CA1054138A - Eductor apparatus having an annular venturi nozzle for vacuum circulation in drilling system - Google Patents

Abstract

EDUCTOR APPARATUS HAVING AN 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 annulus 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.
A diverting valve, havings its input connected to pressurized air from an air compressor, has one output connected to the input of the inductor 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 combina-tion of the two.

Description

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Background of the Invention This lnvention relates generally to the art of drilling a hole in the earth's surface using air as a circula-tion 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 c$rculating 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. However, to the applicant's knowledge, there have been no prior art systems which contemplate the use of an annular venturi nozzle in an eductor to accelerate the motivating air to supersonic velocity prior to mixing with the induced air flow.
It is therefore the primary object of the present invention to provide a new and improved eductor apparatus.
It is also an object of the present invention to provide a new and improved eductor apparatus having a sub-stantially straight-through full bore~opening for the induced air.
The ob~ects of the invention are accomplished, in general, b~- 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 the g~ven dlameter; an annular ~ozzle formed between the first and second t tubular members, the tubular members having their respective central longitudinal axes in co-alignment, the nozzle comprising . ~ an air restrictor and a diffuser having a first end ad~acent the air restrictor and an exit end on the other end of the dap/~Q, - , --` lOS4138 ~iffuser, the diffuser being comprised of first and second diverging walls, the first of the walls bearing an angle of approximately 30 with respect to the aligned central longidudinal axes and the second of the walls bearing an angle of approximately 41 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; and means to introduce compressed air through the restrictor and the diffuser into the second tubular member, thereby inducing air flow from the first tubular member into the second tubular member.
These and other objects, features and advantages of the present invention will be more readily appreciated from a - la -r~ .
dap/ ~

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:
~OS4~38 reading of the following detailed specification and drawing, in which:
~IG. 1 is an elevated view, partly in cross section, of the drilling system embodying the eductor apparatus 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;
and FIG. 3 illus~rates in cross section an elevated view of the eductor apparatus according to the present invention.
Referring now to the drawing in more detail, especially to FIG. 1, an earth boring machine 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 traveling power head or tra~eling frame 3 is mounted for travel along the derrick 8. A drill string unit 10 is connected to the traveling power head 3. The drill string 10, shown in more detail in FIG. 2, is comprised of double walled, concentric tube drill pipe, for example, as is shown in U. S. Patent No.
3,208,539 to ~. I. Henderson.
A swivel 11, shown in more detail in FIG. 2, is connected to 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 substantially matches the bend radius of the hose 13. This provides smooth radius for flow of drill cuttings through the - hose 13. The support wheel 1 is rotatably mounted upon an axle 14. The axle 14 is connected by means of a connecting lOS~38 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 orce 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 clamp 16 to the derrick 8.
An air compressor 21 has its output line 22 connected to the input 23 of a diverting valve which is generally indi-cated by the reference numeral 24. One of the output lines of the diverting valve 24 is connected by the air line 25 to the ~ -motivating air input 26 of the eductor device 15. The other output of the diverting valve 24 is connected by air line 27, preferably being a flexible hose, to the input 28 of the swivel 11. The diverting valve 24 includes a rotor 29 which is rotatable by an operator to control whether air passes through the lines 25 or 27 and the extent of such passage.
Air pressure valves 51 and 52 are located in air 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 tra~eling power head 3(shownin FI5. 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 leakage of the compressed air from the interior of the housing 31. A 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 concentric drill pipe .
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lV541~8 assembly 10. The ports 34 and 35 thus provide a means for the compressed 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 generally 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 constructed in accordance with the teachings of U. S. Patent No. 3,208,539 to H. I. ~enderson. -~
A packer assembly 42 is positioned between the exterior of the drill pipe assembly and the wall 43 of the -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 difficulty in providing 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, that 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 . .

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lOS~38 the annulus 40 ra-ther than escaping past the packer seal 42.
The drilling of a hole begins with the traveling power head 3 near the top of the derrick 8. The drill string 10 is rotated and the drill bit at the bottom of the drill S string 10 disintegrates the earth formations to form the desired borehole. As the borehole penetrates deeper into the earth, the traveling powPr head 3 moves downward. As the compressed air and/or vacuum causes the drill cuttings to pass up through the center passage 40, the cuttings and debris from the earth borehole pass up through the flexible hose 13 into the eductor device 15 and out through the curved stand pipe 9 either onto the surface of the earth or into a collection vehicle. The support wheel 1 supports the con- ~-necting hose 13. As the traveling power head 3 moves downward~ -the support wheel 1 rotates on the axis 14 insuring that a smooth radius of connecting hose will be maintained. The counterbalance 7 provides a lifting force on the support wheel 1 maintaining a slight tension in both ends of 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 FIG. 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 eductor device 15 provide a means for monitoring and allowing the control of the ~ompressed 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 ~ - -~ i air in the line 25 is easily correlated to the vacuum created ., ~...~
by the eductor device 25. Thus, as the dritl stcm 10 and lOS~131~
drill bit 38 are rotated into the earth's surface in drilling a hole, the operator adjusts the rotor 29 to create the desired combination of pressurized air and vacuum to enhance the drilling operation. The Applicant has also discovered that, depending upon the formations being drilled, it is sometimes better to use only pressurized air and other times better to use only the vacuum. In such instances, the rotor 29 is rotated one way or the other to create the desired effect.
It should also be appreciated that another means of determining lQ 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, if the packer 42 is not used, when drill cuttings are blowing out of the borehole around the exterior of the drill pipe assembly 10.
Referring now to FIG. 3, there is illustrated in greater detail the eductor apparatus 15 according to the present invention. The eductor 15 includes a main housing 51 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 at the point 56 ~nd concluding at the end wall 57. Commencing at point 70, the wall of the housing 51 flares ta a greater diameter having side walls 71 defining an inner chamber 54.
A tubular lateral housing member 53 is in fluid communication with the chamber 54 and has an air inlet 2Ç at its end for receiving the high pressure air generally identified as being the "motivating air". A tubular member 50 is located within the chamber 54 and has an internal diameter substantially identical with the internal diameter of the C portion of the housing 51 to thereby create a substantially straight-through bore for the induced air and drill cuttings which enter the 105413~
input port 59 of the tube 50. An O-ring seal 52 is provided between the housing wall 71 and a lateral projection of the tube S0 to provide a seal of the pressurized air introduced into the chamber 54.
The flared wall 71 has a portion of its internal surface wall angled with respect to the center line 60, and the end of the tube 50 away from the inlet port 59 is also angled toward the longitudinal center line 60 by an angle as ~-discussed hereinafter. The angles of the side wall 71 and the end of the tube 50 are chosen such that a diffuser section B is achieved following the restrictor area A. ~ -The Applicant 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 lS providing the restrictor throat A and the diffuser section B
~-hich diverges a~ a controlled angle, the air exiting from the restrictor throat can be accelerated to a supersonic velocity.
According to the Applicant's estimates from observing the e~uctor assembly according to the invention, the velocity achieved with this particular inductor is approximately Mach 1.9.
Since the kinetic energy of the motivating flow is the energy transferred to the flow mixture with the induced air, the Mach 1.9 velocity achieves a kinetic energy approximately 3.6 tImes the energy of Mach 1 flow. No greater input is required to achieve the greater output. The induced air flow which --enters the inlet port S9 along with the drilled cuttings, following a straight-through path through the venturi without making any changes in direction, tends to keep the induced air and drill cuttings moving without sticking or building up on any exposed surfaces~ Although various angles can be used to ~ fabricate the diffuser section B, the Applicant has discovered 105~i38 that the eductor works quite well when the internal surface of the side wall 71 is angled at 30 from the center line 60 to direct the motivating air in toward the central axis 60 along the dotted line 55 to cause effective mixing. The end of the nozzle on the tube 50 is preferably angled at 41 from ~ -the center line 60, thus diverging from the internal surface of the wall 71, to likewise direct the supersonic flow in toward the center line 60 to achieve mixing.
~n the operation of the eductor apparatus of FIG. 3, considered with the system according to FIG.'s 1 and 2, it should be appreciated that the high pressure air, introduced at approximately 100 psi, is coupled into the inlet port 26.
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 di~fuser section B into ana toward the center line 60 causing the induced air to flow from the inlet port 59 toward the end plate 57. This of course creates 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.
Although the preferred em~odiment contemplates the use of the specifically 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 ~he diffuser section D to recover the energy of the compressed mixture as it expands.

Claims (2)

1. THE EMBODIMENTSOF THE INVENTION IN WHICH AN EXCLUSIVE
   PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
   
   l. 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 air 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; and 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.
2. 2. The eductor apparatus according to claim 1, including in addition thereto, a second diffuser section in co-alignment with said second tubular member.