Abstract:
Downhole wellbore tools are actuated by electrically controllable fluids energized by a magnetic field, for example. When energized, the viscosity state of the fluid may be increased by a degree depending on the fluid formulation. Reduction of the controllable fluid viscosity by terminating a magnetic field acting upon the fluid may permit in situ wellbore pressure to actuate a downhole device, such as a wellbore packer.

Description:
The present application is a continuation of U.S. patent application Ser. No. 09/916,617 filed Jul. 27, 2001, which issued as U.S. Pat. No. 6,568,470 on May 27, 2003. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the art of earth boring. In particular, the invention relates to methods and apparatus for remotely controlling the operation of downhole tools. 
   2. Description of Related Art 
   In pursuit of deeply deposited economic minerals and fluids such as hydrocarbons, the art of earthboring involves many physical operations that are carried out remotely under hazardous and sometimes hostile conditions. For example, hydrocarbon producing boreholes may be more than. 25,000 ft. deep and have a bottom-hole pressure more than 10,000 psi and a bottom-hole temperature in excess of 300 F. 
   Transmitting power and control signals to dynamic tools working near the wellbore bottom is an engineering challenge. Some tools and circumstances allow the internal flow bore of a pipe or tubing string to be pressurized with water or other well working fluid. Sustained high pressure may be used to displace sleeves or piston elements within the work string. In other circumstances, a pumped circulation flow of working fluid along the pipe bore may be used to drive a downhole fluid motor or electric generator. 
   The transmission of operational commands to downhole machinery by coded sequences of pressure pulses carried along the wellbore fluid has been used to signal the beginning or ending of an operation that is mechanically executed by battery power such as the opening or closing of a valve. Also known to the prior art is the technique of using in situ wellbore pressure to power the operation of a mechanical element such a well packer or slip. 
   All of these prior art power and signal devices are useful in particular environments and applications. However, the challenges of deepwell drilling are many and diverse. New tools, procedures and downhole conditions evolve rapidly. Consequently, practitioners of the art constantly search for new and better devices and procedures to power or activate a downhole mechanism. 
   “Controllable fluids” are materials that respond to an applied electric or magnetic field with a change in their rheological behavior. Typically, this change is manifested when the fluids are sheared by the development of a yield stress that is more or less proportional to the magnitude of the applied field. These materials are commonly referred to as electrorheological (ER) or magnetorheological (MR) fluids. Interest in controllable fluids derives from their ability to provide simple, quiet, rapid-response interfaces between electronic controls and mechanical systems. Controllable fluids have the potential to radically change the way electromechanical devices are designed and operated. 
   MR fluids are non-colloidal suspensions of polarizable particles having a size on the order of a few microns. Typical carrier fluids for magnetically responsive particles include hydrocarbon oil, silicon oil and water. The particulates in the carrier fluid may represent 25-45% of the total mixture volume. Such fluids respond to an applied magnetic field with a change in rheological behavior. Polarization induced in the suspended particles by application of an external field causes the particles to form columnar structures parallel to the applied field. These chain-like structures restrict the motion of the fluid, thereby increasing the viscous characteristics of the suspension. 
   ER systems also are non-colloidal suspensions of polarizable particles having a size on the order of a few microns. However, with applied power, some of these fluids have a volume expansion of 100%. Some formulations, properties and characteristics of controllable fluids have been provided by the authors Mark R. Jolly, Jonathan W. Bender and J. David Carlson in their publication titled  Properties and Application of Commercial Magnetorheological Fluids , SPIE 5 th  Annual Int. Symposium on Smart Structures and Materials, San Diego, Calif., March, 1998, the body of which is incorporated herein by reference. 
   It is, therefore, an object of the present invention to provide a new downhole operational tool in the form of electrically responsive polymers as active tool operation and control elements. 
   Also an object of the present invention is the provision of a downhole well tool having no moving fluid control elements. 
   Another object of the present invention is a disappearing flow bore plug that is electrically ejected from a flow obstruction position. 
   SUMMARY OF THE INVENTION 
   The present invention provides a method and apparatus for actuation of a downhole tool by placing an electroactive fluid in a container within the tool where the fluid becomes either highly viscous or a solid when a small magnetic field is applied. After deactivation or removal of an electromagnetic field current, the fluid becomes much less viscous. At the lower viscosity value, the fluid may be induced to flow from a mechanical restraint chamber thereby permitting the movement of a slip setting piston. Such movement of a setting piston may be biased by a mechanical spring, by in situ wellbore pressure or by pump generated hydraulic pressure, for example. 
   In another application that is similar to the first, an ER polymer is positioned to expand against setting piston elements when an electromagnetic field is imposed. The polymer expansion may be applied to displace cooperating wedge elements, for example. 
