Generation, migration, and accumulation of deep natural gas in Songliao Basin

The Songliao basin, the main oil-bearing basin of China is a continental sedimentary one. Giant and middle oil fields had been discovered in the past 30 years, but only small gas fields have been discovered in shallow and middle depth. No giant or middle gas fields have been found. The exploration and research work undertaken in recent years has proved that a lot of gas fields occur in the lower and deep oil- and gas-bearing formations. The gas fields are found in two zones: a lower gas-bearing zone (Lower Cretaceous Quantou Group) and deep gas-bearing zone (Lower Cretaceous Denlouku Group and Upper Jurassic). This paper describes the geochemistry, sedimentary structure, and the various types of gas reservoirs of Lower Cretaceous and Upper Jurassic formations; analyzes the generation, migration, accumulation of natural gas; and points out that the source rock is the black mudstone and coal bed of Upper Jurassic. The gas was coal-formed gas that migrated upward along the faults and accumulated in the sandstone of Lower Cretaceous (Quantou Group and Denlouku Group). Finally, the paper points out the prospect of deep gas in Songliao basin.