US3429387A - Pump out drill bit - Google Patents

Description

Feb. 251, 1969 c. c. BRQWN 3,429,387

PUMP OUT DRILL BIT Filed March 6, 1967 Sheet 1 of 2 A TTO/PNEV Feb. 25, 1969 c. c. BROWN 3,429,387

PUMP OUT DRILL BIT Filed March 6, 1967 Sheet 2 of 2 29 ll L @26 Z/ Z7 23 28 24 6 4 2 22 l 23 I] H a c/cmo a ROWN INVE TOR.

A T TORNE) 3,429,387 PUMP OUT DRILL BIT Cicero C. Brown, Brown Oil Tools, Inc.,

R0. Box 19236, Houston, Tex. 77024 Filed Mar. 6, 1967, Ser. No. 620,807 US. Cl. 175237 Int. Cl. EZlb 9/22, 23/04 9 Claims ABSTRACT OF THE DISCLOSURE Background of the invention In many operations in connection with the drilling of oil and gas wells, it is often necessary to perform various types of operations in the well bore, many of which may be termed repair operations" which involve placing cement plugs in the well casing to seal up leaks or improperly located perforations. These must then be followed by drilling out the cement plug and reperforating or performing other operations necessary or appropriate to the procedures involved.

In conventional operations of the type described, a series of runs with drill pipe, tubing, or wire line strings must be made to introduce the successive forms of tools required to perform the several operations which may be involved. Each time a string of pipe carrying well tools is run into and out of a well, a considerable amount of time is involved which can be very expensive, particularly where the operations must be conducted at great depths as is often the case.

For example, in a not uncommon situation where a well casing has been perforated at a location which does not communicate with the producing formation, it is necessary to shut-off these perforations and re-perforate at the correct locations. Closing off of the undesired perforations is generally done by packing-off the well bore at proper points and placing a body of cement in the well bore at a location such as to plug the incorrectly located perforations. Very often this is done under pres sure to squeeze oflf the perforations. This operation requires the running of a string of pipe and other equipment, as may be required for placing the cement, and this equipment must then be removed from the well bore. Thereafter, as soon as the cement has hardened a drilling string carrying a drill bit must be run back into the well to drill out the cement plug to clear the bore hole. This string must then be withdrawn from the well and replaced by a pipe or wire line string carrying a perforating gun to re-perforate the casing at the proper location.

Thus, it will be seen that several trips, requiring running and withdrawing pipe strings, must be made into and out of the well bore to complete the series of operations outlined above, all of which necessarily require a substantial amount of time which, in a conventional deep well drilling operation, is very costly.

Summary of the invention The present invention is directed to an improved form of drill bit which may be carried into a well bore on a drill string and is constructed to permit carrying out a series of operations, such as those described above, with 3,429,387 Patented Feb. 25, 1969 the same pipe string without having to withdraw the drill string from the well bore during the performance of the several operations involved.

In accordance with the present invention the drill bit comprises a two-part structure consisting of a main bit which includes a tubular body connectible in the usual manner to the lower end of a drill string, and carrying full-gauge cutters and a pilot bit including a tubular shank carrying pilot cutters. The two-sets of cutters are arranged and dimensioned to cover the cross-sectional area of the bore hole to be drilled thereby. The shank of the pilot bit is coaxially inserted in the bore of the main bit and secured thereto by releasable means.

The releasable means may be of any suitable and known form, such as shear pins or latches, which are re leasable in response to a relative downward force applied to the shank of the pilot bit. This downward force is provided by dropping a ball or other conventional plugging device through the pipe string carrying the bit to seat on and plug the shank of the pilot bit. Thereupon, application of pump pressure to drilling fluid or other fluid in the pipe string will develop the hydraulic force necessary to actuate the release means to release the pilot bit and expel it from the bore of the main bit. This action will clear the bore of the main bit body. As the bore of the main bit body, in accordance with this invention, is preferably made to substantially the same diameter as the bore of the pipe string, a full bore passage will be provided through the pipe string and bit for movement of various tools into the well bore below the bit for con ducting the desired operations.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates usefu embodiments in accordance with this invention.

In the drawing:

FIG. 1 is a view, partly in elevation and partly in section, of a bit in accordance with one embodiment of this invention, the bit being shown in assembled condition for drilling;

FIG. 2 is a view similar to FIG. 1, showing the pilot bit being expelled from the main bit;

FIG. 3 is a lower end view of the bit of FIG. 1 as viewed upwardly from line 3-3 of FIG. 1;

FIG. 4 is a view similar to FIG. 1 of an alternate embodiment illustrating a modified form of the releasable connection means between the pilot and main bits;

FIG. 5 is a view similar to FIG. 4, showing the pilot bit being expelled from the main bit; and

FIG. 6 is a cross-sectional view taken generally along line 6-6 of FIG. 4.

