US2999464A

US2999464A - Tandem hydraulic pump system

Info

Publication number: US2999464A
Application number: US527971A
Authority: US
Inventors: Clarence J Coberly
Original assignee: Kobe Inc
Current assignee: Kobe Inc
Priority date: 1955-08-12
Filing date: 1955-08-12
Publication date: 1961-09-12
Anticipated expiration: 1978-09-12

Description

Sept. 12, 1961 c. J. coBERLY 2,999,464

TANDEM HYDRAULIC PUMP SYSTEM Filed Aug. l2, 1955 6 Sheets-Sheet 1 LLAFEA/c-E I CaSe/e1.

J2ME/vra Sept. l2, 1961 c. J. COBERLY 2,999,464

TANDEM HYDRAULIC PUMP SYSTEM Filed Aug. 12, 1955 e sheets-sheet 2 iff@ 9,

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TANDEM HYDRAULIC PUMP SYSTEM Filed Aug. l2, 1955 6 Sheets-Sheet 5 f E n if@ 7 ,vir 1./

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Sept. 12, 1961 c. J. coBERLY 2,999,464

TANDEM HYDRAULIC PUMP SYSTEM Filed Aug. 12. 1955 6 sheets-sheet 6 gy MS Awww/sys:

ted tates The present invention relates in general to hydraulic oil well pumping and a primary object of the invention is to provide an oil well pumping system of -this nature which includes two or more duid-operated pumps structurally connected in tandem and having pump sections hydraulically connected in parallel.

As is well known in the art, fluid-operated oil well pumps of the reciprocating type include interconnected motor and pump sections containing interconnected motor and pump pistons. In such a pump, an engine or motor valve controls the application of operating fluid pressure to the motor or engine piston to produce reciprocatory movement thereof, the operating diuid being admitted through an operating fluid intake and being discharged through an operating fluid exhaust, both communicating with the engine section of the pump. The reciprocatory movement of the motor piston is communicated to the pump piston, which takes production fluid from the well through a production tluid inlet and discharges it at a higher pressure through a production uid outlet, both communicating with the pump section of the pump. Suitable inlet and outlet valves are provided in the pump section to control the admission and discharge of production fluid.

In many wells which are produced by hydraulic pumping, the productive capacity of the well is so low that one small fluid-operated pump, such as a two-inch pump, is capable of producing the well satisfactorily.

However, in many wells, the productive capacity is so high, especially where a great deal of water enters the well bore along with the oil, that it is impossible to obtain the necessary pumping capacity with one uid-operated pump because the necessary bottom-hole assembly and tubing system cannot safely be run into the well bore. The present invention, by providing a pump assembly including two huid-operated pumps which are structurally connected in tandem and the pump sections of which `are hydraulically connected in parallel, solves this problem, which is an important feature thereof.

Another object of the invention iS to provide a tandem fluid-operated pump system which is -a free-pump system, i.e., wherein the pump assembly is movable between the surface `and its operating position in the bottom-hole assembly through one of the tubings of the tubing system, preferably hydraulically.

An important object is to utilize the tubing through which the tandem pump assembly is movable as the production tubing for conveying the production fluid discharged by the pumps to the surface. By doing this, the largest tubing of the tubing system is utilized as the production tubing to minimize ow resistance in the production uid column, which is an important feature of the invention.

Another object is to provide a tandem fluid-operated pump system which is a closed system, i.e., a system wherein the spent operating fluid is returned to the surface independently of the lproduction uid through a `separate return tubing, as contrasted to an open system wherein the spent operating fluid is mixed with the production uid from the well and is returned to the surface therewith through the production tubing.

Considering some advantages of the invention as embodied in a closed, tandem, fluid-operated, free-pump system, the size of the production tubing is materially atent i Patented Sept. l2, 1961 reduced `from that which would be required with a single huid-operated free pump having the same pumping capacity, but is still amply large to handle the production fluid discharged by the tandem pumps with minimum friction in the production column. Also, by embodying the invention in a closed system, the friction in the operating fluid supply land return columns can be held within reasonable limits even though sutcient operating fluid is being circulated to operate two or more pumps in parallel. Another advantage arising from the use of fluid-operated pumps in tandem is that the cost of the resultant smaller production tubing through which the pump assembly is displaced between its operating position and the surface costs much less than the larger production tubing which would be required to handle a larger Huid-operated pump having the same capacity as the tandem pumps.

Considering the present invention more specifically now, an object is to provide a tandem fluid-operated pump assembly for free-pump closed-system operation which includes a packer nose assembly at its upper end, an upper sealing adapter connected to the lower end of the packer nose assembly and provided with an operating duid intake and an operating uid exhaust for an upper fluid-operated pump connected to the lower end of the upper sealing adapter, an interpump sealing adapter connected to the lower end of the upper pump and provided with a production uid inlet for the upper pump and an operating luid intake and an operating liuid exhaust for a lower pump connected to the lower end of the interpump sealing adapter, and a lower sealing adapter providing a production tluid inlet for the lower pump and carrying a lower plug engageable with a seat for they tandem pump assembly. The lupper and lower pumps are provided with production Huid outlets respectively located between the upper sealing adapter and the interpump sealing adapter and between the interpump sealing adapter and the lower sealing adapter.

Another object is to provide a bottom-hole assembly to receive and house the tandem pump assembly and providing means for hydraulically connecting the two or more pumps in parallel With respect to the admission and discharge of both the production fluid and the operating uid so that the pumps operate independently of each other.

More particularly, an object is to provide a bottomhole assembly which includes an upper sealing collar cooperating with the upper sealing adapter, a lower sealing collar cooperating with the interpump sealing adapter, and a bottom shoe or lower plug cooperating with the lower sealing adapter, the upper and lower sealing collars being interconnected by an upper pump housing tube for the upper pump, and the lower sealing collar and the bottom shoe being interconnected by `a lower pump housing tube for the lower pump.

Another object is to provide a bottom shoe which carries a standing valve assembly providing the aforementioned seat for the tandem pump assembly and providing a production fluid inlet means communicating with the well.

Another object is to provide the upper sealing collar with an operating-huid intake means connectible to the lower end of an operating-duid supply tubing., an operating-fluid exhaust means connectible to the lower end of an operating-fluid return tubing, and a production-fluid outlet means or production tubing adapter connectible to the lower end of a production tubing, the latter being aligned with the pump-assembly housing provided by the sealing collars, pump housing tubes and bottom shoe to provide for movement of the pump assembly between its operating position and the surface through the production tubing.

Another object is to provide a bottom-hole assembly which includes passage means for connecting the operating-fluid intake means to the operating-fluid intakes of the pumps in parallel, passage means for connecting the operating-duid exhausts of the pumps to the operatingfluid exhaust means in parallel, passage means for connecting the production-fluid inlet means to the production-fluid inlets of the pumps independently of each other, and passage means for connecting the production-fluid outlets of the pumps, independently of each other, to the production-fluid outlet means leading to the production tubing.

Another object is to provide a bottom-hole assembly wherein the upper pump housing tube is connected to one of the sealing collars by means of tapered threads and is connected to the other sealing collar by means of extended threads, a lock nut being Yin engagement with the extended threads and being seated against the corresponding sealing collar to lock the members together. With this construction, the two sealing collars may be oriented angularly relative to each other'for proper alignment of various passages, and the like, therein, as will become apparent. Similar considerations are applicable to the manner in which the lower pump housing tube is connected to the lower sealing collar and the bottom shoe, the lower pump housing tube being connected to one of these members with tapered threads and being connected to the other with extended threads and a lock nut.

Another object of the invention is to provide a bottomhole assembly having passage means for connecting the operating-Huid exhaust means to a pump-assembly unseating chamber to apply pressure to a downwardlyfacing area of the pump assembly, whereby the pump assembly may be unseated by application of pressure to the operating-fluid exhaust means from the surface by way of the operating-fluid return tubing.

Another object of the invention is to provide a tandem fluid-operated pump assembly wherein the upper and inter-pump sealing adapters mentioned are provided with external O-ring grooves connected in fluid communication with axial operating-fluid passages forming parts of the operating-fluid intakes for the upper and lower pumps. With this construction, O-rings in the O-ring grooves mentioned are forced outwardly into sealing engagement with the upper and lower sealing collars upon application of fluid pressure to the operating-fluid supply tubing at the surface, which is an important feature.

Another object of the invention is to provide a standing valve assembly which includes a standing valve seat, a standing valve engageable with the seat, a magnet tending to hold the standing valve olf its seat, and means preventing direct contact between the standing valve and the magnet so that the back flow of lluid through the standing valve assembly can pull the standing valve away from the magnet and seat it more readily so as to avoid excessive hydraulic shock.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be apparent to those skilled in the art, may be attained with the exemplary embodiment of the invention which is illustrated in the accompanying drawings and which isl described in detail hereinafter. Referring to the drawings:

FIG. 1 is a vertical sectional view on a reduced scale illustrating in diagrammatic form the tandem lluid-operated free-pump closed system of the invention which is illustrated in specific detail throughout the remainder of the drawings;

FIG. 2 is a vertical sectional view illustrating the upper end of the tandem Huid-operated free-pump closed system of the invention in speciiic detail;

FIG. 3 is a downward continuation of FIG. 2;

FIG. 4 is a downward continuation of FIG. 3j,

FIG. 5 is a downward continuation of FIG. 4;

FIGS. 6, 7 and 8 are enlarged, transverse sectional views respectively taken along the arrowed lines 6 6, 7 7 and 8 8 of FIG. 3, the latter being taken along the arrowed line 3 3 of FIG. 7;

FIG. 9 is a vertical sectional view taken at the same level as FIG. 3 and along the arrowed line 9 9, of FIG. 6;

FIGS. 10, 1l, 12 and 13 are enlarged transverse sectional views respectively taken along the arrowed lines 10-10, 11-11, 12 12 and 13 13 of FIG. 4 of the drawings;

FIG. 14 is a vertical sectional view taken at the same level as FIG. 4 and as indicated by the arrowed line 14-14 of FIG. 1l;

FIGS. l5, 16 and 17 are enlarged transverse sectional views respectively taken along the arrowed lines 15 15, 16 16 and 17-17 of FIGf 5, the latter being taken along the arrowed line 5 5 of FIG. l5;

FIG. 18 is a vertical sectional view taken at the same level as FIG. 5 and as indicated by the arrowed line 18 1S of FIG. 16; and

FIG. 19 is an enlarged, fragmentary sectional view taken alongthe arrowed line 19 19 of FIG. 13 of the drawings.

Referring particularly to FIG. l of the drawings, thc well pumping system of the invention includes a bottomhole assembly 20 which receives and houses a lluid-operated free-pump assembly 22 and which is suspended in a well casing 24' provided at its lower end with a perforated liner 26 through which production fluid from a surrounding productive formation 28 may enter the well. The bottom-hole assembly 2,0 is suspended in the casing 24 by a tubing system which includes an operating-Huid supply tubing 30, an operating-fluid return tubing 32 and a production tubing 34 the free-pump assembly 22 being hydraulically movable between its operating position in the bottom-hole assembly 20 and the surface through the production tubing.

Considering the bottom-hole assembly 20 in a general way, it includes an upper sealing collar 36 to which the lower ends of the supply and return

tubings

30 and 32 are connected, and to which the production tubing 34 is connected through an enlarged production tubing adapter 38 which serves as a production-fluid outlet means, or outlet passage means 4t) for the pump assembly 22. As will be described in more detail hereinafter, the upper sealing collar 36 provides an operating-duid intake means, or intake passage means 42 which communicates with the supply tubing 3.0 and with the pump assembly 22. Similarly, the upper sealing collar 36, provides an operatingfluid exhaust means, or exhaust passage means 44 which communicates between the pump. assembly 22 and the return tubing 32.

Connected to the lower end of the upper sealing collar 36 is an upper pump housing' tube 4,6 to the lower end of which is connected a lower sealing collar 4S. The upper end of a lower pump housing tube 50 is connected to the lower end of the lower sealing collar 48, a bottom shoe or lower plug 52 being connected to the lower end of the lower pump housing tube. The production tubing adapter 38, the upper sealing collar 36, the upper pump housing tube 46, the lower sealing collar 4:8',v the lower pump housing tube 50 and the bottom shoe 52 are all aligned with the productionA tubing so that the pump assembly 22 may pass therethrough into,l its operating position within the bottom-hole assembly 2li.

Considering the pump assembly 22 itself in a general way, it includes at its upper end a packerl nose assembly 54 which makes a duid-tight seal with the production tubing 34 as, the pump.l assembly is moved upwardly through the production tubing, and` which is. disposed in the enlarged production tubing adapter 38 when the pump assembly is in its Operating position so. that. the. productica duid discharged by the pump assembly may How past assures the packer nose assembly. Connected to the lower" end of the packer nose assembly is an upper sealing adapter 56 which cooperates with the upper sealing collar 36 in a manner to be described, the pump assembly also including an interpump sealing adapter 58 and a lower sealing adapter 60 which similarly cooperate with the lower sealing collar 48 and the bottom shoe 52. Between and connected to the upper sealing adapter 56 and the interpump sealing adapter S8 is an upper duid-operated pump 62, and disposed between and connected to the interpump sealing adapter and the lower sealing adapter 60 is a lower fluid-operated pump 64. The lower sealing adapter 60 carries an inlet plug 66 through which production duid from the well is admitted to the pump assembly 22, and which seats on a pump-assembly seat 68 when the pump assembly is in its operating position. The pump-assembly seat 68 is provided by a standing valve assembly 70 which is carried by the bottom shoe 52 by being seated on a seat 72 therefore provided by the bottom shoe.

