Characteristics and geologic implication of fluid inclusions of Carboniferous Huanglong Formation in well Paishen 1, Jianghan Plain

The Jianghan Plain is one of the under-explored regions in southern China.Fracture (vug) fillings and aplite dolomites in cores of Huanglong Formation in well Paishen 1 of the study area were analyzed systematically using polarizing microscope,fluorescence microscope and cooling-and-heating bench.Abundant brine water inclusions and hydrocarbon-bearing brine water inclusions were found in the samples.Studies of the formation periods of single sample indicated that,dolomites,calcite veins and aplite dolomites all contained multiphase inclusions,mainly generated from multiphase filling or the mineral remains of early inclusions.Based on homogenization temperature distribution and the mineral types of host as well as the time of various veins (vugs),the inclusions were divided into 5 phases corresponding to homogenization temperature intervals 74.7-86.4,94.6-106.5,111.1-131.8,141.3-152.9 and 158-162.6 ℃,respectively.Combined with the studies of burial and thermal histories,it was concluded that inclusions were formed from the late Triassic to Cretaceous,and were influenced by stages of tectonic movement.From the late Indosinian Movement to the early Yanshanian Movement,gaseous hydrocarbon charged; however,the charging rates were smaller than the dispersing rates,and accumulations failed to form.