Referring first to the embodiment illustrated in FIGS. 1 to 3, the bit consists of a two-part structure comprising a main bit, designated generally by the numeral 1, and a pilot bit, designated generally by the numeral 2.

The main bit comprises a tubular body 3 having an internally threaded box 4 at its upper end for attaching the bit to a conventional drill pipe string (not shown), and having an axial bore 5 which will preferably be made to the same internal diameter as the pipe string to which the bit is attached. Body 3 carries a plurality of angula-rly spaced, radially extending cutting blades 6 terminating at their lower ends in hard-surfaced teeth 7.

Pilot bit 2 comprises a tubular shank 8, having an axial bore 9, which is slidably receivable in the lower end of bore 5 of the main bit and is secured thereto by suitable releasable means, such as conventional frangible shear pins 10. A seal packing 11 is arranged in a packing groove 12 provided about the exterior of shank 3 adjacent its upper end to sealingly engage the wall of bore 5. The lower end of shank 8 carries a plurality of angularly spaced, radially extending cutting blades 13 having cutting teeth 14 at their lower ends. The upper ends 15 of blades 13 are receivable in correspondingly shaped slots 16 provided in the lower end of body 3 of the main bit and function as keys for locking the main and pilot bits against relative rotation to thereby relieve shear pins from torsional forces which would otherwise be exerted between the main and pilot bits. The pilot bit will be oriented relative to the main bit so that blades 13 of the pilot bit will be angularly interspersed with blades 6 of the main bit. The angular spaces between blades 13 of the pilot bit define passages 17 (FIG. 3) through which fluid my be discharged from the pipe string to which the bit is attached. The upper end of shank 8 surrounding bore 9 may be bevelled at 18 to provide a seat for sealing engagement by a plugging element such as a ball 19, which may be delivered from the surface through the pipe string carrying the bit.

The arrangement of the cutting blades of the main and pilot bits is such as to enable the composite structure to drill out a hole to the full diameter of the circle defined by outer edges of blades 6 of the main bit which determine the gauge of the bit. The blades 13 and teeth 14 of the pilot bit will cover the center portion of the circular area cut by the bit.

By way of example of one application of the bit in accordance with this invention, it will be assumed that it is desired to plug off improperly placed perforations in a well casing and to then re-perforate the well.

The bit, constructed as described herein, will be attached to a string of drill pipe and run into the well bore to a point above the improper perforations. Cement may now be introduced through the pipe string, passages 17 provided in the bit permitting the drill pipe string to be used as a cementing string. When the cement has been placed, the pipe string will be elevated only enough to raise the bit clear of the cement body, or excess cement adjacent the bit may be circulated out in accordance with conventional practices, and the cement allowed to harden. The drill pipe string carrying the bit having been retained in the well bore, it is now employed to drill out the cement plug to uncover the section of the well wall which is to be re-perforated. Fluid will be circulated through the pipe string and the well bore in the usual manner during this drilling operation.

When the hole has thus been cleared, a plugging device such as ball 19 will be dropped into the pipe string and pumped down to engage seat 18 and plug bore 9. Thereupon, application of pump pressure to the fluid on top of ball 19 will be increased to a pressure great enough to break shear pins 10, whereupon the pilot bit will be expelled bodily from bore 5 of the main bit providing a full bore opening through the bit.

Now it becomes possible to lower a perforating gun of conventional design on a suitable operating string, which may be either a wire line or small diameter pipe or cable, through the bore of the pipe string and bore 5 of the main bit into position for perforating the well wall as desired. When this operation has been completed, the drill pipe string carrying the main bit may be withdrawn and production pipe run, if desired, or the drill pipe string may be left in the well bore as the production string should that prove desirable.

It will be understood that in operations such as described, the pipe string may also carry packers and other devices commonly used in sealing off sections of the bore hole to permit pressurizing or squeezing the cement.

As may be seen from the foregoing, the employment of a bit in accordance with this invention, permits the performance of a plurality of operations in a well bore without requiring a multiplicity of runs into and out of the well bore of pipe strings as conventionally required for performing the sequence of operations heretofore described.

The bit may, of course, be used for conventional drilling operations and either or both the main and pilot bits may be equipped with the well-known and conventional rotary cutters instead of the blade cutters illustrated and described herein.

FIGS. 4 to. 6 illustrate a modification in which the releasable means securing the pilot bit to the main bit is in the form of latching dogs held and released by a mandrel slidably positioned in the bore of the shank of the pilot bit.

Referring to FIGS. 4 to 6, the releasable connection means includes a plurality of angularly spaced latches 20 disposed for radial movement in correspondingly shaped openings 21 in the wall of shank 8. The dogs are shaped to be projected outwardly of shank 8 into an annular latching groove 22 provided in the wall of bore 5 of the main bit. The inner faces of latches 20 carry vertically spaced, inwardly projecting lugs 23 -23. A release sleeve or mandrel 24 is slidably mounted in bore 9 of the pilot bit shank and carries outwardly projecting vertically spaced lugs 25 positioned to register with lugs 23 at one position of the mandrel (FIG. 4) which will hold latches 20 in projected latching position in groove 22. Mandrel 24 is initially secured in this position by means of shear pins which extend through the wall of main bit body 3 and the wall of pilot bit shank 8 adjacent its upper end. Thus shear pins 110 initially secures shank 8 to the main bit and also secures mandrel 24 in the locking position. A seal packing, such as an O-ring 26, is mounted in a groove 27 about the exterior or mandrel 24 to seal with the wall of bore 9 of the pilot bit shank. Mandrel 24 has an axial bore 28 which will allow fluid flow through passages 15 of the bit. The upper end of bore 28 terminates in a bevelled seat 29 for engagement by a plugging device such as ball 19.

The latching arrangement illustrated in FIGS. 4 to 6 is of a known form, one example of which is illustrated in U.S. Patent No. 3,115,188, and the details thereof do. not, therefore, form a part of this invention but are illustrated and described as an example of another form of releasable connection means between the main and pilot elements of the bit herein described.

In operation of the modification illustrated in FIGS. 4 to 6, when ball 19 is dropped on to seat 28 and fluid pressure applied thereto, the inner end portions of shear pins 110 which extends between shank 8 and mandrel 24 will first be severed allowing mandrel 24 to be shifted downwardly relative to shank 8 to the position shown in FIG. 5, at which lugs 25 will move out of registration with and into interspersed relation to lugs 23. This will free latches 20 for movement inwardly of mandrel 24 and out of groove 22. The pressure on mandrel 24 will now be transmitted through the interspersed lugs to shank 8 and the increasing downward force exerted by the fluid through mandrel 24 will break the portions of shear pins 110 Which extend between body 3 and shank 8, thereby releasing the latter to permit expulsion of the pilot bit from the bore of the main bit, as seen in FIG. 5. Seals 11 and 26 will prevent leakage of pressure fluid during application of fluid pressure to ball 19 after it is seated.

It will be understood that other modifications and changes may be made in the details of the illustrative embodiments within the scope of the appended claims but without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A drill bit, comprising, a main bit attachable to a drill string and including a body having an axial through bore, a pilot bit including a tubular shank coaxially inserted in said bore and adapted to be plugged by a plugging element passed through said drill string, and releasable means connecting the pilot bit to said body, said means being releasable by fluid pressure exerted through said bore when said shank has been plugged whereby to expel the pilot bit from the bore of the main bit, said releasable means comprising: latch elements mounted for radial movement through the wall of said shank, a latching groove in the wall of said bore positioned for engagement with said latch elements, and a tubular mandrel mounted in the bore of said shank for longitudinal movement between one position holding said latch elements in latching engagement with said groove and a second position releasing said latch elements for movement out of said groove.

2. A drill bit according to claim 1 including annular seal means arranged between said shank and the Wall of said bore.

3. A drill bit according to claim 1, wherein said releasable means comprises frangible shear pins.

4. A drill bit according to claim 1 including means additional to said releasable means carried by said main and pilot bits for initially locking said bits against rotation relative to each other and operable to be released upon release of said releasable means.

5. A drill bit according to claim 4, wherein said additional means comprise cooperating longitudinally engaged key-and-slot elements.

6. A drill bit according to claim 1, wherein said main and pilot bits carry cooperating cutter elements constructed and arranged to drill a bore hole of predetermined diameter.

7. A drill bit according to claim 6, wherein the cutter elements on each of said bits comprise a plurality of angularly spaced, longitudinally disposed, radially extending blades, and wherein the blades on the pilot bit are angularly offset with respect to those on the main bit.

8. A drill bit according to claim 7, wherein the upper ends of the blades on said pilot bit form keys slidably receivable in complementary slots in the lower end of said body of the main bit whereby to lock the main and pilot bits against relative rotation.

9. A well drilling bit comprising, a main bit including a tubular body having an axial bore, a pilot bit having a tubular shank extending coaxially into the bore of said body, and releasable means securing said shank to said body and releasable therefrom in response to fluid pressure exerted through said bore when said bore is plugged to expel the pilot bit from said bore, whereby to provide a full bore opening through said main bit to permit passage therethrough of other well tools, said releasable means comprising: latch elements mounted for radial movement through the wall of said shank, a latching groove is the wall of said bore positioned for engagement with said latch elements, and a tubular mandrel mounted in the bore of said shank for longitudinal movement between one position holding said latch elements in latching engagement with said groove and a second position releasing said latch elements for movement out of said groove.

References Cited UNITED STATES PATENTS 2,793,833 5/1957 Daniel 1751 2,883,154 4/1959 Daniel l1 2,890,861 6/1959 Cook 1 X 2,902,094 9/1959 Nelson et al 175317 DAVID H. BROWN, Primary Examiner.

US. Cl. X.R. l75392, 412

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