The invention relates to a complete system for reducing diameter of tubular pipes more precisely it relates to a drill string system for plug and abandoning of wells, the present invention relates to devices and methods of such a system.

The invention relates to a complete system for reducing diameter of tubular pipes.

For plug and abandonment of oil wells, the casing of the well has to be fully or partly removed before plugging. Removal of casing is a demanding task as the casing is normally bonded to concrete in between the underground formation and the casing. WO 2008118697 discloses a system of common use for recovering casing from the abandoned wells.

The present invention enables casing section removal with milling only parts of a tubular/casing.

Also for other purposes such as within water and sewerage it is often of interest to shrink and remove sections of piping's.

According to the present invention it is provided a shrinkage tool assembly for shrinkage and recovery of a wellbore tubular according to claim 1, a shrinkage forming die according to claim 6 and a method for shrinkage and recovery of a wellbore tubular according to claim 8.

According to the invention, the forming die may consist of at least one mechanical mean for guiding the tubular into the die, where the mechanical mean will be activated by mean of an actuating system.

According to another aspect of the invention, the recovered tubular section may have at least one helical or straight groove along the longitudinal axis of the tubular.

According to the present invention, it is also provided a shrinking tool, which may utilize the method s indicated above and where the shrinking tool is adjacent to a milling tool, where the milling tool is adapted to mill at least one radial groove and at least one axial or helical groove along the longitudinal axis of the tubular.

The shrinking tool may be pulled by mean of a moving tractor or other means like as wireline or drillstring from inside the tubular.

It is also disclosed a shrinking tool where the tool comprises at least one anchoring mean for pulling one section of the tubular, where the separated section consist of at least on helical or axial groove along the longitudinal axis of the tubular.

To make the following description more readily understandable the following discussion will make reference to the accompanying drawings in which,

• Figure 1 shows a perspective view of a system according to the present invention;
• FIG. 2 shows a view of the system according to the present invention;
• FIG. 3 shows a cross sectional view of the system according to the present invention ;
• FIG. 4 shows a tractor according to the present invention;
• FIG. 5a shows an example of a milling tool/milling section in accordance with the present invention;
• Fig 5b shows an example of a milling tool with expand able rotary side mill in neutral and working position
• Fig 5c shows a schematics view of one driving system according to one aspect of the invention using hydraulic mud motor and bevel gears,
• FIG. 6 shows a forming die according to the present invention;
• Fig. 7a shows a cross sectional view of the forming die outlet view with retracted or non-activated guiding arm;
• Fig. 7b shows a cross sectional view of the forming die outlet view with activated guiding arm;
• FIG. 8 shows the forming die and a casing section with a premade axial groove;
• Fig. 9 shows the forming die seen in figure 2;
• Fig. 10 shows the forming die, a casing with a premade axial grove and a shrinked casing;
• Fig. 11 shows a casing with helical grooves and the same in shrinked version according to one embodiment of the present invention, and
• Fig. 12 shows a casing with helical grooves and the same in shrinked version according to one embodiment of the present invention.

The invention will now be described with reference to the accompanying drawings, which are not to scale, however it shall be understood that the drawings are only meant to facilitate the understanding of the invention and they are in no way limiting the scope of the claimed invention.

The invention relates to a system 1, i.e. a shrinkage tool assembly for shrinkage and recovery of a wellbore tubular, for abandoning and plugging of oil wells as well as a system made for shrinking sections of tubular. The system comprises a forming die 15, which can be used in oil, gas and deep-water wells, mining and underground operations. The tools enable to shrink a section of a tubular 91 and reduce the diameter. In particular, it is disclosed a forming tool integrated in a shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular. The shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular comprises the mentioned forming die 15, a milling section 13 including means for milling out helical or axial grooves in tubulars 92 and at least a tractor 10 or pulling means 10.

The forming die 15 according the present invention can be used to shrink a casing while the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular moves axially inside the tubular. This enables to pull out and recover a section of the tubular/casing through the rest of the tubular/casing that remains in the well. In addition, the forming die 15 reduces the de-bonding force for the tubular from the cement/formation.

In the following the wording system 1 shall be understood as the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular except if nothing else is explicitly mentioned.

As indicated above the present invention relates to a system, which is adapted to take out sections of casings or sections of pipes. The system 1 will now be described with reference to figure 1. The system 1 which is the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular comprises a tractor 10, a milling section 13 and a forming die section 15.

The tractor 15 is the front end of the system with reference to the active travel direction that is, when the system 1 is actively milling and shrinking tubulars or casings. Following the tractor is the milling section 13, the milling section includes at least one cutting tool 14.

Further, up the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular is the forming die 15, the forming die 15 is adapted to shrink casings or tubulars, which already has been prepared by the milling, section 13 so that the tubulars or casing has premade axial or helical grooves.

The tractor 10 is the propulsion unit of the drill string, it is shown in detail in figure 4. The tractor comprises two pistons 42, 43 connected with a push pull piston rod 12 there between. The push pull piston rod can move the end piston 42 relative to the near piston 43 and the rest of the shrinkage tool assembly (1) for shrinkage and recovery of a wellbore tubular in an axial direction.

Moving forward, that is in the X-direction in figure 4 starts with the near piston 43 and the end piston 42 in a retracted position, that is the distance between them are minimal, the near end piston 43 expands its anchor pads 11 to get into a fixed grip with its surrounding such as the casing. The anchor pads 13 of the end piston 42 is in a retracted position. The next step is that the end piston is moved in the x-direction by the piston rod 12. When the end piston 42 is in a maximum distance from the near piston 43, the end piston anchor itself to the surrounding walls or casings by expanding its anchor pads 13 radially. Following this step, the near piston 43 retracts its anchor pads 11 and the end piston 42 can pull the near piston 43 with its drillstring in the x-direction thereby causing the whole drillstring including the milling section and the die form 15 to move in the x-direction.

The milling section 13 follows the tractor and is in between the forming die 15 and the tractor 10.

The milling section according to a first embodiment shall provide axial grooves in piping-sections or casing sections. As the groove shall be axial the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular will not rotate around its axis A - A (fig 2). As the tractor 10 provides movement of the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular the milling section provides axial grooves. One or more side cutters 14 are integrated in the milling section 13. The one or more side cutters rotate around its axis of rotation, where the axis of rotation is substantially normal to the axis A-A and the surrounding walls.

The cutter 14 or cutters 14 can be retractable and expandable. In its expandable positon with one or more rotating cutters, an axial groove will be made in the casing / surrounding tube.

The cutter 14 or cutters 14 can be rotated by using hydraulic driven/mud motor system placed inside the main housing. However many other means of driving systems can be utilised, it is the individualisation of powering the cutters 14 that is important. An internal hydraulic driving system can be placed, axial to the side cutters or axial to the direction of the milling tool and to rotate the side cutters 14 by using a gear/transmission system or by direct drive. The driving means can be electric motors with gear transmission drive or by direct drive.

Side cutters 14 can be rotated by internal mud motors and thereby use the hydraulic energy of circulating mud. However, drill string mechanical energy or electric motors can also be used for driving the side cutters. FIGS. 5c shows an example of use of internal mud motor(s) including a proper gear transmission system 67 for driving the side cutters 14. Any suitable gear type can be utilised. Different gear types such as worm or bevel can be used depending on the tool design. In addition, high torque hydro-motors can also be employed without gear system, the same applies to electric motors.

Each side cutter has individual driving system and can be operated independent of the other side cutters.

A shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular is shown in figure 1, 2 and 3. The figures 6 - 10 shows a forming die 15 in detail.

According to one embodiment, the forming die has a c-shape entrance opening (fig. 7a, 7b) which has similar diameter D1 as a grooved tubular 72 in an entrance end and a smaller diameter DB at the exit end. According to this embodiment, while the shrinkage tool assembly 1 for shrinkage and recovery of a wellbore tubular moves axially within the grooved wellbore tubular, the tubular is pushed into the C shaped die entrance opening 83 and inside the C-outer sleeve 75 of the forming die 15. While the die 15 moves relative to the grooved tubular the grooved tubular is consequently fed into the c-shaped opening 83 (fig 7) and through the die and is shrinked into a reduced diameter when exited from the exit end of the forming die 15. It shall be noted that the part 63 of the die 15 where the grooved tubular or a grooved casing enters into the c-shaped opening (fig 7) of the die 15 is tapered with an input diameter approximately similar to the tubing D1, and an exit diameter DB, where DB<D1. According to this embodiment, the forming die consists of a mechanical means 16 for guiding the grooved tubular 72 or grooved casing into the opening entrance of the die. This mechanical means is an expandable guiding arm 16, which radially expands out of the tool body 15 when needed.

The following dimension restrictions applies:

• Z1 > Z2
• Z3 and Z1 are approximately of the same width.
• D1 > D2

The forming die 15 and the milling tool 13 are adapted to be pulled by a moving tractor 10 or any other means through the wellbore longitude axis. Another mean for pulling the die 15 can be by wire, cable or drillstring. According to this embodiment, the milling tool 13 with actively driven side rotational cutters 14 can drill hole and mill axial, helical or radial grooves inside the tubular sidewalls.

The invention has been described with reference to figure 1 - 10, this system 1 includes components, which together facilitates abandonment and plugging of oil wells and dismantling in sewerage systems. In another embodiment of the invention (fig 11 and 12), the milling tool 13 can create at least one helical groove and at least two radial grooves inside the casing downhole in the well. One way of achieving this is to use a rotational milling tool with one or more rotational side cutters 14. This enables to create a separated casing section from the tubular. According to this embodiment, the separated casing section with at least one helical groove can be pulled in an axial direction, which causes casing shrinkage and de-bonding from the formation cement. According to this embodiment, the separated casing can then be pulled out through the remaining casing inside the well. The moving tractor or other means, for example the drillstring or wire line, can pull the separated casing section. 1 Shrinkage tool assembly 10 Moving tractor 11 Anchor pad 12 Push pull cylinder, push pull piston rod 13 Active milling tool 14 Side rotational cutter 15 Forming die 16 Expandable guiding arm 42 Piston, end piston 43 Piston, near piston 61 Die inlet 62 Die outlet-rear 63 Die body 66 67 Gear transmission system, individual driving means 71 72 Grooved tubular 73 75 C-outer sleeve 81 First element 82 Second element 83 C shaped die entrance opening; inlet; c-shaped lofted cut 91 Tubular 92 Tubulars DA DB Diameter, exit diameter, DB < D1 D1 Diameter, D1 > DB; D1 > D2 D2 Diameter, D2 < D1 Z1 Z1 > Z2, Z3 and Z1 are approximately of the same width Z2 Width of first element 81, Z2 < Z3 Z3 Width of second element, Z3 > Z2, Z3 and Z1 are approximately of the same width