To which extent does the EIA study represents a governing factor in oil & gas projects?

I personally think such study is definitely important considering environmental impacts when deciding whether or not to proceed with a project.
Secondly, in case such study is not made and it may result to major delays or maybe failure of the project.
So its always a good idea to have this at planning stage so that any diversions, amendments etc.
can be made at right time

The biggest part of my career was in Oil & Gas (19.5 years) in a parastatal company.
Pre initiation - an Environmental Impact Study is required before the government will allow any drilling activities.
With Climate Change and Global Warming - more 'watchdog' companies keep a close eye on Oil & Gas activities.
With Global Change - specifically to fuelling stations - a white paper is out that requires32 ppm max gas emmission from fuel brands used by consumers.

I am not in the sector of the oil and gases, I am in the sector of IT, but any technical study make you expert in that technical field but not in the managerial field.