Introduction

The present invention is an auxiliary rig and a method of removing a well tubing from a petroleum well. More specifically, the auxiliary rig is arranged for a continuous sequence of using an elevator mechanism for pulling up a long tubing from a well one length at a time until a desired length extends above the deck, holding the tubing using slips at the deck level, cutting off the length of tubing extending above the deck, removing the cut-off tubing from the auxiliary rig, taking a new grip on the tubing and proceeding pulling the a subsequent length of tubing extends above the deck level, and so on, until the entire free tubing is pulled out of the well and the cut off lengths moved away. The auxiliary rig thus comprises a tubing collar elevator with a tubing collar grip, it utilizes slips in the deck, it comprises a tubing cutter tool, and it comprises a tubing remover for removing the cut-off lengths away from the auxiliary rig.

Problem to be solved:

A drilling rig is used for heavy well intervention operations such as drilling using a top drive drilling motor driven drill string, casing insertion, mud pumps for drilling mud circulation, cementing pumps for circulation in cement. The drilling rig is a heavy structure which usually is jacked horizontally from one well slot to another. The drilling rig takes much space, is expensive to operate, and slow to move. Tubing such as well tubing or casing is removed section by section from a well by hoisting out and unscrewing the tubing section by section (or stand by stand) and using a manipulator arm to lay down the disconnected tubing section and transporting it out of the V-door to storage in the pipe rack. The process is slow and inefficient thus costly, and the removed tubing is usually to be considered as scrap metal and not for re-use. While removing a long length of tubing from the well much of the drilling rig remains unused, and could have been used for constructive purposes such as lining, drilling, intervention, sidetracking or plugging operations which require the full capacity of the drilling rig, and the tubing pulling could advantageously be left to a lighter, cheaper rig to build, move, and operate.

From prior art one should refer to WO 2017/091142 Al, which discloses an apparatus for recovering and/or installing conductor casing which comprises a base and a mast having a bottom end pivotally mounted to the base and hydraulically actuable to move between a vertical position and a horizontal position, the mast having a clamp and a tension table for releasably securing a conductor casing segment in tension.

Brief summary of the invention

The present invention solves the above problems and is defined in the attached claims.

The invention is a petroleum platform auxiliary rig (20) comprising a base frame (22), a pivotable arm (21) and a tubing cutter tool (42), said auxiliary rig (20) characterized by

- the pivotable arm (21) comprises a tubing collar elevator (32) having a first tubing gripper (33) arranged for travelling at least in the vertical direction, wherein

- said arm (21) is arranged for being pivotable between a vertical orientation over a wellhead (12) of a well (10), and a horizontal orientation;

- said tubing collar gripper (33) is arranged for releasably engaging a tubing collar (2) of a tubing (1) protruding out above said wellhead (12) into said auxiliary rig (20);

- a second gripper (24) is arranged in a deck slot below said pivotable arm (21) and above said wellhead (12); said second gripper (24) is arranged for holding said tubing (1) and preventing said tubing (1) from dropping back into said well (10), and for releasably allowing upward travel of said tubing (1);

- the tubing cutter tool (42) is arranged near a lower end of said auxiliary rig, arranged for cutting off a tubing length (L) of said tubing (1), when pulled up of said well (10);

- said pivotable arm (21) comprising a pivot actuator (56) and a pivot actuator link (210) arranged to lay down said cut-off tubing length (L) to a horizontal orientation,

- a control system (60) with a control line (330') to elevator actuator (330), a control line (42') to tubing cutter tool (42), a control line (56') to pivot actuator (56), a control line (33') to first tubing gripper (33), and a control line (24) to second tubing gripper (24).

Advantages Advantages of the present auxiliary rig and the method are:

- The auxiliary rig needs no drilling motor. There is no need to rotate the tubing sections to mutually unscrew them at the tubing collars, the desired lengths of tubing to be cut off are simply cut by a tubing cutter independent of the collar joints.

- The auxiliary rig needs no main hook, it uses a simple tubing collar grip arranged on the tubing collar elevator to pull the tubing up length by length from the well.

