It is estimated that tens of thousands of wells currently suffer from surface annular pressure (SAP), and cement cannot overcome this challenge. Similarly, in increasingly challenging completions, cement fails to fulfill its primary purpose. The Welltec Annular Barrier (WAB) was developed with the primary application of segregating production between different reservoirs in cementless lower completions. The WAB functions by applying pressure from within the completion string to the engineered sleeve through the valve system and hydraulically conforming the sleeve to the formation (or casing) within which it is set. Once conformed to the encircling structure, the WAB seals off the annulus around the liner upon which it is mounted, preventing undesired pressure migration across the WAB along the wellbore. The WAB gives users the ability to protect themselves against SAP by overcoming the use of cement as the only primary well barrier. The WAB builds upon solid-expandable knowledge Welltec has developed in the last half-decade but augments the material strength of expanded steel with transferred annular pressure. This technique of repurposing pressure to create a more robust seal is a novel approach to an old problem.