Dense-phase carbon dioxide injection system

Abstract

The invention discloses a dense-phase carbon dioxide injection system. The device comprises an injection device and a control system, wherein a liquid inlet control valve I of the injection device, a buffer tank, a pump liquid inlet valve, a filter, a pump liquid inlet flow meter, an injection pump, a pump liquid outlet one-way valve, a pump liquid outlet flow meter and a pump liquid outlet valve are sequentially connected through a pipeline; the conveyed medium enters the tank body of the buffer tank, and the temperature of the medium in the tank body is regulated and controlled by the refrigerating device; the buffer tank and the pipeline are further provided with a pressure, temperature and flow monitoring device connected with the control system, the monitoring device transmits data in the operation process of the injection device to the control system in real time, and the control system adjusts and controls the optimal operation efficiency of the injection system. The control system has the beneficial effects that the structural design and the control system design are reasonable, the inlet medium pressure and temperature are automatically adjusted and stabilized, the pump efficiency reduction caused by the reduction of the pump inlet medium density in the pump operation process is reduced, and the injection system is controlled to operate in a high-efficiency interval.

Description

Technical Field

[0001] This invention relates to a carbon dioxide injection system, and more particularly to a dense-phase carbon dioxide injection system, belonging to the field of oil and gas development technology. Background Technology

[0002] Carbon dioxide enhanced oil recovery (COLOR) is a method used in oil and gas development to improve oil recovery rates and is considered the best way to improve resource utilization efficiency. In recent years, the application of COLOR technology in unconventional and challenging reservoirs has become increasingly economically feasible. Based on reservoir deployment and implementation schedules, an economical model of low-pressure supercritical transport and high-pressure supercritical injection has been established, optimizing supercritical compressor injection into dense-phase injection for greater economic efficiency. Pure carbon dioxide has a critical point of 7.38 MPa and 31.1℃; it exists in a dense-phase state when the carbon dioxide pressure is higher than the critical pressure and the temperature is lower than the critical temperature.

[0003] Currently, the pump efficiency of high-density phase carbon dioxide plunger injection pumps is relatively low. Although the efficiency of dense phase injection pumps is low, they still have a certain cost-benefit advantage compared to compressors. Therefore, improving pump efficiency is a current research direction. The density of dense phase carbon dioxide is greatly affected by temperature and pressure. Increased temperature and decreased pressure will cause its density to drop sharply. After the density of the liquid entering the injection pump decreases, the pump efficiency drops exponentially. In order to ensure that the injection device operates in the high-efficiency range, there is an urgent need to develop an intelligent automatic control injection system. Summary of the Invention

[0004] To overcome the low pump efficiency of existing high-density phase carbon dioxide plunger injection pumps, this invention provides a dense phase carbon dioxide injection system.

[0005] The technical solution adopted by the present invention to solve its technical problem is: a dense phase carbon dioxide injection system, including an injection device and a control system. The injection device consists of an inlet control valve I, a buffer tank, a pump inlet valve, a filter, a pump inlet flow meter, an injection pump, a pump outlet check valve, a pump outlet flow meter, and a pump outlet valve connected in sequence through pipelines.

[0006] The transported medium enters the buffer tank, and the temperature of the medium inside the tank is regulated by a refrigeration unit.

[0007] The buffer tank and pipeline are also equipped with pressure, temperature and flow monitoring devices connected to the control system. The monitoring devices transmit the data of the injection device operation process to the control system in real time, and the control system adjusts the injection device to achieve the best working efficiency.

[0008] A liquid inlet branch line is provided in parallel with the liquid inlet control valve I. The liquid inlet branch line is provided with liquid inlet control valve II and a shielded booster pump in sequence.

[0009] The buffer tank is an insulated vortex buffer tank. The head, tank body, and settling end of the buffer tank are connected in sequence from top to bottom, and an insulation layer is provided on the outside of the tank body.

[0010] The end cap is equipped with a pressure transmitter for monitoring the pressure inside the buffer tank; the tank body is equipped with a buffer tank temperature transmitter.

[0011] The buffer tank inlet pipe enters the tank tangentially, and an erosion-resistant plate is provided at the end of the inlet pipe that causes the medium to swirl along the tank wall.

[0012] The refrigeration exchanger of the refrigeration device is located inside the tank, and the refrigeration unit is installed outside the tank. The refrigeration exchanger and the refrigeration unit are connected by pipelines and establish a circulation.

[0013] The pump inlet flow meter and the injection pump are connected by a pump inlet pressure transmitter and a pump inlet temperature transmitter.

