Biogenic Gas Exploration and Development in Bentu PSC, Central Sumatra Basin, Indonesia

Yuwono, Radig W.; Djaelani, Setiabudi; Sjafwan, Benny; Kirana, Pintarwan S.; Fitriani, Bayu S.
Exploration, Energi Mega Persada, South Jakarta, Indonesia.

Biogenic Gas has become an economic target of exploration and exploitation due to high demand of gas. It is easily intepreted on geological occurence, significantly widespread, shallow and have a good quality of gas with >98% content of CH4, low S and CO2 content. Bentu blocks are Biogenic Gas fields in Central Sumatra Basins with up to 300 bcf of gas reserves. Production test from this blocks resulted peak of production rate are 50 MMscfd from Segat field. This paper presents the summary of Geology, Geochemistry and Geophysical aspect to assess Biogenic Gas accumulation in Bentu block.

Biogenic gas origins were shown by carbon isotope analysis with δ13C CH4 value -62 to -66 ‰. The main gas bearing reservoir are 7-25 feet thick sand layer over Late Miocene to Pliocene Binio formation with a depth of 600-2000 feet below sea level. Binio formation were deposited in coastal environment that reflects the onset of marine regression. The gas is trapped along NW-SE anticlinal system related to reverse fault.

Seismically, existing data clearly exhibits strong amplitude anomalies or "bright spot" as a Direct Hydrocarbon Indicator. Furthermore, advance geophysical analysis : AVO, seismic attribute and LMR methods, were carried out to confirm gas occurences. The result of this analysis helpful to distinguish between coal and gas bearing reservoir, when coal was shown by a similar appereance in the seismic data. Seismic data also important for delineate lateral gas distribution and explore some prospect & lead in Bentu block.

Growing interests in gas exploration and development, and also high demand of gas supply, encourage the study of Biogenic gas, which nowadays became important. Characteristic of Biogenic Gas that occurs on shallow depth and high quality of gas made this gas to be economically produced. Bentu area, as one of proven and potential Biogenic gas provide a typical integration of Geology, Geochemistry and also Geophysical aspect to assess gas accumulation.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012