Riser Analysis of a New Dry Completion Concept for a Monocolumn Platform

In recent years, PETROBRAS has developed the concept of a monocolumn platform to be used as a floating production unit in deep and ultra-deep water oil fields. This platform, referred as MonoBR, is characterized by low heave and pitch induced motions, even in hurricane conditions, allowing its use as an alternative for locations such as Campos Basin and the Pre-Salt Area in Brazil, and also for the Gulf of Mexico. Despite their low vertical motions, this platform is not generally regarded as a dry completion unit. However, PETROBRAS and two public institutions in Brazil, UFRJ/COPPE and USP/POLI, have studied and designed an innovative mechanism to be installed in MonoBR, called Inverted Cup, which is a sliding floating body installed inside the MonoBR moonpool. In such way, the platform transmits only horizontal motions and rotations to the Inverted Cup; the heave responses of both bodies are decoupled. The Inverted Cup is then designed and dimensioned to receive dry completion X-mas trees and risers. The aim of this paper is to present the results of the riser analysis performed under this new concept — Inverted Cup system — to allow dry completion in the MonoBR. The environmental conditions refer to fields in the Gulf of Mexico and in the Tupi Field (Pre-Salt). The results point to a technically feasible mechanism to allow dry completion, according to adopted criteria.