The measurement of water content in crude oil is of great significance. The existence of water in crude oil can introduce serious problems in the petroleum refining process and transportation. Many measurement technologies have been developed for determining water content in crude oil. When it comes to different measurement technologies, the trade-off between measurement accuracy and speed is the first to be mentioned. For example, a water concentration measurement accuracy of about 0.05% can be achieved using a distillation method lasting several hours.
Recently, terahertz time-domain spectroscopy (THz TDS) has been successfully applied to measurements of water content in oil [1]. This methodology is comparable in accuracy to the distillation technique, but is characterized by a higher measurement speed. In our work, we further investigated the potential of the THz TDS methodology for measuring water content in oil. For greater certainty, absorption measurements were supplemented by refractive index studies (Fig. 1), as well as various types of oil were examined.
In this work, it was shown that apart from the sample preparation time, the absorption and refractive index measurement of a single sample can be performed in 0.4 seconds without significantly compromising the measurement accuracy. This shows the perspective of the THz TDS methodology not only for laboratory measurements, but also for real-time oil monitoring in oil production and transportation facilities.