A dense-phase carbon dioxide separation and reinjection device and its control method

Abstract

The present invention relates to a dense-phase carbon dioxide separation and reinjection device and a control method thereof, which includes: a first process pipeline, a second process pipeline, a gas-phase process pipeline, a liquid-phase process pipeline, a third process pipeline, a fourth process pipeline, a high-pressure injection pipeline, a first temperature and pressure regulation system, a gas-liquid separation system, a second temperature and pressure regulation system, a dense-phase carbon dioxide separation system, a separation speed control system, a high-pressure reinjection system, and a reinjection pressure control system. The dense-phase carbon dioxide separation and reinjection device and the control method thereof can utilize the physical property differences between gas-phase light hydrocarbon gas and dense-phase carbon dioxide to achieve the separation and reinjection of carbon dioxide in well-stream oil and gas products, greatly reducing the cost of dense-phase carbon dioxide separation and utilization on offshore production platforms and increasing the oil and gas field production.

Description

Technical Field

[0001] The present invention relates to a dense-phase carbon dioxide separation and reinjection device and its control method, belonging to the field of offshore oil and gas production. Background Art

[0002] Under the background of the "dual carbon goal", the application of CCUS technology in the offshore oil and gas production system is promoted. Dense-phase carbon dioxide reinjection can effectively increase the production of offshore oil and gas fields. The increase in the carbon dioxide content of the well stream in offshore oil and gas fields has brought a series of problems such as a decrease in the calorific value of natural gas products and an increase in the risk of pipeline corrosion. Therefore, it is necessary to separate and reinject carbon dioxide on the offshore production platform for enhanced oil recovery.

[0003] At present, the main methods for carbon dioxide separation in the oil and gas production process are: membrane separation, amine method, and supersonic separator. Among them, the membrane separation technology and the amine method involve more equipment, which will greatly increase the operating cost of the offshore production platform; the supersonic separator has high requirements for process parameters and is difficult to apply to the actual carbon dioxide separation process of offshore oil and gas fields with dynamic component changes. Therefore, it is necessary to develop a device and process method suitable for the separation and reinjection of dense-phase carbon dioxide on offshore oil and gas platforms in combination with the process flow characteristics of offshore platforms and the different phase characteristics of dense-phase carbon dioxide. On the premise of ensuring system economy, reduce the carbon dioxide emissions during the production process of offshore oil and gas fields and increase the oil and gas field production. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a dense-phase carbon dioxide separation and reinjection device and its control method, which can utilize the physical property differences between gaseous light hydrocarbon gas and dense-phase carbon dioxide to achieve the separation and reinjection of carbon dioxide in the well stream oil and gas products, greatly reducing the cost of separating and utilizing dense-phase carbon dioxide on the offshore production platform and increasing the oil and gas field production.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a dense-phase carbon dioxide separation and reinjection device, including a first process pipeline, a second process pipeline, a gas-phase process pipeline, a liquid-phase process pipeline, a third process pipeline, a fourth process pipeline, a high-pressure injection pipeline, a first temperature and pressure regulation system, a gas-liquid separation system, a second temperature and pressure regulation system, a dense-phase carbon dioxide separation system, a separation speed control system, a high-pressure reinjection system, and a reinjection pressure control system;

[0007] The first process pipeline is used for the production well product flow to flow in. The first temperature and pressure regulation system is arranged on the first process pipeline to regulate the temperature and pressure of the fluid in the first process pipeline. The outlet of the first process pipeline is communicated with the second process pipeline;

[0008] The outlet of the second process pipeline is connected to the gas-liquid separation system. The gas-liquid separation system separates the gas phase and the liquid phase of the fluid. The liquid phase enters the crude oil treatment system through the liquid phase process pipeline, and the gas phase enters the second temperature and pressure regulation system through the gas phase process pipeline;

[0009] The second temperature and pressure regulation system is used to compress the gas phase into a mixture of dense-phase carbon dioxide and light hydrocarbons. The outlet of the second temperature and pressure regulation system is connected to the third process pipeline;

[0010] The third process pipeline is connected to the dense-phase carbon dioxide separation system. The dense-phase carbon dioxide separation system is used to separate the dense-phase carbon dioxide and light hydrocarbons. The separation speed control system is arranged on the third process pipeline to control the separation speed of the dense-phase carbon dioxide separation system;

[0011] The outlet of the dense-phase carbon dioxide separation system is connected to the high-pressure injection system through the fourth process pipeline. The high-pressure injection system injects the dense-phase carbon dioxide back into the bottom of the well through the high-pressure injection pipeline. The injection pressure control system is arranged on the high-pressure injection pipeline to control the injection pressure.

[0012] Further, the first temperature and pressure regulation system includes a first temperature and pressure sensor, a first pressure regulating valve, a first pressure sensor, a first pressure controller, and a first parameter calculator. The first temperature and pressure sensor and the first pressure sensor are respectively arranged upstream and downstream of the first pressure regulating valve. The first temperature and pressure sensor is used to detect the pressure and temperature of the fluid in the first process pipeline and feed the detected data back to the first parameter calculator. The first parameter calculator sends a control instruction to the first pressure regulating valve for pressure control to meet the platform design pressure. The first pressure sensor is used to detect the pressure in the first process pipeline after regulation and feed the detected value back to the first controller.

[0013] Further, the second temperature and pressure regulation system includes a multi-stage compressor system and a heat exchange system. The multi-stage compressor system and the heat exchange system are respectively used to adjust the pressure and temperature of the gas phase to compress the gas phase into a mixture of dense-phase carbon dioxide and light hydrocarbons. The multi-stage compressor system includes a first-stage compressor and a second-stage compressor, which are connected in sequence. The gas-phase flow pipeline is connected to the first-stage compressor, and the second-stage compressor is connected to the third flow pipeline. The heat exchange system includes a second temperature and pressure sensor, a second heat exchanger, a second controller, and a second parameter calculator. The second temperature and pressure sensor is used to detect the temperature and pressure of the gas phase in the gas-phase flow pipeline and feed the detected data back to the second parameter calculator. The second parameter calculator sends a control instruction to the second controller, and the second controller controls the heat exchange temperature of the second heat exchanger and the frequency conversion of the first-stage compressor and the second-stage compressor to realize the transformation of carbon dioxide in the gas-phase mixture from the gas phase to the dense phase state.

[0014] Further, the second temperature and pressure regulation system further includes a third temperature and pressure sensor and a first densitometer provided on the third flow pipeline. The third temperature and pressure sensor is used to detect the temperature and pressure of the mixture of dense-phase carbon dioxide and light hydrocarbons in the third flow pipeline, and the first densitometer is used to detect the density of the mixture of dense-phase carbon dioxide and light hydrocarbons in the third flow pipeline. The third temperature and pressure sensor and the first densitometer feed the detected data back to the second parameter calculator. The second parameter calculator controls the fluid flow rate in the second heat exchanger and the frequency conversion of the multi-stage compressor system according to the data detected by the third temperature and pressure sensor, the first densitometer, and the second temperature and pressure sensor, thereby realizing the transformation of carbon dioxide in the gas-phase mixture from the gas phase to the dense phase state.

[0015] Further, the dense-phase carbon dioxide separation system includes a multi-stage vertical separator. The multi-stage vertical separators are connected in sequence through pipelines. A carbon dioxide membrane is provided in each vertical separator. The carbon dioxide membrane is used to separate the light hydrocarbons and the dense-phase carbon dioxide. The adjacent two-stage vertical separators are connected through a first pipeline and a second pipeline. The first pipeline and the second pipeline are respectively used for the light hydrocarbons and the dense-phase carbon dioxide to pass through. One outlet of the multi-stage vertical separator is used for discharging the light hydrocarbons, and the other outlet is connected to the high-pressure reinjection system through the high-pressure injection pipeline.

[0016] Further, the multi-stage vertical pipe separator includes three stages, and carbon dioxide membranes are provided in all three stages of the vertical pipe separator. An primary light hydrocarbon regulating valve and a primary carbon dioxide regulating valve are respectively provided on the first pipeline and the second pipeline between the primary vertical pipe separator and the secondary vertical pipe separator. A secondary light hydrocarbon regulating valve and a secondary carbon dioxide regulating valve are respectively provided on the first pipeline and the second pipeline between the secondary vertical pipe separator and the tertiary vertical pipe separator;

[0017] The separation speed control system includes the primary light hydrocarbon regulating valve, the primary carbon dioxide regulating valve, the secondary light hydrocarbon regulating valve, the secondary carbon dioxide regulating valve, a second densitometer provided on the fourth process pipeline, a third controller, and a processing unit. A self-learning model is stored in the processing unit. The third temperature and pressure sensor, the first densitometer, and the second densitometer feedback the detected signals to the processing unit. The processing unit sends control instructions to the third controller according to the signals detected by the processing unit, and the third controller controls the primary light hydrocarbon regulating valve, the primary carbon dioxide regulating valve, the secondary light hydrocarbon regulating valve, and the secondary carbon dioxide regulating valve to act according to the control instructions.

[0018] Further, the high-pressure reinjection system includes an injection pump and a dense-phase carbon dioxide outlet valve. The inlet of the injection pump is communicated with the fourth process pipeline, and the outlet is communicated with the high-pressure injection pipeline. The dense-phase carbon dioxide outlet valve is provided on the high-pressure injection pipeline; the reinjection pressure control system includes a fourth temperature and pressure sensor and a fourth controller. The fourth temperature and pressure sensor is provided at the outlet end of the injection pump for detecting the outlet pressure of the injection pump and feeding back the detected data to the fourth controller. The fourth controller adjusts the motor speed of the injection pump according to the feedback signal to meet the pressure requirements for dense-phase carbon dioxide reinjection.

[0019] On the other hand, the present invention also provides a control method for a dense-phase carbon dioxide separation and reinjection device as described above, including the steps of:

[0020] Controlling the temperature and pressure of the well fluid in the first process pipeline to make the temperature and pressure of the well fluid in the first process pipeline meet the platform design requirements;

[0021] Controlling the temperature and pressure of the gas phase in the gas phase process pipeline to convert the carbon dioxide in the gas phase into dense-phase carbon dioxide;

[0022] Controlling the separation rate of the dense-phase carbon dioxide and the light hydrocarbon in the multi-stage vertical pipe separator to separate the dense-phase carbon dioxide and the light hydrocarbon;

[0023] Controlling the reinjection pressure of the high-pressure reinjection system.

[0024] Further, the controlling the temperature and pressure of the well fluid in the first process pipeline includes the steps of:

[0025] The pressure and temperature of the fluid in the first process pipeline are detected by the first temperature and pressure sensor, and the detected data are fed back to the first parameter calculator. The first parameter calculator sends a control instruction to the first pressure regulating valve for pressure control to make the pressure in the first process pipeline meet the platform design pressure. The first pressure sensor detects the pressure in the first process pipeline after regulation and feeds the detected data back to the first controller;

[0026] The heat exchange temperature of the first heat exchanger is controlled by the first parameter calculator according to the data of the first temperature and pressure sensor and the first pressure regulating valve;

[0027] The controlling the temperature and pressure of the gas phase in the gas phase process pipeline includes the steps of:

[0028] The second parameter calculator calculates and obtains the temperature control target of the second heat exchanger and the outlet pressure control values of the first-stage compressor and the second-stage compressor based on the temperature and pressure parameters at the gas phase outlet of the production separator, the temperature and pressure parameters at the outlet of the second-stage compressor, and the density parameters of the first densitometer;

[0029] The temperature control target of the second heat exchanger and the outlet pressure control values of the first-stage compressor and the second-stage compressor are fed back into the control parameters of the controller for controlling the fluid flow rate of the heat exchanger and the frequency converters of each stage of the compressor, thereby realizing the transformation of carbon dioxide in the gas mixture from the gas phase to the dense phase state.

[0030] Furthermore, controlling the separation rate of the dense-phase carbon dioxide and light hydrocarbons in the multi-stage vertical separator includes:

[0031] Based on the observed values of the second temperature and pressure sensor, the first densitometer, and the second densitometer, they are brought into the self-learning model for optimizing the calculation of the separation rate of the dense-phase carbon dioxide and light hydrocarbons in each stage of the separator. The calculation results are fed back into the third controller for adjusting the outlet regulating valves of the dense-phase carbon dioxide and light hydrocarbons in each stage of the vertical separator.

[0032] Due to the adoption of the above technical solutions, the present invention has the following advantages:

[0033] 1. By adopting a calculation module introduced based on the dynamic change prediction of oil and gas components and instrument observation data, the temperature and pressure at the inlet of the platform production separator are dynamically controlled.

[0034] 2. Integrating online simulation technology, based on the flash calculation at the gas phase outlet of the production separator, the process parameters of the compressor and the heat exchanger are dynamically controlled through a cascade controller.

[0035] 3. Based on the physical properties of dense-phase carbon dioxide, by making full use of the density difference between the dense-phase carbon dioxide and light hydrocarbons through a vertical separator, the separation of dense-phase carbon dioxide is promoted, and the separation effect of the traditional separation membrane is improved.

[0036] 4. Introduce a self - learning model into the control system of the multi - stage vertical pipe separator. Combine the monitoring data such as pressure, temperature, density, etc. and the physical property analysis of dense - phase carbon dioxide to achieve intelligent regulation of the separation system. The present invention can be widely applied to the separation and reinjection of dense - phase carbon dioxide on offshore production platforms in high - carbon - dioxide oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components.

[0038] In the drawings:

[0039] Figure 1 is a schematic structural diagram of the dense - phase carbon dioxide separation and reinjection device of the present invention.

[0040] The reference numerals in the drawings are represented as follows:

[0041] 1 - First process pipeline, 2 - First temperature - pressure sensor, 3 - First pressure regulating valve, 4 - First controller, 5 - First pressure regulating valve, 6 - First parameter calculator, 7 - Second controller, 8 - First heat exchanger, 9 - Heat exchanger outlet temperature sensor, 10 - Heat exchanger outlet valve, 11 - Heat exchanger bypass valve, 12 - Second process pipeline, 13 - Inlet regulating valve, 14 - Production separator, 15 - Safety valve, 16 - Liquid level sensor, 17 - Fifth controller, 18 - Liquid - phase process pipeline, 19 - Regulating valve, 20 - Gas - phase process pipeline, 21 - Second temperature - pressure sensor, 22 - Second heat exchanger, 23 - First - stage compressor, 24 - Second - stage compressor, 25 - Second controller, 26 - Second parameter calculator, 27 - Third temperature - pressure sensor, 28 - Third process pipeline, 29 - First densitometer, 30 - Processing unit, 31 - Third controller, 32 - First - stage vertical pipe separator, 33 - Second - stage vertical pipe separator, 34 - Third - stage vertical pipe separator, 35 - First - stage carbon dioxide membrane, 40 - Second - stage carbon dioxide membrane, 41 - Third - stage carbon dioxide membrane, 42 - Second densitometer, 43 - Fourth process pipeline, 44 - Injection pump, 45 - Dense - phase carbon dioxide outlet valve, 46 - High - pressure injection pipeline, 47 - Fourth temperature - pressure sensor, 48 - Fourth controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0043] The present invention provides a dense-phase carbon dioxide separation and reinjection device and its control method, which includes: a first process pipeline, a second process pipeline, a gas-phase process pipeline, a liquid-phase process pipeline, a third process pipeline, a fourth process pipeline and a high-pressure injection pipeline, a first temperature and pressure regulation system, a gas-liquid separation system, a second temperature and pressure regulation system, a dense-phase carbon dioxide separation system, a separation speed control system, a high-pressure reinjection system and a reinjection pressure control system. The dense-phase carbon dioxide separation and reinjection device and its control method can utilize the physical property differences between the gas-phase light hydrocarbon gas and the dense-phase carbon dioxide to achieve the separation and reinjection of carbon dioxide in the well-stream oil and gas products, greatly reducing the cost of separating and utilizing the dense-phase carbon dioxide on offshore production platforms and increasing the oil and gas field production.