[0014] An accumulator, a pump outlet temperature transmitter, and a pump outlet pressure transmitter are installed on the connecting pipe between the injection pump and the pump outlet check valve.

[0015] The pipeline is equipped with two or more vent valves.

[0016] The control system includes:

[0017] Preset unit, sets the boundary condition values ​​of control parameters;

[0018] The monitoring unit monitors the operating data of the injection device and transmits the data to the control system in real time.

[0019] The control unit, based on the calculation and analysis results of the injection device operation data transmitted by the monitoring unit, issues operation commands to control the injection system to start / stop / alarm.

[0020] The execution unit adjusts and controls the operating state of each component in the injection device according to the instructions issued by the control unit, so as to achieve the optimal efficiency of the injection system.

[0021] The preset unit presets the parameter values ​​of the pumped medium, including: the pressure and temperature of the pumped liquid, the flow difference alarm value, the filter pressure difference alarm value, and the boundary condition values ​​of the control program.

[0022] The monitoring unit monitors the following operating data of the injection device: buffer tank pressure, buffer tank temperature, pump inlet flow rate, pump inlet pressure, pump inlet temperature, pump outlet pressure, pump outlet temperature, and pump outlet flow rate. It also transmits the monitored operating data of the injection device to the control unit in real time.

[0023] The control unit is equipped with an automatic control program that includes pump inlet pressure, pump inlet temperature, flow alarm, filter alarm, injection system start-up, and injection system stop.

[0024] The execution unit controls the state of relevant components according to the program of the control unit. The relevant components include: inlet control valve I, inlet control valve II, shielded booster pump, pump inlet valve, reflux cut-off regulating valve, pump outlet valve, buffer tank drain valve, pump inlet pipeline vent valve, pump outlet pipeline vent valve I, and pump outlet pipeline vent valve II.

[0025] The start / stop procedure of the injection system can be automatic or manual.

[0026] The beneficial effects of the invention are that the structural design and control system design are reasonable, automatically adjusting and stabilizing the inlet medium pressure and temperature, reducing the decrease in pump efficiency caused by the decrease in the density of the pump inlet medium during pump operation, controlling the injection system to operate in the high-efficiency range; realizing automatic acquisition, analysis, calculation, real-time recording and display of system injection efficiency, and improving the intelligence and automation of the injection system. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the dense phase carbon dioxide injection device of the present invention.

[0028] Figure 2 This is a schematic diagram of the control system of the present invention.

[0029] Figure 3 This is a flowchart of the injection system startup control of the present invention.

[0030] Figure 4 This is a flowchart of the injection system stop control of the present invention.

[0031] Figure 5 This is a flowchart of the pressure limiting control of the present invention.

[0032] Figure 6 This is a flowchart of the temperature limiting control of the present invention.

[0033] Figure 7 This is a flowchart of the flow alarm control of the present invention.

[0034] Figure 8 This is a flowchart of the filter alarm control process of the present invention.

[0035] In the diagram: 1. Inlet control valve I, 2. Inlet control valve II, 3. Shielded booster pump, 4. End cap, 5. Buffer tank pressure transmitter, 6. Erosion-resistant plate, 7. Buffer tank temperature transmitter, 8. Refrigerator, 9. Buffer tank drain valve, 10. Tank body, 11. Refrigeration exchanger, 12. Settling end, 13. Pump inlet valve, 14. Filter, 15. Pump inlet flow meter, 16. Pump inlet pressure transmitter, 17. Pump inlet temperature transmitter, 18. Injection pump, 19. Pump outlet safety valve, 20. Accumulator, 21. Pump outlet temperature transmitter 22. Pump outlet pressure transmitter, 23. Reflux shut-off regulating valve, 24. Reflux check valve, 25. Pump outlet check valve, 26. Pump outlet flow meter, 27. Pump outlet valve, 28. Pump inlet line vent valve, 29. Pump outlet line vent valve I, 30. Pump outlet line vent valve II, 31. Pipeline, 32. Inlet line, 33. Inlet branch line, 34. Buffer tank vent line, 40. Buffer tank, 50. Refrigeration unit, 100. Preset unit, 200. Monitoring unit, 300. Control unit, 400. Execution unit. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments. However, those skilled in the art should understand that the present invention is not limited to the specific embodiments listed, and any embodiment that conforms to the spirit of the present invention should be included within the scope of protection of the present invention.

[0037] In the description of this invention, it should be noted that the terms "vertical", "up", "down", "left", "right", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing or simplifying the description of this invention, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, a connection can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection, or an integral connection; it can be a mechanical connection or an indirect connection through an intermediate medium; it can also refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] The present invention provides a dense phase carbon dioxide injection system, comprising an injection device and a control system.

