BAKER HUGHES INCORPORATED
`AND
`BAKER HUGHES OILFIELD
`BAKER HUGHES INCORPORATED
`OPERATIONS, INC.
`Exhibit 1016
`Exhibit 1017
`
`Page 1 of 6
`
`

`
`United States Patent
`Vann et al.
`
`[19]
`
`[1 1]
`[45]
`
`4,434,854
`* Mar. 6, 1984
`
`[54] PRESSURE ACTUATED VENT ASSEMBLY
`FOR SLANTED WELLBORES
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventors; Roy R. Vann; George W. Ribble;
`Flint R. George, all of Houston.
`Tex.
`
`166/3'.-'4
`3,662,834 5/ 1972 Young
`
`4,330,039 5/ I932 Venn et al. ........................ .. 166/29’?
`
`Primary Exam1'ner—Stephen J . Novosad
`
`['.-'3] Assignee: Geo Vann, Ine., Houston, Tex.
`
`[57]
`
`ABSTRACT
`
`[ * ] Notice:
`
`The portion of the term of this patent
`subsequent to May 18, 1999 has been
`disclaimed.
`
`[211 App]. No.: 373,155
`
`[22] Filed:
`
`May 14, 1982
`
`[63]
`
`Related US. Application Data
`Continuation of Ser. No. 166,547. Jul. 7, I980. Pat. No.
`4,330,039.
`
`[s1}
`
`rm. c1.= ................... .. E2lB 34/10; 5213 43/117;
`E2lB 43/12
`[52] U.s. Cl. ................................. .. 166/386; 166/55.1;
`166/319; 166/323; 166/374
`[53] Field of Search ............. .. 166/299, 319, 31?, 321,
`use/55.1, 323, 374, 386, 373; 175/452. 4.51,
`4.56
`
`A pressure actuated vent assembly for completing a
`slanted wellbore. The assembly is connected in series
`relationship within a tubing string at a location below a.
`packer, and the packer elements are located between
`the casing and the tubing string, thereby dividing the
`casing annulus into an upper and lower annular area.
`The vent assembly includes a ported sliding sleeve
`which is slidably received about a ported main body
`member. The sleeve is held into position by a shear pin.
`Guide pins maintain the ports of‘ the sleeve and main
`body member aligned with one another. When pressure
`is applied to the inside of the tubing, the sliding sleeve is
`forced to slide from an upper closed position, in a down-
`ward direction, where the sleeve locks into the opened
`position. The vent assembly is especially useful
`in
`slanted boreholes because various tools may be circu-
`lated down through the axial passageway of the assem-
`bly and downhole to perform a number of different
`downhole operations. such as completing a new well-
`bore, for example.
`
`ll} Claims, 3 Drawing Figures
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`BAKER HUGHES INCORPORATED
`Exhibit 1016
`
`Page 1 of 6
`Page 1 of 6
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`U.S.Patent
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`Page 2 of 6
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`1
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`4,434,854
`
`PRESSURE ACTUATED VENT ASSEMBLY FOR
`SLANTED WELLBORES
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`This application is a continuation of application Ser.
`No. 166.541 filed July 7, 1980, now, U.S. Pat. No.
`4,330,039 issued May I8, 1932.
`BACKGROUND OF THE INVENTION
`
`In the art of producing hydrocarbons from under-
`ground production zones, it is usually necessary to form
`a wellbore down through the oil bearing strata, cement
`a casing into the wellbore; and, thereafter communicate
`the hydrocarbon containing formation with the surface
`of the earth. This is generally accomplished in all sorts
`of different specific manners by perforating the casing
`and thereafter flowing the hydrocarbons up a tubing
`string. It is advantageous to isolate the lower produc-
`tion zone by the employment of a packer device inter-
`posed between the casing and the tubing string, so that
`flow from the formation can be confined to the upper
`tubing string.
`In U.S. Pat. No. 3,706,344 to Roy R. Vann, there is
`taught a permanent completion method and apparatus
`by which the above can be accomplished in an im-
`proved manner so that more economical production can
`be obtained. In U.S. Pat. Nos. 3,8".-'I,448; 3,932,855; and
`4,040,485 to Roy R Vann, et al
`there is disclosed a
`packer actuated vent assembly by which the before
`mentioned well completion techniques can be accom-
`plished. These techniques work satisfactory when car-
`ried out in vertical boreholes, but when the borehole is
`slanted, sometimes difficulty is encountered, especially
`when the slanted part of the borehole approaches the
`horizontal. as seen in the Vann U.S. Pat. No. 4,194,S7'.";
`for example.
`There are many instances where the lower marginal
`end of a borehole approaches a horizontal plane. For
`example, when drilling multiple boreholes from a single
`platform.
`it is not unusual
`to form a multiplicity of
`slanted boreholes which radiate from a single platform.
`The present
`invention provides a vent assembly
`which enables the method set forth in U.S. Pat. No.
`3,706,344 to be carried out in slanted boreholes in a
`more satisfactory manner.
`SUMMARY OF THE INVENTION
`
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`A pressure actuated vent assembly for connection in
`series relationship within a tubing string. A paclter de-
`vice is located above the vent assembly for packing off
`the upper annulus from the lower annulus. When the
`casing is perforated and the vent assembly moved into -
`55
`the open position, fluid can flow from a production
`zone, through the casing perforations, into the lower
`borehole annulus, up the annulus into the vent assem-
`bly, and up the tubing string to the surface of the earth.
`The vent assembly includes an outer sub having an
`upper end by which it is connected into the upper tub-
`ing string.
`A hollow mandrel has one end affixed to the interior
`of the sub, and a marginal
`length of the mandrel
`is
`spaced from a skirt of the sub to form a downwardly
`opening, circumferentially extending annulus. The
`lower end of the mandrel is connected to the lower
`tubing string. Ports are formed through the skirt of the
`mandrel. An axial passageway extends through the vent
`
`65
`
`2
`assembly to provide unobstructed access to the lower
`tubing string.
`A sliding sleeve is received within the annulus, with
`there being a variable chamber formed between the
`sliding sleeve and the upper blind end of the down-
`wardly opening annulus.
`Ports are formed within the sliding sleeve, and when
`the sleeve is moved respective to the mandrel and sub.
`the ports of the sleeve and the mandrel come into regis-
`try with one another. Guide means cause the ports to be
`indexed in registered relationship with one another
`when the sliding sleeve is moved to the open position.
`Seal means between the mandrel. sliding sleeve, and
`skirt prevent fluid flow from the assembly when the
`sleeve is in the closed position.
`A shear pin releasably locks the sleeve in the closed
`position, while a detent and latch means capture the
`sleeve so that it is latched into the opened position.
`In carrying out the method of the present invention,
`a predetermined pressure is applied to the interior of the
`tubing string, causing a downward force to be applied
`to the sliding sleeve, until
`the shear pin is sheared
`whereupon the sleeve is forced to move into the latched
`opened position, and flow can occur
`through the
`aligned opened ports.
`Accordingly, a primary object of the present inven-
`tion is the provision of a pressure actuated vent assem-
`bly for use downhole in a slanted borehole for commu-
`nicating a lower borehole annulus with the interior ofa
`tubing string.
`Another object of this invention is the provision of a
`pressure actuated vent assembly which for1'ns part of a
`fluid conduit. and which includes closed flow ports
`which are moved to the opened position when a prede-
`termined elevated pressure is exerted upon the interior
`of the vent assembly.
`Still another object of this invention is the provision
`of a pressure actuated vent assembly which is held in
`the closed position until a predetermined pressure is
`exerted thereon, whereupon the ports of the vent assem-
`bly are moved into an open position.
`A still further object of this invention is the provision
`of a pressure actuated vent assembly having an annular
`piston which is forced to move when subjected to a
`predetermined pressure to thereby align spaced ports so
`that flow can occur into the assembly.
`Another and still further object of this invention is
`the provision of a pressure actuated vent assembly
`which enables an unobstructed flow path to be main-
`tained from the surface of the ground downhole to the
`bottom of a tubing string, and at the same time enables
`communication to be achieved between a lower bore-
`hole annulus and a marginal length of the tubing string
`by applying pressure internally of the tubing string so as
`to open a flow port.
`These and various other objects and advantages of
`the invention will become readily apparent to those
`skilled in the art upon reading the following detailed
`description and claims and by referring to the accompa-
`nying drawings.
`Thc above objects are attained in accordance with
`the present invention by the provision of a combination
`of elements which are fabricated in a manner substan-
`tially as described in the above abstract and summary.
`
`Page 3 of 6
`Page 3 of 6
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`3
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`4,434,854
`
`BRIEF DESCRlP’I‘ION OF THE DRAWINGS
`
`FIG. 1 is a diagrammatical, hypothetical view of a
`cross-section of a borehole extending downhole into the
`earth and having apparatus made in accordance with
`the present invention associated therewith;
`FIG. 2 is an enlarged, longitudinal. cross—sectional
`view of part of the apparatus disclosed in FIG. 1 with
`the right side thereof showing the apparatus in one
`position and the left side thereof showing the apparatus
`in another; and.
`FIG. 3 is a cross-sectional view taken along line 3-3
`of FIG. 2.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`In FIG. 1, there is disclosed a borehole which extends
`downhole into the earth. The borehole has the usual
`wellhead 10 connected to a casin g 12 or 12'. The casing
`extends downhole to a production zone 14. Tubing
`string 16 also extends from the wellhead. down through
`the casing, and includes a packer device 18 which packs
`off a marginal, annular area between the tubing and
`casing. The packer therefore divides the casing annulus
`into a lower annulus 20 and an upper annulus 22. The
`borehole can be vertical. as illustrated, or slanted. as
`seen at 12’.
`
`A pressure actuated vent assembly 24. made in accor-
`dance with the present invention, is interposed in series
`relationship within the tubing string. The apparatus
`includes a vent port 26. Other apparatus, such as a per-
`forating gun 28. is included in the tubing string.
`As seen illustrated in FIGS. 2 and 3. the pressure
`actuated vent assembly 24 of the present invention in-
`cludes an outer sub 30 having an upper threaded surface
`32 by which the vent assembly can be connected to the
`box end of the tubing string. The sub has a downwardly
`extending outer skirt 34 which terminates at
`lower,
`circumferentially, extending edge portion 35.
`The interior of the sub includes a threaded surface 36
`formed along an upper marginal length of the interior
`thereof. A hollow mandrel 33 has a threaded surface at
`the upper marginal end thereof which threadedly en-
`gages threads 36 of the sub so that the resultant co-
`acting concentrically arranged sub and mandrel present
`a downwardly opening annular space at 42. The man-
`drel has an axial passageway 44 which permits commu-
`nication from the upper tubing string, down through
`the vent assembly, and on down through the lower
`tubing string so that communication between apparatus
`28 of FIG. I and the surface of the ground can be ef-
`fected. The inside diameter 46 of the sub is therefore
`spaced from the outside diameter 48 of the mandrel to
`form a downwardly opening chamber 50 therebetween.
`A sliding sleeve 52 has an uppermost end 54 spaced
`from end wall 56 of chamber 50. The lower end 58 of
`the sliding sleeve can be appreciated toward a circum-
`ferentially extending shoulder 60 formed on the exterior
`of the mandrel. The cylindrical wall 46 of the sub in-
`creases at the circumferentially extending shoulder 62
`to form a larger i.d. cylindrical wall 64 on the interior of
`the skirt member.
`The sliding sleeve has a relative small o.d. length 66
`which is enlarged to form a relatively large o.d. length
`at 6?. Annular grooves 68 and 69 are formed within the
`exterior surface 66 of the sleeve. Shoulder 72 is formed
`between surfaces 66 and 6'.-'. and abuttingly engages
`interior shoulder 62 of the sub. Accordingly. there are
`
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`two expansion chambers, that is. upper chamber 50 and
`lower chamber '70, as will be discussed more fully later
`on in this disclosure.
`The mandrel has a plurality of radially spaced ports
`'74 which come into registry with ports 26 of the sliding
`sleeve when the sleeve is in its downwardmost position.
`0-rings 76-82 seal the intervening surface between the
`mandrel and the sliding sleeve, and between the sliding
`sleeve and the skirt member. so that when the sleeve is
`in the uppermost or closed position, fluid flow through
`the co—acting elements of the tool is confined to the axial
`passageway.
`A shear pin 83 is force fitted into the sleeve and re-
`ceived within a small drilled hole 84 formed within a
`sidewall of the mandrel. An index pin 85 is received in
`fixed relationship within drilled hoie 86 of the sleeve,
`and moves within the vertical aligned groove 87. This
`arrangement of the co-acting parts maintains the ports
`74 of the mandrel in aligned relationship respective to
`the ports 26 of the sleeve so that when the sleeve moves
`in a downward direction, the ports are brought
`into
`registry respectively to one another.
`Flow port 88 is formed through the sidewall of the
`mandrel and communicates chamber 70 with the axial
`passageway 44. A spring loaded latch assembly 90 is
`comprised of a removal plug 92 which compresses the
`illustrated spring against a piston 94. so that the piston is
`urged against the sidewall 66 of the mandrel. so that the
`piston is received within the annular groove 68 when
`the sleeve is reciprocated in a downward or opened
`direction. This action locks the ports into the opened
`position as the ports move into registry with one an-
`other. Passageway 96 communicates the expansion
`chamber 70 with the axial passageway 44.
