Patent Grant
10344578
The present invention relates to the field of hydrocarbon resource processing, and, more particularly, to an antenna assembly isolator and related methods.
Energy consumption worldwide is generally increasing, and conventional hydrocarbon resources are being consumed. In an attempt to meet demand, the exploitation of unconventional resources may be desired. For example, highly viscous hydrocarbon resources, such as heavy oils, may be trapped in sands where their viscous nature does not permit conventional oil well production. This category of hydrocarbon resource is generally referred to as oil sands. Estimates are that trillions of barrels of oil reserves may be found in such oil sand formations.
In some instances, these oil sand deposits are currently extracted via open-pit mining. Another approach for in situ extraction for deeper deposits is known as Steam-Assisted Gravity Drainage (SAGD). The heavy oil is immobile at reservoir temperatures, and therefore, the oil is typically heated to reduce its viscosity and mobilize the oil flow. In SAGD, pairs of injector and producer wells are formed to be laterally extending in the ground. Each pair of injector/producer wells includes a lower producer well and an upper injector well. The injector/production wells are typically located in the payzone of the subterranean formation between an underburden layer and an overburden layer.
The upper injector well is used to typically inject steam, and the lower producer well collects the heated crude oil or bitumen that flows out of the formation, along with any water from the condensation of injected steam. The injected steam forms a steam chamber that expands vertically and horizontally in the formation. The heat from the steam reduces the viscosity of the heavy crude oil or bitumen, which allows it to flow down into the lower producer well where it is collected and recovered. The steam and gases rise due to their lower density. Gases, such as methane, carbon dioxide, and hydrogen sulfide, for example, may tend to rise in the steam chamber and fill the void space left by the oil defining an insulating layer above the steam. Oil and water flow is by gravity driven drainage urged into the lower producer well.
Operating the injection and production wells at approximately reservoir pressure may address the instability problems that adversely affect high-pressure steam processes. SAGD may produce a smooth, even production that can be as high as 70% to 80% of the original oil in place (OOIP) in suitable reservoirs. The SAGD process may be relatively sensitive to shale streaks and other vertical barriers since, as the rock is heated, differential thermal expansion causes fractures in it, allowing steam and fluids to flow through. SAGD may be twice as efficient as the older cyclic steam stimulation (CSS) process.
Many countries in the world have large deposits of oil sands, including the United States, Russia, and various countries in the Middle East. Oil sands may represent as much as two-thirds of the world's total petroleum resource, with at least 1.7 trillion barrels in the Canadian Athabasca Oil Sands, for example. At the present time, only Canada has a large-scale commercial oil sands industry, though a small amount of oil from oil sands is also produced in Venezuela. Because of increasing oil sands production, Canada has become the largest single supplier of oil and products to the United States. Oil sands now are the source of almost half of Canada's oil production, while Venezuelan production has been declining in recent years. Oil is not yet produced from oil sands on a significant level in other countries.
U.S. Published Patent Application No. 2010/0078163 to Banerjee et al. discloses a hydrocarbon recovery process whereby three wells are provided: an uppermost well used to inject water, a middle well used to introduce microwaves into the reservoir, and a lowermost well for production. A microwave generator generates microwaves which are directed into a zone above the middle well through a series of waveguides. The frequency of the microwaves is at a frequency substantially equivalent to the resonant frequency of the water so that the water is heated.
Along these lines, U.S. Published Patent Application No. 2010/0294489 to Dreher, Jr. et al. discloses using microwaves to provide heating. An activator is injected below the surface and is heated by the microwaves, and the activator then heats the heavy oil in the production well. U.S. Published Patent Application No. 2010/0294488 to Wheeler et al. discloses a similar approach.
U.S. Pat. No. 7,441,597 to Kasevich discloses using a radio frequency generator to apply radio frequency (RF) energy to a horizontal portion of an RF well positioned above a horizontal portion of an oil/gas producing well. The viscosity of the oil is reduced as a result of the RF energy, which causes the oil to drain due to gravity. The oil is recovered through the oil/gas producing well.
U.S. Pat. No. 7,891,421, also to Kasevich, discloses a choke assembly coupled to an outer conductor of a coaxial cable in a horizontal portion of a well. The inner conductor of the coaxial cable is coupled to a contact ring. An insulator is between the choke assembly and the contact ring. The coaxial cable is coupled to an RF source to apply RF energy to the horizontal portion of the well.
