--> --> ABSTRACT: Structural Style and Evolution of a Half Graben Bounding Normal Fault Array, Oseberg Fault Block, North Viking Graben, Norwegian North Sea, by de Boer, Jord P.; Gawthorpe, Robert L.; Jackson, Christopher A.; Sharp, Ian; Whipp, Paul; #90142 (2012)
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Structural Style and Evolution of a Half Graben Bounding Normal Previous HitFaultNext Hit Array, Oseberg Previous HitFaultNext Hit Block, North Viking Graben, Norwegian North Sea

de Boer, Jord P.*1; Gawthorpe, Robert L.1; Jackson, Christopher A.2; Sharp, Ian 3; Whipp, Paul 3
(1) Earth Science, University of Bergen, Bergen, Norway.
(2) Earth Science & Engineering, Imperial College, London, United Kingdom.
(3) Statoil, Bergen, Norway.

This study integrates 3D seismic and well data to gain insights into the geometry and evolution of a half-graben bounding normal Previous HitfaultNext Hit system geometry and related Previous HitfaultNext Hit propagation folding. Integrating structure and stratigraphic analysis allows us to reconstruct the growth, interaction and linkage of normal Previous HitfaultNext Hit segments and their associated Previous HitfaultNext Hit perpendicular and parallel hangingwall folds during the formation of a crustal-scale tilted Previous HitfaultNext Hit block. We focus on the 140 km long Brage - Oseberg Ost - Veslefrikk Previous HitfaultNext Hit system, using a 7500 km2, merged 3D seismic survey and multiple wells. This normal Previous HitfaultNext Hit system forms the eastern boundary of the Oseberg Previous HitFaultNext Hit-Block, on the eastern flank of the North Viking Graben, North Sea. The normal Previous HitfaultNext Hit system has a dominantly N-S strike, with prominent NNE- and NNW-trending Previous HitfaultNext Hit jogs. Overall, displacement decreases away from the centre of the Previous HitfaultNext Hit system and local displacement anomalies (lows) occur associated with the Previous HitfaultNext Hit jogs.

Analysis of sequential isopachs, stratal geometries and well data show that individual (Previous HitfaultNext Hit parallel) depocentres formed during the early rift initiation stages (Bathonian; c. 168 Ma) and that these merge to form a laterally extensive depocentre in the immediate hangingwall of the Previous HitfaultNext Hit system during later rift climax (Callovian -Kimmeridgian; c. 162 - 152 Ma). The early formed depocentres were associated with Previous HitfaultNext Hit parallel folds above blind normal faults and their length was related to the length of the blind Previous HitfaultNext Hit segments. In contrast Previous HitfaultNext Hit-perpendicular hangingwall anticlines separated the initial synclinal depocentres along strike and are located adjacent to the short Previous HitfaultNext Hit jogs and displacement lows. This evolving structural template allows inferences to be made on the timing and origin of sediment sources and main sediment transport system(s).

Major rift shoulder and local footwall uplift and erosion during rifting accompanied deposition of more than 5 km of Upper Jurassic syn-rift sediments on the western side of the normal Previous HitfaultNext Hit system. Resulting from the evolving structural template, the orientations and interactions of normal faults and folds defined the location of the hangingwall depocentres, the Previous HitfaultTop scarp related sediment input and the associated relay ramps defined the local pathways for the coarse grained clastic sediments that have been delivered into adjacent basins and readjusted the regional rift shoulder drainages.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California