First Use of Cesium Formate on a Live HPHT Well in the North Sea

Cabot Corporation has carried out a third major application of Cabot Specialty Fluids' new Cesium Formate drilling and completion fluid. The innovative, high density, solids-free fluid continued its successful campaign in another major well completion operation for Elf Exploration UK. The completion operation was conducted on Elf's Elgin/Franklin Development Project located in block 22/30c in the Central Graben Area of the Central North Sea. The Elgin/Franklin Field is operated by Elf Exploration UK, and is considered the most challenging high pressure, high temperature (HPHT) development yet undertaken in the North Sea.

The 22/30c-G3 well utilized 2.19 s.g. (18.3 ppg) Cesium Formate in an ultra high pressure, high temperature completion operation where reservoir pressure is 1105 bar (16,000 psi) and bottom hole temperatures reached 205°C (401°F). The well had a measured depth (MD) of 6,446 meters (21,143 ft), a true vertical depth (TVD) of 5,503 meters (18,050 ft), with a maximum deviation of 45°.

The well was originally suspended with 2.16 s.g. (18.0 ppg) low-toxicity oil-mud, which upon re-entry was displaced to synthetic oil-based mud. This subsequently exhibited severe barite sag, a problem difficult to manage in solids-laden fluids at high temperature and high wellbore deviation. Elf engineers, concerned with the extreme temperatures and their effect on solids-laden fluids, turned to Cesium Formate earlier than originally planned to resolve this problem and went on to complete the well successfully.

"In this, the third application of Cesium Formate, the fluid continues to validate the exceptional characteristics we have measured in the laboratory," said U.R. Weems, president of Cabot Specialty Fluids Division. "In fact, the true measure of any new technology is it's performance in the field. Cesium Formate met the challenge of one of the world's most difficult reservoir completion operations, lifting the level of confidence throughout the industry."

Elf Exploration's innovative well engineers utilized Cesium Formate in this phase of the project because of the fluid's solids-free nature; temperature stability, ease of handling for crews, and environmental acceptability. The fluid was also shown to be compatible with all major elements of completion equipment (metals and elastomers), under extreme conditions of temperature and pressure.

The well was subsequently flowed successfully and then suspended pending installation of the platform production facilities.

This is the third successful application of Cesium Formate in the United Kingdom sector of the North Sea, following its use during completion operations for Shell UK Exploration and Production (Shell Expro) and Total Oil Marine.