This invention relates to downhole wire line systems and, in particular,
to a method of making a wire line system that includes small-diameter tubing with
one or more signal and/or power conductors extending through the tube, and articles
of manufacture useful in the method.
Downhole instruments or tools for subterranean wells are lowered down
a well bore and operated in a subterranean reservoir to measure, for example, formation
characteristics such as bottom hole pressures and temperatures as a function of
time, and to perform many other measuring, control and operational tasks in a well.
Tools of this type are typically lowered on a conductive wire line.
The wire line is formed of coiled metal tubing ranging from 3mm-13mm (1/8"- 1/2")
in diameter, within which one or more conductors capable of transmitting a signal
and/or power are located. These conductors can be insulated conductor wires, optical
fibers or any other conductor capable of transmitting signals and/or power to or
from a downhole location.
The use of electrical conductors within a wire line is known, and
are described in U.S. patents 5,122,209 and 5,495,755, both of which are incorporated
herein by reference. Because wire line tubing of this type comes in lengths greater
than 3km (10,000 feet), up to and longer than 6km (20,000 feet), there has been
difficulty in inserting the conductor in such lengths of tubing.
In the past, as described in U.S. patent 5,122,209, a plurality of
electrical conductors have been formed within the coiled tubing by feeding a flat
metal strip and the conductors simultaneously through a series of tube-forming dies,
and then forming the tubing with the conductors in it by welding the elongated edges
of the metal strip around the conductors. Such methods have proved useful in the
past, but problems have arisen.
For example, fabrication of a wire-in-a-tube by using this method
often resulted in an imperfection in the tube before the entire length of product
is completed, which cannot be repaired. This adds significant cost to the manufacturing
process because of the high scrap rate.
Moreover, with the advent of much deeper wells, those 5km (16,000
feet) and deeper, relatively small diameter tubing formed of a high strength material
such as INCOLOY 825®, which has a relatively thick wall that is useful in such
wells, cannot be formed with a conductor in it. Annealing the tubing and drawing
it down in size are necessary for eliminating microscopic circumferential cracks
in the weld and increasing the strength due to work hardening of the material. These
steps cannot be performed with a conductor in the tubing.
Thus, there is a need for a method of making conductive wire line,
especially those useful in today's deep wells, which eliminates these problems.
US-A-4 616 705 discloses a method in accordance with the pre-characterising
parts of claims 1 and 14, as well as a weight in accordance with the pre-characterising
part of claim 24.
Problems discussed above have been solved by the invention described
in detail below, which involves inserting a length of conductor into an elongated
length of coiled metal tubing after the tubing is formed. The conductor can either
be in the form of an insulated conductor wire, optical fibers, other conductors
for conducting signals and/or power, or some combination thereof.
The invention provides a method as set forth in claim 1, a method
as set forth in claim 14, a conductive wire line as set forth in claim 19, a weight
as set forth in claim 24, and apparatus as set forth in claim 27.
The invention includes the steps of inserting the tubing into a substantially
vertical passageway such as a well bore, and providing an open upper end of the
tubing that is accessible to an operator. The leading end of the conductor is inserted
into the upper end of the tubing.
The leading end of the conductor includes an elongated weight connected
to the conductor. The weight must be heavy enough to straighten the conductor so
it can fall though the coiled tubing. The weight must also be flexible enough to
move through small bends or other irregularities in the coiled tubing.
A weight capable of performing these functions is one that has essentially
no stiffness so that it can fall freely through irregularities in the coiled tubing
without imparting a side load onto the inner surface of the coiled tubing, which
would prevent further downward movement. Such a weight can be formed of an elongated
segmented structure such as a chain with interlocking links or the like.
In embodiments of the invention where the weight must be pushed initially
into the coiled tubing, the weight must have a minimum bend radius that is great
enough to prevent the segments of the weight from bunching up or jamming when a
bend or other irregularity is encountered, but which has essentially no stiffness
and does not impart a side load until the minimum bend radius is reached. A preferred
form of such a weight is a chain with interlocking links that has been roll-formed
to provide the characteristics described above.
After the conductor and weight are inserted into the coiled tubing,
they are allowed to fall by gravity through the tubing at a controlled speed until
the desired length of conductor is inserted in the tubing. In embodiments where,
for example, the chain must travel through 90° or 180° bends before it can fall
vertically in the tubing, a push tool can be used to assist the initial insertion
of the chain into the tubing until there is enough weight in the tubing to allow
the weight to fall by gravity and pull the conductor into the tubing.
The helical pitch of the coiled tubing is regulated so that the frictional
contact between the outer surface of the conductor and the inner surface of the
tubing is great enough to support the weight and conductor for preventing the conductor
from breaking. After the conductor is inserted into the tubing, the conductive wire-line
assembly is wound on a reel and is ready for use.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be better understood when the detailed description
of preferred embodiments described below are considered in conjunction with the
appended drawings, in which:
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
- Figure 1 is a schematic view of a conductive wire line being run into an underground
- Figure 2 is a sectional view of an insulated conductor inside a section of coiled
metal tubing of the conductive wire line shown in Fig. 1;
- Figure 3 is a schematic view of the conventional prior art method of forming
conductive wire line;
- Figure 4 is a schematic view of dies forming a strip of metal into coiled tubing
in accordance with the method of Fig. 3;
- Figure 5 is a schematic view, in accordance with the present invention, of conductor
being inserted into coiled tubing that has been run into an underground well from
a conventional wire line truck;
- Figure 6 is a plan view of the outer surface of the downhole end of the coiled
tubing in Fig. 5, with its outer surface shaped by a forming tool in accordance
with the present invention so that a weight in the form of a sinker bar can be connected
to the tubing for pulling the tubing into the well bore and sealing the tubing;
- Figure 7 is a partial sectional view of the weight connected to the tubing;
- Figure 8 is a partial sectional view of the connection between the exposed end
of the coiled tubing and a holding fixture connected to the wire line truck;
- Figure 9 is a partial sectional view of the coiled tubing in Fig. 5 inside a
lubricator of an underground well showing in particular the helical shape of the
tubing after it has hit the bottom of the well and the tension in the tubing is
- Figure 10 is a schematic view of a conductor extending into the coiled tubing
and being unwound from a reel;
- Figures 11 and 12 are front and side plan views of a section of jeweler's chain
useful as a weight for lowering a conductor into the tubing;
- Figure 13 is a partial sectional view of the connection between the chain of
Figs. 11 and 12 and the conductor;
- Figure 13A is a schematic drawing showing a minimum bend radius in the chain
of Figs. 11 and 12;
- Figure 14 is a schematic view of the pusher tool for pushing the chain of Figs.
11 and 12 into the tubing; and
- Figures 15-17 are partial sectional views of the pusher tool and chain in Fig.
14, showing in particular the chain being pushed into the tubing.
The invention relates to an improved method of inserting one or more
conductors in a length of coiled tubing of the type used in conductive wire line
for downhole operations. In broad general terms, the method involves inserting the
conductor into the coiled tubing and letting the conductor fall by gravity after
the tubing is run into a well or the like. The invention also relates to various
articles of manufacture that are useful in performing the method.
Coiled tubing is a relatively small diameter metal conduit that is
wound on a reel, which has a helical shape or residual curvature when the tubing
is unwound from the reel due to an inherent memory in the metal. Conductive wire
line is a length of coiled tubing used primarily in downhole applications, which
includes one or more signal or power transmitting conductors extending through the
A typical use for conductive wire line is shown in Fig. 1, where a
wire line 10 is spooled or coiled on a drum or reel 12 that is mounted on a wire
line truck 14. The wire line 10 is unwound from the drum 12 and, after passing through
rollers 16 and over sheaves 18 and 20, is lowered into an underground well 22 through
a lubricator 24 and a well head. A tool 26, for example, a logging tool, is mounted
on the end of the wire line 10 for performing a down hole operation.
The lubricator 24 includes a packing 28 at the upper end for forming
a seal around the wire line 10 and an isolating valve 30 at the lower end for isolating
the lubricator 24 from the well. A hydraulic pump 32 located outside the lubricator
24 pressurizes the packing 28 for effecting the seal.
