This study examines the effects of drilling, completion, and production operations and their associated cyclic stresses on a cement sheath. The operations performed after cement placement can damage cement-sheath integrity and the bond with the casing or formation, resulting in loss of zonal isolation and in sustained casing pressure, often requiring remediation and reducing productivity.
Introduction
The study reported here is a derivative of a long-term investigation aimed at improving zonal isolation for horizontal wells drilled in the Marcellus shale. The impetus for this long-term study is to optimize drilling and completion practices to reduce cost, improve zonal isolation, and improve well-success rate.
One of the initial actions of the study was assessment of well performance in the Marcellus play. Interestingly, the well-success rate was much lower in the intermediate string than in either the production casing or the surface casing.
