A chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding, and a preparation method and application thereof

Abstract

The present application relates to a kind of for reducing carbon dioxide oil displacement minimum miscibility pressure chemical system and its preparation method and application, especially reduce the minimum miscibility pressure (MMP) in carbon dioxide oil displacement process.It includes the following mass percentage of raw materials:0.01~6% main agent, 0.01~2% cosolvent, 0.01~2% solubilizer, 0.01~3% solubility regulator, basic agent 0.01~1%, supercritical carbon dioxide content 86~99.95%;Wherein, the main agent is alcohol ether solvent;The cosolvent is alcohol system;The solubilizer is alcohol amine;The solubility regulator is carbonyl compound;By this specific combination, the chemical system aims to improve the solubility and dispersibility of carbon dioxide in oil reservoir, thereby reducing MMP, improve the recovery of oilfield.

Description

Technical Field

[0001] This application belongs to the field of petroleum extraction technology, and in particular relates to a chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding, its preparation method and application. Background Technology

[0002] Currently, approximately 73% of global carbon emissions originate from the energy sector. Global energy-related carbon dioxide emissions total approximately 33 billion tons, with developed economies accounting for about one-third of these emissions. In terms of the sources of energy-related carbon dioxide emissions, the combustion of coal and oil is currently the primary source, accounting for approximately 75% combined. By sector, the power sector, transportation, and industry rank as the top three emitters.

[0003] With the continuous increase in greenhouse gas concentrations, climate change has become one of the most serious challenges facing all of humanity in the 21st century. In response, countries around the world have taken action to address climate change and set carbon emission reduction targets, and "carbon peaking and carbon neutrality" has gradually become a global issue.

[0004] Carbon dioxide enhanced oil recovery (CED) is a method for improving oil field recovery. Typically, large amounts of crude oil in oil reservoirs cannot be extracted through natural production mechanisms. When carbon dioxide is injected into the reservoir, it interacts with the oil components, making the crude oil more fluid and easier to extract. This increases the oil field's recovery rate and extends its production life. The carbon dioxide used in CED comes from industrial emission sources; after being injected into the oil field, it is permanently locked underground, reducing the amount of carbon dioxide emitted into the atmosphere and helping to mitigate climate change. CED is an integrated technology used in CCUS (Chemical Enhancing Systems) to improve oil recovery while reducing greenhouse gas emissions.

[0005] Carbon capture, utilization, and storage combined with enhanced oil recovery (CCUS-EOR) is currently considered a realistic, effective, and feasible carbon dioxide emission reduction technology. Its core concept is to inject captured carbon dioxide gas into oil fields to improve oil extraction efficiency while simultaneously permanently storing this carbon dioxide to reduce greenhouse gas emissions into the atmosphere. CCUS-EOR is currently the most realistic, effective, and feasible carbon dioxide emission reduction technology, effectively supporting the green, low-carbon, and sustainable development of fossil fuel enterprises and making significant contributions to the national energy transition and the achievement of "dual-carbon" goals. Carbon dioxide flooding (CFD) is a method of enhancing oil recovery by injecting carbon dioxide into the reservoir to replace crude oil. However, the efficiency of carbon dioxide utilization is limited by the minimum miscibility pressure (MMP), which is the lowest pressure at which carbon dioxide begins to mix with crude oil to form a single phase. High MMP limits the application of CFD; therefore, developing chemical systems that can reduce MMP is of great significance.

[0006] Carbon dioxide (CO2), as a highly efficient oil displacement solvent, is currently a major technology for addressing the challenges of energy replenishment and low recovery rates in tight, low-permeability, and ultra-low-permeability reservoirs, as well as shale reservoirs. CO2 flooding technology, as an effective method to improve oilfield recovery, has been widely applied in traditional oilfields. However, in unconventional resources such as tight, low-permeability, and ultra-low-permeability reservoirs, and shale reservoirs, CO2 flooding faces more severe challenges. One key issue is that due to the low content of light hydrocarbons in crude oil, the minimum miscibility pressure (MMP) during CO2 flooding is high, making it difficult to achieve miscible displacement under existing formation pressure conditions. This limits the effective application of CO2 in these special reservoirs. A high MMP means that higher pressure is required for CO2 to mix with crude oil, forming a single phase, and thus driving oil towards production wells. However, in low-permeability and ultra-low-permeability reservoirs, high pressure can lead to formation damage, increasing development risks and costs. Furthermore, the unique properties of shale reservoirs, such as microfractures and low porosity, also present additional challenges to CO2 flooding.

[0007] Carbon dioxide flooding only yields good economic benefits when miscible displacement is achieved. Technically, miscible displacement can be achieved by reducing the minimum miscibility pressure between carbon dioxide and crude oil.

[0008] Therefore, developing a chemical system suitable for these special conditions to reduce the minimum miscibility pressure of carbon dioxide flooding is key to improving the efficiency and feasibility of carbon dioxide flooding in unconventional reservoirs. Summary of the Invention

[0009] The technical problem this application aims to solve is to overcome the shortcomings of existing technologies and provide a chemical system for reducing minimum miscibility pressure (MMP) in carbon dioxide flooding, its preparation method, and its application. The system provided by this invention mainly comprises a polyether surfactant as the main agent, and an optimized combination of alcohols, esters, and amines. Through this specific combination, the chemical system aims to improve the solubility and dispersibility of carbon dioxide in the reservoir, thereby reducing MMP and improving oilfield recovery.

[0010] This application adopts the following technical solution to solve the above-mentioned technical problems:

[0011] First aspect:

[0012] This application provides a chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding, comprising the following raw materials by mass percentage: 0.01-6% main agent, 0.01-2% co-solvent, 0.01-2% solubilizer, 0.01-3% solubility modifier, 0.01-1% alkalinity agent, and supercritical carbon dioxide content of 86-99.95%;

[0013] Wherein, the main agent is an alcohol ether solvent; the substance is an alcohol; the solubilizer is an alkanolamine; and the solubility regulator is a carbonyl compound.

[0014] In some embodiments, the raw materials include the following mass percentages: 0.01–2% alcohol ether solvents, 0.01–1% alcohols, 0.01–1% alkanolamines, 0.01–1% carbonyl compounds, 0.01–2% alkaline agents, and 93–99.95% supercritical carbon dioxide.

[0015] In some embodiments, the alcohol ether solvent includes at least one selected from ethylene glycol isopropyl ether, butanediol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol isopropyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, and propylene glycol ethyl ether.

[0016] The alkaline substance is one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, sodium tetraborate, propylamine, propylenediamine, methylamine, ethylamine, butylamine, and aniline.

[0017] The alcohols include at least one of ethanol, isopropanol, butanol, ethylene glycol, glycerol, hexanediol, polyether triol, and sorbitol;

[0018] The alkanolamine includes at least one of ethanolamine, diethanolamine, triethanolamine, propylamine, propylenediamine, methylamine, ethylamine, butylamine, and aniline;

[0019] The carbonyl compounds include ester compounds and / or ketone compounds.

[0020] In some embodiments, the ester compounds include, for example, methyl formate and / or ethyl acetate;

[0021] The ester compounds include ether ester compounds; preferably, the ether ester compounds include at least one of ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, and ethyl 3-ethoxypropionate.

[0022] The ester compounds include methyl formate and / or ethyl acetate;

[0023] The ketone group includes saturated ketones; preferably, the saturated ketone includes at least one of acetone, butanone, methyl ketone, acetophenone, and cyclohexanone.

[0024] In some embodiments, the specific steps of the preparation method of the chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding as described above are: mixing the main agent, the co-solvent, the solubilizer and the solubility regulator.

[0025] In some embodiments, the mixing temperature is 30°C;

[0026] The mixing time is 1.5 to 3 hours;

[0027] The mixing speed is 800 rpm / min.

[0028] In some embodiments, the mixing is performed under ultrasound at a frequency of 20–80 kHz.

[0029] The present invention also provides a chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding as described above, which is prepared by any one of the methods in claims 5 to 7.

[0030] The present invention also provides a chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding as described above, which is used in crude oil extraction.

[0031] The second aspect:

[0032] The present invention has found that polyether surfactants, as a major component of a chemical system, can effectively reduce the surface tension at the oil-water interface, increase the interfacial contact between carbon dioxide and crude oil, thereby promoting the dissolution and dispersion of carbon dioxide.

[0033] This invention, through research, has discovered that alcohol-based chemical agents possess effective carbon dioxide-loving groups that can interact with carbon dioxide through hydrogen bonds. Using alcohol-based chemical agents can improve the dispersibility and permeability of carbon dioxide, allowing it to enter the reservoir more uniformly and reducing the high pressure differential required before displacement. Alcohol-based chemical agents can increase the compatibility between carbon dioxide and crude oil, making them easier to mix. This helps reduce the mean maximal pressure (MMP), enabling carbon dioxide to mix more effectively with crude oil, thereby improving carbon dioxide reversibility. Alcohols can also improve the mutual solubility between carbon dioxide and crude oil, reducing the pressure required for miscibility.

[0034] This invention, through research, has discovered that amine compounds can adjust the pH value of the system, improving overall stability. They can also act as carbon dioxide capture agents, reacting chemically with carbon dioxide to form carbonates, facilitating the transfer of carbon dioxide from the gas phase to the liquid phase, increasing the solubility of carbon dioxide in oil, promoting carbon dioxide dissolution, maintaining an alkaline environment, and reducing oil-water interfacial tension. This enhances the efficiency of the interaction between carbon dioxide and crude oil, thereby improving oil recovery. Simultaneously, amine compounds improve the interaction between carbon dioxide and crude oil by forming stable emulsions or increasing the solubility of carbon dioxide, effectively reducing miscibility pressure. This contributes to improving the efficiency and economy of carbon dioxide flooding.

[0035] This invention has discovered that the carbon-oxygen double bond in carbonyl compounds can form hydrogen bonds with carbon dioxide, thereby enhancing carbon dioxide affinity and increasing the solubility of crude oil in carbon dioxide in the reservoir. Because ethers and esters have good oleophilicity, they can promote the mixing of carbon dioxide and crude oil, improve the solubility of carbon dioxide in crude oil, improve the solubility and distribution of carbon dioxide, reduce the viscosity and interfacial tension of crude oil, and thus improve the recovery rate of the reservoir.

[0036] This invention has found that saturated ketones increase the solubility of carbon dioxide, reduce the viscosity of crude oil, and reduce interfacial tension. In addition, the presence of ketone compounds can change the phase behavior within the reservoir, such as promoting the formation of the oil and gas phases, thereby helping to improve the uniformity of carbon dioxide distribution in the reservoir and thus improving oil displacement efficiency. Ketone compounds can also improve the temperature and pressure conditions of the reservoir, making it more suitable for carbon dioxide flooding, especially in deep reservoirs with high temperature and high pressure.

[0037] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this application.

[0038] All reagents and raw materials used in this application are commercially available.

[0039] The positive advancements of this application lie in the fact that the system mainly comprises a polyether surfactant as the main agent, along with an optimized combination of alcohols, esters, and amines. Through this specific combination, the chemical system aims to improve the solubility and dispersibility of carbon dioxide in the reservoir, thereby reducing MMP and increasing oilfield recovery. Attached Figure Description

[0040] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings. These drawings, together with the detailed description below, are included in and form part of this specification, and are used to further illustrate preferred embodiments of the application and explain its principles and advantages.

[0041] in:

[0042] Figure 1 The minimum miscibility pressure for carbon dioxide flooding in long capillary tubes when adding the product prepared in Example 1;

[0043] Figure 2 The minimum miscibility pressure for carbon dioxide drive in long thin tubes when adding the product prepared in Example 2.

