| 摘要 |
A downhole tool comprising an inner sleeve with a plurality of sleeve ports and a housing positioned radially outwardly of the inner sleeve and having a plurality of housing ports, with the housing and inner sleeve partially defining a space radially therebetween. The space is occupied by a shifting sleeve. A fluid path extends between the interior flowpath of the tool and the space. A fluid control device, such as a burst disk, occupies at least portion of the fluid path. In one state, the shifting sleeve is in a first position between the housing ports and the sleeve ports to prevent fluid flow between the interior flowpath and exterior of the tool. The fluid control device may selectively permit fluid flow, and thus pressure communication, into the annular space to cause a differential pressure across the shifting sleeve. When a sufficient differential pressure is reached, the shifting sleeve is moved to a second position, which opens the communication paths through the housing and sleeve ports between the interior flowpath and exterior flowpath of the tool. |
