Patent Publication Number: US-7717167-B2

Title: Switchable power allocation in a downhole operation

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The application claims priority under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 60/633,226, filed Dec. 3, 2004, which application is incorporated herein by reference. 
   RELATED APPLICATIONS 
   This application is related to, HEATING AND COOLING ELECTRICAL COMPONENTS IN A DOWNHOLE OPERATION, Ser. No. 11/293,041, filed Dec. 2, 2005; and RECHARGEABLE ENERGY STORAGE DEVICE IN A DOWNHOLE OPERATION, Ser. No. 11/292,943, filed Dec. 2,2005. 

   TECHNICAL FIELD 
   The application relates generally to petroleum recovery operations. In particular, the application relates to a configuration for use of electronics in downhole tools for such operations. 
   BACKGROUND 
   During drilling operations, Measurement-While-Drilling (MWD) and Logging-While-Drilling (LWD systems as well as wireline systems provide wellbore directional surveys, petrophysical well logs and drilling information to locate and extract hydrocarbons from below the surface of the Earth. Different tools used in these operations incorporate various electrical components. Examples of such tools include sensors for measuring different downhole parameters, data storage devices, flow control devices, transmitters/receivers for data communications, etc. Downhole temperatures can vary between low to high temperatures, which can adversely affect the operations of the electrical components. 
   SUMMARY 
   In some embodiments, an apparatus includes a tool to operate downhole. The tool includes a heater. The tool also includes a cooler. The tool includes a controller to control allocation of power between the heater and the cooler based on a temperature downhole, power usage, a time delay or a pressure downhole. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention may be best understood by referring to the following description and accompanying drawings which illustrate such embodiments. The numbering scheme for the Figures included herein are such that the leading number for a given reference number in a Figure is associated with the number of the Figure. For example, a tool  100  can be located in  FIG. 1 . However, reference numbers are the same for those elements that are the same across different Figures. In the drawings: 
       FIG. 1  illustrates a tool for downhole operations that includes a configuration for electrical components operable at high temperatures, according to some embodiments of the invention. 
       FIG. 2  illustrates a more detailed diagram of a tool for downhole operations that includes a configuration for electrical components operable at high temperatures, according to some embodiments of the invention. 
       FIGS. 3A-3B  illustrate mechanical spring configurations as energy storage devices, according to some embodiments of the invention. 
       FIGS. 4A-4B  illustrate hydrostatic chamber configurations as energy storage devices, according to some embodiments of the invention. 
       FIGS. 5A-5B  illustrate elevated mass configurations as energy storage devices, according to some embodiments of the invention. 
       FIGS. 6A-6B  illustrate differential pressure drive configurations as energy storage devices, according to some embodiments of the invention. 
       FIGS. 7A-7B  illustrate compressed gas drive configurations as energy storage devices, according to some embodiments of the invention. 
       FIG. 8  illustrates a more detailed diagram of a tool for downhole operations that includes a configuration for controlling power flow between heating and cooling, according to some embodiments of the invention. 
       FIG. 9  illustrates a plot of the temperatures of two phase change materials as a function of time, according to some embodiments of the invention. 
       FIG. 10  illustrates power and heat flow in a tool for downhole operations that includes a configuration for controlling power flow between heating and cooling, according to some embodiments of the invention. 
       FIG. 11  illustrates a flow diagram for controlling power flow between heating and cooling, according to some embodiments of the invention. 
       FIG. 12  illustrates power flow in a tool for downhole operations that includes a rechargeable energy storage device, according to some embodiments of the invention. 
       FIG. 13  illustrates heat flow in a tool for downhole operations that includes a rechargeable energy storage device, according to some embodiments of the invention. Heat flows from a turbine generator  806  and a cooler  804  to a mud flow  808 . 
       FIG. 14A  illustrates a more detailed diagram of a tool for downhole operations that includes rechargeable energy storage devices to supply power downhole, according to some embodiments of the invention. 
       FIG. 14B  illustrates a more detailed diagram of a tool for downhole operations that includes rechargeable energy storage devices to supply power downhole, according to other embodiments of the invention. 
       FIG. 15A  illustrates a drilling well during wireline logging operations that includes the heating and/or cooling downhole, according to some embodiments of the invention. 
       FIG. 15B  illustrates a drilling well during MWD operations that includes the heating and/or cooling downhole, according to some embodiments of the invention. 
   

   DETAILED DESCRIPTION 
   Methods, apparatus and systems for heating and cooling downhole are described. In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. 
   Some embodiments include configurations that have electrical components that are operable at high temperatures in combination with heat exhausting cooling systems. Some embodiments include different Commercial Off The Shelf (COTS) electronics (such as high density memory and microprocessors) that are enclosed in a thermally insulating container that may be cooled by a heat exhausting cooling system. The cooling system may include heat sinks, heat exchangers and other components for enhancing thermal energy transfer. Moreover, the configuration may include components capable of exhausting heat to the surrounding environment. For example, the tool pressure housing, drill string, etc. may be coupled to a heat sink, a heat exchanger, etc. to exhaust the heat. In some embodiments, certain electrical components may be operable at high temperatures. For example, the electrical components that are part of the power source (such as a flow-driven generator), the sensors, the telemetry components, etc. may be operable at high temperatures. Some embodiments allow the use of COTS microprocessors and memory downhole that are operable at low temperatures. Accordingly, the speed of processing may be greater and the density of the memory may be higher that can be obtained using high-temperature electrical components. 
   Some embodiments include a power generator that is switchably operated to provide power to both a heater and a cooler downhole. For example, if the temperature is low, some or all of the power may be switched to a heater that may be used to raise the temperature of an energy storage device. Conversely, if the temperature is high, some or all of the power may be switched to a cooler that may be used to lower the temperature of electronics. 
   Some embodiments include a rechargeable energy storage device, which may be used in combination with an alternative power source (such as a turbine generator powered by mud flow downhole). The rechargeable energy storage device may be operable a high temperatures. Rechargeable energy storage device operable at high temperatures exceed the operating temperature limit of standard energy storage devices (such as standard lithium batteries). Moreover, recharging the energy storage devices downhole may allow for a smaller storage device payload than would be required with non-rechargeable energy storage devices. 
   While described with reference to the removal of heat from electrical components, such embodiments may be used to remove heat from any type of component. For example, the component may be mechanical, electromechanical, etc. In the following description, the definition of high temperature and low temperature are defined for various components. Such definitions of temperature are relative to the component and may or may not be independent of temperatures of other components. For example, a high temperature for component A may be different than a high temperature for component B. 
