US2726605A - Gas lift for wells - Google Patents

Description

Dec. 13, 1955 W, F TEBBETTS 2,726,605

GAS LIFT FOR WELLS Filed NOV. l, 1952 W/LL/AM. TEETTs (Ittorneu United States Patent O GAS LIFT FOR WELLS William F. Tebbetts, Huntington Park, Calif.

Application November 1, 1952, Serial No. 318,156

9 Claims. (Cl. 103-46) This invention relates to a gas lift for material in the bottom of a well and concerns itself more particularly with a gas-driven pump for oil wells where there is a low bottom-hole llowing pressure.

The pumps now in use that use gas to obtain production from wells that have low bottom-hole owing pressure, in order to be efficient, require that there be a substantial head of liquid in the well. Then, by forcing down said head by pressure gas in one tube until said gas can escape from the bottom of said tube into a second concentric tube, said gas moves upward in said second tube, carrying with it production fluid. In general, in such devices, the greater the head pressure the greater will be the amount of liquid that can be lifted. Therefore, when there is low submersion present, there cannot be sufficient gas pressure applied to the bottom of the concentric tubes to lift production to the top of the Well. Frequently, the gas escapes into the well itself and creates a back pressure in the well formation that inhibits the liquid ow into the well from the surrounding formation.

It is, therefore, an object of this invention to provide a novel and improved gas-driven pump that will efficiently produce ow in a well that has low bottom-hole flowing pressure and is independent in its operation of the degree of pressure in the well and also independent of the amount of submersion in the well Huid.

Another object of the invention is to provide a gasdriven pump of the character indicated in which the production flow is unrestricted in that the same does not pass through control valves..

A further object of the invention is to provide a gasdriven pump that alternately and automatically reverses its stroke.

A further object of the invention is to provide a gasdriven pump having operating pistons that are loosely fitted to, thereby, reduce friction and lower the cost of manufacture. l

A still further object of the invention isto provide a pump as indicated that embodies a reciprocating differential piston and includes novel means controlled by the movement of said piston to reverse said movement.

The invention also has for its objects to provide such means that are positive in operation, convenient in use, easily installed in a working position and easily disconnected therefrom, economical of manufacture, relatively simple, and of general superiority and serviceability.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. However, the drawing merely shows and the following description merely describes one embodiment of the present invention, which is given by way of illustration or example only.

In the drawing, like reference characters designate similar parts inthe several views.

Figs. l and 2 are similar longitudinal sectional views of a gas-driven pump according to the invention shown, respectively, at the top and'bottom stroke positions.

` ice The present pump 5 is positioned within a well casing or eduction tube, there being a packing or seal 7 between said pump andtube preferably near the upper end 'of the former. Power tubing 8 supports the pump from above and is employed as a conduit to supply gas under pressure to the pump.

The pump 5 is provided with a head 9 that is connected to the lower end of power tubing 10, a chamber 11 in said head receiving gas from the passage 8 of said power tubing.

An outer tubular casing 12 extends from head 9 and terminates, at its lower end,'in a'housing 13 that is provided with a foot check valve 14 permitting flow of well liuid from the area 15 within the well casing and below packing 7 into chamber 16 of housing 13 and checking against reverse flow. The upper end of chamber 16 is closed by a transverse wall 17 and, adjacent said Wall,

chamber 23 that extends between said Wall and head 9.

Ports 24 in tubular extension 19 communicate chamber 23 and annular space 20. v

A second shorter downwardly directed tubular extension 25, within and concentric with extension 19, terminates substantially above wall 22. A transverse wall 26 within extension 25 divides the interior thereof into a lower bottom-open chamber 27 that is in communication with an annular space 28 between extensions 19 and 25, and an upper chamber 29, the top of which is dened by a bottom transverse wall 30 n head 9. Ports 31 communicate chamber 29 and annular space 28. Acentral port 32 is provided in wall 30 to communicate chambers 11 and 29. A set of ports 33, of which one is shown, communicates annular space 28 with eduction space 34 of the well casing, said space being above packing 7 and extending to the top of the well.

A differential piston unit 35 is disposed on the longi# tudinal center of the pump and has its stem 36 in `sliding engagement in aligned holes provided therefor in walls 17, 22 and 26. A piston 37 is provided at the lower end of stem 36 and is arranged to operate in housing 13 between foot valve 14 and ports 18. Said piston is designed to seal against the inner face of said housing.

Pistons 38 and 39 on stem 36 are disposed to loosely t and operate in chambers 21 and 23, respectively, the loose t enabling bleeding flow between the peripheries of said pistons and the inner face of tubular extension 19.

Pistons 40 and 41 on stem 36, both smaller in area than pistons 39 and 40,y are disposed to loosely tit and operate in chambers 27 and 29, respectively, the loose tit enabling bleeding flow between the peripheries of said latter pistons and the inner face of tubular extension 25.

A longitudinal passage 42 extends from a bottom port 43 in piston unit 35 to a port 44 above piston 39, said passage 42, thereby communicating chamber 16 with annular space 28 and, through ports 33, with eduction space 34.

.A second longitudinal passage 45 extends from the upper end of piston unit 35 to a port 46 immediately above piston 38 and is provided with ports 47 immediately above piston 40, said passage 45, thereby, communicating chamber 21, above piston 38, and chamber 27, above piston 40, with chamber 29 and through port 32, with chamber 11 and power tubing 8.

Head 9, in line with and above port 32, is provided with a port 48 that is controlled by an upwardly-opening 3 check valve 49. yA passage 50 connects chamber 51, above .said valve, .with .annular .space .20. A .plug `61 closes chamber 51.

A double-acting valve 52 alternately controls ports 321and 48 and is=carried by a Vstem '53 slidingly supported by Apiston unit"35,1as 'by a `spider 554. AA compression spring 55, -around stem S3, extends --between said spider and 1a `collar 56 above said spider, anda sim'ilar'spring 57 extends Ibetween saidrspider and acollar 58 on Ithe lower end of stern 53.

`l-`o allow Jcheck -valve -49 to close against pressure that 'may be trapped in Aport 48, 'a relief passage 59 is provided lbetweensaid :port `and annular space 28.

.Operation The upstroke and downstroke of "the piston unit are dependent on :the .position of .valve .52. Assuming that the pressurefof gasfrom power tubing is holding said valve up Ito fclose :port 48, said :pressure gas `will pass through portZ to `act on theupper face Vof pistons 41, 40 and `38. The .total .inlet :pressure on said pistons is resisted by whatever `exhaust pressure there is present in the llower portions of chambers 29 and 27 and in chambers 23 and V21 below the respective vpistons 39 and `3:8. Since thesechambers are all open to annular space zrthroughports 31 and `24'and the clearance annularsspace .around piston 39, the ltotal inlet pressure is substantially greater than Athe total exhaust pressure and `the :piston `unit 35 will move .down and displace upwardly in :passage 42 Aany uid trapped in chamber ll'by lfoot valve 14.

During the initial part of this downward movement, spring 57 remains uncompressed so `that gas pressure retains valve in Aits-original up position. As the downward movement continues, spider 54 gradually compresses spring 57 until `the compressive force of the spring `becomes vgreater than lthe total gas pressure on valve 52'. Said valvewill then snap down, because of the stored Aenergy of spring 57, and instantly close port 32-and `open port 48.

During application of inlet pressure to pistons 41, and 38, their lloose tit results in some of this pressure-:escapinglinto annular :space 28 .and combining with the exhaust pressure to enhance lthe lift of -uid displaced from chamber 16.

At the instant that port 32 Ais closed by valve 52, the initial inlet pressure on pistons 41, 40 and 38 begins to-dissipate by bleeding around the peripheries of said pistons. At -this time, gas under pressure unseats check valve 49, as seen in Fig. 2, and gas .pressure is applied to #the under faces-ofpstons 39 vand 38. The gas pressure on pistons 39 and 38 'easily forces the piston unit up against anyrdiminishing residual pressure in the upper parts of chambers 29, 27 and 21. The upper face of piston 39, lbeing directly open to Vannular Yspace 28, has exhaustpressure thereon. As said unit moves up, foot -valve ll4is1unseated by pressure in area 15 and iluid in said area willlilow past `va'lve -14 intochamber 16.

During the initial 'portion -of said `upward movement ofithe 1piston`unit, .spring 55 remains uncompressed and 'gas pressure'from Yabove holds valve 52 in position to Vmaintain port 32 closed. As theupward movement continues,'spring`55 is `'graduallycompressed until Vthe stored force -therein :overcomes the gas pressure on valve 52 and snaps said lvalve to the positionvof Fig. l wherein the same instantly and simultaneously yopens port 32 and closes port 4S. The pump is now in the initial assumed position from which the cycle of operation continuesfas above described.

ltwill 'beclear that fluid from area 15 `below packing `7 "is :intermittently displaced upwardly into reduction area :34 'above 'said 'packing by the means and `in the manner herein set k"forth It is also clear'that'ball check 49 and plug 61 can'be 'dispensed with, as might be advisable .under certain conditions of high productivity and high differential be- .tween.the.operating.and.exhaust.pressures. .1n.such.case, it is clear that the sum of active motive piston areas causing the downstroke must be greater than opposing motive piston areas. The pressure gas will be in contact with the lower faces of pistons 39 and 38 con tinuously, and the control valve 52 will be held in its up position during the downstroke by spring 55. During the upstroke, spring will gradually be compressed until it throws Vvalve 52 to the yup position as aforementioned.

The present disclosure has a tandem arrangement of smaller and larger differential vpistons and the lsame, without enlarging the dametral sizeof the pump, increases the motive area and can be operated by a lower unit gas pressure. It will be clear that pistons 40 and 39 may be omitted, providing the same are made proportionally larger for the same gas pressure used.

During the lowering of the pump into the well, well liquid may find its way into the device and also -into the lower portion of the `power tubing. 1n suchcase, the device will simply function as an hydraulicallyoper ated mechanism until such liquid is displaced into the eductor tube.

-In gas lifts, generally, itiisrconventional to use a series of kick-off valves, carried by the power tubing and opening -into the eductor tube. While not shown, such valves may be used for the two fold purpose 4oli regulating, to the most eiicient quantity, the amount of gas used 4in lifting the `well liquid and to start the'lift after a -shut-down. These kick-off valves operate automatically and successively from the top down.

In operation, the speed of reciprocation of thepiston unit 35 and, therefore, of the production capacity olf the pump, is a vfunction of the amount of pressureof the gas supplied. The mechanical factors, -such as `the bleeding yor relief clearances and -spring action, have a relatively unimportant function in the operation.

The usual travelling valve .isprovided in the lower end -of piston unit 35 to check against return of liquid displaceddnto passage V42.

-Whilethe invention that has been illustrated and described is now regarded as the preferred embodiment, the construction is, of course, subject to modification without-departing from the spirit and scope of the invention. IIt is, therefore, not desired to restrict the invention yto =the particular form of construction illustrated and described, but to cover all modifications `that may fall within the scopeof the appendedclaims.

Having thus described theinvention, what `Iclaimand desire to secure by Letters Patent is:

`1. yAfgas'lift comprising a housing having a foot 'valve and located within a well casing, power tubing connected to the upper end of the housing to conduct pressure gas into said housing, a diterentialpiston untslidingly mountedwithin the housing and provided with at least two -pistons one above the other 'and the lower'piston being larger than the upper piston, a control valve carried by the 'piston -unit to control -tiow of pressure Vgas from vthe power tubing to the upper face ofthe upper piston and to `the lower face of the lower piston, selec tively, a lost-motion connection between said control valve and fthe piston unit operated by the piston 'unit at the `endsof the up and down strokes of the'piston unit as imparted by thepressure `gas 'to control the mentioned gas -flow, and a displacement pump including a travellingvalve carried 'by the piston unit and operative to displace tluid moving past the foot valve upwardly within the well casing.

2. A gas lift according to .claim l: concentric .tubes vrespectively .housing the .two .diierential pistons, ,there being a gas-bleed between the .upper piston `and said respective .concentric tubes.

3. A gas lift according to claim 2: the lost-motion connection including compressible means .tostore energy at 'the ends of the stroke of the piston unit to move the control valve from one position to the other against the pressure thereon of the pressure gas.

4. A gas lift comprising a housing having a foot valve and located within a well casing, power tubing connected to conduct pressure gas into said housing, a differential piston unit slidingly mounted in the housing and comprising two small and two larger differential pistons and the small pistons both being above the larger pistons, a two-position control valve to control flow of pressure gas from the power tubing to said differential piston unit, passages within said unit to conduct pressure gas, when said control valve is in one position, to the upper faces of both small pistons and of the lowermost larger piston and to conduct pressure gas, when the control valve is in the other position, to the under faces of both larger pistons, a lost-motion connection between said control valve and the piston unit to control flow of the pressure gas in said passages at the ends of the up and down strokes of the piston unit as imparted by the pressure of gas on the pistons thereof, and a displacement pump including a travelling valve on the piston unit and operative to displace uid moving past the foot valve upwardly within the well casing.

5. A gas lift according to claim 4: two concentric tubes respectively housing the smaller and larger differential pistons, there being a loose gas-bleeding fit between the peripheries of said pistons and said respective concentric tubes.

6. A gas-driven pump comprising power tubing to conduct pressure gas, an eduction tube, a head having an interior chamber receptive of said gas, a tubular housing extending downwardly from said head, a bottomopen tube concentric within said housing and provided with a transverse wall dividing said latter tube into upper and lower chambers, a second and shorter bottom-open tube concentric within the first bottom-open tube and provided with a transverse wall dividing said second bottom-open tube into upper and lower chambers, `said housing and two concentric tubes being spaced to provide annular spaces therebetween, said pump being adapted to be positioned within a well casing, ports interconnecting said aforementioned chambers and said annular spaces and a port connecting the latter with said eduction tube, a piston unit having pressure pistons in the mentioned upper and lower chambers of the two concentric tubes, there being a pressure bleed from one side to the other side of said pistons, a displacement pump ou the lower end of the pump housing and cornprising a pump piston on said piston unit, a housing in which said latter piston operates, and a foot check valve controlling flow of material in the lower part of the well casing into the latter housing, a passage in said piston unit communicating said latter housing with said interconnected chambers, concentric spaces and ports, a valve controlling gas ow from the interior chamber of the head selectively to the top and bottom faces of the pressure pistons, and a lost-motion connection be- `tween said piston unit and said control valve to move the latter against the pressure in said interior chamber at the ends of the stroke of the piston unit.

7. A gas-driven pump comprising power tubing to conduct pressure gas, an eduction tube, a head having an interior chamber receptive of said gas, a tubular housing extending downwardly from said head, a bottom-open tube concentricwithin said housing and provided with a transverse wall dividing said latter tube into upper and lower chambers, a second and shorter bottom-open tube concentric within the rst bottom-open tube and provided with a transverse wall dividing said second bottom-open tube into upper and lower chambers, said housing and two concentric tubes being spaced to provide annular spaces therebetween, said pump being adapted to be positioned within a well casing, ports interconnecting said aforementioned chambers and said annular spaces and a port connecting the latter with said eduction tube, a piston unit having pressure pistons loosely fitted in the mentioned upper and lower chambers of the two concentric tubes, a displacement pump on the lower end of the pump housing and comprising a pump piston on said piston unit, a housing in which said latter piston operates, and a foot check valve controlling flow of material in the lower part of the well casing into the latter housing, a passage in said piston unit communicating said latter housing with said interconnected chambers, a travelling check valve controlling flow in said passage and concentric spaces and ports, a passage and ports in the piston unit extending from the upper end thereof to communicate the upper chamber of the innermost tube with the lower chamber of said tube and the lower chamber of the larger tube, a Valve controlling gas flow from the interior chamber of the head to said upper chamber of the innermost tube and, thereby, to the upper faces of the pressure pistons in said innermost tube and the lower pressure piston in the larger tube and, selectively, to the under faces of the pressure pistons in said larger tube, and a 10st-motion connection between said piston unit and said control valve to move the latter against the pressure in said interior chamber at the ends of the stroke of the piston unit.

8. A gasdriven pump according to claim 7: said lostmotion connection including compressible means to store energy at the ends of the stroke of the piston unit to quickly move the control valve from one position to the k other.

9. A gas-driven pump according to claim 7: said lostmotion connection including compressible means to store energy at the ends of the stroke of the piston unit to quickly move the control valve from one position to the other, and a check valve opening to gas ow to the under faces of the pressure pistons in the larger tube and closing to pressure in said chambers, annular passages, and connecting ports.

References Cited in the file of this patent UNITED STATES PATENTS 1,885,820 Gothard et al Nov. l, 1932 2,220,334 Holmberg Nov. 5, 1940 2,245,501 Richardson June 10, 1941 2,342,855 Green Feb. 29, 1944

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