Wortel-1 is being drilled as a vertical well to test the equivalent limestone reservoir to the Oyong oil and gas field 7km west, in a fault-dependent structural closure.
The well is expected to take about 20 days to reach a total depth of 1500m.
The Sampang PSC JV comprises Santos (operator with a 40.5% stake), Singapore Petroleum (36%), Cue Energy (13.5%) and PT Petrogas (10%).