US2643612A - Fluid-operated pump with singleacting direct-connected booster pump - Google Patents

Description

June 30, 1953 c. J. coBERLY FLUID OPERATED PUMP WITH SINGLEFACTING DIRECT-CONNECTED BOOSTER PUMP 3 Sheets-Sheet l Filed Jan. 22, 1949 June 30, 1953 c. J. coBERLY l 2,643,612

' FLUID OPERATED PUMP vWITH SINGLEACTING DIRECT-commun BoosTER PUMP Fld Jan. 22, 1949 3 Sheets-Sheet 2 HHRH, Fosa/Ni HAR/ws @Y w m C. J. COBERLY FLUID OPERATED P DIRECT-CONNEC 2,643,612 UMP WITH SINGLE-ACTING TED BOOSTER PUMP June 3 0, 1953 5 Sheets-Sheet 3 Filed Jan. 22, 1949 ,Pstentedf- June 3o, 1953 FLU'ID-OPERATED PUMP WITH SINGLE- ACTING DIRECT-CONNECTED BOOSTER PUMP Clarence J. Coberly, Los Angeles, Calif., assignor, by mesne assignments, to Dresser Equipment Company, Ohio Cleveland, Ohio, a corporation oi` Application January 22, 1949, Serial No. 72,108

, l My invention relates to fluid-operated pumps for wells, and more particularly, to a fluidoperated pumping device comprising a fluidoperated. main pump having an auxiliary or booster pump associated therewith for boosting the pressure of the well fluid delivered Ato the inlet of the main pump.

Reference is hereby made to my co-pending application Serial No. 45,048, filed August 19, 1948; Serial No. 46,776, filed August 30, 1948; and Serial No. 77,588, filed February 21, 1949.

Fluid-operated pumps are commonly used in the oil industry for pumping oil from wells, such a pump comprising, in general, a coupled motor and pump combination set in the Well at the level from which oil is to be pumped. In such a combination, the motor comprises a motor piston which is actuated by alternatively admitting an operating fluid, such as clean crude oil, under relatively high pressure into opposite ends of a motor cylinder in which the motor piston is disposed so as to reciprocate the motor piston. The reciprocatory motion of the motor piston is communicated to a pump piston in the pump section of the combination so that the pump piston pumps oil from the well. Y

The fluid being pumped from a well may contain, in addition to oil, various other fluids such as water and natural gas, the gas being present in solution or in suspension in the oil in varying quantities depending upon the pressure and temperature conditions prevailing in the well. Also, if the well is being pumped beyond its capacity to produce, air may be present in the fluid being pumped. If the oil is saturated or supersaturated with natural gas at the conditions of pressure and temperature prevailing at the level at which the pump is set, a large portion of the gas may be released during the suction stroke of the pump piston to form a gas pocket in the pump cylinder. Also, of course, in many wells the well fluid is merely a, froth composed largely of gas with a relatively small volume of oil. In either case, or if air is drawn into the pump cylinder, a pocket of gas or air in the pump cylinder results. Such pockets result in a material reduc tion in the pumping load until such time as the pump piston compresses the gas or air present and strikes solid well fluid in the cylinder.

Such fluid-operated pumps are frequently set at relatively great depths and, consequently,'a large volume of `operating fluid under relatively high pressure is confined in the supply tubing between the pump in the Well and the apparatus on the surface which delivers the operating fluid 1o claims. (c1. 10s-5) to the pump. Due tothe appreciable compressibility of this large volume of operating fluid, and due to the expansion of the supply tubing under the relatively high pressure at which the operating iiuid is maintained, a large amount of energy is stored under normal operating condi" tions. If, because of the presence of gas or air in the pump cylinder, the load on the pump piston decreases, a sudden increase in the rate of iiow of operating uid to the pump occurs, thereby accelerating the motor and pump pistons. The speed ultimately attained may be excessive and the pump may race for a portion of a stroke or'for a number of strokes, which is normally detrimental to various Vcomponents `of the pump. Various expediente for preventing damage to the pump mechanism under such conditions have been employed. For example, flow regulators disposed in the supply line for the operating fluid have been employed to maintain the rate of delivery of operating iiuid to the motor section of the pump below a value which might be harmful to the pumping equipment. While such ow governors are practical under most conditions of operation, they have some disadvantages in that they increase thev cost of the pumping equipment and render the equipment rather complicated. Also, there is some lag in their operation since they respond only after the condition requiring compensation has already developed.

Also, the presence of gas or air in the pump cylinder has a detrimental effect on the eiciency 0f such a fluid-operated pump. For example, if, in a given installation, thirty percent of the pump cylinder of the huid-operated pump contains free gas or air, the efliciency of the pump, i. e., the percentage of the volume of the pump cylinder which contains solid well fluid, will be only seventy percent. In other words, under such conditions, the fluid-operated pump will pump well iiuid from the well at only seventy percent of capacity.

In view of the foregoing considerations, it is a primary object of the present invention to provide, in combination with aV conventional fluid-operated pump, an auxiliary or booster pump which is adapted to draw well fluid from the well and to deliver it to the inlet of the uidoperated pump atr an increased pressure such that the major portion of the gas or air in the well fluid will not flash out to form a pocket in the pump cylinder of the main pump. I accomplish this by providing a` booster pump which will maintain the pressure of the well uid pass- 3 ing into the pump cylinder of the main pump at a value equal to or above the pressure prevailing in the well at the inlet of the pumping device. A further object of the invention is to provide a booster pump which `will compress :any free gas or air entrained in the well fluid to a substantial extent before it is delivered to the inlet of the main pump.

It will be apparent that employing pump in combination with a fluideoperated main pump in the foregoing manner will obviate, or at least minimize, the diiiiculties hereinbefore disa .booster piston having pressure relief valve means for bypassing well fluid from the high pressure end of the booster pump cylinder to the low pressure end thereof in the event that the pressure ofthe welllfluid 'delivered tothe accumulator and/or to the inletV of themain pump tends to exceed a predetermined value.

' `-.Another object of the invention is to provide vsuch 4a.pumping,.device wherein the rod means cussed. In otherrwords, thewemployment .oriabooster pump will tend to obviate-A racing ci'A the main pump and to increase the pumping-let;- ciency thereof. As an example, let it be as- .connecting the .various pistons is hydraulically balanced withrespect to well fluid pressure.

The foregoing objects and advantages of the :present-invention. together with various other i objects and advantages thereof which will besumed that the pumping efficiencyy ofuthemain pump is only seventy percent when the pressure at the inlet thereof is approximately equal to*Y atmospheric pressure. With the present invention, V.if Athe particular .booster pump.i utilized .is

adapted to. increasezthe pressurezoff thef-wellzluid delivered to the:inlet.of; theamainpumpftothree hundred pounds perxsquareY inch, .the freegas` or air which otherwise .would occupyfthirty percent.

of thevolume of the-pump cylinderl oithe. main pump will becompressedtooccupy only approximately 1.4 percent 'of the volume of the pumpr cylinder, thereby increasingithe eiciency of the main pump to approximately -98.6percent under .l

such conditions.

Another object of the present'invention is to provide such a pumping device,;i. e=,- such a fluid--` operated main pump 4and booster pump, combination, in which they booster-pump is directly connected tothe mainxpumpsoas to beoperable thereby.r More specically,;it isfan obectv to `provide a fluid-operated pumping device wherein the booster pumpv'includes4 a booster pump piston directlyconnected4 by rod means to oneof the pistons of the main pump,rpr eferably the pump piston. thereof.V

-A furtherobject of the invention is gto pro-` cumulator ofY annular cross` section, .which 4is adapted to. receive and sulfzstantialhgv enclose .the-

main pump.

Another object istofprovide-a pumpingtdevicef wherein the tubular accumulatorghaslmeans con.-Y

nected theretorforproviding -agpump-rseatior; the

main pump. f

Another object-istoprovide a pumping devicewherein the main pump .is removable iromg'the tubular accumulator and-wherein. the booster pump piston is removable from the boosterpump cylinderl concomitantly.withremoval of themain pump from the accumulator;

Another-.object is to providefafpumping-'device wherein thezaccumulator andthe` boosterV pump cylinder. are connectedrbyv-a tubular-fitting which provides-.thepump seat-for-the mainfpump and .throughwhich the .booster pump piston may be withdrawn fromtheboosterpump cylinder, the rod means connecting therbooster pump pistonY with oneof the pistonsoi the; main pump extending through` such tubular fitting.

