U.S. patent application number 14/098437 was filed with the patent office on 2014-06-12 for cooling system and method for a downhole tool.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Kamal Kader, Mari Yoshida.
Application Number | 20140158429 14/098437 |
Document ID | / |
Family ID | 47561262 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140158429 |
Kind Code |
A1 |
Kader; Kamal ; et
al. |
June 12, 2014 |
Cooling System and Method for A Downhole Tool
Abstract
Present embodiments relate to systems and methods for providing
cooling to temperature sensitive components of a downhole tool with
an intermittent power supply. To provide one example, a downhole
tool may include a temperature sensitive component, an enclosure, a
cooling unit, and a heat exchanger. The enclosure may be designed
to provide thermal insulation to the temperature sensitive
component. The cooling unit may intermittently provide active
cooling while the downhole tool is being operated. The heat
exchanger may facilitate heat transfer from the temperature
sensitive component to the cooling unit when the cooling unit is
providing the active cooling. The heat exchanger may also disable
heat transfer between the temperature sensitive component and the
cooling unit when the cooling unit is not providing the active
cooling.
Inventors: |
Kader; Kamal; (Minato-Ku,
JP) ; Yoshida; Mari; (Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
Sugar Land
TX
|
Family ID: |
47561262 |
Appl. No.: |
14/098437 |
Filed: |
December 5, 2013 |
Current U.S.
Class: |
175/40 |
Current CPC
Class: |
E21B 36/001 20130101;
E21B 44/005 20130101; E21B 47/017 20200501 |
Class at
Publication: |
175/40 |
International
Class: |
E21B 44/00 20060101
E21B044/00; E21B 36/00 20060101 E21B036/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2012 |
EP |
12306533.6 |
Claims
1. A downhole tool, comprising: a temperature sensitive component
of the downhole tool; an enclosure configured to provide thermal
insulation to the temperature sensitive component; a cooling unit
configured to intermittently provide active cooling while the
downhole tool is being operated; and a heat exchanger configured to
facilitate heat transfer from the temperature sensitive component
to the cooling unit when the cooling unit is providing the active
cooling, and configured to disable heat transfer between the
temperature sensitive component and the cooling unit when the
cooling unit is not providing the active cooling.
2. The downhole tool of claim 1, wherein the heat exchanger is
configured to disable heat transfer between the temperature
sensitive component and the cooling unit when power is not supplied
to the heat exchanger.
3. The downhole tool of claim 1, wherein the heat exchanger is
configured to facilitate heat transfer based on a control
signal.
4. The downhole tool of claim 1, wherein the cooling unit is
configured to receive power from a generator of a drilling
system.
5. The downhole tool of claim 1, wherein the cooling unit is
configured to provide the active cooling when the cooling unit
intermittently receives power.
6. The downhole tool of claim 1, wherein the cooling unit is
configured to provide the active cooling based on a control
signal.
7. The downhole tool of claim 1, wherein the heat exchanger
comprises a pump configured to pump fluid through a flowpath loop
between the cooling unit and the temperature sensitive
component.
8. The downhole tool of claim 1, wherein the heat exchanger
comprises an electromagnetic switch configured to disable the heat
transfer.
9. The downhole tool of claim 1, wherein the enclosure comprises a
vacuum flask.
10. The downhole tool of claim 1, wherein the cooling unit
comprises a phase change cooling system, a sterling pump, a pulse
tubing pump, a thermoelectric cooler, or any combination
thereof.
11. A drilling system, comprising: a generator configured to
intermittently provide electrical power to components of a downhole
tool; a cooling unit of the downhole tool configured to provide
active cooling when the electrical power is provided; a temperature
sensitive component of the downhole tool; an enclosure configured
to thermally insulate the temperature sensitive component; and a
heat exchanger configured to facilitate heat transfer from the
temperature sensitive component to the cooling unit when the
electrical power is provided; wherein the heat exchanger is
configured to prevent heat transfer between the temperature
sensitive component and the cooling unit when the electrical power
is not provided.
12. The drilling system of claim 11, wherein the heat exchanger
comprises a heat pipe configured to provide unidirectional heat
transfer from the temperature sensitive component coupled to a
lower vertical end of the heat pipe to the cooling unit coupled to
an upper vertical end of the heat pipe.
13. The drilling system of claim 11, wherein the heat exchanger
comprises a pump configured to pump fluid through a flowpath loop
between the cooling unit and the temperature sensitive component
when the electrical power is provided.
14. The drilling system of claim 11, wherein the heat exchanger
comprises an electromagnetic switch configured to close a bridge of
conductive material between the cooling unit and the temperature
sensitive component when the electrical power is provided.
15. The drilling system of claim 11, comprising control circuitry
configured to provide control signals to the cooling unit and/or to
the heat exchanger to control the heat transfer from the
temperature sensitive component to the cooling unit.
Description
BACKGROUND
[0001] The present disclosure relates generally to downhole tools
and, more particularly, to systems and methods for providing
consistent cooling to temperature sensitive components of a
downhole tool.
[0002] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the
present techniques, which are described and/or claimed below. This
discussion is believed to be helpful in providing the reader with
background information to facilitate a better understanding of the
various aspects of the present disclosure. Accordingly, it should
be understood that these statements are to be read in this light,
and not as admissions of prior art.
[0003] A drill bit attached to a string of drill pipe, generally
referred to as the drill string, may be used to drill a borehole
for an oil and/or gas well. In addition to the drill bit, the drill
string may also include a variety of downhole tools to measure or
log properties of the surrounding rock formation or the conditions
in the borehole. To generate power for these tools to operate, a
turbine generator may convert hydraulic power of drilling fluid
moving through the drill string. Some downhole tools may include
batteries that provide limited power for tool operation.
[0004] Downhole tools often include electronics, sensors, or other
components that may be susceptible to the high ambient temperatures
of the downhole environment. Such components are designed to
operate only within a certain range of temperatures, and these
acceptable temperatures may be lower than the temperature in the
borehole. In such contexts, maintaining the temperature sensitive
components within the acceptable temperature range may prevent
heat-related failures. Various systems have been developed to
provide protection to such temperature sensitive components. These
systems, however, have several disadvantages. For example, thermal
insulation of the temperature sensitive components alone is
generally not effective for providing long-term cooling in a
downhole environment. Active cooling systems can provide more
long-term cooling, but these systems rely on power to operate.
Unfortunately, downhole tools incorporated into the drill string
receive only an intermittent or limited power supply, since the
drilling fluid is not constantly flowing through the drill string,
and onboard batteries may not provide enough power for active
cooling.
SUMMARY
[0005] A summary of certain embodiments disclosed herein is set
forth below. It should be understood that these aspects are
presented merely to provide the reader with a brief summary of
these certain embodiments and that these aspects are not intended
to limit the scope of this disclosure. Indeed, this disclosure may
encompass a variety of aspects that may not be set forth below.
[0006] Present embodiments relate to systems and methods for
providing cooling to temperature sensitive components of a downhole
tool with an intermittent power supply. To provide one example, a
downhole tool may include a temperature sensitive component, an
enclosure, a cooling unit, and a heat exchanger. The enclosure may
be designed to provide thermal insulation to the temperature
sensitive component. The cooling unit may intermittently provide
active cooling while the downhole tool is being operated. The heat
exchanger may facilitate heat transfer from the temperature
sensitive component to the cooling unit when the cooling unit is
providing the active cooling. The heat exchanger may also disable
heat transfer between the temperature sensitive component and the
cooling unit when the cooling unit is not providing the active
cooling.
[0007] In another example, a drilling system may include a
generator used to intermittently provide electrical power to
components of a downhole tool. The drilling system also may include
a cooling unit of the downhole tool, and this cooling unit may
provide active cooling when the electrical power is provided. In
addition, the drilling system may include a temperature sensitive
component of the downhole tool and an enclosure to thermally
insulate the temperature sensitive component. Further, the drilling
system may include a heat exchanger that facilitates heat transfer
from the temperature sensitive component to the cooling unit when
the electrical power is provided. The heat exchanger may prevent
heat transfer between the temperature sensitive component and the
cooling unit when the electrical power is not provided.
[0008] A method in accordance with an embodiment may involve
reducing heat transfer to a temperature sensitive component of a
downhole tool via a thermally insulating enclosure located about
the temperature sensitive component. The method also may involve
transferring heat from the temperature sensitive component to a
cooling unit that may provide active cooling when the cooling unit
receives power. In addition, the method may involve preventing heat
transfer between the cooling unit and the temperature sensitive
component when the cooling unit does not receive power.
[0009] Various refinements of the features noted above may exist in
relation to various aspects of the present disclosure. Further
features may also be incorporated in these various aspects as well.
These refinements and additional features may exist individually or
in any combination. For instance, various features discussed below
in relation to one or more of the illustrated embodiments may be
incorporated into any of the above-described aspects of the present
disclosure alone or in any combination. Again, the brief summary
presented above is intended only to familiarize the reader with
certain aspects and contexts of embodiments of the present
disclosure without limitation to the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Various aspects of this disclosure may be better understood
upon reading the following detailed description and upon reference
to the drawings in which:
[0011] FIG. 1 is a schematic diagram of a drilling system that may
employ a downhole tool with a cooling system, in accordance with an
embodiment;
[0012] FIG. 2 is a block diagram of components of a downhole tool
with an intermittent power supply, in accordance with an
embodiment;
[0013] FIG. 3 is a flowchart of a method for operating the
components of FIG. 2 when power is supplied to the downhole tool,
in accordance with an embodiment;
[0014] FIG. 4 is a flowchart of a method for operating the
components of FIG. 2 when no power is supplied to the downhole
tool, in accordance with an embodiment;
[0015] FIG. 5 is a schematic block diagram of an example of the
components of FIG. 2, in accordance with an embodiment;
[0016] FIG. 6 is a schematic block diagram of another example of
the components of FIG. 2, in accordance with an embodiment; and
[0017] FIG. 7 is a schematic block diagram of another example of
the components of FIG. 2, in accordance with an embodiment.
DETAILED DESCRIPTION
[0018] One or more specific embodiments of the present disclosure
will be described below. These described embodiments are only
examples of the presently disclosed techniques. Additionally, in an
effort to provide a concise description of these embodiments, all
features of an actual implementation may not be described in the
specification. It should be appreciated that in the development of
any such actual implementation, as in any engineering or design
project, numerous implementation-specific decisions must be made to
achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which may vary
from one implementation to another. Moreover, it should be
appreciated that such a development effort might be complex and
time consuming, but would nevertheless be a routine undertaking of
design, fabrication, and manufacture for those of ordinary skill
having the benefit of this disclosure.
[0019] When introducing elements of various embodiments of the
present disclosure, the articles "a," "an," and "the" are intended
to mean that there are one or more of the elements. The terms
"comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements. Additionally, it should be understood that
references to "one embodiment" or "an embodiment" of the present
disclosure are not intended to be interpreted as excluding the
existence of additional embodiments that also incorporate the
recited features.
[0020] As mentioned above, this disclosure relates to cooling
temperature sensitive components in a downhole tool with an
intermittent power supply, such as a downhole tool used in a drill
string. Specifically, drilling a borehole for an oil and/or gas
well often involves a drill string--several drill pipes and a drill
bit, among other things--that grinds into a rock formation when
drilling fluid is pumped through the drill string. In addition to
the drill bit, the drill string may also include several
electrically powered tools. The tools in the drill string may
include, for example, logging-while-drilling (LWD) tools,
measurement-while-drilling (MWD) tools, steering tools, and/or
tools to communicate with drilling operators at the surface. In
general, the borehole may be drilled by pumping drilling fluid into
the tool string, causing the drill bit to rotate and grind away
rock as the drilling fluid passes through. The hydraulic power of
the drilling fluid may also be used to generate electricity.
Specifically, a turbine generator may convert some of the hydraulic
power of the drilling fluid into electrical power. The electrical
power may be used to operate one or more downhole tools.
[0021] A downhole tool may include temperature sensitive equipment
that may fail if the temperature of the equipment exceeds a
particular range. Presently disclosed embodiments are directed to
systems and methods for providing such cooling to the temperature
sensitive equipment. However, power supplied to the downhole tool
is intermittent because the drilling fluid is not always being
pumped into the tool string. The downhole tool may therefore
utilize a heat exchanger that facilitates unidirectional or
disableable heat transfer from the temperature sensitive components
to a cooling system. When power is available, the cooling system
provides active cooling and the heat exchanger facilitates heat
transfer from the temperature sensitive components to the cooling
system. When no power is available, the heat exchanger prevents
heat transfer between the cooling system and the temperature
sensitive components. The temperature sensitive components may be
located within a thermally insulating enclosure to reduce heat
transfer from the environment to the temperature sensitive
components, regardless of the availability of power. Thus, despite
an intermittent power supply, the temperature of the temperature
sensitive components of the downhole tool may remain relatively
stable.
