Note: Descriptions are shown in the official language in which they were submitted.
CA 02504247 2007-06-13
A METHOD AND APPARATUS FOR CREATING A CEMENTED
LATERAL JUNCTION SYSTEM
BACKGROUND
Hydrocarbon exploration drilling and production schemes have in more recent
years made regular use of multilateral wellbores. By definition such wellbores
include
intersections between lateral boreholes and primary boreholes. These
intersections are
called junctions. Junctions are rated with respect to their specific
attributes from level I to
level 6 in the Technical Advancement of Multilaterals (TAML) characterization
system
with level 1 being the lowest level of complexity and function and level 6
being the highest
level of complexity and function. There are many tools and/or systems
available to create
a lateral junction system, one of which is a product offered commercially by
Baker Oil
Tools, Houston, Texas and known to the industry as a hook hanger liner system.
The
system is known to be very effective in creating level 3 multilateral
junctions according to
the Technical Advancement of Multilaterals (TAML) characterization system.
These
systems are very popular and effective for their intended purpose but cannot
be relied upon
to provide a cemented junction that would be required for a TAML 4 rating.
While the
hook hanger liner system is sometimes cemented and can result in a cemented
junction that
is not the cun:ent expectation. Currently the cementing and cleaning process
is intended to
cement an annulus around the lateral liner but not to cement up the junction
because as a
practical matter the cleaning process will wash cement out of the junction
area.
Since cemented junctions are often desirable and the hook hanger liner system
is a
popular and effective multilateral tool, it would be well received by the
industry to have a
hook hanger liner system capable of achieving a cemented level 4 junction in
those wells
that require one.
SUMMARY
Accordingly, in one aspect of the present invention there is provided an
apparatus
for creating a cemented lateral junction system comprising:
a sleeve;
a premachined opening in said sleeve;
a cover disposed at said opening; and
a release material disposed at said cover and exposed to environment exterior
to
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According to another aspect of the present invention there is provided a
method
for constructing a wellbore comprising:
preparing a sleeve with a premachined window, a cover positioned to occlude
said
window and a release material isolating at least a portion of said cover
exposed to
environment through said window, said release material facilitating
displacement of said
cover in one piece, for running in the wellbore;
installing said sleeve in the wellbore; and
applying a hardenable agent to an annulus of said wellbore around said sleeve.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings wherein like elements are numbered alike in the
several Figures:
Figure 1 is a cross-sectional schematic view of a premachined window joint
with
a cover therein;
Figure 2 is a cross-sectional elevation view of a lateral junction system a
borehole; and
Figure 3 is a view of the embodiment of Figure 2 with a cementing process just
finished; and
Figure 4 is a view of the embodiment of Figure 2 with the main bore reopened.
DETAILED DESCRIPTION
Taught herein by way of example is a method and apparatus to cause a component
placed downhole and cemented to be removable from the placed position after
setting of
the cement. The component may be of a large number of types and includes
tubulars (i.e.,
removability of an entire joint), tubular with windows covered
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(discussed hereunder), etc. This requires that the adhesive properties of the
cement be
defeated with respect to the component that is intended to be removable. For
this
purpose a release agent is applied to the component such that cement cannot
stick
thereto. The release agent is a physical barrier between the cement and the
component. Release agents may be of a number of types providing the bond of
the
release agent to the component is insufficient to prevent defeat thereof by
pulling in a
normal well operation using normal equipment.
The method and apparatus disclosed herein maybe embodied (see Figure 1) in
a tubular member 10 having a premachined window 12 therein and a cover 14 for
the
opening. The cover is to have a portion which will prevent ingress of cement
through
the window and which portion is at least partly coated with a release agent 16
to
prevent or reduce adherence of cement thereto. In such condition, the cover
14,
which may be a sleeve, can be easily removed after a cementing operation. With
the
cover removed, drilling out the cement from beyond the premachined window is a
simple matter. It is of course notable that no metal need be drilled away as
the cover,
if metal, was removed prior to or contemporaneously with the drilling
operation.
One embodiment of the foregoing concept is the formation of a cemented
junction. The concept facilitates fully cementing a junction, allowing the
cement to
set and then having the ability to remove the cover in order to drill for
access back to
the main bore. Clearly the concept, both method and apparatus can be utilized
to
form any kind of junction needing merely location, orientation and depth, it
is
convenient to describe the concept by example with reference to a Hook Hanger
Liner
System cornmercially available from Baker Oil Tools, Houston, Texas.
As the hook hanger liner system will be familiar to those of skill in the art,
it is
used as one example of the type of apparatus and method disclosed herein. The
description of its components and the method of using the same is abbreviated
herein.
The description herein is focused upon the distinctions relevant to the
disclosure
hereof and the relative position of components making up such distinctions
over a
prior art hook hanger liner system. For purposes of this discussion it is
assumed that
at least a primary or main borehole and a lateral root extending therefrom are
in
existence. It is also noted that the term primary or main are intended to be
relative
terms only and denote the bore from which a lateral bore exits. In fact, such
primary
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or main bore may actually itself be a lateral bore from another primary bore,
and so
on. One of ordinary skill in the art will appreciate how such structure can be
generated. Such is not germane to this disclosure.
Referring to Figure 2, a summary of components and relative locations is
given for a hook hanger liner system. Primary or main borehole 110 is
illustrated
with casing 112, window 116 and lateral borehole 118 extending therefrom. The
following equipment is installed on the end of a section of drill string 124.
First, a
liner running tool 128 together with a liner setting sleeve with tieback
extension 130
and liner sleeve 132 is mounted to drill pipe 124. Attached to the liner
sleeve 132
near the liner running tool 128 is an external casing packer 134. An optional
external
casing packer 134 remains in the main borehole 110.
Attached to the liner running tool 128 inside the liner sleeve 132 is a tail
pipe
136 which has movable opposing swab cups 138 attached to tail pipe 136. A
cross-
over 140, which allows the rest of liner sleeve 132 to be a smaller diameter,
is located
about 2/3 of the length along liner sleeve 132. Also, near the end of the
tailpipe 136
there is an external casing packer 142 which can be used to cement the annular
space
between liner sleeve 132 and lateral borehole 118. A cementing valve 144 is
located
on liner sleeve 132 just above external casing packer 142.
Below external casing packer 134 is a premilled window 152 in liner sleeve
132 which allows for re-entry into the primary borehole 110 after completion
of the
junction between lateral borehole 118 and primary borehole 110. A"hook" 146 is
displayed on liner sleeve 132 , the "hook" has primary functions (among
others)
including:
(1) acting as a stop to preclude the liner sleeve 132 from exiting the window
116; and
(2) hanging the weight of liner sleeve 132 and any induced or other associated
loads.
On an inside diameter of liner sleeve 132 is positioned a lateral diverter 160
to
temporarily block access through window 152 to main bore 110. Lateral diverter
also
provides additional stiffness to liner sleeve 132. In one embodiment, lateral
diverter
160 further includes seals 162 at uphole and downhole ends thereof such as o-
rings.
In embodiments using seals 162, liner sleeve 132 may also include polished
seal
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bores, on an inside diameter of liner sleeve 132 where seals 162 contact the
inside
diameter of liner sleeve 132. Lateral diverter 160 is mounted in the position
shown in
Figure 1 prior to running the tool in the hole and is treated with a material
164 on the
outside diameter thereof. As noted above, the purpose of material 164 (release
agent)
is to prevent the adhesion of later applied cement to the portion (or at least
a portion)
of lateral diverter 160 that would but for the material be exposed through
window
152. One appropriate material is silicone rubber, another is polyurethane, yet
another
is latex paint, but it will be appreciated that any material facilitative of
removal of the
diverter 160 after setting and/or curing of the cement is acceptable.
Effectively, this
means that a material that creates not more than a weak bond with diverter 160
or
with the cement (it is not significant which interface releases, diverter-to-
material, or
material-to-cement as the same result will be achieved), weak being defined
merely as
allowing the diverter to be separated therefrom and pulled uphole without
special
procedures not normally associated with pulling diverters from wellbores would
be an
acceptable material. It should be stated that in some applications a "weak"
bond at the
release material-to-cement interface may be preferred in some situations since
in that
instance more of the release material would be carried out of the well still
adhered to
the diverter or cover. This would reduce ancillary contamination of the well.
Materials that have higher bonding properties may still be employed providing
an
additional release agent is interposed between said higher bonding material
and said
diverter 160 to effect the desired release characteristics. Diverter 160 and
its material
together prevent the entrance of cement during a cementing operation from
entering
the inside diameter of liner sleeve 132.
It should be noted that other properties of the release agent or material may
be
relevat to particular operations. For example, it may, in some applications be
desirable for the material to be resilient whereas in others, resiliency of
the material
may not be needed. It is anticipated by the inventors hereof that resilient
material will
more often be preferred since when the cover, diverter, etc. is removed and
some if
not all of the material is released into the well fluid, resilient material is
less likely to
cause ancillary damage. Too, the thickness of the applied material should be
taken
into consideration. While only a thin layer of material is necessary to
prevent cement
bonding, thin material is shed form the interface after separation, in thin
sheets. thick
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application of material is shed in thicker chunks. Depending upon what well
equipment is to be encountered, thin sheets or thick chunks may be more
desirable. In
addition, other factors such as degree of resiliency desired may affect the
selection of
material thickness, a thicker application of material will be more resilient.
Finally it
should be appreciated that other hardenable agents beyond cement may be
employed
in a process similar to those described herein. In such event the chemical
makeup of
the material/release agent should be considered for compatibility in order to
achieve
the desired end which as stated is releasability of a diverter, cover, sleeve,
etc. from a
set hardenable agent.
Referring back to Figures 2-4 in the event a cement column extending above
the location of diverter 160 in a wellbore is large, thus creating high
pressure on the
material 164, it is possible where the material is a softer elastomer like
silicone, for
such material to be extruded into the inside diameter of liner sleeve 132
along with
some of the surrounding cement. Clearly this is undesirable as it is the
consequence
which the teaching hereof is intended to prevent.
In such situation, such extrusion can be prevented by the employment of seals
162 as discussed and shown. Seals 162 create a hydraulic seal which
effectively
prevents extrusion of the material 164 into liner sleeve 132. Where a high
pressure is
not anticipated, the seals 162 are not needed for this function although may
be
employed for another function.
The hook hanger liner system described above is run into the primary borehole
110. The "hook" liner system self orients the liner sleeve 132 after sleeve
132
traverses window 116.
Following correct orientation, lateral exit and setting operations with
respect
to the hook hanger liner system, a cementing operation is perfonned (see
Figure 2).
Cement is caused to flow out of a downhole location of liner sleeve 132 or a
liner
extending therefrom (not shown). Cement 153 is flowed through cementing valve
144 and into annulus 151. When the cement 153 has been delivered to the target
area
in an amount calculated to ensure that it has extended a desired distance back
into the
main bore 110, pumping of cement 153 will be terminated.
When cement 153 reaches window 116 it begins to move through window 116
into main bore 110. Temporary plug 114 prevents migration of the cement to
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downhole areas of the main bore 110 where it is not intended to go. Temporary
plug
114 may be created in a number of ways such as building a sand bridge, heavy
gel
pills, bridge plugs, etc. Any of these may be placed as schematically
illustrated at 114
in Figures 1 and 2. Which plug is selected depends upon a number of factors
including but not limited to pressure, hole angle, etc. One of ordinary skill
in the art
is aware of how to make the determination.
Returning to the cementing operation, since the cement cannot migrate past
plug 114 it is forced to migrate in the uphole direction and thus to surround
the
junction and continue up main bore 110 for a selected distance, generally to
the
vicinity of the top of the liner sleeve 132. Cement that spills over the top
of liner
sleeve 132 can be cleaned up with conventi nal cleaning operations.
During the cleaning operations lateral diverter 160 is still in place witliin
sleeve liner 132. This is distinguished from the prior art because without the
release
capability of material 164, diverter 160 would have to be pulled prior to
setting of the
cement or it would be adhered thereto. The subsequent cleaning operation would
wash out the cement at the junction. Leaving the diverter 160 in place, as
noted
previously, prevents the entry of cement to the ID of sleeve liner 132 but
also prevents
the washout of cement around the junction during the cleaning operation.
Once the errant cement is cleaned out, the properly situated cement is allowed
to set. Post setting, the diverter 160 may be removed at any time. In some
cases it
will be left in place for some time during other well activity or indeed even
no
activity. In other cases it will be immediately removed after cement set to
regain
access to the main bore 110.
When it is determined the diverter 160 should be pulled from the well it is
retrieved by any of a number of retrieval methods which are known to the art.
Due to
the release material installed prior to running and described above, the bond
with the
diverter 160 is broken and the diverter may easily be withdrawn. Once the
diverter is
removed, a main bore diverter may be run in the hole and a milling tool or
other
appropriate tool depending upon type of temporary plug 114 may be run. The
milling
tool will mill the cement that is between window 152 and temporary plug 114
(and
will mill the plug too if that was intended) and if a plug is to be retrieved,
a retrieval
tool may be run to effect the same.
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Access is available to both lateral and main bore for further creation of
laterals
or for completion of the wellbore or other operation. Advantageously the
junction is
completely cemented. In this condition the hook hanger liner system achieves a
level
4 TAML rating.
While preferred embodiments of the invention have been shown and
described, various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly, it is to be
understood that the present invention has been described by way of
illustration and
not limitation.
What is claimed:
