Ultrahigh-strength ceramsite proppant and preparation method thereof

Abstract

The invention relates to the technical field of oil and gas exploitation, and discloses an ultrahigh-strength ceramsite proppant and a preparation method thereof. The method comprises the following steps: mixing bauxite tailings, fly ash, high titanium slag and alpha alumina powder according to a mass ratio of (30-50): (20-30): (10-25): (15-20), carrying out ball-milling granulation to obtain green pellets, and sintering to obtain the high titanium slag-containing bauxite-alumina composite material. The obtained ceramsite proppant takes industrial solid waste as a main raw material, realizes resource utilization, is low in cost, environment-friendly and excellent in performance, has the crushing rate of less than 9% under the closing pressure of 159 MPa, the acid solubility of less than 7%, the sphericity of 0.8, the volume density of 1.70-1.85 g / cm < 3 > and the apparent density of 3.00-3.25 g / cm < 3 >, and can meet the strict requirements of deep and ultra-deep oil and gas well fracturing operation on high strength of the proppant.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, specifically to an ultra-high strength ceramic proppant and its preparation method. Background Technology

[0002] Petroleum proppant (ceramsite sand) is a ceramic particle product with high compressive strength. It is mainly used in oil and gas field well water fracturing operations to support rock fractures and improve oil and gas conductivity, thereby increasing oil and gas production. It is an environmentally friendly product.

[0003] With the rapid development of the alumina and ceramsite industries, the demand for bauxite, as an important industrial raw material, has been increasing year by year. However, due to declining reserves and limited raw material availability, prices have soared. Furthermore, the recent shift from coal to gas and electricity to gas has led to the use of sintering methods for commonly used ceramsite proppant, resulting in high energy consumption and excessively high production costs. It is well known that the actual preparation of ceramsite proppant also presents numerous problems such as significant environmental pollution, high production costs, and high energy consumption. Therefore, reducing or eliminating the use of bauxite is particularly important. Bauxite tailings generated during mining are considered one of the "three wastes" due to their difficulty and high processing costs. Nearly half of the mineral resources are concentrated in mine tailings. If these tailings resources are not reused, it will result in resource waste. Moreover, from an environmental protection perspective, the long-term stockpiling of tailings causes serious environmental pollution. Therefore, the redevelopment and utilization of bauxite tailings is an urgent priority.

[0004] Fly ash is one of the largest industrial wastes discharged in my country. With the development of the power industry, the amount of fly ash emitted by coal-fired power plants has been increasing year by year. Large amounts of fly ash, if left untreated, will generate dust and pollute the atmosphere; if discharged into waterways, it will cause river siltation, and the toxic chemicals it contains will harm human health and other organisms. The comprehensive utilization of fly ash, turning waste into treasure and harm into benefit, has become an important means of resolving the contradiction between environmental pollution and resource scarcity. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength ceramsite proppant and its preparation method, in order to solve the technical problem of achieving a high-strength structure with low breakage rate of ceramsite proppant under ultra-high closure pressure by synergistic compounding of multiple solid wastes and sintering to reconstruct the crystal phase.

[0006] The technical solution of the present invention is as follows: An ultra-high strength ceramsite proppant comprises bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, wherein the mass ratio of the bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder is 30-50:20-30:10-25:15-20; the ceramsite proppant has a particle size of 40-70 mesh, a breakage rate of <9% under a closing pressure of 159 MPa, an acid solubility of <7%, and a sphericity of 0.8.

[0007] Further optimization revealed that the chemical composition of the bauxite tailings, expressed as a percentage by mass, was: Al2O3 36-50wt%, SiO2 20-30wt%, CaO + MgO 1-10wt%, Fe2O3 1-12wt%, TiO2 1-12wt%; and its loss on ignition was 10-15%.

[0008] Further optimization is achieved by specifying the chemical composition of the fly ash as a percentage by mass: Al2O3 20-30wt%, SiO2 40-50wt%, Fe2O3 5-15wt%, CaO 5-10wt%, MgO 3-7wt%, K2O+Na2O 0.5%-4%.

[0009] Further optimization revealed that the chemical composition of the high-titanium slag, expressed as a percentage by mass, was: TiO2 75-85wt%, SiO2 3.5-11wt%, Al2O3 1.5-6wt%, MnO2 1-2wt%, Fe2O3 <5wt%.

[0010] Further optimization is achieved by specifying the chemical composition of the α-alumina micro powder as follows (by mass percentage): αAl2O3 > 98.5 wt%, Fe2O3 ≤ 0.1%, Na2O ≤ 0.3%, and SiO2 ≤ 0.2%.

[0011] A method for preparing an ultra-high strength ceramic proppant includes the following steps: mixing and ball milling the raw materials in the prescribed amounts, granulating them, and sintering the resulting particles at 1100-1250℃ for 1.5-2 hours to obtain the proppant.

[0012] Further optimization involves a ball milling time of 1-3 hours, resulting in a mixed powder with a particle size <600 mesh and a sieve residue of <5%.

[0013] Further optimization yields green pellets with a particle size of 30-60 mesh, and the roundness and sphericity of these green pellets are 0.9-1.0.

[0014] Further optimization involves cooling the material to below 50°C after sintering.

[0015] The beneficial effects of this technical solution are: 1. This invention uses bauxite tailings, fly ash and high-titanium slag solid waste as the main raw materials, replacing the increasingly scarce and expensive high-quality bauxite resources in the traditional preparation process. It not only effectively solves the land occupation and environmental pollution problems caused by the stockpiling of these solid wastes, but also significantly reduces the procurement cost of raw materials, achieving a unity of environmental and economic benefits, and promoting the development direction of compound circular economy and green manufacturing. 2. This invention uses small-particle-size α-alumina micro-powder to fill the pores between particles, resulting in a relatively dense semi-finished green body. This fundamentally ensures that the sintered ceramic particles are relatively dense, thus improving compressive strength. Because bauxite tailings have a low alumina content, mixing them with fly ash (which has a higher impurity content) and the fluxing effect of MnO2 allows a liquid phase to appear at a lower temperature during sintering, causing the green body to shrink. At this time, a small amount of highly active alumina micro-powder reacts with SiO2 to form mullite, further promoting the full reaction of alumina and SiO2 to form mullite. The TiO2 contains Ti... 4+ With Ai in alumina 3+ Due to their similar ionic radii, they can dissolve in corundum or mullite lattices and generate lattice defects, reducing the sintering activation energy and enabling them to achieve tight particle bonding at lower temperatures. The breakage rate under a closure pressure of 159 MPa is <9%, improving the density and compressive strength of the ceramic proppant. It also has reduced acid solubility of <7% and good sphericity of 0.8. These key performance indicators show that it has strong corrosion resistance and good conductivity, making it particularly suitable for hydraulic fracturing operations in deep wells, ultra-deep wells, and high-stress reservoirs, which helps to improve oil and gas recovery. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the morphology of the ultra-high strength ceramic particle support obtained in Example 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0021] An ultra-high strength ceramsite proppant comprises bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, wherein the mass ratio of the bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder is 30-50:20-30:10-25:15-20; the ceramsite proppant has a particle size of 40-70 mesh, a breakage rate of <9% under a closing pressure of 159 MPa, an acid solubility of <7%, and a sphericity of >0.8.

[0022] The chemical composition of the bauxite tailings, expressed as a percentage by mass, is as follows: Al2O3 36-50wt%, SiO2 20-30wt%, CaO + MgO 1-10wt%, Fe2O3 1-12wt%, TiO2 1-12wt%; its loss on ignition is 10-15%.

[0023] The chemical composition of fly ash, by mass percentage, is: Al2O3 20-30wt%, SiO2 40-50wt%, Fe2O3 5-15wt%, CaO 5-10wt%, MgO 3-7wt%, K2O+Na2O 0.5%-4%.

[0024] The chemical composition of high-titanium slag, expressed as a percentage by mass, is as follows: TiO2 75-85wt%, SiO2 3.5-11wt%, Al2O3 1.5-6wt%, MnO2 1-2wt%, Fe2O3 <5wt%.

[0025] The chemical composition of the α-alumina micro powder, expressed as a percentage by mass, is: αAl2O3 > 98.5 wt%, Fe2O3 ≤ 0.1%, Na2O ≤ 0.3%, SiO2 ≤ 0.2%.

[0026] The bauxite tailings used in this invention are from Jiajiawa in Mianchi, the fly ash is from Huaneng Power Plant in Mianchi, the high-titanium slag is from Shuangrui in Luoyang, and the moisture content of the α-alumina micro powder is all <3‰.

[0027] Example 1 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder. The preparation method includes the following steps: Bauxite tailings, fly ash, high-titanium slag, and α-alumina micro powder were mixed in a mass ratio of 40:20:25:15 and ball-milled to 600 mesh. The residue on the sieve was 5% to obtain a mixed powder. The mixed powder was granulated into green balls of 30-60 mesh, sintered at 1100℃ for 1.5h, and cooled to 42℃ to obtain ultra-high strength ceramic proppant.

[0028] Example 2 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder. The preparation method includes the following steps: Bauxite tailings, fly ash, high-titanium slag, and α-alumina micro powder were mixed in a mass ratio of 45:20:25:15 and ball-milled to 600 mesh. The residue on the sieve was 5% to obtain a mixed powder. The mixed powder was granulated into green balls of 30-60 mesh, sintered at 1150℃ for 1.5h, and cooled to 45℃ to obtain ultra-high strength ceramic proppant.

[0029] Example 3 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder. The preparation method includes the following steps: Bauxite tailings, fly ash, high-titanium slag, and α-alumina micro powder were mixed in a mass ratio of 45:25:25:20 and ball-milled to 600 mesh. The residue on the sieve was 5% to obtain a mixed powder. The mixed powder was granulated into green balls of 30-60 mesh, sintered at 1200℃ for 2 hours, and cooled to 32℃ to obtain ultra-high strength ceramic proppant.

[0030] Example 4 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder. The preparation method includes the following steps: Bauxite tailings, fly ash, high-titanium slag, and α-alumina micro powder were mixed in a mass ratio of 45:25:20:20 and ball-milled to 600 mesh. The residue on the sieve was 5% to obtain a mixed powder. The mixed powder was granulated into green balls of 30-60 mesh, sintered at 1250℃ for 2 hours, and cooled to 40℃ to obtain ultra-high strength ceramic proppant.

[0031] Comparative Example 1 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, including the following steps: 1. Mix bauxite tailings, fly ash, high-titanium slag and α-alumina powder in a mass ratio of 35:25:25:15 to form a mixture. 2. Grind the mixture until 5% residue remains on a 600-mesh sieve to obtain a mixed powder; 3. Granulate the mixed powder into 40-70 mesh green balls; 4. Sinter the green pellets at 1300℃ for 1.5h and cool them to <50℃ to obtain 159MPa ultra-high strength ceramic proppant.

[0032] Comparative Example 2 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, including the following steps: 1. Mix bauxite tailings, fly ash, high-titanium slag and α-alumina powder in a mass ratio of 50:15:15:10 to form a mixture. 2. Grind the mixture until 5% residue remains on a 600-mesh sieve to obtain a mixed powder; 3. Granulate the mixed powder into 40-70 mesh green balls; 4. Sinter the green pellets at 1350℃ for 1.5h and cool them to <50℃ to obtain 159MPa ultra-high strength ceramic proppant.

[0033] Comparative Example 3 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, including the following steps: 1. Mix bauxite tailings, fly ash, high-titanium slag and α-alumina powder in a mass ratio of 35:25:25:15 to form a mixture. 2. Grind the mixture until 5% residue remains on a 600-mesh sieve to obtain a mixed powder; 3. Granulate the mixed powder into 40-70 mesh green balls; 4. Sinter the green pellets at 1400℃ for 2 hours and cool them to <50℃ to obtain 159MPa ultra-high strength ceramic proppant.

[0034] Comparative Example 4 This embodiment provides an ultra-high strength ceramsite proppant, comprising bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, including the following steps: 1. Mix bauxite tailings, fly ash, high-titanium slag and α-alumina powder in a mass ratio of 40:25:20:15 to form a mixture. 2. Grind the mixture until 5% residue remains on a 600-mesh sieve to obtain a mixed powder; 3. Granulate the mixed powder into 40-70 mesh green balls; 4. Sinter the green pellets at 1450℃ for 2 hours and cool them to <50℃ to obtain 159MPa ultra-high strength ceramic proppant.

[0035] Experimental Example The breakage rate, acid solubility, roundness and sphericity of Examples 1-4 and Comparative Examples 1-4 were tested respectively, and the test results are shown in Table 1 and Table 2.

[0036] Table 1 Performance parameters of ceramsite proppant in Examples 1-4 Item Industry standard Example 1 Example 2 Example 3 Example 4 Firing temperature (°C) / 1100 1150 1200 1250 Bulk density (g / cm 3 )]]> ≤1.65 1.70 1.72 1.85 1.80 Specific gravity (g / cm3) 3 )] ≤3.00 3.21 3.23 3.20 3.25 Roundness ≥0.7 0.8 0.8 0.8 0.8 Sphericity ≥0.7 0.8 0.8 0.8 0.8 Haze (FTU) ≤100 70 73 78 74 Acid solubility (%) ≤7 6.0 6.6 6.5 6.9 Crushing rate / 86Mpa (%) ≤9 2.1 2.3 2.0 2.2 Crushing rate / 159Mpa (%) / 8.3 8.1 7.8 8.6 Table 2 Performance parameters of ceramsite proppant in Comparative Examples 1-4 Item Industry standard Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Firing temperature (°C) / 1300 1350 1400 1450 Bulk density (g / cm 3 )]]> ≤1.65 1.68 1.71 1.73 1.42 Apparent density (g / cm3) 3 ​ ≤3.00 3.10 3.30 3.40 2.61 Roundness ≥0.7 0.8 0.8 0.8 0.8 Sphericity ≥0.7 0.8 0.8 0.8 0.8 Haze (FTU) ≤100 70 71 78 70 Acid solubility (%) ≤7 4.3 4.4 4.5 4.2 Crushing rate / 86Mpa (%) ≤9 2.1 2.3 2.0 2.2 Crushing rate / 159Mpa (%) / 10.6 11.0 10.9 10.1 This invention utilizes bauxite tailings, fly ash, high-titanium slag, and α-alumina micro powder to prepare an ultra-high strength ceramsite proppant with a strength of 159 MPa, suitable for use in deeper oil wells. As shown in Table 1, the high-strength ceramsite proppants prepared in Examples 1-4 have a particle size of 30-60 mesh and a bulk density of 1.70-1.85 g / cm³. 3 The apparent density is 3.00-3.25 g / cm³. 3 The acid solubility is 6.0-6.9%, the sphericity is 0.8, and the breakage rate under a closing pressure of 159MPa is <9%. The breakage rate of Example 3 is the lowest, reaching 7.8%. In contrast, the breakage rate of Comparative Example 2 in Table 2 is higher than that of Example 3.2%. This invention does not require the use of natural resources such as bauxite, and the product has high strength.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A high-strength ceramic proppant, characterized in that, The material comprises bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder, wherein the mass ratio of the bauxite tailings, fly ash, high-slag titanium, and α-alumina micro powder is 30-50:20-30:10-25:15-20; the ceramsite proppant has a particle size of 40-70 mesh, a breakage rate of <9% under a closure pressure of 159 MPa, an acid solubility of <7%, and a sphericity of >0.

8.

2. The ultra-high strength ceramsite proppant according to claim 1, characterized in that, The chemical composition of the bauxite tailings, expressed as a percentage by mass, is as follows: Al2O3 36-50wt%, SiO2 20-30wt%, CaO + MgO 1-10wt%, Fe2O3 1-12wt%, TiO2 1-12wt%; its loss on ignition is 10-15%.

3. The ultra-high strength ceramsite proppant according to claim 1, characterized in that, The chemical composition of the fly ash is expressed as a percentage by mass: Al2O3 20-30wt%, SiO2 40-50wt%, Fe2O3 5-15wt%, CaO 5-10wt%, MgO 3-7wt%, K2O+Na2O 0.5%-4%.

4. The ultra-high strength ceramsite proppant according to claim 1, characterized in that, The chemical composition of the high-titanium slag is expressed as follows by mass percentage: TiO2 75-85wt%, SiO2 3.5-11wt%, Al2O3 1.5-6wt%, MnO2 1-2wt%, Fe2O3 <5wt%.

5. The ultra-high strength ceramsite proppant according to claim 1, characterized in that, The chemical composition of the α-alumina micro powder, expressed as a percentage by mass, is: αAl2O3 > 98.5 wt%, Fe2O3 ≤ 0.1%, Na2O ≤ 0.3%, SiO2 ≤ 0.2%.

6. A method for preparing an ultra-high strength ceramsite proppant, characterized in that, The process includes the following steps: mixing and ball milling the raw materials in the specified amounts, granulating them, and sintering the resulting particles at 1100-1250℃ for 1.5-2 hours to obtain the final product.

7. The method for preparing an ultra-high strength ceramsite proppant according to claim 6, characterized in that, The ball milling time is 1-3 hours, and the ball milling yields a mixed powder with a particle size of <600 mesh and a sieve residue of <5%.

8. The method for preparing an ultra-high strength ceramsite proppant according to claim 6, characterized in that, The granulation process yields green pellets with a particle size of 30-60 mesh, and the roundness and sphericity of these green pellets are 0.9-1.

0.

9. The method for preparing an ultra-high strength ceramsite proppant according to claim 6, characterized in that, After sintering, the temperature is cooled to below 50°C.

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