Diaphragm-shaped viscoelastic composite material with solid-fluid conversion characteristic and application of diaphragm-shaped viscoelastic composite material

Abstract

The invention discloses a diaphragm-shaped viscoelastic composite material with a solid-fluid conversion characteristic and application thereof. The preparation method of the material comprises the following steps: adding a bio-based Gemini anionic surfactant into a buffer solution, heating and stirring to form a mixed solution, and standing to obtain a diaphragm-shaped viscoelastic composite material with a solid-fluid conversion characteristic; the bio-based Gemini anionic surfactant is a gemini surfactant formed by connecting a bio-based single-chain anionic surfactant and N, N '-diphenyl-1, 3-propane diamine through an amido bond. The diaphragm-shaped viscoelastic composite material can be applied to oil and gas field development, low-viscosity flowing during injection is met through the solid-fluid conversion characteristic of the diaphragm-shaped viscoelastic composite material so that the diaphragm-shaped viscoelastic composite material can enter the deep part of a stratum to achieve deep profile control and displacement of an oil reservoir, and high-viscoelastic plugging is achieved after injection; the diaphragm-shaped viscoelastic composite material disclosed by the invention is used as a deformable plugging agent and a profile control and flooding agent for plugging and profile control and flooding operation of micro-nano pore throat strata.

Description

Technical Field

[0001] The invention relates to a membrane-shaped viscoelastic composite material with solid-fluid transition characteristics, belonging to the technical field of petroleum extraction. Background Art

[0002] In recent years, with the sustained and stable growth of my country's economy, demand for energy sources such as oil and natural gas has increased exponentially. By 2024, my country's crude oil production will be approximately 213 million tons, while imports will be approximately 553 million tons, resulting in a high foreign dependence rate of 70%. This represents a significant increase, far exceeding the 61% threshold stipulated in the 12th Five-Year Plan for Energy Development. Therefore, enhancing oil recovery (EOR) is an urgent issue and a key guarantee for stabilizing and increasing my country's crude oil production. Currently, with the gradual depletion of readily accessible oilfields, oilfield development is shifting towards complex reservoirs such as deep, extra-heavy oil, shale oil, and high-water-cut oil reservoirs, significantly increasing the difficulty and cost of recovery. Due to formation heterogeneity, injected water or displacement fluids are prone to "water channeling" along dominant pathways, resulting in reduced sweep efficiency and the retention of large amounts of residual oil in low-permeability areas, severely impacting oilfield development. Currently, profile control and water shutoff technology has become a key and effective means of improving waterflooding effectiveness and enhancing oilfield recovery in high-water-cut oilfields.

[0003] Profile control and water plugging technology involves injecting oilfield plugging agents into the formation to seal high-permeability channels and redirect fluid flow, thereby improving displacement efficiency and enhancing oil recovery. Therefore, oilfield plugging agents have become key chemicals for adjusting reservoir permeability, plugging high-permeability layers or fractures, and enhancing oil recovery (EOR). Currently, the most widely used plugging agents in oilfields are viscoelastic materials with a three-dimensional network structure formed by cross-linking polymers and cross-linking agents at a certain temperature. These materials are also known as gel plugging agents. Commonly used polymers in gel plugging agents include polyacrylamide (HPAM) and partially hydrolyzed polyacrylamide (HPAM). Cross-linking agents primarily include organic cross-linkers such as aldehydes, phenolic aldehydes, and organic ions, inorganic cross-linkers such as chromium ion systems and zirconium ion systems, and composite cross-linkers such as metal ion complexes. These cross-linkers function by causing the polymer to undergo dehydration condensation, cross-linking polymerization, or coordination reactions to form a three-dimensional network structure.

