Abstract: Longterm crude oil exploitation has led to soil deterioration in Shengli Oilfield.Knowledge about accumulation and speciation of heavy metals in oilpolluted soil is the key to clear understanding of soil quality issue at this region.We analyze the speciation and content of 4 heavy metals (Zn, Pb, Cd and Ni) through modified BCR and DTPA extraction methods, taking the soil of Gudao oil region as an example.Results reveal that Zn and Cd have higher activity and bioavailability in the soil, so potential pollution risk exists.On the other hand, we discover that the source and speciation of Cd and Ni are probably affected by oil pollution in the soil by analysis of available form of heavy metals in well soil of different exploitation ages.

Key words: oil field, heavy metals, soil, speciation analysis, available form