The present invention relates generally to selection of a lined shaft-based and tunnel-based method and system for installing, operating and servicing wells for recovery of hydrocarbons from pressurized soft-ground reservoirs, 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 continued recovery from conventional oil deposits. The development of the Athabasca oil sands in particular has resulted in increased proven world reserves of over 170 billion barrels from the application of surface mining and in-situ technologies. There are also large untapped reserves in the form of stranded oil deposits from known reservoirs. Estimates as high as 300 billion barrels of recoverable light and heavy oil have been made for North America. Recovery of stranded oil requires new recovery techniques that can overcome, for example, the loss of drive pressure required to move the oil to nearby wells where it can be pumped to the surface. These two sources of oil, oil sands and stranded oil, are more than enough to eliminate the current dependence on outside sources of oil and, in addition, require no substantial exploration.
Shaft-sinking or shaft-drilling are well-developed areas of civil and mining construction. Applications in civil construction include for example ventilation shafts for transportation tunnels, access shafts for water drainage and sewage system tunnels and Ranney wells for recovering filtered water from aquifers. Applications in mining include for example ventilation and access shafts for underground mine works. Shafts have been sunk in hard rock and drilled or bored into soft-ground. Soft-ground shafts are commonly concrete lined shafts and are installed by a variety of methods. These methods include drilling and boring techniques often where the shaft is filled with water or drilling mud to counteract local ground pressures. There are casing drilling machines that use high torque reciprocating drives to work steel casing into the formation. There are also shaft sinking techniques for sinking shafts underwater using robotic construction equipment. There are secant pile systems, where several small diameter bores are drilled in a ring configuration, completed with concrete and then the center of the ring excavated to create the shaft. There is the caisson sinking method, which formation materials are removed from below the center of caisson, creating a void and causing the casing to sink under its own weight. Soft-ground shafts can be installed with diameters in the range of about 3 to about 10 meters.
Drilling technology for oil and gas wells is well developed. Drilling technologies for soft and hard rock are also well known. Water jet drilling has been implemented in both oil and gas well drilling, geothermal drilling, waste and groundwater control as well as for hard rock drilling. An example of water jet drilling technology is provided in published papers such as “Coiled Tubing Radials Placed by Water Jet Drilling: Field Results, Theory, and Practice” and “Performance of Multiple Horizontal Well Laterals in Low-to-Medium Permeability Reservoirs” which are listed as prior art references herein. 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.
One of the present inventors has developed a hybrid drilling method using a modified pipe-jacking process in conjunction with a augur cutting tool and a plasticized drilling mud to install horizontal wells from the bottom of a distant shaft into a river bottom formation. This technique was successfully used to develop a Ranney well with a long horizontal collector well.
Vertical, inclined and horizontal wells may be installed from the surface by well-known methods. In many cases surface access is restricted and installing wells from an underground platform such as the bottom of a shaft or a tunnel may be a more practical and cost-effective approach to installing wells. Machine and methodology developments, particularly in the heavy civil underground construction sector, have opened up new possibilities for an underground approach for installing wells. Discussing some of these techniques, the present inventors have filed U.S. provisional patent application Ser. No. 60/685,251, filed May 27, 2005 entitled “Method of Collecting Hydrocarbons from Tunnels”, and U.S. Ser. No. 60/753,694, filed Dec. 23, 2005 entitled “Method of Recovering Bitumen” both of which are incorporated herein by this reference.
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.
Robotic excavators have been used in a variety of difficult situations such as excavating trenches undersea or preforming excavation functions underground in unsafe environments. An example of this technology can be found, for example, in U.S. Pat. No. 5,446,980, entitled “Automatic Excavation Control System and Method”.
The mining and heavy civil underground industries have developed other processes that may be applied to forming drilling rooms for underground recovery of hydrocarbons. These include for example:
1. Hydraulic mining—Hydraulic mining techniques have been successfully demonstrated in the Alberta oil sands. Proposals have been put forward which involve mining the oil sand by hydraulic means through wells sunk from the surface. Such efforts are described, for example, in “Feasibility of Underground Mining of Oil Sand”, Harris and Sobkowicz, 1978 and “Feasibility Study for Underground Mining of Oil Sand”, Hardy, 1977. Johns in U.S. Pat. No. 4,076,311 issued Feb. 28, 1978 entitled “Hydraulic Mining from Tunnel by Reciprocated Pipes” discloses a method of hydraulic underground mining of oil sands and other friable mineral deposits. The present inventors have disclosed a method of hydraulic mining in oil sands in U.S. Provisional Patent Application 60/867,010 entitled “Recovery of Bitumen by Hydraulic Excavation” filed Nov. 22, 2006. The method of hydraulic mining disclosed includes: several means of drilling production and tailings injection wells; several means of augmenting hydraulic excavation for example by inducing block caving; means of isolating the underground personnel areas from formation gases and fluids; and means of backfilling the excavated volumes with tailings.
2. Horizontal secant pile—Secant pile walls or tunnels may be formed by constructing a longitudinal assembly of piles which contact each other to define a tunnel. The volume contained inside the pile assembly is excavated using the piles as ground support. The piles may be fabricated, for example, from steel tubes or reinforced concrete. The piles may be installed by pipe-jacking, pile driving, drilling or augering. Primary piles are installed first with secondary piles constructed in between primary piles once the latter gain sufficient strength. Pile overlap is typically in the order of about 50 to 100 mm.
3. Soil Mixing—Various methods of soil mixing (sometimes referred to as jet grouting), mechanical, hydraulic, with and without air, and combinations of both types have been used widely in Japan for about 20 years and more recently have gained wide acceptance in the United States. The soil mixing, ground modification technique, has been used for many diverse applications including building and bridge foundations, retaining structures, liquefaction mitigation, temporary support of excavation and water control. Names such as Jet Grouting, Soil Mixing, Cement Deep Mixing (CDM), Soil Mixed Wall (SMW), Geo-Jet, Deep Soil Mixing, (DSM), Hydra-Mech, Dry Jet Mixing (DJM), and Lime Columns are known to many. Each of these methods has the same basic root, finding the most efficient and economical method to mix cement (or in some cases fly ash or lime) with soil and cause the properties of the soil to become more like the properties of a soft rock.
4. Ground modification (also known as ground freezing)—Historically, ground modification for civil applications has been used primarily on large projects where groundwater and caving soils create an unstable situation and ground freezing represents the only possible solution. Ground freezing has been used to stabilize excavation walls in caving soils and to prevent groundwater seepage into the deep excavations near existing structures. The technology has been applied in Europe and North America for more than a century on a variety of construction and mining projects. The freezing method aims to provide artificially frozen soil that can be used temporarily as a support structure for tunneling or mining applications. It is a versatile technique that increases the strength of the ground and makes it impervious to water seepage. Excavation can proceed safely inside the frozen ground structure until construction of the final lining provides permanent support. In contrast to grouting works the freezing method is completely reversible and has no environmental impact. Ground freezing is not limited by adverse ground conditions and may be used in any soil formation, regardless of structure, grain size, permeability or moderate groundwater flow.
5. NATM—New Austrian Tunnelling Method (NATM) As defined by the Austrian Society of Engineers and Architects, the NATM “ . . . constitutes a method where the surrounding rock or soil formations of a tunnel are integrated into an overall ring-like support structure. Thus the supporting formations will themselves be part of this supporting structure.” In world-wide practice, however, when shotcrete is proposed for initial ground support of an open-face tunnel, it is often referred to as NATM. In current practice, for soft-ground tunnels which are referred to as NATM tunnels, initial ground support in the form of shotcrete (usually with lattice girders and some form of ground reinforcement) is installed as excavation proceeds, followed by installation of a final lining at a later date. Soft ground can be described as any type of ground requiring support as soon as possible after excavation in order to maintain stability of the NATM for soft ground. As long as the ground is properly supported, NATM construction methods are appropriate for soft-ground conditions. However, there are cases where soft-ground conditions do not favor an open face with a short length of uncompleted lining immediately next to it, such as in flowing ground or ground with short stand-up time (i.e., failure to develop a ground arch). Unless such unstable conditions can be modified by dewatering, spiling, grouting, or other methods of ground improvement, then NATM may be inappropriate. In these cases, close-face shield tunneling methods may be more appropriate for safe tunnel construction.
