Method for recovering tubular structures from a well and a downhole tool string
This invention relates to a method for recovering a tubular structure ( 3 ) from a well ( 1 ), wherein a so-called free point is defined as the location where the tubular structure is stuck in the well. The method comprising providing a downhole tool string comprising a pipe-severing tool and an upper part of the downhole tool string; lowering the downhole tool string into the tubular structure to release the free pipe. Before the step of triggering the pipe-severing tool to sever the tubular structure, the method includes releasing the pipe-severing tool and subsequent withdrawing the upper part, of the downhole tool string away from the free point towards the surface over at least a predefined distance. The invention relates to a downhole tool string for use in such method.
1. Method for recovering a tubular structure ( 3 ) from a well ( 1 ), wherein a free point ( 4 ) is defined as a location ( 2 ) where the tubular structure ( 3 ) got stuck in the well ( 1 ), wherein a free pipe is defined as a part ( 3 u ) of the tubular structure ( 3 ) which is downstream of the free point ( 4 ), and wherein a stuck pipe is defined as another part ( 3 d ) of the tubular structure ( 3 ) which is upstream of the free point ( 4 ), the method comprising steps of:
providing a downhole tool string ( 100 ) comprising a pipe-severing tool ( 5 ) and an upper part ( 7 ) of the downhole tool string ( 100 );
lowering the downhole tool string ( 100 ) into the tubular structure ( 3 ) to a depth that the pipe-severing tool ( 5 ) is at the free point ( 4 ) of the tubular structure ( 3 ), and
triggering the pipe-severing tool ( 5 ) to sever said tubular structure ( 3 ) to release the free pipe ( 3 u ),
before the step of triggering the pipe-severing tool ( 5 ) to sever said tubular structure ( 3 ), releasing the pipe-severing tool ( 5 ) and subsequently withdrawing the upper part ( 7 ) of the downhole tool string ( 100 ) away from the free point ( 4 ) towards a surface over at least a predefined distance (d).
2. The method according to claim 1 , further comprising, before releasing the pipe-severing tool ( 5 ), anchoring said pipe-severing tool ( 5 ) in the tubular structure ( 3 ).
3. The method according to claim 1 , further comprising, after triggering the pipe-severing tool ( 5 ) to sever said tubular structure ( 3 ), steps of:
lowering the upper part ( 7 ) of the downhole tool string ( 100 ) to the pipe severing tool;
coupling the upper part ( 7 ) of the downhole tool string ( 100 ) to the pipe severing tool, and
lifting the downhole tool string ( 100 ) to a surface.
4. The method according to claim 1 , further comprising removing the free pipe ( 3 u ) from the well ( 1 ).
5. The method according to claim 1 , wherein, in the step of providing the downhole tool string ( 100 ), the pipe-severing tool ( 5 ) comprises a pipe-severing unit ( 10 ) selected from a group consisting of: a chemical cutter tool, a jet cutter tool, a radial cutting torch, a drill collar-severing tool, and a string-shot back-off tool.
6. The method according to claim 1 , wherein, in the step of providing the downhole tool string ( 100 ), the downhole tool string ( 100 ) further provides a wireline tractor ( 60 ) in the upper part ( 7 ) for conveying the downhole tool string ( 100 ) to a depth in the well ( 1 ).
7. The method according to claim 1 , wherein the tubular structure ( 3 ) comprises a drill pipe string.
8. The method according to claim 1 , wherein the well ( 1 ) comprises a highly deviated or horizontal well bore.