苏丹M盆地原油地球化学特征与母质的沉积环境探讨

通过对苏丹M盆地萨加隆起带的原油地球化学特征分析 ,探讨了生成原油的烃源岩的母质的沉积环境。该带原油主要有两种类型 ,一种是正常原油 ,另一种是生物降解油。原油的地球化学特征表明 :正常原油具有较高的饱和烃含量 ,生物降解原油饱和烃含量低 ,非烃含量高 ;碳同位素表明为典型的湖相Ⅰ Ⅱ有机质生成的原油 ;原油饱和烃具有较低的异戊二稀烃 ,Pr/Ph一般在 1.5左右 ,表现为弱的姥鲛烷优势 ,具有较完整的重排甾烷和新藿烷系列 ,γ蜡烷含量较低 ;重排甾烷含量高 ,C2 7、C2 8、C2 9甾烷呈“V”字型分布 ,具有较丰富的4 甲基甾烷。原油地球化学指标显示主要的烃源岩为弱氧化—弱还原、淡水—微咸水的沉积环境 ,有机质为水生生物和细菌改造的陆源有机质的混合输入 ,为一种以生油为主生气较少的母质类型。

GEOCHEMICAL CHARACTERISTICS OF CRUDE OIL AND SEDIMENTARY ENVIRONMENT OF ROCKS IN SAJIA RISE OF M BASIN, SUDAN

The M Basin is a very typical continental depositional basin, where hydrocarbon source rocks are represented by the Abu Gabra Formation of Cretaceous and oil layers are mainly distributed in the upper Abu Gabra, Bentiu and Darfur. There are two types of crude oil, one is normal crude oil and the other is biological degradation crude oil in the Sajia Rise. Geochemical characteristics of the crude oil showed that there are very complete 18α(H)21β(H)-neohopanes and 17α(H)-diahopanes lower gammacerane , C 27,C 28,C 29 sterane distributed in "V" shape and plentiful 4-methysterane. The depositional environment of main hydrocarbon source rocks was a weak reducibility-reducibility, limnic depositional environment and organic matter was supplied mainly by aquatic organisms, and terrigenous organic matter is lower.