MILLS FOR WELLBORE OPERATIONS

Abstract: A wellbore mill (10) has been invented that, in certain aspects, has a body (12) having a top and a bottom and, optionally, a fluid flow channel (20) extending therethrough from top to bottom with, optionally, one or more fluid jetting ports (22) in fluid communication with the fluid flow channel, milling apparatus (21, 23, 26) on the body including a plurality of milling inserts (26, 28), each insert mechanically secured in a corresponding recess (25) in the body, said mechanical securement sufficient for effective milling in a wellbore. A wellbore milling method for milling an opening in a selected tubular of a tubular string in a wellbore has been invented that includes installing and using such a mill.

Description: MILLS FOR WELLBORE OPERATIONS This invention is related to wellbore mills, wellbore milling processes, milling tools and whipstocks; and in one aspect to milling processes which employ a diverter or a whipstock. Various milling methods and systems are disclosed. In wellbore operations, milling tools are used to cut out windows or pockets from a tubular, e.g. for directional drilling and sidetracking; and to remove materials downhole in a well bore, such as pipe, casing, casing liners, tubing, or jammed tools. Many wellbore milling tools have a plurality of cutting elements or "inserts" secured to milling blades and/or milling surfaces. Typically these inserts are fixed on the blades by brazing or welding. In certain prior art mills, holes are provided into which part of the insert is inserted and by which the insert is held in place prior to brazing or welding. A variety of problems are associated with efforts to braze or weld inserts onto milling tools. Many types of welding require specific material pretreatments and specific heat treatments before, during, and after welding. When welding methods are used undesirable temperature- induced changes to a base metal or to an insert may result. These changes can be irreversible. Also with such methods inserts may be secured inconsistently, i.e. adhesion may differ from insert to insert. Variations in thermal coefficients of expansion between materials e.g. between carbides and bonding materials, can result in undesirable cracks during cooling. Verification of adhesion quality is difficult. If brazing is employed, carbide selection may be limited, e.g. possibly coated carbides may not be usable. With certain welding methods inserts are not precisely located and are placed inconsistently. The prior art discloses various types of milling or cutting tools provided for cutting or milling existing pipe or casing previously installed in a well. These tools have cutting blades or surfaces and are lowered into the well or casing and then rotated in a cutting operation. With certain tools, a suitable drilling fluid is pumped down a central bore of a tool for discharge beneath the cutting blades and an upward flow of the discharged fluid in the annulus outside the tool removes from the well cuttings or chips resulting from the cutting operation. A section of existing casing can be removed from a well bore with a milling tool, e.g. to permit a sidetracking operation in directional drilling, or to provide a perforated production zone at a desired level. Also, milling tools are used for milling or reaming collapsed casing, for removing burrs or other imperfections from windows in the casing system, for placing whipstocks in directional drilling, or for aiding in correcting dented or mashed-in areas of casing or the like. Certain prior art sidetracking methods use cutting tools of the type having cutting blades and use a deflector such as a whipstock to cause the tool to be moved laterally while it is being moved downwardly in the well during rotation of the tool to cut an elongated opening pocket, or window in the well casing . Various prior art well sidetracking operations employ a whipstock and a variety of different milling tools used in a certain sequence. This sequence of operation requires a plurality of "trips" into the wellbore. For example, in certain multi-trip operations, a packer is set in a wellbore at a desired location. This packer acts as an anchor against which tools above it may be urged to activate different tool functions. The packer typically has a key or other orientation indicating member. The packer's orientation is checked by running a tool such as a gyroscope indicator into the wellbore. A whipstock-mill combination tool is then run into the wellbore by first properly orienting a stinger at the bottom of the tool with respect to a concave face of the tool's whipstock. Splined connections between a stinger and the tool body facilitate correct stinger orientation. A starting mill is secured at the top of the whipstock, e.g. with a setting stud and nut. The tool is then lowered into the wellbore so that the packer engages the stinger and the tool is oriented. Slips extend from the stinger and engage the side of the wellbore to prevent movement of the. tool in the wellbore. Moving the tool then shears the setting stud, freeing the starting mill from the tool. Rotation of the string with the starting mill rotates the mill. The starting mill has a tapered portion which is slowly lowered to contact a pilot lug on the concave face of the whipstock. This forces the starting mill into the casing to mill off the pilot lug and cut an initial window in the casing. The starting mill is then removed from the