Sandstone reservoir distribution of late-middle Miocene Arang formation, West Natuna basin, Indonesia

West Natuna Basin is one of Indonesia’s most prolific petroleum basins. This basin was formed since the Oligocene and has experienced several tectonic events, one of which was a change in the tectonic regime, from extensional to compressional regime (tectonic inversion) in late miocene. This change of tectonic regimes had affected depositional environment and post-depositional conditions of Arang Formation, which has reservoir potential in the basin. We used high-quality (resolution at target depth is 15 m), 3D seismic reflection data to investigate the distribution and depositional environment of the Arang Formation through seismic facies analysis and attributes. Well data were also used to interpret lithofacies of the formation (sandstones, interbedded sandstones and claystone with coal streak, and interbedded claystone and sandstone) and petrophysical properties of the reservoir. We found that the tectonic inversion strongly influenced the Arang Formation in terms of: (i) distribution (co-eval sedimentation and structural growth), (ii) depositional environment (i.e. fluvial-dominated transitional environment with tide influence), and (iii) formation of post-depositional structures (anticline and faults). Insights on interactions between sedimentation and structural processes in this area could be taken further not only for reservoir characterization to produce hydrocarbon, but also for assessing reservoir potential as a candidate for CO2 injection.