Wells – Processes – Assembling well part
Reexamination Certificate
2001-10-15
2002-05-07
Schoeppel, Roger (Department: 3672)
Wells
Processes
Assembling well part
C166S384000, C166S077200, C166S085500, C166S242200
Reexamination Certificate
active
06382322
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for contacting and Supporting coiled tubing during its injection into and withdrawal from a well bore. More particularly, the invention relates to drive rollers having a central driven arcuate wheel and multiple idler tires mounted on either side of the central driven wheel. The idler tires have arcuate surfaces with the same diameter as the driven wheel surface and concentric with the arcuate surface of the central driven wheel, thereby supporting the tubing over a large arc without causing severe rubbing from differential motion between the wheel assembly and the tubing.
BACKGROUND OF THE INVENTION
Devices and methods for injecting coiled tubing into and retrieving it from wells are well known. Prior art coiled tubing injection systems include U.S. Pat. Nos. 6,142,406; 5,842,530; 5,839,514; 5,553,668; 5,309,990; 5,244,046; 5,234,053; 5,188,174; 5,094,340; 4,899,823; 4,673,035; 4,655,291; 4,585,061; and many other similar disclosures. In the prior art an injector at the wellhead is used to grip and control the injection and withdrawal of the tubing.
Conventional track injectors utilize gripper blocks mounted on two continuous parallel and opposed conveyor chains which are urged or pushed against the outer surface of the tubing. The interface forces between the gripper blocks and the tubing permit developing frictional forces which are used to transfer tangential loads from the conveyor chains to the tubing and vice versa. If insufficient interface force is applied to the tubing by the gripper blocks, slippage with attendant loss of control and wear occurs between the blocks and tubing. If excessive interface force is applied to the tubing by the gripper blocks, the tubing wall may be distorted and damaged or the injector may be damaged. A problem with such tracks results when the track is rotated into or out of engagement with the tubing from the sprockets at the ends of the track mounting assembly. This rotation can cause differential movement between the track and the tubing in the direction of the tubing axis so that rubbing occurs. As used in this description, the term “rubbing” represents any of the effects induced by metal pieces moving relative to each other when in contact, such as galling, abrasion, tearing, scrubbing, or skidding. Rubbing causes undesirable wear of both the tubing and the gripper blocks.
Historically, the approach used to increase the injection forces with conventional track injectors has been to lengthen the injector while maintaining a sufficiently safe interface force between the individual gripper blocks and the tubing. U.S. Pat. No. 5,842,530 for example shows provision of substantially more gripper blocks along the length of its injector.
Other injectors utilizing two continuous, parallel, and opposing track injectors having grooved shoes or blocks mounted thereon are known in the art. These opposing track units have facing portions where the multiplicity of gripping blocks run parallel for gripping the tubing therebetween and are typically positioned in line, directly adjacent and above the wellhead.
Another approach has been to utilize a large diameter driven wheel with an annularly grooved outer diameter to conform to and support the tubing. Relatively small-diameter hold-down idler rollers radially press the tubing against the wheel to provide extra interface force between the tubing and the wheel so that high tangential frictional forces can be imparted to the tubing by the wheel without maintaining large back tensions. These hold-down rollers have arcuate faces to match the tubing, but pronounced rubbing occurs between the tubing and the roller due to differential movement at different rotational diameters of the roller face. While the mechanism of wheel type injectors is simple, inexpensive, and reliable, wheel size can be a limitation, especially for larger tubing diameters. One such wheel type injector is disclosed in U.S. Pat. No. 5,839,514.
A more recent injector system known in the art is a linear injector which pulls on only one side of the tubing. For this type of device, coiled tubing is driven along a single linear section of an endless chain conveyor with an opposing linear array of small-diameter arcuate face hold-down idler rollers. These hold-down rollers are sized to conform to the tubing, but they as a result cause the previously mentioned differential rubbing motion between the tubing and the roller face. Such a linear or one-track injector eliminates the necessity of synchronizing the two opposed sides of a conventional track type injector and is less damaging to the surface of the coiled tubing, but it requires a much longer unit, which of necessity extends much higher and requires additional overhead clearance. Additionally, such an injector is more expensive because it requires a considerable number of gripper blocks and rollers and a longer support track.
Copending U.S. Provisional Patent Application “Coiled Tubing Injector Utilizing Opposed Drive Modules and Having an Integral Bender”, filed Jul. 11, 2001, utilizes a novel approach to imparting tangential injection forces to the tubing. That invention provides support over a larger portion of the tubing circumference by the driving means around the circumference of the tubing. By using a plurality of sets of opposed individually driven annularly grooved rollers which closely conform to the tubing and alternating the orientations of adjacent roller sets so that they are 90° apart about the through axis of the injector, excellent tubing support is provided. That invention is light weight, compact, easy to service and changeout for different tubing sizes, low cost, and efficient. However, the small-diameter arcuate rollers of this device exhibit the same undesirable rubbing action between the roller face and the tubing as the previously mentioned injectors.
A major problem with tubing injectors of all types is differential movement between the tubing and the portion of the injector mechanism which contacts the tubing. For instance, for opposed track type machines, when the drive chain carrying the gripper blocks has a link coming off of or entering onto the sprockets of the track drive, differential motion relative to the axis of the tubing occurs as a result of the difference in rotational radii for the surface of the support groove of the rotating gripper block. This differential motion results in an axial direction rubbing of the tubing surface which results in wear of both the contact block and the tubing. While this situation also exists for the large drive wheel of wheel type injectors, rubbing due to the small difference in circumferential speed at the different radii of the tubing support blocks is small enough to not be important for the wheel. This, however, is not the case for any small-diameter hold-down rollers used with either wheel-type injectors or linear injectors. Similarly, for the simple small-diameter arcuate drive rollers used in the copending U.S. Patent Application for “Coiled Tubing Injector Utilizing Opposed Drive Modules and Having an Integral Bender,” rubbing becomes more significant when the supporting arc of the drive roller is increased to provide more tubing support.
Elimination or minimization of the rubbing between the drive and hold-down rollers and the tubing in tubing injectors utilizing small diameter wheels is desirable for reducing both wheel and tubing wear. Minimizing such rubbing is particularly difficult when it is desirable to provide support for the tubing over a large arcuate surface in order to minimize tubing ovaling under the action of lateral loads. A significant need exists for improvements which will permit simultaneously minimizing the erosive action of rubbing and maximizing tubing support.
SUMMARY OF THE INVENTION
The present invention utilizes a novel means and method for improving the injecting of coiled tubing into and from a well by reducing the rubbing action of arcuate wheels or rollers used to guide and react against the tubing
Coiled Tubing Solutions, Inc.
Hall Elizabeth R.
Schoeppel Roger
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