Unfortunately, long production times, for example, due to a failed start-up, to extract oil using SAGD may lead to significant heat loss to the adjacent soil, excessive consumption of steam, and a high cost for recovery. Significant water resources are also typically used to recover oil using SAGD, which impacts the environment. Limited water resources may also limit oil recovery. SAGD is also not an available process in permafrost regions, for example, or in areas that may lack sufficient cap rock, are considered “thin” payzones, or payzones that have interstitial layers of shale. While RF heating may address some of these shortcomings, further improvements to RF heating may be desirable. For example, it may be relatively difficult to install or integrate RF heating equipment into existing wells.
In view of the foregoing background, it is therefore an object of the present disclosure to provide a hydrocarbon recovery system that is efficient and robust.
This and other objects, features, and advantages in accordance with the present disclosure are provided by a hydrocarbon recovery system comprising an RF source, and an RF antenna assembly coupled to the RF source and within a wellbore in a subterranean formation for hydrocarbon resource recovery. The RF antenna assembly may include first and second tubular conductors, a dielectric isolator, and first and second electrical contact sleeves respectively coupled between the first and second tubular conductors and the dielectric isolator so that the first and second tubular conductors define a dipole antenna. The RF antenna assembly may comprise an RF transmission line comprising an inner conductor and an outer conductor extending within the first tubular conductor, and a feed structure coupled to a distal end of the RF transmission line. The feed structure may comprise a first radially compressible connector coupled to the outer conductor of the RF transmission line to slidably engage adjacent portions of the first electrical contact sleeve. The feed structure may also comprise a second radially compressible connector coupled to the inner conductor of the RF transmission line to slidably engage adjacent portions of the second electrical contact sleeve, and a dielectric tube coupled between the first and second radially compressible connectors. Advantageously, the RF antenna assembly may be readily assembled within the wellbore.
Additionally, the first electrical contact sleeve may comprise a first outer sleeve and a first inner electrically conductive liner therein, and the second electrical contact sleeve may comprise a second outer sleeve and a second inner electrically conductive liner therein. The first and second inner electrically conductive liners may each comprise stainless steel. The first radially compressible connector may comprise a plurality of first watchband springs, and the second radially compressible connector may comprise a plurality of second watchband springs.
In some embodiments, the RF antenna assembly may include a plurality of first seals associated with the plurality of first watchband springs, and a plurality of second seals associated with the plurality of second watchband springs. More specifically, the dielectric isolator may comprise a tubular dielectric member and a polytetrafluoroethylene (PTFE) coating thereon. The tubular dielectric member may comprise cyanate ester. The RF antenna assembly may comprise an insulating coating on the first and second electrical contact sleeves and at least a portion of the first and second tubular conductors. For example, the insulating coating may comprise PTFE.
Another aspect is directed to an RF antenna assembly to be positioned within a wellbore in a subterranean formation for hydrocarbon resource recovery. The RF antenna assembly may include first and second tubular conductors, a dielectric isolator, and first and second electrical contact sleeves respectively coupled between the first and second tubular conductors and the dielectric isolator so that the first and second tubular conductors define a dipole antenna. The RF antenna assembly may include an RF transmission line comprising an inner conductor and an outer conductor extending within the first tubular conductor, and a feed structure coupled to a distal end of the RF transmission line. The feed structure may include a first radially compressible connector coupled to the outer conductor of the RF transmission line to slidably engage adjacent portions of the first electrical contact sleeve, a second radially compressible connector coupled to the inner conductor of the RE transmission line to slidably engage adjacent portions of the second electrical contact sleeve, and a dielectric tube coupled between the first and second radially compressible connectors.
Yet another aspect is directed to a method for making an RF antenna assembly positioned within a wellbore in a subterranean formation for hydrocarbon resource recovery. The method may include positioning first and second tubular conductors, first and second electrical contact sleeves, and a dielectric isolator in the wellbore and so that the first and second electrical contact sleeves are respectively coupled between the first and second tubular conductors and the dielectric isolator. The first and second tubular conductors may define a dipole antenna. The method may include coupling a feed structure to a distal end of an RF transmission line. The RF transmission line may include an inner conductor and an outer conductor. The feed structure may include a first radially compressible connector coupled to the outer conductor of the RF transmission line to slidably engage adjacent portions of the first electrical contact sleeve, a second radially compressible connector coupled to the inner conductor of the RF transmission line to slidably engage adjacent portions of the second electrical contact sleeve, and a dielectric tube coupled between the first and second radially compressible connectors. The method may include positioning the RF transmission line within the wellbore and extending within the first tubular conductor.
The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which several embodiments of the invention are shown. This present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. Like numbers refer to like elements throughout.
In typical hydrocarbon recovery via RF heating, in order to heat surrounding media and more easily facilitate extraction of hydrocarbon product from the ground, an antenna is deployed underground in proximity to an oil well producer, necessitating an electrically insulative, non-energy absorbing structural element to support the radiating components of a center-feed, dipole antenna assembly. The dipole antenna assembly may need a design: with minimal dielectric heating; that can survive extreme temperatures; and that can survive exposure to environmental fluids (i.e. corrosive materials) while maintaining structural integrity and preventing arcing between elements at high RF power.
Referring initially to
The RF antenna assembly 104 illustratively includes first and second tubular conductors (e.g. comprising high strength steel) 106, 107, a dielectric isolator 108, and first and second electrical contact sleeves (e.g. comprising high strength steel) 109, 110 respectively coupled between the first and second tubular conductors and the dielectric isolator so that the first and second tubular conductors define a dipole antenna. The hydrocarbon recovery system 100 illustratively includes a debris seal packer 260 between an intermediate casing, upward portion of the wellbore 255, and the RF antenna assembly 104.
The RF antenna assembly 104 illustratively includes an RF transmission line 103 comprising an inner conductor 257 (
The RF transmission line 103 illustratively includes a build section (not shown) extending from a surface of the subterranean formation 102 to a heel portion of the wellbore 255, and an electromagnetic choke assembly section 114 coupled to the build section. The electromagnetic choke assembly section 114 comprises a heel isolator 118 surrounding the RF transmission line 103. The RF electromagnetic choke assembly section 114 illustratively includes a plurality of tool centralizers 117a-117e coupled to the RE transmission line 103 and longitudinally spaced apart thereon. The RF transmission line 103 illustratively includes a guide string 113 at a distal end, and the RF antenna assembly 104 also comprises a plurality of tool centralizers 115a-115f longitudinally spaced apart on the guide string.
Referring now additionally to
Helpfully, in embodiments where the heel dielectric tube 119 comprises a composite material (e.g. cyanate ester), the heel outer and inner coatings 122, 123 provide chemical and mechanical abrasion protection from breakdown of the heel dielectric tube 119 during hydrocarbon resource production. In particular, the heel outer and inner coatings 122, 123 protect the heel dielectric tube 119 from the effects of hydrolysis (i.e. steam), corrosive gases/fluids, all fluids (e.g. hydrocarbon, oil, bitumen, seawater, water, etc.), and hydrogen sulfide.
The RF antenna assembly 104 (
The feed structure 135 illustratively includes a second radially compressible connector 137 coupled to the inner conductor 257 of the RF transmission line 103. The second radially compressible connector 137 is configured to slidably engage adjacent portions of the second electrical contact sleeve 110, thereby electrically coupling the inner conductor 257 to the second electrical contact sleeve. The feed structure 135 illustratively includes a dielectric tube (e.g. cyanate ester) 138 coupled between the first and second radially compressible connectors 136, 137. (
Additionally, the first electrical contact sleeve 109 illustratively includes a first outer sleeve 155a and a first inner electrically conductive liner 155c therein. The second electrical contact sleeve 110 illustratively includes a second outer sleeve 155b and a second inner electrically conductive liner 155d therein. In some embodiments, the first and second inner electrically conductive liners 155c-155d may each comprise stainless steel for corrosion resistance with sufficient electrical conductivity.
In the illustrated embodiment, the first and second tubular conductors 106, 107, the dielectric isolator 108, the first and second electrical contact sleeves 109, 110 are all part of the well casing, i.e. these components directly contact adjacent portions of the subterranean formation 102. As discussed herein, this reduces the complexity of the installation of the hydrocarbon recovery system 100 within the subterranean formation 102.
Referring now additionally to
The dielectric isolator 108 may comprise a tubular dielectric member (e.g. cyanate ester) 124, an outer coating (e.g. PTFE) 125a on the tubular dielectric member, and an inner coating (e.g. PTFE) 125b on the tubular dielectric member. The outer and inner coatings 125a, 125b may be, for example, 0.10-0.250 inches thick. The tubular dielectric member 124 may comprise cyanate ester, for example. In some embodiments, the tubular dielectric member 124 and the heel dielectric tube 119 may each comprise longitudinally spaced outer diameter abrasion rings. These outer diameter abrasion rings are portions of the tubular dielectric member 124 and the heel dielectric tube 119 that have increased thickness, for example, 0.100 inches thicker, and provide enhanced mechanical strength.
The dielectric isolator 108 illustratively includes opposing ends 129a-129b fitted onto respective ends of the tubular dielectric member 124. As perhaps best seen in
Referring now additionally to
Advantageously, in the disclosed RF antenna assembly 104, the dipole antenna is assembled in-situ and part of the well casing. The RF transmission line 103 is assembled above ground and pushed downward into the wellbore 255. Accordingly, there needs to be some longitudinal give built into the design to maintain a continuous electrical coupling with the dipole antenna elements, i.e. the first and second electrical contact sleeves 109, 110, as the wellbore 255 increases in temperature, causing the RF transmission line 103 to elongate.
A consequence of this design, the dipole antenna elements, i.e. the first and second tubular conductors 106, 107, the first and second electrical contact sleeves 109, 110, and the dielectric isolator 108, will remain in the wellbore 255 for the life of the well. Positively, the insulating coating 126a-126b will provide chemical and mechanical abrasion (mainly during installation) protection for the RF antenna assembly 104 while is sits in the wellbore 255. Another facet of the RF antenna assembly 104 is that the first and second tubular conductors 106, 107, the first and second electrical contact sleeves 109, 110, and the dielectric isolator 108 include mechanical strength to support the structural loads during installation and operation.
The first radially compressible connector 136 illustratively includes a plurality of first watchband springs 153a-153d, which are electrically coupled to the outer conductor 256 of the RF transmission line 103. (See
The second radially compressible connector 137 illustratively includes a plurality of second watchband springs 142a-142d, which are electrically coupled to the inner conductor 257 of the RF transmission line 103. In the illustrated embodiment, the RF antenna assembly 104 illustratively includes a plurality of second seals (e.g. swellable seals) 144a-144b associated with the plurality of second watchband springs 142a-142d, a plurality of second wipers 143a-143b associated with the plurality of second watchband springs, and a second spring loaded spacer 145 associated with the second radially compressible connector 137. Advantageously, due to the second wipers 143a-143b, second seals 144a-144b, and second watchband springs 142a-142d, the second radially compressible connector 137 maintains solid and clean mechanical contact with the second inner electrically conductive liner 155d.
As perhaps best seen in
Referring now additionally to
Advantageously, the disclosed RF antenna assembly 104 is of appropriate dimensions to structurally support the radiating elements of the in-situ dipole antenna, and the dielectric isolator 108 of a length providing adequate standoff distance to ensure no arcing between the polarized components over a wide range of environmental conditions. The disclosed RF antenna assembly 104 comprises materials of sufficient electrical properties to provide minimal absorption of radiated energy, and with retention of structural integrity. Moreover, the disclosed RF antenna assembly 104 provides electrical segregation of component parts over long duration at environmental extremes, and includes dielectric tubes with quartz/S-Glass reinforced cyanate ester in a thick walled form, length, as required for performance plus margin. The disclosed RF antenna assembly 104 uses end-fittings with rounded features, blind-pinned, and bonded to prevent arcing from field concentration at sharp edges, and the disclosed RF antenna assembly is sealed for fluid and gas pressure.
As noted above, the RF antenna assembly 104 must withstand the rigors of the wellbore 255 for the life of the well. The operational parameters are, for example: maximum temperature T=300° C. (572° F.); maximum external pressure DP=870 psi×1.0 ft2; maximum overburden pressure at 500 meter depth DP=6,000 kPa (870 psi) associated with formation collapse, based on 12 kPa/meter gradient; and maximum axial force that can develop prior to deployment of thermal compensator: 50 kpsi.
Referring now to
In
In
Referring now to
Yet another aspect is directed to a method for making an RF antenna assembly 104 positioned within a wellbore 255 in a subterranean formation 102 for hydrocarbon resource recovery. The method may include positioning first and second tubular conductors 106, 107, first and second electrical contact sleeves 109, 110, and a dielectric isolator 108 in the wellbore 255 and so that the first and second electrical contact sleeves are respectively coupled between the first and second tubular conductors and the dielectric isolator. The first and second tubular conductors 106, 107 define a dipole antenna. The method may include coupling a feed structure 135 to a distal end of an RF transmission line 103, the RF transmission line comprising an inner conductor 257 and an outer conductor 256. The feed structure 135 may include a first radially compressible connector 136 coupled to the outer conductor 256 of the RF transmission line 103 to slidably engage adjacent portions of the first electrical contact sleeve 109, a second radially compressible connector 137 coupled to the inner conductor 257 of the RF transmission line to slidably engage adjacent portions of the second electrical contact sleeve 110, and a dielectric tube 138 coupled between the first and second radially compressible connectors. The method includes positioning the RF transmission line 103 within the wellbore 255 and extending within the first tubular conductor 106.
In particular, the method may include the first steps of drilling the vertical portion of the wellbore 255 and installing the associated well casing. The method includes drilling the horizontal portion of the wellbore 255, and installing the horizontal well casing, i.e. the first and second tubular conductors 106, 107, the first and second electrical contact sleeves 109, 110, and the dielectric isolator 108. The method includes a heavy reverse circulation step to remove debris from the build section. Afterwards, the drilling rig is removed, and the method includes installing a tubing hangar and wellhead cap at the surface. The method includes installing the RF transmission line 103 segment-by-segment, starting with feed structure 135.
Referring again to
Accordingly, in typical approaches, the RF source 101 would comprise multiple RF transmitters, such as a first initial high frequency start-up RF transmitter and a second sustaining RF transmitter (having a different lower operational frequency and power consumption). The first transmitter would desiccate the adjacent portions of the wellbore 255, and the second transmitter (e.g. lower frequency transmitter) would be subsequently coupled to the RF transmission line 103. In a typical hydrocarbon recovery operation, efficiency is critical. This is due to the costly nature of powering RF transmitters in hydrocarbon recovery.
Advantageously, in the disclosed embodiments, the RF antenna assembly 104 has the insulating coating 126a-126b on the first and second electrical contact sleeves 109, 110 and at least a portion of the first and second tubular conductors 106, 107. In other words, the dipole antenna has a minimum starting antenna length, and a single RF transmitter can be used, i.e. the first RF transmitter can be eliminated. Since the first RF transmitter is not needed, capital expenditures are reduced. Moreover, these RF transmitters are large and ungainly, making them expensive to swap out. Yet further, the insulating coating 126a-126b helpfully provides for impedance control for the dipole antenna, and improves dielectric breakdown levels.
Referring now additionally to
In chart 180, the insulating coating 126a-126b is inch thick and 40 m in length. The desiccation cylinder has a 1 m radius, and a variable length in meters of 5, 10, 15, 20, 25, 30, 35, and 40, respectively, with curves 181-188. In chart 190, the insulating coating 126a-126b is ½ inch thick and 50 meters in length. The desiccation cylinder has a 1 m radius, and a variable length in meters of 5, 10, 15, 20, 25, 30, 35, and 40, respectively, with curves 191-198.
In chart 200, the insulating coating 126a-126b is inch thick and 60 meters in length. The desiccation cylinder has a 1 m radius, and a variable length in meters of 5, 10, 15, 20, 25, 30, 35, and 40, respectively, with curves 201-208. In chart 210, the insulating coating 126a-126b is ½ inch thick and 70 meters in length. The desiccation cylinder has a 1 m radius, and a variable length in meters of 5, 10, 15, 20, 25, 30, 35, and 40, respectively, with curves 211-218. In chart 220, the insulating coating 126a-126b is ½ inch thick and 80 meters in length. The desiccation cylinder has a 1 m radius, and a variable length in meters of 5, 10, 15, 20, 25, 30, 35, and 40, respectively, with curves 221-228.
In charts 230, 235, 240, 245, 250, parametric sweeps were performed with the following values: sweep ½ inch Teflon coating with 80 m length, transmitter power 1 kW/m (800 kW), sweep 0.2 to 0.8 MHz, 0.05 MHz step, and duration of 20 days, 1 day step. Curves 231, 236, 241, 246, and 251 represent performance at start-up, 1 day, 2 days, 3 days, and 4 days, respectively.
Other features relating to hydrocarbon recovery are disclosed in U.S. Pat. No. 9,376,897 to Ayers et al., all incorporated herein by reference in their entirety.
Many modifications and other embodiments of the present disclosure will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the present disclosure is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 7441597 | Kasevich | Oct 2008 | B2 |
| 7891421 | Kasevich | Feb 2011 | B2 |
| 9376897 | Ayers et al. | Jun 2016 | B2 |
| 20100078163 | Banerjee et al. | Apr 2010 | A1 |
| 20100294488 | Wheeler et al. | Nov 2010 | A1 |
| 20100294489 | Dreher, Jr. et al. | Nov 2010 | A1 |
| 20140224472 | Parsche | Aug 2014 | A1 |
| 20160245059 | Wright | Aug 2016 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20180223639 A1 | Aug 2018 | US |
