Lacustrine Petroleum System in South Atlantic Region Angola

Murthy Inkollu, Leonor Binga, and Carlos Figueiredo
Sonangol, Luanda, Angola

Along the South Atlantic region of Angola, a network of rift basins is distributed from Cabinda in the north to Walvis ridge to the south. Well-developed rift basins are known at the rift accommodation and basement hinge zones. These lacustrine rift basins are Neocomian, Barremian to early Aptian in age. Within these basins, lacustrine source rock deposition occurred at several intervals from late Neocomian to early Aptian. The source rocks possess an average total organic content that range between 2 to 5 percent. Many found oils at onshore and near shore are attributed to the said sources.

In order to understand the hydrocarbon generation, migration and trapping and to better assess the lacustrine petroleum system, basin modeling work is conducted with the aid of Temis 2D software application. Key 2D profiles were used from Cabinda, Benguela and Namibe to explain the timing of hydrocarbon generation from the key source rock intervals. The results of these and other parameters such as temperature and pressure in the lacustrine basin are indicated on the effect of maturity and migration of oils.

From the modeling, it is estimated that the timing of hydrocarbon generation from the late Neocomian source is early Albian, the middle Barremian source is in Eocene/Paleocene, the upper Barremian source is in early Miocene and, the early Aptian source is middle Miocene to present. Depending on the burial depth, it is noted some of the said sources are in present day oil window.

The composition of lacustrine oils and source rocks are reviewed for a better understanding of this key source rock interval for the oils of Angola.