Multilateral
A Well in Which Multiple
Boreholes or Laterals Are
Drilled From a Single
Wellbore
They May Be Horizontal or
Deviated in Order to Reach
Different Bottomhole
Locations
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Multilateral
The application of drilling
Multilateral has been around
since the 1920’s
Development of technology in
the 70’s and 80’s made it much
more practical
Most multilaterals were originally
associated with horizontal
drilling
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Multilateral
Drilled from existing well
Drilled as a new well using
special casing equipment
Complexity depends upon
formation integrity and junction
isolation requirements
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Multilateral
Well
Laterals are well
bores drilled Radial
Trunk
from the main
wellbore Junction
Branches are Lateral
well bores
drilled from a Branch
Splay
horizontal lateral
into the
horizontal plane
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Multilateral
Well
Splays (fish
Trunk
hook or herring- Radial
bone) are well
Junction
bores drilled
from a Lateral
horizontal lateral
Splay
in the vertical Branch
plane
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Multilateral
Stacked laterals are two laterals
departing from the same wellbore at
different depths
Dual lateral is a multilateral with two
laterals. Opposed laterals are where
the laterals are opposed at 180º
Crow’s foot is the drilling of multiple
directional wells from a single
wellbore but not necessarily
horizontal
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Multilateral
Well
Junctions are the
Trunk
intersecting Radial
points from which
Junction
laterals intersect
with the main well Lateral
bore or branches
Splay
intersect with the Branch
lateral
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Multilateral
Two categories of multilateral
junction
Uncased junction
There is no casing in the lateral and the
main well bore may be cased or not
Uncased junctions are more common,
easier to construct and less expensive
Must have competent formations to
prevent collapse or sand production
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Multilateral
Uncased
Junction similar
to some of the
first multilateral
wells in the
Austin Chalk
Formation
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Multilateral
Cased junction
A junction in which there is casing in the
lateral that is joined to the main well
bore
This can be done mechanically through
proper positioning and cementing, with
expandable metals, or by drilling larger
holes and installing pre-manufactured
junctions
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Multilateral
Cased junction
with Sperry Suns
liner tieback
system (LTBS)
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Multilateral
Reasons for drilling a multilateral
Mechanical or construction reasons –
Typically associated with cost savings
or slot savings
This is the primary reason to date for
drilling a multilateral
The offshore industry uses it to increase
the number of wells with the same
number of slots on a platform or subsea
template
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Multilateral
Reservoir or production reasons –
Typically associated with improved
drainage patterns or modified
injection profiles
A more accurate understanding of the
reservoir is required to use multilaterals
for this purpose
Will accelerate production and can
increase recoverable reserves
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Multilateral
Multilateral used to
develop
compartmentalized
reservoir
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Multilateral
To date, most
multilaterals are
associated with
horizontal
drilling
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Multilateral
Multilaterals are categorized by
the type of junction
They are Level 1 through 6
As the level number increases, the
complexity and cost will increase
As complexity increases, risk will
increase
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Multilateral
Level 1
A level one junction is one in which
the main bore and lateral are uncased
at the junction
This is one of the most common type
of multilaterals due to simplicity and
lower costs
The formations must be competent
so that the wells can be completed
open hole
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
Open hole laterals
casing Level 5
Pressure integrity
at the junction
achieved with the
completion
have limited re-entry
capability
There is no isolation of
Level 4
Level 3
Lateral cased and
the laterals
tied into parent but
Almost any hole size
Lateral and parent not cemented
cemented, but no
pressure
Integrity
and configuration
imaginable
Level 2
Can be drilled by
Lateral open hole or
casing not tied into
parent
almost any service
Level 1
Open hole,
unsupported junction company
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Multilateral
Level 2
With a Level 2 junction, the main bore
is typically cased and cemented while
the lateral is left open hole
This is the second most common
type of lateral
Usually done from existing wellbore
using a whipstock to sidetrack out of
the casing
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
In a new well,
casing Level 5
Pressure integrity
at the junction
achieved with the
completion
sidetracks can be
accomplished with pre-
milled windows
Level 3
Lateral cased and
Pre-milled windows
Level 4 tied into parent but
are much more
Lateral and parent not cemented
cemented, but no
pressure
Integrity
expensive
Can require drilling a
Level 2
Lateral open hole or
casing not tied into
parent larger hole to
accommodate pre-
Level 1
Open hole,
unsupported junction
milled joint
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Multilateral
A liner can be dropped off outside the
window to case the lateral
Most service companies offer a
retrievable whipstock to sidetrack out of
existing casing
A whipstock should be placed in the
body of the casing to prevent milling a
connection
With Level 2, there is limited reentry
capability and laterals are not isolated
