An ambitious and completely unscrupulous young man uses his guts and his guile to become one of the biggest oilmen in Oklahoma. In the end, after years of backstabbing and dirty dealings, he must fight the enemies earned over a lifetime to hang on to his empire.

Echo Nir's concerns - I'm not sure how you're going to get around the inevitable comparisons to Paul Thomas Anderson's brilliantly crafted "There Will Be Blood," unless you've got something radically different in terms of setting, character, or underlying story.

I see, in that case unless your planning on an epic rise from dust to power ala' Citizen you know who...

Better to focus the logline so it reflects his specific action that make him rich and the obstacle that he had to overcome to achieve it.

I would add also that in some ways the rise to power and money has been done many times in many ways. That's not to say it isn't a good idea rather I suggest thinking of how can you make it more interesting. Have you considered a woman as the MC then she would have to fight all the same battles a man would only with the added burden of other people's sexist behaviors.

This is going to sound a bit "out there" but this is a forum for suggestions of improvement and better to suggest than not I find. How about you give her an impairment such as; being def, having one leg being bi polar, etc...
The reason is that the external obstacles she or he will face are one layer of difficulty. Whereas the personal disability could add another layer for the MC to struggle with and as a rule of thumb the greater the struggle the sweeter the prize.

Gilgamesh and Nir Shelter, thanks for taking the time to crit my logline. The story is mostly about the MC's rise to the top, but that serves to set up the battle in the end. Good idea re: being more specific about the antagonist.