Publications

The Kendeng zone is one of the most challenging exploration areas in the East Java region. It is characterised by present-day regional low gravity anomaly spanned west-east from northern Yogyakarta to the north of Bali Island. Top basement configuration identification is one of the critical challenges because of poor seismic imaging quality and limited well penetration to the Paleogene and older stratigraphic unit. The paper discusses the work on basement configuration interpretation using joint inversion of gravity and magnetotelluric data, structural reconstruction, Paleogene gross depositional environment, and petroleum system implication, involving new geochemistry data from surface oil “pool”.

A series of northwest-southeast trending anomalies from bandpass filtered Bouguer Anomaly has been marked in the eastern Kendeng area, spanning from the Ngawi – Madiun – Nganjuk - Jombang – Pasuruan, that could be related to the present-day basement configuration. Subsurface mapping guided by gravity data identified several horsts and graben systems, showing the northwest-southeast trend that is believed to be associated with the development of the Eocene – Oligocene trans-tensional basin.

Geochemistry analysis results and oil-to-source rock correlation from two new hydrocarbon seepages in the Jombang area indicate that all samples are similar to the character of “Ngimbang Oil,” which is generated from transitional source rocks. This result significantly supports the interpretation of paleo geography during the Eocene – Oligocene and marked the active petroleum system in the study area.

The onshore Kendeng area became one of the region's significant hydrocarbon producers, mainly from shallow Pliocene – Pleistocene Plays. New geological interpretation of basement configuration and Paleoegene stratigraphy architecture might be an alternative reference to explore the deeper exploration target associated with Paleogene – Early Miocene petroleum system plays.