Due to inefficiency of steam injection caused by technical, economic, and operational reasons, solvent methods have received special attention in heavy oil and bitumen recovery recently. A solvent can be injected in the form of vapor extraction process at reservoir temperature. Hot solvent injection can be applied to improve the recovery rate at lower temperatures than steam injection. These solvent driven recovery processes are quite complex on account of their "asphaltene destabilization" that takes place due to changes in temperature, pressure, and solvent dissolved in oil. As a result of this destabilization, the asphaltene precipitates, flocculates, and eventually plugs the pores in the reservoir. In this research, the de-asphalting of a heavy oil sample was evaluated in a PVT cell with optical visualization. The experiments were undertaken at different temperature ranges (50°C to 80°C) and pressure (30psig to 500psig), which is the suggested range for hot solvent injection. Three light hydrocarbons (propane, n-hexane, and n-decane) were used as solvents. Applying standard SARA analysis (ASTM D2007 and ASTM D2549), the characteristics of the asphaltene precipitated at the bottom of the PVT cell, were determined quantitatively. Moreover, a methodology for "asphaltene precipitation concentration analysis" was developed in order to determine the effect the temperature, pressure, and solvent type had on asphaltene destabilization. This quantitative analysis was complemented through visual observations of asphaltene characteristics on the PVT cell as well as using optical microscopy. In addition, the refractive index measurements at the onset of precipitation were used to evaluate the changes in the oil after interacting with the solvent at different temperatures and pressures. Finally, a comparative analysis of the esults was provided. Based on the quantitative and qualitative observations, the characteristics of asphaltene were classified in terms of their shape, size, and amount for different oil/solvent types, pressure, and temperature. This study will eventually lead to the identification of the effects of asphaltene characteristics on pore plugging during heavy-oil/bitumen recovery by gravity drainage from oilsands.

During solvent‐based heavy‐oil and bitumen recovery processes, viscosity reduction occurs through dilution of oil by mixing process. However, asphaltene precipitation may take place, eventually resulting in organic deposition (maltenes and asphaltenes) in the reservoir causing a reduction in permeability through pore plugging and unfavourable wettability reversal. In this paper, two identical porous media (unconsolidated glass bead packs) with significant contrast in wettability were used to investigate these phenomena. The oil‐wet and water‐wet glass bead models were exposed to constant rate solvent injection (propane, n‐hexane, n‐decane, and distillate hydrocarbon). The thickness of the multilayer organic deposition was determined using focused ion beam (FIB/SEM) and scanning electron microscope (SEM). Three points from the models were analyzed to determine the level of asphaltene deposition and oil trapping (maltenes) on the surface of the glass beads and pore spaces. The results showed that the asphaltene migrated through the glass bead pack model. As a consequence, asphaltene deposition was observed at the middle and bottom points of the vertically situated glass bead packs with an injection point at the top, in addition to accumulated oil trapping at the production (bottom) end. Moreover, elemental mapping from the organic deposition visualization was conducted using the energy dispersive X‐ray (EDX) analysis. Heteroatom elements were found in the sample along with carbon and iron elements.