Abstract: The geochemical research of soil hydrocarbon geochemical test profile in Ejina Qi region shows that the geochemical indices of acid hydrocarbon display higher hydrocarbon background value and stronger hydrocarbon anomaly, being characterized by heavier methane carbon isotope and bigger drying coefficient. The Carboniferous-Permian distribution and structures control the abundance changes of hydrocarbon indices on the profile. The background values of methane and heavy hydrocarbon are higher in the deep buried area of Carboniferous-Permian, and also the higher anomaly section corresponds well to the local structural highs of Carboniferous-Permian. It shows that the anomaly of soil acid hydrocarbon reflects the information of oil and gas accumulation related to Palaeozoic hydrocarbon source rocks.

Key words: Ejina Qi, hydrocarbon geochemical exploration, hydrocarbon anomaly, Palaeozoic, hydrocarbon source rock