CUTTING TOOL FOR USE IN A WELLBORE

Abstract: A cutting tool (10) for use in a wellbore to cut into its wall has a body (40, 50) disposable at a desired location in the wellbore, at least one first blade (70) pivotally mounted on the body at a first location, at least one second blade (60) pivotally mounted on the body at a second location spaced axially from the first location, the blades being movable from a retracted position against the body and an operating position extending from the body, the first blades being shorter in length than the second blades.

Description: CUTTING TOOL FOR USE IN A WELLBORE This invention is directed to wellbore cutting tools, and in particular, to drilling, reaming and milling tools; and, in one particular aspect, to an underreamer for enlarging an uncased borehole or a borehole cased with one or more tubular members. Earth-boring operations for drilling oil and gas wells use drill strings that drill to great depths. Typically a drilling "mud" is pumped down the drill string for cooling the drill bit. Often there is a need to "underream" the hole, that is to enlarge its diameter at some location below the surface. A variety of under- reamers and hole openers have been developed. With such tools, the fluid pressure of the drilling mud can be employed for actuation. Often the drill string is withdrawn from the hole and a suitable underreamer is installed either alone or in series with a conventional pilot drill. After the drill string has been inserted back into the hole, pressurised drilling fluid is ap- plied and, through any of a variety of mechanisms, cutter arms on the underreamer are urged outwardly for enlarging the selected portion of the hole. Then the cutter arms are retracted and the underreamer is with¬ drawn from the hole. In certain aspects such underrea- mer arms are extended whenever drilling fluid pressure is applied, i.e. at all times when drilling is being conducted. Certain known underreaming tools have a body struc¬ ture formed of inner and outer body sections, with cutter arms pivotally secured on the outer body section, and a piston and cylinder defined between the inner and outer body sections to receive hydraulic fluid to effect telescopic movement of the body sections in one relative direction so that a cam surface mechanically engages and forces the cutter arms out to their underreaming or bore hole enlarging positions. When the underreaming operation is completed, the cutter arms of these known devices are retracted by raising the operating string on which the body structure is supported, so that the expanded or projecting arms contact the shoulder formed at the juncture of the upper end of the enlarged underreamed portion with the origi¬ nal smaller bore. Continued raising of the operating string exerts a force on the extended cutter arms to endeavour to force them inwardly to a retracted position relative to the body structure. When obstructions or mud prevent relative longitu¬ dinal telescopic movement between the inner and outer body sections so that the cutter arms can retract, then it has been generally customary to continue exerting a pull on the operating string until some portion of the bore hole enlarging structure breaks, so that the struc¬ ture may then be withdrawn from the well bore. If the structure of the known tools malfunctions or breaks, so that the inner and outer bodies are locked against relative telescopic movement with the arms in their extended positions, then the arms have to be forced to their retracted positions by pulling up on the operating string, or by breaking whatever part of the structure is necessary to enable the tool to be withdrawn from the bore hole. When the arms of the bore hole enlarger are exten¬ ded during drilling operations to underream or drill an enlarged portion in a bore hole, there are various forces that act upon them. These forces include an upwardly-directed force on the outer end of the arm due to the reaction from the weight of the operating string during drilling operations; a force which tends to move the cutter arms back towards their retracted position due to the angle of the hole; a force due to the reac- tion from rotation while drilling the formation, which tends to retract the cutter arms inwardly, and a force which arises from rotation during bore hole enlarging operations so that force applied against the leading face of the arm along its axial extent tends to flex the cutter arm. These forces are transmitted from the cutter arms to the pivot arrangement of the cutter arms on the body structure and cam surface relied upon to move and main¬ tain the cutter arms in their extended cutting posi- tions. In some circumstances, these forces may be sub¬ stantial and, in some instances damage or break compo¬ nents of the tool. In certain known tools expandable arms are moved outwardly by means of a pressure-actuated piston mounted within the main bore of a tool housing. The ends of the expandable arms may be provided with a machined surface, cutting material, or cutting inserts for engaging cer¬ tain types of formations and cutting a larger hole than created by the drill bit. There are several patents which disclose various underreaming tools. US 2,822,150 discloses a rotary expansible drill bit having upper and lower cutters pivotally mounted on a main body and connected by a rack and pinion mechanism to a plunger for simultaneously expanding the cutters outwardly from the main body. US 4,809,793 discloses a downhole cutting tool which includes longitudinal bores which are opened to fluid flow when the cutting members are moved to their extended positions. The tool has upper and lower sub- assemblies connected together through an adapter which establishes an angular offset between an upper and lower pair of extendable cutter members. However, in both the upper and lower sub-assemblies, one passage is contin¬ uously open to fluid flow at all times, and the other passage is initially closed and opens only on predeter- mined movement of the piston or pistons which open the extendable cutters. The present invention has a different sequence of operations, resulting from a different internal con- struction. In the cutting tool of the present inven¬ tion, the flow passages in both the upper and lower body portions are not open to flow until the upper piston has first moved to open the upper flow passages. US 2,548,931, 2,644,673 and 3,050,122 disclose underreamers having cutter blades pivotally mounted on a main body and connected by link members to a plunger for simultaneously expanding the cutters outwardly from the main body. US 2,756,968 discloses an expansible well scraper having scraper blades pivotally mounted on a main body and connected by a toothed mechanism to a plunger for simultaneously expanding the cutters outwardly from the main body. US 4,565,252 discloses an underreamer or milling tool having simultaneously-expansible arms pivotally mounted on a main body. A rotary fluid housing is mounted within each arm and includes a body nozzle for receiving fluid from the body, and an expandable arm nozzle for directing fluid into a bore which extends through the arm to provide circulating fluid outwardly of the expandable arm. US 5,497,842 discloses a reaming apparatus for enlarging a borehole which has a tubular body with primary blade(s) and secondary blade(s) which extend a lesser radial distance from the body than the primary blade(s) . US 5,495,899 discloses a multi-bladed reaming apparatus with blades unequally spaced around a tool body. Problems associated with through-tubing underream- ing include the failure to underream out to a suffici¬ ently-large diameter and the inability to handle relat¬ ively large torques. The present invention relates to a tool which is useful for milling or underreaming. In one embodiment, the tool has an outer body within which a mandrel is movably disposed. The mandrel is connected at one end to an item in a tubular or drill string, e.g. threadedly connected to a top sub having a flow channel there- through from top to bottom which is in fluid communica¬ tion with a flow channel through the mandrel which extends from the top to the bottom of the mandrel. A spring between, and biased against, the mandrel and the outer body initially urges the outer body down- wardly with respect to the mandrel; and a plurality of cutter arms pivotally connected to the outer body are initially positioned against the body in a non-extended fashion. An open orifice at the other end of the mandrel restricts fluid flow out from the mandrel. An increase of fluid flow above a certain amount increases pressure within the mandrel. When this pressure reaches a cer¬ tain desired level, e.g. about 3.45 bar, pressure build¬ up in a pressure chamber of the mandrel in fluid commu- nication with the mandrel's central flow bore compresses the spring. This results in the outer body moving upwardly. This upward movement brings "kick-out" sur¬ faces of the mandrel into contact with the pivotable cutter arms causing them to pivot to an extended cutting position. One or more of the cutter arms (lower, upper, or all ) has a support which is also pivotally connected to the mandrel and which moves out to engage and support the cutter arm releasably. In certain embodiments a washout port is provided through the mandrel, in fluid communication with the central flow bore of the mandrel, which is sized, configured, and disposed so that a portion of the fluid flow through the central flow bore exits through the washout port to clean the blades. Such a port may be provided for each blade. In certain embodiments, one or more (two, three, four, or more) first blades of a first length are provi¬ ded at a first part of the tool. The or each first blade is provided near one end of the tool. One or more (two, three, four or more) second blades are provided at a second part of the tool, spaced from the first part, and the or each second blade is longer than the first blade. In this way, the "bite" which the second blade takes out of the tubular surround, and/or formation to be milled or underreamed, is reduced and more-efficient operation is achieved. One particular tool according to the present inven¬ tion initially has an outside diameter of 43mm; three first blades spaced apart 120° around the tool's circum- ference, each first blade being about 50mm long (i.e. from pivot pin center to blade end); and three second blades spaced apart 120° around the tool's circumfer¬ ence, each second blade being about 125mm long. In this tool, the first blades are about 170mm up from a shoul- der on the lower end of the mandrel, about 150mm up from the shoulder; the second blades are about 120mm up from the shoulder; and about 100mm up from the shoulder. The blades are offset at the different levels; i.e., in a top view a blade appears every 60° with first and second blades alternating. (Although it is within the scope of this invention for the first and second blades to be axially aligned or spaced apart angularly by any desired amount. ) The cutting surfaces of the blades, including bottom, side, and top surfaces, may be dressed with any 47849 PC17GB97/01507 - 7 - known matrix, diamond or carbide material (e.g. Klu- strite, Zitco, Kutrite (all trademarks)), or diamond dressing; any cutting insert may be applied to the blades in any pattern or in any manner; or any combina- tion thereof (all collective referred to as "cutting material" ). The inner mandrel has kick-out surfaces disposed so that only one set of blades is initially extended and then, with increased fluid pressure and resulting addi- tional outer body movement, the second set of blades is extended. Accordingly, in a tool with three or more blade sets, the sets can be extended either simultan¬ eously or sequentially. Once the blades are extended, cutting, milling and/or underreaming is initiated by rotating a drill string to which the tool is connected, or by activating a down-hole motor to which the tool is connected. Any system or apparatus for orienting a down-hole tool, and for indicating the position of a down-hole tool, may be used with a tool according to the present invention. In certain embodiments, with two or more sets of blades at different heights on the tool, all the blades are the same length and extend outwardly from the tool the same distance. In other embodiments blades at one location are longer than blades at a different location. In one embodiment, some blades in one set are the same length as blades in another set and some of the blades are longer than the other blades. In one embodiment blades in one set which are the same length as blades in another set alternate with blades of longer length, e.g. around the tool's circumference at one location a short¬ er blade is between two longer blades, etc., e.g. in one embodiment one blade is about 2.5mm shorter than an adjacent blade. Accordingly, the present invention provides a cutting tool which is as claimed in the appended claims. Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood. The present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. IA is an axial cross-sectional view of a cutting tool according to the present invention; Fig. IB is a cross-sectional view along line IB-IB of Fig. IA; Fig. 1C is a cross-sectional view along line 1C-1C of Fig. IA; Fig. 2A is a view of the tool of Fig. IA in a different position; Fig. 2B is a cross-sectional view along line 2B-2B of Fig. 2A; Fig. 2C is a cross-sectional view along line 2C-2C of Fig. 2A; Fig. 2D is a cross-sectional view along line 2D-2D of Fig. 2A; Fig. 2E is a side view of a blade of the tool of Fig. 2A; and Fig. 2F is a bottom view of the blade of Fig. 2E. Referring now to Fig. 1, a tool 10 according to the present invention has a top sub 20 threadedly connected to a mandrel 30 about which is movably disposed a con¬ nector 40 to which is threadedly connected an outer body 50. A first set of blades 60 is pivotally connected to the outer body 50 at one location on the outer body 50, and a second set of blades 70 is pivotally connected to the outer body 50 at a second location spaced axially from the first location. The blades 70 are shorter in length than the first blades 60. Blade supports 80 support the first blades 60 when they are extended. The top sub 20 is connectable to any typical member of a tubular or drill string, such as a mud motor, a measurement-while-drilling system, or a shock sub. The top sub 20 has an upper (as viewed) externally screw-threaded end 21, and a lower internally screw- threaded end 22. A flow bore 23 extends from one end of the sub to the other. A locking screw 24 in a bore 25 extends into a groove 35 of the mandrel 30 to prevent the sub from separating from the mandrel. The mandrel 30 has an upper externally screw-threa¬ ded end 31, with an 0-ring 32 in a recess 34 to seal the mandrel/sub interface. A flow restrictor, or choke 149, is secured in a recess 36 at the down-hole end of the mandrel and is held in place by a snap-ring 37. An 0- ring may be used between the choke and the surface of the mandrel. The choke may be any size to restrict to a desired extent the flow of fluid from the mandrel. As shown, the choke has a central bore the same diameter as the narrower bore through the mandrel but the bore through the choke may be smaller in diameter than the bore through the mandrel. A port 38 permits fluid flowing through bore 33 to flow from within the mandrel 30 into a chamber 41 formed by the mandrel 30 and the connector 40. The lower flow bore 39 is of a lesser diameter than that of the upper flow bore 33. O-rings 131, 132 seal the mandrel/outer body interface. A shoulder 133 provides a surface against which a spring is seated. A kick-out surface 134 is positioned adja- cent each blade support 80; a kick-out surface 135 is positioned adjacent each blade 60, and a kick-out sur¬ face 136 is positioned adjacent each blade 70. A wash¬ out port 137 for fluid flow to the blades is positioned adjacent each blade 60, and a washout port 138 for fluid flow to the blades is positioned adjacent each blade 70. The connector 40 has a lower screw-threaded end 41 threadedly connected to the outer body 50. An 0-ring 42 seals the connector/outer body interface. A skirt 44 defines part of the chamber 41. A central bore 43 extends through the connector 40 from one end to the other . The outer body 50 has an upper screw-threaded end 51 which is threadedly connected to the lower screw- threaded end 41 of the connector 40. O-rings 151, 152 seal the mandrel/outer body interface. A spring 52 is biased against the shoulder 133 of the mandrel 30 and against a shoulder 54 of the outer body 50. Initially this spring urges the outerbody 50 downwardly with respect to the mandrel 30 and maintains these parts in the position shown in Fig. IA. Each blade support 80 is pivotally mounted to the outer body 50 with a pivot pin 55. A holding pin 86 in a channel 87 holds the pivot pin 55. Each blade 60 is pivotally mounted to the outer body 50 with a pivot pin 58. A holding pin 66 in a channel 67 holds the pivot pin 58. Each blade 70 is pivotally mounted to the outer body 50 with a pivot pin 59. A holding pin 76 in a channel 77 holds the pivot pin 59. A bore 53 extends through the outer body 50 from one end to the other. A lower end 157 of the outer body 50, having a shoulder 158, is connectable to any typical member of a drill string, tubular string, or string with a down-hole or mud motor. Each blade 60 (see Figs. IA, 2E and 2F) has a cutter face 61, an end face 62, a shoulder face 63, a back face 64, a torque notch 65 and a pivot pin hole 68. As shown, the blades 60 have a crushed carbide cutting matrix 69 on the face 61 and part of the end face 62. Of course, the entire blade may be covered with such a matrix. Cutting inserts may be positioned in one or more faces in any disposition, pattern or array for such inserts as known for drilling, milling, or reaming tools, with or without chipbreakers on each insert. As shown in Fig. 2A, fluid under pressure (e.g. drilling fluid, mud, water, etc. ) flowing through the tool 10 may increase pressure within the chamber 41 to such a level that the force of the spring 52 is overcome and the connector 40 and outer body 50 moved upwardly with respect to the mandrel 30. This movement brings an end of each blade support 80 into contact with its respective kick-out surface 134, forcing each blade support 80 outwardly. Upward movement of the outer body 50 also brings an end of each blade 60 into contact with its respective kick-out surface 135, forcing each blade 60 outwardly. The end of each blade support 80 moves into a torque notch 65 of its respective blade 60 to stop further pivotal movement of each blade 60 and to support each blade 60 during cutting. Upward movement of the outer body 50 also brings an end of each blade 70 into contact with its respective kick-out surface 136, forcing each blade 70 outwardly. Pivotal movement of each blade 70 ceases when it abuts a stop surface 159 of the outer body 50. As shown in Fig. 2A, each blade 60 is positioned so that fluid flowing from the washout ports 137 flushes material away from the blade. Each blade 70 is posi¬ tioned so that fluid flowing from the washout ports 138 flushes material away from the blade. As shown in Figs. 2B and 2C the blades 60 are 60° offset from the blades 70. When the fluid pressure in the tool is reduced, the spring 52 urges the outer body downwardly, and the blades are retracted. Alternatively, by an upwards pull applied to the top sub 20 and mandrel 30, the blade supports 80 and blades 60, 70 may be moved off their respective kick-out surfaces and pivot back into the outer body 50. In one typical operation of the tool 10, the tool's upper end is connected to a mud motor, and the tool's lower end is connected to a mill or bit. The tool is passed through a tubing string with a relatively small inner diameter and into a casing of larger diameter. The blades are extended and reaming commences. Upon completion of the reaming operation, the blades are retracted and the tool is removed from the wellbore. In certain "through-tubing" applications, the tool 10 is sized so that, initially, it can be inserted through tubing, e.g. tubing with an inside diameter of 50.7mm.

