U.S. patent application number 13/987707 was filed with the patent office on 2014-03-13 for downhole shutoff tool.
The applicant listed for this patent is Larry Rayner Russell. Invention is credited to Larry Rayner Russell.
Application Number | 20140069655 13/987707 |
Document ID | / |
Family ID | 50232058 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069655 |
Kind Code |
A1 |
Russell; Larry Rayner |
March 13, 2014 |
Downhole shutoff tool
Abstract
A downhole drilling valve tool, positioned above the drill bit,
which utilizes a ball valve having a through bore for normal flow.
The ball valve is operated bidirectionally by a piston driven
mechanism between an open position and a closed position. The
piston mechanism is responsive to a reference accumulator pressure
on a first side and the pressure in the apparatus bore above the
ball valve on a second side. Whenever the valve apparatus is
lowered at least a minimum distance into the well bore, a pressure
relief valve is used to maintain a fixed margin between the flowing
bore pressure and the accumulator pressure. Closure of the ball
valve occurs when the accumulator pressure exceeds the bore
pressure during pump stoppages. The downhole drilling valve tool
offers a more wear resistant sealing means, as well as higher
pressure operability than conventional downhole check valves.
Inventors: |
Russell; Larry Rayner;
(Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Russell; Larry Rayner |
Houston |
TX |
US |
|
|
Family ID: |
50232058 |
Appl. No.: |
13/987707 |
Filed: |
August 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61743629 |
Sep 7, 2012 |
|
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|
Current U.S.
Class: |
166/319 |
Current CPC
Class: |
E21B 21/10 20130101;
E21B 34/08 20130101; E21B 2200/04 20200501 |
Class at
Publication: |
166/319 |
International
Class: |
E21B 34/08 20060101
E21B034/08 |
Claims
1. A downhole shutoff valve for operation in a drillstring,
including: a) a housing having a through bore; b) an accumulator
positioned within the housing, wherein a gas chamber within the
accumulator is selectably chargeable with a gas to create an
accumulator pressure, and wherein the accumulator is in fluid
communication with a bore pressure present in the bore through a
pressure relief valve; c) a ball valve rotatable between a closed
position and an open position; d) an axially reciprocable piston
exposed to the accumulator pressure on a first side and the bore
pressure on a second side; and e) a valve rotational mechanism
connected to and operable by the piston, wherein the ball valve is
closed by the valve rotational mechanism when the accumulator
pressure exceeds the bore pressure and wherein the ball valve is
opened by the valve rotational mechanism when the bore pressure
exceeds the accumulator pressure.
2. The downhole shutoff valve of claim 1, wherein whenever the
accumulator pressure is greater than a pressure exterior to the
downhole shutoff valve by a predetermined margin, a pop off valve
opens and releases to the tool exterior an excess of the
accumulator pressure over the pressure external to the downhole
shutoff tool.
3. The downhole shutoff valve of claim 2, wherein the pop off valve
consists of a carrier and a poppet closed with a shear pin and
opened by shearing the shear pin.
4. The downhole shutoff valve of claim 1, wherein the through bore
has a latch groove.
5. The downhole shutoff valve of claim 4, further including a
lockopen tool that selectably interacts with the latch groove to
position the lockopen tool in the through bore to prevent opening
or closing of the valve.
6. A downhole shutoff valve for use in a drillstring including: a)
a housing having a through bore; b) a pressure relief valve in
fluid communication with the through bore; c) an accumulator
positioned within the housing having (i) an accumulator bore, (ii)
an accumulator charging port that provides selectable fluid
communication between an exterior of the accumulator and a gas
chamber to create an accumulator pressure, (iii) a mud chamber in
fluid communication with the through bore through a pressure relief
valve, and (iv) a separator piston having the mud chamber on a
first side and the gas chamber on a second side; d) a ball valve
rotatable between a closed position and an open position; e) an
axially reciprocable piston movable between a first position and a
second position, the reciprocable piston having the gas chamber
positioned on a first piston side and a through bore chamber in
fluid communication with the through bore positioned on a second
piston side; and f) a valve rotational mechanism interconnecting
the valve and the piston, wherein when the piston is in the first
position the ball valve is in the closed position and when the
piston is in the second position the ball valve is in the open
position.
7. The downhole shutoff valve of claim 6, wherein the reciprocable
piston is exposed to the accumulator pressure on the first piston
side and a through bore fluid pressure on the second piston
side.
8. The downhole shutoff valve of claim 7, wherein the reciprocable
piston is the first position when the accumulator pressure exceeds
the through bore fluid pressure and wherein the reciprocable piston
is in the second position when the through bore fluid pressure
exceeds the accumulator pressure.
9. The downhole shutoff valve of claim 6, wherein whenever the
accumulator pressure is greater than a pressure exterior to the
downhole shutoff valve by a predetermined margin, a pop off valve
opens and releases to the tool exterior an excess of the
accumulator pressure over the pressure external to the downhole
shutoff tool.
10. The downhole shutoff valve of claim 6, further including a
lockopen tool that selectably interacts with a latch groove in the
through bore to position the lockopen tool in the through bore to
prevent opening or closing of the valve.
11. A downhole shutoff valve for use in a drillstring including: a)
a first module having (i) a first body having a first end, a second
end, and a first through bore, (ii) a flow port extending into the
first body, wherein the flow port is parallel to and offset from
the first through bore, and (iii) a pressure relief valve in fluid
communication with the first through bore and the flow port,
wherein the pressure relief valve opens when a pressure in the
first through bore exceeds a pressure in the flow port by a
predetermined amount; b) an accumulator module having (i) a second
body having a first module end, a second module end, and a second
through bore, wherein the first module end is attached to the first
module, (ii) a bore extension tube connected to the first through
bore at the second end of the first module and extending into the
second through bore, wherein the bore extension tube has a smaller
outer diameter than a diameter of the second through bore, (iii) an
axially reciprocable separator piston having a first side facing
the first module, the separator piston encircling the bore
extension tube between an exterior surface of the bore extension
tube and an interior surface of the second through bore, (iv) an
accumulator charging port providing selectable communication
between an exterior of the accumulator module and a gas chamber
located between the second through bore and the exterior surface of
the bore extension tube on a second side of the separator piston,
and (v) a mud chamber in fluid communication with the flow port,
the mud chamber located between the second through bore and the
exterior surface of the bore extension tube on a second side of the
separator piston; and c) a third module having (i) a housing
attached to the accumulator module, (ii) a ball valve rotatable
between a closed position and an open position, (iii) a third
through bore, wherein the third through bore is coaxially aligned
and in fluid communication with the first through bore and a bore
of the bore extension tube, (iv) a tool bore pressure chamber in
fluid communication with the third through bore, (v) an axially
reciprocable piston movable between a first position and a second
position, the reciprocable piston having the gas chamber positioned
on a first piston side and the through bore chamber positioned on a
second piston side, and (vi) a valve rotational mechanism
interconnecting the valve and the reciprocable piston, wherein when
the piston is in the first position the ball valve is in the closed
position and when the piston is in the second position the ball
valve is in the open position.
12. The downhole shutoff valve of claim 11, wherein the gas chamber
is precharged with nitrogen to create an accumulator pressure.
13. The downhole shutoff valve of claim 12, wherein the
reciprocable piston is exposed to the accumulator pressure on the
first piston side and a through bore fluid pressure on the second
piston side.
14. The downhole shutoff valve of claim 11, wherein the
reciprocable piston is in the first position when the accumulator
pressure exceeds the through bore fluid pressure and wherein the
reciprocable piston is in the second position when the through bore
fluid pressure exceeds the accumulator pressure.
15. The downhole shutoff valve of claim 11, wherein the first
module further includes a pop off valve in fluid communication with
the flow port.
16. The downhole shutoff valve of claim 12, wherein whenever the
accumulator pressure is greater than a pressure exterior to the
downhole shutoff valve by a predetermined amount, the pop off valve
opens and releases to the tool exterior an excess of the
accumulator pressure over the pressure external to the downhole
shutoff tool.
17. The downhole shutoff valve of claim 11, wherein the pop off
valve consists of a carrier and a poppet closed with a shear pin
and opened by shearing the shear pin.
