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This application claims the benefit, pursuant to 35 U.S.C. §119, to U.S. Patent Application Serial No. 60/298,691, filed on Jun. 15, 2001. 
    
    
     BACKGROUND 
     The invention generally relates to a power system for a well, such as a power system to deliver power to electrical equipment of a subsea well, for example. 
     A subterranean well typically includes various pieces of electrical equipment (an electrical submersible pump and an electrical flow pump, as examples) that are located downhole inside the well. For purposes of providing power to operate this electrical equipment, electrical cables may be run through an annular area between a production tubing and casing string of the well down to the electrical equipment. 
     The primary purpose of production tubing is to communicate produced well fluids from subterranean formations of the well to the surface of the well. Typically, a tubing hanger interface suspends the production tubing in the well. In this manner, the tubing hanger interface is secured to a well tree of the well, and the top end of the production tubing typically is threaded into the tubing hanger interface. 
     One or more electrical cables typically communicate power from an external power source (i.e., a power source that is located outside of the well) to the electrical cable(s) that are located inside the well. For purposes of forming electrical connections between the electrical cable(s) that are inside of the well and the electrical cable(s) that are outside of the well, a conventional technique involves penetrating the well tree with electrical connections so that these electrical connections enter the well either through the tubing hanger interface or above the tubing hanger interface. In this manner, downhole electrical cables typically are connected to these penetrating electrical connections and routed through the tubing hanger interface into the annular area between the production tubing and casing string. The electrical cables extend down the annular area to the downhole electrical equipment. 
     The above-described arrangement may present various design challenges. For example, the tubing hanger body is often crowded due to the presence of electrical connections, hydraulic control lines, etc. Therefore, to prevent the tubing hanger body from becoming too constricted, a limitation may be imposed on the cross-sectional area of each electrical cable, and a limitation may be imposed on the total number of electrical cables that may be extended downhole. These limitations, in turn, restrict the amount of power that may be communicated downhole. 
     Thus, there is a continuing need for a technique and/or system for delivering power to electrical equipment that is located in a well. 
     SUMMARY 
     In an embodiment of the invention, a system that is usable with a well includes a structure that has a region that is adapted to receive a tubing hanger interface. The system also includes at least one communication connection that penetrates the structure below the region that receives the tubing hanger interface. 
     In another embodiment of the invention, a power system for providing power communications to downhole devices in a well that has a tubing hanger interface includes an external power source, a downhole structure and a power structure. The downhole structure has external electrical contacts that are connected therethrough the downhole structure to internal electrical contacts. The external electrical contacts are in communication with the external power source and are located below the tubing hanger interface. The power structure has outer electrical contacts in communication with inner electrical contacts. The outer electrical contacts are adapted for communication with the internal electrical contacts of the downhole structure, and the inner electrical contacts are adapted to supply power to the downhole devices. 
     Advantages and other features of the invention will become apparent from the following description, drawing and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram of a well before installation of a power hanger and a tubing hanger interface according to an embodiment of the invention. 
     FIG. 2 is a schematic diagram of an electrical connector of the well of FIG. 1 according to an embodiment of the invention. 
     FIG. 3A is a schematic diagram of the well of FIG. 1 after the entry of a power hanger and a power hanger running tool into the well according to an embodiment of the invention. 
     FIG. 3B is a more detailed schematic diagram of a selected portion of the well of FIG. 3A depicting electrical connections according to an embodiment of the invention. 
     FIG. 4A is a schematic diagram of the well of FIG. 1 after the installation of the power hanger according to an embodiment of the invention. 
     FIG. 4B is a more detailed schematic diagram of a selected portion of the well of FIG. 4A depicting electrical connections according to an embodiment of the invention. 
     FIG. 5A is a schematic diagram of the well of FIG. 1 after the installation of a tubing hanger interface according to an embodiment of the invention. 
     FIG. 5B is a more detailed schematic diagram of a selected portion of the well of FIG. 5A depicting electrical connections according to an embodiment of the invention. 
     FIG. 6A is a schematic diagram of a well according to another embodiment of the invention depicting the well before installation of a tubing hanger interface. 
     FIGS. 6B and 6C are more detailed schematic diagrams of selected portions of the well of FIG. 6A depicting electrical connections according to an embodiment of the invention. 
     FIG. 7A is a schematic diagram of the well of FIG. 6A after the installation of the tubing hanger interface according to an embodiment of the invention. 
     FIGS. 7B and 7C are more detailed schematic diagrams of selected portions of the well of FIG. 7A depicting electrical connections according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 depicts an embodiment  10  of a well (a subsea well, for example) in accordance with the invention. The full cross-sections of tubular members in FIG.  1  and the proceeding figures are not shown, but rather, the left-hand cross-sections of these members are shown in relation to a longitudinal axis  14  of the well. Thus, it is understood that the left-hand cross-sections of a particular tubular member may be rotated about the longitudinal axis  14  to form the corresponding right-hand cross-section of the tubular member. 
     One such tubular member that is depicted in FIG. 1 is a wellhead  12 , a structure that provides support for a well casing that extends into the wellbore. For a subsea well, the wellhead  12  extends into the sea floor. Depending on the particular embodiment of the invention, either a small diameter well casing hanger  34  (from which a small diameter casing  40  hangs and extends into the wellbore) or a larger diameter well casing hanger  36  (from which a larger diameter well casing  42  hangs and extends into the wellbore) may be secured to the wellhead  12 . The well casing hanger  34  may be sealed to the wellhead  12  via a seal  30 , and the well casing hanger  36  may be sealed to the wellhead  12  via a seal  32 . 
     The well  10  may have one or more pieces of downhole electrical equipment  17 , such as flow pumps and submersible pumps (as examples), that need electrical power to operate. As described below, the well  10  has features that facilitate the communication of electrical power from wires of an external electrical power cable assembly  16  to the electrical equipment  17  inside the well. The power cable assembly  16  communicates power from an external power source  18 . As an example, the external power source  18  may be located on a surface platform for the case in which the well  10  is a subsea well. 
     In some embodiments of the invention, for purposes of communicating electrical power from outside the well to inside the well, insulated electrical conduits  26  penetrate the sidewall of the wellhead  12 . Seals are formed between the conduits  26  and the sidewall of the wellhead  12  where the conduits  26  penetrate the sidewall to preserve the pressure sealing capability of the wellhead  12 . The conduits  26  are electrically connected to electrical connectors  22  that are exposed on the exterior surface of the sidewall of the wellhead  12 . A power interface connector  20  mates with the connectors  22 , seals the connectors  22  from the surrounding environment and communicates electricity from wires of the cable assembly  16  to the connectors  22 . 
     The conduits  26  extend through the sidewall of the wellhead  12  to electrical connectors  28  that are exposed on an interior surface on the sidewall of the wellhead  12 . As described below, a power hanger (not depicted in FIG. 1) is installed inside the wellhead  12  for purposes of extending electrical connections from the connectors  28  to one or more power cables (not depicted in FIG. 1) that are run downhole to the electrical equipment  17 . 
     As described below, a tubing hanger interface (not depicted in FIG. 1) is installed in the well  10  above the connectors  28  in a region  15  (see also FIG. 5A) that is adapted to receive the tubing hanger interface. As described below, this region  15  may be formed by part of a well tree of the well. Due to the penetration of the electrical connections below the tubing hanger interface, the downhole cable(s) that are electrically connected to the connectors  28  may be run along the outside surface of a production tubing (not depicted in FIG. 1) of the well  10 , and are not limited to the restrictions imposed through the tubing hanger body. 
     Referring to FIG. 2, as an example, a particular connector  28  may include an interior electrically conductive region  50 , in some embodiments of the invention. This conductive region  50  provides a contact point for purposes of electrically mating the connector  28  with a corresponding electrically conductive region of another connector (described below) inside the well  10 . The conductive region  50  is surrounded by a dielectric material  52  that insulates the conductive region  50  from the surrounding conductive wellhead  12 . Other connectors described herein may have a similar structure. Other types of connectors may alternatively be used in other embodiments of the invention. 
     FIG. 3A depicts the well  10  when a power hanger running tool  70  is disposed within the well  10 . FIG. 3B depicts a more detailed illustration of a portion  59  of the well  10 , showing the electrical connections that penetrate the wellhead  12 . Referring both to FIGS. 3A and 3B, as its name implies, the power hanger running tool  70  is used to run a power hanger  74  in the wellhead  10 . The power hanger  74  provides protection for the electrical connectors  28  (FIG.  3 B), as well as provides electrical connections between these connectors  28  and electrical connectors (described below) of a tubing hanger extension. 
     The power hanger  74  is run downhole inside the well  10  via the tool  70  and is attached to the wellhead  12  by activation of the running tool  70 . In this manner, for purposes of running the tool  70  into the well  10 , the power hanger  74  is latched or secured to the running tool  70 . When the power hanger  74  is in the appropriate position inside the well  10 , the running tool  70  activates a locking mechanism (dogs, for example) of the power hanger  74  so that the power hanger  74  latches onto the interior surface of the sidewall of the wellhead  12 . 
