Vail Valley Voices: Roots of the spill
Vail, CO, Colorado
Back in the 1990s, I spent some time north of the Arctic Circle in Russia’s far east, along the Kolyma River. I was there installing a satellite network that would link a gold mine with its operations centers on the Siberian coast and offices in Denver.
It was harsh country, though I gained a respect for the Russian people who’d grown up there, survived the collapse of their government and were, even after 50 years of “cold war,” friendly and hospitable to me, their former enemy.
I remember thinking one morning as we assembled a 7 meter Russian-made satellite antenna in minus 40 Celsius temperatures that people sure went a long, long way and suffered a lot of hardship chasing a few tons of metal.
Gold, after all, is just a metal. It’s precious, but until you’ve seen how far out in the harsh wilderness people go to find it, you’ll never appreciate how precious it really is.
I was reminded of that morning in Siberia this past week as a giant oil rig caught fire, burned, then sank into the Gulf of Mexico.
Eleven people died in pursuit of oil, “black gold,” a substance still traded as if it is a commodity but, given its place as the foundation of modern civilization, a mineral that should have long been priced million times higher than it is today since like all minerals, it is finite. Finite, and at the same time, the source of the energy that powers and is the foundation of civilization.
Oil has an energy density per pound greater than anything else on Earth except uranium, and it is still cheaper per gallon than milk.
Oil is getting harder and hard to find. According to media reports, the rig that was lost, the Deepwater Horizon and its crew, had drilled an exploratory well to its final depth of more than 13,000 feet beneath the surface of the ocean floor. The ocean floor was another 5,000 feet below the surface and the rig.
The ill fated crew was injecting cement around the steel casing at the time of the explosion, a blast that resulted in tragedy for the families of the workers lost and the environment, as crude oil now pours into the gulf at the rate of 5,000 or more barrels a day. (In addition, the huge rig held 700,000 gallons of diesel when it sank. There’s no word on what has or will become of this.)
According to the rig’s owner, Transocean, the rig was built in 2001 in South Korea and is designed to operate in water up to 8,000 feet deep, drill 5.5 miles down, and accommodate a crew of 130. It floats on pontoons and is moored to the sea floor by several large anchors.
Hot and deep
According to the U.S. Department of Energy, the average depth of oil wells is between 5,000 and 6,000 feet below the surface of the Earth.
As a rule of thumb, since this does vary from area to area, if there’s no volcanic activity and a well is not near a plate margin, the first couple hundred feet will be around 55 degrees fahrenheit, and after that the ground temperature starts increasing about 1degree per 100 feet. Therefore, 5,000 feet below the ground, the average oil well depth, the temperature of the rock (and oil or gas deposits) is around 100 degrees.
Now drill down to 13,000 feet. The rock temperature, and therefore oil “pool” at this depth, will be 280 degrees, if that rock depth was measured from the Earth’s surface at sea level.
This wellhead is 5,000 feet below the ocean’s surface, meaning the rock surface is not withstanding a mere 14.7 pounds per square inch of pressure but nearly 2,200 pounds of pressure per square inch.
Because of this, the temperature and depth “rule of thumb” doesn’t apply, since the weight of the ocean adds to the pressure of the rock under the sea, which increases the temperature ratio as one drills into the ocean floor. I’m many years away from my physics classes, but a geologist could compute the estimated increase in temperature easily, I’m sure.
So we have a situation in which, in the best case, a drill has tapped an oil deposit some 13,000 feet deep, oil that is at minimum, about 300 degrees and under thousands of pounds of pressure, obviously more than the seawater’s 2,200 psi pressure trying to keep the oil in the ground. Media reports indicate that BP estimates the oil’s wellhead pressure is between an astounding 15,000 to 70,000 psi.
At this temperature, the oil is already partially “refined,” and consists of “natural gas liquids,” petroleum gases and natural gas itself. Volatile stuff.
The crew was in the process of injecting a concrete slurry around the well casing down to the first layer of bedrock to seal the well against leakage when the deep drill casing is removed.
A sudden blowout — a burst of high pressure oil and natural gas — caused an explosion at the surface on the floating rig. While this is all that’s known, it clearly illustrates the increased dangers faced when one is working with highly flammable substances that are already at high pressure, high temperatures and partially refined into lighter grade more volatile liquids and gases.
Stopping the leak
At this time, BP is planning to lower a 40-foot-tall, multi-ton steel “funnel” to the sea floor to cover the broken wellhead so that the escaping oil can flow up a riser well pipe into a tanker.
Details of this procedure are sketchy. But given that there’s nothing but gravity to secure the funnel to the sea floor, with the mass of the funnel additionally weighted by the mass of a mile of steel pipe rising to the surface, the now obvious changes in oil pressure at this site seem to complicate this idea significantly.
If the oil is gushing into this recovery system at 15,000 to 70,000 psi and the surrounding seawater is pushing into the funnel is only 2,200 psi, a structure with no bottom seal other than 30 feet of seafloor mud doesn’t seem as if it can remain stable or sealed over time.
There certainly cannot be any restrictions in the flow through the riser pipe. If there are, the funnel will spring a mud-seal leak quickly at best and pop off like a cork at worst.
For now, it is the only idea that even might work, so we’ll all see how well it operates within a few days.
Given that most of the world’s oil that’s left to exploit is going to be hot, deep and more highly volatile than the shallow feilds we have experience with, the tragedy of the Deepwater Horizon should serve as testament to not only how far mankind will go for gold of any color but how costly the next generation of oil energy will be to recover safely. If it even can be recovered safely.
Bill Sepmeier lives off the grid on Sweetwater Creek.