Stanley R. Wharton1, D. Shepherd2, T. Rampersad2, G. Weir2, J. Bhajan2, R. Ramkhalawan3
(1) BP Trinidad and Tobago, Port-of-Spain, Trinidad and Tobago
(2) BP Trinidad and Tobago, Port-of-Spain
(3) BP Trinidad and Tobago
The Columbus Basin offshore Trinidad and Tobago represents a world class depositional Basin with identified reserves of over 3 billion barrels oil and 20 TCF gas. Over 40,000 ft. of Pliocene/Pleistocene sediment was deposited in the Basin from an easterly prograding Proto-Orinoco deltaic system. Successive aggradational/progradational depositional sequences within this Basin show eustatic and tectonic controls on deltaic sedimentation. A modern analogue of the seafloor in the SE part of the Basin reveals a deltaic depositional continuum from shelf to upper slope which can probably be applied to deeper horizons.
3D seismic facies and sequence stratigraphic analysis were applied to 3D seismic data to better define depositional environments for play analysis. Gross depositional sequences were identified using toplap/downlap relationships and facies associations to define clinoforms, prograding complexes and associated upper slope deposits within the Pleistocene delta. Interpretations were corroborated with seismic facies classifications using neural network technology to define gross depositional environments. At least two major prograding complexes were identified in the shelf edge position with each displaying downcutting relationships with underlying sequences probably as a result of base level changes. Younger horizons separately display transitional elements from delta to shelf edge to upper slope setting defined by distal rotational slumps. Deeper horizons reveal an upper slope setting characterized by fairly thin channel deposits probably associated with slump deposits near the shelf edge. The application of 3D seismic facies and sequence analysis allowed for better play analysis through an understanding of the depositional processes in a prograding delta complex.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado