摘要
The upper Yangtze platform of South China is rich in marine oil and gas.As located in different tectonic zones,its adjacent areas have distinct deformation styles,which leads to various cap rock and preservation conditions of marine hydrocarbon.Based on revealing the Meso-Cenozoic tectonic deformation characteristics of Sanjiang region in upper Yangtze block,and combined with the evolution of lithofacies and hydrocarbon accumulation factors,this paper discusses on the process that post-tectonic events controls on the distribution of marine hydrocarbon and formation of low mature oil & gas in plateau.It is suggested that early marine source-reservior-cap assemblages were destructed in Indo-China movement which resulted in growth of new reservoir forming assemblages in foreland subsidence as well.During the time of Yansinan movement,the basin rifting led to marine-flooding lacustrine mudstone deposition,not only acting as excellent source rocks,but also as regional cap rocks.From Cretaceous to Paleogene,the reservoir rocks of Jingxing Formation(K1j)and plaster rock grew in the process of basin atrophy.The critical cover of plaster rock is very important to marine over mature cracked gas.After Neogene,the strong strike-slip activity and plateau uplift has been unfavorable to the later preservation of the marine oil and gas,controlling the formation of a series of small mountain intermittent depression basin which are rich in land-based sources and aquatic organic matter,and the source rock are subjected to microbial degradation,generated immature-low mature oil and gas in low thermo evolution stage.This type of oil and gas resources is limited,but it provides a reference for the low evolution oil and gas exploration of the Tibetan Plateau.