A magnetocaloric cooling system and method for downhole drilling circuits

Abstract

This invention discloses a magnetocaloric cooling system and method for downhole drilling circuits, relating to the field of downhole drilling circuit thermal management technology. The system includes: a magnetocaloric working fluid module, a magnetic field generating and modulating module, and a closed-loop heat transfer fluid circuit. The closed-loop heat transfer fluid circuit is thermally connected to the downhole drilling circuit and the magnetocaloric working fluid module. The magnetocaloric working fluid module is filled with magnetocaloric material. The magnetic field generating and modulating module applies a periodically changing magnetic field to the magnetocaloric working fluid module, causing the magnetocaloric material within the module to undergo periodic magnetization and demagnetization. The closed-loop heat transfer fluid circuit is used to complete the heat transfer and dissipation between the downhole drilling circuit and the magnetocaloric working fluid module. By constructing a magnetocaloric working fluid module, a magnetic field generating and modulating module, and a closed-loop heat transfer fluid circuit, this application utilizes the theoretical advantages of high efficiency and no self-heating accumulation of the magnetocaloric effect, thereby improving the long-term effectiveness and accuracy of downhole drilling circuit thermal management.

Description

Technical Field

[0001] This application relates to the field of downhole drilling circuit thermal management technology, and in particular to a magnetocaloric cooling system and method for downhole drilling circuits. Background Technology

[0002] In advanced technologies such as rotary steered drilling, measurement while drilling (MWD), and logging while drilling (LWD), the downhole circuitry serves as the "brain" for measurement, control, and data processing. Its long-term stability directly impacts drilling accuracy, efficiency, and safety. These circuits typically integrate high-power processors (such as FPGAs), sensors, and communication modules, generating significant heat during operation. Simultaneously, the downhole environment is extremely harsh, with temperature gradients reaching several degrees Celsius per hundred meters. In deep or ultra-deep wells, ambient temperatures often exceed 150°C or even higher. The combined heat from the circuitry itself and the high-temperature environment easily leads to overheating and failure of electronic components, severely restricting the stable operation of instruments under long-term, high-load conditions. Therefore, research on thermal management technology for downhole circuitry is necessary.

[0003] Currently, thermal management of downhole circuits mainly relies on two technical approaches: passive insulation and active cooling. While passive insulation is simple and reliable, during prolonged continuous operation, the heat generated by the circuit itself accumulates, eventually leading to "thermal saturation" of the insulation system. The internal temperature continues to rise, failing to meet the long-term, stable heat dissipation requirements of modern complex electronic systems. Active cooling technology, on the other hand, often employs thermoelectric cooling, which has the advantage of requiring no moving parts and is suitable for the downhole environment. However, the efficiency ratio of thermoelectric coolers decreases sharply with increasing temperature differences between the hot and cold ends. In the high-temperature, high-temperature-difference conditions of downhole environments, their cooling efficiency and reliability are significantly reduced, and the heating generated by the thermoelectric cooling element also exacerbates the overall thermal load of the system.

[0004] In the prior art, Chinese patent CN109798089A discloses a Stirling active cooling system and method for downhole circuits during drilling, comprising: a drill collar body, which has a hot end compartment and a circuit compartment inside; a Stirling chiller, which is a separate chiller, with its cold end connected to the downhole circuit components in the circuit compartment, and its hot end connected to a heat sink installed in the hot end compartment. This prior art uses a Stirling chiller to actively cool down the downhole circuits, without relying on the components themselves to passively "resist temperature"; powered by a downhole generator, it can ensure continuous cooling of the downhole circuits, improving the lifespan and stability of the downhole circuits.

[0005] However, the aforementioned existing technologies have low reliability under harsh working conditions of high temperature and strong vibration downhole, the cooling parameters cannot adaptively match changes in heat load, and the cooling performance is prone to decay during long-term continuous operation. The long-term effectiveness and accuracy of downhole drilling circuit thermal management need to be improved. Summary of the Invention

[0006] This application provides a magnetocaloric cooling system and method for downhole drilling circuits, which addresses the problem that the long-term effectiveness and accuracy of thermal management in downhole drilling circuits need to be improved in the prior art.

