GB2245626A - Enhanced diameter clean-out tool - Google Patents

Abstract

A downhole cutting tool has two lateral slots 116, 216 and a longitudinal cavity communicating with each slot, two cutting members 16a, 16b, 18a, 18b being pivotally mounted in each slot. Means 170, 270 are provided in the cavities for moving the cutting members. A first channel 184, 284 in the body is spaced from each slot and communicates a liquid from the cavities to the outlets of the first channels regardless of the position of the movement means 170, 270 while second channels 190, 290 in the body are spaced from each slot and the first channels to communicate liquid from said cavities to outlets of the second channels in response to said movement means moving from the first to second positions. <IMAGE>

Description

ENHANCED DIAMETER CLEAN-OUT TOOL AND METHOD This invention relates generally to downhole cutting - tools and cleaning methods and more particularly, but not bv way of limitation, to clean-out tools having enhanced stability and including longitudinal fluid channels defined therethrough and used in a method for removing material from a tubular string and/or a borehole.

Casing fixed downhole in a well bore sometimes needs to be cleaned of cement, sand, shale, mud and other types of deposits as is known in the oil and gas industry. This requires a tpe of tool wich can be lowered through a relatively narrow diameter tubing string to clean the tubing string and which can be lowered for subsequent use to clean below the lower end of the tubinc string in the relatively wider diameter casing. This type of tool will be referred to herein as an enhanced diameter clean-out tool, cr simply a clean-out tool.An early from cf such a clean out tocl which has beer: in commercial use is disclosed in ry United States Patent Application Serial No. 888,418, filed July 23, 1986, now abandoned.

Other types of tools have been disclosed to include blades which are to be retracted within the support portion of the tool so that the blade and the tool can pass through tubing strings having an inner diameter smaller than the maximum diameter of the blades when they are extended. Once having passed through the tubing string, the blades can be extended outwardly to cut out a diameter up to substantially the inner diameter of the casing or other borehole surface within which the tool is used.

It is my understanding that some tools which have been proposed or used have utilized springs to extend or retract the blades or have otherwise been mechanically operated to achieve the movement of the blades between their extended and retracted positions. Pistons moved by pressurized fluid have also been used to extend the blades. Some of these tools also have had jet ports through which fluid can be ejected to assist in cutting the raterial an in subsequently flushing the cut material out of the well. Others use ports which are opened to pressure-affectino fluid flow in response to the blades being extended.

Larger diameter tools of z generally similar type have been used in the cutting and parting of casino strings but these have not been of 2 type that can be passed through smaller diameter tubulars.

I ar also aware oV a plpe or casing cutter which cuts pipe cr casing at its outer point and not along its side edges. A. speci- fic type of cutter of which I am aware is 2 Bowen internal pressure pipe cutter having a plurality of knives each separately pivotally connected within a body in which a piston is also dis- posed. The piston is used to drive the blades outwardly to apply pressure by which a pipe is cut.

A formation notching apparatus including two sets of cutting elements is disclosed n U.S. Patent 3,050,ì22.

Although there are various types of downhole cutting devices, there has existed the need for an improved clean-out tool which has enhanced stability so that it can be used effectively, without substantial vibrations being created, on what is known as a coil tubing motor. An example of one such motor is known as a SLIMDRIL motor marketed by SlimDril, Inc. of Houston, Texas.

There has also existed the need for an improved clean-out tool which provides significant liquid flow longitudinally through it for washing out, or otherwise lubricating, cuttings but which also generates through such liquid flow signals indicating when the extendible elements of the tool have opened.

According to the present invention, there is provided a downhole cutting tool, comprising: first cutting members; second cutting members; support means for supporting said first cutting members and said second cutting members at respective axially spaced locations on said support means so that said first cutting membsrs and said second cutting members are pivotable at the respective locations between retracted and extended positions and further so that said first cutting members and said second cutting members are circu::nferentially angularly offset for enhancing rotational stability, said support means with said first cutting tne3bers and said second cutting members adapted to be lowered downhole through a narrow tubing string, which narrow tubing string is disposed in a borehole and has a diameter substantially less than the maximum downhole diameter defined by the borehole or a casing or liner disposed therein; a first piston slidably disposed in said support means adjacent said first cutting members, said first piston movable in response to a pressurized fluid; a second piston slidably disposed in said support means adjacent said second cutting members, said second piston movable in response to the pressurized fluid; first channel means defined in said support means for communicating fluid through said support means around said first cutting members, said first channel means having an inlet defined in said support means near an end of said first piston and further having an outlet defined in said support means below said first cutting members; and second channel means defined in said support means for communicating fluid through said support means around said second cutting members, said second channel means having an inlet defined in said support means near an end of said second piston and further having an outlet defined in said support means below said second cutting members.

The tool has two sets of extendible elements angularly offset relative to each other to provide enhanced stability when the tool is rotated.

In order that the invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which: FIG. 1 is a schematic illustration of a preferred embodiment of the clean-out tool of the present invention located within a turbine strings disposed within a cased well bore, which tocl is shewn as having fluid pressure applied thereto so that extendible members are partially extended to clean the inside of the tubing string.

FIG. 1B is a schematic illustration showing the preferred embodiment of the tool from FIG. 1A in a lower position so that the first set of extendible members (specifically, cutting members) of the tool are opened below the tubing string.

FIG. 1C is a schematic illustration schwing the preferred embodiment of the tool from FIG. 1 in a still lower position so that both the first set of cutting members and the second set of the extendible members, used primarily for stabilization but also possibly providing some cutting, are opened below the tubing string.

FIG. 2 is an elevational view of the tool schematically shown in FIGS. 1A-1C.

FIG. 3 is a top view of the tocl as taken along line 3-3 shown in FIG. 2 but without the illustrated connected conveyancing structure.

FIG. 4 is 2 sectional elevational view, taken along line 4-4 shown in FIG. 3, wherein the sets of extendible elements are i retracted positions.

FIG. 5 is a sectional elevational view as illustrated in FIG.

4, but showing the sets of extendible elements in extended positions.

FIG. 6 is a sectional view taken along line 6-6 shown in FIG.

2.

FIG. 7 is a sectional vie taken along line 7-7 shown in FIG.

2.

FIG. 6 is a sectional elevational vies taken along line 6-8 shown in FIG. 7.

FIG. 9 is a sectional elevational vie as shown in FIG. 8 but showing passageways converging to a central indentation in the bottom of the tool.

FIG. 10 is a schematic illustration of casing in which are disposed two tubing strings of different diameters (but both smaller than the diameter of the casing) connected in line; this illustrates another structure in which the present invention is contemplated to have utility.

FIG. llA schematically shows a portion of another embodiment of the clean-out tocl of the present invention under pressure and positioned in the laxer diameter tubing string of the structure representec in FIG. 10.

FIG. 11 schematically shows the portion of the tocl depicted in FIG. 11A. after it has been lowered into the smaller diameter tubing string of the structure represented in FIG. 10.

FIG. 11C schmetically schws the same portion of the tool depicted in FIGS. 11A and 11B but now lowered below the connected tubing strings no into the casing of the structure represented in FIG. 10.

FIGS. 1A-1C illustrate three stages of usage of the present invention within a downhole environment. This environment includes a well bore 2 having 2 cased or uncased borehole. z.s illustrated, the well bore 2 is cased with suitable casing 4 (e.g., 7-inch casing).

Disposed within the well bore 2 is a tubing string 6 of a suitable type as known to the art (e.g., 41-inch tubing). As illustrated, the tubing string 6 is centered coaxially within the casing 4; however, the present invention is also useful where a tubing string is off-centered.

Lowered into the tubing string 6 is a downhole enhanced diameter clean-out tool 8 schematically shown in FIGS. lA-lC but more particularly described hereinbelow and embodying a preferred embodiment of the apparatus of the present invention. The tool 8 is roved into and out of the tubing string 6 and the well bore 2 on suitable conveyancing means 10 of a tpe as known to the art.

One exarple of such a conveyancing means is a coil tubing motor apparatus of a type as known to the art for rotating and lowering (and subsequently raising) the tocl 8. An example of a coil tubing motor apparatus is one including a SLIMDRIL motor of SlimDril, Inc. of Houston, Texas. Another example of a conveyancing means is a tubing string of smaller diameter than the tubing string 6.

The downhole tool 8 is used to cut material 12 located in the borehole and/or the tubing string 6. An example of such material is cement which has been pumped into the well bore for a known purpose and which has set up ihardened).

FIG. 1A illustrates the tool 8 at an initial stage of cutting. This cutting occurs within the tubing string 6 and is done with cutting elements 14 located on the bottom end (as oriented in FIG. 1A) of the tool 8. The cutting elements 14 have an overall width substantially equal to the width of the main body of the tool 8; therefore, the cutting elements 14 cut material within a path which is in line with the tool 8 and which has a cross-sectional area substantially the same as the maximum crosssectional area of the main body of the tool 8. Cutting is also done in part by extendible members 16, 18 which are partially extended by fluid pressure exerted down through the conveyancing means 10 to the tool 8 in a manner known to the art.The members 16, 18 are only partially extended because they are limited by the inner diameter of the tubing string 6 which is not to be cut by the tool 8. Prior to application of fluid pressure, the members 1E, 18 are fully retracted to the position illustrated in FIG. 4.

As the conveyancing means 1O rotates and lowers the tool 8, cutting continues as just described until the lower set of exten hole members 16 (comprising to pieces 152, 16b in the depicted preferred embodiments an shaped as shown in FIGS. 4 and 5) is moved below the bottom: of the tubing string 6. This position is illustrated in FIG. 1B. At this point of the operation, the fluid (e.a., hydraulic) pressure exerted through the tubinc string 6 opens farther the cutting members 16, which thereafter cut a wider (i.e., enhanced diameter) path radially beyond what the bottom cutting elements 14 cut. As subsecuently described, a signal is generated for communication to the surface at this time so that accurate positioning of the tool 8 can be known (i.e., by indicating that the lower members 16 are just below the tubing string 6, which has a length which is known). Such signal also indicates the opening or extension and the degree or opening or extension of the set of members 16.

Continued rctation and lowering of the tool 8 ultimately moves the upper set of members 18, functioning primarily as set bilizers but also being of a cutting construction (and shaped) the same as the members 16 so that the members 18 are sometimes referred to herein as an upper set of cutting members, below the bottom of the tubing string 6 and into open or extended positions in response to the fluid pressure within the tubing string 6.

This position is illustrated in FIG. 1C. Another signal is gen- erased at this time to mark the position of the tool 8 and the opening (and degree thereof) of the stabilizer members 18 (which are illustrated as including two pieces 18a, 18b).Use of the stabilizers in this exemplary environment, wherein the tocl 8 is driven by 2 coil tubing motor, is important to enhance the stability of the tool 8 during rotation within the wider region below the tubing string 5, which enhanced stability reduces vibrations or "chattering" arising from the tool being rotated within a cut region having a significantly widen diameter than the diameter of the main support body of the tool 8.

With reference to FIGS. 2-9, preferred embodiments of the downhole cutting tool 8 will be more particularly described. The tool 8 includes an elongated support 20 comprising a cylindrical body 22, a cylindrical body 24, and connector means 26 for connecting the two bodies 22, 24 to establish an angle between the set cf cutting members 16 associated with the body 22 and the set of cutting members 18 associated with the body 24. The cylindrical body 22 provides support for a lower subassembly 28, and the cylindrical body 24 provides support for an upper subassembly 30.

In the preferred embodiment of FIG. 2 the two subassemblies are connected through an adapter defined by the connector means 26.

The connector means 26, or adapter, of the preferred embodiments of FIGS. 2-9 has a cylindrical shape defined by an annular wall 1 32 (FIGS. 4 and 5). A. threaded inner surface 34 defines a coupling receptacle for threadedly engaging with a mating portion of the cylindrical body 24. h threaded outer surface 36 is part cf a protuberant portion of the adapter 26 for engaging with a mating portion cf the ctlin ical body 22.The adapter 26 is used in the preferred embodiments to establish a predetermined angle by which a longitudinal plane in which the stabilizing cut tin mertbers 18 are retained is circumferentially offset from a longitudinal plane in which the cutting members 16 are retained.

This offset is obtained by appropriately machining an upper radial surface 38 against which a surface of the body 24 abuts when the body 24 is connected to the adapter 26. That is, by machining the surface 38, one can control the degree to which the cylindrical body 24 can be screwed into the adapter 26 thereby defining the relationship between a longitudinal plane of the cutting members 18 and the body of the adapter 26 and thus the relationship to the lower cylindrical body 22.This angular offset is important to provide for the enhanced rotational stabi li-ty. In the illustrated preferred embodiments the ancle is about 900 (as illustrated, a longitudinal plane for the members 16 could include the sheet containing FIG. 4 and a longitudinal plane for the members 18 would include one perpendicular to the sheet containing FIG. 4). Of course, this relative positioning could be obtained by other suitable means. As is apparent from the drawings, the cylindrical body of the adapter 26 spaces or separates the te bodies 22, 24 from each other but connects therm in line with each other.

In describing the remainder of the preferred embodiments or the tool 8 shown in FIGS. 2-9, reference will be made primarily only tc the lower subassembly 26 because the upper subassembly 30 induces the same type of components.This is indicated by the numbering scheme used hereinbelow wherein the additional compo nets of the lower assembly 28 described hereinbelow will be de=ned with numerals in the 100's with the corresponding compo- nents of the upper subassembly 30 being indicated parenthetically by corresponding numbers in the 200's.

The cylindrical support body 22 (24) has the two overlapping cutting members 16 (18) pivotally mounted therein. A movement means 110 (210) is disposed in the support body 22 (24) for moving the cutting members 16 (18) to their respective extended positions; this movement occurs in response to a force acting on the movement means 110 (210) to move it from a first position to a second position. As previously mentioned the cutting elements 14, effectively defining a mill of a suitable type, are attached to the bottom end of the support body 22 for creating a pilot hole through which the tool 8 moves as it is rotated through the material to be cleaned-out.

The support body 22 (24) of the preferred embodiment is an elongated, hollow cylindrical member having a side wall 112 (212) with an exterior surface 114 (214). Define laterally or diame- trically through the lower (as viewed in the drawings) portion of the body 22 (24) nearer its lower end is a longitudinal slot 116 (216) intersecting diametrically opposite portions of the exter- icr surface 114 (214). Extending above (as viewed in the draw- ings) and communicating with te slot 116 (216) is a longitudinal (specifically, an axial) cavity 118 (218). The cavity 118 (218) extents between an upper end of the support bodv 22 (24) and the slot 116 (216).

The cavity 118 (218) has a longitudinal section defined by an inner surface 120 (220) of the wall 112 (212). Above the surface 120 there is a portion of the cavity 118 which is threaded, as identified b the reference numeral 122, for connecting with the surface 34 of the adapter 26 (as for the body 24, the correspono- inc surface 222 is for connecting with the conveyancing means 1D by which the tool 8 is lowered into a well bore). The lower portion of the surface 120 (220) is a piston-receiving cavity section. Another cavity section, defined by an inner surface 126 (226), has a diameter smaller than the diameter of the surface 120 (220).The surface 126 (226) defines a portion of the cavity 118 (218) for receiving a portion of the movement means 110 (210) as will be more particularly described hereinbelow.

The cutting members 16 (18) are pivotally connected within the slot 116 (216) of the support body 22 (24) by means of a single pin 140 (240). The pin 140 (240) has an overall length which is not longer than the diameter cf the portion of the body 22 (24) in which the pin 140 (240) is retained. The pin 140 (240) is retainer n a diametrical hole 146 (246) defined through the sice wall 112 (212) cf the support body 22 (240.

The win 140 (240) extends through 2 hole defined substan- tially centrally within each of the members o the pair 16 (18) as is apparent from the drawings. These holes are aligned so that the two cutting members themselves are overlapping, as is also apparent from the drawings. The members of the pair 16 (18) pivot simultaneously, but in opposite directions about the axis refined by the pin 140 (240) for moving between the fully retracted position illustrated in FIG. 4 and the fully extended position illustrated in FIG. 5.

The cutting members 16 (18) are constructed so that each has a similar shape and each defines a cutting blade (as for the mem- bers 18, these are also cutting blades in the illustrated preferred embodiment, but they can simply be members which provide the needed stability without necessarily being cutting blades).

Each blade 16a, 16b (18a, 18b) has a lower edge defining a cutting surface having a predetermined length so that, when the mem- bers 16 (18) are held in the overlapping relationship and fully extended position illustrated in FIG. 5, the lower edges substantially align. In the preferred embodiment the overall length defined by the two overlapping, fully extended blades is not greater than the inner diameter o' a casing in which the tool 8 is to be used.

The blades are extended by movement of the movement means 110 (2i0). In the preferred erbociment, the movement means 110 (210) includes a piston 170 (270) slidably mounted in the cavity 118 (218) lSPeciLicall, within the piston receiving section defined b the lower portion of the surface 120 (220)]. The piston 170 (270) induces a diam-tric surface 171 (271) against which pressurized licuic (cr, more generally, fluid) is caused to act when the cutting members 16 (18) are to be moved to their extended positions.The piston 170 (270) has a sealing body portion 172 (272) with a longitudinal surface extending from the diametric surface 171 (271) toward the cutting members 16 (18) and about which is defined a circumferential groove 174 (274) in which a sealing member, such as an O-ring 176 (276), is retained for sealingly engaging the surface 120 (220). The piston 170 (270) has a sufficient diameter across the sealing body portion 172 (272) relative to the diameter across the surface 120 (220) of the cavity 118 (218) to establish a metal-to-metal seal between the longitudinal surface of the piston 170 (270) and the surface 120 (220). A neck portion 178 (278) extends from the portion 172 (272) of the piston 170 (270).The neck portion 178 (278) extends from the cavity portion defined by the surface 120 (220) and through the neck receiving portion defined by the surface 126 (226) into engagenent with the respective cutting members 16 (18). As shown in FIGS. 4 and 5, this engagement occurs when the members i5 (18) are either in the fully retracted positions or the fully extended positions.Although this continual engagement is illustrated in FIGS. 4 and 5, the principal purpose of the piston 17C (27Q) is to move the overlapping cutting members 16 (18) to their respective extended positions so that when the mem- bers 16 (18) are in their fully retracted positions and are not at that time to be moved outwardly, the piston 170 (270) need not necessarily engage the cutting members 15 (18), so long as suitable engagement can subseouently be obtained wnen the cutting members are to be moved to their extended positions. Although there is not one in the illustrated preferred embodiments, the piston 170 (270) could have an axial channel defined longitudi- nally therethrough to allow fluid flow through the piston 170 (270) between the cavity 118 (218) and the slot 116 (216).

Referring again to the body 22 (24), it further includes two channel means 180, 181, (280, 281).

The channel means 180 (280) is defined in the body 22 (24) and circumferentially spaced from the slot 116 (216). The channel means 180 (280) allows communication of a liquid from the cavity 118 (218) to an outlet of the channel means 180 (280) regardless of the position of the piston 170 (270) between its uppermost and lowermost positions.

In the preferred embodiments, the channel means 180 (280) includes a circumferential groove 182 (282) defined in the body 22 (24) in communication with the cavity 118 (218). The groove 162 (282) is disposed adjacent the diametric surface 171 (271) of the piston 170 (270), but it is not covered by the longitudinal surface c' the body portion 172 (272) of the piston 170 (270) When the piston is at its uppermost position. That is, for the orientaticn shown in FIG. 4, for example, the top of the piston 170 (270) is just below the groove 182 (282).

The channel means 180 (280) also includes a passageway ce fin- in the body 22 (24) communicating with the circumferential groove 182 (282) and extending towards an end of the body 22 (24). As illustrated, the passageway is specifically a longitu- dial bore 184 (284) having its upper end connected to the groove 182 (282) and having its lower end, defining the outlet, disposed near the lower end of the body 22 (24). This positioning of the outlet a9..lows liquid to be communicated through the channel means to the cutting means 14. This aids the cutting process, the flushing process by which the cut material is removed from the well bore, and the equalization of pressure between the intericr and exterior of the tool 8. In the embodiment illustrated in FIG. 8, this lower end of the bore 184 opens through the-lcwer end of the body 22. In the embodiment illustrated in FIG. 9, this lower end of the longitudinal bore 184 communicates with a central indentation 300 defined by an axial bore extending upwardly from the bottom surface of the body 22. It is to be note that the two configurations in FIGS. 8 and 9 illustrate only the body 22 cf the lower subassembly 28. As to the upper subassernbly 30, the bore 284 communicates in a configuration similar to FIG.

9 (see FIGS. 4 and 5) with the central passageway cornrnunicating through the adapter 26 into the interior of the body 22.

The channel means 180 (280) of the preferred embodiments further includes another passageway 186 (see FIGS. 6 and 7) (nct shown for channel means 280) defined in the body 22 (24) diame- tricky opposite the longitudinal bore 184 (284). This other passageway communicates with the circumferential groove 182 (282) extends towards the lower end of the body 22 (24). In the preferred embodiments the passageway 186 (not shown for channel means 280) is identical to the longitudinal bore 184 (284) except for its diametrically opposite positioning.

The channel means 181 (281) is defined in the body 22 (24) and spaced from the slot 116 (215) and the channel means 180 (280). The channel means 181 (281) communicates a liquid (or more generally, a fluid) from the cavity 118 (218) to an outlet of the channel means 181 (261) in response to the piston 170 (270) moving from its uppermost position to its lowermost position, which lowermost position is illustrated in FIG. 5.

The channel means 181 (281) includes a circumferential groove 188 (288) defined in the body 22 (24) in.communication with the cavity 118 (218). The groove 188 (288) is disposed between the diametric surface 171 (271) of the piston 170 (270) and the cutting members 16 (18) so that it is covered by the longitudinal surface of the sealing body portion 172 (272) of the piston 170 (270) when the piston 170 (270) is at its uppermost position illustrated in FIG. 4 but so that the groove 188 (288) is unco versed fro such longitudinal surface when the piston 170 (270) is at its lowermost position illustrated in FIG. 5.That is, the groove 188 (28E) is just below (as viewed in the drawings) the groove 182 (282). In the preferred embodiments this positioning is such that the groove 188 (286) is between the groove 182 (282) and the sealing member 176 (275) of the piston 170 (270) regard- less of the positioning of the piston 170 (270) between its uppermost and lowermost positions.Stated differently, the sealing mere 176 (276) is disposed on its piston 170 (270) so that the sealing rnember does not pass the circumferential groove 188 (288) in response to movement of the piston 170 (270) between its lowermost and uppermost positions or movement. Because of the metal-to-metal seal established between the piston 170 (270) and the cavity surface 120 (220), there is no significant leakage into the groove 188 (288) when the piston 170 (270) overlies or blocks the groove 188 (286).

