Abstract: The summary on the anomalous morphological types of upper geochemical exploration for typical oil and gas accumulation in North Tarim, Ordos, Songliao and other regions shows that the basic type of the upper anomaly of oil and gas accumulation is a ring. Generally, the range of ring-like anomaly corresponds to oil and gas regions, and the ring-like belt of high value indicates an oil-water boundary.It is shown by ressearch that fabric anomaly is prior to index content anomaly in the corresponding relationship to a given region and the continuity and natural curved morphology of ring-like anomaly. The ring-like anomaly may reflect the strongest hydrocarbon leakage in the margin of oil and gas fields. The fact that the hydrocarbon concentration and migratory gradient of marginal wells are notably high to those of oil and gas wells and peripheral wells also shows that there are high hydrocarbon-leaching regions related to the development of microfissure system and the mobility and high-dissolved hydrocarbons of edge water in oil-water boun dary.