Patent Application
20090139716
The present invention relates generally to a lined tunnel- and shaft-based method and system for installing, operating and servicing electrodes, heating elements and recovery wells for recovery of hydrocarbons.
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, oil shales, and carbonate deposits containing bitumen or heavy oil; and to a search for new techniques for continued recovery from both conventional and unconventional 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. The anticipated development of carbonate deposits in Alberta and elsewhere represents many billions of additional barrels. Further, there are immense deposits of oil shales in the United States that can be recovered by the methods described herein. 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 sources of oil, oil sands, oil shales, oil carbonates and stranded oil, are more than enough to eliminate dependence on outside sources of oil and, in addition, require no substantial exploration.
In the Athabasca oil sands, when the deposits are too deep for economical surface mining, in-situ recovery methods have been used wherein the viscosity of the bitumen in the oil sand is first reduced so that it can flow. These bitumen mobilization techniques include steam injection, diluent 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.
In the US oil shales, one recovery method being implemented in pilot projects involves the use of resistance heaters and heating elements to raise the temperature of the oil shales so that oil is produced. These methods are being considered for application to both oil sand and carbonate deposits in Alberta. These methods are designed to heat heavy oil and bitumen deposits to mobilize these hydrocarbons for production.
Pilot phase projects currently underway include:
1. Heating of oil sands by electrodes, often referred to as a form of Heat Assisted Gravity Drain (“HAGD”).
2. Direct heating of oil sands by electrically-powered heating elements which is another form of HAGD.
One electrode pilot project in the Athabasca oil sands utilizes an array of vertically placed cathodes, anodes and recovery wells. A voltage difference is applied across anodes and cathodes, causing electrical flow through the brackish, connate, interstitial water that typically adheres to each oil sand grain. The electrical flow generates heat within the formation which lowers the viscosity of the heavy oil so that it will flow to the vertical recovery well. Examples of this approach are described in “Electromagnetic Heating Methods for Heavy Oil Reservoirs” by A. Sahni, M. Kumar and R. B. Knapp, UCRL-JC-138802, May 1, 2000 (this article was submitted to 2000 Society of Petroleum Engineers, SPE/AAPG Western Regional Meeting, Long Beach, Calif., Jun. 19-23, 2000).
Another pilot in the U.S. utilizes electrodes (similar in function the above-described Canadian oil sands project) to heat oil shales to a temperature below the boiling point of the water in the formation. The electrodes are then converted to direct heating elements to further increase the formation temperature so that mobile oil will be liberated from the oil shale. The direct heating elements can increase formation temperatures so that in-situ refining takes place prior to production, for example, kerogens, which are typically not produced from the formation, are converted to producible, synthetic oil at temperatures on the order of 400-600° C. Examples of this approach are described in “E-ICP Project Plan of Operations” (Shell Frontier Oil and Gas Inc., E-ICP Test Project, Oil Shale Research and Development Project, prepared for the Bureau of Land Management, Feb. 15, 2006.
There remains a need for a method of installing a large number of densely spaced heating elements in a reservoir without having to drill through substantial overburden for every placement. Dense spacing of heating elements in a reservoir can increase the control and efficiency of a thermal recovery method including utilizing gravity drain to remove melted bitumen from the reservoir.
The present invention is directed generally to mobilizing and recovering hydrocarbons in an underground deposit, such as a bitumen, heavy oil or oil shale deposit.
In a first embodiment, a method is provided that includes the steps:
(a) forming a manned underground excavation in proximity to and/or in a hydrocarbon-containing deposit;
(b) forming, from the manned underground excavation, a plurality of mobilizing wells extending into the hydrocarbon-containing deposit, each mobilizing well containing at least one of a heating element, steam injector, and diluent injector; and
(c) forming, from the manned underground excavation, at least one recovery well in fluid communication with the hydrocarbon-containing deposit and positioned in proximity to at least some of the plurality of mobilizing wells, wherein the mobilizing wells and recovery wells define a drainage volume and wherein the mobilizing wells mobilize hydrocarbons contained within the drainage volume and the recovery wells collect the mobilized hydrocarbons.
In a second embodiment, a method comprising:
(a) providing a manned underground excavation in proximity to and/or in a hydrocarbon-containing deposit, the manned underground excavation comprising:
(b) generating thermal energy from the heating wells to heat and mobilize the hydrocarbons in the drainage volume for collection by the recovery wells.
In a third embodiment, a system comprising:
(a) a manned underground excavation in proximity to and/or in a hydrocarbon-containing deposit;
(b) at least one heating well extending from the underground excavation into the hydrocarbon-containing deposit, the at least one heating well containing one or more heating elements; and
(c) at least one recovery well in fluid communication with the hydrocarbon-containing deposit and positioned in proximity to the at least one heating well, wherein the at least one heating well and the at least one recovery well define a drainage volume, whereby thermal energy is generated from the at least one heating well to heat and mobilize hydrocarbons in the drainage volume for collection by the recovery wells.
The present invention can provide a method and means of installing and servicing substantially horizontal heating elements and recovery wells in a hydrocarbon deposit from a tunnel or shaft that is driven into, above or under the hydrocarbon deposit. It has the potential to increase hydrocarbon recovery factors, lower costs, increase safety, decrease emissions at the site from the heating process and result in less surface disturbance. It can provide another means of assisting the extraction of hydrocarbons and be used as needed in conjunction with other technologies such as steaming, solvent and diluents, gas or water flooding and hydraulic mining.
In some configurations, the invention can combine shaft and tunneling, in-tunnel and in-shaft drilling, heating element technologies to access, mobilize and produce heavy hydrocarbons from oil sands, oil shales and oil carbonate reservoirs. Production can be accomplished while providing full isolation for workers and operators from formation fluids and gases. The invention can be initiated, for example, from within the hydrocarbon formation or from the underlying rock below the formation.
In one configuration, the invention discloses a method and system for installing a lined shaft and tunnel from which heating elements are installed substantially horizontally into the formation in an array that approximates shape and function of a steam chamber resulting from the SAGD process using horizontal directional well pairs drilled from the surface. To begin, a horizontal recovery well of several hundred meters in length is installed from the tunnel into the bottom of the producing interval. Then horizontal heating elements of several hundred meters in length are installed above the recovery well in a pattern that promotes uniform heating of the bitumen. Once the recovery well is completed, the path of each heating elements is guided while drilling by staying a fixed distance from a ranging transmitter traveling up the recovery well. The chamber heating would be initiated by passing current between the electrodes and uniformly heating the chamber to near the boiling point of water at chamber pressure. At this temperature, since boiling would disrupt the flow of electricity, each heating element would be converted from an electrode to a thermal conduction heater. The thermal conduction heater would then continue to increase chamber temperature until oil flows to the recovery well or wells. The pattern of heating would begin with the center elements so that downward flow along the shortest path to the recovery well or wells is quickly established, followed by heating of the outside elements to produce a flow path down and then sloping toward the recovery well or wells (typically on the order of a 15° slope downward toward the recovery well or wells).
Other configurations of heating elements and recovery wells are contemplated. Heating elements can be installed from the tunnel by drilling equipment that can drill directly upward or at any angle from vertical to horizontal and to below horizontal (if necessary), depending on the target reserves, geology and tunnel configuration.
In some configurations, lateral spacing of the heating elements will depend also on site-specific conditions and accumulated experience. Pilot spacing will be on the order of 15 to 20 meters between heating elements. A heating element would be located directly adjacent to each recovery well to encourage flow into and down to the recovery well. The recovery well may be drained by gravity or with pump assistance.
Although the present invention is discussed with reference to electrodes and thermal conduction heaters, it is understood that other types of heating methods may be employed such as RF antennas.
Another embodiment of the invention is the installation of ohmic or induction electrodes in some situations, thermal conduction heaters in some situations, RF antennas in some situations and various combinations of these elements in other situations.
Another aspect of the present invention is the energy source for the heating elements. Electrical power will most likely be used for all necessary energy for the Heating elements, although some heating elements could be heated by combusting fuel or circulation of a heated working fluid (e.g., molten salt, heated oil or water).
