The FRMO quarterly call [pdf] had some thoughts on optionality of unlevered oil producers:
"Let’s take oil as an example which, I should warn you, isn’t necessarily reflective of what we might have in this fund. Let’s say I wanted to buy an at the money call option on oil. Oil is $30 a barrel, and I want to buy a call option exercisable at $30, and I want it exercisable over the course of 20 years. The writer of the option would calculate the strike price as known, the option expiration period of 20 years, the volatility of oil and then ask some truly astronomical sum as a price for that option. But, effectively, you can buy that option in an unleveraged commodity company, and you get it for free. If you can find one that’s making some money, if you think about it, it’s actually a negative premium."