A high-strength, low-density ceramic proppant and its preparation method

Abstract

This invention provides a high-strength, low-density ceramsite proppant and its preparation method. The high-strength, low-density ceramsite proppant comprises the following raw materials by mass percentage: 60%–65% silica sand, 18%–23% forsterite, 10%–15% hematite, and 1%–5% bentonite; preferably, it comprises the following raw materials by mass percentage: 60% silica sand, 22% forsterite, 15% hematite, and 3% bentonite. The preparation method of the high-strength, low-density ceramsite proppant includes the following steps: S1 grinding, S2 mixing, S3 granulation, S4 drying and sieving, and S5 calcination. This invention makes full use of abundant and inexpensive silica, turning waste into treasure. It not only expands the scope of resource utilization, but also produces a novel ceramsite proppant with low breakage rate, low density, high strength, low acid solubility, and good roundness and sphericity. It can meet the performance requirements of proppants for hydraulic fracturing, effectively replacing bauxite ceramsite proppants, while significantly reducing raw material costs and fuel consumption, thus saving energy and protecting the environment.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and in particular to a high-strength, low-density ceramic proppant and its preparation method. Background Technology

[0002] Hydraulic fracturing (HF) is a method to improve the productivity of oil or gas wells. It involves fracturing low-permeability, high-pressure wells during deep oil and gas well production, causing the oil and gas-bearing rock formations to fracture. Oil and gas then flow through the channels created by the fractures. Fluid is then injected into the basement rock at pressures exceeding the fracture strength of the underlying layers, creating further fractures in the surrounding rock formations and forming a channel with high-level flow capacity. This keeps the fractures open, allowing oil and gas products to flow smoothly. To maintain the open state of the fractures, highly mechanical proppants that do not react with wellbore fluids are injected into the fractures. These proppants are mostly spherical particles that, through fluid penetration, at least partially fill the fractures, forming a permeable, strongly propped framework, thus maintaining high conductivity to facilitate the smooth release of oil and gas from the formation.

[0003] Currently, commonly used proppants can be classified into three types based on their material: quartz sand, coated proppants, and ceramsite proppants. Quartz sand is derived from nature and has advantages such as low cost and easy availability; however, due to its relatively low compressive strength, it is only suitable for shallow reservoirs. Coated proppants improve the compressive strength of the proppant by coating a layer of high-strength polymer material onto the surface of quartz sand, but the preparation cost is high, hindering large-scale application. Compared to quartz sand and coated proppants, ceramsite proppants have high strength, low density, low cost, and good chemical stability, making them more effective at supporting fractures and increasing conductivity, thus becoming the mainstream proppant.

[0004] Conventional ceramsite proppant is made from high-grade bauxite (Al2O3 > 70wt%) as the main raw material, sintered at high temperatures. The higher the alumina content in the bauxite, the greater the density and strength. However, alumina-containing ceramsite proppant has the following disadvantages: ① The calcination temperature is too high (1300℃~1500℃), making the firing process difficult to control; ② The price of bauxite is too high (usually around 800 yuan / ton), resulting in excessively high production costs and significantly reducing manufacturers' profits; ③ Bauxite is a lean material with low plasticity. After granulation, some fine powder, due to insufficient plasticity, cannot bind tightly to the semi-finished product but adheres to its surface. During production and transportation, this powder easily detaches, greatly reducing the strength, roundness, and sphericity of the semi-finished product; furthermore, it easily forms rings during firing, resulting in substandard finished product quality and a lower pass rate.

[0005] Therefore, finding a new type of ceramic proppant that is low-cost, easy to process, low-density, and high-strength has become a research hotspot for researchers. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, the present invention aims to provide a high-strength, low-density ceramsite proppant, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A high-strength, low-density ceramsite proppant comprises the following raw materials by mass percentage: 60%–65% silica sand, 18%–23% magnesium olivine, 10%–15% hematite, and 1%–5% bentonite.

