Cooling system, downhole device, and method

Abstract

A cooling system (1) for cooling a portion of a downhole device (100), the cooling system (1) comprises a main body (2) having a longitudinal axis (96), wherein: - the cooling system (1) comprises a first section (3) and a second section (4) positioned inside the main body (2); - the first section (3) is connected to the second section (4) via a first heat transfer means (62); and - the first heat transfer means (62) is adapted to transfer a heat created in the first section (3) to the second section (5)

Description

[0001] COOLING SYSTEM, DOWNHOLE DEVICE, AND METHOD

[0002] The disclosure relates to a cooling system for cooling a portion of a downhole device, the downhole device comprising the cooling system and a method for cooling the downhole device.

[0003] Designing downhole devices is fraught with challenges. A downhole device may be utilized in a sequence of operations across various production wells. These operations may impose diverse restrictions related to the size of the tubular structure and the types of forces the downhole device must resist. Consequently, these tools must exhibit sufficient strength both longitudinally and circumferentially to endure axial, torsional, and bending forces.

[0004] Furthermore, downhole devices encounter varying well conditions, such as whether the wells are filled with liquid or gas. These conditions may affect the downhole device's ability to transfer heat from heat-generating components of the downhole device and into the surrounding fluid. Heat transfer is generally less efficient into a gas than a liquid. If the surrounding fluid is in motion, it aids in more efficient cooling of the device's exterior compared to stationary fluid.

[0005] To maximize the versatility of the downhole device, it is desirable to minimize modifications of the device within a series of operations. Downhole environments may be extremely hot, necessitating the design of tools that may effectively dissipate heat from the downhole device, fit into most wellbores, and maintain sufficient structural strength.

[0006] As recognized in the field, it is preferable to have shorter downhole devices so that more devices may be safely introduced into the wellbore through a sluice, also known as a lubricator. Moreover, the reliability of electronics decreases when exposed to high temperatures over time. Therefore, it is desirable to keep the temperature of electronics as low as possible to prolong their usable life, reliability, and operational time while downhole.

[0007] US5931000A discloses a cooled electrical system for downhole use. The system includes several thermoelectric coolers adapted to transfer heat between bodies within an electronic section. Heat is transferred radially from the heat-generating components. The system includes springs to ensure good heat transfer contact between two bodies in the radial direction. However, heat is concentrated around and near the heat-generating bodies and transferred radially, thus limiting the cooling area. This results in ineffective heat transfer and restricts the amount of heat that may be generated within a part of the electrical system.

[0008] US20180347336A1 discloses a system for improving the use of a thermoelectric cooler in a downhole tool. The system includes a chassis with printed circuit boards and electric components that generate heat. The chassis is connected to one, two or more thermoelectric coolers, also commonly known as Peltier elements, positioned perpendicularly to the longitudinal axis for transferring heat away from the chassis. Each thermoelectric cooler is connected to a cooling means comprising a cooling fluid for further heat transfer away from the chassis. However, if the cooling fluid leaks within the system, it may reach the thermoelectric coolers or the electronics, potentially causing a short circuit and significant damage to the tool, as well as operational downtime. Furthermore, the cooling fluid needs to be pressure compensated, thereby increasing the complexity and length of the cooling system. Another disadvantage is that the cooling fluid must be kept separate from the electronics during maintenance to prevent contamination, thus complicating maintenance.

[0009] The disclosure has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art. The object is achieved through features, which are specified in the description below and in the claims that follow.

[0010] The disclosure is defined by the independent patent claims. The dependent claims define advantageous embodiments of the disclosure.

[0011] In a first aspect the disclosure relates more particularly to a cooling system for cooling a portion of a downhole device, the cooling system comprising a main body having a longitudinal axis, wherein: - the cooling system comprises a first section and a second section positioned inside the main body;

[0012] - the first section being connected to the second section via a first heat transfer means; and

[0013] - the first heat transfer means being adapted to transfer a heat created in the first section to the second section.

[0014] In an embodiment of the cooling system, the main body may serve multiple purposes. It may provide structural strength to the downhole device, prevent environmental fluid from entering the downhole device or the cooling system, and / or transfer heat created within the downhole device into the surrounding gas or liquid within a wellbore. This heat transfer from the main body to the surrounding fluid may be passive, occurring via conduction, convection, radiation, or a combination thereof.

[0015] In an embodiment, the main body may be situated within an outer body of the downhole device, allowing heat transfer between the main body of the cooling system and the outer body of the downhole device via conduction, convection, radiation, or a combination.

