Résumé -Pompage polyphasique : réalisations et perpectives -Le pompage polyphasique est maintenant largement accepté par l'industrie pétrolière. Le présent article décrit les performances actuelles de la technique de pompage hélico-axiale inventée et développée par l'Institut français du pétrole (IFP). La taille des pompes installées a considérablement augmenté à mesure que l'accumulation de l'expérience obtenue sur les champs, à terre ou offshore, donnait confiance aux exploitants. Une seule pompe peut désormais développer une puissance de 6 MW et les pompes hélico-axiales sont actuellement les plus grosses pompes polyphasiques construites dans le monde. Des travaux de recherche sont toujours effectués par l'IFP pour améliorer les performances des pompes hélico-axiales ainsi que pour développer de nouvelles applications des turbo-machines hélico-axiales : ré-injection des gaz acides en solution, compresseurs de gaz humides, turbines polyphasiques. L'article décrit les principaux axes de travail et les méthodologies utilisées pour ces développements. Les techniques expérimentales et numériques les plus avancées sont utilisées à cet effet : anémométrie Doppler laser du coté expérimental, simulations d'écoulements diphasiques et optimisation des formes par réseau de neurones et algorithme génétique du côté conception et calcul des cellules hydrauliques.Mots-clés : production polyphasique, pompage polyphasique, pompe hélico-axiale, réinjection des gaz acides, turbine polyphasique, compresseur de gaz humide, visualisation d'écoulement, anémométrie Doppler laser, simulation en mécanique des fluides, simulation d'écoulements diphasiques, optimisation des formes. Abstract -Multiphase Pumping: Achievements and Perspectives -Multiphase pumping receive now a widespread acceptance of the oil industry. The paper describes the state of the art performance of the helico-axial technology invented and developed by the Institut français du pétrole (IFP).

This paper reviews field issues related to the planning, installation and operation of the helico-axial multiphase pumps. Interest for multiphase production, which leads to simpler and smaller in-field installations, is primarily dictated by the need for more a cost effective production system. Multiphase pumping is essentially a means of adding energy to the unprocessed effluent which enables the liquid/gas mixture to be transported over long distances without the need for prior separation. The Poseidon helico-axial pumps, under normal operating conditions, are largely unaffected by process fluctuations at pump inlet (changes in pressure, liquid or gas flow rate). They have demonstrated a stable behaviour (self-adaptive capability with regards to instantaneous changes). A multiphase pump set is designed to operate under changing/fluctuating process conditions. An important issue related to pump operability and flexibility has to do with the driver selection: fixed speed vs. variable speed In some cases a fixed speed drive provides sufficient operational flexibility. In other cases variable speed can be chosen. Pump operation & control strategies are presented and discussed. Recommendations and guidelines for the field system designer are given. Introduction When the production of a marginal field or a group of remote wells is considered with an existing central gathering system the traditional options for field development are:–natural flow,–artificial lift,–in-field separation with crude oil transfer pumps, gas to flare, or gas compression systems. With the recent field deployment of numerous multiphase pumps (MPP) new approaches to field development and production have been demonstrated. Typically helico-axial MPP have accumulated over 35,000 operating hours with an average availability of approximately 90%. Considering multiphase flow transient behaviour the operability of MPP is highlighted in the case of a declining offshore field with an increasing water cut. Different levels of pump control are defined depending on the operational requirements. Building on previous ideas a novel control system is introduced. Pump Specification The multiphase pump selection cannot be based solely on one defined operating point (main duty point) as it is commonly done for process pumps or compressors for refinery duty. Field experience shows that actual operating conditions change during the field life and may be different from predictions. Therefore multiphase pumps should be designed to be capable of facing different operating parameters by having a wide working envelope. Flow rates and pressure predictions are bound with uncertainty. The design of production facilities is generally based on extrapolations from the results of exploration well tests, delineation wells and reservoir characterisation. As a result, when the production wells are drilled and completed, the actual production data may be different from the prediction. P. 193

Satellite developments are an attractive solution for producing oil from small marginal fields. However, their application is limited by the distance that the crude oil can travel with the natural pressure of the reservoir. To overcome this limitation the paper proposes to use multiphase pumping to provide energy to the fluid. To implement this technology at low technical risks, the pumping unit could be located at the surface, aboard a small floating support. The production would be exported by means of a reusable flexible pipe to a processing centre.After presenting recent advances in multiphase production, the paper describes the proposed system, designed to produce fields with 20 to 60 millions bbl. of recoverable reserves and located from 10 to 60 km, or beyond, from existing facilities or the shore. The system is characterized by its mobility. After depletion of a field, it can be easily retrieved and moved to another location. In addition to reduced capital expenditures and relocability, the proposed system may accelerate the oil recovery of a field and the produced gas can be processed on the host platform and exported in an existing pipeline system.

The paper describes the main features of the P302 multiphase pump and presents some results of bench tests carried out to check its hydraulic performances. The P302 is a rotodynamic helicoaxial pump based on the Poseidon pumping technology. It is equipped with water lubricated bearings and driven by a high speed electrical motor. The pump was designed to work with a suction pressure much lower than the P300 prototype and to deliver a higher compression ratio. It has fifteen stages of compression cells, in three different series. Before installing the pump on an onshore production site for endurance tests with actual field fluids, the steady-state behaviour and the transient responses of the pump were characterised on the IFP multiphase loop at Solaize (France). The pump was tested both with single phase fluids (liquid or gas) and a diphasic mixture (fuel-oil and nitrogen) at various GVF and suction pressures. In the paper, theoretical predictions are compared to measured data. The good results of these tests confirmed the soundness and versatility of the Poseidon hydraulics and also the calculation model ability to predict accurately the performances of rotodynamic pump over a wide range of operating conditions.References and illustrations at end of paper 153 157