You have to first research oil rigs by selecting the blue tab (blueprin…

You have to first research oil rigs by selecting the blue tab (blueprints) and the 4th button (buildings), and the 4th option (refinery). Now you can build your oil rigs (refineries). You must also have 5 crew workers (yellow tab to buy more crew) and 2,400 material resources (red tab to buy more).