Abstract
This study addresses the design challenge of a relocatable wellhead platform that satisfies the complex operational and environmental requirements of both shallow and deeper water hydrocarbon extraction. A platform design capable of catering to three distinct fields: the shallow water A Field (∼20 m water depth) and the deeper waters B Field (∼40 m water depth) and C Field (∼65 m water depth), each with a production life expectancy of less than 10 years is shown in this study. Other requirements such as the use of dry-tree, simpler fabrication and decommissioning method, and cost effectiveness were also imposed on the proposed solution.
To answer these requirements, a Multi-Column Structure (referred to as “McT”) is proposed as the solution. In the initial stage, McT serve as a gravity-based substructure for the shallower water A Field. The McT’s fabrication and integration with the topside will take place in a dry dock. Subsequently, the integrated McT will be floated to the installation site, where it will be ballasted and placed on the seabed. This wet-tow option provided more flexible, economical, and simpler installation and fabrication method when compared to the jacket type structure. Furthermore, the size of the columns is designed with a dimension where a simple steel rolling devices may be utilized to fabricate the hull. Ring skirts and driven pile are incorporated into the McT’s foundation design to provide the in-place stability and to fulfill seismic requirement during its fixed mode utilization. Notably, well conductors and trees (up to 7 wells) will be situated alongside the McT, facilitating well drilling and production.
This study’s primary objective is to devise a single McT substructure capable of accommodating the operational needs of the A, B, and C Fields. The scope of the study includes the summary of Substructure (Hull) Configuration Design, Foundation Design, Wire Tendon and Suction Pile Design, Global Performance Analysis, Pre-Service stability Analyses, Flexible and Top-Tensioned Riser Design and qualitative cost comparison with jacket type offshore platform. This innovative platform design offers a versatile, relocatable wellhead platform solution, tailored to the specific needs of multiple fields, while satisfying stringent criteria for technology, operational feasibility, and cost-effectiveness.
