Petroleum Plays and Prospectivity in the Kwanza and Benguela Basins of Offshore Angola
Greenhalgh, Jennifer C.¹; Borsato, Ron¹; Mathew, Frances¹; Duncan-Jones, George¹; Pimenta, Idima²; Marques da Silva, Jandira²; Narciso da Silva, Luis³
¹Reservoir, PGS, Weybridge, United Kingdom.
²Exploration, Sonangol, Luanda, Angola.
³Exploration, Geotec, Luanda, Angola.
In 2011, PGS in association with Sonangol acquired a 12,700 km GeoStreamer® regional 2D grid to address the hydrocarbon potential of the Kwanza, Benguela and Namibe Basins.
The unexplored Pre-Salt section of the offshore basins of Angola holds tremendous potential for hydrocarbons. The Angolan basins have marked similarities with the Pre-Salt of the Brazilian margin which abutted the Angola offshore area prior to the opening of the South Atlantic. The Brazilian offshore has become a prolific hydrocarbon producer with giant discoveries. Analyses of oils from both sides of the Atlantic indicate similar source rocks, and seismic data show analogous structures.
The 2D seismic covering the Kwanza and Benguela basins has been migrated to depth. This gives us more accurate imaging of the pre-salt structures, thus improving the regional understanding of tectonic evolution, structure and geology. The better understanding enhances knowledge of Pre-Salt petroleum systems, and thus the prospectivity of the area.
The pre-salt petroleum play has been proven in the Angolan offshore. In 1992, the Falcao-1 well penetrated the pre-salt, encountering ~600 m of organic-rich shales, and encountering reservoir-quality carbonates. In 1996, the Baleia-1 well also drilled into the pre-salt and encountered a 300 foot pre-salt oil column with estimated in-place volumes exceeding 1 BBO. Understanding and exploitation of this resource had been slow to develop, though recent discoveries in Block 21 and Block 23, are indicators of the region's potential.
Discoveries in Brazil's Pre-Salt interval points the way to new exploration opportunities, and have implications in offshore basins along the opposing conjugate Angolan coast. Traps were formed during rift phases and include horsts and tilted fault blocks. These syn-rift structures are now visible in the depth-migrated seismic data, and are of great interest for prospectivity.
There has been a huge demand for high quality, detailed and innovative seismic data which can be set in a regional context, in order to assist in the exploration and de-risking of this potentially prolific hydrocarbon province.
The Kwanza and Benguela Basins of offshore Angola are underexplored, frontier areas with the potential for significant hydrocarbon discoveries. Depth-migrated dual-sensor streamer seismic improves the imaging of syn-rift structures, with further implications for identification and mapping of prospects.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012