Abstract:

Baimiao field,located in the southern part of Dongpu depression, is mainly a condensate gas field,with oil ring at the bottom.The study of biomarkers indicates that the oil in different parts of the structures might be derived from various source rocks.The crude oil in deeper positon (bottom and flank) has been originated from the 2nd submember source rock of 3rd member,Shahejie Fm (Es₃²),and that in the higher part of the structure top has been originated from the Es₃³, Es₃⁴ and even Es₄ source rocks.The former, in comparison to the latter, is characterized by relatively abundant oleanane,gammacerane,C₃₀ diahopane and C₂₉Ts,high values of Ts/Tm and diasterane/regular steranes ratios, and high C₂₉ββ/(αα+ββ)and 20S/(R+S) indexes of C₂₉ steranes. The low values of C₂₉ββ/(αα+ββ)and 20S/(R+S)of C₂₉ steranes indicate the source rocks of Es₃³ and Es₃⁴ submembers might generate hydrocarbons at early maturation stage.

Key words: Dongpu depression, oil source correlation, reservoiring history, biomarker