[0004] As we all know, crossflow plugging agents require excellent injectability and plugging effectiveness. Their viscoelasticity (strength) under formation conditions is the primary factor influencing their plugging effectiveness. To achieve ideal plugging results, gel-based plugging agents require high strength. However, good injectability requires low strength and easy flow. Different reservoirs also have varying strength requirements for plugging agents. Therefore, it is often necessary to introduce a variety of additives to enhance the strength of gel plugging agents, which leads to the fact that the formula of gel plugging agents is usually more complicated. For example, the formula of the water plugging agent developed for Chaoyanggou Oilfield is: 0.7% cationic HPAM + 2% calcium lignin sulfonate (Ca-Ls) + 0.3% organic chromium + 0.15% sodium bicarbonate (NaHCO) + 0.005% thiourea (Journal of Petrochemical Colleges and Universities, 2017, 30(06): 42-47.); the formula of the plugging agent used in Qinghai Oilfield is 0.6% quaternary hydrophobic associating polymer (AM / AMPS / DMC / NVP) + 0.6% polyphenolic resin crosslinker + 0.2% sodium thiosulfate + 0.3% nano-silica (Journal of Xi'an Petroleum University (Natural Science Edition), 2025, 40(1): 65-70). However, while polymer gel plugging agents offer high strength, their dense three-dimensional network structure often makes them difficult to break after plugging, causing serious damage to the formation. Cross-linking agents (such as chromium) can also cause environmental pollution. Furthermore, this three-dimensional network structure can lead to poor fluidity, making injection difficult and preventing them from migrating deep into the formation to achieve deep reservoir displacement. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a novel membrane-like viscoelastic composite material with solid-fluid transition properties, which can be used in the field of oil production for flow control and plugging, thereby effectively improving crude oil recovery.

[0006] The viscoelastic composite material of the present invention is made by dissolving a specific bio-based Gemini anionic surfactant in a buffer solution. It features a simple formulation and is environmentally friendly. The mixed solution has a very low initial viscosity and good fluidity, ensuring excellent injectability. After standing for 5-10 days, the resulting film-like viscoelastic composite material exhibits extremely high viscosity and solid elastic properties, imparting excellent plugging effectiveness. This solid-fluid transition property is of great significance as a plugging agent in the field of oil recovery technology.

[0007] The microstructure of the diaphragm-like viscoelastic composite material of the present invention is a novel flexible diaphragm-like structure with a diaphragm spacing of 50-70nm and an elastic modulus of 1000-6000Pa. This structure is driven by weak interactions between bio-based Gemini anionic surfactant molecules through van der Waals forces, hydrogen bonds, and hydrophobic effects. After the plugging operation is completed, it is easy to break the gel and will not cause damage to the formation.

[0008] The preparation method of the membrane-like viscoelastic composite material with solid-fluid transition properties provided by the present invention is as follows:

[0009] Bio-based Gemini anionic surfactant powder is added to a buffer solution, heated and stirred to form a mixed solution, and allowed to stand to obtain a membrane-like viscoelastic composite material with solid-fluid transition characteristics.

[0010] The bio-based Gemini anionic surfactant is a Gemini surfactant in which a bio-based single-chain anionic surfactant and N,N′-diphenyl-1,3-propanediamine are connected by an amide bond.

[0011] Preferably, the bio-based single-chain anionic surfactant is one of N-lauroyl sarcosine, N-myristoyl sarcosine, N-oleoyl sarcosine, oleoyl-N-β-hydroxyethyl-glycine and lauroyl-N-β-hydroxyethyl-glycine.

[0012] In the mixed solution, the concentration of the bio-based Gemini anionic surfactant is 0.01-0.10 mol / L, preferably 0.05-0.10 mol / L.

[0013] In the method of the present invention, preferably, the buffer solution is a sodium phosphate buffer (NaH2PO4-Na2HPO4) or a potassium phosphate buffer (K2HPO4-KH2PO4);

[0014] The pH range of the buffer solution is 5.29-6.47.

[0015] In the method of the present invention, the main function of the buffer solution is: the buffer solution is acidic and can promote the dissolution of the bio-based Gemini anionic surfactant in the aqueous solution; the amino group -NH2 contained in the bio-based Gemini anionic surfactant receives a proton in an acidic environment and is converted into -NH3 + , some bio-based Gemini anionic surfactants are converted into ionic surfactants. These surfactant molecules and ions are connected together by van der Waals forces, hydrogen bonds and hydrophobic interactions to assemble into membrane structures. However, the metal cations and -NH3 contained in the buffer solution +The existence of electrostatic repulsion will slow down the formation of diaphragmatic structures to a certain extent, resulting in the mixed solution taking a certain amount of time to form a composite material with high viscosity and elasticity, ensuring that the mixed solution has sufficient time to enter the deep reservoir to achieve deep displacement and maintain the pH stability of the solution.

