Development of New Chromatographic Approaches for Bitumen Characterization
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Abstract
A critical stage in the compositional analysis of crude oils is the group-type separation of the components into saturated hydrocarbons (saturates), aromatic hydrocarbons (aromatics), resins, and asphaltenes (SARA). Despite the continuous improvement of the current methods, they are still suffering from insufficiencies in providing fast, accurate, and repeatable results. In this study, an automated SARA High-Performance Liquid Chromatograph (SARA-HPLC) is developed and evaluated to overcome the limitations and enhance SARA analysis. The developed system is equipped with three columns packed manually with different stationary phases. The sample is separated into four fractions by selective retention through interactions with solvent mobile and column stationary phases. However, preparative columns (manually packed) do not allow adequate replication of the developed analytical method by other researchers since the packing procedures may vary. To standardize the developed SARA-HPLC and make it reproducible by other researchers, standard commercially available packed columns were implemented in this work. The original system was modified in different aspects, including the design and configuration of columns. Consistent SARA fractions results were attained, proving the applicability of the new analytical technique to a wide range of crude oil samples, such as heavy oil and bitumen. Also, the performance of the developed SARA-HPLC was compared with the conventional method, demonstrating that it is more efficient, cost-effective, and consistent. A critical step in evaluating the recovery performance of the ES-SAGD method is the accurate measurement of solvent concentration in the produced bitumen. Therefore, another focus of this study is developing a chromatography approach for solvent detection in the produced bitumen. Additionally, the presence of water in the produced streams adds more complexity. In this work, a new chromatography approach was developed by combining the gel permeation chromatography (GPC) and Gas Chromatography (GC) results to fully characterize bitumen samples. The proposed model is validated and used to characterize the bitumen and measuring solvent in the mixture of bitumen/solvent and bitumen/solvent/water mixtures. The proposed method can measure the solvent content of the produced bitumen in the absence and presence of water, eliminating the error in measurements due to solvent loss associated with dewatering procedures.