Multifunctional supramolecular viscosity-reducing oil-displacing agent for cold production of shallow low-temperature heavy oil reservoir and on-site application of multifunctional supramolecular viscosity-reducing oil-displacing agent

Abstract

The invention relates to the technical field of oilfield chemical agents, and discloses a multifunctional supramolecular viscosity-reducing oil-displacing agent for cold production of shallow low-temperature heavy oil reservoirs as well as a preparation method and application of the multifunctional supramolecular viscosity-reducing oil-displacing agent. The oil displacement agent is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, a supramolecular assembly, a wetting reversal agent, a main surfactant, a cosurfactant, a stabilizer and a solvent, and a reversible supramolecular synergistic system is formed through intermolecular non-covalent interaction. The preparation method comprises the following steps: carrying out polymerization reaction under a nitrogen protection condition to obtain a powdery product, and then preparing the powdery product with injected water for use. Under the low-temperature condition, the viscosity of the heavy oil can be effectively reduced, the wettability of rocks is improved, the displacement efficiency is improved, and the low-temperature heavy oil cold recovery agent is suitable for cold recovery development of shallow low-temperature heavy oil reservoirs with the formation temperature of 20-40 DEG C and the burial depth of 200-600 m.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemicals, in particular to a multifunctional supramolecular viscosity-reducing oil-displacing agent for cold production of shallow low-temperature heavy oil reservoirs and its field application. BACKGROUND

[0002] Shallow low-temperature heavy oil reservoirs generally have the characteristics of shallow burial depth, low formation temperature and high crude oil viscosity. In such reservoirs, the content of crude oil gum and asphaltene is high, the intermolecular interaction is strong, and the spatial network structure is easily formed, resulting in poor flowability of crude oil under formation temperature conditions. At the same time, such reservoirs generally have low formation pressure, low permeability, strong reservoir heterogeneity and high clay mineral content, and are prone to pore throat plugging and flow channel restriction during water injection development, further increasing the difficulty of crude oil production.

[0003] At present, shallow low-temperature heavy oil reservoirs in China are mainly distributed in Chagan Sag of Zhongyuan Oilfield, Chunfeng Oilfield of Shengli Oilfield and some oilfields in Northeast China. Due to the reservoir temperature usually being lower than 40℃, the traditional thermal recovery technology represented by steam huff and puff has problems of large heat loss, high energy consumption and poor economic efficiency in such reservoirs, and it is difficult to realize long-term stable and large-scale application. Therefore, cold production gradually becomes an important technical route for the development of shallow low-temperature heavy oil reservoirs.

[0004] Under the condition of cold production, chemical viscosity reduction technology is widely studied and applied. Existing chemical viscosity reducers mainly include surfactant type viscosity reducers, solvent type viscosity reducers and traditional emulsified viscosity reducers. Among them, the surfactant type viscosity reducer has limited ability to reduce interfacial tension under low temperature conditions, poor salt tolerance, and only has single viscosity reduction function, which is difficult to effectively strip the oil film on the surface of the rock; the solvent type viscosity reducer has high cost, is easy to volatilize and disperse, and has insufficient environmental friendliness; the emulsion formed by the traditional emulsified viscosity reducer has poor stability, and has the defects of difficult demulsification or only reducing the apparent viscosity of crude oil without improving the wettability of the rock.

[0005] Under low temperature conditions, the molecular motion ability of traditional viscosity reducers is limited, and the effect on heavy components in heavy oil is significantly decreased, which is difficult to destroy the aggregation structure formed by asphaltene and gum, resulting in low viscosity reduction efficiency, difficulty in starting crude oil, and difficulty in effectively producing remaining oil. The existing technology generally focuses on single action mechanism, lacks a multifunctional synergistic system that can act on the crude oil body, the surface of the rock and the pore throat, and is difficult to meet the dual requirements of high efficiency and economy for the cold production development of shallow low-temperature heavy oil reservoirs.

[0006] Therefore, there is an urgent need to develop a chemical displacement agent that can maintain high activity under low temperature conditions and has multiple functions such as crude oil viscosity reduction, oil film stripping, wetting reversal and pore throat activation, so as to improve the fluidity of heavy oil, increase the displacement efficiency under water flooding and cold production conditions, and realize the economical and effective development of shallow low temperature heavy oil reservoirs. Summary of the Invention

[0007] To overcome the technical challenges of insufficient activity, singular mechanism of action, and inability to simultaneously achieve effective viscosity reduction, oil film stripping on the rock surface, and flow initiation in the cold production of shallow, low-temperature heavy oil reservoirs, traditional viscosity reducers suffer from low cold-temperature conditions. These challenges lead to low cold production displacement efficiency and recovery rates. This invention aims to provide a multifunctional supramolecular viscosity reducer and oil displacement agent for cold production of shallow, low-temperature heavy oil reservoirs, along with its preparation method and application. Based on supramolecular chemistry principles, this invention synergistically designs acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, functional monomers, modified alkyl monomers, and self-made functional hydrophobic and hydrophilic monomers. These are then combined with a main surfactant, co-surfactant, and wetting reversal agent to construct a multifunctional system capable of non-covalent interactions and reversible supramolecular assembly under formation conditions. This system simultaneously acts on the crude oil matrix, rock surface, and pore throats under low-temperature conditions, achieving efficient viscosity reduction, oil film stripping, and flow initiation for heavy oil. By adopting the above technical solution, the present invention can significantly improve the fluidity of heavy oil, increase displacement efficiency and crude oil recovery rate under low temperature cold production conditions, and provide a practical and feasible chemical flooding method for the economical and effective development of shallow low temperature heavy oil reservoirs.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A multifunctional supramolecular viscosity-reducing and oil displacement agent for cold production of shallow, low-temperature heavy oil reservoirs, comprising the following raw materials in parts by weight: 5-30 parts acrylamide; 3-15 parts supramolecular assembly; 2-11 parts wetting reversal agent; 5-16 parts 2-acrylamido-2-methylpropanesulfonic acid; 5-30 parts main surfactant; 2-8 parts co-surfactant; 0.5-5 parts stabilizer; and 20-70 parts solvent.

[0010] Optionally, the main surfactant is a nonionic-anionic gemini surfactant.

[0011] Optionally, the supramolecular assembly is formed by non-covalent interaction of functional monomers, modified alkyl monomers, self-made functional hydrophobic monomers and self-made functional hydrophilic monomers; the functional monomers are monomers containing polar functional groups and capable of hydrogen bonding or π-π stacking with resin and / or asphaltene in crude oil; the modified alkyl monomers are monomers having hydrophobic alkyl chain structure and capable of enhancing molecular hydrophobic interaction and intercalation dispersion capacity; the self-made functional hydrophobic monomers are hydrophobic monomers having hydrophobic groups and capable of participating in supramolecular self-assembly and intercalating asphaltene aggregation structure; and the self-made functional hydrophilic monomers are hydrophilic monomers containing hydrophilic groups and capable of enhancing water solubility of the system and participating in formation of supramolecular assembly structure.

[0012] Optionally, a preparation method of the multifunctional supramolecular viscosity-reducing oil-displacing agent for cold production of shallow low-temperature heavy oil reservoirs comprises the following steps:

[0013] (1) Deionized water is added into a reaction kettle, and acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and functional monomers are sequentially added under the conditions of nitrogen protection and stirring until completely dissolved;

[0014] (2) The pH value of the system is adjusted to 6-8 by using a sodium hydroxide solution;

[0015] (3) Hydrophobic monomers are added into the system, and an emulsifier or a cosolvent is added to uniformly disperse the hydrophobic monomers;

[0016] (4) The system is heated and an initiator is added, and a polymerization reaction is carried out under nitrogen protection to obtain a colloidal product;

[0017] (5) The colloidal product is sheared, granulated, dried and pulverized to obtain a powdery product;

[0018] (6) The powdery product is prepared with water meeting the requirements of an injection block to obtain the multifunctional supramolecular viscosity-reducing oil-displacing agent.

[0019] Optionally, the heating temperature in step (4) is 30-40℃, and the reaction time is 4-8 hours.

[0020] Optionally, the use concentration of the multifunctional supramolecular viscosity-reducing oil-displacing agent in the reservoir is 0.1%-8.0%.

[0021] Optionally, the formation temperature of the shallow low-temperature heavy oil reservoir is 20-40℃.

[0022] Optionally, the burial depth of the shallow low-temperature heavy oil reservoir is 200-600 meters.

[0023] The present application has the following beneficial effects:

[0024] The multifunctional supramolecular viscosity-reducing oil displacement agent provided by the application is based on the principle of supramolecular chemistry, and can effectively act on the colloid and asphaltene components in heavy oil under low-temperature conditions through non-covalent interactions such as intermolecular hydrogen bonds, hydrophobic interactions and π-π stacking, thereby destroying the spatial network structure formed by the aggregation of the components, significantly reducing the structural viscosity of the crude oil and improving the flowability; meanwhile, the oil displacement agent can form a stable supramolecular assembly structure at the oil-water interface, significantly reduce the oil-water interfacial tension, and change the oil-wet property of the rock surface to a water-wet property through the wetting reversal effect, effectively strip the oil film attached to the rock surface, and convert the residual oil that is difficult to mobilize into flowable producible oil; the oil displacement agent can disperse and dredge the waxy and heavy components that are prone to cause pore throat blockage under low-temperature conditions during the injection process, improve the carrying capacity of the water phase for the crude oil, and realize the effective start-up and displacement of the heavy oil under cold production conditions without external heating, thereby reducing the energy consumption and development cost, and improving the displacement efficiency and crude oil recovery of the cold production of the shallow low-temperature heavy oil reservoir. BRIEF DESCRIPTION OF DRAWINGS

[0025] The application will be further described below in combination with the drawings.

[0026] Figure 1 The viscosity-temperature curve of the heavy oil in the Fulaerji oilfield;

[0027] Figure 2 The viscosity-reducing rate curve of the heavy oil in the Fulaerji oilfield;

[0028] Figure 3 The contact angle test result comparison chart;

[0029] Figure 4 The core displacement experiment test result comparison chart. DETAILED DESCRIPTION

[0030] The application will be further described below in combination with the drawings.

[0031] Example 1:

[0032] This example aims to verify that the multifunctional supramolecular viscosity-reducing oil displacement agent can still form a stable system and meet the basic use requirements under the cold production conditions of the shallow low-temperature heavy oil reservoir when the dosages of the components and the reaction conditions are at a low level, thereby illustrating the implementability of the technical solution of the application under low-dosage and low-energy consumption conditions.

[0033] Embodiment 1: by weight, acrylamide 5 parts, supramolecular assembly 3 parts, wetting reversal agent 2 parts, 2-acrylamide-2-methylpropanesulfonic acid 5 parts, main surfactant 5 parts, auxiliary surfactant 2 parts, stabilizer 0.5 parts, solvent 70 parts; the solvent is added in a reaction kettle, under the conditions of nitrogen protection and stirring, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and functional monomers are sequentially added, and stirring is performed until complete dissolution; the pH value of the system is adjusted to 6 by using a sodium hydroxide solution; then, the hydrophobic monomer is added to the system, and an emulsifier or a cosolvent is added to uniformly disperse the hydrophobic monomer; the system is warmed to 30 DEG C, and an initiator is added, and the reaction is performed for 4 hours under nitrogen protection, to obtain a colloidal product; the colloidal product is cut, granulated, dried and pulverized to obtain a powdery product; the powdery product is prepared with water meeting the requirements of an injection block, to obtain a multifunctional supramolecular viscosity-reducing and oil-displacing agent.

[0034] Example 2:

[0035] This embodiment aims to simulate the commonly used medium dosage and medium reaction conditions in actual oilfield applications, and to verify that the multifunctional supramolecular viscosity-reducing and oil-displacing agent can be stably prepared and is applicable to cold production development of shallow low-temperature heavy oil reservoirs when the component proportioning and reaction conditions are in the medium value interval.

[0036] Embodiment 1: by weight, acrylamide 5 parts, supramolecular assembly 3 parts, wetting reversal agent 2 parts, 2-acrylamide-2-methylpropanesulfonic acid 5 parts, main surfactant 5 parts, auxiliary surfactant 2 parts, stabilizer 0.5 parts, solvent 70 parts; the solvent is added in a reaction kettle, under the conditions of nitrogen protection and stirring, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and functional monomers are sequentially added, and stirring is performed until complete dissolution; the pH value of the system is adjusted to 6 by using a sodium hydroxide solution; then, the hydrophobic monomer is added to the system, and an emulsifier or a cosolvent is added to uniformly disperse the hydrophobic monomer; the system is warmed to 30 DEG C, and an initiator is added, and the reaction is performed for 4 hours under nitrogen protection, to obtain a colloidal product; the colloidal product is cut, granulated, dried and pulverized to obtain a powdery product; the powdery product is prepared with water meeting the requirements of an injection block, to obtain a multifunctional supramolecular viscosity-reducing and oil-displacing agent.

[0037] Example 3:

[0038] This embodiment aims to verify that the multifunctional supramolecular viscosity-reducing and oil-displacing agent can be smoothly prepared and keep system stability when the component dosage and reaction conditions are at a higher level, so as to illustrate the applicability and process window width of the technical scheme of the present application under the conditions of high functional components and high reaction intensity.

[0039] Embodiment: take acrylamide 30 parts, supramolecular assembly 15 parts, wetting reversal agent 11 parts, 2-acrylamide-2-methylpropanesulfonic acid 16 parts, main surfactant 30 parts, auxiliary surfactant 8 parts, stabilizer 5 parts, solvent 20 parts by weight; add the solvent in the reaction kettle, under the conditions of nitrogen protection and stirring, add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and functional monomer in turn, stir until completely dissolved; adjust the pH value of the system to 8 with sodium hydroxide solution; then add hydrophobic monomer to the system, and add emulsifier or cosolvent to make the hydrophobic monomer fully and uniformly dispersed; warm the system to 40℃ and add initiator, react for 8 hours under nitrogen protection to obtain a gel product; cut, granulate, dry and crush the gel product to obtain a powdery product; prepare the powdery product with water meeting the requirements of the injection block to obtain a multifunctional supramolecular viscosity-reducing oil displacement agent.

[0040] Comparative Example 1:

[0041] This comparative example aims to verify the change of the comprehensive action ability of the oil displacement agent system when the supramolecular cooperative self-assembly system is missing by removing the key component supramolecular assembly while keeping the medium dosage and medium reaction conditions unchanged, so as to highlight the technical effect of the present application in realizing the multifunctional cooperation of viscosity reduction, separation, start-up, etc. through supramolecular assembly.

[0042] Embodiment: take acrylamide 18 parts, supramolecular assembly 0 parts, wetting reversal agent 6 parts, 2-acrylamide-2-methylpropanesulfonic acid 10 parts, main surfactant 18 parts, auxiliary surfactant 5 parts, stabilizer 2 parts, solvent 45 parts by weight; add the solvent in the reaction kettle, under the conditions of nitrogen protection and stirring, add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and functional monomer in turn, stir until completely dissolved; adjust the pH value of the system to 7 with sodium hydroxide solution; then add hydrophobic monomer and make the hydrophobic monomer uniformly dispersed under the action of emulsifier or cosolvent; warm the system to 35℃ and add initiator, react for 6 hours under nitrogen protection to obtain a gel product; cut, granulate, dry and crush the gel product to obtain a powdery product; prepare the powdery product with water meeting the requirements of the injection block to obtain a viscosity-reducing oil displacement agent comparative system.

[0043] Comparative Example 2:

[0044] This comparative example aims to verify the change of the action ability of the oil displacement agent system when the wetting reversal and oil film separation functions are missing by removing the key component wetting reversal agent while keeping the medium dosage and medium reaction conditions unchanged, so as to highlight the technical advantage of the present application in having multiple functions of wetting reversal, separation and cleaning, etc.

[0045] Embodiment 1: 18 parts of acrylamide, 9 parts of supramolecular assembly, 0 parts of wetting reversal agent, 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 18 parts of main surfactant, 5 parts of auxiliary surfactant, 2 parts of stabilizer, and 45 parts of solvent were taken by weight. The solvent was added into a reaction kettle, and the acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and functional monomer were sequentially added under the conditions of nitrogen protection and stirring, and stirring was performed until complete dissolution. The pH value of the system was adjusted to 7 using a sodium hydroxide solution. Then, the hydrophobic monomer was uniformly dispersed under the action of an emulsifier or a cosolvent. The system was heated to 35°C, and an initiator was added. The reaction was performed for 6 hours under nitrogen protection to obtain a colloidal product. The colloidal product was cut, granulated, dried, and pulverized to obtain a powdery product. The powdery product was prepared with water that met the requirements of the injection block to obtain a viscosity-reducing oil displacement agent comparative system.

[0046] Performance test:

[0047] 1. Viscosity-reducing performance test method

[0048] The crude oil of the target shallow low-temperature heavy oil reservoir was used as the test object, and the viscosity-reducing performance of the multifunctional supramolecular viscosity-reducing oil displacement agent was evaluated under simulated reservoir formation temperature conditions. The multifunctional supramolecular viscosity-reducing oil displacement agent prepared in the example and the comparative system prepared in the comparative example were respectively added to the crude oil at a set concentration, and the viscosity change of the crude oil before and after treatment was measured after the system was mixed and stood under constant temperature conditions until the system was stable. By comparing the improvement degree of the viscosity of the crude oil in the example and the comparative example under the same conditions, the ability of the multifunctional supramolecular synergistic system to reduce the viscosity of heavy oil and improve the flowability of crude oil under low-temperature conditions was evaluated.

[0049] 2. Oil-water interfacial tension test method

[0050] The oil-water interfacial tension test method was used to compare and evaluate the ability of the oil displacement agent systems obtained in the example and the comparative example to reduce the oil-water interfacial tension. The target oil reservoir crude oil was used as the oil phase, and the aqueous solutions of different oil displacement agent systems were used as the water phase. The interfacial tension was tested under simulated formation temperature conditions. By measuring the change of the oil-water interfacial tension, the effect of the multifunctional supramolecular viscosity-reducing oil displacement agent on the formation of supramolecular assembly structure at the oil-water interface, the reduction of interfacial tension, and the improvement of the state of the oil-water interface was evaluated, and the comparative analysis was performed with the comparative example system lacking the key component.

[0051] 3. Wetting transition performance test method

[0052] The effect of the system of the examples and the comparative examples on the wettability of the rock surface is evaluated by using a contact angle test method. Representative rock or simulated mineral surfaces are selected as test substrates. The initial wetting state of the rock surface under the action of crude oil and water is first determined. Then, the rock surface is treated in the oil displacement agent solution of the examples or the comparative examples. After being subjected to a certain time under simulated formation temperature conditions, the change in the contact angle of the rock surface is re-determined. By comparing the change in the contact angle before and after the treatment, the effect of the multifunctional supramolecular viscosity-reducing oil displacement agent on the wettability reversal and oil film stripping is evaluated.

[0053] 4. Core displacement performance test method

[0054] The oil displacement capacity of the oil displacement agent system of the examples and the comparative examples is evaluated by using a core or sand-packed tube displacement experiment. Representative natural cores or sand-packed models are selected. The experiment is carried out under simulated shallow low-temperature heavy oil reservoir formation temperature and pressure conditions. First, conventional water flooding is carried out until the water cut is stable. Then, the oil displacement agent system prepared in the examples or the comparative examples is injected. Subsequent water flooding is continued. By comparing the change in the recovery degree in the water flooding stage and the oil displacement agent composite flooding stage, the performance of the multifunctional supramolecular viscosity-reducing oil displacement agent in improving the recovery degree of remaining oil and improving the displacement efficiency is evaluated.

[0055] Performance analysis: according to the viscosity-temperature relationship of crude oil Figure 1 It can be seen that in the lower temperature range, the viscosity of the crude oil decreases sharply with the increase of temperature, especially when the temperature is lower than 30℃, the viscosity of the crude oil is at a high level, and the flowability is extremely poor. When the temperature continues to rise, the viscosity decreases gradually and tends to be flat. This figure clearly reflects the characteristics of the natural flowability of the shallow low-temperature heavy oil under the formation temperature conditions, and also shows that it is difficult to fundamentally solve the problem of high viscosity of heavy oil by relying on natural warming or limited temperature change. This result confirms from the basic physical property angle that chemical means must be introduced for viscosity reduction and start-up under low temperature conditions. The multifunctional supramolecular viscosity-reducing oil displacement agent of the present application plays a role in this low-temperature high-viscosity range.

[0056] According to the relationship between the concentration of the viscosity reducer and the viscosity reduction rate Figure 2 It can be seen that with the increase of the concentration of the viscosity reducer, the viscosity reduction rate of the crude oil shows a trend of rapid increase first and then tends to be stable. The viscosity reduction effect reaches a high level in the medium concentration range, and the viscosity reduction rate has a limited increase with the further increase of the concentration. The trend of this graph shows that the multifunctional supramolecular viscosity-reducing oil displacement agent of the present application can fully play a role in viscosity reduction in the lower to medium concentration range, which shows that it has a high action efficiency on heavy components of heavy oil through supramolecular synergistic effect. At the same time, this result also reflects that there is a synergistic relationship between the functional components in the system, rather than simply relying on high dosage to achieve viscosity reduction, which is consistent with the design idea of “low temperature and high efficiency, low dosage” in the disclosure.

[0057] According to the wetting contact angle comparison Figure 3 It can be seen that in the absence of oil displacement agent, the droplet on the solid surface shows obvious spherical morphology, and the contact angle is large, indicating that the rock surface shows oleophilicity; while adding the multifunctional supramolecular viscosity reducing oil displacement agent, the droplet on the solid surface spreads obviously, and the contact angle decreases significantly, showing the trend of changing from oleophilicity to hydrophilicity. The figure directly shows that the oil displacement agent of the application can effectively change the wetting state of the rock surface, weaken the adsorption between the oil film and the rock, and is beneficial to the stripping and migration of the oil film. This phenomenon is consistent with the wetting reversal and supramolecular synergistic stripping mechanism described in the understanding.

[0058] According to the core displacement curve Figure 4 It can be seen that in the early stage of injection, the recovery degree gradually increases with the increase of injection multiple; after the end of the conventional water flooding stage, the recovery degree tends to be flat, while after the injection of the multifunctional supramolecular viscosity reducing oil displacement agent, the recovery degree rises again, and the oil content and production pressure difference curves change accordingly, indicating that the oil displacement system has further produced effect on the residual oil. The figure result shows that the oil displacement agent of the application can effectively start the remaining oil in the pore throat on the basis of water flooding, and improve the displacement efficiency, while the comparison stage is difficult to achieve similar recovery improvement, which embodies the comprehensive advantage of the multifunctional supramolecular system in the actual displacement process.

