Patent Publication Number: US-10767459-B2

Title: Hydrocarbon resource recovery system and component with pressure housing and related methods

Description:
TECHNICAL FIELD 
     The present invention relates to the field of hydrocarbon resource processing, and, more particularly, to a hydrocarbon resource recovery system and related methods. 
     BACKGROUND 
     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 typically used to 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&#39;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&#39;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. 
     SUMMARY 
     Generally speaking, a hydrocarbon resource recovery system is for a subterranean formation. The hydrocarbon resource recovery system includes an RF antenna within the subterranean formation for hydrocarbon resource recovery, an RF source aboveground, a coaxial RF transmission line coupled between the RF antenna and the RF source and having an aboveground portion, a dielectric fluid pressure source, and a plurality of pressure members joined together in end-to-end relation to define a pressure housing coupled to the dielectric fluid pressure source and surrounding the aboveground portion of the coaxial RF transmission line. The plurality of pressure members may include at least one straight tubular pressure member, and at least one elbow pressure member coupled thereto. 
     In some embodiments, the coaxial RF transmission line may include a first metal having a first strength, and the pressure housing may include a second metal having a second strength greater than the first strength. The first metal may have a first electrical conductivity, and the second metal may have a second electrical conductivity less than the first electrical conductivity. For example, the first metal may include copper, and the second metal may include steel. 
     Also, the pressure housing may have a pressure rating of at least 100 pounds per square inch. The hydrocarbon resource recovery system may include flanged joints between adjacent pressure members. The at least one elbow pressure member may include upper and lower longitudinal halves having respective opposing longitudinal flanges joined together. The at least one elbow pressure member may include a sealing strip extending along the opposing longitudinal flanges. 
     The coaxial RF transmission line may include an inner conductor, an outer conductor surrounding the inner conductor, and a dielectric fluid between the inner and outer conductors. The RF power source may have a power level of greater than one megawatt, for example. 
     Another aspect is directed to a hydrocarbon resource recovery component in a hydrocarbon resource recovery system for a subterranean formation. The hydrocarbon resource recovery system may include an RF antenna within the subterranean formation for hydrocarbon resource recovery, an RF source aboveground, and a dielectric fluid pressure source. The hydrocarbon resource recovery component may include a coaxial RF transmission line coupled between the RF antenna and the RF source and having an aboveground portion, and a plurality of pressure members joined together in end-to-end relation to define a pressure housing coupled to the dielectric fluid pressure source and surrounding the aboveground portion of the coaxial RF transmission line. The plurality of pressure members may include at least one straight tubular pressure member, and at least one elbow pressure member coupled thereto. 
     Another aspect is directed to a method for assembling a hydrocarbon resource recovery system for a subterranean formation. The method may comprise positioning an RF antenna within the subterranean formation for hydrocarbon resource recovery, positioning an RF source aboveground, and coupling a coaxial RF transmission line between the RF antenna and the RF source and having an aboveground portion. The method may comprise coupling a plurality of pressure members joined together in end-to-end relation to define a pressure housing coupled to a dielectric fluid pressure source and surrounding the aboveground portion of the coaxial RF transmission line. The plurality of pressure members may comprise at least one straight tubular pressure member, and at least one elbow pressure member coupled thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a hydrocarbon resource recovery system, according to the present disclosure. 
         FIG. 2  is a perspective view of a plurality of pressure members from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 3  is an enlarged perspective view of the plurality of pressure members from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 4  is a perspective view of an elbow pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 5  is an exploded view of the elbow pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 6  is a perspective view of the elbow pressure member from the hydrocarbon resource recovery system of  FIG. 1  with an upper half removed. 
         FIG. 7  is a top plan view of a flanged joint between adjacent elbow pressure members from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 8  is an enlarged top plan view of the flanged joint between the adjacent elbow pressure members from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 9  is a perspective view of an end of a straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 10  is a cross-sectional view of the straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 11  is a perspective view of the straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 12  is a perspective view of the straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1  with the coaxial RF transmission line partially withdrawn during assembly. 
         FIGS. 13A-13B  are perspective views of a dielectric insertion plug for the straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIGS. 14A-14B  are cross-sectional views of the dielectric insertion plug within the straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIGS. 15A-15B  are perspective views of the dielectric insertion plug within the straight tubular pressure member from the hydrocarbon resource recovery system of  FIG. 1 . 
         FIG. 16  is a schematic diagram of another embodiment of the hydrocarbon resource recovery system, according to the present disclosure. 
         FIGS. 17-19  are cross-sectional views of a distal end of an inner conductor from the hydrocarbon resource recovery system of  FIG. 16  during latching within a feed structure. 
         FIGS. 20-21  are perspective views of the distal end of the inner conductor from the hydrocarbon resource recovery system of  FIG. 16 . 
         FIGS. 22-23  are cross-sectional views of a portion of the distal end of the inner conductor from the hydrocarbon resource recovery system of  FIG. 16  during the latching within the feed structure. 
         FIG. 24  is a cross-sectional view of a wellhead from the hydrocarbon resource recovery system of  FIG. 16 . 
         FIG. 25  is a schematic diagram of yet another embodiment of the hydrocarbon resource recovery system, according to the present disclosure. 
         FIG. 26  is a schematic diagram of an RF antenna assembly from the hydrocarbon resource recovery system of  FIG. 25 . 
         FIG. 27  is a cross-sectional view of a portion of the RF antenna assembly from the hydrocarbon resource recovery system of  FIG. 25 . 
         FIG. 28  is a flowchart for operating the hydrocarbon resource recovery system of  FIG. 25 . 
         FIG. 29  is a schematic diagram of another embodiment of the hydrocarbon resource recovery system, according to the present disclosure. 
         FIG. 30  is a perspective view of a thermal expansion accommodation device from the hydrocarbon resource recovery system of  FIG. 29 . 
         FIGS. 31 and 32  are side elevational and cross-section views, respectively, of the thermal expansion accommodation device and an adjacent electrical contact sleeve from the hydrocarbon resource recovery system of  FIG. 29 . 
         FIGS. 33-34  are cross-sectional views of portions of the thermal expansion accommodation device from the hydrocarbon resource recovery system of  FIG. 29 . 
         FIG. 35  is a perspective view of an end of a tubular sleeve from the thermal expansion accommodation device from the hydrocarbon resource recovery system of  FIG. 29 . 
         FIG. 36  is an exploded view of the end of the tubular sleeve from the thermal expansion accommodation device from the hydrocarbon resource recovery system of  FIG. 29 . 
         FIGS. 37-39  are perspective views of opposing ends of first and second tubular sleeves from the thermal expansion accommodation device from the hydrocarbon resource recovery system of  FIG. 29  during assembly. 
         FIG. 40  is a cross-sectional view of a portion of the thermal expansion accommodation device from the hydrocarbon resource recovery system of  FIG. 29 . 
         FIG. 41  is a schematic diagram of another embodiment of the hydrocarbon resource recovery system, according to the present disclosure. 
         FIG. 42  is another schematic diagram of the hydrocarbon resource recovery system of  FIG. 41 . 
         FIG. 43  is a schematic diagram of a solvent injector in the hydrocarbon resource recovery system of  FIG. 41 . 
         FIG. 44  is a schematic diagram of a portion of the solvent injector in the hydrocarbon resource recovery system of  FIG. 41 . 
         FIG. 45  is a schematic diagram of the solvent injector in the hydrocarbon resource recovery system of  FIG. 41  during different phases of operation. 
         FIGS. 46A and 46B  are schematic and cross-section views, respectively, of an embodiment of the RF antenna assembly from the hydrocarbon resource recovery system of  FIG. 41 . 
         FIGS. 47A and 47B  are schematic and cross-section views, respectively, of another embodiment of the RF antenna assembly from the hydrocarbon resource recovery system of  FIG. 41 . 
     
    
    
     DETAILED DESCRIPTION 
     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, and prime notation is used to indicate similar elements in alternative embodiments. 
     Referring to  FIGS. 1-3 , a hydrocarbon resource recovery system  60  according to the present disclosure is now described. The hydrocarbon resource recovery system  60  illustratively is installed adjacent and within a subterranean formation  73 . The hydrocarbon resource recovery system  60  illustratively includes an RF antenna  65  within a first wellbore  71  of the subterranean formation  73  for hydrocarbon resource recovery, and an RF source  62  aboveground (i.e. on a surface of the subterranean formation  73 ). The RF antenna  65  illustratively includes first and second tubular conductors  66 ,  68 , and a dielectric isolator  67  coupled between the first and second tubular conductors to define a dipole antenna element. 
     The hydrocarbon resource recovery system  60  illustratively includes a coaxial RF transmission line  64  coupled between the RF antenna  65  and the RF source  62  and having an aboveground portion extending along the surface of the subterranean formation  73 . The coaxial RF transmission line  64  also includes a belowground portion extending within the first wellbore  71 . 
     The hydrocarbon resource recovery system  60  illustratively includes a dielectric fluid pressure source  61 , and a plurality of pressure members joined  74   a - 74   d ,  75   a - 75   c  together in end-to-end relation to define a pressure housing  63  coupled to the dielectric fluid pressure source and surrounding the aboveground portion of the coaxial RF transmission line  64 . In some advantageous embodiments, the dielectric fluid pressure source  61  may integrate a cooling feature to cool and recirculate the dielectric fluid. 
     The RF power source  62  may have a power level of greater than one megawatt (e.g. 1-20 megawatts). The plurality of pressure members  74   a - 74   d ,  75   a - 75   c  illustratively includes a plurality of straight tubular pressure members  74   a - 74   d  and a plurality of elbow pressure members  75   a - 75   c  coupled thereto. The hydrocarbon resource recovery system  60  illustratively includes a producer well  69  within a second wellbore  72  of the subterranean formation  73 , which produces hydrocarbons. 
     The hydrocarbon resource recovery system  60  illustratively includes flanged joints  76   a - 76   e  between adjacent pressure members  74   a - 74   d ,  75   a - 75   c . As shown in the illustrated embodiment, the flanged joints  76   a - 76   e  include a plurality of fasteners, such as a bolts, and may include additionally or alternatively welding. 
     As perhaps best seen in  FIGS. 4-8 , each elbow pressure member  75   a - 75   c  illustratively includes upper and lower longitudinal halves  77   a - 77   b  having respective opposing longitudinal flanges  230   a - 230   c  joined together via a plurality of fasteners  86   a - 86   g . Each elbow pressure member  75   a - 75   c  illustratively includes a sealing strip  81   a - 81   b  extending along the opposing longitudinal flanges. Also, each elbow pressure member  75   a - 75   c  illustratively includes an outer conductor segment  78 , and an outer conductor connector  80  coupled thereto. Each elbow pressure member  75   a - 75   c  illustratively includes an inner conductor segment  90 , an inner conductor connector  79  coupled to the inner conductor segment, and a plurality of dielectric spacers  80 ,  87 ,  88  carrying the inner conductor segment  90  within the outer conductor segment  78 . Each elbow pressure member  75   a - 75   c  illustratively includes a plurality of fasteners  91   a - 91   c  coupling together the inner conductor segment  90  and the inner conductor connector  79 . 
     In another embodiment, each elbow pressure member  75   a - 75   c  could be formed as a single piece, i.e. without the upper and lower longitudinal halves  77   a - 77   b . For example, the outer body of each elbow pressure member  75   a - 75   c  may be forged, and the outer conductor liner can be electroplated on the inner surface of the forged piece, or hydroformed on the forged piece. 
     As shown, each elbow pressure member  75   a - 75   c  includes opposing longitudinal flanges  82   a - 82   b ,  83   a - 83   b  for defining the respective flanged joints  76   a - 76   e  with female and male conductor mating ends. Each elbow pressure member  75   a - 75   c  illustratively includes an O-ring seal  84  carried by the male interface end, and a plurality of lift points  85 ,  89  configured to permit easy installation of the elbow pressure member. As perhaps best seen in  FIG. 8 , the O-ring seal  84  illustratively includes a plurality of gasket seal components  92   a - 92   b.    
     Referring additionally now to  FIGS. 9-11 , each of the plurality of straight tubular pressure members  74   a - 74   d  illustratively includes a tubular housing  94 , flanged ends  93   a - 93   b  at opposing ends of the tubular housing, and an outer conductor segment  98  carried by the tubular housing. In the illustrated embodiment, the outer conductor segment  98  and the tubular housing  94  are spaced apart to facilitate assembly (e.g. nominal air gap of 0.02-1 inches). In another embodiment, the outer conductor segment  98  and the tubular housing  94  may directly contact each other. Also, each of the plurality of straight tubular pressure members  74   a - 74   d  illustratively includes an inner conductor segment  99 , first and second inner conductor connectors  96   a - 96   b  coupled to the inner conductor segment, a plurality of fasteners  100   a - 100   b  coupling the first and second inner conductor connectors together, and an outer conductor connector  95  coupled to the outer conductor segment  98 , and a dielectric spacer  97  carried by the outer conductor spacer. 
     The coaxial RF transmission line  64  illustratively includes a first metal having a first strength, and the pressure housing  63  (i.e. the tubular housing  94  and the upper and lower longitudinal halves  77   a - 77   b ) illustratively includes a second metal having a second strength greater than the first strength. In some embodiments, the first metal has a first electrical conductivity, and the second metal has a second electrical conductivity less than the first electrical conductivity. For example, the first metal may include one or more of copper, aluminum, or beryllium copper, and the second metal may include steel. Also, the pressure housing  63  illustratively has a pressure rating of at least 100 pounds per square inch (psi). 
     Aboveground, the coaxial RF transmission line  64  is defined by the inner conductor segments  90 ,  99  and the outer conductor segments  78 ,  98 , and the dielectric fluid pressure source  61  is configured to circulate pressurized dielectric fluid between the inner conductor segments  90 ,  99  and the outer conductor segments  78 ,  98 . The pressurized dielectric fluid may include a pressurized gas, for example, N 2 , CO 2 , or SF 6 . 
