Fluid characteristics and hydrocarbon preservation conditions in marine facies strata of middle-upper Yangtze region

Based on studies of formation water chemical characteristics,H,O and S isotopes in formation water,natural gas composition,C isotope in alkane,H isotope in methane and light hydrocarbon composition in the middle-upper Yangtze region,combined with petroleum shows and productions,the research area was divided into 5 blocks according to fluid characteristics:the middle and western Sichuan Basin(Ⅰ),the northern,eastern and southern Sichuan Basin(Ⅱ),the southern Jianghan Basin(Ⅲ),the depression in the southeast of Guizhou Province(Ⅳ),as well as the west of Hunan and Hubei Pro-vinces,the middle of Guizhou Province,and the northern Jianghan Basin(Ⅴ).Preservation conditions decrease from I to V.