Key features of the NATM design philosophy are:
For underground recovery of hydrocarbons, there remains a need for modified excavation methods and a selection method to utilize shafts as an underground base to install a network of wells either from the shaft itself or drilling rooms, tunnels and the like, initiated from the shaft. There is 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. It is the objective of the present invention to provide a method and means of selecting the most appropriate process for providing adequate underground workspace by selecting one or more of a number of methods for installing, operating and servicing a large number of wells in various levels of a hydrocarbon deposit which may contain free gas, gas in solution and water zones.
These and other needs are addressed by embodiments of the present invention, which are directed generally to methods for installing underground workspace in or near a hydrocarbon deposit that is an appropriate workspace from which to drill, operate and/or service wells applicable to any of a number of methods of recovering hydrocarbons and selecting an appropriate method for a given application. The present invention includes a number of innovative methods for developing workspace for drilling from a shaft installed above, into, or below a hydrocarbon deposit, particularly when the hydrocarbon reservoir is at significant formation pressure or has fluids (water, oil or gases) that can seep into or flood a workspace. These methods can also be used for developing workspace for drilling from a tunnel installed above, into, or below a hydrocarbon deposit. The entire process of installing the shafts and tunnels as well as drilling and operating the wells in carried out while maintaining isolation between the work space and the ground formation. The present invention also discloses a procedure for evaluating the geology in and around the reservoir and using this and other information to select the most appropriate method of developing workspace for drilling from a shaft and/or tunnel.
In one embodiment, an excavation method includes the steps:
(a) forming a substantially vertically inclined shaft;
(b) at a selected level of the shaft, forming a plurality of recess cavities extending approximately radially outward from the shaft, the selected level of the shaft being adjacent to or near a hydrocarbon-containing formation; and
(c) drilling one or more wells outward from a face of each of the recess cavities, each of the wells penetrating the hydrocarbon-containing formation.
The recess cavities are preferably manned. More preferably, each of the recess cavities has a diameter ranging from about 1 to about 2 meters and a length ranging from about 4 to about 10 meters.
To protect underground personnel and inhibit underground gas explosions, the recess cavities and at least some of the shaft are lined with a formation-fluid impervious liner.
The shaft normally includes a number of spaced apart levels. Each of the spaced apart levels comprises a plurality of approximately radially outwardly extending recess cavities.
In one configuration, the drilling step (c) includes the further steps of:
(c1) from the shaft, drilling through a flange positioned adjacent to a surface of the shaft to form a drilled hole extending outwardly from the shaft;
(c2) placing a cylindrical shield in the drilled hole;
(c3) securing the shield to the surface of the shaft; and
(c4) introducing a cementitious material into an end of the drilled hole to form a selected recess cavity.
When the cementitious material sets, the set cementitious material and shield will seal the interior of the cavity from one or more selected formation fluids.
In one configuration, the drilling step (c) includes the further steps of:
(c1) from the shaft, drilling, by a drill stem and bit, through a flange and sealing gasket, the flange and gasket being positioned on a surface of the shaft, to form a drilled hole extending into the hydrocarbon-containing formation;
(c2) while the hole is being drilled, extending a cylindrical shield into the hole in spatial proximity to the drill bit, the shield surrounding the drill stem;
(c3) pumping a cementitious composition through the drill stem and into a bottom of the drilled hole;
(c4) securing the shield to the flange; and
(c5) after the cementitious composition has set, removing the drill stem from the hole to form a selected recess cavity.
When the cementitious material sets, the set cementitious material and shield will seal the interior of the cavity from one or more selected formation fluids.