wellbore. A window mill, e.g. on a flexible joint of drill pipe, is lowered into the wellbore and rotated to mill down from the initial window formed by the starting mill. Typically then a window mill with a watermelon mill mills all the way down the concave face of the whipstock forming a desired cut-out window in the casing. This may take multiple trips. Then, the used window mill is removed and a new window mill and string mill and a watermelon mill are run into the wellbore with a drill collar (for rigidity) on top of the watermelon mill to lengthen and straighten out the window and smooth out the window-casing- open-hole transition area. The tool is then removed from the wellbore. There has long been a need for an efficient and effective milling method which is not dependent on an insert brazing or welding method. There has long been a need for wellbore milling with an optimum density of cutting inserts. These has long been a need, recognized by the present inventors, for a mill with inserts installed without brazing or welding. There has long been a need for such a mill with precisely placed inserts. There has long been a need for such a mill that is effective in milling relatively hard material that is difficult to machine, e.g. but not limited to, high chrome casing. According to a first aspect, the present invention provides a wellbore mill comprising a body having a top and a bottom, milling apparatus on the body,- the milling apparatus comprising a plurality of milling inserts, each insert secured mechanically in a corresponding recess in the body, said mechanical securement sufficient for effective milling of an opening through a tubular in a wellbore . Further features of preferred embodiments are set out in claims 2 to 24. According to a second aspect, the present invention provides a mill body for a wellbore mill, the mill body comprising a body member, at least one opening in the body member for holding a milling insert, and energy dissipating structure in the at least one opening for dissipating energy imposed on an insert in the at least one recess. Further features of preferred embodiments are set out in claims 26 to 32. According to a third aspect, the present invention provides a milling insert for use with a wellbore mill, the wellbore mill having a mill body with an opening for receiving the milling insert, the milling insert comprising an insert body, and at least one energy dissipating member on the insert body. Further features of preferred embodiments are set out in claims 34 to 35. According to a fourth aspect, the present invention provides a wellbore milling method for milling an opening in a selected tubular member of a tubular string in a wellbore, the method comprising installing a mill on a working string into the wellbore at a selected desired point for milling an opening in the selected tubular member, the mill comprising a body having a top and a bottom, milling apparatus on the body, and the milling apparatus comprising a plurality of milling inserts, each insert mechanically secured in a corresponding recess in the body, said mechanical securement sufficient for effective milling in a wellbore, and rotating the mill to mill an opening in the selected tubular member. Further features of preferred embodiments are set out in claims 37 to 40. The present invention, in at least certain embodiments, discloses a wellbore mill having a mill body and a plurality of cutting elements or milling inserts mechanically secured in corresponding holes or recesses in the mill body. Such a mill may be any known wellbore mill, including, but not limited to, window mills, starting mills, watermelon mills, pilot mills, section mills, and junk mills. In certain aspects, the inserts are all substantially the same and protrude substantially the same distance out from the mill body. In other aspects, any or all of these parameters differ for different inserts of the plurality of inserts: diameter, length, shape, specific insert material, and depth of securement in the mill body. For example, and not by way of limitation, inserts shapes, viewed e.g. from above, may be circular, elliptical, square, triangular, trepezoidal, rectangular, pentagonal, hexagonal, etc. It is within the scope of this invention to employ any known cutting or milling insert. One particular type of insert useful with mills according to the present invention is a curved top insert used in bits from Mike Henson Bits of San Angelo, Texas which has been used with prior art drill bits and with mills in a wellbore for milling out an item, e.g. a fish, within the wellbore; but not with prior art mills for milling through a tubular lining or casing in a wellbore. In certain of these prior art bits and prior art mills, a portion of a rounded top of the insert lies below the bit's or mill's outer surface. In certain embodiments of mills according to the present invention, inserts are mechanically installed in corresponding holes in the mill body, e.g. by press fit, friction fit, force fit, nitrogen, heat shrink fit, and/or with an appropriate adhesive, e.g. but not limited to epoxy. In addition to, or instead of, a press fit etc., other mechanical securement may be employed according to the present invention to hold a cutting insert in place, e.g. but not limited to, threaded mating with a hole in a mill body, a set screw that projects into an insert, and/or a threaded tightening wedge insert holder. In certain particular embodiments of the present invention, in addition to the mechanical non-weld securement of any cutting elements and inserts disclosed herein, brazing or welding may also be used. In one aspect brazing or welding may be used at a mill -surface/insert-exterior interface. Inserts installed on a mill body as described above may continue to mill (or may resume milling) following breaking off of a portion of the insert. Broken-off inserts in prior art mills may continue to cut, but will do so less effectively than certain of the inserts installed according to the present invention. In one embodiment, a mill according to the present invention is releasably secured to a diverter or a whipstock with or without an anchor, anchor packer, packer, or other anchoring mechanism for a milling operation, particularly for a "single trip" operation. Some preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Fig. 1A is a perspective view of a wellbore milling apparatus ; Fig. IB is a perspective view of a mill of the milling apparatus of Fig. 1A; Fig. 1C is an end view of the mill of Fig. IB; Fig. ID is a side view of the mill of Fig. IB; Figs. IE - 1G are side cross-section views of the mill of Fig. IB; Fig. 1H is a side cross-sectional view of an insert of the mill of Fig. 1A; Fig. II is a side view of a mill; Fig. 1J is a side cross-section view of a mill; Fig. IK, IL and IM are side cross-section views of an insert in a recess in a body of a mill; Figs. 2A and 2B show schematically insert arrays for a mi11 ; Fig. 3A is a side view of a mill; Fig. 3B is an end view of the mill of Fig. 3A; Fig. 3C is a cross-sectional view along line 3C-3C of Fig. 3D; Fig. 3D is an end view of the mill of Fig. 3C; Fig. 4 is a perspective view of a wellbore milling system,- Fig. 5A is a perspective view of a watermelon mill; Fig. 5B is an end view, Fig. 5C a side view, and Fig, 5D a side cross-section view of the mill of Fig. 5A; Fig. 6A is a side cross-section view of a mill Fig. 6B is a side cross-section view of a mill. Fig. 7A is a side view of a mill; Fig. 7B is a partial side view of the mill of Fig. 7A; Fig. 7C is a side view along line 7C-7C of Fig. 7D; Fig. 7D is a cross-section view along line 7D-7D of Fig. 7A; Figs. 7E - 7H are cross-section views at the corresponding points indicated m Fig. 7D; Fig. 8 is a side view partially m cross-section of a milling system; Fig. 9 is a side view in cross-section of a mill; Fig. 10 is a mid cross-section view of a mill; Fig. 11A is perspective view and Fig. 11B is a side view of a mill; Fig. 12A is a side view of a milling system; Fig. 12B presents an enlargement of a portion of the milling system of Fig. 12A. Fig. 13 is a side cross-section view of a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body; Fig. 14 is a side cross-section view of a mill body (or mill blade or structure) , shown partially, and an insert m a recess of the body; Fig. 15 is a side cross-section view of an insert m a hole n a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body; Fig. 16 is a side cross-section view of an insert m a hole m a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body; Fig. 17 is a side cross-section view of an insert in a hole in a mill body (or mill blade or structure) , shown partially, and an insert m a recess of the body; Fig. 18A is a top view of an insert; Fig. 18B is a side cross-section view of the insert of Fig 18A m a recess m a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body; Fig. 19 is a side cross-section view of an insert; Fig. 20A is a top view of an insert; Fig. 20B is a top view of the insert of Fig. 20A; Fig. 21A is a top view of an insert according to the present invention; Fig. 21B is a top view of the insert of Fig. 21A; Fig. 22 is a side cross-section view of an insert in a hole in a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body; Fig. 23A is a side cross-section view of a recess for an insert in a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body; Fig. 23B is a top view of the recess of Fig. 23A; and Fig. 24 is a side cross-section view of a recess for an insert in a mill body (or mill blade or structure) , shown partially, and an insert in a recess of the body. Figs 1A - 1G show a mill 10 with a mill body 12 having a lower enlarged bulb 14 and an upper threaded connector 16 for threadedly connecting the mill 10 to a correspondingly threaded tubular 8 which may in turn be connceted to a tubular string (not shown) run down into an earth wellbore. The tubular 8 and the tubular string have fluid flow bores for directing fluid pumped from the earth surface under pressure to a fluid flow bore 20 of the mill 10. A plurality of side ports 22 and a central port 24 are in fluid communication with the flow bore 20 so that fluid may be jetted therefrom to facilitate milling, cooling, and the movement of milled cuttings and debris away from the mill 10. The bulb 14 of the mill 10 has a plurality of side recesses 25 into which are press fit a plurality of corresponding side inserts 26. The lower end of the bulb 14 has a slightly indented central portion 27 and a plurality of end inserts 28 press fit in corresponding recesses 20. Optionally the mill body may be heated and the inserts installed therein prior to cooling and shrinking for a heat-shrink fit, or any other mechanical securement described herein may be used. As shown the inserts 26 and 28 have a generally cylindrical lower body 23 and a rounded top 21. In one preferred embodiment the lower portions of the rounded top 21 are configured, disposed, and sized so that the edge portions thereof meet the mill body at its surface, while in another embodiment these edge portions are slightly below an outer surface 13 of the mill body 12 (see Fig. 1H) to enhance durability and longevity, although some initial milling performance may be sacrificed. In one aspect the central port 24 is slightly off-center to minimize the size of a milled core produced by milling. Optionally, as with a mill 10a similar to the mill 10 of Fig. 1A, the lower end of a bulb 14a may be convex or as shown in Fig. 1J, stepped with steps 7 with jet ports 6 and with a stub nose 5. The ports 6 are in fluid communication with a flow bore 20a. In certain preferred aspects the central port 24 of the mill 10 is ringed by inserts (e.g. three, four, five or more) as shown, e.g. in Fig. 1C. Thus an insert will "track" behind the port 24 to inhibit coring of the mill. Such a port and such "tracking" inserts may be used with any mill disclosed herein. One or more steps as the steps 7 and/or a stub nose as the stub nose 5 may be used with any mill disclosed herein. Fig. II shows a mill 130 with a body 131 having a top threaded end 132 and a lower bulb end 133. Optionally a fluid flow bore extends through the body 131 and one or more jet ports at the lower bulb end 133 are in fluid communication with the fluid flow bore. A plurality of milling inserts 134 (like any milling insert disclosed herein) are mechanically secured in recesses 135 without welding or brazing. A plurality of conventional prior art milling inserts 136 (of any type) are secured to the body 131 by conventional known prior art welding and/or brazing methods. This illustrates any conventional known prior art inserts may be applied by known welding and/or brazing techniques to any mill disclosed herein in addition to the inserts applied with mechanical securement alone. It is also possible to place the prior art welded and/or brazed inserts below (as viewed, e.g. in Fig. II) the inserts secured mechanically according to the present invention. Fig. IK shows an insert 101 in a recess 203 in a body 103 of a mill (not shown in it entirety; like any mill disclosed herein) . An adjustable and removable set screw 104 partially projects from a hole 105 to releasably secure the insert 101 in the recess 102. Such a mechanical securement may be used with any insert disclosed herein. Fig. IL shows a mill 125 (partially) with a generally cylindrical body 123 having a fluid flow bore 127 therethrough from one end to the other. Each of a plurality of milling inserts 120 (three shown) spaced-apart -around the entire circumference of the body 123 are secured in a corresponding recess 122. Each recess 122 is lined with energy dissipating material 124. As a particular insert 120 impacts a tubular to be milled, e.g. casing 128, it is subjected to a high and relatively quick impact force. The energy dissipating material (e.g. but not limited to plastic, fiberglass, relatively soft metal, and/or elastomeric material) damps the impact force on the inserts thus reducing insert wear and damage. Fig. IM shows a milling insert 110 with threads 111 threadedly secured in a recess 112 of a body 113 of a mill. The recess 112 has threads 114 corresponding to the threads 111. By unscrewing the insert 110 it is removable from the recess 112 and can be replaced with another insert. Any of the inserts of Figs. IK - IM may be used with any mill disclosed herein. Figs. 2A and 2B provide schematic representations of two possible insert layouts and arrays for the mill 10. An overlap of two of the circles in either Fig. 2A or 2B indicates an overlap or "full coverage" cutting capability for enhanced milling effectiveness. Such "full" or "double" coverage optimizes insert cutting life and may allow a mill to continue to mill if an insert fails or wears away. The various numerical values shown for the distance between two lines indicate a distance of an insert in inches from a central axis of the mill along the outside surface of the mill. One circle, e.g. in the first column to the left in Fig. 2A, represents a first ring around the mill which, in this case, includes one insert and twelve circles in the farthest right column indicate twelve inserts in that particular ring around the mill. Figs. 3A - 3D illustrate a mill 30 according to the present invention with a . mill body 32 having a lower bulb 34 and an upper threaded connector 36 for threadedly connecting the mill 30 to a correspondingly-threaded tubular (not shown) which may in turn be connected to a tubular string (not shown) run down into an -earth wellbore. The tubular and the tubular string have fluid flow bores for directing fluid pumped from the earth surface under pressure to a fluid flow bore 40 of the mill 30. Side ports 33 and a central port 35 (like the ports 22, 24 respectively, of the mill of Fig. 1A) are employed. The mill 30 has a gauge ring 31 formed integrally of or secured to the bulb 34 which inhibits excessive wear on the outer diameter of the mill 30 and assists in directing the mill 30 along a desired trajectory within a tubular during the milling process. As shown in Figs. 3B and 3D, the gauge ring may be comprised of projections 31a with spaces therebetween to enhance fluid flow. Optionally, the gauge ring may be a solid integral piece (as viewed in Fig. 3D, e.g.) with or without flow holes therethrough. Figs. 3A - 3D show recesses 39 for inserts. Inserts as in Fig. 1A may be used in each recess. Any insert disclosed herein may be used with the mill 30 (and with any mill disclosed herein) , installed, and secured by any method disclosed herein. Fig. 4 shows a mill apparatus 42 with a tubular member 43 having a watermelon mill 44 according to the present invention and a mill 10 as described above. In one aspect the watermelon mill 44 is sized, configured and located so that it will ream a hole made by the mill 10. In one aspect such a watermelon mill 44 reams such a hole to gauge. In one aspect such a watermelon mill 44 may also lengthen a window made by the mill 10. Figs. 5A - 5D show a watermelon mill 50 (like the watermelon mill 44) with a tubular body 51 having a fluid flow bore 52 running therethrough from top to bottom. A plurality of milling inserts 53 are secured to corresponding recesses 54. Any insert disclosed herein may be used, installed and secured by any method disclosed herein in the mill 50 " . In one aspect, the inserts 53 are secured in place mechanically, e.g. with a press fit only, without welding or brazing (as may be the inserts in the mills of Figs. 1A, 3A, 4, 6A, 7A, 8, 9, 10, 11A and 12) . The inserts 53 may be (as may the._ inserts of other mills disclosed herein) any known suitable insert, including, but not limited to, inserts as shown in Figs. 1A, IE and 1H - IM, installed and secured by any method described herein) . Fig. 6A shows a mill 60 which is similar to the mill 10 in all respects; except a variety of different inserts are used. This illustrates that in any mill disclosed herein, different inserts may be used on one mill, including, but not limited to one or more inserts differing in: length; shape; amount of projection beyond a mill surface; and/or diameter. For example, the insert 61 is wider in diameter than an insert 26 (Fig. IE); an insert 62 is smaller in diameter than inserts 26 and 61; an insert 63 is longer than an insert 26 and 61; the insert 63 projects further into a mill body 64 than does an insert 26 shown in Fig. IE; and inserts 62 and 65 project further out from the mill body 64 than do inserts 26 and 28 from their respective mill body. Of course, corresponding recesses in the mill body are provided for each insert. The inserts may be any as described herein and installed and secured by any method described herein. Fig. 6B shows a mill 70, like the mill 30 of Fig. 3A, but with a variety of insert recesses that includes recesses 71 for inserts smaller than inserts for the recesses 72 (which correspond to the recesses 39, Fig. 3A) . The mill 70 has an optional gauge ring 73 like the ring 31, Fig. 3A. Any mill disclosed herein may use recesses of different sizes for corresponding inserts of different sizes. In one aspect, with inserts with a generally cylindrical body, the recesses have a generally circular shape to correspond to the shape of the insert body. It is within the scope of this invention to use any suitable known insert of any known shape (and correspondingly shaped recess) , including, but not limited to square, rectangular, triangular, parallelogram, elliptical, oval and trapezoidal . Fig. 7A shows a starting mill 70. The mill 70 has a tubular body 72 with a fluid flow bore 71 therethrough extending down from a threaded top end 73. A mill body 75 has a plurality of milling inserts (not shown) in a corresponding plurality of recesses 76. The body 72 has a typical bottom end 74 with a hole 74a for a shear stud. Figs. 7B - 7H illustrate one possible pattern for the recesses 76 and the corresponding inserts. There are six side rows of inserts - labelled W, V, U, T, S, R - 60 apart. (Three, four, five, seven or any desired number of rows may be used.) End or bottom inserts are in recesses or holes A, B, C, and D. Recesses or "holes" "D" are 60 from a mill axis as shown in Fig. 7C. Recesses or "holes" "A," "B, " and "C" are 30 from this axis (see Figs. 7F - 7H) . Each set or pattern of "holes" A, B, C and D are offset 15 from each other. Blackened semi-circles in Fig. 7D indicate fluid flow holes 77 in fluid communication with a flow bore 78. "Hole A to be inline with port" means that the Hole A is lined up with a fluid flow hole. For clarity, some holes are not shown in Figs. 7E - 7H. Fig. 8 shows a mill apparatus 80 with a mill 81 having inserts 82 and 82a like any inserts disclosed above. A shear pin 83 releasably holds a mill pilot end 84 to an upper member 85 of a whipstock 86. Optionally an orienting apparatus 87 (shown schematically) is connected to the whipstock 86 for properly positioning the whipstock in a wellbore. Also optionally, an anchor apparatus 88 is connected to the whipstock (and/or to the orienting apparatus 87) for selectively anchoring the apparatus 80 in a wellbore or in a tubular in a wellbore. Optionally, the whipstock, orienting apparatus, and anchoring apparatus may be "through-tubing" devices for use in wellbore through-tubing operations. Also, the apparatus 80 may be used in a "single trip" window milling operations (as may any mill disclosed herein appropriately releasably secured to a whipstock etc. ) . Fig. 9 shows a mill 90 with a mill body 92 having a top threaded end 91. A lower end 93 has a concave recess 94 with an array of inserts 95. The shape of the recess 94 allows the mill to hold milled material, e.g. but not limited to cuttings from a window milling operation or from milling a tubular T, and to retain what is milled material. This mill may be used, e.g., for milling over