Patent Application
20090032259
1. Field of the Disclosure
The disclosure relates to transferring heat from heat-generating elements in downhole applications.
2. Description of the Prior Art
Oil and gas are recovered from subterranean geological formations by means of oil wells or wellbores drilled through one or more oil producing formation. A variety of tools are used during the drilling of the wellbore and prior to the completion of a wellbore to provide information about various parameters relating to the formations surrounding the wellbore. These tools typically include a variety of sensors, electrical and electronic components, and other devices that can generate heat while in operation. The wellbore temperatures can vary from ambient to above 500° F. (about 260° C.) and pressures from atmospheric to above 20,000 psi (about 137.8 mega pascals). Temperature and pressure conditions such as these can have an adverse effect on instruments used downhole. Heat especially can be undesirable for tools having electronic components. In some instances, excess heat can cause electronic components to work more slowly or even fail. Therefore, it is desirable to maintain certain components of the downhole tools to desired temperature or to transfer heat-away from such components.
The disclosure herein provides an apparatus and method for transferring heat away from certain components in downhole tools.
In one aspect, an apparatus is disclosed that includes an anisotropic nanocomposite element in thermal communication with a heat-generating element for conducting heat away from the heat-generating element along a selected direction.
In another aspect, a method of conveying heat away from a heat-generating element is disclosed that includes transferring heat from the heat-generating element to an anisotropic nanocomposite element that is configured to conduct heat along a selected direction, and transferring heat received by the anisotropic nanocomposite element to a heat-absorbing element.
In still another aspect, a tool for use in a wellbore is disclosed that includes a tool body that contains therein a heat-generating element, a heat conduction device that includes at least one anisotropic nanocomposite element coupled to the heat generating element for conducting heat away from the heat-generating element along a selected direction, and a heat absorbing element coupled to the heat conduction device for absorbing heat from the anisotropic nanocomposite element.
Examples of the more important features of a system for monitoring and controlling production from wells have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features that will be described hereinafter and which will form the subject of the claims.
The disclosure is best understood with reference to the accompanying figures in which like numerals generally refer to like elements, and in which:
The tool 104 may include any tool for performing an operation in the wellbore 102, including but not limited to a resistivity tool, nuclear tool, nuclear magnetic resonance tool, formation testing tool, and an acoustic tool. Additionally, the tool may be made up of a combination of these and other tools. Each of these tools may include a variety of electronic components, such as microprocessors and electrical components, such as motors, pumps, coils, transformers, etc. that generate heat during operation of the tool in the wellbore, which typically is at an elevated temperature, which in some cases may exceed 200 degrees Celsius. The temperature of the heat-generating elements, in some cases, may be several degrees higher than the temperature of the wellbore. Certain exemplary heat-transfer systems and methods for transferring heat from such heat-generating elements are described in reference to
In the configuration of
The heat-absorbing element 205 may be a heat-absorbing ceramic member placed in the tool or a portion of the tool 102, which remains at a temperature lower than that of the heat-generating element during operation of the tool. A metal housing surrounding the tool, drill collar of a drilling assembly that is in contact with circulating drilling fluid in the wellbore, a sorption cooler or a cryogenic device may be used as the heat sink 204. Wireline tool housings and drill collars carrying measurement-while-drilling tools can equilibrate to the temperature of the wellbore fluid after being in the wellbore. However, the electronics components, motors, sensors and the like inside the wireline tool or drill collar can raise the local internal temperature by 5 to 10 degrees centigrade, which temperature can sometimes exceed the operating temperature of such components. Therefore, for a wireline tool, certain metallic sections in the tool may be at a temperature lower than the heat-generating element. Similarly, the drill collar of a drilling assembly may remain colder than the heat-generating element because the temperature of the drilling fluid circulating around the drilling assembly is typically less than that of the heat-generating element. The heat sink 204 may be a passive heat sink, such as the drill collar, which is in contact with the wellbore fluid, a ceramic member and the like or it may be an active heat sink, such as a cryogenic device.
Still referring to
In operation, in one aspect, the controller 304 monitors the temperatures of both the heat-generating elements 202a and/or 202b and the heat-absorbing element 302b. When the temperature of the heat-generating element reaches a preset value, the controller 304 sends a command to the power source to energize the heat transfer device. The controller 304, in accordance with the programmed instructions, maintains the heat transfer device 309 in an energized state until the temperature of the heat generating element falls below the preset temperature value or until the heat-absorbing element 204 reaches a temperature that is too high (a preset threshold value) for efficient heat transfer. At either of these two conditions, the heat transfer device can be de-energized thus allowing for energy conservation. In another aspect, the controller 304 may continuously or substantially continuously control or regulate the power to the heat-transfer device 309 to control the flow of heat from the heat-generating elements 202a and 202b to the heat-absorbing element 204, based on the temperatures of the heat-generating elements 202a and 202b and the heat-absorbing element 204. The temperature difference between the heat generating element 202a and/or 202b and the heat-absorbing element 204 may be used as a criterion for controlling the power to the heat transfer device 309.
In the heat-transfer systems and methods described herein, the anisotropic nanocomposite element may include a base material and aligned or highly-aligned thermally-conductive nano elements, such as nanotubes. The base material may be selected based on the temperature of the end use apparatus and the particular techniques employed to fluidize and solidify the base material. Examples of suitable base materials include polymers, ceramics, glasses, metals, alloys, and other composites. The base material also may be amorphous or crystalline. The base material may further include one or more additives. Examples include as binding agents, surfactants, and wetting agents to aid in dispersing and aligning the nanotubes in the base material.
In some embodiments, the base material used to prepare the nanocomposite element may polymeric. That is, it comprises one or more oligomers, polymers, copolymers, or blends thereof. In one such embodiment, the base material may include a thermoplastic polymer. In another such embodiment, the base material may include a thermoset polymer, such as phenol formaldehyde resins and urea formaldehyde resins. Examples of polymers suitable for use with the apparatus and method of the disclosure include, but are not limited to: polyolefins, polyesters, nonpeptide polyamines, polyamides, polycarbonates, polyalkenes, polyvinyl ethers, polyglycolides, cellulose ethers, polyvinyl halides, polyhydroxyalkanoates, polyanhydrides, polystyrenes, polyacrylates, polymethacrylates, polyurethanes, polyether ketones, polyether amides, polyether ether ketones, polysulfones, liquid crystal polymers and copolymers and blends thereof. In another aspect, the base material may include a polymer precursor or a crosslinkable material. As used herein, the term “polymer precursor” refers to monomers and macromers capable of being polymerized. As used herein, the term “crosslinkable material” refers to materials that can crosslink with themselves or with another material, upon heating or addition of a catalysts or other appropriate initiator. In one aspect, the polymer precursor may include an epoxy resin or a cyanoacrylate.
The nano elements may include any suitable thermally-conductive nano materials. In one aspect, the nano elements may be carbon nanotubes. The carbon nanotubes may be single-walled, which may be a wrapping of a one-atom-thick layer of graphite (such as grapheme) into a seamless cylinder. Such carbon nanotubes may have a diameter of about 1 nanometer (nm), with a tube length that may be substantially greater than the diameter, such as a length of few millimeters to 1.5 centimeters or longer. In another aspect, multiple-walled carbon nanotube may be utilized. A multi-walled nanotube comprises a graphite layer rolled to form a tube that has multiple layers. In addition, nanotubes useful for the disclosed apparatus and methods may be prepared using any material known to be useful for conducting. For example, the nanotubes may be prepared using boron nitride or gallium nitride.