[0007] On the one hand, this application provides a magnetothermal cooling system for a downhole drilling circuit, comprising: a magnetothermal working fluid module, a magnetic field generation and modulation module, and a closed heat transfer fluid circuit disposed in a metal heat sink outside the drill collar, wherein the closed heat transfer fluid circuit is thermally connected to the downhole drilling circuit and the magnetothermal working fluid module respectively.

[0008] The interior of the magnetocaloric working fluid module is filled with magnetocaloric material.

[0009] The magnetic field generation and modulation module is used to apply a periodically changing magnetic field to the magnetocaloric working fluid module, so that the magnetocaloric material in the magnetocaloric working fluid module undergoes periodic magnetization and demagnetization.

[0010] The closed-loop heat transfer fluid circuit is used to complete the heat transfer and shifting between the downhole drilling circuit and the magnetothermal working fluid module.

[0011] In one possible implementation, the magnetothermal working fluid module has two operating states: magnetization heat release and demagnetization heat absorption.

[0012] When in the magnetized heat release working state, the magnetothermal working fluid module releases heat to the heat transfer working fluid flowing through it.

[0013] When in the demagnetization and heat absorption working state, the magnetothermal working fluid module absorbs heat from the downhole drilling circuit.

[0014] In one possible implementation, the magnetothermal working fluid module is internally provided with a microchannel heat exchange channel through which the heat transfer working fluid flows.

[0015] The microchannel heat exchange channel adopts an array of column gap channel structure. The column is a one-piece molded structure of magnetothermal material, and the gap between the columns serves as the flow channel for the heat transfer medium.

[0016] In one possible implementation, the magnetic field generating and modulation module includes a magnetic field generating coil and a magnetic field modulation unit.

[0017] The magnetic field generating coil includes a lower part and an upper part, both of which are planar rectangular spiral coils with identical structures.

[0018] The lower part and the upper part of the magnetic field generating coil are respectively attached to the upper and lower surfaces of the magnetothermal working fluid module to form a whole, and the whole is covered with a thermally conductive silicone grease layer.

[0019] When the magnetic field generating coil is energized, a magnetic field along the vertical direction is generated inside the magnetothermal working fluid module.

[0020] The magnetic field modulation unit is used to periodically control the on / off state or current direction of the magnetic field generating coil to apply a periodically changing magnetic field to the magnetothermal working fluid module.

[0021] In one possible implementation, the magnetic field modulation unit employs an adaptive resonant magnetic field modulation method, comprising the following steps:

[0022] Obtain the temperature change rate and magnetic field response phase difference of the magnetothermal working fluid module.

[0023] The operating frequency of the output pulse magnetic field is dynamically adjusted based on the temperature change rate and the phase difference of the magnetic field response.

[0024] Adjust the width and duty cycle of the output pulse according to the downhole ambient temperature and circuit heat load.

[0025] During the demagnetization phase, a reverse gradient magnetic field pulse sequence is output.

[0026] In one possible implementation, the closed heat transfer fluid loop includes a heat exchange structure, a heat transfer medium, and a pumping unit.

[0027] The heat exchange structure is thermally connected to the downhole drilling circuit and the magnetothermal working fluid module, respectively.

[0028] The heat transfer medium circulates through the interior of the magnetothermal working medium module, transferring the heat from the module to the external metal heat sink of the drill collar.

[0029] The pumping unit is used to drive the heat transfer medium to circulate between the inside of the magnetocaloric medium module and the metal heat sink outside the drill collar.

[0030] In one possible implementation, the heat exchange structure includes a lower part of a metal heat dissipation frame and an upper part of a metal heat dissipation frame.

[0031] The upper part of the metal heat dissipation frame is thermally connected to the top of the downhole drilling circuit and the external metal heat sink of the drill collar, respectively; the downhole drilling circuit, the upper part of the metal heat dissipation frame, and the external metal heat sink of the drill collar form a first heat exchange path.

[0032] The lower part of the metal heat dissipation frame is thermally connected to the bottom of the downhole drilling circuit and the top of the magnetothermal working fluid module, respectively; the downhole drilling circuit, the lower part of the metal heat dissipation frame, the magnetothermal working fluid module, the heat transfer fluid, and the external metal heat sink of the drill collar form a second heat exchange path.

