FIELD OF THE INVENTION

The present invention relates to a winch apparatus and in particular, but not exclusively, to winch apparatus for use with wireline and the like.

BACKGROUND OF THE INVENTION In the oil and gas exploration and extraction industries, tools, valves and other devices are often located in bores using wirelines, slicklines and the like. The wireline is stored on the surface on a motor driven winch drum forming part of a winch assembly. From the winch drum the wireline passes over a a bottom pulley and then a top pulley suspended from a mast above the bore, before passing through a pressure lubricator and wellhead assembly, and then into the bore. To ensure that the wireline spools correctly on the winch drum it is necessary that the aspect angle of the drum to the wireline, known as the fleet angle, is maintained within a predetermined and somewhat limited range. Similarly, when deploying wireline, the fleet angle must remain low to avoid the adjacent coils of wireline chaffing or otherwise interfering with one another and to avoid the possibility of the wireline being pulled across the drum and across adjacent coils, and thus jamming or damaging the wireline on the drum. conventionally, these difficulties are overcome by spacing the winch drum a significant distance

(at least 30 metres) from the bottom pulley. This spacing is necessary to restrict the maximum fleet angle, which is typically no more than 1.25 degrees; the maximum fleet angle is generally measured at the bottom pulley as the angle through which the wireline moves as the line spools across the winch drum between the centre of the drum and an end of the drum. Clearly, in many situations, such as offshore or rough terrain sites, achieving this spacing between the winch drum and pulley may be difficult, if not impossible. In addition, to allow accurate determination of the maximum fleet angle, the winch drum must be carefully aligned with the pulley before the wireline is deployed. Again, in many situations, achieving this alignment is likely to difficult and time consuming. It is among the objects of the present invention to provide a winch apparatus which obviates or mitigates these disadvantages. SUMMARY OF THE INVENTION

According to the present invention there is provided a winch apparatus for use in deploying or taking in line over a pulley spaced from the apparatus, the apparatus comprising a winch drum and alignment means for mounting the drum and permitting the drum to move to maintain the fleet angle of the line relative to drum within a predetermined range.

According to another aspect of the present invention there is provided a method of deploying line from, or taking line in onto, a winch drum over a pulley spaced

therefrom, the method comprising varying the alignment of the drum such that the fleet angle of the line relative to the drum remains within a predetermined range.

In use, the invention allows the fleet angle to _b e maintained within a predetermined range such that the line will self-spool on the drum, and deploy easily and smoothly from the drum. The invention has particular application in the deployment of wirelines, slicklines and the like. Using the present invention, in which the drum may move as the line spools to and fro across the drum, the drum may be located much closer to the pulley than is possible with existing winch arrangements. Also, initial alignment of the winch drum and pulley is not critical, facilitating set-up of the apparatus. Preferably, the apparatus includes means for sensing the fleet angle and actuating the alignment means to maintain the fleet angle within the desired range. For wireline applications, the sensing means may conveniently be mounted on the measuring head of the winch apparatus. The sensing means may comprise a pair of spaced sensors for location one on either side of the line, such that the line contacts one of the sensors as the fleet angle increases, the sensor then actuating the alignment means to move the winch drum in the appropriate direction to reduce the fleet angle, such that the line no longer contacts the sensor. Thus, the winch drum will be moved in a series of small steps as the line spools across the drum.

Preferably also, the winch apparatus includes a

mounting frame and the winch drum is pivotally mounted on the frame, for example on a swivel. The alignment means may be incorporated in the swivel or separately mounted on the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of a typical conventional wireline deployment arrangement;

Figure 2 is a plan view of elements of the arrangement of Figure 1; Figure 3 is a plan view of a winch apparatus in accordance with an embodiment of the present invention; and

Figures 4, 5 and 6 are somewhat schematic plan views of the winch apparatus of Figure 3, in use.

DETAILED DESCRIPTION OF THE DRAWINGS Reference is first made to Figures 1 and 2 of the drawings, which illustrate a typical arrangement for deployment of wireline into a bore, such as utilised in oil and gas exploration and extraction. The wireline 10 is utilised to locate tools, valves, sensors, and the like at a predetermined depth in the bore 12. Wireline 10 is stored and deployed from a winch apparatus 14 incorporating suitable drive motors, braking arrangements and controls, and providing mounting for a winch drum 16. The apparatus 14 also includes a measuring head 18 which measures the length of wireline deployed, and also the tension in the

wireline. From the measuring head 18, the wireline passes around a bottom pulley 20 and then over a top pulley 21 suspended from a crane or mast 22. From the pulley 21 the wireline 10 passes through a pressure lubricator 24 and a well head assembly 26, before passing into the bore 12. In other arrangements, for example for slickline deployment, the top pulley may be supported by the lubricator 24.

To ensure that the wireline 10 spools correctly on the winch drum 16 it is necessary that the maximum fleet angle A of the drum 16 to the wireline 10 is maintained within a predetermined and somewhat limited range (typically less than 1.25'). Similarly, when deploying wireline 10, the angle A must remain low to avoid the adjacent coils of wireline chaffing or otherwise interfering with one another and to avoid the possibility of wireline being pulled across the drum and across adjacent coils, and thus jamming or damaging the wireline 10 on the drum 16. With conventional winch apparatus 14, these potential difficulties are overcome by spacing the winch drum 16 at least 30 metres from the bottom pulley, and further ensuring that a line extending through the centre of the winch drum 16 and the pulley 20 is perpendicular to the drum axis D. With the winch drum 16 aligned in this manner the maximum fleet angle A corresponds to the maximum fleet angle F measured between the wireline 10 and the pulley 20. With the present invention, these difficulties are obviated or mitigated, as will become evident from the following description of an embodiment of the present

invention. Figure 3 is a plan view of a winch apparatus 30 in accordance with an embodiment of the present invention. The apparatus includes a frame 32 which provides mounting for a winch drum 34 driven by a hydraulic motor 36. The drum 34 is mounted on the frame 30 via a swivel 38 and the orientation of the drum 34 on the frame 32 is controlled by a pair of hydraulically actuated arms 40, 41, which engage with respective ends of the drum 34. A further pair of arms 42, 43 extend forwardly from the drum 34 and a bar 44 extends therebetween, parallel to the drum axis. The bar 44 provides mounting for a measuring head (not shown) which is free to move along the bar 44, and which measures the length of wireline deployed from the drum 34 and also the wireline tension. A sensor, including a pair of fingers 46, 47, one positioned on either side of the wireline 10, is mounted on the measuring head. The fingers 46, 47 are attached to respective pneumatic switches (not shown) which in turn actuate the drum arms 40, 41. The fingers 46, 47 detect changes in the fleet angle A of the drum 34 relative to the wireline 10 simply by contact of the wireline with a respective finger. Thus, as the wireline comes into contact with a finger this actuates the arms 40, 41 to pivot the drum 34 in the appropriate direction to bring the fleet angle back within the preferred range and thus bring the wireline out of contact with the respective finger. With particular reference to Figure 3, it will be noted that the wireline 10 is spooling onto the winch drum 34 at the extreme right hand end of the drum 34 (as viewed from

the pulley 20). In this position the fleet angle A is 0*. However, as the wireline 10 continues to wrap on the drum 34, the wireline will spool across the drum in direction X, causing the wireline 10 to come into contact with the finger 46. This actuates the arms 40, 41 to rotate the winch drum 34 in the direction Y to reduce the fleet angle A such that the wirelines 10 no longer contacts the finger 46. The control arrangement for the arms 40, 41 may be arranged such that the arms move in suitable predetermined increments each time the wireline contacts one of the fingers 46, 47.

If reference is now made to Figures 4, 5 and 6 of the drawings, the ranges of movement of the winch drum 34 may be seen, as the wireline spools across the drum from one end (Figure 4), to a central position (Figure 5), to the other end (Figure 6) . However, it will be noted that the fleet angle A of the drum 46 relative to the wireline 10 is maintained close to O', such that the wireline may be deployed and spooled onto the drum without any difficulties. Further, from Figure 5 it will be noted that the fleet angle F of the line 10 relative to the pulley 20 is substantially larger than the maximum fleet angle (1.25*) permitted with conventional fixed position wireline winches, thus permitting the winch apparatus 30 to be located relatively close to the pulley 20 (typically no more than 2 metres spacing required) . The ability to pivot the winch drum 34 also obviates the requirement to accurately align the winch apparatus 30 with the pulley 20.

It will be clear to those of skill in the art that the above-described embodiment is merely exemplary of the present invention and that various modifications and improvements may be made thereto without departing from the scope of the invention.