US2824718A

US2824718A - Mud decoupler

Info

Publication number: US2824718A
Application number: US417032A
Authority: US
Inventors: Gardner D Currie
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1954-03-18
Filing date: 1954-03-18
Publication date: 1958-02-25
Anticipated expiration: 1975-02-25

Description

Feb. 25, 1958 G. D. CURRIE 2,824,713

MUD DECOUPLER Filed March 18, 1954 2 Sheets-Sheet 1 n; 65 I g frzv'enfbr Gardner D. Currie Feb. 25, 1958 G. D. CURRIE 2,824,718

MUD DECOUPLER Filed March 18, 1954 2 Sheets-Sheet 2 Gardnerfl Cur-rte d V'QF 4 a p g United States Patent DECOUPLER Gardner D. Currie, Altadena, -Calili, assignor to Borg- Warner Corporation, Chicago, Ill., a corporation of Illinois Application March 18, 1954, Serial No. 417,032

9 Claims. (Cl'.2554'.4)

The present invention relates ingeneral to earth bore drilling apparatus and more particularly: to an earth boring drill of the type employing a vertically reciprocating drill rod and bit which vibrate ata frequency substantially equal to the resonant vibration frequency or the rod and bit.

More particularly, the present invention is intended to provide an auxiliary device adapted to be utilizedzin i In earth boring apparatus of the typedisclosed in the aforementioned Bodine patent, suitable vibration generating mechanism is utilized for generating sonic vibrations in the drillrod and bitpin order to. provide the necessary force to effect the drilling operation. In suchndrilling devices, the vibratingbit is maintained in engagement with the bottom of the well ,hole and the formation immediately adjacent to the bit is shattered either due. to vibrations imparted thereto by the bit itself or due to thepercussive action of the bit on the formation. In a drill of this type the bit reciprocates or vibrates vertically:.at very nearly the resonant frequency of the'massive drill rod and bit and the amplitude of the vibrations of the drill rod and bit is of the order of three-sixteenths to approximately one-half inch.

As is customary in oil well drilling operations atsuitable mud fluid is pumped into the well hole downwardly through the drill string and drill rod, with the mud fluid emerging from the bottom of the drill rod being forced out of the well hole upwardly around the drill'rod-and drill string inside of the well hole. As the mud fluid rises in the well hole in this manner it takes with it the formation fragments which have been broken up by the bit. When the well hole reaches a depth of severalthousand feet, the hydrostaticpressure existing at the bottom of the well hole, due to the long column of mud fluid, is considerable and is of the order of several thousand pounds per square inch. Further, themud fluid is substantially incompressible. Due to this fact, without some means being provided for acoustically disconnectingor decoupling the mud fluid from the drill rod and bit, substantially all of the energy-which is put into the drill rod and bit by the vibratory mechanism is consumed 'by'the pressure-surges of the mud fluid in the well hole resulting from sound waves generated in the mud fluid at'the bottom of the well hole by the vibrating drill: rod and' bit.

An acoustical disconnecting or sonic decouplingdevice suitable for use with an earth boring drill of thettype disclosed in the aforementioned A. G. Bodine patent=and of the general type disclosed herein, is disclosed and claimed in the copending patent application of'J. P. Selberg and G. D. Currie, Ser. No. 360,706, filedlune 10,

1953, now Patent No. 2,771,270.

The present invention has for its principal 'objecrto provide an improved sonic decoupling device over-that which is disclosed in the aforementioned *Selberg and 2,824,718 Patented Feb. 25, 1858 v.2 Currie application and which will function to acoustically disconnectthe vibrating drill rod and bit from the column of mu'dfluid in" the well hole over a wide range of depths of the well. hole.

5 It will; be. realized that the hydrostatic pressure existing atthe bottom of the well'hole, by virtue of the long column of mud, therein, varies substantially and increases-asthe well hole depth increases or as the height of the column of mud increases. It is therefore necessary thatmeans be provided; for sonically decoupling the'drill rod andbit fromv the mud column over this wide range of hydrostatic pressures at the bottom of the well hole.

It is therefore a'more detailed object of the present inventionrto provide a sonic decoupling device for use with an earth boring drill of the vibrating type which sonic decoupling device comprises a compressible gas filled .chamber and which includes means for increasingthe pressureot. the gas in the chamber as the drill bores Ideeper into-.the earth in order to compensate for the greaterhyidrostatic mud fluid pressures as the bit or :drfllsproceeds downwardly into the earth formation.

" vA:still moredetailed object of the present invention uis. to provide aidecoupler in accordance with the preceding .object of the-present invention wherein a source of very :high pressure .gas is controlled by a differential valve "adapted to open 'whemthe-xmud fluid pressure increases to ca. predeterminedvalue, greater than the gas pressure in :order tokadmit moregas .into the compressible chamber sand thereby-more-near-ly. equalize the pressure of the gas in thexchamber with that of the outsidemud fluid pressure.

A stillfurther object of the present invention is to provide a sonic decoupling device in accordance with the preceding objects wherein the gas chamber of the decoujpling device has a gas pressure relief valve which is differentially controlled by the pressure of the gas inside the chamber and by the pressure of the mud fluid outside of :.the chamber and which relief valve is adapted to blow out "or open-when the mud fluid pressure drops to a predetermined value less than the gas pressure. It will be ap- -parent that this desirable feature of the present invention .makes itpossible to withdraw the sonic decoupling device from the well hole without danger to the drilling rig operators at the surface of the earth above the wellhole.

In this connection, it is contemplated that the pressure relief :device will open after the decoupler cellhas ascended -a portionof the distance between the bottom of the Well ,hole and the surface of the earth and thus the pressure within the gas filled chamber will be relieved so that there will not be any danger ofexplosion of the gas chamber after the decoupling device has been withdrawn from the well hole, which danger would otherwise be present in the .event such pressure relief device were not provided.

The foregoing objects and numerous advantages of the :present invention will become apparent from the follow- .ing detailed description when read in conjunction with .the accompanying drawings, wherein:

Fig. .1 is a more or less schematic illustration showing a typical installation of the surface equipment utilized in drilling the well hole and showing the drilling string -'.'dOWI1 to and including the bit with that portion of the .drill rod including the decoupler cell comprising the subject matter of the present invention-alsobeing shown;

Fig. 2,.is a fragmentary sectional view of'a decoupler cell incorporating the features of the present'invention;

Fig. 3 is ,a sectional view taken substantially along the line f3-3 of Fig. 2 and looking in-the direction of the arrows;

Fig. 4 is a sectional view taken substantially along the line 4-4 in Fig. 2 and looking in the direction of the arrows; and

"FigxS is-afragmentary enlarged sectional 'view'of one of the differential valves for controlling the supply of high pressure gas to the decoupler cells when the mud fluid pressure increases by a predetermined value above the pressure of the gas within the decoupler cell.

Referring now to the drawings, wherein like reference numerals in the different views identify identical parts, and with particular reference to Fig. 1, the equipment disposed on the surface above the well hole will first be described. This equipment is conventional and includes a derrick 10, draw works 11, driving rotary table 12, kelly 13 extending through table 12, swivel 14 coupled to the upper end of the fluid passage through kelly 13, and hook 15 supporting the bail of swivel 14. The hook 15 is suspended through a traveling block 16 and cable 17 from the top of the derrick 10, and the cable 17 is wound on the usual hoisting drum of the draw works 11. Mud fluid, such as is conventionally employed in rotary oil well drilling operations, is pumped through a supply pipe 18 from a supply tank or sump 19 and is delivered under pressure by a pump 20 through a'pipe 21 and hose 22 to the gooseneck of swivel 14, and from this point the mud fluid flows down through the kelly 13 and through a drill pipe string 23 coupled to the lower end of the kelly 13.

The kelly 13 and drill string 23 extend into a bore hole 24 which extends downwardly into the earth. The bore hole 24 is lined for a suitable distance down from the ground surface by surface casing 25 which is supported by a landing flange 26 resting on a concrete footing 27 in the bottom of a pit 28. A blow-out preventer 29 is mounted at the head of the casing 25 and a riser 30 above the blow-out preventer 29 is provided for a mud flow line 31. The mud flow line or delivery pipe 31 is shown as discharging onto a conventional vibratory mud screen 32 and the mud is drained from the mud screen 32 back to the sump 19 by means of a pipe line 33.

The drill pipe string 23 coupled at the lower end of the kelly 13 comprises a conventional drill pipe string and it will be understood that this pipe string is made up of a number of the usual drill pipe lengths coupled together by the usual tool joints. The drill pipe string 23 has an elongated massive drill rod 34 and bit 35 secured at the lower end thereof.

The drill pipe string 23 also includes suitable driving motor means and a vibration generator assembly. The motor means and vibrator assembly are of the type disclosed in the aforementioned patent to Bodine 2,554,005 and the details of operation and construction of the motor and vibrator will not be described in the present case. It will suffice to state herein that the motor and vibrator assembly are capable of vibrating the drill rod and bit below at a frequency approximately equal to the resonant vibration frequency of the drill rod and bit. For further description of the motor and vibrator, reference should be had to the aforementioned Bodine patent.

The entire drill rod 34 and bit 35 are acoustically disconnected from the rest of the drill string 23 and the derrick 10 by means of an acoustic isolator disposed at the upper end of the drill rod 34 and shown in detail in the copending application of H. V. D. Stewart, Ser. No. 417,117, filed March 18, 1954. No detailed description of this acoustic isolator is given herein as it is not necessary for a complete understanding of the present invention. Immediately beneath the motor and vibrator, the drill rod 34 is disposed, the drill rod comprising a massive elongated elastic longitudinally vibratory rod. The drill rod 34 is of substantial mass and length and it is contemplated that it will be made up of a plurality of steel drill collars which may be connected together by means of conventional tool joints. The lowermost drill collar of the drill rod 34 is provided with the sonic decoupler or acoustic disconnector cell comprising the subject matter coupler cell 38is provided for damping the surges of mud of the present invention and described in detail in conjunction with Figs. 25 of the drawings herein. Immeditherein is the bit 35 which may be of any well-known or desired type. The bit 35 is of conventional construction and detailed description thereof herein is not deemed necessary in order to understand the present invention.

The sonic decoupler, comprising the subject matter of the present invention will now be described. The sonic decoupler comprises an outer steel drill collar or sleeve 36 which is provided with a plurality of radially extending perforations or apertures 37 disposed adjacent an upper decoupler cell 38. An internal sleeve member 39 is concentrically positioned within the outer sleeve 36 and is adapted to seat against a suitable abutment ring 40 secured to the outer sleeve 36 by any well-known or desired means. The internal sleeve member 39 is threaded as indicated at 41 and 42 for the purpose of receiving a pair of cooperating

short sleeves

43 and 44 which are adapted to compress the annular ends of a cylindrical rubber bag 45 in order to hold the rubber bag 45 sealed with respect to the sleeve member 39.

The sleeve member 39 is annularly cut away, as indicated at 46, to provide an annular cavity or chamber 47 adapted to be filled with an inert gas. When the pressure within the chamber 47 is at the desired pressure with respect to the external pressure around the sleeve 45, the sleeve 45 is disposed substantially cylindrically as shown in Fig. 2. The outer sleeve or drill collar 36 is cylindrically cut away, as indicated at 48. The cutaway portion 48 of the sleeve 36 communicates with the apertures 37 so that mud from outside of the sleeve 36 may act on the outer surface of the rubber sleeve 45. It is contemplated that the pressure of the gas in the chamber 47 will be maintained substantially equal to the pressure of the mud fluid acting on the outer surface of the sleeve 45 so that the rubber sleeve 45 will tend to remain in substantially the same shape as is shown in Fig. 2.

A lower decoupler cell 49 much like the upper dcfluid within the interior of the drill rod. The lower decoupler cell 49 includes the interior sleeve 39 which is radially perforated at 50 and an intermediate sleeve 51 adapted to be threaded onto the end of the interior sleeve 39 and rigidly disposed within the exterior sleeve 36 is provided. The sleeve 51, when threaded onto the interior sleeve 39 seals a rubber bag or cylinder 52 at the annular ends thereof in order to provide a chamber 53 between the rubber sleeve 52 and the cutaway portion 54 of the sleeve 51. The chamber 53 is adapted to be filled with gas under pressure and the interior sleeve 39 is cut away as indicated at 55 for enabling mud fluid from within the sleeve 39 to act against the interior surface of the rubber sleeve 52. In operation, the

decoupler cells

38 and 49 function in substantially the same manner as the decoupler cells of the copending application of Selberg and Currie in dampening the pressure surges in the mud fluid both within and outside of the drill rod.

