US2869470A

US2869470A - Free pump system with reverse flow

Info

Publication number: US2869470A
Application number: US487303A
Authority: US
Inventors: Clarence J Coberly
Original assignee: Kobe Inc
Current assignee: Kobe Inc
Priority date: 1955-02-10
Filing date: 1955-02-10
Publication date: 1959-01-20
Anticipated expiration: 1976-01-20

Description

Jan. 20, 1959 c. r.1. c'oBERLY 2,869,470

FREE PUMP SYSTEM WITH REVERSE FLow Filed Feb. 1o, 1955 2 Sheets-sheet 1 l. .fau

leef/VCE CI CaBEeLy,

Jan. 20, 1959 c. J. coBERLY FREE PUMP SYSTEM WITH REVERSE ELow 2 Sheets-Sheet 2 Filed Feb. 10. 1955 5y A45 -raQ/vsys.

HQe/s, EcH, Isree A592216.

FREE PUMP SYSTEM WITH REVERSE FLOW' Clarence J. Coberly, SauMarino, Calif., assignor to Kobe,

Inc., Huntington Park, Calif., afcorporatiou of'CaEifrnia Application February 10, 1955,'Serial No. 487,303.

16 Claims. (Cl. 10S-46) The present inventionrelatesjin general to Huid-operated oil well pumping systems and, moreparticularly, to a free pump system of this nature, the present application disclosing subject matter which is disclosed and claimed in mycopending applications Ser. Nos.` 639,497 and 642,127, led February 11, 1957 and February 25, 1957, respectively.

Fluid-operated free pump systems include eithertwo tubings or three tubings, one of the'tubingsin either system being of a size t-o permit circulatingv a fluid-operated free pump therethroughV between the surface and an operating position in the well. In a two-tubing free pump system, often called an open system, the production fluid and the spent operating uid discharged by the pump are mixed and conveyedto the surfacein a single production tubing. In a three-tubing free pump system, commonly called a closed system, the production fluid and the spent operatingfluid are conveyed to the surface seperately in separate production and return tubings.-

For maximum oil production'with either an open system or closed system, it is desirable to employ as large` a pump as possible within the limited space available in the well. Consequently, the tubing through which the pump is circulated between the surface and its operating position in the well must be relatively large. With such a relatively large pump tubing taking up a substantial portion of the space available in the well, any other tubings incorporated in the system must necessarily be relatively small, at least in a parallel tubing system.

In many prior fluid-operated. free pump systems of either the open type or the closed type, the relatively large tubing through which the pump is circulated between the surface and its operating position in the well is also utilized tosupply operating iluid under pressure to the pump to operate the pump. Consequently, the production fluid and the spent operating fluid discharged .by the pump must be conveyed to the surface in a tubing or tubings which are smaller than the pump tubing, the production fluid and spent operating uid being mixed and conveyed to the surface in a single, smaller production tubing in the case of an open system, andl being conveyed. to the surface separately in smaller production and return tubings in the case of a closed system. In such prior systems, the operating fluid under pressure is deliveredto the pump tubing both to move the pump downwardly into its operating position and to operate the pump, the direction of operating fluid ow being reversed to circulate the pump to the surface. ln' other words, the operating fluid is delivered to the production tubing to move the pump upwardly through the supply tubing in the case of an open sytem, and isV delivered to one or both of the production and return tubings to move the pump upwardly through the supply tubing in the case of a closed system.

With systems of' the foregoing nature, there are instances wherein excessive friction losses are encountered due tothe fact that a relatively large volume of productivi; lluid must be conveyed to the surface through a rela- 2,869,470 'Patented Jan. 2o, tess ICS tively small tubing, particularly in wells, such as shallow wells, wherein pumping conditions permit the` use of a huid-operated pump having a pump displacement larger than themotor or engine displacement so that the volume of production uid conveyed to the surface is larger than the volume of operating uid conveyed tothe pump. EX- cessive friction losses may be encountered under such conditions even in a Aclosed system wherein the relatively large volume of production'uid is conveyed to the surface separately from the spent operating fluid discharged byY the pump.` However, the problem is' particularly severe in the case of an'open system' under such conditions because of the fact that the spent operating'iluid, as well as the relatively largelvolurneof production luid, must be conveyed to the surface through a single, small, production tubing.

ln order to minimize friction losses in azuid-operated free pump -systemwherein the volume of production Huid,

or the volume of amixtureof the production uid and;

the spentoperating fluid, is larger thanithe volume of the operating fluid supplied to' the pump, it is desirable to employ the larger, pumptubing as the production tubing and toemploy a smaller tubing as the supply tubing for,l

conveying the operating uid underpressure downwardly to the pump,` and aprimary'object ofthe inventionisto provide a system of this nature.

One known way of accomplishing'the foregoing is by means of theclosed, Huid-operated free pump system disclosed in my Patent No. 2,589,671. In this system, a relatively` large pump tubing is utilized to convey the production fluid dischargedgbyl the pump to the surface. The operating Huid under pressure issupplied to the pump through a relatively small supply tubing, and the spent operating fluid is returned to the surface through a relatively small return tubing. In this system, the pump is is circulated into the hole through the production tubing;4

Another known way of `utilizing a relatively large pump tubing to convey fluid discharged by the pump to theV surface involves a two-tubing, or open, system wherein the production fluid and the spent operating iiuid discharged by the pump are mixed and conveyed to the sur--V In such a system,.- the pumn is circulated into'the hole through the produc-- face in a single production tubing.

tion. tubing by delivering-operating fluid to the upper end of the production tubing, and the pump is operated and circulated to the surface by operating fluid delivered to the smaller, supply tubing. However, a conventional, or standard, free pump cannot be used in an open system of this nature because of the fact that theoperating iiuid for operating the pump and the operating fluid for circulating the pump to the surface are delivered to-tlte supply tubing in both instances. ventional, or standard, free pumn were used, it would be unseated by' the operating fluid delivered theretoA through the supply tubing with the intention of operating the pump. Because of this, some means must be provided for preventing unseating of the pump when operating huid is delivered to the supply tubing to operate the pump,y and for permittingA the pump to unseat and to,

move upwardly through the productiony tubing to theisur face when operating uid is delivered through the supply In order I Consequently, if a con-- tubing for this purpose. With the prior system under consideration, this problem is solved by employing a nonstandard free pump which is incapable of being biased upwardly by operating fluid under pressure delivered thereto through the supply tubing to operate the pump. In order to permit the pump to be biased upwardly by operating uid delivered through the supply tubing when it is desired to circulate the pump to the surface through the production tubing, it is necessary to modify the pump so that it can be-biased upwardly. This is accomplished by circulating a pump retriever downwardly through the production tubing, the pump retriever latching onto the pump. Therafter, the pump may be circulated to the surface through the production tubing by circulating operating fluid downwardly through the supply tubing. However, a substantial period of time is required to circulate the pump retriever downwardly through the production tubing to the pump, which is obviously undesirable since it approximately doubles the length of time required to remove the pump from the well as compared with the time required to remove the pump with prior systems of the nature discussed earlier herein.

Consequently, an important object of the present invention is to provide a fluid-operated free pump system in which a pump unit is circulated between the surface and its operating position through the production tubing without materially increasing the length of time required to remove the unit from the well. Thus, the present invention attains the hereinbefore-discussed advantages of using the pump tubing as the production tubing, without, however, incurring the penalty of a substantial increase in the time required to circulate the pump unit out of the Well, which is an important feature of the invention.

To accomplish the foregoing, the invention provides latch means for latching the pump unit'in its operating position in the well against any upward bias applied thereto by the operating fluid delivered to the unit through the supply tubing to operate the pump thereof, which is an important object of the invention.

Another important object is to provide a latch means 4 latch means in its released or retracted position after it has been released in the manner hereinbefore described, thereby further eliminating any possibility of resetting of the latch means. In this connection, an object is to provide means for preventing the application of fluid pressure to the latch means in a direction tending to reset it after the latch means has once been released or retracted.

which is hydraulically operable from the surface so that it may be set and released readily, depending on whether it is desired to latch the pump unit in its operating position for operation thereof, or to release the unit for circulation to the surface through the production tubing by operating fluid delivered to the Supply tubing.

Another object is to provide means for setting the latch means after the pump unit has vbeen circulate downwardly through the production tubing to its operating position by delivering operating fluid to the supply 'tubing at a pressure less than the operating fluid pressure applied to the Supply tubing to operate the pump.

Another object is to provide means for releasing the latch means by applying to the production tubing a pressure substantially greater than the'pressure required for circulating the pump unit downwardly through the production tubing into its operating position.

Thus, the latch means is set and released by selectively pressurizing the supply and production tubings. The latch means may be set and released in this manner very quickly so that setting and releasing the latch means do not add appreciably to the time required to install and remove the pump unit, which is an important feature of the invention.

By designing the latch means so that it can be set only by operating uid delivered through the supply tubing at a. pressure less than that required to operate the pump, and so that it can be released only by applying to the production tubing a pressure substantially in excess of the pressure required to circulate the'pump unit downwardlyA through the production tubing into its operating position, any possibility of inadvertently setting or releasing the latch means is eliminated, which is an important feature of the invention.

Another object is to provide means for locking the Thus, with the foregoing construction, the pump unit may be installed, operated and removed readily with substantially no increase in the time required to install and remove the unit over the time required with prior' systems, and in much less time than any system which requires the use of a pump retriever. Briefly, with the present invention, the pump unit can be installed, operated and removed by inserting the pump unit into the upper end of the production tubing, supplying fluid to the production tubing above the pump to circulate the pump unit downwardly through the production tubing into its operating position, applying a low fluid pressure to the supply tubing to latch the pump unit in its operating position, applying normal operating-fluid pressure to the supply tubingA to operate the pump, applying to the production tubing a fluid pressure substantially higher than the pressure required to circulate the pump unit into its operating position so as to unlatch the pump unit, and thereafter supplying fluid under pressure to the supply tubing to circulate the pump unit to the surface through the production tubing. The selective pressurization of the supply and production tubings to latch and unlatch the pump unit may be accomplished very quickly, which is an important feature of the invention.

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

Fig. 1 is a vertical sectional view on a reduced scale illustrating a fluid-operated free pump system which embodies the invention;

Fig. 2 is a sectional View taken along the arrowed line 2-2 of Fig. 1;

Fig. 3 is a vertical sectional view taken along the arrowed line 3 3 of Fig. 2;

Figs. 4 and 5 are downward continuations of Figs. 3 and 4, respectively;

Fig. 6 is a vertical sectional view taken along the arrowed line 6--6 of Fig. 2;

Figs. 7 and 8 are enlarged, fragmentary sectional views duplicating a portion of Fig. 3, but illustrating the latch means of the invention in different operating positions;

Fig. 9 is an enlarged, fragmentary sectional view illustrating means for mechanically resetting the latch means of the invention;

Fig. 10 a view of one end of the latch means of the invention; and

Fig. 11 isa view of the other end of the latch means.

Referring particularly to Fig. 1 of the drawings, the numeral 12 designates a well casing which is set in a well and which is provided with perforations, not shown, to admit into the casing fluids from surrounding, productive formations. The casing 12 is equipped with a casing head 14 which supports parallel production and

supply tubings

16 and 18 in the casing, these tubings extending downwardly below the well fluid level in the casing. The production and

supply tubings

16 and 18 communicate at their upper ends with a four-way valve 20 operated by a handle '22, this valve selectively connecting the production tubing and the supply tubing with an operating uid supply line 24 and a production fluid disposal line 26. Thus, by means of the valve Ztl', either the production tubing 16, or the supply tubing 18, may be pressurized with operating iiuid from the supply line 24.

In accordance withthe invention, theproduction tubing,

designated generally by the numeral32'and`which is an.

assembly of components to be described in more detail hereinafter. The housing 32 is connected to the lower end ofthe production tubing l.6land is also connected Vto the supply-tubing 18, all as willbe' discussed in more detail hereinafter.

The pump unit 28 4includes a pump 34 to the upper end of which is connected a packer nose 36. The pumpV 34, except for minor external modifications, may be of any suitable type and contains the usual pump and engine, or motor, sections together with valve means for controlling the operation ofthe engine, or motor, section. latter includes a motor piston which reciprocates a pump piston in the pump section to pump well .fluid from the well and discharge it as production fluid in a well known manner. Since such components' of the pumpl 34 are well known in the art, they are not illustrated in the drawings and are not described further herein.

Referring now to Fig. of the drawings, the housing 32 includes at its` lower end a bottom shoe 148 providing a seat 33 for a standing valve assembly 4t) which extends` downwardly into an intake pipe 42 depending from the bottom shoe. Well uid enters the pump 34 through the standing Valve assembly 40, which will be described in more detail hereinafter. rl`he lower end of the pump 34 is provided with a tubular well-uid intake 44which is insertable into a bore i6 in the standing valve assembly 40, the intake die carrying an O-ring ,48 which engages the wall of the bore 46 to provide a seal which prevents entry of well uid into the housing 32 except through the well-Huid intake.

Continuing to refer to Fig. 5 of the drawings, communicating with the interior of the housing. 32 above the standing valve assembly 4th is a port 50 which communicates, in turn, with a passage 52 in the bottom shoe 14S. The passage 52 communicates at its other end with a pipe 54 which extends upwardly into communication with the lower end of a passage 56, Fig. 4, in a sealing collar 15.16 forming part of the housing 32. The upper end of the passage S6 communicates with the lower end of the supply tubing i3. Thus, operating fluid may be delivered through the supply tubing t8, the passage 56, the pipe Se, the passage 52 and the port 50 to the lower end of the pump 34 to unseat the pump unit 26, i. e.,- withdraw the well-fluid intake 44 from the bore 46, and rue-ve the pump unit upwardly from the housing 32 into the production tubing i6, as will be described in more detail hereinafter. As will be apparent, the O-ring '45t maintains separation between the well iiuid in the standing valve assembly d@ and the operating fluid in the housing 32 at the lower end of the pump 34.

Referring to Fig. 4 of the drawings, the passage 56..

The

essaim.

communicates intermediate its ends with a port 58 in the.:

sealing collar 3.46, the latter communicating withthe interior of the sealing collar.

.34. operating uid under pressure delivered to the'supply tubing l?, tlows downwardly thro-ugh the supply tubing, the passage S6 and port 5S to the operatingiiuid inlet ports 6i). The latter are isolated by O-

rings

62 and 64 engaging a sleeve 65 in the sealing col- The pump 34 is provided' with operating-huid inlet ports 6i) which communicate with the port 53 when the pump unit 2S is in its', operating position. Thus, in order to operate the pumpunder pressurewith.the.production fluid and the spentv operating fluid, as `discussed in more detail '.hereinafter..

Referring now to Fig. 6 of the drawings, the pump.. 34 is provided with outlet ports 66 for spent operating. llid and'discharge ports, not shown, for the production fluid discharged by the pump. Both the outlet vports 66 and the discharge ports communicate with the interior of a pump housing tube intermediate the O `ring 64 and an O-ring 67 engaging a sleeve 68 in the bottom` shoe 14S, the tube i5@ forming part of the housing 32 and connecting the sealing collar 146.

and the bottom shoe 148, Vas hereinafter explained. Thus, the 'O-ring 67 separates the mixture of spent operating uid and production uid from the operating fluid at the lower end of the pump, and the O-ring 64 separates the mixture of spent operating fluid and production fluid from the operating fluid in the vicinity of the operatingfluid inlet ports 60.

The mixture of" spent operating fluid and production fluid owsthrough the tube 150. between it and the pump 345m a port 7? in the botto-m shoe 148, as shownin Fig. 6 of the drawings. The port 70 communicates with a passage 72 in the bottom shoe 146 which communicates atits other end with a pipe 74 leading upwardly to the lower end of a passage 76 in the sealingcollarV 146; the upper end of the latter communicating through a portv 78 with the interior of the sealing collar above the O-ring 62. Thus, the G-ring 62 separates the operating fluid under pressure supplied to the operatinguid inlet ports 6@ from the mixture of spent operating fluid and 'production fluid entering the sealing collar 11E-6.

above'the G-ring 62 by the Vavenue outlined. The interiorof the sealing collar i456" above the O-ring 62 communicates with the lower end of'the production tubing" i6 through a packer housing tube 9G, which forms part of the housing, 32, to provide for upward flow of the' mixture of spent operating iiuid and production iiuid therethrough to the surface.

When the pump unit 28 is in the housing 32 with:

the well-fluid intake i4 in the bore 46, the areav of the well-huid intake 44 is exposed to well iluid pressure and, with operating `tluid pressure applied to the supply tubing 18, such operating iiuid pressure plus the head of operating fluid are applied to an area of the pump 34 equal to the dif-terence between the area ot the pump at the sealing collar 146 and the area of the well-luid intake 44. Both the well lluid pressure and the operating to theV pump unit tending to move the pump upwardlyinto theproduction tubing 16, which, as described in more detail hereinafter, is utilized to circulate the pump f However, when the pump 34 is in op-v eration, the pump Vunit 28 is held in its operating posi-A tion in the housing 32V in opposition to SuChupWard to the surface.

bias by'a latch means 3@ of the invention which will now be described.

Considering the latch means Si) generally, it includes a latch housing 32, which provides a latch guide Sti-'for latches'86 engageable with a downwardly facing annular sh-oulfder 8S inlthe'tube 99. Connected to the upper end" of the latch housing S2 is a nose 92 which is engageable with .a pump catcher carried by the closure 30'as is` well known in the art. Connected to the lower end of` the latch housing 82 is a packer tube 94 which is con-` nected to the upper end of the pump 34, the interior of the packer tube communicating with theop-erating-uid lar M6 to prevent intermingling of the operating fluid 75 inlet ports .60so that, when these ports are in communi- 7 cation with the port 58 and operating fluid under pressure is supplied to the supply tubing 18, operating uid under pressure is also present in the packer tube 94 for a purpose to be discussed. The packer tube 94 carries downwardly facing packers 96 and 98 which are disposed in

enlarged portions

100 and 102, respectively, of the tube 90 when the pump unit 28 is in its operating position, whereby the mixture of spent operating fluid and production tiuid may ow upwardly past the packers 96 and 98 into the production tubing 16. It will be noted that a clearance is provided between the latch housing 82 and the tube 90 for such upward ow of the mixture of spent operating fluid and production fluid. Above the lower packer 96 isa reduced portion 104 of the tube 90 with which the lower packer 96 is engageable after the pump has been unseated in a manner to be described, the lower packer thus forming al seal with the reduced portion 104 so that operating fluid pressure applied beneath the pump will move the pump unit 28 upwardly in the housing 32. By the time the lower packer 96 reaches the upper end of the reduced portion 104 of the tube 90, the upper packer 98 will be within and making a seal with the production tubing 16 to continue the upward movement of the pump. Ultimately, of course, both the packers 96 and 98 will engage and make seals with the production tubing 16 to enable the operating fluid under pressure delivered below the pump 34 for the purpose of circulating the pump unit 28 out of the hole, to perform its intended function.

Considering the latch means 80 now in more detail, the latch guide 84 has the form of a transverse cylindrical bore through the latch housing 82, and the latches 86 have the form of pistons which are slidable in such bore and which are sealed relative to the wall thereof by O-rings 106. The outer ends of the latches 86 are reduced in diameter slightly and are provided with fiats 107, as best shown in Fig. l1. The purpose of this diameter reduction is to permit latch retraction even with a build-up of foreign matter on the outer ends of the latches in use. The two latches 86 are identical', but reversed in position, one fiat 107 on each being engageable with the shoulder 88.

As will be apparent, the outer ends of the latches 86 are exposed to the uid pressure prevailing in the tube 90 surrounding the pump unit 28, i. e., the outer ends of the latches are exposed to the uid pressure in the production tubing 16. The inner ends of the latches v86 are .adapted to be exposed to operating fluid pressure in the packer tube 94 through passages 108 connecting the interior of the packer tube to the interior of the latch guide 84. As will be discussed hereinafter, when the latches 86 are fully retracted, Fig. 8, the O-rings 106 move across the ends of the passages 108 in communication with the latch guide 84 to prevent application of operating fluid pressure to the inner ends of the latches. The latch guide 84 also communicates with the packer tube 94 through a passage 110, a chamber 112 and a passage 114. The passage 110 is adapted to be closed by a check valve 116 to prevent fio-w from the packer tube to the latch guide 84 by way of the passage 114, the chamber 112 and the passage 110. However, the check valve 116 is adapted to unseat to permit tiow in the opposite direction, i. e., to permit flow from the latch guide 84 to the packer tube 94 by way of the passage 110, the chamber 112 and the passage 114. The reasons for this will be discussed hereinafter. The latches 86 are provided with inwardly extending spring fingers 118 having lateral projections 120 provided with inner edges 122 and outer edges 124 engageable with a pin 126 extending across the latch guide. When the latches 86 are in extended positions, as shown in Fig. 7 of the drawings, the inner edges 122 of the spring fingers 118 are out of engagement with the pin 126. However, the free ends of the spring fingers 118 still engage the pin 126 under auch conditions to prevent rotation of the latches 86 in theguide 84. When the latches are in an intermediate position, as shown in Fig. 3 of the drawings, the inner edges 122 of the lateral projections 120 engage the pin 126 to prevent further inward movement of the latches except upon the application of a substantial pressure to the outer ends of the latches. When the latches are in their retracted positions, as shown in Fig. 8 of the drawings, the lateral projections on the spring fingers 118 have moved across the pin 126 so that the outer edges 124 of such projections engage the pin to retain the latches in their retracted positions. It will be noted that, under such conditions, the O-rings 106 on the latches 86 have crossed the ends of the passages 108 in communica- Ytion with the latch guide 84 to prevent application of operating tluid pressure to the inner ends of the latches 86. Thus, once the latches 86 have been moved into their retracted positions, they cannot be hydraulically extended, for reasons which will be discussed hereinafter. In order to prevent cooking of the latches 86 by lateral forces resulting from interengagement of the spring fingers 118 and the pin 126, the latches are provided with inwardly extending backup fingers 128. These fingers are provided with slots 130 therein which permit communication between the packer tube 94 and the latch guide 84 through the passages 108 until such time as such communication is cut off by the O-rings 106.

Considering the operation of the invention, prior to running the pump unit 28 into the well, the latches 86 are placed in their intermediate positions so that the inner edges 122 of the lateral projections 120 of the fingers 118 are seated against the pin 126. If the latches 86 are initially in their retracted positions, they may be extended to their intermediate positions by threading a screw 132 thereinto, as shown in Fig. 9 of the drawings. When in their intermediate positions, the latches 86 are flush with the pump body 34, as shown in Fig. 3 of the drawings. The spring fingers 118 are so designed that they will prevent inward movement of the latches 36 into their retracted positions except upon application of a substantial uid pressure, e. g., 500 p. s. i., to the outer ends of the latches. The pressure required to m'ove the latches 86 into their retracted positions must be higher than the pressure required to circulate the pump into its operating position, 500 p. s. i. being illustrative only.

With the latches 86 in their intermediate positions as hereinbefore described, the closure 30 for the upper end of the production tubing 16 is removed, the pump unit 28 is inserted into the upper end of the production tubing, and the closure is replaced. Thereupon the valve 20 is operated to connect the upper end of the production tubing 16 to the operating fluid supply line 24, the valve simultaneously connecting the supply tubing 18 to the production uid disposal line 26. Preferably, the

valve 20 is provided with some means, not shown, for

limiting the operating uid pressure applied to the production tubing 16 under such conditions to a value less than the pressure required to move the latches 86 into their retracted positions, so as to prevent retraction o? the latches while the pump is being circulated into its operating position.

Under the foregoing conditions, the pump unit 28 is moved downwardly through the production tubing 16 into the housing 32, whereupon the well-iiuid intake 44 at the lower end of the pump 34 enters the bore 46 in the standing valve assembly 40, downward movement of the pump unit being terminated by engagement of a shoulder 134 at the lower end of the pump 34 with the upper end of the standing valve assembly. It will be understood, that, as the pump unit 28 moves downwardly with the operating-huid supply line 24 and to place the production tubing 16 in communication with the production-fluid disposal line 26. A relatively low pressure, e. g., 25 to 100 p. s. i., is slowly developed at the upper end vof the supply tubing 13, the valve Ztl being operated slowly to prevent the development of a pressure under the pump 34 sufficient to unseat the pump unit 28 before the pressure in the latch means S0 builds up enough to extend the latches 86. The relatively low pressure slowly developed in the supply tubing in the foregoing manner is applied, through the packer tube 9 -iand the passages lil-8 connecting the packer tube to the interior of the latch guide 84,' to the inner ends of the latches S6 to displace these latches outwardly into their extended positions. Such a relatively low pressure, however, is insufficient to move the pump unit 28 upwardly in the housing 32 against frictional resistance as long as the pressure is allowed to build up slowly so as to minimize the pressure drop in the various passages leading to the inner ends of the latches.

Subsequently, normal operating fluid pressure is developed in the supply tubing 18 to operate the pump 34. When this occurs, the pump unit 28 moves upwardly in the housing 32 until the extended latches 86 seat against the shoulder 83 to limit upward movement of the pump unit, which is now latched in its operating position, shown in broken lines in Figs. 3 and 5 of the drawings. The pump 34 now begins to operate to pump well fluidfrom the well by way of the well-fluid intake 44 into the production tubing i6 by the avenue hereinbefore discussed. The operating fluid for operating the pumn 3G of course enters the pump through the operating-huid inlet ports 6@ in the manner hereinbefore described, and the spent operating fluid is mixed with the production fluid and discharged into the production tubing 16, also as hereinhefore discussed. The desired separation between fluids is maintained by the various seals described previously.

When it is desired to remove the pump unit 28. the valve 2@ is operated to again place the production tubing 16 in communication with the operating uid supply line 24. The pressure in the production tubing 36 is then increased to a value in excess of that required to move the latches S6 inwardly through their intermediate positions into their retracted positions against the resistance offered by engagement of the spring fingers 11S with the pin 126. The pressure necessary to move the latches into their retracted positions is determined by the stift'- ness of the spring lingers 113 and, as hereinbefore indicated, should exceed the pressure required to circulate the pump unit 2S into the hole. Also, this pressure should be more than any pressure difference resulting. from the presence of water in the production tubing 16 which is only partially balanced by operating uid in the supply tubing 18. Upon application of the reduire-fl pressure to the outer ends of the latches 86 by wav of the production tubing 16, the latches 86 move inwardly to their retracted positions and are locked therein by engagement of the outer edges 124 of the lateral nroiections 120 on the spring fingers MS with the pin 126. lt' should be noted that the check valve 116 opens to permit uid in the latch guide 34 to be displaced into the packer tube 94, thereby permitting the latches to move inwardly into their retracted positions. Also, it should be noted that once the latches have been moved into their retracted positions in the foregoing manner, the -rings R06 have crossed over the ends of the passages 103m communication with the latch guide 8d to prevent any possibility of further application of pressure to the inner ends of the latches 36 tending to move them outwardly to their extended positions again as the pump unit 28 is circulated to the surface. The latches 85 may be reset later, after the pump unit has been removed from the production tubing 16, in any suitable manner, such as` 70 ease of assembly of various components thereof.

the manner illustrated in Fig. 9 of the drawings, and described previously.

Once the latches 36 have been retracted, the valve 2G is again operated to connect the supply tubing 18 in communication with the yoperating-fluid supply line 24 and to connect the production tubing 16 in communication with the production-fluid disposal line 26. Operating fluid under pressure is now delivered downwardly through the supply tubing llS to move the pump unit 28 upwardly 10 out of the housing 32 land through the production tubing l5 to the surface. As hereinbefore discussed, as soon as the pump unit moves upwardly slightly, the lower packer96 engages the reduced portion 104 of the tube 90 to take the operating Huid pressure applied below the pump, the upper packer 985 shortly thereafter entering the lower end of the production tubing 16 to take the operating fluid pressure applied below the pump when the lower packer 96'enters the enlarged portion 102 of the tube 90. Eventually, both packers are in the produc- 20 tion tubing 16 to carry the pump unit upwardly through the production tubing as operating fluid under pressure is delivered to the production tubing below the pump unit through the supply tubing. Once the pump unit 23 reaches the surface, it is caught by the pump catcher' 25 carried by the closure 36, whereupon the closure may be removed to remo-ve the pump unit.

Thus, the latches 86 are set and released very simply merely by pressurizing the supply and production tubings i8 and 16, respectively. The time required to so set and release the latches is very short so that the time required for installing and removing the pump unit 23 is not appreciably increased over prior systems wherein the pump tubing is utilized as the supply tubing and wherein the production fluid and spent operating fluid are conveyed to the surface through a second, smaller tubing. Thus,

the present invention provides the advantages of using the large pump tubing as the production tubing in a fluidoperated free pump system of the open type, without any appreciable increase in the time required for installation 0 and removal of the pump unit which are important features of the invention.

Considering the standing valve assembly 4i) in more detail, it includes an upwardly opening check valve 136 of the poppet type adapted to engage a seat 138 and having a hollow stem 140 disposed in a damping cylinder E42. The check valve 136 is made light in weight and the fit between the stem 140 and the cylinder i142 is such as to give the desired rate of seating. Preferably, the rate of seating is sufficiently low so that the time required for the check valve to move from its fully open position to its closed position is in excess of ten seconds so that the check valve never seats while the pump 34 is in operation, even though the operating speed of such pump is very low. The clearance required to obtain this seating 5 time with a standing valve of the proportions shown is approximately 0.010 inch, i. e., the difference in the diameters of the stem M@ and the cylinder 42 is approximately 0.010 inch. It should be noted that above the valve seat 133 the valve 136 moves through a bore 144 is only a relatively small clearance around the valve until the valve has moved away from the seat 138- a substantial distance, e. g., one-half inch. The valve 1.36 must, therefore, travel at least this distance from its oper- GR ating position to its fully closed position, which, with the t specified between the stern 14) and the cylinder M2, provides a suiiicient seating time.

Another feature of the invention resides in certain aspects of the structure of the housing 32 providing for Considering this feature, the housing includes the sealing collar and the bottom shoe 148, into which the upper and lower ends of the pump housing tube are threaded with extended threads and locked by means of lock 75

nuts

152 and 154. Fluid-tight seals are provided between O which is only slightly larger than the valve so that thereV ii the ends of the tube 150 and the

members

146 and 148 by -

rings

156 and 158, respectively.

' The hereinbefore discussed

pipes

54 and 74 are threaded into the sealing collar 146 with ordinary pipe threads, Figs. 4 and 6, and extend into

bores

160 and 162, respectively, in the bottom shoe 14S, these bores forming parts of the

passages

52 and 72, respectively. The lower ends of the

pipes

54 and 74 are sealed in the bores i60 and 162 by O-

rings

164 and 166, respectively, and the depths of the

bores

160 and 162 exceed the totals of the distances which the respective pipes extend tliereinto and into the sealing collar 146 when completely assembled. With this construction, the lower ends of the

pipes

54 and 74 are inserted into the

bores

160 and 162, respectively, and the

members

146 and 148 and the tube 150 are then assembled and locked with the

lock nuts

152 and 154. Under such conditions, the upper ends of the

pipes

54 and 74 clear the sealing collar 146, the upper ends of these pipes then being screwed into the sealing collar as shown. Upon assembly, the lower ends of the

pipes

54 and 74 are sealed by the O-rings 1 64 and 166. Thus, the present invention provides a very simple method of assembling the foregoing components of the housing 32. Also, by the use 0f the extended threads mentioned on the tube 150, the relative positions of the sealing collar 146 and the bottom shoe 148 may be established accurately despite dimensional errors arising during manufacture, which is an important feature.

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 dened by the claims allowed me and appearing hereinafter.

I claim as my invention:

1. In a fluid-operated free pump system, the combination of: a supply tubing and a production tubing set in a well, said production tubing having a housing at the lower end thereof with which said supply tubing communicates; a free pump unit, including a fluid-operated pump, movable through said production tubing into said housing, said pump being operable in said housing by operating fluid under pressure supplied thereto through said supply tubing to pump fluid from the well into said production tubing, and said pump unit having a downwardly-facing area which is in communication with said supply tubing when said pump unit is in said housing so that said pump unit is biased upwardly in said housing by operating fluid under pressure in said supply tubing; and means for latching said pump unit in said housing against upward movement therein by said upward bias.

l 2. In a fluid-operated free pump system, the combination of: a supply tubing and a production tubing set in a well, said production tubing having a housing at the lower end thereof with which said supply tubing communicates; a free pump unit, including a fluid-operated pump, movable through said production tubing into said housing, said pump fbeing operable in said housing -by operating uid under pressure supplied thereto through said supply tubing to pump fluid from the well into said production tubing, and said pump unit having a downwardly-facing area which is in communication with said supply -tubing when said pump unit is in said housing so that said pump unit is biased upwardly in said housing by operating fluid under pressure in said supply tubing; latch means for preventing upward movement of said pump unit in said housing in opposition to said upward bias, saidlatch means being extensible by fluid pressure appiied to one area thereof to latch said pump unit in said housing, and being retractible by fluid pressure applied to another area thereof to unlatch said pump unit from said housing; and means for selectively applying fluid pressure to said areas of said latch means.

3. In a fluid-operated free pump system, the combination of: a supply tubing and a production tubing set in a well, said production tubing having a housing at the lower end thereof with which said supply tubing cornmunicates; a free pump unit, including a fluid-operated pump, movable downwardly through said production tubing into said housing, said pump being operable in said housing by operating fluid under pressure supplied thereto through said supply tubing to pump fluid from the well into said production tubing and said pump unit having a downwardly-facing area which is in communication with said supply tubing when said pump unit is in said housing so that said pump unit is biased upwardly in said housing by operating fluid under pressure in supply tubing; latch means for latching said pump unit in said housing, said latch means being extensible to latch said pump unit in said housing by fluid pressure applied to one area thereof, and being retractible to unlatch said pump unit from said housing by fluid pressure applied to another area thereof; means connecting said one area of said latch means and said supply tubing in fluid communication; and means connecting said other area of said latch means and said production tubing in fluid communication.

4. A system as defined in claim 3 including means at i the surface for selectively pressurizing said supply and production tubings to selectively extend and retract said latch means. l

5. A system as defined in claim 4 wherein said latch means is carried by said pump unit.

6. In a fluid-operated free pump system, the combination of: a supply tubing and a production tubing set in a well, said production tubing having at the lower end thereof a housing with which said supply tubing communicates; a free pump unit, including a fluid-operated pump, movable downwardly through said production tubing into said housing by fluid supplied to said production tubing above said pump unit, said pump being operable in said housing byl fluid under pressure supplied to said supply tubing to pump fluid from the well into said production tubing and said pump unit having a downwardly-facing area which is in communication with said supply tubing when said pump unit is in said housing so that said pump unit is `biased upwardly in said housing by operating fluid under pressure in said supply tubing; latch means for latching said pump unit in said housing, said latch means being extensible to latch said pump unit in said housing by application to one area thereof of a fluid pressure less than the fluid pressure in said supply tubing required to operate said pump, and

being retractible to unlatch said pump unit from said housing by the application to another area thereof of a fluid pressure greater than the fluid pressure developed in said Production tubing above Said pump unit to move said pump unit downwardly through said production tubing into said housing; means for connecting said one area of said latch means in fluid communication with said supply tubing; means for connecting said other area of said latch means in iluid communication with said production tubing; and means at the surface for selectively pressurizing said supply and production tubings to selectively extend and retract said latch means.

7. A system as defined in claim 6 wherein said latch means is movable from an intermediate position to said extended position, and is movable from said extended position through said intermediate position to a retracted position, said system including means for retaining said latch means in said retracted position.

8. In fluid-operated free pump system, the combination of: a tubing system consisting of a supply tubing and a production tubing, said tubing system being set in a well and said production tubing having a housing fat the lower end thereof with which said supply tubing communicates; a free pump unit, including a fluidoperated pump, movable through said production tubing intosaid housing, said pump being operable in said housing by operating fluid under pressure supplied thereto through said supply tubing so as to pump huid from the well into said production tubing; pump-unit displacing means permanently mounted on said pump unit and having a downwardly-facing area engageable by operating fluid under pressure from said supply tubing for displacing said pump unit upwardly in said housing; and means for rendering said pump-unit displacing means inoperative during operation of said pump by operating uid under pressure supplied thereto through said supply tubing.

9. A fluid-operated free pump system as defined in claim 8 including means operable by a predetermined fluid pressure in said production tubing for rendering said pump-unit displacing means operative.

10. In a huid-operated free pump system, the combination of: supply and production tubings set in a well and connected at their lower ends to a housing; a duid-operated free pump unit movable downwardly through said production tubing into said housing and operable in said housing by operating uid under pressure from said supply tubing to discharge production fluid into said production tubing; latch means for latching said pump unit in said housing, said latch means having areas respectively communicating with said supply and production tubings and being movable to extended and retracted positions by fluid pressures applied to said areas, respectively; and means for selectively pressurizing said tubings to move said latch means to one or the other of said positions l1. In an apparatus for latching a fluid-operated free pump unit in a housing, the combination of: a latch guide; a latch movable in said latch guide from an intermediate position to an extended position and from said extended position through said intermediate position to a retracted position; first fluid-pressure-applying means lfor applying iiuid pressure to one side of said latch to move same from said intermediate position to said extended position; second fluid-pressure-applying means for applying fiuid pressure to the other side of said latch to move same from said extended position to said retracted position; and means for preventing movement of said latch to said retracted position until a predetermined minimum uid pressure has been applied to said other side thereof by said second fluid-pressure-applying means.

12. An apparatus as defined in claim 11 wherein the means last defined includes interengageable elements on said latch and said latch guide.

13. In an apparatus for latching a fluid-operated free pump unit in a housing, the combination of: a latch guide; a latch movable in said latch guide from an intermediate position to an extended position and from said extended position through said intermediate position to a retracted position; first uid-pressure-applying means for applying uid pressure to one side of said latch to move same from said intermediate position to said extended position; second uid-pressure-applying means for applying fiuid pressure to the other side of said latch to move same from said extended position to said retracted position; and means for rendering said first fluidpressure-applying means inoperative to move said latch out of said retracted position once it has been moved into said retracted position by said second huid-pressureapplying means.

14. An apparatus as defined in claim 13 including means for locking said latch in said retracted position, including interengageable elements on said latch and said latch guide.

15. in an apparatus for latching a huid-operated free pump unit in a housing, the combination of: a latch guide; a latch movable in said latch guide from an intermediate position to an extended position and from said extended position through said intermediate position to a retracted position; rst fluidpressureapplying means for applying fluid pressure to one side of said latch to move same from said intermediate position to said extended position; second uid-pressure-applying means `for applying fluid pressure to the other side of said latch tomove same from said extended position to said retracted position; means for preventing movement of said latch from said intermediate position to said retracted position until a predetermined minimum fluid pressure has been applied to said other side thereof by said second iuid-prcssure-applying means; and means for closing uid communication between said first fiuid-pressure-applying means and said one side of said latch when said latch has been moved to said retracted position by the application or" sai-d predetermined minimum fluid pressure to said other side of said latch by said second fluid-pressureapplying means. Y

16. An apparatus as defined in claim l5 including means for mechanically locking said latch in said retracted position.

ieerences Cited in the file of this patent UNITED STATES PATENTS 2,032,838 Eaton Mar. 3, 1936 2,162,151 Wranosky June 13, 1939 2,182,730 McDaniel Dec. 5, 1939 2,230,787 Swain Feb. 4, 1941 2,364,600 Church Dec. 12, 1944 2,369,939 Betts Feb. 20, 1945 2,630,071 Davis Mar. 3, 1953 2,653,545 Dempsey et al. Sept. 29, 1953 2,676,546 Coberly Apr. 27, 1954 2,698,058 Page Dec. 28, 1954