     Belowground, the coaxial RF transmission line  64  is defined by inner conductor segments and outer conductor segments (not shown), and is filled with a dielectric fluid (e.g. mineral oil). The hydrocarbon resource recovery system  60  includes an IOB device at the wellhead and configured to manage the transition from the liquid cooled RF transmission line  64  underground to the gas filled RF transmission line  64  aboveground. 
     Another aspect is directed to a hydrocarbon resource recovery component in a hydrocarbon resource recovery system  60  for a subterranean formation  73 . The hydrocarbon resource recovery system  60  illustratively includes an RF antenna  65  within the subterranean formation  73  for hydrocarbon resource recovery, an RF source  62  aboveground, and a dielectric fluid pressure source  61 . The hydrocarbon resource recovery component illustratively includes a coaxial RF transmission line  64  coupled between the RF antenna  65  and the RF source  62  and having an aboveground portion, and a plurality of pressure members  74   a - 74   d ,  75   a - 75   c  joined together in end-to-end relation to define a pressure housing  63  coupled to the dielectric fluid pressure source  61  and surrounding the aboveground portion of the coaxial RF transmission line. The plurality of pressure members  74   a - 74   d ,  75   a - 75   c  illustratively includes at least one straight tubular pressure member  74   a - 74   d , and at least one elbow pressure member  75   a - 75   c  coupled thereto. 
     Another aspect is directed to a method for assembling a hydrocarbon resource recovery system  60  for a subterranean formation  73 . The method comprises positioning an RF antenna  65  within the subterranean formation  73  for hydrocarbon resource recovery, positioning an RF source  62  aboveground, and coupling a coaxial RF transmission line  64  between the RF antenna and the RF source and having an aboveground portion. The method comprises coupling a plurality of pressure members  74   a - 74   d ,  75   a - 75   c  joined together in end-to-end relation to define a pressure housing  63  coupled to a dielectric fluid pressure  61  source and surrounding the aboveground portion of the coaxial RF transmission line  64 . The plurality of pressure members  74   a - 74   d ,  75   a - 75   c  comprises at least one straight tubular pressure member  74   a - 74   d , and at least one elbow pressure member  75   a - 75   c  coupled thereto. 
     Referring now additionally to  FIGS. 12-15B , the steps for assembling each of the plurality of straight tubular pressure members  74   a - 74   d  are described. In  FIGS. 12 &amp; 14A-14B , the coaxial RF transmission line  64  is installed into the tubular housing  94  while using an installation plug  101  as a centralizer guide. The installation plug  101  illustratively includes a central protrusion  104  defining a passageway  102  and carrying the inner conductor segment  99  as the coaxial RF transmission line  64  is positioned within the tubular housing  94 . The installation plug  101  illustratively includes a peripheral edge  103  configured to abut inner portions of the outer conductor segment  98  during installation. 
     As will be appreciated, during a typical hydrocarbon resource recovery operation, the aboveground portion of the operation is quite complicated and intricate (e.g. complicated by routing of power, fluids, produced hydrocarbons). Indeed, the path for the coaxial RF transmission line  64  is far from a straight line path. Advantageously, the hydrocarbon resource recovery system  60  includes both straight tubular pressure members  74   a - 74   d  and elbow pressure members  75   a - 75   c , which can be rotated before assembly to permit intricate paths, as perhaps best seen in  FIGS. 2-3 . Indeed, the example shown in the illustrated embodiment is merely one of many possible arrangements. Moreover, the pressure housing  63  provides a mechanically strong body for carrying pressurized dielectric fluid. 
     Indeed, in typical approaches, the pressurized dielectric fluid is pumped into a typical coaxial RF transmission line, and the corresponding pressure (typically 15 psi) is limited by the mechanical strength of the outer conductor and respective weld joints between segments. This is due to the annealing of the metal at the welding joints made from aluminum and copper, which are desirable electrical conductors. Moreover, these materials have scrap value and have increased theft rates at secluded sites. In the hydrocarbon resource recovery system  60 , the outer conductor no longer is a limit to pressure, and the dielectric fluid pressure source  61  is configured to pressurize the dielectric fluid at within a range of 100-500 psi. 
     The advantage of this greater pressure is that the RF source  62  can operate at greater power levels without commensurate increases in the size of the coaxial RF transmission line  64  (usually done to achieve high voltage standoff safety requirements). In other words, with the high pressure dielectric fluid between the inner and outer conductors in the hydrocarbon resource recovery system  60 , the power level can be safely increased without changing out the coaxial RF transmission line  64  (commonly done between start-up and sustainment phases), which reduces operational costs. 
     Moreover, the high pressure dielectric fluid keeps moisture out of the system and reduces risk of corrosion, and provides a medium with greater thermal conductivity. Indeed, since the pressure housing  65  components are made from corrosion resistant stainless steel, in some embodiments, the internal sensitive components are protected from the external environment. In short, the pressure housing  65  and the coaxial RF transmission line  64  therein of the disclosed hydrocarbon resource recovery system  60  provide for a more rugged, and more flexible platform for RF heating with the RF antenna  65 . 
     Referring now to  FIGS. 16-24 , another embodiment of a hydrocarbon resource recovery system  105  according to the present disclosure is now described. The hydrocarbon resource recovery system  105  illustratively includes an RF source  106 , and an RF antenna assembly  107  coupled to the RF source and within a wellbore  113  in a subterranean formation  112  for hydrocarbon resource recovery. The RF antenna assembly  107  illustratively includes first and second electrical contact sleeves  110   a - 110   b , first and second tubular conductors  116   a - 116   b  respectively coupled to the first and second electrical contact sleeves, and a dielectric isolator  115  coupled between the first and second tubular conductors. 
     The RF antenna assembly  107  illustratively includes a dielectric coupler  108  between the first and second electrical contact sleeves  110   a - 110   b , a distal guide string  109  coupled to the second electrical contact sleeve, and an RF transmission line  139  comprising an inner conductor (e.g. one or more of beryllium copper, copper, aluminum)  140  and an outer conductor (e.g. one or more of beryllium copper, copper, aluminum)  141  extending within the first tubular conductor  116   a . The outer conductor  141  is coupled to the first tubular conductor  116   a . The RF antenna assembly  107  illustratively includes a feed structure  122  coupled to the second tubular conductor  116   b . The RF antenna assembly  107  illustratively includes a heel isolator  114  coupled to the first tubular conductor  116   a.    
     The inner conductor  140  illustratively has a distal end  117  being slidable within the outer conductor  141  and cooperating with the feed structure  122  to define a latching arrangement having a latching threshold (e.g. 100 lb.) lower than an unlatching threshold (e.g. &gt;3,000 lb.). The hydrocarbon resource recovery system  105  illustratively includes a wellhead  111  on a surface of the subterranean formation  112 . After installation of the inner conductor  140 , the inner conductor string is hung on the wellhead  111  via hanger components  142 - 143  ( FIG. 24 ). Hence, the unlatching threshold is greater than a hanging weight of the inner conductor string. In other words, the inner conductor string is tensioned in a preloaded state, as shown in  FIG. 18 . In particular, the unlatching threshold is adjusted so that it is at least 10% (or greater) of the string weight, permitting the inner conductor can be tensioned slightly higher than the string weight. 
