In the Upper Tertiary primary gas reservoirs and Jurassic secondary gas reservoirs in Qiongxi

Pingluo-ba and Baimamiao gas fields in southern West Sichuan foreland basin

organic inclusions are mainly in gas phase and gas-fluid biphase.They are usually irregular in shape

with dominant size in the range of 3-6 μm

and are mainly distributed in the fissures of quartz grains and in the calcite veins.The homogenization temperature of the fluid inclusions in the 2nd member of Xujiahe Fm is in the range of 60-170℃

with the main peak to be 90-130℃

while that in Jurassic is in the range of 70-130℃

with the main peak to be 80-100℃.Based on the results of homogenization temperature and in combination with the analysis of evolutional history of Triassic source rocks

it is believed that the charging of gas in reservoirs in the 2nd member of Xujiahe Fm is earlier than that in Jurassic gas reservoirs.The gas reservoirs in the 2nd member of Xujiahe Fm has experienced a complete hydrocarbon charging process from small amount of charging in late Indosinian

to large amount of charging in Yanshanian and to adjustment and minor charging in Himalayan

of which Yanshanian(Jurassic-Cretaceous)is the major charging period.The Jurassic gas reservoirs are secondary gas accumulations

with Himalayan as the main charging period.Based on reconstruction of palaeo-fluid potentials of inclusions formed in different geologic periods

it is believed that the fluid potentials of gas reservoirs in the 2nd member of Xujiahe Fm in southern West Sichuan foreland basin are in random distribution.Gas migration is dominated by vertical migration between source rocks and reservoir rocks with unevident lateral migration.