U.S. patent number 3,896,876 [Application Number 05/505,348] was granted by the patent office on 1975-07-29 for subsurface tubing safety valve with auxiliary operating means.
This patent grant is currently assigned to Baker Oil Tools, Inc.. Invention is credited to Talmadge L. Crowe.
United States Patent |
3,896,876 |
Crowe |
July 29, 1975 |
Subsurface tubing safety valve with auxiliary operating means
Abstract
A subsurface tubing safety valve, for wells, in which a sleeve
is held in a first position and shiftable to a second position by a
shifting tool. The safety valve is held open by control fluid
pressure supplied from the top of the well and is closeable by well
fluid pressure when control fluid pressure is reduced. When the
shiftable sleeve is moved to its second position, it also opens the
safety valve and forms a seat for an auxiliary wireline safety
valve adapted to be held open by control fluid pressure and closed
by well fluid pressure.
Inventors: |
Crowe; Talmadge L. (Houston,
TX) |
Assignee: |
Baker Oil Tools, Inc. (Los
Angeles, CA)
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Family
ID: |
26957665 |
Appl.
No.: |
05/505,348 |
Filed: |
September 12, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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275910 |
Jul 28, 1972 |
|
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243806 |
Apr 13, 1972 |
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Current U.S.
Class: |
166/322; 137/498;
166/323; 166/72 |
Current CPC
Class: |
F16K
5/20 (20130101); E21B 34/10 (20130101); E21B
34/14 (20130101); E21B 43/14 (20130101); E21B
2200/04 (20200501); Y10T 137/7785 (20150401) |
Current International
Class: |
F16K
5/00 (20060101); F16K 5/20 (20060101); E21B
34/00 (20060101); E21B 43/00 (20060101); E21B
43/14 (20060101); E21B 34/14 (20060101); E21B
34/10 (20060101); E21b 033/00 () |
Field of
Search: |
;166/72,224R,224A,226
;137/458,494,498 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Attorney, Agent or Firm: Kriegel; Bernard
Parent Case Text
This application is a continuation-in-part of my pending
application Ser. No. 275,910, filed July 28, 1972, which is a
division of application Ser. No. 243,806, filed Apr. 13, 1972 now
abandoned.
Claims
I claim:
1. In a shutoff valve for wells, said valve including an elongated
valve body having a flow passage therethrough, valve means in said
body including a valve element shiftable between a first position
closing said passage and a second position at which said passage is
open, means for shifting said valve member from said second
position to said first position, and control fluid pressure
responsive means for shifting said valve member from said first
position to said second position, said control fluid pressure
responsive means including means defining a control fluid pressure
chamber, valve operating means having an actuator sleeve having a
piston exposed to control fluid pressure in said chamber, and
auxiliary shifting means operable by a shifting tool moveable into
said passage for shifting said actuator sleeve to move said valve
element to said second position from said first position.
2. In a shutoff valve as defined in claim 1, said auxiliary
shifting means having lock means for holding said actuator sleeve
in a position holding said valve element in said second
position.
3. In a shutoff valve as defined in claim 1, said auxiliary
shifting means having lock means for holding said actuator sleeve
in a position holding said valve element in said second position,
and means in said body forming a seat for an auxiliary shutoff
valve in said passage.
4. In a shutoff valve as defined in claim 1, said auxiliary
shifting means comprising a shifting sleeve shiftably disposed in
said passage and movable to shift said actuator sleeve to a
position at which said valve element is in said second position,
said shifting sleeve forming a wall of said pressure chamber when
in an initial position and allowing communication between said
pressure chamber and said passage when said shifting sleeve moves
said actuator sleeve to a position at which said valve element is
in said second position, and seat means in said body forming spaced
seals for an auxiliary shutoff valve in said passage to apply
control fluid pressure from said pressure chamber to said auxiliary
shutoff valve.
5. In a shutoff valve as defined in claim 1, said auxiliary
shifting means comprising a shifting sleeve shiftably disposed in
said passage and movable to shift said actuator sleeve to a
position at which said valve element is in said second position,
said shifting sleeve forming a wall of said pressure chamber when
in an initial position and allowing communication between said
pressure chamber and said passage when said shifting sleeve moves
said actuator sleeve to a position at which said valve element is
in said second position, and seat means in said body forming spaced
seals for an auxiliary shutoff valve in said passage to apply
control fluid pressure from said pressure chamber to said auxiliary
shutoff valve, said body having a bypass passage communicating with
said flow passage at opposite sides of said valve element, bypass
valve means normally closing said bypass passage and operable by
the pressure of control fluid in said pressure chamber to open said
bypass passage, and check valve means for preventing flow of
control fluid from said pressure chamber through said bypass
passage when said shifting sleeve moves said actuator sleeve to
said position at which said valve member is in said second
position.
6. In a shutoff valve as defined in claim 1, said auxiliary
shifting means including a shifting sleeve in said passage
shiftable from an initial position to a position holding said valve
element in said second position, and including latch means for
holding said shifting sleeve in said latter position.
7. In a shutoff valve as defined in claim 1, said auxiliary
shifting means including a shifting sleeve in said passage
shiftable from an initial position to a position holding said valve
element in said second position, and including latch means for
holding said shifting sleeve in said latter position, said latch
means including a resilient latch ring interposed between said body
and said shifting sleeve, one of said shifting sleeve and said body
having latch elements engageable by said latch ring when said
shifting sleeve is in said latter position.
8. In a shutoff valve as defined in claim 1, said auxiliary
shifting means including a shifting sleeve in said passage
shiftable from an initial position to a position holding said valve
element in said second position, and including latch means for
holding said shifting sleeve in said latter position, said latch
means including a resilient latch ring interposed between said body
and said shifting sleeve, one of said shifting sleeve and said body
having latch elements engageable by said latch ring when said
shifting sleeve is in said latter position and the other of said
shifting sleeve and said body having means for forcing said latch
ring into locking engagement with said latch elements to hold said
shifting sleeve in said latter position.
9. In a shutoff valve as defined in claim 1, said auxiliary
shifting means including a shifting sleeve in said passage
shiftable from an initial position to a position holding said valve
element in said second position, and auxiliary shifting tool means
engageable with said shifting sleeve to move said shifting sleeve
to its latter position.
10. In a shutoff valve as defined in claim 1, said auxiliary
shifting means having lock means for holding said actuator sleeve
in a position holding said valve element in said second position,
and means in said body forming a seat for an auxiliary shutoff
valve in said passage including sealing bores at axially spaced
locations spanning said control fluid pressure chamber.
11. In a shutoff valve as defined in claim 1, said auxiliary
shifting means comprising a shifting sleeve shiftably disposed in
said passage and movable to shift said actuator sleeve to a
position at which said valve element is in said second position,
said shifting sleeve forming a wall of said pressure chamber when
in an initial position and allowing communication between said
pressure chamber and said passage when said shifting sleeve moves
said actuator sleeve to a position at which said valve element is
in said second position, and seat means in said body forming spaced
seals for an auxiliary shutoff valve in said passage to apply
control fluid pressure from said pressure chamber to said auxiliary
shutoff valve including sealing bores at axially spaced locations
spanning said control fluid pressure chamber.
12. In a shutoff valve for wells, said valve including an elongated
valve body having a flow passage therethrough, valve means in said
body including a valve element shiftable between a first position
closing said passage and a second position at which said passage is
open, means for shifting said valve member from said second
position to said first position, and control fluid pressure
responsive means for shifting said valve member from said first
position to said second position, said control fluid pressure
responsive means including means defining a control fluid pressure
chamber, valve operating means having an actuator sleeve having a
piston exposed to control fluid pressure in said chamber, and
auxiliary shifting means for shifting said actuator sleeve to move
said valve element to said second position from said first position
by application of pressure to the flow passage above said auxiliary
shifting means.
13. In a shutoff valve for wells as defined in claim 10, said
auxiliary shifting means comprising a shifting sleeve shiftably
disposed in said passage and movable to shift said actuator sleeve
to a position at which said valve element is in said second
position, and a shifting tool responsive to said application of
pressure to the flow passage above said auxiliary shifting means
for shifting said shifting sleeve.
14. In a shutoff valve for wells as defined in claim 12, said
auxiliary shifting means comprising a shifting sleeve shiftably
disposed in said passage and movable to shift said actuator sleeve
to a position at which said valve element is in said second
position, said shifting sleeve forming a wall of said pressure
chamber when in an initial position and allowing communication
between said pressure chamber and said passage when said shifting
sleeve moves said actuator sleeve to a position at which said valve
element is in said second position, and seat means in said body
forming spaced seals for an auxiliary shutoff valve in said passage
to apply control fluid pressure from said pressure chamber to said
auxiliary shutoff valve.
15. In a shutoff valve for wells as defined in claim 12, said
auxiliary shifting means comprising a shifting sleeve shiftably
disposed in said passage and movable to shift said actuator sleeve
to a position at which said valve element is in said second
position, said shifting sleeve forming a wall of said pressure
chamber when in an initial position and allowing communication
between said pressure chamber and said passage when said shifting
sleeve moves said actuator sleeve to a position at which said valve
element is in said second position, seat means in said body forming
spaced seals for an auxiliary shutoff valve in said passage to
apply control fluid pressure from said pressure chamber to said
auxiliary shutoff valve, and an auxiliary shutoff valve assembly in
said passage and having spaced sealing means engaged with said
spaced seals in said body, said auxiliary shutoff valve means
having a fluid inlet between said spaced sealing means for the
admission of control fluid pressure from said pressure chamber.
16. In a shutoff valve for wells as defined in claim 12, said
auxiliary shifting means comprising a shifting sleeve shiftably
disposed in said passage and movable to shift said actuator sleeve
to a position at which said valve element is in said second
position, said shifting sleeve forming a wall of said pressure
chamber when in an initial position and allowing communication
between said pressure chamber and said passage when said shifting
sleeve moves said actuator sleeve to a position at which said valve
element is in said second position, and seat means in said body
forming spaced seals for an auxiliary shutoff valve in said passage
to apply control fluid pressure from said pressure chamber to said
auxiliary shutoff valve including sealing bores at axially spaced
locations spanning said control fluid pressure chamber.
17. In a shutoff valve for wells as defined in claim 12, said
auxiliary shifting means comprising a shifting sleeve shiftably
disposed in said passage and movable to shift said actuator sleeve
to a position at which said valve element is in said second
position, said shifting sleeve forming a wall of said pressure
chamber when in an initial position and allowing communication
between said pressure chamber and said passage when said shifting
sleeve moves said actuator sleeve to a position at which said valve
element is in said second position, seat means in said body forming
spaced seals for an auxiliary shutoff valve in said passage to
apply control fluid pressure from said pressure chamber to said
auxiliary shutoff valve, and an auxiliary shutoff valve assembly in
said passage and having spaced sealing means engaged with said
spaced seals in said body, said auxiliary shutoff valve means
having a fluid inlet between said spaced sealing means for the
admission of control fluid pressure from said pressure chamber,
said spaced seals and spaced sealing means spanning said control
fluid pressure chamber.
Description
In the production of well fluids, such as oil and/or gas, from
wells, it has been the practice to provide automatically closeable
shutoff or saftey valves which are located downhole in the well and
are held open by control fluid pressure, the valves closing
automatically when control fluid pressure is purposely reduced to
allow the valves to close or damage occurs to the control fluid
system at the well head or on an offshore platform.
Such valves are employed below the well head, and in the case of
offshore wells the valves are installed below the mudline at such
depth as may be desired or established by regulation, so that in
the event of damage to the well caused by shifting earth or
subsidence, the wells can be shut in to avoid loss of valuable well
fluids into the water and, also, to avoid contamination of the
water and the shore.
Many offshore wells are produced from spaced well zones through
separate strings of production tubing, and a safety or shutoff
valve is required for each zone. Since, from time to time, it is
necessary to perform various remedial operations through the tubing
strings, it is preferred that the safety valves have a full bore
opening which will allow wireline tools to pass through the safety
valves. On the other hand, it is also preferred that the safety
valves be easily removed from the well for service or repair. While
safety valves adapted to be run into the well and landed in a seat
on a wireline and retrieved on wireline are relatively simple to
run and retrieve without requiring that the tubing string be pulled
from the well, such wireline valves, in general, do not have a full
bore opening through which remedial operations can be performed
through the production tubing, particularly if the well is cased
with comparatively small casing so that the valves must be small in
diameter.
Full opening valves have been made up in the tubing strings and run
into the well in the tubing string. Accordingly, repair or service
of such tubing string safety valves has required that the entire
tubing string be hoisted, at least until the valve is accessible.
