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In recent years, the Flory-Huggins-Zuo Equation of State (FHZ EoS) has been utilized to treat asphaltene gradient data in many oilfield reservoirs. The FHZ EoS employs asphaltene species from the Yen-Mullins model consisting of molecules, nanoaggregates and clusters of nanoaggregates; the specific species used depends primarily on the concentration of asphaltenes but also on the asphaltene stability...
Hydrocarbon reservoir fluids often undergo dynamic processes such as multiple hydrocarbon charges and biodegradation over geological time. These processes change the spatial distribution of hydrocarbon components in reservoirs and include diffusion, advection and phase change over geologic time. To better understand reservoir fluid geodynamics (RFG), a set of generalized diffusion-advection equations...
Optimization of production depends heavily on crude oil composition and its variation within and across multiple reservoirs. In particular, asphaltene content has enormous impact on crude oil viscosity and the economic value of reservoir fluids. Thus, it is important to understand the primary controls on crude oil composition and asphaltene distributions in reservoirs. This paper examines a complex...
Asphaltene expulsion appears to be an important mechanism in the formation of a heavy oil layer and/or a tar mat at the base of an oil column during gas charges. To better understand this dynamic process, a multicomponent diffusion model has been developed to simulate the diffusion during gas charge processes in oil reservoirs. In this model, a complex moving boundary diffusion problem has been converted...
Electron beam technology, as a promising energy-efficient process, is used as a new treatment for ultra-heavy asphaltic petroleum fluids. Over the past few decades, heavy oil resources have been recognized to be among the most abundant sources of energy. However, extraction, transportation, and processing problems of these fluids still remain to be a challenge in the petroleum industry. The contribution...
Downhole fluid analysis data from several deepwater oil wells in the Gulf of Mexico are examined. The primary question addressed is whether there is lateral fluid-flow connectivity of the “A” Sand that spans two wells. The predominant fluid gradient observed in the A Sand is the variable dissolved asphaltene content. To perform thermodynamic modeling of the asphaltene gradients, the Flory–Huggins–Zuo...
The hierarchical nanocolloidal structure of asphaltenes in solvent and even in crude oil has recently been delineated by a variety of techniques. It is highly desirable to compare results for the same samples from various techniques dependent on different physics. Here, the critical nanoaggregate concentration (CNAC) of specific asphaltenes is determined using both DC-conductivity and centrifugation;...
Using fluorescence correlation spectroscopy (FCS) we measure the translational diffusion coefficient of Iino coal asphaltenes and UG8 petroleum asphaltenes dispersed in toluene at extremely low concentrations (0.03–3.0mg/L). Using a simple scaling argument we compare them with several molecules of known size and molecular weight. We find that Iino coal asphaltene molecules – which have a comparatively...
The molecular weight of asphaltenes has been a controversy for several decades. In recent years, several techniques have converged on the size of the fused ring system; indicating that chromophores in virgin crude oil asphaltenes typically have 4–10 fused rings. Consequently, the molecular weight debate is equivalent to determining whether asphaltenes are monomeric (one fused-ring system per molecule)...
Previously, fluorescence depolarization techniques (FD) have been shown to measure asphaltene molecular size, thereby establishing the substantial difference between asphaltenes derived from crude oil vs from coal. Here, FD is used to track the changes of the asphaltenes from a petroleum atmospheric resid feedstock that has been subjected to increasing thermal severity of catalytic hydrothermal cracking...
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