A salt system formulation and application of a surfactant for efficient oil displacement

Abstract

The present invention relates to a salt system formula, preparation process and application of a surfactant for efficient oil recovery. It mainly solves the problem of alkali-induced corrosion failure of equipment and clogging of injection pumps in existing ternary composite flooding systems. It is characterized by the following weight percentages of the components: 0.05-0.4% fatty amine polyoxyethylene ether surfactant; 0.2-1.5% salt; 0.1-0.3% water-soluble polymer; and the balance being water. The salt system of the surfactant for efficient oil recovery prepared by the present invention can be used in oil recovery in mines. The salt system formula of the surfactant for efficient oil recovery avoids the addition of alkaline substances, has good compatibility with surfactants and polyacrylamide, a wide range of ultra-low interfacial tension and strong emulsification properties, and is a salt system with less corrosion to injection and production equipment and the formation environment.

Description

Technical field:

[0001] The present invention relates to the technical field of mine oil recovery, and in particular to a salt system formula of a surfactant for high-efficiency oil recovery and its application. Background technology:

[0002] Mineral oil recovery is generally categorized into primary, secondary, and tertiary recovery. In primary recovery, mineral oil automatically flows to the surface through the borehole after drilling begins due to the reservoir's inherent pressure. In secondary recovery, water is injected into the reservoir through injection wells to maintain or increase pressure, driving the extraction of mineral oil. As formation oil saturation decreases, the extraction of remaining oil becomes increasingly difficult, necessitating the use of chemical flooding and other methods to further enhance oil recovery, a process known as tertiary oil recovery.

[0003] Ternary composite flooding technology is a key technology that impacts oil recovery efficiency. Ternary composite flooding technology refers to the application of a ternary composite system consisting of an alkaline agent, a surfactant, and a polymer flooding agent (ASP) in tertiary oil recovery in oil fields. Existing oil displacement agent formulations are divided into strong-base ternary systems and weak-base ternary systems based on the type of alkali. Due to the strong corrosiveness of sodium hydroxide, the sodium hydroxide component in the strong-base ternary system can cause a series of problems during use, such as corrosion and scaling of injection and production equipment. Furthermore, the strong-base component, when injected into the formation, can cause a certain degree of impact and damage to the formation environment. During the continuous injection of the weak-base ternary system solution, the carbonate ions in the solution react with the calcium and magnesium ions contained in the wastewater to form hard scale. This scale can cause the injection pump to become blocked, significantly increasing the equipment failure rate and repair rate. Furthermore, some scale increases the suspended solids content, affecting the injection system and damaging the formation. Summary of the invention:

[0004] The present invention aims to overcome the problems of alkali-induced corrosion failures on equipment and injection pump blockage in existing ternary composite flooding systems, and to provide a salt system formulation for a highly efficient oil recovery surfactant. This highly efficient oil recovery surfactant salt system formulation exhibits excellent compatibility with surfactants and polyacrylamide, a wide ultra-low interfacial tension range, and strong emulsification properties. Furthermore, it exhibits minimal corrosion to injection and production equipment and low impact on the formation environment. This formulation can reduce the oil-water interfacial tension to 1.0×10 -3 mN / m order of magnitude, emulsification water separation rate (1h) ≤ 20%, and crude oil recovery rate increased by more than 35% compared with water flooding.

[0005] The present invention solves the problem through the following technical solution: the salt system formula of the surfactant for efficient oil displacement has the following weight percentages of the components: 0.05-0.4% of fatty amine polyoxyethylene ether surfactant; 0.2-1.5% of salt; 0.1-0.3% of water-soluble polymer; and the balance of water.

[0006] Preferably, the fatty amine polyoxyethylene ether surfactant is octadecylamine polyoxyethylene ether.

[0007] Preferably, the salt is an inorganic salt.

[0008] Preferably, the inorganic salt is any one of sodium chloride and potassium chloride.