The channel means 181 (261) includes a passageway defined in the body 22 (24) in communication with the circumferential groove 188 (288) and extending towards an end of the body 22 (24). This passageway is defined in the preferred embodiment by a longitudi- nal bore 190 (290) having an end disposed within the body 22 (24) nearer the lowermost position of the piston 170 (270) and having another end, defining the outlet of the channel means 181 (281), disposed near an en of the body 22 (24). This other, or lower the preferred embodiments, en of the longitudinal bore 190 (290) is disposed near the lower end cf the bady 22 (24) so that lics is communicated to the cutting area through the channel means 181 (281) in response to the piston 170 (270 moving from its uppermost position to its lowermost position as illustrated by the change in positions shown in FIGS. 4 and 5. With respect to the lower subassembly 28, the lower end of the bore 190 opens directly through the lower end surface of the body 22 (FIG. 8) or trough communication with the central indentation 300 (FIG. G), With respect to the upper subassembly 30, the lower end of the channel 290 communicates with the lower axial passageway co:r.- municating through the adapter 26 into the lower subassembly 28 in a manner analogous to the configuration shown in FIG. 9 for the lower subassembly 26.

The channel means 181 (281) of the preferred embodiments further includes another passageway 192 (see FIG. 7) (not shown for the channel means 281), which is defined in the body 22 (24) diametrically opposite the bore 190 (290). The passageway 192 (not shown for the channel means 281) is constructed the same as the bore 190 (290) and communicates with the circumferential groove 188 (288) and extends towards the lower end of the body 22 (24).

With the foregoing construction of the channel means 180, 181 280, 281, the two support bodies 22, 24 are connected through the hollow adapter 26 so that the outlets of the channel means 280, 281 communicate fluid with the cavity 118 of the body 22 as is best illustrated in FIG. 4 and 5.With this construction, liquid cr other fluid present within the cavity 218 of the body 24 is continuously communicated through the passageway or bore 284 and the diametrically opposite one into the cavity 118 of the body 22 and through the passageways or bores 184, 186 of the bop 22. Additonal liquid cr fluid is communicated through the passageway cr bore 290 and the corresponding diametrically oppc- site one when the piston 27C is in its lower position, and addi- tional liquid or fluid is communicated through the passageways or bores 190, 192 then the piston '70 is in its lower position.

This communication through the passageways or bores 190, 192, 290 and the one diametrically opposite the bore 290 provides the means by which signals can be generated and sent to the surface for indicating when the respective pistons 170, 270 have moved to their respective lower position, which movement opens the respec tive pair of cutting members 16, 18. The magnitudes of these pressure signals indicate how far open the grooves 188, 288 and the cutting members 16, 18 are.

with reference again to FIGS. lA-iC, the operation of the tool S will be more particularly described. The lower and upper subassemblies 28, 30 are connected through the connector means 26 so that the plane of the cutting members 16 is angularly offset by the predetermined amount (about 900 in the preferred embodi- ment) from the longitudinal plane of the cutting members 18.

This assembly is connected to a carrier tubing string or other conveyancing means 10, such as t coil tubing motor apparatus, for carrying the tool 8 into the well bore. For the environmont illustrated in FIGS. lA-lO, this carrying occurs by lowering the tocl 8 on the conveyancing means 10 through the tubing string 6.

This lowering occurs until the lower end of the tool 8, which contains the cutting or milling elements 1z, reaches the top of the material which is to be cut. At this location, the tool 5 is rotated so that the cutting elements 14 mill or bore through the material 12 located in the tubing string 6. During this boring operation, the cutting members 16, 18 remain retracted within the tool 8 unless the fluid pressure is applied to extend partially the members 16, 18 as is the case illustrated in FIG. 1A.

The clean-out tool 8 cf the preferred embodiments is rotated and lowered against the material 12 in the tubing string 5 so that the lower cutting elements 14 and partially extended members 16, 18 cut a path through the material 12 in the tubing string 6 and on into the wtider diameter region below the tubing string 6 within the casing 4. During this operation a pressurized fluid is applied to the tool 8 down through the conveyancing means 10 and into the cavity 218 of the upper subassembly 30.This pressurized fluid acts against the diametric surface 271 of the piston 270 in the upper subassembly 30, and this pressurized fluid also passes through the circumferential groove 282 and the bore 284 and the corresponding diametrically opposite one which extend from the groove 282.The fluid passing through these bores enters the cavity 118 cf the lower subassembly 28 whereupon it acts upon the diametric surface 171 of the piston 170 and also passes through the bores 1 6. This application o pressurized fluid moves the cutting members 16 to respective extended cutting position when this pair of cutting members is lowered below the lower end of the tubing string 6 and into the bcrehcle, which is cased with the casing 4 for the environment illustratec ir. FIGS. 1A-1C.This position of the tool 8 is illustrated in FIG. 1B. This opening occurs through the action of the piston 170 pushing downwardly on the pair of cutting mer.- bers 16 to obtain the relationship illustrated in FIG. 5.

With the cutting members 16 in their extended positions, the tool e is continued to be rotated and lowered against the material 12 so that both the cutting elements 14 and the cutting members 16 cut through the material 12 within the casing 4.

During this continued rotation and lowering and the opening of the cutting members 16, there is transmitted to the surface from which the borehole of the well bore 2 and the tubing string 6 extend a signal indicating the cutting members 16 have moved to extended positions within the borehole below the tubing string 6.

This signal is generated by the opening of the groove 188 and the bores 190, 192 and the consequent flow of fluid therethrough, whereby a pressure drop in the pressurized fluid, which drop can be detected at the surface, occurs due to the increased flow volume then permitted by the opened bores 190, 192. Less than full extension of the blades 16a, 165 would be indicated by a smaller pressure drop if the piston 170 remained blocking part of the groove 188.

The method of cutting using the preferred embodiment cf the present invention further includes maintaining applying a pressurized fluid to the tool 8 so that the cutting members 18 are moved to their cutting positions when these members are lowered below the tubing string E and into the borehole. During this Zr; ; the method further includes maintaining rotating and lowering the tocl 8 against the material 12 in the borehole through and after the aforementioned step of transmitting signal to the surface.

The method further includes transmitting to the surface another signal, this one indicating that the members 18 have moved to extended, stabilizing positions within the borehole below the tubing string 6. This transmission occurs in response to the piston 270 moving below the groove 288 so that the liquid or fluid within the cavity 218 then also passes through the bore 290 and the corresponding diametrically opposite bore, whereby another pressure drop in the pressurized fluid occurs due to this increased flow volume. Again, partial extension would be indicated by a smaller pressure drop when the piston 270 remains blocking part of the groove 288.

With both sets of cutting members 16, 18 open, the method induces maintaining the two pairs of cutting members in their respective extended positions simultaneously, and concurrently continuing rotating and lowering the tool 8 against the material i2 in the borehole. Having the merbers 16 open cuts the material 12 fro the casing 4 (without damaging the casing 4), and having the meers 18 dozen stabilizes the rotating tool 8.It is contemplated that additional sections corresponding to the sub assembly 30 car. be attached to obtain other sets of stabilizing members. - When the cutting operation has been completed, pressure is removea from. the tool 8, and thus from the pistons 170, 270 so that as the tool 8 is extracted from the well bore, the tubing string 6, or any other encountered obstacle of sufficient oppos- ing force, engages the extended portions of the cutting members i6, 18 anti forces them downwardly into their retracted positions illustrated in FIG. 4.

Another application of the present invention includes cleaning out downhole tubulars within regions having more than two different cross-sectional areas. In FIG. 10 there is schematically illustrated a combination of tubulars including a casing 400 having the largest diameter illustrated in FIG. 10, a lower tubing string 402 having the smallest diameter of the tubulars illustrated in FIG. 10, and an upper tubing string 404 having an intermediate diameter. The tubing strings 402, 404 are interfaced and connected linearly through a suitable adapter joint 406 having a frusto-conical (inwardly tapering in going from upper to lower end as viewed in FIG. 10, thereby defining a constriction in the tubing surface 408.A profile nipple 409 is shown connected to the lower enc of the tubing string 402.

If the material to be cut or cleaned-out extends up into the tubing string 404, the cutting tool of the present invention is operated: initially within the string 404 wherein the extendible cutting members are concurrently opened by fluid pressure to an intermediate position substantially equal to the inner diameter of the upper portion of the tubing string 404; then secondly within the string 402 wherein the extendible cutting members are concurrently opened by fluid pressure to an extent less than where they were positioned within the string 404 but substantially equal to the inner diameter of the lower portion tubing string 402; and then thirdly within the casing string 400 wherein the extendible cutting members are opened by fluid pressure to their farthest of the three exemplary locations of usage (i.e., substantially the inner diameter of the casing 400). At each of these locations the tool is rotated when the members are opened to achieve cutting. Three such locations are illustrated in FIGS. llA, llB and llC, respectively. These drawings show only a lower portion of a tool 410 of the present invention wherein a pair of extendible cutting blades 412a, 412b are pivotally mounted.The tool 410 is identical to any of the previously described preferred embodiments of the tool 8 except that the blades Al2a, 4125 (otherwise corresponding to the cutting members 16) have a different shape from that shown in FIGS. 4 and 5 for the members lSa, 16b. One or more upper sets of extendible members which correspond to the members 18 have, in the embodiment depicted in FIGS. llA-liC, the same shape as the blades 412a, 412b.

