Characteristics and Exploration Potential of Petroleum Systems in M Basin, South Sudan

M Basin in South Sudan is a complex Meso-Cenozoic intracontinental superimposed rift basin formed under the action of oblique rifting in the Central African Shear Zone. The oil and gas resources discovered in M Basin are concentrated in the upper Paleogene reservoir of the North Sub-basin, and few discoveries have been made in other sub-basins. In order to analyze the rules of hydrocarbon accumulation in the basin and reveal the exploration potential of various sub-basins, using the petroleum system theory as a guide and based on the analysis of reservoir elements, this paper carries out the analysis of the geochemical characteristics of crude oils, oil-source rock correlation, and the evaluation of petroleum systems and points out the exploration direction for different petroleum systems. (1) Two sets of source rocks have been formed in the basin, and the lacustrine mudstone in the upper part of the Lower Cretaceous succession is the primary source rock. (2) The petroleum systems in the basin are classified into three known petroleum systems and three predicted petroleum systems. For the Northern Petroleum System in the North Sub-basin, there are two critical periods, namely, the end of the Paleogene and the beginning of the Neogene. The end of the Paleogene is a period of large-scale hydrocarbon charging, and the beginning of the Neogene is a period of continuous oil charging. The near-source lithologic-stratigraphic trap in the lower part is an important zone with great potential for future exploration. (3) To a certain extent, the crude oil of the Southern Petroleum System in the North Sub-basin is genetically related to the two sets of source rocks mentioned above. For this petroleum system, there is only one critical period, namely, the end of the Paleogene. The upper Paleogene structural trap is a favorable zone with great exploration potential. (4) Except for the M Petroleum System in the South Sub-basin, which is speculated to be similar to the Northern Petroleum System in the North Sub-basin, the Cretaceous successions of the petroleum systems in other sub-basins are shallowly buried and only have limited exploration potential. This study not only provides an effective means for the study of petroleum systems, but it also further enriches and develops the connotation of petroleum systems in rift basins.