Earth Boring Tool

The prior art relative to replaceable roller type roller reamers is discussed in the prior pending U.S. patent application of William R. Garrett, the present applicant, filed May 23, 1977, Ser. No. 799,770, entitled "REAMER".

The prior art relative to junk baskets is discussed in the patent application of said William R. Garrett, Ser. No. 872,729, filed Jan. 26, 1978 entitled "JUNK BASKET, BIT AND REAMER-STABILIZER".

This invention relates to earth boring apparatus useful in the rotary system of boring holes in the earth, e.g. petroleum wells. Elements of such a system include a tubular drill string extending from the bottom of the bore to the surface and means at the surface for rotating the drill string and for raising and lowering same in the earth bore and for circulating drilling fluid, e.g. down the drill string and back up the bore annulus. At the lower end of the drill string is a drill bit. Borings and other detritus is carried to the surface by the drilling fluid and filtered out of the drilling fluid so it can be reused.

Detritus which is too dense to be carried away by the drilling fluid may be caught in a junk basket incorporated in the drill string. Examples of junk baskets are found in U.S. Pat. Nos.

A difficulty with junk baskets is that they must be disconnected from the drill string to be inverted to dump out the junk.

In order to keep the drill bit centralized in the well bore it is usual to provide a stabilizer just above the drill bit. In deep drilling where the drill bit may wear down and bore an undergage hole, instead of a stabilizer a reamer is provided just above the bit to ream the hole to at least full gage. The reamer also performs the function of a stabilizer and is sometimes called a reamer-stabilizer. Reamers may be of either the fixed blade type or the roller type. Examples of roller reamers with replaceable rollers are found in U.S. Pat. Nos.

There are limitations upon how much reaming can be done. For example, when the bit gets too worn it is apt to come apart in the hole. Or a reamer above a worn out bit may wear out rapidly and roller fragments or other parts fall into the hole. Broken bits and other metal parts are a frequently encountered form of detritus which must be removed by a junk basket.

In the case of modern carbide toothed roller cutter bits with sealed lubricated bearings, a limiting factor on bit life is often wear on a bit leg sufficient to damage a seal. Following loss of a seal lubricant is lost; then the bearing locks, cutter rotation stops, and bit efficiency is greatly reduced, wasting valuable rig time.

To avoid wearing the bit down too far, various devices have been contrived to signal to the driller that a bit change is in order. See for example, U.S. Pat. Nos.

It has also been proposed to provide above the bit a roller stabilizer having rollers with rough bands which will engage the well bore and increase the drill string torque when the earth bore diameter immediately above the drill bit becomes too small. The increased torque signals to the driller that it is time to change the bit. See U.S. Pat. No. 3,306,381 -- Garrett and Moore. However, this construction may be undesirable in that it places a heavy load on the bearing surfaces of the reamer rollers and their shafts. Also, when worn rollers are replaced the torque bands are discarded and wasted even if not worn out. *

3,703,096 -- Vitter, Jr. (torque)

3,820,613 -- White (bearing block 4, inserts 8)

3,897,837 -- Peterson (carbide wear inserts 200)

It is also known to provide hard metal inserts or buttons on shoes formed on the legs or other body parts of a roller cone carbide tooth rock bit, e.g. for stabilization and wear reduction. See U.S. Pat. No. 3,628,616 -- Neilson and the advertisement:

"Introducing the `A-Team`"

Pages 24, 25, September 1977, issue of The American Oil & Gas Reporter.

However, such inserts or buttons have a radial extent determined by their function as stabilizers and wear reducers rather than as bit wear indicators. Even if viewed as torque-up buttons, such construction has the disadvantage that the buttons must be thrown away with the bit.

A further difficulty with previous tools is that a choice had to be made as to whether the junk basket, stabilizer, or torque indicator should be placed immediately adjacent to the bit, when it is desirable that all three should be so placed. Various combinations of reamers and junk baskets with other devices have been disclosed in U.S. Pat. Nos.

1,803,669 -- Grant -- reamer with expander

1,886,789 -- Carlson -- reamer and core bit

2,061,057 -- Bigler -- reamer with spring load

2,675,879 -- Middleton -- junk basket and bit

2,898,086 -- Freeman -- junk basket and bit.

None of these constructions integrates in one tool a wear indicator, a junk basket and a stabilizer.

It is an object of the invention to provide an earth boring apparatus which will overcome the aforementioned difficulties with reamers, junk baskets and wear signalling devices.

According to the invention there is provided a carbide tooth, stepped, roller reamer which incorporates a wear indicator and a junk catcher, whereby all three functions are effected close to the bit. Wear indication is accomplished by provision of minimum gage surfaces on the lower mounting blocks for the roller shafts, such surfaces being defined by the outer ends of tungsten carbide inserts in the blocks, such minimum gage equalling the minimum diameter to which it is desired to let the bit wear down below full gage, the minimum gage surfaces creating increased drill string torque when the hole bored by the bit is of only minimum gage and thus signalling the driller it is time to change the bit. The minimum gage surfaces of the blocks protect the lower ends of the rollers, the lowest, smaller diameter lands of the stepped-rollers having a less radial extent from the tool axis than the minimum gage surfaces of the lower blocks, whereby the penetration of the teeth on the lowest lands into the wall of the well bore will be limited, thereby limiting the shear load applied to the teeth. The shaft mounting blocks for the rollers make drive fits with sockets in the reamer body as in the construction of the aforementioned pending Garrett application, Ser. No. 799,770 the body being provided with tool access slots extending under the blocks to facilitate their removal. These slots extend downwardly to the lower end of the tool body. Upper portions of these slot extensions are deep and have their lower parts covered with sliding panels, thereby forming junk catching pockets. The pockets can be emptied by elevating the panels, thereby eliminating the need to disconnect the tool from the drill string to invert it for dumping the pockets. The panels are recessed leaving flow channels therepast, which in combination with the slot extensions therebelow form flow passages over the surface of the body of the tool to allow upflow of large pieces of material too large to flow between the well bore and the full diameter part to the tool body. Additional flow passages for the same purpose can be provided by flats on the exterior of the tool body between the slots extending from the lower end of the body to above the slots. The area of the body just above the junk pockets and below the body cavities in which the rollers are disposed is of reduced diameter forming a circumferential flow passage about the body of the tool whereby particles of junk and detritus flowing upwardly between the pockets can travel circumferentially and fall into the pockets. In addition, the reduced diameter of the body increases the cross sectional area of the well bore annulus around the tool's body, thereby lowering the fluid velocity in the annulus and causing dense particles entrained in the fluid to fall into the junk pockets. The lower mounting blocks overlying the tops of the junk pockets restrict upflow of the dense particles, tending to cause them to be retained in the pockets. The lower end of the tool is bevelled, forming a circumferential flow passage facilitating circumferential movement of junk, detritus, and other dense particles into the flow passage leading up to the junk pockets. The vertical space between the tops of the junk pockets and the bottoms of the lower mounting blocks provides both access for block removal tools, and room for upward opening movement of the sliding panels covering the junk pockets, as well as entrance for junk into the pockets when the sliding panels are in their normal downward positions.

For a detailed description of a preferred embodiment of the invention reference will now be made to the accompanying scale drawings wherein:

FIGS. 1, 2 and 3 together form an elevation, partly in section, of the lower end of a drill string incorporating a drill collar, a tool according to the invention, and a three cone rock bit;

FIGS. 4 and 5 are sections taken at planes 4--4 and 5--5 indicated on FIGS. 1 and 2;

FIG. 6 is an elevation of a junk pocket panel used in the tool of the invention;

FIG. 7 is a fragmentary view similar to FIG. 2 but showing the junk pocket panel moved upwardly to its open or emptying position;

FIG. 8 is an elevation showing a modification; and

FIG. 8A is a fragmentary elevation showing a further modification.

The drawings are shaded and hatched to show the tool materials, which in this case are all metal, namely steel, except for the inserts which are made of tungsten carbide.

1. Lower Drill String Assembly

Referring now to FIGS. 1, and 2, there is shown a well bore 11 within which is disposed the lower end of a drill string including a drill collar 13, a well tool 15 incorporating the invention, and a worn-out (minimum gage) three cone inserted tungsten carbide tooth rock bit 17.

Tool 15 includes a generally cylindrical body 18. At the upper end of tool 15 is a taper threaded box 19 for making a rotary shouldered connection with a correlative pin 21 on the lower end of collar 13. At its lower end tool 15 is provided with a taper threaded box 23 for making a rotary shouldered connection with a correlative pin 25 on the upper end of bit 17. A central flow passage 27 extends axially from the upper end of tool 15 to the lower end thereof. At its lower end passage 27 communicates with axial flow passage 31 in the pin 25 of bit 17. Boxes 19 and 23 may be identical.

2. Drill Bit

Referring now particularly to FIG. 2, bit 17 includes three roller cones 35, 37, 39 each provided with a plurality of inserted tungsten carbide gage teeth 41 and inner teeth 43. The cones are rotatably mounted on shafts (not shown) extending radially inwardly and downwardly from three bit legs 45. Flow passage 31 communicates with a plurality of diverging flow passages 47 which conduct drilling fluid to the bottom 49 of the well bore, flowing past the cones to keep them clean, the drilling fluid then flowing upwardly in the well bore annulus 51 to carry the cuttings back to the surface. Tungsten carbide insert bits such as bit 17 and other rock bits suitable for use with the invention are disclosed on pages 5145 through 5159 of the Composite Catalog of Oil Field Equipment and Services published by World Oil, copyright 1976 by Gulf Publishing Company. Any other suitable type of bit may be employed in conjunction with the tool of the invention.

3. Reamer Portion of Tool

Referring now to FIGS. 1 and 4, in the upper or reamer part of the tool body 18 there are plural, e.g. three cavities 55, equiazimuthally spaced apart about the outer periphery of the body. Within each of these is mounted a stepped roller 57 having plural, e.g. three lands 59, 61, 63 of decreasing diameters progressing downwardly, each land being studded with a plurality of inserted tungsten carbide teeth 64.

Each roller 55 is rotatably mounted on a generally cylindrical shaft 65 mounted at its ends in upper and lower shaft mounting blocks 67, 69. The blocks are press fitted into sockets 71, 73 (see esp. FIG. 4) and are further retained by cap screws 75. To remove and replace an assembly of roller, shaft, and mounting blocks one need only remove the cap screws and remove the blocks. To the latter end body 18 is provided with slots 77, 78 extending above block 67 and below block 69. A suitable wedge can be inserted in one of these slots and beneath a block, which can then be driven out with the wedge.

Further details of the above described replaceable roller reamer construction are to be found in the aforementioned pending prior filed Garrett U.S. patent application. The invention is also applicable to other forms of reamers, but especially roller reamers using removable shaft mounting blocks and to such construction in which there are longitudinal slots in the reamer body extending above and below the blocks, as shown for example on pages 2155-2157 of the aforementioned catalog, whereat is described the Drilco Rotary Reamer.

4. Bit Wear Indicator Part of Tool

Referring now particularly to FIGS. 2 and 4, according to the invention lower mounting blocks 69 have outer peripheral surfaces 79 which are cylindrical in contour, with a cylinder axis coaxial with tool axis 80. The complete cylindrical surface 81, which includes cylindrical surfaces 79, has a gage equal to the minimum gage to which bit 45 (FIG. 2) is to be allowed to wear down. This is to be compared with full gage cylindrical surface 83, which has the diameter reamed by rollers 57, equal to the diameter of well bore 11 above rollers 57 as shown in FIG. 1, and which is the initial size of bit 45 when it is new. Preferably the mounting blocks are bevelled or relieved at each side as shown at 82, 84 to reduce shear loads on the protuberant blocks in case of contact with a rock protruding in from bore 11. Likewise, the top edge 86 of the upper block and the bottom edge 88 of the lower block are similarly bevelled.

As shown in FIGS. 1 and 2, the inserted teeth 64 in lowermost land 63 increase the well bore gage slightly in excess of the minimum gage surface 81, and the teeth in intermediate land 61 enlarge the well bore still more, and finally the teeth in the uppermost land 59 increase the bore to full gage at 83. If desired, as explained in aforementioned U.S. Pat. No. 3,306,381--Garrett and Moore

the teeth in the uppermost land can increase the bore to slightly over full gage.

The condition shown in FIGS. 1, 2 and 4 represents the maximum amount of reaming which is to be done by the subject well tool. Cylindrical surfaces 79 on the lower mounting blocks are in contact with the well bore and the torque in the drill string is increased by the drag created by surface 79 sliding over the inner periphery of the well bore. The increased torque signals to the driller that the bit is worn down to minimum gage and should be changed.

Since surfaces 79 contact the side of the well bore when performing their signalling function, they are provided with flush mounted cylindrical tungsten carbide inserts 85 (see FIGS. 2 and 4). Wear inserts 85 are to prevent surfaces 79 from wearing down below minimum gage, and in case the surfaces wear down anyway, the inserts will continue to extend radially to minimum gage. In a sense therefore, the inserts are the bodies which define minimum gage.

Suitable radial differences between full gage and minimum gage for three cone, inserted tungsten carbide tooth rock bits of various sizes are exemplified by the following chart:

If the lower mounting blocks lose gage, they can be readily replaced. If it is desired to define a different minimum gage for use with particular kinds of drill bits, the tool may be dressed with lower mounting blocks having the desired minimum gage.

It is preferred that surfaces 79 and wear bodies 85 extend radially somewhat past lowermost lands 63, e.g. to half the extent of the teeth 64 therein, so as to protect the lower ends of the rollers and limit the amount of penetration of these teeth into the formation forming the sides of the well bore. This limits the amount of shear load on the teeth. In other words, it is not desired to ream with the flat lower ends 87 of the rollers (FIG. 1), and it is preferred not to have the teeth 64 in lowermost lands 63 completely bury themselves in the formation, although it is recognized that as a reamer becomes nearly worn out some of these things may occur.

5. Junk Catcher Part of Tool

Referring now to FIGS. 1, 2, 5, 6 and 7, just below lower shaft mounting blocks 69, slots 78 widen and deepen into pockets 91. Body 18 is provided with a wide circumferential channel or reduced diameter portion 93 interconnecting the upper parts of the pockets 91. Below channel 93 each slot is provided with a slidable panel 95. As shown in FIG. 5, panels 95 slide in vertical grooves 97,99 in the sides of pockets 91. In order to keep the panels in whatever position they are placed, the upper ends of the panels are given a slight curvature at 101, as shown in FIG. 6, which, due to the resilience of the steel of which the panels are formed, causes the panels frictionally to engage the sides of grooves 97,99. The latter arrangement is sometimes called a semi-locking device in that a certain amount of force, larger than what would otherwise be required if the panels were completely free to slide, is needed in order to cause movement of the panels. If desired, the panels can be made of spring steel, but ordinary steel will have sufficient elasticity to serve the purpose. To facilitate moving the panels, each is provided with a tool grip comprising a hole 103.