In another embodiment, a drilling method includes the steps:
(a) from a manned excavation, drilling through a flange positioned adjacent to a surface of the excavation to form a drilled hole extending outwardly from the excavation;
(b) placing a cylindrical shield in the drilled hole;
(c) securing the shield to the surface of the excavation; and
(d) introducing a cementitious material into an end of the drilled hole to form a selected recess cavity.
When the cementitious material sets, the set cementitious material and shield will seal the interior of the hole from one or more selected formation fluids.
In the drilling step, a drill stem and attached bit drill through a flange and the sealing gasket and into a hydrocarbon-containing formation. The flange and gasket are positioned on a surface of the excavation. During the drilling step, a cylindrical shield is preferably extended into the hole in spatial proximity to the drill bit, the shield surrounding the drill stem. The shield may or may not rotate in response to rotation of the bit.
In yet another embodiment, an excavation method includes the steps:
(a) excavating a shaft, the excavated shaft being at least partially filled with a drilling fluid and having a diameter of at least about 3 meters; and
(b) an automated and/or remotely controlled excavation machine forming an excavation extending outwards from the shaft, the excavation machine being positioned below a level of and in the drilling fluid when forming the excavation.
The position of the excavation machine is preferably determined relative to a fixed point of reference in the shaft. The excavation machine is typically immersed in the drilling fluid when forming the excavation, and, to track the machine's position, the excavation machine is normally connected to the fixed point of reference. The excavation machine is controlled remotely by an operator.
In one configuration, the excavation machine is at least partially automated, and the excavation is located in a hydrocarbon-containing formation.
The method can include the further steps:
(c) removing the excavation machine from the excavation;
(d) filling, at least substantially, the excavation with a cementitious material that displaces the lighter drilling fluid from the filled portion of the excavation;
(e) repositioning the excavation machine in the shaft at an upper surface of the cementitious material, after the cementitious material has set, with the repositioned excavation machine still being immersed in the drilling fluid;
(f) removing, by the repositioned excavation machine, at least a portion of the set cementitious material to form a lined excavation; and
(g) installing, in the lined excavation and while the lined excavation is filled with the drilling fluid, a permanent liner, the permanent liner being positioned interiorly of the remaining cementitious material.
In yet another embodiment, an excavation method includes the steps:
(a) drilling a plurality of substantially horizontal drill holes, the drill holes defining an outline of a volume to be excavated;
(b) filling, at least substantially, the drill holes with a cementitious material, to inhibit the passage of a selected formation fluid between the adjacent, filled drill holes and/or to provide structural support; and
(c) thereafter excavating the volume to be excavated.
The volume to be excavated is positioned preferentially in a hydrocarbon-containing formation, and each of the drill holes has a normal diameter of at least about 0.33 meters and a length of up to about 800 meters.
The filling step (b) can include the further steps of: (b1) after a selected hole is drilled and while a drill stem is positioned in the selected hole, pumping the cementitious material through the drill stem and into the hole and
(b2) while the cementitious material is being introduced into the selected hole, removing gradually the drill stem from the selected hole, the rate of removal being related to the rate of introduction of the cementitious material into the selected hole.
In yet another embodiment, a method for recovering a bitumen-containing material is provided that includes the steps:
(a) determining, for a selected in situ hydrocarbon-containing deposit, a set of possible underground and/or surface excavation methods;
(b) determining a set of surface restrictions above and around the deposit;
(c) determining a set of regulatory requirements applicable to excavation of the deposit;
(d) determining a set of physical limitations on underground excavation of the deposit;
(e) determining a set of physical limitations on surface excavation of the deposit;
(f) determining a set of data for the deposit;
(g) determining a set of geotechnical data for at least one formation other than the deposit;
(h) based on the sets of surface restrictions, regulatory requirements, physical limitations, deposit data, and geotechnical data, assigning a recovery cost to each member of the set of possible excavation methods;
(i) based on a comparison of the recovery costs of the members, selecting a preferred excavation method to be employed;
(j) in response to the preferred excavation method being an underground method, performing the following substeps:
Typically, the deposit data include deposit depth, areal extent, and geology, and the geotechnical data are for a formation positioned above the deposit.