     Before the running tool  70  sets the power hanger, a dielectric fluid may be injected into the well for purposes of cleaning the exposed electrical connections in the well. In this manner, this cleaning ensures effective electrical contacts and effective insulation surrounding these contacts. Thus, in some embodiments of the invention, when the power hanger running tool  70  is positioned near the electrical connectors  28 , a dielectric fluid may be injected into the well to clean exposed electrical connectors, such as the connectors  28 . As an example, the dielectric fluid may be injected into the well via radial ports  53  (FIG. 3A) of the running tool  70 . The dielectric fluid may be introduced from the surface of the well and flow downhole from the surface to these ports  53 , in some embodiments of the invention. 
     For purposes of setting the power hanger  74 , the running tool  70  orients the position of the power hanger  74  so that the electrical connectors  28  are aligned with corresponding electrical connectors  29  (FIG. 3B) of the power hanger  74 . When the power hanger  74  is set, the electrical connectors  28  and  29  mate. As an example, the electrical connectors  28  may be female connectors, and the electrical connectors  29  may be male connectors. Other variations are possible. 
     When latched to the power hanger  74 , the running tool  70  has electrical connectors  63  (FIG. 3B) that mate with corresponding electrical connectors  62  of the power hanger  74 . The electrical connectors  62  are located on the inner surface of the tubing hanger  74  and are connected to the connectors  29  on the outer surface of the tubing hanger  74  via insulated electrical conduits  69 . Due to this arrangement, the tool  70  may communicate with circuitry at the surface of the well for purposes of determining whether the running tool  70  has placed the power hanger  74  in the proper position inside the wellhead  12 . In this manner, proximity to the electrical contacts  28  may be sensed by using the electrical connectors  29  so that the orientation of the tool  70  (and power hanger  74 ) may be determined. In some embodiments of the invention, power from the power cable assembly  16  may be used to power the running tool  70  either before or after the power hanger  74  has been set, according to the particular embodiment of the invention. 
     Among the other features depicted in FIG. 3A, in some embodiments of the invention, the power hanger  74  includes a protective sleeve  76  that is positioned on the interior surface of the power hanger  74 . In this manner, the sleeve  76  includes a dielectric material and is biased (by a spring, for example) to extend upwardly to place the dielectric material over the connectors  62  after installation of the power hanger  74  and removal of the running tool  70 . However, when the tool  70  is run downhole with the power hanger  74  attached, the protective sleeve  76  is retracted, a position that removes the dielectric material from the connectors  62 , thereby preventing exposure to the connectors  62  so that the connectors  62  may be electrically coupled to the corresponding connectors  63  of the running tool  70 . 
     FIG. 4A depicts the well  10  after the power hanger  74  has been set and the running tool  70  has been retrieved. The electrical connections in the well  10  are depicted in more detail in the portion  59  (of the well  10 ) that is shown in FIG.  4 B. Referring both to FIGS. 4A and 4B, commands may be sent from the surface to cause the running tool  70  to set the power hanger  74 . After verifying that the power hanger  74  has been properly set, commands may be communicated from the surface to unlatch the running tool  70  from the power hanger  74 . In response to the running tool  70  being released and removed from the power hanger  74 , the protective sleeve  76  extends to its protective position to cover the otherwise exposed electrical connectors  62  (FIG. 4B) on the interior surface of the power hanger  74 . 
     FIG. 5A depicts the well after installation of a production tubing  110 . FIG. 5B depicts a more detailed schematic diagram of the portion  59  showing electrical connections in the well  10 . Referring to FIGS. 5A and 5B, for purposes of completing the well  10 , the production tubing  110  is inserted into the wellbore of the well  10  with the top of the tubing  110  being connected (threadably connected, for example) to a tubing hanger extension  92 . The extension  92 , in turn, is threadably coupled to a tubing hanger interface  90 . In this manner, the tubing hanger interface  90  rests on a corresponding annular shoulder  100  (part of the region  15 ) of the well tree  12  such that in this position, the production tubing  110  hangs into the wellbore. 
     As depicted in FIGS. 5A and 5B, the electrical connections for the well  10  penetrate the well  10  beneath the tubing hanger interface  90 . This arrangement permits a cable  112  to be run downhole along the outside of the production tubing  110 . In this manner, in some embodiments of the invention, the tubing hanger extension  92  includes electrical connectors  93  that, when the extension  92  is installed, align with the interior surface connectors  62  (FIG. 5B) of the power hanger  74 . When the tubing hanger extension  92  is run into the well  10 , the extension  92  pushes down on the protective sleeve  76  to retract the sleeve  76  for purposes of exposing the electrical connectors  62 . Insulated electric wires  95  of the extension  92  extend through the tubing hanger extension  92  down to the cable  112  that houses the wires  95 . The cable is located on the exterior surface of the production tubing  110  (FIG. 5A) and may be attached to the tubing  110  by clamps  114  (FIG.  5 A), for example. 