As shown in FIG. 2, panels 95 are in their lowermost positions in which the lower ends of plates 105 rest in correlative recesses 109 in bottoms 111 of the pockets. In such position the bottoms of pockets 91 are closed while their tops are open to receive junk, detritus, and other dense material 113. In FIG. 7 panel 95 is shown in an elevated position, opening the bottom of pocket 91 at 115, whereby material 113 falls out.*

As shown in FIGS. 2, 5, and 7, grooves 97, 99 in which panels 103 slide are set back from the outer periphery of body 18 so that channels 117 are formed outside the panels. These channels join channels 119 in the outer periphery of the body, which extend all the way to the lower end of the body. Channels 117, 119 form a longitudinal flow passage. At its lower end, body 18 is circumferentially bevelled at 121, forming a circumferential flow passage 123. Circumferential flow passage 123 allows dense material from the bottom of the bore to move easily into the longitudinal flow passages 119, 117 and upwardly through the latter. On reaching circumferential channel 93 the dense material is carried inwardly by the slowing drilling fluid and is deposited in pockets 91. Smaller particles of dense material flowing upwardly between the full diameter part of body 18 and the well bore in between the flow passages formed by channels 117, 119, can move horizontally in circumferential channel 93 and then fall into one of pockets 91. Dense material moving upwardly in one of the longitudinal flow passages formed by channels 117, 119 is inhibited in further upward flow not only by the velocity reduction of the drilling fluid due to the enlarged cross-section for fluid flow presented by channel 93 but is to some extent blocked against upflow by lower mounting blocks 69. This reduces the amount of dense material that flows past junk pockets 91 without being trapped but which falls back down again, possibly causing damage to the reamer rollers or the bit cones.

It will be seen from the foregoing description that the various portions of the well tool; stabilizer, wear indicator, and junk catcher, all cooperate to provide an efficient well tool that is placed immediately above the drill bit where the functions of the tool can be most efficiently effected.

6. Modification

Referring now to FIG. 8 there is shown the lower portion of a tool incorporating a modification of the invention. In this Figure, except as hereinafter noted, the parts are the same as in FIGS. 1 and 2 and hence have been given like reference numbers except primed. In this modified tool, there are provided a plurality of flats 131, three of them, around the outer periphery of the tool body 18', in between junk pockets 91'. Flats 131 extend from the bottom of the tool to circumferential channel 93' and provide additional passages for the flow of drilling fluid and large material up from the bottom of the hole and the bit to junk pockets 91'.

FIG. 8 also illustrates a further modification wherein bands 133 of tungsten carbide particles, flush with the outer cylindric surface of the lower mounting blocks and welded into grooves thereacross, are substituted for the tungsten carbide inserts 85 of the first described embodiment. Such bands could be used also in the first embodiment and the inserts could be used in the FIG. 8 embodiment. The bands and the inserts can be above or below screws 75 or 75' or both above and below or all over the outer surface of the block.

Instead of using bands or inserts of tungsten carbide to protect the lower mounting blocks when they contact the well bore, other kinds of hard facing could be employed or the outer surfaces of the blocks could be carburized or hard metal could be used for the blocks themselves or the blocks could be left unprotected although that is not preferred. These variations are equally applicable to the described and illustrated embodiments.

The subject invention of a combined reamer and junk catcher but without the bit wear indicator is applicable not only to roller reamers but also to blade type reamers. Such blade type reamers are shown, for example, in U.S. Pat. No. 3,680,646--Hughes and Garrett issued Aug. 1, 1972. FIG. 8A illustrates the use of a blade 135 in place of roller 85. FIG. 8A is an upward continuation of FIG. 8 and hence need not be described in detail, except to note that the lower mounting block would be as shown in the Hughes-Garrett patent and would not function as a wear indicator.

Note also that the invention is applicable to reamers in which the blades or rollers are slant mounted, i.e. tangent to a helix concentric with the body as described in the Hughes-Garrett patent.

While preferred embodiments of the invention have been shown and described, other modifications can be made by one skilled in the art without departing from the spirit of the invention.