U.S. patent number 3,845,818 [Application Number 05/387,348] was granted by the patent office on 1974-11-05 for well tools.
This patent grant is currently assigned to Otis Engineering Company. Invention is credited to Thomas M. Deaton.
United States Patent |
3,845,818 |
Deaton |
November 5, 1974 |
WELL TOOLS
Abstract
A well tool in the form of a flapper-type safety valve for use
in a well bore to provide flow control in the well bore operable
from the surface. The valve is particularly characterized by a
flow-cut protected equalizing valve assembly for reducing the
pressure differential across the flapper valve preliminary to
opening the valve. The safety valve includes a housing, a
flapper-type valve at the lower end of the housing to control flow
into the housing, a valve operator tube positioned for longitudinal
movement in the housing for opening the flapper valve responsive to
a controlled pressure from the surface, a piston on the valve tube,
an annular chamber around the piston communicatable to the surface
for applying a fluid pressure from the surface to the piston to
bias the piston and valve tube downwardly, a spring between the
valve tubing and the housing biasing the valve tubing upwardly, and
an equalizing valve assembly for equalizing the pressure between
the interior and exterior of the housing on opposite sides of the
flapper valve preliminary to opening the flapper valve. The
equalizing valve, which is shown in two forms, includes a first
bubble tight valve having a resilient seal and a second valve using
a metal-to-metal seal. The equalizing valve assembly is arranged to
open and close in sequences which protect the resilient seal
against flow cutting.
Inventors: |
Deaton; Thomas M. (Dallas,
TX) |
Assignee: |
Otis Engineering Company
(Dallas, TX)
|
Family
ID: |
23529492 |
Appl.
No.: |
05/387,348 |
Filed: |
August 10, 1973 |
Current U.S.
Class: |
166/322; 137/629;
166/324 |
Current CPC
Class: |
E21B
34/105 (20130101); E21B 2200/05 (20200501); Y10T
137/86936 (20150401) |
Current International
Class: |
E21B
34/00 (20060101); E21B 34/10 (20060101); E21b
043/12 (); F16k 011/14 () |
Field of
Search: |
;166/224S
;137/629,630,630.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Attorney, Agent or Firm: Garland; H. Mathews
Claims
What is claimed is:
1. A well tool for controlling fluid flow in a tubing string in a
well bore comprising: a housing having a longitudinal bore
therethrough for flow of fluids; a valve secured at the lower end
of said housing for movement between open and closed positions for
controlling the flow of fluids into said bore of said housing; a
valve operator tube supported for longitudinal movement in said
housing, a lower end of said operator tube being engageable with
said valve for moving said valve from a closed to an open position
responsive to downward movement of said operator tube; means
associated with said operator tube for biasing said tube upwardly
to an upper position at which said valve is closed; means for
selectively urging said operator tube downwardly to a lower
position for opening and holding said valve open; and means
associated with said operator tube in said housing for equalizing
the pressure across said valve when said valve is closed to reduce
the force required for opening said valve including first and
second equalizing valve means, said first and second equalizing
valve means being opened and closed in a sequence adapted to
prevent flow cutting of said first equalizing valve means.
2. A well tool in accordance with claim 1 wherein said second
equalizing valve means opens after the opening of said first
equalizing valve means during the opening of said valve and said
second equalizing valve means closes in advance of the closing of
said first equalizing valve means during the closing of said
valve.
3. A well tool in accordance with claim 2 wherein said first
equalizing valve means comprises an annular resilient ring seal
disposed in an internal annular recess of said housing and an
external annular flange on said operator tube engageable with said
resilient seal when said tube is at a position at which said valve
is closed and said second equalizing valve means includes an
annular tapered valve seat within said housing around said operator
tube between said first equalizing valve means and said valve and a
sleeve member having an annular tapered seat engageable with said
seat of said housing, means biasing said sleeve member toward said
housing seat, and means on said operator tube for engaging and
retracting said sleeve to open said second equalizing valve means
by pulling said sleeve valve seat away from said housing valve seat
after said first equalizing valve means is opened.
4. A well tool in accordance with claim 3 including a spring around
said operator tube within said housing engaged at one end with a
flange in said housing and at the other end with said sleeve member
of said second equalizing valve means comprising said means for
biasing said sleeve member toward said valve seat in said housing
whereby said sleeve remains engaged with said seat until said
flange on said valve operator tube is disengaged from said
resilient seal during the opening of said valve and said sleeve
member re-engages said valve seat in said housing in advance of the
engagement of said valve operator tube flange with said resilient
seal during the closing of said valve.
5. A well tool in accordance with claim 3 including a spring on
said valve operator tube engaged between said sleeve member of said
second equalizing valve means and said valve operator tube
comprising said means for biasing said sleeve member toward said
valve seat of said housing whereby said second equalizing valve
means remains closed until said first equalizing valve means is
opened and said second equalizing valve means closes in advance of
the closing of said first equalizing valve means.
6. A well tool in accordance with claim 1 wherein: said means for
urging said operator tube downwardly includes a piston on said
valve operator tube, an annular control fluid chamber around said
valve operator tube within said housing, said piston being movable
in said control fluid chamber, and means for supplying a control
fluid into said chamber for applying a control fluid pressure to
said piston for moving said valve operator tube toward said valve
to open said valve; and said means for equalizing the pressure
across said valve when said valve is closed includes means defining
a side port in said housing to communicate with a well bore around
said well tool, means providing a port in said valve operator tube
communicating with the bore of said well tool, means defining an
annular flow space around said operator tube within said housing
between said side port in said housing and said side port in said
operator tube, said first and second equalizing valve means being
positioned along said annular space between said side ports for
controlling flow between said ports within said annular space to
equalize the pressure between the bore of said well tool above said
valve and a well bore around said well tool housing, said first and
second equalizing valve means being operable responsive to
longitudinal movement of said valve operator tube and including a
resilient internal annular seal within an annular recess of said
housing around said valve operator tube, an external annular
tapered first flange on said valve operator tube engageable with
said resilient seal when said flange is longitudinally aligned with
said seal forming said first valve means, an internal annular
tapered metal valve seat within said housing between said resilient
seal and said valve, a valve sleeve member movably disposed on said
operator tube within said annular space and having an annular
tapered valve seat engageable with said housing valve seat forming
said second equalizing valve means, a second external annular
flange on said valve operator tube spaced from said first flange
and movable within said valve sleeve member for actuating said
valve sleeve member relative to said housing seat, said sleeve
member having an internal annular operator shoulder facing said
valve engageable by said second flange on said operator tube
limiting movement of said operator tube away from said valve at a
position to align said first flange within said resilient seal,
said sleeve member having means providing internal operating
surfaces facing away from said valve for engagement by said second
flange on said operator tube to move said sleeve member toward said
valve to open said second equalizing valve means, the distance
between said operator shoulder of said member and said operator
surfaces being greater than the length of said second flange on
said second flange on said operator tube whereby said first
equalizing valve means opens before said second flange engages said
valve sleeve member to open said second equalizing valve means and
a spring engaged with said valve sleeve member biasing said valve
sleeve away from said valve toward said valve housing seat.
7. A well tool in accordance with claim 6 wherein said spring is
confined between a shoulder in said housing facing away from said
valve and the end of said valve sleeve member facing said
valve.
8. A well tool in accordance with claim 6 wherein said valve sleeve
member is provided with resilient collet fingers projecting toward
the valve, said collet fingers having inwardly turned collet heads
defining said internal operating shoulder in said valve sleeve
member and a spring confined within said valve sleeve member around
said valve operator tube between said flange on said operator tube
and said operator shoulder in said valve sleeve member facing said
valve providing means biasing said valve sleeve toward said housing
seat on said valve operator tube.
Description
This invention relates to well tools and more particularly relates
to a downhole type safety valve for use in a well bore.
Downhole safety valves are common well tools used for the control
of the flow of well fluids such as oil and gas so that hazardous
conditions may be minimized at the surface by closing the valves to
shut-in wells below the surface. Such valves may be operable
responsive to flow conditions at the valve or may be remotely
controlled from the surface responsive to various desired surface
conditions, including such factors as temperature, pressure changes
due to ruptured lines, and the like. The present invention is
particularly concerned with valves which are remotely controlled
from the surface. Where such valves are of the flapper type as in
the present invention, the flapper valve element normally opens
downwardly so that when closed a substantial pressure differential
may exist across the valve element requiring a large downward force
on the valve to open it unless some pressure equalization is
effected. In equalizing the pressure between the interior and
exterior of a valve under pressure differential conditions of large
magnitude, fluid flow can occur which is damaging to the equalizing
valve means used unless features are employed which minimize the
abrasive effects of the fluid flow. At least one available type of
flapper valve with equalizing means is known. It does not include a
protective feature which reduces the effects of flow cutting on the
valve member during the pressure equalization.
It is an object of the invention to provide a new and improved
downhole safety valve for wells.
It is a particularly important object of the invention to provide a
downhole safety valve of the flapper type which includes an
equalization valve assembly having means for minimizing flow
cutting of the resilient seal in the assembly.
It is another object of the invention to provide a downhole safety
valve having pressure equalization means which includes a
metal-to-metal seal and a separate resilient seal for effecting a
bubble tight sealed relationship at the equalization valve
means.
It is another object of the invention to provide one form of
downhole safety valve which includes a first spring means biasing
the valve closed and a second spring means biasing the flapper
valve and one valve of the pressure equalizing valve assembly
closed.
It is another object of the invention to provide a downhole safety
valve of the flapper type which uses a valve operator tube provided
with a piston portion exposed to the pressure of a control fluid
variable from the surface for selectively operating the valve
responsive to predetermined surface conditions.
It is another object of the invention to provide another form of
flapper-type safety valve using a single spring to bias the flapper
element closed and another spring which only biases one of the
valves of the equalizing valve assembly closed.
In accordance with the invention, there is provided a downhole
safety valve for use in a well bore having a housing connectible
into a tubing string or with a locking mandrel for use in a landing
nipple in a well bore, a flapper valve at the lower end of the
housing for controlling fluid entry into the housing, a valve
operating tube longitudinally movable in the housing and having a
piston portion exposed to an annular space in the housing around
the operator tube communicating with a fluid pressure source for
supplying a fluid pressure to bias the operator tube downwardly for
selectively opening and closing the flapper valve from the surface,
and a pressure equalizing valve assembly associated with the
housing and valve operator tube for equalizing the pressure across
the flapper valve preliminary to opening the valve to prevent
flapper valve operation against a full well pressure differential
across the valve.
The foregoing objects and advantages together with the specific
details of preferred embodiments of a safety valve constructed in
accordance with the invention will be understood from the following
detailed description taken in conjunction with the accompanying
drawings wherein:
FIGS. 1A through 1D taken together form a longitudinal view in
section and elevation of a preferred form of flapper-type safety
valve including the features of the invention and showing the valve
closed;
FIG. 2 is a fragmentary view in section and elevation of the valve
of FIGS. 1A-1D showing particularly the pressure equalizing valve
assembly at an intermediate stage in valve operation;
FIGS. 3A-3C taken together form a longitudinal view in section and
elevation showing the flapper valve open;
FIG. 4 is a view in section taken along the lines 4--4 of FIG.
1C;
FIG. 5A is a fragmentary view in section and elevation of an
alternate form of pressure equalizing valve assembly and showing
the valve assembly closed;
FIG. 5B is a fragmentary view in section and elevation showing the
equalizing valve assembly of FIG. 5A open.
Referring to the FIGS. 1A-1D, a flapper-type downhole safety valve
10 embodying the features of the invention includes a valve housing
11 having a central bore 12, a flapper valve 13 at the lower end of
the housing, a valve operator tube 14 including an operator piston
15, and a pressure equalizing valve assembly 20. The flapper valve
is opened and closed by the operator tube 14 which is movable
longitudinally responsive to fluid pressure applied from the
surface to the piston 15. The pressure equalizing valve assembly 20
relieves the pressure differential across the flapper valve
preliminary to opening the valve.
The valve housing 11 includes a top sub 21 which is internally
threaded at 22 for connection with a tubing string extending to the
surface end of a well bore in which the valve is installed on a
locking mandrel for supporting the valve in a landing nipple as
represented by the reference numeral 23. The top sub is internally
threaded along a lower portion 24 of reduced wall thickness which
is secured on an upper external threaded end portion 25 of a
packing mandrel section 30. The top sub 21 is further reduced in
wall thickness along a lower end portion 32 which is provided with
an internally threaded side port 33 located between the upper and
lower internal ring seals 34 and 35 disposed within internal
annular recesses above and below the side port. The seals 34 and 35
seal with the outer wall surface of the packing mandrel which is
provided with a side port 40 located between the seals 34 and 35
communicating with the side port 33. The side port 33 may be
connected with a control fluid line to the surface or may
communicate directly to an annular space within a well bore such as
within a landing nipple which is supplied with a control fluid for
operating the safety valve. The packing mandrel section 30 has an
internal flange 41 provided with an internal annular recess 42 in
which a ring seal 43 is disposed to seal between the packing
mandrel and the outer surface of the valve operator tube 14
defining the upper end of a control fluid annulus 44 between the
packing mandrel and the valve operator tube below the seal 43. The
packing mandrel section is enlarged at 45 providing an upwardly
spacing stop shoulder 50 for supporting the lower end of an annular
packing assembly 51 which is confined between the lower end face 52
of the top sub and the packing mandrel shoulder 50. In the
particular form of the safety valve 10 illustrated, the packing
assembly 51 seals with the inner wall surface of a landing nipple
in which the safety valve is supported from a suitable standard
locking device, not shown, which includes a similar annular packing
assembly for sealing with the landing nipple wall above the side
port 33. Control fluid communicated to the landing nipple will be
confined within an annular space around the valve above the packing
assembly 51 on the valve housing and below the packing assembly of
the locking device so that the control fluid is directed to the
side port 33 for operating the safety valve from the surface. As
shown in FIG. 1B, the enlarged portion 45 of the packing mandrel
section has an internally threaded lower end portion 53 which is
secured on the upper threaded end portion 54 of a housing adapter
sub 55.
The flapper valve operator tube 14 comprises an upper tubular
section 60 which is enlarged and internally threaded along a lower
end portion 61 defining the operator piston 15 provided with an
external annular recess 62 carrying an external ring seal 63 to
seal within the valve housing packing mandrel section 45 around the
operator tube piston portion. The seal 63 is the lower end of the
control fluid annulus 44. The valve operator tube section 60 is
secured along the lower end portion 61 with a tubular shaped prong
section 64 which comprises the major portion of the operator tube
extending downwardly to open the flapper valve. The piston portion
15 has an internal recess 65 which holds a ring seal 66 to seal
between the piston portion and the prong section 64. The valve
housing packing mandrel section 45 and the prong section 64 are
concentrically arranged in spaced relation defining a spring
chamber 70 in which a biasing spring 71 is positioned confined
between an upper end 72 of the sub 55 and a spring ring 73 on the
upper end of the spring. The ring 73 bears against the lower end
edge of the piston portion 15 of the valve operator tube so that
the spring 71 biases the valve operator tube upwardly to the
position of FIGS. 1A-1D at which the flapper valve is closed. A
ring seal 74 in an external annular recess of the adapter sub 54
seals around the sub within the lower end portion of the packer
mandrel 30 of the housing.
The adapter sub 55 has a side port 75 for admitting pressure to an
annular space 80 within the adapter sub around the valve operator
tube section 64 to equalize the pressure across the flapper valve
when the equalizing valve assembly 20 is open. The adapter sub is
reduced and externally threaded along the lower end portion 81
which is engaged in the upper end portion of a lower housing
section 82. A ring seal 83 in an external annular recess at the
upper end of the lower threaded end portion of the adapter sub
seals around the adapter sub within the housing section 82.
The adapter sub 55 has an internal annular flange 84 which supports
an internal annular resilient seal 85 within an internal recess of
the flange to effect a bubble tight seal with an external annular
flange 90 on the valve operator tube section 64 when the operator
tube is in the valve-closed position of FIGS. 1A-1D. The seal 85
and valve operator tube 90 comprise a first valve of the equalizing
valve assembly 20. The lower end of the adapter sub has an internal
downwardly and outwardly sloping valve seat surface 91 which is
engageable by a similar downwardly and outwardly sloping valve seat
92 on a tubular valve member 93 forming the second valve of the
equalizing valve assembly 20. The valve seats 91 and 92 are formed
of a suitable metal alloy such as Colmonoy -5 providing a
metal-to-metal seal. The valve member 93 includes an upwardly and
inwardly tapered head portion 94 and a tubular skirt portion 95.
The lower end of the head portion 94 defines an internal stop
shoulder 100 which is engageable with the top surface of an
external annular flange 101 on the valve operator tube section 64
spaced below the external flange 90 on the tube section. The flange
101 has an external annular recess provided with a ring seal 102 to
seal around the flange with the internal wall surface of the skirt
portion 95 of the valve member 93. The valve skirt 95 has an
internal annular recess 103 in which three segments 104 of a split
ring are retained by a stop ring 105 having a tubular body portion
110 and a lower flange portion 111. The stop ring 105 which fits
into the lower end of the valve member skirt 95 to hold the three
ring segments 104 in place within the recess 103 to provide an
upwardly facing flange for the lower end of the valve operator tube
flange 101 to engage so that when the valve operator tube moves
downwardly the flange 101 contacts the ring segments 104 pulling
the valve member 93 downwardly with the valve operator tube.
