US2902937A - Sonic well pump with critically tuned elastic support system and vibration isolator - Google Patents

Description

2,902,937 TUNED ELASTIC SUPPORT Sept 8, .1959 A. 4cs. BoDlNE, .JR

SONIC WELL PUMP WITH CRITICALLY SYSTEM AND VIBRATION ISOLATOR Filed oct. 22, 195e United States Patent O 2,902,937 SONIC WELL PUMP WHTH CRITICALLY TUNED ELASTIC SUPPORT SYSTEM AND VIBRATION ISOLATOR Albert G. Bodine, Jr., Van Nuys, Calif. Application Gctober 22, 1956, Serial No. 617,413 1 Claim. (Cl. 10S-'76) This invention relates to sonic pumps of the general nature disclosed in my Patent No. 2,444,912, operating by periodic Waves of compression and tension at sonic frequencies in an elastic column such as the pump tubing or a rod string, and the object of the invention is the provision of improvements in such pumps in the direction, first, of increased power utilization, and therefore increased pumping effort, for a given power unit, and second, of isolation of the vibratory action in the pump tubing or rod string from its stationary means of support at the ground surface.

In the aforementioned patent I disclosed several embodiments of the type of sonic pump to which the present invention broadly pertains, including forms in which the wave motion is transmitted down an elastic pump tubing, and other forms in which the wave motion is transmitted down an elastic rod string. Taking the first class as representative, the elastic tubing may typically be suspended from a spring-mounted platform at the ground surface, the spring means thereof being in turn borne by suitable earth mounted support means. A vibration igenerator or oscillator such as an eccentrically weighted flywheel combination is mounted in bearings supported on the platform in a housing which is mounted atop the tubing, and serves, when driven at high rotational velocity, to supply a vertical oscillatory force which longitudinally reciprocates the upper end of the tubing through a short displacement distance in such a manner as to transmit down it alternate deformation waves of tension and compression. Points along the tubing are thus set into vertical oscillation. Preferably, the Waves are generated at such a frequency relative to the length of the tubing that the tubing is resonated and there is produced therein, in a manner well known to those familiar with the acoustic art, a standing wave characterized by alternate nodal and anti-nodal regions of minimum and maximum oscillatory movement. lOne or more fluid impelling and check valve units are mounted in the tubing, preferably at points of maximum oscillatory movement (velocity anti-nodes), so as to participate in the vertical oscillation of the portions of the tubing in which they are mounted, whereby increments of uid are pumped upwardly past the check valves to be elevated in the tubing.

Considering the operation of such a pumping system under idealized conditions, with the assumption of an operating frequency which resonates the tubing, and with the mass, or mass reactance, of the oscillator at lirst neglected, a velocity anti-node occurs at the upper end of the tubing, at the point where the oscillator is mounted thereon, and a first node, or stress anti-node, occurs at a spacing distance one-quarter wavelength down the down the tubing from its upper end. The vibratory tubing system in such assumed state would be ideally prepared for eflicient, maximum amplitude drive by the oscillator. However, in practice, the considerable mass of the oscillator unfavorably modiiies the wave action in the tubing. Acting as a terminating untuned mass reactance, its effect is to reduce the distance down the tubing to the rst stress anti-node to considerably less than a quarter Wavelength, and at the same time to correspondingly reduce the oscillation amplitude of the tubing at its upper end, i.e., at the velocity anti-node.

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Thus, while a maximized rst stress anti-node is attained, less than a maximized velocity anti-node is attained at the upper end, and power input into the tubing suffers accordingly.

I have discovered that maximized oscillation amplitude may be attained at the upper end of the tuning for a given oscillator and and a given stress maxima at the first stress anti-node by critically tuning the elastic oscillatory system consisting of the oscillator and the spring mounting for the tubing to the operating frequency of the oscillator. With such tuning, the mass reactance of the oscillator is balanced by the stiffness or elasticity reactance, and a full amplitude velocity antinode is secured at the upper end of the tubing. |This is accompanied by a downward shift of the irst stress anti-node to a full quarter wavelength below the upper end of the tubing. This oscillatory force exerted by the oscillator on the upper end of the tubing then acts throughout a longer stroke, with consequent increased power flow into the tubing.

I have further discovered that by critically tuning the elastically vibratory system consisting of the oscillator and the spring support for the tubing to resonate at the oscillation frequency of the oscillator, I effectively isolate the entire vibratory pump system from its stationary support means at the ground surface. This has several important advantages, including conservation of the vibratory energy delivered by the oscillator, elimination of undesirable Vibration in the ground-mounted support means for the spring-mounted tubing support platform, and avoidance of opposition to free oscillation of the pump system by the tubing support means.

