Note: Descriptions are shown in the official language in which they were submitted.
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DRILL STRING RETRIEVING ~4PPARATUS
This invention relates to a. tool for use in tripping
out drill string, and in particular to a tool fox use in
pumping-out drill string.
The drilling of a bore to, for example, access sub
s surface hydrocarbon-bearing formations, is typically
achieved using a drill bit mounted on the lower end of a
hollow rotating drill string formed of drill pipe sections.
During a drilling operation, drilling fluid, or "mud", is
pumped from the surface through the drill string to
lubricate and cool the bit and to carry cuttings out of the
bore. The drill string may be rotated from the surface by
a driven rotary table coupled to the string by a kelly.
The rotary table defines a square or hexagonal central
opening and the kelly, which extends through the opening,
is of corresponding cross-section. The lower end of the
kelly is connected to the upper end of the drill string and
thus as the rotary table is driven its rotation is
transferred via the kelly to the string. The upper end of
the kelly, which is typically around 55 feet long, is
suspended from a swivel having a bail supported on a hook
on a travelling block. A fluid circulating hose carries
mud from pumps to the upper end of the swivel, which
comprises appropriate seals and bearings to allow mud to be
pumped into the upper end of the rotating kelly, and then
through the kelly into the drill string.
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During a drilling operation, sections of drill pipe,
which are approximately 9 metre: (30 feet) long, are added
to the upper end of the drill. string as the drill bit
advances and the depth of the bore increases. Similarly,
when retrieving the drill string, or "tripping out", drill
pipe sections are removed from the upper end of the drill
string as the string is lifted out of the bore.
Tripping out may simply consist of lifting the drill
string and removing the uppermost length of drill pipe.
However, in certain situations iii is necessary or desirable
to pump-out the drill string, tlnat is to continue to pump
drilling mud into the bore as the string is withdrawn.
Most commonly, this is necessary to provide a positive
pressure within the bore to prevent the bore wall from
collapsing.
In a kelly-driven rig, as described above, mud is
pumped through the kelly and into the drill string while
the kelly is lifted using the block, until the lower end of
the drill pipe length connected to the kelly is lifted
through the rotating table and above the drilling floor.
The upper end of the next section of drill pipe is secured
at the rotary table using slips, to support the drill
string. The mud pumps are then shut down and the drill
pipe connection above the rotary table broken out, leaving
a length of drill pipe suspended from the kelly. The kelly
is then lowered to position the attached drill pipe section
in a "mouse-hole" adjacent the rotary table, before being
uncoupled from the drill pipe sesction and made-up to the
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next drill pipe section in the string, which now forms the
upper end of the drill string. The mud pumps are then
started again and the drill string lifted another 9 metres
(30 feet) before repeating this process. Clearly, this is
time-consuming, and pumping-out a drill string of any
length will take a considerable time.
Savings in time may be achieved by using a top drive
assembly to drive and support the' drill string, rather than
a kelly and rotary table, as this allows the drill string
to be lengthened and shortened in 27 metre (90 feet)
intervals equating to a drill stand made up of three drill
pipe sections. However, many rigs are not equipped with
top drives or may not be capab:Le of accommodating a top
drive; and there are a number of situations where it is
necessary or desirable to utilise a kelly-driven rig.
It is among the objectiv~:s of embodiments of the
present invention to provide a tool which facilitates the
pumping-aut of a drill string in a kelly-driven rig.
According to the present invention there is provided
a tool for use in retrieving a tubular drill string from a
bore, the tool comprising:
a body for suspending from <~ support;
a fluid inlet for communicai:.ion with a fluid source;
a fluid outlet for communication with a drill string
bore; and
a coupling which may be selectively actuated to engage
a drill string.
The present invention also relates to a method of
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using such a tool.
In use, the tool and an elevator may be suspended in
a rig from a travelling block:, with the drill string
suspended from the elevator and the tool connected to the
tool joint above the elevator. Fluid is supplied to the
tool and flows through the tool into the string and bore.
The block is raised to lift a portion of the drill pipe
string above the drill floor. The supply of fluid is-
interrupted and the string broken at an appropriate point
above the drill floor, leaving one or more drill pipe
lengths suspended from the elevator. The tool coupling is
then disconnected from the drilT_ pipe lengths. The tool
may then be positioned and the cc>upling actuated to engage
the upper end of the drill string. The supply of fluid
through the tool and into the drill string then
recommences, and the next section of string is lifted from
the bore by the drill pipe elevator and block.
Preferably, the coupling is :fluid actuated. Thus, the
coupling may be actuated by the fluid being supplied via
the tool to the drill string, such that no separate supply
of power for the coupling is required. Most preferably,
means is provided fox maintaining the coupling in actuated
configuration, and in engagement with the string, after
the supply of fluid has been interrupted prior to breaking
the string. Conveniently, said means is in the form of a
one-way valve, which valve is preferably operator
releasable to allow disengagement of the coupling.
Preferably also, a valve is provided in the body fox
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restricting or preventing passage of fluid to the fluid
outlet until the supply fluid pressure has reached a
predetermined level equal to or in excess of the pressure
required to actuate the coupling. Accordingly, in use,
fluid will not flow through the' tool and into the drill
string until the coupling has ~angaged the drill string.
This feature simplifies the coupling operation, as an
operator is only required to carry out the single task of
turning on the mud pumps to achieve both the actuation of
the coupling and the initiation of flow into the string.
Of course this arrangement also simplifies the construction
of the tool.
Preferably also, the coupling includes a fluid
actuated sealing arrangement, for selectively providing a
seal between the fluid outlet and the drill string.
Preferably also, the coupling includes a radially
expandable segmented male portion, typically in the form of
a threaded pin cannection, for selective engagement with a
corresponding female portion of a drill string. The male
portion may be mounted on a resilient body itself mounted
on a rigid support, and introduction of actuating fluid
into a volume between the resil~_ent body and the support
causes radial expansion of t:he resilient body and
corresponding radial expansion of the segmented male
2S portion. The resilient body may extend beyond an end of
the male portion so that the body may be expanded into
sealing contact with the drill string female portion.
Preferably also, a pressure transmitting medium is
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provided between the fluid inlet and the coupling, most
preferably the medium comprising a fluid, such as oil,
isolated from the drilling fluid in the body, preferably by
a piston. The piston may be biassed to release the
coupling.
These and other aspects of the present invention will
now be described, by way of example, with reference to the
accompanying drawings, in which:
Figure l is a plan view of a pump-out tool in
accordance with a preferred eonbodiment of the present
invention;
Figure 2 is a sectional view on line A-A of Figure 1,
the tool being illustrated in a first configuration; and
Figure 3 is a sectional view corresponding to Figure
2 and illustrating the tool in a second configuration.
The drawings illustrate a pump-out tool 30 in
accordance with a preferred en;ibodiment of the present
invention. The tool is utilised in pumping-out a drill
string, the upper end of which i:> indicated at 11; that is
when a drill string 11 is tripped out of a bore while
drilling fluid is being pumped. into the bore to, for
example, prevent collapse of the bore casing.
The tool 10 comprises a generally cylindrical body 12
which, in use, is suspended from a travelling block (not
shownf. A circulating hose 14 is. coupled to a fluid inlet
16 of a passage 18 extending through the body 12 to an
outlet 20 in communication with the upper end a drill pipe
section forming the upper end of a drill string 11. A
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threaded pin coupling 22 is pro~;rided on the lower end of
the body 12 for selectively engaging a corresponding box
coupling 24 as provided on the drill pipe section, as will
be described.
Located in the passage 18 i,s a normally-closed valve
26 which is spring-biassed to prevent flaw through the
passage 18. The valve 26 comprises a two-part sleeve 28,
the lower end of the sleeve being cut-away to define flow
passages 30. Mounted to the lower end of the sleeve 28 is
a valve closure 32 accommodating a one-way valve 34, which
permits restricted upward flow. The closure 32 comprises
a central part 36 accommodating the valve 34 and having a
rounded upper face and an annular- outer part 38 defining a
ledge 40. With the valve 26 in the closed position, as
illustrated in Figure 3, the ledge 40 engages a
corresponding face 42 defined by a seat 44 mounted on the
wall of the passage 18. The seat 44 sits on a ledge 46 and
has an upper face 48 supporting a coil spring 50, the upper
end of which engages an opposing face 52 defined by the
upper part of the sleeve 28. Normally, the spring 50
extends to lift the sleeve 28 upwardly in the passage 18
such that the closure 32 engages the seat 44. However, the
spring rating is selected such that a pressure differential
of 10,000 psi across the closure 32 provides sufficient
force to compresses the spring 50 and open the valve 26.
The upper end of the body accommodates two cylinders
54, 55 accammodating respective pistons 56, 57. The upper
ends of the cylinders 54, 55 are closed by threaded plugs
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58, 59 each defining a port 61 in communication with a
respective fluid line (not shown) leading to a ane-way
valve 60 which is located in a V-shaped cut-out 63 in the
upper end of the body 12. The valve 60 permits flow of
fluid from the upper part of the passage 28, through fluid
port 62, to the cylinders 54, 55, and prevents flow in the
opposite direction. However, the valve 60 may be released
by an operator to permit flow from the cylinders 54, 55
into the passage 18.
