Application and Evaluation of a New Type of Solvent to Reduce the Viscosity of Heavy and Extra-Heavy Oil
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Increasing global demand for oil, coupled with high depletion rates of conventional oil resources, make the exploitation and production of unconventional oil resources necessary. Heavy and extra-heavy oil have been investigated for two decades as potentially productive unconventional resources. However, the production and transportation of highly viscous heavy and extra-heavy crude oils are two of the paramount concerns in the oil industry due to logistical difficulties and cost. Viscosity is highly sensitive to asphaltene content of heavy oils and bitumen. Asphaltene, the most polar and aromatic component of heavy oil, has a high propensity for self-association. These aggregation and self-association mechanisms affect the viscosity significantly. Chemical and thermal methods are traditional techniques for viscosity improvement of heavy crude oils. The present work proposes a new type of plant-based solvent that contains functionalized molecules that are able to interact with asphaltene at the molecular level to modify viscosity. Various dosages of solvent, ranging from 5 to 20 wt%, were added to tested heavy-oil samples with high concentration of asphaltene, and viscosity measurements were conducted under a temperature range of 70 to 140⁰F and shear rates of 3 to 60 s^-1. Effects of solvent on the functional groups of asphaltene were evaluated both qualitatively and quantitatively by Fourier Transform Infrared (FTIR) analysis. Sensitivity of asphaltene aromaticity and stacking to solvent were evaluated by curve deconvolution and fitting routines of X-ray diffraction (XRD) patterns of solid asphaltenes. The proposed solvent is a plant-based, non-hazardous substitute for the conventional hazardous solvents, e.g., toluene, that provides more efficient viscosity reduction compared to its conventional alternatives by interacting with asphaltene molecules and hindering self-association and aggregation processes. Asphaltene critical concentration in the heavy oil was delayed by adding the solvent, requiring more precipitating agent to separate asphaltene from oil. Furthermore, asphaltene aromaticity was decreased by addition of solvent. Its application also increases asphaltene solubility in the oil and decreases the probability of asphaltene precipitation and deposition.
Afra, Salar (2016). Application and Evaluation of a New Type of Solvent to Reduce the Viscosity of Heavy and Extra-Heavy Oil. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /158600.