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GUILLIER, BERTRAND, Institue Francais des Etudes Andines, Santa Cruz, Bolivia; PATRICE BABY, Institut Francais de Recherche Scientifique pour le DEveloppement en CoopEration; JAIME OLLER and EDGAR MENDEZ, Yacimientos Petroliferos Fiscales Bolivianos; JEAN-CLAUDE LECONTE, JEAN LETOUZEY, and MARTIN SPECHT, Institute Francais du PEtrole; and JEAN-PIERRE GRATIER, Universite Joseph Fourier

ABSTRACT: Restoration of Geological Surface -- UNFOLD Method -- A Validation of Complex Structural Mapping Interpretation in the Andean Thrust Belt

One of the most important problems in petroleum structural geology is to be sure of the interpretation of structural maps obtained by seismic and sub-surface data. Lot of methods can be used to validate geometry of geological structures like balancing cross-section, this technique allows to check the geometry of cross-section by return to its initial horizontal state, but can not be used in case of 3D halokinesis, shale tectonics, structures formed by polyphased noncoaxial tectonic events, strike slip and wrench faulting. An alternative approach is to test the restoration of folded and faulted surfaces to verify 3D structures by balancing geological surfaces represented by structural map. This method tests the geometry of studied horizon and faults, and is based on the fact that actua folded/faulted structures were initially continuous at their deposition time. The balancing surface program UNFOLD restores the actual geological surface to its initial state. Misfitting along faults implied bad drawing of structural maps -or strong internal deformation- of the geological level-. So by trial and error method, we return to initial data to modify interpretation. This method have been applied to 2D and 3D seismic structural interpretation in different structural styles environment -rift and salt basins, wrench faulting, thrust belt, etc. Some applications to oil field structures in the Andean Thrust Belt has been done to check and validate the complex structural mapping interpretation.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.