Lost circulation is a common problem in the massive Simsima and Umm El Radhuma carbonate formations that extend across all United Arab Emirates fields and the Gulf countries. To minimize losses during drilling, 8.10-lbm/gal emulsion mud or aerated mud is often used.
As the result of corrosive brines presence across the formations extending to the shallow depths and causing casing corrosion problems, one of the main objectives of cementing the 9 5/8-in. casing is to ensure well integrity and casing protection by having cement to surface.
In these carbonates, multistage cementing tools have operational problems and frequently develop casing leaks over the life of a well. Top jobs do not guarantee complete linear and radial coverage of the casing along the whole interval. Complete losses are expected with conventional lightweight cement systems, and their set cement properties do not meet requirements for casing corrosion protection. These issues make successful cementing in these formations a real challenge.
To overcome the challenges, a new ultralightweight cement system (ULC) with a density close to that of water and superior set cement properties was used to ensure good casing protection and zonal isolation. This paper addresses the challenge to measure the low density of the slurry and the tools necessary to differentiate between mix fluid and the final slurry.
The new ultra-lightweight cement was evaluated using standard cement evaluation logs, and case studies are presented that confirm successful zonal isolation.