Short fiber reinforced fracturing propping agent and preparation method thereof

Abstract

The invention discloses a short fiber reinforced fracturing propping agent and a preparation method thereof. The short fiber reinforced fracturing propping agent provided by the invention comprises the following components in percentage by mass: 38-52% of bauxite, 30-38% of ferrochrome tailings, 2-6% of kaolin, 3-6% of manganese ore, 10-15% of basalt fiber and 3-5% of a binder. According to the fracturing proppant, basalt fibers are converted into mullite fibers in the firing process of the proppant to enhance the strength of a ceramsite matrix, so that the compressive strength of the proppant is improved. The mechanical strength and chemical stability of the proppant are enhanced by utilizing a spinel phase generated by reaction of MgO in the ferroalloy tailings with Al2O3 and Cr2O3 and an Al2O3 corundum phase generated by high temperature of bauxite, meanwhile, high-value utilization of the tailings is realized, and the problem of disposal of ferroalloy tailings industrial wastes is solved.

Description

Technical Field

[0001] This invention relates to the field of petroleum fracturing proppant technology, specifically to a short fiber reinforced fracturing proppant and its preparation method. Background Technology

[0002] In the field of oil and gas extraction, fracturing technology is an important means to increase oil and gas production, and fracturing proppant plays a key role. As oil and gas field development moves towards deeper and more complex formations, the performance requirements for fracturing proppants are becoming increasingly stringent. They need higher compressive strength to withstand greater formation pressure and good chemical stability to resist formation fluid corrosion, thereby ensuring the long-term effectiveness of fractures and improving oil and gas recovery. Currently, there are various types of fracturing proppants on the market. For example, natural quartz sand is low in cost but lacks sufficient compressive strength, making it suitable for shallow formations; ceramsite proppant has high strength but relies on resources such as bauxite and has high energy consumption; resin-coated sand has good impact resistance but poor high-temperature resistance and is prone to aging. Therefore, the development of high-performance, environmentally friendly fracturing proppants has become an inevitable trend in the industry.

[0003] Meanwhile, the ferrochrome alloy industry faces a severe solid waste disposal problem. According to surveys, every ton of ferrochrome alloy product generates 1.0-1.2 tons of tailings, with annual tailings emissions exceeding 50 million tons. These tailings are mainly composed of minerals such as olivine, spinel, and chromite, exhibiting low calcium oxide and silicon oxide content, but high magnesium and chromium content. Due to the lack of mature treatment technologies and the imperfect relevant technical standards and regulations, the engineering utilization of ferrochrome slag is severely hampered. Currently, the treatment of ferrochrome tailings both domestically and internationally still relies primarily on landfilling, which not only occupies a large amount of land but also poses significant environmental risks. Heavy metals such as Cr6+ in the tailings are highly susceptible to leakage, causing pollution to soil, water bodies, and other ecological environments. Therefore, exploring high-value utilization pathways for ferrochrome slag has become crucial for the ferroalloy industry to overcome its development predicament. Summary of the Invention

[0004] The purpose of this invention is to provide a short fiber reinforced fracturing proppant and its preparation method. This proppant has the characteristics of high strength and corrosion resistance, and can reduce the amount of raw materials such as bauxite while reducing the energy consumption in the proppant firing process, and effectively utilize ferrochrome tailings, thereby solving the problem of resource utilization and disposal of ferrochrome tailings.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] On one hand, the present invention provides a method for preparing a short fiber reinforced fracturing proppant, characterized by comprising the following steps:

[0007] Step 1: Take 38-52% bauxite, 30-38% ferrochrome tailings, 2%-6% kaolin, 3-6% manganese ore, 10-15% basalt fiber and 3-5% binder by weight percentage and set aside.

[0008] The ferrochrome alloy tailings contain 32%-42% silicon oxide, 22%-28% aluminum oxide, 18%-26% magnesium oxide, 5%-10% chromium oxide, and the remainder are impurities.

[0009] Step 2: Add bauxite, ferrochrome tailings, kaolin, manganese ore and grinding balls to a ball mill and ball mill to obtain a mixed powder. The material-to-ball ratio is 1:3 and the powder particle size is controlled to D90 < 2.6 μm.

[0010] Step 3: Add the mixed powder and basalt fiber to the mixing equipment and stir to mix. During the stirring process, slowly add the binder to obtain the composite blank.

[0011] Step 4: The composite material is pelletized and sieved in a disc granulator to obtain raw material pellets; the raw material pellets are dried and then fed into a rotary kiln, heated to 1320-1380℃ at a heating rate of 5℃ / min, and fired. After cooling in the kiln, they are ground and sieved to obtain short fiber reinforced fracturing proppant.

