Petroleum fracturing propping agent for resource utilization of fly ash and preparation method of petroleum fracturing propping agent

Abstract

The invention provides a petroleum fracturing propping agent for resource utilization of fly ash and a preparation method of the petroleum fracturing propping agent, and belongs to the technical field of fracturing propping agents. The invention relates to a petroleum fracturing propping agent for resource utilization of fly ash. The petroleum fracturing propping agent comprises the following raw materials in parts by weight: 10-20 parts of fly ash, 50-60 parts of low-grade bauxite, 10-15 parts of magnesite tailings, 5-10 parts of phosphogypsum and 6-15 parts of a fluxing agent. Through resource utilization of the fly ash and other solid wastes or hazardous wastes, the density of the ceramsite proppant is further reduced and the crushing resistance of the ceramsite proppant is improved based on the component complementation and synergistic effect of the raw materials, so that the ceramsite proppant better meets the requirements of petroleum fracturing exploitation.

Description

Technical Field

[0001] The present invention belongs to the technical field of fracturing proppants, and particularly relates to an oil fracturing proppant for resource utilization of fly ash and a preparation method thereof. Background Art

[0002] With the gradual depletion of world oil and gas resources, people have to develop low-permeability oil and gas reservoirs that are difficult to exploit. Since the oil and gas reservoirs themselves have low permeability and cannot be exploited by conventional means, hydraulic fracturing technology must be used to obtain industrial production. During the fracturing process, in order to prevent the hydraulic fracture from closing, an oil fracturing proppant needs to be added to ensure the fracture conductivity.

[0003] Ceramsite proppant belongs to a kind of oil fracturing proppant and is a solid particle with a certain strength used to support the rock fracture during the hydraulic fracturing operation. It is mainly applied to the oil and gas hydraulic fracturing technology. The basic principle is to inject the fracturing fluid containing a certain amount of proppant material into the oil and gas layer through the high-pressure pump system on the ground. When the hydraulic pressure is much higher than the rock fracture pressure, fractures will appear in the oil and gas layer. After the proppant enters the fracture, on the one hand, it can make the fracture continue to extend, and on the other hand, it can keep the fracture open, ensuring that after the fracturing is completed and the fracturing fluid is discharged from the wellbore, the oil and gas layer still has fractures with a certain length and width, improving its permeability and increasing production.

[0004] Traditional ceramsite proppants are high-strength, high-density dark spherical particles sintered from high-quality bauxite ore mixed with other minerals and additives. Its main component is Al2O3, and the common phases are corundum phase and mullite phase. It has the advantages of high compressive strength, high sphericity, smooth surface, good corrosion resistance, etc., making the porosity formed by the accumulation between the oil and gas rock layers large and enhancing the oil and gas conductivity. It is widely used in deep wells / low-permeability oil and gas fields. However, the increasingly scarce bauxite resources cannot support the large consumption of aluminous ceramsite proppants. Therefore, at present, it is more inclined to use low-cost minerals or solid wastes as the main raw materials to prepare ceramsite proppants with low density and environmentally friendly characteristics.

[0005] Fly ash is the solid particulate matter in the flue gas ash generated after garbage combustion (excluding fly ash generated by coal-fired power plants) and belongs to hazardous waste. The main sources of fly ash are garbage incineration and other hazardous waste incineration, and the fly ash generated by garbage incineration accounts for 3%-5% of the total garbage volume. Garbage incineration power generation has become one of the important sources of fly ash. At present, some studies have disclosed the use of fly ash to produce ceramic proppants. For example, the patent application document CN110590338A discloses a method for preparing fracturing sand using fly ash from garbage incineration, including the following steps: drying the fly ash from garbage incineration, bauxite, and manganese ore powder, and respectively grinding the powders through a 325-mesh standard sieve using a planetary ball mill; fully mixing the obtained raw materials in proportion, spraying them into balls in a disk granulator, and screening to obtain semi-finished fracturing proppants with a particle size of 20-40 mesh; putting the semi-finished products into a porcelain ark and drying them in an oven; placing the dried semi-finished products in a muffle furnace and sintering them at 1200°C - 1400°C for 1-3 hours, cooling them to room temperature with the furnace, and screening to obtain fracturing proppant products with a particle size of 20-40 mesh. Another example is that the patent application document CN114292637A discloses a method for resource treatment of fly ash, including the following steps: drying the fly ash and graphite powder, and respectively grinding the powders through a 200-mesh sieve using a ball mill; mixing the fly ash and graphite powder after passing through the 200-mesh sieve evenly in proportion, spraying water mist containing sodium sulfide in a disk granulator to obtain the first pellets; fully stirring and mixing the first pellets with a capturer in a stirrer, and drying to obtain the second pellets; mixing lime slurry, quicklime, quartz fiber, bauxite, silicon carbide, and water evenly in proportion to form a slurry, coating the slurry on the second pellets, and drying to obtain the third pellets; performing microwave sintering on the third pellets to obtain high-strength sand. However, this technology has a complex process, and the use of sodium sulfide and the capturer may cause secondary pollution. Graphite powder belongs to high-value-added industrial raw materials with a high cost, poor economy, and is difficult to promote.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a petroleum fracturing proppant for resource utilization of fly ash, which improves the anti-breaking ability of the petroleum fracturing proppant while reducing the density, aiming at the deficiencies of the existing technology.

[0008] To solve the above technical problem, the technical solution adopted by the present invention is: a petroleum fracturing proppant for resource utilization of fly ash, including the following raw materials in parts by weight: 10-20 parts of fly ash, 50-60 parts of low-grade bauxite, 10-15 parts of magnesite tailings, 5-10 parts of phosphogypsum, and 6-15 parts of a fluxing agent.

[0009] Optionally, the fluxing agent includes waste glass and boron mud, and the mass ratio of the waste glass to the boron mud is (5-10):(1-5).

[0010] Optionally, the fly ash contains 30 - 50% by mass of SiO2, 15% - 30% by mass of Al2O3, 5% - 15% by mass of CaO, and 3% - 10% by mass of Fe2O3 Optionally, the low - grade bauxite contains ≤45% by mass of Al2O3, 20% - 30% by mass of SiO2, 5% - 15% by mass of Fe2O3, and 1% - 3% by mass of TiO2.

[0011] Optionally, the magnesite tailings contain 30% - 35% by mass of MgO, 5% - 10% by mass of CaO, 5% - 15% by mass of SiO2, 0.5 - 2% by mass of Al2O3, and ≤3% by mass of Fe2O3.

[0012] Optionally, the waste glass contains 70% - 75% by mass of SiO2, 10% - 15% by mass of Na2O, 5% - 10% by mass of CaO, and 1% - 3% by mass of Al2O3.

[0013] Optionally, the phosphogypsum contains ≥75% of CaSO4·2H2O.

[0014] Optionally, the boron mud contains 20% - 30% by mass of MgO, 15% - 20% by mass of SiO2, ≤10% by mass of Fe2O3, and ≤3% by mass of B2O3.

[0015] Optionally, for the oil - well fracturing proppant for resource utilization of fly ash, the mass percentages of its effective chemical components are: 45 - 60% of Al2O3, 20 - 35% of SiO2, 1 - 5% of MgO, 3 - 8% of Fe2O3, 2 - 6% of CaO, 0.5 - 2% of B2O3, and 1 - 3% of Na2O.

[0016] Optionally, the particle sizes of the fly ash, low - grade bauxite, magnesite tailings, waste glass, phosphogypsum, and boron mud are ≤100 mesh.

[0017] The present invention also provides a preparation method of an oil - well fracturing proppant for resource utilization of fly ash, including: mixing fly ash, low - grade bauxite, magnesite tailings, waste glass, phosphogypsum, and boron mud, stirring, granulating, sintering, cooling, and screening to obtain the product.

[0018] Optionally, the process parameters of the sintering include: first pre - sintering at 300 - 500°C for 1 - 2 h; then heating at a rate of 2.5 - 3.2°C / min to 1150 - 1250°C and holding for 2 - 4 h.

[0019] In the pre-sintering stage, it is pre-sintered at 300 - 500 °C for 1 - 2 h to remove the residual organic matter, crystal water (dehydration of CaSO4·2H2O in phosphogypsum), and unburned carbon in fly ash in the raw materials, avoiding the violent release of gas in the high-temperature stage that may cause the structure to crack; meanwhile, Al2O3 and SiO2 in low-grade bauxite begin to form pre-mullite, and MgCO3 in magnesite tailings decomposes into active MgO, laying a foundation for subsequent high-temperature reactions. If the temperature in the pre-sintering stage is too low, the volatile components cannot be completely removed. If it is too high, some components may be sintered prematurely, inhibiting subsequent foaming. If the time is too short, volatile components remain, and high-temperature foaming gets out of control. If the time is too long, energy consumption increases and excessive formation of Fe2O3 may be triggered. In the high-temperature sintering stage, it is heated to 1150 - 1250 °C at a rate of 2.5 - 3.2 °C / min and held for 2 - 4 h. The waste glass and boron mud form a low-viscosity liquid phase, wrapping the Al2O3 - SiO2 particles and promoting densification. The decomposition of phosphogypsum (CaSO4 → CaO + SO3↑) and the oxidation of unburned carbon in fly ash (C + O2 → CO2↑) release gases, which are captured by the glass phase to form closed pores, reducing the density. At the same time, Al2O3 and SiO2 form mullite (3Al2O3·2SiO2); MgO and Al2O3 form spinel (MgAl2O4); the dual-phase structure significantly improves the compressive strength and the anti-crushing performance. If the rate is too slow, the glass phase flows prematurely, gas escapes, and the open porosity increases. If the rate is too fast, thermal stress cracks are induced. If the holding time is too short, the crystal phase does not develop completely. If the time is too long, the spinel grains coarsen and the brittleness increases.

[0020] Optionally, the process parameters for cooling include: cooling the sintered product to 800 - 850 °C at 15 - 20 °C / min, then cooling to 400 - 450 °C at 4 - 5 °C / min, and finally cooling to room temperature at 12 - 17 °C / min.

[0021] In the cooling process, first, a rapid cooling stage is carried out (cooling to 800 - 850 °C at 15 - 20 °C / min), locking the closed pore structure to prevent the pore walls from softening and collapsing at high temperatures; quickly passing through the spinel - mullite grain growth temperature range to maintain the grain size; if the cooling rate is too low, it will lead to excessive grain growth and a decrease in strength; if the rate is too high, thermal stress microcracks will be generated, weakening the anti - fragmentation performance. Then, a medium - speed cooling stage (cooling to 400 - 450 °C at 4 - 5 °C / min) is carried out to eliminate the residual stress inside the glass phase and avoid spontaneous cracking in the later stage. If the rate is too fast, phase - change stress concentration will occur and the open - pore rate will increase; if the rate is too slow, the production cycle will be extended and the economy will decline. Finally, it is quickly cooled to room temperature (12 - 17 °C / min), quickly passing through the low - temperature crystallization range to prevent the secondary crystallization of borate or silicate from destroying the structural uniformity and ensure the stability of the pore structure and crystal phase distribution. If the rate is too low, local crystallization may occur, reducing the acid - corrosion resistance; if the rate is too high, it is demanding on equipment and there is no obvious performance gain.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses fly ash, low - grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud to prepare ceramic proppants. Through the complementary composition and synergistic effect of each raw material, the density of the ceramic proppant is further reduced while its anti - fragmentation performance is improved, making it better meet the requirements of oil fracturing exploitation.

[0023] In the present invention, fly ash: rich in SiO2 and Al2O3, supplements the insufficient silicon - aluminum components in low - grade bauxite, reacts with bauxite at high temperature to form mullite, enhancing the high - temperature strength. The unburned carbon in fly ash oxidizes and releases CO2 during sintering, synergistically forming a composite closed - pore structure with the SO3 released by phosphogypsum; at the same time, the spherical particles in fly ash combine with the waste - glass melt, improving the particle packing density, reducing the open - pore rate, and improving the anti - fragmentation performance while reducing the product density.

[0024] Low - grade bauxite: As the main aluminum source (the Al2O3 content is preferably 40% - 45%), provides the basic framework of the ceramic proppant, reduces the raw - material cost, forms corundum and mullite phases at high temperature, provides compressive strength, and the Fe2O3 therein improves toughness through solid - solution strengthening, and TiO2 promotes sintering densification. Reacts with MgO in magnesite tailings to form spinel (MgAl2O4), whose Vickers hardness is significantly higher than that of mullite, enhancing the anti - fragmentation property.

[0025] Magnesite tailings: Provides MgO, forms magnesium - aluminum spinel with Al2O3 and SiO2, whose thermal expansion coefficient matches that of mullite, reducing the risk of thermal - stress cracking, improving the high - temperature resistance and compressive strength of the ceramic proppant. The high melting point of MgO inhibits high - temperature deformation and reduces the sintering shrinkage rate. Forms a borate - magnesium glass phase with B2O3 in boron mud, filling the grain - boundary pores and enhancing the density.

[0026] Waste glass: It provides SiO2 and Na2O, which act as fluxes to reduce the sintering temperature and simultaneously reduce energy consumption; the molten glass phase wraps the raw material particles, improving fluidity and sphericity. Na in the glass phase + reacts with Ca decomposed from phosphogypsum 2+ to form calcium sodium silicate, enhancing the stability of the closed-cell structure.

[0027] Phosphogypsum: It mainly contains CaSO4·2H2O, which decomposes into CaO and SO3 gas at high temperature. CaO reacts with SiO2 / Al2O3 to form calcium silicate or calcium aluminate, enhancing the strength; the gas is wrapped by the glass phase to form a closed-cell structure, reducing the density.

[0028] Boron mud: It contains MgO and a small amount of B2O3, which acts as a flux to further reduce the sintering temperature (about 100 - 150 °C), promotes densification and reduces porosity. Boron mud forms a B2O3-SiO2 network with SiO2 in waste glass, enhancing the temperature resistance.

[0029] The present invention improves and optimizes the preparation process in combination with the characteristics of raw materials, especially the sintering and cooling processes, and through the synergistic cooperation of the above raw materials, achieves the balance between density and strength, effectively improves the anti-breaking ability while reducing the density. The particle size specification of the obtained proppant for petroleum fracturing is 20 / 40 mesh, the bulk density ≤ 1.35 g / cm 3 , the crushing rate at 52 MPa ≤ 4.0%, the sphericity and roundness ≥ 0.80, the acid solubility ≤ 4.0%, the raw material cost is reduced by more than 40%, and it can replace traditional bauxite ceramsite, having market competitiveness. The present invention passes the leaching toxicity test (GB5085.3 - 2007), and the measured leaching concentrations of Pb and Cd meet the standard requirements. Specific Embodiments

[0030] To better understand the present invention, the content of the present invention will be further clearly elaborated below in combination with embodiments, but the protection scope of the present invention is not limited to the following embodiments only. In the following description, a large number of specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0031] In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values.

[0032] Unless otherwise specified, all raw materials are sourced from commercially available products, and unless otherwise specified, they do not contain other components not explicitly mentioned except for inevitable impurities.

[0033] In the following cases, the chemical compositions of the respective raw materials are as follows: The mass percentage of SiO2 in fly ash is 30 - 50%, the mass percentage of Al2O3 is 15% - 30%, the mass percentage of CaO is 5% - 15%, and the mass percentage of Fe2O3 is 3% - 10% The low - grade bauxite contains Al2O3 with a mass percentage of 40% - 45%, SiO2 with a mass percentage of 20% - 30%, Fe2O3 with a mass percentage of 5% - 15%, and TiO2 with a mass percentage of 1% - 3%.

[0034] The magnesite tailings contain MgO with a mass percentage of 30% - 35%, CaO with a mass percentage of 5% - 10%, SiO2 with a mass percentage of 5% - 15%, Al2O3 with a mass percentage of 0.5 - 2%, and the mass percentage of Fe2O3 ≤ 3%.

[0035] The waste glass contains SiO2 with a mass percentage of 70% - 75%, Na2O with a mass percentage of 10% - 15%, CaO with a mass percentage of 5% - 10%, and Al2O3 with a mass percentage of 1% - 3%.

[0036] The phosphogypsum contains CaSO4·2H2O ≥ 75%.

[0037] The boron mud contains MgO with a mass percentage of 20% - 30%, SiO2 with a mass percentage of 15% - 20%, Fe2O3 with a mass percentage ≤ 10%, and B2O3 with a mass percentage ≤ 3%.

[0038] A kind of petroleum fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 45 - 60%, SiO2 20 - 35%, MgO 1 - 5%, Fe2O3 3 - 8%, CaO 2 - 6%, B2O3 0.5 - 2%, Na2O 1 - 3%, and the balance is inevitable impurities.

