FITZSIMMONS, ROY, ROBERT HOOPER, and CHRIS PARRY, Conoco Inc., Houston

Abstract: Deltaic Evolution, the Complex Interaction of Structure and Stratigraphy: Examples from the Deep-Water East Niger Delta

Recent 2 and 3-D seismic surveys have provided a high quality, regional dataset, which enabled the tectono-stratigraphic evolution of the Niger Delta to be interpreted. Within the study area, regional and counter-regional growth faults, toe-of-slope thrusts and mud-diapirism created complex stratal geometries within the syn-depositional Tertiary strata. The stratigraphy includes the shelf, slope and base-of-slope depositional successions, dominated by wave/tide deltaics, turbidite channels and basin-floor fans respectively.

The dynamic controls on active tectonism were analyzed through the study of sand-box models, which formed geometries similar to those, observed in seismic. Complex feedback loops existed between active growth-faults and thrust's (push-pull stresses), which were ultimately exploited by mobile shale movement. The syn-depositional tectonism was observed as the primary control on the creation of accommodation space.

Although this "tectonic" accommodation space controlled the gross spatial development of stratigraphic architecture, its affect was often subdued at higher frequency scales (intra-reservoir scale). At times of coarse clastic input, each intra-reservoir event responded not only to the space created by the original tectonism, but also to the change in space, which occurred through deposition of the preceding event (the "depositional" accommodation space).

Ultimately, as sediment distributed itself in response the controls above, it became a fundamental control mechanism driving the regional tectonism.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England