Abstract:
A piloting actuator valve controls flow in a well. The piloting actuator valve is combined with a downhole completion and utilizes a pilot valve to control actuation of a main valve. A controllable actuator is coupled to the pilot valve and enables selective control over the pilot valve which, in turn, controls the state of the main valve.

Description:
This application claims the benefit of U.S. Provisional Application 60/605,562 filed on Aug. 30, 2004. 

   BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention pertains to pilot valves used in downhole completions, and particularly to a pilot valve using an actuator to control the state of the pilot valve, and thereby the state of the main valve. 
   2. Related Art 
   Pilot valves are used in gas lift product lines such as intermittent gas lift applications. Existing pilot valves are typically driven by a bellows operating in response to a pressure differential, similar to what is used in other types of gas lift valves. Although the present invention can be used for intermittent gas lift, it is not limited to that application. 
   Actuator valves such as solenoid valves, for example, are used in various industrial and downhole applications. Because of the linear relationship between the port size and solenoid force requirement, pilot valves have been used in many solenoid-actuated valves to maximize pressure ratings. In many existing downhole tool designs, two bellows are used to seal and isolate reservoir fluids from the fluid in the interior of the solenoid. In addition, the two-bellows configuration allows the pressure to balance between those fluids. The most intuitive way of configuring two bellows is to have two separate bellows; one for sealing and the other for pressure balancing. However, because of space constraints, it may be more advantageous to achieve both functions using only one fluid contact surface. In U.S. Pat. No. 2,880,620, Bredtschneider describes a system having two telescoping bellows for this purpose. In U.S. Pat. No. 5,662,335, Larsen describes a system that achieves the same purpose by assembling two bellows in an end-to-end arrangement. 
   SUMMARY 
   The present invention provides for a pilot valve used in a well and in which the state of the pilot valve is controlled by an actuator. 
   Advantages and other features of the invention will become apparent from the following description, drawings, and claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  shows a schematic view of a piloting actuator valve constructed in accordance with the present invention. 
       FIG. 2  is a schematic view of the piloting actuator valve of  FIG. 1  showing a spring disposed in the main valve. 
       FIG. 3  is a schematic view of an embodiment of a solenoid used in the piloting actuator valve of  FIG. 1 . 
       FIG. 4  is a schematic view showing a cluster of piloting actuator valves being used in a well. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a piloting actuator valve  10  having a housing  12  enclosing a pilot valve  14  and a main valve  16 . Pilot valve  14  comprises an actuator  18 , bellows  20 ,  22 , and a plunger  24 . Actuator  18  can be one of various mechanical or electromechanical devices. For example, actuator  18  may be a solenoid, a piezoelectric device, a shape-memory alloy, a linear motor, or a conventional electric motor. In the embodiment of  FIG. 1 , and in the discussion below, a solenoid is described as the actuating member. However, the above alternatives may readily be adapted to replace the solenoid and serve as the actuating member. 
   Referring to  FIG. 1 , solenoid  18  comprises a core  26  and windings  28  wrapped on core  26 . Windings  28  at least partially circumferentially enclose one end of plunger  24 . The opposite end of plunger  24  has a sealing surface  30  that mates with a pilot seat  32 . Bellows  20 ,  22  mount to housing  12  inside a cavity  34  in housing  12  and to plunger  24 , at least partially circumferentially enclosing plunger  24 . Plunger  24  extends into cavity  34 . A pilot injection port  36  allows fluid communication between cavity  34  and the exterior of housing  12 . The exterior of housing  12  is subjected to fluids upstream of piloting actuator valve  10 . 
   In the embodiment of the  FIG. 1 , bellows  20 ,  22  are disposed in housing  12  in a telescoping arrangement. Bellows  20 ,  22  provide a seal between the downhole fluids and actuator  18 . Bellows  20 ,  22  also provide pressure balancing between the fluids in the interior of actuator  18  and the downhole fluids in contact with bellows  20 ,  22 . In addition, the spring force of bellows  20 ,  22  may be used as a return mechanism of plunger  24 . An optional spring or springs (not shown) may also be used to provide this force. 
   Main valve  16  comprises a piston  38  disposed in a main chamber  40  within housing  12 . Piston  38  has a piston head  42  on one end that divides main chamber  40  into first and second sides. Piston head  42  is in sliding, sealing contact with the walls of main chamber  40 . On the end of piston  38  opposite piston head  42  is a main seal  44 . Main seal  44  seals against a main seat  46  when main valve  16  is closed. Piston  38  has a piston passageway  48  that allows fluid communication between the first side of main chamber  40  and the downstream side of main valve  16  (typically production tubing). A pilot passageway  50  allows fluid communication between cavity  34  and the first side of main chamber  40  when sealing surface  30  is not engaged with pilot seat  32 . A main injection port  52  allows fluid communication between the second side of main chamber  40  and the exterior of housing  12  (typically the well annulus). An optional spring  54  ( FIG. 2 ) may be used to improve functional characteristics of main valve  16 . 
   In the embodiment shown in  FIG. 3 , solenoid  18  has a plunger ring  56  and a retainer ring  58 . Plunger ring  56  slides on plunger  24  but its movement is limited by retainer ring  58 . Electrical current passing through windings  28  produces magnetic forces on plunger  24  and plunger ring  56  that, in this embodiment, tend to pull plunger  24  into an upper gap  60  while pulling plunger ring  56  into a lower gap  62 . The force on plunger ring  56  is initially transferred to plunger  24  via shoulder  64 . Because upper gap  60  is larger than lower gap  62 , as plunger  24  travels into and narrows upper gap  60 , lower gap  62  narrows and then closes. As plunger  24  continues moving to further narrow upper gap  60 , plunger ring  56  slides on plunger  24  until upper gap  60  closes completely. Because the magnetic force is inversely proportional to the width of the gap, the force created at lower gap  62  contributes significantly because of the smaller gap distance. Furthermore, this increase in force at the original position of plunger  24  is not achieved by sacrificing travel because the larger upper gap is the total intended travel of plunger  24 . 
   There are various operational states for piloting actuator valve  10 , including permutations of pilot valve  14  being open or closed and injection fluid pressure being greater or less than production fluid pressure. 
   In operations in which solenoid  18  is energized, core  26  is magnetically energized by windings  28 . In the arrangement shown, the magnetic field exerts a pulling force on plunger  24 . Solenoid  18  opens pilot valve  14  by pulling sealing surface  30  from sealing engagement with pilot seat  32 . Alternative actuator mechanism would similarly control the state of pilot valve  13 . 
   If injection fluid pressure exceeds production fluid pressure while pilot valve  13  is open, the net force on piston  38  drives piston  38  such that main valve  16  is held in its open state, and injection fluid flows downhole. That occurs because fluid pressure entering through pilot injection port  36  passes through pilot passageway  50  and bears on piston head  42 . Fluid flow is choked in piston passageway  48 . Therefore, the pressure of the fluid drops from injection pressure at one end of piston passageway  48  to production pressure at the other end. Since the injection fluid pressure is greater than the production fluid pressure bearing on the opposite end of piston  38 , main seal  44  is driven off of main seat  46 . Injection fluid entering through main injection port  52  flows through open main valve  16 . 
   If production fluid pressure exceeds injection fluid pressure while pilot valve  14  is open, piston  38  is similarly driven such that main valve  16  is held in its open state. That is because the higher pressure production fluid passes through piston passageway  48  in to the first side of main chamber  40 , through pilot passageway  50  into pilot chamber  34 , and out pilot injection port  36 . However, the flow restrictions represented by those various passageways and ports allow pressure in first side of main chamber  40  to build up to nearly that of the production fluid pressure, and that pressure bears on one end of piston head  42 . Pressure in the second side of main chamber  40  is the lower injection fluid pressure, and that bears on the other end of piston head  42 . Thus, the forces on piston  38  are not balanced and main valve  16  is held open.