Jelawat-1ST1 Post-well Analysis Revisited & the Main Reason for Failure in Finding Effective Hydrocarbon Accumulation

Summary Jelawat-1ST1 was a wildcat exploration well drilled by Amerada Hess (Malaysia) Limited in 2004 testing an anticlinal feature of the Bunguran Trough Fold-Thrust Belt located in the current JX Nippon operated Block 2F. Late Miocene turbidites of Cycle V sequence with high amplitude anomalies were the deepest targeted objectives of Jelawat-1ST1 well; however, only tight reservoirs with minor gas shows were encountered. No other effective reservoir intervals were encountered in the overlying shallower section, which is predominantly made up of silty sands and shales. In 2011, a paper presented by Ong et al. (2011) based on the outcomes of Fluid Inclusion Stratigraphy (FIS) analysis suggested that the Jelawat-1ST1 well (annotated as “Well A” in the paper) showed sparse low gas anomalies throughout the studied interval with no visible liquid hydrocarbon inclusions in the analysed thin sections, albeit their 3D basin modelling study suggesting adequate hydrocarbon generation and migration to any potential entrapments. However, it was concluded that late deposition of the regional top seal is ineffective to retain any economical hydrocarbon accumulations.