The platform was in the Chinese port of Zhoushan for planned maintenance and is due to drill a well at the Yuzhno-Kirinskoye field, the agency said.
Washington put the field under sanctions in 2015 for Moscow's role in the Ukraine crisis.
Industry sources and analysts have said that natural gas from the fields off Sakhalin could be used for a pipeline to China. Moscow and Beijing agreed in early 2022 to boost supplies of Russian gas via a new pipeline, which would export 10 billion cubic metres (bcm) of gas a year.
The field, part of the Kirinsky block in the Sea of Okhotsk, also contains oil.
The sanctions are related to exploration for or production of oil or gas in Russian deep waters.
The U.S. sanctions prevent foreign companies from tapping hydrocarbons at such fields, and possible gas exports from Yuzhno-Kirinskoye could indicate that Russia has learned how to get around the sanctions.
Russia now supplies gas to China via the Power of Siberia pipeline, which began operations in December 2019 under a 30-year contract worth more than $400 billion. It is due to reach full capacity of 38 bcm a year in 2025.
According to Gazprom's data, Yuzhno-Kirinskoye's reserves amount to 711.2 billion cubic metres of natural gas, 111.5 million tonnes of gas condensate and 4.1 million tonnes of oil. Production of gas is seen there at 21 bcm per year.
The rig was put into operations in 2011. It is capable of carrying out exploration and production drilling of gas and oil wells to a depth of up to 7,500 metres at sea depths in the range of up to 500 metres.
