EXPLORATION PLAY HOT ZONES IN WESTERN INDONESIAN MATURE BASINS: 15 YEARS EXPLORATION REVIEW

Indonesia in term of geological aspects can be divided in to two major regions which are Western part and Eastern part. The Western part mainly forms Sunda Platform meanwhile the Eastern part is mainly originated from Australian continent. The Western Indonesia which consists of Sumatra, Natuna, Java, and Kalimantan islands, has been recognized as a major prolific hydrocarbon producing field with 11 producing basins, 5 discovery basins, and 20 basins with no discovery status.

The exploration efficiency in Western Indonesia is around 45% which reflects a good exploration strategy. This percentage is driven by the development of Western Indonesia’s exploration play concepts by moving to deeper targets and older ages. Unfortunately most of the exploration activities concentrated in the producing basins. From 950 exploration wells that had been drilled only 1% was conducted in non-producing basins hence resulted in small amount of gas discovery.

In the last 15 years of campaign exploration in Western Indonesia region, several significant discoveries have been found with greater than 7,5 BBOE total hydrocarbon in place. More than half of the total number comes from 16 discoveries, which each of them containing > 100 MMBOE hydrocarbon in place. The exploration plays of the discoveries are Oligocene Fluvio-deltaic Sandstone in Sumatra, Late Pliocene Shallow Marine Sandstone in offshore East Natuna, Basement & Oligo-Miocene Fluvial Sandstone in West Java, Oligo-Miocene Kujung Carbonate and Eocene Ngimbang Target in East Java, and Deepwater Turbiditic play in offshore Kalimantan.

This paper will explain the exploration plays in Western Indonesia from G&G aspects and exploration activities, especially where > 100 MMBOE hydrocarbon in place were discovered. Based on our data, the hottest zone from the 5 exploration plays stated previously is the Oligo-Miocene Kujung Carbonate in East Java basin, where > 2 BBOE total hydrocarbon in place was discovered only from 5 structures as the results of large traps (vertically thick or laterally broad carbonates), good reservoir quality due to diagenetic process, charging from multiple mature source rocks, good seals and migration pathways, and match timing of generation-migration-trapping.