The concentric spaced relationship of the valve housing section 82
and the valve operator tube section 64 below the adapter sub 55
defines an annulus 112 for fluid flow to equalize the pressure
across the flapper valve and to house the spring 113 confined
between the stop ring flange 111 at the upper end of the spring and
an internal upwardly facing annular shoulder 114 in the housing
section 82 at the lower end of the spring. The spring 113 biases
the valve member 93 upwardly to a sealed seated relationship
against the seat 91 when the safety valve is fully closed as in
FIG. 1C and provides an upwardly directed force against the valve
operator tube and the valve member 93 when the flapper valve is
open as represented by FIGS. 3B and 3C. The lower end portion of
the valve operator tube probe section 64 has a side port 115 to
provide communication from within the tube into the annulus 112 for
pressure equalization. The valve housing section 82 has a lower end
portion 120 provided with a first reduced bore portion 121 which is
larger than the tube section 64 to permit communication into the
operator tube side port 115 when the tube is at the position shown
in FIG. 1D. The housing lower end portion 120 has a further reduced
bore portion 122 which is sized to provide a slip fit relationship
with the valve operator tube so that the tube may move down
longitudinally for operating the flapper valve.
The lower end portion 120 of the valve housing section 82 is
externally threaded at 123 and connected into a bottom section 124
which supports and encloses the flapper valve 13. The flapper valve
includes a valve plate 125 formed integral with a hinge arm 130
which is pivotally mounted on a lateral hinge pin 131 secured in a
pair of aligned bores 132 through opposite wall portions of the
valve housing section 124 near one side and aligned perpendicular
to the longitudinal axis of the housing section. The outer opposite
ends of the hinge pin are ground to the curvature of the outer
cylindrical surface of the valve housing 124 to provide a smooth
outer surface along the housing at the pin locations. The housing
section 124 has a longitudinal slot 133 aligned between the two
bores 132 to provide space for the hinge arm 130 and to allow the
hinge arm to swing between the positions of FIG. 1D and FIG. 3C for
opening and closing the flapper valve. A spring 134 is wound about
the hinge pin with one end of the spring engaged with the flapper
valve plate 125 and the other end extending along the inner face of
the valve housing below the slot 133 as seen in FIG. 1D to bias the
flapper valve plate to the closed position of FIG. 1D. The flapper
valve plate has an upwardly and inwardly tapered annular seat
surface 135 which is engageable with a downwardly and outwardly
tapered annular valve seat 140 of a hardened metal alloy secured at
the lower end of the housing section 82. The lower end portion 141
of the housing section 124 is increased in wall thickness providing
a reduced downwardly flared bore 142 and an upwardly facing tapered
stop shoulder 143 engageable by the lower end edge 64a of the valve
operator tube section 64 to limit the downward movement of the
operator tube after flapper valve is opened as shown in FIG.
3C.
The safety valve 10 in the particular form illustrated may be
installed in a well bore in a landing nipple having a side port
connected with a control line extending from the surface. The
safety valve is supported from a suitable locking mandrel 23, not
shown, which carries a packing assembly similar to the packing
assembly 51 for cooperating with the packing assembly 51 to seal
off an annular space in the landing nipple to direct the control
fluid to side port 33 of the safety valve. Installations of this
type are shown, for example, at Page 3501 of the Composite Catalog
of Oil Field Equipment and Services, 1972-73 Edition, published by
WORLD OIL, Houston, Texas. Locking mandrels of the type which may
be used are shown at Page 3458 of the Composite Catalog of Oil
Field Equipment and Services, supra. Additionally, a landing nipple
arrangement which may be employed is illustrated in FIGS. 13 and 14
of U. S. Pat. No. 3,292,706 issued Dec. 20, 1966 to G. C. Grimmer,
et al and assigned to Otis Engineering Corporation.
