On Mon, 11 Aug 2008 20:36:44 -0400, Gene Kearns
wrote:

You missed the most obvious benefit. Rigs are hi-rise condos for all
types of marine life! Its all about the fishing!

Yes and no.

The common belief is that rigs and production platforms are fish
factories and that's not the case at all. In fact, there is some
evidence that the platforms may hurt the reproductive cycle because
fish won't leave the vicinity of the structure to reproduce.

That is by no means definitive, but tracking studies suggest that is
the case with certain species - in particular red snapper.

Having said that, certain types of reef fish thrive very nicely near
the structures - species like grouper for example have actually had
something of a resurgence because of the platforms.

The other issue is exactly what kinds of fish are attracted to the
platforms and what depths they can find shelter. For example, in the
North Sea, they have found that creating shelters creates some habitat
for cod fish, but that turns off other types of fish like haddock.
Haddock like to hang along linear objects placed around the platforms,
but that creates problems for cod.

I know in California, they've done a lot of research on this and have
developed some differing techniques depending on the dominant speices
where the rig resides. As it's more economically feasible for the
major oil companies to just leave the rigs in place rather than
disassemble them, they need to show some sort of benefit from doing so
and the exact benefit for leaving them in place has been hard to pin
down.

One interesting factoid is that the deep water rigs seem to attract
pelagic species at a higher rate that originally expected.

It's an interesting subject.