In one configuration, the method includes the further substep:
Preferably, the method is embodied as a computer program recorded, in the form of processor-executable instructions, on a computer readable medium.
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.
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 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. 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.
The present invention can provide a number of advantages. First, the various excavation methods can provide a cost effective, safe way to recover hydrocarbons, particularly bitumen, from hydrocarbon-containing materials, even those located beneath otherwise inaccessible obstacles, such as rivers, lakes, swamps, and inhabited areas. The methods can permit excavation to be performed safely in the hydrocarbon-containing materials rather than from a less economical or effective location above or below the material. The excavation selection method can permit one to select the optimal, or near optimal, excavation method for a given set of conditions and restraints. The selection method considers not just the excavation methods described herein but other known methods that have proven track records in non-hydrocarbon-containing materials.
The following definitions are used herein:
It is to be noted that the term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably.
The term automatic and variations thereof, as used herein, refers to any process or operation done without material human input when the process or operation is performed. However, a process or operation can be automatic even if performance of the process or operation uses human input, whether material or immaterial, received before performance of the process or operation. Human input is deemed to be material if such input influences how the process or operation will be performed. Human input that consents to the performance of the process or operation is not deemed to be “material”. The terms determine, calculate and compute, and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique.
The term module as used herein refers to any known or later developed hardware, software, firmware, artificial intelligence, fuzzy logic, or combination of hardware and software that is capable of performing the functionality associated with that element. Also, while the invention is described in terms of exemplary embodiments, it should be appreciated that individual aspects of the invention can be separately claimed.
A cementitious material refers to material that, in one mode, is in the form of a liquid or slurry and, in a different mode, is in the form of a solid. By way of example, cement, concrete, or grout-type cementitious materials are in the form of a flowable slurry, which later dries or sets into cement, concrete, or grout, respectively.
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. Bitumen particles may be mobilized by some hydraulic mining techniques using cold water.
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.
Soft ground means any type of ground requiring substantial support as soon as possible after the excavated opening is formed ion in order to maintain stability of the opening. Soft-ground is generally easy to excavate by various mechanical or hydraulic means but requires some form of ground support to maintain the excavated opening from collapse. Ground support may include, for example, permanent solutions such as grouting, shotcreting, or installation of a concrete or metal liner; or temporary solutions such as freezing or soil modification.
A drilling room as used herein is any self-supporting space that can be used to drill one or more wells through its floor, walls or ceiling. The drilling room is typically sealed from formation pressures and fluids.
Hydraulic mining means any method of excavating a valuable ore by impact and/or erosion of high pressure water from a hose or water jet nozzle.
Secant Pile means an opening formed by installing intersecting concrete piles by either drilling, augering, jacking or driving the piles into place and then excavating the material from the interior of the opening formed by the piles. A secant pile (sometimes called the tangent) may be formed using primary piles installed first and then secondary piles installed in between or overlapping the primary piles, once the primary piles attain sufficient strength.
Ground modification typically means freezing the ground to stabilize an excavation in soft ground especially caving soils and to prevent groundwater seepage into the excavation. The freezing method provides artificially frozen soil that can be used temporarily as a support structure for tunneling or mining applications. The process increases the strength of the ground and makes it impervious to water seepage so that excavation can proceed safely inside the frozen ground structure until construction of the final lining provides permanent support.
NATM means “New Austrian Tunneling Method” and is generally a method where the surrounding rock or soil formations of a tunnel are integrated into an overall ringlike support structure and where the supporting formations will themselves be part of this supporting structure.
Soil mixing means any of various methods of soil mixing or jet grouting methods based on mechanical, hydraulic devices used with or without air, and combinations of each. Soil mixing typically involves methods of mixing, for example, cement, fly ash or lime with the in-situ soil so as to cause the properties of the soil to become more like the properties of a soft rock.
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.
a-h is a sequence illustrating installing a recess under pressure.
a-c illustrate a sequence illustrating installing a recess by pipe-jacking. The method is applicable when a recess is to be installed form inside a lined shaft into the surrounding formation when the surrounding formation has or is thought to have a formation pressure and/or the possibility of substantial water or gas inflow. The ground formation in which the recess is sunk is on the side 2602.
Key features of this installation are the junctions 109 between the shaft 104 and the tunnel 106. 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 109 during installation is described in
A drill rig suitable for drilling from a shaft or tunnel is prior art. As can be appreciated, the drill rig must be compact. As can be seen in
a-h illustrates a method of installing a well-head recess when there is significant formation pressure. The method is applicable to formation pressures as high as about 20 bars above the ambient pressure inside the shaft. The method is applicable when a recess is to be installed from inside a lined shaft into the surrounding formation when the surrounding formation has or is thought to have a formation pressure and/or the possibility of substantial water or gas inflow.
e shows how the drill bit 706 is now withdrawn a small distance inside the steel shield 707 leaving an excavated void 711. The steel shield 707 is not allowed to move any significant amount. The withdrawal distance is in the range of about 0.3 steel shield diameters to about 1 steel shield diameter.
The drill bit shown in
The sequence of operations shown in
a is a plan view of a circular well pattern drilled from a shaft. Wells such as 901 may be drilled out approximately radially as shown to drain a circular area of reservoir. Many wells may be drilled from a limited number of recesses as described in
Shaft costs are diameter dependent so deep, large diameter shafts (shafts with diameters in the range of about 10 to 35 meters) can be very costly. A shaft for oil recovery needs a large diameter workspace near or at the bottom to accommodate drilling and well-head equipment. As described above, one method of providing space for drilling and well-head equipment is to install recesses such as described above. Another method is to enlarge the bottom of a shaft as described in subsequent figures. As with the previous method, these installations are not straightforward when in the presence of formation pressures and fluids. Robotic excavators have been used for a variety of excavation operations under water, including deep-sea operations. Robotic excavators can be used to enlarge the bottom of a shaft in a cost-effective and safe manner.
a shows a shaft 1401 being drilled by a large rotary bit 1403. Drilling mud 1404 is forced down the center of drill rod 1402 and re-circulates up the annulus between the drill rod 1402 and the open shaft wall 1401 as indicated by the flow arrows. This procedure is well-known and used to drill soft-ground shafts in the approximately 3 to 5 meter diameter range.
b shows the shaft 1405 at its maximum depth.
d shows a robotic excavator 1415 which has been positioned at the bottom of an open shaft 1411. The excavator 1415 is excavating a room 1413 at the bottom of shaft 1411 while immersed in drilling mud 1412 whose pressure is providing stability for the walls of both the shaft 1411 and room 1413. The excavator 1415 is attached to reference pin 1414 at the bottom of the shaft to provide a known reference point for the remotely located operator to guide the progress of the room excavation. As can be appreciated, it may require more than one excavator to complete the room excavation. For example, a small robotic excavator may be used to form an excavation slightly larger in diameter than the shaft so that a large robotic excavator can continue to enlarge the room. Excavation cuttings are carried away by circulating mud.
e shows the finished but unlined room 1413 and the unlined shaft 1411 where both are stabilized by the column of drilling fluid 1412. Reference pin or marker 1414 is also shown at the bottom of the shaft.
f shows a drilling bit 1419 lowered to the top entrance to the excavated room. A weak mix of concrete (for example a 2 sack mix) is injected down the center conduit of the drill rod and drill bit and displaces the drilling fluid 1420 back up the annulus between the drill rod and the shaft walls and replaces the drilling fluid 1420 in the room with weak concrete 1421. As can be appreciated, another specially designed apparatus can be used to inject the concrete and displace the drilling fluid.
g shows the drilling apparatus or other specially designed apparatus withdrawn, leaving the room 1422 full of weak concrete 1421 while the shaft 1411 remains open with its walls supported by the pressure of mud column 1423. A second reference pin or marker may be installed in the top portion of the concrete as shown.
h shows a robotic excavator 1427 now excavating a room in the concrete 1423. The open or unlined shaft 1411 and the excavated portion of the concrete continue to be filled with drilling mud 1422 for support. The excavator is attached to reference pin or marker at the bottom of the shaft so that it can excavate within the concrete and leave walls of a desired sufficient thickness to provide ground support when the drilling fluid is removed.
i shows the room excavation completed with concrete walls 1425. Unlined shaft 1411 continues to be filled with drilling mud 1422 for support.
j shows a concrete liner 1423 being installed in the shaft. The liner is installed by any of several well known methods. As shown in
k shows the process of lining the shaft completed so that a lined shaft 1430 is not connected and sealed to a lined room 1431. The interior 1432 of the shaft and room can now be purged of all drilling mud and filled with air. The system is now ready for installation of the remaining shaft utilities and equipment and the room is ready for well-drilling operations to begin.
a through 14k illustrate a method of forming a room at the bottom of a shaft in soft-ground. As can be appreciated, any number of rooms of any of a number of shapes can be formed in this way. It is also possible to form the shaft liner by displacing the drilling mud in the shaft with a weak concrete and re-drilling the shaft into the concrete column, leaving concrete shaft walls of a desired thickness.
Compared to jet grouting or other soil mixing techniques, this approach would anticipate the following advantages:
There are many conventional and unconventional hydrocarbon reservoirs that have yet to be exploited because of surface restrictions or because of the economics of recovery. For example, a reservoir may lay under, for example, a large lake, a town, a national park or a protected wildlife habitat. If the reservoir can be accessed from underground, it is possible to remove most of the surface footprint of a recovery operation to an underground workspace and therefore bypass most if not all the surface restrictions. Some reservoirs may require a dense network of wells to achieve an economically viable recovery factor. It may be less expensive to develop underground drilling workspace where a large number of short wells can be installed rapidly rather than to drill all the wells from the surface through unproductive overburden to reach the reservoir.
There are many factors that go into determining whether a recovery operation should be carried out from the surface or from underground. There are even more factors that go into determining how a recovery operation should be carried out once underground access is achieved. The following decision processes illustrate a method of making these complex decisions based on first on initial delineation of the reservoir to subsequent adaptation to foreseen or unforseen conditions once underground access to the reservoir is achieved. The following decision process is one of many that can be taken and is illustrative primarily of a decision process that might apply to an underground reconvey operation.
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
The present invention includes 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 include that between the shaft walls and the formation. 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.
There are other advantages of the present invention not discussed in the above figures. For example, the logic embodied in
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.
The present application is a continuation of U.S. patent application Ser. No. 11/737,578 filed on Apr. 19, 2007, entitled “METHOD OF DRILLING FROM A SHAFT FOR UNDERGROUND RECOVERY OF HYDROCARBONS” which claims the benefits, under 35 U.S.C. §119(e), of U.S. Provisional Application Ser. No. 60/793,975 filed Apr. 21, 2006, entitled “Method of Drilling from a Shaft” to Brock, Kobler and Watson; U.S. Provisional Application Ser. No. 60/868,467 filed Dec. 4, 2006, entitled “Method of Drilling from a Shaft” to Brock, Kobler and Watson; and U.S. Provisional Application Ser. No. 60/867,010 filed Nov. 22, 2006 entitled “Recovery of Bitumen by Hydraulic Excavation” to Brock, Squires and Watson, all of which are incorporated herein by these references. Cross reference is made to U.S. patent application Ser. No. 11/441,929 filed May 25, 2006, entitled “Method for Underground Recovery of Hydrocarbons”, which is also incorporated herein by this reference.
Number | Date | Country | |
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60868467 | Dec 2006 | US | |
60867010 | Nov 2006 | US | |
60793975 | Apr 2006 | US |
Number | Date | Country | |
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Parent | 11737578 | Apr 2007 | US |
Child | 13364913 | US |