Note: Descriptions are shown in the official language in which they were submitted.
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Pulsed Deployment Of A Cable Through A Conduit Located In A Well
Background
The invention generally relates to the deployment of a cable in a conduit by
use of
fluid drag. More particularly, the invention relates to such deployment of a
fiber optic cable
in an oil and gas well in which gas or liquid is pulsed to create the fluid
drag.
As disclosed in EP 108,590 and others, it is known in the prior art to install
a fiber
optic cable in a conduit by passing a fluid through the conduit at a high
enough velocity to
propel the cable along the conduit by way of fluid drag. Also, as disclosed in
US Reissue
37,283, this deployment technique has even been used to deploy fiber optic
cable within a
conduit located inside of an oil and gas well.
In some cases, particularly at high temperatures and/or high pressures, the
use of
liquid as the propelling fluid leads to increased attenuation in the fiber
optic cable. This
situation is alleviated by the use of gas as the propelling fluid. However,
depending on the
relative cross-sectional areas of the cable and conduit, the use of gas as the
propelling fluid
greatly diminishes, if not stops, the rate of deployment of the cable.
Thus, there exists a continuing need for an arrangement and/or technique that
addresses one or more of the problems that are stated above.
Summary
A system and method for deployment of a cable, such as a fiber optic cable,
through a
conduit located in a well. A fluid is pulsed through the conduit, which pulse
intermittently
forces the cable to pass through the conduit. The cable may include at least
one measurement
location to measure a parameter of interest within the well. The fluid pulsing
technique may
also be used to deploy the cable in a conduit adapted to be located in other
locations.
Brief Description Of The Drawing
Fig. 1 is a general schematic of the system used to deploy a cable into a
conduit.
Fig. 2 is a more detailed view of one embodiment of the system.
Fig. 3 is a schematic of the system used to deploy a cable into a conduit
located within
an oil and gas well.
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Detailed Description
Figure 1 shows a system 10 used to propel at least one cable 12 into a conduit
14.
The cable 12 may include a sensor 16 for sensing a physical parameter.
Alternatively, the
cable 12 may include multiple sensing locations along its length. An
interrogation unit 18 is
functionally attached to the cable 12 and interrogates the signals sent
through the cable 12
from the sensor 16 or sensing locations in order to make a measurement of the
parameter of
interest. A cable installation unit 20 installs the cable 12 within the
conduit 14 and includes a
fluid unit 22 for propelling the fluid into the conduit 14. The installation
unit 20 may also
include a lead-in section 24 for providing a distance to enable sufficient
fluid drag on the
cable 12 as it enters the conduit 14. The cable 12 is shown wound up on a drum
26. The
cable 12 and sensor 16 may be deployed to a remote location S, such as an oil
and gas well.
The cable 12 may be one or more optical fiber cables. These may be
hermetically
sealed with carbon coating, may have high temperature coatings such as
polyimide, or
silicone or polytetrafluoroethylene, or may have combinations of these
coatings. The cable
12 may also be acrylate-coated fibers.
The sensor 16 or sensing locations on cable 12 may be one or more optical
fiber
sensors. The sensors may include sensors for measuring temperature,
distributed
temperature, pressure, acoustic energy, electric current, magnetic field,
electric field, flow,
chemical properties, or a combination thereof. The cable 12 itself may act as
the sensor, such
as taught by US Patent Nos. 4,823,166 and 5,592,282 issued to Hartog wherein
the sensor is
an optical fiber that acts as a distributed temperature sensor.
The interrogation unit 18 may be instrumented electronics. The interrogation
unit 18
may be an electro-optic electronic readout system suitable for interrogating
the appropriate
optical fiber cable and sensors and may include one or more optical fiber
amplifiers.
The interrogation unit 18 need not be connected to the cable 12 while the
cable 12 is
pumped through the conduit 14 to the remote location 5. In many instances it
is preferable to
remove the installation unit 20 once the cable 12 is properly located at the
remote location 5,
form a seal around the cable 12 where it enters or exits conduit 14, and then
connect cable 12
to the interrogation unit 18 with a separate cable specially designed for
surface cabling.
The conduit 14 may be high-pressure tubing with an inside diameter and
pressure
rating to make it suitable for deploying the cable 12 and sensor. When
deployed in an oil and
gas well, the conduit 14 may be steel hydraulic control line commonly used in
the oil and gas
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industry having an external diameter of 1/8" to 3/4". Alternatively, the
conduit 14 may be
coiled tubing commonly used in the oil and gas industry having an external
diameter of 3/4"
to 2".
In one alternative embodiment, the cable 12 is first pumped through the
conduit 14,
and the conduit 14 is then properly disposed in the remote location 5.
For this invention, fluid unit 22 propels a fluid into the conduit 14, but it
does so by
pulsing the fluid into the conduit 14. The fluid may be a liquid or a gas, or
a combination
thereof. The fluid unit 22 may include at least one gas bottle, a gas
compressor, a fluid pump,
or a combination of any of these. The gas bottles may be manifolded together.
The fluid
may be any fluid that does not adversely react with the cable 12 (such as by
causing optical
cable attenuation) or surrounding environment. Adequate gas types include
nitrogen, air, and
gases from the family of inert gases (argon, helium, neon, xenon, krypton,
radon). Adequate
liquid types include water and other appropriate liquids.
Figure 2 shows one embodiment of the system 10. An orifice 28, which can be a
capillary, enables the passage of the cable 12 from the drum 26 to the
interior of the
installation unit 20. Fluid unit 22 injects the fluid through passage 32 and
into lead-in section
24 to propel cable 12 therein and within conduit 14. The pressure provided by
fluid unit 22
may act against orifice 28 and may therefore also act to somewhat prevent the
ingress of the
cable 12 from the drum 26 into the installation unit 20. In order to ensure
that such ingress is
not prevented, a governor 30 may be inserted within installation unit 20 in
order to amplify
the force provided to cable 12 by the fluid in the direction of the remote
location S. The force
amplification by the governor 30 ensures that the force in the direction of
the remote location
is greater than the force that may act against the orifice 28; thus, the cable
12 is propelled
by the fluid unit 22 in the correct direction.
As previously discussed, the fluid unit 22 pulses fluid through passage 32 and
into
lead-in section 24. It has been found that, depending on the fluids used as
the propelling
medium, forward movement of the cable 12 tends to stop after a short distance
if the fluid is
injected in a continuous manner. The stoppage is perhaps caused by the cable
12 sticking to
the inside wall of the conduit 14. If the fluid injection is pulsed, each
fluid pulse lifts and
propels the cable 12 a distance farther down the conduit 14. Each fluid pulse
creates a new
pressure differential, which intermittently carries the cable 12 forward.
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Each fluid pulse lasts a specific duration of time, which may be a function of
the
length of conduit, after which time the fluid injection is stopped. The
pressure within each
fluid pulse may also be varied. For instance, fluid may be injected at a
specific pressure
initially and thereafter at a higher pressure until the end of the fluid
pulse. The initial lower
pressure provides enough time for a substantial amount of the cable 12 to be
within or
immersed in the fluid pulse. This initial lower pressure induces the movement
of the cable
12. The subsequent higher pressure is then able to increase the rate of
movement of the cable
12 until the end of the fluid pulse. The variation of pressure during a fluid
pulse is specially
useful when there is a limited amount of compressed fluid on hand, specially
if there is a
limited amount of higher pressure compressed gas on hand.
If the fluid is a gas, in order to minimize the amount of liquid present in
the interior of
the conduit 14 (which liquid may lead to the cable 12 sticking to the inside
wall of the
conduit 14), the conduit 14 may be prepared prior to the deployment of the
cable 12 within
the conduit 14. The preparation of the conduit 14 can be specially useful in
the conduits 14
used in oil and gas applications, since such conduits are normally pressure
tested by the
manufacturer with either water or another liquid prior to shipment. The goal
in the
preparation of the conduit 14 is to clean the interior of the conduit 14 and
to remove as much
moisture and liquid from the interior of the conduit 14 as possible. One way
to do this is to
flush the conduit 14 with a rapidly evaporating solvent, such as isopropanol,
methanol, or
acetone. As the solvent is pumped through the conduit 14, it will clean the
interior diameter
of the conduit 14. In addition, the solvent will evaporate rapidly leaving the
interior wall of
the conduit 14 clean and very dry. As previously stated, the cable 12 will
tend to move a
farther distance down the conduit 14 with each fluid pulse if the interior
wall of the conduit
14 is clean and dry.