Claims

1. A multifunctional supramolecular viscosity reducer and oil displacement agent for cold production of shallow, low-temperature heavy oil reservoirs, characterized in that, The multifunctional supramolecular viscosity reducer and oil displacement agent comprises the following raw materials in parts by weight: 5-30 parts acrylamide; 3-15 parts supramolecular assembly; 2-11 parts wetting reversal agent; 5-16 parts 2-acrylamide-2-methylpropanesulfonic acid; 5-30 parts main surfactant; 2-8 parts co-surfactant; 0.5-5 parts stabilizer; and 20-70 parts solvent.

2. The multifunctional supramolecular viscosity reducer and oil displacement agent according to claim 1, characterized in that, The main surfactant is a nonionic-anionic gemini surfactant.

3. The multifunctional supramolecular viscosity reducer and oil displacement agent according to claim 1, characterized in that, The supramolecular assembly is formed synergistically by functional monomers, modified alkyl monomers, self-made functional hydrophobic monomers, and self-made functional hydrophilic monomers through non-covalent interactions; the functional monomers are monomers containing polar functional groups that can undergo hydrogen bonding or π-π stacking interactions with colloids and / or asphaltenes in crude oil. The modified alkyl monomer is a monomer with a hydrophobic alkyl chain structure, used to enhance molecular hydrophobic interactions and intercalation dispersion capabilities; the self-made functional hydrophobic monomer is a hydrophobic monomer with hydrophobic groups, capable of participating in supramolecular self-assembly and intercalating into asphaltene aggregate structures; the self-made functional hydrophilic monomer is a hydrophilic monomer containing hydrophilic groups, capable of enhancing the water solubility of the system and participating in the formation of supramolecular assembly structures.

4. A method for preparing a multifunctional supramolecular viscosity reducer and oil displacement agent for cold production of shallow, low-temperature heavy oil reservoirs, characterized in that, The preparation method includes the following steps: (1) Add deionized water to the reactor, and under nitrogen protection and stirring conditions, add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and functional monomer in sequence, and stir until completely dissolved; (2) Adjust the pH of the system to 6-8 using sodium hydroxide solution; (3) Add hydrophobic monomers to the system, and add emulsifiers or cosolvents to make the hydrophobic monomers uniformly dispersed; (4) Heat the system and add an initiator, and carry out the polymerization reaction under nitrogen protection to obtain a gel-like product; (5) The gelatinous product is cut, granulated, dried and pulverized to obtain a powdered product; (6) The obtained powdered product is mixed with water that meets the requirements of the injection block to obtain a multifunctional supramolecular viscosity reducing and oil displacement agent.

5. The preparation method of a multifunctional supramolecular viscosity-reducing and oil displacement agent for cold production of shallow, low-temperature heavy oil reservoirs according to claim 4, characterized in that, In step (4), the heating temperature is 30-40°C and the reaction time is 4-8 hours.

6. The application of a multifunctional supramolecular viscosity-reducing and oil displacement agent as described in any one of claims 1 to 3 in the cold production of shallow, low-temperature heavy oil reservoirs, characterized in that, The concentration of the multifunctional supramolecular viscosity-reducing and oil displacement agent used in the reservoir is 0.1% to 8.0%.

7. The application of a multifunctional supramolecular viscosity-reducing and oil displacement agent as described in any one of claims 1 to 3 in the cold production of shallow, low-temperature heavy oil reservoirs, characterized in that, The formation temperature of the shallow, low-temperature heavy oil reservoir is 20–40℃.

8. The application of a multifunctional supramolecular viscosity-reducing and oil displacement agent as described in any one of claims 1 to 3 in the cold production of shallow, low-temperature heavy oil reservoirs, characterized in that, The shallow, low-temperature heavy oil reservoir is buried at a depth of 200–600 meters.

Images