Marcellus gas-shale trends have transformed the regional and national outlook for natural gas supply and are particularly attractive for their proximity to high demand markets and existing pipeline infrastructure. Marcellus shale plays offer unique operational and regulatory challenges during mud removal, cementing, and completion operations. Sustained casing pressure (SCP) is one of the greatest challenges encountered after completion. The Department of Environmental Protection (DEP) in Pennsylvania has enacted strict policies regulating cementing practices in Pennsylvanian Marcellus shale trends to reduce the risk of inter-zonal communication and SCP due to substandard annular cement sheath integrity.
To ensure compliance with DEP cementing guidelines, a flexible, expanding cement system (FECS) was developed with fit-for-purpose mechanical properties. A further FECS blend modification included an additive to promote bulk cement expansion during hydration. Since implementation, this approach, coupled with good mud removal and cementing best practices, resulted in rapid static gel strength (SGS) development, acceptable compressive strength development and waiting on cement (WOC) time, and improved flexible and expansive properties.
Since introduction in 2010, six jobs (two intermediate and four production strings) have been successfully cemented with FECS technology. A Marcellus shale trend case study will be presented in this paper that discusses the successful application of FECS during cement placement around a production casing. After completion of each job, a successful shoe test was performed. After stimulation/fracturing treatments, SCP was not reported by the client in Marcellus wells cemented with FECS.
Since implementation in 2010, FECS technology has become a proven approach for cementing Marcellus horizontal tight-gas shale environments where long-term zonal isolation and minimal SCP are required. This approach has been applied to Marcellus shale and Permian Basin formations while other applications are currently being explored.