Rapid Heterogeneous Asphaltene Precipitation with Dispersed Solids

Abstract

Inorganic solids are often present in real heavy oil systems, but are typically absent in asphaltene laboratory studies. For the first time, we investigate the influence of inorganic solids on the kinetic precipitation of asphaltenes. In contrast to potentially slow kinetics in homogeneous liquid petroleum mixtures, rapid kinetic precipitation of asphaltenes was observed when inorganic solids were present in the system. A combined homogeneous aggregation and diffusion-limited heterogeneous nucleation model was developed to quantify the rate of asphaltene precipitation under the explored experimental conditions. The rate of heterogeneous nucleation was generally observed to be faster than the rate of homogeneous aggregation; however, this trend was reversed as the solvent strength decreased and greater quantities of asphaltenes precipitated. The inorganic solids were characterized, and kaolinite clay was observed in the studied samples. This investigation leads to a clearer understanding of the complex asphaltene aggregation process that occurs in real and heterogeneous systems. The competing pathways of asphaltene precipitation provide novel insight into asphaltene precipitation and deposition, in addition to new experimental strategies to measure asphaltene solubility.

Structure of Asphaltenes during Precipitation Investigated by Ultra-Small-Angle X-ray Scattering

“…This finding also suggests that the presence of insoluble asphaltenes in a system causes asphaltenes to precipitate at a higher rate. This observation may be related to a recently reported heterogeneous precipitation mechanism where asphaltenes stick to interfaces to phase separate from solution . The surface formed by insoluble asphaltenes may increase the overall rate of precipitation.…”

“…This observation may be related to a recently reported heterogeneous precipitation mechanism where asphaltenes stick to interfaces to phase separate from solution. 32 The surface formed by insoluble asphaltenes may increase the overall rate of precipitation.…”

“…7,20,22,23 Numerous mechanisms have been applied to model asphaltene precipitation and phase behavior: liquid−solid or liquid−liquid phase transition, 10,24−27 colloidal aggregation, 9,28−31 and heterogeneous nucleation. 32 However, the microscopic mechanism of asphaltene destabilization is still poorly understood, 3,15 and the lack of direct observation on how asphaltenes arrange in solvents limits the validation of modeling approaches. Numerous methods have been applied to study asphaltene structural changes during destabilization.…”

“…Slow kinetics of precipitation for asphaltenes were uncovered by Maqbool et al and other researchers and demonstrate that the time required for transition from the nanoscale to the macroscale can vary between seconds to months based on the solution conditions. , After adding a precipitant to an asphaltene system, the mass of precipitated asphaltenes increases as a function of mixing time until the equilibrium quantity is obtained. ,,, Numerous mechanisms have been applied to model asphaltene precipitation and phase behavior: liquid–solid or liquid–liquid phase transition, ,− colloidal aggregation, ,− and heterogeneous nucleation . However, the microscopic mechanism of asphaltene destabilization is still poorly understood, , and the lack of direct observation on how asphaltenes arrange in solvents limits the validation of modeling approaches.…”

Modeling of Asphaltene Deposition Kinetics

“…Asphaltene precipitation and deposition with a thermodynamic change of the system condition has been the subject of rigorous debate in literature for almost a century . Asphaltenes, still resorting to solubility class definition, are known as a fraction of crude oil that on the contrary to other parts, i.e., saturates, aromatics, and resins, are not soluble in n -alkane solvents and only remain soluble in aromatic solvents. , The high research interest associated with asphaltene can be attributed to their precipitation and afterward deposition inside the porous reservoir medium and more commonly in transportation pipelines, which eventually leads to flow passage restriction or, in severe cases, passage blockage. , The production loss and asphaltene treatment expenses hugely impact the production revenue. − Numerous research studies that have been performed on asphaltenes can be categorized into three classes: asphaltene chemistry, asphaltene thermodynamics, and asphaltene kinetics. Asphaltene chemistry attempts to determine the asphaltene molecular structure and molecular weight.…”