Note: Descriptions are shown in the official language in which they were submitted.
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INFILL WELL METHODS FOR SAGD WELL HEAVY HYDROCARBON RECOVERY
OPERATIONS
FIELD
[0001] The present invention relates to the field of providing, completing and
operating
infill wells in steam assist gravity drainage (SAGD) heavy hydrocarbon
recovery
operations.
BACKGROUND
[0002] Extraction of bitumen from oil sands ore generally includes mining the
ore,
crushing the mined ore and then forming an aqueous oil sands slurry including
the
crushed ore for hydrotransport to a bitumen extraction operation.
[0003] In the bitumen extraction operation, the aqueous oil sands slurry can
be supplied
to a primary separation vessel that produces a primary bitumen froth stream, a
middlings
stream and a tailings stream containing water and coarse mineral solids. The
middlings
stream and the tailings stream can be supplied to additional separation
vessels, which
are often flotation cells, in order to recover additional bitumen. The bitumen
froth can be
further de-aerated to remove air, and combined with a diluent to aid removal
of mineral
solids and water and to produce a high quality bitumen for further upgrading
operations.
[0004] The bitumen extraction operation produces various tailings streams that
can
include coarse mineral solids, fine mineral solids, water and residual
bitumen. Tailings
can be disposed of or subjected to further treatments and separations prior to
disposal.
Tailings can be supplied to tailings ponds for containment of the tailings,
settling of the
solids, and enabling surface water to be recycled back into the bitumen
extraction
operation.
[0005] Tailings ponds can contain significant quantities of unrecovered
bitumen.
However, recovering bitumen from tailings ponds and other tailings sources has
a
number of challenges.
[0006] SAGD has become a widespread process of recovering heavy oil and
bitumen
particularly in the oil sands of Northern Alberta. The SAGD process involves
well pairs
each of which consists of two horizontal wells drilled in the oil sands and
aligned in
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spaced relation one on top of the other. The upper well is a steam injection
well and the
lower well is a producer well. The injected steam forms a steam chamber that
grows
upward and outward within the formation, heating the bitumen or crude oil
sufficiently to
reduce its viscosity and allow it to flow toward the producer well along with
condensed
water.
[0007] Numerous SAGD well pairs are usually provided in groups extending from
central
pads for hundreds of meters. The well pairs of a group often extend parallel
generally
parallel to one another.
[0008] As the SAGD process evolves over time, the steam chamber of each well
pair
increases in size and may change in shape. The steam chambers generally
progress
upward and outward, leaving low-lying bypassed regions along either side of
each well
pair. However, the steam chambers can often be irregularly shaped and defining
a
correspondingly irregular infill region. The SAGD process in fact leaves a
significant
amount of residual bitumen or heavy oil in the infill regions between and
below SAGD
producers at the end of its economic life. Infill wells have been proposed to
recover
some of this residual hydrocarbon.
[0009] Some strategies have been proposed to access the infill region by
drilling single
offset wells. In one known process, as described in US patent No. 6,257,334
(Cyr et al.)
and colloquially known as Fast-SAGD, an offset well is provided and operated
at cyclic
steam stimulation to establish communication with the SAGD well pair and then
converted to a production mode under steam trap control. In anther known
process, as
described in US patent No. 7,556,099 (Arthur et al.), an infill producer well
is located and
operated in a bypassed region in between two well pairs that form a common
mobilised
zone above the infill well before establishing fluid communication between the
infill well
and the common mobilised zone.
[0010] The known processes for providing infill wells in mature SAGD recovery
fields
have a variety of disadvantages related to the speed, efficiency, conformance
to residual
zones and completeness of the recovery.
[0011] There is thus a need for a technology that overcomes at least some of
the
disadvantages of what is known in the field.
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SUMMARY
[0012] The present invention responds to the above-identified need by
providing
methods of infill well completion for SAGD recovery fields.
[0013] Accordingly, the present invention provides a method for providing a
generally
horizontal infill well in an elongated residual zone defined between two SAGD
well pairs.
The residual zone is surveyed and mapped, preferably by 4D seismic methods, to
determine its boundaries selected from overlying, underlying, flanking and
internal
lithological boundaries. An infill bore is then drilled in the residual zone
along a
trajectory conforming to the boundaries. The infill well is then completed in
conformance
with the boundaries and operated to ameliorate bitumen or heavy oil recovery
through
the infill well. The overlying boundary may consist of overburden areas and
SAGD steam
chamber areas, the underlying boundary comprises underburden, the flanking
boundaries comprise steam chambers of neighbouring SAGD well pairs, and the
internal
lithological boundaries may comprise pockets or strata of oil-barren rock
depending on
the given geological formation under development.
