U.S. patent application number 13/985825 was filed with the patent office on 2014-04-17 for method and apparatus for protecting downhole components with inert atmosphere.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. The applicant listed for this patent is Donna Simonetti. Invention is credited to Fabien Cens, Michael Drennan, John Simonetti, Anthony Veneruso, Kyle Wiesenborn.
Application Number | 20140102796 13/985825 |
Document ID | / |
Family ID | 46673148 |
Filed Date | 2014-04-17 |
United States Patent
Application |
20140102796 |
Kind Code |
A1 |
Veneruso; Anthony ; et
al. |
April 17, 2014 |
Method And Apparatus For Protecting Downhole Components With Inert
Atmosphere
Abstract
Methods and systems are provided that enable the removal or
reduction of moisture and any other volatile substances within
downhole tools. A purging gas can be allowed to flow into the
downhole tool, where it begins to interact with and dry the
moisture present as well as dilute the gaseous environment therein.
Then purging gas then can exit the tool, thereby removing the
moisture and any other potentially polluting or corrosive gases in
the tool. A vacuum pump and desiccant jar assembly also can be used
to further remove moisture from the tool.
Inventors: |
Veneruso; Anthony; (Sugar
Land, TX) ; Drennan; Michael; (Carencro, LA) ;
Cens; Fabien; (Igny, FR) ; Wiesenborn; Kyle;
(Richmond, TX) ; Simonetti; John; (Hamilton,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Simonetti; Donna |
Hamilton |
NJ |
US |
|
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
Sugar Land
TX
|
Family ID: |
46673148 |
Appl. No.: |
13/985825 |
Filed: |
February 15, 2012 |
PCT Filed: |
February 15, 2012 |
PCT NO: |
PCT/US12/25227 |
371 Date: |
December 18, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61442952 |
Feb 15, 2011 |
|
|
|
Current U.S.
Class: |
175/57 ;
175/24 |
Current CPC
Class: |
E21B 44/00 20130101;
E21B 47/117 20200501; E21B 47/06 20130101; E21B 47/017
20200501 |
Class at
Publication: |
175/57 ;
175/24 |
International
Class: |
E21B 44/00 20060101
E21B044/00 |
Claims
1. A method for reducing undesired contents in a tool, comprising:
inserting a purging gas into the tool; removing a gaseous mixture
from the tool, the gaseous mixture comprising at least a portion of
the purging gas and undesired contents, the undesired contents
comprising at least one of: moisture, pollution, and corrosive
gasses; and inserting a filling gas into the tool.
2. The method of claim 1, wherein the purging gas comprises at
least one of: dry nitrogen gas, argon, carbon dioxide, helium,
sulfur hexafluoride, and a refrigerant gas.
3. The method of claim 1, further comprising heating the purging
gas prior to removing the purging gas from the tool.
4. The method of claim 1, further comprising: measuring at least
one of a humidity and dew point of the purging gas after the
purging gas has been removed from the tool; and determining whether
to continue reducing moisture based on the measured humidity of the
purging gas.
5. The method of claim 1, further comprising: measuring at least
one of a humidity and dew point of an internal atmosphere of the
tool; and determining whether to bake the tool to reduce
moisture.
6. The method of claim 1, wherein purging gas is inserted into the
tool via a first port of the tool.
7. The method of claim 6, wherein the gaseous mixture is removed
from the tool via the first port of the tool.
8. The method of claim 6, wherein the gaseous mixture is removed
from the tool via a second port of the tool while purging gas is
inserted into the tool via the first port, and wherein after the
gaseous mixture is removed from the tool via the second port while
purging gas is inserted into the tool via the first port, the
gaseous mixture is then removed from the tool via the first port
while purging gas is inserted into the tool via the second
port.
9. The method of claim 1, further comprising reinserting gas
removed from the tool back into the tool.
10. The method of claim 1, wherein the filling gas and the purging
gas comprise the same gas.
11. The method of claim 1, wherein the purging gas is provided by
at least one of: a gas tank and a purging gas generator that
generates purging gas from an atmosphere.
12. The method of claim 1, further comprising pumping, with a
vacuum pump, the undesired contents from the downhole tool; and
heating the tool to vaporize undesired contents.
13. The method of claim 1, further comprising attaching a valve to
a first port on the tool, the valve being disposed within the tool,
the valve directing flow of at least one of a purging gas and a
filling gas.
14. A system for reducing moisture in a tool comprising: a source
of purging gas; and a control box in fluid communication with the
source for controlling a flow of the purging gas into and out of a
first port on the tool.
15. The system of claim 14, wherein the tool further comprises a
second port in fluid communication with the control box.
16. The system of claim 14, further comprising a heater for heating
the purging gas, the heater receiving purging gas from the control
box and heats the purging gas prior to the purging gas entering the
first port.
17. The system of claim 14, wherein the control box comprises at
least one valve for directing a flow of the purging gas.
18. The system of claim 14, further comprising a humidity sensor
for receiving purging gas exiting the tool and a pump in fluid
communication with the tool.
19. The system of claim 14, wherein the tool comprises at least one
of electrical, mechanical, optical, fiber-optic, hydraulic, and
chemical components.
20. The system of claim 19, wherein the mechanical components
comprise at least one of motors, generators, alternators,
solenoids, actuators, relays, windings, conductors, and connectors.
Description
BACKGROUND OF THE DISCLOSURE
[0001] 1. Field of the Disclosure
[0002] The disclosure relates generally to the field of downhole
instruments. More specifically, the disclosure relates to
protecting downhole electronic instruments and controls by reducing
their internal atmosphere of moisture and polluting gases and
filling them with inert gases.
[0003] 2. Background Art
[0004] Some types of inert gas purging can be performed to protect
permanent completion tools and subsea pods from moisture and
polluting gases, but these tools are sealed during manufacturing.
For example, reservoir monitoring tools such as those belonging to
the assignee of the present disclosure have been used with a dry
process for packaging downhole electronics for some time. For these
conventional tools, it is essential to ensure reliable operation
during five years or more, especially at the high downhole
temperatures (i.e., above 100.degree. C.). This dry process
consists of vacuum burn-in, inert gas filling (with argon or dry
nitrogen gas) and installing desiccants into the downhole
electronics during manufacturing. However, this process is only
practical for these permanent tools because it can be done during
their manufacture, before they are sealed shut by welding, after
which they are shipped to the wellsite and installed permanently
downhole.
[0005] A similar drying process is used in the manufacture of
subsea instrumentation and controls (i.e., electronics installed at
the sea bed inside water proof housings or pods). One of the final
steps in manufacture includes replacing the humid air inside the
pod with dry nitrogen gas. However, this process is only practical
during manufacture because this equipment is installed permanently
at the sea bed.
[0006] A different approach is needed for moisture purging and
inert gas filling of while-drilling, wireline, and other downhole
tools and electronics that may be opened for maintenance, service
updates and repairs in the field.
SUMMARY OF THE DISCLOSURE
[0007] In certain aspects, this disclosure can relate to inserting
a purging gas into the tool, removing from the tool a gaseous
mixture that includes a portion of the purging gas and undesired
contents, and inserting a filling gas into to the tool.
[0008] Other aspects and advantages of the disclosure will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates a wellsite system in which the present
disclosure can be employed, according to an example embodiment.
[0010] FIG. 2A is a diagram showing certain components of a single
point purge system, according to an example embodiment.
[0011] FIG. 2B is a diagram showing certain components of a through
purge, according to an example embodiment.
[0012] FIG. 2C is a diagram showing certain components of a closed
loop system, according to an example embodiment.
[0013] FIG. 3A is a diagram showing certain components of a purging
system including a downhole tool with an inlet port for gas,
according to an example embodiment.
[0014] FIG. 3B is a diagram showing certain components of a purging
system including a downhole tool with an inlet port with an
interface, according to an example embodiment.
[0015] FIG. 4 is a chart that plots the inert gas bubble volume
versus N2 pressure within a tool, according to an example
embodiment.
DETAILED DESCRIPTION
[0016] The disclosure provides systems and methods that protect
downhole electronic instruments and controls by purging their
internal atmosphere of moisture and polluting gases and filling
them with dry inert gas. Certain embodiments will be described
below, including in the following Figures, which depict
representative or illustrative embodiments of the disclosure.
[0017] FIG. 1 illustrates a wellsite system in which the present
disclosure can be employed. The wellsite can be onshore or
offshore. In this example system, a borehole 11 is formed in
subsurface formations 106 by rotary drilling in a manner that is
well known. Embodiments of the disclosure can also use directional
drilling, as will be described hereinafter.
[0018] A drill string 12 is suspended within the borehole 11 and
has a bottom hole assembly 100 which includes a drill bit 105 at
its lower end. The surface system includes platform and derrick
assembly 10 positioned over the borehole 11, the assembly 10
including a rotary table 16, Kelly 17, hook 18 and rotary swivel
19. The drill string 12 is rotated by the rotary table 16,
energized by means not shown, which engages the Kelly 17 at the
upper end of the drill string. The drill string 12 is suspended
from a hook 18, attached to a travelling block (also not shown),
through the Kelly 17 and a rotary swivel 19 which permits rotation
of the drill string relative to the hook. As is well known, a top
drive system could be used.
[0019] In the example of this embodiment, the surface system
further includes drilling fluid or mud 26 stored in a pit 27 formed
at the well site. A pump 29 delivers the drilling fluid 26 to the
interior of the drill string 12 via a port in the swivel 19,
causing the drilling fluid to flow downwardly through the drill
string 12 as indicated by the directional arrow 8. The drilling
fluid exits the drill string 12 via ports in the drill bit 105, and
then circulates upwardly through the annulus region between the
outside of the drill string and the wall of the borehole 11, as
indicated by the directional arrows 9. In this well known manner,
the drilling fluid lubricates the drill bit 105 and carries
formation 106 cuttings up to the surface as it is returned to the
pit 27 for recirculation.
[0020] In various embodiments, the systems and methods disclosed
herein can be used with any means of conveyance known to those of
ordinary skill in the art. For example, the systems and methods
disclosed herein can be used with tools or other electronics
conveyed by wireline, slickline, drill pipe conveyance, coiled
tubing drilling, and/or a while-drilling conveyance interface. For
the purpose of an example only, FIG. 1 depicts a while-drilling
interface. However, systems and methods disclosed herein could
apply equally to wireline or any other suitable conveyance means.
The bottom hole assembly 100 of the illustrated embodiment includes
a logging-while-drilling (LWD) module 120, a
measuring-while-drilling (MWD) module 130, a roto-steerable system
and motor, and drill bit 105.
[0021] The LWD module 120 is housed in a special type of drill
collar, as is known in the art, and can contain one or a plurality
of known types of logging tools (e.g., logging tool 121). It will
also be understood that more than one LWD and/or MWD module can be
employed, e.g. as represented at 120A. (References, throughout, to
a module at the position of 120 can mean a module at the position
of 120A as well.) The LWD module includes abilities for measuring,
processing, and storing information, as well as for communicating
with the surface equipment. In the present embodiment, the LWD
module includes a nuclear magnetic resonance measuring device.
[0022] The MWD module 130 is also housed in a special type of drill
collar, as is known in the art, and can contain one or more devices
for measuring characteristics of the drill string and drill bit.
The MWD tool further includes an apparatus (not shown) for
generating electrical power to the downhole system. This may
include a mud turbine generator powered by the flow of the drilling
fluid, it being understood that other power and/or battery systems
may be employed. In the present embodiment, the MWD module includes
one or more of the following types of measuring devices: a
weight-on-bit measuring device, a torque measuring device, a
vibration measuring device, a shock measuring device, a stick slip
measuring device, a direction measuring device, and an inclination
measuring device.
[0023] FIGS. 2A-2C, discussed in more detail sequentially below,
are diagrams showing example details for three of the example gas
purging systems mentioned in the preceding paragraph, according to
various example embodiments. Namely, FIG. 2A is a diagram showing
certain components of a single point purge system 300A, according
to an example embodiment. FIG. 2B is a diagram showing certain
components of a through purge system 300B, according to an example
embodiment. FIG. 2C is a diagram showing certain components of a
closed loop system 300C, according to an example embodiment.
[0024] As shown in FIG. 2A, an example single point purge system
300A can include a gas tank 301, control box 305, downhole tool
with an access port 309, and humidity sensor 313. These components
can be connected to each other via various valves, pumps, pressure
sensors, and the like.
[0025] The gas tank can be filled with any purging gas, such as dry
nitrogen (N2) gas, an inert gas such as Argon or Helium, or an
electrically insulating gas such as Sulfur Hexafluoride (SF6) in a
pressurized cylinder. In various other embodiments, other types of
gas or mixtures of gas such as the chemically inert noble gases,
such as Neon, Krypton, or Xenon, or a relatively inert gas, such as
carbon dioxide can be used. Depending on regulatory requirements
and specific design considerations for the tool's thermal
management, a refrigerant gas may also be used, such as
2,3,3,3-Tetrafluoropropene, or HFO-1234yf, which is a fluorinated
hydrocarbon with the formula CH2=CFCF3. In certain embodiments,
helium may also be used to help transfer heat for power
applications; other possibilities include SF6 and CO2, particularly
in high voltage applications, as helium has a relatively low
dielectric strength (i.e., the maximum electric stress it can
withstand without breakdown or arcing). The choice of gas can be
based on the requirements and constraints of the specific
application. Specifically, the purging gas or mixture of gases
selected can be chemically compatible (i.e., not react chemically)
with the moisture or with any of the tool's internal components,
materials, or any of its out-gassing byproducts, especially over
the tool's temperature range of operation and life cycle. For
example, Helium is inert chemically and it can also be used to
detect leaks in sealed housings. Helium may also be a choice that
can help transfer heat for power applications. Additionally, in
various embodiments, it may be beneficial for the purge gas to be
compatible chemically, electrically, metallurgically,
thermodynamically and/or physically with the tool and its
constituent parts. In other words, it may be desirable for the
purge gas not to arc over or embrittle any metal, swell or crack
elastomers or polymers, contaminate components, or interfere with
its operation or cause it to fail and/or overpressure.
[0026] With the benefit of this disclosure, those skilled in the
art may appreciate the certain example advantages and disadvantages
of each candidate gas and gas mixture based on chemical and
electrical compatibility considerations of the purging gas with the
associated electronics to be protected as well as such
considerations as the gases' cost, safety, availability and
environmental considerations.
[0027] In some embodiments, the gas tank can have a valve 302 that
controls the release and pressure regulation of the purging gas
from the gas tank. Downstream from the gas tank and valve can be a
pressure reducing valve 303, and following the pressure reducing
valve 303 can be a pressure sensor 304. The pressure reducing valve
can regulate the pressure of the purging gas as needed, as measured
by the pressure sensor. In some embodiments, it can be beneficial
to use the pressure reducing valve and pressure sensor to ensure
that the pressure of the purging gas is at an appropriate level. In
some embodiments, an appropriate level can be between 3 and 50 psi
above atmospheric pressure. The particular desired pressure may
depend on a variety of factors as may be recognized by one of
ordinary skill in the art having benefit of the present disclosure,
such as the type and size of the downhole tool, the amount of
moisture likely to be present therein, the components contained
therein, the ability of those components to withstand a given
pressure above atmospheric pressure without damage, cost and the
pressure safety considerations of this gas purging system and its
associated processes, and the like.
[0028] In an example embodiment, the control box 305 can provide a
housing for the components contained therein. The control box can
serve to control gas fill, dwell and purge cycles based on its
sensors that measure temperature and relative humidity (or dew
point temperature) of the gas, as will be discussed in more detail
below. The control box can be designed and produced by those
skilled in the art for operator usability in shop and field
locations. To withstand rugged field use, the box can be made of
appropriate materials, such as aluminum, stainless steel, polymeric
or composite materials and in a form suitable to house the
components and protect them during their use conditions and
lifecycle environment, such as mechanical shocks and vibration,
temperature range, rain, salt spray, or dust. As shown in FIG. 2A,
the control box can include two solenoid valves 306, 312 (e.g., an
inlet valve 306 and an outlet valve 312) and two corresponding
check valves 307, 311, each used for controlling the flow of the
purging gas into and out of the tool.
[0029] In one embodiment, the purging gas from the tank 301 can be
permitted to flow by the operator turning the shutoff valve 302 to
the ON position. Then the gas flows through the pressure reducing
valve 303, enters the control box 305, flows through the inlet
solenoid valve 306 and check valve 307, and then exits the control
box and passes to an optional heater 308 before entering the
downhole tool 121. The heater can heat the purging gas. Such
heating can improve the drying and purging qualities of the purging
gas, in example embodiments. Using techniques known to those
skilled in the state of the art, the rate of heating can be
controlled so as to minimize any risk due to excessive temperature,
thermal shock or high thermal gradients within the tool. This
heater can reduce the need and logistics of using large tool ovens,
which may not always be accessible in the field. Alternately, the
heater can be in the line from the N2 cylinder or directly on the
inlet line to the tool. Other means of adding heat to the N2 or
directly to the tool via the collar or chassis could be devised by
anyone skilled in the art. In example embodiments, the purging gas
can be heated in a variety of different ways, including for
example, by having heating bands or coils disposed on or in the
tool itself.
[0030] After passing through the optional heater 308, the purging
gas then can enter the downhole tool 121 that is to be purged of
moisture. In an example embodiment, the purging gas can enter the
downhole tool via the Read Out Port (ROP) 309. In some embodiments,
the downhole tool can have any number of ports (e.g., an Annular
Pressure While Drilling (APWD) port 310) and any one or more of
those ports can be used as an entry point for the purging gas to
enter the downhole tool. Any number of gas flow ports could be
designed and arranged to manipulate gas flow in selected areas.
Several other logging or other tools can easily be accommodated
with this disclosure, as would be recognized by one of ordinary
skill in the art having benefit of the present disclosure.
Optionally, any port on the tool can make use of a valve for
sealing the port whenever the purging or exhaust tubes are not
attached to the tool. As an example, a variation of the automobile
tire valve known as a Schrader valve can be used. However, the tool
valve design application can have two differences to the tire
valve: 1) this valve can be within the tool; 2) this valve may not
seal against the high pressure environment downhole because high
pressure sealing can be made more effectively by a separate plug or
plug function added to the valve.
[0031] In one embodiment, the inlet valve 306 in the control box
can allow the purging gas to flow into the downhole tool via the
ROP 309. This process can be thought of as the "gas fill" cycle
referenced above, and this gas filling can continue until a
stopping condition has been reached. For example, the flow of
purging gas can continue for a given amount of time, for example 60
seconds), until a given volume of purging gas has passed into the
tool (for example, depending on the volume or size of the downhole
tool), or until the pressure of the purging gas in the downhole
tool reaches a certain level (for example, 5 psi, as measured by
pressure sensor 304.
[0032] In some embodiments, during the gas fill cycle the purging
gas can start to dry the moisture present within the downhole tool,
particularly where the heater was used to enhance the drying
ability of the purging gas. The warm purging gas can start to mix
with the water molecules and any other polluting or corrosive gases
in the tool's atmosphere, causing the moisture in the tool and any
polluting or volatile gases released from within its materials to
diffuse and intermingle with the injected gas. Note this process is
a physical mixing of gases and not a chemical reaction because the
selection of purging gas was specifically made based on its
compatibility with the tool, i.e., so it does not react chemically
with the moisture or with any of the tool's internal components,
materials, or their volatile outgases.
[0033] After the gas fill cycle ends, regardless of whether the
triggering condition is based on time, pressure, volume, or any
other method recognized by one of ordinary skill in the art having
benefit of the present disclosure, the dwell cycle can begin. In
example embodiments, the dwell cycle can constitute a period of
time wherein the flow of purging gas into the downhole tool is
stopped (or reduced), and the purging gas that entered the tool
during the gas fill cycle remains therein and "dwells" in the tool.
During the dwell cycle, the purging gas can continue to dry the
downhole tool and can continue to diffuse and/or mix with any
moisture, polluting or corrosive gases present therein. Those
skilled in the art having benefit of the present disclosure may
appreciate that this mixing can take place by a variety of well
known thermodynamic, gaseous kinetic or transport processes such
as: evaporation of volatile substances within the electronics or
its packaging, turbulent flow whenever the purging gas flows into
the tool, and, when the purging gas flow is stopped, there may be
gaseous convection driven by any pressure or temperature
differences, gaseous diffusion, or adsorption/desorption of gases
onto, into or out of the various materials and surfaces within the
tool.
[0034] In example embodiments, the dwell cycle can continue for a
period of time until a stopping condition has been reached, as
similarly described with reference to the gas fill cycle. The
stopping condition can be based on a given time period, which can
depend on a variety of factors such as the amount and/or pressure
of purging gas, the size of the tool, tortuosity of the gaseous
flow paths, the volume and the properties of the specific materials
contained within the tool, and the like.
[0035] After the dwell cycle, the purge cycle can begin. During the
purge cycle, the purging gas (along with the water molecules and
any other volatile gases mixed therewith) can begin to exit the
downhole tool, thereby removing moisture and gaseous pollution from
the tool. In the embodiment illustrated in FIG. 2A, the purging gas
can exit the downhole tool through the ROP 309. The direction and
speed of gas flow can be regulated by the solenoid valves and check
valves of the control box. Optionally, to regulate the exit of
purging gas, an additional flow restrictor valve can be added
anywhere in-line with the outlet solenoid valve 312 to the humidity
sensor 313 and atmospheric exhaust 314. Specifically, in certain
embodiments, during the purge cycle, the inlet solenoid valve 306
and corresponding check valve 307 can prevent purging gas from
entering the ROP or returning back through the lines to the purging
gas source 301 (as may have been the case during the dwell cycle),
and the outlet solenoid valve 312 and corresponding check valve 311
can allow the purging gas to exit the ROP.
[0036] After the purging gas has exited the downhole tool through
the outlet solenoid valve 312, the purging gas then can pass to the
humidity sensor 313. In an example embodiment, the humidity sensor
313 can include an atmospheric temperature sensor and a dew point
temperature sensor to measure the humidity of the purging gas. In
various other embodiments, any suitable type of humidity sensor can
be used to measure or estimate the humidity of the exiting purging
gas.
[0037] The humidity measurement determined by the humidity sensor
during successive purge cycles can indicate whether sufficient
moisture has been removed from the downhole tool. For example, if
during successive purge cycles, the humidity sensor reveals a
relatively high to low change in the amount of humidity in the
purged gas, this may indicate that an amount of moisture has been
removed from the tool; conversely, a relatively low to high change
in the humidity readings of successive cycles may indicate that
evaporation of moisture or other volatiles is taking place,
therefore moisture has not yet been removed from the tool. Finally,
little or no change in the humidity readings of successive cycles
may indicate that diminishing returns has been achieved for the
overall purging process. Thus, monitoring the humidity
reading--particularly in comparison to the reading for previous
cycles--can indicate whether to continue purging the tool of
moisture, or whether a sufficient amount of moisture has been
removed from the tool.
[0038] After the purging gas has passed through the humidity
sensor, it can be passed into the atmosphere 314. Then, as
discussed in the preceding paragraph, depending on the humidity
sensor reading, the entire process can be repeated to continue
purging the downhole tool of moisture until a desired target value
of humidity or humidity change has been achieved. For example, in
one embodiment, the target value can be around 45% relative
humidity. In some embodiments, the target value can be any suitable
value or range.
[0039] In various embodiments for the single point purge system
300A shown in FIG. 2A, various example configurations can be used.
For example, the valve on the gas tank 302, the pressure reducing
valve 303, and the inlet solenoid valve 306 could theoretically be
combined into one or two valves, instead of the three shown, to
regulate the pressure of the purging gas exiting the tank 301 and
entering the control box 305, heater 308, and downhole tool 301.
Additionally, the two distinct solenoid valves (i.e., inlet 306 and
outlet 312) can be replaced with one three-way solenoid valve. Such
a three-way valve could include one inlet end in connection with
the gas tank 301 and pressure sensor 304, one outlet end in
connection with the atmosphere 314, and one end that can be
switchable between an inlet and an outlet in connection with the
downhole tool. Other suitable modifications, such as those that may
be recognized by one of ordinary skill in the art having benefit of
the present disclosure, also can be used.
[0040] FIG. 2B, above, illustrates an example through-purge system
300B that can include many of the same components as the
single-point purge system 300A of FIG. 2A. As in the single-point
purge system 300A, purging gas can be released from a gas tank 301,
passed through pressure reducing valve 303, and pressure sensor
304, before passing through an inlet solenoid valve 306 (which may
or may not be within a control box as described with reference to
FIG. 2A). The purging gas then can pass through an optional heater
308 and check valve 307 (or in the opposite order) before entering
the downhole tool through the ROP.
[0041] The operation of these components of the through-purge
system 300B can be substantially the same or similar to those of
the single-point purge system 300A, and using these components, the
gas-fill and dwell cycles of the operation can be accomplished. The
operation of the two example systems can differ in the purging
cycle. Instead of the purging gas and moisture exiting the downhole
tool through the ROP, the purging gas and moisture can exit through
another port, such as the APWD. In other embodiments, one or more
additional exit ports can be used.
[0042] After exiting the downhole tool, the purging gas enters a
humidity sensor 313. As discussed previously with reference to the
single-point purging system, the humidity sensor can be used to
determine whether to continue purging moisture from the downhole
tool. After exiting the humidity sensor, the purging gas can flow
through an optional check valve 311, the outlet solenoid valve 312,
and then into the atmosphere 314.
[0043] As shown in FIG. 2B, the purging gas after exiting the
humidity sensor can flow to an optional pump 315. The pump 315 can
operate to pull the purging gas out of the humidity sensor (or push
the gas out of the humidity sensor), and direct it towards an
additional inlet check valve 307', where it is then passed back
into the downhole tool. There are several reasons why it may be
desirable to re-circulate the purging gas back to reenter the tool
after passing through the humidity sensor. Namely, in situations
where the humidity sensor indicates that only a small amount of
moisture is present in the purging gas, it may be beneficial to
pass the purging gas back into the downhole tool to further dwell
and/or mix with the moisture (perhaps for a longer time) and to
extract additional moisture from the tool. This may be preferable
to expelling the purging gas into the atmosphere and having to use
additional purging gas from the gas tank, for conservation
purposes. Optionally, the purging system may be configured so that
the heater 308 is in-line starting from between the junction of the
two inlet check valves 307 and 307' so that the heater's outlet
connects directly to the tool's inlet port 309. By this means the
purging gas may progressively warm the tool's interior to increase
the evaporation of any moisture or other volatiles, which may
outgas as the purging gas circulates around the loop.
[0044] In certain embodiments for the through-purge system 300B,
the effect of displacement can assist in the moving of moisture or
other undesired components toward the exhaust port. However,
stagnant zones outside the main flow channel may behave like a
single point purge where the wire channel acts as both an inlet and
exhaust port. The size of these stagnant zones can be reduced by
cutting additional flow channels into the chassis. In some
embodiments, separate inlet and exhaust streams can be created
using one-way valves along the main flow channel.
[0045] In an example embodiment for the through-purge system 300B,
the three cycles (gas-fill, dwell, and purge cycles) may not be
discretely separated from each other. In other words, instead of
first filling the downhole tool with purging gas, then allowing the
purging gas to dwell, and then finally purging the gas and moisture
from the tool, the purging gas can continually or periodically flow
through the tool via the ROP 309, mix with the moisture, and exit
through the APWD 310. The flow rate of the purging gas may need to
be adjusted accordingly to ensure that the purging gas has
sufficient time in the tool to dry the tool of the moisture and
successfully purge the moisture and any volatiles out gassed from
within the tool.
[0046] FIG. 2C, above, illustrates an example closed loop purge
system 300C. As shown in FIG. 2C, the example closed loop system
300C can include the same components present in the through purge
system 300B of FIG. 2B, with an additional N2 generator 316 (or
other purging gas generator) or concentrator that produces N2 at
the desired flow rate and pressure, and thereby reduces the need
for pressurized N2 cylinders, which can pose health and safety
risks as well as unacceptable logistical costs, especially in
remote field locations. The nitrogen generator 316 could also be
replaced by a pump and dryer (i.e., chilled surface, membrane, or
desiccant) to simply remove water vapor. The operation of the
example closed loop purge system 300C can be similar or identical
to the through purge system 300B of FIG. 2B, with the exception
that instead of purging gas passing into the atmosphere after
passing through the humidity sensor, it can pass into the N2
generator 316 where N2 purging gas is generated, and recycled into
the system, whether into the inlet solenoid valve or into the
heater directly. Additionally the N2 generator 316 can absorb air
from the atmosphere and generate N2 purging gas therefrom.
[0047] Though the closed loop purge system 300C is shown in FIG. 2C
as a modification to the through purge system 300B of FIG. 2B, it
could be used as a modification to a single point purge system,
such as the system 300A of FIG. 2A. In such an embodiment, the
input of the N2 generator 316 could be connected to, for example,
the output of the humidity sensor (whether directly or through a
pump and/or solenoid valve), and the output of the N2 generator
could be connected to, for example, the inlet solenoid valve or the
heater.
[0048] FIGS. 3A and 3B are diagrams showing certain components of a
purging system, according to an example embodiment. Certain of
these components can be used in addition to or instead of the
components described above with reference to FIGS. 2A-2C.
[0049] As shown in FIG. 3A, the illustrated purging system can
include a downhole tool 402 that has an ROP 404 or other inlet port
for gas. A vacuum hose 408 can be connected on one end to the ROP
404 and on the other end to a vacuum pump for removing moisture
from the downhole tool 402. In example embodiments, a vacuum
fixture can be connected to the ROP 404 for facilitating a
connection between the vacuum hose 408 and the downhole tool 402.
The ROP 404 in turn can be connected to a vacuum release hose,
which is in turn connected to one or more desiccant jars 414 having
a vent valve 416.
[0050] FIG. 3B is a diagram showing certain components of a purging
system including a downhole tool 402 with an inlet port with an
interface, according to an example embodiment. FIG. 3B illustrates
example details for the example system shown in FIG. 3A. As shown
in FIG. 3B, the ROP fixture 406 can have a valve 418 and a "quick
connect" interface 420 (having corresponding male 420A and female
parts 420B) for facilitating the connection and disconnection of
the hoses 408, 412 and downhole tool 402.
[0051] Additionally, as shown in FIG. 3B, a vacuum pump 410
assembly can include (in addition to the pump 410 and hose 408) a
female quick connect interface 420B for connecting to the male
quick connect interface 420A of the ROP fixture 406, and can
further include a vacuum gauge 422, a valve 418, and a trap 424.
These components can be used to facilitate the pumping ability of
the vacuum pump 410 and to measure the strength of the vacuum pump
410.
[0052] The embodiment of FIG. 3B additionally shows a desiccant
assembly. The desiccant assembly can include--in addition to the
desiccant jars 414 and valve 418 referenced above--one or more
filters 426, one or more caps 428, tubing 430 or other connections
between the desiccant jars 414, as well as a vent valve 416 and
filter screen 432. In an example embodiment, the filters 426 can
prevent the desiccants or other components from contaminating the
downhole tool 402 or components thereof.
[0053] An example method for utilizing a purging system, such as
the purging system shown in FIGS. 3A-3B is now described. First,
example steps for attaching and using the vacuum pump 410 can
include the following. In some embodiments, an example method can
include attaching the appropriate adapter (depending on collar
being tested) to vacuum station ROP fixture 406 and installing the
fixture 406 into ROP 404 in collar. In some embodiments, an example
method can include attaching the hose 408 from the vacuum pump 410
to the ROP fixture 406, opening the valve 418 on the ROP fixture
406, and turning on the vacuum pump 410. In some embodiments, the
vacuum can be pulled for about 15 minutes; other suitable times are
possible. In some embodiments, the valve 418 on ROP fixture 406 can
be closed and the vacuum gauge 422 can be monitored for 5 minutes
(during which time it may hold about 28 in Hg) without material or
any leakage.
[0054] After the vacuum pump 410 is used, example steps for
releasing the pump 410 and connecting the desiccant jars 414 can
include disconnecting the hose 408 from the ROP fixture 406,
attaching the hose 412 coming off of the desiccant jars 414 to the
ROP fixture 406, open the vent valve 416 on the desiccant jars 414,
and opening the valve 418 on the ROP fixture 406 (this valve 418
should be slightly opened and very slowly to regulate the release
of the vacuum).
[0055] In example embodiments, the example systems, components
thereof, and methods of use therefore, such as the ones of FIGS.
2A-2C and FIGS. 3A-3B can be combined with each other. For example,
a purging system can include both purging gas assemblies as
described in FIGS. 2A-C as well as vacuum pumps 410 and desiccant
jars 414 as described in FIGS. 3A-B. This particular design
combination may be advantageous for those applications where cost,
availability, logistics, or safety considerations make it
prohibitive to use pressurized gas cylinders or where this
combination offers a desired advantage such as faster processing
time or more efficient purging (i.e., to achieve a lower RH target
level) than one of the embodiments described in FIGS. 2A to 2C. In
contrast, this combination may be more complex, more expensive and
less reliable than one of the systems described in FIGS. 2A to 2C,
which may be simpler to operate or automate, less expensive and
more robust because they have fewer parts, i.e., no pump 410, no
desiccants, and no nitrogen generator. Each of the above
embodiments of the basic methods disclosed in this patent offers
advantages as well as disadvantages, depending on the specific tool
402 to be purged as well as on the user's specific requirements and
constraints, which may vary depending on location, skill level, and
use environment. Therefore the selection of a specific purging
system design and its associated options may be made by one of
ordinary skill in the art having benefit of the present
disclosure.
[0056] FIG. 4 is a chart that plots 515 the inert gas bubble volume
505 (as a percentage of available free volume within the tool)
versus N2 pressure (in psi) 510 within a tool, according to an
example embodiment. The inert gas bubble is an imagined worst case
that represents the volume the inert gas would occupy assuming
there was no mixing of gasses within the tool. The model shown is
based on N2 filling as an isentropic thermodynamic process (assumes
ideal gas, no heat transfer and reversible process with no mixing)
P1/P2=(v2/v1) k, where P1 and v1 are the initial pressure and
volume, respectively, within the tool; P2 and v2 are the final
pressure and volume, and k=1.400 for Nitrogen gas. Moreover, FIG. 4
shows that a Nitrogen filling pressure of about 50 psi would help
maximize the dry air exposure within the tool before we really
start getting diminishing returns of bubble volume versus applied
purging pressure. This characteristic behavior is of note because
it provides a basis for selecting the filling pressure design value
in order to achieve efficient purging while avoiding any risk of
damaging the tool's internal components by overpressure. For
example, some electronic circuits, such as quartz crystal
oscillators and multichip modules (MCMs), may be packaged in vacuum
sealed ceramic or metal cans that can sustain only up to a limited
amount of external gas pressure before failing due to deformation
or collapse. The safe range of pressure and temperature for
specific components may be determined by specific analysis or
testing by one skilled in the art.
[0057] A dwell time between filling and exhaust allows moisture and
pollution gases to diffuse and mix with the inert gas to facilitate
its removal during the next exhaust cycle. This minimizes dead
zones and the need for special passages and tubes to circulate gas
within the tool. This makes it possible to fill and purge existing
tools and a wide variety of tool architectures (i.e., tools having
single or multiple ports).
[0058] In some embodiments, if tools were dry for starters, then
heating dry air from 30 deg C. to 150 deg C. may bring the partial
pressure within the tool from 14.7 psi to about 45 psi; however if
liquid water is present (e.g., due to moisture condensation), then
the pressure at 150 deg C. can be as high as about 114 psi if
sufficient mass of liquid water is present. For example, if a
tool's cartridge was moved from an air-conditioned room to a humid
shop, moisture would condense onto the tool and be absorbed by its
wiring harness, electronics and exposed parts.
[0059] If relative humidity inside the tool is about 100%, any
increase in pressure may cause condensation of water vapor.
Therefore, initially, the tool can be flushed with dry gas to
reduce the humidity to some maximum allowable level before starting
pressure cycles.
[0060] To prevent condensation, the maximum pressure applied during
pressure cycles may be limited to maintain relative humidity less
than 100% after compression. This pressure can increase with
increasing gas temperature because generally, saturation pressure
increases with temperature.
[0061] Additional details for various example embodiments exist, as
may be recognized by one of ordinary skill in the art having
benefit of the present disclosure. As non-exhaustive examples only,
the following details of certain example embodiments are offered
herein.
[0062] In some embodiments, a moisture and pollution purging
process can be based on one or more pressure filling and exhaust
cycles of inert gas. The warm dry gas enters via a single valve or
port into the tool and circulates in and out of the tool with each
cycle, thereby evaporating moisture and other volatiles inside the
tool, diluting any pollution gases and exhausting it out to achieve
a desired level of purity with clean dry inert gas, i.e., an
acceptable low level of moisture and pollution within the protected
atmosphere inside the downhole tool.
[0063] In some embodiments, a Nitrogen concentrator unit that
reduces or eliminates the risks, cost and logistics of high
pressure N2 cylinders can be used.
[0064] In some embodiments, the pressurized gas can be cycled in
and out of the tool such that the dry inert gas is introduced
relatively quickly. In such embodiments, the gas may compress and
warm the internal atmosphere to help evaporate and drive out
moisture, followed by a dwell time for the gases to intermix and
dilute any moisture or pollution, and followed by a relatively slow
exhaust to prevent any rapid cooling that could condense moisture
back onto the electronics. Basically, this can take benefit from
the time duration, Tpress, to pressurize the tool from atmospheric
to max pressure, Pm, being less than the time duration, Tex, to
depressurize, or exhaust the gas out of the tool from Pm back down
to atmospheric pressure. The dwell time that may be optimal mixing
or dilution of the moisture with the purging gas depends on the
thermal mass and gas volume inside the tool, and the amount and
type of materials that may contain volatiles and may have absorbed
moisture inside the tool.
[0065] In some embodiments, an automated process can be used for
purging oilfield tools with inert gas using a measurement of the
moisture in the exhausted or circulated gas as a criterion for
continuing or stopping the process at a given desired level of
purity. In some embodiments, the purging process can be done after
the electronic chassis is loaded into its collar, or housing, and
sealed. This means purging can be done at any time: i.e., in
manufacturing prior to shipping the tool, in a location's shop, in
storage, or even on a rig prior to running down hole or immediately
after the tool is retrieved uphole as a crosscheck on the quality
or purity of its internal environment. In some embodiments,
circulating the warm dry gas can avoid or reduce the need for
vacuum prior to filling with inert gas.
[0066] In some embodiments, an instrumented setup with on-line
measurement of the humidity at the exhaust or in-line with the gas
circulation, such as with a Go or No-Go criterion for the internal
atmosphere's purity. Pressure testing during purging can help
ensure that O-rings are in place prior to running in hole.
