KNOX, PAUL R., ERIC R. VON LUNEN, and ROBERT J. FINLEY
Bureau of Economic Geology, The University of Texas at Austin, Austin, TX

Abstract: Shelf-to-Basin Transition: Architecture of Miocene FallingStage Deltaic to Basinal Reservoirs, Matzen Field, Vienna Basin, Austria

The correlation of deltaic depositional systems across the shelf and into the basin is potentially equivocal in the subsurface. Detailed characterization of a Middle Miocene reservoir in Matzen field, Vienna Basin, Austria, supported by OMV AG, provides insights into the shelfto-basin transition in a fluvial-dominated deltaic system through a depositional cycle. Data from more than 1,000 wells, including limited core material, combined with high-quality 3-D seismic coverage, were used to establish the architecture and stacking pattern of sandstones throughout a ~70 km² area that contains platform, slope, and basinal settings. High-frequency flooding surfaces subdivide the 9th Tortonian reservoir (30 to 200m thick) into eight progradational and vertically stacked units (2-35 m thick). Sandstone facies in an initial highstand unit, restricted to the platform, include distribuitary channel and mouth bar (each 3-5 m thick) and bayfill splay (13m thick), with delta lobes varying from 0.25 to 1 km². Four subsequent units are arranged in offlapping to downstepping geometries and contain successively thinner deltaic systems that build to the shelf edge and feed sand across the slope and into the basin. Initial relief from platform to basin is approximately 150 m. Upward-coarsening shelf-margin deltaic deposits up to 15 m in thickness are juxtaposed with upward-fining shelf incision fill deposits reaching 20 m in thickness. Blocky to upward-fining basinal sandstones range from 2 to 20 m thick, typically 10 m or less. Geometries of the uppermost three high-frequency units are progradational to vertically stacked, with outer platform accommodation likely created by compaction of the underlying slope shales. Significant slope and basin deposition occur from early falling stage through late transgressive phase in this reservoir.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas