Western buyers have stopped buying oil from Russia as a result of the invasion of Ukraine.
The company's production was 560,000 barrels a day lower in May than it was in February.
In February, the company was producing 3.8 million barrels a day, but that had fallen to 3.24 million by the middle of the month.
Russia's oil output was 830,000 barrels a day lower over the period, with the majority of the fall coming from the state-owned oil company.
Russian oil was banned by the US and UK.
The European Union wants to ban imports by the end of the year. Many companies on the continent have stopped doing business with Russian energy.
Exxon Mobil pulled out of Russia, including from the giant Sakhalin-1 project. Between February and May, production at Sakhalin-1 dropped by more than 145,000 barrels a day.
Russian producers are getting used to the restrictions and are increasing production in May. Analysts say India has been a key buyer of Russian oil.
Higher oil prices have helped Russia bring in more money through energy sales despite sanctions.
In the first four months of the year, the current account surplus rose to $96 billion, despite a fall in imports.
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