The long-slot debris circulating sub (LSDS) consists of a ceramic cone seated in a ported sub. The long circulation slots enable relatively large debris to fall out into the annulus and not accumulate on the ceramic cone.

The LSDS is positioned between the packer and the perforating guns. The space below the sub is filled with clean fluid.

Underbalance enabling

Before the packer is set, a lighter fluid can be circulated through the tubing to create the required underbalance condition.