Such operations have generally involved killing the well, with
prospective damage to the productive formation, as well as in the
use of heavy hoisting equipment capable of lifting an entire tubing
string which may be many thousands of feet in length.
In addition, when an offshore well is cased with comparatively
small diameter casing, a limitation is inherently imposed on the
size of the tubing valves that can be run into the well on tubing,
as well as on wireline.
In the above identified application of which this application is a
continuation-in-part, there is disclosed a plural zone, subsurface
safety valve system which is conveniently useful in the control of
a multiple zone well. The subsurface valve assembly is run into the
well on upper tubing strings and is landed in a receptacle provided
in a tubing hanger which is anchored in the well casing, say, below
the mudline of an off-shore well, and supports the major production
tubing weight suspended below the tubing hanger. The plural safety
valve can readily be retrieved from the tubing hanger without
requiring that the entire production tubing string be pulled from
the well, and without requiring that the well be killed. However,
even though the pulling of the upper tubing strings and the
subsurface valve assembly from the tubing hanger may be a
comparatively simple task, there is a resultant loss of well
production time from the several well zones.
The present invention provides a subsurface safety valve which has
a valve member closeable by well fluid pressure and adapted to be
held open by control fluid pressure, wherein auxiliary means are
also provided for shifting the valve member to the open position by
other mechanical means if the control fluid pressure responsive
operating means should fail, and it is, nevertheless, desired that
the particular earth zone remain on production until the subsurface
valve assembly is to be pulled from the well for some other
reason.
In addition, the present invention provides a subsurface valve
which has means for receiving an auxiliary wireline retrievable
safety shutoff valve openable by control fluid pressure from the
same source which holds the tubing valve open and closeable by well
fluid pressure, whereby the safety function of the subsurface valve
means is maintained, until the subsurface tubing valve is otherwise
to be pulled.
More particularly, the invention involves providing a subsurface
shutoff valve for production tubing, wherein control fluid pressure
is admitted to a pressure chamber and acts on a piston area of the
tubing valve to overcome well fluid pressure and hold the tubing
valve open. This pressure chamber is separated from the main valve
passage by a sealing sleeve which normally closes a port leading
between the pressure chamber and the main valve passage. The sleeve
is releasable for movement to a second position at which the
normally closed port is open. A wireline retrievable shutoff valve
can then be landed in the sealing sleeve and then opened by control
fluid pressure supplied through the opened port.
Means normally retain the sealing sleeve in its first position and
are releasable to allow movement of the sleeve to its second
position and a shifting tool is adapted to be removably seated in
the tubing valve and operated by fluid pressure supplied to the
tubing to actuate the sealing sleeve to its second position. When
the shifting tool is removed, the sleeve is held by latch means in
its second position for reception of the auxiliary wireline safety
valve.
The tubing valve has equalizing means enabling the equalization of
pressure across the tubing valve when it is closed, whereby opening
of the tubing valve is easier due to the reduction in friction whch
must be overcome. The equalizing means includes a passage which is
closed by back flow preventing valve means when the wireline valve
is in place in the tubing valve so that control fluid cannot flow
into the bypass passage.
In accordance with one form of the invention, the auxiliary shutoff
valve has longitudinally spaced seals which engage within spaced
sealing regions of the tubing hanger body, so as to span the
control fluid pressure regions of the tubing hanger, thereby
preventing leakage in the event of seal failure.
This invention possesses many other advantages, and has other
purposes which may be made more clearly apparent from a
consideration of a form in which it may be embodied. This form is
shown in the drawings accompanying and forming part of the present
specification. It and its method of use will now be described in
detail for the purpose of illustrating the general principles of
the invention; but it is to be understood that such detailed
description is not to be taken in a limiting sense, since the scope
of the invention is best defined by the appended claims.
Referring to the drawings:
FIG. 1 is a diagrammatic illustration showing dual safety valve
apparatus installed in a tubing hanger anchored in a well casing
extending through vertically spaced productive well zones which are
isolated from one another by packers, and from which well fluids
are produced through a pair of production tubing strings;
FIGS. 2a, 2b, 2c, and 2d, together, constitute a view generally in
elevation, but with certain parts broken away, showing the
subsurface valve assembly landed in the tubing hanger, FIGS. 2b
through 2d, respectively, constituting successive downward
continuations of FIG. 2a;
FIG. 3 is a view partly in elevation and partly in section, as
taken on the line 3--3 of FIG. 2d;
FIG. 4 is a horizontal section, as taken on the line 4--4 of FIG.
2b;
FIG. 5 is a horizontal section as taken on the line 5--5 of FIG.
2d;
FIG. 6 is a horizontal section, as taken on the line 6--6 of FIG.
2d;
FIG. 7 is a horizontal section, as taken on the line 7--7 of FIG.
2a;
FIG. 8 is a horizontal section, as taken on the line 8--8 of FIG.
2b;
FIGS. 9a and 9b, together, constitute a vertical section through
one of the subsurface valve assemblies, as taken on the line 9--9
of FIG. 7, FIG. 9b constituting a downward continuation of FIG. 9a,
and the valve being shown in the normally closed condition;
FIGS. 10a and 10b, together, constitute a view generally
corresponding to FIGS. 9a and 9b, but showing the valve assembly in
the open condition;
FIG. 11 is a horizontal section, as taken on the line 11--11 of
FIG. 9a;
FIG. 12 is a horizontal section, as taken on the line 12--12 of
FIG. 9a;
FIG. 13 is a fragmentary horizontal section, as taken on the line
13--13 of FIG. 9b;
FIG. 14 is a fragmentary vertical section, as taken on the line
14--14 of FIG. 7;
FIG. 15 is an exploded detail view in perspective, showing a
typical ball valve and a removable side closure and valve
supporting member;
FIG. 16 is a fragmentary detailed view partly in elevation and
partly in section showing the ball valve in a closed position;
FIG. 17 is a view generally corresponding to FIG. 16, but showing
the ball valve shifted longitudinally downwardly from engagement
with the resilient seal but prior to rotation towards the open
position;
FIG. 18 is a view corresponding to FIGS. 16 and 17, showing the
ball valve rotated towards an open position;
FIG. 19 is a view corresponding to FIGS. 16 through 18, but showing
the ball valve in the full open position;
FIGS. 20a and 20b, together, constitute a vertical section, with
certain parts shown in elevation, showing a shifting tool disposed
in a valve assembly with the valve in the closed position prior to
movement of the valve to the open position by the shifting tool,
FIG. 20b constituting a downward continuation of FIG. 20a;
FIGS. 21a and 21b, together, constitute a view generally
corresponding to FIGS. 20a and 20b, but showing the valve shifted
to the open position by the shifting tool, and the valve being
locked open;
FIGS. 22a and 22b, together, constitute a vertical section with
certain parts shown in elevation and showing a wireline retrievable
shutoff valve seated and locked in the bore of the locked open main
shutoff valve; and
FIGS. 23a and 23b, together, constitute a vertical section with
certain parts shown in elevation showing another form of wireline
retrievable shutoff valve seated in the locked open main shutoff
valve.
As seen in the drawings, the invention is shown in a plural safety
valve for an offshore well. Referring first to FIG. 1, as well bore
W extends downwardly into the earth below the ocean floor F through
vertically spaced well fluid producing zones Z1 and Z2. A casing C
is set in the well bore and perforations P in the casing establish
communication between the productive zones Z1 and Z2 and the casing
C. Set in the casing C is an upper packer P1 located above the
productive zone Z1 and a lower packer P2 located in the casing
between the productive zones Z1 and Z2. A first production tubing
string T1 extends through the packer P1 and opens into the casing
therebelow to communicate with the productive zone Z1, and a second
production tubing string T2 extends downwardly through the upper
packer P1 and downwardly through the lower packer P2 into the
casing therebelow for communication with the productive zone Z2.
The tubing stings T1 and T2 may extend a number of thousands of
feet downwardly in the casing to the packers P1 and P2 and the
tubing string T1 and T2 are supported by tubing hanger means TH
which is set or anchored in the well casing and forms a seat for a
shutoff valve assembly V which comprises dual shutoff valves V1 and
V2 for the respective tubing strings T1 and T2. The tubing hanger
TH and the valve assembly V are located below the ocean floor or
the mudline of a body of water, at a desired or required depth of
say 500 to 1,000 feet, more or less. The casing C extends upwardly
through the water to a production platform or barge PP, as shown in
the diagrammatic illustration. However, as is well known, the well
may be completed at the ocean floor and one or a number of
additional casings (not shown) may be set in larger diameter well
bores, and the casing C may be suspended or hung from a casing
hanger located at the ocean floor, in which case, a conductor pipe
or other casing (not shown) may extend to the production platform
PP. In any event, upper production fluid tubings T3 and T4 extend
upwardly from the respective valves V1 and V2 of the valve assembly
V and are connected with the usual Christmas Trees CT on the
platform PP whereby the flow of well fluids from the well zones Z1
and Z2 may be controlled or manually shutoff. Flow lines FL are
provided to conduct well fluids from the Christmas Trees to
suitable reservoirs or tanks (not shown).
As will be later described, the respective subsurface valves V1 and
V2, which are normally closed, are adapted to be held open, to
enable the flow of production fluids therethrough, by means of
control fluid pressure supplied through a control fluid conduit CF,
or through a pair of such conduits, from a source of control fluid
pressure CP. So long as the control fluid pressure is adequate to
maintain the subsurface valves V1 and V2 open, well fluids may flow
from the zones Z1 and Z2 to the respective flow lines FL, but, if
it is desired for any reason to close either of the shutoff valves
V1 or V2, or in the event of damage of the control fluid tubing,
the control fluid pressure may be reduced so that the subsurface
valves V1 and V2 are automatically closed, thereby shutting the
well in at a location below the ocean floor, to prevent continued
production fluid flow.
The tubing hanger assembly TH and the tubing strings T1 and T2 are
adapted to be lowered from the platform PP downwardly through the
casing C on a setting tool, as more particularly described in the
above identified application Ser. No. 243,806, and the valve
assembly V is thereafter adapted to be lowered through the casing C
into the tubing hanger TH on the upper tubing strings T3 and T4.
Likewise, the valve assembly V can be retrieved from the tubing
hanger TH, so that under normal circumstances requiring repair or
service of the subsurface valve assembly V, it is not necessary to
pull the entire dual tubing strings T1 and T2, as has heretofore
been the practice. Since only the comparatively short upper tubing
strings T3 and T4 need be pulled from the well to remove the valve
assembly V, and the substantially longer tubing strings T1 and T2
remain in the well, the platform PP need not be equipped with or
supplied with high-powered hoisting apparatus. Instead, the
platform PP may simply be provided with a small lowpowered hoist
mechanism or a gin pole hoist. In addition, the tubing strings T1
and T2 can be plugged off at or below the tubing hanger TH to
enable the service or repair of the valves V1 and V2 without
requiring that the well be killed.
As seen in FIGS. 1, 2d, and 5, the tubing hanger TH comprises a
body section 10 having an upwardly extended tubular guide section
11, the upper end edge 12 of which is arched downwardly from a peak
13, in opposite directions, to a vertically extended slot 14 at the
side of the guide section 11 diametrically opposite the peak 13.
Internally of the guide section 11, between the lower end of the
slot 14 and the body section 10, is a thread 15 to which a setting
tool is connectable, as disclosed and claimed in the companion
application Ser. No. 275,911, filed July 28, 1972, for Tubing
Hanger Apparatus. Below the internal thread 15 is an internal
flange 16 which provides a downwardly facing shoulder 17 for
anchoring the valve means V in the hanger TH, as will be later
described.
Extending downwardly into the body section 10 from the guide
section 11, are a pair of diametrically spaced fluid passages 18,
18 at the upper end of each of which, is a cylindrical receptacle
or socket 19. At the lower end of the body section 10, the tubing
strings T1 and T2 are connected thereto in communication with the
respective passages 18, 18.
Anchor means 34 for the tubing hanger may be as described and shown
in the aforementioned application of which this is a
continuation-in-part, and comprise suitable slip elements 46 and 47
which are expansible into anchoring engagement with the casing
C.
When the setting tool has been removed from the well casing, the
tubing hanger assembly is then in condition to receive the dual
valve assembly V, as seen in FIGS. 2a through 2d.
The dual valve assembly V, as previously indicated, comprises, in
the illustrated embodiment, a pair of valves V1 and V2, since the
apparatus is shown as applied to producing from a pair of well
zones Z1 and Z2, but it will be understood that the invention is
applicable, also, to valve assemblies used in the production of
more or less than two well zones.
