I, Paul Buckingham Soderberg, a citizen of The United States of Λneric and with residence at 1716 Huge Oaks, Houston, Texas 77055, USA, hav invented the following described:

Technical Field

This invention relates generally to methods and means for pumpin liquid from oil and gas wells and more particularly, it relates t methods and means for pumping "heavy oils" for which no satisfactor remedies have been available heretofore. "Heavy oil" reservoirs ar abundant but production from such formations has been extremely limite due to a viscosity comparable to tar. Attempts to heat the Heavy Oi as by steam flooding so as to lower its viscosity and thereby render i more flowable, have met with some success however, pumps- used tend t "vapor lock" which prevents formation oil from flowing into the pum chamber so as to be pumped to the surface. Due to the high temperatur of the heated oil, conventional pumping equipment is not suitable fo pumping such oils because of the effect of temperature on seal mater ials and the like and because any water present in the produced fluid will flash into steam as it enters the pump chamber, which togethe with gas in the produced fluids will tend to "vapor lock" a convention al pump, causing it to repeatedly stroke without pumping fluid an thereby destroy itself in a short time by generating heat not carrie off by produced fluids.

Due to the world wide energy shortage, it is necessary that energy- efficient and cost-effective means be provided for pumping "Heavy Oils" from producing formations, such that pump means are operable in the presence of Heavy-Oils and such that no vapor lock occurs and such that pump strokes occur only after the pump chamber has filled with liquid to be produced.

Background Art

Conventional "barrel-type" reciprocating bottom hole pumps have been used for many years as evidenced by the many thousands of pump-jacks

across the country, each pump-jack reciprocating a sucker-rod strin disposed vertically into a well so as to actuate the pump therein Typically, the pump body is suspended near the bottom of a tubin string such that the pump is in the liquid to be pumped from the well A conventional pump body is usually made from a joint of tubing and ha an inlet to receive liquid from the producing formation into the pum chamber or "barrel." A piston is reciprocated within the pump chamber allowing liquid to pass through a first check valve into the pump cham ber during the return stroke and forcing that liquid up through second check valve into the production tubing on the pump stroke. Th piston is affixed to a piston rod of greater length than the pum stroke so as to allow the rod to pass through and be sealed by a seal member which prevents back flow from the production tubing into th pump chamber.

Although methods have been devised to vary the speed and lengths o pump strokes in an attempt to adjust to changing well conditions, suc pumps do not pump at precisely the rate that the well may be producin at any given time. Such a mismatch often leads to: a lower productio rate if the pumping is at too low a rate; or to pump damage and a wast of energy when the pump operates faster than the formation is then pro ducing. Such pumps are also susceptable to vapor-lock wherein gas o vapor accumulates in the pump chamber and expands during the retur stroke and thereby exerts a pressure within the pump chamber which i turn prevents liquid from filling the pump chamber whereupon the nex pump stroke can pump only a fraction of its rated volume.

Although such pumps have operated reasonably well at low pressures an at shallow depths, they are not suited to operate while submerged i hot liquids as occurs in the steam flooding of formations producin heavy oils. Not only would seal materials fail but sucker-rod expan sion due to the heat would inhibit proper performance as would recipro cation of sucker rods through thickening heavy oil as it cools as i flows toward the surface.

The use of sucker rods in crooked holes causes extreme wear on both th rods and the casing which in turn invites casing failure, down time an loss of production.

Both rotary and reciprocating downhole pumps have been driven by pum ing a portion of the fluid produced back down the hole through a sep rate conduit to actuate a bottom hole pump and then to exhaust into t production tubing and return to the surface along with new liquid fr the formation. Such an arrangement requires that the power flu pumped down be at a much higher pressure than the formation pressur Also it is required that the net volume of oil produced is substantial ly less than the total volume pumped up the tubing because some must returned to power the bottom hole pump. Such pumps are also subject vapor-lock as well as the obvious loss of energy required to continual ly circulate the high pressure, power fluid. Since fluid produced fro the formation will have fine sand particles entrained therein, so wil the fluid separated at the surface for use as power fluid, making i necessary to filter and degas the fluid before admitting it to a hig pressure surface pump. Even though filtered, fine abrasive particle remain in the fluid and act to damage the surface pump and the downhol pump as wel 1.

Various gas lift methods have beem employed on wells of limited dept however, such a practice can be economically justified only if a suffi cient quantity of gas at an excessive pressure is available. B nature, gas lift is inefficient and the cost to repressure gas fo lifting a high liquid-gas ratio well is no longer practical as it migh have been when gas was of little value. Various methods are disclose in U.S. Patents 1,845,181; 3,410,217; 3,941,510 and 3,991,825, none o which would be practical for use in deep wells or for lifting heav oil. Expansion of the gas would cool the heavy oil to a non-flowabl condition and thereby lock up the tubing.

Therefore, some objects of this invention are to provide methods means, and systems to pump liquids from wells such that: vapor-lock o the pump does not occur; the pump is operated so as not to allow damag to pump parts caused by unnecessary contact with the produced fluid; the pump does not stroke unless the pump chamber is full of liquid; n sucker-rods are required to operate within a column of Heavy-oil; no recirculation of a fluid to the pump is required; the pump chambe pressure may be reduced to as low as atmospheric pressure while forma¬ tion fluid is flowing into the pump chamber so as to maximize the

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differential flowing pressure and thereby increase productivity of th producing formation; pumping of the well is effected with substantial savings of energy.

The first paragraph of U.S. Patent No. 3,123,007 discloses a pum "employing a reciprocating column of liquid to operate the reciprocat ing plunger or traveling valve of a pump", in the first paragrap thereof, and as discussed in column 1, line 36, "The present inventio provides an actuator for a well pump of conventional design". The sam patent also discloses the actuator to employ an annular piston as i column 1, line 56. Many other patents disclose similar devices bu lack the intelligence in the downhole pump itself to sense when th pump chamber is full of liquid, as does the subject invention.

Other generally known attempts to use reciprocating columns of fluid to operate downhole pumps were unsuccessful because too much energy wa expended in compressing the power fluid for each power stroke.

Disclosure of Invention

This invention provides a new and novel method, means and system fo pumping liquid from a well of any depth without vapor-lock and withou loss of volumetric efficiency of the pump. This invention also pro vides means to pump hot oils, as may be necessary in oil wells produc ing heavy-oils after steam flooding, such that water in the produce fluid does not cause vapor-lock as it flashes into steam within th pump chamber.

A reciprocating pump member which may be a piston, a diaphra or suc operating within a pump chamber is caused to begin a pump stroke onl after the pump chamber is filled with liquid, substantially all gas an vapor that has entered the pump chamber from the producing formation, having been vented to the surface. Venting of gas and vapor may b accomplished through a vent valve mounted with the upper fixed end o the pump chamber such that as gas, vapor and liquid from the producin

- formation enter the lower portion of the pump chamber but above th piston, through suitably mounted inlet ports or inlet check valves, ga and vapor rise above the liquid and pass through the vent valve an

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through a suitable vent passage to the surface. Just as liquid rise to the top of the pump chamber to fill ^' it completely with liquid, float of sufficient bouancy for operation in the liquid acts to clos the vent valve and thereby prevent liquid from entering the vent valve Closing of the vent valve triggers a signal generator-transmitter whic may then cause a surface mounted receiver-controller to actuate a pum stroke of high volumetric efficiency. As the piston is powered upward ly, an inlet check valve may close and liquid is forced through an out let check valve mounted with the upper fixed end of the pump chamber and through the production string toward the surface until the pisto reaches the uppermost position, being stopped by contact with the uppe fixed end of the pump chamber or other suitable stop means.

To power the pump stroke as described above, the receiver-controller upon receiving a suitable signal from the generator-transmitter, ma close a vent valve mounted on a power conduit extending from a flui pressure source at the surface to a pressure chamber mounted below th piston such that as the controller acts in sequence to open a valv from the fluid pressure source, fluid pressure at the predetermine pressure level is admitted from the pressure source through the powe conduit to the pressure chamber below the piston so as to drive th piston upwardly through the power stroke. As the piston reaches th uppermost position and contacts stop means as described above, th pressure source may then increase pressure in the power conduit to level above that necessary to operate the piston power stroke such tha the increased pressure triggers a preset pressure switch mounted wit the power conduit to cause the controller to close the valve from th power source and to open the vent valve mounted with the power condui so as to reduce the pressure in the power conduit and in the pressure chamber below the piston, to hydrostatic pressure only. Piston return means of suitable force to overcome the hydrostatic force acting below the piston may then return the piston to its lower-most position to begin filling of the pump chamber as described above for the next pump stroke. Piston return means may comprise a mechanical coil spring, a gas chamber or any suitable means to achieve proper piston return. As the piston begins its return stroke, the outlet check valve closes and inlet check valves open whereupon the vent valve is opened by the float being of suitable weight and having lost bouancy as the piston returns

to its lowermost position to create temporarily an empty pump chamber. It is therefore evident that fl uid reciprocates in the power condui and in the pressure chamber, which with the spring member, causes th piston to reciprocate so as to pump liquid to the surface. Becaus fluid in the power conduit is not subject to contamination by mingling with fluids from the producing formation, no filtering, degassing, chemical treatment or such is required as is the case with conventional fluid-powered downhole pumps and additionally, an optimum power fluid may be used, selected for best service at service conditions such a temperature, depth, viscosity, density and such, practically withou regard to cost of the fluid.

The pump of this invention may be installed in the well by any o several means such as lowering the pump within an intermediate string of casing by means of a centrally disposed string of production tubing sealably attached to the top of the pump, so as to allow an outwardl disposed shoulder formed around the pump to be sealingly supported b an inwardly disposed radial flange formed around the bottom of the intermediate casing string. The annulus between the production strin and the intermediate casing string may be used as the power conduit and the annulus outwardly of the intermediate casing string may be used as the vent path. Liquid flowing up through the production tubing may flow through a conventional wellhead manifold to conventional storage tanks or flow lines.

The surface pressure source may comprise a conventional surface mounted pump or other suitable sources of pressurized fluids arranged to supply the power fluid at sufficient pressures and flow rates as required to operate the pump, upon the opening of a valve communicating with the fluid pressure power source and the power conduit, on command from the controller.

The signal generator, transmitter, receiver and controller may be of any compatible conventional type such as sonic, electrical, pneumatic or hydraulic, depending on well conditions and owner preference. An ultrasonic transmitter-receiver combination is depicted on the drawings whereas an electrical line would be requied between an electrical transmitter-receiver combination and a pressure conduit would be

required between the pneumatic or hydraulic combination.

Although conventional inlet and outlet check valves are depicted an described, other valves such as slide valves may be used withou departing from the spirit and scope of this invention.

Mounting of the pump may be by any of several conventional means suc as being: run in attached to the lower end of the tubing string; bein pumped through the tubing; being run through the tubing on a wire lin or a string of smaller tubing.

The embodiment described below and depicted in the drawings, routes produced well liquids up the tubing; power fluid to operate the pum through the smaller annular passage; vented gas through a second annu lar passage; however, other suitable routings including small tubing run through the production tubing or an annulus may be used withou departing from the spirit or scope of the present invention.

Although the present invention normally operates with an automatic pum cycle, it may be desirable to override the automatic function so as t pump fluid down the power conduit, for instance to replenish retur fluid in the gas chamber or for other reasons such as to inject chemi cals into the well bore to inhibit corrosion. For the purpose of over riding the automatic pump function, the valve in the power conduit ma be provided with conventional selective controls so as to shift th valve so as to inject fluid into the power conduit even though no sig nal has been received from the receiver-controller. Increase of pres sure in the power conduit to a predetermined level above the normal operating pressure may then cause a differential pressure valve in the pump to open and admit fluid from the power conduit as desired.

When it is desired to increase the amount of fluid in said gas chamber, said differential pressure valve may be connected so as to admit fluid from the power conduit into the gas chamber upon a predetermined pres- sure being caused across said differential valve.

The use of specific types of oils as power fluids may have several advantages and several disadvantages for instance: oil is more

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compressible than water and should the entire power conduit be filled with oil, much energy could be wasted compressing the oil for every pump stroke; oil may withstand a higher temperature than water without vaporizing. Therefore an object of the present invention is to make more efficient the use of a power fluid that is to be reciprocated in a conduit so as to power a downhole pump, by filling the downhole pump and the lower portion of the power conduit with a hydraulic oil having a specific gravity greater than water and filling the rest of the power conduit with a less compressible fluid such as water.

Brief Description of the Drawings

Figure 1 is a schematic of a vertical section of a well producing both gas and liquids, comprising the present invention wherein well fluid is allowed to flow from the producing formation into the pump chamber because the piston is at the bottom of its stroke.

Figure 2 is similar to Figure 1 except that the piston is at the top of its stroke, after forcing liquid toward the surface.

Figures 3 and 4 illustrate one embodiment of the pump of the present invention, the upper part in Figure 3 and the Tower part in Figure 4.

Figure 5 is an enlarged partial view taken from Figure 4 so as to more clearly depict the differential valve within the pump.

Description of the Preferred Embodiment

As shown in Figures 1 and 2 well 10 producing both liquid and gas as at 12 from formation 14 by method, system and means of the present inven¬ tion, gas (B) being produced at the surface from flowline 16, liquid being produced at the surface from flowline 18. A conventional well¬ head 20 may be used for providing mounting and sealing attachment with production tubing 22, and casing strings 24 and 26. Produced liquids (L) flow up through tubing 22 to flowline 18, power fluid (F) flows through annulus 28 formed around tubing 22 within casing 24, and pro¬ duced gas (G) flows upwardly through annulus 30 formed around casing 24 and within casing 26 to flowline 16. Screen 32 may be connected to the

l ower end of casing 26 so as to prevent particles of sand and grave from fl owing into the wel l from the formation . Shoulder 34 may b formed inwardly on the lower end of casing 26 for supporting the lowe portion of casing 24 ^' having shoul der 36 formed outwardly for coopera tion with shoulder 34. Shoulder 36 may be provided with seal 38 fo seal ing the lower end of annul us 30. Pump 40 may be attached to th l ower end of tubing 22 as at 42 in any suitable manner so as to regis ter gas passage 44 in seal ing communication with passage 46 through th wel l of casing 24. Pump 40 comprises upper end wal l 48 which ma house: l iquid outl et check val ve 50 for passing liquid frm pump cham ber 52 formed by tubul ar member 53, to within tubing 22 only; ven valve 54 for passing only gas from pump chamber 52 to passage 44, ven val ve 54 sized of suitabl e material so as to be cl osed when immersed i well liquid due to its bouancy and being open when not immersed in well l iquid due to its weight in gas . End wal l 48 may al so house conven tional generator- transmitter 56 arranged to be triggered by stem 58 o vent val ve 54 when vent val ve 54 moves from open position as shown i Figure 1 to the cl osed position of Figure 2.

Receiver-control ler 670 may be mounted with the upper portion of tubing 22 so as to receive signal s as at 61 from generator- transmitter 56 so as to direct motor val ve 62 to move to the position as shown in Figure 2 such that power fl uid (F) is al l owed to fl ow from pressure source (P) through condui ts 66 and 68 and annul us 28 to act against the lower end 70 of piston 72. Pressure switch 74 may be mounted wi th conduit 68 to sense a predetermined level of pressure of power fl uid (F) so as to direct motor val ve 62 to move to the position as shown in Figure 1 such that power fl uid (F) is al l owed to fl ow from annul us 28, through con¬ duits 68 and 75 to surface tank 64 as spring 76 returns piston 72 from the upper position as shown in Figure 2 to the l ower position as shown in Figure 1 . Conduit 78 may be connected so as to return power fl uid from surface tank 64 to power source (P) for reuse during another pump cycle, check valve 80 preventing fl ow from the pressure source to tank 64 which may cause overpressure of the tank. Pressure rel ief val ve 82 may be set at atmospheric pressure as a vent or may be set at some higher pressure so as to bal ance the bottom hol e pressure of the power fl uid with the formation pressure and spring 76 as may be desired for most efficient operation. f OM

Power source (P) may be a conventional pump, a gas-over-l iquid accumu¬ lator or other well-known sources of fl uid power. Although power fl uid (F) is depicted as a liquid, should a source of pressurized gas as from another well be avail able, conduit 78 may be omitted such that gas may flow to move the piston up per Figure 2 and then may be allowed to flow out conduit 76 to a fl owl ine not shown.

Piston 72 maintains sl idable seal ing contact with inner wal l 84 of pump chamber 52 by means of annul ar seal 85 positioned within groove 83 formed in wall 84 so as to prevent co-mingl ing of power fl uid (F) and well liquid (L) or wall gas (G) . Conduit 86 all ows well fl uids to flow from formation 14 through screen 32 through the wall of casing 24, through the wall of tubular member 53 and into pump chamber 52 when piston 72 is in its lowermost position depicted in Figure 1. Annular seal 88 suitably mounted within groove 90 formed with the inner wall 84 of the pump chamber is positioned so as to contact cyl indrical surface 92 of piston 72 as shown in Figure 2, immediately after piston 72 begins upward movement from its lowermost position.

Liquid-gas interface 94 of Figure 1 rises as liquid and gas flow into chamber 52, gas passing through vent valve 54, conduit 44, annul us 30 to flowl ine 16 until vent valve 54 cl oses to initiate a pump cycle as described herein bel ow.

Tubular-member 53 may be provided with inwardly displ ace radial shoul¬ der 96 for supporting end 97 of spring 76 against upward movement such that spring 76 can provide sufficient force to return piston 72 to its lowermost position against the pressure of the power fl uid as in Figure 1 . Piston 72 may be formed with stem 98 having outwardly disposed shoulder 99 to act against lower end 100 of spring 76 so as to transmit a downwardly acting force from spring 76 to pi ston 72.

Figure 2 depicts a generator- transmitter 56 and receiver-controller 60 as being of a sonic or sonar type; however, other suitable conventional subsystems such as el ectrical , pneumatic or hydraul ic may be empl oyed without departing from the spirit or scope of this invention. Such other subsystems may require a cabl e or conduit (not shown) between the transmitter and receiver but well known in the art.

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Although Figures 1 and 2 depict conduits 44 and 86 being formed int gral with tubing 22 and casing 24, ^' it should be understood that an number of suitable connections, seals and supports may be utilized as to adapt system components for best installation, operation an maintenance for any given well conditions.

For conditions where it is desired that the pump be run into the hol by means of the production tubing 122, Figure 3 depicts a preferre embodiment of the pump of the present invention generally depicted a 140, suspended and sealed at the lower end of casing 124 by means of inwardly disposed annular shoulder 134 formed on casing 124; outwardl disposed annular shoulder 136 formed on the upper end of tubular membe 253; shoulder seal 138 and annular seal 137. Outer casing 126 may b formed at its lower end so as to receive and suspend well screen 13 for purposes described above. The inner wall of casing 126 and th outer wall of casing 124 form annular passage 130 and the inner wall o casing 124 and outer wall of tubing 122 form annular passage 128.

The lower portion of tubing 122 may comprise a side door valve show generally at 235 to enable the operator to selectively circulate dow the tubing 122, through valve 235 and up annulus 128. The constructio of valve 235 may include outwardly extending annular shoulder 23 formed around the lower end of tubing 122, shoulder 236 formed wit groove 238 so as to retain annular seal 237 for sealing contact betwee shoulder 236 and inner cylindrical surface 284 of body 285. Annula recess 239 formed bewteen end shoulders 241 and 243 within body 218 provide for an axial length sufficient for shoulder 236 to reciprocat therein. Shoulder seal 245 may be provided for sealing between the lower surface of shoulder 236 and shoulder 241 of valve body 235. Shear pins as at 247 may be provided to maintain valve 235 closed as shown in Figure 3 until removal of the pump is desired. Side ports as at 249 are provided through the wall of body 235 so as to allow liquid from within tubing 122 to flow around the lower surface of shoulder 236, through ports 249 and into annulus 128 after pins 247 are sheared, tubing 122 is lifted up through recess 239 so as to disengage seals 237 and 245, for purposes to be described below.

The lower end of valve body 285 may comprise tubular conduit 251 having

end wall 148 for support of and sealing engagement with ball check 15 arranged to allow fluid flow from pump chamber 152 into conduit 25 only. Conduit 251 is retained centrally disposed within tubular membe 153 by means of connecting walls 248 and 250 so as to form annula chamber 252 of sufficient volume to allow for proper operation of th pump as later described. Vent valve 154 may be provided with floa 155, float 155 having sufficient bouancy in the produced well liquid s as to close the vent valve immediately before liquid rises to the ven valve level, within chamber 152. Sonic generator-transmitter 156 ma be mounted with conduit 251 so as to be triggered by the closing o vent valve 154 to thereby transmit a proper signal to receiver-control ler 60 as described above. Conduit 144 connecting annular chamber 25 with annulus 130 may be provided with a check valve as at 244 so as t allow gas to flow from space 252 into annulus 130 but to prevent wel fluid from rising in annulus 130 and entering chamber 252. Annula piston 201 may be provided for operation within tubular member 253 an around tubular conduit 251, piston 201 having conventional slidin seals as at 202 and 203 respectively, axial movement of piston 20 being limited by the lower surface of valve body 285 and end wall 250 such that a selected operating fluid 254 may be used in annulus 12 below piston 201, fluid 254 being more suitable for flow through, lowe passages of the pump than power fluid (F) above piston 201 in annulu 128. Pump chamber 152 is formed by tubular member 153, end walls 148 248 and piston 172 with sufficient length to allow for a full stroke o piston 172. When piston 172 is at its lowermost position as shown i Figure 4, well fluid may flow from the producing formation, throug ports 186 and into pump chamber 152. As the upper end of piston 17 rises past ports 186 and the outer cylindrical wall 192 engages annula seal 188 within annular groove 190 formed in inner wall 191 of chambe 152, flow is stopped through ports 186 to thereby allow piston 172 t force liquid up past ball check 150 toward the surface. Sliding annu lar seal 185 may be mounted within groove 183 formed in inner wall 19 for sealing cooperation with outer surface 192 of piston 172 so as t prevent downward leakage past the piston for the full stroke.

Whereas Figures 1 and 2 depict coil spring 76, Figure 3 depicts a ga spring which may be used to approximate a constant force spring an thereby reduce the range of pressure required of the power fluid (F)

End wall 301 within tubular member 253 defines the lower extremity o annulus 128 and the upper extremity of annulus 128 and the upper ex tremity of fluid chamber 176, chamber 176 being further defined by tub ular member 253 and lowermost end wall 302. Bladder 303 is attache around the inner surface of tubular member 253 as at 304 so as to main tain separate, gas below the bladder and a suitable operating flui above the bladder, the gas being charged to a pressure level suitabl for operation under given well conditions which imparts the same pres sure to the operating fluid 305 above the bladder. Centrally dispose rod 306 may be mounted with and project upwardly from end wall 301 terminating with annular flange 307. Piston 172 is formed at its lowe end with bore 308 sized for close sliding fit around rod 306 such tha annular seal 309 mounted in the wall of bore 308 maintains a slidin seal against fluid from either direction. Annular seal 310 is suitabl mounted with annular flange 307 so as to provide a sliding seal agains inner wall 311 of enlarged bore 312 immediately above bore 308. Cham ber 313 is formed by tubular wall 314 of piston 172, end wall 315 o piston 172 and annular flange 307 such that the volume of chamber 31 will increase as piston 172 rises and will decrease as piston 17 decends with respect to flange 307. Fluid passage 316 is internal t and axially aligned with rod 306 so as to provide for communication o fluid 254 between chamber 313 and annulus 128. Fluid passage 317 i internal to and axially aligned with rod 306 so as to provide for com munication of fluid 305 between enlarged bore 312 and chamber 176, above bladder 303. It may thus be understood that a compressed gas i chamber 176 and below bladder 303 will serve as a spring to store energy from and return energy to fluid 305 which in turn flows through passage 317 to and from enlarged bore 312. As fluid 254 is forced at sufficient pressure down annulus 128, up passage 316 and into chamber 313 to act against end wall 315, piston 172 may be caused to move upwardly against well fluid within pump chamber 152 and against the pressure of fluid 305 within enlarged bore 312. Such movement will cause fluid 305 to flow from bore 312, through passage 317 and into chamber 176 above bladder 303 which in turn forces the bladder down- wardly and thereby further compresses gas below the bladder. It may also be understood that when the pressure of fluid 254 within chamber 313 is reduced to a sufficient pressure level by reducing the pressure within annulus 128, the pressure of the compressed gas wi

176 will be sufficient to reverse flow of fluid 305 so as to retur piston 172 to its lowermost position. —

The construction of Figure 3 allows for casing 126, screen 132 an casing 124 to be installed in a conventional manner after which th pump of the invention may be lowered within casing 124 by means of pro duction tubing 122 so as to be supported by shoulder 134 on the lowe end of casing 124 as shoulder 136 is landed thereon to also effec sealing action of seals 137 and 138 so as to seal annulus 128 fro communication with annulus 130.

Referring now to Figure 5, a differential pressure valve 400 may b mounted in the wall ^" 410 formed below annular passage 128 and abov chamber 176 so as to admit fluid from annular passage 128 which is con nected with the power conduit, into the upper portion of chamber 176 s as to mingle with fluid 305. Differential valve 400 may compris closure member 402 mounted in an opening through wall 410 such tha cooperating sealing surfaces 408 between wall 410 and member 402 ma serve to close said opening. Nut 406 may be screwed onto a shank por tion of member 402 so as to adjustably retain coil spring 404 under predetermined load such that surfaces 408 will remain sealed unles pressure in annular passage 128 is sufficiently greater than the pres sure of fluid 305 to casue member 402 to move downwardly and admit som fluid from passage 128 to mingle with fluid 305, until the pressure o fluid 305 is great enough to act with spring 404 and cause surfaces 40 to once again contact and cause valve 400 to close.

The lower portion of the power conduit and the downhole pump chamber and passages such as 315, 316, 128 and 28 may be filled with a suitabl hydraulic oil having a specific gravity greater than water so as t retain the oil below any water in the system. Most of the power con duit may then be filled with water up to the earth's surface, the wate remaining above the oil due to the difference in specific weights Should high temperatures be expected at the producing formation such a may be the case when steam is used to extract heavy oils, an oil havin a high boiling point may be used for the lower portion of the powe fluid so as to prevent steam flashing and vapor lockup of the pum power system as could occur in a shallow steam flooded well.

Operation of the Invention

The system and method of operation of the invention may be best unde stood by referring to Figures 1 and 2. Now referring to Figure operating fluid (F) is allowed to return to tank 64 from annulus 28 d to the position of motor valve 62 such that the pressure of fluid ( acting upwardly on piston 72 is reduced to a pressure level not suffi cient to hold the piston upwardly against the force of spring 76 ther by allowing spring 76 to move piston 72 to its lowermost position p Figure 1. Also any gas that may have accumulated within pump chamb 52 is vented to the surface through open vent valve 54, gas passage 4 annulus 30 and flow line 16 so as to maintain a pressure within pu chamber 52 low enough for formation fluid to readily flow into chamb 52.

As both gas and liquid flow from formation 14 through screen 32, parti cles of sand and gravel are retained with the formation and gas an fluid continue flowing through contuits as at 86 into pump chamber 52 As the gas-liquid interface rises within chamber 52, gas is continuall vented to the surface as previously described until such time tha liquid rises to the level of vent valve 54 which thereby increase bouancy of the valve so as to close as depicted in Figure 2 and preven liquid from entering the vent. Per Figure 2, the closing of vent valv 54 moves stem 58 upwardly to trigger signal generator-transmitter 5 and cause it to transmit a sonic signal 61 upwardly through productio tubing 22 to receive-controller 60 which in turn directs motor valve 6 to move to the position as depicted in Figure 2 so as to allow flui from pressure source (P) to increase the pressure of fluid (F) suffi ciently to move piston 72 to its uppermost position per Figure 2. A piston 72 begins to rise from its lowermost position: chamber 52 i full of liquid, gas having been vented through vent valve 54; th upper cylindrical portion of piston 72 contacts annular seal 88 to sto back flow from chamber 52 to formation 14; annular seal 85 prevent fluid flow between piston 72 and inner wall 84; spring 76 is progres sively compressed to store energy sufficient for returning piston 72 t its lowermost position; liquid in chamber 52, being confined an increased in pressure to a pressure level greater than the pressur level in tubing 22 immediately above endwall 48 by upward movement o

piston 72, causes conventional check valve 50 to open and allow pro duced well fluid to flow from chamber 52 into tubing 22 and thenc toward the surface.

Continued flow of power fluid (F) from pressure source (P) through con duit 66, valve 62, conduit 68, annulus 28, around the lower end o tubular member 53, upwardly within tubular member 53 to act upwardl against the lower end of piston 72 causes: continued compression o spring 76; continued flow of liquid within chamber 52 to flow towar the surface; check valve 50 to remain open for passage of the produce liquid; piston 72 to expel substantially all fluid from pump chamber 5 so as to achieve a maximum volumetric efficiency as piston 72 reache its uppermost position as shown in Figure 2. Immediately after pisto 72 reaches its uppermost position, continued i put of fluid (F) fro pressure source (?) causes the pressure level of power fluid (F) t increase to a predetermined pressure level in excess of that require to raise piston 72 to its uppermost position, whereupon preset pressur switch 74 causes motor valve 62 to move from the position of Figure to the position of Figure 1 such that flow from pressure source (P) i stopped and pressure relief of power fluid (F) within annulus 28 i accomplished by the flow of power fluid (F) through conduit 68, valv 62, and conduit 75 to tank 64. Pressure relief valve 82 may be prese to maintain the pressure level within tank 64 at any desired level s as to maintain the pressure of fluid (F) below piston 72 within desired operating range as determined by the fluid pressure level with in formation 14 and other well conditions.

