Publications

This paper presents the successful application of the Advanced Mass Spectrometer (AMS) technology in drilling wells targeting oil bearing reservoirs which consist of laminated clastic rocks in an oil field offshore Indonesia. During the 2019 drilling campaign, Medco Energi drilled two wells targeting the Gabus sandstones reservoir for the oil rim production in the Belanak field. The main challenge of the field was the high presence of CO2 in alternating sandstone and shale within the reservoir interval. This rather complex layering poses some degree of difficulties in identifying vertically non-connected layers of oil and water from these CO2 bearing reservoirs. The AMS significantly helped optimizing the perforation plan to de-risk the CO2 presence in the production intervals. AMS was utilized to support logging-while-drilling (LWD) measurement and downhole sampling optimization. This tool also enabled identification of minor variations of gas composition and variation within the overburden interval, and down toward the targeted reservoir, it also successfully recognized reservoir fluids such as condensate, oil, oil-water-contact and the water table beside clear indication of the presence of CO2. Application of AMS provided gas data that could be used in fluid typing with confidence while the wells were drilled until they reached Total Depth (TD). Moreover, the technology was also useful as one of the bases for perforation program decision, even if LWD and wireline data are not available due to tool failure.