Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SURFACE CONTROLLED SUBSURFACE SAFETY VALVE
BACKGROUND OF THE INVENTION
This inven-tion relates to surface controlled
subsurface safety valves used in the oil and gas industry
and particularly to hydraulically operated valves with
small piston areas and metal-to-metal seal systems.
DESCRIPTION OF RELATED ART
It is common practice to complete oil and gas
producing wells with safety systems including a subsurface
safety valve controlled from the well surface to shut off
fluid flow in the well tubing string. Generally such a
valve is controlled in response to fluid pressure conducted
to the valve from a remote location a-t the well surface via
a small diameter conduit (con-trol line) permitting the well
to be selectively shu~ in as well conditions require. The
surface controller is typically equipped to respond to
emergency conditions such as fire, broken flow lines, oil
spills, etc. Frequently it is necessary to conduct well
servicing operations through a subsurface safety valve.
The well servicing operation may require extending a
wireline tool string through the subsurface safety valve.
Examples of such services are pressure and temperature
testing. Additional well servicing procedures-are-required
to retrieve damaged downhole equipment.-- These procedures -
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result in periodic opening and closing of the safety valve.
2 ~3172~(~
Subsurface safety valves are shown in the following US
Patent Nos. 3,860,066; 3,8Z2,935; 4,344,602, 4,356,867; and
4,449,587. The present invention is shown within a flapper
type valve closure in the subsurface safety valve. US
Patent 3,860,066 teaches that a longitudinally movable
operator tube may control the opening and closing of ball,
poppet, or flapper type valve closure means within a
subsurface safety valve.
For some well completions, it is desirable to
install the safety valve at deep depths. For thesecompletions a small piston area is one way to minimize the
effect of hydrostatic fluid pressure from the control line
leading to the well surface. Pistons having a small cross
section in comparison to the cross section of the comple-te
valve assembly have been used in surface controlled
subsurface safety valves (SCSSV).
Examples of such pistons are shown in:
US PATENT TITLE
2,780,290 Surface Controlled Subsurface Tubing
Pressure Shut-Off Valve
2,798,561 Blowout Preventer for Wells
4,049,052 Subsurface Annulus Safety Valve
4,161,219 Piston Actuated Well Safety Valve
4,444,266 Deep Set Piston Actuated Well Safety
Valve
US Patent 4,378,931 teaches a surface controlled
subsurface safety valve which is operated by a
reciprocatiny hydraulic motor or piston mounted on the
~3.~728~
1 exterior of the safety valve housing.
Since a tubing retrievable safety valve cannot be
easily removed from the well bore for routine maintenance,
any failure of a fluid seal or accumulation of debris within
the safety valve can be very expensive to correct. All
sealing systems are subject to failure depending upon the
operating environment and design of the seals. For some
environments metal-to-metal seals produce longer life as
compared to elastomeric materials. Elastomeric, polymeric,
and metal-to-metal seal system have been used in SCSSV's.
Examples of metal-to-metal seal systems are shown in:
US PATENT TITLE
4,452,310 Metal-to-Metal High/Low Pressure
Seal
4,467,870 Fluid Pressure Actuator for
Subterranean Well Apparatus
4,475,598 Ball Valve Actuating Mechanism
4,527,630 Hydraulic Actuating Means for
Subsurface Safety Valve
4,583,596 Dual Metal Seal for a Well SaEety
Valve
US Patent 4,723,606 teaches an operator tube and a
valve closure means which can be cycled open and closed wi~h
a wireline tool.
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1 SUMMARY OF THE INVENTION
The present invention relates primarily to tubing
retri~vable safety valves having a housing connectable with
a well tubing string and a bore therethrough for
communicating well fluid flow with the tubing string, a
valve closure means mounted in the housing for movement
between a first open position and a second closed position,
and an operator tube in the housing to control movement of
the valve closure means between its first position and its
second position. ~he operator tu~e normally moves in
response to control ~luid pressure acting on a small
diameter piston and a spring biasing the operator tube to
move in opposition to the piston.
The present invention allows ~or the use of
metal-to-metal seals as desired to accommodate downhole
well conditions. Also, the present invention minimizes the
possibility of debris accumulation and allows for movement
of the operator tube by a wireline tool if it should
become stuck. The net result is a subsurface sa~ety valve
with increased downhole service life even though the well
fluids flowing therethrough may be harmful to the sealing
system or may contain sand, para~fin, calcium, sr other
materials.
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The outside diameter of the operator tube is
smaller than the inside diameter of the housing means
adjacent thereto This difference in diame-ters allows the
operator tube to slide longitudinally within the housing
means. The difference in diameters creates an annular
space which has a tendency to accumulate sand or other
debris carried by well fluids. If such deposits are
allowed to accumulate in the annular space, they may
prevent satisfactory functioning of the safety valve~
It is a principal object of the present invention
to provide a subsurface safety valve for use at greater
depths in oil and gas wells which minimizes the possibility
for sand or other debris to hinder proper functioning of
the safety valve.
It is another object of the invention to provide
a subsurface safety valve having an operator tube and
improved piston means which minimizes the number of
potential fluid leakage paths. The present invention has
one metal-to-metal seal which blocks well fluids from
entering the control line when the safety valve is in its
closed position.
It is a further object of the invention to
provide a subsurface safety valve having an operator tube
and piston means with a metal-to-metal seal system.
It is another object of the invention to provide
a subsurface safety valve having an operator tube with a
single, small diameter piston means offset from the
longitudinal axis of the operator tube. A bearing assembly
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1 and a flexible coupling between portions of the operator
tube are provided to minimize eccentric loading.
It is a further object of the invention to provide
a subsurface safety valve including flow channels hetween
the operator tube and valve housing to flush sand or other
debris which might hinder movement of the operator tube.
It is an object of the invention to provide an
operator tube and valve closure means which can be opened
and closed with a wireline tool.
Accordingly, in one aspect, this invention resides
in a safety valve for downhole use in a well comprising:
a. housing means having a longitudinal bore extending
therethrough;
b. valve closure means mounted in the housing means to
control fluid flow through the longitudinal bore;
c. the valve closure means having a first positlon
which allows fluid flow through the longitudinal bore and a
second position which blocks fluid flow therethrough;
d. an operator tube in the housing means to shift the
valve closure means from its second position to its first
position;
e. piston means for moving ~he operator tube in
res~onse to control fluid pressure from the well surface;
.
i 25
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- 6A -
1 f. the piston means disposed within the housing means
offset from the longitudinal bore
g. a bearing assembly carried on the exterior of the
operator tube with a plurality of ball bearings disposed
between an upper bearing race and a lower bearing race and
its outer diameter compatible with the interior of the
housing means and slidably disposed around the exterior of
the operator tube; and
h. the piston means engaging the bearing assembly to
transmit force to the operator tube.
In another aspect, this invention resides in a
- surface controlled subsurface tubing supported well safety
valve comprising:
a. tubular housing means having a longitudinal bore
therethrough and means on opposite ends for connecting the
housing means in a well tubing string to form a portion
thereof;
b. valve closure means mounted in the housing means to
control fluid flow through the longitudinal bore;
c. the valve closure means having a first position
which allows fluid flow through the longitudinal bore and a
second position which blocks fluid flow therethrough;
d. an operator tube in the housing means to shift the
valve closure means from its second position to its first
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- 6B -
1 pOSition;
e. the operator tube having first and second positions
which correspond respectively to the first and second
positions for the valve closure means;
f. piston means for moving the operator tube and valve
closure means to their first position;
g. means for biasing the operator tube to its second
position;
h. further means for bringing the valve closure means
to its second position;
i. the piston means including a single rod partially
disposed within a passageway offset from the longitudinal
bore; and
j. a bearing assembly carried on the exterior of the
operator tube between the piston means and the operator tube
biasing means whereby the bearing assembly isolates the
piston means from rotational forces generated by the
operator tube biasing means;
k. the operator tube biasing means further comprising
a first spring disposed on the exterior of the operating
tube between a first shoulder on the operator tube and a
shoulder on the interior of the housing means:
1. a load ring around the exterlor of the operator
tube intermediate the ends thereof;
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l m. one end of the rod securely engaged with the load
ring;
n. the load ring abutting the bearing assembly;
o. means for transmitting longitudinal force from the
piston means via the load ring to the operator tube, and;
p. the means for transmitting longitudinal force from
the piston means via the load ring to the operator tube
comprising a second shoulder on the exterior of the operator
tube and a second spring between the second shoulder and the
load ring.
In a further aspect, this invention resides in a
surface controlled subsurface tubing supported well safety
valve comprising:
a. tubular housing means having a longitudinal bore
therethrough and means on opposite ends for connecting the
housing means in a well tubing string to form a portion
thereof;
b. valve closure means mounted in the housing means to
control fluid flow through the longitudinal bore;
c. the valve closure means having a first position
which allows fluid flow through the longitudinal bore and a
second position which blocks fluid ~low therethrough;
d. means for biasing the valve closure means to its
second position;
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- 6D --
1 e. an operator tube in the housing means to shift the
valve closure means from its second position to its first
position;
f. the operator tube having first and second positions
which correspond respectively to the first and second
positions for the valve closure means;
g. means for biasing the operator tube to its second
position comprising a first spring disposed on the exterior
of the operator tube between a shoulder on the interior of
the housing means and a first shoulder on the operator tube;
h. piston means for moving the operator tube and valve
closure me3ns to their first position;
i. the piston means including a single rod partially
disposed within a passageway offset from the longitudinal
bore;
j. a load ring around the exterior of the operator
tube intermediate the ends thereof and one end of the single
rod securely engaged with the load rings
k. a bearing assembly carried on the exterior of the
operator tube between the load ring and the operator tube
biasing means;
1. the load ring abutting the bearing assembly to
apply force from the piston means to one side of the bearing
assembly and the biasing means applying force to ~he other
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- 6E -
1 side of the bearing assembly whereby the bearing assembly
isolates the piston means from rotational force6 generated
by the operator tube biasing means;
m. the load ring disposed on the exterior of the
operator tube between the first shoulder and the operator
tube biasing means whereby longitudinal force from the
operator tube biasing means is transmitted via the bearing
assembly and the load ring to the first shoulder on the
operator tube; and
n. means for transmitting longitudinal force from the
piston means via the load ring to the operator tube
comprising a second shoulder on the exterior of the operator
tube and a second spring between the second shoulder and the
load ring.
Additional objects and advantages of the present
invention will be apparent to those skilled in the art from
studyiny the following detailed description in conjunction
with the accompanying drawings in which several preferred
embodiments of the invention are shown. In the drawings:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view in section and
elevation of a typical well completion including a tubing
retrievable subsurface safety valve with a flapper type
valve closure means.
2 8 ~
- 6F -
1 Figures 2A and 2B taken together form a
longitudinal view in section with positions broken away of a
subsurface safety valve and operator tube incorporating the
present invention showing the safety valve in its open
position.
Figure 3 is a drawing in longitudinal section wi-th
portions broken away of the subsurface safety valve shown in
Figures 2A and in its closed position.
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7 131 ~280
Figure 4 is a drawing in section -taken along line
4-4 of Figure 3.
Figure 5 is an enlarged view in section with
portions broken away showing improved pis-ton means offset
from the operator tube.
Figure 6 is an exploded orthographic projection
of the components of the pis-ton means, the bearing
assembly, and flexible coupling.
Figure 7 is an enlarged drawing in section with
portions broken away showing a first adapter to attach a
control line conduit to the subsurface safety valve of
Figure 2A.
Figure 8 is an enlarged drawing in section with
portions broken away showing a second adaptor to attach a
control line conduit to the subsurface safety valve of
Figure 2A.
Figure 9 is an enlarged drawing in section with
portions broken away showing an enlarged view of the
flexible coupling and bearing assembly with an alternative
small spring.
Figure 10 is a drawing in section with portions
broken away showing an al-ternative piston means as compared
to Figure 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the following description, like parts are
designed throughout the specification and drawings with the
same reference numerals. The drawings are not necessarily
to scale. Portions of some parts have been exaggerated to
8 :~3~2~
better illustrate details of the present invention.
Referring to Figure 1, well completion 20
includes casing s-tring 28 extending from the well surface
to a hydrocarbon producing formation (not shown). Tubing
string 21 is c~ncentrically disposed within casing 28 and
extends from wellhead 23 through production pack~r 22 which
seals between tubing string 21 and casing 28. Packer 22
directs formation fluids such as oil, gas, water, and the
like into tubing string 21 from perforations (not shown) in
casing 28 which admit formation or well fluids into the
well bore. Well fluids frequently carry sand or other
debris which may accumulate at locations in tubing string
21 having low fluid velocity. Flow control valves 24a and
24b at the well surface control fluid flow from tubing
string 21. Wellhead cap 27 is provided on wellhead 23 to
permit servicing well 20 via tubing strin~ 21 by wireline
techniques which include the installation and removal of
various downhole -tools (not shown) within tubing string 21.
Other well servicing operations which may be carried out
through tubing string 21 are bottom hole temperature and
pressure surveys.
