US3223187A

US3223187A - Means for controlling drill bit torque in rotary percussive drilling

Info

Publication number: US3223187A
Application number: US236006A
Authority: US
Inventors: James M Cleary
Original assignee: Atlantic Refining Co
Current assignee: Atlantic Richfield Co
Priority date: 1962-11-07
Filing date: 1962-11-07
Publication date: 1965-12-14
Anticipated expiration: 1982-12-14

Description

' Dec. 14, 1965 J. M. CLEARY MEANS FOR CONTROLLING DRILL BIT TORQUE IN ROTARY PERGUSSIVE DRILLING Filed NOV. '7, 1962 INVENTOR,

" Cleary M offal- AtiOrney United States Patent This invention has to do with a means of rotary percussive drilling and, more particularly, to the reduction of torsional stress during impact of a percussion means.

In rotary percussive drilling, a drill bit or equivalent cutting means is rotated by suitable surface equipment and the bit is impacted longitudinally against a formation by suitable percussion means. In drilling shallow holes, the percussion means may remain at the surface and the impact energy is transmitted to the bit by way of a rod or other tubular means which extends from the bit to the surface. In deep well drilling, the percussion means is usually suspended on a hollow drill string just above the drill bit.

Normally, that portion of the percussion means which imparts the blow is called the hammer, and that part receiving the blow is called the anvil which is located on a shank connected to the drill bit. The shank is usually slideably mounted in the percussive unit so that, upon impact, it may move quickly forward driving the drill bit longitudinally against the formation. Since the drill bit is to be rotated as it is impacted, the shank is designed to prevent relative rotation between the telescoping parts of the percussive unit. Prior percussive units have utilized rigid, nonyielding, torsional drive means such as cooperating splines, or keyways and keys, or some other equivalent means that transmits torque from one telescoping member to another. The telescoping members of prior percussive devices are, therefore, rigidly connected to prevent any relative rotational movement between the members. For many reasons, this adversely affects the operation and reduces the efiiciency of prior rotary percussive systems. In such systems, when the hammer strikes the anvil driving the cutters of the drill bit longitudinally against and into the formation, the speed of rotation of the bit is greatly reduced or stopped completely causing a high torsional shock on the cutters and creating a torsional shock wave traveling up the drill string. Before the hammer rebounds for its next blow, the drill string and drill bit must recover from this shock so that the cutters of the bit are rotated or indexed to a new position for a new bite. If the next blow of the hammer occurs before the bit is reindexed, the cutters of the bit will remain in one position and be driven deeper and deeper into the formation by succeeding blows.

The above phenomena contribute to such problems as loss of drilling efficiency, excessive wearing and breaking of the cutters, the need for frequent bit replacement and adjustments to the drilling system, metal fatigue, malfunction of the percussive unit, stuck drill bits, and other related problems.

In view of these problems and the fact that there are many factors which determine a rotary percussive drilling systems effectiveness and eificiency and the relative effect of each factor differs pronouncedly with the depth, type, and frequency of change of the formation being drilled and the design of the bit, drill string, and percussive mechanism, it is extremely diflicult to properly design a rotary percussive drilling system. In addition, it is often necessary to compromise the desirable design characteristics of one element of the drilling system to reduce the effects of shortcomings of another element.

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Accordingly, it is one object of the present invention to provide a rotary percussive drilling method and apparatus especially characterized by its ability to drill effectively and efiiicently through a wide variety of earth formations with maximum drilling rates and minimum susceptibility to changing drilling conditions.

It is another object of this invention to provide a rotary percussive drilling system that permits greater freedom in design of the various elements which affect the efficiency and elfectiveness of a rotary percussive drilling system.

Still another object of this invention is to provide a percussive earth drilling unit especially noted for reducing torsional strain on the drill bit during impact of the hammer and eliminating many of the problems found in prior rotary percussive drilling devices.

It is still another purpose of this invention to provide a rotary percussive drilling system that allows the drill string to rotate relative to the drill bit during impact of the hammer and that supplies the necessary rotary driving strength to the drill bit at the desired moment after such impact.

Yet another object of this invention is to solve the above problems by providing a rotary drilling process wherein torsional energy is accumulated and released at the most opportune moment.

Various other objects and advantages of this invention will appear from the following description of this invention together with the accompanying drawings and appended claims.

In the drawings:

FIGURE 1 is a fragmented, elevational view illustrating a typical arrangement for a fluid operated percussive earth drilling system employing this invention.

FIGURE 2 is an elevational, partial, cross-sectional view of a percussive unit having a torque control means embodying the principles of this invention.

FIGURE 3 is an enlarged transverse, cross-sectional view taken as indicated by 33 on FIGURE 2 and illustrating one embodiment of the torque control means.

FIGURES 4 and 5 show two alternative embodiments of the torque control means.

The rotary percussive drilling system of this invention is comprised of rotary means, percussive means, torque control means and drilling means. A system of this type is illustrated in FIGURE 1 wherein drilling means 11 is located at the bottom of borehole 13. Above drilling means 11 is torque control means 15 which means is adapted to transmit torque to the drilling means in a unique way as will be discussed hereafter in more detail. Communicating with torque control means 15 is percussive means 17 which is any means suitable for imparting at time space intervals a longitudinal force to impact drilling means 11 against the bottom of borehole 13. Preferably, as shown in FIGURE 2, torque control means 15 is a part of percussive means 17.

Above percussive means 17 is rotary means 19 which includes rotary drive means 21 which is preferably lo cated at the earths surface and which for this invention must always be located above torque control means 15. Rotary drive means 21 is any of the many known devices for imparting rotary motion to a drill bit. Rotary means 19 also includes tubular means 23 which is commonly termed a drill string or drill rod and forms a flow pas sage for fluid to operate percussive means 17 and to flush drill cuttings from borehole 13. Tubular means 23 con nects rotary drive means 21 to percussive unit 17.

Rotary means 19 must rotate continuously above torque control means 15. Frequently, therefore, it is necessary to increase the angular momentum at the point just above the torque control means by either increasingthe rotational speed of rotary drive means 21 or by placing high polar moment of inertia members at this point, or both. In FIGURE 1, such members are shown by drill collars 25. These drill collars, if employed in the drilling system of this invention, must always be placed above torque control means 15 for reasons hereafter made apparent. Preferably, they will be placed immediately above percussive means 17. In accord with standard drilling practices, components may be taken from or added to rotary means 19 as long as the rotary means provides the necessary torsional energy to rotate the drilling means.

To complete the description of a typical rotary earth percussive drilling system, at the top of tubular means 23 is shown swivel head 27 by which the drill string is raised and lowered into the borehole. Associated with swivel head 27 is fluid inlet means 29 which acts as an inlet passage for the flushing and operating fluid. Typically, near the top of borehole 13 is seal means 31 and fluid outlet means 33 for safely discharging the flushing and operating fluid from the borehole.

Consider now torque control means 15 in more detail. Torque control means 15 is one of the essential elements of this invention and cooperates with percussive means 17. The torque control means permits every component of the drilling system above the torque control means to undergo rotational movement relative to drilling means 11 over the entire interval during which percussive means 17 applies its longitudinal or axial force to the drilling means. The amount of relative rotational movement must be limited as hereafter set forth and the specific design of torque control means 15 will depend on the particular percussive unit being employed since the duration of the impact force or the internal of application of this longitudinal force varies with different percussion units as does the interval or time between successive applica tions of the force. For any given percussive unit, the maximum amount or angle of relative rotational movement allowed by torque control means 15 must be greater than the distance or angle that the drilling means would normally move during a time period equal to the interval of application of this longitudinal force and less than the angle or distance that the drilling means would normally rotate during the period between applications of said force. For example, if the drilling means were being rotated at 25,200 per minute (70 r.p.m.) and the duration of application of the longitudinal force were 0.001 second, the minimum relative rotational movement allowable by the torque control means will exceed 0.42, and if the force were applied twenty times a second so that the time between such applications were 0.049 second, the maximum relative rotational movement allowable by the torque control means will be less than 20.5 8. Preferably, torque control means 15 should be able to allow everything above it to rotate for a period greater than the duration of the interval of application of the longitudinal force and less than 0.6 of the time between successive hammer blows or intervals of application of the longitudinal force to the drilling means. It is also preferred that torque control means 15 absorb torsional energy substantially elastically during the period or angle of relative rotational movement of the drilling means to every component above the drilling means so that drilling means 11 will quickly return to its former position relative to rotary means 19 as soon as the torque control means starts accelerating the speed of rotation of drilling means 11 after each impact of the percussive means.

The location of torque control means 15 above drilling means 11 aifects the extent of the benefits derived from its use. The amount of beneficial result increases as the torque control means is moved nearer to the drilling means. Torque control means 15 should, therefore, be located as near to drilling means 11 as is possible, or immediately adjacent thereto. The torque control means will generally be within 6 feet thereof and preferably should be within 2 feet thereof.

Shown in FIGURES 2 through 5 are specific examples of torque control means 15. To facilitate understanding, only that portion of the percussive unit containing torque control means 15 is shown in FIGURE 2 where shank 35 telescopes in the usual fashion into the housing of percussive unit 17. Above the shank represented by reference numeral 37 is a typical hammer means for applying periodic longitudinal or axial forces to the shank. The shank is preferably connected to the drill bit or is an integral part thereof. Between the shank and the percussive unit housing is torque control means 15 which is formed in the following manner. Shank 35 has at least one shank keyway or groove 39 which corresponds and cooperates with percussive unit groove 41 in percussive unit 17 to form a cavity. As shown, there are four such cavities or sets of grooves. Into each cavity is inserted means for absorbing torsional strain energy elastically for a limited amount of rotational movement of percussive unit 17 relative to shank 35 which means in FIG- URES 2 and 3 is S-shaped spring 43.

In FIGURE 4, the means for absorbing and storing torsional energy is bent key 45. In FIGURE 5, modified shank groove 3'9 has only half the width of percussive unit groove 41. In addition, shank 35' is formed with at least one Wing-like extension 47 that fits into and occupies half of percussive unit groove 41 thereby forming space 49. Space 49 can be utilized in a number of ways. Space 49 may be filled with an elastic material having the necessary properties, or with a compressible fluid, or with a fluid whose pressure is controlled by communication with other parts of the drilling system.