[0016] The downhole device may include a gas-filled pressure chamber housing heat-generating components, such as electronic components. In an embodiment, the main body may form parts of the pressure chamber and may form part of or form the outer body of the downhole device. Given that gas is less efficient at transferring heat and electronics are more reliable in a gas-filled environment compared to a liquid-filled one, this presents challenges in transferring heat away from any thermal component in a gas-filled environment to maintain an as low temperature as possible for increased reliability.

[0017] The downhole device may be any device with heat-creating components, such as electronic boards, image sensors, lighting means, or any other suitable downhole device with heat-creating components that may be cooled by the cooling system.

[0018] In an embodiment, the downhole device may be an inspection device comprising a plurality of image sensors, each accompanied by at least one lighting means. The image sensors and the lighting means may be connected to an electronics section that includes a printed circuit board with heat-creating electronic components. In this embodiment, it is desirable to have an efficient cooling system that transfers heat away from areas where heat is concentrated.

[0019] The first section may accommodate a first thermal component. In an embodiment of the cooling system, the first section may accommodate a plurality of first thermal components arranged in a circumferential array. Each first thermal component may be similarly oriented with respect to the longitudinal axis in, such as facing radially outward in a plane. For increased reliability and predictability, it is desirable to cool these thermal components equally so that the temperature in each first thermal component is substantially equal to that of adjacent thermal components.

[0020] The first section may be designed such that the first thermal component may be positioned on it with a complementary fit. The first thermal component may include a heat transfer surface, and the first section may include a heat receiving surface. The heat transfer surface and the heat receiving surface may have a complementary fit that allows heat transfer via conduction. The heat transfer surface may be defined as the area where the majority of the heat created by the first thermal component is concentrated. This may be a surface facing in the opposite direction of the lighting means, which may be a LED. While the LED may be mounted on a large circuit board, only a small portion of the board may actually be heated by the LED. Therefore, the area where most of the LED's heat is concentrated may be defined as the heat transfer surface. In an embodiment, heat may be transferred radially inwardly into the first section towards the longitudinal axis from the first thermal component, such as the lighting means or the image sensor, which points radially outwardly. This design facilitates efficient heat dissipation from the components that creates the most heat.

[0021] The first thermal component may be an electric device. In an embodiment of the cooling system, the first thermal component may be the image sensors or the lighting means. A plurality of image sensors may be positioned in an image plane to inspect a circumferential sector of the environment surrounding the first section. Alternatively, or additionally, a plurality of lighting means may be positioned in a lighting plane in a circumferential ar- ray and face radially outwardly to illuminate the circumferential sector in the surrounding environment.

[0022] In an embodiment of the cooling system, the image sensor may be accompanied by the lighting means arranged in the circumferential array on each side and at a distance from the image sensor relative to the longitudinal axis.

[0023] Thus, heat may be concentrated in the first section in cross-sections perpendicular to the longitudinal axis, making it difficult to dissipate heat radially outwardly into a fluid surrounding the downhole device since heat is created radially.

[0024] The main body houses the first section and the second section, which are connected via the first heat transfer means. The first section and the second section may be connected in series along the longitudinal axis. This arrangement allows heat from the first thermal component to be transferred into the first section and then actively moved into the second section along the longitudinal axis. This active transfer of heat facilitates efficient dissipation of heat over a larger area away from the heat source.

[0025] The term "actively" in the context of heat transfer may be defined as the process of moving heat energy from one side of a heat transfer means to the opposite side. This process results in a decrease in heat energy, or a lowering of temperature, on one side of the heat transfer means, and a corresponding increase in heat energy, or a rise in temperature, on the opposite side. Therefore, heat or heat energy is actively transported from one side to the other side of the heat transfer means.

[0026] The first heat transfer means may be a heat pump, a heat exchanger, or any other suitable device for actively transferring heat.

[0027] In an embodiment, the first heat transfer means may be a Peltier element. This allows heat transfer without using a cooling fluid.

[0028] In an embodiment, the first heat transfer means may be an annular Peltier element. This allows efficient heat transfer along the longitudinal axis and may also serve as part of a wireguide for guiding wires between the first section and the second section. The annular Peltier element may have an outer diameter close to an inside / inner diameter of the main body, and an inner diameter adapted to accommodate a desired number of wires. The annular Peltier element may provide substantially equal cooling of the first thermal components in a cooling system comprising the plurality of first thermal components arranged in the circumferential array.

[0029] The second section may comprise a second thermal component. The second thermal component may be an electronic board with electrical components for controlling and processing inputs and outputs from the first thermal component. The inclusion of the second thermal component within the second section allows for a more compact design of the downhole device. This is because the second section serves a dual purpose: it not only receives heat from the first section but also houses the second thermal component. This efficient use of space results in a shorter downhole device compared to a design where the second section is solely for receiving heat from the first section.

