A nano desorbent for gas well and a preparation method thereof

Abstract

The present application belongs to the technical field of oil and gas exploitation, and relates to a nano desorption agent for gas well and a preparation method thereof. The desorption agent uses special pretreated biochar as a core carrier, loads specific proportion of bimetallic oxide nanoparticles, and is supplemented with an environmentally friendly surfactant for surface modification. Through the synergistic effect of nano size effect, catalysis / electron transfer effect of metal oxide, physical adsorption and pore transport effect of biochar, and interfacial tension reduction effect of surfactant, the adsorption energy barrier of gas molecules such as methane on the rock surface is significantly reduced, and the efficient desorption is promoted. At the same time, all components and preparation processes are environmentally friendly and harmless to human body.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction technology, and relates to a nano-desorbent for gas wells and its preparation method. Background Technology

[0002] In the extraction of unconventional natural gas (such as shale gas and coalbed methane), a large amount of natural gas in the formation exists in an adsorbed state on the surface of the micro- and nano-pores of rocks (such as shale and coal). Traditional depressurization extraction methods have low desorption efficiency for this adsorbed gas, resulting in low recovery rates. Developing efficient and safe desorbents to promote the desorption of adsorbed gas from the rock surface and its conversion into free gas is one of the key technologies for improving natural gas recovery rates.

[0003] Existing desorbents are mainly divided into three categories: alcohol ether chemical agents (such as methanol and ethylene glycol ethers). These desorbents only promote gas flow by reducing the gas-liquid interfacial tension, but cannot break the adsorption bonds between gas molecules and the rock surface (such as van der Waals forces and electrostatic attraction). They have low desorption efficiency, are prone to volatilization and failure at high temperatures downhole, and are highly toxic and pollute groundwater. Single nano-metal oxides (such as nano-SiO2 and Al2O3 suspensions). These nanoparticles are prone to agglomeration and sedimentation due to their high surface energy, making it difficult to enter the nanoscale rock micropores. They lack targeted active sites, have weak interference ability with the adsorption bonds of gases such as methane, require high-temperature calcination for preparation, have high energy consumption, and have a wide particle size distribution. Ordinary biochar-supported materials. The pores of biochar are easily blocked by ash (silicates and metal salts), resulting in insufficient specific surface area and low loading rate of active components. Unmodified biochar has few functional groups on its surface, weak binding force with metal oxides, and the nanoparticles are prone to detachment and deactivation after injection into the formation. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a nano-desorbent for gas wells and its preparation method. This desorbent utilizes specially pretreated biochar as a core carrier, loading a specific proportion of bimetallic oxide nanoparticles, and is further surface-modified with an environmentally friendly surfactant. Through the synergistic effect of nanosize, the catalytic / electron transfer effect of the metal oxides, the physical adsorption and pore transport of biochar, and the interfacial tension reduction effect of the surfactant, the adsorption energy barrier of methane and other gas molecules on the rock surface is significantly reduced, promoting their efficient desorption. Simultaneously, all components and the preparation process are designed to be environmentally friendly and harmless to humans. Specifically, the following steps are included:

[0005] Step 1: Crush the biochar to a powder size ≤100μm. Mix the biochar powder with 0.5-1mol / L hydrochloric acid solution at a mass ratio of 1:(4-6). Stir at 55-65℃ and 120-150rpm for 1.5-2.5h. After the reaction is complete, filter and remove the filtrate. Wash the filter residue with deionized water until the washing liquid is neutral. Then, under nitrogen protection, microwave the filter residue at 650-750W for 4-6min. Immediately after microwave treatment, immerse the biochar in liquid nitrogen. In a solution of biochar and liquid nitrogen at a mass ratio of 1:(1-2) at ≤-196℃, the biochar is soaked for 25-35 min and then dried at 75-85℃ for 11-13 h to obtain highly active biochar powder. The highly active biochar powder, oil phase separator, emulsifier and deionized water are mixed at a mass ratio of (50-70):(15-25):(1-3):(350-450) and sheared at 4000-6000 rpm for 10-20 min to obtain an oil-in-water emulsion.

[0006] Preferably, the oil phase separator is white oil, and the emulsifier is sorbitan monooleate.

