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The AAPG/Datapages Combined Publications Database

CSPG Bulletin

Abstract


Alberta Society of Petroleum Geologists News Bulletin
Vol. 1 (1953), No. 9. (September), Pages 6-6

Abstract: Seismic Techniques in the Alberta Foothills

L. H. Reed

Seismic programs in the Alberta foothills area differ from those of a normal plains project in that structural features of a complex tectonic nature are the prime objective. The obstacles are twofold in nature: technical and operational. One of the most serious technical problems in some foothills areas is the difficulty experienced in acquiring usable Previous HitreflectionNext Hit records, due to: disturbed conditions at Previous HitreflectionNext Hit horizons depths, rough surface topography, and steeply dipping surface beds. Another serious problem is the influence of rapid lateral variations in vertical velocity caused by excessive thickness of a high or low velocity bed due to repetition by faulting. Wherever the velocity abnormality occurs in the section, all horizons below it will have the Previous HitreflectionNext Hit time and apparent depth affected. From an operational view, continuous Previous HitreflectionNext Hit shooting is restricted by limited accessibility can be minimized by the use of the Previous HitrefractionNext Hit type of shooting. This method requires an essentially straight line which need be accessible at points 1 to 1-1/4 miles apart. The velocity of the Paleozoic limestones are markedly higher than the Mesozoic shales and sands. Therefore, a high speed marker bed exists, overlain by lower speed material. This situation is essential to successful Previous HitrefractionNext Hit shooting. It is usually impossible to map a bed below the first high speed Paleozoic marker capable of transmitting Previous HitrefractionNext Hit energy. The Previous HitrefractionNext Hit method is usually used as a reconnaisance tool with detail being established by Previous HitreflectionTop shooting.

Abstract by R. R. Williams, P & N G Conservation Board.

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