Saturday, July 10, 2010

Why No Oil Wells Off Oregon's Coast?

Simple answer: no oil. There's some minor gas, both offshore and on (with commercial development at Mist, as a minor producer and as a storage site). The gas was thought by Allan Niem, my first term geo prof, and a sedimentary petrologist specializing on the Oregon Coast Range, to have resulted from "cooking" of organic-rich sediments by re-intrusion of Columbia River Basalts into the unconsolidated mud, silt and sand. As a result, gas is not abundant, and is spotty in its occurrence- Mist is the only producing gas field in Oregon.

For oil you need several factors that come together. First you need an organic-rich source rock. Second you need an appropriate thermal history- the sediment needs to be heated and held at 60 to 120 degrees Celsius- the so-called "oil window." Third, you need a reservoir rock- a porous and permeable rock that can store the petroleum; this is typically a sandstone or fragmental limestone. And fourth, you need a trap. The reservoir must be overlain by rocks that don't permit further upward migration of gas and oil, and the two units must be oriented in such a way that oil and gas won't migrate to the surface and be lost.

I suspect Oregon is fine with respect to the first and fourth factors there. The third I'm really not sure about- we have plenty of sandstone, but a lot of it is full of clay. There's some porosity, but I'm guessing permeability is pretty poor. But the killer is the thermal history- few of the coast range rocks have ever been hot enough to generate oil. I suspect there are plenty of potential source materials- particularly in the northern portion, where there is a higher mud to sand ratio, I'd be surprised if there weren't structures that would be appropriate for trapping oil, I'm really not sure about the quality of potential reservoir rocks, but the cooking just hasn't been there.

So that's the answer to this specious little bit of sanctimony in today's OregonLive:
As we all know, drilling for oil off the Oregon coast didn't happen. I don't really know why. Today I can't seem to find anyone who remembers anything about the issue. Whatever the reason, it was a victory for the Oregon coast. Oregon's drilling scheme died in 1981 and seemed buried for all time when Congress banned drilling for oil and gas in offshore waters.
I'm curious if Mr. Love has a car, and how many miles he drives per year. Two Sundays ago, I got into a car for the first time in a year and a half... and it was with a twinge of regret and guilt. Once again, I was just as guilty as the author and everyone else for the ongoing disaster in Louisiana.

Oregon's lack of oil wells is no victory of environmental consciousness. "Drilling for oil off the Oregon coast didn't happen" because there's no oil there. The only real conclusion I can draw from this op-ed, which concludes, "Do we ever learn anything from our history in this country?" is no, we really don't. And that extends to op-ed writers who pointedly note their ignorance even as they assert some opinion on subjects of which they are ignorant.

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