The BP-operated Rhum field in the North Sea consists of three subsea development wells tied back to the Bruce platform. The field offered a number of development challenges, including:
One of BP’s requirements during the well completion phase was a minimum of one mechanical barrier and one fluid barrier while running the completions. This was seen as essential risk mitigation for safely running completions in a subsea environment. Only two clear fluids were capable of delivering the required brine weight of 2.19 g/cm3 (18.28 lb/gal), namely cesium formate and zinc bromide. The HSE risks of working with zinc bromide were deemed unacceptable, leaving cesium formate brine as the only clear fluid matching the performance requirements.
From well production testing it was concluded that perforating in dynamic underbalance with cesium formate brine matched well performance in the appraisal well DST after a standard underbalanced perforation. The kill pill has therefore been nondamaging and the perforation programme has achieved the desired productivity.
The results of the e-line operation show that the combination of cesium formate brine kill pills and on-balance perforating can deliver wells with low mechanical skins. The use of dynamic underbalanced perforating with cesium formate brine across the entire range of completion operations brings significant HSE benefits by:
This case history and all others are downloadable here.
Roy, A. M., Twynam, A. J., Parke, J., Morrison, A. and Downs, J. (2008, May 5). An Evaluation of Perforating Techniques and Use of Caesium Formate Kill Pills to Maximise Productivity in HPHT Gas Wells and Minimise HSE Risks. Proc., Offshore Technology Conference, Houston, Texas, USA. OTC-19242-MS. doi.org/10.4043/19242-MS.