The Interaction of Asphaltenes with Solvents Water and Clays During Bitumen Extraction through Solvent-Steam Injection
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AbstractCo-injection of solvents with steam increases the oil recovery factor and reduces significantly the environmental impact of steam injection processes. Nevertheless, the quality of the extracted bitumen is important to evaluate the process performance which is affected by the solvent-bitumen interaction. This interaction might lead to emulsion formation and asphaltene precipitation. These unfavorable flow assurance problems are associated with the behavior of asphaltenes in solvent-steam processes. Thus, it is important to observe the factors affecting the interfacial forces among asphaltenes-solvents-water prior to any field application. This work investigates the fundamental aspects of the solvent-bitumen interaction during solvent-steam injection processes. A Canadian bitumen was studied. The role of individual saturates, aromatics, resins, and asphaltenes (SARA) fractions of bitumen on solvent-steam process performance was examined both at liquid and vapor water conditions. The behavior of asphaltenes was investigated through systematic microscopic analyses with the absence and presence of reservoir rock. Also, the asphaltenes behavior after toluene (asphaltene soluble aromatic hydrocarbon) and n-pentane (asphaltene insoluble aliphatic hydrocarbon) addition was observed under the microscope. While toluene completely dissolves asphaltenes immediately, n-pentane leads to asphaltenes precipitation with bigger clusters. After these control experiments, the same tests were carried out with the addition of saturates and/or aromatics fractions of crude oil to the asphaltenes fraction. It showed that saturates lead to aggregation of asphaltene clusters at a higher rate than n-pentane, while aromatics dissolve the asphaltenes at a lower rate than toluene. Hence, it was found that the asphaltenes precipitating power of saturates is higher than n-pentane. However, results reveal that asphaltenes mainly interact with water and aromatics fraction of bitumen. The water-asphaltene interaction causes the emulsion formation and the aromatics-clay interaction is responsible for clay migration and higher amount of asphaltene precipitation. The results of this study help us to understand the factors acting upon displacement of bitumen during solvent-steam processes.
