U.S. patent application number 14/437011 was filed with the patent office on 2016-01-28 for bottom hole assembly fiber optic shape sensing.
The applicant listed for this patent is HALLIBURTON ENERGY SERVICES, INC.. Invention is credited to Rahul Ramchandra GAIKWAD, Bhargav GAJJI, Ratish Suhas KADAM, Ankit PUROHIT.
Application Number | 20160024912 14/437011 |
Document ID | / |
Family ID | 53199507 |
Filed Date | 2016-01-28 |
United States Patent
Application |
20160024912 |
Kind Code |
A1 |
GAJJI; Bhargav ; et
al. |
January 28, 2016 |
BOTTOM HOLE ASSEMBLY FIBER OPTIC SHAPE SENSING
Abstract
One or more of these thermomechanical properties of an
underground formation can be monitored using a monitoring system.
An example monitoring system includes a signal processing module, a
visualization module, a signal source module, a signal detection
module, and one or more optical fibers. Each fiber includes one or
more sensors. The signal source module emits an optical signal into
one or more optical fibers. The one or more sensors along the fiber
interact with the optical signal, and alter the optical signal in
response to one or more detected thermomechanical properties. The
resulting optical signal is detected by the signal detection
module. Based on the detected optical signal, the signal processing
module determines the one or more thermomechanical properties that
were detected by the sensors. An operator can view and monitor the
detected thermomechanical properties using the visualization
module.
Inventors: |
GAJJI; Bhargav; (Pune,
IN) ; PUROHIT; Ankit; (Pune, IN) ; KADAM;
Ratish Suhas; (Pune, IN) ; GAIKWAD; Rahul
Ramchandra; (Pune, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HALLIBURTON ENERGY SERVICES, INC. |
Houston |
TX |
US |
|
|
Family ID: |
53199507 |
Appl. No.: |
14/437011 |
Filed: |
November 27, 2013 |
PCT Filed: |
November 27, 2013 |
PCT NO: |
PCT/US2013/072256 |
371 Date: |
April 20, 2015 |
Current U.S.
Class: |
340/854.7 |
Current CPC
Class: |
E21B 47/06 20130101;
E21B 47/135 20200501; E21B 47/007 20200501; E21B 17/00
20130101 |
International
Class: |
E21B 47/12 20060101
E21B047/12 |
Claims
1. A system, comprising: a bottom hole assembly (BHA) comprising
one or more drill collars and a drill bit connected to the one or
more drill collars; and a sensor system for monitoring the BHA,
comprising: one or more lengths of optical fiber helically wound
and extending along the one or more drill collars; a signal source
module arranged to emit an optical signal into the one or more
lengths of optical fiber; a signal detection module arranged to
detect the optical signal guided from the signal source module by
the one or more lengths of optical fiber; a signal processing
module in communication with the detection module; and an operator
interface in communication with the signal processing module,
wherein the signal processing module is programmed to, during
operation of the system: determine measurement information, based
on the detected optical signal, about a thermomechanical property
at multiple different locations on the one or more drill collars
while the BHA is used to bore a well, and send a signal to the
operator interface when measurement information exceeds a
threshold.
2. The system of claim 1, wherein the signal processing module is
further programmed to, during operation of the system, provide a
recommendation to the operator interface based on the measurement
information and the threshold.
3. The system of claim 1, wherein the thermomechanical property is
strain.
4. The system of claim 1, wherein the thermomechanical property is
temperature.
5. The system of claim 1, wherein the thermomechanical property is
pressure.
6. The system of claim 1, wherein the thermomechanical property is
a shape of the BHA.
7. The system of claim 1, wherein the BHA comprises at least two
drill collars connected to each other via a coupler; wherein the
coupler comprises a tube-shaped wall extending from a first end and
a second end and a channel between the first end and the second
end; wherein the one or more lengths of optical fiber pass through
the channel to continuously extend across the at least two drill
collars and the coupler.
8. The system of claim 1, wherein the one or more lengths of
optical fiber are disposed in one or more channels that extend
helically along the BHA.
9. The system of claim 8, further comprising a protective cladding
disposed in the one or more channels.
10. The system of claim 1, wherein the signal source module is
positioned between the one or more drill collars and the drill
bit.
11. The system of claim 1, further comprising a visualization
module in communication with the signal processing module, wherein
the visualization module is programmed to display the measurement
information and an indication of a location that corresponds to the
measurement information during operation of the system.
12. A method of monitoring a bottomhole assembly (BHA) comprising:
directing an optical signal into one or more lengths of optical
fiber helically wound around and extending along one or more drill
collars of the BHA; detecting the optical signal after the optical
signal is guided by the one or more lengths of optical fiber;
determining, based on the detected optical signal, measurement
information about a thermomechanical property at multiple different
locations on the one or more drill collars while the BHA is used to
bore a well; and sending a signal to an operator interface when the
measurement information exceeds a threshold.
13. The method of claim 12, further comprising providing a
recommendation to the user based on the measurement information and
the threshold.
14. The method of claim 12, wherein the thermomechanical property
is strain.
15. The method of claim 12, wherein the thermomechanical property
is temperature.
16. The method of claim 12, wherein the thermomechanical property
is pressure.
17. The method of claim 12, wherein the thermomechanical property
is a shape of the BHA.
18. The method of claim 12, further comprising displaying the
measurement information and an indication of the locations on the
BHA that corresponds to the measurement information.
19. A sensor system for monitoring a bottom hole assembly (BHA)
comprising: one or more lengths of optical fiber adapted to be
helically wound and extended along a BHA; a signal source module
arranged to emit an optical signal into the one or more lengths of
optical fiber; a signal detection module arranged to receive the
optical signal guided from the signal source module by the one or
more lengths of optical fiber; a signal processing module in
communication with the detection module; and an operator interface
in communication with the signal processing module, wherein the
signal processing module is programmed to, during operation of the
system: determine measurement information about a thermomechanical
property at multiple different locations on the BHA , and send a
signal to the operator interface when the measurement information
exceeds a threshold.
20. The system of claim 19, wherein the signal processing module is
further programmed to, during operation of the system, provide a
recommendation to the operator interface based on the measurement
information and the threshold.
21. The system of claim 19, wherein the thermomechanical property
is strain.
22. The system of claim 19, wherein the thermomechanical property
is temperature.
23. The system of claim 19, wherein the thermomechanical property
is pressure.
24. The system of claim 19, wherein the thermomechanical property
is a shape of the BHA.
25. The system of claim 19, wherein the signal source module is
positioned between a drill collar and a drill bit.
26. The system of claim 19, further comprising a visualization
module in communication with the signal processing module, wherein
the visualization module is programmed to display the measurement
information and an indication of the locations on the BHA that
corresponds to the measurement information during operation of the
system.
27. The system of claim 19, further comprising a coupler that
connects a first portion of the BHA to a second portion of the BHA;
wherein the coupler comprises a tube-shaped wall extending from a
first end and a second end and a channel between the first end and
the second end; wherein the one or more lengths of optical fiber
pass through the channel to continuously extend across the at least
two drill collars and the coupler.
Description
TECHNICAL FIELD
[0001] This invention relates to well construction, and more
particularly to monitoring properties of down-hole tools during the
construction of a well.
BACKGROUND
[0002] Wells are commonly used to access regions below the earth's
surface and to acquire materials from these regions, for instance
during the location and extraction of petroleum oil hydrocarbons
from an underground location. The construction of wells typically
includes drilling a borehole and constructing a pipe structure
within the borehole. Upon completion, the pipe structure provides
access to the underground locations and allows for the transport of
materials to the surface.
[0003] A variety of tools are conventionally used during well
construction and monitoring systems may be used to evaluate the
integrity of the tools while in use. For example, a drillstring
with a bottom hole assembly (BHA) can be used to drill a borehole,
and monitoring systems may be used to monitor parameters related to
the integrity of the BHA during drilling in order to ensure that
the BHA does not malfunction when subjected to extreme
environmental conditions (e.g., high temperatures and/or
pressures). These monitoring systems allow an operator to maintain
down-hole tools within safe operating limits.
DESCRIPTION OF DRAWINGS
[0004] FIG. 1 shows an example system for drilling a borehole
[0005] FIG. 2 is a schematic diagram of an example monitoring
system.
[0006] FIG. 3 is a schematic diagram of an example fiber with Bragg
gratings.
[0007] FIG. 4 shows light interference due to reflections in an
example fiber.
[0008] FIGS. 5A-D show different views of an example BHA and
fiber.
[0009] FIG. 6 shows another example BHA and fiber.
[0010] FIGS. 7A-C show different views of an example coupling
member.
[0011] FIG. 8A shows an example drill collar.
[0012] FIGS. 8B-C show example arrangements of drill collars and
coupling members. Like reference symbols in the various drawings
indicate like elements.
DETAILED DESCRIPTION
[0013] Well construction typically includes drilling a borehole and
constructing a pipe structure within the borehole. For instance, as
illustrated in FIG. 1, an operator can use a measure while drilling
(MWD) or logging while drilling (LWD) system 100 to drill a
borehole 102. The system 100 includes a surface control unit 110
and a drillstring 120.
[0014] Drillstring 120 includes a bottom hole assembly (BHA) 122
along its lower portion, and a drillpipe 128 that extends between
the BHA 122 and the surface control unit 110.
[0015] BHA 122 is a component that allows drillstring 120 to drill
through the surrounding medium 130, and provides the mechanical
force and structural support necessary to perform a drilling
operation. BHA 122 includes one or more components to provide this
functionality. For example, BHA 122 includes one or more drill bits
124. Drill bit 124 is positioned at the end of the BHA 122, and
includes one or more moveable drilling elements. During operation,
drill bit 124 crushes, scrapes, or cuts the surrounding medium 130
through pounding or rotational motion of its drilling elements.
[0016] BHA 122 also includes one or more drill collars 126. Drill
collars 126 are positioned between the drill bit 124 and the drill
pipe 128, and provide structural support for the drill bit 124 and
the other components of the BHA 122. Drill collars 126 are
generally of a tubular shape, and allow for the passage of fluids
from the drillpipe 128 to the drill bit 124 through an internal
channel. Drill collars 126 also apply weight on the drill bit 124,
and through their weight provide the downward force needed for
drill bit 124 to efficiently drill into the surrounding medium
130.
[0017] BHA 122 can also include other components that support the
operation of drillstring 120. For example, BHA 122 can include one
or more motors (not shown) to operate the drill bit and/or to
circulate drilling fluid.
[0018] BHA 122 is connected to the surface by drillpipe 128.
Drillpipe 128 provides a conduit for the transfer of power, fluid,
and/or communications signals between the BHA 122 and the surface
control unit 110, and also provides a connection through which the
surface control unit 100 to raise, lower, and rotate the BHA 122.
Using the surface control unit 110, an operator can direct the BHA
122 along a three dimensional path (e.g., variably drilling
perpendicular, horizontal, or at an intermediate angle with respect
to the surface), creating the borehole 102.
