Oil samples from the seventh member of the Yanchang Formation in Longdong area of Ordos Basin were found to be mature-highly mature crudes of a same family that were generated by mixed lower algae and higher plants under a weak oxidation-reduction and fresh-brackish water setting and were extensive in plane distribution.Most previous studies were focused on the vertical migration and accumulation of the crude

and the horizontal migration and charging of the oil was largely neglected.Based on the thermostability analyses of rearranged hopane (diahopane)/hopane (C

30

*

/C

30

H) ratios

we studied the possibility of using C

30

*

/C

30

H ratio to trace crude migration and charging and came with supportive results.The ratios of mature-highly mature crude were observed to be a biomarker not only for thermal maturity but also for crude migration and charging

as it shows a positive correlation with two other parameters:MDR and exposure/shielding alkyl dibenzothiophenes.By applying the ratio to trace the crude charging direction in the seventh member of the Formation

we found that the crude was migrating and charging continuously southwest-and northeast-ward in the modes of wavefront to Huachi area.The result verified the idea of using the ratio as an effective parameter for tracing oil charging pathways.