The nanocomposite materials useful for the apparatus and methods of the disclosure are anisotropic due to the alignment of the nanotubes. For the purposes of this disclosure nano elements or tubes may be dispersed and aligned or highly-aligned by any method known for preparing such materials. For example, the nanotubes may be fixed with a magnetic element and then dispersed within a liquid or highly plastic base material. The base material may then be subjected to a magnetic field to align the nanotubes and then curing the base material to maintain the alignment of the nanotubes. In another method, the nanotubes may be aligned by extrusion through a very small aperture. In another method, the nanotubes may be aligned by encapsulating nanotubes of known orientation in a polymer by mechanically applying the nanotubes to a surface of a polymer to form a first material and then extruding a layer of the same or a different polymer around the first material to produce a fully encapsulated nanocomposite.
For the apparatus and methods of the disclosure, the nanocomposite material may be of any shape or configuration known to be useful. For example, the nanocomposite material may be in the shape of a cylinder or a rod with the nanotubes aligned to conduct temperature from one end toward the other end with minimal heat being conducted to the sides or walls of the cylinder or rod. In another aspect, the nanocompo site element may be a rectangular or curved sheet wherein heat is preferentially conducted along either the width or length of the sheet. In another aspect, the nanocomposite element may be in the form of a stack of such sheets. Also, the nanocomposite element may be rigid or it may be flexible so that it may be shaped in any desired form, such as shown in
Thus, in one embodiment, the disclosure provides an apparatus that includes an anisotropic nanocomposite element in thermal communication with a heat-generating element for conducting heat away from the heat-generating element along a selected direction. In one aspect, the anisotropic nanocomposite element contains highly-aligned thermally-conductive nano material, such as carbon nanotubes, to conduct substantially all of the heat in the direction of the alignment of the nano material. In one aspect, the apparatus may further include a heat-absorbing element placed in thermal communication with the anisotropic nanocomposite element for receiving heat from the anisotropic nanocomposite element. In another aspect, the apparatus may further include a heat-transfer device in thermal communication with the anisotropic nanocomposite element for transferring heat from the anisotropic nanocomposite element to the heat absorbing element. In another aspect, the apparatus may further include an interface element between the heat generating element and the anisotropic nanocomposite element for transferring heat from the heat conducting element to the anisotropic nanocomposite element. The nanocomposite element may include a base material and aligned thermally-conductive nanotubes. The nanotubes may be made from, carbon, boron nitride or gallium nitride. Further the nanocomposite element may be made using a stack of sheets, each sheet containing a base material and aligned thermally-conductive nanotubes. The heat-absorbing element may be any suitable member or device, including a metallic member, ceramic member, laminate of a metallic or ceramic or their combination, metal and non-metal composite, fluid, sorption cooler or a phase change device. Also, the heat-transfer element may be any active heat transfer device, including a Peltier cooler, closed-loop cooling unit, or heat pump that employs a Joule-Thompson effect or Stirling Engine. The apparatus, in one aspect, may also include a controller that controls the heat-transfer device in response to a temperature measurement of the heat-generating element or the heat-absorbing element. The controller may control power to the heat transfer device to control the transfer of heat away from the heat-generating element. The apparatus may further include an insulating element proximate to the heat-generating element for directing heat from the heat generating element toward the anisotropic nanocomposite element.
The disclosure in another aspect provides a method for conducting heat away from an element that includes the features of transferring heat from the heat-generating element to an anisotropic nanocomposite element that is configured to conduct heat along a selected direction and transferring heat from the anisotropic nanocomposite element to a heat-absorbing element. The method may further include transferring heat from the anisotropic nanocomposite element to the heat-absorbing element using a heat transfer device. The method also may include transferring heat from the heat-conducting element to the anisotropic nanocomposite element using an interface placed between the heat-conducting element and the anisotropic nanocomposite element. The method may further include directing heat from the heat generating element toward the anisotropic nanocomposite element. Additionally, the method may include controlling transfer of heat from the heat-generating element based at least in part on the temperature of the heat-generating element.
The foregoing disclosure is directed to the certain exemplary embodiments and methods. Various modifications, however, will be apparent to those skilled in the art. It is intended that all such modifications shall be deemed within the scope of the appended claims and be embraced by the foregoing disclosure. Also, the abstract is provided to meet certain statutory requirements and is not to be used to limit the scope of the claims in ay manner.
