WO2022133579A1

WO2022133579A1 - Method and apparatus for heavy oil recovery

Info

Publication number: WO2022133579A1
Application number: PCT/CA2021/051621
Authority: WO
Inventors: Dan SAVELA
Original assignee: Radiance Oil Corp.
Priority date: 2020-12-23
Filing date: 2021-11-16
Publication date: 2022-06-30

Abstract

A method, and a corresponding system, for extracting heavy oil from an underground reservoir, comprising: delivering heat to a heating zone of the reservoir via a closed-loop heat transfer well by injecting a hot heat transfer medium through a downcomer pipe, thereby indirectly heating the heavy oil, rendering it less viscous to form a reservoir fluid; and extracting the reservoir fluid via a production well; wherein the heat transfer well includes: a closed-end casing having a radiant heat portion in thermal contact with the heating zone; the downcomer pipe, extending from the surface to the radiant heat portion; a pump and return pipe, disposed within the closed-end casing, for returning cooled heat transfer medium to the surface; wherein the closed-end casing encases the downcomer pipe and the return pipe.

Description

METHOD AND APPARATUS FOR HEAVY OIL RECOVERY

TECHNICAL FIELD

[001] The present disclosure relates to the field of heavy oil extraction, and more specifically to methods and systems for extracting heavy oil from subterranean formations.

BACKGROUND

[002] A variety of techniques are known that may be applied in heavy oil production. For example, various methods are known in which steam may be used to thermally stimulate heavy oil reservoirs so as to enable or enhance oil production. For heavy crude oil and bitumen formations (such as may be found in the Albertan “oil sands”, for example) particularly, steam-assisted gravity drainage (“SAGD”) technologies have been widely employed and are well known. Other techniques such as cyclic steam stimulation (“CSS”) and steam flooding (both of which are often commonly referred to as “steam injection” techniques) are also known. The general principle employed by these techniques is to use steam to transfer heat to the heavy oil or oil sands in the reservoir, so that they become less viscous, and thus recoverable by conventional production methods.

[003] There are a number of limitations associated with such methods, such as formation thickness and the requirement for a source of water (which can have implications from an environmental perspective). It is contemplated that many or at least some of these limitations may be addressed or mitigated by the disclosed invention.

[004] Background prior art includes the following:

[005] US Patent No. 3,338,306 discloses a method for recovery of heavy oil which involves running a circuit of small pipe conduits around a formation, and indirectly heating the formation using a heating fluid. This is contemplated for use particularly with shallow reserves, accessed by excavation and does not involve drilled wells. Further, this involves multiple small heating conduits rather than a single large bore lined well. [006] Canadian Patent No. 2,419,325 discloses a method for heavy oil recovery from a formation, using a closed loop circulation of heat transfer medium through a slanted well, thereby indirectly heating the heavy oil and promoting drainage by gravity of reservoir fluid to a flow conduit for collecting said fluid.

[007] US Patent Application No. 14/393,030 (Publication No. 2015/0159917) discloses an apparatus having a heat extraction system for generating geothermal heat from within a drilled well.

[008] US Patent No. 6,588,500 discloses a closed loop heat transfer system for circulating a hot fluid through a tubing. The tubing extends around the outer surface of a production string. The heat transfer system is used to warm the production fluids around the production string in order to prevent paraffins from coagulating around the production string and to lower the viscosity of the oil.

[009] International Application No. PCT/US2017/055872 (WO 2018/071378) discloses a closed loop heating system for enhanced oil recovery. The heating conduit enters one side of the reservoir and exits out the other side (u-shaped).

SUMMARY

[0010] In accordance with one aspect of the present invention, disclosed herein is a method and system for extracting heavy oil. The general concept involves using a closed-loop, non-perforated pipe to deliver heat to a heavy oil reservoir through a heat transfer medium, thereby rendering the heavy oil less viscous and thus extractable using conventional lifting methods.

