Conclusion
Dual-activity drillships are unique in that they are capable of performing multiple functions in association with field development. In the past, some of these functions have required mobilization and demobilization of one or more additional large construction vessels for completion. Implementation of the same vessel that performs well drilling and completion operations for other activities such as subsea equipment installation, central production facilities installation, and flowline/pipeline construction results in overall project cost savings. Further, potential downtime and resultant cost occurring when one vessel waits for the other to complete their activities is negated. Finally, unexpected delays occurring from one field development operation do not result in downtime and associated cost since the dual-activity drillship can perform tasks as assigned.
The drillship Discoverer Enterprise has been featured in this paper because of its “first of a kind” status. Future launchings of additional dual-activity drillships will allow the practice of single vessel usage for multiple field development tasks to become more prevalent. This capability is especially timely in light of reduced oil prices from recent years, making vessel utilization and cost reduction prime factors in the ability to develop new fields economically.
Acknowledgements
The authors would like to acknowledge Transocean Offshore Inc. for their consideration and assistance in developing dual- activity drilling rig information, Mr. Andrew Macfarlane of H.O. Mohr & Associates, Inc. for his assistance in developing graphics associated with dual-activity drillship utilization concepts and Ms. Peggy Reyna of Aker Engineering, Inc. for cleanup and handling of this manuscript.
References
1. Aibaugh, E. Kurt: “Offshore Pipeline Installation and Burial Contractors and Vessels”, Offshore (June 1998).
