What determines potential oil drilling sites?

What land characteristics do they look for when deciding on a place to drill for oil?What determines potential oil drilling sites?
Well petroleum today typically occurs km's below the surface so the land does not always give you good characteristics for where exactly to look. However if you know extensive faulting and folding have occured where oceanic sediments are located, this might be a good place as oil/gas accumulate in high areas and faulting aids in the migration of petroleum. Also in large sedimentary basins, offshore where you know the depositional processes have been occuring for a long time. But basically you can have completly flat land and tons of oil underneath. This is why you need to apply exploration to find out what might be subsurface.