Seismic evidence for gas hydrates in the North Makassar Basin, Indonesia

This paper describes the distribution, seismic characteristics and potential volume of gas hydrates in the eastern part of the North Makassar Basin, Indonesia. Identification of the gas hydrates depends entirely on the presence of extensive bottom simulating reflectors (BSR) which are distributed primarily within the offshore extension of the West Sulawesi Fold Belt. Turbidite deposition within the fold belt mini-basins provides a reservoir and a source of organic material for the production of biogenic methane gas. Several seismic examples are shown, including a suspected palaeo-BSR on the crest of an eroded anticline, a submarine mud volcano and an occurrence of rotated slump blocks and debris flows that glide along the hydrate/free gas interface.

Geothermal gradients derived from the BSR database averaged 4.7°C/100 m, whilst derived heat flow values varied from 20 mW m−2 to 60 mW m−2, comparing favourably with regional heat flow data. Gas-in-place estimations for the most contiguous accumulation of gas hydrates (c. 8000 km2) yielded an estimated 1.89×1012 m3 (67×1012 SCF) of methane gas. Free gas in place below the hydrate zone within the same area was estimated to be 379×109 m3 (13×1012 SCF).