U.S. patent application number 14/182132 was filed with the patent office on 2014-08-21 for downhole tool control.
This patent application is currently assigned to NOV Downhole Eurasia Limited. The applicant listed for this patent is NOV Downhole Eurasia Limited. Invention is credited to Alan Martyn Eddison.
Application Number | 20140231096 14/182132 |
Document ID | / |
Family ID | 48048684 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140231096 |
Kind Code |
A1 |
Eddison; Alan Martyn |
August 21, 2014 |
DOWNHOLE TOOL CONTROL
Abstract
A method of operating a downhole tool in a no-flow configuration
in which a piston and a flow-restriction cooperate to occlude a
tool throughbore. The tool is reconfigured to an intermediate
configuration by flowing fluid through the tool at an intermediate
flow-rate lower than an operating flow-rate and axially translating
the piston to an intermediate position in which the piston and
flow-restriction cooperate to define an intermediate flow area.
Axial translation of the piston between a no-flow position and the
intermediate position includes an occlusional stage of a first
axial extent during which the piston and the flow-restriction
occlude the tool throughbore, and a transitional stage of a second
axial extent during which the piston and the flow-restriction
cooperate to provide a step-change in flow area. The tool is
reconfigured to an operating configuration by flowing fluid through
the tool at the operating flow-rate and axially translating the
piston.
Inventors: |
Eddison; Alan Martyn; (York,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOV Downhole Eurasia Limited |
Gloucestershire |
|
GB |
|
|
Assignee: |
NOV Downhole Eurasia
Limited
Gloucestershire
GB
|
Family ID: |
48048684 |
Appl. No.: |
14/182132 |
Filed: |
February 17, 2014 |
Current U.S.
Class: |
166/374 ;
166/155 |
Current CPC
Class: |
E21B 23/006 20130101;
E21B 23/04 20130101 |
Class at
Publication: |
166/374 ;
166/155 |
International
Class: |
E21B 23/04 20060101
E21B023/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2013 |
GB |
1302981.4 |
Claims
1. A method of operating a downhole tool, the method comprising:
providing a downhole tool in a no-flow configuration in which an
axially movable tubular piston and a flow-restriction cooperate to
substantially occlude a tool throughbore; reconfiguring the tool to
an intermediate configuration by flowing fluid through the tool at
an intermediate flow-rate lower than an operating flow-rate and
axially translating the piston to an intermediate position in which
the piston and the flow-restriction cooperate to define an
intermediate flow area, wherein axial translation of the piston
between a no-flow position and the intermediate position comprises
an occlusional stage of a first axial extent during which the
piston and the flow-restriction substantially occlude the tool
throughbore and a transitional stage of a second axial extent
during which the piston and the flow-restriction cooperate to
provide a step-change in flow area; holding the tool in the
intermediate configuration by flowing fluid through the tool at the
intermediate flow-rate; and reconfiguring the tool to an operating
configuration by flowing fluid through the tool at an operating
flow-rate and axially translating the piston to an operating
position in which the tool defines an operating flow area.
2. The method of claim 1, wherein the second axial extent is less
than the first axial extent.
3. The method of claim 1, comprising providing the tool in the
no-flow configuration and then reconfiguring the tool to the
intermediate configuration by pumping fluid through the tool at the
intermediate flow-rate and axially translating the piston from the
no-flow position to the intermediate position, the axial
translation of the piston comprising an initial occlusional stage
and a secondary transitional stage.
4. The method of claim 3, comprising subsequently reducing the
flow-rate to return the tool to the no-flow configuration.
5. The method of claim 3, comprising subsequently increasing the
flow-rate to the operating flow-rate to reconfigure the tool to the
operating configuration.
6. The method of claim 1, comprising providing the tool in the
operating configuration and then reconfiguring the tool to the
intermediate configuration by reducing the flow-rate through the
tool from the operating flow-rate to the intermediate flow-rate and
permitting the piston to assume the intermediate position.
7. The method of claim 1, comprising reconfiguring the tool from
the no-flow configuration to the operating configuration by
increasing the flow-rate directly from zero to the operating
flow-rate.
8. The method of claim 1, comprising reconfiguring the tool from
the operating configuration to the no-flow configuration by
decreasing the flow-rate directly from the operating flow-rate to
zero.
9. The method of claim 1, wherein reconfiguring the tool to the
operational configuration involves a degree of translation of the
piston from the no-flow position greater than the degree of
translation of the piston from the no-flow position to the
intermediate position.
10. The method of claim 1, comprising removing the flow-restriction
from the tool.
11. The method of claim 1, comprising controlling the sequence of
reconfiguration of the tool by a cam arrangement.
12. The method of claim 1, comprising: flowing fluid through the
tool at the operating flow-rate and with the tool in a first
operating configuration; reducing the flow through the tool to the
intermediate flow-rate and reconfiguring the tool to the
intermediate configuration; and increasing the flow through the
tool from the intermediate flow-rate to the operating flow-rate and
reconfiguring the tool from the intermediate configuration to a
second operating configuration.
13. The method of claim 12, comprising reducing the flow-rate
directly from the operating flow-rate to zero and reconfiguring the
tool directly from the first operating configuration to the no-flow
configuration, and then increasing the flow-rate directly from zero
to the operating flow-rate to reconfigure the tool to the first
operating configuration.
14. The method of claim 12, further comprising: ceasing fluid flow
through the tool and reconfiguring the tool from the second
operating configuration to the no-flow configuration.
15. The method of claim 12, further comprising: ceasing fluid flow
through the tool and reconfiguring the tool from the first
operating configuration to the no-flow configuration.
16. A downhole tool having utility in an operator-selectable
intermediate configuration and in an operating configuration, the
tool comprising: a tubular body; a piston axially movably mounted
in the body, the piston being movable between a no-flow position,
an intermediate position and an operating position; and a flow
restriction cooperating with the piston to vary a flow area of the
tool; wherein, in the no-flow position, the piston and the
flow-restriction cooperate to substantially occlude the through
bore; wherein, in the intermediate position, the piston and the
flow-restriction cooperate to define an intermediate flow area,
axial translation of the piston between the no-flow position and
the intermediate position comprising an occlusional stage of a
first axial extent during which the piston and the flow-restriction
cooperate to substantially occlude the through bore and a
transitional stage of a second axial extent during which the piston
and the flow-restricting member cooperate to provide a step-change
in flow area; and wherein, with the piston in the operating
position, the tool defines an operating flow restriction.
17. The tool of claim 16, wherein the piston is biased towards the
no-flow position.
18. The tool of claim 16, wherein the flow restriction includes an
elongate flow-restricting member mounted in the body.
19. The tool of claim 18, wherein the flow-restricting member is
coaxial with the piston.
20. The tool of claim 18, wherein the flow-restricting member is
received within the piston.
21. The tool of claim 18, wherein the flow-restricting member
includes a substantially cylindrical portion which is received in a
complementary passage in the piston when the piston is in the
no-flow position and during the occlusional stage of translation
between the no-flow position and the intermediate position.
22. The tool of claim 16, wherein the flow restriction includes an
elongate flow restriction mounted on the piston which cooperates
with a complementary restriction in the body.
23. The tool of claim 16, wherein the piston defines a piston flow
restriction, such that increasing flow through the piston creates
an increasing axial fluid pressure force on the piston.
24. The tool of claim 23, wherein the piston flow restriction
cooperates with a body-mounted flow-restricting member.
25. The tool of claim 16, wherein the piston and body cooperate to
define a differential piston, wherein an area of the piston is
exposed to internal tool pressure and an oppositely directed area
of the piston is exposed to external tool pressure.
26. The tool of claim 16, comprising a cam arrangement for
controlling the movement of the piston relative to the body.
27. A method of reconfiguring a downhole device between a no-flow
configuration, a first flow configuration and a second flow
configuration, the method comprising: providing a device in a
no-flow configuration; flowing fluid through the device at an
operating flow-rate and reconfiguring the device to a first flow
configuration; maintaining fluid flow through the device at the
operating flow-rate and maintaining the device in the first flow
configuration; reducing the fluid flow through the device from the
operating flow-rate to an intermediate flow-rate lower than the
operating flow-rate and reconfiguring the device to an intermediate
flow configuration between the no-flow configuration and the first
flow configuration; and increasing the fluid flow through the
device from the intermediate flow-rate to the operating flow-rate
and reconfiguring the device from the intermediate configuration to
a second flow configuration.
28. The method of claim 27, further comprising: stopping fluid flow
through the device and reconfiguring the device from the second
flow configuration to the no-flow configuration, or stopping fluid
flow through the device and reconfiguring the device from the first
flow configuration to the no-flow configuration.
29. The tool of claim 16, wherein the piston is a tubular piston
defining a throughbore and the flow area varied by the flow
restriction cooperating with the piston is a flow area of the
throughbore of the tool.
30. The tool of claim 22, wherein the elongate flow restriction
mounted on the piston is received in a complementary restriction in
the body when the piston is in the no-flow position.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of GB Patent Application
No. 1302981.4, filed on Feb. 20, 2013, the entire contents of which
are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to the control of a downhole tool or
device, utilizing fluid pressure or flow.
