New Zealand Oil & Gas' half-year profit rose 30% as a result of returns from the Tui oilfield and almost $20 million in foreign exchange gains.
The oil exploration company made $54 million in the six months to December, compared with $41.4 million in the same period a year earlier.
Revenue increased 8% to $103.2 million.
Tui oil was fetching about $US152 a barrel in the first three months of the period, but prices later fell as low as $US40 a barrel.
Oil & Gas chief executive David Salisbury says revenue in the second half of the year will not be as strong.
Revenue will also be affected by falling production from the Tui field, in which Oil & Gas holds a 12.5% stake.
However, the Kupe gas field, in which the company is a 15% partner, is expected to start production later this year.
The company has no debt.