Carbonate Characteristics of Banyu Urip, Kerendan, Arun, and Natuna D‐Alpha Fields: Cenozoic Isolated Carbonate Platforms as Major Reservoirs in Indonesia

Abstract

Situated at tropical latitudes with a humid paleoclimate, the area of the present-day Indonesian archipelago was very suitable for production and accumulation of carbonate sediment during much of the Cenozoic. Following early Paleogene rifting that resulted in development of horst and graben structures, the peak of carbonate production occurred from the late Oligocene to Mio–Pliocene. This paper summarizes several Indonesian isolated carbonate platforms that formed on marine horsts. Of these examples, Banyu Urip in Java, Kerendan in Kalimantan, and Arun Field in Sumatra have provided important contributions to Indonesian oil and gas production for the last few decades, whereas Natuna D-Alpha in the Natuna Sea will become a giant gas field in the future.To achieve the objective of characterizing Cenozoic carbonate platform reservoirs of Indonesia, this study reviews the Cenozoic carbonates in the East Java Basin, Kutei Basin, North Sumatra Basin, and Natuna area and places them in the context of the regional geology of Sundaland. Insights from previously published work are supplemented by new descriptions of cores, well-log analyses, and interpretations of two- and three-dimensional seismic facies analysis, well-log correlation, and sequence stratigraphy. These geological and geophysical data have been integrated with dynamic reservoir data to validate the geological and geophysical interpretations.The results reveal that the Indonesian carbonates of Banyu Urip, Kerendan, Arun, and Natuna D-Alpha are classic isolated carbonate platforms and can serve as examples to recognize reservoir character. Those platforms developed in the same general regional geologic setting relative to the Sundaland continent and share certain similarities, but local geologic variations and distinct processes gave each platform particular characteristics. Reservoir quality of the carbonate platforms is influenced by relative changes in sea level, the position relative to the shoreline or fully open-marine settings, and the influences of both regional and local tectonic events. The fields thus illustrate several conceptual models of carbonate reservoirs in isolated platforms. Understanding the character and variety of Indonesian reservoirs as related to their depositional processes and regional position provides insights for exploration and reservoir management of analogs elsewhere.