BHP confirmed on Wednesday it had smashed full-year export guidance in its flagship iron ore division, while either beating or meeting guidance in the petroleum, copper and coking coal businesses.

The higher-than-expected sales in the company's core assets are expected to more than offset price falls in several of those commodities, and push BHP towards full-year net earnings of more than $US14billion.

Crucially for investors, the better-than-expected production levels should push BHP to the brink of its $US25billion net debt target. Mr Mackenzie has nominated that debt target as the impetus for considering a special round of shareholder returns such as share buybacks.

Most analysts were on Wednesday expecting buybacks to be announced next month, albeit in a more modest fashion than the $US6billion round of buybacks that was tipped earlier this year.

BHP's iron ore division began the 2014 financial year promising to export 207 million tonnes, but ultimately shipped 223 million tonnes and produced 225 million tonnes.

The strong result was built on a campaign of improving and clearing bottlenecks in rail and port infrastructure, particularly around Port Hedland.

BHP indicated on Wednesday it was not finished sweating those infrastructure assets, forecasting that it will grow iron ore exports again in 2015 to reach 245 million tonnes.

UBS analyst Glyn Lawcock said the 2015 iron ore guidance was much more aggressive than analysts had expected, and was one of the major highlights in a strong set of results.

''That is a lot of additional volume at pretty good margins that is going to hit the bottom line next year for iron ore, and this has all come at very low capex so that is a very commendable job by BHP's iron ore business,'' he said.

BHP's second-biggest earner, petroleum, also performed better than expected by producing 246 million barrels of oil equivalent during the 2014 financial year.

The better-than-expected production levels completed a good year for the petroleum division, which saw natural gas prices in the US finally bounce back and spend much of the past six months above $US4 per unit.

The outlook for petroleum production in 2015 was not as strong as hoped, with BHP predicting production to grow modestly to 255 million barrels of oil equivalent.

But Mr Lawcock said the main driver of that lower-than-expected guidance was the gas assets, whereas production of the higher-value liquids would still be in line with original expectations.

The coking coal mines in Queensland continued to export rapidly despite low commodity prices, with production of 45 million tonnes easily beating analysts' expectations of 43.5 million tonnes.

Copper production was in line with expectations at 1.7 million tonnes.

Mr Mackenzie said the numbers added up to a 9 per cent rise in production across the entire suite of products. ''We expect to maintain strong momentum and remain on track to generate group production growth of 16 per cent over the two years to the end of the 2015 financial year,'' he said.

There was little new information about the prospect of a demerger at BHP, with Mr Mackenzie saying he was focused on ''value over volume'' as he considers the next phase of ''portfolio simplification''.

While the most important commodities performed well, there were some underwhelming performances among the non-core assets. Nickel production was 7 per cent lower than the prior year, which was unfortunate given nickel prices have boomed over the past six months in particular. BHP reported its average received price for nickel was 20 per cent higher in the second half of the financial year compared with the first half.

Production at the Nickel West assets in Western Australia was 4 per cent lower over the year, due mainly to the closure of the Perseverance mine in December. The Nickel West assets remain in the shop window.

BHP also warned it could wear a charge of up to $US1.3billion at its financial results in August. The expected charge was linked to redundancies at several operations, impairments on the South African thermal coal assets and impairments on certain mine site rehabilitation costs.