Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BLOWDOWN METHOD FOR THERMAL RECOVERY PROCESSES
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional application which claims
benefit under
35 USC 119(e) to U.S. Provisional Application Ser. No. 62/470,922 filed March
14,
2017, entitled " BLOWDOWN METHOD FOR THERMAL RECOVERY PROCESS,"
which is incorporated herein in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] None.
FIELD OF THE INVENTION
[0003] The present invention relates generally to thermal recovery
processes. More
particularly, but not by way of limitation, embodiments of the present
invention provide a
method of blowdown for a steam chamber of a thermal recovery process.
BACKGROUND OF THE INVENTION
[0004] Several types of thermal recovery processes have been utilized for
hydrocarbon recovery from subterranean formations. Examples of thermal
recovery
processes include steam assisted gravity drainage (SAGD), expanding solvent
steam
assisted gravity drainage (ES-SAGD) and cyclic steam stimulation (CSS).
[0005] Significant amounts of oil and/or heat could be left behind in the
steam
chamber of the subterranean formation after thermal recovery. It is desired to
investigate
post-thermal recovery processes that could recover and collect any remaining
oil and/or
heat to make the entire thermal recovery process more efficient and
economical.
[0006] It has been previously proposed to inject a non-condensable gas into
the steam
chamber through a horizontal injector after steam injection. This method may
recover
some additional oil, but will not be able to produce the desired sweep
efficiency.
Furthermore, gas injection will not provide any heat scavenging from the steam
chamber.
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BRIEF SUMMARY OF THE DISCLOSURE
[0007] In certain illustrative embodiments, a method of blowdown for a
steam
chamber of a thermal recovery process is provided. A blowdown mixture is
introduced
into the steam chamber. The blowdown mixture can include glycol and water.
Heat can
be adsorbed from the steam chamber onto the blowdown mixture. A viscosifying
agent
can also be introduced into the steam chamber. Oil from the steam chamber can
be
viscosified with the viscosifying agent to increase the sweep efficiency and
produce oil.
The blowdown mixture and emulsified oil can both be recovered from the steam
chamber.
[0008] In certain aspects, the heat from the steam chamber can be adsorbed
onto the
glycol in the blowdown mixture. The blowdown mixture and the viscosifying
agent can
be introduced into the steam chamber after shut-in of steam injection. The
rate of steam
injection into the steam chamber can be reduced prior to blowdown. The
pressure of
injected steam into the steam chamber can also be reduced prior to blowdown.
The
temperature of the injected steam is therefore reduced prior to blowdown.
[0009] The steam injection into the steam chamber can occur via the
injector well.
The blowdown mixture and the viscosifying agent can be recovered from the
producer
well. The blowdown mixture and the viscosifying agent can also be recovered
from both
the producer well and the injector well.
[0010] In certain aspects, the thermal recovery process can include,
without
limitation, steam assisted gravity drainage, expanding solvent steam assisted
gravity
drainage and cyclic steam stimulation.
[0011] In certain aspects, the blowdown mixture and the viscosifying agent
can travel
through the steam chamber via gravity drainage. The blowdown mixture and the
viscosifying agent can be injected into the steam chamber from one or more of
a
delineation well and a horizontal well. The horizontal well can be disposed
above the
steam chamber. The viscosifying agent can include a polyol. The polyol can
include one
or more of glycerol and/or a polymer in water. The glycerol can include one or
more of
ethylene glycol and propylene glycol. The polymer can include one or more of
polyacrylamide and polysaccharide.
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[0012] In certain illustrative embodiments, a method of recovering primary
oil and
residual oil from a steam chamber in a reservoir is provided. This method
could be
applied to a thermal recovery process with a steam chamber. The thermal
recovery
process can include steam injection into the steam chamber, recovering primary
oil from
the steam chamber, terminating steam injection into the steam chamber,
introducing a
blowdown mixture and a viscosifying agent into the steam chamber, adsorbing
heat from
the steam chamber onto the blowdown mixture, sweeping the residual oil in the
steam
chamber with the viscosifying agent and both recovering the blowdown mixture
and oil
from the steam chamber. The produced oil may be an emulsion that had been
formed
with the viscosifying agent and the oil. In certain aspects, the thermal
recovery process
can be, for example, steam assisted gravity drainage, expanding solvent steam
assisted
gravity drainage or cyclic steam stimulation. The reservoir can be an oil sand
reservoir.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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 in which:
[0014] Fig. 1 is an illustration of a blowdown method for a steam chamber
in an
illustrative embodiment.
[0015] While certain embodiments will be described in connection with the
preferred
illustrative embodiments shown herein, it will be understood that it is not
intended to
limit the invention to those embodiments. On the contrary, it is intended to
cover all
alternatives, modifications, and equivalents, as may be included within the
spirit and
scope of the invention as defined by the claims.
DETAILED DESCRIPTION
[0016] 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
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.
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[0017] FIG. 1 is an illustration of a blowdown method for a steam chamber
in an
illustrative embodiment of the presently disclosed subject matter. The
blowdown method
can be utilized to recover additional oil and heat from a reservoir of the
steam chamber
after implementing steam assisted gravity drainage or a similar thermal
recovery process.
[0018] In certain illustrative embodiments, the blowdown method can be
implemented as a late life process after a thermal recovery process such as
steam assisted
gravity drainage (SAGD), expanding solvent steam assisted gravity drainage (ES-
SAGD)
or cyclic steam stimulation (CSS) has already been implemented to recover
primary oil.
The presently disclosed blowdown method can utilize existing delineation
wells. The
presently disclosed blowdown method can also be implemented with horizontal
wells
drilled at the top of the reservoir. A set of chemical mixtures can be
injected in sequence
into a depleted steam chamber to recover heat and residual oil left behind
within the
chamber. The blowdown method can enhance oil production from these wells as
well as
reduce operation costs due to recovered heat being utilized to generate
additional steam.
[0019] In certain illustrative embodiments, the steam injection rate and
steam
injection pressure can be gradually declined towards the end of a thermal
recovery
process. This will decrease the required steam injection temperature, thus
reducing the
amount of energy required to produce steam towards the end of the process.
Once the
steam injection is shut in, a selected blend of chemicals can be injected into
the reservoir.
In certain illustrative embodiments, the chemicals can be injected from a
delineation well
or from a newly drilled horizontal well at the top of the reservoir. The steam
injector
could also be converted into a producer at this point. In a vertical well
scenario, such as
when implementing cyclic steam stimulation for a heavy oil field, a horizontal
well could
be drilled at the top of the reservoir to increase the area swept by this
proposed blowdown
method.
[0020] In certain illustrative embodiments, the selected blend of chemicals
can
include a glycol/water mixture. The injected mixture can sweep the reservoir
from the
top down to the location of the horizontal producer. As the glycol moves
through the
depleted steam chamber, it can scavenge heat left behind in the reservoir. The
glycol can
also adsorb some water along the way. Some oil can also be produced due to the
glycol
push using the gravity forces through the steam chamber. The produced glycol
can be
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separated and the adsorbed heat can be used to generate more steam. It has
been
estimated in reservoir simulation studies that about one third of the injected
heat (in the
form of steam) is generally left behind in the reservoir. If a considerable
amount of this
heat can be adsorbed onto the glycol according to the presently disclosed
blowdown
method, it can have a significant impact on project economics.
[0021] In certain illustrative embodiments, the selected blend of chemicals
can also
include a viscosifying agent. For example, a viscosifying agent such as
glycerol or
polymer in water can also be injected into the reservoir after the
glycol/water mixture has
been injected into the reservoir for a period of time. The viscosifying agent
can be
injected from a delineation well or a horizontal well at the top of the pay
zone. The
viscosifying agent can provide a viscous drive that improves the sweep
efficiency of the
reservoir and to yield an incremental oil recovery.
[0022] In certain illustrative embodiments, the glycol can be ethylene
glycol, but
other glycols such as propylene glycol could also be used for this blowdown
process.
Any polyol including but not limited to glycerol or a polymer such as
polyacrylamide or
polysaccharide can also be used. Polyols are preferred because they are
typically less
expensive than commercially available polymers for enhanced oil recovery
applications.
Polyols/glycerol and their derivatives are also less toxic and more
environmentally
friendly. They are more readily available since glycerol is a byproduct of
biodiesel.
Also, glycerol is completely soluble in water, but not in oil, and therefore
would not
create stable emulsions that are difficult to process. Glycols are only weakly
toxic and
are readily available as well. Glycols are also less expensive than most other
chemicals
such as polymers or surfactants used in enhanced oil recovery operations.
[0023] The presently disclosed blowdown method can provide additional oil
recovery
as well as scavenge heat that is left behind in the reservoir. As a result,
the proposed
blowdown method can reduce operational costs and improve overall project
economics.
The blowdown method can be implemented in any heavy oil reservoir where a
thermal
recovery process has been implemented.
[0024] At least one embodiment is disclosed herein. Variations,
combinations, and/or
modifications of the embodiment(s) and/or features of the embodiment(s) made
by a
person having ordinary skill in the art are within the scope of the
disclosure. Alternative
CA 2998161 2018-03-14
embodiments that result from combining, integrating, and/or omitting features
of the
embodiment(s) are also within the scope of the disclosure.
[0025] Use of the term "optionally" with respect to any element of a claim
means that
the element is required, or alternatively, the element is not required, both
alternatives
being within the scope of the claim. Use of broader terms such as comprises,
includes,
and having may be understood to provide support for narrower terms such as
consisting
of, consisting essentially of, and comprised substantially of Accordingly, the
scope of
protection is not limited by the description set out above but is defined by
the claims that
follow, that scope including all equivalents of the subject matter of the
claims. Each and
every claim is incorporated as further disclosure into the specification and
the claims are
embodiment(s) of the present disclosure.
[0026] While several embodiments have been provided in the present
disclosure, it
may be understood that the disclosed embodiments might be embodied in many
other
specific forms without departing from the spirit or scope of the present
disclosure. The
present examples are to be considered as illustrative and not restrictive, and
the intention
is not to be limited to the details given herein. For example, the various
elements or
components may be combined or integrated in another system or certain features
may be
omitted, or not implemented.
[0027] In addition, the various embodiments described and illustrated in
the various
embodiments as discrete or separate may be combined or integrated with other
systems,
modules, techniques, or methods without departing from the scope of the
present
disclosure. Other items shown or discussed as coupled or directly coupled or
communicating with each other may be indirectly coupled or communicating
through
some interface, device, or intermediate component whether electrically,
mechanically, or
otherwise. Other examples of changes, substitutions, and alterations are
ascertainable by
one skilled in the art and may be made without departing from the spirit and
scope
disclosed herein.
[0028] 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. At the
same time, each
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and every claim below is hereby incorporated into this detailed description or
specification as additional embodiments of the present invention.
[0029] Although the systems and processes described herein have been
described in
detail, it should be understood that various changes, substitutions, and
alterations can be
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.
REFERENCES
[0030] All of the references cited herein are expressly incorporated by
reference. 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 data after the priority
date of this
application. Incorporated references are listed again here for convenience:
U.S. Pat. Pub. No. 2014/0332209 (Wickramathilaka); "Polyol for Improving Sweep
Efficiency in Oil Reservoirs" (published Nov. 13, 2014); Assignee:
ConocoPhillips
Company, Houston, TX.
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