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TECHNICAL FIELD 
   The present invention relates in general to downhole operations and the production of electrical power within an oil producing wellbore. More specifically, the invention relates to a system for generating power from fluid flow through production tubing in a wellbore. Still more specifically, the invention relates to such a system using a magnetized rotation member that operates on principles similar to a Darrieus rotor and that is capable of generating a magnetic field to produce useable power. 
   BACKGROUND OF THE INVENTION 
   Downhole well applications, such as those used to extract crude oil from one or more production zones underneath the earth&#39;s surface, often require downhole power in order to operate components such as pressure and temperature sensors in the well. Current systems requiring downhole power include intelligent wells and permanent gauge installations where sensors or actuators are used in order to operate chokes and restrict fluid flow into a well at different levels for multiple zone production. Such systems are often necessary for control of pressure and flow from various zones. 
   Prior art downhole power generating systems include the use of an umbilical to power sensors and actuators from the surface. A typical umbilical comprises a protected electrical tethered line that can be used to deliver both power and data to the component as well as other downhole devices requiring power. In addition, wireless telemetry methods have proven useful for communications and general interfacing with such components and as a means of facilitating data transmission between the surface operator and the downhole device. Finally, batteries and battery packs can be used for short term power applications. 
   While such downhole power systems have proven useful, they do not meet the long term power needs of modern day production operations. For example, while the use of an umbilical is suitable for providing power and data communications to devices, the practical difficulties related to their installation and maintenance limits their long term usefulness. At the same time, umbilical systems can interfere with and obstruct the well, production tubing, and other down hole structures by restricting passage of tools and other components into the wellbore. The use of wireless telemetry with batteries has been contemplated, but such systems suffer from an inability to provide useful levels of power or sustain power over long periods of time. 
   Therefore, a long term downhole power solution that is suitable for use in a modem wellbore operation would provide numerous advantages. 
   SUMMARY OF THE INVENTION 
   The present invention provides a robust and efficient system for downhole power generation. The system utilizes a rotation member that operates on principles similar to those of a Darrieus rotor providing full access to the wellbore for passing tools into the wellbore. The airfoil is efficient, long lasting and can operate under a wide variety of flow conditions. 
   According to one embodiment, disclosed is a system for generating power from fluid flow in a wellbore. The system comprises a rotation member having a passageway through which objects may pass into the wellbore. A support mechanism is coupled to the rotation member inside the wellbore such that fluid flow through the passageway causes the rotation member to rotate. The rotation member is magnetized such that when it rotates it generates a magnetic field that produces usable power. Magnetic pickups are arranged about the rotation member within the magnetic flux lines of the magnetic field. 
   This system may further comprise a power conditioning unit and leads extending from magnetic pickups to a power conditioning unit such that a magnetic field generated by the rotational motion of the rotation member induces a current within the leads that is received by the power conditioning unit. The power conditioning unit may include a rectifier circuit to control the characteristics of the power generated by the rotation member. 
   The system may also comprise an output terminal coupled to the power conditioning unit and a lead extending from the output terminal to a component requiring power within the wellbore. The power conditioning unit may comprise one or more batteries, a capacitive bank, or a fuel cell adapted for storing the power generated by the rotation member. According to another embodiment, a starter rotor is provided comprising a pair of offset drag members which provide resistance to fluid flow within the wellbore and thereby facilitate rotation of the airfoil along the direction of fluid flow within the wellbore. A means of controlling the rotation of the rotation member may be provided, the means comprising a motor for starting and stopping the rotation of the rotation member and a control lead extending from outside the wellbore to the motor for allowing human operation of the motor from a point outside the wellbore. 
   Also disclosed is a power generating system for a oil producing operation having production tubing in a downhole wellbore. The system comprises a magnetized rotation member coupled to the wellbore within the production tubing, the rotation member having a passageway through which objects may be passed within the production tubing. A support mechanism couples the rotation member to the production tubing and allows the rotation of the rotation member within the production tubing. Magnetic pickups are predisposed about the rotation member within the wellbore and a power conditioning unit is provided with leads extending from the magnetic pickups to the power conditioning unit. The system operates such that fluid flow through the production tubing causes the rotation member to rotate and induce a magnetic field on the magnetic pickups such that electrical energy is produced and delivered to the power conditioning unit, the power conditioning unit capable of delivering usable power to any one of several electronic components within the wellbore. 
   The power generating system may further comprise a rectifier circuit for controlling the characteristics of the power stored in the power conditioning unit. A starter rotor may be used to assist the rotation of the rotation member, the starter rotor comprising a pair of offset and curved drag members which provide resistance to fluid flow within the wellbore and thereby facilitate rotation of the rotation member along the direction of fluid flow within the production tubing. In one embodiment, a DC-to-DC converter circuit is provided for delivering a stable DC voltage. 
   Also disclosed is a system for extracting fluids from a plurality of production zones intersected by a wellbore, the system including downhole power generation. The system comprises production tubing extending along a substantial length of the wellbore, the production tubing including at least one valve at each of the plurality of production zones with passages extending from the production zones to, each valve permitting the flow of fluid from the plurality of production zones into the production tubing via the valve. The system further comprises at least one magnetized rotation member coupled within the production tubing and predisposed to make contact with fluid flowing through the production tubing as a valve opens to permit fluid to flow from a production zone, the rotation member having a passageway through which objects may pass into the wellbore via the production tubing, wherein fluid flow through the passageway causes the rotation member to rotate thereby generating a magnetic field that produces useable power. 
   In one embodiment, the system further comprises a rotation member at each production zone intersected by the wellbore. The rotation members may be coupled together in series or parallel for high voltage and/or high current applications. 
   An advantage of the present invention is that it provides full access to the components in the wellbore and does not restrict the diameter of the production tubing, allowing tools to pass through the wellbore without clogging. 
   Another advantage of the present invention is that the rotation member provides a downhole power generation system with a relatively long life compared to umbilical systems and batteries. 
   Still another advantage of the present invention is the ability to provide downhole electrical power for long periods of time. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above advantages and specific embodiments will be understood from consideration of the following detailed description taken in conjunction with the appended drawings in which: 
       FIG. 1  is a figure illustrating a typical wellbore intersecting a plurality of production zones; 
       FIG. 2  shows a downhole operation with production tubing installed; 
       FIG. 3  illustrates a magnetized rotation member according to the present invention; 
       FIGS. 4A ,  4 B, and  4 C illustrate use of the downhole power generating system of the present invention; 
       FIGS. 5A and 5B  show two configuration of the rotation member according to the present invention; 
       FIG. 6  is a circuit schematic of a power generating system; 
       FIGS. 7A and 7B  illustrate the positioning of an rotation member within production tubing; 
       FIG. 8  show the use of multiple rotation members for generating downhole power; and 
       FIG. 9  illustrates a downhole operation for extracting fluids such as crude oil from a plurality of production zones intersected by a wellbore having a system for downhole power generation according to the invention. 
   

   References in the detailed description correspond to like references in the figures unless otherwise indicated. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention provides a system for generating power within a wellbore and, more specifically, a downhole operation utilizing production tubing to remove fluids, such as crude oil, from one or more production zones underneath the earth&#39;s surface. With reference now to the figures, and in particular to  FIG. 1 , therein is shown a typically downhole operation, denoted generally as  10 , in which the present invention may be utilized. In essence, the downhole operation  10  provides an excavation underneath the earth&#39;s surface  14  which is created using well known techniques in the energy industry. The operation  10  includes a wellbore  12  with wall  16  lined with casing  18  which has a layer of cement between the wellbore  12  and the casing  18  such that a hardened shell is formed along the interior of the wellbore  12 . For convenience, the singular and plural of a term (“passageway” and “passageways”, “zone” or “zones”, “sleeve” or “sleeves”, “packer” or “packers”, etc.) will be used interchangeable throughout and with the same reference number associated with both forms of the term. 
     FIG. 1  also shows a plurality of production zones  20  in which drilling operations are concentrated for the extraction of oil. Each production zone  20  is shown to have one or more passageways  22  leading from the production zone  20  to the interior of the wellbore  12 . The passageways  22  allow a flow of fluid from a production zone  20  into the wellbore  12  for extraction using methods well known to those of ordinary skill. Typically, the excavation of a wellbore, such as wellbore  12 , is a time consuming and costly operation and involves the drilling underneath the surface  14  to great depths. Therefore, it is expected that the wellbore  12  will be utilized for a relatively long period of time such that the operator can justify the investment in time and money. 
   Turning now to  FIG. 2 , therein is shown an example downhole operation with production tubing  40  installed within the wellbore  12 . Essentially, the production tubing  40  provides the means of extracting fluids from the production zones  20  via a passageway extending underneath the surface  14  to above the earth. As shown, production tubing  40  consists of tube sections  42 A,  42 B,  42 C with end  44 , although the production tubing  40  may consist or more or less segments. The sections  42 A,  42 B,  42 C are joined together with sleeves  50 , each sleeve  50  being contained in an area defined by packers  60 , the use of which are well known in the industry. The physics governing the flow of fluids from a production zone  20  through the production tubing  40  is well known. As described below, the present invention utilizes the pressure regions defined by the packers  60  to provide the power generation functions of the present invention. 
   Seal  70  caps the production tubing  40  near the surface  14  of the downhole operation  10 . Each sleeve  50  has a corresponding valve  52  which can be operated via control lead  80  which provides a cable and means for passageway and closing valves  52 . In this way, the wellbore operator is able to control the flow of oil from any one of the available production zones  20  at any given time and at a desired level underneath surface  14 . Thus, the basic components of an oil drilling operation suitable for extracting oil from production zones  20  have been described. 
   Still referring to  FIGS. 1 and 2 , the control lead  80  runs within an area known as an annulus  90  between the casing  16  and the production tubing  40 . The control lead  80  is operably coupled to sensors  92  which are positioned at different levels of the wellbore  12  about corresponding production zones  20 . In addition, the control lead  80  is operably coupled to chokes  94  which are used to operate corresponding valves  52 , and thereby restrict fluid flow into the wellbore  12  at different levels, permitting production out of multiple zones intersected by the production tubing  40 . As is well known in the art, by controlling fluid flow in this manner, the wellbore operator can have production from both a high pressure zone and a lower pressure zone. Moreover, by placing valves  52  at various levels where oil: producing formations are found, oil can be extracted using a singular piece of production tubing  40 , thereby optimizing the production operation for multiple zones at the same time and over a relatively long period of time. 
   Given that a typical wellbore operation, such as downhole operation  10 , is in use for years, it is often necessary to provide power to various components and devices within the wellbore  12 , but it may not be possible or desirable. Examples of such components include the sensors  92 , chokes  94 , and valves  52  used to control fluid flow. Prior art systems for power generation within the wellbore  12  include umbilical systems, batteries, and wireless telemetry, among others. The problems associated with such prior art power generation system are discussed above and relate generally to their inability to provide a long term source of power that does not interfere with production operations and allows the operator complete access to the wellbore  12  and production tubing  40 . For example, while the control lead  80  can be placed within an electrical tethered line that forms an umbilical into the passageway formed by the wellbore  12 , running such a line through the packers  60 , and through the entire length of the wellbore  12  can be a complicated and time-consuming task. 
   Moreover, while the data and control interface to the sensors  92  may be achieved using wireless telemetry, power must still be provided with a physical line coupled to the electrical components in the wellbore  12 . Apart from the difficulties of running a power line within the wellbore  12 , there is the added consideration that a physical line consumes space and therefore may interfere with access to the wellbore  12  and/or restrict the diameter of the wellbore  12  such that tools cannot pass into the wellbore  12 . At the same time, once the production tubing  40  is in place within the wellbore  12 , it may not be possible or desirable to remove the tubing  40  in order to replace sensors  92  or batteries needed to power them. Thus, what is needed is an efficient and robust solution for downhole power generation. 
