Patent Application
20060096754
The present invention relates to an apparatus and method for injecting tubing into a well utilizing a drive chain, and, more particularly, to such an apparatus and method for monitoring stretching of the chain. The phrase “chain stretch” or “stretch” is commonly used in the industry to indicate the net lengthening of the chain due to wear of the members (rollers, pins, etc.) comprising the chain. Stretching does not mean that the metal members of the chain have elongated due to elastic or plastic deformation.
Coiled tubing injectors are often used to inject coiled tubing into an oil or gas well to facilitate the servicing of the well. These injectors usually include a pair of chains that extend to either side of the coiled tubing, and gripper blocks mounted to the chains for engaging the coiled tubing and driving it into the well. Also, depth indicators are often used that engage the chain and provide an indication of the depth of the coiled tubing based on the movement of the chain.
However, the chains can stretch with use and age, leading to ultimate failure of the chain, and, in the meantime, causing erroneous readings from the depth indicators.
Therefore, what is needed is a system and method for monitoring chain stretch so that the above problems can be avoided.
Referring to
A spool 18 of coiled tubing 20 is positioned at a predetermined location away from the injector 10. The unspooled tubing 20 passes from the spool 18 and under a measuring device, such as a wheel 22, and between several (seven in the example of
The injector 10 is constructed and arranged in a manner to be described to drive the tubing 20 into the well 12, and the depth sensing device 16 includes a wheel (not shown) that engages an outer surface of the tubing 20, and an encoder to provide an output signal corresponding to the linear motion of the tubing 20 as it passes into the well 12. Since the depth sensing device 16 is conventional, it will not be described in further detail.
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 28a via a pair of carrier lugs 31a and 31b. The carriages 30a and 30b drive the tubing 20 through the wellhead 14 and into the well 12.
The carriages 30a and 30b are depicted in greater detail in
The carriage 30a includes a gripping chain 36 extending between, and engaged with, two spaced sprockets 38 (one of which is shown in
A roller chain 40 is also provided that extends within the gripping chain 36 and engages two spaced sprockets 42 (one of which is shown in
It is understood that a motor (not shown) is provided to drive at least one of the sprockets 38, and therefore the gripping chain 36. The outer surface of the roller chain 40 is in engagement with the inner surface of the gripping chain 36 and is free wheeling about its sprockets 42 and the engagement between the chains 36 and 40 is such that the gripping chain 36 drives the roller chain 40 which functions to support the gripping chain 36.
A rotation sensing device 50, preferably in the form of a rotation wheel/encoder, is mounted on one of the sprockets 38 (the upper one as viewed in
The carriage 30b (
As shown in
In operation, and referring to
The depth sensing device 16 and the rotation sensing devices 50 associated with the carriages 30a and 30b function to produce output signals corresponding to the depth, or linear motion, of the tubing 20, as it passes into the well 12, and the rotation of one of the sockets 38 associated with the carriages 30a and 30b, respectively. As shown in
When the gripping chain 36 of each carriage 30a and 30b is unstretched, the outputs of the corresponding sensing devices 16 and 50 are calibrated to produce a predetermined output. Thus, a given amount of linear motion (length) of the tubing 20 passing by the depth sensing device 16 will cause a specific amount of rotation of the sprockets 38 associated with the carriages 30a and 30b. As a non-limitative example, the system could be calibrated so that a predetermined amount of linear motion, or length, of the tubing 20 will produce a specific rotation of the sprockets 38 associated with the carriages 30a and 30b. The linear motion and the revolutions are sensed by the sensing devices 16 and 50, respectively, and corresponding output signals are sent from the sensing devices 16 and 50 to the processor 54.
Assuming that the gripping chain 36 associated with the carriage 30a stretches over time and with use, this ratio will change, since the same sensed linear motion of the tubing 20 will cause less revolutions of the sprocket 38 associated with the carriage 30a as sensed by the corresponding rotation sensing device 50. The processor 54 is programmed to respond to this change and provide a corresponding output signal or visual indication, to alert an operator that the gripping chain 36 has stretched and the degree of stretching. Of course, any stretching of the gripping chain 36 of the carriage 30b will result in a similar output from the processor 54. Thus, the stretched chain(s) 36 can be replaced to prevent the problems discussed above.
The embodiment of
In operation, the tubing 20 is driven into the well 12 in the same manner as described above, while the depth sensing device 16 senses the linear motion of the tubing 20 as it is injected into the well 12. The proximity sensing device 52 senses the frequency of passage of the components, or links, of the gripping chain 36, and provides corresponding output signals to the processor 54.
Thus, the system could be calibrated so that, when the gripping chain 36 is unstretched, a predetermined amount of linear motion, or length, of the tubing 20, as sensed by the depth sensing device 16, will result in a corresponding frequency of passage of the components, or links, of the gripping chain 36, as sensed by the proximity sensing device 52. Corresponding output signals are sent from the sensing devices 16 and 52 to the processor 54.
When the gripping chain 36 stretches over time and with use, fewer components of the gripping chain 36 pass by and are sensed by the proximity sensing device 52 during the same amount of sensed linear motion of the tubing 20, due to the fact that the components are farther apart due to the stretching. The processor 54 receives corresponding output signals from the sensing devices 16 and 52 and is programmed to respond to this change and provide a corresponding output signal, or visual indication, to alert an operator that the gripping chain 36 has stretched and the degree of stretching. Of course, any stretching of the gripping chain 36 of the carriage 30b will result in a similar output from the processor 54. Thus, the stretched gripping chain(s) 36 can be replaced to prevent the problems discussed above.
Although this embodiment was described in connection with the gripping chain 36 on the carriage 30a, it is understood that a sensing device identical to the proximity sensing device 52 can also be mounted on the carriage 30b of the injector 10 (
According to another embodiment, the proximity sensing device 52 could be designed to sense linear motion of the gripping chain 36 as it passes by the proximity sensing device 52, and send a corresponding output signal. This could be done in any conventional manner such as providing the proximity sensing device 52 with a laser scanner that is pointed at the gripping chain 36 and providing indicia, or the like, on the gripping chain 36 that is scanned by the laser scanner. Thus, the system could be calibrated so that, when the gripping chain 36 is unstretched, a predetermined amount of linear motion, or length, of the tubing 20, as sensed by the depth sensing device 16 will result in a corresponding amount of linear motion of the gripping chain 36, as sensed by the proximity sensing device 52; and corresponding output signals would be sent from the sensing devices 16 and 52 to the processor 54.
When the gripping chain 36 stretches over time and with use, the amount of linear motion of the gripping chain 36 sensed by the proximity sensing device 52 decreases during the same amount of sensed linear motion of the tubing 20, due to the fact that the sensed indicia are farther apart due to the stretching. The processor 54 receives corresponding output signals from the sensing devices 16 and 52 and is programmed to respond to this change and provide a corresponding output signal or visual indication, to alert an operator that the gripping chain 36 has stretched and the degree of stretching.
Although this embodiment was described in connection with the gripping chain 36 on the carriage 30a, it is understood that a sensing device identical to the proximity sensing device 52 can also be mounted on the carriage 30b of the injector 10 (
It is understood that variations may be made in the foregoing embodiments without departing from the scope of the invention. For example, the rotation sensing device 50 of the embodiment of
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.
