Abstract:
Disclosed herein is an actuatable downhole member. The actuatable downhole member includes, a downhole member with a selected density, the selected density being comparable to an anticipated downhole fluid density such that a difference in the density of the downhole member and the density of the downhole fluid creates a bias on the downhole member to actuate the downhole member.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Actuating downhole devices such as check valves, for example, often is accomplished by remote control via a slickline or wireline. Such actuation can include movement of a downhole member directly through movement of the wireline or can include communication to a downhole actuator such as an electric motor, for example, through the wireline. In either case the actuation is initiated remotely. Other systems have been developed that do not require remote actuation but instead rely on a downhole change in pressure to initiate an actuation. Such systems may use a pressurized cavity with a membrane set to rupture at a selected pressure, for example. Automated actuation of downhole tools is desirable and systems enabling automated actuation would be well received in the art. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0002]    Disclosed herein is an actuatable downhole member. The actuatable downhole member includes, a downhole member with a selected density, the selected density being comparable to an anticipated downhole fluid density such that a difference in the density of the downhole member and the density of the downhole fluid creates a bias on the downhole member to actuate the downhole member. 
         [0003]    Further disclosed herein is a method of malting a density actuatable downhole member. The method includes, determining a target density for the downhole member based on an estimated downhole fluid density and forming the downhole member such that it has the target density. 
         [0004]    Further disclosed herein is a method of actuating a downhole member. The method includes, positioning the downhole member having a target density downhole where it is submergible in fluid and actuating the downhole member through buoyancy forces acting upon the downhole member in response to fluid at least partially submerging the downhole member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0006]      FIG. 1  depicts a partial cross sectional view of an actuatable downhole system disclosed herein in a closed configuration; 
           [0007]      FIG. 2  depicts a cross sectional view of the actuatable downhole system of  FIG. 1  in an open configuration; 
           [0008]      FIG. 3  depicts a perspective view of the actuatable downhole member shown in the system of  FIG. 1 ; 
           [0009]      FIG. 4  depicts a cross sectional view of the actuatable member of  FIG. 1  taken at arrows  4 - 4 ; and 
           [0010]      FIG. 5  depicts a cross sectional view of an alternate embodiment of the actuatable member of  FIG. 1  taken at arrows  5 - 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0012]    Referring to  FIGS. 1 ,  2  and  3 , an actuatable downhole system  10  including an embodiment of the actuatable downhole member  14  disclosed herein is illustrated. In addition to the downhole member  14 , shown in this embodiment as a flapper valve, the downhole system  10  includes, a first tubular  18 , a second tubular  22  and a third tubular  26 . The first tubular  18  and the second tubular  22  define a first chamber  30  by the clearance therebetween. Similarly, the second tubular  22  and the third tubular  26  define a second chamber  34  by the clearance therebetween. The second tubular  22  isolates the first chamber  30  from the second chamber  34 . A port  38  through the second tubular  22  fluidically connects the first chamber  30  to the second chamber  34 . This fluidic connection is interruptible by the flapper  14 . The flapper  14 , in this embodiment, is attached to the second tubular  22  by a hinge  42  such that the flapper  14  rotates about the hinge  42  between a closed configuration  46  as shown in  FIG. 1  and an open configuration  50  as shown in  FIG. 2 . In the closed configuration  46  the flapper  14  is sealed to a seal surface  54  of the second tubular  22  thereby preventing flow through the port  38 . Alternately, in the open configuration  50  the flapper  14  is pivoted away from the second tubular  22  thereby allowing fluid to flow through the port  38 . 
         [0013]    Forces to actuate the flapper  14  between the closed configuration  46  and the open configuration  50  can be generated by a difference in density between the flapper  14  and a fluid within which the flapper  14  is at least partially submerged. A description of the mechanics of such actuation will be presented below after embodiments of controlling density of the flapper  14  during fabrication thereof are discussed. 
         [0014]    Referring to  FIG. 4 , a flapper  14  with a selected density is disclosed. Controlling the density of a flapper  14  during fabrication thereof can be done in various ways, a few of which are described herein. Powdered metallurgy is one process that can be used in the fabrication of downhole components such as valves and flappers. The powdered metallurgy process includes generating a metal powder  58 , compressing the metal powder  58  into a “green” shape, which is similar to the final shape that the component will take. The green shape is heated and compressed further, in a process referred to as sintering, to cause the powdered metal particles to adhere together to form the final, or near final, part. Powdered metallurgy allows for some control of the density of the final part through control of such things as physical properties of the metal powder  58  and temperatures and pressures used during the sintering process, for example. The potential density range is also due, in part, to the size, shape, quantity and distribution of voids  62  in the interstices between particles of the metal powder  58 . The density ranges achievable with the foregoing methods, however, are limited. Such limitation is, in part; due to variations in mechanical properties of the final part that result from changes in the foregoing methods. For example, using low pressure during the sintering process can produce a low-density part, however, the same low pressure may result in unacceptable surface finishes or a part with insufficient mechanical strength. 
         [0015]    An alternate embodiment can provide additional variation in density through controlling the number, size and shape of voids in the finished part without sacrificing mechanical properties. This embodiment includes using a metal powder  58  made up of hollow or foamed particles. As such the density of the finished part can have a greater density range than systems using solid particles. Alternately, the density can be controlled by use of particles other than metal, such as ceramic or glass, for example. Inadequate adhesion of particles to one another with such alternate materials, however, can weaken the finished part. An embodiment disclosed herein therefore, addresses this concern by coating or plating the nonmetallic particles prior to use in the powdered metallurgy process. One method of coating the particles is through chemical vapor deposition or CVD. The chemical vapor deposition process can controllably grow a coating of a specific metal onto surfaces of the powdered material particles. The metal coating can have excellent adhesion to the individual particles and provide an exterior surface on each particle, susceptible to adhesion, to other particles in the sintering process, thereby providing greater strength in the finished part. The use of nonmetallic powder material prior to the CVD process permits a greater range of density of the finished part, as well as allowing for control of other properties such as electrical conductivity, magnetic properties, coefficient of thermal expansion and thermal conductivity, for example. 
         [0016]    Referring to  FIG. 5 , a cross sectional view of an alternate embodiment of the flapper  74  is illustrated. The flapper  74  includes a core  78  made of a first material and a coating  82 , or plating, made of a second material. The material used to make the core  78  could be less dense than a density of fluid into which the flapper  74  is expected to be at least partially submerged. The material used for the coating  82  could be denser than the expected fluid density. Thus, by controlling the amount of coating  82  applied the overall density of the flapper  74 , based on the finished part&#39;s volume and mass, can be accurately set. As such, the flapper  74  can be made to be denser or less dense than a fluid into which it will be at least partially submerged to thereby control actuation of the flapper  74  due to its density relative to the density or change in density of the fluid. Alternately, an embodiment with a core  78  that is denser than the fluid could be used with a coating  82  that is less dense to achieve similar results of relative densities. 
         [0017]    The foregoing embodiments could also be combined to create yet another embodiment by, for example, making the core  78  with a powdered metallurgical process with hollow, foamed or nonmetallic particles, the individual particles of which may or may not be coated as disclosed above. This powdered metal core  78  could then be coated, possibly with a CVD process, for example, to attain the target density of the finished part. 
         [0018]    How the density of the flapper  14  effects actuation of the flapper  14  will be discussed here in more detail. Forces acting upon the flapper  14  can be proportional to the mass of the flapper  14 . A few examples of such forces are gravitational force and forces due to acceleration such as centripetal force, for example. In addition to acting upon the flapper  14 , these forces also act upon everything that has mass, including any fluid, that may be near or in contact with the flapper  14 . 
         [0019]    Additionally, if the flapper  14  is at least partially submerged in the fluid there will also be buoyancy forces acting upon the flapper  14  by the fluid. The buoyancy forces are proportional to the difference in density of the flapper  14  and the fluid for the portion of the flapper  14  that is submerged within the fluid. The buoyancy forces act in a direction opposite to that of the gravitational or centripetal forces. As such, changes in the buoyancy forces can be used to actuate the flapper  14 . Changes in buoyancy forces can result from changes in either the density of fluid into which at least a portion of the flapper  14  is submerged or changes in the amount of the flapper  14  that is submerged in the fluid. As such, by selecting a density and actuation direction of the flapper  14  relative to the density of the fluid and direction of the forces acting thereupon, the flapper can be set to automatically actuate in response to changes in density and position of the fluid with respect to the flapper  14 . Such automated control of a downhole system  10  may be desirable for multiple reasons including, faster response than an operator initiated system and system simplification with lower costs as compared to systems utilizing a communication link between surface and the downhole actuatable member. 
         [0020]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.