| 摘要 |
<p>The present invention relates to a downhole string (1) for drilling through a low pressure zone (Zlow) in a formation in a well (3), comprising a drawdown casing (2) having a first end (4) closest to a top (5) of the well and a second end (6), and an operational tool (8) connected to the second end of the drawdown casing, wherein the downhole string further comprises an annular barrier (10) having an expandable metal sleeve (11) surrounding the drawdown casing, each end of the expandable metal sleeve being connected with the drawdown casing, the expandable metal sleeve being adapted to contact a wall (16) of a borehole or another casing so that after expansion of the expandable sleeve, the drawdown casing can rotate and slide in relation to the annular barrier. Furthermore, the present invention relates to a downhole system and to a downhole method.</p> |