     In some embodiments of the invention, part of the string may include radial ports  93  to inject dielectric fluid into the well prior to the mating of the electrical connectors  93  with the connectors  62 . Similar to the radial ports  53  (FIG.  3 A), the radial ports  93  flush the exposed electrical contact areas to improve contact connections and improve electrical insulation around these contacts. The flushing may be performed via a string that is run downhole separately from the string containing the tubing hanger  90  and tubing hanger extension  92 , in some embodiments of the invention. 
     In some embodiments of the invention, the power connections pierce the well tree below the tubing hanger and do not pierce the wellhead. In this manner, FIG. 6A depicts a well  200  with such an arrangement. FIGS. 6B and 6C depict more detailed schematic diagrams of portions  201  and  203 , respectively, of the well, showing in more detail the electrical connections in the well  200 . 
     Referring to FIGS. 6A,  6 B and  6 C, in some embodiments of the invention, the power cable  16  extends from the power source  18  to a connector  240  that has contacts that mate with corresponding connectors  242  (FIG. 6B) that are located on the exterior surface of a sidewall of a well tree  204 . Each connector  242  is associated with and connected to a different insulated conduit  241 . The conduits  241 , in turn, communicate electricity from the connectors  242  to corresponding connectors  247  (FIG. 6B) that are located on the interior surface of the sidewall of the well tree  204 . 
     The well tree  204  is threadably connected to an interior sleeve  260  that has connectors  261  (FIG. 6B) that mate with the connectors  247 , and furthermore, the sleeve  260  includes internal insulated wires  250  (FIG. 6B) that extend along the longitudinal length of the sleeve  260  to lower electrical connectors  264  (FIG. 6C) that are exposed on the interior surface of the sidewall of the sleeve  260 . In some embodiments of the invention, a dielectric material of a protective sleeve  266  (FIG. 6C) covers the contacts  264  in an extended position of the sleeve  266 . Similar to the protective sleeve  76 , the protective sleeve  266  is biased (by a spring, for example) to extend to cover the contacts  264  when not pushed down by the presence of a tubing hanger extension, described below. 
     Also depicted in FIG. 6A, the well  200  may include a casing hanger  220  that is sealed to a wellhead  210  of the well  200  via a seal  214 . The casing hanger  220  hangs a smaller diameter casing  232  into the well  200 . Alternatively, a casing hanger  222  may be used in place of the casing hanger  220 . The casing hanger  222  hangs a larger diameter well casing  230  into the well. 
     Referring to FIG. 7A, the electrical connections described above work in the following manner after a tubing hanger interface  270  and a tubing hanger extension  274  are installed in the well  200 . FIGS. 7B and 7C depict more detailed schematic diagrams of portions  201  and  203 , respectively, of the well, showing in more detail the electrical connections in the well  200 . 
     Referring to FIGS. 7A,  7 B and  7 C, the tubing hanger extension  274  is threadably coupled to the lower end of the tubing hanger interface  270 . The tubing hanger interface  270 , in turn, rests on a corresponding annular shoulder  277  of the well tree  204 . 
     After the tubing hanger  270  and tubing hanger extension  274  are installed, electrical connectors  271  (FIG. 7C) of the tubing hanger extension  274 , which are formed on the exterior surface of the sidewall of the tubing hanger extension  274 , contact corresponding electrical connectors  264  that extend on the interior sidewall of the sleeve  260 . Insulated wires  280  of the tubing hanger extension  274  extend to a cable  292  that houses the wires  280 . The cable  292  extends downhole on a production tubing  290  that is connected (threadably connected, for example) to the tubing hanger extension  274 . The cable  292  may be held in place, for example, by one or more clamps  294  (FIG.  7 A). Other variations are possible. 
     Similar to the other arrangements described above, in some embodiments of the invention, part of the string that includes the tubing hanger  270  and tubing hanger extension  274  may be used to inject dielectric fluid into the well prior to the mating of the electrical connectors  271  with the connectors  264 . In this manner, the dielectric fluid flushes the exposed electrical contact areas to improve contact connections and improve electrical insulation around these contacts. The flushing may be performed via a string that is run downhole separately from the string that contains the tubing hanger  270  and tubing hanger extension  274 , in some embodiments of the invention. 
     Other embodiments are within the scope of the following claims. For example, in some embodiments of the invention, the techniques and systems described above for electrical penetration of the well below the tubing hanger interface may be applied to extend chemical injection into the well. In this manner, the techniques described above may be applied to extending any type of communication into the well tree or wellhead below the tubing hanger interface. Such techniques and systems allow an effective increase in the cross-sectional area of the production tubing. As another example, the communication lines that penetrate the well tree or wellhead below the tubing hanger interface may be hydraulic control lines. Other variations are possible. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.

Summary:
A system that is usable with a well includes a structure that has a region that is adapted to receive a tubing hanger interface. The system also includes at least one communication connection that penetrates the structure below the region to receive the tubing hanger interface.