[0014] The surveillance of the residual zone's boundaries and the adjustment
of infill
well drilling, completion and operation to conform to the boundaries of the
residual zone,
improves the heavy oil recovery operation in mature SAGD operations.
[0015] In one aspect, the method comprises:
surveying a residual zone to determine an underburden boundary;
drilling an infill well bore in the residual zone so as to comprise:
a low-lying sump bore section below the underburden boundary between
heels of the SAGD well pairs; and
an upper bore section communicating with the low-lying bore section and
extending above and along the underburden boundary topward the toes of
the SAGD well pairs;
completing the infill well such that a downhole pump is located in the low-
lying
bore section and a production liner section is located in the upper bore
section.
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[0016] This downhole pump location notably allows the infill well to maximize
hydrocarbon recovery potential from the residual zone, benefit from a longer
economic
life, facilitate the hydrocarbon transport from the toe toward the heel of the
infill well, and
diminish the risk of steam breakthrough near the pump location throughout the
infill well
operational evolution.
[0017] In another aspect, the method comprises:
surveying the residual zone to determine hump zones and a vertically unbroken
zones in between the two SAGD well pairs, wherein:
each hump zone is defined by an overlying and flanking steam chamber
boundaries;
each vertically unbroken zone is defined by an overburden boundary and
flanking steam chamber boundaries;
drilling a horizontal infill well bore in the residual zone through the hump
zones
and the vertically unbroken zones to avoid steam breakthrough; and
completing the infill well such that in the hump zone steam breakthrough is
avoided from the flanking and overlying steam boundaries and in the unbroken
zone steam breakthrough is avoided from the flanking boundaries, optionally
via
perforation and blank arrangements in the liner.
[0018] In yet another aspect, the method comprises:
surveying the residual zone to determine a hump zone defined by an overlying
and flanking steam chamber boundaries, to determine an offset distance between
the overlying steam chamber boundary and a projected infill well bore
trajectory
along the hump zone, thereby identifying a latent steam breakthrough location;
drilling a horizontal infill well in the hump zone;
completing the infill well such that the completion proximate the latent steam
breakthrough location comprises reduced inflow, optionally via blanks or
reduced
size perforations or slots.
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[0019] In still another aspect, the method comprises:
surveying the residual zone to determine reservoir lows and elevated
hydrocarbon accumulations as well as steam chamber boundaries proximate
such reservoir lows and such oil accumulations;
drilling an infill well bore in the residual zone to comprise a main
horizontal bore
along the residual zone and multilateral branch bores extending into the
reservoir
lows and oil accumulations, such that the multilateral branch bores are spaced
away from the steam chamber boundaries by an offset distance;
completing the infill well so as to comprises a main production well and
branch
side wells, such that the branch side wells are sufficiently distant to avoid
steam
breakthrough therein;
operating the branch side wells to maintain conformance, optionally by
avoiding
steam breakthrough via liners comprising blanks or varied perforation size or
frequency, or by encouraging steam fingering.
[0020] In another aspect, the method comprises:
surveying the residual zone to determine flanking steam chamber boundaries
defining its respective flanks;
drilling an infill well in the residual zone to comprise a main horizontal
bore along
the residual zone and multilateral branch bores which are each spaced away
from the flanking steam chamber boundaries by a common offset distance;
completing the infill well so as to comprise a main well and branch side
wells;
operating the infill well such that the main well comprises blanks and varied
perforations and the branch side wells blanks and varied perforations, so as
to
avoid steam breakthrough from the flanking boundaries.
[0021] In another aspect, the method comprises:
surveying the residual zone to determine flanking steam chamber boundaries
defining its respective flanks;
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drilling an infill well in the residual zone to comprise a main horizontal
bore along
the residual zone and multilateral branch bores which are each spaced away
from the flanking steam chamber boundaries by a common offset distance;
completing the infill well so as to comprise a main well and branch side
wells;
operating each branch side wells to cause growth of steam fingers away from
the
flanking boundaries toward the corresponding branch side wells.
[0022] In another aspect, which may combined with any one of the above
aspects, the
method further comprises:
performing time-lapse surveillance of the residual zone to determine the
evolution
of at least one of its boundaries, thereby determining a predicted boundary
for a
given stage of the infill well drilling, completion or operation;
adjusting the drilling, completion or operation of the infill well according
to the
predicted boundary of the residual zone to avoid of steam breakthrough.
