Salt-tolerant coalbed methane desorption promoting agent and preparation method thereof

Abstract

The invention discloses a salt-tolerant coalbed methane desorption promoting agent, which is a novel amphoteric fluorocarbon surfactant (FNC for short) designed and synthesized on the basis of short fluorocarbon chain-C4F9, not only has good salt tolerance and temperature resistance, but also can avoid the chromatographic separation effect with nonionic and anionic surfactants during compounding. Cationic group quaternary ammonium ions and anionic group carboxylate radicals are introduced, N, N '-dimethyl-1, 3-propane diamine can be subjected to nucleophilic substitution and quaternization due to the fact that N, N'-dimethyl-1, 3-propane diamine has primary amine and tertiary amine structures, FNC-1 is generated through nucleophilic substitution of N, N '-dimethyl-1, 3-propane diamine and perfluorobutanesulfonyl fluoride, FNC-1 and Cl (CH2) nCH = CH2 or Cl (CH2) nCH3 are subjected to quaternization to generate FNC-2, finally, FNC-2 and Cl (CH2) nCOOH or Cl (CH2) nSO3H are subjected to quaternization to generate FNC-2, and NNC-2 and Cl (CH2) nCOOH or Cl (CH2) nSO3H are and carrying out nucleophilic substitution reaction to generate the ampholytic surfactant FNC.

Description

Technical Field

[0001] The invention belongs to the technical field of coal seam development, and particularly relates to a salt-resistant coal seam gas desorption promoting agent and a preparation method thereof. Background Art

[0002] As oil resource extraction enters the middle and late stages, the difficulty of extracting unconventional tight oil and gas reservoirs increases. The increasing demand for crude oil resources and the impact of international oil price fluctuations have made it difficult to balance energy supply and demand. Currently, research on improving the recovery rate of unconventional tight oil and gas reservoirs is very active both domestically and internationally, and surfactant flooding is one of the key technologies for improving recovery rates.

[0003] Surfactants are primarily classified into three categories: nonionic surfactants, anionic surfactants, and zwitterionic surfactants. While anionic surfactants offer high interfacial activity and excellent temperature resistance, they have poor salt tolerance and are unsuitable for use in highly saline oil and gas reservoirs. Nonionic surfactants, while highly salt-tolerant, suffer higher adsorption losses in formations than anionic surfactants and exhibit poor high-temperature resistance. Zwitterionic surfactants are generally suitable for use in highly saline, high-temperature oil and gas reservoirs and can avoid chromatographic separation effects with nonionic and anionic surfactants when formulated.

[0004] It is well known that surfactants can not only reduce the surface tension of aqueous solutions and change the wettability of coal seam surfaces, but also reduce the interfacial tension between oil and water and improve oil washing efficiency. Fluorocarbon chain surfactants, as a special type of surfactant, have many advantages that ordinary hydrocarbon chain surfactants do not have, typically including high thermal stability, high chemical stability, high surface activity, and hydrophobicity and oleophobicity. Despite their high prices, they have been gradually applied to many fields over the past few decades and have great application value. For example, Rosen proposed that fluorinated surfactants have a great effect on reducing the surface tension of solutions; Tadros's research pointed out that fluorocarbon chain surfactants have better wettability than hydrocarbon chain surfactants; Song L found through research that in the process of forming micelles, the efficiency of a -CF2 unit is 1.5 times that of -CH2.

[0005] However, studies have found that when the fluorinated carbon chain of long-chain linear perfluoroalkyl derivatives (-CF2≥6) is high, the environmental problems caused by its high stability, degradation difficulties, bioaccumulation, and severe toxicity have led to the gradual replacement and prohibition of C n F 2n Therefore, there is an urgent need to develop new, environmentally friendly fluorocarbon chain surfactants. Summary of the Invention

[0006] The present invention aims to address, at least to some extent, one of the technical problems in the related art. To this end, the present invention primarily aims to provide a salt-tolerant coalbed methane desorption promoter, designed to address the problem of promoting desorption and increasing production of coalbed methane at high salinity. The present invention also provides a method for preparing the salt-tolerant coalbed methane desorption promoter.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A salt-tolerant coalbed methane desorption promoter, characterized in that its molecular formula is:

[0009] Where n is 3-11.

[0010] A method for preparing a salt-tolerant coalbed methane desorption promoter comprises the following steps:

[0011] 1) Dissolve triethylamine and N,N'-dimethyl-1,3-propylenediamine in dichloromethane, stir until uniform, and then slowly add perfluorobutylsulfonyl fluoride dropwise. After the addition is complete, perform a synthesis reaction, then filter and dry to obtain a white solid powder FNC-1;

[0012] 2) Weigh the white solid powder FNC-1 and Cl(CH2) n CH=CH2(n=3-8) or Cl(CH2) n CH3 (n = 3-11) was dissolved in acetonitrile and refluxed. After the reaction was complete, it was distilled under reduced pressure and dried to obtain white crystalline powder FNC-2;

[0013] 3) Weigh the white crystalline powder FNC-2 and Cl(CH2) n COOH, (n = 3-6) or Cl(CH2) n SO3H (n=3-9) and triethylamine are dissolved in acetonitrile and refluxed. After the reaction is complete, vacuum distillation is performed and dried to obtain a white paste solid FNC fluorocarbon surfactant, i.e., a salt-resistant coalbed methane desorption promoter.

[0014] wherein Cl(CH2) n CH=CH2 (n=3-8) includes one or more of 3-chloro-1-propene, 4-chloro-1-butene, 5-chloro-1-pentene, 6-chloro-1-hexene, 7-chloro-1-heptene, and 8-chloro-1-octene;

[0015] wherein Cl(CH2) n CH3 (n=3-11) includes, for example, 1-chloropropane, 1-chlorobutane, 1-chloropentane, 1-chlorohexane, 1-chloroheptane, 1-chlorooctane, 1-chlorononane, 1-chlorodecane, 1-chloroundecane, or one or more thereof;

[0016] wherein Cl(CH2) n COOH (n=3-6), including one of 3-chloropropionic acid, 4-chlorobutyric acid, 5-chlorovaleric acid, and 6-chlorohexanoic acid;

[0017] wherein Cl(CH2) n SO3H (n=3-9), including one or more of 3-chloropropanesulfonic acid, 4-chlorobutanesulfonic acid, 5-chloropentanesulfonic acid, 6-chlorohexanesulfonic acid, 7-chloroheptanesulfonic acid, 8-chlorooctanesulfonic acid, and 9-chlorononanesulfonic acid;

[0018] The preparation method of the salt-tolerant coalbed methane desorption accelerator provided by the present invention has the following synthesis route:

[0019]

[0020]

[0021] In certain specific embodiments, the mass ratio of triethylamine, N,N'-dimethyl-1,3-propylenediamine and perfluorobutylsulfonyl fluoride in step 1) is 3-8:4-6:10-20.

[0022] In certain embodiments, the stirring in step 1) is performed in a low-temperature reaction bath at -3-0°C.

[0023] In certain specific embodiments, the process conditions of the synthesis reaction in step 1) are: heating to 10-20°C and continuing stirring for 3-5h; the drying temperature in step 1) is 50-70°C.

[0024] In certain embodiments, the FNC-1 and Cl(CH2) in step 2) n CH=CH2 or Cl(CH2) n The mass ratio of CH3 is 17-21:7-11.

[0025] In certain specific embodiments, the process conditions of the reflux reaction in step 2) are: stirring and reflux reaction in a magnetic stirring oil bath at 70-90° C. for 15-25 hours.

[0026] In certain embodiments, the FNC-2, Cl(CH2) in step 3) n COOH or Cl(CH2) n The mass ratio of SO3H and triethylamine is 14-18:3-5:3-5.

[0027] In certain specific embodiments, the process conditions of the reflux reaction in step 3) are: placing the mixture in a magnetic stirring oil bath at 70-90° C. and stirring the mixture under reflux for 15-25 hours.

[0028] Compared with the prior art, the present invention has at least the following advantages:

[0029] 1) The preparation method of the present invention is based on a short fluorocarbon chain -C4F9, and a new type of amphoteric fluorocarbon surfactant (abbreviated as FNC) is designed and synthesized, and its performance, including salt resistance, temperature resistance, surface activity, etc., is studied by surface tension and contact angle. Specifically, by introducing a fluorocarbon chain, the surfactant has many advantages that ordinary hydrocarbon chain surfactants do not have, typically including high thermal stability, high chemical stability, high surface activity, hydrophobicity and oleophobicity, etc.; in order to further improve the salt resistance and temperature resistance of the surfactant, amphoteric surfactants are designed and synthesized, which not only have good salt resistance and temperature resistance, but also can avoid the chromatographic separation effect with non-ionic and anionic surfactants during compounding. Therefore, we introduce the cationic group quaternary ammonium ion and the anionic group carboxylate, and N, N'-dimethyl-1,3-propylenediamine has a primary amine and tertiary amine structure, which can undergo nucleophilic substitution and quaternization reaction. It is a commonly used intermediate in organic synthesis. It is generated by nucleophilic substitution with perfluorobutylsulfonyl fluoride to generate FNC-1, and FNC-1 then reacts with Cl(CH2) n CH=CH2 or Cl(CH2) n CH3 undergoes quaternization reaction to generate FNC-2, and finally FNC-2 reacts with Cl(CH2) n COOH or Cl(CH2) n SO3H undergoes a nucleophilic substitution reaction to generate the amphoteric surfactant FNC.

[0030] 2) The salt-tolerant coalbed methane desorption promoter provided by the present invention has excellent desorption promoting performance. The addition of the desorption promoter FNC significantly increases the methane desorption amount to 1.17 mL / g, which is 1.27 times higher than that of pure water. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.

[0032] Figure 1 This is the infrared spectrum of the desorption promoter (FNC) in Example 2 of the present invention;

[0033] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the desorption accelerator (FNC) in Example 2 of the present invention;

[0034] Figure 3 γ-lgC curve of the CMC value of the desorption promoting agent (FNC) in Example 2 of the present invention;

[0035] Figure 4The surface tension of FNC solution under different NaCl (a) and CaCl2 (b) concentrations of the present invention;

[0036] Figure 5 The interfacial tension of FNC solution under different NaCl (a) and CaCl2 (b) concentrations of the present invention;

[0037] Figure 6 The present invention promotes the desorption of the agent (FNC) in clear water at 0.4% concentration and different concentrations (0.1%, 0.2%), 2×10 5 Contact angle at mg / L NaCl concentration;

[0038] Figure 7 The figure shows the methane decomposition amount of the decomposition promoter (FNC) of the present invention at different addition amounts. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are merely illustrative and non-restrictive, and should not be used to limit the scope of protection of the present invention.

[0040] When expressing a certain amount, concentration or other value or parameter in the form of a range, preferred range, or preferred upper and lower numerical limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper range limits or preferred numerical values ​​with any lower range limit or preferred numerical value, without considering whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within the range.

[0041] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.

[0042] The materials, methods, and examples herein are illustrative and, unless otherwise indicated, are not to be construed as limiting.

[0043] In the following examples, triethylamine and dichloromethane were of analytical grade and purchased from Chengdu Kelong Chemical Co., Ltd.; N,N'-dimethyl-1,3-propanediamine, perfluorobutylsulfonyl fluoride, 5-chloro-1-pentene, acetonitrile, 3-chloropropionic acid, acetone, sodium chloride, and calcium chloride were of analytical grade and purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0044] In the following embodiments, the experimental or testing equipment used are: S312-90 low-speed stirrer, Shanghai Shensheng Co., Ltd.; HX1002T electronic balance, Cixi Tiandong Instrument Factory; DHG-9023A electric constant temperature blast drying oven, Hangzhou Instrument and Motor Co., Ltd.; Sigma 700 meter / interfacial tension meter, Sweden Bolin Co., Ltd.; JNM-ECZ400S / L1 liquid nuclear magnetic resonance (NMR), JEOL Ltd.; Tensor-27 Fourier transform infrared spectrometer, Germany Bruker Co., Ltd.; RE-201D rotary evaporator, Zhengzhou Tel Instrument Equipment Co., Ltd.; DF-101S constant temperature heating magnetic stirring water bath, Hangzhou Jingfei Instrument Technology Co., Ltd.; LC-DFY-10 / 20 cold well, Lichen Technology Co., Ltd.; SDC-200S contact angle meter, Dongguan Shengding Precision Instrument Co., Ltd.

