Features of Fluid Inclusion and Their Implications for Hydrocarbon and Carbon Dioxide Charging Periods in the Eighth Member of the Shihezi Formation, Tianhuan Area, Ordos Basin

Ordos basin is an important petroliferous basin with abundant reservoirs in China. Regarding the reservoir of Upper Paleozoic Section 8 of Shihezi of Tianhuan area as the study object, the facieology, homogenization temperature and compositions of the fluid inclusion were studied, with the analytic and testing data from core observation. Combined with the history of basin geothermal evolution and burial, the forming time of petroleum reservoir and reservoir formation period as well as the coupling relationship between diagenetic evolution and hydrocarbon accumulation were studied and illustrated.

The experimental data showed that the homogenization temperature of fluid inclusions of the study area was 70 160°C，with the peak at 110 140°C. CH₄ and CO₂ were measured. After two-time fluid inclusions capture events in Tianhuan area，the fluid inclusions were restored in two types of minerals,such as the micro fractures of cutting through the quartz grains and the micro fractures of the quartz enlarged edge. Synthetically considering the burial history and the homogenization temperature of the fluid inclusion, it is indicated that the Tianhuan area had one phase gas filling, i.e. the Middle Jurassic - Early Cretaceous.