The subsurface formations and reservoir conditions encountered in certain areas of the Barents Sea offer some unique challenges for the operators and the drilling industry. These areas of the Norwegian Barents Sea consist of naturally fractured and weathered carbonate formations which may incorporate open karsts. Drilling into large open fractures or karsts will result in total losses and mud cap drilling practices must be employed to enable further progress. Such locations may require some unique solutions to drill effectively and safely while conforming to local rules and regulations; including deploying winterized rigs capable of year-round operations in Arctic environment.

This paper describes the process of selecting a viable solution for drilling in such an area where potential mud cap drilling practices could be required, the rig integration process, class notation process, development of operational procedures, risk assessment, training and testing of equipment prior to commencing the operation.

This was a fast track project which incorporated developing new mud cap drilling procedures and processes when operating the Controlled Mud Level (CML) system. Since mud cap drilling practices from a floater on the Norwegian Continental Shelf (NCS) is a rare occurrence, it required close cooperation between the operator, the drilling contractor and the service provider. To facilitate the process and assure sound practices a third party with experience on mud cap operations was also engaged. The paper will also briefly describe the Controlled Mud Cap Drilling (CMCD) principle and the results from drilling the well.