Abstract

The deepwater South Makassar basin lies offshore South Sulawesi in water depths averaging 2000m and is an under-explored region that was only drilled at its periphery. Talisman operates the Sageri, South Sageri and Sadang PSCs located in the central part of the basin.

This basin belongs to the South-Eastern margin of the Sundaland geological province and is thought to be composed of extended continental crust.

Tertiary sediment deposition was initiated due to a rifting period of Eocene age, during which crustal extension created a tilted basement blocks topography, progressively filled with continental to shallow-water syn-rift clastic sediments composed of volcanics, sands, coals, and shales.

Carbonate development followed as more marine conditions prevailed by mid Eocene time. Rifting terminated at the end of Eocene and the water depth gradually increased, resulting in the progressive drowning, then burial of most carbonate buildups during Oligo-Miocene times.

Sediment input was limited during Oligocene and Early Miocene, but became high during Neogene until present time. However sedimentation never caught up with the post-rift subsidence of the basin, which remained “under filled”, resulting in the accumulation of argillaceous sediments in deepwater conditions.

Recent interpretation of proprietary 2D seismic and new biostratigraphic analyses have led to revise the age of rift development (mid-Eocene) and subsequent Neogene megasequences. Improving the timing of these events has been critical to the understanding of related sequence boundaries and the development of a new 3D basin model which has been employed to interpret the hydrocarbon generation over the entire basin.

A seabed data acquisition campaign including heat flow measurements and the interpretation of the BSR (Bottom Simulating Reflector) horizon provided the necessary calibration. The heat flow was mapped in the South Makassar Basin, with values of 40 – 70 mW/m2, overall higher than in the adjoining North Makassar Basin (20 – 60 mW/m2).

Results indicate a significant present-day gas generative window in the centre of the basin and less mature kitchens in the southern grabens toward the south Platform. The primary structural traps are in place and receiving early hydrocarbons since the Mid-Miocene, but the trapping efficiency and degree of late stage gas flushing are unknown.

The South Makassar basin is one of the few remaining high potential frontier areas to be explored within Indonesia. Talisman’s methodology to strategically apply a multi-disciplined regional analysis to this basin has led to an early qualified evaluation of the basin’s petroleum system. This has allowed for timely business decisions to be made within a competitive Industry environment.