Method and system for sealing an annulus enclosing a tubular element

Abstract

The invention provides a method and system for sealing an annulus enclosing a tubular element in a wellbore. The method comprises the steps of: i) introducing a first drilling fluid in the wellbore; ii) drilling an open hole section of the wellbore using a drilling tool suspended at the end of a tool string; iii) pumping a second drilling fluid comprising particles into the wellbore; iv) filtering the particles out of the second drilling fluid near a downhole end of the tubular element; v) extending the tubular element into the open hole section of the wellbore while directing at least part of the filtered particles to an annulus between the tubular element and a wellbore wall. Steps i) to v) may be repeated as often as required.

1 . A method for sealing an annulus enclosing a tubular element in a wellbore,
 wherein the tubular element is an expandable tubular element enclosing a tool string, wherein a downhole end portion of a wall of the expandable tubular element is bent radially outward and in axially reverse direction defining an expanded tubular section extending around an unexpanded tubular section, the method comprising the steps of:   i) introducing a first drilling fluid in the wellbore;   ii) drilling an open hole section of the wellbore using a drilling tool suspended at the end of the tool string;   iii) pumping a second drilling fluid comprising particles into the wellbore;   iv) filtering the particles out of the second drilling fluid near a downhole end of the tubular element;   v) extending the tubular element into the open hole section of the wellbore by pushing the unexpanded section into the expanded tubular section, while directing at least part of the filtered particles to an annulus between the expanded tubular section and a wellbore wall.   
     
     
         2 . The method of  claim 1 , comprising the step of:
 vi) repeating steps i) to v).   
     
     
         3 . The method of  claim 1 , wherein the particles directed to the annulus fill said annulus with a layer of particles. 
     
     
         4 . The method of  claim 1 , wherein the step of filtering the particles comprises:
 moving a drill string provided with a filter member uphole, until said filter member engages a downhole end of the tubular element.   
     
     
         5 . The method of  claim 4 , wherein the step of introducing a first drilling fluid in the wellbore comprises:
 moving the drill string provided with the filter member downhole until the filter member is disengaged from the downhole end of the tubular element.   
     
     
         6 . The method of  claim 1 , wherein the step of filtering uses a filter means, comprising:
 a filtering section extending from a downhole end of the tubular section into the wellbore; and   a flexible flap arranged at the downhole end of said filtering section to at least partially close an annulus between said filtering section and a drill string.   
     
     
         7 . The method of  claim 6 , wherein the flexible flap will at least partially open said annulus between the filtering section and the drill string when a pressure differential across said flap exceeds a threshold pressure. 
     
     
         8 . The method of  claim 6 , wherein said flap is comprised of one or more flap sections, together constituting a circular shape. 
     
     
         9 . The method of  claim 1 , wherein the particles are at least partially ferromagnetic, and wherein the step of filtering the particles comprises:
 arranging a magnet at the downhole end of the tubular member to attract at least a part of the particles.   
     
     
         10 . The method of  claim 1 , wherein at least some of the particles will swell when contacted with a predetermined fluid. 
     
     
         11 . The method of  claim 10 , wherein said predetermined fluid comprises water or hydrocarbons. 
     
     
         12 . The method of  claim 1 , comprising the steps of:
 arranging an impermeable pipe at the downhole end of the tubular element, having an outer diameter smaller than the wellbore and including a (moving) seal between said impermeable pipe and the downhole end of the tubular element, thus creating an annular space downstream of the downhole end of the tubular element;   ensuring that the particles in the second drilling fluid have a particle density lower than a mud density of the second drilling fluid;   wherein the step of filtering the particles out of the second drilling fluid includes accumulating the particles in the annular space due to their buoyancy.   
     
     
         13 . A system for sealing an annulus enclosing a tubular element in a wellbore, comprising:
 a tool string having a drilling tool suspended at a downhole end for drilling an open hole section of the wellbore;   an expandable tubular element enclosing the tool string, wherein a downhole end portion of a wall of the expandable tubular element is bent radially outward and in axially reverse direction defining an expanded tubular section extending around an unexpanded tubular section;   means for introducing a first drilling fluid in the wellbore;   means for pumping a second drilling fluid comprising particles into the wellbore;   a filter means arranged near the downhole end of the tubular element for filtering particles out of the second drilling fluid and for directing at least part of the filtered particles to an annulus between the expanded tubular section and a wellbore wall.   
     
     
         14 . The system of  claim 13 , wherein the filter means is selected from the group of:
 a filtering section extending from a downhole end of the tubular section into the wellbore and a flexible flap arranged at the downhole end of said filtering section to at least partially close an annulus between said filtering section and a drill string; and   an impermeable pipe arranged at the downhole end of the tubular element, having an outer diameter smaller than the wellbore and including a (moving) seal between said impermeable pipe and the downhole end of the tubular element, thus creating an annular space downstream of the downhole end of the tubular element.   
     
     
         15 . The system of  claim 13 , for carrying out the method according to any of the previous claims.