The Perth-based company today said average flow rates on September 11, prior to the start of running tubing, were 81 barrels per day of oil, 1107bpd of water and 106 million cubic feet of gas per day through a 20/64-inch choke.

Aurora said the 92% water cut was well above the expected 50% obtained from testing of the equivalent zone in the discovery well and is inconsistent with logs.

Company secretary Alex Neuling said this is most likely because the fraccing operation penetrated the underlying water zone, despite being “specifically designed not to do so”.

“This first development well in the North Belridge Oil Discovery will produce oil at a rate significantly below the expected 500bopd due to the unintended connection of the reservoir to water during the frac operation,” he said.

“On the positive side, the vertical pilot hole drilled approximately 180 feet of log interpreted oil pay and the horizontal well has confirmed recoverable oil over the almost 5000ft horizontal length of the well, which increases confidence in the reserve potential of the discovery.”

Aurora said the information gathered from the well would be applied to the next development well in the field, which is expected to start drilling in October or November.

Meanwhile, the company said clean-up flow operations through a separator have continued at its Dolores-1 well as part of its onshore Texas gas project in West Black Lake.

Aurora said most frac fluids have been recovered but gas flow rates have continued to fall to about 600,000 cubic feet of gas per day.

Testing at Delores-1 has now stopped so a workover rig can clean 39ft of fill out of the well and to reset production tubing about 200ft deeper in to the reservoir.

Aurora said preliminary data had revealed the frac had been ineffective and did not increase gas flow at the level expected.

“A further period of several days of flow, followed by a pressure build-up test, will enable the effectiveness of the frac to be properly evaluated,” the company said.

“Further action will be considered when the data has been analysed.”