Session: 01-01-02 Offshore Platforms-II

Paper Number: 124034

124034 - Conceptual Design of Innovative Relocatable Wellhead Platform Using Multi-Column Structure “Mct” With Both Bottom Founded and Floating In-Place Capabilities. 

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. The project's key client, tasked PT Mineering Energi Internasional with developing a wellhead platform capable of catering to two distinct fields: the shallow water A Field (~15-25 m water depth) and the deeper waters B Field (~35-45 m water depth) and C Field (~60-70 m water depth), each with a production life expectancy of less than a decade. 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 design 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.

Upon the conclusion of the production phase in the A Field, the McT will be refloated and towed to a quayside for necessary modifications. These modifications will encompass the inclusion of appurtenances for tendons as well as potential alterations to the topside facility. Dry docking for the McT will not be required during this phase. The adapted McT will then transition into its role as a floating platform (Tension Leg Platform, TLP) for deployment in the B and C Fields. Wire tendons and suction or driven piles will be preinstalled at the installation site. After the McT platform's arrival, tendon connections will be established, and the McT will be de-ballasted to tension the tendons. By utilizing the pre-tensioned wire tendons, the McT will effectively behaves like a tensioned leg platform. In this floating tensioned leg platform configuration, the motion of the platform can be minimized so that dry tree can be used. Furthermore, by utilizing the floating platform configuration, earthquake and land subsidence effect that is notoriously occurs in the vicinity of the field can be minimized.

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.

Presenting Author: Farid Putra Bakti PT Mineering Energi Internasional

Presenting Author Biography: -

Authors:

Farid Putra Bakti PT Mineering Energi Internasional
Arcandra Tahar Offshore Technology Consultant