Composite oil displacement system and preparation method thereof
By combining polyacrylamide and viscoelastic in a composite oil displacement system, the problems of small coverage and high cost of existing oil displacement systems are solved, achieving low-cost and high-efficiency oil displacement in old oilfields with high water cut.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-04
- Publication Date
- 2026-05-08
AI Technical Summary
In existing technologies, polymer flooding systems have a small impact range and high cost. Although polymer/surfactant flooding systems can improve oil recovery, they are also expensive and difficult to achieve low-cost and efficient oil displacement in old oilfields with high water cut.
A composite oil displacement system is adopted, which includes polyacrylamide and viscoelastic. Viscoelastic is prepared through polymerization reaction, and the thickening and suspending ability of polyacrylamide is used to carry the viscoelastic to form a heterogeneous composite system, which increases the swept volume and viscoelasticity, improves the recovery rate and reduces costs.
By increasing the viscosity of polyacrylamide by 1 to 2 times, the oilfield recovery rate is improved, the cost is reduced by about 55%, and it can adapt to the reservoir temperature and salinity environment, with a viscosity retention rate of over 80%, thus achieving low-cost and high-efficiency oil displacement.
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Abstract
Description
Technical Field
[0001] This application relates to the field of oilfield development technology, and in particular to a composite oil displacement system and its preparation method. Background Technology
[0002] Currently, most oilfields have entered the development stage of high water cut and high recovery rate. The ineffective cycle of water injection is intensifying, and the difficulty of stabilizing production and improving recovery rate is increasing year by year. It is necessary to continuously tackle the tertiary oil recovery technology suitable for old oilfields with high water cut, so as to effectively support the long-term stable production of old oilfields.
[0003] Among related technologies, polymer flooding systems and polymer / surfactant flooding systems are more commonly used. However, polymer flooding systems have a relatively small affected area, resulting in limited improvement in oil recovery. While polymer / surfactant flooding systems can improve oil recovery, they are costly. Therefore, it is necessary to provide an oil displacement system that can improve oilfield recovery while maintaining a lower cost. Summary of the Invention
[0004] This application provides a composite oil displacement system and its preparation method. The composite oil displacement system can improve oilfield recovery while maintaining low cost. The technical solution is as follows:
[0005] On the one hand, a composite oil displacement system is provided, the composite oil displacement system comprising the following components:
[0006] Polyacrylamide, viscoelastic and water,
[0007] Wherein, the concentration of the polyacrylamide is 1500 mg / L, and the concentration ratio of the viscoelastic to the polyacrylamide is 3:7 to 5:5;
[0008] The viscoelastic is obtained by the polymerization reaction of acrylamide and N,N-methylenebisacrylamide.
[0009] In one possible implementation, the raw materials for preparing the viscoelastic body further include: an initiator, anhydrous sodium carbonate, and water.
[0010] In another possible implementation, the viscoelastic body is prepared in the following mass proportions:
[0011] The acrylamide is 15-20 parts, the N,N-methylenebisacrylamide is 1-5 parts, the initiator is 0.1-2 parts, the anhydrous sodium carbonate is 3-6 parts, and the water is 45-60 parts.
[0012] In another possible implementation, the viscoelastic body is prepared according to the following method:
[0013] According to the mass fractions of each component, the water is added to the reaction vessel, the acrylamide monomer is added to the reaction vessel, and the mixture is stirred until the solid dissolves to obtain the first solution;
[0014] The N,N-methylenebisacrylamide was added to the first solution and stirred until the solid dissolved to obtain the second solution;
[0015] The initiator and the anhydrous sodium carbonate are added to the second solution and stirred until the solid dissolves to obtain the third solution;
[0016] The third solution is reacted at a preset temperature for a preset time to obtain the viscoelastic body.
[0017] In another possible implementation, the initiator is ammonium persulfate.
[0018] In another possible implementation, the preset temperature is 40℃~45℃ and the preset duration is 24~30 hours.
[0019] In another possible implementation, the mass fractions of each component in the viscoelastic material during preparation are as follows:
[0020] The composition includes 17 parts of acrylamide, 4 parts of N,N-methylenebisacrylamide, 0.5 parts of initiator, 5 parts of anhydrous sodium carbonate, and 59 parts of water.
[0021] In another possible implementation, the concentration of the viscoelastic is 1000 mg / L.
[0022] In another possible implementation, the concentration of the viscoelastic is 1500 mg / L.
[0023] On the other hand, a method for preparing a composite oil displacement system is provided, the method comprising:
[0024] Determine the volume of water and the concentration of viscoelasticity;
[0025] Based on the volume of water and the concentration of the viscoelastic, the mass of the viscoelastic and the mass of the polyacrylamide are determined.
[0026] Weigh out the appropriate amounts of polyacrylamide and viscoelastic;
[0027] Add the appropriate volume of water to the reaction vessel, add the appropriate mass of polyacrylamide to the reaction vessel, and stir until homogeneous;
[0028] Add the appropriate mass of viscoelastic material to the reaction vessel and stir until homogeneous to obtain the composite oil displacement system.
[0029] This application provides a composite oil displacement system comprising polyacrylamide and viscoelastic. The system utilizes the thickening and suspending properties of polyacrylamide to carry the viscoelastic, increasing the system viscosity by 1-2 times compared to systems using only polyacrylamide, significantly enhancing the system's viscoelasticity. Compared to polymer flooding systems, this system can more effectively improve oilfield recovery. Compared to polymer / surfactant flooding systems, the system cost can be reduced by approximately 55%. Therefore, the composite oil displacement system provided by this application can both improve oilfield recovery and has a lower cost.
[0030] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this disclosure. Detailed Implementation
[0031] To make the technical solution and advantages of this application clearer, the embodiments of this application will be described in further detail below.
[0032] On the one hand, embodiments of this application provide a composite oil displacement system, which includes the following components:
[0033] Polyacrylamide, viscoelastic and water,
[0034] The concentration of polyacrylamide is 1500 mg / L, and the ratio of viscoelastic concentration to polyacrylamide concentration is 3:7 to 5:5.
[0035] Viscoelastics are obtained by the polymerization reaction of acrylamide and N,N-methylenebisacrylamide.
[0036] In the embodiments of this application, the concentration of polyacrylamide is 1500 mg / L. Based on the ratio of the concentration of viscoelastic to the concentration of polyacrylamide, the concentration of viscoelastic can be calculated to be 643 mg / L to 1500 mg / L.
[0037] Correspondingly, the concentration of viscoelastic can be 643 mg / L, 650 mg / L, 700 mg / L, 800 mg / L, 900 mg / L, 1000 mg / L, 1100 mg / L, 1200 mg / L, 1300 mg / L, 1400 mg / L, or 1500 mg / L, without any specific limitation.
[0038] This application provides a composite oil displacement system comprising polyacrylamide and viscoelastic. The system utilizes the thickening and suspending properties of polyacrylamide to carry the viscoelastic, increasing the system viscosity by 1-2 times compared to systems using only polyacrylamide, significantly enhancing the system's viscoelasticity. Compared to polymer flooding systems, this system can more effectively improve oilfield recovery. Compared to polymer / surfactant flooding systems, the system cost can be reduced by approximately 55%. Therefore, the composite oil displacement system provided by this application can both improve oilfield recovery and has a lower cost.
[0039] In one possible implementation, the viscoelastic is obtained by polymerizing acrylamide and N,N-methylenebisacrylamide.
[0040] In this method, the raw materials for preparing the viscoelastic also include: an initiator, anhydrous sodium carbonate, and water.
[0041] The mass fractions of each component are as follows:
[0042] 45-60 parts water, 15-20 parts acrylamide, 1-5 parts N,N-methylenebisacrylamide, 0.1-2 parts initiator, and 3-6 parts anhydrous sodium carbonate.
[0043] In this embodiment, the synthesis route of the viscoelastic is as follows:
[0044]
[0045] Based on the above-mentioned raw materials and their mass fractions, viscoelastic materials can be prepared by the following methods:
[0046] (1) Add water to the reaction vessel according to the mass fraction of each component, add acrylamide monomer to the reaction vessel, stir until the solid dissolves, and obtain the first solution.
[0047] Accurately weigh a certain amount of water and acrylamide monomer according to the mass fractions of each component, add water to the reaction vessel, then add acrylamide monomer, and stir until the acrylamide monomer is completely dissolved to obtain the first solution.
[0048] (2) Add N,N-methylenebisacrylamide to the first solution and stir until the solid dissolves to obtain the second solution.
[0049] Accurately weigh a certain mass of N,N-methylenebisacrylamide, add the N,N-methylenebisacrylamide to the first solution, stir until the solution becomes clear and the solid is completely dissolved to obtain the second solution.
[0050] (3) Add the initiator and anhydrous sodium carbonate to the second solution and stir until the solid dissolves to obtain the third solution.
[0051] The initiator can be ammonium persulfate or other initiators. In this embodiment, ammonium persulfate is used as an example for illustration.
[0052] Accurately weigh a certain mass of ammonium persulfate and anhydrous sodium carbonate, add the ammonium persulfate and anhydrous sodium carbonate to the second solution, and stir until the solid is completely dissolved to obtain the third solution.
[0053] In the embodiments of this application, the main function of the initiator is to initiate the polymerization reaction of acrylamide and N,N-methylenebisacrylamide. Under the initiation of ammonium persulfate, acrylamide and N,N-methylenebisacrylamide react to generate a water-absorbing bulk adhesive with a three-dimensional network structure.
[0054] (4) The third solution is reacted at a preset temperature for a preset time to obtain a viscoelastic body.
[0055] The preset temperature and preset duration can be set and changed as needed. For example, the preset temperature can be 40℃~45℃ and the preset duration can be 24~30 hours. In this embodiment, only the preset temperature of 40℃~45℃ and the preset duration of 24~30 hours are used as an example for illustration.
[0056] Accordingly, step (4) is: placing the third solution at 40℃~45℃ for 24~30 hours to allow it to undergo a polymerization reaction. After the reaction is completed, a viscoelastic body is obtained, which is a negatively charged bulk gel with carboxyl groups.
[0057] The preset temperatures can be 40℃, 41℃, 42℃, 43℃, 44℃, or 45℃, and the preset durations can be 24 hours, 25 hours, 26 hours, 27 hours, 28 hours, 29 hours, or 30 hours.
[0058] In the embodiments of this application, the addition of anhydrous sodium carbonate can hydrolyze the bulk adhesive formed by acrylamide and N,N-methylenebisacrylamide into a negatively charged bulk adhesive with carboxyl groups, making the negatively charged bulk adhesive easily hydrolyzed and thickened, and less prone to forming insoluble substances. Furthermore, anhydrous sodium carbonate undergoes a hydrolysis reaction in aqueous solution, making the solution alkaline. Polyacrylamide hydrolyzes under alkaline conditions, converting the amide groups (-CONH2) into carboxyl groups (-COOH). + Under certain conditions, sodium carboxylate groups (-COONa) are obtained. The negatively charged bulk adhesive with carboxyl groups readily forms electrostatic repulsion with the sodium carboxylate groups obtained from the hydrolysis of polyacrylamide, which is beneficial to the stretching of polyacrylamide molecular chains, thereby increasing the viscosity of the system.
[0059] In one possible implementation, the preferred mass proportions of each component in the viscoelastic preparation process are: 17 parts acrylamide, 4 parts N,N-methylenebisacrylamide, 0.5 parts initiator, 5 parts anhydrous sodium carbonate, and 59 parts water.
[0060] In the embodiments of this application, when the viscoelastic prepared by using the above-mentioned components in parts by mass is compounded with polyacrylamide, it has a good viscosity retention rate, and the viscosity retention rate can still reach more than 80% after 90 days. At the same time, the system has good temperature resistance and salt resistance thermal stability.
[0061] In one possible implementation, the concentration of the viscoelastic is preferably 1000 mg / L or 1500 mg / L.
[0062] In the embodiments of this application, the highest improvement in oilfield recovery was achieved when a viscoelastic mixture of 1500 mg / L and polyacrylamide was used. A significant improvement in oilfield recovery was also achieved when a viscoelastic mixture of 1000 mg / L and polyacrylamide was used, while the cost was also lower.
[0063] The composite oil displacement system provided in this application is a heterogeneous composite phase oil displacement system. This system consists of a high-viscosity polymer and heterogeneous viscoelastic particles. The polymer's viscosity-enhancing and suspending capabilities carry the heterogeneous viscoelastic particles, increasing the system viscosity by 1 to 2 times compared to a single polymer system. This system can adapt to reservoir temperatures of 40–90℃ and salinity ≤30000 mg / L, demonstrating good temperature and salinity resistance and thermal stability. Furthermore, the viscosity retention rate after 90 days can reach over 80%. Applying this system to oil reservoirs can, on the one hand, expand the swept volume using polyacrylamide; on the other hand, the addition of heterogeneous viscoelastic particles significantly increases the system's viscoelasticity, expanding the oil sweeping area and thus achieving a substantial increase in oil recovery.
[0064] On the other hand, embodiments of this application provide a method for preparing a composite oil displacement system, the method comprising:
[0065] Step 1: Determine the volume of water and the concentration of viscoelastic.
[0066] The volume of water is determined based on the on-site preparation requirements. For example, if 1 cubic meter of composite oil displacement system needs to be prepared on-site, the volume of water is 1 cubic meter, or 1000L; if 10 cubic meters of composite oil displacement system needs to be prepared on-site, the volume of water is 10 cubic meters, or 10000L.
[0067] First, determine the ratio of viscoelastic concentration to polyacrylamide concentration. Then, based on the polyacrylamide concentration and the ratio of viscoelastic concentration to polyacrylamide concentration, determine the concentration of viscoelastic.
[0068] For example, if the ratio of viscoelastic concentration to polyacrylamide concentration is 5:5, and the concentration of polyacrylamide is known to be 1500 mg / L, then the concentration of viscoelastic is 1500 mg / L.
[0069] For example, if the ratio of viscoelastic concentration to polyacrylamide concentration is 4:6, and the concentration of polyacrylamide is known to be 1500 mg / L, then the concentration of viscoelastic is 1000 mg / L.
[0070] Step 2: Determine the mass of the viscoelastic and the mass of the polyacrylamide based on the volume of water and the concentration of the viscoelastic.
[0071] The mass of the viscoelastic body is obtained by multiplying the volume of water by the concentration of the viscoelastic body.
[0072] The mass of polyacrylamide is obtained by multiplying the volume of water by the concentration of polyacrylamide.
[0073] Step 3: Weigh out the appropriate amounts of polyacrylamide and viscoelastic.
[0074] Step 4: Add the appropriate volume of water to the reaction vessel, add the appropriate mass of polyacrylamide to the reaction vessel, and stir until homogeneous.
[0075] Step 5: Add the appropriate mass of viscoelastic material to the reaction vessel, stir evenly, and obtain the composite oil displacement system.
[0076] In this embodiment, adding polyacrylamide to water first, followed by viscoelasticity, yields a homogeneous and stable composite oil displacement system. Adding viscoelasticity to water first, followed by polyacrylamide, makes the polyacrylamide difficult to dissolve, affecting the homogeneity and stability of the composite oil displacement system.
[0077] It should be noted that the water used in preparing the composite oil displacement system can be distilled water, tap water, or on-site water, and the water used in preparing the viscoelastic body can be distilled water, tap water, or on-site water; there are no specific limitations on these.
