Abstract: Numerous faults were developed on the crest of anticline E in deep water of Niger Delta.They were observed to dip mostly in the same direction and arrange in a domino style.Uncertainties remain in such domains as what their me-chanism is,how many stages they had experienced,and what role they played in dividing oil from water.Based on structural analysis,we studed the axial plane migration of E anticline through structural balanced sections and back-stripping of pa-leotectonic maps.Guided by the theory of fracture nucleation,we identified the active stages and mechanisms of the faults and then categorized the faulting systems to further perform assessment of sealing capacity of the faults.Gravitational sli-ding was identified as the evolution mechanism of the normal faults at the crest of the anticline.A correspondence of multiple stages between the domino-style normal faults and the anticline axial plane migration was also established.We proposed that the E structure had experienced four evolution stages and developed 7 types of faulting systems,among which,3 were gravitational sliding step-faults -quite unique in the area-and were controlled and deformed by gravity against a paleo-anticline setting.Thrust faults and faults with multi-stage movement are the best sealing faults,gravitational sliding step-faults have sealing potential,and later extensional faults have no sealing capacity.About 16 faults were selected as potential sealing faults.The results show a critical SGR value of 8% for weak sealing,and 20% for fully sealing.There were 8 fully-sealed faults that could form different oil/water units in its hanging and foot walls,respectively.There were 4 weakly-sealed faults that could not separate oil from water but only influence responses to water flooding.The study can be used to guide drilling and injection-production planning of oil fields in the area.

Key words: fault evolution, fault sealing capacity, oil and water distribution, deep water anticline, Niger Delta