The Kendeng-Randublatung zone constitutes the southernmost expression of the Cenozoic East Java petroleum basin. It is a narrow, <100km wide, E-W trending zone extending from onshore East Java to offshore Madura Strait, bounded northward by the inverted RMK zone and southward by the intruded range of the Southern Mountains. The Kendeng-Randublatung zone records a unique rift-like deposystem during the Paleogene-Oligocene period. From the Miocene times, Kendeng undergoes major thin-skin thrusting, forming a wedge-top depozone at the northern fore front of the southern Mountains, while Randublatung evolves as a counterpart foredeep depozone and remains virtually undeformed.

The onshore part of the Kendeng-Randublatung zone has seen very limited exploration to date, in sharp contrast to its extension offshore in the Madura Strait. Thick sedimentation, massive overpressure and development of mud volcanoes in Randublatung, thrust-fold structural complexity in Kendeng, and the presence of recent volcanic deposits further south, have all contributed to limitations in seismic imaging of the subsurface, with the few early wells drilled on this basis leading to disappointing outcomes.

We hereby provide new insights for the characterization of the Kendeng-Randublatung zone with focus on recent advancements in thermal modeling to constrain the activation of the sub-thrust Paleogene graben system and its hydrocarbon generation history. Integrated with gravimetry and seismic interpretation, gross depositional environment mapping, structural restoration and geochemical characterization of seepages, our finds support that multiple source rocks from various deposystems/depozones have been activated onshore Kendeng-Randublatung.