As a result, the Perth-based explorer said it had agreed with operator Beach Petroleum to drill three more appraisal/development wells at the field, which began production in November.

Drilling is expected to start in early September using a Hunt Energy rig.

Cooper said the three wells were targeting 2.58 million barrels of recoverable oil reserves, over which Beach has a 75% claim and Cooper has 25%.

If successful, Cooper estimates the ultimate recoverable Callawonga reserves would increase from 1.6MMboe to 4.18MMboe.

To date, Callawonga has produced about 250,000 barrels of oil.