GB2588416A

GB2588416A - Apparatus for and method of setting slips around a drill string

Info

Publication number: GB2588416A
Application number: GB1915306.3A
Authority: GB
Inventors: Lien Geir; Mydland Petter
Original assignee: Mhwirth AS
Current assignee: Mhwirth AS
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2021-04-28
Anticipated expiration: 2039-10-23
Also published as: GB2588416B; GB201915306D0

Abstract

An apparatus for setting slips 326 around a drill string comprises a base 302 and a robot arm 304. The arm 304 has a first end 304a rotatably mounted to the base 302 and pivotable about a first axis P perpendicular to the floor. The arm 304 has a second end 304b provided with a slip lifting tool 326. The arm 304 comprises a first portion 308 and a second portion 310 which are connected by a rotatable joint 312 which pivots about a second axis Q which is perpendicular to the first axis P. The arm 304 can include a slip lifting tool 306 and a holder 318. The arm apparatus 300 sets slips around drill string and tubulars on the drill floor in order to reduce or avoid personnel in the red zone.

Description

Apparatus for and Method of Setting Slips around a Drill String The present invention relates to an apparatus for and method of setting slips around a drill string, particularly but not exclusively, on a drilling rig.

Drilling rigs commonly have a platform directly under a derrick which provides a work area in which the rig crew can work, and this platform is known as the drill floor. The driller's cabin, from which the major components of the rig are controlled, is located on or adjacent the drill floor.

The drill floor is among the most dangerous location on a drilling rig because of the heavy equipment which is moved around the area, yet many tasks associated with the running of a drilling operation are currently carried out manually by personnel working on the drill floor. The most dangerous area of the drill floor is commonly known as the red zone.

In drilling operations, it is common to build a string of tubulars, such as a drill string, on the drill floor above the well centre opening. The string is usually assembled using a series of threaded pipe sections, where the threaded connections are made up (or broken out) using appropriate machines, such as pipe handling machines and power tongs. A bottom hole assembly (BHA) including a drill bit, is mounted at the lowermost end of the drill string.

When making or breaking the connection between pipe sections, it is known to suspend the drill string from the drill floor using slips which comprise three or more steel wedges that are hinged together and form a near circle around the drill string, with the thicker end of each wedge above the thinner end. The radially inwardly facing surface of each wedge can be provided with a roughened gripping surface, which may comprise replaceable steel teeth, to provide increased friction between the slips and the outer surface of the drill string.

The slips are positioned around the drill string just above the well centre opening -an aperture in the drill floor through which the drill string extends, and then set by lowering the drill string so that the slips engage with the drill floor. The taper of the wedges is matched to the taper of the edges of the well centre opening and so the taper generates from the downward force from the drill string a radially inward compressive force which pushes the slips against the drill string. The drill string is thus gripped by the slips, and the engagement of the slips with the drill floor acts to prevent any further downward movement of the drill string relative to the drill floor. The drill string is thus supported by the drill floor.

The slips are removed by raising the drill string to release the grip of the slips on the drill string, and the slips lifted off from around the drill string.

Typically, personnel working in the red zone are involved in manual setting of the slips. They can be assisted using equipment such as a pneumatically or hydraulically powered arm which is pivotally mounted on a base secured around the well centre opening. The slips are mounted on the free end of the arm, and the arm pivoted about an axis which is generally parallel to the drill floor, to lower and position the slips around the drill string. Manual intervention is required to bring the slips to the well centre and to mount the slips on arm, however.

According to a first aspect we provide an apparatus for setting slips around a drill string comprising a base and an arm, the base being configured to support the arm on a drill floor of a drilling rig, the arm having a first end which is mounted on the base for pivoting about a first axis which, when the base is supporting the arm on the drill floor, is generally perpendicular to the drill floor, a second end at which is provided with a slip lifting tool, the arm comprising a first portion and a second portion which are connected by a joint by means of which the second portion may rotate with respect to the first portion about a second axis which is generally perpendicular to the first axis, the first portion extending from the first end of the arm to the joint, and the second portion extending from the joint to the second end of the arm.

The apparatus may further comprise a first actuator which is operable to pivot the arm relative to the base about the first axis.

The apparatus may further comprise a second actuator which is operably to pivot the second portion of the arm relative to the first portion of the arm about the second axis.

The slip lifting tool may comprise a spring which can be connected to slips mounted on the slip lifting tool to urge the slips to an open position.

The slip lifting tool may comprise a gripper having first and second clamp parts and a gripper actuator which is operable to move the first and second clamp parts towards one another to a grip position, and away from one another to a release position. The slip lifting tool may further comprise a separate slip holder which has a connector by means of which the slip holder can be mounted on the slips and a grip part which is shaped to be gripped by the gripper by placing the first and second clamp parts around the grip part and using the actuator to move the clamp parts to the grip position. The connector may comprise an elongate support beam which has a longitudinal axis, a first end to which the grip part is connected, and a second end provided with a plurality of prongs which extend generally downwardly perpendicular to the longitudinal axis of the support beam The slip holder may comprise at least one spring a first end of which is connected to the slip holder and a second end of which is adapted to be connected to the slips on which the slip holder is mounted.

The slip lifting tool may be pivotally mounted on the second end of the arm for rotation with respect to the arm about a third axis which is generally perpendicular to the longitudinal axis of the second portion of the arm. The slip lifting tool may be pivotally mounted on the second end of the arm for rotation with respect to the arm about a fourth axis which is generally perpendicular to the longitudinal axis of the second portion of the arm and to the third axis.

The apparatus may further comprise a third actuator which is operable to pivot the slip lifting device relative to the arm about the third axis.

The apparatus may further comprise a fourth actuator which is operable to pivot the slip lifting device relative to the arm about the fourth axis.

The or each actuator may be hydraulically or pneumatically driven.

According to a second aspect of the invention we provide a drilling rig having a drill floor with a well centre aperture and slip lifting apparatus according to the first aspect of the invention, the base of the slip lifting apparatus being mounted on the drill floor at a location spaced from the well centre aperture.

According to a third aspect of the invention we provide a method of mounting slips around a drill string extending through the well centre aperture on a drilling rig according to the second aspect of the invention, the method comprising: a) with the second end of the arm of the slip lifting apparatus positioned at a location which is spaced from the well centre aperture, first mounting slips on the slip lifting tool, b) then pivoting the arm of the slip lifting apparatus about the first axis to move the slips around the drill string, and c) then pivoting the second portion of the arm of the slip lifting apparatus about the second axis to lower the slips down the drill string.

Step b may also comprise pivoting the second portion of the arm of the slip lifting apparatus about the second axis.

The slip lifting tool may comprise a gripper having first and second clamp parts and a gripper actuator which is operable to move the first and second clamp parts towards one another to a grip position, and away from one another to a release position, and a separate slip holder which has a connector by means of which the slip holder can be mounted on the slips and a grip part which is shaped to be gripped by the gripper by placing the first and second clamp parts around the grip part and using the gripper actuator to move the clamp parts to the grip position, step a of the method may comprise the steps of: al) positioning the slips at a storage location on the drill floor spaced from the well centre aperture, a2) mounting the slip holder on the slips, a3) then, with the clamps parts of the slip lifting tool in their release position, pivoting the arm of the slip lifting apparatus about the first axis and / or the second portion of the arm of the slip lifting apparatus about the second axis and operating the gripper actuator so that the clamp parts move to the clamp position, and such movement causes the grip part of the slip holder to be gripped by the gripper.

The connector of the slip lifting tool may comprise an elongate support beam which has a longitudinal axis, a first end to which the grip part is connected, and a second end provided with a plurality of prongs which extend generally downwardly perpendicular to the longitudinal axis of the support beam, and step a2 may comprise inserting the prongs into corresponding apertures provided in the slips.

The slip holder may comprise at least one spring a first end of which is connected to the slip holder and a second end of which is adapted to be connected to the slips on which the slip holder is mounted, and step a2 may comprise attaching the second end of the spring to an attachment point on the slips.

The slip lifting tool may be pivotally mounted on the second end of the arm for rotation with respect to the arm about a third axis which is generally perpendicular to a longitudinal axis of the second portion of the arm, and step b of the method may further comprise pivoting the slip lifting tool about the third axis. The slips may have a longitudinal axis which arranged to be generally parallel to the longitudinal axis of a drill string when the slips are mounted around a drill string, the third axis may be generally parallel to the drill floor, and step b of the method may further comprise pivoting the slip lifting tool in a first direction about the third axis to rotate the slips to bring the longitudinal axis of the slips towards the horizontal prior to positioning the slips around the drill string, and pivoting the slip lifting tool in a second opposite direction about the third axis to rotate the slips so that the longitudinal axis of the slips is generally horizontal whilst positioning the slips around the drill string.

The slip lifting tool may be pivotally mounted on the second end of the arm for rotation with respect to the arm about a fourth axis which is generally perpendicular to the longitudinal axis of the second portion of the arm and to the third axis, and step b of the method may further comprise pivoting the slip lifting tool about the fourth axis.

In one aspect, a tool assembly for handling slips on a drill floor may comprise: an arm comprising a plurality of articulated parts, the arm rotatably mounted on a base which is fixed in relation to the drill floor; a slips lifting tool; a holder or holder means for the slips lifting tool, the holder or holder means arranged on the arm and operable to hold the slips lifting tool; the slips lifting tool comprising a connector operable to engage and carry the slips.

The holder or holder means may be operable to releasably engage and hold the slips lifting tool.

The holder or holder means may comprise a gripper operable to grip and hold a grip part of the slips lifting tool.

The slip lifting apparatus or the arm may be remotely controlled from an operator station.

The slip lifting tool may comprise a slips carrier having a first connector fixed to the slips and a second connector operable to engage the holder.

The second connector may be a grip part operable to be gripped or clamped by the holder or holder means.

The slip lifting apparatus or the tool assembly may be arranged on a movable trolley. The movable trolley may comprise drive units or drive means operable to drive the trolley on or around the drill floor.

Embodiments of the invention will now be described with reference to the following figures of which: Figure 1 shows an illustration of a slip lifting apparatus and assembly with slips mounted on the slip lifting tool, Figure 2 shows a schematic illustration of a drilling rig having a slip lifting apparatus and assembly arranged on a drill floor, and Figures 3 and 4 illustrate an embodiment of a slip lifting apparatus and assembly arranged on a movable trolley.

Referring now to Figure 1, there is shown a slip lifting apparatus 300 for setting slips around a drill string comprising a base 302 and an arm 304, the base 302 being configured to support the arm 304 on a drill floor of a drilling rig, the arm 304 having a first end 304a which is mounted on the base for pivoting about a first axis P, a second end 304b at which is provided with a slip lifting tool 306. The arm 304 comprises a first portion 308 and a second portion 310 which are connected by a joint 312 by means of which the second portion 310 may rotate with respect to the first portion 308 about a second axis Q which is generally perpendicular to the first axis P, the first portion 308 extending from the first end 304a of the arm 304 to the joint 312, and the second portion 310 extending from the joint 312 to the second end 304b of the arm 304. When the base 302 is supporting the arm 304 on a drill floor, the first axis P is generally perpendicular to the drill floor, whilst the second axis Q is generally parallel to the drill floor.

The apparatus 300 further comprises a first actuator 314 which is operable to pivot the arm 304 relative to the base 302 about the first axis P, and a second actuator 316 which is operable to pivot the second portion 310 of the arm 304 relative to the first portion 308 of the arm 304 about the second axis Q. In this embodiment, the slip lifting tool 306 comprises a gripper 318 having first and second clamp parts 318a, 318b and a gripper actuator 320 which is operable to move the first and second clamp parts 318a, 318b towards one another to a grip position (illustrated in Figure 1), and away from one another to a release position. The slip lifting tool 306 further comprises a separate slip holder 322 which has a connector 324 by means of which the slip holder 322 can be mounted on slips 326, and a grip part 328 which is shaped to be gripped by the gripper 318 by placing the first and second clamp parts 318a, 318b around the grip part 328 and using the gripper actuator 320 to move the clamp parts 318a, 318b to the grip position, as illustrated in Figure 1.

As described above, slips 326 generally comprise three or more steel wedges that are hinged together and form a near circle around the drill string. In this example, the slips 326 comprise just three wedges 326a, 326b, 326 each of which has two longitudinal edges. One longitudinal edge of the central wedge 326b is connected to one of the longitudinal edges of the first outside wedge 326a by means of one or more hinges, and the other longitudinal edge of the central wedge 326b is connected to one of the longitudinal edges of the second outside wedge 326c by means of one or more hinges. The wedges 326a, 326b, 326c are curved so that when the outside wedges 326a, 326c are pivoted about the hinges towards one another to a closed position, the outside longitudinal edges of the outside wedges 326a, 326b come into engagement or come very close to one another and the three wedges form an annulus or a near complete annulus. The outside wedges 326a, 326c can be pivoted about the hinges to an open position in which the outside longitudinal edges of the outside wedges 326a, 326c are separated, as illustrated in Figure 1.

In use, as described above, the slips are mounted around a drill string with the thicker end of each wedge above the thinner end. As such, the slip lifting tool 306 is configured to hold the slips 326 in this orientation. In this embodiment, the connector 324 comprises an elongate support beam 330 which has a longitudinal axis, a first end 330a to which the grip part 328 is connected, and a second end 330b provided with two prongs which extend generally downwardly perpendicular to the longitudinal axis of the support beam 330. The thicker end of the central wedge 326b of the slips is provided with two apertures, with the prongs of the connector 324 inserted into these apertures.

The slip holder 306 also, in this embodiment, comprises two springs 332, 334 a first end of each of which is connected to the slip holder 306 and a second end of which is connected to one of the outside wedges 326a, 326c of the slips 326. The springs 332, 334 are stretched when the slips 326 is in its closed configuration, and therefore act on the outside wedges 326a, 326c to pivot about their hinges and pivot away from one another.

In this example, the slip lifting tool 306 is pivotally mounted on the second end 304b of the arm 304 for rotation with respect to the arm 304 about a third axis R which is generally perpendicular to the longitudinal axis of the second portion 310 of the arm 304. The apparatus 300 further comprises a third actuator 336 which is operable to pivot the slip lifting tool 306 relative to the arm 304 about the third axis R. The slip lifting tool 306 may also be pivotally mounted on the second end 304b of the arm for rotation with respect to the arm about a fourth axis which is generally perpendicular to the longitudinal axis of the second portion 310 of the arm 304 and to the third axis R. In this case, advantageously, the apparatus 300 further comprises a fourth actuator which is operable to pivot the slip lifting tool 306 relative to the arm 304 about the fourth axis.

In this example, the connection between the base 302 and the first portion 308 of the arm 304 is configured such that the arm 304 can pivot about a fifth axis S which is parallel to the second axis Q, in addition to the first axis P. A further actuator 338, which is operable to pivot the second portion 308 of the arm 304 relative to the base 302 is also provided.

The or each actuator 314, 316, 320, 336, 338 may, for example, be hydraulically, electrically or pneumatically driven The slip lifting apparatus 300 may be mounted on a drilling rig 220, as illustrated in Figure 2. The drilling rig 220 has a drill floor 222 with a well centre aperture 232 and the base 302 of the slip lifting apparatus 300 is on the drill floor at a location close to but spaced from the well centre aperture 232. The base 302 of the apparatus 300 may be fixed in relation to the rig floor 222 (e.g. on the rig floor 222 itself or on a structure adjacent the rig floor 222), or it may be mounted on a trolley which is movable around the rig floor 222 (described in further detail below). A drill string 234 is suspended from a derrick 230 and extends through the well centre aperture 232 into a well bore (not shown).

The slip lifting apparatus may be used as follows.

With the slip lifting tool 306 mounted on the second end 304b of the arm 304 of the slip lifting apparatus 300, all or some of the actuators 314, 316, 320, 336, 338 are operated to move the arm 304 and slip lifting tool 306 in such a way as to insert the prongs of the slip holder 322 into the apertures in the central wedge 326b of the slips 326. One or more of the actuators 314, 416, 320, 336, 338 are then operated to lift the slips 326 and to move the slips 326 towards the drill string 234, and to mount the slips 326 around the drill string 234.

In order to ensure that the prongs of the slip lifting tool 306 do not simply slide out of the apertures in the slips 326, the slip lifting tool 306 is advantageously tilted before the slips 326 are lifted off the drill floor 222. This can be achieved by the operation of actuator 336 to pivot the slip lifting tool 306 relative to the second portion 310 of the arm 304 about the third axis R. It could also be achieved by operating actuator 316 to pivot the second portion 310 of the arm 304 relative to the first portion 308 about the second axis Q, or actuator 338 to pivot the first portion 308 of the arm 304 about the fifth axis S. Alternatively, a combination of two or more of these actuators could be used, to ensure that the slips 326 still rest on the drill floor 222 until the required degree of tilt is achieved.

Preferably the actuator or actuators 336, 316, 338 are operated so as to tilt the slips 326 backwards, so that radially inward facing surface of the central wedge 326b faces upwards, and the radially outward facing surface of the central wedge 326b is turned towards the drill floor 222. This can be achieved by moving the thicker (upper) end of the central wedge 236b towards the base 302 of the slip lifting apparatus 300.

In addition to ensuring that the slips 326 stay on the slip lifting tool 306, tilting the slips 326 in this direction assists the springs 332, 334 in maintaining the slips 326 in its open position, since gravity causes the outside wedges 326a, 326c to pivot about their hinges away from one another. It is even possible to omit the springs 332, 334 and to rely on gravity and the tilting of the slips 326 to open the slips 326.

One or more of the actuators 314, 316, 336, 338, is/are then operated to lift the slips 326 off the drill floor 222. Preferably, this is achieved by operating actuator 316 to pivot the second portion 310 of the arm 304 about the second axis Q so that the second end 304b of the arm 304 rises. Actuator 338 can also be operated to pivot the first portion 308 of the arm 304 about the fifth axis S so that the first portion 308 moves towards a vertical orientation.

Once the slips 326 have been lifted off the drill floor 222, actuator 314 can be operated to pivot the arm 304 relative to the base 302 about the first axis P to move the slips 326 towards the drill string 234, with the actuator 338 being operated, if necessary, to bring the lowermost end of the central wedge 326b into engagement with the drill string 234.

One or more of the actuators 336, 3316, 338 is/are then operated to tilt the slips 326 towards a generally vertical position in which the central wedge 326b engages with the drill string 234 along substantially its entire length. If the slips 326 are not provided with springs, this may be sufficient to cause the outer wedges 326a, 326c to pivot to the closed positon. However, where springs are provided, as in the illustrated embodiments, the springs may retain the slips 326 in its open position. In this case, it may be necessary for the drill string 234 to extend through a generally conical bushing, the uppermost end of the bushing having a greater internal diameter than the lower end. The internal diameter of the upper end of the bushing is set so that the lower end of the slips 326 can be inserted into the upper end of the bushing whilst the slips 326 is in the open position, and the internal diameter of the lower end of the bushing is set that when the slips 326 are in the closed position, the lowermost end of the slips 326 can fit into and it supported by the bushing. One or more of the second, third or fourth actuators 316, 336, 338are then operated to lower the slips 326 down the drill string 234 until the drill string 234 is supported by the drill floor 222. Where a conical bushing is provided, an internal surface of the bushing engages with the outer surfaces of the wedges 326a, 326b, 326c and, by virtue of the conical nature of the bushing, the outer wedges 326a, 326c are pushed together into the closed position as the slips 326 move down the drill string 234.

