Nigeria's first offshore oil field came on stream over Christmas in southeastern Rivers State, Nigerian TV reported on Tuesday. The Okono oil field, one of two deep offshore fields discovered by Nigerian engineers in 1983, has now been completed with the drilling of four wells, state television said. Anchored to the four wells is the temporary floating production, storage and overloading tanker vessels which can store up to 200,000 barrels per day and process another 20,000 per day. The commissioning of this oil field marks the beginning of Nigeria's own production of offshore crude oil, the television reported. The other Nigerian offshore oil field, Okpoho, is expected to come into service in the next eighteen months.