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Bashir Koledoye1, Atilla Aydin2
(1) Chevron Nigeria Limited, Lagos, Nigeria
(2) Shale Smear Project, Stanford University, Stanford, CA

Abstract: A New, Process-based Methodology for Shale Smear Analyses in the Niger Delta

3D seismic and well log data from the producing Okan field in the Niger Delta and a working conceptual model derived from field observations and theoretical considerations were used to map the three dimensional geometry of a representative normal fault with shale smear. We interpret the seismic data as showing clear fault segmentation in the dip direction with extensional relays occupied by smeared shale units. Log data help to identify lithologic horizons throughout the field and in some cases, where the wellbores crossed the fault, to quantitatively determine the amount of smeared shale within the fault zone. Conceptual models provide means to interpret crucial details of the fault geometry and the distribution of fault rock beyond the conventional resolution of a 3D seismic data set. Combining these three approaches, we have developed a procedure to determine the fault geometry and to assess the nature of the smeared shales and their evolving configurations as a function of fault throw and the thickness of corresponding shale units. The result is a new and improved technique to visualize fault architecture and to interpret fault rock, both of which lead to constructing structurally realistic juxtaposition diagrams and physically sound fault seal analyses in reservoirs.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana