The drilled but uncompleted wells, commonly known as DUCs, are oil and natural gas wells that have been drilled but have not yet undergone well completion activities to start producing hydrocarbons.

The well completion process involves casing, cementing, perforating, hydraulic fracturing, and other procedures required to produce crude oil or natural gas.

As shown below, the number of DUCs has increased since 2016.

Credit: EIA

A high inventory of DUCs may be attributable to economic factors or resource constraints. For example, a low oil and natural gas price environment may postpone well completion activities in areas where the wellhead break-even price is too high relative to the current market price.

Another example may be the lack of available well completion crews to perform hydraulic fracture activities in areas of high demand. Takeaway capacity, or the ability to transport hydrocarbons through pipelines away from the resource, may also place additional constraints when pipeline networks are insufficient to accommodate supply.

Credit: EIA

In addition, according to EIA, the DUC count has been observed in regions dominated by oil production, mostly in the Permian region that spans western Texas and eastern New Mexico.

As of March 2019, nearly half of the total DUCs included in the DPR were in the Permian region.

Additional pipeline projects are scheduled or are currently being constructed.

In contrast to oil-directed regions, the number of DUCs in natural gas-dominated DPR regions such as the Appalachian and Haynesville regions has decreased by nearly half over the past three years, from 1,230 wells in March 2016 to 713 wells in March 2019.

New pipelines in these regions have increased the ability to transport natural gas to demand centers in the Northeast and Midwest.

Production in the seven DPR regions, which are characterized by tight oil or shale gas formations, achieved the 8.2 million barrels per day of crude oil and 77.1 billion cubic feet per day of natural gas in February 2019, or 70% of total U.S. crude oil production and 71% of total U.S. natural gas production.

Concluding, EIA estimates that DUC counts might be different from other sources because of differences in methodology and assumptions.