The offshore Tengiz oil field should return to usual production rates within a week, Kazakhstan’s energy minister said today, as quoted by Reuters. The Tengiz field stopped pumping oil earlier this month after a fire destroyed three transformers. The incident has cost Kazakhstan 7.2 million barrels in lost oil production. Earlier this week, the power distribution system of the field was restarted, the consortium operating the field said in a statement. The Chevron-led group also said it had begun restarting oil production at the field. Tengiz…