PETROLEUM GEOLOGY OF MELUTH BASIN & THE GREAT PALOCH FIELD, SOUTH SUDAN

This paper overviews the framework, structural and petroleum aspects of the Melut rift Basin in South Sudan. The database is from mainly proprietary exploration work consisting of more than 20,000km of seismic profiles, 200km. sq of 3D seismic and more than 50 exploration wells. There have been more than 15 oil & gas discoveries.

The Melut basin is a Meso-Cenozoic rift basin accompanied by the formation & development of the Central African Shear Zone [CASZ] on the pre-Cambrian crystalline metamorphic basement of lower relief. Three stages of rift development & fracturing have been identified, stronger in the Early Cretaceous & Paleogene and weaker in the Late Cretaceous. Source rocks are the Lower Cretaceous lacustrine shales whereas reservoirs & seals are both Paleogene & Upper Cretaceous. Dominant structural styles are large-scale anticlines in the Paleogene sequences & antithetic normal fault blocks in the Upper Cretaceous. Heavy to light oils and gas have been discovered in the Paleogene & only light oils and gas have been discovered in the Upper Cretaceous pay zones. The Great Paloch Field, with ultimate recoverable oil reserves of more than 900 million barrels was discovered in the northern Melut Basin. The gentle slopes of each subbasin are favorable petroleum accumulations and enrichment.