But BHP says the fundamental outlook for oil remains positive despite the late-2018 Brent tumble tumble and is underpinned by rising demand from the developing world and natural field declines.
It thinks the long term outlook for gas is also positive and "depleting domestic gas supplies in some major consuming markets will help LNG to grow faster than overall gas demand".
Total revenue from petroleum for the half year ended December was US$3.2 billion, with underlying EBITDA of $2.3 billion a rise of $625 million over the same period in 2017, D&A of $818 million, underlying EBIT of $1.44 billion and capital expenditure of $339 million.
The oil profit was thanks to higher average realised prices with crude at $69.91 per barrel in 2018 compared with $54.27/bbl the previous corresponding period, natural gas at $4.67 per million cubic feet compared $4.13MMcf and LNG at $10.19/MMcf compared with $7.46/MMcf.
BHP saw higher uptime in the Gulf of Mexico and Australia and increased tax barrels in Trinidad and Tobago were "more than offset by planned Pyrenees dry-dock maintenance and natural field decline across the portfolio," it said.
There was however additional maintenance at its Australian assets worth $60 million and higher exploration expenses of $37 million due to the Ocean Bottom Node survey acquisition in the Gulf of Mexico and an expensing of the Bongos-1 and Conception-1 wells over mechanical failure.
It expects conventional petroleum unit costs to increase 10% to $11.14 per barrel of oil equivalent thanks to planned maintenance and lower volumes in the second half of financial 2019.
Unit cost guidance for financial 2019 is unchanged at under $11/bbl assuming an exchange rate of A$0.75 to greenback.
In the medium term it expects unit costs of less than $13/bbl thanks to field decline.
Earlier this month it approved the development of Atlantis Phase 3 in the Gulf of Mexico which planned to increase production by 38,000bopd at its peak from eight new wells. Joint venture partner BP sanctioned the project.
Spend on exploration for the half-year ending December was $316 million, with $166 million expensed, and activity focussed around the US Gulf of Mexico, Trinidad and Tobago, and Mexico with a $750 million spend planned for the full financial year.
Further delineation of Samurai is ongoing and in the southern part of the Wilding Sub-basin with BHP in assessing the potential resource with further appraisal; drilling is now expected in financial 2020.
In the Western Gulf of Mexico it expects processed data from seismic delivered during the March 2020 quarter.
Phase 3 of Bingos in Trinidad and Tobago has been accelerated and drilling will begin in the second half of the financial year with Phase 3 to test wells on three prospects in the northern licence area.
In Mexico it spud Trion-2DEL appraisal well in November 2018 and after positive results plans an additional appraisal well 3DEL to "further delineate the scale and characterisation of the resource " and expects to drill in the second half of the 2019 calendar year.
It is also looking to Eastern Canada after bidding successfully for licenses in October in the Orphan Basin and is now working with local petroleum boards to meet regulatory requirements.
It will pay an interim dividend of US$0.55 with an additional 18cs above the maximum 50% payout policy