[0033] On the other hand, this application provides a magnetocaloric cooling method for a downhole drilling circuit, applied to the aforementioned magnetocaloric cooling system for a downhole drilling circuit, comprising the following steps:

[0034] Start the closed heat transfer fluid loop to circulate the heat transfer medium.

[0035] The control magnetic field generation and modulation module operates by applying a periodically changing magnetic field to the magnetothermal working fluid module.

[0036] The magnetothermal working fluid module absorbs heat from the downhole drilling circuit when it is in the demagnetization and heat absorption working state.

[0037] When the magnetothermal working fluid module is in the magnetized heat release working state, it releases heat to the heat transfer working fluid flowing through it, and disperses the heat to the metal heat sink outside the drill collar through a closed heat transfer fluid loop.

[0038] The magnetocaloric cooling system and method for downhole drilling circuits disclosed in this application have the following advantages:

[0039] By constructing a magnetocaloric working fluid module, a magnetic field generation and modulation module, and a closed-loop heat transfer fluid circuit, the advantages of high theoretical efficiency and no self-heating accumulation of the magnetocaloric effect are utilized to improve the long-term effectiveness and accuracy of downhole drilling circuit thermal management. Specifically, active cooling is achieved by directly utilizing the intrinsic entropy change effect of magnetocaloric materials under the action of a periodic magnetic field. This overcomes the limitation of traditional passive insulation technology, which is prone to thermal saturation during long-term operation, and also overcomes the bottleneck of rapid energy efficiency degradation of active thermoelectric cooling in the high-temperature and large-temperature-difference environment downhole. This achieves significant advantages of high theoretical energy efficiency and strong cooling capacity.

[0040] The proposed microchannel heat exchange channel adopts an array of column gap channel structure. The column is a one-piece molded structure of magnetocaloric material. The gap between the columns serves as a flow channel for the heat transfer medium, achieving a large specific surface area and high heat exchange efficiency. This significantly improves the heat transfer rate between the magnetocaloric material and the heat transfer medium, and realizes the miniaturization of the overall system.

[0041] The proposed adaptive resonant magnetic field modulation method includes the following steps: acquiring the temperature change rate and magnetic field response phase difference of the magnetothermal working fluid module; dynamically adjusting the operating frequency of the output pulse magnetic field based on the temperature change rate and the magnetic field response phase difference; adjusting the width and duty cycle of the output pulse based on the downhole ambient temperature and circuit heat load; and outputting a reverse gradient magnetic field pulse sequence during the demagnetization stage. This achieves precise adjustment of the magnetic field strength, frequency, and operating rhythm, thereby enabling highly intelligent operation with controllable cooling power and precise temperature regulation.

[0042] The proposed heat exchange structure is thermally connected to both the downhole drilling circuit and the magnetocaloric working fluid module. The heat transfer fluid circulates through the interior of the magnetocaloric working fluid module, transferring heat from the module to the external metal heat sink of the drill collar. A pumping unit drives the heat transfer fluid to circulate between the interior of the magnetocaloric working fluid module and the external metal heat sink of the drill collar. This allows for the sustainable and efficient transfer of heat from the downhole drilling circuit to the external metal heat sink of the drill collar, preventing heat accumulation and ensuring excellent stability and reliability of the system under long-term, high-load downhole operations. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 A schematic diagram of a magnetocaloric cooling system for a downhole drilling circuit provided in this application embodiment;

[0045] Figure 2 This is a schematic diagram of the downhole drilling circuit provided in the embodiments of this application;

[0046] Figure 3 This is a schematic diagram of the working state of the magnetocaloric working fluid module provided in the embodiments of this application;

[0047] Figure 4 This is a schematic diagram of the internal structure of the magnetocaloric working fluid module provided in an embodiment of this application;

[0048] Figure 5 This is a schematic diagram of the internal structure of the magnetic field generating coil provided in an embodiment of this application;

[0049] Figure 6 A schematic flowchart of the adaptive resonant magnetic field modulation method provided in the embodiments of this application;

