Investigation of asphaltene deposition in flowing condition

Abstract

Asphaltenes are one of the most problematic compounds in crude oil. They have high tendency to aggregate and deposit on the surface of pipeline and production equipment. In this work, a packed-bed of large spheres flow-loop apparatus was designed and built to investigate asphaltene deposition. For the first time, an asphaltene deposition apparatus has been proven to have good performance and high reproducibility. Experimentally, a crude oil was initially mixed with heptane to destabilize asphaltenes then the oil-heptane mixture was flown through the packed- bed column at a given superficial velocity for a certain period of time. The deposit mass was measured for different deposition time and the deposition rate can be obtained. It was observed that the asphaltene deposition rate initially increases then decreases as the superficial velocity increases. The initial increasing of deposition rate is limited by mass transfer of the asphaltene particles to surface. However, the deposition is suggested to be inhibited by shear force at high superficial velocity causing the deposition rate to decrease. This observation shows that the asphaltene deposition rate has a strong dependency on the superficial velocity of the flow. Moreover, the value of dependency of the asphaltene deposition rate on superficial velocity of the flow has been established for asphaltene deposition rate in both regimes and the mechanism of asphaltene deposition is uncovered.