Consider now the operation of the above system. Briefly, the process is comprised of rotating the rotary means, percussive unit, and drilling means and periodically applying longitudinal force to the drilling means to impact it against the bottom of the borehole. During intervals of application of this longitudinal force, every component of the drilling system above the torque control means is rotated relative to the drilling means and between periods of application of the longitudinal force, the speed of rotation of the drilling means is increased. Preferably, elastic energy is stored during the period when the speed of rotation of the drilling means is retarded, and every component above the torque control means rotates relative thereto. This stored energy is released at the desired predetermined moment after application of the force to increase the speed of rotation of the drilling means and during the moments when the drilling means rotates faster than the remainder of the drilling system.

Referring now to FIGURE 1, consider the process in more detail. Wit-h drilling means 11 on the bottom of borehole 13, the drilling system is rotated by rotary means with torque being transferred from percussive means 17 to the drilling means by way of torque control means 15 so that the bit will normally rotate therewith. At time spaced intervals, percussive means 17 applies a longitudinal force against drilling means 11 impacting it against the formation. As the force is applied, the cutters of drilling means 11 are driven into the formation retarding its rotation. This creates a torsional shock wave in the cutters which is transmittted upward quickly to torque control means 15. Torque control means 15 allows every component of the drilling system above it to continue rotation relatively unimpeded. This quickly creates a wave that returns to the drilling means to counterbalance and relieve any torsional shock strain energy on the drill cutters. When the longitudinal force applied by the percussion means ceases and before the next interval of application of a similar force, the speed of rotation of the drilling means is increased and the bit is indexed for a new bite. The amount of relative rotational movement allowed is greater than the duration of the longitudinal force and less than the time between successive blows, and preferably less than 0.6 of this time. In addition, preferably, during this period of relative rotational movement while the speed of the drill bit is retarded, torsional energy is absorbed and stored substantially elastically in torque control means 15, and this elastic energy is released when the speed of the drilling means is increased. This enables the drilling means to rotate faster than components above the torque control means and recover its position relative to these components before the force is reapplied.

It is understood that various changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of this invention, may be made Within the principle and scope of this invention.

I claim:

1. In a rotary percussive earth drilling system wherein a drilling means is rotated by a rotary means and is impacted against an earth formation by a periodic longitudinal force applied by a percussive means, the improvement comprising torque control means between said drilling means and said rotary means and adapted to allow limited rotational movement of every component of said drilling system above said torque control means relative to said drilling means when said longitudinal force is applied by said percussive means, said limited rotational movement being greater than the angle that said drilling means would normally rotate during an interval equal to the interval of application of said longitudinal force and less than the angle that said drilling means would normally rotate during the period between applications of said longitudinal force, and said torque control means adapted to cause said drilling means to recover its position relative to every component of said drilling system above said torque control means during the period between applications of said longitudinal force.

2. The improvement of claim 1 wherein the torque control means is located within 6 feet of the cutters of the drilling means.

3. The improvement of claim 1 wherein the torque control means is adapted to absorb torsional energy substantially elastically during the interval of said relative rotational movement.

4. The improvement of claim 1 wherein the limited rotational movement is greater than the angle that said drilling means would normally rotate during an interval equal to the interval of application of said longitudinal force and less than 0.6 of the angle that said drilling means would normally rotate during the period between applications of said longitudinal force.

5. A rotary percussive drilling system comprising in combination earth drilling means, percussive means adapted to impart a longitudinal force at time separated intervals to said drilling means, rotary drive means adapted to rotate said drilling means and said percussive means, torque control means between said drilling means and said rotary drive means and adapted to allow limited rotational movement of every component of said drilling system above said torque control means relative to said drilling means during said intervals when said longitudinal force is imparted to said drilling means therefor, said limited rotational movement being greater than the angle that said drilling means would normally rotate during a period equal to said interval of application of said longitudinal force and less than the angle that said drilling means would normally rotate during the period between applications of said longitudinal force, and said torque control means adapted to cause said drilling means to recover its position relative to every component of said drilling system above said torque control means during the period between applications of said longitudinal force.

6. The drilling system of claim 5 wherein the torque control means is located within 6 feet of the cutters of the drilling means.

7. The drilling system of claim 5 wherein the torque control means is adapted to absorb torsional energy substantially elastically during the interval of said relative rotational movement.

8. The drilling system of claim 5 wherein the limited rotational movement is greater than the angle that said drilling means would normally rotate during a period equal to said interval of application of said longitudinal force and less than 0.6 of the angle that said drilling means would normally rotate during the period between applications of said longitudinal force.

References Cited by the Examiner UNITED STATES PATENTS 2,325,132 7/ 1943 Haushalter -56 2,825,534 3/1958 Reid 175-405 2,911,192 11/1959 Bouoher 175-56 3,033,011 5/1962 Garrett 175-320 X CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDE'IT, Examiner.