Output over the nine-month period totalled 184.1 million barrels of oil equivalent, a 4% drop compared to the same period a year earlier when output totalled 192.5 million boe.
BHP blamed the fall in output on the deferral of development activity at its onshore US unconventional assets which offset steady production from its conventional portfolio.
The company's onshore liquids volumes in the US fell 4%, to 38.7