As shown in Fig. 2, the wire line 10 is a conductive wire line formed
of coiled tubing 34 and a conductor 36 that extends through the tubing 34, which
is capable of transmitting signals or power. In use, the conductor 36 maintains
a helical shape inside the tubing 34, due to its own inherent memory, which has
the advantage of supporting the conductor 36 inside the tubing 34 through the frictional
interface between the outer surface of the conductor and the inner surface of the
tubing, as described in U.S. patent 5,495,755. Without this support, for the lengths
typically used, the weight of the conductor 36 in the well bore is greater than
its break strength. Thus, the conductor 36 cannot support its own weight and would
break without this frictional hold-up force.
This inherent helical shape of the conductor is one of the problems
that must be overcome if the conductor is to be inserted into the tubing in accordance
with the present invention. Thus, unless the conductor is straightened, the conductor
cannot fall by gravity through the coiled tubing. At the same time, however, there
must be sufficient frictional contact between the outer surface of the conductor
and the inner surface of the coiled tubing so that the weight of the conductor is
supported by the tubing.
Moreover, when a length ofcoiled tubing in excess of 300m (1,000 ft),
and up to and greater than 6km (20,000 ft), is unwound from a reel and suspended
in a well, the coiled tubing also has an inherent helical shape. The conductor,
in addition to being straight, must also be able to travel through the helical bends
in the tubing and bends or curves caused by any irregularities in the well.
In addition to these problems, the difficulty of inserting conductors
in coiled tubing that has already been formed can be appreciated considering the
relatively small inner diameter of the tubing (an outer diameter of 3mm-13mm [1/8"-1/2"]
minus the wall thickness) and length of the tubing (greater than 300m [1,000 ft]
and up to and greater than 6km [20,000 ft]), and the fragile nature of the conductors
(e.g., insulated electrical wire, optical fibers and the like). The challenge is
especially daunting for inserting a wire of, for example, about 1.4mm (0.055") in
diameter in a length of coiled tubing in excess of 300m (1,000 ft), and up to and
greater than 6km (20,000 ft), having an inner diameter as small as 2.26mm (0.089"),
which is less than two times the diameter of the conductor 36. The invention described
in detail below provides a solution for this extremely difficult technical problem.
In the past, such wire-in-a-tube, conductive, wire-line assemblies
were manufactured by forming the tubing around a conductor, as described in detail
in U.S. patent 5,122,209. Briefly, by way of background, Figs. 3 and 4 illustrate
the method described in that patent, in which a conductor 36 that is spooled on
a reel 42 is fed simultaneously with a metal strip 44 that is spooled on a reel
46. The metal strip 44 and conductor 36 are fed through a series of rollers 48,
50 and 52, which bend and roll the strip 44 into the tubing 34, with the conductor
36 inside the tubing 34. A spring 54 extends into the tubing 34 before the edges
of the strip 44 are welded together by a welding station 56, for protecting the
conductor 36 from damage. The final wire-in-a-tube product is then wound on a reel
While this process has been successful in forming conductive wire
line, the process is expensive and prone to a high rejection rate. Oftentimes, an
imperfection occurs along the length of the tubing. Such imperfections cannot be
repaired, requiring that length of tubing to be scrapped, which adds substantially
to the manufacturing costs of the final product.
The method of the present invention is an improvement over previously
used methods of placing one or more conductors in coiled tubing. The method utilizes
coiled tubing manufactured by conventional techniques without any conductors in
it. Generally, this tubing is lowered in a conventional way into an underground
well or other type of vertical passageway through which the tubing can extend. A
conductor is then inserted into the tubing and allowed to fall by gravity through
A novel weight formed of an elongated segmented structure with essentially
no stiffness (described in greater detail below), is connected to the leading end
of the conductor for pulling the conductor straight and providing sufficient weight
for gravitational forces to cause the conductor to fall to the bottom of the tubing.
Preferably, this weight is formed of a chain with interlocking links,
which has sufficient flexibility to pass through bends or other irregularities in
the coiled tubing caused by its inherent helical shape, by irregularities in the
well casing, or by other bends formed in the manufacturing and handling of the coiled
tubing. A chain with interlocking links is also important because it can be formed
with a relatively high density to reduce the length of the weight. Such a chain
can also be formed with a minimum bend radius for preventing the links from bunching
up or jamming when the chain must be pushed into the tubing to get it started when,
for example, the conductor must pass though bends of 90° or 180° before it can fall
vertically into the tubing. Details of a preferred embodiment of the weight are
described in greater detail below.
The use of such a chain is the first time a known workable method
has been developed for inserting one or more conductors in coiled tubing that is
suspended in a well or the like. Although several prior art patents suggest some
of the problems that might be encountered, no workable solutions were disclosed.
For example, in U.S. patent 3,835,929, a "guide means" is generally
mentioned as being removably attached to the lower end of a cable to assure that
the cable would not "kink" in the tubing. However, no structure is described for
this so-called guide means. An alternative method involving pumping the cable through
the tubing is mentioned, which does not work because a sufficient force cannot be
applied to move the cable through the tubing.
In U.S. patent 4,616,705, for a different application where a thermocouple
in an elongated wire is described as being lowered through coiled tubing extending
along the outer surface of well casing, a sinker line formed of aircraft wire with
beads crimped onto the wire about 13mm (S") apart, is described as being able to
pull an elongated sensing means downward and straighten any bends in it. The wire,
although it is said to be flexible, is too stiff to travel through short radius
bends because it imparts a side load on the wall of the tubing due to its inherent
stiffness. Thus, neither of these patents constitutes an enabling disclosure of
a workable way of inserting a conductor in coiled tubing that has already been placed
in a substantially vertical passageway by allowing the conductor to fall freely
by gravity through any small bends or other irregularities in the tubing until the
conductor is fully inserted.
One way of performing the invention, which solves these problems,
is shown in Fig. 5. The tubing 34 is spooled on a reel 60 that is mounted on a conventional
wire line truck 62. The tubing 34 is transported to a well site or other location
where a vertical passageway of suitable depth is situated. A second reel 100 on
which conductor 36 is spooled can also be mounted on the wire line truck 62. Alternatively,
a facility can be situated near a well site or the like for performing the function
of the wire line truck 62.
The coiled tubing used in conjunction with the invention is preferably
formed of stainless steel or nickel alloys, but other suitable materials known in
the art can be used. This type of coiled tubing typically has an outer diameter
of 3mm-13mm (1/8"-1/2"). A material for which the invention is particularly useful
is a high-strength nickel alloy used in deep wells (greater than 5km [16,000 ft])
called INCOLOY 825® (a trademark of the International Nickel Company), which
has an outer diameter of 5mm (3/16"), and a relatively thick wall of about 1.25mm
(0.049"), resulting in an inner diameter of about 2.26mm (0.089").
The conventional method for placing a conductor in tubing of this
type, which is described in above and shown in Figs. 3 and 4, has been found to
be unsuitable. After the tubing is initially formed, it is annealed and then drawn
down to a smaller diameter for eliminating any minute circumferential cracks in
the weld, refining grain structure of the material and making the tubing stronger
through work hardening. These post-forming steps cannot be performed with the conductor
in the tubing.
The type of conductor that can be used in conjunction with the invention
is preferably an insulated copper wire 38 formed of stranded 20 gauge nickel-plated
copper wire. The conductor 36 has an insulation covering 40 of polyimid tape (KAPTON®
a trademark ofDuPont), mill spec MIL-8138/12. A secondary coating of aromatic polyimid
resin is applied in a known way to seal the tape and improve durability. However,
a wide variety of other insulated electrical conductors could also be used.
Alternatively, the conductor 36 could be one or more optical fibers
that are capable of transmitting signals. Other types of conductors could also be
used. The invention contemplates encompassing any type of signal or power transmitting
conductor, or some combination thereof, that is capable of being inserted in tubing
and used in down hole applications.
The tubing 34 is run into the well in a known way, by first connecting
a weight, such as known type of sinker bar 86 (see Figs. 6 and 7), to the leading
end of the tubing 34. The connection between the tubing 34 and the sinker bar 86
is formed by first preparing the leading end of the tubing 34 as shown in Fig. 6.
A forming tool (not shown) of the type shown and described in U.S.
patent application S.N. 666,846, filed June 6, 1996, entitled "Roll-Formed Seat
and Retainer ...", which issued as U.S. Patent No. 5,907,966 on June 1, 1999, is
used to form tapered surfaces 78, 80 and 82 in the outer surface of the tube 34.
The tube 34 is then inserted through an opening 84 formed in a the sinker bar 86,
as shown in Fig. 7. The sinker bar 86 includes an upper section 86A that has a chamber
88 in which a known type of fitting made by Swagelok Corporation is used to connect
the sinker bar 86 to the tubing 34 and seal the leading end of the tubing 34 from
fluids in the well.
The Swagelok® fitting includes ferrules 78A, 80A and 82A for engaging
the grooves 78, 80 and 82, respectively. The ferrules 80A and 82A are held in place
between nuts 77 and 79, and a union 81. The ferrule 78A is held between a nut 83,
a fitting 85 and a seal cap 87. The sinker bar 86 also includes a lower section
86B that is threaded onto the upper section 86A after the sinker bar is connected
to the tubing 34 as described. The sinker bar also includes a fishing neck 89 for
retrieving the sinker bar 86 from the well.
As shown in Fig. 5, the tubing 34 (including the sinker bar 86 connected
its leading end), is passed over a lower sheave 64 that is connected through a cable
68 to a well head 66, and over an upper sheave 70 that is fixed to the lubricator
67. The lubricator 67 includes the packing, isolating valve and hydraulic pump shown
in Fig. 1 for effecting a seal as discussed above, but these features have been
omitted from Fig. 5 for ease of illustration.
As the tubing is unwound from the reel 60, it has a helical shape
caused by the inherent memory of the material of the tubing. Initially, the weight
of the sinker bar 86 straightens the coiled tubing 34 and pulls it into the well.
After gravitational forces pull the sinker bar 86 and tubing 34 a certain distance,
the weight of the tubing 34 in combination with the weight of the sinker bar 86
will straighten the tubing 34 and pull it to the bottom of the well or until the
sinker bar 86 is stopped by a bridge plug (not shown) set at a desired depth in
the well. At this point in time, when there is no pulling force acting on the coiled
tubing 34, it will have a helical shape inside the lubricator 67 and in the well
as shown schematically in Fig. 9.
The tubing 34 is then disconnected from the reel 60, and connected
to the truck by using a holding fixture 91 like the one shown in Fig. 8, so that
the conductor 36 can be inserted in tubing 34. Because the tubing is resting on
the bottom of the well or on a bridge plug or the like in the well, the tubing 34
can be disconnected from the reel 60 and not held at the well surface. Alternatively,
the tubing 34 could be held in place in the well by using known slips or the like.
The tubing 34 is then connected to the truck in this embodiment of
the invention through an arm 89 that is connected to the truck 62. The tubing 34
is mounted in a holding fixture 91 that is connected to the arm 89 through a bolt
93. After a groove 95 is formed in the outer surface of the tubing 34 as shown in
Fig. 8 by the same grooving tool mentioned above and described in U.S. patent No.
5,907,966, described above, a standard Swagelok® fitting 97 (including a ferrule
97A and backwards nut 97B) is used to connect the tubing 34 to the fixture. A plastic
guide bushing 99 can be placed on the end of the tubing 34 for preventing the insulation
or cladding on the outer surface of the conductor 36 from dragging on the sharp
inside edge of the tubing 34 when it is inserted in the direction of arrow C as
shown in Fig. 8.
Because of the inherent memory of the coiled tubing 34, it maintains
a helical shape in the lubricator 67 and in the well, as shown in Fig. 9, when the
truck 62 is not pulling on the tubing 34 and holding it in tension. The pitch of
this helical shape can be regulated, for the reasons discussed below, by moving
the truck 62 back and forth as indicated by two-headed arrow 74 in Fig. 5, which
movement straightens or relaxes the tubing 34.
Before the conductor 36 is inserted into the coi led tubing, an elongated
weight such as a chain 118 shown in Figs. 11 and 12 is connected to the leading
end 116 of the conductor 36 (see Fig. 13) for straightening the conductor 36 and
pulling the conductor 36 into the tube 34. The elongated weight must have essentially
no stiffness so that it can fall through small bends and other irregularities in
the coiled tubing without imparting a side load onto the inner surface of the tubing,
which would result in a frictional hold-up force. Such a weight can be formed of
an elongated segmented structure such as a chain with interlocking links or the
like. Alternatively, a beaded chain (not shown) of the type used as a pull for light
fixtures could be used provided it had sufficient density to provide the needed
weight. Segmented weights of these types have sufficient flexibility to pass through
irregularities in the coiled tubing caused by its inherent helical shape or by irregularities
in the well casing that cause bends in the coiled tubing.
In embodiments of the invention where the weight must be pushed initially
into the coiled tubing to get it started, for example, where it must pass through
bends of 90° or 180° before it can fall vertically, the weight must be formed with
a minimum bend radius for preventing the links from bunching up or jamming when
such irregularities are encountered. The minimum bend radius ofa chain of the type
shown in Figs. 11 and 12 is illustrated in Fig. 13A. The radius line R depicts the
minimum bend radius of the chain 118 when it is looped, and the ends of the chain
118 are pulled in the direction of arrows 119 until the chain locks and will not
bend any further.
A weight found to satisfy these requirements is 180 S.A. 54 jewelry
chain, which is formed of brass. As shown in Figs. 11 and 12, the links of this
chain are different from the links in a conventional chain because they have been
roll-formed into a round cross-sectional shape, to where the ends of each link are
oriented at about 90° relative to each other as shown in the link 120 in Fig. 11.
This shape substantially reduces the gaps between adjacent links and has the effect
ofproviding a chain with a relatively high density (approximately 7 specific gravity),
so that the weight has more weight per unit of length. A distinct advantage of this
higher density chain is that a shorter length can be used to provide the required
weight for initially pulling the conductor 36 into the tubing 34.
The interlocking links 120 can be compressed for controlling the minimum
bend radius of the chain 118. For the purposes of the invention, a minimum bend
radius is preferably set within a range of about 6mm-60cm (1/4"-24"), and more preferably
at about 10 cm (4"). The chain can be purchased with the links already roll formed.
The links can be compressed by passing the chain through a rolling mill of the type
known to jewelers. A length of about 180cm (600 ft) of roll-formed brass chain (180
S.A. 54) with a minimum bend radius of about 10cm (4"), which weighed 2.7-3.2 kg
(6-7 lb.), was found satisfactory to perform the method in accordance with the invention
An advantage of the roll-formed chain 118 shown in Figs. 11 and 12
is that it can be pushed into the coiled tubing without bunching up and jamming
when it reaches a bend or other irregularity. When the invention is performed in
a well of the type shown in Fig. 1, which has a lubricator and well head, the ability
to push the chain initially through 90° and/or 180° bends over several pulleys and
into the well can be important.
However, if the chain can be dropped directly into the well as it
is unwound from a reel, it might not have to be pushed. In such a case, the weight
can be formed of a conventional linked chain that does not have any significant
minimum bend radius. The interlocking links provide sufficient flexibility for allowing
the chain to pass through small bends and irregularities in the tubing.
Although conventional linked chain can be used in such situations,
a roll-formed and compressed chain of the type shown in Figs. 11 and 12, where the
links are twisted so that the ends of each link are oriented at 90° relative to
each other, has the advantage that it has about twice the density of the conventional
linked chain and is therefore about twice the weight per unit length, so that only
half the length must be used.
The chain 118 with interlocking links constructed as described above,
is connected to the leading end 116 of the conductor 36, as shown in Fig. 11, by
using a known type ofcrimp connection. The insulation 40 is stripped from the leading
end 116 exposing a short length of wire 38. The wire 38 is inserted into one end
of a crimp connection 122. A loop of steel wire 124 is passed through the outside
link 120 of the chain 118 and inserted into the other end of the crimp connection
122. A known crimping tool (not shown) is used to crimp the connection 122 onto
the wire 38 and wire loop 124 for connecting the chain 118 to the wire 38.
The chain 118 is then introduced into the tubing 34. However, because
the tubing 34 is not, in many cases, located directly over the well, an assist in
such cases must be provided for the chain 118. An assist found to be useful is provided
by a push tool 126 of the type shown in Figs 14-17. The push tool 126 frictionally
engages the outer surface of the chain 118 and pushes it into the tubing 34 a sufficient
distance until gravitational forces begin acting on the chain 118 and cause it to
fall of its own weight. The push tool 126 should be able to push at least 20-30
m (70-100 ft) of chain into the tubing 34.
As shown in Figs. 14-17, the push tool 126 includes a pair of gripping
jaws, such as those provided by a pair of VICE-GRIPS®, on which a pair of guides
128 and 130 are mounted. The guides 128 and 130 and guide extensions 128A and 130A
(Fig. 17) form a hollow opening 132 through which the chain 118 can pass, when the
guides are closed by moving the guide 128 in the direction of arrow 129 as shown
in Fig. 17. A small electric motor 124 is connected to one of the guide extensions
130A, which drives a wheel 134 formed of rubber or other compressible elastomer.
As the chain 118 passes between the drive wheel 134 and an adjacent idler wheel
135, rotation of the drive wheel 134 in the direction of the arrow 138 pushes the
chain 118 in the direction of the arrows 136.
A guide tube 140 positioned between the guide extensions 128A and
130A guides the chain 118 into the tubing 34. After the chain 118 is pushed into
the tubing 34 a sufficient distance, gravity will begin operating on the chain118
so that it falls of its own weight. The wire line truck 62 is moved in the direction
of the arrow 74 (Fig. 5) to adjust the helical pitch of the tubing 34 for maintaining
an acceptable tension in the conductor 36 below its break strength resulting from
the frictional contact between the outer surface of the conductor 36 and the inner
surface of the tubing 34.
The rate of descent of the chain 118 and conductor 36, preferably
at about 60m/min (200 ft/min) is governed by a gear motor 102 connected to the reel
100, shown in Fig. 10, which controls the rate of rotation of the reel 100. Thus,
if the pitch of the helix in the tubing is maintained constant, the tension in the
conductor (e.g., the weight of the chain 118 and conductor 36 being supported in
the tubing by the conductor) will be maintained at a constant level during the entire
insertion process. The gear motor 102 regulates the speed of descent and the helical
shape of the tubing 34 supports the weight of the conductor 36.
For an insulated electrical conductor wire of the type described above,
the break strength is about 267N (60 lb), which is less than the combined weight
of the conductor 36 and the chain 118 after the conductor 36 is inserted to predetermined
depth. However, by regulating the pitch of the tube 34, the conductor 36 is able
to support its own weight and will not break as it falls by gravity through the
As shown in Fig. 10, as the conductor is unwound from the reel 100,
it moves in the direction of arrows 108, over idler pulleys 110, 112 and pulley
106, through alignment rollers 114, and into the tubing 34 which is mounted in the
holding fixture 91. A tension indicating device in the form of a scale 104 can be
connected to the conductor 36 through the pulley 106 for maintaining a continuous
reading of the tension load in the conductor 36, which is an indication of the weight
being carried by the conductor 36. It was found that a weight of about 1.36-5.44
kg (3-12 lbs.) carried in a conductor having a break strength of about 267N (60
lbs), provided a workable range.
After the conductor 36 is completely inserted into the tubing 34,
the tubing 34 is then re-connected to the reel 60 and the wire-in-a-tube is removed
from the well and wound on the reel 60. Thus, a conductive wire-line assembly is
formed in a way that eliminates the need to place the conductor in coiled tubing
as it is formed, which has the advantages described above.
While a preferred embodiment for practicing the invention has been
described, it should be understood that there are many modifications, variations
and improvements that can be made that are within the scope of the invention, as
defined by the appended claims.