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BISCHKE, R. E. and D. J. TEARPOCK*, Subsurface Consultants and Associates, LLC, Lafayette, LA

Abstract: A New Technique for Projecting Large Growth Faults to Depth Using Imaged Hangingwall Structure

Often geoscientists are required to work on the edge of, or below, coherent seismic data. Large listric normal faults may be present in the poor data zone. If a proposed well crosses a large growth fault, then an unexpected stratigraphic section is encountered. The result is often disappointment, followed by confusion regarding the encountered geology.

On the Gulf of Mexico shelf, rollover structures form downthrown to listric growth faults. These rollover folds form as the hanging wall geometry conforms to the shape of the fault and the shape of the fold. This relationship between fault shape and rollover shape allows industry to predict fault shape from rollover shape.

Often rollover structures are well-imaged at shallow depths, but the image may deteriorate at greater depths. We present a graphical technique for projecting large growth faults to depth using well-imaged portions of rollover structures. The technique, which is based on inclined shear collapse, is subject to measurement errors. Therefore, only two or three bends in a listric fault can be projected into poor data zones. In order to compare the theory to observation we present constrained examples of projected fault surfaces using well-imaged portions of Gulf of Mexico rollovers. 

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana