Note: Descriptions are shown in the official language in which they were submitted.
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DUAL BARRIER INJECTION VALVE
WITH A VARIABLE ORIFICE
BACKGROUND OF INVENTION
1. Field of the Invention
This invention is directed to an injection valve typically used in conjunction
with an
injection well. Injection wells are drilled for example in close proximity to
hydrocarbon
producing wells that have peaked in terms of their output. Fluid for example
water is
pumped under pressure into an injection well to maintain the pressure of the
underlying
formation as the well is produced. Injected water acts to force the
hydrocarbons into adjacent
producing wells thus increasing the yield.
2. Description of Related Art
U.S. Patent No. 7,866,401 discloses an injection safety valve having a
restrictor, also
known as an orifice, create a pressure differential so as to move a flow tube
past a flapper
valve. The diameter of the restrictor is fixed.
A problem with injection valves is a phenomenon known to those of normal skill
in
the art as "chattering". Chattering occurs when the injection rate is
insufficient to allow the
valve to fully open, whereby the flow across the fixed orifice (the standard
in injection
valves) is too low to compress the power spring and shift the flow tube into a
position to
hold the flapper into the fully open and protected position.
Chattering causes the flapper to intermittently and rapidly slam into the
flapper seat
causing premature failure of either the flapper and/or seat. Such failure can
cause an unsafe
well condition necessitating premature, immediate shut in of the well, and
expensive well
remediation,- sometimes costing tens of millions of dollars in the instance of
subsea wells.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the invention includes providing a tubing retrievable
injection
valve having a full bore internal diameter when running and retrieving the
valve. A "slick-
line" or "wireline" retrievable "nozzle assembly" having an orifice is carried
by and affixed
in the wellbore by a lock assembly. The nozzle assembly is retrievable without
removing the
injection valve. Consequently the diameter of the nozzle may be changed on the
surface. The
injection valve also has a temporary lock out feature so that the valve may be
placed in the
well in a lock out mode. In certain situations where the flow rate of the
water may vary, an
embodiment of the invention includes a nozzle assembly with a variable orifice
to provide an
infinitely variable downhole nozzle. The nozzle is designed to generate a
pressure drop
sufficient to hold the flapper valve fully open. This prevents the flapper
valve from
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"chattering" and isolates the flapper valve from fluid flow during injection
both of which are
harmful to the flapper valve assembly.
Additionally, in yet further embodiment of the invention, a pair of opposite
pole
magnets are provided. One magnet is attached to an upper sleeve of the nozzle
assembly and
a second magnet is attached to a middle sleeve member which carriers a
variable orifice. In
the run-in position, the flapper valve is locked out and the variable orifice
insert permits flow
of liquid in both directions. In the set position within the well, the upper
sleeve and middle
sleeve are locked together and injection into the well is permitted. Once the
flowrate is
decreased at the surface, the variable orifice insert resets into the fully
closed position while
a return spring returns the flow tube to the initial position allowing the
flapper to close. Once
injection resumes, the differential pressure across the variable orifice
insert is very high
because it's held in a closed position by the strong magnets. Hence the
variable orifice insert
moves to a position which opens the flapper valve before any flow is
established through the
injection valve. In this manner, no flapper chattering is possible. As the
injection flow rate is
increased, the variable orifice insert will open a greater area in response to
the flow rate to
allow more flow to pass through the internal restriction. As the restriction
is opened by flow,
the magnet force is decreased allowing very low operational differential
pressure during
operation. The operating differential pressure must be above the opening
differential pressure
for the flow tube and flapper valve to stay open during injection. When the
injection flowrate
is decreased, the flapper will close thus protecting the valve surface from
produced injection
water.
The variable output nozzles are designed so that as flow occurs, the flow tube
will
first move in a direction to open the flapper valve and then the output area
of the nozzle will
increase with increased flow rates.
The nozzle assembly can either be run pre-installed in the injection valve
prior to
running or after the injection valve has been set, utilizing
wireline/slickline operations to
insert and or remove the nozzle assembly from the injection valve.
A further embodiment of the invention is directed to a wireline retrievable
injection
valve that includes a flapper valve at one end and an axially movable sleeve
within which is
mounted to a second valve. The second valve is pressure responsive and
includes a variable
orifice.
According to another embodiment of the invention, the valve may be designed as
a
flapperless injection valve thus simplifying the design and construction of
the valve.
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BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
FIG. 1 is a cross sectional view of an embodiment of the valve in a lock out,
running
position.
FIG. 2 is a cross sectional view of an embodiment of the valve in a pre-
injection
position with the valve member closed.
FIG. 3 is a cross-sectional view of the retrievable orifice selective lock
assembly.
FIG. 4 is a perspective view of the retrievable nozzle selective lock
assembly.
FIG. 5 is a cross sectional view of a valve showing the retrievable nozzle
selective
lock assembly located within the valve body.
FIG. 6 is a cross sectional view of a valve in an open injection position.
FIG. 7 is a cross-sectional view of a second embodiment of a retrievable
nozzle
selection lock assembly according to the invention.
FIG. 8 is a cross-sectional view of the embodiment of FIG. 7 shown in a fully
open
condition.
FIG. 9 is a cross-sectional view of a third embodiment of a retrievable nozzle
selective lock assembly according to the invention.
FIG. 10 is a cross-section view along line 10-10 of FIG. 11 of a fourth
embodiment
of a retrievable nozzle selective lock assembly according to the invention.
FIG. 11 is an end view of the retrievable nozzle assembly of FIG. 10.
FIG. 12 is a cross-sectional view of the nozzle core member of the embodiment
of
FIG. 10.
FIG. 13 is a cross-sectional view of an embodiment of the valve according to
the
invention with the variable nozzle assembly of the embodiment shown in FIG. 10
in the
closed position.
FIG. 14 is a cross-sectional view of the embodiment shown in FIG. 13 with the
flapper valve in the open position.
FIG. 15 is a cross-sectional view of the embodiment shown in FIG. 13 with the
flapper valve in the open position and the variable orifice in the open
position.
FIG. 16 is a cross-sectional view of a further embodiment of the invention
showing
the valve in the open position.
FIG. 17 is a cross-sectional view of the axially movable valve assembly with
the
secondary valve in the open position.
FIG. 18 is across-sectional view taken along., line H? 18-18 of FIG. 17.
FIG. 19 is a cross-sectional view of the axially moveable valve assembly with
the
secondary valve in the closed position.
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FIG. 20 is a cross-sectional view of a flapperless safety valve according to
an
embodiment of the invention.
FIG. 21 is a schematic representation of an injection well.
FIG. 22 is a schematic showing of an injection valve positioned within a
tubular
string of an injection well.
FIG. 23 is a view similar to FIG. 16 showing the flapper valve in the closed
position.
FIG. 24 is a perspective view of a further embodiment of a retrievable
variable outlet
assembly according to the invention.
FIG. 25 is a cross-sectional view of the embodiment of Fig 24 showing the
variable
outlet in a closed position.
FIG. 26 is a cross-sectional view of the embodiment of Fig 24 showing the
variable
outlet in an open position.
FIG. 27 is a view showing the position of the outer sleeve in the run-in
position.
FIG. 28 is a view showing the position of the inner movable valve member in
the
run- in position.
FIG. 29 is a view showing the resetting position of the outer sleeve in the
resetting
position.
FIG. 30 is a view showing the position of the inner movable valve member in
the
resetting position.
FIG. 31 is a view showing the position of the outer sleeve in the operational
position.
FIG. 32 is a view showing the position of the inner movable valve in the
operational
position.
FIG. 33 is cross sectional view of the variable orifice insert positioned in
the
injection valve housing showing the valve in the run-in position.
FIG. 34 is a cross sectional view of the variable orifice insert in the valve
housing in
the injection position.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, an embodiment of the injection valve 10 includes a
pressure
containing body comprising an upper valve body member 11, a tubular middle
valve body
member 12 suitably attached to the upper valve body member 11 by threads at
29, for
example, and a lower valve body member 13 which is connectable to a tubular at
its
downhole end. Valve body members 12 and 13 are secured to each other by
threads for
example at 34.
The injection valve 10 further includes an upper flow tube having a first
section 17
and a second section 14 which are secured together. Section 17 has an interior
nipple profile
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at 16 for receiving a tool. Section 14 has an elongated sleeve portion 19 that
extends to valve
seat 26 when the valve is in the position shown in FIG. I. Elongated sleeve
portion 19
includes a plurality of slots 32 as shown in FIG. 1. Ridges 33 are formed on
the inner
surface of sleeve 19 around slots 32 thus forming a collet. A shiftable lower
flow tube 31 is
positioned within the elongated sleeve portion 19 of the upper flow tube.
Shiftable lower
flow tube 31 has two annular grooves 35 and 36 on its outer periphery located
so as to form a
profile for engagement with ridges 33 on the inner surface of elongated sleeve
portion 19.
Shiftable flow tube 31 also has shifting profiles 39 and 38 at each end
thereof.
Middle body member 12 has a reduced diameter portion 25 that carries an
annular
valve seat 26. A flapper valve 27 is pivotably connected at 28 to valve seat
26 and is
resiliently biased to a closed position on valve seat 26 as is known in the
art.
A coil spring 18 is positioned about elongated sleeve portion 19 and is
captured
between shoulder 14 of the upper flow tube and an internal shoulder 41
provided within
middle valve body member 12.
In the temporary lock out running position shown in FIG. 1, shiftable flow
tube 31 is
positioned within the valve body so as to extend beyond valve seat 26 thereby
maintaining
flapper valve 27 in an open position.
When the valve is positioned within the well at the desired location, a
suitable
running tool is lowered into the well and engages the upper shifting profile
39 of shiftable
flow tube 31 and the flow tube is moved upwardly, to the position shown in
FIG. 2. The
uphole end portion 91 of the shiftable lower flow tube 31 will abut a shoulder
portion 92 of
the upper flow tube 15 as shown in FIG. 2. In this position, the resiliently
biased flapper
valve will be in the closed position.
The retrievable nozzle selective lock assembly (RNSLA) will now be discussed
with
reference to FIGs. 3 and 4. The RNSLA 50 includes a sleeve formed by generally
cylindrical
members 51, 52, 56 and, 53 having an interior flow passage 61. An inner
tubular member 56
is located within cylindrical member 52 and carries nozzle 53. A plurality of
selective
locking dogs 58 are located around a portion of its periphery as shown in FIG.
4. Leaf
springs 59 are positioned under locking dogs 58. RNSLA 50 includes an annular
packing
assembly 55. A replaceable and retrievable orifice nozzle 53 is releaseably
attached to the
body portion of the RNSLA and includes an orifice 54. Nozzle 53 may be
replaced on the
surface with another nozzle having a different size orifice 54.
FIG. 5 illustrates the position of the RNSLA within the injection valve prior
to the
injection stage. RNSLA may be lowered into the valve body by a suitable tool
to a position
where the selective locking dogs 58 engage the selective nipple profile 16 in
upper flow tube
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15. At this point the RNSLA will be physically connected to the upper flow
tube; however
flapper valve 27 is still in the closed position.
The next step in the process is to pump a fluid such as water under pressure
into the
valve body. As the fluid flows through the RNSLA, a pressure drop will occur
across orifice
54 which will cause the RNSLA and upper flow tube assembly 15, 14, as well as
shiftable
flow tube 31 to move downhole as shown in FIG. 6.
This movement will compress spring 18. The downhole portions of both the upper
flow tube and lower flow tube will be forced into contact with flapper valve
27 and as they
are moved further by the pressure differential, they will open the flapper
valve to the position
as shown in FIG. 6.
As long as the fluid is being pumped the injection valve will remain open.
However
when the pumping stops, compressed spring 18 will move the RNSLA and the upper
and
lower flow tubes back to the position shown in FIG. 5 in which the flapper
valve is in the
closed position.
FIG. 7 illustrates a second embodiment of the invention. In this case a
variable
output nozzle assembly 100 replaces the nozzle 53 shown in FIGS. 3 and 4.
Variable output nozzle assembly 100 includes an outer tubular cylindrical
casing
101. An axially moveable cylindrical sleeve 103 having an enlarged portion 107
is
positioned within casing 101 and has an end face 114 that extends outwardly of
casing 101.
Sleeve 103 has an interior flow passage 105 and also has a plurality of outlet
ports 104 that
are axially and radially spaced about its longitudinal axis. Sleeve 103
terminates in an end
face 116 that includes an outlet orifice 115. A coil spring 102 is positioned
between the
inner surface of casing 101 and the outer surface of sleeve 103 as shown in
FIG. 7. In the
relaxed position of FIG. 7, one end of the coil spring 102 abuts against
shoulder 108 on
enlarged portion 107 of sleeve 103 and the other end abuts against end face
109 of the casing
101.
At lower flow rates, the pressure drops across orifice 115 will be sufficient
to move
the lower flow tube to a position keeping flapper valve 27 open. As the flow
rate increases,
sleeve 103 is moved axially to sequentially move outlet ports 104 past the end
face 109 of
casing 101 as shown in FIG. 8, thereby allowing more fluid to exit the nozzle
to proceed
downhole of the flapper valve.
FIG. 9 illustrates a variation from the shape and location of the outlet
ports. In this
embodiment outlet ports may be relatively large circular openings 114 that are
axially offset
with respect to one another. Openings 114 may also be elliptical or wedged
shape or of any
geometric shape.
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The spring constants of springs 18 and 102 are chosen so that as fluid flow
begins,
the RNSLA will first move in a downhole direction opening the flapper valve
before sleeve
103 moves in a downhole direction.
FIGS. 10 ¨ 12 illustrate yet a further embodiment of the invention.
In this embodiment the variable output nozzle assembly includes a first fixed
portion
including a cylindrical tubular casing 124 having a solid conical core member
139 supported
therein by a plurality of struts 129 as shown in FIGS. 11 and 12. An outer
tubular sleeve
member 120 is fitted over casing 124 and includes a constricted portion 122
and conical
portions 131 and 132 on either side of constricted portion 122. Conical member
139 has a
first enlarged portion 130 followed by a tapered cone portion 123. Outer
sleeve member
120 includes a thin walled portion 121 that extends to an annular shoulder 126
such that an
annular space 133 is formed between casing 124 and thin walled portion 121. A
coil spring
125 is positioned within space 133 such that one end of the spring abuts
against a shoulder
134 on enlarged portion 126 of thin walled portion 121 and abuts against a
shoulder 135
provided on tubular casing 124. Thin wall portion 121 is detachably secured to
outer sleeve
member 12 at 140 for example by threads. In the position shown in FIG. 10, the
outer
surface of core member 139 engages constriction 122 so as to prevent flow.
As the flow rate of fluid is increased, outer sleeve member 120 will move to
the right
as viewed in FIG. 10. Due to the tapering of cone section 123, the outlet area
of the nozzle
at 122 will increase as the flow rate increases. Thus at lower flow rates
sufficient force will
be provided to maintain the flapper valve in the open position as well as at
high flow rates.
The embodiments according to FIGS. 7 ¨ 12 provide an infinitely variable
nozzle
which will minimize pressure drop over a range of injection flow rates. They
provide full
open flapper protection over the full range of injection rates thus
eliminating flapper chatter
due to partial valve opening during injection.
The variable output nozzles of FIGS. 7 ¨ 12 can be substituted for the nozzle
53
shown in FIG. 3 so that they can be placed and retrieved as a part of the
RNSLA shown in
FIGS 3 and 4.
FIGS. 13 ¨ 15 shown the sequential opening of the flapper valve and the
variable
orifice as flow is initiated in the well according to the embodiment of the
variable orifice
shown in FIG. 10. The difference between FIGS. 5 and 6 and FIGS. 13 ¨ 15 is
that the
nozzle assembly 53 of FIGS. 5 and 6 has been replaced by the nozzle assembly
of FIG. 10.
In the position shown in FIG. 13, the flapper valve 27 is closed and the outer
surface
of core member 139 engages constriction 122 so as to prevent flow through the
nozzle. The
lower ends of upper flow tube 19 and lower flow tube 31 are positioned
adjacent the flapper
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valve 27. As fluid flow begins the upper and low flow tube along with the
variable orifice
nozzle assembly will move downwardly to the position shown in FIG. 14 due to
fluid
pressure thereby compressing spring 18. The spring constants for spring 18 an
spring 125
are selected so that during initial fluid flow the upper and lower flow tube
as well as the
variable orifice nozzle assembly will move to the position shown in FIG. 14
with the
variable orifice 122 still in a closed position. However, as fluid pressure
and flow increases,
outer sleeve member 120 will move downwardly with respect to tubular casing
124 in which
cone member 139 is fixed to the position shown in FIG. 15. In this position
fluid will flow
through variable orifice 122.
FIG. 16 illustrates a further embodiment of a wireline retrievable valve, as
is well
known by those with ordinary skill in the art, shown with the flapper valve in
an open,
injection position. Valve 200 includes a valve body having an upper lock
adapter 201, and
intermediate body housing 202 and a lower body housing 203 in which a
conventional
flapper valve element 224 is rotatably mounted. Valve element 224 is spring
biased to a
closed position as shown in FIG. 23. Valve 200 also includes an inlet 205 and
outlet 226.
An axially movable valve assembly 250 shown in FIGS. 17 and 19 is positioned
within the valve body and includes an inlet portion 204, an intermediate
portion 221 and a
sleeve portion 223. A spring 211 is captured between a shoulder 240 formed in
the outer
surface of inlet portion 204 and a step 241 formed in the interior surface 213
of intermediate
body housing 202. A tear drop body member 206 similar to body 130 shown in
FIG. 12 is
supported within inlet portion 204 by a plurality of struts 207. An axially
movable nozzle
215 is positioned within inlet portion 204 and intermediate portion 221 of the
valve
assembly. Body 206 and movable nozzle 215 form a secondary valve having a
variable
annular fluid passageway 262 as shown in FIG. 17.
Nozzle 215 has a converging inlet section 216, a throat portion 261 and a
diverging
outlet section 208. Nozzle 215 moves axially with the second valve assembly
between
shoulder 230 in inlet portion 204 and a shoulder 231 formed on intermediate
portion 221 of
the second valve assembly as shown in FIGS. 17 and 19. A spring 214 is
positioned between
a shoulder 210 on the outer surface of the nozzle and a step 209 on the
intermediate portion
221. Axial movement of the nozzle 215 in a downward direction will compress
spring 214
as shown in FIG. 17. Nozzle 215 and body 206 form a valve.
Second valve assembly 250 includes an elongated sleeve 223 coupled to
intermediate
portion 221 for example by threads. Sleeve 223 is adapted to move downwardly
to open
flapper valve 224 as shown in FIG. 16 when fluid is pumped into the well via
tubing 403
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shown in FIG. 21. Further downward movement of sleeve 223 is restrained by a
shoulder
225 formed in lower body housing 203.
FIG. 21 shows the location of the valve 406 within a well. A well bore 607
extends
down to a formation 405 where the injected fluid is to be delivered. A tubular
string 403 is
connected to the well head 402 which typically includes a plurality of valves
409. A packer
404 is placed between the tubular string 403 and the well casing.
In operation, injection fluid is pumped through the well head into tubular
string 403
in which valve 406 is located. As shown in FIG. 22, valve 406 can be
selectively positioned
within the tubing string by a wireline nipple 407 for the tubulars 403 and by
wireline lock
411 having dogs 412 that cooperate with a groove 413 in the nipple in a manner
well known
in the art. Wireline lock 411 has packing 412 to seal the lock within the
nipple 407.
Fluid pressure will initially cause second valve assembly 250 to move
downwardly
to the position shown in FIG. 16 such that sleeve 223 moves flapper valve to
the open
position shown in FIG. 16. Continued fluid flow will cause nozzle 215 to move
downwardly
away from body 206 as shown in FIG. 17 to thereby allows fluid flow through
second valve
assembly 250.
Yet a further embodiment of the invention is illustrated in FIG. 20. This is
an
embodiment of the injection valve without a flapper valve. The valve 300
includes a main
body housing 301 and a lower body housing 322 attached to main body housing
301 via
threads 324 as an example.
Main body portion 301 has an upper connection 325 suitable for connection to a
wireline lock 411 for example. The valve includes an inlet 309 and outlet 323
for the
injection fluid. A solid tear-shaped body 302 is fixed within the main body
housing 301 by a
plurality of struts 303. A nozzle member 304 includes a converging inlet 308
and a
diverging outlet 311. A valve seat 305 is formed between the conveying and
diverging
portions of the nozzle and cooperates with body 302 to form a variable
constricted flow
passage through the valve as nozzle 304 moves axially. Nozzle 304 is moved
downwardly
against spring 306 in spring chamber 307 by a pressure differential. Spring
306 is captured
between a shoulder 310 on the exterior surface of the nozzle and a step 312
formed on the
upper end of lower body housing 322.
When fluid is pumped down to the valve, nozzle 304 will move downwardly to
open
up an annular fluid passageway between body 302 and nozzle 304. When fluid
flow is
terminated. spring 306 which is compressed as nozzle 304 is moved downwardly
will shift
nozzle 304 in an upward direction thus bringing surface 305 into contact with
body 302
thereby closing the annular fluid passageway and preventing flow back of
fluid.
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FIG. 24-34 depict a further embodiment of the dual barrier valve of the
invention.
FIG. 24 illustrates a retrievable nozzle select lock assembly (RNSCA) 500
which
includes a variable orifice insert similar to that shown in FIG 13 and 14 at
19, 31, and 124.
The RNSCA is designed to be positioned within an injection valve which
includes an upper
valve body member 11, a middle valve body member 12 and a lower valve body
member 13
which includes a flapper valve assembly 26, 27.
The RNSCA includes an upper sleeve 501 have a standard internal fishing neck
profile 510. A middle sleeve 508 is attached to upper sleeve 501 by a
plurality of pins 506. A
first set of magnets 502 is positional between the upper and middle sleeves.
Middle sleeve
508 terminates in a tapered valve seat 516. An outer sleeve member 521 is
axially movable
with respect to middle sleeve 508. A pair of magnets 503 are attached to outer
sleeve
member 521 and move with the sleeve 521. Magnets 502 and 503 have opposite
poles that
attract each other. Pin 512 is secured to middle sleeve 508 and is positioned
within a
J-slot 542 formed in outer sleeve 521.
A gap 504 is formed between upper sleeve 501 and outer sleeve 521. A slightly
compressed spring 507 is positioned between middle sleeve 508 and outer sleeve
521 as
shown in FIG 25.
The RNSCA includes a plurality of seals 532 and a locking tab 533. A lower
sleeve
515 is attached to outer sleeve 521 by one or more pins 513. Lower sleeve 515
supports
inner valve member 520 by a plurality of struts 514. A spring guide sleeve 518
surrounds
middle sleeve 508.
FIGS. 27 and 28 show the portion of inner vale member 520 in the run in
position.
Pin 512 is located in the hook portion of the J-slot of outer sleeve 521. In
this position inner
valve member 520 is slightly spaced from valve seat 516 so that as the dual
valve assembly
is lowered into the well, fluid in the well may escape to the well head via an
annular orifice
551 between valve seat 516 and valve number 520 as shown in FIG 28.
In the resetting position of FIGS. 29 and 30, outer sleeve 521 and lower
sleeve 515
are movable down hole by fluid flow within the valve body and pin 512 is
positional with the
slot 542 as shown in FIG 29.
This allows outer sleeve 521 and valve body 520 to move upwardly thereby
closing
the valve. The valve is now ready for operation as shown in FIG 32. Water
under a given
pressure will move lower sleeve 515 in a downward direction to open flapper
valve 27. As
shown in FIG 26 increased pressure will act to move valve body 520 away from
valve seat
516 to allow injection of water into the well.
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Figure 33 and 34 show the variable orifice insert positioned within an
injection valve
housing which includes upper body member 11, middle body member 12 and lower
body
member 13. A power spring 570 is positioned between a flange 571 which is
attached to
upper flow tube 572 and the flapper support 26. As the variable orifice insert
moves in a
down hole direction, spring 570 is compressed as shown in FIG. 34.
F1G.33 shows the valve in the run-in position with pin 512 positioned within
slot 542
as shown in Fig. 27. Fig. 34 shows the valve in the resetting position where a
low resetting
flowrate will develop to fully stroke and lock the flow tubes together. Power
spring 570 is
compressed by shoulder 571 of upper flow tube 572. Pin 512 moves to the
position shown in
FIG. 29. When the flowrate is decreased the variable orifice insert resets
into the fully closed
position as shown in FIG. 31 and 32. Power spring 570 returns the upper flow
tube 572 to
the initial position of FIG. 33 along with lower flow tube 31.
In this position the flapper valve 27 and the variable orifice insert are both
in the
fully closed position thus providing a dual barrier check valve for any fluid
flowing out of
the well. When injection resumes, the differential pressure developed across
the insert is
relatively high because it's held closed by the magnets. The variable orifice
insert opens the
flapper valve before any flow is established through the tool.
Consequently no flapper chattering is possible. As the flow rate is increased,
the
variable orifice inset will open to allow flow to pass through the variable
orifice. As the
orifice is opened by the flow, the magnetic force is decreased allowing very
low operational
differential pressure during injection operation. The operating differential
pressure must be
above the opening differential pressure for the flow tube and flapper system
to stay open
during injection. When the injection flowrate is decreased below a certain
valve, the flapper
will close protecting the surface from produced injection water.
The opening of the valve due to fluid flow is resisted by the spring force as
it is
displaced, by the spring pre load-force and by the magnetic force. These
forces balance each
other with the result that a low operating differential pressure is maintained
which results in
higher injection efficiency.
The following graph depicts the performance of the variable orifice nozzle
insert of
the present invention vs. the fixed orifice of the prior art.
The horizontal axis is the injection flowrate and the vertical axis represents
the
differential pressure across the orifice.
With a fixed orifice nozzle, as the flowrate increases and the pressure
differential is
below 20 psi, the flapper element will chatter as shown in the shaded area
until the opening
differential pressure is above 20 psi.
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Also the fixed orifice will take significantly higher flow to attain the
required
opening differential pressure. Also, the fixed orifice will require an even
higher flow for re-
setting the flow tube. Potentially, the re-setting differential pressure might
not be achieved at
all rendering the system useless.
In contrast, the variable nozzle of the present invention does not open until
the
flapper valve is moved to an open and protected position thereby completely
eliminating
chatter.
The variable orifice allows the user to re-set the valve with minimal flow and
will
consequently always operate above the flapper chattering zone.
Variable vs. Fixed Orifice
Insert Performance
Re-setting Differential
Pressure
Cr
vaT I, Orifice
To 0 ----------------
Opening Differential
\µ\\ Pressure
3 Flapper
Throttling Zone
0 ________________________________________________________
0 Injection Flowrate
Magnets 502 and 503 may be made of rare earth materials. The various sleeves
and
housing may be formed of austenitic stainless steels. The portion of the
assembly susceptible
to erosion, for example, the valve body 520 and lower sleeve 515 could be made
of erosion
resistant material such as tungsten carbide, ceramic material, hard faced
carbon steel, hipped
zirconium and stellite.
All of the embodiments may be deployed or retrieved using a wireline or
slickline
and are easily redressable and repairable. Furthermore, when injection flow is
stopped the
valve automatically will close, thereby protecting the upper completion from
back flow or a
blowout condition.
Although the present invention has been described with respect to specific
details, it
is not intended that such details should be regarded as limitations on the
scope of the
invention, except to the extent that they are included in the accompanying
claims.
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