The prospect of a Turkish attack on Iraq, which has contributed to the rise in oil above $90, has revived the debate over whether the US-led invasion of 2003 was a "war for oil".

Alan Greenspan’s remark in his memoirs that "the Iraq War is largely about oil" was seized on by some commentators. But the conspiracy theorising was overdone: he was hardly revealing the secret masterplan behind the invasion. Mr Greenspan was far from the heart of policy-making, although he did apparently make his views known. It looks more as though he is simply trying to make sense of a strategy that otherwise defies rational explanation. As Thomas Powers put it in the the New York Review of Books last month: "Not knowing why we went in allowed us to go in".

In the London Review of Books, Jim Holt attempts to make the argument that "It’s the oil", but his charges do not really stick. "The draft law that the US has written for the Iraqi congress would cede nearly all the oil to Western companies," he writes, which is true if you believe that those same companies control all the oil in Russia or Venezuela. The draft oil law allows for a range of different investment structures, and ultimate control over the resources always lies with the government. If Iraq needs foreign investment, which it desperately does, then it has to offer investors sufficiently attractive commercial terms.

It is not as if western companies have been rushing to take advantage of the invasion supposedly conducted for their benefit. Decisions on investing in Iraq are very difficult, and while much of the country is in flames, and the country’s politicians are so bitterly divided, none of the oil majors will be prepared to make significant commitments. Iraq’s oil production has hardly vindicated a decision to go to war for oil, either: it is running at about 2m barrels per day, down from 2.5m just before the invasion. Rupert Murdoch’s pre-war assertion that "the greatest thing to come out of this for the world economy, if you could put it that way, would be $20 a barrel for oil" looks more deluded than ever.

Mr Holt writes "In terms of realpolitik, the invasion of Iraq is not a fiasco; it is a resounding success." If only that were true.

Chevron, the US’s second largest energy group, is close to admitting it should have known kickbacks were being paid to Saddam Hussein, during Iraq’s oil-for-food programme with the United Nations, Claudio Gatti of Il Sole 24 Ore, the Italian newspaper, reports. For an English version, picked up by the New York Times, go here. Chevron will pay $25m-30m in fines, about how much it earned in half a day’s work last year. But if the settlement with US attorneys goes ahead, it sets a precedent for other major oil companies, almost all of which, were accused in a report by Paul Volcker, former chairman of the Federal Reserves, of having bought Iraqi oil through middlemen who paid kickbacks on their behalf.

Iraq’s long-awaited oil law will be delayed a while longer, it seems. Kurdistan’s regional government has raised "serious concerns" about draft annexes to the law, talking about unacceptable concentration of power, breaches of constitutional agreements, and a "return to old regime methods."

AP, at the International Herald Tribune site, reports that Kurdish law-makers will try to block the legislation in parliament.

Over at the Oil Drum blog, my story about the IHS report on Irag’s undiscovered potential (press release is here) sparked a lively debate. As the writer of the original post observes, all that oil is not much use to anyone if it is too dangerous to extract, and no-one knows who owns it. Getting an oil law passed, and accepted by all sides, may not be a sufficient condition for getting Iraq’s oil industry to begin its recovery, but it is certainly a necessary one.

A postscript to my story in the FT on April 19 about estimates of huge undiscovered oil reserves in Iraq. I was called by Felicity Arbuthnot, a London-based journalist, who interviewed Tariq Aziz, the then deputy prime minister of Iraq, when Saddam Hussein was in power, for the online newspaper the Palestine Chronicle. His key quote: "Iraq has the second largest oil reserves, actually the first. You can find oil wherever you drill in Iraq. The US wishes to dominate oil, Saudi Arabia and the Gulf. They want to keep us dormant, bring in a pro-US government and present that as bringing about ‘democracy’ and ‘human rights’." It seems that on the question of Iraq’s oil reserves, at least, he may have been on to something.

Iraq is known more for its oil reserves (the world’s third largest) than its gas fields. But at least one major oil company is betting that the way to Iraq’s oil may well be through the gas fields in the country’s disputed, but slightly less violent northern region. That company is Royal Dutch Shell, which has been focusing increasingly on exploiting gas deposits around the world as opportunities in oil have dwindled. The story first broke on wires reporting from Iraq before Shell reluctantly confirmed it was in preliminary discussions (with Iraqi officials and the Turkish companies, including state-controlled TPAO). But Shell said Iraq needed a more peaceful existence before it could send its people to the country and a viable hydrocarbon law before it could finalise any deal. Peace was nowhere in sight yesterday when a bomb killed eight people inside its parliamentary building, the very place in which the hydrocarbon law will need to be passed.