With the safety valve installed in a well bore and prior to the
application of control fluid pressure through the side port 33 in
the valve, the valve is closed with the various component parts of
the valve being positioned as illustrated in FIGS. 1A-1D. The
springs 71 and 113 are each expanded to the maximum length
permitted by the relation of the various parts of the valve holding
operator tube at an upper end position and the equalizing valve
assembly closed. The lower end of the tube 14, as seen in FIG. 1D,
is spaced above the flapper valve plate 125 of the valve assembly
13. Both valves of the equalizing valve assembly 20 are closed as
seen in FIG. 1C. The valve seat 92 on the valve member 93 is
engaged with the valve seat 91 within the lower end of the adapter
sub 55. Since the valve member 93 is limited from any further
upward movement and the top face of the flange 101 on the valve
operating tube section 64 is engaging the downwardly facing
shoulder 100 within the valve member 93, the valve operator tube 14
cannot move further upwardly. At this longitudinal position on the
valve operator tube, the vale flange 90 is aligned with and engages
the ring seal 85 of the adapter sub thereby closing the first valve
of the pressure equalizing valve assembly 20. The spring 134
together with any pressure differential that may exist across the
flapper valve plate 125 holds the flapper valve tightly closed as
shown in FIG. 1D. It will be recognized that the spring 71 bearing
against the spring ring 73 at the lower end of the piston 15 on the
valve operator tube 14 holds the operator tube at an upper end
position limited by the engagement of the flange 101 with the
internal shoulder surface 100 of the valve member 93. The force of
the spring 113 bearing against the ring 105 engaging the lower end
of the valve member 93 holds the valve member upwardly against the
seat 91.
When the safety valve 10 is to be opened, the control fluid
pressure as applied through side port 33 is increased so that the
pressure within the annulus 44 between the seals 43 and 63 is
raised. It is assumed for purposes of this discussion that a
pressure differential exists across the flapper valve 13 so that
effort to move the valve plate 125 downwardly is applied against
well pressure. When the force of the control fluid pressure
increase over the annular area on the piston and valve operator
tube defined by the seals 62 and 43 exceeds upward forces of the
spring 71 and the well pressure on the valve operator tube and
piston as communicated into the safety valve housing through the
side port 75, the valve operator tube 14 is moved downwardly.
During the initial downward movement of the valve operator tube,
the spring 71 is compressed and the flange 101 on the probe section
moves downwardly away from the shoulder 100 within the valve member
93 leaving the valve member 93 in seated engagement with the valve
seat 91. Because of the dual of the equalizing valve assembly and
the proximity of valve function the seal 85 to the engaged valve
seats 91 and 92, the fluid, if any, which may occur past the seal
85 when the flange 90 moves below the seal is considered negligible
so that the seal is protected against flow cutting during
equalization of pressures. FIG. 2 illustrates an intermediate stage
in the opening of the valve showing the valve operator tube flange
90 disengaged from and below the seal 85 with the valve member 93,
however, still closed. The valve operator tube continues downwardly
with the lower end edge of the flange 101 engaging the split ring
segments 104 to apply downward force to the valve member 93 which
is thereafter carried downwardly by continued downward movement of
the valve operator tube. When the flange 101 engages the split ring
segments, the separation of the valve seats 91 and 92 begins.
As soon as the valve member 93 moves downwardly off the seat 92,
the well pressure as applied to the safety valve housing through
the port 75 is communicated downwardly between the seats 91 and 92,
around the valve member 93, and through the annulus 112 to the side
port 115 to initiate pressure equalization between the well
pressure exterior of the safety valve housing and the bore through
the safety valve above the flapper valve 13. The lag between the
opening of the second valve of the equalization valve assembly 20
by downward movement of the valve member 93 and the time when the
lower end 64a of the valve operator tube probe section 64 engages
the flapper valve is scaled to provide adequate time for
substantial pressure equalization across the flapper valve so that
essentially the only resistence to opening the flapper valve is
provided by the spring 134. As the valve operator tube continues
downwardly, the lower end edge 64a of the operator tube probe
section engages the top face of the flapper valve plate 125 to
pivot the valve plate downwardly on the pin 131. The concave
configuration of the top surface of the flapper valve plate is
designed to cause the lower end edge 64a of the valve operating
tube to first engage the flapper valve plate along the opposite
side of the plate from the hinge pin 131 so that maximum leverage
is obtained by the downward force of the tube on the valve plate to
start the opening of the valve. The valve operator tube continues
downward movement until the lower end edge 64a of the tube engages
the stop shoulder 143 within the valve housing bottom section 124
at which time the flapper valve is fully open. FIGS. 3A, 3B, and 3C