[0040] See appendix Figure 1The injection device consists of an inlet control valve I1, a buffer tank 40, a pump inlet valve 13, a filter 14, a pump inlet flow meter 15, an injection pump 18, a pump outlet check valve 25, a pump outlet flow meter 26, and a pump outlet valve 27, which are connected in sequence via a pipe 31.

[0041] The transported medium (dense phase liquid carbon dioxide) enters the tank body 10 of the buffer tank 40, and the temperature of the medium inside the tank body 10 is regulated by the refrigeration device 50.

[0042] The buffer tank 40 and pipeline 31 are also equipped with pressure, temperature and flow monitoring devices connected to the control system. The monitoring devices transmit the data of the injection device operation process to the control system in real time, and the control system adjusts and controls the injection system to achieve the best working efficiency.

[0043] An inlet pipeline 32 connected to the inlet control valve I1 is connected in parallel with an inlet branch line 33. An inlet control valve II2 and a canned booster pump 3 are sequentially installed on the inlet branch line 33. When the pump inlet pressure delivered by the inlet pipeline 32 meets the inlet pressure limit, the inlet control valve I1 is opened, and the inlet control valve II2 and the canned booster pump 3 on the inlet branch line 33 are closed. When the pump inlet pressure in the inlet pipeline 32 is lower than the pump inlet pressure limit, the inlet control valve I1 is closed, and the inlet control valve II2 and the canned booster pump 3 on the inlet branch line 33 are opened.

[0044] The buffer tank 40 is an insulated vortex buffer tank. The medium being transported swirls inside the tank, ensuring that heavy impurities in the medium are separated away from the outlet of the buffer tank due to gravity, while stabilizing the pressure of the medium inside the buffer tank and reducing pressure pulsation.

[0045] The buffer tank 40 is connected from top to bottom in the form of end cap 4, tank body 10, and settling end 12. An insulation layer is provided on the outside of the tank body 10 to slow down the heat exchange between the medium inside the tank 10 and the external environment.

[0046] The end cap 4 is equipped with a buffer tank pressure transmitter 5, and the tank body 10 is equipped with a buffer tank temperature transmitter 7, which are used to monitor the pressure and temperature inside the buffer tank 40 and transmit the monitoring data to the control system in real time.

[0047] The inlet pipe of the buffer tank 40 enters the tank body 10 tangentially. An erosion-resistant plate 6 is installed at the end of the inlet pipe entering the tank body 10 to cause the medium to swirl along the tank wall. The erosion-resistant plate 6 forces the medium to form a swirling flow along the tank wall, effectively resisting erosion and extending the service life of the tank. The buffer tank body 10 is provided with an inlet pipe and an outlet pipe for conveying the medium. Preferably, the inlet pipe is positioned higher than the outlet pipe.

[0048] The refrigeration device 50 includes a refrigeration exchanger 11 and a cooler 8. The refrigeration exchanger 11 is installed inside the tank 10, and the cooler 8 is installed outside the tank 10. The refrigeration exchanger 11 and the cooler 8 are connected by pipelines and establish circulation. According to the settings of the control system, the temperature of the medium in the buffer tank 40 is adjusted to meet the process design requirements.

[0049] The settling end 12 is welded and fixed to the lower end of the tank body 10. The settling end 12 is funnel-shaped, and the lower outlet of the settling end 12 is connected to the buffer tank venting pipeline 34, which is equipped with a buffer tank drain valve 9.

[0050] A pump inlet pressure transmitter 16 and a pump inlet temperature transmitter 17 are installed on the connecting pipe between the pump inlet flow meter 15 and the injection pump 18; an accumulator 20, a pump outlet temperature transmitter 21, and a pump outlet pressure transmitter 22 are sequentially installed on the connecting pipe between the injection pump 18 and the pump outlet check valve 25. The accumulator 20 is used to stabilize the pump outlet medium pressure and reduce pressure pulsation.

[0051] The pipeline 31 is equipped with two or more vent valves, including but not limited to: a pump inlet vent valve 28 on the connecting pipeline between the pump inlet valve 13 and the filter 14; a pump outlet safety valve 19 on the connecting pipeline between the injection pump 18 and the pump outlet accumulator 20; a reflux check valve 24, a reflux shut-off regulating valve 23, and a pump outlet vent valve I 29 sequentially installed on the connecting pipeline between the pump inlet flow meter 15 and the injection pump 18; and a pump outlet vent valve II 30 on the connecting pipeline between the pump outlet check valve 25 and the pump outlet flow meter 26. When venting is required during the operation of the injection device, the relevant vent valves are opened and closed to ensure the safety of the injection system. The vent valves of the injection device can be connected to the control system for automatic control or can be manually controlled.

[0052] The control system includes a preset unit 100, a monitoring unit 200, a control unit 300, and an execution unit 400, wherein:

[0053] The preset unit 100 sets the boundary condition values ​​of the control parameters.

[0054] The preset unit 100 presets the parameter values ​​of the pumped medium, including: the pressure and temperature of the pumped liquid, the alarm value of the difference between the inlet and outlet flow rates of the injection pump 18, the alarm value of the difference between the inlet and outlet pressures of the filter 14, and the boundary condition values ​​of the set control program.

[0055] The monitoring unit 200 monitors the operating data of the injection device and transmits the data to the control system in real time.

[0056] The monitoring unit 200 monitors the operation data of the injection device, including but not limited to: buffer tank pressure, buffer tank temperature, pump inlet flow rate, pump inlet pressure, pump inlet temperature, pump outlet pressure, pump outlet temperature, pump outlet flow rate, etc., and transmits the monitored operation data of the injection device to the control unit 300 in real time.

[0057] The control unit 300, based on the calculation and analysis results of the injection device operation data transmitted by the monitoring unit 200, issues operation commands to control the injection system to start / stop / alarm.

[0058] The control unit 300 is equipped with an automatic control program that includes pump inlet pressure, pump inlet temperature, flow alarm, filter alarm, injection system start-up, and injection system stop. The injection system start / stop program can be automatically controlled by the control system or manually controlled.

[0059] The execution unit 400 adjusts and controls the operating state of each component in the injection system according to the instructions issued by the control unit 300, so as to achieve the optimal efficiency of the injection system.

[0060] The execution unit 400 controls the state of relevant components according to the program of the control unit 300; the relevant components include, but are not limited to: inlet control valve I1, inlet control valve II2, shielded booster pump 3, pump inlet valve 13, reflux cut-off regulating valve 23, pump outlet valve 27, buffer tank drain valve 9, pump inlet pipeline vent valve 28, pump outlet pipeline vent valve I29, pump outlet pipeline vent valve II30, etc.

[0061] Example

[0062] A dense phase carbon dioxide injection system includes an injection device and a control system. The injection device delivers dense phase liquid carbon dioxide as the medium. During the medium delivery process, it maintains a stable temperature and pressure and automatically controls the injection system to ensure that the injection system operates in a high-efficiency range.

[0063] The injection device's inlet control valve I1, buffer tank 40, pump inlet valve 13, filter 14, pump inlet flow meter 15, injection pump 18, pump outlet check valve 25, pump outlet flow meter 26, and pump outlet valve 27 are connected sequentially via pipe 31 (e.g., Figure 1 (As shown).

[0064] An inlet pipeline 32 connected to the inlet control valve I1 is connected in parallel with an inlet branch line 33. An inlet control valve II2 and a canned booster pump 3 are sequentially installed on the inlet branch line 33. When the pump inlet pressure delivered by the inlet pipeline 32 meets the inlet pressure limit, the inlet control valve I is opened, and the inlet control valve II2 of the inlet branch line 33 and the canned booster pump 3 are closed. When the pump inlet pressure of the inlet pipeline 32 is lower than the pump inlet pressure limit, the inlet control valve I1 is closed, and the inlet control valve II2 of the inlet branch line 33 and the canned booster pump 3 are opened, thereby ensuring that the pressure of the delivered medium meets the process design requirements.

[0065] The buffer tank 40 and pipeline 31 are equipped with pressure, temperature, and flow monitoring devices connected to the control system. These monitoring devices transmit data from the injection system to the control system in real time, allowing the control system to adjust the injection system to its optimal operating efficiency. Specifically, the standard end cap 4 of the buffer tank 40 is equipped with a buffer tank pressure transmitter 5, and the tank body 10 is equipped with a buffer tank temperature transmitter 7, used to monitor the pressure and temperature inside the buffer tank 40. The connection pipeline between the pump inlet flow meter 15 and the injection pump 18 is equipped with a pump inlet pressure transmitter 16 and a pump inlet temperature transmitter 17; the connection pipeline between the injection pump 18 and the pump outlet check valve 25 is sequentially equipped with an accumulator 20, a pump outlet temperature transmitter 21, and a pump outlet pressure transmitter 22, transmitting the monitored pressure, temperature, and flow data to the control system in real time.

[0066] The buffer tank 40 is an insulated vortex buffer tank. The buffer tank 40 includes a standard end cap 4, a tank body 10, and a settling end 12 welded from top to bottom. An insulation layer is provided on the outside of the tank body 10 to slow down the heat exchange between the medium inside the tank body 10 and the external environment.

[0067] The inlet pipe of the buffer tank 40 enters the tank body 10 tangentially. At the end of the inlet pipe entering the tank body 10, there is an erosion-resistant plate 6 that causes the medium to swirl along the tank wall. The erosion-resistant plate 6 forces the medium to form a swirling flow along the tank wall, which can effectively resist the erosion of the medium.

[0068] The buffer tank 40 is equipped with a refrigeration device 50 for regulating the temperature of the medium inside the tank 10. The refrigeration exchanger 11 of the refrigeration device 50 is located inside the tank 10, and the cooler 8 is installed outside the tank 10. The refrigeration exchanger 11 and the cooler 8 are connected by pipelines and establish circulation. According to the settings of the control system, the temperature of the medium inside the buffer tank 40 is adjusted to meet the process design requirements.

[0069] The settling end 12 is funnel-shaped, and the lower outlet of the settling end 12 is connected to a buffer tank venting pipe 34, which is equipped with a buffer tank drain valve 9.

[0070] The injection device's connecting pipe 31 is equipped with multiple vent valves, including: a pump inlet vent valve 28 on the connecting pipe between the pump inlet valve 13 and the filter 14; a pump outlet safety valve 19 on the connecting pipe between the injection pump 18 and the pump outlet accumulator 20; a reflux check valve 24, a reflux shut-off regulating valve 23, and a pump outlet vent valve I 29 sequentially installed on the connecting pipe between the pump inlet flow meter 15 and the injection pump 18; and a pump outlet vent valve II 30 on the connecting pipe between the pump outlet check valve 25 and the pump outlet flow meter 26. All vent valves of the injection device are connected to the control system, and the control system controls the state of the vent valves.

[0071] The control system includes a preset unit 100, a monitoring unit 200, a control unit 300, and an execution unit 400 (e.g., ...). Figure 2 As shown), where:

[0072] The preset unit 100 sets the boundary condition values ​​(limited values) of the control parameters.

[0073] The preset parameter values ​​of the preset unit 100 include: the pressure and temperature of the pump inlet liquid, the flow difference alarm value, the pressure difference alarm value of the filter 14, and the boundary condition values ​​of the set control program.

[0074] The monitoring unit 200 monitors the operating data of the injection device and transmits the data to the control system in real time.

[0075] The monitoring unit 200 monitors the following operating data of the injection device: buffer tank pressure, buffer tank temperature, pump inlet flow rate, pump inlet pressure, pump inlet temperature, pump outlet pressure, pump outlet temperature, and pump outlet flow rate. It also transmits the monitored operating data of the injection device to the control unit 300 in real time.

[0076] The control unit 300, based on the calculation and analysis results of the injection device operation data transmitted by the monitoring unit 200, issues operation commands to control the injection system to start / stop / alarm.

[0077] The control unit 300 is equipped with an automatic control program that includes pump inlet pressure, pump inlet temperature, flow alarm, filter alarm, injection system start-up, and injection system stop. The injection system start / stop program includes both automatic and manual control.

[0078] The execution unit 400 adjusts and controls the operating state of each component in the injection device according to the instructions issued by the control unit 300, so as to achieve the optimal efficiency of the injection system.

[0079] The execution unit 400 controls the state of relevant components according to the program of the control unit 300; the relevant components include: inlet control valve I1, inlet control valve II2, shielded booster pump 3, pump inlet valve 13, reflux cut-off regulating valve 23, pump outlet valve 27, buffer tank drain valve 9, pump inlet pipeline vent valve 28, pump outlet pipeline vent valve I29, pump outlet pipeline vent valve II30, etc.

[0080] See appendix Figure 2-8 The relevant control program for the injection system is as follows:

[0081] (1) Automatic control program for pump inlet pressure (e.g.) Figure 5 (As shown)

[0082] The system reads the pump inlet pressure limit value from the preset unit 100 and analyzes and judges the status of the pump inlet valve 13. If the pump inlet valve 13 is not open, an alarm will be set to "Pump inlet valve closed" and the display will show "Pump inlet valve closed". If the pump inlet valve 13 is open, the display will show "Pump inlet valve open".

[0083] The system periodically collects monitoring data from the pump inlet pressure transmitter 16 and displays the pump inlet pressure in real time. The control system analyzes and judges whether the pump inlet pressure is higher than or equal to the pump inlet pressure limit value. If the pump inlet pressure is higher than or equal to the pump inlet pressure limit value, it opens the inlet control valve I1 and displays "Inlet control valve I open", closes the canned booster pump 3 and displays "Canned booster pump closed", and closes the inlet control valve II2 and displays "Inlet control valve II closed". If the pump inlet pressure is lower than the pump inlet pressure limit value, it opens the inlet control valve II2 and displays "Inlet control valve II open", opens the canned booster pump 3 and displays "Canned booster pump open", and closes the inlet control valve I1 and displays "Inlet control valve I closed".

[0084] (2) Automatic control program for pump inlet temperature (e.g.) Figure 6 (As shown)

[0085] The system reads the pump inlet temperature limit value from the preset unit 100, analyzes and judges the status of the pump inlet valve 13. If the pump inlet valve 13 is not open, it will alarm: "Pump inlet valve closed" and display: "Pump inlet valve closed"; if the pump inlet valve 13 is open, it will display: "Pump inlet valve open".

[0086] The system periodically collects monitoring data from the pump inlet temperature transmitter 17 and displays the pump inlet temperature in real time. The control system analyzes and judges whether the pump inlet temperature is higher than or equal to the pump inlet temperature limit value. If so, it shuts off the cooler 8 and displays "Cooler Off"; if so, it turns on the cooler 8 and displays "Cooler On".

[0087] (3) Automatic flow alarm control (e.g.) Figure 7 (As shown)

[0088] The system reads the flow difference alarm limit value of the preset unit 100, analyzes and judges the status of the pump inlet valve 13. If the pump inlet valve 13 is not open, the alarm is "Pump inlet valve closed" and the display is "Pump inlet valve closed"; if the pump inlet valve 13 is open, the display is "Pump inlet valve open".

[0089] The control system analyzes and judges the status of the pump outlet valve 27. If the pump outlet valve 27 is not open, it will alarm: "Pump outlet valve closed" and display: "Pump outlet valve closed"; if the pump outlet valve 27 is open, it will display: "Pump outlet valve open".

[0090] The control system analyzes and judges the status of the reflux shut-off regulating valve 23. If the reflux shut-off regulating valve 23 is not closed, an alarm will be set to "Reflux shut-off regulating valve is open" and the display will show "Reflux shut-off regulating valve is open". If the reflux shut-off regulating valve 23 is closed, the display will show "Reflux shut-off regulating valve is closed".

[0091] The system monitors the pump outlet flow rate and pump inlet flow rate of the injection device. The control system analyzes and judges the difference between the pump outlet flow rate and the pump inlet flow rate. If the difference is greater than the flow difference alarm limit value, it displays "Flow difference abnormal" and alarms "Flow difference too large, please check equipment status, injection pump stop", and starts the injection system shutdown procedure; if the difference is less than or equal to the flow difference alarm limit value, it displays "Flow normal".

[0092] (4) Automatic alarm control for filters (e.g.) Figure 8 (As shown)

[0093] The differential pressure alarm limit value of filter 14 in preset unit 100 is read, and the control system analyzes and judges the status of pump inlet valve 13. If pump inlet valve 13 is not open, an alarm is set to "pump inlet valve closed" and the display shows "pump inlet valve closed"; if pump inlet valve 13 is open, the display shows "pump inlet valve open".

[0094] The pressure in buffer tank 40, i.e., the upstream pressure of the filter, is monitored by buffer tank pressure transmitter 5. The pump inlet pressure, i.e., the downstream pressure of the filter, is monitored by pump inlet pressure transmitter 16. The control system analyzes and judges the difference between the upstream and downstream pressures of the filter. If the difference is greater than the filter differential pressure alarm limit, an alarm is triggered: "Filter blocked"; if the difference is less than or equal to the filter differential pressure alarm limit, the display shows: "Filter normal".

[0095] (5) Injection system startup control (e.g.) Figure 3 (As shown)

[0096] Upon receiving the start command, the control program of the injection system is initiated.

[0097] Close the buffer tank drain valve 9, and the display will show: "Buffer tank drain valve closed"; open the inlet control valve I1, and the display will show: "Inlet control valve I open"; open the pump inlet valve 13, and the display will show: "Pump inlet valve open"; open the reflux shut-off regulating valve 23, and the display will show: "Reflux shut-off regulating valve open"; open the pump outlet tank pipeline vent valve II30, and the display will show: "Pump outlet pipeline vent valve II open"; warning: "Pipeline venting".

