This paper describes a forensic investigation on six wildcat wells drilled in the Randugunting Block, North East Java Basin in order to determine why the wells failed to discover commerical hydrocarbon, learn from those failures and to apply that knowledge for the success of the subsequent wells.
The first step of investigation was to evaluate any possible mechanical problem during drilling and testing that may lead to inconclusive well. After passing that screening, all available subsurface data including seismic, well log, mud log, and cores were then utilized using petroleum system approach to find out the most likely element of petroleum system that responsible for the lack of hydrocarbon accumulation in the particular dry hole well.
This study indicates that reservoir problem was the main reason for the failure of wells targeting Kujung and Ngimbang carbonates. The drilling results showed that the wells penetrated either tight limestones or shale sequences instead of good porosity and permeable limestones. Our current investigation concluded that the wells were previously incorrectly interpreted to be located in a Paleo-high.
Furthermore, timing of migration and trapping problem were suspected to be the major reasons of failure for well targeting Ngrayong and Tuban formations. C-1 well was located in a strongly inverted structure which was in existence after the main phase of oil generation and migration.
All these findings suggest that the next carbonate target should focus on the northwest and southeast area where Paleohighs are proven to exist. On the other hand, exploration for Ngrayong and Tuban targets should first concentrate to map the migration and remigration routes of HC in order to locate preferable structural/stratigraphic traps.
Authors : Miftah Mazied, Iwan Rudiyanto, Budi Prasetyo, Tran Nam Thang