Surface controlled subsurface safety valve 30
embodying -the features of the invention is installed in
well completion 20 as a part of tubing string 21 to
~5 control fluid flow to the well surface via tubing string 21
from a downhole location. Safety valve 30 is operated by
control fluid conducted from hydraulic manifold 25 at the
well surface via control line conduit 26 which directs the
9 ~ 3 ~
control fluid signal to safety valve 30. Hydraulic
manifold 25 generally includes pumps, a fluid reservoir,
accumulators, and control valves for the purpose of
providing control fluid pressure signals for holding valve
30 open or allowing valve 30 to close when desired.
Manifold 25 also includ~s apparatus which functions in
response to temperature, surface li~e leaks, and other
emergency conditions under which well 20 should be shut in.
Safety valve 30 includes flapper type valve
closure means 31 mounted on hinge 34 for swinging between
its closed position schematically represented in Figure 1
and i-ts open posi~ion in Figure 2B which permits fluid flow
through tubing string 21. When a predetermined pressure
signal is applied to safety valve 30 through control line
26 from manifold 25, valve closure means or flapper 31 is
maintained in its first or open position. When the control
pressure signal is released, valve 30 is allowed to move it
to its second or closed position.
Details for construction of the preferred form of
valve 30 are shown in Figures 2A and 2B. Subsur*ace safety
valve 30 has housing means 60 formed by housing
subassemblies 61,62, and 63 which are suitably
interconnected by threaded joints 65. Subassemblies 61,62,
and 63 could be interconnected by welded joints or by a
combination of threads and elastomeric seals. Welding is
sometimes unsatisfactory due to requirements for heat
treating before and after. Elastomeric seals in some
environments (high pressure, high temperature gas) have a
lo ~ ~72~
tendency to fail during pressure transients. Threaded
joints 65 are preferred because they have mechanical
strength comparable to a welded connection and a metal-to-
metal seal. US Patent 2,992,019 discloses threads and a
metal-to-metal seal sys-tem similar to thraaded joint 65.
Threaded joint 65 is sometimes referred to as a
two-s-tep thread because the diameter of threaded portion
65a is substantially larger than threaded portion 65b.
Depending upon the type of ma-terials used to manufacture
housing means 60, diameter 65b and the length of threaded
portions 65a and 65b may be increased or decreased so that
threaded joint 65 has mechanical s-trength equal to or
greater than any other portion of housing means 60u
Threaded joint 65 is particularly desirable because it
allows many alternative with respect to designing housing
means 60 but is relatively easy to manufacture and
assemble.
Housing means 60 can be generally d~scribed as a
long thick walled cylinder with longitudinal bore 67
extendiny therethrough. The ends of housing subassemblies
61 and 63 may be internally or externally threaded to
provide means on opposite ends of housing means 60 for
connection with tubing string 21. A lockout sleeve ~not
shown) could be incorporated into safety valve 30 if
desired to hold valve closure means 31 open. Lockout
sleeves which can be shifted by wireline tools to
permanently or temporarily hold valve closure means 31 open
are known in the art.
11 ~ 3172~
Housing subassembly 61 has threaded connection 29
to attach control line 26 to safety valve 30. Control
fluid pressure signals are communicated from -the well
surface via control line 26, threaded connection ~.9,
drilled passageway 66, and offset passageway 80.
Passageway 80 is machined in the wall of housing
subassembly 61 parallel with but offset from longitudinal
bore 67. Passagew~y 80 has two portions, namely upper
chamber 81 and piston chamber 82. Inside diamet~r 81a of
upper chamber 81 is smaller than inside diameter 82a of
piston chamber 82. This change in diameters creates
seating surface 83 therebetween. Both inside diameters 81a
and 82a are substan-tially smaller than the inside diameter
of longitudinal bore 67 adjacent thereto.
Operator tube 40 is slidably disposed within
longitudinal bore 67 to shift valve closure means 31 from
its second, closed position as shown in Figure 3 to its
first, open position as shown in Figure 2B. Operator tube
40 is constructed from two or more generally hollow,
cylindrical sections designated 40a and 40b. Sections 40a
and 40b are ~oined together by ~lexible coupling means 70.
Piston means 90, disposed in housing means 60 offset from
longitudinal bore 67, moves operator tube 40 in response to
control fluid pressure from the well surface. A portion of
piston means 90 is slidably disposed in offset passageway
80.
Piston means 90 has two main components -- seal
assembly 91 and cylindrical rod 100. O-ther components of
12 13~72~
piston means 90 ~re shown in F'igures 5, 6 and 10. Seal
assembly 91 includes seat insert 92 and piston ring carrier
93. Seat insert 92 i5 similar -to a machined bolt. Head 94
of insert 92 has metal seating surface 95 machined thereon
to mate with seating surface 83 of offset passageway 80.
Insert 92 is attached to piston ring carrier 93 by threads
96. Pr~ferably, resilient seal ring 97 is disposed between
head 94 and carrier 93.
Resilient seal ring 97 functions as a backup for
metal-to-metal seating surfaces 83 and 95.
The configuration of seal assembly 91 within
offset passageway 80 results in only one possible leak path
for well fluids to enter control line 26 when safety valve
30 is closed. This leak path is blocked by engagement of
metal-to-metal seating surfaces 83 and 95 when safety valve
30 is closed as shown in Figure 3. Spring 54 assists in
maintaining this metal-to-metal seal when there is only a
small difference between control fluid pressure and well
fluid pressure. NOTE: Well fluid pressure would only be
present at seating surfaces 83 and 95 if valve closure
means 31 was also leaking. Normally, valve closure means
31 blocks well fluid flow when safety valve 30 is in its
closed position~
Three piston rings 98 are disposed in separate
grooves on the e~terior of carrier 93. Piston rings 98 are
sized to fit snugly within inside diameter 82a and
su~stantially limit fluid flow past seal assembly 91.
Metal seatin~ surfa~e 99 is provided on the end of carrier
13 ~ 3~
93 opposite from head 94. Seal assembly 91 is attached to
the upper end o rod 100 hy threads 101. Therefore, seal
assembly 91 and rod 100 move as a single unit in response
to control fluid pressure in piston chamber 82. Me-tal
sea-ting surface 99 may be provided on rod 100 as shown in
the alternative embodiment of Figure 10.
The exterior of opera-tor tube 40 and the interior
of housing subassembly 62 partially defines annulus 50
therebetween. Piston rod 100 extends from the lower end of
housing subassembly 61 into annulus 50. During assembly of
safety valve 30, seat insert 92 is engaged with piston ring
carrier 93 to form seal assembly 91. Cylindrical rod 100
and seal assembly 91 are then threaded together to form
piston means 90 and partially disposed within offset
passageway 80 of housing subassembly 61~ Metal seat insert
102 is sized to slide over rod 100 and thread into piston
chamber 82 at its exit from the lower end of housing
subassembly 61. Piston rod 100 is sized to slide
longitudinally through metal seat insert 10~. However,
seal assembly 91 is too large to move therethrough. One
function of metal seat insert 102 is -to re~ain seal
assembly 91 within piston chamber 82. Resilient seal ring
104 and retainer ring 103 are preferably disposed on the
end of insert 102 within chamber 82. Resilient seal ring
104 is sized to engage metal seating surface 99 o~ seal
assembly 91 and to form a fluid barrier therewith.
Resilient seal ring 104 is ins~alled to provide a backup
for metal-to~metal seals 99.
14 13~72~
- Flange 41 is machined on the exterior of operator
tube 40 -to fit within annulus 50. Flange 41 has a
generally circular cross section except for flat 42 and
notch 43 milled on opposite sides therefor. Flat 42
provides clearance for piston rod ~00 to extend through
annulus 50 past flange 41~ The lower end of piston rod 100
is engaged with load ring 106 which is sized to fit around
the exterior of operator tube 40 within annulus 50. Load
ring 106 has threaded holes 107 and 108 diametrically
opposite from each other. Hole 107 is provided to receive
threads 105 of piston rod 100. Hoie 10~ is provided to
receive alignment pin 109 having similar threads 105.
Alignment pin 109 is sized to fit within notch 43. Pin 109
and notch 43 cooperate to prevent rotation ~f load ring 106
relative to operator tube 40. Piston means 90 can apply
forces to load ring 106 which are -transferred to operator
tube 40 to open valve closure means 31. An opposing force
is applied to Load ring 106 by biasing means or spring 54
to move operator tube 40 and allow valve closure means 31
to move to its closed position. Load ring 106 is also
disposed between flange (first shoulder) 41 and coupling
means (second shoulder) 70 on the exterior of operator tube
40.
Biasing means or spring 54 is carried on the
exterior of operator tube 40 in spring chamber 53 which is
a portion of annulus 60. Spring chamber 53 is defined in
part by shoulder 62a and the inside diameter of housing
subassembly 62. Biasing means 54 appiies a force to slide
~3 ~7~
operator tube 40 longitudinally opposite from the force of
control fluid pressure in piston c~amber 82 acting on
piston means 90. When control fluid pressure in chamber 82
is decreased below a preselected valve spring 54 moves
operator tube 40 longitudinally upward to allow valve
closure means 31 to return to its second, closed position.
Spring 35 coiled around hinge 34 assists in moving flapper
31 to its closed position.
Operator tube 40 could be designed to allow
spring 54 to directlyh contact a shoulder on its exterior.
Such design is frequently used in commercially available
subsurface safety valves. Compression of spring 54 ~Figure
2B) and expansion of spring 54 (Figure 3) produces
torsional forces in addition to longitudinal forces.
Therefore, bearing assembly 120 is disposed on the exterior
of operator tube 40 between load ring 106 and spring 54.
Bearing assembly 120 isolates torsional forces generated by
spring 54 from operator tube 40 and piston means 90.
Longitudinal force from spring 54 is transmitted
via bearing assembly 120 to load ring 106 and then to Eirst
shoulder (flange) 41 on the exterior of operator tube 40.
Longitudinal force from piston means 90 is transmitted via
load ring 106 and small sprin~ 57 to second shoulder
(flexible coupling) 70 on the exterior of operator tube 40.
Longitudinal force to shift valve closure means
31 to its open position is initiated by supplying a
preselected amount of control fluid pressure to piston
chamber 82. Piston means 90 converts control fluid
16 '~ ~1728~
pressure to a longitudinal force which is transferred via
rod 100 to load ring 106. A small spring 57 is positioned
between flexible coupling means 70 and load ring 106.
Longitudinal force on load ring 106 via small spring 57 is
transferred to flexible coupling means 70. Since flexible
coupling means 70 is an integral portion of operator tube
40, the longitudinal force will move operator tuhe 40 to
open valve closure means 31.
At the same time as load ring 106 is applying
longitudinal force to flexible coupling means 70,
longitudinal force is also being applied to spring 54 via
bearing assembly 120 and flange ll9. Keeper sleeve 118 is
generally cylindrical and sized to fit around operator tube
40 and flexible coupling means 70. Flange 119 on the
exterior of keeper sleeve 118 provides a rest for bearing
assembly 120. Spring 54 contacts the bo-ttom of flange 119
and bearing assembly 120 the top. Thus, torsional forces
from compressing spring 54 are isolated from piston nteans
90. An alternative design, keeper sleeve 118a, is shown in
Figure 9.
Longitudinal ~orce to shift operator -tube 40 in
the opposite direction to allow valve closure means 31 to
move to its closed position is supplied primarily by
biaslng means or spring 54. First control fluid pressure
in piston chamber 82 is decreased below a preselected
valve. Spring 54 can then expand. Longitudinal force from
expansion of spring 54 is applied to operator tube 40 via
flange 119, bearing assembly 120, and load ring 106.
17 ~ ~ ~ 7 r~ ~ ~
During expansion of spring 54, load rlng 106 contacts the
bottom of flang~ 41 to return operator tube 40 to its
second position. Bearing assembly 120 isolates operator
tube 40 and piston means ~0 from torsional forces generated
by expansion of spring 54.
Stationary scraper seal 54 is carried on the
interior of housing subassembly 61 near the upper end of
operator tube 40. Stationary seal 45 acts as a scraper or
trash barrier to prevent sand or other debris from entering
annulus 50.
If desired, operator tube 40 could be machined
fro~ a single piece of raw material or sections 40a and 40b
joined together by threads. However, such construction
requires adherence to many close tolerances for proper
functioning o~ operator tube 40 within longitudinal bore
67~ Also during slam closure of flapper 31, operator tube
40 may be damaged by high stress loading. Operator tube 40
as shown in Figures 2A and 2B compensates for variations in
manufacturing tolerances and provides for easier assembly
by using fle~ible coupling or connecting means 70.
Flexible coupling 70 also compensates for slam closure
forces. As best shown in Figure 6, flexible coupling 70
comprises two split rings 71 and 72. Each split ring 71
and 72 has a pair of inwardly facing flanges 73 and 74 that
engage matching grooves 75 and 76 on operator tube sections
40a and 40b respectively. Recesses 77 and 78 are machined
into the end of sections 40a and 40b respec-tively facing
each other. Sand barrier ring 79 fits within recesses 77
18 l3~L7?~80
l and 78 between sections AOa and 40b. During assembly, ring
79 is inserted into recess 77. Section 40b is then
positioned adjacent to and aligned with section 40a with
ring 7g partially disposed in recess 78. Split rings 71
and 72 are next engaged with groov2s 75 and 76. Split
rings 71 and 72 cause operating tube sections 40a and 40b
to move together in unison within longitudinal bore 67
while allowing limited flexing to compensate for minor
variations in dimensional tolerances bet~een operator tube
40 and th~ interior of housing means 60. During slam
closure, section 40b can be axially displaced a limited
; amount without transferring this force to section 40a or
piston means 90. Keeper sleeve 118 is sized to slide over
the exterior of operator tube section 40b and to securely
engage split rings 71 and 72 with each other. Sand barrier
ring 79 restricts fluid flow between the adjace~t ends of
sections 40a and 40b. Ring 79 can be manufactured from a
wide variety of elastomers and copolymers. Teflon based
material has proven satisfactory for ring 79.
For ease of manufacture and assembly, valve seat
37 is machined as part of housing subassembly 62 within
longitudinal bore 67. Valve seat 37 could be manufactured
as a separate component and inserted into housin~
subassembly 62. V~lve seat 37 as shown in Figures 2B and 3
has a circular cross section. Valve seat 37 has a hardened
surface 140 to form a metal-to-metal fluid seal with
matching surface 141. Copolymeric or resilient seal means
147 is carried by valve seat 37 to provide a backup fluid
*Trademark
8 ~
19
seal when valve closure means 31 is in its second, closed
position. An important feature of valve seat 37 is flow
channels 38 machined on the inside diameter o~ housing
subassembly 62. Hardened metal seating surfaces 140 and
141 are particularly desirable when valve closure means 31
is subjected to slam closure. Resilient seal means 147 is
particularly beneficial for providing a fluid tight barrier
at low pressures.
SAND OR DEBRIS CONTROL
Sand or other debris, contained in the well
fluids, has a tendency to settle out or accumulate in areas
of low fluid flow velocity. Examples of such areas are the
top of operator tube 40 when safety valve 30 is open and
spring chamber 53. A plurality of small ports or flow
nozzles 46 extend through the upper end of operator tube
40. Flow nozzles 46 are machined at an acute angle
relative to the longitudinal axis of operator tube 40 and
are evenly spaced around the circumference thereof. A
portion of the well fluids flowing through operator tube 40
wlll exit via flow nozzles 46 and create turbulent flow
within housing means 60 adjacent thereto. Turbulant flow
at this location tends to scour the inside diameter of
housing means 60 and to prevent debris accumulation on top
of scraper ring 45. The number, size, and acute angle
associated with flow nozzles 46 can be varied to
accommodate the internal dimensions of safety valve 30 and
the characteristics of the well fluids flowing
728~
therethrough.
Another potential area to accumulate debris is
annulus 50 between the inside diameter of housing means 60
and the outside diameter of operator tube 40. Coupling
means 70 with ring 79 blocks well fluid flow between the
ends of operator tube sections 40a and 40b. When safety
valve 30 is in its full open position as shown in Figure
2B, lower end 49 of operator tube 40 contacts tapered
shoulder 68 to form a fluid barrier therewith. Spring 57
(Figure 2, 3 and 6) or alternative spring 157 (Figure 9) is
positioned between load ring 106 and coupling means ~second
shoulder) 70 on the exterior of operator tube 40. Spriny
57 or 157 is used to protect lower end 49 of operator tube
40 and tapered shoulder 69 during slam opening of safety
valve 30. They function as a lost motion device to allow
limited movement of load ring 106 relative to operator tube
40. Spring 57 or 157 controls the amount of force with
which lower end 49 contacts tapered shoulder 69. The
amount of force is a significant factor in de-termining the
sealing characteristics of this fluid barrier. Thus the
present invention minimizes the entrance points for well
fluids to carry debris into annulus 50.
Spring chamber 53 is generally filled with
stagnate well fluid. During the opening and closing of
valve closure means 31, spring 54 will expand and contract
within spring chamber 53. This movement of spring 54 will
result in some well fluid flow into and out of spring
chamber 53. The lower portion of section 40b is
21 ~3~7~
substantially reduced as compared to the other portions of
operator tube 40 and valve seat 37. Therefore, while
operator tube 40 is moving valve closure means 31 from i-ts
closed position to its open position, well fluids and
debris will be discharged from spring chamber 53 via flow
channels 38. The dimensions for flow channels 38 are
selected to provide ~echanical support for the portion of
operator tube 40 adjacent thereto during slam closure.
Fluid will exit from spring chamber 53 when valve closure
means 31 is intermediate its first and second position.
The reduced diameter portion of secti~n 40b also minimizes
the possibility of operator tube 40 damaging valve seat 37
during slam closure of flapper 31.
ALTERNATIVE EMBODIMENTS
The previous description has been directed
towards an operator tube which opens a flapper type valve
closure means. US Patent 3,860,066 to Joseph L Pearce et
al demonstrates that operator tube 40 could be modified to
open and close ball type and poppet valve closure means in
addition to flapper 31. Therefore, the presen-t invention
is not limited to flapper valves.
Figures 7 and 8 show alternative control line
adapters 207 and 208 respectively which may be used to
attach control line 26 to housing means 60. Both adapters
207 and 208 have threads on their exterior for engagement
with threaded connection 29 of housing subassembly 61. The
lo~er portion of each adapter 207 and 208 forms metal-to-
22 :~3:L7~
metal seal 209 with the interior of drilled passageway 66
to prevent control fluid leaks. Control line 26 may be
sscured within openings 211 or 212 by welding, brazing,
fine pitch threads or a comhination thereof. Figures 7 and
5 8 demonstrate the flexibility of the present invention to
accommodate various adapters while maintaining fluid tight
integrity with metal-to-metal seals such as 209.
An important feature of the presen-t invention is
the metal-to-metal seal established by seati~g surface 95
of seal assembly 91 contacting seating surface 83 of offset
passageway 80 when safety valve 30 is in its second, closed
position. See Figure 3. Figure 9 shows the use of heavy
duty spring 157 between load ring 106 and flexible coupling
means (second shoulder) 70 on the exterior of operator tube
40. Spring 157 comprises a plurality of Belleville washers
to exert additional force on operator tube 40 to help hold
seating surfaces on lower end 49 and tapered shoulders 69
in fluid tigh-t contact. Coupling means 70 of Figure 9
shows a modified keeper sleeve 118a. Flange 119 has been
eliminated as compared to keeper sleeve 118 of Figures 2B,
3 and 6. The configuration shown in Figure 9 allows spring
54 to directly contact bearing assembly 120. Depending
upon installation depth, well fluids ~gas or liquid) and
control line fluid, spring 157 and keeper sleeve 118a may
offer improved performance as compared to spring 57 and
keeper sleeve 118 with flange 119.
Many varia-tions to seal assembly 91 of piston
means 90 are made possible by the present invention. Seal
23 ~3~7~
1 assembly 91 can be easily modi~ied to accommodate a wide
variety of downhole environments. Spring loaded piston
rings 98 are used to minimize yalling with honed inside
diameter 82a. Three piston rings 9 a are shown in the
drawings. This number may be increased or decreased as
required in specific well conditions and control line
fluids. Also, one or more metal piston rings 98 could be
replaced by an elastomeric or polymeric seal ring. Ryton
or Teflon based compounds may be used for some
applications.
Seal assembly 91a of Figure 10 shows the use of
u-cup (Variseals) seals ~20 and 221 on opposite ends
thereof. U-cup seals 220 and 221 are similar in design
construction to scraper ring 45. In particularly harsh
environments, they will assist with cleaning inside
diameter 82a during movement of piston means 90. U-cup
seals 220 and 221 may also function as a backup for metal-
to-metal seating surfaces 95 and 99 in the same manner a
previously described for resilient (Teflon) seal rings 97
and 104. The use of one or both u cup seals is optional
depending upon the well environment. U-cup seal 221 is
helpful to prevent gas migration into control line 26
during travel of piston means 90 between the first open
position and the second closed position.
For some downhole environments (high pressure gas
wells), a complete fluid tight harrier between annulus 50
and longitudinal flow passageway 67 may subject operator
tube 40 to excessive differential pressure. Various
*Trademark
- :~ 3 .11 ~ 8 ~
2~
modifications to operator tube 40 and i-ts associated seals
are possible to allow pressure equalization if required.
These modifications include placing one or more small
notches (not shown) in lower end 49 or drilling one or more
small holes (not shown) radially through the reduced
diameter portion of section 40b. These modifications would
be sizeds to prevent any substantial 1uid flow into
annulus 50.
The preceding written description explains only
some embodiments of the present invention. Those skilled
in the art will readîly see other modifications and
variations without departing from the scope of the
invention.
