A kind of middle-deep heat exchange well photovoltaic auxiliary heating structure and energy-saving drilling process

Abstract

This invention discloses a photovoltaic-assisted heating structure and energy-saving drilling technology for medium-deep heat exchange wells. The well includes a single-sleeve and a double-sleeve configuration. A double-sleeve is coaxially inserted within the single-sleeve, and an inner heat exchange tube is coaxially inserted within the double-sleeve. An annular gap is formed between the single and double sleeves, within which a heating coil is installed. A double-sleeve cementing layer is laid on the outer wall of the double-sleeve, covering the heating coil and filling the annular gap. A photovoltaic power supply system and a control system are installed on the surface. The electrical output end of the photovoltaic power supply system is connected to the heating coil and the control system, while the thermal output end is also connected to the heating coil. In winter, the heating coil preheats the heat exchange medium, overcoming the cooling caused by low shallow ground temperatures and increasing heat extraction. In summer, it stores solar energy in the shallow rock and soil, achieving cross-seasonal heat storage and solving the problem of shallow ground temperature decay. The photovoltaic power supply system provides power to the heating coil and the control system, alleviating power supply difficulties in remote areas.

Description

Technical Field

[0001] This invention relates to the field of medium-deep geothermal development technology, and in particular to a photovoltaic-assisted heating structure and energy-saving drilling process for medium-deep heat exchange wells. Background Technology

[0002] Medium-deep geothermal energy is a clean and renewable energy source, with 2500-3000 meter coaxial heat exchange wells being one of the mainstream forms of medium-deep geothermal development. In practical applications, during winter heating, the heat exchange medium flows through the 0-400 meter shallow section, where the ground temperature is low, causing the medium temperature to drop and resulting in a low initial temperature when entering the deeper section, thus limiting the overall heat extraction efficiency. After the heating season ends in summer, the geothermal wells are idle, and the shallow soil and rock masses do not receive heat replenishment. In winter, the shallow ground temperature further decreases, and the heat extraction decreases year by year. Existing technologies use independent shallow buried pipes for heat storage, but this requires additional drilling, occupies a large area, and significantly increases investment costs. In addition, geothermal wells are usually built in areas far from buildings, and the wellhead monitoring equipment relies on the traditional power grid for power supply, resulting in high connection costs and construction difficulties. Summary of the Invention

[0003] To improve the heating efficiency of heat exchange wells, this application provides a photovoltaic-assisted heating structure and energy-saving drilling technology for medium-deep heat exchange wells.

[0004] The technical solution provided in this application for a photovoltaic-assisted heating structure and energy-saving drilling process for medium-deep heat exchange wells adopts the following: A photovoltaic-assisted heating structure and energy-saving drilling technology for a medium-deep heat exchange well includes a well located within a formation. The formation includes at least a first thermal reservoir and a second thermal reservoir from top to bottom along the drilling depth. An outer fixed casing covering the entire drilling depth is provided within the well. The outer fixed casing includes at least a first-opening casing and a second-opening casing, both with their upper ends positioned on the ground. The first-opening casing is inserted through the first thermal reservoir. The second-opening casing is coaxially inserted within the first-opening casing, passing through both the first and second thermal reservoirs. An inner heat exchange tube is coaxially inserted within the second-opening casing. A heat exchange channel is formed between the inner heat exchange tube and the outer fixed casing. The inner heat exchange tube has a circulation channel. The circulation channel is connected to the heat exchange channel, and heat exchange medium flows through both the circulation channel and the heat exchange channel. Both the circulation channel and the heat exchange channel are used to connect to the ground heating system. An annular gap is formed between the first open sleeve and the second open sleeve. A heating coil is installed in the annular gap. A second open cementing layer is laid on the outer wall of the second open sleeve. The second open cementing layer partially fills the annular gap and covers the heating coil. A photovoltaic power supply system and a control system are provided on the ground. The control system is used to control the automated operation of the heat exchange well. The photovoltaic power supply system has an electrical energy output terminal and a heat energy output terminal. The electrical energy output terminal is connected to the heating coil and the control system, respectively. The heat energy output terminal is connected to the heating coil.

