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|United States Patent Application
;   et al.
October 27, 2005
Optical fiber equipped tubing and methods of making and using
The present invention relates to an optical fiber equipped tubing and
methods of making and using the same. The optical fiber equipped tubing
comprises a fiber optic tube deployed within a tubular, the fiber optic
tube having at least one optical fiber disposed within a duct, the duct
typically being a metallic metal compatible with wellbore environments.
The present invention also relates to a method of making an optical fiber
equipped tubing comprising pumping a fluid into a tubular and deploying a
fiber optic tube into the tubular by propelling it in the flow of the
pumped fluid. The present invention also provides a method of
communicating in wellbore using a fiber optic tube disposed within a
wellbore tubular. In certain embodiments, this communication may be
combined with a wireless communication system at the surface. In certain
embodiments, the tubular may be coiled tubing and the fiber optic tube
may be deployed in the coiled tubing while the tubing is spooled on a
reel or while the tubing is deployed in a wellbore.
Gay, Michael; (Dickinson, TX)
; Adnan, Sarmad; (Sugar Land, TX)
; Lovell, John; (Houston, TX)
SCHLUMBERGER TECHNOLOGY CORPORATION
IP DEPT., WELL STIMULATION
110 SCHLUMBERGER DRIVE, MD1
April 21, 2005|
|Current U.S. Class:
||166/380; 166/242.1; 166/66 |
|Class at Publication:
||166/380; 166/066; 166/242.1 |
||E21B 019/16; E21B 043/00|
What is claimed is:
1. An optical fiber equipped tubing comprising a fiber optic tube disposed
within a tubular.
2. The tubing of claim 1 wherein the fiber optic tube comprises more than
one optical fiber.
3. The tubing of claim 1 wherein the fiber optic tube comprises a duct
comprising a metallic material.
4. The tubing of claim 1 wherein the tubular is coiled tubing.
5. The tubing of claim 4 wherein the coiled tubing is spooled on a reel.
6. The tubing of claim 4 wherein the coiled tubing is deployed in a
7. The tubing of claim 1 wherein the fiber optic tube is internally
8. The tubing of claim 1 wherein the fiber optic tube further contains an
9. The tubing of claim 1 wherein the fiber optic tube further contains a
10. A method of making an optical fiber equipped tubing comprising pumping
a fluid into a tubular; and deploying a fiber optic tube into the fluid
as pumped in the tubular, the tube having at least one optical fiber
disposed therein, wherein the flow of the pumped fluid propels the tube
along the tubular.
11. The method of claim 10, wherein the tubular is coiled tubing.
12. The method of claim 11 wherein the fluid is pumped into the coiled
tubing whilst the tubing is at least partially spooled on a reel.
13. The method of claim 11 wherein the fluid is pumped into the coiled
tubing whilst the tubing is deployed in a wellbore.
14. The method of claim 10, wherein the at least one optical fiber is
disposed in the fiber optic tube in an inert environment.
15. A method of communicating in a wellbore comprising deploying an
optical fiber equipped tubing into a wellbore, said tubing comprising a
fiber optic tube having at least one optical fiber disposed therein, the
fiber optic tubing being disposed in the tubing by fluid flow;
determining a property in the wellbore; and transmitting the determined
property via at least one of the optical fibers disposed in the fiber
16. The method of claim 15 wherein the property is determined by the least
one optical fiber.
17. The method of claim 15 further comprising disposing at least one
sensor in the wellbore, wherein at least one sensor determines the
18. The method of claim 15 wherein the determined property is transmitted
from the wellbore to the surface.
19. The method of claim 15 further comprising deploying an apparatus into
the wellbore and transmitting a signal to the apparatus via at least one
of the optical fibers disposed in the fiber optic tubing.
20. The method of claim 15 wherein the tubing is coiled tubing and the
step of deploying the tubing comprises unspooling the coiled tubing from
a reel into the wellbore.
21. The method of claim 20 further comprising the step of retrieving the
coiled tubing from the wellbore by spooling the coiled tubing onto the
22. The method of claim 21 wherein the apparatus is conveyed on the tubing
into the wellbore.
23. The method of claim 15, further comprising transmitting a signal from
the surface via at least one of the optical fibers.
24. The method of claim 15 wherein the transmission includes wireless
25. The method of claim 24 wherein said fiber optic tubing is disposed on
a reel and a wireless apparatus is mounted on the reel.
26. The method of claim 15 wherein more than one optical fiber is disposed
within the fiber optic tubing; and further comprising disposing more than
one sensor in the wellbore, wherein at least two of the sensors
determines a property, each determined property being transmitted on
different ones of the optical fibers within the fiber optic tubing.
CROSS-REFERENCE TO RELATED APPLICATIONS
 This application claims the benefit of U.S. Patent Application
60/564,934 filed Apr. 23, 2004.
FIELD OF THE INVENTION
 The present invention relates generally to oilfield operations and
more particularly methods and apparatus using fiber optics in coiled
tubing operations in a wellbore.
BACKGROUND OF THE INVENTION
 Coiled tubing operations are used commonly in the oilfield
industry, for example to pump fluids to a desired location in the
wellbore or to manipulate oilfield assemblies. One advantage of coiled
tubing is that it is provided on reels such that coiled tubing is
unreeled as it is inserted into a wellbore for a particular use and then
reeled or spooled back on the reel as it is extracted from the wellbore.
Coiled tubing reels may be conveniently stored or moved, and spooled
coiled tubing may be transported on a trailer, flat, or truck. The use of
coiled tubing as a different type of wellbore conveyance in wellbore
applications is increasing, resulting in an increasing need for downhole
apparatus and methods adapted for use with coiled tubing. Difficulties
inherent with using conventional downhole electromechanical apparatus
with coiled tubing include lack of power to the downhole apparatus and
the lack of telemetry from the downhole apparatus to the surface.
 It is known to use conventional wireline in coiled tubing to
provide communications between downhole operations and the surface,
including transmitting uphole data measured by a variety of wellbore
tools and transmitting commands downhole to effect a variety of
operations. Use of wireline cable in coiled tubing presents logistical
challenges, however, such as installation of the wireline cable in the
coiled tubing and the reduced fluid capacity of the coiled tubing owing
to the space taken by the wireline cable.
 The addition of wireline to a coiled tubing string significantly
increases the weight of a coiled tubing string. Installation of the
wireline into the coiled tubing string is difficult and the wireline is
prone to bunch into a "bird nest" within the coiled tubing. This, and the
relatively large outer diameter of wireline compared to the internal
diameter of coiled tubing, can undesirably obstruct the flow of fluids
through the coiled tubing, such flow through the coiled tubing frequently
being an integral part of the wellbore operation. Furthermore, some
fluids routinely pumped through coiled tubing, such as acid, cement and
proppant-bearing fracturing fluids, may have an adverse affect on the
integrity or performance of wireline cable. In addition, pumping fluid
down the coiled tubing can create a drag force on the wireline cable
owing to the frictional force between the fluid and the surface of the
 Installation of wireline or other electrical cable into coiled
tubing is difficult and cumbersome as its weight and bending stiffness
can contribute to a high friction force between the cable and the
interior of the coiled tubing. Methods for installing wireline in coiled
tubing are discussed in U.S. Pat. No. 5,573,225 and U.S. Pat. No.
5,699,996, each of which is incorporated herein by reference. The methods
described in each of these patents require a significant installation
apparatus at the surface to overcome the high frictional force between
the cable and the coiled tubing and to convey the cable into the coiled
tubing. The size of such an apparatus makes it unfeasible for use in some
operations, particularly in offshore operations.
 Use of optical fiber in various applications and operations is
increasing. Optical fiber provides many advantages over wireline when
used as a transmission medium such as small size, lightweight, large
bandwidth capacity, and high speed of transmission. A significant
challenge to using optical fibers in subterranean oilfield operations is
that the free hydrogen ions will cause darkening of the fiber at the
elevated temperatures that are commonly found in subterranean wells. The
use of optical fiber in wireline cable is known such as that described in
U.S. Pat. No 6,690,866 incorporated herein in its entirety by reference.
This patent teaches adding a hydrogen absorbing material or scavenging
gel to surround the optical fibers inside a first metal tube. This patent
also teaches that wireline cable disclosed therein requires significant
tensile strength and teaches that this strength can be obtained by
rigidly attaching the first metal tube to the interior of a second metal
tube. Both teachings can significantly add to the cost and weight of the
cable. In U.S. Pat. No. 6,557,630, incorporated herein in its entirety by
reference, a method of deploying a remote measurement apparatus in a
wellbore, the apparatus comprising a conduit in which a fiber optic
sensor and a fiber optic cable is disposed, the cable being propelled
along the conduit by fluid flow in a conduit. In GB Patent 2362909,
incorporated herein in its entirety by reference, a method is proposed
for placing sensors that relies upon first installing first a hollow
conduit into the coiled tubing and then subsequently pumping a single
fiber into that conduit. None of these patents teach or suggest
propelling an optically enabled conduit or cable into a tubular using
 Methods of installing optical fibers in tubulars often are directed
towards installing the optical fiber by pumping or dragging the fiber
into the tubular. In U.S. patent application Publication 2003/0172752,
incorporated herein by in its entirety by reference, methods for
installing an optical fiber through a conduit in a wellbore application
using a fluid, wherein a seal is provided between the optical fiber and
the conduit are described. To install an optical fiber in coiled tubing
using these methods would require 1) unreeling the coiled tubing, 2)
extending the coiled tubing (either in a wellbore or on the surface) and
3) deploying the optical fiber. Such a process is directed toward the
installation of a single optical fiber in a tubular; it is time consuming
and thus costly from an operational perspective. Furthermore, these
methods are directed toward installing a single optical fiber in a
tubular and are not conducive to installation of multiple fibers in a
tubular. In addition, these methods do not contemplate recovery or reuse
of the optical fiber.
 Use of multiple optic fibers however may provide advantages in many
situations over the use of a single optical fiber. Using multiple fibers
provides operational redundancy in the event that any particular fiber
becomes damaged or broken. Multiple fibers provide increased transmission
capacity over a single fiber and permit flexibility to segregate
different types of transmissions to different fibers. These advantages
may be particularly important in downhole applications where access is
limited, environmental conditions may be extreme, and dual-direction
(uphole and downhole) transmission is required. Using multiple optical
fibers also allows an individual optical fiber to be used for a specific
apparatus or sensor. This configuration is useful as some sensors, such
as Fabry-Perot devices, require a dedicated optical fiber. The
configuration also is useful for sensors with digital telemetry for which
a separate fiber may be required. Sensors using Fiber-Bragg grating for
example require a separate fiber from the fiber used for carrying digital
 For clarity, the term "duct" is used herein to identify a small
tube or hollow carrier that encompasses an optical fiber or fibers. The
term "optical fiber" refers to a fiber or a waveguide capable of
transmitting optical energy. The term "fiber optic tube" or "fiber optic
tether" is used to identify the combination of an optical fiber or
multiple optical fibers disposed in a duct. The term "fiber optic cable"
refers to a cable, wire, wireline or slickline that comprises one or more
optical fibers. "Tubular" and "tubing" refers to a conduit to any kind of
a round hollow apparatus in general, and in the area of oilfield
applications to casing, drill pipe, metal tube, or coiled tubing or other
 Various methods of manufacturing fiber optic tubes are known. Two
examples are laser welding, such as described in U.S. Pat. No. 4,852,790,
incorporated herein in its entirety, and tungsten inert gas welding (TIG)
such as described in U.S. Pat. No. 4,366,362, incorporated herein in its
entirety. Neither patent teaches or suggests the insertion of such tubes
into a spooled tubular by fluid flow.
