Abstract:

Based on the systematic collection of outcrop and drilling data, we evaluated the sedimentary facies of the lower Yangtze and the favorable zone. According to the researches, we found that the basin facies and the continental shelf facies were the favorable facies for the development of the hydrocarbon source rocks. Thereinto, in the upper Sinian, they were distributed in Wannan and Changzhou-Shanghai; in the lower Cambrian, they were in Chuzhou, Yancheng, Shitai-Anji and Dexing-Tonglu; in the lower-middle Ordovician, they were in Wuxi-Nanshan; in the lower Silurian, they were in Wuwei-Nanjing and Ningguo-Changxing. The favorable facies of lower ancient reservoirs were the marginal facies of the platform and the shallow facies of the restricted platform. Thereinto, in the upper Sinian, they were distributed in Wuxi-Yixing-Dongzhi and Wuwei-Taizhou; in the middle and upper Cambrian, they were in Wuxi-Yixing-Dongzhi and Ningzhen-Chaoxian; in the lower Ordovician, they were in Jingxian-Wuxi and Chaohu-Taizhou. The favorable facies of the lower Paleozoic mainly included the lower Cambrian, lower Silurian basin and continental shelf facies. Two sets of conventional reservoir assemblages could form in the lower Paleozoic of the lower Yangtze. One was taking the mud rocks in Sinian-lower Cambrian as the sours rocks, the dolomite in Dengying formation of Sinian as the reservoir, and the mud rocks in Hetang formation of lower Cambrian as the source-reservoir-cap rock group of cap rocks. The other was taking the mud rocks in Hetang formation of lower Cambrian as the sours rocks, the limestone and dolomite in middle-upper Cambria-Ordovician as the reservoir, and the mud rocks in Gaojiabian formation of lower Silurian as the source-reservoir-cap rock group of cap rocks. After the comprehensive assessment, Rugao-Sheyang area and Wangjiang-Liyang area were the the favorable area for gas reservoir exploration in lower Paleozoic.

Key words: lower Yangtze, lower Paleozoic, sedimentary facies, advantageous area