[0044] Example 1

[0045] As Figure 1 shown, an embodiment of the present invention provides a dense-phase carbon dioxide separation and reinjection device, which includes a first process pipeline 1, a second process pipeline 12, a gas-phase process pipeline 20, a liquid-phase process pipeline 18, a third process pipeline 28, a fourth process pipeline 43 and a high-pressure injection pipeline 46, a first temperature and pressure regulation system, a gas-liquid separation system, a second temperature and pressure regulation system, a dense-phase carbon dioxide separation system, a separation speed control system, a high-pressure reinjection system and a reinjection pressure control system.

[0046] The first process pipeline 1 is used for the production well production fluid to flow in. The inlet of the first process pipeline 1 is connected to the subsea pipeline connecting the production well. The first temperature and pressure regulation system is arranged on the first process pipeline 1 and is used to regulate the temperature and pressure of the fluid in the first process pipeline 1. The outlet of the first process pipeline 1 is communicated with the second process pipeline 12.

[0047] The first temperature and pressure regulation system includes a first pressure regulation system. The first pressure regulation system includes a first temperature and pressure sensor 2, a first pressure regulating valve 3, a first pressure sensor 5, a first pressure controller 4, and a first parameter calculator 6. The first temperature and pressure sensor 2 and the first pressure sensor 5 are respectively arranged upstream and downstream of the first pressure regulating valve 3. The first temperature and pressure sensor 2 is used to detect the pressure and temperature of the fluid in the first process pipeline 1 and feed the detected data back to the first parameter calculator 6. The first parameter calculator 6 sends a control instruction to the first pressure regulating valve 3 for pressure control. The first pressure sensor 5 is used to detect the pressure in the first process pipeline 1 after regulation, so that the pressure value of the first pressure sensor 5 conforms to the platform design pressure.

[0048] The first temperature and pressure regulation system further includes a heat exchange system. The heat exchange system includes a first heat exchanger 8, a heat exchanger outlet temperature sensor 9, a heat exchanger outlet valve 10, and a heat exchanger bypass valve 11. The first parameter calculator 6 controls the heat exchange temperature of the first heat exchanger 8 according to the data of the first temperature and pressure sensor 2 and the first pressure regulating valve 3. The heat exchanger outlet temperature sensor 9 is used to detect the temperature of the fluid at the outlet of the first heat exchanger 8. The heat exchange temperature of the temperature regulation system is set based on the first temperature and pressure sensor 2 at the platform inlet, the throttling condition of the first pressure regulating valve 3, and the first parameter calculator 6 to automatically determine whether heat exchange is required and dynamically set the heat exchange temperature. According to the set value, the first controller 4 controls the regulating valve inside the first heat exchanger 8 to control the flow rate and pressure of the cold fluid.

[0049] The outlet of the second process pipeline 12 is connected to the gas-liquid separation system. The gas-liquid separation system separates the gas phase and the liquid phase of the fluid. The liquid phase enters the crude oil treatment system through the liquid phase pipeline 18, and the gas phase enters the second temperature and pressure regulation system through the gas phase pipeline 20.

[0050] The gas-liquid separation system includes a production separator 14, an inlet regulating valve 13, and a safety valve 15 arranged inside the production separator 14. An inlet regulating valve 13 and a safety valve 15 are arranged in the production separator 14. In case of abnormal platform pressure, fire, etc., the inlet regulating valve 13 is cut off, and the safety valve 15 is used for relief.

[0051] The gas-liquid mixture of the heat exchange system enters the production separator 14 through the second process pipeline and the inlet regulating valve 13. Gas-liquid separation is achieved in the production separator 14. The separated liquid enters the crude oil treatment system through the liquid phase pipeline 18 and the regulating valve 19. The fifth controller 17 controls the regulating valve 19 on the pipeline 18 entering the crude oil treatment system according to the liquid level sensor 16 of the production separator 14.

[0052] The second temperature and pressure regulation system is used to compress the gas phase into a mixture of dense-phase carbon dioxide and light hydrocarbons. The second temperature and pressure regulation system is arranged on the gas-phase process pipeline 20 and is used to regulate the temperature and pressure of the fluid in the gas-phase process pipeline 20. The outlet of the second temperature and pressure regulation system is communicated with the third process pipeline 28.