[0012] Furthermore, the basalt fiber mentioned in step one has a diameter of 0.4μm-1.0μm and a length of 2μm-5μm; the amount of binder added is 5% of the total material mass, and the binder is an aqueous solution of polyvinyl alcohol.

[0013] Furthermore, the stirring time in step three is 1-2 hours.

[0014] Furthermore, the drying described in step four is carried out in an oven at 60℃-80℃.

[0015] Furthermore, the firing time described in step four is 2 hours.

[0016] On the other hand, the present invention also provides a short fiber reinforced fracturing proppant, wherein the proppant contains a composite reinforcing phase, the composite reinforcing phase including a mullite fiber reinforcing phase transformed from basalt fibers during the sintering process, a spinel phase generated by the reaction of MgO with Al2O3 and Cr2O3 in ferroalloy tailings, and an Al2O3 corundum phase generated at high temperature from bauxite.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention introduces basalt fibers into a proppant matrix. Typically, basalt fibers in proppant matrices exist primarily in the form of silicate glass, with a smooth surface and weak "pull-out" effect when bonded to the matrix, making it difficult to provide fiber reinforcement. However, after firing with other raw materials of the ceramic proppant, the basalt fibers react and bond with the matrix material interface, enhancing their "pull-out" effect. Furthermore, during firing, they transform into mullite fibers, whose strength is far superior to that of glassy basalt fibers. This forms a "fiber bridging" effect with the proppant matrix, significantly improving the compressive strength of the proppant and inhibiting crack propagation. Simultaneously, compared to resin-based ceramic proppants, the sintering of basalt fibers with the proppant matrix forms a high-strength ceramic with significantly higher strength and temperature and pressure resistance. This method of proppant preparation reduces the complex processes of material surface modification and the use of chemical reagents. In the raw materials used for this proppant, MgO from ferrochrome alloy tailings reacts with the proppant components Al2O3 and Cr2O3 to form a spinel phase, introducing a composite reinforcing phase that combines high strength and chemical stability. Simultaneously, the ferrochrome alloy tailings replace part of the bauxite, reducing the amount of high-quality bauxite used and calcination energy consumption, lowering production costs, achieving high-value utilization of industrial waste, and reducing the environmental harm caused by heavy metals such as chromium. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be described in detail below with reference to specific embodiments.

[0020] Example 1

[0021] A method for preparing a short fiber reinforced fracturing proppant includes the following steps:

[0022] Step 1: Take 38% bauxite, 38% ferrochrome alloy tailings, 6% kaolin, 5% manganese ore, 10% basalt fiber, and 3% polyvinyl alcohol aqueous solution by mass percentage, and set aside. The basalt fiber has a diameter of about 0.4 μm and a length of about 5 μm. The ferrochrome alloy tailings contain 38% silicon dioxide, 28% aluminum oxide, 25% magnesium oxide, and 5% chromium oxide, with the remainder being impurities.

[0023] Step 2: Add bauxite, ferrochrome alloy tailings, kaolin, manganese ore and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0024] Step 3: Add the mixed powder and basalt fiber to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0025] Step 4: The composite preform is pelletized and sieved in a disc granulator to obtain raw pellets; the raw pellets are dried in an oven at 60°C; the dried raw pellets are fed into a rotary kiln and heated to 1320°C at a heating rate of 5°C / min for firing. After firing for 2 hours, they are cooled with the kiln, ground and sieved to obtain short fiber reinforced fracturing proppant.

[0026] Example 2:

[0027] A method for preparing a short fiber reinforced fracturing proppant includes the following steps:

[0028] Step 1: Take 52% bauxite, 30% ferrochrome alloy tailings, 2% kaolin, 3% manganese ore, 10% basalt fiber, and 3% polyvinyl alcohol aqueous solution by mass percentage, and set aside. The basalt fiber has a diameter of about 1.0 μm and a length of about 2 μm. The ferrochrome alloy tailings contain 32% silicon oxide, 28% aluminum oxide, 20% magnesium oxide, and 6% chromium oxide, with the remainder being impurities.

[0029] Step 2: Add bauxite, ferrochrome alloy tailings, kaolin, manganese ore and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0030] Step 3: Add the mixed powder and basalt fiber to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0031] Step 4: The composite preform is pelletized and sieved in a disc granulator to obtain raw pellets; the raw pellets are dried in an oven at 80°C; the dried raw pellets are fed into a rotary kiln and heated to 1380°C at a heating rate of 5°C / min for firing. After firing for 2 hours, they are cooled with the kiln, ground and sieved to obtain short fiber reinforced fracturing proppant.

[0032] Example 3:

[0033] A method for preparing a short fiber reinforced fracturing proppant includes the following steps:

[0034] Step 1: Take 45% bauxite, 34% ferrochrome alloy tailings, 4% kaolin, 4% manganese ore, 10% basalt fiber, and 3% polyvinyl alcohol aqueous solution by mass percentage, and set aside. The basalt fiber has a diameter of about 0.5 μm and a length of about 3 μm. The ferrochrome alloy tailings contain 32% silicon oxide, 22% aluminum oxide, 18% magnesium oxide, and 5% chromium oxide, with the remainder being impurities.

[0035] Step 2: Add bauxite, ferrochrome alloy tailings, kaolin, manganese ore and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0036] Step 3: Add the mixed powder and basalt fiber to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0037] Step 4: The composite preform is pelletized and sieved in a disc granulator to obtain raw pellets; the raw pellets are dried in an oven at 80℃; the dried raw pellets are fed into a rotary kiln and heated to 1360℃ at a heating rate of 5℃ / min for firing. After firing for 2 hours, they are cooled with the kiln, ground and sieved to obtain short fiber reinforced fracturing proppant.

[0038] Example 4:

[0039] A method for preparing a short fiber reinforced fracturing proppant includes the following steps:

[0040] Step 1: Take 41% bauxite, 32% ferrochrome alloy tailings, 4% kaolin, 3% manganese ore, 15% basalt fiber, and 5% polyvinyl alcohol aqueous solution by mass percentage, and set aside. The basalt fiber has a diameter of approximately 0.8 μm and a length of approximately 4 μm. The ferrochrome alloy tailings contain 35% silicon dioxide, 22% aluminum oxide, 26% magnesium oxide, and 8% chromium oxide, with the remainder being impurities.

[0041] Step 2: Add bauxite, ferrochrome alloy tailings, kaolin, manganese ore and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0042] Step 3: Add the mixed powder and basalt fiber to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0043] Step 4: The composite preform is pelletized and sieved in a disc granulator to obtain raw pellets; the raw pellets are dried in an oven at 70°C; the dried raw pellets are fed into a rotary kiln and heated to 1340°C at a heating rate of 5°C / min for firing. After firing for 2 hours, they are cooled with the kiln, ground and sieved to obtain short fiber reinforced fracturing proppant.

[0044] Example 5:

[0045] A method for preparing a short fiber reinforced fracturing proppant includes the following steps:

[0046] Step 1: Take 42% bauxite, 32% ferrochrome alloy tailings, 3% kaolin, 6% manganese ore, 13% basalt fiber, and 4% polyvinyl alcohol aqueous solution by mass percentage, and set aside. The basalt fiber has a diameter of about 0.4 μm and a length of about 2 μm. The ferrochrome alloy tailings contain 42% silicon oxide, 25% aluminum oxide, 18% magnesium oxide, and 10% chromium oxide, with the remainder being impurities.

[0047] Step 2: Add bauxite, ferrochrome alloy tailings, kaolin, manganese ore and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0048] Step 3: Add the mixed powder and basalt fiber to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0049] Step 4: The composite preform is pelletized and sieved in a disc granulator to obtain raw pellets; the raw pellets are dried in an oven at 80°C; the dried raw pellets are fed into a rotary kiln and heated to 1350°C at a heating rate of 5°C / min for firing. After firing for 2 hours, they are cooled with the kiln, ground and sieved to obtain short fiber reinforced fracturing proppant.

[0050] Compare with Example 1:

[0051] A petroleum fracturing proppant and its preparation method, comprising the following steps:

[0052] Step 1: Prepare a solution by mass percentage of 80% bauxite, 4% kaolin, 3% manganese ore, 10% basalt fiber, and 3% polyvinyl alcohol aqueous solution; the basalt fiber should have a diameter of approximately 0.4 μm and a length of approximately 4 μm.

[0053] Step 2: Add bauxite, kaolin, manganese ore, and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0054] Step 3: Add the mixed powder and basalt fiber to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0055] Step 4: The composite material preform is pelletized and sieved in a disc granulator to obtain raw material pellets; the raw material pellets are dried in an oven at 80°C; the dried raw material pellets are sent to a rotary kiln for high-temperature firing at 1350°C for 2 hours, then cooled with the kiln, polished and sieved to obtain short fiber reinforced fracturing proppant.

