Publications

The Kangean area is poorly constrained in terms of maturity variations, and the types and locations of active pods of source rocks at the origin of the known accumulations are often subject to debate. A previous published attempt to determine the provenance of the large gas resources of Pagerungan concluded that the accumulation originates from mature coaly organo-facies of the Ngimbang source rocks, situated in a syncline just north of the field and part the Northern Platform. However, a series of shortfalls in the proposed workflows and calibrations, raise legitimate doubts on the validity of this model. The doubts are further amplified by recent finds on the expulsion efficiency of coaly organo-facies of the East Java Sea, and the presence of a preserved Pre-Cenozoic synform underlying the Kangean area. Could there be a valid alternative model to explain the charging of the Pagerungan Field? A 3-D numerical basin model was constructed over the Kangean area to compute the maturity, identify active types and pods of source rocks, and determine the migration paths towards the known accumulations. The maturity inputs for the 3-D model were generated by developing new regional structural deformation and thermal models for the Kangean area, based on a calibration method excluding the use of Vitrinite Reflectance, potentially affected by suppression. Subsequent dynamic simulations reveal the Northern Platform to be immature and the Pagerungan gas to originate from a high maturity pod of Ngimbang mudstones located south. The active pod corresponds with a Paleogene extensional structure that was later inverted during the Late Neogene, forming the Central High. Coaly organo-facies are not activated. Investigating the charging model of the known accumulations of the East Java Sea is critical in the de-risking process of Ngimbang-sourced prospects, especially as exploration shifts towards deep water acreage.