Asphaltene precipitation, flocculation and deposition during solvent injection at elevated temperatures for heavy oil recovery

Asphaltene destabilization during solvent-based heavy oil and bitumen recovery applications is a common problem due to continuous changes of temperature, pressure, and oil composition. The effects of these characteristics on the recovery performance should be investigated for a wide range of solvent and oil types. In this paper, two heavy oil samples from fields in Alberta, Canada were destabilized using three different types of paraffin: propane, n-hexane, and n-decane. The solvent-based process was conducted at different reservoir conditions with alterations made to the temperature, pressure, and oil composition to determine the effect on asphaltene flocculation in the produced fluid and its deposition on the rock surface. Initially, experiments were carried out using a pressure, volume, and temperature (PVT) cell at different reservoir pressures and under different temperature conditions. Next, a Focused Ion Beam (FIB) and Scanning Electron Microscope (SEM) were used to characterize the morphology of the organic deposition on the glass beads surface through core flooding experiments. The results obtained through these two sets of experiments showed that temperature, pressure and oil compositions have a critical influence on asphaltene solubility. The PVT cell experiments and organic deposition surface roughness calculations were fundamentally important to explain the plugging formation in the reservoir under different operational conditions and with different oil types.