Development of a magnetoelastic resonance sensingsystem for water cutapplications.

[摘要] ENGLISH ABSTRACT: Precise measurement of the water fraction in oil (i.e. water cut) is of critical importance innumerous applications. In the oil and gas industry, for example, knowledge of the amount ofwater production and where it comes from is necessary before any remedial action can be taken.Currently, cost-effective, reliable and accurate measurement technologies capable of full rangethree phase measurements are not commercially available.The development of an ultra-low power, low-cost, wireless and non-corrosive resonance sensoris considered. The sensor is based on magnetoelastic technology that has been implemented byan amorphous ribbon and electromagnetic interrogation. The magnetoelastic ribbon's resonantfrequency is dependent on the vibrational damping effect of the surrounding medium, whichin turn is determined by the dynamic viscosity of the medium. This enables distinguishing allthree gas, water, and oil phases with measured sensor signal amplitude changes of 75% and99% and resonant frequency shifts of 0.46% and 3.88% respectively, compared to the gasphase. The sensor shows sensitivity in the water-cut range from 10% - 90% WC and ischaracterised by a linear response from 10% - 80% WC. When immersed in water/oilemulsions the sensor power consumption ranges from 160 nW to 500 nW. A rapid decay ofthe magnetic properties has been observed in high salinity solutions due to corrosion of thesensor material, which represent typical environments in industrial applications. A solution forthis has been found through coating the sensor ribbons with Teflon by dip coating, acting as ananti-corrosion layer that enables sensor deployment for extended periods of time in harsh environments. This study shows that a magnetoelastic resonance sensor possesses the requiredcharacteristics and sensitivity which make it suitable for use in water-cut applications. Thepossibility of inline WC measurement has been explored through the design of a modifiedsensor housing. The sensor incorporates a set of excitation and detection coils and allows theflow of liquid across the amorphous ribbon surface. Tests conducted in a flowrate controlledwater flow loop show a shift of 150 Hz in resonant frequency from flowrates of 0.2 m/s – 0.63m/s due to the increased surface drag on the sensor surface. However, this is consideredinsignificant as viscosity induced shifts are in the kHz range, therefore concluding that thesensor is insensitive to variations in flow rate.Furthermore, the sensor system design is expanded as a Portable Readout Device (PRD)capable of in-field measurements. The design consists of a battery powered microcontroller circuit that integrates with a smartphone via a mobile application. The peak frequency datasampled from the sensor is displayed on the smartphone. The PRD sampling algorithm hasbeen tested with a 100% correlation in sampled data compared to a bench setup usingHelmholtz coils and an oscilloscope. The PRD consumes 3.25 W of power during samplingand is capable of remote operation through the implementation of Bluetooth connectivity.

[发布机构] Stellenbosch University