Reservoir Properties and Pores Geometry of Bentiu and Aradeiba Formations, Hamra East Oil Field—Muglad Rift Basin (Sudan)

Muglad Rift Basin is the largest basin of Sudan’s interior basins, which covers around 120,000 km2 in NW–SE orientation, containing up to 13 km of Cretaceous-Tertiary continental sediments as a result of the extension due to the formation of Central African share zone. The mid-Cretaceous Bentiu and Aradeiba formations are the main reservoirs in Muglad Rift Basin that have been investigated by many authors over the last decade. Nevertheless, a detailed and precise analysis of the reservoir petro-physical properties such as porosity, permeability, electrical properties and water saturation is still needed. For these reasons, this study investigated the effects of diagenetic process in the Hamra East Oil field focusing on pores geometry classification and distribution in Bentiu and Aradeiba reservoirs. The analytical methods included well log interpretation, thin-section analysis, mercury injection porosimetry, electrical properties and a conventional air permeameter. The variation of facies association, reservoir properties, pore geometry and diagenesis process allows dividing Bentiu and Aradeiba formations into four reservoir units. Pores types vary from macropores (A), macropores (B) and mesopores, while the pore-throat size distribution varies from unimodal to trimodal. Scarce porosity/permeability in Aradeiba formation is due to precipitation of carbonate and clay minerals and compaction while high porosity/permeability in Upper Bentiu is due to dissolution of some detrital grains and authigenic cement.