New application of THz technique on water evaluation in crude oil

Water content in crude oil is closely related to the prediction of water level of oil wells, the evaluation of oil reservoir exploitation and the development of mining. Therefore, the accurate measurement of water content is significant not only for forecasting the capacity of an oil field before mining and estimating working status, but also for grading and evaluating oil products.

In order to optimize production, simple and secure methods have been proposed for detecting the water content in crude oil. Terahertz (THz) radiation is a newly developed, non-contact and secure method that be absorbed by organics and water molecules in different degrees, which has been used to evaluate the quality of oil and oil products.

In the article, water content in oil-water mixtures from 1.8 percent to 90.6 percent was measured by using specially designed samplers for high-water-content oil, which are fabricated via additive manufacturing. The researchers write, "Water content of oil-water mixtures with high water content is quantitatively characterized by the combination of THz spectroscopy and 3D-printing technology."

The study was published in the journal Science China Physics, Mechanics & Astronomy. The strong absorption of water in the THz range leads to a decrease in SNR (signal-to-noise ratio), applying the additive manufactured samplers, the problem that signals usually affected by the significant signal attenuation can be resolved.

Detailed analysis shows the relationships among THz parameters such as signal peak, time delay, and refractive index as well as absorption coefficient and water content in crude oil. Therefore, these THz parameters can be used to continuously monitor the moisture content.

In summary, the combination of THz spectroscopy and AM technique can be applied in oil characterization, even when the oilfield enters the high-water-bearing period. This combination could be a promising selection for measuring water content of fluid with good accuracy, which in turn could open up a new area of research.

More information:
LiMei Guan et al, Terahertz-dependent evaluation of water content in high-water-cut crude oil using additive-manufactured samplers, Science China Physics, Mechanics & Astronomy (2017). DOI: 10.1007/s11433-016-0491-3

Provided by Science China Press