Indonesian Petroleum Systems and Exploration Efficiency

J. V. C. Howes and Suherman Tisnawijaya

The Republic of Indonesia has over 40 productive petroleum systems and more than 100 speculative petroleum systems. Since the first oil discoveries in the 1880s, cumulative discovered ultimately recoverable petroleum resources in Indonesia have reached 50 billion barrels of oil equivalent. There are eight principal producing areas and nearly 1,000 oil and gas fields. Most of these resources have been found in the last 50 years. Successful exploration continues; at least two discoveries per year are made which exceed 50 million barrels of oil equivalent reserves. Productive petroleum system source types are split almost equally between marine and deltaic-lacustrine facies. The majority of source rocks are Tertiary in age; Mesozoic source rocks are restricted to Eastern Indonesia.

Discovery process analysis indicates generally high exploration efficiency in Indonesia. An upwardly convex discovery process curve typifies many systems, reflecting both exploration efficiency and maturity; this pattern is well displayed in areas such as Central Sumatra and Salawati. A much more random or straight line process curve, as seen in West Natuna, occurs where more complex petroleum systems have inhibited exploration efficiency. An inverted, or concave upward curve, seen in some Java petroleum systems, is probably economically driven, related to development of domestic Indonesian gas markets. Several curves, such as those for the North Sumatra/Bampo-Peutu and East Kalimantan/Tanjung systems are dominated by single fields. Different exploration phases can be recognized in ma y of the producing petroleum systems, each phase having its own specific exploration statistics.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California