Resonant cavity water cut meter with automatic resonance tracking system

Abstract

Multiphase measurement is still a challenge in the petroleum industry, and water cut measurement is a particular problem. Resonant Cavity Sensors (RCS) have been employed to measure water cut in water-oil and water-gas flows. The noninvasive and nondestructive characteristic of this technology is one of its main advantages, since the sensors do not interfere in the flow and do not change its physical characteristics. Once the measurement is based on the sensor's resonance frequency, it is necessary to implement an automatic approach for real-Phase time measurement, rather than frequency scanning, to find the resonant frequency. We propose an automatic resonance tracking Frequency system for the water fraction monitoring of a water cut meter with a resonant cavity sensor. The implemented system is based on a Phase-Locked Loop (PLL) mechanism operating in the radio frequency (RF) range and the circuit was implemented with off-the-shelf RF components. The technique was validated by measuring a stratified water-air flow. We found that the automatic system can measure the water cut in a full range (0% to 100%) of water fraction with a resolution around 0.1%.