[0044] Figure 3 The minimum miscibility pressure for carbon dioxide flooding in long capillary tubes when adding the product prepared in Example 3;

[0045] Figure 4The minimum miscibility pressure for carbon dioxide flooding in long capillary tubes when adding the product prepared in Example 4;

[0046] Figure 5 The minimum miscibility pressure for carbon dioxide flooding in long capillary tubes when adding the product prepared in Example 5;

[0047] Figure 6 The minimum miscibility pressure for carbon dioxide flooding in long capillary tubes when adding the product prepared in Example 6;

[0048] Figure 7 The minimum miscibility pressure of the long capillary carbon dioxide drive system in Comparative Example 1 without the addition of a demisting agent is the minimum miscibility pressure.

[0049] Figure 8 The graph shows the interfacial tension and pressure changes of crude oil-carbon dioxide interfacial tension in a system with added demixing agent, determined by the interfacial tension method.

[0050] Figure 9 This is a diagram showing the contact miscibility of crude oil and carbon dioxide under different pressures in Example 2. Detailed Implementation

[0051] The present application is further illustrated below by way of embodiments, but these embodiments are not intended to limit the scope of the present application. Experimental methods not specifically described in the following embodiments are performed according to conventional methods and conditions, or as selected in accordance with the product instructions.

[0052] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0053] All raw materials used in the following examples are commercially available.

[0054] Example 1

[0055] The raw material composition is shown in Table 1.

[0056] Table 1

[0057] composition substance proportion Chemical system main agent Butylene glycol methyl ether 0.30％ Cosolvent Polyether triol 0.30％ Solubilizer ethanolamine 0.10％ solubility regulator Ethylene glycol methyl ether acetate 0.10％ carbon dioxide Supercritical carbon dioxide margin

[0058] The preparation method is as follows:

[0059] The main agent, co-solvent, solubilizer, and solubility regulator were mixed together to prepare a chemical system. The mixture was stirred at 25°C using a magnetic stirrer for 2 hours, followed by ultrasonic oscillation to ensure uniformity of the main agent, co-solvent, solubilizer, and solubility regulator in the chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding, thus ensuring complete dissolution of the additives and obtaining the chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding.

[0060] Example 2

[0061] The difference from Example 1 is only in the component ratio. The raw material ratio is shown in Table 2. All other conditions are the same as in Example 1.

[0062] Table 2

[0063] composition substance proportion Chemical system main agent Ethylene glycol butyl ether 0.5％ Cosolvent Ethylene glycol 0.20％ Solubilizer diethanolamine 0.10％ alkaline substances Ethylamine 0.20％ solubility regulator Ethylene glycol butyl ether acetate 0.10％ carbon dioxide Supercritical carbon dioxide margin

[0064] Example 3

[0065] The difference from Example 1 is only in the component ratio. The raw material ratio is shown in Table 3. All other conditions are the same as in Example 1.

[0066] Table 3

[0067]

[0068]

[0069] Example 4

[0070] The difference from Example 1 is only in the component ratio. The raw material ratio is shown in Table 4. All other conditions are the same as in Example 1.

[0071] Table 4

[0072] composition substance proportion Chemical system main agent Ethylene glycol butyl ether 0.50％ Cosolvent Glycerol 0.40％ Solubilizer Triethanolamine 0.10％ alkaline substances Propylenediamine 0.20％ solubility regulator acetone 0.05％ carbon dioxide Supercritical carbon dioxide margin

[0073] Example 5

[0074] The difference from Example 1 is that the only difference is the component ratio. The raw material ratio is shown in Table 5. All other conditions are the same as in Example 1.

[0075] Table 5

[0076]

[0077]

[0078] Example 6

[0079] The difference from Example 1 is only in the component ratio. The raw material ratio is shown in Table 6. All other conditions are the same as in Example 1.

[0080] Table 6

[0081] composition substance proportion Chemical system main agent Diethylene glycol butyl ether 0.50％ Cosolvent Hexanediol 0.40％ Solubilizer Methyldiethanolamine 0.10％ alkaline substances Methylamine 0.20％ carbon dioxide Supercritical carbon dioxide margin

[0082] Comparative Example 1

[0083] The difference from Example 1 is that no downmixing system was added; all other conditions are the same as in Example 1.

[0084] Application Example 1

[0085] Minimum miscibility pressure determination

[0086] The experimental oil was prepared according to the components listed in the table, and the parameters were as follows:

[0087] Table 7 shows the composition of crude oil in the formation of oil wells in the target block.

[0088] Table 7

[0089]

[0090] Model preparation

[0091] (1) Heat the capillary model to a certain temperature and clean it with a certain volume of suitable solvent (such as toluene, petroleum ether and methanol) until the chromatographic analysis results of the product are the same as the solvent components and are stable, indicating that the capillary has been completely cleaned.

[0092] (2) Dry the solvent in the capillary tube with dry, high-pressure nitrogen and test the experimental procedure. The pressure drop should be less than 0.05 MPa after 1 hour of testing to be considered acceptable.

[0093] (3) Connect the thin tube to the evacuation process, and after the vacuum degree reaches 133Pa, continue evacuation for 2h-5h.

[0094] Carbon dioxide displacement

[0095] (1) Keep the injected gas sample constant at the experimental temperature.

[0096] (2) Fill and flush the pipeline to the inlet valve of the thin tube model with injection gas. Adjust the injection gas pressure to 0.08 MPa higher than the experimental pressure and record the initial reading of the pump at this pressure.

[0097] (3) Under experimental temperature and pressure, at a constant injection rate, the injected gas displaces the formation crude oil sample in the capillary model. The displacement rate is generally 10 cm. 3 / h.

[0098] (4) During the displacement process, the displacement pressure difference between the injection pressure of the thin tube model and the experimental pressure set by the back pressure hole joint should be less than 0.5 MPa. If the displacement pressure difference is too high, the injection speed should be reduced.

[0099] (5) During the displacement process, for every 0.1 times the pore volume injected, the volume of oil and gas produced at each measuring point is recorded, along with the pump reading, injection pressure, and back pressure. The composition and properties of the produced oil and gas can be determined, and the phase state and color changes of the fluid in the annular pressure observation window can be observed. After the gas breakthrough, the data acquisition density should be increased as much as possible.

[0100] (6) Stop displacement when the cumulative feed into the pump exceeds 1.20 times the pore volume or when oil production ceases.

[0101] Determination of minimum miscibility pressure:

[0102] (1) Select 5 to 7 pressure points above the formation oil saturation pressure to conduct capillary displacement experiments;

[0103] (2) Conduct a series of experiments under formation pressure, determine whether the phase is miscible based on the recovery rate, and use the gradual approximation method to determine other displacement pressure points in turn;

[0104] (3) At least two or more test pressure points are required in both the immiscible and miscible phases;

[0105] (4) Plot the curves of the relationship between the recovery rate and the displacement pressure when each group of experiments is displaced by 1.2 PV. The pressure corresponding to the intersection of the fitting lines of the miscible and immiscible sections is the minimum miscible pressure.

[0106] Example 1

[0107] The chemical system provided by this invention shows significant effectiveness in reducing the minimum miscibility pressure of carbon dioxide flooding. This not only improves the efficiency of carbon dioxide flooding but also helps reduce the cost and environmental impact of oilfield development. Furthermore, the composition of this system can be adjusted according to the characteristics of different reservoirs, exhibiting high applicability and flexibility.

[0108] Indoor experiments using the capillary tube method for carbon dioxide displacement are a common approach to simulating reservoir pore structure. This method can accurately simulate the fluid displacement process in an oil reservoir under different pressure conditions, thereby determining the minimum miscibility pressure between carbon dioxide and crude oil. By plotting the pressure versus oil recovery rate in the experiment, the minimum miscibility pressure of the system can be obtained visually. The advantage of the capillary tube method lies in its ability to approximate reservoir conditions to the greatest extent possible, providing an effective experimental tool for studying carbon dioxide enhanced oil recovery (EOR) technology.

[0109] In this invention, the experimental design used a long, thin tube model with a length of 20m, an inner diameter of 6mm, a permeability of 4685mD, and a porosity of 35%.

[0110] Table 8

[0111] Length (m) Inner diameter(mm) Permeability (mD) Porosity (%) 20 6 4700 35

[0112] According to the industry standard SY / T 6573-2016, the minimum miscibility pressure was experimentally determined using a long, thin tube for indoor oil displacement experiments. Under formation temperature and pressure conditions, pure carbon dioxide flooding and carbon dioxide + chemical flooding experiments were conducted. Curves showing the relationship between recovery rate and displacement pressure at 1.2 PV displacement were plotted for each group of experiments. The pressure corresponding to the intersection of the fitted lines of the miscible and immiscible sections is the minimum miscibility pressure. The results are shown in […]. Figures 1-7 See Table 9.

[0113] The minimum miscibility pressure of carbon dioxide flooding in a certain block was determined to be 31.17 MPa through long thin tube experiments. Since the formation pressure in this block is low, by reducing the minimum miscibility pressure, the carbon dioxide enhanced oil recovery (EOR) technology can be applied to a wider range of oil fields.

[0114] Table 9

[0115] Sample number Minimum miscibility pressure (unit: MPa) Comparative Example 1 31.17 Example 1 27.37 Example 2 24.74 Example 3 25.38 Example 4 26.2 Example 5 27.53 Example 6 28.73

[0116] The results show that the chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding prepared in this application can effectively combine ether groups, alcohols, amines, carbonyl compounds and saturated ketones, making it suitable for carbon dioxide flooding and significantly reducing the minimum miscibility pressure. In particular, in Example 2, the minimum miscibility pressure was reduced by 25%.

[0117] Table 10: Changes in Minimum Miscibility Pressure After Addition of Chemical System

[0118]

[0119] Depend on Figures 1-8 As shown in Table 10, the addition of the chemical systems prepared in Examples 1-6 of this application for reducing the minimum miscibility pressure of carbon dioxide flooding can significantly reduce the miscibility pressure. Furthermore, the system provided in Example 2 can help improve the uniformity of carbon dioxide distribution in the reservoir, thereby improving the oil displacement efficiency. The ketone compounds can also improve the temperature and pressure conditions of the reservoir.

[0120] Comparative Example 1: No chemical agents were added, and the minimum miscibility pressure remained unchanged at 31.17 MPa, with a change rate of 0%.

[0121] Example 1: After adding the chemical agent, the minimum miscibility pressure decreased from 31.17 MPa to 27.37 MPa, a reduction of 3.8 MPa, representing a change rate of 12.19%. This indicates that the added chemical agent can significantly reduce the minimum miscibility pressure and help improve the miscibility effect.

[0122] Example 2: After adding the chemical agent, the minimum miscibility pressure dropped to 24.74 MPa, a reduction of 6.43 MPa, representing a change rate of 20.63%. This is the largest decrease in minimum miscibility pressure among all examples, indicating that the chemical agent is most effective in reducing miscibility pressure.

[0123] Example 3: After adding the chemical agent, the minimum miscibility pressure dropped to 25.38 MPa, a reduction of 5.79 MPa, with a change rate of 18.58%. It also showed a significant pressure reduction effect, second only to Example 2.

[0124] Example 4: After adding the chemical agent, the minimum miscibility pressure dropped to 26.2 MPa, a reduction of 4.97 MPa, with a change rate of 15.94%. Although the reduction was slightly less than that in Example 3, it still showed a significant pressure reduction effect.

[0125] Example 5: After adding the chemical agent, the minimum miscibility pressure dropped to 27.53 MPa, a reduction of 3.64 MPa, with a change rate of 11.68%. The pressure reduction effect was relatively low, but it still showed some effectiveness.

[0126] Example 6: After adding the chemical agent, the minimum miscibility pressure dropped to 28.73 MPa, a decrease of 3.64 MPa, with a change rate of 7.83%. This is the smallest decrease in minimum miscibility pressure among all examples, indicating that the chemical agent has a weak effect on reducing miscibility pressure.

[0127] Comprehensive analysis: In all embodiments, the addition of chemical agents reduced the minimum miscibility pressure to varying degrees.

[0128] Examples 2 and 3 showed the most significant pressure-reducing effects, with changes of 20.63% and 18.58% respectively, indicating that these chemicals have a strong pressure-reducing ability at this temperature (130°C).

[0129] Example 6 showed the least blood pressure reduction effect, at only 7.83%, indicating that the chemical agent was relatively weak.

[0130] The comparison shows that different chemical agents have significantly different effects on minimum miscibility pressure. Selecting a suitable chemical agent can significantly reduce the minimum miscibility pressure, thereby improving the miscibility performance.

[0131] Table 11 Summary of interfacial tension data between crude oil and carbon dioxide in Example 2

[0132]

[0133]

[0134] The interfacial tension of Example 2 was measured using a high-temperature and high-pressure interfacial tension meter, as shown in Table 11 and... Figure 9 It can be seen that as pressure increases, the interfacial tension between the added chemical agent of Example 2 and crude oil / carbon dioxide gradually decreases. This indicates that the solubility of the added chemical agent of Example 2 and carbon dioxide in crude oil increases with increasing pressure, thereby reducing the interfacial tension.

[0135] At 20 MPa, the interfacial tension decreased to a minimum of 1.32 mN / m after adding the chemical agent from Example 2, indicating that the dissolution effect of adding the chemical agent from Example 2 combined with carbon dioxide is optimal at higher pressures. Further increasing the pressure may continue to reduce the interfacial tension until a certain limit is reached. The results of Example 2 demonstrate that in oilfield applications, adding the product system provided in this application can effectively reduce the interfacial tension of crude oil, thereby improving oil production efficiency.

[0136] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof in this application are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0137] Although this application has been disclosed above through the description of specific embodiments, it should be understood that those skilled in the art can devise various modifications, improvements, or equivalents to this application within the spirit and scope of the appended solutions. Such modifications, improvements, or equivalents should also be considered to be included within the scope of protection claimed in this application.

Claims

1. A chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding, characterized in that, The raw materials include the following percentages by mass: 0.01–2% alcohol ether solvents, 0.01–1% alcohols, 0.01–1% alkanolamines, 0.01–1% carbonyl compounds, 0.01–2% alkaline agents, and supercritical carbon dioxide content of 93–99.95%; The alcohol ether solvents include at least one of ethylene glycol isopropyl ether, butanediol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol isopropyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, and propylene glycol ethyl ether. The alcohols include at least one of ethanol, isopropanol, butanol, ethylene glycol, glycerol, hexanediol, polyether triol, and sorbitol; The alkaline agent includes one or more of propylamine, propylenediamine, methylamine, ethylamine, butylamine, and aniline; The alkanolamine includes at least one of ethanolamine, diethanolamine, triethanolamine, methylethanolamine, diisopropanolamine, aminoethanol, and N-methyldiethanolamine; The carbonyl compounds include ester compounds and / or ketone compounds; The ester compounds include at least one of ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, and ethyl 3-ethoxypropionate. The ketone compounds include at least one of acetone, butanone, methyl vinyl ketone, acetophenone, and cyclohexanone.

2. The chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding as described in claim 1, characterized in that, The ester compounds include methyl formate and / or ethyl acetate.

3. The chemical system for reducing the minimum miscibility pressure of carbon dioxide flooding as described in claim 1, characterized in that, Applications in crude oil extraction.

Images