> Speculating on oil price happens mostly on paper (derivatives and other contracts). It is cheaper than paying for its storage. Speculating using futures is t

> Speculating on oil price happens mostly on paper (derivatives and other contracts). It is cheaper than paying for its storage. Speculating using futures is the (roughly) the same marginal cost as speculating by storing it in tankers and storage depots. Otherwise there would be an arbitrage opportunity where you could empty your tanks today, save the storage costs, and get the same quantity back x months in the future.