[0050] Figure 7 A schematic diagram of the heat exchange structure, magnetocaloric working fluid module, magnetic field generation and modulation module, and downhole drilling circuit provided in the embodiments of this application;

[0051] Figure 8 This is a schematic flowchart of a magnetocaloric cooling method for a downhole drilling circuit provided in an embodiment of this application.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1-External metal heat sink of drill collar, 2-Water eye, 3-Lower part of magnetic field generating coil, 31-Planar rectangular spiral coil, 32-Thermoconductive silicone grease layer, 4-Magnetic thermal working fluid module, 41-Microchannel heat exchange channel, 42-Column, 5-Upper part of magnetic field generating coil, 6-Lower part of metal heat dissipation frame, 7-Upper part of metal heat dissipation frame, 8-Downhole drilling circuit, 81-Three-phase rectifier circuit, 82-Rectifier diode, 83-Magnetic field modulation unit. Detailed Implementation

[0054] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0055] like Figure 1 As shown, this application embodiment provides a magnetothermal cooling system for a downhole drilling circuit 8, including: a magnetothermal working fluid module 4 disposed in a metal heat sink 1 outside the drill collar, a magnetic field generation and modulation module, and a closed heat transfer fluid circuit, wherein the closed heat transfer fluid circuit is thermally connected to the downhole drilling circuit 8 and the magnetothermal working fluid module 4 respectively.

[0056] The interior of the magnetocaloric working fluid module 4 is filled with magnetocaloric material.

[0057] The magnetic field generation and modulation module is used to apply a periodically changing magnetic field to the magnetocaloric working fluid module 4, so that the magnetocaloric material in the magnetocaloric working fluid module 4 undergoes periodic magnetization and demagnetization.

[0058] The closed-loop heat transfer fluid circuit is used to complete the heat transfer and transfer between the downhole drilling circuit 8 and the magnetothermal working fluid module 4.

[0059] like Figure 2 As shown, specifically in this embodiment, the downhole drilling circuit 8 is a three-phase rectifier circuit 81. The three-phase rectifier circuit 81 is equipped with several rectifier diodes 82, which are used to convert the AC power output from the downhole generator into DC power to supply the downhole control system. When the three-phase rectifier circuit 81 is working, it generates a large amount of heat due to the conduction voltage drop of the rectifier diodes 82 and the switching losses, becoming one of the main heat sources in the system.

[0060] For example, the magnetothermal working fluid module 4 has two working states: magnetization heat release and demagnetization heat absorption.

[0061] When in the magnetized heat release working state, the magnetothermal working fluid module 4 releases heat to the heat transfer working fluid flowing through it.

[0062] When in the demagnetization and heat absorption working state, the magnetothermal working fluid module 4 absorbs heat from the downhole drilling circuit 8.

[0063] like Figure 3 As shown, specifically in this embodiment, the magnetization heat release working state is as follows: when an external magnetic field is applied, the magnetic moments inside the magnetocaloric material are arranged in an orderly manner, the entropy decreases, and thus sensible heat is released to the surrounding environment.

[0064] Demagnetization and heat absorption working state: When the external magnetic field is removed or weakened, the magnetic moment of the magnetocaloric material becomes disordered, the entropy increases, and it absorbs heat from the surrounding environment to achieve a cooling effect.

[0065] The theoretical cooling capacity of the magnetocaloric working fluid module 4 in a single cycle is directly related to the magnetocaloric effect intensity of the material, and can be calculated using the following formula:

[0066] .

[0067] in, This represents the average cooling power. Let be the magnetic field circulation frequency, and m be the effective mass of the magnetocaloric material. It is an isothermal magnetic entropy change. and These are the temperatures of the cold end (circuit side) and the hot end (heat dissipation side), respectively.

[0068] In high-temperature and high-pressure downhole environments, the magnetic entropy change of magnetocaloric materials varies significantly with temperature and pressure, which can be described using a modified Landau theoretical model:

[0069] .

[0070] in, Indicates the magnetocaloric material at a given temperature and pressure Isothermal entropy change under the following conditions Let be the magnetization, and a, b, and c be the material-related thermodynamic coefficients. The permeability of free space, The external magnetic field strength, Using the magnetic moment, this model can accurately characterize the performance evolution of magnetocaloric materials under combined conditions of high temperature (>150°C) and high pressure (>100 MPa).

