The present invention relates to an injector for injecting coiled tubing into an oil or gas well.
Coiled tubing injectors are often used to inject coiled tubing into an oil or gas well to facilitate the servicing of the well. For some well-servicing applications, the diameter of the tubing must be increased in the upper sections of the tubing for reasons related to the well-servicing process.
One technique for accommodating an increase in diameter is to dispose a tapered connector between a relative small-diameter section and a relatively large diameter section. However, a problem arises in connection with this technique especially when the tubing passes through an injector for injecting it into the well. In particular, due to the rigidity of the injector structure, substantially all of the loading on the tubing provided by the injector is applied to the area of the connector having the relatively larger diameter. This results in a relatively small percentage of the exterior surface of the connector bearing substantially all of the loading, creating high stress areas at the points of contact with the injector, and possibly causing failure in the connector and/or the tubing.
Therefore, what is needed is an injector for passing coiled tubing through an injector that overcomes this problem.
Referring to
A spool of coiled tubing 18 is positioned at a predetermined location away from the injector 10. Unspooled tubing 20 passes from the spool and under a measuring device, such as a wheel 22, and between several (seven in the example of
The injector 10 includes a frame 28 having a base 28a, and a pair of substantially similar carriages 30a and 30b mounted on the base via a pair of carrier lugs 31a and 31b. The carriages 30a and 30b drive the tubing 20 into the stuffing box 16 for passage through the well-head 14 and into the well 12.
The carriages 30a and 30b are depicted in greater detail in
Two rods 34a and 34b extend out from the cylinders 32a and 32b, respectively, with one end of each rod being connected to its corresponding piston and the other end connected to the carriage 30a by two mounting brackets 35a and 35b, respectively. It is understood that the cylinders 32a and 32b are connected in a hydraulic circuit (not shown) so that fluid is selectively introduced and discharged from the cylinders to cause corresponding contraction and extension of the cylinders. An example of the hydraulic circuit that may be used is disclosed in co-pending patent application Ser. No. 10/840,787 the disclosure of which is incorporated herein by reference in its entirety. This contraction and extension of the cylinders 32a and 32b causes corresponding movement of the carriages 30a and 30b towards each other to grip the tubing 20, and away from each other to release the tubing. It is understood that two other cylinders (not shown), identical to the cylinders 32a and 32b, are connected to the carriages 30a and 30b on the other sides of the carriages.
The carriage 30a includes a gripping chain 36 extending between, and engaged with, two spaced sprockets 37 (one of which is shown in
The outer surface of the chain 40 is in engagement with the inner surface of the chain 36 and is free wheeling about its sprockets 42. It is understood that a motor (not shown) is provided to drive at least one of the sprockets 37, and therefore the chain 36. The engagement between the chains 36 and 40 is such that the chain 36 drives the chain 40 which functions to support the chain 36.
Since the carriage 30b is identical to the carriage 30a the above components of the carriage 30a will be referred to by the same reference numerals in connection with the carriage 30b.
During the general operation, and referring to
The beam 44 associated with the carriage 30a is shown in detail in
As better shown in
As shown in
Although the tubing 20 is depicted in
In operation, the tubing 20, including one or more tubing sections 20a and 20b joined by a connector 56, is unspooled through a pathway defined by the rollers 24 and is straightened as it passes through the rollers and enters the injector 10. In this context, it is understood that the connector 56 and the relatively large-diameter tubing section 20b follow a relatively small section 20a as the tubing is unspooled and that the rollers 24 are adapted to pivot, retract, or the like, in a conventional manner to accommodate the connector 56 and the relatively large section 20b.
The cylinders 32a and 32b (as well as the two cylinders located on the back sides of the carriages 30a and 30b) are actuated via the above-mentioned hydraulic circuit to draw the carriages 30a and 30b towards each other in the manner described above until the gripper elements 38 on the gripping chains 36 engage the tubing 20 at a predetermined loading. The above-mentioned motors are then activated to drive the sprockets 37 and the gripping chain 36 of each carriage 30a and 30b, thereby gripping and lowering the tubing 20 into the well 12. Each gripping chain 36 also drives its corresponding roller chain 40 about the sprockets 42, with the roller chains providing support for their respective gripping chains.
During the passage of the tubing 20 through the injector 10 in the above manner, when a connector 56 enters the region of the injector 10 between the gripping chains 36 of the carriages 30a and 30b, the variable increasing diameter of the connector 56 creates a radially directed force that gradually increases along the length of the tubing. This force is applied directly to the chains 36 and 40 and deflects the chains radially outwardly causing a corresponding deflection of the plates 52 against their corresponding elastomer plates 50. As a result, the plates 50 are compressed against their corresponding beam plates 44b to accommodate this increase in diameter of the tubing 20.
Each elastomer plate 50 will continue to compress further as the diameter of the connector 56 gradually increases as it passes through the path defined between the carriages 30a and 30b. Thus compression of the plates 50 will increase along their respective lengths so that the respective inner surfaces of the plates will take a tapered shape corresponding to the shape of the outer surface of the connector, as shown in
Since the lengths of the plates 50 and 52 extend for substantially the length of the carriages 30a and 30b, a substantial number of gripper elements 38 of each of the chains 36 will contact the connector 56 during this gradual diameter increase of the tubing 20. Therefore, a uniform force distribution will be maintained along the length of the connector 56 which prevents the creation of isolated high stress areas.
It is understood that the above technique is the same when the tubing 20 is withdrawn from the well 12 and spooled back on the spool 18, with the direction of movement being opposite that discussed above.
It is understood that variations may be made in the foregoing without departing from the scope of the invention. For example, the invention may be used without the connector 56, such as with a spool of coiled tubing having a gradually increasing diameter along its entire length or with a spool of coiled tubing having a substantially constant diameter. Also, the plates 50 and/or 52 can be fastened to the beam plate 44b via fasteners other than shoulder bolts, such as with studs rigidly connected to and extending from the beam plate 44b. Further, the quantity of cylinders 32a and 32b may vary as long as an evenly distributed load is applied to the tubing 20 via the gripper elements 38. Moreover, any type of hydraulic circuit may be utilized to extend and retract the cylinders.
Any foregoing spatial references, such as “upper,” “between,” “front,” “right side,” “side,” “above,” etc., are for the purpose of illustration only and do not limit the specific spatial orientation of the structure described above.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
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Number | Date | Country | |
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20050247454 A1 | Nov 2005 | US |