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Multilateral
Reentry can
be guaranteed
with an entry
nipple
Adds a little
cost Entry
Reentry only Nipple
through tubing Orienting
Packer
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
casing Level 5
Pressure integrity
at the junction
achieved with the
completion
Level 3
Level 3 junctions
have mechanical
integrity at the Level 3
Lateral cased and
junction but no
Level 4 tied into parent but
Lateral and parent not cemented
cemented, but no
pressure
Integrity
hydraulic isolation
The lateral is
cased but not
Level 2
Lateral open hole or
casing not tied into
parent
cemented
Level 1
Open hole,
unsupported junction
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
casing Level 5
Pressure integrity
at the junction
Can be
achieved with the
completion
accomplished by
mechanically
tying the lateral to
the main bore or Level 4
Lateral and parent
cemented, but no
Level 3
Lateral cased and
tied into parent but
not cemented
installing casing pressure
Integrity
strings in both the
lateral and main Level 2
bore
Lateral open hole or
casing not tied into
parent
Level 1
Open hole,
unsupported junction
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Multilateral
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Multilateral
Usually installed where the formations at the
junction are not competent but do not have
to worry about water or gas production
Sperry Sun Liner
Tieback System,
LTBS
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Multilateral
The LTBS uses a pre-milled window joint
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Multilateral
Baker Hook Hanger System
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Multilateral
Level three may or
may not have
access to both the
lateral and the main
bore
Selective reentry
may or may not be
possible
Can be substantially
more expensive
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
casing Level 5
Pressure integrity
at the junction
achieved with the
completion
Level 4
A Level 4 junction
is one in which
Level 3
Lateral cased and
both the lateral
and main bore
Level 4 tied into parent but
Lateral and parent not cemented
cemented, but no
pressure
Integrity
are cased and
cemented
Level 2
Lateral open hole or
casing not tied into
parent
Level 1
Open hole,
unsupported junction
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Multilateral
The junction has mechanical integrity
but are assumed to have no pressure
integrity, even though it might have
pressure integrity
Reentry is possible in most cases
All methods involve drilling a lateral
with a whipstock, running a liner and
cementing
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Multilateral
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Multilateral
One option is to
wash over the
liner from the
main bore
recovering the
liner and
whipstock
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Multilateral
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Multilateral
Second option is to
mill a hole through
the casing and
whipstock
One hole size is lost
in the main bore
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Multilateral
The third method
is to perforate the
hollow whipstock
There is no
access to lower
lateral
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
casing Level 5
Pressure integrity
at the junction
achieved with the
completion
Level 5
Level 5
junctions build
Level 3
Lateral cased and
upon the Level
4 system
Level 4 tied into parent but
Lateral and parent not cemented
cemented, but no
pressure
Integrity
Level 2
Lateral open hole or
casing not tied into
parent
Level 1
Open hole,
unsupported junction
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Multilateral
They include running tubing and
isolation packers to provide pressure
integrity
If a problem develops in the tubulars
above the packer, pressure integrity
is lost
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Multilateral
Much more
expensive
More risky to run
Allows access to
both wellbores
usually through
tubing
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Multilateral
Another system
uses a diverter
packer assembly
The liner is run
and diverted into
the lateral
When the liner is
at TD, sting into
diverter assembly
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Multilateral
Level 6
Pressure integrity
at the junction
achieved with
casing Level 5
Pressure integrity
at the junction
achieved with the
completion
Level 6
Level 6
junctions are
Level 3
Lateral cased and
one in which full
pressure
Level 4 tied into parent but
Lateral and parent not cemented
cemented, but no
pressure
Integrity
integrity is
achieved with
Level 2
Lateral open hole or
casing not tied into
parent
the main casing
string
Level 1
Open hole,
unsupported junction
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Multilateral
Most common is expandable metal
junction
Another type is the splitter
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Multilateral
Expandable metal junction
New installation only
Must underream the hole where the junction will
be placed
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Multilateral
Splitter
Requires drilling a
much larger
diameter hole to the
kickoff point
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Multilateral
Costs and risks
Of course, multilaterals cost more
money
The multilateral must save money as
compared to drilling multiple wells
The deeper the junction, the more
likely the multilateral will be cost
effective
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Multilateral
The more wells drilled, the cheaper
the technology. There is a learning
curve to drilling multilaterals as there
is to any drilling program.
The more laterals drilled from a single
wellbore, the lower the incremental
cost
Short radius is typically more
expensive than medium radius
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Multilateral
The simpler the well design, the less
it costs
Commingled production is cheaper
than separating production
Wells without built-in reentry
mechanisms are less expensive
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