The pistons 56, 57 are biassed upwardly by respective
coil springs 64, 65 and serve to contain a hydraulic oil
reservoir utilised in actuating the coupling 22, as will be
described. Oil flow channels 66, 67 lead from the lower
end of each cylinder 54, 55 t:o the lower end of the
passage 18. The channels 66, 67 open into the passage 18
at an annular oil relief groove 68 defined in an outer face
of a wash-pipe 70 forming part of the coupling 22.
The wash pipe 70 defines a central through bore 72
having a flared upper end which opens into a part-spherical
intermediate portion of the passage 18. The larger
diameter upper end of the wash-pipe 70 is threaded and
engages a corresponding thread provided in the passage
wall. Mounted on the wash pipe 70 is a sectioned pin
connection 74 defining an extE:rnal thread. The pin
connection is divided axially into four parts and is
coupled to the wash pipe 70 by ,a rubber sleeve 76 which
extends above and below the connE:ction 74. The wash pipe
70, connection 74 and sleeve 76 are formed as an integral
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unit, by moulding the rubber sleeve 76 between the pipe 70
and connection 74. Prior to introducing of the flowable
moulding material, a release material is applied to a
portion of the surface of the wash pipe 78 such that the
rubber will not bond to the surface 78. Accordingly, fluid
may be pushed, through oil flow channel 80 leading from the
relief groove 68, into a volume 82 between the wash pipe 70
and sleeve 76, to "inflate" the sleeve 76, and radially
extend the connection 74, as illustrated in Figure 2.
The wash pipe assembly is :locked to the body 12 by a
threaded collar 84 defining a ledge for supporting a flange
86 on the upper end of the connection 74.
In use, the body will be suspended from a travelling
block with the circulating hose 14 connected to the fluid
inlet 12. The coupling 22 is positioned in the box
connection 24 of the upper end of a drill string 11
supported in the drilling floor by appropriate slips. The
rig mud pumps are turned on and drilling mud flows into the
upper end of the passage 18, which is initially closed by
the valve 26. The mud flows, vi<~ the port 62 and the one-
way valve 60, into the cylinders .54, 55 and, as the mud
pressure rises, the pistons 56, 57 are pushed downwardly in
the cylinders 54, 55, displacing the oil below the pistons
56, 57 through the oil flow channels 66, 67, 80 into the
volume 82 between the wash pipe 70 and the rubber sleeve
76. The expanding volume 82 pushes the segments of the
connection 74 radially outwardly and into engagement with,
the box connection 24.
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As the mud pressure rises further, the valve 26 is
opened and permits mud to flow through the body passage 18
and down. through the drill string. The slips are then
released and the tool l0 is raised by the block and drill
5 string elevator, to lift the drill string and draw a
section of drill pipe through the drill floor. The slips
are then set again, to support the drill string from the
drill floor. The mud pumps are shut down and the string
broken adjacent the drill floor; any excess pressure in the
10 string bore is relieved through the valve 34 in the valve
closure 32. One or more drill pipe lengths are then left
suspended from the drill pipe elevator, at this stage the
one-way valve 60 preventing rele<~se of the fluid pressure-
actuated coupling 22 providing t:he fluid tight connection
between the tool 10 and the string. The block and elevator
are then lowered to locate the drill pipe lengths in the
mouse hole in the drill floor. To disconnect the drill
pipe 11 from the coupling 22, the one-way valve 60 is
released by an operator, allowing the springs 64, 65 to
lift the pistons 56, 57 and di:~place the drilling fluid
from the cylinders 54, 55. The upward movement of the
pistons 56, 57 draws the oil from the volume 82,
"deflating" the rubber sleeve 76 and retracting the
segments of the connection 74. Once the elevator is
uncoupled from the drill pipe, the tool 10 is lifted clear
of the drill pipe and the connection 74 positioned in the
box of the drill pipe length forming the upper part of the
drill string, and the process repeated.
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The invention is particularly suited for use in kelly-
driven rigs, and the relativ~s ease of making-up and
breaking connections between the tool and the drill pipe,
and the ability to omit the kelly, allow a drill string to
be pumped-out of a bore relativE:ly quickly and easily.
The description above refers to drilling fluid and
drilling mud, and those of skill in the art will understand
that these terms are not intended to limit the fluids which
may be utilised in the operation of the tool 10. Also, it
will be apparent from an examination of the accompanying
drawings that, in the interests of brevity, the provision
and location of various seals and other minor parts of the
tool 10 have not been described in detail, on the basis
that these features will be read:Lly apparent to the person
of skill in the art.
It will also be clear to those of skill in the art
that the above described embodiment is merely exemplary of
the present invention and that various modifications and
improvements may be made thereto 'without departing from the
present invention.
