Poseidon is a new offshore production system that is very particularly geared to the development of oil fields situated in severe environments (deep water, rough seas, etc.) well away from the coast (up to several hundred kilometers). The principal feature of Poseidon is that all equipment and facilities are under water, thus doing away with all installations that are conventionally set up on the surface, either above the site or in proximity to it, by way of fixed or floating platforms. The other main characteristic is that no processing is done on the site. As it comes out of the wells all the production is directly pumped to shore through one pipeline, by way of multiphase pumps. The subsea installation is composed of the following main parts
subsea wellheads,
a modular subsea station serving as a manifold housing pumps and pipeline operation systems,
2 phase pumps
a pipeline to transport the production.
The complete Poseidon project consists of two phases:
study of the main system components and, as a matter of priority, of the special to type Poseidon sub-assemblies
proving trials of the major components.
The work is now well advanced and has already produced some quite promising results. The Poseidon project is being managed by a term of three companies: IFP (French Petroleum Institute), Total and the Norwegian firm Statoil.
Multiphase pumping of untreated well fluids is recognized as one of the most economical ways to develop a satellite or marginal offshore oil field, to enhance the production potential of exiting field and ultimately to develop deep-sea field (Table I)
The technical challenge lies principally in two main areas
two phase flow in pipelines,
development of multiphase pumping systems.
The scenario for multiphase pumping systems.
Table I Multiphase pumping (available in full paper)
The use of light unmanned platform protecting surface well-heads and multiphase pumps to transfer production to an existing processing platform considerably reduces investment and operating costs. Furthermore, this system is applicable to fields with low-productivity wells, while a development with subsea completions implies, due to the high cost of subsea wells, a high per-well productivity.
For example, a development based on a ‘Tension Leg Wellhead Platform’ supporting the wells only is made at a water depth of 550 m. the untreated production is then delivered without pumping through a 19-km line to a classical treatment jacket platform erected in reasonable water depths. The use of multiphase pumps on this TLWP could allow increased productivity per well by decreasing wellhead flowing pressure (by avoiding the pressure loss due to the 19 km pipe and the 600m up flow to the surface).
Using a multiphase pump will also allow for a lower wellhead flowing pressure, thus increasing ultimate recovery. The other advantages include :-
valorization of the associated gas,
reduced running costs from using one pipe instead of two
the increased safety of an unmanned platform