[0023] In one instance, the flanking steam chamber boundaries are subjected to
time-
lapse surveillance after drilling and prior to completion of the infill well,
and the predicted
flanking boundary is determined to have an area that will impinge upon a
previously
planned slotted section of the well completion liner. The liner arrangement is
adjusted
accordingly so as to comprise a blank liner in the predicted impingement area
of the
flanking boundary.
[0024] In another instance, the flanking steam chamber boundaries are
subjected to
time-lapse surveillance before drilling the infill bore, and the predicted
flanking boundary
is determined to have an area that will impinge upon a previously planned bore
trajectory. The drilling is adjusted accordingly so as to bypass the predicted
impingement
area of the flanking boundary. Preferably, a second predicted flanking
boundary is
determined to adapt the completion of the infill well.
[0025] In another instance, the flanking steam chamber boundaries are
subjected to
time-lapse surveillance to determine predicted steam impingement areas along
the infill
well trajectory. The infill well is then completed with inflow control devices
proximate the
predicted steam impingement areas. During recovery of heavy hydrocarbons
through the
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infill well in production mode, the recover characteristics are appraised and
time-lapse
surveillance is performed to revise downhole flow conditions using the inflow
control
devices. Preferably, the inflow is reduced in the main or branched parts of
the infill well in
areas proximate the predicted steam impingement areas prior to steam
breakthrough.
Preferably, the operation based on predicted boundaries is performed to
achieve uniform
production along the infill well.
[0026] In some implementations, there is provided a method for providing a
generally
horizontal infill well in an elongated three-dimensional residual zone defined
between
two Steam Assisted Gravity Drainage (SAGD) steam chamber areas for recovery of
heavy hydrocarbons, the method comprising:
determining boundaries of the residual zone, wherein the boundaries:
vary along a length dimension of the three-dimensional residual zone;
include one or more of: an overlying boundary, an underlying boundary, a
flanking boundary and an internal lithological boundary; and
include at least one boundary defined by the SAGD steam chamber
areas;
drilling an infill bore in the residual zone along a trajectory determined
based on
the boundaries; and
completing an infill well in the infill bore; and
wherein the infill well is configured to recover heavy hydrocarbons from the
residual zone.
[0027] In some implementations, the infill well is further configured such
that heat
provided by the two SAGD chamber areas facilitates the recovery of heavy
hydrocarbons.
[0028] In some implementations, the step of determining boundaries of the
residual zone
comprises performing four-dimensional seismic surveillance of the residual
zone.
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[0029] In some implementations, the process includes, for at least one
boundary of the
residual zone, predetermining an offset distance between the boundary and the
infill
well; and determining the trajectory of the infill bore to be spaced away from
each of the
at least one boundary by at least the corresponding offset distance.
[0030] In some implementations, at least one boundary for which an offset
distance is
determined is defined by the SAGD steam chamber areas.
[0031] In some implementations, predetermining the offset distance comprises
selecting
a distance that is sufficient in order to avoid steam breakthrough from one of
the SAGD
steam chamber areas into the infill bore.
[0032] In some implementations, predetermining the offset distance comprises
selecting
a distance that is sufficient in order to encourage steam to grow from one of
the SAGD
steam chamber areas toward the infill well.
[0033] In some implementations, the process includes identifying a latent
steam
breakthrough location from one of the SAGD steam chamber areas into the infill
well.
[0034] In some implementations, the completing of the infill well further
comprises
providing reduced inflow completion proximate the latent steam breakthrough
location.
[0035] In some implementations, the reduced inflow completion comprises blank
liners.
[0036] In some implementations, the reduced inflow completion comprises liners
comprising reduced size perforations or reduced size slots.
[0037] In some implementations, the step of drilling the infill bore comprises
providing a
low-lying sump bore section positioned below an underlying boundary of the
residual
zone.
[0038] In some implementations, the underlying boundary comprises underburden
between heels of SAGD well pairs.
[0039] In some implementations, the step of completing the infill well further
comprises
providing a downhole element located in the low-lying bore section.
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[0040] In some implementations, the step of drilling the infill bore further
comprises an
upper bore section communicating with the low-lying sump bore section and
extending
above and along the underlying boundary toward toes of the SAGD well pairs.
[0041] In some implementations, the step of completing the infill well further
comprises
providing a production liner section located in the upper bore section.
[0042] In some implementations, the production liner comprises a slotted
liner.
[0043] In some implementations, the drilling of the infill bore comprises
determining the
trajectory so as to be spaced away from the flanking boundaries defined by the
SAGD
steam chamber areas, by an offset distance that is substantially the same on
either side
of the trajectory.
