The Islamic State (IS) militant group has destroyed a crucial flow tank at the Ajil oil field near Tikrit, rendering the entire field offline for at least a year.”Ajil produces oil from the wells and gathers it into one flow tank from which we used to pump the crude to Kirkuk,” said a senior official from the state-run North Oil Company (NOC), which operates the field. “That flow tank does not exist anymore.”The tank was hit during a rocket attack by IS militants late Monday and early Tu…