Secondary barrier for use in conjunction with an isolation device in a horizontal wellbore

A secondary barrier for use in conjunction with an isolation device in a portion of a non-vertical wellbore comprises: a swellable material, wherein the swellable material: (A) has dimensions such that, prior to swelling, the secondary barrier is capable of being placed into the portion of the non-vertical wellbore, and (B) fills a void within the portion of the non-vertical wellbore, wherein the swellable material fills the void after the swelling of at least a portion of the swellable material has occurred, wherein the secondary barrier is positioned adjacent to the isolation device in the portion of the non-vertical wellbore. A method of creating a secondary barrier comprises: introducing the secondary barrier into the portion of the non-vertical wellbore; and contacting or allowing the swellable material to come in contact with the swelling fluid or the increase in temperature.