Publications

This paper reviews the fascinating 130 years history of hydrocarbon exploration of the Ngrayong sandstones in the East Java Basin from the early petroleum exploration to the advance of modern technology. It also characterizes the play concept, play fairways and assess the oil yet-to-find from the play. The Ngrayong Formation consists of fluvio-deltaic, shallow marine, deep slope and basin floor depositional facies. Sandy fluvio-deltaic and shallow marine facies are widely distributed across the paleo shelf in the northern part of the basin. Thick shale dominates along E-W paleo slope situated along present day northern coast of East Java and Madura islands. In the basin floor, further to the south, dominated by pelagic and hemipelagic shales with a number of submarine fan complexes. The basin floor fan in the Cepu area has been accounted for 250 MMBO productions today. The potential of the other fans to the east are still needs to be tested. The main risks are reservoir presence and its’ quality which require more 3D seismic data to better define the presence and geometry of these fans. The deltaic and shallow marine play has been proven by the Kepodang gas field in the Northern platform. Scanning of any DHI on seismic is worth doing to identify more of this play. However, the play has a major risk in CO2 content. Isotope data indicates that the CO2 is of magmatic origin and restricted only in the Muriah Trough and Bawean arch. Future exploration on the Ngrayong sandstones should focus on the under-explored basin floor fan play in the offshore area where large hydrocarbon resources could possibly exist. More 3D seismic data and better understanding of petroleum system will be required to be successful in exploring this play.