18. The downhole shutoff valve of claim 11, wherein the first
module further includes a latch groove.
19. The downhole shutoff valve of claim 18, wherein a lockopen tool
is selectably latched into the latch groove and positioned to pass
through a through hole in the ball valve, thereby preventing the
ball valve from rotating into the closed position.
20. The downhole shutoff valve of claim 19, wherein the lockopen
tool is selectably removable from the downhole shutoff valve to
permit the ball valve to rotate between the closed position and the
open position.
21. The downhole shutoff valve of claim 11, wherein the pressure
relief valve has an opening pressure less than an estimated maximum
flow-induced pressure produced in the first tool bore.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application, pursuant to 35 U.S.C. 111(b),
claims the benefit of the earlier filing date of provisional
application Ser. No. 61/743,629 filed Sep. 7, 2012 entitled
"Drillstring Shut-Off Valve."
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates in general to a method and
apparatus for controlling fluid flow within a drill pipe. More
particularly, the invention relates to a method and apparatus for
isolating the interior of a drill pipe from external pressure
whenever pumped flow through said drill pipe ceases.
[0004] 2. Description of the Related Art
[0005] The use of check valves in a drill pipe in order to prevent
reverse flow is a general practice in petroleum drilling. Use of
such valves is necessary in order to avoid the tendency of the
normally down flowing drilling fluid to reverse flow during
disconnections of the drill pipe from the rig pumps. Backflow from
the drill pipe can stow operations and result in loss of expensive
drill fluids due to typically higher fluid density in the well
annulus compared to the well bore. If the backflow rate is high,
hazardous conditions result on the surface, and loss of well
control is highly possible.
[0006] The check valves used typically are poppet type or flapper
type check valves. These conventional valves when flowing always
have flow directly contacting their seats and sealing plugs. Both
types are notably short lived in drilling applications as a
consequence of erosion resulting from the presence of abrasive
particles in the drilling fluid and the very high fluid velocities
passing through the valves.
[0007] There is a critical need for major improvements to the valve
means for preventing well backflow during drilling operations for
reasons of both safety and economics, particularly for deep wells
and offshore wells. Additionally, a critical need exists for longer
lived means for controlling well backflow during drilling
operations.
SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention provide a method and
apparatus for isolating the interior of a drill pipe from external
pressure whenever pumped flow through the drill pipe ceases.
Embodiments of the present invention provide a downhole tool using
a ball valve, rotatable between a closed position and a fully open
position, that operates in response to differences between the tool
bore pressure and the pressure in a reference accumulator. The
accumulator is charged downhole to a pressure equal to the highest
bore pressure to which the tool has been exposed minus the cracking
pressure of a relief valve unidirectionally admitting bore fluid
into the accumulator.
[0009] One embodiment of the present invention is a downhole
shutoff valve for operation in a drillstring, including: a) a
housing having a through bore; b) an accumulator positioned within
the housing, wherein a gas chamber within the accumulator is
selectably chargeable with a gas to create an accumulator pressure,
and wherein the accumulator is in fluid communication with a bore
pressure present in the bore through a pressure relief valve; c) a
ball valve rotatable between a closed position and an open
position; d) an axially reciprocable piston exposed to the
accumulator pressure on a first side and the bore pressure on a
second side; and e) a valve rotational mechanism connected to and
operable by the piston, wherein the ball valve is closed by the
valve rotational mechanism when the accumulator pressure exceeds
the bore pressure and wherein the ball valve is opened by the valve
rotational mechanism when the bore pressure exceeds the accumulator
pressure.
[0010] Another embodiment of the present invention is a downhole
shutoff valve including: a) a housing having a through bore; b) a
pressure relief valve in fluid communication with the through bore;
c) an accumulator positioned within the housing having (i) an
accumulator bore, (ii) an accumulator charging port that provides
selectable fluid communication between an exterior of the
accumulator and a gas chamber to create an accumulator pressure,
(iii) a mud chamber in fluid communication with the through bore
through a pressure relief valve, and (iv) a separator piston having
the mud chamber on a first side and the gas chamber on a second
side; d) a ball valve rotatable between a closed position and an
open position; e) an axially reciprocable piston movable between a
first position and a second position, the reciprocable piston
having the gas chamber positioned on a first piston side and a
through bore chamber in fluid communication with the through bore
positioned on a second piston side; and f) a valve rotational
mechanism interconnecting the valve and the piston, wherein when
the piston is in the first position the ball valve is in the closed
position and when the piston is in the second position the ball
valve is in the open position.
[0011] Yet another embodiment of the present invention is a
downhole shutoff valve including: a) a first module having (i) a
first body having a first end, a second end, and a first through
bore, (ii) a flow port extending into the first body, wherein the
flow port is parallel to and offset from the first through bore,
and (iii) a pressure relief valve in fluid communication with the
first through bore and the flow port, wherein the pressure relief
valve opens when a pressure in the first through bore exceeds a
pressure in the flow port by a predetermined amount; b) an
accumulator module having (i) a second body having a first module
end, a second module end, and a second through bore, wherein the
first module end is attached to the first module, (ii) a bore
extension tube connected to the first through bore at the second
end of the first module and extending into the second through bore,
wherein the bore extension tube has a smaller outer diameter than a
diameter of the second through bore, (iii) an axially reciprocable
separator piston having a first side facing the first module, the
separator piston encircling the bore extension tube between an
exterior surface of the bore extension tube and an interior surface
of the second through bore, (iv) an accumulator charging port
providing selectable communication between an exterior of the
accumulator module and a gas chamber located between the second
through bore and the exterior surface of the bore extension tube on
a second side of the separator piston, and (v) a mud chamber in
fluid communication with the flow port, the mud chamber located
between the second through bore and the exterior surface of the
bore extension tube on a second side of the separator piston; and
c) a third module having (i) a housing attached to the accumulator
module, (ii) a ball valve rotatable between a closed position and
an open position, (iii) a third through bore, wherein the third
through bore is coaxially aligned and in fluid communication with
the first through bore and a bore of the bore extension tube, (iv)
a tool bore pressure chamber in fluid communication with the third
through bore, (v) an axially reciprocable piston movable between a
first position and a second position, the reciprocable piston
having the gas chamber positioned on a first piston side and the
through bore chamber positioned on a second piston side, and (vi) a
valve rotational mechanism interconnecting the valve and the
reciprocable piston, wherein when the piston is in the first
position the ball valve is in the closed position and when the
piston is in the second position the ball valve is in the open
position.
[0012] The foregoing has outlined rather broadly several aspects of
the present invention in order that the detailed description of the
invention that follows may be better understood. Additional
features and advantages of the invention will be described
hereinafter which form the subject of the claims of the invention.
It should be appreciated by those skilled in the art that the
conception and the specific embodiment disclosed might be readily
utilized as a basis for modifying or redesigning the structures for
carrying out the same purposes as the invention. It should be
realized by those skilled in the art that such equivalent
constructions do not depart from the spirit and scope of the
invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present invention,
and the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
[0014] FIG. 1 shows the downhole shutoff tool of the present
invention in a longitudinal sectional view. The downhole shutoff
tool is shown in its precharged configuration prior to its being
entered into a well.
[0015] FIG. 2 shows a longitudinal sectional view of the housing
section of the upper module of FIG. 1.
[0016] FIG. 3 shows an exploded view of the upper module of FIGS. 1
and 2.
[0017] FIG. 4 shows an exploded view of the pressure relief valve
shown in FIG. 2.
[0018] FIG. 5 shows an exploded view of the pop off valve shown in
FIG. 2.
[0019] FIG. 6 shows a longitudinal sectional view of the assembled
pressure relief valve shown in FIG. 4.
[0020] FIG. 7 shows a longitudinal sectional view of the assembled
pop off valve shown in FIG. 5.
[0021] FIG. 8 is a longitudinal quarter sectional view of the
annular floating separator piston of the upper module.
[0022] FIG. 9 is a transverse sectional view taken through the
accumulator charging port which shows the elements of the
accumulator precharging system in their closed position following
precharging.
[0023] FIG. 10 is an exploded view showing the components used for
the filling of the accumulator housing in FIG. 9.
[0024] FIG. 11 shows a longitudinal sectional view of the lower
module with the ball valve in its closed position.
[0025] FIG. 12 is an exploded view of the internal components of
the lower module showing the ball, its seat, its supporting
structure, and the actuating piston.
[0026] FIG. 13 is a longitudinal sectional view which shows the
downhole shutoff tool after it has been lowered into the well and
has had drilling fluids pumped through its bore. Drilling fluid
from the bore of the tool has entered the upper end of the
accumulator module through the pressure relief valve assembly.
Because the rig pumps are turned off, the ball is closed due to the
bore pressure exceeding the reference accumulator pressure.
[0027] FIG. 14 is a longitudinal sectional view which shows the
valve in its open, flowing position with the circulation pressure
in the drillstring exceeding the reference accumulator
pressure.
[0028] FIG. 15 is a longitudinal sectional view showing the
downhole shutoff tool closed in normal operation downhole when the
mudpump is turned off.
[0029] FIG. 16 is a transverse cross-sectional view of the pop off
valve when the shear pin has been sheared to vent mud from the
accumulator chamber during tool retrieval to the surface.
[0030] FIG. 17 is longitudinal sectional view when a tubular
lockopen tool has been landed in the bore of the drillstring
shutoff tool in order to prevent closure of the ball valve.
[0031] FIG. 18 is a longitudinal sectional view of the lockopen
tool shown in FIG. 17.
[0032] FIG. 19 is a longitudinal sectional view of the upper tube
of the lockopen tool of FIGS. 17 and 18.
[0033] FIG. 20 shows the relationships between the pressures in the
accumulator of the tool and the tool bore above the ball valve when
the downhole shutoff tool of the present invention is in use.
[0034] FIG. 21 is a detail view taken from FIG. 9 showing the
closed sealing system for isolating the charged accumulator.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] Embodiments of the present invention provide a method and
apparatus for isolating the interior of a drill pipe from external
pressure whenever pumped flow through the drill pipe ceases. For
example, embodiments of the present invention provide an automatic
valving means for isolating the interior of a drill string from
external pressures in a well bore whenever internal pressure in the
drill string is reduced below a predetermined amount. The downhole
shutoff tool described herein permits drill pipe connections even
when the external pressure in the well bore greatly exceeds the
hydrostatic pressure within the drill string.
[0036] Embodiments of the present invention are shown in the
attached figures and are described herein in reference to those
figures. Unless otherwise noted, the materials of the downhole
shutoff tool are high strength low alloy steel or stainless
steel.
[0037] Referring to FIG. 1, the downhole shutoff tool 10 of the
present invention is shown in a longitudinal sectional view. The
righthand end of the tool 10 is the upper end. The downhole shutoff
tool configuration in FIG. 1 is its initial arrangement prior to
its reference accumulator being charged and the tool being run
downhole. When the accumulator is precharged, the configuration is
the same, with the piston 62 abutting the lower end of the upper
module. The downhole shutoff tool 10 includes three coaxially
connected modules 11, 70 and 89 which are joined by pressure
containing threaded connections.
[0038] The main portion of the upper module 11, seen in detail in
FIG. 2, consists of a tubular upper body 12 having transverse ends,
a pressure relief valve 24, and a pop off valve 27. FIG. 3 is an
exploded view of the entire upper module 11.
[0039] The tubular upper body 12 has a through bore 13 with an
intermediate lock open sleeve latching groove 14, a tapered upper
end female thread 15 and a tapered lower end male thread 20. The
thread 15 permits the tool 10 to be sealingly attached to a drill
string. At its lower end, the through bore 13 has a lower end
counterbore 16. The lower end counterbore 16 in sequential order
from its lower end has a lower end female thread 17, a female
O-ring groove 18 containing a female O-ring set 19, and a reduced
diameter straight portion of the counterbore 16. The female O-ring
set 19 consists of an O-ring with two backup rings.
[0040] A gundrilled off axis mud port 22 is laterally offset from
the axis of the upper body 12 and extends from the lower transverse
end of the body to approximately the midlength of the upper body.
At its upper end, the off axis mud port 22 intersects the radial
pressure relief valve counterbore 23. The pressure relief valve
counterbore 23 is coaxially connected to the through bore 13 of the
upper body 12 by radial mud entry port 21.
[0041] The outwardly opening pressure relief valve counterbore 23
has a frustroconical interior end which radially outwardly
increases in diameter from its intersection with the radial mud
entry port 21. Extending radially outwardly from the frustroconical
interior end, the pressure relief valve counterbore 23 has first
straight counterbore section and a female threaded enlarged
counterbore section on its outer end. The off axis mud port 22
intercepts the first straight counterbore section of the relief
valve counterbore 23.
[0042] A vent port 25 extends radially outwardly from its
intersection with the off axis mud port 22. The short length vent
port 25 intersects the mud port 22 at a position between the radial
mud entry port 21 and the transverse shoulder at the upper end of
the male lower end thread 20. The outwardly opening pop off valve
cavity 26 extends radially outwardly from the vent port 25 and has
a coaxial larger constant diameter bore with female snap ring
groove 28 near its outer end.
[0043] Referring to exploded view FIG. 3, the pressure relief valve
24 with its locking screw 36 and the pop off valve 27 with its
retaining snap ring 54 are seen positioned for installation in the
pressure relief valve counterbore 23 and the pop off valve cavity
26, respectively. FIG. 4 is an exploded view of the components of
the pressure relief valve 24, and FIG. 6 shows a longitudinal
cross-sectional view of the assembled valve 24.
[0044] Referring to FIG. 2, FIG. 6, and the exploded view in FIG.
4, the components of the pressure relief valve 24 in sequential
order from the interior end of the valve are the poppet 30, a set
of Belleville spring washers 31, a male O-ring set 32, a spring
abutment 34 with a coaxial poppet guide hole 35, and the locking
screw 36.
[0045] The poppet 30 has a frustroconical interior end with a
concentrically positioned elastomeric sealing washer bonded to its
frustroconical surface. The frustroconical inner end of the poppet
30 and of the inner end of the pressure relief valve counterbore 23
are sealingly comatable. The outwardly extending upper end of the
poppet 30 has a coaxial reduced diameter right circular cylinder
which has a slip fit with the poppet guide hole 35 of the spring
abutment 34.
[0046] The spring abutment 34 is a right circular cylindrical body
having a male O-ring groove at its lower end and an enlarged male
thread at its upper end. The male O-ring groove of the spring
abutment mounts the O-ring set 32, which consists of an O-ring and
two backup rings. The O-ring set 32 sealingly comates with the
unthreaded portion of the pressure relief valve counterbore 23. The
spring abutment 34 is threadedly engaged with the female threads of
the pressure relief valve counterbore.
[0047] The poppet guide hole 35 is a blind hole which extends
coaxially from the inner end of the spring abutment 34. The poppet
guide hole 35 is sufficiently deep to permit the Belleville spring
washers 31 between the intermediate upwardly oriented transverse
face of the poppet 30 and the lower face of the spring abutment 34
to fully flatten if the poppet is unseated by sufficient pressure.
The male threaded locking screw 36 is a short right circular
cylinder with a central hole and having multiple pin holes offset
from the part axis in order to permit a wrench to tighten the screw
36 against the spring abutment 34 sufficiently to ensure both
retention of the pressure relief valve assembly 24 and a
preselected preload on the springs 31 for biasing the poppet 30
closed.
[0048] The pop off valve 27, shown in FIG. 2, a longitudinal
sectional view in FIG. 7, and an exploded view in FIG. 5, consists
of a carrier 40, a poppet 48, a shear pin 52, a perforated retainer
plate 53, and a male snap ring 54. The carrier 40 has a cylindrical
outer surface with transverse upper and lower ends and a coaxial
stepped upwardly enlarging stepped through bore. On its exterior,
the carrier 40 has an intermediate male O-ring groove 41 mounting
an O-ring set 44 consisting of an O-ring with two backup rings.
[0049] From its lower end, the bore 46 of the carrier 40 has a
reduced diameter bore, an upwardly facing frustroconical poppet
seat 42 which serves as an abutment for the poppet 48, an
intermediate enlarged bore, and a larger upper bore. A through
shear pin hole 43 is located on a diameter penetrating the
intermediate enlarged bore of the carrier 40. The cylindrical shear
pin 52 has a close fit to shear pin hole 43. Multiple regularly
spaced radially oriented elongated flow notches 45 which are
parallel to the axis of the carrier 40 extend through the carrier
cylindrical wall between the larger upper bore and the exterior of
the carrier.
[0050] The poppet 48 of the pop off valve 27 is a stepped right
circular cylinder having a short reduced diameter lower end, a
frustroconical downwardly facing shoulder, and an enlarged upper
end. A male O-ring groove 41 is located intermediate to the length
of the enlarged upper end of the poppet. O-ring set 44 consisting
of an O-ring with two backup rings is located in O-ring groove 41.
The lower cylindrical section is a close fit to the reduced
diameter bore at the lower end of the carrier 40, while the upper
cylindrical section is a close slip fit to the intermediate bore of
the carrier. The O-ring set 51 seals between the poppet 48 and the
carrier 40. The downwardly facing frustroconical shoulder joining
the lower and upper cylindrical sections of the poppet 48 has the
same angle and orientation as the frustroconical shoulder of the
carrier 40.
[0051] A shear pin hole 50 which has a close slip fit to a shear
pin 52 diametrically penetrates the lower cylindrical section of
the poppet 48. When the poppet 48 has its frustroconical face
abutted against the corresponding frustroconical face of the
carrier 40, the shear pin holes 43 and 50 can be oriented coaxially
so that a cylindrical shear pin 52 can temporarily connect the two
parts.
[0052] The perforated retainer plate 53 is a thin circular disk
with a regular array of circular through holes spaced apart from
the axis of the disk. The entire pop off valve assembly 27 is
contained in the pop off valve cavity 26 by a male snap ring
54.
[0053] Referring to the exploded view of FIG. 3, the upper assembly
11 is seen to include on its lower end a bore extension tube 58 and
an annular floating separator piston 62. The bore extension tube 58
has a straight through bore 59 and an exterior with a short reduced
diameter upper end, a slightly larger upper end male thread 60, and
a elongated larger outer diameter lower section 57. The reduced
diameter upper end has a close slip fit to the lower end
counterbore 16 of the upper body 12 and is sealingly engaged with
the O-ring set 19. The male thread 60 is threadedly engaged with
the lower end female thread 17 of the upper body 12.
[0054] The annular floating separator piston 62 is a short right
circular cylindrical section with external male O-ring groove 63 on
its outer cylindrical surface and internal female O-ring groove 66
located in its straight through bore 65. O-ring groove 63 contains
male O-ring set 64, while O-ring groove 66 contains female O-ring
set 67. Each O-ring set 64 and 67 consists of an O-ring and two
backup rings. The bore 65 of piston 62 has a close slip fit with
the outer diameter 57 of the lower section of the bore extension
tube 58, and the O-ring set 67 seals with surface 57 of the bore
extension tube.
[0055] The accumulator module 70, seen in FIG. 1, mainly consists
of an elongated tubular housing 71 having transverse ends, the same
outer diameter as the upper body 12, a concentric straight through
bore 72, and the female tapered threads 73 and 74 at the upper and
lower ends respectively of the module 70. The upper thread 73 is
threadedly comatable with the lower end male thread 20 of the upper
body 12. At assembly, the transverse upper end of housing 71
sealingly comates with the transverse intermediate downwardly
facing external shoulder of the upper body 12 of the upper module
11.
[0056] Likewise, the lower female tapered thread 74 of the
accumulator housing 71 is threadedly comatable with the upper end
male thread 91 of the lower housing 90 of lower module 89. At
assembly, the transverse lower end of housing 71 sealingly comates
with the transverse intermediate upwardly facing external shoulder
of the lower housing 90.
[0057] The straight through bore 72 of the accumulator housing 71
has a close slip fit to the outer diameter of the annular floating
separator piston 62 of the upper module 11, and O-ring set 64 seals
the annular gap between piston 62 and bore 72. Separator piston 62
is able to freely move axially in the annular space between the
bore 72 of housing 71 and the outer diameter 57 of bore extension
tube 58.
[0058] This annular space between the bore 72 of the accumulator
housing 71 and the exterior 57 of the bore extension tube 58 serves
as a reference accumulator chamber for the downhole shutoff valve
10. The space below the separator piston 62 serves as an
accumulator gas chamber 87, while the space above the piston 62
serves as an accumulator mud chamber 88.
[0059] As seen in FIGS. 9, 10, and 21, two intersecting ports 76
and 79 for charging the lower accumulator gas chamber 87 are
located in a transverse plane approximately one through bore 72
diameter above the lower end female thread 74 at the end of the
accumulator housing 71. The radially positioned accumulator
charging port 76 penetrates to the bore 72 and has on its inner end
a short small diameter first hole penetrating into the bore 72 of
the accumulator housing 71. At the outer end of the charging port
76, an outwardly diverging frustroconical shoulder 77 serves as a
valve seat for a steel sealing ball 83 which can be forced to
sealing mate with the frustroconical shoulder. The diameter of ball
83 is slightly less than that of the outside of the frustroconical
shoulder 77.
[0060] A first counterbore 78 of charging port 76 is drilled to the
frustroconical shoulder 77. Radially outwardly from the
frustroconical shoulder 77, the first counterbore 78 has a long
straight bore, an O-ring recess for a straight thread/O-ring
fitting 85, and an enlarged second section of counterbore to permit
the hex head of straight thread/O-ring plug or charging port
isolation screw 85 to be fully recessed in the body of the
accumulator housing 71. The first counterbore 78 is tapped from the
O-ring recess to a point about two bore diameters outwardly from
the frustroconical shoulder 77. The hex head charging port
isolation plug 85 is sealingly engaged with the threads and O-ring
groove of the first counterbore 78.
[0061] The clamping screw 84 from its lower transverse end has a
first diameter cylindrical section which has a close slip fit to
the unthreaded portion of the first counterbore 78. A male O-ring
groove containing an O-ring 68 is positioned intermediate to the
length of the lower cylindrical section of the clamping screw 84.
The O-ring 68 seals the annular gap between the unthreaded portion
of the first counterbore 78 and the clamping screw 84. Above the
lower cylindrical section, the clamping screw has an enlarged male
thread threadedly engagable with the threaded portion of the first
counterbore 78 of the accumulator housing 71. A hex Allen wrench
socket is positioned on the upper transverse end of the clamping
screw 84.
[0062] A second port, the small diameter gas fill port 79, extends
from the exterior of housing 71 and perpendicularly intersects the
accumulator charging port 76 outwardly of the frustroconical valve
seat 77 by approximately the diameter of the sealing ball 83. The
diameter of the second port near its intersection is approximately
the same as that of the inner end of the first counterbore 78 of
the accumulator charging port 76. At its outer end, the gas fill
port 79 has a tapped counterbore with a straight thread/O-ring
groove and recess for the hex head of the straight-thread/O-ring
gas fill port isolation screw 86.
[0063] The lower module 89 of the downhole shutoff valve 10 is
shown in a longitudinal sectional view in FIG. 11 and the internals
of the lower module are shown in an exploded view in FIG. 12.
Except for the piston assembly 147, the internals of the lower
module 89 are housed within the lower housing 90. The main elements
of the lower module are the lower housing 90, the valve retainer
100, a ball valve 111 and the ball valve seat 106, the ball rest
116, the lower 120 and upper 129 ball holders, the Lamming arms
assembly 134, and the piston assembly 147.
[0064] Sequentially from its upper end, the exterior of the lower
housing 90 has a transverse upper end, a short reduced diameter
right circular cylindrical section 97 with a circumferential male
O-ring groove 95, a tapered male thread 91, a transverse sealing
face, a long right circular cylindrical external surface, and a
transverse lower end. The outer diameter of the upper end
cylindrical section has a close slip fit with the bore 72 of the
accumulator housing 71.
[0065] A male O-ring set 98 consisting of an O-ring and two backup
rings is positioned in O-ring groove 95 in order to provide sealing
between the cylindrical section 97 of the lower housing 90 and the
bore 72 of the accumulator housing 71. From its upper end, the
interior of the lower housing 90 has a through bore 94, a larger
valve mounting counterbore 93, a straight female retainer thread
96, and a larger tapered lower end female thread 92. The diameter
of the retainer thread 96 is slightly larger than the diameter of
the counterbore 93. The length of the through bore 94 is equal to
approximately 45% of the length of the lower housing 90.
[0066] The valve retainer 100, seen best in FIG. 12, is a right
circular ring with a straight bore, a male external thread 101, and
a short reduced diameter external nose. The thread 101 is comatable
with thread 96 of the lower housing 90. On its lower face, the
valve retainer 100 has multiple drive pin holes 102 for engagement
with spanners.
[0067] Abutting the upper end of valve retainer 100 is ball valve
seat 106. Ball valve seat 106 has a transverse lower end and a
straight through bore which has the same diameter as the bore of
the ball valve 111. On its stepped outer cylindrical surface, the
larger outer diameter segment of ball valve seat 106 has an O-ring
groove mounting a male O-ring set 108 consisting of an O-ring and
two backup rings. The larger outer diameter section has a close
slip fit to the valve mounting counterbore 93 of the lower housing
90, while the smaller outer diameter section has a close slip to
the lower end bores of the lower 120 and upper 129 ball holders.
The O-ring set 108 seals between the ball seat 106 and the valve
mounting counterbore 93.
[0068] A transverse upwardly facing exterior shoulder of the valve
seat 106 which abuts the lower ends of the lower 120 and upper 129
ball holders connects the two outer diameter sections of the ball
valve seat 106. The upper end of the actual seat 107 of the ball
valve seat 106 is spherical and has a close fit to the ball valve
111. An elastomeric sealing element is molded into a central
annular groove in the spherical face of the seat 107 to seal
between the ball 111 and the metal portion of the valve seat.
[0069] The ball valve 111 is best seen in its open position shown
in FIG. 12 and its closed position in FIG. 11. The ball valve 111
has a spherical sealing surface with a through hole 115 located on
a diameter. Two parallel opposed flats 113 are parallel to and
equally offset from the axis of the through hole 115. In the center
of each flat 113 is an outwardly extending central pin 112 which is
perpendicular to its flat. Each flat 113 has a rectangular
cross-section camming groove 114 spaced a short distance from its
central pin and extending radially outwardly 45.degree. from the
axis of the through hole 115. Each camming groove 114 exits through
the spherical outer surface of the ball valve 111. The camming
grooves are symmetrical about the midplane between the flats 113 of
the ball.
[0070] The ball rest 116, seen in FIGS. 11 and 12, is formed from
an axially short, right circular cylindrical piece with a straight
through bore 118, a spherical lower end, a transverse upper end,
and a stepped outer diameter. The bore of the ball rest 116 is the
same as the through bore 115 of the ball valve 111. The spherical
lower end is a close fit to the spherical surface of the ball valve
111. On its upper end, the ball rest 116 outer diameter has a
larger section which extends for approximately half of the axial
length of the ball rest. This larger section is a close slip fit to
the valve mounting counterbore 93 of the lower housing 90. The
larger cylindrical outer surface of the ball rest 116 is
interrupted by two mirror image flats 117 parallel to the axis of
the part and having a separation equal to the smaller outer
diameter. This separation distance of the ball rest flats 117 is
equal to the separation distance of the flats 113 on the ball
111.
[0071] The lower ball holder 120, best seen in FIG. 12, is made
from a half cylindrical part having a constant outer diameter which
has a close slip fit to the valve mounting counterbore 93 of the
lower housing 90. The upper end of the bore of the half cylinder
has a radius which is a close slip fit to the smaller cylindrical
outer surface diameter of the ball valve seat 106. A rectangular
cut transverse to the longitudinal midplane of symmetry of the
source half cylinder and having two sides parallel to the axis of
symmetry of the half cylinder is made with one edge a short
distance from the lower end of the half cylinder and the opposed
edge about 40% of the length of the lower ball holder 120 from the
transverse upper end of the part. The side 121 of the rectangular
cut farthest from the part axis of the lower ball holder 120 is
tangent to the larger diameter bore of the source half cylinder and
extends to the bore diameter transition of the source half
cylinder.
[0072] A ball pin hole 122 perpendicular to the flat side 121 of
the cut and located on the longitudinal midplane of the lower ball
holder 120 is a close fit to a central pin 112 of the ball valve
111 and serves as a support for the ball. An elongated rectangular
slot 123 offset from the longitudinal midplane of the lower ball
holder 120 and normal to the flat interior side 121 of the
rectangular window cut penetrates to the outer cylindrical surface
of the lower ball holder 120. This slot 123 offers lateral guidance
to the lower camming arm 141 of the camming arm assembly 134. The
upper end of the slot 123 extends to within approximately a quarter
diameter of the lower ball holder 120 and the slot lower end is
located at approximately the lower end of the rectangular cut in
the ball holder.
[0073] A drilled and tapped stroke limiter hole 124 perpendicularly
intercepts the lower transverse end of the lower ball holder 120
and mounts a first stroke limiter set screw 125 which is used to
limit the downward stroke of the lower arm 141 of the camming arms
134. A similar but longer drilled and tapped hole 124 coaxial with
the first hole 124 penetrates both the upper end of the lower ball
holder 120 and the upper end of the slot. This second hole 124
mounts another screw 125 which serves to limit the upward stroke of
the lower camming arm 141 of the camming arm assembly 134.
[0074] The upper ball holder 129 is a mirror image of the lower
ball holder 120 and also uses the same stroke limiter set screws
125 to limit travel of the upper camming arm 139.
[0075] The camming arm assembly 134 consists of an elongated thin
walled right circular tubular body 135 having a male thread 137 at
its upper end and a radial through hole 136 spaced a short distance
below the thread 137. At its lower end, a pair of mirror image
external arms 139, 141 laterally offset from the longitudinal axis
of the tube extend downwardly. The opposed inner faces of the arms
are parallel and are separated by a distance slightly larger than
the separation of the flats 113 of the ball valve 111. The outer
faces of the arms 139, 141 opposed to their inner faces are
cylindrical and are a slip fit to the valve mounting counterbore 93
of the lower housing 90.
[0076] The lateral sides of the camming external arms 139, 141 are
parallel and are a slip fit to the camming arm guide slots 123 of
the lower 120 and upper 129 ball holders when the ball holders are
assembled around the camming arms assembly 134. The difference
between the length of the camming external arms 139, 141 and the
tips of the stroke limiter screws 125 at the interior ends of the
camming arm guide slots 123 of the lower and upper ball holders
determines the stroke travel of the camming arms assembly for
rotating the ball valve 111. The lower screws 125 are adjusted to
ensure full alignment of the ball through bore 115 with the axis of
the tool 10 when the valve 111 is opened. Likewise, the upper
screws 125 are adjusted to ensure the elastomer 107 of the seat 106
fully seals on the closed ball.
[0077] Coaxial holes 140, 142 respectively at the lower ends of the
individual camming arms 139, 141 and normal to the longitudinal
midplane of the camming arms assembly each serve to mount an
inwardly extending camming pin 144. The camming pins 144 are short
with a larger diameter portion which has a slip fit to a camming
slot 114 on the ball valve 111 and a smaller diameter portion which
has an press fit with the mounting holes 140 or 142 on the lower
end of the camming arms 139, 141.
[0078] The piston assembly 146, seen in FIGS. 11 and 12, consists
of piston 147, a male O-ring set 149, and two female O-ring sets
152 and 154. The piston 147 of the piston assembly is a right
circular cylindrical body of revolution with transverse ends. The
upper exterior portion 148 of piston 147 has a reduced diameter
extending approximately half of the length of the part, while the
lower exterior portion has a close slip fit to the through bore 72
of the accumulator housing 70. An annular male O-ring groove 150
located on the larger diameter exterior cylindrical surface of the
piston 147 mounts a male O-ring set 150 consisting of an O-ring
with two backup rings. The male O-ring set seals between the piston
147 and the bore 72 of the accumulator housing 70.
[0079] The through bore of the piston 147 has from its upper end a
straight counterbore 156 extending about half of the length of the
piston. The diameter of the counterbore 156 is a close slip fit to
the outer diameter of the lower tube surface 57 of the bore
extension tube 58. A first female O-ring groove 153 houses a female
O-ring 152 set composed of an O-ring with two backup rings to
provide dynamic sealing between the piston assembly 147 and the
lower end of the bore extension tube 58.
[0080] The central portion of the bore of piston 177 has a reduced
diameter with a female thread 151. The female thread 151 is
threadedly comatable with the male thread 137 at the upper end of
the camming arm assembly 134. Below the female thread 151 of piston
147 is a short counterbore which is a close slip fit to the outer
diameter of the tubular body 135 of the camming arm assembly 134. A
second female O-ring groove 155 in the lower counterbore mounts a
static O-ring set 154 consisting of an O-ring and two backup rings
for sealing between the piston 146 and the camming arm assembly
134.
[0081] A tool bore pressure chamber 158 is created in the assembled
tool 10 between the lower end of the piston assembly 147 and the
upper end of lower housing 90 of the lower module 89. The tool bore
pressure chamber 158 is bounded on its outer diameter by the
through bore 72 of the accumulator housing 71 and on its inner
diameter by the outer diameter of the tubular body 135 of the
camming arm assembly 134.
[0082] Pressure from the through bore of the camming arms assembly
134 and, hence, the bore of the entire downhole shutoff valve 10 is
communicated to the tool bore pressure chamber 158 through the
communication port 136 of the camming arms assembly. This bore
pressure is applied to the lower end of the piston assembly 147.
The pressure in the gas chamber 87 of the accumulator module 70
acts on the upper end of the piston assembly.
[0083] In some cases, it is advisable for operational reasons to
lock open ball 111 of the downhole shutoff valve 10 either before
or after the tool has been run downhole. FIGS. 17, 18, and 19 show
a possible means for accomplishing the locking open of the ball
valve 111 of the downhole shutoff valve 10.
[0084] Referring to FIG. 18, the details of a pumpdown lockopen
tool 160 can be seen. The lockopen tool consists of a main tube
161, a guide nose 162, a middle tube 164, a shear pin 170, an
external latch ring 171, a set of four travel limiting screws 172,
a frangible disk 173, and an upper tube 176.
[0085] FIG. 17 shows the tubular lockopen tool 160 which has been
inserted inside the drillstring at the surface and pumped down to
land in a position to prevent the ball valve 111 from closing. The
pumping causes the ball valve 111 to open, permitting the
downwardly traveling lockopen tool 160 to insert its main tube 161
through the open bore of the tool 10 and the bore 115 of the ball.
When the lockopen tool 160 has moved sufficiently downwardly, it
latches its external latch ring 171 into the lockopen sleeve
latching groove 14 in the through bore 13 of the upper body 12. The
pumping down of the lockopen tool 160 is possible because its bore
is temporarily blocked by a thin frangible disk 173.
[0086] Referring to the longitudinal sectional view of the lockopen
tool 160 in FIG. 18, the round main tube 161 is relatively long,
with a pointed stabbing guide nose 162 composed of three plates
welded into its lower end, as seen in FIG. 18. The outer diameter
of the main tube 161 is a loose slip fit to the through bore 115 of
the ball 111. At its upper end, the main tube is coaxially welded
to the middle tube 164.
[0087] The middle tube 164 is only slightly longer than its outer
diameter. The middle tube 164 at its lower end has the same inner
and outer diameters as the main tube 161. The exterior of the
middle tube has a short lower section, a upwardly facing transverse
shoulder, and then a reduced diameter cylindrical neck 165 at its
upper end. The bore of the middle tube from the bottom end inwardly
converges and then has a constant diameter extending to the upper
transverse end of the part.
[0088] The upper portion of the middle tube 164 has a relatively
thin wall. Just below its upper end, the middle tube has four guide
slots 167 circumferentially equispaced and elongated in the axial
direction of the part. A radial drilled and tapped shear pin hole
166 to accommodate a shear pin 170 is spaced upwardly from the
intermediate outer transverse shoulder of the middle tube 164.
[0089] An external latch ring 171 has a thin wall with a short
axial length and relatively large external chamfers on its upper
and lower sides. The external latch ring outer diameter is the same
as the outer diameter of the lock open sleeve latching groove 14 of
the upper body 12 of the upper module 11, and the axial length of
latch ring 171 is such that it has a loose fit in the groove 14.
The external latch ring 171 has a small section of its
circumference removed in order to permit it to be radially
contracted in order to pass through the through bore 13 of the
upper body 12 of the upper module 11. The material of the latch
ring 171 is hardened steel in order to permit it to be compressed
in the through bore of the upper body without experiencing
permanent distortion.
[0090] The upper tube 176 of the lockopen tool 160 is shown in a
longitudinal sectional view in FIG. 19. The upper tube 176 has a
transverse lower end external shoulder 179, a lower counterbore 177
which has a slip fit with the reduced diameter neck 165 of the
middle tube 164, a downwardly facing inwardly extending transverse
shoulder, and a reduced diameter upper bore which contains an
elongated intermediate internal latch groove 178. The internal
latch groove 178 is configured to accept an industry standard
wireline retrieval tool. The length of the lower end counterbore is
slightly more than the length of the reduced diameter neck of the
middle tube.
[0091] On its exterior, the upper tube 176 has from its lower end a
short first reduced diameter ring expander section 179 which has a
diameter equal to or slightly less than the diameter of lockopen
sleeve latching groove 14 of the upper module 11 minus the
difference in outer and inner diameters of the external latch ring
171. Adjacent to the ring expander section 179 on its upward side
is a short latch ring recess 180. The diameter of the latch ring
recess 180 is slightly less than the inner diameter of the through
bore 13 of the upper body 12 of the upper module minus the
difference of the outer and inner diameters of the latch ring 171.
The length of the latch ring recess 180 is slightly more than the
axial length of the latch ring 171. A chamfer joins the ring
expander section 179 and the latch ring recess 180.
[0092] The relatively long external cylindrical surface 183 of the
upper tube 176 is located immediately above the latch ring recess
180. An outwardly extending downwardly facing transverse shoulder
joins the external cylindrical surface 183 of the upper tube 176 to
the latch ring recess 180. The diameter of the external cylindrical
surface 183 is a loose slip fit to the through bore 13 of the upper
body 12 of the upper module 11. At the upper end of the upper tube
176, a short outwardly and upwardly extending inclined external
landing shoulder 184 is configured to abut the transition from the
upper end female thread 15 to the through bore 13 of the upper body
12 of the upper module 11.
[0093] Four circumferentially equispaced drilled and tapped radial
screw holes 181 in a common transverse plane of the upper tube 176
penetrate the tube a short distance upwardly of the transition
between the latch ring recess 180 and the external cylindrical
surface 183. Each hole mounts an inwardly projecting travel
limiting screw 172. The travel limiting screws 172 are half dog
point set screws with short reduced diameter cylindrical tips. The
tips of the screws 172 are engaged in the guide slots 167 of the
middle tube. When the lockopen tool is in its assembled running
position shown in FIG. 18, the tips of the screws 172 are
positioned in the lower end of the guide slots 167.
[0094] The frangible disk 173 is an axially thin cylindrical member
made either from a brittle material of limited strength or a metal
disk scored to provide lines of failure. When the frangible disk is
exposed to high transverse pressure, it will rupture. The diameter
of the disk 173 is a close slip fit to the lower counterbore 177 of
the upper tube 176.
[0095] A radial drilled and tapped shear pin hole 182 is match
drilled and match tapped with the upper tube 176 and the middle
tube 164 assembled to abut each other with the travel limiting
screws 172 and the frangible disk 173 installed as shown in FIG.
18. The shear pin hole 166 of the middle tube 164 is produced by
this operation. The threaded brass shear pin 170 has a screw slot
in its upper end and is threadedly engaged with both the shear pin
hole 182 of the upper tube 176 and the shear pin hole 166 of the
middle tube 164.
[0096] The lockopen tool is assembled by placing the frangible disk
173 at the upper end of the middle tube and then abutting the
shoulder at the upper end of the lower counterbore 177 of the upper
tube 176 against the disk. At that point, the travel limiting
screws are engaged both through the screw holes 181 of the upper
tube 176 and the guide slots 167 of the middle tube 164. Following
this, the shear pin 170 is engaged in the drilled and tapped shear
pin hole 182 of the upper tube 176 and the shear pin hole 166 of
the middle tube 161.
OPERATION OF THE INVENTION
[0097] The drillstring shutoff tool in service will be mounted near
the lower end of a drillstring, typically very close to the drill
bit. When the drillstring shutoff tool 10 of the present invention
is initially assembled prior to being precharged and mounted in a
drillstring, it has the configuration shown in FIG. 1. The floating
separator piston 62 may possibly be spaced apart from the lower end
of the upper body 12, but after the accumulator module 70 gas
chamber 87 is precharged with nitrogen, the piston will be abutted
against the lower end of the body 12 by the retained nitrogen
pressure.
[0098] The nitrogen precharge is introduced into the accumulator
gas chamber 87 in the following manner. First, the gas port
isolation plug 86 is removed and a nitrogen source is connected to
the threaded counterbore 80 of the gas fill port 79. Following
this, the charging port isolation plug 85 is removed and the
clamping set screw 84 is backed off sufficiently to allow the
sealing ball 83 to lift from its seated position on the valve seat
77. At this point, pressurized nitrogen at a preselected regulated
pressure can flow into the accumulator gas chamber 87. Following
its filling to a desired pressure, the accumulator gas chamber is
again isolated by reversing the procedure for admitting gas into
the accumulator.
[0099] The amount of nitrogen precharge in the accumulator is
predetermined by the expected range of operational depths for the
tool 10. Typically, the precharge pressure will range from a few
atmospheres to approximately 1500 psi. The precharge pressure is
limited to be at least slightly less than the anticipated initial
downhole hydrostatic pressure at the bottom of the drillstring
minus the cracking pressure of the pressure relief valve 24.
However, as a practical matter, it is desirable to keep pressures
to which operational personnel are exposed at fairly low
values.
[0100] The pressure relief valve assembly 24 has its Belleville
spring washer set 31 preloaded so that its poppet 30 will open for
a certain differential pressure across the valve. Normally, this
differential pressure will be on the order of a few hundred psi.
When the shutoff tool 10 is lowered into a well, the ball initially
will be shut, as shown in FIG. 1. Normally, the drillstring is
filled with drilling fluid either intermittently as it is being
lowered into the well or when it has reached the bottom of the
well. This produces hydrostatic pressure in the bore of the
drillstring at the elevation of the tool 10. When this hydrostatic
pressure exceeds the opening pressure of the relief valve assembly
24, that valve opens and admits drilling fluid to the off axis mud
port 22. The pressure relief valve 24 does not permit reverse
flow.
[0101] The resultant flow through the relief valve 24 then is
enabled to enter the space between the separator piston 62 and the
bottom end of the upper body 12. When the hydrostatic pressure at
the level of the tool minus the cracking pressure of the relief
valve 24 exceeds the accumulator precharge pressure, the separator
piston 62 will begin to be displaced downwardly thereby
establishing an accumulator mud chamber 88, as shown in FIG. 13.
FIG. 15 shows how the separator piston 62 is displaced downwardly
when the tool 10 has reached its drilling depth.
[0102] As the shutoff tool is lowered into the well in the usual
well situation, at the depth of the tool, the external hydrostatic
pressure will be equal to or will exceed the hydrostatic in the
bore of the tool. Since the pop off valve 27 is thus not
experiencing a positive pressure differential between the pressure
in the off axis mud port 22 and the exterior of the tool, it
remains closed.
[0103] When the tool reaches the bottom of the well, the
drillstring is completely filled with drilling fluid using the mud
pumps. This results in sufficient drilling fluid entry into the
relief valve 24 so that the accumulator pressure increases and
becomes substantially the same on both sides 87 and 88 of the
separator piston 62. The retained accumulator pressure at that time
is equal to the hydrostatic bore pressure in the bore of the tool
10 minus the cracking pressure of the relief valve 24. The
increased pressure in the accumulator chambers 87 and 88 results in
substantial downward displacement of the separator piston 62, as
shown in FIG. 15.
[0104] Since the drillstring shutoff tool 10 is intended for use in
drilling, in service a drill bit having restrictive flow nozzles
will be installed below the tool 10. When the drill rig mud pumps
are running and causing fluid to flow down the drillstring at a
typically high flow rate, a significant pressure drop develops
across the bit flow nozzles. Thus, when the rig is pumping, a
differential is developed between the pressure external to the
drillstring and the internal pressure in the drillstring and the
tool 10. For this situation at the depth at which the tool is
located, the pressure in the drillstring is higher than the
combined hydrostatic and flow induced pressure in the well annulus
between the drillstring and the well bore.
[0105] In the active drilling situation, the pressure in the bore
of the drillstring shutoff tool 10 is equal to the hydrostatic
pressure plus the mud pump output pressure minus the flow induced
pressure losses inside the drillstring between the mud pump and the
tool. The pressure in the drilling fluid inside the accumulator is
essentially the combined drilling pressure at the level of the tool
minus the cracking pressure of the relief valve 24. When the
mudpumps are being stopped, the pressure in the bore of the tool
also is being reduced, but the volume of drilling fluid in the
accumulator mud chamber 88 cannot reduce, since the relief valve 24
will not exhaust fluid.
[0106] The Belleville spring washer set 31 is selected and
preloaded to carefully control the opening differential pressure of
the pressure relief valve assembly 24. The relief valve 24 opening
pressure is selected to be a fraction of the anticipated pressure
drop across the bit nozzles for the drilling assembly. Normally,
the drilling rig mud pumps are run at or near their maximum speed,
as the drilling rate is closely related to the flow rate through
the bit.
[0107] Relatively low forces on piston assembly 146 are required to
operate the ball valve 111, so by way of example, the opening
pressure for the pressure relief valve assembly 24 would be
selected to be in the range of 20% to 60% of the minimum pressure
drop across the bit nozzles with the pumps running at full speed
during a run of the downhole shutoff valve 10. The lower limit of
the opening pressure differential for the pressure relief valve 24
is selected to ensure that adequate closing force is available to
overcome frictional forces resisting closure of the ball valve 111.
Use of a relatively lower opening pressure for the pressure relief
valve 24 avoids excessive fluid erosive wear on the ball 111 during
opening and closing.
[0108] FIG. 20 illustrates the relationships between the pressure
retained in the accumulator and the pressure in the bore during
drilling. The pressure retained in the accumulator chambers 87 and
88 is indicated by a dashed line, while the pressure in the through
bore of the drilling shutoff tool is illustrated by a solid line.
For simplicity, it is assumed that the bore of the drill string is
continually filled as the tool 10 is lowered into the well.
Additionally, the drilling fluid density is assumed constant, the
effects of temperature change on the accumulator gas pressure are
ignored, and the pumps are always run at the same speed. The
relatively small changes in accumulator gas chamber pressure 87 as
the piston 146 attached to the camming arm assembly 134 strokes are
also ignored herein for simplicity.
[0109] Initially, no drilling fluid enters the accumulator through
the pressure relief valve 24. This is because the accumulator gas
chamber pressure 87 plus the cracking pressure of the pressure
relief valve 24 initially exceeds the hydrostatic pressure of the
drilling fluid in the drillstring. However, when the hydrostatic
pressure at the depth of the lowering tool exceeds the accumulator
pressure plus the cracking pressure of the relief valve 24,
drilling fluid will enter the accumulator. At this point, the
accumulator pressure curve in FIG. 20 begins to increase from its
precharged value. In response to the positive pressure differential
between the bore of the tool and the accumulator chamber 87, the
piston 146 and its attached camming arms 139, 141 move upwardly.
The camming pins 144, mounted on the camming arm assembly 134 and
engaged in the camming grooves 114, apply an off axis force to the
ball 111, causing it to rotate to its open position, thereby
permitting flow through the drill bit and into the well bore.
[0110] When the mud pumps of the rig are first turned on with the
drillstring filled, assuming that the pumps are run at the same
speed each time, the pressure in the bore of the tool increases by
approximately the same amount, but the accumulator pressure always
lags by the amount of the relief valve 24 cracking pressure when
the mud pumps are running. Relatively minor reductions with
increase in depth in the circulating bore pressure for the tool due
to flow losses in the drillstring are not treated here for
simplicity. Whenever the rig pumps turn off, the pressure in the
bore of the tool decreases to the hydrostatic pressure of the
drilling fluid column in the drillstring due to closure of the ball
valve 111 of the tool 10.
[0111] However, as long as the differential between the flowing
pressure and the nonflowing pressure at the exterior of the tool 10
when the pumps are stopped does not exceed the opening pressure of
the pop off valve 27, the difference between the accumulator
pressure and the flowing pressure in the tool bore is constant.
When the drillstring is filled and the pumps are turned on, the
pressure in the tool bore increases to a point at which the
pressure communicated through the communication port 136 of the
camming arms to the tool bore pressure chamber 158 will exceed the
pressure in the accumulator gas chamber 87. This pressure
differential produces an upwardly acting differential pressure
acting on the piston 146 attached to the camming arm assembly 134,
thereby causing the ball valve 111 to open.
[0112] As the rig pumps slow down in the process of stopping, the
tool bore pressure drops below the retained pressure in the gas
chamber 87 of the accumulator 70. The piston assembly 146 attached
to the camming arm assembly 134 is exposed to the pressure of the
gas chamber 87 on its upper side and on its lower side to the tool
bore pressure communicated through the communication port 136 to
the tool bore pressure chamber 158. In response to the pressure
differential, the piston 146 and its attached camming arm assembly
134 move downwardly. The camming pins 144, mounted on the camming
arm 139, 141 and engaged in the camming grooves 114, apply a
downward off axis force to the ball 111, causing it to rotate to
its closed position.
[0113] When the drilling shutoff valve 10 is being withdrawn from
the well, the hydrostatic pressure decreases, but the pressure in
the accumulator chambers 87 and 88 is trapped until the shear pin
52 of the pop off valve 27 shears, releasing the drilling fluid
retained in the accumulator mud chamber 88. The shear pin 52 shears
in response to sufficiently high forces on the poppet 48 of the pop
off valve 27 due to the pressure differential between the
accumulator mud chamber 88 and the exterior of the tool. The
pressure of the nitrogen in the accumulator gas chamber 87 then
urges the floating separator piston 62 upwardly until it abuts the
lower end of the upper body 12. No nitrogen is released at this
point, so the nitrogen pressure stays the same except for
temperature induced variations as the drilling shutoff tool is
pulled from the well.
[0114] The pop off valve 27 is always exposed to the pressure in
the off axis mud port 22 and hence the pressure on the upper side
of the separator piston 62 in the accumulator 70. The accumulator
pressure directly acts on the cross sectional area of the outer end
of the valve poppet 48. When the outwardly acting differential
pressure force on the poppet 48 exceeds the shear strength of the
shear pin 52, the poppet shifts radially outwardly until it abuts
the perforated retainer plate 53. The shifting of the poppet
permits drilling fluid on the upper side of the separator piston 62
to be forced past the poppet from the accumulator mud chamber 88,
thereby dropping the pressure in the accumulator to its initial
precharge pressure.
[0115] The lockopen tool 160 uses latching of its external latch
ring 171 to retain the tool 160 in position to prevent closure of
the ball 111. As the downwardly moving lockopen tool 160 enters the
open ball 111, the external latch ring 171 is forced to constrict
its outer diameter by being forced into the through bore 13 of the
upper body 12 of the upper module 11. Internal forces acting on the
compressed latch ring 171 urge it radially outward so that it can
recess in the latch ring recess 180 of the upper tube 176 of the
lockopen tool. When the lockopen tool moves sufficiently
downwardly, the radially compressed latch ring 171 will expand and
engage in the latching groove 14 to trap the lockopen tool 160 so
that it prevents closure of the ball valve 111.
[0116] If a force shoves the lockopen tool upwardly, the latch ring
171 will slide both to abut the upwardly facing shoulder of the
middle tube 164 and to be supported radially by resting on the
outer diameter of the lower end external shoulder 179. In this
position, there is no force on the shear pin 170 and the latch ring
cannot collapse sufficiently to release the lockopen tool.
[0117] Retrieval of the lockopen tool 160 is possible by applying
upward tension on the upper tube 176. This tension can be applied
by latching a industry standard wireline retrieval tool into the
internal latch groove 178 of the upper tool and then exerting
sufficient upward pull on the wireline to shear the shear pin
170.
[0118] Prior to the shearing out of the latched lockopen tool 160,
the pull of the wireline produces a reactive force between the
latch ring 171 and the groove 14 in the upper module 11. This
causes the latch ring 171 to bear on the intermediate upwardly
facing transverse shoulder of the middle tube 164. When the
resultant shear force in the shear pin 170 is sufficient to fail
the pin 170, a gap opens up between the lower end of the upper tube
176 and the upwardly facing intermediate shoulder of the middle
tube 164. The radial inward forces applied to the latch ring 171 by
its abutting against the upper end of the latching groove 14 of the
upper module 11 cause the ring to collapse sufficiently to permit
lockopen tool retrieval. The travel limiting screws 172 prevent
separation of the middle tube 164 and the upper tube 176, so that
the lockopen tool 160 remains an integral unit during
retrieval.
[0119] The lockopen tool 160 can be utilized to hold the downhole
shutoff valve 10 open by positioning the lower end of the main tube
161 through the bore of the open ball 111. This can be done in
either of two ways. The first way is by assembling the downhole
shutoff valve 10 prior to its being precharged with nitrogen with
its ball initially open and the main tube of the lockopen tool 160
inserted through the bore 115 of the ball 111. The external latch
ring 171 of the lockopen tool 160 must be engaged in the latching
groove 14 of the upper body 12 and the frangible disk 173 omitted
from the assembled lockopen tool in this case. This permits the
downhole shutoff valve 10 to be run into the well in an open
condition so that the drillstring will freely flood without pumping
fluid into the drillstring. For this first method of operation, the
lockopen tool must be retrieved by wireline to enable normal
downhole shutoff valve operation.
[0120] The second method for using the lockopen tool 160 is to pump
it into place downhole. In this situation, the ball 111 of the
downhole shutoff valve 10 is open due to the pump flow, so that the
guide nose 162 and the main tube 161 can freely enter the bore 115
of the ball and thereby prevent ball closure. When the lockopen
tool 160 has latched into the bore of the downhole shutoff valve
10, further pumping will rupture the frangible disk 173. As a
result, bidirectional flow is then possible through the locked open
drilling shutoff valve 10, and the drillstring can freely drain as
it is retrieved from the well.
ADVANTAGES OF THE INVENTION
[0121] The downhole shutoff valve of the present invention provides
a more reliable means of preventing backflow into a drillstring
when the rig mud pumps are stopped. Conventional flapper type or
poppet type check valves have proved to be unreliable in downhole
drilling service.
[0122] The downhole shutoff valve disclosed herein experiences far
less wear than conventional downhole check valves because, unlike
the case for those valves, the valve seat and sealing surface of
the valve are not exposed to erosive flow.
[0123] The accumulator precharging pressure is relatively low, and
the venting of the pop off valve of the retrieved downhole shutoff
valve prevents exposure of personnel to the pressures higher than
the precharging pressure of the tool. Another advantage of the
present invention is that it automatically compensates for changes
in its operating depth.
[0124] A further advantage of the tool is that an accessory tool,
the wireline run and retrieved lockopen tool disclosed herein, can
be used to avoid the necessity of filling the drillstring prior to
initial operation downhole. Additionally, the pump in installation
of the lockopen tool permits pulling the drillstring with fluid
retained in the pipe.
[0125] The construction and assembly/disassembly of the downhole
shutoff valve are relatively simple. Conventional materials used
for mechanical oilfield downhole tools are also used for the
downhole shutoff valve. These and other advantages will be obvious
to those skilled in the art.
[0126] As well may be understood by those skilled in the art,
certain features of the downhole shutoff valve of the present
invention may be modified without departing from the spirit of the
invention. By way of example, the ball valve could be operated by a
rack and pinion arrangement. The pressure relief valve and the pop
off valve could be connected to the accumulator by separate flow
paths. The accumulator could be recharged through a check valve
without using a separate, intersecting flow path. The downhole
shutoff valve could be operated without using a lockopen tool. The
configuration of the latching and retrieval means of the lockopen
tool could be altered. However, these changes would not depart from
the spirit of the invention.
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