Before jumping directly into APIs, we’re gonna start with a short quiz we pulled from Well Servicing Magazine to give us a little background. Match the petroleum to its description:

1) West Texas sour
2) Kern River crude
3) Thunder Horse oil
4) Alberta oil sand

a) API gravity: about 32 degrees. Transported to shore by the Mardi Gras Transportation System.
b) Does not float in fresh water. Consists of bitumen.
c) Stinks to high heaven. Sulfur content > 1 percent.
d) API gravity: about 13 degrees. Thick as molasses.

How petroleum occurs in nature ultimately affects how it is produced and refined. Because of this, testing crude oil is an essential part of our business.

When oil is allowed to sit in a tank undisturbed, it eventually stratifies and the heaviest oil particles settle to the bottom of the tank. These heavier oil particles will have a lower API than the lighter particles that float near the top…

Now, if we take only one sample to determine the API of our tank, and that sample is taken near the bottom of the tank, our measured tank API will be lower than its true API average.

Many contracts in the oil purchasing business read something like this:

“Each party shall have the right to have a representative present to witness all gauges, tests and measurements; however, in the absence of either party’s representative, the gauges, tests and measurements of the other party shall be deemed to be correct.”

But let’s face it, most pumpers are to busy to oversee the sale of every tank. And, we realize that a slight variation may mean no consequences to the seller. However, the API level between the top and the bottom of a tank can vary by as many as 2 points. A faulty API determination could throw an entire tank of oil into a lower price bracket.

How to keep this from occurring? 

To make sure you receive your due, GreaseBook recommends that pumpers take three measurements from every tank (one from the bottom, middle, and top). We understand this is a tough practice to implement, but if nothing else, make sure they take that measurement from the center of the tank. Hopefully your pumper will recognize and report any discrepancies between the purchaser’s API levels and his own.

By the way, here are the answers to the short quiz:  <1) c; 2) d; 3) a; and 4) b.>

And, here’s a little extra info to boot…

Petroleum comes in many different forms. West Texas sour crude oil is drawn from the Permian Basin and normally has a sulfur content in the 1-2 percent range. Produced with the assistance of steam heat, Kern River crude comes from California and is a heavy oil. Discovered by BP and ExxonMobil, Thunder Horse is one of the biggest finds in the Gulf of Mexico. It’s located about 125 miles southeast of New Orleans, and lies below a water depth of about 6,000 feet. Oil sand from Canada has to be processed to make synthetic crude.

Happy Operating!

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