Note: Descriptions are shown in the official language in which they were submitted.
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
TITLE: STEAM INJECTION APPARATUS FOR STEAM ASSISTED
GRAVITY DRAINAGE TECHNIQUES
INVENTORS: KEVIN FORBES
NIHAT OVUTMEN
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional Patent
Application No.
60/911,156, filed April 11, 2007 and U.S. Non Provisional Patent Application
No. 11/778,233
filed July 16, 2007.
BACKGROUND
Field of the Invention
[0002] This invention relates generally to oil recovery methods using steam
assisted
gravity drainage (SAGD) technology.
Description of the Prior Art
[0003] In many areas of the world, large deposits of viscous petroleum exist,
and these
deposits are often referred to as "tar sand" or heavy oil" deposits due to the
high viscosity of the
hydrocarbons which they contain. These tar sands may extend for many miles and
occur in
varying thicknesses of up to more then 300 feet. Although tar sand deposits
may lie at or near
the earth's surface, generally they are located under a substantial overburden
which may be as
great as several thousand feet thick. Tar sands located at these depths
constitute some of the
world's largest presently known petroleum deposits. The tar sands contain a
viscous
hydrocarbon material, commonly referred to as a bitumen, in an amount which
typically ranges
from about 5 to about 20 percent by weight. While bitumen is usually immobile
at typical
reservoir temperatures, the bitumen generally becomes mobile at higher
temperatures and has a
substantially lower viscosity at higher temperature than at the lower
temperatures.
1
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
[0004] Since most tar sand deposits are too deep to be mined economically, a
serious need
exists for an in situ recovery process wherein the bitumen is separated from
the sand in the
formation and produced through a well drilled into the deposit. Two basic
technical
requirements must be met by any in situ recovery process: (1) the viscosity of
the bitumen must
be sufficiently reduced so that the bitumen will flow to a production well;
and (2) a sufficient
driving force must be applied to the mobilized bitumen to induce production.
[0005] Hydrocarbon recovery may be enhanced in certain heavy oil and bitumen
reservoirs
by using SAGD. When using SAGD, horizontal production and steam injection
wellbores are
drilled into the hydrocarbon reservoir formations and steam is injected into
the steam injection
wellbore. The production and steam injection wellbores relatively are closely
spaced in the
vertical direction, and the injection of steam into the steam injection
wellbore causes the heavy
hydrocarbons in the production wellbore to become mobile due to the reduction
of in situ
viscosity. The benefits of SAGD over conventional secondary thermal recovery
techniques
include higher oil productivity relative to the number of wells employed and
higher ultimate
recovery of oil in place.
[0006] U.S. Patent No. 6,988,549 discusses certain problems associated with
typical
SAGD projects. According to the '549 patent: (a) the economics of such
projects is significantly
impacted by the cost associated with generating steam; (b) SAGD does not
typically employ the
use of super-saturated steam because of the high cost of producing this steam
with conventional
hydrocarbon-fired tube boilers which results in using steam that is less
efficient in transferring
heat to the heavy oil reservoir; and (c) the produced water associated
hydrocarbon production
from these operations is typically disposed of in a commercially operated
disposal well for a fee.
[0007] It is believed that the economics of SAGD may have been adversely
impacted by
the mechanisms heretofore utilized to inject steam and that the economics may
be substantially
increased by providing a homogeneous distribution of steam in the steam
injection wellbore.
This novel and useful for result is achieved with the apparatus of the present
invention.
2
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
SUMMARY OF THE INVENTION
[0008] In accordance with the present invention, steam injection pipe string
apparatus is
provided for use in the steam injection wellbore in a SAGD operation. A steam
injection pipe
string according to the present invention comprises an elongated tubular
structure having first
and second ends which is inserted into the steam injection wellbore and which
is utilized to
provide steam to that wellbore. Steam injection pipe string apparatus
according to the present
invention comprises a plurality of orifices, e.g. nozzles, which are disposed
in and along the
length of the elongated tubular structure. The sizes of the nozzles vary
between the first and
second ends of the elongated tubular structure, and, in one embodiment, the
sizes of the nozzles
increase between the first and second ends of the elongated tubular structure.
The orifices in the
elongated tubular structure are thus sized to yield equalized
pressure/temperature steam injection
at each section along the steam injection wellbore.
[0009] Steam injection pipe string apparatus according to the present
invention may be
implemented by using a plurality of blank pipes in threaded engagement with
one another.
Nozzles may be formed in the blank pipes utilizing milling techiques or by
forming threaded
apertures in the blank pipe and installing a nozzle in each threaded aperture.
[0010] Alternatively, pipe string apparatus according to the present invention
may be
formed by joining a plurality of subs together. In this latter instance, each
sub has a different
size nozzle depending upon its location in the steam injection pipe string.