BACKGROUND OF THE INVENTION
[0003] In the oil and gas industry it is well known to utilize
variations in flow though a drill string to actuate or control
actuation of downhole tools or devices. Flow through a restriction
in a spring-loaded sleeve may be utilized to create a pressure
differential across the sleeve, the pressure differential moving
the sleeve downwards from a first or no-flow position, against the
action of the spring, to a second or flow position associated with
activation or actuation of an associated device. The movement of
the sleeve may be controlled by means of a cam arrangement, such as
a J-slot or cam track and cam follower pin. The cam track may be
configured to provide for two or more flow positions. One flow
configuration may be associated with actuation of an associated
device, and in another flow configuration the device may remain
inactive. The operator may achieve these positions simply by
cycling the surface pumps on and off. However, if the pumps are
cycled for other reasons, such as to make a connection at surface,
the operator may have to cycle the pumps a number of times to
achieve or regain the desired configuration. There is also a risk
that the operator will have a mistaken belief that a tool is in a
certain configuration when it is not, which may have significant
operational and safety implications.
[0004] In other arrangements the cam track may define alternative
paths. U.S. Pat. No. 6,289,999 describes a fluid flow control
device in which an operator may select a path associated with a
flow-through mode or a path associated with a valve control mode.
The selection is made by the operator remotely tracking the
movement of a lug along a ratchet path following the actuation of
fluid pumps. At a certain relative position of the lug on the
ratchet path, shutting off the fluid pumps causes the lug to track
back along the ratchet path, a corner in the ratchet path then
deflecting the lug from a first operational mode path into a second
path. The relative position of the lug on the ratchet path where
shutting off the pumps will result in the change of mode path is
described as the "window of opportunity" and is signaled to the
operator on surface by fluid pulse signals created by an external
flange on an inner piston aligning with flanges on an outer housing
as the piston translates relative to the housing. Such an argument
requires the operator to actively monitor a pressure gauge and
recognize the appropriate fluid pulse signals.
SUMMARY OF THE INVENTION
[0005] According to the present invention there is provided a
method of operating a downhole tool, the method comprising:
[0006] providing a downhole tool in a no-flow configuration in
which an axially movable tubular piston and a flow-restriction
cooperate to substantially occlude a tool throughbore;
[0007] reconfiguring the tool to an intermediate configuration by
flowing fluid through the tool at an intermediate flow-rate lower
than an operating flow-rate and axially translating the piston to
an intermediate position in which the piston and flow-restriction
cooperate to define an intermediate flow area, wherein axial
translation of the piston between a no-flow position and the
intermediate position comprises an occlusional stage of a first
axial extent during which the piston and the flow-restriction
substantially occlude the tool throughbore and a transitional stage
of a second axial extent during which the piston and the
flow-restriction cooperate to provide a step-change in flow
area;
[0008] holding the tool in the intermediate configuration by
flowing fluid through the tool at the intermediate flow-rate;
and
[0009] reconfiguring the tool to an operating configuration by
flowing fluid through the tool at the operating flow-rate and
axially translating the piston to an operating position in which
the tool defines an operating flow area.
[0010] The tool may be reconfigured between the different
configurations in any appropriate order or sequence.
[0011] For example, the tool may be provided in the no-flow
configuration and then reconfigured to the intermediate
configuration by activating surface pumps to circulate fluid
through the tool at the intermediate flow-rate and axially
translate the piston from the no-flow position to the intermediate
position. In this sequence, the axial translation of the piston
will comprise an initial occlusional stage and a secondary
transitional stage. The flow-rate may subsequently be reduced to
zero to return the tool to the no-flow configuration, or
alternatively the flow-rate may be increased to the operating
flow-rate to reconfigure the tool to the operating
configuration.
[0012] Alternatively, or in addition, the tool may be provided in
the operating configuration and then reconfigured to the
intermediate configuration by reducing the flow-rate through the
tool from the operating flow-rate to the intermediate flow-rate and
permitting the piston to assume the intermediate position.
[0013] Alternatively, or in addition, the tool may be directly
reconfigured from the no-flow configuration to the operating
configuration by increasing the flow-rate directly from zero to the
operating flow-rate without seeking to maintain the flow-rate at an
intermediate level and thus attain and then maintain the
intermediate configuration. Similarly, decreasing the flow-rate
directly from the operating flow-rate to zero may directly
reconfigure the tool from the operating configuration to the
no-flow configuration.
[0014] Thus, embodiments of the invention permit an operator to
reliably attain and hold an intermediate configuration of the
downhole tool, increasing the activation options available when
compared to a conventional flow-activated tool, which is likely to
be only reliably maintained in a no-flow configuration and an
operating flow configuration. This degree of control may be
achieved merely by selecting an appropriate flow-rate of fluid
through the tool, typically by control of surface pumps used to
circulate fluid through a downhole tubing string incorporating the
tool.
[0015] The provision of the occlusional stage of axial translation
of the piston between the no-flow configuration and the
intermediate position may provide the operator with assurance that
the piston has moved to the intermediate position and achieved the
desired function, for example a tool activation or setting
associated with the intermediate tool configuration. In certain
embodiments, even a relatively small flow-rate will ensure that the
intermediate configuration is achieved. Further, in certain
embodiments an intermediate flow-rate within a relatively broad
range will achieve the desired intermediate configuration. The
interaction of the flow-restriction and the piston serves to
facilitate attaining the intermediate configuration from the
operating configuration, the step-change in flow area at the
transitional stage tending to maintain the tool in the intermediate
configuration over a range of flow-rates below the operating
flow-rate.
[0016] The second axial extent of the transitional stage may be
less than the first axial extent of the occlusional stage.
[0017] The reconfiguration of the tool to the operating
configuration may involve a degree of translation of the piston
from the no-flow configuration greater than the degree of
translation of the piston from the no-flow position to the
intermediate position.
[0018] The method may comprise removing the flow-restriction from
the tool, moving the restriction out of cooperating engagement with
the piston, or otherwise reconfiguring the restriction, to improve
access to the tool throughbore below the restriction location or to
increase the flow area through the tool. For example, a
flow-restricting member provided in the body may be retrievable or
otherwise removable.
[0019] The order or sequence of reconfiguration of the tool may be
controlled or guided, for example a cam or J-slot arrangement may
be provided between the piston and a tool body. In one embodiment
one element of the tool may define a cam track and another element
may define a cam follower, such as a pin. The cam track may define
alternative or multiple paths or branches and the path followed may
be operator-determined by selecting a particular sequence of
configurations.
[0020] In one embodiment the method may be utilized to allow
selection of a first operating configuration and a second operating
configuration, the method comprising:
[0021] flowing fluid through the tool at the operating flow-rate
and with the tool in a first operating configuration;
[0022] reducing the flow through the tool to the intermediate
flow-rate and reconfiguring the tool to the intermediate
configuration; and
[0023] increasing the flow through the tool from the intermediate
flow-rate to the operating flow-rate and reconfiguring the device
from the intermediate configuration to a second operating
configuration.
[0024] In an alternative operating sequence, if the flow-rate is
reduced directly from the operating flow-rate to zero the tool may
be reconfigured directly from the first operating configuration to
the no-flow configuration, and if the flow rate is then increased
directly from zero to the operating flow-rate the tool may be
reconfigured to the first operating configuration. Thus, for
example, in normal operations in which the flow-rate is varied
directly between zero and the operating flow-rate as the surface
pumps are switched on and off, the tool may be cycled between the
no-flow configuration and the first operating configuration. Only
if the operator selects to operate the surface pumps to provide a
particular sequence of flow-rates, for example reducing the
flow-rate to the intermediate flow-rate and then increasing the
flow-rate to the operating flow-rate, will the tool assume the
second operating configuration.
[0025] The second operating configuration may be associated with a
branch or path of a cam track distinct from a branch or track
associated with the first operating configuration.
[0026] The method may further comprise: [0027] ceasing fluid flow
through the tool and reconfiguring the tool from the second
operating configuration to the no-flow configuration, or [0028]
ceasing fluid flow through the tool and reconfiguring the tool from
the first operating configuration to the no-flow configuration.
[0029] According to another aspect of the present invention there
is provided a downhole tool having utility in an
operator-selectable intermediate configuration and in an operating
configuration, the tool comprising:
[0030] a tubular body;
[0031] a tubular piston axially movably mounted in the body and
defining a through bore, the piston being movable between a no-flow
position, an intermediate position and an operating position;
and
[0032] a flow-restriction cooperating with the piston to vary the
flow area of the through bore;
[0033] in the no-flow position the piston and flow-restriction
cooperating to substantially occlude the through bore;
[0034] in the intermediate position the piston and flow-restriction
cooperating to define an intermediate flow area, axial translation
of the piston between the no-flow position and the intermediate
position comprising an occlusional stage of a first axial extent
during which the piston and the flow-restriction cooperate to
substantially occlude the through bore and a transitional stage of
a second axial extent during which the piston and the
flow-restriction cooperate to provide a step-change in flow area;
and
[0035] with the piston in the operating position the tool defining
an operating flow area.
[0036] The flow restriction may take any appropriate form. In one
embodiment the flow restriction may include an elongate
flow-restricting member mounted in the body. The flow-restricting
member may be coaxial with the piston. The flow-restricting member
may be received within the piston. The flow-restricting member may
be axially movable relative to the piston.
[0037] In one embodiment the flow-restricting member may include a
substantially cylindrical portion which cooperates with a
complementary passage or restriction in the piston when the tool is
in the no-flow configuration and during the occlusional stage of
translation between the no-flow position and the intermediate
position. The transitional stage of translation occurs when the
cylindrical portion of the flow-restricting member and the
complementary passage or restriction separate to provide a
step-change in flow area. Of course other configurations of
flow-restricting member and piston may be utilized to achieve a
similar effect, such as a flow-restricting member with a stepped
profile which provides the step change in area.
[0038] Alternatively, or in addition, the flow restriction may
include an elongate flow restriction or probe mounted on the piston
which cooperates with a complementary passage or restriction in the
body.
[0039] The piston may define a flow restriction, for example a
nozzle, such that increasing flow through the piston creates an
increasing axial fluid pressure force on the piston. If the piston
is biased towards the no-flow position, increasing flow may tend to
increase the distance of the piston from the no-flow position. In
some embodiments the piston flow restriction may cooperate with a
body-mounted flow-restricting member. In other embodiments the
piston and body may cooperate to define a differential piston,
wherein an area of the piston is exposed to internal tool pressure,
which may be drill string pressure, and an oppositely directed area
of the piston is exposed to external tool pressure, which may be
annulus pressure. Accordingly, a higher internal pressure may be
utilized to urge the piston towards the operating position.
[0040] According to an aspect of the present invention there is
provided a method of reconfiguring a downhole device between a
no-flow configuration, a first flow configuration and a second flow
configuration, the method comprising:
[0041] providing a downhole device in a no-flow configuration;
[0042] flowing fluid through the downhole device at an operating
flow-rate and reconfiguring the device to a first flow
configuration;
[0043] maintaining fluid flow through the downhole device at the
operating flow-rate and maintaining the device in the first flow
configuration;
[0044] reducing the fluid flow through the downhole device from the
operating flow-rate to an intermediate flow-rate lower than the
operating flow-rate and reconfiguring the device to an intermediate
flow configuration between the no-flow configuration and the first
flow configuration; and
[0045] increasing the fluid flow through the downhole device from
the intermediate flow-rate to the operating flow-rate and
reconfiguring the device from the intermediate configuration to a
second flow configuration.
[0046] The method may further comprise: [0047] stopping fluid flow
through the downhole device and reconfiguring the device from the
second flow configuration to the no-flow configuration, or [0048]
stopping fluid flow through the downhole device and reconfiguring
the device from the first flow configuration to the no-flow
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] These and other aspects of the invention will now be
described, by way of example, with reference to the accompanying
drawings, in which:
[0050] FIGS. 1a, 1b, 1c and 1d are schematic illustrations of a
tool in accordance with a first embodiment of the present
invention;
[0051] FIGS. 2a, 2b and 2c are schematic illustrations of a tool in
accordance with a second embodiment of the present invention;
[0052] FIG. 3 is a schematic illustration of a cam track of a tool
in accordance with an embodiment of the present invention;
[0053] FIGS. 4a, 4b and 4c are schematic illustrations of a tool in
accordance with another embodiment of the present invention;
and
[0054] FIG. 5 is a schematic illustration of a tool in accordance
with a further embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0055] Reference is first made to FIGS. 1a, 1b, 1c, and 1d of the
drawings, which are schematic illustrations of a tool 10 in
accordance with a first embodiment of the present invention. The
tool 10 is intended to form part of a downhole tubular string, such
as a drill string, tool string, or the like. Accordingly, the tool
10 includes a cylindrical body 12 having appropriate end
connections (not shown) for incorporation in the associated string.
Mounted within the body 12 is a tubular piston 14 including an
internal flow restriction in the form of a nozzle 16, such that
circulation or flow of fluid in the normal direction, that is from
surface towards the distal end of the string, creates a fluid
pressure force across the piston 14, tending to translate the
piston downwards, against the action of a compression spring
18.
[0056] A cylindrical flow restriction in the form of a probe 20 is
mounted to the body 12 and, with the piston 14 in the raised
position (FIG. 1c), the probe 20 extends into the piston 14 and
through the nozzle 16. The probe 20 is coaxial with the piston 14
and has an outer diameter only slightly smaller than the internal
diameter of the nozzle 16. Accordingly, while the probe 20 is
located within the nozzle 16 the tool body is substantially
occluded.
