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Geochemical significance of sedimentary organic matter associated with inorganic matrix of overburden from Athabasca oil sands deposits Majid, Abdul
#30
Geochemical Significance of Sedimentary Organic Matter Associated with
Inorganic Matrix of Overburden from Athabasca Oil Sands Deposits
Abdul Majid
Institute for Environmental Chemistry, National Research Council of Canada, Ottawa, Ontario, Canada, K1A 0R9
Abstract
Investigations involving sedimentary organic matter associated with two samples of overburden from Athabasca oil sand deposits in Alberta, Canada will be reported. Organic fractions such as bitumen and strongly adsorbed organic matter insoluble in organic solvents were isolated using methodology used previously. Strongly adsorbed organic matter was demineralised using HCl-HF mineral dissolution scheme reported elsewhere. These fractions were then characterized by elemental analyses, infrared and CP/MAS 13C NMR spectroscopy. Comparisons were then made
between the data obtained from this study and the data for humic materials from oil oil sands and related feedstocks reported previously.
INTRODUCTION
Substantial amounts of solvent insoluble organic matter (SIOM) is associated with the oil sands mineral matter. Most of this SIOM is strongly associated with the fines fractions of the solids. This organic matter consist of both humic and non-humic components, each containing numerous oxygen functionalities. Previously, we have isolated and characterized SIOM from various samples of oil sands and tailings streams. Based on comparison of this SIOM with peat, coal, asphaltenes from bitumen and humic acids, it was concluded that this material was immature compared with humic acids from lignite or subbituminous coals. In the present investigation we have isolated and characterized SIOM fractions from two overburden samples from Athabasca oil sands deposits.
OBJECTIVE
The objectives of this investigation were twofold: firstly to compare the SIOM isolated from overburden material with the previously reported results for SIOM isolated from oil sands and related materials and secondly to assess the geochemical relevance of this SIOM to the organic matter associated with oil sandads.
RESULTS
Tabl1 1. H/C atomic ratios and ash content of various fractions
Fraction H/C Ratio Ash (w/w%)
SIOM from OB sample 1 1.27 8.5
SIOM from OB sample 2 1.15 11.0 SIOM from Low grade oil sands 1.14 43.0 Humic Acids from Oil Sands 1.11 4.4 Humic Acids from Overburden 0.87 7.2 Humic Acids from Coal 0.76 -Humic Acids from Soil 1.11
Table 2. Heavy Metal Concentrations
Sample ID Heavy Metal Concentrations (mg per g of organic C) V/Ni ratio
Ni V Cu Cr Fe Ti Zr
SIOM from OB sample 1 23 128 23 16 5800 5300 175 5.5
SIOM from OB sample 2 36 280 80 445 1600 20000 296 7.7
SIOM from OS sample1 318 530 794 106 370 480 3177 1.7
CONCLUSIONS
The elemental composition of the demineralised insoluble organic matter (IOM) derived from overburden was significantly different from the elemental composition of the corresponding fraction from oil sands.
The elemental composition of the IOM from overburden has resemblance with the elemental composition of asphaltenes rather than humic matter.
Humic and fulvic acid content of overburden was very low compared with oil sand samples. This suggests that organic matter associated with overburden was incorporated into the sediment through a pathway that did not involve fulvic or humic acid stage. Van Krevelen diagrams for the plots of H/C versus O/C ratios is consistent with the
above suggestion.
A comparison of the V/Ni ratio for IOM from overburden and oil sands suggests that the organic matter associated with overburden is of low maturity compared with the organic matter of oil sands.
The demineralised, humic matter free organic concentrate from overburden constituted over 70% of the total IOM of the feedstock. This suggests two possibilities; either the organic matter from overburden is relatively immature or it could be of non-humic nature such as degraded mature oil.
The NMR results are consistent with the interpretation of elemental analyses results. IR data suggests the presence of hydrogen bonded phenols, alcohols, ethers,
polysaccharides, polyaromatics with long paraffinic chains, carboxylic acids, quinines and ketones.