`Those skilled in the art, having digested the foregoing
`disclosure material of this specification, will probably
`realize that the sliding sleeve is captured between the
`mandrel and sub, and acts as a piston; and. when pres-
`sure is elfected within the axial passageway, the pres-
`sure differential forces the piston to move downwardly
`against shoulder 60.
`In operation, the vent assembly is connected into the
`tubing string of the permanent comptetion apparatus in
`the manner of FIG. 1. As noted in FIGS. 2 and 3. it is
`possible to circulate or drop a tool 97 of various config-
`urations down through the tubing string, whereupon
`the tool
`travels through the upper
`tubing string,
`through the axial passageway 44 of the vent assembly.
`and down to a jet perforating gun 28, for example,
`thereby detonatin g the gun firing head 98 and complet-
`ing the well.
`Assuming the well to be slanted as set forth in patent
`application Ser. No. 132.765, prior to circulating a bar
`97 downhole, the internal pressure of the tubing is ele-
`vated by employing a suitable power pump which is
`monitored with a chart
`type pressure recorder. The
`tubing preferably is liquid filled. and liquid is pumped
`into the upper tubing string in order to elevate the inter-
`nal
`tubing pressure. although nitrogen or other inert
`gases can be employed for this pressure elevation. if
`desired.
`
`As the bottomhole tubing pressure reaches a value of
`approximately two thousand psi above the annulus pres-
`sure, with the annulus pressure being measured at a
`location below the packer, the pin 83 will shear. and the
`sleeve 52 will slam down and lock, thereby opening the
`vents as ports 26 and 74 move into aligned relationship
`respective to one another.
`
`Page 4 of 6
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`5
`The slope of the pressure curve will change as the
`tubing and the casing fluid pressures equalize. Pumping
`into the upper tubing string is continued to cause the
`tubing pressure to further increase. The pressure is next
`bled off, and increased again to the same previous vol-
`ume of liquid or gas. The relative configuration of the
`two recorded curves indicate whether or not the vent
`
`assembly has been actuated to the opened position,
`thereby indicating that the well completion technique
`can be continued safely.
`The annular area at 42, that is. the cross-sectional area
`of the annulus defined by the cylinder walls 46 and 48,
`multiplied by the pressure effected through ports 88 and
`96. determine the downward force exerted upon the
`sliding sleeve. The shear pin must be sized according to
`this calculated force.
`As the pin shears, the sleeve is rapidly forced down-
`wardly until edge portion 58 thereof abuttingly engages
`the shoulder 60 of the mandrel. During this time,
`the
`guide pin 36 rides within the vertical groove 87, thereby
`aligning port '.-'4 with port 26. The circurnferentially
`extending groove 68 moves into aligned relationship
`with respect to the spring loaded plug or look 96 which
`is received therewithin so that the sleeve is positively
`locked into the opened position.
`Initially, just as the pin shears, there is pressure ef-
`fected within both chambers 50 and 70, as seen as 50'
`and 70‘ on the right half of FIG. 2. After the pin shears
`and the sleeve travels a short distance, the passageway
`96 is closed as it passes the lower end of groove 87. This
`effectively reduces the cross-sectional area of the sleeve
`which is subjected to the internal tubing pressure. Ac-
`cordingly, the sleeve commences opening under a large
`force and then is ‘subjected to a reduced force during the
`final part. of its downward stroke. This reduction in
`force is adequate to ensure full stroke of the sleeve,
`while the sleeve is protected from damage which may
`result from excessive impact against the shoulder 6|].
`Hence. the opening stroke of the sleeve is carried out in
`two steps; a large opening force to assure that the pin
`shears, and a reduced force to assure full travel of the
`sleeve. The groove 87 serves as a guide means for guide
`pin 86 as well as a passageway for llow from 4-4, 88, 87,
`96, and into annular chamber 70. Flow from 44 through
`84 and into chamber 50 occurs about the upper marginal
`end of the sleeve, the tolerance between the coacting
`sliding surfaces being of a value which enables a small
`flow to occur into chamber 50.
`the
`Accordingly, upon initial opening movement,
`entire cross-sectional area of the sleeve is subjected to
`the pressure at 44, and thereafter, only the upper re-
`duced diameter cross-sectional area of the sleeve is
`subjected to the pressure effected at 44.