[0005] By adopting the above technical solution, a heating coil is installed within the annulus of the shallow section. In winter, the descending heat exchange medium can be actively preheated, ensuring it reaches a higher temperature before entering the deep, high-temperature region. This overcomes the cooling problem caused by low shallow ground temperatures, increases the initial temperature of the deep heat extraction section, and thus increases the overall heat extraction. In summer, the same heating coil stores the solar energy collected by the photovoltaic power supply system into the shallow soil and rock mass, restoring and raising the shallow ground temperature. In winter, the stored heat is released to preheat the medium, achieving cross-seasonal storage and utilization of solar energy. This solves the problem of annual shallow ground temperature decay and eliminates the need for additional drilling and land occupation. The ground-based photovoltaic power supply system simultaneously provides power to the heating coil and control system, reducing the wellhead equipment's dependence on the power grid and alleviating power supply difficulties in remote areas.

[0006] Optionally, the heating coil is a spiral coil, and the heating coil is spirally distributed along the outer wall of the two-part sleeve.

[0007] By adopting the above technical solution, the spiral coils are uniformly distributed along the outer wall of the two-stage casing, providing a longer heat exchange path within the limited annular gap height, increasing the heat transfer area, and making preheating more thorough. The spiral shape induces lateral flow disturbances in the medium within the annular gap, disrupting the laminar boundary layer, reducing thermal resistance, increasing the heat transfer coefficient, and accelerating the medium's heating rate. The uniform spiral distribution makes the circumferential temperature of the annular gap tend to be consistent, avoiding local overheating or undercooling, reducing the risk of thermal stress cracking during cementing solidification, and ensuring structural stability under long-term alternating hot and cold operation, thereby improving the long-term reliability of cross-seasonal heat storage and preheating functions.

[0008] Optionally, the thermal conductivity of the second cementing layer gradually changes along the depth direction.

[0009] By adopting the above technical solutions, the high thermal conductivity of the shallow section allows for rapid injection of solar heat into the soil and rock during summer heat storage and rapid transfer of coil heat to the heat exchange medium during winter preheating, shortening the thermal response time. The low thermal conductivity of the deep section reduces heat loss of deep geothermal energy along the casing, concentrating heat extraction in the high-temperature zone at the bottom of the well. The gradual change in thermal conductivity avoids thermal stress concentration at abrupt interfaces, preventing cracking of the cementing layer or deformation of the casing due to thermal expansion differences, ensuring the long-term effectiveness of the heating coil's encapsulation and fixing structure, thereby guaranteeing the continuous and stable operation of cross-seasonal heat storage and preheating functions.

[0010] Optionally, the outer fixed sleeve includes a three-section sleeve, the upper end of which is coaxially connected to the lower end of the two-section sleeve, and the lower end of the inner heat exchange tube is located in the three-section sleeve.

[0011] By adopting the above technical solution, the upper end of the three-sleeve casing is coaxially connected to the lower end of the two-sleeve casing, allowing the heat exchange channel to continue extending downwards from the bottom of the two-sleeve casing. By drilling to the third thermal reservoir and lowering the three-sleeve casing, the heat exchange channel can reach formation regions with higher temperatures, and the heat exchange medium can achieve a higher temperature rise in the deeper sections, thereby increasing the heat carrying capacity per unit volume of circulating water.

[0012] Optionally, the photovoltaic power supply system is a photovoltaic integrated module, including a photovoltaic power supply unit and a photothermal collection unit. The photovoltaic power supply unit has the power output terminal, and the photothermal collection unit has the heat output terminal.

[0013] By adopting the above technical solutions, the photovoltaic power supply system integrates photovoltaic power generation and solar thermal collection into a single component, reducing the footprint and installation costs of ground equipment. The photovoltaic power supply unit provides electric heating energy for the heating coil and also independently powers the control system, reducing the wellhead equipment's dependence on the external power grid and alleviating the difficulty of power supply in remote areas. The solar thermal collection unit directly utilizes solar energy to heat the circulating medium fed into the coil. Its solar thermal conversion efficiency is higher than that of photovoltaic power generation followed by electrothermal conversion. When there is sufficient sunlight, solar thermal energy can be preferentially used for preheating, reducing energy consumption and lowering the energy demand on the energy storage unit, thus improving the overall economic efficiency of solar energy utilization.

[0014] Optionally, the photovoltaic power supply system further includes an energy storage unit for storing excess electrical energy, and the photovoltaic power supply unit includes a power conversion module for converting the electrical energy output by the photovoltaic power supply unit into an appropriate voltage and distributing it to various devices.

[0015] By adopting the above technical solution, the energy storage unit stores excess photovoltaic power during the day and continuously supplies power to the heating coils and control system at night or on cloudy days, ensuring uninterrupted preheating function around the clock and avoiding preheating interruptions caused by changes in sunlight, thus maintaining stable heat extraction efficiency. During the summer heat storage period, the energy storage unit can extend the daily heat storage time, increasing the total cross-seasonal heat storage volume. The power conversion module converts unstable DC power into the stable voltage required by various devices, possessing voltage stabilization and filtering functions to prevent voltage fluctuations from interfering with the control system and sensors, thereby improving the reliability and safety of equipment operation.

[0016] This application also provides an energy-saving drilling process, including the aforementioned photovoltaic-assisted heating structure for medium-deep heat exchange wells, implemented using the following steps: S1: Install a photovoltaic power supply system on the ground and connect the photovoltaic power supply system to the drilling equipment; S2: Perform staged drilling, including at least a first-stage drilling and a second-stage drilling, wherein the second-stage drilling includes: drilling to the second heat reservoir, fixing the heating coil to the outer wall of the second-stage casing, and lowering the second-stage casing; S3: Lay a second-stage cementing layer on the outer wall of the second-stage casing and fill the annular gap; S4: Lower the inner heat exchange tube into the outer fixed casing.

[0017] By adopting the above technical solution, this drilling process prioritizes the installation of a photovoltaic power supply system and its connection to the drilling equipment before operations begin, enabling subsequent drilling procedures to directly utilize photovoltaic power and reducing dependence on the power grid. In staged drilling, the heating coil is fixed to the outer wall of the second-stage casing before the casing is lowered, utilizing the open surface space for construction and avoiding the difficulty of fixing the coil in the narrow annular gap downhole, thus ensuring installation quality. Subsequently, a cementing layer is laid to cover and fix the coil, preventing loosening due to operational vibrations. Simultaneously, the cementing layer acts as a heat transfer medium, ensuring efficient heat transfer. Finally, the inner heat exchange tube is lowered to form a complete circulation channel, providing the structural foundation for heat extraction and storage.

[0018] Optionally, step S2 includes drilling to the first thermal reservoir, running the first casing, and laying a cementing layer on the outer wall of the first casing.

[0019] By adopting the above technical solution, after the first casing is run in, a cementing layer is laid between its outer wall and the formation. This cementing layer fills the annulus between the first casing and the formation, sealing off shallow groundwater and preventing surface water from seeping into the well and causing contamination of the heat exchange medium and heat loss. The cementing layer provides axial support and compressive strength for the first casing, preventing it from being struck by the drill bit or crushed by formation pressure during subsequent second drilling, thus ensuring the stability of the first casing throughout the entire drilling and operation period.

[0020] Optionally, the two ends of the heating coil are connected to the wellhead, and a connection interface for the photovoltaic power supply system is reserved.

[0021] By adopting the above technical solution, a closed-loop connection is established between the coil and the heat output and regenerating medium ends of the photovoltaic power supply system, enabling the directional transmission of solar heat from the ground to the shallow underground section, providing an energy transmission channel for winter preheating and summer heat storage. The extended design at both ends also provides cable access points for the electric heating scheme, enhancing the flexibility of the heating method.

[0022] Optionally, in step S2, the drilling equipment preferentially uses the electrical energy provided by the photovoltaic power supply system.

[0023] By adopting the above technical solution, the main energy consumption of the drilling process is borne by solar energy, reducing the consumption of electricity from the power grid. When there is sufficient sunlight, the photovoltaic output power is high, which can meet most of the electricity demand, and the power grid is only used as a backup, thereby reducing the grid connection capacity and construction costs.

[0024] The key feature of this invention is the innovative auxiliary heating structure for medium-deep geothermal wells, which can help achieve carbon reduction or even zero carbon throughout the entire life cycle from drilling to operation.

[0025] In summary, this application includes at least one of the following beneficial effects: 1. The heating coil can receive electrical or thermal energy from the photovoltaic power system and generate heat, allowing the heat exchange medium to achieve an initial temperature rise before entering the deeper layers. This overcomes the problem of medium cooling caused by low shallow ground temperatures, significantly increasing the initial temperature of the deep heat extraction section and thus increasing the overall heat extraction. In summer, the heating coil can store the solar heat collected by the photovoltaic power system into the shallow soil and rock mass, realizing the cross-seasonal storage and utilization of solar energy and solving the problem of the gradual decline of shallow ground temperature.

[0026] 2. By configuring the heating coil as a spiral coil and distributing it spirally along the outer wall of the two-layer casing, combined with a gradient energy-saving cementing layer whose thermal conductivity gradually changes along the depth direction, a synergistic effect of efficient heat exchange in shallow layers and effective insulation in deep layers is achieved. The gradient cementing layer has high thermal conductivity in the shallow section, allowing for rapid injection of stored heat into the rock and soil in summer and rapid transfer of preheated heat to the heat exchange medium in winter; in the deep section, it has low thermal conductivity, reducing heat loss of deep geothermal energy upwards along the casing. The combination of these two elements improves the overall heat exchange efficiency and ensures structural stability under long-term alternating hot and cold operation.

[0027] 3. The photovoltaic power supply system adopts integrated photovoltaic modules, which integrate photovoltaic power supply units and solar thermal collection units, and is equipped with energy storage units and power conversion modules to provide independent electrical and thermal energy for heating coils and control systems. This reduces the dependence of geothermal wells on traditional power grids during drilling and operation, thereby achieving energy-saving heating. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of a photovoltaic-assisted heating structure for a medium-deep heat exchange well in an embodiment of this application.

[0029] Figure 2 This is a partial structural schematic diagram of a photovoltaic-assisted heating structure for a medium-deep heat exchange well, as described in an embodiment of this application.

[0030] Figure 3 This is a schematic diagram of the heating coil and the two-part sleeve in the embodiments of this application.

[0031] Explanation of reference numerals in the attached figures: 1. Formation; 11. First thermal reservoir; 12. Second thermal reservoir; 13. Third thermal reservoir; 2. First-stage casing; 3. Second-stage casing; 4. Inner heat exchange tube; 5. Heating coil; 51. Fixing frame; 6. Second-stage cementing layer; 7. Third-stage casing; 8. First-stage cementing layer; 9. Third-stage cementing layer; 100, heat exchange channel; 200, circulation channel. Detailed Implementation

[0032] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0033] This application discloses a photovoltaic-assisted heating structure for a medium-deep heat exchange well. (Refer to...) Figure 1 and 2The system includes a well located within formation 1. Formation 1 includes a first thermal reservoir 11 and a second thermal reservoir 12 from top to bottom along the drilling depth. An outer fixed casing covering the entire drilling depth is provided in the well. The outer fixed casing includes a first open casing 2 and a second open casing 3, both with their upper ends set on the ground. The first open casing 2 is inserted through the first thermal reservoir 11. The second open casing 3 is coaxially inserted through the first open casing 2. The second open casing 3 is inserted through the first thermal reservoir 11 and the second thermal reservoir 12. An inner heat exchange tube 4 is coaxially inserted through the second open casing 3. A heat exchange channel 100 is formed between the inner heat exchange tube 4 and the outer fixed casing. The inner heat exchange tube 4 has a circulation channel 200, which is connected to the heat exchange channel 100. A heat exchange medium flows through the circulation channel 200 and the heat exchange channel 100. Both the circulation channel 200 and the heat exchange channel 100 are used to connect to the surface heating system. An annular gap is formed between the first-stage casing 2 and the second-stage casing 3. A heating coil 5 is installed within the annular gap. A second-stage cementing layer 6 is laid on the outer wall of the second-stage casing 3, partially filling the annular gap and covering the heating coil 5. A first-stage cementing layer 8 is provided between the first-stage casing 2 and the formation 1. The second-stage casing 3 is coaxially inserted inside the first-stage casing 2, forming an annular gap between them. The heating coil 5 is a spiral coil, spirally distributed along the outer wall of the second-stage casing 3. In some embodiments, the inner heat exchange tube 4 is a composite tube with an insulation layer, such as a high-density polyethylene tube or a steel tube with a polyurethane foam insulation layer. Its outer diameter is smaller than the inner diameter of the second-stage casing 3, forming an annular heat exchange channel 100 between them. The heat exchange medium is water or antifreeze. In some embodiments, the heating coil 5 is a metal coil with high temperature resistance, corrosion resistance, and high thermal conductivity, such as 304 stainless steel, 316L stainless steel, copper-nickel alloy, etc., which is not limited here. In some embodiments, the wall thickness of the heating coil is 1.5-3mm and the diameter is DN20-32, which is not limited here. The heating coil 5 is spirally wound along the outer wall of the two-opening sleeve 3 with a spiral spacing of 400-800mm, covering a shallow depth range of 0-400 meters.

[0034] The coaxial nested structure of the first casing 2 and the second casing 3 naturally separates the shallow geothermal storage area from the deep geothermal extraction area in terms of depth. As the heat exchange medium descends within the heat exchange channel 100, it passes sequentially through the first geothermal reservoir 11 and the second geothermal reservoir 12. After absorbing geothermal energy at depth, it ascends through the circulation channel 200 to the surface heating system, forming a complete closed-loop circulation path. The first-stage cementing layer 8 anchors the first casing 2 to the formation 1, sealing off shallow groundwater and preventing surface water from seeping into the well and contaminating the heat exchange medium. The annular gap between the second casing 3 and the first casing 2 provides an independent installation space for the heating coil 5, ensuring that active preheating and natural heat exchange with the formation 1 do not interfere with each other. The uniform width of the annular heat exchange channel 100 between the inner heat exchange tube 4 and the second casing 3 ensures a stable flow velocity of the heat exchange medium and improves the deep geothermal absorption efficiency. Spiral coils provide a longer heat transfer path within a limited annular gap. The spiral distribution induces lateral disturbance of the medium, reducing thermal resistance, increasing the heat transfer coefficient, and ensuring sufficient preheating and uniform circumferential temperature.

[0035] A photovoltaic power supply system and a control system are installed on the ground. The control system is used to control the automated operation of the heat exchange well. The photovoltaic power supply system has an electrical output terminal and a heat output terminal. The electrical output terminal is connected to the heating coil 5 and the control system, respectively, while the heat output terminal is connected to the heating coil 5. A wellhead device is installed at the top of the well, which is sealed to the top of the first casing 2, the second casing 3, and the inner heat exchange tube 4. The wellhead device integrates pressure and temperature sensors for real-time monitoring of the pressure and temperature of the heat exchange medium. The photovoltaic power supply system provides both electricity and heat. The electrical output terminal allows the heating coil 5 to be electrically heated even without sunlight, while the heat output terminal prioritizes direct preheating using solar heat during the day. The two complement each other to ensure all-weather auxiliary heating. The pressure and temperature sensors monitor the pressure and temperature of the wellhead medium in real time. When the pressure rises abnormally, the circulation pump is automatically shut off and an alarm is triggered. When the temperature falls below a set threshold, the heating coil 5 is automatically activated to prevent the heat exchange medium from freezing or leaking due to overpressure.

[0036] In a preferred embodiment, refer to Figure 3 The outer wall of the double-sleeved sleeve 3 is provided with multiple fixing brackets 51, and the heating coil 5 is fixed on the fixing brackets 51. During the prefabrication of the double-sleeved sleeve 3, reinforcing bars for connection are pre-embedded in the outer wall. During the installation of the heating coil 5, the fixing brackets 51 are welded to the pre-embedded reinforcing bars, thus completing the installation of the fixing brackets 51. Then, the heating coil 5 is fixed to the fixing brackets 51 by welding or binding. In some embodiments, the fixing brackets 51 are L-shaped supports, and the materials can be 304 stainless steel, 316L stainless steel, etc. The vertical section of the L-shaped support is welded to the pre-embedded reinforcing bars. A group of two fixing brackets 51 are set at regular intervals along a spiral line. The fixing brackets 51 are evenly distributed along the spiral line, so that the heating coil 5 is constrained in both the axial and circumferential directions. During the lowering process, the coil will not slip due to gravity or friction, and it will not loosen due to thermal expansion during operation.

[0037] In a preferred embodiment, refer to Figure 1 and 2 The outer fixed casing includes a three-section casing 7, the upper end of which is coaxially connected to the lower end of a two-section casing 3. The lower end of the inner heat exchange tube 4 is located within the three-section casing 7. In some embodiments, the three-section casing 7 is directly connected to the bottom end of the two-section casing 3. A three-section cementing layer 9 is provided between the three-section casing 7 and the formation 1. The three-section cementing layer 9 is a conventional oil well cement solidified body, which simultaneously covers the outer side of the lower end of the two-section casing 3 and the outer side of the three-section casing 7, making the two integrated downhole. The lower end of the inner heat exchange tube 4 extends to near the bottom of the three-section casing 7. After the three-section casing 7 is coaxially connected, the heat exchange channel 100 extends downward to the third thermal reservoir 13. The heat exchange medium can obtain a higher temperature rise, increasing the heat carrying capacity per unit circulating water volume.

[0038] In a preferred embodiment, refer to Figure 1 and 2 The thermal conductivity of the second-stage cementing layer 6 gradually changes along the depth direction. In some embodiments, the second-stage cementing layer 6 is divided into three sections: a shallow section (0-150 meters) with high thermal conductivity, incorporating 10% graphite powder, with a thermal conductivity of 1.5-2.3 W / (m·K); a middle section (150-300 meters) with transitional thermal conductivity, incorporating 5% graphite powder, with a thermal conductivity of 1-1.5 W / (m·K); and a deep section (300-400 meters and below) with low thermal conductivity, incorporating 15-25% hollow glass microspheres, with a thermal conductivity of 0.3-0.8 W / (m·K), which is not limited here. The sections naturally form gradual interfaces through continuous pumping of slurry with different proportions, without clear boundaries. The shallow high thermal conductivity section allows solar heat to be rapidly injected into the rock and soil in summer, and during winter preheating, the heat from the coil is quickly transferred to the heat exchange channel 100. The deep, low-thermal-conductivity section forms a thermal barrier, reducing the conduction loss of deep geothermal energy upwards along the casing, allowing more heat from the bottom of the well to be absorbed by the heat exchange medium. The gradient interface avoids thermal stress cracks caused by abrupt changes in thermal conductivity. The cemented layer remains crack-free after 100 cycles of hot and cold cycling from -10℃ to 80℃, ensuring long-term structural integrity.

[0039] In a preferred embodiment, the photovoltaic power supply system is an integrated photovoltaic module, including a photovoltaic power supply unit and a solar thermal collection unit. The photovoltaic power supply unit has an electrical output terminal, and the solar thermal collection unit has a thermal output terminal. In some embodiments, the photovoltaic power supply unit consists of multiple photovoltaic panels connected in series, outputting AC power via an MPPT controller and an inverter. The solar thermal collection unit is a flat-plate or vacuum tube solar collector, with antifreeze as the internal circulating medium. The heat medium from the collector outlet is sent to the heating coil 5 via an insulated pipeline. The photovoltaic power supply unit provides basic electrical energy to ensure uninterrupted operation of the control system and electric heating; the solar thermal collection unit provides direct heating with high thermal efficiency when there is sufficient sunlight, which is 2-3 times higher than the overall efficiency of photovoltaic power generation followed by electrothermal conversion.

[0040] In a preferred embodiment, the photovoltaic power supply system further includes an energy storage unit for storing excess electrical energy. The photovoltaic power supply unit includes a power conversion module for converting the electrical energy output from the photovoltaic power supply unit into an appropriate voltage and distributing it to various devices. In some embodiments, the energy storage unit is a battery pack. The power conversion module converts the DC power output from the photovoltaic power supply unit into AC power required by the heating coil and circulating pump, as well as low-voltage DC power required by the control system and sensors. The energy storage unit stores excess photovoltaic energy during the day, which can continuously power the heating coil 5 at night or on cloudy days, ensuring uninterrupted preheating function around the clock, avoiding preheating interruptions caused by changes in sunlight, and maintaining stable heat extraction efficiency. During summer heat storage, the energy storage unit can extend the daily heat storage duration, increasing the total cross-seasonal heat storage. The power conversion module converts fluctuating DC power into stable AC power and low-voltage DC power, preventing voltage fluctuations from burning out heating elements or interfering with sensor signals.

[0041] In a preferred embodiment, the control system is housed in a control cabinet near the wellhead, and includes a built-in temperature control module and a power distribution module. The temperature control module is used for precise regulation of the heat exchange temperature, while the power distribution module distributes the electricity generated by the photovoltaic power supply system to the shallow heating coil 5, the circulating pump, and the control system itself. The control system is electrically connected to the pressure and temperature sensors within the wellhead assembly to monitor the pressure and temperature of the heat exchange medium in real time. The control system is also responsible for controlling the circulation of the heat exchange medium, monitoring operating parameters, and managing power distribution. The wellhead assembly is sealed to the top of the first casing 2, the second casing 3, and the inner heat exchange tube 4, and has pressure and temperature monitoring functions.

[0042] In some implementations, the temperature control module employs a PID controller, receiving signals from temperature and pressure sensors to adjust the circulation pump speed and electric heating power. The power distribution module uses an intelligent distribution box with multiple output circuits, corresponding to the heating coil 5 heating elements, the circulation pump, and various units within the control system. The temperature control module automatically adjusts the heating power based on the real-time monitored temperature of the heat exchange medium, stabilizing the outlet water temperature at the design value to avoid overheating and wasting energy or insufficient heating. The power distribution module prioritizes power supply to each power-consuming unit, ensuring uninterrupted monitoring and control when photovoltaic power fluctuates.

[0043] This application also discloses an energy-saving drilling process, including the aforementioned photovoltaic-assisted heating structure for medium-deep heat exchange wells, implemented using the following steps: S1: Install a photovoltaic power supply system on the surface and connect it to the drilling equipment; S2: Perform staged drilling, including at least a first-stage drilling and a second-stage drilling, wherein the second-stage drilling includes: drilling to the second thermal reservoir 12, fixing the heating coil 5 to the outer wall of the second-stage casing 3, and lowering the second-stage casing 3; S3: Laying a second-stage cementing layer 6 on the outer wall of the second-stage casing 3 and filling the annular gap; S4: Lowering the inner heat exchange tube 4 into the outer fixed casing. The first-stage drilling in step S2 includes: drilling to the first thermal reservoir 11, lowering the first-stage casing 2, and laying a first-stage cementing layer 8 on the outer wall of the first-stage casing 2. In some embodiments, the photovoltaic panel array of the photovoltaic power supply system is pre-installed and debugged in step S1 to ensure that it is connected to the grid before drilling begins. In step S2, the heating coil 5 is pre-wound onto the two-section sleeve 3 in the ground shed and locked with the fixing bracket 51.

[0044] In a preferred embodiment, in step S2, the drilling equipment preferentially uses electricity provided by the photovoltaic power supply system. In some embodiments, the drilling equipment includes a top drive, mud pump, winch, rotary table, and solids control system. The photovoltaic power supply system is connected to the main circuit of the drilling equipment through an intelligent distribution cabinet, which is equipped with a dual-power automatic transfer switch. When the photovoltaic output power exceeds the real-time demand of the drilling equipment, the equipment is entirely powered by photovoltaics; when the photovoltaic output power is insufficient, it automatically switches to the grid or a backup generator for power supply. The drilling equipment's preferential use of photovoltaic power can meet most of the total energy consumption of drilling when there is sufficient sunshine, significantly reducing grid power consumption and electricity costs. The automatic dual-power transfer ensures drilling continuity and prevents drilling stoppages due to photovoltaic fluctuations.

[0045] In a preferred embodiment, step S1 of the energy-saving drilling process includes preliminary preparation and photovoltaic system construction: geological surveys are conducted in the target area to clarify the distribution of strata 1, the location of geothermal reservoirs, and solar energy resources, determining the drilling trajectory and the installation location of the photovoltaic system; subsequently, a photovoltaic power supply system is prioritized for construction in an open area on the drilling site, including laying photovoltaic panels, installing energy storage units, and debugging power conversion modules, while simultaneously completing the circuit connection between the photovoltaic power supply system and subsequent drilling equipment. Prioritizing photovoltaic construction before drilling ensures that clean electricity can be used from the outset, reducing drilling energy consumption and avoiding interference with surface facilities from later photovoltaic installations. The energy storage units ensure uninterrupted drilling at night and on cloudy days, and the power conversion modules provide suitable voltage. After drilling is completed, the system quickly switches to heating mode, shortening the construction cycle. This process achieves full lifecycle synergy of "photovoltaic construction first, energy-saving drilling, and self-sufficient operation."

[0046] In a preferred embodiment, step S3 includes: connecting both ends of the heating coil 5 to the wellhead, and reserving a connection interface for the photovoltaic power supply system. In some embodiments, both ends of the heating coil 5 are extended above the wellhead before the two-way sleeve 3 is lowered, and are respectively equipped with flanges and sealing plugs. After the two-way sleeve 3 is in place, the plugs are removed, and the coil inlet is connected to the circulating pump outlet of the heat output terminal of the photovoltaic power supply system using a thermally insulated hose, and the coil outlet is connected to the collector return water inlet.

[0047] The above are all preferred embodiments of this application. These embodiments are merely explanations of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A photovoltaic-assisted heating structure for a medium-deep heat exchange well, characterized in that: The well includes a well located within a formation (1), which, from top to bottom along the drilling depth, includes at least a first thermal reservoir (11) and a second thermal reservoir (12). The well is equipped with an outer fixed casing covering the entire drilling depth. The outer fixed casing includes at least a first-opening casing (2) and a second-opening casing (3), both with their upper ends positioned on the ground. The first thermal reservoir (11) is permeated by the first-opening casing (2), and the second-opening casing (3) is coaxially permeated within the first-opening casing (2). The second-opening casing (3) is inserted into the first thermal reservoir (11). The inner heat exchange tube (4) is coaxially inserted in the two-opening sleeve (3). A heat exchange channel (100) is formed between the inner heat exchange tube (4) and the outer fixed sleeve. The inner heat exchange tube (4) has a circulation channel (200) which is connected to the heat exchange channel (100). A heat exchange medium flows in the circulation channel (200) and the heat exchange channel (100). Both the circulation channel (200) and the heat exchange channel (100) are used to connect to the ground heating system. An annular gap is formed between the first open casing (2) and the second open casing (3). A heating coil (5) is provided in the annular gap. A second open cementing layer (6) is laid on the outer wall of the second open casing (3). The second open cementing layer (6) partially fills the annular gap and covers the heating coil (5). The ground is equipped with a photovoltaic power supply system and a control system. The control system is used to control the automated operation of the heat exchange well. The photovoltaic power supply system has an electrical energy output terminal and a heat energy output terminal. The electrical energy output terminal is connected to the heating coil (5) and the control system respectively, and the heat energy output terminal is connected to the heating coil (5).

2. The photovoltaic-assisted heating structure for a medium-deep heat exchange well according to claim 1, characterized in that: The heating coil (5) is a spiral coil, and the heating coil (5) is spirally distributed along the outer wall of the two-open sleeve (3).

3. The photovoltaic-assisted heating structure for a medium-deep heat exchange well according to claim 1, characterized in that: The thermal conductivity of the second cementing layer (6) gradually changes along the depth direction.

4. The photovoltaic-assisted heating structure for a medium-deep heat exchange well according to claim 1, characterized in that: The outer fixed sleeve includes a three-section sleeve (7), the upper end of which is coaxially connected to the lower end of the two-section sleeve (3), and the lower end of the inner heat exchange tube (4) is located in the three-section sleeve (7).

5. The photovoltaic-assisted heating structure for a medium-deep heat exchange well according to claim 1, characterized in that: The photovoltaic power supply system is a photovoltaic integrated photovoltaic module, including a photovoltaic power supply unit and a photothermal collection unit. The photovoltaic power supply unit has the power output terminal, and the photothermal collection unit has the heat output terminal.

6. The photovoltaic-assisted heating structure for a medium-deep heat exchange well according to claim 5, characterized in that: The photovoltaic power supply system also includes an energy storage unit for storing excess electrical energy. The photovoltaic power supply unit includes a power conversion module for converting the electrical energy output by the photovoltaic power supply unit into an appropriate voltage and distributing it to various devices.

7. An energy-saving drilling process, characterized in that, The photovoltaic-assisted heating structure for medium-deep heat exchange wells as described in any one of claims 1-6 is implemented using the following steps: S1: Install a photovoltaic power supply system on the ground and connect the photovoltaic power supply system to the drilling equipment; S2: Staged drilling, including at least a first-stage operation and a second-stage operation, wherein the second-stage operation includes: drilling to the second thermal reservoir (12), fixing the heating coil (5) to the outer wall of the second-stage casing (3), and lowering the second-stage casing (3); S3: Lay a two-stage cementing layer (6) on the outer wall of the two-stage casing (3) and fill the annular gap; S4: Insert the inner heat exchange tube (4) into the outer fixed sleeve.

8. The energy-saving drilling process according to claim 7, characterized in that... Step S2 includes drilling to the first thermal reservoir (11), lowering the first casing (2), and laying a first cementing layer (8) on the outer wall of the first casing (2).

9. The energy-saving drilling process according to claim 7, characterized in that, Step S3 includes: connecting both ends of the heating coil (5) to the wellhead, and reserving a connection interface with the photovoltaic power supply system.

10. The energy-saving drilling process according to claim 7, characterized in that: In step S2, the drilling equipment preferentially uses the electrical energy provided by the photovoltaic power supply system.

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