By David Winning

SYDNEY--Santos Ltd. made a half-year net loss as it booked hefty writedowns on its assets, illustrating how this year's rout of the oil price and impact of the coronavirus pandemic is hurting the energy sector.

Santos reported a net loss of US$289 million for the six months through June, compared to a profit of US$388 million a year earlier. The result was dragged down by a US$756 million pretax impairment of assets, mostly against its GLNG project that turns coal seam gas into liquefied natural gas for export.

Directors of the company declared an interim dividend of 2.1 U.S. cents a share, down from the payout of 6.0 U.S. cents at the corresponding stage of 2019.

Santos had signaled the writedowns on July 20, including an impairment of exploration assets mainly located in the Cooper and Amadeus Basins. Woodside Petroleum Ltd. last week reported a US$4.07 billion first-half loss after lowering oil-price assumptions used to value its assets, and Oil Search Ltd. has also said it expects to take an impairment charge in its half-year results.

The scale of the writedowns masked a strong operational performance by Santos, with oil and natural gas production of 38.5 million in the six months through June representing a new record. Santos has benefited from higher domestic gas production in Western Australia, robust production from onshore fields and early benefits from its recently completed purchase of Northern Australia assets from ConocoPhillips.

Half-year sales revenue fell by 16% on year to US$1.7 billion as weakness in energy prices more than offset higher domestic gas and liquefied natural gas revenue.

Write to David Winning at david.winning@wsj.com