地层学杂志

近年来的研究和生产实践表明,扬子区的上奥陶统五峰组和志留系龙马溪组是我国页岩气勘探的主要目标层位,精确划分对比这套黑色页岩并揭示其地理分布特点,对页岩气有利层位的选定和有利区块的圈定具有重要意义。根据扬子区五峰组和龙马溪组露头剖面和井下岩芯的笔石生物地层最新研究成果,提出五峰组的WF2(Dicellograptus complexus笔石带)-WF3(Paraorthograptus pacificus笔石带)和龙马溪组的LM2-3(Akidograptus ascensus笔石带-Parakidograptus acuminatus笔石带)到LM6(Demirastrites triangulatus笔石带)下部是页岩气勘探的有利层位。同时,根据这套黑色页岩的地理展布特点,对扬子覆盖区内五峰组和龙马溪组黑色页岩划分出6个页岩气有利区块:重庆—川滇区块,马边—西昌区块,大巴山南缘,秭归盆地和远安盆地,江汉盆地和下扬子区块。

Recent investigation of unconventional shale gas in South China indicates that black shales of the Wufeng Formation(uppermost Ordovician)and the Lungmachi Formation(Llandovery,Silurian)are among the major targets for shale gas exploration.Therefore,a fine subdivision and reliable correlation of these black shales is critical to the selection of favorable targets for shale gas exploration.Based on our latest study of graptolite biostratigraphy of outcrops and drill cores,we propose that the following two intervals are favorable targets for shale gas exploration,namely the Dicellograptus complexus Biozone to the Paraorthograptus pacificus Biozone(late Katian age,Upper Orodvician)and the Akidograptus ascensus Biozone-Parakidograptus acuminatus Biozone to the Demirastrites triangulatus Biozone(Rhuddanian to early Aeronian age,Llandovery,Silurian).The temporal and spatial extension of these intervals is discussed.Based on their stratigraphic and lithological characteristics,six favorable areas for shale gas in the Yangtze Region are recognized,including 1)Chongqing and the border area of Sichuan and Yunnan provinces,2)Mabian-Xichang area(southwestern Sichuan Province),3)Southern margin of the Dabashan Mountains,4)Zigui Basin and Yuan'an Basin(Hubei Province),5)Jianghan Basin,and 6)Lower Yangtze region.