U.S. patent application number 11/441929 was filed with the patent office on 2007-03-01 for method for underground recovery of hydrocarbons.
This patent application is currently assigned to Oil Sands Underground Mining, Inc.. Invention is credited to Dana Brock, Michael Helmut Kobler, John David Watson.
Application Number | 20070044957 11/441929 |
Document ID | / |
Family ID | 37452986 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070044957 |
Kind Code |
A1 |
Watson; John David ; et
al. |
March 1, 2007 |
Method for underground recovery of hydrocarbons
Abstract
The present invention discloses a method for installing,
operating and servicing wells in a hydrocarbon deposit from a lined
shaft and/or tunnel system that is installed above, into or under a
hydrocarbon deposit. The entire process of installing the shafts
and tunnels as well as drilling and operating the wells is carried
out while maintaining isolation between the work space and the
ground formation. In one aspect of the invention, well-head devices
may be precast into the tunnel or shaft lining to facilitate well
installation and operation in the presence of formation pressure
and/or potential fluid in-flows. In another aspect of the
invention, the tunnel itself can be used as a large diameter well
for collecting hydrocarbons and, if required, for injecting steam
or diluents into a formation to mobilize heavy hydrocarbons such as
heavy crude and bitumen.
Inventors: |
Watson; John David;
(Evergreen, CO) ; Kobler; Michael Helmut;
(Sebastopol, CA) ; Brock; Dana; (Sebastopol,
CA) |
Correspondence
Address: |
SHERIDAN ROSS PC
1560 BROADWAY
SUITE 1200
DENVER
CO
80202
US
|
Assignee: |
Oil Sands Underground Mining,
Inc.
Calgary
CA
|
Family ID: |
37452986 |
Appl. No.: |
11/441929 |
Filed: |
May 25, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60685251 |
May 27, 2005 |
|
|
|
60753694 |
Dec 23, 2005 |
|
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Current U.S.
Class: |
166/245 ;
166/242.1; 166/50; 166/52 |
Current CPC
Class: |
E21B 33/03 20130101;
E21B 43/305 20130101; E21B 43/00 20130101; E21C 41/24 20130101;
E21D 9/08 20130101; E21D 11/083 20130101 |
Class at
Publication: |
166/245 ;
166/050; 166/052; 166/242.1 |
International
Class: |
E21B 43/12 20060101
E21B043/12 |
Claims
1. A method for extracting hydrocarbons from a
hydrocarbon-containing deposit, comprising: (a) forming an
underground excavation having a section extending through a
hydrocarbon deposit; (b) forming a substantially fluid impermeable
liner extending along the section of the excavation; and (c) from
the section of the excavation, forming, through the liner, a
plurality of wells extending into the hydrocarbon deposit, wherein
the wells at least one of inject a fluid into the hydrocarbon
deposit and extract a hydrocarbon from the deposit.
2. The method of claim 1, wherein the liner, as formed, comprises
at least one tool to facilitate at least one of well drilling, well
completion, and hydrocarbon extraction from the deposit.
3. The method of claim 1, wherein the at least some of the wells
inject a fluid into the hydrocarbon deposit and at least some of
the wells extract a hydrocarbon from the deposit, wherein the fluid
mobilizes the hydrocarbon for extraction, wherein the fluid is at
least one of steam, a diluent, water, carbon dioxide, nitrogen, and
air and wherein the liner extends substantially around the
periphery of the excavation.
4. The method of claim 2, wherein the tool comprises at least one
of an anchor point for engaging a device used in the at least one
of well drilling, well completion, and hydrocarbon extraction, and
a sensor for measuring and/or monitoring fluid flow and/or
formation pressure.
5. The method of claim 2, wherein, after completion, the interior
of the excavation is at least substantially sealed from fluids in
the well.
6. The method of claim 1, wherein, during formation of the
underground excavation, the interior of the excavation behind an
excavation device forming the excavation is at least substantially
sealed from the hydrocarbon deposit, wherein excavating and muck
removal by a cutter head of the excavation device is at a higher
pressure than a pressure in the excavation behind the excavation
device, and wherein the excavation device is a slurry or earth
pressure balance tunnel boring machine.
7. The method of claim 1, wherein the liner is at least partially
surrounded by a backfill material positioned between the wall of
the excavation and the liner.
8. Hydrocarbon produced from the wells of claim 1.
9. A method for extracting a hydrocarbon, comprising: (a) providing
an underground excavation; (b) forming a liner in the underground
excavation; and (c) forming a plurality of wells passing through
the liner and into a hydrocarbon-containing deposit, wherein the
liner, when formed, comprises at least one tool to facilitate at
least one of well drilling, well completion, and hydrocarbon
production from a well.
10. The method of claim 9, wherein the tool is at least one of: an
anchor point for engaging a wellhead control assembly used in the
at least one of well drilling, well completion, and hydrocarbon
extraction; and a sensor for measuring and/or monitoring fluid flow
and/or formation pressure.
11. The method of claim 9, wherein the tool is a ring assembly
embedded in a liner section, the ring assembly engaging a mounting
device for a wellhead control assembly and wherein the liner
section comprises one or more ring assemblies positioned at
selected intervals around the liner section.
12. The method of claim 11, wherein a gasket is positioned at the
interface between the mounting device and the ring assembly to form
a seal therebetween.
13. The method of claim 11, wherein ring assembly comprises first
and second ring halves, each ring half comprising threaded holes
spaced at substantially equal angles around the ring half to allow
the wellhead control assembly to be positioned at any of a number
of angles around the tunnel liner.
14. The method of claim 9, wherein the tool is at least one of an
injection port for injecting fluids and a drain port for collecting
fluids located between the liner and the adjacent wall of the
excavation.
15. The method of claim 9, wherein the tool is a flange operable to
engage well-head equipment in communication with a well in spatial
proximity to the flange.
16. Hydrocarbon produced from the wells of claim 9.
17. A liner for an excavation, comprising: (a) a liner section; and
(b) a tool embedded in the liner section at selected intervals
along a length of the section, wherein the tool is at least one of
an attachment point, an injection port for a fluid to be injected
into a hydrocarbon-containing formation, and a collection port for
collection of hydrocarbon-containing fluids from the formation.
18. The liner of claim 17, wherein the tool is an attachment point,
wherein a wellhead control assembly is attached to the tool.
19. The liner of claim 18, wherein the tool comprises a ring
positioned substantially around the periphery of the liner section
and a plurality of connectors positioned at selected intervals
along the length of the ring to engage the wellhead control
assembly.
20. The liner of claim 19, wherein the ring comprises first and
second interconnected ring halves, each half being positioned
adjacent to one another and containing a subset of the connectors,
and wherein the connectors are positioned at equal angles around
the ring, thereby allowing the device to be positioned at any of a
number of discrete angles along a length of the ring.
21. The liner of claim 18, wherein the tool comprises a gasket to
form a seal between the wellhead control assembly and a surface of
the liner.
22. The liner of claim 17, wherein the liner section further
comprises a plurality of drain ports for collecting fluids located
between the liner and the adjacent wall of the excavation, the
plurality of drain ports being in communication with a fluid
collection system.
23. The liner of claim 17, wherein the tool is the injection
port.
24. The liner of claim 17, wherein the tool is the collection
port.
25. The liner of claim 23, wherein injection ports are positioned
in an upper portion of a first liner section.
26. The liner of claim 25, wherein a the first liner section
comprises collection ports positioned in a lower portion of the
liner section.
27. The liner of claim 25 wherein the injection ports are elongated
and comprise a screen to inhibit particulate material from passing
through the ports.
28. The liner of claim 26, wherein the collection ports are
elongated and comprise a screen to inhibit particulate material
from passing through the ports.
29. A method for recovering hydrocarbons, comprising: (a) in an
underground excavation providing a lined excavation, the lined
excavation extending through a hydrocarbon-containing formation,
and a liner in the lined excavation comprising a plurality of fluid
injection ports; (b) injecting a fluid, through the fluid injection
ports, into the hydrocarbon-containing formation; and (c)
collecting hydrocarbons mobilized by the injected fluid.
30. The method of claim 29, wherein the lined tunnel has an
impervious material positioned between at least first and second
fluid permeable annular spaces positioned between the liner and a
surface of the excavation to inhibit the movement of the injected
fluid from the first annular space to the second annular space,
wherein the fluid is one of steam and a diluent, and further
comprising: (d) transporting the fluid from the surface through the
underground excavation to a set of injectors in communication with
the injection ports and with the first and second annular spaces,
wherein the temperature and/or pressure of the steam is returned to
a selected level during transportation.
31. The method of claim 29, wherein the fluid is injected into at
least one annular space defined by the liner and a wall of the
excavation and in the absence of a well.
32. The method of claim 29, wherein the liner comprises a plurality
of collection ports and wherein the hydrocarbons pass through the
collection ports in the absence of a well casing.
33. Hydrocarbon produced from the wells of claim 29.
34. A method for recovering hydrocarbons, comprising: (a) in an
underground excavation providing a lined excavation, the lined
excavation extending through a hydrocarbon-containing formation,
and a liner in the lined excavation comprising a plurality of
collection and injection ports; (b) injecting a fluid into the
hydrocarbon-containing formation; and (c) collecting, at the
collection ports, hydrocarbons mobilized by the injected fluid.
35. The method of claim 34, wherein the liner comprises a plurality
of injection ports, wherein the lined tunnel has an impervious
material positioned between at least first and second fluid
permeable annular spaces positioned between the liner and a surface
of the excavation to inhibit the movement of the injected fluid
from the first annular space to the second annular space, wherein
the fluid is steam, and further comprising: (d) transporting the
fluid from the surface through the underground excavation to a set
of injectors in communication with the injection ports and with the
first and second annular spaces, wherein the temperature and/or
pressure of the steam is returned to a selected level during
transportation.
36. The method of claim 34, wherein the fluid is injected into at
least one annular space defined by the liner and a wall of the
excavation and in the absence of a well.
37. The method of claim 34, wherein the hydrocarbons pass through
the collection ports in the absence of a well casing.
38. Hydrocarbon produced from the wells of claim 34.
39. A method for recovering hydrocarbons, comprising: (a) forming
an excavation in a hydrocarbon-containing formation; and (b)
maintaining an interior of the excavation behind an excavation
device substantially sealed from selected fluids in the
formation.
40. The method of claim 39, wherein the excavation device is a
tunnel boring machine, wherein a first seal is maintained between a
cutter head and a muck removal system using a ground modifying
material and maintaining the modified excavated material at a
pressure that is approximately the pressure of the formation.
41. The method of claim 40, wherein a periphery of the tunnel
boring machine shield forms a second seal with a liner section.
42. The method of claim 41, wherein a third seal is formed in the
excavation behind the tunnel boring machine using a liner.
43. The method of claim 42, wherein a fourth seal is formed between
all the joints of the liner.
44. The method of claim 42, wherein the liner comprises a plurality
of interconnected sections and wherein a sealing gasket is
positioned between adjacent interconnection sections.
45. The method of claim 42, wherein the liner comprises a plurality
of interconnected sections and wherein step (b) comprises: (i)
positioning a sealing material between adjacent liner sections;
(ii) interconnecting the adjacent liner sections; and (iii) the
tunnel boring machine apply a force to the interconnected adjacent
liner sections, thereby causing the sealing material to form a seal
along a joint between the adjacent liner sections.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefits, under 35
U.S.C..sctn. 119(e), of U.S. Provisional Application Ser. No.
60/685,251 filed May 27, 2005, entitled "Method of Collecting
Hydrocarbons from Tunnels" to Kobler and Watson; and U.S.
Provisional Application Ser. No. 60/753,694, filed Dec. 23, 2005,
entitled "Method of Recovering Bitumen" to Brock, Kobler and
Watson; both of which are incorporated herein by these
references.
FIELD
[0002] The present invention relates generally to a lined shaft and
tunnel-based method and system for installing, operating and
servicing wells for recovery of hydrocarbons, wherein the
underground space is always isolated from the formation.
BACKGROUND
[0003] Oil is a nonrenewable natural resource having great
importance to the industrialized world. The increased demand for
and decreasing supplies of conventional oil has led to the
development of alternative sources of crude oil such as oil sands
containing bitumen or heavy oil and to a search for new techniques
for more complete recovery of oil stranded in conventional oil
deposits.
[0004] The Athabasca oil sands are a prime example of a huge
alternative source of crude and is currently thought to have proven
reserves of over 200 billion barrels recoverable by both surface
mining and in-situ thermal recovery methods. There are also equally
large untapped reserves of stranded light and heavy oil deposits
from known reservoirs throughout North America which cannot be
recovered by traditional surface drilling methods. These two
sources of oil, bitumen and stranded oil, are more than enough to
eliminate dependence on other sources of oil and, in addition,
require no substantial exploration.
Recovering Bitumen
[0005] The current principal method of bitumen recovery, for
example, in the Alberta oil sands is by conventional surface mining
of shallower deposits using large power shovels and trucks to
excavate the oil sand which is then delivered to a primary bitumen
extraction facility.
[0006] Some of these bitumen deposits may be exploited by an
appropriate underground mining technology. Although intensely
studied in the 1970s and early 1980s, no economically viable
underground mining concept has ever been developed for the oil
sands. In 2001, an underground mining method was proposed based on
the use of large, soft-ground tunneling machines designed to
backfill most of the tailings behind the advancing machine. A
description of this concept is included in U.S. Pat. No. 6,554,368
"Method and System for Mining Hydrocarbon-Containing
Materials".
[0007] When the oil sands deposits are too deep for economical
surface mining, in-situ recovery methods are being used wherein the
viscosity of the bitumen in the oil sand must first be reduced so
that it can flow. These bitumen mobilization techniques include
steam injection, solvent flooding, gas injection, and the like. The
principal method currently being implemented on a large scale is
Steam Assisted Gravity Drain ("SAGD"). Typically, SAGD wells or
well pairs are drilled from the earth's surface down to the bottom
of the oil sand deposit and then horizontally along the bottom of
the deposit and then used to inject steam and collect mobilized
bitumen.
[0008] The SAGD process was first reduced to practice at the
Underground Test Facility ("UTF") in Alberta, Canada. This facility
involved the construction of an access shaft through the overburden
and oil sands into the underlying limestone. From this shaft,
self-supported underground workings were developed in the
underlying limestone from which horizontal well pairs were drilled
up and then horizontally into the oil sands formation. The UTF is
an example of "mining for access", a technique that is also
described below for recovery of stranded oil. With the advent of
horizontal drilling techniques, it became possible to install SAGD
well pairs by drilling from the surface and this is now the
commonly used method of implementing the SAGD process.
Mining for Oil
[0009] Until recently, oil economics have precluded efforts to
recover what is known as stranded oil. Most heavy and light oil
reserves are recovered by drilling wells from the surface.
Typically, these operations recover 5% to 30% of the oil-in-place.
Additional oil (up to, in some cases, 50% of the original oil in
place) can be recovered from the surface by secondary and tertiary
methods (also known as Enhanced Oil Recovery or EOR methods) such
as, for example, water flooding, gas flooding and hydraulic
fracturing. Nevertheless, a substantial fraction of the oil remains
in the ground and is not recovered and is deemed stranded. Much of
this stranded oil is mobile and can be recovered by a combination
of mining and/or drilling methods with known reservoir engineering
practice. It is estimated that billions of barrels of recoverable
light and heavy oil remains in known deposits in the US and Canada.
Recovery awaits the right combination of economics and
technology.
[0010] The literature describes three basic oil mining
approaches:
[0011] (1) Surface extractive mining. Surface extractive mining is
currently being implemented on a large scale in Alberta's Athabasca
oil sands as discussed above. This method is generally applicable
to oil deposits that are within a few tens of meters of the
surface.
[0012] (2) Underground extractive mining. Several methods of
underground mining have been investigated especially in the past
when oil prices have risen rapidly. For example, a number of
studies were conducted in the 1980s for direct extraction of
bitumen in oil sands and for direct mining of stranded light and
heavy oil deposits in the US. These efforts were discontinued when
oil prices subsequently fell. The economics of these methods were
not competitive with conventional exploration and surface drilling
at lower oil prices, and they were thought to be potential
difficulties with safety and environmental issues using the
underground technology available at the time.
[0013] (3) Mining for access. The 1980s studies referred to above
also described methods of "mining for access" to oil deposits. For
example, a method was described wherein shafts were sunk and
tunnels driven from the shafts to the rock beneath an oil deposit.
Rooms were then excavated on either side of the tunnels in the rock
underlying the reservoir. These rooms were used for drilling rigs
that could drill up into the oil deposit. The wells would collect
oil driven by a combination of gravity, gas or water drive. The
mining for access approach was considered the most promising
technique for economially recovering oil using underground mining
methods.
[0014] The principal mining method of interest for stranded oil
continues to be mining for access. Some studies indicate that up to
80 percent of the oil remaining after primary and EOR techniques
may be recovered using mining for access methods on deposits that
are as deep as 1,500 meters. Mining for access can also be used to
provide an underground platform for drilling rigs that can drill
downward into a hydrocarbon formation below. Such a method could be
applied, for example, to an offshore deposit. These mining methods,
while well-known and feasible, do not adequately protect the
underground workers from the gas, oil and water hazards associated
with hydrocarbon reservoirs (both seepage of fluids and vapors as
well as substantial inflows of water and gas, especially during
installation of tunnels and drifts). An exemplary form of mining
for access available during this time period is described in U.S.
Pat. No. 4,458,945 entitled "Oil Recovery Mining Method" and U.S.
Pat. No. 4,595,239 entitled "Oil Recovery Mining Apparatus" which
describe how drainage wells may be drilled into the overlying roof
of a tunnel cut into a competent rock zone below oil deposits
containing unrecovered or stranded oil.
Heavy Civil Underground Technology
[0015] In recent years, there has been a substantial progress in
heavy civil underground construction methods, especially in the
area of soft-ground shaft sinking and tunneling.
[0016] Soft-ground shafts are commonly concrete lined shafts and
are sunk by a variety of methods often in the presence of
pressurized aquifers. These methods include drilling and boring
techniques sometimes where the shaft is filled with water or
drilling mud to counteract local ground pressures. There are also
shaft sinking techniques for sinking shafts under water using
robotic construction equipment.
[0017] Soft-ground tunnels can be driven through water saturated
sands and clays or mixed ground environments using large slurry,
Earth Pressure Balance (" EPB") or mixed shield systems. This new
generation of soft-ground tunneling machines can now overcome
water-saturated or gassy ground conditions and install tunnel
liners to provide ground support and isolation from the ground
formation for a variety of underground transportation and
infrastructure applications
[0018] Developments in soft-ground tunneling led to the practice of
micro-tunneling which is a process that uses a remotely controlled
micro-tunnel boring machine combined with a pipe-jacking technique
to install underground pipelines and small tunnels. Micro-tunneling
has been used to install pipe from twelve inches to twelve feet in
diameter and therefore, the definition for micro-tunneling does not
necessarily include size. The definition has evolved to describe a
tunneling process where the workforce does not routinely work in
the tunnel.
[0019] Drilling technologies for soft and hard rock are also well
known. Conventional rotary drilling and water jet drilling, for
example, have been utilized in oil and gas well drilling,
geothermal drilling, waste and groundwater control as well as for
hard rock drilling.
[0020] To date, underground access to hydrocarbon reservoirs has
relied principally on mining methods that have not yet provided a
fully safe working environment for accessing and producing oil and
gas from underground.
[0021] There therefore remains a need for safe and economical
process of installing a network of hydrocarbon recovery wells from
an underground work space while maintaining isolation between the
work space and the ground formation. Such an invention would have
the potential to develop inaccessible deposits such as those under
rivers, increase hydrocarbon recovery factors, lower costs, result
in less surface disturbance while providing a safe working
environment.
SUMMARY
[0022] These and other needs are addressed by the present invention
which is directed generally to removal of hydrocarbons,
particularly flowable or fluid hydrocarbons, from
hydrocarbon-containing formations using underground
excavations.
