In wellbores, annular barriers are used for different purposes, such as for providing a barrier to flow within an annulus, from above and below the annular barrier. The annular barriers are mounted as part of the well tubular structure. An annular barrier has an inner wall surrounded by an annular expandable sleeve. The expandable sleeve is typically made of a metallic material, but may also be made of an elastomeric material. The sleeve is fastened at its ends to the inner wall of the annular barrier.
In order to create zones within the annulus, a second and subsequent annular barrier can be used. The first annular barrier is expanded at one side of the zone to be sealed off and the second and subsequent annular barrier is expanded. Thus, several zones are created and sealed off from each other.
The pressure envelope of a well is governed by the burst rating of the tubular and the well hardware etc. used within the well construction. In some circumstances, the expandable sleeve of an annular barrier is expanded by increasing the pressure within the tubular structure of the well, which is the most cost-efficient way of expanding the sleeve.
When expanding the expandable sleeve of an annular barrier by pressurising the tubular structure from within, several annular barriers are expanded simultaneously. However, if one expandable sleeve cracks or develops a leak, fluid is let into the annulus and then the pressure drops in the tubular structure, and further expansion of the annular barriers stops. The operator then has to isolate the annular barrier having a crack in the expandable sleeve before being capable of continuing the expansion of the rest of the annular barriers.
The expandable sleeve may crack or leak for a number of reasons, e.g. due to defects in the material, damage during manufacturing, scratch or wear during deployment, etc.