Preparation method and application of reinforcing agent for deep coal bed gas well cementation prepad fluid

Abstract

The preparation method comprises the following steps: mixing epoxy resin, acetylacetone, triethylamine and deionized water, carrying out a stirring reaction at 80-90 DEG C for 2-4 h, then adding adipic acid for several times, keeping the temperature, continuing the reaction for 6-12 h, carrying out reduced pressure distillation to remove acetylacetone, and carrying out reduced pressure distillation to obtain a reinforcing agent for deep coal bed gas well cementation prepad fluid; an intermediate product M1 is obtained; weighing the intermediate product M1, adding a silane coupling agent, a dispersing agent, sodium silicate, calcium salt and aluminate into the intermediate product M1 in a stirring state, stirring for 5-10 minutes, standing, and reacting at 35-40 DEG C to obtain a hydrated nano material intermediate product M2; and weighing the intermediate product M2, adding fibrous sepiolite into the intermediate product M2, and uniformly mixing. The reinforcing agent can enable the surface of coal rock to be wetted and modified to be hydrophilic, and when the reinforcing agent is used for deep coal bed gas well cementation prepad fluid, the well cementation quality of a deep coal bed gas horizontal well is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas wells, and in particular to a preparation method and application of an enhancer for deep coalbed methane cementing pre-fluid. Background Art

[0002] Coalbed methane, as a mineral resource associated with coal, is an unconventional natural gas and a clean, high-quality energy source. my country is rich in coalbed methane resources and has enormous potential for recoverable reserves, making it an important supplement to the country's energy supply. Deep coalbed methane extraction is primarily based on horizontal wells. Deep coalbed methane reservoirs are characterized by complex geological structures and high temperature gradients. The coal rock matrix is ​​primarily composed of organic matter, and the surface exhibits strong oil-wet and hydrophobic properties, resulting in extremely poor interfacial bonding with conventional cement slurry (hydrophilic). This results in insufficient bonding strength between the cementing interface, which can easily lead to problems such as wellbore instability, gas channeling, and annular pressure. In addition, the low mechanical strength of coal rock makes it easy to form a "big-bellied" wellbore during drilling, which intensifies the requirements for wellbore wetting modification and flushing stability of the pre-fluid. Currently, CBM cementing faces major challenges, including coal-rock collapse, strong adhesion of the drilling fluid's mudcake, difficulty flushing, low interface flushing efficiency, difficulty ensuring the quality of the reservoir's oil-wet interface cementation, irregular wellbore diameters caused by alternating coal-mud and rock inclusions, limited operation flow rates due to the high stress sensitivity of the coal rock, low displacement efficiency, and high contamination of the drilling mud with the cement slurry. These issues present numerous safety hazards during cementing operations. For CBM cementing, traditional cementing pre-fluid systems (such as conventional polymer pre-fluids and low-density drilling fluids) struggle to meet these requirements. For example, wettability mismatches prevent effective changes in the wetting state of the coal-rock surface, leading to micro-annuli at the interface between the cement slurry and the coal rock. Furthermore, these systems lack rheological parameters that match those of the drilling fluid and cement slurry, resulting in low displacement efficiency and a high risk of residual contamination.

[0003] Patent CN112521924A discloses a pre-pad fluid and a preparation method thereof. By adding chloroprene rubber latex as a surface modification material to the pre-pad fluid, the high molecular weight polymer in the system can play a synergistic role with the surfactant, and can tightly adsorb the coal core and densely spread on the surface of the coal core, so that the surface modification of the coal core is uniform, and the bonding quality of the cementing is effectively improved. As a result, the coalbed methane well cementing pre-pad fluid provided by the present invention not only has good compatibility with drilling fluid and cement slurry, but also has a good improvement in the surface wettability of coal, so that the coal core has excellent water wettability and improves the bonding strength of the second interface of cementing. All performance indicators meet the requirements of on-site cementing. However, it does not have a certain sealing effect on the micro-gaps of the coal seam, and the large amount of pre-pad fluid loss is easy to affect the later development.

[0004] In Zhao Qi's "Study on a Pre-Flush System for Improving the Secondary Interface Bonding Quality of Multi-Coalbed Methane Well Cementing," he developed a composite interface enhancer with the goal of improving the wettability and scour resistance of coal rock surfaces. After modification of the coal seam interface, the wetting angle remained at 0°, and after 30 minutes of scouring, the wetting angle remained below 30°, demonstrating excellent wettability and scour resistance. By optimizing the selection of latently active gelling materials, suspension stabilizers, and fluid loss additives, this system was developed into a two-interface enhanced pre-flush system that improves the quality of coal seam cementing and isolation. The system exhibits excellent fluid loss and sedimentation stability, but the retarder has a narrow applicable temperature range and cannot fully meet the temperature requirements of deep coalbed methane reservoirs in horizontal sections.

[0005] Therefore, it is very critical to effectively improve the hydrophilicity of the coal rock surface, the interface bonding strength, the flushing efficiency of the drilling fluid filter cake, the replacement efficiency of the drilling fluid in the horizontal section, and the cementing quality of deep coalbed methane horizontal wells in deep coalbed methane cementing. Summary of the Invention

[0006] In response to the defects of the existing technology, the present invention provides a preparation method and application of an enhancer for deep coalbed methane cementing pre-fluid. The prepared enhancer is an organic composite enhancer, which effectively solves the problem of low bonding strength between the two interfaces of coalbed cementing, can significantly shorten the waiting time for cementing construction, reduce construction risks, and lower construction costs.

[0007] A method for preparing an enhancer for deep coalbed methane cementing pre-fluid comprises the following steps: Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, stir and react at 80-90°C for 2-4 hours, then add adipic acid in portions, maintain the temperature and continue to react for 6-12 hours, and remove acetylacetone by distillation under reduced pressure to obtain intermediate product M1, which is a hydrophilic epoxy resin; Step 2: Weigh the intermediate product M1, add a silane coupling agent, a dispersant, sodium silicate, a calcium salt, and an aluminate thereto while stirring, stir for 5-10 minutes, and then allow to stand and react at 35-40° C. to obtain a hydrated nanomaterial intermediate product M2; Step 3: Weigh the intermediate product M2, add fibrous sepiolite thereto, and mix well.

[0008] Preferably, the particle size D of the hydrated nanomaterial intermediate product M2 is 50 The wavelength is 700-850 nm and the mass concentration is 30%-35%.

[0009] Preferably, in step 1, the weight ratio of the epoxy resin, acetylacetone, and triethylamine is (75-90): (12.5-25.5): (0.5-3); the weight ratio of the deionized water and hexamethylenediamine is (150-200): (2-5); and the total weight of the epoxy resin, acetylacetone, and triethylamine accounts for 30-45% of the weight of the deionized water.

[0010] Preferably, in step 2, the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminum salt is (0.55-1): (2-5): (15-35): (25-35.5): (25.5-35.6); the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate is 8.5-35% of the weight of the intermediate product M1.

[0011] Preferably, in step 3, the weight ratio of the intermediate product M2 to the fibrous sepiolite is 100:(10-25).

[0012] Preferably, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; the calcium salt is at least one of tricalcium silicate or dicalcium silicate; the aluminate is at least one of tricalcium aluminate or dicalcium aluminate; and the length of the fibrous sepiolite is 1-3 mm.

[0013] Preferably, the stirring rate in step 1 is 200-300 r / min; and the stirring rate in step 2 is 30-50 r / min.

[0014] The enhancer prepared by the preparation method of the present invention is used in deep coalbed methane cementing pre-fluid.

[0015] Preferably, the deep coalbed methane cementing prefluid is composed of the following raw materials in parts by weight: 100 parts of water, 25-120 parts of quartz sand, 5-25 parts of reinforcing agent, 0.5-2 parts of suspension stabilizer, and 0.2-0.6 parts of drag reducer.

[0016] Preferably, the particle size of the quartz sand is 100-200 mesh; the suspension stabilizer is an AMPS-AM type suspension stabilizer; and the drag reducer is a ketone-aldehyde condensation polymer.

