Chemical Visualization of Asphaltenes Aggregation Processes Studied in Situ with ATR-FTIR Spectroscopic Imaging and NMR Imaging

Crude oil phase behavior and asphaltene precipitation have been studied by two complementary chemical imaging methods for the first time. ATR-FTIR spectroscopic imaging approach has revealed the chemical composition of agglomerated and precipitated asphaltenes upon dilution with a flocculant. Asphaltenes, containing oxygen and nitrogen heteroatomic functional groups, have been detected to be least stable. Aromatic abundant asphaltenes have been observed to have relatively high solubility in crude oil/heptane blends. NMR imaging approach, capable of imaging in the bulk of crude oil samples, has demonstrated that n-heptane causes aggregation which can lead to the stable suspension or to the sedimentation followed by the formation of deposits, depending on flocculant concentration. These processes have been monitored for small and large amounts of heptane added to crude oil. The data obtained by ATR-FTIR spectroscopic imaging and NMR imaging have been correlated to propose a possible link between the chemical structure of asphaltenes and a mechanism of the formation of deposits.