Note: Descriptions are shown in the official language in which they were submitted.
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EROSION-RESISTANT MULTILATERAL JUNCTIONS
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates generally to the design of multi-lateral
junctions used
in downhole hydrocarbon production and methods for creating such junctions in
a
wellbore.
2. Description of the Related Art
[0002]
Multilateral wellbores are used to increase the efficiency of drilling and
production. A multilateral wellbore includes a main wellbore, which is drilled
from the
surface, and at least one lateral leg which branches out from the main
wellbore. The
main wellbore, or at least a portion thereof, is typically vertical or
substantially
vertical in orientation. The lateral leg(s) usually have a horizontal or
deviated
orientation with respect to the main wellbore and may be capable of accessing
hydrocarbons that are not accessible from the main wellbore.
[0003] A downhole junction is used to branch a lateral leg from a central,
usually
substantially vertical main wellbore. Current mechanical junction arrangements
allow formation exposure gaps to develop which increase the risk of erosion
and
possible intrusion of debris at the junction itself.
SUMMARY OF THE INVENTION
[0004] The
present invention provides devices and methods for providing
multilateral junctions in a wellbore. In a described embodiment, a lateral
junction is
provided by a hanger and a seal bore diverter (SBD). The SBD includes a
tubular
body with an elongated window formed within. In preferred embodiments, the
lower
end of the elongated window includes an engagement hook. The hanger includes a
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straight portion and a deviated portion which can pass through the elongated
window
of the SBD. It is noted that while the deviated portion will be depicted
herein as
deviating from, and actually will deviate from the axis of the straight
portion when
installed in the wellbore, the hanger will typically be a substantially
straight tubular
when manufactured and run into the wellbore. The hanger also features lateral
windows formed in its body as well as an engagement tab. In accordance with
preferred embodiments, an orientation mechanism is provided which angularly
orients the hanger within the SBD.
[0005] In operation to create a lined lateral junction in a multilateral
wellbore, a
to SBD is first landed within the main bore of a multilateral wellbore,
oriented so that its
elongated window faces a lateral leg which diverges from the main bore.
Thereafter,
a hanger is lowered into the main bore so that the deviated portion of the
hanger
enters the central bore of the SBD. If an orientation mechanism is provided,
the
hanger is then angularly oriented within the SBD so that the deviated portion
of the
Is hanger will be pointed toward and exit through the elongated window of
the SBD.
[0006] When the hanger is fully seated within the SBD, an engagement hook on
the SBD will become interlocked with an engagement tab on the hanger. The
interlocking engagement will preferably occur at the crux of the acute angular
junction where the hanger and SBD meet. The interlocking engagement is formed
at
20 the interior portion of the junction between the hanger and SBD. The
completed
assembly provides a lined junction within which completions or other tools can
be
run.
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[0006a] In a described embodiment, a lateral junction for a multilateral
wellbore
having a main bore and a lateral leg which extends away from the main bore is
provided comprising: a seal bore diverter to be inserted into the main bore,
the seal
bore diverter comprising a generally tubular body defining a central bore
along its
length; an elongated window formed in the tubular body of the seal bore
diverter; a
hanger to be landed within the central bore of the seal bore diverter to
create the
lateral junction, the hanger having a generally tubular body with a straight
portion
and a deviated portion which is shaped and sized to be disposed through the
central
bore of the seal bore diverter and exit through the elongated window; an
engagement mechanism to interlock the hanger and seal bore diverter together;
and
an orientation mechanism for angularly orienting the hanger within the seal
bore
diverter as the hanger is inserted into the seal bore diverter, the
orientation
mechanism comprising: an angled upper end surface on the seal bore diverter;
an
orientation sleeve operably associated with the hanger, the orientation sleeve
presenting a lower shoulder that is shaped and sized to be complementary to
the
angled upper end surface, and wherein the hanger is angularly oriented within
the
seal bore diverter as the lower shoulder is brought into engaging contact with
the
angled upper end surface.
[0006b] In a described embodiment, a lateral junction for a multilateral
wellbore
having a main bore and a lateral leg which extends away from the main bore is
provided comprising: a seal bore diverter to be inserted into the main bore,
the seal
bore diverter comprising a generally tubular body defining a central bore
along its
length; an elongated window formed in the tubular body of the seal bore
diverter; a
hanger to be landed within the central bore of the seal bore diverter to
create the
lateral junction, the hanger having a generally tubular body with a straight
portion
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and a deviated portion which is shaped and sized to be disposed through the
central
bore of the seal bore diverter and exit through the elongated window; and an
engagement mechanism to interlock the hanger and seal bore diverter together,
wherein the seal bore diverter and hanger form a crux when the hanger is
landed
within the seal bore diverter, and wherein the engagement mechanism interlocks
the
hanger and seal bore diverter together at the crux.
[0006c] In a
described embodiment, a method of forming a lateral junction within a
multilateral wellbore having a main bore and a lateral leg which extends away
from
the main bore is provided comprising: disposing a seal bore diverter within
the main
bore of the wellbore, the seal bore diverter having a generally tubular body
defining a
central bore along its length and an elongated window formed within the body;
inserting a hanger into the central bore of the seal bore diverter, the hanger
having a
generally tubular body with a straight portion and a deviated portion which is
shaped
and sized to be disposed through the central bore of the seal bore diverter
and exit
through the elongated window; causing the deviated portion of the hanger to
exit the
seal bore diverter through the elongated window, a crux being formed between
the
deviated portion of the hanger and the body of the seal bore diverter; and
forming an
interlocking engagement between the hanger and the seal bore diverter at the
crux.
2b
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BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a thorough understanding of the present invention, reference is
made to
the following detailed description of the preferred embodiments, taken in
conjunction
with the accompanying drawings, wherein like reference numerals designate like
or
similar elements throughout the several figures of the drawings and wherein:
[0008] Figure 1 is a side, cross-sectional view of an exemplary wellbore
having a
main bore and a single lateral leg and a seal bore diverter landed within.
[0009] Figure 2 is a side, cross-sectional view of the wellbore shown in
Figure 1
with a hanger now landed within the seal bore diverter.
[0010] Figure 3 is an external isometric view of an exemplary hanger being run
into
an exemplary seal bore diverter.
[0011] Figure 4 is an external isometric view of the hanger and seal bore
diverter
of Figure 3, now with the hanger having been angularly oriented within the
seal bore
d iverter.
[0012] Figure 5 is an external isometric view of the hanger and seal bore
diverter
shown in Figure 3, now with the hanger having been fully landed within the
seal bore
diverter.
[0013] Figure 6 is a side, cross-sectional view of a hanger landed within
a seal
bore diverter.
[0014] Figure 7 is an isometric view of an axial cross-section of a hanger
landed
within a seal bore diverter to illustrate an exemplary engagement hook in
greater
detail.
[0015] Figure 8 is an external view of an exemplary hanger illustrating
exemplary
lateral window placement.
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[0016]
Figure 9 is an external view of an exemplary seal bore diverter illustrating
an exemplary design for an elongated window formed therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The term "multilateral," as used herein, will refer to wellbores
having a
main bore, or leg, and at least one lateral leg which branches off from the
main bore.
Figure 1 illustrates an exemplary multilateral wellbore 10 that has been
drilled
through the earth 12 from the surface (not shown). The depicted wellbore 10
includes a main bore, or main leg 14. The main bore 14 has been lined with
metallic
io casing 16 and cement 18, as is known in the art. A casing window 20 has
been
previously milled through the casing 16 and cement 18 and a lateral leg 22 has
been
drilled which extends outwardly from the main bore 14. A metallic liner 24 has
been
secured within the main bore 14 below the casing window 20 with packer 26.
[0018] In Figure 1, a seal bore diverter (SBD) 28 has been run into the
wellbore 10
is and its lower end 30 is landed within the liner 24. The SBD 28 has a
tubular body 32
which defines a central bore 34 along its length. An elongated window 36 is
formed
in the body 32. A SBD 28 is illustrated in Figure 9 showing an exemplary
elongated
window 36. When the SBD 28 is landed in the liner 24, the elongated window 36
is
oriented to face the casing window 20.
20 [0019] An interior ramp shoulder 38 is formed within the central bore 34
of the SBD
28. The ramp shoulder 38 is formed by thickening the body 32 of the SBD 28 to
form the ramp shoulder 38, as best appreciated by reference to Figure 6. Upper
end
surface 40 of the SBD 28 is angled to serve as a mechanism for orienting a
hanger
within the SBD 28, as will be described. An engagement hook 42 is located at
the
25 lower end of the elongated window 36.
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[0020] As shown in Figures 2-6 a hanger 44 is then landed within the SBD 28 in
order to form an erosion-resistant lateral junction 45. The hanger 44 includes
a
straight portion 46 and a deviated portion 48. It is noted that, in Figures 1-
6, the
angle of departure between the deviated portion 48 of the hanger 44 and the
straight
portion 46 is exaggerated for the purposes of better illustrating the
invention. The
deviated portion 48 should depart from the axis of the straight portion 46 at
an angle
that generally matches the angle at which the lateral leg 22 departs from the
main
bore 18. The hanger 44 has a generally tubular body 50 which defines a central
bore 52 along its length. It is noted that the elongated window 36 of the SBD
28
should be wide enough to permit the deviated portion 48 of the hanger 44 to
pass
through. Preferably, an outer orientation sleeve 54 surrounds an upper portion
of the
straight portion 46 of the hanger 44. The orientation sleeve 54 presents an
angled
lower shoulder 55 which is complementary to the angled upper end 40 of the SBD
28.
