Note: Descriptions are shown in the official language in which they were submitted.
MULTILATERAL OBSERVATION WELLS
FIELD OF THE INVENTION
[0001] Embodiments of the invention relate to observation wells for
monitoring
reservoir conditions during hydrocarbon recovery.
BACKGROUND OF THE INVENTION
[0002] Bitumen recovery from oil sands presents technical and economic
challenges
due to high viscosity of the bitumen at reservoir conditions. Thermal recovery
processes
such as steam assisted gravity drainage (SAGD) inject steam to heat the
bitumen. The
bitumen with reduced viscosity due to this heating then drains and is
recovered.
[0003] Uniqueness of each reservoir due to factors, such as formation
heterogeneities,
creates uncertainties with respect to employing SAGD. Optimization of the SAGD
to
improve economics relies on understanding performance issues even though
occurring
underground making the issues often unknown. Since not possible to detect all
desired
information from well pairs used for the injection and production, prior
approaches
utilize separate vertical mono-bore observation wells.
[0004] The observation wells whether utilized in SAGD or other hydrocarbon
production processes including water flood or other enhanced oil recovery
procedures
collect various data, such as reservoir temperature profiles. For example, the
temperature
profile provides indication of a resulting steam chamber development, which
information
may lead to making technical or operational adjustments. However, coverage at
more
than one vertical location through the reservoir may require intensive
drilling to form
several of the mono-bore observation wells.
[0005] Therefore, a need exists for methods and systems for cost effective
monitoring
of a reservoir during hydrocarbon production.
BRIEF SUMMARY OF THE DISCLOSURE
[0006] In one embodiment, a method of monitoring conditions in a
hydrocarbon
reservoir includes injecting steam into the reservoir and producing a mixture
of
hydrocarbons and condensate of the steam from the reservoir. The method
further
includes detecting vertical development of a resulting steam chamber in the
reservoir
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with a multilateral observation well. The observation well includes branched
bores in
which temperature sensors are disposed.
[0007] According to one embodiment, a method of monitoring conditions in a
hydrocarbon reservoir includes drilling a multilateral observation well having
branches
that extend to form a first bore and a second bore. In addition, the method
includes
disposing a first sensor in the first bore and a second sensor in the second
bore.
Obtaining data on the conditions with the sensors during hydrocarbon recovery
operations occurs without use of the observation well for fluid communication
with the
reservoir in the hydrocarbon recovery operations.
[0008] For one embodiment, a system for monitoring conditions in a
hydrocarbon
reservoir includes a steam injection well extending toward horizontal in the
reservoir and
a production well extending toward horizontal in the reservoir for production
of fluids
heated by steam introduced through the injection well. A multilateral
observation well
includes bores branched in a formation above the reservoir such that the bores
enter the
reservoir at spaced locations and traverse downward through the reservoir.
Temperature
sensors disposed in the bores of the observation well monitor a steam chamber
resulting
from introduction of the steam through the injection well into the reservoir.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A more complete understanding of the present invention and benefits
thereof
may be acquired by referring to the following description taken in conjunction
with the
accompanying drawings.
[0010] Figure 1 is a schematic of a well configuration with a multilateral
observation
wellbore for monitoring two steam assisted gravity drainage well pairs,
according to one
embodiment of the invention.
DETAILED DESCRIPTION
[0011] Turning now to the detailed description of the preferred
arrangement or
arrangements of the present invention, it should be understood that the
inventive features
and concepts may be manifested in other arrangements and that the scope of the
invention
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is not limited to the embodiments described or illustrated. The scope of the
invention is
intended only to be limited by the scope of the claims that follow.
[0012] Embodiments of the invention relate to monitoring conditions in a
hydrocarbon reservoir with a multilateral observation well. The observation
well may
detect vertical development of a steam chamber that forms in the reservoir
during thermal
hydrocarbon recovery operations. Further, the observation well may include
branches
that extend to form vertical bores with temperature sensors for the
monitoring, which
may occur during the recovery operations performed in other wells since the
observation
well may be dedicated to only the monitoring.
[0013] Figure 1 illustrates an exemplary system with a multilateral
observation well
100. For some embodiments, the observation well 100 enables sensing conditions
during
a thermal recovery operation, such as steam assisted gravity drainage (SAGD)
as
depicted. Various other recovery operations and alternative wellbore
configurations may
also utilize the observation well 100 and features described herein.
[0014] A first injection well 102, a first production well 104, a second
injection well
106 and a second production well 108 all extend into a hydrocarbon reservoir
110 in
proximity to the observation well 100 to enable monitoring of the conditions
during
hydrocarbon recovery operations using the injection and production wells 102,
104, 106,
108. The injection and production wells 102, 104, 106, 108 may each include
horizontal
lengths traversing through the reservoir 110. The first injection and
production wells
102, 104 provide a first SAGD well pair spaced in a lateral direction from a
second
SAGD well pair formed by the second injection and production wells 106, 108.