[0019] During the drilling process, components of system 100 are
commonly subjected to harsh environmental conditions, for instance
force, pressure, temperature, and other external stressors. When
the components of system 100 are exposed to these stressors, this
can result in changes to the temperature of the components, changes
in the shape of the components (e.g., distortions to the shape due
to pressure and/or heating), and/or changes to the strain, stress,
or pressure experienced by these components. In an example, the
surrounding medium 130 may apply a physical force to BHA 122, which
can increase the strain or stress experienced by BHA 122. In
another example, the surrounding medium 130 may be hotter or colder
than BHA 122, and can cause BHA 122 to heat up or cool down as it
traverses through the surrounding medium 130. In another example,
the surrounding medium 130 may apply a physical force to BHA 122,
which can cause the BHA 122 to deform. As BHA 122 can be damaged if
it experiences extreme strain, stress, pressure, and temperature,
or if the BHA 122 undergoes an extreme change in shape, an operator
uses a monitoring system to monitor the thermomechanical properties
of the BHA (e.g., the strain, stress, and pressure experienced by
the BHA 112, the shape of the BHA, or the temperature of the BHA)
during operation, in order to maintain BHA 122 within safe
operating limits. These operating limits typically define the
conditions under which the BHA 122 can be safely operated in order
to avoid damage or destruction. In general, operating limits can
differ between different BHAs, and can be determined based on
theoretical safety limits for a particular BHA, or can be
determined empirically based on previously obtained performance
information. In some implementations, the safe operating limits are
used to establish thresholds for one or more of the
thermomechanical properties, e.g., defining a maximum and/or
minimal safe value for each thermomechanical property. One or more
of these thermomechanical properties of the BHA 122 can be
monitored using a fiber optic monitoring system, allowing an
operator to stop or modify the operation of BHA 122 before
exceeding a damage threshold for the BHA. An example fiber optic
monitoring system 200 is shown schematically in FIG. 2. Monitoring
system 200 includes a signal processing module 202, a visualization
module 212, a signal source module 204, a signal detection module
206, and one or more optical fibers 208. Each fiber 208 includes
one or more sensors 210. Signal source module 204 produces an
optical signal and emits the optical signal into one or more
optical fibers 208. The one or more sensors 210 along fiber 208
interact with the optical signal, and alter the optical signal
based on the thermomechanical properties of the sensor 210. The
resulting optical signal is detected by signal detection module
206. Based on the detected optical signal, signal processing module
202 determines information regarding the one or more
thermomechanical properties of the sensors 210. This information is
displayed to an operator using the visualization module 212.
[0020] When optical fibers 208 are positioned against BHA 122, such
that the optical fibers 208 conform to the shape of the BHA 122 and
are subject to similar environmental stressors as the BHA 122, the
monitoring system 200 provides an estimate for the thermomechanical
properties of the BHA 122. Thus, an operator can use monitoring
system 200 to view and monitor information regarding the
thermomechanical properties of the BHA 122 during the operation of
the drillstring 120.
[0021] Signal source module 204 produces light and modulates the
light to produce an optical signal. Signal source module 204 is
coupled to fiber 208 so the produced optical signals are emitted
into the fiber 208. A signal source module can produce optical
signals of a single wavelength, or it can produce optical signals
composed of more than one wavelength. For example, in some
implementations, signal source module 204 includes one or more
optical transmitters that can produce a spectrum of optical signals
over a range of wavelengths. In some implementations, the optical
transmitters can produce optical signals with varying data
transmission rates. In some implementations, signal source module
204 is in communication with signal processing module 202, and the
operation of signal source module 204 can be controlled by signal
processing module 202.
[0022] Signal source module 204 includes an optical transmitter in
order to produce the optical signal. Example optical transmitters
include semiconductor devices such as light-emitting diodes (LEDs)
and laser diodes. In some implementations, an optical transmitter
includes an LED that is made in part, for example, of Indium
gallium arsenide phosphide or gallium arsenide.
[0023] Signal detection module 206 detects optical signals guided
by fibers 208 and allows system 200 to interpretation of the
optical signals. Signal detection module can detect optical signals
over a range of wavelengths, and over a range of data transmission
rates. In some implementations, signal source module 204 is in
communication with signal processing module 202, and information
collected by signal detection module 206 can be interpreted by
signal processing module 202.
[0024] Signal detection module 206 includes an optical receiver. An
optical receiver converts light into electricity using the
photoelectric effect, and allows for an electric system to detect
and interpret optical signals. Example optical receivers include
photodetectors or other optical-electrical converters. In some
implementations, a photodetector includes a semiconductor-based
photodiode that is made in part, for example, of Indium gallium
arsenide.
[0025] In some implementations, the functions of signal source
module 204 and signal detection module 206 can be combined. For
instance, a transceiver can be used to combine the optical signal
transmission functions of signal source module 204 and the optical
signal detection functions of signal detector module 206. In an
example, a transceiver includes both an optical transmitter and an
optical receiver. The optical transmitter and the optical receiver
can share common components, for instance common circuitry or a
common housing.
[0026] In some implementations, the monitoring system 200 can
measure one or more thermomechanical properties of the BHA 122
before, during, or after the drilling process. For example, the
monitoring system 200 can monitor pressure, stress, or strain
experienced by the BHA 122, the shape of the BHA 122, or the
temperature of the BHA 122 during a drilling operation. In some
implementations, the monitoring system can gather information about
one or more of these properties in real-time or near-real-time, and
displays this information to an operator (e.g., an operator using
surface control unit 110), such that an operator is able to
continuously monitor the operation of the drillstring 120. In some
implementations, the monitoring system can retain the information,
so that it can be reviewed at a later time.
[0027] In some implementations, the monitoring system 200 can
determine spatial information related to the thermomechanical
properties. That is, the monitoring system 200 can measure a
thermomechanical property, and determine the location, direction,
and/or orientation of the measurement relative to the drillstring
120. As an example, monitoring system 200 can measure a localized
strain experienced by a BHA 122, and can further identify the
location on the BHA 122 that experienced the localized strain and
the orientation of the strain measurement (e.g., whether the strain
was measured from a sensor located on the top of BHA 122, the
bottom of BHA 122, the side of BHA 122, and so forth).
[0028] In some implementations, the monitoring system 200 can
monitor the shape of one or more components of a drill string 120.
For instance, monitoring system 200 can detect the shape of the BHA
122 (e.g., the one of more drill collars 126) and/or the drillpipe
128. This allows an operator to observe the shape and relative
orientation of the components of drillstring 120, so that the
operator can determine if the components of drillstring 120 are
positioned and arranged as expected. This also allows the operator
to determine if one or more components are bending or buckling
during the drilling operation, and allows the operator to determine
if the drillstring 120 is bending or buckling in a manner that
could damage or disable the drillstring 120. In this manner, the
operator can use the monitoring system 200 to safely direct the
operation of the drillstring 120.
[0029] Visualization module 212 displays information pertaining to
monitoring system 200 to the operator through an operator
interface. The displayed information can include, for example, one
or more thermomechanical properties measured by monitoring system
200, characteristics of monitoring system 200 (e.g., the
operational status of monitoring system 200 and/or one or more of
its components, or the operating parameters of monitoring system
200), or other information related to the operation of system 200.
Information can be displayed either as textual information,
graphical information, or a combination of textual and graphical
information. For example, an operator interface can display
information in the form of tables (e.g., a table of
thermomechanical properties), charts (e.g., a chart of
thermomechanical properties over time), or images (e.g., an image
illustrating locational information about one or more
thermomechanical properties, or an image illustrating the shape of
the components of the drillstring).
[0030] In some implementations, signal processing module 202 sends
a signal to the operator interface in order to alert the operator
when a measured property crosses a particular threshold, for
example a known safety threshold. For instance, if the measured
property has not crossed the threshold, the signal processing
module 202 sends an appropriate signal to the operator interface,
and the operator interface provides an indication that the BHA 122
is operating safely. If the measured property is close to crossing
the threshold, the signal processing module 202 sends an
appropriate signal to the operator interface, and the operator
interface provides an indication that the BHA 122 is approaching
its safety limits. If the measured property crosses the threshold,
the signal processing module 202 sends an appropriate signal to the
operator interface, and the operator interface provides an
indication that the BHA 122 has exceeded its safety limits. As an
example, if the measured shape of the BHA 122 cross a particular
threshold (e.g., if its curvature exceeds a particular curvature
threshold), the signal processing module 202 sends a signal to the
operator interface, and the operator interface provides an
indication that the shape of the BHA 122 has exceeded its safety
limits.
[0031] In some implementations, the signal processing module 202
provides recommendations to the operator interface that assist the
user in maintaining BHA 122 within safe operating limits. For
example, if a measured property is close to crossing a safety
threshold, the signal processing module 202 provides
recommendations to the operator interface on how to avoid unsafe
operation (e.g., recommendations to retract the drillstring 120,
cease or slow down drilling operations, or change other aspects of
the operation of drillstring 120). If the measured property crosses
the safety threshold, the signal processing module 202 provides
recommendations to the operator interface on how to avoid further
unsafe operation. These recommendations can be displayed to the
user for review.
[0032] The signal processing module 202 and operator interface can
provide safety indications and recommendations based on the most
recently obtained measurement, or based on a historical trend of
multiple measurements. In an example, in some implementations, the
signal processing module 202 and the operator interface provide an
indication that the BHA 122 is returning to safe operating limits
when it determines that a property is descending at a rate that
would bring it below the threshold within a particular period of
time, and provide a recommendation to continue the current
operation. In another example, signal processing module 202 and the
operator interface provide an indication that the BHA 122 is
operating in an unsafe manner if the signal processing module 202
determines that a property is ascending at a rate that will exceed
the threshold within a particular period of time, and provide a
recommendation to cease the current operation.
[0033] In some implementations, the system can automatically (i.e.,
without further input from an operator) shut down or otherwise
modify the operation of the BHA when a safety threshold is
exceeded.
[0034] Visualization module 212 can include one or more display
devices for representing information to an operator, for instance
status indicators (e.g., lights that illuminate to indicate
information), or a video display, such as a flat panel display
(e.g., a liquid crystal display (LCD) monitor). In some
implementations, visualization module 212 is located at surface
control system 110, so that an operator can view information
pertaining to monitoring system 200 during the operation of
drillstring 120.
[0035] Monitoring system 200 can detect thermomechanical properties
in various ways. For instance, sensors 210 may be Fiber Bragg
Grating (FGB) sensors that can provide measurements at one or more
discrete points along fiber 208. Referring to FIG. 3, an example
FGB sensor 210 includes multiple Bragg gratings 302 positioned with
a period of X, (i.e., the wavelength of the FBG sensor) along the
length of a single-mode optical fiber 208 (i.e., an optical fiber
that carries a single ray of light).
[0036] In some implementations, fiber 208 include a smaller inner
core (e.g., about 4 to 9 .mu.m in diameter) and an outer part
(i.e., a cladding) of a larger diameter (e.g., about 125 .mu.m in
diameter). The inner core can be made, for instance, of glass
(SiO.sub.2), and has a high refraction index caused by high
elemental doping, for instance Germanium doping. The difference in
refraction indexes between the inner core and the cladding causes
light to propagate only inside the inner core.
[0037] Each Bragg grating 302 has a region with a refractive index
that differs from that of the fiber 208, and as a result, reflects
light of a particular bandwidth at its fringe (i.e., the interface
between the grating 302 and the fiber 208). For example, referring
to FIG. 3, light emitted by signal source module 204 having
wavelengths of .lamda..sub.a and .lamda..sub.b are not reflected,
and are guided by fiber 208 to signal detection module 206.
However, a portion of light of wavelength .lamda..sub.c is
reflected by the fringes of each Bragg grating 302 back to signal
source module 204, while a portion of the light continues onto
signal detection module 206. The reflection factor (i.e., the
fraction of light that is reflected by each Bragg grating fringe)
can be relatively small, for example between 0.001% and 0.1%.
