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This paper describes low-energy gamma-ray densitometry using a 241Am source for the determination of void fraction and flow regime in oil/gas pipes. Due to the reduced shielding requirements of this method compared to traditional gamma-ray densitometers using 137Cs sources, the low-energy source offers a compact design and the advantage of multi-beam configuration. One of the aims of this investigation was to demonstrate the use of a neural network to convert multi-beam gamma-ray spectra into a classification of the flow regime and void fraction, as well as to determine which detector positions best serve this purpose. In addition to spectra obtained from measurements on a set of phantom arrangements, simulated gamma-ray spectra were used. Simulations were performed using the EGS4 software package. Detector responses were simulated for void fractions covering the range from 0 - 100%, and the simulations were performed with homogeneous, annular and stratified flows. Neural networks were trained on the simulated gamma-ray data and then used to analyse the measured spectra. This analysis allowed determination of the void fraction with an error of 3% for all of the flow regimes, and the three types of flow regime were always correctly distinguished. It has thus been shown that multi-beam gamma-ray densitometers with detector responses examined by neural networks can analyse a two-phase flow with high accuracy.

There are many principles for interface level detection in separation tanks based on capacitance, ultra sound, microwave, nuclear radiation etc. These principles work well in many situations, in others they fail.The high frequency magnetic field principle works in most of the situations that will occur in separation tanks for crude oils for detection of the clean water level, the layers of water continuous water/oil emulsion and the oil continuous oil/water emulsion, the oil level, the thickness of the foam layer and the gas.When a coil is dipped into a fluid its electrical impedance will be dependent on the characteristics of the fluid. If the material is electrical conductive the impedance of the coil will be reduced due to the eddy currents induced in the material, setting up a magnetic field directed against the field generated by the coil. The inductance will increase but still remain low also in the water continuous water/oil emulsion zone, but will rapidly increase in the oil continuous oil/water emulsion zone. In pure crude oil the inductance will be high and even higher in gas. The coil inductance is measured by connecting the coil to a LC-oscillator.