Image copyright PA

BP's job announcement later today, including a few hundred job losses in Aberdeen, is being made because it does not expect the oil price to bounce any time soon.

The oil price has dropped around 60% since June, to $48 a barrel, and I understand that BP expects that it will stay in the range of $50 to $60 for two to three years.

Although no oil company has a crystal ball, this matters - especially since it has a big impact on its investment and staffing ambitions.

So plans that it had already initiated to reduce costs have taken on a new element, namely postponement of investments in new capacity that have not been started, and shelving of plans to extend the life of older fields where residual oil is more expensive to extract.

Aberdeen is an important centre for BP, and it employs around 4000 there. And it is in no sense withdrawing - it is continuing to invest in the Greater Clair and Quad 204 offshore properties.

But the reduction of several hundred in the numbers it will henceforth employ in the Aberdeen area is symbolic of a city and industry that faces a severe recession.

Hardest hit will be North Sea companies with stakes in older fields, where production costs are on a rising trend - and whose profitable life will be significantly shortened if the oil price does not recover soon.

The reason BP expects the oil price to stay in the range of $50 to $60 for some years is for reasons you have read about here - it is persuaded that the Saudis, Emiratis and Kuwaitis are determined to recapture market share from US shale gas.

This means keeping the volume of oil production high enough such that the oil price remains low enough to wipe out the so-called froth from the shale industry - to bankrupt those high-cost frackers who have borrowed colossal sums to finance their investment.

Image copyright Getty Images Image caption Drilling for shale gas in the US: Saudis are determined to recapture market share

This does not simply require some US frackers to be bankrupted and put out of business, but also that enough banks and creditors are burned such that the supply of finance to the shale industry dries up.

If BP is right, most big oil-producing companies will have to write off the value of older, more expensive oil fields

Only in that way could Saudi could be confident of reinvigorating its market power.

And, as I have also been banging on about, Saudi is not thought to be weeping that a lower oil price hurts its supposed nemesis, Iran, reduces the resources of an an oil-financed Islamic state and mullers the economy of a Russia that it sees as having been too supportive of Syria.

Meanwhile although the US shale industry is in pain, the lower price will probably reinforce the US economic recovery - and the White House doesn't massively worry that Russia and Venezuela are in dire economic straits.

If BP is right, most big oil-producing companies will have to write off the value of older, more expensive oil fields. That is particularly true of European companies, because of accounting rules here.

In fact BP is less exposed to such losses than many - because it sold $43bn of mostly older oil properties over the past few years, to pay the enormous bills of its Gulf-of-Mexico oil spill.

But BP can't be immune to the upheaval. Today its job announcement is focused on the UK. But it won't be long till it announces staff reductions in Houston, another of its important centres.

What we are seeing, therefore, is a massive shift in corporate and economic power, from producers to consumers - with oil-producing countries as robust as Norway wincing and with a massive manufacturer like China quietly grateful that its own difficult economic reconstruction is being oiled (as it were) by the tumbling price of energy.