Publications

Samboja Structure is located in the Lower Kutai Basin, East Kalimantan. This field was discovered in 1897. Recently, 330 wells have been drilled within an area of 18.5 km with cumulative production of 1.4million barrel oil (2017). Prior to the discovery of the Samboja deep zone prospect (>800MTVDSS), this field was not considered as the backbone oil producer. The sedimentology and biostratigraphy analysis from the recent appraisal wells (SBJ-A and B), which penetrated the deep zone, created a paradigm shift in facies interpretation, from the classical proto-Mahakam type fluvio deltaic facies to the overlooked non-deltaic shallow marine sandstone facies (offshore to lower shoreface). In order to delineate the pay zone distribution, typical several methods such as Extended Elastic Impedance (EEI) Inversion and passive seismic were applied. EEI was applied to infer Vp/Vs volume from 3D seismic data. To fine tune the prospect distribution into more detailed anomaly map, passive seismic derived V/H distribution map at frequency window of 1-4 Hz were utilized. The oil probability map has been generated in favor of both maps (EEI and V/H) with 70% and 30% weighting values respectively. This method has been successfully applied to map the pay zone in the Samboja deep prospect, validated by blind test using the appraisal wells. The oil probability map shows a strong anomaly with NE to SW trend along western flank of the Samboja Structure, this trend is consistent with the interpreted Mid Miocene paleo-coastal orientation. This study has successfully identified 8.1 million barrel oil from the Samboja deep zone. This study has led a new insight into the Samboja field development strategy (e.g. stratigraphic trap concept, step out drilling programs to the west flank, reservoir geometry and reserves re-calculation).