[0045] Example 1

[0046] This embodiment provides a method for preparing a salt-tolerant coalbed methane desorption promoter, which comprises the following steps:

[0047] 1) In a 250 mL round-bottom flask, dissolve 3 g of triethylamine and 4 g of N,N'-dimethyl-1,3-propylenediamine in 120 mL of dichloromethane. Stir the mixture in a 0°C reaction bath. Slowly add 10.2 g of perfluorobutylsulfonyl fluoride dropwise. After the addition is complete, heat the mixture to 15°C and continue stirring for approximately 4 h. After the reaction is complete, filter under reduced pressure to obtain a white solid powder, FNC-1. Dry the powder in a 60°C oven, weigh it, and bag it.

[0048] 2) In a 250 mL round-bottom flask, 17 g of FNC-1 and 7.128 g of 5-chloro-1-pentene were dissolved in 120 mL of acetonitrile. The mixture was stirred in an 80°C oil bath under reflux for 18 h. After the reaction was complete, the acetonitrile solvent was removed by vacuum distillation and dried to obtain FNC-2 as a white crystalline powder.

[0049] 3) In a 250 mL round-bottom flask, 14 g of FNC-2, 4 g of 3-chloropropionic acid, and 4.02 g of triethylamine were dissolved in 120 ml of acetonitrile, placed in an 80 ° C magnetic stirring oil bath, stirred and refluxed for 20 h. After the reaction was complete, the solvent acetonitrile was removed by vacuum distillation, and then dried to obtain a white paste solid FNC fluorocarbon surfactant, which is a salt-resistant coalbed methane desorption promoter.

[0050] Example 2

[0051] This embodiment provides a method for preparing a salt-tolerant coalbed methane desorption promoter, which comprises the following steps:

[0052] 1) In a 250 mL round-bottom flask, 5.83 g of triethylamine and 5.1 g of N,N'-dimethyl-1,3-propylenediamine were dissolved in 120 mL of dichloromethane. The mixture was stirred in a 0°C low-temperature reaction bath. 15.1 g of perfluorobutylsulfonyl fluoride was slowly added dropwise. After the addition was complete, the mixture was heated to 15°C and stirred for approximately 4 h. After the reaction was complete, the mixture was filtered under reduced pressure to obtain a white solid powder, FNC-1. The powder was dried in a 60°C oven, weighed, and bagged.

[0053] 2) In a 250 mL round-bottom flask, 19.2 g of FNC-1 and 9.437 g of 5-chloro-1-pentene were dissolved in 120 mL of acetonitrile. The mixture was stirred in an 80°C oil bath under reflux for 18 h. After the reaction was complete, the acetonitrile solvent was removed by vacuum distillation and dried to obtain FNC-2 as a white crystalline powder.

[0054] 3) In a 250 mL round-bottom flask, 15.6 g of FNC-2, 3.26 g of 3-chloropropionic acid, and 3.33 g of triethylamine were dissolved in 120 ml of acetonitrile, placed in an 80 ° C magnetic stirring oil bath, stirred and refluxed for 20 h. After the reaction was complete, the solvent acetonitrile was removed by vacuum distillation, and then dried to obtain a white paste solid FNC fluorocarbon surfactant, which is a salt-resistant coalbed methane desorption promoter.

[0055] Example 3

[0056] This embodiment provides a method for preparing a salt-tolerant coalbed methane desorption promoter, which comprises the following steps:

[0057] 1) In a 250 mL round-bottom flask, 8 g of triethylamine and 5.8 g of N,N'-dimethyl-1,3-propylenediamine were dissolved in 120 mL of dichloromethane. The mixture was stirred in a 0°C low-temperature reaction bath. 20 g of perfluorobutylsulfonyl fluoride was then slowly added dropwise. After the addition was complete, the mixture was heated to 15°C and stirred for approximately 4 h. After the reaction was complete, the mixture was filtered under reduced pressure to obtain a white solid powder, FNC-1. The powder was dried in a 60°C oven, weighed, and bagged.

[0058] 2) In a 250 mL round-bottom flask, 20.8 g of FNC-1 and 10.896 g of 5-chloro-1-pentene were dissolved in 120 mL of acetonitrile. The mixture was stirred in an 80°C oil bath under reflux for 18 h. After the reaction was complete, the acetonitrile solvent was removed by vacuum distillation and dried to obtain FNC-2 as a white crystalline powder.

[0059] 3) In a 250 mL round-bottom flask, 18 g of FNC-2, 4.67 g of 3-chloropropionic acid, and 4.86 g of triethylamine were dissolved in 120 ml of acetonitrile, placed in a magnetic stirring oil bath at 80 ° C, stirred and refluxed for 20 h. After the reaction was complete, the solvent acetonitrile was removed by vacuum distillation, and then dried to obtain a white paste solid FNC fluorocarbon surfactant, which is a salt-resistant coalbed methane desorption promoter.

[0060] Performance testing:

[0061] This application takes Example 2 as an example to conduct a performance test on the prepared salt-tolerant coalbed methane desorption accelerator, specifically:

[0062] 1) Structural characterization of FNC fluorocarbon surfactants

[0063] 11) Infrared spectroscopy

[0064] This test uses the German Tensor-27 Fourier infrared spectrometer to analyze FNC, with a measurement range of 400 to 4000 cm -1 ;

[0065] The test results of infrared spectrum are as follows Figure 1 As shown, FNC-1: 3424cm -1 The (NH) stretching vibration absorption peak is at 1633 cm -1 The in-plane bending vibration absorption peak of (-NH) at 1356 cm -1 The asymmetric vibration absorption peak of (-SO2NH) is at 1190cm -1 The peak at (CF) stretching vibration is the nucleophilic substitution reaction between the primary amine in the product FNC-1 and the F on the sulfonyl group; FNC-2: 3416 cm -1 The (NH) stretching vibration absorption peak is at 1632 cm -1 The in-plane bending vibration absorption peak of (-NH) is 1591 cm -1 The stretching vibration absorption peak of (C=C) is located at 3422 cm, which shows that the Cl in 5-chloro-1-pentene undergoes quaternization reaction with the tertiary ammonium in FNC-1; FNC: 3422 cm -1 The (OH) stretching vibration absorption peak is at 3148 cm -1 The peak at 1630 cm is the (=CH) stretching vibration absorption peak. -1 The (C=O) stretching vibration absorption peak is 1591 cm -1 The stretching vibration absorption peak at (C=C) indicates that 3-chloropropionic acid undergoes a nucleophilic substitution reaction with the secondary amine in FNC-2.

[0066] 12) H NMR spectroscopy analysis

[0067] This test uses Japan JNM-ECZ400S / L1 liquid nuclear magnetic resonance ( 1 H NMR) was used to analyze FNC in deuterated acetonitrile as the solvent.

[0068] H NMR spectra Figure 2 As shown, from Figure 2 It can be seen that 1 H NMR (400 MHz, ACETONITRILE-D3) δ 6.11 (m, 2H), =CH2; 5.62 (dd, J = 9.5, 3.0 Hz, 1H), =CH; 3.54 (m, 2H), N-CH2-CO; 3.41 (m, 2H), N-CH2; 3.32-3.21 (m, 2H), N-CH2; 3.00 (s, 6H), N-CH3; 2.62 (m, 2H), =C-CH2; 2.66–2.51 (m, 4H), =C-CH2,NC-CH2; 2.04 (m, 2H), CH2. The above analysis shows that the obtained product is the target product.

[0069] 2) Surface and interfacial tension test

[0070] The Sigma 700 surface / interfacial tension meter was used to test the surface tension of the samples under different FNC concentrations and different NaCl concentrations (5×10 3 mg / L, 2×10 4 mg / L, 4×10 4 mg / L、8×10 4 mg / L, 2×10 5 mg / L), different CaCl2 concentrations (5×10 3 mg / L, 1×10 4 mg / L、3×10 4 mg / L) surface / interfacial tension; all solutions were prepared with deionized water.

[0071] 21) Surface tension test

[0072] At room temperature, deionized water was used to prepare FNC surfactant solutions of different concentrations (concentration logarithm lgC ranged from -2.0 to -1.0) for surface activity testing. The test data were plotted as a graph of surface tension γ-mN / m and concentration logarithm lgC, as shown in the figure. Figure 3 As shown in the figure: With the increase of FNC concentration, the surface tension of the solution decreases significantly. When it decreases to a certain concentration, the surface tension change tends to be stable. This is because FNC has completed the adsorption on the gas / liquid interface and reached saturation. Figure 3The turning point of the middle curve corresponds to a CMC value of 6×10 -2 g / L.

[0073] Use deionized water to prepare different concentrations of CaCl2 and NaCl mineral water solutions, then weigh different masses (0.00-0.30%) of FNC and add them to the prepared mineral water to obtain solutions with different FNC concentrations at different mineralization levels. Each group was tested 3 times and the average value was taken. Figure 4 As shown: Figure 4 In (a), at the same CaCl2 concentration, as the FNC concentration continues to increase, the surface tension continues to decrease, and the downward trend is significant; as the CaCl2 concentration increases, the surface tension of the FNC solution at the same concentration increases, but the increasing trend is not obvious. When the FNC concentration increases to 0.3wt%, as the CaCl2 concentration increases, the surface tension of the solution remains almost unchanged, maintaining at around 25.5mN / m. Figure 4 In (b), as the concentration of NaCl increases, the surface tension of the solution decreases, reaching its lowest point when the concentration of NaCl is 8×10 4 mg / L, and the surface tension was 22.5 mN / m when the FNC content was 0.3 wt%, indicating that FNC not only has good surface activity but also has excellent salt tolerance.

[0074] 22)Interfacial tension test

[0075] Figure 5 The interfacial tension at different FNC concentrations (0.10-0.30%) and different salinities (NaCl, CaCl2) is shown in the figure. As can be seen from the figure, the interfacial tension decreases rapidly with the increase of FNC mass fraction. Figure 5 As can be seen from (a), the interfacial tension of FNC solution decreases with the increase of NaCl concentration. 4 mg / L, the interfacial tension of FNC solution was always higher than that of FNC solution in clear water, but when the NaCl concentration was higher than 2×10 4 mg / L, and when the mass fraction of FNC is greater than 0.2%, the interfacial tension of the solution is lower than that of the FNC solution in clear water. Figure 5 As can be seen from (b), in CaCl2 solution, the interfacial tension of FNC in pure water is always lower than that in CaCl2 solution, but when the CaCl2 concentration is greater than 1×10 4 When the concentration of CaCl2 increased, the interfacial tension gradually decreased, indicating that FNC has excellent salt tolerance.

[0076] 3) Contact angle test

[0077] The SDC-200S contact angle meter was used to test the contact angle of FNC in water at 0.4% concentration and different concentrations (0.1%, 0.2%), 2×10 5 Contact angle at mg / LNaCl concentration. All solutions were prepared with deionized water. Figure 6 As shown in Table 1:

[0078] Table 1 Contact angles of NaCl at different concentrations

[0079]

[0080] From the data in Table 1 and Figure 6 It can be seen that the salt-resistant coalbed methane desorption promoter provided in this application has a low contact angle and surface tension.

[0081] 4) Promote analytical performance

[0082] Test method: Place the sealed desorption tank containing 450g of sample in a constant temperature (50℃) device at the reservoir temperature (50℃) for desorption. Connect the desorption tank to the gas meter with a hose. First, desorb naturally for 8 hours, then ball mill crush for 20 minutes (60 minutes for coal with high ash content or high coal rank), place in the constant temperature device, and start measuring after the reservoir temperature is restored; then repeat the crushing and desorption until the gas volume of two consecutive crushing and desorption is less than 10cm 3 The rapid gas content measurement is completed when . For each measurement, record the ball milling time, desorption time, desorbed gas volume, ambient temperature and atmospheric pressure.

[0083] During natural desorption, measurements are taken at regular intervals, which depend on the pressure in the tank. The sample is first measured within 5 minutes of filling the tank, then at 10-minute intervals for 1 hour (6 measurements), then at 15-minute intervals for 1 hour (4 tests), then at 30-minute intervals for 1 hour (2 tests), then once at 60-minute intervals, and finally twice at 120-minute intervals, for a total of 8 hours.

[0084] The results of the test are as follows Figure 7 The results show that compared to pure water, the addition of the desorption enhancer FNC significantly increases the amount of methane desorbed. At concentrations between 0.1% and 0.3%, the amount of methane desorbed increases with increasing FNC concentration. However, at concentrations between 0.4% and 0.5%, the amount of methane desorbed decreases. This indicates that using FNC to enhance desorption effectively increases the amount of methane desorbed to 1.17 mL / g, a 1.27-fold increase compared to pure water.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A salt-tolerant coalbed methane desorption agent, characterized in that: Its molecular formula is: Where n is 3-11.

2. A method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 1, characterized in that: The steps include: 1) Dissolve triethylamine and N,N'-dimethyl-1,3-propylenediamine in dichloromethane, stir until uniform, and then slowly add perfluorobutylsulfonyl fluoride dropwise. After the addition is complete, perform a synthesis reaction, then filter and dry to obtain a white solid powder FNC-1; 2) Weigh the white solid powder FNC-1 and Cl(CH2) n CH=CH2, where n=3-8 or Cl(CH2) n CH3, wherein n=3-11, is dissolved in acetonitrile and refluxed. After the reaction is complete, it is distilled under reduced pressure and dried to obtain white crystalline powder FNC-2; 3) Weigh the white crystalline powder FNC-2 and Cl(CH2) n COOH, where n=3-6 or Cl(CH2) n SO3H, wherein n=3-9, and triethylamine are dissolved in acetonitrile and subjected to reflux reaction. After the reaction is complete, vacuum distillation is performed and dried to obtain a white paste solid FNC fluorocarbon surfactant, i.e., a salt-resistant coalbed methane desorption promoter.

3. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 2, characterized in that: The mass ratio of triethylamine, N,N'-dimethyl-1,3-propylenediamine and perfluorobutylsulfonyl fluoride in step 1) is 3-8:4-6:10-20.

4. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 2, wherein: The stirring in step 1) is carried out in a low-temperature reaction bath at -3-0°C.

5. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 4, characterized in that: The process conditions of the synthesis reaction in step 1) are: heating to 10-20°C and continuing stirring for 3-5 hours; the drying temperature in step 1) is 50-70°C.

6. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 5, characterized in that: In step 2), FNC-1 and Cl(CH2) n CH=CH2 or Cl(CH2) n The mass ratio of CH3 is 17-21:7-11.

7. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 6, characterized in that: The process conditions of the reflux reaction in step 2) are: stirring and reflux reaction in a magnetic stirring oil bath at 70-90° C. for 15-25 hours.

8. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 5, characterized in that: FNC-2, Cl(CH2) in step 3) n COOH or Cl(CH2) n The mass ratio of SO3H and triethylamine is 14-18:3-5:3-5.

9. The method for preparing the salt-tolerant coalbed methane desorption accelerating agent according to claim 8, characterized in that: The process conditions of the reflux reaction in step 3) are: placing the mixture in a magnetic stirring oil bath at 70-90° C. and stirring the mixture under reflux for 15-25 hours.

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