T The Banyumas Basin is a Tertiary sedimentary basin with shallow oilpotential located in the south, of Central Java, Indonesia. This basin is divided intotwo sub-basins there are Banyumas Sub-Basin and Purbalingga Sub-Basin arecontrolled by the regional geological structure of the Kebumen - Muria left strikeslip fault and the Pamanukan - Cilacap right strike-slip fault that produces an oilseepage and indicating the petroleum system is active. The methodology isgeological mapping, creating the stratigraphic log composites, and geochemicalanalysis of source rock and oil seepage to determine the components of thepetroleum system. There are three lithological units, such as: the sandstoneinterbedded with claystone that has an age of Late Early Miocene - Early MiddleMiocene with a sedimentation rate is ± 23.3529 cm/kyr and suspected as sourcerock by the value of TOC is 0.64 that identifies the maturity is fair, probable toproduce the hydrocarbon gas prone, formed by organic maceral is vitrinite, lowwaxy - waxy and the source facies is deposited in terrestrial. Then, sandstone hasan age of Middle Miocene - Late Miocene with a sedimentation rate is ± 21.8824cm/kyr and suspected probably to be overburden rock to increase the maturity ofsource rock and the tuffaceous sandstone interbedded with claystone has an age ofEarly Pliocene – Late Pliocene with a sedimentation rate is ± 3,2593 cm/kyr andpotentially to be seal rock. The characteristic of oil seepage is heavy oil and highlybiodegraded and the source facies is in open marine to estuarine or bay. Thecorrelation between source rock to oil seepage is negative. There are nine phasesof geological history and nine elements of the petroleum system event chart toreconstruct the forming of sub-basin and evaluate the potential hydrocarbon.