Full depth drilling system and method

Abstract

A system for drilling a cased wellbore includes a casing string and a drill bit coupled to the casing string, an end of the casing string being substantially aligned with an end of the drill bit. The system also includes a telescoping section formed in the casing string, the telescoping section having a variable length between a first open position and a second closed position, the first open position forming a longer overall casing string length than the second closed position.

1 . A system for drilling a cased wellbore, comprising:
 a casing string;   a drill bit coupled to the casing string, an end of the casing string being substantially aligned with an end of the drill bit; and   a telescoping section formed in the casing string, the telescoping section having a variable length between a first open position and a second closed position, the first open position forming a longer overall casing string length than the second closed position.   
     
     
         2 . The system of  claim 1 , wherein the telescoping section comprises:
 a first segment of casing string;   a second segment of the casing string, the second segment arranged radially outward from the first segment and at least partially overlapping the first segment; and   a void between an end of the first segment and the second segment, wherein a void length between the end of the first segment and the second segment is greater in the first open position than in the second open position.   
     
     
         3 . The system of  claim 2 , wherein the first segment moves into the void when the telescoping section transitions to the second closed position. 
     
     
         4 . The system of  claim 1 , wherein the telescoping section further comprises:
 a structural member maintaining the first open position.   
     
     
         5 . The system of  claim 4 , wherein the structural member comprises a dissolvable component. 
     
     
         6 . The system of  claim 4 , wherein the structural member comprises a shear pin. 
     
     
         7 . The system of  claim 1 , wherein the telescoping section further comprises a j-slot, comprising:
 an extension extending from a radially inward portion of the casing string; and   a slot formed in a radially outward portion of the casing string, the extension moving through the slot in response to rotation of at least a portion of the casing string.   
     
     
         8 . A wellbore system, comprising:
 a first casing positioned within a wellbore, the first casing being secured to an underground formation at a first landing location;   a second casing, extending through a bore of the first casing, the second casing having a drill bit positioned at an end to extend a borehole formed downhole of the first casing, the second casing comprising:
 a first segment; and 
 a second segment, arranged radially outward from the first segment, at least a portion of second segment overlapping the first segment and the first and second segments being axially movable relative to one another to adjust a second casing length; 
   wherein a second casing length is reduced after the borehole is extended to a predetermined location and the second casing is landed at a second landing location.   
     
     
         9 . The wellbore system of  claim 8 , wherein at least a portion of the first segment and at least a portion of the second segment forms a telescoping section of the second casing. 
     
     
         10 . The system of  claim 9 , wherein the telescoping section further comprises:
 a structural member arranged between the first segment and the second segment, the structural member maintaining an extended second casing length during a drilling operation.   
     
     
         11 . The system of  claim 10 , wherein the structural member is configured to disengage to facilitate movement between the first segment and the second segment to form a collapsed second casing length. 
     
     
         12 . The system of  claim 10 , wherein the structural member comprises a dissolvable component. 
     
     
         13 . The system of  claim 10 , wherein the structural member comprises a shear pin. 
     
     
         14 . The system of  claim 10 , wherein the structural member comprises a resilient member. 
     
     
         15 . The system of  claim 10 , wherein the second casing further comprises:
 an extension extending from the first segment; and   a slot formed in the second segment, the extension moving through the slot in response to rotation of at least a portion of the second casing string.   
     
     
         16 . The system of  claim 10 , wherein engagement between the first casing and the second casing drives axial movement of the first segment and the second segment relative to one another. 
     
     
         17 . A method for drilling a full depth wellbore, comprising:
 positioning a first casing string in a wellbore at a first landing location;   positioning a second casing string through the first casing string, the second casing string including a drill bit;   extending a borehole length, via the drill bit, to a predetermined location; and   landing the second casing string at a second landing location, wherein the borehole length extends beyond a second casing string end after the second casing string is positioned at the second landing location.   
     
     
         18 . The method of  claim 17 , further comprising:
 collapsing a telescoping section of the second casing string.   
     
     
         19 . The method of  claim 18 , wherein collapsing the telescoping section of the second casing string comprises:
 disengaging a structural member of the second casing string; and   axially moving a first segment of the second casing string and a second segment of the second casing string relative to one another, the movement reducing a second casing string length.   
     
     
         20 . The method of  claim 19 , wherein the structural member comprises at least one of a shear pin, a dissolvable component, a resilient member, or a j-slot.