Re-settable locking mechanism for downhole tools

Abstract

The present invention generally comprises a tubular body which is adapted to be attached to a drill string, where the body defines a bore therethrough which accommodates a piston slidably disposed between a first and second position. This piston is aligned generally normally respect to an actuating piston and an expandable tool. This piston is actuated by hydraulic pressure which moves the piston from a first, biased position to a second position where it engages the actuating piston of expandable tool to lock the piston in a locked or closed position. The flow restrictor serves to create a selected time delay before the piston is exposed to an increase in hydraulic pressure within the borehole. In such a fashion, an increase in hydraulic pressure in the borehole will overcome the bias of the piston only where the pressure is maintained for a selected period of time. The hydraulic pressure at which the piston in the locking mechanism overcomes the spring bias is substantially less than the pressure necessary to overcome this spring bias of the piston and the expandable tool.

1 . A locking mechanism for an expandable downhole tool which defines a pass-through diameter, said downhole tool including one or more elements which may be deployed from a first position defining a diameter less than or equal to the pass-through diameter to a second position defining a diameter which exceeds the pass-through diameter, the movement of said elements from said first to said second position occurring when well fluid under a first fluid pressure is applied for a time “t” to a first actuating piston disposed in a first bore formed in said tool such that said first piston moves from a closed to an unclosed position relative to said elements, said locking mechanism comprising: 
 a body defining a second bore therein to accommodate a second piston where said second bore communicates with said first bore, said second piston being slidably disposed in said second bore between first and second positions where said piston is biased in said first position by a first biasing mechanisms;    said second piston actuated when well fluid under a second fluid pressure is applied for a time “y” to overcome said first biasing mechanism so as to move said second piston to a second position to engage said first actuating piston so as to lock said elements in a first position;    wherein said second pressure is less than said first pressure; and    wherein said time “y” is greater than said time “t”.    
   
   
       2 . The locking mechanism of  claim 1  further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.  
   
   
       3 . The locking mechanism of  claim 1  wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a first position so as to prevent reciprocation of first piston in said first bore.  
   
   
       4 . The locking mechanism of  claim 1  further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber in said bore.  
   
   
       5 . The locking mechanism of  claim 4  where said chamber is filled with a substantially non-compressible fluid.  
   
   
       6 . The locking mechanism of  claim 4  further including a bulkhead disposed in said chamber between said second and third pistons where said bulkhead includes a flow restrictor and a check valve to regulate fluid flow through said bulkhead upon the application or release of well fluid pressure.  
   
   
       7 . The locking mechanism of  claim 1  where the biasing means comprises a spring.  
   
   
       8 . The locking mechanism of  claim 1  further including a deadbolt coupled to a first end of said second piston where said deadbolt is receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.  
   
   
       9 . The locking mechanism of  claim 1  wherein said first and second pistons are oriented transverse to each other.  
   
   
       10 . A locking system for a downhole tool which includes cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure beyond a value “p” as applied for a time “t”, where said pressure is applied to an actuating piston moveable in a first bore formed in a first body between a first and second orientation where in said second orientation said first piston urges or allows said elements to move to an expanded orientation, said body adapted to be coupled to a drill string, said locking system comprising: 
 a second body defining a second bore therein to accommodate a second piston moveable between a first and second position, where said piston is biased in said first position by a biasing means;    said second body coupled to said first body such that said first bore is disposed in communication with said second bore;    said second first piston moveable to said second position by the application of a second fluid pressure applied for a time “y”;    wherein in said second position said second piston engages said first piston so as to prevent said first piston from moving to said second position;    where said second pressure is less than said first pressure; and    where said time “y” is greater than said time “t”.    
   
   
       11 . The locking system of  claim 10  further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.  
   
   
       12 . The locking system of  claim 10  wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.  
   
   
       13 . The locking system of  claim 10  further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween in said bore.  
   
   
       14 . The locking system of  claim 13  where said chamber is filled with a substantially non-compressible fluid.  
   
   
       15 . The locking system of  claim 13  where said chamber is comprised of a first and second chamber where said chambers communicate through a flow restrictor and a check valve upon the application or release of well fluid pressure as applied to said third piston.  
   
   
       16 . The locking system of  claim 10  where the biasing means comprises a spring.  
   
   
       17 . The locking system of  claim 10  where said first piston includes first and second end, where said first end terminates in a key receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.  
   
   
       18 . The locking mechanism of  claim 10  wherein said first and second pistons are oriented transverse to each other.  
   
   
       19 . A locking system for a downhole tool which includes cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure to an actuating piston moveable in a first bore formed in a first body between a first and second orientation where in said second orientation said first piston urges or allows said elements to move to an expanded orientation, said body adapted to be coupled to a drill string, said locking system comprising: 
 a second body defining a second bore therein to accommodate a drive mechanism operable to move a locking pin between a first and second position;    said second body coupled to said first body such that said first bore is disposed in communication with said second bore;    said drive mechanism adapted to move said locking pin between said first and second positions upon the application of an electrical signal;    wherein in said second position said locking pin engages the actuating piston so as to prevent said piston from moving to said second position.    
   
   
       20 . The locking system of  claim 19  wherein said drive means comprises a stepper motor.  
   
   
       21 . The locking system of  claim 19  wherein said drive means is actuated by an electrical battery  
   
   
       22 . The locking system of  claim 19  further including sensor means operatively coupled to said drive mechanism.  
   
   
       23 . The locking system of  claim 19  wherein the second piston is receivable in a recess formed in the first piston when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.  
   
   
       24 . The locking system of  claim 19  further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween.  
   
   
       25 . An expandable downhole tool which defines a pass-through diameter, said downhole tool including one or more elements which may be deployed from a first position defining a diameter less than or equal to the pass-through diameter to a second position defining a diameter which exceeds the pass-through diameter, the movement of said elements from said first to said second position occurring when well fluid under a first fluid pressure is applied for a time “t” to a first actuating piston disposed in a first bore formed in said tool such that said first piston moves from a closed to an unclosed position relative to said elements, said tool further comprising: 
 a body defining a second bore therein to accommodate a second piston where said second bore communicates with said first bore, said second piston being slidably disposed in said second bore between first and second positions where said piston is biased in said first position by a first biasing mechanisms;    said second piston actuated when well fluid under a second fluid pressure is applied for a time “y” to overcome said first biasing mechanism so as to move said second piston to a second position to engage said first actuating piston so as to lock said elements in a first position;    wherein said second pressure is less than said first pressure; and    wherein said time “y” is greater than said time “t”.    
   
   
       26 . The expandable tool of  claim 25  further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.  
   
   
       27 . The expandable tool of  claim 25  wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a first position so as to prevent reciprocation of first piston in said first bore.  
   
   
       28 . The expandable tool of  claim 25  further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber in said bore.  
   
   
       29 . The expandable tool of  claim 28  where said chamber is filled with a substantially non-compressible fluid.  
   
   
       30 . The expandable tool of  claim 28  further including a bulkhead disposed in said chamber between said second and third pistons where said bulkhead includes a flow restrictor and a check valve to regulate fluid flow through said bulkhead upon the application or release of well fluid pressure.  
   
   
       31 . The expandable tool of  claim 25  where the biasing means comprises a spring.  
   
   
       32 . The expandable tool of  claim 25  further including a deadbolt coupled to a first end of said second piston where said deadbolt is receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.  
   
   
       33 . The expandable tool of  claim 25  wherein said first and second pistons are oriented transverse to each other.  
   
   
       34 . A downhole tool which comprises 
 cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure to an actuating piston moveable in a first bore formed in a first body between a first and second orientation where in said second orientation said first piston urges or allows said elements to move to an expanded orientation;    said body adapted to be coupled to a drill string;    a second body defining a second bore therein to accommodate a drive mechanism operable to move a locking pin between a first and second position;    said second body coupled to said first body such that said first bore is disposed in communication with said second bore;    said drive mechanism adapted to move said locking pin between said first and second positions upon the application of an electrical signal;    wherein in said second position said locking pin engages the actuating piston so as to prevent said piston from moving to said second position.    
   
   
       35 . The downhole tool of  claim 34  wherein said drive means comprises a stepper motor.  
   
   
       36 . The downhole tool of  claim 34  wherein said drive means is actuated by an electrical battery.  
   
   
       37 . The downhole tool of  claim 34  further including sensor means operatively coupled to said drive mechanism.  
   
   
       38 . The downhole tool of  claim 34  wherein the second piston is receivable in a recess formed in the first piston when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.  
   
   
       39 . The downhole tool of  claim 34  further comprising a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween.  
   
   
       40 . A downhole tool adapted to be coupled to a drill string comprising: 
 cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure beyond a value “p” as applied for a time “t”;    said pressure being applied to an actuating piston moveable in a first bore formed in a first body between a first and second orientation;    where in said second orientation said first piston urges or allows said elements to move to an expanded orientation;    a second body defining a second bore therein to accommodate a second piston moveable between a first and second position, where said piston is biased in said first position by a biasing means;    said second body coupled to said first body such that said first bore is disposed in communication with said second bore;    said second first piston moveable to said second position by the application of a second fluid pressure applied for a time “y”;    wherein in said second position said second piston engages said first piston so as to prevent said first piston from moving to said second position;    where said second pressure is less than said first pressure; and    where said time “y” is greater than said time “t”.    
   
   
       41 . The downhole tool of  claim 40  further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.  
   
   
       42 . The downhole tool of  claim 40  wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.  
   
   
       43 . The downhole tool of  claim 40  further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween in said bore.  
   
   
       44 . The downhole tool of  claim 43  where said chamber is filled with a substantially non-compressible fluid.  
   
   
       45 . The downhole tool of  claim 43  where said chamber is comprised of a first and second chamber where said chambers communicate through a flow restrictor and a check valve upon the application or release of well fluid pressure as applied to said third piston.  
   
   
       46 . The downhole tool of  claim 40  where the biasing means comprises a spring.  
   
   
       47 . The downhole tool of  claim 40  where said first piston includes first and second end, where said first end terminates in a key receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.  
   
   
       48 . The downhole tool of  claim 40  wherein said first and second pistons are oriented transverse to each other.