Low-density support material and preparation method thereof

Abstract

The invention belongs to the field of oil-gas field development, and particularly relates to a low-density supporting material and a preparation method thereof. The low-density supporting material with the density of 0.82-0.96 g / cm < 3 > is prepared by selecting the screened mineral supporting material with the mesh size of 30-100 and taking ethylene as a carbon source under the protection of argon, and the breakage rate after the supporting material bears the pressure of 52 MPa is 0.81%-49% correspondingly, so that compared with the prior art, the density is obviously reduced, and meanwhile, the pressure bearing strength is improved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development, specifically relating to a low-density support material and its preparation method. Background Technology

[0002] In the field of oil and gas field development, low-density proppant materials are mainly used to support fractures during fracturing operations in oil and gas wells. The core objective is to achieve efficient fracture support at a relatively low density to optimize oil and gas extraction. Therefore, low-density proppant materials often strive for even lower density and higher compressive strength. However, existing low-density proppant materials suffer from the following problems:

[0003] (1) Difficulty in balancing strength and density: Low-density proppants often struggle to maintain high compressive strength while reducing density. For example, some low-density proppants with hollow structures, despite their low density, are prone to breakage under high closure stress, affecting the conductivity of cracks.

[0004] (2) Insufficient durability: In complex underground environments, the durability of low-density proppant faces challenges. Some proppants may experience wear and corrosion during long-term oil and gas extraction, leading to a decline in their performance.

[0005] (3) Limited conductivity: Although low-density proppant can reduce settling velocity, its conductivity still needs to be further improved in practical applications. Some low-density proppants have relatively large resistance to oil and gas flow due to their insufficiently optimized pore structure.

[0006] For example, CN105733553A, entitled "An Ultra-Low Density Ceramsite Proppant Prepared Using Copper Tailings," discloses a proppant with a bulk density generally between 1.2 and 1.5 g / cm³. 3 (1200-1500kg / m 3 The apparent density is 2.60 g / cm³. 3 The breakage rate at 35 MPa is 6.5%. However, its density is still insufficient to effectively support the micro-cracks at the crack tip and improve the filling efficiency of artificial cracks; therefore, a low-density support material with lower density and higher compressive strength is needed in this field. Summary of the Invention

[0007] To address the aforementioned deficiencies, the first technical solution of this application discloses a low-density support material, which is a porous structure composed of a mineral-based support material and a surface coating of carbon atoms, with a particle size of 30-100 mesh and a density of <1 g / cm³. 3 .

[0008] The second technical solution of this application discloses a method for preparing the aforementioned low-density support material, which includes using ethylene as a carbon source, pyrolyzing or catalytically cracking it in the presence of a mineral support material to carbonize it into a carbon material, and depositing or coating the surface and / or interior of the mineral support material to obtain the material.

[0009] Preferably, the mineral support material includes, but is not limited to, any one of coal ash particles, quartz sand, ceramsite, and glass microspheres.

[0010] Furthermore, the relationship between the amount of mineral support material added and the amount of ethylene added is that for every 300-500g of mineral support material, ethylene is introduced at a rate of 0.2L / min-0.5L / min.

[0011] Furthermore, it also includes the introduction of argon gas during the pyrolysis or catalytic cracking.

[0012] Preferably, the pyrolysis or catalytic cracking temperature is ≥700℃.

[0013] Furthermore, the low-density support material obtained according to the above preparation method and its application in oil and gas well fracturing operations.

[0014] The beneficial effects of this invention are as follows:

[0015] The low-density proppant material of this invention, having passed the evaluation criteria in SYT 5108-2014 "Performance Test Method for Proppants Used in Hydraulic Fracturing and Gravel Packing Operations", has a density of 0.82-0.96 g / cm³. 3 Between these values, the breakage rate after bearing pressure of 52MPa is 0.81%-49%; compared with existing technologies, it significantly improves compressive strength while reducing density. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the reaction apparatus;

[0017] Figure 2 Images of the low-density support material before and after the carbonization reaction in this application. Detailed Implementation

[0018] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0019] In existing technologies, while low-density proppants can reduce fracturing costs and energy loss, the decrease in density often affects their strength. For example, ceramsite proppants prepared from bauxite have a relatively high sintering temperature and a bulk density of generally 1.2 g / cm3. If additives such as dolomite are added to reduce the density, the proppant breakage rate may increase, failing to meet the pressure-bearing requirements.

[0020] The preparation method of the present invention enables the improvement of the performance of low-density proppants (such as quartz sand, ceramsite, glass microspheres, etc.) by secondary processing of mineral proppants with low density characteristics but low strength. The secondary processing process uses ethylene as a carbon source and decomposes it into carbon-coated proppant at high temperature.

[0021] Therefore, the first embodiment of this application discloses a method for preparing a low-density support material, which includes using ethylene as a carbon source, pyrolyzing or catalytically cracking it in the presence of a mineral support material to carbonize it into a carbon material, and depositing or coating the surface and / or interior of the mineral support material to obtain the material; wherein the mineral support material includes, but is not limited to, any one of coal ash particles, quartz sand, ceramsite, and glass microspheres.

[0022] In this embodiment, the ethylene pyrolysis or catalytic cracking process is as described in formula (1):

[0023]

[0024] In the formula:

[0025] C2H4 — Ethylene, an organic compound composed of two carbon atoms and four hydrogen atoms;

[0026] (g) — indicates that the substance is in a gaseous state;

[0027] Δ ——— represents heating or temperature change, and is a commonly used symbol in chemical reactions, indicating that the reaction requires heat;

[0028] 2C — This indicates that two carbon atoms have been generated, which attach to the coal ash particles to form a low-density support material.

[0029] (s) ——— indicates that the substance is in a solid state;

[0030] 2H2 — This indicates that two hydrogen molecules were generated.

[0031] During this process, the mineral support material forms a porous structure during ethylene carbonization, causing the C atoms generated during ethylene carbonization to either deposit inside the mineral support material or coat its surface. This reduces the density of the mineral support material and significantly improves its mechanical properties, such as strength and modulus.

[0032] The process uses mineral-based support materials, which are sieved to the required 30-100 mesh size using standard screening. The primary carbon source in the process is ethylene, which participates in the carbonization reaction. Ethylene is a small-molecule hydrocarbon compound with a high carbon content. During the carbonization of the support material, ethylene acts as a carbon source, generating carbon materials through reactions such as pyrolysis or catalytic cracking, which are then deposited on the surface or inside the support material.

[0033] In this process, the relationship between the amount of mineral support material added and the amount of ethylene added is that for every 300-500g of mineral support material, ethylene is introduced at a rate of 0.2L / min-0.5L / min.

[0034] To prevent the support material from oxidizing during carbonization, argon gas is introduced during the pyrolysis or catalytic cracking to remove oxygen from the air, which can significantly reduce the oxidation rate of the material and thus maintain its mechanical and chemical properties.

[0035] The preferred pyrolysis or catalytic cracking temperature is ≥700℃.

[0036] In a preferred embodiment of this application, a quartz glass reaction apparatus is disclosed. This apparatus utilizes chemical vapor deposition (CVD) with ethylene as a carbon source to carbon-coat a support material, thereby improving the performance of low-density support materials, reducing costs, and expanding applications. Figure 1 As shown, the reactor includes a feed inlet 1, a gas outlet 2, a reactor 3, a heating furnace 4, a distribution plate 5, and a gas inlet 6. The feed inlet 1 is used for the proppant inlet; the gas outlet 2 is the outlet for the carbon source ethylene and the protective gas argon; the reactor 3 is used for high-temperature carbonization of the proppant; the heating furnace 4 is used for heating and can complete carbonization at ≥700℃; the distribution plate 5 is used to prevent the proppant from leaking out of the reactor after being poured in, therefore a distribution plate with a particle size higher than that of the proppant is set up; the gas inlet 6 is used as the inlet for the carbon source ethylene and the protective gas argon.

[0037] In this embodiment, the reaction apparatus mainly consists of a quartz glass reactor and a tubular furnace, wherein the temperature control range of the tubular furnace can reach 1200℃, which is sufficient to achieve the temperature required for this preparation.

[0038] This implementation utilizes the suspension characteristics of particles in a quartz glass reaction apparatus, allowing reactant gases to be uniformly distributed within a fluidized bed and undergo a chemical reaction. The resulting solid products are then uniformly deposited on the particle surface. This technology combines the high heat and mass transfer efficiency of fluidized beds with the uniform deposition characteristics of chemical vapor deposition, making it suitable for the preparation and surface modification of various materials. The process ensures uniformity; the particles within the fluidized bed are in a suspended state, and the reactant gases are evenly distributed, guaranteeing a uniform deposition layer. It also enables large-scale production; the large volume of the fluidized bed reactor makes it suitable for large-scale industrial production. Temperature control of the fluidized bed is achieved through a multi-stage fluidized bed design, allowing operation in different temperature ranges, optimizing reaction conditions, and offering versatility. It can be used for various applications such as particle coating, nanomaterial preparation, and polycrystalline silicon production.

[0039] The technical effects of this application will be specifically explained below through specific embodiments.

[0040] Example 1: Preparation of Low-Density Support Material

[0041] Using coal ash particles as raw material, the initial coal ash particles or slag proppant are first screened with a standard sieve to select the required particle size range. 500g of the raw material is measured and carbon-coated with 12L of ethylene at a high temperature of 700℃ to finally form a low-density proppant material invented in this paper. The properties of coal ash particles of different mesh sizes before and after the reaction are shown in Table 1.

[0042] The methods for preparing low-density proppant from coal ash particles of different particle sizes are as follows.

[0043] (1) Carbon growth of 30-mesh coal ash: 0.94 g / cm³ 3 Supporting materials

[0044] First, the initial coal ash particles are sieved using a standard sieve, and 300g of 30-mesh coal ash particles are selected as raw materials. Then, the coal ash particles are poured into a reactor made of quartz glass. Argon gas is connected to the bottom of the reactor and heated to 700°C using a tubular heater at an atmosphere of 0.2L / min. Then, ethylene gas is introduced and continuously injected into the reactor at a flow rate of 0.2L / min for 30 minutes to carbonize the coal ash. After completion, the temperature is turned off and the material is allowed to cool down to form the low-density support material of this invention.

[0045] (2) Carbon growth of 40-70 mesh coal ash: 0.93 g / cm³ 3 Supporting materials

[0046] First, the initial coal ash particles are sieved using a standard sieve, selecting 40-70 mesh coal ash particles. 400g of these particles are then measured as raw material. The coal ash particles are then poured into a reactor made of quartz glass. Argon gas is connected to a gas line at the bottom of the reactor, and the temperature is raised to 700℃ using a tubular heater at an atmosphere of 0.35L / min. Then, ethylene gas is introduced and continuously injected into the reactor at a flow rate of 0.35L / min for 30 minutes to carbonize the coal ash. After completion, the temperature is turned off and the material is allowed to cool completely, forming the low-density support material of this invention.

[0047] (3) Carbon growth of 80-100 mesh coal ash: 0.82 g / cm³ 3 Supporting materials

[0048] First, the initial coal ash particles were sieved using a standard sieve, selecting 80-100 mesh particles. 500g of these particles were measured as raw material and poured into a reactor made of quartz glass. Argon gas was connected to the bottom of the reactor and heated to 700℃ using a tubular heater at a flow rate of 0.5L / min. Then, ethylene, the reactive gas, was continuously introduced into the reactor at a flow rate of 0.5L / min for 30 minutes to carbonize the coal ash. After this process, the temperature was turned off, and the material was allowed to cool completely, forming the low-density support material of this invention. A comparison of the reaction before and after is shown in the figure. Figure 2 As shown.

[0049] Table 1. Statistical table of coal ash particle performance before and after reaction.

[0050]

[0051] As shown in Table 1, there are significant differences in the properties of coal ash particles before and after carbonization. Specifically, the density of the low-density support material obtained after treatment with the method of this application is reduced to varying degrees for all coal ash particles of different sizes, and the breakage rate at 52 MPa is also significantly reduced compared to the untreated material, especially in the 80-100 mesh particle size range. Therefore, it can be determined that the preparation method of this application can improve the compressive strength of existing mineral-based support materials while reducing their density.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-density support material, characterized in that, It is a porous structure composed of mineral-based support material and surface-coated carbon atoms, with a particle size of 30-100 mesh and a density of <1 g / cm³. 3 .

2. The method for preparing the low-density support material according to claim 1, characterized in that, This includes using ethylene as a carbon source, pyrolyzing or catalytically cracking it in the presence of a mineral-based support material to carbonize it into a carbon material, and then depositing or coating it onto the surface and / or interior of the mineral-based support material.

3. The preparation method according to claim 2, characterized in that, The mineral support materials include, but are not limited to, any one of the following: coal ash particles, quartz sand, ceramsite, and glass microspheres.

4. The preparation method according to claim 2, characterized in that, The relationship between the amount of mineral support material added and the amount of ethylene added is that for every 300-500g of mineral support material, ethylene is introduced at a rate of 0.2L / min-0.5L / min.

5. The low-density support material according to claim 1, characterized in that, It also includes the introduction of argon gas during the pyrolysis or catalytic cracking.

6. The low-density support material according to claim 1, characterized in that, The pyrolysis or catalytic cracking temperature is ≥700℃.

7. The low-density support material obtained by any of the preparation methods according to claims 2-6.

8. The application of the low-density support material according to claim 1 or 7 in oil and gas well fracturing operations.

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