[0098] The control system analyzes and judges the data of pump inlet temperature and buffer tank temperature. If the pump inlet temperature is higher than the buffer tank temperature, it will issue a warning: "Pump to start, pipeline venting". If the pump inlet temperature is lower than or equal to the buffer tank temperature, it will close the pump outlet pipeline venting valve II30 and display: "Pump outlet pipeline venting valve II closed".

[0099] Start the injection pump 18, and the display will show: "Injection pump on"; open the pump outlet valve 27, and the display will show: "Pump outlet valve on"; close the reflux shut-off regulating valve 23, and the display will show: "Reflux shut-off regulating valve closed".

[0100] The automatic control program for pump inlet pressure, automatic control program for pump inlet temperature, automatic alarm control program for flow rate, and automatic alarm control program for filter are started. The system displays "System starting up" and the injection system begins operation.

[0101] (6) Injection system stop control (e.g.) Figure 4 As shown):

[0102] Upon receiving a stop command, the stop control program of the injection system is initiated.

[0103] Open the reflux shut-off regulating valve 23 and the display will show: "Reflux shut-off regulating valve open"; close the pump outlet valve 27 and the display will show: "Pump outlet valve closed"; close the injection pump 3 and the display will show: "Injection pump closed"; close the pump inlet valve 13 and the display will show: "Pump inlet valve closed".

[0104] The control system analyzes and judges the status of the inlet control valve I1. If the inlet control valve I1 is closed, the shielded booster pump 3 is turned off and the display shows: "Shielded booster pump closed". The inlet control valve II2 is turned off and the display shows: "Inlet control valve II closed". If the inlet control valve I1 is open, the inlet control valve I1 is turned off and the display shows: "Inlet control valve I closed".

[0105] Open the vent valve: Open the vent valve 28 of the pump inlet line, display: "Pump inlet line vent valve open" and warning: "Line venting". Open the vent valve I29 of the pump outlet line, display: "Pump outlet line vent valve I open" and warning: "Line venting". Open the vent valve II30 of the pump outlet line, display: "Pump outlet line vent valve II open" and warning: "Line venting".

[0106] The control system shown analyzes and judges the pump inlet pressure and pump outlet pressure. If the pump inlet pressure is equal to 0 and the pump outlet pressure is also equal to 0, then the pump inlet vent valve 28 is closed and the display shows: "Pump inlet vent valve closed"; the pump outlet vent valve I 29 is closed and the display shows: "Pump outlet vent valve I closed"; the pump outlet vent valve II 30 is closed and the display shows: "Pump outlet vent valve II closed".

[0107] Open the buffer tank drain valve 9, display: "Buffer tank drain valve open" and warning: "Pipeline vented"; The control system analyzes and judges the buffer tank pressure. If the buffer tank pressure is equal to 0, close the buffer tank drain valve 9 and display: "Buffer tank drain valve closed".

[0108] At the same time, the automatic control of pump inlet pressure, automatic control of pump inlet temperature, automatic flow alarm control, and automatic filter alarm control are stopped, and the system is displayed as "System stopped".

[0109] The dense-phase carbon dioxide injection system of this invention sets pressure and temperature limits for the pump inlet, flow difference alarm values, and filter pressure difference alarm values ​​in the control system. It monitors and collects data such as temperature, pressure, and flow rate of the injection system and transmits it to the control system in real time. The control program controls the states of inlet control valve I, inlet control valve II, the shielded booster pump, the pump inlet valve, the reflux shut-off regulating valve, the pump outlet valve, the buffer tank drain valve, the pump inlet pipeline vent valve, the pump outlet pipeline vent valve I, and the pump outlet pipeline vent valve II, solving the problem of unstable pump inlet medium pressure and temperature in conventional carbon dioxide liquid injection systems. It can automatically adjust and stabilize the inlet medium pressure and temperature, avoiding a decrease in pump efficiency due to a drop in pump inlet medium density, and ensuring the injection system always operates in the high-efficiency range. Simultaneously, it achieves automatic data acquisition, analysis, and calculation, and can record and display the system injection efficiency in real time, improving the intelligence and automation of the injection system.

[0110] This invention relates to a dense phase carbon dioxide injection system that ensures the injection pump inlet pressure and temperature fluctuate within a reasonable range. It automatically analyzes and judges the collected real-time data of the injection system, controls and adjusts the pump inlet pressure and temperature, and calculates and records the system injection efficiency in a timely manner. It is suitable for injection operations where the density of the medium is greatly affected by temperature and pressure, and is especially suitable for pressurized operations. It can be used for dense phase carbon dioxide injection operations in fields such as coalbed methane and oil and gas extraction.

[0111] It should be noted that the above embodiments are examples and not limitations of the present invention, and those skilled in the art will be able to design many alternative embodiments without departing from the scope of the claims of this patent.

Claims

1. A dense-phase carbon dioxide injection system, comprising an injection device and a control system, characterized in that: The injection device consists of inlet control valve I, buffer tank, pump inlet valve, filter, pump inlet flow meter, injection pump, pump outlet check valve, pump outlet flow meter, and pump outlet valve connected in sequence via pipelines. The transported medium enters the buffer tank, and the temperature of the medium inside the tank is regulated by the refrigeration unit; The buffer tank and pipeline are also equipped with pressure, temperature and flow monitoring devices connected to the control system. The monitoring devices transmit the data of the injection device operation process to the control system in real time, and the control system adjusts the injection device to achieve the best working efficiency.

2. The dense-phase carbon dioxide injection system according to claim 1, characterized in that: A liquid inlet branch line is provided in parallel with the liquid inlet control valve I. The liquid inlet branch line is provided with liquid inlet control valve II and a shielded booster pump in sequence.

3. The dense-phase carbon dioxide injection system according to claim 1 or 2, characterized in that: The buffer tank is an insulated vortex buffer tank. The head, tank body, and settling end of the buffer tank are connected in sequence from top to bottom, and an insulation layer is provided on the outside of the tank body. The end cap is equipped with a pressure transmitter for monitoring the pressure inside the buffer tank; the tank body is equipped with a buffer tank temperature transmitter. The buffer tank inlet pipe enters the tank tangentially, and an erosion-resistant plate is provided at the end of the inlet pipe that causes the medium to swirl along the tank wall.

4. The dense-phase carbon dioxide injection system according to claim 3, characterized in that: The refrigeration exchanger of the refrigeration device is located inside the tank, and the refrigeration unit is installed outside the tank. The refrigeration exchanger and the refrigeration unit are connected by pipelines and establish a circulation.

5. The dense-phase carbon dioxide injection system according to claim 4, characterized in that: The pump inlet flow meter and the injection pump are connected by a pump inlet pressure transmitter and a pump inlet temperature transmitter. An accumulator, a pump outlet temperature transmitter, and a pump outlet pressure transmitter are installed on the connecting pipe between the injection pump and the pump outlet check valve.

6. The dense-phase carbon dioxide injection system according to claim 5, characterized in that: The pipeline is equipped with two or more vent valves.

7. The dense-phase carbon dioxide injection system according to claim 1, characterized in that: The control system includes: Preset unit, sets the boundary condition values ​​of control parameters; The monitoring unit monitors the operating data of the injection device and transmits the data to the control system in real time. The control unit, based on the calculation and analysis results of the injection device operation data transmitted by the monitoring unit, issues operation commands to control the injection system to start / stop / alarm. The execution unit adjusts and controls the operating state of each component in the injection device according to the instructions issued by the control unit, so as to achieve the optimal efficiency of the injection system.

8. The dense-phase carbon dioxide injection system according to claim 7, characterized in that: The preset unit presets the parameter values ​​of the pumped medium, including: the pressure and temperature of the pumped liquid, the flow difference alarm value, the filter pressure difference alarm value, and the boundary condition values ​​of the control program.

9. The dense-phase carbon dioxide injection system according to claim 8, characterized in that: The monitoring unit monitors the following operating data of the injection device: buffer tank pressure, buffer tank temperature, pump inlet flow rate, pump inlet pressure, pump inlet temperature, pump outlet pressure, pump outlet temperature, and pump outlet flow rate. It also transmits the monitored operating data of the injection device to the control unit in real time.

10. The dense-phase carbon dioxide injection system according to claim 9, characterized in that: The control unit is equipped with an automatic control program that includes pump inlet pressure, pump inlet temperature, flow alarm, filter alarm, injection system start-up, and injection system stop.

11. The dense-phase carbon dioxide injection system according to claim 10, characterized in that: The execution unit controls the state of relevant components according to the program of the control unit; The relevant components include: inlet control valve I, inlet control valve II, shielded booster pump, pump inlet valve, reflux shut-off regulating valve, pump outlet valve, buffer tank drain valve, pump inlet line vent valve, pump outlet line vent valve I, and pump outlet line vent valve II.

12. The dense-phase carbon dioxide injection system according to claim 9, characterized in that: The start / stop procedure of the injection system can be automatic or manual.

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