The geochemical assessment of a shale gas reservoir in the Telisa Formation in the South Sumatra Basin was carried out to identify the potential shale gas distribution. The objective of this paper is to characterize the core sample by analyzing the total organic carbon (TOC) content, kerogen type and thermal maturity of shale gas layers in terms of vertical resolution based on log data from four well log data. In addition, a seismic interpretation approach including a seismic attribute analysis and an inverted acoustic impedance is explored to spatially distribute the shale gas potential based on TOC values. Geochemical assessment of the Telisa shale gas reservoir revealed that the organic richness of the reservoir is classified as fair to good in quality. Kerogen type in the reservoir is considered a mixture of type II/III (oil/gas prone) to type III (gas prone). In terms of maturity, the Telisa shale gas reservoir is categorized as “in a mature stage”, representing an oil window up to a wet gas window. The prospective reservoir distribution is indicated by a shale lithology characterized by a high acoustic impedance range of 20,000–24,000 ft/s g/cc. In contrast, the organic richness of the Telisa shale reservoir is classified as “of fair quality”, with TOC in the range of 0.75–1 wt%.