US2252168A - Well bit - Google Patents

Description

Alllg- 12, 1941v 1'.. A. cRElGHToN Y 2,252,168

ticularly effective Patented Aug. 12, 1941 WELL BIT Thomas A. Creighton,

Long Beach, Calif., assigner of one-half to Martha H. Wright, Los Angeles,

Calif.

Application June 17, 1940, Serial No. 340,959

(Cl. Z55- 61) 6 Claims.

This invention relates to Well drilling tools and relates more particularly to a well bit for use in the rotary method of well drilling. A general object of this invention is to provide a simple and practical rotary Well drilling bit embodying a parinner cutting means or core Cutting means.

With the present day rotary well drilling methods the circulation fluid is delivered to the drilling tool in substantial volumes and at high pressures and drag type drilling bits have been developed having a single central port of large diameter for discharging the fluid at the lower end of the bit to assure a thorough flushing action and to provide for the eroding of the earth formation by the fluid. The large central fluid port is located Within the annular series of principal cutting blades leaving a substantial area that is not acted on by the principal blades. For this reason it has been necessary to provide core breaking means or inner cutting means for cutting away the core of earth formation that otherwise would remain in the center of the bore. These core breaking means or core cutting means have materially interfered with the free discharge of the circulation uid from the single discharge port reducing the efficiency of the tools.

Another object of this invention is to provide a Well drilling bit or pilot bit having a single central fluid discharge port and characterized by a l cutting means for cutting away the core or central portion of the earth formation, which does not interfere with cr appreciably reduce the free discharge of the fluid from the central port.

Another object of this invention is to provide a well bit of the character referred to in which the inner cutting means comprises a single cutting part or blade formed and arranged to entirely cut away the earth formation remaining Within the zone of operation of the outer blades.

Another object of this invention is to provide a well bit of the character referred to in which the inner blade is formed and located so that the core cannot enter the fluid discharge port and so that the cuttings from the core cannot choke or enter the port.

Another object of thisinvention is toprovide a bit of the character mentioned in which the inner cutting blade may be inexpensively embodied in the tool as a rigid permanent element.

Another object of this invention is to provide `a well bit of the character referred to including a choke bushing or bean adapted to be passed down through the drilling string to the bit to cause the circulation fluid to discharge at an increased velocity so that it is more effective in its eroding action.

A further object of this invention is to provide a Well bit of the character referred to in which the inner cutting blade forms a stop and support for the choke bushing or bean serving tosupport the bean Where it is most efficient in its nozzle action.

The various -objects and features of my invention will be fully understood from the following detailed description of a typical preferred form and application of the invention, throughout which description reference is made to the aocompanying drawing, in which:

Fig. l is a side elevation of the improved Well bit of the invention. Fig. 2 is a vertical detailed sectional View taken substantially as indicated by line 2-2 on Fig. 1 with the upper portion in side elevation. Fig. 3 is a transverse detailed sectional view taken as indicated by line 3--3 on Fig. 2 and Fig. 4 is a fragmentary vertical detailed sectional View of the lower portion of the bit showing the choke bushing or bean in position in the port.

The present invention is capable of embodiment in drilling bits for forming full sized well bores and in pilot bits to be run below reamers or bore enlarging tools. The tool herein described may be considered either a drilling bit or a pilot bit and where I herein employ the term bit it is to be understood as meaning either a drilling bit or a pilot bit.

The Well drilling bit of the present invention may be said to comprise, generally, a body I 0 having a central fluid port II, outer cutting blades I2 on the body I0, an inner cutting blade I3 on one of the blades I2 and a choke bushing or bean I4 adapted to be run into the port I I.

The bit body It] is adapted to be secured to the lower end of a well drilling string and serves to carry the several cutting parts. In practice the body It may be an elongate generally cylindrical member provided at its upper end with suitable means for facilitating its connection with the drilling string4 In the particular case illustrated the upper end of the body I0 is provided with a tapered screw threaded pin I5 to be threaded into a part of the drilling string. The lower end portion of the body I0 preferably tapers or curves downwardly and inwardly to a flat horizontal end face I6. The central fluid passage or port II extends longitudinally through the body ID from one end to the other. The upper end of the port I I, occurring at the top of the pin I5, is adapted to communicate with the interior of the drilling string and the lower end of the port II discharges downwardly at the end face I6. In accordance with the invention the port I I is uniform in diameter and is preferably cylindrical. I prefer to make the port II of large diameter or fluid capacity so that it may handle a substantial volume of fluid. As will be later described, the outlet end of the port II may be restricted or provided with a nozzle means where operating conditions make this desirable.

The outer cutting blades I2 project from the lower portion of the body I to cut or form the outer part of the well bore. There are two or more circumferentially spaced outer cutting blades I2. In the construction illustrated there are three equally spaced blades I2. The blades I2 are formed on the lower rounded portion of the body I0 and project a substantial distance downwardly from the body. The outer blades I2 also project outwardly or laterally from the body I0 to provide ample clearance for the body and the drilling string. The blades I2 are substantially vertical although it is preferred to have them slope downwardly and forwardly relative to the right hand direction of rotation. The forward faces II of the blades I2 are flat and are substantially radial relative to the central longitudinal axis of the tool. The rear faces of the blades I2 may be convex or rounded and their lower parts curved downwardly and forwardly to join the forward faces I'I at lower cutting edges I8. rIhe outer edges or reaming edges I9 of the blades I2 may be straight and substantially vertical. 'Ihe inner edges or sides 22 of the blades I2 are substantially vertical and may be fiat, as illustrated. In practice the inner faces 20 of the blades I2 may occupy planes tangential to a circle of substantially the same diameter as the port I I and concentric with the port. Because of this disposition of the inner edges or faces 29 the blades I2 do not interfere with the free discharge of fluid from the port II and are eroded or cut out to a minimum extent by the fluid discharged from the port. The main or outer cutting blades I2 are preferably quite long to be long wearing. The blades I2 formed and arranged as above described, assure the free passage of fluid between them so that there is a minimum tendency of the bit to ball up with mud and cuttings.

The inner cutting blade I3 is provided to cut away the central portion of the earth formation left by the outer blades I2. It is an important feature of the invention that the blade I3 is formed and positioned so that it does not interfere with the free discharge of fluid from the port II. In accordance with the invention the blade I3 is a part integrally or at least rigidly formed or provided on an inner face 20 of one of the outer blades I2. The core cutting blade I3 is located entirely below the lower face I of the body III and, therefore, is entirely below the port II where it cannot interfere with the fluid discharge from the port. It is preferred to shape and proportion the blade E3 so that it projects inwardly to or immediately adjacent the central longitudinal axis of the tool to entirely cut away the earth formation that may remain between the outer blades I2.

'The shape of the inner blade I3 may be varied considerably, however, it is preferred to form or shape the blade substantially as illustrated. In the construction illustrated the upper edge 22 of the blade I3 slopes or curves inwardly and downwardly relative to the central axis of thetool. The lower edge or cutting edge 23 is substantially aataies straight and extends horizontally to join the curved edge 22 at or immediately adjacent the central vertical axis of the tool. The forward face 2li of the blade I3 is flat and may be vertical, as illustrated, or may lie in the sloping plane occupied by the adjacent forward face I'I of the cutting blade I2, which carries the blade I3. As best illustrated in Fig. 3 of the drawing, the rear side of the blade I3, relative to the direction of rotation of the bit, slopes outwardly and rearwardly so that the blade is of substantial thickness where it merges with its carrier blade I2. The upper edge of the blade I3 is beveled to shed or divert the down flowing fluid to the best advantage. The cutting edge 23 is preferably provided with hard metal or other abrasion resisting material.

The inner blade I3 formed and arranged, as just described, is effective in entirely cutting away the core of earth formation with a minimum of interference to the free flow of fiuid from the port I I. The blade I3 is below the port I I so that it does not interfere with the fluid discharge and so that the cuttings from the core cannot enter the port. The blade I3 occupies substantially the same vertical plane as its carrier blade I2 so that its presence beyond the end of the port II offers practically no interference to the free flow of uid between the blades I2 and so that there is no tendency for the cuttings to accumulate about it. The fluid flushing past the forward and rear faces of the carrier blade I2 fully clears the inner blade I3 of all cuttings.

The choke bushing or bean III is not always essential or required but may be desirable in situations where it is necessary or preferred to increase the velocity of the circulation fluid as it discharges from the port II. When the bit is in in the well the bushing or bean Ill is adapted to be lowered or dropped through the drilling string to assume an operative position in the port II. In other cases the bean I4 may be installed in the bit before the bit is run into the well. The bushing or bean III is a tubular element formed of erosion and abrasion resisting material and is proportioned to rather accurately t the port II. The inside diameter of the bean I4 may be varied to increase the Velocity of the circulation fluid to any selected extent. The lower end 26 of the bushing or bean I4 may be rounded to guide the bean through the drilling string and is adapted to engage and rest on the upper edge 22 of the inner lblade I3. If desired, the upper edge 22 of the blade I3 may be formed with a seat or face to receive the bean I4. As shown in Fig. 4 of the drawing the lower end 25 of the bean III engages on the upper edge 22 of the blade I3 at or immediately adjacent the lower face I6 of the body III so that the bean Ill is substantially entirely confined to the port II. The upper end 21 of the bushing or bean III may be tapered downwardly and inwardly to direct the fluid through the bean.

In the use or operation of the bit provided by this invention the body I is secured to the lower end of the drilling string so that the bit is operated inthe lower end of the well bore. When the drilling string is rotated and fed downwardly the outer cutting blades I2 cut the well bore or the pilot bore to gauge, serving to drill away the major portion of the earth formation. The inner cutting blade I3 operates to remove or cut away the central core of earth formation that may remain within the series of outer blades I2.

'The inner blade I3 projects inwardly to or adjacent the central vertical axis of the bit to entirely cut away the core. The blades I2 and I3 may be formed of or faced with hard cutting and abrasion resistant material to be long wearing and to be effective in their drilling action. The hard or hardfaced blades I2 and I3 are resistant to the abrasive and erosive action of the circulation fluid discharged from the port I I.

During the drilling operation circulation fluid is continuously pumped through the drilling string under pressure to discharge from the port II. The circulation fluid discharging from the port II impinges against the bottom of the well bore to have an erosive action on the same and passes upwardly and outwardly between the bla-des I2 to clear the blades of cuttings. The core cutting blade I3 is entirely below the port II and occupies the same vertical plane as its carrier blade I 2 so that it does not interfere with or restrict the discharging fluid from the port I I. The fluid discharging downwardly around the blade I3 fully flushes the blade and as the blade is unconfined and wholly outside of the port II and the body I there is no tendency for cuttings to accumulate on the blade I3. Thus, the cuttings from the central core of earth formation cannot accumulate to restrict or interfere with the free discharge of the circulation fluid. It will be observed that the blade I3 arranged on the inner face 20 of a blade I2 does not interfere with the passage of the circulation fluid across the faces of the blades I2 and does not cause the cuttings, mud, etc. to accumulate on the blades I2.

If it is desired to increase the velocity of the fluid discharging from the port I I the choke bushing or bean I4 is dropped or lowered through the drilling string. The bean I4 passes down through the port I I and comes to rest against the blade I3. The bean I4 may, of course, be positioned in the bit before the bit is run into the well. The upper edge 22 of the blade I3 forms a seat or support for the bean I4 serving to hold or stop the bean where its lower end 26 is immediately adjacent the lower end of the body Ill. With the bean I4 is positioned against the blade I3 it beans down the fluid flow increasing the velocity of the fluid discharged from the port. This may materially aid in the drilling action and may assure the better flushing of the cutting parts. If desired, the bean I4 may be removed at any time for replacement.

Having described only a typical preferred form and application of my invention, I do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims:

Having described my invention, I claim:

1. A rotary well bit comprising a body having a substantially central fluid port discharging at its lowerend, outer cutting parts projecting from the lower end of the body and spaced from the central vertical axis of the body to leave a central core of earth formation, and a single inner cutting blade carried by one of the outer cutting parts and projecting inwardly toward said axis below the lower end of the body to cut away said core, said blade having a beveled downwardly and inwardly sloping upper edge to shed the fluid discharged by the port and having a lower cutting edge which is transverse of the longitudinal axis of the bit.

2. A rotary well bit comprising a body having a substantially central fluid port discharging at its lower end, spaced outer cutting blades projecting from the lower end of the body and spaced from the central vertical axis of the body to be clear of said port, the outer blades lying in spaced generally vertical planes, and a single inner blade projecting inwardly from one outer blade below the lower end of the body to cut away the core of earth formation left by the outer blades, the inner blade lying within the same generally vertical plane as the outer blade which carries it to offer no interference to the passage of fluid between the outer blades.

3. A rotary well bit comprising a body having a substantially central fluid port discharging at its lower end, spaced outer cutting blades propecting from the lower end of the body and spaced from the central vertical axis of the body to be clear of said port, the outer blades lying in spaced generally vertical planes, and a single inner blade projecting inwardly from an outer blade below the lower end of the body to have its inner end adjacent said axis, the inner blade having its upper edge beveled to shed the fluid from said port with a minimum of interference and having a lower cutting edge to cut away the earth formation left within the series of outer blades.

4. A well bit for use on a tubular rotary well drilling string comprising a body to be secured to the lower end of the string and having a fluid passage communicating with the string to receive the circulation fluid therefrom, said passage discharging at the lower end of the body, cutting parts on the lower end of the body, one of the cutting parts projecting inwardly below the lower end of the passage, and a choke bushing adapted to move down the string and through said passage to rest on said cutting part in a position to form a nozzle for said passage.

5. A well bit for use on a tubular rotary well drilling string comprising a body to be secured to the lower end of the string and having a fluid passage communicating with the string to receive the circulation fluid therefrom, said passage discharging at the lower end of the body, an outer cutting blade projecting from the lower end of the body, and spaced from the central vertical axis of the body to be clear of said passage, an inner cutting blade projecting from the inner edge of the outer blade below the lower end of the 'body to cut away the core of earth formation left by the outer blade, and a choke bushing resting on the inner blade where it forms a nozzle at the lower end of the passage.

6. A well bit for use on a tubular rotary well drilling string comprising a body to be secured to the lower end of the string and having a fluid passage communicating with the string to receive the circulation fluid therefrom, said passage discharging at the lower end of the body, spaced outer cutting blades projecting from the lower end of the body, the outer blades having their inner edges spaced from the central vertical axis of the body to bel clear of said passage, a choke bushing for said passage, and an inner blade projecting inwardly from the inner edge of an outer blade to cut away the core left by the outer blades and adapted to support said choke bushing in its operative position.

THOMAS A. CRElGI-ITON.

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