Retrievable stimulation frac plug with ball and seat

Abstract

A retrievable stimulation frac plug for a well casing, having an elongate mandrel having a fluid bore, a valve seat, adapted to receive a sealing member for selectively sealing the fluid bore, a sealing mechanism for releasably sealing between the mandrel and the casing, a slip mechanism for releasably engaging the well casing, and a valve seat bypass, moveable between a closed position and an open position, adapted to provide a bypass past the valve seat.

What is claimed is: 
     
         1 . A retrievable stimulation frac plug for a well casing, comprising:
 an elongate mandrel having a fluid bore;   a valve seat, adapted to receive a sealing member for selectively sealing the fluid bore;   a sealing mechanism for releasably sealing between the mandrel and the well casing;   a slip mechanism for releasably engaging the well casing; and   a valve seat bypass, moveable between a closed position and an open position, adapted to selectively provide a bypass past the valve seat.   
     
     
         2 . The retrievable stimulation frac plug of  claim 1 , the valve seat bypass comprising a bypass sleeve extending along the mandrel, the mandrel having bypass port, and the bypass port sealed when the bypass sleeve is in a closed position, and the bypass port open when the bypass sleeve is in an open position. 
     
     
         3 . The retrievable stimulation frac plug of  claim 2 , further comprising a shear pin for retaining the bypass sleeve in the closed position. 
     
     
         4 . The retrievable stimulation frac plug of  claim 2 , wherein the bypass sleeve extends around the outside of the mandrel. 
     
     
         5 . The retrievable stimulation frac plug of  claim 2 , wherein the valve seat is a ball seat. 
     
     
         6 . The retrievable stimulation frac plug of  claim 2 , wherein the sealing member is a ball. 
     
     
         7 . The retrievable stimulation frac plug of  claim 1 , further comprising a lower retrieval tool, the lower retrieval tool proximate a downhole end of the retrievable stimulation frac plug, wherein the lower retrieval tool is adapted to engage a lower stage retrievable stimulation frac plug. 
     
     
         8 . The retrievable stimulation frac plug of  claim 7 , the lower retrieval tool comprising:
 a retrieval sleeve, adapted to fit over the valve seat of the lower stage retrievable stimulation frac plug, providing a lower circulation passage between the lower retrieval tool and the lower stage retrievable stimulation frac plug;   a bypass actuator adapted to move a lower stage bypass sleeve into an open position to open a lower stage bypass port through a lower stage mandrel of the lower stage retrievable stimulation frac plug; and   a lower connector, adapted to engage an upper connector of the lower stage retrievable stimulation frac plug.   
     
     
         9 . A method of conducting a well operation in a well casing, comprising:
 a. providing a retrievable stimulation frac plug having:
 an elongate mandrel having a fluid bore; 
 a valve seat, adapted to receive a sealing member for selectively sealing the fluid bore; 
 a sealing mechanism for releasably sealing between the mandrel and the well casing; 
 a slip mechanism for releasably engaging the well casing; and 
 a valve seat bypass, moveable between a closed position and an open position, adapted to selectively provide a bypass past the valve seat; 
   b. locating and setting the retrievable stimulation frac plug in the well casing;   c. sealing the fluid bore; and   d. conducting a well operation in the well casing above the retrievable stimulation frac plug.   
     
     
         10 . The method of  claim 9 , the sealing the fluid bore comprising providing a ball into the valve seat to seal the fluid bore. 
     
     
         11 . The method of  claim 9 , the well operation comprising perforating the well casing or frac-stimulation of a formation adjacent the well casing or both. 
     
     
         12 . The method of  claim 9 , further comprising repeating (a), (b), (c), and (d) for an additional number (n−1) of stages for a total number (n) stages. 
     
     
         13 . The method of  claim 12 , further comprising:
 a. providing a retrieval tool having a lower connector adapted to engage the stage n retrievable stimulation frac plug and actuate the valve bypass;   b. deploying the retrieval tool to engage the stage n retrievable stimulation frac plug actuate the valve bypass;   c. releasing the sealing mechanism and the slip mechanism of the stage n retrievable stimulation frac plug;   d. moving the retrieval tool and the stage n retrievable stimulation frac plug down the well casing towards a stage n−1 retrievable stimulation frac plug, such that the lower retrieval tool of the stage n retrievable stimulation frac plug engages the stage n−1 retrievable stimulation frac plug.   
     
     
         14 . The method of  claim 13 , further comprising circulating fluid through the circulation passage and through the fluid bore of the stage n retrievable stimulation frac plug prior to and/or while engaging the stage n−1 retrievable stimulation frac plug. 
     
     
         15 . The method of  claim 13 , further comprising retrieving at least the stage n retrievable stimulation frac plug and the stage n−1 retrievable stimulation frac plug out of the well casing in a single run. 
     
     
         16 . The method of  claim 13 , further comprising retrieving at least five retrievable stimulation frac plugs in a single run. 
     
     
         17 . The method of  claim 13 , further comprising retrieving substantially n retrievable stimulation frac plugs in a single run.