[0009] The high-strength, low-density ceramsite proppant preferably comprises the following raw materials by mass percentage: 60% silica sand, 22% magnesium olivine, 15% hematite, and 3% bentonite.

[0010] The silica sand contains ≥90% SiO2, the forsterite contains ≥40% MgO, the hematite contains ≥65% Fe2O3, and the bentonite contains ≥60% SiO2.

[0011] A method for preparing a high-strength, low-density ceramsite proppant includes the following steps:

[0012] S1, Grinding

[0013] The four raw materials, silica sand, magnesium olivine, red iron ore, and bentonite, are finely ground into 600-mesh powder, and then weighed and mixed according to the formula.

[0014] S2, Mixing

[0015] Add the weighed raw material powder and an appropriate amount of grinding steel balls into the cylinder mill and mix until the mixture is uniform.

[0016] S3, Granulation

[0017] The mixed raw material powder is added to the fully automatic granulator. The material is fed in a quantitative manner by a quantitative belt scale and water is added in a quantitative manner by a water flow meter. The water is atomized and sprayed out through a high-pressure nozzle and granulation is achieved by rolling and rotating.

[0018] S4. Drying and sieving

[0019] The prepared granules were dried in a dryer for 1 hour, and then granules with a particle size of 0.5 mm to 1.0 mm were screened out.

[0020] S5, Firing

[0021] The sieved particles are placed into a sagger and fired in an electric furnace. After firing, the particles are cooled to room temperature and then passed through a 20-40 mesh sieve to obtain the finished product.

[0022] In step S1, an ultrafine airflow mill is used to pulverize the raw materials.

[0023] In step S2, the raw materials are added into the cylinder mill in the order of silica sand, red iron ore, magnesium olivine and bentonite, and then an appropriate amount of grinding steel balls are added and mixed together for more than 30 minutes.

[0024] In step S3, the weight of water added during granulation is 8% to 12% of the total weight of the raw material powder.

[0025] In step S5, the firing temperature is 1100℃±20℃, the heating rate of the electric furnace is 5℃ / min, and the firing temperature is maintained for 1 hour after reaching the firing temperature.

[0026] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0027] This invention provides a high-strength, low-density ceramsite proppant and its preparation method. It utilizes abundant and inexpensive silica sand to replace high-alumina bauxite, adds appropriate amounts of magnesium olivine and hematite as fluxes, lowers the sintering temperature, and selects 1%–5% bentonite to improve the plasticity of the raw materials and increase the strength of the semi-finished product. The equipment required for the preparation process is new in the industry, simple and efficient to operate, and easily achievable for large-scale production. This invention not only expands the scope of resource utilization but also greatly reduces environmental pollution. Furthermore, the performance of the prepared novel ceramsite proppant (20-40 mesh, 86 MPa) meets the SY / T5108-2014 technical standard, exhibiting low breakage rate, low density, high strength, low acid solubility, and good roundness and sphericity. It can meet the performance requirements of proppants used in hydraulic fracturing, effectively replacing bauxite ceramsite proppants.

[0028] This invention fully utilizes abundant and inexpensive silica, turning waste into treasure, improving the market structure and current situation of fracturing proppant both domestically and internationally, and alleviating the pressure of excessive demand and insufficient supply of bauxite. Calculations show that the price of raw materials has decreased significantly from 800 yuan / ton to 30 yuan / ton. Simultaneously, the firing temperature has been reduced by 200℃~400℃, resulting in a substantial decrease in fuel consumption, further reducing production costs and meeting relevant energy-saving and environmental protection requirements. Detailed Implementation

[0029] The present invention will now be described in further detail.

[0030] A high-strength, low-density ceramsite proppant comprises the following raw materials by mass percentage: 60%–65% silica sand, 18%–23% magnesium olivine, 10%–15% hematite, and 1%–5% bentonite.

[0031] The preferred composition includes the following raw materials by weight percentage: 60% silica sand, 22% magnesium olivine, 15% hematite, and 3% bentonite;

[0032] The preferred composition includes the following raw materials by weight percentage: 65% silica sand, 23% magnesium olivine, 10% hematite, and 2% bentonite.

[0033] Among the above raw materials, the SiO2 content in silica sand is ≥90%, the MgO content in forsterite is ≥40%, the Fe2O3 content in hematite is ≥65%, and the SiO2 content in bentonite is ≥60%.

[0034] Based on the SiO2-MgO-Fe2O3 ternary phase diagram, the addition amount of silica sand in the above raw materials is determined to be 60%–65%. Silica sand is inexpensive, effectively reducing production costs. Magnesium oxide in forsterite can increase the strength of the proppant and broaden the sintering range; its addition amount is 18%–23%. Adding 10%–15% hematite can effectively lower the firing temperature and improve the yield. Adding 1%–5% bentonite improves the plasticity of the raw materials and increases the strength of the semi-finished product.

[0035] A method for preparing a high-strength, low-density ceramsite proppant includes the following steps:

[0036] S1, Grinding

[0037] Grind the four raw materials into 600-mesh fine powder separately, and then weigh and mix them according to the formula.

[0038] This step uses an ultrafine airflow mill to pulverize the raw materials. The ultrafine airflow mill has many advantages: high fineness, large capacity, low energy consumption, no temperature rise during the process, wide applicability, and PCI intelligent control; the finished product fineness is adjustable from 100 mesh to 3000 mesh, and it is environmentally friendly with no dust. The material enters the pulverizing chamber through a quantitative feeding system and is continuously impacted, rubbed, and sheared in the counter-current jet flow field formed at the bottom of the pulverizing chamber by the supersonic jet airflow; the crushed material rises with the airflow to the impeller flow field; coarse particles are thrown against the cylinder wall under centrifugal force and fall back into the pulverizing chamber for secondary pulverization.

[0039] When silica sand is ground to 600 mesh, it mainly contains amorphous active SiO2, which can act as both a binder and a sintering agent. On the one hand, it can improve the strength of the green body; on the other hand, due to its high activity, it can promote sintering and increase strength.

[0040] S2, Mixing

[0041] Put the prepared raw materials and an appropriate amount of grinding steel balls into the cylindrical mill and mix them evenly.

[0042] Specifically, the raw materials are added to the cylindrical mill in the order of silica sand, red iron ore, magnesium olivine, and bentonite, and then an appropriate amount of grinding steel balls are added and mixed evenly for more than 30 minutes.

[0043] S3, Granulation

[0044] The thoroughly mixed raw material powder is added to the fully automatic granulator. The material is fed in a quantitative manner by an adjustable quantitative belt scale, and water is added in a quantitative manner by a water flow meter. The water is atomized and sprayed out through a high-pressure nozzle. Granulation is achieved by rolling and rotating. The granules produced in this way have high density and good roundness and sphericity.

[0045] The weight of water added during granulation is 8% to 12% of the total weight of the raw material powder.

[0046] The fully automatic granulator used in this step has the following advantages: accurate metering of raw starch and water; high density, good roundness and sphericity of the granules; uniform particle size; fast granulation; fast drying; high efficiency; energy saving and low consumption; greatly reducing labor intensity and improving labor efficiency.

[0047] S4. Drying and sieving

[0048] The prepared granules were dried in a dryer at 105℃~110℃ for 1 hour, and granules with a particle size of 0.5mm~1.0mm were screened out.

[0049] S5, Firing

[0050] The sieved particles are loaded into a sagger and fired in an electric furnace at a temperature of 1100℃±20℃. The furnace is heated at a rate of 5℃ / min, and the temperature is maintained for 1 hour after reaching the firing temperature. After firing, the particles are cooled to room temperature and passed through a 20-40 mesh sieve to obtain the finished ceramsite proppant.

[0051] Experiments have shown that a firing temperature of 1100℃±20℃ can ensure product quality and greatly improve the product qualification rate.

[0052] The novel ceramsite proppant prepared using the above process meets the technical standard of "SY / T5108-2014 Test Method for Performance of Proppants for Hydraulic Fracturing and Gravel Packing Operations".

[0053] The present invention will now be described in detail with reference to embodiments.

[0054] In the following embodiments, the chemical composition of the raw materials used is as follows:

[0055] <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> CaO MgO LOI <![CDATA[MnO2]]> silica sand 0.58 90.87 0.01 1.32 0.02 7.20 / Magnesium olivine 1.58 32.40 10.67 6.63 41.68 7.04 / Red iron ore 9.59 10.71 68.08 0.25 0.13 11.24 / Bentonite 13.36 68.77 1.98 2.11 2.34 11.44 / manganese ore 11.37 11.76 6.84 0.22 0.58 13.45 55.78

[0056] The chemical composition of the bauxite used in the comparative example is as follows:

[0057]

[0058] Example 1

[0059] A high-strength, low-density ceramsite proppant comprises the following raw materials by weight percentage: 60% silica sand, 22% magnesium olivine, 15% hematite, and 3% bentonite.

[0060] Its preparation method includes the following steps:

[0061] S1, Grinding

[0062] An ultrafine airflow mill was used to grind the four raw materials into 600-mesh fine powder, and then the ingredients were weighed and mixed according to the formula.

[0063] S2, Mixing

[0064] Add the raw materials into the cylinder mill in the following order: silica sand, red iron ore, magnesium olivine, and bentonite. Then add an appropriate amount of grinding steel balls and mix them together for more than 30 minutes to ensure uniform mixing.

[0065] S3, Granulation

[0066] The thoroughly mixed raw material powder is added to the fully automatic granulator. The powder is fed quantitatively using an adjustable quantitative belt scale, and water is added quantitatively using a water flow meter. The amount of water added is 10% of the total weight of the raw material powder. The water is atomized and sprayed out through a high-pressure nozzle, and granulation is achieved through rolling and rotation. The resulting granules have high density and good roundness and sphericity.

[0067] S4. Drying and sieving

[0068] The prepared granules are placed in a dryer and dried at 105℃~110℃ for 1 hour, and granules with a particle size of 0.5mm~1.0mm are screened out.

[0069] S5, Firing

[0070] The sieved particles are loaded into a sagger and fired in an electric furnace at a temperature of 1100℃±20℃. The furnace is heated at a rate of 5℃ / min, and the temperature is maintained for 1 hour after reaching the firing temperature. After firing, the particles are cooled to room temperature and passed through a 20-40 mesh sieve to obtain the finished ceramsite proppant.

[0071] Examples 2 and 3 both adopted the above method, and comparative examples 1, 2, and 3 were provided for comparative experiments to control the content of raw materials. Comparative example 4 served as a comparative example of example 1, using bauxite instead of silica sand. Comparative example 5 used the ultra-low density ceramic proppant prepared by the scheme of example 1 in Chinese patent CN201610655633.5. The raw material input amounts and preparation method parameter controls of examples 1 to 3 and comparative examples 1 to 4 are shown in the table below.

[0072]

[0073]

[0074] The ceramic proppant prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was subjected to performance testing in accordance with the "SY / T5108-2014 Performance Test Method for Proppants Used in Hydraulic Fracturing and Gravel Packing Operations". The performance test results are shown in the table below.

[0075]

[0076] The performance test results above show that the ceramsite proppants prepared in Examples 1 to 3 all have low apparent density (<2.35 g / cm³). 3 It features high strength (breakage rate less than 7% under closure pressure at 86MPa), low turbidity (less than 40NTU), and low acid solubility (less than 6). It also has good roundness (not less than 0.9) and sphericity (not less than 0.9). Its quality meets the relevant requirements of the SY / T5108-2014 standard and is sufficient to meet the support performance requirements of the hydraulic fracturing process.

[0077] Comparative Examples 1 to 4 varied the content of the raw materials. Comparative Examples 1 and 2 had lower silica sand content and higher content of forsterite and hematite. Comparative Example 3 had higher silica sand content and lower hematite content. Comparative Example 4 used bauxite instead of silica sand, resulting in a higher alumina content in the raw material. Tests showed that the bonding properties between the raw material powders in these four comparative examples were poor, leading to a significantly higher breakage rate at 86 MPa. Turbidity and acid solubility also increased significantly compared to Examples 1 to 3. Furthermore, the roundness and sphericity of the particles differed from the examples, failing to meet the relevant requirements of the SY / T5108-2014 standard. This indicates that the component ratio of the raw materials in this invention has a significant impact on the bonding properties between components; changing the existing ratio may result in poor bonding between components and an unacceptable product breakage rate.

[0078] Meanwhile, Comparative Example 4, by using bauxite instead of silica sand for firing, resulted in an extremely high firing temperature and a significant increase in production costs; moreover, its product breakage rate was more than twice that of the embodiment of the present invention, with a huge performance difference, which indirectly proves that the raw material components of the present invention have a relationship of mutual influence, mutual cooperation and mutual interaction.

[0079] The performance comparison data with Comparative Example 5 shows that the ceramic proppant of Examples 1 to 3 is close to the performance parameters of existing ultra-low density bauxite ceramic proppant in all performance indicators, proving that the product of the present invention can be used as a substitute for existing bauxite ceramic proppant and meet the support requirements of the downhole hydraulic fracturing process.

[0080] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A high-strength, low-density ceramic proppant, characterized in that... It is composed of the following raw materials by mass percentage: 60%–65% silica sand, 18%–23% magnesium olivine, 10%–15% hematite, and 1%–5% bentonite; The preparation method of the high-strength, low-density ceramsite proppant includes the following steps: S1, Grinding The four raw materials, silica sand, magnesium olivine, red iron ore, and bentonite, are finely ground into 600-mesh powder, and then weighed and mixed according to the formula. S2, Mixing Add the raw materials into the cylinder mill in the order of silica sand, red iron ore, magnesium olivine and bentonite, and then add an appropriate amount of grinding steel balls to mix together for more than 30 minutes. S3, Granulation The mixed raw material powder is added to the fully automatic granulator. The material is fed in a quantitative manner by a quantitative belt scale and water is added in a quantitative manner by a water flow meter. The water is atomized and sprayed out through a high-pressure nozzle and granulation is achieved by rolling and rotating. S4. Drying and sieving The prepared granules were dried in a dryer for 1 hour, and then granules with a particle size of 0.5 mm to 1.0 mm were screened out. S5, Firing The sieved particles are loaded into a sagger and fired in an electric furnace at a temperature of 1100℃±20℃. The heating rate of the electric furnace is 5℃ / min. After reaching the firing temperature, the furnace is held at that temperature for 1 hour. After firing, the particles are cooled to room temperature and then passed through a 20-40 mesh sieve to obtain the finished product.

2. The high-strength, low-density ceramic proppant according to claim 1, characterized in that... It is composed of the following raw materials by weight percentage: 60% silica sand, 22% magnesium olivine, 15% hematite, and 3% bentonite.

3. A high-strength, low-density ceramic proppant according to any one of claims 1 or 2, characterized in that: The silica sand contains ≥90% SiO2, the forsterite contains ≥40% MgO, the hematite contains ≥65% Fe2O3, and the bentonite contains ≥60% SiO2.

4. The high-strength, low-density ceramsite proppant according to claim 1, characterized in that: In step S1, an ultrafine airflow mill is used to pulverize the raw materials.

5. The high-strength, low-density ceramsite proppant according to claim 1, characterized in that: In step S3, the weight of water added during granulation is 8% to 12% of the total weight of the raw material powder.

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