Source: U.S. Energy Information Administration, Monthly Crude Oil and Natural Gas Production
Total U.S. crude oil production grew by 1.24 million barrels per day (b/d) (11%) in 2019. This increase in production was led by relatively light, less dense crude oil and was largely the result of the growth in crude oil production from shale and tight rock formations. Shale and tight rock formations are now more accessible because of the continued advances in horizontal drilling and hydraulic fracturing. U.S. refinery inputs have also become lighter over the years as refineries use less of the heavier, imported crude oil and more of the lighter, domestically produced crude oil to process into petroleum products.
Crude oil with a higher API gravity is lighter, or less dense. Production of crude oil with an API gravity greater than 40 degrees grew from 5.8 million barrels per day (b/d) in 2018 to 6.7 million b/d in 2019. Production of crude oil of 40 degrees or greater accounted for 57% of total Lower 48 states' production in 2019, an increase from 50% in 2015, the earliest year for which the U.S. Energy Information Administration (EIA) reported crude oil production data by API gravity.
API gravity can differ greatly by production area. For example, oil produced in Texas—the largest crude oil-producing state—has a relatively broad distribution of API gravities, and most crude oil produced there ranges from 30 degrees to 50 degrees API.
Relatively light crude oil with an API gravity from 40 degrees to 50 degrees accounted for most of Texas’s production in 2019, at 56%. Crude oil in this API gravity range—the fastest-growing category overall—reached 2.9 million b/d in 2019, driven by increasing production in the tight oil plays of the Permian and Eagle Ford shale formations.
The crude oil produced in North Dakota’s Bakken formation also tends to be relatively light. Conversely, the crude oil produced in California and the Federal Offshore Gulf of Mexico tends to be heavier.
In contrast to the light crude oil that is increasingly produced in the United States, the crude oil that the United States imports tends to be heavier. In 2019, 6.5 million b/d (96%) of imported crude oil had an API gravity of 40 degrees or lower, compared with 5.1 million b/d (43%) of domestically produced crude oil. Imports of relatively heavy crude oil (API gravity of 40 degrees or lower) decreased by 971,000 b/d, or 13%, in 2019, and domestic production of relatively light crude oil (with API gravity of 40 degrees or higher) increased by nearly 900,000 b/d, or 16%.
The United States continues to import crude oil because of the variations in crude oil quality. U.S. refining capacity is configured for a diverse range of crude oil inputs, allowing refineries to run the variety of crude oil that is most economical. Heavier crude oil tends to be priced lower than lighter crude oil, providing an incentive for refiners to run the heavier crude oil if they have the capability to do so.
The average API gravity of domestic and imported crude oil used in U.S. refineries has increased from a low of 30.2 degrees in 2004 to a record-high average of 32.9 degrees in 2019. Since 2009, U.S. imports of crude oil have decreased 23%. During the same time period, domestic production grew 138% and, as a result, provided a greater share of refinery inputs.
EIA publishes API gravity production data by state in the Monthly Crude Oil and Natural Gas Production report. EIA also reports company-level crude oil import quality data and volumes to better inform analysis of refinery inputs and utilization, crude oil trade, and regional crude oil pricing.