When the

decoupler cells

38 and 49 are first assembled preparatory to the insertion of the sonic decoupler into the well hole, they are charged with some inert gas, such as nitrogen, and brought to a pressure of the order of 1500 p. s. i., This pressure is considered to be safe while the decoupler cells are outside of the well hole with the outside of the dec'ouplers subjected only to atmospheric pressure and a pressure of the order of 1500 p. s. i. within the decoupler cells38 and 49 is sufficient to give the necessary decoupling action during drilling down to depths of the order of 2000 feet. When the drilling proceeds deeper, it is necessary to increase the pressure of the gas within the-

chambers

47 and 53 as the mud pressure is greater at increasing depths, in fact so great that the

flexible rubber membranes

45 and 52 are compressed to such an extent that the

chambers

47 and 53 are incapable of absorbing the surges or waves induced in the mud fluid by the vibrating-drill rod 34 and bit 35. The mechanism for. increasing the pressure of the inert gas within the

chambers

47 and 53 will now be described.

Afi annular cylinder 56, disposed between the end of exte ior sleeve 36,. is rovided as a storage tank for very high pressure. gas.

The storage tank 56 may be filled through an inlet 58 having asuitable check valve 59 therein. 'The storage tank 56' is of sufficient strength to withstand very high pressures therein. The storage tank 56 has two

outlet conduits

60 and 61 adapted to connect respectively with conduits 62 and'63 formed in the sleeve member 51. A gas pressure supply line 64 connects with the conduit 62 and leads to a differentially controlled valve 65. The c'onduit'63 is connected with a second differentially controlled valve 66 by means of a suitable line 67 which extends through the chamber 53, through sleeve 51 and through sleeve into the chamber. 47.

"Each of the valves '65 and '66 comprises a tapered plug 68 disposed within a corresponding tapered opening 69, which tapered plug closes the conduit leading to the valve. Each of the valves is provided with a stem 70 having a rounded head 71 adapted to engage the rubber membranes. A suitable compression s ring 72 normally tends to hold the valve in a closed position.

It will be noted that the rubber membranes or sleeves are adapted to engage the heads 71 of the respective valves, and when the mud pressure acting on the outside of the sleeves is sufficiently greater than the pressure of. the gas within the

chamber

47 or 53, the membranes will depress the valve members so as to open the valves and allow gas from the high pressure storage tank 56 to enter into the

compressible chamber

47 or 53. When the gas pressure within the chamber increases sufiiciently, the rubber sleeve will be forced away from the valve 71 and the spring 72 will then be able to close the valve. As is obvious, the high pressure of the gas in the supply line acts on the head of the tapered portion 68 of the valve to also aid in maintaining the valve in a closed condition.

After the drill penetrates the earth several thousand feet, the pressure of the gas within the

compressible chambers

47 and 53 increases to such an extent that it would be dangerous to withdraw the

decoupler cells

38 and 49 from within the bore hole 24 and therefore the present invention includes means for relieving the pressure of the gas within the

chamber

47 and 53 in the event that the pressure within the chambers becomes sufliciently greater than the pressure exterior of the chambers to cause a dangerous condition. This means comprises a pair of devices 73 disposed in suitable conduits leading through the sleeve '39 into the interior of the sleeve 39. Each of the devices 73 merely comprises adiiferentially responsive plug valve which is adapted to blow out when the pressure on one side exceeds the pressure on the other side of the valve by a predetermined value. Since it is contemplated that the

compressible chambers

47 and 53 will initially be charged with gas at a pressure of the order of 1500 p. s. i. it will be apparent that it is not desirable that the plugs 73 be designed so as to blow at pressures below any pressure up to and slightly greater than a pressure differ- 'ence of 1500 p. s. i. between the chambers and outside of the chambers. It is contemplated that as a practical matter, the devices 73 will blow out to relieve the pressure within the

chambers

47 and 53 when the pressure of the gas within the chambers exceeds the pressure exterior to -the chambers by a value of approximately 2000 p. s. i.