[0071] For example, the magnetothermal working fluid module 4 is provided with a microchannel heat exchange channel 41 through which the heat transfer working fluid flows.

[0072] The microchannel heat exchange channel 41 adopts an array of column 42 gap channel structure. The column 42 is a one-piece structure of magnetothermal material, and the gap between the columns 42 serves as a flow channel for the heat transfer medium.

[0073] like Figure 4 As shown, specifically in this embodiment, the interior of the magnetothermal working fluid module 4 is filled with magnetothermal material except for the microchannel heat exchange channel 41, forming a compact structure in which the magnetothermal material and the heat exchange channel are highly coupled to improve heat exchange efficiency.

[0074] Specifically, the magnetocaloric material uses a gadolinium (Gd)-based alloy series, Gd-Si-Ge. By adjusting the Si / Ge ratio, its Curie temperature can be fine-tuned within the range of 280 K to 295 K to adapt to the downhole environment. Material preparation employs a vacuum induction melting followed by directional solidification process to obtain a bulk material with consistent grain orientation and high thermal conductivity. This material is then crushed, sieved, and sintered to form a porous bed with a porosity of [missing information]. The permeability K satisfies:

[0075] .

[0076] in, The average diameter of the magnetocaloric particles is used to balance heat transfer efficiency and flow resistance.

[0077] For example, the magnetic field generating and modulation module includes a magnetic field generating coil and a magnetic field modulation unit 83.

[0078] The magnetic field generating coil includes a lower part 3 and an upper part 5, both of which are planar rectangular spiral coils 31 with identical structures.

[0079] The lower part 3 and the upper part 5 of the magnetic field generating coil are respectively attached to the upper and lower surfaces of the magnetothermal working fluid module 4 to form a whole, and the whole is covered with a thermally conductive silicone grease layer 32.

[0080] When the magnetic field generating coil is energized, a magnetic field along the vertical direction is generated inside the magnetothermal working fluid module 4.

[0081] The magnetic field modulation unit 83 is used to periodically control the on / off state or current direction of the magnetic field generating coil to apply a periodically changing magnetic field to the magnetothermal working fluid module 4.

[0082] like Figure 5 As shown, specifically, in this embodiment, the magnetic field strength at the center of the coil... Linear control can be achieved by adjusting the excitation current I, and the relationship is as follows:

[0083] .

[0084] in, ρ is the permeability of free space, and n is the number of turns per unit length of the coil.

[0085] Specifically, the magnetic field modulation unit 83 is implemented based on a full-bridge inverter circuit. It controls the on and off of the power switching transistors through a PWM signal, thereby periodically changing the direction and magnitude of the current flowing into the coil to generate a square wave or sine wave magnetic field of the required frequency. The modulation unit integrates temperature and magnetic field sensors to form a closed-loop control, which can adjust the frequency and intensity of the magnetic field in real time according to the circuit's thermal load.

[0086] The dynamic cooling response of the system can be expressed by the following transfer function. describe:

[0087] .

[0088] in, The change in the input control signal. For system gain, For the time lag, It is a time constant. As a transfer function operator, this model is used to achieve rapid temperature control by taking control parameters into account.

[0089] like Figure 6 As shown, exemplarily, the magnetic field modulation unit 83 employs an adaptive resonant magnetic field modulation method, including the following steps:

[0090] The temperature change rate and magnetic field response phase difference of the magnetothermal working fluid module 4 are obtained.

[0091] The operating frequency of the output pulse magnetic field is dynamically adjusted based on the temperature change rate and the phase difference of the magnetic field response.

[0092] Adjust the width and duty cycle of the output pulse according to the downhole ambient temperature and circuit heat load.

[0093] During the demagnetization phase, a reverse gradient magnetic field pulse sequence is output.

[0094] Specifically, in this embodiment, the temperature change rate of the magnetic thermal working fluid module 4 is obtained. Phase difference with magnetic field response Control signals during the magnetization stage for:

[0095] .

[0096] in, The temperature change rate sensitivity coefficient, As a reference temperature change rate threshold, The fundamental magnetic field oscillation frequency, Gain modulated by heat load, For circuit heat load, This is the design value for the maximum heat load.

[0097] Based on the temperature change rate and the magnetic field response phase difference, if resonance matching is not satisfied, the operating frequency of the output pulse magnetic field is dynamically adjusted. :

[0098] .

[0099] in, Based on the base frequency, This is the frequency adjustment coefficient. For rectified linear unit functions, This is the normalized magnetic field control signal.

[0100] Adjust the width and duty cycle of the output pulse according to the downhole ambient temperature and circuit heat load. :

[0101] .

[0102] in, Based on duty cycle, This is the duty cycle adjustment coefficient. For the normalized reference amplitude, Downhole ambient temperature, This is a reference temperature.

[0103] During the demagnetization phase, a reverse gradient magnetic field pulse sequence is output:

[0104] .

[0105] in, This is the control signal for the demagnetization stage. This is the normalized value of the maximum magnetic field strength. The decay rate coefficient, This is the demagnetization start time. For the first The center time of each pulse For adaptive pulse width, For reference heat load, The coupling coefficient between ambient temperature and heat load. For temperature scale.

[0106] For example, the closed heat transfer fluid loop includes a heat exchange structure, a heat transfer medium, and a pumping unit.

[0107] The heat exchange structure is thermally connected to the downhole drilling circuit 8 and the magnetothermal working fluid module 4, respectively.

[0108] The heat transfer medium circulates through the interior of the magnetothermal working medium module 4, transferring the heat from the magnetothermal working medium module 4 to the external metal heat sink 1 of the drill collar.

[0109] The pumping unit is used to drive the heat transfer medium to circulate between the inside of the magnetothermal medium module 4 and the metal heat sink 1 outside the drill collar.

[0110] Specifically, in this embodiment, a fluorinated liquid with high heat capacity, low viscosity, and high boiling point is selected as the heat transfer medium, which remains in a liquid state within the operating temperature range (150-200°C).

[0111] The pumping unit employs a magnetically coupled miniature plunger pump. The pump body and drive unit are completely sealed by an isolation cover, achieving leak-free operation. The pump's flow rate... Based on system heat load and working fluid temperature rise design:

[0112] .

[0113] in, For cooling capacity, For the working fluid density, The heat capacity of the working fluid.

[0114] Pressure loss in the fluid circuit under high temperature and high pressure conditions Permeability of porous media is required Coupled calculations with pipeline flow:

[0115] .

[0116] in, The dynamic viscosity of the fluid. For flow rate, The length of the flow channel. Equivalent diameter The friction factor is used in this model to optimize pumping power and system efficiency.

[0117] like Figure 7 As shown, exemplarily, the heat exchange structure includes a lower metal heat dissipation frame 6 and an upper metal heat dissipation frame 7.

[0118] The upper part 7 of the metal heat dissipation frame is thermally connected to the top of the downhole drilling circuit 8 and the external metal heat sink 1 of the drill collar; the downhole drilling circuit 8, the upper part 7 of the metal heat dissipation frame, and the external metal heat sink 1 of the drill collar form a first heat exchange path.

[0119] The lower part 6 of the metal heat dissipation frame is thermally connected to the bottom of the downhole drilling circuit 8 and the top of the magnetothermal working fluid module 4, respectively; the downhole drilling circuit 8, the lower part 6 of the metal heat dissipation frame, the magnetothermal working fluid module 4, the heat transfer fluid, and the metal heat sink 1 outside the drill collar form a second heat exchange path.

[0120] Specifically, in this embodiment, through the first heat exchange path, the upper part 7 of the metal heat dissipation frame absorbs part of the heat generated by the rectifier diode 82 of the downhole drilling circuit 8 during operation and conducts it to the metal heat sink 1 outside the drill collar.

[0121] Through the second heat exchange path, the lower part 6 of the metal heat dissipation frame absorbs another part of the heat generated by the rectifier diode 82 of the downhole drilling circuit 8 during operation. The heat is then transferred to the external metal heat sink 1 of the drill collar through the magnetothermal working fluid module 4 and the heat transfer working fluid, and finally discharged to the outside with the help of the drilling fluid in the water hole 2.

[0122] Through the coordinated operation of the first and second heat exchange paths, the system can form a complete heat transfer path, thereby achieving continuous and efficient cooling of the heat-generating parts of the downhole drilling circuit 8.

[0123] like Figure 8 As shown, this application embodiment also provides a magnetocaloric cooling method for a downhole drilling circuit 8, applied to the aforementioned magnetocaloric cooling system for a downhole drilling circuit 8, comprising the following steps:

[0124] Start the closed heat transfer fluid loop to circulate the heat transfer medium.

[0125] The control magnetic field generation and modulation module operates to apply a periodically changing magnetic field to the magnetothermal working fluid module 4.

[0126] When the magnetothermal working fluid module 4 is in the demagnetization and heat absorption working state, it absorbs heat from the downhole drilling circuit 8.

[0127] When the magnetothermal working fluid module 4 is in the magnetized heat release working state, it releases heat to the heat transfer working fluid flowing through it, and disperses the heat to the metal heat sink 1 outside the drill collar through a closed heat transfer fluid loop.

[0128] This application embodiment utilizes the advantages of high theoretical efficiency and no self-heating accumulation of the magnetocaloric effect by constructing a magnetocaloric working fluid module 4, a magnetic field generation and modulation module, and a closed heat transfer fluid loop, thereby improving the long-term effectiveness and accuracy of thermal management in the downhole drilling circuit 8. Specifically, it directly utilizes the intrinsic entropy change effect of the magnetocaloric material under the action of a periodic magnetic field for active cooling, breaking through the limitation of traditional passive insulation technology that is prone to thermal saturation during long-term operation, and also overcoming the bottleneck of the rapid decline in energy efficiency ratio of active thermoelectric cooling in the high-temperature and large-temperature-difference environment downhole, achieving significant advantages of high theoretical energy efficiency and strong cooling capacity.

[0129] The proposed microchannel heat exchange channel 41 adopts an array of column 42 gap channel structure. The column 42 is an integrally formed structure of magnetocaloric material. The gap between the columns 42 serves as a flow channel for the heat transfer medium, achieving a large specific surface area and high heat exchange efficiency. This significantly improves the heat transfer rate between the magnetocaloric material and the heat transfer medium, and realizes the miniaturization of the overall system.

[0130] The proposed adaptive resonant magnetic field modulation method includes the following steps: acquiring the temperature change rate and magnetic field response phase difference of the magnetothermal working fluid module 4; dynamically adjusting the operating frequency of the output pulse magnetic field based on the temperature change rate and the magnetic field response phase difference; adjusting the width and duty cycle of the output pulse based on the downhole ambient temperature and circuit heat load; and outputting a reverse gradient magnetic field pulse sequence during the demagnetization stage. This achieves precise adjustment of the magnetic field strength, frequency, and operating rhythm, thereby enabling highly intelligent operation with controllable cooling power and precise temperature regulation.

[0131] The proposed heat exchange structure is thermally connected to the downhole drilling circuit 8 and the magnetocaloric working fluid module 4, respectively. The heat transfer fluid circulates through the interior of the magnetocaloric working fluid module 4, transferring the heat from the module to the external metal heat sink 1 of the drill collar. The pumping unit drives the heat transfer fluid to circulate between the interior of the magnetocaloric working fluid module 4 and the external metal heat sink 1 of the drill collar. This allows for the sustainable and efficient transfer of heat from the downhole drilling circuit 8 to the external metal heat sink 1 of the drill collar, preventing heat accumulation and ensuring excellent stability and reliability of the system under long-term, high-load downhole operations.

