M Basin located in African Plate is a intracontinental fault-depressed basin developed on Pre-Cambrian basement during Meso-Cenozoic.The basin mainly consists of EW and NW directional tectonic systems.According to fault scales

their control over the basin and their formation and faulting times

the faults of the basin can be divided into five grades

which correspond to the three major evolution stages of the basin.The long-term inherited developed structural belts are favourable for oil and gas accumulation;the faults developed in late period did destruction to the pools formed in early period

and the traps formed in late period didn't possess pool-forming condition.Since faults developed well in the basin

oil and gas migrated vertically.The faults developed earlier(before AM Formation deposition)have sealing function.