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16 Proceedings Fall 2015 www.uscg.mil/proceedings sulfur-content crudes. Now, how- ever, the crude oil from Eagle Ford has an API from 38 to 60 degrees and Bakken crude oil from North Dakota ranges from 36 to 44 degrees API. The quality of both are almost iden- tical to WTI, which is 40 degrees API, but it is also the higher API, which indicates that these crudes are more volatile. 6 The lightest crude oils — conden- sates — contain natural gas liquids that can come out of solution and form explosive gases, which pres- ents problems during transportation. Pipelines can safely handle the vol- umes with minimal leakage because the product that is concentrated in field-gathering systems moves to refning locations still contained in the pipeline system. However, when very light crude oil must be handled outside of pipeline con- tainment, remaining volatile compounds can come out of solution as the production is handled from wells to storage tanks to surface transportation modes to refnery unload. Transport A number of incidents have occurred during light crude rail shipment, most notably from Bakken-producing loca- tions, which are remote and not well connected to markets. Transportation for this land-locked crude is primarily via rail, as only one small refnery is located in North Dakota and there is limited pipeline capacity for transport to market hubs. In response, U.S. and Canadian safety regulators have responded with new requirements for rail carriage. 7 This is not to say there aren't problems transporting the lighter crudes via pipeline. Lighter crude oil can pose chal- lenges to the gatherers who purchase the crude oil in the feld. Most pipelines will require that the crude oil have an API of not greater than 42 degrees, though it will vary by pipeline, and some have a cap of 45 degrees. Midstream pipeline operators must then blend lighter crude oil with heavier crudes to meet pipeline restrictions. The Global Market Heavier crudes with an API of 32–28 degrees can be mixed with the lighter crudes of API 50 and above to achieve a medium blend crude oil with a resulting API of 42 degrees or less. This is not a simple process, and it requires facili- ties located in oil felds near producing wells, pipeline net- works, and experienced professionals who understand the gravity, so it is heavier than water, and will sink. Most crude oils will measure between 10 and 70 degrees API. Even within crude types, there will be variations, so these char- acteristics are usually given or quoted as ranges. "Light" crude oil has an API greater than 31 degrees, "medium"- grade crude oil has an API between 22 and 31 degrees, and "heavy" crude oil has an API of less than 22 degrees. 4 In the U.S., crude oil production has grown by 1.8 million barrels per day from 2011 to 2013, and roughly 96 percent of this is light, sweet-grade oil. These crudes generally have API gravity of 40 or above and sulfur content of 0.3 percent or less. 5 Market Efect Crude oil chemical evaluation provides hydrocarbon data for refners, oil traders, and producers. It can help refneries determine if a crude oil feedstock is compatible for a par- ticular petroleum refnery or if the crude could cause yield, quality, production, environmental, or other problems. Lighter crude oils are valued more in the market, as they do not require technically complex refning facilities for pro- cessing and will refne more easily into "light ends," mean- ing they can produce a greater quantity of gasoline, diesel, kerosene, and naphtha. Heavier crudes will produce more gasoil, residual fuel oil, and asphalt, which are priced lower and therefore result in lower proft margins for refners. To keep feedstock prices low, and because the worldwide trend appeared to be toward producing heavier crude oil, refners reconfgured facilities to process the heavier, high U.S. Crude Oil Production by API Type A comparison of the yields from various types of crude oil from the U.S. (Bakken, Eagle Ford, WTI, and Louisiana Light Sweet or LLS); U.K. (Forties and Brent); Russia (Urals); Nigeria (Bonny Light); and Mexico (Maya heavy). U.S. Energy Information Administration data. Note: Higher API numbers indicate lighter crude oil.