At its lower end, as seen in FIGS. 2d and 3, the valve assembly V
is adapted to be received in the upper tubing hanger body section
11 and to be latched in place by releasable latch means 125 beneath
the internal flange 16 in the hanger body section. At diametrically
spaced locations in a cross-head 126 of the latch means 125, the
latch means 125 has elongated laterally opening spaces 127, 127
accommodating flow tubes 128 and 129 which are respectively adapted
to establish communication between the tubing strings T1 and T2 and
the valve assemblies V1 and V2, respectively.
At their lower ends, the flow tubes 128 and 129 have sealing end
portions 130 and 131, respectively, each having sealing ring means
132 engageable within the bores or receptacles 19 in the tubing
hanger body 10. The flow tube 128 extends upwardly from the
cross-head 126 and is connected at 133 to a length of tubing 134
which extends further upwardly a suitable distance, and is
connected at 135 to the housing 136 of the upper valve assembly V1,
which will be hereinafter described. The flow tube 129 also extends
upwardly from the cross-head 126 and is connected at 137 to the
valve assembly V2, which is spaced vertically downwardly from the
valve assembly V to enable utilization of valve assemblies V1 and
V2 having full bore flow passages, as will also be later described.
Extending upwardly from the valve housing 138 through swivel means
139 is a rotatable tubular member 140 which is connected at its
upper end by a coupling 141 to the tubing string T4 above the
connection of the tubing string T3 to the valve assembly V1, as
seen in FIG. 2a. Rotation of the tubing string T4 and, thus, the
tubular member 140 is utilized to engage and release the latch
means 126 when the valve assembly V is run into the tubing hanger
TH.
The flow tubes are retained in parallel, assembled relation by a
vertically split body 142 comprising opposed half sections 143 and
144, as seen in FIG. 6, clamped together by fasteners 145. The body
sections 143, 144 have internal grooves 146 which receive annular
ribs 147 on the flow tubes 128, 129 to hold the latter against
relative axial movement.
When the valve assembly V is being lowered into the tubing hanger
TH, a key 148 on one side of the assembly, shown on the flow tube
129, and engageable with the peak 13 of the hanger body section 11
will cause rotation of the valve assembly V, as the key 148 rides
downwardly on the inclined surface 12 and is guided into a vertical
slot 14, whereby the lower ends 130, 131 of the flow tubes 128, 129
will be properly positioned or oriented so as to be stabbed into
the bores or receptacles 19 in the hanger body 11.
The latch means 125 referred to above, comprises a plurality of
resilient, normally retracted collett fingers 150 depending from
the cross-head 126 and having outwardly projecting latch lugs 151
at their lower ends. The lower ends of the latch fingers 150 are
expansible outwardly by a wedge surface 152 on the split body 142
when the cross-head 126 is moved downwardly relative to the body
142, from the position of FIG. 2d to the position of FIG. 3. Means
155 are provided for normally holding the latch fingers 150 in the
retracted positions, and spring means 156 are provided for
actuating the cross-head 126 downwardly to cam the fingers 150
outwardly.
More particularly, a pair of bolts 157 extend through the
cross-head 126 and have their heads 158 engageable beneath the
cross-head 126 to hold the latter in an upper position, as seen in
FIG. 2d. These bolts 157 are threaded into a plate 159 which is
connected to a pull rod 160, the pull rod extending upwardly
alongside the length of tubing 134 and being connected, as seen in
FIG. 2b, to a non-rotatable nut 161, having a notch 162 for
straddling the tubing 134 to prevent rotation of the nut. The nut
161 has a threaded bore 163, in which a complemental thread 164 on
the rotatable tubing section 140 is engaged. Accordingly, when the
tubing string T4, which, as previously indicated, is connected to
the tubing section 140, is rotated, the nut 161 is moved axially on
the tubing section 140, downwardly, from the position of FIG. 2b,
to allow downward movement of the plate 159 and the bolts 157.
The spring means 156 are operable to force the cross-head 126
downwardly and comprises a pair of coiled compression springs 165
disposed about the bolts 157 and seating at their lower ends in
bores 166 in the cross-head 126 and at their upper ends against a
spring seating plate 167 which abuts beneath the lower valve
housing 138. When the cross-head 126 is moved downwardly by the
springs 166, the lugs 151 on the latch fingers 150 are cammed by
the cam surface 152, ourwardly for engagement beneath the latch
shoulder 17 of the tubing hanger body section 11.
As seen in FIGS. 2a through 2c, the control fuid conduit CF is
connected by a fitting 170 to the upper valve housing 136 of the
valve V1 and passage means 171 in the housing 136 conduct control
fluid to an outlet fitting 172 which is connected to a conduit 173
leading to an inlet fitting 174 for the lower valve V2. However, if
preferred, plural control fluid tubings CF may be employed to
supply control fluid pressure to the valves V1 and V2.
The fluid pressure responsive shutoff valve V1 is made according to
the invention and is representative of the two valves V1 and V2 and
will now be described.
In this form, as seen in FIGS. 9a, 9b, and 10a, 10b, the valve
assembly comprises the outer body 136 and an upper tubular sub 136a
which is connected with the lower end of the tubing string T3. The
upper body 136a is threadedly connected at 175, at its lower end to
the body 136, which, in turn, as previously described, is
threadedly connected at 135 to the flow tube 134, which seats in
one of the bores or receptacles 19 in the tubing hanger body
10.
A ball valve 176 is disposed within the body 136 and has a passage
177 for the flow of well fluid when the ball valve is in the open
position, with the passage 177 aligned with the body 136, the ball
valve being rotatable 90.degree., as will be later described, to a
closed position, in which flow of well fluid through the body 136
is prevented.
Normally, the ball valve 176 is biased to a closed position by a
lower sealing and actuating sleeve 178, which is reciprocable in
the valve body 136 between an upper position, as seen in FIG. 9b,
and a lower position, as seen in FIG. 10b. The sleeve 178 is
piloted in a reduced bore 179 in the body 136, and the lower end of
the sleeve extends into a bore 180 in the upper end of the tube
134. A coiled compression spring 181 is disposed between the upper
end of the tube 134 and a seating shoulder or ring 182 on the
sleeve 178, and biases the sleeve 178 and the ball valve 176
upwardly. Externally, the ball valve 176 has a spherical sealing
surface 183 sealingly engageable by a companion sealing end surface
184 at the upper end of the sleeve 178.
