High expansion sealing device with leak path closures

A high expansion packer or bridge plug is described. It features an external portion of a soft material that flows into spiral exterior leak paths formed when the sealing element is subjected to longitudinal compression. Preferably, the sealing element is an elastomer such as cured rubber, while the outer material is a soft uncured or somewhat cured rubber. The outer covering may itself be covered for protection when running in with such protective covering breaking or otherwise getting out of the way during the element compression process. As a result of compression, the soft material occupies the exterior helical or other leak paths for a sufficient length along the sealing element to withstand high differential pressures, without leakage.