Publications

Pore pressure distribution in South Sumatra has received little attention in literature. Until this time, the pore pressure in this region has only been determined for new wells before drilling activity. This paper discusses an integrated pore pressure study with the input data comes from several different sources: wireline logs (gamma ray, density, sonic, and resistivity) from eighty-one wells, seismic velocities, drilling data and clay mineralogical analysis. The objectives of the study were to understand the pore pressure regime, distribution and mechanisms so the overpressure zone(s) in future wells in the Corridor Block, South Sumatra could be predicted. The analysis revealed that both hydrostatic and overpressure regimes are present in the study area. In accordance with the regional pore pressure regime from Ramdhan et al., 2018, if the depth to basement is greater than 6500 feet, overpressure in the Tertiary section will be present. From the study, the observed overpressure regime was divided into four regimes, OP-1, OP-2, OP-3, and OP-4. These regimes are distinguished from one another by geological formation and magnitude of overpressure. The mechanisms that generate overpressure in this area have been classified into disequilibrium compaction due to rapid burial during the last 20 Ma and hydrocarbon generation. In addition, clay mineral transformation can also contribute to overpressure, but this is regarded as a minor phenomenon in the study area. To estimate the overpressure magnitude, a single normal compaction trend (NCT) in the study area has been generated. It was constructed using sonic logs and it was corrected with the amount of erosion. The application of the single NCT together with Eaton; equation gives a reasonably good pore pressure estimation. In general, the overpressure distribution may be used to estimate pore pressure over the study area. This integrated analysis could predict pore pressure in the area without well control and give more comprehensive analysis of pore pressure distribution.