OCTOS1000 Template Manifold Transport and Installation Using Anchored Rigs

Abstract

This paper describes the OCTOS 1000 template manifold transport and installation method for its first location in Alhacora field, offshore Brazil. The original idea consisted in using a barge and a dynamically positioned rig But as it has imposed some operational restrictions, another method had to be developed. The selected one foresees the use of a PETROBRAS owned semi-submersible to transport the template sea fastened to the rig lower deck, allowing a dry tow of the structure towards its final location. The method described may be used to transport and install other kinds of templates and manifolds, using a rig'of opportunity as it requires minimum modifications on the rig. Its selection mainly depends on the foundation project and on the levelling devices of the subsea equipment, OCTOS 1000 concept features that simplify the installation task, and also on the relation between the overall dimensions of the equipment to be installed and the clearance area below the rig lower deck. INTRODUTION The exploitation of deep water oil fields is the principal goal of several studies and projects carried on by PETROBRAS. Considering the existing alternatives for Campos Basin Albacora and Marlim fields development, subsea completion and floating production system was the chosen one, basically due to the evaluated costs and to our know how on those systems for shallow water fields. However, some components of this scenario had to he upgraded in order to overcome the challenge of going deeper. The OCTOS 1000 template manifold project represents an evolution on the basic concepts for adeepwater template design, based on simplicity, reliability, safety and field experience. Orthogonally shaped with a central manifold and seven wells spaced in a radial way, it is linked to the production platform by the 8th arm's sales lines base. The foundations design consists on a central foundation and eight radial ones located at its eight arms extremities. Installation planning and designing followed thesame principles of the main project but aiming to maximize the use of our own human and material resources, in order to do it "in house". FORMER STUDIES The OCTOS 1000 transport and installation couldbe easily performed by a heavy lift vessel with dynamic positioning, for example, being this idea putaside at first to avoid high daily rates and mobilization fees. As one of the premises of the whole project was 1,000 m (3,281 ft) water depth rating, contracting an anchored lift barge or semi-submersible to perform the joh would result in a difficult anchoring and positioning over the location and in high costs also, due to the small availability of those units. The research was directed to dynamic positioned (OP) rigs, preferably with a long term contract under way. The structure design and installation initial studies considered the drillship Pacnorse II or the semi-submersible Sedco 709 as the rigs which could launch the OCTOS 1000 into the water.