The answer is, because we demanded it, you and I.
"It" being a reasonably inexpensive, plentiful and secure supply of petroleum products, gasoline in particular. We don't like gas lines or $8.00 per gallon. We really don't like gas lines and $8.00 per gallon.
(And "we" includes every American, with the possible exception of St. Ed Begley, Jr. )
We also decided that we didn't want it to come from our own back yards. It shouldn't mess up our postcard views from 30 story condo developments. We also decided we didn't want it to interfere with the nesting season of the sage grouse or the mating habits of the pronghorn antelope.
We want gasoline to be as reliable as electricity, and we don't want to give any thought to where it comes from.
In order to satisfy our demand, large multinational oil companies must find oil in large fields, capable of producing at high rates of flow. Most of the producing basins in the U.S. are so mature, so "picked over", that the odds of finding a new, world class discovery comparable to those in the Middle East or Africa, are very, very low.
Operating in the developing world has its special risks. Many oilfields and much of the infrastructure that has been developed by Western companies has been expropriated by local regimes in places like Saudi Arabia, Libya, Venezuela, and most recently, Ecuador.
The political risk is less in the U.S., where (at least historically) there has been respect for contracts, land title and the rule of law.
We've placed promising areas like the Eastern Gulf of Mexico, the East Coast, offshore California, offshore Alaska and ANWR off limits. This current spill will provide ammunition for the anti development folks. But since our collective thirst for petroleum will be unabated, that will mean more oil and refined products will have to be imported in tankers, with their accompanying risk of spill.
BP looked for oil in the deepwater off Louisiana, partly because (paraphrasing Willie Sutton) that's where the oil is, but also, domestically, it's one of the few places where they had access.
The only place in the U.S. that is both welcoming to the petroleum industry and highly prospective for large discoveries is the deepwater Gulf of Mexico. In the last few years, successful drilling has indicated the potential of billions of barrels of reserves. But drilling there has its risks, as we have all learned.
And there's the frustration. Some will want use this spill in 5,000 feet of water as the reason to stop drilling anywhere domestically. Deepwater drilling is challenging for several reasons. Geomechanically, the wells are more challenging to drill than land wells, requiring more casing strings to be set for hole stability. On land or in shallow water, the blowout preventer is at the surface; in deepwater they are on the seafloor, much less accessible by men & equipment. Divers can dive to fix things in 50 feet of water, but not 5,000.
Shelf drilling in the Gulf of Mexico has been relatively spill-free for 40 years. Industry has learned how to drill on land from small, minimally impacting footprints. We should not react emotionally to the Deepwater Horizon disaster, but learn from its lessons and figure out a more sensible domestic exploration policy that builds on existing conventional technologies.
Cross-posted to VladEnBlog.