SequenceLithofacies Paleogeographic Study on Huanglong Formation in Eastern Chongqing Western Hubei Area

Key words: 
• the eastern Chongqing western Hubei area

Abstract: Due to intensive tectonic uplift and denudation affection in early Hercynian, the majority of the study area only keeps unsound Huanglong Formation of Upper Carboniferous in Eastern ChongqingWestern Hubei area. The Huanglong Formation is one of the most important natural gas reservoirs in the eastern Sichuan area and one of the most favourite horizons for exploring new gas sources. Based on core description, measured crosssection and thin section analysis, and combined with sedimentary marks of lithology, palaeontology, logging analysis, and so on., the Huanglong Formation is divided into four main sedimentary facies: sabkha, beachbarrier coast, gulf shelf and open shelf. During the field investigation, passageway of sea water connecting the gulf of the eastern Sichuannorthern Chongqing with open sea of the western Hubei has been found, which has important meaning to furthur understand the regional sedimentary facies. On the basis of sequece stratigraphy, and used the three system tracts: LST, TST and EHST as the maping units, three paleogeographic maps have been mapped and lithofacies paleographic characteristics of each system tract has been described. Combined with the reservoir characteristics of all sorts of sedimentary facies, the barrier grain beach and offshore grain beach are thought to be the most favourite reservoir facies.