江南断裂带周边地区志留系层序地层特征及页岩气勘探前景

Characteristics of Silurian sequence stratigraphy around the Jiangnan fault zone and analysis of shale gas potential

运用露头层序地层原理和方法,以古生物、红层和碎屑锆石U-Pb年龄资料为基础,研究江南断裂带周边地区志留系层序地层特征、富有机质页岩的产出特征及页岩气勘探前景。结果表明:江南断裂带以北高家边组具有形成页岩气藏的优越条件,可作为页岩气勘探的有利目的层系。江南断裂带周边地区高家边组和坟头组(江南断裂以南称霞乡组、河沥溪组和康山组)仍划归于下志留统,茅山组(江南断裂以南称唐家坞组)划归于上志留统,缺失中志留统;富有机质页岩主要发育于SSQ1三级层序低水位体系域(lowstand systems tract,LST)、海侵体系域(transfressive systems tract,TST)和SSQ4三级层序凝缩段(condensation section,CS)。

Based on the principle and method of outcrop sequence stratigraphy,paleontology,red beds and detrital zircon U-Pb ages,the Silurian sequence stratigraphic characteristics,organic-rich shale occurrence and shale gas exploration prospects around the Jiangnan fault zone are studied.The study shows that the Gaojiabian Formation in the north of the Jiangnan fault zone has superior conditions for the formation of shale gas reservoirs,which can be listed as a target area for shale gas exploration.The Gaojiabian and Fentou formations around the Jiangnan fault zone,which are called Xiaxiang,Helixi and Kangshan formations in the south of the Jiangnan fault zone,should be classified into the Lower Silurian,while the Maoshan Formation(Tangjiawu Formation in the south of the Jiangnan fault zone)should be classified into the Upper Silurian,with Middle Silurian sediments missing.The organic-rich shale mainly occurs in the SSQ1 third-order sequence in the lowstand systems tract(LST)and the transfressive systems tract(TST)and the SSQ4 third-order sequence in the condensed section(CS).From the perspective of thickness and TOC value,the Gaojiabian Formation in the Lower Yangtze transitional rock combination shoudl be a favorable target layer for shale gas exploration.