Tail water recharge system of middle-deep geothermal well and working method

Abstract

The invention discloses a tail water recharge system of a middle-deep geothermal well and a working method, and particularly relates to a recharge well, a vacuum breaker, a flowmeter, a control system, a remote monitoring device, a steady flow tank, an impurity filtering device, a vacuum detection device and a temperature control device. According to the tail water recharge system of the middle-deep geothermal well and the working method, the vacuum breaker is additionally arranged in the recharge well, so that the problem of negative pressure generated in the recharge process is effectively solved, a vacuum column is prevented from being formed in a heating system, the heating effect is improved, the geothermal dynamic monitoring work is simplified, and the working efficiency is improved. The vacuum breaker is arranged so that tail water can be smoothly recharged into a heat storage layer, the situation that air enters a recharge system is avoided, the quality of the tail water is kept, a recharge channel is prevented from being blocked, the recharge efficiency is improved, complex equipment such as a sand remover, a filtering tank and an exhaust tank does not need to be arranged, the system structure is simplified, and the system cost is reduced. And meanwhile, the recharge efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of geothermal reinjection, and in particular to a tailwater reinjection system and its working method for medium-deep geothermal wells. Background Technology

[0002] Geothermal energy, as a renewable energy source, has broad application prospects, including power generation, heating, and greenhouse aquaculture. However, the geothermal extraction process generates a large amount of tailwater. Direct discharge of this tailwater causes thermal and chemical pollution and leads to a gradual decline in the static water level of geothermal wells, resulting in geothermal water depletion. To address this issue, geothermal tailwater reinjection technology has emerged. By reinjecting tailwater into the geothermal reservoir, the reservoir pressure is maintained, extending the lifespan of the geothermal field. Currently, geothermal tailwater reinjection mainly employs two methods: pressurized reinjection and negative pressure reinjection. Pressurized reinjection is typically used when the aquifer permeability of the reinjection well is poor, while negative pressure reinjection is used when the aquifer permeability is high. However, both methods have certain limitations. For example, negative pressure reinjection may lead to the formation of a vacuum column in the heating system, affecting the heating effect and making geothermal dynamic monitoring difficult. Furthermore, conventional negative pressure suppressors may allow air to enter the reinjection system, altering the tailwater quality and clogging the reinjection channels. To overcome these problems, researchers have been exploring more effective reinjection technologies. Existing reinjection systems typically include equipment such as desanders, filter tanks, and venting tanks. These devices not only increase the complexity and cost of the system but may also affect reinjection efficiency. In addition, while increasing the number of reinjection wells can increase the reinjection volume, it also significantly increases investment costs. Therefore, there is an urgent need for an innovative technology that can improve reinjection efficiency, reduce costs, and ensure stable system operation in order to achieve more efficient geothermal tailwater reinjection.

[0003] For example, CN112413914A discloses a negative pressure-free geothermal reinjection system and reinjection method. The system includes a flow stabilizing tank and a nitrogen compensation device. By setting up the flow stabilizing tank, the unstable pressure at the geothermal tailwater inlet is converted into a controllable pressure inside the flow stabilizing tank. The nitrogen compensation device is used to adjust the pressure balance between the flow stabilizing tank and the geothermal reinjection well. However, in practical applications, the system still has the problem that the structure design of the flow stabilizing tank is not optimized enough, making it difficult to completely convert the unstable pressure into a controllable pressure.

[0004] CN217489304A provides a tailwater reinjection system and working method for medium-deep geothermal wells. The system includes a reinjection wellbore, multiple well pipe segments, and a well pipe adjustment device. The well pipe adjustment device flexibly adjusts the opening or closing of each well pipe segment to determine the actual reinjection layer and pressure aquifer. However, in practical applications, the system still suffers from insufficient stability and reliability of the well pipe adjustment device.

[0005] Existing technologies have the following drawbacks: Conventional negative pressure reinjection systems may lead to the formation of vacuum columns within the heating system, affecting heating efficiency and making geothermal dynamic monitoring difficult. Furthermore, conventional negative pressure suppressors may allow air to enter the reinjection system, altering tailwater quality and clogging reinjection channels. Existing reinjection systems typically include desanders, filter tanks, and venting tanks, which not only increase system complexity and cost but may also affect reinjection efficiency. Traditional reinjection systems suffer from insufficient stability and reliability in the design of well casing adjustment devices, making it difficult to flexibly adjust the opening or closing of various well casing segments to determine the true reinjection layer and pressure aquifer. Existing reinjection systems still lack accuracy in wellhead pressure gauges and pressure meters, making it difficult to accurately monitor and control reinjection wellhead pressure and prevent the formation of negative pressure and air columns at the reinjection wellhead. Current reinjection systems lack intelligent control and remote monitoring capabilities, failing to automatically adjust reinjection volume and temperature based on the geothermal well's operating status and the treatment of geothermal tailwater, making it difficult to ensure the balance of geothermal energy storage and the sustainable development of geothermal wells during the reinjection process. Summary of the Invention

[0006] The main objective of this invention is to provide a tailwater reinjection system for medium-deep geothermal wells, which can effectively solve the problems of inaccurate flow meter data, low reinjection efficiency, and complex system structure caused by excessive negative pressure in the reinjection system.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A tailwater reinjection system for a medium-deep geothermal well includes a reinjection well, a vacuum breaker, a flow meter, a control system, a remote monitoring device, a flow stabilizing tank, an impurity filtration device, a vacuum detection device, and a temperature control device.

[0009] The reinjection well has 5 well pipe segments inside the well body, which are connected by an adjustable well pipe adjustment device; the wellhead of the reinjection well is equipped with a pressure gauge and a pressure meter for real-time monitoring and control of the wellhead pressure.

[0010] The vacuum breaker is installed at the wellhead of the reinjection well. Its structure includes a breaker shell, a breaker core, and a sealing ring. The breaker core has eight channels inside, and tiny pores are installed in the channels to evenly disperse the fluid flow rate and prevent fluid impact. The breaker shell is sealed to the wellhead to ensure airtightness.

[0011] The flow meter is installed below the wellhead of the reinjection well, with a measurement range of 0-100 L / min and a measurement accuracy of ±1%, and is used to monitor the reinjection flow rate in real time.

[0012] Preferably, the control system includes a PLC central controller, a nitrogen compensation device, a second electric valve, and a third electric valve. The PLC central controller is connected to a pressure gauge and a pressure meter signal, and is used to automatically control the opening and closing of the nitrogen compensation device, the second electric valve, and the third electric valve according to pressure feedback information to regulate the pressure in the reinjection well.

[0013] Preferably, the remote monitoring device includes a wireless communication module and a remote terminal. The remote terminal is installed in the control room of the geothermal well. The wireless communication module is used to transmit pressure, flow, temperature and system operating status data to the remote terminal in real time. The staff can monitor the system operation and adjust parameters through the remote terminal.

[0014] Preferably, the stabilizing tank is connected to the reinjection well via a pipeline to mitigate pressure fluctuations during the reinjection process and ensure reinjection stability.

[0015] Preferably, the impurity filtration device includes a filter screen and a sedimentation pipe. The filter screen is installed at the inlet of the reinjection pipe to filter larger impurities, and the sedimentation pipe is installed at the bottom of the reinjection pipe to filter sediment.

[0016] Preferably, the vacuum detection device includes a vacuum sensor and a vacuum relay. The vacuum sensor is used to detect the vacuum level in the reinjection well. The vacuum relay is connected to the vacuum sensor and the vacuum breaker. When the vacuum level reaches a preset threshold, the vacuum breaker is triggered to start and eliminate the negative pressure.

[0017] Preferably, the temperature control device includes a temperature sensor and a temperature control valve. The temperature sensor is used to detect the reinjection temperature, and the temperature control valve is connected to the temperature sensor and the PLC central controller to adjust the reinjection temperature according to the temperature signal.

[0018] This invention also discloses a working method for a tailwater reinjection system based on the aforementioned medium-deep geothermal well, the working steps of which are as follows:

[0019] S1: Start the reinjection system. The pressure gauge and pressure meter monitor the wellhead pressure in real time, the flow meter monitors the reinjection flow rate in real time, and the temperature sensor monitors the reinjection temperature in real time.

[0020] S2: The vacuum sensor detects the vacuum level in the reinjection well. When the vacuum level reaches a preset threshold, the vacuum relay triggers the vacuum breaker to start. The fluid flow rate is evenly dispersed through the 8 channels and pores in the breaker core to eliminate negative pressure.

[0021] S3: The PLC central controller receives pressure feedback information from the pressure gauge and pressure meter, and automatically controls the opening and closing of the nitrogen compensation device, the second electric valve and the third electric valve to adjust the pressure in the reinjection well; at the same time, it controls the temperature control valve according to the signal from the temperature sensor to adjust the reinjection temperature to the range that meets the requirements of geothermal energy storage.

[0022] S4: The wireless communication module transmits pressure, flow, temperature and system operating status data to a remote terminal in real time, allowing staff to monitor system operation through the remote terminal;

[0023] S5: Adjust the conduction or closure status of the five well pipe segments through the well pipe adjustment device to determine the actual reinjection layer and the pressure aquifer, and ensure that the tailwater is accurately reinjected into the thermal reservoir.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. By installing a vacuum breaker in the reinjection well, the negative pressure problem generated during the reinjection process is effectively solved, preventing the formation of a vacuum column in the heating system, improving the heating effect, and simplifying the geothermal dynamic monitoring work. The vacuum breaker allows the tailwater to be smoothly reinjected into the geothermal reservoir, avoiding the entry of air into the reinjection system, maintaining the water quality of the tailwater, preventing blockage of the reinjection channel, improving the reinjection efficiency, and eliminating the need for complex desanders, filter tanks, and air vents, thus simplifying the system structure, reducing system costs, and improving reinjection efficiency.

[0026] 2. By setting up a vacuum breaker, the conduction or closure status of each well section of the reinjection well can be flexibly adjusted, achieving precise control over the actual reinjection layer and the pressure aquifer, improving the stability and reliability of the reinjection system. Furthermore, the reinjection system has excellent intelligent and remote monitoring functions, and can automatically adjust the reinjection volume and temperature according to the operating status of the geothermal well and the treatment of the geothermal tailwater, achieving a balance of geothermal energy storage during the reinjection process and ensuring the sustainable development of the geothermal well. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the system flow of the present invention. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0029] Example 1

[0030] like Figure 1As shown, a tailwater reinjection system for a medium-deep geothermal well includes a reinjection well, a vacuum breaker, a flow meter, a control system, a remote monitoring device, a flow stabilizing tank, an impurity filtration device, a vacuum detection device, and a temperature control device.

[0031] The reinjection well has 5 well pipe segments inside the well body, which are connected by an adjustable well pipe adjustment device; the wellhead of the reinjection well is equipped with a pressure gauge and a pressure gauge for real-time monitoring and control of the wellhead pressure.

[0032] The vacuum breaker is installed at the wellhead of the reinjection well. Its structure includes a breaker shell, a breaker core, and a sealing ring. The breaker core has 8 channels inside, and tiny pores are installed in the channels to uniformly disperse the fluid flow rate and prevent fluid impact. The breaker shell is sealed to the wellhead to ensure airtightness.

[0033] The flow meter is installed below the wellhead of the reinjection well, with a measurement range of 0-100 L / min and a measurement accuracy of ±1%, and is used to monitor the reinjection flow rate in real time.

[0034] The control system includes a PLC central controller, a nitrogen compensation device, a second electric control valve, and a third electric control valve. The PLC central controller is connected to pressure gauges and pressure meters to automatically control the opening and closing of the nitrogen compensation device, the second electric control valve, and the third electric control valve based on pressure feedback information, thereby regulating the pressure in the reinjection well.

[0035] The remote monitoring device includes a wireless communication module and a remote terminal. The remote terminal is installed in the control room of the geothermal well. The wireless communication module is used to transmit data on pressure, flow, temperature and system operating status to the remote terminal in real time. Staff can monitor the system operation and adjust parameters through the remote terminal.

[0036] The stabilizing tank is connected to the reinjection well via a pipeline to mitigate pressure fluctuations during the reinjection process and ensure reinjection stability.

[0037] The impurity filtration device includes a filter screen and a sedimentation pipe. The filter screen is installed at the inlet of the reinjection pipeline to filter larger impurities, and the sedimentation pipe is installed at the bottom of the reinjection pipeline to filter sediment.

[0038] The vacuum detection device includes a vacuum sensor and a vacuum relay. The vacuum sensor is used to detect the vacuum level in the reinjection well. The vacuum relay is connected to the vacuum sensor and the vacuum breaker. When the vacuum level reaches a preset threshold, the vacuum breaker is triggered to start and eliminate the negative pressure.

[0039] The temperature control device includes a temperature sensor and a temperature control valve. The temperature sensor is used to detect the reinjection temperature, and the temperature control valve is connected to the temperature sensor and the PLC central controller to adjust the reinjection temperature according to the temperature signal.

[0040] The method for reinjecting tailwater from medium-deep geothermal wells based on the above system includes the following steps:

[0041] S1: Start the reinjection system. The pressure gauge and pressure meter monitor the wellhead pressure in real time, the flow meter monitors the reinjection flow rate in real time, and the temperature sensor monitors the reinjection temperature in real time.

[0042] S2: The vacuum sensor detects the vacuum level in the reinjection well. When the vacuum level reaches the preset threshold, the vacuum relay triggers the vacuum breaker to start. The fluid flow rate is evenly dispersed through the 8 channels and pores in the breaker core to eliminate negative pressure.

[0043] S3: The PLC central controller receives pressure feedback information from the pressure gauge and pressure meter, and automatically controls the opening and closing of the nitrogen compensation device, the second electric valve and the third electric valve to regulate the pressure in the reinjection well; at the same time, it controls the temperature control valve according to the signal from the temperature sensor to adjust the reinjection temperature to the range that meets the requirements of geothermal energy storage.

[0044] S4: The wireless communication module transmits pressure, flow, temperature and system operating status data to a remote terminal in real time, allowing staff to monitor system operation through the remote terminal;

[0045] S5: Adjust the conduction or closure status of 5 well pipe segments through the well pipe adjustment device to determine the actual reinjection layer and pressure aquifer, and ensure that the tailwater is accurately reinjected into the thermal reservoir.

[0046] Example 2

[0047] A tailwater reinjection system for a medium-deep geothermal well includes a reinjection well, a vacuum breaker, a flow meter, a control system, a remote monitoring device, a flow stabilizing tank, an impurity filtration device, a vacuum detection device, and a temperature control device.

[0048] The reinjection well has 6 well pipe segments inside the well body, which are connected by an adjustable well pipe adjustment device; the wellhead of the reinjection well is equipped with a pressure gauge and a pressure gauge for real-time monitoring and control of the wellhead pressure.

[0049] The vacuum breaker is installed at the wellhead of the reinjection well. Its structure includes a breaker shell, a breaker core, and a sealing ring. The breaker core has 10 channels inside, with tiny pores installed in the channels to evenly disperse the fluid flow rate and prevent fluid impact. The breaker shell is sealed to the wellhead to ensure airtightness.

[0050] The flow meter is installed below the wellhead of the reinjection well, with a measurement range of 0-120 L / min and a measurement accuracy of ±1%, and is used to monitor the reinjection flow rate in real time.

[0051] The control system includes a PLC central controller, a nitrogen compensation device, a second electric control valve, and a third electric control valve. The PLC central controller is connected to pressure gauges and pressure meters to automatically control the opening and closing of the nitrogen compensation device, the second electric control valve, and the third electric control valve based on pressure feedback information, thereby regulating the pressure in the reinjection well.

[0052] The remote monitoring device includes a wireless communication module and a remote terminal. The remote terminal is installed in the control room of the geothermal well. The wireless communication module is used to transmit data on pressure, flow, temperature and system operating status to the remote terminal in real time. Staff can monitor the system operation and adjust parameters through the remote terminal.

[0053] The stabilizing tank is connected to the reinjection well via a pipeline to mitigate pressure fluctuations during the reinjection process and ensure reinjection stability.

[0054] The impurity filtration device includes a filter screen and a sedimentation pipe. The filter screen is installed at the inlet of the reinjection pipeline to filter larger impurities, and the sedimentation pipe is installed at the bottom of the reinjection pipeline to filter sediment.

[0055] The vacuum detection device includes a vacuum sensor and a vacuum relay. The vacuum sensor is used to detect the vacuum level in the reinjection well. The vacuum relay is connected to the vacuum sensor and the vacuum breaker. When the vacuum level reaches a preset threshold, the vacuum breaker is triggered to start and eliminate the negative pressure.

[0056] The temperature control device includes a temperature sensor and a temperature control valve. The temperature sensor is used to detect the reinjection temperature, and the temperature control valve is connected to the temperature sensor and the PLC central controller to adjust the reinjection temperature according to the temperature signal.

[0057] The method for reinjecting tailwater from medium-deep geothermal wells based on the above system includes the following steps:

[0058] S1: Start the reinjection system. The pressure gauge and pressure meter monitor the wellhead pressure in real time, the flow meter monitors the reinjection flow rate in real time, and the temperature sensor monitors the reinjection temperature in real time.

[0059] S2: The vacuum sensor detects the vacuum level in the reinjection well. When the vacuum level reaches the preset threshold, the vacuum relay triggers the vacuum breaker to start. The fluid flow rate is evenly dispersed through the 10 channels and pores in the breaker core to eliminate the negative pressure.

[0060] S3: The PLC central controller receives pressure feedback information from the pressure gauge and pressure meter, and automatically controls the opening and closing of the nitrogen compensation device, the second electric valve and the third electric valve to regulate the pressure in the reinjection well; at the same time, it controls the temperature control valve according to the signal from the temperature sensor to adjust the reinjection temperature to the range that meets the requirements of geothermal energy storage.

[0061] S4: The wireless communication module transmits pressure, flow, temperature and system operating status data to a remote terminal in real time, allowing staff to monitor system operation through the remote terminal;

[0062] S5: Adjust the conduction or closure status of 6 well pipe segments through the well pipe adjustment device to determine the actual reinjection layer and pressure aquifer, and ensure that the tailwater is accurately reinjected into the thermal reservoir.

[0063] It should be noted that the specific installation methods, circuit connection methods, and control methods of the electronic components in this invention are all conventional designs, and will not be described in detail in this invention.

Claims

1. A tailwater reinjection system for a medium-deep geothermal well, characterized in that, include: Recharge well, vacuum breaker, flow meter, control system, remote monitoring device, flow stabilizing tank, impurity filtration device, vacuum detection device, and temperature control device; The reinjection well has 5 well pipe segments inside the well body, which are connected by an adjustable well pipe adjustment device; the wellhead of the reinjection well is equipped with a pressure gauge and a pressure meter for real-time monitoring and control of the wellhead pressure. The vacuum breaker is installed at the wellhead of the reinjection well. Its structure includes a breaker shell, a breaker core, and a sealing ring. The breaker core has eight channels inside, and tiny pores are installed in the channels to evenly disperse the fluid flow rate and prevent fluid impact. The breaker shell is sealed to the wellhead to ensure airtightness. The flow meter is installed below the wellhead of the reinjection well, with a measurement range of 0-100 L / min and a measurement accuracy of ±1%, and is used to monitor the reinjection flow rate in real time.

2. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that: The control system includes a PLC central controller, a nitrogen compensation device, a second electric control valve, and a third electric control valve. The PLC central controller is connected to a pressure gauge and a pressure meter signal, and is used to automatically control the opening and closing of the nitrogen compensation device, the second electric control valve, and the third electric control valve according to the pressure feedback information, so as to regulate the pressure in the reinjection well.

3. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that: The remote monitoring device includes a wireless communication module and a remote terminal. The remote terminal is installed in the control room of the geothermal well. The wireless communication module is used to transmit pressure, flow rate, temperature and system operating status data to the remote terminal in real time. The staff can monitor the system operation and adjust parameters through the remote terminal.

4. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that: The stabilizing tank is connected to the reinjection well via a pipeline to mitigate pressure fluctuations during the reinjection process and ensure reinjection stability.

5. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that: The impurity filtration device includes a filter screen and a sedimentation pipe. The filter screen is installed at the inlet of the reinjection pipeline to filter larger impurities, and the sedimentation pipe is installed at the bottom of the reinjection pipeline to filter sediment.

6. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that: The vacuum detection device includes a vacuum sensor and a vacuum relay. The vacuum sensor is used to detect the vacuum level in the reinjection well. The vacuum relay is connected to the vacuum sensor and the vacuum breaker. When the vacuum level reaches a preset threshold, the vacuum breaker is triggered to start and eliminate the negative pressure.

7. The tailwater reinjection system for a medium-deep geothermal well according to claim 1, characterized in that: The temperature control device includes a temperature sensor and a temperature control valve. The temperature sensor is used to detect the reinjection temperature, and the temperature control valve is connected to the temperature sensor and the PLC central controller to adjust the reinjection temperature according to the temperature signal.

8. A method for operating a tailwater reinjection system based on any one of claims 1 to 7 of the preceding claims, characterized in that, The work steps are as follows: S1: Start the reinjection system. The pressure gauge and pressure meter monitor the wellhead pressure in real time, the flow meter monitors the reinjection flow rate in real time, and the temperature sensor monitors the reinjection temperature in real time. S2: The vacuum sensor detects the vacuum level in the reinjection well. When the vacuum level reaches a preset threshold, the vacuum relay triggers the vacuum breaker to start. The fluid flow rate is evenly dispersed through the 8 channels and pores in the breaker core to eliminate negative pressure. S3: The PLC central controller receives pressure feedback information from the pressure gauge and pressure meter, and automatically controls the opening and closing of the nitrogen compensation device, the second electric valve and the third electric valve to adjust the pressure in the reinjection well; at the same time, it controls the temperature control valve according to the signal from the temperature sensor to adjust the reinjection temperature to the range that meets the requirements of geothermal energy storage. S4: The wireless communication module transmits pressure, flow, temperature and system operating status data to a remote terminal in real time, allowing staff to monitor system operation through the remote terminal; S5: Adjust the conduction or closure status of the five well pipe segments through the well pipe adjustment device to determine the actual reinjection layer and the pressure aquifer, and ensure that the tailwater is accurately reinjected into the thermal reservoir.

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