or through a tubular in a wellbore. The recess 94 may be any concave, recessed, inverted or conical shape. Fig. 10 discloses a shape for a mill body 96 with a wavy or scalloped outer surface 97 which may be used to enhance mechanical support of inserts on the projecting body portions and to enhance fluid flow in the valleys therebetween for any mill disclosed herein. In one aspect inserts 98 (as any disclosed herein) are located in the projecting body portions as shown in Fig. 10. Optionally inserts as inserts 98a may be used in any or all of the valleys. Optionally inserts in the valleys or on the projections may be deleted. An optional flow bore 99 extends through the body 96 to optional flow ports 99a. Any suitable inserts and corresponding recesses (as described herein) may be used. Such a scalloped surface may be used for any mill body disclosed herein. Figs. 11A - 11B shows a mill 100 with a tubular body 102 having a flow bore 104 therethrough. A gauge ring 103 (with spaced apart projections or helical blades) is secured to or formed of the body 102. An array of milling inserts 104, as any inserts disclosed herein are secured in corresponding recesses on the body 102 (and/or on blades of the ring 103) using any securement method described herein. A tapered end 106 of the projections or blades of the gauge ring 103 facilitates mill movement through tight spots in a string. A tapered end may be provided on either end of the mill body to enhance mill movement either going into or coming out of a wellbore. Spaces 107 between ring parts facilitate fluid flow. Figs. 12A and 12B show a mill 110 with inserts 112 secured in corresponding recesses 114 on a mill body 116 which is connected to a tubular string 118 (shown partially) . A shear pin 130 releasably holds the mill 110 to a whipstock 132. Optionally, an anchor device 134 (shown schematically) is connected to the whipstock 132 (any suitable known anchor apparatus) . In a typical single-trip operation with such a mill 110 with an anchor 134, the mill is tripped into a wellbore; the whipstock is properly oriented with (optional) orienting apparatus 136 (shown schematically connected to the anchor or, optionally, to the whipstock) and the anchor is set; the pin 130 is sheared, freeing the mill; and milling commences by rotating the string 118 from the surface or downhole with a downhole motor (as may be done with any mill disclosed herein) . Such a system may be a "thru-tubing" system (with a thru-tubing anchor device) and/or a "milling/drilling" system and any system disclosed herein may have such thru-tubing and/or milling- drilling devices and apparatuses . With respect to any insert described herein, the mechanical securement of the insert in a corresponding recess or hole greatly facilitates replacement of a worn or broken insert since in cases in which there is no brazing or welding, no weld material or braze material needs to be dealt with. In certain cases according to this invention in which some weld or braze material is used it is significantly less than the amount of weld or braze material used in prior art devices and insert removal and replacement is much easier. Fig. 13 shows an insert 140 in a recess 141 in a mill body (blade, structure, and/or bulb, etc.) 142. The insert 140 is generally cylindrical and tapers from a top wider portion to a lower narrower portion, as does the recess 141 that corresponds in shape to the tapered shape of the insert 140. Any mechanical securement disclosed herein may be used to secure the insert 140 in the recess 141. In other aspects, such securement is used with known welding or brazing techniques. Any insert disclosed herein may be provided with such a taper. Fig. 14 shows an insert 145 in a hole 146 in a mill member 147 (body, blade, structure and/or bulb, etc.). The insert 145 tapers from a narrower portion at the top (as viewed in Fig. 14) to a wider portion at the bottom (as viewed in Fig. 14) . Any mechanical securement disclosed herein may be used to secure the insert 145 in the recess 146. In other aspects, such securement is used with known welding or brazing techniques. Any insert disclosed herein may be provided with such a taper. Fig. 15 shows an insert 148 like the insert 145 in the member 147, but the insert is like the inserts 26 and has two edge portions disposed below (as viewed in Fig. 17) an upper surface of the member 147. Fig. 16 shows an insert 150 in a recess 151 in a mill member 152. A washer or plug 153 enhances securement of the insert 150 in the recess 151. The insert 150 and/or plug 153 may be threaded to threadedly mate with corresponding threads on the interior of the recess 151. Additionally or alternatively, any other mechanical securement disclosed herein may be used. In other aspects welding or brazing is also employed to secure the insert 150 and/or plug 153 in place. Fig. 17 shows an insert 155, like the insert 150, in a recess 156 in the member 152; but (as with the insert/securement shown in Fig. 15) the insert 155 has two edges disposed beneath (as viewed in Fig. 17) a top surface of the member 152. The inserts shown in Figs. 13-24 may have any shape and/or configuration (e.g. square, triangular, etc. as viewed from above) disclosed herein. Fig. 18A shows an insert 160 which has a generally cylindrical tapered body 161 with a projecting tab 162. This tab 12 may be used for proper positioning and alignment of an insert in a recess 163 in a mill member 164, as shown in Fig. 18B. Any insert disclosed herein may have one or more such tabs. Any mechanical securement disclosed herein may be used with the insert 160. In one particular aspect the tab 162 is made of energy dissipating material Fig. 19 shows an insert 165 according to the present invention with a generally cylindrical tapered body 166 and with an energy dissipating member 167 secured thereto or formed thereof. The member 167 is made of energy dissipating material. Figs. 20A and 20B show an insert 170 with a generally cylindrical body 171 and an energy dissipating member 172 secured thereto or formed thereof. The member 172 is made of energy dissipating material. Any insert disclosed herein may have one or more members 172 spaced therearound. In one aspect the entire circumference or periphery of an insert is encompassed by a member 172. Figs. 21A and 21B show an insert 175 whose side surface or surfaces and whose bottom surface is encapsulated in an energy dissipating member 176 made of energy dissipating material secured to or formed of the insert 175. Any insert disclosed herein may be so encapsulated. Such encapsulation (and any energy dissipating structure or member disclosed herein) may be a desired thickness for achieving desired energy dissipation while also achieving desired mechanical securement in a hole or recess. Fig. 22 shows an insert 180 according to the present invention like the insert of Fig. 17, in a recess 181 in a mill member 182 held in place by a plug 183. An energy dissipating member 184 is emplaced between the plug 183 and the bottom end of the insert 180. All three or any of the pieces 180, 1813, 184 may be threaded to threadedly mate with threads in the interior of the recess 181. Such a member 184 may be used with any insert disclosed herein. Figs. 23A and 23B show a recess 185 according to the present invention in a mill member 186. A plurality of energy dissipating members 187 are spaced-apart around the recess 185. The members 187 are made of energy dissipating material secured to or formed of the recess's interior. Any recess disclosed herein may be provided with one or more of the members 187.

Claims: CLAIMS : 1. A wellbore mill comprising a body having a top and a bottom, milling apparatus on the body, the milling apparatus comprising a plurality of milling inserts, each insert secured mechanically in a corresponding recess in the body, said mechanical securement sufficient for effective milling of an opening through a tubular in a wellbore. 2. The wellbore mill of claim 1, wherein the inserts are mechanically secured in the recesses by a method from the group consisting of adhesive epoxying, press fit, friction fit, and heat-shrink fit. 3. The wellbore mill of claim 1, further comprising for each insert of the plurality of milling inserts, a screw extending through the body and into each insert for releasably securing each insert in a corresponding recess. 4. The wellbore mill of claim 1, 2 or 3, further comprising each insert having a taper from one end to the other and each recess having a corresponding taper. 5. The wellbore mill of any preceding claim, wherein each insert of the plurality of milling inserts has a generally cylindrical body with a top that is round as viewed from above, the top having a mid-portion and two spaced-apart side portions, the spaced apart side portions extending downwardly below the mid-portion of the top. 6. The wellbore mill of claim 5, wherein the recess for each insert is sized and configured so that outer edges of the two side portions of the insert are disposed below an upper edge of the recess in which the insert is secured. 7. The wellbore mill of any preceding claim, further comprising a fluid flow channel extending through the body from top to bottom, and at least one fluid flow port at the bottom of the body in fluid communication with the fluid flow channel . 8. The wellbore mill of claim 7 wherein at least one milling insert is aligned with an exit opening of the at least one fluid flow port for milling an area passed over by the at least one fluid flow port . 9. The wellbore mill of claim 7 or 8 , wherein the at least one fluid flow port is positioned off centre with respect to a central longitudinal axis of the body. 10. The wellbore mill of any preceding claim, further comprising a gauge ring on the body spaced-apart from the milling inserts. 11. The wellbore mill of claim 10, wherein the gauge ring comprises a series of spaced-apart projections extending outwardly from the body. 12. The wellbore mill of claim 1, wherein the body has a central indented portion in the bottom thereof . 13. The wellbore mill of any preceding claim, further comprising a whipstock selectively releasably connected to the body of the wellbore mill. 14. The wellbore mill of claim 13 further comprising an anchor apparatus connected to the whipstock for selectively anchoring the whipstock in a wellbore or in a tubular in a wellbore . 15. The wellbore mill of any preceding claim, wherein the body has a lower portion with a stepped configuration as viewed from a side. 16. The wellbore mill of claim 13, 14 or 15, further comprising orientating apparatus connected to the whipstock for orientating the whipstock. 17. The wellbore mill of any of claims 13 to 16, wherein the whipstock is a through-tubing whipstock. 18. The wellbore mill of any of claims 13 to 17, wherein the anchor apparatus is a through-tubing anchor apparatus. 19. The wellbore mill of any preceding claim, wherein the body has a scalloped cross-section defined by a series of alternating projections and valleys. 20. The wellbore mill of claim 19, wherein at least some of the plurality of milling inserts are disposed in at least some of the projections. 21. The wellbore mill of any preceding claim, wherein the mill is a window mill. 22. The wellbore mill of claim 21, in combination with a watermelon mill spaced-apart therefrom. 23. The wellbore mill of any of claims 1 to 20, wherein the mill is a watermelon mill. 24. The wellbore mill of any preceding claim, wherein each insert is also secured in a recess by welding or brazing. 25. A mill body for a wellbore mill, the mill body comprising a body member, at least one opening in the body member for holding a milling insert, and energy dissipating structure in the at least one opening for dissipating energy imposed on an insert in the at least -one recess. 26. The mill body of claim 25, wherein the energy dissipating structure is secured to or formed of an interior of the at least one opening. 27. The mill body of claim 25, further comprising an insert held in the at least one opening and wherein the energy dissipating structure is on an insert. 28. The mill body of claim 25, wherein the energy dissipating structure is an energy dissipating member emplaced into the at least one opening. 24 29. The mill body of any of claims 25 to 28 further comprising a removable plug removably disposed within the at least one opening for holding an insert therein. 30. The mill body of any of claims 25 to 29, wherein the at least one opening comprises a hole through the body member . 31. The mill body of any of claims 25 to 29, wherein the at least one opening comprises a recess in the mill body. 32. The mill body of claim 31, wherein the energy dissipating structure is an energy dissipating member on a bottom of the recess. 33. A milling insert for use with a wellbore mill, the wellbore mill having a mill body with an opening for receiving the milling insert, the milling -insert comprising an insert body, and at least one energy dissipating member on the insert body. 34. The milling insert of claim 33, wherein the at least one energy dissipating member is a series of spaced-apart members on an outer surface of the milling insert. 35. The milling insert of claim 33, wherein the at least one energy dissipating member encapsulates a portion of the milling insert. 36. A wellbore milling method for milling an opening in a selected tubular member of a tubular string in a wellbore, the method comprising installing a mill on a working string into the wellbore at a selected desired point for milling an opening in the selected tubular member, the mill comprising a body having a top and a bottom, milling apparatus on the body, and the milling apparatus comprising a plurality of milling inserts, each insert mechanically secured in a corresponding recess in the body, said mechanical securement sufficient for effective milling in a wellbore, and rotating the mill to mill an opening in the selected tubular member. 37. The wellbore milling method of claim 36, wherein the body has a fluid flow channel extending therethrough from top to bottom, the method further comprising creating a core of material of the selected tubular member by milling the selected tubular member, said core received into at least a lower end of the fluid flow channel, and separating with said mill said core from said selected tubular member. 38. The wellbore milling method of claim 36, wherein the body of the mill has a whipstock selectively releasably connected thereto and an anchor apparatus is connected to the whipstock, the method further comprising installing the mill on a working string into the wellbore further comprising activating the anchoring apparatus to anchor the mill and whipstock at a desired location in the tubular string, releasing the mill from the whipstock, and commencing milling of the selected tubular member. 39. The wellbore milling method of claim 36, wherein the body of the mill has a whipstock selectively releasably connected thereto and an orientation apparatus is connected to the whipstock, the method further comprising, prior to milling the selected tubular member, orientating the whipstock to a desired position within the wellbore. 40. The wellbore milling method of claim 38, wherein the anchor apparatus is a through-tubing anchor apparatus and the whipstock is a through-tubing whipstock, the tubular string in the wellbore comprising a first string portion with a first inner diameter and a second string portion connected to and below the first string portion, the second string portion having an inner diameter greater than that of the first string portion, and the selected tubular member part of the second string portion, the method further comprising prior to commencing milling, inserting the mill, whipstock, and anchor apparatus through the first string portion into the second string portion to a location adjacent the selected tubular member.

Inventors: BAILEY THOMAS, BRUNNERT DAVID JOSEPEH, CARTER THRUMAN B, HART SHANE PAUL, HAUGEN DAVID M, HENSON MICHAEL, MCLUNG GUY LAMONTE, BAILEY, THOMAS, BRUNNERT, DAVID, JOSEPEH, CARTER, THRUMAN, B., HART, SHANE, PAUL, HAUGEN, DAVID, M., HENSON, MICHAEL, MCLUNG, GUY, LAMONTE
Applicants: HARDING RICHARD PATRICK, WEATHERFORD LAMB, HARDING, RICHARD, PATRICK, WEATHERFORD/LAMB, INC.
Application year: 2000
Main classification: E21B10
IPC codes: E21B10, E21B17, E21B29