Abstract
This paper reports the performance of a research prototype of a new multiphase flow instrument to non-invasively measure the phase flow rates, with the capability to rapidly image the flow distributions of two- and three-phase (gas and/or oil in water) flows. The research prototype is based on the novel concepts of combining vector Electrical Impedance Tomography (EIT) sensor (for measuring dispersed-phase velocity and fraction) with an electromagnetic flow metre (EMF, for measuring continuous-phase velocity with the EIT input) and a gradiomanometer flow-mixture density metre (FDM), in addition to on-line water conductivity, temperature and absolute pressure measurements. EIT–EMF–FDM data fusion embedded in the research prototype, including online calibration/compensation of conductivity change due to the change of fluids' temperature or ionic concentration, enables the determination of mean concentration, mean velocity and hence the mean flow rate of each individual phase based on the measurement of dispersed-phase distributions and velocity profiles. Results from first flow-loop experiments conducted at Schlumberger Gould Research (SGR) will be described. The performance of the research prototype in flow-rate measurements are evaluated by comparison with the flow-loop references. The results indicate that optimum performance of the research prototype for three-phase flows is confined within the measuring envelope 45–100% Water-in-Liquid Ratio (WLR) and 0–45% Gas Volume Fraction (GVF). Within the scope of this joint research project funded by the UK Engineering & Physical Sciences Research Council (EPSRC), only vertical flows with a conductive continuous liquid phase will be addressed.
Highlights
EH9 3JL, UK.problematic wells, optimise artificial lift operations and build dynamic reservoir models [19].Commonly used methods for measuring multiphase flows are based on γ-ray attenuation, RF/microwave and/or electrical impedance techniques in combination with a differential-pressure device such as a Venturi flowmeter [15,19]
This paper presented initial gas-oil-water three-phase flow measurement results from an Electrical Impedance Tomography combined with an electromagnetic flow metre and a gradiomanometer flow-mixture density metre, and with online water-conductivity and temperature sensors
The results indicate that the error of the measured water flow rate is within 710% when the flow is water continuous and of moderate Gas Volume Fraction (GVF) (GVFo $ 45%)
Summary
Phase fraction measurement based on γ-ray attenuation methods is elegant; there are practical or logistical difficulties to overcome when an intense radiation source is used to achieve the temporal resolution at the expense of increasing safety precautions [16]. Using sequences of images obtained from a dual-plane EIT flow sensor, the local flow velocity of the dispersed phase(s) can be deduced based on pixel–pixel cross-correlation methods [11,13,3]. This demands an EIT system to have a rapid response time [18] in order to measure multiphase flows with phase distributions changing in space and time. Since spatial- and time-averaged phase flow rates are the dominant parameters in multiphase flow measurement, an EIT is considered to be a good candidate for the fraction and/or velocity measurement of dispersed phases, e.g. gas- and/or oil-in-water
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