An Investigation of the Effect of Asphaltene Polydispersity on Asphaltene Precipitation and Deposition Tendencies

Abstract

It is well-known that asphaltenes are a polydisperse fraction present in crude oil with a broad distribution of sizes and molecular characteristics. However, in practice, asphaltenes are often treated both in the laboratory and in modeling work as a monodisperse fraction. In this work, asphaltene deposition tests with two model oils with the same total amount of asphaltenes but with different asphaltene polydispersity distributions were conducted using a high-pressure, high-temperature packed-bed deposition column. Although the asphaltenes used to prepare the two oils were extracted from the same source, a drastic difference in the amount of asphaltene deposited was observed, which is attributed to the difference in the asphaltene polydispersity between the two samples. Additionally, using UV−visible spectroscopy, it is possible to observe some similarities between the aromaticity of asphaltene subfractions obtained from different geographical locations. Modeling results provide additional insights into the impact of asphaltene polydispersity on the onset and the amount of asphaltene precipitation. The results presented in this work suggest that asphaltene polydispersity plays a major role in determining asphaltene precipitation and deposition tendencies observed in different oils.

Phase Behavior and Reversibility Mechanisms of Asphaltene Precipitation for High-Pressure High-Temperature CO2–Oil Systems

“…The following sections use the SDS to calculate the asphaltene precipitation in CO 2 –oil mixtures. The asphaltene content from ASTM-D3279 (6.10 wt %) and the SDS (10.864 wt %) has a discrepancy of 4.764 wt %, attributed to the asphaltene polydisperse nature. − Several authors present the asphaltene content between (1.7269–9.4302 wt %); (0.03–23.4 wt %); and (0.4–9.8 wt %); for different crude oils. In general, it can infer that the asphaltene content can vary from 0.03 to 23.4 wt % for light crude oils.…”

High-Field (3.4 T) Electron Paramagnetic Resonance, 1H Electron-Nuclear Double Resonance, ESEEM, HYSCORE, and Relaxation Studies of Asphaltene Solubility Fractions of Bitumen for Structural Characterization of Intrinsic Carbon-Centered Radicals

“…The toluene-to-heptane solvent transfer-free energies of steam-cracked tar and petroleum asphaltenes are consistent with the observation that more alkane-soluble subfractions will be dominated by smaller molecules [ 49 , 50 ]. The results of papers [ 10 , 51 , 52 , 53 ] suggest that asphaltene polydispersity plays a major role in determining asphaltene precipitation and deposition tendencies observed in different oils.…”

2022 Pioneers in Energy Research: Oliver Mullins

“…48 To understand asphaltene precipitation and deposition tendencies, Prof. Vargas from Rice University and collaborators from the industry obtained insights from studying the polydispersity and aromaticity of asphaltenes. 49 Saturate, aromatic, resin, and asphaltene (SARA) analyses are widely used to model asphaltene precipitation and assess crude oil stability. To address the high uncertainty problem in SARA analysis, Prof. Yarranton from the University of Calgary (Canada) proposed a new method based on the SimDist assay to improve the prediction of the saturate content in crude oils.…”

“…To address the asphaltene deposition problem, Prof. Naumov of New York University Abu Dhabi (United Arab Emirates) led co-workers in developing asphaltene inhibitors based on effectiveness evaluated using a quartz crystal microbalance with dissipation . To understand asphaltene precipitation and deposition tendencies, Prof. Vargas from Rice University and collaborators from the industry obtained insights from studying the polydispersity and aromaticity of asphaltenes . Saturate, aromatic, resin, and asphaltene (SARA) analyses are widely used to model asphaltene precipitation and assess crude oil stability.…”