Bow Energy today said as of this morning, Donga-4 was running in the hole with the drilling assembly and conditioning the hole, after the rig was repaired over the weekend.

Before the problems, the well was at a depth of 1475m, estimated to be some 90m above the primary target, and was continuing to run several metres high to prognosis.

But on Saturday evening, the rotary clutch failed and the drilling assembly pulled back to the casing shoe while repairs took place.

Bow said drilling is expected to resume later today and the primary target penetrated in the next 24 hours.

The primary target is the Triassic aged basal Moolayember sandstone, which was productive at Donga-3.

Bow said if Donga-4 is successful, the rig will immediately move to drill the Donga-5 appraisal well, about 550m north.

Located 1km southwest of Donga-4, the Donga-3 well was drilled in October last year and on test recovered 23 barrels of light oil and 39bbl of formation water from the Donga sandstone.

Near the end of an extended production test, the well was flowing about 50bbl of fluid per day, of which a quarter was oil, and was interpreted to have intersected the oil-water contact of the field.

A recent assessment by Bow indicated the field had the potential to contain 2.2-5 million barrels of oil, with recovery depending on adequate water drive.

Bow holds an 85% interest in ATP 805P, while VicPet owns 15%.