Patent Publication Number: US-9416621-B2

Title: Coiled tubing surface operated downhole safety/back pressure/check valve

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to devices and methods for operation of downhole valves. In particular aspects, the invention relates to the control of valves used in wellbore intervention technology. 
     2. Description of the Related Art 
     Following a primary production period for a wellbore, wellbore intervention is often needed to pump fluids, chemicals, etc. or transport tools into and out of the wellbore. Deviated or horizontal wellbores or wellbore portions can preclude the use of wireline intervention. Where tubulars, and particularly coiled tubing, are used to facilitate such interventions, the string will typically require one or more internal safety valves such as flapper-type or check-type valves. These safety valves prevent the flow of wellbore hydrocarbons into the coiled tubing but also may limit some preferable intervention operations. 
     SUMMARY OF THE INVENTION 
     The present invention provides systems and methods for allowing intervention into a wellbore with a valve assembly that can be selectively opened and closed. In described embodiments, the present invention relates to an intervention work string having a multi-cycle open/close valve assembly. The valve assembly is preferably used in a coiled tubing intervention bottom hole assembly wherein the coiled tubing has electrical or fiber optic communication within it. The valve assembly could be run in in either a normally-opened or normally-closed position and functioned by means of communication from the surface via electric or fiber optic conduit. 
     In a described embodiment, the valve assembly includes a plurality of flapper valves that are spring biased toward a closed position. The valve assembly also includes a valve actuation mechanism that can move each of the flapper valves between closed and open positions. An exemplary valve actuation assembly includes a roller screw member that is rotatable within the valve housing. Rotation of the roller screw member will move a prong member axially within the valve housing to urge the flapper valves open. Rotation of the roller screw member in the opposite direction will move the prong member axially within the valve housing in the opposite direction, thereby allowing the flapper valves to close. 
     When the valve assembly is in an open position, various intervention related tasks can then be performed. For example, tools could be passed down through the intervention work string and emplaced in the wellbore. In addition, fluids or chemicals could be flowed into the wellbore or out of the wellbore internally via the coiled tubing conduit. 
    
    
     
       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 drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein: 
         FIG. 1  is a side, cross-sectional view of an exemplary wellbore containing an intervention work string constructed in accordance with the present invention. 
         FIG. 2  is an enlarged cross-sectional view of the valve assembly of the intervention work string shown in  FIG. 1  with the valve assembly in a closed position. 
         FIG. 3  is an enlarged cross-sectional view of the valve assembly of  FIG. 2  with the valve assembly in a partially open position. 
         FIG. 4  is an enlarged cross-sectional view of the valve assembly of  FIGS. 2-3  with the valve assembly now in a fully open position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an exemplary wellbore  10  that has been drilled through the earth  12  from the surface  13  down to a hydrocarbon-bearing formation  14 . The wellbore  10  is partially lined with a metallic casing  16  of a type known in the art. The wellbore  10  has a substantially vertical portion  18  and a deviated, or horizontal portion  20 . 
     An intervention work string  22  is disposed within the wellbore  10 . The intervention work string  22  can be used to perform workover tasks, such as pumping chemicals into the wellbore  10  or running tools into the wellbore  10 . The exemplary intervention work string  22  includes a coiled tubing running string  24  that is injected from surface  13  in a manner known in the art. Although a land-based well is depicted, those of skill in the art will understand that the systems and methods of the present invention can also be applied to subsea wells. 
     A multi-cycle open/close safety valve assembly  26  is secured to the distal end of the coiled tubing string  24 . Referring now to  FIG. 2 , an exemplary valve assembly  26  includes an outer housing  28  that defines an interior flow bore  30 . A connection  32  extends from the housing  28 . One, or preferably two, spring-biased flapper valves  34 ,  36 , of a type known in the art, are located within the housing  28 . The flapper valve(s)  34 ,  36  are axially spaced apart from each other. Each flapper valve  34 ,  36  includes a valve seat  38 . A flapper member  40  pivots about hinge  42  and is spring-biased into a closed position against its valve seat  38 . 
     A valve actuation mechanism  44  is located within the flow bore  30  proximate the flapper valves  34 ,  36 .  FIG. 2  illustrates an exemplary valve actuation mechanism  44  which includes an electrical motor and/or battery operated system  46  which rotates a rotary shaft  48 . Power and data commands are supplied to the motor  46  from surface via a conductor or fiber optic cable  50 . In certain embodiments, the conductor  50  is tubewire which may be operable to transmits data uphole to the surface  13 . The term “tubewire”, as used herein, refers to a tube which may or may not encapsulate a conductor or other communication means, such as, for example, the tubewire manufactured by Draka Cableteq of North Dighton, Mass. Tubewire for example, might consist of a ⅛″ outer diameter by 0.023″ wall of stainless steel or Incoloy 825 tube containing 16-18 gauge stranded copper wire covered by Halar™ or Teflon™ insulator. In this example, the insulator is tight against the tube and the wire. In the alternative, the tubewire may encapsulate one or more fiber optic cables or a mixture of wire(s) and fiber optic cable(s). The tubewire may consist of multiple tubes and may be concentric or may be coated on the outside with plastic or rubber. 
     The exemplary valve actuation mechanism  44  also includes a gear wheel  52  that is affixed to the rotary shaft  48 . A tubular roller screw member  54  is disposed within the flow bore  30 . The roller screw member  54  is rotatable within the outer housing  28  and is retained against axial movement within the flow bore  30  by locking ring  56 . The roller screw member  54  presents a toothed upper end  58  whose teeth intermesh with teeth  60  on gear wheel  52 . In addition, the roller screw member  54  has a radially interior surface with threading  62  formed thereupon. 
     A prong member  64  is located within the roller screw member  54 . Preferably, the prong member  64  includes a radially enlarged upper end  66  and a reduced diameter prong portion  68 . An axial passageway  70  is defined through the prong member  64 . The outer radial surface  72  of the enlarged upper end  66  has threading formed thereupon which is complementary to the threading  62  on the roller screw member  54 . As a result of the intermeshing of the threading on the outer radial surface  72  of the prong member  64  and the threading  62 , the prong member  64  will be moved axially within the housing  28  when the roller screw member  54  is rotated within the housing  28 . The prong member  64  will be moved axially either upwardly or downwardly depending upon the direction of rotation of the roller screw member  54 . 
     In operation, the intervention work string  22  is disposed within the wellbore  10  until the valve assembly  26  is located at a point wherein it is desired to perform an intervention task. A particular intervention task might be flowing chemicals through the coiled tubing string  24  and the valve assembly  26 . Alternatively, flow or circulation (reverse) may be performed. In order to do these things, the valve assembly  26  must be opened. 
     Opening of the valve assembly  26  is depicted in  FIGS. 3 and 4 . The motor  46  is energized by power/commands, provided via the conductor  50  so that the shaft  48  is rotated. The roller screw member  54  is rotated within the housing  28  which translated the prong member  64  axially downwardly within the housing  28  due to the interface of the threaded portions  62 ,  72 . The prong portion  68  of the prong member  64  will first urge the upper flapper valve  34  to an open position, as shown in  FIG. 3 . As the prong member  64  is moved further downwardly within the housing  28 , the prong portion  68  will urge the lower flapper valve  36  to an open position. 
     Once the valve assembly  26  has been opened, one or more intervention-related tasks can be performed through the open valve assembly  26 . For example, fluids or chemicals could be flowed downwardly or upwardly through the intervention work string  26 . 
     An operator can also close the flapper valve assemblies  34 ,  36  by energizing the motor  46  to rotate the shaft  48  and gear wheel  52  in the opposite direction. This will rotate the roller screw member  54  in the opposite direction and cause the prong member  64  to move axially upwardly within the housing  28 . 
     Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.