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Sub-Seismic Lithofacies Prediction in the Puchkirchen Formation, Upper Austria: Calibrating Fine-Scale Statistics with Seismic Attributes to Interpret the Sedimentology of a Mass-Transport Dominated Deep-Water Depositional System

Stright, Lisa 1; Bernhardt, Anne 2
1 Graduate Program in Earth, Energy and Environmental Sciences, Stanford University, Stanford, CA.
2 Geological and Environmental Sciences, Stanford University, Stanford, CA.

Lithofacies prediction from seismic-reflection profiles in deep-water depositional systems is inherently challenging due to scale differences between data and the heterogeneous nature of deep-water sedimentary deposits. When sedimentary packages are below seismic resolution, seismic-reflection profiles are difficult to interpret due to limited impedance contrasts between successive fine-scale layers. Nonetheless, sub-seismic scale prediction is critical, particularly in cases where exploration targets are subtle, such as sub-seismic stratigraphic traps, or when sub-seismic heterogeneities impact reservoir performance and must be included in flow simulation predictions.

This paper presents a novel approach to predict fine-scale reservoir and non-reservoir lithofacies proportions and average bed thicknesses in the Puchkirchen gas reservoir within the Molasse Basin of Upper Austria. A multi-scale, multi-attribute calibration is used to propagate these fine-scale statistics throughout the seismic volume, using multiple seismic attributes from elastic inversion. The resulting volume of fine-scale statistics is then used to infer sub-seismic scale reservoir and non-reservoir architecture.

Although reservoir sandstone of the Puchkirchen reservoir is poorly resolved in the seismic-reflection profile, sand deposition was largely influenced by the distribution of underlying mass transport deposits. Fortunately, these mass transport deposits, composed of conglomerate and shale lithofacies, can be reliably predicted directly from seismic attributes due to larger average bed thicknesses and stronger acoustic contrasts. Using fine-scale statistics from the calibration, reservoir sandstone quality is delineated based the probability of encountering high proportions of gas-saturated sandstone.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009