`AND
`BAKER HUGHES OILFIELD
`OPERATIONS, INC.
`BAKER HUGHES INCORPORATED
`Exhibit 1016
`Exhibit 1015
`Page 1 of 8
`
`
`
`I|||||||||||l||||||||||||||||||||||||||||||||||||||l||||||||||||||||l||||||
`
`USO(}594?2U4A
`
`United States Patent
`Barton
`
`[191
`
`[11] Patent Number:
`
`5,947,204
`
`[451 Date of Patent:
`
`Sep. 7, 1999
`
`I54]
`
`PRODUCTION FLUID CONTROL DEVICE
`AND METHOD FOR OILANIJIOR GAS
`WELLS
`
`[75]
`
`Inventor:
`
`John Andrew Barton, Arlington, Tex.
`
`[73]
`
`Assignee: Dresser Industries, 11113., Dallas, Tex.
`
`4,fi91,7'.-‘S W108? Lustig et at. .
`1tt6."3i':' X
`4.718.488
`131988 Pringle et al.
`.... .. 1b()r'3l7
`4_.'.-‘Z4308
`2.31988 Pringle
`
`4,834,l7"fi
`531989 Renfroe ............................. ..
`It’if)t’3i? X
`5_.l3?,(l88
`8.t'l9‘_}2 Farley at at}.
`.
`5.205.361
`‘H1993 Farley et at. _
`5,27-'l.465
`l2.t'l‘)‘)3- Schntidt ct al. .
`5_.."t1l,(il?
`M906 Snider el al.
`
`Iti61*3t't‘ X
`
`I31]
`
`Appl. No.: 09,I'[|93,744
`
`[22
`
`Filecl:
`
`Jun. 8, 1998
`
`[60]
`
`I51]
`[53]
`
`I53!
`
`l56l
`
`Related U.S. Application Data
`Provisional application No. 1jU.:tt6tt,o0t, Sep. 23, 1997.
`
`Int. Cl.“ .................................................... .. ICZIB 34fl0
`U.S. Cl.
`........................ ..
`l66,t'3'l7; 166E319; 166E324;
`166K374; [6631 I
`Field of Search ................................... ..
`l66f3]7, 319.
`M63324, 325, 374, 31 1, 321
`
`References Cited
`
`U.S. PAl"l_-".N'l' DOC UMIENTS
`
`3,831,£i8tt
`4_.o5<;_. 15?
`4.231.715
`4.658.902
`
`BflI)'.t‘4 Edwards et at. .
`ttIt9T.F Crows.
`811981 Farley ................................... .. 1663317
`«H108? Wesson at al. .
`
`Pr1‘ntr1.r_y IExrmtr'ner—Roger Schoeppel
`A.-‘rorrtey, /igem, or Ft't‘m—l~layItes and Boone, LLP
`
`[57]
`
`ABSTRACT
`
`A device and method for selectively controlling the flow of
`production fluid through a tubing string in an oil and gas
`well according to which 3 housing is connected to a tubing
`string for insertion into the well, and well
`lluid is passed
`from the ground surface into the housing. The housing is
`provided with :1 plug to establislt well fluid pressure in the
`housing to actuate a packer andfor other ancillary devices.
`The plug can be removed from the hosing by increasing the
`pressure of the well fluid in the housing above a predeter-
`mined value, thus permitting the How of production lluid
`from the formation zone, through the housing and the tubing
`string, and to the ground surface.
`
`11 Claims, 3 Drawing Sheets
`
`BAKER HUGHES INCORPORATED
`Exhibit 1015
`Page 1 of 8
`Page 1 of 8
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`Sep. 7, 1999
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`5,947,204
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`5 ,947,204
`
`1
`PRODUCTION FLUID CONTROL DEVICE
`AND METHOD F()R OILANIJIOR GAS
`Wl1lI.I.S
`
`CROSS-REFERENCE TO RELATED
`APl"LlCA'.l‘ION
`
`'lhis application is based on provisional application Ser.
`No. 6Uf060,69l filed Sep. 23, 1997.
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to a fluid control device for
`use in an oil andfor gas well and, more particularly, to such
`a device for selectively controlling the flow of production
`fluid from a producing formation adjacent the well, through
`the well, and to the ground surface.
`In a typical oil and gas production well, a casing is
`provided to line the well and is provided with perforations
`adjacent
`the formation to receive the production fluid. A
`tubing string is run into the casing and has an outer diameter
`less than that of the inner wall of the casing to form an
`annulus. A packer is placed in the annulus.
`to direct
`the
`production fluid into the lower end of the tubing string for
`passage upwardly through the tubing string for recovery
`above ground.
`to
`It
`is often advantageous, and sometimes necessary,
`utilize hydraulically-actuated packers and other ancillary
`devices, especially when operating in deviated or horizontal
`well sections. To this end, the flow of production fluid into
`and through the tubing string is blocked, and well fluid is
`introduced into the tubing string fron1 the ground surface, to
`create a
`relatively high fluid pressure which is used to
`actuate these devices. After this operation is completed the
`tubing string must be opened to permit the flow pf produc-
`tion fluid through the string and to the ground surface.
`'l‘heret‘ore, pu mp-out plugs, or the like, are often provided in
`the tubing string which normally block fluid flow through
`the string and which are ejected from the string when the
`flow of production fluid is desired. However, these plugs are
`relatively large and, when ejected, must either be removed
`from the wellbore by coiled tubing or the like, which is very
`expensive, or left in the wellbore, which may cause prob-
`lems during the life of the well.
`Also, disc subs have been used which incorporate a disc
`that normally blocks fluid flow through the tubing string and
`which breaks in response to fluid pressure acting thereon
`when flow is desired. However, these disc subs suffer from
`the fact that the pressure that has to be applied to break the
`disc is often excessive and unpredictable. Therefore, other
`techniques have been devised to break the discs to permit
`fluid flow. For example, steel bars have been used which are
`dropped into the well or run on wirelinc or coiled tubing.
`This has disadvantages since the broken disc forms debris in
`the wellbore and, if the well has a deviated or horizontal
`section, a drop bar or wirelinc run is very unreliable.
`Still other techniques for selectively blocking the flow of
`production fluid through the tubing string involve wireline
`settrelrieved tubing plugs. However, these devices require a
`"proiile” sub that has to be added to the tubing string and
`require the use ofwireline intervention, as well as increased
`risk and expense.
`Therefore, what is needed is a relatively inexpensive and
`reliable device for selectively controlling the flow of pro-
`duction fluid through a tubing string in an oil andfor gas well
`which minimizes the amount of debris left in the wellbore
`
`yet which can be activated with a predictable and relatively
`
`ll)
`
`15
`
`'
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`60
`
`65
`
`2
`low amount of fluid pressure. Also what is needed is a device
`of the above type which does not require a profile sub or any
`actuation device to be dropped into the tubing string or run
`into the string on wireline or coiled tubing.
`
`SUMMARY OF THE INVENTION
`
`The present invention, accordingly, is directed to a device
`for selectively controlling the flow of production fluid
`through a tubing string in an oil and gas well according to
`which one end of a housing is connected to a tubing string
`for insertion into the well, and well fluid is passed from the
`ground surface the one end of the housing. The other end of
`the housing is closed to establish well fluid pressure in the
`housing to actuate a packer andfor other ancillary devices.
`The other end of the housing can be opened by increasing
`the pressure of the well
`fluid in the housing above a
`predetermined value, thus permitting the flow of production
`fluid from the formation, through the housing and the tubing
`string, and to the ground surface.
`Several advantages result from the device and method of
`the present
`invention. For example,
`they are relatively
`inexpensive and reliable, yet minimize the amount of debris
`left in the wellbore. Also, the device can be activated with
`a predictable and relatively low amount of fluid pressure,
`and does not require a profile sub or any actuation device
`that must be dropped into the tubing string or run into the
`string on wireline or coiled tubing.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a partial elevation-partial sectional view depict-
`ing an installation in an oil andfor gas well including the
`device of the present invention.
`FIGS. 2 and 3 are vertical sectional views of the device of
`the present invention depicting two operational modes of the
`device.
`FIGS. 4 and 5 are views identical to those of FIGS. 2 and
`3, respectively, but depicting an alternate embodiment of the
`device of the present invention.
`DESCRIPTION OF TIIE PREFERRED
`EMBODIMENT
`
`The well fluid control device of the present invention is
`designed to be used downhole in an oil andior gas wall
`depicted in FIG. 1. The reference numeral 10 refers,
`in
`general to a well casing that lines the well bore and receives
`a tubing string 12 having an outer diameter that is less than
`the casing to define an annulus 14 between the tubing string
`and the casing. The tubing string 12 can be lowered into the
`casing II] from the ground surface in any conventional
`manner such as by using a wireline, coiled tubing, or the
`like. A packer 16 is disposed in the annulus 14 and extends
`around a lower portion of the tubing string 12, as viewed in
`FIG. 1. 'I'l'1e packer 16 is preferably hydraulically actuated
`and since it is conventional, it will not be described in detail.
`A plurality of perforations 10.0‘ are formed through the
`casing 10 below the end of the tubing string 12. The
`perforations 10:1 permit production fluid from a formation
`Zone F to flow into the casing 10 and through the tubing
`string to the ground surface, in a manner to be described.
`The control device of the present invention is referred to,
`in general, by the reference numeral 20, and is attached to
`the lower end portion of the tubing string 12. The control
`device 2|] is adapted to selectively control the flow of the
`production [luid through the tubing string 12 and to the
`ground surface, and to permit well fluid from the ground
`
`Page 5 of 8
`Page 5 of 8
`
`
`
`5 ,947,2l]4
`
`3
`surface to be introduced into the tubing string 12 and
`pressurized sulficiently to actuate the packer. and any ancil-
`lary devices.
`the control
`To this end. and with reference to FIG. 2,
`device 20 comprises a sub 22 which is internally threaded at
`its upper end portion 225', as viewed in FIG. 2, to mate with
`a corresponding externally threaded lower end portion of the
`tubing string 12 (FIG. 1). The control device 20 also
`includes a tubular housing 24 having an internally threaded
`upper end portion 240 that threadedly engages :1 correspond-
`ing externally threaded lower end portion 22!: of the sub 22.
`A plurality of set screws 26, one of which is shown in FIG.
`2, are angularly spaced around the circumference of the
`upper end portion 244: of the housing 24 and extend through
`aiigned opening in the latter end portion and the lower end
`portion 22b of the sub 22, to secure the sub to the housing.
`A seal ring 28 extends between an outer surface portion of
`the sub 22 and a corresponding inner surface portion of the
`housing 24.
`A lower sub 30 is also provided which has an internally
`threaded upper end 3|lrr portion that threadedly engages a
`corresponding externally threaded lower end portion 24b of
`the housing 34. A plurality of set screws 32, one of which is
`shown in FIG. 2. are angularly spaced around the circum-
`ference of the upper end portion 30:? of the lower sub 30 and
`extend through aligned opening in the latter end portion and
`the lower end portion 24b of the housing 24, to secure the
`connection between the sub and the housing. Aseal ring 34
`extends between and outer surface portion of the housing 24
`and a corresponding inner surface portion ofthe sub 30. The
`lower end portion of the lower sub 30 is externally threaded
`so as to enable internally threaded subs of ancillary equip-
`ment (not shown) to be attached to the device 20 as needed.
`A tubular piston 40 is slidably mounted in the housing 24
`and its outer surface is stepped to define an upper end
`portion 40rr, an intermediate portion 4% extending just
`below the upper end portion, and a portion 400 that extends
`from the intermediate portion 40b to the lower end of the
`piston. The outer diameter of the intermediate portion 40b is
`greater than the diameter of the portions 400 and 40c, and a
`pair of axially spaced seal rings 42:1 and 42b extend between
`the outer surface pfitrtiorl of the intermediate portion 40b and
`corresponding inner surface portions of the housing 24. The
`lower end of the piston 40 tapers to a relative sharp point for
`reasons to be described.
`
`ill
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`A ring 46 is disposed in a space delined between the outer
`surface of the upper end portion 400' of the piston 40 and the
`corresponding inner surface of the housing 24. The ring 46
`receives a plurality of angularly-spaced shear pins 48 that
`extend through aligned openings in the ring 44 and the upper
`end portion ofthe piston 40. The shear pins 48 thus normally
`retain the piston 40 in its upper position shown in FIG. 2, but
`are adapted to shear in response to a predetermined shear
`force applied thereto to release the piston and permit slidahle _
`movement of the piston downwardly in the housing 24, as
`will be explained. A plurality of angularly-spaced openings
`400'. one of which is shown in the drawings, extend through
`the upper end portion 406: of the piston 40 just below the
`openings that receive the shear pins 48, for reasons that will
`also be explained.
`The inner surface of the housing 24 is stepped so that the
`inner diameter of its lower portion is less than that of its
`upper portion to define an annular chamber 50 between the
`inner surface of the upper portion of the housing 24 and a
`corresponding outer surface of the piston 40. The relatively
`large-diameter intermediate portion 40b of the piston 40
`
`60
`
`65
`
`4
`delines the upper boundary of the chamber 5|], and the
`reduced-diameter portion of the housing 24 delines its lower
`boundary. The chamber 50 accommodates movement of the
`intermediate portion 40b of the piston 40 during iLs down-
`ward movement. Ascal ring 52 extends between an outer
`surface portion of the piston portion 400 and a correspond-
`ing inner surface portion of the reduced-diameter portion of
`the housing 24-. Thus, the chamber 50 extends between the
`seal rings 42b and 52 to isolate the chamber from fluids and
`to maintain the pressure in the chamber at atmospheric
`pressure for reasons to be described.
`The lower sub 30 has a stepped inner surface that defines
`a shoulder that receives a frangible disc 56, and a seal being
`58 extends between the shoulder and the disc. The disc 56
`is made of frangible material, such as glass that is adapted
`to shatter when impacted by the pointed lower end of the
`piston 40 with sufficient force. The end of the housing 24
`abuts the disc 56, and a seal ring 60 is disposed between the
`latter end and the disc. A seal ring 62 extends between the
`outer surface of the disc 56 and the corresponding inner
`surface of the sub 30. The disc 56 is capable ofwithstanrling
`relatively large differential pressures acting on its respective
`upper and lower surfaces far in excess of the amount of force
`required to shears the pins 48 as will be described.
`in operation, a well fluid is introduced into the casing 10
`from the ground surface at a sullicient pressure to block the
`How of production fluid from the formation zone F (FIG. 1)
`through the perforations 10:1 and into the casing 10. When
`it is desired to recover the production fluid, the tubing string
`12 is run into the casing 10 with the device 20 attached to
`the lower end of the string, and with the packer 16 provided
`in a section of the string just above the device 20.
`The presence of the disc 56 in the lower end portion of the
`device 20 pen'nits well lluid from the ground surface to be
`introduced into the tubing string 12 at an increased pressure
`to establish a hydrostatic load to allow the packer 16, audio:
`any ancillary devices to be hydraulically set in a conven-
`tional manner. During this operation, the pressure of the well
`fluid in the device 20 acts on the upper end of the piston 40
`in a downwardly direction and on the lower end of the piston
`in an upwardly direction. Since the area of the annular upper
`end surface of the piston 40 is greater that the area of its
`annular lower end surface, a differential force is established
`which applies a shear force to the pins 48. However, the pins
`48 are designed to normally resist
`the force and thus
`maintain the piston in its upper, static position of FIG. 2.
`This increased fluid pressure in the device 20 is controlled
`so that the resultant differential pressure across the disc 56
`caused by the latter pressure acting on the upper surface of
`the disc 56, and the well fluid in the annulus 14 acting on the
`lower surface of the disc, does not exceed the design limit
`of the disc.
`
`When the packer 16, and any ancillary devices, have been
`set in accordance with the above and it is then desired to
`recover production fluid from the formation zone F.
`the
`pressure of the well fluid in the tubing string 12 is increased.
`Since the upper end surface of the piston 4-I] has a larger area
`than its lower end, the shear force applied to the pins 48 will
`be increased until the pins are sheared, with the openings
`40d increasing the volume of well fluid available to act on
`the upper surface of the piston 40. The piston 40 is thus
`forced downwardly and its pointed lower end strikes the disc
`56 with enough force to shatter it.
`It
`is noted that
`the
`relatively low atmospheric pressure existing in the chamber
`50 does not impede this downward movement of the piston
`40 and that the above increase in hydrostatic load is selected
`so that the disc 56 can withstand the resulting differential
`
`Page 6 of 8
`Page 6 of 8
`
`
`
`5 ,947,204
`
`5
`pressure acting on its upper and lower surfaces. The pressu re
`of the well lluid in the tubing string 12 is then reduced as
`necessary to allow the well fluid in the annulus, and then the
`production fluid from the formation none F, to flow through
`the device 20 and the tubing string 12 to the ground surface
`and be recovered.
`
`The device 20 thus enjoys several advantages. For
`example,
`it is relatively inexpensive and reliable, yet can
`withstand a great deal of difierential fluid pressure and be
`activated with a predictable and relatively low amount of
`fluid pressure. Also, the amount of debris left in the wellbore
`is minimized since the material used in the frangible disc 56
`is such that, one broken by the piston 40,
`it
`is reduced to
`small slivers or particles that can be flowed or circulated
`from the well. Further, the device 20 does not restrict the
`inner diameter of the well bore and thus allows other tools
`to pass through it and it does not require a profile sub or any
`actuation device that must be dropped into the tubing string
`or run into the string on wireline or coiled tubing.
`The embodiment of FIGS. 4 and 5 is similar to the
`embodiment of FIGS. 2 and 3 and identical components are
`given the same reference numerals. According to the
`embodiment of FIGS. 4 and 5, a device 20'
`is provided
`which is identical to the device 20 of the embodiment of
`FIGS. 2 and 3 with the exception that, in the former device,
`a plurality of angularly-spaced ports, one of which is shown
`by the reference numeral 24:: in FIGS. 4 and 5, are provided
`through the wall of the housing 24. The ports 24¢ are axially
`located relative to the housing 24 so that they register with
`the lower portion of the chamber 50 when the piston 40 is
`retained in its upper, static position by the shear pins 48 as
`shown in FIG. 4. Titus, the above—mentioned well fluid that
`is initially in the annulus 14 to maintain the production fluid
`in the formation zone 1-‘, as discussed above, will enter the
`chamber 50 through the ports 24c and exert an upwardly-
`directed pressure against the lower annular surface of the
`relative large diameter portion 40b of the piston 40.
`As in the previous embodiment, the upper surface of the
`piston 40 has a greater surface area than the lower surface
`due to the relatively large diameter portion 40!). Therefore,
`there is one downwardly-directed force caused by the well
`fluid in the interior of the housing 24 acting on the upper
`surface of the piston 40 as described above and an upwardly
`directed force caused by the well fluid in the interior of the
`housing acting on the lower surface of the piston, also as
`described above.
`In addition,
`there is an additional
`upwardly-directed force by the well fluid in the annulus 14
`acting on the lower annular surface of the relatively large
`diameter portion 40b of the piston. Also as in the previous
`embodiment, the shear pins 48 are designed to shear at a
`predetermined shear force applied thereto based on the
`difference of the abovc—mentioned forces acting on the
`piston 4-0. l-lowever, in this embodiment, the shear force can
`be much less than that of the embodiment of FIGS. 2 and 3
`due to the presence of the last-mentioned upwardly directed
`force. Otherwise the operation of the device 20' is identical
`to that of the device 20 of the embodiment of FIGS. 2 and
`3.
`
`ll)
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`The device 20' of the embodiment of FIGS. 2 and 5 thus
`enjoys all of the advantages of the device 20 of the embodi-
`ment of FIGS. 2 and 3 and, in addition, the amount of shear
`force required to shear the pins 48, and therefore actuate the
`piston 40 of the former device is mush less than that of the
`latter device.
`It
`is understood that variations can be made in the
`
`60
`
`65
`
`foregoing without departing from the scope of the invention.
`
`6
`For example, although the tubing string 12 and the devices
`20 and 20' are shown extending vertically, it is understood
`that this is only for the purpose ofexamplc and that, in actual
`use, they can extend at an angle to the vertical. Therefore,
`the use of the terms “upper”. “lower", “upwardly”,
`“downwardly", and the like, are only for the purpose of
`illustration only and do not limit the specific orientation and
`position of any of the components discussed above.
`It is understood that other modifications, changes and
`substitutions are intended in the foregoing disclosure and in
`some instances some features of the invention will be
`employed without a corresponding use of other features.
`Accordingly, it is appropriate that the appended claims be
`construed broadly and in a manner consistent with the scope
`of the invention.
`What is claimed is:
`l. A method for controlling the tlow of production fluid
`from a formation zone in an oil andfor gas well to the ground
`surface, the method comprising the steps of introducing a
`fluid into the well
`for normally preventing the flow of
`production fluid from the formation zone, inserting a tubing
`string including a packer and a housing into the well, passing
`well fluid from the ground surface into one end of the
`housing, closing the other end of the housing for creating a
`well fluid pressure in the housing to set the packer in the
`annulus between the tubing string and the wall of the well,
`increasing the pressure of the well
`fluid in the housing
`sufficient
`to open the other end of the housing and thus
`permit the flow of production fluid from the formation none
`through the housing and the tubing string and to the ground
`surface.
`2. The method of claim 1 comprising the steps of retaining
`a piston in the housing, the increased-pressure well fluid in
`the housing releasing the piston and sliding the piston in the
`housing against the plug for opening the housing.
`3. The method of claim 2 wherein a plug closes the other
`end of the housing and the piston fractures the plug.
`4. The method of claim 2 wherein the well fluid in the
`housing acts on the respective ends ofthe piston with a force
`corresponding to the respective areas. of the surfaces of the
`latter ends, wherein the area of the surface ofone of the ends
`of the piston is greater than the area of the surface of the
`other end of the piston to create a differential force, and
`wherein the piston slides in response to the differential force
`exceeding a predetermined value.
`5. The method of claim 4 wherein the housing and the
`piston extend substantially vertically, with the surface of the
`upper end of the piston having a greater area that the surface
`of the lower end of the piston so that
`the piston slides
`substantially downwardly in the housing.
`6. A device for controlling the flow of production fluid
`from a formation none in an oil andtor gas well to the ground
`surface, the device comprising:
`a housing adapted to be connected at one end to a tubing
`string for insertion into the well and forming an annulus
`between the outer surface of the housing and the inner
`surface of the well, the one end of the housing being
`open for receiving well lluid front the ground surface;
`a plug disposed in the other end of the housing for
`permitting the increase in pressure of the well tluid in
`the housing;
`a piston disposed in the housing;
`a plurality of shear pins connected to the piston for
`normally retaining the piston in the housing, the shear
`pins responding to the pressure of the well lluid in the
`housing exceeding a predetermined value for shearing
`
`Page 7 of 8
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`5 ,947,204
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`7
`to penrtit slidahle movement of the piston in the
`housing against the plug to remove the plug from the
`housing and open the other end ofthe housing to permit
`the [low of production fluid from the fonnation zone,
`through the housing and the tubing string and to the
`ground surface;
`a packer extending in the annulus, that portion of the
`annulus extending between the packer and the forma-
`tion zone containing well fluid under pressure to nor-
`mally maintain the production fluid in the formation
`zone; and
`a port defined in the wall of the housing to permit the latter
`well
`fluid to enter the housing and act against the
`piston.
`T. A method for controlling the flow of production fluid
`from a fonnation zone in an oil andior gas well to the ground
`surface, the method comprising the steps of:
`connecting one end of a housing to a tubing string for
`insertion in a vertical orientation into the well;
`passing well fluid from the ground surface into the one
`end of the housing;
`normally closing the other end of the housing for creating
`a well fluid pressure in the housing;
`retaining a piston in the housing so that the well fluid in
`the housing acts on the respective ends of the piston,
`the area of the surface of the upper end of the piston
`being greater than the area of the surface of the lower
`end of the piston so that the fluid acts on the respective
`ends of the piston to create a differential force;
`the piston sliding downwardly in the housing in response
`to the differential
`force exceeding a predetermined
`value to open the other end of the housing and thus
`permit the flow of production fluid from the formation
`zone through the housing and the tubing string and to
`the ground surface;
`forming an annulus between the outer surface of the
`housing and the inner surface of the well;
`setting a packer in the annulus;
`maintaining pressurized well fluid in that portion of the
`annulus extending between the packer and the forma-
`tion zone to normally maintain the production fluid in
`the formation zone; and
`permitting the latter well fluid to enter the housing and act
`against the piston to change the dilIerential force.
`
`8
`8. A device for controlling the how of production fluid
`from a formation zone in an oil andfor gas well to the ground
`surface, the device comprising:
`a housing adapted to be connected at one end to a tubing
`string for insertion into the well, the one end of the
`housing being open for receiving well fluid from the
`ground surface;
`a frangible plug extending in the housing and closing the
`other end of the housing being closed to permit the
`pressure of the well fluid in the housing to build up; and
`a piston normally retained in the housing and having a
`pointed end, the piston being responsive to the pressure
`of the well fluid in the housing exceeding a predeter-
`mined value for sliding in the housing towards the plug
`so that the pointed piston end fractures the frangible
`material ofthe plug to open the other end of the housing
`and permit
`the [low of production fluid from the
`formation zone,
`through the housing and the tubing
`string and to the ground surface.
`9. The device of claim 8 further comprising a plurality of
`shear pins connected to the piston for normally retaining the
`piston in the housing,
`the shear pins responding to the
`pressure of the well
`fluid in the housing exceeding the
`predetermined value for shearing to permit
`the slidable
`movement of the piston.
`10. A method for controlling the [low of production fluid
`from a formation zone in an oil andtor gas well to the ground
`surface, the method comprising the steps of:
`connecting one end of a housing to a tubing string for
`insertion into the well; passing well
`fluid from the
`ground surface into the one end of the housing; closing
`the other end of the housing with a frangible plug for
`creating a well fluid premure in the housing; and
`providing a piston having a sharp end in the housing and
`adapted to respond to the pressure of the well lluict in
`the housing exceeding a predeterrnined value and to
`slide in the housing until its sharp end fractures the plug
`to open the other end of the housing to permit the flow
`ofproduction fluid from the formation zonethrough the
`housing and the tubing string and to the ground surface.
`11. The method of claim 10 further comprising the step of
`retaining the piston in the housing by a plurality of shear
`pins, the shear pins responding to the pressure of the well
`fluid in the housing exceeding the predetermined value for
`shearing to permit the slidable movement of the piston.
`39¢
`*
`it
`It
`at
`
`5
`
`ll)
`
`15
`
`25
`
`3-0
`
`35
`
`40
`
`45
`
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