Operator Bow Energy today said the DST of the well, in permit ATP805P, over the interval 1563 to 1568m recovered the small amount of light sweet crude and drilling mud with no formation water present.

The Brisbane-based company said initial review of the DST charts indicated there appeared to be some blockage during the test, which restricted the flow of fluids into the tool.

A detailed analysis is due to be carried out today.

Bow Energy said at 8.30am (EST) this morning the well was at 1578m and drilling towards total depth, which will be followed by wireline logging.

Once the wireline log data and DST results are analysed, the ATP 805P joint venture will decide whether to case and suspend the well for future production.

Bow said preliminary correlations indicate the top Donga sandstone on Donga-1 is at least 18m above the oil water contact of the field, which is interpreted to have been intersected by Donga-3.

It has previously said if Donga-4 were successful, the rig would 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. The well was interpreted to have intersected the field's oil-water contact.

A recent assessment by Bow indicated Donga could 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%.