Differential fill valve assembly for cased hole

Abstract

A differential fill valve assembly for application in float collars or shoes in a well casing can provide locking mechanisms to limit premature movement of an activating sleeve while facilitating desired advancement of the activating sleeve. The valve assembly comprises a backpressure flapper valve and an activating sleeve slidably disposed within a housing. The activating sleeve initially maintains the flapper valve in an open position while the activating sleeve is maintained in its position by upper and/or lower lock rings on either side of a shoulder of the activating sleeve. A tripping ball is dropped to seat in the activating sleeve. Pressure applied on the ball moves the activating sleeve downward, releasing the backpressure flapper valve, after which the tripping ball exits the bottom of the assembly. The lower lock ring maintains the activating sleeve in its lower position.

What is claimed is: 
     
         1 . A valve assembly, comprising:
 a flapper valve biased to move from a restrained position to a released position to cover an entry bore;   an activating sleeve retaining the flapper valve in the restrained position and having a shoulder;   an upper radial lock mechanism that prevents movement of the shoulder toward the entry bore and past the upper radial lock mechanism;   a lower radial lock mechanism positioned axially between the shoulder and an exit bore, the lower radial lock mechanism preventing movement of the shoulder toward the exit bore and past the lower radial lock mechanism until a force threshold is exceeded.   
     
     
         2 . The valve assembly of  claim 1 , wherein, when the shoulder is axially positioned between the lower radial lock mechanism and the exit bore, the lower radial lock mechanism prevents movement of the shoulder toward the entry bore. 
     
     
         3 . The valve assembly of  claim 1 , wherein the upper radial lock mechanism is positioned axially between the shoulder and the entry bore. 
     
     
         4 . The valve assembly of  claim 1 , wherein the upper radial lock mechanism has an inner cross-sectional dimension that is smaller than an outer cross-sectional dimension of the shoulder. 
     
     
         5 . The valve assembly of  claim 1 , wherein the lower radial lock mechanism has an inner cross-sectional dimension that is smaller than an outer cross-sectional dimension of the shoulder. 
     
     
         6 . The valve assembly of  claim 1 , wherein the flapper valve, in the released position, allows fluid flow from the entry bore to the exit bore and prevents fluid flow from the exit bore to the entry bore. 
     
     
         7 . The valve assembly of  claim 1 , further comprising an annular lip defined within the activating sleeve and having an inner cross-sectional dimension that is smaller than an outer cross-sectional dimension of a tripping ball sized to travel through the entry bore to the activating sleeve. 
     
     
         8 . A tool string, comprising:
 a casing;   a float collar within the casing;   a valve assembly within the float collar, the valve assembly comprising:
 a flapper valve biased to move from a restrained position to a released position to cover an entry bore; 
 an activating sleeve retaining the flapper valve in the restrained position and having a shoulder; 
 an upper radial lock mechanism that prevents movement of the shoulder toward the entry bore and past the upper radial lock mechanism; 
 a lower radial lock mechanism positioned axially between the shoulder and an exit bore, the lower radial lock mechanism preventing movement of the shoulder toward the exit bore and past the lower radial lock mechanism until a force threshold is exceeded. 
   
     
     
         9 . The tool string of  claim 8 , wherein, when the shoulder is axially positioned between the lower radial lock mechanism and the exit bore, the lower radial lock mechanism prevents movement of the shoulder toward the entry bore and past the lower radial lock mechanism. 
     
     
         10 . The tool string of  claim 8 , wherein the upper radial lock mechanism is positioned axially between the shoulder and the entry bore. 
     
     
         11 . The tool string of  claim 8 , wherein the upper radial lock mechanism is an expandable lock ring having an inner cross-sectional dimension that is smaller than an outer cross-sectional dimension of the shoulder. 
     
     
         12 . The tool string of  claim 8 , wherein the lower radial lock mechanism is an expandable lock ring having an inner cross-sectional dimension that is smaller than an outer cross-sectional dimension of the shoulder. 
     
     
         13 . The tool string of  claim 8 , wherein the flapper valve, in the released position, allows fluid flow from the entry bore to the exit bore and prevents fluid flow from the exit bore to the entry bore. 
     
     
         14 . The tool string of  claim 8 , further comprising an annular lip defined within the activating sleeve and having an inner cross-sectional dimension that is smaller than an outer cross-sectional dimension of a tripping ball sized to travel through the entry bore to the activating sleeve. 
     
     
         15 . A method, comprising:
 providing a valve assembly with an activating sleeve that retains a flapper valve in a restrained position and an upper radial lock mechanism that prevents movement of a shoulder of the activating sleeve toward an entry bore of the valve assembly and past the upper radial lock mechanism;   advancing the activating sleeve toward an exit bore by locating a tripping ball on the activating sleeve; and   releasing the flapper valve to move from a restrained position to a released position to cover the entry bore.   
     
     
         16 . The method of  claim 15 , further comprising preventing the activating sleeve from advancing toward the exit bore with a lower radial lock mechanism positioned axially between the shoulder and the exit bore is configured to prevent the advancing until a force threshold is exceeded. 
     
     
         17 . The method of  claim 16 , wherein advancing the activating sleeve toward the exit bore comprises exceeding a force threshold of the lower radial lock mechanism and thereby moving the shoulder past the lower radial lock mechanism. 
     
     
         18 . The method of  claim 15 , further comprising:
 allowing fluid flow from the entry bore to the exit bore through the flapper valve with the flapper valve in the released position; and   preventing fluid flow from the exit bore to the entry bore with the flapper valve in the released position.   
     
     
         19 . The method of  claim 15 , wherein advancing the activating sleeve comprises:
 seating the tripping ball on an annular lip defined on an inner surface of the activating sleeve; and   creating a pressure differential across the activating sleeve.   
     
     
         20 . The method of  claim 19 , further comprising advancing the tripping ball through the annular lip.