Abstract:
The existence and rate of corrosion in a section of a well tubing or well casing is determined and monitored by installing at predetermined locations as the string is placed in the well bore, sections of pipe ( 20 ) that have been fitted with an array of piezoelectric transducers ( 26 ) and a microprocessor ( 28 ) that controls signals going to and from each array of transducers and signals going to and received from controls and intrumentation apparatus located at the earth&#39;s surface. The microprocessors at varying locations along the string are electrically connected to the surface control and instrumentation apparatus by conductor cables and/or by wireless means using the pipe string as the conductive path for electrical signals.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of the following U.S. Provisional Applications, all of which are hereby incorporated by reference:  
                                                 COMMONLY OWNED AND PREVIOUSLY FILED       U.S. PROVISIONAL PATENT APPLICATIONS            T&amp;K #   Ser. No.   Title   Filing Date               TH 1599   60/177,999   Toroidal Choke Inductor for   Jan. 24, 2000               Wireless Communication and               Control       TH 1600   60/178,000   Ferromagnetic Choke in   Jan. 24, 2000               Wellhead       TH 1602   60/178,001   Controllable Gas-Lift Well   Jan. 24, 2000               and Valve       TH 1603   60/177,883   Permanent, Downhole, Wire-   Jan. 24, 2000               less, Two-Way Telemetry               Backbone Using Redundant               Repeater, Spread Spectrum               Arrays       TH 1668   60/177,998   Petroleum Well Having   Jan. 24, 2000               Downhole Sensors,               Communication, and Power       TH 1669   60/177,997   System and Method   Jan. 24, 2000               for Fluid Flow               Optimization       TS 6185   60/181,322   A Method and Apparatus for   Feb. 9, 2000               the Optimal Predistortion               of an Electromagnetic Signal               in a Downhole Communica-               tions System       TH 1599x   60/186,376   Toroidal Choke Inductor for   Mar. 2, 2000               Wireless Communication and               Control       TH 1600x   60/186,380   Ferromagnetic Choke in   Mar. 2, 2000               Wellhead       TH 1601   60/186,505   Reservoir Production Control   Mar. 2, 2000               from Intelligent Well Data       TH 1671   60/186,504   Tracer Injection in a Pro-   Mar. 2, 2000               duction Well       TH 1672   60/186,379   Oilwell Casing Electrical   Mar. 2, 2000               Power Pick-Off Points       TH 1673   60/186,394   Controllable Production   Mar. 2, 2000               Well Packer       TH 1674   60/186,382   Use of Downhole High   Mar. 2, 2000               Pressure Gas in a Gas               Lift Well       TH 1675   60/186,503   Wireless Smart Well Casing   Mar. 2, 2000       TH 1677   60/186,527   Method for Downhole Power   Mar. 2, 2000               Management Using               Energization from Distributed               Batteries or Capacitors               with Reconfigurable               Discharge       TH 1679   60/186,393   Wireless Downhole Well   Mar. 2, 2000               Interval Inflow and Injection               Control       TH 1681   60/186,394   Focused Through-Casing   Mar. 2, 2000               Resistivity Measurement       TH 1704   60/186,531   Downhole Rotary Hydraulic   Mar. 2, 2000               Pressure for Valve               Actuation       TH 1705   60/186,377   Wireless Downhole Measure-   Mar. 2, 2000               ment and Control For               Optimizing Gas Lift Well               and Field Performance       TH 1722   60/186,381   Controlled Downhole   Mar. 2, 2000               Chemical Injection       TH 1723   60/186,378   Wireless Power and   Mar. 2, 2000               Communications Cross-Bar               Switch                  
 
         [0002]    The current application shares some specification and figures with the following commonly owned and concurrently filed applications, all of which are hereby incorporated by reference:  
                                                 COMMONLY OWNED AND CONCURRENTLY FILED U.S PATENT       APPLICATIONS                        Filing       T&amp;K #   Ser. No.   Title   Date               TH 1601US   09/                          Reservoir Production Control                   from Intelligent Well Data       TH 1671US   09/                          Tracer Injection in a Production               Well       TH 1672US   09/                          Oil Well Casing Electrical               Power Pick-Off Points       TH 1674US   09/                          Use of Downhole High Pressure               Gas in a Gas-Lift Well       TH 1675US   09/                          Wireless Smart Well Casing       TH 1677US   09/                          Method for Downhole Power               Management Using Energization               from Distributed Batteries or               Capacitors with Reconfigurable               Discharge       TH 1679US   09/                          Wireless Downhole Well               Interval Inflow and               Injection Control       TH 1681US   09/                          Focused Through-Casing               Resistivity Measurement       TH 1704US   09/                          Downhole Rotary Hydraulic               Pressure for Valve               Actuation       TH 1705US   09/                          Wireless Downhole Measure-               ment and Control For               Optimizing Gas Lift Well               and Field Performance       TN 1722US   09/                          Controlled Downhole Chemical               Injection       TH 1723US   09/                          Wireless Power and               Communications Cross-Bar               Switch                  
 
