High-frequency magnetic field probe for determination of interface levels in separation tanks

Abstract

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.

Magnetic induction tomography methods and applications: a review

“…A single channel MIT system has been used to measure the water content in multi-phase flow using experimental phantom recordings. It was found that the correlation between the position of the coil and the water/oil interface could be overcome by a full tomographic system [60] (a similar conclusion has also been drawn in [61]).…”

Multiple Measurement Vector-Based Complex-Valued Multifrequency ECT

“…However, ERT sensors require direct contact with the conductive media, which is not suitable for long-term metering in oil wells, since the wax or deposits might stick to the electrodes and block the conductive path between electrodes. To avoid direct contact with the flow, Hammer et al proposed high frequency magnetic methods for two phase flow measurement [8][9][10]. Another contactless tomography modality, i.e.…”