Note: Descriptions are shown in the official language in which they were submitted.
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ORIENTING DOWNHOLE TOOLS
BACKGROUND
The invention relates to orienting downhole tools.
To complete a well, one or more formation zones
adjacent a wellbore may be perforated to allow fluid from
the formation zones to flow into the well for production to
the surface. A perforating gun string may be lowered into
the well and guns fired to create openings in casing and to
extend perforations into the surrounding formation.
When performing downhole perforating operations in
a wellbore, there may be a need to orient the perforating
gun string. This need may arise, for example, if
perforations are desired to be shot in alignment with a
preferred fracture plane in the surrounding formation (e. g.,
generally normal to the minimum stress plane of the
formation) to help in fracture stimulation of the well to
improve well performance. By aligning perforations properly
with respect to the preferred fracture plane, improved fluid
flow occurs through the formations.
Other situations also exist in which oriented
perforating or other downhole operations may be desirable.
Thus, a need exists for improved mechanisms and techniques
to orient perforating equipment or other downhole equipment
in a wellbore.
SUMMARY
In general, in one embodiment, a method of
orienting a tool in a wellbore includes identifying a
desired orientation of an oriented device in the tool at a
given wellbore interval. The oriented device is angularly
positioned with respect to a positioning device, and a tool
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is lowered downhole with the positioning device guiding the
tool so that the oriented device is at substantially the
desired orientation when the tool reaches the given wellbore
interval.
In general, in another embodiment, an apparatus
for orienting a tool in a wellbore includes a motor coupled
to the tool, an anchor to fix the apparatus in the wellbore,
and a measurement device adapted to measure a relative
bearing of the tool. The motor is activable to rotate the
tool with respect to the anchor based on the relative
bearing data received from the measurement device.
According to one aspect of the present invention,
there is provided a method of orienting a downhole device in
a wellbore, comprising: running an orientation string into
the wellbore, the orientation string including a positioning
device, a measurement device, and the downhole device;
positioning the orientation string in a predetermined
interval in the wellbore with the positioning device;
measuring the azimuthal orientation of the orientation
string with the measurement device; removing the orientation
string from the wellbore; and running a tool string
including the downhole device into the wellbore such that
the tool string follows substantially the same path as the
orientation string.
Other embodiments and features will become
apparent from the following description and from the claims.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram of an embodiment of a tool string positioned in a cased
wellbore.
Figs. 2A and 2B are diagrams of tool strings according to one embodiment used
to
perform natural orientation.
Fig. 3 is a diagram of a tool string according to another embodiment that
includes an
inclinometer sonde and a motor capable of rotating portions of the tool
string.
Fig. 4 is a diagram of a modular tool string according to a further embodiment
that is
capable of connecting to a number of different sondes.
Figs. 5 and 6 illustrate position devices in the tool strings of Figs. 2A and
2B.
Fig. 7 illustrates relative bearing and azimuthal angles associated with a
downhole tool.
DETAILED DESCRIPTION
In the following description, numerous details are set forth to provide an
understanding of
the present invention. However, it wilt be understood by those skilled in the
art that the present
invention may be practiced without these details and that numerous variations
or modifications
from the described embodiments may be possible. For example, although
reference is made to
perforating strings in some embodiments, it is contemplated that other types
of oriented
downhole tool strings may be included in further embodiments.
Refernng to Fig. 1, a formation zone 102 having producible fluids is adjacent
a wellbore
104 lined with casing 100. The location of the formation zone 102 and its
stress characteristics
(including the minimum and maximum stress planes) may be identified using any
number of
techniques, including open hole (OH) logging, dipole sonic imaging (DSI),
ultrasonic borehole
imaging (UBI), vertical seismic profiling (VSP), formation micro-imaging
(FMI), or the
Snider/Halco injection method (in which tracers are pumped into the formation
102 and a
measurement tool is used to detect radioactivity to identify producible
fluids).
Such logging techniques can measure the permeability of the formation 102.
Based on
such measurements, the depth of a zone containing producible fluids can be
determined. Also,
the desired or preferred fracture plane in the formation 102 can also be
determined. The preferred
fracture plane may be generally in the direction of maximum horizontal
stresses in the formation
102. However, it is contemplated that a desired fracture plane may also be
aligned at some
predetermined angle with respect to the minimum or maximum stress plane. Once
a desired
fracture plane is known, oriented perforating equipment 108 may be lowered
into the wellbore to
create perforations that are aligned with the desired plane.
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In another embodiment, oriented perforating may also be used to minimize sand
production in weak formations. In addition, oriented perforating may be used
to shoot away from
other downhole equipment to prevent damage to the equipment, such as
electrical cables, fiber
optic lines, submersible pump cables, adjacent production tubing or injection
pipe, and so forth.
Oriented perforating may also be practiced for doing directional squeeze jobs.
If the current
surrounding the pipe contains a void channel, the direction of that channel
can be determined
using a variety of methods and tools such as the USIT (Ultrasonic Imaging
Tool). Once the
direction is known, oriented perforating may be executed accordingly. Further
embodiments may
include oriented downhole tools for other operations. For example, other
downhole tools may
perform oriented core sampling for formation analysis and for verification of
a core's direction,
for setting wireline-conveyed whipstocks, and for other operations.
With a vertical or near vertical wellbore 104 having a shallow angle of
trajectory (e.g.,
less than about 10°), it may be difficult to use the force of gravity
to adjust the azimuthal
orientation of a perforating gun string or other tool string carried by a non-
rigid carrier (e.g.,
wireline or slick line) from the surface. According to some embodiments of the
invention, an
oriented perforating string includes an orienting mechanism to orient the
perforating string in a
desired azimuthal direction. It is contemplated that some embodiments of the
invention may also
be used in inclined wellbores.
Several different embodiments of oriented perforating equipment are described
below. In
a first embodiment, a "natural orientation" technique is employed that is
based on the principle
that the path of travel and position of a given tool string (or of
substantially similar strings)
within a given section of a well is generally repeatable provided that
steering effects from the
cable (e.g., cable torque) are sufficiently eliminated (e.g., by using a cable
swivel). It may also
be necessary to keep most operational and tool conditions generally constant.
Such conditions
may include the following, for example: components in the tool string; length
of tool string;
method of positioning (e.g., lowering and raising) the tool string; and so
forth. Thus, in the
natural orientation technique, a first orientation string including a
positioning device may be run
in which a measurement device can determine the position and orientation of
the string after it
has reached its destination. The positioning device in one embodiment may be a
mechanical
device (e.g., including centralizing or eccentralizing arms, springs, or other
components). In
another embodiment, the positioning device may be an electrical or magnetic
device. Once the
natural orientation of the tool string is determined based on the first trip,
the tool's angular
position may be adjusted (rotated) at the well surface to the desired
position. A second run with a
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tool string including a positioning device is then performed by lowering the
tool string into the
wellbore, which tends to follow generally the same path.
In a variation of this embodiment, it may be assumed that in wells that have
sufficient
inclination (e.g., perhaps about 2° or more), the positioning device
will position the tool string at
S some relationship with respect to the high or low side of a wellbore once
the tool string has been
lowered to a predetermined depth. An oriented device in the tool string may
then be angularly
aligned at the surface before lowering into the wellbore so that the oriented
device is at
substantially a desired orientation once it is lowered to a given wellbore
interval. In this
variation, one run instead of two runs may be used.
In other embodiments, a motorized oriented tool string includes a motor and
one or more
orientation devices lowered into the wellbore, with the tool rotated to the
desired azimuthal or
gravitational orientation by the motor based on measurements made by the
orientation devices.
Referring to Figs. 2A-2B, tools for performing natural orientation of downhole
equipment
(such as a perforating string) are shown. In one embodiment, natural
orientation involves two
runs into the wellbore 104. In another embodiment, natural orientation may
involve one run into
the wellbore. In the embodiment involving two runs, a first run includes
Lowering an orientation
string 8 (Fig. 2A) into the wellbore to measure the orientation of the string
8. Once the
orientation of the tool string 8 is determined based on the first trip, the
device 28's angular
position may be adjusted (rotated) with respect to the tool string 8 at the
well surface to the
desired position.
Next, a tool string 9 (Fig. 2B), which may be a perforating string, for
example, is lowered
downhole that follows substantially the same path as the orientation string 8
so that the tool string
9 ends up in substantially the same azimuthal position as the orientation
string 8. Thus, the first
trip is used for determining the natural orientation of the tool string 8
after it has reached a given
interval (depth}, while the second trip is for performing the intended
operation (e.g., perforating)
in that interval after the tool string 9 has been lowered to the given
interval and positioned in
substantially the same natural orientation.
On the first trip, a gyroscope device 10 may be included in the string 8 to
measure the
azimuthal orientation of the string in the wellbore interval of interest. An
inclinometer tool 25
which can be used for providing the relative bearing of the orientation string
8 relative to the high
side of the wellbore may also be included in the string. A few passes with the
orientation string 8
can be made, with the relative bearing and azimuthal orientation information
measured and stored
in a log. Each pass may include lowering and raising the orientation tool
string 8 one or more
times. The toal positions for the up and down movements in a pass may be
different. The
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direction (up or down) in which better repeatability may be achieved can be
selected for
positioning the tool.
The orientation string 8 and the tool string 9 are designed to include as many
as the same
components as possible so that the two strings will substantially follow the
same path downhole
in the wellbore. On the second trip, the gyroscope device 10 may be removed
from the string 9,
but the remaining components may remain the same. Next, the device (e.g., a
perforating gun 28)
in the tool string 9 for performing the desired operation is oriented, at the
surface, to place the
device at an angular position with respect to the rest of the string 8 based
on the natural
orientation determined in the first trip. Any special preparation such as
arming guns may also be
performed prior to re-entering the well for the second trip. The inclinometer
tool 25 may remain
in the tool string 9 to measure the relative bearing of the tool string 9 to
determine if tool string 9
is following generally the same path as the orientation string 8.
Removal of the gyroscope device 10 is performed to reduce likelihood of damage
to the
gyroscope. However, with a gyroscope that is capable of withstanding the shock
associated with
1 S activating a perforating gun 28, the gyroscope device 10 may be Left in
the string 9. Further, in
oriented downhole tools that do not perform perforation, the gyroscope may be
left in the tool
string as the shock associated with perforating operations do not exist.
The gyroscope device 10 in the orientation string 8 is used to identify the
azimuthal
orientation of the string 8 with respect to true north. In one example
embodiment, the gyroscope
device 10 may be coupled above a perforating gun 28. Weighted spring
positioning devices
(WSPD) 14A and 14B are coupled to the perforating gun 28 with indexing
adapters 18A and
18B, respectively. The indexing adapters 18A and 18B may allow some degree
(e.g., 5°) of
indexing between the gun 28 and the rest of the tool string. Based on the
desired orientation of
the gun 28 with respect to the rest of the string, the gun 28 can be oriented
by rotating the
indexing adapters 18A and 18B to place the gun 28 at an angular position with
respect to the rest
of the string 9 so that the gun 28 is at a desired azimuth orientation once
the string 9 reaches the
target wellbore interval.
According to some embodiments, one or more WSPDs 14 are adapted to steer the
string
in a natural direction and to reduce the freedom of transverse movement of the
orientation string
8 as it is lowered in the wellbore 104. The WSPD 14A is located above the gun
28 and the
WSPD 14B is located below the gun 28.
In each WSPD 14, one side is made heavier than the other side by use of a
segment with a
narrowed section 30 and a gap 32. Thus, in a well having some deviation (e.g.,
above 1 °
deviation), the heavy side-the side with the narrowed section 30-of the WSPD
14 will seek the
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low side of the wellbore 104. Each WSPD 14 also has a spring 16 on one side
that presses
against the inner wall 106 of the casing 100 to push the other side of the
WSPD 14 up against the
casing 100. The WSPDs also reduce the freedom of movement of the orientation
string 8 by
preventing the orientation string 8 from freely rotating or moving
transversely in the wellbore
104. The offset weights of the WSPDs 14A and 14B aid in biasing the position
of the tool string
8 to the low side of the wellbore 104.
The inclinometer tool 25 includes an inclinometer sonde (such as a highly
precise bi-axial
inclinometer sonde) attached by an adapter 12 to the gyroscope device 10
below. The
inclinometer tool 25 may also include a CCL (casing collar locator) that is
used to correlate the
depth of the orientation string 8 inside the casing 100. As the orientation
string 8 is lowered
downhole, the inclinometer sonde provides relative bearing information of the
string 8 and the
CCL provides data on the depth of the tool string 8. Such data may be
communicated to and
stored at the surface (or, alternatively, stored in some electronic storage
device in the tool string
8) for later comparison with data collected by an inclinometer sonde in the
gun string 9. If the
relative bearing data of the orientation string 8 and the gun string 9 are
about the same, then it can
be verified that the gun string 9 is following substantially the same path as
the orientation string
8.
Referring to Fig. 7, the azimuthal angle of the tool string 8 or 9 can be
defined as the
angle between north (I~ and a reference (R) in the inclinometer tool 25. The
relative bearing
angle of each of the orientation string 8 and tool string 9 is measured
clockwise from the high
side (HS) of the wellbore 104 to the reference {R) in the inclinometer tool
25. In one
embodiment, the reference (R) may be defined with respect to one or more
longitudinal grooves
50 in the outer wall of the inclinometer tool 25. The positions of the
sensors) in the inclinometer
tool 25 are fixed (and known) with respect to the longitudinal grooves 50.
Further, when the
string 8 or 9 is put together, the position of the components of the string 8
or 9 in relation to the
grooves 50 are also known.
The tool string 8 may be attached at the end of a non-rigid carrier 26 (e.g.,
a wireline or
slick line). In one embodiment, to keep torque applied to the carrier 26 from
swiveling the
orientation string 8 as it is being lowered downhole, a swivel adapter 24 may
be used. The
Garner 26 is attached to the string 8 by a cannier head 20, which is connected
by an adapter head
22 to the swivel adapter 24. The swivel adapter 24 in one example may be a
multi-cable or a
mono-cable adapter, which decouples the tool string 8 from the carrier 26
(torsionally). Thus,
even if a torque is applied to the carrier 26, the orientation string 8 can
rotate independently.
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Alternatively, the swivel adapter 24 can be omitted if the elasticity of the
non-rigid carrier 26
allows the carner to follow the tool string 8 as it is rotating in traversing
the path downhole.
The orientation string 8 is lowered according to a predetermined procedure
from the
surface. The steps used in this procedure are substantially repeated in the
second run of the
natural orientation technique to achieve the same positioning in the second
run. The orientation
of the string 8 as it makes entry into the wellbore 104 is known. The
equipment for lowering the
string 8 is also known. As the orientation string 8 is lowered downhole, the
string naturally
positions itself in the hole. According to one procedure, the orientation
string 8 is lowered
downhole past the well interval defined by the formation zone 102. The
orientation string $ may
then be raised back up to the interval and measurements taken using the
gyroscope device 10 and
inclinometer sonde and CCL 25 to determine the position of the orientation
string 8. This
procedure can be repeated several times with the orientation string 8 to
ensure repeatability of
orientation.
There may be cases where the orientation string 8 may not be able to go past
the interval
defined by the formation zone 102, such as when other equipment are located
further below. In
such cases, a modified procedure can be used, such as lowering the orientation
string 8 into the
interval, stopping, making the measurement, and then raising the string.
After measurements have been made, the orientation string 8 is raised out of
the wellbore
104. At the surface, before the second run is made, the gyroscope device 10
may be removed.
All other components can remain the same as those in the orientation string 8.
Like components
have the same reference numerals in Figs. 2A and 2B.
In the tool string 9, the indexing heads 18A and 18B may be rotated to adjust
the
perforating gun 28 to point in the desired direction. The oriented tool string
9 is then lowered
downhole following the same procedure used for the orientation string 8.
Because the
components of the two strings are substantially the same, the strings will
tend to follow the same
path. The inclinometer tool 25 (including the inclinometer sonde and CCL) in
the gun string 9
can confirm if the string 9 is following about the same path as the
orientation string 8. If the
comparison of the relative bearing data indicates a suff ciently significant
difference in the travel
path, the gun string 9 may be pulled out, repositioned, and lowered back into
the wellbore 104.
Further, if desired, additional components (such as a sub 27 in Fig. 2B) may
be connected
in the oriented tool string 9 to make it be about the same length as the
orientation string 8. Tests
have shown that repeatability of orientation of the strings is good. For
example, in a slightly
deviated well, such as an about 1 ° well, variation of about 7°
in the orientation of the gun strings
was observed over several runs. Any variation below ~ 10° rnay be
considered acceptable.
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In alternative embodiments, the order of the components in tool strings 8 and
9 may be
varied. Further, some components may be omitted or substituted with other
types of components.
For example, the CCL may be part of the gyroscope device 10 instead of part of
the inclinometer '
tool 25. In this alternative embodiment, when the gyroscope device 10 is taken
out to form tool
string 9, a CCL may be put in its place.
In a variation of the natural orientation embodiment, one run instead of two
may be
employed to perform oriented downhole operations. If a desired fracture plane
or some other
desired orientation of a downhole device is known beforehand, an oriented
device (such as a
perforating gun) may be angularly positioned with respect to the WSPDs 14 at
the surface. The
WSPDs 14 will likely guide the tool string to a given orientation with respect
to the high side of
the wellbore. Thus, when the tool string is lowered to the targeted wellbore
interval, the oriented
device in the tool string will be at the desired orientation. This may be
confirmed using an
inclinometer, for example.
Referring to Fig. S, a more detailed diagram of the upper WSPD 14A is
illustrated. The
housing 200 of the WSPD 14A has a threaded portion 202 at a first end and a
threaded portion
204 at the other end to connect to adjacent components in the orientation or
tool string 8 or 9. A
connector 206 may be provided at the first end to receive electrical cables
and to route the
electrical cables inside the housing 200 of the WSPD 14A, such as through an
inner bore 208.
As illustrated, the upper WSPD 14A includes a segment having the narrowed
section 30A
and the gap 32A. The eccentering spring 16A that is generally parabolically
shaped is attached to
one side of the housing 200 of the WSPD 14A. In one embodiment, the spring 16A
may be
attached to the housing 200 by dowel pins 210. In another embodiment, the
spring 16A may be
made with multiple layers. A wear button 212 may also be attached to the
centering spring 16A
generally at its apex. In one example embodiment, the wear button 212 may be
attached to the
eccentering spring 16A with a bolt 218 and a washer 216. The purpose of the
wear button 2I2 is
to protect the eccentering spring 16A from damage due to sliding contact with
the inside of the
casing 100. In further embodiments, the size of the wear button 212 may be
increased or
reduced.
A pair of tracks 220 are also defined in the housing 200 in which the dowel
pins 210 are
received. The dowel pins 210 are moveable in their respective tracks 220 to
allow the spring 16A
to be compressed toward the housing 200 of the WSPD 14A. Allowing the ends of
the spring
16A to be spread along the tracks 220 due to compression as the orientation or
tool string 8 or 9
is lowered downhole reduces the likelihood of deformation of the spring 16A.
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Referring to Fig. 6, the lower WSPD 14B is illustrated. The WSPD 14B includes
a
housing 250 having a threaded portion 252 at one end to connect to the rest of
the orientation or
tool string 8 or 9. The housing 250 includes segment having the narrowed
section 30B and the
gap 32B. The eccentering spring 15B is attached by dowel pins 260 to the
housing 250 in side
tracks 270. A wear button 262 may be attached to the eccentering spring 16B
with a bolt 268 and
a washer 266.
Referring to Fig. 3, an oriented tool string 120 according to an alternative
embodiment of
the invention includes components for orienting the string 120 so that
multiple runs into the
wellbore 104 for orienting tool strings can be avoided. Thus, whereas the tool
string 9 of Fig. 2B
can be referred to as a passive orienting system, the string 120 shown in Fig.
3 can be referred to
as an active system.
An adapter 128 attaches the string 120 to a carrier 126 (e.g., wireline, slick
line, coiled
tubing, and so forth). An anchor 132 is attached below the adapter 128. In
addition, a motor 136
is attached under the anchor 132 that is controllable to rotate a downhole
perforating gun 142, for
example. The anchor 206 presses against the inner wall 106 of the casing 100
to anchor the tool
string 120 while the gun 142 is rotated by the motor 136 with respect to the
anchor 132.
