Interpreting unconformities in seismic records and outcrop
conference paper
Understanding the nature and formation of unconformities allows for better interpretations of the sediment architecture within a basin and, hence, a more accurate play and reservoir evaluation. Sequence stratigraphy assumes that 1) relative sea-level controls the generation of sequences and unconformities to the exclusion of all other mechanisms, and 2) all unconformities on seismic profiles are unconformities in the rock record. Studies of the geometry of carbonate and siliciclastic shelves from seismic profiles showed that unconformities can form as the result of changes in the geometry of sediment dispersal systems and may be independent sea-level. In addition, unconformities on seismic records may represent rapid transitions when studied in outcrop. Seismic modelling of carbonate platforms showed that, when using typical industrial frequencies, there are apparent truncations of the margin and significant basinward shifts in the point of onlap. The low resolution of the seismic tool also results in apparent pinchouts and pseudo-unconformities. Unconformities on seismic profiles need not correspond to unconformities in the lithological record. The seismic modelling of outcrops ultimately provides a means for evaluating the accuracy of unconformity interpretations based solely on seismic response. New constraints in the interpretation of unconformity geometry will lead not only to more accurate play evaluations but possibly also to revision of the `Vail' sea-level curve which is based largely on the interpretation of unconformity geometries from industrial seismic profiles.
Topics
TNO Identifier
280625
ISSN
01603663
Publisher
Offshore Technology Conference
Source title
Proceedings of the 25th Annual Offshore Technology Conference. Part 1 (of 4), 3 May 1993 through 6 May 1993, Houston, TX, USA
Place of publication
Dallas, TX, United States
Pages
257-263
Files
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