Drilling fluid cooling and waste heat recovery system based on phase-change heat exchange

Abstract

The invention discloses a drilling fluid cooling and waste heat recovery system based on phase-change heat exchange, and belongs to the field of drilling engineering. The system comprises a drilling fluid circulation module, a heat exchanger module, a secondary refrigerant circulation and waste heat utilization module and an intelligent control module. The high-temperature drilling fluid is efficiently cooled through phase-change heat exchange of the low-boiling-point secondary refrigerant; meanwhile, the turbine generator is driven by vaporization of the secondary refrigerant, and waste heat recovery is achieved. The system supports intelligent series-parallel connection switching of multi-stage heat exchangers so as to adapt to different working condition requirements. The system has the advantages of high cooling efficiency, low energy consumption, high waste heat utilization rate and the like, and is suitable for high-temperature operation environments such as deep drilling and geothermal development.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of drilling engineering, in particular to a drilling fluid cooling and waste heat recovery system based on phase change heat exchange, which is used for the cooling system of high-temperature drilling fluid and realizes waste heat recovery and energy cascade utilization. BACKGROUND

[0002] With the development of deep oil and gas drilling, geothermal resource development and scientific deep drilling engineering, the downhole temperature can reach 240-260 DEG C, and the circulating temperature of drilling fluid often exceeds 180 DEG C. High temperature leads to the deterioration of the performance of drilling fluid, which easily causes wellbore instability, drill tool thermal fatigue and other safety hazards. Although the forced cooling technology (such as refrigeration unit and cooling tower) commonly used at present can realize temperature reduction, the energy consumption is high, and 60-70% of the medium and low temperature waste heat is directly discharged, causing energy waste and not meeting the requirements of green drilling. There is a lack of an integrated system which can not only cool drilling fluid efficiently, but also recycle waste heat in the prior art. SUMMARY

[0003] In view of the technical problem in the prior art that the forced cooling technology (such as refrigeration unit and cooling tower) of high-temperature drilling fluid can realize temperature reduction, but the energy consumption is high, and 60-70% of the medium and low temperature waste heat is directly discharged, causing energy waste, a drilling fluid cooling and waste heat recovery system based on phase change heat exchange is provided, which realizes the integration of high-efficiency cooling of drilling fluid and waste heat power generation, improves the energy utilization rate and reduces the energy consumption of drilling operation.

[0004] The present application adopts the following technical scheme: A drilling fluid cooling and waste heat recovery system based on phase change heat exchange, comprising: a drilling fluid circulating module for circulating and temperature monitoring of drilling fluid; a heat exchanger module comprising a pressure-resistant heat exchanger group for heat exchange between drilling fluid and a cooling medium; a cooling medium circulating and waste heat utilization module for circulating, vaporization power generation and condensation recovery of the cooling medium, wherein the cooling medium is a low-boiling-point and easily-vaporized working medium; a parameter monitoring and control module for real-time monitoring and intelligent control of system operation parameters.

[0005] Further, the drilling fluid circulating module comprises a drilling fluid tank, a variable frequency mud pump and a drilling fluid temperature control variable frequency pump, and the drilling fluid forms a closed loop circulation circuit through the variable frequency mud pump and the drilling fluid temperature control variable frequency pump; a high-precision temperature sensor is built-in the drilling fluid tank to monitor the circulating fluid temperature in real time; a flow meter is arranged at the outlet of the drilling fluid temperature control variable frequency pump, and the drilling fluid at the outlet of the drilling fluid temperature control variable frequency pump is connected to the drilling fluid inlet of the heat exchanger module after being monitored by the flow meter.

[0006] Furthermore, the series and parallel modes of the pressure heat exchanger group can be switched using valves.

[0007] Furthermore, the pressure heat exchanger group is activated in series mode to improve the vaporization rate, and the pressure heat exchanger group is activated in parallel mode to balance the distribution of cooling capacity.

[0008] Furthermore, the refrigerant circulation and waste heat utilization module includes a turbine generator set for converting the refrigerant vaporization energy into electrical energy.

[0009] Furthermore, the parameter monitoring and control module is based on a PLC and can automatically adjust the operating mode according to the coolant pressure and drilling fluid temperature.

[0010] Furthermore, the system also includes an energy storage unit for storing the electrical energy output by the turbine generator set.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces a low-boiling-point working fluid (such as liquid ammonia) as a circulating refrigerant. Utilizing this refrigerant's phase change heat transfer with the high-temperature drilling fluid within a pressure-resistant heat exchanger, the heat transfer efficiency is significantly improved, resulting in faster and more thorough cooling of the drilling fluid. Simultaneously, the waste heat from the drilling fluid (approximately 60%-70%) that is directly discharged in traditional technologies is effectively captured by the system: the refrigerant absorbs heat and vaporizes, driving a turbine generator set to convert medium- and low-temperature thermal energy into directly usable electrical energy, achieving integrated energy cascade utilization of "cooling as power generation." This design not only solves the operational risks posed by high-temperature drilling fluids but also transforms the traditional "high-power-consumption refrigeration + inefficient heat waste" model into an energy-saving closed loop of "high-efficiency heat exchange + energy regeneration," significantly improving the overall energy efficiency of the system and directly reducing drilling operation energy consumption and carbon emissions.

[0012] 2. The system integrates a PLC-based intelligent control module, which can monitor multi-dimensional parameters such as drilling fluid temperature, refrigerant pressure, and flow rate in real time, and dynamically adjust pump frequency, valves, and cold source output through algorithms. Its core innovation lies in the heat exchanger module's support for online intelligent switching between multi-stage series and parallel modes: when insufficient refrigerant vaporization is detected, the system automatically switches to series mode, extending the heat exchange path to enhance vaporization; when the drilling fluid temperature is below a set threshold, it switches to parallel mode to evenly distribute cooling capacity and prevent overcooling. This adaptive control strategy enables the system to flexibly respond to downhole heat load fluctuations and ambient temperature changes, ensuring precise control of drilling fluid temperature while maintaining the continuity and stability of the waste heat power generation process, significantly improving the system's reliability and safety under different operating conditions. Attached Figure Description

[0013] Figure 1 A schematic diagram of the drilling fluid cooling system and waste heat recovery system provided by the present invention; Figure 2This is a schematic diagram of the heat exchanger module structure of the present invention; Figure 3 This is a schematic diagram of the heat exchanger module structure using three sets of heat exchangers in this invention.

[0014] The markings in the diagram are as follows: 1-Wellbore, 2-Variable frequency mud pump, 3-Mud solids control equipment, 4-Drilling fluid tank, 5-Drilling fluid temperature-controlled variable frequency pump, 6-Heat exchanger module, 7-Refrigerator variable frequency pump, 8-Refrigerator tank, 9-Gas-liquid separator, 10-Pressure stabilizing tank, 11-Turbine generator set, 12-Check valve, 13-Condenser, 14-Refrigeration unit, 15-Electric energy storage unit, 16-Pressure-resistant heat exchanger assembly. 17-Heat Exchanger 1, 18-Heat Exchanger 2, 19-Heat Exchanger 3, 101-Valve 1, 102-Valve 2, 103-Valve 3, 104-Valve 4, 201-Valve 5, 202-Valve 6, 203-Valve 7, 204-Valve 8, 205-Valve 9, 206-Valve 10, 301-Valve 11, 302-Valve 12, 303-Valve 13, 304-Valve 14. Detailed Implementation

[0015] To enable those skilled in the art to fully understand the technical solutions and innovations of the present invention, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the described embodiments are merely typical application scenarios of the technical solutions of the present invention and are not exhaustive enumerations of all implementation methods. Equivalent modifications or extensions based on the principles of the present invention all fall within the protection scope of the present invention.

[0016] A drilling fluid cooling and waste heat recovery system based on phase change heat, such as Figure 1 As shown, the system includes a drilling fluid circulation module, a heat exchanger module, a coolant circulation and waste heat utilization module, and a parameter monitoring and control module.

[0017] The drilling fluid circulation module is used for drilling fluid circulation and temperature monitoring, and includes a drilling fluid tank 4, a variable frequency mud pump 2, a flow meter, a drilling fluid temperature control variable frequency pump 5, and a temperature sensor.

[0018] The variable frequency mud pump 2 is installed on the pipeline between the drilling fluid tank 4 and the wellbore 1. The outlet of the drilling fluid tank 4 is connected to the inlet of the variable frequency mud pump 2 through the pipeline. The outlet of the variable frequency mud pump 2 is connected to the inlet of the working pipeline of the wellbore 1. The outlet of the working pipeline of the wellbore 1 is connected to the drilling fluid inlet of the mud solids control equipment 3. The drilling fluid outlet of the mud solids control equipment 3 is connected back to the inlet of the drilling fluid tank 4, forming a closed loop circulation circuit.

[0019] The drilling fluid temperature-controlled variable frequency pump 5 is installed on the pipeline between the drilling fluid tank 4 and the heat exchanger module 6. The drilling fluid in the drilling fluid tank 4 is transported by the drilling fluid temperature-controlled variable frequency pump 5 to the drilling fluid inlet channel of the heat exchanger module 6, and the drilling fluid outlet of the heat exchanger module 6 is connected back to the inlet of the drilling fluid tank 4.

[0020] The drilling fluid tank 4 has a built-in high-precision temperature sensor to monitor the circulating fluid temperature in real time; the flow meter is installed at the outlet of the drilling fluid temperature-controlled variable frequency pump 5. The drilling fluid from the outlet of the drilling fluid temperature-controlled variable frequency pump 5 is connected to the drilling fluid inlet of the heat exchanger module 6 after being monitored by the flow meter. The variable frequency mud pump 2, the drilling fluid temperature-controlled variable frequency pump 5, the flow meter and the temperature sensor all interact with the parameter monitoring and control module.

[0021] The drilling fluid temperature control variable frequency pump 5 is at least a large-displacement horizontal sand pump, but not limited to horizontal sand pumps. The displacement of horizontal sand pumps can generally be higher than that of drilling pumps.

[0022] like Figure 2 As shown, the heat exchanger module 6 is used for heat exchange between drilling fluid and refrigerant, and includes a pressure-resistant heat exchanger group 16. The valves in the heat exchanger module 6 are configured as multi-way valve groups. The heat exchanger module 6 also includes a sensor network and piping. The heat exchangers in the heat exchanger module 6 are pressure-resistant heat exchangers, specifically brazed plate heat exchangers or shell-and-tube heat exchangers, capable of withstanding operating pressures above 10 MPa. Their number can be expanded to 1-5 groups according to heat load requirements. Each group of heat exchangers is equipped with independent control valves for the drilling fluid inlet / outlet and the refrigerant inlet / outlet, and thermodynamic parameters are collected in real time through temperature and pressure sensors. The drilling fluid channels of adjacent heat exchangers can be connected in series or in parallel by valve switching. A one-way valve 12 is installed between the refrigerant channels to prevent backflow. All valve and sensor signals are connected to the parameter monitoring and control module. The pressure-resistant heat exchanger group 16 can be switched between series and parallel modes via valves.

[0023] Series mode: When the refrigerant outlet pressure is less than the set threshold, multiple heat exchangers are activated in series to extend the heat exchange path and improve the vaporization rate.

[0024] Parallel mode: When the drilling fluid outlet temperature is less than the set threshold, switch to multiple heat exchangers in parallel to balance the distribution of cooling capacity and avoid overcooling.

[0025] The refrigerant circulation and waste heat utilization module is used for refrigerant circulation, vaporization power generation, and condensation recovery. The refrigerant is a low-boiling-point, easily vaporized chemical substance; the refrigerant circulation and waste heat utilization module includes a turbine generator set 11, a refrigerant tank 8, a refrigerant variable frequency pump 7, a gas-liquid separator 9, a condenser 13, a pressure stabilizing tank 10, and a cold source.

[0026] The turbine generator set 11 consists of a turbine and a generator. The turbine rotor is driven by gas to rotate, which in turn drives the turbine shaft system to rotate. The turbine directly drives the generator rotor through the shaft system, and power generation is achieved through the interaction between the rotating magnetic field and the stator coil. It is used to convert the vaporization energy of the refrigerant into electrical energy.

