If it cannot sell the gas, Russia may have to shut down fields, which may affect future production.
Production in the first half of August was 36pc lower than during the same two weeks last year according to figures from ICIS.
Output since June has also been lower than in 2020, when demand fell due to the pandemic, noted Mr Marzec-Manser.
The slump in gas production comes after the International Energy Agency last week warned that Western sanctions against Russia were having only a “limited impact” on Russia’s oil production.
The IEA said demand had increased in India, China and Turkey even as exports to Europe and the US dropped, blunting the financial impact of sanctions on the Kremlin.
Russia’s oil production in July was less than 3pc below pre-war levels.
The fall in Russia’s gas exports has pushed gas prices in Europe and the UK to record levels, triggering a major cost of living crisis and soaring inflation.
This has also dented the impact on Russia’s coffers, as higher prices make up for lost volumes.
In a stark warning yesterday, Gazprom claimed gas prices in Europe this winter could climb above $4,000 per 1,000 cubic metres, which would equate to about €372 per megawatt hour – about 40pc higher than current high prices.
