Optical fiber sensor for assessing asphaltene content in crude oil

An optical fiber sensor is described for monitoring asphaltene content in crude oil samples, utilizing a no-core fiber segment spliced between two multimode fibers. Light transmitted through the no-core fiber section is attenuated due to the presence of scattering and absorbing effects in the surrounding medium. The sensor assesses asphaltene precipitation in a crude oil/n-heptane solution, correlating asphaltene concentration with the resulting transmission loss. Tests on four crude oil samples from different extractions and oil deposits, with asphaltene content ranging from 1% to 8.4% w/w, revealed a distinct transmission loss per sample and an exponentially increasing loss trend with regard to asphaltene content. The recorded transmission loss (after 1 hour of precipitation), measured with the non-core optical fiber sensor, ranged from 1.9 dB to 8.5 dB for the aforementioned asphaltene content values.