As the pressure level of power fluid (F) is relieved to a predetermine value, the force of compressed spring 76 is sufficient to return pisto 72 to its lowermost position as shown in Figure 1, displacing a volum of fluid from tubular member 53 and a like volume from annulus 28 int tank 64, whereupon: pump chamber 52 is again empty; piston 72 is dis engaged from annular seal 88 so as to allow well fluid to again flo from formation 14, through conduits 86 into chamber 52 and begi another cycle. As piston 72 begins its downward movement, check valv 50 closes to prevent back flow of liquid from tubing 22 into chamber 5 causing a partial vacuum to occur within chamber 52 which in additio to the fact that no liquid is present within chamber 52 to provid jmlEΛ

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bouancy for vent valve 54, causes vent valve 54 to open due to its o weight.

Should power source (P) comprise a pump, power fluid (F) may be reci culated from tank 64 through check valve 80 and conduit 78 to the pu intake, the pump being sufficient to provide fluid power for prop operation of the downhole pump as previously described.

Since gas is vented through vent valve 54 and pump chamber 52 is fu of liquid as piston 72 begins its upward pump stroke and since ve valve 54 opens to allow further venting of gas to the surface as pist

72 begins its downward stroke, no pressurized gas can be trapped with chamber 52 to prevent a free flow of well fluid into chamber 52 fr formation 14 as may occur in conventional downhole pumps, such adverse condition being known as vapor-lock. Therefore it is cle that the present invention is not subject to vapor-lock which wi allow pump strokes with pump chambers only partially filled with liqu which causes: reduced efficiency per stroke; reduced production rat of well fluids; waste of energy due to recompression of gas trapped the pump chamber.

It is also clear that the present invention initiates a pump stro only when the formation production rate has caused the pump chamber be filled with liquid which prevents adverse effects that may occur i conventional bottom hole pumps such as the waste of energy due to pu strokes on partially filled pump chambers and extreme wear of pu parts due to the lack of produced liquid to carry off the heat of fric tion between the pump parts.

It is also clear that the system and method of operation of the presen invention maintains the power fluid for operation of the bottom hol pump separate from produced well fluids so as to prevent contaminatio of the power fluid and the need to replace it, which in turn allows fo optimum selection of power fluid regardless of well fluids produced.

It is also clear that the present invention automatically adjusts t changing well production rates and without the need for expensive tim consuming well tests and calculations as in required by conventiona

systems and methods.

Installation and operation of the preferred construction for the pum of the present invention as depicted in Fugure 3 may be as follows Casing 126 and screen 132 may be set in a conventional manner afte which, casing 124 may be run inside of casing 126 to a depth near th producing formation such that shoulder 134 is properly positioned t later receive the downhole pump. Casing 124 may be suspended an sealed in a conventional well head assembly so as to provide flow pas sages as schematically shown in Figures 1 and 2. Before lowering th downhole pump into casing 124, enlarged bore 312, passage 317 and portion of chamber 176 above bladder 303 is filled with a suitable oi or other operating fluid compatable with all parts contacted. Chambe 176 below bladder 303 is then filled with a gas at a suitable pressur for given well conditions so as to provide a spring action as previ ously described. Annulus 128 below annular piston 201 and passage 31 may be similarly filled. The downhole pump, substantially containe within tubular member 253, may then be attached to the lower end o tubing 122 by any suitable means and lowered into casing 124 in a con ventional manner to the depth that shoulder 136 of tubular member 25 lands on shoulder 134 of casing 124 so as to support the weight an fluid forces acting thereon and so as to activate seals 137 and 138 an thereby seal annulus 128 from annulus 130. Tubing 122 may then be sus pended from and sealed with a conventional well head so as to provid flow passages and system components as schematically depicted i Figures 1 and 2.

Tank 64 and annulus 128 above annular piston 201 may then be fille with suitable power fluid (F) for pumping action as previousl described. Beginning with piston 172 in the lowermost position a depicted in Figure 3, well fluid comprising both liquid and gas ma flow through conduits as at 112 over the top of piston 172 and int pump chamber 152. While liquid is not present in chamber 152 at th level of float 155, vent valve 154 remains open and vents formation ga into annular chamber 252, through check valve 244 and up annulus 13 toward the surface. As chamber 152 becomes filled with liquid from th formation, formation gas having been vented through vent valve 154, th presence of liquid around float 155 provides sufficient bouancy so a

to close vent valve 154 and thereby prevent flow of liquid into th vent. The closing of vent valve 154 moves stem 158 which trigger generator-transmitter 156 to cause pressurization of power fluid (F) i annulus 128 as previously described. Power fluid (F) then flows fro annulus 128 up passage 316 to chamber 313 at sufficient pressure to ac against the lower surface of end wall 315 and thereby cause piston 17 to rise against the forces of well liquid above piston 172 and agains the fluid pressure within enlarged bore 312 acting against the lowe end wall of piston 172. Chamber 176 may be large with respect to th volume of enlarged bore 312 so as to provide a substantially constan spring force acting downwardly on piston 172, however, as piston 172 moves upwardly, fluid is forced from enlarged bore 312 down passage 317 and into chamber 176 so as to move bladder 303 downwardly and thereb further compress gas below the bladder which stores energy for later use to return piston 172 to its lowermost position. As the upper cylindrical surface of piston 172 contacts annular seal 188k back flow of liquid from chamber 152 to formation 140 is stopped which allows an increase of pressure for the liquid within chamber 152 which in turn causes check valve ball 150 to open and allow flow of liquid from cham- ber 152 into tubular member 251 and thence up tubing 122 toward the surface.

As piston 172 reaches the uppermost position, continued prepressuriza- tion of annulus 128 causes an increase in pressure above that required to raise piston 172 which in turn causes pressure switch 74 to relieve pressure within annulus 128 as previously described which in turn allows stored energy of compressed gas within chamber 176 to force operating fluid from chamber 176 up passage 317 and into enlarged bore 312 so as to act against the lower end wall of piston 172 so as to return piston 172 to its lowermost position. As piston 172 moves down¬ wardly, upper end wall 315 acts against operating fluid within chamber 313. to force it through passage 316 and into annulus 128 to then move up annulus 128 and cause annular piston 201 to rise to its uppermost position against the reduced pressure of power fluid (F). As piston 172 begins to decend, float 155 is no longer immersed in liquid and so loses the bouancy that effected closing of vent valve 154 such that the weight of vent valve causes it to open and return chamber 152 to the pressure of vent annulus 130. Simultaneously, liquid pressure above

J Z A OMFI

ball check 150 causes the ball to close and prevent back flow of th liquid into chamber 152 when piston 172 thus returns to its lowermos position, conduits as at 186 are once again open for another pump cycl to begin as the liquid production rate of the well may determine at constant or erratic rate of production.

Should it be necessary to remove the bottom hole pump from the well fo any reason, tubing 122 may be pressured internally from the surface t a pressure level required to act against the pressure defined withi the diameter of seal 245 so as to shear pins 247 and to cause shoulde 236 at the lower end of tubing 122 to move upwardly with respect t shoulder 241 such that fluid may flow between the interior of tubin 122 and annulus 128 which allows displacement of power fluid (F) fro annulus 128 to the surface simply by pumping a heavier liquid down tub ing 122, so as to recover the power fluid for future use before th seal at the bottom of casing 124 is broken, causing contamination b inflow of well fluids into annulus 128. Tubing 122 may then be pulle from the well in a conventional manner which in turn, lifts the down hole pump from its mounting on shoulder 134, to the surface.

Should it be required to increase the amount of operating fluid 30 within chamber 176, said conventional selective controls may be operat ed to shift valve 62 into the position as depicted in Figure 2 so as t allow fluid from pressure source (P) to flow down the power conduit t the pump as depicted in Figures 3 and 4. Pressure source (P) may the be caused to furnish pressurized fluid to the pump at pressures suffi ciently above normal operating pressure so as to cause valve 400 t open and thereby admit fluid from passage 128 to enter the upper por tion of chamber 176, above bladder 303. As pressure of fluid 305 rise to desired level by further compressing gas 176, valve 400 closes an fluid flow stops. The conventional selective controls may then b deactivated and thereby return the system to automatic operation.

To operate in accord with the power fluid utilization method, the pum power chambers 313 and 316 may be filled with a suitable oil 254 afte assembly of the pump and retained by any suitable seal until installa tion in a well, whereupon any number of successive joints of tubing ma be added to the power conduit as the pump is being lowered in the wel

in the conventional manner. After such joints of tubing are adde they may be filled with high density oil until a sufficient predete mined amount of oil is added for that installation. As the remaini joints are added to the power conduit the power conduit may then filled with water which remains above the hydraulic oil due to the di ference in specific weights. After the downhole pump is lowered to t desired depth, the power conduit and other necessary conduits are co nected with their respective units at the surface in a convention manner.

The power conduit, being connected at the surface as depicted Figure 1 and 2 may now be pressurized by pressure source (P) whi pressurizes the water in the power conduit which in turn pressuriz the hydraulic oil in the lower portion of the power conduit so as operate the downhole pump as before described.

It is thus made clear that a compact and efficient pump construction i provided by the present invention as is necessary to operate in accor with the method of and in cooperation with the system of the presen invention so as to gain all of the advantages and objectives thereof.

Other embodiments, advantages and uses of the present invention wil become evident to those skilled in the art upon study of this teachin and upon review of the drawings attached hereto.