Without elaborating on the nature of the problems identified during commissioning, Origin said first gas sales were now due late next month, with production ramp-up and plant testing continuing into June.

“While there has been good progress, the commissioning phase continues to reveal a significant number of unexpected construction defects, which must be remedied before the plant commences production,” managing director Angus Guthrie said.

In January, Origin said product sales would start in March, while full production was expected later this month. These plans were already a month behind schedule, due to delays connecting the accommodation support vessel, Safe Astoria, to the Yolla A Platform.

Despite the most recent delays, Origin said commissioning was continuing. Gas from the Victorian grid was introduced to the onshore gas processing plant at Lang Lang early last month for the final phases of equipment testing, preparations, and plant dry-out before introducing raw gas from offshore.

Origin said another significant milestone was achieved when Victoria WorkSafe Authority completed its assessment and verification for the Lang Lang plant, and subsequently granted the company a three-year operating licence.

Work is also continuing on the Yolla platform, with the Safe Astoria vessel remaining alongside to provide logistical support.

BassGas is a partnership between Origin Energy as operator (42.5%), AWE (30%), CalEnergy (15%) and Wandoo Petroleum (12.5%).