Contactless asphaltene solid particle deposition monitoring using active microwave resonators

In this paper, asphaltene precipitation and deposition are monitored in real-time and contactless fashion using ultra-high resolution active planar microwave sensor. In the core of the sensor, a half-wavelength resonator is designed at 1.53 GHz whose quality factor is enhanced from 270 (passive mode) by 40 times (in active mode) for high-resolution readout. High quality factor of the sensor and its sensitivity to ambient permittivity variation, enables high resolution readout and thus real time monitoring of asphaltene solid particle deposition. Model oil samples are mixed with n-heptane resulting in the precipitation of asphaltene aggregated particulates. We monitored the precipitation and deposition for 6 minutes over two concentrations of 0.1875% and 0.625% asphaltene samples (diluted in toluene) with the sensor, and observed resonant-frequency shifts of 50 and 80 kHz, respectively. This new contactless approach is shown to be highly sensitive and repeatable.