Block 21 is located in the deep-water offshore south-central Kwanza Basin, some 200 Km southwest of Luanda. The water depth in the block is 300 to 1,600 meters.

The block comprises basin shelf-slope over its eastern portion and salt mini-basin development in the central and western portions. A well-defined arcuate rift half-graben is seen all along the edge of the basement hinge. Numerous leads are recognized in Albian carbonates and in Miocene channels. These are seen as four-way closures, fault-bounded traps or salt roll-over traps. Albian leads are well identified in the shelf-slope area. Geological models indicate that these features contain high-energy carbonate shoal reservoirs. This block has potential at Albian and Miocene alone in the salt mini-basin domain.​