Petroleum geology of the Melut Basin and the Great Palogue Field, Sudan

This paper overviews the framework, structural and petroleum geology aspects of the Melut rift Basin in Sudan. The data base is from mainly proprietary exploration work consisting of more than 20,000 km of seismic profiles, 2000 km2 of 3D seismic, and more than 50 exploration wells. There have been more than 15 oil and oil and gas discoveries.The Melut Basin is a Meso-Cenozoic rift basin accompanied by the formation and development of the Central African Shear Zone (CASZ) on the pre-Cambrian crystalline and metomorphic basement of lower relief. Three stages of rift development and fracturing have been identified, stronger in the Early Cretaceous and Paleogene and weaker in the Late Cretaceous. Source rocks are the Lower Cretaceous lacustrine shales, whereas reservoirs and seals are both Paleogene and Upper Cretaceous. Dominant structural styles are large-scale anticlines in the Paleogene sequences and antithetic normal fault-blocks in the Upper Cretaceous and Paleogene. Heavy to light oils (8.87–61.5° API) and gas have been discovered in the Paleogene and only light oils and gas in the Upper Cretaceous pay zones. The primary pay zone in the Melut Basin is the Paleogene. The Great Palogue 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 areas for petroleum accumulation and enrichment. The faulted anticlines within the Paleogene syn-rift sequences are the main trap types, whereas the antithetic fault-blocks of the Upper Cretaceous sequences are secondary.