The reason for this is because America leads the world in offshore technology.
Overseas contracts vary according to a company's type of work and job location.
This is when the drilling company sends its employees overseas to work and then sends them back home when their hitch is completed. Then on your time off, you can tour the country you are working in or go home. Any time you commute back and forth to the US like this, all expenses are paid by the oil company that has leased the rig. Some will even give you a little carry-around cash for drinks, cigarettes, etc. On this type of assignment the employee and sometimes his entire family and household goods are moved into the country in which the drilling or work will take place, or into a nearby country.