全球奥陶系碳酸盐岩油气藏综述

奥陶系碳酸盐岩油气田主要分布于北美、北欧、中国和澳大利亚。在北美,油气藏主要分布于下奥陶统El-lenburger组选择性白云岩化和经喀斯特改造的碳酸盐岩层系中;上奥陶统的Trenton-Black River灰岩,特别是Trenton灰岩段的构造破碎和白云岩化作用是影响油气成藏的主控因素;Red River组油藏则受控于构造圈闭。北欧哥特兰岛Klasen灰岩储集空间则以灰泥丘原生孔隙和断裂、缝合线为主。中国奥陶系油气藏分布于鄂尔多斯盆地和塔里木盆地,成藏条件相对复杂:在鄂尔多斯盆地,主要与膏云岩经大气淡水淋滤作用形成的风化壳密切相关,也有白云岩、生物礁等多种储集体;而塔里木盆地塔中地区储集体集中于礁滩相,还包括台地灰岩和台缘浅滩白云岩等其他相带,沉积间断面上的古喀斯特作用是成藏的主控因素。澳大利亚的坎宁盆地是较新的勘探区,其油气聚集方式与北美Ellenburger组相似。

A REVIEW OF THE ORDOVICIAN CARBONATE RESERVOIRS IN THE WORLD

Ordovician carbonate-type reservoirs are mainly distributed in North America,North Europe,China and Australia.In North America,the key reservoirs occur in the Lower Ordovician Ellenburger Formation,Upper Ordovician Trenton-Black River limestone and Red River Formation.The Ellenburger Formation is mainly affected by selective dolomitization and karstification,and the Trenton-Black River limestone by tectogenetic break and dolomitization,while the reservoirs respond to structural trap in the Red River Formation.The reservoirs in Gotland of northern Europe occur in mud mounds,which correspond to primary porosity and stylolites.In China,the situation is more complex,and Ordovician reservoirs include weathering crusts of gyp-dolomitite,dolomitite,reef reservoirs in Ordos Basin,and reef-bank facies,platform limestone,shallow bank dolomitite in platform margin of the Central Tarim Basin.The Canning Basin in Australia is a new exploration area,whose reservoir type is similar to the Ellenburger Formation.