[0044] In some implementations, the offset distance is selected in order to be
sufficient
to avoid steam breakthrough from the SAGD steam chamber areas into the infill
well.
[0045] In some implementations, the residual zone comprises:
at least one hump zone extending part of the length of the residual zone, each
hump zone being defined by:
an overlying steam boundary defined by the SAGD steam chamber areas;
and
opposed flanking steam boundaries defined by the SAGD steam chamber
areas, wherein the SAGD steam chambers defining the overlying steam
boundary and the opposed flanking steam boundaries are in fluid
communication.
[0046] In some implementations, the residual zone comprises:
at least one vertically unbroken zone extending part of the length of the
residual
zone, each vertically unbroken zone being defined by:
an overlying reservoir boundary defined by part of the reservoir; and
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opposed flanking steam boundaries defined by the SAGD steam chamber
areas.
[0047] In some implementations, drilling the infill bore comprises drilling a
horizontal
main bore along the length of the residual zone; and drilling multilateral
branch bores.
[0048] In some implementations, the process includes drilling the multilateral
branch
bores at regularly spaced intervals.
[0049] In some implementations, the process includes drilling the multilateral
branch
bores so as to be spaced away from the SAGD steam chamber areas by an offset
distance selected in order to be sufficient to avoid steam breakthrough from
the SAGD
10 steam chamber areas into the infill well.
[0050] In some implementations, the process includes drilling the multilateral
branch
bores at a toe end of the residual zone.
[0051] In some implementations, drilling the infill bore comprises drilling a
horizontal
main bore along the length of the residual zone; and drilling multilateral
branch bores in
the vertically unbroken residual zone.
[0052] In some implementations, completing the infill well comprises
completing a main
well in the main bore; and completing branch side wells in the branch bores.
[0053] In some implementations, the branch side wells are configured to
encourage
growth of steam fingers from the SAGD steam chamber areas.
[0054] In some implementations, the branch side wells are configured to avoid
steam
breakthrough from the SAGD steam chamber areas into the branch side wells.
[0055] In some implementations, completing the infill well comprises providing
the
branch side wells with a liner.
[0056] In some implementations, the liner is slotted or perforated. In some
implementations, liner comprises slots or perforations of varied size or
frequency.
[0057] In some implementations, completing the infill well comprises providing
the infill
well with a blank liner section.
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[0058] In some implementations, the blank liner section is provided proximate
to a
boundary defined by one of the SAGD steam chamber areas.
[0059] In some implementations, determining boundaries of the residual zone
comprises
time-lapse monitoring of the residual zone to determine the evolution of at
least one of
the boundaries; and determining at least one predicted boundary for a stage of
the
drilling of the infill well and/or the completing of the infill well.
[0060] In some implementations, the process includes adjusting the drilling of
the infill
well and/or the completing of the infill well according to the at least one
predicted
boundary of the residual zone.
[0061] In some implementations, the at least one predicted boundary of the
residual
zone is defined by the SAGD steam chamber areas and further defined by a
predicted
steam impingement area within at least one of the SAGD chamber areas, and the
adjusting is performed to provide sufficient offset distance between the
infill bore and/or
the infill well from the predicted steam impingement area to avoid steam
breakthrough
into the infill bore and/or the infill well.
[0062] In some implementations, the adjusting of the completion of the infill
well
comprises providing the infill well with an inflow control device proximate
the predicted
steam impingement area.
[0063] In some implementations, the process further includes recovering the
heavy
hydrocarbons through the infill well in production mode; monitoring recovery
characteristics of the infill well and/or evolution of at least one of the
boundaries of the
residual zone; and adjusting downhole flow conditions using the inflow control
devices in
accordance with the recovery characteristics and/or the evolution of at least
one of the
boundaries of the residual zone.
[0064] In some implementations, the step of drilling the infill bore comprises
adapting the
trajectory according to baseline topology of the underlying boundary.
[0065] In some implementations, the baseline topology of the underlying
boundary is
undulating.
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[0066] In some implementations, the drilling of the infill bore is adjusted
based on
azimuthal resistivity.
[0067] In some implementations, the drilling of the infill bore is adjusted
based on
density measurements.
[0068] In some implementations, there is provided a method for recovering
heavy
hydrocarbons from an elongated three-dimensional residual zone defined between
two
Steam Assisted Gravity Drainage (SAGD) steam chamber areas, the method
comprising:
operating an infill well positioned in the residual zone along a trajectory
based on
determined boundaries, wherein the boundaries:
vary along a length dimension of the three-dimensional residual zone;
include one or more of: an overlying boundary, an underlying boundary, a
flanking boundary and an internal lithological boundary; and
include at least one boundary defined by the SAGD steam chamber
areas;
wherein the operating comprises producing heavy hydrocarbons from the infill
well to recover heavy hydrocarbons from the residual zone.
[0069] In some implementations, the infill well bore comprises a low-lying
sump bore
section positioned below an underlying boundary of the residual zone, wherein
the
underlying boundary comprises underburden between heels of SAGD well pairs.
[0070] In some implementations, the infill well comprises a downhole pump
element that
is located in the low-lying bore section.
[0071] In some implementations, the infill well bore further comprises an
upper bore
section communicating with the low-lying sump bore section and extending above
and
along the underlying boundary toward toes of the SAGD well pairs.
[0072] In some implementations, the infill well comprises a production liner
section that
is located in the upper bore section.
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[0073] In some implementations, the residual zone comprises:
at least one hump zone extending part of the length of the residual zone, each
hump zone being defined by:
an overlying steam boundary defined by the SAGD steam chamber areas;
and
opposed flanking steam boundaries defined by the SAGD steam chamber
areas, wherein the SAGD steam chambers defining the overlying steam
boundary and the opposed flanking steam boundaries are in fluid
communication.
[0074] In some implementations, the residual zone comprises:
at least one vertically unbroken zone extending part of the length of the
residual
zone, each vertically unbroken zone being defined by:
an overlying reservoir boundary defined by part of the reservoir; and
opposed flanking steam boundaries defined by the SAGD steam chamber
areas.
[0075] In some implementations, the trajectory of the infill well is located
with at least
one offset distance from at least one of the boundaries of the residual zone
defined by
the SAGD steam chamber areas, the at least one offset distance being
sufficient in order
to avoid steam breakthrough from one of the SAGD steam chamber areas into the
infill
well.
[0076] In some implementations, the at least one offset distance is sufficient
in order to
encourage steam to grow from one of the SAGD steam chamber areas toward the
infill
well
[0077] In some implementations, the infill well comprises reduced inflow
completion
proximate a latent steam breakthrough location from one of the SAGD steam
chamber
areas into the infill well.
[0078] In some implementations, the reduced inflow completion comprises blank
liners.
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[0079] In some implementations, the reduced inflow completion comprises liners
comprising reduced size perforations or reduced size slots.
[0080] In some implementations, the trajectory of the infill well is spaced
away from the
flanking boundaries defined by the SAGD steam chamber areas by an offset
distance
that is substantially the same on either side of the trajectory.
[0081] In some implementations, the offset distance is selected in order to be
sufficient
to avoid steam breakthrough from the SAGD steam chamber areas into the infill
well.
[0082] In some implementations, the infill well comprises a horizontal main
well along
the length of the residual zone; and multilateral branch wells extending from
the main
well into the residual zone.
[0083] In some implementations, the multilateral branch wells are provided at
regularly
spaced intervals.
[0084] In some implementations, the multilateral branch wells extend at an
offset
distance with respect to the SAGD steam chamber areas selected to be
sufficient in
order to avoid steam breakthrough from the SAGD steam chamber areas into the
infill
well.
[0085] In some implementations, the multilateral branch wells are located at a
toe end of
the residual zone.
[0086] In some implementations, the multilateral branch wells are located in a
vertically
unbroken residual zone.
[0087] In some implementations, the multilateral branch wells are configured
to
encourage growth of steam fingers from the SAGD steam chamber areas.
[0088] In some implementations, the multilateral branch wells are configured
to avoid
steam breakthrough from the SAGD steam chamber areas into the multilateral
branch
wells.
[0089] In some implementations, the multilateral branch wells comprise a
liner.
[0090] In some implementations, the liner is slotted or perforated.
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[0091] In some implementations, the liner comprises perforations of varied
size or
frequency.
[0092] In some implementations, the multilateral branch wells comprise a blank
liner
section.
[0093] In some implementations, the blank liner section is provided proximate
to a
boundary defined by one of the SAGD steam chamber areas.
[0094] In some implementations, the method includes adjusting the operation of
the infill
well according to at least one predicted boundary of the residual zone, the at
least one
predicted boundary being determined by time-lapse monitoring of the residual
zone.
10 [0095] In some implementations, the at least one predicted boundary of
the residual
zone is defined by a predicted steam impingement area of the SAGD steam
chamber
areas.
[0096] In some implementations, the adjusting of the operation of the infill
well
comprises controlling inflow proximate the predicted steam impingement area.
[0097] In some implementations, the process includes adjusting downhole flow
conditions using inflow control devices in accordance with recovery
characteristics
and/or evolution of at least one of the boundaries of the residual zone.
[0098] In some implementations, the operating of the infill well further
comprises
injecting steam into the infill well to enhance mobility of the hydrocarbons
in the residual
zone.
[0099] In some implementations, the operating of the infill well further
comprises
alternating between production and steam injection modes to enhance mobility
of the
hydrocarbons in the residual zone.
[0100] In some implementations, there is provided a method for recovering
heavy
hydrocarbons from an elongated three-dimensional residual zone defined between
two
Steam Assisted Gravity Drainage (SAGD) steam chamber areas, the method
comprising:
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operating an infill well positioned in the three-dimensional residual zone
defined
by boundaries that vary along a length dimension of the residual zone, wherein
the residual zone comprises:
at least one hump zone extending part of the length of the residual zone,
each hump zone being defined by:
an overlying steam boundary defined by the SAGD steam
chamber areas; and
flanking steam boundaries defined by the SAGD steam chamber
areas, wherein the SAGD steam chamber areas defining the
overlying steam boundary and the opposed flanking steam
boundaries are in fluid communication; and
at least one vertically unbroken zone extending part of the length of the
residual zone, each vertically unbroken zone being defined by:
an overlying reservoir boundary defined by part of the reservoir;
and
opposed flanking steam boundaries defined by the SAGD steam
chamber areas;
wherein the infill well comprises a completion in the at least one hump zone
configured to avoid steam breakthrough into the infill well; and
wherein the operating comprises producing heavy hydrocarbons from the infill
well.
[0101] In some implementations, there is provided a method for providing an
infill well in
an elongated three-dimensional residual zone defined between two Steam
Assisted
Gravity Drainage (SAGD) steam chamber areas for recovery of heavy
hydrocarbons, the
method comprising:
drilling an infill bore in the residual zone along a trajectory based on
boundaries
of the residual zone, wherein the boundaries:
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vary along a length dimension of the three-dimensional residual zone;
include one or more of: an overlying boundary, an underlying boundary, a
flanking boundary and an internal lithological boundary; and
include at least one boundary defined by the SAGD steam chamber
areas;
wherein the drilling comprises:
drilling a horizontal main bore along the length of the residual zone; and
drilling multilateral branch bores extending from the main bore into the
residual zone;
completing an infill well in the infill bore;
wherein the infill well is configured to recover heavy hydrocarbons from the
residual zone.
[0102] In some implementations, the process includes drilling the multilateral
branch
bores at regularly spaced intervals.
[0103] In some implementations, the process includes drilling the multilateral
branch
bores so as to be spaced away from the SAGD steam chamber areas by an offset
distance selected so as to be sufficient in order to avoid steam breakthrough
through the
multilateral branch bores.
[0104] In some implementations, the offset distance is substantially the same
for each of
the multilateral branch bores.
[0105] In some implementations, the offset distance is sufficient in order to
allow
encouragement of steam growth from the SAGD steam chamber areas toward the
multilateral branch bores when the infill well is operated.
[0106] In some implementations, the process includes drilling the multilateral
branch
bores at a toe end of the residual zone.
[0107] In some implementations, the residual zone comprises:
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at least one hump zone extending part of the length of the residual zone, each
hump zone being defined by:
an overlying steam boundary defined by the SAGD steam chamber areas;
and
flanking steam boundaries defined by the SAGD steam chamber areas,
wherein the SAGD steam chambers defining the overlying steam
boundary and the opposed flanking steam boundaries are in fluid
communication; and
at least one vertically unbroken zone extending part of the length of the
residual
zone, each vertically unbroken zone being defined by:
an overlying reservoir boundary defined by part of the reservoir; and
opposed flanking steam boundaries defined by the SAGD steam chamber
areas; and
wherein the method further comprises drilling the multilateral branch bores to
extend
into the vertically unbroken residual zone.
[0108] In some implementations, completing the infill well comprises
completing a main
well in the main bore; and completing branch side wells in the multilateral
branch bores.
[0109] In some implementations, the branch side wells are configured to
encourage
growth of steam fingers from the SAGD steam chamber areas toward the branch
side
wells.
[0110] In some implementations, the branch side wells are configured to avoid
steam
breakthrough from the SAGD steam chamber areas.
[0111] In some implementations, the branch side wells comprise a liner. In
some
implementations, the liner is slotted or perforated. In some implementations,
the liner
comprises perforations of varied size or frequency.
[0112] In some implementations, the branch side wells comprise a blank liner
section.
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[0113] In some implementations, the blank liner section is provided proximate
to a
boundary defined by one of the SAGD steam chamber areas.
[0114] In some implementations, the branch side wells are at an oblique angle
with
respect to the main well.
[0115] In some implementations, the branch side well sections extend obliquely
toward a
toe end of the residual zone.
[0116] In some implementations, the branch side wells comprise completions
allowing
injection and production.
[0117] In some implementations, the branch side wells extend to recover lows
or oil
accumulations in the residual zone.
[0118] In some implementations, the process includes controlling the branch
side wells
with inflow control devices.
[0119] In some implementations, the drilling of the infill well comprises
drilling junctions
of the multilateral branch bores and the main horizontal bore in competent
rock below
the reservoir.
BRIEF DESCRIPTION OF THE DRAWINGS
[0120] Figs la-le are plan view schematics of single SAGD well pairs with
steam
chambers in dotted lines.
[0121] Figs 2a-2b are lateral cross-sectional view schematics of SAGD well
pairs with
steam chambers in dotted lines.
[0122] Figs 3a-3b are perspective view schematics of sections of residual
zones formed
between neighbouring SAGD well pairs.
[0123] Fig 4a-4e are perspective view schematics of different types of
residual zones
formed between neighbouring SAGD well pairs.
[0124] Fig 5 is a longitudinal cross-sectional view schematic, with vertical
dimension
exaggerated, of an infill well with a downhole sumped pump.
CA 02684049 2014-03-26
[0125] Fig 6 is a longitudinal cross-sectional view schematic, with vertical
dimension
exaggerated, of an infill well with a blank liner proximate a steam chamber
boundary.
[0126] Fig 7 is a perspective isolation view schematic of neighbouring SAGD
well pairs
and an in-between infill well with a main section and branched side sections.
[0127] Fig 8 is a block diagram flow chart.
[0128] Fig 9 is a seismic plan view image representing a residual zone in
between
neighbouring SAGD well pairs and an infill well. The warmer colours represent
the
presence of steam, while the "anomaly" in blue is a vertically unbroken zone.
[0129] Fig 10 is a seismic longitudinal cross-sectional image from line X.
10 [0130] Fig 11 is a seismic lateral cross-sectional image along line Xl.
DETAILED DESCRIPTION
[0131] The infill completion methods of the present invention allow improved
conformance to complex infill lithology, base topography and neighbouring
steam
chamber boundaries in an accurate and adaptive manner.
[0132] Unlike prior techniques, which understate or overlook the complex three-
dimensional and constantly evolving nature of SAGD residual zones for infill
opportunities, the methods of the present invention take into account the
three-
dimensional boundaries of such residual zones.
[0133] Referring to Figs la-le, a given SAGD well pair 20 can generate a
variety of
20 steam chambers 22 or mobilised hydrocarbon zones, with different plan
view shapes
and orientations.
[0134] Referring to Figs 2a-2b, when two SAGD well pairs 20 are located beside
each
other, their steam chambers 22 usually grow upward and outward. Depending on
their
separation distance, the operation of the SAGD well pairs and the lithology of
the
formation, the steam chambers 22 can remain separate as shown in Fig 2a or
they may
join together form a common steam chamber as shown in Fig 2b.
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[0135] Referring now to Fig 3a, when the steam chambers remain separate, the
resulting residual zone may be referred to as a "vertically unbroken zone" 24.
This type
of zone often has an elongated shape with an overlying boundary following the
overburden, an underlying boundary following the underburden topology and
flanking
boundaries which are often concave defined by the adjacent steam chambers.
[0136] Referring to Fig 3b, when the steam chambers of neighbouring SAGD well
pairs
coalesce to form a common steam chamber, the resulting residual zone may be
referred
to as a "hump zone" 26. This type of zone often has an elongated shape with an
underlying boundary following the underburden topology, while the overlying
and
flanking boundaries are both defined by the common steam chamber.
[0137] Referring now to Figs 4a-4e, various combinations of hump zones 26 and
vertically unbroken zones 24 can co-exist along a single infill residual zone
30. Each of
these scenarios calls for a corresponding adapted infill well.
[0138] Referring to Figs 5-7, a horizontal infill well 31 is provided in the
residual zone 30.
[0139] Referring to Fig 5, there may be provided a low point in the infill
well trajectory in
the underburden 32. A downhole pump 34 may be sited at the low point. The
infill well
31 is completed in reservoir, e.g. with a slotted liner 36. The infill well 30
may be
provided approximately parallel to and midway between the neighbouring SAGD
well
pairs, depending on steam configuration. The downhole pump and well trajectory
are
preferably adapted to the baseline topology.
