The petroleum industry on the Norwegian Continental Shelf is in a time with well construction time and cost as an increased challenging factor. The operators desire to discontinue this trend and are currently cutting cost. Consequently, a contractor similar to COSL Drilling AS meets a demand for a more efficient operation. This thesis presents an overview over the responsibility distribution between the different parties associated with the drilling operation. Wells drilled by the semisubmersible rig, COSL Pioneer is analyzed. The operation is divided into groups to give an overview over the operation and reveal where time is spent and where the potential for improvement is high. The relationship between the technical limit and the invisible lost time in the drilling operation is analyzed, and the possible advantage of reducing the invisible lost time to a minimum is presented. To find one specific area that would drastically improve the operation efficiency is difficult. For COSL Drilling AS to fulfill the vision of being the preferred supplier of drilling services in the North Sea, they need to be best in all work processes and small parts of the operation. Specific improvement potentials related to the drilling contractor have been found and pointed out in this thesis.

Master's thesis in Petroleum engineering