[0030] Furthermore, the second section comprising the second thermal component allows the second thermal component to be positioned close to the first thermal component. This proximity may lead to reduced noise in electronic communication between the first and second thermal components, assuming they are connected. This may enhance the overall performance and reliability of the system.

[0031] While it may seem counterintuitive to place the second thermal component in the second section due to potential heat transfer from the first section, this is acceptable in some embodiments of the cooling system. The second thermal component may produce less heat than the first thermal component, and heat transferred from the first section may dissipate before reaching the second thermal component.

[0032] To protect critical components like electronics from elevated temperatures, the second thermal component may comprise a chassis. The chassis may shield the second thermal component, such as the electronic board, from heat transferred from the first section to the second section. In an embodiment, the chassis may at least partially shield the second thermal component. The chassis may be adapted to shield such that heat is not transferred from the second section to the second thermal component via conduction, radia- tion, and / or convection or at least that such transfer is significantly limited.

[0033] The second section may comprise a second heat transfer means adapted to transfer heat from the second thermal component and into the main body via the second section. In an embodiment, the second heat transfer means may establish a connection between the second thermal component and a portion of the second section that may be particularly suited for transferring heat into the main body. The portion suitable to transfer heat to the main body may be where is transferred from the second section to the main body mainly via conduction. Alternatively, or additionally, the portion suitable to transfer heat to the main body may be where heat is transferred via convection and / or radiation sufficiently efficient to avoid overheating the first thermal component and the second thermal component.

[0034] In an embodiment, the second thermal component may have the capability to transfer heat into the chassis. The chassis, in turn, may be connected to the aforementioned portion of the second section that is adept at transferring heat into the main body. This connection may be facilitated by the second heat transfer means. As a result of this arrangement, the chassis undergoes cooling and subsequently forms a cooling shield. This shield, enveloping at least a part of the electronics board, aids in its thermal management.

[0035] The second heat transfer means may actively transfer heat from the second thermal component into the portion of the second section suitable for heat transfer into the main body, primarily via conduction. In an embodiment, heat may also be transferred via convection and / or radiation from the second thermal component to the second section.

[0036] In an embodiment, the second heat transfer means may comprise a Peltier element, such as the annular Peltier element. The Peltier element may extend in a plane that is perpendicular to the longitudinal axis. This configuration enables the heat from the second thermal component to be transferred further away from the first section along the longitudinal axis. In an embodiment, the heat may then be transferred into the main body. The part of the main body that is suitable for this heat transfer may be positioned adjacent to the second thermal component, along the longitudinal axis. The second heat transfer means may be a Peltier element extending along the longitudinal axis. This configuration allows heat to be transferred radially into the portion of the main body that is suitable for heat transfer. It also enables heat to be transferred over a larger area in an axial direction, as the envelope for heat transfer may be more limited in relation to a plane perpendicular to the longitudinal axis compared to a plane oriented along the longitudinal axis. Consequently, heat may be transferred from the first section along the longitudinal axis into the second section, and from the second section radially into the main body. This allows heat to be transferred into the fluid surrounding the downhole device over a larger area compared to if heat were solely transferred radially from where heat is created.

[0037] Elevated temperatures over time, particularly in electronics, may reduce reliability. Therefore, it is desirable to keep the temperature in the first thermal component and / or the second thermal component as low as possible. The cooling system may comprise a third section, where the third section may be positioned inside the main body and connected to the first section in an opposite end from where the second section is connected. This arrangement allows heat to be transferred via conduction from the first section to the third section. Thus, heat may be transferred from the first section to both the second section and the third section, allowing heat to be transferred from the first section in both directions along the longitudinal axis. This provides an efficient way of transferring heat from the first section, which may be the section that creates the most heat and / or is the most heat-sensitive section.

[0038] In an embodiment, the first section and the third section may be connected via a third heat transfer means. The third heat transfer means may actively transfer heat from the first section to the third section, thereby actively cooling the first section where the second and third sections are connected. Having the first section actively cooled from each side of the first section, relative to the longitudinal axis, allows for substantially uniform cooling of the first thermal component from each side.

[0039] The third heat transfer means may be an annular Peltier element. This allows heat to be transferred from the first section to the third section while a wire guide may be created such that wires may be guided from the first section into the third section. The annular Peltier element may be positioned concentric with the longitudinal axis and the first section. The annular Peltier element connecting the first section to the third section may be similar or equal to the annular Peltier element connecting the first section to the second section.

[0040] In an embodiment of the cooling system that includes a plurality of first thermal components arranged in a circumferential array, the annular Peltier element connecting the first and third sections provides substantially equal cooling of the first thermal components since the annular Peltier element cools a cross-section equally.