   The present invention provides a way of powering components, such as sensors  92 , chokes  94 , and valves  52  within the wellbore  12  of a typical oil producing operation, such as downhole operation  10 . With the present invention, a downhole power generation system is provided that allows electrical power to be generated for a long period of time (5 to 10 years, for example) without disturbing the production tubing  40  or restricting access to the wellbore  12 . While the invention is described as useful in providing power to component in a well, such as wellbore  12 , it should be understood that the principles disclosed may have application in numerous production systems such as those where you may use more than one well or where you have multi-lateral wells. 
   Therefore, having described the components and general aspects of a typical downhole operation, reference is made to  FIG. 3 , which illustrates the downhole wellbore power generation system, denoted generally as  100 , according to the invention. Power generation system  100  can be used to generate electrical power from fluid flow, such as crude oil, through production tubing  40 . As shown, the power generation system  100  includes a rotation member  110  with a passageway  112  through which objects may be passed. The passageway  112  facilitates the passage of tools into the wellbore  12  and, specifically, through the production tubing  40 . 
   The downhole power generation system  100  operates on similar principles as a Darrieus rotor. Fluid flow, indicated by arrow  102 , causes the rotation member  110  to rotate in the direction of arrow  104  which, in turn, generates a magnetic field which induces a current. The rotation member  110  comprises a rotation member or may be formed from two (2) arched and semi-circular arms that join at the first and second braces  170 ,  172  which provide a support mechanism for the rotation member within the production tubing  40 . The braces  170 ,  172  are but one form of a suitable support mechanism and those skilled in the art will readily recognize that other ways of supporting the rotation member  110  may be employed, such as a U-shaped hold, or single brace arm. Braces  170 ,  172  provide free rotation of the rotation member  110  in the direction of arrow  104 . No specific means of rotation is required, although internal bearings (not shown) may be used to provide rotation as well as other designs as would be well understood by those of ordinary skill in the art. 
   In one embodiment, the rotation member  110  is made of a magnetic material. Alternatively, one or more magnets may also be attached to or otherwise connected to or within the rotation member  110  to create the desired field effects. In addition, one or more starter rotors  120  may be provided to assist the rotation member  110  during initial rotation after the onset of fluid flow. As shown, the power generation system  100  is contained within a section  130  of the production tubing  40  such as, for example, a sleeve  50  between two packers  60 . 
   It should be understood that the rotation member  110  can be used not only in production wells, but in injection wells such as those where water floods or steam floods are used, to produce power in those wells. Furthermore, the rotation member  110  can also be located in the annulus section of the well to be turned by lift gas that is injected down the annular which, as is well known in the art, is used to help lift the production fluids. Thus, any type of fluid moving through the well can be used to cause the rotation member to produce energy. Moreover, it will be readily appreciated that the rotation member  110  may be used in lateral wells as opposed to or in combination with the main well fork to keep the rest of the well bore clear and to provide easier access for getting tools in and out to all of the various laterals. 
   With reference to  FIGS. 4A ,  4 B, and  4 C, the rotational motion of the rotation member  110  within production tubing  40  is illustrated in more detail.  FIG. 4A  shows rotation member  110  partially blocking passageway  140  of section  130  of the production tubing. As fluid flows through passageway  140 , it is caught by the starter rotor  120  which is configured to translate the pressure of the fluid flow to the rotation member  110 . As seen more clearly in  FIG. 4B , the starter rotor  120  is comprised of a pair of offset and curved drag members  121 ,  122  which provide resistance to fluid flow within the wellbore  12  and thereby facilitate rotation of the rotation member  110  along the direction of fluid flow. Rotation member  110  is fixed about an axis of rotation X within the production tubing  40  such that it rotates from a position of partial obstruction ( FIG. 4A ) to no obstruction (FIG.  4 B). As shown, the axis of rotation X lies substantially perpendicular to the lengthwise axis Y of the wellbore  12  and production tubing  40 . Thus, full access to the wellbore  12  is maintained in at least one position of the rotation member  110 . Braces  170 ,  172  provide rotation points and couple the rotation member  110  to section  130 . 
   Magnetic pickups  150 ,  152  are positioned about the rotation member  110  and configured to translate the rotational motion of the rotation member  110  into electric energy in the form of current  160 . A magnetic field  180  is generated by the rotational action of the rotation member  110  which induces current  160  which traverses leads  154  and  156  extending from the magnetic pickups  150 ,  152  to a load or to a power conditioning unit for storage and rectification. Preferably, the rotation of the rotation member  110  can be operator controlled from the outside such that the rotation member  110  can be maintained in the open position ( FIG. 4B ) permitting full access to the wellbore  12  and passage of tools. Since the rotation member  110  and other components are self-contained and can be made using high strength and long lasting materials, the power generation system  100  of the invention is robust and efficient. 
   With reference to  FIGS. 5A and 5B , therein is shown the use of the downhole power generating system  100  of the present invention according to different configurations. Specifically, in  FIG. 5A  the rotation member  110  is located within a sleeve  50  of the production tubing  40  inside the wellbore  12 . Also, the magnetic pickup  150  extends from an area outside the sleeve  50  but within the distance of the magnetic flux lines of the field  180  produced by the rotation member  110  as it rotates. The magnetic pickup  150  has lead  154  extending through packer  60 , and coupled to power conditioning unit  200  where current induced on the magnetic pickup  150  is delivered. The power conditioning unit  200  can include power storage  202  and a rectifier circuit  204  that provide the ability to store and deliver a steady power value for use by a load, such as a sensor  92  within the wellbore  12 . Many forms of a suitable power storage  202  are envisioned including batteries, a capacitive bank, or fuel cell, as examples. 
     FIG. 5B  shows the positioning of the rotation member  110  about tube section  42 A of the production tubing  40 . In this location, the rotation member  110  can be positioned anyplace where fluid flow is encountered thereby providing simple installation and the ability to place multiple rotation members  110  through the wellbore  12 . The use of multiple rotation members is illustrated in more detail in  FIGS. 8 and 9 . 
     FIG. 6  is a circuit diagram of the power generating system of the present invention. Current I is generated by source  250  coupled to bridge circuit  252 . The bridge circuit  252  provides an interface between the power storage and the source  250 . As shown, the power storage is a capacitor  254  although other forms of storing a charge, such as a battery or fuel cell, may be used. A DC-to-DC converter circuit  260  is capable of rectifying the energy stored in capacitor  254  and delivering a steady amount of power to load  270  representing the electrical component inside the wellbore  12  to be powered. 
     FIGS. 7A and 7B  illustrate the placement of the rotation member  110  within production tubing  40 . Line X intersects the rotation member  110  about its axis of rotation which is substantially perpendicular to the lengthwise axis Y of the wellbore  12  and production tubing  40 .  FIG. 7B  shows the cross-section of the rotation member about line X and in particular how the magnetic pickups  150 ,  152  can be located to be adjacent to the rotation member  110 . The magnetic pickups  150 ,  152  fit in the area between the casing  18  and the production tubing  40  known as the annulus  90 . Since no obstruction of the annulus  90  and the production tubing  40  takes place, full access to the wellbore  12  is provided. As shown, magnets  300 ,  302  are attached to the rotation member  110  at a location near the magnetic pickups  150 ,  152 . 
   Therefore, the present invention provides a power generating solution that may be configured according to the power needs of the downhole operation. For example,  FIG. 8  shows the use of multiple rotation members  110  within the production tubing  40  of a wellbore, the rotation members  110  coupled to each other via leads  350  and  352  and extending to load  270 . Thus, rotation members  110  may L=be stacked in a series or parallel configuration for high voltage and/or high current applications as required by the load  270 . Moreover, the current generated by the rotation members  110  may be controlled via control lead  360  which couples one or more of the rotation members  110  within and allows operator control of the rotating action of the rotation members  110  from above the earth&#39;s surface. In this way, an operator can control when one or more of the rotation members  110  start and stop rotation as well as the speed of rotation which, in turn, controls the strength of the magnetic field and the amount of current induced in the magnetic pickups. 
     FIG. 8  shows each rotation member  110  having its own power conditioning unit  200 . It should be understood, however, that other ways of conditioning the power generated by the rotation members  110  may be employed. For example, a single power conditioning unit  200  may be sufficient to service all rotation members  110  according to the electrical power needs of the downhole operation.  FIG. 9  shows the use of multiple rotation members  110  in place within the production tubing  40  of a downhole operation with control lead  360  extending through the production tubing  40  and to each rotation member  110 . An electromechanical motor  400  is provided and coupled to the control lead  360  for starting and stopping the rotating action of the rotation members  110  as well as speed of rotation. Activation of the rotation member  110  can be done achieved either by surface control or in response to sensors and control systems down hole. If done from the surface, it can be done by any of a number of methods all well known in the art, such as direct hard wire connection, hydraulic lines, acoustic telemetry, radio wave signals, pressure pulses or changes, etc. Likewise, the rotation member  110  may be turned ON and OFF in response to conditions down hole or as needed by equipment down hole, and may be activated or de-activated based upon those needs. For instance, if a high percentage of water is being detected coming in from one zone, the rotation member  110  can be activated by a down hole command and the control system can activate the rotation member to generate power to be used to shut the sliding sleeve and cut off the intruding water. 
   As shown, each rotation member  110  is associated with its own power conditioning unit  200 , although other configurations may be used. Also, each power conditioning unit  200  has an output terminal  380  leading to a component requiring power, in this case sensors  92 . Thus, the present invention provides a system for extracting crude oils, or other fluids, from a plurality of production zones  20  intersected by a wellbore  12  with downhole power generation. 
   It should be understood that the fluid moving past the rotation member  110  can come from a number of sources besides those discussed above. For example, the fluid may come from injected fluid, such as lift gas, or steam, or water used for flooding for secondary recovery purposes. The fluid movement can also be from fluid being moved from one zone in the well bore to another, as in the case where water comes out of a down hole oil water separator that&#39;s being transferred down and pumped into, or transferred to and pumped into a disposal zone at some other location within the well bore. 
   Moreover, while the rotation member  110  is shown located within the production tubing  40 , the rotation member  12  may be located in other locations of the well bore that allows fluid movement, i.e. where sufficient fluid movement occurs and where enough space is found to hold a rotation member  110 . For instance, the rotation member  110  may be located in the annular space where lift gas is being pumped in or possibly in the perforations or sliding sleeve ports where production fluid is entering the tubing  40  or annular areas. 
   Likewise, the invention can also be used in drilling systems to provide power down hole to operate the usual devices that are well known in the art in drilling operations such as, but not limited to, the directional drilling motors, logging equipment, data transmission equipment, etc. The rotation member  110  could be positioned in the general vicinity of the tools to minimize the transmission distance necessary, although other configurations may also be employed. Moreover, a downhole power generating system according to the present invention may work equally well with whatever type of drilling fluid is being used, including drilling muds and foams. 
   Therefore, the embodiments shown and described above are only exemplary. Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description together with details of the invention, the disclosure is illustrative only and changes may be made within the principles of the invention. It is therefore intended that such changes be part of the invention and within the scope of the following claims.

Summary:
A power generating system ( 100 ) for a downhole operation ( 10 ) having production tubing ( 40 ) in a wellbore ( 12 ) includes a magnetized rotation member ( 110 ) coupled to the wellbore ( 12 ) within the production tubing ( 40 ), the rotation member ( 110 ) having a passageway ( 112 ) through which objects, such as tools, may be passed within the production tubing ( 40 ). Support braces ( 170, 172 ) couple the rotation member ( 110 ) to the production tubing ( 40 ) and allow the rotation member ( 110 ) to rotate within the production tubing ( 40 ). Magnetic pickups ( 150, 152 ) are predisposed about the rotation member ( 110 ) within the wellbore ( 12 ) and a power conditioner ( 200 ) is provided to receive currents from the magnetic pickups ( 150, 152 ) for storage and future use. The rotation member ( 110 ) rotates due to the flow of fluid, such as crude oil, through the production tubing ( 40 ) which causes the rotation member ( 110 ) to rotate and induce a magnetic field on the magnetic pickups ( 150, 152 ) such that electrical energy is transmitted to the power conditioner ( 200 ), the power conditioner able to store, rectify, and deliver power to any one of several electronic components within the wellbore ( 12 ).