Carbon dioxide and surfactant mixing apparatus and displacement simulation method

Abstract

The application provides a carbon dioxide and surfactant mixing device and a displacement simulation method. The carbon dioxide and surfactant mixing device comprises a proportioning tank, a plurality of injectors arranged in a primary space, at least one of the injectors being used for injecting carbon dioxide, and at least another one of the injectors being used for injecting surfactant; a polymerizer arranged in the primary space and located below the injectors, wherein the carbon dioxide and the surfactant injected by the injectors are preliminarily mixed into gas-liquid mixed bubbles above the polymerizer, the gas-liquid mixed bubbles are polymerized in the polymerizer, and then flow into a secondary space; a cutting device arranged in the secondary space, wherein the cutting device is used for cutting the gas-liquid mixed bubbles flowing from the polymerizer into fine micro-nano bubbles; and a fusion device arranged in a tertiary space, wherein the fusion device is used for fully mixing the carbon dioxide and the surfactant. The application solves the problem that carbon dioxide and surfactant molecules are difficult to be uniformly mixed in the prior art physical simulation experiment device.

Description

Technical Field

[0001] This invention relates to the field of oilfield development equipment technology, and more specifically, to a carbon dioxide and surfactant mixing device and a displacement simulation method. Background Technology

[0002] With the rise of industry, carbon emissions are gradually increasing, causing a great impact on the environment. The research, promotion and application of CCUS technology (Carbon Capture, Utilization and Storage) can make an important contribution to reducing carbon emissions.

[0003] Studies have found that mixing carbon dioxide with surfactants significantly improves reservoir recovery efficiency. Research indicates that while many gases can enhance crude oil displacement efficiency, only CO2 can reduce residual oil saturation to near zero. Laboratory research on CO2 displacement for enhanced oil recovery began in the 1950s, with field trials starting in the 1960s. In the 1970s, with the laying of CO2 pipelines, the scale of research expanded. In recent years, research on CO2 flooding in my country has increased significantly, and field applications have been implemented in some oilfields. However, CO2 flooding suffers from low displacement efficiency because the gas viscosity is much lower than that of crude oil, leading to severe gravitational differentiation between the two gases, resulting in gas bypassing and fingering. As early as 1955, some researchers recognized that injecting surfactants to form foam within the reservoir during gas flooding could reduce gas mobility. Field practice has proven that foam is very effective in reducing CO2 mobility, generally reducing CO2 mobility by more than 50%, and improving the flow of displacing fluid in heterogeneous oil reservoirs. It controls gas fingering, delays the breakthrough time of CO2 gas, and combines the advantages of both CO2 flooding and foam flooding—high displacement efficiency and good mobility control capability.

[0004] Currently, physical simulation experimental devices for carbon dioxide and surfactants are still very imperfect. Generally, a co-current pump is used to directly inject CO2 gas and surfactant solution at a certain flow rate after compression (An apparatus and method for determining the surfactant concentration distribution of CO2 emulsion during seepage, CN 104792938B; A method for improving carbon dioxide enhanced oil recovery using surfactants, CN 105257264 A). However, the molecular structure and properties of surfactants determine that they form micelles in water, which are tiny particles formed by the aggregation of surfactant molecules. These micelles can move and diffuse freely in water, but they cannot effectively form micelles in carbon dioxide. Therefore, surfactant molecules tend to aggregate on the surface of the liquid or gather in certain areas, resulting in uneven mixing. Therefore, current technical methods cannot effectively solve the problem of uneven mixing (Luo, 2018, Effects of the non-ionic surfactant (CiPOj) on the interfacial tension behavior between CO2 and crudeoil, Energy & Fuel). In addition, the difference in compatibility between carbon dioxide and surfactants may also lead to uneven mixing (Kuang Nianjie, 2020, Research status of surfactants in reducing the minimum miscibility pressure of CO2 drive, Petrochemical Application).

[0005] Carbon dioxide is a nonpolar gas, while surfactant molecules are polar. Therefore, when they are mixed, the interaction between carbon dioxide and surfactant molecules is relatively weak, making it difficult to form a homogeneous mixture. Conventional experimental methods typically involve directly injecting carbon dioxide into a model at a specific ratio to allow mixing within the model. However, due to the differences in properties between carbon dioxide and the fluid, it is difficult to achieve a uniform distribution of tiny gas-liquid bubbles within the surfactant.

[0006] In other words, existing physical simulation experimental devices suffer from the problem of difficulty in uniformly mixing carbon dioxide and surfactant molecules. Summary of the Invention

[0007] The main objective of this invention is to provide a carbon dioxide and surfactant mixing device and a displacement simulation method to solve the problem that carbon dioxide and surfactant molecules are difficult to mix uniformly in existing physical simulation experimental devices.

[0008] To achieve the above objectives, according to one aspect of the present invention, a carbon dioxide and surfactant mixing apparatus is provided, comprising: a mixing chamber having a primary space, a secondary space, and a tertiary space sequentially connected along the direction of gravity; a plurality of injectors disposed in the primary space, at least one injector for injecting carbon dioxide, and at least another injector for injecting surfactant; a polymerizer disposed in the primary space and located below the injectors, wherein the carbon dioxide and surfactant ejected by the injectors initially mix above the polymerizer to form gas-liquid mixed bubbles, which then polymerize within the polymerizer and flow into the secondary space; a cutting device disposed in the secondary space for cutting the gas-liquid mixed bubbles flowing into the polymerizer into fine micro-nano bubbles; and a fusion device disposed in the tertiary space for fully mixing the carbon dioxide and surfactant.

[0009] Furthermore, the injector is a grid-shaped injector so that the injected surfactant is in the form of small bubbles.

[0010] Furthermore, the polymerizer has a conical polymerization surface, with the smaller diameter end of the conical polymerization surface closer to the secondary space than the larger diameter end of the conical polymerization surface, and the conical polymerization surface has multiple first outlets.

[0011] Furthermore, the carbon dioxide and surfactant mixing device also includes a converging plate located below the cutting device. The converging plate has multiple second outlets, through which micro- and nano-bubbles in the secondary space flow into the tertiary space. The first outlet and the second outlet are circumferentially offset.

[0012] Furthermore, the converging plate is conical, and its cross-sectional area gradually decreases towards the tertiary space.

[0013] Furthermore, the cutting device includes: a driving device; and a cutting impeller, wherein the driving device is driven to the cutting impeller to drive the cutting impeller to rotate, and the cutting impeller is used to cut the gas-liquid mixed bubble into fine micro-nano bubbles.

[0014] Furthermore, the fusion device includes multiple rotating blade devices, which are arranged at intervals from top to bottom in a three-level space, and each rotating blade device rotates at a different speed.

[0015] Furthermore, among the multiple rotating blade devices, the rotating blade device closest to the secondary space has the highest rotational speed.

[0016] Furthermore, the rotational speed of the multiple rotating blade devices decreases progressively from top to bottom.

[0017] Furthermore, the fusion device also includes a multi-stage variable speed planetary drive motor, and multiple rotating blade devices are connected to the multi-stage variable speed planetary drive motor.

[0018] Furthermore, the mixing chamber has a conical structure, and the cross-sectional area of ​​the mixing chamber gradually decreases from the first-level space to the third-level space.

[0019] According to another aspect of the present invention, a displacement simulation method is provided, which employs the aforementioned carbon dioxide and surfactant mixing device. The displacement simulation method includes: step S10: preparing a simulated oil of a preset viscosity according to reservoir conditions; step S20: preparing a physical model based on reservoir parameters and testing the basic parameters of the physical model; step S30: preparing carbon dioxide and surfactant, as well as two injection pumps, and connecting the injection pumps to the injectors of the carbon dioxide and surfactant mixing device; step S40: calculating the preset injection rate of carbon dioxide and the preset injection rate of surfactant according to the ratio and the required environmental conditions; step S50: mixing carbon dioxide and surfactant according to the ratio... The carbon dioxide and surfactant are injected into the mixing device at the preset injection rate to form a compound agent; Step S60: After extracting and drying the natural rock core, the natural rock core is arranged and fully saturated with formation water, and the saturation amount is recorded; Step S70: The water in the natural rock core is displaced by the prepared saturated oil sample to establish the oil-water distribution of the physical model and calculate the bound water saturation; Step S80: The mixed compound agent is injected into the physical model through the delivery pipeline to conduct reservoir displacement experiments and the displacement data is recorded; Step S90: After each set of experiments, the natural rock core is cleaned and dried, the ratio of carbon dioxide to surfactant is changed, and the above steps S40 to S90 are repeated until all ratio experiments are completed.

[0020] Furthermore, during the process of injecting the mixed compound agent into the physical model through the delivery pipeline to conduct reservoir displacement experiments and record displacement data, the displacement time, pump reading, injection pressure, injection speed, annular pressure and back pressure are recorded, and the produced gas-oil ratio and the amount of separated oil, gas and water are monitored.

[0021] Furthermore, during the cleaning of the natural rock cores after each set of experiments, the natural rock cores were first cleaned with petroleum ether and anhydrous alcohol, and then blew with nitrogen gas.

[0022] Furthermore, the oil-water distribution in the physical model simulates the original oil-water distribution of the formation.

[0023] According to the technical solution of this invention, the carbon dioxide and surfactant mixing device includes a mixing tank, multiple injectors, a polymerizer, a cutting device, and a fusion device. The mixing tank has a primary space, a secondary space, and a tertiary space connected sequentially along the direction of gravity. Multiple injectors are arranged in the primary space, with at least one injector for injecting carbon dioxide and at least another injector for injecting surfactant. The polymerizer is arranged in the primary space and is located below the injectors. The carbon dioxide and surfactant ejected by the injectors initially mix above the polymerizer to form gas-liquid mixed bubbles, which then polymerize in the polymerizer and flow into the secondary space. The cutting device is arranged in the secondary space and is used to cut the gas-liquid mixed bubbles flowing into the polymerizer into fine micro-nano bubbles. The fusion device is arranged in the tertiary space and is used to fully mix the carbon dioxide and surfactant.

[0024] The mixing chamber provides a mixing space for carbon dioxide and surfactants, ensuring their uniform mixing. Multiple injectors within the primary space separately inject carbon dioxide and surfactants, with the surfactants emitted as small bubbles, increasing the contact area between the surfactant and carbon dioxide. A polymerizer positioned below the injectors allows for rapid contact and polymerization of the injected carbon dioxide and surfactant. Once the gas-liquid mixture formed by carbon dioxide and surfactants reaches a certain volume, it flows into the secondary space. A cutting device in the secondary space breaks the gas-liquid mixture into tiny micro- and nano-bubbles, effectively increasing the gas-liquid contact area and thus ensuring more thorough mixing of carbon dioxide and surfactants. After being broken down into micro- and nano-bubbles, the gas-liquid mixture enters the tertiary space, where a fusion device mixes the micro- and nano-bubbles to ensure uniform mixing of carbon dioxide and surfactants. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 A schematic diagram of a carbon dioxide and surfactant mixing device according to an optional embodiment of the present invention is shown;

[0027] Figure 2 It shows Figure 1 A view of the aggregator from one angle;

[0028] Figure 3 It shows Figure 1 A view of the central converging plate from one angle;

[0029] Figure 4This diagram illustrates the fluid distribution within a three-level space according to an alternative embodiment of the present invention.

[0030] Figure 5 A schematic diagram of the structure of a multi-stage variable speed planetary drive motor in an optional embodiment of the present invention is shown;

[0031] Figure 6 A schematic diagram of the rotating blade device in an optional embodiment of the present invention is shown;

[0032] Figure 7 A schematic diagram of the structure of the shaft retainer in an optional embodiment of the present invention is shown;

[0033] Figure 8 The oil displacement efficiency of different mixing ratio experimental groups in this invention is shown.

[0034] The above figures include the following reference numerals:

[0035] 10. Proportioning box; 11. Primary space; 12. Secondary space; 13. Tertiary space; 20. Ejector; 30. Aggregator; 31. Conical aggregation surface; 311. Small diameter end; 312. Large diameter end; 313. First outlet; 40. Cutting device; 41. Cutting impeller; 50. Fusion device; 51. Rotating blade device; 52. Multi-stage variable speed planetary drive motor; 60. Converging plate; 61. Second outlet. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0038] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0039] The main objective of this invention is to provide a carbon dioxide and surfactant mixing device and a displacement simulation method to solve the problem that carbon dioxide and surfactant molecules are difficult to mix uniformly in existing physical simulation experimental devices.

[0040] like Figures 1 to 8As shown, the carbon dioxide and surfactant mixing device includes a mixing tank 10, multiple injectors 20, a polymerizer 30, a cutting device 40, and a fusion device 50. The mixing tank 10 has a primary space 11, a secondary space 12, and a tertiary space 13 connected sequentially along the direction of gravity. The multiple injectors 20 are arranged in the primary space 11, with at least one injector 20 used to inject carbon dioxide and at least another injector 20 used to inject surfactant. The polymerizer 30 is arranged in the primary space 11 and is located below the injectors 20. The carbon dioxide and surfactant ejected by the injectors 20 are initially mixed above the polymerizer 30 to form gas-liquid mixed bubbles, which then polymerize in the polymerizer 30 and flow into the secondary space 12. The cutting device 40 is arranged in the secondary space 12 and is used to cut the gas-liquid mixed bubbles flowing into the polymerizer 30 into fine micro-nano bubbles. The fusion device 50 is arranged in the tertiary space 13 and is used to fully mix the carbon dioxide and surfactant.

[0041] The mixing chamber 10 provides a mixing space for carbon dioxide and surfactants to ensure uniform mixing. Multiple injectors 20 are installed in the primary space 11, each injecting carbon dioxide and surfactant into the space. The surfactants ejected by the injectors 20 are small bubbles, increasing the contact area between the surfactant and carbon dioxide. A polymerizer 30 is installed below the injectors 20 to facilitate rapid contact and polymerization of the injected carbon dioxide and surfactant. Once the gas-liquid mixture formed by carbon dioxide and surfactant has polymerized to a certain quantity, it flows into the secondary space 12. A cutting device 40 in the secondary space 12 cuts the gas-liquid mixture into tiny micro- and nano-bubbles, effectively increasing the gas-liquid contact area and thus ensuring more thorough mixing of carbon dioxide and surfactant. After being cut into micro- and nano-bubbles, the gas-liquid mixture enters the tertiary space 13, where a fusion device 50 mixes the micro- and nano-bubbles to ensure uniform mixing of carbon dioxide and surfactant.

[0042] Specifically, the injector 20 is a grid-shaped injector, which causes the injected surfactant to be in the form of small bubbles. By using a grid-shaped injector to make the injected surfactant into small bubbles, there is a larger contact area when the surfactant and carbon dioxide first come into contact, which is conducive to the thorough mixing of carbon dioxide and surfactant and effectively improves the mixing efficiency of carbon dioxide and surfactant.

[0043] exist Figure 1In the specific embodiment shown, the polymerizer 30 has a conical polymerization surface 31. The smaller diameter end 311 of the conical polymerization surface 31 is closer to the secondary space 12 than the larger diameter end 312 of the conical polymerization surface 31. The conical polymerization surface 31 has multiple first outlets 313. Providing the conical polymerization surface 31 on the polymerizer 30 is beneficial for the rapid polymerization of gas-liquid mixed bubbles and for the rapid flow of gas-liquid mixed bubbles into the secondary space.

[0044] The first outlet 313 is located near the edge of the conical polymerization surface 31 relative to the center of the conical polymerization surface 31, or in other words, the first outlet 313 is located at the upper part of the conical polymerization surface 31, so that the gas-liquid mixed bubbles gather to a certain amount and then flow into the secondary space 12 through the first outlet 313.

[0045] Optionally, the small-diameter end 311 of the conical polymerization surface 31 is a solid structure so that the fluid flows downward through the first outlet 313.

[0046] like Figures 1 to 3 As shown, the carbon dioxide and surfactant mixing device also includes a converging plate 60, located below the cutting device 40. The converging plate 60 has multiple second outlets 61. Micro- and nano-bubbles in the secondary space 12 flow into the tertiary space 13 through the second outlets 61. The first outlet 313 and the second outlet 61 are circumferentially offset. The converging plate 60 is used to converge the micro- and nano-bubbles formed after being cut by the cutting device 40, so that the micro- and nano-bubbles can quickly converge into the tertiary space 13 for mixing. The circumferential offset between the first outlet 313 and the second outlet 61 means that the projection of the first outlet 313 onto the converging plate 60 is offset from the second outlet 61, so as to prevent the gas-liquid mixed bubbles that flow into the secondary space 12 through the first outlet 313 from directly flowing into the tertiary space 13 through the second outlet 61, effectively increasing the mixing effect of carbon dioxide and surfactant.

[0047] like Figure 1 As shown, the converging plate 60 is conical, and its cross-sectional area gradually decreases towards the tertiary space 13. Setting the converging plate 60 in a conical shape facilitates the rapid convergence of micro- and nano-bubbles on the converging plate 60 and their flow into the tertiary space 13.

[0048] exist Figure 3 In the specific embodiment shown, the second outlet 61 is close to the edge of the converging plate 60 relative to the center of the converging plate 60, or in other words, the second outlet 61 is located on the upper part of the converging plate 60 so that the micro-nano bubbles flow into the tertiary space 13 after they have gathered to a certain amount.

[0049] Optionally, the conical apex of the converging plate 60 is a solid structure, so that the fluid flows into the tertiary space 13 through the second outlet 61.

[0050] like Figure 1As shown, the cutting device 40 includes a driving device and a cutting impeller 41. The driving device is connected to the cutting impeller 41 to drive it to rotate at high speed. The cutting impeller 41 is used to cut the gas-liquid mixed bubbles into tiny micro- and nano-bubbles. The driving device drives the cutting impeller 41 to rotate, and the high-speed rotating cutting impeller 41 breaks the gas-liquid mixed bubbles into tens of nanometers to several micrometers, ultimately forming micro- and nano-scale micro- and nano-bubbles. The more micro- and nano-bubbles there are, the larger the surface area they have compared to large bubbles, effectively increasing the contact area between carbon dioxide and surfactants and improving the uniformity of the mixing of carbon dioxide and surfactants. Through cooperation with the converging plate 60, the micro- and nano-bubbles are gathered to a certain amount and then flow into the tertiary space 13.

[0051] like Figure 1 As shown, the fusion device 50 includes multiple rotating blade devices 51, which are arranged at intervals from top to bottom within the three-level space 13. Each rotating blade device 51 rotates at a different speed. The different speeds of the multiple rotating blade devices 51 allow for more thorough fusion of carbon dioxide and the surface fusion agent.

[0052] Specifically, among the multiple rotating blade devices 51, the rotating blade device 51 closest to the secondary space 12 has the highest rotational speed. This arrangement ensures that the uppermost rotating blade device 51 rotates the fastest, catching the mixed fluid flowing out of the secondary space 12 and causing the mixed fluid to move rapidly downwards. This causes the surfactant and carbon dioxide to form a transverse and longitudinal flow circulation in the tertiary space, that is, the surfactant and carbon dioxide flow in a spiral shape in the tertiary space.

[0053] Specifically, the rotational speed of the multiple rotating blade devices 51 decreases progressively from top to bottom. The lower rotating blade device 51 rotates relatively slowly, which helps to overcome the effects of gravitational separation and achieve thorough mixing of carbon dioxide and surfactant.

[0054] like Figure 5 As shown, the fusion device 50 also includes a multi-stage variable speed planetary drive motor 52, and multiple rotating blade devices 51 are connected to the multi-stage variable speed planetary drive motor. By setting the multi-stage variable speed planetary drive motor, the multiple rotating blade devices 51 rotate together, but the rotational speed of the multiple rotating blade devices 51 decreases step by step.

[0055] Of course, the fusion device 50 may include multiple motors, and the multiple motors are connected one-to-one with multiple rotating blade devices 51. During operation, different motors are set to different speeds.

[0056] like Figure 1As shown, the mixing tank 10 has a conical structure, and its cross-sectional area gradually decreases from the primary space 11 to the tertiary space 13. By setting the mixing tank 10 to a conical structure, it is beneficial for the mixed fluid to quickly converge and flow downwards, and for carbon dioxide and surfactant to mix thoroughly.

[0057] The working principle of the carbon dioxide and surfactant mixing device in this application is to use a grid-shaped injector to disperse the surfactant into very small bubbles. In the primary space 11, carbon dioxide and surfactant come into contact and mix, accelerating the mixing speed. The initially mixed fluid is then introduced into the secondary space 12 through the polymerizer 30. The high-speed rotating cutting impeller 41 cuts the gas-liquid mixed bubbles into tens of nanometers to several micrometers to form micro-nano bubbles.

[0058] Due to the difference in gravity between surfactants and carbon dioxide, surfactants and carbon dioxide are prone to detach, resulting in uneven mixing. In order to produce a uniformly mixed fluid, a step-by-step mixing method is adopted in the three-level space to achieve a more uniform mixing effect.

[0059] This application effectively increases the gas-liquid contact area by employing a grid-shaped injector and a polymerizer 30 with a large surface area, thereby increasing the mixing speed. The cutting device 40 with a cutting impeller 41 can increase the volume of micro-nano bubbles, and the mixing device 50 with step-by-step stirring allows the mixture to be mixed step-by-step in space, thereby achieving a more uniform mixing effect.

[0060] The carbon dioxide and surfactant mixing device can effectively improve mixing efficiency and mixing quality, thereby improving the performance and reliability of the mixed fluid. Compared with the existing CO2 compound displacement simulator, this application can not only conveniently control the displacement effect of different CO2 and surfactant ratios on the reservoir, but also the carbon dioxide and surfactant can be mixed more uniformly, and can play a better role when injected into the model. Under the same injection volume, the oil displacement efficiency is increased, which greatly increases the economic benefits.

[0061] This application also provides a displacement simulation method, which uses the aforementioned carbon dioxide and surfactant mixing device. The displacement simulation method includes: Step S10: preparing simulated oil with a preset viscosity according to reservoir conditions; Step S20: preparing a physical model based on reservoir parameters and testing the basic parameters of the physical model; Step S30: preparing carbon dioxide and surfactant, as well as two injection pumps, and connecting the injection pumps to the injector 20 of the carbon dioxide and surfactant mixing device; Step S40: calculating the preset injection rate of carbon dioxide and the preset injection rate of surfactant according to the ratio and the required environmental conditions; Step S50: mixing carbon dioxide and surfactant according to the corresponding preset ratios. The process involves several steps: Step S60: After injecting carbon dioxide and surfactant into a mixing device at the injection rate, a compound agent is formed; Step S70: After extracting and drying the natural rock core, the natural rock core is arranged and fully saturated with formation water, and the saturation level is recorded; Step S80: The water in the natural rock core is displaced using a prepared saturated oil sample to establish the oil-water distribution in a physical model and calculate the bound water saturation; Step S90: The mixed compound agent is injected into the physical model through a delivery pipeline to conduct a reservoir displacement experiment and the displacement data is recorded; Step S91: After each set of experiments, the natural rock core is cleaned and dried, the ratio of carbon dioxide to surfactant is changed, and steps S40 to S90 are repeated until all ratio experiments are completed.

[0062] A physical model refers to the permeability, pore size, and location simulated from a core sample based on the reservoir conditions.

[0063] The displacement simulation method uses the aforementioned carbon dioxide and surfactant mixing device to easily control the ratio of carbon dioxide and surfactant, so as to simulate the displacement effect of the mixed fluid on the reservoir under different ratios, which is beneficial to selecting the ratio with the best displacement effect.

[0064] It should be noted that the physical model simulates reservoir conditions.

[0065] Specifically, during the displacement experiment of the reservoir by injecting the mixed compound agent into the physical model through the delivery pipeline and recording the displacement data, the displacement time, pump reading, injection pressure, injection rate, annular pressure, and back pressure should be recorded. The produced gas-oil ratio and the amount of oil, gas, and water separated should also be monitored. Recording these parameters facilitates comparison under various formulations to select the optimal formulation.

[0066] Specifically, during the cleaning of the natural rock cores after each set of experiments, the cores were first cleaned with petroleum ether and anhydrous alcohol, and then purged with nitrogen. This process effectively removes any residual carbon dioxide and surfactant mixture from the previous set of experiments, preventing it from affecting the next set and thus improving the accuracy of each experiment.

[0067] Specifically, the physical model simulates the original oil-water distribution in the formation. This results in a more accurate simulation, which is beneficial for obtaining better experimental results.

[0068] The following is a detailed explanation using a specific example.

[0069] Step S10: Prepare heavy oil with a specific gravity of 0.88 according to the reservoir conditions.

[0070] Step S20: Prepare a physical model based on reservoir parameters and test the basic parameters of the physical model.

[0071] Step S30: Prepare carbon dioxide and surfactant, prepare two injection pumps, one for injecting carbon dioxide gas and the other for injecting the pre-selected surfactant, and connect the injection pumps to the injector 20 of the carbon dioxide and surfactant mixing device.

[0072] Step S40: Mix carbon dioxide and surfactant in a ratio of 5:1, and calculate the injection rates of surfactant and carbon dioxide.

[0073] Step S50: Control the flow rate to inject carbon dioxide gas and surfactant into the mixing tank 10 simultaneously in proportion. Set the environmental conditions in the mixing tank 10 (45℃, 10MPa). The injector injects carbon dioxide and surfactant into the primary space 11 in a preset ratio for uniform mixing. After accumulating to a certain liquid volume in the polymerizer 30, it enters the secondary space 12. The cutting device 40 quickly cuts it to form micro-nano bubbles. Then it enters the tertiary space 13 and is graded and mixed by the fusion device 50 to form a compound agent.

[0074] Step S60: After extracting and drying the natural rock core, arrange the natural rock core in a container, fully saturate it with formation water, and record the saturation level.

[0075] Step S70: Displace the water in the natural rock core with the prepared saturated oil sample, establish the oil-water distribution of the physical model, and calculate the bound water saturation.

[0076] Step S80: The mixed compound agent is injected into the physical model through the delivery pipeline to carry out the displacement experiment of the oil reservoir. During the displacement process, the displacement time, pump reading, injection pressure, injection speed, annular pressure and back pressure are recorded. The produced gas-oil ratio and the amount of oil, gas and water separated are monitored. The displacement data are sorted and analyzed.

[0077] Step S90: After the experiment, clean the natural rock core and dry it. Repeat steps S40 to S80 by changing the ratio of carbon dioxide to surfactant to 3:1 and 1:1 respectively.

[0078] The conventional method group uses a horizontal flow pump to mix CO2 and DLS at a ratio of 5:1 and injects them into the physical model under environmental conditions (45℃, 10MPa).

[0079] Example Result Analysis: Based on Figure 8 It can be seen that, when comparing the oil displacement efficiency of different mixing ratio experimental groups, the 3:1 ratio of carbon dioxide to surfactant (DLS) is the best, followed by 1:1, and the worst is 5:1. When comparing the oil displacement efficiency of the traditional injection method and the new injection method, it was found that the oil displacement efficiency of the new method is higher than that of the traditional injection method at different time periods. Under the same mixing ratio, the oil displacement efficiency of the new injection method is about 10% higher than that of the traditional injection method.

[0080] Example Conclusion: When CO2 is mixed with surfactants for reservoir displacement, different ratios have a certain impact on reservoir production. Under environmental conditions (45℃, 10MPa), a CO2 to DLS ratio of 3:1 is most suitable for heavy oil extraction with a specific gravity of 0.88.

[0081] Changing the ratio of compound agents has a certain impact on oil recovery efficiency, but it is not as high as the overall oil displacement efficiency of compound agents with a single ratio.

[0082] The surfactant and carbon dioxide mixing device of the present invention changes the traditional rough mixing and injection method, and increases the oil displacement effect without increasing material costs.

[0083] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0084] 1. This invention utilizes a grid-shaped injector to form surfactants and carbon dioxide gas into small molecules, and uses a polymerizer 30 to achieve a larger contact area for mixing, thereby increasing the gas-liquid contact area and improving the mixing effect and speed.

[0085] 2. The present invention utilizes a high-speed rotating cutting impeller 41 and a high-speed cutting device 40 to cut the gas-liquid mixture bubbles into small pieces, which can be cut into tens of nanometers to several micrometers, ultimately forming micro-nano bubbles. This increases the gas-liquid contact area, thereby further improving the mixing efficiency and the number and density of bubbles carried.

[0086] 3. In this invention, surfactants and carbon dioxide are mixed in stages and stirred in a funnel-shaped space to form a circulating flow in three-dimensional space, which makes the mixing of two fluids with large differences in properties more uniform.

[0087] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0088] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0089] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for mixing carbon dioxide and a surfactant, characterized in that, include: The mixing tank (10) has a primary space (11), a secondary space (12) and a tertiary space (13) connected sequentially along the direction of gravity. Multiple injectors (20) are disposed within the primary space (11), at least one of the injectors (20) is used to inject carbon dioxide, and at least another injector (20) is used to inject surfactant; The agglomerator (30) is located in the primary space (11) and below the injector (20). The carbon dioxide and surfactant sprayed by the injector (20) are initially mixed above the agglomerator (30) to form gas-liquid mixed bubbles, which are then polymerized in the agglomerator (30) and flow into the secondary space (12). A cutting device (40) is disposed in the secondary space (12) and is used to cut the gas-liquid mixed bubbles flowing into the polymerizer (30) into tiny micro-nano bubbles. A fusion device (50) is disposed within the three-level space (13) and is used to fully mix carbon dioxide with a surfactant. The aggregator (30) has a conical aggregating surface (31), the small diameter end (311) of the conical aggregating surface (31) is closer to the secondary space (12) than the large diameter end (312) of the conical aggregating surface (31), and the conical aggregating surface (31) has a plurality of first outlets (313). The fusion device (50) includes multiple rotating blade devices (51), which are arranged at intervals from top to bottom in the three-level space (13), and each rotating blade device (51) has a different rotation speed.