[0011] In accordance with one disclosed aspect, there is provided a method for extracting viscous hydrocarbons from an underground reservoir bearing said viscous hydrocarbons, comprising: delivering heat to a heating zone of the reservoir using a hot heat transfer medium via a closed-loop heat transfer well, thereby indirectly heating the viscous hydrocarbons in the heating zone, rendering them less viscous to form a reservoir fluid; and extracting the reservoir fluid via a production well; where the heat transfer well comprises: (i) a closed-end casing, extending from a surface above ground to the heating zone, the closed-end casing having a radiant heat portion extending along the heating zone and in thermal contact therewith; (ii) a downcomer pipe, extending from the surface to a first end of the closed-end casing proximate to the radiant heat portion of the closed-end casing; (iii) an artificial lift pump; and (iv) a return pipe, extending from a second end of the closed-end casing and the surface, the second end distal to the first end; wherein the artificial lift pump and the return pipe are configured to return cooled heat transfer medium to the surface; wherein the closed-end casing encases the downcomer pipe and the return pipe; wherein the step of delivering heat to the heating zone comprises injecting the hot heat transfer medium via the downcomer pipe to the radiant heat portion of the closed-end casing.

[0012] In some aspects of the present invention, the heat transfer medium may be a heating oil, glycol, or a blend of mineral oils, but most preferably a biodegradable, food-grade heating oil.

[0013] In some aspects, the step of extracting the reservoir fluids may involve collecting the reservoir fluid using a perforated collector pipe (i.e. a collector pipe having perforations along at least a portion of its length), a slotted liner or other suitable technology. At least a portion of the collector pipe may be oriented substantially horizontally. In some aspects, the collector pipe may be oriented in order to optimize collection or production of the reservoir fluid e.g. according to the surrounding rock formation.

[0014] In yet another aspect, the radiant heat portion is disposed substantially horizontally within the reservoir.

[0015] In accordance with another aspect of the present invention, disclosed herein is a heat transfer well apparatus for delivering heat to a reservoir bearing heavy oil, comprising: (i) a closed-end casing, extending from a surface to a heating zone of the reservoir, the closed-end casing having a radiant heat portion extending along the heating zone and in thermal contact with the heating zone; (ii) a downcomer pipe, extending from the surface to a first end of the closed-end casing proximate to the radiant heat portion of the closed-end casing, the downcomer pipe configured to deliver hot heat transfer medium to the radiant heat portion thereby indirectly heating the viscous hydrocarbons in the heating zone, rendering the viscous hydrocarbons less viscous to form a reservoir fluid, and causing the hot heat transfer medium to become a cooled heat transfer medium; (iii) an artificial lift pump, disposed within the closed-end casing, and disposed proximate a heel position of the closed-end casing; and (iv) a return pipe, extending from a second end of the closed-end casing to the surface, the second end distal to the first end; wherein the closed-end casing encases the downcomer pipe and the return pipe; wherein the artificial lift pump and return pipe are configured to return cooled heat transfer medium to the surface; and wherein the heat transfer medium is heating oil.

[0016] In some aspects of the present invention, a heater for heating the heat transfer medium into the hot heat transfer medium prior to delivery into the downcomer pipe is provided.

[0017] In accordance with another aspect of the present invention, disclosed herein is a system for extracting viscous hydrocarbons from an underground reservoir bearing said viscous hydrocarbons, comprising: the heat transfer well apparatus; and a production well configured to collect and extract the reservoir fluid from a production zone.

[0018] In some aspects of the present invention, the production well comprises a perforated collector pipe, disposed substantially horizontally along the production zone, and having perforations along at least a portion of its length. At least a portion of the collector pipe may be oriented substantially horizontally. In some aspects, the collector pipe may be oriented and disposed in order to optimize collection or production of the reservoir fluid e.g. according to the surrounding rock formation.

[0019] In some aspects, the radiant heat portion is disposed substantially horizontally within the reservoir.

[0020] In yet other aspects, the system may comprise a heater for heating heat transfer medium into the hot transfer medium prior to delivery into the downcomer pipe. In yet other aspects, the heat transfer medium may be circulated within the heat transfer well by delivering the cooled heat transfer medium that is returned to the surface to the heater to generate hot heat transfer medium. [0021] In accordance with another aspect of the present invention, disclosed herein is a method, and corresponding system, for extracting viscous hydrocarbons from an underground reservoir, comprising: delivering water to a heating zone of the reservoir using a water feed pipe; delivering heat to the heating zone using a hot heat transfer medium via a closed-loop heat transfer well, thereby indirectly heating the water delivered from the water feed pipe and generating steam in the heating zone, which steam heats viscous hydrocarbons in the heating zone, rendering the viscous hydrocarbons less viscous to form a reservoir fluid, and causing the hot heat transfer medium to become a cooled heat transfer medium; and extracting the reservoir fluid from a production zone via a production well; wherein the heat transfer well comprises: (i) a closed-end casing, extending from a surface to the heating zone, the closed-end casing having a radiant heat portion extending along the heating zone and in thermal contact with the heating zone; (ii) a downcomer pipe, extending from the surface to a first end of the closed-end casing, proximate to the radiant heat portion of the closed-end casing; (iii) an artificial lift pump; and (iv) a return pipe, extending from a second end of the closed-end casing to the surface, the second end distal to the first end; wherein the closed-end casing encases the downcomer pipe and the return pipe; wherein the artificial lift pump and the return pipe are configured to return cooled heat transfer medium to the surface; wherein the step of delivering heat to the heating zone comprises injecting the hot heat transfer medium via the downcomer pipe to the radiant heat portion of the closed-end casing; and wherein the heat transfer medium is heating oil.

[0022] In some aspects, the production well may be configured to also operate as the water feed system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the following, embodiments of the present disclosure will be described with reference to the appended drawings. However, various embodiments of the present disclosure are not limited to arrangements shown in the drawings. [0024] Fig. 1 is a simplified, schematic view, illustrating an exemplary closed-loop heat transfer well of the present invention in operation.

[0025] Fig. 2 is a schematic view illustrating an exemplary embodiment of the present invention.

[0026] Fig. 3 is a schematic view illustrating an exemplary embodiment of a production well of the present invention.

[0027] Fig. 4 is a schematic view illustrating an exemplary embodiment of the present invention.

[0028] Fig. 5 is a schematic view illustrating an embodiment of the present invention.

DETAILED DESCRIPTION

[0029] In the context of the present invention, heavy crude oil (sometimes referred to herein as “heavy oil”) generally refers to highly-viscous oil that cannot easily flow to production wells under normal reservoir conditions; generally speaking, this is crude oil or liquid petroleum having relatively high viscosity and high specific gravity. The present invention is illustrated herein in the context of a technique for recovering heavy oil, and it is contemplated that the present invention will find application with such. However, it should be understood that the methods and systems disclosed herein may be applied to any underground hydrocarbon resource, which would benefit from being made less viscous and hence, more mobile. It is contemplated that the present invention could be utilized for a “virgin” underground reservoir bearing heavy oil, or for an underground heavy oil-bearing reservoir from which hydrocarbons have already been partially extracted using conventional techniques (thus maximizing the overall recovery of hydrocarbons from such reservoir). Furthermore, the present invention will tend to find particular application where the hydrocarbon reservoir is not a shallow reservoir, but is relatively deeper underground, such that conventional mining methods would not generally be suitable to extract the hydrocarbon resource. [0030] Fig. 1 provides a simplified, schematic view, illustrating an exemplary closed-loop heat transfer well 25 of the present invention in operation. The closed-loop heat transfer well 25 may also be considered as a closed-loop, non-perforated, in situ heat pipe. The primary function of the heat transfer well 25 is to deliver heat to an underground reservoir 13 bearing heavy oil or such other viscous hydrocarbons, lying some distance below the ground surface 16. A heat transfer medium 19 is used to “carry” the heat (in the form of what is sometimes referred to herein as a hot heat transfer medium) to the reservoir 13. This heat causes the indirect heating of the heavy oil that is present in a heating zone 37 of the reservoir 13, making the heavy oil less viscous (and hence more mobile/flowable), and turning it into a reservoir fluid. The resulting reservoir fluid, comprising heavy oil, may be collected and extracted from a production zone using a production well (not shown in Fig. 1); the production well may be any conventional production apparatus suitable for extracting the heavy oil reservoir fluid from underground and delivering it to the ground surface for further processing (such as cleaning, separation, etc.), where required or appropriate, and/or for use in other applications. The final heavy oil product can be made available for commercial sale.

[0031] Typically, the heavy oil reservoir 13 may lie deep underground, such as from 50m to 1000m. In some cases, the reservoir may be present underground in multiple layers.

[0032] In the context of the present invention, the heat transfer medium 19 may be heating oil, mineral oil, glycol or a blend of the foregoing. Most preferably, the heat transfer medium is a bio-degradable, food-grade heating oil, such as for example those heat transfer fluids which are made commercially available under the Paratherm™ brand. Heating oil is considered a particularly good candidate, since it can generally operate without complications within the range of temperatures that the heat transfer medium might be expected to encounter in operation - for example, between -40°C to 400°C. (In warmer climates, the heat transfer medium will most probably operate in temperatures between 50°C to 400°C, whereas in colder climates such as the Albertan oil sands in winter, the heat transfer medium may need to operate in temperatures between -40°C to 350°C). However, it should be understood that other substances may be used as the heat transfer medium. Further, although it is contemplated that the heat transfer medium is preferably a fluid under typical operating conditions (and indeed, the heat transfer medium is generally described herein as a fluid/liquid), a heat transfer medium that is gaseous may also be used, applying similar principles as described herein. Considerations for a suitable heat transfer medium can include high to moderate specific heat capacity (so that the heat transfer medium is effective in being able to “store” and “release” a reasonable amount of heat), low viscosity, environmental factors, cost, stability (under a wide range of temperatures), low chemical reactivity, availability of the substance, ease and safety of handling, low volatility /low vapour pressure, etc.

[0033] Water or steam has commonly been used as a heat transfer medium in a number of oilfield applications, such as in SAGD for example. As mentioned above, due to the general requirement for a large water source (typically a naturally occurring water source), the use of water often has a number of environmental implications. As such, it is contemplated that, in many circumstances, an effective heat transfer medium other than water would be desirable.

[0034] Referring to Fig. 1 , a closed-loop heat transfer well 25 is shown, extending from the ground surface 16 to within an underground heavy oil-bearing reservoir 13. The closed-loop heat transfer well 25 comprises: a closed-end casing 31 , a downcomer pipe 40, and an artificial lift pump 46, and a return pipe 43.

[0035] The closed-end casing 31 is essentially a closed-loop, large bore pipe extending from the surface 16 at one end to within the reservoir 13 at the other end. The closed-end casing has a radiant heat portion 34 that generally is disposed within the reservoir 13, and more specifically within a heating zone 37 of the reservoir. The heating zone 37 refers to the region of the reservoir, generally surrounding the radiant heat portion 34, from where the viscous heavy oil will be indirectly heated in order to form a reservoir fluid. The radiant heat portion 34 is in thermal contact with the heating zone 37 such that heat may be transferred from radiant heat portion 34 to the heating zone 37 primarily via conduction (and to a lesser extent, convection, and to a much lesser extent, radiation).

[0036] The closed-end casing 31 is generally made from a material that is thermally conductive (to facilitate heat transfer) and relatively strong/sturdy. In a preferred embodiment, the closed-end casing may also be further encased by thermal cement 64 to further facilitate heat transfer to the heating zone.

[0037] The downcomer pipe 40 is an open-ended pipe, having one or more openings 42 at its lower end (in the embodiment shown, only one opening 42 is provided). The downcomer pipe 40 is a narrow bore pipe, having a diameter that is less than the bore of the closed-end casing 31 . The downcomer pipe 40 is disposed inside the closed-end casing 31 , and extends from the surface 16 to a toe position 41 of the closed-end casing, proximate to the radiant heat portion 34. The downcomer pipe 40 is configured to carry and deliver hot heat transfer medium to the radiant heat portion 34 of the closed-end casing 31. This is generally achieved by injecting the hot heat transfer medium 22 under pressure into the downcomer pipe 40. The hot heat transfer medium exits the downcomer pipe 40 out of the opening 42 and flows into the radiant heat portion 34, and circulates therewithin. The amount of heat transfer medium inside the closed-end casing 31 is controlled (by controlling the inflow and outflow/return of the heat transfer medium) such that the fluid level 51 is maintained at or about a desired level; the appropriate fluid level may be determined by various considerations, including, for example, providing for efficient heat transfer, efficient circulation and return of heat transfer medium, and according to the configuration and/or orientation of the radiant heat portion 34. At this point, the hot heat transfer medium 22 circulating in the radiant heat portion 34 transfers some of its heat, primarily through conduction, to the surrounding heating zone 37, thereby warming the viscous heavy oil in the surrounding formation. This renders the heavy oil in the heating zone less viscous and more mobile, forming a reservoir fluid. At the same time, as the hot heat transfer medium loses heat, it becomes cooler - referred to as a cooled heat transfer medium 49.

[0038] The downcomer pipe 40 may be thermally insulated with downcomer insulation 61 , in order to minimize heat loss from the pipe, until the heat transfer medium is delivered to its target destination, within the radiant heat portion 34 - in this case, the toe position 41. In some embodiments, however, heat loss may be less of a concern, or may even be desirable, once the heat transfer medium reaches the radiant heat portion 34; in that case, it may be not necessary (or less so) to insulate that part of the downcomer pipe which is proximate to the radiant heat portion 34.

[0039] The artificial lift pump 46 is shown disposed within the closed-end casing 31 , and disposed proximate to a heel position 50 of the closed-end casing 31. The artificial lift pump 46 may be any of a number of conventional pumps known in the art which may be used to deliver heat transfer medium back to the surface. This may include for example: a Progressive Cavity Pump (“PCP”), an Electrical Submersible Pump (“ESP”), a Sucker Rod Pump (SRP”), compressor, induction pump, hydraulic pump, pump jack, or any other form of circulation pump. Depending on the nature/type of the artificial lift pump 46 employed, in some alternative embodiments, the artificial lift pump may, instead of being disposed in- situ in the reservoir 13, be located at the surface.

[0040] The return pipe 43 is disposed inside the closed-end casing 31 , and is in engagement with the artificial lift pump 46. The return pipe 43 extends from a position proximate the heel position 50 of the closed-end casing, beneath the fluid level 51 of the heat transfer medium 19, to the surface 16. The artificial lift pump 46 and the return pipe 43 are configured to return cooled heat transfer medium 49 to the surface, following which the heat transfer medium can be reheated and recirculated into the closed-loop heat transfer well 25. In the embodiment of Fig. 1 , the artificial lift pump 46 is shown located inside the closed-end casing 31 , and connected to the lower end of the return pipe 43.

[0041] In a preferred embodiment, the radiant heat portion 34 of the closed- end casing 31 is disposed substantially horizontally, as shown in Fig. 1. However, it should be understood that the radiant heat portion 34 may be disposed in other configurations (for example, the radiant heat portion may be slanted or even substantially vertical), as may be considered appropriate in light of factors such as the location/make-up of the reservoir and/or the surrounding formation. [0042] Furthermore, while the downcomer pipe 40 is illustrated herein as a pipe with a single opening 42 at its lower end, so that the hot heat transfer medium is delivered first to a position proximate the toe position 41 of the closed- end casing, it is also contemplated that the downcomer pipe 40 may be provided with multiple openings or perforations at various locations along its length, to allow for relatively even heat distribution along the length of the downcomer pipe (or at least within the radiant heat portion 34) or to otherwise allow for multi-staged heat distribution.

[0043] It should be understood that an alternative configuration for the downcomer pipe 40 and return pipe 43 within the closed-end casing is also possible. Instead of the having the lower end of the downcomer pipe extend to the toe position 41 , and the lower end of the return pipe extend from the heel position 50, this can be reversed so that the downcomer pipe extends to the heel position and the return pipe extends from the toe position, although this is less preferred. What matters is that the lower ends of the downcomer pipe 40 and the return pipe 43 generally be at opposing distal ends of the radiant heat portion 34, so there is a temperature gradient and a flow of hot heat transfer medium, and so that the heat transfer medium that ends up being pumped up through the return pipe 43 has been substantially cooled, i.e. cooled heat transfer medium 49.

[0044] Fig. 2 is a schematic view illustrating some additional details of the closed-loop heat transfer well 25 of Fig. 1 as installed in a heavy oil reservoir; the heavy oil bearing reservoir may also be referred to as an oil zone 28. In this embodiment, a heat medium heater 52 is shown, which is used to heat a supply of heat transfer medium 19 into hot heat transfer medium 22, before it is fed into the downcomer pipe 40 at well head 58. The heat medium heater 52 may be any heat source, or combination of heat sources, which can be utilized to impart heat to the heat transfer medium 19; this could include, for example, an electrical heater, a geo-thermal heater, a compressed gas heat, a natural gas heater, a steam based heater, a solar power-based heater, heat exchanger based upon combustion of flue gas, etc. The return pipe 43 returns cooled heat transfer medium 49 from the heel position to the surface 16. The cooled heat transfer medium 49 is then routed to the heat medium heater 52 to serve as a supply of heat transfer medium, and recirculated into the closed-loop heat transfer well 25. In this manner, the closed-loop heat transfer well operates in a closed loop, with practically no loss of heat transfer medium 19. When heating oil is used as the heat transfer medium, it is contemplated that the temperature of the hot heat transfer medium 22 may be heated preferably to as high as approximately 350°C to 400°C. (Where it is possible to use such higher temperatures of about 350°C to 400°C, this may provide an additional benefit in that it can induce cracking of the heavy oil, thus releasing light end oil which can help create a driving flow of reservoir fluid in the reservoir). In addition, the heat medium heater 52 may be configured to control the temperature of the hot heat transfer medium 22 as it is fed into the closed-loop heat transfer well.

[0045] Fig. 3, a schematic view showing an exemplary embodiment of a production well 67, to be used in conjunction with the closed-loop heat transfer well 25. The production well 67 may be any conventional production well that may be suitably used to collect reservoir fluid 71 and deliver it to the surface 16. The exemplary production well 67 shown in Fig. 3 comprises at least one collector pipe 70, which is generally disposed in a production zone 76, a distance from the heating zone 37. When heavy oil (or other viscous hydrocarbons) in the heating zone 37 is indirectly heated by the heat from the hot heat transfer medium 22 and in the radiant heat portion 34 of a nearby closed-loop heat transfer well 25, the heavy oil becomes less viscous and more flowable, and forms a reservoir fluid 71. Depending on the nature of the surrounding formation, the reservoir fluid 71 may also contain water (e.g. present in the ground water) and be in the form of an emulsion. This reservoir fluid 71 flows to and “pools” at the production zone 76. The at least one collector pipe 70 is generally provided with a number of perforations (not shown) along at least a portion of its length, through which perforations, the reservoir fluid 71 may be made to enter the collector pipe 70. The production well 67 may be provided with a producer pipe 74 disposed therewithin. The producer pipe 74 is in engagement with a production pump 73, which may be any of a number of conventional artificial lift pumps as previously discussed. The production pipe 73 and the producer pipe 74 are configured to deliver the reservoir fluid I heavy oil deposit (in the form of a recovered heavy oil 72) to the surface 16 for further processing. [0046] In some embodiments of the present invention, the collector pipe 70 is positioned proximate to, but a certain distance from, the heating zone 37 (or from the radiant heat portion 34 of a closed-loop heat transfer well 25). In some embodiments, the collector pipe 70 may be positioned a distance substantially vertically below the heating zone 37; in other embodiments, the collector pipe may be positioned a distance substantially vertically above the heating zone 37. In some embodiments, at least a portion of the collector pipe 70 may be substantially horizontal. In other embodiments, the collector pipe 70 may be positioned to generally parallel the radiant heat portion 34 of a closed-end heat transfer well 25. In yet other embodiments, multiple collector pipes 70 may be utilized; for example, multiple collector pipes may be disposed at various locations surrounding the heating zone 37 or the radiant heat portion 34. The collector pipe(s) 70 may be otherwise positioned and/or oriented in order to optimize the collection and production of reservoir fluid, e.g. according to the surrounding rock formation. In yet other embodiments, a project may involve multiple closed-loop heat transfer wells 25 and multiple collector pipes 70 disposed around a heavy oil-bearing reservoir 13.

[0047] It should be understood that the precise specifications for the system 10, comprising a closed-loop heat transfer well 25 and a producer well 67 (including of the heat transfer portion 34 and the at least one collector pipe 70) are largely formation dependent. Such specifications include for example pipe length, diameter, bore size, pipe wall thickness, material of construction, orientation, position, distance between the heat transfer portion and the collector pipes, etc. In practice, for each project or application, such specifications are carefully determined, customized and engineered according to the requirements and operating conditions of such project, and the geology of the surrounding formation, in order to optimize the operation of the system and recovery of heavy oil. However, in order to provide an idea of context, the closed-end casing 31 can generally be a pipe of diameter 8” to 24”. In the case of the collector pipe 70, this can generally be a pipe of 2” to 12” diameter (although it is important to note that in the case of the collector pipe, conventional and industry-proven technology will generally be utilized). The lengths of these pipes can be from several hundred meters to 1 km or greater. The heat transfer portion 34 of a closed-loop heat transfer well and a collector pipe 70 can be positioned such that they are anywhere between 1 m to 100 m apart; it is contemplated that separation distances of between 5 m to 25 m may work well in practice (this is determined to a large extent on the size of the heating zone - the distance beyond the heat transfer portion where viscous heavy oil in the reservoir can be sufficiently heated to generate reservoir fluid - and the flow of the reservoir fluid).

[0048] Referring to Fig. 4, this is a schematic diagram illustrating an exemplary system 10 of the closed-loop heat transfer well 25 and a corresponding production well 67. In this particular embodiment, the closed-loop heat transfer well 25 is also provided with a heat medium storage tank 55 for storing excess heat transfer medium 19 and acts as a ready supply thereof. In the production well 67, the production pipe 73 leads to a water knock-out drum 79 at the surface. Depending on the amount of water in the reservoir 13 generally, the reservoir fluid 71 will often contain water as well as the heavy oil, which together will typically exist as an emulsion. After this reservoir fluid 71 is collected and pumped to the surface, the knock-out drum 79 is utilized to separate the water content and the heavy oil. As shown, a water recovery pump 82 pumps out the water to a water recovery tank 85, where the water is stored. The heavy oil is passed to another stream and stored, for example, in an oil storage tank 88.

[0049] Fig. 5 illustrates another embodiment in which the closed-loop heat transfer well 25 operates in conjunction with a water feed system 90 to generate steam 97. The water feed system 90 functions to deliver water to the heating zone 37. The water is fed through the perforated water feed pipe 94, where it then flows to the heating zone 37. The water feed pipe 94 is generally positioned proximate to the radiant heat portion 34 of a closed-loop heat transfer well 25. As the main purpose of the water feed pipe 94 is simply to deliver water close to where the radiant heat portion is disposed, it may be positioned generally parallel with the radiant heat portion, at a separation therefrom of say, 1 m - 10m or more. In this case, the heat from the radiant heat portion 34 heats up the water delivered from the water feed system 90 into steam 97. The steam may be used to heat the heavy oil or other hydrocarbons in the heating zone 37, as described above, albeit more directly. (Besides the actual heating effect, the steam may additionally also render the heavy oil less viscous - likely through the formation of an emulsion). Again, this will result in the viscous heavy oil becoming less viscous and more mobile, following which, it will flow to a production zone in the form of a reservoir fluid, where it can be collected and extracted by one or more production wells 67 as described before. The water feed system 90 may be a separate system as shown, or it may be incorporated into the production well system 67 shown in Fig. 4. In the latter case, the water that is separated from the reservoir fluid and stored, can be used as a source of water for the water feed system 90. Since the water is recirculated for the most part, this reduces the requirement to have a large and readily available, naturally occurring water source, which may be desirable from an environmental perspective. It is also contemplated that this process of steam generation can be enhanced with the injection of an additional solvent into the water feed system, such as liquefied natural gas (“LNG”), butane or the hydrocarbons.

[0050] The disclosed invention can provide a number of advantages/benefits as compared with the conventional SAGD process (which to date is the only other commercially viable process for in-situ heavy oil extraction in the “Oil Sands”). As compared with SAGD, there is a greatly reduced requirement for fresh water (which is increasingly becoming a significant factor for heavy oil recovery projects due to environmental concerns). Further, it is anticipated that on a per barrel of oil produced basis, the present system will likely result in significantly less greenhouse gas emissions as compared with conventional SAGD processes (due to reduced natural gas consumption). Furthermore, the footprint of the present system, in terms of equipment required and land disturbance, is also likely to less than for an equivalent SAGD operation. In addition, it is contemplated that the present method and system is suitable for use in different kinds of formation, including those that are carbonate, rock and sandladen.

[0051] While specific embodiments have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Claims

1 . A method for extracting viscous hydrocarbons from an underground reservoir bearing said viscous hydrocarbons, comprising: delivering heat to a heating zone of the reservoir using a hot heat transfer medium via a closed-loop heat transfer well, thereby indirectly heating the viscous hydrocarbons in the heating zone, rendering the viscous hydrocarbons less viscous to form a reservoir fluid, and causing the hot heat transfer medium to become a cooled heat transfer medium; and extracting the reservoir fluid from a production zone via a production well; wherein the heat transfer well comprises:

(i) a closed-end casing, extending from a surface to the heating zone, the closed-end casing having a radiant heat portion extending along the heating zone and in thermal contact with the heating zone;

(ii) a downcomer pipe, extending from the surface to a first end of the closed-end casing, proximate to the radiant heat portion of the closed-end casing;

(iii) an artificial lift pump; and

(iv) a return pipe, extending from a second end of the closed-end casing to the surface, the second end distal to the first end; wherein the closed-end casing encases the downcomer pipe and the return pipe; wherein the artificial lift pump and the return pipe are configured to return the cooled heat transfer medium to the surface; wherein the step of delivering heat to the heating zone comprises injecting the hot heat transfer medium via the downcomer pipe to the radiant heat portion of the closed-end casing; and wherein the heat transfer medium is heating oil.