A CCL 131 and electronics device 130 may be attached below the motor 136, with
the
CCL 131 measuring the depth of the string 120 and the electronics device I 30
including various
electronics circuitry, including circuitry for performing shot detection. An
inclinometer sonde
138 is attached below the device 130. Measurements taken by the inclinometer
sonde 138, CCL
131, and electronics device 130 may be transmitted to the surface as the tool
string 120 is being
located into the wellbore 104 to enable a surface operator to control the
motor 136 to rotate the
gun 142. Based on the data measured by the inclinometer sonde 138, the
relative bearing of the
tool string 120 can be derived. Based on the measured relative bearing, the
motor 136 can be
activated to rotate the gun string 120 to the desired azimuthal orientation to
perforate in an
identified horizontal stress plane (the maximum stress plane). Thus, once the
relative bearing of
the tool string 120 in an interval is known, and the direction of the stress
plane is known, then the
tool string can be azimuthally oriented as a function of wellbore inclination.
Such an orientation
technique for a tool string can be successful in a wellbore having a slight
deviation, e.g., as little
as a fraction of 1 °.
Alternatively, a gyroscope can also be added to the perforating gun string 120
so that the
azimuthal orientation of the string 120 can be measured.
To protect the rest of the string 120 from the shock of the gun 142 firing, a
shock absorber
140 may be connected between the gun 142 and the inclinometer sonde 138. In
addition, a safety
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device 144 may be included in the string 120 to prevent or reduce likelihood
of inadvertent
activation of the gun 142. In a modification of the tool string in the Fig. 3
embodiment, the order
of the components can be varied and some components may be omitted or
substituted with other
types of components.
S Referring to Fig. 4, another embodiment of the invention includes a modular
tool string
210 in which different measurement modules can be plugged into the string to
aid in the
performance of the desired orientation. The modules may include sondes that
are plug-in
compatible with the tool string. As with the embodiment of Fig. 3, the modular
tool string 210
includes a motor 208 for rotating the gun 250 {or other downhole device) while
an anchor 206
10 fixes a non-rotating portion of the string 210 to the casing 100.
One of the modular sondes may include an inclinometer sonde 218 that may be
sufficient
for use in a deviated welIbore 104 that has a deviation greater than a
predetermined angle, e.g.,
about 1 °. However, if the wellbore deviation is less than the
predetermined angle, or it is
otherwise desired that a more accurate orientation system be included with the
string 210, then
additional modular sondes may be added or substituted, including a gyroscope
sonde 212.
Another sonde that can be used is an electromagnetic flux sonde 214 that may
include sensors
such as Hall-effect sensors that are sensitive to flux variations to find a
submersible pump cable
so that the orientation of the tool string with respect to the known position
of the submersible
pump cable may be determined. The electromagnetic flux sonde 214 uses a
electromagnetic field
that is propagated about the tool semi-spherically and as the string 210
rotates (controlled by the
motor 208) the flux field is affected by the mass of metal (e.g., completion
equipment or
components such as a submersible pump cable) around it. The measured data can
be transmitted
to the surface as the tool string 210 is lowered into the wellbore so that a
map can be derived of
what is downhole adjacent the perforating gun 250. The goal, depending on the
specific
application, may be to shoot away from or directly into a detected mass of
equipment or
components.
Another modular sonde that can be used is a focused gamma ray sonde 216. A
radioactive source can be associated with one of the downhole component being
protected or
targeted whether it be another production string or pump or sensor cable. The
tool string 210 is
then lowered downhole. As the string 210 is rotated, the gamma ray sonde 216
can detect the
position of the radioactive source.
Other embodiments are within the scope of the following claims. For example,
although
the components are described connected in a particular order, other orders are
possible. The
orientation techniques and mechanisms described can be applied to tool strings
other than
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perforating strings. Additionally, the strings can be lowered downhole using
other types of
carriers, such as coiled tubing.
Although the present invention has been described with reference to specific
exemplary
embodiments, various modifications and variations may be made to these
embodiments without
departing from the spirit and scope of the invention as set forth in the
claims.
What is claimed is:
