潜江凹陷第三系地卟啉的类型及其地球化学意义

TYPES AND GEOCHEMICAL SIGNIFICANCE OF GEOPORPHYRINS IN THE TERTIARY SYSTEM IN QIANJIANG DEPRESSION

通过 UV-VIS 和 MS 等手段的系统分析,研究了江汉盆地潜江凹陷第三系地卟啉的结构类型及其组成特征,发现在类型分布上高碳数(C_(34)—C_(37))双环脱氧叶红初卟啉(D-DPEP)具有明显优势。探讨了其 Di-DPEP 的形成机制,认为它与咸水浮游生物或绿色硫细菌有关,代表了较强的还原环境和较低的成熟度。从地卟啉和其它生物标志物的结合上对潜江凹陷部分地区的油源问题进行了初步探讨,认为潭口—代河地区广华寺组浅层油气藏具有明显的混合油源特征,可能是残存的潭口古油藏在喜山二幕之后,发生穿越剥蚀面的三次运移而形成的岩性油潴聚集体。

The structure types and composition characteristics of geoporphyrins in the tertiary sys- tem in Qianjiang depression,Jianghan basin,were investigated by systematic analyses using UV-VIS,MS and other analytical techniques.It is discovered that the extensive distribution and superiority in some cases of high-carbon-number(C_(34)-C_(37))Di-DPEPs was the obvious character of geoporphyrins in Qianjiang depression.The origin and maehanism of formation of the high-carbon-number Di-DPEPs are related to the green sulfur bacteria and/or other salt lack planktons,indicating a more reduction environment,geochemically,and a lower ma- turity.Combined with the investigations of other biomarkers,the oil and gas source of Qian- jiang depression is discussed.It is suggested that the shallow oil and gas pools in Guanghuasi formation in Tankou-Daihe area is an accumulation from a hybrid hydrocarbon source,which might be mainly accumulated by the tertiary migration of the residuum of Tankou fossil oil pools and had been strongly biodegradated.