Abstract: Tiaohu sag and Malang sag are primary source depressions in Santanghu basin. They are depressions with above medium abundance in petroleum resources. This study showed that a little too high appeared for their estimated value of resources for reasons of insufficient understanding of source- rock-richness in them; the cap rock and carrier rock in the basin are not large in size, so it is not favorable to long-distance hydrocarbon migration. Also, study of the organic matter inclusion enclave showed that hydrodynamic conditions for petroleum migration are relatively poor, dominated by short-distance vertical migration, and only reservoirs with both source and seal are formed. The computed value showed that the source potential index in Santanghu basin is lower, possibly providing medium- and small-sized reserves. Therefore, the target zone should be explored dominantly in Upper Permian Lucaogou formation, and paying attention to its piedmont and foothill overthrust belts for exploration. At present, to understand the piedmont geologic structures is very difficult because the seismic data are insufficient and there exist some problems in interpretations.

Key words: Santanghu basin, sag, organic matter, inclusion enclave, resource extent