[0057] FIG. 1a illustrates the relative positions of the tool
elements in a typical operating configuration, with fluid being
pumped through the tool 10 and the associated string at a normal
operational rate such as required during, for example, a drilling
operation. In this situation the fluid pressure differential
created across the nozzle 16 is sufficient to move the piston 14 to
its lowermost position in the body 12. It will be observed that the
upper end of the piston 14 is spaced from and clear of the probe
20.
[0058] FIG. 1b illustrates the relative positions of the tool
elements when the flow-rate of the fluid flowing through the string
has been reduced to a relatively low intermediate rate such that
there is a minimal if any fluid pressure force created across the
nozzle 16 and the upwards spring force on the piston 14 is greater
than the opposing downwards forces; the piston 14 thus moves
upwards under the influence of the spring 18. However, as the upper
end of the piston 14 approaches the lower end of the probe 20, the
piston 14 and probe 20 cooperate to create a rapid or step-change
restriction in the fluid flow area, the pressure drop resulting
from the flow restriction creating a fluid pressure force which
maintains the piston 14 in the illustrated intermediate
position.
[0059] The piston 14 will remain in this intermediate position
until the flow-rate is increased to generate a sufficient fluid
pressure force across the nozzle 16 to overcome the action of the
spring 18 and move the piston 14 downwards towards the operating
position as illustrated in FIG. 1a, or until the flow-rate is
reduced to a negligible level and the piston 14 translates upwards
towards the no-flow configuration as illustrated in FIG. 1c.
[0060] The configuration of the tool 10 is such that the operator
may hold or retain the piston 14 in the intermediate position over
a range of flow-rates, and it is not necessary for the operator to
achieve a precise flow-rate to cause the piston 14 to hover in the
intermediate position, as would be the case in the absence of the
interaction between the piston 14 and the probe 20; the step-change
in flow area created as the piston 14 and probe 20 move from the
intermediate configuration towards the no-flow configuration tends
to retain the intermediate configuration over a wider range of
flow-rates.
[0061] As noted above, with negligible or no flow, the piston 14
moves upwards such that the probe 20 extends into and through the
piston nozzle 16.
[0062] To return the tool from the no-flow configuration to the
intermediate configuration, the operator initiates flow through the
string, typically by activating the surface pumps. The intermediate
configuration is likely to be achieved simply by turning the pumps
up sufficiently to circulate fluid through the string; the
occlusion of the tool 10 by the interaction of the piston 14 and
the probe 20 causes the piston 14 to move beyond the end of the
probe 20 and thus permit a degree of fluid flow. At very low
flow-rates the tool 10 may experience a degree of chatter, as the
piston 14 moves between a just-open and just-closed position,
however this may be avoided by a small increase in flow-rate.
[0063] Alternatively, if the surface pumps are simply restored to
the normal operating flow-rate the piston 14 will move directly to
the operating position, passing through but not remaining in the
intermediate position. Similarly, simply shutting the pumps down
directly from the normal operating level will cause the tool to
move directly from the operating configuration to the no-flow
configuration, passing through but not remaining in the
intermediate position.
[0064] Reference is now made to FIGS. 2a, 2b and 2c of the
drawings, these Figures being schematic illustrations of a tool 110
in accordance with a second embodiment of the present invention.
The tool 110 operates in a generally similar manner to the tool 10
described above, but includes a number of different features, as
will be described.
[0065] The tool 110 includes a cylindrical body 112 and mounted
within the body 112 is a tubular piston 114 having a cylindrical
inner flow surface 115. A stepped-profile cylindrical flow probe
120 is mounted to the body 112 and, with the tool 110 in the
no-flow configuration and the piston 114 in the raised position
(FIG. 2c), extends into the piston 114. The probe 120 is coaxial
with the piston 114 and has an upper portion 120a with an outer
diameter only very slightly smaller than the internal diameter of
the inner flow surface 115 and a lower portion 120b at the probe
free end with an outer diameter significantly smaller than the
internal diameter of the surface 115. Accordingly, while the probe
upper portion 120a is located within the piston 114 the tool body
is substantially occluded, and while the probe lower portion 120b
is located within the piston 114 fluid may flow through the tool
110.
[0066] FIG. 2a illustrates the relative positions of the tool
elements in a typical operating configuration, with fluid being
pumped through the tool 110 and the associated string at a normal
operational rate such as required during, for example, a drilling
operation. In this situation the fluid pressure differential
created across the piston 114 and the restriction 130a resulting
from the interaction between the piston inner flow surface 115 and
the probe lower portion 120b is sufficient to move the piston 114
to its lowermost position in the body 112, and fully compress the
spring 118. It will be observed that the upper end of the piston
114 is spaced from and clear of the probe upper portion 120a.
