ABSTRACT

This paper outlines the concept of Petrobras OCTOS-1000 project for a template manifold, conceived to suit dlverless and guidelineless requirement to develop deepwater fields. Sane major improvements have been incorporated into the initial concept, mostly related to the control system, the installation procedure and the sales lines connectors.

INTRODUCTION

Petrobras has been working since 1988 on a template-manifold project for deepwater application namely OCTOS-1000. The main purpose of the project is the development, by means of subsea facilities, of the major deepwater fields located at Camps Basin, offshore Brazil. It was conceived to admit either diverless and guidelineless operations accepting Dynamically Positioned (DP) Units application during drilling, completion and workover phases.

The conceptual design was developed in a general basis considering the conditions of Marlim field. However, fusibility studies undertaken for Albacora field pointed out a specific location, at 600m (1,970ft) water, for the pioneerCK!TOS-1000 (fig.1). In accordance to the new stated conditions and field test results of associated projects, some major modifications were introduced, which are described in this paper after a brief discussion of the OCTOS-1000 concept.

OCTOS-1000 CONCEPT

OCTOS-1000 consists of an octogonal shape template-manifold similar to an octopus. Seven arms lodge wells at their endings and the last one lodges the sales lines connectors. At the center, the manifold gathers the production of individual wells sending it to a Stationary Production Unit (SPU) through the export connectors (fig. 2).

The active components, such as valves and chokes are mainly located at the wet Christmas trees, thus resulting in a simple and reliable manifold. Nevertheless, the manifold is retrievable, being enveloped by a protective structure that also helps on guiding reentry jobs.

The template is set over a central foundation remaining above the sea bottom. Drilling cuttings return at mudline level avoiding its accumulation over the structure. The wells are likely self supported due to a special bearing system that also admits angular movements thus avoiding leveling operations. Control and sales lines are layed away and facilities are provided to ease remote operation vehicles (RW) intervention. Reference 1 discusses in more detail the OCTOS-1OOO concept.

MAJOR INNOVATIONS

Major changes occur basically to the control system, to the wet christmas tree (WCT), to the control and sales lines connectors and to the installation procedure:

Control System

During november 1990 a prototype of the electro-hydraulic multiplex control system MUXCOM designed by BRASNOR A/S was installed on the Bonito field at 220m (722 ft) water. The Successful experience has encouraged a revision on the control system proposed to OCTOS-1000.

Originally, a sequence-hydraulic system would work together with a multiplex one for data acquisition and supervision. But with the god field results obtained, the operational flexibility and further cost analysis indicated the multiplex system as a better choice.

On the new configuration, each WCT is equipped with a control pod installed and retrieved with a specially designed control pod running tool.

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