[0056] Compare with Example 2:

[0057] Step 1: Take 42% bauxite, 45% ferrochrome alloy tailings, 4% kaolin, 4% manganese ore and 5% polyvinyl alcohol aqueous solution by mass percentage and set aside; wherein the ferrochrome alloy tailings contain 42% silicon dioxide, 25% aluminum oxide, 18% magnesium oxide and 10% chromium oxide, and the remainder are impurities.

[0058] Step 2: Add bauxite, ferrochrome alloy tailings, kaolin, manganese ore, and grinding balls to a ball mill jar and grind to obtain a mixed powder. The material-to-ball ratio in the ball mill jar is 1:3. After ball milling for 6 hours, the particle size of the mixed powder is controlled to be D90 < 2.6 μm.

[0059] Step 3: Add the mixed powder to the mixing equipment, stir for 2 hours, and then slowly add the polyvinyl alcohol aqueous solution to form a composite material blank;

[0060] Step 4: The composite preform is pelletized in a disc granulator and sieved to obtain raw pellets; the raw pellets are then dried in an oven at 80℃. The dried raw pellets are then fed into a rotary kiln for high-temperature firing at 1350℃ for 2 hours, followed by cooling with the kiln, grinding, and sieving to obtain short fiber reinforced fracturing proppant.

[0061] Performance testing

[0062] The breakage rate test results of the fracturing proppant prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1. A comparison of the results of Examples 1-5 and Comparative Example 1 shows that the fracturing proppant in Examples 1-5 introduces multiphase reinforcement, containing both spinel and corundum phases, as well as mullite short fiber reinforcement phases. Therefore, it has high compressive strength and low breakage rate. In contrast, Comparative Example 1, due to its high bauxite content, has low proppant density and high breakage rate when fired at 1350℃. A comparison of the results of Examples 1-5 and Comparative Example 2 shows that although Comparative Example 2 achieved high density when fired at 1350℃, the lack of short-cut basalt fibers in the proppant formulation prevented the formation of high-strength mullite fibers through phase transformation during high-temperature sintering. This resulted in a lack of effective interfacial bonding between the fibers and the matrix, hindering the "pull-out" and "fiber bridging" reinforcement mechanisms, ultimately leading to low compressive strength and high breakage rate in the proppant.

[0063] Table 1. Fragmentation Rate Test of Petroleum Fracturing Proppants

[0064]

[0065]

Claims

1. A method for preparing a short fiber reinforced fracturing proppant, characterized in that, Includes the following steps: Step 1: Take 38-52% bauxite, 30-38% ferrochrome tailings, 2%-6% kaolin, 3-6% manganese ore, 10-15% basalt fiber and 3-5% binder by weight percentage and set aside. The ferrochrome alloy tailings contain 32%-42% silicon oxide, 22%-28% aluminum oxide, 18%-26% magnesium oxide, 5%-10% chromium oxide, and the remainder are impurities. Step 2: Add bauxite, ferrochrome tailings, kaolin, manganese ore and grinding balls to a ball mill and ball mill to obtain a mixed powder. The material-to-ball ratio is 1:3 and the powder particle size is controlled to D90 < 2.6 μm. Step 3: Add the mixed powder and basalt fiber to the mixing equipment and stir to mix. During the stirring process, slowly add the binder to obtain the composite blank. Step 4: The composite material is pelletized and sieved in a disc granulator to obtain raw material pellets; the raw material pellets are dried and then fed into a rotary kiln, heated to 1320-1380℃ at a heating rate of 5℃ / min, and fired. After cooling in the kiln, they are ground and sieved to obtain short fiber reinforced fracturing proppant.

2. The method for preparing a short fiber reinforced fracturing proppant according to claim 1, characterized in that, The basalt fibers mentioned in step one have a diameter of 0.4μm-1.0μm and a length of 2μm-5μm; the amount of binder added is 5% of the total material mass, and the binder is an aqueous solution of polyvinyl alcohol.

3. The method for preparing a short fiber reinforced fracturing proppant according to claim 1, characterized in that, The stirring time described in step three is 1-2 hours.

4. The method for preparing a short fiber reinforced fracturing proppant according to claim 1, characterized in that, The drying process described in step four is carried out in an oven at 60℃-80℃.

5. The method for preparing a short fiber reinforced fracturing proppant according to claim 1, characterized in that, The firing time described in step four is 2 hours.

6. A short fiber reinforced fracturing proppant prepared by the preparation method according to any one of claims 1-5, characterized in that, The proppant contains a composite reinforcing phase, which includes a mullite fiber reinforcing phase transformed from basalt fibers during the sintering process, a spinel phase generated by the reaction of MgO with Al2O3 and Cr2O3 in ferroalloy tailings, and an Al2O3 corundum phase generated at high temperature from bauxite.

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