[0067] In some embodiments, the design of a gas flow port can be
made by a small plug with two O-rings and a small gas port in the
middle. The plug connects to the gas filling set-up. Pulling on the
plug opens the communication channel with electronics, pushing the
plug back inside closes it.
[0068] In some embodiments, a desiccant bag, whether or not full of
or otherwise containing moisture, can be regenerated after being
baked for several hours. In some embodiments, for certain
permanently installed downhole completion tools, no special
attention need be paid to the desiccant bag. During manufacturing,
this bag is inserted in the electronics housing and it gets
regenerated during the gas filling process at the burn-in
temperature (often about 150 deg C.).
[0069] In some embodiments, a relatively inert gas such as
Nitrogen, Sulfur Hexafluoride, or of Helium (also can be used for
leak testing the same tool), Argon or other inert gas, or mixtures
thereof, can be used. Purging with inert gas pumped into the tool
using pressure above atmospheric pressure can be used to reduce or
eliminate the need for a vacuum pump to achieve multiple
exhaust-fill cycles with the purging gas.
[0070] In some embodiments, closed loop drying by cycling the same
volume of gas through a dehumidification process. The exhaust gas
coming from the tool passes over a chiller to condense water vapor
then the same gas can be passed through a heater before re-entering
the tool to improve evaporation.
[0071] In some embodiments, pressuring the tool with dry gas can
create a "bubble" (as a first approximation) within the tool of dry
warm gas. For the moisture already absorbed into the electronics,
local evaporation rates will vary with the material properties and
the distance from the gas inlet depending on the local vapor
pressure of the gas. Therefore, it is desirable to maximize the
volume of dry air in each pressure cycle to enhance evaporation
rates. For any given volume, FIG. 4 shows this N2 "bubble" will
occupy: 19% of the total volume at 5 psi, 31% of the total volume
at 10 psi, 50% of the total volume at 24 psi, 90% of the total
volume at 354 psi.
[0072] In some embodiments, many of the example system and methods
described herein can be used not only to reduce or remove moisture
from electronic components of downhole tools, but also from
mechanical or other assemblies that may contain electrical
equipment. For example, motors, solenoids, actuators, relays,
windings, conductors, and connections such as alternators,
generators, resolvers, field coils, and the like all may contain
components that can acquire moisture to be removed and/or reduced.
In some embodiments, the components purged accordingly then can be
filled before service with various types of gases such as inert
gases, dielectric insulating gases (e.g., SF6), hydraulic oil,
polymer potting, conformal coating, and/or gel.
[0073] In some embodiments, the example downhole tool system from
which moisture may be removed and/or reduced can include at least
one of electrical, mechanical, hydraulic, and chemical components,
or some combination thereof. Moreover, although a portion of the
disclosure and FIG. 1 relates to a while-drilling downhole system,
in some embodiments, the downhole system can include a variety of
other systems or components thereof, such as a surface connection
system and associated interfaces, such as tubing hanger, subsea
tree, platform tree, and surface land rig tree. As non-limiting
examples only, some additional examples for applications of certain
embodiments of the disclosure can include purging, removing, and/or
reducing moisture from (a) hydraulic systems before filling them
(or refilling them) with hydraulic oil (e.g., safety valves,
isolation valves, packers, flow control valves and their hydraulic
lines and connections to surface); (b) downhole electric
submergible pump systems before filling them with dielectric oil;
(c) downhole perforating tool's explosive charges and their
associated detonators; (d) downhole chemical cutters; (e) downhole
pressure balanced sensors and antennas before they are filled with
dielectric oil or gel, such as in NMR, induction, resistivity,
acoustic, seismic, and inductive coupling tools; and (f) other
tools and/or components that may or may not be used downhole.
[0074] In some embodiments, many of the example systems and methods
described herein relating to removal of moisture can be used in a
variety of other applications. For example, that many of the
methods and systems described herein can apply to pretreating
mechanical assemblies that contain motor windings (e.g.,
alternators, generators, resolvers, field coils, etc.) and are then
filled with hydraulic oil as opposed to gas.
[0075] Additionally, various types of moisture or other polluting
or corrosive gases may able to be categorized, with different
removal systems being more suited for different categories. For
example, moisture that is likely to be easily removed from a tool
(e.g., moisture along a flow path) may be easily and efficiently
removed by a through-purge. Moisture or other gases more difficult
to remove (e.g., that which "hides" in stagnant areas and adsorbed
onto exposed surfaces) could make use of a an optimized purge
process (such as through a single-point purge with suitable dwell
time) or even by using different chassis geometry. A vacuum exhaust
port also may be helpful to efficiently transport the moisture.
Lastly, the most difficult moisture to remove may be that which is
absorbed into hygroscopic materials and cannot be efficiently
removed on a short time scale without heat. However, this moisture
may evaporate slowly after purging as the boards, packages and
potting seek equilibrium with the dried chassis air. This moisture
can also be removed by baking (or without an oven by using our
heater with two or more ports) when appropriate.
[0076] The example methods and steps described in the embodiments
presented previously are illustrative, and, in some embodiments,
certain steps can be performed in a different order, in parallel
with one another, omitted entirely, and/or combined between
different example methods, and/or certain additional steps can be
performed, without departing from the scope and spirit of the
disclosure. Accordingly, such embodiments are included in the
disclosure described herein.
[0077] Although specific embodiments of the disclosure have been
described above in detail, the description is merely for purposes
of illustration. Various modifications of, and equivalent steps
corresponding to, the disclosed aspects of the example embodiments,
in addition to those described above, can be made by those skilled
in the art without departing from the spirit and scope of the
disclosure defined in the following claims, the scope of which is
to be accorded the broadest interpretation so as to encompass such
modifications and equivalent structure.
* * * * *