NAICS 21112 describes the domestic producing industry, while crude oil imports are classified under HTS Chapter 27 (specifically heading 2709) based on physical characteristics such as API gravity. Trade analysts crosswalk the two systems to compare domestic extraction volumes with competing import flows.

Natural gas liquids (NGLs) recovered as a byproduct of crude oil extraction may be included if the establishment's primary activity is crude petroleum production. However, establishments focused primarily on NGL extraction or gas processing are typically classified elsewhere in the NAICS energy hierarchy.