I don't mean to call anyone out or step on any toes, and I don't entirely disagree with TaperPin's sentiment....HOWEVER...Tread lightly. It goes without saying, If the oil field is only leasing the roads, it's still considered private property. Many of the oil companies and oil field workers couldn't care less that you're there, and very well may drive past you and not give it a thought. However, there are plenty of landowners out here that could easily be nominees for the jerk of the year award, and that's putting it very politely. This could possibly be exacerbated if you're an "out of stater".
Like I said, I'm not advising for or against the "beg forgiveness" strategy, but I'd hate to see you get yourself into trouble and your hunt ruined. I suppose my point is just to be aware of the risks of this strategy.