Sure, it is a saleable asset. But you find the price only when you actually sell. You can estimate in principle how much your oil fields are worth, but that does not go into your accounting books, just like if you are a landlord you don't mark to market the price of your rental properties. And if your accounting does not reflect the current market value of your reserves, numbers like "50 cents on the dollar" are plucked out of thin air by journalists who want to shock readers.