The application of a Surface BOP (SBOP) is a well-proven, cost-effective method of extending the water depth operating capacity of semi-submersible drilling units.
General industry focus has been to apply SBOP to 3rd generation moored rigs, allowing them to operate in the deepwater environments, dominated by 4th and 5th generation units. Stena Drilling has taken the SBOP beyond those traditional boundaries by successfully operating it, not only from a 3rd generation anchored rig, but also from a 5th generation Dynamically-Positioned rig; in each case with the objective of providing a more competitive and efficient deepwater option for the Operator.
For environmental protection, Stena Drilling has incorporated a Subsea Shutoff Assembly (SSA) into the SBOP system. This unit allows the well bore to be isolated at the seabed and the casing riser string to be disconnected during an emergency situation. This added functionality meets regional regulatory requirements for a pollution barrier and increases the operating envelope necessary to extend application of the technology from the benign environments of South East Asia to areas with harsher conditions, such as Brazil, West Africa and the Mediterranean.
Stena Drilling is the first drilling contactor to own the complete SBOP and the SSA package, which can be utilised onboard any of its three semi submersible units not only from a conventionally moored Semi-sub, but also from a Dynamically-Positioned Semi-Sub and Drillship. Stena Drilling have a proven and successful track record of delivering Surface BOP projects on Stena and competitor drilling units. Where the Surface BOP packages have been provided for rent in previous projects, Stena Drilling have complimented the rental with Project Management Services. The systems required to handle and run the SBOP on Stena units are designed to minimise the changeover time between conventional and SBOP operations.
By utilising the SBOP system – and without upgrading the existing riser tensioning systems - the operating capacities of the Stena rigs can be extended as follows: