Note: Descriptions are shown in the official language in which they were submitted.
CA 02686298 2009-11-25
DUMP BAILER
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is based on and claims priority to European
Patent Application
No. EP08170190, filed, November 28, 2008.
TECHNICAL [+IELl)
(0002) The present disclosure relates generally to a borehole tool assembly
for use in
depositing materials in boreholes drilled in an underground formation. More
particularly, but not
by way of limitation, the present disclosure relates to dump bailers for use
in boreholes such as
oil and gas wells.
BACKGROUND ART
[0003] Dump bailers have been developed to remove debris or solids deposits
from the
wellbore prior to completing some other task, or to obtain a sample of the
fluid from the area of a
downhole device, by utilizing a suction action similar to a bicycle pump.
Later developments of
bailers became available to deposit cements or chemicals into a wellbore by
simply reversing the
action. However, these bailers do not positively displace their contents in
the true sense, typically
relying on gravity.
[0004] A dump-bailer tool normally includes a tubular chamber for storing the
cement slurry
and a ported valve for the slurry to discharge from the dump-bailer into the
subterranean
wellbore. Dump-bailer tools are well known in the oil and gas industry. They
essentially include
a thin walled concentric fluid chamber consisting of threaded bailer tube
sections. The upper end
of the tubes is connected mechanically to an armored or solid cable that is
spooled on a surface
winch. The lower end of the tool consists of electrical and/or mechanical dump
release
mechanisms, for example a bull-plug which supports and confines the cement
slurry during
conveyance into the wellbore. The bull-plug consists of a valve device or
rupture plug, which is
initiated at the proper dump depth by human interface, either electrically,
hydraulically, or
mechanically initiated.
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[0005] In one example, the dump bailer method expels the cement slurry at a
bridge plug or
other barrier device in the well casing, possibly above perforations to the
reservoir formation
through the casing, prior to making new perforations. The slurry volume
capacity of the dump-
bailer device is limited by the length and internal diameter of the bailer
tubes. Typical dump-
bailer volumetric capacities range from one to six imperial gallons (four to
twenty-eight liters).
After each dump of slurry, the dump bailer is retrieved to the surface and
prepared for
subsequent dump-bail operations.
[0006] Of the gravity feed systems available, most use a glass or ceramic disc
to retain the
cement which is either broken with an explosive charge or by a pin when the
tool is set-down.
Gravity feed systems are not as desirable as they tend to leave some cement in
the tool which
then "strings" out as the tool is pulled out of hole. More runs might be
needed to achieve the
correct amount of cement for the desired plug strength (differential
strength).
[0007] Positive displacement dump bailer systems have been previously
proposed. These
typically run on electric line and release a weight onto a piston which
applies a pressure shock
through the cement which shears a pin at the bottom of the bailer which allows
the cement to fall
out the bottom of the bailer either under its own weight or with the
additional weight of the
actuating system. One known device uses a motor to release the weight and
another uses a
solenoid. One variation uses an explosive bolt which has a similar function as
the solenoid-
Another known bailer is activated either by a timer or by a pressure
transducer, but again only
uses gravity to displace the contents to the wellbore.
[0008] Examples of various prior art documents in this field, include U.S.
2,591,807; U.S.
2,689,008; U.S. 2,696,258; U.S. 2,725,940; U.S. 2,994,378; U.S. 3,187,813,
U.S. 3,202,961;
U.S. 3,208,521; U.S. 3,273,647; U.S. 3,318,393; U-S. 3,379,251; U.S.
6,966,376; and, EP
1,223,303.
[0009] It is to rectifying these and other shortcomings of the current art
that the present
invention is directed. Therefore, the present disclosure is directed to
providing a wireline tool
assembly which provides true positive displacement of its contents into the
borehole and that
does not rely on gravity alone in which to do so.
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BRMF DISCLOSURE OF THE INVENTION
[0010] In view of the foregoing disadvantages, problems, and insufficiencies
inherent in the
known types of methods, systems and apparatus present in the prior art,
exemplary
implementations of the present disclosure are directed to a new and useful
dump bailer.
[0011) In at least one aspect, the dump bailer comprises: a tool body defining
a chamber for
containing a material to be deposited; an outlet in the tool body through
which the material can
be deposited; and a piston assembly slideably mounted in the chamber and
comprising a
swabbing piston, a supply of pressu rizcd fluid, and a valve for releasing the
pressurized fluid to
act on the swabbing piston to drive it along the chamber to expel material
contained therein
through the outlet.
[0012] In one embodiment, the valve is operable to direct pressurized fluid to
act directly on
the swabbing piston. In this case, the supply of pressurized fluid can
comprise a reservoir carried
on the swabbing piston so as to be moveable therewith.
[0013] Another embodiment further comprises an intermediate mechanism through
which the
pressurized fluid can act on the swabbing piston.
[0014] The piston assembly can comprise a first stage piston slideably mounted
in the tool
body, and a second stage piston that is slideably mounted in the first stage
piston, the second
stage piston being connected to the swabbing piston, the valve operating to
release pressurized
fluid between the first and second stage pistons to drive the swabbing piston
along the chamber.
(0015] Preferably, a sliding seal is provided on an inner wall of the tool
body, and the first
stage piston comprises a head end that seals against the inner wall of the
tool body, and a tail end
that has a smaller diameter than the head end and seals in the sliding seal.
[0016] The supply of pressurized fluid can comprise a reservoir defined
between the head end
of the first stage piston and the sliding seal on the tool body and sliding
movement of the first
stage piston in the tool body can cause the reservoir to change in volume.
[0017] It is preferred that there is an opening in the tool body such that the
interior of the tool
body below the sliding seal is open to ambient pressure. The interior of the
tool body above the
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head end of the first stage piston can open to ambient pressure or a
supplementary supply of
pressurized fluid can be connected to the interior of the tool body above the
head end of the first
stage piston by means of a valve. Preferably the pressurized fluid is
pressurized by the effect of
the ambient pressure acting on it.
[001$] The second stage piston is typically mechanically connected to the
swabbing piston, and
the first stage piston defines a cylinder in which the second stage piston is
mounted and into
which the valve can release pressurized fluid to drive the second stage piston
along the cylinder
which in turn drives the swabbing piston along the chamber.
[0019] In this case, the portion of the cylinder below the second stage piston
can be maintained
at an internal pressure that is less than the pressure of the fluid in the
supply when the tool is in
an ambient operating pressure environment.
[0020] The outlet typically comprises a relief valve that is normally held in
a shut position until
the pressure in the chamber rises above an opening pressure due to the action
of the swabbing
piston.
[0021] In one preferred embodiment, the outlet comprises an end fitting having
an opening in a
predetermined azimuthal position on the tool circumference- In another, the
end fitting has a
number of openings at azimuthal positions on the tool circumference. The end
fitting can be
freely rotatable. In which case a drive mechanism to rotate the end fitting
powered by the flow of
fluid from the chamber can be provided.
[0022] The piston system of the present invention is preferably driven by
pressure differentials,
for example between ambient operating pressure and reduced pressure in the
tool, or elevated
pressures in to tool.
[0023] Further aspccts of the invention will be apparent from the following
description.
BRIEF DESCRIPTION OF THE DRAWihGS
[0024] Certain embodiments of the present invention will hereafter be
described with reference
to the accompanying drawings, wherein like reference numerals denote like
elements, and:
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[0025] Figure 1 depicts one embodiment of a dump bailer according to an aspect
of the
invention utilizing ambient pressure as a drive force;
[0026] Figure 2 depicts an alternative embodiment of a dump bailer according
to the invention
utilizing compressed gas as a drive force;
[0027] Figures 3 and 4 depict variations of the embodiment of Figure 1 having
different end
fittings at the outlet;
[0028] Figures 5 and 6 depict an alternative embodiment of an embodiment of
the invention
comprising an actuator which utilizes compressed gas; and,
[0029] Figure 7 depicts a triggering device according to an aspect of the
invention.
DE( FOR CARRYING OU'P' THE INVENTION
[0030] One embodiment of the invention is shown in Figure 1, in which the dump
bailer
comprises a ram assembly is designed to operate by using the difference
between surrounding
wellbore fluid pressure and a void volume in the tool to apply force to a
piston.
[0031 ] The dump bailer of Figure 1 comprises a tool body 10 that can be
connected to a
conveyance system (not shown) such as a wireline cable, coiled tubing or drill
pipe, and lowered
into a well. The tool body comprises a lower section defining a chamber 12 for
containing the
fluid to be deposited in the well, and an upper section 14 comprising an
actuating mechanism
that will be discussed in more detail- below. An outlet 16 is formed at the
lower end of the
chamber 12 and is hold normally closed by a spring loaded relief valve 18 or
other means such as
a shear pin. A swabbing piston 20 is mounted in the chamber so as to be
slideable along the
chamber to drive any fluid contained therein through the outlet 16.
[0032] A sliding seal 22 is formed on the inner wall of the tool body 10 and
defines the top of
the chamber 12 and the bottom of the upper section 14.
[00331 A vent 24 is provided in the tool body 10 below the sliding seal 22 and
above the
swabbing piston 20 so that there is pressure communication between this space
and the ambient
pressure surrounding the bailer.
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[0034] The actuating mechanism in the upper section 14 comprises a two-stage
piston that is
mechanically connected to the swabbing piston 20. A first stage piston 26 is
mounted so as to be
slideable inside the upper section 14. The first stage piston 26 has a head
end 28 that seals
against the inner wall of the tool body lo, and a lower end 30 that is reduced
in diameter with
respect to the head end and defines a cylinder 32. The lower end 30 projects
through the sliding
seal 22. A second stage piston 34 is mounted slideably in the cylinder 32 and
is connected to the
swabbing piston 20 by means of a connecting rod 36.
[0035] The space around the lower end 30 and delimited by the head end 28 and
the sliding
seal 22 defines a reservoir 38 for a working fluid. A passageway 40 connects
the reservoir 38 to
the upper end of the cylinder 32. A valve 42 is provided in the passageway 40.
[0036] A further vent 44 is provided in the tool body 10 above the head end 28
so that there is
also pressure communication between this space and the ambient pressure
surrounding the bailer.
[0037] Alternatively the valve 42 can be positioned at the point where the
vent 44 is described
above, and the passageway 40 will remain as an open channel.
[0038] The space in the cylinder below the second stage piston 34 is not
filled with working
fluid, but contains either air or another gas at or near atmospheric pressure,
or, in an alternative
can be completely or partially evacuated
[0039] As will be appreciated, pressure communication through the vents 24,44
means that the
difference in areas at 22 and 26, on which ambient pressure is acting, causes
the working fluid
within reservoir 38 to be higher than the ambient pressure around the tool- At
a downhole
location, this will be substantially above atmospheric pressure. With the
second stage piston 34
at the top of the cylinder 32 and with the valve 42 closed, the second stage
piston 34 moves little,
if at all, to adopt an equilibrium position in which the pressure above the
second stage piston 34
is the same as that below it. As all pressures in the various sections are
balanced and there is no
way for the different pressure to equalize (the valve 42 being closed), the
swabbing piston 20
does not move.
[0040] When it is desired to evacuate the chamber 12, the valve 42 is opened.
This allows
working fluid from the reservoir 38 at ambient pressure to enter the cylinder
above the second
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stage piston 34. Since this is a substantially higher pressure than is found
below the second stage
piston 34, it is driven downwards, pushing the swabbing piston along the
chamber 13. The
pressure exerted on the fluid in the chamber 12 by the swabbing piston 20
overcomes the force
of the spring in the relief valve 18 and the fluids are deposited in the well.
[0041] As fluid passes from the reservoir 38 into the cylinder 32, the first
stage piston 26
advances along the upper section 14 to accommodate the reduction in volume of
fluid in the
reservoir while maintaining ambient pressure. This will continue until either
the second stage
piston 34 reaches the bottom of the cylinder 32, the swabbing piston 20
reaches the bottom of the
chamber 12 (or some other such mechanical stop point is reached), or until a
pressure
equilibrium between the fluid above the second stage piston 34 and the gas
below it is reached.
(0042] Figure 2 shows a variant of the embodiment of Figure 1. The same
numbers have been
used for corresponding parts. In this case, the vent in the upper section 14
(44 in Figure 1), is
replaced by a gas reservoir 50 and a valve 52. The gas in the reservoir is
held at a pressure higher
than the ambient pressure of the well at the depth of use. In use, both valves
42 and 52 are
opened and operation continues as described previously. The use of a
pressurized gas allows a
higher driving pressure to be applied where the operation is at relatively
shallow depth such that
the pressure differences are low, or where an extra `boost' is needed to
overcome static friction,
or some mechanical blockage.
[0043] Figure 3 shows another variant of the embodiment of Figure 1. In this
case, the outlet 16
is provided with an end fitting 54 having an outlet passage 56 terminating in
an exit port 58 that
directs flow from a side part of the end fitting 54. This particular
embodiment of the invention
can be useful where the chamber 12 is filled with acids and chemicals suitable
for de-scaling and
cleaning operations within the wellbore. The basic operating principle is the
same as described
above to generate the force to displace the contents of the bailer tube. The
exit port 58 can be
configured to have a fixed single or multiple exit orifice which may be
oriented to a particular
azimuth within the well bore using a muleshoc or other mechanical device
(typically used within
well completions such as are used to deploy or retrieve gas-lift valves from
side pocket tools) to
direct a pressure stream or jet of cleaning agent from within the apparatus
during the
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displacement stroke of the ram. The tool could then be vertically oscillated
from the well surface
to direct the stream as required over a longitudinal section of the well
trajectory.
[0044] With reference to Figure 4, another embodiment of the apparatus used
for clean up
purposes has an end fitting 60 with multiple exit jets 62 arranged equally
around its periphery to
direct pressurized streams or jets of cleaning agent around an axial section
of the wellbore. The
end fitting 60 also be made to freely rotate around the longitudinal axis of
the apparatus using the
pressure and flow of displaced fluid from the tube as a driving mechanism
whilst the hydraulic
ram is displacing the contents This arrangement could be used to clean a
landing nipple profile
or seal area of a wellbore or tubing completion.
[0045) Figures 5 and 6 show another embodiment of the invention that uses a
supply of
pressurized gas as the principal driving force. In this can, the dump bailer
comprises a tool body
70 that defines a simple chamber 72 running along it whole length. The
swabbing piston 74 is
able to slide along the whole length of the chamber 72. The swabbing piston 74
has an extended
piston body 76 extending from its rear surface to project through a sliding
seal 78 at the top of
the chamber 72. The piston body 76 includes a reservoir of pressurized gas
(e.g. nitrogen) 80 and
a passage 82 connecting the reservoir 80 to an outlet disposed in the chamber
72 just above the
swabbing piston 74. A valve 84 is provided in the passage 82. Tn use, the
valve 84 is operated to
allow pressurized gas to enter the chamber 72 above the swabbing piston 74
which is forced
down the chamber 72 expelling any fluids through an outlet 86. As the swabbing
piston 74
advances, the piston body is drawn through the sliding seal 78 until the
swabbing piston 74
reaches the bottom of the chamber 72 (Figure 6).
[0046] A trigger section that can be used with the present invention that
essentially corresponds
to a slickline firing head of the type currently used for slickline explosive
applications or to
trigger cutters and set packers and plugs- The trigger is operated by a coded
sequence of tension
pulses on the slickline wire. This coded sequence is converted to pressure
pulses by a strain
sensor in the tool. This unique combination of pulses creates the special
signature required to
communicate with the firing head, or in this case with the dump bailer
actuator.
[0047] A pressure transducer in the tool detects a command from the surface
(pull on the slick
line). Two separate processors in the controller module are required to
independently verify the
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unique command. In addition to the safety of the unique command signature of
the pressure
pulses, the tool must be enabled by a preset hydrostatic pressure, followed by
an arming
command sent from the surface, before it will accept a firing command.
[0048) The trigger works by interpreting changes in downhole pressure as
instructions to
perform specific operations during a job. Pressure changes detected by a
pressure gauge result
from two sources: deviations in ambient hydrostatic pressure (i.e. depth in
the well) and changes
in line tension, which are translated into pressure changes by the strain head
Completion of the
firing sequence requires suitable signals from both sources. The tool will not
fire unless it
reaches a preset minimum pressure specified by the operator. In addition,
jerking on the slickline
causes tension changes detectable by the pressure transducer through the
action of the strain
head. The signal produced by the jerk has unique characteristics that can be
recognized.
Detection of this signal is a slickline trigger event. The tool detects fire
commands by searching
for a predefined sequence of trigger events with specific time spacing.
[0049] Each event has an associated type, reference pressure and reference
time. These events,
each with its own reference time and pressure, are used to locate command
sequences. The tool
typically takes a pressure measurement every 200 ms for use in locating these
events. Each
sample is used for command analysis and saved in memory.
[0050] The trigger section of the tool (refer to Figure 7) comprises a
cylindrical tube housing
90, upper 92 and lower 94 connectors which allow the trigger to be mounted
concentrically to
both the slickline trigger and telescopic ramlactuator section of the tool.
Contained within the
housing is an interface electronics assembly 96 which will obtain and
interpret electrical signals
from the trigger tool at the appropriate time and operate an electric motor or
other electro-
mechanical actuator 98. T motor or electro-mechanical actuator will in turn
operate an output
shaft or rod 100 to operate the valves 42, 52, 84 of Figures 1, 2, 5 and 6.
[0051] Alternatively the tool may be triggered via electric line with a direct
or indirect
electrical connection to the surface, or by a built-in timer which is powered
by an internal battery
and where the delay is set at the surface.
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[0052] Further, those skilled in the art should appreciate that the parameters
and configurations
described herein are exemplary and that actual parameters and/or
configurations will depend on
the specific application in which the systems and techniques of the invention
are used. Those
skilled in the art should also recognize or be able to ascertain, using no
more than routine
experimentation, equivalents to the specific embodiments of the invention. it
is therefore to be
understood that the embodiments described herein are presented by way of
example only and
that, within the scope of the appended claims and equivalents thereto; the
invention may be
practiced otherwise than as specifically described.
[0053] Moreover, it should also be appreciated that the invention is directed
to each feature,
system, subsystem, or technique described herein and any combination of two or
more features,
systems, subsystems, or techniques described herein and any combination of two
or more
features, systems, subsystems, and/or methods, if such features, systems,
subsystems, and
techniques are not mutually inconsistent, is considered to be within the scope
of the invention as
embodied in the claims. Further, acts, elements, and features discussed only
in connection with
one embodiment are not intended to be excluded from a similar role in other
embodiments.
Rather, the systems and methods of the present disclosure are susceptible to
various
modifications, variations and/or enhancements without departing from the
spirit or scope of the
present disclosure. Accordingly, the present disclosure expressly encompasses
all such
modifications, variations and enhancements within its scope.
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