U.S. patent application number 15/554615 was filed with the patent office on 2018-02-22 for wireless run-in position sensing systems methods.
This patent application is currently assigned to Halliburton Energy Services, Inc.. The applicant listed for this patent is Halliburton Energy Services, Inc.. Invention is credited to Eric M. Conzemius, Nicole E. Esposito, Scott L. Miller, Gregory T. Werkheiser, Reid E. Zevenbergen.
Application Number | 20180051554 15/554615 |
Document ID | / |
Family ID | 57199304 |
Filed Date | 2018-02-22 |
United States Patent
Application |
20180051554 |
Kind Code |
A1 |
Werkheiser; Gregory T. ; et
al. |
February 22, 2018 |
WIRELESS RUN-IN POSITION SENSING SYSTEMS METHODS
Abstract
A method of performing real-time position sensing includes
conveying a tool attached to a tubular string in a borehole. The
tool includes a position sensing sub, and the position sensing sub
includes sensing devices. The method further includes recording
measurements taken by the sensing devices. The method further
includes determining based on the measurements, a position along
the borehole of a particular portion of the tubular string. Data
from sensing devices having a higher priority overrides collecting
data from sensing devices having a lower priority. The method
further includes transmitting the position wirelessly.
Inventors: |
Werkheiser; Gregory T.;
(Dallas, TX) ; Zevenbergen; Reid E.; (Frisco,
TX) ; Miller; Scott L.; (Dallas, TX) ;
Esposito; Nicole E.; (Plano, TX) ; Conzemius; Eric
M.; (The Colony, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Halliburton Energy Services,
Inc.
Houston
TX
|
Family ID: |
57199304 |
Appl. No.: |
15/554615 |
Filed: |
April 29, 2015 |
PCT Filed: |
April 29, 2015 |
PCT NO: |
PCT/US15/28159 |
371 Date: |
August 30, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 47/09 20130101;
E21B 43/116 20130101; E21B 43/119 20130101; E21B 47/04 20130101;
E21B 47/16 20130101; E21B 47/13 20200501 |
International
Class: |
E21B 47/09 20060101
E21B047/09; E21B 43/116 20060101 E21B043/116 |
Claims
1. A method of performing real-time run-in position sensing
comprising: conveying a tool attached to a tubular string in a
borehole, wherein the tool comprises a position sensing sub, and
wherein the position sensing sub comprises multiple sensing
devices; recording measurements taken by the sensing devices;
combining the measurements to determine a position along the
borehole of a particular portion of the tubular string, wherein
data from sensing devices having a higher priority overrides
conflicting data from sensing devices having a lower priority; and
transmitting the position wirelessly.
2. The method of claim 1, wherein the sensing device with the
highest priority comprises a radiation sensor that detects a
radioactive tag.
3. The method of claim 1, wherein the sensing devices comprise an
accelerometer and a gyroscope.
4. The method of claim 1, wherein the sensing devices comprise a
roller counter.
5. The method of claim 4, wherein the roller counter comprises
wheels that turn as the tool is conveyed in the borehole, and
wherein recording the measurements comprises determining the
accuracy of the wheels.
6. The method of claim 5, wherein determining the accuracy
comprises determining the wheel that has turned the maximum number
of times over a programmable distance along the borehole and
recording that number as a measurement for use in position
determination.
7. The method of claim 6, comprising repeating the determining and
recording over another programmable distance along the
borehole.
8. The method of claim 1, wherein the tubular string comprises
perforation guns, and wherein determining the position comprises
determining the position of the perforation guns.
9. The method of claim 8, further comprising activating the
perforation guns after determining the position without bringing
the tool out of the borehole.
10. The method of claim 8, wherein the tool is attached to the
tubular string at a known distance from the perforation guns.
11. The method of claim 1, wherein determining the position
comprises determining the position of the position sensing sub.
12. The method of claim 1, further comprising assembling the
tubular string such that the position sensing sub resides below a
packer and above perforation guns when within the borehole.
13. The method of claim 1, wherein programmable events trigger
position determination and updating of an error factor used to
calibrate the position.
14. The method of claim 1, wherein determining the position
comprises determining the position repeatedly over programmable
distances along the borehole.
