MOSCOW, June 3 (Reuters) - Chevron ( CVX )-led

Tengizchevroil (TCO) said on Monday it completed a major

maintenance at giant Tengiz oilfield in Kazakhstan in May, while

already mapping out plans for the next maintenance in August.

In accordance with its policy, TCO has not revealed the

dates of the maintenance, nor production volumes.

Two industry sources said that TCO restored oil output at

the end of last month to around 80,000 metric tons of oil per

day from some 59,000 - 63,000 tons per day in early May.

Sources also said that TCO reduced total oil production last

month by around 312,580 tons from April to a daily average of

66,926 tons (532,732 barrels per day).

TCO exports oil mainly via Caspian Pipeline Consortium's

Black Sea terminal near Russian port of Novorossiisk. Some 5% of

its crude exports also go through the Baku - Tbilisi - Ceyhan

pipeline.

Chevron ( CVX ) holds a 50% stake in TCO, Exxon Mobil ( XOM ) owns

25%, Kazakh state firm Kazmunaigas holds 20% and 5%

belongs to Russia's Lukoil.