Well, let's see the photo first....

This is the so called DeepWater Nautilus, an offshore drilling dig. Never heart about? Well, maybe something about its sister, the very similar DeepWater Horizon?

On the upper right part of the picture there is an oil drilling dig of Montana during year 1954. Proportions are correct.

And so what? Technology is improved, 56 years later we can build bigger, stronger, semi-submersible, ultra deep rigs. As long as we can manufacture higher sky scarpers, GPS driven cars, more powerful computers etc etc.

Yes, sure, but the point of this post is not technological improvement. The point of this blog is about the effort behind technological improvement.

Can you just imagine how many more people, how much more steel, how much more energy has been used to build the Deepwater Nautilus (97 meters height) than the Montana rig (16 meters height)?

Yes, that is the point. A barrel of conventional oil is more or less the same, and has the same amount of energy embedded, that is the energy we can use: 1.472.827 Kcal

So what's the difference between 1954 oil extraction and the 2010 oil extraction by Deepwater Nautilus?

The difference is that energy out of dig is the same 1.472.827 kCal as before, while energy used drawing out that same amount is more, much more. As explained by the difference of size and complexity of two machines in the photo.

EROEI is a number explaining this, it means Energy Return On Energy Invested, and it explains how much energy we spend to get new energy. EROEI 10:1 means we spent 1 to get 10, EROEI 1:1 means we spent 1 to get 1 (thus we did a useless job).

Well, this article asserts that EROEI of US oil was 100:1 in 1930's, that was 30:1 in 1970's and that was 18:1 in 2000.

OK, by the way, below a larger photo of Montana dig....:)