Total green is the only way to settle it - the cost for a mile of road (2M?) is almost all enegry and people cost - tarmac, machines, steel for the machines, etc. - this balances against the greater fuel flow of the helo, and I would bet on the lesser flown routes, the helo wins. Furthermore, building a bridge to an oil rig is really an environmental disaster>
The relative green-ness of a helo is quite nice, thank you. And a helo is lot more fun than a bull dozer is to drive.