[0039] Among them, Al2O3: As the aluminum source of the mullite phase and corundum phase, it provides compressive strength and high - temperature stability, and the crystal phase ratio is reasonably controlled to balance the bulk density and compressive strength. SiO2: Forms a low - viscosity melt with B2O3 and Na2O, wraps the crystal phase, and improves toughness; the high - temperature molten state fills the open pores and promotes the formation of a closed - pore structure. MgO: Generates MgAl2O4 with Al2O3 to improve the anti - crushing property; Mg 2+ solid - solution in the mullite lattice, reduces the thermal expansion coefficient, and reduces micro - cracks. Fe2O3: Fe 3+ replaces A 3+Enter the mullite lattice, causing lattice distortion and enhancing the compressive strength; generate low-melting-point ferrite to reduce the sintering temperature. CaO: React with SO3 decomposed from phosphogypsum to form a CaO-SiO2 glass phase, reducing the melt viscosity and promoting closed pores; generate wollastonite to reduce acid etching. B2O3: Reduce the sintering temperature and promote densification; and form a three-dimensional B-O-Si network to resist acid etching. Na2O: Reduce the melt viscosity and improve the sphericity of granulation; form a Na2O-B2O3-SiO2 eutectic system with B2O3 to accelerate densification.

[0040] The particle sizes of fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud are all 100 mesh.

[0041] In the following examples, an oil fracturing proppant for resource utilization of fly ash is made from the following raw materials in parts by weight: 10-20 parts of fly ash, 50-60 parts of low-grade bauxite, 10-15 parts of magnesite tailings, 5-10 parts of phosphogypsum, and 6-15 parts of flux.

[0042] Example 1: An oil fracturing proppant for resource utilization of fly ash is made from the following raw materials in parts by weight: 15 parts of fly ash, 53 parts of low-grade bauxite, 12 parts of magnesite tailings, 8 parts of waste glass, 8 parts of phosphogypsum, and 4 parts of boron mud.

[0043] An oil fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 47.2%, SiO2 29.3%, MgO 4.2%, Fe2O3 7.8%, CaO 4.1%, B2O3 1.8%, Na2O 2.1%, and the balance is inevitable impurities.

[0044] A preparation method of an oil fracturing proppant for resource utilization of fly ash includes: Mix fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud, stir well, granulate with a roll pelletizer, control the diameter at 10-15 mm, pre-burn at 420 °C for 1.5 h; then heat up to 1230 °C at a rate of 2.7 °C / min and hold for 2.5 h; cool the sintered product to 832 °C at a rate of 17 °C / min, then cool to 420 °C at a rate of 4.5 °C / min, and finally cool to room temperature (25 °C) at a rate of 15 °C / min; screen to obtain the product.

[0045] Example 2: An oil fracturing proppant for resource utilization of fly ash is made from the following raw materials in parts by weight: 12 parts of fly ash, 56 parts of low-grade bauxite, 13 parts of magnesite tailings, 9 parts of waste glass, 5 parts of phosphogypsum, and 5 parts of boron mud.

[0046] An oil fracturing proppant for resource utilization of fly ash, the mass percentages of its effective chemical components are as follows: Al2O3 51.3%, SiO2 30.5%, MgO 3.4%, Fe2O3 5.2%, CaO 2.1%, B2O3 0.8%, Na2O 2.8%, and the balance is inevitable impurities.

[0047] A preparation method of an oil fracturing proppant for resource utilization of fly ash, comprising: Mix fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud, stir well, granulate using a roll pelletizer, control the diameter at 10 - 15 mm, pre-burn at 300 °C for 2 h; then heat up to 1150 °C at a rate of 2.5 °C / min and hold for 4 h; cool the sintered product to 850 °C at a rate of 20 °C / min, then cool to 400 °C at a rate of 4 °C / min, and finally cool to room temperature at a rate of 12 °C / min; screen to obtain the product.

[0048] Example 3: An oil fracturing proppant for resource utilization of fly ash is made from the following raw materials in parts by weight: 17 parts of fly ash, 53 parts of low-grade bauxite, 10 parts of magnesite tailings, 6 parts of waste glass, 10 parts of phosphogypsum, and 4 parts of boron mud.

[0049] An oil fracturing proppant for resource utilization of fly ash, the mass percentages of its effective chemical components are as follows: Al2O3 50.5%, SiO2 32.4%, MgO 5.0%, Fe2O3 3.2%, CaO 2.6%, B2O3 1.1%, Na2O 1.2%, and the balance is inevitable impurities.

[0050] A preparation method of an oil fracturing proppant for resource utilization of fly ash, comprising: Mix fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud, stir well, granulate using a roll pelletizer, control the diameter at 10 - 15 mm, pre-burn at 500 °C for 1 h; then heat up to 1250 °C at a rate of 3.2 °C / min and hold for 2 h; cool the sintered product to 800 °C at a rate of 15 °C / min, then cool to 450 °C at a rate of 5 °C / min, and finally cool to room temperature at a rate of 17 °C / min; screen to obtain the product.