[0007] In this process, hydrochloric acid removes most of the ash (such as silicates, alkali metals, and alkaline earth metals) and some soluble organic matter from the biochar, improving its purity, specific surface area, and reactivity. Microwaves rapidly heat the internal moisture of the biochar, producing a "steam explosion" effect that effectively opens blocked pores, increasing porosity and surface oxygen-containing functional groups (such as carboxyl and hydroxyl groups). The drastic temperature changes caused by liquid nitrogen freezing further induce microcracks in the internal structure of the biochar, optimizing the pore structure distribution and facilitating the loading of metal oxide nanoparticles, thus increasing the pores for gas transport. Tiny white oil droplets are adsorbed or encapsulated on the surface of the biochar particles, providing a local microenvironment in subsequent reactions and limiting the excessive growth and aggregation of metal oxide nanoparticles.

[0008] Step 2: Zinc sulfate heptahydrate, copper sulfate pentahydrate, and deionized water are mixed at a mass ratio of (13-17):(7-8):(180-220) to obtain a metal salt solution. Under the condition of stirring the oil-in-water emulsion at 65-75℃ and 4500-5500rpm, the metal salt solution is added dropwise to the oil-in-water emulsion at a rate of 0.06-0.08mL / s. After the metal salt solution is added, the mixture is stirred for 3-5min. Then, a precipitant is added dropwise to the reaction system at a rate of 0.03-0.05mL / s. After the addition is complete, the mixture is aged at 65-75℃ for 1.5-2.5h. After aging, a demulsifier is added, and the mixture is allowed to stand and separate into layers. The upper oil phase is removed, and the lower mixture is centrifuged at 8000-12000rpm for 8-12min. The supernatant is removed, and the lower precipitate is collected and dried at 75-85℃ for 7-9h to obtain biochar-supported ZnO-CuO nanopowder.

[0009] Preferably, the mass ratio of the metal salt solution, the oil-in-water emulsion, the precipitant, and the demulsifier is (8-12):(35-45):(8-12):(1-2). Most preferably, the precipitant is a 1-2 mol / L sodium hydroxide solution, and the demulsifier is anhydrous ethanol.

[0010] After a metal salt solution enters an oil-in-water emulsion system, Zn 2+ and Cu 2+ The ions disperse rapidly in the aqueous phase, with some adsorbing onto the biochar surface and others diffused to the oil-water interface due to the attraction of the hydrophobic layer of dehydrated sorbitan monooleate. At this point, sodium hydroxide solution is added, and some Zn... 2+ and Cu 2+ Hydroxide precursors (Zn(OH)2 and Cu(OH)2) are generated on the surface of biochar, with some Zn... 2+ and Cu 2+ Due to the interfacial enrichment effect of dehydrated sorbitan monooleate, hydroxide precursors are generated at the oil-water interface. Combined with the encapsulation and confinement effect of white oil droplets, the nucleation and growth of the precursors are restricted to a local area, which is conducive to the formation of small-sized and narrowly distributed nanoparticles. During aging, the hydroxide precursors gradually dehydrate and transform into more stable oxide crystal forms (ZnO and CuO).

[0011] Step 3: Mix the biochar-supported ZnO-CuO nanopowder with the surfactant solution and stir at 200-300 rpm for 10-20 min. During stirring, add the stabilizer solution and homogenize the mixture at 50-100 MPa 3-5 times to ensure that the nanocomposite particles are fully coated by the surfactant and form a highly dispersed and stable suspension under the action of the stabilizer. Adjust the solid content to 5-15 wt% with deionized water and adjust the pH value to 6.5-7.5 with sodium hydroxide or dilute hydrochloric acid solution to obtain the nano-desorbent.

[0012] Preferably, the mass ratio of the biochar-supported ZnO-CuO nanopowder, surfactant solution, and stabilizer solution is (1-2):(3-5):(3-5). Most preferably, the concentration of the sodium hydroxide solution is 0.5-1.5 mol / L, and the concentration of the dilute hydrochloric acid solution is 0.5-1.5 mol / L.

[0013] Preferably, the surfactant solution and stabilizer solution are prepared by mixing a nonionic surfactant with deionized water at a mass ratio of (2-3):(45-55), stirring at 35-45°C and 90-120 rpm until completely dissolved and transparent, to obtain a surfactant solution; and mixing a stabilizer with deionized water at a mass ratio of (1-2):(80-120), stirring at 35-45°C and 90-120 rpm for 10-20 min, to obtain a stabilizer solution. Most preferably, the nonionic surfactant is polyglycerol ricinoleate (PGPR) or Tween 80, and the stabilizer is polyacrylamide (HPAM) with a molecular weight of 10000-20000 Da and a degree of hydrolysis of 20-30%.

[0014] The functions and mechanisms of each component of the nano-desorbent of this invention are as follows:

[0015] The role of biochar and its modification treatment is to provide a huge specific surface area and abundant micro / mesoporous structures, serving as anchoring sites for metal oxide nanoparticles and transport channels for desorbed gases.

[0016] Metal oxide nanoparticles, as the core active material for desorption, are composed of zinc oxide nanoparticles and copper oxide nanoparticles. Zinc oxide nanoparticles have excellent semiconductor properties and certain photocatalytic potential (which can be utilized by weak downhole light sources or thermal radiation), while copper oxide nanoparticles have the ability to promote electron transfer. The two work together to effectively interfere with the adsorption and bonding of gas molecules to the rock surface (such as van der Waals forces and electrostatic attraction), thereby reducing the desorption activation energy.

[0017] The role of PGPR or Tween 80 is to significantly reduce the interfacial tension between the desorbent solution and the rock / gas interface, weaken the capillary force binding the gas, improve the dispersion stability of metal oxide nanoparticles in water-based systems, prevent agglomeration, encapsulate metal oxide nanoparticles, provide a certain steric hindrance, and protect their activity.

[0018] The role of HPAM is to further enhance the long-term dispersion stability of nanoparticles in aqueous solution through steric hindrance, ensure injection performance, and provide a certain viscosity to help the desorbent be retained and covered in the target formation.

[0019] The present invention has the following advantages:

[0020] (1) The desorbent prepared by this invention deeply destroys the gas adsorption bond and significantly improves the desorption efficiency. ZnO-CuO nanoparticles significantly improve the desorption efficiency through the synergistic effect of semiconductor properties and electron transfer. ZnO uses the weak light source / thermal radiation downhole to excite electrons and weaken the electrostatic attraction between gas molecules and rocks. CuO acts as an electron transfer medium to accelerate the breaking of adsorption bonds and reduce the desorption activation energy. Combined with the micropores of biochar as a gas transport channel, the nanoparticles contact the adsorption sites to improve the desorption efficiency. This solves the problem that existing alcohol ether agents only reduce interfacial tension and cannot interfere with adsorption bonds.

[0021] (2) The desorbent nanoparticles prepared by this invention are highly dispersed and resistant to aggregation. The white oil droplets encapsulate biochar to form a "microreactor", which constrains the nucleation space of the Zn(OH)2 / Cu(OH)2 precursor, thus obtaining ZnO-CuO nanoparticles. PGPR / Tween 80 reduces interfacial tension, and HPAM forms a "three-dimensional stable network" through steric hindrance, so that the metal oxide nanoparticles remain monodisperse in the solution and can effectively enter the nanopores, solving the problem that existing nanomaterials cannot enter the micropores due to aggregation.

[0022] (3) The desorbent carrier prepared by this invention maximizes the pore size and active sites, has a long-lasting effect, and is activated by a three-stage process of acid washing, microwave, and liquid nitrogen. Hydrochloric acid removes ash and opens closed pores, while microwave "steam explosion" generates microcracks, increases oxygen-containing functional groups (-COOH, -OH), and improves the specific surface area. Liquid nitrogen rapid cooling expands the crack network, optimizes the pore size distribution, and significantly improves the loading rate, thus solving the problems of pore blockage and low loading rate of ordinary biochar.

[0023] (4) Biochar can be prepared from agricultural and forestry waste. White oil and PGPR are green raw materials with no heavy metal pollution. The entire process does not require high-temperature calcination. Shear emulsification and circulation homogenization are conventional equipment, which significantly reduces energy consumption and solves the problems of high toxicity of traditional chemical agents and high cost of nanomaterial preparation. Detailed Implementation

[0024] The technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] 1. Raw material preparation

[0027] Surfactant solution: PGPR and deionized water are mixed at a mass ratio of 1.5:50 and stirred at 40℃ and 100rpm until completely dissolved and transparent to obtain the surfactant solution.

[0028] Stabilizer solution: Mix stabilizer and deionized water at a mass ratio of 1.5:100, stir at 40℃ and 100 rpm for 15 min to obtain stabilizer solution.

[0029] Biochar: Rice straw biochar purchased from Henan Xingnuo Environmental Protection Materials Co., Ltd.

[0030] 2. Preparation steps

[0031] Step 1: Crush biochar to a powder size ≤100μm. Mix biochar powder with 0.5mol / L hydrochloric acid solution at a mass ratio of 1:5. Stir at 60℃ and 130rpm for 2 hours. After the reaction is complete, filter and remove the filtrate. Wash the filter residue with deionized water until the washing liquid is neutral. Then, under nitrogen protection, microwave the filter residue at 700W for 5 minutes. Immediately after microwave treatment, immerse the biochar in liquid nitrogen (≤-196℃) at a mass ratio of 1:2. After soaking for 30 minutes, dry at 80℃ for 12 hours to obtain highly active biochar powder. Mix the highly active biochar powder, oil phase separator, emulsifier, and deionized water at a mass ratio of 30:10:1:200. Shear emulsify at 5000rpm for 15 minutes to obtain an oil-in-water emulsion.

[0032] Step 2: Zinc sulfate heptahydrate, copper sulfate pentahydrate, and deionized water were mixed at a mass ratio of 15:7.5:200 to obtain a metal salt solution. Under the condition of stirring the oil-in-water emulsion at 70℃ and 5000rpm, the metal salt solution was added dropwise to the oil-in-water emulsion at a rate of 0.07mL / s. After the metal salt solution was added, the mixture was stirred for 4min. Then, a 1.5mol / L sodium hydroxide solution was added dropwise to the reaction system at a rate of 0.04mL / s. After the addition was complete, the mixture was aged at 70℃ for 2h. After aging, anhydrous ethanol was added, and the mixture was allowed to stand and separate into layers. The upper oil phase was removed, and the lower mixture was centrifuged at 10000rpm for 10min. The supernatant was removed, and the lower precipitate was collected and dried at 80℃ for 8h to obtain biochar-supported ZnO-CuO nanoparticles.

[0033] The mass ratio of the metal salt solution, oil-in-water emulsion, sodium hydroxide solution, and anhydrous ethanol is 10:40:10:1.5.

[0034] Step 3: Mix the biochar-supported ZnO-CuO nanopowder with the surfactant solution, stir at 250 rpm for 15 min, add the stabilizer solution during stirring, and homogenize the mixed solution by circulating it at 75 MPa 4 times. Adjust the solid content to 10 wt% with deionized water and adjust the pH value to 7.2 with sodium hydroxide solution to obtain the nano-desorbent.

[0035] Experimental Example 1 (Comparative Experiment on Desorption Efficiency)

[0036] 1. Sample preparation:

[0037] Take 10g of shale core (50-100 mesh) and saturate it with methane for 24 hours in a high-pressure adsorption device at 60℃ and 15MPa. Then inject the following desorbents:

[0038] Experimental group: Nano-desorbent prepared in Example 1.

[0039] Control group 1: 95% methanol (traditional alcohol ether agent).

[0040] Control group 2: Nano SiO2 suspension (nano SiO2 content ≥ 25%).

[0041] Control group 3: The difference from the preparation method in Example 1 is that the biochar was not subjected to acidification-microwave freezing treatment and was directly loaded with ZnO-CuO.

[0042] 2. Desorption process:

[0043] Maintain a temperature of 60℃ and a pressure of 8MPa, and record the cumulative amount of gas desorbed within 0-48 hours.

[0044] Calculate the desorption rate: Desorption rate (%) = (cumulative desorption amount / saturated adsorption amount) × 100%, and the results are shown in Table 1.

[0045] Table 1 Comparison of methane desorption rates with different desorbents

[0046]

[0047]

[0048] Experimental Example 2 (Nanoparticle Dispersibility and Stability Test)

[0049] 1. Particle size distribution test: The D50 and D90 particle sizes of the desorbent of this invention were measured using a laser particle size analyzer and compared with the control group 2.

[0050] 2. Sedimentation stability test: The desorbent was allowed to stand for 30 days, and the sedimentation rate was recorded every 24 hours. The results are shown in Table 2. Sedimentation rate (%) = (bottom sedimentation height / initial suspension height) × 100%.

[0051] Table 2. Data on the dispersibility and stability of nanoparticles

[0052] experimental group Control group 2 D50(nm) 28.5±1.2 86.3±3.5 D90(nm) 49.7±2.1 152.4±5.8 30-day settlement rate (%) 4.2±0.3 98.5±0.5

[0053] Experimental Example 3

[0054] The specific surface area and pore volume of the highly active biochar in the experimental group treated with acid washing, microwave and liquid nitrogen and the untreated ordinary biochar in the control group were determined using a nitrogen adsorption instrument. The results are shown in Table 3.

[0055] Table 3 Comparison of Biochar Carrier Performance

[0056] experimental group Control group 3 <![CDATA[Specific surface area (m 2 / g)]]> 486.3±12.5 102.7±8.3 <![CDATA[Total pore volume (cm 3 / g)]]> 0.63±0.02 0.21±0.01 Average pore size (nm) 3.8±0.2 8.2±0.5

[0057] Experimental Example 4 (Oil-Water Interfacial Tension Test)

[0058] 1. Prepare a desorbent solution as the aqueous phase and n-decane to simulate formation crude oil as the oil phase.

[0059] 2. Measured using a rotating drop tensiometer at 60℃ (simulated downhole temperature):

[0060] Aqueous phase: 1. Desorbent solution for experimental group. 2. Desorbent solution for control group 1. 3. Desorbent solution for control group 2. 4. Deionized water (blank).

[0061] Oil phase: n-Decane

[0062] 3. Record the dynamic interfacial tension (IFT) and take the equilibrium value (t = 30 min), as shown in Table 4.

[0063] Table 4 Comparison of oil-water interfacial tension (60℃)

[0064] Equilibrium interfacial tension (mN / m) The magnitude of the decrease (compared to the blank group) Blank group 48.3±0.5 - Control group 1 22.7±0.4 53.0％ Control group 2 34.1±0.6 29.4％ experimental group 0.008±0.001 ＞99％

[0065] Experimental Example 5 (Test on Changes in Rock Wettability)

[0066] 1. Prepare shale flakes (2×2cm, surface polished to Ra≤0.1μm) and age them in a methane environment at 60℃ for 48 hours to simulate the adsorption state.

[0067] 2. Immerse the rock slices in the desorbent solution of the experimental group and control group 1-2 for 4 hours, respectively, and then remove them and purge the surface liquid with nitrogen.

[0068] 3. Using a contact angle measuring instrument, 3 μL of deionized water was dripped onto the shale surface, and the static contact angle (θ) was recorded. The results are shown in Table 5.

[0069] Table 5. Changes in shale surface wettability (contact angle θ)

[0070]

[0071]

[0072] Experimental Example 6 (Capillary Self-Aspiration Height Experiment)

[0073] 1. Cut the shale core into cylinders with a diameter of 2.5 cm and a height of 5 cm, and dry them at 105℃ to constant weight.

[0074] 2. The core was suspended vertically, and the lower end was immersed in the desorbent solution of the experimental group and control group 1-2, respectively, and deionized water was used as a blank control. The spontaneous aspiration height (h) of the liquid within 30 min was recorded. The results are shown in Table 6.

[0075] 3. Calculate the capillary force: P c =ρgh (ρ is the solution density, g is the gravitational acceleration).

[0076] Table 6 Comparison of capillary self-priming height and binding force

[0077] Self-priming height (mm) <![CDATA[Capillary force P c (kPa)]]> Reduction in binding force (based on water) Deionized water 38.2±1.5 37.5±1.5 - Control group 1 21.3±1.2 20.9±1.2 44.3％ Control group 2 30.5±01.8 29.9±1.8 20.3％ experimental group 24.5±0.9 21.1±0.8 85.3％

[0078] As shown in Tables 1-6, the desorption rate of the desorbent prepared in this invention is significantly higher than that of the control groups 1-3 (reaching 95.6% after 48 hours), due to the synergistic disruption of adsorption bonds by ZnO-CuO and the transport function of biochar pores. The desorbent prepared in this invention has smaller particles (D50 < 30 nm) and a lower sedimentation rate (sedimentation rate < 5% after 30 days), attributed to the PGPR / HPAM stabilizing system. Acid washing-microwave-liquid nitrogen treatment increases the specific surface area of ​​biochar by 374%, optimizes the pore size distribution, and facilitates nanoparticle loading and gas diffusion. Due to the synergistic effect of PGPR / Tween 80, the interfacial tension is reduced to < 1 mN / m, significantly weakening capillary binding. The contact angle is significantly reduced, and the rock surface changes from oleophilic to hydrophilic, which is conducive to gas desorption. The self-adsorption height is significantly reduced, proving that the desorbent greatly weakens the capillary force's retention effect on gas. The low sedimentation rate of the desorbent prepared by this invention ensures that nanoparticles can be injected into micropores of <50nm, the high specific surface area of ​​the carrier increases the loading rate of active components, and there is no heavy metal pollution (the raw material is biochar / PGPR), and the energy consumption is significantly reduced (no high-temperature calcination is required).

[0079] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a nano-desorbent for gas wells, characterized in that, Includes the following steps: Step 1: Crush the biochar and mix it with hydrochloric acid solution, filter it, remove the filtrate, microwave the filter residue, and immediately immerse the filter residue in liquid nitrogen. After soaking, dry it at 75-85℃ for 11-13 hours to obtain highly active biochar powder. Highly active biochar powder, oil phase separator, emulsifier and deionized water are mixed in a mass ratio of (50-70):(15-25):(1-3):(350-450) and sheared to emulsify to obtain an oil-in-water emulsion. Step 2: Zinc sulfate heptahydrate, copper sulfate pentahydrate, and deionized water are mixed at a mass ratio of (13-17):(7-8):(180-220) to obtain a metal salt solution. Under the condition of stirring the oil-in-water emulsion, the metal salt solution is added dropwise to the oil-in-water emulsion. After the addition is completed, stirring is continued, and then the precipitant is added dropwise to the reaction system. After the addition is completed, the mixture is aged, then a demulsifier is added, and the mixture is allowed to stand to remove the upper oil phase. The lower mixture is centrifuged, the supernatant is removed, and the lower precipitate is collected and dried at 75-85℃ for 7-9 hours to obtain biochar-supported ZnO-CuO nanopowder. The mass ratio of the metal salt solution, oil-in-water emulsion, precipitant and demulsifier is (8-12):(35-45):(8-12):(1-2); Step 3: Mix and stir the biochar-supported ZnO-CuO nanopowder with the surfactant solution. Add the stabilizer solution during stirring. Homogenize the mixture by circulation. Adjust the solid content to 5-15 wt% with deionized water and adjust the pH value to 6.5-7.5 with sodium hydroxide or dilute hydrochloric acid solution to obtain the nano-desorbent. The mass ratio of the biochar-supported ZnO-CuO nanopowder, surfactant solution, and stabilizer solution is (1-2):(3-5):(3-5); The oil phase separator mentioned in step one is white oil, and the emulsifier is sorbitan monooleate. The demulsifier mentioned in step two is anhydrous ethanol; The method for preparing the surfactant solution in step three is as follows: nonionic surfactant and deionized water are mixed at a mass ratio of (2-3):(45-55), and stirred at 35-45℃ and 90-120 rpm until completely dissolved and transparent to obtain the surfactant solution. The nonionic surfactant is PGPR; The method for preparing the stabilizer solution in step three is as follows: mix the stabilizer with deionized water at a mass ratio of (1-2):(80-120), stir at 35-45℃ and 90-120 rpm for 10-20 min to obtain the stabilizer solution; The stabilizer is HPAM with a molecular weight of 10,000-20,000 Da and a degree of hydrolysis of 20-30%.

2. The method for preparing a nano-desorbent for gas wells according to claim 1, characterized in that, The precipitant mentioned in step two is a 1-2 mol / L sodium hydroxide solution.

3. The method for preparing a nano-desorbent for gas wells according to claim 1, characterized in that, The concentration of the sodium hydroxide solution in step three is 0.5-1.5 mol / L, and the concentration of the dilute hydrochloric acid solution is 0.5-1.5 mol / L.

4. The nano-desorbent prepared by the method according to any one of claims 1-3.

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