[0078] In summary, the composite oil displacement system provided in this application can solve the problem of inefficient operation caused by crossflow of oil displacement systems along high-permeability layers. On the other hand, it overcomes the practical problem of high cost and limited application of polymer / surfactant oil displacement systems. The cost of the composite oil displacement system in this application is basically equivalent to that of the polymer oil displacement system, and the cost is reduced by about 55% compared with the polymer / surfactant oil displacement system.
[0079] The technical solution of this application will be described in detail below through specific embodiments.
[0080] In the following specific embodiments, unless otherwise specified, all operations are performed under standard conditions or conditions recommended by the manufacturer. Raw materials whose manufacturers and specifications are not specified are all commercially available products.
[0081] Example 1
[0082] According to the mass fractions of each component, add 45 parts of water to a beaker, add 15 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 1 part of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.5 parts of ammonium persulfate and 3 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0083] Example 2
[0084] According to the mass fractions of each component, add 47 parts of water to a beaker, add 15 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 2 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.1 parts of ammonium persulfate and 4 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0085] Example 3
[0086] According to the mass fractions of each component, add 49 parts of water to a beaker, add 15 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 3 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.3 parts of ammonium persulfate and 3 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0087] Example 4
[0088] According to the mass fractions of each component, add 50 parts of water to a beaker, add 16 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 3 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.2 parts of ammonium persulfate and 4 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0089] Example 5
[0090] According to the mass fractions of each component, add 52 parts of water to a beaker, add 17 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 2 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 1 part of ammonium persulfate and 5 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0091] Example 6
[0092] According to the mass fractions of each component, add 54 parts of water to a beaker, add 19 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 3 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 2 parts of ammonium persulfate and 4 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0093] Example 7
[0094] According to the mass fractions of each component, add 55 parts of water to a beaker, add 18 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 4 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 1.5 parts of ammonium persulfate and 3 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0095] Example 8
[0096] According to the mass fractions of each component, add 57 parts of water to a beaker, add 16 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 3 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.8 parts of ammonium persulfate and 4 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0097] Example 9
[0098] According to the mass fractions of each component, add 59 parts of water to a beaker, add 17 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 4 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.5 parts of ammonium persulfate and 5 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0099] Example 10
[0100] According to the mass fractions of each component, add 60 parts of water to a beaker, add 20 parts of acrylamide monomer to the beaker, and stir until the solid dissolves; then add 5 parts of N,N-methylenebisacrylamide to the beaker, and stir until the solution becomes clear and the solid dissolves; then add 0.3 parts of ammonium persulfate and 6 parts of anhydrous sodium carbonate to the beaker, and stir until the solid is completely dissolved. Place the beaker at 40°C for 24 hours to allow the polymerization reaction to occur, and obtain a viscoelastic. Remove the beaker, seal it, and store it at room temperature.
[0101] The formulations of the viscoelastics prepared in Examples 1-10 can also be found in Table 1.
[0102] Table 1
[0103]
[0104] The viscoelastics prepared in Examples 1-10 were compounded with polyacrylamide to prepare a composite oil displacement system. The concentrations of the viscoelastics and polyacrylamide, as well as the viscosity of the composite oil displacement system, can be found in Table 2.
[0105] Table 2
[0106]
[0107]
[0108] According to the data in Table 2, Example 9 showed the best viscosity retention rate. Therefore, a composite oil displacement system was prepared by combining the viscoelastic material from Example 9 with polyacrylamide, and its oil displacement characteristics were studied and analyzed.
[0109] Oil displacement experiment: Three-layer heterogeneous cores bonded with epoxy resin were used in the experiment, with core dimensions of 4.5cm × 4.5cm × 30cm. The displacement process was as follows: 2 PV water flooding, 1 PV transfer to the composite oil displacement system, followed by another 2 PV water flooding to finish. The oil displacement effects of different composite oil displacement systems can be found in Table 3.
[0110] Table 3
[0111]
[0112] Table 3 shows that the composite oil displacement system prepared by combining 1500 mg / L polyacrylamide and 1500 mg / L viscoelasticity has the highest increase in oil recovery, but also the highest cost per unit volume. While the composite oil displacement system prepared by combining 1500 mg / L polyacrylamide and 1000 mg / L viscoelasticity does not increase oil recovery as much, its cost per unit volume is lower. Therefore, considering both technical and economic indicators, the composite oil displacement system prepared by combining 1500 mg / L polyacrylamide and 1000 mg / L viscoelasticity is the most competitive, as it can significantly improve oil recovery while maintaining a lower cost.
[0113] It should be noted that the reason why polyacrylamide was not compounded with higher concentrations of viscoelastic in Table 3 is that increasing the concentration of viscoelastic can indeed increase the recovery rate, but the increase will gradually weaken. At the same time, the system cost will increase significantly. In other words, the increase in technical indicators cannot keep up with the increase in economic indicators, which will result in higher system costs. Therefore, this application determines the optimal combination method from both technical and economic perspectives.
[0114] The above description is only for the purpose of enabling those skilled in the art to understand the technical solution of this application, and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A composite oil displacement system, characterized in that, The composite oil displacement system comprises the following components: Polyacrylamide, viscoelastic and water, Wherein, the concentration of the polyacrylamide is 1500 mg / L, and the concentration ratio of the viscoelastic to the polyacrylamide is 3:7 to 5:5; The viscoelastic is obtained by the polymerization reaction of acrylamide and N,N-methylenebisacrylamide.
2. The composite oil displacement system according to claim 1, characterized in that, The raw materials for preparing the viscoelastic also include: an initiator, anhydrous sodium carbonate, and water.
3. The composite oil displacement system according to claim 2, characterized in that, The mass fractions of each component in the preparation process of the viscoelastic are as follows: The acrylamide is 15-20 parts, the N,N-methylenebisacrylamide is 1-5 parts, the initiator is 0.1-2 parts, the anhydrous sodium carbonate is 3-6 parts, and the water is 45-60 parts.
4. The composite oil displacement system according to claim 3, characterized in that, The viscoelastic body is prepared according to the following method: According to the mass fractions of each component, the water is added to the reaction vessel, the acrylamide monomer is added to the reaction vessel, and the mixture is stirred until the solid dissolves to obtain the first solution; The N,N-methylenebisacrylamide was added to the first solution and stirred until the solid dissolved to obtain the second solution; The initiator and the anhydrous sodium carbonate are added to the second solution and stirred until the solid dissolves to obtain the third solution; The third solution is reacted at a preset temperature for a preset time to obtain the viscoelastic body.
5. The composite oil displacement system according to claim 3 or 4, characterized in that, The initiator is ammonium persulfate.
6. The composite oil displacement system according to claim 4, characterized in that, The preset temperature is 40℃~45℃, and the preset duration is 24~30 hours.
7. The composite oil displacement system according to claim 2, characterized in that, The mass fractions of each component in the preparation process of the viscoelastic are as follows: The composition includes 17 parts of acrylamide, 4 parts of N,N-methylenebisacrylamide, 0.5 parts of initiator, 5 parts of anhydrous sodium carbonate, and 59 parts of water.
8. The composite oil displacement system according to claim 7, characterized in that, The concentration of the viscoelastic is 1000 mg / L.
9. The composite oil displacement system according to claim 7, characterized in that, The concentration of the viscoelastic is 1500 mg / L.
10. A method for preparing the composite oil displacement system according to any one of claims 1 to 9, characterized in that, The preparation method includes: Determine the volume of water and the concentration of viscoelasticity; Based on the volume of water and the concentration of the viscoelastic, the mass of the viscoelastic and the mass of the polyacrylamide are determined. Weigh out the appropriate amounts of polyacrylamide and viscoelastic; Add the appropriate volume of water to the reaction vessel, add the appropriate mass of polyacrylamide to the reaction vessel, and stir until homogeneous; Add the appropriate mass of viscoelastic material to the reaction vessel and stir until homogeneous to obtain the composite oil displacement system.