         [0003]    The current application shares some specification and figures with the following commonly owned and previously filed applications, all of which are hereby incorporated by reference:  
                                                 COMMONLY OWNED AND PREVIOUSLY FILED U.S PATENT       APPLICATIONS                        Filing       T&amp;K #   Ser. No.   Title   Date               TH 1599US   09/                          Choke Inductor for Wireless                   Communication and Control       TH 1600US   09/                          Induction Choke for Power               Distribution in Piping Structure       TH 1602US   09/                          Controllable Gas-Lift Well and               Valve       TH 1603US   09/                          Permanent Downhole, Wireless,               Two-Way Telemetry Backbone               Using Redundant Repeater       TH 1668US   09/                          Petroleum Well Having Down-               hole Sensors, Communication,               and Power       TH 1669US   09/                          System and Method for Fluid               Flow Optimization       TH 1783US   09/                          Downhole Motorized Flow               Control Valve       TS 6185US   09/                          A Method and Apparatus for               the Optimal Predistortion               of an Electro Magnetic               Signal in a Downhole               Communications System                  
 
         [0004]    The benefit of 35 U.S.C. § 120 is claimed for all of the above referenced commonly owned applications. The applications referenced in the tables above are referred to herein as the “Related Applications.” 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0005]    1. Field of the Invention  
           [0006]    The present invention relates to a controllable production well packer. In one aspect, it relates to a petroleum production well packer comprising an electrically powered device, in which the device may comprise an electrically controllable valve, a communications and control module, a sensor, a modem, a tracer injection module, or any combination thereof.  
           [0007]    2. Description of the Related Art  
           [0008]    Petroleum wells (e.g., oil and/or gas wells) typically pass through formations containing multiple zones that may produce differing fluids, as well as impermeable zones. The fluid-bearing zones may produce saline or clear water, oil, gas, or a mixture of these components.  
           [0009]    It is desirable and customary to maintain hydraulic isolation between zones so that the fluids produced from each zone may be received separately at the surface. Even if a particular zone is not producing petroleum products, it is usually necessary to ensure that fluids from that zone do not travel to other zones using the wellbore as a transport path, and to avoid contamination of the fluids in each zone.  
           [0010]    The necessary isolation between zones is often provided by packers. A typical hydraulically set production packer of the prior art is schematically shown in FIG. 1. Packers are mechanical devices that close the annulus between the production tubing and the casing, and seal to both. Packers are typically installed at the time of well. completion by attaching them to a tubing string as it is lowered into the well. Thus, during placement, the packer must pass freely within the casing. Once it is in place, a hydraulic actuator (energized and controlled from the surface) operates the sealing mechanism of the packer, which clamps the packer to the casing and effects a fluid-tight seal in the annular space between the tubing and the casing.  
           [0011]    Packers may provide complete isolation between the annular spaces above and below them, or may be equipped with one or more preset mechanically-actuated valves to control flow past them. When control valves are included, however, their settings can only be altered by mechanically inserting a slick-line tool, which is inconvenient, slow, and relatively costly. Additionally, when there are multiple zones and multiple packers it is often impossible or impractical to reach the lowermost packers with a slick-line tool. This lack of a fast and inexpensive method for controlling valves in a packer is a constraint on well design and production operations.  
           [0012]    Conventional packers are known such as described in U.S. Pat. Nos. 6,148,915, 6,123,148, 3,566,963 and 3,602,305.  
           [0013]    All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes, and indicative of the knowledge of one of ordinary skill in the art.  
         BRIEF SUMMARY OF THE INVENTION  
         [0014]    The problems and needs outlined above are largely solved and met by the present invention. In accordance with one aspect of the present invention, a packer adapted for use in a petroleum well, wherein the packer comprises an electrically powered device, is provided. The electrically powered device may comprise an electrically controllable valve adapted to control fluid communication from one side of the packer to another side of the packer when the packer is operably installed. The electrically powered device may further comprise a communications and control module being electrically connected to the electrically controllable valve, wherein the module comprises a modem adapted to receive control commands encoded within communication signals. The module can be adapted to decode the control commands received by the modem and control the movement of the valve using the control commands when the packer is operably installed. Alternatively, the electrically powered device may comprise a sensor adapted to detect at least one physical characteristic of a surrounding environment and generate data corresponding to the physical characteristic, as well as a modem adapted to receive the data from the sensor and electrically transmit the data in the form of an electrical communication signal. Hence, the electrically powered device can comprise an electrically controllable valve, a sensor, a modem, a communications and control module, a tracer injection module, or any combination thereof.  
           [0015]    In accordance with another aspect of the present invention, a petroleum production well incorporating the packer described above is provided. The petroleum well comprises a piping structure, a source of time-varying current, an electrical return, an induction choke, and the packer. The piping structure of the well comprises an electrically conductive portion extending along at least part of the piping structure. The piping structure can comprise a production tubing string of the well. The source of time-varying current comprises two source terminals. A first of the source terminals is electrically connected to the electrically conductive portion of the piping structure. The electrical return electrically connects between the electrically conductive portion of the piping structure and a second of the source terminals of the time-varying current source. The electrical return can comprise a well casing of the well, part of the packer, another packer, and/or a conductive fluid within the well. The induction choke is located about part of the electrically conductive portion of the piping structure at a location along the piping structure between the electrical connection location for the first source terminal and the electrical connection location for the electrical return, such that a voltage potential is formed between the electrically conductive portion of the piping structure on a source-side of the induction choke, and the electrically conductive portion of the piping structure on an electrical-return-side of the induction choke as well as the electrical return when time-varying current flows through the electrically conductive portion of the piping structure. The induction choke can comprise a ferromagnetic material. Also, the induction choke need not be powered when its size, geometry, and magnetic properties can provide sufficient magnetic inductance for developing the voltage potential desired. The electrically powered device of the packer is electrically connected across the voltage potential such that part of the time-varying current is routed through the device due to the induction choke when the time-varying current flows through the electrically conductive portion of the piping structure.  
           [0016]    In accordance with yet another aspect of the present invention, a method of producing petroleum products from a petroleum well comprising an electrically powered packer is provided.  
           [0017]    A conventional petroleum well includes a cased wellbore having a tubing string positioned within and longitudinally extending within the casing. In a preferred embodiment, a controllable packer is coupled to the tubing to provide a seal of the annular space between the tubing and casing. A valve in the packer (and/or other devices, such as sensors) is powered and controlled from the surface. Communication signals and power are sent from the surface using the tubing and casing as conductors. At least one induction choke is coupled about the tubing downhole to magnetically inhibit alternating current flow through the tubing at a choke. An insulating tubing joint, another induction choke, or another insulating means between the tubing and casing can be located at the surface above a location where current and communication signals are imparted to the tubing. Hence, most of the alternating current is contained between the downhole choke and the insulating tubing joint, or between the chokes when two chokes are used.  
           [0018]    The Related Applications describe alternative ways to provide electrical power from the surface to downhole modules, and to establish bidirectional communications for data and commands to be passed between the surface and downhole modules using surface and downhole modems. A preferred embodiment utilizes the production tubing and the well casing as the electrical conduction path between the surface and downhole equipment. The cost reduction and simplification of installation procedures which accrue from obviating the need for electrical cables to provide power, sensing, and control functions downhole allow wider deployment of active equipment downhole during production.  
           [0019]    In the context of downhole packers, the ability to power and communicate with the packer has many advantages. Such a controllable packer in accordance with the present invention may incorporate sensors, with data from the sensors being received in real time at the surface. Similarly, the availability of power downhole, and the ability to pass commands from the surface to the controllable packer, allow electrically motorized mechanical components, such as flow control valves, to be included in packer design, thus increasing their flexibility in use. Notably, the control of such components in the controllable packer hereof is near real time, allowing packer flow control valves to be opened, closed, adjusted, or throttled constantly to contribute to the management of production.  
           [0020]    In a preferred embodiment, a surface computer having a master modem can impart a communication signal to the tubing, and the communication signal is received at a slave modem downhole, which is electrically connected to or within the controllable packer. The communication signal can be received by the slave modem either directly or indirectly via one or more relay modems. Further, electric power can be input into the tubing string and received downhole to power the operation of sensors or other devices in the controllable packer. Preferably, the casing is used as a conductor for the electrical return.  
           [0021]    In a preferred embodiment, a controllable valve in the packer regulates the fluid communication in the annulus between the casing and tubing. The electrical return path can be provided along part of the controllable packer, and preferably by the expansion of the expansion slips into contact with the casing. Alternatively, the electrical return path may be via a conductive centralizer around the tubing which is insulated in its contact with the tubing, but is in electrical contact with the casing and electrically connected to the device in the packer.  
           [0022]    In enhanced forms, the controllable packer includes one or more sensors downhole which are preferably in contact with the downhole modem and communicate with the surface computer via the tubing and/or well casing. Such sensors as temperature, pressure, acoustic, valve position, flow rates, and differential pressure gauges can be advantageously used in many situations. The sensors supply measurements to the modem for transmission to the surface or directly to a programmable interface controller operating a downhole device, such as controllable valve for controlling the fluid flow through the packer.  
           [0023]    In one embodiment, ferromagnetic induction chokes are coupled about the tubing to act as a series impedance to current flow on the tubing. In a preferred form, an upper ferromagnetic choke. is placed around the tubing below the casing hanger, and the current and communication signals are imparted to the tubing below the upper ferromagnetic choke. A lower ferromagnetic choke is placed downhole around the tubing with the controllable packer electrically coupled to the tubing above the lower ferromagnetic choke, although the controllable packer may be mechanically coupled to the tubing below the lower ferromagnetic choke instead.  
           [0024]    Preferably, a surface computer is coupled via a surface master modem and the tubing to the downhole slave modem of the controllable packer. The surface computer can receive measurements from a variety of sources (e.g., downhole sensors), measurements of the oil output from the well, and measurements of the compressed gas input to the well in the case of a gas lift well. Using such measurements, the computer can compute desired positions of the controllable valve in the packer, and more particularly, the optimum amount of fluid communication to permit into the annulus inside the casing.  
           [0025]    Construction of such a petroleum well is designed to be as similar to conventional construction methodology as possible. That is, after casing the well, a packer is typically set to isolate each zone. In a production well, there may be several oil producing zones, water producing zones, impermeable zones, and thief zones. It is desirable to prevent or permit communication between the zones. For example when implementing the present invention, the tubing string is fed through the casing into communication with the production zone, with controllable packers defining the production zone. As the tubing string is made up at the surface, a lower ferromagnetic choke is placed around one of the conventional tubing strings for positioning above the lowermost controllable packer. In the sections of the tubing strings where it is desired, another packer is coupled to the tubing string to isolate zones. Controllable gas lift valves or sensor pods also may be coupled to the tubing as desired by insertion in a side pocket mandrel (tubing conveyed) and corresponding induction chokes as needed. The tubing string is made up to the surface where an upper ferromagnetic induction choke is again placed around the tubing string below the casing hanger. Communication and power leads are then connected to the tubing string below the upper choke. In an enhanced form, an electrically insulating joint is used instead of the upper induction choke.  
           [0026]    A sensor and communication pod can be incorporated into the controllable packer of the present invention without the necessity of including a controllable valve or other control device. That is, an electronics module having pressure, temperature or acoustic sensors, power supply, and a modem can be incorporated into the packer for communication to the surface computer using the tubing and casing as conductors. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon referencing the accompanying drawings, in which:  
         [0028]    [0028]FIG. 1 is a schematic showing a typical packer of the prior art;  
         [0029]    [0029]FIG. 2 is a schematic showing a petroleum production well in accordance with a preferred embodiment of the present invention;  
         [0030]    [0030]FIG. 3 is a simplified electrical schematic of the embodiment shown in FIG. 2; and  
         [0031]    [0031]FIG. 4 is an enlarged schematic showing a controllable packer, from FIG. 2, comprising an electrically controllable valve. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    Referring now to the drawings, wherein like reference numbers are used herein to designate like elements throughout the various views, a preferred embodiment of the present invention is illustrated and further described, and other possible embodiments of the present invention are described. The figures are not necessarily drawn to scale, and in some instances the drawings have been exaggerated and/or simplified in places for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention, as well as based on those embodiments illustrated and discussed in the Related Applications, which are incorporated by reference herein to the maximum extent allowed by law.  
         [0033]    As used in the present application, a “piping structure” can be one single pipe, a tubing string, a well casing, a pumping rod, a series of interconnected pipes, rods, rails, trusses, lattices, supports, a branch or lateral extension of a well, a network of interconnected pipes, or other similar structures known to one of ordinary skill in the art. The preferred embodiment makes use of the invention in the context of a petroleum well where the piping structure comprises tubular, metallic, electrically-conductive pipe or tubing strings, but the invention is not so limited. For the present invention, at least a portion of the piping structure needs to be electrically conductive, such electrically conductive portion may be the entire piping structure (e.g., steel pipes, copper pipes) or a longitudinal extending electrically conductive portion combined with a longitudinally extending non-conductive portion. In other words, an electrically conductive piping structure is one that provides an electrical conducting path from a first portion where a power source is electrically connected to a second portion where a device and/or electrical return is electrically connected. The piping structure will typically be conventional round metal tubing, but the cross-section geometry of the piping structure, or any portion thereof, can vary in shape (e.g., round, rectangular, square, oval) and size (e.g., length, diameter, wall thickness) along any portion of the piping structure. Hence, a piping structure must have an electrically conductive portion extending from a first portion of the piping structure to a second portion of the piping structure, wherein the first portion is distally spaced from the second portion along the piping structure.  
         [0034]    Note that the terms “first portion” and “second portion” as used herein are each defined generally to call out a portion, section, or region of a piping structure that may or may not extend along the piping structure, that can be located at any chosen place along the piping structure, and that may or may not encompass the most proximate ends of the piping structure.  
         [0035]    Similarly, in accordance with conventional terminology of oilfield practice, the descriptors “upper”, “lower”, “uphole” and “downhole” are relative and refer to distance along hole depth from the surface, which in deviated or horizontal wells may or may not accord with vertical elevation measured with respect to a survey datum.  
         [0036]    Also note that the term “modem” is used herein to generically refer to any communications device for transmitting and/or receiving electrical communication signals via an electrical conductor (e.g., metal). Hence, the term “modem” as used herein is not limited to the acronym for a modulator (device that converts a voice or data signal into a form that can be transmitted)/demodulator (a device that recovers an original signal after it has modulated a high frequency carrier). Also, the term “modem” as used herein is not limited to conventional computer modems that convert digital signals to analog signals and vice versa (e.g., to send digital data signals over the analog Public Switched Telephone Network). For example, if a sensor outputs measurements in an analog format, then such measurements may only need to be modulated (e.g., spread spectrum modulation) and transmitted—hence no analog/digital conversion needed. As another example, a relay/slave modem or communication device may only need to identify, filter, amplify, and/or retransmit a signal received.  
         [0037]    As used in the present application, “wireless” means the absence of a conventional, insulated wire conductor e.g. extending from a downhole device to the surface. Using the tubing and/or casing as a conductor is considered “wireless.” The term “valve” as used herein generally refers to any device that functions to regulate the flow of a fluid. Examples of valves include, but are not limited to, bellows-type gas-lift valves and controllable gas-lift valves, each of which may be used to regulate the flow of lift gas into a tubing string of a well. The internal workings of valves can vary greatly, and in the present application, it is not intended to limit the valves described to any particular configuration, so long as the valve functions to regulate flow. Some of the various types of flow regulating mechanisms include, but are not limited to, ball valve configurations, needle valve configurations, gate valve configurations, and cage valve configurations. The methods of installation for valves discussed in the present application can vary widely.  
         [0038]    The term “electrically controllable valve” as used herein generally refers to a “valve” (as just described) that can be opened, closed, adjusted, altered, or throttled continuously in response to an electrical control signal (e.g., signal from a surface computer or from a downhole electronic controller module). The mechanism that actually moves the valve position can comprise, but is not limited to: an electric motor; an electric servo; an electric solenoid; an electric switch; a hydraulic actuator controlled by at least one electrical servo, electrical motor, electrical switch, electric solenoid, or combinations thereof; a pneumatic actuator controlled by at least one electrical servo, electrical motor, electrical switch, electric solenoid, or combinations thereof; or a spring biased device in combination with at least one electrical servo, electrical motor, electrical switch, electric solenoid, or combinations thereof. An “electrically controllable valve” may or may not include a position feedback sensor for providing a feedback signal corresponding to the actual position of the valve.  
         [0039]    The term “sensor” as used herein refers to any device that detects, determines, monitors, records, or otherwise senses the absolute value of or a change in a physical quantity. A sensor as described herein can be used to measure physical quantities including, but not limited to: temperature, pressure (both absolute and differential), flow rate, seismic data, acoustic data, pH level, salinity levels, valve positions, or almost any other physical data.  
         [0040]    [0040]FIG. 1 is a schematic showing a conventional hydraulically set production packer  20  of the prior art set within a well casing  22  of a well. The packer  20  of FIG. 1 is threaded to a production tubing string  24 . The conventional packer  20  has a tail piece  26  that may terminate with an open or closed end for the lowest packer in the completed well, or the tail piece  26  may be threaded onto tubing (not shown) that passes to lower regions of the well. The conventional packer  20  has a section of slips  28  and a seal section  30 . Both the slips  28  and the seal section  30  can pass freely inside the well casing  22  during placement, and are operated by a hydraulic actuator  32 . When the packer  20  is at its final location in the casing  22 , the hydraulic actuator  32  is used to exert mechanical forces on the slips  28  and the seals  30  causing them to expand against the casing. The slips  28  lock the packer  20  in place by gripping the internal surface of the casing  22  so that the packer cannot be displaced by differential pressure between the spaces above and below the packer. The seal section  30  creates a liquid-tight seal between the spaces above and below the packer  20 . The hydraulic actuator  32  is operated using high-pressure oil supplied from the surface (not shown) by a control tube  34 . However, the conventional packer  20  does not comprise an electrically powered device.  
         [0041]    [0041]FIG. 2 is a schematic showing a petroleum production well  38  in accordance with a preferred embodiment of the present invention. The petroleum production well  38  shown in FIG. 2 is similar to a conventional well in construction, but with the incorporation of the present invention. In this example, a packer  40  comprising an electrically powered device  42  is placed in the well  38  in the same manner as a conventional packer  20  would be—to separate zones in a formation. In the preferred embodiment, the electrically powered device  42  of the packer  40  comprises an electrically controllable valve  44  that acts as a bypass valve, as shown in more detail in FIG. 4 and described further below.  
         [0042]    In a preferred embodiment, the piping structure comprises part of a production tubing string  24 , and the electrical return comprises part of a well casing  22 . An insulating tubing joint  146  and a ferromagnetic induction choke  48  are used in this preferred embodiment. The insulating joint  146  is incorporated close to the wellhead to electrically insulate the lower sections of tubing  24  from casing  22 . Thus, the insulating joint  146  prevents an electrical short-circuit between the lower sections of tubing  24  and casing  22  at the tubing hanger  46 . The hanger  46  provides mechanical coupling and support of the tubing  24  by transferring the weight load of the tubing  24  to the casing  22 . The induction choke  48  is attached about the tubing string  24  at a second portion  52  downhole above the packer  40 . A computer system  56  comprising a master modem  58  and a source of time-varying current  60  is electrically connected to the tubing string  24  below the insulating tubing joint  146  by a first source terminal  61 . The first source terminal  61  is insulated from the hanger  46  where it passes through it. A second source terminal  62  is electrically connected to the well casing  22 , either directly (as in FIG. 2) or via the hanger  46  (arrangement not shown). In alternative to or in addition to the insulating tubing joint  146 , another induction choke (not shown) can be placed about the tubing  24  above the electrical connection location for the first source terminal  61  to the tubing.  
         [0043]    The time-varying current source  60  provides the current, which carries power and communication signals downhole. The time-varying current is preferably alternating current (AC), but it can also be a varying direct current (DC). The communication signals can be generated by the master modem  58  and embedded within the current produced by the source  60 . Preferably, the communication signal is a spread spectrum signal, but other forms of modulation could be used in alternative.  
         [0044]    The electrically powered device  42  in the packer  40  comprises two device terminals  71 ,  72 , and there can be other device terminals as needed for other embodiments or applications. A first device terminal  71  is electrically connected to the tubing  24  on a source-side  81  of the induction choke  48 , which in this case is above the induction choke. Similarly, a second device terminal  72  is electrically connected to the tubing  24  on an electrical-return-side,  82  of the induction choke  48 , which in this case is below the induction choke. In this preferred embodiment, the slips  28  of the packer  40  provide the electrical connection between the tubing  24  and the well casing  22 . However, as will be clear to one of ordinary skill in the art, the electrical connection between the tubing  24  and the well casing  22  can be accomplished in numerous ways, some of which can be seen in the Related Applications, including (but not limited to): another packer (conventional or controllable); conductive fluid in the annulus between the tubing and the well casing; a conductive centralizer; or any combination thereof. Hence, an electrical circuit is formed using the tubing  24  and the well casing  22  as conductors to the downhole device  42  within the packer  40 .  
         [0045]    [0045]FIG. 3 illustrates a simplified electrical schematic of the electrical circuit formed in the well  38  of FIG. 2. The insulating tubing joint  146  and the induction choke  48  effectively create an isolated section of the tubing string  24  to contain most of the time-varying current between them. Accordingly, a voltage potential develops between the isolated section of tubing  24  and the well casing  22  when AC flows through the tubing string. Likewise, the voltage potential also forms between tubing  24  on the source-side  81  of the induction choke  48  and the tubing  24  on the electrical-return-side  82  of the induction choke  48  when AC flows through the tubing string. In the preferred embodiment, the electrically powered device  42  in the packer  40  is electrically connected across the voltage potential between the source-side  81  and the electrical-return-side  82  of the tubing  24 . However in alternative, the device  42  can be electrically connected across the voltage potential between the tubing  24  and the casing  22 , or the voltage potential between the tubing  24  and part of the packer  40  (e.g., slips  28 ), if that part of the packer is electrically contacting the well casing  22 . Thus, part of the current that travels through the tubing  24  and casing  22  is routed through the device  42  due to the induction choke  48 .  
         [0046]    As is made clear by consideration of the electrical equivalent circuit diagram of FIG. 3, centralizers which are installed on the tubing between isolation device  47  and choke  48  must not provide an electrically conductive path between tubing  24  and casing  22 . Suitable centralizers may be composed of solid molded or machined plastic, or may be of the bow-spring type provided these are furnished with appropriate insulating elements. Many suitable and alternative design implementations of such centralizers will be clear to those of average skill in the art.  
         [0047]    Other alternative ways to develop an electrical circuit using a piping structure and at least one induction choke are described in the Related Applications, many of which can be applied in conjunction with the present invention to provide power and/or communications to the electrically powered device  42  of the packer  40  and to form other embodiments of the present invention.  
         [0048]    Turning to FIG. 4, which shows more details of the packer  40  of FIG. 2, it is seen that the controllable packer  40  is similar to the conventional packer  20  (shown in FIG. 1), but with the addition of an electrically powered device  42  comprising an electrically controllable valve  44  and a communications and control module  84 . The communications and control module  84  is powered from and communicates with the computer system  56  at the surface  54  via the tubing  24  and/or the casing  22 . The communications and control module  84  may comprise a modem  86 , a power transformer (not shown), a microprocessor (not shown), and/or other various electronic components (not shown) as needed for an embodiment. The communications and control module  84  receives electrical signals from the computer system  56  at the surface  54  and decodes commands for controlling the electrically controlled valve  44 , which acts as a bypass valve. Using the decoded commands, the communications and control module  84  controls a low current electric motor that actuates the movement of the bypass valve  44 . Thus, the valve  44  can be opened, closed, adjusted, altered, or throttled continuously by the computer system  56  from the surface  54  via the tubing  24  and well casing  22 .  
         [0049]    The bypass valve  44  of FIG. 4 controls flow through a bypass tube  88 , which connects inlet and outlet ports  90 ,  92  at the bottom and top of the packer  40 . The ports  90 ,  92  communicate freely with the annular spaces  94 ,  96  (between the casing  22  and the tubing  24 ), above and below the packer  40 . The bypass control valve  44  therefore controls fluid exchange between these spaces  94 ,  96 , and this exchange may be altered in real time using commands sent from the computer system  56  and received by the controllable packer  40 .  
         [0050]    The mechanical arrangement of the packer  40  depicted in FIG. 4 is illustrative, and alternative embodiments having other mechanical features providing the same functional needs of a packer (i.e., fluidly isolating and sealing one casing section from another casing section in a well, and in the case of a controllable packer, regulating and controlling fluid flow between these isolated casing sections) are possible and encompassed within the present invention. For instance, the inlet and outlet ports  90 ,  92  may be exchanged to pass fluids from the annular space  94  above the packer  40  to the space  96  below the packer. Also, the communications and control module  84  and the bypass control valve  44  may be located in upper portion of the packer  40 , above the slips  28 . The controllable packer  40  may also comprise sensors (not shown) electrically connected to or within the communication and control module  84 , to measure pressures or temperatures in the annuli  94 ,  96  or within the production tubing  24 . Hence, the measurements can be transmitted to the computer system  56  at the surface  54  using the communications and control module  84 , providing real time data on downhole conditions. Also the setting and unsetting mechanism of the packer slips may be actuated by one or more motors driven and controlled by power and commands received by module  84 .  
         [0051]    In other possible embodiments of the present invention, the electrically powered device  42  of the packer  40  may comprise: a modem  86 ; a sensor (not shown); a microprocessor (not shown); a packer valve  44 ; a tracer injection module (not shown); an electrically controllable gas-lift valve (e.g., for controlling the flow of gas from the annulus to inside the tubing) (not shown); a tubing valve (e.g., for varying the flow of a tubing section, such as an application having multiple branches or laterals) (not shown); a communications and control module  84 ; a logic circuit (not shown); a relay modem (not shown); other electronic components as needed (not shown); or any combination thereof.  
         [0052]    Also in other possible embodiments of the present invention, there may be multiple controllable packers and/or multiple induction chokes. In an application where there are multiple controllable packers or additional conventional packers combined with the present invention, it may be necessary to electrically insulate some or all of the packers so that a packer does not act as a short between the piping structure (e.g., tubing  24 ) and the electrical return (e.g., casing  22 ) where such a short is not desired. Such electrical insulation of a packer may be achieved in various ways apparent to one of ordinary skill in the art, including (but not limited to): an insulating sleeve about the tubing at the packer location; a rubber or urethane portion at the radial extent of the packer slips; an insulating coating on the tubing at the packer location; forming the slips from non-electrically-conductive materials; other known insulating means; or any combination thereof. The present invention also can be applied to other types of wells (other than petroleum wells), such as a water well.  
         [0053]    It will be appreciated by those skilled in the art having the benefit of this disclosure that this invention provides a packer comprising an electrically powered device, as well as a petroleum production well incorporating such a packer. It should be understood that the drawings and detailed description herein are to be regarded in an illustrative rather than a restrictive manner, and are not intended to limit the invention to the particular forms and examples disclosed. On the contrary, the invention includes any further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments apparent to those of ordinary skill in the art, without departing from the spirit and scope of this invention, as defined by the following claims. Thus, it is intended that the following claims be interpreted to embrace all such further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments.