Publications

Basin, especially in Karanglewas village, Jatilawang, Banyumas that has had gas seepage for ten years. Gas seepage in this area indicates that there is an active hydrocarbon in the area. Structural control, such as faults, affects the gas seepage in this area. There are two mega shear faults in central Java: the Muria–Kebumen fault in the Northeast- Southwest direction and the Pamanukan–Cilacap fault in the Southeast-Northwest direction (Satyana, 2007). Gas seepage in this area follows the Pamanukan–Cilacap fault lines (Armandita, et al., 2009). The area of research is the Halang Formation, Jatilawang. This formation was formed in Middle Miocene–Late Miocene, so the formation of gas can be thermogenic or biogenic. The Jatilawang area was originally a swamp so the process can affect the formation of biogenic gas in the area. Geoelectrical and geochemical methods are used in this research to know the subsurface geological conditions to find the distribution of the gas seepage in this area. From the reconstruction of Jatilawang’s anticline, a peak anticline is estimated to be around 610 m in the south gas seepage and the depth of the gas cap is 620 m from surface, which is estimated as a source of gas seepage (Purwasatriya and Waluyo, 2011). From the gas chromatography analysis, the natural gas in Jatilawang is composed of the isotope C1. From that analysis, we found that the natural gas in Jatilawang’s field was formed by a thermogenic process with dry gas. The thermogenic process is the process where temperature is dominant. * University of Jendral Sudirman Keywords: Subsurface Mapping, Gas Characteristics, Halang Formation, Banyumas Basin.