Determining the gas accumulation period using fluid inclusion observations: Xiang Zhong Basin, China

Abstract There are a large number of natural gas shows in the Upper Paleozoic central Hunan Basin. However, hydrocarbon accumulation process was complicated due to strong tectonic reformation this area. A study period is significance for determining models. In research, fluid inclusion samples were tested, occurrence characteristics, uniform temperature data, and reservoir evolution analyzed, four diagenetic periods three identified. (i) For syntaxial stage, filling dark nonluminous, captured by overgrowing cement around particles mainly seawater; (ii) (Early) Mesogenetic burial calcite grows or micritic matrix, brine; (iii) (Late) two sets decomposed fissures developed massive colloids with non-luminous gas-rich inclusions within crystals; (iv) Telogenetic weakly fluorescent pure gaseous luminescent veins. The result indicates that organic Lower Carboniferous Basin dominated nonfluorescent rich gas-phase inclusions, stages filling. By integrating average homogenization temperatures on curves, charging orders correspond 260–250 Ma during Late Permian, 249–245 Early Triassic, 208–170 Triassic. Dense characteristics reveal deep basin basin.