Three Sizes of Oil Storage

Oil storage is the subject of this month’s column. As I look around my shop, the only oil storage around here is on the shelf.

On the Shelf

In the area where I live, oil on the shelf means two things. Both are at the extreme end of the scale regarding size and content. There is the oil on my shelf, and there is the oil on the continental shelf. Geologically speaking, the continental shelf is the gently sloping offshore zone, extending usually to a depth of about 200 meters.¹

In the offshore waters of South Louisiana, from three to 1,000 feet, there is an abundance of oil wells in all directions. Many visitors in these southern Louisiana towns expect to see oil wells everywhere. They think they might see something similar to Kilgore, Tex., where at one time there were oil wells throughout the downtown area.

I lived there for the first seven years of my life and remember seeing them as I walked to first grade or went shopping with my mother. But the oil wells in Louisiana are mostly on the water; some are 80 miles offshore in water 10,000 feet deep. There are billions of dollars invested in the oilfield within 30 miles of my house, but you must get in a boat or helicopter to see it.

Small Storage

The storage problems I encounter in my auto shop are concerned with keeping the containers sealed and avoiding cross-contamination. Many years ago, when a one-quart can of oil was opened, it was used in full or was left open, exposed to the atmosphere and the dust which floated around in the shop.

You either used it, or you contaminated the next guy who needed just a pint or so. I remember laying a dirty shop rag across the top of a can and thinking I was doing a good job of keeping the contents clean.

Oddly enough, more attention was paid to keep the brake fluid sealed, which came with a screw-top can. Brake fluid is hygroscopic, meaning it absorbs moisture from the air - a concern in my shop because it’s in a place with high humidity year-round.

The advent of plastic bottles for oil storage has eliminated any dust problems. They have resealable caps and do a wonderful job protecting a partial quart of oil. I do not worry about using fresh oil from a factory-sealed bottle.

I do, however, wonder about the larger shops that buy oil by the barrel and transfer it to your car by a hose and pump. How long has it been since they flushed those hoses?

Has any grit or sludge made its way into the nozzle while it was stored, then been dragged across the components under the hood? It is standard practice in my shop to wipe the funnel with a clean rag before we install new oil, and to use a different funnel for transmission oil and motor oil. Even these practices do not completely prevent particulate contamination during a top-off.

Medium-size Storage

The first part of this column discusses the highly refined and nearly immaculate product that begins with a raw substance, crude oil. This section on storage addresses this unrefined crude and some of its inherent storage problems. Size is the biggest problem, then transportability.

All of the oil wells near my house have a collection point, the large white storage tanks, called tank farms. These are visible near any refinery or oil field. Many of these tanks have tops that float on top of the oil in the tank.²

This kind of seal collects any rain that falls on the roof and diverts it through spouts. Any water that enters the tank around the seal goes to the bottom and is drained off. For years I drove by those tank farms and thought they were solid on top, like a hard-shelled cylinder. The first time I flew a Piper Cub over one, I thought the tank had caved in!

The storage method is evident; those big white tanks are hard to miss. The levees built around them are to contain a catastrophic rupture of the tank. I had a high-school algebra teacher, who for homework gave us the location of several smaller tanks around town. He then had students measure the perimeter and height of the levees surrounding the tanks.

Our assignment was to predict the volume of the tank based on the volume of the enclosure levee. It was an interesting and educational exercise involving local points of interest. Good teachers do things like that.

Large-scale Storage

The U.S. Strategic Petroleum Reserve is located in several salt domes on the Louisiana and Texas Gulf Coasts. It is the largest crude oil storage facility in the world. There are currently about 662 million barrels stored in approximately 50 domes here on the Gulf Coast.³

These domes were selected because they are geologically stable, easy to prepare for oil storage, and close to major oil ports on the Gulf Coast. This is not domestic oil. The oil comes mostly from the North Sea and from Mexico.

The U.S. government has allocated a budget which allows for the maintenance of the sites and annually purchases oil to approach the ultimate goal of about 750 million barrels.

