Cooper Energy-led JV makes gas discovery offshore Otway

The 50-50 joint venture of Cooper Energy Ltd., Adelaide, and Japanese entity Mitsui E&P Australia has reported a natural gas discovery with the Annie-1 wildcat in permit Vic/P44 in the Victorian section of the offshore Otway basin.

190906 Cooper Annie Map

The 50-50 joint venture of Cooper Energy Ltd., Adelaide, and Japanese entity Mitsui E&P Australia has reported a natural gas discovery with the Annie-1 wildcat in permit Vic/P44 in the Victorian section of the offshore Otway basin.

Operator Cooper said the well encountered a gross gas column 70 m thick in sandstones within the Late Cretaceous-age Waarre C formation primary target. Net pay thickness was measured as 62 m.

The deeper Waaree A sandstone secondary target was water wet.

Wireline logging data collected in Annie-1 indicate a consistency with nearby producing fields.

David Maxwell, Cooper managing director, said Annie-1 is the first offshore gas exploration well the company has drilled in Australia and the first of an $80-million (Aus.) campaign by the Cooper-Mitsui JV this year. The discovery also is the first made in the offshore Otway in 11 years.

The well is in the inshore section of the split Vic/P44 permit about 9 km offshore in 58 m of water. The discovery lies between producing Henry field 15 km west in production licence Vic/L30 (in which Cooper has 50% interest) and the now-depleted Minerva gas field 11 km east in Vic L/22 (in which Cooper has 10%).

Maxwell said the JV will complete subsurface assessment and analysis of the Annie discovery during the next few months to provide estimates of the field size and determine the best path to development, including the drilling of an appraisal-development well. Favorable results could see Annie brought on stream during the second half of 2021.

The Cooper/Mitsui JV already produces gas from nearby Casino, Henry, and Netherby fields and Annie’s close proximity to this subsea infrastructure enhances the economics of future development.

Minerva field

Separately, Cooper said the BHP Petroleum Ltd.-operated Minerva field has ceased production. This has triggered acquisition of the onshore Minerva gas plant by the Cooper-Mitsui JV that was announced in May 2018. BHP had 90% of the plant and Cooper Energy, 10%.

Completion of the sale is expected to take 3 months, with the plant being transferred in the meantime to the Cooper-Mitsui JV on a care-and-maintenance basis.

Cooper said once the transaction is completed, the plant will be connected to and process gas from Casino-Henry-Netherby fields as well as, potentially, other Otway fields that may be developed, including the latest Annie discovery.

Planning for engineering and construction works to connect the plant to the Casino-Henry-Netherby gas gathering system is well advanced. The 18-month project will require modification to the Minerva plant, including connection of onshore pipelines and control systems.

The Minerva plant has a processing capacity of up to 150 terajoules/day of gas and is capable of handling hydrocarbon liquids associated with the gas.

Cooper Energy’s significant presence in the offshore Otway is similar to its extensive acreage position in the Gippsland basin offshore eastern Victoria, which was boosted by the award of new permit Vic/P75 earlier this week.

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