The new offshore Otway Basin gas discovery is expected to be brought on stream in 2021 itself owing to existing subsea infrastructure at nearby fields and future access to the Minerva Gas Plant


Image: Map showing the Annie-1 well where the new offshore Otway Basin gas discovery was made (Credit: Cooper Energy)

Cooper Energy and Mitsui E & P Australia have made a new gas discovery in the offshore Otway Basin in Victoria, Australia following the drilling of the Annie-1 exploration well.

The gas discovery has been made in the VIC/P44 block where Cooper Energy is the operator. Cooper Energy and its partner each have 50% stake in the offshore Victorian block.

According to Cooper Energy, the Waarre C and Waarre A Formation sandstones were penetrated within the Annie-1 borehole. The company said that Waarre C primary target was intersected at 2,241m measured depth rotary table (MDRT), which is made up of a gross gas column of 70m with gas-on-rock at its base.

The net pay thickness of the gas column is 62m, said Cooper Energy.

On the other hand, the deeper Waarre A sandstone was intersected at 2,341m MDRT and was water wet, said the company.

Drilling of the Annie-1 well began earlier this month using the Diamond Offshore Ocean Monarch drilling rig. Located nearly 9km off the Victorian coast, and contained in a water depth of 58m, the Annie gas discovery is now the first by an offshore well in the Otway Basin in 11 years after the nearby Netherby field, which was discovered in 2008.

The new offshore Otway Basin gas discovery likely to begin production in 2021

Currently, Cooper Energy and Mitsui E & P Australia draw gas from the Casino, Henry and Netherby fields located near the new gas discovery. The existing subsea infrastructure and future access to the Minerva Gas Plant is expected to help in bringing the Annie gas discovery into production in the second half of 2021.

Cooper Energy managing director David Maxwell said: “Annie-1 is the first offshore gas exploration well Cooper Energy has drilled in Australia and the first of an $80 million drill campaign by the Joint Venture this year to find new gas supply for south-east Australia.

“We are very pleased with the success at Annie. It is very encouraging for future exploration in the offshore Otway Basin and for our strategy to build gas production around the hub of the existing Minerva Gas Plant.”

The Australian oil and gas company said that it has wrapped up wireline logging operations that are needed to collect pressure and sample data to inform estimates of the resource volume and for determining gas composition.

The company further said that the data collected in Annie-1 is in line with adjacent analogue producing fields. In the next few months, Cooper Energy plans to complete the subsurface assessments and analysis of data to refine its estimates of field size and to make announcements about the field development.