[0053] The second temperature and pressure regulation system includes a multi-stage compressor system and a temperature regulation device. The multi-stage compressor system and the temperature regulation device are respectively used to regulate the pressure and temperature of the gas phase so as to compress the gas phase into a mixture of dense-phase carbon dioxide and light hydrocarbons.

[0054] The multi-stage compressor system includes a first-stage compressor 23 and a second-stage compressor 24. The first-stage compressor 23 and the second-stage compressor 24 are connected in sequence. The gas-phase process pipeline 20 is communicated with the first-stage compressor 23, and the second-stage compressor 24 is communicated with the third process pipeline 28. The temperature regulation device includes a second temperature and pressure sensor 21, a second heat exchanger 22, a second controller 25, and a second parameter calculator 26. The second temperature and pressure sensor 26 is used to detect the temperature and pressure of the gas phase in the gas-phase process pipeline 20 and feed back the detected data to the second parameter calculator 26. The second parameter calculator 26 sends a control instruction to the second controller 25. The second controller 25 controls the heat exchange temperature of the second heat exchanger 22 and the frequency conversion of the first-stage compressor 23 and the second-stage compressor 24, so as to realize the transformation of carbon dioxide in the gas-phase mixture from the gas phase to the dense phase state.

[0055] The second temperature and pressure regulation system further includes a third temperature and pressure sensor 27 and a first densitometer 29 arranged on the third process pipeline 28. The third temperature and pressure sensor 27 is used to detect the temperature and pressure of the mixture of dense-phase carbon dioxide and light hydrocarbons in the third process pipeline 28, and the first densitometer 29 is used to detect the density of the mixture of dense-phase carbon dioxide and light hydrocarbons in the third process pipeline 28. The third temperature and pressure sensor 27 and the first densitometer 29 feed back the detected data to the second parameter calculator 26. The second parameter calculator 26 controls the fluid flow rate in the second heat exchanger 22 and the frequency conversion of the multi-stage compressor system according to the data detected by the third temperature and pressure sensor 27, the first densitometer 29, and the second temperature and pressure sensor 21, so as to realize the transformation of carbon dioxide in the gas-phase mixture from the gas phase to the dense phase state.

[0056] The third process pipeline 28 is communicated with the dense-phase carbon dioxide separation system. The dense-phase carbon dioxide separation system is used to separate the dense-phase carbon dioxide and light hydrocarbons. The separation speed control system is arranged on the third process pipeline 28 and is used to control the separation speed of the dense-phase carbon dioxide separation system.

[0057] The dense-phase carbon dioxide separation system includes multiple vertical pipe separators, which are sequentially connected by pipelines in turn. A carbon dioxide membrane is provided in each of the vertical pipe separators. The carbon dioxide membrane is used to separate the light hydrocarbons and dense-phase carbon dioxide. The adjacent two-stage vertical separators are connected by a first pipeline and a second pipeline. The first pipeline and the second pipeline are respectively used for the light hydrocarbons and dense-phase carbon dioxide to pass through. One outlet of the multiple vertical pipe separators is used for the light hydrocarbons to be discharged into the associated gas treatment system, and the other outlet is connected to the high-pressure reinjection system through the fourth process 43 pipeline.

[0058] Specifically, the multiple vertical pipe separators include three stages. A carbon dioxide membrane is provided in each of the three-stage vertical pipe separators. An first-stage light hydrocarbon regulating valve 36 and a first-stage carbon dioxide regulating valve 37 are respectively provided on the first pipeline and the second pipeline between the first-stage vertical pipe separator 32 and the second-stage vertical pipe separator 33. A second-stage light hydrocarbon regulating valve 38 and a second-stage carbon dioxide regulating valve 39 are respectively provided on the first pipeline and the second pipeline between the second-stage vertical pipe separator 33 and the third-stage vertical pipe separator 34.

[0059] The separation speed control system includes the first-stage light hydrocarbon regulating valve 36, the first-stage carbon dioxide regulating valve 37, the second-stage light hydrocarbon regulating valve 38, the second-stage carbon dioxide regulating valve 39, a second densitometer 42 provided on the fourth process pipeline 43, a third controller 31, and a processing unit 30. A self-learning model is stored in the processing unit 30. The third temperature and pressure sensor 27, the first densitometer 29, and the second densitometer 42 feed back the detected signals to the processing unit 30. The processing unit 30 sends a control instruction to the third controller 31 according to the signals, and the third controller 31 controls the first-stage light hydrocarbon regulating valve 36, the first-stage carbon dioxide regulating valve 37, the second-stage light hydrocarbon regulating valve 38, and the second-stage carbon dioxide regulating valve 39 to act according to the control instruction.

[0060] The outlet of the dense-phase carbon dioxide separation system is connected to the high-pressure reinjection system through the fourth process pipeline 43. The high-pressure reinjection system reinjects the dense-phase carbon dioxide to the bottom of the well through the high-pressure injection pipeline 46. The reinjection pressure control system is provided on the high-pressure injection pipeline 46 to control the reinjection pressure. The high-pressure reinjection system includes an injection pump 44 and a dense-phase carbon dioxide outlet valve 45. The inlet of the injection pump 44 is connected to the fourth process pipeline 43, and the outlet is connected to the high-pressure injection pipeline 46. The dense-phase carbon dioxide outlet valve 45 is provided on the high-pressure injection pipeline 46.