[0041] As mentioned, transferring heat along the longitudinal axis away from the first section is beneficial for the first thermal component. Heat transfer within the first section, the second section, and / or the third section may be efficiently achieved by choosing an appropriate material with sufficient heat conductivity, as will be discussed below. To improve heat transfer between the first, second and third sections, the first heat transfer means is included in the cooling system while the second and third heat transfer means may be added if needed.

[0042] For the cooling system to efficiently cool the first and second thermal components, it may be desirable to transfer heat into the fluid surrounding the downhole device at a rate equal to or higher than the heat created within the cooling system. This avoids build-up of heat energy over time.

[0043] Heat transfer between the third section and the main body may occur via conduction, convection, or radiation, which may be less efficient than actively transferring heat between the sections. The third section may have a length along the longitudinal axis that is greater compared to a length perpendicular to the longitudinal axis. This provides a larger heat exchange surface between the third section and the main body compared to between the first section and the third section. Although the heat exchange surface in the third section may lack efficiency in transferring heat between the third section and the main body via conduction when compared to the third heat transfer means actively transferring heat, the third section may compensate with a larger heat exchange surface ex- tending along the longitudinal axis. This allows heat to be transferred to the main body without active transfer. As a result, heat from the first section may be sufficiently transferred to the main body and into the fluid surrounding the downhole device without heat accumulating in the first section and / or the third section.

[0044] In an embodiment of the cooling system, the second section may have a length along the longitudinal axis that is greater compared to a length perpendicular to the longitudinal axis for the same reasons as the third section may have a length along the longitudinal axis that is greater than the length perpendicular to the longitudinal axis.

[0045] To efficiently transfer heat from the third section to the main body and, to avoid an excessive length along the longitudinal axis, the heat transfer preferably occurs primarily via conduction, which is the most efficient method for transferring heat, with only limited transfer via convection and radiation. The third section may be configured to have a clearance fit with the main body during maintenance, and a press fit with the main body when the temperature of the third section reaches a heat transfer temperature. This allows heat to be transferred from the third section to the main body substantially via conduction. The temperature during maintenance may be a common room temperatures. The heat transfer temperature may be a temperature elevated above maintenance temperature where it is desirable to transfer heat away from the first section to avoid excessive temperature for electronics. The heat transfer temperature may depend on the embodiment of the first thermal component and / or the second thermal component. By selecting a material in the main body with a lower coefficient of thermal expansion compared a chosen material in the third section, the third section expands more than the main body with temperature. The clearance between the third section and the main body may be selected such that there is a clearance fit at room temperature where maintenance is usually performed, while at the elevated heat transfer temperature, the third section has expanded more than the main body, resulting in a press fit between the third section and the main body in operation. The clearance between the third section and the main body may be calculated once the material in the main body, which may mainly be determined based on structural strength requirements, and the material in the third section, which may mainly be determined by the heat transfer ability, are determined. The terms "clearance fit" and "press fit" are well-known within the field and will not be elaborated further.

[0046] The first section, the second section, and the third section may be composed of a material with high thermal conductivity, facilitating efficient heat transfer within these sections and into the main body. In an embodiment, the first, second and third sections may not contribute to the structural strength of the downhole device. Therefore, a material that is both thermally conductive and lightweight may be desirable, resulting in a lighter downhole device. Suitable materials may include aluminium, copper aluminium mixes, or any other suitable material for conducting heat.

[0047] In an embodiment of the cooling system, at least one of the first section, the second section, and the third section may provide a heat path for transferring heat within the respective section(s) and / or into adjacently positioned and / or connected sections. This heat path may include aluminium material. The aluminium material may be defined as an aluminium alloy or a material within the different grades of aluminium known in the art. While the first, second, and / or third sections may comprise a plurality of components made of different materials, such as the chassis and the second heat transfer means, the heat path for heat transfer within these sections may primarily be through parts made of aluminium or aluminium alloys. This provides an efficient heat path.

[0048] The wireguide may be formed into and through the second section, and into and through the third section from the first section. As such, the cooling system may include the wireguide for guiding at least one feedthrough wire along the longitudinal axis from one end to the opposite end of the cooling system. The feedthrough wire may be adapted for at least one of power and communication. This allows purpose tools to be positioned above and / or below the cooling system without limiting the purpose tools in terms of power and communication. The wireguide may include grooves and slots and may be partially formed by the annular Peltier elements, as presented above.

[0049] In a second aspect the disclosure relates more particularly to a downhole device comprising a cooling system according to the first aspect of the disclosure;

[0050] - an upper connection adapted to connect to a surface equipment; - a first thermal component in the first section.