15. An apparatus for performing real-time run-in position sensing
comprising: a hierarchy of sensing devices, wherein the sensing
devices measure conditions within a borehole as the apparatus is
conveyed along the borehole while attached to a tubular string; a
processor coupled to the sensing devices, wherein the processor
determines position using data from the sensing devices, and
wherein data from sensing devices having a higher priority
overrides conflicting data from sensing devices having a lower
priority during position determination; and telemetry equipment
coupled to the processor, wherein the telemetry equipment
wirelessly communicates the position.
16. The apparatus of claim 15, wherein the sensing devices further
comprise a radiation sensor for detecting a radioactive tag, a
roller counter, and a collar locator for detecting collars, and
wherein the radiation sensor has the highest priority.
17. The apparatus of claim 15, wherein the processor determines the
position of the apparatus using the data from the sensing
devices.
18. The apparatus of claim 15, wherein the processor determines the
position of perforation guns using the data from the sensing
devices.
19. The apparatus of claim 15, wherein programmable events,
comprising detecting a radioactive tag or detecting a collar,
trigger position determination.
20. The apparatus of claim 15, wherein the sensing devices comprise
an accelerometer, pressure sensor, and gyroscope.
Description
BACKGROUND
[0001] In the oil and gas industry, some operations require
accurate placement of tools downhole. For example, perforation guns
should be carefully positioned to control the location of
perforation points relative to bed boundaries and relative to each
other. In order to achieve such placement, a "dummy run" may be
performed. A dummy run refers to performing a round trip in and out
of the borehole using a partially completed tool string with the
typical objective of confirming the position of a particular
portion of the tool string along the borehole for a subsequent
actual run using a complete tool string. For example, a dummy run
may confirm that the position of perforation guns during the actual
run will be within the relatively small range of positions ideal
for the perforation operation. Such a range is on the order of a
few feet while the borehole may be thousands of feet long.
[0002] As borehole lengths increase, the time and cost required for
the dummy run also increases. Additionally, rented equipment also
adds to the cost. For example, rig rentals may cost up to $1
million per day, and a dummy run may require half of a day or more
to complete. Considering only these two variables, the dummy run
may cost $500,000. Other variables may also increase the cost of
the dummy run, leading to inefficient use of resources.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Accordingly, there are disclosed herein a number of wireless
run-in position sensing systems and methods. In the following
detailed description of the various disclosed embodiments,
reference will be made to the accompanying drawings in which:
[0004] FIG. 1 is a contextual view of an illustrative perforation
environment;
[0005] FIG. 2 is an external view of an illustrative
position-sensing sub;
[0006] FIG. 3 is a function-block diagram of an illustrative
position-sensing sub;
[0007] FIG. 4 is a flow diagram of an illustrative method for
real-time position sensing; and
[0008] FIG. 5 is a contextual view of an illustrative drilling
environment.
[0009] It should be understood, however, that the specific
embodiments given in the drawings and detailed description thereto
do not limit the disclosure. On the contrary, they provide the
foundation for one of ordinary skill to discern the alternative
forms, equivalents, and modifications that are encompassed together
with one or more of the given embodiments in the scope of the
appended claims.
NOTATION AND NOMENCLATURE
[0010] Certain terms are used throughout the following description
and claims to refer to particular system components and
configurations. As one of ordinary skill will appreciate, companies
may refer to a component by different names. This document does not
intend to distinguish between components that differ in name but
not function. In the following discussion and in the claims, the
terms "including" and "comprising" are used in an open-ended
fashion, and thus should be interpreted to mean "including, but not
limited to . . . ". Also, the term "couple" or "couples" is
intended to mean either an indirect or a direct electrical or
physical connection. Thus, if a first device couples to a second
device, that connection may be through a direct electrical
connection, through an indirect electrical connection via other
devices and connections, through a direct physical connection, or
through an indirect physical connection via other devices and
connections in various embodiments.
DETAILED DESCRIPTION
[0011] The issues identified in the background are at least partly
addressed by wireless run-in position sensing systems and methods.
A position-sensing sub that wirelessly transmits position
information in real time enables accurate positioning of an
operational tool without requiring any extra trips or adjustments
of the tool string. Additionally, the tool string need not be
pulled out of the borehole for the reading of logs. Accordingly,
the dummy run may be eliminated, and as a result, the costs
associated with the dummy run may be saved.
[0012] The disclosed systems and methods for implementing such
position sensing are best understood in terms of the context in
which they are employed. As such, FIG. 5 shows an illustrative
drilling environment. A drilling platform 2 supports a derrick 4
having a traveling block 6 for raising and lowering a bottomhole
assembly (BHA) 19. The platform 2 may also be located offshore for
subsea drilling purposes in at least one embodiment. The BHA 19 may
include one or more of a rotary steerable system, logging while
drilling system, drill bit 14, reamer, and downhole motor 26. A top
drive 10 supports and rotates the BHA 19 as it is lowered through
the wellhead 12. The drill bit 14 and reamer may also be driven by
the downhole motor 26. As the drill bit 14 and reamer rotate, they
create a borehole 17 that passes through various formations 18. A
pump 20 circulates drilling fluid 24 through a feed pipe 22,
through the interior of the drill string to the drill bit 14. The
fluid exits through orifices in the drill bit 14 and flows upward
to transport drill cuttings to the surface where the fluid is
filtered and recirculated.
[0013] A data processing system 50 may be coupled to a measurement
unit on the platform 2 by a wired connection 49 or wireless
connection, and may periodically obtain data from the measurement
unit as a function of position and/or time. Software (represented
by information storage media 52) may run on the data processing
system 50 to collect the data and organize it in a file or
database. The software may respond to user input via a keyboard 54
or other input mechanism to display data as an image or movie on a
monitor 56 or other output mechanism. The software may process the
data to optimize oilfield operations as described below.
[0014] Wired telemetry, which uses an electrical line, wireline, or
cable to communicate with the surface, has several disadvantages
compared to wireless telemetry. First, the line must be installed
in or otherwise attached to the drill string. As such, the line is
prone to damage in the harsh downhole conditions. As a result, the
system is unreliable, which results in costly inspection,
servicing, and replacement of the line. Second, the downhole motor
should be particularly designed to accommodate the line because the
movement of the motor degrades the line without such accommodation.
Such customization is expensive.
[0015] In various embodiments, wireless methods, such as acoustic
and electromagnetic (EM) telemetry, are used for communication with
the surface. With regard to acoustic waves, typically, an acoustic
signal is generated near the drill bit 14 and is transmitted
through the drill pipe, mud column, or the earth. Specifically, the
drill string may include an acoustic telemetry transceiver that
transmits telemetry signals in the form of acoustic vibrations in
the tubing wall of the drill string. An acoustic telemetry receiver
may be coupled to the kelly to receive transmitted telemetry
signals. One or more repeaters may be provided along the drill
string to receive and retransmit the telemetry signals. The
repeaters may include both an acoustic telemetry receiver and an
acoustic telemetry transmitter.
[0016] Electromagnetic telemetry can be employed in a variety of
ways. Using one technique, electromagnetic signals are modulated
according to a sensor response to represent one or more parameters
of interest. In one embodiment, these signals are transmitted from
a downhole EM transceiver, through intervening earth formation, and
detected as a voltage or a current using a surface transceiver that
is typically located at or near the surface. The one or more
parameters of interest are extracted from the detected signal.
Using another electromagnetic technique, a downhole transceiver
creates a current within the drill string, and the current travels
along the drill string. This current is typically created by
imposing a voltage across a non-conducting section in the downhole
assembly. The current is modulated according to the sensor response
to represent the one or more parameters of interest. A voltage
between the drilling rig and a remote ground is generated by the
current and is measured by a surface transceiver, which is at the
surface. The voltage is usually between a wire attached to the
drilling rig or casing at the surface and a wire that leads to a
grounded connection remote from the rig. Again, one or more
parameters of interest are extracted from the measured voltage.
Alternately, the one or more parameters of interest can be
extracted from a measure of current.
[0017] The borehole 17 may be thousands of feet long, and an
operational tool such as a perforation sub must be placed
accurately within a few feet in the borehole 17. FIG. 1 illustrates
a position-sensing sub that may be placed on the drill string or a
tool string that enables such placement.
[0018] FIG. 1 shows an illustrative perforation environment 100.
(Though these principles are described in terms of a perforation
operation, they are also applicable to those other operations
requiring accurate placement of tools along the borehole, e.g.
positioning of a shear sub or packer, multi-zone testing
applications, and completion applications.)
[0019] A borehole 118 is cased using multiple concentric casing
strings 116, each string having casing joints attached together by
casing collars 104 having threaded connectors. To preserve the
integrity and rigidity of the casing string 116, the casing collars
104 are made with thicker steel walls. The casing joints have
fairly standard lengths, enabling the collars 104 to serve as
convenient position markers or "milestones". The thicker steel
walls enable the collars to be detected with "casing collar
locators", which may employ induction sensors or permeability
sensors. Selected casing collars or positions along the drillstring
may be additionally tagged with radioactive markers to make them
detectable by a gamma ray logging tool.
[0020] A tubular string, such as a tool string 102, includes
operational tools such as a perforation sub 110 and a
position-sensing sub 114. Perforation is a process used to
establish a flow path of hydrocarbons from the formation to the
borehole by creating one or more holes in the casing and any cement
sheath surrounding the casing. The perforation sub 110 includes
perforation guns 112 to create such holes. The perforation guns 112
may be a known distance from other portions of the tool string 102,
such as the position sensing sub 114, and this distance may be used
in order to accurately position the perforation guns 112.
[0021] The position-sensing sub 114 includes sensing devices such
as an accelerometer, gyroscope, casing collar locator, radiation
sensor, roller counter 106, and the like. In various embodiments,
different combinations of any or all the sensing devices are
included on the position-sensing sub 104. The accelerometer detects
inertial movement along the borehole to measure acceleration. The
gyroscope includes some form of rotation sensor for measuring the
tool's orientation, e.g., a spinning wheel mounted on a gimbal
assembly. The casing collar locator includes two magnetic poles
positioned on either side of a central coil. Magnetic lines of flux
in the casing collar locator are temporarily distorted when the
position-sensing sub 114 passes the thicker walls of a casing
collar. This distortion changes the magnetic field around the
conducting coil, and the change is detected. A radiation sensor
such as a gamma ray log includes a scintillation crystal and a
photomultiplier tube to measure gamma-ray radiation emitted by the
tag or marker. The roller counter 106 detects the distance traveled
by the position-sensing sub 116 along the borehole 114, and is
described in detail with respect to FIG. 2.
[0022] FIG. 2 illustrates an external view of the position-sensing
sub 200, which includes a roller counter 201. The roller counter
201 is a sensing device that measures distance traveled along the
borehole, and the roller counter includes extension arms 204
resiliently coupled to the body of the position-sensing sub 200 by
fasteners such as hinges 206 and biased outwardly to press against
the inner walls of the casing string. The hinges 206 enable the
extension arms 204 to deploy by extending away from the body of the
position-sensing sub 200 such that wheels 202 located at the
opposite end of the extension arms 204 contact the casing string
and turn as the position-sensing sub 200 is conveyed along the
borehole. In at least one embodiment, springs on the extension arms
204 keep the wheels 202 in contact with the casing string. The
wheels 202 are coupled to the extension arms 204 by axles, and the
deployment of the extension arms 204 may be initiated and
controlled from the surface or downhole. As the casing string
decreases in diameter, the hinges 206 enable the extension arms 204
to retract such that the wheels 202 maintain contact with the
casing string. The extension arms 204 may also fully retract when
the tool string is pulled out of the borehole. This retraction may
also be initiated and controlled from the surface or downhole.
[0023] Encoders coupled to the wheels 202 count the rotations of
the wheels 202. One encoder may be used for each wheel 202, and an
encoder may include a rotational counter coupled to the axle of the
corresponding wheel 202. In at least one embodiment, the encoder
transmits a signal, such as an electrical pulse, for every rotation
of the wheel 202, and the pulse is detected and recorded by
circuitry on the position-sensing sub 200. In other embodiments,
fractional rotations or rotations greater than a single rotation
are detected and recorded.
[0024] Multiple extension arms 204 provide centralization of the
position-sensing sub 200 within the borehole; redundancy that
mitigates failure of a wheel 202, such as a seized bearing
preventing rotation; redundancy that mitigates an electrical
connection problem between the wheel, encoder, and circuitry; and
redundancy that mitigates a wheel 202 slipping (not rotating) along
the casing string. Because of such redundancies, outliers in the
data measured by the roller counter may be eliminated during
real-time processing without reducing the accuracy of the final
data set. Such processing may be performed by the processor as
described with respect to FIG. 3.
[0025] FIG. 3 illustrates a block diagram of a position-sensing sub
302. As described above, the position-sensing sub 302 includes
sensing devices 308 such as an accelerometer, gyroscope, collar
locator, radiation sensor, roller counter, and the like to measure
downhole conditions. The position-sensing sub 302 also includes a
processor 304, coupled to memory 306, to process operations, store
data, and calculate the position of various portions of the tools
string in real time using data measured by the sensing devices
308.
[0026] In at least one embodiment, data from sensing devices 308
having a higher priority overrides conflicting data from sensing
devices 308 having a lower priority during position determination,
and the more accurate sensing device (determined a priori in at
least one embodiment) is given the higher priority. For example,
the casing collar locator may be known to fail to detect some
collars while the radiation sensor may be known to detect a
radioactive tag reliably. As such, the radiation sensor is given a
higher priority than the collar locator because the position
information of the radiation sensor is more accurate. Accordingly,
when the data measured by the casing collar locator conflicts with
the data measured by the radiation sensor, the latter is given
priority during position determination. In this way, the sensing
devices 308 make up a hierarchy of higher and lower priority
sensing devices 308 relative to one another. In at least one
embodiment, the radiation sensor has the highest priority, the
casing collar locator has the second-highest priority, and the
roller counter has the third-highest priority. By using a
combination of sensing devices 308 and overriding conflicting data
from lower-priority sensing devices, the position of various
portions of the tool string including the position-sensing sub 302
and operational tools such as a perforation gun may be accurately
determined.
[0027] The position-sensing sub 302 also includes communication and
networking hardware 310 for enabling communications between the
position-sensing sub 302 and the surface. The communication channel
between the position-sensing sub 302 and the surface is wireless.
As such, position information can be communicated to the surface in
real-time and such communication may occur continuously,
automatically after a threshold amount of time or inactivity has
passed, in response to queries or programmable events (discussed
below with respect to FIG. 4), or some combination of the
preceding.
[0028] FIG. 4 is a flow diagram of an illustrative method 400 of
real-time position sensing beginning at 402 and ending at 414. At
404, a tool string is conveyed through a borehole. The tool string
includes a position-sensing sub, and the position sensing-sub
includes sensing devices as described above. The tool string may
also include operational tools that should be positioned accurately
downhole such as a perforation sub, a packer, a shear sub, and the
like. The tool string may be assembled such that the
position-sensing sub resides below a packer and above perforation
guns when within the borehole.
[0029] At 406, measurements taken by the sensing devices are
recorded. Specifically, the sensed data may be processed by a
processor and stored in memory. Such processing may include pruning
sensed data that is unreliable. For example, the accuracy of the
wheels on the roller counter may be determined by identifying the
wheel that has turned the maximum number of times (or at the
fastest speed) over a programmable distance along the borehole.
Such a wheel is a "representative" wheel, meaning that the sensed
data provided by other wheels along the distance is ignored for
purposes of position determination. However, along a subsequent
portion of the borehole, another wheel may be selected as the
representative wheel. By repeating selection of the representative
wheel over several distances along the borehole, the accuracy of
the roller counter increases even though various wheels may fail to
rotate along different portions of the borehole.
[0030] At 408, a query or event trigger is obtained. A query may
include a wireless signal or command sent from the surface
requesting position information, while an event trigger may include
a programmable threshold of time passing, a programmable period of
inactivity passing, a programmable distance traveled, detection of
a collar, detection of a radioactive tag, and the like. If a query
or trigger event is obtained, the current position is determined at
410. If not, the tool string is conveyed further through the
borehole at 404.
[0031] At 410, a position along the borehole of a particular
portion of the tool string is determined based on the recorded
measurements. For example, the position of the position-sensing sub
may be determined or the position of a particular operational tool,
such as a perforation sub or perforation guns, may be determined. A
radiation tag detected by the radiation sensor resides at a known
location in the borehole. As such, the data sensed by the radiation
sensor may be used to determine distance using a database or lookup
table. Collars reside at a known distance apart from each other. As
such, the data sensed by the collar locator may be used to
determine distance by multiplying the amount of collars detected
with the distance between the collars. The roller counter may be
used to determine distance by multiplying the number of rotations
of the representative wheels by the circumference of the wheels.
Finally, the accelerometer and gyroscope may be used to determine
distance by using a dead-reckoning algorithm--i.e. the process of
calculating a current position by using a previously determined
position, or fix, and advancing that position based upon current
speeds over elapsed time and course--with the collars or
radioactive tag as fixes.