     In the illustrated embodiment, the distal end  117  of the inner conductor  140  comprises a plug body  118  having a tapered front end  120 , a radial recess  121  spaced therefrom, and a flanged back end  132  defining a “no-go feature”. The tapered front end  120  illustratively has a slope being shallower than a slope of the radial recess  121 . The plug body  118  defines a passageway (e.g. for a fluid passageway or a thermal probe access point)  119  extending therethrough. 
     Also, the feed structure  122  illustratively includes a receptacle body  126  configured to receive the plug body  118 , and a plurality of biased roller members carried by the receptacle body and configured to sequentially engage the tapered front end  120  and the radial recess  121  of the plug body  118 . Each biased roller member illustratively includes a roller  125   a - 125   b , an arm  134  having a proximal end pivotally coupled to the receptacle body  126  and a distal end carrying the roller, a pin  135  within the proximal end of the arm and permitting the arm to pivot, and a spring (e.g. Bellville spring)  136  configured to bias the proximal end of the arm. Each biased roller member illustratively includes a load adjustment screw  137 , a spring interface  232  between the load adjustment screw and the spring  136 , and a pawl plunger  231  configured to contact the proximal end of the arm  134 . 
     As will be appreciated, the load adjustment screw  137  permits setting of the unlatching threshold. Before installation, the unlatching threshold is calculated so that preloading the inner conductor string can be accomplished without unintentional unlatching of the distal end  117  of the inner conductor  140 . 
     Moreover, the receptacle body  126  is illustratively slidably moveable within the second tubular conductor  116   b  for accommodating thermal expansion of the inner conductor string. As perhaps best seen in  FIG. 23 , the feed structure  122  has a forward stop  126  configured to limit forward travel (during the latching process) of the distal end  117  of the inner conductor  140 . The RF transmission line  139  illustratively includes a plurality of dielectric stabilizers  123   a - 123   b  supporting the inner conductor  140  within the outer conductor  141 . Each of the plurality of dielectric stabilizers  123   a - 123   b  may comprise polytetrafluoroethylene (PTFE) material or other suitable dielectric materials. 
     Referring now specifically to  FIGS. 17-19 , the RF antenna assembly  107  illustratively includes a tubular connector  124  coupled between the dielectric isolator  115  and the second electrical contact sleeve  110   b . The feed structure  122  is electrically coupled to the second electrical contact sleeve  110   b . During an RF heating operation, the inner conductor string heats up and elongates, pushing the receptacle body  126  downhole within the second tubular conductor  116   b . The feed structure  122  illustratively includes a tubular connector  127  electrically coupled to the second tubular conductor  116   b , and first and second electrical connector elements  138   a - 138   b  coupling the tubular connector to the second tubular conductor. 
     The RF antenna assembly  107  illustratively includes a centralizer  128  configured to position the second tubular conductor  116   b  within the wellbore  113 . The centralizer  128  illustratively includes first and second opposing caps  129   a - 129   b , a medial tubular coupler  131  coupled between the first and second opposing caps, and a plurality of watchband spring connectors  130   a - 130   b  carried by the medial tubular coupler. 
     As seen in  FIGS. 20-21 , the inner conductor string is readily assembled onsite via threaded interfaces between adjacent inner conductor segments  133   a - 133   b . The dielectric stabilizers  123   a - 123   b  may be slid on and captured, co-molded onto, or thermally expanded and slid over for seating on the inner conductor segments  133   a - 133   b . In some embodiments, each inner conductor segment  133   a - 133   b  is bimetallic and comprises a higher conductivity outer layer (e.g. copper), and a lower conductivity inner layer (e.g. stainless steel, and/or steel). The outer layer may be hydroformed onto the inner layer, for example. 
     Advantageously, the hydrocarbon resource recovery system  105  permits the inner conductor string to be installed separately from the outer conductor string and the RF antenna assembly  107 . Since the size and weight of the inner conductor string is much less (inner conductor segments  133   a - 133   b  being 1.167″ outer diameter tube, 5′ length), this is easier for onsite personnel. Furthermore, since the inner conductor string is a common failure point in typical use, the hydrocarbon resource recovery system  105  is readily repaired since the distal end  117  of the inner conductor  140  can be unlatched from the feed structure  122  and removed for subsequent replacement. In typical approaches, the entire RF antenna assembly string has to come out to replace the inner conductor. Because of the substantial cost in typical approaches, some wells may go abandoned when this occurs. Positively, the hydrocarbon resource recovery system  105  permits easy replacement of the inner conductor string. 
     Furthermore, since the feed structure  122  can accommodate thermal expansion of the inner conductor  140 , the inner conductor is not damaged by thermal expansion. Indeed, this is a common cause of failure of the inner conductor string. 
     Another aspect is directed to an RF antenna assembly  107  for a hydrocarbon resource recovery system  105  and being positioned within a wellbore in a subterranean formation  112  for hydrocarbon resource recovery. The RF antenna assembly  107  illustratively includes first and second tubular conductors  116   a - 116   b , a dielectric isolator  115  coupled between the first and second tubular conductors, an RF transmission line  139  comprising an inner conductor  140  and an outer conductor  141  extending within the first tubular conductor, the outer conductor being coupled to the first tubular conductor, and a feed structure  122  coupled to the second tubular conductor. The inner conductor  140  includes a distal end  117  being slidable within the outer conductor  141  and cooperating with the feed structure  122  to define a latching arrangement having a latching threshold lower than an unlatching threshold. 
     Another aspect is directed to a method for assembling a hydrocarbon resource recovery system  105 . The method includes positioning first and second tubular conductors  116   a - 116   b  in a wellbore with a dielectric isolator  115  coupled between the first and second tubular conductors, and positioning an outer conductor  141  of an RF transmission line  139  in the wellbore, the outer conductor extending within the first tubular conductor and being coupled to the first tubular conductor. The method comprises positioning a feed structure  122  coupled to the second tubular conductor  116   b , and positioning an inner conductor  140  of the RF transmission line  139  in the wellbore, the inner conductor having a distal end  117  being slidable within the outer conductor  141  and cooperating with the feed structure to define a latching arrangement having a latching threshold lower than an unlatching threshold. The method includes latching the distal end  117  of the inner conductor  140  to the feed structure  122  to define the RF antenna assembly  107  coupled to an RF source. 
     Another aspect is directed to a method for hydrocarbon resource recovery from a subterranean formation  112 . The method includes positioning first and second tubular conductors  116   a - 116   b  in a wellbore  113  in the subterranean formation  112  with a dielectric isolator  115  coupled between the first and second tubular conductors, and positioning an outer conductor  141  of an RF transmission line  139  within the first tubular conductor and being coupled to the first tubular conductor. The method includes positioning an inner conductor  140  of the RF transmission line  139  within the outer conductor  141  and cooperating with a feed structure  122  coupled to the second tubular conductor  116   b  to define a latching arrangement having a latching threshold lower than an unlatching threshold. In some embodiments, the method may include supplying RF power to the RF transmission line  139 . 
     Another aspect is directed to a method for assembling a hydrocarbon resource recovery system  105 . The method includes coupling an RF antenna assembly  107  to an RF source  106  and within a wellbore in a subterranean formation  112  for hydrocarbon resource recovery. The RF antenna assembly  107  includes first and second tubular conductors  116   a - 116   b , a dielectric isolator  115  coupled between the first and second tubular conductors, an RF transmission line  139  comprising an inner conductor  140  and an outer conductor  141  extending within the first tubular conductor, the outer conductor being coupled to the first tubular conductor, and a feed structure  122  coupled to the second tubular conductor. The inner conductor  140  has a distal end  117  being slidable within the outer conductor  141  and cooperating with the feed structure  122  to define a latching arrangement having a latching threshold lower than an unlatching threshold. 
     Referring now to  FIGS. 25-28 , a method for hydrocarbon resource recovery and a hydrocarbon resource recovery system  144  are now described with reference to a flowchart  165 . The hydrocarbon resource recovery system  144  illustratively includes an RF antenna assembly  147  within a first wellbore  148  in a subterranean formation  146  for hydrocarbon resource recovery. The RF antenna assembly  147  illustratively includes first and second tubular conductors  151 - 152 , a dielectric isolator  154  between the first and second tubular conductors so that the first and second tubular conductors define a dipole antenna, and a dielectric coating (e.g. PTFE)  159  surrounding the dielectric isolator, and extending along a predetermined portion of the first and second tubular conductors, for example, defining a start-up antenna length. 
     The RF antenna assembly  147  illustratively includes an RF transmission line  155  comprising an inner conductor and an outer conductor extending within the first tubular conductor. The hydrocarbon resource recovery system  144  also includes an RF source  145  coupled to the RF transmission line  155  and configured to during a start-up phase, operate at a first power level to desiccate water adjacent the RF antenna assembly  147 , and during a sustainment phase, operate at a second power level less than or equal to the first power level to recover hydrocarbons from the subterranean formation  146 . 
     The hydrocarbon resource recovery system  144  also includes a producer well  150  within a second wellbore  149 , and includes a pump  158  configured to move produced hydrocarbons to the surface of the subterranean formation  146 . The dielectric coating  159  may be 1 m up to the full length of the antenna. 
     The RF antenna assembly  147  illustratively includes a dielectric coupler  153  between the first and second electrical contact sleeves  161 ,  162 , a distal guide string  156  coupled to the second electrical contact sleeve, and an RF transmission line  155  comprising an inner conductor (e.g. one or more of Beryllium copper, copper, aluminum) and an outer conductor (e.g. one or more of Beryllium copper, copper, aluminum) extending within the first tubular conductor  151 . The RF antenna assembly  147  illustratively includes a dielectric heel isolator  157  coupled to first tubular conductor  151 . 
     Referring now particularly to  FIG. 27 , the RF antenna assembly  147  illustratively includes an inner conductor  163  extending within the dielectric coupler  153  and the dielectric isolator  154 , and a dielectric purging fluid  160  between the inner conductor and the dielectric coupler. The dielectric purging fluid  160  may comprise, for example, mineral oil (such as Alpha fluid, as available from DSI Ventures, Inc. of Tyler, Tex.). The RF antenna assembly  147  illustratively includes a feed annulus  164  between the dielectric coupler  153  and the dielectric isolator  154 . 
     Referring now particularly to  FIG. 28 , the method of hydrocarbon resource recovery using the hydrocarbon resource recovery system  144  is now described. The method illustratively includes positioning an RF antenna assembly  147  within a first wellbore  148  in a subterranean formation  146 . (Blocks  166 - 167 ). The RF antenna assembly  147  includes first and second tubular conductors  151 ,  152  and a dielectric isolator  154  therebetween defining a dipole antenna, and a dielectric coating  159  surrounding the dielectric isolator and extending along a predetermined portion of the first and second tubular conductors defining a start-up antenna length. The method includes operating an RF source  145  coupled to the RF antenna assembly  147  during a start-up phase to desiccate water adjacent the RF antenna assembly, and operating the RF source coupled to the RF antenna assembly during a sustainment phase to recover hydrocarbons from the subterranean formation  146 . (Blocks  169 - 171 ). 
     In some embodiments, the operating of the RF source  145  during the start-up phase comprises operating the RF source at a first power level, and the operating of the RF source during the sustainment phase comprises operating the RF source at a second power level less than or equal to the first power level. Also, the positioning of the RF antenna assembly  147  within the first wellbore  148  in the subterranean formation  146  comprises positioning the RF antenna assembly in an injector well. The method also includes recovering the hydrocarbon from a producer well  150  in the subterranean formation  146  adjacent the injector well. Moreover, the method illustratively includes purging an interior of the dielectric isolator  154  with a fluid  160  during at least one of the start-up phase and the sustainment phase. (Block  168 ). 
     In some embodiments, the fluid  160  may enter the interior of the dielectric isolator  154  through a fluid passageway defined by an inner conductor  163  of an RF transmission line  155  coupled to the RF antenna assembly  147 . The fluid  160  may exit the interior of the dielectric isolator  154  through first and second electrical contact sleeves  161 ,  162  respectively coupled between the first and second tubular conductors  151 ,  152  and the dielectric isolator. The method further comprises operating the RF source  145  at a frequency between 10 kHz and 10 MHz. The dielectric coating  159  may comprise PTFE material, for example. For instance, the dielectric coating  159  may be between 1 m to full length of antenna with preferred embodiment being 10 m. 
     Another aspect is directed to a method for hydrocarbon resource recovery with an RF antenna assembly  147  within a first wellbore  148  in a subterranean formation  146 . The RF antenna assembly  147  includes first and second tubular conductors  151 ,  152 , a dielectric isolator  154  defining a dipole antenna, first and second electrical contact sleeves  161 ,  162  respectively coupled between the first and second tubular conductors and the dielectric isolator, and a dielectric coating  159  surrounding the dielectric isolator, the first and second electrical contact sleeves, and extending along a predetermined portion of the first and second tubular conductors defining a start-up antenna length. The method includes operating an RF source  145  coupled to the RF antenna assembly  147  during a start-up phase at a first power level and to desiccate water adjacent the RF antenna assembly, and operating the RE source coupled to the RF antenna assembly at a second power level less than or equal to the first power level during a sustainment phase to recover hydrocarbons from the subterranean formation  146 . 
     In some embodiments, the first and second tubular conductors  151 ,  152 , the dielectric isolator  153 , the first and second electrical contact sleeves  161 ,  162  are all part of the well casing. Since the first wellbore  148  can be a damp environment with high conductivity water present, in typical approaches, the impedance of the dipole antenna would be very low, approaching a short circuit with increasing water conductivity. In particular, the bare antenna increases the Voltage Standing Wave Ratio (VSWR), drastically increasing the difficulty (and expense) of the required impedance matching network of the transmitter. For example, the expense of a matching network that could match a 5:1 VSWR load for any phase of reflection coefficient is higher than one designed for a 2:1 VSWR load. This is due not only to the required higher values and tuning ranges of the inductors and capacitors, but the resulting higher currents and voltage stresses that these components would need to tolerate as well. If the VSWR were too high, this would potentially prevent the transmitter from delivering sufficient power to the formation. 
     Accordingly, in typical approaches, the RF source  145  would comprise multiple RF transmitters, such as a first initial high VSWR start-up RF transmitter and a second sustaining transmitter having a lower VSWR requirement. The start-up phase can be quite long, for example, up to six months. The first transmitter would enable desiccation of the adjacent portions of the first wellbore  148 , and the second transmitter (e.g. lower VSWR sustainment) would be subsequently coupled to the RF transmission line  155 . The sustainment phase could last 6-15 years, but due to the costly nature of the start-up transmitter, the operational power costs are about the same, ˜$10-12 million. In a typical hydrocarbon resource recovery operation, efficiency is important. This is due to the costly nature of powering RF transmitters in hydrocarbon resource recovery. 
     Advantageously, in the disclosed embodiments, the RF antenna assembly  147  has the dielectric coating  159  on the first and second electrical contact sleeves  161 ,  162  and at least a portion of the first and second tubular conductors  151 ,  152 . 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, saving more than $10 million. 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. The dielectric coating  159  helpfully provides for impedance control for the dipole antenna, and improves electrical breakdown across the surface of the dielectric isolator  154 . 
     The dielectric coating  159  may be formed on the dielectric isolator  154  and the first and second tubular conductors  151 ,  152  via one or more of the following: composite wrap on the exterior, spraying on the dielectric coating, or via a thermal shrink fit of the dielectric material. 
     Other features relating to the dielectric coating  159  and the manufacture thereof are found in U.S. patent application Ser. No. 15/426,168 filed Feb. 7, 2017, assigned to the present applications assignee, which is incorporated herein by reference in its entirety. 
     Other features relating to hydrocarbon resource recovery are disclosed in U.S. Pat. No. 9,376,897 to Ayers et al., which is incorporated herein by reference in its entirety. 
     Referring now to  FIGS. 29-36 , yet another embodiment of a hydrocarbon resource recovery system  170 . This hydrocarbon resource recovery system  170  illustratively includes an RF source  171 , and an RF antenna assembly  172  coupled to the RF source and within a wellbore  181  in a subterranean formation  173  for hydrocarbon resource recovery. 
     The RF antenna assembly  172  illustratively includes first and second tubular conductors  178 ,  179 , a dielectric isolator  176 , and first and second electrical contact sleeves  174 ,  175  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  172  illustratively includes a heel dielectric isolator  180  coupled to the first tubular conductor  178 . 
     The RF antenna assembly  172  illustratively includes a thermal expansion accommodation device  177  configured to provide a sliding arrangement between the second tubular conductor  179  and the second electrical contact sleeve  175  when a compressive force therebetween exceeds a threshold. In the illustrated embodiment, the thermal expansion accommodation device  172  illustratively includes a first tubular sleeve  182  coupled to the second electrical contact sleeve  175 , and a second tubular sleeve  183  coupled to the second tubular conductor  179  and arranged in telescopic relation with the first tubular sleeve. The first and second tubular sleeves  182 ,  183  may each comprise stainless steel, for example. In the illustrated embodiment, the diameter of the first tubular sleeve  182  is greater than that of the second tubular sleeve  183 , but in other embodiments, this may be reversed (i.e. the diameter of the first tubular sleeve  182  is less than that of the second tubular sleeve  183 ). 
     The thermal expansion accommodation device  177  illustratively includes a first tubular sleeve extension  184  coupled to the first tubular sleeve  182  via a threaded interface  188 , and a plurality of shear pins  187   a - 187   f  extending transversely through the first and second tubular sleeves  182 ,  183 , and the first tubular sleeve extension  183 . When the compressive force therebetween exceeds the threshold, the plurality of shear pins  187   a - 187   f  will break and permit telescoping action of the second tubular sleeve  183  within along an internal surface  190  of the first tubular sleeve  182 . 
     The thermal expansion accommodation device  172  illustratively includes a proximal end cap  185  coupled between the first tubular sleeve  182  and the second electrical contact sleeve  175 . The second tubular sleeve  183  also illustratively includes a threaded interface  186  on a distal end to be coupled to the second tubular conductor  179 . 
     The thermal expansion accommodation device  177  illustratively includes a plurality of watchband springs  194   a - 194   b  electrically coupling the first and second tubular sleeves  182 ,  183 . The second tubular sleeve  183  illustratively has a threaded surface  188  on an end thereof. The thermal expansion accommodation device  177  illustratively includes an end cap  189  having an inner threaded surface  191  ( FIG. 34 ) coupled to the threaded surface  191  of the second tubular sleeve  183 , and a wiper seal  197  carried on an annular edge of the end cap  189 . 
     The thermal expansion accommodation device  177  illustratively includes a plurality of seals  192   a - 192   b  between the first and second tubular sleeves  182 ,  183 , and a lubricant injection port  195  configured to provide access to areas adjacent the plurality of seals. The thermal expansion accommodation device  177  illustratively includes a plurality of fasteners  193   a - 193   c  extending through the end cap  189  and the second tubular sleeve  183 . 
     Also, the RF antenna assembly  172  illustratively includes an RF transmission line  233  comprising an inner conductor  234  and an outer conductor  235  extending within the first tubular conductor  178 . The dielectric isolator  176  may include a tubular dielectric member and a PTFE coating (e.g. as noted in the hereinabove disclosed embodiments) thereon. 
     As perhaps best seen in  FIGS. 36-37 , the proximal end of the second tubular sleeve  183  is shown without the first tubular sleeve  182  installed thereon. The proximal end of the second tubular sleeve  183  illustratively includes a threaded interface  188  configured to engage the threaded interface  191  of the end cap  189 . The thermal expansion accommodation device  177  illustratively includes a wear ring  196  coupled to the proximal end of the second tubular sleeve  183 , and a plurality of spacers  198   a - 198   d  interspersed between the plurality of seals  192   a - 192   b  and the plurality of watchband springs  194   a - 194   b.    
     Another aspect is directed to an RF antenna assembly  172  coupled to a RF source  171  and being within a wellbore  181  in a subterranean formation  173  for hydrocarbon resource recovery. The RF antenna assembly  172  includes first and second tubular conductors  178 ,  179 , a dielectric isolator  176 , and first and second electrical contact sleeves  174 ,  175  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  172  comprises a thermal expansion accommodation device  177  configured to provide a sliding arrangement between the second tubular conductor  179  and the second electrical contact sleeve  175  when a compressive force therebetween exceeds a threshold. 
     Another aspect is directed to a method of hydrocarbon resource recovery. The method includes positioning an RF antenna assembly  172  within a wellbore  181  in a subterranean formation  173 . The RF antenna assembly  172  includes first and second tubular conductors  178 ,  179 , a dielectric isolator  176 , first and second electrical contact sleeves  174 ,  175  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, and a thermal expansion accommodation device  177  configured to provide a sliding arrangement between the second tubular conductor and the second electrical contact sleeve when a compressive force therebetween exceeds a threshold. 