 Therefore it may be seen that there exists a need for an apparatus,
methods of making, and methods of using fiber optic tubing disposed in a
tubular, and in particular, a need for such an apparatus and methods of
using in wellbore applications.
SUMMARY OF THE INVENTION
 The present invention comprises optical fiber equipped tubing and
methods of making and using the same. In a broad sense, the present
invention comprises an optical fiber equipped tubing comprising a fiber
optic tube deployed within a tubular. In many embodiments, the fiber
optic tube comprises a metallic material, and in some embodiments, the
fiber optic tube comprises more than one optical fiber. In many
embodiments, the fiber optic tube will be constructed in an inert
nitrogen environment so that the optical fiber or fibers therein are not
exposed to hydrogen or water during manufacturing. The tubular may be, in
particular, coiled tubing. In another embodiment, the present invention
relates to a method of making an optical fiber equipped tubing comprising
pumping a fluid into a tubular, deploying a fiber optic tube into the
fluid as pumped in the tubular, such that the flow of the pumped fluid
propels the tube along the tubular. When the tubular is coiled tubing,
the fiber optic tube may be deployed in the coiled tubing while the
tubing is spooled on a reel or while the tubing is deployed in a
wellbore. In another embodiment, the present invention provides a method
of communicating in a wellbore comprising deploying an optical fiber
equipped tubing having at least one optical fiber disposed therein, the
fiber optic tubing being disposed in the tubing by fluid flow;
determining a property in the wellbore; and transmitting the determined
property via at least one of the optical fibers disposed in the fiber
optic tubing. In some embodiments, the least one optical fiber senses the
information for transmitting. The method may also comprise disposing at
least one sensor in the wellbore, with the sensor determining the
property, and the sensed information transmitted to the surface via the
optical fiber in the fiber optic tube. In other embodiments, more than
one sensor may be disposed in the wellbore, each sensor transmitting its
sensed property over a different optical fiber in the coiled tubing. In
many embodiments the optical fiber or fibers will be attached to a
wireless communication device via a pressure bulkhead so that the optical
signal can readily transmitted to a surface computer while the coiled
tubing is being spooled into and out of the wellbore. In some
embodiments, the present invention provides an apparatus that is deployed
into the wellbore and in communication with the surface for receiving
signals or transmitting sensed information over the fiber optic tubing.
 While a particular embodiment and area of application is presented
as an exemplar, namely that of fiber optic equipped coiled tubing useful
for wellbore applications, the present invention is not limited to this
embodiment and is useful for any application wherein a fiber optic
equipped tubing is desirable.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 shows an embodiment of the apparatus of the present
 FIG. 2A is a cross-sectional view of an embodiment of the present
 FIG. 2B is a cross-sectional view of another embodiment of the
 FIG. 3 shows a typical configuration for coiled tubing operations.
 The present invention provides an optical fiber equipped tubing and
methods of making and using. The optical fiber equipped tubing of the
present invention comprises one or more fiber optic tubes disposed in a
tubular. An embodiment comprises a method for installing one or more
fiber optic tubes in reeled or spooled tubing such as coiled tubing.
Another embodiment provides a method for installing one or more fiber
optic tubes in coiled tubing deployed in a wellbore.
 Within the present invention is the unexpected recognition that a
fiber optic tube may be deployed a tubular by pumping the fiber optic
tube in a fluid without additional structure or protection. Methods of
pumping cables into a tubular are generally considered infeasible owning
to the inherent lack of compressional stiffness of cables. Furthermore,
the teachings of fiber optic cables suggest that a fiber optic tube needs
additional protection or structure for use in a wellbore environment.
Thus it is counter-intuitive to consider deploying a fiber optic tube
directly in a tubular without encapsulating the tube in additional
layers, providing a protective coating, or encompassing it in armor.
Similarly it is counter-intuitive to consider deploying a fiber optic
tube directly through fluid pumping.
 An advantage of the optical fiber equipped tubing of the present
invention is that the fiber optic tube possesses a certain level of
stiffness in compression, leading it to behave more similar mechanically
to coiled tubing than does cable or optical fiber alone. As such, use of
a fiber optic tube inside coiled tubing avoids many of the slack
management challenges presented by other transmission mechanism.
Furthermore, the cross-section of a fiber optic tube is relatively small
compared to the inner area within coiled tubing, thus limiting the
possible physical influence that the fiber optic tube could have on the
mechanical behavior of coiled tubing during deployment and retrieval. The
small relative diameter of the fiber optic tube combined with its light
weight make it more tolerant of pumping action, which is advantageous to
avoid the "bird-nesting" or bundling within the coiled tubing that
commonly occurs when installing wireline in coiled tubing. Moreover, as
slack management problems are avoided in the present invention, optical
fiber equipped coiled tubing may be deploying into and retrieved from a
wellbore at a quicker rate than coiled tubing with wireline.
 Referring now to FIG. 1, optical fiber equipped tubing 200 is shown
having tubular 105 within which is disposed fiber optic tube 211. In FIG.
1, fiber optic tube 211 is shown comprising duct 203 in which a single
optical fiber 201 is disposed. In other embodiments, more than one
optical fiber 201 may be provided within fiber optic duct 203. Surface
termination 301 or downhole termination 207 may be provided for both
physical and optical connections between optical fiber 201 and one or
more borehole apparatus or sensor 209. The optical fibers may be
multi-mode or single-mode. Types of borehole apparatus or sensor 209 may
include, for example, gauges, valves, sampling devices, temperature
sensors, pressure sensors, distributed temperature sensors, distributed
pressure sensors, flow-control devices, flow rate measurement devices,
oil/water/gas ratio measurement devices, scale detectors, actuators,
locks, release mechanisms, equipment sensors (e.g., vibration sensors),
sand detection sensors, water detection sensors, data recorders,
viscosity sensors, density sensors, bubble point sensors, composition
sensors, resistivity array devices and sensors, acoustic devices and
sensors, other telemetry devices, near infrared sensors, gamma ray
detectors, H.sub.2S detectors, CO.sub.2 detectors, downhole memory units,
downhole controllers, perforating devices, shape -charges, firing heads,
locators, and other devices.
 Referring to FIG. 2A, a cross-sectional view of the fiber optic
equipped tubing 200 of FIG. 1 is shown. Within tubing 105 is shown a
fiber optic tube 211 comprising optical fiber 201 located inside duct
203. Referring to FIG. 2B, another embodiment of the present invention is
shown in cross-sectional view in which fiber optic equipped tubing 200
has more than one fiber optic tube 211 is disposed in tubular 105 and in
which more than one optical fiber 201 is disposed within duct 203 in at
least one of the fiber optic tube 211.
