苏浙皖地区二叠系硅质来源及其与油气关系的探讨

ON THE ORIGINS OF THE PERMIAN SILICEOUS ROCKS IN JIANGSU-ZHEJIANG - ANHUI PROVINCES AND THEIR RELATION WITH THE GENERATION OF OIL AND GAS

研究区的二叠系硅质岩类,主要由大量硅质生物遗骸溶解成溶胶状态的SiO_2并保存在沉积物中,在成岩—后生阶段早期发生交代作用而形成。硅质交代作用填充孔隙,堵塞通道,降低岩石的原生孔隙和渗透性,不利于石油的初次运移和有机质进一步向烃类转化。然而,硅质岩质脆易裂,对于裂隙性原生油藏的形成是有利的。

In the study areas,the Permian siliceous rocks consisting mainly of large amount of siliceous organic remains which dissolved into colloidal solution of SiO2 and preserved in the sediments were formed by the replacement during the early stage of diagenesis - epigenesis. During the siliceous replacement, the original pores and path ways were filled up by replaced siliceo-us matters, the primary porosity and permeability of the rocks thus reduced. Therefore, it is unfavourable for the conversion of organisms into hydrocarbons and the subsequent migration. Nevertheless, the easily fractured siliceous rocks being frail, are favoured to forming fissured-type primary oil pools.