It will, of course, be obvious that the exact value may be any desired value.

During the operation of the drill disclosed herein, the

bit 35 vibrates vertically at a frequency equal substandampen the surges induced in the mud fluid. Therefore, very little energy is lost due to dissipation of the vibrations into the mud'fluiditself.

From the foregoing description of the present invention it is apparent that the present invention provides an improved sonic decoupler adapted to be disposed in the vicinity of, a vibrating bit of the typetused' in an earth boring drill such as is disclosed in the Bodine Patent 2,554,005. The provision of the automatic meansfor increasing the pressure of the gas within the compressible chambers renders the decoupler disclosed herein suitable for use. over a much greater range of depths of drilling and the differential means for relieving the gas pressure within thetdecoupler chambers renders the decoupler safe even when the gas pressure has built up to the extremely high values in the chambers whichare necessary during deep drilling.

It is contemplated that numerous changes and modifications may be made in the present invention without departing from'the spirit or scope thereof.

What is claimed is:

1. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on a drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by V determined pressure greater than the pressure withinsaid chamber and for shutting off the supply of gas from said source to said chamber when the pressure within the chamber increases to a predetermined pressure relative to the pressure of the mud fluid said compressible chamber being cyclically compressible at the vibration frequency of the sound waves in response to thepressure surges in the mud fluid and being thereby effective to absorb said energy consuming pressure surges of mud fluid caused by said sound waves.

2. Sonic decoupling meansadapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on a drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising substantially cylindrical compressible chamber means adapted to be filled with an inert gas under pressure and being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges inthe mud fluid for thereby absorbing said energy consuming pressure surges of mud fluid caused by said .soundwaves, said decoupler cell including a high pressure chamber comprising a source for said inert'gas,-and means including said compressible chamber means responsive to the pressure of the mud fluid in the well hole for admitting gas from said source into said compressible chamber means when the pressure of the mud fluid increasesto a predetermined pressure greater than the gas pressure within said chamber means and for shutting 01f thelsupply of gas from said source to said chamber means when the pressure within the chamber means increases to a pre determined pressure relative to the pressure of the mud fluid. a t t l v 3. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on the drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising a cylindrical rigid sleeve and a cylindrical rubber membrane disposed con centrically with respect to said sleeve and having its annular ends sealed to said sleeve so as to define with said sleeve a compressible chamber, said membrane being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid for thereby absorbing the energy consuming pressure surges of mud fluid and the chamber being adapted to be filled with an inert gas under pressure substantially equal to the pressure of the mud fluid, said decoupler cell including a high pressure source for said inert gas, and means disposed adjacent said membrane and responsive to the pressure of the mud fluid acting on the rubber membrane for admitting gas from said source to said compressible chamber in accordance with predetermined excesses of the mud fluid pressure relative to the pressure of the gas within the chamber and for shutting oif the supply of gas from said source to said chamber when the pressure within the chamber increases to a predetermined pressure relative to the pressure of the mud fluid to thereby maintain the pressure of said inert gas in the compressible chamber substantially equal to the pressure of the mud fluid as it increases when the drill rod and bit progress deeper into the earth.

4. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on the drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising a pair of axially spaced compressible chambers each adapted to be filled with an inert gas under pressure, a high pressure source for said inert gas, and means including the respective chambers responsive to the pressure of the mud fluid in said well hole for admitting gas from said source into said compressible chambers when the pressure of the mud fluid increases to a predetermined pressure greater than the gas pressure within said chambers and for shutting off the supply of gas from said source to said chambers when the pressure within the chambers increases to a predetermined pressure relative to the pressure of the mud fluid, said compressible chambers being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid and being thereby effective to absorb said energy consuming pressure surges .of mud fluid caused by said sound waves.

in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said 7 sound waves, said decoupler cell comprising a compressible chamber adapted to be filled with an inert gas under pressure, a high pressure source for said inert gas, and a valve disposed between said high pressure source and said chamber and responsive to the pressure of the mud fluid in said well hole for admitting gas from said source into said chamber when the pressure of the mud fluid increases to a predetermined pressure greater than the gas pressure within said chamber and for shutting off the supply of gas from said source to said chamber when the pressure within the chamber increases to a predetermined pressure relative to the pressure of the mud fluid, said compressible chamber being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid and being thereby efiective to absorb said energy consuming pressure surges of mud fluid caused by said sound waves.

6. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on the drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising a pair of axially spaced compressible chambers each adapted to be filled with an inert gas under pressure, a high pressure source for said inert gas, a pair of valves respectively disposed between said high pressure source and each of said chambers, and each of said valves being responsive to the pressure of the mud fluid in said well hole for admitting gas from said source into the respective chamber when the pressure of the mud fluid increases to a predetermined pressure greater than the gas pressure within said chambers and for shutting off the supply of gas from said source to the respective chambers when the pressure within the respective chambers increases to a predetermined pressure relative to the pressure of the mud fluid, said compressible chambers being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid and being thereby effective to absorb said energy consuming pressure surges of mud fluid caused by said sound waves.

7. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound Waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on a drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising a compressible chamber adapted to be filled with a gas under pressure, means for increasing the pressure of the gas in said chamber and including means differentially responsive to the pressure of the mud fluid in the well hole and to the pressure of the gas in said chamber and effective when the mud fluid pressure exceeds the gas pressure by a predetermined amount for actuating said gas pressure increasing means for causing the latter to increase the gas pressure in the chamber and for deactuating said gas pressure increasing means for causing the latter to stop increasing the gas pressure in the chamber when the pressure in the chamber increases to a predetermined pressure relative to the pressure of ,the mud fluid, said compressible chamber being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid and being thereby effective to absorb said energy 9 consuming pressure surges of mud fluid caused by said sound waves.

8. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on a drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising a compressible chamber adapted to be filled with a gas under pressure, means for increasing the pressure of the gas in said chamber and including means differentially responsive to the pressure of the mud fluid in the well hole and to the pressure of the gas in said chamber and effective when the mud fluid pressure exceeds the gas pressure by a predetermined amount for actuating said chamber when the pressure in the chamber increases to a predetermined pressure relative to the pressure of the mud fluid, said compressible chamber being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid and being thereby effective to absorb said energy consuming pressure surges of mud fluid caused by said sound waves, and means differentially responsive to said mud fluid pressure and said gas pressure and eflective to relieve the gas pressure in said chamber when the gas pressure exceeds the mud fluid pressure by a predetermined amount.

9. Sonic decoupling means adapted to absorb energy consuming pressure surges of mud fluid in a well hole in the earth caused by sound waves generated by a longitudinally vibrating drill rod and bit, wherein the bit is disposed in contact with the bottom of the well hole and is vibrating at a frequency approximating the resonant vibration frequency of the rod and bit, and comprising a decoupler cell adapted to be mounted on a drill rod in a region thereof which is subject to said energy consuming pressure surges of mud fluid caused by said sound waves, said decoupler cell comprising a compressible chamber adapted to be filled with a gas under pressure, means for increasing the pressure of the gas in said chamber, and including means diflerentially responsive to the pressure of the mud fluid in the well hole and to the pressure of the gas in said chamber and effective when the mud fluid pressure exceeds the gas pressure by a predetermined amount for actuating said gas pressure increasing means for causing the latter to increase the gas pressure in the chamber and for deactuating said gas pressure increasing means for causing the latter to stop increasing the gas pressure in the chamber when the pressure in the chamber increases to a predetermined pressure relative to the pressure of the mud fluid, said compressible chamber being cyclically compressible at the vibration frequency of the sound waves in response to the pressure surges in the mud fluid and being thereby efiective to absorb said energy consuming pressure surges of mud fluid caused by said sound waves, and pressure relief means differentially responsive to said mud fluid pressure and said gas pressure and eflective to relieve the gas pressure in said chamber when the gas pressure exceeds the mud fluid pressure by a predetermined amount.

References Cited in the file of this patent UNITED STATES PATENTS 2,554,005 Bodine May 22, 1951 FOREIGN PATENTS 699,265 Great Britain Nov. 4, 1953