Note: Descriptions are shown in the official language in which they were submitted.
CA 02238500 1998-OS-14
LATERAL LINER TIEBACK ASSEMBLY
Field of the Invention
This invention is directed to a well bore liner and, in particular, to a liner
tieback
assembly for a lateral well bore.
Background of the Invention
A lateral well bore is drilled off a primary well bore at a position along its
length. The
lateral well bore is drilled through the casing or through a preformed window
in the
casing of the primary well bore. Completion of these lateral well bores often
involves
introduction of a liner thereto.
The liner is inserted through the window in the casing and into the lateral
well bore.
According to one method, the liner is then cemented in place and any end
protruding
into the primary well bore is milled off. According to another method, the
liner is hung
off the primary well bore casing by a tieback hanger. The tieback hanger is
formed as
an open ended tube. The first end of the tube conforms to the shape of the
window and
is often inclined relative to the long axis of the tube. The opposite end of
the tube is
connected to the lateral liner. At the first end, the tieback hanger has
formed thereon
a flange, or other engagement means, for catching on the edges of the casing.
When the liner is in place in the lateral well bore and run in pressure is
released, the
liner tends to recoil back towards the primary well bore. Sometimes recoiling
causes
the liner and the attached tieback hanger, if any, to be displaced back into
the primary
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well bore. The liner or tieback hanger then becomes an obstruction to the
passage of
downhole tools through the primary well bore past the lateral well bore.
Summary of the Invention
A tieback hanger has been invented which accommodates recoiling of the lateral
well
bore lining assemblies to prevent these assemblies from being displaced into
the
primary well bore.
In accordance with a broad aspect of the present invention, there is provided
a well
bore tieback hanger comprising a first tube having a first end and an opposite
end and
having a flange extending from its first end; a second tube formed to be
connectable
to a well bore liner, the second tube being connected adjacent the opposite
end of the
first tube and moveable relative to the first tube; and an elastic member
connected to
act between the first tube and the second tube to bias the first tube toward
the second
tube.
The tieback hanger of the present invention is intended for use in latching
the liner of
a lateral well bore to the side wall of a primary well bore and acts as an
interface
between the primary well bore and the lateral liner. As would be understood,
the
primary well bore can be the well bore leading to surface or another well bore
from
which a lateral bore has been drilled.
The tieback hanger and attached liner are inserted through a window formed in
the
sidewall of the primary well bore. The window is the opening to the lateral
well bore.
The window is preferably preformed in the casing of the well bore. However,
the
window can alternately be formed by drilling through the well bore side wall
at the time
of formation of the lateral well bore.
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The first end of the first tube preferably substantially conforms to the
peripheral shape
of the window. In particular, preferably the first end is open and inclines
relative to the
long axis of the tube.
The flange is formed on the first end of the first tube to latch against the
periphery of the
window when the tieback hanger is inserted into the lateral well bore. The
flange is
formed in any suitable way to latch against the periphery of the window. For
example,
the flange can be complete or partial and can be formed integral with or
attached to the
first tube in any suitable way.
The second tube is formed in any suitable way for connection to the lateral
liner. In one
embodiment, the second tube has formed thereon threads for threaded connection
to
the lateral liner either directly or through a coupling. The second tube can
be
connected to the first tube in any suitable way to be movable longitudinally
relative to
the first tube. As an example, the second tube can be telescopically mounted
about or
within the first tube. Alternately or additionally, the second tube can be
connected to
the first tube through the elastic member.
The elastic member is attached to act between the first tube and the second
tube to
bias these tubes together. In one embodiment, the elastic member is formed
separately
from the first tube and the second tube is connected between the tubes by
means such
as, for example, by welding, by threaded connections, by fasteners, by a
housing or by
combinations thereof. In another embodiment, the elastic member is formed
integral
with one of the first or the second tubes. The elastic member can be any
suitable
means for biasing the tubes together, with a consideration as to the bore hole
conditions. In one embodiment, the elastic member is a coil spring. In another
embodiment, the elastic member is a tubular, thin walled spring. In one
embodiment,
the tieback hanger includes a means for preventing over extension of the
elastic
member.
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To facilitate insertion of the liner into the lateral well bore, preferably,
the tieback hanger
includes a swivel selected to act between the first end of the first tube and
the lateral
liner to which the tieback hanger is to be attached. The swivel accommodates
torsional
and/or sideways forces generated between the tieback hanger and the lateral
liner. In
the preferred embodiment, the swivel permits the flange end of the tieback
hanger to
rotate relative to the liner and to flex out of longitudinal alignment with
the liner. This
facilitates both the insertion of the liner and tieback hanger into the
lateral well bore and
the latching of the flange onto the periphery of the window. The swivel can be
positioned anywhere along the length of the tieback hanger.
Where the elastic member connects between the first tube and the second tube,
a
tubular member can be disposed between the tubes to facilitate flow between
the first
and second tubes. The tubular member can be telescopically disposed within or
about
the elastic member. In one embodiment, the tubular member is connected at one
end
only to either the first tube or the second tube.
Brief Descri~,tion of the Drawinas
A further, detailed, description of the invention, briefly described above,
will follow by
reference to the following drawings of specific embodiments of the invention.
These
drawings depict only typical embodiments of the invention and are therefore
not to be
considered limiting of its scope. In the drawings:
Figure 1 shows a sectional view through a well bore having disposed therein a
tieback hanger according to the present invention;
Figure 2 shows a sectional view through a tieback hanger according to the
present invention;
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Figure 3 shows a sectional view through another embodiment of a tieback
hanger according to the present invention;
Figure 4 is a top plan view of the first tube of the tieback hanger of Figure
3;
Figure 5 is a sectional view along line 5-5 of Figure 4
Figure 6A is a top plan view of a tube including a thin walled tubular spring
useful
in the present invention;
Figure 6B is a sectional view along line 6B-6B of Figure 6A
Detailed Description of the Present Invention
Referring to Figure 1, a tieback hanger 10 according to the present invention
is shown
latched to a window 12 formed though the casing 14 of a primary well bore 16.
The
main body of tieback hanger 10 is disposed within a lateral well bore 18.
Tieback hanger 10 includes a first tube 20, a second tube 22 and, connected
therebetween and securing tube 20 to tube 22, an elastic member 24 such as a
spring.
Formed at the first end 20' of tube 20 is a continuous flange 26 for latching
against the
periphery of window 12. In particular, flange 26 is of a size that it cannot
pass through
window 12, but abuts against the edges of the window.
At the opposite end of the tieback hanger, tube 22 forms a pin end 28 for
threaded
connection to a swivel 29 and, through the swivel to a lateral liner 30. The
liner can be
standard-type, slotted, prepacked or modified in any other way.
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Elastic member 24 has a selected tension suitable to bias first tube 20 toward
second
tube 22. Second tube 22 is longitudinally moveable relative to, but remains
connected
to, first tube through elastic member 24.
The components of the tieback hanger including the first and second tubes, the
elastic
member and the flanges are formed of a material, for example L-80 pipe or 4140
18-22
rc steel, which is capable of withstanding downhole conditions.
Tieback hanger 10 acts to prevent the tieback hanger and the liner from being
displaced, by thermal expansion, into primary well bore 16. In use, tieback
hanger 10
is connected to lateral liner 30 at surface. A running tool (not shown) is
inserted
through hanger 10 and is secured to liner 30 in a way that would be readily
appreciated
in the art. The liner is then introduced to the primary well bore 16 and
inserted, liner
end first, through window 12 into lateral well bore 18.
Lateral liner 30 is moved into well bore 18 until flange 26 of first tube 20
abuts against
the periphery of window 12. Once flange 26 abuts against window 12, lateral
liner 30
and attached second tube 22 are inserted a selected additional distance into
well bore
18 against the tension in elastic member 24. The selected distance is selected
to be
greater than the distance that the lateral liner would be displaced under the
thermal
conditions in the well and during production and is selected to be less than
the distance
which would exceed the plastic limit of the elastic member. The weight of the
liner
prevents the elastic member from drawing the liner toward the primary well
bore. This
places elastic member 24 under tension so that flange 26 of tieback hanger 10
is pulled
against the periphery of the window. If liner 30 expands and is displaced
toward the
primary well bore, this displacement will be accommodated in the elastic
member, while
the tension of the spring will maintain flange 26 in engagement with the
window.
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Preferably, as shown, a tubular member 32 is attached to tube 22 to extend
through the
elastic member to provide a fluid conduit through the elastic member. Tubular
member
32 is free to slide within tube 20.
Referring to Figure 2, another tieback hanger 110 according to the present
invention
is shown. The tieback hanger includes a first tube 120 and a second tube 122.
The
first and second tubes can each be formed as one part members or, alternately,
to
facilitate manufacture, the tubes can be formed of a plurality of parts
secured together
by welding, threaded engagement or frictional engagement.
First tube 120 is telescopically disposed about tube 122 at one end 120". An
annular
chamber 123 is formed between the tubes and a coil spring 124 is retained
therein.
Spring 124 acts between an abutting shoulder 125a secured on tube 120 and
another
abutting shoulder 125b formed on tube 122. Spring 124 is compressed between
shoulders 125a and 125b such that tube 120 is biased toward and into
overlapping
relation with tube 122.
Longitudinal slots 127 are formed on tube 122. Tube 120 has rigidly connected
at its
overlapping end 120" a plurality of radially inwardly extending keys 129 which
engage
in slots 127. The cooperation of keys 129 and slots 127 maintains the
connection
between tube 122 and tube 120 and acts to prevent the tubes from rotating
relative to
each other and maintains the tubes in alignment.
End 120' of tube 120 is inclined relative to the long axis 131 of the tieback
hanger to
conform to the periphery of a lateral well bore window. The angle of
inclination of end
120' is selected based on the angle at which the lateral well bore is drilled
off the
primary well bore. Four flanges 126 (only two can be seen in the sectional
view) are
mounted, as by welding, about end 120'. Each flange 126 includes a first wall
126a
mounted onto tube 120 and a second wall 126b (shown in phantom) formed
substantially orthogonally relative to the first wall.
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End 122" of tube 122 is attached by means of a coupling 134 to a short section
of
tubing 136 having integral therewith a swivel ball member 152 for use in the
rotational
and pivotal attachment of a lateral well liner 130.
Generally, it is desirable that the inner diameter (ID) or the outer diameter
of any insert
into a lateral well bore liner are not substantially different in than the ID
and OD of the
liner. Thus, preferably the inner diameter of the tie back assembly is no
smaller than
the inner diameter of the lateral liner and preferably this is accomplished
without
increasing the OD beyond acceptable levels.
Referring to Figure 3, another tieback hanger 210 according to the present
invention
is shown. The tieback hanger includes a thin walled spring 224. A thin walled
spring,
such as that shown, is particularly useful in the present invention since such
a spring
can be used both without increasing the OD, and without decreasing the ID, of
the
tieback hanger beyond acceptable ranges.
Tieback hanger 210 includes a first tube 220 and a second tube 222. Tube 220
is
telescopically disposed over tube 222 at its end 220".
Spring 224 is formed integral with tube 220. In particular, a portion 220a of
tube 220
is formed as a spring. Referring particularly to Figures 4 and 5, the spring
is formed by
making a plurality of circumferential cuts 236 in the tube. Cuts 236 extend
through a
portion of the cross sectional area of each tube leaving a portion 238
attached. The
cuts are formed preferably at regular intervals (i.e. every 0.34 inches) and
the portion
238 in each adjacent cut alternates, preferably 180°, around the
circumference of the
tube. When force is applied to pull the ends 220' 220" of the tube apart at
the cut,
portion 238 acts as a hinge at each cut about which the tube can flex.
To prevent tube 220 from rotating about tube 222, two slots 240 are formed
through
tube 220 and a pin 242 is engaged to tube 222 through each slot 240. Thus,
tube 240
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can ride over tube 222 until limited by abutment of each screw 242 against the
end
walls 240a, 240b of its slot but positioning of pins 242 in slots 240 prevents
rotation of
tube 220 about tube 222.
Two flanges 226 are positioned about end 220' of tube 220. The flanges are
secured
to the tube by welding.
Tube 222 is formed of three connected parts: first end tube 222'; a middle
tube 222";
and a liner attachment end tube 222"'. Liner attachment end tube 222"' is
formed as
a pin end 228. Middle tube 222" and end tube 222"' are connected by means of a
swivel 250. Swivel 250 includes a ball member 252 formed on an end of tube
222"
which is retained in a spherical cavity 254 defined by an end of tube 222"'
and by a
coupling 256. Ball member 252 is rotatable within cavity 254 but is retained
therein.
Thus, end tube 222"' can rotate about the long axis 231, as shown by arrow x,
of the
tieback hanger. Swivel 250 also provides that the tie back hanger can bend, as
shown
by arrow y, such that the long axis of tube 222"' can move out of alignment
with long
axis 231 of the remainder of the tool. This facilitates insertion of the
tieback hanger and
its attached liner into a lateral well bore.
To facilitate surface indication of spring tensioning, a shear screw 260 is
positioned
between tubes 222 and 220. When flanges 226 latch against the window, further
weight on the tube 220 will cause screw 260 to shear. This shearing is
indicated at
surface by an increase in weight
It is to be understood that tubes 222' and 222" could be formed integral, but
are formed
separately in the illustrated embodiment for ease of manufacture.
In one embodiment, the tubes 220 and 222 are formed of steel pipe have 3/a
to'/2 inch
wall thickness. The spring portion is about 20 inches in length and the total
tension in
the tieback hanger spring is 500 to 1,000 Ibs.
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Referring to Figures 6A and 6B, another spring construction is shown. The
spring is
formed by making a plurality of pairs of circumferential cuts 262a, 262b ...
262n in a
tube 220a. Each pair of cuts 262 are positioned at substantially the same
point along
the long axis 231 of the tube and extend through a portion of the cross
sectional area
of the tube leaving two spaced apart connections 264. The pairs of cuts are
formed
preferably at regular intervals (i.e. every 0.34 inches) and the connections
264 in each
adjacent cut alternates, preferably 180°, around the circumference of
the tube. When
force is applied to pull the ends 220a' 220a" of the tube apart at the cut,
connections
264 act as hinges at each pair of cuts about which the tube can flex. This
spring
formation is particularly preferred for larger size tie back assemblies for
use with liners
of about 5.5" OD and greater.
It will be apparent that many other changes may be made to the illustrative
embodiments, while falling within the scope of the invention and it is
intended that all
such changes be covered by the claims appended hereto.
