface of the density bottle clean.

[0146] Weigh the mass of the density bottle filled with the test liquid with an accuracy of 0.01 g. Record its mass.

[0147] Weigh the mass of the weighing dish, then add about 10 g of the proppant sample, and weigh the mass of the weighing dish and the sample accurately to 0.01 g. Calculate the mass of the proppant in grams and record its mass.

[0148] Pour out about half of the liquid in the density bottle and transfer the weighed proppant sample from the weighing dish to the density bottle. Use a funnel that fits the neck of the density bottle.

[0149] At ambient temperature: Add enough test liquid to the fill mark in the density bottle. Rotate the bottle along its vertical axis until all air bubbles in the proppant are expelled. If necessary, add test liquid again to the fill mark and wipe off the test liquid on the surface of the density bottle.

[0150] Weigh the density bottle containing the proppant and the test fluid to an accuracy of 0.01 g and record its mass. Calculate the density of the test fluid using the formula.

[0151] The apparent density is calculated according to the formula: 3. Acid solubility test Prepare a 12:3 HCl:HF solution (density at 20°C is 1.066 g / cm), fill a 1000 ml polyethylene or polypropylene graduated cylinder or bottle with 500 ml of distilled water, add 46.23 g of pure NH 4 HF 2 and dissolved. NH 4 HF 2 The actual weight is less than the 100% purity added and is equal to 46.23 g divided by NH 4 HF 2 Purity, expressed as mass fraction; Add 361 mL of 37% HCl (density 1.19 g / cm' at 20°C). Adjust the volume for different HCl concentrations. Dilute to 1000 mL with distilled water. Stir to ensure thorough mixing.

[0152] Experimental methods: Weigh 5g of proppant (accurate to 0.001g) and place it in the weighing sample pan. The proppant should be dried at 105℃ to constant weight and then cooled in a desiccator. Record the mass of the sample.

[0153] Add the proppant sample to a 150 ml polyethylene beaker containing 100 ml of acid solution. Cover the beaker with a polyethylene cover plate. The acid solution and sample should be kept at room temperature (22°C ± 3°C).

[0154] Place the beaker in a water bath at 66°C for 30 min. Do not stir.

[0155] Dry the funnel and filter paper in an oven at 105°C (221°F) for at least 1 h, or until a constant mass is reached, and record the mass. The filter medium does not need to be weighed but should be cooled in a cooler.

[0156] Transfer the sample and acid mixture from the beaker to the filtration equipment. Filter the sample through a pre-weighed filter crucible (funnel), ensuring that all particles are transferred from the beaker to the filter. Use vacuum filtration technology to remove the acid within 1 minute.

[0157] The sample in the filter apparatus was washed three times with 20 ml of distilled water until the pH was neutral.

[0158] Dry the filter and remaining sample at 105°C for at least 1 hour, or until constant mass is reached. Cool the filter and sample in a cooler before weighing. Weigh the filter and sample and record the mass.

[0159] The acid solubility was calculated according to the formula.

[0160] Table 1: Experimental data on the comprehensive performance comparison of ceramsite proppants Experiments show that the ceramsite proppant of the embodiment is significantly better than the comparative sample in terms of compressive resistance, density control and chemical corrosion resistance. The crushing rate of the embodiment is kept in a low value range at 52MPa and 69MPa, and it shows good structural stability especially under high pressure. This result is due to the precise control of the internal crystalline phase of the ceramsite by the staged sintering process. The uniform generation of calcium silicate and calcium aluminate crystalline phases makes the ceramsite have higher compressive strength and lower risk of pore crushing, while the comparative example is easy to break under high pressure due to insufficient sintering process and uneven distribution of crystalline phases.

[0161] From the density data, the body density and visual density of the embodiment are lower than those of the comparative example, which reflects the advantages of the present invention in terms of lightweight. The rational application of the foaming agent and the synergistic effect of the mineralizer are key factors in reducing the density. In contrast, the comparative example has an unreasonable internal microporous structure due to insufficient foaming agent or improper sintering temperature control, resulting in increased density. In addition, the embodiment avoids the problem of decreased mechanical properties caused by too low density by optimizing the formula ratio, and successfully achieves a balance between lightweight and high strength.