[0023] In a first embodiment of the present invention, a method for
extracting hydrocarbons from a hydrocarbon-containing deposit
includes the steps of: (a) forming an underground excavation having
a section extending through a hydrocarbon deposit; (b) forming a
substantially fluid impermeable liner extending along the section
of the excavation; and (c) from the section of the excavation,
forming, through the liner, a plurality of wells extending into the
hydrocarbon deposit, wherein the wells inject a fluid into the
hydrocarbon deposit and/or extract a hydrocarbon from the
deposit.
[0024] In a second embodiment, a method for recovering hydrocarbons
includes the steps of: (a) forming an excavation in a
hydrocarbon-containing formation; and (b) maintaining an interior
of the excavation behind an excavation device substantially sealed
from selected fluids in the formation. Typically, the excavation
device is a tunnel boring machine.
[0025] A number of different seals are preferably maintained. A
first seal is maintained between an excavation face and an interior
of an excavating machine by modifying the excavated material so as
to maintain the excavated material at a pressure that is
approximately the pressure of the formation. A second seal at the
interface between the tunnel boring machine and the excavation is
formed by a moveable shield that is part of the tunnel boring
machine. A third seal is formed between a rear edge of the shield
and a surface of the liner using a brush seal assembly. A fourth
seal is formed in the excavation behind the tunnel boring machine
using a liner. A fifth seal is formed at the mating surfaces of
tunnel liner segments and sections.
[0026] The maintenance of a sealed work space can provide a safe
working environment for accessing, mobilizing and producing
hydrocarbons from underground. The seals can prevent unacceptably
high amounts of unwanted and dangerous gases from collecting in the
excavation. It can also allow the excavation to be located in
hydrologically active formations, such as formations below a body
of water or forming part of the water table. Prior art underground
mining-for-oil methods require a competent rock formation
underlying the hydrocarbon deposit. Thus, the present invention can
enable development of hydrocarbon deposits from an underground
workspace, such as those deposits overlying soft and/or fractured
ground while always providing a safe working environment. The
underground workspace of the present invention can therefore be
installed below, inside or above the hydrocarbon reservoir.
[0027] In yet another embodiment, a method for extracting a
hydrocarbon is provided that includes the steps of (a) forming a
liner in an underground excavation; and (b) forming a plurality of
wells passing through the liner and into a hydrocarbon-containing
deposit. The liner, when formed, comprises a tool to facilitate at
least one of well drilling, well completion, and hydrocarbon
production from a well. The tool, for example, can be an anchor
point for engaging a wellhead control assembly used in the at least
one of well drilling, well completion, and hydrocarbon extraction,
a sensor for measuring and/or monitoring fluid flow and/or
formation pressure.
[0028] In yet another embodiment, a method for recovering
hydrocarbons includes the steps of: (a) in an underground
excavation, providing a lined excavation, the lined excavation
extending through a hydrocarbon-containing formation, and a liner
in the lined excavation including a plurality of fluid injection
ports; (b) injecting a fluid, through the fluid injection ports,
into the hydrocarbon-containing formation; and (c) collecting
hydrocarbons mobilized by the injected fluid.
[0029] In one configuration, the lined tunnel has an impervious
material positioned between at least first and second fluid
permeable annular spaces positioned between the liner and a surface
of the excavation, to inhibit the movement of the injected fluid
from the first annular space to the second annular space. This
configuration uses the liner as the fluid injection and collection
mechanism in addition to or in lieu of wells drilled into the
formation from the excavation. It therefore can provide substantial
production increases relative to a tunnel configuration used only
to install wells.
[0030] In another configuration, the fluid is steam or a diluent,
and the method further includes the steps of transporting the fluid
from the surface through the underground excavation to a set of
injectors in communication with the injection ports and with the
first and second annular spaces. If the fluid is steam, the
temperature and/or pressure of the steam may be returned to a
selected level during transportation.
[0031] The various embodiments can provide advantages relative to
the prior art. For example, the use of underground excavations to
recover hydrocarbons from many types of hydrocarbon-containing
deposits, such as heavy oil and stranded oil deposits, can provide
higher recovery rates and higher overall recovery factors at
substantial cost savings relative to conventional surface-based
techniques. Because hydrocarbon deposits and surrounding formations
are typically soft and/or fractured rock, the invention can use
tunnel boring machines to form the excavation. Tunnel boring
machines are mature and highly robust continuous excavation
technique. The location of the excavation in the
hydrocarbon-containing formation itself can permit the liner to be
used as the fluid injection and/or collection medium without the
need to drill a large number of wells. Drilling a large number of
wells from underground can be cost effective since each well does
not have to traverse long distances of barren overburden such as is
required by wells drilled from the surface. Finally, the use of
liners can inhibit long-term surface subsidence above the
excavation, thereby limiting the environmental impact of
hydrocarbon recovery and enabling the recovery of hydrocarbons from
deposits under, for example, developed farm lands, small towns,
lakes, rivers and protected wildlife habitats.
[0032] The following definitions are used herein:
[0033] A hydrocarbon is an organic compound that includes
primarily, if not exclusively, of the elements hydrogen and carbon.
Hydrocarbons generally fall into two classes, namely aliphatic, or
straight chain, hydrocarbons, cyclic, or closed ring, hydrocarbons,
and cyclic terpenes. Examples of hydrocarbon-containing materials
include any form of natural gas, oil, coal, and bitumen that can be
used as a fuel or upgraded into a fuel. Hydrocarbons are
principally derived from petroleum, coal, tar, and plant
sources.
[0034] Hydrocarbon production or extraction refers to any activity
associated with extracting hydrocarbons from a well or other
opening. Hydrocarbon production normally refers to any activity
conducted in or on the well after the well is completed.
Accordingly, hydrocarbon production or extraction includes not only
primary hydrocarbon extraction but also secondary and tertiary
production techniques, such as injection of gas or liquid for
increasing drive pressure, mobilizing the hydrocarbon or treating
by, for example chemicals or hydraulic fracturing the well bore to
promote increased flow, well servicing, well logging, and other
well and wellbore treatments.
[0035] A liner as defined for the present invention is any
artificial layer, membrane, or other type of structure installed
inside or applied to the inside of an excavation to provide at
least one of ground support, isolation from ground fluids (any
liquid or gas in the ground), and thermal protection. As used in
the present invention, a liner is typically installed to line a
shaft or a tunnel, either having a circular or elliptical
cross-section. Liners are commonly formed by pre-cast concrete
segments and less commonly by pouring or extruding concrete into a
form in which the concrete can solidify and attain the desired
mechanical strength.
[0036] A liner tool is generally any feature in a tunnel or shaft
liner that self-performs or facilitates the performance of work.
Examples of such tools include access ports, injection ports,
collection ports, attachment points (such as attachment flanges and
attachment rings), and the like.
[0037] A mobilized hydrocarbon is a hydrocarbon that has been made
flowable by some means. For example, some heavy oils and bitumen
may be mobilized by heating them or mixing them with a diluent to
reduce their viscosities and allow them to flow under the
prevailing drive pressure. Most liquid hydrocarbons may be
mobilized by increasing the drive pressure on them, for example by
water or gas floods, so that they can overcome interfacial and/or
surface tensions and begin to flow.
[0038] A seal is a device or substance used in a joint between two
apparatuses where the device or substance makes the joint
substantially impervious to or otherwise substantially inhibits,
over a selected time period, the passage through the joint of a
target material, e.g., a solid, liquid and/or gas. As used herein,
a seal may reduce the in-flow of a liquid or gas over a selected
period of time to an amount that can be readily controlled or is
otherwise deemed acceptable. For example, a seal between a TBM
shield and a tunnel liner that is being installed, may be sealed by
brushes that will not allow large water in-flows but may allow
water seepage which can be controlled by pumps. As another example,
a seal between sections of a tunnel may be sealed so as to (1) not
allow large water in-flows but may allow water seepage which can be
controlled by pumps and (2) not allow large gas in-flows but may
allow small gas leakages which can be controlled by a ventilation
system.
[0039] A shaft is a long approximately vertical underground opening
commonly having a circular cross-section that is large enough for
personnel and/or large equipment. A shaft typically connects one
underground level with another underground level or the ground
surface.
[0040] A tunnel is a long approximately horizontal underground
opening having a circular, elliptical or horseshoe-shaped
cross-section that is large enough for personnel and/or vehicles. A
tunnel typically connects one underground location with
another.
[0041] An underground workspace as used in the present invention is
any excavated opening that is effectively sealed from the formation
pressure and/or fluids and has a connection to at least one entry
point to the ground surface.
[0042] A well is a long underground opening commonly having a
circular cross-section that is typically not large enough for
personnel and/or vehicles and is commonly used to collect and
transport liquids, gases or slurries from a ground formation to an
accessible location and to inject liquids, gases or slurries into a
ground formation from an accessible location.
[0043] Well drilling is the activity of collaring and drilling a
well to a desired length or depth.
[0044] Well completion refers to any activity or operation that is
used to place the drilled well in condition for production. Well
completion, for example, includes the activities of open-hole well
logging, casing, cementing the casing, cased hole logging,
perforating the casing, measuring shut-in pressures and production
rates, gas or hydraulic fracturing and other well and well bore
treatments and any other commonly applied techniques to prepare a
well for production.
[0045] Wellhead control assembly as used in the present invention
joins the manned sections of the underground workspace with and
isolates the manned sections of the workspace from the well
installed in the formation. The wellhead control assembly can
perform functions including: allowing well drilling, and well
completion operations to be carried out under formation pressure;
controlling the flow of fluids into or out of the well, including
shutting off the flow; effecting a rapid shutdown of fluid flows
commonly known as blow out prevention; and controlling hydrocarbon
production operations.
[0046] It is to be understood that a reference to oil herein is
intended to include low API hydrocarbons such as bitumen (API less
than .about.10.degree.) and heavy crude oils (API from
.about.10.degree. to .about.20.degree.) as well as higher API
hydrocarbons such as medium crude oils (API from .about.20.degree.
to .about.35.degree.) and light crude oils (API higher than
.about.35.degree.) .
[0047] Primary production or recovery is the first stage of
hydrocarbon production, in which natural reservoir energy, such as
gasdrive, waterdrive or gravity drainage, displaces hydrocarbons
from the reservoir, into the wellbore and up to surface. Production
using an artificial lift system, such as a rod pump, an electrical
submersible pump or a gas-lift installation is considered primary
recovery. Secondary production or recovery methods frequently
involve an artificial-lift system and/or reservoir injection for
pressure maintenance. The purpose of secondary recovery is to
maintain reservoir pressure and to displace hydrocarbons toward the
wellbore. Tertiary production or recovery is the third stage of
hydrocarbon production during which sophisticated techniques that
alter the original properties of the oil are used. Enhanced oil
recovery can begin after a secondary recovery process or at any
time during the productive life of an oil reservoir. Its purpose is
not only to restore formation pressure, but also to improve oil
displacement or fluid flow in the reservoir. The three major types
of enhanced oil recovery operations are chemical flooding, miscible
displacement and thermal recovery.
[0048] As used herein, "at least one", "one or more", and "and/or"
are open-ended expressions that are both conjunctive and
disjunctive in operation. For example, each of the expressions "at
least one of A, B and C", "at least one of A, B, or C", "one or
more of A, B, and C", "one or more of A, B, or C" and "A, B, and/or
C" means A alone, B alone, C alone, A and B together, A and C
together, B and C together, or A, B and C together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a schematic side view of the excavating process
for installing a lined tunnel in a hydrocarbon formation under
pressure.
[0050] FIG. 2 is a schematic end view of tunnel liner.
[0051] FIG. 3 is an isometric view of a shaft, tunnel and well
complex installed in a hydrocarbon formation.
[0052] FIG. 4 is a plan view of a typical configuration of wells
drilled from tunnels in a hydrocarbon formation.
[0053] FIG. 5 is an end view of multiple tunnels and wells
installed near the bottom of a hydrocarbon formation.
[0054] FIG. 6 is an end view of multiple tunnels and wells
installed from below a hydrocarbon formation.
[0055] FIG. 7 is a sectioned side view through a tunnel liner
segment illustrating a ring assembly embedded in a liner
segment.
[0056] FIG. 8 is an isometric view of a ring assembly such as shown
in FIG. 8.
[0057] FIG. 9 shows an isometric view of a tunnel liner section
with a type of embedded assembly in each liner segment.
[0058] FIG. 10 shows an isometric view of a tunnel liner section
with another type of embedded assembly in each segment.
[0059] FIG. 11 shows a schematic side view of wellhead control
equipment installed in a tunnel or shaft liner.
[0060] FIG. 12 shows a schematic end view of drill rig in travel
position mounted on a tunnel rail car.
[0061] FIG. 13 shows a schematic plan view drill rig in drilling
position to drill a horizontal well through the side of the tunnel
liner.
[0062] FIG. 14 shows a schematic end view of a method for recovery
of hydrocarbons from a backfilled tunnel liner by SAGD.
[0063] FIG. 15 is an isometric view of tunnel liner sections
showing two types of SAGD injector and collector ports.
[0064] FIG. 16 is an end view of a tunnel showing a SAGD steam
chamber.
[0065] FIG. 17 is a side view schematic of a soft-ground TBM
showing its principal sealing points.
[0066] FIG. 18 illustrates features of tunnel liner sealing.
DETAILED DESCRIPTION
[0067] As discussed in the BACKGROUND section, prior art "mining
for access" methods are based on excavating tunnels, cross-connects
and drilling caverns in competent rock above or below the target
hydrocarbon formation. The competent rock provides ground support
for the operation and, being relatively impermeable, to some extent
protects the work space from fluid and gas seepages from the nearby
hydrocarbon deposit. This approach cannot be applied when formation
pressures are high; when the hydrocarbon reservoir is artificially
pressurized for enhanced recovery operations ("EOR"); when the
hydrocarbon formation is heated, for example, by injecting steam;
or when the ground adjacent to the hydrocarbon reservoir is
fractured, soft, unstable, gassy or saturated with ground
fluids.
[0068] The present invention discloses a method for installing,
operating and servicing wells in a hydrocarbon deposit from a lined
shaft and/or tunnel system that is installed above, into or under a
hydrocarbon deposit. The entire process of installing the shafts
and tunnels as well as drilling and operating the wells is carried
out while maintaining isolation between the work space and the
ground formation. In one aspect of the invention, well-head devices
may be precast into the tunnel or shaft liners to facilitate well
installation and operation in the presence of formation pressure
and/or potential fluid in-flows. In another aspect of the
invention, the tunnel itself can be used as a large diameter well
for collecting hydrocarbons and, if required, for injecting steam
or diluents into a formation to mobilize heavy hydrocarbons such as
heavy crude and bitumen.
[0069] In certain embodiments, the present invention discloses a
method for installing an underground workspace suitable for
drilling wells into a hydrocarbon formation wherein the underground
workspace is fully lined in order to provide ground support and
isolation from formation pressures, excessive temperatures, fluids
and gases. The lining also provides anchor points for various
apparatuses or liner tools that allow drilling wells, installing
casing for injection of fluids into the formation, measuring and
monitoring the formation, and collection of fluids from the
formation, all while maintaining a seal between the interior
working space and the formation. The process of maintaining
isolation of the underground work space from the formation includes
the phases of (1) installation of underground workspace and wells
and (2) all production and maintenance operations from the
underground workspace. The underground work space is provided
principally by lined shafts and lined tunnels. The shafts and
tunnels themselves may also serve as large injection and collection
"wells" when they are installed in the hydrocarbon formation.
Because the underground workspace is installed and operated in full
isolation from the formation pressures and fluids, the workspace
can be installed above, inside or below the hydrocarbon formation
in soft or mixed ground.
[0070] In the descriptions below, it is understood that the
functions described for tunnel liners also apply to shaft
liners.
Development of Sealed Underground Workspace
[0071] FIG. 1 is an idealized schematic side view of one aspect of
the present invention. A hydrocarbon formation 102 is shown under
an overlying layer of rock and earth 101 which has a surface 103.
The hydrocarbon deposit 102 lays on top of a basement rock 104. A
soft-ground tunnel boring machine ("TBM") is shown near the bottom
of the hydrocarbon formation 102. In the example of FIG. 1, the TBM
is moving from right to left. The TBM is comprised of a rotating
cutter head 110 and a moveable shield 111. A tunnel liner 112 is
erected by sections 105 inside the shield 111 as the TBM advances.
The tunnel liner 112 may be formed by sections 105 which are joined
together at joints 106 inside the shield 111 during the tunneling
process. The sections 105 are preferably precast concrete segments
but may be fabricated from other structural materials such as, for
example, structural steel or composites of structural steel and
concrete. The sections are preferably formed from a high
temperature concrete mix and well-cured before installation. The
bottom of the finished tunnel is located as shown by separation 107
above the basement formation 104. When placed at the bottom of the
hydrocarbon formation 102, the bottom of the tunnel liner 112 would
typically be located within about 0 to 5 meters of the basement
formation 104 depending on geologic conditions such as for example
a zone of water or water saturated sand lying on the basement
formation 104. The liner 112 remains in place and provides ground
support as the cutting head 110 and shield 111 are moved forward.
Most soft-ground tunnel liners are installed by slurry or
earth-pressure balance ("EPB") tunnel boring machines ("TBMs").
These machines make it possible to excavate and remove material
("muck") in isolation from the workers and operators in the TBM and
tunnel as the tunnel is being installed. The material is excavated
in a forward chamber of the TBM where it may be formed into a
slurry or paste and removed to the surface. In this configuration,
the excavating and muck removal processes are isolated from the
tunnel interior and are often carried out at a different pressure
(usually higher) than that of the interior of the tunnel. The
pressure in the interior of the tunnel is often at or near
atmospheric pressure as it is connected to surface ambient pressure
by other tunnels, drifts and shafts. Typically, a soft-ground
tunnel liner 112 is formed from 3 or 4 segments which are bolted
and gasketed together to form a short cylindrical section 105 of
tunnel liner. As the tunnel is excavated, short liner sections 105
are assembled and positioned within a shield that is part of the
excavating machine, in such a way as to maintain a continuous seal
between the working area and the formation being excavated.
Installing the tunnel liner while sealed against the formation,
controls the seepage of fluids and vapors from the hydrocarbon
deposit into the tunnels and drifts of underground working space.
The liner also allows the TBM crew to control more substantial
water and/or gas inflows encountered during excavation by
well-known methods such as water pumps and ventilation air flows.
Thus the inside of the tunnels of the present invention are sealed
and isolated from the formation at all times during installation of
the tunnel network. This ability to seal the tunnel interior from
the formation during installation makes it possible to install the
tunnel network in the hydrocarbon deposit itself.
[0072] The tunnel diameters envisioned by the present invention are
in the range of about 3 meters to about 12 meters. The tunnel liner
thicknesses are typically in the range of about 75 millimeters to
about 600 millimeters. The liners may be formed from concrete or
other low-cost structural materials and may contain layers of
plastic or rubber materials to provide additional sealing. The
liner may be formed by erecting segments or by continuously
extruding concrete into a form.
[0073] The diameter of the cutter head 110 is typically slightly
larger than the diameter of the shield. The TBM is used to install
a fixed tunnel liner 112 which is shown as having a slightly
smaller diameter than the TBM shield 111. As the TBM advances, it
creates an excavation whose inside diameter is denoted by 109. A
gap 113 is therefore formed between the inner diameter of the
excavation 109 and the outer diameter of the tunnel liner 112. The
width of the gap 113 may be controlled and backfilled with a
suitable material to serve several functions as will be discussed
later. The gap 113 is typically in the range of 25 millimeters to
about 300 millimeters and may be back-filled with an appropriate
material such as grout, gravel or not be backfilled, depending on
the application and ground situation. The tunnel liner 112 is
preferably installed by using a slurry or Earth Pressure Balance
("EPB") tunnel boring machine ("TBM") and conventional tunnel liner
installation technology. This tunneling method allows a liner to be
installed while following the desired trajectory through the
hydrocarbon deposit 102. This trajectory may be designed to follow
the deposit which may have been formed by a river or estuary for
example. The length of the tunnel is dependent on the geology of
the hydrocarbon deposit 102 and may be in the approximate range of
500 meters to 10,000 meters or longer if the deposit persists
and/or if a number of deposits are separated by short sections of
barren ground. The installation of the tunnel liner 112 may be
initiated from a portal developed at the surface or by assembling
the TBM and its equipment using an access shaft excavated from the
surface 103 through the overburden 101 to the bottom of the
hydrocarbon deposit 102. With currently available tunneling
technology, a tunnel liner 112 can be installed to within a few
millimeters of its desired design location. If the tunnel is used
in a thermal recovery operation, this capability therefore places a
desirable low limit on the variance of placement of injection and
collection points that is considerably more precise than is
currently possible with horizontal drilling methods operated from
the ground surface 103. In current practice, soft-ground tunneling
machines are limited to formation fluid pressures of about 10 to 12
bars. This limitation is currently dictated by seal design for
fluid seals between the TBM shield 111 and the section of tunnel
liner 105 erected under the shield 111. This pressure limitation
can be increased by improved seal design. For now, the present
invention is limited to hydrocarbon deposits where ambient
formation fluid pressures do not exceed about 15 bars. It is also
possible, using known tunneling techniques, to locally drain fluids
(dewatering and degassing). If the formation is relatively
impermeable, then this can reduce local formation fluid pressures
and inflow rates to allow the tunneling machine to proceed without
exceeding the pressure limits on its seals. Once the tunnel liner
is installed, the pressure limitation can be considerably higher
than 10 bars as the pressure limit is now dictated by the
structural integrity of the liner and/or the sealing technology
used to form gaskets between liner segments (unless extruded liner
technology, which does not require gaskets, is used). The tunnel
liner serves a number of purposes. These include isolating the
interior of the tunnel from the formation fluids and vapors,
protecting the formation from activities in the tunnel including
sparks and the like which can cause ignition of hydrocarbon vapors
and materials; serving as a base for attaching fluid cutting and
control assemblies used for drilling, logging, operating and
servicing wells drilled through the liner; insulating the interior
of the tunnel from high temperatures if steam injection is used;
and serving as a base for installing drains for collecting oil
around the tunnel itself. The tunnel liner 112 can also be
installed in the basement formation 104 if desired. If the basement
formation is soft or mixed ground, the tunnel would be formed from
liner sections such as described above. If the basement formation
is hard rock, the tunnel can be excavated by a hard rock TBM and
the tunnel walls can be grouted or by other means to provide a
seal. If necessary, the tunnel can be formed by using soft-ground
techniques(including installing a liner) but with a hard rock TBM
cutter head. This latter method may be preferable, for example, if
there were substantial in-flows of water or gas anticipated, as
might be the case for basement formations underlying many
hydrocarbon deposits.
[0074] FIG. 2 is a schematic end section view of a tunnel liner
such as may be installed over, in or under a hydrocarbon reservoir.
This view shows a tunnel liner 201 installed in a hydrocarbon
formation 202. The hydrocarbon formation 202 sits atop an
underlying basement formation 203 and is overlain by a
non-hydrocarbon bearing formation 204 which reaches to the surface
205. The tunnel liner 201 isolates the interior of the tunnel 206
from the hydrocarbon deposit 202. The tunnel liner may have an
optional backfill zone 207 around the liner. The backfill zone is
typically formed during the excavating process as part of the
excavating and tunnel liner erection process. The backfill may
include grout, concrete, sand, pebbles, small rock and the like and
may provide additional sealing capability or drainage around the
tunnel liner 201. The backfill zone 207 is not necessarily circular
in cross-section as shown but may be approximately elliptical in
cross-section with much of the backfill material being above the
spring-line 210 of the tunnel liner cross-section. It is also
possible in some hydrocarbon formations to not backfill the zone
207 but allow the ground to expand and fill in the zone 207. This
may be desirable for some applications, for example, in many oil
sands formations.
[0075] FIG. 3 is an isometric view of a shaft, tunnel and well
complex installed in a hydrocarbon formation. This figure shows a
shaft 305 connecting the surface 301 with a hydrocarbon formation
303. The hydrocarbon formation itself may be comprised of one or
more zones of hydrocarbon, each separated by a thin permeable
barrier. A shaft 305 penetrates the formations 302 overlaying the
hydrocarbon formation 303 and terminating in a basement formation
304. The shaft 305 may be sunk below the hydrocarbon formation 303
to accommodate shaft elevator equipment or provide a sump volume
for the oil produced. In this example, the shaft 305 connects the
surface with two tunnels 306 and 307. The upper tunnel 307 may be
used for example to install producer or injection wells into the
top of the hydrocarbon formation 303. The lower tunnel 306 may be
used for example to install producer or injection wells into the
bottom of the hydrocarbon formation 303. In this figure, blind
wells 308 are shown drilled horizontally into the hydrocarbon
formation. As can be appreciated, wells can be drilled at any angle
into the formation as will be described in subsequent figures. A
key feature of this installation are the junctions 309 between the
shaft 305 and the tunnels 306 and 307. If these junctions are in a
pressurized or gassy or fluid-saturated portion of the formation,
they must be sealed junctions. The junctions are not necessarily
sealed during installation as dewatering, degassing or other well
known techniques can be applied during installation to cope with
fluid or gas inflows. A method for maintaining a seal at such
junctions 309 during installation is described in FIG. 18. As can
be appreciated, wells can be drilled into the formation from the
tunnels or shafts at any time after the tunnels and shafts are
installed. Thus, it is straightforward to drill additional wells
between existing wells to in-fill the well network, creating a
dense network of wells in the formation. When drilled from a tunnel
of the present invention located inside or adjacent to the
hydrocarbon formation, the well lengths are almost entirely in the
hydrocarbon formation and there is no cost to drill through the
overburden as would be the case with wells drilled from the
surface. This is a substantial advantage of the present
invention.
[0076] FIG. 4 is a schematic plan view of a typical configuration
of wells drilled from tunnels in or adjacent to a hydrocarbon
formation. The tunnels themselves may contain provisions for
directly injecting steam and collecting fluids and therefore act as
large wells themselves. One or more tunnels 401 are driven
substantially horizontally into a hydrocarbon formation,
approximately following the path of interest in the formation. In
this embodiment, a plurality of wells 402, 403, 404, 405 and 408
are drilled outwardly from each tunnel 401 into the hydrocarbon
formation. These wells are drilled from the tunnel and are designed
to remain substantially within the hydrocarbon deposit. If more
than one tunnel is installed, then the tunnels are spaced apart by
a distance in the range of approximately 200 to 1,000 meters as
indicated by well 402 which connects two tunnels 401. As shown in
FIG. 4, wells 403, 404, 405 and 408 are drilled from the tunnels
401 and terminate in the hydrocarbon formation as blind wells. The
lengths of the wells 403, 404, 405 and 408 are approximately half
the distance between adjacent tunnels. The lengths of wells are
thus in the approximate range of about 100 to about 400 meters. If
all the wells are drilled as blind wells, the spacing between
tunnels may be as much as about 2,000 meters and the blind wells
may be up to about 1,000 meters in length. Other wells 402 may be
drilled from one tunnel to the other. Other wells 405 may be
drilled into the hydrocarbon formation and then offshoot wells 406
can be additionally drilled. As can be appreciated any number of
offshoot wells 406 can be drilled from the initial well 405. The
wells may be drilled from any location along the length of the
tunnels 401 but are typically spaced in the range of approximately
25 to approximately 150 meters apart. Wells originating from
adjacent tunnels may or may not overlap in lateral extent as shown
by examples 408 (non-overlapping) and 404 (overlapping). As can be
appreciated, wells can be drilled as pairs with one well above the
other to form a well pair such as used in SAGD operations. The
tunnels 401 which can be curved if necessary to follow the
meanderings of a hydrocarbon formation. As can be appreciated,
there can be one two or more tunnels which may or may not be
connected with cross drifts or wells. In the present invention, all
the tunnels and cross drifts are lined; all the wells are sealed
where they penetrate the tunnel liners; and when in production, all
the wells are connected to a closed piping system such that the
produced oil is never exposed to the inside of the tunnel and shaft
network.
[0077] FIG. 5 is a schematic end section view of multiple tunnels
and wells installed near the bottom of a hydrocarbon formation 501
showing a surface 504, an overburden 503 and an underlying basement
formation 502. It is understood that the hydrocarbon formation 501
may be comprised of multiple producing zones, each zone being
separated by a thin permeability barrier. Each tunnel 505 provides
an underground workspace for drilling and operating wells in the
hydrocarbon formation 501. The tunnels 505 are driven roughly
parallel to each other with a spacing 506. The spacing 506 between
adjacent tunnels 505 is typically in the range of about 100 to
about 2,000 meters. The tunnel is formed by a structural liner (as
illustrated, for example, in FIG. 2) which is preferably
constructed of approximately cylindrical sections that are gasketed
and bolted together to form a workspace effectively sealed from the
surrounding formation. The diameter of the tunnels 505 is
preferably in the range of about 3 meters to 12 meters. Several
types of wells may be drilled to connect with the tunnels 505. Well
511 is drilled through the hydrocarbon formation 501 from tunnel to
tunnel, the tunnels 501 being approximately in the range of about
200 meters to about 1,000 meters apart in this case. Well 514 is
drilled out into the hydrocarbon formation 501 and terminates as a
blind well in the hydrocarbon formation 510. A blind well 514 is
typically in the length range of approximately 100 to 1,000 meters
but may be longer as blind drilling techniques are improved.
Inclined well 515 is drilled to various desired locations in the
hydrocarbon formation 510 and may be used, for example, to inject
fluids for enhanced oil recovery ("EOR"). Well 516 is drilled down
from the surface to connect with a tunnel. Well 516 may have a
horizontal section 513 in the hydrocarbon formation 501 as shown.
The horizontal section 513 of well 516 is typically in the length
range of approximately 100 to 1,000 meters but may be longer as
surface drilling techniques are improved. Well 517 is drilled
vertically down and terminates as blind well in the basement
formation 502. Well 517 may be used, for example to sequester
carbon dioxide or other gases or fluids that may be sequestered in
the underlying formation. The diameters of the wells, the lengths
of the wells and the spacing of the wells around the tunnels and
along the length of the tunnels are controlled by the instructions
of the reservoir engineer. The well lengths are limited by the
drilling technology employed but are at least in the range of about
100 to 1,000 meters in length. The well diameters are in the range
of about 50 mm to 1,000 millimeters, depending on the instructions
of the reservoir engineer. The wells may be drilled as single
wells, as well pairs such as commonly used in SAGD thermal recovery
operations or as three well stacks such as used in some advanced
SAGD thermal recovery operations. The methods of drilling from
within the tunnels 505 may include, for example, conventional soft
ground drilling methods using rotary or augur bits attached to
lengths of drill pipe which are lengthened by adding additional
drill pipe sections as drilling proceeds. Drilling methods may also
include, for example, water jet drilling methods. Drilling methods
may also include, for example, micro-tunneling techniques where a
slurry excavation head is used and is advanced into the deposit by
pipe-jacking methods. Forms of directional drilling may be used
from within a tunnel. More conventional directional drilling
methods may be used for wells or well pairs drilled from the
surface to intercept a tunnel such as described in subsequent
discussions. Although not shown, wells may be drilled upwards at an
inclination such as well 515 and then be directionally changed to
be a horizontal well at a new elevation within the formation.
[0078] FIG. 6 is and end view of multiple tunnels and wells
installed, for example, in a basement formation 602 just below a
hydrocarbon formation 601. This figure also shows a surface 604 and
an overburden 603 formation 602. FIG. 6 is similar to FIG. 5 except
the tunnels 605 are driven into an underlying basement formation
602 and the wells 611, 612, 614 and 615 must be drilled upwards out
of the basement formation 602 and then horizontally at or near the
bottom of the hydrocarbon formation 601. The range of tunnel
diameters and spacings and well pair diameters and spacings are the
same as those described in FIG. 5. In the case of the blind well
pairs 614, the techniques for drilling such well pairs from
basement formation 602 into the hydrocarbon formation 601 has been
established previously during the original development of the SAGD
method at the Underground Test Facility ("UTF") in Alberta, Canada.
In this case, the drilling of well pairs was conducted from
underground workings drilled & blasted into limestone
underlying an oil sands deposit. If the wells or well pairs are
drilled from tunnels installed into hard ground, then it is
possible to drill & blast small caverns at each drilling
location to provide additional working space for the well drilling
equipment. Each tunnel 605 provides an underground workspace for
drilling and operating wells in the hydrocarbon formation 601. Even
if the basement formation is rock, the tunnel may formed by a
structural liner (as illustrated in FIG. 2) which is preferably
constructed of approximately cylindrical sections that are gasketed
and bolted together to form a workspace effectively sealed from the
surrounding formation. Several types of wells may be drilled to
connect with the tunnels 605. In the case of the well 611 drilled
between adjacent tunnels 605, the well can be drilled from one
tunnel and ultimately intercept the adjacent tunnel. This will
require an innovation to presently available drilling technology.
One way that this may be accomplished, for example, is to drill
upwards from one tunnel out of the basement layer 602 and then
horizontally at or near the bottom of the hydrocarbon deposit 601
until the horizontal well passes over the adjacent tunnel. It then
is possible to drill upwards from the adjacent tunnel to intercept
the horizontal portion of the well 611 in the hydrocarbon deposit
601. Well pair 614 is drilled out into the hydrocarbon formation
601 and terminates as a blind well pair in the hydrocarbon
formation 610. A blind well pair 614 is typically in the length
range of approximately 100 to 1,000 meters but may be longer as
blind drilling techniques are improved. Inclined well 615 is
drilled to various desired locations in the hydrocarbon formation
610 and may be used, for example, to inject fluids for enhanced oil
recovery ("EOR"). Well 616 is drilled down from the surface to
connect with a tunnel. Well 616 may have a horizontal section 613
in the hydrocarbon formation 601 as shown. The horizontal section
613 of well 616 is typically in the length range of approximately
100 to 1,000 meters but may be longer as surface drilling
techniques are improved. Well 616 can be connected to tunnel 605 in
the same way well 611 is connected. An example of this procedure
was described previously. Well 617 is drilled vertically down and
terminates as blind well in the basement formation 602. Well 617
may be used, for example to sequester gases or fluids. Although not
shown, wells may be drilled upwards at an inclination such as well
615 and then be directionally changed to be a horizontal well at a
new elevation within the formation. The diameters of the wells, the
lengths of the wells and the spacing of the wells around the
tunnels and along the length of the tunnels are controlled by the
instructions of the reservoir engineer. The wells may be drilled as
single wells, as well pairs such as commonly used in SAGD thermal
recovery operations or as three well stacks such as used in some
advanced SAGD thermal recovery operations. If the basement
formation is soft or mixed ground the tunnel would be formed from
liner segments such as described previously. If the basement
formation is hard rock, the tunnel can be excavated by a hard rock
TBM and the tunnel walls can be grouted or lined by other means to
provide a seal unless the basement rock is impermeable. If
necessary, the tunnel can be formed by using soft-ground techniques
but with a hard rock TBM cutter head. This latter method may be
preferable, for example, if there were substantial in-flows of
water or gas anticipated, as might be the case for basement
formations underlying many hydrocarbon deposits. Access to the
basement formation is typically by vertical shafts sunk from the
surface 604 through the overburden layer 603 and hydrocarbon
formation 601 and terminating in the basement formation 602. The
shafts are of a sufficient diameter to accommodate ventilation,
access, and the large components of the tunneling machines.
Utilizing Liners to Maintain Sealing While Drilling
[0079] FIG. 7 is a side view through a liner segment illustrating a
section through a ring assembly embedded in the liner segment. As
will be shown subsequently, this type of ring assembly may serve as
a mounting device for a fluid cutting and control assembly
including blow-out preventers and allows drilling, logging, casing
and servicing of wells to be carried out while the interior
workspace is fully sealed from the formation. This ring assembly
also allows drilling to be initiated from discrete orientations
around the circumference of the tunnel. Threaded holes 705 are
shown in each half 704 of the ring assembly. The holes 705 are on
the inside 701 of the liner segment. The liner segment is commonly
made as a precast concrete 703 component having an inside surface
701 and an outside surface 702. The ring assembly is preferably
made from steel but may be fabricated using other structural
materials such as aluminum, high strength plastics or the like. A
wellhead control assembly (such as shown in FIG. 12) can then be
mounted against the liner ring assembly with a gasket (not shown)
forming a seal with surface 706. This example is meant to
illustrate how well-head equipment can be mounted using mounting
assemblies cast into the tunnel liner. As can be appreciated, other
types of mounting hardware can be cast into the tunnel liner.
[0080] FIG. 8 is an isometric view of the ring assembly shown in
FIG. 7. This view shows two ring halves 801 of the assembly.
Threaded holes 805 are shown on the inside (concave surface) of the
ring halves. Connectors 803 made for example from re-bar hold the
two ring halves together. The connectors 803 and rods 804 also
serve to maintain the ring assembly in position when the concrete
segment is fabricated. The threaded holes 805 are spaced at equal
angles around the ring halves and allow the wellhead control
assembly to be positioned at any of a number of discrete angles
around the finished tunnel liner. For example, the wellhead control
assembly can be mounted at angular spacings of from about 5.degree.
to about 15.degree.. This allows wells to be drilled through the
tunnel liner walls at any angle since a well's final inclination
angle can be adjusted by directional drilling techniques with
drilling angle adjusted through small angles as the well is being
drilled. Once the wellhead control assembly is positioned and
secured to the ring assembly, a drill can penetrate the liner wall
by drilling through the precast concrete in between the connector
bars 803 and, using well known techniques can maintain a seal
between the formation and the interior work space.
[0081] FIG. 9 shows an isometric view of three liner segments, each
segment with a ring assembly 906 such as described in FIGS. 7 and 8
cast into the liner wall. The liner segments are bolted and
gasketed together at overlapping joints 905 to form a short
cylindrical section 901 of tunnel liner. The liner section 901 has
a diameter 902, a length 903 and a wall thickness 904. The ring
assemblies 906 are shown cast into the precast concrete segments.
The ring assemblies are preferably located about halfway along the
length of the segments. As can be appreciated, more than one ring
assembly may be cast into the liner segments and they may be
located anywhere along the length of the segments consistent with
segment structural integrity.
[0082] FIG. 10 shows a liner section 1001 with rows of drain ports
1004 and 1005 installed in the tunnel liner. The tunnel liner 1001
is comprised of segments joined lengthwise as denoted by joint
1002. A bottom platform 1003 may be used to provide a flat surface
for laying tracks or rails along the tunnel for transportation. In
this example, drain ports 1004 are shown located along both sides
of the tunnel liner 1001 under platform 1003. This is a preferred
location for drain ports since they can be plumbed into an oil/gas
collection piping system installed inside the liner 1001 at the
bottom for removing oil/gas that is collected as it drains around
the outside of the tunnel liner 1001. Additional drain ports 1005
are shown located along both sides of the upper portion of the
tunnel liner 1001. This is also a good location for drain ports is
since they can be plumbed into an oil collection piping system for
removing oil that is collected as it drains around the outside of
the tunnel liner 1001 by a piping system hung inside the liner 1001
near the crown of the tunnel liner 1001 and therefore above the
traffic lanes and drilling sites within the tunnel. These drain
ports may be pre-cast into the liner during fabrication of liner
segments or they may be installed in the liner after the liner
itself has been installed in the ground. If pre-cast into the liner
during fabrication of liner segments, the drain ports may be
initially plugged by, for example, a threaded pipe plug compatible
with connections to a piping system for oil/gas removal. If
installed in the liner after the liner itself has been installed,
the drain ports may be installed in a manner similar to that used
to install the fluid cutting and control assemblies described in
FIG. 11.
[0083] FIG. 11 is a close up cutaway side view of a tunnel liner
wall 1107 with well-head equipment 1103 installed. The well-head
equipment 1103 is attached and sealed to the tunnel liner 1107.
Well-head equipment 1103 is secured, for example, to a flange 1104
pre-cast into the tunnel liner wall 1107. A portion of the
well-head equipment 1103 is set into the formation 1105. As shown,
that portion is typical of well-production operations and collects
hydrocarbons and delivers them to a piping system 1106. The
equipment shown is a wellhead control assembly which includes
blow-out preventers. Equipment such as this allows drilling,
logging, casing and servicing of wells to be carried out while the
interior workspace is fully sealed from the formation.
[0084] FIG. 12 shows a drill rig in travel position mounted on a
tunnel rail car. A platform 1202 is installed inside a tunnel liner
1201. Narrow gage rail tracks 1203 are installed along the platform
1202. These tracks are used for small tunnel locomotives and rail
cars used to move men, materials, supplies and the like throughout
the tunnel and, during tunnel driving operations, to supply, for
example, backfilling material to the advancing face and to remove
excavated material from the tunnel. A drill rig car 1204 with
wheels 1205 is shown in a drilling position. Bearing pads 1206 are
shown engaged with the liner walls by hydraulic cylinders 1207 and
act to stabilize the drill rig during drilling, casing and other
operations. This illustrates another advantage of a tunnel liner
which is that it has a predictably smooth bearing surface on which
the drill rig can stabilize itself and it can do so in almost any
angular orientation. The wheels 1205 can also be designed to grip
the rails 1203 when in drilling position to further stabilize the
drill rig during drilling and casing operations. A drill with drill
motor 1209, drill rod 1208 and drill bit 1210 is shown mounted on a
movable mount. The drill can be oriented as indicated by arrow 1212
to drill in any angular orientation around the tunnel liner. The
drill can also be moved up or down as indicated by arrow 1211. As
can be appreciated, the drill can be a mechanical drill such as a
rotary or percussive drill; or a water jet drill; or a micro-tunnel
machine; or a combination mechanical and water jet drill. The drill
rig can be used with well-head equipment such as shown in FIG. 11
to initiate and complete a well while maintaining a seal between
the interior workspace and the formation. The drill rigs used in
the present invention are designed to quickly add additional
lengths of drill rod either by well-designed hand operations or by
automatic addition of drill rod lengths such as practiced in
petroleum drilling.
[0085] FIG. 13 shows a plan view of a drill rig 1303 in drilling
position to drill a horizontal well through the side of the tunnel
liner 1301. Rail tracks 1302 are shown along the platform that
forms the tunnel floor. Bearing pads are shown engaged with the
liner walls by hydraulic cylinders 1304. A drill 1305 is shown in a
number of positions viewed from above with an approximate range of
drilling positions indicated by arrow 1306. The drill rig shown in
FIG. 13 can be raised and lowered from the tunnel centerline
through a distance of approximately about 1/4 of a tunnel diameter.
The drill rig can also be rotated to allow wells to be drilled at
any angular orientation (pitch angle). The drill rig can also be
rotated laterally to direct the drill line at an angle with respect
to normal to the tunnel liner wall (yaw angle).
Utilizing Tunnels for Thermal Recovery
[0086] FIG. 14 shows an end view illustrating a method for using
the tunnel liner for thermal recovery of heavy oil or bitumen. A
backfilled tunnel liner 1404 illustrates a means of isolating steam
from mobilized fluids. An end view of a tunnel is shown here
embedded in an oil sands deposit 1401 just above the underlying
basement rock 1402. A tunnel structural liner 1404 provides ground
support for an excavated bore 1403. As described previously in FIG.
2, the liner 1404 is preferably fabricated using a high-strength,
high-temperature concrete to form short liner segments that can be
installed, gasketed and bolted together as part of the tunneling
process. The excavated tunnel bore and tunnel liner installation
are preferably implemented using a soft-ground tunnel boring
machine and well-known liner segment installation techniques. The
annular spaces 1405, 1411 and 1412 between the liner 1404 and the
inner surface of the excavated bore 1403 are backfilled. In the
bottom portion of the annular space 1405 backfill is provided by a
low cost, readily available material such as, for example, pea
gravel, coarse sand, small rocks and/or the like or combinations of
these materials. For a liner diameter in the range of about 3
meters to about 12 meters, the annular gap 1405, 1411 and 1412 is
preferably in the range of about 25 millimeters to about 300
millimeters wide. The portion of the annular space 1411 above the
previously mentioned annular space 1405 is thereupon backfilled
with a high-temperature grout shown as a solid grey filler. The
portion of the annular space 1412 above the previously mentioned
annular space 1411 is then backfilled with a low cost, readily
available material such as used in annular space 1405. The grout in
annular space 1411 serves to form a seal between the filler
material in annular spaces 1405 and 1412. This feature can prevent
injected steam from communicating or short-circuiting from injector
ports 1407 to collector ports 1409. Steam may be injected through
both ports 1407 and 1409 so as to heat up the oil sand formation
surrounding the tunnel. Steam is not allowed past the grout in
annular space 1411 and cannot go around the grout because of the
un-mobilized bitumen in the formation. The steam mobilizes the
bitumen around the top and bottom portions of the tunnel. At some
point, steam injection through ports 1409 is stopped and the
mobilized bitumen is allowed to remain in place while steam
continues to be injected through injection ports 1407. As bitumen
is drained from around the tunnel through ports 1409, volume is
created for steam to be further injected into the formation through
ports 1407. In this figure, steam is piped down the tunnel and a
portion is injected at each injection port 1407. The steam pipes
may be wrapped with a common insulating material to minimize heat
loss before injection into the formation. This is a significant
advantage that the present invention has over SAGD using well pairs
drilled from the surface. An injection port or ports 1407 are
located preferably in at least every tunnel liner segment as shown
for example in FIG. 15. The steam injection port 1407 can inject
the steam at the outside surface of the liner 1404 or more
preferably just beyond the annular layer 1412 directly into the oil
sand 1401 as shown in the present figure. Since the steam,
generated on the surface or in the tunnel itself, is transported
from its point of origin down the inside of the tunnel liner 1404
by a piping system 1406, its pressure and temperature can be
readily monitored. If the steam conditions degrade with length down
the tunnel, they can be returned to their desired levels by heater
and compressor apparatuses located at intervals along the tunnel.
This later capability can be an important advantage over injector
wells installed by directional drilling and allows the tunnel-based
steam injection system to be as long as required by the oil sands
deposit being drained. The fluids are collected through ports 1409
located near the bottom of the tunnel. In this figure, two ports
are shown at each cross-sectional location, although there may be
any number of ports from one to many at each cross-sectional
location. Along the length of the tunnel, collection ports 1409 are
located preferably in at least every tunnel liner segment as shown
for example in FIG. 15. The collection ports 1409 feed into a
piping system 1408 which allows the collected fluids to be
transported through the tunnel and eventually pumped to the surface
for further processing. As can be appreciated the tunnel liner also
serves to insulate the interior workspace of the tunnel from the
steam-heated formation. It does so by limiting the rate of heat
flow through the liner (which is commonly made of concrete which
has a low thermal conductivity) and by allowing the tunnel
ventilation system to rapidly remove heated air so conducted into
the tunnel. The ability to over-cut a tunnel bore 1403, install an
undersized liner 1404 and fill the resulting annular space with a
number of different materials serving a number of functions, is an
example of how modern tunneling technology can be used to enhance
implementation of a SAGD process.
[0087] FIG. 15 is an isometric view of a tunnel segment 1501
showing an example of a possible layout for slotted or circular
injector and collector ports. This illustrates how a tunnel can be
used, for example, as a large diameter SAGD well. In SAGD as
currently practiced, the injector well is typically made from a
steel tubing with long narrow slots formed into the tubing wall.
The slots are approximately 150 millimeters long and 0.3
millimeters wide. The narrow width of these slots is dictated by
the requirement to prevent sand from entering into the slot when
steam is not being injected and hot fluids (principally mobilized
bitumen and condensed steam) are collected. An injector port slot
1502 of the present invention is shown on top of a tunnel segment
1501. The injector port 1502 is a long slot through which steam is
injected into the formation. The slot can be made during the
fabrication of the tunnel liner segment 1501. It can be covered by
a screen or screens that allow steam to be injected while sand is
prevented from entering the slot when steam is not being injected.
The screen mesh is of a size that allows as much or more injection
area while having openings approximately in the range of the slot
widths used in conventional SAGD well pipe. The collector port
slots 1503 and 1504 can be made in the same way as the injector
port slot 1502. The injector port slot 1502 is typically placed at
or near the top of the segment 1501. One of more collector port
slots are typically located in the bottom half of the segment 1501
as shown for example by the location of slots 1503 and 1504. The
circumferential strength of the liner segment 1501 can be
maintained for example by embedding reinforcing bar in the concrete
liners across the slots in the circumferential direction. The
injection and collection port slots can be made as long slots that
can be almost as long as the tunnel liner segments but, if
necessary, substantially wider than the slots used in conventional
SAGD well tubing. FIG. 15 also shows injector ports 1505 and
collector ports 1506 and 1507. These ports are circular in section
and it is possible to locate one to three circumferential rows of
ports embedded in the liner 1501. These ports can be in the range
of 100 mm to 400 mm in diameter. The length of the tunnel 1500 may
be in the approximate range of 500 meters to 10,000 meters. The
length 1511 of an individual tunnel liner segment 1501 is typically
in the approximate range of 1 to 12 meters. If each tunnel segment
1501 has an injection port 1502 and collection ports 1504, the
injection of steam and the collection of fluids, in effect, occurs
along a line which corresponds to the length of the tunnel. Thus
the tunnel, which need not be straight but can be sinuous as shown
in FIG. 4, acts as a single long horizontal well pair such as used
in conventional SAGD. Because the tunnel can have a diameter in the
range of about 3 meters to about 12 meters, the collection area is
substantially greater than the collection area of a collector well
typically used in conventional SAGD. Since the rate of fluid
production is proportional to the pressure and gravity gradients
and to the natural logarithm of the effective diameter of the
collector, the production rate per unit length of the present
invention should be higher by a factor of about 2 to 4 than the
production rate of a conventional SAGD collector well.
[0088] FIG. 16 is an end view of a tunnel as represented by a
tunnel liner 1609 showing a SAGD steam chamber as represented by
its outwardly moving condensation front 1605. FIG. 16 also shows a
ground surface 1602, an overburden layer 1603, an oil sand deposit
1601 and an underlying basement rock 1604. The steam chamber is
formed by steam injected 1608 through ports embedded in the tunnel
liner 1609 and spaced along the length of the tunnel liner. The
fluids which are comprised of mobilized bitumen and condensed
steam, drain 1606 around the condensation front 1605 of the steam
chamber and are collected through the collector ports spaced along
either or both sides of the bottom half of the tunnel liner 1609 as
also described in FIG. 15. Since the characteristic size of a fully
developed steam chamber is on the order of the thickness of the oil
sand deposit 1601, the collector ports are effectively along a line
located at precise vertical and horizontal distances from the line
formed by the injector ports. This geometry is therefore, in
effect, a steam injection well with a large collector well spaced
appropriately beneath the injector well.
Sealing the Underground Workspace
[0089] The present invention is a method of recovering hydrocarbons
by developing an underground workspace that is isolated from the
formation both during installation and operations. This requires
means of sealing the excavating machines, drilling machines, and
working spaces at all times. The principal points of sealing
are:
[0090] 1. between the shaft walls and the formation
[0091] 2. between the shaft walls and the tunneling machine
[0092] 3. between the shaft walls and the tunnel liner
[0093] 4. between the tunneling machine and the tunnel liner during
installation
[0094] 5. between the tunnel liner sections and segments during
installation and operation
[0095] 6. between the tunnel liner and the wells drilled to or from
the tunnel
[0096] 1. Lined shafts can be sunk in soft ground in the presence
of formation pressure and fluids by well-known methods. For
example, drilling mud can be used in conjunction with a large
diameter drill bit to excavate the shaft and thick concrete walls
can be installed before the mud is pumped out. Often, the
surrounding ground can be dewatered and degassed by various
well-known means to reduce formation pressures and fluid in-flows
sufficiently so the shaft can be installed in short sections by a
sequence of alternately excavating and pouring liner walls without
drilling muds.
[0097] 2. Beginning a tunnel from a shaft is known practice. The
shaft wall must be thick enough that the TBM can be sealed into
place before it actually starts to bore. For example, if the shaft
wall is, say 1.5 meters thick at the penetration point, the inside
1 meter may be recessed into the wall so the curvature of the shaft
would be eliminated and the cutting face of the boring machine can
bear squarely on a boring surface (fibre reinforced concrete for
example) over its entire circumference. The outer shaft wall
remaining would be thick enough to maintain a rigid seal under
formation pressure but would be a boreable material such as for
example by a fiber-reinforced concrete. Specially configured, very
short tunnel liner sections would be bolted into the recess. Then
the TBM machine can bore out of the wall and into the formation as
sealed as it would be for each additional liner section.
[0098] 3. As can be appreciated, the above tunnel started from
inside a shaft results in a tunnel liner section being installed
and grouted in the hole bored through the shaft wall. As can be
appreciated, this joint can be further sealed by additional
grouting the joint and/or by reinforcing it with a structural
sealing ring system.
[0099] 4. The seal between the tunnel boring machine and tunnel
liner as it being installed is described in some detail below by
FIG. 17.
[0100] 5. The seals between the tunnel liner segments and liner
sections are described in some detail below by FIG. 18.
[0101] 6. Once a lined shaft or lined tunnel is installed, wells
can be drilled through the shaft or tunnel wall liners by first
attaching a wellhead control assembly (used for drilling, logging,
operating and servicing wells, for example, at the well-head of a
surface-drilled well) and then using this assembly to drill through
the liner wall while maintaining a seal between the formation from
the inside of the shaft or tunnel liner as illustrated for example
in FIG. 11. This is also a well-known practice.
[0102] FIG. 17 is a side view schematic of a soft-ground TBM
showing its principal sealing points during excavation. This figure
illustrates how an Earth Pressure Balance ("EPB") machine is sealed
against formation pressures and fluids. It is understood that the
seals may not be perfect seals but will substantially reduce the
in-flow of, for example, liquids to an amount that can be readily
controlled by pumps. Similarly, in the case of gases, seals can
substantially reduce the in flow of gas to amounts that can be
readily controlled by ventilation systems. FIG. 17 shows a
schematic of an EPB machine with a cutter head 1701 and muck
ingestion ports 1702. The excavated material or muck is ingested
into a chamber 1706 which is maintained at about local formation
pressure (hence the name earth pressure balance). The excavated
material is mixed with a plasticizer that gives the muck cohesion.
A screw auger 1705, then transfers the plasticized muck to a
conveyor system 1707. The muck in the auger forms an effective seal
between the chamber 1706 and the conveyor 1707. The conveyor system
1707 may therefore be an open or closed system and may be operated
at the ambient pressure in the manned working areas inside the TBM
and tunnel. The cutter head 1701 rotates within a shield 1703 and
is sealed by well-known mechanical rotating sealing means. A tunnel
liner 1711 is assembled within the shield 1703. As the TBM moves
forward(towards the left in FIG. 17), the shield 1703 moves with it
and exposes newly formed liner sections 1712 to the formation. A
series of brush seals between the overlapping portion 1709 of the
shield 1703 and liner sections 1712 form a substantial seal between
the formation and the interior of the TBM/tunnel liner. In current
practice, these brush seals are limited to formation fluid
pressures of about 10 to 12 bars. The tunnel liner 1711 is formed
by joining sections of liner 1712 at joints such 1713. These joints
are sealed as described in the following figure. Once the tunnel
liner is installed, the pressure limitation can be considerably
higher than 10 bars as the pressure limit is now dictated by the
structural integrity of the liner and/or the sealing technology
used to form gaskets between liner sections and segments. A slurry
TBM seals in a slightly different way during excavation. The slurry
TBM cutting head excavates by forming the ground just ahead of it
into a dense slurry. The slurried muck is ingested into a
pressurized chamber and then formed into a transportable slurry by
adding additional water. The slurry may be transported out of the
tunnel at approximately formation pressure in a closed slurry
system. Thus, like the EPB TBM, the excavation and muck removal can
be carried out at or near formation pressure while the working
areas in the TBM and tunnel can remain at ambient pressure and
isolated from the slurried muck.
[0103] FIG. 18 illustrates features of tunnel liner sealing. A
soft-ground tunnel liner is commonly comprised of short cylindrical
liner sections. The sections are in turn comprised of segments.
Alternately, a tunnel liner may be formed by continuously extruding
a concrete liner, a newer method that does not require as much
sealing as a liner assembled from segments and sections. An end
view of a typical tunnel liner is shown in FIG. 18a showing three
segments 1801 joined together at joints 1802 which may include
sealing gaskets (not shown) and may be bolted 1803. The segments
are typically pre-cast and made from a high strength material such
as for example concrete or fibre-reinforced concrete. An additional
optional sealing liner 1804 may be installed to provide additional
sealing. This sealing liner may be made of rubber, urethane or
another tough sealing material. A side view of the tunnel liner is
shown in FIG. 18b illustrating two sections 1810 of outer diameter
1813 joined together by a joint 1811. A longitudinal segment joint
1812 such as described in FIG. 18a is also shown. Once each section
1810 is assembled inside the TBM shield (described previously in
FIG. 17), it is compressed against the previously installed section
by the action of the TBM propelling itself forward by its hydraulic
rams against the end of the tunnel liner. A seal is formed at
section joints 1811 by a sealing gasket such as shown in FIG. 18c
which illustrates a close-up section view between two liner
sections 1820 and their joint surfaces. Typically a sealing gasket
mounting assembly 1821 is cast into the liner segments 1820. A
compressible sealing material 1822 is installed in at least one of
the sealing gasket mounting assemblies 1821. When the liner
sections 1820 are compressed by the propelling action of the TBM,
the sealing material 1822 is compressed forming a seal between
adjacent tunnel liner sections.
[0104] There are other advantages of the present invention not
discussed in the above figures. For example, if there are problems
during the operation of the system after production operations have
begun, it is possible to perform servicing and repair. This could
include for example repair of down hole pumps, valves and other
production equipment. If required, additional wells can be drilled
to offset declining production. Wells can readily be cleaned and
serviced in all weather conditions. Remotely operated robotic
vehicles can be operated inside the tunnel and monitor or observe
problem areas. This can be especially useful when the tunnel is for
thermal production operations such as SAGD. Finally, much of the
installed equipment (piping, pumps, sumps, diagnostics, heaters and
the like) can be retrieved from the tunnel for use in other
tunnel-based hydrocarbon recovery operations.
[0105] A number of variations and modifications of the invention
can be used. As will be appreciated, it would be possible to
provide for some features of the invention without providing
others. The present invention, in various embodiments, includes
components, methods, processes, systems and/or apparatus
substantially as depicted and described herein, including various
embodiments, sub-combinations, and subsets thereof. Those of skill
in the art will understand how to make and use the present
invention after understanding the present disclosure. The present
invention, in various embodiments, includes providing devices and
processes in the absence of items not depicted and/or described
herein or in various embodiments hereof, including in the absence
of such items as may have been used in previous devices or
processes, for example for improving performance, achieving ease
and\or reducing cost of implementation.
[0106] The foregoing discussion of the invention has been presented
for purposes of illustration and description. The foregoing is not
intended to limit the invention to the form or forms disclosed
herein. In the foregoing Detailed Description for example, various
features of the invention are grouped together in one or more
embodiments for the purpose of streamlining the disclosure. This
method of disclosure is not to be interpreted as reflecting an
intention that the claimed invention requires more features than
are expressly recited in each claim. Rather, as the following
claims reflect, inventive aspects lie in less than all features of
a single foregoing disclosed embodiment. Thus, the following claims
are hereby incorporated into this Detailed Description, with each
claim standing on its own as a separate preferred embodiment of the
invention.
[0107] Moreover though the description of the invention has
included description of one or more embodiments and certain
variations and modifications, other variations and modifications
are within the scope of the invention, e.g., as may be within the
skill and knowledge of those in the art, after understanding the
present disclosure. It is intended to obtain rights which include
alternative embodiments to the extent permitted, including
alternate, interchangeable and/or equivalent structures, functions,
ranges or steps to those claimed, whether or not such alternate,
interchangeable and/or equivalent structures, functions, ranges or
steps are disclosed herein, and without intending to publicly
dedicate any patentable subject matter.
* * * * *