[0021] A first lateral window 56 is formed in the body 50 of the hanger 44
in the
vicinity of the elbow 58 which joins the straight portion 46 to the deviated
portion 48.
A second, smaller lateral window 60 is also formed in the body 50 adjacent the
lateral window 56, and an engagement tab 62 is formed between the two lateral
windows 56, 60. Figure 8 more clearly depicts the appearance of exemplary
lateral
windows 56, 60 as well as an engagement tab 62 for a hanger 44. The second
window 60 allows the creation of the engagement tab 62, but the lowermost
taper of
the second window 60 allows that window 60 to fit the outer diameter of the
SBD
tubular body 32. A close fit is important for minimizing erosion.
[0022] In order to land the hanger 44 within the SBD 28, the deviated portion
48 is
slid into the central bore 34 of the SBD 28, as illustrated by Figure 3, in
the direction
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of arrow 64. When the hanger 44 is moved to the position shown in Figure 4,
the
lower shoulder 55 of the orientation sleeve 54 of the hanger 44 will contact
the
angled upper end surface 40 of the SBD 28 and angularly orient the hanger 44
within
so that the deviated portion 48 is directed out of the elongated window 36 of
the SBD
28 and the lateral window 56 of the hanger 44 is oriented toward the ramp
shoulder
38 of the SBD 28. Thus, the orientation sleeve 54 and upper end surface 40 act
as
an orientation mechanism for orienting the hanger 44 with respect to the SBD
28.
[0023] The hanger 44 continues to slide in the direction of arrow 64 until it
is in the
fully landed position depicted in Figure 5. In this fully landed position, a
raised
to shoulder 66 on the outer surface of the hanger 44 will contact and
shoulder out
against the upper end of the orientation sleeve 54 so that further downward
movement of the hanger 44 with respect to the SBD 28 is stopped. If desired,
collets
68 on the straight portion 46 of the hanger 44 will snap into a complementary
profile
(not shown) in the SBD 28 to help lock the hanger 44 and the SBD 28 together.
is [0024] Also in the fully landed position, the engagement hook 42 of
the SBD 28
and the engagement tab 62 of the hanger 44 will interlock. As best shown in
Figs. 6
and 7, the engagement hook 42 of the SBD 28 slides into the smaller lateral
window
60 of the hanger 44. The engagement tab 62 of the hanger 44 will be caught
beneath the engagement hook 42. This interlocking will stabilize the lateral
junction
20 created between the hanger 44 and SBD 28 and will prevent or limit
bifurcation
between the hanger 44 and SBD 28 at the point where the lateral leg 22 departs
from the main bore 14, thereby preventing the later creation of formation
exposure
gaps (i.e., gaps between the hanger 44 and SBD 28) which increase the risk of
erosion and possible intrusion of debris at the junction itself. The interlock
of the
25 engagement hook 42 and the engagement tab 62 is located at the crux 70
(in Fig. 2)
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of the junction between the deviated portion 48 of the hanger 44 and the
central bore
34 of the SBD 28.
[0025] It is preferable to design the SBD window 36 and the central bore 34 of
the
SBD 28 to closely match the outer diameter of the hanger 44 at a predetermined
angle and deviation to minimize any potential exposure gaps. In addition to
the
close fit, the SBD 28 and hanger 44 are anchored relative to each other to
preserve
designed gaps for the remainder of the life of the well. Because the
engagement tab
62 does not protrude from the outer diameter of the hanger body 50, the hanger
body 50 can closely match the inner diameter of the central bore 34 and window
geometry, thereby keeping formation exposure gaps to a minimum. According to
preferred embodiments, the window 36 of the SBD 28 is shaped to fit the hanger
body 50 at a specified angle relative to the tubular SBD body 32. This angle,
as
illustrated by the angle of the deviated portion 48 of the hanger 44, will be
similar to
the angle at which the casing exit was originally milled. Because the outer
diameter
is of the hanger 44 closely matches the interior diameter of the central
bore 34, the
maximum window width will be close to the central bore 34 diameter. The upper
taper of the SBD window 36 is shaped to fit the outer diameter of the hanger
44 at
the predetermined angle or deviation. The lower most portion of the SBD window
36
is for the engagement of the engagement tab 62.
zo [0026] After the hanger 44 is landed within the SBD 28, as
described above, a
completed junction is provided which is fully lined. A user can insert
completions or
other tools through the central bore 34 and into the lateral leg 22 of the
wellbore 10
through the deviated portion 48 of the hanger 44. In addition, a user can have
access to the main bore 14 of the wellbore 10 below the junction 45 in order
to run
25 tools.
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[0027] Those of
skill in the art will recognize that numerous modifications and
changes may be made to the exemplary designs and embodiments described herein
and that the invention is limited only by the claims that follow and any
equivalents
thereof.
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