Subsea Production Systems and the UMC Experience
Authors: Brady M.M. , Henery D. 
Published: December 2007

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering.

Introduction

The Underwater Manifold Center (UMC) project for the Central Connorant fieldis the most advanced system of its kind and is unequalled in size, versatility, and sophistication (Fig. 1). It incorporates a long list of pioneering technological features including re connectable power couplers, satellite and template wells, remote Christmas tree and pipeline connections, long-distance chemical injection and TFL well-servicing capability, insulated pipelines, and a diver less maintenance system that uses a robot-like remote maintenancevehicle (RMV).

In many respects the UMC is a symbol of recent advances in subsea production systems. Components and concepts developed for it will set a standard for and be applied to other subsea systems, and the UMC's performance, accordingly, will be watched closely by the industry, especially over the next few years. From a descriptive and technical point of view, ample information on the UMChas been published recently.1–5

Beyond the technical realm, the UMC development has raised some broader strategic and economic issues of interest to those concerned with the development of subsea production systems in general. This article con entrateson a few of these issues to provide information and guidance based on the UMC project experiences:Why were subsea techniques used to develop the Central Connorantfield?How much did the UMC cost, and how can costs be reduced in the future?What was the single biggest concern of the project?What are the benefits and costs of satellite wells connected to the UMC?In what areas could the next UMC be improved?What key factors contributed to the project's success?

Selecting the UMC for Central Cormorant

There is no single answer or formula for selecting a development plan for an off shore reservoir because of the variety of geological conditions and reservoir characteristics that can be encountered and the many variables involved. Indeed, environmental and safety considerations and the magnitude of investment required demand careful scrutiny of every option. It is not unusual for a development plan to take several years or more to be worked out in detail and approved.

The most that can be said in general is that certain circumstances favor, but do not dictate, certain options. Subsea production systems have been favored mainly for two areas of application: marginal fields and deep water. For the purpose of this discussion, marginal fields are, for example, those shallow-water fields (usually odd-shaped and thin) for which conventional methods - i.e., platforms - are unsuitable and/or lead to uneconomical orbarely economical results. This application accounts for almost all present subsea systems, usually comprising one or more subsea Christmas-tree wellsproducing to a platform. Currently there are more than 190 subsea wells in 70different fields, and their use is growing yearly.