Armored sand-ceramsite bimodal proppant based on performance matching as well as preparation method and application of armored sand-ceramsite bimodal proppant

Abstract

The invention discloses an armored sand-ceramsite bimodal proppant based on performance matching as well as a preparation method and application thereof, and relates to the technical field of oil and gas exploitation. The proppant comprises ceramsite and armored sand which are compounded according to the mass ratio of (20: 80)-(60: 40), the volume density ratio of the ceramsite to the armored sand is 0.9-1.1, the median particle size ratio of the ceramsite to the armored sand is 1.5-3.0, it can be ensured that the proppant is evenly and stably conveyed to a target crack, the ceramsite forms a bearing framework, gaps are filled with the armored sand, and a synergistic and stable composite supporting structure is constructed. According to the proppant, the four-in-one performance matching design of volume density, breakage rate, acid solubility and particle size is adopted, the obtained proppant is superior to a conventional proppant in breakage resistance, acid corrosion resistance and long-term flow guide performance, the preparation cost is low, the defects of performance mismatch, system failure and the like of the conventional proppant can be overcome, and the proppant has wide application prospects in hydraulic fracturing construction of oil and gas fields.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and more specifically to a performance-matched armored sand-ceramsite dual-modal proppant, its preparation method, and its application. Background Technology

[0002] In the exploitation of unconventional oil and gas resources such as shale gas and tight oil, hydraulic fracturing technology has become a key technology for creating artificial fractures, opening up oil and gas flow channels, and achieving economical resource extraction due to the inherent characteristics of low porosity and low permeability in their reservoirs. After fracturing operations, proppant is pumped into the artificial fractures and supports them to remain open, continuously building stable oil and gas flow channels, which directly determines the effectiveness of fracturing operations and the long-term productivity of oil and gas wells.

[0003] Currently, the proppants widely used in the industry are mainly divided into two categories: high-performance ceramsite and low-cost natural quartz sand. However, there is an irreconcilable contradiction between the two in terms of performance and cost, which cannot simultaneously meet the comprehensive performance requirements of proppants for deep unconventional oil and gas extraction. On the one hand, high-performance ceramsite, such as bauxite sintered ceramsite, can adapt to the service environment of deep high pressure and strong corrosion due to its excellent compressive strength, good conductivity and stable chemical stability. However, the preparation of such ceramsite depends on high-grade bauxite raw materials and requires complex processes such as high-temperature sintering, which is costly. On the other hand, natural quartz sand has a wide range of raw material sources and low cost, and is currently the most widely used low-cost proppant. However, its strength is low and it is prone to breakage under deep high pressure environment. The broken particles will block the oil and gas flow channels, causing the fracture conductivity to decay rapidly. It cannot meet the needs of long-term extraction of deep unconventional oil and gas and is only suitable for fracturing operations in shallow and low-pressure reservoirs.

[0004] To balance the performance and cost of proppant, the industry has generally attempted to create composite proppant by simply mixing ceramsite and natural quartz sand in a physical manner, aiming to achieve both high performance and low cost. However, such simple mixtures of composite proppant are ineffective because there is a significant mismatch between ceramsite and natural quartz sand in key performance parameters such as bulk density, breakage rate, acid solubility, and particle morphology. This leads to a series of fatal defects: during pumping, the differences in bulk density and particle morphology can cause gravitational separation, resulting in uneven distribution of the two types of particles and making it impossible to spread them evenly in artificial cracks; during long-term underground service, the mismatch in breakage rate and acid solubility can lead to non-synergistic breakage and selective corrosion, ultimately causing premature failure of the composite proppant structure. Its long-term conductivity may even be lower than that of using ceramsite or quartz sand alone, failing to achieve the expected synergistic effect.

[0005] To address the series of problems caused by the mismatch in component properties of the aforementioned simple physical mixed proppants, existing technologies have attempted to improve the situation by coating the mixed particles with resin. For example, the Chinese patent application No. 202511218828.9 and Publication No. CN121086776A, filed by Xinmi Wanli Industrial Development Co., Ltd. on August 28, 2025, discloses a high-performance composite coated proppant with low conductivity attenuation and its preparation method. This scheme modifies the mixed particles as a whole through a resin coating process, which improves the overall performance of individual particles to a certain extent. However, the core of this scheme is the preparation of composite particles with uniform structure, which is relatively complex. In essence, it still does not solve the problem of mismatch in bulk density, breakage rate, acid solubility, and particle morphology of different components. It cannot solve the core pain points such as gravity differentiation during pumping, non-cooperative breakage under long-term pressure, and selective corrosion in complex formation fluids at the system level. The problem of premature structural failure still occurs, and the composite proppant fails to work synergistically throughout the entire service life.

[0006] Besides the aforementioned resin-coated mixed particle technology, international cutting-edge proppant technologies are also actively exploring improvement paths to address the challenges of balancing proppant performance and cost, and the tendency for composite components to exhibit performance mismatches. Currently, these technologies are primarily developing towards micro-proppants, special coated sands, and morphology-optimized particles. The core idea behind these advancements is to improve the efficiency and service stability of individual proppant particles through material modification or particle morphology optimization. However, these international cutting-edge technologies generally suffer from significant bottlenecks. Their preparation processes rely on high-barrier core processes such as high-temperature sintering and precision molding, leading not only to high proppant preparation costs but also placing extremely high demands on production equipment. This hinders the large-scale application of these foreign technologies and makes it difficult for domestic SMEs to introduce, digest, and absorb them, thus failing to meet the core needs of low-cost, large-scale, and efficient unconventional oil and gas development in China. Furthermore, these technologies have not yet formed an effective design approach for matching component performance, failing to fundamentally solve problems such as structural failures caused by component mismatches in composite proppants.

[0007] In summary, all existing proppant-related technologies have inherent defects. Whether it is a single type of proppant, a simple physical mixture proppant, a resin-coated modified proppant, or an internationally advanced technology, none of them have effectively solved the core technical problems in deep unconventional oil and gas extraction, such as transport differentiation, non-cooperative fragmentation, and premature structural failure caused by the mismatch of internal components in terms of bulk density, fragmentation rate, acid solubility, and particle morphology. They also cannot balance the performance and cost of proppants.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of this invention is to address the problems mentioned in the background section by providing a performance-matched armored sand-ceramsite dual-modal proppant, its preparation method, and its application.

[0010] To achieve the above objectives, the present invention specifically adopts the following technical solution: A performance-matched armored sand-ceramsite bimodal proppant comprises: ceramsite and armored sand in a mass ratio of (20:80) to (60:40); The ceramsite is sintered ceramsite or surface-modified ceramsite; The armored sand is coated and reinforced quartz sand. By total mass of the armored sand, the coating includes 3-10% resin matrix, 0.1-2.0% silane coupling agent, and 0-2% functional modified filler.

[0011] Preferably, the particle size grades of the quartz sand and the ceramsite are at least one of 16 / 30 mesh, 20 / 40 mesh, 30 / 50 mesh, 40 / 70 mesh, and 70 / 140 mesh.

[0012] Preferably, the bulk density ratio of the ceramsite and the armored sand is 0.9 to 1.1, and the median particle size ratio of the ceramsite and the armored sand is 1.5 to 3.0.

[0013] Preferably, the resin matrix includes epoxy resin, polyurethane resin, phenolic resin, or a modified blend; The modified blend includes at least one of modified epoxy resin, modified polyurethane resin, and modified phenolic resin; The silane coupling agent is KH-550 coupling agent or KH-560 coupling agent; The functional modified filler is at least one of nano-silica, rubber microparticles, and acid-resistant filler.

[0014] As having the same inventive concept as the above-mentioned technical solution, this invention also claims protection for a method for preparing a performance-matched armored sand-ceramsite dual-modal proppant, comprising the following steps: S1. Sift both the quartz sand and sintered ceramsite to the target particle size and dry them until the moisture content is <0.5%; S2. Prepare a coating liquid, atomize and spray the coating liquid onto the surface of the quartz sand and sintered ceramsite obtained in step S1 and cure it. After cooling, armored sand and surface-modified ceramsite are obtained. S3. Place the armored sand and surface-modified ceramsite or the sintered ceramsite obtained in step S1 into a three-dimensional mixing machine and mix for 10-30 minutes to obtain armored sand-ceramsite dual-modal support.

[0015] Preferably, step S2 specifically includes: S21. Dissolve the resin matrix, coupling agent and functional modified filler in a solvent and stir evenly to obtain a coating liquid; preheat the quartz sand and sintered ceramsite obtained in step S1 to 60~100℃. S22. Under stirring or fluidization conditions, the coating liquid is atomized and sprayed onto the surface of preheated quartz sand and sintered ceramsite. After spraying, it is cured at 100~150℃ for 40~150min and then cooled to room temperature. The lumps are removed by sieving to obtain the armored sand-ceramsite bimodal support.

[0016] Preferably, the solvent is acetone or ethanol.

[0017] As an inventive concept with the same technical solution described above, this invention also claims protection for the application of a performance-matched armored sand-ceramsite dual-modal proppant in hydraulic fracturing operations in oil and gas fields.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By controlling the median particle size ratio of ceramsite and armored sand to 1.5~3.0, it is possible to ensure that the proppant can be delivered to the target crack evenly and stably, and that the ceramsite forms a load-bearing skeleton and the armored sand fills the gaps, thus constructing a synergistic and stable composite support structure. 2. By adding a resin matrix, a continuous and tough coating layer can be formed, improving the strength, corrosion resistance, and crush resistance of the armored sand; by adding a silane coupling agent, the chemical bonding force between the resin and the quartz sand can be enhanced, ensuring the overall stability of the armored sand's performance; by adding functional modified fillers, the coating's toughness, friction coefficient, density, and chemical stability can be adjusted, further optimizing the armored sand's strength, corrosion resistance, and crush resistance. 3. Through a four-in-one performance matching design of bulk density, breakage rate, acid solubility, and particle size, the armored sand-ceramsite bimodal proppant obtained with a specific mass ratio of ceramsite and armored sand as the core exhibits superior anti-breakage, acid corrosion resistance, and long-term conductivity performance compared to conventional proppants, while also having a lower preparation cost. It can specifically address the defects of conventional proppants such as performance mismatch, system failure, poor conductivity stability, and insufficient component synergy, and has promising applications in hydraulic fracturing operations in oil and gas fields. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The materials and instruments used in the following embodiments are all commercially available.

[0020] In a first aspect, embodiments of the present invention provide a performance-matched armored sand-ceramsite bimodal proppant, comprising: ceramsite and armored sand compounded in a mass ratio of (20:80) to (60:40); the bulk density ratio of the ceramsite and armored sand is 0.9 to 1.1, and the bulk density is determined in accordance with the Chinese petroleum and natural gas industry standard SY / T 5108-2014 or the international standard ISO13503-2; The median particle size ratio of ceramsite and armored sand is 1.5~3.0, which can ensure that the proppant can be delivered to the target crack evenly and stably, and also allow the ceramsite to form a load-bearing skeleton and the armored sand to fill the gaps, thus constructing a synergistic and stable composite support structure. The armored sand is coated and reinforced quartz sand. By total mass of the armored sand, the coating comprises 3-10% resin matrix, 0.1-2.0% silane coupling agent, and 0-2% functional modified filler. The ceramsite is sintered ceramsite or surface-modified ceramsite. Both the quartz sand and the ceramsite have at least one of the following particle size grades: 16 / 30 mesh, 20 / 40 mesh, 30 / 50 mesh, 40 / 70 mesh, and 70 / 140 mesh. Specifically, the resin matrix includes epoxy resin, polyurethane resin, phenolic resin, or modified blends, and the modified blends include at least one of modified epoxy resin, modified polyurethane resin, and modified phenolic resin; the resin matrix can form a continuous and tough coating layer, improving the strength, corrosion resistance, and breakage resistance of the armored sand; the silane coupling agent is KH-550 or KH-560, which can enhance the chemical bonding force between the resin and the quartz sand, ensuring the stability of the overall performance of the armored sand; the functional modified filler is at least one of nano-silica, rubber microparticles, and acid-resistant filler, used to adjust the coating toughness, friction coefficient, density, and chemical stability, further optimizing the strength, corrosion resistance, and breakage resistance of the armored sand.

[0021] In addition, to adapt to the environmental protection and construction process requirements of different application scenarios, the resin matrix in this embodiment can be replaced with environmentally friendly resin systems such as UV-curable resin and water-based polyurethane. The replaced resin system must meet the compatibility requirements with silane coupling agents and functional modified fillers, and the coating formed must have the same adhesion, strength and weather resistance as the original resin matrix coating to ensure the overall performance of the armored sand. The selection of ceramsite can be adjusted according to actual usage requirements and performance matching. In addition to sintered ceramsite and surface-modified ceramsite, it can also be replaced with high-strength sintered materials such as zirconium oxide and mullite-based materials. The above-mentioned alternative materials must meet the performance matching requirements of the armored sand defined in this embodiment, including particle size compatibility, packing synergy and mechanical property compatibility. The replacement will not affect the overall structural stability of the armored sand and aggregate. In this embodiment, a third phase of ultra-low density microparticles, such as high-strength cenospheres, can also be introduced as a conditioning phase. The amount of the third-phase conditioning phase added is based on the premise of not damaging the basic packing and performance synergy of the armored sand and ceramsite, and can be adaptively adjusted according to the actual density and packing requirements.

[0022] Secondly, embodiments of the present invention provide a method for preparing a dual-modal proppant based on performance matching of armored sand and ceramsite, comprising steps S1 to S3.

[0023] S1. Sift both the quartz sand and sintered ceramsite to the target particle size and dry them until the moisture content is <0.5%.

[0024] S2. Prepare a coating liquid, atomize and spray the coating liquid onto the surface of the quartz sand and sintered ceramsite obtained in step S1 and cure it. After cooling, armored sand and surface-modified ceramsite are obtained. S21. Dissolve the resin matrix, coupling agent, and functional modified filler in a solvent and stir evenly to obtain a coating liquid; preheat the quartz sand and sintered ceramsite obtained in step S1 to 60~100℃; wherein, the solvent is acetone or ethanol, and the solvent is used to adjust the viscosity and completely evaporates without residue. S22. Under stirring or fluidization conditions, the coating liquid is atomized and sprayed onto the surface of preheated quartz sand and sintered ceramsite. After spraying, it is cured at 100~150℃ for 40~150min and then cooled to room temperature. The lumps are removed by sieving to obtain the armored sand-ceramsite bimodal support.

[0025] S3. Place the armored sand and surface-modified ceramsite or the sintered ceramsite obtained in step S1 into a three-dimensional mixing machine and mix for 10-30 minutes to obtain armored sand-ceramsite dual-modal support.

[0026] In practical applications, step S3 can be combined with the target reservoir conditions, including reservoir depth, formation pressure, and formation fluid pH value, to select pre-prepared sintered ceramsite or surface-modified ceramsite and armored sand models that match each other's performance parameters from a pre-established performance matching database. After selection, precise measurement and mixing are performed: according to the designed mass ratio, the two types of particles are placed in a three-dimensional mixer and mixed for 10-30 minutes until the two types of particles are uniformly mixed. Among them, the performance matching database is a pre-established data set containing various performance parameters of different types of armored sand and ceramsite. Its core function is to provide accurate data support for the above selection decision and ensure that the two types of particles selected can meet the usage requirements of the target working conditions.

[0027] Thirdly, embodiments of the present invention provide an application of the performance-matched armored sand-ceramsite dual-modal proppant obtained by the aforementioned preparation method in hydraulic fracturing operations in oil and gas fields.

[0028] First, construction design matching: Based on the depth of the target reservoir, closure stress, formation fluid chemical properties (such as pH value) and fracture design parameters (such as fracture length and fracture height), select armored sand and sintered ceramsite or surface-modified ceramsite models with corresponding matching parameters such as bulk density ratio, median particle size ratio, fragmentation rate, and acid solubility from the preset performance matching database, and determine the preferred mixing mass ratio of the two. Secondly, pumping and delivery: The premixed bimodal composite proppant, prepared according to the above design ratio, is mixed evenly with fracturing fluid base fluid (such as slickwater, linear adhesive, or cross-linked gel) at the designed sand ratio. The precisely matched bulk density characteristics of the two types of particles in the composite system ensure that the mixed slurry enters the wellbore uniformly and stably, and is successfully delivered to the target hydraulic fracture. Secondly, the proppant is laid in the fracture and the structure is formed: After the proppant enters the hydraulic fracture with the fracturing fluid, it is naturally laid in the fracture to form a dense and stable main load-bearing and synergistic filling composite support layer by means of the median particle size difference between the ceramsite and the armored sand matched according to the design. That is, the ceramsite with a relatively large particle size is used as the main load-bearing skeleton, and the armored sand with a relatively small particle size fills the gaps in the skeleton, which effectively optimizes the support efficiency and pore connectivity of the fracture. Finally, long-term synergistic pressure bearing and flow conduction: After fracturing, the formation fractures close, and the proppant layer bears the formation closure pressure. Because the crushing rate and acid solubility characteristics of the ceramsite and armored sand are precisely matched in advance, they can achieve synergistic deformation and synergistic corrosion resistance in long-term high-pressure and potentially acidic formation environments. This effectively avoids the instability of the proppant structure caused by premature crushing or corrosion of a single component, thereby maintaining the high and stable flow conduction capacity of the fractures in the long term and ensuring the long-term effectiveness of fracturing operations.

[0029] The present invention will be further described below with reference to specific embodiments and comparative examples; The flow diversion capacity test shall be conducted in accordance with the Chinese petroleum and natural gas industry standard SY / T 5108-2014. The determination of the breakage rate shall be carried out in accordance with the Chinese petroleum and natural gas industry standard SY / T 5108-2014 or the international standard ISO13503-2; The determination of acid solubility shall be performed in accordance with the Chinese petroleum and natural gas industry standard SY / T 5108-2014 or the international standard ISO13503-2.

[0030] Example 1 1. Raw materials and performance parameters: Natural quartz sand with a particle size of 40 / 70 mesh is selected as the armor sand substrate. Epoxy resin is used as the resin matrix for the armor sand coating. The coating weight gain is 5% of the total mass of the armor sand. The bulk density of this armor sand is approximately 1.55 g / cm³. 3The breakage rate under a closing pressure of 69 MPa is 3.5%, and the acid solubility is ≤2.0%. Uncoated bauxite ceramsite with a particle size of 20 / 40 mesh was selected; the bulk density of the bauxite ceramsite was 1.58 g / cm³. 3 The breakage rate under a closing pressure of 69 MPa is 5%, and the acid solubility is 6.5%.

[0031] 2. Preparation process: The bauxite ceramsite and armored sand are compounded at a mass ratio of 40:60, with a bulk density ratio of approximately 1.06 and a median particle size ratio of approximately 2.2. First, the quartz sand and bauxite ceramsite are sieved to their corresponding particle size grades and dried until the moisture content is <0.5%, and then pretreated. The pretreated granular material is preheated to 100°C, and an epoxy resin coating liquid is uniformly coated onto the surface of the quartz sand using an atomization spraying process. After spraying, it is cured at 120°C for 120 minutes, cooled to room temperature, and sieved to remove lumps, thus obtaining armored sand. Finally, the armored sand and bauxite ceramsite are placed in a three-dimensional mixer and mixed for 20 minutes until uniformly mixed, thus obtaining the armored sand-ceramsite bimodal support agent of this embodiment. 3. Expected Results: The armored sand-ceramsite bimodal proppant prepared in this embodiment was subjected to long-term conductivity tests under simulated downhole conditions (closure stress 69 MPa, pH=4 acidic environment, continuous for 30 days). The test results showed that the conductivity retention rate of the armored sand-ceramsite bimodal proppant was more than 80% higher than that of pure quartz sand proppant and more than 30% higher than that of a simple mixed sand-ceramsite proppant system. At the same time, the preparation cost of the armored sand-ceramsite bimodal proppant was only about 60% of that of the all-ceramsite proppant scheme.

[0032] Example 2 1. Raw materials and performance parameters: Natural quartz sand with a particle size of 30 / 50 mesh is selected as the armor sand substrate. The coating of the armor sand uses acid-resistant phenolic resin as the resin matrix, and the coating weight gain is 8% of the total mass of the armor sand. At the same time, 1% of the total mass of the armor sand is added as acid-resistant filler to enhance the acid resistance. The bulk density of this armor sand is approximately 1.60 g / cm³. 3 The breakage rate was 5.5% under a closing pressure of 69 MPa and 10% under a closing pressure of 86 MPa; the acid solubility was ≤3.0%. High-alumina, low-calcium sintered ceramsite with a particle size of 16 / 30 mesh was selected. An acid-resistant coating was applied to the surface of the high-alumina, low-calcium ceramsite, with the coating adding 2% of the total mass of the sintered ceramsite. Its bulk density was 1.62 g / cm³. 3 The breakage rate is 2.5% under a closing pressure of 69MPa and 4% under a closing pressure of 86MPa. The acid solubility is ≤3.5%.

[0033] 2. Preparation Process: High-alumina, low-calcium sintered ceramsite and armored sand are compounded at a mass ratio of 30:70, with a bulk density ratio of approximately 1.01 and a median particle size ratio of approximately 1.6. Quartz sand and high-alumina, low-calcium ceramsite are sieved to their corresponding particle size grades, dried to a moisture content of <0.5%, and pretreated. The pretreated granular materials are preheated to 100°C, and an atomized spraying process is used to coat the quartz sand with an acid-resistant phenolic resin coating liquid, and the high-alumina, low-calcium ceramsite with an acid-resistant coating liquid. After spraying, taking advantage of the high-temperature curing properties of the acid-resistant phenolic resin, it is cured at 150°C for 40 minutes, cooled to room temperature, and sieved to remove lumps, yielding armored sand and surface-modified acid-resistant ceramsite. Finally, the two are placed in a three-dimensional mixer and mixed for 10 minutes until uniformly mixed, thus obtaining the armored sand-ceramsite bimodal proppant of this embodiment. 3. Expected Results: The armored sand-ceramsite bimodal proppant prepared in this embodiment was subjected to long-term conductivity tests under simulated harsh downhole conditions (closure stress 86 MPa, pH=3 acidic environment, continuous for 30 days). The test results showed that, due to the proper matching of various performance parameters, the conductivity retention rate of the armored sand-ceramsite bimodal proppant was more than 120% higher than that of pure quartz sand proppant and more than 50% higher than that of a simple mixed sand-ceramsite proppant system. At the same time, the preparation cost of the armored sand-ceramsite bimodal proppant was only about 50% of that of the all-ceramsite proppant scheme.

[0034] Example 3 1. Raw materials and performance parameters: Natural quartz sand with a particle size of 70 / 140 mesh is selected as the armor sand substrate. Polyurethane resin is used as the resin matrix for the armor sand coating, with a coating weight gain of 10% of the total armor sand mass. Simultaneously, 1.0% of the total armor sand mass of nano-silica is added as a functional modifying filler, along with 0.5% KH-550 silane coupling agent and an appropriate amount of acetone. The bulk density of this armor sand is approximately 1.48 g / cm³. 3 The breakage rate under a closing pressure of 69 MPa is 3.1%, and the acid solubility is ≤2.8%. Uncoated bauxite sintered ceramsite with a particle size of 30 / 50 mesh was selected; the bulk density of the bauxite ceramsite was 1.65 g / cm³, the breakage rate under a closing pressure of 69 MPa was 6%, and the acid solubility was 6.5%. 2. Preparation process: The ceramsite and armored sand are compounded at a mass ratio of 20:80, with a bulk density ratio of approximately 1.11 and a median particle size ratio of approximately 3.0. Quartz sand and bauxite ceramsite are sieved to their respective particle size grades, dried to a moisture content of <0.5%, and pretreated. The pretreated granular material is preheated to 80°C, and the above coating liquid is uniformly coated onto the surface of quartz sand using an atomization spraying process. After spraying, it is cured at 100°C for 60 minutes, cooled to room temperature, and sieved to remove lumps, resulting in multifunctional coated armored sand. Finally, the armored sand and bauxite ceramsite are placed in a three-dimensional mixer and mixed for 30 minutes until uniformly mixed, thus obtaining the armored sand-ceramsite dual-modal proppant of this embodiment. 3. Expected Results: The armored sand-ceramsite bimodal proppant prepared in this embodiment was subjected to long-term conductivity tests under simulated downhole conditions (closure stress 69 MPa, pH=5 acidic environment, continuous for 30 days). The test results showed that the conductivity retention rate of the armored sand-ceramsite bimodal proppant was more than 70% higher than that of pure quartz sand proppant and more than 25% higher than that of a simple mixed sand-ceramsite proppant system. At the same time, the preparation cost of the armored sand-ceramsite bimodal proppant was only about 40% of that of the all-ceramsite proppant scheme.

[0035] Example 4 1. Raw materials and performance parameters: Natural quartz sand with a particle size of 30 / 50 mesh is selected as the armor sand substrate. The coating of the armor sand uses an epoxy-phenolic modified blend as the resin matrix, with a coating weight gain of 7% of the total armor sand mass. It is combined with 1.0% KH-560 silane coupling agent, and 1.5% rubber microparticles are added as functional modified fillers. An appropriate amount of ethanol is also added. The bulk density of this armor sand is approximately 1.52 g / cm³. 3 The breakage rate under a closing pressure of 69 MPa is 7%, and the acid solubility is ≤3.2%. Uncoated fly ash ceramsite with a particle size of 40 / 70 mesh was selected; the bulk density of the fly ash ceramsite was 1.50 g / cm³. 3 The breakage rate under a closing pressure of 69 MPa is 8%, and the acid solubility is 6.8%.

[0036] 2. Preparation process: The ceramsite and armored sand are compounded at a mass ratio of 50:50, with a bulk density ratio of approximately 0.99 and a median particle size ratio of approximately 1.8. Quartz sand and fly ash ceramsite are sieved to their respective particle size grades, dried to a moisture content of <0.5%, and pretreated. The pretreated granular material is preheated to 90°C, and the above coating liquid is uniformly coated onto the surface of quartz sand using an atomization spraying process. After spraying, it is cured at 130°C for 40 minutes, cooled to room temperature, and sieved to remove lumps to obtain armored sand. Finally, the armored sand and fly ash ceramsite are placed in a three-dimensional mixer and mixed for 15 minutes until uniformly mixed to obtain the armored sand-ceramsite bimodal proppant of this embodiment. 3. Expected Results: The armored sand-ceramsite bimodal proppant prepared in this embodiment was subjected to long-term conductivity tests under simulated downhole conditions (closure stress 69 MPa, pH=4 acidic environment, continuous for 30 days). The test results are expected to show that the conductivity retention rate of the armored sand-ceramsite bimodal proppant is more than 90% higher than that of pure quartz sand proppant and more than 35% higher than that of a simple mixed sand-ceramsite proppant system. At the same time, the preparation cost of the armored sand-ceramsite bimodal proppant is only about 55% of that of the all-ceramsite proppant scheme.

[0037] The test results of bulk density, breakage rate, acid solubility and conductivity retention rate of the armored sand-ceramic bimodal proppant obtained in Examples 1-4 are summarized in Table 1. Table 1 Test Results As can be seen from Examples 1-4 and Table 1, the breakage rate, acid solubility, and conductivity retention rate of the armored sand-ceramsite dual-modal proppant of the present invention mainly depend on the armored sand coating formulation and weight gain ratio, the composite ratio of ceramsite and armored sand, and the synergistic matching degree of the raw material properties. These three factors directly determine the proppant's resistance to breakage, acid corrosion, and conductivity stability during downhole service, and are the key to whether the proppant can meet the requirements of downhole working conditions.

[0038] This invention sets up 5 comparative examples to compare and verify the coating from four key dimensions: coating strengthening, component mixing method, coating weight gain range, and volume density matching.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that 40 / 70 mesh quartz sand is used as the substrate, and no coating modification treatment is applied to it, i.e., no armored sand is prepared; the selection of other raw materials, preparation process, mixing ratio and test conditions are the same as in Example 1. Under the same test conditions (69 MPa closure pressure, acidic downhole simulated environment), the expected performance data of the proppant obtained in this comparative example are as follows: bulk density 1.45 g / cm³. 3The breakage rate is ≥40% under a closing pressure of 69MPa; the acid solubility is 4.0%; and the conductivity retention rate is about 30% under the same conditions.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that: there is no component performance matching design, and it is prepared using a conventional simple physical mixing method; Specifically, 40 / 70 mesh uncoated quartz sand (known breakage rate ≥40% under 69MPa closed pressure) and 20 / 40 mesh ceramsite (known breakage rate 5% under 69MPa closed pressure) were selected and mixed directly at a mass ratio of ceramsite to armored sand of 40:60 without any performance adaptation adjustment. The rest of the preparation process and test conditions were the same as in Example 1. The expected performance data of the proppant obtained in this comparative example are as follows: bulk density ratio of approximately 1.09, particle size ratio of approximately 2.2; under a closing pressure of 69 MPa, the breakage rate of the mixture is significantly higher than that of the proppant of this invention; the long-term conductivity retention rate is approximately 50%, which is far lower than the expected value of the proppant of this invention.

[0041] Comparative Example 3 The only difference between this comparative example and Example 1 is that when 20 / 40 mesh ceramsite is used and its surface is modified with a coating, the weight gain of the coating is 5% of the total mass of the ceramsite. The other raw materials, preparation process, mixing ratio and test conditions are the same as those in Example 1. The expected performance data of the proppant obtained in the comparative example are as follows: Due to the excessively thick surface coating, the ceramsite exhibits obvious adhesion, and the particle flowability deteriorates significantly; the bulk density of the mixed system is slightly higher than that of the conventional scheme of this invention; under a closing pressure of 69 MPa, the proppant breakage rate is not significantly different from that of the conventional scheme of this invention, but the mixing uniformity and construction pumping performance are significantly deteriorated, which in turn affects the final flow-guiding effect of the proppant, and the flow-guiding capacity retention rate is lower than that of Example 1.

[0042] Comparative Example 4 The only difference between this comparative example and Example 1 is that: when using 20 / 40 mesh ceramsite and performing surface modification coating treatment, the coating weight gain ratio is 0.2% of the total mass of the ceramsite, or no surface modification coating treatment is performed; the other raw materials, preparation process, mixing ratio and test conditions are the same as those in Example 1. The expected performance data of the proppant obtained in the comparative example are as follows: the coating on the surface of the ceramsite is too thin or there is no coating, which cannot effectively adjust the surface characteristics of the ceramsite (such as the surface friction coefficient and acid resistance); when it is mixed with armored sand, the interfacial compatibility between the ceramsite and the armored sand is poor, and the synergistic improvement of the acid corrosion resistance of the two is limited; the long-term conductivity retention rate is significantly lower than that of the conventional scheme of this invention, and the expected service effect cannot be achieved.

[0043] Comparative Example 5 The only difference between this comparative example and Example 1 is that the bulk density of the proppant component is severely mismatched. Specifically, it was prepared using 70 / 140 mesh uncoated quartz sand (bulk density approximately 1.45 g / cm³). 3 (Crush rate 8% under 69MPa closing pressure, acid solubility ≤4.0%), compared with 40 / 70 mesh corundum ceramsite (polyurethane resin coating, weight gain 3%, bulk density 2.00 g / cm³). 3 The ceramsite and armored sand were mixed at a mass ratio of 60:40 (with a crushing rate ≤2% under a closing pressure of 69MPa and an acid solubility ≤5%). The bulk density ratio after mixing was approximately 1.38, and the particle size ratio was approximately 1.5. The remaining preparation process and testing conditions were the same as in Example 1. Tests were conducted under simulated pumping and a closure stress of 69 MPa. The expected results of this comparative proppant are as follows: Due to the large difference in bulk density between quartz sand and ceramsite, the proppant exhibits severe stratification in the cracks and cannot form a uniform and stable propping system; the long-term conductivity retention rate is lower than that of comparative example 2 (a conventional simple physical mixing system), and the proppant's service performance is completely ineffective.

[0044] The test results of bulk density, breakage rate, acid solubility, and conductivity retention rate of the armored sand-ceramic bimodal proppant obtained in Example 1 and the proppant obtained in Comparative Examples 1-5 are summarized in Table 2. Table 2. Detection results of Example 1 and Comparative Examples 1-5 As can be seen from Example 1, Comparative Example 1 and Table 2, the necessity of armored sand coating reinforcement is verified; uncoated quartz sand has low strength and poor acid corrosion resistance, which cannot meet the core performance requirements of downhole proppant, while epoxy resin coating modification can significantly improve the anti-fracture and acid corrosion resistance of quartz sand, providing a guarantee for excellent flow conduction effect. As can be seen from Example 1, Comparative Example 2 and Table 2, simple mixing alone cannot achieve synergistic effects between components. Due to the mismatch in strength and acid resistance between uncoated quartz sand and ceramsite, the overall performance is significantly reduced. As can be seen from Example 1, Comparative Examples 3-4 and Table 2, the reasonableness of the weight gain range of the modified coating on the surface of ceramsite is that if the coating is too thick, too thin or there is no coating, the effective performance matching between ceramsite and armored sand cannot be achieved, and the synergistic performance of the proppant cannot be brought into play. As can be seen from Example 1, Comparative Example 5 and Table 2, the mismatch of bulk density between components will lead to failure of the proppant function, while the bulk density ratio range defined by the present invention can ensure that the proppant is mixed uniformly and has stable service.

[0045] This invention proposes a four-in-one performance matching design of bulk density, breakage rate, acid solubility, and particle size. Using a specific mass ratio of ceramsite and armored sand as the core, a dual-modal armored sand-ceramsite proppant is obtained. The anti-breakage, acid corrosion resistance, and long-term conductivity of this dual-modal armored sand-ceramsite proppant are verified by examples to be significantly superior to conventional proppants, and the preparation cost is lower. It can specifically solve the defects of conventional proppants such as performance mismatch, system failure, poor conductivity stability, and insufficient component synergy, and has promising applications in hydraulic fracturing operations in oil and gas fields.

Claims

1. A dual-modal proppant based on performance matching of armored sand and ceramsite, characterized in that, include: Ceramsite and armored sand are compounded in a mass ratio of (20:80) to (60:40); The ceramsite is sintered ceramsite or surface-modified ceramsite; The armored sand is coated and reinforced quartz sand. By total mass of the armored sand, the coating includes 3-10% resin matrix, 0.1-2.0% silane coupling agent, and 0-2% functional modified filler.

2. The armored sand-ceramsite dual-modal proppant based on performance matching as described in claim 1, characterized in that, The particle size grades of the quartz sand and the ceramsite are at least one of 16 / 30 mesh, 20 / 40 mesh, 30 / 50 mesh, 40 / 70 mesh, and 70 / 140 mesh.

3. The armored sand-ceramsite dual-modal proppant based on performance matching as described in claim 2, characterized in that, The bulk density ratio of the ceramsite and the armored sand is 0.9~1.1, and the median particle size ratio of the ceramsite and the armored sand is 1.5~3.

0.

4. The armored sand-ceramsite dual-modal proppant based on performance matching as described in claim 1, characterized in that, The resin matrix includes epoxy resin, polyurethane resin, phenolic resin, or modified blends. The modified blend includes at least one of modified epoxy resin, modified polyurethane resin, and modified phenolic resin; The silane coupling agent is KH-550 coupling agent or KH-560 coupling agent; The functional modified filler is at least one of nano-silica, rubber microparticles, and acid-resistant filler.

5. A method for preparing a performance-matched armored sand-ceramsite dual-modal proppant as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Sift both the quartz sand and sintered ceramsite to the target particle size and dry them until the moisture content is <0.5%; S2. Prepare a coating liquid, atomize and spray the coating liquid onto the surface of the quartz sand and sintered ceramsite obtained in step S1 and cure it. After cooling, armored sand and surface-modified ceramsite are obtained. S3. Place the armored sand and surface-modified ceramsite or the sintered ceramsite obtained in step S1 into a three-dimensional mixing machine and mix for 10-30 minutes to obtain armored sand-ceramsite dual-modal support.

6. The preparation method of the armored sand-ceramsite dual-modal proppant based on performance matching as described in claim 5, characterized in that, Step S2 specifically includes: S21. Dissolve the resin matrix, coupling agent and functional modified filler in a solvent and stir evenly to obtain a coating liquid; preheat the quartz sand and sintered ceramsite obtained in step S1 to 60~100℃. S22. Under stirring or fluidization conditions, the coating liquid is atomized and sprayed onto the surface of preheated quartz sand and sintered ceramsite. After spraying, it is cured at 100~150℃ for 40~150min and then cooled to room temperature. The lumps are removed by sieving to obtain the armored sand-ceramsite bimodal support.

7. The preparation method of the armored sand-ceramsite dual-modal proppant based on performance matching as described in claim 6, characterized in that, The solvent is acetone or ethanol.

8. The application of a performance-matched armored sand-ceramsite dual-modal proppant as described in any one of claims 1 to 4 in hydraulic fracturing operations in oil and gas fields.

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