T. M. Egebjerg, P. Viegas, E. Vagnes, F. Van-Dunem, and K. Owe Hager

Sonangol P&P, Block 34 Asset Team, Luanda, Angola

ABSTRACT: Relationship Between Salt Tectonics, Channel Trajectories and (Paleo) Bathymetry in Block 34, Offshore Angola

3D reflection seismic data in Block 34, offshore Angola have revealed channel systems in the Oligocene and Miocene as well as present day channels. Major salt structures are aligned in various directions and our study tries to investigate the relationship between the evolution of salt structures and the trajectories of the channel systems.

Two main salt structure/wall orientations have been identified, a NW-SE and a NE-SW trend. The NW-SE trend is more or less perpendicular to the sediment influx from the Congo Fan that is extending into the northern-middle part of Block 34. The NW-SE salt structures steepens up or are having overhang towards the SW indicating sediment ”push” from the NE. The increased input of sediments towards the North in Block 34 due to the Congo Fan, seems to subdue the surface expression of the salt structures in the northern part, in contrary to the southern salt structures that have large seabottom expression.

Isochore maps that depicts the depocenter – salt structure evolution have been generated within the 3D area as well as in the remaining part of Block 34. In the Late Cretaceous and Paleocene the salt structures evolved primarily into pillow type structures with symmetrical depocenter configurations between them. In the Post Paleocene the depocenters became much more asymmetrical indicating salt structure growth into diapirs.

Present day channels in Block 34 of both erosive and non-erosive nature, are comparable to the identified Oligocene and Miocene channels in both size and nature. One present erosive channel, cuts across major seabottom topography generated by salt structures and does not seems to follow any recent depocenter axes.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado