Publications

The West Coast Exploration Team of PT Caltex Pacific Indonesia is the operator for shareholder companies Chevron and Texaco of the Nias PSC in offshore West Sumatra, Indonesia. The primary exploration play was the Middle Miocene Isolated Reef Play, a biogenic gas play in the frontier block. 3D Seismic data over the Ibusuma Prospect and the subsequent Ibusuma #1 dry hole illustrate key elements in the reservoir development of a Middle Miocene carbonate platform and critical aspects of biogenic gas exploration.Neogene carbonate reefs and platforms are prolific producing reservoirs in Southeast Asia, as seen at the Natuna, Arun and Northwest Java Basin fields in Indonesia, Luconia Platform fields in Malaysia and Yadana field in Myanmar. The Nias Block Middle Miocene Isolated Reef Play, in the Sumatran fore-arc basin, has a typically low geothermal gradient for a fore-arc basin, effectively precluding thermogenic generation of hydrocarbons. The low geothermal gradient favors biogenic gas generation and entrapment. Proven petroleum systems exist in this play (biogenic gas in Miocene pinnacle reefs) as demonstrated by 5 of 6 wells in this play type in the fore-arc being discoveries, including the sourcereservoir system of the Ibusuma #1 well, as demonstrated by the nearby Union Oil Suma #1 well.