Terahertz Spectroscopy for Measuring Multiphase Fractions

Abstract

In this paper, an experimental study was conducted using terahertz (THz) spectroscopy to assess the electromagnetic properties in the THz range of various materials that can be found in oil and gas fields. This includes the absorbance, transmittance, and refraction properties of crude oil (i.e., PS65 oil in this paper), water, solid contaminants, and various mixtures of these contents. The first set of experiments was conducted to assess the effects of temperature on THz absorbance. This revealed that the temperature does not have a substantial effect on the absorbance coefficient. On the other hand, other experiments indicated that the absorbance coefficient is much higher for solid contaminants particles than for either crude oil or water. In addition, when solid contaminants are mixed with the crude oil, the absorbance coefficient varies with respect to the way the solid contaminants are distributed within the sample and increase proportionally to the amount of solid contaminants. In case of crude oil–water mixture, it is found that the absorbance coefficient increases as the water content increases. However, compared to solid contaminants, its absorbance value is much lower. The results obtained for THz spectrums and the corresponding principal component analysis graphs demonstrate the potential that THz-based devices would have in effectively measuring concentrations of solid and liquid multiphase flows, including solid contaminants which can hinder the quality of oil and gas flowing through the pipe. It would also help to monitor the quality of exported oil, which usually still contains water phase, in spite of series of oil–water separation process.