 In fiber optic tube 211, an inert gas such as nitrogen may be used
to fill the space between the optical fiber or fibers 201 and the
interior of the duct 203. The fluid may be pressurized in some
embodiments to decrease the susceptibility of the fiber optic tube to
localized buckling. In a further embodiment, this laser-welding technique
is performed in an enclosed environment filled with an inert gas such as
nitrogen to avoid exposure to water or hydrogen during manufacturing,
thereby minimizing any hydrogen-induced darkening of the optical fibers
during oilfield operations. Using nitrogen to fill the space offers
advantages of lower cost and greater convenience over other techniques
that may require a buffer material, gel, or sealer in the space. In one
embodiment, the duct 203 is constructed by bending a metal strip around
the optical fiber or fibers 201 and then welding that strip to form an
encompassing duct using laser-welding techniques such as described in
U.S. Pat. No. 4,852,790. This gives a significant reduction in the cost
and weight of the resulting fiber optic tube 211 compared to other
optical cables previously known in the art. A small amount of gel
containing palladium or tantalum can optionally be inserted into either
end of the fiber optic tube to keep hydrogen ions away from the optical
fiber or fibers 201 during transportation of the optically enabled tubing
 Materials suitable for use in duct 203 in fiber optic tube 211 of
the present invention provide stiffness to the tube, are resistant to
fluids encountered in oilfield applications, and are rated to withstand
the high temperature and high pressure conditions found in some wellbore
environments. Typically duct 203 in a fiber optic tube 211 is a metallic
material, and in some embodiments, duct 203 comprises metal materials
such as Inconel.TM., stainless steel, or Hasetloy.TM.. While fiber optic
tubes manufactured by any method may be used in the present invention,
laser welded fiber optic tubes are preferred as the heat affected zone
generated by laser welding is normally less than that generated by other
methods such as TIG, thus reducing the possibility of damage to the
optical fiber during welding.
 While the dimensions of such fiber optic tubes are small (for
example the diameter of such products commercially available from K-Tube,
Inc of California, U.S.A. range from 0.5 mm to 3.5 mm), they have
sufficient inner void space to accommodate multiple optical fibers. The
small size of such fiber optic tubes is particularly useful in the
present invention as they do not significantly deduct from the capacity
of a tubular to accommodate fluids or create obstacles to other devices
or equipment to be deployed in or through the tubular.
 In some embodiments, fiber optic tube 211 comprises a duct 203 with
an outer diameter of 0.071 inches to 0.125 inches (3.175 mm) formed
around one or more optical fibers 201. In a preferred embodiment,
standard optical fibers are used, and duct 203 is no more than 0.020
inches (0.508 mm) thick. While the diameter of the optical fibers, the
protective tube, and the thickness of the protective tube given here are
exemplary, it is noteworthy that the inner diameter of the protective
tube can be larger than needed for a close packing of the optical fibers.
 In some embodiments of the present invention, fiber optic tube 211
may comprise multiple optical fibers may be disposed in a duct. In some
applications, a particular downhole apparatus may have its own designated
optical fiber, or each of a group of apparatuses may have their own
designated optical fiber within the fiber optic tube. In other
applications, a series of apparatus may use a single optical fiber.
 Referring now to FIG. 3, a typical configuration for wellbore
operations is shown in which coiled tubing 15 is suitable for use as
tubular 105 in the present invention. Surface handling equipment includes
an injector system 20 on supports 29 and coiled tubing reel assembly 10
on reel stand 12, flat, trailer, truck or other such device. The tubing
is deployed into or pulled out of the well using an injector head 19. The
equipment further includes a levelwind mechanism 13 for guiding coiled
tubing 15 on and off the reel 10. The coiled tubing 15 passes over tubing
guide arch 18 which provides a bending radius for moving the tubing into
a vertical orientation for injection through wellhead devices into the
wellbore. The tubing passes from tubing guide arch 18 into the injector
head 19 that grippingly engages the tubing and pushes it into the well. A
stripper assembly 21 under the injector maintains a dynamic and static
seal around the tubing to hold well pressure within the well as the
tubing passes into the wellhead devices under well pressure. The coiled
tubing then moves through a blowout preventor (BOP) stack 23, a flow tee
25 and wellhead master valve or tree valve 27. When coiled tubing 15
disposed on coiled tubing reel 10 is deployed into or retrieved from a
borehole 8, the coiled tubing reel 10 rotates.
