Significance of focused hydrocarbon migration in the Salawati basin: controls of faults and structural noses

Abstract

Abstract The Salawati Basin, Bird's Head of Irian Jaya, has been extensively explored. Exploration for oil in the basin began in 1906. Up to 1998, 160 exploration wells have been drilled in the basin. The efforts were rewarded with 35 commercial discoveries, 22 of which are still producing oil and gas. Yet, the basin is still interesting for exploration as shown by recent regional petroleum geochemistry and structural studies. Regional evaluation on the present-day structure, paleo-structure, and timing of hydrocarbon generation versus proven hydrocarbon accumulations, have shown that unique migration compartments occurred within the Salawati Basin. The interplay between fault trends with structural noses appears to control the focus of hydrocarbon migration within the basin. The study showed that the foredeep kitchen of the Salawati Basin is connected to the basin's updip areas through regional structural noses. Numerous normal faults are present within the basin, intersect or parallel to the regional noses. Generated hydrocarbons flowed updip through fault fractures and carrier beds of structural noses. Faults and noses control the hydrocarbon migration pathways. High efficiency migration takes place in an area where fault trends are parallel with the structural dip. Proven hydrocarbon accumulations of the Salawati Basin discovered to date are located in such an area. The study has identified areas with high-efficiency faults and regional structural noses that act as migration fairways. This concept of migration has explained the distribution of both proven hydrocarbon accumulations and dry wells within the Salawati Basin. The concept also provides a tool for evaluating migration risks for undrilled prospects.