`It will now be evident to those skilled in the art that
`pressure is effected at 50° by flow which occurs
`through the passageway at 84 and 88. while the cham-
`ber 70‘ is communicated with the pressure source at 44
`by means of passageways 88 and 96.
`The present invention can be used in borehole opera-
`tions which are severely slanted as contrasted to bore-
`holes which are vertically disposed.
`What is claimed is:
`l. A vent assembly in combination with a packer and
`perforating gun suspended on a. tubing string into a
`cased borehole with an open axial passageway extend-
`ing from the perforating gun to the surface for the low-
`ering of a bar to detonate the perforating gun and for
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`4,434,854
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`the flow of production fluids through the vent assembly
`to the surface, comprising:
`a tubular body series connected in the tubing string
`and having a portion of the axial passageway ex-
`tending therethrough;
`a sleeve disposed on said body forming an annular
`chamber;
`piston means received within said annular chamber;
`ports through said body and piston means.
`said piston means being movable between an open
`position where said ports allow fluid flow between
`said axial passageway and borehole and a closed
`position where fluid flow is prevented;
`guide means disposed on said piston means for bring-
`ing said ports into registry in said open position;
`and
`means communicating one portion of said piston
`means with said axial passageway and another por-
`tion of said piston means with the borehole
`whereby a sufficient pressure differential between
`said axial passageway and borehole will cause said
`piston means to move from said closed position to
`said open position.
`2. The circulation valve ofclaim 1 and further includ-
`
`ing latch means for engaging said piston means when
`said piston means moves to said open position so that
`said piston means is latched in the open position.
`3. A vent assembly for opening a tubing string to the
`How of fluids to the surface upon the application of
`tubing pressure predeterminely greater than the annulus
`well pressure, comprising:
`a tubular body series connected in the tubing string
`and having an axial passageway therethrough;
`means forming an annular chamber in said tubular
`body;
`means forming a first port through said tubular body;
`piston means reciprocatingly received within said
`annular chamber and having means forming a sec-
`ond port
`through said piston means in indexed
`relationship relative to said first port in the open
`position;
`means communicating one portion of said piston
`means with said axial passageway and means com-
`municating another portion of said piston means
`with the borehole annulus;
`means releasably affixing said piston relative to said
`body whereby when the tubing pressure becomes
`predeterminely greater than the annulus pressure,
`said releasable means releases said piston and said
`piston means moves into the open position where
`said first and second ports are in an indexed rela-
`tionship and fluids may flow from the formation to
`the surface; and
`latch means for latching said piston in the open posi-
`tion.
`
`4. A pressure actuated vent assembly for connection
`in series relationship within a tubing string comprising:
`a mandrel having an axial passage formed therein;
`a circumferentially extending skirt affixed to said
`mandrel, a marginal length of said mandrel being
`spaced from said skirt to form a circumferentially
`extending annulus:
`a sliding sleeve reciprocatingly received within said
`annulus; means forming a port through said man-
`drel, means forming a port through said sleeve in
`indexed relationship relative to said mandrel port,
`and seal means by which fluid flow is prevented
`from flowing between said sleeve and mandrel;
`
`Page 5 of 6
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`4,434,854
`
`7
`means communicating the upper end of the sleeve
`with said axial passageway so that when pressure is
`effected within said axial passageway. pressure
`forces the sleeve to move into the open position
`whereby Said sleeve and mandrel ports are aligned
`permitting fluid to flow through said sleeve and
`mandrel ports and into said axial passageway;
`means releasably affixing said sliding sleeve relative
`to said mandrel so that said sleeve remains in a
`closed position until an elevated pressure is ef-
`fected within said axial passageway; and
`latch means for engaging said sleeve when said sleeve
`moves to the open position so that said sleeve is
`latched in the open position.
`5. The vent assembly of claims 1. 2, 3, or 4 wherein
`said piston means forms a variable chamber; and further
`including means forming an aperture extending from
`said axial passageway to said variable chamber to pro-
`vide an Opening force during the initial opening move-
`ment of said piston means and thereafter providing a
`relatively smaller force during the final opening move-
`ment.
`
`6. The vent assembly of claims 3 or 4 and further
`including guide means disposed on said piston means for
`bringing said ports into registry in said open position.
`7. In a cased borehole having a tubing string sus-
`pended therein. a packer located along the tubing string
`for closing the casing annulus. and a vent assembly
`series connected in the tubing string below the packer,
`the method comprising the steps of:
`(1) providing the vent assembly with a ported tubular
`body, forming an annular chamber within the said
`body and slidably mounting a ported sleeve within
`the annular chamber;
`(2) closing the port through the body and thus the
`axial passageway of the tubular string to the flow
`of fluids from the casing annulus by sliding the
`ported sleeve to a closed position where the ports
`are nonaligned;
`(3) lowering the tubing string, packer and vent assem-
`bly into the cased borehole in the closed position;
`(4) effecting a pressure differential between the axial
`passageway of the tubing string and the casing
`annulus by elevating the pressure within the axial
`passageway; and
`(5) using the pressure differential of step (4) to force
`the sleeve to slide into the open position where the
`ports are aligned to immediately open a flow path
`allowing the flow of fluids from the casing annulus.
`through the ports and axial passageway, and up to
`the surface.
`8. In a cased borehole having a tubing string sus-
`pended therein, a packer located along the tubing string
`for closing the casing annulus. and a vent assembly
`series connected in the tubing string below the packer,
`the method comprising the steps of:
`(1) providing the vent assembly with a ported tubular
`body, forming an annular chamber within the said
`body and slidably mounted a ported sleeve within
`the annular chamber;
`(2) closing the port through the body and thus the
`axial passageway of the tubular string to the flow
`of fluids from the casing annulus by sliding the
`ported sleeve to a closed position where the ports
`are nonaligned;
`(3) lowering the tubing string, packer and vent assem-
`bly into the cased borehole in the closed position;
`
`8
`(4) effected a pressure differential between the axial
`passageway of the tubing string and the casing
`annulus by elevating the pressure within the axial
`passageway;
`(5) using the pressure differential of step (4) to force
`the sleeve to slide into the open position where the
`ports are aligned to allow the flow of fluids from
`the casing annulus,
`through the ports and axial
`passageway, and up to the surface; and
`(6) latching the sleeve in the open position.
`9. In a cased borehole having a tubing string sus-
`pended therein, a packer located along the tubing strin g
`for closing the casing annulus, and a vent assembly
`series connected in the tubing string below the packer,
`the method comprising the steps of:
`(1) providing the vent assembly with a ported tubular
`body, forming an annular chamber within the said
`body and slidably mounting a ported sleeve within
`the annular chamber;
`(2) closing the port through the body and thus the
`axial passageway of the tubular string to the flow
`of fluids from the casing annulus by sliding the
`ported sleeve to a closed position where the ports
`are nonaligned;
`(3) lowering the tubing string, packer and vent assem-
`bly into the cased borehole in the closed position;
`(4) effecting a pressure differential between the axial
`passageway of the tubing string and the casing
`annulus by elevating the pressure within the axial
`passageway;
`(5) using the pressure differential of step (4) to force
`the sleeve to slide into the open position where the
`ports are aligned to allow the flow of fluids from
`the casing annulus,
`through the ports and axial
`passageway. and up to the surface; and
`(6) reducing the force on the sleeve during step (5)
`after the sleeve initially moves toward the open
`position.
`10. In a cased borehole having a tubing string sus-
`pended therein, a packer located along the tubing string
`for closing the casing annulus, a perforating gun sus-
`pended from the tubing string. and a vent assembly
`series connected in the tubing string between the packer
`and the perforating gun,
`the method comprising the
`steps of:
`.
`(1) providing the vent assembly with a ported tubular
`body, forming an annular chamber within said
`body and slidably mounting at ported sleeve within
`the annular chamber;
`(2) closing the port through the body and thus the
`axial passageway of the tubular string to the flow
`of fluids from the casing annulus by sliding the
`ported sleeve to a closed position where the ports
`are nonaligned;
`(3) lowering the tubing string. packer and vent assem-
`bly into the cased borehole in the closed position;
`(4) extending the axial passageway through the tub-
`ing string from the perforating gun to the surface;
`(5) effecting a pressure differential between the axial
`passageway of the tubing string and the casing
`annulus by elevating the pressure within the axial
`passageway; and
`(6) using the pressure differential of step (5) to force
`the sleeve to slide into the open position where the
`ports are aligned to allow the flow of fluids from
`the casing annulus,
`through the ports and axial
`passageway, and up Lhe axial passageway to the
`surface.
`I
`3
`!-
`1
`t
`
`5
`
`10
`
`I5
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`Page 6 of 6
`Page 6 of 6