HOUSTON, Feb 22 Reuters Exxon Mobil Corp XOM.N on Wednesday warned in a securities filing of potential risks to its Kazakhstan oil operations, which provided 2.5 billion in earnings last year.

Threats to Kazakhstan oil exports have been in the spotlight since Moscow invaded Ukraine a year ago this week. Exxon and Chevron are major holders in the Central Asia country39;s oil production and related export pipeline.

Kazakhstan shares a 4,750 mile 7,644 km border with Russia and its oil exports travel mainly through a Caspian Pipeline Consortium CPC line through Russia and lands at a Russian Black Sea export terminal.

Any closure of the CPC pipeline or terminal would shut in more than 1 of global oil supply and cost its producers billions of dollars in lost income.

Exxon said its stake in Kazak oil fields produced 246,000 barrels of oil and gas per day last year. That oil provided aftertax earnings of about 2.5 billion, the filing said.

Exxon could experience a loss of cash flows of uncertain duration from its operations in Kazakhstan, the filing said, if oil exports through the CPC pipeline are disrupted, curtailed, temporarily suspended.

The U.S. oil major owns a 25 interest in the Chevronled Tengizchevroil TCO oil production joint venture, which controls the Tengiz and Korolev oil fields in Kazakhstan, and a 16.8 working interest in the Kashagan field.

Chevron produces around 380,000 bpd, or more than 12 of its total output from Kazakhstan. The company aims to boost…