[0015] In operation, steam introduced through the horizontal lengths of
the injection
wells 102, 106 heats the hydrocarbons and condenses. A mixture of condensate
and the
hydrocarbons that are heated then drains to the production wells 104, 108,
which may be
disposed below and parallel to respective ones of the injection wells 102,
106. Steam
chambers develop in the reservoir 110 above the injection wells 102, 106 and
below an
overburden layer 111 as a result of the injecting and producing.
[0016] The observation well 100 includes one or more junctions 112 where
at least
one lateral borehole originates. For example, the observation well 100
branches to form a
first bore 121, second bore 122, third bore 123 and fourth bore 124. Placement
of the
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junctions 112 above the reservoir 110 and in an area of formation, such as the
overburden
layer 111, may avoid operational difficulties and unwanted rapid steam chamber
coalescence between each of the bores 121-124 of the observation well 100.
[0017] The overburden layer 111 provides lower permeability to fluid flow
than the
reservoir 110. Therefore, the overburden layer 111 obstructs or prevents fluid
communication between the reservoir 110 and lengths of the bores 121-124 above
the
reservoir 110 and may be impermeable to flow of fluids, such as steam. For
some
embodiments, formations of shale form the overburden layer 111.
[0018] The bores 121-124 of the observation well 100 may extend from the
junctions
112 toward horizontal while remaining above the reservoir 110. The bores 121-
124 may
then turn downward and enter the reservoir 110. Since the bores 121-124 may
diverge
from one another in radial directions from the junctions 112, each of the
bores 121-124
may enter the reservoir 110 at spaced locations to facilitate avoidance of the
steam
chamber coalescence.
[0019] Upon entering the reservoir 110, the bores 121-124 traverse
downward in a
vertical direction through the reservoir 110 toward a depth of the injection
wells 102,
106. In some embodiments, the first bore 121 passes through the reservoir 110
closer to a
toe of the first injection well 102 than a heel of the first injection well
102. The second
bore 122 may pass closer to the heel than the toe of the first injection well
102 to enable
monitoring the conditions at different targeted locations along the first SAGD
well pair.
[0020] The observation well 100 may further provide ability to monitor the
second
SAGD well pair with the third bore 123 and fourth bore 124. As such, the first
bore 121
and second bore 122 of the observation well 100 may pass closer to the first
injection
well 102 than the second injection well 106. The third bore 123 and fourth
bore 124 of
the observation well 100 furthermore pass closer to the second injection well
106 than the
first injection well 102.
[0021] Sensors 114, such as temperature and/or pressure sensors, disposed
in the
bores 121-124 measure the conditions and may facilitate monitoring the steam
chamber
developing in the reservoir 110. For example, detection of a vertical
temperature profile
along the bores 121-124 identifies height of the steam chamber based on where
the
temperature drops due to the steam chamber not yet reaching higher in the
formation.
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The observation well 100 may include several of the sensors 114 spaced along
vertical
lengths of each of the bores 121-124 to provide such profiles at desired
locations in the
reservoir 110.
[0022] In some embodiments, the detecting with the observation well 100
takes place
concurrent with the injecting and producing through the injection and
production wells
102, 104, 106, 108. Such hydrocarbon recovery operations occur without relying
on fluid
communication through the observation well 100 between surface and the
reservoir 110
since this flow pathway may be blocked. Collection of data from the
observation well
100 reduces uncertainties related to reservoir description or process
performance and
allows operators to improve recovery by adjusting at least one of the
injecting and the
producing based on the data.
[0023] For example, indication from the first bore 121 of relative smaller
steam
chamber development compared to indication from the second bore 122 may
trigger
adjustment of flow control devices to direct additional steam to the toe
compared to the
heel of the first injection well 102. Likewise, the first bore 121 and second
bore 122 may
detect a relative smaller steam chamber development compared to that detected
by the
third bore 123 and fourth bore 124. Adjustment of steam injection into each of
the
injection wells 102, 106 relative to one another may facilitate desired
merging of the
steam chambers between adjacent well pairs.
[0024] Completion of the observation well 100 includes logging each of the
bores
121-124 intersecting different sections of the reservoir 110 to enhance
understanding of
the reservoir properties. The observation well 100 utilizes a single surface
well pad to
reduce drilling days and lower capital expenditure compared to intensive
drilling
otherwise required to form individual unbranched wells. Further, use of only
one well
pad with the observation well 100 instead of multiple well pads to obtain
desired data
reduces surface footprint and undesired land disturbances.
[0025] In closing, it should be noted that the discussion of any reference
is not an
admission that it is prior art to the present invention, especially any
reference that may
have a publication date after the priority date of this application.
[0026] Although the systems and processes described herein have been
described in
detail, it should be understood that various changes, substitutions, and
alterations can be
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made without departing from the spirit and scope of the invention as defined
by the
following claims. Those skilled in the art may be able to study the preferred
embodiments and identify other ways to practice the invention that are not
exactly as
described herein. It is the intent of the inventors that variations and
equivalents of the
invention are within the scope of the claims, while the description, abstract
and drawings
are not to be used to limit the scope of the invention. The invention is
specifically
intended to be as broad as the claims below and their equivalents.
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