US3139146A

US3139146A - Suspension system for sonic well drill or the like

Info

Publication number: US3139146A
Application number: US833784A
Authority: US
Inventors: Jr Albert G Bodine
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-09-21
Filing date: 1959-08-14
Publication date: 1964-06-30
Anticipated expiration: 1981-06-30

Description

June 30, 1964 A. G. BODINE, JR

SUSPENSION SYSTEM FOR SONIC WELL DRILL OR THE LIKE 3 Sheets-Sheet 1 Original Filed Sept. 2l, 1956 xii INVENToR. Azmr G50/mfr. Je.

BY A

inl/15545151. IIIIII-Il A fram/y June 30, 1964 A. G. BoDlNE, JR 3,139,145

SUSPENSION SYSTEM FOR SONIC WELL DRILL OR THE LIKE Original Filed Sept. 2l, 1956 5 Sheets-Shee .2

v /05 5.4 A w /00 gi /62 I sa 5 V u INVENTOR. ,4.4 55m a//s/f, Je.

Jll'ne June 30, 1964 A. G, BOBINE, JR 3,139,146

SUSPENSION SYSTEM FOR SONIC WELL DRILL OR THE LIKE Original Filed Sept. 2l, 1956 3 Sheets-Shee 3 ll w...

Jaar/2 5/ United States Patent O 3,139,146 SUSPENSON SYSTEM FOR SONIC WELL DRILL R THE LIKE Albert G. Bodine, Jr., Sherman Oaks, Calif. (7877 Woodley Ave., Van Nuys, Calif.)

Original application Sept. 21, 1956, Ser. No. 611,131, now

Patent No. 2,903,242, dated Sept. 8, 1959. Divided and this application Aug. 14, 1959, Ser. No. 833,784

2 Claims. (Cl. 17d-56) This invention relates to suspension systems for sonic vibratory devices in general, and, in Van illustrative application, to a suspension system for a so'nic well drill.

The principally known sonic drill of the class here referred to, disclosed and claimed in my Patent No. 2,554,005 (sometimes known as a half, or full, wavelength drill, though it can be any multiple of half wavelengths), comprises an elastic column such as a section of heavy steel drill collar suspended from a conventional drill string, the collar being coupled at its lower end to a drill bit, and a longitudinal sonic standing wave being maintained in this collar by a suitable mechanical oscillator coupled thereto. free pattern whereby velocity anti-nodes occur at both ends thereof. The velocity anti-node condition at the lower end is useful in the vibration at this point is required in order to vibrate the bit. node at the upper end, however, in absence of countermeasures, undesirably sends sonic waves up the `drill string. Such leakage of sonic waves up the drill string represents a serious loss of sonic energy, and vibration of the drill string is in any event highly undesirable for obvious reasons.

The sonic drill assembly may comprise an elastic vibratory column made up of from one to several hundred feet of drill collar, in addition to the bit, oscillator, and oscillator drive. It is accordingly very heavy, and the means by which this assembly is suspended from the drill string must be robust, as well `as having the necessary compliance so that no restraint against vibration of the sonic drill is imposed thereby. A prime'requisite is that this suspension means must be of such nature as will 'eiiectively isol-atethe vibratory drill assembly from the drill string, since, of sonic energy up the drill string represents a serious power loss, shakes the derrick, and is generally undesirable. The suspension means must also, of course, be very 4fatigue resistant. Still further, in a rotary drilling system, the suspension means must be capable` of transmitting torque, and it must have provision for conducting a stream of drilling fluid. Moreover, it usually must be of such design that it can Vaccommodate variable loading of the drill collar by either pushing or .pulling on the drill string.

A general object of the present invention is the provision of an improved sonic drilling system wherein vibrations are prevented from transmission from the vibra tory drilling assembly to and uprthe supporting drill string. l

A further object is the provision of amode of suspension of a sonic drill from a drill string involving coupling to a velocity node, or stress anti-node, of the vibratoryl assembly. l

A still further object is the provision of a sonic drill wherein the upper end region of the `vibratory assembly is the location of a stress anti-node, to which the drill string is directly coupled.

A further .object is the provision of a suspension means for a half or full wave type of sonic drill assembly, to be interposed between the drill assembly and the drill string, characterized by` effective isolation of the vibratory drill assembly from the drill string.

This standing Wave is a free-` The velocity anti` as stated above, transmission ICC A further object is the provision of a suspension means as defined in the preceding object, having sucha degree of dynamic compliance that Ysubstantially no restraint to vibration is imposed thereby upon the sonic drilling assembly.

A still further object is a suspension system having low damping.

A still further object is` the provision of a suspension means which is fatigue proof over long periods `of service.

A still further object is the provision of a suspension system for a half or full wave son-ic drill, designed als'o for effective transmittal of torque, for conduction of drilling uid, and for accommodation of imposition oteload by the drilling string, or reduction of load by exerting tension in the drill string.

Further objects of the invention are the provision of corresponding improvements in suspension systems for other vibratory systems where corresponding or 'analogous conditions and problems are encountered and must be met.

Generally stated, the present invention contemplates coupling of the supporting drill string `directly to a velocity node (stress anti-node) i.e., a region of high mechanical impedance, of the elastically vibratory system of the sonic drill. The concept of mechanical impedance will be understood -to signify, in a mechanical, elastically vibrating system, the ratio of cyclic peak 'force acting at any given point in the system Vto displacement velocity at that point in the system. It will be seen that a `region of high mechanical impedance is one at which cyclic force amplitude is maximized, but displacement velocity, and therefore also vibration amplitude, is minimized, or reduced substantially to zero. It will be seen that coupling of the drill string directly to a stress anti-node of the sonic drill, in accordance with the invention, is in direct contrast to some prior sonic drilling systems of the'half wave type, wherein the upper end portion of the vibratory system is the location of a velocity anti-node, and the drill string. It may be noted in passing that efforts have been made to introduce vibration insulators between the vibratory upper end portion of a half wave or full wave type sonic drill and the drill string, `but-that, as experience has demonstrated, such attempts, because of the high power involved, have met with `great d-itliculty. Good drilling rates have been attained, but relatively severe Vibration of the drill string has not been prevented when drilling `at high power.

