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Oil and gas exploration activities in the South Sumatra Basin area had been in a mature phase and were starting to be intense with deep drilling activities or targeting unconventional reservoirs. New exploration discovery from Pertamina Hulu Rokan in South Sumatra Basin would be a breakthrough insight. A new play was found in the pyroclastic sandstone reservoir of the Air Benakat Formation with high gamma ray and low resistivity characteristics with relatively located in shallow depths caused by the last tectonic inversion. This kind of sandstone reservoir which relatively have high natural gamma-rays and low resistivity was easy to be mistaken for a claystone or shale layer and may lead to the loss some of discoveries opportunity. The log characteristic property showed a high gamma-ray value of around 60–120 API at the objective interval. The high value of gamma rays was known inherited by the radioactive composition of potassium (K). The high GR sandstone reservoir is mainly caused by abnormally high pyroclastic composition and not by potassium feldspar. This acknowledgment of new play discovery contributes to future exploration that may need to have spectral gamma-ray and nuclear magnetic resonance logs for better identification of formation property evaluation.