- The auxiliary rig needs no mud circulation system, it may utilize existing pumps to circulate in sea water in the tubing and tubing annulus before the tubing is pulled.

- The auxiliary rig needs no drill pipe string stands handling system, in an embodiment a vertical component of the auxiliary rig constitutes its own vertical to horizontal (VTH) arm, as the embodiment is pivoting in the level of the tubing cutter tool and may lay the vertical arm of the auxiliary rig down to the horizontal so as for the cut-off tubing length to be removed away from the auxiliary rig, and the auxiliary rig's arm to be re-erected.

- The absence in the present auxiliary rig of a drilling motor, a main hook, a mud circulation system, a tubing manipulator arm, a stands handling system, as otherwise compared to a drilling rig, saves much weight and cost.

Brief figure captions

Fig. 1 illustrates an auxiliary rig of the invention arranged over a slot with a wellhead, and with an upper end of a well tubing protruding above the wellhead and into the lower part of the auxiliary rig. The auxiliary rig has a pivotable arm which is erect here.

Fig. 2 illustrates the tubing elevator having gripped the tubing collar and pulled it up a desired length, preferably at least one tubing section length.

Fig. 3 illustrates the elevated gripper holding the tubing collar and the deck slips hold the tubing at deck level while the tubing cutter tool cuts the tubing near the lower end of the vertical arm of the auxiliary rig.

Fig. 4 illustrates the auxiliary rig's pivotable arm with its gripper holding the severed-off tubing length being laid down. Releasing the now horizontal severed off tubing section (or stand) and transporting it away from the auxiliary rig to a basket for scrap tubing is a simple task. Fig. 5 illustrates the auxiliary rig's main components including a control system for actuators.

Embodiments of the invention

The invention provides a method of removing a well tubing using an auxiliary rig, and the auxiliary rig itself.

The invention provides a method of removing a well tubing (1) from a well (10), said well tubing (1) being made up of tubing sections (3) joined by tubing collars (2), said well tubing (1) extending into said well (10). The well tubing is free or a long length of it is cut free and extends out of the well, ready for being pulled. The length of the well tubing (1) may be considerable, such as 500 metres or more. Tubing may comprise well tubing, well casing, well liner, or similar.

The method comprises the following steps: a) - arrange an auxiliary rig (20) over a wellhead (12), wherein said auxiliary rig (20) has a base frame (22) and a pivotable arm (21) with a tubing collar elevator (32) with a first tubing gripper (33) arranged for travelling at least in the vertical direction. b) - the pivotable arm (21) comprises a pivot actuator (56) and a pivot actuator link (210) arranged to lay down said cut-off tubing length (L) to a horizontal orientation or raise it to the vertical direction. Use the control system (60) to command the pivot actuator (56) to hold said pivotable arm (21) in a vertical orientation use said control system to command to lower said first tubing gripper (33) at a protruding tubing collar (2) of said well tubing (1) extending out above said wellhead (12) and into a lower part of said auxiliary rig (20). Please see Fig. 1. c) - use said control system (60) to command said first tubing gripper (33) to engage with said protruding tubing collar (2). d) - use said control system (60) to command said tubing collar elevator (32) to pull said gripper (33) to travel upwardly with said upper tubing collar (2), thus also said well tubing (1), at least until a subsequent tubing collar (2) protrudes in the lower part of said auxiliary rig (20). This is shown in Fig. 2. use said control system (60) to command said elevator actuator (333) to pull up one, two or more tubing sections at a time, depending on the allowable stroke length of the tubing collar elevator. Here is shown only one tubing length is illustrated. f) - use said control system (60) to command a second tubing gripper (24) such as sli ps(241) near the deck slot, to engage with said well tubing (1) below said subsequent tubing collar (2). This is to secure that the remaining long tubing shall not fall back into the well. g) - use said control system (60) to command a tubing cutter tool (42) of said auxiliary rig (20) to cut off a tubing length (L) of said tubing (1) at or above said subsequent tubing collar (2). The design of the tubing cutter tool may in an embodiment resemble a cutting gate valve of a BOP. h) while holding said cut-off tubing length (L) in said first tubing gripper (33), preferrably in an upper part, of said pivotable arm (21) of said auxiliary rig (20), use said control system (60) to command said pivot actuator (56) to lay down said pivotable arm (21) with said cut-off tubing length (L) to a horizontal orientation. The cut-off length may be of approximately the same length as a tubing length, but the cut off tubing length may in principle be cut to other lengths than that and cut independent of the position of the tubing collars.

I) - said control system (60) to command release said first tubing gripper (33) and remove said cut-off tubing length (L) from said pivotable arm (21); j) - said control system (60) commands raise said pivotable arm (21) back to the vertical orientation. For conducting the entire operation, the control system (60) is arranged to go to step (b) and repeat the sequence to (j) until the entire tubing has been hoisted stepwise to the surface and cut into cut sections and transported away.

- a control system (60) with a control line (330') to elevator actuator (330), a control line (42') to tubing cutter tool (42), a control line (56') to pivot actuator (56), a control line (33') to first tubing gripper (33), and a control line (24) to second tubing gripper (24).

In an embodiment of the invention the tubing is fished up to having its upper end protruding into the lower part of the auxiliary rig by means of a spear tool. In an embodiment of the invention the spear tool is non-rotating for setting and release, and arranged for engaging and setting in the tubing by pull up, and for releasing by push down. The auxiliary rig (20) comprises an auxiliary rig frame (21) arranged for being pivotable from a vertical to a horizontal position about a pivot axle (54) near the base of said auxiliary rig (20)'s horizontal base (22), and in level with said first tubing cutter tool (42);

In an embodiment of the invention, initially, before step (a), in order to bring the top of the tubing into position for being engaged by the vertical elevator's clamp,

- extend a spear into the top of said well tubing (1) in the well,

- use said tubing collar elevator (32) with said tubing gripper (33) to pull said spear with said tubing (1) up until a first, upper casing collar (2) extends out above said wellhead (12) and into the lower part of said auxiliary rig.

The invention is also a device, a petroleum platform auxiliary rig (20) comprising a base frame (22) and a pivotable arm (21) with a tubing collar elevator (32) having a first tubing gripper (33) arranged for travelling at least in the vertical direction, wherein

- said arm (21) is arranged for being pivotable between a vertical orientation over a wellhead (12) of a well (10), and a horizontal orientation;

- said tubing collar gripper (33) is arranged for releasably engaging a tubing collar (2) of a tubing (1) protruding out above said wellhead (12) into said auxiliary rig (20);

- a second gripper (24) such as deck slips is arranged in a deck slot below said pivotable arm (21) and above said wellhead (12); said second gripper (24) is arranged for holding said tubing (1) and preventing said tubing (1) from dropping back into said well (10), and for releasably allowing upward travel of said tubing (1);

- a tubing cutter tool (42) is arranged near a lower end of said auxiliary rig, arranged for cutting off a tubing length (L) of said tubing (1), when pulled up of said well (10);

- said pivotable arm (21) is arranged to lay down said cut-off tubing length (L) to a horizontal orientation.

In an embodiment the tubing cutter tool (42) arranged near a lower portion of said auxiliary rig frame (21).

In an embodiment the pivoting arm (21) , the "vertical to horizontal arm" has a pivot point in level with said tubing cutter tool (42). The cut-off tubing may be sent to a basket for horizontal storage and transport away from the rig.

Fig. 5 shows an embodiment of the invention wherein the auxiliary rig's (20) pivoting arm (21)'s elevator actuator (33) comprises an elevator cylinder (331) with an elevator piston (332) carrying a elevator sheave (333) for an elevator cable (334) which is attached in its first end to a yoke for lifting rods holding the first tubing gripper (33), and the other end in a base near the top of the pivoting arm (21). When stroked out the elevator piston (332) will raise the sheave (333) one piston stroke length but the tubing gripper will move almost the double stroke length of the piston. Thus the auxiliary rig may be made rather compact considering its lifting length capacity. A pivot actuator (24) is arranged for laying down and erecting the pivoting arm (21). It may be hydraulically actuated, wherein the hydraulics is not illustrated here.

Fig. 5 further illustrates a pivot actuator (56) for pivot actuator link (210). The pivot actuator (56) is hydraulic or electric. The pivot actuator link (210) is a pivot actuator link between the pivotable arm and the base frame (22).

Fig. 5 further illustrates the petroleum platform auxiliary rig (20) comprising a base frame (22), a pivotable arm (21) and a tubing cutter tool (42), said auxiliary rig (20) comprising

- the pivotable arm (21) comprises a tubing collar elevator (32) having a first tubing gripper (33) arranged for travelling at least in the vertical direction, wherein

- said arm (21) is arranged for being pivotable between a vertical orientation over a wellhead (12) of a well (10), and a horizontal orientation;

- said tubing collar gripper (33) is arranged for releasably engaging a tubing collar (2) of a tubing (1) protruding out above said wellhead (12) into said auxiliary rig (20);

- a second gripper (24) is arranged in a deck slot below said pivotable arm (21) and above said wellhead (12); said second gripper (24) is arranged for holding said tubing (1) and preventing said tubing (1) from dropping back into said well (10), and for releasably allowing upward travel of said tubing (1);

- the tubing cutter tool (42) is arranged near a lower end of said auxiliary rig, arranged for cutting off a tubing length (L) of said tubing (1), when pulled up of said well (10); - said pivotable arm (21) comprising a pivot actuator (56) and a pivot actuator link (210) arranged to lay down said cut-off tubing length (L) to a horizontal orientation,

- a control system (60) with a control line (330') to elevator actuator (330), a control line (42') to tubing cutter tool (42), a control line (56') to pivot actuator (56), a control line (33') to first tubing gripper (33), and a control line (24) to second tubing gripper (24).

Simplifed version:

In the above we have described the invention wherein the gripper (33) grips the tubing collars (2). In an embodiment of the invention the gripper (33) is arranged for clamping anywhere on the tubing (1) irrespective of the position of the collars (2). Then the method is simplified to: a) - arrange an auxiliary rig (20) over a wellhead (12), wherein said auxiliary rig (20) has a base frame (22) and a pivotable arm (21) with a tubing collar elevator (32) with a first tubing gripper (33) arranged for travelling at least in the vertical direction. b) - hold said pivotable arm (21) in a vertical orientation and lower said first tubing gripper (33) at a protruding end of said well tubing (1) extending out above said wellhead (12) and into a lower part of said auxiliary rig (20). Please see Fig. 1. c) - engage said first tubing gripper (33) near said protruding tubing (1) end. d) - use said tubing collar elevator (32) to pull said gripper (33) to travel upwardly with said upper tubing (1) end, thus also said well tubing (1), at least until a desired length (L) of tubing has been pulled up, this is shown in Fig. 2. One may pull up one, two or more tubing sections at a time, depending on the allowable stroke length of the tubing collar elevator. Here is shown only one tubing length is illustrated. f) - engage a second tubing gripper (24) such as slips near the deck slot, with said well tubing (1) to secure that the remaining long tubing shall not fall back into the well. g) - use a tubing cutter tool (42) of said auxiliary rig (20) to cut off a tubing length (L) of said tubing (1) above said second tubing gripper (24). The design of the tubing cutter tool may in an embodiment resemble a cutting gate valve of a BOP. h) while holding said cut-off tubing length (L) in said first tubing gripper (33) in an upper part of said pivotable arm (21) of said auxiliary rig (20), lay down said pivotable arm (21) with said cut-off tubing length (L) to a horizontal orientation. The cut-off length may be of approximately the same length as a tubing length, but the cut off tubing length may in principle be cut to other lengths than that and cut independent of the position of the tubing collars. h) - release said first tubing gripper (33) and remove said cut-off tubing length (L) from said vertical arm (21);

I) - raise said pivotable arm (21) back to the vertical orientation.

Now the tubing gripper (33) is ready to repeat the process from item (a).

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