[0061] The re-injection pressure control system includes a fourth temperature and pressure sensor 47 and a fourth controller 48. The fourth temperature and pressure sensor 47 is arranged at the outlet end of the injection pump 44 for detecting the outlet pressure of the injection pump 44 and feeding the detected data back to the fourth controller 48. The fourth controller 48 adjusts the rotational speed parameter of the motor of the injection pump 44 according to the fed-back signal to meet the pressure requirement for dense-phase carbon dioxide re-injection.

[0062] Another embodiment of the present invention further provides a control method for the carbon dioxide separation and re-injection device, including the following steps:

[0063] S1. Control the temperature and pressure of the well stream in the first process pipeline 1 so that the temperature and pressure of the well stream in the first process pipeline 1 meet the platform design requirements;

[0064] S2. Control the temperature and pressure of the gas phase in the gas phase process pipeline 20 so that the carbon dioxide in the gas phase is converted into dense-phase carbon dioxide;

[0065] S3. Control the separation rate of the dense-phase carbon dioxide and light hydrocarbons in the multi-stage riser separator so that the dense-phase carbon dioxide and light hydrocarbons are separated;

[0066] S4. Control the re-injection pressure of the high-pressure re-injection system.

[0067] The control of the temperature and pressure of the well stream in the first process pipeline includes:

[0068] Based on the platform design pressure, when the first controller 4 controls the regulating valve, the pressure of the oil-gas mixture meets the platform design requirements; based on the experimental data or predicted data of the well stream components and the monitoring data of the first temperature and pressure sensor 2, perform PVT calculation and dynamic simulation of the separation process, optimize the heat exchange temperature setting of the first heat exchanger 8, and realize the parameter control of the first heat exchanger 8 through the first controller 4;

[0069] The control of the temperature and pressure of the gas phase in the gas phase process pipeline includes:

[0070] Based on the temperature and pressure parameters at the gas phase outlet of the production separator 14, the temperature and pressure parameters and density parameters at the outlet of the second-stage compressor 24 are fed back to the second parameter calculator 26 for calculation to obtain the heat exchanger temperature control target and the outlet pressure control value of the second-stage compressor 24, which are fed back to the control parameters of the second controller 25 to control the fluid flow rate of the heat exchanger and the frequency converters of each stage of the compressor, thereby realizing the transformation of carbon dioxide in the gas phase mixture from the gas phase to the dense-phase state;

[0071] Controlling the separation rate of the dense-phase carbon dioxide and light hydrocarbons in the multi-stage riser separator includes:

[0072] Based on the observed values of the third temperature and pressure sensor 27, the first densitometer 29, and the second densitometer 42, they are brought into the self-learning model for optimizing the calculation of the separation rates of dense-phase carbon dioxide and light hydrocarbons in each stage of the separator. The calculation results are fed back to the set values of the control parameters of the third controller 31 for adjusting the outlet regulating valves of dense-phase carbon dioxide and light hydrocarbons in each stage of the separator.

[0073] The control of the dense-phase carbon dioxide injection pressure includes:

[0074] Based on the bottom-hole pressure prediction data, the current injection pressure is determined and set in the fourth controller 48. The rotation speed of the dense-phase carbon dioxide injection pump 44 is adjusted by using the PID control method based on the observed data of the fourth temperature and pressure sensor 47.

[0075] In step S2, for the physical property characteristics of the carbon dioxide and light hydrocarbon mixture, relevant experimental analyses are carried out to determine the influence of light hydrocarbons on the physical properties of carbon dioxide. Based on dynamic simulation, real-time flash calculation is performed on the gas-phase components under the current temperature and pressure conditions to determine the temperature and pressure conditions required for the current gas-phase component carbon dioxide to reach the dense phase. Considering that the temperature of the compressed gas will further increase, the temperature setting for heat exchange is first controlled to be near the calculated temperature. Then, according to the target outlet pressure of the second-stage compressor and the compressor performance curve, the frequency conversion control of each stage of the compressor is carried out in the form of cascade control to make it meet the dense-phase conditions.

[0076] In step S3, for the separation process of the multi-stage separator driven by the gravity and separation membrane of dense-phase carbon dioxide and light hydrocarbons, considering the carbon dioxide content and temperature and pressure conditions in the mixed components, combined with the separator size, dynamic simulation and relevant experimental studies are carried out. The research results are stored in the form of a database and brought into the data-driven model for modeling. Considering the deviation between the on-site data and the simulation and experimental results, an adaptive correction term is added to the model, and a self-learning model 30 can be finally formed based on the on-site data for parameter adjustment. Using this model, the separation rate parameters of dense-phase carbon dioxide and light hydrocarbons in the multi-stage separator are set, and the third controller 31 is designed by using the multi-input multi-output model-free adaptive method.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dense-phase carbon dioxide separation and reinjection device, characterized in that, it includes a first process pipeline, a second process pipeline, a gas-phase process pipeline, a liquid-phase process pipeline, a third process pipeline, a fourth process pipeline, a high-pressure injection pipeline, a first temperature and pressure regulation system, a gas-liquid separation system, a second temperature and pressure regulation system, a dense-phase carbon dioxide separation system, a separation speed control system, a high-pressure reinjection system and a reinjection pressure control system; The first process pipeline is used for the production well production fluid to flow in. The first temperature and pressure regulation system is arranged on the first process pipeline and is used to regulate the temperature and pressure of the fluid in the first process pipeline. The outlet of the first process pipeline is communicated with the second process pipeline; The outlet of the second process pipeline is communicated with the gas-liquid separation system. The gas-liquid separation system separates the gas phase and the liquid phase of the fluid. The liquid phase enters the crude oil treatment system through the liquid-phase process pipeline, and the gas phase enters the second temperature and pressure regulation system through the gas-phase process pipeline; The second temperature and pressure regulation system is used to compress the gas phase into a mixture of dense-phase carbon dioxide and light hydrocarbons. The outlet of the second temperature and pressure regulation system is communicated with the third process pipeline; The third process pipeline is communicated with the dense-phase carbon dioxide separation system. The dense-phase carbon dioxide separation system is used to separate the dense-phase carbon dioxide and light hydrocarbons. The separation speed control system is arranged on the third process pipeline and is used to control the separation speed of the dense-phase carbon dioxide separation system; The outlet of the dense-phase carbon dioxide separation system is communicated with the high-pressure reinjection system through the fourth process pipeline. The high-pressure reinjection system reinjects the dense-phase carbon dioxide to the bottom of the well through the high-pressure injection pipeline. The reinjection pressure control system is arranged on the high-pressure injection pipeline and is used to control the reinjection pressure; The first temperature and pressure regulation system includes a first temperature and pressure sensor, a first pressure regulating valve, a first pressure sensor, a first pressure controller and a first parameter calculator. The first temperature and pressure sensor and the first pressure sensor are respectively arranged upstream and downstream of the first pressure regulating valve. The first temperature and pressure sensor is used to detect the pressure and temperature of the fluid in the first process pipeline and feed the detected data back to the first parameter calculator. The first parameter calculator sends a control instruction to the first pressure regulating valve for pressure control to meet the platform design pressure. The first pressure sensor is used to detect the pressure in the first process pipeline after regulation and feed the detected value back to the first pressure controller; The first temperature and pressure regulation system further includes a first heat exchange system. The first heat exchange system includes a first heat exchanger, a heat exchanger outlet temperature sensor, a heat exchanger outlet valve, and a heat exchanger bypass valve. The first parameter calculator controls the heat exchange temperature of the first heat exchanger according to the data of the first temperature and pressure sensor and the first pressure regulating valve. The heat exchanger outlet temperature sensor is used to detect the temperature of the outlet fluid of the first heat exchanger. The heat exchange temperature setting of the first temperature and pressure regulation system is automatically determined whether heat exchange is required and the heat exchange temperature is dynamically set based on the first temperature and pressure sensor, the throttling condition of the first pressure regulating valve, and the first parameter calculator. According to the set value, the first pressure controller controls the regulating valve inside the first heat exchanger to control the flow rate and pressure of the cold fluid. The second temperature and pressure regulation system includes a multi-stage compressor system and a second heat exchange system. The multi-stage compressor system and the second heat exchange system are respectively used to regulate the pressure and temperature of the gas phase to compress the gas phase into a mixture of dense-phase carbon dioxide and light hydrocarbons. The multi-stage compressor system includes a first-stage compressor and a second-stage compressor. The first-stage compressor and the second-stage compressor are connected in sequence. The gas phase flow pipeline is communicated with the first-stage compressor, and the second-stage compressor is communicated with the third flow pipeline. The second heat exchange system includes a second temperature and pressure sensor, a second heat exchanger, a second controller, and a second parameter calculator. The second temperature and pressure sensor is used to detect the temperature and pressure of the gas phase in the gas phase flow pipeline and feed the detected data back to the second parameter calculator. The second parameter calculator sends a control instruction to the second controller. The second controller controls the heat exchange temperature of the second heat exchanger and the frequency conversion of the first-stage compressor and the second-stage compressor to realize the transformation of carbon dioxide in the gas phase mixture from the gas phase to the dense phase state. The second temperature and pressure regulation system further includes a third temperature and pressure sensor and a first density meter arranged on the third flow pipeline. The third temperature and pressure sensor is used to detect the temperature and pressure of the dense-phase carbon dioxide and light hydrocarbon mixture in the third flow pipeline. The first density meter is used to detect the density of the dense-phase carbon dioxide and light hydrocarbon mixture in the third flow pipeline. The third temperature and pressure sensor and the first density meter feed the detected data back to the second parameter calculator. The second parameter calculator controls the fluid flow rate in the second heat exchanger and the frequency conversion of the multi-stage compressor system according to the data detected by the third temperature and pressure sensor, the first density meter, and the second temperature and pressure sensor, thereby realizing the transformation of carbon dioxide in the gas phase mixture from the gas phase to the dense phase state.

