Note: Descriptions are shown in the official language in which they were submitted.
CA 03045336 2019-05-28
WO 2018/106347 PCMJS2017/057826
EXPLOSIVE DISCONNECT
Background
[0001] This disclosure relates to the field of well pressure control
apparatus. More
particularly, the disclosure relates to methods and devices for quickly
disconnecting a
lower marine riser package (LMRP) or other device from a well pressure control
device
coupled to a subsea wellhead.
[0002] Marine wellbore drilling techniques known in the art include the use
of a pressure
control apparatus such as a blowout preventer ("BOP") disposed proximate the
water
bottom and coupled to the upper end of a surface conduit or casing disposed in
the well
(e.g., a "wellhead"). The BOP may comprise one or more sets of reversibly
operable
"ram=type" pressure control elements, for example, "blind rams" and "shear
rams", and
in some embodiments an annular seal. Blind rams fully close an interior bore
of the BOP
housing to hydraulically isolate the well below the BOP housing. Shear rams
may be
provided to enable cutting through conduit and/or drilling tools disposed
within the
interior bore in the BOP housing and subsequently closing to hydraulically
isolate the
well below the shear rams. Annular seals may be used where it is desired to
hydraulically isolate the well while enabling a conduit such as drill pipe, or
other drilling
tools to pass through the interior bore of the BOP housing.
[0003] Each of the foregoing ram-type pressure control elements may be
disposed in
opposed pairs on the BOP housing and may be operated by respective hydraulic
ram
actuators, e.g., pistons disposed in respective cylinders. Hydraulic fluid
pressure to
operate the various ram-type pressure control elements and/or the annular seal
may be
controlled by an hydraulic fluid line extending from a control valve manifold
to a drilling
platform on the water surface, and by providing a plurality of accumulators
each having
hydraulic fluid and gas (e.g., nitrogen) under pressure to supply a relatively
large volume
of fluid rapidly in the event it becomes necessary to close any one or more of
the pressure
control elements in the BOP. The accumulators also can supply hydraulic fluid
even in
the event the hydraulic fluid line to the surface becomes blocked or
disconnected. A
1
plurality of the foregoing types of pressure control elements may be connected
to each
other along the respective interior bores to form a BOP "stack."
100041 A BOP "stack" (i.e., two or more of the foregoing types of well
pressure control
devices arranged longitudinally one atop the other) may be coupled, at one
longitudinal
end opposed to the longitudinal end connected to the wellhead, to a conduit
(e.g., a
"riser") that extends to a drilling platform proximate the water surface.
Coupling to the
riser may be through a set of devices called a "lower marine riser package"
(LMRP). In
certain situations, for example, adverse weather conditions, that make it
desirable to
move the riser and the drilling platform away from the well location, it then
becomes
necessary to disconnect the riser from the BOP stack. Disconnection may be
performed,
for example, by uncoupling the LMRP from the BOP stack after closing one or
more
pressure control elements in the BOP stack. Uncoupling may include, for
example and
without limitation, unthreading threaded connectors, removing coupling bolts
from
mating flanges and/or releasing a profile connector by rotating components of
the LMRP.
100051 Disconnecting the LMRP from the BOP stack in a station keeping
emergency is a
very important function for a BOP stack. It is known in the art to take one
minute or
longer to complete an emergency disconnect. Using known methods for LMRP
disconnection such as by uncoupling the example devices described above may
require
that disconnection decisions are made early, e.g., dynamic positioning watch
circles need
to consider the disconnect time. In addition, permissible LMRP connector
release angles
can be smaller than flex joint angle ratings. That is, the LMRP release angle
can be
governing as to the amount of movement of the drilling platform during
disconnect
operations.
Summary
10005.11 In accordance with an aspect of at least one embodiment, there is
provided a
coupling system, comprising: a connector comprising a double mandrel having a
lower
mandrel and an upper mandrel; a lower marine riser package having the upper
mandrel
coupled at a bottom end thereof; at least one blowout preventer pressure
control element
coupled to a wellhead and having the lower mandrel coupled at an upper end
thereof;
2
Date Recue/Date Received 2020-09-08
explosively frangible fasteners comprising explosively frangible nuts disposed
to couple
the upper mandrel on the lower marine riser package to the lower mandrel on
the at least
one blowout preventer pressure control element.
[0005.2] In accordance with an aspect of at least one embodiment, there is
provided a
method for separating a lower marine riser package from a blowout preventer
coupled to
a subsea wellhead, comprising: closing at least one pressure control element
in the
blowout preventer; wherein a connector comprising a double mandrel having a
lower
mandrel and an upper mandrel is configured to link the blowout preventer to
the lower
marine riser package; detonating at least one explosively frangible fastener
coupling the
lower mandrel to the upper mandrel to separate the blowout preventer from the
lower
marine riser package, the at least one explosively frangible fastener
comprising an
explosively frangible nut; and lifting the lower marine riser package from the
blowout
preventer.
100061 A coupling system according to one aspect of the present disclosure
includes a
lower marine riser package having a connector at a bottom end and at least one
blowout
preventer pressure control element coupled to a wellhead and having a
connector at an
upper end. Explosively frangible fasteners are used to couple the connector on
the lower
marine riser package to the connector on the at least one blowout preventer
pressure
2a
Date Recue/Date Received 2020-09-08
CA 03045336 2019-05-28
WO 2018/106347 PCT/US2017/057826
control element. A method for separating a lower marine riser package from a
blowout
preventer coupled to a subsea wellhead includes closing a least one pressure
control
element in the blowout preventer. At least one explosively frangible fastener
coupling the
blowout preventer to the lower marine riser package is detonated. The lower
marine riser
package is then lifted from the blowout preventer.
[0007] In some embodiments the connector on the lower marine riser package
is coupled
to the connector on the at least one blowout preventer pressure control
element by the
explosively frangible fasteners being disposed through a corresponding bolt
flange on
each of the connector on the lower marine riser package and the connector on
the at least
one blowout preventer pressure control element.
[0008] In some embodiments the explosively frangible fasteners comprise
explosively
frangible nuts.
[0009] In some embodiments the connector on the at least one blowout
preventer
pressure control element comprises a profile connection at one longitudinal
end.
[0010] In some embodiments the connector on the lower marine riser package
comprises
a profile connection to couple the connector on the lower marine riser package
to the
lower marine riser package.
[0011] In some embodiments a plurality of blowout preventer pressure
control elements
are coupled to the wellhead.
[0012] In some embodiments the lower marine riser package comprises at
least one
blowout preventer pressure control element.
[0013] A method for separating a lower marine riser package from a blowout
preventer
coupled to a sub sea wellhead according to another aspect of the present
disclosure
includes closing at least one pressure control element in the blowout
preventer. At least
one explosively frangible fastener coupling the blowout preventer to the lower
marine
riser package is detonated. The lower marine riser package is then lifted from
the blowout
preventer.
3
CA 03045336 2019-05-28
WO 2018/106347 PCT/US2017/057826
[0014] In some embodiments, prior to detonating the at least one
explosively frangible
fastener, at least one auxiliary line extending between the lower marine riser
package and
the blowout preventer is uncoupled.
[0015] In some embodiments a connector on the lower marine riser package is
coupled to
a corresponding connector on the blowout preventer by a plurality of
explosively
frangible fasteners being disposed through a corresponding bolt flange on each
of the
connector on the lower marine riser package and the connector on the blowout
preventer.
[0016] In some embodiments the explosively frangible fasteners comprise
explosively
frangible nuts.
[0017] In some embodiments the connector on the blowout preventer comprises
a profile
connection at one longitudinal end.
[0018] In some embodiments the connector on the lower marine riser package
comprises
a profile connection to couple the connector on the lower marine riser package
to the
lower marine riser package.
Brief Description of the Drawings
[0019] FIG. 1 shows an example embodiment of a LMRP connected to a subsea
BOP
stack, wherein the subsea BOP stack is connected to a subsea wellhead.
[0020] FIG. 2 shows the example embodiment of FIG. 1 wherein the LMRP has
been
disconnected from the subsea BOP stack. The LMRP is shown canted at a
relatively large
angle with reference to the subsea BOP stack.
[0021] FIG. 3 shows a cross-section of an example embodiment of an
explosive quick
disconnect mandrel system according to the present disclosure.
[0022] FIG 4 shows a perspective side view of the example embodiment shown
in FIG
3.
[0023] FIG. 5 shows a cross-section of the example explosive quick
disconnect system of
FIG. 3 after explosive removal of fasteners (e.g., studs and threaded nuts)
that join an
upper mandrel to a lower mandrel.
4
CA 03045336 2019-05-28
WO 2018/106347 PCT/US2017/057826
[0024] FIG. 6 shows a perspective side view of the illustration of FIG. 5.
Detailed Description
[0025] FIG. 1 shows an example embodiment of a lower marine riser package
(LMRP)
12 connected to a subsea BOP "stack" 14 (i.e., a plurality of vertically
assembled
wellbore pressure control elements assembled to each other to produce a series
connected
set of well shut in valves), wherein the subsea BOP stack 14 is connected to a
subsea
wellhead (not shown) using a connector 16. A connector such as a double
mandrel 10
may be used to connect the LMRP 12 to the BOP stack 14. The LMRP 12 may itself
comprise one or more pressure control elements, or in some embodiments the
LMRP 12
may not have any such pressure control elements.
[0026] The double mandrel 10 may comprise a lower mandrel 10A coupled to an
upper
end of the BOP stack 14 and an upper mandrel 10B coupled to a lower and of the
LMRP
14. The lower mandrel 10A may be connected to the BOP stack 14, e.g., by a
profile
coupling, bolted flange, or any other connection known in the art. The upper
mandrel
10B may be connected to the LMRP 12, for example, in any similar manner as the
connection between the lower mandrel 10A and the BOP stack 14. A riser (not
shown)
may extend from the top of the LMRP 12 to a drilling platform (not shown) on
the water
surface Although the BOP stack 14 shown in the various drawing figures and
described
herein may include a plurality of wellbore pressure control elements, for
purposes of the
present disclosure only one such pressure control element is needed.
[0027] FIG. 2 shows the LMRP 12 disconnected from the BOP stack 14 by
uncoupling
the lower mandrel 10A from the upper mandrel 10B. The lower mandrel 10A and
upper
mandrel 10B may be configured such that much greater angle between the
longitudinal
axis of the LMRP 12 and the BOP stack 14 may be obtained than by disconnect
devices
and methods known in the art.
[0028] In the present example embodiment, and referring to FIG. 3, such
uncoupling may
comprise detonating explosive frangible fasteners, for example explosively
frangible nuts
CA 03045336 2019-05-28
WO 2018/106347 PCT/US2017/057826
10C and/or explosively frangible studs 10D which may couple a flange 10B1 on
the
upper mandrel 10B to a corresponding flange 10A1 on the lower mandrel 10A Such
explosively frangible nuts and/or explosively frangible studs may be obtained,
for
example, from Pacific Scientific Energetic Materials Company, 7073 West Willis
Road,
Chandler, Arizona 85226. Example products sold by the foregoing organization
comprise frangible nuts which are broken apart by detonation of an explosive
charge and
explosive bolts which are similarly broken apart. In the present example
embodiment,
such frangible nuts 10C may be used on one or both ends of studs 10D that pass
through
openings in the upper mandrel flange 10B1 and lower mandrel flange 10A1. FIG.
4
shows a perspective side view of the coupled upper mandrel 10B and lower
mandrel 10A,
wherein explosive nuts 10C are used on one end of the studs 10D.
[0029] FIGS. 5 and 6 show, respectively, a cross section view and a
perspective side
view of the upper mandrel 10B being separated from the lower mandrel 10A after
detonation of the explosively frangible fasteners (e.g., nuts 10C in FIGS. 3
and 4). The
upper mandrel 10B may be separated from the lower mandrel 10A simply by
lifting the
LMRP (12 in FIG. 2) from the BOP stack (14 in FIG. 2). Profile connections
10B2 and
10A2 may be provided on one longitudinal end of each of the upper mandrel 10B
and
lower mandrel 10A respectively whereby the upper mandrel 10B may be coupled to
the
LMRP (12 in FIG. 2) using the profile connection 10B2. When the upper mandrel
10B is
separated from the lower mandrel 10A, the profile connection 10A2 on the lower
mandrel
10A may provide a mechanism to enable attaching devices to the lower mandrel
10A,
e.g., to reconnect either the LMRP (12 in FIG. 2) or a capping stack to the
BOP stack (14
in FIG. 2).
[0030] A system according to the present disclosure may comprise a BOP
stack which is
connected to the wellhead by a connector. A first mandrel with explosively
frangible
fasteners is located on top of the BOP stack. A lower marine riser package
(LMRP) is
connected to the mandrel by means of a connector. In some embodiments, the
connector
may be a second mandrel having a bolt flange corresponding to a bolt flange on
the first
mandrel. In some embodiments, the second mandrel may have a profile connector
at one
end for coupling to the LMRP. In some embodiments, the first mandrel may
comprise a
6
profile connector similar in configuration to the profile connector on the
second mandrel,
whereby after separation of the two mandrels, a connection may be provided on
the first
mandrel to reconnect the LMRP or to connect a capping stack or other device to
the BOP
stack.
100311 Auxiliary connections between the LMRP and the BOP stack may
comprise
choke and kill lines, boost lines, hydraulic and/or electric power lines and
sensors.
100321 In some embodiments, a double mandrel arrangement with explosive
nuts may be
used between the BOP stack and the LMRP. This would allow the first mandrel to
be
released from the lower stack but would still maintain an intact mandrel
connection to
reconnect either the LMRP or capping stack to the lower stack.
100331 In some embodiments the explosively frangible fasteners could be
attached to any
other flanged connection on the BOP stack or LMRP. In some embodiments,
explosively
frangible studs, bolts, or another type of explosively frangible fastener
could be used
instead of explosively frangible nuts.
100341 A method for separating a LMRP from a BOP stack according to some
embodiments may comprise closing a pressure control element, e.g., a shearing
element
(either a static force operated shear ram or a kinetic energy operated shear
ram ) in a BOP
stack coupled at its upper end to a lower marine riser package (LMRP). All
auxiliary
connections between the BOP stack and LMRP (if any are present) are
disconnected.
Explosively frangible fasteners that couple the LMRP to the BOP stack are
detonated to
separate the LMRP from the BOP stack. In some embodiments, reconnection of the
LMRP to the BOP stack or coupling of another device such as a capping stack
may be
performed by latching dogs onto a connecting profile at one end of the mandrel
or
connector on an upper longitudinal end of a mandrel on the BOP stack.
100351 Although only a few examples have been described in detail above,
those skilled
in the art will readily appreciate that many modifications are possible in the
examples.
Accordingly, all such modifications are intended to be included within the
scope of this
disclosure as defined in the following claims.
7
Date Recue/Date Received 2020-09-08