   This description of the embodiments is divided into four sections. The first section describes a tool in a downhole operation. The second section describes different configurations for a switchably operated downhole power source for heating and cooling in a downhole tool. The third section describes different configurations using a rechargeable energy storage devices downhole. The fourth section describes example operating environments. The fifth section provides some general comments. 
   Downhole Tool having Heating and/or Cooling 
     FIG. 1  illustrates a tool for downhole operations that includes a configuration for electrical components operable at high temperatures, according to some embodiments of the invention. In particular,  FIG. 1  illustrates a tool  100  that may be representative of a downhole tool that is part of an MWD system, a tool body that is part of a wireline system, a temporary well testing tool, etc. Examples of such systems are described in more detail below (see description of  FIGS. 10A-10B ). The tool  100  includes a high-temperature power source  102 , a cooler module  104 , a thermal barrier  106  and a high-temperature sensor section  108 . 
   In some embodiments, the cooler module  104  includes one or more heat exchangers or other components for thermal energy transfer. The heat exchangers may be parallel-flow heat exchangers, wherein two fluids enter an exchanger at a same end and travel the exchanger parallel relative to each other. The heat exchangers may be counter-flow heat exchangers wherein the two fluids enter an exchanger at opposite ends. The heat exchangers may also be cross-flow heat exchangers, plate heat exchangers, etc. The heat exchangers may be comprised of multiple layers of different materials, such as copper flow tubes with aluminum fins or plates. In some embodiments, the cooler module includes a thermoacoustic cooler which is capable of removing heat from one area of the tool, such as that area occupied by thermally sensitive electronics, and transferring this heat to some other area which is not as temperature sensitive. 
   The thermal barrier  106  may be a thermally insulating container. The thermal barrier  106  may house different electronics or electrical components. For example, the thermal barrier  106  may house electronics or electrical components that are operable at low temperatures. In some embodiments, such electronics or electrical components are COTS electronics. The high-temperature sensor section  108  includes one to a number of different sensors that include electrical components that are operable at high temperatures. Alternatively, some of the electrical components that are capable of operating at high temperature may be housed in the thermal barrier  106  and operable at low temperatures. 
     FIG. 2  illustrates a more detailed diagram of a tool for downhole operations that includes a configuration for electrical components operable at high temperatures, according to some embodiments of the invention. In particular,  FIG. 2  illustrates a more detailed block diagram of the tool  100 . The tool  100  includes a high-temperature power source  202 , high-temperature power conditioning electronics  204 , an energy storage device  203 , the cooler module  104 , low-temperature electronics  206 , the thermal barrier  106 , high-temperature telemetry  212  and sensors  214 A- 214 N. In some embodiments, not all of the components of the tool  100  illustrated in  FIG. 2  are incorporated therein. For example, the tool  100  may not include the energy storage device  203 . In another example, the tool  100  may not include the high-temperature telemetry  212 . 
   The high-temperature power source  202  is coupled to the high-temperature power conditioning electronics  204 . The high-temperature power source  202  may provide power to different electrical loads in the tool  100 . For example, the different electrical loads may include the low-temperature electronics  206 , the cooler module  104 , the sensors  214 A- 214 N, the high-temperature telemetry  212 , the energy storage device  203 , etc. The high-temperature power source  202  may be of different types. The high-temperature power source  202  may produce any power waveform including alternating current (AC) or direct current (DC). For example, the high-temperature power source  202  may be a flow-driven generator that derives its power from the mud flow in the borehole, a vibration-based generator, etc. The high-temperature power source  202  may be of the axial, radial or mixed flow type. In some embodiments, the high-temperature power source  108  may be driven by a positive displacement motor driven by the drilling fluid, such as a Moineau-type motor. 
   The high-temperature power conditioning electronics  204  may receive and condition the power from the high-temperature power source  202 . The high-temperature power source  202  may be positioned near the sensors  214 A- 214 N which may be near the drill bit of the drill string. The high-temperature power source  202  may be positioned further uphole near the repeaters that may be part of the telemetry system. 
   The high-temperature power source  202  and the high-temperature power conditioning electronics  204  may include electrical components that are operable at high temperatures. The electrical components may be composed of Silicon On Insulator (SOI), such as Silicon On Sapphire (SOS). In some embodiments, high temperatures in which the electrical components in the high-temperature power source  102  and the high-temperature power conditioning electronics  204  are operable include temperature above 150 degrees Celsius (° C.), above 175° C., above 200° C., above 220° C., in a range of 175-250° C., in a range of 175-250° C., etc. 
   The thermal barrier  106  hinders heat transfer from the outside environment to the electronics or electrical components housed in the thermal barrier  106 . In some embodiments, the thermal barrier  106  may include an insulated vacuum flask, a vacuum flask filled with an insulating solid, a material-filled chamber, a gas-filled chamber, a fluid-filled chamber, or any other suitable barrier. In some embodiments, there may be a space between the thermal barrier  106  and the outside wall of the tool  100 . This space may be evacuated, thereby hindering the heat transfer from outside the tool  100  to the electrical components within the thermal barrier  106 . In some embodiments, the thermal barrier  106  may house the low-temperature electronics  206 , at least part of the cooler module  104  and at least part of the sensors  214 A- 214 N. The low temperatures at which these electrical components may be operable include temperatures below 150° C., below 175° C., below 200° C., below 220° C., below 125° C., below 100° C., below 80° C., in a range of 0-80° C., in a range of −20-100° C., etc. 
   In some embodiments, the sensors  214 A- 214 N are composed of high-temperature electronics and are not housed in thermal barrier  106 . Accordingly, the sensors  214 A- 214 N may withstand direct contact with an environment at excessive temperatures. In some embodiments, at least part of the sensors  214 A- 214 N have components not capable of operation at excessive environmental temperatures. In such a configuration, the thermally sensitive components of these sensors  214 A- 214 N may be partially or totally enclosed in the thermal barrier  106 . Alternatively or in addition, these thermally sensitive components of these sensors  214 A- 214 N may be coupled to the cooler module  104 . Therefore, these thermally sensitive components may be maintained at or below their operating temperatures. The sensors  214 A- 214 N may be representative of any type of electronics or devices for sensing, control, data storage, telemetry, etc. 
   The sensors  214 A- 214 N may be different types of sensors for measurement of different parameters and conditions downhole, including the temperature and pressure, the various characteristics of the subsurface formations (such as resistivity, porosity, etc.), the characteristics of the borehole (e.g., size, shape, etc.), etc. The sensors  214 A- 214 N may also include directional sensors for determining direction of the borehole. The sensors  214 A- 214 N may include electromagnetic propagation sensors, nuclear sensors, acoustic sensors, pressure sensors, temperature sensors, etc. 
   The electrical components within the high-temperature part of the sensors  214  may be composed of Silicon On Insulator (SOI), Silicon On Sapphire (SOS), Silicon Carbide, etc. In some embodiments, high temperatures in which the electrical components of the high-temperature parts of the sensors  214  are operable include temperature above 150 degrees Celsius (° C.), above 175° C., above 200° C., above 220° C., in a range of 175-250° C., in a range of 175-250° C., etc. In some embodiments, the low temperature at which the electrical components of the low-temperature parts of the sensors are operable includes temperature below 150° C., below 175° C., below 200° C., below 220° C., below 125° C., below 100° C., below 80° C., in a range of 0-80° C., in a range of −20-100° C., etc. In some embodiments, high temperatures in which the electrical components of the high-temperature telemetry  212  are operable include temperature above 150 degrees Celsius (° C.), above 175° C., above 200° C., above 220° C., in a range of 175-250° C., in a range of 175-250° C., etc. 
   Power may be supplied to the cooler module  104  from the high-temperature power source  202 . Alternatively or in addition, power may be supplied to the cooler module  104  directly from the flow of the fluid in the borehole. If the cooler module  104  is driven by the fluid flow, a magnetic torque coupler may be used to avoid the use of dynamic seals by allowing mechanical coupling through a mechanical fluid barrier. This arrangement provides for direct mechanical powering of the cooler. Additionally, mechanical power provided by the fluid flow may be used to drive a hydraulic or pneumatic pump which can then be used to drive a hydraulic or pneumatic motor or other components to provide the mechanical drive for the cooler. In some embodiments, the cooler module  104  may include a thermoacoustic cooler. A thermoacoustic cooler typically operates at substantially the same speed, while the fluid flow rate may vary significantly. Therefore, a variable speed clutch may be used to provide a constant rotation rate to the cooler module  104 . The variable speed clutch may have a mechanical transmission or may use a variable rheological fluid, such as magnetorheological fluid. Additionally, the rotation rate may be varied by changing the angle of the fin on the blades of the generator in the fluid flow. At high flow rates, a brake may be used to limit the rotation speeds of the blades. The power from the high-temperature power source  202  may be electrical and/or mechanical. For example, the cooler module  104  may be powered directly with mechanical energy. In other words, the fluid flow may cause mechanical motion, which provides the power to the cooler module  104 . Alternatively or in addition, the fluid flow may cause mechanical motion that generates electrical energy that generates mechanical motion, which provides the power to the cooler module  104 . 
   The energy storage device  203  may be any energy storage device suitable for providing power to downhole tools. Examples of energy storage devices include a primary (i.e., non-rechargeable) battery such as a voltaic cell, a lithium battery, a molten salt battery, or a thermal reserve battery, a secondary (i.e., rechargeable) battery such as a molten salt battery, a solid-state battery, or a lithium-ion battery, a fuel cell such as a solid oxide fuel cell, a phosphoric acid fuel cell, an alkaline fuel cell, a proton exchange membrane fuel cell, or a molten carbonate fuel cell, a capacitor, a heat engine such as a combustion engine, and combinations thereof. The foregoing energy storage devices are well known in the art. Suitable batteries are disclosed in U.S. Pat. No. 6,672,382 (describes voltaic cells), U.S. Pat. Nos. 6,253,847, and 6,544,691 (describes thermal batteries and molten salt rechargeable batteries), each of which is incorporated by reference herein in its entirety. Suitable fuel cells for use downhole are disclosed in U.S. Pat. Nos. 5,202,194 and 6,575,248, each of which is incorporated by reference herein in its entirety. Additional disclosure regarding the use of capacitors in wellbores can be found in U.S. Pat. Nos. 6,098,020 and 6,426,917, each of which is incorporated by reference herein in its entirety. Additional disclosure regarding the use of combustion engines in wellbores can be found in U.S. Pat. No. 6,705,085, which is incorporated by reference herein in its entirety. 
   The energy storage device  203  may provide power to different electrical loads in the tool  100 . For example, the different electrical loads may include the low-temperature electronics  102 , the cooling system  104 , the sensors  114 A- 114 N, the high-temperature telemetry  112 , etc. The energy storage device  203  may have relatively high minimum operating temperatures, which are commonly determined and provided by suppliers and/or manufacturers of energy storage devices. By way of example, the minimum operating temperatures of some high-temperature energy storage devices are as follows: a sodium/sulfur molten salt battery (typically a secondary battery) operates at from about 290° C. to about 390° C.; a sodium/metal chloride (e.g., nickel chloride) molten salt battery (typically a secondary battery) operates at from about 220° C. to about 450° C.; a lithium aluminum/iron disulfide molten salt battery operates near about 500° C.; a calcium/calcium chromate battery operates near about 300° C.; a phosphoric acid fuel cell operates at from about 150° C. to about 250° C.; a molten carbonate fuel cell operates at from about 650° C. to about 800° C.; and a solid oxide fuel cell operates at from about 800°C. to about 1,000° C. 
   In some embodiments, the energy storage device  203  may be based on different types of mechanical spring configurations.  FIGS. 3A-3B  illustrate mechanical spring configurations as energy storage devices, according to some embodiments of the invention.  FIG. 3A  illustrates an energy storage device that includes a torsional power spring, according to some embodiments of the invention. In particular,  FIG. 3A  illustrates an energy storage device  300  that includes a torsional power spring  302  to store power. The torsional power spring  302  is coupled to a power source  308  through a drive shaft  304 . Accordingly, the torsional power spring  302  may supply power to the power source  308  for powering components in the tool  100 . 
     FIG. 3B  illustrates an energy storage device that includes a compression spring, according to some embodiments of the invention. In particular,  FIG. 3B  illustrates an energy storage device  320  that includes a spring  322  within an exhaust chamber  324 . The spring  322  is to store power. The spring  322  is coupled to a power source  328  through a hydraulic fluid  326 . Accordingly, the spring  322  may supply power to the power source  328  for powering components in the tool  100 . 
   In some embodiments, the energy storage device  203  may be based on different types of hydrostatic chamber configurations.  FIGS. 4A-4B  illustrate hydrostatic chamber configurations as energy storage devices, according to some embodiments of the invention.  FIG. 4A  illustrates an energy storage device that includes a hydrostatically-driven mechanical system, according to some embodiments of the invention. In particular,  FIG. 4A  illustrates an energy storage device  400  that includes hydrostatic pressure  402 . The hydrostatic pressure  402  is positioned adjacent to a drive piston  404  (that may be non-rotating). The energy storage device  400  also includes a torsion shaft  406  positioned adjacent to the drive piston  404  (opposite the hydrostatic pressure  402 ). The energy storage device  400  includes a speed increaser  406  positioned adjacent to the torsion shaft  406  (opposite the drive piston  404 ). The energy storage device  400  includes a drive shaft  410  positioned adjacent to the speed increaser  408  (opposite the torsion shaft  406 ). The energy storage device  400  includes a power source  412  positioned adjacent to the drive shaft  410  (opposite the speed increaser  408 ). The energy storage device  400  also includes an exhaust chamber  414  positioned adjacent to the power source  412  (opposite the drive shaft  410 ). 
     FIG. 4B  illustrates an energy storage device that includes a hydrostatically-driven hydraulic system, according to some embodiments of the invention. In particular,  FIG. 4B  illustrates an energy storage device  420  that includes hydrostatic pressure  422 . The hydrostatic pressure  422  is positioned adjacent to a piston  424  (that may be floating). The energy storage device  420  also includes a hydraulic fluid  426  that is positioned adjacent to the piston  424  (opposite the hydrostatic pressure  422 ). The energy storage device  420  includes a power source  428  that is positioned adjacent to the hydraulic fluid  426  (opposite the piston  424 ). The energy storage device  420  includes an exhaust chamber  430  that is positioned adjacent to the power source  428  (opposite the hydraulic fluid  426 ). 
   In some embodiments, the energy storage device  203  may be based on different types of elevated mass configurations.  FIGS. 5A-5B  illustrate elevated mass configurations as energy storage devices, according to some embodiments of the invention.  FIG. 5A  illustrates an energy storage device that includes a mass-driven mechanical system. In particular,  FIG. 5A  illustrates an energy storage device  500  that includes a mass  502 . The mass  502  is positioned adjacent to a torsion shaft  504 . The energy storage device  500  also includes a speed increaser  506  positioned adjacent to the torsion shaft  504  (opposite the mass  502 ). The energy storage device  500  also includes a drive shaft  508  positioned adjacent to the speed increaser  506  (opposite the torsion shaft  504 ). The energy storage device also includes a power source  510  positioned adjacent to the drive shaft  508  (opposite the speed increaser  506 ). 
     FIG. 5B  illustrates an energy storage device that includes a mass-driven hydraulic system. In particular,  FIG. 5B  illustrates an energy storage device  520  that includes a mass  522  within an exhaust chamber  524 . The exhaust chamber  524  is positioned adjacent to hydraulic fluid  526 . The energy storage device  500  also includes a power source  528  positioned adjacent to the hydraulic fluid  526  (opposite the exhaust chamber  524 ). 
   In some embodiments, the energy storage device  203  may be based on different types of differential pressure drive configurations.  FIGS. 6A-6B  illustrate differential pressure drive configurations as energy storage devices, according to some embodiments of the invention.  FIG. 6A  illustrates an energy storage device that includes a differential pressure-driven mechanical system. In particular,  FIG. 6A  illustrates an energy storage device  600  that includes an annulus pressure port  602 . The annulus pressure port  602  is positioned adjacent to a drive piston  604  (which may be non-rotating). The energy storage device  600  also includes a torsion shaft  606  positioned adjacent to the drive piston  604  (opposite the annulus pressure port  602 ). The energy storage device  600  also includes a speed increaser  608  positioned adjacent to the torsion shaft  606  (opposite the drive piston  604 ). The energy storage device  600  also includes a drive shaft  610  positioned adjacent to the speed increaser  608  (opposite the torsion shaft  606 ). The energy storage device  600  also includes a power source  612  positioned adjacent to the drive shaft  610  (opposite the speed increaser  608 ). The energy storage device  600  includes a tubing pressure port  614  positioned adjacent to the power source  612  (opposite the drive shaft  610 ). 
     FIG. 6B  illustrates an energy storage device that includes a differential pressure-driven hydraulic system. In particular,  FIG. 6B  illustrates an energy storage device  620  that includes an annulus pressure port  622 . The annulus pressure port  622  is positioned adjacent to a piston  624  (which may be floating). The energy storage device  620  also includes hydraulic fluid  626  positioned adjacent to the piston  624  (opposite the annulus pressure port  622 ). The energy storage device  620  also includes a power source  628  positioned adjacent to the hydraulic fluid  626  (opposite the piston  624 ). The energy storage device  620  also includes a tubing pressure port  630  positioned adjacent to the power source  628  (opposite the hydraulic fluid  626 ). 
   In some embodiments, the energy storage device  203  may be based on different types of compressed gas drive configurations.  FIGS. 7A-7B  illustrate compressed gas drive configurations as energy storage devices, according to some embodiments of the invention.  FIG. 7A  illustrates an energy storage device that includes a compressed gas-driven mechanical system. In particular,  FIG. 7A  illustrates an energy storage device  700  that includes an inert gas charge  702 . The inert gas charge  702  is positioned adjacent to a drive piston  704  (which may be non-rotating). The energy storage device  700  also includes a torsion shaft  706  positioned adjacent to the drive piston  704  (opposite the inert gas charge  702 ). The energy storage device  700  also includes a speed increaser  708  positioned adjacent to the torsion shaft  706  (opposite the drive piston  704 ). The energy storage device  700  also includes a drive shaft  710  positioned adjacent to the speed increaser  708  (opposite the torsion shaft  706 ). The energy storage device  700  also includes a power source  712  positioned adjacent to the drive shaft  710  (opposite the speed increaser  708 ). The energy storage device  700  includes an exhaust chamber  714  positioned adjacent to the power source  712  (opposite the drive shaft  710 ). 
     FIG. 7B  illustrates an energy storage device that includes a compressed gas-driven hydraulic system. In particular,  FIG. 7B  illustrates an energy storage device  720  that includes an inert gas charge  722 . The inert gas charge  722  is positioned adjacent to a piston  724  (which may be floating). The energy storage device  720  also includes hydraulic fluid  726  positioned adjacent to the piston  724  (opposite the inert gas charge  722 ). The energy storage device  720  also includes a power source  728  positioned adjacent to the hydraulic fluid  726  (opposite the piston  724 ). The energy storage device  720  includes an exhaust chamber  730  positioned adjacent to the power source  728  (opposite the hydraulic fluid  726 ). 
   Therefore, as described, some embodiments provide a combination of low-temperature electrical components (such as those housed in the thermal barrier  106 ) with high-temperature electrical components (such as those that are part of the high-temperature power source  202 , high-temperature power conditioning electronics  204 , high-temperature telemetry  212 , sensors  214 , etc) for downhole operations. 
   Switchably Operated Downhole Power Source for Heating and Cooling 
   In some embodiments, a controller may be used to control the flow of power in the tool  100 .  FIG. 8  illustrates a more detailed diagram of a tool for downhole operations that includes a configuration for controlling power flow between heating and cooling, according to some embodiments of the invention. In particular,  FIG. 8  illustrates a more detailed block diagram of parts of the tool  100 .  FIG. 8  includes a power source  802  coupled to a controller  824 . The controller  824  is coupled to sensors  812 . The controller  824  is also coupled to heaters  806  and a cooler module  822 . The heaters  806  are thermally coupled to an energy storage device  804 . The cooler module  822  is thermally coupled to the electronics  820 . The thermal coupling may be through conduction, convection, radiation, etc. An optional thermal barrier  816  may also at least partially surround the heaters  806 , the sensor  812  and the energy storage device  804 . An optional thermal barrier  818  may also at least partially surround the cooler module  822 , the electronics  820  and the sensor  812 . The heaters  806  may be ohmic resistive heaters. The power source  802  and the cooler module  822  may be similar to the power source and the cooler module, illustrated in  FIG. 2 , respectively. 
   Optional heat sinks  835  may be thermally coupled to the heaters  806 . The heat sinks  835  for the heaters  806  allows for heat energy to be given to the energy storage device  804  at times when energy is not be consumed by other components. For example, the heat may be given to the phase change material within the heat sinks  835  near the surface from a power source near the surface. The heat sinks  835  may supply heat to the energy storage device  804  during transit through the cold part of the borehole. Additionally, the heat sinks  835  coupled to the heaters  806  may increase the duration where the heaters  806  may remain off, thus providing additional time for using the electronics  820 . 
   An optional heat sink  836  may be thermally coupled to the electronics  820 . In some embodiments, the heat sink  835  and/or the heat sink  836  include a phase change material. In some embodiments, the heat sink  835  and/or the heat sink  836  include more than one phase change material. Such a heat sink may be used to trigger events based on the state of the phase change material. In some embodiments, the heat sinks  835 / 836  may be composed of two phase change materials.  FIG. 9  illustrates a plot of temperature of two phase change materials within a heat sink as a function of time, according to some embodiments of the invention. As illustrated, a graph  900  includes temperature as a function of time for phase change material A and phase change material B. The melting temperature of material A ( 902 ) is lower than the melting temperature of material B ( 904 ). The temperature rises until a melting temperature of material A is reached ( 906 ). After the material A is melted, the temperature rises ( 908 ). The temperature rises until the melting temperature of material B is reached ( 910 ). This second plateau provides a warning that the two phase change materials in the heat sink are about to be exhausted. 
   For example, the impending exhaustion of the phase change material may trigger one or more events. An example of an event may be the turning down or off of high-powered devices to reduce the amount of heat generated. In another example, a given change in the phase change material may trigger a signal to the operator to exit the hole. For example, a change in the phase change material may represent an overheating downhole. Another example of an event may be a feedback indicator to the heater/cooler system that more or less power needs to be applied to increase or decrease the heating/cooling capability. Another example of an event may be an activation of an auxiliary or backup heating/cooling supply (such as an exothermal/endothermal chemical reaction). In some embodiments, the state of the phase change material may serve as a predictor of the performance of the system, diagnostic evaluation, etc. The temperature of the phase change material may be monitored to optimize the performance of the heating and/or cooling system. 
   While described with two phase change materials, a lesser or greater number of material may be used. If more parts are used, a more precise estimate of the usage of the heat sink may be obtained. In some embodiments, the parts of the phase change material are not miscible. The miscibility may be controlled by making the materials hydrophobic/hydrophilic, by making emulsions of the phase change materials. In some embodiments, if the phase change materials are mixed together, the materials may be physically separated. For example, one of the materials may be encapsulated in metal, plastic, glass, ceramic, etc. The phase change materials could both be placed in the voice space of a foam. 
   With reference to  FIG. 9 , the two phase change materials may be applied with a wide ΔT between the melting of material A and material B. In such a situation, the electrical components thermally coupled to the heat sink (e.g., the energy storage device  804  (shown in  FIG. 8 )) may be configured to operate in the temperature range between the melting temperature of material A and the melting temperature of material B. Thus, there is a heat sink, material A, to keep the electrical component cool enough for operation. There is also a heat sink, material B, to prevent the electrical component from over heating when the ambient temperature is too high, the thermostat on the heater failed, the internal heating from high power usage generated too much heat, etc. The composition of the heat sinks  835 / 836  is not limited to phase change material. For example, the heat sinks  835 / 836  may also be composed of various metals, such as copper, aluminum, etc. 
   Returning to  FIG. 8 , energy stored in the energy storage device  804  may be used to supply power to an electrical load  810 , the heaters  806 , the cooler module  822 , the electronics  820 , etc. The electrical load  810  may represent different electrical loads downhole. Referring to  FIG. 2 , for example, the electrical load  810  may include the sensors  214 , the high-temperature telemetry  212 , etc. The power source  802  may also supply power to the electrical load  810 , the electronics  820 , etc. 
   Moreover, the power source  802  may be switchably operated to provide power to both the heaters  806  and the cooler module  822 . In some embodiments, at a low temperature, a greater percentage or all of the power from the power source  802  is supplied to the heaters  806 . Conversely, at a high temperature, a greater percentage or all of the power from the power source  802  is supplied to the cooler module  822 . 
   Power scheduling among the heating and cooling may allow for a smaller power generator. In particular, the total power for the simple sum of the loads may be larger than the power that can be provided by the power source  802 . This is possible because in some embodiments, not all of the loads are used simultaneously. In some embodiments, the power source  802  derives power from the mud flow downhole. Power scheduling may allow for full operation at lower flow rates. 
   The controller  824  may be a direct wire connection, an inductive couple, a feedback controller, a feedforward controller, a pre-programmed timing-based controller, a neural network controller, an adaptive controller, etc. that allows power to flow between the power source  802  and the heaters  806 , and the power source  802  and the cooler module  822 . For example, in some embodiments, the controller  824  may be a pulse-width modulation controller that changes the pulse widths to adjust the duty cycle of the applied voltage. 
