Athabasca bitumen properties

Recently, studies have been made to determine the properties of Utah bitumens (I, 2). Others (3-9) have studied the properties of Athabasca bitumens. The analyses of the bitumens have generally included physical properties, elemental analyses, distillation, and infrared... 

Table I. Properties of Athabasca Bitumen and Conventional Crude Oil...

In the more localized context of the Athabasca deposit, inconsistencies arise presumably because of the lack of mobility of the bitumen at formation temperature (approximately 4°C, 39°F). For example, the proportion of bitumen in the tar sand increases with depth within the formation. Furthermore, the proportion of the nonvolatile asphaltenes or the nonvolatile asphaltic fraction (asphaltenes plus resins) in the bitumen also increases with depth within the formation that leads to reduced yields of distillate from the bitumen obtained from deeper parts of the formation. In keeping with the concept of higher proportions of asphaltic fraction (asphaltenes plus resins), variations (horizontal and vertical) in bitumen properties have been noted previously, as have variations in sulfur content, nitrogen content, and metals content. Obviously, the richer tar sand deposits occur toward the base of the formation, but the bitumen is generally of poorer quality. 

Several studies of the rheological properties of Athabasca bitumen have been reported (38, 41, 43). For all practical purposes, Athabasca bitumen can be considered to be Newtonian in character except at quite low temperatures and very low shear rates (38, 43). In an early study of bitumen viscosity, Ward and Clark (41) found that the values vary with the type (location) of the host oil sand, the method by which the bitumen was extracted for study, and with temperature. Other studies (43—46) concentrated on the influence of gas saturation and pressure. For bitumen in the... 

Conversion (upgrading) of bitumen and heavy oils to distillate products requires reduction of the MW and boiling point of the components of the feedstocks. The chemistry of this transformation to lighter products is extremely complex, partly because the petroleum feedstocks are complicated mixtures of hydrocarbons, consisting of 10 to 10 different molecules. Any structural information regarding the chemical nature of these materials would help to understand the chemistry of the process and, hence, it would be possible to improve process yields and product quality. However, because of the complexity of the mixture, the characterization of entire petroleum feedstocks and products is difficult, if not impossible. One way to simpHfy this molecular variety is to separate the feedstocks and products into different fractions (classes of components) by distillation, solubility/insolubility, and adsorption/desorption techniques. For bitumen and heavy oils, there are a number of methods that have been developed based on solubility and adsorption. The most common standard method used in the petroleum industry for separation of heavy oils into compound classes is SARA (saturates, aromatics, resins, and asphaltenes) analysis. Typical SARA analyses and properties for Athabasca and Cold Lake bitumens, achieved using a modified SARA method, are shown in Table 1. For comparison, SARA analysis of Athabasca bitumen by the standard ASTM method is also shown in this table. The discrepancy in the results between the standard and modified ASTM methods is a result of the aromatics being eluted with a... 

Schramm, L.L. Kwak, J.C.T. The rheological properties of an Athabasca bitumen and some bituminous mixtures and dispersions,/ Can. Pet Technol, 1988,27,26-35. 

The data available are generally for the Athabasca materials, although workers at the University of Utah (Salt Lake City) have carried out an intensive program to determine the processibiUty of Utah bitumen and considerable data have become available. Bulk properties of samples from several locations (Table 3) (9) show that there is a wide range of properties. Substantial differences exist between the tar sands in Canada and those in the United States a difference often cited is that the former is water-wet and the latter, oil-wet (10). 

The Relation of Surfactant Properties to the Extraction of Bitumen from Athabasca Tar Sand by a Solvent-Aqueous-Surfactant Process... 

Product properties from Athabasca tar sand bitumen feedstock ... 

Properties of Utah and Athabasca Tar Sand Bitumens, Fuel, 1979, 58(3), 183. 

A study of MW distribution for precipitated asphaltenes and the derivation of conclusions about bitumen or asphalt properties from it has severe limitations since this complex mixture exhibits a considerable overlap of GPC curves for all the fractions obtained in a conventional separation procedure. Similarly, the resins separated on clay and the eluted hydrocarbons exhibit overlap, as shown by Figures 5 and 6. Figure 5 demonstrates the GPC profiles of Athabasca asphaltenes (nC5) and resins (Attapulgus clay—total resin eluent)... 

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