Subsea Gas-liquid And Water-hydrocarbon Separation: Pipe Solutions For Deep And Ultra Deepwater
Authors: Abrand Stephanie , Shaiek Sadia , Anres Stephane Jean , Hallot Raymond 
Published: June 2014

The Oil and Gas industry is currently investigating innovative solutions in order to develop new fields in deep-water, remote areas and to increase the recovery of mature fields.

Subsea separation solutions enhance production while better managing hydrates (gas/liquid separation) or allow the debottlenecking of topside water treatment (water/hydrocarbon separation and subsea water re-injection).

SAIPEM is currently developing several subsea separation systems made of pipes working in parallel: The MULTIPIPE for the subsea gas/liquid separation and the SPOOLSEP for subsea water/hydrocarbon separation.

For each technology, the design is relying on flow split and operation of pipes in parallel. Extensive qualification tests were undertaken focusing on the symmetry of the system and its operability for subsea application.

These separators with reduced wall thicknesses, compared to single large diameter vessels, are especially well suited to deep water and /or high pressure applications. Moreover these solutions are reliable as they rely on gravity separation and allow for standard manufacturing and installation procedures as well as conventional installation and maintenance vessels.

The gas/liquid Multipipe separator has been qualified through several test campaigns, including a first JIP with tests with real crude under pressure to simulate subsea operation showing its versatility for deepwater application. A second JIP with Petrobras, Total and ENI has been completed early 2013. It has covered the qualification of the whole subsea station and the performance of additional flow performance tests. Further qualification actions including tests have been identified in view of some recent high pressure application cases.

Following the positive results on the Multipipe Saipem has initiated the development of the water/hydrocarbon SpoolSep separator. The paper presents the results of the first qualification tests on separation performance which started early this year as well as the way forward which includes a JIP for the performance of tests with real crude.

Introduction

The Oil and Gas industry is currently investigating subsea processing solutions to develop future fields in deep-water, remote areas and sometimes with difficult oils.

Saipem is currently developing several solutions made of pipes working in parallel for subsea separation as alternates to single large diameter vessels. The targets are deep-water and/or high pressure applications and the objective is to ease procurement, manufacturing and installation, having modular systems, still keeping the ability to deal with large flow-rates, transient slugging conditions or challenging production requirements such as heavy oils, always relying on gravity separation. These pipes solutions can also increase the manufacturing performed on the local yards.

For each developed system, the design is relying on flow split and operation of pipes in parallel. Extensive qualification tests were undertaken or are currently on going, focusing on the symmetry of the system and its operability for subsea application.