Open File Report 1993-25

Open File Report 1993-25

OFR 1993-25

Geochemical Studies - 4 Physical and Chemical Properties of Sediments and Bitumen from Some Alberta Oil Sands Deposits.

Author(s) Hitchon, B. Date 1993-01-01

A suite of 33 oil sand samples was obtained from five oil sand deposits (Athabasca, Cold Lake, Loon River, Peace River, Wabasca). The samples came from 14 wells and sampling was designed to evaluate possible significant differences in the areal and vertical compositions of the oil sands. All samples were classed as ''good oil sand'' on initial visual inspection. The bitumen was removed by Soxhlet extraction, and separated into major hydrocarbon fractions (saturates, aromatics, resins, asphaltenes) in which the elemental (CHONS) composition was determined. Specific gravity, viscosity (at three temperatures) and an elemental (CHONS) analysis were carried out on the clean bitumen, with 25 trace elements determined on 14 samples. The bitumen-free sands were analyzed for: major oxides; sand, silt and clay fractions; clay mineral composition; and composition (Cr. Fe, Mn, rid Zr) of the heavy mineral fraction from the clay sized (<2µ) and heavy fraction (p>2.95), respectively. Microfossils were identified in shales associated with some of the oil sand samples.

A Q-mode statistical factor analysis of the chemical, textural and heavy mineral data for the bitumen-free sand showed that although there are clearly differences among the samples, they appear sufficiently homogeneous that an R-mode analysis of the data was justified. The R-mode varimax solution of five factors (Eigenvalues >0.5) showed that the chemical data should be factored separately from the textural and heavy mineral data. Chemical factors indicate three separate influences on the chemical composition of the sands: (1) quartz opposed by non-quartz minerals (feldspars and ferro-magnesian minerals) representing more than one-third of the variance among the variables; (2) an independent carbonate mineral factor; and (3) an independent TiO2 mineral factor.

With respect to the composition of the bitumen and bitumen fractions, two main features were identified. First, the Loon River and Peace River bitumens are richer in S (mean 6.16%) and have higher mean contents of resins (46.0%) and asphaltenes (19.6%) and lower mean contents of saturates (15.2%) than bitumen from the other deposits. Cold Lake bitumen has the lowest mean S content (4.25%), highest mean saturates (23.7%), and lowest mean resins (38.8%). Bitumen from the other deposits occupies intermediate positions. Athabasca bitumen has the highest mean content of aromatics. with respect to vertical variations in composition, there is some evidence that the content of asphaltenes increases with depth, as sometimes does the content of total resins; there is a corresponding decrease in the content of saturates. The most important observation on the trace element content of the bitumens is the 5.74 ppm of Hg in the single sample from the Peace River oil sand deposit, a value which suggests contamination and which requires confirmation.

Hitchon, B. (1993): Geochemical studies - 4: Physical and chemical properties of sediments and bitumen from some Alberta oil sands deposits.; Alberta Research Council, ARC/AGS Open File Report 1993-25, 108 p.