Note: Descriptions are shown in the official language in which they were submitted.
LINEAR TUBULAR ASSIST DEVICE AND METHOD
FIELD
[0001] This invention is in the field of oil and gas, and more specifically to
installation of
tubulars in horizontal sections of oil and gas wells.
BACKGROUND
100021 In the oil and gas industries, coiled tubing refers to a long metal
pipe in diameter which is
supplied spooled on a large reel. The main benefits is the ability to push the
coil tubing into the
hole rather than relying on gravity.
SUMMARY
[0003] The aspects as described herein in any and/or all combinations. In an
aspect, there is
provided a linear motor for moving a ferromagnetic object in a horizontal bore
of a well. The
linear motor may comprise: a hollow cylindrical casing; a conductive coil
wrapped around the
cylindrical casing; a cable electrically connected to the conductive coil and
configured to
energize the conductive coil to generate a magnetic field within the
cylindrical casing; and the
magnetic field inducing motion of the ferromagnetic object along the
cylindrical casing.
DESCRIPTION OF THE DRAWINGS
[0004] While the invention is claimed in the concluding portions hereof
example embodiments
are provided in the accompanying detailed description which may be best
understood in
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conjunction with the accompanying diagrams where like parts in each of the
several diagrams are
labeled with like numbers, and where:
100051 Figure 1 is a side cross-sectional view of a drill site;
100061 Figure 2 is a side view of a tubular assist device; and
100071 Figure 3 is a side cross-sectional view demonstrating an electrical
configuration for the
tubular assist device.
DETAILED DESCRIPTION
[0008] As shown in FIG. I, a side cross-sectional view of a drill site 100 is
shown. The drill site
100 may comprise a drill rig 102, or other type of rig, such as for example a
coiled tubing unit
(not shown) or a workover/service rig (not shown), located above a bore 104
that has been
drilled by a drill bit (not shown). The bore 104 extends down from the drill
rig 102 in a vertical
portion 106 to a heel 108 at which the bore 104 changed to a generally
horizontal portion 110 to
the toe (not shown) where the bore 104 ends. The bore 104 may comprise a
casing 132 formed
of concrete sections (not shown).
[0009] The casing 132 may receive coiled tubing 130 fed from the drill rig
102. The coiled
tubing 130 may be pushed using a pushing force from the surface 308 to the toe
of the bore 104.
The coiled tubing 130 may be sufficiently flexible for the coiled tubing 130
to bend such that the
coiled tubing 130 may pass through the heel 108. At the end of the coiled
tubing 130 may be a
tool string 112. The tool string 112 may comprise bottom hole assemblies such
as a mud motor
and bit, jetting tool, cup tool, packers, and/or perforating guns. In this
aspect, the tool string 112
may comprise a material responsive to a magnetic field, such as a
ferromagnetic (e.g. iron,
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carbon steel). In other aspects, the tool string 112 may comprise an
electromagnet. In some
aspects, the coiled tubing 130 may comprise the material responsive to the
magnetic field and/or
the electromagnet.
[0010] When the coiled tubing 130 contacts the casing 132, the coiled tubing
130 experiences
friction. For example, if a section of the coiled tubing 130 is in tension
when passing through a
curved portion of the bore 104, such as the heel 108, the tension causes the
coiled tubing 130 to
be pushed against an inside of the curve. With increased tension, a radial
load is greater pushing
the coiled tubing 130 against the wall of the casing 132 resulting in
friction. Similarly, when the
coiled tubing 130 is in compression, the coiled tubing 130 is pushed against
the outside curve
also resulting in friction. When the coiled tubing 130 passes through the heel
108 in this manner,
the friction forces may be known as a capstan effect.
100.11.1 When the coiled tubing 130 is pushed horizontally along the
horizontal portion 110 of the
bore 104, the pushing force required to push the coiled tubing 130 is equal to
a total weight of
the coiled tubing 130 and the tool string 112 in the casing 132 multiplied by
a friction coefficient
between the casing 132 and the coiled tubing 130. As the length of the coiled
tubing 130
increases, the force required to overcome the friction force also increases.
When the pushing
force exceeds a sinusoidal buckling load, the coiled tubing 130 starts to form
a sinusoid within
the casing 132 at the toe end.
[0012] When the coiled tubing 130 is continued to be pushed, a first portion
of the coiled tubing
130 may continue to be straight in the casing 132 and a second portion will be
lying in a sinusoid
on the bottom of the casing 132. Once the pushing force exceeds a helical
buckling load, the
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coiled tubing 130 forms a helix portion within the casing 132. The helix
causes additional wall
contact forces that increases the friction between the coiled tubing 130 and
the casing 132.
100131 As the coiled tubing 130 is pushed further into the bore 104, the helix
portion of the
coiled tubing 130 increases in length at the toe end. The increase in the
helix portion results in
increased wall contact forces resulting in a helical lockup where the coiled
tubing 130 may be
pushed no further into the bore 104 no matter how much axial force may be
applied. The helical
lockup may limit a maximum length of the horizontal portion 110.
[0014] Further details regarding calculating coiled tubing forces may be
provided by "Basic
Tubing Forces Model (TFM) Calculation" by Ken Newman & Kenneth Bhalla, CTES,
L.P.,
published January 13, 1999, herein explicitly incorporated by reference in its
entirety and
updated in "Basic Tubing Forces Model (TFM) Calculation" by Ken Newmann,
Kenneth Bhalla,
and Albert McSpadden, CTES L.P., published October, 2003, herein explicitly
incorporated by
reference in its entirety.
100151 The problems associated with helical lockup are generally a result of
the coiled tubing
130 being pushed from the surface 308. Some of the friction may be addressed
through the use
of lubricants between the coiled tubing 130 and the casing 132 of the bore
104. In some aspects,
lubricants may be insufficient, expensive, and/or unsuitable
100161 In this example, one or more linear motors 120, 122 may be placed along
the horizontal
portion 110 of the bore 104. The linear motors 120, 122 may provide a motive
force to the
coiled tubing 130 and/or the tool string 112. The motive force may pull on the
toe end of the
coiled tubing 130 causing the coiled tithing 130 to maintain a straight
configuration within the
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casing 132 and thereby reducing a probability of helical lockup and/or
frictional forces between
the casing 132 and the coiled tubing 130.
100171 Turning to FIG. 2, a linear motor 200 may comprise a section 240 of
casing 132
constructed of concrete, carbon steel, or similar material. The linear motor
200 may be
constructed by using a joint of the production casing 132. Once installed in
the well, the casing
132 may be cemented in place. The cementing of the casing 132 may be performed
by pumping
a cement slurry through the casing 132 and displacing fluid until an annulus
between the casing
132 and the well bore wall is full of cement. Once this operation is completed
the linear motor
200 may be permanently installed in the well. In some aspects, the cement may
comprise
thermal cement in order to prevent degradation over time due to heat produced
by the linear
motor 200.
[0018] After installation, the section 240 may comprise a cylinder having a
generally hollow
interior 202 for receiving the coiled tubing 130. In some aspects, the
diameter of the section 240
may comprise casing diameters selected from 4.1/2, 5.1/2', and 7". The section
240 may
comprise a threaded end 260 where the threads are on the exterior of the
section 240 for
screwing the section 240 into other sections of casing 132. Opposite the
threaded end 260 may
be a coupler 250 configured to receive the threaded end of other sections of
casing 132. In this
aspect, the coupler 250 may be threaded on the interior of the section 240.
[0019] A conductive coil 230 may be wrapped around the section 240 of casing
132. In this
aspect, the conductive coil 230 may be a copper material or any other type of
conductor,
although copper may be the most cost-effective conductor. A maximum thickness
of the coil
230 may be equal to the outer diameter of the particular casing's coupling.
For example, a 5.1/2"
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casing may have a thickness of 1" and therefore, the thickness of the coil 230
may be less than or
equal to 1". The conductive coil 230 may be covered with an insulating coating
230 electrically
insulating the conductive coil 230 from the bore 104. In this aspect, the
coating 230 may
comprise a polyurethane material to protect the coil windings as the
conductive coil 230 is
.. installed into the well. The conductive coil 230 may be electrically
connected to a cable
connection 210 on the coupler end 250 of the section 240. The cable connection
210 may have a
positive and a negative/ground terminal.
[0020] Turning to FIG. 3, a cable 302 comprising at least two electrical
lines, one for ground and
one for power (not shown) may be run along the exterior of the casing 132 and
may be banded to
the exterior of the casing 132. The electrical cables 302 run from the surface
308 to the cable
connection 210 on the linear motor 200 forming an electrical circuit. In some
aspects with more
than one linear motor 200, the cable 302 may comprise a control line (not
shown) that may
communicate a signal to activate a relay (or similar electrical device) 312
associated with each of
the linear motors 200. When a particular relay 312 becomes activated, the
linear motor 200
associated with the relay 312 passes current through the linear motor 200. In
some aspects, each
linear motor 200 may be installed at least 1000-m apart. The cable 302 may
then continue on to
the relay 312 of the next linear motor 310.
[0021] When the conductive coil 230 is energized using the pair of electrical
lines, a magnetic
field may be induced within the center of the coil 230. Since the tool string
112 may comprise
.. the magnetic responsive material, the magnetic field may induce motion of
the tool string 112.
For example, when the current flows in one direction through the coil 230, the
magnetic field
generated pulls on the tool string 112 in one direction. When the current
flows in the opposite
direction through the coil 230, the magnetic field generated pulls on the tool
string 112 in the
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opposite direction. An amount of current required to move the magnetic
responsive material
may be determined based, in part, on the casing size, length of cable, the
size of the linear motor
200, and/or a combination thereof. A plurality of linear motors 200 may be
placed adjacent to
each other and turned on sequentially in order to further accelerate the tool
string 112 in one
direction or another. The pulling of the tool string 112 may alleviate
problems associated with
the helical lockup of the coiled tubing 130 by pulling on the end of the
coiled tubing 130
reducing sinusoidal buckling and/or helical buckling.
[0022] To use and control the linear motor 200, an electrical generator 304
and a Variable
Frequency Drive 306 may be connected to the cable at the surface 308. The VFD
306 may
control a frequency, a duration, the current, and/or a direction of the motive
force on the tool
string 112 and/or coiled tubing 130 passing within the linear motor 200.
[0023] To install the linear motor 200, the section 240 may be threaded into
other sections of the
casing 132 forming a casing string. The casing string may be landed past the
heel 108 of the
well 100 in the horizontal section 110. Once the casing string has been
landed, cementing of the
casing string may take place. A casing slip and seal assembly (not shown) may
then be installed
and the electrical cable may be routed out of a port in a tubing hanger
section (not shown) of the
wellhead 102.
[0024] Although the aspects described herein demonstrate the linear motor 200
acting on the tool
string 112, other aspects may have the linear motor 200 acting on the coiled
tubing 130, tubulars,
telemeters, and/or other downhole tools.
100251 The dimensions depicted in the figures may not be to scale. Certain
features may have
been exaggerated in order to facilitate identification.
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10026] The foregoing is considered as illustrative only of the principles of
the invention.
Further, since numerous changes and modifications will readily occur to those
skilled in the art,
it is not desired to limit the invention to the exact construction and
operation shown and
described, and accordingly, all such suitable changes or modifications in
structure or operation
which may be resorted to are intended to fall within the scope of the claimed
invention.
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