A biomass gel and its preparation method and application

Abstract

The present application relates to the field of gel material, disclose a kind of biomass gel and its preparation method and application, the method comprises: (1) in inert atmosphere 1, in the presence of mixed solvent 1, polyether, 2-acrylamide-2-methylpropane sulfonic acid, dimethylaminoethyl methacrylate, divinyl benzene and initiator are polymerized to obtain intermediate;(2) in inert atmosphere 2, in the presence of mixed solvent 2, the intermediate is crosslinked with biomass raw material, ferric salt, to obtain biomass gel;The biomass raw material is selected from at least one of alkali lignin, dealkalized lignin, sodium lignosulfonate, calcium lignosulfonate, tannic acid, cellulose and inulin;Using the method of the application, a kind of biomass gel resistant to high temperature, salt and not easy to dissociate can be prepared.

Description

Technical Field

[0001] This invention relates to the field of gel materials, specifically to a biomass gel, its preparation method, and its applications. Background Technology

[0002] Currently, most oil reservoirs are terrestrial sedimentary formations, exhibiting significant heterogeneity, severe fracture development, and pronounced gas and water channeling, resulting in poor oil displacement and storage performance. In complex deep and ultra-deep environments (such as supercritical CO2, high temperature, and high salinity), the channeling and sealing systems have poor tolerance, making long-term channeling and sealing difficult.

[0003] Gels are an effective means of sealing cross-contamination channels, but traditional polyacrylamide-based sealing systems have poor temperature and salt resistance, and are prone to dehydration and degradation under supercritical CO2, leading to system failure. Furthermore, most organic gels undergo structural dissociation under high temperature (140℃), high salt (2% KCl), and long-term (12 months) acidic conditions. In addition, in-situ gel injection presents chromatographic separation problems; the porous nature of gel particles due to particle packing prevents them from filling cracks, resulting in reduced sealing strength. Moreover, most existing CO2-responsive polymers use non-biobased materials as the matrix, which are non-degradable after use.

[0004] CN119192479A discloses a high-performance leak-proof and plugging gel for fractured formations and its preparation method. The gel comprises the following components by weight percentage: 20-30% copolymer monomers; 15-25% ultrafine plant fibers; 0.5-6.0% surfactant; 0.1-2.0% initiator; 0.1-2.0% cosolvent; 0.05-0.5% accelerator; 1-5% polymer powder; 0.5-5% brine solution; and the balance being water. The copolymer monomers are a combination of hydrophilic monomers, hydrophobic monomers, and functionalized group molecules. The mass ratio of hydrophilic monomers to hydrophobic monomers and functionalized group molecules in the copolymer monomers is 5-7:2-4:1. The gel prepared by this method suffers from poor rheological properties, poor temperature and salt resistance, low mechanical strength, and poor responsiveness to CO2 stimulation.

[0005] CN110746614A discloses a high-strength, impact-resistant physical hydrogel, whose structure is a three-dimensional network formed by the cross-linking of polymerizable charged monomers and neutral polymers, and the three-dimensional network structure contains metal ions. This hydrogel suffers from poor stability. Summary of the Invention

[0006] The purpose of this invention is to provide a biomass gel that is resistant to high temperatures and salt and does not easily dissociate.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a biomass gel, the method comprising:

[0008] (1) In an inert atmosphere 1, in the presence of a mixed solvent 1, a polyether, 2-acrylamide-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene and an initiator are subjected to a polymerization reaction to obtain an intermediate; the polyether has a weight-average molecular weight of 8000-15000 Da.

[0009] (2) In an inert atmosphere 2, in the presence of a mixed solvent 2, the intermediate is cross-linked with biomass raw materials and ferric salts to obtain a biomass gel.

[0010] The biomass raw material is selected from at least one of alkali lignin, dealkali lignin, sodium lignin sulfonate, calcium lignin sulfonate, tannic acid, cellulose and inulin;

[0011] The mixed solvent 1 and the mixed solvent 2 may be the same or different, and each is independently selected from a mixture of organic solvent and water.

[0012] A second aspect of the present invention provides a biomass gel prepared by the method described in the first aspect.

[0013] A third aspect of the invention provides the use of the biomass gel described in the second aspect in reservoir profile control and plugging agents.

[0014] The present invention has at least the following advantages:

[0015] (1) In this invention, a polyether structure with excellent thermosensitivity is introduced as the molecular skeleton of the gel material. Combined with 2-acrylamide-2-methylpropanesulfonic acid containing a large number of sulfonic acid groups, dimethylaminoethyl methacrylate with tertiary amine groups, divinylbenzene and an initiator, an intermediate with a two-dimensional topological structure is obtained. Based on the intermediate structure, trivalent iron ions and green biodegradable biomass materials rich in a large number of hydroxyl groups are further introduced to further increase the intermolecular molecular forces, resulting in a three-dimensional biomass gel with significantly improved temperature resistance, salt resistance and CO2 stimulation response.

[0016] (2) The method for preparing biomass gel in this invention has the technical advantages of low cost and simple process. Attached Figure Description

[0017] Figure 1 Raman spectra of the biomass gels prepared in Examples 2 and 3 are shown.

[0018] Figure 2 The thermogravimetric-infrared spectrum of the biomass gel prepared in Example 3 is shown.

[0019] Figure 3 The image shows a scanning electron microscope (SEM) image of the intermediate and biomass gel prepared in Example 3.

[0020] Figure 4 The images show a comparison of the biomass gel prepared in Example 3 before and after supercritical CO2 stimulation.

[0021] Figure 5 The images show a comparison of the weather resistance of biomass gels and some intermediates in Examples 1-3, 7, 8 and Comparative Example 3.

[0022] Figure 6 The diagram shows the high-temperature rheological characterization of the biomass gels prepared in Examples 2, 3, 3, and 4.

[0023] Figure 7 The rheological properties of the biomass gels prepared in Examples 1-4 and Comparative Examples 2-4 are shown in the figure. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] In this invention, the CO2 stimulus responsiveness refers to the characteristic of a material to change its physical or chemical properties according to changes in CO2 concentration or partial pressure; in this application, it is mainly reflected in the change of volume expansion, which will cause a protonation reaction.

[0026] As previously described, a first aspect of the present invention provides a method for preparing a biomass gel, the method comprising:

[0027] (1) In an inert atmosphere 1, in the presence of a mixed solvent 1, a polyether, 2-acrylamide-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene and an initiator are subjected to a polymerization reaction to obtain an intermediate; the polyether has a weight-average molecular weight of 8000-15000 Da.

[0028] (2) In an inert atmosphere 2, in the presence of a mixed solvent 2, the intermediate is cross-linked with biomass raw materials and ferric salts to obtain a biomass gel.

[0029] The biomass raw material is selected from at least one of alkali lignin, dealkali lignin, sodium lignin sulfonate, calcium lignin sulfonate, tannic acid, cellulose and inulin;

[0030] The mixed solvent 1 and the mixed solvent 2 may be the same or different, and each is independently selected from a mixture of organic solvent and water.

[0031] In the technical solution of this invention, a polyether with a weight-average molecular weight of 8000-15000 Da is used to construct the chemical molecular framework of the gel material. Simultaneously, dimethylaminoethyl methacrylate containing tertiary amine groups and 2-acrylamido-2-methylpropanesulfonic acid containing sulfonic acid groups are introduced. Combined with divinylbenzene and an initiator, these components effectively enhance the gel material's high-temperature resistance, salt resistance, and responsiveness to CO2 stimulation. Furthermore, the introduction of a trivalent iron ion physical gel network, which incorporates biomass materials rich in hydroxyl groups and enhances intermolecular coordination and hydrogen bonding, effectively improves the gel's viscosity properties, thereby increasing its flexibility and water retention capacity. This ensures that the gel material maintains excellent stability even under extreme conditions, such as high temperature, high salt, and the effects of supercritical CO2.

[0032] According to a preferred embodiment, in step (1), the polyether is first mixed and stirred with the mixed solvent 1 to obtain solution 1; then the solution 1 is subjected to the polymerization reaction with the 2-acrylamide-2-methylpropanesulfonic acid, the dimethylaminoethyl methacrylate, the divinylbenzene and the initiator to obtain the intermediate. The inventors discovered that by preferentially reacting a specific polyether with a mixed solvent 1, a polyether solution with a self-crosslinking chemical network can be obtained. This polyether solution acts as a rigid framework, effectively enhancing the stability of the structure. Secondly, the specific polyether solution undergoes a free radical copolymerization reaction with 2-acrylamido-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene, and an initiator. This free radical copolymerization forms a second layer of chemical crosslinking network, enhancing the overall mechanical strength and stabilizing its stability. Finally, by using an intermediate with two layers of chemical crosslinking network, biomass, and ferric ions to form a physical crosslinking network, the gel material gains dynamic flexibility and biocompatibility. The specific three-step reaction, with layered feeding, allows the crosslinking reaction of each layer to proceed under relatively mild conditions, avoiding the damage to the previous layer structure caused by high temperatures and strong acids / alkalis. This simplifies the preparation process; that is, by optimizing the interlayer interactions through the layered feeding sequence and designing a functional gradient, the production process is simplified, resulting in superior overall performance of the gel material.

[0033] Preferably, the mixing and stirring process is carried out at a temperature of 10-30°C for 2-4 hours and at a stirring speed of 500-1000 rpm.

[0034] Preferably, the polyether comprises polyethylene glycol and / or polyoxypropylene ethylene glycerol ether. The inventors of this invention have discovered that, under these preferred conditions, the prepared gel exhibits superior high-temperature resistance, salt resistance, and excellent CO2 stimuli responsiveness.

[0035] Preferably, in step (1), the mass ratio of the polyether, the 2-acrylamide-2-methylpropanesulfonic acid, the dimethylaminoethyl methacrylate, the divinylbenzene and the initiator is 100:120-350:200-720:5-30:0.5-3.

[0036] Preferably, in step (2), the mass ratio of the intermediate, the biomass raw material and the trivalent iron salt is 1:0.5-1:0.1-0.3.

[0037] Preferably, the trivalent iron salt is selected from at least one of ferric chloride, ferric sulfate, and ferric nitrate.

[0038] Preferably, the initiator is selected from at least one of azobisisobutyronitrile, potassium persulfate, and benzoyl peroxide.

[0039] More preferably, the initiator is azobisisoheptanenitrile. Under these preferred conditions, the prepared gel material exhibits superior stability.

[0040] According to a preferred embodiment, the polymerization reaction conditions include a temperature of 50-70°C and a time of 6-12 hours.

[0041] In a preferred embodiment, the polymerization reaction is carried out under stirring at a speed of 500-1000 rpm.

[0042] Preferably, the conditions for the crosslinking reaction include: a temperature of 55-60°C and a time of 12-24 hours.

[0043] Preferably, in step (2), the water content of the intermediate is ≤90wt%.

[0044] According to a preferred embodiment, the method in step (1) further includes:

[0045] The product obtained by polymerizing the polyether, 2-acrylamide-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene, and the initiator was subjected to dialysis and freeze-drying treatment in sequence to obtain the intermediate.

[0046] The present invention does not impose any particular restrictions on the conditions of the freeze-drying process, as long as the water content of the intermediate is within the preferred conditions of the present invention. For example, the conditions of the freeze-drying process include: a vacuum degree of 1-5 Pa, a temperature of -65°C to -40°C, and a time of 20-30 h.

[0047] In a preferred embodiment, the dialysis process includes: dialyzing the product in distilled water for 5-8 days, with a dialysis membrane molecular cutoff of 40,000-50,000 Da.

[0048] Preferably, the inert atmosphere 1 and the inert atmosphere 2 are the same or different, and each is independently selected from at least one of nitrogen, argon and helium.

[0049] Preferably, the mixed solvent 1 and the mixed solvent 2 may be the same or different, and each is independently selected from at least one of glycerol aqueous solution and n-dodecane aqueous solution.

[0050] In some embodiments of the present invention, the amount of the mixed solvent 1 is 8-25 mL relative to 1 g of the polyether; the volume content of the organic solvent in the mixed solvent 1 is 50-70%.

[0051] In some embodiments of the present invention, the amount of the mixed solvent 2 is 15-20 mL relative to 1 g of the intermediate; the volume content of the organic solvent in the mixed solvent 2 is 40-60%.

[0052] According to a particularly preferred embodiment, the polyether exhibits excellent thermosensitivity, and the lowest critical co-solution temperature of the polyether in aqueous solution is 15-37°C. The inventors of this invention have discovered that, under these preferred conditions, the prepared gel material exhibits even better stability.

[0053] As previously stated, a second aspect of the present invention provides a biomass gel prepared by the method described in the first aspect.

[0054] Preferably, the biomass gel has a high temperature resistance of ≥270℃, a salt resistance of ≥400,000 ppm, and an expansion rate of 660%-900% after being treated with supercritical carbon dioxide at 40℃ and 15MPa for 72 hours.

[0055] More preferably, the biomass gel has an applicable pH range of 3-9 and an elastic modulus > 10. 5 Pa, viscous modulus > 10 4 Pa.

[0056] As previously stated, a third aspect of the present invention provides the application of the biomass gel described in the second aspect in reservoir profile control and plugging agents.

[0057] In the following embodiments, unless otherwise specified, all raw materials are commercially available products.

[0058] Polyethylene glycol: Polyethylene glycol 8000, CAS No.: 25322-68-3; weight average molecular weight: 8000 Da; purchased from McLean Company;

[0059] Polyoxypropylene ethylene glycerol ether: Model F127; CAS No.: 9003-11-6; Weight average molecular weight: 13000 Da; Purchased from McLean Company;

[0060] Polyoxypropylene ethylene glycerol ether: Model F188; CAS No.: 9003-11-6; Weight average molecular weight: 8000-10000 Da, purchased from McLean Company;

[0061] Fatty alcohol polyoxyethylene ether: CAS No.: 68213-23-0; weight average molecular weight: 538 Da; purchased from McLean Company;

[0062] Poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol): CAS No.: 9003-11-6; weight average molecular weight: 14600 Da; purchased from Maclean Company;

[0063] Inulin: CAS No.: 9005-80-5, purchased from McLean Company;

[0064] Nanocellulose: CAS: 9004-34-6, purchased from Aladdin Company;

[0065] Alkali lignin: CAS: 8068-05-1, purchased from Aladdin Company;

[0066] Alkali-degraded lignin: CAS 9005-53-2, purchased from Aladdin Company;

[0067] Mixed solvent 1-1: an aqueous solution of glycerol with a volume concentration of 69%;

[0068] Mixed solvent 1-2: an aqueous solution of glycerol with a volume concentration of 53%;

[0069] Mixed solvent 2: an aqueous solution of n-dodecane with a volume concentration of 43%.

[0070] Example 1

[0071] (1) Under a nitrogen atmosphere, mixed solvent 1 and polyether were mixed and stirred at 25°C and 600 rpm for 3 hours to obtain solution 1;

[0072] (2) Under a nitrogen atmosphere, solution 1, 2-acrylamide-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene and initiator were subjected to a polymerization reaction (stirring speed of 800 rpm) to obtain product 1;

[0073] (3) Product 1 was subjected to dialysis and freeze-drying in sequence to obtain an intermediate;

[0074] The dialysis process involved dialyzing product 1 in distilled water for 7 days, with a molecular cutoff of 50,000 Da for the dialysis membrane. The freeze-drying conditions were: vacuum of 2 Pa, temperature of -65 °C, and time of 24 h.

[0075] (4) Under a nitrogen atmosphere, in mixed solvent 2, the intermediate, biomass raw material and ferric salt are cross-linked to obtain biomass gel;

[0076] The specific process parameters are shown in Table 1.

[0077] Examples 2-10

[0078] The same process as in Example 1 was used, except that the types of raw materials or process parameters were different, as shown in Table 1, to obtain biomass gel.

[0079] Comparative Examples 1-4

[0080] The same process as in Example 1 was used, except that the types of raw materials or process parameters were different, as shown in Table 2, to obtain biomass gel.

[0081] Table 1

[0082]

[0083] Note: M represents polyether, S represents 2-acrylamide-2-methylpropanesulfonic acid, Z represents dimethylaminoethyl methacrylate, B represents divinylbenzene, J represents initiator, W represents intermediate, Y represents biomass feedstock, and T represents ferric chloride.

[0084] Continued from Table 1

[0085]

[0086]

[0087] Table 2

[0088]

[0089] Note: M represents polyether, S represents 2-acrylamide-2-methylpropanesulfonic acid, Z represents dimethylaminoethyl methacrylate, B represents divinylbenzene, J represents initiator, W represents intermediate, Y represents biomass feedstock, and T represents ferric chloride.

