Publications

The Central Sumatra Basin was Indonesia’s premier oil producing province for many decades producing more than 1,000,000 bopd during its heyday in 1973 declining to 200,000 bopd today (at end 2023). Being located onshore and being oily the basin has been heavily drilled with ~740 exploration wells being drilled during the 1930’s to present day period making it the most densely drilled basins in Indonesia. Historically the basin was dominated by one operator namely PT Caltex (Chevron & Texaco) which throughout it’s 30 year tenure over the premium acreage (relinquished by Shell) was systematic and efficient with timely application of new technology such that the perception from external companies is that the basin is very mature with limited material remaining exploration potential. The absence of any material (100MMboe+) exploration discovery since the mid 1970’s, some 500 exploration wells ago, is normally cited as proof of such conclusions. With the recent departure of all of the major historical operators including Caltex at the end of their production licences the major producing fields are now operated by Pertamina and the peripheral fields and acreage is held largely by domestic Indonesian companies. With the national goal of increasing oil production from ~600,000 now to 1,000,00 bopd production in 2030 SKK Migas and Pertamina, the national regulator and NOC respectively, commissioned a series of regional studies/compilations over the main prospective basins to help re-invigorate exploration and find new larger discoveries. In the Central Sumatra Basin a series of quality regional prospectivity reviews were done by Lemigas in 2020 where they had access to most of the 2D seismic and exploration wells. These studies were supplied to GIS-Pax as input into a more modern play analysis, beyond the traffic light map approach used by Lemigas, and S&P data was also integrated into the analysis.

The results have highlighted a series of areas where traditional plays have been overlooked, one being a regional closure with >1billion boe potential. New play types such as lacustrine turbidites and deltaic sands within stratigraphic traps in the source Brown Shale Formation have been identified plus “Basement as a Seal” plays such as subthrust traps against basement leads which are clearly present and are likely untested adjacent to proven kitchen areas.

The results suggest significant exploration potential remains within the proven charge portions of the basin and if well and seismic data is made available via farmout that larger E&P companies should review the details. The existing oily nature of the petroleum system, the ullage in the pipelines and the improving fiscal terms also assists in making these areas more attractive than previous perceptions would suggest.