In the scope of the SEPCOMP (subsea oil separation with composite materials) project, the benefits of using composite materials in the design of a subsea oil/water separation module have been evaluated. These studies are mainly focused on four points:

  • The hull of the horizontal gravity separator (30 m3) made of a sandwich cylinder (skins, carbon filament winding; and core, foam) and two hemispheric end closures (RTM, carbon fibres)

  • The composite pipes of the module

  • The support frame of the module made of composite beams

  • The protection cover of the installation made of sandwich plates

Two different water depths are considered (1500 and 3000m). The expected benefits are:

  • Lower costs of deployment mainly due to the reduction of the module weight

  • Lower costs of maintenance mainly due to the reduction of corrosion problems

  • New design possibilities in the envisaged water depths

  • Standardisation of a number of structural parts

On the other hand, the higher costs of manufacturing composite parts are considered to evaluate the economic gain of the composite design compared to a metallic design.


The main concern of the SEPCOMP project is the exploitation of deep and ultra-deep offshore oil fields. In these cases, the dimensions of the production lines between the surface and the sea ground can be reduced by using a subsea oil/water separator. Consequently, the weight of the surface support is also reduced. The specifications of a subsea separator can lead to design a heavy unique module or several lighter ones. In each case, the setting up will be expensive. The object of the project is to evaluate the impact of using composite materials on the manufacturing, deployment and maintenance of a separation module settled in a large water depth. Potential materials for each part of the separator (structure, piping, separator, etc.) were identified and studied. The comparative study is based on the DIPSIS project (DORIS Engineering), whose design is mainly based on metallic materials. Due to the large water depths considered (1500 to 3000 m), the composite materials offer advantages?weight saving, absence of corrosion, fatigue strength?which make possible a global weight reduction and cost savings.

Simplified Specification of the Separator Module
Subset Definition

All the technical studies are undertaken with the aim of replacing each metallic subset by one functionally equivalent that is made of composite materials. This approach does not lead to a high level of optimisation, but it was selected because it allows for:

  • Organisation the technical studies by competence field

  • Running of the prototype tests subset by subset

  • Moreover, the gradual but soon introduction of these subsets in operational structures without modifying the global design

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