[0016] In the method of the present invention, the heating temperature is 60-80°C;

[0017] The stirring rate is 500-1000 r / min, and the stirring time is 5-10 minutes;

[0018] The standing time is 10-15 days.

[0019] Preferably, the bio-based Gemini anionic surfactant is prepared by the following method:

[0020] 1) adding the bio-based single-chain anionic surfactant and the N,N-diphenyl-1,3-propylenediamine to an organic solvent and performing a reflux reaction for 24-36 hours;

[0021] The molar ratio of the bio-based single-chain anionic surfactant to the N,N-diphenyl-1,3-propylenediamine is 4:1-2:1;

[0022] The organic solvent is ethanol, tetrahydrofuran, chloroform or N,N-dimethylformamide;

[0023] 2) adding acetonitrile to the system of step 1), stirring and refluxing to separate a white precipitate, wherein the stirring rate is 800 to 1200 r / min;

[0024] 3) dissolving the white precipitate in toluene and refluxing, washing with water through ultrasonic wave, filtering and drying to obtain the product.

[0025] The membrane-like viscoelastic composite material provided by the present invention can be applied to the development of oil and gas fields. The membrane-like viscoelastic composite material has the solid-fluid transition characteristics to meet the low-viscosity flow during injection to enter deep formations to achieve deep reservoir flooding, and high viscoelasticity to seal after injection.

[0026] The diaphragm-shaped viscoelastic composite material is used as a deformable plugging agent and displacement agent for plugging and displacement operations in micro-nano-scale pore throat formations.

[0027] The most widely used polymer gel plugging agent in oil fields at present has the technical bottleneck of poor injectability and difficulty in breaking gel due to its three-dimensional network structure, and it is urgent to develop new plugging agents. The surfactant viscoelastic materials reported are generally prepared by compounding two anionic and cationic surfactants in aqueous solution. Due to the strong electrostatic attraction between anions and cations, ion pairs are formed. Once the two surfactants are mixed in aqueous solution, they immediately form a viscoelastic material with high viscosity and poor fluidity. This feature leads to problems such as difficulty in injecting it into the formation and inability to migrate in the pores, thereby limiting its application in the field of oil extraction. Although reducing the concentration of the two surfactants can reduce the viscosity of the system to a certain extent and improve its fluidity, it will also lead to poor viscoelastic properties after entering the formation, and it is impossible to achieve an effective plugging effect, resulting in an unsatisfactory effect of improving the recovery rate. The present invention has a membrane-like viscoelastic composite material with solid-fluid transition characteristics. It innovatively dissolves an environmentally friendly bio-based Gemini anionic surfactant in a weakly acidic buffer solution to obtain an initial solution with extremely low viscosity, ensuring that it has good injectability. Then, a weakly acidic buffer solution is used to provide a proton to the amino group -NH2 of the bio-based Gemini anionic surfactant molecule to convert it into -NH3 + , so that part of Gemini nonionic fluorocarbon surfactants are converted into ionic surfactants, and then driven by van der Waals forces, hydrogen bonds and hydrophobic interactions, these surfactant molecules and ions are connected together to assemble into a membrane structure. At the same time, the metal cations and -NH3 contained in the buffer solution + Electrostatic repulsion slows the formation of the diaphragm structure to a certain extent, so the initial solution takes a certain amount of time to form a composite material with high viscoelasticity, ensuring that the initial solution has sufficient time to penetrate deep into the reservoir for deep profile adjustment and subsequent plugging operations. The unique solid-fluid transition characteristics and flexible diaphragm structure of the present invention give it a low initial viscosity, facilitating injection into the formation. Once it migrates smoothly into the deep reservoir, it possesses high viscoelasticity to achieve a plugging effect.

