Innovative Drilling Rig for Deepwater Dry Tree Floating Platform

Abstract

The deep water development in the Gulf of Mexico (GOM) harsh environment could potentially reduce the capital cost with the self-contained drilling unit on the production floater. This paper studies the technical feasibility of a complete drilling package; an independent pipe deck combined drilling support structure on top of the ultra deepwater production floater. A dry-tree support semi-submersible is used for this study for water depths from 7000 to 9000 ft. The objective of the paper is to reduce the drilling costs with the use of an onboard platform rigs over dry trees. In this design, a 2.5 million hook load drilling rig in association with the drilling support modules on a box-on-box concept structure type is considered.The substructure skids are over the strong back in the transverse direction and the strong back skids are over the platform capping beam in the longitudinal direction. The substructure contains a trip tank and an independent mud separate system. The larger mud process system and the power units are isolated from the substructure that allows the substructure to be lighter and easy to move both longitudinal and transverse to cover the matrix of the well pattern. A bridge type structure communicates between the drill floor and the drilling support structure by transporting the pipe to and fro from the pipe deck to the drill floor. The bridge is also used to make up and break up the pipes in addition to the pipe-conveyer work. The substructure is designed as a box-on-box type thus easing the fabrication, transportation and rig-up. This paper conceptually engineers the drilling structure with the selection of major equipment accordingly, to meet the proposed platform requirement for the dry-tree support semi-submersible with production unit.The merits are the reduction in the overall drilling, operating and well enhancement cost. Additionally, the advantages are early production with accelerated production revenues leading to a reduction in the overall development capital requirement. Also the ease of well intervention field requirements to enhance the well performance is feasible. This paper also defines and illustrates a suitable dry tree vessel for ultra deepwater harsh environment to make the GOM ultra deepwater development reliable, feasible and cost effective.