Engineering the DEEPSEP Subsea Boosting System
Authors: Eyre G.P. , Day A. , Galletti Robin , Ray John 
Published: October 2008

DEEPSEP is a subsea processing system that utilises separation and conventional pumps to achieve production boosting. Following completion of a feasibility study, that showed that the system could be successfully deployed and operated in 1000 m water depth, work has begun on the engineering of a commercial prototype for deployment at a specific subsea test site.

The test site conditions are described along with some of the engineering solutions developed for some of the key aspects of the system including:Sand HandlingProduction SeparationWell TestingInstrumentation and ControlInstallation and InterventionReliability

A pragmatic engineered approach is being adopted during the development of DEEPSEP which minimises the use of novel solutions and equipment contiguraticms. The "commercial prototype" will be engineered such that following proving tests it may be redeployed into full commercial operation.

Introduction

Increasingly offshore producing fields in deep waters are being targeted for production in an oil price environment that demands that the most cost effective production technology is deployed to achieve worthwhile returns for operators and investors. Addhionally many of these deep water finds have low reservoir drives that ideally require some form of pressure boosting to achieve flow to surface production facilities. The Campos Basin and West of Shetland provide several examples of fields thatrequire such support.

DEEPSEP is a production system that specifically addresses the problems posed by such fields. The concept is illustrated in figure 1. A DEEPSEP unit would be placed adjacent to subsea wells in deep waterand would boost production back to facilities in shallow water. The equipment that would be provided in the unitis illustrated in figure 2. The contlguration has been selected to provide a strong foundation for overallreliability and availability, it comprises these main elements:2 × 100 % Sand Handling Modules2 × 100 % Test/Production Separators3 x50% Production Pumps

This total system has already been shown to provide economic benefits when the development of such fields is considered - see reference 1. The purpose of this paper is to show the steps now being taken to prove the engineering viability of this Concept. A prototype is being developed that incorporates all of the key features of the Concept. Successfti proving of the prototype willallow the Concept to be underwritten for full commercial application.

Specifically the paper describes:the key featuresof the Concept.the engineering of the prototype unit:Test site conditionsAvailability CriteriaEquipment ConfigurationSand Handling ModuleTest/Production Separation ModuleInstrumentation and ControlInstallation and Intervention

The engineering philosophy adopted during all phases of development of DEEPSEP wiII be, and has been, one that minimises the use of untried equipment.TM is not to say that innovation has not been incorporated within the design. Subsea boosting is an innovation and as suchrequires new technology to handle aspects such as sand production and control of dynamic processes. Even so the engineering solutions developed have tended to be based on the use of existing subsea components and equipment.