[0067] FIG. 2b illustrates the relative positions of the tool
elements when the flow-rate of the fluid flowing through the string
has been reduced to a relatively low level such that there is a
minimal fluid pressure force created across the restriction 130a.
The upwards spring force on the piston 114 is thus greater than the
opposing downwards forces and the piston 114 moves upwards under
the influence of the spring 118. However, as the upper end of the
piston 114 approaches the step or transition 120c between the upper
and lower probe portions 120a, 120b, the piston 114 and probe
transition 120c cooperate to create a rapid or step-change
restriction in the fluid flow area, the pressure drop resulting
from the resulting restriction 130b creating a fluid pressure force
which maintains the piston 114 in the illustrated intermediate
position.
[0068] The piston 114 will remain in this intermediate position
until the flow-rate is increased to generate a sufficient fluid
pressure force across the restriction 130b to overcome the action
of the spring 118 and move the piston 114 downwards, or until the
flow-rate is reduced to a negligible level and the piston 114
translates upwards towards the no-flow configuration as illustrated
in FIG. 2c.
[0069] As with the tool 10 described above, the configuration of
the tool 110 is such that the operator may retain the piston 114 in
the intermediate position over a range of flow-rates, and it is not
necessary for the operator to achieve a precise flow-rate to cause
the piston 114 to hover in the intermediate position, as would be
the case in the absence of the interaction between the piston 114
and the probe transition 120c; the step-change in flow area created
as the piston 114 and probe 120 move from the intermediate
configuration tends to retain the configuration over a wider range
of flow-rates.
[0070] With negligible or no flow, the piston 114 moves upwards
such that the entire probe 120 extends into the piston 114 and the
upper probe portion 120a substantially occludes the piston 114.
[0071] To return the tool 110 to the intermediate configuration as
illustrated in FIG. 2b, the operator initiates flow through the
string, typically by activating the surface pumps. The intermediate
configuration is likely to be achieved simply by turning the pumps
up sufficiently to circulate fluid through the string; the
occlusion of the tool 110 by the interaction of the piston 114 and
the probe upper portion 120a causes the piston 114 to move beyond
the end of the probe transition 120c in the presence of a
relatively low flow rate.
[0072] The upper end of the probe 120 includes a wireline overshot
profile 132 and a probe-mounting spider 134 which secures the probe
120 to the body 112 via shear pins 136, thus permitting removal of
the probe 120 from the tool 110 if desired. Retrieval of the probe
120 removes the bore restriction created by the probe 120 and also
provides unrestricted access to the string bore below the tool
110.
[0073] Reference is now made to FIG. 3 of the drawings, which is a
schematic illustration of a cam track 50 of a tool, such as one of
the tools 10, 110 as described above, in accordance with an
embodiment of the present invention. As will be described, this
embodiment permits an operator to configure the tool in two
distinct operating configurations.
[0074] The cam track 50 is formed on the inner diameter of the tool
body 12, and a cam follower pin 52 extends radially outwards from
the piston 14. In normal flow conditions the piston 14 is urged
downwards with the interaction of the pin 52 and track 50 holding
the piston 14 in a first position 1 corresponding to a first
operating configuration, for example as illustrated in FIG. 1a. If
the fluid flow is then reduced to the intermediate flow-rate the
pin 52 moves up the track 50 to a second position 2, corresponding
to the intermediate configuration, as illustrated in FIG. 1b of the
drawings. If the flow is held at the intermediate flow-rate for a
short period, given the manner in which the piston 14 and probe 20
interact, the operator can be confident that the intermediate
configuration has been achieved. If the pumps are then brought up
to normal flow, the pin 52 will travel back down the track 50 but
will move into a blind track branch 50a and to a third position 3,
which permits the piston 14 to be translated further downwards to a
second operating configuration, as illustrated in FIG. 1d of the
drawings. This extra stroke may be utilized to perform a desired
tool activation, for example to actuate or extend a cutting blade
on a reaming tool.
[0075] However, if the tool is in the first operating
configuration, with the pin 52 in position 1, and flow is stopped
completely, the pin will move directly from position 1 to a fourth
position 4, corresponding to the no-flow configuration, as
illustrated in FIG. 1c. If the pumps are then restarted the pin 52
will move to the next position 1, corresponding to the first
operating configuration. Accordingly, if the pumps are stopped, for
example to make a connection at surface, and then restarted, the
tool 10 will not be activated. If activation is required the
flow-rate must be reduced to and preferably held at the
intermediate flow-rate and then increased again without stopping
the pumps.
[0076] Reference is now made to FIGS. 4a, 4b and 4c of the
drawings, schematic illustrations of a tool 210 in accordance with
another embodiment of the present invention. The tool 210 operates
in a manner which is generally similar to the tools 10, 110
described above but has some different constructional features, as
will be described.
[0077] Mounted within the tool body 212 is a tubular piston 214
including an internal nozzle 216, such that flow of fluid through
the tool in the normal direction, that is from surface towards the
distal end of the drill string incorporating the tool 210, creates
a fluid pressure force across the piston 214, over seal area at
seal diameter B, tending to translate the piston downwards, against
the action of a compression spring 218. A cylindrical probe 220 is
mounted on the upper end of the piston and cooperates with a
restriction 215 provided in the body 212 above the piston 214. With
the piston 214 in the raised position (FIG. 4c), the probe 220
extends into the restriction 215. The probe 220 has an outer
diameter only slightly smaller than the internal diameter of the
restriction 215. Accordingly, while the probe 220 is located within
the restriction 215 the tool body is substantially occluded.
[0078] FIG. 4a illustrates the relative positions of the tool
elements in a typical operating or drilling configuration, with
fluid being pumped through the tool 210 at a normal operational
rate, for example while drilling. In this situation the fluid
pressure differential created across the nozzle 216 is sufficient
to move the piston 214 to its lowermost position in the body 212 in
which the lower end of the body restriction 215 is spaced from and
clear of the upper end of the piston probe 220. The relatively
large seal area at least diameter B minimized the pressure drop
required across the nozzle 216, thus minimizing the pump pressure
required to maintain the piston in the operating or drilling
position.
[0079] FIG. 4b illustrates the relative positions of the tool
elements when the flow-rate of the fluid flowing through the string
has been reduced to a relatively low, intermediate rate such that
there is minimal if any fluid pressure force created across the
nozzle 216 and the upwards spring force on the piston 214 is
greater than the opposing downwards forces; the piston 214 thus
moves upwards under the influence of the spring 218. As the upper
end of the probe 220 approaches the lower end of the restriction
215, the probe 220 and the restriction 215 cooperate to create a
rapid or step-change restriction in the fluid flow area. The fluid
pressure force now acting over diameter A, corresponding to the
diameter of the probe 220, maintains the piston 214 in the
illustrated intermediate position.
[0080] The piston 214 will remain in this intermediate position
until the flow-rate is increased to generate a sufficient fluid
pressure force across the nozzle 216 to overcome the action of the
spring 218 and move the piston 214 downwards towards the operating
position as illustrated in FIG. 4a, or until the flow-rate is
reduced to a negligible level and the piston 214 translates upwards
to the no-flow configuration as illustrated in FIG. 4c.
[0081] Reference is now made to FIG. 5 of the drawings, which
illustrates a tool 310 in accordance with a further embodiment of
the invention. The tool 310 is illustrated in the intermediate or
reduced flow position, with fluid pressure acting over area at seal
diameter X [[A]], the area of the upper end of the piston probe
320. It will be noted that the tool 310 is similar to the tool 210
described above in a number of respects. However, the piston 314
does not feature an internal nozzle. Rather, movement of the piston
314 to the operating position is achieved utilizing differential
pressure, as described below.
[0082] The piston 314 carries external seals [[B]] 321, [[C]] 322
which engage the inner wall of the body 312, the volume between the
seals [[B]] 321, [[C]] 322 being in communication with the tool
exterior. A port to annulus 324 is provided in body 312.
Accordingly, in use, the volume will be in communication with the
annulus. The upper seals [[B]] 320 describe a larger diameter than
the lower seals [[C]] 322.
[0083] When flow through the string is increased to the normal
operating rate the pressure differential between the interior of
the tool and the drill string, at pressure P1, and the annulus
surrounding the drill string, at pressure P2, will increase due to
drill bit pressure losses and the like. This pressure differential
will act on both seal areas at seal diameters Y [[B]] and Z [[C]],
and because seal area at seal diameter & [[B]] is larger than
seal area at seal diameter Z [[C]] the piston 314 will move down
within the body 312 to the operating position. However, there is no
pressure drop in the fluid flowing through the piston 314 such that
there is no increase in pump pressure required at the operating
fluid flow rate.
[0084] It will be apparent to those of skill in the art that the
above-described embodiments are merely exemplary of the present
invention.
[0085] It will also be apparent that the advantages provided by the
various embodiments of the present invention are applicable to many
different tools and devices. For example, the ability to reliably
achieve and maintain a fluid flow or pressure activated tool in an
intermediate position or configuration provides additional
functionality to tools which previously offered only two
configurations (a no-flow configuration and a flow
configuration).
* * * * *