中非地区B盆地下白垩统烃源岩地球化学特征

中非地区B盆地下白垩统泥岩是该盆地目前唯一证实的烃源岩。对该套烃源岩的地球化学研究表明,盆地烃源岩有机质丰度高,为好烃源岩,有机质类型主要为Ⅱ₁型;由于构造反转、剥蚀和高地温梯度,现今生烃门限深度普遍偏浅;平面上,由北西西向南东东方向生烃门限深度变深;有效烃源岩为下白垩统阿普第阶下部和巴列姆阶;盆地北部斜坡带浅层油气存在生物降解作用,与其深层油藏存在明显亲缘关系;推测盆地存在多个生烃灶。

Geochemical Characteristics of Source Rock of Lower Cretaceous in B Basin, Central Africa Region

The shale of Lower Cretaceous is uniquely verified to be source rock in B basin of Central Africa region. The geochemistry study indicates that the source rock in B basin is characterized by high organic matter abundance with II1 type of organic matter, being a good hydrocarbon source rock. Influenced by the tectonic inversion, erosion and high geothermal gradient, the present depths of hydrocarbon generation threshold are usually shallower than the normal. From NWW to SEE, the depth of threshold becomes deeper. The shale of lower Aptian stage and Barremian stage of Lower Cretaceous is the effective source rock. The oil and gas in shallow zone of slope belt in northern B basin undergo biodegradation, and have obvious relativeness with oils in deeper zone by analyzing their biological markers. It is predicted that there exist several oil kitchens in B basin.