Claims: CLAIMS : 1. A cutting tool (10) for use in a wellbore, the tool comprising an inner mandrel (30) connectable to a tubular string extending from a surface of the wellbore down to a subterranean location in the wellbore, an outer body (40, 50) disposed about the inner mandrel and movable longitudinally with respect thereto, at least one blade (60) pivotally mounted to the outer body at one location, and at least one other blade (70) pivotally mounted to the outer body at a second location spaced axially from the first location, the blades being pivotable from a retracted posi- tion against the outer body to a cutting position ex¬ tending from the outer body when the outer body moves longitudinally with respect to the inner mandrel. 2. A cutting tool as claimed in Claim 1, wherein there is a set of the said one blades spaced apart angularly around the outer body. 3. A cutting tool as claimed in Claim 1 or 2, wherein there is a set of the said other blades spaced apart angularly around the outer body. 4. A cutting tool as claimed in any preceding claim, wherein the or each other blade is longer than the or each one blade. 5. A cutting tool as claimed in Claims 2 and 3, wherein the blades of one set are spaced apart angularly from the blades of the other set. 6. A cutting tool as claimed in any preceding claim, wherein at least one blade is dressed with cutting material. 7. A cutting tool as claimed in any preceding claim, wherein at least one blade, or each blade of the respective set has a support notch (65), the tool further comprising a support arm (80) corresponding to each respective notched blade, the support arm being pivotally connected to the outer body and pivotable outwardly by contacting the inner mandrel (30) as the outer body moves longitu¬ dinally with respect to the inner mandrel, and being movable so that a portion thereof moves into the support notch of the blade and is releasably held therein. 8. A cutting tool as claimed in any preceding claim, wherein a spring (52) disposed between the mandrel and the outer body biases them apart, and wherein the mandrel has a bore (33) for fluid flow extending therethrough, and a fluid exhaust port (38) for exhausting fluid from the mandrel bore into a pressure chamber (41) defined by a portion of an exterior surface of the inner mandrel and the outer body, the pressure chamber being adapted to receive fluid under pressure pumped down the inner mandrel and to hold sufficient fluid to overcome the spring bias to activate the cutting tool by urging the outer body longitudinally with respect to the inner mandrel thereby pivoting the various blades from their retracted to their cutting positions. 9. A cutting tool as claimed in Claim 8, wherein the mandrel has a flow restriction (148) to facilitate a desired build up of fluid pressure in the pressure chamber. 10. A cutting tool as claimed in any preceding claim, com- prising a fluid flow bore (33) through the inner mandrel from one end to the other, and washout ports (137, 138) adjacent the blade pivots, the washout ports being in fluid communication with the fluid flow bore and disposed for jetting fluid toward the blades when in their cutting positions. 11. A cutting tool as claimed in any preceding claim, in which the inner mandrel is movable longitudinally by mechanical force applied to it after the blades have been extended, so that the blades retract against the outer body . 12. A cutting tool as claimed in any preceding claim, wherein at least one blade or set thereof has surfaces (134, 135, 136) adapted to contact an adjoining kick-out surface as the outer body moves longitudinally with respect to the inner mandrel to pivot each blade out¬ wardly from the outer body. 13. A cutting tool as claimed in Claim 12, wherein both blades or sets thereof have contact surfaces, and where- in the inner mandrel has kick-out surfaces adjacent each blade so that as the outer body moves with respect to the inner mandrel, all the blades are moved outwardly from the outer body. 14. A cutting tool as claimed in any preceding claim, in which the outer body has a compartment for each blade, from which each blade is outwardly pivotable, each blade being initially positionable in a respective compartment so that the blade does not project beyond an outer surface of the outer body prior to outward exten- sion of the blades. 15. A cutting tool as claimed in Claim 14, in which the inner mandrel has an indented portion adjacent each blade for receiving a portion of each blade prior to blade extension. 16. A cutting tool as claimed in any preceding claim, comprising a downhole motor connected to the cutting tool. 17. A cutting tool as claimed in any of Claims 1 to 15, comprising a measurement-while-drilling system connected to the cutting tool. 18. A cutting tool as claimed in any of Claims 1 to 15, comprising a mill connected to a lower end of the cut¬ ting tool. 19. A cutting tool as claimed in any of Claims 1 to 15, comprising a drill bit connected to a lower end of the cutting tool. 20. A cutting tool (10) for use in a wellbore, the tool comprising an inner mandrel ( 30 ) connectable to a tubular string extending from a surface of the wellbore down to a subterranean location in the wellbore, an outer body (40, 50) disposed about the inner mandrel and movable longitudinally with respect thereto, a plurality of first blades (60) spaced apart angularly and pivotally mounted to the outer body at one location on the outer body, a plurality of second blades (70) spaced apart angularly and pivotally mounted to the outer body at a second location spaced axially from the first location, each second blade having a rear surface ( 64 ) with a support notch (65) therein, all the blades being movable between a retracted position against the outer body and a working position extending from the outer body when the outer body moves upwardly with respect to the inner mandrel, the second blades being longer than the first blades, a support arm (80) corresponding to each of the second blades, the support arm being pivotally connected to the outer body and movable outwardly by contacting the inner mandrel as the outer body moves upwardly with respect to the inner mandrel, to a position in which the end of the arm is engaged in the support notch of the corresponding second blade and is releasably held therein, the inner mandrel being movable axial after the blades have been extended to retract the blades against the outer body, each blade having a contact surface and the inner mandrel having a kick-out surface (135, 136) adjacent each blade so that as the outer body moves upwardly with respect to the inner mandrel each blade contacts a respective kick-out surface and is thereby moved out¬ wardly from the outer body.

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