2. The dense-phase carbon dioxide separation and reinjection device according to claim 1, characterized in that The dense-phase carbon dioxide separation system includes multiple vertical pipe separators, which are sequentially connected by pipelines. A carbon dioxide membrane is provided in each of the vertical pipe separators. The carbon dioxide membrane is used to separate light hydrocarbons from dense-phase carbon dioxide. The adjacent two-level vertical pipe separators are connected by a first pipeline and a second pipeline. The first pipeline and the second pipeline are respectively used for light hydrocarbons and dense-phase carbon dioxide to pass through. One outlet of the multiple vertical pipe separators is used for discharging the light hydrocarbons, and the other outlet is connected to the high-pressure injection system through the high-pressure injection pipeline.

3. The dense-phase carbon dioxide separation and injection device according to claim 2, characterized in that the multiple vertical pipe separators include three levels. A carbon dioxide membrane is provided in each of the three-level vertical pipe separators. A first light hydrocarbon regulating valve and a first carbon dioxide regulating valve are respectively provided on the first pipeline and the second pipeline between the first-level vertical pipe separator and the second-level vertical pipe separator. A second light hydrocarbon regulating valve and a second carbon dioxide regulating valve are respectively provided on the first pipeline and the second pipeline between the second-level vertical pipe separator and the third-level vertical pipe separator; The separation speed control system includes the first light hydrocarbon regulating valve, the first carbon dioxide regulating valve, the second light hydrocarbon regulating valve, the second carbon dioxide regulating valve, a second densitometer provided on the fourth process pipeline, a third controller, and a processing unit. A self-learning model is stored in the processing unit. The third temperature and pressure sensor, the first densitometer, and the second densitometer feedback the detected signals to the processing unit. The processing unit sends control instructions to the third controller according to the detected signals. The third controller controls the actions of the first light hydrocarbon regulating valve, the first carbon dioxide regulating valve, the second light hydrocarbon regulating valve, and the second carbon dioxide regulating valve according to the control instructions.

4. The dense-phase carbon dioxide separation and injection device according to claim 2, characterized in that the high-pressure injection system includes an injection pump and a dense-phase carbon dioxide outlet valve. The inlet of the injection pump is connected to the fourth process pipeline, and the outlet is connected to the high-pressure injection pipeline. The dense-phase carbon dioxide outlet valve is provided on the high-pressure injection pipeline; the injection pressure control system includes a fourth temperature and pressure sensor and a fourth controller. The fourth temperature and pressure sensor is provided at the outlet end of the injection pump for detecting the outlet pressure of the injection pump and feeding back the detected data to the fourth controller. The fourth controller adjusts the motor speed of the injection pump according to the feedback signal to meet the pressure requirements for dense-phase carbon dioxide injection.

5. A control method for a dense-phase carbon dioxide separation and injection device according to any one of claims 2 to 4, characterized in that it includes the steps of: controlling the temperature and pressure of the well fluid in the first process pipeline to make the temperature and pressure of the well fluid in the first process pipeline meet the platform design requirements; controlling the temperature and pressure of the gas phase in the gas phase process pipeline to convert the carbon dioxide in the gas phase into dense-phase carbon dioxide; Control the separation rate of dense-phase carbon dioxide and light hydrocarbons in the multi-stage riser separator to separate the dense-phase carbon dioxide and light hydrocarbons. Control the injection pressure of the high-pressure injection system.

6. The control method according to claim 5, characterized in that the control of the temperature and pressure of the well stream in the first process pipeline includes the steps of: Detect the pressure and temperature of the fluid in the first process pipeline through the first temperature and pressure sensor and feed the detected data back to the first parameter calculator. The first parameter calculator sends a control instruction to the first pressure regulating valve for pressure control to make the pressure in the first process pipeline meet the platform design pressure. The first pressure sensor detects the pressure in the adjusted first process pipeline and feeds the detected data back to the first pressure controller; Control the heat exchange temperature of the first heat exchanger by the first parameter calculator according to the data of the first temperature and pressure sensor and the first pressure regulating valve; The control of the temperature and pressure of the gas phase in the gas phase process pipeline includes the steps of: The second parameter calculator calculates the temperature control target of the second heat exchanger and the outlet pressure control values of the first-stage compressor and the second-stage compressor based on the temperature and pressure parameters at the gas phase outlet of the production separator, the temperature and pressure parameters at the outlet of the second-stage compressor, and the density parameter of the first densitometer; Feed the temperature control target of the second heat exchanger and the outlet pressure control values of the first-stage compressor and the second-stage compressor back into the control parameters of the controller to control the fluid flow rate of the heat exchanger and the frequency converters of each stage of the compressor, so as to realize the transformation of carbon dioxide in the gas phase mixture from the gas phase to the dense phase state.

7. The control method according to claim 5, characterized in that controlling the separation rate of dense-phase carbon dioxide and light hydrocarbons in the multi-stage riser separator includes: Bring the observed values of the second temperature and pressure sensor, the first densitometer, and the second densitometer into the self-learning model for optimization calculation of the separation rates of dense-phase carbon dioxide and light hydrocarbons in each stage of the separator. The calculation results are fed back into the third controller for adjusting the outlet regulating valves of dense-phase carbon dioxide and light hydrocarbons in each stage of the riser separator.

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