Note: Descriptions are shown in the official language in which they were submitted.
CA 02438289 2003-11-26
STRAIGHTENING SYSTEM FOR TUBING
Background of the Invention
In the oil industry, long or continuous lengths of downhole pipes or tubing
are often
wrapped or coiled on spools for storage or transport. Uncoiling or removing
the tubing from
the spool without straightening results in tubing that has been elastically
deformed in two
planes and that wants to stay bent. That is, the tubing is deformed about the
axis of the spool
as well as the length or width of the spool and (when released from the spool)
will have the
visual appearance of a helical or corkscrew shape. More specifically, the
direction of
deformation is bi-planer, namely in planes X and Z which are orthogonal with
respect to one
another. In both the X and Z planes, the coiled tubing is sinusoidally
deformed. As a result of
this deformation, in many applications or uses, the tubing must be
straightened prior to use.
Past devices used to straighten tubing, while effective for certain downhole
applications, are not acceptable in other applications either as a result of
failing to fully
straighten the tubing or by being operationally unwieldy. For example, some
straightening
systems fail to adequately straighten the tubing due to the design of the
straightening system.
Other systems may require that the coiled tubing be subjected to multiple
passes through
straightening equipment to adequately straighten the tubing. While multiple
passes may
ultimately provide a straight tube, multiple passes are difficult to perform
as well as being
time and operationally inefficient. In other systems, other problems include
tube buckling
when tubes are pushed through the straightening system under pressure.
An example of a prior art straightening system is shown in Figure 1. Figure 1
shows a
straightening system having two sets of three straightening rollers. When
deformed coiled
tubing is passed through each set of rollers, as it is impossible to fully
yield the tubing in
opposite directions, the position of the rollers in one plane will result in
tubing having either
alternately straight and curved sections or tubing having a constant bend
radius. While such a
system may ultimately be able to provide straight tubing by subjecting the
tubing to multiple
passes and thereby render the tubing sufficiently straight for some
applications, such systems
are inefficient and may not be sufficient for all downhole applications.
Accordingly, there continues to be a need for straightening systems which can
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CA 02438289 2003-11-26
straighten coiled tubing in a single pass in order that the tubing is straight
enough to be used
in various applications, and in particular those requiring torsion such as
driving down-hole
pumps.
Examples of past systems include those described in US Patent 5,309,746, US
Patent
4,663,955, US Patent 3,855,835, US Patent 4,724,733, US Patent 6,279,363, US
Patent
3,690,136 and US Patent 5,676,009, none of which provide a tube straightening
systems that
contemplate fully yielding tubing in two planes for use downhole.
Summary of the Invention
In accordance with the invention, there is provided a tube straightening
system having
two orthogonally positioned sets of rollers for straightening tubing in a
first and second plane
wherein each set of rollers includes two pairs of opposing and corresponding
rollers and
wherein the position of the two pairs of opposing rollers with respect to the
corresponding
pair yields tubing passing through the set of rollers in two directions to
produce a straightened
tube in either of the first or second plane respectively.
In accordance with another embodiment of the invention, there is provided tube
straightening system comprising a first set of four rollers having a first
pair of rollers in an
opposing relationship and a second pair of rollers in an opposing relationship
and wherein the
first and second pairs of rollers are aligned such that a tube to be
straightened passing between
the first and second pairs of rollers is fully yielded in a first plane and a
second set of four
rollers having a third pair of rollers in an opposing relationship and a
fourth pair of rollers in
an opposing relationship and where the third and fourth pairs of rollers are
aligned such that
tube to straightened passing between the third and fourth pairs of rollers is
fully yielded in a
second plane and wherein the first plane is orthogonal to the second plane.
In accordance with a still further embodiment, there is provided method of
straightening tubing comprising: passing coiled tubing to be straightened
through a first set of
rollers having opposed pairs of rollers to yield the tubing within the first
set of rollers in a first
plane; and passing the coiled tubing through a second set of rollers having
opposed pairs of
rollers to yield the tubing within the second set of rollers in a second plane
that is orthogonal
to the first plane.
Brief Description of the Drawings
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CA 02438289 2003-11-26
Figure 1 is a schematic view of a three-roller straightening system
in~accordance with
the prior art;
Figure 2 is a plan view of a four roller straightening system in accordance
with the
invention; and,
Figure 3 is a schematic diagram showing dimensional details of a roller in
accordance
with the invention.
Description of the Invention
With reference to Figure 2, a straightening system 10 for coiled tubing or
solid rod is
described. The straightening system enables coiled lengths of tubing or solid
rod that are
helically deformed in two orthogonal planes to be effectively yielded in both
planes to
produce straight tubing.
The system 10 includes two sets of four rollers orthogonally oriented with
respect to
each other. Generally, a length of coiled tubing is actively advanced through
a first set of
rollers to produce tubing straightened in the first plane whereby the position
of the rollers with
respect to the dimensions of the tubing applies a yielding force to opposing
sides of the tubing
so as to completely yield the tubing on opposing sides of the tubing.
Advancing the tubing
through a second set of rollers yields the tubing in the second plane.
With reference to Figure 2, the straightening system includes a first set of
rollers A
and a second set of rollers B at a 90 degree orientation (orthogonal planes)
with respect to the
first set A. Both sets of rollers are substantially identical to each other in
design and function.
A length of tubing 210 is shown within each roller set. With reference to set
B, four rollers or
wheels 202, 204, 206, 208 are rotatable about a first axis (perpendicular to
the plane of the
page) operatively connected to a platform 212. Rollers 202, 204 and 208 are
passively
rotatable whereas roller 206 is actively driven by a motor (not shown) so as
to actively
advance the tubing 210 through the system. In addition, rollers 202 and 204
are mounted in
appropriate guide slots 218, 220 so as enable adjustment of the spacing
between rollers 202,
204 and rollers 206 and 208. As shown, adjustment of the spacing between
opposing rollers is
controlled by hydraulic pumps 214, 216 operatively connected to rollers 202
and 204
respectively and which may be set by an appropriate controller (not shown)
based on various
parameters including tubing diameter, materials and environmental conditions.
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CA 02438289 2003-11-26
Roller 206 is actively driven to advance tubing through the straightening
system. As is
best shown in Figure 2 for roller set A and corresponding roller 226, a drive
motor 224 is
provided to advance the tubing 210 through roller set A. Active drive prevents
buckling of the
tubing at entry point E.
The first three rollers 202, 204, 206 are positioned to completely yield the
tubing in a
first direction on one side of the tubing in order to ensure that the same
memory is applied to
the entire length of tubing as the coiled tubing passes through the first
three rollers of the
straightening system. The tubing is yielded again on the opposite side of the
tubing to yield it
to a straight configuration with the fourth roller 208.
Fig. 3 shows a cross section of one of the rollers, for example, roller 202,
having a
curved tubing contacting surface 304 and body 306. The curved tubing
contacting surface 304
accommodates tubing 210 while the tubing passes through the rollers.
Preferably, the
diameter of the curved centre is slightly larger than the size of the tubing's
diameter to
prevent both scuffing marks on the side of the tubing as well as to
accommodate tubing
having marginally non-symmetrical cross-sections. In a preferred embodiment,
the diameter
of the curved tubing-contacting surface of the roller is approximately 0.5%
larger than that of
the diameter of the tubing running through the roller.
The edge 308 between the outer part 306 and the curved centre 304 in a
preferred
embodiment is provided with a rounded corner to prevent scoring.
In operation, the straightening system of the present invention can be used to
continuously straighten pipes and tubing in the field without multiple passes.
The system is
particularly useful in driving rotating down-hole pumps in the production of
oil fields.
This description is written in the context of coiled tubing but it is
understood that the
process and apparatuses described herein apply to all types of solid or hollow
lengths of pipes
or tubing.