The blades 412a, 412b have rounded corner ends 414a, 414b, respectively, as best seen in FIG. llC. The curvature of these ends is sufficient to cause the blades 412a, 4125 to ride down the sloped surface A06 and to be pushed thereacainst, by the weicht cf the conveyancing string on which the tool 410 is carried, into a more retracted position so that the blades 412a, 412b are pushed into the body of the tool 410 sufficiently to enable the tool 410 to fit into the smaller diameter tubing string 4C2.The curvature of the outer corners 414a, 4145 is also sufficient to enable the blades 412a1 412b to ride through the even smaller diameter of the profile nipple 409 without damaging the nipple 409. This curvature for the preferred embodiment depicted in FIGS. llA-llC causes the lower edges of the blades 412a, 412b to extend obliquely above horizontal when the blades 412a, 412b are fully extended as illustrated in FIG. llC.

To accommodate the change in outer periphery of the blades so that adequate full retraction and extension can still be achieved, changes to the blade inner surfaces engaging the respective pistons and to the abutment surfaces of one blade against which the other blade abuts in full retracted or extended position are made consistent with a specific curvature used on the corner ends AlAa, 414b (and the remainder of the outer periphery if it, toc, is curved, such as is illustrated in FIGS.

llA-llC).

It is further contemplated that the present invention can be use in other combinations of one, two or more SiZES o- inner diameters within a borehole, whether going from larder to smaller diameter or vice-versa as between any two consecutive portions.

From the foregoing it is apparent that the preferred embodi- ments of the present invention provide a structure which has an enhanced stability within the borehole when both pairs of exten edible members are in their extended positions. Such preferred embodiments also provide two signals confirming that the cutting members have opened and accurately indicating where the tool is. These signals are generated through a construction which also directs the liquid or fluid flow to the lower cutting region to assist in flushing the cuttings from the well bore.

The present application describes and claims subject matter disclosed in co-pending application number 8800624.2 from which the application was divided.

Claims (7)

1. A downhole cutting tool, comprising: first cutting members; second cutting members; support means for supporting said first cutting members and said second cutting oembsrs at respective axially spaced locations on said support means so that said first cutting members and said second cutting members are pivotable at the respective locations between retracted and extended positions and further 8o that said first cutting members and said second cutting members are circumferentially angularly offset for enhancing rotational stability, said support means with said first cutting members and said second cutting members adapted to be lowered downhole through a narrow tubing string, which narrow tubing string is disposed in a borehole and has a diameter substantially less than the maximum downhole diameter defined by the borehole or a casing or liner disposed therein; a first piston slidably disposed in said support means adjacent said first cutting members, said first piston movable in response to a pressurized fluid; a second piston slidably disposed in said support means adjacent said second cutting members said second piston movable in response to the pressurized fluid; first channel means defined in said support means for coxnunicating fluid through said support means around said first cutting members, said first channel means having an inlet defined in said support means near an end of said first piston and further having an outlet defined in said support means below said first cutting members; and second channel means defined in said support means for communicating fluid through said support means around said second cutting members, said second channel means having an inlet defined in said support means near an end of said second piston and further having an outlet defined in said support means below said second cutting members.

2. A downhole cutting tool as defined in claim 1, wherein: said support means includes a first slot having said first cutting members disposed therein, and a second slot having said second cutting members disposed therein

3. A downhole cutting tool as defined in claim 2, wherein:: said first channel means includes first and second longitudinal passageways extending within said support means between said inlet and outlet of said first channel means outside said first slot so that said first and second longitudinal passageways do not communicate directly with said first slot; said second channel means includes third and fourth longitudinal passageways extending within said support means between said inlet and outlet of said second channel means outside said second slot so that said third and fourth longitudinal passageways do not communicate directly with said second slot.

4 A downhole cutting tool as defined in claim 3, wherein said first and second longitudinal passageways are diametrically Opposite, and wherein said third and fourth longitudinal passageways are diametrically opposite.

5. A downhole cutting tool according to claim 2, 3 or 4, wherein said support means includes a first cylindrical body, wherein said first slot is a first longitudinal slot defined laterally therethrough and further including a first longitudinal cavity defined therein between an end of said first body and said first slot, said first cavity having said first piston disposed therein; wherein said support means further includes a second cylindrical body, where said second slot is a second longitudinal slot defined laterally therethrough and further including a second longitudinal cavity defined therein between an end of said second body and said second slot, said second cavity having said second piston disposed therein, said first and second cylindrical bodies connected together to define the circumferential angular offset between said first and second cutting members.

6. A downhole cutting tool according to any preceding claim, wherein said first and second channel means conduct all the fluid entering said inlets thereof to said outlets thereof.

7. A downhole cutting tool according to any preceding claim, wherein said first and second cutting members have equal diameters in their respective fully extended positions.