Preliminary evaluation of chemical indicators for the analysis of production losses from tar sand recovery

This report presents the results of a preliminary investigation to evaluate changes in the chemical composition of thermally altered tar sand bitumen. The objective of the study was to determine if changes in the chemical composition of the tar sand bitumen can be correlated to chemically related production losses or thermal history of the bitumen. Tar sand samples from the Tar Sand Triangle deposit in southeastern Utah were thermally altered under autogenous conditions at temperatures of 380/sup 0/C, 400/sup 0/C, and 420/sup 0/C for time periods ranging from 1 to 24 hours. The thermally altered tar sands was serially extracted with normal heptane, toluene, and pyridine. The normal heptane extracts from each thermal alteration experiment were analyzed by combined gas chromatography/mass spectrometery (GC/MS) to determine the presence of several classes of compounds. The heptane fractions from the thermally altered tar sand represent a complex mixture that can not be evaluated using conventional combined GC/MS techniques. For this reason, the presence of the different classes of compounds was determined by profiling ions selected to represent each class of targeted compounds. The classes of compounds targeted for this analysis included normal alkanes, tricyclic diterpanes, pantacyclic triterpanes, and aromatic species having general empiricalmore » formulas ranging from C/sub n/H/sub 2n-6/ through C/sub n/H/sub 2n-40/. The results of this investigation indicate that the pentacyclic triterpanes are the only class of compounds that follow a trend with the thermal alteration conditions. The relative intensity of the pentacyclic triterpanes decreases with increasing exposure time for each temperature investigated. This class of compounds may be useful for tracing the thermal history of tar sand bitumen in a process. 12 refs., 2 figs., 17 tabs.« less