New Algorithm to Discriminate Phase Distribution of Gas-Oil-Water Pipe Flow With Dual-Modality Wire-Mesh Sensor

Abstract

Three-phase gas-oil-water flow is an important type of flow present in petroleum extraction and processing. This paper reports a novel threshold-based method to visualize and estimate the crosssectional phase fraction of gas-oil-water mixtures. A 16x16 dual-modality wire-mesh sensor (WMS) was employed to simultaneously determine the conductive and capacitive components of the impedance of fluid. Then, both electrical parameters are used to classify readings of WMS into either pure substance (gas, oil or water) or two-phase oil-water mixtures (foam is neglected in this work). Since the wire-mesh sensor interrogates small regions of the flow domain, we assume that the three-phase mixture can be segmented according to the spatial sensor resolution (typically 2-3 mm). Hence, the proposed method simplifies a complex three-phase system in several segments of single or two-phase mixtures. In addition to flow visualization, the novel approach can also be applied to estimate quantitative volume fractions of flowing gas-oil-water mixtures. The proposed method was tested in a horizontal air-oil-water flow loop in different flow conditions. Experimental results suggest that the threshold-based method is able to capture transient three-phase flows with high temporal and spatial resolution even in the presence of water-oil dispersion regardless of the continuous phase.

Combined Finite Element and Electronic Circuit Model of a Wire-Mesh Sensor

“…As tap water (∼420 µS/cm) was used during the experiments and the sensor was operating at 5 MHz, both conductivity and relative permittivity contribute to the absolute admittance signal. In this case, the static calibration to obtain the absolute admittance distribution is performed as presented in [25]. Once the admittance distribution is obtained, it can be converted to phase fraction by using analytic mixture models according to the structure of the flow.…”

“…Data acquisition was performed at frequency of 2 kHz for 1 minute each. The raw data were converted to absolute admittance by using two measurements as references [36], [25]. The first reference data was obtained with the sensor filled up with tap water and the second one with the sensor completely empty.…”

“…The WMS is a slightly intrusive device able to measure the local phase fraction of up to × 128 points into the flow domain with temporal and spatial resolutions of up to 10 kHz and 1-3 mm, respectively. The sensor can be designed to measure the conductivity [22] or relative permittivity distribution [23] for two-phase flow systems and the complex admittance/impedance [24], [25] for three-phase flow measurement. Such electrical properties can subsequently be converted to phase fractions based on assumptions of the flow structure, i.e.…”

“…Such electrical properties can subsequently be converted to phase fractions based on assumptions of the flow structure, i.e. depending on how the mixture is geometrically distributed into the interrogated control volume [25]- [27]. Since the control volume represents only a small fraction of the flow domain, many researchers have used the parallel model (linear relationship) to estimate the phase fraction, which has shown good agreement with other measurement techniques in many flow regimes.…”

Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions

“…The latter one is, however, not considered in the present study. In contrast, recently developed dual-modality sensors [ 7 , 8 ], which combine both measurement principles in order to differentiate phases in three-phase flows of oil, water and gas, may benefit from the temperature compensation approach proposed in this article.…”