Determining the Onset of Asphaltene Flocculation in Solvent-Diluted Bitumen Systems
Abstract
The past several decades have seen conventional oil resources reaching plateau which triggered a shift in oil exploration towards heavier crudes such as heavy oil and bitumen. Light hydrocarbons, mainly consisting of light paraffins, are widely used as diluents in the production and upgrading of heavy crudes. The addition of a diluent to heavy oil or bitumen alters the chemical forces within the mixture initiating the aggregation of asphaltene particles. Temperature and pressure may also vary during reservoir depletion operations. A crucial and challenging side effect of such thermodynamic changes is solid deposition, which can significantly diminish production, damage the reservoir, or even necessitate early reservoir abandonment. Solid deposition in reservoirs, production wells, and top-side facilities is mainly composed of asphaltenic materials, sand, clay, and corroded metals. Asphaltene is the deposition material of interest in this study.
In order to avoid asphaltene precipitation or develop a remedial action plan for the associated problems, it is essential to understand the fundamental variables driving asphaltene precipitation in oil. The first step is to determine the conditions under which asphaltene dispersed in crude oil flocculates out to form an asphaltene-rich solid phase.
The current study was designed to locate the onset of asphaltene flocculation with respect to changes in the thermodynamic conditions. Extensive experimental work and mathematical modelling were conducted to predict the incompatibility region of solvent-diluted bitumens. The precipitants in this study, n-pentane, n-hexane, and n-heptane, were chosen from the most common hydrocarbon cuts used in solvent-assisted heavy oil recovery methods in Alberta. Two Alberta bitumens were considered in this study.
The effects of temperature, pressure, and composition on the onset of flocculation were investigated for various systems of solvent-diluted bitumens. Experimental values for the viscosity and density of the n-alkane-bitumen mixtures produced a pattern from which the onset of asphaltene flocculation could be accurately determined. In the modelling section, a CPA-EOS model was successfully tuned to predict asphaltene precipitation from solvent-diluted bitumens.
Description
Keywords
Engineering--Petroleum
Citation
SATTARI, MARYAM. (2016). Determining the Onset of Asphaltene Flocculation in Solvent-Diluted Bitumen Systems (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25611