Abstract

Swan Hills formation (Frasnian stage) carbonate buildups of the Beaverhill Lake group are generally of low relief and considerable areal extent and are overlain by and encased within the relatively high-velocity shale of the Waterways formation, which thins but does not drape across the reefs. Consistent with this picture, prereef seismic events are not significantly pulled up beneath the reefs nor are postreef events draped across them. Indeed, the seismic images of these reefs are effectively masked by the high-amplitude reflections from the overlying top of the Beaverhill Lake group and underlying Gilwood member and cannot be distinguished from those of the basin fill. However, it is possible to identify the reefs indirectly on conventionally processed seismic sections because the image of the encompassing Beaverhill Lake/Gilwood interval varies significantly from onreef to offreef positions.One such Swan Hills formation field at Snipe Lake has an areal extent of about 90 km2 and typical reef relief of some 50 m above the platform facies. This reef is shown to be recognizable on three example seismic lines from interference phenomena that vary laterally in association with the lateral variations in thickness of the Swan Hills formation. These phenomena include an offreef peak that is one half-cycle below the Beaverhill Lake reflection trough and that dies out laterally going onreef, a tendency for the amplitude of the Gilwood event to decrease beneath the reef, and thinning of the order of 5 ms of the onreef section relative to the offreef section. Through seismic modeling, these seismic-image characteristics are seen to be predictable geophysical manifestations of the inherent geologic variations.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Devonian; Frasnian; Reef Reservoir; Seismic Signature; Canada, Alberta, Snipe Lake; Lakes; Seismic Prospecting; Seismic Waves; Seismology; Carbonate Build-up; High Amplitudes; Interference Phenomena; Lateral Variations; Seismic Lines; Seismic Model; Seismic Sections; Seismic Signatures, Reefs

Geographic Coverage

Alberta, Canada

International Standard Serial Number (ISSN)

168033

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 1989 Society of Exploration Geophysicists, All rights reserved.

Included in

Geology Commons

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