Exploring for Stratigraphically Trapped Gas in Deep-Water Channel Deposits of the Austrian Molasse Basin

Gas is produced from deep-water sandstone and conglomerate of the Puchkirchen and basal Hall Formations (Oligocene-Lower Miocene) in the Molasse foreland basin of Upper Austria. The basin is mature, with >2000 wells drilled to date, and an extensive seismic reflection dataset that covers much of the paleo-basin foredeep has recently been acquired in the study area. Seismic stratigraphic analysis has revealed that deep-water sedimentation in the basin was dominated by a channel belt up to 5 km wide that transported sediment derived from the Central and Eastern Alps eastward along the basin axis (Linzer, 2001; de Ruig, 2003; de Ruig and Hubbard, 2006). New exploration models for stratigraphic traps associated with the recently developed channel model are necessary for future success in the basin. Channel abandonment and migration were important processes that resulted in a stratigraphic configuration consisting of coarse-grained sandstone and conglomerate overlain by channel and overbank mudstone. This represents an ideal reservoir architecture, including porous reservoir facies sealed by impermeable deposits, and may be an important play concept for future exploration in Upper Austria.