2. The method of claim 1 , wherein the step of extracting the reservoir fluids comprises collecting the reservoir fluids using a perforated collector pipe.

3. The method of claim 1 , wherein the radiant heat portion is disposed substantially horizontally within the reservoir.

4. The method of claim 1 , wherein prior to the step of delivering heat, a heat transfer medium is heated in a heating step to form the hot heat transfer medium.

5. A heat transfer well for delivering heat to a heating zone of an underground reservoir bearing viscous hydrocarbons, comprising:

(i) a closed-end casing, extending from a surface to the heating zone of the reservoir, the closed-end casing having a radiant heat portion extending along the heating zone and in thermal contact with the heating zone;

(ii) a downcomer pipe, extending from the surface to a first end of the closed-end casing proximate to the radiant heat portion of the closed-end casing, the downcomer pipe configured to deliver hot heat transfer medium to the radiant heat portion thereby indirectly heating the viscous hydrocarbons in the heating zone, rendering the viscous hydrocarbons less viscous to form a reservoir fluid, and causing the hot heat transfer medium to become a cooled heat transfer medium;

(iii) an artificial lift pump; and

(iv) a return pipe, extending from a second end of the closed-end casing to the surface, the second end distal to the first end; wherein the closed-end casing encases the downcomer pipe and the return pipe; and wherein the artificial lift pump and the return pipe are configured to return cooled heat transfer medium to the surface; and wherein the heat transfer medium is heating oil.

6. The heat transfer well of claim 5, wherein the radiant heat portion is disposed substantially horizontally within the reservoir.

7. The heat transfer well of claim 5, additionally comprising a heater for heating heat transfer medium into the hot transfer medium prior to delivery into the downcomer pipe.

8. A system for extracting viscous hydrocarbons from an underground reservoir bearing said viscous hydrocarbons, comprising: a heat transfer well; and a production well, wherein the heat transfer well comprises:

(i) a closed-end casing, extending from a surface to a heating zone of the reservoir, the closed-end casing having a radiant heat portion extending along the heating zone and in thermal contact with the heating zone;

(ii) a downcomer pipe, extending from the surface to a toe position of the closed-end casing proximate to the radiant heat portion of the closed-end casing, the downcomer pipe configured to deliver hot heat transfer medium to the radiant heat portion thereby indirectly heating the viscous hydrocarbons in the heating zone, rendering the viscous hydrocarbons less viscous to form a reservoir fluid, and causing the hot heat transfer medium to become a cooled heat transfer medium;

(iii) an artificial lift pump; and

(iv) a return pipe, extending from a heel position of the closed-end casing to the surface; wherein the closed-end casing encases the downcomer pipe and the return pipe; and wherein the artificial lift pump and return pipe are configured to return cooled heat transfer medium to the surface; wherein the production well is configured to extract the reservoir fluid from a production zone; and wherein the heat transfer medium is heating oil.

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9. The system of claim 8, wherein the production well comprises a perforated collector pipe disposed substantially horizontally along the production zone.

10. The system of claim 8, wherein the radiant heat portion is disposed substantially horizontally within the reservoir.

11 . The system of claim 8, additionally comprising a heater for heating heat transfer medium into the hot transfer medium prior to delivery into the downcomer Pipe.

12. A method for extracting viscous hydrocarbons from an underground reservoir bearing said viscous hydrocarbons, comprising: delivering water to a heating zone of the reservoir using a water feed pipe; delivering heat to the heating zone using a hot heat transfer medium via a closed-loop heat transfer well, thereby indirectly heating the water delivered from the water feed pipe and generating steam in the heating zone, which steam heats viscous hydrocarbons in the heating zone, rendering the viscous hydrocarbons less viscous to form a reservoir fluid, and causing the hot heat transfer medium to become a cooled heat transfer medium; and extracting the reservoir fluid from a production zone via a production well; wherein the heat transfer well comprises:

(iii) an artificial lift pump; and

(iv) a return pipe, extending from a second end of the closed-end casing to the surface, the second end distal to the first end;

19 wherein the closed-end casing encases the downcomer pipe and the return pipe; wherein the artificial lift pump and the return pipe are configured to return cooled heat transfer medium to the surface; wherein the step of delivering heat to the heating zone comprises injecting the hot heat transfer medium via the downcomer pipe to the radiant heat portion of the closed-end casing; and wherein the heat transfer medium is heating oil.

13. The method of claim 12, wherein the production well is configured to operate as the water feed system.

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