     Referring now additionally to  FIGS. 37-40 , the steps for assembling the thermal expansion accommodation device  177  are now described. In  FIG. 37 , the assembled proximal end  199  of the second tubular sleeve  183  is inserted into the first tubular sleeve  182 . In  FIG. 38 , an outer wear band  202  and a retainer band  201  are fitted over the second tubular sleeve  183 . The first tubular sleeve  182  and the first tubular sleeve extension  184  are threaded together and an annular weld  200  is formed. Thereafter, the second tubular sleeve  183  is against the mechanical stop formed by the proximal end of the first tubular sleeve extension  184 , thereby matching drilled holes for the plurality of shear pins  187   a - 187   f . The plurality of shear pins  187   a - 187   f  is then press fitted into the drilled holes, and a lubricant is dispensed through the injection port  195 . 
     In the illustrated embodiments, the thermal expansion accommodation device  177  uses threaded interfaces for coupling components together. Of course, in other embodiments, the threaded interfaces can be replaced with fastener based couplings or weld based couplings. Also, in another embodiment, the first tubular sleeve  182  may include an outer sleeve configured to provide a corrosion shield. Also, in another embodiment, the first tubular sleeve  182  may be elongated to protect the inside wall from both internal and external environment. 
     Advantageously, the thermal expansion accommodation device  177  provides an approach to thermal expansion issues within the RF antenna assembly  172 . In typical approaches, one common point of failure when the first and second tubular conductors  178 ,  179  experience thermal expansion is the dielectric isolator  176  and the heel dielectric isolator  180 . In the hydrocarbon resource recovery system  170  disclosed herein, instead of the dielectric isolator  176  or the heel dielectric isolator  180  buckling under compressive pressure, the plurality of shear pins  187   a - 187   f  will break and permit telescoping action of the second tubular sleeve  183  within along an internal surface  190  of the first tubular sleeve  182 . Indeed, during typical operation, the plurality of shear pins  187   a - 187   f  will shear, and when the RF antenna assembly  172  is removed from the wellbore  181 , the mechanical stop formed by the proximal end of the first tubular sleeve extension  184  will enable the thermal expansion accommodation device  177  to be removed. 
     Moreover, the thermal expansion accommodation device  177  is flexible in that the threshold for the compressive force is settable via the plurality of shear pins  187   a - 187   f . Also, the thermal expansion accommodation device  177  provides a solid electrical connection during the thermal growth of the first and second tubular sleeves  182 ,  183 , which provides corrosion resistance and reservoir fluid isolation. 
     Referring now to  FIGS. 41-45 , another embodiment of a hydrocarbon resource recovery system  203  is now described. The hydrocarbon resource recovery system  203  illustratively includes an RF source  204 , a producer well pad  240 , an injector well pad  241 , and a plurality of RF antenna assemblies  206   a - 206   c  coupled to the RF source and extending laterally within respective laterally spaced first wellbores  236  in a subterranean formation  208  for hydrocarbon resource recovery. Each RF antenna assembly  206   a - 206   c  illustratively includes first and second tubular conductors  213 ,  215 , and a dielectric isolator  214  coupled between the first and second tubular conductors to define a dipole antenna. 
     The hydrocarbon resource recovery system  203  illustratively includes a plurality of solvent injectors  205   a - 205   c  within respective laterally extending wellbores extending transverse (i.e. between 65-115 degrees of canting) and above the RF antenna assemblies  206   a - 206   c  and configured to selectively inject solvent into the subterranean formation  208  adjacent the RF antenna assemblies. Also, the hydrocarbon resource recovery system  203  illustratively includes a plurality of producer wells  207   a - 207   c  extending laterally in respective second wellbores  237  in the subterranean formation  208  for hydrocarbon resource recovery and being below the RF antenna assemblies  206   a - 206   c , and a pump  216  within each producer well and configured to move produced hydrocarbons to a surface of the subterranean formation  208 . Although in the illustrated embodiment, there are a plurality of RF antenna assemblies  206   a - 206   c  and a corresponding plurality of producer wells  207   a - 207   c , in other embodiments, there may be more or fewer well pairs within the subterranean formation  208 . 
     In the illustrated embodiment, the plurality of RF antenna assemblies  206   a - 206   c  and the plurality of producer wells  207   a - 207   c  extend from the producer well pad  240 . Also, the plurality of solvent injectors  205   a - 205   c  extends from the injector well pad  241 . 
     In the illustrated embodiment, each solvent injector  205   a - 205   c  includes a plurality of flow regulators (e.g. injection valves, chokes, multi-position valves that may include chokes, or other flow controlling devices)  217   a - 217   f  respectively aligned with respective ones of the plurality of RF antenna assemblies  206   a - 206   c . It is noted that for enhanced clarity of explanation, only three well pairs are depicted in  FIG. 41  rather than the six well pairs  206   a - 206   f ,  207   a - 207   f  depicted in  FIG. 43 . Each flow regulator  217   a - 217   f  may have a selective flow rate, permitting flexible solvent injection. The selective flow of each flow regulator  217   a - 217   f  may be enabled via hydraulic control, electric control, a combination of electric and hydraulic control, or via a coil tube shifting feature, for example. In some embodiments, each flow regulator  217   a - 217   f  may have three or more positions (i.e. flow rates). In some embodiments, external control lines could be used, and a single coil instrumentation string with pressure/temperature sensors would be bundled inside each solvent injectors  205   a - 205   c . Each flow regulator  217   a - 217   f  may comprise a steam valve, as available from the Halliburton Company of Houston, Tex. 
     Each solvent injector  205   a - 205   c  may comprise a lateral well (e.g. 7″ in diameter) with a blank casing with slotted liner or wire wrapped sections aligned with the RF antenna assemblies  206   a - 206   c . The plurality of solvent injectors  205   a - 205   c  is situated above the plurality of RF antenna assemblies  206   a - 206   c , for example, about 3 m±1 m. 
     Each solvent injector  205   a - 205   c  illustratively includes a plurality of isolation packers  218 ,  219  (e.g. a thermal diverter pair, as available from the Halliburton Company of Houston, Tex.) with a respective flow regulator  217   a - 217   f  therebetween. Each of the plurality of isolation packers  218 ,  219  may enable feedthrough of control lines and measurement lines, hydraulic, electric, and optic fiber. The exemplary thermal diverter is suitable for high temperature applications which do not require perfect sealing, such as SAGD. For lower temperature applications, like this solvent injection method, other types of packers should also be considered, for example, swellable elastomeric packers, or cup type packers that use more common elastomers (e.g. Hydrogenated Nitrile Butadiene Rubber (HNBR)) than the high temperature thermoplastics used for thermal diverters. 
     Moreover, the plurality of solvent injectors  205   a - 205   c  includes a first solvent injector well  205   a  aligned with a proximal end (i.e. a heel portion of the injector well) of the plurality of RF antenna assemblies  206   a - 206   c , a second solvent injector  205   b  aligned with a medial portion (i.e. the first tubular conductor  213  of the plurality of producer wells  207   a - 207   c ) of the plurality of RF antenna assemblies  206   a - 206   c , and a third solvent injector  205   c  aligned with a distal end (i.e. the second tubular conductor  215  of the injector well) of the plurality of RF antenna assemblies  206   a - 206   c.    
     Each RF antenna assembly  206   a - 206   c  illustratively includes a dielectric heel isolator  212  coupled to the first tubular conductor  213 . Also, each RF antenna assembly  206   a - 206   c  illustratively includes an RF transmission line  209  coupled to the RF source  204 , first and second electrical contact sleeves  239   a - 239   b  respectively coupled between the first and second tubular conductors  213 ,  215  and the RF transmission line, a dielectric coupler  211  coupled between the first and second electrical contact sleeves, and a guide string  210  coupled to the second electrical contact sleeve. In some embodiments ( FIG. 45 ), the RF antenna assemblies  206   a - 206   c  may be phased with each other to selectively or preferentially heat between the well pairs. 
     In  FIG. 44 , the plurality of isolation packers  218 ,  219  are double acting, in other words, they can oppose differential pressure from either direction. As such, half of each of the plurality of isolation packers  218 ,  219  is redundant, as shown in  FIG. 45  (i.e. since pressure is coming only from one direction). In other embodiments, the distal portion of each isolation packer can be omitted. 
     Another aspect is directed to a method of hydrocarbon resource recovery with a hydrocarbon resource recovery system  203 . The hydrocarbon resource recovery system  203  includes an RF source  204 , and at least one RF antenna assembly  206   a - 206   c  coupled to the RF source and extending laterally within a first wellbore  236  in a subterranean formation  208  for hydrocarbon resource recovery. The at least one RF antenna assembly  206   a - 206   c  includes first and second tubular conductors  213 ,  215 , and a dielectric isolator  214  coupled between the first and second tubular conductors to define a dipole antenna. The method comprises operating a plurality of solvent injectors  205   a - 205   c  within respective laterally extending wellbores extending transverse and above the at least one RF antenna assembly  206   a - 206   c , the plurality of solvent injectors selectively injecting solvent into the subterranean formation  208  adjacent the at least one RF antenna assembly. 
     In operation, the RF source  204  is operated in two phases. During the start-up phase, the power level of the RF source  204  is slowly ramped up to a target power level of 2.0 kW/m of antenna length or greater. Once fluid communication is established with the producer well  207   a - 207   c , the solvent injection can begin. The heating pattern around the plurality of RF antenna assemblies  206   a - 206   c  should follow a zip line path. Once antenna impedance is stabilized, the power level of the RF source  204  is reduced to 1-1.5 kW/m for the sustainment 
     Also, helpfully, this embodiment of the hydrocarbon resource recovery system  203  provides an alternative approach to other systems where the solvent injecting apparatus and the RF antenna are integrated within the same wellbore. In the hydrocarbon resource recovery system  203 , the separation of the solvent injection feature from the RF antenna assemblies  206   a - 206   c  may reduce complexity and enhance reliability. Moreover, the plurality of solvent injectors  205   a - 205   c  may provide improved selectivity as solvent application can be tightly controlled over several injector/producer well pairs. 
     Several benefits are derived from the hydrocarbon resource recovery system  203 . First, the antenna liner is reduced in diameter, which reduces drilling and material costs. Additionally, since the injector well pumps are removed, costs and complexity are further reduced. Also, the complex solvent crossing at the dielectric heel isolator  212  is removed. 
     Referring now to  FIGS. 46A-46B , each RF antenna assembly  206   a - 206   c  illustratively defines first and second fluid passageways  220 ,  221  configured to circulate a dielectric fluid from the surface (e.g. wellbore surface) of the subterranean formation  208 . The first wellbore  236  illustratively includes a cased wellbore  223  defining the first and second fluid passageways  220 ,  221  between a respective RF antenna assembly  206   a - 206   c  and the cased wellbore. Here, the cased wellbore  223  refers to an antenna that has been cemented into place, i.e. fully cased in concert. The first fluid passageway  221  is the supply path from the surface of the subterranean formation  208 , and the second fluid passageway  220  (surrounding the RF transmission line  224 ) is the return path back to the surface of the subterranean formation. Each RF antenna assembly  206   a - 206   c  defines an annular space  222  between the respective RF antenna assembly and the cased wellbore  223 . 
     Advantageously, this embodiment may cause the antenna to be instantly in electromagnetic mode, i.e. no start-up phase or zip lining. Also, the thermal limits on dielectric isolator  214  are reduced and corrosion concerns are largely eliminated. The cased wellbore  223  would be circulated clean and filled with a high temperature mineral oil or dielectric type fluid. Positively, the antenna liner could be reduce to 9⅝″ (from 10¾″ with in typical approaches) in diameter, and electrical corner cases would be reduced using this configuration. Lastly, this embodiment provides for a known fluid within the dielectric isolator  212 ; and around the common mode current choke XXX. 
     This embodiment controls the fluid around the electromagnetic heating tool and puts a known fluid around the center node and choke assembly. Here, the antenna wellbore (case hole) was cemented, which allows the antenna of this embodiment to have a electrically isolating layer around it which could allow the antenna to instantly be in electromagnetic mode, i.e. no zip lining, or at least allow zip lining to occur at a much fast rate. 
     Referring now additionally to  FIGS. 47A-47B , another embodiment of the RF antenna assembly  206 ′ is now described. In this embodiment of the RF antenna assembly  206 ′, those elements already discussed above with respect to  FIGS. 42-47B  are given prime notation and most require no further discussion herein. This embodiment differs from the previous embodiment in that this RF antenna assembly  206 ′ has a different fluid passageway arrangement. 
     The first wellbore  236 ′ illustratively includes a cased wellbore  229 ′ defining first, second, and third fluid passageways  225 ′,  227 ′,  228 ′ between a respective RF antenna assembly  206 ′ and the cased wellbore, and an N 2  core  226 ′ surrounding the first fluid passageway. Here, the cased wellbore  229 ′ refers to an antenna that has been cemented into place, i.e. fully cased in concert. The first and second fluid passageways  225 ′,  227 ′ are the supply path from a surface of the subterranean formation  208 ′, and the third fluid passageway  228 ′ is the return path back to the surface of the subterranean formation. 
     This embodiment may cause the antenna to be instantly in electromagnetic mode, i.e. no start-up or zip lining. The RF transmission line is N 2  filled with oil flowing down inner and outer bodies and returning up casing annulus, which will provide for a power efficiency improvement. Also, the antenna liner could be reduced to 9⅝″ in diameter, providing the benefits noted above. 
     Other features relating to hydrocarbon resource recovery systems are disclosed in co-pending applications: titled “HYDROCARBON RESOURCE RECOVERY SYSTEM AND RF ANTENNA ASSEMBLY WITH LATCHING INNER CONDUCTOR AND RELATED METHODS,” titled “METHOD FOR OPERATING RF SOURCE AND RELATED HYDROCARBON RESOURCE RECOVERY SYSTEMS,” titled “HYDROCARBON RESOURCE RECOVERY SYSTEM AND RF ANTENNA ASSEMBLY WITH THERMAL EXPANSION DEVICE AND RELATED METHODS,” and titled “HYDROCARBON RESOURCE RECOVERY SYSTEM WITH TRANSVERSE SOLVENT INJECTORS AND RELATED METHODS,” 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.