Intelligent system and method for treating shale reservoir fracturing flowback fluid by using solar energy

Abstract

The application relates to an intelligent system and method for treating shale reservoir fracturing flowback fluid by using solar energy, wherein the intelligent system and method for treating shale reservoir fracturing flowback fluid by using solar energy comprises an evaporation mechanism, a bearing base, an upper reflector, a lower reflector, an auxiliary heating unit and an intelligent control unit, the evaporation mechanism is arranged on the bearing base, the bearing base is provided with universal wheels, the evaporation mechanism is a trapezoidal glass transparent pool body, an inclined glass cover plate is sealingly arranged at the top of the pool body, a water collecting groove is arranged at a low sidewall in the pool body, the rest of the pool body is an evaporation chamber, a heat absorbing plate is laid at the bottom of the evaporation chamber, the heat absorbing plate is made of black galvanized material and adopts a triangular structure, the evaporation chamber is provided with an inlet and a concentrated salt water outlet, and the water collecting groove is provided with a treated water outlet; the upper end of the high sidewall of the pool body is hingedly connected with the upper reflector, and the upper end of the low sidewall is hingedly connected with the lower reflector. The application significantly reduces the system energy consumption and operation cost, reduces the dependence on traditional power and fossil fuels, and is especially suitable for remote oilfield blocks.

Description

Technical Field

[0001] This invention relates to the field of shale reservoir fracturing flowback fluid treatment technology, specifically to an intelligent system and method for treating shale reservoir fracturing flowback fluid using solar energy. Background Technology

[0002] Shale oil and gas, as an important component of unconventional oil and gas resources, is playing an increasingly prominent role in my country's energy strategy. In 2024, China's shale oil production exceeded 6 million tons, a year-on-year increase of over 30%, and shale oil and gas development is becoming an important direction for increasing oil and gas production in my country. Hydraulic fracturing, as a key means of shale reservoir stimulation and shale oil and gas production enhancement, involves injecting large amounts of high-pressure fluid containing chemical agents into the ground to form a complex network of fractures in the rock formation. During fracturing, some fracturing fluid is flowed back to the surface, forming what is known as fracturing flowback fluid. Fracturing flowback fluid has a complex composition, characterized by high salinity, high oil content, and the presence of various chemical agents. Improper handling can easily lead to serious environmental pollution and water waste. The recycling and reuse of fracturing flowback fluid has become an inevitable choice for cost reduction, efficiency improvement, and green development in shale oil and gas development. Fracturing flowback fluid can be used to prepare polymer solutions or as a base fluid for fracturing fluids, but its high salinity severely limits its reuse effectiveness. High concentrations of inorganic salt ions cause polymer molecular chains to coil and reduce their free movement, thus significantly decreasing solution viscosity. This not only weakens the oil displacement efficiency of polymer solutions but also reduces the sand-carrying capacity of fracturing fluids, ultimately affecting oilfield production. Therefore, desalination is a core step in fracturing flowback fluid treatment.

[0003] Currently, technologies applied to the desalination of fracturing flowback fluid mainly include membrane separation, electrochemical methods, and thermal evaporation. Membrane separation, such as reverse osmosis and nanofiltration membranes, has the advantage of operating at room temperature and having low energy consumption. However, high concentrations of organic matter, oil, and suspended solids in fracturing flowback fluid easily cause membrane fouling and clogging, leading to high desalination costs. Electrochemical methods use an external electric field to drive the directional migration or adsorption of ions, thereby separating inorganic salt particles. However, they face drawbacks such as high processing costs and easy electrode fouling, making large-scale promotion in oilfields difficult. Thermal evaporation is currently the mainstream solution for fracturing flowback fluid desalination. This method separates water from dissolved salts through the principle of phase change, exhibiting strong adaptability to influent water quality and good anti-fouling capabilities. However, traditional thermal evaporation technology consumes a large amount of energy and relies on conventional energy sources, especially in remote oilfield blocks lacking inexpensive heat sources, where energy costs become a major obstacle to its application.

[0004] How to effectively reduce the energy consumption of thermal evaporation in treating fracturing flowback fluid and improve its applicability has become a key issue that the industry urgently needs to address. Designing an intelligent process system and control method for treating shale reservoir fracturing flowback fluid using solar energy is particularly important. Summary of the Invention