[0051] Example 4: An oil fracturing proppant for resource utilization of fly ash is made from the following raw materials in parts by weight: 10 parts of fly ash, 60 parts of low-grade bauxite, 14 parts of magnesite tailings, 5 parts of waste glass, 6 parts of phosphogypsum, and 5 parts of boron mud.

[0052] An oil fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 59.3%, SiO2 22.3%, MgO 1.1%, Fe2O3 4.6%, CaO 6.0%, B2O3 2.0%, Na2O 1.5%, and the balance is inevitable impurities.

[0053] A preparation method of an oil fracturing proppant for resource utilization of fly ash, comprising: Mix fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud, stir well, granulate with a roll pelletizer, control the diameter at 10 - 15 mm, pre-burn at 350 °C for 2 h; then heat up to 1210 °C at a rate of 3.0 °C / min and hold for 3.5 h; cool the sintered product to 820 °C at 16 °C / min, then cool to 420 °C at 4.3 °C / min, and finally cool to room temperature at 13 °C / min; screen to obtain the product.

[0054] For the preparation methods of Examples 5 - 8 below, refer to Example 1 and will not be elaborated.

[0055] Example 5: An oil fracturing proppant for resource utilization of fly ash, made from the following raw materials in parts by weight: 11 parts of fly ash, 54 parts of low-grade bauxite, 13 parts of magnesite tailings, 10 parts of waste glass, 9 parts of phosphogypsum, and 3 parts of boron mud.

[0056] An oil fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 49.5%, SiO2 25.6%, MgO 4.2%, Fe2O3 8.0%, CaO 5.1%, B2O3 1.3%, Na2O 3.0%, and the balance is inevitable impurities.

[0057] Example 6: An oil fracturing proppant for resource utilization of fly ash, made from the following raw materials in parts by weight: 20 parts of fly ash, 50 parts of low-grade bauxite, 11 parts of magnesite tailings, 7 parts of waste glass, 7 parts of phosphogypsum, and 5 parts of boron mud.

[0058] An oil fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 45.2%, SiO2 34.3%, MgO 3.1%, Fe2O3 7.1%, CaO 4.5%, B2O3 1.5%, Na2O 1.1%, and the balance is inevitable impurities.

[0059] Example 7: An oil fracturing proppant for resource utilization of fly ash, made from the following raw materials in parts by weight: 18 parts of fly ash, 58 parts of low-grade bauxite, 13 parts of magnesite tailings, 5 parts of waste glass, 5 parts of phosphogypsum, and 1 part of boron mud.

[0060] An oil fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 52.3%, SiO2 31.2%, MgO 2.1%, Fe2O3 6.3%, CaO 3.0%, B2O3 0.5%, Na2O 1.3%, and the balance is inevitable impurities.

[0061] Example 8: An oil fracturing proppant for resource utilization of fly ash is made from the following raw materials in parts by weight: 15 parts of fly ash, 55 parts of low-grade bauxite, 15 parts of magnesite tailings, 6 parts of waste glass, 7 parts of phosphogypsum, and 2 parts of boron mud.

[0062] An oil fracturing proppant for resource utilization of fly ash, the mass percentage of its effective chemical components is: Al2O3 46.8%, SiO2 27.5%, MgO 3.5%, Fe2O3 7.5%, CaO 5.5%, B2O3 1.7%, Na2O 2.7%, and the balance is inevitable impurities.

[0063] Comparative Example 1: An oil fracturing proppant, which is different from Example 1 in that: waste glass is omitted from the raw materials, and the addition of waste glass is omitted in the corresponding preparation method.

[0064] Comparative Example 2: An oil fracturing proppant, which is different from Example 1 in that: boron mud is omitted from the raw materials, and the addition of boron mud is omitted in the corresponding preparation method.

[0065] Comparative Example 3: An oil fracturing proppant is made from the following raw materials in parts by weight: 10 parts of fly ash, 60 parts of low-grade bauxite, 20 parts of magnesite tailings, 5 parts of waste glass, 5 parts of phosphogypsum, and 10 parts of boron mud.

[0066] Comparative Example 4: An oil fracturing proppant is made from the following raw materials in parts by weight: 10 parts of fly ash, 70 parts of low-grade bauxite, and 20 parts of magnesite tailings.

