System for drilling a wellbore

Abstract

A system is disclosed for drilling a wellbore ( 1 ) into an earth formation. The system comprises an expandable tubular element ( 4 ) extending into the wellbore, whereby a lower end portion ( 11 ) of the wall of the tubular element ( 8 ) extends radially outward and in axially reverse direction so as to define an expanded tubular section ( 10 ) extending around a remaining tubular section ( 4 ) of the tubular element. The expanded tubular section is extendable by downward movement of the remaining tubular section relative to the expanded tubular section whereby said lower end portion ( 14 ) of the wall bends radially outward and in axially reverse direction.

1 . A system for drilling a wellbore into an earth formation, comprising
 an expandable tubular element extending into the wellbore, wherein a lower end portion of the wall of the tubular element extends radially outward and in an axially reverse direction so as to define an expanded tubular section extending around a remaining tubular section of the tubular element, the expanded tubular section being extendable by downward movement of the remaining tubular section relative to the expanded tubular section such that said lower end portion of the wall bends radially outward and in an axially reverse direction; and   a drill string extending through the remaining tubular section, wherein the tubular element and the drill string are arranged for transferring a thrust force from the tubular element to the drill string, and wherein the drill string includes a jetting head for deepening the wellbore by jetting a stream of fluid against the bottom of the wellbore.   
     
     
         2 . The system of  claim 1 , further comprising means for centralising the jetting head in the remaining tubular section. 
     
     
         3 . The system of  claim 1  wherein the expanded tubular section has an outer diameter, and wherein the drill string is provided with a reamer for reaming the wellbore to at least the outer diameter of the expanded tubular section. 
     
     
         4 . The system of  claim 1  wherein the remaining tubular section and the drill string are arranged for simultaneous lowering in the wellbore. 
     
     
         5 . The system of  claim 4 , wherein said lower end portion of the wall is arranged for lowering into the wellbore at substantially the same speed as lowering of the drill string during drilling of the wellbore. 
     
     
         6 . The system of  claim 1  wherein the wall of the tubular element includes a material susceptible of plastic deformation during said bending of the wall so that the expanded tubular section retains an expanded shape as a result of said plastic deformation. 
     
     
         7 . The system of  claim 1  wherein the remaining tubular section is subjected to an axially compressive force acting to induce said downward movement of the remaining tubular section. 
     
     
         8 . The system of  claim 7 , wherein said axially compressive force results at least partly from the weight of the remaining tubular section. 
     
     
         9 . The system substantially as described hereinbefore with reference to the drawings.