[0140] Referring to Fig 6, which shows a similar strategy to that of Fig 5,
the completion
include a liner with a blank section 38 proximate to the steam chamber
boundary. It
should be understood that the steam chamber boundary may be determined by
seismic
surveying, preferably using a time-lapse seismic method which can allow a
predicted
steam chamber boundary and thus foresee certain problematic locations along
the infill
well. Depending on the timing of the seismic surveying (before or after
drilling,
completion or operation), the infill well can be adapted accordingly.
[0141] Referring to Fig 7, the infill well may include a main section 40 and
multilateral
branch sections 42,44. The multilateral branches target reservoir lows and oil
accumulations, for example. The infill well has both main wellbore and side-
tracks slotted
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or perforated to allow injection and production. The branch wells can also be
controlled
to maintain conformance. The pump in this case is preferably sumped as
illustrated in
the previous Figs.
[0142] In one variant, when appropriate the infill well could have regularly
spaced
branches extending close enough to the SAGD well pairs to encourage growth of
a
"fingered" steam zone away from the SAGD well pairs. The branches may be
provided to
target vertically unbroken zones and zones at the toe end of the SAGD well
pairs.
[0143] Referring to Figs 9-11, which are seismic images, the warmer colours
(yellow,
red) represent presence of steam and thus a hump zone 26 below, what could be
referred to as an "anomaly" here, and the blues represent absence of steam and
thus a
vertically unbroken zone 24. The proposed infill well 30 lies closer to one
SAGD well pair
than the other (plan view), and passes below a roughly elliptical "hole"
representing
where steam has not formed a combined steam region (plan view again). For Figs
10
and 11, note that "Devonian" unconformity is the interface between sand and
carbonate
rock. The parallel and perpendicular views clearly show that the steam chamber
is not
connected everywhere above the infill well.
[0144] Some aspects and embodiments of the present invention have the
following
features or characteristics:
¨ Time-lapse (4D) seismic enables for later optimization steps depending on
oil
distribution.
¨ A downhole pump located low in the reservoir enables to drain low-lying
reservoir.
¨ Inflow control enables to retain good conformance as oil in the inflow
region is
depleted and the overlying steam zone changes with time.
¨ Depending on the configuration of infill oil (e.g. low "pockets" in the
reservoir
base), sidetrack wells will be helpful in maximizing recovery.
¨ Time-lapse seismic surveys are conducted periodically ¨ typically once
per year
¨ and well control is tuned based on new oil distribution..
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¨ Seismic data interpretations are used to characterize the target oil
accumulation
and calibrate numerical simulation models
¨ Numerical models are used to develop a performance expectation for the
infill
resource.
¨ Infill well is drilled and concurrently appraised with appropriate logging
while
drilling technology then completed using adaptive completion technology in one
of the configurations depicted, or combinations or variations thereof
¨ Steam is injected if required ¨ perhaps alternating with periods of oil
production-
to enhance infill oil mobility
¨ Once continuity with the SAGD chambers is established wells are operated to
maximize recovery by gravity drainage
¨ Optionally: If downhole flow meters are incorporated (nearly commercial at
present), the inflow is adjusted more frequently to maintain uniform
production
along the well
¨ Embodiments tune the design of the infill well based on the observable
distribution of oil in the target region and allows the flow performance of
the well
to be repeatedly optimized over the life of the infill well.
¨ Improvement over conventional practices which undoubtedly leave
significant
remaining oil above the infill well due to poor conformance along the well,
and
considerable oil below the well due to undulating reservoir base topography.
¨ Improvement over conventional practices of infill wells that are provided
approximately midway between adjacent SAGD well pairs and completed
essentially at the same elevation as neighbouring SAGD producers, more-or-
less horizontally oriented and with standard completions (e.g. uniform
slotting or
perforation along the infill well).
¨ For embodiments comprising multilateral branches, where sidetrack wells
are
tied to the main wellbore, it may be advantageous if the junctions are located
in
competent rock below the reservoir than in unconsolidated oilsands.
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¨ Embodiments of the invention utilize direct observation of the target
infill oil and
reservoir base topography to design an optimal infill well completion. The
result
is faster and more complete recovery of the oil in the infill region.
¨ Thermally capable downhole flow sensors may be incorporated and used in
conjunction with ICDs to optimize performance of the infill well throughout
its
lifetime.
[0145] It should be understood that the present invention is not limited to
the
embodiments or aspects described herein.
