Publications

Onshore Central Kalimantan is a frontier area for exploration. In 2015, ConocoPhillips Kalimantan (CKEL) and Petronas acquired the Kualakurun production sharing contract (PSC), an exploration block situated in a structurally complex area with exhumed pre-Cenozoic �basement� and Paleogene sedimentary section. Initial exploration programs consisted of geological fieldwork, biostratigraphy and geochemical analyses to determine the lithostratigraphic character, thickness, and distribution in this area. This work preceded high-resolution geological mapping from satellite data, which further improved the understanding of these lithostratigraphic units and overall structural character. This integrated surface geology reconnaissance provided sufficient evidence of exploration potential within the block to support further exploration programs through gravity-gradiometry and 2D seismic acquisitions. Satellite mapping revealed NE-SW-trending folds and (positive) inversion faults, clearly seen at the surface and proven by field data, particularly in the northwestern part of the PSC. Biostratigraphic data revealed exposed Paleogene rocks encircling the pre-Cenozoic �basement� outcrops in the northern area, while outcrops of Neogene sedimentary rocks are predominantly located to the south. The exhumed Paleogene rocks are interpreted as inverted Paleogene rifts, an extension of the rift-fabrics seen in the Upper Kutai Basin to the NE. Hand samples collected at several outcrop locations prove high quality Eocene carbonaceous shales and waxy coals source rocks are present and distributed across this area. Vitrinite-reflectance of these rocks have a maturity equivalent to the early-mid oil window. Hydrocarbon occurrences in Kualakurun are evidenced by an oil seep and bitumen-filled sandstone outcrops, both of which suggest the existence of a working petroleum system in the area. The integrated geological analyses presented in this paper have provided new insight about the regional structures and stratigraphy of the Kualakurun block and highlight the petroleum prospectivity of this frontier and previously overlooked area, in onshore Kalimantan.