Asphaltene Content Measurement Using an Optical Spectroscopy Technique

A new spectrophotometry technique for quantifying the asphaltene content of black oil samples improves data quality, reduces measurement time, and reduces solvent volume in comparison with conventional methods. According to this method, asphaltenes are quantified by subtracting the visible spectrum of the maltenes from that of the oil. We found that the difference in spectra of oil and maltenes correlated well with the modified ASTM D6560 method for a large sample set that covered a wide range of geographic locations, which points to the existence of a global correlation between the visible spectrum of asphaltenes and their concentration. The repeatability of the measurements, even for low-asphaltene samples, was far better than that achieved with conventional methods. The measurement time was reduced to less than 3 h from 2 days in conventional measurements, and the solvent volume was reduced from 250 mL using the conventional technique to 40 rnL using the optical method, thereby reducing the environmental footprint of the measurement.