Publications

The Late Pliocene carbonate facies assemblage of the Kalitik-Ngepung-Selorejo or Kalinges Formation is widely distributed in the Northeast Java Basin. It outcrops mainly in the Kendeng and Kembang zones, the rest remains in the subsurface in the Randublatung zone and possibly extends under the alluvial plain of Ngawi-Baantas and Pati-Rembang areas.Based on extensive field and laboratory studies, the Late Pliocene carbonate facies assemblage of the Kalitik-Ngepung-Selorejo or Kalinges Formation is interpreted as a shallowing upward sequence deposited during a global drop in sea level that started in the Late Pliocene. about 2.9 MA.A shallowing upward trend within the Kalinges Formation is indicated by the deposition of different carbonate facies. This begins with the marls of the of the Kalibeng - Mundu or Kalimu interval and is followed successively by the Globigerina Marl facies, Globigerina Limestone facies, Reefal Limestone facies, Limestone Debris facies and Mollusc Limestone facies. This sequence was finally covered by the clays of the Lidah Formation.The best reservoir potential is found within the Globigerina Limestone facies. These high porosity and permeability limestones are composed almost entirely of sand size planktonic foraminifera that have retained their primary interparticle porosity. Significant quantities of gas (Balun gas field) and oil (Lidah, Kruka, Kuti, Metatu and Bogomiring oil fields) have been produced from this facies.Detailed palaeogeographic studies and subsurface mapping of the Late Pliocene carbonate facies are still needed to locate and map the distribution of the best reservoir facies and to aid in the continuing exploration and development of the areas oil and gas potential.