U.S. patent application number 15/954176 was filed with the patent office on 2019-10-17 for thermal barrier for downhole flasked electronics.
This patent application is currently assigned to Baker Hughes, a GE company, LLC. The applicant listed for this patent is Baker Hughes, a GE company, LLC. Invention is credited to RICHARD E. BAILEY, SAEED RAFIE.
Application Number | 20190316442 15/954176 |
Document ID | / |
Family ID | 68161481 |
Filed Date | 2019-10-17 |
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United States Patent
Application |
20190316442 |
Kind Code |
A1 |
RAFIE; SAEED ; et
al. |
October 17, 2019 |
THERMAL BARRIER FOR DOWNHOLE FLASKED ELECTRONICS
Abstract
Apparatus including an assembly associated with a downhole tool
and configured to thermally isolate a thermally sensitive
component. Components of the assembly include a thermal housing; a
chassis interior to the thermal housing; at least one thermally
sensitive component mounted on the chassis; and a thermal isolation
support connecting the chassis to the tool. The thermal isolation
support comprises an elongated thermal isolator having a first end
and a second end opposite the first end, the thermal isolator
connected to the tool at the first end and connected to the chassis
at the second end, and a heat sink thermally coupled to the
elongated thermal isolator at the second end. The second end of the
elongated thermal isolator may comprise the only points of thermal
coupling between the heat sink and the components other than the
heat sink.
Inventors: |
RAFIE; SAEED; (Houston,
TX) ; BAILEY; RICHARD E.; (The Woodlands,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Baker Hughes, a GE company, LLC |
Houston |
TX |
US |
|
|
Assignee: |
Baker Hughes, a GE company,
LLC
Houston
TX
|
Family ID: |
68161481 |
Appl. No.: |
15/954176 |
Filed: |
April 16, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 47/017 20200501;
E21B 36/001 20130101 |
International
Class: |
E21B 36/00 20060101
E21B036/00; E21B 47/01 20060101 E21B047/01 |
Claims
1. An apparatus for use in a borehole intersecting an earth
formation, the apparatus comprising: an assembly associated with a
downhole tool and configured to thermally isolate a thermally
sensitive component, the assembly comprising components including:
a thermal housing; a chassis interior to the thermal housing; at
least one thermally sensitive component mounted on the chassis; a
thermal isolation support connecting the chassis to the tool,
wherein the thermal isolation support comprises: an elongated
thermal isolator having a first end and a second end opposite the
first end, the thermal isolator connected to the tool at the first
end and connected to the chassis at the second end, and a heat sink
thermally coupled to the elongated thermal isolator at the second
end.
2. The apparatus of claim 1, wherein the second end of the
elongated thermal isolator comprises the only points of thermal
coupling between the heat sink and the components other than the
heat sink.
3. The apparatus of claim 1, wherein a center of mass of the heat
sink is oriented further from the thermally sensitive component
than the second end.
4. The apparatus of claim 1, wherein the heat sink is elongated and
comprises: a coupled end coupled to the second end of the elongated
thermal isolator, and a decoupled end opposite the coupled end, the
decoupled end thermally decoupled from the elongated thermal
isolator.
5. The apparatus of claim 4, wherein the decoupled end is oriented
further from the thermally sensitive component than the coupled
end.
6. The apparatus of claim 4, wherein the decoupled end is located
proximate the first end of the elongated thermal isolator.
7. The apparatus of claim 1, wherein the elongated thermal isolator
comprises a sleeve.
8. The apparatus of claim 1, wherein the heat sink is interior to
the elongated thermal isolator.
9. The apparatus of claim 1, wherein a length of the heat sink is
substantially the same as a length of the elongated thermal
isolator.
10. The apparatus of claim 1, wherein the heat sink is a
substantially solid cylinder.
11. The apparatus of claim 1, wherein the at least one thermally
sensitive component comprises at least one downhole electronic
component.
12. The apparatus of claim 1, wherein the chassis is supported
substantially exclusively by the thermal isolation support.
13. The apparatus of claim 1, wherein the heat sink is thermally
coupled to the elongated thermal isolator only at the second
end.
14. The apparatus of claim 1, wherein the elongated thermal
isolator comprises a mesh tube of connected members.
15. An apparatus for use in a borehole intersecting an earth
formation, the apparatus comprising: an assembly associated with a
downhole tool and configured to thermally isolate a thermally
sensitive component, the assembly comprising components including:
a thermal housing; a chassis interior to the thermal housing; at
least one thermally sensitive component mounted on the chassis; a
thermal isolation support connecting the chassis to the tool,
wherein the thermal isolation support comprises: an elongated
thermal isolator having a first end and a second end opposite the
first end, the thermal isolator connected to the tool at the first
end and connected to the chassis at the second end, and wherein the
elongated thermal isolator comprises a mesh tube of connected
members.
16. The apparatus of claim 15, wherein the thermal isolation
support comprises a heat sink thermally coupled to the elongated
thermal isolator at the second end.
17. The apparatus of claim 15, wherein a majority of the connected
members of the mesh tube are substantially non-parallel with a
longitudinal axis of the downhole tool.
Description
FIELD OF THE DISCLOSURE
[0001] In one aspect, this disclosure relates generally to
thermally isolating heat sensitive components used in downhole
applications in a borehole in an earth formation.
BACKGROUND OF THE DISCLOSURE
[0002] Drilling wells for various purposes is well-known. Such
wells may be drilled for geothermal purposes, to produce
hydrocarbons (e.g., oil and gas), to produce water, and so on. Well
depth may range from a few thousand feet to 25,000 feet or more.
Downhole tools, used during and after drilling, often incorporate
various sensors, instruments and control devices in order to carry
out any number of downhole operations. Thus, the tools may include
sensors and/or electronics for formation evaluation, fluid
analysis, monitoring and controlling the tool itself, and so
on.
[0003] Borehole temperatures can vary from ambient up to about
500.degree. F. (260.degree. C.) and pressures from atmospheric up
to about 30,000 psi (206.8 mega pascals). Temperature and pressure
conditions such as these can have an adverse effect on instruments
used downhole. Heat especially can be undesirable for tools having
electronic components. Elevated temperatures in the borehole
("downhole heat") may cause thermally sensitive electronic
components to work inaccurately or even fail.
[0004] One historical method for dealing with downhole heat is to
avoid it. For example, it is known in the art that a system that
includes a plurality of temperature sensors distributed in an oil
well in the wellbore where at least some of the sensors are in a
heat affected zone can be monitored using a downhole processor
positioned proximate and substantially outside of the heat affected
zone to receive and digitize temperature measurements. Elevated
temperature (or "hot") conditions, as referred to herein may be
defined as an ambient temperature which compromises or impairs the
structural integrity, operating efficient, operating life, or
reliability of a given tool, device, or instrument.
[0005] Other methods of dealing with downhole heat are also known.
Available techniques may include eliminating the incoming heat to
the system and cooling the heat sensitive components using either
active or passive cooling methods. Due to the nature of the
operation, since the earth temperature gets hotter as true depth
increases, the first option is not feasible. A tool configured for
either active or passive cooling may operate in a hot downhole
environment, including logging and drilling operations.
SUMMARY OF THE DISCLOSURE
[0006] Aspects of the disclosure include apparatus for use in a
borehole intersecting an earth formation. The apparatus may
comprise an assembly associated with a downhole tool and configured
to thermally isolate a thermally sensitive component. The assembly
may comprise components including: a thermal housing; a chassis
interior to the thermal housing; at least one thermally sensitive
component mounted on the chassis; and a thermal isolation support
connecting the chassis to the tool. The chassis may be supported
substantially exclusively by the thermal isolation support. The
thermal isolation support may comprise an elongated thermal
isolator having a first end and a second end opposite the first
end, the thermal isolator connected to the tool at the first end
and connected to the chassis at the second end; and a heat sink
thermally coupled to the elongated thermal isolator at the second
end.
[0007] The second end of the elongated thermal isolator may
comprise the only points of thermal coupling between the heat sink
and the components other than the heat sink. A center of mass of
the heat sink may be oriented further from the thermally sensitive
component than the second end. The heat sink may be interior to the
elongated thermal isolator.
[0008] The heat sink may be thermally coupled to the elongated
thermal isolator only at the second end. The heat sink may be
elongated and comprise a coupled end coupled to the second end of
the elongated thermal isolator and a decoupled end opposite the
coupled end, with the decoupled end thermally decoupled from the
elongated thermal isolator. The decoupled end may be oriented
further from the thermally sensitive component than the coupled
end. The decoupled end may be located proximate the first end of
the elongated thermal isolator.
[0009] The elongated thermal isolator may comprise a sleeve. The
length of the heat sink may be substantially the same as the length
of the elongated thermal isolator. The heat sink maybe a
substantially solid cylinder. The at least one thermally sensitive
component may comprise at least one downhole electronic component.
The elongated thermal isolator may comprise a mesh tube of
connected members.
[0010] In other general embodiments, the apparatus comprises an
assembly associated with a downhole tool and configured to
thermally isolate a thermally sensitive component. The assembly
comprises components including: a thermal housing; a chassis
interior to the thermal housing; at least one thermally sensitive
component mounted on the chassis; and a thermal isolation support
connecting the chassis to the tool. The thermal isolation support
comprises an elongated thermal isolator having a first end and a
second end opposite the first end, the thermal isolator connected
to the tool at the first end and connected to the chassis at the
second end. The elongated thermal isolator may comprise a mesh tube
of connected members. The thermal isolation support may comprise a
heat sink thermally coupled to the elongated thermal isolator at
the second end. A majority of the connected members of the mesh
tube may be substantially non-parallel with a longitudinal axis of
the downhole tool.
[0011] Examples of some features of the disclosure may be
summarized rather broadly herein in order that the detailed
description thereof that follows may be better understood and in
order that the contributions they represent to the art may be
appreciated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a detailed understanding of the present disclosure,
reference should be made to the following detailed description of
the embodiments, taken in conjunction with the accompanying
drawings, in which like elements have been given like numerals,
wherein:
[0013] FIG. 1 shows a schematic diagram illustrating downhole tool
systems in accordance with embodiments of the present
disclosure;
[0014] FIG. 2 illustrates example assemblies for isolating an
electronics package from heat;
[0015] FIG. 3 shows a perspective view of an example thermal
isolation support in accordance with embodiments of the present
disclosure;
[0016] FIG. 4 shows a schematic tool diagram illustrating
additional assemblies in accordance with embodiments of the present
disclosure.
DETAILED DESCRIPTION
[0017] Aspects of the present disclosure relate to thermally
isolating a thermally sensitive component in a tool downhole from a
high-temperature environment. The present disclosure relates to
devices and methods isolating heat sensitive components from a
wellbore environment and/or heat generated by downhole components.
In particular, aspects of the disclosure relate to flask-type
thermal isolation systems. Aspects include apparatus for
investigating a borehole or other use in a borehole intersecting an
earth formation.
[0018] Aspects of the present disclosure provide a novel way of
thermally isolating electronics inside downhole drilling or logging
tools. Embodiments disclosed herein may include an assembly
associated with a downhole tool and configured to thermally isolate
a thermally sensitive component. The assembly may include a thermal
housing; a chassis interior to the thermal housing; at least one
thermally sensitive component mounted on the chassis; and a thermal
isolation support connecting the chassis to the tool. In aspects,
the present disclosure includes apparatuses related to drilling a
borehole in an earth formation, performing well logging in a
borehole intersecting an earth formation, and so on.
[0019] The thermal isolation support may include an elongated
thermal isolator having a first end and a second end opposite the
first end, the thermal isolator connected to the tool at the first
end and connected to the chassis at the second end; and a heat sink
thermally coupled to the elongated thermal isolator at the second
end. The thermal isolator and heat sink may be integrated. The heat
sink may be thermally decoupled from the elongated thermal isolator
proximate the first end. Thus, the heat sink is thermally isolated
from the elongated thermal isolator proximate the first end. The
second end of the elongated thermal isolator may be the only points
of thermal coupling between the heat sink and the components of the
assembly other than the heat sink. A center of mass of the heat
sink may be oriented further from the thermally sensitive component
than the second end.
[0020] Thus, the elongated thermal isolator experiences a graduated
elevation in temperature along its length as the tool is exposed to
elevated temperatures, with the first end experiencing greater
changes in temperature (and more quickly) than the second end. The
heat sink coupled at the second end functions as a spillover
reservoir for environmental heat absorbed by the elongated thermal
isolator, by efficiently absorbing thermal energy at the second end
of the isolator and thereby vastly reducing thermal energy absorbed
by the chassis.
[0021] The term "thermally sensitive component" (or "heat sensitive
component") shall hereinafter be used to refer to any tool,
electrical component, sensor, electronic instrument, structure, or
material that degrades either in performance or in integrity when
exposed to temperatures above 200 degrees centigrade. For purposes
of discussion, a wellbore may be considered "hot" if the ambient
temperature compromises or impairs the structural integrity,
operating efficient, operating life, or reliability of a given
tool, device, or instrument.
[0022] Techniques described herein are particularly suited for use
in measurement of values of properties of a formation downhole or
of a downhole fluid while drilling, through the use of instruments
which may utilize components as described herein, or otherwise for
use in conducting operations downhole. These values may be used to
evaluate and model the formation, the borehole, and/or the fluid,
and for conducting further operations in the formation or the
borehole.
[0023] Conventionally, Dewar vacuum-type flasks (e.g., AWS flask-
or NKW flask-style housing) are used to protect the heat sensitive
components from high downhole temperatures for a short period of
time (e.g., approximately 8-10 hours). Although, these flasks
provide a thermal barrier, some undesirable external heat can leak
into the flask. The traditional thermal isolators are designed
based on a slotted tube filled with felt. This slotted-tube design
provided a tortuous path for the heat to reach sensitive
components. In addition to the improved heat sink configuration, a
thermal isolator in accordance with embodiments of the present
disclosure may be implemented in the form of a meshed tube or
cylinder. The heat sink may be inserted inside the tube (e.g., the
heat sink may be encircled by the cylinder), so the new thermal
isolator is shorter and more efficient than the existing thermal
isolators.
[0024] Referring to FIG. 1, a wireline well logging tool 10 is
shown being lowered into a wellbore 2 penetrating earth formations
13. The tool 10 may be lowered into the wellbore 2 and withdrawn
therefrom by a carrier 14 (e.g., an armored electrical cable). In
one embodiment, circuitry associated with the tool may be
configured to take measurements using instruments associated with
the tool as the tool moves along the longitudinal axis of the
borehole (`axially`). The cable 14 can be spooled by a winch 7 or
similar device known in the art. The cable 14 may be electrically
connected to a surface recording system 8 of a type known in the
art which can include a signal decoding and interpretation unit 16
and a recording unit 12. Signals transmitted by the logging tool 10
along the cable 14 can be decoded, interpreted, recorded and
processed by the respective units in the surface system 8.
[0025] Systems in accordance with the present disclosure may
alternatively include a conventional derrick and a conveyance
device, which may be rigid or non-rigid, which may be configured to
convey the downhole tool 10 in the wellbore. Drilling fluid (`mud`)
may be present in the borehole. The carrier may be a drill string,
coiled tubing, a slickline, an e-line, a wireline, etc. Downhole
tool 10 may be coupled or combined with additional tools,
including, e.g., some or all the information processing system as
implemented by hardware environment 20. Thus, depending on the
configuration, the tool 10 may be used during drilling and/or after
the wellbore has been formed. While a land system is shown, the
teachings of the present disclosure may also be utilized in
offshore or subsea applications. The carrier may include a bottom
hole assembly, which may include a drilling motor for rotating a
drill bit.
[0026] Aspects of the present disclosure are subject to application
in various different embodiments. In some general embodiments, the
carrier is implemented as a tool string of a drilling system, and
the acoustic wellbore logging may be characterized as
"logging-while-drilling" (LWD) or "measurement-while-drilling"
(MWD) operations.
[0027] The toolstring as well as the logging tool may include
thermally sensitive components. Such components include those that
incorporate transistors, integrated circuits, resistors,
capacitors, and inductors, as well as electronic components such as
sensing elements, including accelerometers, magnetometers,
photomultiplier tubes, and strain gages. The thermal isolation
systems provided by the present disclosure, such as those shown in
the Figures, may be utilized to protect these components from the
hot wellbore environment. The toolstring may also include
communication devices, transmitters, repeaters, processors, power
generation devices, or other devices that may incorporate heat
sensitive components. In many applications, the drilling system may
be operated for well over eight hours downhole.
[0028] Conventional systems for thermal isolation are known. One
type of conventional system employs a container designed to protect
heat sensitive components from high temperature environments, such
as a Dewar-like vacuum flask. The sensitive components may be
positioned within the container and conveyed into a wellbore. The
container may be directly inserted into a wellbore tool string, or
may be positioned in a housing (e.g., a sub, a module or other
suitable structure). The container provides a thermal barrier that
isolates heat sensitive components from ambient wellbore
temperatures. The container may employ a conventional double wall
construction with an interstitial vacuum typical of Dewar flasks,
but may be of any suitable configuration that prevents or reduces
heat transfer from the downhole environment to the electronics
package.
[0029] More recently, an improved thermal isolation device,
described in U.S. Pat. No. 7,440,283 to Rafie, commonly owned with
the present application and incorporated herein by reference in its
entirety, includes one or more heat sinks and a thermal isolator.
The thermal isolator mechanically connects an assembly including
the internal components to the container. The heat sinks are
positioned in a chain between the isolator and electronic
components. Traditionally, heat sinks provide thermal storage by
diverting heat flow away from heat sensitive components. A first
heat sink may be configured to absorb heat primarily from an
electronics package and a second heat sink may be configured to
primarily absorb heat applied by the wellbore environment. The heat
sinks may be configured to have the same thermal response or
different thermal responses or absorb the same or different amounts
of heat (e.g., a stepped thermal response or a graduated thermal
response). It should be noted that the heat sinks of Rafie are
connected in a linear fashion, such that the heat sink operatively
closest to the container heats up first and the furthermost
position of the heat sink (which experiences the latest temperature
increase) is proximate the chassis housing the electronic
components.
Improved Thermal Isolation for Vacuum-Flask Type Isolation
Systems
[0030] General embodiments of the present disclosure may include a
tool for performing well logging in a borehole intersecting an
earth formation. Aspects of the present disclosure may be utilized
to increase temperature survival time of downhole tools and thereby
increase the time heat sensitive equipment may be deployed in a
wellbore. As will be appreciated, the present invention is
susceptible to embodiments of different forms. There are shown in
the drawings, and herein will be described in detail, specific
embodiments of the present invention with the understanding that
the present disclosure is to be considered an exemplification of
the principles of the invention, and is not intended to limit the
invention to that illustrated and described herein. Further, while
embodiments may be described as having one or more features or a
combination of two or more features, such a feature or a
combination of features should not be construed as essential unless
expressly stated as essential.
[0031] FIG. 2 shows a schematic tool diagram illustrating
assemblies in accordance with embodiments of the present
disclosure. FIG. 2 illustrates an exemplary assembly 200 for
isolating an electronics package 202 from applied heat and/or
generated heat. The electronics package 202 may include one or more
heat sensitive components 202a and may be mounted on and supported
by a chassis 203. In one arrangement, the heat sensitive components
202a communicates with external devices via a cable 204. The
components 202a may be positioned within a thermal housing 208 and
conveyed into a wellbore. The thermal housing 208 provides a
thermal barrier that isolates heat sensitive components from
ambient wellbore temperatures.
[0032] The thermal housing 208 may comprise a container 206
positioned within an outer member 209, such as a sub, a module or
other suitable structure (e.g., tubular), or may consist of the
container or outer member alone. The thermal housing 208 may
include multiple containers. In some embodiments, the container 206
may be a Dewar-like vacuum flask employing a conventional double
wall construction with an interstitial vacuum typical of Dewar
flasks, and the outer member 209 may be a steel tubular that is
adapted for conveyance in the borehole and protects the electronics
from damage. However, the thermal housing 208 may be of any
suitable configuration that prevents or reduces heat transfer from
the downhole environment to the electronics package 202.
[0033] As will be discussed in greater detail below, the assembly
200 provides passive cooling for the electronics package 202 by
isolating the electronics package 202 from applied heat and/or heat
generated from other tool components. The mechanisms for providing
thermal isolation include providing a barrier to heat flow and
absorbing heat. The thermal housing 208 and other elements of the
downhole tool may also cooperate to provide active cooling for the
electronics package 202.
[0034] A thermal isolation support 220 connects the chassis 203 to
the tool 201. The thermal isolation support 220 mechanically
connects the internal components, such as the chassis 203 and
electronics package 202 (and, optionally, heat sinks 210) to the
container 206. The chassis may be supported substantially
exclusively by the thermal isolation support. The chassis 203 may
include a metallic plate to support a printed circuit board (PCB),
electronics and sensors. The thermal isolation support 220 may
include an elongated thermal isolator 222 having a first end 224
and a second end 226 opposite the first end. The thermal isolator
222 is connected to the tool 201 at the first end 224 and connected
to the chassis 203 at the second end. The thermal isolator 222 may
be made of a material having a relatively low thermal conductivity,
such as titanium, or a composite material.
[0035] The thermal isolation support 220 may include a heat sink
230 thermally coupled to the elongated thermal isolator 222 at the
second end 226. The heat sink 230 may be elongated, and may be a
substantially solid cylinder made of a material having a high
thermal capacity, such as copper or stainless steel. The elongated
thermal isolator maybe implemented using a sleeve with the heat
sink interior to the sleeve. The length of the heat sink 230 may be
substantially the same as a length of the elongated thermal
isolator 222.
[0036] As described above, the second end 226 of the elongated
thermal isolator 222 has the only points of thermal coupling
between the heat sink 230 and the components other than the heat
sink (e.g., elongated thermal isolator 222, chassis 203, components
202a, container 206). In particular implementations, a center of
mass of the heat sink is oriented further from the thermally
sensitive component 202a) than the second end 226. Thus, the heat
sink may include a coupled end 236 coupled to the second end 226 of
the elongated thermal isolator 222, and a decoupled end 234
opposite the coupled end 236. The decoupled end 234 is thermally
decoupled from the elongated thermal isolator, and may be oriented
further from thermally sensitive components 202a than the coupled
end 236. The isolator 222 is configured to minimize axial heat
transfer from other tool components to the chassis 203.
[0037] FIG. 3 shows a perspective view of an example thermal
isolation support in accordance with embodiments of the present
disclosure. The thermal isolation support 320 includes an elongated
thermal isolator 322 comprising a mesh tube 340 of connected
members (e.g., a mesh sleeve) 340, attached to a base 350 for
connection with the tool. All or a portion of the elongated thermal
isolator 322 may be generated using additive manufacturing. The
spiral mesh structure may be manufactured at an angle to increase
the heat path distance through the part. A second end 336 of the
heat sink 330 is coupled to the second end 326 of the elongated
thermal isolator 322.
[0038] In operation, a considerable temperature difference may
develop between the ends of the thermal isolation support 320.
While using a sleeve alone may result in the temperature of the
sleeve being substantially uniform along the length of the sleeve
(e.g., a difference of less than five or ten degrees F. over the
length), modeled results for the thermal isolation support 320 of
FIG. 3 show differences of 50 degrees F. or more. That is, the end
of the support closer to the heat sensitive components increases in
temperature more slowly than the end proximate the tool coupling.
The lower temperature is desirable in logging instruments to
prolong the logging time.
[0039] FIG. 4 shows a schematic tool diagram illustrating
additional assemblies in accordance with embodiments of the present
disclosure. Tool 401 includes similar features to tool 201. In
embodiments, however, the assembly 400 includes one or more
additional heat sinks 410. The chassis 403 may also provide a
medium to conduct heat from the electronics package 404 to the heat
sinks 410 and therefore may be formed of a relatively high thermal
conductivity material such as aluminum. The heat sinks 410 may be
an object or mass configured to absorb and store thermal energy
from internal heat-generating components and/or from the outside
environment. Thus, the heat sinks 410 provide thermal isolation by
diverting heat flow away from heat sensitive components.
[0040] Heat sinks described herein (e.g., heat sinks 230, 430, 410)
may be solid elements or include cavities such as bores. In one
embodiment, the heat sinks are made from a eutectic phase changing
material, such as bismuth alloys or lead with a high latent heat
and low melting temperature. Eutectic materials change phase
between their solid and liquid phases at the eutectic temperature
(phase change temperature). The eutectic temperature stays
substantially constant until the material completely changes the
phase. In other embodiments, metals such as stainless steel may be
used. The heat sinks may be configured to have the same thermal
response or different thermal responses or absorb the same or
different amounts of heat. For example, a first heat sink may be
configured to have a stepped thermal response and a second heat
sink may be configured to have a graduated (gradient) thermal
response. Additionally, a first heat sink may be configured to
absorb heat primarily from the electronics package and a second
heat sink may be configured to primarily absorb a heat applied by
the wellbore environment. For instance, the heat sink 430 that is
positioned proximate the thermal isolator 422 may be configured to
absorb the heat applied by the wellbore environment whereas the
heat sink 410 that is positioned distant from the thermal isolation
support 420 may be configured to absorb heat from the electronics
package 402.
[0041] In one embodiments, the heat sinks may be formed of two or
more masses 412 that are separated by spaces 414. In some
embodiments, the spaces 414 include air or other gases. In other
embodiments, the spaces 414 have a vacuum. In still other
embodiments, the spaces 414 include a material having a low thermal
conductivity, e.g., felt. Other such materials include nanoporous
material. Nanoporous thermal insulating material is available from
ASPEN AEROGELS and is commercially available under the trademark
"PYROGEL". Nanoporous materials have an open cell structure that
provide a relatively high proportion of free void volume (typically
greater than 90 percent) compared to conventional solid materials.
Their high pore volume, low solid content, and torturous path
amorphous structure give rise to lower values for thermal
conductivity. Other suitable materials exhibiting low thermal
conductivity include ceramics. In one sense, the structure of the
heat sink 110 may be described as a segmented body having a
plurality of elements formed of material that have high thermal
energy absorption properties, each of the plurality of elements
being separated by an element having low thermal conductivity.