[0005] The purpose of this invention is to provide an intelligent system for treating shale reservoir fracturing flowback fluid using solar energy. This intelligent system for treating shale reservoir fracturing flowback fluid using solar energy is used to solve the technical problems of high energy consumption, high cost and high dependence on traditional energy in existing treatment technologies. Another purpose of this invention is to provide an intelligent control method for this intelligent system for treating shale reservoir fracturing flowback fluid using solar energy.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: This intelligent system for treating shale reservoir fracturing flowback fluid using solar energy includes an evaporation mechanism, a support base, an upper reflector, a lower reflector, an auxiliary heating unit, and an intelligent control unit. The evaporation mechanism is mounted on the support base, which has casters. The evaporation mechanism is a trapezoidal transparent glass tank with an inclined glass cover sealed at the top. A water collection tank is located on the lower side wall of the tank, and the rest of the tank is the evaporation chamber. A heat-absorbing plate is laid at the bottom of the evaporation chamber. The heat-absorbing plate is made of black galvanized material and has a triangular structure. The evaporation chamber has an inlet and a concentrated brine outlet, and the water collection tank has a treated water outlet. The upper reflector is hinged to the upper end of the high side wall of the tank, and the lower reflector is hinged to the upper end of the low side wall. The auxiliary heating unit includes a photovoltaic module, a battery charge and discharge controller, and a battery pack. The intelligent control unit is a closed-loop control system composed of a temperature sensor, a digital controller, a PWM modulator, a solid-state relay, and an electric heater. The temperature sensor and the electric heater are located inside the evaporation chamber.

[0007] In the above scheme, the supporting base is a metal frame structure, including four support legs connected by crossbeams. A polyurethane insulation buffer layer is set between the crossbeams and the bottom of the pool. Each crossbeam connected to the high and low side walls is equipped with a metal frame. A reflector frame is hinged to the upper end of each metal frame. The upper and lower reflectors are respectively set on a reflector frame. The reflector frame is connected to the metal frame by an adjustable hinge, which realizes flexible adjustment of the reflector angle. The reflection angle is adjusted according to the position of the sun to maximize the absorption of solar radiation and improve thermal efficiency.

[0008] In the above scheme, all reflectors are made of mirror material, the width of each reflector is equal to the width of the pool, and the length of each reflector is one-third of the length of the pool. The optimal tilt angle θ of the upper reflector u The optimal tilt angle θ of the lower reflector l Calculations are performed using equations (1) and (2) respectively: (1) (2) In the formula, α is the angle between the heat absorber and the horizontal plane; βThis is the solar altitude angle; (3) In the formula, φ is the local geographical latitude, with positive values ​​for north latitude and negative values ​​for south latitude; δ is the solar declination angle; (4) In the formula, n represents the number of days in the calendar that year.

[0009] In the above scheme, the upper end of the pool body is sealed to the glass cover plate with a rubber ring, and the lower end of the pool body is sealed to each side wall with silicone sealant. The evaporation mechanism treats the fracturing flowback fluid based on the phase change principle. The flowback fluid evaporates under the heating effect of solar radiation and heat absorption plate. The water vapor rises to the surface of the glass cover plate and condenses into droplets. The condensate flows down the glass cover plate and collects in the water collection tank. Finally, it is discharged through the treated water outlet. The treated concentrated brine accumulates at the bottom of the evaporation chamber and is periodically discharged through the concentrated brine outlet to achieve continuous treatment of the fracturing flowback fluid.

[0010] In the above scheme, both the high and low sidewalls are covered with a black polyvinyl chloride insulation layer.

[0011] The auxiliary heating unit in the above scheme also includes a DC / DC converter and a DC / AC converter. The photovoltaic module is composed of multiple solar cells connected in series and parallel, used to convert solar radiation energy into DC power. The DC / DC converter converts the unstable voltage output of the photovoltaic module into a constant voltage. The DC / AC converter converts the DC power into AC power to supply power and heat the AC load. The battery pack balances energy supply and demand by storing and releasing electrical energy. The battery charge and discharge controller is used to control the charging and discharging process of the battery, including voltage and current regulation and state switching. During the operation of the auxiliary heating unit, the photovoltaic module converts the received solar radiation energy into DC power and sends it to the DC / DC converter. The DC / DC converter performs voltage regulation on the input DC power and outputs a stable DC voltage. The DC / AC converter converts the DC power into AC power to drive the heating equipment. Under sufficient sunlight conditions, excess electrical energy is stored in the battery pack, and when sunlight is insufficient, the battery pack releases electrical energy.

[0012] The glass cover plate in the above scheme is 5mm thick and has an angle of 15° with the horizontal plane; the polyurethane insulation buffer layer is 1cm thick.

[0013] In the above scheme, the heat absorption plate is a galvanized heat absorption plate with a thickness of 1.5mm. The heat absorption plate is composed of several continuously arranged triangular grooves with a groove angle of 90°, two right-angled sides with a side length of 5cm, and a groove depth of 3.5cm.

[0014] In the above scheme, the hinge angle adjustment range between the reflector frame and the metal frame is 45°~135°.

