US3282358A - Drilling tool - Google Patents

Description

Nov. 1, 1966 w. s. CAROTHERS 3,232,358

DRILLING TOOL Filed April 15, 1964 J36 INVENTOR.

WILLIS S. CAROTHERS his ATTORNEY United States Patent Ofilice 3,282,358 Patented Nov. 1, 1966 Pennsylvania Filed Apr. 13, 1964, Ser. No. 359,291 Claims. (Cl. 175-411) This invention relates to a drilling tool and more particularly to a junk mill for drilling hard formations, metal or other obstructions from a well bore.

Those concerned with the development of oil well tools have long recognized the need for drilling tools of various types for penetrating hard formations or drilling up objects lost or otherwise mispositioned in the bottom of a Well bore such as pieces of drill pipe, casing or tools which cannot be readily removed in any other manner. Most of the milling tools used for this purpose have been combined with a junk basket and the mill has been of the coring variety where only a peripheral portion of the junk has been removed by milling leaving a central or core portion to be removed by the action of the junk basket. Such devices have served the purpose under most circumstances and are still being used with success when circumstances are such as to allow the core portion to be retrieved Without being drilled up. However, under conditions that prevent retrieving the junk in a single piece it is necessary to completely drill up the junk, reducing it to fine particles which can be removed from the hole by circulation of drill mud. Under such circumstances the milling tool of the present invention is very useful since this milling tool comprises a plurality of cutting surfaces disposed at a variety of angles with respect to the axis of the well bore and at least some of which extend more than half way across the face of the mill so that no central or core portion of the junk is left in the bore to be retrieved by a junk basket or like apparatus.

It is therefore an object of this invention to provide a new and improved junk mill.

It is a further object of this invention to provide a new and improved junk mill having a cutting face with a plurality of cutter blades thereon.

It is another object of this invention to provide a new and improved junk mill operable in a well bore and hav ing a cutting face substantially normal to the axis of such well bore with a plurality of cutting surfaces arranged on the cutting face in a particular manner that provides cutting action over the whole area within the well bore.

It is still another object of this invention to provide a new and improved junk mill having a plurality of cutting surfaces of varied length and angular positioning so as to provide efficient cutting and smooth nonchattering operation in drilling metallic objects or hard formations which obstruct the bore of a well being formed in earth strata.

These and other objects and advantages of this invention will be more readily apparent upon consideration of the following description and drawings in which:

FIGURE 1 is an end elevational View of a junk mill constructed according to the principles of this invention with a portion broken away to show construction features;

FIGURE 2 is a sectional view taken substantially on line 22 of FIGURE 1; and

FIGURE 3 is a sectional view taken substantially on line 3-3 of FIGURE 1.

Referring now to the drawings, in FIGURE 2 there is shown a portion of a well bore 6 being formed in earth strata by ordinary drilling methods wherein at least a portion of the bore 6 is lined with a casing 8 of a type well known in the art. Within the casing 8 there I is shown a fragmentary portion of the box end 10 of a drill pipe or tool joint suspended within the casing 8 in the usual manner for axial movement within the casing 8 and powered for rotation about the axis 9 of the casing 8 in a manner well known in the art. The box end 10 is provided with tapered internal threads which mate with and threadedly engage upwardly tapering external threads 12 on an upper portion 11 of a junk mill 15 constructed according to the principles of this invention. The junk mill 15 comprises an axially elongated, hollow, generally cylindrical mill body member 14 having a nearly flat bottom face portion 16 substantially normal to the axis of the casing 8 at the bottom end of the body member 14. Extending radially outward from the body portion 14 is a plurality (shown as 5) of axially elongated guide members 18 extending from a point downwardly adjacent the upper portion 11 to a substantial distance below the face portion 16. The guide members 18 have axially extending arcuate surfaces forming portions of the periphery of a circle having a diameter slightly smaller than the inside diameter of the casing 8 so that the guide members 18 provide for a smooth rotation of the junk mill 15 within the casing 8. The downwardly extended portions of the guide members 18 provide mounting surfaces, hereinafter described, for cutting elements mounted at the bottom end of the junk mill 15.

Extending downwardly within the body portion 14 for approximately half its length is an axial bore 20 which widens into an enlarged axial cavity 22 extending downwardly within the body portion 14 approximately another third of the length of the body portion 14 which cavity 22 communicates with the face portion 16 through a plurality of bores 24 (see FIGURE 1). At its upper end the axial bore 20 communicates with the central bore of the box end 10 which in turn communicates at the upper end of the well with a source of pressurized fluid such as drill mud as is well known in the art. The bore 20, the cavity 22 and the bores 24 together with the spaces between the guide members 18 provide for fluid circulation to remove solid particles formed in the milling operation.

The portion of each guide member 18 which extends downwardly beyond the face portion 16 forms a cutter support 19 having a fiat rearward face 26 parallel to the axis of the casing 8, terminating in an edge 27 sub- :stantially parallel to end surface 16 and an upwardly stepped forward face 28 (see FIGURE 3) forming a series of alternating horizontal and vertical surfaces 29 and 29' respectively. A matrix 30 of material such as brass or other soft metal in which is mixed a quantity of coarse particles 32 of a very hard material such as sintered tungsten carbide or the like is deposited on, and bonded to, the surfaces 29 and 29 forming a cutter element 33 on each cutter support 19. One suitable material for this purpose is Kutrite mill formula which is a registered trademark of the B & W Metals Company, Inc. of Houston, Texas and is supplied in the form of rods or separate sintered particles of various sizes. The embedded particles 32 and the matrix 30 are, of course, not limited to the Kutrite formula but can be any particles, of suitable size and hardness for the conditions to be encountered in the milling operation, embedded in a suitable matrix. The direction of rotation of the junk mill 15 being counterclockwise as viewed in FIG- URE 1 and from right to left as viewed in FIGURE 3 and shown by the arrows 34, the stairstep design of the forward face 28 provides back-up support and reinforcement for the matrix 30 and the particles 32 comprising the cutter elements or blades 33 when the mill 15 is being operated as hereinafter described.

It is to be noted that the rearward faces 26 of the cut ter support elements 19 are not radial to the axis 9 but are portions of planes parallel to the axis 9 at varying distances from the axis 9 so that the orientation of the surfaces 26 is random and provides random spacing between the various cutter elements 33. The rearward faces also vary in chordal length and in axial dimension with the faces of shorter chordal length having greater axial dimensions so that the smallest of the cutter elements 33 becomes the leading element of the series of cutters and the largest cutter is the final element of the series. At least one of the cutter supports 19 extends across the surface 16 beyond the axis 9 to provide full cutting action over the cross sectional area within the casing 8.

The outer surfaces of the cutter support elements 19 and small adjacent portions of the respective guide members 18 are of a reduced diameter to allow for the deposition of a layer 36 of finely divided tungsten carbide or other hard particles on the outside of the cutter support elements 19 and the lower portion of the guide members 18 to assure that the mill 15 will provide clearance for the remaining portions of the guide members 18 as it progresses downwardly in the cutting operation.

In operating the junk mill 15 of this invention the mill 15 is threadedly secured on the lower end of a drill string and lowered into a well casing in the usual manner. The guide members 18 being of a size to slide readily through the casing 8 until an obstruction in bore 6 is reached.

When the cutting surfaces approach the obstruction, rotation is applied to the drill string and mill 15 in the usual manner while the mill is still above the obstruction in the well bore 6. As the mill continues downward the particles 32 begin to contact the obstructing material as for instance metal objects with the smallest of the blades or cutter elements 33 making the first contact. The small blade removes a portion of the material and is followed by larger and larger blades contacting the obstructing material as the mill 15 progresses downwardly. The non-radial orientation of the blades in addition to the variations in axial dimension and chordal length provide a very good cutting action with superior penetration and smoother cutting than is obtainable by known cutters of the prior art wherein the blades are radial and of equal chordal length and axial dimension.

Other advantages of the present invention reside in the provision of the massive cutting elements 33 containing the relatively small sharp edged particles 32 of extremely hard material with the cutting elements 33 sup-ported and reinforced by the backup stair step design of the cutter support elements 19 as well as by the massive one-piece design of the body member 14 and the guide members 18 with no separate pieces susceptible of being loosened or damaged by vibration inherent in the cutting action, such vibration being especially troublesome when odd shaped pieces of junk are being encountered. With such design heavy feed pressure can be used resulting in rapid cutting with a concomitant saving in job time.

A further advantageous feature of this design is that the elongated, radially extended guide members 18 can be machined to fit a variety of casing sizes without Change in the body member 14 and without losing the advantage of random positioning and non-radial orientation described above. Such machining can include the complete removal of the guide members 18 leaving the cutter support elements 19 extending only from the end surface 16 without departing from the principles of this invention.

It is to be realized that a preferred embodiment of the present invention has been described and illustrated herein. However, other forms of this invention are possible and envisioned for the future. It is therefore respectfully requested that this invention be interpreted as broadly as possible and be limited only by the prior art.

In practice the bottom face portion 16 has been made as a frusto-conical, concave surface and can be convex to flat to suit particular situations.

I claim:

1. A milling tool for rotation within a well bore comprising: an elongated body member having an end surface substantially normal to the axis of rotation of said body member; said body member having a plurality of cutter support members extending axially at least in part from said end surface, said cutter support members having rear surfaces with respect to a direction in which said body member is rotated, said rear surfaces extending from said end surfaces and terminating in outer edges substantially parallel to said end surface, said cutter support members extending chordally across respective portions of said end surface, at least some of said edges being of nonradial orientation with respect to said axis, said cutter support members having forward areas with respect to said direction of rotation extending generally inwardly from said outer edges and forwardly to said end surface; and cutter means formed upon and bonded to each of said forward areas.

2. A milling tool as specified in claim 1 wherein said cutter means comprises a relatively soft matrix having relatively hard particles embedded therein.

3. A milling tool as specified in claim 1 wherein said cutter support members differ in chordal length.

4. A milling tool as specified in claim 3 wherein those of said cutter support members having greater chordal lengths have lesser axial dimensions.

5. A milling tool for rotation within a well bore comprising: an elongated body member having an end surface substantially normal to the axis of rotation of said body member; said body member having a plurality of cutter support members extending axially at least in part from said end surface, said cutter support members having rear surfaces with respect to a direction in which said body member is rotated, said rear surfaces extending from said end surface and terminating in outer edges substantially parallel to said end surface, said cutter support members extending chordally across respective portions of said end surface, at least one of said cutter support members extending more than half way across said end surface, and at least some of said edges being of nonradial orientation with respect to said axis, said cutter support members having forward areas with respect to said direction of rotation extending generally inwardly from said outer edges and forwardly to said end surface; and cutter means formed upon and bonded to each of said forward areas.

6. A milling tool for rotation within a well bore comprising: an elongated body member having an end surface substantially normal to the axis of rotation of said body member; said body member having a plurality of cutter support members extending axially at least in part from said end surface, said cutter support members having rear surfaces with respect to a direction in which said body member is rotated, said rear surfaces extending from said end surface and terminating in outer edges substantially parallel to said end surface, said cutter support members having different axial lengths and extending chordally across respective portions of said end surface, at least some of said edges being of non-radial orientation with respect to said axis, said cutter support members having forward areas with respect to said direction of rotation extending generally inwardly from said outer edges and forwardly to said end surface, and cutter means formed upon and bonded to each of said forward areas.

7. A milling tool as specified in claim 6 wherein at least one of said cutter support members extends more than halfway across said end surface.

8. A milling tool for rotation within a well bore comprising; an elongated body member having an end surface substantially normal to the axis of rotation of said body member. elongated guide members extending radially out wa-rdly from said body member, each said guide member extending axially along said body member from an intermediate portion of said body member to a line substantially beyond said end surface and substantially parallel to said end surface to form a cutter support member, said cutter support members having planar rear surfaces with respect to the direction of such rotation said rear surfaces extending from said line to said end surface and being portions of planes parallel to said axis, said cutter support members extending across respective portions of said end surface and at least some of said rear surf-aces being of non-radial orientation with respect to said axis, said cutter support members having stepped front surfaces extending forwardly in steps from said line to said end surface, and cutter means formed upon and bonded to each of said cutter support members.

9. A milling tool for rotation within a well bore comprising: an elongated generally cylindrical body member having an end surface substantially normal to the axis of rotation of said body member; a plurality of circumferentially spaced, elongated guide members extending radially outward from said body member; each said guide member extending axially along said body member from an intermediate portion of said body member to a line substantially beyond said end surface and substantially parallel to said end surface to form a cutter support member, said cutter support members having planar rear surfaces with respect to the direction of such rotation, said rear surfaces extending from said line to said end surface and being portions of planes parallel to said axis, said cutter support members extending across respective portions of said end surface, at least some of said rear surfaces being of non-radial orientation with respect to said axis, said cutter support members having stepped front surfaces extending forwardly in steps from said line to said end surface; a cutter element formed upon and bonded to each of said cutter support members, each said cutter element comprising a relatively soft matrix having relatively hard particles embedded therein.

10. A milling tool for rotation Within a well bore comprising: an elongated generally cylindrical body member having an end surf-ace substantially normal to the axis of rotation of said body member; a plurality of circumferentially spaced, elongated guide members extending radially outward from said body member; each said guide member extending axially along said body member from an intermediate portion of said body member to a line substan tially beyond said end surface and substantially parallel to said end surface to form a cutter support member, said cutter support members having planar rear surfaces with respect to the direction of such rotation, said rear surfaces extending from said line to said end surface and being portions of planes parallel to said axis, said cutter support members extending across respective portions of said end surface, and having random chordal lengths and axial dimensions wherein the support members of shorter chordal length have greater axial dimensions than the support members of greater chordal lengths, at least some of said rear surfaces being of non-radial orientation with respect to said axis, said cutter support members having stepped front surfaces extending forwardly in steps from said line to said end surface; a cutter element formed upon and bonded to each of said cutter support members, each said cutter element comprising a relatively soft matrix having relatively hard particles embedded therein.

References Cited by the Examiner UNITED STATES PATENTS 2,507,222 5/1950 Phipps 4l8 X 2,855,994 10/1958 Kammerer 175411 X 3,127,945 4/1964 Bridwell 175-329 3,163,244 12/1964 Zimmerman 175398 CHARLES E. OCONNELL, Primary Examiner.

N. C. BYERS, Assistant Examiner.

Claims (1)

1. A MILLING TOOL FOR ROTATION WITHIN A WELL BORE COMPRISING; AN ELONGATED BODY MEMBER HAVING AN END SURFACE SUBSTANTIALLY NORMAL TO THE AXIS OF ROTATION OF SAID BODY MEMBER; SAID BODY MEMBER HAVING A PLURALITY OF CUTTER SUPPORT MEMBERS EXTENDING AXIALLY AT LEAST IN PART FORM SAID END SURFACE, SAID CUTTER SUPPORT MEMBERS HAVING REAR SURFACES WITH RESPECT TO A DIRECTION IN WHICH SAID BODY MEMBER IS ROTATED, SAID REAR SURFACES EXTENDING FROM SAID END SURFACES AND TERMINATING IN OUTER EDGES SUBSTANTIALLY PARALLEL TO SAID END SURFACE, SAID CUTTER SUPPORT MEMBERS EXTENDING CHORDALLY ACROSS RESPECTIVE PORTIONS OF SAID END SURFACE, AT LEAST SOME OF SAID EDGES BEING OF NONRADIAL ORIENTATION WITH RESPECT TO SAID AXIS, SAID CUTTER SUPPORT MEMBERS HAVING FORWARD AREAS WITH RESPECT TO SAID DIRECTION OF ROTATION EXTENDING GENERALLY INWARDLY FORM SAID OUTER EDGES AND FORWARDLY TO SAID END SURFACE; AND CUTTER MEANS FORMED UPON AND BONDED TO EACH OF SAID FORWARD AREAS.

Images