US Patent 7743825 Packer sealing element with shape memory material

A packer or bridge plug uses a sealing element made from a shape memory polymer (SMP). The packer element receives heat or other stimulus to soften the SMP while the element is compressed and retained. While so retained, the heat or other stimulus is removed to allow the SMP to get stiff so that it effectively seals a surrounding tubular. High expansion rates are possible as the softness of the material under thermal input allows it to be reshaped to the surrounding tubular or to the surrounding open hole from a smaller size during run in and to effectively retain a sealed configuration after getting stiff on reduction in its core temperature while longitudinally compressed. The SMP or equivalent material whose modulus is changeable can be covered on the outside, the inside or both with an elastic material that protects the SMP and enhances the seal in the wellbore and against the mandrel.