 Fiber optic tube 211 may be inserted into the coiled tubing 15
through any variety of means. One embodiment comprises attaching a hose
to the reel 10 to the other end of which hose is attached a Y-joint. In
this configuration, fiber optic tube 211 may be introduced into one leg
of the Y and fluid pumped into the other leg. The drag force of the fluid
on fiber optic tube 211 then propels the tube down the hose and into the
reel 10. It has been found, that in preferred embodiments wherein the
outer diameter of the tether is less than 0.125 inches (3.175 mm), a pump
rate as low as 1-5 barrels per minute (2.65-13.25 liters per second) is
sufficient to propel the tether the full length of the coiled tubing even
while it is spooled on the reel.
 In the method and apparatus of the present invention, a fluid, such
as gas or water, may be used to propel a fiber optic tube 211 in a
tubular 105. Typically, fiber optic tube 211 is disposed in an
unrestrained manner in the pumped fluid. As the fluid is pumped into the
tubular, the fiber optic tube is permitted to self-locate in the tubular
without the use of external apparatus such as pigs for conveyance or
placement or restricting anchors. In particular embodiments, the fluid is
pumped and the fiber optic tube or tubes are deployed into coiled tubing
while it said coiled tubing is configured in a spooled state on a reel.
These embodiments provide logistical advantages as the fiber optic tube
or tubes can be deployed into the coiled tubing at a manufacturing plant
or other location remote from a wellsite. Thus the optical fiber equipped
tubing of the present invention may be transported and field-deployed as
a single apparatus, thereby reducing costs and simplifying operations.
 The optical fiber equipped tubing 200 of the present invention may
be used in conventional wellbore operations such as providing a
stimulation fluid to a subterranean formation through coiled tubing. One
advantage of the present invention is that fiber optic tube 211 tolerates
exposure to various well treatment fluids that may be pumped into the
coiled tubing; in particular, the fiber optic tube or tubes of the
present invention can withstand abrasion by proppant or sand and exposure
to corrosive fluids such as acids. Preferably the fiber optic tube is
configured as a round tube having a smooth outer diameter, this
configuration providing less opportunity for degradation and thus a
longer useful life for the fiber optic tube.
 The optical fiber equipped tubing of the present invention is
useful to perform a variety of wellbore operation including determining a
wellbore property and transmitting information from the wellbore.
Determining includes, by way of example and not limitation, sensing using
the optical fiber, sensing using a separate sensor, locating by a
downhole apparatus, and confirming a configuration by a downhole
apparatus. The optical fiber equipped tubing of the present invention may
further comprise sensors such as fiber optic temperature and pressure
sensors or electrical sensors coupled with electro-optical converters,
disposed in a wellbore and linked to the surface via a fiber optic tube
211. Wellbore conditions that are sensed may be transmitted via fiber
optic tube 211. Data sensed by electrical sensors may be converted to
analog or digital optical signals using pure digital or wavelength,
intensity or polarization modulation and then provided to the optical
fiber or fibers in fiber optic tube 211. Alternatively, optical fiber 201
may sense some properties directly, for example when optical fiber 201
serves as a distributed temperature sensor or when optical fiber 201
comprises Fiber-Bragg grating and directly senses strain, stress,
stretch, or pressure.
 The information from the sensors or the property information sensed
by optical fiber 201 may be communicated to the surface via fiber optic
tube 211. Similarly, signals or commands may be transmitted from the
surface to a downhole sensor or apparatus via fiber optic tube 201. In
one embodiment of this invention, the surface communication includes a
wireless telemetry link such as described in U.S. patent application Ser.
No. 10/926,522, which is incorporated herein in its entirety by
reference. In a further embodiment, the wireless telemetry apparatus may
be mounted to the reel so that the optical signals can be transmitted
while the reel is rotating without the need of a complicated optical
collector apparatus. In yet a further embodiment, the wireless apparatus
mounted to the reel may include additional optical connectors so that
surface optical cables can be attached when the reel is not rotating.
 It is to be appreciated that the embodiments of the invention
described herein are given by way of example only, and that modifications
and additional components can be provided to enhance the performance of
the apparatus without deviating from the overall nature of the invention
* * * * *