2. The carbon dioxide and surfactant mixing device according to claim 1, characterized in that, The injector (20) is a grid injector so that the injected surfactant is in the form of small bubbles.

3. The carbon dioxide and surfactant mixing device according to claim 1, characterized in that, The carbon dioxide and surfactant mixing device also includes a converging plate (60), which is located below the cutting device (40). The converging plate (60) has multiple second outlets (61), through which micro-nano bubbles in the secondary space (12) flow into the tertiary space (13). The first outlet (313) and the second outlet (61) are misaligned in the circumferential direction.

4. The carbon dioxide and surfactant mixing device according to claim 3, characterized in that, The converging plate (60) is conical, and the cross-sectional area of ​​the converging plate (60) gradually decreases toward the tertiary space (13).

5. The carbon dioxide and surfactant mixing apparatus according to claim 1, characterized in that, The cutting device (40) includes: Drive unit; A cutting impeller (41) is connected to the driving device to drive the cutting impeller (41) to rotate. The cutting impeller (41) is used to cut gas-liquid mixed bubbles into tiny micro-nano bubbles.

6. The apparatus for mixing carbon dioxide and surfactant according to any one of claims 1 to 5, characterized in that, The rotating blade device (51) closest to the secondary space (12) among the plurality of rotating blade devices (51) has the highest rotational speed.

7. The apparatus for mixing carbon dioxide and surfactant according to any one of claims 1 to 5, characterized in that, The rotational speed of the plurality of rotating blade devices (51) decreases progressively from top to bottom.

8. The apparatus for mixing carbon dioxide and surfactant according to any one of claims 1 to 5, characterized in that, The fusion device (50) also includes a multi-stage variable speed planetary drive motor, and the plurality of rotating blade devices (51) are connected to the multi-stage variable speed planetary drive motor.

9. The apparatus for mixing carbon dioxide and surfactant according to any one of claims 1 to 5, characterized in that, The mixing tank (10) has a conical structure, and the cross-sectional area of ​​the mixing tank (10) gradually decreases from the first-level space (11) to the third-level space (13).

10. A displacement simulation method, characterized in that, The displacement simulation method employs the carbon dioxide and surfactant mixing apparatus as described in any one of claims 1 to 9, and the displacement simulation method includes: Step S10: Prepare simulated oil with a preset viscosity according to reservoir conditions; Step S20: Prepare a physical model based on reservoir parameters and test the basic parameters of the physical model; Step S30: Prepare carbon dioxide and surfactant, as well as two injection pumps, and connect the injection pumps to the injector (20) of the carbon dioxide and surfactant mixing device accordingly; Step S40: Calculate the preset injection rate of the carbon dioxide and the preset injection rate of the surfactant based on the ratio and the required environmental conditions; Step S50: The carbon dioxide and the surfactant are injected into the carbon dioxide and surfactant mixing device at the corresponding preset injection rate to form a compound agent; Step S60: After extracting and drying the natural rock core, arrange the natural rock core in a container, fully saturate it with formation water, and record the saturation level. Step S70: Displace the water in the natural rock core with the prepared saturated oil sample, establish the oil-water distribution of the physical model, and calculate the bound water saturation. Step S80: The mixed compound agent is injected into the physical model through the delivery pipeline to conduct a reservoir displacement experiment and the displacement data is recorded; Step S90: After each group of experiments, clean the natural rock core and dry it. Change the ratio of carbon dioxide to surfactant and repeat steps S40 to S90 until all ratio experiments are completed.

11. The displacement simulation method according to claim 10, characterized in that, During the process of injecting the mixed compound agent into the physical model through the delivery pipeline for reservoir displacement experiments and recording displacement data, the displacement time, pump reading, injection pressure, injection speed, annular pressure and back pressure are recorded, and the produced gas-oil ratio and the amount of separated oil, gas and water are monitored.

12. The displacement simulation method according to claim 10, characterized in that, During the cleaning process after each set of experiments, the natural rock core was first cleaned with petroleum ether and anhydrous alcohol, and then purged with nitrogen.

13. The displacement simulation method according to claim 10, characterized in that, The oil-water distribution in the physical model simulates the original oil-water distribution of the formation.

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