[0028] The present invention has the following beneficial technical effects:

[0029] (1) The membrane-like viscoelastic composite material with solid-fluid transition properties for oil and gas fields of the present invention has a simple preparation method and formula and is easy to obtain. It is made by dissolving a specific bio-based Gemini anionic surfactant in a buffer solution. The initial solution viscosity is very low and the fluidity is good. After standing for 10-15 days, it transforms into a viscoelastic composite material with extremely high viscosity and elastic properties unique to solids, showing solid-fluid transition properties.

[0030] (2) The membrane-shaped viscoelastic composite material with solid-fluid transition properties for oil and gas fields of the present invention is green and environmentally friendly, can achieve low-viscosity flow during injection, and can be smoothly transported to the deep reservoir to achieve high-viscoelastic sealing. It can be used as a deformable plugging agent and displacement agent for plugging and displacement operations in micro-nano-scale pore throat formations.

[0031] (3) The membrane-like viscoelastic composite material with solid-fluid transition characteristics for oil and gas fields of the present invention has a "flexible" membrane-like structure in its microstructure. The membranes are connected by weak intermolecular interactions, which can ensure that they can be squeezed and deformed when passing through the pores of the oil reservoir, and the structure is not easily damaged and has good shear resistance. It can also ensure that after the sealing operation is completed, the structure can be destroyed by injecting an alkaline solution to achieve gel breaking and avoid damage to the formation.

[0032] (4) The membrane-like viscoelastic composite material with solid-fluid transition properties for oil and gas fields of the present invention can simply adjust the concentration of the bio-based Gemini anionic surfactant to control its viscosity and elasticity, ensuring that the viscoelastic composite material meets the performance requirements of different oil reservoirs for different viscosities and elasticities when used for oil field plugging and displacement.

[0033] (5) The present invention provides a membrane-like viscoelastic composite material with solid-fluid transition properties, which has a novel and unique structure and performance, enriches the existing research field of surfactant viscoelastic composite materials, and expands its application in the field of oil extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a picture of the solid-flow transition characteristics of the membrane-shaped viscoelastic composite material in Example 1 of the present invention.

[0035] Figure 2 This is a microstructure photograph of the film-shaped viscoelastic composite material according to Example 1 of the present invention.

[0036] Figure 3 This is the viscoelasticity of the film-shaped viscoelastic composite material of Example 1 of the present invention.

[0037] Figure 4 This is the shear resistance of the film-shaped viscoelastic composite material of Example 1 of the present invention.

[0038] Figure 5 This is a small-angle X-ray scattering (SAXS) curve of the film-shaped viscoelastic composite material of Example 1 of the present invention.

[0039] Figure 6 This is the sealing performance of the membrane-shaped viscoelastic composite material of Example 1 of the present invention.

[0040] Figure 7 This is the oil displacement effect of the membrane-shaped viscoelastic composite material of Example 1 of the present invention.

[0041] Figure 8 This is a microstructure photograph of the film-shaped viscoelastic composite material according to Example 2 of the present invention.

[0042] Figure 9 This is a small-angle X-ray scattering (SAXS) curve of the film-shaped viscoelastic composite material of Example 2 of the present invention.

[0043] Figure 10 This is the viscoelasticity of the film-shaped viscoelastic composite material according to Example 2 of the present invention.

[0044] Figure 11 This is a picture of the solid-flow transition characteristics of the membrane-shaped viscoelastic composite material of Example 3 of the present invention.

[0045] Figure 12 This is a microstructure photograph of the film-shaped viscoelastic composite material of Example 3 of the present invention.

[0046] Figure 13 This is the viscoelasticity of the membrane-shaped viscoelastic composite material of Example 3 of the present invention.

[0047] Figure 14 This is a small-angle X-ray scattering (SAXS) curve of the film-shaped viscoelastic composite material of Example 3 of the present invention. DETAILED DESCRIPTION

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0049] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0050] The membrane-like viscoelastic composite material involved in the present invention refers to a functional material formed by dissolving a bio-based Gemini anionic surfactant in a buffer solution. Its microstructure is a flexible membrane-like network, which has both solid elasticity and fluid deformation ability.

[0051] The solid-fluid transition property involved in the present invention refers to the property of the membrane-like viscoelastic composite material of the present invention transforming from the low-viscosity flow state (low elastic modulus, high fluidity) of the initial solution to the solid state (high elastic modulus, low fluidity). This property is achieved by the protons released by the acidic buffer solution regulating the self-assembly of the solution to form a membrane-like structure.

[0052] The bio-based Gemini anionic surfactant involved in the present invention refers to a double-chain surfactant composed of two hydrophobic chains and two hydrophilic head groups covalently connected by a rigid connecting group (amide bond).

[0053] Example 1-2

[0054] 2.10 g of N-myristoylsarcosine and 0.51 g of N,N-diphenyl-1,3-propanediamine were added to 500 mL of ethanol and stirred at reflux for 24 hours at room temperature; then 500 mL of acetonitrile was added, and the acetonitrile and the above solution were stirred and refluxed to separate a white solid precipitate; the obtained precipitate was dissolved in 200 mL of toluene and refluxed for 2 hours, and then the product was ultrasonically washed with water and filtered. The process was repeated three times and dried to obtain a white powdery solid of a bio-based Gemini anionic surfactant.

[0055] The white powdery solid of the bio-based Gemini anionic surfactant was added to the NaH2PO4-Na2HPO4 buffer solution with a pH of 5.29 to prepare an initial solution with a concentration of 0.1 mol / L. Its viscosity was 9.21 mPa·s. Figure 1 As shown in the figure, the fluidity is good. The temperature is controlled at 65℃, the stirring rate is 800r / min, the stirring is carried out for 5 minutes, and then the mixture is allowed to stand at room temperature for 10 days.

[0056] The viscoelastic composite material prepared in this embodiment is as follows Figure 1 As shown, the reagent bottle is fluid when tilted, but basically does not flow when tilted after standing for 10 days, indicating its solid properties ( Figure 1 After adding 0.1 mol / L NaOH solution to the reagent bottle, the viscoelastic composite material loses its solid properties and becomes a fluid liquid, demonstrating its excellent gel-breaking performance.

[0057] The microstructure photo of the viscoelastic composite material prepared in this example is shown in FIG. Figure 2 As shown, the membrane-like structure can be clearly seen from the electron microscope photo, and the membrane is folded, indicating that it has good "flexibility", thus ensuring that it can be deformed through micro-nanoscale pore throats.

[0058] The rheological properties of the viscoelastic composite material prepared in this embodiment are as follows: Figure 3 As shown in the figure, it can be seen that it has high viscoelasticity, with an elastic modulus of 5000Pa and a viscous modulus of 700Pa. The thixotropy test results are shown in the figure. Figure 4 As shown in the figure, with the increase of shear rate, the viscosity of the composite material decreases significantly; when the shear effect is removed, the upward curve and the downward curve of the solution basically coincide, with only a small difference at low shear rates, indicating that the viscosity gradually returns to its original state and the microstructure does not change, proving that the structure of the composite material of the present invention is not easily destroyed under shear action and has good shear resistance.

[0059] Small angle X-ray scattering results ( Figure 5) proves that the distance between the diaphragms of the viscoelastic composite material prepared in this embodiment is 49.92 nm, and the diaphragms are connected by weak intermolecular interactions. Therefore, after the diaphragms are deformed through the pore throats, the weak intermolecular interactions between the diaphragms will be rebuilt, which is why it has shear resistance.

[0060] Further high permeability core plugging experiments and low permeability fracture core oil displacement experiments were designed to clarify the plugging effect and oil displacement performance of the membrane-like viscoelastic composite material with solid-fluid transition characteristics of the present invention.

[0061] In the plugging performance test, the plugging rate is used to evaluate the plugging performance of the plugging agent. The plugging rate is a key indicator for measuring the system's ability to plug high-permeability channels in the formation. It indicates the plugging strength of the membrane-like viscoelastic composite material with solid-fluid transition properties after injection. The specific steps are as follows:

[0062] (1) Fill the water tank with prepared simulated water, mix and stir the bio-based Gemini anionic surfactant and buffer solution, and then put them into the chemical tank; (2) Inject simulated water at a certain speed for water drive until the pressure at the front end of the core holder is stable, and calculate the permeability of the artificial core with a stable pressure reading. Then inject a mixed solution of bio-based Gemini anionic surfactant and buffer solution at the same injection rate as the water injection rate until it can be collected at the outlet end to ensure that the solution is evenly filled in the entire core. Finally, seal the injection end and the tail end. (3) After standing for 10 days, open both ends of the core holder to release the pressure, open the water bottle to start the second water drive, keep the injection rate the same as before, and continue to inject until the pressure is stable. Calculate the data curve of pressure change with injection volume and calculate the core permeability and gel plugging rate after gel plugging. The results are as follows Figure 6 shown.

[0063] The calculation shows that the plugging rate of the system for a 1000 mD core is 98.55%, indicating that the membrane-like viscoelastic composite material with solid-fluid transition characteristics of the present invention has a good plugging effect.

[0064] The performance of the membrane-like viscoelastic composite material with solid-fluid transition characteristics of the present invention in enhancing oil recovery was tested using low-permeability fractured cores. The specific experimental steps were as follows: (1) the treated core was placed in a core holder to begin saturating with crude oil, recording and calculating the crude oil saturation and saturation volume of the core. The core that was completely saturated with crude oil and aged was removed and the fractured core was prepared according to the fracture preparation method. The prepared fractured core was placed in a core holder; (2) the water tank was opened and the crude oil displacement experiment was started at a flow rate of 0.2 mL / min, and the recovery rate and pressure change data were recorded; (3) after no oil was produced at the tail end, the water tank was closed and the newly prepared bio-based Gemini anionic surfactant and buffer solution mixture was injected. After the required PV solution was injected, the injection end and tail end of the core holder were sealed. After standing for 10 days, the subsequent water flooding experiment was continued, and the crude oil recovery rate and pressure change data were recorded. The experiment was stopped when no oil was produced at the tail end.

[0065] The core flooding test results are as follows Figure 7 As shown, for a fractured core with a fracture aperture of 0.2 mm and a core permeability of 10 mD, the primary waterflooding pressure was approximately 216 kPa, resulting in a recovery of 7.56%. The displaced crude oil primarily consisted of crude oil remaining in the fractures after aging. After injection of a mixture of a bio-based Gemini anionic surfactant and a buffer solution, the solution primarily flowed along the dominant pores into the core fissures, increasing the injection pressure to 520 kPa per 1 PV. After the solution was converted into a viscoelastic composite, a secondary waterflood was performed. Since the viscoelastic composite blocked the fractures, simulated water began to enter the unaffected small pores, causing a sharp increase in pressure and an increase in recovery, ultimately resulting in a 24.23% increase in recovery. These results demonstrate that the membrane-like viscoelastic composite material of the present invention exhibits excellent sealing and oil displacement effects.

[0066] A viscoelastic composite material system was prepared according to the above formula and method, except that the white powdery solid of the bio-based Gemini anionic surfactant was added to a NaH2PO4-Na2HPO4 buffer solution with a pH of 5.29 to prepare an initial solution with a concentration of 0.05 mol / L, as Example 2. In this example, the viscosity of the initial solution was 5.32 mPa@s, and after standing for 10 days, the final viscoelastic composite material was still in the form of a membrane ( Figure 8 ), but the distance between the diaphragms is 69.16nm ( Figure 9 ), elastic modulus and viscous modulus are 1000 and 600 Pa respectively ( Figure 10 ), indicating that the viscoelasticity of the viscoelastic composite material can be effectively adjusted by changing the concentration of the bio-based Gemini anionic surfactant, thus giving it solid-fluid transition properties.

[0067] Example 3

[0068] 4.06 g of lauroyl-N-β-hydroxyethyl-glycine and 1.20 g of N,N-diphenyl-1,3-propylenediamine were added to 500 mL of ethanol and stirred at reflux for 24 hours at room temperature; then 500 mL of acetonitrile was added, and the above solution was stirred and refluxed with acetonitrile to separate a white solid precipitate; the obtained precipitate was dissolved in 200 mL of toluene and refluxed for 2 hours, and then the product was ultrasonically washed with water and filtered. The process was repeated three times and dried to obtain a white powdery solid of a bio-based Gemini anionic surfactant.

[0069] The white powdery solid of the bio-based Gemini anionic surfactant was added to the pH 6.15 NaH2PO4-Na2HPO4 buffer solution to prepare an initial solution with a concentration of 0.1 mol / L, and its viscosity was 8.65 mPa@s. Figure 11 As shown in the middle left figure, it has good fluidity. The temperature is controlled to 80℃, the stirring rate is 900r / min, stirring for 10 minutes, and then standing at room temperature for 15 days. The viscoelastic composite material prepared in this embodiment is obtained, as shown in FIG. Figure 11 As shown in the middle right image, the material exhibits fluidity when tilted, but becomes virtually non-fluid when tilted after 15 days, demonstrating its solid properties. Adding 0.1 mol / L NaOH solution to the material causes the viscoelastic composite to lose its solid properties and become a fluid, demonstrating its excellent gel-breaking properties.

[0070] The microstructure photo of the viscoelastic composite material prepared in this example is shown in FIG. Figure 12 As shown, the membrane-like structure can be clearly seen from the electron microscope photo, and the membrane is folded, indicating that it has good "flexibility", thus ensuring that it can be deformed through micro-nanoscale pore throats.

[0071] The rheological properties of the viscoelastic composite material prepared in this embodiment are as follows: Figure 13 As shown, it can be seen that it has high viscoelasticity, with an elastic modulus of 2000 Pa and a viscous modulus of 1000 Pa. Small angle X-ray scattering results ( Figure 14 ) proves that the distance between the diaphragms of the viscoelastic composite material prepared in this embodiment is 58.42 nm.

Claims

1. A method for preparing a film-like viscoelastic composite material having solid-fluid transition properties, comprising the following steps: A bio-based Gemini anionic surfactant is added to a buffer solution, heated and stirred to form a mixed solution, and allowed to stand to obtain a membrane-like viscoelastic composite material with solid-fluid transition characteristics.

2. The preparation method according to claim 1, wherein: The bio-based Gemini anionic surfactant is a Gemini surfactant in which a bio-based single-chain anionic surfactant and N,N′-diphenyl-1,3-propanediamine are connected via an amide bond.

3. The preparation method according to claim 1 or 2, characterized in that: The buffer solution is a sodium phosphate buffer or a potassium phosphate buffer with a pH range of 5.29-6.

47.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In the mixed solution, the concentration of the bio-based Gemini anionic surfactant is 0.01-0.10 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The heating temperature is 60-80°C; The stirring rate is 500-1000 r / min and the time is 5-10 minutes; The standing time is 10-15 days.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The bio-based Gemini anionic surfactant is prepared by the following method: 1) adding a bio-based single-chain anionic surfactant and N,N-diphenyl-1,3-propylenediamine to an organic solvent and performing a reflux reaction for 24-36 hours; The molar ratio of the bio-based single-chain anionic surfactant to the N,N-diphenyl-1,3-propylenediamine is 4:1-2:1; The organic solvent is ethanol, tetrahydrofuran, chloroform or N,N-dimethylformamide; 2) adding acetonitrile to the system of step 1), stirring and refluxing to separate a white precipitate, wherein the stirring rate is 800 to 1200 r / min; 3) dissolving the white precipitate in toluene and refluxing, washing with water through ultrasonic wave, filtering and drying to obtain the product.

7. The preparation method according to claim 6, characterized in that: The bio-based single-chain anionic surfactant is one of N-lauroyl sarcosine, N-myristoyl sarcosine, N-oleoyl sarcosine, oleoyl-N-hydroxyethyl-glycine and lauroyl-N-hydroxyethyl-glycine.

8. A film-like viscoelastic composite material having solid-fluid transition properties prepared by the method according to any one of claims 1 to 7.

9. Application of the membrane-like viscoelastic composite material according to claim 8 in oil and gas field development, wherein the membrane-like viscoelastic composite material has a solid-fluid transition characteristic that satisfies low-viscosity flow during injection to enter deep formations for deep reservoir displacement, and high viscoelasticity sealing after injection.

10. The use according to claim 9, characterized in that: The diaphragm-shaped viscoelastic composite material is used as a deformable plugging agent and displacement agent for plugging and displacement operations in micro-nano-scale pore throat formations.

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