[0090] Test example:

[0091] 1. Raman spectroscopy detection: The Renishaw inVia Raman spectroscopy was used for testing, with a measurement power of 100%, a grating of 1200 L / mm, a 785 nm laser, and a 50X objective lens.

[0092] 2. Scanning electron microscopy (SEM) examination: A German ZEISS sigma 560+ Peltier cold stage was used. The gel sample was frozen and quenched in liquid nitrogen at -25°C. Imaging conditions: Accelerating voltage (Vacc): 1 kV; objective aperture diameter (Aperture Size): 30 μm; detector: SE2 secondary electron detector.

[0093] 3. Thermogravimetric-Infrared (TGI) Testing: Simultaneous thermal analyzer (NETZSCH STA449F5 Jupiter, Germany) and infrared spectrometer (BRUKER, Germany) were used for testing. The test temperature range was 10-600℃, the heating rate was 10℃ / min, the atmosphere was N2, and the scan wavenumber was 4000 cm⁻¹. -1 -550cm -1 Resolution: 4cm -1 Beam splitter: KBr, detector: TE-DLaTGS.

[0094] 4. Gel rheology test: The test was conducted using a HAAKE Mars60 rheometer, with the following parameters set: 20mm plate, 0.1% deformation, and a test range of 0.1-10Hz.

[0095] 5. Gel temperature resistance, acid resistance, and salt resistance tests:

[0096] (1) Temperature resistance test: The intermediate and biomass gel prepared in the example were placed in an ampoule, and then the ampoule was placed in a reaction vessel. The reaction vessel was placed in an oven at 270°C and left to stand for 15 days.

[0097] (2) Acid resistance test: The intermediate and biomass gel prepared in the example were placed in ampoules containing hydrochloric acid aqueous solution with pH value of 3, and the reaction vessel was left to stand for 7 days and 15 days respectively to observe the swelling phenomenon.

[0098] (3) Salt tolerance test: The intermediate and biomass gel prepared in the example were placed in ampoules containing sodium chloride aqueous solution with a salinity of 400,000 ppm. The reaction vessel was then left to stand for 7 days and 15 days respectively, and the swelling phenomenon was observed.

[0099] (4) Referring to the industry standard SY-T 5590-2004 "Comprehensive Test of Performance Evaluation Method of Profile Control Agent": the intermediate and biomass gel prepared in the example were placed in a hydrothermal reactor containing hydrochloric acid aqueous solution with a salinity of 400,000 ppm and a pH of 3, and then placed in an oven at 270°C for 15 days.

[0100] 6. Gel supercritical CO2 stimulus response test:

[0101] The LFDA-3 prepared in Example 3 was placed in a high-pressure reactor with CO2 introduced into it, and the pressure inside the reactor was kept at 15 MPa and the temperature at 40°C. The reactor was then left to stand for 3 days.

[0102] The present invention exemplarily in Figure 1 The document provides Raman spectra of LFDA-2 and LFDA-3, as well as the Raman spectrum of polyoxypropylene vinyl glycerol ether; [The document is constructed from...] Figure 2 It can be determined that the wave number is 831 cm⁻¹. -1 The position is a CO bond, 1043 cm⁻¹ -1 The location is a CN bond, 1653cm -1 and 1732cm -1 As a C=O compound, comparison with polyoxypropylene ethylene glycerol ether raw material proved that LFDA-2 and LFDA-3 products have been successfully grafted.

[0103] The present invention exemplarily in Figure 2 Thermogravimetric Infrared Spectroscopy (TGA) of LFDA-3 is provided, in which... Figure 2 (a) in the figure is the thermogravimetric spectrum of LFDA-3 from 10℃ to 600℃. Figure 2 (b) shows the infrared spectra of LFDA-3 at different temperatures.

[0104] Depend on Figure 2 As shown in (a), LFDA-3 exhibits good thermal stability before 270.5℃, but begins to decompose at 270.5℃; Figure 2 From (b), it can be seen that when the temperature is 270.5℃, at 1739cm - 1 and 1719cm - The presence of a C=O stretching vibration originating from a carbonyl or ester group at point 1 indicates that the polyether in LFDA-3 has begun to decompose; 1376 cm⁻¹ - 1 and 1339cm - 1 is a characteristic peak of CH bending vibration or partial CO bond, which is a characteristic functional group of polyether; therefore, it can be seen that LFDA-3 begins to decompose at 270.5℃, mainly releasing light volatile organic compounds; at 298.6℃, at 2863 cm⁻¹... -1 and 2941cm -1 The signal peaks of the CH stretching vibrations originating from hydrocarbons or methyl groups begin to weaken, indicating that volatile organic substances are released from LFDA-3. Thus, when the temperature is raised to 298.6℃, the biomass gel begins to release more medium-molecular-weight organic components; when the temperature is raised to 395.3℃, the biomass begins to release a large amount of CO2 and other decomposition products, indicating that the biomass gel has basically decomposed at this point.

[0105] The present invention exemplarily in Figure 3The image provides scanning electron microscope (SEM) images of FDA-3 and LFDA-3, among which... Figure 3 (a) shows a scanning electron microscope image of FDA-3. Figure 3 (b) shows a scanning electron microscope image of LFDA-3.

[0106] Depend on Figure 3 As shown in (a), the FDA-3 network structure exhibits an irregular and intricate fibrous structure, indicating that good cross-linking occurred during the preparation process. Numerous cross-linking points were formed between the chain segments, resulting in a denser and more complex network structure. Cross-linking points are crucial for constructing a three-dimensional network structure. The FDA-3 network structure connects molecular chain segments through chemical bonds, and this complex network structure provides a large specific surface area and good structural stability. Figure 3 As shown in (b), the LFDA-3 structure is a chemical-physical cross-linked composite three-dimensional network structure, and the pores in the structure are uniformly and regularly distributed, which is related to the chemical-physical cross-linking mechanism. This indicates that the preparation process simultaneously experienced the synergistic effect of chemical cross-linking and physical cross-linking. In the chemical-physical cross-linking system, the network formed by chemical cross-linking will spatially restrict the polymer chain segments, while the physical cross-linking process (such as thermal phase separation or solvent phase separation) will further drive the chain segments to self-assemble, thereby forming a regular pore distribution in a limited space.

[0107] The present invention exemplarily in Figure 4 The image provided shows the physical response of LFDA-3 to supercritical CO2 (40℃, 15MPa) stimulation; among them, Figure 4 (a) shows the changes in LFDA-3's response before and after 3 days of supercritical CO2 stimulation. Figure 4 In the middle (b), LFDA-3 was cut into two pieces before the experiment. After 3 days of supercritical CO2 stimulation (40℃, 15MPa), the two gels expanded in volume and achieved self-healing.

[0108] Depend on Figure 4 As shown in (a), after 3 days of stimulation response, LFDA-3 underwent significant volume expansion, increasing 7 times in volume compared to its untreated state, a 660% expansion rate. This was primarily due to supramolecular interactions between CO2 and the solvent or polymer segments in LFDA-3. The protonation reaction stimulated the expansion of the hydroxyl and amine groups in the biomass gel, leading to the expansion of the biomass gel's network structure. Figure 4 As shown in (b), the two split biomass gels after being injected with supercritical CO2 underwent self-healing during the volume expansion process.

[0109] The present invention exemplarily in Figure 5The document provides comparative images of FDA-3, LFDA-1, LFDA-2, LFDA-3, LFDA-7, LFDA-8, and DLFDA-3 after undergoing temperature resistance, acid resistance (prepared with hydrochloric acid solution), and salt resistance (NaCl) tests; among them, Figure 5 (a) in the table represents the blank control group before FDA-3, LFDA-1, LFDA-2, LFDA-3, LFDA-7, LFDA-8 and DLFDA-3 were tested. Figure 5 (b) in the figure represents the test specimens of FDA-3, LFDA-1, LFDA-2, LFDA-3, LFDA-7, LFDA-8, and DLFDA-3 after being kept at 270°C for 7 days. Figure 5 (c) in the figure represents the test specimens of FDA-3, LFDA-1, LFDA-2, LFDA-3, LFDA-7, LFDA-8, and DLFDA-3 after being kept at 270°C and pH=3 for 7 days. Figure 5 (d) in the figure represents the test specimens of FDA-3, LFDA-1, LFDA-2, LFDA-3, LFDA-7, LFDA-8 and DLFDA-3 after being kept at 270℃ and NaCl concentration of 400,000 ppm for 7 days. Figure 5 (e) in the figure represents the test results of FDA-3, LFDA-1, LFDA-2, LFDA-3, and DLFDA-3 after being kept at 270℃, NaCl concentration of 400,000 ppm, and pH=3 for 15 days. Among them, after LFDA-1, LFDA-2, LFDA-3, and DLFDA-3 were inverted, DLFDA-3 showed obvious dehydration.

[0110] Depend on Figure 5 As shown in (b), FDA-3, LFDA-1, LFDA-2, LFDA-3, LFDA-7, and LFDA-8 did not show significant decomposition under the aforementioned conditions, while DLFDA-3 partially decomposed into gel. Figure 5 As shown in (c), FDA-3, LFDA-1, LFDA-2, and LFDA-3 did not show significant decomposition under the aforementioned conditions, LFDA-7 and LFDA-8 decomposed slightly, and DLFDA-3 partially dehydrated. Figure 5 As shown in (d), LFDA-1, LFDA-2, LFDA-3, and DLFDA-3 did not show significant decomposition under the aforementioned conditions, LFDA-7 and LFDA-8 partially decomposed, and FDA-3 decomposed and dehydrated. Figure 5As shown in (e), LFDA-1, LFDA-2, and LFDA-3 showed no significant decomposition, while DLFDA-3 and FDA-3 decomposed and dehydrated. From the above, it can be concluded that DLFDA-3 gel has poor water retention and is easily decomposed; LFDA-7 and LFDA-8 decompose slightly and have better performance than DLFDA-3; while LFDA-1, LFDA-2, and LFDA-3 have good stability, with LFDA-3 exhibiting the best stability.

[0111] The present invention exemplarily in Figure 6 The figure provides a graph showing the relationship between the swelling ratio and time of LFDA-2, LFDA-3, DLFDA-3, and DLFDA-4 in terms of salt and acid resistance at room temperature (25℃); among them, Figure 6 (a) is a graph showing the relationship between the swelling ratio and time of LFDA-2, LFDA-3, DLFDA-3 and DLFDA-4 in salt tolerance (400,000 ppm NaCl); Figure 6 (b) is a graph showing the relationship between the acid resistance (pH=3) swelling ratio and time for LFDA-2, LFDA-3, DLFDA-3 and DLFDA-4.

[0112] Depend on Figure 6 From (a), it can be seen that the swelling ratio of LFDA-3 in a 400,000 ppm solution at 5000 min is greater than 1145%, while that of LFDA-2 is 937%. The swelling ratio of DLFDA-3 in a 400,000 ppm NaCl solution at 5000 min is 469%, and that of DLFDA-4 is 436%. This means that the salt-resistant swelling kinetics of LFDA-3 and LFDA-2 are superior to those of DLFDA-3 and DLFDA-4. Figure 7 As shown in (b), LFDA-3 achieved a swelling ratio of 356% in hydrochloric acid solution with pH=3 at 5000 min, which is superior to LFDA-2 (310%), DLFDA-3 (258%) and DLFDA-4 (232%). LFDA-3 has the best acid resistance.

[0113] The present invention exemplarily in Figure 7 The document provides rheological characterization diagrams of LFDA-1, LFDA-2, LFDA-3, LFDA-4 and DLFDA-2, DLFDA-3, DLFDA-4 at room temperature (25℃) and high temperature (270℃), respectively. Figure 7 (a) shows the relationship between the elastic modulus and frequency at room temperature (25℃) for LFDA-1, LFDA-2, LFDA-3, LFDA-4, and DLFDA-2, DLFDA-3, DLFDA-4. Figure 7(b) is a graph showing the relationship between the viscous modulus and frequency at room temperature (25°C) for LFDA-1, LFDA-2, LFDA-3, LFDA-4 and DLFDA-2, DLFDA-3, DLFDA-4. Figure 7 (c) shows the relationship between the high-temperature (270℃) elastic modulus and frequency for LFDA-2, LFDA-3, DLFDA-3, and DLFDA-4. Figure 7 The middle (d) graph shows the relationship between the high temperature (270℃) viscous modulus and frequency for LFDA-2, LFDA-3, DLFDA-3, and DLFDA-4.

[0114] Depend on Figure 7 As shown in (a), the elastic modulus of LFDA-3 at room temperature (25°C) reaches 10. 5 Pa, the elastic modulus of all other products is lower than that of LFDA-3, meaning that LFDA-3 has the highest crosslinking density, a stable gel network structure, and high strength. Figure 7 As shown in (b), LFDA-3 has a viscosity modulus of 10 at room temperature. 4 Pa, the viscosity modulus of all other products is lower than that of LFDA-3, which means that LFDA-3 has the highest crosslinking viscosity and excellent adhesion properties. Figure 7 The LFDA-3 prepared in step (c) still maintains a G' of 10 after aging at 270°C. 5 Pa indicates that the introduction of a biomass network alters the molecular structure and cross-linking state of the gel, increasing its flexibility and mobility, thereby increasing the gel's elastic modulus; ​ As shown in (d), LFDA-3 still maintains a viscosity modulus of 10 after aging at 270℃. 4 Pa, at high temperatures, will cause the hydrogen bonds or van der Waals forces between LFDA-3 molecules to rearrange and strengthen under certain conditions, thereby increasing the viscous modulus of the material. It can be seen that LFDA-3 exhibits better thermal stability at high temperatures due to the combined effects of thermal crosslinking, chain segment movement, phase transformation and intermolecular interactions, reducing the material degradation or damage caused by high temperature, thus maintaining a high elastic modulus and having excellent self-healing ability.

[0115] As can be seen from the above, the biomass gel prepared by the method of the present invention has excellent temperature resistance, salt resistance and excellent CO2 stimulation response performance.

[0116] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing biomass gel, characterized in that, The method includes: (1) In an inert atmosphere 1, in the presence of a mixed solvent 1, a polyether, 2-acrylamide-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene and an initiator are subjected to a polymerization reaction to obtain an intermediate; the mass ratio of the polyether, the 2-acrylamide-2-methylpropanesulfonic acid, the dimethylaminoethyl methacrylate, the divinylbenzene and the initiator is 100:120-350:200-720:5-30:0.5-3; the weight average molecular weight of the polyether is 8000-15000 Da; the polyether includes polyethylene glycol and / or polyoxypropylene ethylene glycerol ether. First, the polyether is mixed and stirred with the mixed solvent 1 to obtain solution 1; then, solution 1 is subjected to the polymerization reaction with 2-acrylamide-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, divinylbenzene and the initiator to obtain the intermediate; (2) In an inert atmosphere 2, in the presence of a mixed solvent 2, the intermediate is cross-linked with biomass raw materials and ferric salts to obtain a biomass gel; The intermediate has a water content of ≤90 wt%; The biomass raw material is selected from at least one of alkali lignin, dealkali lignin, sodium lignin sulfonate, calcium lignin sulfonate, tannic acid, cellulose and inulin; The mixed solvent 1 is an aqueous solution of glycerol, and the mixed solvent 2 is an aqueous solution of n-dodecane.

2. The method according to claim 1, characterized in that, In step (2), the mass ratio of the intermediate, the biomass raw material and the trivalent iron salt is 1:0.5-1:0.1-0.

3.

3. The method according to claim 1 or 2, characterized in that, The ferric salt is selected from at least one of ferric chloride, ferric sulfate, and ferric nitrate; And / or, the initiator is selected from at least one of azobisisobutyronitrile, potassium persulfate, and benzoyl peroxide.

4. The method according to claim 1 or 2, characterized in that, The conditions for the polymerization reaction include: a temperature of 50-70℃ and a time of 6-12h; And / or, the conditions for the crosslinking reaction include: a temperature of 55-60°C and a time of 12-24 hours.

5. The biomass gel prepared by the method according to any one of claims 1-4.

6. The biomass gel according to claim 5, characterized in that, The biomass gel is resistant to high temperature of 270℃ and salt tolerance of 400,000 ppm NaCl. The expansion rate of the biomass gel after treatment with supercritical carbon dioxide at 40℃ and 15MPa for 72 hours is 660%-900%. And / or, the applicable pH range of the biomass gel is pH = 3-9, and the elastic modulus is > 10. 5 Pa, viscous modulus > 10 4 Pa.

7. The application of the biomass gel according to claim 5 or 6 in reservoir profile control and plugging agents.

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