Restoration of annular zonal isolation using localized casing expansion (LCE) technology: A proof of concept based on laboratory studies and field trial results

Abstract

Sustained casing pressure (SCP), surface casing vent flow (SCVF) and other expressions of annular fluid migration are widely encountered zonal isolation issues. Conventional solutions for SCP/SCVF include perforate and squeeze cementing, or section milling and recementing. Regrettably, the former approach shows only limited success rates, while the latter involves time and cost intensive operations that require a drilling rig. We will show that localized casing expansion (LCE) technologies offer promising alternatives, enabling rigless remediation of annular fluid migration. The LCE concept involves imposing permanent deformation on the casing pipe to locally enlarge its diameter. The associated annular volume reduction causes closure of defects such as micro-annuli and cement fractures, plus potentially even larger voids, and results in an overall densification of the cement microstructure. The Shell-developed Local Expander tool is e-line deployable and imposes the required casing deformation in a mechanical, fully controlled manner. Tailored-shaped energetic charges offer valuable supplementary means for achieving expansion. We will demonstrate the sealing effectiveness of LCE in both laboratory experiments and field trials, describe how the radial deformation impacts the casing and cement, and generally discuss the current state of knowledge, capabilities and limitations of LCE with respect to SCP/SCVF remediation.