US2975768A - Subsurface hydraulic pump - Google Patents

Description

March 21, 1961 D. E. MARQUIS SUBSURFACE HYDRAULIC PUMP INVENTOR. D.E. MARQUIS 2 Sheets-Sheet 1 BY HtbuiSmK Filed Jan. 2, 1959 A T7'ORNEVS March 21, 1961 D. E. MARQUIS 2,975,768

SUBSURFACE HYDRAULIC PUMP Filed Jan. 2, 1959 2 Sheets-Sheet 2 93 FIG. 6

Ill

INVENTOR. D.E. MARQUIS BY Nadia &M

A T TO/PNEVS design of the engine and; pump pistons;

2,975,768 g snns'unmen HYDRAULIC P Duane Marquis, llartiesville, kla., assignor, to P-hillips Petroleum Company, a corporation of Delaware I Filetl Jan. 2, 1959, see. No. 784,800 9Claims'. ((11. 12 1-158 I of production involves theme of a hydraulic subsurface pump. This type of pump is actuated by fluid pressure in the-form of power oil supplied from the surface to operatea hydraulic engine in the well which in turn actuates a. displacement pump, the producedxoil being pumped to the surface along with exhaustedpower oil. The engines used are reciprocating enginesrandmustxof necessity have reversing or directional valvesto change the direction of the engine piston when the latter reaches the ends of its strokes. Many of the prior .art' subsurface atent O I tion installed therein;

hydraulic pump .of this invention;

* 2 duction .unit or subsurface hydraulic pumpof this inven- Figure 2 is a detailed sectional view of the subsurface Figure 3 is an enlargedsectional view, showing a-p ortion of Figure 2 in detail, in-particular the-reversing valve when the latter is in its downstroke position;

Figure 4 is a view similar to Figure 3 illustrating the reversing valve in its upstroke position; and

Figures 5 and 6 are cross-sectional views ofFig ure 4 taken along the planes indicated. 9

Referring now to the drawing inidetail, wherein like parts have been designated with like reference numbers, andto Figure l in particular, there is shown a borehole 10 having a casing string .11 therein, the lower end of which is provided with spaced perforation 12 adjacent an oil producing formation 13. A casing head-14 is attached in a conventional mannerto the upper end of easing string 1].. Depending within casing string his a power oil tubing string 16, the upper end 'ofwhich extends through casing head 14 and is provided with a conventional cap 17. The lower end of tubing 16-terrninates in a shoe assembly 18 to which isattacheda small string of'production-exhaust power oil tubing 19,,oft en hydraulic pumps relyon mechanicaltrippingdevices, such it as springs, trip rods, push rods, and the likexto :reverse 1 ,or changc the directionof theengine pistonv Such mechanical tripping devices aretoften unreliable'inthat the mechanically tripped reversing ordirec'tionalvalve often referred to as a macaroni string, the upper end of' the latter extending through casing head'f lsl. The annular space 21 between'casing 11 and tubing strings-16, '19

communicates at itsupperend withpa surface pipe'22,

having a valve therein, forthewithdrawalof anygas accumulating 'Witliinthe upper endof annular space '21.

Theaupper end of tubingrstring 316 communicates at the surface with a power oil supply pipe 23" having a valve 24 therein, this pipe beingin communication with the outlet of a pump 26 which in turn communicates viaipipe 27 with the' upper end of an oil-water separator "28. The

upper endof'the macaroni-tubing string 19 communicates stalls at dead center or at .ano-start positiom. Asia result, V

inorder-to remedy this situation, it is. often-necessary to pullthefhydraulic pump from the Well, disassemble. the same and repair the trippin'g mechanism." In addition, in

the operation of many of these prior art hydraulic pumps the power oil input pressureracts on a piston'area smaller l than=that ofthe productionplunger, therebymaking'it *impossible to' vary the-engine and pump areas to gain hydraulic ratio advantage. Many of these mechanically trippedreversing valves are 'dependent uponathe stroke; 7

length 'of the pump, thereby placing limitations onxthe Accordingly, 'an-object'of this invention isto provide an irfnpr'ovedsubsurface hydraulicpump. -Another'object is to-provide a fluid-actuated subsurface hydraulic pump,

the reciprocating engine of which is controlledbva novel fluid-actuated reversing or directional valve.- Another object'isto provide an improved reversing valve tsfor a fluid-actuated reciprocating engine. Another object is to provide a reversing valve forfa fluid-actuated engine, which valve is independent ofithei stroke length of the pump. Another object is to provide a reversingwalve for-aiiuid-actuated reciprocating engine, which :valve is not susceptible to the stalling, clead-center,zand no-start disadvantages associated-with mechanicaltripping devices;

Another objectlisto provide reversing valve "which. is independent of thehydr'aulid engine and displacement pump so that the "hydraulic ratio. advantagegcan be drawing in which:

r atthe surface with a production-exhaust poweroilpipe' 29,having a valve: 31 therein,this line communicating withan extension 32which in turn communicateswith pipe 33 coinmunicates at one end with power oil supply oil-water separator 28' nearthe middle thereof; Surface :"pipe 23, downstreamof pump 26, 'and communicates at its other end with'the production-exhaust power oil pipe 29 at a point upstream of valve 31, pipe 33 having a valve34 therein. Surface pipe 36 communicates 'at 'one end with power oil supplypipe 23 and communicates at --the otheren'cl withpipeiaz, pipe 36'having a valve'37 1 therein; Oil iswithdrawn from the upper end of oil-water separator ZSi and conveyed via line 38 h) an oil: storage V *tank'39."

" Referring now to Figure'Z, whereinthe subsurface hydraulic pump ofthis inventionis illustrated in detail,

the lower -endof poweroil tubingflfi is threadedlyise .cured to a tubing extension '15 by means of collar '41. i

Tubing extension'1'5 houses their'nproved subsurface hydraulic pump of this invention, this pur'np being generally designated 42 in thedrawing. The upper end of the hy= fdraulic pump '42 is prqvidedlwith a conventional fishing i I neck 43 and: a conventional flexible packer cup 44; shown in its relaxed position, which is heldji place byfa lock I nut46; flheqlower; end of fishing neck'43 is; threadedly =fixed tot-a toplpump plug 47 :which has an outerdiameter slightly smallenthanthe inner diameter OffiOllfilfljQ-l,

,a' pump; seal 48, such as an O -rin'g, being interposedthere.

betweenftofseal the upper power. oil supply passage 49 fromthe annular; space Sl btweentubing ,extensionllS ,andt ep od a uni 42- Aj y ndr h us n ms her SZJis'threa'dedIy secured at its uppe'r end to the lower periphery ofpunip plug '47, 'said ;housing terminating at, its lower fend in a bottom pump plug 53., The latter is I provided with a tapered nose portion 5 4 which; is adapted :16 seat inthe upperendof a; tubing standing valve -hous ing 56. The latter is rigidly disposed within a pump inlet passage 57 in shoe assembly 18, the pump inlet passagebemg in communication with the oil which accumulates m the lower end of the casing 11. Standing valve I housing 56 is provided with the usual ball valve 58 and stop or cage 59, this standing valve preventing flow of fluid from the interior of tubing extension to the exterior thereof, butallowing the flow of oil from the ex- "terior of tubing extension 15 to the interior thereof via the inlet passage 61 of the standing valve. The bottom pump plug 53 is similarly provided with a standing valve,

the latter comprising an inlet passage 62, which communicates with inlet passage 61, and the usual ball valve 63 and stop 64, the standing valve in the bottom pump plug similarly permitting only upward flow of oilfrom the exterior of the pumping unit 42 to the interior thereof.

.. The lower end of macaroni string 19 is secured to the shoe assembly 18 and communicates at its lower end with a passage 66 that in turn communicates with the interior of tubing extension 15 and annular space 51.

When it is desired to produce the oil from formation 13, tubing string 16 and macaroni string 19 are inserted within casing 11 and the pumping unit 42 is introduced into the upper end of tubing string 16 and allowed to fall therewithin until it comes to rest at the lower end of the tubing string 16, the tapered nose S4 of the bottom pump plug 53 seating on the standing valve housing '56 of the shoe assembly 18. When it is desired to re move the pumping unit 42 from the well, for example after. completing the production of the oil zone 13 or to make minor repairs, this can be accomplished by pumping power oil down macaroni string 19 and up annular space 51, the resulting pressure acting on seal 48 causing the release of the production unit 42 and then causing the expansion of the packer cup 44, which results in ber 68 is an engine piston 72, the top and bottom portions of which have reduced outer diameters slightly smaller than dashpot chambers 70, 71, respectively. Slidably disposed within pumpchamber 69 is a displacement piston the power oil supply passage 49 of tubing string 16 via passage 92 in top pump plug 47 and fishing neck 43.

Referring now to Figures 3 to 6 of the drawing, reversing valve 86 comprises a reversing valve housing 93 the upper end of which is threadedly secured to the periphery of top plug 94 and the lower end of which is secured and closed by a bottom plug 96. Disposed within reversing valve housing 93 is a main or directional valve housing 97 and disposed within the lower portion of the reversing 73. Engine piston 72 and displacement piston 73 are rigidly connected together by means of a connecting rod 74 which passes through an opening 76 in partition 67, a positive seal being effected betweenengine chamber 68 and pump chamber 69 by means of suitable packing 77.

Displacement piston 73 is provided with a traveling valve comprising ball valve 78 and passages 79, 81. Ball valve 78 is adapted to seat on a shoulder within 'passage 81, the latter communicating with the lower portion of pump chamber 69 and passage 79 communicating with the upper portion of pump chamber 69.

.Pump chamber 69 communicates at its upper end with annular space 51 viatransverse bores 82. If desired, the lower end of housing 52 adjacent pump chamber 69 can be provided with a plurality of vertical passages 83 which communicate at their lower end with annular space 51 via bores 84. a e

Disposed within the upper portion of the production unit 52 is the novel reversing or directional valve of this invention, which valve is schematically-shown in Figure 2 and generally designated 86. The upper end of engine chamber 68 communicates with reversing valve 86 via axial passage 87. The lower end of engine chamber 68 communicates with transverse bores 88 in partition 67, these bores communicating in turn with a plurality of vertical bores 89 which communicate at their upper ends.

with reversing valve 86. Reversing valve 86 communivalve housing 93 is a pilot valve housing 98. Main valve housing 97 is provided with a central main valve chamber 99 in which is vertically and slidably disposed a cylindrical main valve member 101, the latter being provided with enlarged portions 101a, b, and 0 having diameters slightly smaller than that of chamber 99. Similarly, pilot valve housing 98 is centrally provided with a pilot valve chamber 102 in which is vertically and slidably disposed a pilot valve member 103. The upper end of the main valve chamber 99 has a reduced diameter 104 and the upper end of pilot valve chamber 102 is similarly provided with a reduced diameter 106.

Main valve housing 97 is provided with a plurality of transverse bores 107, 108, 109, 111, and 112 which communicate at their inner ends with the central part of the I main valve chamber 99. The upper end of the reduced main valve chamber 104 communicates with a passage 113 in plug 94 which in turn communicates via vertical bores 115 with the annular space 116 between the production housing 52 and the reversing valve housing 93, passage 113 also communicating via bores 115 with an annular space 114 in pump plug 47, which space in turn communicates with the power oil supply passage 92.

The outer ends of transverse bore 107 communicate with the annular space 117 between the reversing valve housing 93 and the upper portion of main valve housing 97. The upper end of annular space 117 communicates via bores 90 in top plug 94 with exhaust power oil passage 91 in pump plug 47. A transverse bore 107 also communicates with the vertical bore 118 in the mam valve housing 97. The outer end of transverse bore 108 communicates with a vertical bore 119 in the main valve housing 97. The outer ends of transverse bores 109 communicate with annular space 116 via a plurality of openings 121 in the reversing valve housing 93. The outer ends of transverse bores 111 communicate with the annular space 122 between the lower portion of the main valve housing 97 and the reversing valve housing 93. The outer end of transverse bore 112 also communicates with the vertical passage 118 in the main valve housing 97.-

The upper reduced portion 106 of the pilot valve chamber'102 communicates at its upper end with transverse bore 120, and portion 106 communicates at its middle with the inner ends of a plurality of transverse bores 123, 124, and 125. Bore 120 communicates at its outer end with the lower end of vertical bore 119. Communication between the inner ends of bores 124 and 125 is obtained via annular groove 126 in the upper portion of pilot valve 103 when the latter is in its lower position, as shown in Figure 3. Similarly, communication between the inner endsof transverse bores 123 and 124 is obtained via the annular groove 126 when the pilot valve 103 is in'its upper position, as shown in Figure 4. The

lower portion of main valve chamber 99 communicates with a bore 127 in the upper end of the pilot valve housing 98, passage 127 communicating at its lower end with transverse bore 124. The outer end of transverse bore 123 communicates with the lower end of the vertical passage 118 which extends from the main valve housing 97 into the upper end of the pilot valve housing 98. Similarly, the outer end of the transverse bore communicates via vertical bore and inlet 128 with the annular passage 116 between the production unit housing 52 and the reversing valve housing 93. Communication'between, the annular space 122, formed between the lower portion of the main valve housing 97 and the central 1 portion of the main v reversing valve housing'93, with the annular rspac'e 131,

formed between the lower'portion of thepilot valve housing 98 and reversingvalve housing 93, isrhad by passages 132 formed in the upper end of the pilot valve housing 98. Annular space ,131' communicates inturn [with the lower enlarged portion 130 of the pilotvalve chamber 102 via passages 133 formed in the tion of the pilot valvehousing98. v

central por- '3 and outlets described hEIClHbGfOIQSllCh as here 109,

inlets 121', and annular spaces 117, 122 are sealed off with sealing rings, suchas O-rings, but for purposes of brevity, these have not been described although they are shown in the drawing.

In operation, power oil, or other hydraulic" liquid, is pumped from tank 28 at the surface via pipes 27 and 23 into the upper end of the production tubing 16, the

power oil supply. flowing down the tubing passage49 to the lowerend thereof. To accomplish this normal supply of power oil, valves 24 and 31 are opened, and valves 34 and 37 are closed. Power oil is thus introduced into the production unit 42 at the upper end thereof through inlet passage 92. The poweroil from inlet 92 flows into the annular passage 114, Figure'3, in the pump plug 47 and then flows downwardly via bores llS into the annular space116 between the productionunit housing 52 l and reversing. valve housing 913, this power oil being in: troduced via main valve inlets 121 into the main'valve housing'97, From inlets 121, the power oil enters the alve chamber 99 vialateral bores109.

On the downstroke,:power oil supplied via lateral bores 109 to the central portion'of the main valve chamber99 flows from ther'nain valve chamber via lateral bores 111 into the annular space 122 surrounding the lower end of the main ,valve housing 9.7 andthe upper end of the pilot valv e housing 98. The {power oil from the annular space 122 thenfiows via passages 132 into the .annulars'pace 131 and via passages l33 'in'to the upper end ofthe enlarged portion 130 of thepilotvalve chamber 102. The

power oil then passes through passages 138 in the piston 134 andflows at a predetermined rate through orifice 137 into engine inlet 87, and then into the dash pot enlargement 70 of the enginecharnber 68.

Fluid pressure from the power oil is also'supplied to the upper end of the main valve chamber 99 1mm the annular chamber;114.via passage 113, this fluid pressure being'applied to the upper end of the mairivalve 'member101.-

The -power oil in annular space 116 also enters "the pilot valve housing 98 via inlet, 128, the power oil thus introduced flowing via verticalbore 135 into :the lateral bore 125, andthen passing via the-annularggroove1126 88, the-exhausted oil flows upwardly-in the eommunicat- 'ing annular spaces 89 and 116, and thence into inlets 1'21. "Exhaust power oil from below engine piston 72 travels "via bores88, 89to mingle with primary power oil in bore-116. Engine piston "72 will still move down as described because the total area exposed on the top of enginev piston 72 is greater than the effective area at the bottom of engine piston 72 because of the efiect of connesting rod 74; Therefore even though the actual'pressures are equal, the total force (pressure times area) is greater-at the top of the engine piston 72 and it willfin fact move downwardly while at'the same time displacing power oil from beneaththe engine piston, said displaced power oil actually mingling withthe power oil above the iston. p Oil from formation 13 in the lower part of'pu'mp chamber 69below the displacement piston 73 ispumpedupwardly through the traveling valve passages 79, 81 inthe displacement piston 73, the standing valve in the bottom plug 53 of the production unit 42 preventing the formation oilin the pump chamber 69 from passing to'the exterior thereof. As displacement piston 73 moves downwardly within pump chamber 69, the formation oil flows via openings 82, 84 into the annular space 51 between the'production unit 42 and the tubing extension 15.

. This pumped oil then flows into the lower 'end of the macaroni string 19 and is pumped viathe same to the surface pipes 29, 32 intothe oil-water separator. Near the end of the downstroke, the lower portion 71 'of the engine chamber'68 functions as a dash pot and cushions the movement of the engine piston 7'2.

Duringthe downstroke, the only oil entering macaroni string 19 is a portion of the formation oil thatenteredthe lower end of pump chamber 69 on the previous-upstroke. There is no exhaust power oilentering macaroni string 19 on the downstroke.

'Thelf0110wing is apism the'valvIpositiohing' forces determining the positions of the main-valve 101 andgpilot valve 103 0111116 pump downstroke. These .forces are derived from the pressure P of the power "oil 'in supply inlet"92 and"thatpressure P of exhaust power oil and/or pumped oil inmacaroni s'tring 19, thislatter pressure being the sameas'tliat in exhaustfpower oil passage 9l. There is also a-pressure P whichis'less than- 12, by an amount determined by the pressuredrop through 'For purposes of discussion, the topface or area of the upper end of main valve member 101 can be called A the top face or exposedarea of main valve portionilqla can be called A and bottom face or area of the main valve member 101 called Also, the top face orarea of pilot valve member 103 can becalled A and the "top face or exposed areaof pilot valve piston'134 called A and the bottom face or area or this piston'called A1,.

The'valve'positioningforces tending 'to positionthe main valve member ,101on the downstroke are products A 1 AgP ,'and A 1 the first two of these forces opposing the last-mentioned force. Thus, the following relationship exists: A P +AP A P and the main valve the downstroke.

formed in the upper end of'pilot=valve member 130 into i the lateral bore 124. From the :latter, the power oil is supplied via passage'127- intothe lower eud ofniainvalve I chamber 99.

, The fluid entering the upper-end of the efiginechamfbel 68, Figure'Z, causes the-engine piston 72*to. move downwardly, thismovement--being translated t'o' 'the dis; placement piston 73 byfreasonofconnecting rod74. 901i 1 moving downwardly, the engine piston 72 -displaces 'the oil in 3 the lower. portion "of the engine chamber 68 via member101 is held in the positionshown in Figure 3 on The valve positioning forces tendin'gfto holdpilot valve 103 in the position shown inFigure 3 during-a downgstroke are the products of A4P A' P andjA Pg'the first two of these forces opposing the 'last-mentioned force.

'ThUS', the following relationship exists:

lateral[bores88 in the partition 67 separating the engine i chaniber 68 and pump chaniber 69t From-latera1 bores When the engine piston 72 reaches the endof its d'ownstroke fluid can no longer pass through orifice 137 and pressure P becomes equal to pressure 'P and 'the new relationship exists: A P 14 P +A P ,"therefore; the pilot valve member 103 moves in'the other direction, i.e.,

upward andoccupies the position shown in Figure 4. In

this'iposition,"-lateral bores -124"and-125' ai e"nolonger in I 123, 124, 127 are now in communication with vertical 'passage 118 and via lateral bores 107 with annular space 117, the latter communicating with the macaroni string :.19.'via passages 90, 91 and annular space 51.

Now, a new set of forces act on main valve member 101 to position and hold the same in that position shown in Figure 4, the pressure force relationship being In a similar manner, the pilot valve member 103 will reverse its position at the end of an upstroke and in so doing will reverse theposition of the main valve member 101, thus returning the system to the condition shown in Figure 3.

On the upstroke, with the main valve 101 and pilot valve 103 occupying the positions shown in Figure 4, the a power oil in annular space 116 flows via openings 88 into the lower end of engine chamber 68, causing engine piston 72 to move upwardly. The upward movement of engine piston 72 is translated by connecting rod 74 to the 1 displacement piston 73 causing its upward movement. As

the displacement piston 73 moves upwardly, ball 78 of the traveling valve in piston 73 is seated, and the ball 63 r of the standing valve in the lower end of the production unit is unseated, as is the ball 58 of the standing valve in the shoe assembly 18, thereby opening passages 61 and 62. As a'result, formation oil which has accumulated in the'casingbelow the production unit flows upwardly into thelower portion of the pump chamber 69. The formation oil in the upper portion of pump chamber 69 is forced out bores 82, 84 into annular space 51 and is pumped up macaroni string'19. Simultaneously, exhaust power oil from the upper end of engine chamber 68 flows via passages 87, 137, 138, 133, annular space 131, passage 132, annular space 122, lateral bores 111, 112, vertical bore 118, lateral bores 107, annular space 117, passages 90, 91, annular space '51, into macaroni string 19. It is to be noted that on the upstroke, macaroni string 1 19 conveys both exhaust power oil and formation oil to the surface.

When the engine piston 72 approaches the end of its upstroke, the upper reduced portion 70 of the engine chamber 68 acts as a dash pot, cushioning the upward movement of the engine piston 72 at its upper extremity. When the engine piston 72 reaches the end of its upstroke, the fluid pressures acting on the upper and lower surfaces of the pilot valve piston 134 becomes equal. Then because of the full pressure of the power oil acting on the upper end of pilot valve 103, the latter is forced downwardly to the position shown in Figure 3. As a result, bores 125, 124 are now again in communication via annular groove 126, and the fluid pressure of the power oil is againapplied to the lower end of the main valve 101 causing the same to move upwardly and occupy the main valve position shown in Figure 3. On the downstroke, the aforementioned cycle is again repeated. 1

When it is desired to remove the production unit 42 7 from the well, valves 24 and 31 are closed, and valves the foregoing discussion and accompanying drawing, and

it should be understoodthat this invention is not limited thereto.

l Iclaimz' v 1.;A-fluid pressure actuated reversing valve for use in combinationwith a fluid actuated, double acting recipsaid pilot valve adapted to change positions in accordance with the changes in operating pressure on the opposite sides of said pilot valve whenever said engine piston reaches the end of a power stroke.

2. The apparatus according to claim 1, wherein said directional valve has a small diameter portion and a large diameter portion, said portions defining three faces upon which valve positioning pressures are applied; said pilot h valve being adapted to alternately change the pressure applied to one of said faces to cause said directional valve to move from a first to a second position and vice versa. 7

3. The apparatus according to claim 2, wherein said pressures are power fluid pressure and exhaust fluid pressure.

4. The apparatus according to claim 1, wherein said pilot valve has a small diameter portion and a large diameter portion, said large diameter portion having an orifice therein adapted to permit the passage of said power fluid to said engine for moving said engine piston toward a first position, said orifice also adapted to permit the passage of exhaust power fluid when said engine piston moves in an opposite direction toward a second position.

5. The apparatus according to claim 4, wherein said small and large diameter portions of said pilot valve define first, second, and third faces upon which fluid pressures are adapted to act, said directional. valve adapted to alternately permit power fluid pressure and exhaust fluid pressure to act on said first face, said second and third faces adapted to be subjected to the pressures of said power fluid and exhaust fluid modified by a pressure drop across said orifice, said pressures acting on said second and third faces being equal whenever said engine piston reaches the end of a stroke.

6. A fluid pressure actuated reversing valve for use in combinationwith a fluid actuated engine having an engine piston reciprocally movable within an engine cylinder between first and second positions, said reversing valve comprising: a housing; .directional valve means within said housing; pilot valve means within said housing; said directional and pilot valve means each movable between first and second positions; said directional valve means adapted to alternately supply power fluid pressure to first and second sides of said engine piston, said power fluid being supplied via an orifice in said pilot valve means to said first side of said engine piston tending to move the same toward its said first position when said directional and pilot valve means are in their first positions, and said power fluid being supplied to said second side of said engine piston and tending to move said engine piston toward its second position when said directional and pilot valve means are in their second positions; said pilot valve means adapted to cause said directional valve means to move to its first and second positions; said pilot valve means adapted to move to either of its first and second positions in accordance with the cessation of flow through said orifice whenever said engine piston reaches either of its said first and second positions.

7. A fluid pressure actuated reversing valve for use in combination with a fluid actuated engine having an engine piston reciprocally movable within an engine cylin' der between first and second positions, said reversing valve comprising: a housing provided with a directional valve cylinder and a pilot valve cylinder; a directional valve reciprocally movable within said directional valve cylinder between first and second positions; a pilot valve reciprocally moveable within said pilot valve cylinder between first and second positions; a power fluid supply passage system adapted to convey power fluid under pressure; and exhaust power fluid passage system adapted to convey exhaust power fluid under a lesser pressure; said power fluid supply passage system adapted to permit the application of a first valve positioning force on a first end of said directional valve, and to supply said power fluid via a port in said directional valve to said pilot valve chamber and thence through an orifice in said pilot valve to a first end of said engine piston, thereby app-lying a fluid pressure on the latter and tending to move it toward its said first position; .said power fluid supp-1y passage system also adapted to supply via ports in said pilot valve a second greater valve positioning force to a second end of said directional valve tending to maintain the latter in its said first position; said ex- =haust power passage system adapted to permit the application of a third valve positioning force to an intermediate portion of said directional valve, said exhaust power fluid passage system also adapted to apply via ports in said directional valve a valve positioning force to a first end of said pilot valve which together with a pressure diflerential across said orifice tends to maintain said pilot valve in its said first position; said pressure differential becoming zero when said engine piston reaches its said first position, whereby said pilot valve is subsequently caused to move toward its second position; said pilot valve in its said second position permitting the release of said second valve positioning force from said second end of said directional valve, and permitting the appli cation of exhaust fluid pressure via ports in said pilot valve to said second end of said directional valve tending to allow the latter to move toward its said second position; said directional valve in its said second position permitting the application of said power fluid pressure to a second and opposite end of said engine piston, thereby causing said engine piston to move toward its said second position and causing exhaust power fluid to be exhausted via said orifice and via a port in said directional valve to said exhaust power fluid passage system; the differential pressure across said orifice again becoming zero when said engine piston reaches its said second position, whereby said pilot valve is subsequently caused to move toward its said first position, and thus causing said directional valve to move toward its said first position, thereby completing a cycle and permitting the repetition thereof.

8. In combination, a fluid actuated, double acting reciprocating engine and a fluid pressure actuated reversing valve, said engine comprising an engine piston reciprocalv 1y movable within an engine cylinder and a displacement piston reciprocally movable by said engine piston within a displacement cylinder which is adapted to communicate with a source of fluid desired to be pumped, said reversing valve comprising a directional valve adapted to connect a first side of said engine piston alternately to an exhaust fluid passageway and to both a second side of said engine piston and a source of power fluid, and a pilot valve adapted to change the position of said directional valve, said pilot valve adapted to change positions in accordance with the changes in operating pressure on said opposite sides of said engine piston whenever the latter reaches the end of a power stroke.

9. A subsurface hydraulic reciprocating pump adapted to be suspended in a well traversing an oil zone, said pump comprising a fluid actuated reciprocating engine and a fluid pressure actuated reversing valve, said engine comprising an engine piston reciprocally movable within an engine cylinder and a displacement piston reciprocally movable by said engine piston Within a displacement cylinder which is adapted to communicate with said oil producing zone, said engine piston adapted to move between first and second positions, said reversing valve comprising a housing; directional valve means within said housing; pilot valve means within said housing; said directional and pilot valve means each movable between first and second positions; said directional valve means adapted to alternately supply power fluid pressure to first and second sides of said engine piston, said power fluid being supplied via an orifice in said pilot valve means to said first side of said engine piston tending to move the same toward its said first position when said directional and pilot valve means are in their first positions, and said power fluid being supplied to said second side of said engine piston and tending to move said engine piston toward its second position when said directional and pilot valve means are in their second positions; said pilot valve means adapted to cause said directional valve means to move to its first and second positions; said pilot -valve means adapted to move to either of its first and second positions in accordance with cessation of flow through said orifice whenever said engine piston reaches either of its said first and second positions.

References Cited in the file of this patent UNITED STATES PATENTS 883,935 Champ Apr. 7, 1908 2,688,314 Holm Sept. 7, 1954 2,773,486 Albers Dec. 11, 1956 2,838,910 Bacchi June 17, 1958

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