A type of impairment in cement bond quality. Can occur opposite poorly consolidated formations after cemented casing has been subjected to internal pressure. The application of internal pressure results in an expansion of the casing and the cement sheath into soft formations. Removal of the pressure and the resultant contraction of the pipe leaves a microannulus between the casing and the cement sheath. Can be produced. for example, by pressure testing, perforating, fracturing, or cement squeeze operations.