[0015] The control method of the intelligent system for treating shale reservoir fracturing flowback fluid using solar energy is as follows: a temperature sensor measures the system operating temperature in real time and feeds the collected data back to the digital controller. The digital controller calculates the deviation between the measured temperature and the target operating temperature, calculates the deviation signal using a PID control algorithm, and limits the output result. The processed output signal is sent to a PWM modulator to generate corresponding control pulses, which then drive the electric heater through a solid-state relay to achieve intelligent control of the system operating temperature. The calculation for the limiting process is as follows: (8) In the formula, u k This is the output calculated for an unlimited PID controller; u k,clamped This is the output after clipping; u max The output limit is 100; u min The lower limit for output is 0.

[0016] Beneficial effects: (i) This invention treats shale fracturing flowback fluid based on the principle of phase change separation, achieving efficient removal of high concentrations of mineral particles, oils, and suspended solids from shale fracturing flowback fluid. This process uses solar evaporation as the core treatment method, significantly reducing system energy consumption and operating costs, and decreasing dependence on traditional electricity and fossil fuels. It is particularly suitable for remote oilfield blocks, possessing both good economic efficiency and environmental applicability.

[0017] (II) Compared with traditional fracturing flowback fluid evaporation treatment devices, this invention has optimized and innovated in terms of system structure and energy utilization. The evaporation mechanism is equipped with a black galvanized heat-absorbing plate with triangular grooves, effectively increasing the heat transfer area and enhancing heat exchange and evaporation efficiency. Furthermore, two angle-adjustable mirror reflectors are installed on the outside of the evaporation mechanism, which can reflect more solar radiation to the heat-absorbing surface, effectively improving the collection and utilization efficiency of solar radiation and further enhancing the system's processing capacity.

[0018] (III) This invention consists of an evaporation unit and an auxiliary heating unit, resulting in a simple system structure and high operational stability. The system exhibits excellent anti-pollution and anti-scaling properties, is less prone to clogging during processing, and requires minimal maintenance. Furthermore, the system is easy to install and disassemble, and can be flexibly arranged according to the actual production needs of the oilfield, demonstrating strong applicability and practical value.

[0019] (iv) This invention introduces a photovoltaic power generation system to provide auxiliary heating for the evaporation mechanism, effectively improving the processing efficiency of shale fracturing flowback fluid. The photovoltaic modules convert solar energy into electrical energy; a portion is directly used to drive the heating device to assist evaporation, while the other portion is stored in a battery bank for continuous power supply when sunlight is insufficient, ensuring stable operation of the system under various weather conditions. This design effectively overcomes the limitations of solar evaporation due to weather conditions and significantly improves the processing capacity per unit time.

[0020] (V) This invention measures the system operating temperature in real time using a temperature sensor and compares the measured value with the set value in the digital controller. The resulting deviation is used as the input to the PID control algorithm. The calculated output signal is amplitude-limited and sent to a PWM modulator to generate corresponding control pulses, which then drive the electric heater through a solid-state relay, thereby achieving intelligent regulation of the system operating temperature. When processing reservoir fracturing flowback fluid in oilfields, users can set a target temperature in the digital controller. When the system operating temperature is lower than the target temperature, the electric heater maintains a stable operating temperature, thus ensuring a stable flow rate of treated water.

[0021] (vi) Combining solar energy with traditional thermal evaporation technology to construct a solar-driven fracturing flowback fluid treatment process is an effective way to solve the problems of high energy consumption and reliance on fossil fuels in traditional processes. In particular, in remote oilfield blocks with abundant solar energy resources but scarce traditional energy resources, the economic efficiency and applicability of the treatment process can be significantly improved, providing a green and economical solution for the treatment of fracturing flowback fluid. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the evaporation mechanism; Figure 2 This is a schematic diagram of the structure of the present invention; Figure 3 This is a schematic diagram of the hinge structure; Figure 4 Schematic diagram of the auxiliary heating unit; Figure 5 This is a schematic diagram of the intelligent control method.

[0023] In the diagram: 1. Glass cover plate; 2. Fracturing flowback fluid inlet; 3. Water collection tank; 4. Treated water outlet; 5. Concentrated brine outlet; 6. Heat absorber plate; 7. Thermal insulation buffer layer; 8. Reflector frame; 9. Lower reflector; 10. Upper reflector; 11. Hinge; 12. Metal frame; 13. Photovoltaic module; 14. DC / DC converter; 15. DC / AC converter; 16. Battery charge / discharge controller; 17. Battery pack; 18. Temperature sensor; 19. Digital controller; 20. PWM modulator; 21. Solid-state relay; 22. Electric heater; 23. Intelligent control unit. Detailed Implementation

[0024] The invention will be further described below with reference to the accompanying drawings: This intelligent system for treating shale reservoir fracturing flowback fluid using solar energy includes an evaporation mechanism, a support base, an upper reflector 10, a lower reflector 11, an auxiliary heating unit, and an intelligent control unit 23. The evaporation mechanism is mounted on the support base, which has casters and a handle. As sunlight changes throughout the day, the system can be moved to areas with stronger sunlight as needed. The evaporation mechanism is a trapezoidal, transparent glass tank with a sloping glass cover at the top. A water collection trough is located on the lower side wall of the tank, and the remaining part of the tank is the evaporation chamber. A heat-absorbing plate, made of black galvanized material and with a triangular structure, is laid at the bottom of the evaporation chamber. The evaporation chamber has an inlet and a concentrated brine outlet, while the water collection trough has a treated water outlet. The upper reflector is hinged to the upper end of the high side wall of the tank, and the lower reflector is hinged to the upper end of the low side wall. The auxiliary heating unit includes photovoltaic modules, a battery charge / discharge controller, and a battery pack. The intelligent control unit is a closed-loop control system composed of a temperature sensor, a digital controller, a PWM modulator, a solid-state relay, and an electric heater. The temperature sensor and the electric heater are located inside the evaporation chamber.

[0025] The fracturing flowback fluid treatment unit's evaporation mechanism is constructed entirely of glass in a trapezoidal design. The top is covered by an inclined glass cover, sealed with a rubber ring. The lower part of the tank and side walls are further reinforced with silicone sealant. The evaporation mechanism has a fracturing flowback fluid inlet at the rear cover, an internal water collection tank, and treated water and concentrated brine outlets at the bottom. To enhance the absorption efficiency of solar heat radiation and improve the unit's processing capacity, the evaporation mechanism is equipped with a black galvanized heat-absorbing plate. This plate has a triangular structure to increase the contact area with the flowback fluid, further enhancing heat transfer and evaporation. The evaporation mechanism treats the fracturing flowback fluid based on the phase change principle. The flowback fluid evaporates under solar radiation and heating by the heat-absorbing plate, and the water vapor rises to the surface of the upper glass cover, condensing into droplets. Because the glass cover is inclined, the condensate flows along the cover and collects in the water collection tank, eventually being discharged through the treated water outlet. The treated concentrated brine accumulates at the bottom of the tank and is periodically discharged through the concentrated brine outlet, thereby achieving continuous treatment of the fracturing flowback fluid.

[0026] The fracturing flowback fluid treatment unit's support base: Made of metal, the support base securely supports the evaporation mechanism and external reflector assembly. Equipped with four support legs, it ensures overall structural stability. The support base supports the evaporation mechanism via metal beams, with a polyurethane insulation buffer layer between the beams and the tank bottom to reduce vibration and enhance thermal insulation. Black PVC insulation layers cover both sides of the support base to minimize heat loss from the evaporation mechanism and maintain stable system operating temperature. Additionally, the base features two metal frames for securing the detachable upper and lower reflectors. The lower reflector is located on the lower side of the evaporation mechanism, while the upper reflector is on the higher side. The reflector frames are connected to the metal frame via adjustable hinges, allowing for flexible adjustment of the reflector angle based on the sun's position to maximize solar radiation absorption and further improve the overall system thermal efficiency.

[0027] Reflector Structure and Optimal Tilt Angle Determination Method: To further enhance the absorption efficiency of solar radiation energy by the absorber plate, two external reflectors are installed at the upper and lower parts of the evaporation mechanism. The structure and tilt angle of the external reflectors are key to improving the efficiency of the solar desalination device. The reflectors are made of mirror material, with a width consistent with the evaporation mechanism and a length one-third of the evaporation mechanism. This size ratio maximizes the light reflection coverage area while ensuring structural lightweighting and stability, avoiding increased wind load or installation difficulties due to excessive size. Solar radiation is reflected by the reflectors to the absorber plate inside the evaporation mechanism, significantly increasing the amount of heat radiation absorbed per unit area, thereby improving evaporation efficiency. This design ensures both light reflection coverage area and structural lightweighting and stability.

[0028] The reflector tilt angle is a crucial optimization parameter, and its optimal tilt angle needs to be dynamically calculated and adjusted based on local latitude, seasonal variations, and solar altitude angle. The optimal tilt angle θ for the upper reflector... u The optimal tilt angle θ of the lower reflector t The calculations can be performed using equations (1) and (2) respectively: (1) (2) In the formula, α The angle between the heat absorber and the horizontal plane is °; β This is the solar altitude angle, in °.

[0029] Considering that solar radiation is strongest at noon, optimizing the reflector's tilt angle to the optimal angle at noon can maximize the amount of solar radiation reflected. The solar altitude angle at noon can be calculated using equation (3): (3) In the formula, φ is the local geographical latitude (positive for north latitude and negative for south latitude), °; δ is the solar declination angle, °.

[0030] The solar declination angle can be calculated using equation (4): (4) In the formula, n represents the number of days in the calendar that year.

[0031] Photovoltaic Power Generation and Energy Storage Integrated Auxiliary Heating Unit: The system's processing capacity depends on the intensity of solar radiation, making it susceptible to weather changes and resulting in unstable water treatment volume. To address this issue, an integrated photovoltaic power generation and energy storage auxiliary heating system is designed. When sunlight is abundant, the system utilizes photovoltaic power generation and stores excess electrical energy. When sunlight is insufficient, it releases the stored energy to provide auxiliary heating to the evaporation mechanism, thereby ensuring stable water treatment volume. The auxiliary heating unit mainly consists of photovoltaic modules, a DC / DC converter, a DC / AC converter, a battery charge / discharge controller, and a battery bank. The photovoltaic modules, composed of multiple solar cells connected in series and parallel, convert solar radiation energy into direct current (DC). The DC / DC converter transforms the unstable voltage output of the photovoltaic modules into a constant voltage. The DC / AC converter converts DC to AC to power and heat the AC load. The battery bank, as the system's energy storage core, balances energy supply and demand by storing and releasing electrical energy, ensuring continuous and stable system operation. The battery charge / discharge controller controls the charging and discharging process of the battery, including voltage and current regulation and state switching.

[0032] During the operation of the auxiliary heating unit, the photovoltaic modules first convert the received solar radiation energy into direct current (DC) power and send it to the DC / DC converter. The DC / DC converter regulates the input DC power, outputting a stable DC voltage. The DC / AC converter further converts the DC power into alternating current (AC) power to drive the heating equipment. Under sufficient sunlight conditions, the system stores excess electrical energy in the battery bank; when sunlight is insufficient, the battery bank releases the electrical energy.

[0033] Intelligent control methods for fracturing flowback fluid treatment systems: A temperature sensor, digital controller, PWM modulator, solid-state relay, and electric heater together constitute a closed-loop control system for precise regulation of the system's operating temperature. The temperature sensor measures the system's operating temperature in real time and feeds the collected data back to the digital controller. The digital controller calculates the deviation between the measured temperature and the target operating temperature, uses a PID control algorithm to calculate this deviation signal, and limits the output result. The processed output signal is then sent to the PWM modulator to generate corresponding control pulses, which in turn drive the electric heater via the solid-state relay, achieving intelligent control of the system's operating temperature.

[0034] The basic principle of PID control algorithm is to perform proportional, integral, and derivative calculations on the deviation between the setpoint and the actual measured value, thereby driving the controlled object and forming a closed-loop feedback regulation. The calculation formula for continuous-time PID control algorithm is shown in equation (5): (5) In the formula, u(t) represents time. t Control output quantity at time; K p K is the proportional gain coefficient. i K is the integral gain coefficient; d Differential gain coefficient.

[0035] The formula for calculating the deviation e(t) is given in equation (6): (6) In the formula, SP represents the target temperature, in °C; PV(t) represents... t The measured temperature at any given time, in °C.

[0036] The digital controller operates at a fixed sampling period T. s The operating temperature of the processing system is sampled and calculated. Therefore, the continuous integral and differential operations need to be discretized. Specifically, the integral... Transform into a cumulative sum ,differential Transform into difference

[0037] The time-discrete PID control algorithm is shown in equation (7): (7) To prevent control commands from exceeding the operating range of the actuator, the calculated output value of the PID controller needs to be limited. The calculation formula for the limiting process is shown in equation (8): (8) In the formula, u k This is the output calculated for an unlimited PID controller; u k,clamped This is the final output after clipping; u max This is the upper limit of the output (typically 100 for heaters); u min This is the lower limit of the output (typically 0 for heaters).

[0038] PWM modulation converts the analog control signal of a PID control algorithm into a digital switching signal to drive a solid-state relay. Its basic principle is to adjust the proportion of the high-level signal of a square wave signal within a fixed time period to equivalently output the required average power. The larger the duty cycle, the higher the average output power, thus achieving continuous and precise control of the controlled object. Within a fixed period T... pwmInside, the heater is energized for a period of time T. on With power outage time T off The calculation formulas are (9) and (10) respectively: (9) (10).

[0039] Example: In this embodiment, the trapezoidal evaporation mechanism has a base length and width of 1.5m and 1.2m, respectively, and its two vertical walls have different heights of 1m and 1.4m, respectively. The glass cover plate on top of the evaporation mechanism is 5mm thick and has an angle of 15° with the horizontal plane. A galvanized heat-absorbing plate with a thickness of 1.5mm and dimensions of 1.4m and 1.1m, respectively, is installed inside the evaporation mechanism. The heat-absorbing plate consists of several continuously arranged triangular grooves with an angle of 90°, two right-angled sides of 5cm each, and a groove depth of 3.5cm.

[0040] A mirror with a thickness of 5mm was selected as the reflector. The reflector is 1.5m long and 0.4cm wide.

[0041] The support base is 50cm off the ground, and the polyurethane insulation and buffer layer is 1cm thick. The hinge connecting the metal frame and the metal border is 5cm thick and 12cm in diameter. The hinge angle adjustment range connecting the reflector frame and the metal border is 45°~135°.

[0042] The photovoltaic modules use 182mm×182mm monocrystalline PERC cells, arranged in a 3×4 array to form a cell string, with a total of 6 strings connected in series to form the entire photovoltaic module. The battery pack uses long-life, high-safety lithium iron phosphate batteries with a capacity of 200Ah and a system voltage of 48V.

[0043] The electric heater is a U-shaped immersion heater with a single arm length of 500mm and a tube diameter of 10mm. The entire heater is housed in 316L stainless steel. The digital controller integrates ADC and DAC modules, enabling the conversion between analog and digital signals, and facilitating data acquisition and intelligent control during the production process. The temperature sensor features a stainless steel housing and a waterproof design, converting the measured system operating temperature into a 20mA electrical signal input to the digital controller.

[0044] Figure 1This is a schematic diagram of the evaporation mechanism of the present invention. Shale reservoir fracturing flowback fluid enters the evaporation mechanism from the fracturing flowback fluid inlet 2 and evaporates under the heating effect of solar radiation and heat absorber plate 6. Water vapor rises to the surface of glass cover plate 1 and condenses into droplets. The condensate collects in the collection tank 3 and is discharged through the treated water outlet 4. Temperature sensor 18 measures the system operating temperature in real time and transmits the data to digital controller 19, which then activates electric heater 22 to assist evaporation as needed. The treated concentrated brine accumulates at the bottom of the tank and is periodically discharged through concentrated brine outlet 5. Figure 2 As shown, an insulating buffer layer 7 is provided between the evaporation mechanism and the support base to reduce vibration and enhance heat insulation. The support base has two reflector frames 8, which are used to fix the detachable upper and lower reflectors respectively. The lower reflector 9 is located on the lower side of the evaporation mechanism, and the upper reflector 10 is located on the higher side. The reflector frames 8 are connected to the metal frame 12 by an adjustable hinge 11. Figure 4 In the schematic diagram of the auxiliary heating unit, the photovoltaic module 13 converts the received solar radiation energy into DC power and sends it to the DC / DC converter 14 for voltage regulation. When there is sufficient sunlight, excess energy is stored in the battery pack 17; when sunlight is insufficient, the battery pack provides power. The battery charge / discharge controller 16 manages the charging and discharging process of the battery. The digital controller 19 receives signals from the temperature sensor 18 and outputs control commands to the PWM modulator 20. The solid-state relay 21 drives the electric heater 22 to operate based on the control pulses generated by the PWM modulator and the AC power provided by the DC / AC converter 15.

[0045] The evaporation mechanism is entirely made of glass and designed in a trapezoidal structure. The top is covered by an inclined glass cover plate 1, sealed with a rubber ring. The lower part of the tank and the side walls are further reinforced with silicone sealant. The rear cover of the evaporation mechanism has a fracturing flowback fluid inlet 2, an internal water collection tank 3, and a treated water outlet 4 and a concentrated brine outlet 5 at the bottom. To enhance the absorption efficiency of solar heat radiation and improve the processing capacity, the evaporation mechanism is equipped with a black galvanized heat-absorbing plate 6. This heat-absorbing plate has a triangular structure to increase the contact area with the flowback fluid, further enhancing heat transfer and evaporation. The evaporation mechanism treats the fracturing flowback fluid based on the phase change principle. The flowback fluid evaporates under the heating effect of solar radiation and the heat-absorbing plate, and the water vapor rises to the surface of the upper glass cover plate 1 and condenses into droplets. Because the glass cover plate 1 is inclined, the condensate flows along the cover plate and collects in the water collection tank 3, and is finally discharged through the treated water outlet 4. The treated concentrated brine accumulates at the bottom of the tank and is periodically discharged through concentrated brine outlet 5, thereby achieving continuous treatment of fracturing flowback fluid.

[0046] The support base is made of metal to securely support the evaporation mechanism and external reflector assembly. The base is equipped with four support legs to ensure overall structural stability. The evaporation mechanism is supported by a metal beam, and a polyurethane insulation buffer layer 7 is installed between the beam and the pool bottom to reduce vibration and enhance thermal insulation performance. To maintain system operating temperature and improve processing efficiency, the left and right sides of the support base are covered with black polyvinyl chloride insulation layers, which effectively suppress heat loss from the evaporation mechanism. In addition, two metal frames 8 are provided on the base to fix the detachable upper and lower reflectors. The lower reflector 9 is located on the lower side of the evaporation mechanism, and the upper reflector 10 is located on the higher side. The reflector frames are connected to the metal frame 12 by adjustable hinges 11, allowing for flexible adjustment of the reflector angle. The reflection angle can be adjusted according to the sun's position to maximize the absorption of solar radiation and further improve the overall thermal efficiency of the system.

[0047] To further enhance the absorption efficiency of solar radiation energy by the absorber plate, two external reflectors are installed at the upper and lower parts of the evaporation mechanism. The structure and tilt angle of the external reflectors are crucial for improving the efficiency of the solar desalination device. The reflectors are made of mirror material, with a width consistent with the evaporation mechanism and a length one-third that of the mechanism. This size ratio maximizes the light reflection coverage area while maintaining structural lightweight and stability, avoiding increased wind load or installation difficulties due to excessive size. Solar radiation is reflected by the reflectors to the absorber plate 6 within the evaporation mechanism, significantly increasing the amount of heat radiation absorbed per unit area, thereby improving evaporation efficiency. This design ensures both light reflection coverage area and structural lightweight and stability. The reflector tilt angle is an important optimization parameter; its optimal tilt angle needs to be dynamically calculated and adjusted based on local latitude, seasonal variations, and solar altitude angle.

[0048] The system's processing capacity depends on solar radiation intensity, making it susceptible to weather changes and resulting in unstable water treatment volume. To address this issue, an integrated photovoltaic power generation and energy storage auxiliary heating system is designed. When sunlight is abundant, the system utilizes photovoltaic power generation and stores excess electrical energy. When sunlight is insufficient, it releases the stored energy to provide auxiliary heating to the evaporation mechanism, thereby ensuring stable water treatment volume. The auxiliary heating unit mainly consists of photovoltaic modules 13, a DC / DC converter 14, a DC / AC converter 15, a battery charge / discharge controller 16, and a battery pack 17. The photovoltaic modules 13, composed of multiple solar cells connected in series and parallel, convert solar radiation energy into direct current (DC). The DC / DC converter 14 converts the unstable voltage output of the photovoltaic modules into a constant voltage. The DC / AC converter 15 converts DC to AC to power and heat the AC load. The battery pack 17 serves as the system's energy storage core, balancing energy supply and demand by storing and releasing electrical energy to ensure continuous and stable system operation. The battery charge / discharge controller 16 controls the charging and discharging process of the battery, including voltage and current regulation and state switching.

[0049] During the operation of the auxiliary heating unit, the photovoltaic module 13 first converts the received solar radiation energy into direct current (DC) power and sends it to the DC / DC converter 14. The DC / DC converter 14 regulates the input DC power and outputs a stable DC voltage. The DC / AC converter 15 further converts the DC power into alternating current (AC) power to drive the heating equipment. Under sufficient sunlight conditions, the system stores excess electrical energy in the battery pack 17, and releases electrical energy from the battery pack when sunlight is insufficient.

[0050] Temperature sensor 18, digital controller 19, PWM modulator 20, solid-state relay 21, and electric heater 22 together constitute a closed-loop control system for precise regulation of the system's operating temperature. Temperature sensor 18 measures the system's operating temperature in real time and feeds the collected data back to digital controller 19. Digital controller 19 calculates the deviation between the measured temperature and the target operating temperature, uses a PID control algorithm to calculate this deviation signal, and limits the output result. The processed output signal is sent to PWM modulator 20 to generate corresponding control pulses, which in turn drive electric heater 22 via solid-state relay 21, achieving intelligent control of the system's operating temperature.

[0051] This invention utilizes solar energy to treat fracturing flowback fluid and combines it with a photovoltaic-driven auxiliary heating device to improve processing efficiency. At the same time, it employs intelligent control methods to regulate the system's operating temperature. Compared to high-cost and high-energy-consumption fracturing flowback fluid treatment processes, this invention provides an effective way to significantly reduce operating energy consumption and maintenance costs, and improve the applicability of the treatment process.

Claims

1. An intelligent system for treating shale reservoir fracturing flowback fluid using solar energy, characterized in that: This intelligent system for treating shale reservoir fracturing flowback fluid using solar energy includes an evaporation mechanism, a support base, an upper reflector, a lower reflector, an auxiliary heating unit, and an intelligent control unit. The evaporation mechanism is mounted on the support base, which is equipped with casters. The evaporation mechanism is a trapezoidal, transparent glass tank with a sloping glass cover sealed at the top. A water collection trough is located on the lower side wall of the tank, and the remaining part of the tank is the evaporation chamber. A heat-absorbing plate made of black galvanized material with a triangular structure is laid on the bottom of the evaporation chamber. The evaporation chamber has an inlet and a concentrated brine outlet, while the water collection trough has a treated water outlet. The upper reflector is hinged to the upper end of the high side wall of the tank, and the lower reflector is hinged to the upper end of the low side wall. The auxiliary heating unit includes photovoltaic modules, a battery charge / discharge controller, and a battery pack. The intelligent control unit is a closed-loop control system composed of a temperature sensor, a digital controller, a PWM modulator, a solid-state relay, and an electric heater. The temperature sensor and the electric heater are located inside the evaporation chamber.

2. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 1, characterized in that: The supporting base is a metal frame structure, including four support legs connected by crossbeams. A polyurethane insulation buffer layer is installed between the crossbeams and the bottom of the pool. Each crossbeam connected to the high and low side walls has a metal frame, and a reflector frame is hinged to the upper end of each metal frame. The upper and lower reflectors are respectively set on a reflector frame. The reflector frame is connected to the metal frame by an adjustable hinge, which allows for flexible adjustment of the reflector angle. The reflection angle is adjusted according to the position of the sun to maximize the absorption of solar radiation and improve thermal efficiency.

3. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 2, characterized in that: Each reflector is made of mirror material, the width of each reflector is equal to the width of the pool, and the length of each reflector is one-third of the length of the pool. The optimal tilt angle θ of the upper reflector u The optimal tilt angle θ of the lower reflector l Calculations are performed using equations (1) and (2) respectively: （1） （2） In the formula, α is the angle between the heat absorber and the horizontal plane; β This is the solar altitude angle; （3） In the formula, φ is the local geographical latitude, with positive values ​​for north latitude and negative values ​​for south latitude; δ is the solar declination angle; （4） In the formula, n represents the number of days in the calendar that year.

4. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 3, characterized in that: The upper end of the pool body is sealed to the glass cover plate with a rubber ring, and the lower end of the pool body is sealed to each side wall with silicone sealant. The evaporation mechanism treats the fracturing flowback fluid based on the phase change principle. The flowback fluid evaporates under the heating effect of solar radiation and heat absorption plate. The water vapor rises to the surface of the glass cover plate and condenses into droplets. The condensate flows down the glass cover plate and collects in the water collection tank, and is finally discharged through the treated water outlet. The treated concentrated brine accumulates at the bottom of the evaporation chamber and is periodically discharged through the concentrated brine outlet, realizing the continuous treatment of fracturing flowback fluid.

5. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 4, characterized in that: Both the high and low sidewalls are covered with a black polyvinyl chloride insulation layer.

6. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 5, characterized in that: The auxiliary heating unit also includes a DC / DC converter and a DC / AC converter. The photovoltaic module is composed of multiple solar cells connected in series and parallel, used to convert solar radiation energy into DC power. The DC / DC converter converts the unstable voltage output of the photovoltaic module into a constant voltage. The DC / AC converter converts the DC power into AC power to supply power and heat the AC load. The battery pack balances energy supply and demand by storing and releasing electrical energy. The battery charge and discharge controller is used to control the charging and discharging process of the battery, including voltage and current regulation and state switching. During the operation of the auxiliary heating unit, the photovoltaic module converts the received solar radiation energy into DC power and sends it to the DC / DC converter. The DC / DC converter regulates the input DC power and outputs a stable DC voltage. The DC / AC converter converts the DC power into AC power to drive the heating equipment. Under sufficient sunlight conditions, excess electrical energy is stored in the battery pack, and when sunlight is insufficient, the battery pack releases electrical energy.

7. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 6, characterized in that: The glass cover is 5mm thick and has an angle of 15° with the horizontal plane; the polyurethane insulation buffer layer is 1cm thick.

8. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 7, characterized in that: The heat-absorbing plate is a galvanized heat-absorbing plate with a thickness of 1.5mm. The heat-absorbing plate is composed of several continuously arranged triangular grooves with an angle of 90°, two right-angled sides with a side length of 5cm, and a groove depth of 3.5cm.

9. The intelligent system for treating shale reservoir fracturing flowback fluid using solar energy according to claim 8, characterized in that: The hinge angle between the reflector frame and the metal frame can be adjusted from 45° to 135°.

10. A control method for an intelligent system for treating shale reservoir fracturing flowback fluid using solar energy, as described in claim 6, characterized in that: A temperature sensor measures the system's operating temperature in real time and feeds the collected data back to the digital controller. The digital controller calculates the deviation between the measured temperature and the target operating temperature, uses a PID control algorithm to calculate this deviation signal, and performs amplitude limiting on the output result. The processed output signal is then sent to a PWM modulator to generate corresponding control pulses, which in turn drive the electric heater via a solid-state relay, achieving intelligent control of the system's operating temperature. The amplitude limiting calculation is as follows: (8) In the formula, u k This is the output of the PID calculation without limiting; u k,clamped This is the output after clipping; u max The output limit is 100; u min The lower limit for output is 0.

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