[0038] In addition, because each Bragg grating 302 reflects light
with different phase shifts, interference occurs and most of the
reflected light is canceled. However, the reflections with equal
phase shift accumulate to a strong reflection peak. This is
illustrated in FIG. 4. The top of FIG. 4 shows a fiber 208 with a
10-fringe Bragg grating 402. Light enters from the left side of the
fiber 208. Below, there are three light beams 404a-c with different
wavelengths. The upper light beam 404a has precisely the wavelength
.lamda..sub.0 of the grating period and all single fringe
reflections are reflected in phase, and therefore add up to a
reflected energy level 406a of ten times a single fringe
reflection. The next light beam 406b has a 10% higher frequency so
that 11 light periods .lamda..sub.0+1 have the length of the 10
grid periods .lamda..sub.0. All single fringe reflections therefore
have different phases and cancel, resulting in a reflected energy
level 406b of zero. A similar cancelling effect occurs with the
lowest light beam 404c, which has a 10% lower frequency so that 9
light periods .lamda..sub.0-1 have the length of 10 grid periods
.lamda..sub.0, and results in a reflected energy level 406c of
zero.
[0039] As such, the bandwidth of reflection and the resulting
reflected energy function is dependent on the wavelength .lamda. of
the FBG sensor. This wavelength .lamda. is dependent on various
thermomechanical properties experienced by the fiber 208. For
instance, strain and temperature is related to the wavelength
.lamda. according to the following equation:
.DELTA..lamda. .lamda. 0 = k * + .alpha. .delta. * .DELTA. T ,
##EQU00001##
where
.DELTA..lamda.=wavelength shift,
.lamda..sub.0=base wavelength start,
k=1-p,
p=photo-elastic coefficient,
k=gauge factor,
.DELTA.T=temperature change in K,
.alpha..sub..delta.=change of the refraction index,
.alpha. .delta. = .delta. n / n .delta. T . ##EQU00002##
In an example implementation, the photo-elastic coefficient p is
0.22, the gauge factor k is 0.78, and the change of the refraction
index .alpha..sub..delta.is
5 - 8 * 10 - 6 K . ##EQU00003##
[0040] The first expression (k*.epsilon.) of the equation describes
the strain impact caused by force (.epsilon..sub.m) and temperature
(.epsilon..sub.T). The second expression
(.alpha..sub..delta.*.DELTA.T) describes the change of the glass
refraction index n caused only by temperature. [0041] Further,
[0041] .epsilon.=.epsilon..sub.m+.epsilon..sub.T,
where
.epsilon..sub.m=mechanically caused strain,
.epsilon..sub.T=temperature caused strain,
.epsilon..sub.T=.alpha..sub.sp*.DELTA.T,
.alpha..sub.sp=expansion coefficient per K of the specimen.
This yields the following equations which describe the behavior of
an FBG sensor under the impact of both strain and temperature:
.DELTA..lamda. .lamda. 0 = ( 1 - p ) * ( m + .alpha. sp * .DELTA. T
) + .delta. n / n .delta. T * .DELTA. T , and ##EQU00004##
.DELTA..lamda. .lamda. 0 = k * ( m + .alpha. sp * .DELTA. T ) +
.alpha. .delta. * .DELTA. T . ##EQU00004.2##
[0042] In the case of a pure temperature sensor, a Bragg grating is
not stressed. The FBG sensor .DELTA..lamda./.lamda..sub.0 signal
then changes only with temperature. In this case, .alpha. is the
thermal expansion coefficient .alpha. is the termal expansion
coefficient .alpha..sub.glass of the fiber.
.DELTA..lamda. .lamda. 0 = ( 1 - p ) * ( .alpha. glass * .DELTA. T
) + .delta. n / n .delta. T * .DELTA. T , or ##EQU00005##
.delta..lamda. .lamda. 0 = ( k * .alpha. glass + .alpha. .delta. )
* .DELTA. T , ##EQU00005.2##
yielding the equation for a temperature-measuring FBGS:
.DELTA. T = 1 k * .alpha. glass + .alpha. .delta. * .DELTA..lamda.
.lamda. 0 . ##EQU00006##
[0043] The expansion coefficient .alpha..sub.glass of the fiber is
very low. For example, in an example implementation,
.alpha..sub.glass=0.55*10.sup.-6/K. The biggest impact results from
the temperature dependent change of the refraction index
.alpha..sub..delta.. When the fiber is fixed to a specimen, the FBG
sensor signal .DELTA..lamda./.lamda..sub.0 changes with the strain
(.epsilon..sub.m+.epsilon..sub.T) of the specimen and therefore the
thermal expansion coefficient is .alpha..sub.sp then and not
.alpha..sub.glass. Thus,
.DELTA..lamda. .lamda. 0 = k * m + ( k * .alpha. sp + .alpha.
.delta. ) * .DELTA. T , ##EQU00007##
yielding the equation for a strain-measuring FBG sensor:
m = 1 k * .DELTA..lamda. .lamda. 0 - ( .alpha. sp + .alpha. .delta.
k ) * .DELTA. T . ##EQU00008##
When the FBG sensor is fixed to the specimen on a region without
mechanical strain (.epsilon..sub.m=0), it works as temperature
compensation FBG sensor. Its signal calculates according to the
equations:
.DELTA..lamda. .lamda. 0 = ( k * .alpha. sp + .alpha. .delta. ) *
.DELTA. T , .DELTA. T = 1 k * .alpha. sp + .alpha. .delta. *
.DELTA..lamda. .lamda. 0 . ##EQU00009##
As such, the FGB sensor can determine information the strain and
temperature at discrete points along the fiber based on
measurements of the reflected sensor signal, using the above
relationships. Based on this information, additional information
can also be determined regarding the stress at discrete points
along the fiber. For instance, for materials with a known
stress-strain relationship, information regarding stress can be
determined as a function of the measured strain.
[0044] In some implementations, one or more wavelengths of light
may be guided through fiber 208, and the FGB sensor can interact
with each wavelength of light differently. In some implementations,
an optical signal that includes a spectrum of light is guided
through fiber 208, and the reflection spectrum is analyzed to
measure multiple FBG signals simultaneously. The reflection
spectrum can be analyzed, for example, using an interferometer to
separate the spectrum according to the wavelengths of its component
light rays.
[0045] In some implementations, FBG sensors can be used to
determine the shape of the fiber 208. For example, in some
implementations, a fiber 208 includes at two or more cores spaced
apart, where each core includes multiple sensors 210. As described
above, the sensors 210 of each core of the fiber 208 can be used to
determine strain information regarding the fiber 208. If the cores
are mounted such that they are non-coplanar, when fiber 208 is
bent, each core will experience a different strain. The difference
in strain between each core can be used to determine curvature
along discrete points along fiber and can be used to determine the
shape of fiber 208. By detecting strain along multiple non-coplanar
cores, a multi-dimension differential strain vector can be
determined. Using this differential strain vector, information
about the curvature and shape of fiber 208 can be determined. In an
example implementation, a fiber 208 with three non-coplanar cores
can be used to determine three-dimensional shape information about
the fiber 208. In some implementations, multiple fibers 208, each
with single cores, can be used instead of a single fiber 208 with
multiple cores. In some implementations, shape sensing can be
implemented using commercially-available tools, such as using
Optical Distributed Sensor Interrogator, Distributed Sensing
System, or Optical Backscatter Reflectometer line of products by
Luna Innovations Incorporated (Roanoke, Va.).
[0046] In some implementations, the monitoring system 200 can
determine spatial information related to each of the measurements.
That is, the monitoring system 200 can measure a thermomechanical
property, and determine the location, direction, and/or orientation
of the measurement relative to the drillstring 120. This can be
implemented in various ways. For instance, in some implementations,
monitoring system 200 can provide measurements from discrete points
of fiber 208. If the spatial arrangement of fiber 208 is known,
monitoring system 200 can use this information to determine the
specific position and/or orientation of the measurement's source.
As an example, if fiber 208 is known to wrap helically around a BHA
122, a measurement from a discrete point of fiber 208 can be
correlated to a specific point along this helix. This point can be
used to determine the location, direction, and orientation of the
measurement relative to the drillstring 120. In some
implementations, spatial information can be determined, in part,
based on the measured shape of fiber 208.
[0047] In some implementations, instead of FBG sensors, monitoring
system 200 can include other types of sensors 210, such as
micro-bend sensors, interferometric sensors, polarimeter sensors,
or combinations or two or more different types of sensors. For
instance, sensors 210 may be micro-bend sensors. In an example
implementation, when a fiber 208 is subjected to a small
deformation (i.e., a "micro-bend"), light rays in the inner core of
the fiber can exceed a critical angle of the inner core. This
causes a redistribution of the energy between the inner core and
the cladding modes. The guided higher order inner core modes couple
to the cladding modes, causing the light propagating in the fiber
to decrease. This mode coupling can be achieved, for instance, by
placing the fiber in contact with a series of periodically
positioned deformers. Hence, micro-bending causes the light
intensity to decrease due to light leakage into the cladding. By
monitoring and correlating the loss of light intensity, different
types of micro-bend sensors can be designed which can give the
measurement of the forces acting on them. In some implementations,
micro end sensors are easier to implement than other types of fiber
optic sensors, and can potentially be implemented at a lower
cost.
[0048] Fiber 208 and its sensors 210 may be positioned on one or
more components of system 100 in order to monitor the
thermomechanical properties experienced by those components. For
example, referring to FIG. 5A, fiber 208 may be positioned on the
drill collar 126 of BHA 122. Fiber 208 can be wound around drill
collar 126, for example in a helical pattern, such that it
continuously wraps around the circumferential periphery of drill
collar 126 as it extends the length of drill collar 126. This
allows monitoring system 200 to gather information continuously
along the axial length of drill collar 126, as well as continuously
in radial directions surrounding drill collar 126. Fiber 208
conforms to the shape of drill collar 126, and is fixed with
respect to the channel, such that any deformation of the drill
collar 126 results in a corresponding deformation of the fiber
208.
[0049] Fiber 208 can be positioned within a channel 502, such that
it is recessed from the outer periphery of the drill collar 126.
This is illustrated in FIG. 5B, which shows the dotted region of
FIG. 5A in greater detail. Like fiber 208, channel 502 can extend
the length of drill collar 126, and may wind around drill collar
126 helically.
[0050] In some implementations, fiber 208 is protected by a
cladding 504. For example, referring to FIGS. 5C-D, a cladding 504
surrounds fiber 208 within channel 502, protects fiber 208 from the
external environment, and ensures that fiber 208 is fixed with
respect to the drill collar 126. Cladding 504 can be added by any
process that adds a hard material over fiber 208, for instance
welding or plasma transferred arc (PTA) techniques.
[0051] Fiber 208 can connect to the other components of monitoring
system 200 and system 100 in various ways. For instance, referring
to FIG. 6, an example BHA 122 can include one or more drill collars
126 with a fiber 208 positioned within a channel 502 that extends
along the lengths of drill collars 126. A drill collar 126 is
connected on one axial end to a source sub 602, which houses the
signal source modules 204 (not shown) of system 200. Source sub 602
is connected to drill collar 126 along the lower portion of BHA 122
and provides a connection point between fiber 208 and the signal
source modules 204, such that an optical signal produced by the
signal source modules 204 is guided along the length of fiber 208
towards the upper end of BHA 122.
[0052] The signal detection modules 206 can be positioned on the
opposite end as the signal source modules 204, for example in the
MWD/LWD collars 604, on another portion of drillstring 120, or on
the surface (e.g., at surface control unit 110). Signal source
modules 204 are connected to fiber 208 at the opposite end as
signal source modules 204, and can provide information on the
reflection behavior of the optical signals as it passes through
fiber 208.
[0053] Signal processing module 202 can be placed in various
locations, for instance along drillstring 120, or at the surface
(e.g., at surface control unit 110). Signal processing module 202
is connected to signal source modules 204 and signal detection
modules 206 through one or more signal transmitters (e.g., wired or
wireless signal transmission connections). Signal processing module
202 controls the operation of signal source modules 204 and signal
detection modules 206, and processes the optical signal in order to
determine information regarding one or more properties and its
associated location and orientation along fiber 208.
[0054] As shown in FIG. 6, two or more components of drillstring
120 (e.g., BHA 122) can be connected by a coupling member 606.
Coupling member 606 provides a secure connection between two
adjacent components, and allows fiber 208 to pass between the two
components. For example, MWD/LWD collar 604 can be connected to a
drill collar 126a using a coupling member 606a. In another example,
two drill collars 126a-b can be connected using a coupling member
606b. In yet another example, a drill collar 126b and the source
sub 602 can be connected using a coupling member 606c. In each of
these examples, fiber 208 passes continuously across the two
connected components.
[0055] Coupling member 606 is show in greater detail in FIGS. 7A-C.
Coupling member 606 is generally tubular and includes a protrusion
702 at one axial end, and a recess 704 at the other axial end.
Protrusion 702 and recess 704 allow coupling member 606 to be
securely inserted into a component with a corresponding recess or
protrusion, respectively. Coupling member 606 includes two channels
706 and 708. Channel 706 is positioned at the axial center of
coupling member 606, and allows the flow of material between two
interconnected components. For instance, in some implementations,
when coupling member 606b is connected between two drill collars
126a-b, channel 706 allows for the flow of drill fluid between each
of the drill collars 126a-b. Channel 708 is positioned along a
radial periphery of coupling member 606, and allows a fiber 208 to
pass between two interconnected components. For instance, in some
implementations, when coupling member 606b is connected between two
drill collars 126a-b, channel 708 allows for a fiber 208 to pass
between the channel 502 of a first drill collar 126a to the channel
502 of a second drill collar 126b. Coupling member 606 can also
include one or more sleeves 710, which can slide over an ends of
coupling member 606 in order to secure the connection point between
coupling member 606 and a connected component.
[0056] To ensure that a fiber 208 can pass continuously between two
interconnected components, one or more components can include one
or more portions with reduced outer diameters. Referring to FIG.
8A, an example drill collar 126 includes an end portion 802 with a
protrusion 804 that corresponds to the recess 704 of a coupling
member 606. Drill collar 126 also includes a portion 806 with a
reduced outer diameter relative to that of the main extension 808
of the drill collar 126. As shown in FIG. 8B, when protrusion 804
of drill collar 126 is fit into recess 704 of coupling member 606,
the portion 806 remains outside of coupling member 606. This
portion 806 allows for a fiber 208 to smoothly pass from channel
502 of drill collar 126 into channel 708 of drill collar 606, such
that it can continuously pass between the two components. As shown
as FIG. 8C, a coupling member 606 can be used in this manner to
connect two components together (e.g., two drill collars 126a-b),
such that fiber 208 passes continuously between each of the
connected components.
[0057] In some implementations, more than one fiber 208 may be
used. For instance, a drill collar 126 can include two or more
fibers 208 wrapped along its periphery. The fibers can be
positioned such that they are equally spaced from each other (e.g.,
positioned so that they maintain a constant distance from each
other along the drill collar 126), or they can be positioned in
other arrangements. For example, in some implementations, fibers
208 can be positioned such that at one or more locations, fibers
208 are closer to each other than in one or more other locations.
In some implementations, one or more fibers 208 are bundled
together, such that they each run in parallel in close proximity
along their length of extension.
[0058] In some implementations, fiber 208 may be positioned in
different arrangements. For example, in some implementations, fiber
208 may wrapped with a varying pitch, such that it wraps more
frequently around certain portions relative to other portions. In
some implementations, instead of a helical pattern, fiber 208 may
be positioned such that it runs substantially parallel to the axial
length of the drill collar 126. In some implementations, fiber 208
can be positioned according to any other arbitrary arrangement. In
some implementations, fiber 208 can include combinations of two or
more of these arrangements. For example, in some implementations, a
fiber 208 can have a portion with a constant helical pattern, a
portion with a parallel pattern, and a portion with a varying
helical pattern.
[0059] In some implementations, signal source module 204 and signal
detection module 206 may be placed on the same end of fiber 208,
instead of on opposite ends. The signal detection module 206 may
include an interferometer to analyze the spectrum of the reflected
wavelengths of light in order to determine one or more
thermomechanical properties.
[0060] The techniques described above can be implemented in digital
electronic circuitry, or in computer software, firmware, or
hardware, including the structures disclosed in this specification
and their structural equivalents, or in combinations of one or more
of them. For example, signal processing module 202 can include an
electronic processor, and the electronic processor can be used to
process optical signals detected by signal detection module 206 in
order to determine one or more thermomechanical properties, as
described above. In another example, the electronic processor can
be used to control the operation of signal source module 204,
signal detection module 206, and/or visualization module 212.
[0061] The term "electronic processor" encompasses all kinds of
apparatus, devices, and machines for processing data, including by
way of example a programmable processor, a computer, a system on a
chip, or multiple ones, or combinations, of the foregoing. The
apparatus can include special purpose logic circuitry, e.g., an
FPGA (field programmable gate array) or an ASIC (application
specific integrated circuit). The apparatus can also include, in
addition to hardware, code that creates an execution environment
for the computer program in question, e.g., code that constitutes
processor firmware, a protocol stack, a database management system,
an operating system, a cross-platform runtime environment, a
virtual machine, or a combination of one or more of them. The
apparatus and execution environment can realize various different
computing model infrastructures, such as web services, distributed
computing and grid computing infrastructures.
