南盘江盆地古油藏沥青地球化学特征及成因

南盘江地区生物礁古油藏的储层沥青主要分布在上二叠统和中上泥盆统。古油藏的储集层均为生物礁滩灰岩,沥青的主要储集空间以洞、缝为主,其次为基质孔隙和生物体腔内。南盘江古油藏沥青的成熟度很高, H／C原子比小于0．4,主要由残碳构成,这是沥青的非极性和极性抽提无抽提物的直接原因。在古油藏沥青地球化学特征研究的基础上,综合分析认为南盘江古油藏沥青主要源自泥盆系烃源岩,其次可能与下二叠统烃源岩有关。南盘江古油藏沥青与生物降解沥青和沉淀沥青质有很大的区别,其成因是油藏深埋时在高温、高压的作用下原油裂解成气后的焦沥青。

Geochemistry and Genesis of Bitumen in Paleo-oil Reservoir in the Nanpanjiang Basin,China

Reef paleo-oil reservoirs in the Nanpanjiang Basin were mainly distributed in Permian and Devonian strata. Reservoir of paleo-oil is mainly bioherm limestone. Bitumen mainly occurs in cavities and fractures, and also in matrix pores and biological coelomata. The maturity of the bitumen is very high, and the atomic ratio of hydrogen to carbon of the bitumen is less than 0. 4. So, the bitumen is mainly composed of carbon residue, which is the reason that there is no extract in the bitumen by non-polarity or polarity extracting. Based on the geochemistry of paleo-oil reservoir, it is concluded that the bitumen in paleo-oil reservoir is mainly from Devonian source rock and secondly from Permian source rock in the Nanpanjiang Basin. The bitumen of the paleo-oil reservoirs in the Nanpanjiang Basin is pyrobitumen formed of oil cracking under high temperature and pressure in depth, much different from biodegradation bitumen and asphaltene bitumen.