The offshore SW Java constitutes one of the few remaining frontier petroleum provinces of Western Indonesia. Open to the Indian Ocean, the area is also subject to disruptive sea and weather conditions, lack infrastructure for logistics support, and neighbours a protected national park. A handful of exploration wells in the 50m water depth range have been drilled previously in the area. While all past operators have opted for high-cost drillship or semi-submersible rigs, does a cost-optimized solution can be evidenced and can it be implemented successfully?

An extensive and high resolution digital database of the last 25 years of sea and weather data from the offshore SW Java was assembled and used to perform an advanced statistical assessment of the area. The objective of the study was to constrain the uncertainties around the actual environmental conditions during the most favourable window of December-March, and feed an operational and financial risk model associated with the mobilization of a Jack Up rig during this period.

The assessment was able to evidence the low risks associated with the use of a Jack Up rig during this given period to drill shallow to medium deep targets (<2500m) in shallow water (<100m). On this basis, the Cula-1 wildcat well was eventually spudded early February 2016, in 65m of water and with a target at approximately 2400m-ss, using the Soehanah Jack Up rig. The operational phase lasted less than 2 months and within the Jack Up rig based approved budget. The environmental assessment was notably instrumental in getting it right first time, avoiding any waiting on weather during rig mobilization and demobilization, and bringing efficiency for jacking up and jacking down. No Lost Time Incident were experienced during the operations, drilling being even performed faster than planned. All operational objectives were met, and the well delivered key geological inputs to the exploration team.

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