(580f) Comprehensive Study On Gas / Crude Oil / Water Separation - Experimental and Numerical Analysis

The increasing interest in the development of deep offshore separation units incited IFP and TOTAL to develop a large program of research to have a better understanding of three-phase (gas, oil, water) separation phenomena. In that program, a new test facility, named GOwSP Loop (Gas Oil water Separation Plat-Form) has been built in 2006 at Solaize (France), on the IFP-Lyon site. The topic consists in improving the design of separator faced to operating conditions, behaviour of fluids in deep offshore conditions and heavy crude oil.

The GOwSP plat-form is an industrial test facility designed for the separation research program, and also for testing multiphase equipments such as separators, pumps, monitoring or flow-meters for instance. The closed loop is under pressure and temperature control. Mixing devices (blade static mixer and controlled valves) may be used to manage emulsion flow shear rate. Used fluids are crude oil, water (pure or salted water) and natural gas.

Tests on GOwSP loop have been performed since the year 2007 on a basic three phase gas/oil/water horizontal separator with different crude oils. The separator has been designed and implemented with specific instrumentations : a perforated plate located at the inlet forms a tranquilliser area upstream the decantation zone ; two interface profiler gauges give the spatial distribution of water fraction and interfaces (water/emulsion, emulsion/oil, oil/gas) along a vertical axis at the entrance and near the weir of the separator. Finally, the global efficiency as well as the local description of flow within the separator, coupling with sampling, are analysed according to the change of operating conditions such as flow rates, water fraction, pressure or also fluids viscosity via temperature.

The aim of the research study is to couple physical models of coalescence and sedimentation with the hydrodynamic fluids behaviour. Those models are now implemented in 2D or 3D computational simulations performed by using a commercial CFD code based on three phases flow (gas/oil/water).

In the document, experimental results performed with one crude oil are described and compared to non-stationary CFD simulations. The predicted heights of the emulsion inside the tank due to several operating conditions are in good accordance with the measurements. Moreover, simulations with the CFD code adapted to separation study are able to predict the real efficiency of the separator with a good accuracy.