Few case studies have demonstrated the importance of small-scale fault zone complexities on across fault fluid flow and little progress has been made in modeling and implementing them in reservoir simulation models. In this study, we use a high quality 4D seismic dataset from offshore West Africa to investigate the relationship between small-scale fault zone complexities and fluid migration. A 4D seismic signal occurs across a relay zone of a normal fault where throws are the lowest (less than 10m) while reservoir thickness varies between 10 and 20m. The shape of the 4D seismic signal shows that aquifer water crosses low-displacement tips of overlapping fault segments. At several other faults (with higher displacements) at the southern rim of the field 4D seismic signals are bound by the faults and clear evidence for across fault water migration cannot be observed. Hence, the 4D seismic signal at fault F1 shows that northward water migration across the fault occurs only where throws are smaller than ca 10m.The investigated fault is then modeled using non-pillar based methods which permit geometrically accurate fault representation in a reservoir grid. Flow simulations are performed to reproduce fluid migration as observed by 4D seismic signals.


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