Multilayer organic deposition on the rock surface with different wettabilities during solvent injection for heavy‐oil recovery

Abstract

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.

Surface Morphology: Theoretical Model and Correlation with Experimental Results

“…The solid surfaces, unlike the mobile interfaces present in the liquid -liquid, and liquid -gas systems, are characterized by presenting a constant surface area [1], which exhibits a rough character whose manifestation depends on the size of the observed system [2]. This roughness, which is related to the fact that the height of the solid interface changes randomly with the observed area, is the result of two fundamental factors: one is associated with the possibility of action of external forces that cause deposition or detachment of particles [3,4], which in turn influences the value of the specific surface area and the other that relates to the processes of solid formation that take place on the microscopic scale. The roughness causes that the real surface area of the solid cannot be determined by Euclidean geometry [5,6], and the use of experimental methods is necessary for its determination.…”