[0032] The distance determined from sensed data from the multiple
sensing devices may be compared to identify error and update an
error factor in any of the sensing devices. For example, using dead
reckoning, each time the accelerometer and gyroscope sensors
encounter a "fix," the fix distance may be compared with the
estimated distance at the location of the fix. A fix is evidence of
a known location, in this case, evidence of a known distance along
the borehole. The difference between the two values is the error
factor, and as more fixes are encountered, the error factor is
updated. Ultimately, when no more fixes are encountered, the error
factor may be used to adjust the distance measurement derived from
the accelerometer and gyroscope measurements. In this way, the
lower-priority devices may be recalibrated when presented with
conflicting data from higher-priority devices. For example, the
collar count is recalibrated every time a radiation marker is
detected, and the accelerometer and gyroscope are recalibrated
whenever a collar is detected.
[0033] The distances determined from sensed data from the multiple
sensing devices may be combined to determine the current position
of the position-sensing sub and/or the position of an operational
tool. For example, the casing collar locator measurements may
supplement the radiation sensor measurements because casing collars
are more frequently passed than radioactive tags. In the same way,
the accelerometer and gyroscope measurements may supplement the
casing collar locator measurements for positions between casing
collars. Such supplementation may occur if the data does not
conflict. If the data does conflict, then data from the
higher-priority devices will override data from the lower-priority
devices during the combining. For example, the data from the
lower-priority devices may be ignored during the combining. As
another example, the data from the lower-priority devices may be
given less weight during the combining. However, such overriding
does not apply to all data from a lower-priority device, i.e. the
lower-priority device is not eliminated from providing data
entirely. Rather, only those portions along the borehole where a
higher-priority device provides conflicting information will be
subject to such override.
[0034] At 412, the position is reported. For example, the position
information is transmitted to the surface wirelessly in real time.
After the position information is reported, the operational tool,
such as the perforation guns on the perforation sub, is activated
without bringing the tool string out of the borehole in at least
one embodiment.
[0035] A method of performing real-time position sensing includes
conveying a tool attached to a tubular string in a borehole. The
tool includes a position sensing sub, and the position sensing sub
includes sensing devices. The method further includes recording
measurements taken by the sensing devices. The method further
includes determining, based on the measurements, a position along
the borehole of a particular portion of the tubular string. Data
from sensing devices having a higher priority overrides conflicting
data from sensing devices having a lower priority. The method
further includes transmitting the position wirelessly.
[0036] The sensing device with the highest priority may include a
radiation sensor that detects a radioactive tag. The sensing
devices may include an accelerometer and a gyroscope. The sensing
devices may include a roller counter. The roller counter may
include wheels that turn as the tool is conveyed in the borehole,
and recording the measurements may include determining the accuracy
of the wheels. Determining the accuracy may include determining the
wheel that has turned the maximum number of times over a
programmable distance along the borehole and recording that number
as a measurement for use in position determination. The method may
include repeating the determining and recording over another
programmable distance along the borehole. The tubular string may
include perforation guns, and determining the position may include
determining the position of the perforation guns. The method may
include activating the perforation guns after determining the
position without bringing the tool out of the borehole. The tool
may be attached to the tubular string at a known distance from the
perforation guns. Determining the position may include determining
the position of the position sensing sub. The method may include
assembling the tubular string such that the position sensing sub
resides below a packer and above perforation guns when within the
borehole. Programmable events may trigger position determination
and updating of an error factor used to calibrate the position.
Determining the position may include determining the position
repeatedly over programmable distances along the borehole.
[0037] An apparatus for performing real-time positon sensing
includes a hierarchy of sensing devices. The sensing devices
measure conditions within a borehole as the apparatus is conveyed
along the borehole while attached to a tubular string. The
apparatus further includes a processor coupled to the sensing
devices. The processor determines position using data from the
sensing devices. Data from sensing devices having a higher priority
overrides conflicting data from sensing devices having a lower
priority during position determination. The apparatus further
includes telemetry equipment coupled to the processor, and the
telemetry equipment wirelessly communicates the position.
[0038] The sensing devices may include a radiation sensor for
detecting a radioactive tag, a roller counter, and a collar locator
for detecting collars. The radiation sensor may have the highest
priority. The processor may determine the position of the apparatus
using the data from the sensing devices. The processor may
determine the position of perforation guns using the data from the
sensing devices. Programmable events, which may include detecting a
radioactive tag or detecting a collar, may trigger position
determination. The sensing devices may include an accelerometer,
pressure sensor, and gyroscope.
[0039] While the present disclosure has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations.
* * * * *