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Pr and Ph are preferentially oxidized compared to n C 17 and n C 18 , leading to decrease in Pr/ n C 17 and Ph/ n C 18 ratios with thiaadamantanes concentrations, a measure of the extent of TSR in Tazhong oils and condensates. • TSR does not preferentially deplete triterpanes and α,β hopanes over Ts. • Pr and Ph are preferentially oxidized over n C 17 and n C 18. • i C 4 was preferentially depleted over n C 4 only during earlier TSR stage. • Relative oxidization sequence during TSR overlaps significantly. Tazhong and four other well-known TSR-altered petroleum reservoirs from around the world were analyzed for their molecular and carbon isotopic compositions of saturated hydrocarbons, thiaadamantanes concentrations or H 2 S contents to determine the relative stability of saturated hydrocarbons during thermochemical sulfate reduction (TSR). We find that TSR does not preferentially deplete tricyclic terpanes and 17α, 21β hopanes with the "exposed" tertiary carbon atoms compared to 18α (H)-22, 29, 30-trisnorhopane (Ts) and C 29 Ts that have no tertiary carbon atoms, as proposed by Xia and Gong [35]. However, pristane (Pr) and phytane (Ph) seem to have been preferentially oxidized over normal C 17 and C 18 alkanes, respectively, resulting in decreasing Pr/ n C 17 and Ph/ n C 18 ratios with increasing extent of TSR for the Tazhong and Nisku oils and condensates. i C 4 appears to be preferentially depleted relative to n C 4 during early TSR stage. At later TSR stage both n C 3 and n C 4 are oxidized more readily than i C 4 in the Mobile Bay Norphlet Formation condensates. Thus, we tentatively propose that relative oxidization order during TSR may start with long chain iso -alkanes followed by n -alkanes, then cycloalkanes, C 2 -C 4 alkanes and finally methane; however, it seems that oxidization of these compounds overlaps significantly. [ABSTRACT FROM AUTHOR]