Abstract

Statistics indicate that most onshore sedimentary basins with significant hydrocarbon production or discoveries show evidence of seepage. In unexplored offshore basins the ability to detect seeping hydrocarbons is crucial to establishing an active source system. BP Research in conjunction with BP Exploration Operating Company Ltd. (BPX) have developed the Airborne Laser Fluorosensor (ALF) to detect the presence of such leakage at the sea surface.

In response to a Pertamina proposal, and on their behalf, BPX acquired ALF surveys over several unlicenced frontier basins in Indonesia. The aim of the study was to determine whether hydrocarbons were leaking from these basins, thus significantly lowering source risk, and hence promoting future exploration activity in these areas.

During a six month period (first and second quarter 1991), Pertamina/BPX acquired ALF surveys over:

• Sumatra Forearc Basins

• Java Forearc Basins

• Billiton Basin

• Salayar, Spermonde, South and North Makassar Basins

• Bone Basin

• Gorontalo Basin

• Halmahera Basin

Interpretation of the results suggest hydrocarbons are seeping to a variable extent from all of these basins, with the exception of the Java forearcs, though further analysis is required in some areas to confirm this. Geological models are proposed to explain the pattern of interpreted seepage. The areas of greatest potential interest are the Billiton, southern Bone and South Makassar basins.