Abstract: Oil sand in quartz sandstone of the Lower Devonian Pingyipu Formation has been found for the first time in the Tianjingshan structure in the Northwest of Sichuan through detailed surveying and evaluating of oil sand resource in the Sichuan Basin. The authors have analyzed the ore-forming conditions for this mineral occurrence according to oil geology and metallogenic theory. The hydrocarbon source rock of oil sand is likely to be the Early Cambrian and Early Silurian black shales. During the Indosinian orogeny, liquid hydrocarbons were migrated through reverse faults of the Indosinian orogeny and were concentrated in the traps of the Lower Devonian Pingyipu Formation to form oil enriched reservoirs. The reservoirs were uplifted to be exposed and be denuded and were changed into the present oil sands finally during the Himalayan movement. It is calculated that the oil sand resource below 500 meters of the surface in the Tianjingshan structure, based on the calculating method proposed by the new nationwide evaluation program of oil and gas resource, are about 5 356.4×10⁴ t.

Key words: Sichuan Basin, Tianjingshan structure, Devonian stratum, oil sand resource evaluation, oil sand-forming conditions