Another aspect of this invention is the design of the heating elements. Steel in its various forms (carbon, high tensile, stainless) casing is a prime candidate as the heating elements must withstand the torque and axial loads during drilling.
Another aspect of this invention is the drilling system, which preferably includes a surface casing installation rig, drill rig and possibly a completion rig, as well as drill pipe, mud system and downhole tools. The drill bit may consist of a rotary, percussive or jetting bit, depending on formation characteristics. The mud composition may be water or oil, bentonite and/or polymer based. The mud system would include facility for mud cleaning. Pressure control may be necessary and wellhead, blow-out prevention (“BOP”) can be adapted from standard oil field equipment in accordance with regulatory agency requirements, such as, for example, the regulations imposed by the Alberta Energy Utilities Board. Drilling is anticipated to be underbalanced, but could be overbalanced or balanced. Guidance for the recovery well may be by Measurement While Drilling (“MWD”) or other guidance systems that are known in the art. Guidance for the heating elements may be by paralleling a ranging tool advancing up the recovery well while drilling the guidance hole.
Another aspect of this invention is the tunnel liner which serves a number of purposes. These include protecting 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 create fires; serving as a base for attaching fluid cutting and control assemblies used for drilling, logging, operating and servicing wells drilled through the liner; and serving as a base for drains for oil collected around the tunnel itself. Oil field wellhead and blow-out prevention equipment would be modified to compact form suitable for regulatory approval.
Another aspect of this invention is that the use of heating elements could be combined with other extraction technologies advanced from the tunnel or shaft. For example, the heating elements could be used as a formation pre-heater in electrode mode or thermal conduction heater mode, then the formation could be steamed, diluent injected or other method advanced from the underground workings or the ground surface.
The following definitions are used herein:
Kerogen is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks such as oil shales. When heated to the right temperatures, some types of kerogen release oil or gas.
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 mobilizing well as used herein is a well whose function is to cause bitumen, heavy oil or another hydrocarbon which does not readily flow, to be mobilized and able to flow to a recovery well. A well containing heating elements is an example of a mobilizing well. A well from which steam or diluent may be injected into a producing formation is another example of a mobilizing well. A well that can be used to operate a combination of heating elements, steam and diluent injection either simultaneously or at different times is, in general, defined herein as a mobilizing well. A mobilizing well may also be converted to a recovery well.
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.
A recovery well is a well from which a mobilized hydrocarbon such, as for example, bitumen or heavy oil may be recovered.
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.
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°). A reference to bitumen is also taken to mean a reference to low API heavy oils.
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.
Mobilizing hydrocarbons such as bitumen or heavy oil, for example from oil sands, may be accomplished using steam to heat the bitumen or heavy oil, or by injecting diluents to increase the API rating of the bitumen or heavy oil. Other heating methods besides steam may also be used. These include, for example:
Where any of these heating methods may be used, they are referred to herein generally as heating elements. When a specific type of heating method is intended, it will be referred to by its specific name (i.e., ohmic electrode, thermal conduction heater, induction electrode, RF antenna).
A mobilizing well as used herein is a well whose function is to cause bitumen, heavy oil or another hydrocarbon which does not readily flow, to be mobilized and able to flow to a recovery well. A well containing heating elements is an example of a mobilizing well. A well from which steam or diluent may be injected into a producing formation is another example of a mobilizing well. A well that can be used to operate a combination of heating elements, steam and diluent injection either simultaneously or at different times is, in general, defined herein as a mobilizing well. A mobilizing well may also be converted to a recovery well.
A recovery well as used herein is a well from which a mobilized hydrocarbon such, as for example, bitumen or heavy oil may be recovered.
A heating well as used herein is a well containing any of the heating elements described above.