   The controller  824  is shown to control the distribution of power based on input from the sensors  812 . The sensors  812  are shown to monitor the temperature of the energy storage device  804  and the electronics  820 . Embodiments are not so limited. For example, the controller  824  may control based on input from either (and not necessarily both) of the sensors  812 . Alternatively or in addition, the controller  824  may control based on another sensor (not shown) that is positioned to measure the ambient temperature downhole. Alternatively or in addition, the controller  824  may control based on the temperature of the phase change material within the heat sink  835  and/or the heat sink  836 . In some embodiments, the heaters  806  and the cooler module  822  may adjust the amount of power to accept from the controller  824 . For example, if the cooler module  822  does not need power for cooling, the cooler module  822  may include its own controller to adjust how much power to accept. Optional thermostats may be coupled to the heaters  806  and the cooler module  822 . Control may be based on a temperature reference from the thermostats for the energy storage device  804 /electronics  820  or for the heat sinks  835 / 836 . 
   In some embodiments, the energy storage device  804  may be the thermal barrier  818 . Accordingly, the energy storage device  804  may be such devices that are operable at low temperatures (such as a primary lithium battery). In some embodiments, the tool may include multiple energy storage devices where one or more may be positioned outside the thermal barrier  818  and one or more may be housed in the thermal barrier  818 . In some embodiments, the heat sink  836  may be positioned between the cooler module  822  and the electronics  820 . In one such configuration, the heat sinks  835  may be absent. 
     FIG. 10  illustrates power and heat flow in a tool for downhole operations that includes a configuration for controlling power flow between heating and cooling, according to some embodiments of the invention. The power flow and the heat flow are illustrated by the solid lines and dashed lines, respectively. The power source  802  is represented as a turbine  1006  that receives power from a flow  1004  of mud downhole. 
   The controller  824  is coupled to receive power from the turbine  1006 . The controller  824  is coupled to switchably supply power to the cooler module  822  and the heaters  806 . The controller  824  is also coupled to switchably supply power to the electronics  820  and the energy storage device  804 . In some embodiments, power may be supplied to the electronics  820  and the energy storage device  804  simultaneously or to either. 
   The controller  824  may be configured to receive power from multiple sources. For example, the controller  824  may receive power from a generator and an energy storage device. Power from the generator may be allocated to and by the controller  824  in varying proportion to any or all of the energy storage device  804 , cooler module  822 , the electronics  820 , the heaters  806 , the electronics  820  (including sensors) and the controller  824 . In some embodiments, power from the energy storage device  804  may be allocated to and by the controller  824  in varying proportion to the electronics  820  (including sensors). It is possible that power from the energy storage device  804  may be allocated to the cooler module  822  or heaters  806  for a short period of time. 
   With regard to heat flow, heat may be exchanged between the heat sink  836  and the cooler module  822 . Heat may also be exchanged between the heat sink  835  and the heaters  8806 . Heat may also flow from the electronics  820  to the cooler module  822  and to the energy storage device  804 . Heat may also flow from the cooler module  822  to the environment  418  and to the heaters  806 . Heat may also flow from the heaters  806  to the energy storage device  804 . 
   The heat flow and power flows are not limited to those shown in  FIG. 10 . For example, with regard to heat flow, the direction is dependent on the relative temperatures. In some embodiments, heat flows between the electronics  820  and the heat sink  836 , between the heat sink  836  and the cooler module  822 , and between the cooler module  822  and the environment  418 . Heat may also flow between the heaters  806  and the energy storage device  804 . 
   The operations of the configuration illustrated in  FIG. 8  are now described. In particular,  FIG. 11  illustrates a flow diagram for controlling power flow between heating and cooling, according to some embodiments of the invention. The flow diagram commences at block  1102 . 
   At block  1102 , a downhole temperature (or alternatively a rate of change of the downhole temperature) is determined. With reference to  FIG. 8 , the controller  824  may make this determination. The controller  824  may make this determination based on data from one of more of the sensors downhole. For example, the controller  824  may determine the temperatures of the environment external or internal to the tool. The controller  824  may determine the temperatures of the energy storage device  804  and/or the electronics  820 . The controller  824  may also determine a temperature of one or more phase change materials within one of more of the heat sinks (e.g., the heat sink  835  or the heat sink  836 ). The flow continues at block  1104 . 
   At block  1104 , power from a power source is allocated between a heater and a cooler that are part of a tool used for a downhole operation based on the downhole temperature. With reference to  FIG. 8 , the controller  824  may make this allocation. The controller  824  may allocate different percentages, all and none, etc. based on the downhole temperature. For example, if the downhole temperature is below a minimum value, the controller  824  may allocate all power to the heaters  806 . If the downhole temperature is above the minimum value but below a threshold value, the controller  824  may allocate a higher percentage of the power to the heaters  806 . If the downhole temperature is above the threshold value, the controller  824  may allocate all of the power to the cooler module  822 . In some embodiments, the controller  824  may allocate a preponderance of the power to the heaters  806 , if the downhole temperature is defined as low. The controller  824  may allocate a preponderance of the power to the cooler module  822 , if the downhole temperature is defined high. For example, a low temperature may be defined as a temperature less than 100° C.; a high temperature may be defined as a temperature of 100° C. or greater. Therefore, the controller  824  may allocate power between the heater and cooler using a number of different techniques. While described such that allocation is between the heaters and the cooler module, embodiments are not so limited. For example, the controller  824  may allocate power to other components of the tool. In particular, the controller  824  may allocate power between the heaters  806 , the cooler module  822 , the electronics  820 , the heat sinks  836 , the heat sink  835 , etc. 
   Downhole Rechargeable Energy Storage Device 
   In some embodiments, rechargeable energy storage devices are used to power electrical components downhole. For example, with reference to  FIGS. 2 and 8 , the energy storage device  203 / 804  may be rechargeable. The rechargeable energy storage devices may be charged by a downhole power source. For example, a turbine generator may be used to recharge the rechargeable energy storage devices. In some embodiments, the rechargeable energy storage devices may be charged at the surface. In other words, the rechargeable energy storage device is being charged prior to be placed in the well. In some embodiments, the rechargeable energy storage devices may be different types of batteries (such as molten salt batteries). The rechargeable energy storage devices may be operable at high temperatures. High temperatures at which the rechargeable energy storage devices may be operable include temperature above 60° C., above 120° C., above 175° C., above 220° C., above 600° C., in a range of 175-250° C., in a range of 220-600° C., etc. Below these temperatures, the rechargeable energy storage devices may provide electrical power but are defined as “not operable” due to an increase in internal resistance, a reduction in capacity, a reduction in cycle life, or some other temperature-dependent behavior. In some embodiments, the rechargeable energy storage devices may be operable at low temperatures. The low temperature at which the rechargeable energy storage devices are operable includes temperature below 100° C., below 150° C., below 175° C., below 200° C., below 220° C., below 125° C., below 100° C., below 80° C., in a range of 0-80° C., in a range of −20-100° C., etc. At higher temperatures, these rechargeable energy storage devices may provide electrical power but are defined as “not operable” due to an increase in self discharge, a reduction in cycle life, a reduction in current output, a decrease in safety, or some other temperature-dependent behavior. 
   The energy storage device and the rechargeable energy storage device may store energy in electro-chemical reactions, such as batteries, capacitors, and fuel cells. The energy storage device and rechargeable energy storage device may store energy in mechanical potential energy, such as springs and hydraulic assemblies, or in mechanical kinetic energy, such as flywheels and oscillating assemblies. 
   The electrical components downhole may be powered by a combination of a power source (such as a turbine generator powered by the flow of mud downhole), a vibration-based power generator powered by vibrations of the tool string, a vibration-based power generator powered by fluid-induced vibrations, a nuclear power source powered by atomic decay, a hydraulic accumulator-based power source, a gas accumulator-based power source, a flywheel-based power source, a hydrostatic dump chamber-based power source, and one or more rechargeable energy storage devices. An example of such a configuration is illustrated in  FIG. 2 . For example, the electrical components may be powered directly by the power generator while there is a sufficient fluid flow. Power not consumed by the electrical components may be used to charge the one or more rechargeable energy storage devices. During no flow condition, all or some of the electrical components may be powered by the one or more rechargeable energy storage devices. For example, when drill stands are being changed (no fluid flow), the cooling system and/or heaters may be switched off and power for select sensors and/or electronics may be supplied by the rechargeable energy storage devices. 
   Some embodiments use a controller (similar to the one shown in  FIG. 8 ) to control power distribution from among a power generator, a rechargeable energy storage device and an energy storage device. Accordingly, the controller serves as a power hub to direct power from the power generator, the rechargeable energy storage device, and the energy storage device to the different electrical loads downhole.  FIGS. 12 and 13  illustrate power flow and heat flow, respectively, for parts of a tool that includes a rechargeable energy storage device, according to some embodiments of the invention. In particular,  FIG. 12  illustrates power flow in a tool for downhole operations that includes a rechargeable energy storage device, according to some embodiments of the invention. 
   As shown, a power generator  1206  and a cooler  1204  receive power from a flow  1208 . A controller is coupled to receive power from the power generator  1206 , a rechargeable energy storage device  1210  and an energy storage device  1214 . The controller  1202  distributes power to the cooler  1204  and the electronics  1212 . Accordingly, the cooler  1204  may receive power directly from the flow  1208  or from the controller  1202 . The energy storage device  1214  may also be coupled to supply power to the power generator  1206 . The controller  1202  may also distribute power from the power generator  1206  and the energy storage device  1214  to the rechargeable energy storage device  1210 . 
     FIG. 13  illustrates heat flow in a tool for downhole operations that includes a rechargeable energy storage device, according to some embodiments of the invention. Heat may flow from a power generator  1306  and a cooler  1304  to a mud flow  1308 . Heat is exchanged between the cooler  1304  and a rechargeable storage device  1310 . Heat may also be exchanged between the cooler  1304  and an energy storage device  1314 . Accordingly, the heat from the cooler  1304  may increase the efficiency of the rechargeable storage device  1310  and the energy storage device  1314  (especially if such devices are operable at high-temperatures). Alternatively, the cooler  1304  may provide additional cooling to the rechargeable storage device  1310  and the energy storage device  1314  when the ambient temperature exceeds a maximum operating temperature for such devices. Heat may be exchanged between the cooler  1304  and electronics  1312 . Accordingly, the cooler  1304  provides cooling to the electronics  1312  by accepting heat there from. The cooler  1304  may also provide heat to the electronics  1312  if a constant temperature reference is needed. Heat may be exchanged between the rechargeable energy storage device  1310  and the energy storage device  1314 . Heat flows from electronics  1312  to the rechargeable energy storage device  1310  and the energy storage device  1314 . 
   DC power sources (such as the rechargeable energy storage devices) may provide a cleaner source of power to electrical components in comparison to AC power sources. Therefore, in some embodiments, the turbine generator (or other AC power source downhole) may be used to recharge the rechargeable energy storage devices, which then power the electrical components. In other words, in such a configuration, the power generator is not used to directly supply power to the electrical components.  FIGS. 14A and 14B  illustrates different types of such configurations.  FIG. 14A  illustrates a more detailed diagram of a tool for downhole operations that includes rechargeable energy storage devices to supply power downhole, according to some embodiments of the invention. An AC power source  1402  may receive mechanical power from the fluid flow or drill string motion and may convert the mechanical power into electrical power. The AC power source  1402  may be any type of power generator (such as a turbine generator, as described above). The electrical power from the AC power source  1402  may be received by a transformer  1404 . 14The transformer  1404  steps up or steps down the alternating current from the AC power source  1402 . The transformed current from the transformer  1404  may be coupled to be input into a rectifier  1406 . The rectifier  1406  converts the current into a DC current, which may then be used to recharge the rechargeable energy storage device  1408  and the rechargeable energy storage device  1410 . The rechargeable energy storage device  1408  and the rechargeable energy storage device  1410  may supply DC power to electronics  1412 . A controller  1407  may be coupled to the rectifier  1406 , the rechargeable energy storage device  1408  and the rechargeable energy storage device  1410 . The controller  807  controls which of the rechargeable energy storage devices is being recharged and which of the rechargeable energy storage devices is supplying power to the electronics  1412 . Accordingly, DC current power source may be used to supply power to the electronics  1412  based on an AC current power source. In some embodiments, as one rechargeable energy storage device is being recharged, the other may be being used to supply power to the electronics downhole. The controller  1407  may control the switching based on amount of energy storage in each of the devices. For example, if the rechargeable energy storage device  1408  is supplying power and is almost deplete of stored energy, the controller  1407  may switch such that the rechargeable energy storage device  1410  is supplying power while the rechargeable energy storage device is being recharged. 
     FIG. 14B  illustrates a more detailed diagram of a tool for downhole operations that includes rechargeable energy storage devices to supply power downhole, according to other embodiments of the invention.  FIG. 14B  has a similar configuration as  FIG. 14A . However, the rectifier  1406  first receives the power from the AC power source  1402 . A converter  1405  is coupled to receive the DC power from the rectifier  1406 . The converter  1405  may perform a DC-to-DC step-up conversion to raise the DC voltage. 14While  FIGS. 14A-14B  are described in reference to an AC power source, embodiments are not so limited. The tool shown in  FIGS. 14A-14B  may include any other type of power. 
   Embodiments illustrated herein may be combined in various combinations. For example, the configuration of  FIG. 8  (having the controller  824  for switching between heating and cooling) may be combined with the configurations of  FIGS. 14A-14B  (having an AC power source in combination with multiple rechargeable energy storage devices). 
   System Operating Environments 
   System operating environments for the tool  100 , according to some embodiments, are now described.  FIG. 15A  illustrates a drilling well during wireline logging operations that includes the heating and/or cooling downhole, according to some embodiments of the invention. A drilling platform  1586  is equipped with a derrick  1588  that supports a hoist  1590 . Drilling of oil and gas wells is commonly carried out by a string of drill pipes connected together so as to form a drilling string that is lowered through a rotary table  1510  into a wellbore or borehole  1512 . Here it is assumed that the drilling string has been temporarily removed from the borehole  1512  to allow a wireline logging tool body  1570 , such as a probe or sonde, to be lowered by wireline or logging cable  1574  into the borehole  1512 . Typically, the tool body  1570  is lowered to the bottom of the region of interest and subsequently pulled upward at a substantially constant speed. During the upward trip, instruments included in the tool body  1570  may be used to perform measurements on the subsurface formations  1514  adjacent the borehole  1512  as they pass by. The measurement data can be communicated to a logging facility  1592  for storage, processing, and analysis. The logging facility  1592  may be provided with electronic equipment for various types of signal processing. Similar log data may be gathered and analyzed during drilling operations (e.g., during Logging While Drilling, or LWD operations). 
     FIG. 15B  illustrates a drilling well during MWD operations that includes the heating and/or cooling downhole, according to some embodiments of the invention. It can be seen how a system  1564  may also form a portion of a drilling rig  1502  located at a surface  1504  of a well  1506 . The drilling rig  1502  may provide support for a drill string  1508 . The drill string  1508  may operate to penetrate a rotary table  1510  for drilling a borehole  1512  through subsurface formations  1514 . The drill string  1508  may include a Kelly  1516 , drill pipe  1518 , and a bottom hole assembly  1520 , perhaps located at the lower portion of the drill pipe  1518 . 
   The bottom hole assembly  1520  may include drill collars  1522 , a downhole tool  1524 , and a drill bit  1526 . The drill bit  1526  may operate to create a borehole  1512  by penetrating the surface  1504  and subsurface formations  1514 . The downhole tool  1524  may comprise any of a number of different types of tools including MWD (measurement while drilling) tools, LWD (logging while drilling) tools, and others. 
   During drilling operations, the drill string  1508  (perhaps including the Kelly  1516 , the drill pipe  1518 , and the bottom hole assembly  1520 ) may be rotated by the rotary table  1510 . In addition to, or alternatively, the bottom hole assembly  1520  may also be rotated by a motor (e.g., a mud motor) that is located downhole. The drill collars  1522  may be used to add weight to the drill bit  1526 . The drill collars  1522  also may stiffen the bottom hole assembly  1520  to allow the bottom hole assembly  1520  to transfer the added weight to the drill bit  1526 , and in turn, assist the drill bit  1526  in penetrating the surface  1504  and subsurface formations  1514 . 
   During drilling operations, a mud pump  1532  may pump drilling fluid (sometimes known by those of skill in the art as “drilling mud”) from a mud pit  1534  through a hose  1536  into the drill pipe  1518  and down to the drill bit  1526 . The drilling fluid can flow out from the drill bit  1526  and be returned to the surface  1504  through an annular area  1540  between the drill pipe  1518  and the sides of the borehole  1512 . The drilling fluid may then be returned to the mud pit  1534 , where such fluid is filtered. In some embodiments, the drilling fluid can be used to cool the drill bit  1526 , as well as to provide lubrication for the drill bit  1526  during drilling operations. Additionally, the drilling fluid may be used to remove subsurface formation  1514  cuttings created by operating the drill bit  1526 . 
   General 
   In the description, numerous specific details such as logic implementations, opcodes, means to specify operands, resource partitioning/sharing/duplication implementations, types and interrelationships of system components, and logic partitioning/integration choices are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that embodiments of the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure the embodiments of the invention. Those of ordinary skill in the art, with the included descriptions will be able to implement appropriate functionality without undue experimentation. 
   References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
   A number of figures show block diagrams of systems and apparatus for heating and cooling downhole, in accordance with some embodiments of the invention. A figure shows a flow diagram illustrating operations for heating and cooling downhole, in accordance with some embodiments of the invention. The operations of the flow diagram are described with references to the systems/apparatus shown in the block diagrams. However, it should be understood that the operations of the flow diagram could be performed by embodiments of systems and apparatus other than those discussed with reference to the block diagrams, and embodiments discussed with reference to the systems/apparatus could perform operations different than those discussed with reference to the flow diagram. 
   Some or all of the operations described herein may be performed by hardware, firmware, software or a combination thereof. For example, the operations of the different controllers as described herein may be performed by hardware, firmware, software or a combination thereof. Upon reading and comprehending the content of this disclosure, one of ordinary skill in the art will understand the manner in which a software program can be launched from a machine-readable medium in a computer-based system to execute the functions defined in the software program. One of ordinary skill in the art will further understand the various programming languages that may be employed to create one or more software programs designed to implement and perform the methods disclosed herein. The programs may be structured in an object-orientated format using an object-oriented language such as Java or C++. Alternatively, the programs can be structured in a procedure-orientated format using a procedural language, such as assembly or C. The software components may communicate using any of a number of mechanisms well-known to those skilled in the art, such as application program interfaces or inter-process communication techniques, including remote procedure calls. The teachings of various embodiments are not limited to any particular programming language or environment. 
   In view of the wide variety of permutations to the embodiments described herein, this detailed description is intended to be illustrative only, and should not be taken as limiting the scope of the invention. What is claimed as the invention, therefore, is all such modifications as may come within the scope and spirit of the following claims and equivalents thereto. Therefore, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.