Origin currently holds 85.23% of the 117 million OCA shares on issue and Origin executive director, commercial Bruce Beeren said the move was an attempt to tie up loose ends.

"85% ownership is neither here nor there when it comes to ownership so we basically wanted to confirm our position."

Under a pre-bid agreement with Santos Ltd, Santos has agreed to accept the offer in respect of 2.9 million shares, giving Origin a relevant interest in 87.69% of the issued capital. Origin has held a majority share in OCA since the mid 80's

Apart from Santos' commitment for 2.9 million OCA shares, the Santos Group holds a further 11.8 million shares in OCA. Santos will consider the Origin offer in respect of its remaining holding in OCA, taking into account the independent expert's report, which will accompany the target's statement, the recommendation of the OCA independent director and any other offers that eventuate.

The offer will not be subject to any defeating conditions.