[0017] Advantages of the present invention: (1) The enhancer provided by the present invention adsorbs the hydroxyl groups on the surface of the coal rock through its oleophilic groups, wherein the ether groups as the main hydrophilic groups are oriented outward to form a hydrophilic layer, thereby modifying the wettability of the coal rock surface from oleophilic to hydrophilic; (2) When the intermediate product M1 hydrophilic epoxy resin and the silane coupling agent in the reinforcing agent are used in combination, the silane coupling agent can protect some of the hydrophilic epoxy resin molecules around it from separating from the coal rock surface under the action of scouring shear force, thereby improving the long-term wetting modification effect of the coal rock surface; (3) When the enhancer is used in deep coalbed methane cementing pre-fluid, it effectively improves the hydrophilicity of the coal rock surface to enhance the interface bonding strength with the cement sheath, thereby improving the performance of the deep coalbed methane cementing pre-fluid and thus improving the cementing quality of deep coalbed methane horizontal wells; (4) The raw materials for synthesizing the enhancer are widely available, low in cost, mature in preparation conditions, easy to use, and have good prospects for promotion and application. DETAILED DESCRIPTION

[0018] The suspension stabilizer used in the present invention is an AMPS-AM suspension stabilizer, which is a copolymer suspension stabilizer of 2-acrylamido-2-methylpropanesulfonic acid and acrylamide. It is prepared by a free radical aqueous solution polymerization method. Specifically, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylamide (AM) are used as comonomers, a mixed monomer with a molar ratio of AMPS to AM of 2:1 is added to deionized water, and the total mass of the mixed monomer is 25% of the mass of the deionized water. Potassium persulfate as an initiator is added in an amount of 0.6% of the total mass of the mixed monomer and deionized water. The pH value of the solution is adjusted to 7, and the reaction is carried out at 65° C. for 8 hours. The obtained product is a copolymer suspension stabilizer of 2-acrylamido-2-methylpropanesulfonic acid and acrylamide. The drag reducer used was ketone-aldehyde condensate USZ produced by Weihui Chemical Co., Ltd. The dispersant used is dispersant AKN-2290.

[0019] Example 1 A method for preparing an enhancer for deep coalbed methane cementing pre-fluid, characterized by comprising the following steps: Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, stir and react at 80° C. for 2 hours at a stirring rate of 200 r / min, then add adipic acid in two portions, maintain the temperature and continue to react for 6 hours, and remove acetylacetone by distillation under reduced pressure to obtain an intermediate product M1; wherein the weight ratio of the epoxy resin, acetylacetone, and triethylamine is 75:12.5:0.5, the weight ratio of the deionized water and hexamethylenediamine is 200:5, and the total mass of the epoxy resin, acetylacetone, and triethylamine accounts for 30% of the weight of the deionized water; Step 2: Weigh the intermediate product M1, add silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate thereto under stirring, stir at a stirring rate of 50 r / min for 10 minutes, then let it stand and react at 40°C until the particle size D of the obtained hydrated nanomaterial intermediate product M2 is 50 The particle size is 700-850 nm and the mass concentration is 30%; the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt and aluminum salt is 0.55:3:35:25:30; the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt and aluminate is 25% of the weight of the intermediate product M1; the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; the calcium salt is tricalcium silicate; and the aluminate is tricalcium aluminate; Step 3: Weigh the intermediate product M2, add fibrous sepiolite with a length of 1-3 mm thereto, wherein the fibrous sepiolite accounts for 10% of the weight of the intermediate product M2, and mix them evenly. The obtained reinforcing agent is recorded as H1.

[0020] Example 2 In step 2, the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate is 30% of the weight of the intermediate product M1; the fibrous sepiolite accounts for 15% of the weight of the intermediate product M2. Other conditions are the same as in Example 1, and the obtained reinforcing agent is recorded as H2.

[0021] Example 3 In step 2, the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate is 35% of the weight of the intermediate product M1; the fibrous sepiolite accounts for 20% of the weight of the intermediate product M2. Other steps are the same as in Example 1. The obtained reinforcing agent is recorded as H3.

