The big international oil companies are reporting one of their worst annual performances in decades and signaling that the pandemic could continue to challenge their businesses in 2021. Exxon Mobil Corp. XOM 1.58% and BP BP -6.57% PLC on Tuesday disclosed annual losses of $22 billion and $18.1 billion respectively, following Chevron Corp. CVX 0.75% , which on Friday reported a $5.5 billion loss for 2020.

Exxon posted its fourth consecutive quarterly loss for the first time in modern history, driven by a more than $19 billion write-down. Excluding the impairment, Exxon turned a quarterly profit of $110 million. BP reported a replacement cost profit—a metric similar to the net income figure that U.S. oil companies report—of $825 million for the three months ended Dec. 31, from a loss of $4 million in the year-earlier period.

Covid-19 has sapped demand for oil, hitting prices and prompting the world’s biggest energy companies to slash spending, cut jobs and write down the value of their assets. Amid the crisis, Exxon and Chevron discussed a merger of the U.S. oil giants last year, according to people familiar with the matter, although the talks didn’t progress.

“The past year presented the most challenging market conditions Exxon Mobil has ever experienced,” said Chief Executive Darren W. Woods.