Pressure-boost device for downhole tools

Abstract

A pressure-boosting apparatus particularly amenable for use in downhole applications is disclosed. The pressure-boosting apparatus employs an unbalanced piston which is initially fixated in a run-in position. The piston has a flowpath therethrough in which is mounted a check valve. Initially, pressure is applied to above and below the piston which results in an unbalanced force on the piston due to its configuration. Flow to the tool initiates its actuation at this time. When the unbalanced force reaches a predetermined level, the piston is no longer fixated to the housing and begins to accelerate. Acceleration of the piston closes the check valve due to the sudden decrease in pressure behind the check valve and an increase in pressure in front of the check valve as the fluid volume in front of the piston is compressed. Due to the proportional relationship between pressure and area, a magnification of force originally delivered by the pump is achieved for completion of the setting of a downhole tool such as a packer or bridge plug or the like.

1. A pressure-boosting apparatus In combinaton  in combination with a downhole tool and operated by a wireline-powered downhole pump, comprising:
 a pressure-actuated downhole tool operably connected to a wireline-powered downhole pump;  
 said pressure-boosting apparatus In  in flow communication with said downhole pump, and further comprises: 
 a body having an inlet to receive a  an inlet pressure source and an outlet connected to the downhole tool;  
 a piston movably mounted In  in said body, said piston having opposed faces of dissimilar cross-section;  
 said piston comprises a towpath  flowpath therethrough to allow, at least for a time, flow through said flowpath to the downhole tool to initiate Its  its operation without piston movement, whereupon the creation of an unbalanced force on said piston due to said flow through said towpath  flowpath, said piston Is  is urged to move toward said downhole tool;  
 said flowpath further comprises a check valve which allows flow toward said downhole tool until sufficient movement of said piston toward said downhole tool forces said check valve to close, which results in the pressure applied to said inlet being magnified at said outlet of said body and said downhole pump to thereby allow said pump, due to said pressure magnification, to produce sufficient pressure to fully operate said downhole tool; and  
   said check valve is closed without application of said inlet pressure .  
 
 
     
     
       2. The apparatus of  claim 1 , wherein:
 said check valve is operable responsively to pressure on said check valve resulting from movement of said piston.  
 
     
     
       3. The apparatus of  claim 2 , wherein:
 said check valve is automatically actuated to a closed position upon movement of said piston toward the downhole tool.  
 
     
     
       4. The apparatus of  claim 3 , wherein:
 said check valve is opened upon application of said first  inlet pressure to said inlet.  
 
     
     
       5. The apparatus of  claim 4 , wherein:
 said valve is biased closed until application of said first  inlet pressure at said inlet.  
 
     
     
       6. The apparatus of  claim 5 , wherein:
 said valve comprises a seat coupled with a spring-loaded ball.  
 
     
     
       7. The apparatus of  claim 6 , wherein:
 said spring keeps said ball against said seat until said first  inlet pressure is applied at said inlet, whereupon said ball is driven off said seat; and upon a subsequent application of a force of a predetermined value on said piston, said piston moves to assist in actuation of the downhole tool;  
 said spring reseats said ball on said seat as movement of said piston increases pressure on the downhole tool, which tends to move said ball to said seat.  
 
     
     
       8. The apparatus of  claim 7 , wherein:
 said piston is initially retained to said body unit  until application of said first pressure creates a sufficient force to break loose said piston to allow it to accelerate.  
 
     
     
       9. The apparatus of  claim 7 , further comprising:
 a biasing member acting on said piston upon removal of said first applied pressure to restroke said piston toward said inlet to facilitate reuse of the apparatus without removal from the wellbore.  
 
     
     
       10. The apparatus of  claim 1 , wherein:
 said piston is initially retained to said body until application of said first pressure create a sufficient force to break loose said piston to allow it to accelerate.  
 
     
     
       11. The apparatus of  claim 10 , wherein:
 said check valve is opened upon application of said first  inlet pressure to said inlet.  
 
     
     
       12. The apparatus of  claim 11 , wherein:
 said check valve is biased closed until application of said first  inlet pressure at said inlet.  
 
     
     
       13. The apparatus of  claim 12 , wherein:
 said check valve comprises a seat coupled with a spring-loaded ball.  
 
     
     
       14. The apparatus of  claim 13 , wherein:
 said spring keeps said ball against said seat until said first pressure is applied at said inlet, whereupon said ball is driven off said seat; and upon a subsequent application of a force of a predetermined value on said piston, said piston moves to assist in actuation of the downhole tool;  
 said spring reseats said ball on said seat as movement of said piston increases pressure on the downhole tool, which tends to move said ball to said seat.  
 
     
     
       15. The apparatus of  claim 1 , further comprising:
 a biasing member acting on said piston upon removal of said first applied pressure to restroke said piston toward said inlet to facilitate reuse of the apparatus without removal from the wellbore.