Referring now particularly to the half or full wave type of Vsonic drill, broadlyconsidered, the invention contemplates, as lstated above, the coupling of the -drill string directly to a velocity node, or in other words to a stress anti-node of the vibratory system. It will be recalled that a half or full wave `sonic drill has velocity antinodes (regions of maximum vibration amplitude) at thel upper and Alower ends of its elastic vibratoryrcolumn (from which circumstance such aicolumn is described acoustically as a free-free bar or column) and `that the first velocity node, or stress anti-node, is spaced a quarter wavelength distance down from the upper end. Accordingly, in one form `of the invention, the drillstring isattached to -the vibratory assembly at-such stress anti-node region, located a quarter wavelength distancedown from` ing a region of high mechanical impedance, whereat it,`

is attached to the drill string, and `having also a region `of low mechanical impedance, whereat it is coupled to a low impedance region of the elastic column of the sonic drilling assembly. By use of a suspension system having high impedance at its drill string attachment point, there results minimal acoustic coupling to the drill string above; and by the provision of a suspension ysystem having low impedance at its point of connection to a low impedance region of the sonic drill assembly, there is offered minimal blocking impedance to the sonic drill. Y

Mechanical impedance is, ofcourse, the vector resultant of resistive and reactive components. The resistive component can be made low by providing for low damping, The reactive component at the point of coupling to the drill can be made low bytuning the suspension system to resonance at the frequency of operation of the drill, either fundamental, orharmonic, depending upon which is to be combatted. This may be done by a suitable choice of mass and compliance within the suspension, eg., in a lumped constant system, by Vsuch a relationship of mass to elastic compliance that the system is selectively frequency responsive, or resonant at the operating frequency of the drill. VIt may also be accomplished v by use of a distributed constant system having such mass, elasticity, and distribution yof both mass and elasticity as to provide a resonant standing wave system that is frequency responsive tothe operating frequency of the drill. Such a system has both velocity anti-node and pressure anti-node regions, the former a region of low impedance, affording a suitable coupling point for the drill, and the latter a region of high impedance which affords a suitable coupling point for the drill string.

One physical example of the last mentioned type of Y suspension system, having such acoustic properties, corn- Vprises a heavy mass directly coupled to the drill string,

. additional configurations are within the scope ofthe invention, and some of these will be described hereinafter.

Another formrof the present invention involves a modication in the configuration of the sonic drill which facilitates direct coupling of the drill string to the stress anti-node region of the drill, this form of sonic drill hav- Ving-been first disclosed in my prior application Ser. No. 442,805, led Iuly 12, 1954, entitled Polyphase Sonic Earth Boring Drill and Process, of which the present application is a continuation-in-part. This configuration results from the folding of a half wave sonic drill into a doubley (or plural) legged elastic bar structure, the inidpoint of which is uppermost, with the legs, of quarter wavelength, depending therefrom. The resulting structure may form-an inverted U or a depending fork, or two concentric legs joined at thetop. The now uppermost midpoint ofthe structure remains the location of a stress anti-node, or velocity node, after the described folding In accordance with the present inventiomthe drill stem is then directly coupled to this non-vibratory uppermost midpoin of the plural leg structure. Analyzed acoustically, I have provided a plurality of coupled acoustic` supi port elements (acoustic elastically vibratory bars) operating with a balanced phase difference and joined at respective high impedance regions to achieve a non-vibra-V tory support point,`which is therefore incapable of transmitting'vibration'al energy into any means coupled thereto; and -I have rdirectly coupledthe suspension drill stringV illustrative embodiments of the invention:

FIG. 1 is an elevational View of a typical half wave sonic drill assembly showing a fragmentary lower end portion of a suspension means in accordance with the invention;

FIG. 2 is a view partly in elevation and partly in section, with longitudinal portions of the sonic drill assembly broken away, showing one illustrative suspension means according to the invention, coupled to the sonic drill of the type represented in FIG. l;

FIGS. 3, 4, 5 and 6 are views similar to FIG. 2, but showing modifications; Y

FIG. 5a shows a modification of a portion of FIG. 5;

FIG. 7 is a View, partly in elevation and partly in section, showing a lumped constant type of suspension means for a sonic drill;

FIG. 8 is an elevational view, partly in section, showi ing another embodiment of the invention;

FIG. 9 is a longitudinal medial section of the embodiment of FIG. 8, extending downwardly to a point just below the head of the fork structure;

FIG. l0 is a longitudinal medial section of theV lowy end portion of the embodiment of FIG. 8;

FIG. l1 is a section taken on line 11-11 of FIG. l0; FIG. 12 is a bottom elevational View of the embodiment of FIG. 8;

FIG. 13 is a section taken on line 13-13 of FIG. l0; FIG. 14 is a section taken on line 14-14 of FIG. l1; and Y FIG. l5 is a section taken on line 1S15 of FIG. 1l. Referring first to FIG. l, numeral 10 designates generally a typical half wave sonic drill assembly, comprising, in this instance,v an elastic column, rod or bar,rmade up of three more or less conventional drill collars 11, connected'to one another by' conventional drill collar couplings 12, and bit 13 coupled to the lower-most drill collar 11, and an oscillator and driver or powerV means therecollar. in the form of a plurality of rotating eccentric weights,

' so arranged that while longitudinal components ofvistring. This bar 18 has circulation boreV 19 for drillingv end portion of the drill string is indicated at 16, and be-V tween this drill string and the sonic drill is intercoupled the suspension system or isolator I of the invention. This isolator includes a massive'tbar 18, conventionally'coupled, as indicated at 18a, to the lower end of the drill fluid. In a typical embodiment, the bar '1S may be of a v length of, for example, 40 feet, an outside diameter of Vof operation of the drill.'V

eight inches, and may comprisea section of conventional drill collar. The isolator further includes a relativelyV slender pipe 20, of a typical length of approximately70 to feet, and which may comprise two intercoupled sections of conventional drill pipe, coupled at its upper end to thelower end of bar 18, and at its lower end to oscillator and power unit 14, all as clearly indicated in FIG. 2. Assuming the sonic drill assembly 10l to vibrate in its fundamental half wavelength standing Wave mode, and to have an over-all length of feet, it will be seen that the slender pipe section 20 is of quarter wavelength (or slightly more, in view'of the fact thatthe massof bar 18 is not innite) for the fundamental .resonant frequency responsive to the drill.

In operation and still assuming the sonic drilling as-, sembly 10. to vibrate in a half-wavelength mode, the

slender', elastically compliant pipe section Zt) then vibrates at the sameifrequency in a quarter Wavelength mode, its

l It is, in other words, frequency.

vibrating vertically in consonance with the vertical vibration of the upper end portion of the sonic drilling assembly lt). The intercoupled lower end portion of pipe 20 and upper end portion of drilling assembly Will be seen to be at a velocity anti-node of the vibration system, and the intercoupled upper end portion of pipe 2t) and massive bar 18 to be at what is effectively a velocity node, or stress anti-node, of the system. The massive bar 18 will further be seen to be a region of the system characterized by high mechanical impedance, and the point of interconnection between the lower end of pipe 20 and sonic drilling assembly 1t) to be a region of low mechanical impedance of the system.

Under the conditions as stated, bar 18 remains rm and steady, and does not transmit material vibratory energy up the drill string 16. The pipe 20, however, is a relatively compliant member for the critical frequency, and its lower end portion vibrates naturally in consonance with the vibration of the upper end portion of the sonic drilling assembly, so that the vibration of the latter is unirnpeded. It will be observed that Aby having given the pipe 20 effectively a quarter wavelength for the natural resonant frequency of vibration of the sonic drilling assembly, it has been pre-tuned, in combination with mass 18, to vibrate resonantly at the fundamental frequency of 0peration of the sonic drilling assembly. It accordingly participates in the wave action generated in the sonic drilling assembly without presentation of material blocking impedance. It will further be observed that the bar 18 and compliant pipe section 20 are adapted equally for imposing compressional loading on the sonic drilling assembly, or for exerting tension thereon, thus not intertering with controlled application of bias loading on the sonic drill. It will further be evident that the system is one of low damping, and therefore of low energy dissipation.

As described in the immediately preceding passages, the suspension system has been tuned to respond to the fundamental resonant frequency of the sonic drill. However, the sonic drill may have important and sometimes troublesome overtone frequencies, and it will be evident that the suspension system, or isolator, may alternately be designed to respond critically to these. Such overtone frequencies may be initially induced, or may be stimulated and/ or augmented by striking of the bit against the rock. For example, assuming that it is the second harmonic of the sonic drill that is to be combatted, the isolator device, instead of being a one-quarter wavelength device for the fundamental frequency of the sonic drill, is made to be a quarter wavelength device for the second harmonic of the sonic drill. In other words, the length of its elastic column for this case is halved. Also, I may `use two of the suspension systems in tandem, one dimensioned for critical response to the fundamental, and the other for critical response to the harmonic.

AAs mentioned above, the sonic drill may be designed for full wavelength vibration, in which case the elastic column, or drill collar, 'has a velocity anti-node at each end, and another velocity anti-node at its niid-point.- If the operatingfrequency remains the same Vas for the half wave case, the length of the drill collar is doubled, and becomes 280 feet. The length dimension for the isolator, however, remains the same, since the length of a quarter wave along the system has not been altered. The same.

result would Vfollow for a sonic drill having a collar length of one and` one-half wavelengths. It might be here mentioned that for increasing the weight on the bit a full wavelength sonic drill is desirable and quite feasible, as isa system of one and one-half wavelengths; and that for these cases, it is `advantageous lto maintain the frequency by operating at the higher harmonic, so asto b e thus able to increase the over-all length of the system without lower'- ing the operating frequency. It is also to be pointed out that when operating a sonic drill at a frequency to give one full wavelength performance, for example, a half 34 are -mtercoupled to oneanother, and to the lower end wavelength mode, as well as higher harmonics (second harmonic and above) may be set up therein by reason of impacting against the formation. Isolators properly dimensioned for response to any or all such frequencies may obviously be used in the system.

It will be seen that for each example given above, the isolator is dimensioned for quarter wavelength performance at the critical frequency of the component of vibrationof the drill that is to be combatted. In terms of impedance, it has a low impedance where connected to the drill, and a high impedance where connected to the drill string. It should further be understood that these impedance characteristics are self-contained characteristics in the isolator, at the critical frequency for which it is dimensioned, and are not contributed to by either the sonic drill or the drill string. The requisite is that the impedance of the isolator where connected to the sonic drill be low, i.e., comparable to the low impedance of the sonic drill at the connection point, so as to present minimal blocking impedance to the drill; and that the impedance be high at the point of connection to the drill string, so as `to have minimal vibratory motion at that connection point, and therefore minimal acoustic orI vibratory coupling to the drill string.

FIG. 3 shows a modified isolator I1, the same type of sonic drill again being designated by numeral 10, and comprising a column of drill collars 11` and bit 13, and oscillator and driver 14. At the top of the figure is fragrnentarily illustrated the lower end portion of a massive bar 36, formed with circulation bore 31, and this bar, like bar 18 of FIG. 2, may comprise a section of conventional drill collar of a typical length of 40 feet, it being further understood that the upper end of collar 30 is coupled in conventional manner to the drill string above, not shown in FIG. 3, but understood to be arranged in a manner similar to that shown in FIG. 2.

Screw-threaded onto the -lower end of collar 30 is a long suspension sleeve 32, whose lower end is furnished with an internal screw-threaded coupling to the lower end of a relatively slender opstanding pipe column 33 reaching nearly to the lower end of collar 30. This pipe column 33 may conveniently comprise two intercoupled lengths of `conventional drill pipe, as illustrated, suitable annular working clearance being provided between pipe 33 and sleeve 32. A slender pipecolumn 34, equivalent in length and cross section to the pipe 33, is coupled to the lower end of pipe 33 below the lower extremity of sleeve 32, and its lower end is coupled to oscillator and power unit 14 of the sonicdrill, as indicated. This pipe 34 may also be composed of two lengths of conventional drill pipe, the lower end of the lower length being adapted for coupling into the larger'diameter unit 14.

Assuming the sonic drill assembly 10 again to vibrate in a 4half wavelength standing wave mode, i.e., as a freefree bar, and 4to have an over-alllength,ofl40feet, pipe sections 33 and 34 each may have a length of approximately 7 0 feet, and Veach is accordingly of quarter wavelength for the `fundamental resonant frequency of operation of the drill. In other words pipe sections 33 and 34 taken together comprise a half wave system, being 'effectively `what is known in acoustics as a free-free bar, whereby the whole vibrating system is one full wavelength.

In operation, with sonic drilling assembly 10 vibrating in itshalf wavelength mode, the elastic suspension column made up of pipe sections 33 and 34 vibrates also, at the same frequency, in a half Wavelength mode, `its lower end vibrating in consonance with the vertical vibration of the upper Vend portion of the sonicdrilling assembly 10, its upper end vibrating equally and oppositely` thereto, and its center section, where the two pipe sections 33 and of suspension'sleeve 32, standing substantially stationary. The two pipe sections'33 and 34 thus are dynamically opposed to one another during this vibratoryoperation. The intercoupled lower end portion of pipe section 34 and stantially equal to the length of the 7 Y the upper end portion of drilling assembly 1t) are then at a velocity anti-node of the over-all vibratory system, the upper end portion of pipe 33 is at another velocity antinode of the system, and the intercoupled lower end portion of pipe 33 and upper end portion of pipev 34 are at a velocity node of the system. Each velocity anti-node Will be at a low impedance region of the vibratory system, and the intercoupled end portions of pipes 33 and 34 vare at a region of high mechanical impedance'of the system. Sleeve 32 is somewhat exiole and elastic, and of substantially quarter wavelength (or slightly longer in View of the fact that the mass 30 is not infinite) for the fundamental resonant frequency of the system. Accordingly, any small remaining vibration in the high impedance region where the pipes 33 and 34 are coupled to point between collar 30 and sleeve 32 functions as aV highly rigid anchorage, and transmission of any vibratory energy up the collar 30 is reduced to negligible amplitude. The isolator, considered as a unit apart from the remainder of the system, will be seen to have a point of low impedance for the criticalrvibration frequency Vwhere it is to' be connected to they sonic drill, ie., of magnitude comparable to the low'order of impedance magnitude at the top end of the drill, and a high impedance' region at its mid-point, where theY pipe column 33, 34 is hung from the sleeve 32. The sleeve 32, in turn has a relatively low impedance where connected to the column 33, 34, such that any small vibration at this junction point can beV transmitted to the sleeve. The Ymass 30 at the top, however, is of very high impedance, and holds the upper end of sleeve 32 rigid, such that-a small amplitude quarter wave type vibration can occur in the sleeve, but is blocked from upward transmission by the mass 30. As with the systemof FIG. 2, the system of FIG. 3 may also be adapted for critical response to a harmonic component of standing wave vibration present in the over-all wave pattern of the sonic drill. To design it for critical response to the first overtone, for example, the length ofthe pipes 33 and 34 and ofthe sleeve 32 are simply halved. The discussion given above of the various modes of vibration ythat can occur in the sonic drill, and the dimensioning of the isolator for critical response'thereto, applies here in similar manner. Y f

FIG. 4 shows another embodiment of suspension means or isolator I2 in accordance with the invention, the sonic drill, of the same type as in the preceding gures, being again designated by numeral 10, and being made up of components as before, bearing the same reference numerals. Coupled to the upper end of oscillator and driver unit 14 for the sonic drill is the lower end of a long, heavy section, elastic pipe memberfi, Whose length, assuming it to be designed for critical response to the fundamental resonant frequency of the sonic drill, and assuming' the drill to be driven in its half wave mode, is subsonic drill assembly l0. This piper40 is here shown to be of the same outside diameter as the drill collars 1l. At its midpoint, the

pipe 4ll`has an internally reduced and internally screwthreaded section'41, into which is coupled the screwthreaded coupling pin on the lower extremity of elongated drill pipe 42, suitable annular clearance being provided between pipe 42 and the bore of pipe 40, as illustrated.

Y 34 of the embodiment described immediately above. ThatV is to say, the lower end portion of pipe 40 vibrates in 'con-v sonance with the upper end portion of the sonic drill,

the upper end portion of pipe 4t) vibrates in opposition to the lower end portion of said pipe, and the intermediate section of pipe 4d stands substantially stationary. In acoustic terms, the lower and upper end portions of pipe 4t) are low impedance, velocity anti-node regions, while the intermediate section of the pipe is a high impedance, velocity node region of the system. The high impedance intermediate section of pipe 4i) thus standing substantially stationary, vibrations in the sonic drill assembly and in the upper and lower regions of the pipe 4t) are isolated from the drill pipe 42.. The fuller theoretical discussion given in connection with the earlier described embodiments applies here as Well.

With further reference to FIG. 4, the isolator I2 shown therein has been properly described in the foregoing as a device interposed between the `upper end ofthe elastic collar column of a half wave sonic drill and the lower end of apdrillstring. It is also correct. however, to view the interposed isolator device as a half-wave length upward extension of the elastic drill collar or column of the sonic drill, thus converting the elastic column of a half-wave sonic drill, for example, to full wavelength, with provision being made for direct coupling of the drilling string to the stress anti-node regionat the mid-point of the said half wavelength extension. The device I2 may, indeed, be readily fabricated from two drill collars, connected by a double-pin sub, to which sub the drill string is coupled by a suitable threaded joint. In short, the embodiment of FlG. 4 may be regarded, broadly, as made up of a free-free vibratory elastic column, with a drill string suspension coupling attached directly to an intermediate high irnpedance or stress anti-node region of the column. Moreover, the column length may be equal to any number of half wavelengths, including unity.

FIG. 5 shows another embodiment, used again with a sonic drill comprised of drill collars ll, bit 13, and oscillator or Vpower unit 14. The suspension system in this case contains components similar to those of the system of FIG. 2, including drill collar l suspended fromv drill pipe 16', and slender pipe Ztl coupling the lower end ofV collar 18 to the lupper end of the sonic drill. The lengths of the members may also be as in FIG. 2. That is to say, pipe 2h is of quarter wavelength Vfor the resonant frequencyfof interestof the sonic drill. The embodiment of FIG. 5 differs from that of FIG. 2 in that an elastic sleeve 45 surrounds the pipe Ztl', its upper end being firmly joined, as by a suitableA screw-threaded coupling,`

condition depending upon the heavy massafforded by .the collar 18'. The collar 18' provides a substantial blocking impedance for the vibratory energy otherwise traveling'up the system. Considering now the pipe 45, this added component furnishes a dynamic'means forbalancing Y the vibratorystanding waveaction in the pipe 20', and

may be used either together with massive collar 18', for

additional stability and'isolation, or as an alternative therefor. Accordingly, considering the system in absence of the heavy mass afforded by the collar 18', it is found that. the quarter wavelengthelastic sleeve 45, extending downwardly around the quarter wavelength pipe section 20', is set into quarter wave standing wave action in4 phase opposition tothe standing wave experienced by the pipe 20.V Thus, as pipe 20 elastically contracts, sleeve 45 Yelastically elongates, and vice verse. By designing the sleeve 45 to have elasticity and mass distribution equivalent to that of pipe 20', the upper'end juncture of the two stands substantially stationary, and becomes a high impedance, velocity nodal region of a folded 1/2 wavelength standing wave system. The performance is analogous to that obtained with the system of FIG. 4, with the exception that the two quarter wavelength portions of the system of FIG. 5 comprised of the pipe 20 and sleeve 45, which are again in phase opposition, lie alongside each other, such that longitudinal forces are again everywhere dynamically balanced. The upper end juncture of pipe 20 with sleeve 45 accordingly stands sub stantially stationary, and is a point to which the drill pipe above might be directly attached. It is deemed of further advantage, however, to include the heavy drillwcollar 18' so as to have an additional inertial type of high impedance in the system, which affords additional assurance of substantially total isolation of the vibratory system from the drill stem.

FIG. 6 shows still another embodiment of the system, using again a sonic drill 10 including oscillator or power unit 14, drill collars 11, and bit 13. In this case, as in FIG. 2, the drill pipe 16 is coupled at its lower end to a massive drill collar, here indicated at 50, and a compliant coupling 51 whose effective critical frequency is made responsive to the resonant frequency of interest of the sonic drill.

For compactness the coupling 51 is formed of three telescoped tubular elements, an outside tube 52 screwthreadedly attached at its upper end to the lower end of collar 50, an intermediate tube.53 annularly spaced inside tube 52 and screw-threadedly connected at its lower end to the lower end of pipe 52, and an inside pipe 54, annularly spaced inside intermediate pipe 53, and screwthreadedly connected at its upper end to the upper end of pipe 53. The lower end of pipe 54 is coupled to the upper end of the sonic drill, as shown. The total elective length of the three sections 52, 53 and 54, is made equivalent to a single, straight quarter wavelength pipe. Owing to the doubling back or folding of the coupling, however, the total over-all length of the coupling for quarter wave operation analogous to that of FIG. 2 is generally found to be somewhat less than that of a straight pipe. This is a matter depending somewhat upon the masses of the coupling elements and the mechanical design, which cause the system to behave somewhat as one having lumped constants, with resulting reduced length for the same resonant frequency. Frequency response, however, is equally important.

The elastic coupling 51 behaves essentially as does the coupling pipe 20 of FIG. 2. However, the inside pipe 54 and outside sleeve 52 are always in tension, or compression, at the same time, whereas the intermediate member 53 is in compression while members 54 and 52 are in tension, and is in tension while members 54 and 52 are in compression. The members thus cooperatively elastically contract, or elongate, as the casemay be, to give a folded quarter wavelength performance which is the equivalent of that of FIG. 2. Of course, the amplitude.

of elastic elongation and/or contraction is a maximum at the lower end portion of thelinside pipe 54 and progressively diminishes to substantially zero at the point of coupling of the outside pipe 52 with the collar 50.

It will be seen that in .the system of FIG. 6, the circulation fluid passes through the bore of collar 50, to be received by pipe 54 and thence conducted to the sonic drill.

FIG. 7 shows a lumped constant type of isolator suitable for a free-free sonic drill, and which is analogous in basic respects to that of the standing wave systems of the first described embodiments. In this case, the lower end portion of a drill collar (which may be similar, for example, to the drill collar 18 of FIG. 2, and may be similarly suspended from the more slender drill pipe above) has been formed at its lower end with a threaded pin 61 which is screwed into the threaded box 62 of a tool joint 63 integrally joined with the upper `end of heavy helical spring 65. Integral with the lower end of spring 65 is a tool joint 66 having threaded pin 67 adapted to be screwed into a coupling box at the upper end of a sonic drill such as represented in the earlier figures of the drawings. The spring 65 is here shown to be furnished with a fluid pipe whose upper extremity is received in a bore 71 extending up into tool joint 63, an enlarged threaded bore 72 above bore 71 receiving an annular ange 73 on the upper extremity of pipe 70, and a threaded retaining ring 74 being screwed into bore 72 to fix the pipe 70 in assembly with the upper tool joint 63. The lower end portion of pipe 70 is slidably received within a bore 74' extending downwardly into tool joint 66, suitable packing being used at 75, as clearly shown.

This helical spring isolator is designed with such mass and elasticity constants as to have a natural resonant vibration frequency matched to the vibration frequency of interest, fundamental or harmonic, of the sonic drill to which it is coupled. This is determined by the formula in which m is equivalent mass, k is effective spring constant and f is the frequency to be isolated. Such frequency to be isolated. Such frequency response match having been provided, the spring elongates and contracts in consonance with the vertical vibration of the upper end of the sonic drill, the upper end of the spring, where connected to the massive collar 60, standing substantially stationary. Circulation uid is conveyed through the spring by the pipe 70, previously described as ixedly mounted within the tool joint 63 at the upper end of the spring, and fitted for relative sliding movement within the lower tool joint 66.

Reference is next directed to FIGS. `8 to 15, showing an illustrative plural -legged quarter wavelength sonic drill with an uppermost common high impedance stress antinode region, and direct coupling between the drill string and such high impedance region. The illustrative drill shown employs a leg structure comprising a center leg and an outside tubular leg depending from a unitary head. This embodiment utilizes an unbalanced rotor type of vibrator in one leg, in this instance, in the lower portion of the centerleg, and this vibrator is driven by a turbine which is located above the head of the structure and which is driven by the circulated mud iluid conventionallyl used in oil well drilling.

At 100 is designated a relatively long, steel tubular' formed at the top with a threaded box 101 for coupling to a conventional drill pipe string, indicated fragmentarily at 90. In most cases, the drill string includes one or more standard drill collars a, coupled to the upper end of member at box 101, giving added weight on bottom, and the conventional drill pipe is then coupled to the upper end of these collars. The lower end of the member 100 has a threaded box 102 into which is screwed the coupling pin 102a on the upper end of a cylindrical member 103 forming the lower end portion of the outside leg structure. This member 103 has a central longitudinal slot 104 running nearly from end to end, in which is received, with good clearance, a vibrator housing 105,

later described in more particular. `The lower end portion of. body 103 is tapered outwardly, as at`106, to furnish a tubular lower extremity 107 of somewhat enlarged diameter, and inset in this .lower extremity are hardened bit elements as indicated typically at 108.

The'vibrator mechanism inside housing 105 is driven through a long vertical transmission shaft 109 from a mudfdriven turbine 110 housed in the upper endportion` of tubular member 100. The bladed turbine stators 111 are supported within the tubular member 100 by means ofa shoulder formed at` 112, and the stators are separated by intervening spacers 113. Engaging the upper stator 111 is a sleeve 114, held in place by a retainer 115 screwed into box 101, and provided with radial vanes or ribs 116 supporting a central distributor hub 117 shaped to guide the mud fluid from above downwardly to the turbine blades, as indicated. The turbine shaft 124i has near its upper extremity a tapered section 121 on which is tightly mounted' a turbine rotor head 122, the latter having a downwardly extending sleeve portion 123 formed with an outwardly extending flange 124 at its lower end. Mounted on sleeve 123 and supported by the flange 124 are the bladed turbine rotors 125, separated by spacers 126. A cap 127 engages the top rotor andthe parts are held in assembly by means of a nut 128` screwed down onto the threaded upper extremity 129 of the turbine shaft. The blades of the stator and rotor of the turbine will be understood to be properly inclined, in accordance with conventional practice in fluid` driven turbines.

The section 120:1 of the turbine shaft'is furnished with suitable packing, as indicated at 1,30, carried by a reduced tubular upward extension 131 of a tubular bearing housing 132 annularly spaced inside the tubular exterior memberl 100 by positioning lugs 13211 formed on said housing, the extension 131 being received, with clearance, inside the turbine rotor sleeve 123, as indicated. The annular space 134 between the bearing housing 132 and the outside tube i) forms a channel for the mud fluid dischargedfrom the turbine, Below the section 129e, the turbine shaft has a flange or collar 135 -furnishing a shoulder which engages a washer 136 supported by the inner race ring of the uppermost of a stack of roller bearings 137, the lowermost being retained by a nut 158 threaded on the shaft. The outer race rings of these bearings are received in a bore in the housing 132, and. supported therein by a re` tairier 139. y

Threaded into the lower end of bearing housing 132 is the reduced neck of an oil housing 14), of the same diameter as bearing housing 132, the mud iluid channel 134 thus continuing down around the'outside of the housing .1149. The turbine shaft 120, whoselowerendportion frorrra point just below collar 135, and this bore is tapered downwardly within the portion 129k of the shaft,

as'indicated at 146f The turbine shaft portion 12011 isv also tapered downwardly, and itslOWerend is formed as a spur gear 147Y meshing with internal gear teeth 148 Vin a cup-like couplingmember 149 tightly mounted on the upper endl of transmission shaft 109. Oil ports 150 are provided in the lower portion of cup 149.

Oil is maintained in housing 140 to such a level as indicatedat L, and is supplied lthrough ports 150 to the bottom end of the hollow turbine shaft.` The aforementioned washer 136 is radially drilled, as at 151, and the turbine shaft is formed with drill holes 152 establishing Vcornrruinication between the interior of the hollow shaft yand thedrill holes in the washer. When the turbine shaft rotates, voil climbs in the tapered Vportions of the bore through centrifugal force, and fills the hollow turbine shaft up tothe level of the drill holesV 152. 'Oil is forced out through the drill holes 152, and thence out through the drill holes 151 in washer 136 to lubricate the bearings.

' The lower end of oil housing 140 is flanged and bolted, as'rindicated at 154, Vto corresponding ilange formations Y on the upper'end of a long, generally cylindrical steel shank or rod 155, .which forms va portion of the head and together to produce a tight wedge lit, and thus become structurally integrated to one another in the region of the tapered joint.

This'region of said members comprises the high impedance head structure -15j8 of the device. It is the location of a stress anti-node, .or velocity node, during operation.

I ust below Vthe taper, the internal diameter of bore member 1li@ is enlarged, as indicated at 159 (FIGS. 48 and 9), to provide a crotch and an annular mud fluid channel between the

members

100 and 155. This channel 169 receives mud fluid from channel 134 via a suitable number of passages 161 extending through the upper end portion 155a of the shank 155,1as clearly shown in FlG. 9. The channel is continued for a short distance down into member 163, as at 166:1 (FIG. l0), where communication is had via ports 161e with two longitudinal mud slots 162formed in opposite sides of the member 105 (see also FlG.V 14). The mud slots 162 are closed on the outside by cover plates 163 welded in position, as indicated, and discharge at their lower ends, via ports 164, into the space inside the lower tubular extremity 107 of member 1G13, from which linal'discharge takes place at the bottom of the well hole.

The shank 155 has acentral bore 165, extending downwardly from a similar bore 167 through-the bottom of oil housing 14@ and these bores receive bearing bushings 16S for transmission shaft 1G59, the bushings being spaced by sleeves 169. A plug 17d screwed into the top of bore 167 holds the bushings and spacers in assembly at the top,

.and has sullicient clearance-with shaft '169 to pass oil from housing leiidown into the space 171 around the shaft. Press fitted on the lower end of shaft 1119 (FIG. l0) is' a drive sleeve 172 having internal splines 173 meshing with splines 174'on vibrator drive shaft 175. The lower end of shank 155 is formed with an internally threaded box 180 Vto receive a threadedpin 181 on a flanged head member 182 at the upper end of the vibrator housing 165.

. The vibrator housing is longitudinally split into two halvesV 105e and 105i), bolt connected as at 183 (FIGS. l0, ll and 15). The two housing halves are formed with a plurality of mating shaft portions 184, `surrounded by bushings 1&5, and journalled on these bushings are eccentrically weighted vibrator rotors 187. In the illustrated embodiment, there are four such rotors 187, all in vertical alignment, and interconnected by suitable gears. Each rotor is formed ywith* a spur gear 188, and the spur gears of the two upper rotors are in mesh with 'one another, as are the spur gears of the two lower rotors. The lower gear of the upper pair is interconnected withthe upper gearof the lower pair through an idlerv gear member 189. The gear on the upper rotor is driven from the vibrator driveshaft'175 through a gear set 190.

TheV weights W of the unbalanced rotors are positioned so that allmove vertically in unison, which is accomplished if for instance they are all initially positioned with their weights at the bottom, as in FIG. 1l'. evident that each eccentrically weighted rotor will exert a thrust at its bearing as it rotates. Only the thrust in the verticaldirection is, however, useful. By arranging the rotors in pairs of oppositely rotating members, the

, vertical components of thrust are additive, while the lateral' components are cancelled. Also, by use of the idler 189, thetwo inside rotors tum in the same direction,- and the two'outside rotors also turn in the same direction, thus achieving balance against couples." Y f Vibrator shaft yis journalled in suitable bearings contained in a bearing housing 196 received in a bore 197 formed'in the upper end of vibrator housing 195, the housing 196having at the top alleinige-1,98 engaging the top end of housing 195. A packingv retainer 199 has a, similar flange 209 engaging the flange 198, and this re-v tiner contains a suitable'packing 291 around. Vthe shaft 175 toprevent oil from 'above leaking downinto the inside of the `,vibrator housing. A flanged packing retainer 202 is placed between the flange 2% and the aforementioned head member 182 (FIG. 11), the parts being secured in assembly by means of screws 205 passing down through head member'182 and flanges 202, 290 and 19d to engage in threaded socketsin thetwohalves of the: Y

vibrator housing.`

n win be Y A anged tting 210 is secured to the lower end of housing 105, as by screws 211, and .has a threaded coupling pin 212 engaging the threaded box 213 of an inside bit member 214, the latter being provided, in this instance with a hardened insert blade .215 extending transversely across the space inside the outside tubular part 107. The bit element 215 is here shown asV elevated somewhat above the outside bit elements 108, being designed to disintegrate large fragments of formation initially broken free by action of the outside bit elements 108. It will be evident, however, that the bit element 215 may alternatively be placed on a level with the elements 108, and no limitation to the illustrated arrangement is accordingly to be implied. Also the bit element 215 may be omitted, leaving the outside bit to do the work on the formation, the inside leg then being less damped, and contributing greater fly-Wheel effect to the system as a whole. Moreover, the drill can be arranged with a bit only on the inside leg, so that the outside leg functions as a counterbalancing vibrator, with minimum damping.

It will be seen that the drill of FIGS. 8415 forms a structure having a central leg formed by the shank 155 and vibrator, and an outside leg structure comprised of the centrally slotted body 103 and the portion of the outside tubular member 100 below the juncture of the latter with the shank member 155. The region of the member 155 and the member 100 wherein said members are integrated structurally to one another, in this instance by the long taper joint at 156, 157, forms the high impedance, stress anti-nodal head structure 158 of the device. The length of the legs below the head structure, i.e., from the crotch 159 to their lower extremities, has an essential relationship to the frequency at which said legs will vibrate, as mentioned earlier. For an operating frequency of 120 cycles per second, this leg length should be approximately 33 feet.

Operation is as follows: the turbine is driven by mud uid pumped down the usual drill string, the mud uid being eventually discharged to the bore hole at the bottom, and forming a iluid column rising to the ground surface around the drill string, in the usual way. The turbine shaft 120 drives the vibrator connected to the lower end of the central leg of the structure through the connections previously described, causing the Vibrator to create an alternating force in a vertical direction at a frequency dependent upon the speed at which the turbine is driven by the mud ow. This speed is governed by the rate at which mud uid is pumped through the drill string at the ground surface. The vertical alternating force developed by the vibrator is exerted on the lower end of the shank 155, which comprises the central leg of the structure. When the turbine is driven at such speed that the vibrator frequency approaches or coincides with the resonant frequency of the device, the shank 155 vibrates in the vertical direction with substantial amplitude. This frequency for resonant operation is given by the ratio where S is the speed of sound in the material of the structure and L is the length of the legs. Each of the legs is capable of elastic vibration in a longitudinal direction as a fixed-free bar of quarter wavelength, or odd multiple thereof, assuming it to be acted upon by an alternating force of resonant frequency. Such resonant elastic vibration is set up in the centralV leg by direct drive from the vibrator when operated at the resonant frequency. A velocity anti-node then exists at the lower end of the central leg, and at quarter wave spacing from the velocity antinode, a high impedance stress anti-node exists at its upper end, where it is structurally integrated to the outside leg, i.e., within the head structure 15S, as' earlier stated. The cyclic stresses so set up in the head or upper end juncture of the legs so react on the upper end of the outside leg structure 100-103 that sympathetic longitudinally elastic vibrations, like those in the central leg to which the vibrator is directly connected, are set up in the outside leg structure, but at phase difference. The result is that both the inside and outside leg structures undergo elastic elongation and contraction, their joined upper end structures standing substantially stationary, and their free lower bit-carrying ends reciprocating, the motions of the two leg structures being similar but at 180 phase difference. Thus the bit element carried by the lower end of the outside leg structure is descending, and vice versa.

As stated earlier, the unitary head structure for the legs is 4a high impedance region (stress anti-node, or velocity node), and is hence inherently substantially non-vibratory. This stationary head structure is of course at substantially one-quarter wavelength spacing from the oscillator in the lower portion of the central leg. Further, the turbine, located immediately above the head structure, can be `seen from the drawings to be located in a region substantially `one-quarter wavelength distance from the oscillator. Such location is of course desirable, in that the turbine is thereby located substantially at a node of the standing wave vibration in the leg structure, where it is protected against pounding vibration. Moreover, the drill string, coupled to this high impedance head structure point of the drill, is inherently isolated from the vibration in the drill structure. In this fundamental and generic respect, the quarter wave, fixed-free, drill of FIGS. 8-15 is an acoustic analogue of the free-free drill of FIG. 4.

In a more specific aspect, the drill configuration of FIGS. 8-15 is analogous also to the isolator configuration of FIG. 5. Viewing the device of FIG. 5 in this aspect, it can be seen that the central leg 20' and the concentric outside leg 45 comprise a unitary resonant circuit structure having a stationary node at the juncture with element 18. This unitary structure, viewed together with the oscillator and driver unit 14 for oscillatory drive purposes, and assuming the massive energy-storing vibratory collar 11 to be disconnected or omitted, would have a characteristic resonant mode of operation exhibiting the above mentioned stationary juncture point and also exhibiting outof-phase, or opposed, vibration of the lower ends of leg 20 (with unit 14) and leg 45. It then becomes possible, I have found, to add, in place of the eliminated heavy collar 11 a very light and thin walled tubing which becomes a part of and vibrates in the resonant circuit comprising the

members

20', 45 and 14. The elimination of the large mass of collar 11 causes the

legs

20 and 45 to become a major or substantial portion of the resonant acoustic circuit structure, thus tuning out the mass of the oscillator and drive unit 14. The substituted light tubing becomes a part of the

resonant circuit

20, 45 and 14, )and vibrates as a part of this circuit without wastage of force.

In FIG. 5a I have shown a modification of the lower portion of the system of FIG. 5, wherein. a thin walled tubing 11a, such as referred to above, has been substituted for the massive collar 11,

Members

20 and 45 are made fairly substantial, so as to handle substantial energy ilow and storage in the system, and the substituted light tubing 11a then need not possess great energy storage capacity. In the illustrative embodiment of FIG. 5a, the tubing 11a has a plain, flat end at the bottom, providing a thin annular edge in lieu of a drill bit. This configuration, I have found, will drill rapidly through the earth, and functions very well for taking cores at any chosen region. Moreover, by simply giving such thin walled element 11a a greater diameter than any other part of the drill, a continuous coring type of drilling operation can be carried out.

This application is a division of my original application of the same title, tiled September 21, 1956, Serial No. 611,131, now Patent No. 2,903,242.

A number of illustrative embodiments of the invention have now been described and are illustrated in the drawi 1 5 ings. It is to beV understood, however, that these are but representative of various forms in which the invention may be embodied in practice, and that various additional speciiic embodiments are within the scope of the claims appended hereto.

I claim:

1. In aV sonic well drilling system, the combination of: a drill pipe string, a resonant'elastically vibratory column of half-wavelength for the operating frequency of the drilling system attachment means connected to said drill pipe string for suspending said column from said drill pipe string and attached to said column at a velocity node thereof, an oscillator coupled to the lower end of said column, and a massive elastic drill rod having a bit on the lower endthereof, said drill rod being coupled to said oscillator for'vibratory` drive thereby at said operating frequency, said massive elastic drill rod combined with at least a portion of saidoscillator constituting an elasticallyvibrating drilling column having a length equal to a Whole number of half-wavelengths.

2. In a sonic well drilling system, the combination of a drill pipe string, a resonant elastically vibratory column of half-wavelength for the operating frequency of th drilling system attachment means connected to said drill pipe string for suspending said column from said drill pipe string and attached to said column at a velocity node thereof, an oscillator coupled to the lower end of said column, and a massive elastic drill rod having a bit on the lower endV thereof, said drill rod being coupled to said oscillator for vibratory drive thereby at said operating frequency, said massive elastic drill rod combined with said oscillator constituting an elastically vibratory drilling columnhaving a length equal to a Whole number of halfwavelengths.

References cited in the me of this parent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 139,146 June 30, 1964 Albert G. Bodne, Jr.

It s hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read es corrected below Column 15, line 10, and column 16, line 2, after "system-M each occurrence, insert a comma.

Signed and sealed this 16th day of March 1965o (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Altesting Officer CommissionerI of Patents

Claims

1. IN A SONIC WELL DRILLING SYSTEM, THE COMBINATION OF: A DRILL PIPE STRING, A RESONANT ELASTICALLY VIBRATORY COLUMN OF HALF-WAVELENGTH FOR THE OPERATING FREQUENCY OF THE DRILLING SYSTEM ATTACHMENT MEANS CONNECTED TO SAID DRILL PIPE STRING FOR SUSPENDING SAID COLUMN FROM SAID DRILL PIPE STRING AND ATTACHED TO SAID COLUMN AT A VELOCITY NODE THEREOF, AN OSCILLATOR COUPLED TO THE LOWER END OF SAID COLUMN, AND A MASSIVE ELASTIC DRILL ROD HAVING A BIT ON THE LOWER END THEREOF, SAID DRILL ROD BEING COUPLED TO SAID OSCILLATOR FOR VIBRATORY DRIVE THEREBY AT SAID OPERATING FREQUENCY, SAID MASSIVE ELASTIC DRILL ROD COMBINED WITH AT LEAST A PORTION OF SAID OSCILLATOR CONSTITUTING AN ELASTICALLY VIBRATING DRILLING COLUMN HAVING A LENGTH EQUAL TO A WHOLE NUMBER OF HALF-WAVELENGTHS.