Sedimentary facies and seismic responses in the Upper Jurassic Suining Formation,Luodai Gas Field

The Suining Formation gas pools as newly-explored gas pools in Luodai have an explored reserve of more than 10¹⁰ m³ of natural gas. The sedimentary environments are dominated by ephemeral shallow lakes, where the prograded delta front subfacies deposits are developed. The favourable sedimentary microfacies consist of the delta front subaqueous distributary channel, channel-mouth bar and sheet sands. The clastics are predominantly derived from the Longmen Mountains west of the western Sichuan depression. The Xindu-Luodai zone on the eastern slope of the depression is occupied by the delta facies with the intercalations of sandstone and mudstone, in which a number of Suining Formation lithologic traps are developed. Several sets of reservoir-seal associations near the underlying source rocks facilitate the accumulation and preservation of natural gas. The integration of synthetic well logs and Jason inversion shows that the seismic responses of the Suining Formation gas-bearing sandstones are manifested by the model of " strong wave trough, moderate-strong wave crest and low wave impedance". The discovery of these large-sized lithologic gas pools opened up a vast range of prospects for the shallow gas exploration in western Sichuan.The Suining Formation gas pools will serve as the key target of extended assessment and risk exploration of the shallow gas in the study area.