Premier said it booked a pre-tax charge impairment of $652 million after reducing Solan’s proven and probable reserves by 10 million barrels.

The downgrade follows problems in the eastern part of the reservoir, home to the P2 well, which came on stream in August.

Chief executive Tony Durrant said poorer than expected reservoir quality and more complex faulting has meant that the water injection well “is not connecting with the oil leg as efficiently as it should”.

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