If the fluid is a liquid, in order to minimize the amount of liquid that is
not miscible
with the deployment fluid that is present in the interior of the conduit 14
(referred to as "Non-
miscible liquid")(which Non-miscible liquid may lead to the cable 12 sticking
to the inside
wall of the conduit 14), the conduit 14 may be prepared prior to the
deployment of the cable
12 within the conduit 14. The preparation of the conduit 14 can be specially
useful in the
conduits 14 used in oil and gas applications, since such conduits are normally
pressure tested
by the manufacturer with a Non-miscible liquid prior to shipment. The goal in
the
preparation of the conduit 14 is to clean the interior of the conduit 14 and
to remove as much
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Non-miscible liquid from the interior of the conduit 14 as possible. One way
to do this is to
flush the conduit 14 with a rapidly evaporating solvent, such as isopropanol,
methanol, or
acetone. As the solvent is pumped through the conduit 14, it will clean the
interior diameter
of the conduit 14. In addition, the solvent will evaporate rapidly leaving the
interior wall of
the conduit 14 clean and very dry. As previously stated, the cable 12 will
tend to move a
farther distance down the conduit 14 with each fluid pulse if the interior
wall of the conduit
14 is clean and dry.
Prior to passing the solvent into the conduit 14 and particularly useful in
oil and gas
applications, a gas may be injected to first displace any of the standing
water or liquid within
the conduit 14. Moreover, once the solvent is passed into the conduit 14, the
solvent may be
left in the conduit 14 for a period of time, such as 20-30 minutes for
example. The solvent
may be purged out of the conduit 14 by passing gas through the conduit 14.
Figure 3 shows the use of the system 10 in an oil and gas well 100. The well
100 may
include a casing 102, a well head 104, a length of production tubing 106
through which oil
flows from a reservoir 108, and a packer 110 for isolating the pressure from
the reservoir
from the surface. In one embodiment, conduit 14 is strapped to the production
subbing 106
using straps 112. The conduit 14 passes down the well 100 and may pass through
packer
110, such as by packer penetrators and/or feedthroughs. The conduit 14 may be
configured
in a U-shape so that the conduit 14 turns around at U-bend 114 and passes back
up the well
100 again. Conduit 14 enters and exits wellhead 104 via ports 116.
In use, the conduit 14 may be installed in the well 100 as the production
tubing 106 is
being deployed in the well. Once the installation of the other components of
the well 100 is
complete, the conduit 14 may be prepared as previously disclosed, such as by
purging any
standing liquid in the conduit 14 with gas, passing a solvent through the
conduit 14, letting
the solvent stand in the conduit 14 for a period of time, and purging the
solvent from the
conduit 14 with gas. Once the conduit 14 is clean and dry, the cable 12 is
installed within the
conduit 14 by connecting the system 10 to conduit 14 and pulsing the cable 12
through
conduit 14 using fluid (as previously disclosed). Any fluids can be collected
at the far end 15
of cable 14 by a vessel 70. Alternatively, the far end 1 S can be routed back
to the system 10.
The cable 12 is deployed within the well 10 so that it is adequately
positioned to enable the
sensor 16 or sensor location to measure the parameters of interest.
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In another embodiment, instead of having a return line or U-shape, the conduit
14 is
single-ended and includes a check valve so that the cable 14 can be deployed
hydraulically
therein. The check valve allows the deployment fluid to be released into the
well 100 while it
is pressurized (during deployment) but thereafter seals the conduit 14.
In another embodiment, the cable 12 is pumped into the conduit 14 at the
surface, and
the conduit 14 with the cable 12 already therein is deployed into the well
100.
Following installation, the conduit 14 external to the well 100 may be removed
taking
care not to sever the cable 12, and the cable 12 is then connected to the
interrogation unit 18.
The cable 12 and sensor 16/sensor locations can then be used to measure the
parameter of
interest.
As previously disclosed, depending on the sensors used, a variety of
parameters may
be measured within well 100, including temperature, distributed temperature,
pressure,
acoustic energy, electric current, magnetic field, electric field, flow,
chemical properties, or a
combination thereof. In one embodiment, the cable 12 is a fiber optic cable
and together with
the appropriate interrogation unit 18 comprises a distributed temperature
system which
measures distributed temperature along the length of the cable 12 (such as
Sensor Highway
Limited's DTS units). Although different techniques can be used, in one
technique called
optical time domain reflectometry pulses of light at a fixed wavelength are
transmitted from
the unit 10 down the fiber optic cable 12. Light is back-scattered from every
point along the
cable 12 and returns to the interrogation unit 18. Knowing the speed of light
and the moment
of arnval of the return signal enables its point of origin along the cable 12
to be determined.
Temperature stimulates the energy levels of the silica molecules in the cable
12. The back-
scattered light contains upshifted and downshifted wavebands (such as the
Stokes Raman and
Anti-Stokes Raman portions of the back-scattered spectrum) which can be
analyzed to
determine the temperature at origin. In this way the temperature of each point
in the cable 12
can be calculated by the interrogation unit 18, providing a complete
temperature profile along
the length of the cable 12. This general fiber optic distributed temperature
system and
technique is known in the prior art. The U-shaped return line may provide
enhanced
performance and increased spatial resolution to the temperature sensor system.
Although the oil and gas installation has been described with the conduit 14
attached
to a production tubing 106, it is understood that conduit 14 (and therefore
the fluid pulsing
deployment technique) may be deployed inside a well in a variety of manners
(such as by
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itself or cemented behind a well casing), each of which is within the scope of
this invention.
Furthermore, the use if this invention is applicable to all types of wellheads
and well
locations, including subsea wells.
In one embodiment, in order to further decrease the chance of fiber optic
cable
attenuation, once the cable 12 is properly deployed and located within the
conduit 14, the
pressure caused by the fluid injection within the conduit 14 may be released.
The conduit 14
is at atmospheric pressure at that point. An inert displacement gas with a
greater specific
weight than ambient atmospheric gas may help to ensure that no or fewer
unwanted
molecules pass into the core of the fiber optic cable 12 (which will tend to
lead to
attenuation).
In another embodiment, fluid pressure is maintained in the conduit 14 to
ensure that
flow is outwardly from the conduit 14 in the event there is a leak in the
conduit 14. If flow is
inwardly into the conduit 14, then well fluids (including liquids) may enter
the conduit 14 and
come into contact with the cable 12, which occurrence may damage the cable 12.
Thus, in
this embodiment, the fluid pressure maintained in the conduit 14 should be
higher than the
pressure in the exterior of the conduit 14. This pressure should also be
maintained despite the
presence of a leak; therefore, fluid may need to be continuously injected to
maintain this
pressure.
In any embodiment, different fluids (those fluids as previously described) may
be
used during the process. For instance, in the embodiment described in the
previous paragraph
in which fluid pressure is maintained in the conduit 14, cable 12 may be
deployed with one
fluid (for example nitrogen), and the fluid pressure may be held with another
fluid (for
example argon).
As previously described, the conduit 14 is first deployed in the well 100 and
then the
cable 12 is installed in the conduit 14. In another embodiment, the cable 12
is first installed
in the conduit 14 (as previously described) on the surface and then the
conduit 14 (with the
cable 12 disposed inside) is deployed in the well 100. In this embodiment,
pressure in the
interior of the conduit 14 may be maintained at an elevated pressure (as
previously disclosed)
during the deployment of the conduit 14 in the well 100.
It is understood that more than one cable 12 may be concurrently passed
through
conduit 14.
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Although described for use in an oil and gas well, the deployment method
described
herein may also be used in other non-oil and gas well applications. Thus, at
least one cable
12 may be pulsed into a conduit 14 (that is not adapted to be located in an
oil and gas well),
as previously described, to a remote location. Remote locations may comprise
pipelines
(including subsea pipelines), tunnels, and power lines. And, the cable 12 may
provide
measurements of parameters of interest along the conduit, as previously
described.
While the invention has been disclosed with respect to a limited number of
embodiments, those skilled in the art, having the benefit of this disclosure,
will appreciate
numerous modifications and variations therefrom. It is intended that the
appended claims
cover all such modifications and variations as fall within the true spirit and
scope of the
invention.