show the relative positions of the valve parts when the valve is
open. It will be noted in FIG. 3C that the flapper valve plate 125
swings fully downwardly and outwardly to a vertical position into
an annular space defined between the tube section 64 and the
housing section wall. It will be noted in FIG. 3B that the flange
90 and the valve member 93 of the equalizing valve assembly are
substantially below the seal 85 and the seat 91. It will also be
noted that the seal 85 engages the valve operator tube along a wall
portion which would appear to form a seal between the housing and
the operator tube. In practice the operator tube at this location
along the tube is only about 0.006 to 0.010 inches larger than the
outside diameter of the flange 90, so some sealing may occur with
the seal 85, though it will be recognized that sealing is not
essential when the valve is fully open as there is no pressure
differential across the seal 85 and thus no tendency toward a fluid
flow along the seal which might cut it. Well pressure is applied
laterally inwardly into the housing in the port 74, and also well
pressure exists in the valve upwardly around the valve operator
tube and the valve member 93 to below the seal 85. It will be
recognized that from the time the flange 101 engaged the ring
segments 104 to move the valve member 93 downwardly, the spring 113
was compressed until the valve operator tube reached the lower end
of the stroke as represented in FIG. 3C. Thus, with the valve fully
open, the control fluid pressure applied through the side port 33
into the annulus must supply sufficient force on the piston 15 to
overcome the upward forces of the springs 71 and 113 and well
pressure on the piston 15. The well pressure acts upwardly on the
valve operator tube assembly over the annular area defined by the
lines of sealing engagement of the seals 43 and 63. The safety
valve remains open so long as the control fluid pressure is
maintained at a sufficiently high level. The control fluid pressure
will be maintained so long as well production is desired. The
control fluid pressure may be reduced to close the safety valve at
any time the well is to be shut in. Also the control fluid pressure
may be supplied by surface means designed to respond to such
conditions as fire, line rupture, and the like to shut in the well
under emergency conditions.
The safety valve 10 is closed by relieving the control fluid
pressure applied through the side port 33. When the force upon the
piston 15 from the control fluid pressure decreases below a value
which exceeds the force of the springs 71 and 113 together with the
well pressure, the valve operator tube 14 is lifted upwardly. The
operator tube is raised by forces from both the springs and the
well pressure until the tube and the associated parts of the valve
including those forming the pressure equalizing valve means 20 are
returned to the positions represented in FIGS. 1A-1D. At the lower
end position of the operator tube, both the springs 71 and 113 bias
the tube upwardly. Both springs lift the tube from the position of
FIGS. 3A-3C until the valve member 93 is closed as in FIG. 2.
Thereafter, the spring 71 only lifts the operator tube. As the
operator tube moves upwardly, the valve seat 92 on the valve member
93 engages the seat 91 in the valve housing before the operator
tube flange 90 contacts the seal 85. When the valve member 93
reaches the upper end position shown in FIG. 2, the valve operator
tube then continues upward movement until the flange 101 engages
the downwardly facing stop shoulder 100 within the valve member 93
at which time the flange 90 has moved into a seated relationship
within the seal 85. From the time that the seats 91 and 92 of the
second valve of the pressure equalization assembly engage shutting
off flow through the valve assembly, there is no fluid flow to cut
the seal 85 during the step of moving the sealing flange 90 on the
valve tube into engagement with the seal 85. As soon as the lower
end edge 64a of the valve operator tube probe section moves above
the seat 140, FIG. 1D, the spring 134 swings the flapper valve
plate 125 on the pin 131 upwardly toward the closed position at
which the valve plate is engaged with the seat 140 and is fully
closed. It will be evident that if there is any flow in the wall,
as soon as the flapper valve begins to restrict fluid entry into
the safety valve developing a pressure differential across the
valve, the valve plate will be rapidly closed by the fluid flow
into the valve bore. The valve will remain closed so long as the
control fluid pressure is below the level sufficient to overcome
the springs and the well pressure.
An alternate form 20A of the pressure equalizing valve assembly is
illustrated in FIGS. 5A and 5B. The valve assembly 20A discharges
the same pressure equalizing functions as the valve assembly 20
without the use of the large spring 113. With the exception of the
modification and elimination of parts required for the specific
structure of the valve assembly 20A, a safety valve using such
valve assembly is otherwise identical to the valve 10. Thus, the
reference numerals used in describing the structure of FIGS. 5A and
5B shall be the same as those used in conjunction with the other
figures with the exception that modified valve parts shall be
referred to with the suffix A. The valve operator tube used with
the modified equalization valve assembly 20A includes a tube probe
section 64A having an external annular elongated flange 101A.
Formed on the tubular section at the upper end of the flange 101A
is an enlarged tubular portion 150 which functions as a spring
guide or centralizer. The upper end of the tubular portion 150 also
serves as an upper end stop for the operator tube engaging the
bottom face of the valve member head properly positioning the
flange 90A aligned with the seal 85. A valve member 93A which is
functionally identical to the valve member 93 is disposed around
the flange 101A within the valve housing section 82 for movement
between open and closed positions as shown in FIGS. 5A and 5B,
respectively. The valve member 93A has a head portion 94A to which
is secured the annular alloy seat 92 which is engageable with the
seat 91 within the valve housing. The valve member has a skirt
portion 95A to which are secured a plurality of circumferentially
spaced dependent or downwardly extending L-shaped collet fingers
151 for retaining the valve member on the flange 101A and
permitting the flange to pull the valve member downwardly. A spring
152 is confined between the internal downwardly facing shoulder
100A of the valve member head and the upper end face of the
operator tube flange 101A for biasing the valve member 93A upwardly
on the operator tube section thereby performing the same function
relative to the valve member as the spring 113.
In operation the equalizing valve assembly 20A functions to
equalize the pressure differential across the flapper valve 13 when
the valve is closed preliminary to opening the flapper valve in the
manner previously described. As the valve operator tube section 64A
moves downwardly in the process of opening the flapper valve, the
external flange 90A moves out of engagement with and below the seal
85 the distance permitted by the lag or spacing between the lower
end edge of the flange 101A and the lower ends of the collet
fingers 151. During the initial travel of the operator tube section
64A, prior to the engagement of the lower end edge of the flange
101A with the lower ends of the collet fingers 151, the spring 152
biases the valve member 93A upwardly holding the valve member seat
92 engaged with the valve housing seat 91. As soon as the
downwardly moving operator tube engages the collet fingers 151 at
the time of contact of the lower end edge of the flange 101A with
the lower ends of the collet fingers, the downwardly moving tube
pulls the valve member 93A downwardly with the tube to open the
second valve of the valve equalizing assembly as the valve seat 92
moves downwardly from the valve seat 91. The valve member 93A is
carried downwardly by the operator tube as the operator tube moves
to the lower end position of FIG. 5B for fully opening the flapper
valve.
The valve member 93A remains in the position of FIG. 5B until
closure of the flapper valve. when the valve operator tube moves
back upwardly to close the flapper valve, the spring 152 retains
the valve member 93A at the upper end position of FIG. 5B until the
seat 92 on the valve member engages the valve housing seat 91 which
is substantially in advance of the movement of the valve tube
flange 90A into engagement with the ring seal 85. With the valve
member 93A closed, the valve operator tube continues moving
upwardly compressing the spring 152 until the upper limit of travel
of the operator tube is reached at which position the operator tube
flange 90A is engaged with the ring seal 85 thereby fully reclosing
both valve portions of the equalizing valve assembly. The
engagement of the upper end of the flange portion 150 with the
bottom face of the valve member head 94A stops the upward movement
of the operator tube and correctly positions the flange 90A aligned
with the seal 85.
While the safety valve 10 has been discussed in terms of use in a
landing nipple in a well bore supported from a locking mandrel
engaged with locking recesses of the landing nipple, it will be
understood that the safety valve is also usuable as an integral
part of a tubing string to which a control line is run from the
surface. In this form, the safety valve may be referred to as a
"tubing retrievable" type safety valve connected in the general
arrangement illustrated at Page 3503 of the Composite Catalog of
Well Field Equipment and Services, supra. In this arrangement the
safety valve functions identically as previously described with the
control line extending from the surface connecting into the side
port 33 through a suitable fitting of the type illustrated at the
reference.
It will be seen that a new and an improved form of flapper-type
downhole safety valve has been described and illustrated. It will
be further seen that the safety valve includes a pressure
equalizing valve assembly to reduce the pressure differential
across the flapper valve element preliminary to opening the valve
so that the valve is not opened against a full well pressure. The
equalizing valve assembly essentially comprises two valves, one of
which uses a metal-to-metal seal arrangement while the other
includes a resilient member providing a bubble tight seal. In both
forms of the equalizing valve assembly illustrated and described,
the closing and opening of the two valves of the assembly during
both the closing and opening of the safety valve occur in an order
which essentially eliminates fluid flow across the resilient valve
seal. Thus, during the opening of the safety valve the resilient
valve opens first followed by the opening of the metal-to-metal
valve. During the closing of the safety valve, the metal-to-metal
valve closes first followed by the closing of the resilient valve.
With this arrangement, there is no metering of fluid past the
resilient seal so that the seal is protected from flow cutting.
* * * * *