Is Friday prayer obligatory for oil field workers who reside there for five weeks, and if they perform it, is it valid and sufficient in lieu of Dhuhr prayer, or must it be re-offered as Dhuhr?

What appears is that you are obligated to establish Jumu'ah in the aforementioned place, and you are not obligated to repeat it as Dhuhr, because it is your obligatory prayer and you have already performed it.