I interviewed a friend who retired from the Petroleum Reserve’s project management office in New Orleans. He told me an interesting story of the abandonment of the Weeks Island salt dome in 1994.⁴

In the flat marsh and prairie lands of South Louisiana are some of the most beautiful and productive wildlife habitats on earth. These areas are quite often less than 10 feet above sea level, but the landscape is dotted with mounds measuring 100 yards across and several feet higher than the surrounding land.

The geologic salt structures underground push up the earth and create a dome. Salt has been mined from these domes in Louisiana for generations. The Petroleum Reserve bought a salt mine located near Avery and Weeks islands.⁵ Avery Island has beautiful jungle gardens and adjacent to them is the place where McIhenny’s Tabasco™ sauce is produced.

This area along the coast of South Louisiana features tropical gardens, Tabasco, beautiful wildlife and salt mines, all on the same piece of property.

The Weeks Island mine had about 70 million barrels of oil in storage. Weeks Island is close to Vermilion Bay and the Gulf of Mexico. In the interview, I learned that a few years ago, fresh water was detected in the mine. This is problematic, because fresh water can erode the salt walls and crack them. There is potential for oil to escape, and in this case, it could leak into the Gulf of Mexico. Such a disaster would have been epic in scale.

By comparison, the Exxon Valdez oil spill was about 257,000 barrels (11 million gallons / 38,800 metric tons)⁶ in size and Weeks Island had the potential of 70 million barrels; approximately 275 times the size of the Exxon Valdez spill. The crude stored at Weeks Island was immediately withdrawn and was sent to nearby domes or sold to refinery sites.

A rapid withdrawal might have worsened the problem. Fresh water could have seeped in at an increasing rate, crack the walls even more. Liquid nitrogen was injected into drilled holes to freeze the danger area. The fresh water was held back while oil was drawn out and replaced with brine water. After several months, there was a sigh of relief, as the efforts of the Petroleum Reserve were successful.

The Weeks Island dome was unusual. It was originally a salt mine, only 500 to 700 feet deep and was located close to the Gulf of Mexico. The other domes in the Petroleum Reserve are deeper, more than 1,200 feet, where geologic pressures will seal any fractures in the salt barrier. Because they are further from the Gulf, no problems have occurred nor are anticipated in the future.

One-quart bottles of oil don’t compare to 70 million barrels, but one quart spilled in my shop can be a nasty, hazardous mess.

On the Home Front

Keep oil bottles sealed from dirt and moisture. Never store gasoline in any thing other than a sealed container, and keep it away from your home if possible. Brake fluid should be purchased and stored only in small amounts. Antifreeze should be kept sealed and away from pets. My friend’s Labrador died because a leaky water pump spilled antifreeze on the garage floor and the dog lapped it up.

Car Tip

If your car has more than 30,000 miles on it, look at the brake fluid reservoir. If the fluid is dark brown or cloudy rather than a clear light amber color, it is contaminated. Flush, but do not bleed your brakes. Flushing is a complete replacement whereas bleeding just adds to contaminated fluid.

Modern cars with antilock brake systems can be easily and expensively damaged by contaminated brake fluid. Use DOT 3 fluid unless otherwise directed by your owners manual. DOT 5 silicon brake fluid is better and has less heat fade (due to a higher boiling point), but it contaminates easily. Only race drivers, who change their fluid after most races, need to use this fluid.

References

1. Larousse Dictionary of Science and Technology. Peter Walker, ed. (1995).
2. http://www.spectrex-inc.com/applications/fpso.htm
3. http://www.fe.doe.gov/programs/reserves/
4. http://www.fe.doe.gov/news/techlines/98/tl_sprwks_ brine.html
5. http://lagic.lsu.edu/SatelliteTour/AveryWeeks/zoomin_ files/slide0006.htm
6. http://www.evostc.state.ak.us/facts/
7. http://www.fe.doe.gov/news/techlines/99/tl_wkfil.html
8. http://www.brakesafely.com/whychange.htm

Related Reading
Ramsey, P. “Look in the Book!” Machinery Lubrication, May-June 2002.