Above the ball valve 176 is an upper valve actuating and sealing
sleeve 185 having a lower end sealing surface 186, which is
complemental to the spherical valve surface 183 of the ball valve
176. At its upper end, the sleeve 185 has an enlarged piston
section 187 which is slideably disposed within a cylinder portion
188 of the valve body 136. Below the piston section 187 is a
cylindrical section 189 smaller than the outside diameter of the
piston section 187. Between the cylindrical section 189 and the
cylindrical wall 188 is a sleeve 190 engaged by an external seal
ring 191 on the cylindrical section 189 and having an external seal
192 engaging with the cylinder wall 188. At its lower end, the
sleeve 190 abuts with an upwardly facing shoulder 193. The
difference between the annular cross-sectional area of the sleeve
190 and the annular cross-sectional area of the upper end 194 of
the piston section 187 constitutes the net piston area of the
piston section 187 exposed, as will be later described, to control
fluid pressure to hold the ball valve 176 open. The piston section
187 extends into an annular space 195 defined between the
cylindrical wall 188 and a sleeve 196 which is releasably connected
by suitable means such as shear screws 197 to a skirt 198 on the
lower end of the upper body section 136a, the sleeve 196 carrying a
seal ring 199 engageable within the skirt 198, and the skirt 198
having a seal ring 200 engageable in the cylindrical wall 188. This
sleeve 196 will be more particularly described hereinafter.
The control fluid passage 171, previously referred to, communicates
through a port 201 with the annular space 195 which constitutes a
control fluid pressure chamber in which control fluid pressure is
operable on the net piston area of the piston section 187 of the
sleeve 185 to provide a downward force adapted to overcome the
upward force applied to the ball valve 176 by the lower valve
actuating sleeve 178, when the ball valve 176 is to be opened by
moving the ball valve from the position of FIG. 9b to the position
of FIG. 10b, as the upper valve actuating and sealing sleeve 185 is
forced downwardly. When the over-riding control fluid pressure is
relieved, the pressure of production fluid acts, to close the ball
valve 176, across the combined areas of the upper sleeve or piston
section 187 and the secondary sleeve 190 when the latter shoulders
at 190a, as seen in FIG. 10a.
Preferably, the valve assembly includes resilient sealing means 202
engageable with the ball valve 176 when it is in the closed
position. In the embodiment now being described, the resilient
sealing means 202 comprises a seal carrier ring 203 having an
annular elastomeric seal ring 204 engageable with the ball valve
176 externally of the seating surface 186 at the lower end of the
sleeve 185. The seal carrier ring 203 is normally biased downwardly
by a coiled compression spring 205 which seats against a seating
ring 206 carried within the valve body 136.
The respective valve assemblies V1 and V2 are full opening valve
assemblies through which remedial operations can be performed when
the ball valve is opened. The valve assembly, as shown, is more
particularly the subject matter of the companion application Ser.
No. 286,151, filed September 5, 1972.
In order to provide a ball valve 176 of maximum diameter, the ball
valve 176 is installed in the body 136 through a side opening 207
which is closed by a valve supporting closure member 208 which fits
within the opening 207, and is sealed therein by a suitable seal
ring 209. Referring again to FIG. 2b, it will be noted that the
closure and valve support member 208 is adapted to be secured to
the valve body 136 by a suitable number of fasteners 210, as best
seen in FIG. 8, the closure member 208 includes a guide section 211
having a bore 212 through which the tubular member 140 rotatably
extends.
In order to support the ball valve 176 and cause rotation thereof
in response to movement of the ball longitudinally between the
sleeves 185 and 178, the valve supporting member 208 has a pin or
lug 213 projecting therefrom in aligned opposition to a
corresponding pin or lug 214 carried within the valve body 136, and
the ball valve 176 has at its opposite sides corresponding slots
215 in which the respective pins or lugs 213 and 214 are engageable
for rotating the ball valve 176 between the opened and closed
positions, as best illustrated in FIGS. 16 through 19. In these
views, the side of the ball valve 176 supported by the closure 208
is illustrated, but similar structure will be understood to be
located at the other side of the ball valve, also. In FIG. 16, the
valve is shown fully closed and sealed by the sleeves 178 and 185
as well as by the resilient sealing means 202. In FIG. 17, the
valve 176 has been shifted downwardly away from the resilient seal
means 202 through an initial increment of non-rotative longitudinal
movement. In FIG. 18, the ball valve 176 is in the partially opened
position. In FIG. 19, the ball valve 176 is in the fully opened
position.
More particularly, the ball valve member 176 on each of its
opposite sides has a chordal flat surface 216 adjacent to the
diametrically opposite portions of the body 136 and the support
208. The slot 215 extends radially with respect to the axis of
rotation to the ball valve member 176, and at right-angularly
spaced locations, the ball face 190 is recessed to form a stop
surface 217 and a stop surface 218 cooperable with fixed stop lug
surfaces 217a and 218a on the closure 208 to limit rotation of the
ball 176 between the extremes of FIG. 16 and FIG. 19. When the ball
valve member 176 is in the position of FIG. 16, the stop surface
217 engages the vertical stop surface 217a, thereby limiting
rotation of the valve member 176 to the position at which the valve
is open. The stop surface 218 engages the stop surface 218a, as
shown in FIG. 19 to limit rotation of the valve member 176 to the
position at which the valve is closed. Such rotation between the
open and closed positions is caused by longitudinal or vertical
movement of the valve member 176 relative to the body 136. As
previously indicated, the ball member 176 is actuated or shifted
longitudinally by longitudinal movement of the upper actuator
sleeve 185 and the lower actuator sleeve 178, as indicated by the
arrows in FIGS. 17 and 18. The slot 215 is formed in such a manner
as to cause such rotation of the valve member 176 as the latter
moves vertically or longitudinally within the body 136. Thus, as
seen in FIG. 16, the slot 215 is formed on the valve member 176 by
opposed walls which are disposed at a right angle to one another
and designated 215a and 215b and which respectively are parallel to
the stop surfaces 217a and 217b. At the apex of the angle defined
between the walls 215a and 215b, the slot opens radially inwardly
at 215c. Thus, the relationship between the pin 213 and the wall
215b is such that the ball valve 176 will be rotated from the
position of FIG. 16 to the position of FIG. 19 when the valve
member 176 moves downwardly relative to the pin 213, and,
conversely, the flat wall 215a will engage the pin 213 and rotate
the ball valve member from the position of FIG. 19 to the position
of FIG. 16 upon upward movement of the valve member 176. However,
it will be noted that when the valve member 176 is in the position
of FIG. 19, the pin 213 clears the flat wall 215a so as to allow
freedom of longitudinal movement of the ball valve 176 after the
stop surface 218 engages the stop 218a, and correspondingly limited
free downward movement of the ball valve 176 is permitted when the
ball valve is open, as seen in FIG. 16, where the pin 213 clears
the slot wall 215a, and the stop surface 217 engages the stop 217a.
Such free or lost motion connection of the ball valve 176 and the
rotating pin 213 relieves the connection of damaging forces when
the ball valve is in either of its closed positions, and in
addition saves the resilient seal 202 from relative rotative
movement of the ball valve 176.
When the ball valve 176 is closed and is to be opened by applying
control fluid pressure to the piston chamber 195, there may be
substantial differential pressure across the valve tending to hold
it closed, and in order to equalize the pressure across the valve,
equalizing valve means 220 are provided, as best seen in FIG. 14,
for establishing communication between a port 221 below the ball
valve 176 (FIG. 9b) and a port 228 in the valve 176 (FIG. 9a), via
the elongated passage 223 in the valve body 136. The port 221
communicates with the annular space 224 between the body 136 and
the lower valve actuating sleeve 178 which communicates with the
passage through the tubular member 134 through radial ports 225 in
the upper end of the member 134, when the valve 176 is closed, as
seen in FIG. 9b. Above the ball valve 176, the skirt 198 of the
upper valve body section 136a has a number of radial ports 226
communicating between the flow passage through the valve assembly
and an annulus 227 which in turn communicates through a port 228
with a chamber 229 of the equalizing valve means 220. The
equalizing valve chamber 229 is provided by a tubular insert 230
retained in a bore 231 in the body 136 by a sealing plug 232. Seals
234 and 234a on the insert 230 engage in the bore 231 and a reduced
bore 235. A valve member 236 is reciprocable in the insert 230 and
has its lower end 237 provided with a seal 238 slideably engaging
within the insert 230 below inlet ports 239 in the insert which
establish communication between the port 228 and the valve chamber
229, so that above the seal 238, the chamber 229 is exposed to the
flow passage through the upper valve body 136a. At the upper end of
the equalizing valve member 236 is a head 240 engageable with a
seat 241 under the influence of pressure below the ball valve 176
supplied to an inlet chamber 242, above the head 240, via the
passage 223 and via a radial port 243 in the body 136 and ports 244
in the insert 230. A rod 245 slideably extends downwardly through
the lower end of the insert 230 and into the bore 235, and a coiled
spring 246 engages the insert 203 and an adjustable spring seat 247
on the rod to provide a downward bias closing the head 240 against
the seat 241. Leading into the bore 235 of the equalizing valve 220
is a port 248 which communicates with the control fluid chamber 195
of the shutoff valve means.
It will now be apparent that so long as the pressure differential
across the closed ball valve 176 is such that well pressure in the
equalizing valve chamber 242 and the spring 246 cause a net
downward force holding the valve head 240 seated, in excess of the
force upwardly caused by control fluid pressure in the bore 235,
there will be no communication between the ports 221 and 228,
respectively, below and above the ball valve 176. However, as
control fluid pressure is increased to open the shutoff valve 176,
the increased pressure acts upwardly on the effective piston area
at the lower end of the equalizing valve member 236 and will open
the equalizing valve head 240, whereby pressure will equalize
between the lower ports 221, through passage 223, ports 243 and
244, valve chambers 242 and 229, ports 239, and the upper
equalizing port 228.
The effective areas in the equalizing valve means 220 and the force
of the spring 246 are selected, as compared with the effective area
of the shutoff valve actuating piston section 187 of the sleeve
185, so that the equalizing valve means 220 will open first, and
thereby relieve the main shutoff valve 176 from the effect of
differential pressure thereacross.
In order to assure that no back flow can occur when the shutoff
valve 176 is open and the well is flowing therethrough, a back flow
preventing valve 223a is provided between the equalizing valve
chamber 242 and the passage 223.
In order to enable control fluid pressure to be supplied to both of
the valve assemblies V1 and V2 in the valve means V, as previously
indicated, the control fluid pressure chamber or bore 235 of the
equalizing valve means 220 of the upper valve V1 has a passage 235a
leading to the fitting 172, which in turn communicates with the
lower valve assembly V2.
In the use of shutoff valves, such as the valve assembly V1 or V2,
to control flow from a plurality of well zones, it may occur, under
various circumstances, such as seal failure, that one or more of
the shutoff valves will not open under applied control fluid
pressure. In such event, it may be necessary to pull the shutoff
valve means from the well in order to repair and repalce the
shutoff valve means. In accordance with the present invention,
however, means are provided whereby the valve V1 or the valve V2
may be opened mechanically and locked open to allow continued
production from one or both of the well zones Z1 and Z2. In
addition, the present invention enables the use of an auxiliary or
secondary shutoff valve, adapted to be run into and anchored in the
locked open valve assembly V1 or V2.
As seen in FIGS. 9a, 9b, and in FIGS. 10a, 10b, the sleeve 196 is
held by the shear screws 197 in an initial upper position, as
previously described, and the sleeve 196 cooperates with the body
136 to form the control fluid pressure chamber or annular space
195. Initially released lock means 250 are provided, whereby, when
the sleeve 196 is shifted downwardly, it will be locked in the
lower position. When the sleeve 196 is shifted downwardly, it
engages a shoulder 251 on the sleeve 185 and shifts the latter
downwardly to open the ball valve 176. The sleeve shifting tool SS
of FIGS. 20a, 20b, and FIGS. 21a, 21b provides means for shifting
the sleeve 196 downwardly.
More particularly, the lock means 250 includes a resiliently
contractable, split lock ring 252 having external upwardly facing
buttress teeth 253. Beneath the lock ring 252 is an expander 254
which is secured to the sleeve 196 by fasteners 255 and has an
expander surface 256 engageable within the lock ring 250 to expand
the latter when it is lockingly engaged with internal teeth 257
within the body 136.
The sleeve shifting tool SS, as seen in FIGS. 20a and 20b,
comprises an inner mandrel 260 connected by a rope socket 261 to a
wireline 262, and having an inner rod 264 connected thereto at 265
and extending downwardly therefrom. The inner rod 264 has an
elongated slot 266 through which a pin 267 extends. This pin 267 is
carried by an actuator sleeve 268 which is slideably disposed upon
an elongated support sleeve 269, also having an elongated slot 270
through which the pin 267 extends. The support sleeve 269 is
threadedly connected at 271 to a tubular body 272 about which is a
suitable packing means 273 sealingly engageable within the upper
body section 136a of the shutoff valve body 136. Above the packing
273 is a nut 274 having a downwardly facing shoulder 275 adapted to
abut with the upwardly facing shoulder 276 in the body section
136a. The mandrel 260 is slideably disposed within an upward
extension 277 of the nut 274 communicating via ports 278 in the nut
274 and ports 279 in the lower end of the mandrel 260 with an inner
annular space 280, so that fluid pressure in the tubing string T3
is applicable to the piston section 281 of the actuator sleeve 268,
the piston section 281 having a seal ring 282 slideable within the
valve body section 136a.
At its lower end, the actuator sleeve 268 slideably engages the
support sleeve 269 below the slot 270 and has a seal ring 283
sealingly engaged with the support sleeve 269. At its lower end,
the middle rod 264 has an enlarged end 284 initially sealingly
engaged within a cylindrical wall 285 of the support sleeve 269,
above a longitudinally ported spring seat 286. A coiled compression
spring 287 engages the spring seat 286 and acts upwardly on a latch
sleeve 288 having a plurality of normally retracted resiliently
outwardly expansible fingers 289 on which are upper end lugs 290.
Upward movement of the latch sleeve 288 is limited by a collar 291
on the support sleeve 269 and engaged by a solid ring section 292
on the latch sleeve 288. The lugs 290 on the fingers 289, when the
shoulders 275 and 276 limit downward movement of the sleeve
shifting tool SS in the valve body section 126a, are located above
the upper end 293 of the sleeve 196 which, as previously indicated,
is initially held in its upper position by the shear screws 197, so
that the seal ring 199 on the sleeve 196 is initially disposed
above a number of radial ports 294 in the skirt portion 198 of the
upper body section 136a of the valve assembly V1 or V2.
In order to shift the sleeve 196 downwardly, the actuator sleeve
268, to which fluid pressure is applicable to move the latter
downwardly, initially engages the upper ends of the fingers 289
with a lower cam surface 295 of the actuator sleeve 268 and flexes
the fingers outwardly so that the lugs 290 thereon are engageable
with the upper end 293 of the valve sleeve 196. Above the cam
surface 295 on the actuator sleeve 268 is a downwardly facing
shoulder 296 which, upon further downward movement of the actuator
sleeve 268, engages the upper ends of the fingers 289 to transmit
thereto a downward force, whereby, as seen in FIGS. 21a and 21b,
the sleeve 196 shears the shear screws 197 and moves downwardly.
Since the sleeve 196 engages the shoulder 251, as previously
described, on the upper valve actuator sleeve 185, the latter is
also moved downwardly, thereby opening the ball valve 176, as also
previously described.
Such downward movement of the sleeve 196 causes the latch means 250
to be engaged, that is, the lock ring 252 engages the internal
teeth 257 within the valve body 136, thereby holding the valve
actuating sleeve 185 in its lower position.
Thereafter, the sleeve shifting tool SS may be removed from the
valve body section 136a by simply lifting the mandrel 260 with the
wireline 262, thereby lifting the middle rod 264 until the bottom
266a of the slot 266 contacts the pin 267, thereby lifting the
actuator sleeve 268 until it again engages the tubular body 272, at
which time, the resilient fingers 289 will again flex inwardly,
retracting the lugs 290 to their original positions.
When the sleeve 196 is locked by the locking means 250, in the
lower position, holding the shutoff valve 176 open, the sleeve 196
and the valve body section 136a are adapted to receive a
conventional wireline retrievable auxiliary shutoff valve assembly
V3, as seen in FIGS. 22a and 22b and in FIGS. 23a and 23b. In the
arrangement of FIGS. 22a and 22bthe wireline retrievable valve
assembly V3 comprises a valve body 300, at the upper end of which
is a typical running and retrieving neck 301. Spaced axially along
the body 300 is an upper packing means 302 sealingly engageable
within the valve body section 136a of the main shutoff valve
assembly V1 or V2 and a lower packing means 303 sealingly engaged
within the sleeve 196, and straddling the ports 226 and the ports
294 in the skirt 198 of the upper body section 136a which are both
in communication with an annular space 304 defined between the
skirt 198 and the valve body 300, this annular space 304 being in
communication, via the ports 294, with the annular space or control
pressure chamber 195 of the valve assembly V1 or V2. Thus, control
fluid pressure supplied to the annular space 195 via the inlet port
201 is admitted through a valve port 305 in the valve body 300 to
operate the wireline retrievable valve V3 in the well known manner
to open the same.
Suitable releasable latch means 306 including a number of
retractable latch elements 307 engageable beneath a shoulder 308 in
the valve body section 136a are adapted to retain the valve
assembly V3 seated in the valve assembly V1 or V2 until it is
desired that the valve assembly V3 be removed. Thus, without
requiring recovery of the entire valve assembly V in order to
effect service or repair of one of the valve assemblies V1 or V2,
the utilization of the auxiliary valve assembly V3 enables the
continued production of both well zones while maintaining control
of the production by the auxiliary shutoff valve V3 in the
otherwise inoperative shutoff valve V1 or V2.
Another auxiliary shutoff valve arrangement is seen in FIGS. 23a
and 23b which assures operability of the auxiliary valve V4. In
this form the auxiliary valve has an elongated body 400 having at
its upper end the usual running and retrieving neck 401. Spaced
axially of the body 400 is an upper sealing ring or packing unit
402 and a lower sealing ring or packing unit 403. The body 400
between the seals or packings 402 and 403 spans the length of the
main shutoff valve assembly so that the upper seal 402 engages in
the bore of the upper body section 136a and the lower seal 403
engages in the bore at the upper end of the tubing 134. The ports
226 and 294 establish communication with the annular space 404
defined between the auxiliary valve V4 and the main shutoff valve,
and control fluid is applicable to the auxiliary valve via a body
port 405 from the control fluid pressure chamber 195 of the main
valve. The details of the auxiliary valve construction are not
germane to the present invention and it may be of a desired known
type, having latch fingers 406 engageable with a downwardly facing
shoulder 408 in the upper body 136a to releasably retain the
auxiliary valve in place.
It will be noted that in this form the seals 402 and 403 straddle
all of the seals of the main valve so that if any of the main valve
seals are faulty, control fluid pressure is, nevertheless, confined
in the space between the main and auxiliary valves to operate the
auxiliary valve.
* * * * *