[0062] Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processors of any kind of
digital computer. Generally, a processor will receive instructions
and data from a read only memory or a random access memory or both.
The essential elements of a computer are a processor for performing
actions in accordance with instructions and one or more memory
devices for storing instructions and data. Generally, a computer
will also include, or be operatively coupled to receive data from
or transfer data to, or both, one or more mass storage devices for
storing data, e.g., magnetic, magneto optical disks, or optical
disks. However, a computer need not have such devices. Moreover, a
computer can be embedded in another device, e.g., a mobile
telephone, a personal digital assistant (PDA), a mobile audio or
video player, a game console, a Global Positioning System (GPS)
receiver, or a portable storage device (e.g., a universal serial
bus (USB) flash drive), to name just a few. Devices suitable for
storing computer program instructions and data include all forms of
non-volatile memory, media and memory devices, including by way of
example semiconductor memory devices, e.g., EPROM, EEPROM, and
flash memory devices; magnetic disks, e.g., internal hard disks or
removable disks; magneto optical disks; and CD ROM and DVD-ROM
disks. The processor and the memory can be supplemented by, or
incorporated in, special purpose logic circuitry.
[0063] In general, in an aspect, a system includes a bottom hole
assembly (BHA) that includes one or more drill collars and a drill
bit connected to the one or more drill collars. The system also
includes a sensor system for monitoring the BHA. The sensor system
includes one or more lengths of optical fiber helically wound and
extending along the one or more drill collars, a signal source
module arranged to emit an optical signal into the one or more
lengths of optical fiber, a signal detection module arranged to
detect the optical signal guided from the signal source module by
the one or more lengths of optical fiber, a signal processing
module in communication with the detection module, and an operator
interface in communication with the signal processing module. The
signal processing module is programmed to, during operation of the
system, determine measurement information, based on the detected
optical signal, about a thermomechanical property at multiple
different locations on the one or more drill collars while the BHA
is used to bore a well. The signal processing module is also
programmed to, during operation of the system, send a signal to the
operator interface when measurement information exceeds a
threshold.
[0064] Implementations of this aspect may include one or more of
the following features. The signal processing module may be further
programmed to, during operation of the system, provide a
recommendation to the operator interface based on the measurement
information and the threshold. The thermomechanical property may be
strain. The thermomechanical property may be temperature. The
thermomechanical property may be pressure. The thermomechanical
property may be a shape of the BHA. The BHA may include at least
two drill collars connected to each other via a coupler, where the
coupler includes a tube-shaped wall extending from a first end and
a second end and a channel between the first end and the second
end, and where the one or more lengths of optical fiber pass
through the channel to continuously extend across the at least two
drill collars and the coupler. The one or more lengths of optical
fiber may be disposed in one or more channels that extend helically
along the BHA. The system may further include a protective cladding
disposed in the one or more channels. The signal source module may
be positioned between the one or more drill collars and the drill
bit. The system may further include a visualization module in
communication with the signal processing module, where the
visualization module is programmed to display the measurement
information and an indication of a location that corresponds to the
measurement information during operation of the system.
[0065] In general, in another aspect, a method of monitoring a
bottomhole assembly (BHA) includes directing an optical signal into
one or more lengths of optical fiber helically wound around and
extending along one or more drill collars of the BHA, detecting the
optical signal after the optical signal is guided by the one or
more lengths of optical fiber, determining, based on the detected
optical signal, measurement information about a thermomechanical
property at multiple different locations on the one or more drill
collars while the BHA is used to bore a well, and sending a signal
to an operator interface when the measurement information exceeds a
threshold.
[0066] Implementations of this aspect may include one or more of
the following features. The method can further include providing a
recommendation to the user based on the measurement information and
the threshold. The thermomechanical property may be strain. The
thermomechanical property may be temperature. The thermomechanical
property may be pressure. The thermomechanical property may be a
shape of the BHA. The method may further include displaying the
measurement information and an indication of the locations on the
BHA that corresponds to the measurement information.
[0067] In general, in another aspect, a sensor system for
monitoring a bottom hole assembly (BHA) includes one or more
lengths of optical fiber adapted to be helically wound and extended
along a BHA, a signal source module arranged to emit an optical
signal into the one or more lengths of optical fiber, a signal
detection module arranged to receive the optical signal guided from
the signal source module by the one or more lengths of optical
fiber, a signal processing module in communication with the
detection module, and an operator interface in communication with
the signal processing module. The signal processing module is
programmed to, during operation of the system, determine
measurement information about a thermomechanical property at
multiple different locations on the BHA , and send a signal to the
operator interface when the measurement information exceeds a
threshold.
[0068] Implementations of this aspect may include one or more of
the following features. The signal processing module may be further
programmed to, during operation of the system, provide a
recommendation to the operator interface based on the measurement
information and the threshold. The thermomechanical property may be
strain. The thermomechanical property may be temperature. The
thermomechanical property may be pressure. The thermomechanical
property may be a shape of the BHA. The signal source module may be
positioned between a drill collar and a drill bit. The system may
further include a visualization module in communication with the
signal processing module, where the visualization module is
programmed to display the measurement information and an indication
of the locations on the BHA that corresponds to the measurement
information during operation of the system. The system may further
include a coupler that connects a first portion of the BHA to a
second portion of the BHA, where the coupler includes a tube-shaped
wall extending from a first end and a second end and a channel
between the first end and the second end, and where the one or more
lengths of optical fiber pass through the channel to continuously
extend across the at least two drill collars and the coupler.
[0069] A number of embodiments have been described. Other
embodiments are within the scope of the following claims.
* * * * *