US 20070044957 A1
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.
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
3. The method of
4. The method of
5. The method of
6. The method of
7. The method of
8. Hydrocarbon produced from the wells of
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
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
12. The method of
13. The method of
14. The method of
15. The method of
16. Hydrocarbon produced from the wells of
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
19. The liner of
20. The liner of
21. The liner of
22. The liner of
23. The liner of
24. The liner of
25. The liner of
26. The liner of
27. The liner of
28. The liner of
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
(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
32. The method of
33. Hydrocarbon produced from the wells of
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
(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
37. The method of
38. Hydrocarbon produced from the wells of
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
41. The method of
42. The method of
43. The method of
44. The method of
45. The method of
(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.
The present application claims the benefits, under 35 U.S.C.§ 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.
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.
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.
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.
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.
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”.
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.
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
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.
The literature describes three basic oil mining approaches:
(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.
(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.
(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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The following definitions are used herein:
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Well drilling is the activity of collaring and drilling a well to a desired length or depth.
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.
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.
It is to be understood that a reference to oil herein is intended to include low API hydrocarbons such as bitumen (API less than ˜10°) and heavy crude oils (API from ˜10° to ˜20°) as well as higher API hydrocarbons such as medium crude oils (API from ˜20° to ˜35°) and light crude oils (API higher than ˜35°) .
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.
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.
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.
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.
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.
In the descriptions below, it is understood that the functions described for tunnel liners also apply to shaft liners.
Development of Sealed Underground Workspace
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.
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.
Utilizing Liners to Maintain Sealing While Drilling
Utilizing Tunnels for Thermal Recovery
Sealing the Underground Workspace
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:
1. between the shaft walls and the formation
2. between the shaft walls and the tunneling machine
3. between the shaft walls and the tunnel liner
4. between the tunneling machine and the tunnel liner during installation
5. between the tunnel liner sections and segments during installation and operation
6. between the tunnel liner and the wells drilled to or from the tunnel
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.
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.
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.
4. The seal between the tunnel boring machine and tunnel liner as it being installed is described in some detail below by
5. The seals between the tunnel liner segments and liner sections are described in some detail below by
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
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.
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.
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.
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.