Inorganic components, though not the basic components of oil and gas, are very intimately connected with the formation and migration of oil-gas hydrocarbon. Hence the analysis and study of associated elements in the oil and gas field make up an effective geochemical method in search for oil and gas. Studies show that the effective trace element indices in oil and gas evaluation are mainly Hg, V/Ni, V/Fe and subordinately N/Org.C, Pb and U. Trace element anomalies for oil and gas geochemical exploration are in the ring form, with the low value area over the oil and gas accumulation and the high value anomalous area on the edge of the oil and gas accumulation.