Preparation method and application of a reinforcing agent for deep coal bed methane well cementing prepad fluid

Abstract

The application discloses a preparation method and application of an enhancer for deep coal bed gas well cementing preflush fluid, and the preparation method comprises the following steps: mixing epoxy resin, acetylacetone, triethylamine and deionized water, stirring and reacting at 80-90 DEG C for 2-4 h, then adding adipic acid in batches, keeping the temperature and continuously reacting for 6-12 h, removing acetylacetone through reduced pressure distillation, and obtaining an intermediate product M1; weighing the intermediate product M1, adding a silane coupling agent, a dispersant, sodium silicate, a calcium salt and an aluminate to the intermediate product M1 in a stirring state, stirring for 5-10 min, then standing and reacting at 35-40 DEG C, to obtain a hydrated nanometer material intermediate product M2; weighing the intermediate product M2, and adding fibrous sepiolite to the intermediate product M2 and uniformly mixing. The enhancer can modify the wettability of a coal rock surface into hydrophilicity, and when the enhancer is used for deep coal bed gas well cementing preflush fluid, the well cementing quality of a deep coal bed gas horizontal well is improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well technology, specifically to a method for preparing and applying an enhancer for pre-solidification fluid in deep coalbed methane wells. Background Technology

[0002] Coalbed methane (CBM), a by-product of coal mining, is an unconventional natural gas and a clean, high-quality energy source. my country possesses abundant CBM resources with enormous recoverable reserves, making it a crucial supplement to the country's energy supply. Deep CBM extraction primarily utilizes horizontal wells. Deep CBM reservoirs are characterized by complex geological structures, high temperature gradients, and a coal matrix dominated by organic matter with a strongly oleophilic and hydrophobic surface, resulting in extremely poor interfacial bonding with conventional cement slurry (which is hydrophilic). This leads to insufficient cementing strength at the interface, easily causing wellbore instability, gas channeling, and annular pressure issues. Furthermore, the low mechanical strength of the coal and rock formations during drilling easily creates a "bulge" wellbore, exacerbating the requirements for wellbore wetting modification and scour stability from the pre-flush fluid. Currently, coalbed methane cementing mainly faces problems such as coal and rock collapse, strong adhesion of drilling fluid mud cake, difficulty in flushing, low interface flushing efficiency, difficulty in ensuring the cementing quality of the reservoir's oleophilic interface, irregular well diameter caused by alternating coal and mud inclusions, limited construction displacement due to the high stress sensitivity of coal and rock, low displacement efficiency, and strong contamination of cement slurry by drilling mud, posing numerous safety hazards during cementing operations. For coalbed methane cementing, traditional cementing pre-fluid systems (such as conventional polymer-based pre-fluids and low-density drilling fluids) are insufficient to meet the requirements. For example, there are issues such as wettability mismatch, inability to effectively change the wetting state of the coal and rock surface, resulting in micro-annular gaps at the cement slurry-coal-rock interface; and mismatch with the rheological parameters of drilling fluid and cement slurry, resulting in low displacement efficiency and easy residual contamination.

[0003] Patent CN112521924A discloses a pre-filling fluid and its preparation method. By adding chloroprene latex as a surface modifier to the pre-filling fluid, the polymer in this system can play a synergistic role with the surfactant, which can tightly adsorb the coal core and densely spread it on the surface of the coal core, making the surface modification of the coal core uniform and effectively improving the cementing quality. Thus, the pre-filling fluid for coalbed methane well cementing provided by this invention not only has good compatibility with drilling fluid and cement slurry, but also has a good improvement on the surface wettability of coal, giving the coal core excellent water wettability and improving the cementing strength of the second interface of cementing. All performance indicators meet the requirements of field cementing. However, it does not have a certain sealing effect on the micro-fractures in the coal seam, and the leakage of the pre-filling fluid is relatively large, which can easily affect the later development.

[0004] In Zhao Qi's research on "Research on Pre-flush Fluid System for Improving the Bonding Quality of Cementing Interfaces in Multi-Coalbed Methane Wells," a composite interface enhancer was developed with the aim of improving the wetting modification and erosion resistance of the coal and rock surfaces. After modifying the coal seam interface, the wetting angle is 0°, and after 30 minutes of erosion, the wetting angle remains less than 30°, exhibiting excellent wetting modification and erosion resistance. This system, through the optimal selection of latently active cementing materials, suspension stabilizers, and fluid loss reducing agents, constructs a two-interface enhanced pre-flush fluid system to improve the bonding and sealing quality of coal seams. It exhibits good filtration and settling stability; however, the applicable temperature range of this retarder is relatively small and cannot fully meet the temperature requirements of deep coalbed methane horizontal reservoir sections.

[0005] Therefore, it is crucial to effectively improve the hydrophilicity of coal and rock surfaces, the interfacial bonding strength, the flushing efficiency of drilling fluid filter cake, and the displacement efficiency of drilling fluid in horizontal sections during cementing of deep coalbed methane wells, thereby enhancing the cementing quality of horizontal wells in deep coalbed methane. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing and applying an enhancer for pre-cementing fluid in deep coalbed methane cementing. The prepared enhancer is an organic composite enhancer, which effectively solves the problem of low bonding strength at the interface between the two sides of coalbed methane cementing, significantly shortens the cementing time, reduces construction risks, and lowers construction costs.

[0007] A method for preparing an enhancer for cementing pre-fill fluid in deep coalbed methane includes the following steps:

[0008] Step 1: Mix epoxy resin, acetylacetone, triethylamine and deionized water, stir and react at 80-90℃ for 2-4 hours, then add adipic acid in portions, maintain the temperature and continue to react for 6-12 hours, remove acetylacetone by vacuum distillation to obtain intermediate product M1, which is hydrophilic epoxy resin.

[0009] Step 2: Weigh the intermediate product M1, add silane coupling agent, dispersant, sodium silicate, calcium salt and aluminate to it while stirring, stir for 5-10 minutes, then let it stand and react at 35-40℃ to obtain hydrated nanomaterial intermediate product M2.

[0010] Step 3: Weigh the intermediate product M2, add fibrous sepiolite to it, and mix evenly.

[0011] 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%.

[0012] Preferably, in step 1, the weight ratio of epoxy resin, acetylacetone, and triethylamine is (75-90):(12.5-25.5):(0.5-3); the weight ratio of deionized water and adipic acid is (150-200):(2-5); and the total weight of epoxy resin, acetylacetone, and triethylamine accounts for 30-45% of the weight of deionized water.

[0013] Preferably, in step 2, the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate 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.

[0014] Preferably, in step 3, the weight ratio of the intermediate product M2 to fibrous sepiolite is 100:(10-25).

[0015] Preferably, the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane; 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 fibrous sepiolite has a length of 1-3 mm.

[0016] Preferably, the stirring rate in step 1 is 200-300 r / min; the stirring rate in step 2 is 30-50 r / min.

[0017] The application of the enhancer prepared by the method described in this invention in the pre-filling fluid for cementing deep coalbed methane wells.

[0018] Preferably, the deep coalbed methane cementing pre-fill fluid is composed of the following raw materials in parts by weight: 100 parts water, 25-120 parts quartz sand, 5-25 parts reinforcing agent, 0.5-2 parts suspension stabilizer, and 0.2-0.6 parts drag reducer.

[0019] Preferably, the quartz sand has a particle size of 100-200 mesh; the suspension stabilizer is an AMPS-AM type suspension stabilizer; and the drag-reducing agent is a ketaldehyde condensate.

[0020] Advantages of this invention:

[0021] (1) The reinforcing agent provided by the present invention adsorbs together with the hydroxyl groups on the surface of coal and rock through the lipophilic groups therein, wherein the ether group, which is the main hydrophilic group, forms a hydrophilic layer facing outward, thereby changing the surface of coal and rock from lipophilic to hydrophilic.

[0022] (2) When the intermediate product M1 hydrophilic epoxy resin and 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 detaching from the coal and rock surface under the action of scouring shear force, thereby improving the long-term wetting modification effect of the coal and rock surface.

[0023] (3) When the enhancer is used in the pre-cementing fluid for deep coalbed methane cementing, it improves the interfacial bonding strength with the cement sheath by effectively improving the hydrophilicity of the coal and rock surface, thereby improving the performance of the pre-cementing fluid for deep coalbed methane cementing and thus improving the cementing quality of horizontal wells in deep coalbed methane.

[0024] (4) The raw materials for synthesizing this reinforcing agent are widely available and abundant, the cost is low, the preparation conditions are mature, it is easy to use, and the prospects for promotion and application are good. Detailed Implementation

[0025] The suspension stabilizer used in this invention is an AMPS-AM type suspension stabilizer, which is a copolymer suspension stabilizer of 2-acrylamido-2-methylpropanesulfonic acid and acrylamide. It is prepared by free radical aqueous solution polymerization, specifically as follows: 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. The total mass of the mixed monomer is 25% of the mass of deionized water. Potassium persulfate is added as an initiator. The amount of potassium persulfate added is 0.6% of the total mass of the mixed monomer and deionized water. The pH of the solution is adjusted to 7. The reaction is carried out at 65°C for 8 hours. The product obtained is the copolymer suspension stabilizer of 2-acrylamido-2-methylpropanesulfonic acid and acrylamide.

[0026] The drag-reducing agent used is the ketone-aldehyde condensate USZ from Weihui Chemical Co., Ltd.

[0027] The dispersant used is AKN-2290.

[0028] Example 1

[0029] A method for preparing an enhancer for cementing pre-filling fluid in deep coalbed methane, characterized by comprising the following steps:

[0030] Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, and stir 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 the reaction for 6 hours. Remove acetylacetone by vacuum distillation to obtain intermediate product M1. The weight ratio of epoxy resin, acetylacetone, and triethylamine is 75:12.5:0.5, the weight ratio of deionized water and adipic acid is 200:5, and the total mass of epoxy resin, acetylacetone, and triethylamine accounts for 30% of the weight of deionized water.

[0031] Step 2: Weigh the intermediate product M1, and add silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate to it under stirring. Stir at 50 r / min for 10 min, then let it stand and react at 40℃ until the particle size D of the obtained hydrated nanomaterial intermediate product M2 reaches the specified value. 50 The wavelength is 700-850 nm, and the mass concentration is 30%. The weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate 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 intermediate product M1. The silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane. The calcium salt is tricalcium silicate. The aluminate is tricalcium aluminate.

[0032] Step 3: Weigh the intermediate product M2, add fibrous sepiolite with a length of 1-3 mm, the fibrous sepiolite accounting for 10% of the weight of the intermediate product M2, mix evenly, and the resulting reinforcing agent is denoted as H1.

[0033] Example 2

[0034] In step 2, the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate is 30% of the weight of intermediate product M1; the fibrous sepiolite accounts for 15% of the weight of intermediate product M2, and the rest is the same as in Example 1. The resulting reinforcing agent is denoted as H2.

[0035] Example 3

[0036] In step 2, the total weight of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate is 35% of the weight of intermediate product M1; the fibrous sepiolite accounts for 20% of the weight of intermediate product M2, and the rest is the same as in Example 1. The resulting reinforcing agent is denoted as H3.

[0037] Example 4

[0038] A method for preparing an enhancer for cementing pre-filling fluid in deep coalbed methane, characterized by comprising the following steps:

[0039] Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, and stir 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 the reaction for 6 hours. Remove acetylacetone by vacuum distillation to obtain intermediate product M1. The weight ratio of epoxy resin, acetylacetone, and triethylamine is 90:25.5:3, the weight ratio of deionized water and adipic acid is 150:2, and the total mass of epoxy resin, acetylacetone, and triethylamine accounts for 45% of the weight of deionized water.

[0040] Step 2: Weigh the intermediate product M1, and add silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate to it under stirring. Stir at 30 r / min for 5 min, then let it stand and react at 35℃ until the particle size D of the obtained hydrated nanomaterial intermediate product M2 reaches the specified value. 50 The particle size is 700-850 nm, and the mass concentration is 35%; the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate 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 intermediate product M1; the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane; the calcium salt is dicalcium silicate; and the aluminate has a particle size of dicalcium aluminate.

[0041] Step 3: Weigh the intermediate product M2, add fibrous sepiolite with a length of 1-3 mm, the fibrous sepiolite accounting for 25% of the weight of the intermediate product M2, mix evenly, and the resulting reinforcing agent is denoted as H4.

[0042] Example 5

[0043] A method for preparing an enhancer for cementing pre-filling fluid in deep coalbed methane, characterized by comprising the following steps:

[0044] Step 1: Mix epoxy resin, acetylacetone, triethylamine, and deionized water, and stir 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. Remove acetylacetone by vacuum distillation to obtain intermediate product M1. The weight ratio of epoxy resin, acetylacetone, and triethylamine is 80:20:2, the weight ratio of deionized water and adipic acid is 200:4, and the total mass of epoxy resin, acetylacetone, and triethylamine accounts for 40% of the weight of deionized water.

[0045] Step 2: Weigh the intermediate product M1, and add silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate to it under stirring. Stir at 50 r / min for 8 min, then let it stand and react at 40℃ until the particle size D of the obtained hydrated nanomaterial intermediate product M2 reaches the specified value. 50 The wavelength is 700-850 nm, and the mass concentration is 30%. The weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate 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 intermediate product M1. The silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane. The calcium salt is tricalcium silicate. The aluminate is tricalcium aluminate.

[0046] Step 3: Weigh the intermediate product M2, add fibrous sepiolite with a length of 1-3 mm, the fibrous sepiolite accounting for 10% of the weight of the intermediate product M2, mix evenly, and the resulting reinforcing agent is denoted as H5.

[0047] Example 6

[0048] The reinforcing agent prepared in Example 1 was used to prepare a pre-filling fluid for cementing deep coalbed methane, as follows: The following parts by weight of raw materials were taken: 100 parts water, 30 parts quartz sand with a particle size of 100 mesh, 20 parts reinforcing agent, 2 parts suspension stabilizer, and 0.5 parts drag reducer. The mixture was stirred evenly at a speed of 4000 rpm to obtain a pre-filling fluid for cementing deep coalbed methane, denoted as Hd1.

[0049] Example 7

[0050] The reinforcing agent prepared in Example 2 was used to prepare a pre-solidification fluid for deep coalbed methane, as follows: The following parts by weight of raw materials were taken: 100 parts of water, 30 parts of quartz sand with a particle size of 100 mesh, 25 parts of reinforcing agent, 2 parts of suspension stabilizer, and 0.5 parts of drag reducer. The mixture was stirred evenly at a speed of 4000 rpm to obtain a pre-solidification fluid for deep coalbed methane, denoted as Hd2.

[0051] Example 8

[0052] The reinforcing agent prepared in Example 3 was used to prepare a pre-solidification fluid for deep coalbed methane, as follows: The following parts by weight of raw materials were taken: 100 parts of water, 120 parts of quartz sand with a particle size of 200 mesh, 20 parts of reinforcing agent, 2 parts of suspension stabilizer, and 0.2 parts of drag reducer. The mixture was stirred evenly at a speed of 4000 rpm to obtain a pre-solidification fluid for deep coalbed methane, denoted as Hd3.

[0053] Example 9

[0054] The reinforcing agent prepared in Example 4 was used to prepare a pre-solidification fluid for deep coalbed methane, as follows: The following parts by weight of raw materials were taken: 100 parts of water, 60 parts of quartz sand with a particle size of 200 mesh, 15 parts of reinforcing agent, 1 part of suspension stabilizer, and 0.6 parts of drag reducer. The mixture was stirred evenly at a speed of 4000 rpm to obtain a pre-solidification fluid for deep coalbed methane, denoted as Hd4.

[0055] Example 10

[0056] The reinforcing agent prepared in Example 5 was used, and the rest was the same as in Example 1. The resulting deep coalbed methane cementing pre-fill fluid was denoted as Hd5.

[0057] Comparative Example 1

[0058] Without adding a silane coupling agent, everything else is the same as in Example 1, and the resulting reinforcing agent is denoted as S1.

[0059] Comparative Example 2

[0060] Step 1 is omitted. In step 2, deionized water is used instead of intermediate product M1. Everything else is the same as in Example 1. The resulting reinforcing agent is denoted as S2.

[0061] Comparative Example 3

[0062] Step 3 is omitted; everything else is the same as in Example 1. The resulting reinforcing agent is denoted as S3.

[0063] Comparative Example 4

[0064] The reinforcing agent obtained in Comparative Example 1 was used, and the rest was the same as in Example 6. The resulting pretreatment solution was denoted as Sd1.

[0065] Comparative Example 5

[0066] The reinforcing agent obtained in Comparative Example 2 was used, and the rest was the same as in Example 6. The resulting pretreatment solution was denoted as Sd2.

[0067] Comparative Example 6

[0068] The reinforcing agent obtained in Comparative Example 3 was used, and the rest was the same as in Example 6. The resulting pretreatment solution was denoted as Sd3.

[0069] Comparative Example 7

[0070] Without adding any enhancer, the process is the same as in Example 6, and the resulting pretreatment solution is denoted as Sd4.

[0071] Performance testing

[0072] I. Particle Size Detection

[0073] The experiment was conducted at room temperature. The size and distribution of intermediate product M2 in the preparation of each reinforcing agent were determined using a Mastersizer 3000 laser particle size analyzer. Each group of experiments was tested 3 times, and the final result was the average value.

[0074] Table 1. Test results of particle size distribution of reinforcing agent

[0075]

[0076] As shown in Table 1, the main active components of the reinforcing agents prepared in each embodiment and comparative example are all nanoscale at room temperature, indicating that nano-hydration materials have been formed.

[0077] II. Hydrophilic Modification Ability

[0078] In order to improve the cementing quality during the on-site cementing process, the pre-flush fluid system is usually injected first according to the designed usage, and then the cement slurry is injected according to the designed usage. Therefore, the wetting modification of the coal and rock surface can be performed to improve the bonding quality between the cement sheath and the coal seam. Take experimental coal samples, smooth the upper and lower surfaces with sandpaper, and use an optical contact angle / interfacial tension meter to titrate with distilled water. The wetting angle of the experimental coal and rock surface was measured to be greater than 90°. Then, at different locations on the same coal sample, the titrant was changed from distilled water to a 25wt% enhancement agent, and the wetting angle was measured and compared with the measurement results of distilled water titration.

[0079] The testing process was as follows: the coal sample was fixed with clamps and placed in a sample solution of a certain concentration being stirred by a magnetic stirrer. The upper and lower surfaces of the coal block were parallel to the liquid surface to simulate the flushing process of the pre-fluid on the coal seam surface. After rinsing the surface for 10 minutes, the sample was removed and dried. The average value of three points was taken to measure the wetting angle of the reinforcing agent titration. Because, according to the cementing operation procedure, after the pre-fluid wets and modifies the coal seam surface, it will face the replacement of the cement slurry. It is necessary to determine whether the surfactant molecules attached to the coal seam surface will remain unchanged after being flushed by the cement slurry system, and whether the degree of modification will change. Therefore, after testing the wetting angle of the reinforcing agent titration, the above simulated flushing process was then carried out. The results are shown in Table 2.

[0080] Table 2 Results of hydrophilic modification ability test

[0081]

[0082] Table 2 shows that the lipophilic groups in the reinforcing agent combine with the organic matter on the coal surface, causing it to be uniformly adsorbed onto the coal surface, resulting in a change in the wettability of the coal surface from lipophilic to hydrophilic. The degree of modification of the coal surface by the reinforcing agent fluctuates with the content of hydrophilic epoxy resin in intermediate product M1. Comparative Example 1 shows that the silane coupling agent can effectively improve the hydrophilicity of the coal sample after rinsing. Without the addition of the silane coupling agent, the coal surface begins to return to an oily state after rinsing for 10 minutes, and the surface modification of the reinforcing agent fails. Comparative Example 2 shows that without intermediate product M1, its surface modification of the coal is also ineffective.

[0083] III. Compatibility and fluid loss test of pre-cementing fluid and cement slurry

[0084] A pre-cementing fluid and cement slurry were prepared for deep coalbed methane well cementing. The density of the cement slurry system was 1.67 g / cm³. -3It exhibits good rheological and filtration properties. The cement slurry formula (parts by weight) is: 100 parts Jiahua G-grade cement + 30 parts silica sand + 2.5 parts water loss reducer + 0.1 parts defoamer + 55 parts water (the water loss reducer is G310 multi-component copolymer from Weihui Chemical Co., Ltd., and the defoamer is DF-900). The two are mixed at different volume ratios, and after thorough stirring, the mixed slurry is poured into an atmospheric pressure thickener and cured at 90℃ for 30 min. After curing, its water loss performance at 60℃ and 6.9MPa is tested using a high-temperature and high-pressure water loss instrument. The experimental results are shown in Table 3.

[0085] Table 3. Results of Compatibility-Drainage Tests of Cement Pre-Cementing Fluid and Cement Slurry

[0086]

[0087] As shown in Table 3, the water loss of the mixed slurry within 30 minutes decreased slightly with the increase of the pre-ferment mixing volume ratio, indicating that the two have good compatibility in terms of filtration performance. The comparative example shows that the addition of hydrophilic resin intermediate M1 and fibrous sepiolite in the reinforcing agent has a certain impact on the water loss of the system. The addition of these two substances makes it easier to form a dense filter cake, thus improving the filtration performance of the system.

[0088] IV. Compatibility and Thickening Time Test of Cementing Pre-fill Fluid and Cement Slurry

[0089] As described above, for the compatibility-water loss test, pre-filled fluid and cement slurry for cementing deep coalbed methane were prepared. Cement slurry mixed with pre-filled fluid in different volume ratios was tested for thickening time according to the national standard "Oil Well Cement" (GB / T 10238-2015). The two were mixed in different volume ratios, stirred thoroughly, and the mixed slurry was poured into a high-temperature and high-pressure thickener. The test was conducted at 110℃ and 45MPa. The thickening time of cement slurry without pre-filled fluid was 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 have good compatibility. The experimental results are shown in Table 4 below.

[0090] Table 4. Test results of compatibility and thickening time between cementing pre-fill fluid and cement slurry.

[0091]

[0092] Table 4 shows that after mixing the pre-filled liquid for deep coalbed methane cementing with the cement slurry, no shortening of the thickening time of the cement slurry was observed, indicating that the two have good compatibility. The experiment with a mixing volume ratio of 50:50 shows that the pre-filled liquid system without the reinforcing agent (Comparative Example 7) has little effect on the thickening time of the mixed system. Comparative Example 5 indicates that the addition of the intermediate product M1 hydrophilic resin in the reinforcing agent has a certain impact on the thickening performance of the system.

[0093] V. Compatibility and compressive strength test of pre-cementing fluid and cement slurry

[0094] As described above, compatibility-dehydration tests were conducted to prepare pre-filled cement fluid and cement slurry for deep coalbed methane cementing wells. Cement slurries mixed with different volume ratios of pre-filled cement fluid were prepared according to GB / T 19139-2012 "Test Methods for Oil Well Cement". These samples were cured in a 60℃ water bath for 24h, 48h, and 72h, and their compressive strength was measured using a compressive strength testing machine. The effect of different interface-reinforcing pre-filled cement fluid dosages on cement strength was compared and analyzed with the original cement slurry. The experimental results are shown in Table 5.

[0095] Table 5. Compatibility and compressive strength test results of pre-cementing fluid and cement slurry.

[0096]

[0097] As shown in Table 5, the compressive strength of the cement slurry system gradually decreases as the volume ratio of the pre-flush liquid in the mixed slurry increases. In wellbore with large boreholes, where the displacement efficiency cannot reach 100%, a 25:75 blend can ensure good strength within 2 days if the displacement efficiency is not lower than 75%. If the displacement efficiency is not lower than 50%, a 50:50 blend can ensure a strength of over 3 MPa within 72 hours, effectively meeting the performance requirements of coalbed methane cementing construction.

[0098] VI. Compatibility and interfacial bonding strength test of pre-cementing fluid and cement slurry

[0099] As described above, for the compatibility-water loss test, pre-filling fluid and cement slurry for cementing deep coalbed methane were prepared. Cement slurry mixed with pre-filling fluid in different volume ratios was poured into a cylindrical steel mold with a bottom diameter D=6cm and a height H=5cm. The whole mold was placed in a 60℃ water bath for 24h, 48h and 72h. The maximum shear force at the cement block-steel mold interface, i.e. the cement stone interface bonding strength, was measured.

[0100] Table 6. Test results of compatibility and interfacial bonding strength between cementing pre-fill fluid and cement slurry.

[0101]

[0102] As shown in Table 6, the interfacial bonding strength of the cement slurry system gradually decreases as the volume ratio of the pre-flush fluid in the mixed slurry increases. In wellbore sections with large boreholes, a 25:75 blend can guarantee a certain interfacial bonding strength within 2 days if the displacement efficiency is not less than 75%; a 50:50 blend can guarantee a certain interfacial bonding strength within 72 hours if the displacement efficiency is not less than 50%, effectively meeting the performance requirements of coalbed methane cementing construction and ensuring the safety of cementing operations.

Claims

1. A method for preparing an enhancer for pre-flooding fluid in deep coalbed methane cementing, characterized in that: Includes the following steps: Step 1: Mix epoxy resin, acetylacetone, triethylamine and deionized water, stir and react at 80-90℃ for 2-4 hours, then add adipic acid in portions, maintain the temperature and continue to react for 6-12 hours, remove acetylacetone by vacuum distillation to obtain intermediate product M1. Step 2: Weigh the intermediate product M1, add silane coupling agent, dispersant, sodium silicate, calcium salt and aluminate to it while stirring, stir for 5-10 minutes, then let it stand and react at 35-40℃ to obtain hydrated nanomaterial intermediate product M2. Step 3: Weigh the intermediate product M2, add fibrous sepiolite to it, and mix evenly.

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

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

4. The method for preparing an enhancer for pre-flooding fluid in deep coalbed methane cementing according to claim 3, characterized in that: In step 2, the weight ratio of the silane coupling agent, dispersant, sodium silicate, calcium salt, and aluminate 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 intermediate product M1.

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

6. The method for preparing an enhancer for pre-flooding fluid in deep coalbed methane cementing according to claim 5, characterized in that: The silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane; 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 fibrous sepiolite has a length of 1-3 mm.

7. The method for preparing an enhancer for pre-flooding fluid in deep coalbed methane cementing 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. The application of the enhancer prepared by the method according to any one of claims 1-7 in the pre-filling fluid for cementing deep coalbed methane.

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

10. The application according to claim 9, characterized in that: The quartz sand has a particle size of 100-200 mesh; the suspension stabilizer is an AMPS-AM type suspension stabilizer; and the drag-reducing agent is a ketaldehyde condensate.

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