Proceedings, Indonesian Petroleum Association
Thirty-Fifth Annual Convention & Exhibition, May 2011
Sorong Fault Tectonism and Detachment of Salawati Island: Implications for Petroleum Generation and Migration in Salawati Basin, Bird’s Head of Papua
Awang Harun Satyana*, Neni Herawati**
** JOB Pertamina-PetroChina Salawati
Sorong Fault, bordering the SalawatiBasin to the north and west, has strongly influencedthe geology and petroleum system of the SalawatiBasin since mid-Pliocene times. The fault reversed the basin’s polarity from the basin with the southern depocenter before the Pliocene to the basin with the present northern depocenter. The subsidence of the basin to the north has resulted in thegeneration of petroleum from main source rocks of Miocene Kais-Klasafet carbonates and shales.
As the Sorong Fault continued to deform the basin, SalawatiIsland, once attached to the mainland of the Bird’s Head of Papua, detached. The island rotated counter-clockwise, opening the SeleStrait wide at the north end,close to the main trace of the Sorong Fault and narrow at the south, close to the pivot point of rotation. Following this rotation, SalawatiIsland translated southwestward, emplacing it into its present position.
Counter-clockwise rotation and southwestward translation of Salawati Island is considered to havedeformed surfaces within Kais, Klasafet and Lower Klasaman, resulting in anticlinorium belts forming regional noses, trending dominantly northwest-southeast. These regional noses have proven to be main pathways of migration in the SalawatiBasin. Petroleum generated in the northwest-northern depocenter has migrated along the regional noses and away from the adjacent regional lows.
Reconstruction of the SalawatiIsland rotation and translation, relative to the optimum time of generation and migration, as well as formation of the regional noses, has revealed which areas in the SalawatiBasin receive maximum charging of petroleum through effective migration. Integrated studies,comprising basin evolution, structure, carbonate sedimentology and petroleum geochemistry have reduced exploration risks related to migration and trapping of petroleum.