[0022] Example 4 A method for preparing an enhancer for deep coalbed methane cementing pre-fluid, characterized by comprising the following steps: Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, stir and react at 90° C. for 2 hours at a stirring rate of 300 r / min, then add adipic acid in two portions, maintain the temperature and continue to react for 6 hours, and remove acetylacetone by distillation under reduced pressure to obtain an intermediate product M1; wherein the weight ratio of the epoxy resin, acetylacetone, and triethylamine is 90:25.5:3, the weight ratio of the deionized water and hexamethylenediamine is 150:2, and the total mass of the epoxy resin, acetylacetone, and triethylamine accounts for 45% of the weight of the deionized water; Step 2: Weigh the intermediate product M1, add silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate thereto under stirring, stir at a stirring rate of 30 r / min for 5 minutes, then let it stand and react at 35°C until the particle size D of the obtained hydrated nanomaterial intermediate product M2 is50 The particle size of the intermediate product M1 is 700-850 nm and the mass concentration is 35%; the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt and aluminum salt is 1:2:15:35.5:25.5; the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt and aluminate is 8.5% of the weight of the intermediate product M1; the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; the calcium salt is dicalcium silicate; the aluminate is dicalcium aluminate with a particle size of 2.5; Step 3: Weigh the intermediate product M2, add fibrous sepiolite with a length of 1-3 mm thereto, wherein the fibrous sepiolite accounts for 25% of the weight of the intermediate product M2, and mix them evenly. The obtained reinforcing agent is recorded as H4.

[0023] Example 5 A method for preparing an enhancer for deep coalbed methane cementing pre-fluid, characterized by comprising the following steps: Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, stir and react at 85° C. for 4 hours at a stirring rate of 250 r / min, then add adipic acid in three portions, maintain the temperature and continue the reaction for 12 hours, and remove acetylacetone by reduced pressure distillation to obtain an intermediate product M1; wherein the weight ratio of the epoxy resin, acetylacetone, and triethylamine is 80:20:2, the weight ratio of the deionized water and hexamethylenediamine is 200:4, and the total mass of the epoxy resin, acetylacetone, and triethylamine accounts for 40% of the weight of the deionized water; Step 2: Weigh the intermediate product M1, add silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate thereto under stirring, stir at a stirring rate of 50 r / min for 8 minutes, then let it stand and react at 40°C until the particle size D of the obtained hydrated nanomaterial intermediate product M2 is 50 The particle size is 700-850 nm and the mass concentration is 30%; the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt and aluminum salt is 0.55:5:25:30:35.6; the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt and aluminate is 25% of the weight of the intermediate product M1; the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; the calcium salt is tricalcium silicate; and the aluminate is tricalcium aluminate; Step 3: Weigh the intermediate product M2, add fibrous sepiolite with a length of 1-3 mm thereto, wherein the fibrous sepiolite accounts for 10% of the weight of the intermediate product M2, and mix them evenly. The obtained reinforcing agent is recorded as H5.

[0024] Example 6 The enhancer prepared in Example 1 was used to prepare a deep coalbed methane cementing prefluid, specifically as follows: the following raw materials in parts by weight were taken: 100 parts of water, 30 parts of quartz sand with a particle size of 100 mesh, 20 parts of the enhancer, 2 parts of the suspension stabilizer, and 0.5 parts of the drag reducer; the mixture was mixed and stirred evenly at a speed of 4000 rpm to obtain a deep coalbed methane cementing prefluid, which was recorded as Hd1.

[0025] Example 7 The enhancer prepared in Example 2 was used to prepare a deep coalbed methane cementing prefluid, specifically as follows: the following raw materials in parts by weight were taken: 100 parts of water, 30 parts of quartz sand with a particle size of 100 mesh, 25 parts of enhancer, 2 parts of suspension stabilizer, and 0.5 parts of drag reducer; the mixture was mixed and stirred evenly at a speed of 4000 rpm to obtain a deep coalbed methane cementing prefluid, which was recorded as Hd2.

[0026] Example 8 The enhancer prepared in Example 3 was used to prepare a deep coalbed methane cementing prefluid, specifically as follows: the following raw materials in parts by weight were taken: 100 parts of water, 120 parts of quartz sand with a particle size of 200 mesh, 20 parts of the enhancer, 2 parts of the suspension stabilizer, and 0.2 parts of the drag reducer; the mixture was mixed and stirred evenly at a speed of 4000 rpm to obtain a deep coalbed methane cementing prefluid, which was recorded as Hd3.

[0027] Example 9 The enhancer prepared in Example 4 was used to prepare a deep coalbed methane cementing prefluid, specifically as follows: the following raw materials in parts by weight were taken: 100 parts of water, 60 parts of quartz sand with a particle size of 200 mesh, 15 parts of enhancer, 1 part of suspension stabilizer, and 0.6 parts of drag reducer; mixed them, and stirred evenly at a speed of 4000 rpm to obtain a deep coalbed methane cementing prefluid, recorded as Hd4.

[0028] Example 10 The enhancer prepared in Example 5 was used, and other aspects were the same as in Example 1. The obtained deep coalbed methane cementing pre-fluid was recorded as Hd5.

[0029] Comparative Example 1 No silane coupling agent was added, and other procedures were the same as in Example 1. The prepared reinforcing agent was denoted as S1.

[0030] Comparative Example 2 Step 1 was omitted, and deionized water was used in place of the intermediate product M1 in step 2. Other steps were the same as in Example 1. The prepared enhancer was designated as S2.

[0031] Comparative Example 3 Without step 3, the other steps are the same as those in Example 1, and the prepared enhancer is recorded as S3.

[0032] Comparative Example 4 The enhancer obtained in Comparative Example 1 was used, and the other conditions were the same as in Example 6. The prepared pre-fluid was denoted as Sd1.

[0033] Comparative Example 5 The enhancer obtained in Comparative Example 2 was used, and the other conditions were the same as in Example 6. The prepared pre-fluid was denoted as Sd2.

[0034] Comparative Example 6 The enhancer obtained in Comparative Example 3 was used, and the other conditions were the same as in Example 6. The prepared pre-fluid was denoted as Sd3.

[0035] Comparative Example 7 No enhancer was added, and other procedures were the same as in Example 6. The prepared prepad solution was recorded as Sd4.

[0036] Performance testing 1. Particle size detection The experiments were conducted at room temperature. The particle size and distribution of the intermediate product M2 during the preparation of each enhancer were determined using a Mastersizer 3000 laser particle size analyzer. Each group of experiments was tested three times, and the final results were averaged. Table 1 Test results of particle size distribution of reinforcing agent As can be seen from Table 1, the main active ingredients of the enhancers prepared in various examples and comparative examples are all nanometer-scale at room temperature, indicating that nano-hydrated materials are formed.

[0037] 2. Hydrophilic modification ability To improve cementing quality during on-site cementing, a pre-fluid system is usually injected according to the designed usage volume, followed by cement slurry injection according to the designed volume. Therefore, the coal rock surface can be modified to improve the bonding quality between the cement sheath and the coal seam. An experimental coal sample was taken, and the upper and lower surfaces were smoothed with sandpaper. Using an optical contact angle / interfacial tension meter, the surface wetting angle of the experimental coal rock was measured to be greater than 90°. The titration liquid was then replaced with a 25wt% enhancer at different locations on the same coal sample, and the wetting angle was measured and compared with the distilled water titration result. The test procedure is as follows: a coal sample is secured with a clamp and placed in a sample solution of a certain concentration, stirred by a magnetic stirrer. The upper and lower surfaces of the coal block are parallel to the liquid surface, simulating the flushing process of the pre-pad fluid on the coal seam surface. After 10 minutes of flushing, the surface is removed and air-dried. Three measurements are taken and the average value is calculated to determine the wetting angle (using the enhancer titration method). According to cementing procedures, after the pre-pad fluid wets and modifies the coal seam surface, it is likely to be displaced by the cement slurry. Whether the surfactant molecules attached to the coal seam surface remain intact after flushing with the cement slurry system, and whether the degree of modification has changed, is crucial. Therefore, after testing the wetting angle (using the enhancer titration method), the simulated flushing process described above is repeated. The results are shown in Table 2. Table 2 Hydrophilic modification ability test results Table 2 shows that the lipophilic groups in the reinforcing agent bind to organic matter on the coal rock surface, causing it to adsorb evenly on the surface, altering the wettability of the coal rock from lipophilic to hydrophilic. The degree of surface modification by the reinforcing agent varies with the hydrophilic epoxy resin content in the intermediate product M1. Comparative Example 1 demonstrates that the silane coupling agent effectively improves the hydrophilicity of the washed coal sample. Without the silane coupling agent, the coal rock surface begins to return to an oil-wet state after 10 minutes of washing, indicating the ineffectiveness of the reinforcing agent's surface modification. Comparative Example 2 demonstrates that the surface modification of the coal rock also fails when the intermediate product M1 is not present.

[0038] 3. Compatibility of cementing pre-fluid and cement slurry - water loss test Prepare deep coalbed methane cementing pre-fluid and cement slurry. The density of the cement slurry system is 1.67 g / cm -3 The cement slurry formula (by weight) is as follows: 100 parts Jiahua G-grade cement + 30 parts silica sand + 2.5 parts fluid loss additive + 0.1 part defoamer + 55 parts water (the fluid loss additive is multi-polymer G310 from Weihui Chemical Co., Ltd., and the defoamer is defoamer DF-900). The two are mixed in different volume ratios, stirred thoroughly, and then poured into a normal pressure viscosifier. Cured at 90°C for 30 minutes, the mixture was tested for fluid loss performance at 60°C and 6.9 MPa using a high-temperature and high-pressure fluid loss instrument. The experimental results are shown in Table 3. Table 3 Compatibility and water loss test results of cementing pre-pad fluid and cement slurry Table 3 shows that as the prepad volume ratio increases, the 30-minute water loss of the mixed slurry decreases slightly, indicating good compatibility between the two in terms of fluid loss performance. The comparative example demonstrates that the addition of the hydrophilic resin intermediate M1 and fibrous sepiolite to the enhancer has a certain impact on the fluid loss of the system. Their addition improves the fluid loss performance of the system by facilitating the formation of a dense filter cake.

[0039] 4. Cementing Fluid Compatibility with Cement Slurry - Thickening Time Test As described above, the compatibility-water loss test was conducted to prepare deep coalbed methane cementing pre-pad fluid and cement slurry. The cement slurry mixed with pre-pad fluid in different volume ratios was subjected to a thickening time test in accordance with the national standard "Oil Well Cement" (GB / T 10238-2015). The two were mixed in different volume ratios, stirred thoroughly, and then poured into a high-temperature and high-pressure thickener. The test was conducted at 110°C and 45 MPa. The thickening time of the cement slurry without pre-pad fluid was also compared and analyzed. If the thickening time of the mixed slurry is not less than that of the cement slurry, it indicates that the two are compatible. The experimental results are shown in Table 4 below. Table 4 Compatibility test results of cementing pre-pad fluid and cement slurry - thickening time Table 4 shows that after mixing the deep coalbed methane cementing pre-pad fluid with the cement slurry, the thickening time of the cement slurry did not decrease, indicating good compatibility between the two. Experiments with a 50:50 mixing volume ratio show that the pre-pad system without a reinforcing agent (Comparative Example 7) has little effect on the thickening time of the mixed system. Comparative Example 5 demonstrates that the addition of the intermediate M1 hydrophilic resin in the reinforcing agent has a certain impact on the thickening performance of the system.

[0040] 5. Cementing pre-fluid and cement slurry compatibility - compressive strength test Deep coalbed methane cementing pre-pad fluid and cement slurry were prepared as described above for compatibility and water loss testing. Cement slurries mixed with different volume ratios of pre-pad fluid were prepared according to GB / T 19139-2012, "Test Methods for Oil Well Cement." These samples were cured in a 60°C water bath for 24, 48, and 72 hours, and their compressive strength was measured using a compressive strength testing machine. The effects of different interface-strengthening pre-pad fluid dosages on cement strength were compared with the original cement slurry to analyze the effects. The experimental results are shown in Table 5. Table 5 Compatibility and compressive strength test results of cementing pre-pad fluid and cement slurry Table 5 shows that the compressive strength of the cement slurry system decreases as the volume ratio of the prepad fluid in the mixed slurry increases. In the "big belly" wellbore, when the displacement efficiency cannot reach 100%, a 25:75 mix ratio, if it is at least 75%, can ensure good strength within two days. If the displacement efficiency is at least 50%, a 50:50 mix ratio can also ensure strength above 3 MPa within 72 hours, effectively meeting the performance requirements of coalbed methane cementing operations.

[0041] 6. Compatibility of cementing pre-fluid and cement slurry - Interface bonding strength test Deep coalbed methane cementing pre-pad fluid and cement slurry were prepared as described above for the compatibility-water loss test. Cement slurries mixed with pre-pad fluid at different volume ratios were poured into cylindrical steel molds with a bottom diameter of 6 cm and a height of 5 cm. The molds were then placed in a 60°C water bath and cured for 24, 48, and 72 hours. The maximum shear force at the cement block-steel mold interface, i.e., the cement-stone interfacial bond strength, was measured. Table 6 Compatibility of cementing pre-fluid and cement slurry - interface bonding strength test results Table 6 shows that as the volume ratio of the prepad in the mixed slurry increases, the interfacial bonding strength of the cement slurry system gradually decreases. In the "big belly" wellbore, if the displacement efficiency is not less than 75%, a 25:75 mixing ratio can ensure a certain interfacial bonding strength within two days. If the displacement efficiency is not less than 50%, a 50:50 mixing ratio can ensure a certain interfacial bonding strength within 72 hours, which can effectively meet the performance requirements of some coalbed methane cementing operations and ensure the safety of cementing operations.

Claims

1. A method for preparing an enhancer for deep coalbed methane cementing pre-fluid, characterized by: The following steps are involved: Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, stir and react at 80-90°C for 2-4 hours, then add adipic acid in portions, maintain the temperature and continue to react for 6-12 hours, and remove acetylacetone by distillation under reduced pressure to obtain intermediate product M1; Step 2: Weigh the intermediate product M1, add a silane coupling agent, a dispersant, sodium silicate, a calcium salt, and an aluminate thereto while stirring, stir for 5-10 minutes, and then allow to stand and react at 35-40° C. to obtain a hydrated nanomaterial intermediate product M2; Step 3: Weigh the intermediate product M2, add fibrous sepiolite thereto, and mix well.

2. The method for preparing a reinforcing agent for deep coalbed methane cementing pre-fluid according to claim 1, characterized in that: The particle size D of the hydrated nanomaterial intermediate product M2 50 The wavelength is 700-850 nm and the mass concentration is 30%-35%.

3. The method for preparing a reinforcing agent for deep coalbed methane cementing pre-fluid according to claim 1, characterized in that: In step 1, the weight ratio of the epoxy resin, acetylacetone, and triethylamine is (75-90): (12.5-25.5): (0.5-3); the weight ratio of the deionized water and hexamethylenediamine is (150-200): (2-5); and the total weight of the epoxy resin, acetylacetone, and triethylamine accounts for 30-45% of the weight of the deionized water.

4. The method for preparing a reinforcing agent for deep coalbed methane cementing pre-fluid according to claim 3, characterized in that: In step 2, the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminum salt is (0.55-1): (2-5): (15-35): (25-35.5): (25.5-35.6); the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate is 8.5-35% of the weight of the intermediate product M1.

5. The method for preparing a reinforcing agent for deep coalbed methane cementing pre-fluid according to claim 4, characterized in that: In step 3, the weight ratio of the intermediate product M2 to the fibrous sepiolite is 100:(10-25).

6. The method for preparing a reinforcing agent for deep coalbed methane cementing pre-fluid according to claim 5, characterized in that: The silane coupling agent is γ-methacryloxypropyltrimethoxysilane; the calcium salt is at least one of tricalcium silicate or dicalcium silicate; the aluminate is at least one of tricalcium aluminate or dicalcium aluminate; and the length of the fibrous sepiolite is 1-3 mm.

7. The method for preparing a reinforcing agent for deep coalbed methane cementing pre-fluid according to claim 1, characterized in that: The stirring rate in step 1 is 200-300 r / min; the stirring rate in step 2 is 30-50 r / min.

8. Use of the enhancer prepared by the preparation method according to any one of claims 1 to 7 in deep coalbed methane cementing pre-fluid.

9. The application according to claim 8, characterized in that: The deep coalbed methane cementing pre-fluid is composed of the following raw materials in parts by weight: 100 parts of water, 25-120 parts of quartz sand, 5-25 parts of reinforcing agent, 0.5-2 parts of suspension stabilizer, and 0.2-0.6 parts of drag reducer.

10. The application according to claim 9, characterized in that: The particle size of the quartz sand is 100-200 meshes; the suspension stabilizer is an AMPS-AM type suspension stabilizer; and the drag reducer is a ketone-aldehyde condensation polymer.

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