As more fully disclosed in my Patent No. 2,311,157, each of the

pumps

62 and 64 is of the reciprocating type and includes an upper, engine or motor section and a lower, pump section, each engine section being controlled by an engine valve and the engine and pump sections respectively being provided with engine and pump pistons which are interconnected so that reciprocatory movement of the engine piston results `in similar movement of the pump piston. Operating uid under pressure is admitted to the engine sections of the upper and

lower pumps

62 and 64 through an upper operatingfluid intake 74 in the upper sealing adapter 56 and a lower operating-duid intake 76 in the interpump sealing adapter 58, respectively, the intakes 74 and 76 respectively communicating with the operating-fluid intake means 42 through upper and

lower intake passages

78 and 80 provide-d by the bottom-hole assembly 20. Spent operating tluid discharged by the engine sections of the upper and

lower pumps

62 and 64 is exhausted therefrom through an upper operating iluid exhaust 82 in the upper sealing adapter 56 and a lower operating fluid exhaust 84 in the interpump sealing adapter 58, respectively, the exhausts 82 and 84 respectively communicating with the operatingfluid exhaust means 44 through upper and

lower exhaust passages

86 and 88 provided by the bottom-hole assembly 20.

Production iluid from the well enters the pump section of the lower pump `64 through a lower production-fluid inlet 90 in the lower pump, the inlet 90 communicating with a production-duid inlet means 92 provided by the standing Valve assembly 70, through a lower inlet passage v 94 in the lower sealing adapter 60 and the inlet plug 66.

Production Huid from the well is admitted to the pump section of the upper pump 62 through an upper production-fluid inlet 96 in the interpump sealing adapter 58, this inlet communicating with the production-duid inlet means 92 through an upper inlet passage 98 provided by the bottom-hole 4assembly 20 and extending through the lower sealing adapter 60 and the inlet plug 66. The upper and

lower pumps

62 and 64 are provided intermediate their ends with upper and lower production-duid outlets 100` and 102, respectively, these outlets communicating with upper and

lower outlet passages

104 and 106 provided by the bottom-hole assembly 20 and communicating with the production-fluid outlet means 40 in a manner to be described in more detail hereinafter, It will be noted that each of the production-

fluid outlets

100 and 102 includes two axially spaced sets of ports, which is characteristic of a double-acting pump section. However, it will be understood that the invention is not limited to a fluid-operated pump having a double-acting pump section. p

The bottom shoe 52 provides a pump-assembly unseating chamber 108 just above the standing valve assembly 70, this chamber communicating with the operating-duid exhaust means 44 through a pump-assembly unseating passage 1110. When pressure is applied to the unseating chamber 108 through the unseating passage 110, such pressure acts on a downwardly-facing area 112 of the inlet plug 66 to unseat the pump assembly 22 and move it upwardly in the bottom-'hole assembly 20 a distance suincient to cause the packer nose assembly 54 to move from the production tubing adapter 38 into the production tubing 34. The manner in which fluid pressure is applied to the area 112 to unseat the pump assembly 22 will be discussed in more detail hereinafter.

The foregoing completes a very general description of the structure of the pumping system of the invention and the operation thereof will now be considered in the same way. Subsequently, the structure and operation of the pumping system -will be considered in detail.

In order to run the pump assembly 22 into its operating position in the bottom-hole assembly 20, it is inserted into the upper end of the production tubing 34 and is displaced downwardly into its operating position by introducing operating fluid into the upper end of the production tubing above the pump assembly. The downward movement of the pump assembly 22 through the production tubing 34 is produced primarily by gravity, and to some extent by introducing operating luid into the production tubing above the pump assembly under slight pressure. Any fluid in the production tubing 34 below the pump assembly 22 is displaced upwardly to the sunface through the supply and return

tubings

30 and 32 as the pump assembly moves downwardly.

After the pump assembly has been moved downwardly into its operating position wherein it is seated on the pump-assembly seat 68, it is held on its seat by the pressure of Ithe column of duid in the production tubing 34 acting on the entire cross-sectional area of the pump assembly. It will be noted that the pressure of the column of fluid in the return tubing 32 acts upwardly on only the area 112 exposed to fluid pressure in the pump-assembly unseating chamber K108, the remainder of the cross-sectional area of the pump assembly being exposed to the upwardly acting pressure in the Well, which is normally much less than the pressure in the production tubing 34. Consequently, a pressure force differential exists which holds the pump assembly on its seat until it is desired to unseat it.

Under the foregoing conditions, the pump assembly 22 is operated by introducing operating uid under high pressure into the supply tubing 30. From the supply tubing, the operating uid under high pressure flows through the intake passage means 42 and the upper and lower intake passages 78 `and 80 into the operating-fluid intakes 74 and 76 of the upper and

lower pumps

62 and 64 to operate the pumps. The spent operating fluid discharged by the pumps 62 `and 64 through the operatingfluid exhausts 82 and 84 ows through the upper :and

lower exhaust passages

86 and 88 into the exhaust passage means 44, and thence into the return tubing 32 for return to the surface. It will be apparent that the operating fluid flows through the

pumps

62 and 64 in parallel so that the two pumps operate completely independently of each other, even though the operating iluid for the two pumps is supplied through the tubing 30 and returned through the tubing 32.

The foregoing operating uid tlow through the engine sections of the

pumps

62 and 64 produces reciprocatory movement of the engine and pump pistons, whereby the pump sections of the

pumps

62 and 64 receive production fluid from the well through the

inlets

96 and 90 and `discharge such fluid at a higher pressure through the outlets and 102. As hereinbefore discussed, the production uid flows from the production-fluid inlet means 92 to the

inlets

96 and 90 through the upper and

lower inlet passages

98 and 94, respectively. The production fluid discharged by the outlets `100 and `1112 of the

pumps

62 and 64 enters the outlet passages uit and 106, which are connected to the outlet passage means 40 leading to the production tubing 34. Thus, the production fluid liows through the pump sections of the

pumps

62 and 64, from the production-fluid inlet means 92 to the production-huid outlet means 4i), in parallel, the pump sections of the

pumps

62 and 64 thus operating independently of each other also.

When it is desired to remove the pump assembly 22 from the well, operating lluid under pressure is supplied to the return tubing 32, the pressure of such fluid being applied to the pump-assembly unseating chamber 188 through the pump-assembly unseating passage 11i). This pressure thus acts on the downwardly-facing area 112 to unseat the pump and move it upwardly in the bottomhole assembly 20, back flow into the Iwell being prevented by the standing valve assembly 78. As soon as ythe pump assembly 22 has been moved upwardly slightly, the packer nose assembly 54 enters the production tubing 34 from the production tubing adapter 38, whereupon the operating fluid under pressure acts on the packer nose assembly to move the pump assembly upwardly through the production tubing to the surface. Once the pu-mp assembly 22 has been unseated, operating -luid under pressure for moving the pump assembly upwardly may be supplied through either or both of the supply and return

tubings

38 and 32, as more fully set forth in my Patent No. 2,589,671, issued March 18, 1952.

Considering the bottom-hole assembly in detail, the upper sealing collar 36 is provided ywith a bore 114 therethrough and

counterbores

116 and 118 therein at the upper and lower ends of the bore 114. The production tubing adapter 38 and the pump housing tube 46 are threaded into the

counterbores

116 and 118, respectively, with tapered threads. Pressed into the bore 114 is a sleeve 120 which receives the upper sealing adapter 56 when the pump assembly 22 is in its operating position, as will be `discussed in more detail hereinafter.

Referring to FIG. 4 of the drawings, the lower sealing collar 48 is also provided with a bore 122 and counterbores 1124 and 126. The pump housing tubes 46 and Sil' are threaded into the

counterbores

124 and 126, respectively, by means of extended threads to permit orienting the lower sealing collar 48 properly with respect to the upper sealing `collar 36 and the bottom shoe 52. ln other words, the extended threads connecting the pump housing tubes 46 and Sil to the lower sealing collar 48 provide for proper angular orientation of the lower sealing `collar to align the various passages therein with the coresponding passages in the upper sealing collar 36 and the bottom shoe 52. `Once the proper orientation for the sealing collar 48 has been established,

lock nuts

128 and 130 on the pump housing tubes 46 and Sti are tightened against the upper and lower ends of the lower sealing collar.

The bore 122 through the lower sealing collar 48 has a sleeve 132 pressed thereinto. This sleeve receives the interpump sealing adapter 58 when the pump assembly 22 is in its operating position, as will be discussed in more detail hereinafter.

Similarly, as shown in FIG. 5, the bottom shoe 52 is provided with a bore 134 therein into which a sleeve 136 is pressed, this sleeve receiving the lower sealing adapter 6i) when the pump assembly 22 is in its operating position. The bore 134 is provided with a counterbore 138 at its upper end into which the pump housing tube 50 is threaded by means of tapered threads. These tapered threads prevent rotation of the bottom shoe 52 relative to the pump housing tube Sil when tight, the same function being performed by the tapered threads which connect the upper pump housing tube 46 to the upper sealing collar 36. Pressed into the lower end of the -bore 134 in the bottom shoe 52 is an annular member 14d` which provides the seat 72 for the standing valve assembly 7G, the annular member 140 being seated on an internal annular flange 142. Threaded into the bottom shoe 52 below the annular flange -142 is an inlet pipe 144 which houses the standing valve assembly 7 0 and through which production iluid from the well enters this assembly.

Adverting to FIG. 3 of the drawings, the supply tubing 30 is threaded into the upper end of the upper sealing ycollar 36 in ycommunication with the operating-huid intake means 42, the latter having the form of a bore 146 through the upper sealing collar. The upper intake passage 78 includes an arcuate channel or groove 148 in the upper sealing member 36 and communicating with the bore 146. The groove 148 communicates with the operating-huid intake 74 of the upper pump 62 through an external annular channel 150 in the sleeve 120, radial ports 152 in this sleeve, and an internal annular channel 154 therein. Thus, the operating-fluid intake 74 communicates with the supply tubing 3i) through the upper intake passage 78 and the operating-fluid intake means 42. Similarly, the lower intake passage 80 connects the intake means 44 to the operating-Huid intake 76 for the lower pump 64. The lower intake passage 841 includes the bore 146, into the lower end `of which is threaded a pipe 156. The lower end of the pipe 156 is disposed in a counterbore i158 in the lower sealing collar 48, FIG. 4, and is provided thereon with an 0-ring 160` which engages the wall of the counterbore in a huid-tight manner. With this construction, as the pump housing tube 46 is threaded into the upper and

lower sealing collars

36 and 48 during assembly, the lower end of the pipe 1'56 is slidably inserted into the counterbore 158, the upper end of this pipe having previously been threaded into the upper sealing collar. Various other pipes to be ldescribed hereinafter are assembled with the upper and

lower sealing collars

36 and 48 and the bottom shoe 52 in a similar manner so that a detailed description of the mode of assembly will not be necessary each time one of these pipes is described.

Continuing to consider the lower intake passage 80, the counterbore 158 in the lower sealing collar 48 communicates at its lower end with a bore 162 which, in turn, communicates with an arcuate channel or groovev 164 in the lower se-aling collar, as best shown in FIGS. 4 and 10. This groove communicates with the operatingfluid intake 76 of the lower pump 64 through an external annular channel 166 in the sleeve 132, radial ports 168 through this sleeve and an internal annul-ar channel 170 therein.

Considering the upper exhaust passage 86 connecting the operating-fluid exhaust 82 of the upper pump 62 to the operating-fluid exhaust means 44, and referring to FIG. 3, the upper operating-fluid exhaust 82 communicates with an internal annular channel 172 in the sleeve 120. Radial ports 174 in the sleeve 120y communicate with the channel 172 and lead to an external annular channel 176 in this sleeve. As best shown in FIGS. 8 and 9, the upper sealing collar 36 is provided with an arcuate groove or channel 178 therein which communicates with the channel 176 and which communicates with a bore 180 extending longitudinally through the sealing collar 36. This bore forms the operatinglluid exhaust means 44 and threaded into the upper end thereof is the return tubing 32.

Considering the lower exhaust passage 88 for conveying spent operating -fluid from the lower operatingfluid exhaust 84 to the operating-fluid exhaust means p 44, the sleeve 132 in the lower sealing collar 48, FIGS.

4 and 12, is provided with an internal annular channel 182 which communicates with the operating-huid exhaust 84 for the lower pump 64, this sleeve having radial ports 184 therein which communicate with an external annular channel 186 therein. Communicating with the external annular channel 186 in the sleeve 132 is an arcuate channel or groove 188 in the lower sealing collar 48, this channel communicating with a longitudinal bore 190 through the lower sealing collar. At the upper end of bore 190 is a counterbore 192 into which is slidably 1nserted the lower end of a pipe 194 having thereon an O-ring 196 to make a fluid-tight seal with the wall of the counterbore 192. The upper end of the pipe 194 is threaded into the lower end of the bore 180 through the upper sealing collar 36. Thus, the lower operatingfluid exhaust 84 is connected to the return tubing 32 by the lower exhaust passage 88.

Continuing to consider the operating-fluid exhaust system, the pump-assembly unseating passage 110 communicates therewith and will now be described. The unseating passage 110 includes a pipe 198 which, as best shown in FIG. 14, is threaded into the lower end of the bore 190, the 4latter ultimately leading to the return tubing 32 as hereinbefore discussed. The pipe 198 is slidably inserted into a counterbore 200 in the bottom shoe 52 at its lower end, the pipe 198 carrying an O-ring 202 which makes a Huid-tight seal with the wall of the counterbore 200. The lower end of this counterbore communicates with a bore 204 which communicates at its lower end with an arcuate groove or channel 206, FIGS. 16 and 18, in the bottom shoe 52. The groove 206 communicates with the pump-assembly unseating chamber 108, whereby operating fluid under pressure may be delivered through the supply tubing and the unseating passage 110 to the unseating chamber 10S toact on the downwardly-facing area 112 to unseat the pump assembly 22 when this is desired.

Considering now the manner in which production iluid from the well flows through the pump sections of the

pumps

62 and 64 to the production tubing 34, the standing valve assembly 70 will be taken up lirst for convenience. As best shown in FIG. 5 of the drawings, the standing valve assembly 70 includes, at its upper end, a tubular member 208 which is tapered externally to seat on the seat 72 and which is tapered internally to provide the pump-assembly seat 68 engageable by the lower end of the inlet plug 66 of the pump assembly 22. Threadedly connected to the lower end of the tubular member 208 is another tubular member 210 which carries a knockout plug 212 for draining the bottomhole assembly 20 and the supply, return and production tubings 30, 32 and 34 to permit removal of the standing valve assembly 70 when desired. As is well known, the knockout plug 212 may be broken by means of a knockout bar, not shown, lowered into the well on a wire line, the standing valve assembly 70 being removed from the well by a suitable tool on a wire line. Connected to the lower end of the tubular member 210 is a tubular member 214 which provides an internal annular shoulder 216 therein. Pressed into the tubular member 214 and abutting the annular shoulder 216 is a valve seat 218, the latter being engageable by a standing valve 221, which -is shown as a ball valve. As will be apparent, when the standing valve 221 is seated, it prevents back flow into the well.

In order to hold the standing valve 221 off its seat 218 during operation of the pump assembly 22 to prevent the pressure fluctuations which would result from constant seating and unseating of the standing valve, the ball valve is formed of a magnetic material and is held off its seat, as shown in broken lines, by a magnet 222, such as an Alnico magnet. An important object of the present invention is to control the magnetic attraction of the magnet 222 for the standing valve 221 in such a manner as to avoid any requirement for an excessive back flow through the standing valve assembly 70 to seat the standing valve, such excessive back flow producing an excessive hydraulic shock when the ball valve hits its seat. For this purpose, the standing valve 221 is prevented from contacting the magnet 222 directly by means of a soft steel cage 224 which carries the magnet and which provides a seat 226 for the standing valve. The relative positions of the magnet 222 and the seat 226, and the diameter of the ball valve 221, are such that the ball valve does not contact the magnet. Consequently, any

10 necessity' for a high back ow into the well to seat the' standing valve 221 is avoided to prevent development of excessive hydraulic shock, which is an important feature.

The cage 224 is provided with a plurality of radial arms 228, FIG. 17, which are clamped between the lower end of the tubular member 210 and an internal annular shoulder on the tubular member 4214 to hold the cage in place, while permitting `flow of production lluid from the well through the standing valve assembly '70, which provides the production-huid inlet means 92, as hereinbefore indicated.

The lower inlet passage 94, leading from the inlet means 92 to the production-Huid inlet 90 of the pump section of the lower pump 64, includes a bore 230 through the lower sealing adapter 60. The bore 230 registers with a counterbore 232 in the inlet plug 66, the counterbore 232 communicating at its lower end with a bore 234 which communicates with the inlet means 92.

Considering the inlet passage 98 leading to the pump section of the upper pump 62, it includes radial ports 236 through the lower sealing adapter 60 which communicate at their inner ends with the bore 230 and which communicate at their outer ends with an externall annular channel 238 in the adapted 60. O-rings 240 in external annular grooves in the lower sealing adapted 60 on opposite sides of the external annular channel 238 therein engage the sleeve 136 in a fluid-tight manner to isolate the channel 23S from the pump-assembly unseating chamber 108 therebelow and from the lower outlet passage `106 thereabove. The channel 238 in the lower sealing adapted 60 communicates with an internal annular channel 242 in the sleeve 136, the channel 242 communicating with radial ports 244 through this sleeve. The ports 244 communicate at their outer ends with an internal annular channel 246 in the bottom shoe 52, the channel 246 communicating with an arcuate channel or groove 248, IFIG. 15, in the bottom shoe 52. The groove 248 communicates with the lower end of a bore 250 in the bottom shoe. The upper end of this bore communicates with a counterbore 252 in the bottom shoe 52, and slidably inserted into this counterbore is the lower end of a pipe 254 having thereon an O-ring 256 to provide a fluid-tight seal with the wall of the counterbore 252. Referring to FIG. 4 of the drawings, the pipe 254 is threaded at its upper end into the lower end of a bore 258 in the lower sealing collar 48. The upper end of the bore 258 communicates with an arcuate channel or groove 260 in the sealing member 48, the groove 260 communicating, in turn, with an internal annular channel 262 in the lower sealing member. The channel 262 communicates with radial ports 264 through the sleeve 132 in the lower sealing member 48, these ports communieating at their inner ends with an internal annular channel 266, formed in the sleeve 132, which communicates with the production-fluid inlet 96 of the upper pump 62.

`Considering now the production-

fluid outlet passages

104 and 106, the outlet passage 104 includes, as shown in FIGS. 3 and 4 of the drawings, an annular space 268 around the upper pump 62 and between it and the upper pump housing tube 46. The annular space 268, as hereinafter discussed in detail, receives production fluid discharged -by the lower pump, and independently receives production fluid discharged by the upper pump 62 through the production-Huid outlet 100, as shown in FIG. 3 of the drawings. Thus, the pump sections of the upper and

lower pumps

62 and 64 are connected in parallel with respect to their respective outlets and 102, the annular space 268 merely serving as a common receiving space for the production uid discharged by both pumps. The annular space 268 communicates at its upper end with the counterbore 118 at the lower end of the upper sealing collar 36. -In order to by-pass the upper sealing adapter 56, the upper sealing collar 36 is provided with a diagonal port l270 which leads to a longitudinal bore 272 in the -upper sealing collar, the bore 272 communicating with a diagonal port 274 which leads to the upper counterbore 116 in the sealing collar 36. The counterbore 116 communicates with the production-fluid outlet means 40 provided by the production tubing adapter 38. Thus, the port 270, the bore 272 and the port 274 bypass the upper sealing adapter 56 to carry the production fluid discharged by both

pumps

62 and 64 from the upper pump housing tube 46 into the production tubing adapter 38.

Considering the outlet passage 106 for production fluid discharged by the lower pump 64, it includes an annular space 276, FIG. 5, around the lower pump 64 and between it and the lower pump housing tube S0, this annular space communicating with the production iiuid outlet 102 of the lower pump. The annular space 276 communicates at its lower end with the counterbore 138 at the upper end of the bottom shoe 52. The lower end of this counterbore communicates with a diagonal port 278, FIG. 18, located at the upper end of the sleeve 136 to prevent sand accumulations in the counterbore 138. The port 278 communicates at its outer end, as best shown in FIG. 18, with a longitudinal bore 280 in the bottom shoe 52. The upper end of this bore communicates with a counterbore 282 into which is slidably inserted the lower end of a pipe 284 having thereon an O-ring 286 for sealing purposes. The upper end of the pipe 284 is threaded into the lower end of a bore 288 in the lower sealing collar `48, as best shown in FIG. 14. The upper end of the bore 288 communicates with a diagonal port 290 which leads to the counterbore 124 at the upper end of the lower sealing collar 48, which counterbore communicates with the lower end of the hereinbef-ore discussed annular space 268, wherein the production rli-uid from the lower pump 64 is mixed with that discharged independently by the upper pump 62.

The foregoing completes the description of the structure of the bottom-hole assembly 20 and the structure of the free-pump assembly 22 will now be considered in detail, beginning at the upper end thereof. Referring to FIG. 2 of the drawings, the packer nose assembly at the upper end of the pump assembly 22 includes a packer mandrel which carries at its upper end a tapered head 294 engageable by a pump catcher, not shown, at the surface of the ground when the pump assembly is moved to the surface hydraulically. The packer mandrel 292 carries packer cups 296 which clear the inner wall of the production tubing adapter 38 to permit the production fluid discharged by the

pumps

62 and 64 to ow upwardly therepast into the production tubing 34. However, these packer cups make fluid-tight seals with the production tubing 34 itself upon slight upward movement of the pump assembly 22 as hereinafter discussed.

The lower end of the packer mandrel 292 is threadedly connected to the upper end of the upper sealing adapter 56, which is provided therethrough with an axial bore 298 communicating at its upper end with an axial bore 360 in the packer mandrel. The purpose of the

bores

298 and 300 is to permit a pilot valve rod, not shown and forming part of t-he engine valve of the motor section of the upper pump 62, to move upwardly to the upper end of its stroke as the motor and pump pistons of the upper pump move upwardly to the upper ends of their strokes. The bore 298 through the upper sealing adapter 56 also conducts operating tluid under pressure from the operating-Huid intake 74 downwardly into the engine section of the upper pump 62 to operate same as is well known in the art. The operating-fluid intake 74 includes an external annular channel 382 in the upper sealing adapter 56, this channel registering with the internal annular channel 154 in the sleeve 120. The channel 302 communicates with the bore 29S through radial ports 304. Q-

rings

306 and 308 in grooves in the upper sealing adapter 56 above and below the channel 302 separate the operating-Huid intake 74' from the production column 75 thereabove and from the operating-fluid exhaust 82 therebelow, respectively.

The upper sealing adapter 56 is provided, below the O-ring 308, with an external annular channel 310 which forms part of the operating-duid exhaust 82 for the upper pump 62 and which registers with the internal annular channel 172 in the sleeve 120. Communicating with the channel 310 are radial ports 312 and longitudinal passages 314 leading into the engine section of the upper pump 62. The sealing adapter 56 carries an O-ring 316 in a groove below the channel 310 to separate the spent operating fluid discharged by the upper pump 62 from the production iluid in the annular space 268 around the upper pump 62.

The grooves containing the O-

rings

306, 308 and 316 are connected to the bore `298 through the sealing adapter 56 by radial passages 318. When the operating-Huid pressure necessary to operate the upper pump 62 is developed in the bore 298, this pressure is communicated to the inner sides of the C-

rings

386, 308 and 316 through the radial passages 318 to force these O-rings outwardly into sealing engagement with the sleeve 120. The O-

rings

306, 308 and 316 have interference `fits with the sides of their grooves to accomplish the foregoing without leakage from the radial passage 318 past the O-rings. With this construction, the O-

rings

306, 308 and 316 may be disposed in deep grooves so that they do not contact the sleeve until they are forced outwardly by the operating-duid pressure applied in the foregoing manner. This prevents wear of these O-rings as the pump assembly is run into and out of the well, which is an important feature. The hereinafter-described O-ring installation on the interpump sealing adapter 58 operates in a similar manner so that a detailed description of the operation at the time the structure thereof is described will not be necessary.

Turning now to FIG. 4 of the drawings for a detailed description of the interpump sealing adapter 58, it is threadedly connected directly to the lower end of the upper pump 62 and is threadedly connected at its lower end to an extension tube 320 which, in turn, is connected at its lower end to the upper end of the lower pump 64. Within the extension tube 320 is an inner extension tube 322 which is inserted into a recess 324 in the upper end of the lower pump 64 and which is inserted into a counterbore 326 in the lower end of the interpump adapter 58. The ends of the inner extension tube 322 are sealed by O-rings 328. The extension tube `322 communicates at its upper end with a central bore 330 in the interpump sealing adapter 58, the extension tube 322 and the bore 330 receiving the pilot valve rod of the engine valve incorporated in the engine section of the lower pump section 64, when it is at the upper end of its stroke, in much the same manner as the pilot valve rod of the engine valve of the upper pump 62 is received by the bore 298 through the upper sealing adapter 56 and the bore 300 in the packer mandrel 292 when it is at the upper end of its stroke.

The bore 330 in the interpump sealing adapter 58 communicates, adjacent its upper end, with radial ports 332 which lead outwardly to an external annular channel 334 forming part of the operating-fluid intake 76 for t-he lower pump 64. This channel registers with the internal annular channel in the sleeve 132, and is isolated by O- rings 336 and 338 respectively disposed thereabove and therebelow in grooves in the adapter 58. Thus, operating fluid under pressure entering the operating-duid intake 76 of the lower pump 64 ows through the radial ports 332 into the central bore 330, and then through the inner extension tube 322 into the engine section of the lower pump.

Continuing to refer to FIG. 4 of the drawings, the spent operating fluid discharged by the engine section ofthe lower pump 64 Hows upwardly through longitudinal passages 340 in the upper end of the pump 64'. From the passages 340, the spent operating duid-enters an annular space 342 between the

extension tubes

320 and 322, this annular space communicating at its upper end with longitudinal passages 344 in the adapter 58. The upper ends of the passages 344 communicate with radial ports 346 which communicate at their outer ends with an external annular channel 348 in the adapter 58, this channel forming part of the operating-fluid exhaust 84 for the lower pump 64 and registering with the internal annular channel 182 in the sleeve 132. The channel 348 is isolated by O-rings 350 and 352 respectively disposed in grooves in the adapter 58 above and below the channel 348.

The O-

rings

336, 338, 350 and 352 are urged outwardly into sealing engagement with the sleeve 132 by operating fluid under pressure introduced behind these O-rings from the central bore 330 through radial passages 354, FIG. 19, Thus, these O-rings may be entirely within their grooves except when operating fluid under pressure is being delivered to the lower pump 64 to operate same, thereby minimizing wear of these O-rings.

Still referring to FIG. 4 of the drawings, the interpump sealing adapter 58 is provided with an external annular channel 356 which is located between and isolated by the O-rings 338 and 350, this channel forming part of the production-duid inlet 96 of the upper pump 62 and registering with the internal annular channel 266 in the sleeve 132. This channel, i.e., the channel 356, communicates with radial ports 358 which extend inwardly to longitudinal passages 360 in the adapter 58, the passages 360 leading upwardly into the pump section of the upper pump 62.

The foregoing completes the detailed description of the structure of the well pumping system of the invention and its operation will now be considered in detail.

Operation In order to -run the pump assembly 22 into its operating position in the bottom-hole -assembly 20, it is inserted into the upper end of the production tubing 34 and operating fluid under slight pressure is then admitted to the production tubing above the pump assembly. The operating ilnid introduced above the pump assembly 22, plus the action of gravity on the pump assembly, move the pump assembly downwardly through the production tubing 34 into its operating position in the bottom-hole assembly 20 and seat the inlet plug 66 on the pump-assembly seat 68. The uid in the production tubing 34 `and the bottom-hole assembly 20 below the pump assembly 22 is displaced upwardly to the surface through the supply and return

tubings

30 and 32, the supply, return and production tubings all being interconnected in open ilud communication as long as the pump assembly is some- What above its operating position. Any fluid trapped below the pump assembly Aafter the lower sealing adapter 60 has entered the sleeve 136 in the bottom shoe 52 merely flows into the pump section of the lower pump 64 through the bore 234, the counterbore 232, the bore 230 Iand the production-fluid inlet 90 of the lower pump, this uid displacing the pump piston in the pump section to displace duid from the pump section into the production tubing 34 through the passages hereinbefore discussed. In other words, the displacement of the pump piston in the pump section of the lower pump 64 displaces uid through the production-huid outlet 102, which tluid ows through the annular space 276, the port 278, the bore 280, the counterbore 282, the pipe 284, the bore 288, the port '290, the annular space 268, the port 270, the bore 272,

With the pump assembly 22 in its operating position, operating uid under high pressure is Idelivered to the supply tubing 30 to operate the

pumps

62 and 64. Operating uid from the supply tubing 30 reaches the upper .pump 62 through the bore 146, the groove 148, the channel 150, the ports 152, the channel 154, the channel 302, the ports 304 and the bore 298. Operating fluid from the supply tubing 30 reaches the lower pump 64 through the bore 146, the pipe 156, the counterbore 158, the bore 162, the groove 164, the channel 166, the ports 168, the channel 170, the channel 334, the ports 332, the bore 330 and the extension tube 322. rlhus, the operating uid under pressure flows to the motor sections of the upper and

lower pumps

62 and 64 in parallel.

The operating fluid under pressure in the bore 298 leading to the engine section of the upper pump 62 enters the radial passages 3118 to bias the O-rings306, 308 and 316 into sealing engagement with the sleeve '120, thereby preventing fluid intermingling. Similarly, the operating huid under pressure in the bore 330 leading to the engine section off the lovver pump 64 acts through the radial passages 354 to bias the 0rings 336, 338, 350 fand 352 outwardly into sealing engagement with the sleeve 132 in the lower sealing collar 48 to separate the various uids from each other.

The spent operating uid discharge by the upper pump 62 leaves the engine section thereof through the passages 314 and flows through the ports 312, the channel 310, the channel 172, the ports 174, the channel 176, the groove 178 and .the bore 180 into the return tubing 312. Spent operating uid from the lower pump 64 leaves the engine section thereof through the passages 340 and flows through the space 342, the passages 344, the ports 346, the channel 348, the channel 18.2, the ports 184, the channel 186, the groove 188, the bore 190, .the counterbore 192, the pipe 194 and the bore 180 into t-he return tubing 32. Thus, the operating uid discharged by the two pumps flows into the return tubing 32 in parallel.

As the engine sections of the

pumps

62 and 64 are operated independently of each other in the foregoing manner, the motor pistons reciprocate the pump pistons of the two pumps to pump ilnid `from the well into the production tubing 34, wherein the production fluid discharged by the two pumps lovvs upwardly to the surface with a minimum of resistance due to the large diameter attained by making the production tubing the tubing through which the pump assembly is movable between the :surface and its operating position. Considering the production fluid ow paths, the production uid entering the lower pump 64 flows through the standing valve assembly 70 in the manner hereinbefore described and then flows through the bore 234, the counterbore 232 and the bore 230 into the productionfluid inlet leading into the pump section of the lower pump. The production fluid for the upper pump 62 diows through the standing valve assembly 70, the bore 234, the counterbore 232, the ports 236, the channel 238, the channel 242, the ports 244, the channel 246, the groove 248, the bore 250, the counterbore 252, the pipe 254, the bore 258, the groove 260, the channel 262, the ports 264, the channel 266, the channel 356, the ports 358 and the passages 360 into -the pump section of the upper pump 62. Thus, the two-

pumps

62 and 64 draw production fluid from the well thereinto in parallel.

Similarly, the two

pumps

62 and 64 discharge the production fluid at higher pressures inrparallel. More particularly, the lower pump 64 discharges production Huid at higher pressure from its production-duid outlet 102 into the annular space 276. From this space, the production uid from the lower pump 64 iiows through the diagonal port 278, the `bore 280, the counterbore 282, the pipe 284, the bore 288, the diagonal port 290 and the counterbore 124 into the annular space 268. In this space, the production uid discharged by the lower pump 6,4 mixes with the production fluid discharged by the upper pump 62 through its production-fluid outlet 100. The production lluid from the two pumps then ows upwardly through the annular space 268, the diagonal port 270, the bore 272, the diagonal port 274, the counterbore 116 and the production tubing 38 into the production tubing 34.

The operating and production fluids flow through the

pumps

62 and 64 in parallel along the foregoing paths as long as operating fluid under pressure is delivered to the supply tubing 30. The two pumps 62 and 64 operate completely independently of each other so that the operation of one does not aiiect the other in any way. Consequently, if desired, the assembly 22 may be operated until it is convenient to remove the assembly from the well even if one of the pumps becomes inoperative for `any reason.

When it is desired to remove the pump assembly 22 from the well, operating fluid under pressure is delivered to the return tubing 32 and ilows through the bore 180, the pipe 194, the counterbore 192, the bore 190, the pipe 198, the counterbore 200, the bore 4 and the groove 206 into the pump-assembly unseating chamber 108, wherein it acts upwardly on the downwardly-facing area 112 of the inlet plug 66. The operating iluid under pressure acting on this area moves the pump assembly 22 upwardly off `its seat 63, whereupon the operating fluid under pressure acts on the entire crosssectional area of the pump assembly to displace it upwardly. Back ow into the well is prevented by the standing valve 221 as this occurs. By the time the pump assembly 22 has been displaced upwardly sufciently that the lower sealing adapter 60 leaves the sleeve 136, the uppermost packer cup 246 leaves the production tubing adapter 238 and enters the production tubing 34 proper to prevent by-passing of the pump assembly by the operating fluid under pressure introduced therebelow. Continued delivery of operating iiuid under pressure through the return tubing 32, and through the supply tubing at this stage if desired, results in continued upward movement of the pump assembly 22 through the production tubing 34 to the surface, at which point it may be engaged by a pump catcher, not shown, designed to receive the head 294 of the packer nose assembly 54 therein.

It will be understood that although a pump assembly 22 `including only Itwo pumps 62 and 64 has been disclosed, the number 0f pumps may be increased indefinitely if desired to obtain 'a greater pumping capacit-y, corresponding 'additions being made to the bottom-hole assembly 20 to convey operating iluid and production fluid to the various pumps and to convey operating fluid and production duid therefrom.

The foregoing has primarily been concerned with a pump assembly 22 wherein the motor sections of the

pumps

62 and 64, as well as the pump sections thereof, are hydraulically connected in parallel. However, as briefly mentioned earlier herein, the motor sections may in some instances be connected `in series. This may be accomplished by providing the bottom-hole assembly 20 with passage means, not shown, connecting the upper operating fluid exhaust 82 to the lower operating iluid intake 76 so that the operating uid flows through the upper and lower motor sections in series.

Although I have disclosed `an exemplary embodiment of my invention herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims allowed to be and appearing hereinafter.

I claim as my invention:

1. In a bottom-hole assembly for a fluid-operated pump assembly, the combination of: an upper sealing collar engageable with the pump assembly adjacent the upper end thereof; an upper pump housing tube below and connected to said upper sealing collar and adapted to receive an upper portion of the pump assembly; a lower sealing collar below and connected to said upper pump housing tube and engageable with the pump assembly intermediate the ends thereof; a lower pump housing tube below and connected to said lower sealing collar and adapted to receive a lower portion of the pump assembly; a bottom shoe below and connected to said lower pump housing tube and engageable with the pump assembly adjacent the lower end thereof; operating-fluid intake means on said upper sealing collar and connectible to an operating-fluid supply tubing; upper and lower intake passages respectively connecting said operatinguid intake means to the interiors of said upper and lower sealing collars; production-duid inlet means on said bottom shoe and adapted to communicate with a well and communicating with the interior of said bottom shoe; an upper inlet passage connecting said productioniluid inlet means to the interior of said lower sealing collar; production-duid outlet means on said upperseal-` ing collar and connectible to a production tubing; means connecting said upper pump housing tube to said production-fluid outlet means; and means connecting said lower pump housing tube to said production-fluid outlet means.

2. A bottom-hole assembly as dened in claim l including an operating-fluid exhaust means on said upper sealing collar and connectible to an operating-Huid re-v turn tubing; and upper and lower exhaust passages respectively connecting said operating-fluid exhaust means to, the interiors of said upper and lower sealing collars.

3.. In a tandem fluid-.operated pump system for a well, the combination of: a single supply tubing set Yin the well and extending downwardly therein from the surface and connectible at its upper end to a source of operating Huid under pressure; a single production tubing set in the well and extending downwardly therein from the surface and connectible at its upper end to a point of discharge for production fluid; a bottom-hole assembly set in the well and connected to the lower ends of said supply and production tubings and providing a pump-assembly housing; a tandem fluid-operated pump assembly comprising two independent fluid-operated pumps structurally connected in tandem and removably disposed in said pump-assembly housing, each of said pumps including a motor section provided with an intake for operating iuid under pressure and an exhaust for spent operating iiuid, and each of said pumps including a pump section connected to and operable by said motor section thereof and provided with an inlet for production fluid from the well and an outlet for production fluid; intake means carried by said bottom-hole assembly externally of said pump assembly and connecting the lower end of said supply tubing to said intakes in parallel; outlet means carried by said bottom-hole assembly externally of said pump assembly and connecting the lower end of said production tubing to said outlets in parallel; inlet means carried by said bottom-hole assembly externally of said pump assembly and connecting the well to said inlets in parallel; exhaust means carried by said bottom-hole assembly externally of said pump assembly and connected to said exhausts in parallel; and means in the well and communicating with said exhaust means for returning spent operating fluid to the surface.

4. The pump system set forth in claim 3 wherein the means Ylast deiined comprises a single return tubing separate from said supply and production tubings, said return tubing extending upwardly in the well from substantially the level of said pump assembly to the surface and being connectible at its upper end to a point of discharge for spent operating iluid, said return tubing being connected at its lower end to said bottom-hole assembly in communication with said exhaust means.

5. The pump system set forth in claim 4 wherein said pump-assembly housing registers with the lower end of one of said tubings and wherein said pump assembly is movable from the surface downwardly through said one tubing and into said pump-assembly housing.

References Cited in the le of this patent UNITED STATES PATENTS 1,630,902 Parrish May 31, 1927 2,022,781 Pigott Dec. 3, 1935 2,104,799 Evans Ian. 11, 1938 2,242,166 Bennett May 13, 1941 2,499,356 Coberly Mar. 7, 1950 2,499,357 Coberly Mar. 7, 1950 2,605,712 Davis et al. Aug. 5, 1952 2,631,871 Stone Mar. 17, 1953 2,649,114 Wttman Aug. 18, 1953 15 (Church), published by Wiley (New York) 1955. (Pages 161 and 162.)