The stratigraphic framework of the Agadir-Tarfaya basin is characterized by six major mega-sequences that correspond to the major tectonic episodes that shaped the Mesozoic– Cenozoic history of the basin. These mega-sequences record the development of major phases of source, reservoir and trap development in the deep water Atlantic Margin, offshore Morocco. Multiple terrigeneous-clastic reservoir and source rock intervals in the Jurassic, Cretaceous and Paleogene sections produce stacked reservoirs and source, with numerous migration pathways and traps defined by abundant deep and shallow salt structures. Shell is operator in two deep water blocks in the basin and is preparing to spud the first wildcats early in 2004. Drilling results of earlier exploration campaigns over the last 20 or so years on the shelf— supplemented by DSDP and outcrop data—provide the control points to calibrate some 7000 km² of 3D seismic.

The overall structural style of the basin is controlled by its original rift-margin architecture, while the timing of defined salt structures broadly spans the entire Jurassic to recent depositional history of the basin (Figure 1). Development of isolated salt diapirs, including a central belt of more laterally connected salt stock canopies with local salt overhangs, characterizes the structure of the bulk of the deep-water basin. A regionally extensive salt nappe moved more than 10 km basinward over the toe-of-slope to abyssal plain setting along the distal, seaward edge of the original salt basin. The up-dip margin of the basin is characterized by a series of salt-cored inversion structures developed during convergent to transpressional movements along the steep, northwestward-facing structural edge of the basin. These later movements are associated with the Atlas orogenic episode, beginning during the Late Cretaceous and extending into the Tertiary.

Current work focuses on prospect maturation — i.e., structural mapping of salt and traps and reservoir de-risking through seismic facies and geophysical analyses. Amplitude (AVO) analysis and additional seismic attributes (e.g., seismic facies classification, spectral decomposition techniques, semblance or coherency volumes) provide useful tools for detecting and imaging the external geometries of potential reservoir bodies such as channels, as well as other depositional features such as mass-transport complexes. These analyses have revealed several reservoir-prone intervals in the Cretaceous and lower Tertiary and have enabled identification of

Figure 1. 3D visualization of a Cretaceous horizon showing the associated salt structures.

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numerous large submarine slide complexes containing abundant kilometer-scale rafted sediment blocks that some explorers had previously interpreted on 2D seismic as channelized, reservoir-prone sections. The Agadir-Tarfaya basin is a promising unexplored deep water area; the wildcats to be drilled in 2004 will be critical to test its deep water hydrocarbon potential.

Acknowledgments

The authors acknowledge the contributions of team members Ahmed Attallah, Tracy Burke, Elizabeth Harvey-Lorenzetti and Dave Robertson.

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