A number of technologies proposed for recovery of hydrocarbons, including heavy oil and bitumen, are based on mining for access. For example, a system of underground lined shafts and lined tunnels has been proposed to allow wells to be installed from under or from within a reservoir. This approach overcomes a number of problems such as surface access, product lifting difficulties and reliability of downhole pumps. In these mining for access technologies, the wellhead and its associated equipment is readily accessible and is typically only a few meters from the formation. Also, the wells are installed from the underground workspace either horizontally or inclined upwards. A discussion of these mining for access methods can be found in U.S. patent application Ser. No. 11/441,929 entitled “Method for Underground Recovery of Hydrocarbons” and U.S. patent application Ser. No. 11/737,578 entitled “Method of Drilling from a Shaft”, both of which are incorporated herein by reference.
Installing wells from an underground workspace, rather than drilling the wells from the surface, opens up possibilities for improving the economics of, for example, SAGD and HAGD by reducing the cost of installing wells, minimizing steam transmission losses and enabling more accurate placement of well pairs. This approach also allows deposits that have surface restrictions to be exploited.
When drilling is carried out from inside a lined tunnel, the tunnel liner serves a number of purposes. These include protecting 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 create fires; serving as a base for attaching fluid cutting and control assemblies used for drilling, logging, operating and servicing wells drilled through the liner; serving as a base for blow-out prevention equipment; and serving as a base for drains for oil collected around the tunnel itself. Some of these techniques are discussed in U.S. patent application Ser. No. 11/441,929 entitled “Method for Underground Recovery of Hydrocarbons” and U.S. patent application Ser. No. 11/737,578 entitled “Method of Drilling from a Shaft”.
Recovering Bitumen from Tunnel and Shaft with Heating Elements
The heating elements 403 are installed into the formation in an array to form a melt chamber 401 that approximates shape and function of a steam chamber resulting from the SAGD process using horizontal directional well pairs drilled from the surface. To begin, a horizontal recovery well 402 several hundred meters in length is installed from a tunnel or shaft into the bottom of the producing interval. Then horizontal heating elements 403 are installed above the recovery well 402 in a pattern that promotes uniform heating of the bitumen once the bitumen is mobilized and flow is established. Once the recovery well 403 is completed, the path of each heating element 402 is guided while drilling by staying a fixed distance from a ranging transmitter traveling up the recovery well. The melt chamber heating may be initiated by passing current between electrodes 403 and uniformly heating the chamber 401 to near the boiling point of water at chamber pressure. At this temperature, since boiling would disrupt the flow of electricity, each electrode 403 would be converted from an electrode to a thermal conduction heater. The thermal conduction heaters 403 would then continue to increase melt chamber 401 temperature until oil flows to the recovery well 402. As will be described in
Other configurations of heating elements 403 and recovery wells 402 are contemplated. Heating elements can be installed from a tunnel (not shown) by drilling equipment (similar to that shown in
In the foregoing examples as described in
As can be appreciated, other pre-heating and melting scenarios are possible. For example, preheating can be carried out sequentially from the center zone out towards the edges of the projected melt chamber while direct heating could follow a similar pattern but delayed in time so that melting always progresses into a preheated zone. This illustrates an advantage of HAGD over SAGD. SAGD uses steam which convects heat into pore space from which bitumen has been mobilized and drained. The growth of a SAGD steam chamber thus is constrained to an expanding chamber emanating from the injector/collector well pair. In a HAGD recovery operation, the preheating and melting phases can be carried out in a different pattern by choreographing either or both the placement and the timing of the heating elements. This capability could be used for example, to form a melt chamber around a thief zone in such a way as to isolate the thief zone and prevent a precipitous loss of heating energy. As can be appreciated, pre-heating can be accomplished, for example, using RF antenna heaters or induction electrodes instead of ohmic electrodes.
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. For example, the use of horizontal heating elements could be combined with other extraction technologies advanced from the tunnel or shaft. For example, the heating elements could be used as a formation pre-heater in electrode mode, then the formation could be steamed, diluent injected or other method advanced from the underground workings or the ground surface.
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 claims the benefits, under 35 U.S.C. §119(e), of U.S. Provisional Application Ser. No. 60/992,001, filed Dec. 3, 2007, entitled “Method of Recovering Bitumen from Tunnel and Shaft With Electrodes, Heating Elements and Recovery Wells” to Brock et al, which is incorporated herein by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 60992001 | Dec 2007 | US |
