Fishing operations to retrieve a severed drill string encountered additional borehole stability problems, according to executive director Gary Jeffery.

“An attempt was also made to run wireline logs to the top of the parted drill string, but logging tools could not pass below the top of the Anderson Formation at around 1700 metres,” he said.

Completion of wireline logging was a prerequisite for proposed drill stem testing of three hydrocarbon show intervals in sandstones of the Anderson Formation and Fairfield Group.

“Since borehole conditions have deteriorated to a point where no further logging or testing is possible, the decision has been made to abandon the current hole drilled to a total depth of 3466m and suspend the Valhalla well at the casing shoe depth of around 900 metres,” Jeffery said.

A cement plug will be placed at the 244mm casing shoe, which will enable a future sidetrack and further evaluation of results to date from drilling the Valhalla prospect.

Jeffery said the inability to test the current well was disappointing, but the early indications from the well were positive.

“The presence of numerous oil and gas shows, and anomalous log responses sufficient to support proposed drill stem testing across three geologically separate intervals, in the Valhalla well are very encouraging for future exploration in EP371,” he said.

The well bore stability and drilling problems encountered will be further investigated to enable more efficient future drilling operations in the Valhalla area, according to Jeffery.

The drilling rig is now being mobilised to the next well in Arc’s Canning exploration program, the Yulleroo-2 appraisal well location in the basin’s west.