Once the drill string 324 is supported by the drill floor 222, the gripper actuator 320 to move the clamp parts 318a, 318b to the release position, and then operating the arm actuators 314, 316, 336, 338 to move the arm 204 away from the drill string 234.

When the slips 326 are to be removed, this process is reversed. One or more of the arm actuators 314, 316, 336 and 338 are operated to move the clamp parts 318a, 318b of the gripper 318 around the grip part 328 of the slip holder 322, the operating the gripper actuator 320 to move the clamps parts 318a, 318b to the closed position, in which they are gripping the slip holder 322.

One or more of the arm actuators 316, 336, 338 are then operated to lift the slips 326 upwards relative to the drill string 324, out of the conical bushing, if provided. Where springs are provided the removal of the slips 326 from the bushing releases the slips and allows the springs to return the outer wedges to the open position. One or more of the arm actuators 314, 316, 336, 338 may then be operated to move the slips 326 away from the drill string 234, and return the slips 326 to the storage location. If no springs are provided, it may first be necessary to operate one or more of the arm actuators 314, 316, 336, 338 to tilt the slips 326 so that the radially inward facing surface of the central wedge 326b faces upwards, and the radially outward facing surface of the central wedge 326b is turned towards the drill floor 222, so that gravity acting on the outer wedges 326a, 326c causes them to fall open.

It will be appreciated, that the apparatus may be used in conjunction with a further robot arm which is used to assist in opening and closing the slips 326.

The apparatus 300 may also be part of a tool assembly for handling slips 326 on the drill floor 222. The tool assembly may comprise the arm 304 having a plurality of articulated parts 308,310 and rotatably mounted on the base 302 which is fixed in relation to the drill floor 222, a slips lifting tool 306, a holder 318 or holder means 318 for the slips lifting tool 306, where the holder 318 or holder means 318 is arranged on the arm 304 and operable to hold the slips lifting tool 306. The slips lifting tool 306 may comprise a connector 324 operable to engage and carry the slips 326.

The holder 318 or holder means 318 may be operable to releasably engage and hold the slips lifting tool 306. For example, the holder 318 or holder means 318 may comprise a gripper 318a,b operable to grip and hold a grip part 328 of the slips lifting tool 306. Alternatively, other types of connection mechanisms may be used, such as a prong engaging a corresponding receiver (the prong arranged on the holder 318 or the slips lifting tool 306), a click-on type connector, or the like.

Illustrated in Fig. 2, in any of the embodiments herein, the apparatus 300 or individual functions, such as the arm 304, may be controlled from a remote location. This may, for example, be a driller's cabin 228 arranged on or adjacent the drill floor 222. Optionally, the remote control may be done from another operator station.

The slip lifting tool 306 may comprise a slips carrier 322 having a first connector 324 fixed to the slips 326 and a second connector 328 operable to engage the holder 318. The second connector 328 can be a grip part 328 operable to be gripped or clamped by the holder 318 or holder means 318. The first connector may be, for example, prongs arranged in corresponding receiver parts in the slips 326, or alternatively a different type of connection, such as a bolted connection, clamps, or the like.

Illustrated in Figs 3 and 4, in any of the embodiments herein, the apparatus 300 or tool assembly may be arranged on a movable trolley 399. The movable trolley 399 may be arranged with drive units or drive means 398 operable to drive the trolley 399 on or around the drill floor 222. As shown in Fig. 4, in this embodiment the trolley 399 is illustrated with wheels 398 on an underside of the trolley 398 and operable to move the trolley 398 on an underlying surface, such as the drill floor 222 or a deck adjacent the drill floor 222. Alternatively, the drive units or drive means 398 can, for example, be wheels engaging rails or tracks on the drill floor 222.

By providing the apparatus 300 or tool assembly on a movable trolley 399, they can be moved away from the well centre 232 when required, for example when carrying out operations in which the slip lifting tool 306 is not required.

The invention is not limited to the embodiments described herein; reference should be had to the appended claims.

Claims

Claims 1. An apparatus for setting slips around a drill string, the apparatus comprising a base and an arm, the base being configured to support the arm on a drill floor of a drilling rig, the arm having a first end which is mounted on the base for pivoting about a first axis which, when the base is supporting the arm on the drill floor, is generally perpendicular to the drill floor, a second end at which is provided with a slip lifting tool, the arm comprising a first portion and a second portion which are connected by a joint by means of which the second portion may rotate with respect to the first portion about a second axis which is generally perpendicular to the first axis, the first portion extending from the first end of the arm to the joint, and the second portion extending from the joint to the second end of the arm.
2. The apparatus according to claim 1 further comprising a first actuator which is operable to pivot the arm relative to the base about the first axis.
3. The apparatus according to claim 1 or 2 further comprising a second actuator which is operably to pivot the second portion of the arm relative to the first portion of the arm about the second axis.
4. The apparatus according to any preceding claim wherein the slip lifting tool comprises a spring which can be connected to slips mounted on the slip lifting tool to urge the slips to an open position.
5. The apparatus according to any preceding claim wherein the slip lifting tool comprises a gripper having first and second clamp parts and a gripper actuator which is operable to move the first and second clamp parts towards one another to a grip position, and away from one another to a release position.
6 The apparatus according to any preceding claim wherein the slip lifting tool further comprises a separate slip holder which has a connector by means of which the slip holder can be mounted on the slips and a grip part which is shaped to be gripped by the gripper by placing the first and second clamp parts around the grip part and using the actuator to move the clamp parts to the grip position.
7. The apparatus according to claim 6 wherein the connector comprises an elongate support beam which has a longitudinal axis, a first end to which the grip part is connected, and a second end provided with a plurality of prongs which extend generally downwardly perpendicular to the longitudinal axis of the support beam.
8 The apparatus according to claim 6 or 7 wherein the slip holder comprises at least one spring a first end of which is connected to the slip holder and a second end of which is adapted to be connected to the slips on which the slip holder is mounted.
9 The apparatus according to any preceding claim wherein the slip lifting tool is pivotally mounted on the second end of the arm for rotation with respect to the arm about a third axis which is generally perpendicular to the longitudinal axis of the second portion of the arm.
10. The apparatus according to claim 9 wherein the slip lifting tool is pivotally mounted on the second end of the arm for rotation with respect to the arm about a fourth axis which is generally perpendicular to the longitudinal axis of the second portion of the arm and to the third axis.
11. The apparatus according to claim 9 or 10 further comprising a third actuator which is operable to pivot the slip lifting device relative to the arm about the third axis.
12. The apparatus according to any one of claims 9 to 11 further comprising a fourth actuator which is operable to pivot the slip lifting device relative to the arm about the fourth axis.
13.A drilling rig having a drill floor with a well centre aperture and slip lifting apparatus according to any one of claims 1 to 12, the base of the slip lifting apparatus being mounted on the drill floor at a location spaced from the well centre aperture.
14.A method of mounting slips around a drill string extending through the well centre aperture on a drilling rig according to claim 13, the method comprising: a) with the second end of the arm of the slip lifting apparatus positioned at a location which is spaced from the well centre aperture, first mounting slips on the slip lifting tool, b) then pivoting the arm of the slip lifting apparatus about the first axis to move the slips around the drill string, and c) then pivoting the second portion of the arm of the slip lifting apparatus about the second axis to lower the slips down the drill string.
15. The method of claim 14 wherein step b also comprises pivoting the second portion of the arm of the slip lifting apparatus about the second axis.
16 The method of claim 13 or 14 wherein the slip lifting tool comprises a gripper having first and second clamp parts and a gripper actuator which is operable to move the first and second clamp parts towards one another to a grip position, and away from one another to a release position, and a separate slip holder which has a connector by means of which the slip holder can be mounted on the slips and a grip part which is shaped to be gripped by the gripper by placing the first and second clamp parts around the grip part and using the gripper actuator to move the clamp parts to the grip position, and step a of the method comprises the steps of: al) positioning the slips at a storage location on the drill floor spaced from the well centre aperture, a2) mounting the slip holder on the slips, a3) then, with the clamps parts of the slip lifting tool in their release position, pivoting the arm of the slip lifting apparatus about the first axis and / or the second portion of the arm of the slip lifting apparatus about the second axis and operating the gripper actuator so that the clamp parts move to the clamp position, and such movement causes the grip part of the slip holder to be gripped by the gripper.
17. The method of any one of claims 13 to 16 wherein the connector of the slip lifting tool comprises an elongate support beam which has a longitudinal axis, a first end to which the grip part is connected, and a second end provided with a plurality of prongs which extend generally downwardly perpendicular to the longitudinal axis of the support beam, and step a2 comprises inserting the prongs into corresponding apertures provided in the slips.
18. The method of claims 16 or 17 wherein the slip holder comprises at least one spring a first end of which is connected to the slip holder and a second end of which is adapted to be connected to the slips on which the slip holder is mounted, and step a2 comprises attaching the second end of the spring to an attachment point on the slips.
19. The method of any one of claims 13 to 18 wherein the slip lifting tool is pivotally mounted on the second end of the arm for rotation with respect to the arm about a third axis which is generally perpendicular to a longitudinal axis of the second portion of the arm, and step b of the method further comprised pivoting the slip lifting tool about the third axis.
20. The method of claim 19 wherein the slips have a longitudinal axis which arranged to be generally parallel to the longitudinal axis of a drill string when the slips are mounted around a drill string, the third axis may be generally parallel to the drill floor, and step b of the method further comprises pivoting the slip lifting tool in a first direction about the third axis to rotate the slips to bring the longitudinal axis of the slips towards the horizontal prior to positioning the slips around the drill string, and pivoting the slip lifting tool in a second opposite direction about the third axis to rotate the slips so that the longitudinal axis of the slips is generally horizontal whilst positioning the slips around the drill string.
21. The method of any one of claims 19 or 20 wherein the slip lifting tool is pivotally mounted on the second end of the arm for rotation with respect to the arm about a fourth axis which is generally perpendicular to the longitudinal axis of the second portion of the arm and to the third axis, and step b of the method further comprises pivoting the slip lifting tool about the fourth axis.
22.A tool assembly for handling slips (326) on a drill floor (222), the tool assembly comprising: an arm (304) comprising a plurality of articulated parts (308,310), the arm (304) rotatably mounted on a base (302) which is fixed in relation to the drill floor (222); a slips lifting tool (306); a holder (318) or holder means (318) for the slips lifting tool (306), the holder (318) or holder means (318) arranged on the arm (304) and operable to hold the slips lifting tool (306); the slips lifting tool (306) comprising a connector (324) operable to engage and carry the slips (326).
23.A tool assembly according to the preceding claim, wherein the holder (318) or holder means (318) is operable to releasably engage and hold the slips lifting tool (306).
24.A tool assembly according to any one of the two preceding claims, wherein the holder (318) or holder means (318) comprises a gripper (318a,b) operable to grip and hold a grip part (328) of the slips lifting tool (306).
25.A tool assembly according to any one of the three preceding claims, wherein the arm (304) is remotely controlled from an operator station (228).
26.A tool assembly according to any one of the four preceding claims, wherein the slip lifting tool (306) comprises a slips carrier (322) having a first connector (324) fixed to the slips (326) and a second connector (328) operable to engage the holder (318).
27.A tool assembly according to the preceding claim, wherein the second connector (328) is a grip part (328) operable to be gripped or clamped by the holder (318) or holder means (318).
28.A tool assembly according to any one of the six preceding claims, wherein the tool assembly is arranged on a movable trolley (399).
29.A tool assembly according to the preceding claim, wherein the movable trolley (399) comprises drive units (398) or drive means (398) operable to drive the trolley (399) on or around the drill floor (222).