[0011] Additionally, steam injection pipe string apparatus according to the
present
invention may be implemented using sand-screen sections where the nozzle is
arranged to direct
the injected steam choked flow parallel to the wellbore. By using such sand
screen apparatus,
the flow of steam dissipates somewhat upon exiting the steam injection pipe
string so as not to
erode the wellbore. In another words, the use of a sand-screen apparatus to
inject the steam into
the steam injection wellbore lessens erosion of that wellbore.
[0012] In accordance with the present invention, a system is provided for
injecting steam
into a wellbore. The system comprises a source of steam and a steam injection
pipe string. The
steam injection pipe string comprises an elongated tubular structure with
first and second ends,
where the first end is operatively coupled to the source of steam and where
the steam injection
3
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
pipe string comprises a plurality of orifices which increase in size from the
first to the second
end of the tubular structure. The elongated tubular structure may comprise a
plurality of blank
pipes in threaded engagement with one another or a plurality of subs in
threaded engagement
with one another with different sized orifices in each of the subs. The
orifices may, for example,
comprise nozzles which may either be formed in the elongated tubular member
using milling
techniques or which may be installed in threaded apertures formed in the
elongated tubular
member. The orifices may also comprise sand screen apparatus.
[0013] In accordance with the present invention, a steam assisted gravity
drainage system
is provided comprising a horizontal production wellbore and a horizontal steam
injection
wellbore which is vertically spaced from and in proximity to the production
wellbore. A source
of steam is provided which is connected to one end of a steam injection pipe
composed of an
elongated tubular structure and a plurality of orifices in that structure. The
orifices increase in
size as the distance from the end of the tubular structure connected to the
steam increases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the accompanying drawings:
[0015] FIG. 1 is an elevation view in partial cross-section illustrating a
production
wellbore and a steam injection wellbore containing one embodiment of apparatus
in accordance
with the present invention.
[0016] FIG. 2 is an elevational drawing in cross-section of the injection and
production
wellbores in FIG. 1.
[0017] FIG. 3 is a cross-sectional of a steam injection wellbore containing
steam injection
pipe string apparatus implemented using sand screen apparatus.
[0018] FIGS. 4 and 5 are cross-sectional drawings illustrating alternative
configurations
for an inflow control device.
[0019] FIG. 6 is a perspective view in partial cross-section of another
embodiment of
steam injection pipe string apparatus implemented using a plurality of subs.
[0020] FIG. 7 is an elevation view in partial cross-section of one embodiment
of a metal-
to-metal seal that may be utilized in the inflow control devices of FIGS. 4
and 5.
4
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
[0021] FIG. 8 is an elevation view in partial cross-section of one embodiment
of a
combination of an inflow control device and sand screen apparatus that may be
utilized by the
present invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0022] It will be appreciated that the present invention may take many forms
and
embodiments. In the following description, some embodiments of the invention
are described
and numerous details are set forth to provide an understanding of the present
invention. Those
skilled in the art will appreciate, however, that the present invention
practiced without those
details and that numerous variations from and modifications of the described
embodiments may
be possible. The following description is thus intended to illustrate and not
limit the present
invention.
[0023] With reference first to FIG. 1, there is illustrated a system
comprising a source of
steam 20 located at the earth's surface. The source of steam 20 is coupled to
one end of steam
injection pipe string apparatus 10 in accordance with the present invention.
Steam injection pipe
string apparatus 10, as illustrated, is an elongated tubular structure and is
located in steam
injection wellbore 12. In SAGD operations, steam injection wellbore 12 is
typically not cased
and is closely spaced in the vertical direction from a production wellbore
12a.
[0024] Steam injection pipe string 10 comprises a plurality of orifices 14-19
which are
disposed at spaced intervals along the length of steam injection pipe string
10. Orifices 14 are
the closest orifices in steam injection pipe string 10 to the source of steam
20, while orifices 19
are the orifices which are furthest away from source of steam 20.
[0025] In accordance with the present invention, orifices 14-19 are sized in
steam injection
pipe string 10 to yield equalized pressure/temperature steam injection along
the length of steam
injection wellbore 12. Accordingly, the size of the orifices in steam
injection pipe string 10
increases as the distance of the orifice from the source of steam 20
increases. In the exemplary
embodiment illustrated in FIG. 1, orifices 14 would be the smallest orifices
in size in the steam
injection pipe apparatus 10 and the sizes of orifices 15-19 would increase
with the size of
orifices 19 being the largest in the exemplary embodiment illustrated in FIG.
1.
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
[0026] In some circumstances, the sizes of the orifices 14-19 may vary across
the length of
steam injection pipe string 10 based on wellbore parameters, e.g.,
permeability of the zones of
interest. Further, the nozzles 14-19 in steam injection pipe string 10 may
have variable orifices,
where the openings in such orifices may be varied from a control line (not
shown) or based on
the temperature in steam injection pipe string 10. For example, the opening in
a variable orifice
may constrict or choke more under higher temperatures than at lower
temperatures.
[0027] Steam injection pipe apparatus according to the present invention may
be
implemented in a number of ways. Still referring to FIG. 1, a steam injection
pipe string
apparatus 10 may be implemented using a plurality of blank pipes which are
connected in
threaded engagement and which have orifices formed therein according to the
orifice sizing
criteria discussed above. The orifices may comprise nozzles and may be formed
in the blank
pipe utilizing standard and well-known milling techniques. Alternatively,
threaded apertures
may be formed in the blank pipe and a nozzle may be installed in each threaded
aperture.
[0028] With reference to both FIGS. I and 2, steam injection pipe string
apparatus 10 may
be disposed in injection wellbore 12 such that the steam is not directed to
the portion of the
earth's crust between injection wellbore 12 and production wellbore 12a.
Rather, steam
injection pipe string apparatus 10 is disposed in injection wellbore 12 such
that the injected
steam is directed toward the top of injection wellbore 12, as illustrated in
FIG. 2. Directing the
injected steam in the manner illustrated in FIG. 2 assists in preventing
erosion of that portion of
the earth's crust between the two wellbores.
[0029] With reference now to FIG. 6, a system comprising a source of steam 20
and a
steam injection pipe string apparatus 45 is illustrated. Steam injection pipe
apparatus 45 is
disposed in steam injection wellbore 46 which is closely spaced in the
vertical direction from
production wellbore 46a. Steam injection pipe apparatus 45 comprises a
plurality of subs 32-37
where each sub has a different size orifice from the other subs in apparatus
45. For example, sub
32 comprises orifices 38 which are the smallest orifices in steam injection
pipe string 45. The
orifices 39-43 in subs 33-37, respectively, increase in size and according to
the orifice sizing
criteria discussed above. The subs 32-37 may, for example, be coupled together
using threaded
connections (not shown).
6
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
[0030] With reference to FIG. 3, steam injection pipe apparatus 10 of FIG. 1
may be
implemented using sand-screen apparatus comprising a plurality of sections 26,
where each
section 26 contains a plurality of orifices 26(i), and where the orifices are
sized as discussed
above. In the section of sand-screen apparatus illustrated in FIG. 2, orifice
26(i) comprises a
nozzle which is arranged to direct the flow of steam out of the sand screen
apparatus in a
direction parallel to the wellbore. In the arrangement of FIG. 2, the flow of
steam dissipates
somewhat upon exiting the steam injection pipe string at opening 30 so as not
to erode the sides
of wellbore 31. Once type of sand screen apparatus which is believed to be
especially
appropriate for use in a steam injection pipe string is the inflow flow
control device described in
U.S. Patent Application Publication No. US 2006/0048942, which is incorporated
herein by
reference.
[0031] Referring to FIGS. 4 and 5, alternative configurations of inflow
control devices are
illustrated. In FIG. 4, inflow control device 61, which includes housing 61a,
is formed on tubing
60, which is resident in steam injection pipe string apparatus according to
the present invention.
Steam may be directed through opening 62 in tubular member 60 and then through
orifice 63
and into the injection wellbore. Orifice 63 may, for example, comprise a
nozzle.
[0032] In FIG. 5, the inflow control device 71 is formed on tubing 70 and
comprises
housing 71 a. Orifice 73, which may also comprise a nozzle is installed in an
aperture formed in
tubing 70 as illustrated. Protection layer 74 is applied to the bottom of
housing 71 a to prevent
the steam from directly contacting the housing 71 a of inflow control device
71. Protective layer
74 may, for example, comprise a ceramic or a tungsten carbide coating which
covers all or part
of the portion of the housing 71a of inflow control device 71, which would be
exposed to the
steam.
[0033] The inflow control devices illustrated in FIGS. 4 and 5 employ seals
which are
represented schematically by reference designators 64 and 74. With reference
now to FIG. 7,
there is illustrated a metal-to-metal embodiment of such seals. In FIG. 7,
seal 80 comprises ring
81 which is forced against ring 82 containing nozzle 86. This results in a
shrink fit seal 84
toward the base pipe 83. Openings 85 are formed in base pipe 83 to permit the
flow of steam
from the base pipe through nozzle 86 and into a steam injection wellbore.
7
CA 02622939 2008-02-27
PATENT
Attorney Docket No.: 68.0716
[0034] Referring now to FIG. 8, there is illustrated inflow control device 90
which is
utilized with sand screen apparatus 91. An opening 92 is formed in base pipe
93 to permit the
flow of steam through nozzle 94 and into the steam injection wellbore via sand
screen apparatus
91. The inflow control device 90 in FIG. 8 utilizes a plurality of C-type
metal seals 95.
[0035] In accordance with the present invention, steam injection pipe string
apparatus
according to the present invention may further comprise Distributed
Temperature Sensing (DST)
apparatus, such as is available from the assignee of the present application.
Such DST apparatus
advantageously utilizes fiber optic cables containing sensors to sense the
temperature changes
along the length of the injection apparatus and may, for example, provide
information from
which a temperature profile for the well may be prepared.
[0036] The foregoing description has focused on utilization of inflow control
devices in
the steam injection wellbore in SAGD operations. Those skilled in the art will
appreciate that
inflow control devices may also be utilized in the production wellbore.
8
