In an effort to better present crude oil storage capacity and use across the United States, EIA has prepared new tables as part of the semiannual Working and Net Available Shell Storage Capacity Report. The new series show crude oil stocks held at refineries crude oil in tanks and underground storage in each Petroleum Administration for Defense District (PADD). Previously, this information was only available at the national level.
Crude oil stocks in tanks and underground storage are used to calculate storage capacity utilization rates and to derive the quantity of crude oil held in pipelines and in transit by rail and water. Refinery stocks and storage capacity data by PADD have both been available since 2011, but the new table brings together these two sets of data to simplify the task of calculating utilization rates by PADD.
EIA updates storage capacity data twice each year, reflecting capacities as of the end of March and September. EIA has crude oil inventory data back to 1981, but storage capacity data were first reported by EIA for the end of March 2011.
EIA reports crude oil inventories held in four types of locations:
- At refineries
- In pipelines and tank farms, which are further classified as:
- In tanks and underground storage
- In pipelines, and other forms of transit (by rail, by water)
- On producing leases (storage on production sites)
All four of these categories are considered when calculating inventories, but only two categories are relevant to calculating capacity utilization: crude oil held at refineries and in tanks and underground storage.
Some of the stocks reported as being held at refineries are actually in transit (on their way to the refinery), but these volumes are assumed to be minimal relative to stocks in refinery tanks and refinery storage capacity.
Some of the more significant changes in crude oil storage have occurred in the Midwest, where 26% of the nation’s working storage capacity, including storage at Cushing, Oklahoma, is located. Storage utilization at Midwest refineries (as defined by PADD 2) in March 2015 reached 80%, the highest storage utilization rate observed for any month since EIA started collecting storage capacity data. Again, the refinery storage utilization rate may be somewhat overstated, as the refinery stock data include volumes of crude oil in transit by rail and water being transported to refineries.
In the case of crude oil stocks held in tank farms and pipelines, crude oil in transit by pipeline, water, and rail can be separately tabulated. These volumes are not measured directly but rather are derived by subtracting the stocks in tanks and underground storage from the combined pipeline and tank farm quantity.
In the Midwest, stocks in pipelines and in transit by rail and water increased from 25.3 million barrels in March 2011 to 35.0 million barrels in March 2015. This increase occurred primarily because of pipeline expansions and increased quantities of crude oil being transported by rail and water. Because pipelines must be full in order to operate, stocks held in pipelines (known as pipeline fill) are not considered in the storage utilization calculation. Utilization of working capacity of tanks and underground storage was 73% in March 2015, nearly equal to the rate in March 2011, as Midwest crude oil stocks and storage capacities increased at similar rates.
Utilization of combined storage capacity at Midwest refineries and tank farms was 74% at the end of March 2015, the highest PADD 2 storage capacity utilization rate recorded in the five years EIA has been collecting data. In absolute amounts, the crude oil stored at Midwest refineries and tank farms in March 2015 was 103.7 million barrels, slightly lower than the total Midwest working storage capacity four years before. Because storage capacity has increased, however, the March 2015 utilization rate is only about 2 percentage points above the previous high of 72% at the end of March 2011.