CA1055475A - Eductor apparatus having a variable orifice annular venturi nozzle for vacuum circulation in drilling system - Google Patents

Abstract

EDUCTOR APPARATUS HAVING A VARIABLE
ORIFICE ANNULAR VENTURI NOZZLE FOR
VACUUM CIRCULATION IN DRILLING SYSTEM
Abstract of the Disclosure. A drill system uses double walled concentric pipe and a drill bit attached at one end of the drill pipe and a power swivel at its upper end having means for applying compressed air to the outer annulus within the drill pipe and means for attaching a vacuum line to the center annulus of the drill pipe. A
flexible hose attached to the vacuum portion of the drill pipe has an eductor assembly using compressed air to create a vacuum to remove the cuttings during the drilling operation.
The eductor assembly includes an annular nozzle surrounding a straight-through bore providing an obstruction-free passage for induced air and drill cuttings. Motivating air flowing through the nozzle passes through flow restriction, then diverging diffuser, to accelerate air to supersonic velocity.
Means are provided to vary the nozzle orifice in response to changes in the pressure of the motivating air to optimize the pressure drop across the orifice and thus compensate for varying air volume flow rates. A diverting valve, having its input connected to pressurized air from an air compressor, has one output connected to the input of the eductor and its other output connected to the outer annulus portion of the drill pipe. The diverter valve provides the operator the ability to pressure reverse circulate, to vacuum reverse circulate, or an infinitely variable combination of the two.

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Description

~(~55~5 Rel-~29.~ell8~ This application relates to an improvement upon the invention embodied within my Canadian Patent Application Serial No. ~44,617, filed January 30l 1976, for "EDUCTOR APPARATUS HAVING AN ANNULAR VENTURI NOZZLE FOR
YACUUM CIRCULATION I~ DRILLING SYSTEM".

B;ackground of the invention. This invention relates generally to the art of drilling a hole in the earth's surface using air as a circulation medium, and specifically to an improved apparatus for creating a high volume of vacuum-induced air and a straight-through full bore opening for allowing drill cuttings and induced air to pass therethrough.
It is well known in the prior art to use air as a drilling fluid for circulating the drill cuttings to the earth's surface. It has also been known in the art to employ a vacuum system for removing the drill cuttings in lieu of using pressurized air. Furthermore, it is also known to create a vacuum with an eductor apparatus, for example, as shown in :
U.S. Patent No. 3,031,127 to R. A. Duhaime et al~ Further ~ still, my above-noted related application discloses the use of j 20 an annular venturi nozzle in an eductor to accelerate the ~:
-~ motivating air to supersonic velocity prior to mixing with :.
- .
: khe induced air flow. :: :.

~ However, when using a source of compressed air which . .
may have a varying rate of air flow, the pressure drop across the nozzle will vary and thus possibly be less than optimum.
Broadly ~peaking, the present invention provides an :~
eductor apparatus compri~ing: a first tubular member having a given internal diametex; a second tubular member having an internal diameter substantially the same as the given diameter; .

an annular nozæle formed between the first and second tubular memb~rs r the tu~ular members having their respective central :~
longitudinal axe~ in co-alignment, the nozzle comprising an air restrictor and a dif~user having a first end adjacent the .: . , : , ,., , , , . ............................... :
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11;)55475 air restrictor and an exit end on the other end of the diffuser, the diffuser being co~prised of first and second diverging walls, the first of the walls bearing an angle of approximately 30 with respect to the aligned central longitudinal axes. and the second of the walls bearing an angle of approximately ~lG with respect to the axes, the exit end of the diffuser having a smaller cross-sectional area than any cross-sectional area in the second tubular member; means to introduce compressed air througb the restrictor and the diffuser into the second tubular member, there-by inducing air flow from the first tubular member into the second tubular member; and means to vary the size of the restrictor and thereby vary the pressure drop across the nozzle.
These and other featùres and advan-tages of the present invention will be more readily appreciated from a reading of the following detailed specification and drawing, in which;
FIG. 1 is an elevated view, partly in cross-section, o the drilling system embodying the eductor appara-tus according ,. - " :
to the present invention;
FIG. 2 is a diagrammatic view, partly in cross section, - .
illustrating a circulation swivel and drill bit attached to the -double walled drill pipe which finds utility with the eductor apparatus according to the present :invention; :~
FIG. 3 illustrates in cross section an elevated view o:E :~the eductor apparatus according to the present invention; and FIG. 4 is an expanded diagrammatic view, partly iu cross section, of the controller apparatus illustrated in FIG. 3 according to the present invention.
Referring now to thé drawing in more detail, especially to FIG. 1, an earth boring maching generally designated by the reference number 12 is shown positioned at a drill site. The earth boring machine 12 includes a derrick 8 that provides a .. .
support frame. A travelling power head or travelling frame 3 is mounted for travel along the derrick 8. A drill string unit 10

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'. . :, ' . ' ' - . ' ' , :~ , , ~1~559L~5 is connected to the travelling powe~ head 3. The drill string 10, shown in more .

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~55~75 detail in FIG. 2, is comprised of double walled, concentric tube drill pipe, Eor example, as is shown in U. S. Patent No.

3,208,539 to H. I. Henderson.
A swivel 11, shown in more detail in FIG. 2, is connected ~o the top part of the drill string and in turn is attached to a flexible hose 13 which passes over a support wheel 1 which is suspended from a pair of sheaves 5 and 6 attached to the derrick 8. The radius of the support wheel 1 subs antially matches the bend radius of the hose 13. This provides smoo~h radius for flow of drill cuttings through ~he hose 13. The support wheel 1 is rotatably mounted upon an axle 14. The axle 1.~ is connected by means of a connecting line 4 to the sheaves 5 and 6. The connecting line 4 is also attached to a counterbalance weight 7. The counterbalance weight 7 provides a counterbalance force substantially equal to the weight of the hose 13.
. The flexible hose 13 is connected at its other end ::
to the eductor device generally designated by the reference number 15, such device being shown in greater detail in FIG. 3.
The lower end of the eductor device 15 is connected to a stand pipe 9 by means of a cla~p 16 to the derrick 8.
An air compressor 21 has its output line 22 connected : : to the input 23 o a diverting valve which is generally indi- :
~: ; cated by the reference numeral 24. One o~ the output lines of the diverting valve 24 is connected by the air line 25 to the , ~ motivating air input 26 o~ the eductox de~ice lS. The other i output o the diverting valve 24 is connacted by air line 27, preferably being a flexible hose, to the input 28 of the swivel 11. T~ diverting valve 24 includes a rotor 29 which i~ rotatable b~ an operator to control whether air passes thxough the lines 25 or 27 and the extent o such passage.
Alr pres3ure valves 5~ and 52 are located in air ,. , .
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~C~S5475 ' lines 27 and 25, respectively.
. .
Referring now to FIG, 2, the swivel 11 is shown in greater detail. The swivel 11 includes a housing 31 which surrounds the double walled drill pipe 10 and which is adapted to remain stationary with respect to the travelli~gpower head 3 (shown in FIG. 1) and which allows the drill pipe 10 to ; rotate therein. A pair of packing elements 32 and 33 are provided to seal off the compressed air which enters input port 28 and thus prevent leakaye o the compressed air from the interior of the housing 31. ~ plurality of ports, shown as ports 34 and 35, are located between the packing rings 32 ;~
and 33 in the outer wall 36 of the'concentxic drill pipe ' assembly 10. The ports 34 and 35 thus pro~ide a means for the oompressed air which enters at input port 28 to pass from the interior of the housing 31 to the annulus 39 between the outer ~
drill pipe wall 36 and the inner drill pipe wall 37. ;
A drill bit assembly, shown ger.erally by the reference numeral 38, is attached to the lower end of the drill string assembly 10. The drill bit assembly 38 can be of various designs well known to those'skilled in the art which allow ~'~
communication between the outer annulus 39 and the borehole and also between the borehole and the inner annulus 40 through which the drill cuttings are returned to the earth's surface, If desired, the drill'bit 38 can be con~tructed in accordance with the'teachings of IJ.S. Patent No. 3,208,539 to H. I, Henderson~
or in accordance with Canadian Patent Application Serial No.
243,678, filed January 16, 1976, for "VACUUM, VACUUM-PRESSURE, :, OR PRESSURE- REVERSE CIRCULATION BITI', and assigned to the assiynee of the present application~ ' A pa~ker assembly 42 is positioned between the '' exterior of th~ drill pipe assembly and the wall 43 of the .,~' ' ' . .

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10~5~75 borehole for purposes as explained hereinafter~
Referring now to the operation of the apparatus according to FIG.'s 1 and 2, it should be appreciated that unless the packer 42 shown in FIG. 2 provides a good seal between the drill string 10 and the wall 43 of the borehole, the introduction of compressed air into the annulus 39 is very likely to cause the drill cuttings 41 to go past the packer 42 instead of up through the center annulus 40 of the drill pipe. The Applicant has sometimes experienced diffi-culty in pxoviding a good seal by the use of the packer 42, especially when drilling under arctic conditions through regions of permafrost and in other unconsolidated formations. :::
The Applicant has discovered, however, ~hat by maintaining the vacuum within the center annulus 40 stronger or greater than the compressed air in the annulus 39, based on a per unit volume, the drill cuttings 41 will pass up through the annulus 40 rather than escaping past the packer seal 42.
The drilling of a hole begins with the traveling power head 3 near the top o the derrick 8. The drill string 10 is rotated and the drill bit at the bottom of the drill string 10 disintegrates the earth formations to fonm the desired borehole. As the borehole p~netrates deeper into the earth, the traveling power head 3 moves downward. As the compressed air and/or vacuum causes the drill cuttings ~ 25 to pass up through the center passage 40, the cuttings and ::
J debris from the earth borehole pass up through the ~lexible hose 13 into the eductor device 15 and out through the curved ~tand pipe 9 ~ither onto the surface.of the earth or into a collection v~hicle. ~he support wheel 1 supports the con-necting hose 13. As the ~raveling power ~ead 3 moves downward, the support wheel 1 rotates on the axis 14 insuring that a smooth radius o connecting hose will be maintained. The ,. ' , : ' ~LCI 5S475 counterbalance 7 provides a.lifting force on the support wheel 1 maintaining a slight tension in both ends o~ the connecting hose 13. The connecting hose 13 is maintained :
in a vertical position as the traveling power head 3 moves in the derrick 8.
As shown in FIGo 1~ the rotation of the rotor 29 by the drilling operator controls the amount of air which passes to the swivel 11 and also to the eductor device 15. The . . valve 51 in the air line 27 passing to the swivel 11 and the valve 52 in the air line 25 passing to the educ~ox device 15 provide a means or monitoring and allowing the control of the compressed air which is put into the annulus 39 and the vacuum :.
which is created in the center annulus 40. Based upon cali-bration charts, the valve 52 which is indicative of compressed air in the line 25 is easily correlated to the vacuum created by the eductor device 15. Thus, as the drill stem 10 and drill bit 38 are xotated into the earth's surface in dxilling : a hole, the operator adjusts the rotor 29 to create the desired combina~ion o~ pressurized air and ~acu~m to enhance . ;
the drilling operation. The Applicant has also discovered : that, dsipending upon the ormations being drilled, lt is sometimes better to use only pressurized air and other times bettér to use only the vacuum. In such instances, the ro~or 29 is rotated one way or the other to create the desired e~fe~t.
It should also be appreciated that another means of determining when the vacuum is exceeding the compressed air is determined by whether the drill cuttings are attempting to leak past the packer 42 or, alternatively, i~ the packer 42 is not used, when drill cuttin~s are blowing out of the borehole around the exte~ior o~ ~he dxill pipe asse:mbly 10~
Re~erring now to FIG. 3, there is illus~rated in greater detail the educ~or apparatus 15 according to the ~ 6 , ,',;,', ;',.',;..'~"',',. '. ,~,',, .' ,' '''.;'"',;''' ~C~55475 present invention. The eductor 15 includes a main housing Sl which includes a substantiaLly straight-through bore around the longitudinal center line 60. The housing 51 includes a mixing section C having a tubular wall of substantially uniform internal diameter and a diffuser section D commencing a~ the point 56 and concluding at the end wall 57. Commencing at point 70, the wall of the housing 51 flares to a greater diameter having side walls 71 defining an inner cha~ker 54.
A tubular lateral housing member 53 is in fluid communication io with the chamber 54 and has an air inlet 26 at its end for receiving the high pressure air generally identified as being the "moti~ating air". A tubular mem~er 50 is located within the chamber 54 and has an internal diameter substantially identical with the internal diameter o~ the C portion of the housing 51 to thereby create a substantially straight-through bore for the induced air and dxill cuttings which enter the input port 59 of the tube 50. The hose 13 is clamped onto the end of tube 50 having the input port 59 by clamp 80. An O-ring seal 52 ~s provided between the housing wall 71 and a l~teral pxojection 90 of the tube 50 to provide a seal of the pressurized air introduced into the chamber 54.
The flared wall 71 has a po~tion of its internal I sur~ace wall angled with respect to the center li~e 60, and .
the end of the tu~e 50 away from the inlet port 59 is also angled toward the longitudinal center line 60 by an angle as discussed hereinafter. The angles o~ the side wall 71 and the end o~ tha tube 50 are chosen such that a dif~user section B i~ achieved ~ollowing the restrictor area A~
A pr~ssure sensor 51 is mounted inside the housing .
53 tor alterna~ively within chamber 54) to monitor the air ` pre~ure from the air compressor 21 (shown in FI~. 1). The sensor 81 is connected to the controller apparatus 82 by the .
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~ 5~75 pneumatic line 83. A hydraulic cylinder 84, shown in greater detail in FIG. 4, is coupled to the controller 82 by means of flexible hydraulic lines 85 and 86. A piston 87 (see FIG. 4) ;i within the cylinder 84 is attached by a piston rod to an end plate 88 which in turn is attached to the lug 89 of housing member 53. It should be appreciated that the lateral projec-tion 90 will slide with respect to the end plate 88 and the lug 89 and that the O-ring 52 thus provides a dynamic seal therebetween. Furthermore, the bottom side of cylinder 84 is firmly attached, for example, by welding, to the lateral projection 90.
Referring now to FIG. 4, there is diagrammatically shown, in greater detail, the controller 82 and cylinder 84.
The pneumatic, or alternatively, electric, line 83 from pressure sensor 81 drives a pump selector switch 91 which determines whether the sensed air pressure is higher or lower than a given predetermined range. The outputs of ! switch 91 are electrically connected by conductors 92 and 93 , to the hydraulic pumps 94 and 95, respectively. The output of pump 95 i5 connected by hydraulic line 86 to the chamber 96 in cylinder 84. Likewise, the output of pump 94 is connected by hydraulic line 85 to chamber 97 in cylinder 84.
The chamber 96 is connected by hydraulic line 98 to a fluid reservoir 99 and the chamber 97 is connected to the reservoir 99 by the hydraulic line 100. The reservoir 99 is connected back to the pumps 94 and 95 by the flexible return hydraulic lines 101 and 102, respectively. It should be appreciated that the reservoir 99 also contains the necessary val~es and control lines or receiving hydraulic , 30 fluid from ~h~ chambers 96 and 97 in cylinder 84 and for returning the hydraulic fluid to the pumps 94 and 95 in a manner ~7ell known in the art.

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The Applic~nt has discovered that he is able to achieve supersonic flow through this annular nozzle. It should be appreciated that without special arrangements, Mach 1 flow is the maximum which can be achieved in a nozzle.
By providing the restrictor throat A and the diffuser section B which diverges at a controlled angle, the air exiting from the re~trictor throat can be accelerated to a supersonic velocity. According to the Applicant's estimates from observing the eductor assembly according to the invention, the velocity achieved with this particular inductor is approximately Mach l.9~ Since the kinetic energy of the motivating flow is the energy transferred to the flow mixture with the induced air, the Mach ~.9 velocity achieves a kinetic energy approximately 3.6 times the energy of ~ach 1 flow.
No greater input is requi~ed to achieve the greater outpu~.
The induced air flow which enters the inlet port ~3 (FIG. 3) along with the drilled cuttings, ollowing a straight-through path through the venturi without making any changes in direc-tion, tends to keep the induced air and drill cut-tings moving without sticking or building up on any exposed surfaces.
Although variouç angles can be used to fabricate the diffuser ~ection B, the Applicant has discovered that the eduotor work~ ~uite well when he internal sur~ace of the side wall 71 i~ angled at 30 from the center line 60 to direct the motivating air in toward the central axis 60 along the dotted I line 55 to cause effective mixinyO The end of the noz~le onI
the tube 50 is preferably angled at 41 from the center line 60, thus div~xging from the internal surface of the wall 71, to likewise direct the supersonic flow in toward the center l~ne 60 to ac~ieve mixing.
In the operation of the eductor apparatus o~
; FlG. ' 5 3 and 4, cons~dered with the syntem according to - ., , . , . . " . :.
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1~35S~75i FIG.'s 1 and 2, it should be appreciated that the high pressure air, preferably introduced at approximately 95 psi, is coupled into the inlet por~ 26. The pressure to be maintained in chamber 54 should preferably be slightly less than the pressure at which the compressor starts to "throttle back". Thus, if the compressor 21 begins to "throttle back" at 100 psi, a maintained pressure of 95 psi keeps the engine compressor at near full throttle. This air is also coupled into the chamber 54 which surrounds the tube 50 and which is restricted . :
by the restrictor A. After passing through the restrictor A, . .
the air is accelerated in the diffuser section B into and ,! ' .,',' .. , toward the center line 60 causing the induced air to flow from the inlet port 59 toward the end plate 57. This of course create~ a vacuum within the hose 13 and the center passage in the string of drill pipe 10 for withdrawing the drill cuttings 41 from the bottom of the drilled hole. If the operator decides to divert some of the available compressed . air by means of the diverter valve 24 to the outer annulus 39 .~ in the drill string, the pressure will drop in the chamber 54.
20 Since the kinetic energy of the motivating air is increased by an increased pressure drop across the nozzle, it is desirable to increase the pressure in chamber 54. This is accomplished by the apparatus of FIG.'s 3 and 4 by the following operation.
As the pressure sensor 81 detects a drop in pressure r ~
the pump selector switch 91 activates pump 94 which causes .- ..
cylinder 84 to slide toward end plate 88 and thus tend to "close the nozzle" by varying the size of restrictor A since I the tube 50 i3 connected to the cylinder 84. This then i 30 creates a bigg~r pressure drop across the nozzle and increases the pressure in char~er 54. Conversely, if the pressure is . too high, for exarnple, greater than 95 psi, as sensed by ~ ~.
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sensor 81, pump 95 is activated which causes cylinder ~4 to slide away from end plate 88 and thus create a greater orifice within the nozzle.
Although the preferred embodiment contemplates the use of the speclfically disclosed angles within the diffuser section B, quite obviously other angles can be used to form such a diffuser section to accelerate the motivating air to supersonic flow. The inertia of the motivating air is trans-ferred to the induced flow and drill cuttings as the motivating ~ -flow and the induced flow are mixed. The mixed flow then expands into the diffuser section D to recover the energy of the compressed mixture as it expands. Furthermore, although the preferred embodiment contemplates that the restrictor A
be varied automatically in response to the sensed pressure upstream o~ the nozzle, those skilled in the art will appre-ciate that an operator can also move the tube 50 manually to vary the nozzle orifice to optimize the pressure drop across the nozzle. Those skilled in the art will also recognize that although the preferred embodiment contemplates the use of a hydraulically actuated cylinder to move the tube 50 with respect to the other side of the nozzle, uariousother means can also be used to provide relative movement, for example, an electric motor and worm gear drive arrangement located therebetween.

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Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. an eductor apparatus comprising:
a first tubular member having a given internal diameter;
a second tubular member having an internal diameter substantially the same as said given diameter;
an annular nozzle formed between said first and second tubular members, said tubular members having their respective central longitudinal axes in co-alignment, said nozzle comprising an air restrictor and a diffuser having a first end adjacent said restrictor and an exit end on the other end of said diffuser, said diffuser being comprised of first and second diverging walls, the first of said walls bearing an angle of approximately 30° with respect to said aligned central longitudinal axes and the second of said walls bearing an angle of approximately 41°
with respect to said axes, the exit end of said diffuser having a smaller cross-sectional area than any cross-sectional area in said second tubular member;
means to introduce compressed air through said restrictor and said diffuser into said second tubular member, thereby inducing air flow from said first tubular member into said second tubular member; and means to vary the size of said restrictor and thereby vary the pressure drop across said nozzle.

2. The eductor apparatus according to claim 1, including in addition thereto, a second diffuser section in co-alignment with said second tubular member.