[0022] A drilling system 10, shown in FIG. 1, may benefit from the
heat exchanger mentioned above. The drilling system 10 of FIG. 1
includes a drill string 12 used to drill a borehole 14 into a rock
formation 16. A drill collar 18 of the drill string 12 encloses the
various components of the drill string 12. Drilling fluid 20 from a
reservoir 22 at the surface 24 may be driven into the drill string
12 by a pump 26. The hydraulic power of the drilling fluid 20
causes a drill bit 28 to rotate, cutting into the rock formation
16. The cuttings from the rock formation 16 and the returning
drilling fluid 20 exit the drill string 12 through an annulus 30.
The drilling fluid 20 thereafter may be recycled and pumped, once
again, into the drill string 12.
[0023] A variety of information relating to the rock formation 16
and/or the state of drilling of the borehole 14 may be gathered
while the drill string 12 drills the borehole 14. For instance, a
measurement-while-drilling (MWD) tool 32 may measure certain
drilling parameters, such as the temperature, pressure, orientation
of the drilling tool, and so forth. Likewise, a
logging-while-drilling (LWD) tool 34 may measure the physical
properties of the rock formation 16, such as density, porosity,
resistivity, and so forth.
[0024] These tools and others may rely on electrical power for
their operation. As such, a turbine generator 36 (e.g., generator
coupled to a drilling fluid turbine) may generate electrical power
from the hydraulic power of the drilling fluid 20. The turbine
generator 36 may provide a generally stable supply of electrical
power as the drilling fluid 20 is pumped through the drill string
12. There may be periods of time throughout a drilling operation,
however, when the pump 26 does not drive the drilling fluid 20
through the drill string 12. For example, when new lengths of drill
pipe are added to the drill string, or services are performed on
the drilling equipment, the pump 26 may not provide the drilling
fluid 20 to the turbine generator 36. Consequently, the turbine
generator 36 may generate intermittent power for operation of the
MWD tool 32 and the LWD tool 34. These downhole tools may include
systems for cooling and thermally protecting temperature sensitive
equipment that would otherwise overheat in the borehole 14. Such
systems, described in detail below, may protect the temperature
sensitive equipment both when the turbine generator 36 supplies
power to the downhole tools and when the generator 36 is not
generating power.
[0025] As seen in FIG. 1, the drill string 12 is generally aligned
along a longitudinal z-axis. Components of the drill string 12 may
be located within the drill string 12 at various radial distances
from the z-axis, as illustrated by a radial r-axis. Certain
components, such as the turbine generator 36, may include parts
that rotate circumferentially along a circumferential c-axis. The
coordinate system shown in FIG. 1 will be used throughout the
various drawings discussed below to represent the spatial
relationship between various system components.
[0026] Certain components of a downhole tool 50 are shown as a
block diagram in FIG. 2. The downhole tool 50 may include the MWD
tool 32, the LWD tool 34, or any other tool containing one or more
temperature sensitive components 52. As shown in FIG. 2, the
downhole tool 50 also includes a thermal enclosure 54, a cooling
unit 56, and a heat exchanger 58. The temperature sensitive
component 52 is located within the enclosure 54, which may
substantially reduce heat exchange between the downhole environment
and the temperature sensitive component 52. The heat exchanger 58
may be disableable or unidirectional, allowing heat transfer from
the temperature sensitive component 52 to the cooling unit 56 when
the cooling unit 56 is active. The heat exchanger 58 may prevent or
significantly reduce heat transfer between the cooling unit 56 and
the temperature sensitive component 52 when the cooling unit 56 is
off. Embodiments of the heat exchanger 58 are provided in detail
below.
[0027] There may be many different types of temperature sensitive
components 52 that can be protected via components of the downhole
tool 50 provided in FIG. 2. For example, the temperature sensitive
component 52 may include one or more electronic components,
electronics boards, sensors, or any other temperature sensitive
equipment located in the downhole tool 50. Such sensors and
electronics may perform various functions in the downhole tool 50,
such as determining physical properties of formation fluid samples,
sensing drilling parameters, executing control functions within the
downhole tool 50, and so forth. The temperature sensitive component
52 may operate effectively within a certain temperature range,
which may include temperatures below a target temperature. For
example, the target temperature may be approximately 175 U, while
the downhole environment, depending on the depth of the borehole 14
and type of rock formation 16, may have a temperature between
approximately 150 U and 250 U. As a result, the temperature
sensitive component 52 may be susceptible to overheating due to the
high temperatures of the downhole environment. This may damage or
negatively affect performance of the temperature sensitive
components 52, or make the components operate outside a desired
temperature range, unless appropriate cooling is provided by other
components of the downhole tool 50.
[0028] The enclosure 54 may provide protective thermal insulation
of the temperature sensitive component 52 when no power is
available to the downhole tool 50. To that end, the enclosure 54
may be formed from any suitable thermally insulating material. In
an embodiment, the enclosure 54 may include a vacuum flask (e.g.,
Dewar flask), which includes two nested flasks with a vacuum pulled
between them to reduce an amount of heat transfer between the
outside flask and the inside flask. This reduces an amount of heat
transfer between the outside environment and the enclosed
temperature sensitive component 52, for a certain amount of time.
However, the enclosure 54 may not be effective at thermally
insulating the temperature sensitive component 52 over long periods
of time. In addition, the enclosure 54 may not be appropriate for
reducing heat transfer to the temperature sensitive component 52
when the component itself generates heat. Therefore, the enclosure
54 may be particularly useful for shielding the temperature
sensitive component 52 from high ambient temperatures of the well
during periods of limited power supply to the downhole tool 50.
[0029] The cooling unit 56 may include any system capable of
providing active cooling to components of the downhole tool 50. For
example, the cooling unit 56 may include one or more phase change
coolers, sterling pumps, pulse tubing pumps, thermoelectric
coolers, heat pumps, or any other system that uses power to provide
cooling. As mentioned previously, the power supplied to the
downhole tool 50 may not be consistent over time, because the
drilling fluid 20 is not continuously pumped through the drill
string 12 and past the turbine generator 36. As a result, the
cooling unit 56, which runs on this power supply, may
intermittently provide active cooling while the downhole tool 50 is
being operated. The cooling unit 56 may be operable through the use
of mechanical power, electrical power, or any other power available
to the downhole tool 50. When no power is available, however, the
active cooling provided by the cooling unit 56 may stop
altogether.
[0030] The heat exchanger 58 may act as an efficient thermal
conduit between the cooling unit 56 and the temperature sensitive
equipment 52 held in the enclosure 54. That is, the heat exchanger
58 allows heat transfer from the temperature sensitive component 52
to the cooling unit 56 when the cooling unit 56 is providing active
cooling. This is the case when power is available to the downhole
tool 50. When power is not available, however, the cooling unit 56
may turn off and begin to increase in temperature, no longer
providing active cooling. To keep excess heat of the cooling unit
56 from heating the temperature sensitive component 52, it may be
desirable for the heat exchanger 58 to be disableable or
unidirectional. Disabling the heat exchanger 58 may interrupt or
greatly reduce an amount of heat transferred between the cooling
unit 56 and the temperature sensitive component 52. Unidirectional
embodiments of the heat exchanger 58 may facilitate heat transfer
only (or preferentially) from the temperature sensitive component
52 to the cooling unit 56, and not the other way around. Whether
disableable or unidirectional, the heat exchanger 58 may facilitate
heat transfer from the temperature sensitive component 52 to the
cooling unit 56 when power (and therefore active cooling) is
available, and prevents heat transfer between these components when
no power is available. During periods of no available power, heat
exchange between the temperature sensitive component 52 and the
environment may be limited to thermal leaks of the enclosure 54.
This may maintain the temperature sensitive component 52 within a
desirable temperature range for a longer time, until power returns
to make the cooling unit 56 operational again.
[0031] The downhole tool 50 also may include power/control
circuitry 60, which provides power and/or control signals to the
various components of the downhole tool 50. The power available
through the circuitry 60 may be generated by the turbine generator
36, as described with reference to FIG. 1. The control signals
communicated from the circuitry 60 may be signals output from a
processor of the circuitry 60 based on whether power is supplied to
the circuitry 60. In some embodiments, the control signals may be
generated based on sensor feedback, which may include feedback
indicative of a temperature in the downhole tool 50.
[0032] The circuitry 60 may provide intermittent power generated by
the turbine generator 36 to the cooling unit 56 to facilitate
active cooling. Simultaneously, the circuitry 60 may provide power
to the heat exchanger 58, enabling heat transfer from the
temperature sensitive component 52 to the cooling unit 56. When
power is no longer provided to the heat exchanger 58, heat transfer
between the cooling unit 56 and the temperature sensitive component
52 may be disabled. In some embodiments, the cooling unit 56 may
provide an amount of active cooling based on a control signal
received from the circuitry 60. Similarly, the heat exchanger 58
may facilitate heat transfer from the temperature sensitive
component 52 to the cooling unit 56 based on a control signal. The
circuitry 60 may provide such control signals based on a desired
amount of cooling and/or heat transfer to be provided to the
temperature sensitive component 52. This may be based on
temperature feedback collected via a sensor in the downhole tool
50.
[0033] FIGS. 3 and 4 describe methods 80 and 82, respectively, of
operating components of the downhole tool 50 of FIG. 2.
Specifically, FIG. 3 describes how cooling is provided to the
temperature sensitive components of the downhole tool 50 when power
(block 84) is available. FIG. 4 describes how cooling is provided
when no power (block 86) is available. The method 80 of FIG. 3
shows that when power (block 84) is supplied to the downhole tool
50, the enclosure 54 may reduce (block 88) heat transfer from an
outside environment to the temperature sensitive component 52. In
addition, the method 80 may include transferring (block 90) heat
from the temperature sensitive component 52 to the cooling unit 56.
This heat transfer is enabled via the heat exchanger 58 since the
power (block 84) is available to facilitate active cooling via the
cooling unit 56. Further, the method 80 may include controlling
(block 92) the heat transfer from the temperature sensitive
component 52 to the cooling unit 56, via a control signal from the
circuitry 60. The method 82 of FIG. 4 shows that when no power
(block 86) is available, the enclosure 54 may reduce (block 94)
heat transfer from an outside environment to the temperature
sensitive component 52. It should be noted that the enclosure 54
may provide thermal insulation in this manner regardless of whether
any power is supplied to the downhole tool 50. The method 82 also
may include preventing (block 96) heat transfer between the
temperature sensitive component 52 and the cooling unit 56 via the
heat exchanger 58. In some embodiments, this may include the heat
exchanger 58 disabling heat transfer between these parts of the
downhole tool 50. In other embodiments, the heat exchanger 58 may
only allow heat transfer in one direction (from the temperature
sensitive component 52 to the cooling unit 56), which may not occur
unless power is provided to the cooling unit 56.
[0034] FIG. 5 illustrates an embodiment of the cooling components
used in the downhole tool 50 of FIG. 2. The heat exchanger 58 of
this particular embodiment includes a pump 110, which may provide
disableable heat transfer from the temperature sensitive component
52 to the cooling unit 56. In addition, the heat exchanger 58 may
include piping 112 through which the pump 110 circulates a cooling
fluid. The piping 112 may function as a flowpath loop between the
temperature sensitive component 52 and the cooling unit 56. The
flow of the cooling fluid through the piping 112 may facilitate
heat transfer through forced convection.
[0035] In the illustrated embodiment, the enclosure 54 may be a
Dewar flask equipped with plugs 114 to allow passage of the piping
112 into the enclosure 54. Although not shown, the enclosure may
also be equipped with an electrical feedthrough for providing power
and other connections between components inside and outside the
enclosure 54. In other embodiments, the enclosure 54 may include
any enclosure made from a thermally insulating material. The
cooling unit 56, in the illustrated embodiment, includes a
thermoelectric cooler 116 that converts electrical energy into
forced heat transfer. More specifically, the thermoelectric cooler
116 may include two plates 118 and 120 with several semiconductors
122 located therebetween. When a current is applied to the
thermoelectric cooler 116, the plate 118 (e.g., cold plate) absorbs
heat exchanger 58 and the plate 120 (e.g., hot plate) expels the
absorbed heat from the heat according to the Peltier effect. In
this way, the cooling unit 56 provides active cooling of whatever
structures (e.g., heat exchanger 58) are thermally coupled to the
cold plate 118. From the hot plate 120, the heat may be expelled to
a heat sink 124, or to a heat spreader 126 in contact with the heat
sink 124. The heat sink 124 may include an external structure, such
as a chassis or housing, of the downhole tool 50. The heat sink 124
may otherwise include an internal structure used to direct the heat
from the hot plate 120 to the chassis or the housing. It should be
noted that the cooling unit 56 could include any active cooling
system that uses electrical or mechanical power to provide cooling
to a portion of the heat exchanger 58.
[0036] In addition to the pump 110 and the piping 112, the heat
exchanger 58 may include a hot block 128 thermally connected to the
temperature sensitive component 52 and a cold block 130 thermally
connected to the cooling unit 56. In some embodiments, the hot
block 128 may include part of the temperature sensitive component
52, and the cold block 130 may include the cold plate 118 of the
thermoelectric cooler 116. As illustrated, the hot block 128 may be
located inside the enclosure 54 with the temperature sensitive
component 52. The piping 112 may be thermally connected to both the
hot block 128 and the cold block 130. Specifically, the piping 112
forms a loop for routing a cooling fluid between the hot block 128
and the cold block 130, and the pump 110 circulates the cooling
fluid through the loop. The cooling fluid may include water, oil,
molten metals, or any other fluid appropriate for the desired
amount of heat transfer through the heat exchanger 58.
[0037] The illustrated components may be arranged in any desired
orientation and/or configuration relative to each other and to
other components of the downhole tool 50. For example, the piping
112 may extend in a longitudinal direction, as shown, and this
longitudinal direction may align with the z-axis of the drill
string 12. In other embodiments, the piping 112 may include various
bends for routing the cooling fluid between other components of the
downhole tool 50. It may be desirable to position the hot block 128
and the cold block 130 a certain distance away from each other in
the downhole tool 50, so that no heat transfer may occur between
the components except via the heat exchanger 58.
[0038] When power is supplied to the cooling unit 56, heat may be
pumped from the cold plate 118 to the hot plate 120 and expelled
from the hot plate 120 to the heat spreader 126 and heat sink 124.
The power may also activate the pump 110, which circulates the
cooling fluid through the piping 112. In some embodiments, the pump
110 may be activated to pump the cooling fluid at a constant flow
rate whenever the power is available. In other embodiments, the
pump 110 may be activated based on a control signal from the
power/control circuitry 60. The control signal may be generated
based on a processed sensor signal indicating a desired amount of
cooling for the temperature sensitive component 52. Once activated,
the pump 110 may be controlled to move the cooling fluid through
the piping 112 at one of multiple pre-determined flow rates based
on a control signal. To that end, the pump 110 may be designed to
operate at a continuously variable pump speed or at two or more
discrete pump settings, to facilitate controllable heat transfer
through the heat exchanger 58.
[0039] Again, when power is available to the downhole tool 50, the
heat exchanger 58 is able to transfer heat from the temperature
sensitive component 52 to the cooling unit 56. In the illustrated
embodiment, this involves a movement of heat from the temperature
sensitive component 52 to the hot block 128. The cooling fluid
being pumped through the piping 112 then transfers the heat via
forced convection from the hot block 128 to the cold block 130.
From the cold block 130, the heat is transferred through the
cooling unit 56 (from the cold plate 118 to the hot plate 120)
before being rejected to the heat sink 124.
[0040] When no power is available to the illustrated downhole tool
50, the thermoelectric cooler 116 and the pump 110 may stop
functioning. The cold block 130 no longer receives active cooling
from the thermoelectric cooler 116, and thus may return
progressively to an ambient temperature of the downhole tool 50. At
the same time, the pump 110 stops circulating the cooling fluid
through the piping 112, effectively disabling heat transfer through
the heat exchanger 58. This may keep any accumulated heat in the
cold block 130 from transferring back to the temperature sensitive
component 52. The enclosure 54 may provide thermal insulation of
the temperature sensitive component 52 until the downhole tool 50
is operational again.
[0041] Another embodiment of the downhole tool 50 may include a
unidirectional heat pipe configuration of the heat exchanger 58, as
shown in FIG. 6. The heat exchanger 58 includes a heat pipe 150 for
facilitating heat transfer from the temperature sensitive component
52 to the cooling unit 56. The cooling unit 56 in the illustrated
embodiment includes the same type of thermoelectric cooler 116
introduced in FIG. 5, which cools the cold block 130 when power is
supplied to the downhole tool 50. The heat pipe 150 may include a
tube containing a heat exchange fluid. A first end 152 of the heat
pipe 150 may be coupled with the cold block 130, thermally
connecting the first end 152 with the cold plate 118 of the
thermoelectric cooler 116. Similarly, a second end 154 (opposite
the first end 152) of the heat pipe 150 may be coupled with the hot
block 128, thermally connecting the second end 154 with the
temperature sensitive component 52.
[0042] Heatpipes are generally used vertically, transferring heat
from the bottom end (e.g., second end 154) to the top end (e.g.,
first end 152). The heat transfer fluid inside the heat pipe 150
may be in a liquid state at the second end 154, and as the
temperature increases in the hot block 128 the liquid evaporates to
become gaseous. The heated gaseous fluid rises up the heat pipe 150
before recondensing at the first end 152. This state change in the
heat pipe 150 transfers heat from the temperature sensitive
component 52 to the cooling unit 56, but not the other way around.
Therefore, the heat pipe 150 may function as a unidirectional heat
exchanger 58 for the purposes of the present disclosure. Since the
heat pipe 150 relies on gravity to operate, it may be beneficial to
maintain the heat pipe 150 in a vertical position, as shown,
oriented substantially parallel to the z-axis. For this reason, it
may be desirable to use another embodiment of the heat exchanger 58
for drilling inclined wells, horizontal wells, and the like. It
should be noted, however, that the heat pipe 150 may function at an
incline, as long as the first end 152 is maintained relatively
higher than the second end 154.
[0043] When power is supplied to the downhole tool 50, the cooling
unit 56 may operate to cool the cold block 130, facilitating heat
transfer up the heat pipe 150. When no power is supplied to the
downhole tool 50, the cooling unit 56 may shut down, allowing the
cold block 130 to progressively increase in temperature. Eventually
the temperature of the cold block 130 (and cooling unit 56) may
increase above the temperature of the hot block 128 (and
temperature sensitive component 52). Due to operating principles of
the heat pipe 150, heat transfer between the first and second ends
152 and 154 may be substantially limited at this time. No liquid
would evaporate from the second end 154 and no gas would recondense
at the first end 152, because the first end 152 would be at a
higher temperature than the second end 154. This allows the heat
pipe 150 to function as a unidirectional heat exchanger 58,
preventing the transfer of heat between the cooling unit 56 and the
temperature sensitive component 52 during periods of no power.
[0044] Another embodiment of components of the downhole tool 50 is
illustrated in FIG. 7. In this embodiment, the heat exchanger 58
may include a switch 170 capable of disabling heat transfer across
the heat exchanger 58. The switch 170 may include an
electromagnetic switch that receives intermittent electrical power
from the turbine generator 36. In addition, the heat exchanger 58
may include thermally conductive materials 172 that may form a
bridge between the temperature sensitive component 52 and the
cooling unit 56. The thermally conductive materials 172 may have
any desired shape, including bars, blocks, and so forth. In
addition, the thermally conductive material 172 may have a thermal
conductivity within a range that facilitates a desired level of
heat transfer between the downhole components. The illustrated
switch 170 may actuate a portion of the thermally conductive
material 172 based on whether power is provided to the downhole
tool 50. For example, the switch 170 may close a thermally
conductive bridge between the temperature sensitive component 52
and the cooling unit 56 when power is provided to the downhole tool
50. As current flows to the switch 170, the switch may generate a
magnetic field that brings a portion of the thermally conductive
material 172 into contact with the other thermally conductive
materials in the heat exchanger 58. This may allow heat transfer to
occur from the temperature sensitive component 52 to the cooling
unit 56 across the conductive bridge. When no power is provided to
the switch 170, no current may flow to the switch 170 for
generating a magnetic field to hold the thermally conductive
material 172 in place. This may effectively break the link between
the temperature sensitive component 52 (or block 128) and the
cooling unit 56 (or block 130).
[0045] Although the illustrated embodiment specifically features an
electromagnetic actuator (e.g., switch 170), any other type of
actuator may be used to move a portion of the conductive material
in one direction when power is available and to move the portion in
another direction when the power is unavailable. In certain
embodiments, the switch 170 may be controlled via a control signal
from the power/control circuitry 60. More specifically, the switch
170 may actuate the portion of thermally conductive material 172
into partial contact with the other thermally conductive materials
172. This may reduce an amount of heat transfer possible through
the portion of thermally conductive material 172 based on an
increased resistance to heat transfer through the portion.
[0046] The specific embodiments described above have been shown by
way of example, and it should be understood that these embodiments
may be susceptible to various modifications and alternative forms.
It should be further understood that the claims are not intended to
be limited to the particular forms disclosed, but rather to cover
all modifications, equivalents, and alternatives falling within the
spirit and scope of this disclosure.
* * * * *