鄂西渝东地区震旦系灯影组古岩溶作用特征

摘要

鄂西渝东地区中寒武统蒸发岩类盖层之下的震旦系灯影组海相岩溶地层是我国南方的重要勘探目的层。基于野外地质调查、系统薄片观察以及地球化学资料，认为这一地区存在桐湾运动两个幕次的隆升过程以及相关的古岩溶作用。在灯影组上部和中部分别形成了1个和2个洞缝带，其充填作用规律性强，以化学沉淀充填为主。上部洞缝带依次被泥晶白云石、微晶白云石以及粉晶至粗晶白云石三期充填，而中部的两个洞缝带依次被泥晶白云石、微晶白云石、纤状白云石以及粒状白云石四期充填。初步认为这些充填物发育与否主要受下渗的饱和碳酸盐流体的流动路径、流速等因素控制，残存孔隙是现今储集层的主要储集空间。灯影组古岩溶型储层应是今后这一地区油气勘探中需要关注的重点之一。%The thick Sinian Dengying marine dolostone karst reservoir overlaid by Middle Cambrian evaporate rock is the important target of exploration in the western Hubei-eastern Chongqing area. Two episodes of tectonic uplifting and karstification related with Tongwan movement occurred in this area, which brought in one and two fracture-cave zones respectively in the upper and middle parts of Dengying Formation. These fracture-cave zones are dominantly filled with regular chemical precipitation, including the fillings of micritic dolomite, dolomicrite, fine-coarse crystalline dolomite in the upper part and the fillings of micritic dolomite, dolomicrite, nematodolomite and granular dolomite in the middle part. It is indicated that the development of fillings is influenced by flowing paths and rates of the leakin g saturated carbonate fluid, and the residual secondary pores provide space for the present reservoirs.