[0132] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0133] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A magnetocaloric cooling system for a downhole drilling circuit, characterized in that, include: A magnetothermal working fluid module, a magnetic field generation and modulation module, and a closed heat transfer fluid circuit are installed inside the metal heat sink outside the drill collar. The closed heat transfer fluid circuit is thermally connected to the downhole drilling circuit and the magnetothermal working fluid module, respectively. The interior of the magnetic-thermal working fluid module is filled with magnetic-thermal material; The magnetic field generation and modulation module is used to apply a periodically changing magnetic field to the magnetocaloric working fluid module, so that the magnetocaloric material in the magnetocaloric working fluid module undergoes periodic magnetization and demagnetization. The closed-loop heat transfer fluid circuit is used to complete the heat transfer and shifting between the downhole drilling circuit and the magnetothermal working fluid module; The magnetothermal working fluid module is internally equipped with a microchannel heat exchange channel through which the heat transfer working fluid flows. The microchannel heat exchange channel adopts an array of column gap channel structure. The column is a one-piece structure of magnetocaloric material, and the gap between the columns serves as a flow channel for the heat transfer medium. The heat exchange structure includes a lower metal heat dissipation frame and an upper metal heat dissipation frame; The upper part of the metal heat dissipation frame is thermally connected to the top of the downhole drilling circuit and the external metal heat sink of the drill collar, respectively; the downhole drilling circuit, the upper part of the metal heat dissipation frame, and the external metal heat sink of the drill collar form a first heat exchange path; The lower part of the metal heat dissipation frame is thermally connected to the bottom of the downhole drilling circuit and the top of the magnetocaloric working fluid module, respectively; the downhole drilling circuit, the lower part of the metal heat dissipation frame, the magnetocaloric working fluid module, the heat transfer fluid, and the metal heat sink outside the drill collar form a second heat exchange path. The magnetic field generating and modulation module includes a magnetic field generating coil and a magnetic field modulation unit; The magnetic field generating coil includes a lower part and an upper part, and the lower part and the upper part are planar rectangular spiral coils with the same structure. The lower part and the upper part of the magnetic field generating coil are respectively attached to the upper and lower surfaces of the magnetothermal working fluid module to form a whole, and the whole is covered with a thermally conductive silicone grease layer. When the magnetic field generating coil is energized, a magnetic field along the vertical direction is generated inside the magnetic thermal working fluid module. The magnetic field modulation unit is used to periodically control the on / off state or current direction of the magnetic field generating coil to apply a periodically changing magnetic field to the magnetothermal working fluid module. The magnetic field modulation unit employs an adaptive resonant magnetic field modulation method, including the following steps: Obtain the temperature change rate and magnetic field response phase difference of the magnetocaloric working fluid module; The operating frequency of the output pulse magnetic field is dynamically adjusted based on the temperature change rate and the phase difference of the magnetic field response. Adjust the width and duty cycle of the output pulse according to the downhole ambient temperature and circuit heat load; During the demagnetization phase, a reverse gradient magnetic field pulse sequence is output.

2. The magnetocaloric cooling system for a downhole drilling circuit according to claim 1, characterized in that, The magnetocalor module has two working states: magnetization heat release and demagnetization heat absorption. When in the magnetized heat release working state, the magnetothermal working fluid module releases heat to the heat transfer working fluid flowing through it; When in the demagnetization and heat absorption working state, the magnetothermal working fluid module absorbs heat from the downhole drilling circuit.

3. The magnetocaloric cooling system for a downhole drilling circuit according to claim 1, characterized in that, The closed heat transfer fluid loop includes a heat exchange structure, a heat transfer medium, and a pumping unit. The heat exchange structure is thermally connected to the downhole drilling circuit and the magnetothermal working fluid module, respectively. The heat transfer medium circulates through the interior of the magnetocaloric medium module, transferring the heat from the magnetocaloric medium module to the external metal heat sink of the drill collar. The pumping unit is used to drive the heat transfer medium to circulate between the inside of the magnetocaloric medium module and the metal heat sink outside the drill collar.

4. A magnetocaloric cooling method for a downhole drilling circuit, applied to a magnetocaloric cooling system for a downhole drilling circuit as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Start the closed heat transfer fluid loop to circulate the heat transfer medium. The control magnetic field generation and modulation module operates by applying a periodically changing magnetic field to the magnetothermal working fluid module; When the magnetothermal working fluid module is in demagnetization and heat absorption mode, it absorbs heat from the downhole drilling circuit. When the magnetothermal working fluid module is in the magnetized heat release working state, it releases heat to the heat transfer working fluid flowing through it, and disperses the heat to the metal heat sink outside the drill collar through a closed heat transfer fluid loop.

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