[0009] Preferably, the water-soluble polymer is a water-soluble polyacrylamide with a molecular weight of 12 million to 31 million.

[0010] The present invention also provides a high-efficiency oil-displacement surfactant salt system prepared by using a high-efficiency oil-displacement surfactant salt system formula.

[0011] Another aspect of the present invention provides the use of a salt system of a surfactant for high-efficiency oil recovery in oil recovery at a mine.

[0012] Preferably, the application comprises the following steps:

[0013] Arrange development well patterns based on residual oil accumulation areas, including water injection wells and oil production wells;

[0014] Inject bulking particles into the water injection well. According to the experiment, the optimal concentration of bulking particles is 5000 mg / L.

[0015] Under the hydraulic drive of the water injection well, the salt system of the high-efficiency oil recovery surfactant can diffuse toward the residual oil accumulation area based on the vertical and / or inclined downward driving force exerted by the water on the bulk-swelling particles output by the water injection well; drive the residual oil to migrate toward the oil production well, and the residual oil is finally produced through the oil production well.

[0016] Preferably, the factors affecting the diffusion rate of the salt system on the residual oil accumulation area include at least the injection flow rate of the water injection well, wherein when the injection flow rate of the water injection well is increased, the diffusion rate of the salt system formula on the residual oil accumulation area increases, so that the salt system formula can increase the diffusion range of the residual oil accumulation area centered on the water injection well, and drive the residual oil to migrate to the oil production well.

[0017] Preferably, the distance between the injection well and the oil production well is a first distance, and the initial concentration of the salt system formula is positively correlated with the first distance, wherein when the first distance increases, the initial concentration tends to increase.

[0018] The present invention's method for applying a salt-based formulation of a high-efficiency oil-displacement surfactant to mine flooding involves adjusting the ratio of the three components within a concentration range that achieves effective oil displacement, thereby varying the concentration and viscosity of the mixture formed by the salt-based formulation. This allows the salt-based formulation to achieve optimal oil displacement results by selecting a suitable mixture for each specific mine environment.

[0019] The additional maintenance cost caused by scaling is the main problem of ternary flooding formula during use. The ternary flooding formula in the prior art contains strong base or weak base. When the ternary flooding formula is used in the formation or equipment, the sewage inside the formation contains scaling cations Ca 2+ Mg 2+ 、Ba 2+ The scaling cations first react with the OH produced by the high concentration alkali dissolved in the liquid. - Combined with, some hydroxides will also react with HCO3 in water - Converted or existing CO3 2- Combined with other minerals, these compounds form water-insoluble carbonates. These carbonates and hydroxides deposit in equipment pipelines, filters, valve components, and the wellbore, forming scale. Scaling increases the frequency of well pump inspections and the workload of cleaning the deposits.

[0020] The formula provided by the present invention does not contain strong or weak base components, and is mainly composed of surfactants and salt components. In the prior art, in order to ensure the oil displacement effect, alkaline substances need to be added to the reagents. However, in actual use, when the oil displacement agent or oil displacement formula containing weak or strong base substances acts on the formation, the alkaline substances will affect and damage the formation environment. At the same time, scaling will also form on the metal equipment, causing the injection pump to be blocked, and the equipment failure rate and repair rate will be greatly increased. Specifically, during the continuous injection process of the weak base ternary system solution, the carbonate ions in the solution and the calcium and magnesium ions contained in the sewage form hard scaling. The formula provided by the present invention can achieve ultra-low interfacial tension in crude oil and sewage environments. The formula of the present invention avoids the addition of alkaline substances to alleviate the damage to the formation or surface caused by strong alkali corrosion, which is of great significance to the protection of the geological environment.

[0021] Compared with the above background technology, the present invention has the following beneficial effects:

[0022] (1) The mixed solution prepared by the present invention can achieve ultra-low interfacial tension with crude oil. For example, when the concentration of the fatty amine polyoxyethylene ether surfactant is 0.05-0.4 wt.%, and the sodium chloride concentration is 0.4-1.4 wt.%, the interfacial tension can be reduced to 1.0×10 -2mN / m or less, the system emulsification and water separation rate (1h) ≤ 20%, which is better than the weak base ternary composite system.

[0023] (2) The present invention uses a specific fatty amine polyoxyethylene ether surfactant, an inorganic salt such as sodium chloride or potassium chloride, and polyacrylamide to form a salt system composite oil displacement system, which can effectively increase the recovery rate of crude oil to more than 35%.

[0024] (3) The salt system formula disclosed in the present invention can effectively solve the problems of strong corrosion of the strong base system of sodium hydroxide or the weak base system of sodium carbonate on the injection and production equipment, and the blockage of the injection and production machine pump, and effectively alleviate the damage of strong corrosion to the formation, which is of great significance to the protection of the geological environment. Description of the drawings:

[0025] Figure 1 It is a dynamic line graph of interfacial tension of Example 1 and Comparative Example 1 provided by the present invention;

[0026] Figure 2 is a line graph of interfacial tension stability of Example 1 and Comparative Example 1 provided by the present invention;

[0027] Figure 3 It is a broken line graph of the emulsification water separation rate of Example 1 and Comparative Example 1 provided by the present invention;

[0028] Figure 4 It is a dynamic line graph of interfacial tension of Example 2 and Comparative Example 2 provided by the present invention;

[0029] Figure 5 is a line graph of interfacial tension stability of Example 2 and Comparative Example 2 provided by the present invention;

[0030] Figure 6 It is a broken line graph of the emulsification water separation rate of Example 2 and Comparative Example 2 provided by the present invention;

[0031] Figure 7 It is a dynamic broken line graph of interfacial tension of Example 3 and Comparative Example 3 provided by the present invention;

[0032] Figure 8 is a line graph of interfacial tension stability of Example 3 and Comparative Example 3 provided by the present invention;

[0033] Figure 9 It is a broken line graph of the emulsification water separation rate of Example 3 and Comparative Example 3 provided by the present invention;

[0034] Figure 10 This is the interfacial tension activity diagram of the salt ternary system provided by the present invention;

[0035] Figure 11 This is the interfacial tension activity diagram of the weak base ternary system provided by the present invention;

[0036] Figure 12 This is a bar graph showing the adsorption resistance of the salt ternary system and the weak base ternary system provided by the present invention;

[0037] Figure 13 It is a schematic diagram of the injection process of Example 5 provided by the present invention.

[0038] In the figure: 600 - water injection well; 700 - oil production well; 800 - residual oil accumulation area. Specific implementation method:

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0040] The invention provides a salt system formula of a surfactant for efficient oil displacement, wherein the weight percentage of each component is as follows: 0.05-0.4% of fatty amine polyoxyethylene ether surfactant; 0.2-1.5% of salt; 0.1-0.3% of water-soluble polymer; and the balance is water.

[0041] The fatty amine polyoxyethylene ether surfactant is octadecylamine polyoxyethylene ether (denaturant 1815); the salt is an inorganic salt; the inorganic salt is any one of sodium chloride and potassium chloride; the water-soluble polymer is a water-soluble polyacrylamide with a molecular weight of 12 million to 31 million.

[0042] The present invention also provides a high-efficiency oil-displacement surfactant salt system prepared by using a high-efficiency oil-displacement surfactant salt system formula.

[0043] Another aspect of the present invention provides an application of a salt system of a surfactant for high-efficiency oil recovery in mine oil recovery.

[0044] The following is a detailed description with reference to the accompanying drawings and specific embodiments.

[0045] The interfacial tension test method in the following examples is carried out with reference to the SY-T6424-2000 standard. The test method is:

[0046] Use a microsyringe to draw up the low-density phase liquid and inject it into the measuring tube to form a suitable droplet. There should be no bubbles in the measuring tube. Start the interfacial tension meter and adjust the speed to 5000 rpm. Measure the droplet diameter d and length L. Measure the droplet length and diameter every 10-20 minutes. If the difference between the three consecutive measurements is less than 0.01, the droplet is considered balanced and the readings are recorded. For dynamic interfacial tension measurements, record the droplet diameter and length at different times.

[0047] Emulsification performance test method of the following embodiment:

[0048] 1. Prepare emulsion;

[0049] 2. Add the corresponding emulsifier to the prepared emulsion at a mass fraction of 0.3%, fully emulsify under high-speed stirring at 10,000 r / min, and let it stand for 6 hours;

[0050] 3. When there are dilute W / 0 emulsion layers (i.e., oil layers containing small water droplets), W / 0 emulsion layers and water layers in the system, the interface between the oil layer and the emulsion layer is often unclear, so the water separation rate is often used to characterize the stability of the emulsion. For W / 0 emulsions, especially when the oil phase is opaque, the water separation rate of the emulsion can be used to characterize the stability of the emulsion. Specifically, the water separation rate = V1 / V0, where V1 is the volume of the precipitated water layer at a certain moment, and V0 is the total volume of the water phase in the emulsion.

[0051] Generally, the water separation ratio varies from 0 to 1. When the water layer contains an emulsified oil phase, the water separation ratio may be greater than 1. After the emulsion is left to stand for a period of time, if the water separation ratio is large, the emulsion is unstable; if the water separation ratio is small, the emulsion is stable.

[0052] Example 1

[0053] Take 0.025g of a specific fatty amine polyoxyethylene ether surfactant octadecylamine polyoxyethylene ether (effective matter content 40%), 0.12g of sodium chloride, 6g of a water-soluble polymer polyacrylamide with a molecular weight of 19 million (the sewage preparation concentration is 5000ppm), and 13.855g of wellhead sewage to prepare a salt ternary system formula.

[0054] Comparative Example 1

[0055] A weak base ternary system formula was prepared by taking 0.025 g of a specific petroleum sulfonate surfactant (effective content 40%), 0.12 g of sodium carbonate, 6 g of a water-soluble polymer polyacrylamide with a molecular weight of 19 million (the sewage preparation concentration is 5000 ppm), and 13.855 g of wellhead sewage.

[0056] Test Example 1

[0057] The interfacial tension test was carried out on the samples of Example 1 and Comparative Example 1. The results are as follows: Figure 1 The interfacial tensions of the salt ternary system and the weak base ternary system provided in this embodiment are the same at different time points.

[0058] The interfacial tension stability test was carried out on the samples of Example 1 and Comparative Example 1. The results are as follows: Figure 2 The interfacial tension stability of the salt ternary system and the weak base ternary system provided in this embodiment is basically the same after being placed for different days.

[0059] The emulsification performance of the two samples of Example 1 and Comparative Example 1 was tested, and the results were as follows: Figure 3As shown. Emulsion is a dispersed system obtained by mixing two immiscible pure liquids. Due to the large interfacial area between the two phases, the system is very unstable and will quickly separate. Since the emulsion is a multiphase system that depends on the existence of interfacial tension, the emulsification properties of the solution can be used to determine the separation ability between the solutions. In the mineral oil production process, the oil displacement agent needs to increase its solubility in mineral oil. The salt ternary system provided in this embodiment has a more superior emulsification and water separation rate than the weak base ternary system.

[0060] Example 2

[0061] Take 0.05g of a specific fatty amine polyoxyethylene ether surfactant octadecylamine polyoxyethylene ether (effective matter content 40%), 0.2g of sodium chloride, 8g of a water-soluble polymer polyacrylamide with a molecular weight of 19 million (the sewage preparation concentration is 4000ppm), and 11.75g ​​of wellhead sewage to prepare a salt ternary system formula.

[0062] Comparative Example 2

[0063] A weak base ternary system formula was prepared by taking 0.05 g of a specific petroleum sulfonate surfactant (effective content 40%), 0.2 g of sodium carbonate, 8 g of a water-soluble polymer polyacrylamide with a molecular weight of 19 million (the sewage preparation concentration is 4000 ppm), and 11.75 g of wellhead sewage.

[0064] Test Example 2

[0065] The interfacial tension test was carried out on the samples of Example 2 and Comparative Example 2. The results are as follows: Figure 4 As shown in the figure, interfacial tension varies with the different contacting substances, and its magnitude varies with the force applied to the molecules in the interfacial layer. The greater the difference, the greater the interfacial tension. Figure 4 The results shown show that the interfacial tensions of the salt ternary system and the weak base ternary system provided in this example are the same at different time points.

[0066] The interfacial tension stability test was carried out on the samples of Example 2 and Comparative Example 2. The results are as follows: Figure 5 The interfacial tension stability of the salt ternary system and the weak base ternary system provided in this embodiment is basically the same after being placed for different days.

[0067] The emulsification performance of the two samples of Example 2 and Comparative Example 2 was tested, and the results were as follows: Figure 6 shown. Figure 6 The results shown indicate that the salt ternary system provided in this embodiment has a superior emulsification and water separation rate compared to the weak base ternary system.

[0068] Example 3

[0069] Take 0.15g of a specific fatty amine polyoxyethylene ether surfactant octadecylamine polyoxyethylene ether (effective matter content 40%), 0.24g of sodium chloride, 8g of a water-soluble polymer polyacrylamide with a molecular weight of 19 million (the sewage preparation concentration is 4000ppm), and 11.61g of wellhead sewage to prepare a salt system formula.

[0070] Comparative Example 3

[0071] A weak base ternary system formula was prepared by taking 0.15 g of a specific petroleum sulfonate surfactant (effective content 40%), 0.24 g of sodium carbonate, 8 g of a water-soluble polymer polyacrylamide with a molecular weight of 19 million (the sewage preparation concentration is 4000 ppm), and 11.61 g of wellhead sewage.

[0072] Test Example 3

[0073] The interfacial tension test was carried out on the samples of Example 3 and Comparative Example 3. The results are as follows: Figure 7 The interfacial tensions of the salt ternary system and the weak base ternary system provided in this embodiment are the same at different time points.

[0074] The interfacial tension stability test was carried out on the samples of Example 3 and Comparative Example 3. The results are as follows: Figure 8 The interfacial tension stability of the salt ternary system and the weak base ternary system provided in this embodiment is basically the same after being placed for different days.

[0075] The emulsification performance of the two samples of Example 3 and Comparative Example 3 was tested, and the results were as follows: Figure 9 The salt ternary system provided in this embodiment has a superior emulsification and water separation rate compared to the weak base ternary system.

[0076] Test Example 4

[0077] Bailey core simulation experiments were conducted on Examples 1-3 and Comparative Examples 1-3 to evaluate the oil recovery effectiveness of the salt ternary system. The Bailey core simulation data are shown in Table 1. Table 1 shows that, under the same viscosity conditions, the total recovery factor of the salt ternary system of Examples 1-3 is over 15% higher than that of the weak base ternary system of Comparative Examples 1-3. The salt ternary system provided by the present invention exhibits superior oil recovery effectiveness.

[0078] Table 1 Berea core physical model experiment

[0079]

[0080] Test Example 5

[0081] The interfacial tension activity diagrams of Examples 1-3 are shown in Figure 10 , the interfacial tension activity diagram of comparative examples 1-3 is as follows Figure 11The interfacial tension activity of the salt ternary system provided by the present invention within a salt concentration range of 0.2-1.4% and a surfactant concentration range of 0.05-0.4% is comparable to that of the weak base ternary system within a base concentration range of 0.2-1.4% and a surfactant concentration range of 0.05-0.4%. The oil-water separation performance of the salt ternary system provided by the present invention is comparable to that of the base ternary system. The oil displacement performance of the salt ternary system is comparable to that of the base ternary system.

[0082] Test Example 6

[0083] Figure 12 This is a graph showing the adsorption resistance of the salt ternary system of Example 3 and the weak base ternary system of Comparative Example 3. Under the same conditions, the interfacial tension of the salt ternary system remains ultra-low after the third oil sand adsorption, one more than the base ternary system, demonstrating that the salt ternary system of the present invention has stronger adsorption resistance than the base ternary system.

[0084] Preparation Example 1

[0085] During tertiary oil recovery (TER) processes, oil-displacing agents reduce interfacial tension at the oil-water and water-rock interfaces, facilitating the flow of crude oil and the spreading of water. Oil-displacing agents also exhibit an emulsification mechanism, dispersing and stripping crude oil adhered to rock surfaces during oil-water two-phase flow, forming an oil-in-water emulsion. This improves the mobility ratio of the oil-water phase and increases crude oil recovery. The oil-displacing agent provided by the present invention exhibits strong oil-washing capacity, excellent stability, good compatibility with formation water, and resistance to aging.

[0086] Underground oil reservoirs in the later stages of exploitation are often distributed in various underground fractures. Such reservoirs cannot be accessed through simple extraction, thus the emergence of water flooding and oil flooding methods. In the prior art, oil-displacing agents are injected into the formation's fracturing to access the reservoir. During the injection process, resisting underground pressure becomes a significant factor affecting the injection of the oil-displacing agent and the access to the reservoir. The present invention provides a method for applying a salt system formulation of a high-efficiency oil-displacing surfactant based on a multi-component hybrid power to generate the pressure required for injection into the well or during fracturing.

[0087] A method for preparing a salt system formulation of a surfactant for high-efficiency oil displacement comprises the following steps:

[0088] Weighing the water-soluble polymer, adding it to water, and stirring at room temperature to dissolve the water-soluble polymer to obtain a water-soluble polymer solution;

[0089] Weighing the salt component and adding it to water to obtain a salt component solution;

[0090] Weigh the fatty amine polyoxyethylene ether surfactant and add it to water to obtain a surfactant solution;

[0091] The salt system formulation comprises a specific ratio of 0.05-0.4% by weight of a fatty amine polyoxyethylene ether surfactant, 0.2-1.5% by weight of a salt component, 0.1-0.3% by weight of a water-soluble polymer, and the balance of water. The salt component solution and the surfactant solution are added to the water-soluble polymer solution and stirred at room temperature to uniformly mix the components. This mixture does not contain strong or weak bases, so the application device is not affected by scaling during mixing, which could hinder the oil displacement process.

[0092] Application Example 1

[0093] When injecting an oil-displacing agent into a mine to increase crude oil extraction efficiency, the oil-displacing agent can migrate in the residual oil accumulation area 800 based on water flow. By diffusing the oil-displacing agent in the residual oil accumulation area 800, the flow ratio between the water phase and the oil phase is improved, and the flow resistance of the displacement phase is increased. The underground environment is usually a heterogeneous stratum, forming a preferential flow path in the low-oil area. In addition, due to the density difference between the injected solution and the groundwater, the oil-displacing agent may float or sink during migration in the aquifer. This density effect causes the oil-displacing agent migration process to form a bypass phenomenon. The oil-displacing agent circulating from the water injection well 600 first migrates horizontally and then vertically. The concentration of the oil-displacing agent remains unchanged or decreases, resulting in the oil-displacing agent reaching the residual oil accumulation area 800 also flowing out with the water. The oil-displacing agent migrates obliquely downward, and the vertical migration effect is poor. On the basis of the oil-displacing agent being gradually diluted as it circulates, the cumulative effect of concentration cannot be achieved. Expansive particles are commonly used in existing technologies to block water flow and address bypass issues. However, without external forces (e.g., ultrasound or stirring), the particles are inefficiently integrated with heavy oil. This results in effective contact between the particles and the oil, forming a catalytic interface that only acts as a water blocker, failing to emulsify the oil. Therefore, they must be used in conjunction with a high-efficiency oil displacement agent. However, these particles are sensitive to alkali and fail to swell in the presence of alkali, making them difficult to use with alkali-based ternary composite flooding. The alkali-free salt system of the present invention, however, has minimal impact on the particles, allowing their combined use to achieve both plugging and oil displacement.

[0094] The present invention provides a method for applying a salt system of a surfactant for efficient oil displacement, comprising the following steps:

[0095] A development well pattern is arranged according to the residual oil accumulation area 800, and the well pattern includes a water injection well 600 and an oil production well 700; the bulk-swelling particles are injected into the water injection well 600; under the hydraulic drive of the water injection well 600, the salt system formula of the high-efficiency oil displacement surfactant can diffuse toward the residual oil accumulation area 800 based on the vertical and / or oblique downward driving force exerted by the water mixed with the bulk-swelling particles output from the water injection well 600, driving the residual oil to migrate toward the oil production well 700, and finally produced through the oil production well 700, as shown in FIG. Figure 13 shown.

[0096] Driven by the water injection well 600, the hydraulic stimulation of the water injection well 600 increases the vertical force component, allowing the oil-displacing agent to effectively penetrate the residual oil accumulation area 800. As the water injection well 600 continues to operate, the salt system formula of the high-efficiency oil-displacing surfactant in the residual oil accumulation area 800 can be maintained at a high concentration, allowing the residual crude oil to be effectively acted upon by the oil-displacing agent.

[0097] The bulk-swelling particle concentration was optimized using concentrations ranging from 2000 to 8000 mg / L. The experimental results for this optimization are shown in Table 2. Table 2 shows that the bulk-swelling particle blocking efficiency for the bottom dominant channel increases with increasing concentration. When the particle concentration reaches 5000 mg / L or higher, the blocking efficiency exceeds 90%, effectively preventing bypass flow. Therefore, the bulk-swelling particle concentration is preferably 5000 mg / L.

[0098] Table 2 Experimental optimization of bulking particle concentration

[0099]

[0100]

[0101] The bulk-swelling particles are solid substances with a density greater than that of the water phase. Based on the power of the water injection well 600, they undergo solid-liquid and gravity separation with the oil-displacing agent, and can preferentially diffuse downward to block the dominant seepage channels with low oil saturation at the bottom of the oil layer. The high-efficiency oil-displacing salt system formula is advanced at the top of the oil layer, achieving the optimal effect on the crude oil in the residual oil accumulation area 800.

[0102] The manufacturer of the bulk-expanding particles used in the application example is Daqing Xinwantong Technology Development Co., Ltd.

[0103] According to a preferred embodiment, the factors affecting the diffusion rate of the salt system formula of the present invention on the residual oil accumulation area 800 include at least the injection flow rate of the water injection well 600, wherein when the injection flow rate of the water injection well 600 is increased, the diffusion rate of the salt system formula on the residual oil accumulation area 800 increases, so that the salt system formula can increase the diffusion range of the residual oil accumulation area 800 centered on the water injection well 600. During oil production, the water injection well 600 acts as a device that can promote the filling and flow of injected water in the underground uneven layer to increase the pressure of the injected water on the underground layer. The greater the injection flow rate of the water injection well 600, the greater the vertical force it exerts on the downwardly diffusing bulk particles and oil displacement agent, and therefore the larger the radius of the downward diffusion of the bulk particles affected by it. Compared with the defect of the prior art in which the migration of the oil-displacing agent is uncontrollable after it is injected into the ground, the present invention changes the diffusion radius of the oil-displacing agent by changing the injection flow rate of the water injection well 600, so that the range of the oil-displacing agent affecting the crude oil accumulation area is preliminarily controllable, and therefore the diffusion radius of the oil-displacing agent can be adjusted in a targeted manner according to the size of the crude oil accumulation area.

[0104] Based on the first distance between injection well 600 and production well 700, the initial concentration of the salt system formulation is positively correlated with the first distance, wherein the initial concentration tends to increase as the first distance increases. When the first distance is less than 100 m, the low-concentration oil-displacing agent formulation of Example 1 should be selected for multiple short-segment injections. When the first distance is between 101 m and 124 m, the medium-concentration oil-displacing agent formulation of Example 2 can be selected for a single long-segment injection. When the first distance is greater than 124 m, the high-concentration oil-displacing agent formulation of Example 3 can be selected for a single long-segment injection. This approach improves crude oil extraction efficiency in residual oil accumulation area 800, and the amount of oil-displacing agent used is more reasonable. Preferably, high-concentration oil-displacing agent Example 3 can be injected into areas with low-concentration crude oil or crude oil accumulations containing large amounts of asphalt and other colloids. Under the hydraulic stimulation of injection well 600, the high-concentration oil-displacing agent receives vertical and / or oblique downward forces and effectively migrates toward the crude oil accumulation area below.

[0105] It should be noted that the above-mentioned specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the present invention specification and its drawings are illustrative and do not constitute a limitation of the claims. The scope of protection of the present invention is defined by the claims and their equivalents. The present invention specification contains multiple inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally", all of which indicate that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to file a divisional application based on each inventive concept. Throughout the text, the features guided by "preferably" are only an optional method and should not be understood as having to be set, so the applicant reserves the right to abandon or delete the relevant preferred features at any time.

Claims

1. A salt system formula of a surfactant for efficient oil displacement, characterized in that The weight percentage of each component is as follows: fatty amine polyoxyethylene ether surfactant is 0.05-0.4%; salt is 0.2-1.5%; water-soluble polymer is 0.1-0.3%; the balance is water; The fatty amine polyoxyethylene ether surfactant is octadecylamine polyoxyethylene ether; The salt is an inorganic salt; The water-soluble polymer is a water-soluble polyacrylamide with a molecular weight of 12 million to 31 million.

2. The salt system formulation of the high-efficiency oil displacement surfactant according to claim 1, characterized in that : The inorganic salt is any one of sodium chloride and potassium chloride.

3. A salt system of a high-efficiency surfactant for oil displacement prepared according to the salt system formula of a high-efficiency surfactant for oil displacement according to any one of claims 1 to 2.

4. Use of the salt system of the surfactant for high-efficiency oil recovery as claimed in claim 3 in oil recovery in a mine.

5. The use according to claim 4, characterized in that The following steps are involved: Arranging a development well pattern according to the residual oil accumulation area (800), wherein the well pattern includes water injection wells (600) and oil production wells (700); Injecting bulking particles into the water injection well (600), the bulking particle concentration being preferably 5000 mg / L according to experiments; Under the hydraulic driving action of the water injection well (600), the salt system of the high-efficiency oil displacement surfactant can diffuse toward the residual oil accumulation area (800) based on the vertical and / or oblique downward driving force exerted on it by the water of the volume-swelling particles output from the water injection well (600); The residual oil is driven to migrate toward the oil production well (700), and the residual oil is finally produced through the oil production well (700).

6. The application method according to claim 5, characterized in that: The factors affecting the diffusion rate of the salt system on the residual oil accumulation area (800) include at least the injection flow rate of the water injection well (600), wherein when the injection flow rate of the water injection well (600) is increased, the diffusion rate of the salt system formula on the residual oil accumulation area (800) increases, so that the salt system formula can increase the diffusion range of the residual oil accumulation area (800) centered on the water injection well (600), driving the residual oil to migrate to the oil production well (700).

7. The application method according to claim 5, characterized in that: The distance between the injection well (600) and the oil production well (700) is a first distance, and the initial concentration of the salt system formula is positively correlated with the first distance, wherein when the first distance increases, the initial concentration tends to increase.

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