东濮凹陷白庙构造油气源与成藏史

HYDROCARBON ORIGIN AND RESERVOIRING HISTORY OF BAIMIAO FIELD IN DONGPU DEPRESSION

白庙构造是东濮凹陷南部地区的一个含油环、凝析油的富气构造。生物标志物研究表明该构造不同部位的原油来源于不同的烃源岩。构造低部位 (底部和翼部 )的原油来源于沙河街组三段 2亚段。这类原油奥利烷、γ -蜡烷、C3 0 重排藿烷和C2 9Ts等生物标志物含量相对较高 ,Ts/Tm比值和重排甾烷 /规则甾烷比值高 ,以及甾烷C2 9ββ/ (αα +ββ)和 2 0S/ (R +S)指标高。构造高部位的原油则来源于沙河街组三段 3,4亚段甚至沙河街组四段 ,生物标志物组成特征与低部位的原油正好相反 ,具有早期生烃的特征 ,甾烷异构化指标C2 9ββ/ (αα +ββ)和2 0S/ (R +S)比值低。

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 (Es 2 3),and that in the higher part of the structure top has been originated from the Es 3 3 , Es 4 3 and even Es 4 source rocks.The former, in comparison to the latter, is characterized by relatively abundant oleanane,gammacerane,C 30diahopane and C 29Ts,high values of Ts/Tm and diasterane/regular steranes ratios, and high C 29ββ/(αα+ββ)and 20S/(R+S) indexes of C 29 steranes . The low values of C 29ββ/(αα+ββ)and 20S/(R+S)of C 29 steranes indicate the source rocks of Es 3 3 and Es 4 3 submembers might generate hydrocarbons at early maturation stage.