Experimental study of asphaltene deposition: Focus on critical size and temperature effect

Modeling of Asphaltene Deposition Kinetics

“…It has been shown that Brownian fluctuation in the vicinity of the tube wall, regardless of the flow regime (laminar or turbulence), has a major contribution to aggregate transportation. In addition, it has been shown , that there is a critical value for the aggregate size; which beyond that, their deposition is prevented (critical size concept). Furthermore, as the deposited layer grows (thicken), the heightened shear stress begins to limit the deposition process; to the extent that after reaching the upper critical value, no deposition is allowed …”

“…The maximum energy barrier relation (eq ), proposed by Haji-Akbari et al, can capture the change in collision efficiency as a result of temperature or oil composition variation but fails to capture the change as a result of the aggregates size or fractal dimension variation. Furthermore, critical size argues that there is a critical value for the aggregate size; which beyond, the deposition could not occur. , Therefore, implementing the term in deposition kernel is a correction that considers both of these observations.…”

“…In reality, it is expected that due to continuous oil supply and processes of precipitation, aggregation, breakage, and possible deposition, in each location of the pipeline, aggregates of submicron sizes were to be present. Recent studies have revealed , that these submicron aggregates have a major contribution to the deposition process. In more recent work, Hashmi et al by employing the same methodology as Jamialahmadi et al developed a semimodel to capture asphaltene deposition in the regime where the shear effect is ignorable.…”

“…Their structure consists of a precipitation term that predicts the precipitation rate of primary aggregates by employing the PC-SAFT module, advection and diffusion terms that take into account axial transport rates of primary aggregates, an aggregation term that predicts the rate of primary aggregates’ disappearance as they go through aggregation, and the deposition term. The major assumption in their work is that primary aggregates or aggregates of a specific size (i.e., micron size) are allowed to deposit, which is inconsistent with the critical size concept. , Furthermore, although they acknowledge the non-uniformity of the axial-deposited layer profile, the impact of fluid shear on deposition was completely ignored. Hence, it could not predict deposition behavior as the flow rate changes.…”

Molecular Modeling of Nanostructured Additives to Asphaltic Materials

“…In recent years, many studies employing molecular simulation on the study of asphaltene aggregates have been carried out [38,39,40,41,42,43,44,45]. There is a consensus that the asphaltene aggregates have around 6 nm, and are built of at most 10 molecules [38,39,40,41,42,46,47]. Murgich et al [39] have investigated the aggregation of resins and a highly aromatic asphaltene model (24 aromatic rings) using molecular mechanics.…”