[0042] In embodiments, the tool 401 includes strategically
positioned nanoporous material within the container 406 to reduce
heat transfer to the electronics package 402. One exemplary
location is between adjacent masses 412. Another is the space
between 430 and 422. Another exemplary location is around the heat
sinks 410 or otherwise where the nanoporous material reduces heat
transfer from the walls of the container 406 to the electronics
package 402. Another exemplary location includes open spaces which
may otherwise be filled with air, which can be filled with a layer
of nanoporous material instead.
[0043] The heat sensitive components associated with the logging
tool are protected from the downhole environment using any of the
thermal isolation devices previously described in connection with
the electronics package 202. The logging tool may be in the
wellbore for eight hours or longer. During this time, the tool may
be subjected to temperatures in excess of 200 degrees Celsius.
Components 202a are initially protected from the high wellbore
temperatures by the container 206, 406, which functions as a heat
shield or barrier. Heat flow from the thermal isolation support 220
at the end of the container 206 to the container interior is
impeded in at least two ways. First, in embodiments where the
thermal isolation support 220 is formed of titanium or other
material having low thermal conductivity, or is otherwise designed
to prevent heat transfer, the thermal isolation support 220 itself
impedes heat transfer. Second, the heat sink 230, 330, 430
thermally coupled to the thermal isolation support 220 mitigates
heat transferred along the thermal isolation support 220.
[0044] The foregoing description is directed to particular
embodiments of the present invention for the purpose of
illustration and explanation. It will be apparent, however, to one
skilled in the art that many modifications and changes to the
embodiment set forth above are possible without departing from the
scope of the invention. It is intended that the following claims be
interpreted to embrace all such modifications and changes.
[0045] The term "conveyance device" or "carrier" as used above
means any device, device component, combination of devices, media
and/or member that may be used to convey, house, support or
otherwise facilitate the use of another device, device component,
combination of devices, media and/or member. Exemplary non-limiting
conveyance devices include drill strings of the coiled tube type,
of the jointed pipe type and any combination or portion thereof.
Other conveyance device examples include casing pipes, wirelines,
wire line sondes, slickline sondes, drop shots, downhole subs,
BHA's, drill string inserts, modules, internal housings and
substrate portions thereof, self-propelled tractors. As used above,
the term "sub" refers to any structure that is configured to
partially enclose, completely enclose, house, or support a device.
The term "information" as used above includes any form of
information (Analog, digital, EM, printed, etc.). The term
"processor" or "information processing device" herein includes, but
is not limited to, any device that transmits, receives,
manipulates, converts, calculates, modulates, transposes, carries,
stores or otherwise utilizes information. An information processing
device may include a microprocessor, resident memory, and
peripherals for executing programmed instructions. The processor
may execute instructions stored in computer memory accessible to
the processor, or may employ logic implemented as
field-programmable gate arrays (`FPGAs`), application-specific
integrated circuits (`ASICs`), other combinatorial or sequential
logic hardware, and so on. Thus, configuration of the processor may
include operative connection with resident memory and peripherals
for executing programmed instructions.
[0046] Given the extended time that the logging tool may be exposed
to the downhole environment, a strictly passive thermal isolation
system may not be sufficient to fully protect heat sensitive
components from the heat applied by the downhole environment and/or
the heat generated by devices such as electrical components. Thus,
in embodiments, in conjunction with the thermal isolation systems
previously described, an active cooling system may be utilized to
cool heat sensitive components. In one arrangement, heat sensitive
electronic components are juxtaposed with one or more refrigeration
devices such as sorbent coolers. The active cooling system may be a
powered device selected from a group consisting of a: (i) Peltier
cooler; (ii) closed-loop cooling unit; and (iii) heat pump that
employs one of: (a) Joule-Thompson effect and (b) Stirling Engine.
Of course, active cooling may also be utilized with heat sensitive
components conveyed by non-rigid conveyance devices.
[0047] While the foregoing disclosure is directed to the one mode
embodiments of the disclosure, various modifications will be
apparent to those skilled in the art. It is intended that all
variations be embraced by the foregoing disclosure.
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