Capturing Structural Uncertainty in Fault Seal Analysis – A Multi-throw Scenario Approach

Abstract

Summary An intrinsic challenge of fault seal analyses is the large uncertainties that have to be considered. Parameters used in fault seal analyses - sedimentary architecture, Vshale distribution and fault geometry – all have large uncertainties. Commonly, uncertainty in sedimentary architecture and Vshale distribution are addressed by building multiple 3D property models ( Freeman et al., 2010 ). Uncertainty in fault geometry, however, is often not treated adequately since only one 3D structural framework model or one fault interpretation is mostly being utilised. In this study, a grid modification tool is used to capture structural uncertainty to assess likely throw scenarios and their impact on fault weak points. This multi-throw scenario analysis was performed on a fault bounded prospect in the Gulf of Suez, Egypt. Seismic imaging in this area is poor and the structural uncertainty of the seismic interpretation is therefore high. Juxtaposition analysis with the original seismic interpretation showed a good lateral seal, whereas a major fault weak point was detected at 70% and 60% throw scenarios. In consequence, the structural uncertainty was found to be too high and the prospect was discarded. This study therefore shows how valuable testing of structural uncertainty is to make better choices in prospect assessment.