Application of aminated molecular sieve in enhanced CO2-ECBM assisted hydraulic fracturing exploitation of coalbed methane

Abstract

The invention discloses an application of an aminated molecular sieve in enhanced CO2-ECBM assisted hydrofracture exploitation of coalbed methane, which is characterized in that the aminated molecular sieve is injected into a coalbed methane reservoir along with a fracturing fluid to support a fracture network structure formed by hydrofracture and improve the CO2 storage efficiency of the coalbed during subsequent CO2-ECBM secondary coalbed methane production increase, and the CO2 storage efficiency of the coalbed is improved. The purpose of improving the CH4 productivity is achieved; wherein the aminated molecular sieve is prepared by selecting a molecular sieve as a matrix, introducing an amino functional group into the surface or pores of the molecular sieve, and washing, drying and calcining a reaction product; the amino functional group of the aminated molecular sieve is easy to interact with CO2 molecules, so that the physical and chemical adsorption selectivity effect between the molecular sieve and CO2 is enhanced, the storage capacity and stability of a coal seam to CO2 are improved, and a new scheme is provided for improving the efficiency of CO2-ECBM-assisted hydraulic fracturing development of coal seam gas.

Description

Technical Field

[0001] The present invention relates to the application of an aminated molecular sieve in enhancing coalbed methane extraction by CO2-ECBM assisted hydraulic fracturing, belonging to the fields of unconventional oil and gas resource development and carbon dioxide geological sequestration. Background Art

[0002] The exploration and development of coalbed methane (the main component is methane, CH4) is of great strategic significance for optimizing China's current energy consumption structure, reducing the external dependence on energy, and alleviating the environmental pollution problems caused by the consumption of traditional fossil fuels such as coal. In addition, the development of coalbed methane can effectively avoid coal mine gas disasters and reduce the emissions of greenhouse gases such as CH4 during the development and utilization of coal resources. China has rich reserves of coalbed methane resources. The proven reserves of coalbed methane in the coal seams less than 2000 m deep in 39 basins within China's territory are as high as 30.05×10 12 m 3 , ranking third in the world. However, the physical properties of China's coalbed methane reservoirs are poor, and their permeability is generally less than 1.0 mD, which is not conducive to the effective migration of coalbed methane within the reservoir, and usually there is no natural production capacity. Therefore, it is necessary to transform the coalbed methane reservoir to improve the overall permeability of the reservoir by forming a good artificial fracture network structure, and then realize the commercial exploitation of coalbed methane.

[0003] At present, hydraulic fracturing technology is mainly used for the transformation of coalbed methane reservoirs. Compared with North American countries such as the United States and Canada, the single-well production of coalbed methane using hydraulic fracturing technology in China is generally low, and the production capacity reaching rate is only 45%. The analysis shows that the gap is mainly due to: most of China's coalbed methane reservoirs are characterized by low reservoir pressure, low permeability, low gas saturation, low porosity and high heterogeneity, which increases the difficulty of coalbed methane exploitation; the Young's elastic modulus of China's coalbed methane reservoirs is low and the Poisson's ratio is high, resulting in a low reservoir brittleness index and poor fracturability. In addition, when implementing hydraulic fracturing technology to exploit coalbed methane in China, the following bottlenecks are also faced: the areas with relatively rich coalbed methane resources in China are relatively short of water resources, and implementing hydraulic fracturing will exacerbate the water shortage; most of the landforms where the current coalbed methane demonstration areas in China are located are hilly and mountainous, and the transportation conditions are poor, which is not conducive to large-scale construction and the layout of large construction equipment frequently and in multiple wells; the burial depth of China's coalbed methane reservoirs is generally greater than that of North American countries, and the self-owned degree of China's hydraulic fracturing equipment and fracture network monitoring technology is relatively low, resulting in an increase in the cost of horizontal well drilling, completion and hydraulic fracturing; fracturing fluids usually contain a large amount of chemical substances and various heavy metal elements, and there is a risk of polluting groundwater, surface water and soil during the injection and flowback stages. Therefore, combined with the current coalbed methane exploitation technology, it is necessary to develop a cleaner, more efficient and lower operating cost coalbed methane exploitation process.

[0004] In recent years, the technology of using coalbed methane reservoirs to sequester CO2 and enhance coalbed methane production (CO2-ECBM) has the dual benefits of carbon emission reduction and clean energy development. The difference in the adsorption capacities of the coal matrix for CO2 and CH4 is the main reason for injecting CO2 into the coal seam and causing CH4 desorption. Research shows that the forces between the coal matrix and fluid molecules mainly include Debye induction force and London dispersion force, thus forming an attractive potential, that is, the depth of the adsorption potential well (Ea). Ea is related to the polarizability and ionization potential of fluid molecules in the coal seam. The polarizability and ionization potential of CO2 molecules are both higher than those of CH4 molecules. Therefore, there is a deeper adsorption potential well between the coal matrix and CO2 molecules, that is, the adsorption effect is stronger. The above microscopic interaction laws between the coal body and CO2 and CH4 molecules constitute the theoretical basis for using coal seams to sequester CO2 and simultaneously displace CH4. In actual hydraulic fracturing operations, fracturing fluid is usually injected into the target coalbed methane reservoir together with proppants to form a well-developed fracture network structure. Traditional proppants include quartz sand, ceramsite, etc. They can effectively prevent the closure of newly formed fractures after fracturing and maintain the fracture conductivity, thereby improving the pore / permeability performance of the coalbed methane reservoir; the above proppants have a weak adsorption affinity for CO2 and insufficient surface active sites. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides an application of aminated molecular sieve in enhancing CO2-ECBM assisted hydraulic fracturing for coalbed methane production; in the process of hydraulic fracturing operation, the present invention introduces aminated molecular sieve as a proppant, and the aminated molecular sieve is injected into the coalbed methane reservoir together with the fracturing fluid. It can effectively support the newly formed fracture network and provide more CO2 retention sites. While increasing the fracturing production, the aminated molecular sieve is used to enhance CO2 sequestration and CH4 production.

[0006] The aminated molecular sieve of the present invention selects a molecular sieve with a specific surface area of 500-2000 m 2 / g as the matrix, and uses the equal-volume impregnation method, amine grafting method or bottom-up amination synthesis method to introduce amine functional groups on the surface or inside the pores of the molecular sieve to enhance its adsorption affinity for acidic CO2 molecules. The reaction product is washed, dried and calcined to obtain.

[0007] Among them, the amine grafting method is to use the silanol (Si-OH) or aluminol (Al-OH) on the surface of the molecular sieve to undergo a condensation reaction with an amine-functionalized ionic liquid containing a silyl group, so that the amine functional group is grafted onto the molecular sieve framework by a covalent bond. The bottom-up amination synthesis method is to directly introduce an amine source into the synthesis system at the initial stage of molecular sieve preparation, so that it is synchronously embedded or encapsulated into the molecular sieve framework or pores during the nucleation and crystallization process.

[0008] In the stage of implementing hydraulic fracturing to transform the reservoir by the method of the present invention, the aminated molecular sieve is used as the main or auxiliary proppant and is injected into the coalbed methane reservoir together with the fracturing fluid. The particle size of the aminated molecular sieve is between 20 and 80 mesh, and it is mixed with the fracturing fluid to form a modified proppant slurry, and the placement concentration is between 1.0 and 60 kg / m 2 . The ground high-pressure pump unit is used to inject the proppant slurry at a rate of 3 - 15 m 3 / min into the well until the pressure at the bottom of the well is higher than the in-situ stress and the formation fracture pressure to generate artificial fractures; the injected aminated molecular sieve fills and supports the newly formed fractures under high-pressure conditions. The aminated molecular sieve proppant is gradually and stably placed in the fracture network and prevents the fractures from closing, forming "sand-filled fractures" with a certain geometric size and shape, ensuring that the fractures can be effectively supported and maintain good conductivity, and at the same time providing more retention sites for the subsequent injection of CO2.

[0009] After the hydraulic fracturing operation is completed and the flowback fluid is removed, on the basis of the conventional extraction of coalbed methane, a CO2 injection operation is carried out on the coal seam. The surface of the aminated molecular sieve in the fracture has basic sites that can provide lone pairs of electrons, and thus electron coordination or chemical bonding occurs with the CO2 molecules entering the pores of the molecular sieve. Specifically, a weak covalent bond is formed between the amine functional group and the central carbon atom of the CO2 molecule, and even a stable amine-carbonate or amine-carbamate structure is further formed, realizing the chemical fixation of CO2. In addition, the pore structure of the molecular sieve itself with a high specific surface area also provides a rich physical adsorption space for CO2 molecules, and it promotes the adsorption and enrichment of CO2 near the pore wall by means of van der Waals forces. After amine functionalization, the local polar interaction and hydrogen bond interaction between the molecular sieve and CO2 molecules are enhanced, significantly improving the adsorption capacity and selectivity; through the physical-chemical interaction of the molecular sieve pores, amine functional groups and CO2 molecules, the CO2 sequestration efficiency of the coal seam is improved, and thus a larger-scale adsorption-sequestration area is formed in the coal seam.

[0010] The molecular sieve is an MFI framework, FAU framework with a dense structure and some aluminophosphate molecular sieves, mainly including ZSM-5 molecular sieve, HZSM-5 molecular sieve, SBA-16 molecular sieve, Silicalite-1 molecular sieve, TS-1 molecular sieve (MFI framework), X-type zeolite (FAU framework), Y-type zeolite (FAU framework), SAPO-34 molecular sieve (aluminophosphate molecular sieve);

[0011] The inorganic amine solution used in the equal-volume impregnation method is ammonium chloride solution or ammonia water; the organic amine solution is selected from methylamine solution, ethylamine solution, ethanolamine solution, n-propylamine solution, and toluidine solution.

[0012] The amino-functionalized ionic liquids used in the amino grafting method are selected from 1-aminoethyl-3-methylimidazole, 1-aminopropyl-3-methylimidazole cationic ionic liquids, and bis(trifluoromethanesulfonyl)imide anionic ionic liquids.

[0013] The amine sources used in the bottom-up amination synthesis method are selected from tetrapropylammonium hydroxide (TPAOH), triethanolamine (TEA), piperazine, ethylenediamine, 3-aminopropyltriethoxysilane (APTES), and N-β(aminoethyl)-γ-aminopropyltriethoxysilane (AEAPTES).

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

[0015] (1) Good operability and applicability: The aminated molecular sieve can be used for sand-carrying injection in conventional fracturing construction processes without excessive modification of existing hydraulic fracturing equipment and processes, having high technical feasibility and economic efficiency;

[0016] (2) Enhanced CO2 adsorption and sequestration: The amino functional groups on the surface of the aminated molecular sieve significantly improve the binding force to CO2 molecules, enhancing the physical and chemical adsorption selectivity between the molecular sieve and CO2, and improving the sequestration capacity and stability of the coal seam for CO2;

[0017] (3) Improved coalbed methane recovery rate: It creates a more abundant and effective flow channel for subsequent CO2 injection and CH4 replacement; since the aminated molecular sieve as a proppant has a stronger selective adsorption for acidic CO2, it can effectively promote CH4 desorption and production at the wellhead, achieving a significant increase in coalbed methane production capacity. Description of the Drawings

[0018] Figure 1 Shows the enhanced CO2 adsorption effect of inorganic aminated NaY molecular sieve;

[0019] Figure 2 Shows the TEM image and N element distribution schematic diagram of organically aminated ZSM-5 molecular sieve;

[0020] Figure 3 Shows the enhanced CO2 adsorption effect of NH2-SBA-16 molecular sieve;

[0021] Figure 4 Shows the promoting effect of organosilane aminated Silicalite-1 molecular sieve on CH4 desorption. Detailed Embodiments

[0022] The technical solutions of the present invention will be further described in detail below through examples. However, the content of the present invention is not limited thereto. In the examples, the methods are conventional methods unless otherwise specified, and the materials, reagents, etc. are obtained from commercial sources or prepared by conventional methods unless otherwise specified;

[0023] Example 1

[0024] (1) Preparation of amino-functionalized molecular sieve

[0025] The NaY molecular sieve (SiO2 / Al2O3 = 6.5) was added to 0.2 mol / L NaOH solution at a ratio of 30 mL / g. After stirring at 70 °C for 1 hour, it was centrifuged and filtered. The solid was washed 3 times with deionized water. Then, the NaY molecular sieve impregnated with NaOH was added to 0.2 mol / L NH4Cl solution at a ratio of 30 mL / g, and ion exchange was carried out 3 times at 80 °C. Then, it was centrifuged and filtered. The solid was dried at 105 °C and calcined at 550 °C for 6 hours to obtain inorganic amino-functionalized NaY molecular sieve;

[0026] (2) In hydraulic fracturing operations, the inorganic amino-functionalized NaY molecular sieve was added to the pre-prepared water-based fracturing fluid at a laying concentration of 30 kg / m 3 , and after being fully mixed into a uniform suspension at room temperature using a high-efficiency stirring device, it was continuously pumped into the pipeline at a flow rate of 10 m 3 / min through a ground pump device. When the pressure gradually rose to 50 MPa, the piston inside the device was opened, and the high-pressure jet carried the inorganic amino-functionalized NaY molecular sieve and ejected from the hydraulic jet port, directly acting on the target coalbed methane reservoir for fracturing; Subsequently, the discharge of the high-pressure liquid caused a short-term negative pressure in the pipeline, and the piston reset under the action of the high-pressure spring; The ground pump device continued to supplement liquid and increase the pressure, causing the pressure above the piston to change periodically within the range of 40 - 70 MPa, thereby achieving continuous pulsed fracturing with a variable pulse frequency within the range of 0.5 - 3 Hz. During this process, the pressure in the piston sealed area was finely adjusted through the frequency modulation port to achieve real-time control of the pulse frequency and impact energy, so that the amino-functionalized molecular sieve was fully carried and evenly dispersed into the newly formed or expanded fractures under the repeated action of high-pressure pulses, and jointly completed the deep transformation and effective temporary plugging of the formation with the fracturing fluid;

[0027] The results are shown in Figure 1 and Table 1. The results show that the introduction of the inorganic amino-functionalized NaY molecular sieve enhances the CO2 adsorption capacity of the coal body;

[0028] Table 1 Effect of inorganic amino-functionalized molecular sieve on CO2 adsorption capacity under different equilibrium pressures

[0029]

[0030] Example 2

[0031] (1) Preparation of amino-functionalized molecular sieve

[0032] ZSM-5 molecular sieve (SiO2 / Al2O3 = 50) was added to 0.5 mol / L ethanolamine solution at a ratio of 10 mL / g. After standing this mixture at room temperature for 1 hour, the mixture was sonicated in an ultrasonic instrument with a frequency of 53 kHz for 10 min, and then placed in a constant temperature water bath at 60 °C and stirred for 1 hour until the mixture became powdery; finally, it was dried in an oven at 80 °C for 12 hours to obtain organoaminated ZSM-5 molecular sieve. The TEM image and N element distribution of the molecular sieve are shown in Figure 2 , from which it can be seen that the N element is evenly distributed on the molecular sieve, indicating that the molecular sieve was successfully aminated.

[0033] (2) At a laying concentration of 5 kg / m 3 , the organoaminated ZSM-5 molecular sieve was added to the water-based fracturing fluid, which contained 2.0% KCl to stabilize clay minerals and 0.5% polyacrylamide to control the increase in friction. The above mixture was homogenized at room temperature by high-speed stirring for 30 min to form a stable suspension dispersion of the aminated molecular sieve in the liquid phase. Then, the mixed liquid was pumped into the wellbore at an injection flow rate of 5 m 3 / min. When the wellhead pressure gradually increased to 40 MPa, the conventional hydraulic fracturing operation was started. The injection rate was adjusted in real time by monitoring the formation pressure change and fluctuated within the range of 3 - 6 m 3 / min, and the total injection time was controlled to be about 70 min. During this process, the organoaminated ZSM-5 molecular sieve entered the newly formed or extended fractures with the high-pressure liquid flow, and achieved good dispersion and filling inside the fractures with its excellent surface activity, greatly enhancing the fracture conductivity and laying a foundation for subsequent improvement of coalbed methane recovery rate; after fracturing, it was confirmed by the conventional flowback process that the aminated molecular sieve maintained good suspension stability in the bottom hole and formation, and no obvious agglomeration or excessive settlement occurred, and the overall transformation effect reached the expected requirements; the results of the CO2 adsorption capacity of the organoaminated ZSM-5 molecular sieve at different equilibrium pressures are shown in Table 2;

[0034] Table 2 Effect of organoaminated ZSM-5 molecular sieve on CO2 adsorption capacity at different equilibrium pressures

[0035]

[0036] Example 3

[0037] (1) Preparation of aminated molecular sieve

[0038] Under magnetic stirring, 0.5 g of 1-aminopropyl-3-methylimidazolium nitrate was slowly added to 20 mL of absolute ethanol. After ultrasonic oscillation for 1 hour, 1 g of HZSM-5 molecular sieve (SiO2 / Al2O3 = 300) was added. The mixture was magnetically stirred at room temperature for 3 hours, and then ultrasonicated for another 6 hours. The mixture was centrifuged and filtered, and the solid was dried in an oven at 100 °C for 6 hours to obtain 1-aminopropyl-3-methylimidazole grafted HZSM-5 molecular sieve;

[0039] (2) At a laying concentration of 45 kg / m 3 The 1-aminopropyl-3-methylimidazole grafted HZSM-5 molecular sieve was mixed with the water-based fracturing fluid, and 1.5% of a small molecule quaternized polyethyleneimine clay stabilizer was added to ensure excellent fluidity and stability under high displacement and high concentration sand-carrying conditions; After stirring at room temperature for 40 min, the high-concentration molecular sieve fracturing fluid was rapidly injected into the formation at a flow rate of 10 m 3 / min. When the wellhead pressure exceeded 70 MPa, the pulse device was activated and the initial frequency was set to 3.0 Hz, which could be dynamically adjusted within the range of 2.5 - 3.5 Hz. At this time, the continuous pulsed high-frequency impact significantly improved the jet penetration ability. The 1-aminopropyl-3-methylimidazole grafted HZSM-5 molecular sieve could be carried to extremely deep fractures and gradually deposited in the alternating cycle of multiple pulse releases and negative pressure drops, forming an effective fracture support and temporary plugging network; After about 90 min of high-load operation, a multi-level fracture network was successfully formed in the target coalbed methane reservoir, greatly improving the seepage channels and reservoir utilization degree of the coalbed methane reservoir, providing a strong guarantee for later production increase; The results of the CH4 desorption effect of the 1-aminopropyl-3-methylimidazole grafted HZSM-5 molecular sieve on different coal samples are shown in Table 3;

[0040] Table 3 CH4 desorption effect of 1-aminopropyl-3-methylimidazole grafted HZSM-5 molecular sieve on different coal samples

[0041]

[0042] Example 4

[0043] (1) Preparation of amino-functionalized molecular sieve

[0044] The 13X molecular sieve (SiO₂ / Al₂O₃ = 2.6) was added to a 0.15 mol / L Zr(NO₃)₂ solution at a ratio of 15 mL / g, and ion exchange was carried out twice at 70 °C. Then, it was centrifuged and filtered, dried at 105 °C, and calcined at 500 °C for 6 hours to obtain Zr-doped 13X molecular sieve. The Zr-doped 13X molecular sieve was added to 100 mL of dilute nitric acid with a concentration of 0.5 mol / L, stirred in a water bath at 80 °C for 4 hours, and then the solid was filtered and washed with deionized water until neutral, and dried in an oven at 80 °C for 12 hours to obtain 13X molecular sieve containing a large amount of Si-OH. Finally, 1-aminoethyl-3-methylimidazole was grafted onto 13X through an ultrasonic-vibration step to obtain 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve;

[0045] (2) The composite transformation of 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve and fracturing fluid was implemented in the inclined well section using the sliding sleeve staged fracturing technology, aiming to reduce the bridge plug operation steps while performing multi-stage continuous fracturing;

[0046] At a laying concentration of 15 kg / m 3 the 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve was placed in a water-based fracturing fluid containing 3.0% KCl and 0.8% corrosion inhibitor, and stirred at room temperature for 30 min to obtain a uniform suspension system with a viscosity of about 35 mPa·s. The well section was divided into four sliding sleeve sections, and the length of each section was between 200 - 250 m. After installing the sliding sleeve, it was lowered into the well in a predetermined order and aligned with the target formation. During injection, the fracturing fluid containing the molecular sieve was injected into the wellbore at a flow rate of 6 m 3 / min. When the wellhead pressure gradually increased to 45 MPa, the first set of sliding sleeves was started. After continuous fracturing for 25 min, the next sliding sleeve was closed and then opened in sequence for the next stage of fracturing. During the entire operation process, the injection flow rate was continuously monitored and fine-tuned to 5 - 7 m 3 / min to adapt to the formation pressure and fracture extension situation, ensuring that the 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve was batchwise and deeply filled in multiple fractures. The total injection time for the four stages was about 120 min. After stopping the pump, the sliding sleeves were closed and locked, and the drainage sampling analysis showed that the 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve maintained a high proportion after backflow. The results of the CO₂ adsorption capacity of 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve at different equilibrium pressures are shown in Table 4;

[0047] Table 4 Effect of 1-aminoethyl-3-methylimidazole-Zr-13X molecular sieve on CO₂ adsorption capacity at different equilibrium pressures

[0048]

[0049] Example 5

[0050] (1) Preparation of Amino-functionalized Molecular Sieve

[0051] Using sodium silicate as the silicon source, cetyltrimethylammonium bromide (CTAB) as the template agent, and ethylenediamine as the amine source, NH2-SBA-16 molecular sieve was prepared by the direct synthesis method. Specifically, CTAB was dissolved in deionized water, and after stirring in a water bath at 40 °C for 1 hour, sodium silicate and ethylenediamine were added and stirred to form a homogeneous colloid. The molar ratio of the mixed sol was 0.2 (CTAB):1 (SiO2):0.02 (ethylenediamine):40 H2O. The pH value of the system was adjusted to about 10 with dilute sulfuric acid, and after continuing to stir for 0.5 hour, it was aged for 4 hours. The aged colloid was transferred into a stainless-steel autoclave and crystallized at 110 °C for 24 hours. After filtration, washing, and drying, the product was calcined in air at 550 °C for 6 hours to obtain NH2-SBA-16 molecular sieve;

[0052] (2) At a laying concentration of 55 kg / m 3 , NH2-SBA-16 molecular sieve was mixed with an aqueous fracturing fluid containing 1.5% sodium dodecyl sulfate and 2.0% hydroxypropyl guar gum in order to form a more perfect fracture support system under conditions of a higher concentration of molecular sieve and multi-stage segmentation. After stirring evenly at room temperature for 40 min, a horizontal section of about 2000 m was divided into six segments by using a combined bridge plug-sliding sleeve segmentation method: the first four segments were separated by drillable bridge plugs, and the last two segments were fractured by windowing using sliding sleeve tools. The entire fracturing process was carried out at an injection flow rate of 8 m 3 / min. The initial wellhead pressure was about 50 MPa. After each perforation or windowing was completed, the injection rate was adjusted in a range of 7 - 9 m 3 / min in a timely manner by monitoring the wellbore pressure and fracture extension indication, and it took about 180 min. During the process of multiple pressurized fractures and segmented potential tapping of the formation, NH2-SBA-16 molecular sieve was deeply migrated and dispersed in the newly formed fracture network, enhancing the fracture network conductivity. After the fracturing was completed, short-term liquid drainage was used in cooperation with bridge plug drilling and sliding sleeve closing and resetting. The final evaluation results showed that this multi-stage operation significantly increased the effective transformation volume, and the amino-functionalized molecular sieve was evenly deposited in different fracture segments, ultimately enhancing the CO2 adsorption effect of the target coalbed methane reservoir. The results are shown in Figure 3 , Table 5;

[0053] Table 5 Effect of NH2-SBA-16 Molecular Sieve on CO2 Adsorption Capacity under Different Equilibrium Pressures

[0054]

[0055]

[0056] Example 6

[0057] (1) Preparation of aminated molecular sieve

[0058] Using tetraethyl orthosilicate (TEOS) as the silicon source and CTAB as the template agent, organic silane amine was doped by the direct synthesis method. Add 2.7 g of CTAB and 10 mL of 3-aminopropyltriethoxysilane into a conical flask (250 mL), then add 125 mL of deionized water and stir until completely dissolved. Subsequently, slowly dropwise add 33 mL of 25% ammonia water and slowly drip 14 mL of TEOS; transfer the mixed solution to a hydrothermal reaction kettle after stirring at 35 °C for 30 min and crystallize at 110 °C for 52 hours; wash the filtered solid with distilled water until the pH = 7 and dry at 120 °C for 12 hours; calcine at 550 °C for 6 hours at a heating rate of 1 °C / min to obtain organosilane aminated Silicalite-1 molecular sieve;

[0059] (2) At a laying concentration of 10 kg / m 3 , add the organosilane aminated Silicalite-1 molecular sieve into the water-based fracturing fluid containing 2.0% KCl and 1.0% guar gum, and treat it by high-speed stirring at room temperature for 40 min to ensure that the molecular sieve particles are fully wetted in the liquid phase and form a uniform suspension dispersion. Subsequently, lower the jet bit and the special hydraulic jet tool into the target well section, aim at the sandstone layer to be transformed, and continuously inject the mixed fracturing fluid at a flow rate of 5 m 3 / min using a ground high-pressure pump. When the wellhead pressure gradually rises to about 35 MPa, start the high-pressure nozzle of the jet bit, and the jet flow generates directional erosion on the wellbore wall underground and induces crack propagation. The entire jet fracturing process lasts about 60 min, and the flow rate at the wellhead is fine-tuned by 4 - 6 m 3 / min at different times to adapt to the formation stress change and maintain an appropriate jet impact intensity. Once the high-pressure erosion forms a crack channel, the organosilane aminated Silicalite-1 molecular sieve migrates with the jet flow and deposits inside the newly formed cracks, enhancing the support and plugging effects inside the cracks. After the operation, both conventional liquid drainage and well logging analysis show that an obvious multi-porous channel structure is formed in the near-wellbore zone of the wellbore, the aminated molecular sieve is evenly distributed, improving the fracture conductivity, and at the same time enhancing the subsequent CH4 recovery potential. The results of the CH4 desorption effect of the organosilane aminated Silicalite-1 molecular sieve on different coal samples are shown in Figure 4 and Table 6;[[ID=!7]]

[0060] Table 6 CH4 desorption effect of organosilane aminated Silicalite-1 molecular sieve on different coal samples

[0061]

[0062]

Claims

1. Application of an aminated molecular sieve in enhancing coalbed methane extraction by CO2-ECBM assisted hydraulic fracturing, characterized in that: Inject the aminated molecular sieve into the coalbed methane reservoir together with the fracturing fluid to support the fracture network structure formed by hydraulic fracturing, improve the CO2 sequestration efficiency of the coal seam during the subsequent implementation of CO2-ECBM for secondary enhanced coalbed methane production, and achieve the purpose of increasing CH4 production capacity; Among them, the aminated molecular sieve selects a molecular sieve with a specific surface area of 500-2000 m 2 / g as the matrix, and amino functional groups are introduced on the surface or inside the pores of the molecular sieve by the equal-volume impregnation method, the amino grafting method or the bottom-up amination synthesis method, and the reaction product is washed, dried and calcined to obtain the product.

2. The application according to claim 1, wherein: The molecular sieve is selected from ZSM-5 molecular sieve, HZSM-5 molecular sieve, SBA-16 molecular sieve, Silicalite-1 molecular sieve, TS-1 molecular sieve, X-type zeolite, Y-type zeolite, SAPO-34 molecular sieve.

3. The application according to claim 1, wherein: The inorganic amine solution used in the equal-volume impregnation method is ammonium chloride solution or ammonia water; the organic amine solution is selected from methylamine solution, ethylamine solution, ethanolamine solution, n-propylamine solution, toluidine solution.

4. The application according to claim 1, characterized in that: The amino-functionalized ionic liquid used in the amino grafting method is selected from 1-aminoethyl-3-methylimidazole, 1-aminopropyl-3-methylimidazole cationic ionic liquid, bis(trifluoromethanesulfonyl)imide anionic ionic liquid.

5. The application according to claim 1, characterized in that: The amine source used in the bottom-up amination synthesis method is selected from tetrapropylammonium hydroxide, triethanolamine, piperazine, ethylenediamine, 3-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane.

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