[0162] The acid resistance test shows that the acid solubility of the ceramsite in the embodiment is significantly better than that in the comparative example, which proves the innovation of the present invention in chemical corrosion resistance. The crystal phase structure introduced by the mineralizer in the embodiment, such as calcium silicate and calcium aluminate, significantly improves the adaptability of ceramsite to acidic environment. However, the comparative example sample has an incomplete sintering reaction and insufficient crystal phase, resulting in a high acid solubility rate. This result further verifies the advantages of the technical solution of the present invention in resource utilization and formation adaptability.

[0163] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Ultra-low density and high strength ceramsite proppant made from fly ash, characterized in that: The raw materials include the following components, calculated by weight: Fly ash: 20 to 60 parts; Clay: 20 to 40 parts; Quartz sand waste: 10 to 30 parts; Waste electrical porcelain: 10 to 20 parts; Waste porcelain pieces: 5 to 10 parts; Mineralizer: 1 to 10 parts; Binder: 1 to 5 parts; Organic fiber explosion-proof agent: 0.5 to 5 parts; Foaming agent: 0.5 to 2 parts.

2. The ultra-low density and high strength ceramsite proppant made from fly ash according to claim 1, characterized in that: The fly ash is fly ash that has been dried at 105°C to 110°C.

3. The ultra-low density and high strength ceramsite proppant made from fly ash according to claim 1, characterized in that: The clay is one or more of kaolin, bentonite or common clay.

4. The ultra-low density and high strength ceramsite proppant made from fly ash according to claim 1, characterized in that: The mineralizer is a mixture of one or more of the following: high-purity calcite, lime powder, dolomite, magnesia, talc, forsterite, wherein the proportion of calcite is preferably more than 50% of the total amount of the mineralizer.

5. The ultra-low density and high strength ceramsite proppant made from fly ash according to claim 1, characterized in that: The binder is polyvinyl alcohol.

6. The ultra-low density and high strength ceramsite proppant made from fly ash according to claim 1, characterized in that: The organic fiber explosion-proof agent is natural plant fiber or artificial synthetic fiber. The natural plant fiber is one or more of paper fiber, straw fiber, hemp fiber or cotton fiber. The artificial synthetic fiber is polyethylene fiber or polypropylene fiber.

7. The ultra-low density and high strength ceramsite proppant made from fly ash according to claim 1, characterized in that: The foaming agent is sodium lauryl sulfate or sodium α-olefin sulfonate.

8. A method for preparing an ultra-low density and high strength ceramsite proppant made from fly ash, characterized in that: The method of using the ultra-low density and high strength ceramsite proppant made of fly ash according to any one of claims 1 to 7 comprises the following steps: S1. Weigh and mix fly ash, clay, quartz sand waste, waste electric porcelain, waste porcelain pieces, mineralizer, and binder in proportion; S2. The mixed raw materials are ground, sieved and spray granulated to obtain a semi-finished product; S3. After the semi-finished product is dried, it is sintered in the range of 600° C. to 1300° C., and after cooling, it is sieved to obtain a finished ceramsite proppant.

9. The method for preparing the ultra-low density and high strength ceramsite proppant made from fly ash according to claim 8, characterized in that: The sintering process includes staged temperature control, wherein the temperature of the low temperature stage is 600°C to 900°C, the temperature of the medium temperature stage is 900°C to 1100°C, and the temperature of the high temperature stage is 1100°C to 1300°C.

10. The method for preparing an ultra-low density and high-strength ceramsite proppant made from fly ash according to claim 8, characterized in that: The raw materials also include an organic fiber explosion-proof agent and a foaming agent. The foaming agent is added in the raw material mixing stage and is uniformly stirred and mixed with other components; the organic fiber explosion-proof agent is added to the raw materials before granulation and is uniformly mixed.

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