[0027] The refrigerant tank 8 outlet is pressurized by the refrigerant variable frequency pump 7 and delivered to the refrigerant inlet of the heat exchanger module 6. The heat-absorbing and vaporized gas-liquid two-phase flow enters the gas-liquid separator 9 through the heat exchanger outlet. The high-temperature gas separated by the gas-liquid separator 9 enters the pressure stabilizing tank 10, which controls the inlet pressure of the turbine generator set 11 within a preset range. The high-temperature gas in the pressure stabilizing tank enters the turbine generator set 11 at the preset pressure, driving the turbine to generate electricity. After the gas is discharged from the turbine generator set 11, it merges with the liquid phase of the gas-liquid separator 9 into the condenser 13, where it is cooled and liquefied by an external cold source (such as air or spray cooling), and finally flows back to the refrigerant tank 8 to complete the regeneration cycle.

[0028] The parameter monitoring and control module is used for real-time monitoring and intelligent control of system operating parameters. The parameter monitoring and control module is built based on a programmable logic controller (PLC) and integrates a multi-channel data acquisition card and an actuator drive unit. It receives analog / digital signals from temperature sensors, pressure sensors, and flow meters in real time, and dynamically adjusts the flow rate of the variable frequency mud pump 2, the delivery pressure of the coolant variable frequency pump 7, the output power of the cold source, and the opening and closing status of the valve group of the heat exchanger (achieving series / parallel mode switching) through a PID algorithm. It can automatically adjust the operating mode according to the coolant pressure and drilling fluid temperature.

[0029] The phase change drilling fluid cooling and waste heat recovery system also includes an electrical energy storage unit 15 for storing electrical energy output from the turbine generator set 11.

[0030] Waste heat recovery: When the turbine inlet pressure is greater than the set threshold, power generation is started. The electrical energy is rectified and inverted and stored in the energy storage unit 15. The energy storage unit 15 can be a battery pack for use by well site equipment.

[0031] The operation process of this phase change drilling fluid cooling and waste heat recovery system includes: Main loop flow: After circulation, the drilling fluid is returned through wellbore 1, processed in mud solids control equipment 3, and then enters drilling fluid tank 4. Subsequently, it is transported by drilling fluid temperature-controlled variable frequency pump 5 to the drilling fluid inlet channel of heat exchanger module 6. In pressure-resistant heat exchanger group 16, high-temperature drilling fluid and low-temperature refrigerant exchange heat countercurrently, and after cooling to the target temperature, it returns to drilling fluid tank 4 to form a closed loop. It is then input into the well by variable frequency mud pump 2 for drilling operations. At the same time, the liquid low-temperature working fluid in the refrigerant circulation and waste heat utilization module is pressurized by refrigerant variable frequency pump 7 and injected into the refrigerant inlet of heat exchanger module 6. After absorbing heat from the drilling fluid, it undergoes phase change vaporization. The gas and liquid two-phase flow is separated by gas-liquid separator 9. The high-temperature gas drives turbine generator set 11 to generate electricity and outputs power. After power generation, the gas and some unvaporized refrigerant are cooled and liquefied by condenser 13 and returned to refrigerant tank 8, forming an energy closed loop.

[0032] The working fluid in the refrigerant tank 8 is delivered to the heat exchanger module 6 at an initial preset pressure via the refrigerant variable frequency pump 7, and its flow rate is monitored in real time by an electromagnetic flow meter. After heat exchange, the gas-liquid mixture enters the gas-liquid separator 9. When the gas phase pressure exceeds the preset energy storage pressure, the turbine generator set 11 is triggered to generate electricity, which is then stored after AC / DC conversion. The liquid phase flows directly into the condenser 13 via the one-way valve 12. The refrigeration unit 14 regulates the water flow and fan speed through the PLC module to ensure that the condensing temperature remains stable within the preset range.

[0033] Multistage heat exchanger group mode adjustment: This embodiment is configured with a three-stage brazed plate heat exchanger, such as Figure 3 Heat exchangers 1-17, 2-18, and 3-19 support two intelligent switching modes: Mode 1: Series Mode (Capacity Expansion, Enhanced Vaporization) Initial state: Only heat exchanger one is enabled (valve 101 and valve 303 are open), and the refrigerant outlet pressure threshold is set to the preset initial pressure; First-stage expansion: If the pressure is less than the preset initial pressure (insufficient vaporization), close valve 101 and valve 303, and open valve 2102, valve 4104, valve 6202 and valve 9205 to switch heat exchanger 17 and heat exchanger 218 to be connected in series.

[0034] Secondary expansion: If the pressure is still insufficient, close valves 6 (202) and 9 (205), and open valves 7 (203), 10 (206), 12 (302), and 14 (304) to form a three-stage series connection, thereby increasing the outlet pressure to exceed the preset initial pressure.

[0035] Mode 2: Parallel mode (optimization, cooling capacity distribution) Baseline operating condition: single heat exchanger operation (valve 101 and valve 303 are open), drilling fluid outlet temperature is set to the preset initial temperature; First-level parallel connection: If the temperature is less than the preset initial temperature (overcooled), open valve 5 201, valve 6 202, valve 8 204 and valve 9 205 to activate heat exchanger 1 17 and heat exchanger 2 18 in parallel and adjust the cooling capacity distribution ratio; Two-stage parallel connection: If the temperature remains below the preset initial temperature, valve group 11 (301), valve 12 (302), valve 13 (303), and valve 14 (304) will be opened to achieve three-stage parallel connection, so as to distribute the cooling capacity evenly and ensure that the temperature is stable within the set range.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A drilling fluid cooling and waste heat recovery system based on phase change heat transfer, characterized in that, The system comprises: a drilling fluid circulation module for circulation and temperature monitoring of the drilling fluid; a heat exchanger module comprising a set of pressure-resistant heat exchangers for heat exchange between the drilling fluid and the coolant, adjacent pressure-resistant heat exchangers being connected in series or in parallel through valves; a coolant circulation and waste heat utilization module for circulation, vaporization power generation and condensation recovery of the coolant, the coolant being a low-boiling-point and easily-vaporized working medium which exchanges heat with the high-temperature drilling fluid in the pressure-resistant heat exchangers; a parameter monitoring and control module for real-time monitoring and intelligent control of system operation parameters.

2. The phase change material based drilling fluid cooling and waste heat recovery system of claim 1, wherein, The drilling fluid circulation module comprises a drilling fluid tank, a variable-frequency mud pump and a drilling fluid temperature control variable-frequency pump, and the drilling fluid forms a closed loop circulation circuit through the variable-frequency mud pump and the drilling fluid temperature control variable-frequency pump; the drilling fluid tank is provided with a high-precision temperature sensor for real-time monitoring of the circulating fluid temperature; a flow meter is arranged at the outlet of the drilling fluid temperature control variable-frequency pump, and the drilling fluid at the outlet of the drilling fluid temperature control variable-frequency pump is connected to the inlet of the heat exchanger module after being monitored by the flow meter.

3. The drilling fluid cooling and waste heat recovery system based on phase change heat transfer of claim 1, wherein, The series mode and the parallel mode of the set of pressure-resistant heat exchangers can be switched through valves.

4. The drilling fluid cooling and waste heat recovery system based on phase change heat transfer of claim 3, wherein, The set of pressure-resistant heat exchangers is started in series mode to improve the vaporization rate, and is started in parallel mode to balance the cold distribution.

5. The phase change material based drilling fluid cooling and waste heat recovery system of claim 1, wherein, The coolant circulation and waste heat utilization module comprises a turbine generator set for converting the vaporization energy of the coolant into electric energy.

6. The phase change material based drilling fluid cooling and waste heat recovery system of claim 1, wherein, The parameter monitoring and control module is based on PLC and can automatically adjust the operation mode according to the pressure of the coolant and the temperature of the drilling fluid.

7. The phase change material based drilling fluid cooling and waste heat recovery system of claim 1, wherein, The system further comprises an electric energy storage unit for storing the electric energy output by the turbine generator set.

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