Publications

Mubadala Energy's recent drilling campaign in the Andaman Sub-basin, offshore Aceh, Indonesia has resulted in material gas discoveries, most notably in the South Andaman Block. The wells within the South Andaman Block uncovered substantial quantities of gas, highlighting the basin's potential. In addition to routine mud logging, real-time mud gas isotope analysis was conducted. The primary objective of this analysis was to assist with post-well evaluation, particularly in assessing charge focus, seal competency, source type and the thermal maturity of the gas. In the event of a dry hole, it was also anticipated that the isotope profile through the overburden would significantly assist in differentiating between general seal failure and the absence of thermogenic charge.

In a basin rich in direct hydrocarbon indicators and with significant shallow gas present above certain traps, questions inevitably arose regarding the potential presence of low-saturation gas prior to drilling. The real-time mud gas isotope data of the recent Andaman area discovery wells have consistently shown that gas isotopes present increasing positive values starting several hundred meters above the reservoir, giving early and strong indication for high-saturation gas accumulations to be present in the targeted reservoir. In contrast, dry hole cases associated with seal failure and charge issue, as observed in Malaysian well analogs, exhibit distinct isotopic trend with depth that aids in differentiating productive from non-productive drilling outcomes.

These results emphasize the importance of real-time isotope logging in hydrocarbon exploration, providing valuable insights into methane isotope behavior and its contribution to geological research. By offering a comprehensive methodology for gas sampling and evaluation, these findings have significant implications for future exploration efforts in the Andaman Sub-basin and beyond.