Abstract

Subsea water separation offers several advantages for deep and ultra-deepwater production (1500 m and more). The paper presents a project of subsea unit developed in order to reduce the water cut to a maximum of 10% near well heads, before transporting the production to surface facilities.

Benefits of water separation include prevention of hydrate formation, improved well productivity, reduction of back-pressure on wells, reduction of flowline size and complexity, reduction of thermal insulation requirements, increased capacity on existing mature field within the limit of their actual water treatment capacity ...

The components of the DIPSIS processing unit are described with emphasis on specific deep water constraints and requirements, especially the need for a high reliability.

Introduction

Offshore field developments extend now in deep and ultra deep waters, down to 2200 m below surface. In such water depths, which will be probably exceeded in the years to come, the combined effect of hydrostatic pressure and friction pressure losses produce high back pressure on the wells and limit production rates.

The back-pressure issue will become even more acute for future deep-water satellite fields. Several smaller discoveries have been made between 20 km and 50 km (or beyond) from the today developments. Although significant, their size will not allow an economical stand-alone development. The production transportation to existing surface facilities over a long horizontal distance will increase pressure losses and impair potential flow assurance problems.

The interest of subsea processing increases with increased water depths. Subsea processing includes subsea separation with water re-injection and/or oil, gas or multiphase boosting. This is made possible by many advances in development and deployment of key elements, such as deep water subsea boosting, flow lines instrumentation, electrical distribution and connections, and also in mastering flow assurance issues.

The aim of the DIPSIS subsea station (Deep Integrated Production Separation and Injection System) is to separate the water from the hydrocarbons at the mudline level, as close as possible to the well heads and to inject the water directly into a disposal well. Only a maximum of 10% residual water cut is expected downstream the station. It has been developed to be part of an anti-hydrate strategy in deep water (1500 m or more) allowing treatment of a reasonable quantity of produced water with Low Dosage Additives.

The project was initiated and developed by a group of companies involved in offshore subsea developments: Doris Engineering (project leader, in charge of engineering and co-ordination), Prosernat, Sulzer Pumps and Cybernetix, IFP and ECA.

BLOCK 1 - - FORUM 1 47 SUBSEA WATER SEPARATION: A COST-EFFECTIVE

This content is only available via PDF.
You can access this article if you purchase or spend a download.