Patent ID: 7669653

Claim:
A system for maintaining zonal isolation in a wellbore, characterized in that said system comprises, within a pathway at a specific location along said wellbore, a sealing element to block said pathway, said sealing element being able to deform both during and after placement and wherein the sealing element is maintained under compression after completion of the placement, thereby urging the deformable sealing element into contact with less deformable material bounding the pathway so as to maintain a seal against fluid migration along the pathway, wherein the sealing element is a sealing ring, said sealing ring being confined in a volume surrounded by materials of high Young's modulus, greater than 1000 MPa, comprising well tubing, formation surrounding the wellbore and cement injected into the wellbore, said cement injected into the wellbore comprising a first sheath portion and a second sheath portion, wherein the sealing ring comprises a sealing material which has a Young's modulus below 1000 MPa., is contained between and contacts said first sheath portion and said second portion and is connected to a fluid communication element adapted to supply pressurizing fluid after placement and thereby maintain pressure within at least part of the sealing element.