APPARATUS AND METHOD FOR CUTTING A TUBULAR IN A WELLBORE

Abstract: An apparatus for cutting a tubular in a wellbore which apparatus comprises a mandrel (14), a cutting blade (24) and means (56) for moving said cutting blade radially outwardly from a retracted position to an extended position with respect to said mandrel (14), characterised in that said apparatus further comprises a stabilizer (22) and means (54) for moving said stabilizer radially outwardly from a retracted position to an extended position with respect to said mandrel (14).

Description: Apparatus and Method for Cutting a Tubular in a Wellbore This invention relates to an apparatus and a method for cutting a tubular in a wellbore. Prior to the present invention, apparatus for cutting a tubular in a wellbore comprised cutting blades which could be expanded radially outwardly from a mandrel which was lowered on the end of, for example, coiled tubing. However, the cutting operation often resulted in poor quality cuts, uneven wear on the cut- ting blades and slow cutting. The aim of the present invention is to help reduce this problem. According to the present invention, there is provided an apparatus for cutting a tubular in a wellbore which apparatus comprises a mandrel, a cutting blade and means for moving said cutting blade radially outwardly from a retracted position to an extended position with respect to said mandrel, characterised in that said apparatus further comprises a stabilizer and means for moving said stabilizer radially outwardly from a retracted position to an extended position with respect to said mandrel . Advantageously, said means to move said stabilizer is arranged to move said stabilizer to its extended position before said means to move said cutting blade has extended said cutting blade to its fully extended position. Preferably, said stabilizer comprises three or four stabilizer arms spaced around said mandrel at 120 ° or 90 ° intervals respectively . Advantageously, said means for moving said stabilizer radially outwardly comprises a kick-out member . The kickout member preferably has a profile which is perpendicular to the horizontal axis of said mandrel , but may be of any suitable profile or gradient . Preferably, the stabilizer is mounted on an outer body which is slidable along said mandrel. Advantageously, the kick-out member is fixed to the mandrel so that, in use, relative movement between the mandrel and the outer body moves the stabilizer radially outwardly. Preferably, the stabilizer is movable about a pin. The pin preferably is retained in the outer body. Advantageously, the outer body is slidable along said mandrel against a spring. Preferably, the apparatus further comprises a hydraulic piston which acts between the outer body and the mandrel to facilitate relative movement therebetween. Advantageously, the piston acts against said spring. Preferably, the stabilizer resides substantially within the outer body when in the retracted position. Advantageously, the stabilizer is retractable. Most preferably the stabilizer and/or cutting blade is retractable by retracting the piston, most advantageously by relieving hydraulic pressure from the piston. In the event retraction of the cutting blade or stabilizer fails or is impeded, pulling up on the piston (which, in one aspect, is interconnected with coiled tubing extending to the surface) assists the spring or alone provides for stabilizer and blade retraction. Preferably, the outer body is inhibited from radial movement with respect to said mandrel by a set screw in a longitudinal channel in said mandrel so that the stabilizers rotate with the mandrel and the cutting blades on activation of a downhole motor or on activation of a rotary table. Preferably, the stabilizer is provided with a bearing material such as brass on the ends thereof to inhibit friction between the stabilizer and the tubular to be cut. The ends may alternatively, be hardfaced. In one embodiment the apparatus has an outside diameter in a retracted position of 9.5cm (3.75 inches) or less for through-tubing use. Preferably, said apparatus further comprises at least one wash port disposed below said cutting blade. The cutting blades may be driven by a downhole mud motor. The cutting blades may be dressed completely or partially with any known matrix milling material, hard- facing, or inserts, with or without one or more chip- breakers or chipbreaking surfaces. The stabilizer ( s ) may be at substantially the same longitudinal location on the apparatus or they may be at different levels. The cutting blades may be at substantially the same longitudinal location on the apparatus or they may be at different levels. There is also provided a method of cutting a tubular in a wellbore using an apparatus in accordance with the invention, which method comprises the steps of lowering said apparatus in a wellbore, moving said stabilizer radially outwardly from a retracted position to an extended position with respect to said mandrel before said cutting blade moves radially outwardly to said extended position. For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings, in which: - Fig. 1 is a side cross-sectional view of one embo- diment of an apparatus according to the invention; Fig. 2 is a side cross-sectional view of one part of the apparatus of Fig. 1; Fig. 3 is a side cross-sectional view of another part of the apparatus of Fig. 1; Fig. 4 is a side cross-sectional view, to an enlarged scale, of a further part of the apparatus of Fig. l; Fig. 5 is a side cross-sectional view of a further part of the apparatus of Fig. 1; Fig. 6 is a is a top plan view of an alternative cutting blade for an apparatus according to the invention; Fig. 7 is a side view of the blade of Fig. 6; and Fig. 8 is a side view of a stabilizer of the appar- atus of Fig. 1. Referring now to Figures 1 to 5 there is shown an apparatus for cutting a tubular. The apparatus, which is generally identified by the reference numeral 10, comprises an outer body 16 which has a bore 30 there- through. The upper end of the outer body 16 is thread- edly connected by threads 46, 78 to a top cap 12. A seal 70 is provided between the outer body 16 and the top cap 12 above threads 46, 78. A mandrel 14 is provided with threads 74 at the upper end thereof which engage with threads 76 of a top sub 18. A seal 68 is provided between the mandrel 14 and the top sub 18 above the threads 74, 76. The top cap 12 is slidably arranged on mandrel 14. A seal 64 is provided between the top cap 12 and the mandrel 14. A spring 20 biased against a shoulder 48 on the mandrel 14 and a shoulder 34 on the outer body 16 urges the outer body 16 downwardly with respect to the mandrel 14. Fig. 1 shows schematically an expansion joint 25 positioned in a string 29 between the apparatus 10 and a downhole motor 27 that is used, in one aspect, to rotate the apparatus 10. Three stabilizers 22 are spaced around the outer body 16 at 120° intervals and are each pivotably connec- ted to the outer body 16 by a pin extending through a hole 84 in the stabilizer 22 and a hole 36 in the outer body 16. Another pin may be inserted through a hole in the pivot pins to secure them in place or through a half-moon recesses in the pivot pin. The stabilizers 22 reside wholly (or substantially) within recesses 40 in the outer body 16 and preferably do not project or extend therefrom when in a retracted position. In through-tubing operations this facilitates insertion of the tool through relatively small inner diameter tubu- lars (e.g., in certain aspects, as small as 4.5cm (1.8 inches) with the tool outer diameter with stabilizers 22 retracted of about 4.4cm (1.75 inches) or a tool with an outer diameter of 5.4cm (2.125 inches) in tubing with an inner diameter of 5.7cm (2.25 inches)). Three cutting blades 24 are spaced around the outer body 16 at 120° intervals below the stabilizers 22 and are pivotably connected to the outer body 16 by pivot pins 96 extending through a hole 97 in each cutting blade 24 and a hole 38 in the outer body 16. The cut- ting blades 24 reside wholly (or substantially) within recesses 42 in the outer body 16. Three set screws 66 spaced around the outer body 16 at 120° intervals above stabilizers 22 are arranged in respective holes 98 in the outer body 16 and project into longitudinal channels 13 on the mandrel 14 to prevent rotation of the mandrel 14 with respect to the outer body 16. In use, fluid under pressure is introduced into the apparatus 10 from the surface through a tubular string 29 (shown schematically) (e.g. drill pipe, coiled tubing, tubing, or casing), through the bore 26 of the top sub 18, through a bore 28 of the mandrel 14, through a piston port 99, and into a chamber 52 defined by walls of the mandrel 14 and the outer body 16 and a lower end of the top cap 12. Seals 72 are provided between the mandrel 14 and the outer body 16 below chamber 52. Seals 62 are also provided between the mandrel 14 and the outer body 16 at the bottom of the tool between a lower end 58 of the mandrel 14 and a lower end 44 of the outer body 16. Fluid under pressure provided, for example by a pump system at the surface enters the chamber 52 which pushes the top cap 12 and the outer body 16 up against the force of the spring 20. As the outer body 16 moves up with respect to the mandrel 14, each stabilizer contacts a kick-out member 54 and is pivoted outwardly from the apparatus 10. The kickout member 54 is provided with a straight profile which is perpendicular to the longitudinal axis of the mandrel 14. As the outer body 16 moves up with respect to the mandrel 14, each cutting blade 24 contacts a kick-out member 56 and pivots outwardly from the apparatus 10. Due to the difference in longitudinal spacing between the kick-out members 54 and the stabilizers 22 and the kick-out members 56 and the cutting blades 24 and the difference in gradient of the kick-out members 54, 56 with respect to the mandrel 14, the stabilizers 22 extend fully before extension of the cutting blades 24. As shown in Fig. 1, the stabilizers 22 are fully extended while the cutting blades 24, moving on the shallow gradient of the kick-out members 56, are still extending. Shortly after the position of Fig. 1, the cutting blades 24 are also fully extended (horizontal with respect to the outer body 16). One or more fluid wash ports 17 allow fluid under pressure from within the mandrel 14 to wash the cutting blades 24 as they cut. Preferably at least one wash port is associated with and adjacent each cutting blade 24. The lower end 19 of the top sub 18 provides a stop to limit upward movement of the top cap 12 and the outer body 16. Figs. 6 and 7 show a cutting blade 90 for use as an alternative cutting blade 24 in the apparatus 10. The cutting blade 90 has a body 93 with a mounting hole 92 and a cutting insert 94 which is either bolted to the blade 90 or welded thereto. One or more cutting inserts may be used. Fig. 8 shows one of the stabilizers 22 with a curved portion 88, a bevelled top edge 82, and an outer end 80 (dressed e.g. with brass). In one aspect an apparatus as shown in Fig. 1 has an outside diameter with stabilizers and cutting blades within the tool body (non-extended) of: no greater than 9.5cm (3.750 inches); about 9.5cm (3.75 inches); or about 5.2cm (2.06 inches). In an embodiment with an outer diameter of about 5.2cm (2.06 inches) the cutting blades extend a maximum of about 9.5cm (3.75 inches) from the outer body 16 when horizontal with respect to the outer body 16.

Claims: CLAIMS : 1. An apparatus for cutting a tubular in a wellbore, which apparatus comprises a mandrel ( 14 ) , a cutting blade (24) and means (56) for moving said cutting blade radially outwardly from a retracted position to an extended position with respect to said mandrel (14), characterised in that said apparatus further comprises a stabilizer (22) and means (54) for moving said stabilizer radially outwardly from a retracted position to an extended position with respect to said mandrel (14). 2. An apparatus as claimed in Claim 1, wherein said means (54) to move said stabilizer is arranged to move said stabilizer (22) to its extended position before said means (56) to move said cutting blade has extended said cutting blade (24) to its fully extended position. 3. An apparatus as claimed in Claim 1 or 2, wherein said stabilizer comprises three or four stabilizer arms (22) spaced around said mandrel at 120° or 90° intervals respectively. 4. An apparatus as claimed in Claim 1, 2 or 3, wherein said means for moving said stabilizer radially outwardly comprises a kick-out member ( 54 ) . 5. An apparatus as claimed in any preceding claim, wherein said stabilizer (22) is mounted on an outer body (16) which is slideable along said mandrel (14). 6. An apparatus as claimed in Claims 4 and 5, wherein said kick-out member (54) is fixed to said mandrel (14) so that, in use, relative movement between said mandrel (14) and said outer body (16) moves said stabilizer (22) radially outwardly. 7. An apparatus as claimed in Claim 6, wherein said stabilizer (22) is movable about a pin. 8. An apparatus as claimed in Claim 5, 6 or 7, wherein said outer body (16) is slidable along said mandrel (14) against a spring (20). 9. An apparatus as claimed in any of Claims 5 to 8, further comprising a hydraulic piston (12, 14, 16, 52, 99) which acts between said outer body (16) and said mandrel (14). 10. An apparatus as claimed in Claims 8 and 9, wherein said piston (12, 14, 16, 52, 99) acts against said spring (20). 11. An apparatus as claimed in any of Claims 5 to 10, wherein said stabilizer (22) resides substantially within the outer body (16) in said retracted position. 12. An apparatus as claimed in any preceding claim, wherein said stabilizer (22) is retractable. 13. An apparatus as claimed in any of Claims 5 to 12, wherein said outer body (16) is inhibited from radial movement with respect to said mandrel (14) by a set screw (66) in a longitudinal channel (13) in said mandrel (14). 14. An apparatus as claimed in any preceding claim having an outside diameter in a retracted position of 9.5cm (3.75 inches) or less for through-tubing use. 15. An apparatus as claimed in any preceding claim, further comprising at least one wash port (17) disposed below said cutting blade ( 24 ) . 16. An apparatus as claimed in any preceding claim, and a downhole mud motor for rotating said apparatus. 17. A method of cutting a tubular in a wellbore using the apparatus of any preceding claim comprising the steps of lowering said apparatus in a wellbore, moving said stabilizer radially outwardly from a retracted position to an extended position with respect to said mandrel before said cutting blade moves radially outwardly to said extended position.

Inventors: BEEMAN ROBERT STEPHEN, BEEMAN, ROBERT, STEPHEN
Applicants: LUCAS BRIAN RONALD, WEATHERFORD LAMB, LUCAS, BRIAN, RONALD, WEATHERFORD/LAMB, INC.
Application year: 1997
Main classification: E21B29
IPC codes: E21B10, E21B29