Publications

The BDA-1 exploration well is located in the West of Ogan Komering block, Southern part of South Sumatra Basin. Drilled in 2014, this well has discovered gas and condensate in basement reservoirs and was tested at 3.4 MMSCFD (@ 56/64” Choke) and 73.3 BOPD (54.7ᵒ API). The well has penetrated a 128 meter basement interval which consists of granodiorite, marble, basalt, and phyllite lithologies. This paper presents the summary of the geology of this fractured basement reservoir based on drilling data, petrography analysis and gas geochemistry. Drilling and logging while drilling data showed development of a fractured zone through the basement interval. When the well entered the basement, gas readings from the gas chromatograph (GC) peaked, the rate of penetration (ROP) increased, and the density and resistivity decreased indicating the presence of a fractured basement reservoir. The fractured zone is developed in upper basement group. The upper basement group consist of granodiorite, marble and basalt lithologies. No fractured zone was identified in the lower part of basement which consist of phyllite lithologies. The gas tested in the BDA-1 exploration well has a composition of 78.9 mole % methane and a carbon isotope value (δ13C) for the CH4 of -39.4 ‰. The isotopic ratio plot of ethane and propane suggests that gas expulsion occurred at 1.4% Vitrinite Reflectance Equivalent (VRE) and gas was expelled from possible marine source from the nearest kitchen of Bandar Agung sub basin. Structurally, BDA-1 well is on a basement high adjacent to the possible kitchen to the Southeast of the well. Existing 3D seismic data shows “chaotic” amplitudes with several lineaments in the basement interval indicating the development of a fractured zone in this area. The discovery of fractured basement play has become more important today since discoveries in conventional reservoirs are decreasing. Better understanding of this unconventional play will improve the possibility of another fractured basement play discovery.