Note: Descriptions are shown in the official language in which they were submitted.
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LOCK ASSEMBLY
The present invention relates to a lock assembly for
locking an outer tubular element to an inner tubular
element extending through the outer tubular element. Such
lock assemblies are, for example, applied in a wellbore
for the production of hydrocarbon fluid from an earth
formation. In such application the outer tubular element
can be connected to (or integrally formed with) the
wellbore casing or a wellbore production tubing, and the
inner tubular element is adapted to receive a wellbore
device (e.g. a valve).
A problem with such applications comes to light when
the lock assembly is subjected to longitudinal forces.
For example, when the inner element is subjected to a
longitudinal force due to fluid pressure of produced
hydrocarbon fluid, such force can lead to relative
movement between the two elements leading to loosening of
the lock connection. Furthermore, such relative movement
prevents adequate transmission of signals, e.g. acoustic
or electric signals, between the inner and outer tubular
elements. A further problem occurs with applications
involving conventional dog and lock shoulders whereby the
inner tubular element is subjected to radially inward
forces upon application of a pulling force, thus
requiring an increased wall thickness of the inner
tubular element.
Accordingly it is an object of the invention to
provide an improved lock assembly which overcomes the
problems of the conventional lock assemblies.
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In accordance with the invention there is provided
a lock assembly for locking an outer tubular element to an
inner tubular element extending through the outer tubular
element, the assembly comprising a lock mandrel connected to
one of said tubular elements and being provided with a
recess facing the other one of said tubular elements, the
recess having two inwardly diverging side surfaces, a lock
member arranged between the first and second tubular
elements in a locking relationship with the other one of the
tubular elements, the lock member extending into said recess
and being operable between a retracted mode in which the
lock member is movable relative to the recess and an
expanded mode in which the lock member is expanded against
the inwardly diverging side surfaces, the assembly further
comprising an actuator means for expanding the lock member
in said recess against said diverging side surfaces
characterized in that the lock member comprises a first part
and a second part rotatable relative to the first part about
an axis extending substantially in a circumferential
direction and that the lock member is operable between the
retracted mode and the expanded mode by rotating said first
and second parts relative to each other within the recess
such that the first part is in contact with a first side
surface and the second part is in contact with a second side
surface of the recess.
It is thereby achieved that when the lock member
is in the expanded mode, a load applied to the lock
assembly, e.g. a longitudinal pulling force, induces the
.lock member to become even more firmly locked in the recess
due to the inwardly diverging side surface of the recess.
Thereby the locking action of the assembly is enhanced.
Furthermore, it is thereby ensured that the inner and outer
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elements are in firm contact with each other allowing
adequate transmission of electric or acoustic signals.
The invention will be described hereinafter in
more detail with reference to the accompanying drawings in
which:
Fig. 1 schematically shows a first embodiment of a
wellbore assembly according to the invention;
Fig. 2 shows detail A of Fig. 1 in a first mode of
operation;
Fig. 3 shows detail A of Fig. 1 in a second mode
of operation;
Fig. 4 schematically shows a lock member for use
in the first and second embodiments;
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Fig. 5 shows the lock member of Fig. 4 in another
mode of operation; and
Fig. 6 schematically shows a second embodiment of a
wellbore assembly according to the invention;
In the detailed description below like reference
numerals relate to like components.
Referring to Fig. 1 there is shown a lock assembly 1
extending in a wellbore (not shown) formed in an earth
formation, the assembly 1 having a central longitudinal
axis 2 substantially coinciding with the with the
longitudinal axis of the wellbore. The lock assembly is
symmetrical with respect to axis 2, therefore only one
half of the lock assembly is shown in Fig. 1. The lock
assembly includes an outer tubular element in the form of
a wellbore casing 3 arranged in the welibore. A lock
mandrel 5 is connected to the casing 3 by welds 7, 8 so
as to form an integral part of the casing 3.
Referring in more detail to Fig. 2, an annular
recesses 10 is formed in the casing 3 at the inner
surface thereof, the recess 10 having inwardly diverging
side surfaces 12, 14 arranged opposite each other and an
end surface 15 extending parallel to the longitudinal
axis 2.
An inner tubular element 16 is concentrically
arranged within the casing 3, the inner tubular
element 16 including a first actuating member 18, a
second actuating member 20, and a rotatable sleeve 22 in
co-operating arrangement with the first actuating member
by means of a left hand threaded connection 24 and in co-
operating arrangement with the second actuating member 20
by means of a right hand threaded connection 26. As shown
more clearly in Fig. 2, an annular space 28 of variable
length is thereby defined between the actuating
members 18, 20. Thus upon rotation of the sleeve 22, the
actuating members 18, 20 move relative to each other in
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longitudinal direction between an extended mode in which
the space 28 is relatively long and a retracted mode in
which the space 28 is relatively short. The location of
the inner tubular element 16 relative to the recess 10 is
such that the centre of space 28 is located opposite the
centre of recess 10. The ends of the actuating
members 18, 20 facing the space 28 have end surfaces 30,
32 diverging in outward direction.
Two or more lock members 34 (only one of which is
shown) are arranged in the annular space 28, the lock
members 34 being interconnected by one or more circular
springs 35 acting as retracting springs keeping the lock
members in place against actuating members 18, 20.
As shown in more detail in Figs. 4 and 5, each lock
member 34 includes a first part 36 and a second part 38,
the parts 36, 38 being mutually rotatable about a rod 40
extending in circumferential direction. The rod 40 can be
an integral part of one of the lock members 34. Part 36
has an outer surface 41a, an outer side surface 41b, and
an inner side surface 41c. Part 38 has an outer
surface 42a, an outer side surface 42b, and an inner side
surface 42c.
The parts are held together by a leaf spring 44
biasing the parts 36, 38 to a retracted position in which
the outer surfaces 41a, 42a extend at an angle so as to
form a concave radially outer end of the lock member 34.
The dimensions of the lock member 34 are such that the
lock member is capable of passing into the recess 10 when
the parts 36, 38 are in the retracted position.
Referring to Fig. 3, the orientation of the outer
side surfaces 41b, 42b is such that when the parts 36, 38
are rotated to an expanded position (shown in Fig. 5) in
which the outer surfaces 41a, 42a are aligned, the lock
member 34 fits in the recess 10 whereby the outer
surfaces 41a, 42a are in contact with the radially outer
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surface 15 of the recess, and wherein the outer side
surfaces 41b, 42b are in contact with the respective side
surfaces 12, 14 of the recess 10. Furthermore, the
orientation of the inner side surfaces 41c, 42c is such
that when the parts 36, 38 are rotated to the expanded
position the inner side surfaces 41c, 42c are in contact
with the respective end surfaces 30, 32 of the actuating
members 18, 20.
The second actuating member 20 is provided with an
orienting/holding slot 50 (Fig. 1) for orienting and
holding an actuator (not shown) in the inner tubular
element 16. A wellbore tool (not shown), for example a
downhole production valve or a downhole safety valve, is
connected to the actuating member 18. The first actuating
member 18 is internally provided with a set of primary
slots 54 and the sleeve 22 is provided with a set of
secondary slots 56. The actuator is adapted to engage the
slot 50 and includes two parts rotatable relative to each
other, each part having a set of fingers capable of
gripping into the respective sets of slots 54, 56.
During normal operation the inner tubular element 16
is lowered into the wellbore casing 3 with the actuator
attached thereto, and whereby the actuating members 18,
20 are in the extended mode thereby allowing the leaf
spring 44 of each lock member 34 to retract the lock
member parts 36, 38 to their retracted position. Lowering
is stopped when the lock members 34 are positioned
opposite the annular recess 10, as shown in Fig. 2. The
actuator is then activated whereby the sets of fingers of
the actuator grip into the respective sets of slots 54,
56. The two actuator parts are then rotated relative to
each other so as to rotate the sieeve 22 in a direction
that the first and second actuating members 18, 20 move
relative to each other to the retracted mode. As a result
the diverging end surfaces 30, 32 of the actuating
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members push each lock member 34 into the recess 10
whereby the outer surfaces 41a, 42a of the respective
lock member parts 36, 38 contact the end surface 15 of
the recess 10. Upon further rotation of the sleeve 22
the parts 36, 38 rotate relative to each other around the
rod 40 until the lock member 34 becomes in the expanded
position in which the outer surfaces 41a, 42a are aligned
and in full contact with the end surface 15, and the
outer side surfaces 41b, 42b are in full contact with the
respective side surfaces 12, 14 of the recess 10. In this
position the lock members 34 are locked into the
recess 10.
It is thus achieved that a form fit connection
between the inner tubular 16 and the casing 3 is created,
which provides an excellent acoustic or electrical link.
In case the wellbore tool or the inner tubular element 16
are subjected to a longitudinal force, for example due to
pressure of hydrocarbon fluid fiowing through the
wellbore, the lock members 34 become even more firmly
locked into the recess 10 due to the outwardly diverging
shape of the recess 10 and lock member 34. It is thereby
prevented that the connection between inner tubular
element 16 and casing becomes loose or that the inner
tubular element 16 collapses due to inward movement of
the lock members. Furthermore, the tight connection
ensures that acoustic signals for wellbore control or
information transfer are adequately transferred between
the inner tubular element 16 and the casing 3.
Reference is further made to the second embodiment of
the lock assembly according to the invention, as shown in
Fig. 6. The lock assembly is symmetrical with respect to
longitudinal axis 58, therefore only one half of the lock
assembly is shown in Fig. 6. The second embodiment is
largely similar to the first embodiment, except that the
sleeve for moving the actuating members 18, 20 relative
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to each other has been replaced by a set of shaped memory
alloy actuators 60 (hereinafter referred to as SMA
actuators), whereby one end of each SMA actuator 60 is
fixedly connected to actuating member 18 by fasteners 62,
and the other end of the SMA actuator is fixedly
connected to actuating member 20 by fasteners 64. Each
SMA actuator 60 has a transition temperature above which
the SMA actuator has an increased length, and below which
the SMA actuator has a reduced length. The sets of
slots 54, 56 of the first embodiment are absent in the
second embodiment.
Normal operation of the second embodiment is similar
to normal operation of the first embodiment, except that
instead of using the actuator tool to move the actuating
members 18, 20 relative to each other, such movement is
induced by contraction of the SMA actuators. This is
achieved by installing a heater (not shown) in the inner
tubular element 16 and operating the heater during
lowering of the inner tubular element 16 into the casing
so that the temperature of the SMA actuators is above the
transition temperature. Thereafter the heater is turned
off so that the temperature of the SMA actuators drops
below the transition temperature whereby the SMA
actuators contract and thereby move the actuating
members 18, 20 to their retracted mode.
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