Following the installation in production fields of several tens of Two Phase Helico Axial Pumps, IFP and DBGP have recently launched a R&D program for the development of Two Phase Helico-Axial Turbines. These turbines may be used in many process applications in replacement of let down valves for energy recovery but also to increase the cooling duty or the liquid production. They may also be used in systems including a two phase separator with single phase expanders / turbines in view of reducing the number of equipment, space and weight. These turbines, suitable for all gas fractions, may find applications in the production of hydrocarbons (HP/HT wells, fractured reservoirs, oil stabilisation, electricity production in remote areas) but also in hydrocarbon treatment or in gas liquefaction. These applications cover a broad range in flow rate, pressure, temperature, gas fraction and fluid composition. A two phase helico-axial turbine prototype has been tested during the present year confirming the expected hydraulic performance. The hydraulic efficiency was found satisfactory to provide significant energy and liquid recoveries in many applications.
Introduction
Multiphase pumping is a long-established activity at IFP. First works were initiated in the seventies to extend the application of downhole electrical pumps. In the mid-eighties, multiphase pumping raised a renewed interest to transport the production of subsea satellite fields. At that time, subsea satellite developments were frequently substituted to stand-alone platforms in the North Sea to reduce offshore development costs. As tied-back distances to existing facilities were limited between 15 and 20 km due to the available natural reservoir pressure, multiphase pumps were a possible means of increasing these distances by adding energy to the liquid-gas mixture (Falcimaigne, 1992).
After an extensive test programme on an IFP multiphase loop to investigate the hydraulic and mechanical behaviour in steady-state and slug flows, the P300 pump prototype was tested in 1991. This prototype is still in service in the IFP experimental loop, twelve years later, to boost multiphase mixtures.
In 1994, first field applications of the Poseidon technology were characterised by relatively low flow rates and powers. Typical examples are the pump installed in the TotalFinaElf Pecorade field, in south of France, with a capacity of 360 m3/hr and drive power of 600 kW (Figure 1.1 - Falcimaigne et al., 1994, Leporcher and Taiani, 1995), or the pump installed in the Statoil Gullfaks A Platform in the North Sea with a total capacity 200 m3/hr and drive power of 750 kW (Vangen et al. 1995). A subsea helico-axial turbo-pump was also installed in 1994 at the Draugen field in the North Sea by Norske Shell.
The progressive accumulation of field experience secured the oil operators to apply the technology on a larger scale. The power of recent Poseidon pumps reaches 4.5 MW for the TotalFinaElf Dunbar field in the North Sea and 6 MW for the Youkos Priobskoye oilfield in Siberia (total flowrate capacity : 3300 m3/hr). At present, helico-axial pumps are the largest multiphase pumps in the world both in capacity and power, and also the deepest in the world for subsea applications (750 m water depth in Ceiba field, Gulf of Guinea).