The phenomena referred to in the preceding paragraph fcan be better appreciated by use of the concept of mechanical impedance, which is the ratio of cyclic peak force acting at any given point in an elastically vibrating system to displacement velocity at that point in the system. A velocity anti-node region is a region of low mechanical impedance. The upper end of the pump tubing, where supported by the spring-mounted platform, is accordingly a region of low mechanical impedance; and it will be seen that the greater the stroke, the greater will be the displacement velocity, and therefore the lower will be the mechanical impedance. The ground supported mounting for the spring support means that carries the tubing is so constructed as to be a region of high mechanical impedance. It will be seen that the steadier or more stationary this mounting can be made to stand, the higher will be the mechanical impedance at this point. It will be evident that a high impedance at this point denotes minimization of transmission of vibratory energy into this mounting and to the ground, giving the advantage of conservation of vibratory energy, as well as absence of undesirable shaking of the mounting and the surrounding ground area. It will further be evident that a low impedance at the point of support of the tubing by the spring-mounted platform minimizes blocking impedance to free vibration of the upper end portion of the tubing. These desired impedance conditions are obtained, in accordance with the invention, by the above described critical tuning of the elastic vibratory system consisting of oscillator and spring support means to the frequency of operation of the oscillator, together with the provision of a steady or rigid mounting for said spring support means.

summarizing, the described critical tuning of the oscillator and spring support means for the tubing raises power inflow into the tubing, and by combining therewith a high impedance point of support for said spring support means, there is further accomplished minimized leakage of vibratory energy from the system, minimized shaking of the ground supported mounting for the equipment, and mini.-

Patented Sept. 8, 1959 f tubing by the spring support means.

The invention will be better understood by referring now to the following. detailed description of an illustrative embodiment of the invention, reference being'hadl to the accompanying drawings, in which:

Fig. l is a longitudinal sectional view of the upper end portion ofr a sonic well pump in accordance with` the inventijon;

Fig. 2 shows the lower end portion of the pump tube; and

Pigs. 3 and' 4 are diagrams. of sonic pumps and their Wave characteristics, with and without, respecitvely, the provisions of the present invention.

In the drawings an illustrative sonic oil well pumping installation is showin, the well bore being shown to be lined part way down by surface casing 10,.while annularly spaced inside casing is production casing 11, perforated at its lower end, as at 11a, and inside of which has been suspended the elastic steel. pump tubing 12. Mounted at the top of casings 10 and 11 is a suitable casing head 13, and the pump tubing 12 extends upwardly through the casing head and has mounted at its upper end `a vibration generator or oscillator G. This generator G'. comprises a. housing 16 containing a device for vibrating the upper end of the tubing 12 in a direction longitudinally of the latter, thereby exerting a vertical oscillatoryforce upon the upper end of the tube.

' The means for generating the vibratory action is here shown of a simple type embodying meshingl oppositely rotating spur gears 17` carrying eccentric weights 18 which balance. out horizontal vibrations but act additively to produce a substantial resultant oscillatory force in a vertical direction. The generator has a` driving pulley 19 driven through belt 20 from electric drive motor 2,1. Since this vibrator is employed to generate elastic waves of tension and compression in the pumpA tubing which are of the. sameY nature as sound waves and travel with the speed of sound in the. pipe, I may properly refer to this vibrator as a sonic wave generator.

Extending upwardly from casing head 13, at an annular spacing outside tubing string 12, is a short and relatively sti pipe section 24, and mountedv on the upper end ofthe latter is a supporting head having. at the topA a ange 26. Bolted to ange 26 is a ange 27 of a tubular fitting 28. on the bottom of a relatively heavy stationary lower platform 29 for the spring support device 30 for the tubing string and vibration generator G, the tubing being packed by a stuing -box at 29a. The large diameter outer casing 10, cemented in the well, as indicated at 10a, together with casing head 13, pipe 12, tting 25, and the relatively massive platform 29, constitute in this case the ground supported mounting means for the spring support device 30. The platform 29 and system on which it is mounted constitute a considerable mass, andthe pipe section 24 and casing 10, down to the support of thecasing, constitutes a high elastic stiffness. The platform 29 hence has high inertial properties, and provides a rm high impedance base for support device 30.

Spring support device 30 includes an upper plate or platform 31, supported from lower platform 29 by a plurality of coil springs 32, vertical guide rods 33 being used inside these coil springs, and these rods will be understood to be set tightly into lower platform 29- and to` pass freely through apertures in platform 31. A collar 35 near the upper end of the tubing string overhangs an upwardly facing seating shoulder 36 formed in the member 31, and it will be understood that the weight of the tubing string and vibrator G are transferred to theV member 31 and, through springs 32, to the rigid platform 29. Y

A fitting 40 at the top end of the pump tubing, between the tubing and generator:V G, delivers production fluid to delivery line 41.

vAs is disclosed in my aforementionedV Patent No. 2;.444,912the pump tubing contains one, or more llid impelling assemblies, in the illustrative case, including check valves, such as indicated at C, and such valves may comprise a tubular fluid displacing member 50 mounted in the tubing string, preferably at the calculated location of a velocity anti-node of the wave set up in the tubing, and a check valve element 52 seating at the top end of the fluid passage 53 through the member 50. In some instances the valve element 52 is urged -towards its seat by a biasing spring 54.

Theessential operation of such a pump is fully set forth in my aforementioned patent. Briefly, operation is as follows: It will be recalled that periodic deformation waves of tension and compression travel down the pump tubing as a result, of the vertical oscillating force applied to the upper end thereof by theY generator G. These waves set localvelocity anti-node regions of the tubing into vertical oscillationV through an amplitude up to say 1/z inch. 'Ihe tubular valve members 50 accordingly have this vertical oscillation. On eachdownstroke, the member 50 travels with an acceleration suflicient to separate from the valve element 52, and fluidY displacing by member 5,0 travels upwardly therethrough and past the then unseated valve element 52. On the upstroke, valve element 52 seats, andthe column of welluid thereabovc is elevated. The columnof well fluid above the4 valve element 52 does not substantially drop during theV downstroke, because the acceleration of the parts onv the down-stroke, considerably exceeds theV acceleration of gravity.,

In accordancefwith, the present invention, the vibratory system consisting of oscillator or generator G, the platform 31 and `the supportingl springs 32 is critically tuned to resonate at thev frequency ofV operation of generator G. Thisas willbe readily appreciated by those skilled in the art, may be accomplished by giving the components of thel system the proper mass and elasticity properties` to satisfy the.. equation k frn n in which m is the equivalent vibratory mass of the several vibrating components, k is the spring constant, and f is the frequency for resonance. In the preferred practice of the invention, the generator G is operated at a frequency to resonate the pump tubing, establishnig fixed nodal and. anti-nodal regions as heretofore explained.

The. elastically oscillatory system consisting of the generator, platform 31 and springs 32- is thenltuned, asex plained, tothis predetermined operating frequency of the generator G.

Reference to the diagrams of Figs. 3 and 4 willV make clear the improved performance accomplished by the invention. Fig, 3; depicts a sonic pump with an untuned elastic, support system, and at w1 is represented the corresponding Standing wave in the tubing. A velocity antinodeV1r occurs' at the upper endofthe tubing, where supported by platform 31. The rst stressl anti-node S1 is shown at a; considerable levelabove a quarter wavelength distance down-the tubing, and the velocity and stressanti.- nodes V2,V S2, V3, etc., are spaced below stress anti-node S1 at normal quarter waveA intervals. The oscillation displacement amplitude atvelocity anti-node V1, at the upper end of the tube, is represented on wave. w1 at d. The completion of the upper quarter wavelength of the standing wave w1 above the levelof V1, is indicated in phantom lines, and at da is indicated the theoretical displacement amplitude that would occur at the upper end portion of the tubing at V1, if it were not for the upward shift of the wave pattern. It will be understood from the foregoing that the reason for the illustrated upward shift or displacement of 'wave pattern w1, with first stress anti'- node S1 located at considerably less than a quarter wavelength down thetubing from its upper end, has resulted fromy the untuned mass of oscillator G, platform 31, andthe springs 32. It will be evident that theactual Ioscillation displacement d asa consequence of the conditions described is materially less than the maximum displacement do that would be available were it not for the high position (substantially less than a quarter wavelength from the top) of the iirst stress anti-node.

Fig. 4 shows the performance attained when the vibratory system consisting of the oscillator G, platform 31 and springs 32 is critically tuned to resonate at the frequency of operation of oscillator G. In this case, the first stress anti-node S1 is a full quarter wavelength down the tubing from the top, and the resulting standing wave is as represented, with the maximum oscillation amplitude d1 obtained at the top end of the tubing. It is thus seen that the described tuning results in maximized oscillation amplitude at the upper end of the tubing, and it will be appreciated from what has gone before that this results in maximized power ow from the generator into the tubing. To repeat what has previously been stated, a given oscillating force applied by the generator to the upper end of the tubing now acts throughout a greater displacement distance, Which directly translates into correspondingly increased power transmission into the tubing. Looked at somewhat differently, because of the high upper node S1 in the case of Figure 3, caused by the untuned mass of the oscillator on the upper end of the pipe 12, the oscillator is forced to drive the pipe 12 at a comparatively high impedance region thereof, i.e., at a point undesirably close to the node. It must be realized that the pipe cannot be driven at all at a node, which is a point of very high impedance; is most effectively driven at an antinode, which is a point of minimum impedance; and the closer the point of drive to the node, the greater is the impedance of the pipe at the drive point, and the greater the applied oscillatory force must therefore be to attain a given vibration amplitude at the velocity antinodes V2, V3, etc., along the pipe. Hence, a given oscillator having a given effective unbalanced drive force weight, connected in the prior art system of Figure 3, so as to attain the vibration amplitude represented at the velocity antinodes V2 and V3, can be replaced in the system of Figure 4 by an oscillator having smaller unbalanced drive force, without reduction of the vibration amplitude at the nodes V2 and V3. Or, using the same oscillator, increased vibration amplitude would be realized at the antinodes in the case of Figure 4. The explanation of these phenomena is that, considering the over-all vibration system as a whole, the effective mass reactance of the oscillator is tuned out of the system by selecting the springs 32 such that the spring reactance is equated to this mass reactance at the operating frequency. The mass reactance of the oscillator being thus reduced to zero, the pipe 12 vibrates as in Figure 4, as though the entire effective mass loading of the oscillator on the pipe had been removed; and in consequence, the upper node S1 drops to a full quarter-wave-length distance down from the top end of the pipe, and the vibration amplitude at the top, for a given oscillator, increases from d to d1. The concept of tuning the springs 32 to the `mass of the oscillator at the frequency of vibration of the oscillator and pipe is also applicable in case the pipe is not vibrated at resonance, and does not therefore exhibit a standing wave pattern, in that, in such case also, it is an important improvement to achieve a low impedance output from the oscillator (maximized amplitude of oscillation), so that maximized wave energy is delivered to the pipe. It will be evident that by tuning the springs 32 to the effective mass of the oscillator, a secondary vibratory system is provided which is a part of the over-all vibratory system, and which is resonant at the operating frequency whether or not standing wave resonance is established in the pipe. The benefit gained has been found in practice to be very material and important.

As explained earlier herein, the velocity anti-anode region V1 of the, tubing is a region of low mechanical impedance, while the support point for the springs 32, consisting in this case of the firmly mounted platfOl'm 29,

is a region of high mechanical impedance. yIt Will be clear from a consideration of Fig. 1 that vibration transmission from the tubing through the springs 32 to the platform 29, and from the latter down the supporting pipe 24 to the casing head, and thence through casing 10 to the earth, would be a highly undesirable condition. It should further be evident that, aside from the mere problem of undesired shaking, any such vibration transmission represents a power leak from the vibratory system. It should further be clear that any impedance 0ffered to the vibratory tubing 12 by the spring supporting system is highly undesirable. All these conditions are taken care of by the described critical tuning of the elastically vibratory system consisting of generator G, platform 31 and the springs 32, combined with a firm or solid base for said springs. These conditions being met, a low impedance exists at the coupling point between tubing and spring supported platform 31, a high irnpedance exists at the spring supporting platform 29, and all of the foregoing objectives of the invention are attained.

The invention has now been disclosed in one specific illustrative form. It will be understood, however, that the embodiment illustrated is illustrative only, and various changes are within the scope of the inventions. It will further be understood that the invention is not limited in application to sonic pumps in which the vibratory column is a pump tubing, but is equally applicable, as will readily be recognized by those skilled in the art, to sonic pumps in which the vibratory column is a rod string inside the tubing, as particularly shown in my Patent No. 2,553,541.

I claim:

A deep well pump which comprises: a fluid impelling means positioned in the well, a wave transmitting elastic column extending from the ground surface to said iiuid impelling means and operatively connected thereto, a mechanical oscillator for exerting an oscillatory force on the upper end of said elastic column at a predetermined frequency, said oscillator having oscillatory force means operable at said predetermined frequency, and said force means being connected to said column in force transmitting relationship, and an oscillatory spring support means for supporting said column near the point of said connection of said oscillator, including a firm supporting base, means on said column adjacent said point of said connection, and spring means connected between said base and said means on said column, said column, oscillator and oscillatory spring support means constituting an over-all vibratory system, and said spring means being tuned so as to have a spring constant so related to the combined eiective oscillating mass of the oscillatory spring support means and oscillator that the portion of said over-all vibratory system composed of said oscillatory spring support means and oscillator comprises a secondary oscillatory system which has a resonance at said predetermined frequency, such that the mass reactance in the over-all vibratory system oiered by said mechanical oscillator and said support means is vectorially opposed and counterbalanced by the stiffness reactance of said spring means, and maximized output force applied through maximized oscillation amplitude distance is thereby exerted by said oscillator on said column, and all in such manner that said spring support means olers minimized impedance to said wave transmitting elastic column, and said supporting base offers maximized impedance to said oscillatory spring support means, whereby vibrational energy is substantially confined against leakage through said supporting base, and said spring support means presents minimal blocking impedance to said wave transmitting elastic column.

References Cited in the file of this patent UNITED STATES PATENTS 2,444,912 Bodine July 13, 1948 2,553,541 Bodine May 22, 1951 2,572,977 Bodine Oct. 30, 1951

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