Publications

The term ‘unconventional hydrodynamic trap’ refers to a field with a tilted hydrocarbon-water contact caused by fluid flow driven by overpressure gradient. This is in contrast to conventional hydrodynamic traps where fluid flow is a result of hydraulic head gradient. The unconventional hydrodynamic trap has been proven to be present in several major petroleum provinces in the world, i.e. the North Sea, and the Caspian Sea. In Indonesia, the giant Peciko and Tunu gas accumulations in the Lower Kutai Basin have been proven as unconventional hydrodynamic traps. Recently, some reservoirs in Nilam Field in the same basin also are recognised as having unconventional hydrodynamic traps. in the giant Arun Field, tilted gas-water contacts were recognised by previous investigators but with no satisfactory explanation. Also, in the giant Tangguh Field, variable gas-water contacts and flank accumulations have been recognised, and are partly explained by the concept of perched water. In this paper, the authors offer the unconventional hydrodynamic trap as a plausible hypothesis to explain the circumstances in the two giants above. Clearly, this hypothesis needs to be tested by carefully analysing pressure data and presenting it in the form of overpressure maps and pressure – depth plots. Unconventional hydrodynamic traps are relatively new exploration concepts in Indonesia’s sedimentary basins, and hence the basins can be said as under-explored with respect to this concept. Revisiting the two giants above may be a good test of this concept, with the hope of awakening other giants.