   In yet another application, an MR fluid may be used to control a failsafe lock system wherein a fluid lock keeps a valve blocking element open against a mechanical spring bias until an electromagnetic power current is removed. When the current is removed and the magnetic field decreases, the MR fluid is expressed from a retention chamber under the bias of the spring to allow closure of the valve blocking element. 
   Under some operational circumstances, it is necessary to temporarily but completely block the flow bore of a production tube by such means as are characterized as a “disappearing” plug. Distinctively, when the disappearing plug is removed to open the tubing flow bore, little or no structure remains in the flow bore to impede fluid flow therein. To this need, the invention provides a bore plug in the form of a thin metal or plastic container in the shape of a short cylinder, for example, filled with MR fluid. The MR fluid filled cylinder may be caged across the tubing flow bore in a retainer channel. An electromagnet coil is positioned in the proximity of the retainer channel. At the appropriate time, the coil is de-energized to reduce the MR fluid viscosity thereby collapsing from the retainer channel and from a blocking position in the tubing bore. 
   An ER fluid may be used as a downhole motor or linear positioning device. Also, an ER fluid may be used as a direct wellbore packing fluid confined within a packer sleeve and electrically actuated to expand to a fluid sealing annulus barrier. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawing wherein: 
       FIG. 1  illustrates a longitudinal half-section of a well tool actuation piston in which an MR fluid functions as a valve to release the actuating piston of a pipe slip for displacement under the drive force of in situ wellbore pressure; 
       FIG. 2  illustrates a longitudinal half-section of a remotely actuated flapper valve; 
       FIG. 3  illustrates a longitudinal half-section of a check valve or safety valve that is locked at an open position by a controllable fluid; 
       FIG. 4  illustrates a longitudinal half-section of a controllable fluid filled bore plug; and, 
       FIG. 5  schematically illustrates several hydraulically powered well service tools in which the hydraulic conduit circulation is controlled by discretely placed magnet windings. 
       FIG. 6  is a schematic illustration of a packer sleeve, in accordance with the present invention, that is electrically actuated to expand to a fluid sealing annulus barrier. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , the slip actuating section of a downhole tool is illustrated in schematic quarter section. Typically, the tool is assembled within a casement or housing pipe  10 . Concentrically within the casement is an internal mandrel  12  around a central fluid flow bore  14 . Slip wickers  17  are distributed around the mandrel circumference to overlie the ramped face  19  of an actuating cone  18 . The cone  18  is secured to the mandrel  12 . The slip wickers  17  are translated axially along the mandrel by the ram edge of a piston  16 . As the piston  16  advances axially along the mandrel surface against the wickers  17 , the wickers slide along the face of ramp  19  for a radially outward advancement against a well bore wall or casing. 
   One face of the piston  16  is a load bearing wall of a wellbore pressure chamber  32 . One or more flow ports  34  through the casement wall  10  keep the chamber  32  in approximate pressure equilibrium with the wellbore fluid pressure. The opposing face of piston  16  is a load bearing wall of the electrically controlled fluid chamber  30 . An orifice restrictor  42  is another load bearing wall of the controlled fluid chamber  30  and is designed to provide a precisely dimensioned orifice passageway  40  between the restrictor and the piston  16  sleeve. 
   Constructed into the outer perimeter of the casement  10  adjacent to the controlled fluid chamber  30  is an electromagnet winding  20 . Typically, the winding is energized by a battery  24  carried within the tool, usually near an axial end of the tool. A current controller  22  in the electromagnet power circuit comprises, for example, a signal sensor and a power switching circuit. The signal sensor may, for example, be responsive to a coded pulse sequence of pressure pulsations transmitted by well fluid as a carrier medium. 
   Opposite of the orifice  40  and restrictor  42  is a low pressure chamber  36 . Frequently, the low pressure chamber is a void volume having capacity for the desired quantity of controlled fluid as is expected to be displaced from the chamber  30 . Often, the tool is deployed with ambient pressure in the chamber  36 , there being no effort given to actively evacuate the chamber  36 . However, downhole presure may be many thousands of pounds per square inch. Consequently, relative to the downhole pressure, surface ambient pressure is extremely low. 
   As the tool is run into a well, the winding  20  is energized to polarize the controllable fluid in the chamber  30  and prevent bypass flow into across the restriction  40  into the low pressure chamber  36 . When situated at the desired depth, the coil is de-energized thereby permitting the controllable fluid to revert to a lower-viscosity property. Under the in situ pressure bias in chamber  32 , the slip actuating piston  16  displaces the controllable fluid from the chamber  30  into the low pressure chamber  36 . In the process, the actuating piston  16  drives the slip wicker  17  against the conical face  19  of the actuating cone  18  thereby forcing the slip wicker radially outward against the surrounding case wall. 
   With respect to the  FIG. 2  embodiment of the invention, a selectively controlled flapper valve is represented. The valve body  50  surrounds a fluid flow bore  52  with a closure seat  54 . A flapper element  56  is pivotably secured to the housing  50  by a hinge joint  58 . Rotation of the flapper element arcs about the hinge  58  from an open flow position shown in dashed line to the flow blocking position shown in solid line as contacting the closure seat  54 . 
   Also pivotally connected to the flapper element at the hinge joint  51  is piston rod  53  extended from a piston element  60 . The piston translates within a chamber  62 . On the rod side of the chamber space is a coil spring  64  that biases the piston away from the hinge axes and toward the head end  66  of the chamber space. The head end  66  of the chamber  62  is charged with controllable fluid and surrounded by an electromagnet coil  68 . The piston may or mat not be perforated between the head face and rod face by selectively sized orifices that will permit the controllable fluid to flow from the head chamber  66  into the rod chamber under the displacement pressure bias of the spring  64  when the coil is de-energized. As shown with the rod hinge  51  on the inside of the flapper hinge  58 , advancement of the piston  60  into the head chamber  66  will rotate the flapper  56  away from the closure seat  54  to open the flow bore  52 . The opposite effect may be obtained by placing the rod hinge  51  on the outside of the flapper hinge  58 . 
     FIG. 3  represents another valve embodiment of the invention wherein an axially sliding sleeve element  70  is translated to a position that blocks the rotation of valve flapper  72  about the hinge axis  74  as shown by the dashed line position of the sleeve  70 . In this case, the valve body  76  includes a fluid pressure chamber  78  ringed by a magnet winding  80 . A piston  82  and integral rod  84  translates within the chamber  78 . The distal end of the rod  84  is channeled  86  to mesh with an operating tab  87  projecting from the locking sleeve  70 . A coil spring  89  bears against the distal end of the rod  84  to bias the sleeve  70  to the un-lock position. Opposing the bias of spring  89  is the force resultant of pressurized controllable fluid in the head chamber  90 . After a pumped influx of controllable fluid into the head chamber  90  drives the piston  82  and rod  84  to the rod end of the chamber  78  against the bias of spring  89 , the coil  80  is energized to hold the position by substantially solidifying the ER fluid within the head chamber  90 . Resultantly, the controllable fluid pressure in the head chamber  90  may be relaxed while simultaneously holding the locking sleeve  70  in the position of blocking the rotation of flapper  72 . 
     FIG. 4  illustrates a disappearing plug embodiment of the invention wherein the plug tool body  100  includes a channeled insert  102  that encompasses a fluid flow bore  101 . The channeled insert includes a magnet winding  103  integrated therein. The plug  104  comprises an outer membrane skin  106  of polymer or thin, malleable metal. The membrane  106  encapsulates a body of controllable fluid  108 . The plug  104  is positioned in the channel  102  while in the de-energized plastic state. When positioned, the magnet winding is energized to rigidify the controllable fluid  108  and hence, secure the plug at a fluid flow blocking position. At a subsequent moment when it is desired to open the flow bore  101 , the winding  103  is de-energized. When the magnetic field is removed from the controllable fluid, the plug rigidity sags to facilitate removal of the plug to from the bore  101 . Although the plug remains within the fluid flow conduit, the loose, malleable nature of the de-energized may be easily accommodate by shunting or purging. 
   The invention embodiment of  FIG. 5  represents a series of hydraulically powered well service tools  110 ,  111  and  112 . The power fluid pumped within the fluid circulation lines  114 ,  116 ,  118  and  120  is a controllable fluid. Magnet windings  122 ,  123  and  124  are selectively positioned around the non-magnetic fluid circulation lines. When a winding is energized, the controllable fluid within the associated conduit congeals in the proximity of the winding to block fluid flow within the conduit. Thus, by selectively energizing any one or more of the windings  122 ,  123  or  124 , the fluid flow route through the conduits may be selectively directed or stopped. 
     FIG. 6  depicts, in schematic fashion, an embodiment of the invention wherein a tubing string  130  carries a wellbore packer  131  with a packer sleeve, or elastomeric bladder,  132  that contains ER fluid as an inflation fluid. Magnetic windings  134  are associated with the packer sleeve  132  to create a magnetic field when energized. When the windings  132  are energized, the ER fluid within the packer sleeve  132  congeals in the proximity of the windings  134  to selectively expand the packer sleeve  132  across annulus  136  to form a fluid annulus sealing barrier as shown in FIG.  6 . The packer sleeve  132  is expanded from a retracted position (indicated by dashed lines  136  in  FIG. 6 ) wherein the packer sleeve  132  does not present a fluid barrier. 
   Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that the description is for illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those of ordinary skill in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described and claimed invention.