Crude oil which US refineries process has generally grown lighter since 2011 because both imports and domestic production have changed, the US Energy Information Administration reported on Oct. 11.
Refinery crude slates have become lighter on the East, West, and Gulf Coast and slightly heavier in the Midwest and Rocky Mountains, EIA said.
API gravity is measured by the inverse of a petroleum liquid’s density relative to water, the federal energy analysis and forecasting service explained. The higher the API gravity, the lower the density of the petroleum liquid, so light oils have high API gravities. Crude with an API gravity of 38° or more is considered light, while one with API gravity of 22° or less is considered heavy.
Crudes processed along the Gulf Coast—the region with the most US refining capacity—has had the largest API gravity increase, increasing from an average of 30° in 2011 to an average of 32.6° in 2018, EIA said. The West Coast had the heaviest crude slate in 2018 at 29.2°, while the East Coast had the lightest at 34.8°, it noted.
Production of increasing lighter US crude has contributed to the overall lightering of US refiners’ crude oil slate, EIA said. The fastest growing category of domestic crude production has been oil with a more than 40° API gravity, according to data in EIA’s monthly crude oil and natural gas report, it added.
It said that since 2015, when it began collecting crude production data by API gravity, light crude production from the Lower 48 has risen from an annual average of 4.6 million b/d to 6.4 million b/d in the first 7 months of 2019.
What refiners consider
When setting crude slates, EIA said that refiners consider logistical constrains and transportation costs as well as their plants’ unique configurations. For example, nearly all (more than 99% in 2018) crude imports to the Midwest and Rocky Mountains came from Canada because of geographic and existing transportation (pipeline and rail) systems between the regions.
Crude imports from Canada, which are mostly heavy, have grown by 67% since 2011 because of more production above the border, according to EIA. They also have accounted for a greater share of refinery inputs in the Midwest and Rocky Mountains, leading to heavier refinery crude slates in the two regions.
By comparison, EIA continued, crude produced in Texas tends to be lighter. The Lone Star State accounted for half of the US-produced crude above 40° API during 2018. The share of domestic crude in the Gulf Coast refinery slate grew from 36% in 2011 to 70% in 2018, the biggest change among all US regions.
Nick Snow
NICK SNOW covered oil and gas in Washington for more than 30 years. He worked in several capacities for The Oil Daily and was founding editor of Petroleum Finance Week before joining OGJ as its Washington correspondent in September 2005 and becoming its full-time Washington editor in October 2007. He retired from OGJ in January 2020.