[0067] Comparative Example 5: Different from Example 1, in the preparation method, pre-sintering is carried out at 350 °C for 3 h; then the temperature is raised to 1130 °C at a rate of 2 °C / min and held for 3 h.

[0068] Comparative Example 6: Different from Example 1, in the preparation method, the sintered product is cooled to room temperature (25 °C) at a rate of 10 °C / min.

[0069] Next, the content of the evaluation test will be described.

[0070] The petroleum fracturing proppants prepared in Examples 1-5 and Comparative Examples 1-6 were subjected to performance tests in accordance with the relevant provisions of the standard SY / T5108-2014 Test Method for Performance of Proppants for Hydraulic Fracturing and Gravel Packing Operations, and the leaching toxicity was tested in accordance with GB5085.3-2007. The test results are shown in Table 1 below.

[0071] Table 1 Performance Test Results The above results show that the bulk density of the petroleum fracturing proppant obtained in the present invention is ≤1.35 g / cm 3 , the breakage rate at 52 MPa is ≤4.0%, the sphericity and roundness are ≥0.80, and the acid solubility is ≤4.0%; the leaching concentrations of Pb and Cd meet the standard requirements. The results of Comparative Example 1 show that omitting the addition of waste glass has an obvious impact on the bulk density, sphericity and roundness of the product; the results of Comparative Example 2 show that omitting boron mud has an obvious impact on the acid solubility of the product; the results of Comparative Example 3 show that the ratios of the raw materials have an obvious impact on the bulk density and breakage rate of the product; the results of Comparative Example 4 show that the raw materials and their ratios have obvious impacts on all the properties of the product; the results of Comparative Examples 5 and 6 show that the preparation steps and process parameters have obvious impacts on the performance of the petroleum fracturing proppant.

[0072] It can be seen that the raw materials and their ratios of the fracturing proppant of the present invention are scientific and reasonable, and the performance of the prepared product meets the relevant standard requirements. In particular, a better balance is achieved between the bulk density and the breakage rate, which can better meet the requirements of petroleum fracturing operations.

[0073] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A petroleum fracturing proppant for resource utilization of fly ash, characterized in that: The invention comprises the following raw materials in parts by weight: 10-20 parts of fly ash, 50-60 parts of low-grade bauxite, 10-15 parts of magnesite tailings, 5-10 parts of phosphogypsum and 6-15 parts of flux.

2. The petroleum fracturing proppant for resource utilization of fly ash according to claim 1, characterized in that: The flux comprises waste glass and boron mud, and the mass ratio of the waste glass to the boron mud is (5-10): (1-5).

3. The petroleum fracturing proppant for resource utilization of fly ash according to claim 2, characterized in that: The low-grade bauxite contains Al2O3 of ≤45% by mass, SiO2 of 20%-30% by mass, Fe2O3 of 5%-15% by mass, and TiO2 of 1%-3% by mass.

4. The petroleum fracturing proppant for resource utilization of fly ash according to claim 3, characterized in that: The mass percentages of its effective chemical components are: Al2O3 45-60%, SiO2 20-35%, MgO 1-5%, Fe2O3 3-8%, CaO 2-6%, B2O3 0.5-2%, and Na2O 1-3%.

5. The petroleum fracturing proppant for resource utilization of fly ash according to claim 4, characterized in that: The particle sizes of the fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud are ≤100 meshes.

6. The method for preparing a petroleum fracturing proppant by resource-utilizing fly ash according to any one of claims 1 to 5, characterized in that: include: The product is obtained by mixing fly ash, low-grade bauxite, magnesite tailings, waste glass, phosphogypsum and boron mud, stirring, granulating, sintering, cooling and screening.

7. The method for preparing a petroleum fracturing proppant by resource-utilizing fly ash according to claim 6, characterized in that: The sintering process parameters include: pre-sintering at 300-500° C. for 1-2 hours; then heating to 1150-1250° C. at a rate of 2.5-3.2° C. / min and keeping the temperature for 2-4 hours.

8. The method for preparing a petroleum fracturing proppant by resource-utilizing fly ash according to claim 7, characterized in that: The cooling process parameters include: cooling the sintered product to 800-850°C at 15-20°C / min, then cooling to 400-450°C at 4-5°C / min, and finally cooling to room temperature at 12-17°C / min.

Images