Publications

Mature basins, including many of those in Western Indonesia, are ones that have been intensively explored, typically over many decades in a competitive environment where the full technological armory available to explorers today has been routinely applied (e.g. 3D seismic imaging and depth conversion, AVO) such that all of the significant simple structural traps (anticlines, high- side fault blocks/horsts etc.) have been drilled and explorers are left with the smaller typically sub economic simple traps and larger more complicated trap types. Many of these more complex trap types involve base seals, fault seals and/or pinch outs making them inherently more risky than the simple high-side traps which only require an effective top seal (and flank seals where there are faults). The challenge for explorers is firstly to recognize that DHI’s are very unlikely to provide silver bullets in such mature settings and hence it’s back to the question of how to collate what is typically a voluminous dataset of geological data from wells and seismic data in such a way that the most prospective areas for looking for subtle traps can be efficiently determined together with a calibrated understanding relative to historical success rates and discovery sizes for these different trap types. The former is delivered via the application of well-established play fairway mapping methods such that areas of proven reservoir, seal and charge are mapped out spatially on a play by play basis. There are many methods of doing this but the best method, particularly in areas of complex and laterally variable geology, is the construction of “split risk” CRS maps where the shared and independent risk components are separated for each risk element (Longley & Brown 2016). The latter challenge is the systematic classification of the well failure, discovery and prospect inventory in these proven areas. In this way failures of complex traps beyond the proven play fairway are excluded, the explorer gets a spatial focus and the real exploration record for such tests and why they failed can be determined and the best prospects quickly high-graded. An example of how this approach can be applied to data from the East Java basin is presented to show the methodology and highlight remaining exploration potential both within proven and unproven play areas. This methodology is repeatable and applicable to other western Indonesian Basins. The key is to collate the key failure and discovery data in the more heavily explored portions of the basin to assist the exploration effort. Large complex trap discoveries are not common globally and are frequently solitary (e.g. Buzzard in the Inner Moray Firth) but when they occur they are transformational for exploration companies and treasuries alike and always re-invigorate exploration efforts in what were previously relatively inactive or fallow basins.