[0051] The downhole device may be an inspection tool and the first thermal component may be defined by a at least one of an image sensor, a lighting means, a processor, and an electronic section. The inspection device may include a plurality of image sensors and / or a plurality of lighting sensors, arranged in an image plane and a lighting plane, respectively. These planes may be oriented perpendicularly to the longitudinal axis.

[0052] The second section of the device may comprise a second thermal component. The second thermal component may be an electronic system adapted for controlling and processing inputs and outputs to and from the first thermal component. This arrangement ensures efficient operation and thermal management of the device.

[0053] The downhole device may comprise a pressure chamber inside the main body.

[0054] The downhole device may comprise a wireguide for a feedthrough wire between the upper connection and a distal end thereof.

[0055] In a third aspect the disclosure relates more particularly to a method for cooling a portion of a downhole device, wherein the method comprises the steps of:

[0056] - providing a downhole device according to the second aspect of the disclosure;

[0057] - activating the first thermal component;

[0058] - transferring heat from the first section to the second section using the first heat transfer means.

[0059] The first section and the second section may be connected in series along the longitudinal axis via the first heat transfer means. The method may further comprise the step of transferring heat, created by the first thermal component, into the second section via the first heat transfer means, and then transferring the heat into the main body via the second section.

[0060] The first thermal component may also be heat sensitive or create a significant amount of heat. In such cases, radial heat transfer outwardly may be insufficient. Therefore, heat may need to be transferred away from the first thermal component before it is trans- ferred into the main body and further out into the fluid surrounding the downhole device. Heat may be transferred along the longitudinal axis from the first section into the second section before heat is radially transferred into the main body. This method effectively manages the heat from the first thermal components, which may be closely positioned, making heat dissipation challenging.

[0061] The second section may comprise a second thermal component and a second heat transfer means, the method may further comprise the step of transferring heat created by the second thermal component into the main body via the second heat transfer means and the second section.

[0062] The cooling system may comprises a third section which may be connected in series with the first section along the longitudinal axis via a third heat transfer means, the first section may be positioned between the second section and the third section, the method may further comprise the step of transferring heat, created by the first thermal component, into the third section via the third heat transfer means, and then transferring the heat from the third section into the main body via at least a conductive heat transfer.

[0063] To prevent repetition in the description of features, technical effects, and disclosed embodiments, any information disclosed in relation to the first, second, or third aspect may be equally applicable to all three aspects of the disclosure. This approach ensures a comprehensive understanding of the disclosure without unnecessary repetition.

[0064] In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:

[0065] Fig. 1 shows, in a sideview, a downhole device in form of an inspection device;

[0066] Fig. 2 shows a cross-sectional view A-A as indicated in Fig 1, and details of a cooling system;

[0067] Fig. 3a shows a cross-sectional view B-B, as indicated in Fig 1;

[0068] Fig. 3a shows a cross-sectional view C-C, as indicated in Fig 1; Fig. 3c shows a sideview a third section of the cooling system; and

[0069] Fig. 4 shows a method for cooling the downhole device using the cooling system.

[0070] Any positional indications refer to the position shown in the figures. In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

[0071] Fig. 1 shows a downhole tool illustrated as an inspection device 100. The inspection device 100 comprises a main body 2 that establishes a longitudinal axis 96. The main body 2 comprises an upper connection 22 linked to a downhole tool 97, and a lower connection 24 attached to a crossover 98, which provides threaded interfaces for other downhole tools. The inspection device 100 is situated within a tubular structure 92, which is part of a wellbore. The inspection device 100 is connected to a wireline 99 via the upper connection 22, which in turn connects the inspection device 100 to surface equipment, not depicted in the figure.

[0072] Turning now to Figs. 1 and 2, the main body 2 constitutes a portion of a pressure chamber filled with gas, making the inspection device 100 gas-filled. The main body 2 is also a component of a cooling system 1. The cooling system 1 comprises a first section 3 connected to a second section 4 located within the main body 2. The first section 3 is connected to the second section 4 through a first heat transfer means 62, designed as an annular Peltier element. The first heat transfer element 62 is designed to convey heat from the first section 3 to the second section 4. The first section 3 and the second section 4 are connected in series along the longitudinal axis 96.

[0073] A third section 5 is connected to the first section 3 at an end opposite the second section 4. The third section 5 is connected to the first section 3 through a third heat transfer means 66, which is also an annular Peltier element similar to the one in the first heat transfer element 62. The third heat transfer element 66 is designed to convey heat from the first section 3 into the third section 5. The first heat transfer element 62 and the third heat transfer element 66 are arranged perpendicularly to the longitudinal axis 96. Therefore, the first section 3, the second section 4, and the third section 5 are connected in series along the longitudinal axis 96, with the first heat transfer element 62 and the third heat transfer element 66 designed to transfer heat away from the first section 3 along the longitudinal axis 96.

[0074] The second section 4 forms a heat exchange surface 76 positioned adjacent to an inner surface 78 of the main body 2, allowing heat from the second section 4 to be transferred radially into the main body 2. Similarly, the third section 5 forms a heat exchange surface 76 positioned adjacent to the inner surface 78 of the main body 2, enabling heat from the third section 5 to be transferred radially into the main body 2. The heat exchange surfaces 76 and the inner surfaces 78 are part of a heat path 7, which allows for efficient heat transfer, as explained in further detail below.

[0075] Referring now to Figs. 1, 2, 3a, and 3b, the first section 3 houses a plurality of first thermal elements, denoted 32.x, where x denotes a specific embodiment. The first thermal components 32.x are depicted as image sensors, denoted 32.4, and lighting means, denoted 32.6, which are illustrated as LED light emitters. The first section 3 houses a plurality of image sensors 32.4 arranged in a circumferential array 38 in an image plane 34. The first section 3 also houses a plurality of lighting means 32.6 arranged in the circumferential array 38 in two lighting planes 36. One lighting plane 36 is arranged on each side of the image plane 34 along the longitudinal axis 96. Both the image sensors 32.4 and the lighting means 32.6 face radially outwardly from the longitudinal axis 96, enabling the inspection of a circumferential sector of the inspection device's 100 surrounding environment, such as the inside of the tubular structure 92.

[0076] Referring now to Figs. 3a and 3b. Fig. 3a shows the cross-sectional view B-B along the image plane 34. The image sensors 32.4 form a heat transfer surface 72, and the first section 3 forms a heat receiving surface 74. The heat transfer surface 72 and the heat receiving surface 74 have a complimentary fit, allowing for substantial heat transfer via conduction. Similarly, Fig. 3b shows the cross-section C-C along one lighting plane 36, where the lighting means 32.6 forms the heat transfer surface 72 having the complimentary fit with the heat receiving surface 74 in the first section 3. This arrangement allows for substantial heat transfer via conduction from the lighting means 32.6 to the first section 3. Thereby, heat is efficiently transferred into the first section 3 from the image sensors 32.4 and the lighting means 32.6.

[0077] Due to the arrangement of the first thermal components 32.x, heat is created in three planes, namely, one image plane 34 and two lighting planes 36. The first heat transfer element 62 and the third heat transfer element 66, being in the form of annular Peltier elements, allow each image sensor 32.4, arranged in the image plane 34, to have substantially the same temperature. Similarly, each lighting means 32.6, arranged in the two lighting planes 36, will have substantially the same temperature. This arrangement allows the electronic components to be exposed to the same temperature, thereby increasing reliability and predictability.

[0078] Now referring to Fig. 2. The second section 4 includes a second thermal component 42.x, where x denotes a specific embodiment, which is illustrated in the form of an electronics board 42.2. The electronics board 42.2 comprises heat-generating and heat-sensitive electrical components. The electronics board 42.2 is connected to a chassis 44, allowing heat to be transferred from the electronics board 42.2 into the chassis 44. The chassis 44 shields at least a heat-sensitive portion of the electronics board 42.2, preventing heat transferred from the first section 3 into the second section 4 from radiating into the electronics board 42.2. The chassis 44 is connected to the second section 4 via a second heat transfer means 64, here in the form of elongated Peltier elements extending along the longitudinal axis 96. The second heat transfer means 64 is designed to transfer heat from the chassis 44 into the second section 4. This arrangement allows the chassis 44 to be colder compared to the second section 4, thereby functioning as a cooling shield for the electronics board 42.2.

[0079] Each of the first section 3, the second section 4, and the third section 5 includes a heat transfer body composed of a material with sufficient thermal conductivity to transfer the heat expected to be created in the first section 3 and the second section 4. In the illustrated embodiment, the heat transfer body is made of aluminium. The cooling system 1 forms a plurality of heat paths 7. Heat transfers through the aforementioned heat transfer surfaces 72 and the heat receiving surfaces 74 into the first section 3. Heat is then transferred via a first heat path 7 formed along the longitudinal axis 96, extending through the first section 3 and into the third section 5 via the third heat transfer means 66. Heat then transfers through the third section 5 into the main body 2 via the heat exchange surface 76 and the inner surface 78 of the main body 2. A second heat path 7 is formed through the aforementioned heat transfer surfaces 72 and the heat receiving surfaces 74 and along the longitudinal axis 96, extending through the first section 3 and into the second section 4 via the first heat transfer means 62. Heat then transfers through the second section 4 into the main body 2 via the heat exchange surface 76 and the inner surface 78 of the main body 2. A third heat path 7 is formed from the electronic board 42.2 into the chassis 44, and from the chassis 44, heat is transferred into the heat transfer body in the second section 4 via two second heat transfer means 64. Heat then continues through the second section 4 and transfers into the main body 2 from the heat exchange surface 76 into the inner surface 78 of the main body 2.

[0080] Both the second section 4 and the third section 5 have a length along the longitudinal axis 96 that is longer than the length in a direction perpendicular to the longitudinal axis 96. In the illustrated embodiment, the length perpendicular to the longitudinal axis 96 corresponds to a diameter of the second section 4 and the third section 5. This allows for a sufficiently large surface of the main body 2 to be used to transfer heat transferred from the second section 4 and the third section 5 and into the fluid surrounding the inspection tool 1.

[0081] Fig. 3c shows the third section 5 connected to the third heat transfer means 66. The main body 2 is made of high strength steel, while the third section 5 is made of aluminium. Therefore, the coefficient of thermal expansion of the third section 5 is higher compared to the main body 2. The third section 5 and the main body 2 are designed such that there is a clearance fit between the heat exchange surface 76 and the inner surface 78 of the main body 2 at temperatures suitable for performing maintenance, typically in a workshop. At a heat transfer temperature, such as found in downhole operations, the third section 5 has expanded more than the main body 2 due to the elevated downhole tem- perature. At the heat transfer temperature, there is therefore a pressfit between the third section 5 and the main body 2. This allows for efficient heat transfer between the third section 5 and the main body 2 when heat transfer is desirable.

[0082] Now referring to Fig. 2, a wireguide 8 extends from the upper connection 22 to the lower connection 24, allowing a feedthrough wire to provide communication and / or power.

[0083] Fig 4 illustrates an exemplary method 200 that includes a step of providing 202 the downhole device, illustrated as an inspection device 100, which includes the cooling system 1. The method also includes a step of activating 204 a first thermal component 32.x and then a step of transferring 206 heat from the first section 3 to the second section 4 using the first heat transfer means 62.

[0084] In an embodiment of the cooling system 1 where the first section 3 and the second section 4 are connected in series via the first heat transfer means 62 along the longitudinal axis 96, the method may include a step of transferring heat 206, created by the first thermal component 32.x, into the second section 4 via the first heat transfer means 62, and then transferring heat radially into the main body 2.

[0085] In an embodiment of the cooling system 1 that includes the second thermal component 42.x and the second heat transfer means 64, the method may include a step of transferring 208 heat, created by the second thermal component 42.x, into the main body 2 via the second heat transfer means 64 and the second section 4.

[0086] In an embodiment of the cooling system 1 that includes the third section 5, which is connected in series to the first section 3 along the longitudinal axis 96 via a third heat transfer means 66, and where the first section 3 is positioned between the second section 4 and the third section 5, the method 200 may include the step of transferring 210 heat, created by the first thermal component 32.x, into the third section 5 via the third heat transfer means 66, and then transferring heat radially from the third section 5 into the main body 2 via at least a conductive heat transfer.

[0087] The method 200 may further include a step of continuing 212 the downhole operation to a new stage, such as relocating to a new position within the wellbore 92 for a new inspec- tion, or removing the inspection device 100 from the wellbore 92 if the operation is complete.

[0088] The illustrated cooling system 1 does not include a cooling liquid, thus the electronics are more reliable compared to other systems where the electronics are in direct contact or in accidental contact with the cooling liquids.

[0089] If such as the second thermal component is not present, there may not be a need for the second heat transfer element, however the third heat transfer element may still be present. Thus, the numbering of the heat transfer elements does not imply that a lower numbered heat transfer element is required to be present for a subsequent heat transfer element to be present. The naming using numbers is for easier identification of different parts, and not to specify an order of presence and / or use.

[0090] A person skilled in the art will understand that in heat transfer, and when it is described that heat is transferred substantially via conduction, it may be implicit that some heat may also transfer via convection and radiation between parts.

[0091] It should be noted that the above-mentioned embodiments illustrate rather than limit the disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0092] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

C l a i m s1. A cooling system (1) for cooling a portion of a downhole device (100), the cooling system (1) comprises a main body (2) having a longitudinal axis (96), c h a r a c t e r i s e d i n that:- the cooling system (1) comprises a first section (3) and a second section (4) positioned inside the main body (2);- the first section (3) is connected to the second section (4) via a first heat transfer means (62); and- the first heat transfer means (62) is adapted to transfer a heat created in the first section (3) to the second section (5).

2. The cooling system (1) according to claim 1, wherein the first section (3) accommodates a first thermal component (32.4, 32.6).

3. The cooling system (1) according to claim 2, wherein the first thermal component (32.4, 32.6) is an electric device.

4. The cooling system (1) according to any one of the preceding claims, wherein the first section (3) and the second section (4) are connected in series along the longitudinal axis (96).

5. The cooling system (1) according to any one of the preceding claims, wherein the first heat transfer means (62) is an annular Peltier element.

6. The cooling system (1) according to any one of the preceding claims, wherein the second section (4) comprises a second thermal component (64).

7. The cooling system (1) according to any one of the preceding claims, wherein the second section (4) comprises a second heat transfer means (64) adapted to transfer heat from the second thermal component (42.2) into the main body (2) via the second section (4).

8. The cooling system (1) according to claim 7, wherein the second heat transfer means (64) is a Peltier element extending along the longitudinal axis (96).

9. The cooling system (1) according to any one of the preceding claims, wherein the cooling system (1) comprises a third section (5), the third section (5) is positioned inside the main body (2) and connected to the first section (3) in an opposite end from where the second section (4) is connected.

10. The cooling system (1) according to claim 9, wherein the first section (3) and the third section (5) are connected via a third heat transfer means (66).

11. The cooling system (1) according to claim 10, wherein the third heat transfer means (66) is an annular Peltier element.

12. The cooling system (1) according to any one of claims 9 to 11, wherein the third section (5) has a length along the longitudinal axis (96) which is greater compared to a length perpendicular to the longitudinal axis (96).

13. The cooling system (1) according to any one of claims 9 to 12, wherein the third section (5) is configured to have a clearance fit with the main body (2) during maintenance, and a press fit with the main body (2) when a temperature of the third section (5) reaches a heat transfer temperature.

14. The cooling system (1) according to any one of claims 9 to 13, wherein at least one of the first section (3), the second section (4) and the third section (5) provide(s) a heat path (7) for transferring heat within the respective section(s) (3, 4, 5) and / or into adjacently positioned and / or connected parts (2, 3, 4, 5), the heat path (7) comprises an aluminium.

15. The cooling system (1) according to any one of the preceding claims, wherein the cooling system (1) comprises a wireguide (8) for guiding at least one feedthrough wire along the longitudinal axis (96) from one end to an opposite end of the cooling system (1).

16. A downhole device (100), c h a r a c t e r i s e d i n that:- the downhole device (100) comprise a cooling system (1) according to any one of claims 1 to 15;- the downhole device (100) comprises an upper connection (22) adapted to connect to a surface equipment;- the downhole device (100) comprises a first thermal component (32.4, 32.6) in the first section (3).

17. The downhole device (100) according to claim 16, wherein the downhole device (100) is an inspection tool and the first thermal component is created by a at least one of an image sensor (32.4), a lighting means (32.6), a processor, and an electronic section.

18. The downhole device (100) according to claim 16 or 17, wherein the second section (5) comprises a second thermal component (42.2).

19. A downhole device (100) according to any one of claims 16 to 18, wherein the downhole device (100) comprises a pressure chamber inside the main body (2).

20. The downhole device (100) according to any one of claims 16 to 19, wherein the downhole device (100) comprises a wireguide (8) for a feedthrough wire between the upper connection (22) and a distal end (24).

21. Method (200) for cooling a portion of a downhole device (100), c h a r a c t e r i s e d i n that method comprises the steps of:- providing (202) a downhole device (100) according to any one of claims 16 to 20;- activating (204) the first thermal component (32.4, 32.6);- transferring (206) heat from the first section (3) to a second section (5) using a first heat transfer means (62).

22. The method (200) according to claim 21, wherein the first section (3) and the second section (5) are connected in series along a longitudinal axis (96) via the first heat transfer means (62), the method further comprising the step of transferring (208) heat, created by the first thermal component (32.4, 32.6), into the second section (4) via the first heat transfer means (62), and then transferring the heat into the main body (2).

23. The method (200) according to claim 21 or 22, wherein the second section (5) comprises a second thermal component (42.2) and a second heat transfer means (64), the method further comprising the step of transferring (210) heat created by the second thermal component (42.2) into the main body (2) via the second heat transfer means (64) and the second section (5).

24. The method (200) according to any one of claims 21 to 23, wherein the cooling system (1) comprises a third section (5) which is connected in series to the first section (3) along the longitudinal axis (96) via a third heat transfer means (66), the first section (3) is positioned between the second section (4) and the third section (5), the method (200) comprises the step of transferring (210) heat, created by the first thermal component (32.4, 32.6), into the third section (5) via the third heat transfer means (66), and then transferring the heat from the third section (5) into the main body (2) via at least a conductive heat transfer.

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