I'll readily confess I failed to read much of Capital. Then again, I'm no marxist.
Since you seem to be somewhat of an authority about this, can you confirm that Marx ignores "rent" *as far as the theory of value is concerned*? Saying that parasites extract "rent" from the "profit pool" is something else than saying that the value of certain commodities is partly derived from the scarcity of the resource, just like "rent". It's not merely an academic distinction: resources are not likely to be conserved if they're not thought to be intrinsically valuable.

I don't know what the correlation between the price of oil and oil industry profits is supposed to show. It's hardly surprising.

I don't think I am much of an authority, but yes, rent is ignored insofar as it comes into play only much later, when lots of people (some Marxists included) have already stopped reading.

What you write about the value of commodities and them being valuable in themselves is exactly what Marx is criticising in the very first chapter of the first volume of Capital: One needs to distinguish first and foremost between "use value" and "exchange value" (and then also between exchange value and price).

The only value that commodities have in themselves is use value (the physical properties that make them useful to us), but they have this use value independent of whether they are commodities or not - a loaf of bread (ideally) is the same, whether I made it only for my own consumption or for selling on the market.

On the other hand, commodities have exchange value (or for short just "value") only because they are commodities, and they get their value in the process of exchange against other commodities; therefore, their individual value is relative to all other commodities. Gold (or possibly any other commodity) is then attributed a special place in this relation of values because it is used as a "universal equivalent", that is: one central commodity against which all other commodities are valued, and this brings with it a lot of confusion, which is only made worse when, later, money supersedes gold (or what ever commodity was used) as the universal equivalent, seemingly taking on a life of its own, making possible the creation of capital ...

But I really can't explain even the first chapter (and especially not the first chapter) of Capital in some short paragraphs.

If you look closely, the graph does not state a correlation between oil price and absolute profits of the oil industry, but between oil price and relative profits of the oil industry, which means that when the oil price is high, the oil industry gets higher rents, compared with the rest of the economy and independent of how the rest of the economy is doing, which I think is at least a little bit surprising, because the inverse is also true: low oil price means low rent, irrespective of the general state of the economy.

I've read much of the first volume and I think I understand what Marx is trying to say in this particular instance... but I don't think it's a useful way to think about finite resources.

As to the graph, you're right: I misread it.
But you might be misreading it as well: I don't know what data it uses exactly but I guess it's about the profits of companies listed on some exchanges. So the comparison is not with the rest of the economy (listed companies aren't representative). Also, IOC profits comprise more than their rent. Finally, the IOC's rent is not representative of the gross oil rent.
That the correlation is so good over a long period is indeed surprising. But I still don't see why you say it's remarkable there is some correlation. Are you saying it supports Marx's notions?

Well I think it is useful for critiques of Capitalism and as a starting point for thinking about overcoming it (note that Capital's subtitle is Critique of Political Economy).

About the graph: I was just saying that the kinds of correlations one would postulate based on Marx' theories can also be had without the Law of Value. Ditching the Law of Value (which is what Bichler and Nitzan do) makes you a non-Marxist in the eyes of most Marxists.

But, yes, what this graph really means is becoming less and less clear to me. As much as I could gather it is based on some worldwide index of listed companies, so it describes a correlation between a subset of economic actors, and yes, "rent" is wrong, it's just profits pure and simple, but nevertheless an indicator of accumulation.

The first chapter of the first volume of Capital is where the rubber meets the road. If you can get through the first three chapters, the rest is a bobsled ride.
Volume 3 is very interesting, but incomplete.
Ricardo and Rent, are still relevant, and have held up for all these years.
If you actually want to understand what Marx was saying, here is the best place to start