Why there are eight sixes and not nine is a mystery lost in time. Less of a mystery is the fact that slightly more than a third of those shares are owned by Shell Energy Holdings Australia.

Well, at least that’s what you and The Slug thought until a little bit of digging was done and few subtle differences were noted – differences that may, or may not, signal the start of a process that could result in more far-reaching changes in the ownership structure of Woodside.

At the extreme end of the change spectrum is the possibility that movement on the Woodside share register could ultimately trigger the shuffle of assets between Shell and its friends at BHP Billiton.

Both of the big boys would love to own a lot more of Woodside, a company sitting on a priceless collection of gas fields and exploration acreage along Australia’s northwest coast, but never quite having the capital or technical expertise to maximise the potential of what’s in the ground.

Shell’s desire has been very transparent, going as far as a couple of takeover attempts that failed when Australian Treasurer Peter Costello invoked the national interest clause of the foreign investment powers he controls.

BHPB’s desire has been more subtle. It sold its big shareholding in Woodside many years ago, preferring to retain a direct interest in the liquefied natural gas export phase of the Woodside-managed North West Shelf project.

The result of these conflicting desires, and political interference, is that nothing has happened on the Woodside share register, as everyone has kept a sharp lookout for anyone else making a sudden movement.

However, now The Slug has noticed not sudden movement, but movement nonetheless. And movement of any sort on the Woodside share register will re-focus attention on the ultimate ownership of Australia’s most valuable collection of natural resource assets.

First step in the change process came on December 7, without any Australian news media noticing the event. It was an announcement of the “Activation of the Woodside Dividend Reinvestment Plan” – the DRP.

For readers who lack the financial basics, a DRP scheme is a process that lets shareholders take additional shares in their company rather than cash.

It serves two purposes. It means the company keeps more cash to pay for capital works (such as Pluto LNG), and it lets shareholders avoid potential tax on cash payments. Future capital gains tax is another matter.

Woodside shareholders approved their DRP scheme three years ago, but the scheme was not activated because management didn’t believe the company had the capital at the time, and also because of the thorny question of what would Shell do with its 228,456,275 shares – take the cash or take the shares?

Now Woodside has decided to trigger its DRP, prompting a couple of curly questions:

1. If Shell does take additional shares but some shareholders prefer the cash, won’t that increase Shell’s percentage stake in Woodside and cause a fresh referral to Costello?

2. If Shell prefers the cash, won’t that water its stake down and re-invigorate the debate about BHPB or someone else taking a close look at Woodside?

The answers to those questions appear to be available to anyone with a fine-tooth comb and access to a copy of Woodside’s DRP Rules book. If you haven’t got one, trawl through the Woodside website, and look under the investors tag.

Once into the detail of the DRP Rules you will find that Shell’s status is carefully spelt out – even to the point of introducing a new name into the Woodside ownership equation because it seems that while Shell Energy Holdings is the registered holder of Shell’s Woodside shares, the name Shell can also mean Shell Australia, “or any company in the group of companies ultimately controlled by NV Koninklijke Nederlandsche Petroleum Maatschappij and The Shell Transport and Trading Company PLC which holds the shares”.

The legal mumbo-jumbo may be nothing more than legal mumbo jumbo but it does appear to The Slug that the true-blue, dinky-di owner of Shell’s 34.27% stake in Woodside can be any company in the Shell group that someone in Holland deems it to be given that the Woodside annual report names Shell Energy Holdings, and the DRP Rule book suggests a few more names.

Whether this means that Shell’s shares in Woodside shares could be packaged up neatly (and quickly) and sold to someone else is a debatable point – and far beyond the knowledge of anyone in Australia.

But it does mean Shell has carefully thought through its Woodside position and its status post the start of the DRP, which is either March 2, the date when entitlement is calculated, or March 28, the payment date.

It is between these two periods that Shell will have the opportunity, under Rule 5 of the DRP, to adjust its stake in Woodside to remain at 34.27%, presumably by buying, selling, or varying its entitlement.

Whatever happens with the detail, Costello, Woodside chief executive Don Voelte and BHPB will be watching very carefully.

And the ultimate outcome of all this? Perhaps nothing.

But The Slug’s experience in these matters is that once you start fiddling around with a share register a lot of people have their interest re-activated, and start thinking of all sorts of combinations and permutations – such as BHPB making a takeover bid for Woodside to bolster its somewhat sluggish petroleum division and creating a new and bigger business controlled by BHPB and Shell.

Fanciful, perhaps. But stranger things have happened in the oil patch and share register changes are just the catalyst needed to get reactive juices flowing in the investment banking world.

First published in the January issue of Petroleum magazine