Another Objectis to provide agboosterv pump come apparent, maybe attained through the utilization of the exemplary embodiment of the in- -ventionwhich .is-.illustrated in the accompanying drawings and which is described in detail hereina-iter;v Referring to the drawings:

Fig. l is a utility view on a reduced scale showingr a iiuid-operatedpumping vdevice which embodiesithe inventionasinstalled in a well Vliiglla` isa longitudinal sectional View taken alongthearrowed .line l'a-lc .of 1 of the drawing;

Eig-.12A is; alongitudinal sectional view of the upper end of a preferredi'booster pump of the invention and is taken. along vthe `broken line 2-2 oiFig. l ofithe drawings;

Fig.y Suis a downward continuation of Fig. 2`

and is taken alongfthebrokenline 3-'3 of Fig. l; fEig. lis'atransverse'sectional view taken along therbroken line 4--41 offEig'. 1;/

Figs.Y 5 and .6 are transverse sectional views taken.alongthegbroken.lines5?-5 and 6*(5, respectively, of' Fig-..2 rand Y vFigir isa transversesectionalzview taken along the'broken. line 1-:1 cf;'1ig..3.of` the drawings.

Referring. particularly .to;Fig. 1 of the draw- .:ings, I. show-.anoil well` lined. with a casing IG havingperforations I l; whichregister with` an oil producing formation t2 andxthrough which oil and. other fluids mayflowv into the interior of the casing, the-fluids entering the casing being Acollectively..referredto hereinafter as the well fluid. Extending downwardly: into the casing It) is a .production tubing lf3` which. is adapted to convey well' fluid tothe surface of the ground, and extending downwardly into the production r ytubingin the particularv construction illustrated is a power'tubing'l'd havingia fluid-operated main or primary pump l5 connected to the lower end thereof. Connected to theilower.- endv of the production tubing' lf3. is a tubular fitting le which,

r ,a asbest. shownv in Fig'. 2: of the-drawings, provides a tapered pump seat H. orxthe main pump l5. Secured relative to the. lower end of the main pumpy l5 in axial-alignment therewith is an auxiliary Yor boosterpumpl' which is adapted to pump well fluid from the casing l0 to the inlet of themain pump at a pressure higher than that obtaining at the intake. of 'the booster pump, as will be discussed inY more detail hereinafter.

The fluid-operated main pump t5 may be of any conventional type, Asuch as that shown in my Patent No. 2,081,220', issued May 25, 1937, which is adapted to pump welliiuid from the casing lil4 upwardly through the production tubing i3 to the surface. As shown best in Fig. la o the drawings, the huid-operated main pump i5 is provided'witha motor=cylinder 2l having a motor piston 22 therein, and'. is provided with a pump cylinder 23 having a pump piston 24 therein,4 the motor; and pump pistons respectively being provided with. longitudinal passages A25- and 26 therethrough. Connected to the upper end of the motor piston 22 and communicating with the passage therethrough is an upper tubular rod 21 which extends into a balance chamber 28 at the upper end of the main pump I5. Connecting the motor pump pistons 22 and 24 and communicating with the passages 25 and 26 therethrough is an intermediate tubular rod 23, and connected to the lower end of the pump piston is a lower tubular rod 35 for directly connecting the main pump I5 to the booster pump I8 as will be discussed in more detail hereinafter, the lower tubular rod extending through the tubular fitting l5. l f

Briey, the fluid-operated main pump I5 operates as follows: Operating uid, such as clean crude oil, under relatively high pressure is alternatively admitted into the ends of the motor cylinder 2! to reciprocate the motor piston 22 therein, such reciprocatory motion of the motor piston being communicated to the pump piston 24 by the intermediate tubular` rod 29. rihe pump piston 24 discharges fluid intothe production tubing I3, which conveys the fluid upwardlyto the surface.

Considering the pumping devicein more detail, the main pump i5 terminates at its lower end in a tting 33 having a tapered head 34 which is adapted to seat on the pump seat I1: provided by the tubular tting I5, and having a stem 35 which is insertable into the tubular fitting I6. The ritting 331s provided with a bore 36 therethrough for the lower tubular rod 3i), the latter being encircled by packing 31. As best shown in Figs. 2, 5 and 6 of the drawings, the iitting 33 is provided with a plurality of longitudinal passages 38 therethrough which act as inlet ports for the main pump i5, and isprovided with a plurality of longitudinal passages li which terminate in radial passages 4I communicating with an annular space i2 between the production tubing I3 and the main pump i5 so as to deliver fluid pumped by the main pump to the production tubing, the passages 40 and 4I providing outlet ports for the main pump.

Connected to the lower end of the tubular fitting i5 in axial alignment with the motor and pump cylinders 2| and 23 of the main pump i5 is a pump cylinder 45 of the booster pump I8, the booster pump cylinder #i5 being provided with an intake port i5 which communicates with the well casing i5 to admit well iiuid into the booster pump cylinder. Outflow from the booster pump cylinder through the intake port 45 is prevented by a check valve 41.

Reciprocabie in the booster pump cylinder 45 is a booster pump piston 55 which, as best shown in Fig. 3 of the drawings, includes a tubular upper section 5i, a tubular intermediate section 52, and a tubular lower section 53 in the particular construction illustrated. The lower tubular rod 3@ is threaded into a stem 5d on the upper section 5I of the booster pump piston so as to communicate reciprocatory motion of the motor and pump pistons 22 and 24 of the main pump I5 to the booster pump piston, as will be discussed in more detail hereinafter. As will be apparent from Fig. 3 of the drawings, the lower end of the lower tubular rod 3@ is exposed to well iuid pressure, and such pressure is also communicated to the balance chamber 25 at the upper end of the main pump i5 through the lower tubular rod 35, the passage 26 through the main pump piston 25, the intermediate tubular rod 29,

the passage 25 through the motor piston 22, and

y that of the lower end of the lower tubular rod 35 so that the rod assembly is hydraulically balanced with respect to well fluid pressure, which i is a feature of the invention.

' Referring againto Fig. 3 of the drawings, clamped between the intermediate and lower sections 52 and 53 of the booster pump piston 55 is a packing cup 51, the latter surrounding a portion of the intermediate piston section 52 in the particular construction illustrated. Surrounding a portion of the lower piston section 53 is another packing cup 58 which is clamped between the lower piston section and a washer 59, the latter being retained by a flange 6I! on a tube 6I whichis threaded into the intermediate piston section ,52.r Extending through the tube 6I and threaded into the upper piston section 5i is a tube 62 having a flange 63 at its lower end, a compression spring 64 encircling the tube 62 and being seated at its ends against the flanges Sii and 63. The lfunction of the spring 64 is to maintain complementarily tapered surfaces S5 and 66 on the respective piston sections 5I `and 52 in uid-tight engagement, unless the pressure in the booster'pump cylinder 45 above the piston 50 exceeds a predetermined value.v If this occurs, the spring 64 is compressed to permit separation of the tapered surfaces 65 and 6E to permit fluid to flow from the upper Vend of the booster pump cylinder 45 into the lower end thereof by way of radial openings 61 in the tube 62. Thus, the booster pump piston 53 provides a pressure relief valve means for by-passing fluid from the high pressure side of the booster pump piston 50 to the low pressure side thereof, i. e., from the upper end of the booster pump cylinder 45' to the lower end thereof, in the event that the pressure on the high pressure side of the booster pump piston exceeds a value determined by the spring 64,2which is a feature of the invention.

The upper section 5I of the booster pump piston 50 is provided with longitudinal passagesJi which communicate with an annular groove12 therein, the latter communicating with the interior of the tubular upper section 5I. Thus, during downward movement of the booster pump piston 50, well fluid from therebeneath may flow upwardly therethrough by way of the tube 52, the ,tubular upper section 5I, the annular groove 12 in the tubular upper section, and the longitudinal passages 1I therein. Reverse flow through `the booster pump piston 50 "during upward movement thereof is prevented by a check valve means 13 comprising a plurality of ball valves 14 which are adapted to close the longitudinal passages 1I, the upper piston section 5I being provided with inserts 15 which serve as seats for the ball valves. The ball valves 14 are held by a retainer 16 which is urged downwardly to retain the ball valves in engagement with their seats by a compression spring 11, the latter being seated against a nut 13 threaded on the stem 54 on the upper piston section5I. As will be apparent, the spring 11'prevents opening of the check valve means 13 during the upward, or working stroke of the booster pump piston 55, and permits opening thereof during the downward stroke of the booster pump piston. Thus, the booster pump i8 is of the single-acting type, fluid being discharged from the boosterpump cylinder 45 during the upward stroke of the booster pump 50. v f

Z Fludpdisplacedg-by',thefboosterpump piston ,-50 duringi itsyworkingVV stroke is :discharged from the upperA endv of the booster; pump cylinder 45' through discharge ports. 8l which` communicate Y with the inletyports: 3.8 .for Vthe main pump l through an annular space 82. The. annular space'ris defined by asleeve 3-3 pressedon a1 reduced-diameter. portionof the fitting 33, andthe discharge ports 3l are formedin a valve seat member-8.4whichisseated againstthe lower end of the sleeve 83, the valve seat. member being retained byma nut 85V threaded on a sleeve 86 which .encircles the tubular,l lower rod and is threaded into the lower end` ofthe bore 36v through'A the. fitting v311i; l

A` check valve means; 901 similari to the `check valve means "I3 permits-.upward now throughthe discharge portsal ,duringfthe upward or. work-- ing :stroke .of thel booster .pump piston and preventsidownwardflow. therethrough during the downward stroke: of l therbOosterA pump piston, the check; valve means 9i) comprising. a plurality of ballvalvesll Yadaptedlto seat on inserts 92v carried; by the i-'valvef seat memberi 84: and-encircling the discharge ports. 8l therethrough. The ball valves 9i fare retainedby a retainer 93. and are adapted to be heldseatedagainst theinserts 92 by acompressionspring .94 whichfis disposed be'- tween theretainer 93- and the lower end of the fitting 33.

Inorderf to maintain theuid delivered to the inlet ports 3.87ct themain pump; l5 under pressure; during the-downward"V stroke of the booster pump piston` SLI provide anV accumulator 166 which `communicates 'with the inlet ports 33 throughradial passages? lili .inthe tubular fitting I6, anannular groovev H12 yin this tting, and radial passages H33 infthe tting. 33. The accumulatcr. lis tubular, i. e., of annular cross section, and: comprises an annular space |05 between the production tubing |43 and a tube or. shell IOB which 'encircles the lower end of the production tubing and which is connected at-` its lower. end to and .extends upwardly from the'tubular tting I6, as best. shown in Fig. 2 of the drawings. The, shell |06 Ymay extend upwardly from the` tubular fitting l5 a distance such thattheV accumulator Ireceives a column of fluid of sulhcient height to maintain theY desired pressure inthe-inlet ports 38 of the main pump l5 hydrostatically, in which case the accumulator may be; open. at itsupper end. However, in order toavoid thenecessity of employingan accumulator l'of excessive length, particularly when a high pressurey is to be maintained in the inlet ports 38, I prefer to close the accumulator lui! at its-upper end, as by meansof aseal'ingiring {D'I- (Figs. l and 4)V interposedbetween the shell [66 .and the production tubing The operationoi my pumping device will be apparentfromthe foregoing'so that only a general description thereof is thought to be necessary. During the downward stroke of the motor and pump pistons 22 and 24 of the main pump i5, the boosterpump piston 50 is moved downwardly initscylinder 45, fluid from the lower end of the booster pump. cylinder iiowing through the booster pump vpiston into the upper end thereof by wayV of the check valve means 13. During thedownward stroke Vof the booster pump piston, downward` iiow ,through the discharge portsrl isaprevented by thefcheck valve means 90. As the motorpiston22 moves upwardly, it moves the booster pump piston 50 Vupwardly by means ofthe .intervening connection so that: the booster-"pump piston displaces fluid from the upper. endofitheboosterpump cylinder past the check valve means vSi), now through the booster pump pistonduring its workingstroke being preventedv by thecheckvalve means 73. The fluid discharged-by the booster pump I3 in this manner is deliveredeither tothe main pump i5, or to the accumulator Hill.V During the downward, or nonworking stroke of the booster pump piston, fluid flows into theinlet ports 38 of the main pump from the accumulator |06, thelatter maintaining the desired pressure. in the inlet ports during the nonworking stroke of the booster pump piston.. Thus, the accumulator lili] provides a continuous flow of. iluid at substantially constantpressure to the-inlet `ports 33 of the main pump l5.

Thus, the auxiliary or booster pump I8 delivers well uidto the inletports 38 of the uid operating mainpump l5 at an elevated pressure to minimize the formation of gas or air pockets inthe pumpcylinder-23: of the main pump, whereby 4to increase the-eiiiciency of the main pump and to minimize the possibility of damage to the components thereof which may result from the formation oigasor air pockets in the pump cylinder `3 as previously discussed. The booster pump. I8 preferably delivers a relatively large volume of well fluid to the main pump at a relatively low pressure, the effective cross-sectional area of the boosterrpump piston 50 being substantially larger than that of the motor iston 22 to accomplish this. In practice, the ratioof booster pump piston area to motor piston area may be 4- to l, for example. rihus, the major portion ofthe work necessary toV pump weligfluid tothe-surface sperformed by the main pump i5, the function of the booster pump I8 being to deliver the Welluidto the main pump at a pressure suicient only to prevent excessive formation ofv gas pockets inthe pump cylinder 2-3k of themain. pump, which pressure preferably exceeds thev pressure obtaining at the intake port 46 of the booster pump.

Intheeventthat'the pressure developed in the accumulator lill)V rises above the value determined by the,l spring 64 for any reason, the pressure relief valvemeans incorporated in the pump piston 50 will operate to by-pass iiuid from the high Vpressure side of the booster pump piston to the low pressure side thereof, as hereinbefore discussed.

Inorder tofacilitate removal of the main and booster pumps I5 and I8 for servicing or repair, the ,internal diameter of the tubular fitting i6 is preferably at least equal to the diameter of thebocster pumpV piston 50 so that the latter may be; removed from its cylinder through the tubular fitting V1 6 concomitantly with removal of the main pump from the tubular accumulator N39. Thus, with the exception of the booster pump cylinder 45 and the check valve 4l controlling fiow through the intake port 46, all components of the pumping device which are subject to wear may be pulledin a single operation without any necessityofpulling the production tubing i3 and the-accumulator l E26, whichis a feature of the invention.

Although I have disclosed an exemplary embodiment of theinventionfor purposes of illustration, it will be understood that various changes, modications and., substitutions may be incorporated the'. speciiic embodiment disclosed Without .necessarily departing from the .-facfracia l. In a fluid-operated pumping device, fthe;

combination of: a tubularv accumulator adapted to be positioned in a well; means providing a pump seat secured to said'accumulator; a uidoperated main pump of thereciprocating type adapted to seat on said pump seat, said main pump being provided with an inlet port; a singlef acting, auxiliary pump of the reciprocating type secured relative to said main pump in axial alignment therewith, said auxiliary pump being provided with an intake port adapted to communicate with the well and being provided with a discharge port communicating with said inletv port; means providing iiuid communication between said accumulator and said discharge and inlet ports; and means mechanically connecting said auxiliary pump to said main pump for operating said auxiliary pump so as to pump Well fluid from the Well into said inlet port and said accumulator at a pressure higher than that in said intake port.

2. A duid-operated pumping device as set forth in claim 1 wherein said pump seat is located adjacent the lower end of said accumulator and wherein said accumulator,substantially encloses said main pump.

3. A fluid-operated pumping device as set forth in claim 1 wherein said auxiliary pump comprises a cylinder secured to said accumulator and having a pump piston therein, and wherein said main pump comprises connected motor and pump pistons, said means mechanically connecting said `auxiliary pump to said main pump comprising rod means for connecting said pump piston of said auxiliary pump to said pistons oi' said main pump.

4. In a huid-operated pumping device, the combination of: a tubular accumulator adapted to be positioned in a well; a tubular iitting connected to the lower end of said accumulator and provided with a pump seat; a fluid-operated main pump of the reciprocating type adapted to be positioned in said accumulator and to seat on said pump seat, said main pump including axially aligned and connected motor and pump pistons and being provided with an inlet port, asingleacting, auxiliary pump provided with an intake port adapted to communicate withthe well and a discharge port adapted to communicate with said accumulator and with said inlet port, saidy auxiliary pump including a pump cylinder secured to the lower end of said tubular fitting and including a pump piston in said pump cylinder; passage means for connecting said discharge port,

Vsaid accumulator and said inlet port;'and rod means extending through said tubular fitting and directly connecting said pump piston of said auxiliary pump to said pistons of said main pump for operating said auxiliary pump so as to pump weil fluid from the well into said inlet port and said accumulator at a pressure higher than that in said intake port.

5. In a fluid-operated pumping device, the combination of: a tubular fitting adapted to be positioned generally vertically in a well and provided with a pump seat; a fluid-operated main pump of the reciprocating type adapted to seat on said pump seat and including axially aligned, connected motor and pump pistons, said main pump being provided with an inlet port for well iuid and `being adapted to pump well fluid from e 10 thewell to the surface; an auxiliary pump of the reciprocating type including a pumpy cylinder con- 'fnected to the lower end of said tubular tting and axially aligned with said motor and pump pistons of said main pump, kand including a pump piston reciprocablein said pump cylinder, said auxiliary pump having anintake port adapted to -communicate with the well andhaving a dis- Y chargeport; passage means independent of and outof fluid communication with said intake port for connecting said discharge port to said inlet port; and rod meansV extending through said tubular iitting and -connecting said pump piston of 'said auxiliary pumpV to said motor and pump pistons of said main pump for operating said auxiliary pump so as to pump well fluid from the well into said inlet port at a pressure higher than that in said intake port.

6. A fluid-operated pumping device as set forth in claim 5 wherein the internal diameter of said tubular fitting is at least equal to the diameter of said pump piston of said auxiliary pump to permit Withdrawal of said piston of said auxiliary pump through said tubular fitting.

7. In a huid-operated pumping device, the combination of: a fluid-operated main pump having a balance chamber, a motor cylinder, a pump cylinder and 4an inlet port communicating with said pump cylinder, said main pump including a tubular motor piston in said motor cylinder, a tubular pump piston in said pump cylinder and a main tubular rod means connecting and cornmunicating with the interiors of said motor and pump pistons and having an end extending into said balance chamber; an auxiliary pump of the reciprocating type secured relative to said main pump and including a pump cylinder having a tubular pump piston therein, said auxiliary pump being provided with an intake port adapted to communicate with the well and a discharge port communicating with said inlet port; and anv auxiliary tubular rod means connecting said pump piston of said auxiliary pump to said motor and pump pistons of said main pump for operating said auxiliary pump so as to pump well fluid from the Well into said inlet port at a pressure higher than that in said intake port, said auxiliary tubular rod means communicating with said main tubular rod means and said intake port.

8. In combination with production and power tubings set in a well and a pump seat connected to one of said tubings in alignment therewith, a fluid-operated pumping device movable downwardly in the well through said one tubing to seat on said pump seat and including: a iiuidoperated main pump of the reciprocating type actuable by an operating fluid under pressure in said power tubing to pump well uid into said production tubing, said main pump having an' inlet port; an auxiliary pump of the reciprocating type provided with an intake port adapted to communicate with the well to receive well iluid from the well and provided with a discharge port for well iiuid; means for connecting said discharge port in fluid communication with said inlet port so as to deliver well fluid discharged by said auxiliary pump to said main pump to be pumped thereby into said production tubing; and means mechanically connecting said auxiliary pump and said main pump for actuating said auxiliary pump so as to pump well fluid from said intake port into said inlet port at a pressure higher than that in said intake port.

V9. A combination according to claim 8, including in addition: a tubular member connected to

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