Stability of asphaltenes is affected mainly by the change in pressure and temperature within the reservoir or in production lines. Destabilized asphaltenes results in several flow assurance problems due to their higher precipitation tendency. While there are numerous studies investigating the role of pressure and temperature on asphaltenes stability, the role of reservoir components on asphaltenes stability still remains unknown.
Hence, this study investigates the effect of reservoir rock-asphaltenes interaction on asphaltenes stability. 11 different crude oil samples from all around the world and their asphaltenes were analyzed. Both n-pentane and n-heptane asphaltenes surfaces were visualized under scanning electron microscope (SEM). Inorganic (mainly salts and clays) presence was observed on asphaltenes surfaces, which might be the consequence of the reservoir rock-oil interaction. Thus the inorganic content of separated asphaltenes were investigated by mixing asphaltenes and deionized water vigorously by a centrifuge to separate the inorganic content of asphaltenes from asphaltenes’ surfaces. The supernatant of these mixtures was subjected to total dissolved solids (TDS), pH, and conductivity measurements.
The TDS level was observed high which proves the physical interaction of asphaltenes with reservoir rock and this interaction is also found to generate high conductivity mainly due to sodium salts. The electrostatic charges created in water due to inorganic content of asphaltenes were determined by zeta potential. Precipitation tendency of the colloids were found very high for most of the asphaltenes samples and they are mainly because of the presence of excessive amount of negatively charged particles. Particle sizes of those particles were also measured high which increases the chances of the particles to come together for precipitation.
This study proves the presence of electrical charges on asphaltenes surface and highlights its importance on asphaltenes stability.